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D2.2 Draft Overall 5G RAN Design

Arnold, Paul,Bayer, Nico,Belschner, Jakob,Rosowski, Thomas,Zimmermann, Gerd,Ericson, Mårten,Da Silva, Icaro Leonardo,Bulakci, Ömer,Kaloxylos, Alexandros,Spapis, Panagiotis,Ibrahim, Ahmed M.,Yang, Yang,Singh, Shubhranshu,Celik, Haris,Monserrat del Río, Jo · 2016

Abstract

This deliverable provides the consolidated preliminary view of the METIS-II partners on the 5 th generation (5G) radio access network (RAN) design at a mid-point of the project. The overall 5G RAN is envisaged to operate over a wide range of spectrum bands comprising of heterogeneous spectrum usage scenarios. More precisely, the 5G air interface (AI) is expected to be composed of multiple so-called AI variants (AIVs), which include evolved legacy technology such as Long Term Evolution Advanced (LTE-A) as well as novel AIVs, which may be tailored to particular services or frequency bands.

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D2.2 Draft Overall 5G RAN Design

Author: Arnold, Paul,Bayer, Nico,Belschner, Jakob,Rosowski, Thomas,Zimmermann, Gerd,Ericson, Mårten,Da Silva, Icaro Leonardo,Bulakci, Ömer,Kaloxylos, Alexandros,Spapis, Panagiotis,Ibrahim, Ahmed M.,Yang, Yang,Singh, Shubhranshu,Celik, Haris,Monserrat del Río, Jo
Year: 2016
DOI: 10.13140/RG.2.2.17831.14245
Source: https://riunet.upv.es/bitstream/10251/76703/1/METIS-II_D2.2_V1.0.pdf
Mobile and wi eless communica ions Enable s o he Twen y- wen y
In o ma ion Socie y-II
Deli e able D2.2
D a O e all 5G RAN Design
Ve sion: 1.0
2016-06-30
h p://www.5g-ppp.eu/
2
Deli e able/Repo D2.2
D a O e all 5G RAN Design
G an Ag eemen Numbe : 671680
P ojec Name: Mobile and wi eless communica ions Enable s o he
Twen y- wen y In o ma ion Socie y-II
P ojec Ac onym: METIS-II
Documen Numbe : METIS-II/D2.2
Documen Ti le: D a O e all 5G RAN Design
Ve sion: 1.0
Deli e y Da e: 2016-06-30
Edi o (s): Pa ick Ma sch, Nokia Bell Labs
Öme Bulakci, Huawei Technologies ERC
Ica o Da Sil a, E icsson
Au ho s: Paul A nold, Nico Baye , Jakob Belschne , Thomas
Rosowski, Ge d Zimme mann, Deu sche Telekom
Må en E icson, Ica o Leona do da Sil a, E icsson
Öme Bulakci, Alexand os Kaloxylos, Panagio is Spapis,
Huawei Technologies ERC
Ahmed M. Ib ahim, Yang Yang, In el
Shubh anshu Singh, ITRI
Ha is Celik, KTH
Jens Gebe , Pa ick Ma sch, A hul P asad, Fe nando
Sanchez Moya, Mikko Säily, Nokia Bell Labs
Milos Tesano ic, Da id Gu ie ez Es e ez, Meh dad
Sha ia , Samsung
En ico Bu achini, Robe o Fan ini, Alessand o T ogolo,
Telecom I alia
Jose F. Monse a , Uni e si a Poli ecnica de Valencia
Keywo ds: 5G, RAN design, equi emen s, CP/UP design, ai in e ace
landscape, ha moniza ion, spec um, CN/RAN in e ace,
unc ional design, ne wo k slicing
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Execu i e Summa y
This deli e able p o ides he consolida ed p elimina y iew o he METIS-II pa ne s on he 5 h
gene a ion (5G) adio access ne wo k (RAN) design a a mid-poin o he p ojec .
The o e all 5G RAN is en isaged o ope a e o e a wide ange o spec um bands comp ising
o he e ogeneous spec um usage scena ios. Mo e p ecisely, he 5G ai in e ace (AI) is
expec ed o be composed o mul iple so-called AI a ian s (AIVs), which include e ol ed legacy
echnology such as Long Te m E olu ion Ad anced (LTE-A) as well as no el AIVs, which may
be ailo ed o pa icula se ices o equency bands. The e is he common iew ha he e
should be a high deg ee o ha moniza ion among he di e en AIVs in oduced in 5G, o
ins ance enabling a la ge-scale euse o ne wo k unc ions and p ocessing blocks o he sake o
educed implemen a ion complexi y and a lean s anda ds speci ica ion.
The METIS-II pa ne s u he sha e he iew ha he e should be a logical spli be ween co e
ne wo k (CN) and RAN, allowing o an independen e olu ion o bo h domains, hough i is
expec ed ha he e will be some shi o unc ionali y om he CN o he RAN, o ins ance
ela ed o mobili y and paging. I is gene ally o eseen ha LTE-A e olu ion and no el AIVs
should be in eg a ed on RAN le el, o ins ance based on use plane agg ega ion on packe
da a con e gence p o ocol (PDCP) le el, enabling a as se up o no el adio links and as
swi ching among hese. Such RAN-le el in eg a ion sugges s o also ha e common CN
unc ions, and a common in e ace be ween CN and RAN o he di e en adio echnologies.
The e a e a ious conside a ions on how he p o ocol s ack unc ions could di e in 5G
compa ed o legacy echnology. Fo ins ance, unc ions could be ailo ed o speci ic
se ices, o ce ain unc ions may be u ned on o disabled o ce ain se ices, wi h a ious
examples p o ided in his documen . The e is he conside a ion o mo e hose unc ions o he
adio link con ol (RLC) laye which a e ypically ope a ed in a ime-synch onous manne o he
medium access con ol (MAC) laye , while keeping sepa a e logical channels. This way, he e is
a clea spli be ween asynch onous and synch onous unc ionali ies be ween he new RLC and
MAC, which could be a good unc ion spli poin o cen alized and dis ibu ed deploymen s.
Fu he , he e is he common iew ha ce ain ne wo k unc ions could ope a e on a as e
ime scale in 5G han in legacy sys ems. Fo ins ance, a ic s ee ing may no be pe o med
in he o m o hando e on adio esou ce con ol (RRC) le el be ween echnologies, as
be ween 3G and 4G, bu could be done in a much mo e agile way and on a as e ime scale
and on lowe laye s wi hin he RAN when applied among 5G AIVs.
Beyond gene al design aspec s, he deli e able lis s speci ic unc ional design conside a ions
de eloped in METIS-II, such as a no el RRC s a e and ela ed mobili y unc ions enabling
de ice-d i en mobili y o inac i e de ices ha does no in ol e CN / RAN signaling, and RAN-
based paging allowing he acking o de ices on cell-le el. Fu he , de ailed conside a ions on
he possible applica ion o agile esou ce managemen (RM) among 5G AIVs a e p o ided.
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Con en s
1 In oduc ion ......................................................................................................................... 9
1.1 Mo i a ion and Scope o his Deli e able ..................................................................... 9
1.2 S uc u e o his Deli e able ........................................................................................11
2 The METIS-II Vision on 5G ................................................................................................12
2.1 En isioned 5G Se ice Landscape .............................................................................12
2.2 Key Inno a ion Pilla s needed o 5G ..........................................................................13
3 Key 5G RAN Design Requi emen s ...................................................................................16
3.1 Design Requi emen s speci ically ela ed o di e se Se ices and Ne wo k Slicing .....17
3.2 Design Requi emen s speci ically ela ed o Ai In e ace In eg a ion in 5G .................18
4 Ai In e ace Landscape en isioned o 5G.........................................................................19
4.1 5G Spec um Scena ios, Requi emen s and Aspec s o Bands abo e 6 GHz ............19
4.1.1 Spec um Scena ios and Requi emen s o 5G ....................................................19
4.1.2 Ra ionale o 5G Bands abo e 6 GHz ..................................................................20
4.1.3 Co e age aspec s o bands abo e 6 GHz ...........................................................21
4.2 Ai In e ace Design Conside a ions ............................................................................22
4.2.1 5G AI E alua ion C i e ia and Design P inciples ..................................................22
4.2.2 O e all 5G AI P oposals unde In es iga ion ........................................................24
5 O e all Sys em A chi ec u e ...............................................................................................30
5.1 Co e Ne wo k ..............................................................................................................31
5.2 CN / RAN spli .............................................................................................................31
5.3 Ne wo k In e aces ......................................................................................................33
5.4 O e all Con ol / Use Plane A chi ec u e ....................................................................36
5.4.1 Possible Changes in P o ocol Func ions o he new AIVs w. . . LTE-A, and he
Usage o Common Speci ica ions ......................................................................................37
5.4.2 CP / UP A chi ec u e o he In e wo king o LTE-A e olu ion wi h no el AIVs......41
5.4.3 CP / UP A chi ec u e o he In e wo king o no el AIVs .......................................44
5.5 Physical A chi ec u e and Func ion Deploymen .........................................................44
5.5.1 Deploymen Scena ios Conside ed ......................................................................44
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5.5.2 Possible Func ion Spli s and ela ed In a-RAN In e aces ...................................46
5.5.3 Speci ic Mapping Conside a ions o Logical o Physical A chi ec u e in METIS-II 49
5.6 A chi ec u al Enable s o Ne wo k Slicing ..................................................................50
5.7 Ne wo k Managemen and O ches a ion ....................................................................54
6 Func ional Design Conside a ions ......................................................................................59
6.1 Gene al Conside a ions ..............................................................................................59
6.1.1 Se ice-Tailo ed Ne wo k Func ions in 5G ...........................................................59
6.1.2 Beam-cen ic Design ............................................................................................61
6.1.3 Lean and Fu u e-P oo Design .............................................................................62
6.1.4 Ene gy E icien Design and RAN Mode a ion in 5G ............................................64
6.1.5 Na i e Relaying, Sel -backhauling and D2D Suppo in 5G ..................................65
6.2 Func ions ela ed o Agile T a ic S ee ing and Resou ce Managemen ......................68
6.2.1 Mul i-AIV Resou ce Mapping ...............................................................................68
6.2.2 Resou ce Managemen o Ne wo k Slices ..........................................................72
6.2.3 RAN Enable s o In e e ence Managemen .......................................................74
6.2.4 No el UE Con ex Managemen in 5G .................................................................75
6.3 Func ions o Ini ial Access and Mobili y ......................................................................76
6.3.1 RACH Se ice P io i iza ion .................................................................................76
6.3.2 RRC S a e Managemen ......................................................................................77
6.3.3 RAN-based Paging ..............................................................................................79
6.3.4 Mobili y Managemen ...........................................................................................80
6.4 Summa y ....................................................................................................................81
7 Key RAN Design Ques ions Add essed .............................................................................85
8 Summa y and Ou look .......................................................................................................89
Re e ences ...............................................................................................................................90
A Appendix ............................................................................................................................93
A.1 Da a Ra e Requi emen s o di e en F on haul In e ace Op ions ...............................93

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Lis o Abb e ia ions and Ac onyms
3GPP
3 d Gene a ion Pa ne ship P ojec
4G
4 h Gene a ion o mobile ne wo ks
5G PPP
5 h Gene a ion Public-P i a e-
Pa ne ship
ACDC
Applica ion speci ic Conges ion
con ol o Da a Communica ion
AI
Ai In e ace
AIV
AI Va ian
AM
Acknowledged Mode
AMC
Adap i e Modula ion and Coding
API
Applica ion P og amming In e ace
ARQ
Au oma ic Repea Reques
AS
Access S a um
BLER
BLock E o -Ra e
BS
Base S a ion
BSS
Business Suppo Sys ems
C-RAN
Cen alized/Cloud-RAN
CAPEX
Capi al Expendi u e
CN
Co e Ne wo k
CoMP
Coo dina ed Mul iPoin
CP
Con ol Plane
CPRI
Common Public Radio In e ace
CQI
Channel Quali y Indica o
CSI
Channel S a e In o ma ion
CU
Cellula Use
D2D
De ice- o-De ice
DL
Downlink
DMRS
DeModula ion Re e ence Signal
DRX
Discon inuous Recep ion
E-
UTRAN
E ol ed-UTRAN
E2E
End- o-End
ECM
EPS Connec ion Managemen
eICIC
Enhanced ICIC
EM
Elemen Managing
EPC
E ol ed Packe Co e
EPS
E ol ed Packe Sys em
ETSI
Eu opean Telecommunica ions
S anda ds Ins i u e
FBMC
Fil e bank Mul i-Ca ie
FEC
Fo wa d E o Co ec ion
FFT
Fas Fou ie T ans o m
FQAM
F equency Shi Keying and
Quad a u e Ampli ude Modula ion
HARQ
Hyb id ARQ
HO
HandO e
HSDPA
High Speed Downlink Packe
Access
HW
Ha dWa e
GHz
Giga He z
I2I
Indoo o indoo
I/Q
In-phase/Quad a u e
ICIC
In e -Cell In e e ence Coo dina ion
IE
In o ma ion Elemen
IFFT
In e se FFT
IMS
IP Mul imedia Sub-sys em
IMT
In e na ional Mobile
Telecommunica ions
IMT-2020
IMT o yea 2020 and beyond
IoT
In e ne o Things
IP
In e ne P o ocol
ISG
Indus y Speci ica ion G oup
ITU
In e na ional Telecommunica ion
Union
ITU-R
ITU – Radiocommunica ion Sec o
KPI
Key Pe o mance Indica o
L2/L3
Laye 2 (MAC + RLC + PDCP) /
Laye 3 (RRC)
LAA
License Assis ed Access
LSA
Licensed Sha ed Access
LTE (-A)
Long Te m E olu ion (-Ad anced)
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LTE-M
Va ian o LTE o M2M
communica ions
MAC
Medium Access Con ol
MANO
Managemen and O ches a ion
MBB
Mobile B oadband
MBMS
Mul imedia B oadcas Mul icas
Sys em
MBSFN
Mul icas -B oadcas Single-
F equency Ne wo k
MC
Mul i Connec i i y
MIMO
Mul iple-Inpu Mul iple-Ou pu
mMTC
Massi e MTC
MTC
Machine-Type Communica ions
NAS
Non-Access S a um
NF
Ne wo k Func ion
NFV
Ne wo k Func ion Vi ualiza ion
NGMN
Nex Gene a ion Mobile Ne wo ks
NLoS
Non-Line-o -Sigh
O2I
Ou doo o indoo
O2O
Ou doo o ou doo
OAM
Ope a ions, Adminis a ion and
Main enance
OFDMA
O hogonal F equency Di ision
Mul iple Access
OPEX
Ope a ional Expendi u e
OSS
Ope a ions Suppo Sys em
PDCCH
Physical Downlink Con ol Channel
PDCP
Packe Da a Con e gence P o ocol
PDU
P o ocol Da a Uni
P-GW
Packe Ga eway
PHY
Physical laye
QoE
Quali y o Expe ience
QoS
Quali y o Se ice
RACH
Random Access CHannel
RAN
Radio Access Ne wo k
RAT
Radio Access Technology
RB
Resou ce Block
RF
Radio F equency
RLC
Radio Link Con ol
RLF
Radio Link Failu e
RM
Resou ce Managemen
RNC
Radio Ne wo k Con olle
RRC
Radio esou ce con ol
RRM
Radio RM
RRU
Remo e Radio Uni
RS
Re e ence Signal
S-GW
Se ing Ga eway
SAP
Se ice Access Poin
SDN
So wa e De ined Ne wo king
SDR
So wa e De ined Radio
SDU
Se ice Da a Uni
SINR
Signal- o-In e e ence and Noise
Ra io
SLA
Se ice Le el Ag eemen
SN
Sequence Numbe
SON
Sel O ganizing Ne wo ks
SRS
Sounding Re e ence Signals
SW
So Wa e
TB
T anspo Block
TeC
Technology Componen
TCP
T ansmission Con ol P o ocol
TDD
Time-Di ision Duplex
TTI
T ansmi Time In e al
UC
Use Case
UDN
Ul a-dense Ne wo k
UDP
Use Da ag am P o ocol
UE
Use Equipmen
UL
Uplink
UM
Unacknowledged Mode
uMTC
Ul a- eliable MTC
UMTS
Uni e sal Mobile
Telecommunica ions Sys em
UP
Use Plane
UTRAN
Uni e sal Te es ial RAN
V2X
Vehicle- o-Any hing
VNF
Vi ual Ne wo k Func ion
VoLTE
Voice o e LTE
WG
Wo king G oup
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WLAN
Wi eless Local A ea Ne wo k
WP
Wo k Package
WRC-15
Wo ld Radiocommunica ion
Con e ence in 2015
WRC-19
Wo ld Radiocommunica ion
Con e ence in 2019
xMBB
Ex eme Mobile B oadband
xHaul
Backhaul / Midhaul / F on haul
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1 In oduc ion
1.1 Mo i a ion and Scope o his Deli e able
The main objec i e o he METIS-II p ojec is o de elop an o e all 5G adio access ne wo k
(RAN) design acco ding o “ echnology le el 2”, and ob ain consensus among key playe s in he
ield on he key RAN design pa adigms he ein. To achie e his objec i e, METIS-II builds upon
echnology componen s (TeCs) ha ha e al eady been de eloped in ea lie p ojec s (e.g.
METIS [METIS] o 5G NOW [5GNOW]), o which a e being de eloped in METIS-II as such,
complemen s hese wi h any enable s ha a e equi ed, and de elops comp ehensi e o e all
unc ionali y amewo ks o he 5G RAN. This o e all p ocess, which is being pu sued in
indi idual wo k packages (WPs) in METIS-II as well as in he o e all RAN design, is depic ed in
Figu e 1-1.
Figu e 1-1. 5G RAN design p ocess pu sued in he di e en echnical WPs in METIS-II.
This deli e able cap u es he s a us o he METIS-II 5G RAN design a a mid-poin in he
p ojec . In pa icula , i highligh s he consensus ha has al eady been ound on key RAN
design ques ions ha we e posed a he beginning o he p ojec , and desc ibes he cu en iew
on he o e all 5G RAN a chi ec u e and i s unc ional design. I has o be no ed ha di e en
aspec s o he 5G RAN design ha e ob ained a di e en le el o ma u i y so a , as also
indica ed in Figu e 1-1. Fo some aspec s, in pa icula whe e a ich se o TeCs was al eady
a ailable be o e, he wo k has ocused on he in eg a ion o hese (as o ins ance he wo ks
ela ed o ai in e ace (AI) design, see Sec ion 4.2). In o he ields, howe e , he METIS-II ocus
has so a been on he de elopmen o addi ional and missing TeCs (as o ins ance aspec s
ela ed o he unc ional design o he 5G RAN, see Chap e 6).
I should u he be no ed ha his deli e able only p o ides a compac high-le el o e iew on
he METIS-II 5G RAN design, summa izing a ious o he deli e ables ha ha e ecen ly
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3 Key 5G RAN Design Requi emen s
Going beyond he a o emen ioned key inno a ion ields ha we e al eady lis ed be o e he
p ojec s a , METIS-II has du ing i s un ime iden i ied he ollowing gene al a chi ec u al o
unc ional equi emen s acco ding o which he 5G RAN should be designed in o de o mee he
di e se se ice equi emen s s a ed in Sec ion 2.1:
 The 5G RAN should be highly scalable in e ms o h oughpu , he numbe o de ices,
he numbe o connec ions e c. To enable his, i should be able o handle and scale
use plane (UP) and con ol plane (CP) independen ly. Fu he conside a ions on he
suppo o di e se se ice equi emen s a e lis ed in Sec ion 3.1.
 The 5G RAN should suppo he Ne wo k Slicing
1
ision om NGMN [NGM15-WP],
aiming o add ess he deploymen o mul iple logical ne wo ks as independen business
ope a ions on a common physical in as uc u e. The implica ion o Ne wo k Slicing on
he RAN design is a METIS-II esea ch opic by i sel and is also elabo a ed in mo e
de ail in Sec ion 3.1 and la e in Sec ion 5.6.
 One enable o he sys em o handle he di e se se ice equi emen s s a ed be o e is
ha he o e all ne wo k (bo h RAN and CN) should be so wa e-con igu able. This
means, o ins ance, ha i is con igu able which se s o logical and physical en i ies a e
o be a e sed by CP and UP packe s.
 The 5G RAN mus be designed o ope a e in a wide spec um ange wi h a di e se
ange o cha ac e is ics such as bandwid hs and p opaga ion condi ions, as discussed in
Sec ion 4.1. Fo highe equency bands such as mmWa e bands, beam o ming will
become essen ial, o ins ance in he o m o massi e mul iple inpu mul iple ou pu
(MIMO) echnology. The e o e, he RAN should suppo p ocedu es ha ely on
beam o ming in an e icien way.
 The 5G RAN should enable a igh in e wo king be ween LTE-A e olu ion and no el
5G adio echnology on RAN le el. I has o be no ed ha his does no imply any
pa icula ela ionship be ween LTE-A e olu ion and no el 5G adio, e.g. bo h
echnologies may o ins ance ac as mobili y ancho o he o he , o be ope a ed s and-
alone, as desc ibed in mo e de ail in Sec ion 5.4.
1
A “ne wo k slice” suppo s he communica ion se ice o a pa icula connec ion ype wi h a speci ic way
o handling he CP and UP o his se ice h oughou co e ne wo k (CN) and RAN, and is seen om a
cus ome pe spec i e as a sepa a ed logical ne wo k [NGM15-WP, MII16-WP].

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 The 5G RAN should na i ely and e icien ly suppo mul i-connec i i y, i.e. he case
when he UE is connec ed o mo e han one node (in e -node, i.e. no co-loca ed) and /
o mo e han one AI (which may be co-loca ed o no ). This is de ailed in Sec ion 5.4
 I should u he na i ely suppo ne wo k-con olled D2D (i.e. poin - o-poin , mul i-
cas and b oadcas ), and he op ion ha some 5G de ices could lexibly ac as i hey
we e in as uc u e nodes, one example being sel -backhauled, possibly nomadic
access nodes. See Sec ion 6.1.5 o de ails.
 The 5G RAN should be designed such ha i can maximally le e age om cen alized
p ocessing o adio laye s, bu also ope a e well in he case o dis ibu ed base
s a ions wi h impe ec backhaul / midhaul / on haul (xHaul) in as uc u e, wi h so
deg ada ion o pe o mance as a unc ion o xHaul quali y. Mo e p ecisely, METIS-II has
de ined ou physical a chi ec u e deploymen scena ios [MII15-R21], including also a
wi eless sel -backhauling scena io, which should all be suppo ed by any 5G RAN
design concep s. Please ind mo e de ails in Sec ion 5.5.
 The 5G RAN design mus be ene gy e icien . Fo he aim o assessing he ene gy
e iciency o he design, ene gy- ela ed KPIs ha e o be assessed ollowing adequa e
me hodologies. A desc ip ion o ene gy e iciency KPI and i s associa ed assessmen
me hodology a e gi en in [MII16-D21].
 The 5G RAN design mus be u u e p oo , i.e. i should enable an e icien in oduc ion
o new ea u es and se ices (e.g., by minimizing he sp eading o signals o e adio
esou ces and acili a ing he in oduc ion o new physical channels) and gua an ee
backwa d-compa ibili y o de ices in u u e eleases.
3.1 Design Requi emen s speci ically ela ed o
di e se Se ices and Ne wo k Slicing
Beside he a o emen ioned design equi emen s, he en isioned se s o se ices and hei
di e se and pa ially con lic ing equi emen s will likely pose he ollowing u he
equi emen s on he 5G RAN design:
 T a ic di e en ia ion: The RAN should suppo mo e sophis ica ed mechanisms o
a ic di e en ia ion han legacy sys ems in o de o be able o ea he e ogeneous
se ices di e en ly and ul ill mo e s ingen QoS equi emen s. Po en ial solu ions a e
desc ibed in Sec ion 6.2.
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 Resou ce euse: 5G ne wo ks should suppo a s ong euse o esou ces (e.g., adio,
unc ional, and in as uc u e esou ces; see he ex ended no ion o a esou ce in
[MET16-D51]) o enable an economically iable solu ion o eme ging 5G se ices.
An e icien join u iliza ion o in as uc u e esou ces by mul iple se ices and di e en ia ed
se ice ea men also p epa e he g ounds o Ne wo k Slicing in 5G. Beyond hese aspec s,
some addi ional equi emen s ha e been iden i ied ha a e speci ic o Ne wo k Slicing:
 Slice-awa e RAN: Slices (o some abs ac ion he eo , such as pa icula g oups o
lows o bea e s) should be isible o he RAN CP o enable a ea men ela ed o join
KPIs conce ning all se ices wi hin a slice o ac oss slices. Fo example, all se ices
wi hin one slice may join ly occupy only a ce ain ex en o some esou ces (e.g., adio
esou ces and unc ional esou ces, as s a ed abo e), while o he esou ces (e.g.,
ha dwa e, HW, and so wa e, SW, pla o ms) may be sha ed be ween slices.
 Slice p o ec ion: The RAN should suppo slice isola ion, e.g., by p o iding ela ed slice
p o ec ion mechanisms so ha e en s wi hin one slice, such as conges ion, do no ha e
a nega i e impac on ano he slice.
 Slice managemen and se up: The RAN should suppo e icien managemen
mechanisms, e.g., o e icien ly se up and ope a e slices.
 Slice-speci ic ne wo k managemen : The RAN should allow o e ing slice-speci ic
ne wo k managemen unc ions as a se ice.
3.2 Design Requi emen s speci ically ela ed o
Ai In e ace In eg a ion in 5G
Due o he need o he 5G RAN o suppo a ious se ices and equency bands, i is clea ha
he e canno be a one-size- i s-all AI in 5G, e.g. in he sense o a single PHY nume ology o
5G, o he exac ly same p o ocol s ack ins an ia ion o all se ices. Ins ead, he e is clea
consensus ha he o e all 5G AI will consis o mul iple di e en AI solu ions – in METIS-II
e med AIVs – ha will be in eg a ed wi h each o he and wi h e ol ed LTE-A, see Sec ion 4.2.
In his espec , u he 5G RAN design equi emen s ela ed speci ically o AIV in eg a ion a e:
 The 5G RAN should be designed in such a way ha a lean speci ica ion is possible,
i.e. ha a limi ed numbe o speci ica ion documen s is used o co e mul iple se ices o
mul iple equency bands, o ins ance by using pa ame e iza ion o allow ailo ing o
ce ain concep s, unc ionali ies e c. o di e en se ices o bands.
 The unc ionali ies ailo ed o di e en se ices, bands e c. should be ha monized
o he la ges ex en possible wi hou sac i icing he pe o mance o indi idual
se ices, bands e c., o enable maximum SW and HW euse on ne wo k and de ice side
and hence educed implemen a ion complexi y, and o enable use plane agg ega ion o
con ol plane in eg a ion among mul iple AIVs. See Sec ion 4.2 o de ails.
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4 Ai In e ace Landscape
en isioned o 5G
The o e all 5G RAN is en isaged o ope a e o e a wide ange o spec um bands comp ising o
he e ogeneous spec um usage scena ios, in o de o cope wi h he demand o highe
pe o mance and capaci y, bu also o p o ide highe eliabili y and lowe la ency. In his
chap e , we ini ially summa ize in Sec ion 4.1 he ou come o he spec um- ela ed wo k
conduc ed so a in METIS-II, and he ecommenda ions de i ed om ha , and hen en u e in
Sec ion 4.2 in o he de ailed AI design conside a ions in METIS-II.
4.1 5G Spec um Scena ios, Requi emen s and
Aspec s o Bands abo e 6 GHz
4.1.1 Spec um Scena ios and Requi emen s o 5G
Radio spec um usage can gene ally be au ho ized in wo ways: Indi idual Au ho iza ion
(Licensed) and Gene al Au ho iza ion (Licence Exemp / Unlicensed). Au ho iza ion modes
ecognized as ele an o wi eless communica ions a e P ima y use mode, LSA (Licensed
Sha ed Access) mode and Unlicensed mode [MET14-D53]. Fu he mo e, i e basic spec um
usage scena ios can be iden i ied o hese au ho iza ion modes: dedica ed licensed spec um,
limi ed spec um pool, mu ual en ing, e ical sha ing and unlicensed ho izon al sha ing [MII16-
D11]. The LAA (License Assis ed Access) app oach conside ed o LTE-A is a combina ion o
“dedica ed licensed spec um” and “unlicensed ho izon al sha ing” by using ca ie agg ega ion
[3GPP16-36889].
F equencies below 6 GHz a e likely mos sui able o suppo mMTC se ices whe e co e age is
mos impo an , whe eas spec um abo e 6 GHz is essen ial o p o ide he massi e capaci y
demanded by xMBB applica ions. An exclusi e use o spec um should emain he main and
p e e ed solu ion, while a sha ed use o spec um may be a complemen o inc ease spec um
a ailabili y [MII16-WP]. The equi emen s o he METIS-II 5G use cases (see Sec ion 2.1)
conce ning spec um can be b oadly ca ego ized in o h ee main g oups [MII16-D31]:
 Capaci y o cope wi h high a ic pe a ea: his can be add essed h ough highe
spec al e iciency, highe si e densi y, bu mos impo an ly in his con ex by a la ge
amoun o p e e ably con iguous spec um.
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 Co e age o ensu e he a ailabili y o 5G e e ywhe e: his could pa ially be
add essed h ough, e.g., massi e deploymen s and massi e MIMO, bu he mos
e icien app oach is o use lowe equency bands.
 Reliabili y o ul il he demands o c i ical se ices, equi ing s able and p edic able
ope a ion condi ions: his can o ins ance be inc eased h ough di e si y in ime,
equency and space (e.g. h ough mul i-connec i i y), and is g ea ly acili a ed by
ha ing dedica ed spec um.
Figu e 4-1: Rela ion be ween METIS-II 5G use cases
and he h ee spec um equi emen ca ego ies.
The ela ionship be ween he METIS-II 5G use cases and he h ee ca ego ies de ined abo e is
illus a ed in Figu e 4-1. I is ob ious ha a combina ion o di e en sui able equency bands is
necessa y o cope wi h he use case equi emen s.
4.1.2 Ra ionale o 5G Bands abo e 6 GHz
In [MII15-R31], i is demons a ed ha he h ee basic means o inc ease wi eless ne wo k
capaci y, namely access poin densi y, spec um e iciency and spec um bandwid h, a e
exchangeable o some ex en in con en ional mac o-cell en i onmen s. Howe e , densi ica ion
o access poin s becomes p og essi ely ine icien in supe -dense en i onmen s, so ha
addi ional spec um becomes he mos e ec i e solu ion o p o iding high capaci y in such
cases. In [MII15-R31] i is also shown ha con iguous spec um o e s ad an ages o e mul iple
agmen ed equency bands wi h ega d o de ice complexi y, signaling o e head, gua d bands
and in e e ence. The e o e, addi ional wide con iguous equency bands a e needed o ul ill 5G
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capaci y equi emen s. WRC-15 has ag eed ha ITU-R will conduc sha ing and compa ibili y
s udies o a numbe o equency bands be ween 24.25 GHz and 86 GHz (see Figu e 4-2) in
ime o WRC-19. Some o hese equency bands enable wide con iguous bandwid hs, which
would allow coping wi h he equi emen s o high bandwid h demanding applica ions.
Figu e 4-2: F equency bands o be s udied in ITU-R o IMT-2020 un il WRC-19.
4.1.3 Co e age aspec s o bands abo e 6 GHz
Assessmen esul s o a 5G sys em pe o mance e alua ion – based on a simple link budge
calcula ion o equencies up o 100 GHz – indica e ha he highe p opaga ion losses wi h
inc easing ca ie equencies migh be compensa ed o some ex en p o ided ha la ge
channel bandwid hs a e a ailable han o lowe ca ie equencies, o by implemen a ion o
ad anced an enna sys ems. Ne e heless, o he ou doo o indoo (O2I) scena io, he mo e
challenging adio p opaga ion condi ions impose mo e es ic ions o he cell size. Depending
on p opaga ion condi ions and equipmen deployed, equencies up o a ound 30 GHz a e in
pa icula sui able since all h ee conside ed s a iona y scena ios, i.e., O2I, non-ligh o sigh
(NLoS) ou doo o ou doo (O2O), and indoo o indoo (I2I), a e easible. Wi h ca ie
equencies in he ange o 30-60 GHz, he O2O and I2I scena ios appea o be easible wi h he
conside ed dis ance assump ions i ad anced beam o ming echnologies wi h high an enna gain
a e applied. Wi h ca ie equencies abo e 60 GHz, dedica ed indoo se ices could s ill be
easible, no ing ha a hose equencies he e is also he possibili y o ob aining e y la ge
con iguous channel bandwid hs [MII16-D31]. The co e age easibili y o e equency anges o
di e en deploymen scena ios is illus a ed in Figu e 4-3.
Figu e 4-3. Indica i e co e age easibili y o di e en deploymen scena ios
in di e en equency anges.
I2I
NLoS s a iona y O2O
O2I
100GHz
30GHz 60GHz
Feasible scena ios

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4.2 Ai In e ace Design Conside a ions
METIS-II conside s he o e all 5G AI
2
o be comp ised o mul iple so-called AIVs
3
, which may
o ins ance be cha ac e ized by ailo ed nume ology and/o ea u es o ce ain equency
anges (see p e ious sec ion), se ices, o cell ypes e c.
Mo e p ecisely, METIS-II en isions ha beside he e olu ion o LTE-A, no el AIVs a e needed
o ul ill all he pe o mance equi emen s o he en isioned new use cases. These include some
ex eme low la ency use cases, ul a- eliable ansmission and xMBB equi ing addi ional
capaci y ha is only a ailable a e y high equencies, as well as mMTC wi h ex emely densely
dis ibu ed senso s and e y long ba e y li e equi emen s. Designing an adap able and lexible
5G AI, which will ackle hese use cases while o e ing na i e mul i-se ice suppo , is one o he
key challenges in designing a 5G RAN, wi h a - eaching impac on o e all sys em design.
Fu he , a key ques ion is how he di e en AIVs, including LTE-A e olu ion, can be in eg a ed
in o one o e all 5G AI, such ha his design maximally bene i s om he wide landscape o
bands, cell ypes e c., and such ha bo h he complexi y o he s anda d and ha o he
implemen a ion a e minimized, while he pe o mance o indi idual echnologies is no
sac i iced. To his end, METIS-II has d awn up an e alua ion amewo k o 5G AI candida es,
wi h one key ocus on he ex en o ha moniza ion ac oss unde pinning componen s in o e all AI
conside a ions. The ex en o ha moniza ion can be assessed h ough a se o c i e ia such as
he u iliza ion o adio esou ces, implemen a ion complexi y, s anda diza ion e o , o wa d
compa ibili y, and in e ac ion wi h legacy sys ems [MII16-D41]. Addi ional e alua ion c i e ia
include UP- ela ed design p inciples and equi emen s posed om CP conside a ions. The
combined e alua ion c i e ia esul om wide consensus eached wi hin METIS-II and a e well-
aligned wi h 3GPP while o e ing a long- e m, in eg a ed sys em iew.
De ails on he METIS-II AI design conside a ions a e p o ided in [MII16-D41]. In his sec ion, we
b ie ly summa ize he key design p inciples ha ha e been ollowed, and he di e en p oposals
o he o e all 5G AI ha a e cu en ly being in es iga ed.
4.2.1 5G AI E alua ion C i e ia and Design P inciples
The METIS-II AI candida e selec ion is pe o med acco ding o AI e alua ion c i e ia classi ied
in o he ollowing ou ca ego ies:
2
An AI is he e de ined as he RAN p o ocol s ack (i.e. PHY / MAC / RLC / PDCP / RRC o 5G equi alen s, o subse he eo ) and all
ela ed unc ionali ies desc ibing he in e ac ion be ween in as uc u e and de ice and co e ing all se ices, bands, cell ypes
e c. ha a e expec ed o cha ac e ize he o e all 5G sys em.
3
An AIV is de ined in he same way as an ai in e ace, bu co e s only a subse o se ices, bands, cell ypes expec ed o
cha ac e ize he o e all sys em.
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 The sui abili y o an AI p oposal o mee he o e all 5G KPIs and di ec ly ela ed UP
design equi emen s;
 Addi ional UP- ela ed AI design p inciples, which a e de ailed below;
 Requi emen s posed om CP conside a ions on he design o AIs;
 The ex en o ha moniza ion ac oss AIVs in o e all AI conside a ions.
The abo e-men ioned UP- ela ed AI design p inciples ha e been de i ed om he gene al
a chi ec u al and unc ional equi emen s s a ed in Chap e 3. These ensu e he equi ed
lexibili y in achie ing 5G KPIs which LTE-A and i s e olu ion canno ul il in hei en i e y, and
a e he e desc ibed in mo e de ail:
 Flexibili y by design: 5G AI needs o be adap able and lexible in o de o p o ide he
equi ed lexibili y o mul i-se ice suppo and non- adi ional applica ions. A single bu
su icien ly wide ha monized AI would allow his lexibili y. Mo e speci ically, he ex en o
ha moniza ion al eady men ioned is an impo an METIS-II 5G AI design KPI o achie e
his lexibili y by design.
 5G AI should be o wa d-compa ible: This is needed o ensu e u u e-p oo ness o
upcoming a ian s o exis ing 5G se ices as well as po en ial new se ices no
necessa ily in he xMBB, uMTC o mMTC ca ego ies. Such a u u e-p oo design needs
o allow he in oduc ion o new physical channels.
 5G AI should o e easy in e wo king wi h e olu ion o LTE-A: I is assumed in METIS-II
ha he 5G RAN should allow o in eg a e LTE-A e olu ion and no el 5G AIVs.
The exac mechanics o his in e wo king a e unde s udy in METIS-II.
 The design o he 5G AI should minimize signaling o e head and unnecessa y
ansmissions.
 The 5G AI design should ake in o accoun he la es in o ma ion on bands a ailable (o
o be made a ailable sho ly) o mobile: 5G sys ems will ope a e ac oss a wide ange o
mmWa e and cmWa e equencies. The 5G AI design should, he e o e, conside a
beam-cen ic app oach, i.e., con ol and use plane signaling should be designed ha ing
in mind ha hese will o en be ansmi ed in beams.
 The 5G AI design should ake in o accoun e minal complexi y. The ex en o
ha moniza ion again plays an impo an ole he e, since he implemen a ion o one
widely ha monized AI is expec ed o dec ease e minal complexi y compa ed o he
implemen a ion o i s AI componen s in a non-ha monized way.
 5G AI design should enable Applica ion P og am In e aces (APIs) o highe laye s, on
bo h de ice and ne wo k sides, so as o acili a e he implemen a ion o ne wo k slicing.
Beyond ha moniza ion, METIS-II in es iga es o which ex en UP ins ances ela ed o di e en
bands can be logically agg ega ed on ce ain laye s, and beyond which laye he e would be a
single CP ins ance. Di e en AI designs may o e di e en suppo o such agg ega ion and
in eg a ion ea u es, which also needs o be conside ed.
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4.2.2 O e all 5G AI P oposals unde In es iga ion
A single AI amewo k is he main goal o METIS-II, bu his does no mean a “one-size- i s-all”
solu ion. Di e en use cases will likely need some le el o di e en ia ion in he AI. How o
achie e his di e en ia ion is ano he key ques ion. Addi ionally, cu en p oposals o o e all AI
landscapes di e in he echnology componen s hey a e comp ised o , and in he ype and hei
inhe en ex en o ha moniza ion. As each METIS-II p oposal cu en ly unde s udy is a single
amewo k comp ised o mul iple AIVs selec ed o ul ill he pe o mance o he di e en use
cases and scena ios, a uni ied way o desc ibing he 5G AI design p oposals using a 5G se ice
/ equency mapping is used, as depic ed in Figu e 4-4. In his abs ac example, i is shown how
he o e all space o main se ice ypes and equency bands may possibly be co e ed by one
(le side o he igu e) o mul iple ( igh side o he igu e) wa e o m amilies. Fo he mo e
de ailed o e all AI conside a ions lis ed in he sequel, he same kind o mapping will be used o
illus a e how di e en AIVs a e join ly en isioned o co e he o e all se ice and band space.
Figu e 4-4. Desc ip ion o 5G AI p oposals h ough se ice / equency mapping.
Exis ing 5G AI p oposals di e in he echnology componen s hey a e comp ised o , and in he
unde lying ype and ex en o ha moniza ion. The ollowing a e he di e en AI p oposals unde
s udy in METIS-II:
1. A ha monized laye 1-3 solu ion based on cyclic p e ix o hogonal equency di ision
mul iplex (OFDM) o sub-1 GHz o 100 GHz ca ie : scalable Cyclic P e ix-OFDM based
solu ion wi h a ha monized physical laye (PHY) / medium access con ol (MAC) / packe
da a con e gence p o ocol (PDCP) and con en ion-based access suppo .
2. Ha monized Cyclic P e ix-OFDM o mul iple bands wi h enhancemen s o mul i-se ice
suppo : Cyclic P e ix-OFDM based solu ion wi h scaling/ lexible nume ology, u ilizing
ad anced single-ca ie (SC) equency di ision mul iple access (FDMA) and allowing
lexible ime di ision duplex (TDD).
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3. Mul i-se ice suppo wi h uni e sal il e ed (UF) OFDM: elies on inc eased wa e o m (WF)
con igu abili y and econ igu a ion (wi h possible use o cyclic p e ix and ze o pos ix) and
p o ides s ong equency and ime con inemen .
4. A quali a i e, ea u e-d i en AIV design o he 5G landscape: ailo ing AIVs o speci ic
se ice ypes and ha monizing hem s a ing a he PHY laye .
5. AI design based on pulse-shaped OFDM (P-OFDM): gi es lexible nume ology and ame
s uc u e, uses adap i e pulse shape il e , suppo s asynch onous mul iple access and
esul s in imp o ed esilience agains Dopple .
6. Quad a u e ampli ude modula ion (QAM) – il e -bank mul i-ca ie (FBMC) and OFDM
ha monized solu ion: mul i-WF solu ion (QAM-FBMC o lowe equencies and Cyclic P e ix
-OFDM o highe equencies), suppo o asynch onous scena ios in lowe bands,
beam o ming solu ions o highe bands.
7. OFDM based solu ion wi h lexible nume ology and ame s uc u e: OFDM-based solu ion
wi h lexible ame s uc u e, suppo ing equency keying and quad a u e ampli ude
modula ion (FQAM) in lowe bands o enhanced cell-edge pe o mance, beam o ming
solu ions o highe bands.
8. Mul i-AIV (o se quad a u e ampli ude modula ion (OQAM)-FBMC, Cyclic P e ix-OFDM)
ha moniza ion aspec s o abo e PHY laye : Cyclic P e ix-OFDM used ac oss he en i e
ange o equencies wi h scalable nume ology and adap i e beam o ming in highe
equencies, OQAM-FBMC suppo ed a lowe equencies.
9. Adap i e Fil e ed OFDM wi h Regula Resou ce G id: OFDM-based wi h lexible nume ology
and a egula esou ce g id, ocus on massi e MIMO and beam o ming suppo , as well as
asynch onous mul iple access.
10. Ha moniza ion aspec s o D2D communica ions: ocus on WFs and co esponding
nume ologies ha a e obus o some lack o synch onism (UF-OFDM and OQAM-FBMC).
To demons a e he challenge o ha monizing ea u es o di e en AIVs and in eg a ing hem
in o an o e all AI, wo o he abo e solu ions (which ake di e en app oaches o AI design) and
he ele an equency/se ice mappings a e desc ibed he e in mo e de ail. Fo ull de ails o
hese and all o he p oposals he eade is e e ed o [MII16-D41].
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 Allow o an independen e olu ion o RAN and CN unc ionali y in o de o speed up
in oduc ion o new echnology;
 Enables o make he CN unc ions o a subse o hem independen o he access (e.g.
common UP p ocessing);
 Facili a es mobili y since some CN unc ions (CP and / o UP) can be kep (ancho ed)
when UEs mo e o ano he RAN node;
 Allows c oss-laye op imiza ions in some deploymen s when he unc ions a e co-
deployed, i.e. loca ed in he same physical en i y;
 A logical sepa a ion also acili a es mul i- endo CN / RAN in e ope abili y.
The METIS-II baseline o he unc ional spli be ween he RAN and CN is he same as in he
EPS. Howe e , al e na i e CN / RAN spli s and/o c oss laye op imiza ions a e cu en ly being
s udied. To gi e one example, METIS-II is cu en ly in es iga ing he design o RAN-based
paging solu ions o add ess densi ied deploymen s and a connec ed inac i e s a e op imized o
inac i i y pe iods be ween small packe ansmissions, along de ice mobili y wi hou in ol ing
CN / RAN signaling. Bo h app oaches hence imply a shi o unc ionali y om CN o RAN. Mo e
de ails can be ound in Sec ions 6.3.3 and 6.3.2, espec i ely. The highligh ed assump ions a e
also endo sed in he ecen ly app o ed SA2 s udy i em abou he 5G a chi ec u e en i led “S2-
153651 S udy on A chi ec u e o Nex Gene a ion Sys em” [3GPP15-153651].
I should be emphasized ha he conside ed CN / RAN spli is a logical spli and is mainly a
s anda diza ion p ac icali y o enable a mul i- endo ecosys em whe e one endo can p o ide
he CN, and ano he endo he RAN, wi h bo h sub-sys ems ope a ing well wi h each o he .
This does no o bid a all any so o sma implemen a ion on he ne wo k side i a single
manu ac u e builds bo h CN and RAN domains in he same ne wo k. Fo ins ance, a
manu ac u e may design bo h CN and RAN unc ions as a single solu ion, collapse hese, spli
hese in o CP and UP, co-loca e hese e c. o join op imiza ion, as illus a ed in Figu e 5-2.
Figu e 5-2. Possible lexible deploymen and co-op imiza ion o CN and RAN unc ions.

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5.3 Ne wo k In e aces
METIS-II p oposes an in eg a ion o no el AIVs and he e olu ion o LTE ha goes beyond he
exis ing in e wo king be ween access echnologies, ul illing he ision o wha NGMN calls a
“5G RAT amily”. Tha should enable a high pe o ming mul i-RAT mobili y be ween he new
AIVs and LTE-A e olu ion and a leas UP agg ega ion inspi ed in he Dual Connec i i y
solu ion. Conside ing hese equi emen s and he p e ious assump ion ha di e en accesses
could bene i om common 5G CN unc ions, i seems easonable o assume a common CN /
RAN in e ace o he new AIVs and he LTE-A e olu ion. METIS-II acknowledges ha his CN /
RAN in e ace, deno ed he ein S1*, will ha e a subs an ial amoun o no el ea u es designed o
add ess he new u u e demands o he 5G a chi ec u e. Fo ins ance, i is en isioned ha his
will equi e he suppo o :
 E2E Ne wo k Slicing (whe e each slice may ha e i s own se o CN unc ions);
 New 5G se ices wi h di e ging equi emen s (e.g. wi h se ice-op imized CN unc ions);
 Enhanced mul i-RAT in eg a ion wi h common CN unc ions whe e some could be
designed o be independen o he access;
 Po en ially new UP / CP spli s in he 5G CN (designed o ollow an SDN / NFV-na i e
a chi ec u e, see Sec ion 5.7);
 New connec ed s a e, op imized o ba e y sa ings bu enabling as ansi ion o ac i e.
A common CN/RAN in e ace has many bene i s, such as:
 I makes i possible o e y quickly es ablish dual connec i i y o a UE i s connec ed o
a single RAT since he e is no need o pe o m any ex a CN/RAN signaling o non-
access s a um (NAS) signaling when adding he second RAT
 I makes i possible o ha e a common e olu ion o LTE and no el AIVs whe e new CN
ea u es will bene i bo h RATs a he same ime a oiding sepa a e speci ica ion wo k.
 I simpli ies he UE implemen a ion since a single NAS laye is needed o bo h LTE and
no el AIVs, hence a oiding a dual p o ocol s ack a he UE.
 I simpli ies he RAN / CN in e ac ion since a single CP connec ion is used. This gi es
clea ad an ages when handling:
o Mobili y: a single hando e p ocedu e will be able o mo e he connec ions a UE
has wi h each ac i e adio accesses;
o S a e ansi ions: Only a single EPS Connec ion Managemen (ECM) s a e
needs o be kep . UE, RAN and CN beha io due o such single s a e a e g ea ly
simpli ied and he isk o losing s a e synch oniza ion is educed.
 O he signaling: a single CP connec ion a oids possible ace condi ions and e o cases
occu ing i signaling is un o e wo independen connec ions.
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To acili a e his en isioned in eg a ion o LTE-A wi h no el 5G AIVs, METIS-II assumes ha his
new in e ace will ha e he S1 in e ace [3GPP15-36300] as baseline. A main challenge needing
u he in es iga ion is how o align he CN / RAN signaling e olu ion o LTE-A and no el AIVs.
Wi hin he RAN, METIS-II ini ially en isions a new logical in e -node RAN in e ace, deno ed
he ein X2*, designed o add ess possibly new ea u es (see Chap e 6) such as:
 In a-RAN mobili y, also co e ing mobili y be ween LTE-A e olu ion and no el AIVs;
 Mul i-connec i i y in non-colloca ed deploymen s o nodes om he same o di e en
AIVs (e.g. no el cmWa e and mmWa e AIVs o LTE-A e olu ion);
 Suppo o RAN-based paging, whe e a acking a ea may encompass mul iple AIVs;
 Suppo o unc ions ela ed o s a e ansi ions om Inac i e o Connec ed such as
con ex e ching;
 Suppo o no el in e e ence managemen schemes;
 Suppo o RAN mode a ion o inc ease o e all ne wo k ene gy e iciency.
Ano he aspec ha needs o be aken in o accoun is he ac ha in addi ion o dis ibu ed
deploymen s i should p ope ly also suppo cen alized ones, i.e., a cen alized con ol o
mul iple synch onous unc ions ( adio link con ol, RLC / medium access con ol, MAC / physical
laye , PHY) by cen alized asynch onous unc ions (packe da a con e gence p o ocol, PDPC
and / o adio esou ce con ol, RRC) ha could be possibly implemen ed in a cen alized cloud.
To acili a e he en isioned mul i-RAT in eg a ion wi h LTE-A e olu ion, METIS-II assumes ha
his new in e ace will ha e X2 [3GPP15-36300] as i s baseline. De ails abou he new in e aces
a e s ill being esea ched in METIS-II. The cu en wo king assump ion on he logical 5G RAN
a chi ec u e is cap u ed in Figu e 5-3.
Figu e 5-3. Cu en wo king assump ion o he logical RAN a chi ec u e.
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Conside a ions on RAN in e nal in e aces
Du ing he ea ly s anda diza ion phase o LTE, he e was a clea equi emen om ope a o s
ha LTE should ha e a la all-IP a chi ec u e. The backg ound o his was ha ope a o s we e
no sa is ied wi h he Uni e sal Mobile Telecommunica ions Sys em (UMTS) a chi ec u e
spli ing RAN le el unc ionali y be ween he RNC and NodeB. Issues wi h he adio ne wo k
con olle (RNC) included hings such as spli o owne ship o esou ces be ween NodeB and
RNC and RLC e mina ion poin in he RNC, pu ing s ic equi emen on low con ol be ween
he NodeB and RNC. Fu he mo e, he UMTS a chi ec u e equi ed subs an ial changes du ing
he s anda diza ion o High Speed Downlink Packe Access (HSDPA), whe e some unc ionali y
o iginally in oduced in he RNC was mo ed o he NodeB (such as MAC scheduling).
The ou come o he esea ch done a ha ime was an LTE a chi ec u e comp ised o a single
logical RAN node (eNB) which e mina es he S1 and X2 in e aces. Ne e heless i has been
shown ha he LTE a chi ec u e does allow o a high le el o a chi ec u e lexibili y, e.g.
owa ds cen alized baseband pooling, e.g., acili a ing coo dina ed mul ipoin (CoMP) solu ions
ac oss se e al ansmission poin s. I is also possible in he implemen a ion o example o
u he cen alize and i ualize highe laye s o he adio access p o ocol s ack i ha is ound o
be bene icial.
I is also wo h no ing ha a lo o new ea u es (e.g., Mul imedia B oadcas Mul icas Sys em
(MBMS), home eNB, sel o ganizing ne wo ks (SON) enhancemen s, IP mul imedia sub-sys em
oice o e LTE (IMS VoLTE), Imp o ed Access Con ol, Mobili y enhancemen , ca ie
agg ega ion, dual connec i i y, machine- ype communica ions (MTC) enhancemen , Wi eless
Local A ea Ne wo k (WLAN) in eg a ion, Relays, P oximi y based se ices, D2D
communica ions, Posi ioning, MIMO enhancemen , use equipmen (UE) speci ic demodula ion
e e ence signal (DMRS), CoMP, enhanced in e -cell in e e ence coo dina ion (eICIC), Ne wo k
sha ing, e c.) ha e been added o LTE since Rel-8 wi hou equi ing any undamen al changes
o he RAN in e nal a chi ec u e as speci ied in 3GPP. This la RAN a chi ec u e has he e o e
accele a ed he s anda diza ion o he abo e-men ioned unc ionali y. Mo e impo an ly, i also
simpli ied he implemen a ion and in pa icula he in e -ope abili y- es ing.
I E ol ed-Uni e sal Te es ial RAN (E-UTRAN) would ha e been spli in o se e al RAN
in e nal nodes (as o me ly done in UTRAN), he in e aces and he unc ional spli be ween
hese nodes would ha e also been impac ed leading o he ollowing p oblems:
 Delayed s anda diza ion o new adio ea u es since also in e nal in e aces would ha e
needed o be s anda dized;
 Delayed and mo e complex implemen a ion and es ing o he new ea u es;
 A isk ha ea ly decisions o he unc ional spli be ween he in e nal nodes would ha e
been sub-op imal o la e ea u es in oduced in LTE which ei he would ha e mean
ha sub-op imal solu ions would ha e had o be adop ed, o a majo edesign would
ha e been needed;
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 Di e en endo ’s implemen a ions could ha e made i di icul o ag ee on he p e e ed
spli , po en ially leading o sub-op imal solu ions being adop ed in he s anda d. Such
subop imal solu ions could ha e esul ed in lack o in e endo in e ope abili y and
highe in eg a ion cos s.
The UMTS a chi ec u e on he o he hand has a emp ed o speci y a p o ocol spli by
s anda dising he Iub in e ace be ween NodeB and RNC. This has p o en o be a he
ine icien , some o he issues being as ollows:
 One o he unc ions o he Iub in e ace is o allow Radio RM (RRM) om he RNC o
he NodeB. RRM is made o p op ie a y algo i hms in ol ing p ocesses sha ed by he
RNC and NodeB. I is ex emely di icul o ha e an e icien ly wo king Iub in e ace in a
mul i- endo RNC-NB deploymen because o he ailo ed endo speci ic p ocesses
each node would suppo , and ha canno be suppo ed by a s anda dized in e ace;
 The p ocesses un o e he Iub can be e y delay-sensi i e, examples can be
scheduling coo dina ion, UL/DL powe con ol e c. In si ua ions whe e he RNC-NB
connec ion is no su icien ly pe o ming i is e y di icul o make he Iub ope a e in an
e icien way. In such scena ios a di e en RAN a chi ec u e spli would ha e been mo e
sui able.
The issues abo e ela ed o he UMTS echnologies e ealed o be di icul o sol e, which is
why he wo k on a la LTE a chi ec u e was igge ed and why his choice has been made. In
he 5G e a, i is impo an o ha e his his o y o a chi ec u e app oaches in mind when deciding
on no el RAN-in e nal in e aces.
5.4 O e all Con ol / Use Plane A chi ec u e
This sec ion is spli in o wo pa s: Sec ion 5.4.1 in es iga es o which ex en p o ocol unc ions
in he new AIVs would need o di e om he cu en ones in LTE-A ( aking Release-13 as a
e e ence) o mee he equi emen s in 5G. I also elabo a es on he ques ion o which ex en
one would likely ha e di e en speci ica ions o LTE-A e olu ion and he no el AIVs. Sec ions
5.4.2 and hen en u e in o he o e all con ol / use plane a chi ec u e as such, o he case o
he LTE-A e olu ion in eg a ion wi h no el AIVs, o he in eg a ion o no el AIVs among each
o he , espec i ely.
Be o e s a ing, i may be aluable o say a ew wo ds abou he de ini ion o “use plane” and
“con ol plane” as such: The unc ions o p o ocols designed o ca y end-use da a (such as IP
packe s) a e ypically called UP unc ions, while unc ions ela ed o con ol a e called CP
unc ions. In his espec , he RRC, esponsible o unc ions such as mobili y con ol,
connec ion con ol and sys em in o ma ion ansmission / acquisi ion, is a clea CP unc ionali y.
The PDCP, howe e , is p edominan ly used o comp ession and decomp ession o IP da a
lows, ans e o da a, secu i y, and main enance o PDCP sequence numbe s e c., hence
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aspec s ela ed o UP p ocessing, while a he same ime also being used o con ey RRC-
ela ed in o ma ion om and o he lowe laye s. The same applies o he MAC and physical
PHY, which a e ele an o bo h CP and UP. Fo his eason, he CP p o ocol s ack o he RAN
is ypically d awn om PHY up o RRC, and he UP p o ocol s ack om PHY up o PDCP.
5.4.1 Possible Changes in P o ocol Func ions o he new AIVs
w. . . LTE-A, and he Usage o Common Speci ica ions
A key ques ion in METIS-II is o which ex en p o ocol unc ions o he new AIVs may ha e o be
subs an ially modi ied o mee he 5G equi emen s. In his subsec ion, we will hence explo e
he di e en p o ocol s ack laye s, lis hei cu en unc ions as in LTE-A, and elabo a e on any
po en ial changes in 5G. F om his, we can also de i e he no ion o whe he LTE-A and new
AIVs should use common speci ica ions in he u u e.
Radio Resou ce Con ol (RRC)
In LTE-A, he RRC unc ions a e esponsible o he b oadcas o sys em in o ma ion o NAS
and access s a um (AS), paging, connec ion handling, alloca ion o empo a y iden i ie s,
con igu a ion o lowe laye p o ocols, quali y o se ice managemen unc ions, secu i y
handling a he access ne wo k, mobili y managemen , and measu emen epo ing and
con igu a ion, e c.
New enhancemen s a e expec ed o be pa o he LTE-A e olu ion, such as he ligh weigh
connec ion Wo k I em based on he Suspend/Resume p ocedu e and possibly some paging
enhancemen s [3GPP15-23720]. Howe e i is no clea whe he ha will lead o RRC changes
o no o he LTE-A e olu ion.
Fo he new AIVs, i is expec ed ha he ole o he RRC p o ocol will in gene al s ay he same
and mos o he p e iously men ioned unc ions would s ill be necessa y. Ha ing he same ole,
howe e , does no necessa ily mean he same exac design. One po en ial change compa ed o
LTE-A RRC would be he need o suppo beam-based measu emen s and epo ing
mechanisms (o he le els migh exis as in LTE-A e.g. based on PHY laye and channel s a e
in o ma ion- e e ence signal, CSI-RS), see Sec ion 6.1.2. In addi ion, he design o new ways
o dis ibu e and encode sys em in o ma ion is also being conside ed, as elabo a ed in mo e
de ail in Sec ion 6.1.3. Ano he conside ed change is he in oduc ion o a new RRC s a e (see
Sec ion 6.3.1), bu since he ligh weigh connec ion WI [3GPP15-23720] is s ill ongoing, one
canno eally say how dis up i e his will be compa ed o LTE-A e olu ion. Ano he change is
he suppo o igh in e wo king be ween LTE and he new AIVs, including mobili y o
ac i e/inac i e UEs and UP agg ega ion (mo e de ails in Sec ion 5.4.2). Since LTE-A e olu ion
and he new AIVs should be possibly suppo ed as ancho s, an RRC ins ance needs o allow

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he es ablishmen o a seconda y link o ano he AIV and ice e sa o UEs ha ing one o he
new AIVs as ancho .
All hese po en ial design changes seem o jus i y he de ini ion o a new RRC speci ica ion o
he new AIVs, al hough hey migh use he LTE-A RRC speci ica ions as i s baseline. Howe e ,
due o he igh in e wo king be ween LTE and he new AIVs, i is e y likely ha a leas some
le el o in e ac ion be ween he speci ica ions will be necessa y, which is o be u he
esea ched.
Packe Da a Con e gence P o ocol (PDCP)
In LTE-A, PDCP is esponsible o comp ession and decomp ession, ans e o UP and CP
da a, secu i y (i.e. enc yp ion), main enance o sequence numbe s e c. An o e iew on all
PDCP unc ions and possible changes in 5G is p o ided in Table 5-1.
Table 5-1. PDCP unc ionali ies in LTE-A and possible changes in 5G.
Func ionali y in LTE-A (Release 13)
Conside a ions o no el AIVs in 5G
Comp ession and decomp ession o
ansmission con ol p o ocol /use da ag am
p o ocol/IP (TCP/UDP/IP) heade s, which is
essen ial o small payloads whe e he ela i e
heade o e head is la ge.
Fo no el AIVs, comp ession and
decomp ession may be ailo ed o di e en
se ices. Fo ins ance, heade comp ession
may be omi ed i he payload is ai ly la ge
and/o la ency is c ucial (e.g. some xMBB o
uMTC applica ions), while being mo e
p onounced in he con ex o mMTC.
Secu i y unc ions, e.g. ciphe ing and
deciphe ing o UP and CP da a. In eg i y
p o ec ion and in eg i y e i ica ion o CP da a.
Fo elay nodes, in eg i y p o ec ion and
in eg i y e i ica ion o UP da a.
No changes o eseen. PDCP is s ill seen as
he mos sui able laye o ciphe ing /
deciphe ing, as in 5G deploymen s he lowe
laye s may mo e o en be placed in use -
deployed en i ies which may be comp omised.
Main enance o PDCP sequence numbe s
(SNs), duplica e de ec ion/elimina ion and
disca ding, and ime -based disca d.
No changes o eseen.
Rou ing and eo de ing o PDCP p o ocol
da a uni s (PDUs) in he case o spli bea e s
(RLC acknowledged mode, AM).
No changes o eseen. This unc ionali y is
seen as pa icula ly impo an o he
widesp ead usage o mul i-connec i i y in 5G.
Da a- eco e y p ocedu e o spli bea e s in
DC ( o RLC AM), o ins ance needed when
pa o he da a ansmi ed o e one adio leg
is los due o bad adio condi ions.
No changes o eseen, hough in 5G he da a-
eco e y p ocedu e will need o be de ined o
bo h mul i-connec i i y among LTE-A e olu ion
and no el 5G adio, as well as among mul iple
no el AIVs.
Re ansmission o PDCP se ice da a uni s
(SDUs) a hando e : The hando e case is
e y simila o he use case o he da a-
eco e y p ocedu e.
No changes o eseen.
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As can be seen om Table 5-1, he e a e no majo changes expec ed o be in oduced o
PDCP, excep a be e ailo ing o di e en se ices ypes, and he usage o he da a- eco e y
p ocedu e o also co e mul i-connec i i y among LTE-A e olu ion and no el 5G AIVs which
migh no equi e s anda d changes o PDCP. Since he PDCP laye will be an impo an laye
o he agg ega ion o mul iple AIVs, in pa icula he agg ega ion be ween LTE-A e olu ion and
no el AIVs, as we will see la e in Sec ion 5.4, i is howe e impo an , ha a ious o ms o
in e wo king be ween he LTE-A and PDCP speci ica ion a e possible. Fo ins ance, i an LTE-A
e olu ion adio and a no el 5G adio would be agg ega ed on PDCP le el, his PDCP ins ance
may ollow he 5G speci ica ion and should hence also be able o u ilize he se ices p o ided
by he LTE-A lowe laye s. I may also be conside ed o use he LTE-A speci ica ion o he
common PDCP ins ance, which should hen also in e ope a e wi h he RLC, MAC and PHY
laye s o he no el 5G AIV, as discussed u he in Sec ion 5.4.2 and illus a ed in Figu e 5-4.
Radio Link Con ol (RLC)
Fo RLC laye , he main unc ion is au oma ic epea eques (ARQ) and da a
segmen a ion/conca ena ion, based on which mode (acknowledged o unacknowledged mode)
is con igu ed. The ollowing able summa izes he RLC unc ionali ies de ined in LTE in mo e
de ail, and elabo a es on he po en ial changes conside ed by METIS-II pa ne s o 5G.
Table 5-2 . RLC unc ionali ies in LTE-A and possible changes in 5G.
RLC unc ionali y in LTE-A
Conside a ions o no el AIVs in 5G
T ans e o uppe laye PDUs
No change o eseen.
E o co ec ion h ough ARQ (only o AM
da a ans e ). By con igu ing AM RLC, ARQ
is suppo ed wi h an ex a laye o
e ansmission eliabili y.
Fo no el 5G AIVs, he combina ion o ARQ
and hyb id ARQ (HARQ) should be u he
s udied. Since i may be possible o imp o e
he eliabili y o MAC HARQ, he ARQ may in
some use cases po en ially be omi ed.
Conca ena ion, segmen a ion and
eassembly o RLC SDUs (only o
unacknowledged mode, UM, and AM da a
ans e ), o he pu pose o gene a ing RLC
PDUs o app op ia e size om he incoming
RLC SDUs.
Since conca ena ion and segmen a ion
equi e he knowledge on he MAC anspo
block sizes, his RLC unc ionali y is igh ly
ied o he MAC and hence has o happen on
synch onous ime scale. A conside a ion is o
mo e his unc ionali y in o he MAC, while
keeping indi idual queues pe RLC en i y o
a oid head-o -line blocking. This way, he
emaining RLC unc ions would be
asynch onous, and a unc ion spli be ween
RLC and MAC would be a spli be ween
asynch onous and synch onous unc ions,
see Sec ion 5.5.2. I ye has o be cla i ied o
which ex en his would ouch
s anda diza ion, o be a ma e o
implemen a ion.
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Re-segmen a ion o RLC da a PDUs (only
o AM da a ans e ), in he case ha hese
do no i o he ac ual anspo blocks.
In no el 5G AIVs, he usage o his unc ion
may be ex ended o new scena ios, o
example, he usage o unlicensed spec um,
whe e he ansmission may be blocked by
channel acquisi ion. Then, he RLC PDU
could be e-segmen ed o i he nex
ansmission.
Reo de ing o RLC da a PDUs, duplica e
de ec ion and RLC SDU disca d (only o
UM and AM da a ans e ), RLC e-
es ablishmen , and p o ocol e o
de ec ion (only o AM da a ans e )
No changes o eseen.
In summa y, he se ices and unc ions suppo ed by RLC in LTE-A should be he baseline o
he 5G design, bu some speci ic changes a e o eseen o no el 5G AIVs, such as he dynamic
usage o ARQ depending on H-ARQ eliabili y and use case, a eloca ion o conca ena ion,
segmen a ion and eassembly o he MAC, and he ailo ing o e-segmen a ion o he usage o
unlicensed spec um. In his espec , i is clea ha no el 5G AIVs will ha e a speci ica ion
which is dis inc om he LTE-A speci ica ion.
Medium Access Con ol (MAC)
The design o MAC in LTE-A has allowed keeping a low complexi y wi h an e icien and as
handling by any ype o de ices o he anspo block. This has been achie ed by keeping a
minimalis ic app oach o he packe handling unc ions ha a e mainly esponsibili y o RLC and
concen a ing in he unc ions ha allows he op imal ope a ion and u iliza ion o he physical
laye ( his would o cou se change o pa o he RLC unc ionali y is mo ed o he MAC, see
p e ious RLC desc ip ion). The main se ices and unc ions o he MAC sublaye include:
 Mapping be ween logical channels and anspo channels
 Mul iplexing / demul iplexing o MAC SDUs belonging o one o di e en logical channels
in o / om anspo blocks (TBs) deli e ed o / om he physical laye
 P io i y handling be ween logical channels o one UE. The handling o di e en p io i ies
and an e icien use o spec um mo i a es o implemen hese unc ions in MAC.
 Ini ial Access using he Random Access Channel o eques ing uplink esou ces.
 Scheduling in o ma ion epo ing. The epo ing o he UE scheduling in o ma ion is an
e icien and as unc ion ha allows he ne wo k o p o ide he UE wi h UL g an s. In a
ully scheduled sys em, his unc ion will be s ill equi ed o he same pu pose.
 E o co ec ion h ough HARQ. The bene i s o HARQ e ansmissions mo i a e he
need o p o ide HARQ e ansmissions in MAC o se ices ha equi e high eliabili y.
 P io i y handling be ween UEs by means o dynamic scheduling;
 T anspo o ma selec ion;
 Padding.
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These unc ions a e o eseen o be also equi ed by he MAC laye o new AIVs. Some o hem
migh equi e adjus men s in o de o p o ide highe lexibili y o add ess he equi emen s o he
new 5G use cases. Fo example, in o de o each e y high da a a es wi h he deploymen o
wide ca ie s, a new se o anspo o ma s a e needed o be de ined and possibly a new
anspo o ma selec ion p ocedu e needs o be upda ed acco ding o he newly de ined con ol
channels o new AIVs. Ano he example is he imp o emen s o he UL g an ing signaling o
enable a g ea e g anula i y and con ol o logical channels when mul iplexing da a. As
men ioned du ing he desc ip ion o he RLC laye , i is conside ed o mo e synch onous RLC
unc ionali ies such as conca ena ion and segmen a ion o he MAC laye , hence ex ending he
lis abo e. Fu he mo e, conside ing beam-cen ic design (see Sec ion 6.1.2), MAC may also be
in ol ed in beam- ela ed epo ing, e.g., in case o dynamic a ic s ee ing.
5.4.2 CP / UP A chi ec u e o he In e wo king o LTE-A
e olu ion wi h no el AIVs
A igh in e wo king be ween LTE-A e olu ion and no el AIVs has been assumed in METIS-II
om he e y beginning o he p ojec . These assump ions ha e been la e adop ed in 3GPP,
whe e TR 38.913 desc ibes ha he 5G RAN should suppo high pe o ming mul i-AIV
4
mobili y
and UP agg ega ion as equi emen s o igh in e wo king [3GPP16-38913].
Fo ac i e UEs, high pe o ming in e -AIV mobili y can be ansla ed in o high obus ness
agains packe losses (lossless), hando e (HO) and adio link ailu es (RLF); low in e up ion
delays (seamless) and low signaling o e head in he adio in e aces (i.e. LTE-A and no el
AIVs) and in he ne wo k side. METIS-II has concluded ha a high pe o ming in e -AIV
mobili y be ween LTE-A e olu ion and no el AIVs should be ealized on a RAN le el, i.e.
wi hou necessa ily in ol ing CN signaling.
A key echnology in his espec will be mul i-connec i i y be ween LTE-A and no el AIVs. F om
a UP pe spec i e, he mos simple ealiza ion o such is o agg ega e LTE-A and no el 5G AIVs
on PDCP le el, i.e. ha e a common PDCP ins ance o bo h. Fo his o m o mul i-connec i i y,
he lowe p o ocol s ack laye s may ha e independen speci ica ions, which was ac ually
ecommended in Sec ion 5.4.1. Due o he a o emen ioned aspec ha bo h LTE-A and no el
AIVs could se e as an ancho laye , ei he echnologies should be able o pe o m he PDCP
low spli , and bo h he PDCP speci ica ion o he 5G AIV and ha o LTE-A should be able o
ely on se ices p o ided by he lowe laye s o he espec i e o he echnology. This is depic ed
in Figu e 5-4.
4
In 3GPP e e ed o as mul i-RAT
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Resul s show ha spli op ion M1 equi es signi ican ly highe da a a es compa ed o he o he
spli op ions. Compa ed wi h M2, M1 equi es app oxima ely ou imes highe da a a es. This
can be explained by he ac ha M1 has o ca y he da a a e /be o e he in e se as Fou ie
ans o m/ as Fou ie ans o m (IFFT / FFT). This means ha I/Q samples o all subca ie s
a e ans o ma ion in he ime domain ha e o be ansmi ed, also o he subca ie s ca ying
no da a. The FFT size (i.e., he o e all numbe o subca ie s) is 2048. Conside ing also 144
samples o he cyclic p e ix esul s in a o al numbe o 2192 samples pe OFDM symbol, while
he numbe o subca ie s ca ying da a only co esponds o 1200. Ano he di e ence comes
om he numbe o quan iza ion bi s o each signal componen . Fo M1 a alue o 15 is used
and o M2 a alue o 7.
In addi ion o da a a e equi emen s, also la ency aspec s a e a c i ical issue o he selec ion
o sui able spli s, o ins ance limi ing he implemen a ion o ce ain unc ionali ies (e.g. CoMP
p ocessing) in he case o some deploymen scena ios. In his espec , p elimina y analyses
[MET15-D64] ha e concluded ha in pa icula in he con ex o la ency-p one backhaul /
on haul, as in deploymen scena io 1, ime-synch onous unc ions (in LTE hese a e PHY,
MAC and RLC unc ions such as scheduling, link adap a ion, powe con ol, in e e ence
coo dina ion e c.), should ideally be placed close o he adio uni s. Many o hese unc ions a e
also di icul o i ualize, as hey o en depend on ha dwa e accele a ion. Func ions which a e
ime-asynch onous o he adio in e ace (in LTE hese a e PDCP and RRC unc ions ela ed o
measu emen con ol and epo ing, hando e p epa a ion and execu ion, dual connec i i y,
andom access, RRC s a e ansi ion e c.), howe e , could be implemen ed as VNFs and
possibly cen alized, as hey can ypically cope wi h la ge la ency (e.g. ens o milliseconds in
LTE-A).
In his con ex , a key conside a ion is o design 5G RAN unc ions o a oid s ic iming ela ions
be ween he p o ocol laye s, and ha e a clea e spli be ween ime-synch onous and ime-
asynch onous unc ions. One speci ic design conside a ion in 5G, as al eady s a ed in Sec ion
5.4.1, is o ins ance o mo e he ime-synch onous unc ionali ies o segmen a ion and
conca ena ion om he RLC laye o he MAC laye , such ha he RLC only con ains ime-
asynch onous unc ionali ies. This way, he spli be ween RLC and MAC could be a sui able
poin o an in a-RAN in e ace, in pa icula in he con ex o a la ency-p one on haul /
backhaul in as uc u e. This would co espond o spli op ion M7 in Figu e 5-7. I a eliable low-
la ency on haul is a ailable, a iable op ion would be spli op ion M5 – his allows o cen alize
uppe MAC unc ions such as scheduling, bu s ill subs an ially elaxes he on haul bandwid h
equi emen s as compa ed o he s a e o he a , i.e. a Common Public Radio In e ace (CPRI)
in e ace (spli op ion M1).

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5.5.3 Speci ic Mapping Conside a ions o Logical o Physical
A chi ec u e in METIS-II
As an abs ac unc ion spli model applicable o all physical deploymen scena ios, METIS-II is
conside ing he model depic ed in Figu e 5-9. As one can see, he conside a ion is o gene ally
spli he NFs in he RAN in o a lowe , middle and uppe laye . This spli may be done di e en ly
o UP and CP. Le us now see how he spli s may be ealized o he speci ic physical
deploymen s conside ed in METIS-II in Figu e 5-6.
5G CN
CPNFs UPNFs
RU
EPC
CPNFs-H
CPNFs-M
CPNFs-L
UPNFs-H
UPNFs-M
UPNFs-L
RU RU
LTE
eNB
Digi al Domain
RF Domain
S1*-C S1*-U
Figu e 5-9. Abs ac unc ion spli model conside ed in METIS-II.
 Scena io 1 (s and-alone access nodes wi h impe ec backhaul in as uc u e): In his
case, he uppe NFs could comp ise he asynch onous laye s (RRC and PDCP, and also
RLC i a o emen ioned changes a e applied), and be mapped o agg ega ion poin s,
while he middle and lowe NFs would comp ise o he PHY and MAC laye s and be
mapped o he adio uni s. This would co espond o spli op ions M8 o M7 in Figu e 5-7.
 Scena io 2 (cen alized p ocessing wi h pe ec on haul): In his case, a la ge ex en o
cen aliza ion could be ob ained. The in e ace be ween his node wi h cen alized
unc ions and he adio si es could be based on classical CPRI in e aces (co esponding
o spli M1 in Figu e 5-7), o , in o de o alle ia e he CPRI bandwid h equi emen s in
pa icula in he con ex o la ge sys em bandwid h and a la ge numbe o indi idually ed
an enna elemen s, a spli in he MAC laye such as M5 could be pu sued.
 Scena io 3 (locally cen alized baseband p ocessing): This would cons i u e a
combina ion o scena ios 1 and 2: The asynch onous laye s RRC and PDCP would be
placed in cen alized clouds, using in e aces M8 o M7 owa ds edge clouds. The
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in e aces owa ds he adio uni s could be based on CPRI (op ion M1) o on a spli
wi hin he MAC (op ion M5).
 Scena io 4 (sel -backhauling): This scena io has no ye been concluded in METIS-II.
No e ha one impo an equi emen o he 5G RAN is o p o ide su icien lexibili y o
placemen o NFs, bu on he o he side, he numbe o in e aces be ween he NFs, clus e ed
on a ho izon al laye s uc u e acco ding o he adio p o ocol s ack, should be as small as
possible. This is impo an in o de o keep he s anda diza ion e o (as hese in e aces ha e
o be ully open-s anda dized) and es ing e o lean (as all al e na i e combina ions ha e o be
es ed be o e going in o ope a ion, which may be mo e s essed by mul i- endo
implemen a ions and in e -ope abili y es ing). Hence, i is no ye clea o which ex en
a o emen ioned op ions should be s anda dized o no . One possibili y is o p o ide s age-2
speci ica ions o hese in e aces, lea ing he exac deg ee o s anda diza ion open.
5.6 A chi ec u al Enable s o Ne wo k Slicing
In his sec ion, we will now elabo a e on pa icula a chi ec u e enable s ha ha e been
iden i ied as impo an o suppo he no ion o ne wo k slices, i.e. he ope a ion o logical
ne wo ks se up o pa icula business cases. This opic is cu en ly also unde in es iga ion in
3GPP. In [3GPP16-22864], i is o ins ance men ioned ha “One key concep o achie e he
goal o lexibili y is ne wo k slicing. Ne wo k slicing allows he ope a o o p o ide dedica ed
logical ne wo ks wi h cus ome speci ic unc ionali y, wi hou losing he economies o scale o a
common in as uc u e”. Also he cu en unde s anding in 3GPP SA2 is ha “A ne wo k slice is
composed o all NFs ha a e equi ed o p o ide he equi ed se ices and ne wo k capabili ies,
and he esou ces o un hese NFs.“
I should be poin ed ou ha a ne wo k slice is expec ed o be ela ed o a pa icula business
cons ella ion in he 5G e a, i.e. he in e ela ion o di e en playe s such as ne wo k ope a o (s),
o e - he- op playe s, e icals, eselle s, in as uc u e owne s e c., which is likely cap u ed in
he o m o se ice le el ag eemen s (SLAs) among he playe s. Such a business cons ella ion
may ela e o one o mul iple se ice ypes (see he in oduc ion o he main 5G se ices ypes
in Sec ion 2.1). As an example, he e could be a business cons ella ion in ol ing a mobile
ne wo k ope a o , a ca manu ac u e and an applica ion p o ide , which could be ela ed o
enabling sa e y-c i ical communica ion be ween ca s, as well as p o iding xMBB o ca s o he
pu pose o in-ca en e ainmen . SLAs would be se up ha desc ibe which QoS me ics a e
expec ed o be gua an eed, possibly also deno ing a minimum amoun o spec um o be
dedica ed o his business cons ella ion e c. In his espec , i is impo an o poin ou ha he e
is no one- o-one ela ion be ween ne wo k slices and se ices, i.e. a single ne wo k slice
may con ain a mix o se ices, and he same ype o se ice may also be p o ided ia mul iple
ne wo k slices. As an example o he la e , a mobile ne wo k ope a o may p o ide mul iple
ehicula sa e y ela ed se ices, in each case in ol ing di e en pa ies and di e en SLAs, and
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hence using sepa a e ne wo k slice ins ances o hese. I is expec ed ha he se up and
con igu a ion o ne wo k slices, and hence also he decision on how many slices o es ablish o
which pu pose, is le o he mobile ne wo k ope a o .
I is clea ha many use cases in 5G will no succeed om a business pe spec i e unless hey
sha e he same in as uc u e wi h o he use cases. As an example, ehicula sa e y could likely
no be economically p o ided i his would equi e he oll-ou o dedica ed in as uc u e. In he
con ex o ne wo k slicing, his means ha mul iple slices will likely euse in as uc u e o a la ge
ex en . Wi hin he CN, his would likely mean ha mul iple slices use di e en i ual machines
o UP and CP p ocessing, bu hese would be un on he same physical da a cen es as o he
slices. In he RAN, i is likely ha mul iple slices and he se ices he ein would in ac be
mul iplexed in o a common MAC, PHY and adio wi h o he slices, hough his need no always
be he case (e.g. a pa icula slice may use dedica ed spec um and/o dedica ed access nodes
and hence also use a dedica ed MAC/PHY e c.). No e ha many a ian s a e possible, e.g. i
could make sense o ha e a dedica ed MAC schedule o pa icula slices o se ices. Also,
e en i mul iple slices a e mul iplexed in o a common MAC/PHY, ce ain NFs could be highly
slice- o se ice-speci ic (e.g. speci ic H-ARQ con igu a ion). The end owa d se ice
mul iplexing on lowe laye s is depic ed in Figu e 5-10. To ha e he comple e pic u e o
suppo ing slicing in RAN, i is impo an o no e ha hese al e na i es ha e o be conside ed
unde he ligh o he possibili y o suppo di e en unc ional spli s as discussed in Sec ion 5.5.
Figu e 5-10.T end owa ds mul iplexing o slices in o common lowe laye s, while each
ne wo k slice emains a logical ne wo k om E2E pe spec i e.
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The METIS-II pa ne s ha e u he iden i ied he ollowing aspec s ela ed o ne wo k slicing:
 Ne wo k slices (o an abs ac ion he eo , such as g oups o se ice lows) need o be
isible o he RAN, such ha NFs can ake in o accoun o e all slice-speci ic me ics o
cons ain s ( o ins ance, he cons ain ha all se ices belonging o a slice may join ly
only occupy a ce ain amoun o adio esou ces).
 Isola ion among slices: Slice isola ion is essen ially abou managing ne wo k and
compu ing esou ces in a way ha he pe o mance o one slice is no a ec ed by he
ope a ion o ano he slice. Thus, i is equi ed o ha e mechanisms o p o ec common
channels o esou ces used o UEs accessing sys em so ha conges ion in one slice
does no ha e a nega i e impac on ano he slice. Cu en ly, 3GPP sys ems p o ide
some suppo o p o ec ing common con ol channels o ex ensi e load om di e en
se ices. These mechanisms include Access Class Ba ing, Enhanced Access
Ba ing, Se ice Speci ic Access Ba ing, as well as implemen a ion speci ic
admission con ol e c. Mo eo e , ano he 3GPP mechanism is he Applica ion
speci ic Conges ion con ol o Da a Communica ion (ACDC). As desc ibed a
[3GPP16-22011], ha is an access con ol mechanism o he ope a o o allow/p e en
new access a emp s om pa icula , ope a o -iden i ied applica ions in he UE in idle
mode. Fu he in es iga ions a e needed o adap hese mechanisms o slice
speci ic ela ed unc ions. As a po en ial echnology componen suppo ing slice
isola ion, METIS-II is in es iga ing means o se ice p io i iza ion, whe e a combina ion
o andom access channel (RACH) p eambles is being used o he di e en ia ion
among high and low p io i y se ices du ing ini ial access; his combina ion enables
minimum e ec o he o he slices/se ices [MII16-D61].
 In o de o he slicing concep o allow o e icien usage o common esou ces such as
adio spec um, adio in as uc u e, and anspo be ween he slices sha ing o
esou ces should be possible. In hese cases i may also be needed o ha e
app op ia e scheduling schemes ha will ake ca e o as luc ua ions o a ic in
di e en slices. Only in special cases (e.g., ying o ul ill ul a eliable ansmission o
messages wi h 99.999% success ul ansmissions a e y sho delays such as 1-5msec,
o in cases whe e special egula ions exis )_ i should be assumed ha a slice could be
assigned dedica ed (s a ic) esou ces (e.g. based on egula o y and/o legal
equi emen s), since his may se e ely educe he esou ce e iciency. Finally, since
di e en slices equi e he ul illmen o di e en KPIs, in e -slice RRM schemes need
also o be examined, since o example an a emp o inc ease he h oughpu o he
UEs in a speci ic a ea may in e e e wi h adio nodes suppo ing o he slices (e.g., V2X
slice). Please ind mo e de ails on such schemes in Sec ion 6.2.2.
 Slice selec ion: An in e es ing ques ion which is s ill unde in es iga ion is how a de ice
o se ice would be mapped o a pa icula slice. The simples op ion would be o use
p e-con igu ed in o ma ion (e.g., s o ed in he SIM ca d). This op ion has he bene i o
being e y simple and p e e able in se e al cases (e.g., use o cheap, s a ic senso s).
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On he o he hand, his op ion may lack he equi ed lexibili y o ope a o s o be able o
deploy mo e dynamically slices in a ea o e en using di e en slice iden i ie s. Ano he
solu ion is o de ine a de aul slice which all de ices o se ices will use du ing hei ini ial
a achmen so as o collec in o ma ion abou he a ailable slices in an a ea. Upon hei
a achmen a his slice, a UE has he possibili y o be e-di ec ed by a ne wo k o a
ailo -cu slice o he UE. Finally, ano he al e na i e could be o use b oadcas
in o ma ion by he ne wo k so ha UE does no ha e o pe o m he a ach p ocedu e
wice like in he o me al e na i e. Also, he ne wo k will be able o dynamically upda e
he b oadcas ed in o ma ion abou a ailable slices in an a ea. Ul ima ely, i is no ye
clea o which ex en he a o emen ioned aspec s ha e o be s anda dized o a e
implemen a ion-speci ic.
 Mul i-slice connec i i y e e s o he no ion o ha ing a single de ice in ol ed in
mul iple slices. A po en ial scena io would be he ollowing. A ca may be equipped wi h
one 5G modem ha can be connec ed o bo h a V2X slice o au onomous d i ing and a
he same ime be connec ed o an xMBB slice so as o ac as a elay o he mobile
phones o he passenge s. No e ha i has o be cla i ied whe he his is ac ually a iable
op ion, o whe he legal easons would a he manda e he usage o indi idual de ices
o ehicula sa e y and xMBB. In gene al, mul i-slice connec i i y would open signi ican
issues o he UEs especially i hey would ha e o suppo mo e han one RRC ins ance
(i.e. one pe slice). The added complexi y o such a choice is some hing ha has o be
ca e ully e alua ed. O cou se, al e na i e solu ions would equi e ha a UE may suppo
mul i-slice connec i i y using one RRC machine, bu hen some o he RRC unc ions
would equi e u he in es iga ions.
 Dynamic RAN slice con igu a ion. The need o be o wa d compa ible equi es ha
he RAN allows, o some ex en , he possibili y o dynamically con igu ing o ac i a ing
he slices in he RAN. This means ha he ne wo k should be able o pa ame e ize,
ac i a e o de-ac i a e unc ions in a dynamic manne and based on he business d i en
needs o he cus ome s. This will equi e he de ini ion o app op ia e managemen
unc ionali ies o adio econ igu a ion (see Sec ion 5.7).
 Pe o mance moni o ing solu ions (e.g. coun e s, aces and KPIs) need o be
agg ega ed pe slice o e i y he ul illmen o SLAs and/o p ope ly ope a e he di e en
businesses associa ed o di e en slices;
 Con igu a ion managemen , SON e c. could be ailo ed, u ned on/o and/o possibly
con igu ed indi idually o di e en slices.

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5.7 Ne wo k Managemen and O ches a ion
5
The inal RAN design o METIS-II is in ended o ul il NGMN’s ision o he o e all 5G
a chi ec u e, as desc ibed in he 5G Whi e Pape [NGM15-WP]. NGMN en isions a na i e
SDN/NFV-based a chi ec u e ha is se up on di e en laye s co e ing aspec s anging om
de ices, (mobile/ ixed) in as uc u e, NFs, alue enabling capabili ies e c., up o all he
managemen unc ions needed o o ches a e he 5G sys em (E2E Managemen and
O ches a ion, MANO). This app oach is gene ally conside ed in he a chi ec u al desc ip ion
p o ided by he 5G PPP Wo king G oup (WG) “A chi ec u e” (see Figu e 5-11 o a high le el
o e iew [5GARCH16-WP]). Design p inciples de eloped by METIS-II on 5G RAN a e also
inco po a ed in o ha a chi ec u e.
Figu e 5-11. Managemen amewo k o he in eg a ion o mobile b oadband
and e ical se ices [5GARCH16-WP].
This E2E MANO is esponsible o he ansla ion o 5G use cases and business models in o
conc e e se ices and ne wo k slices. Dependen on de ined SLAs i de e mines o each slice
ins ance and co esponding se ice lows, espec i ely, all ele an NFs, AIVs, and pa ame e
con igu a ions, and inally maps hem on o he a ailable 5G in as uc u e (slice/se ice
chaining) consis ing o HW and SW pa s including ne wo king ( adio, anspo , e c.), compu ing
and s o age esou ces, adio equency (RF) uni s and cables. The ne wo k slicing concep
5
The ne wo k managemen and o ches a ion amewo k is no a main esea ch opic in METIS-II,
he e o e only issues wi h ele ance o RAN design a e no ed in he ollowing.
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leads o high esou ce u iliza ion e iciency, scalabili y and adap abili y since each slide is
designed and managed o dynamically p o ide he equi ed amoun o esou ces. Clea ly,
MANO equi es in e -slice coo dina ion, which has o suppo slice clus e ing and global
managemen unc ionali ies. The MANO amewo k is also needed o sha e he in as uc u e
among mul iple slices and o p o ide e icien li ecycle managemen mechanisms o slice
ins ances (i.e., deploymen , ope a ion, moni o ing, and e mina ion). I u he manages scaling
o he capaci y o indi idual NFs and hei geog aphic dis ibu ion, as well as
Ope a ions/Business Suppo Sys ems (OSS/BSS), Elemen Managing (EM), and SON.
The E2E app oach o MANO has also o co e use cases whe e slices, e.g. o achie e global
business a ailabili y, ha e o be gene a ed ac oss mul iple domains wi h di e en adminis a i e
owne s (ope a o s, in as uc u e p o ide s, e c.). Beside he espec i e echnical implica ions,
no el business in e aces and cha ging models ha e o be de ined o such app oaches
[5GEx16-WP].
MANO in 5G is gene ally based on p inciples de i ed wi hin he wo k o he Eu opean
Telecommunica ions S anda ds Ins i u e (ETSI) Indus y Speci ica ion G oup (ISG) NFV [ETSI-
NFV, ETSI14-MAN], bu he e a e also aspec s going beyond cu en speci ica ions, especially
o he RAN pa , o achie e equi ed lexibili y and p og ammabili y (see e.g. [5GN15-D31]).
F om a long- e m esea ch pe spec i e, ne wo k slicing could bene i om SDN and So wa e
De ined Radio (SDR) concep s. SDN is based on he decoupling o con ol and da a planes so
as o inc ease in he e icien use o compu a ional esou ces. The design esul ing om he join
implemen a ion o NFV and SDN concep s is expec ed o g ea ly educe capi al expendi u e
(CAPEX) and ope a ional expendi u e (OPEX) o u u e mobile sys ems since i limi s he usage
o speci ic ha dwa e in as uc u es, as ound in adi ional a chi ec u es, and op imizes he
u iliza ion e iciency o he ne wo k esou ces. I is impo an o cla i y ha NFV and SDN a e
independen and a he complemen a y concep s. The basic idea o SDR is de ining speci ic
adio p ocedu es ha can p o ide lexibili y, agili y, and esponsi eness o be easily adap ed
and deployed on he i ualized baseband uni s, including he RF pa . Speci ically, SDR-
enabled base s a ions can be ope a ed on demand on he mos app op ia e AIV (e.g. ela ed o
a speci ic equency band), and he i ual unc ional spli may depend on whe he hey need o
p o ide one o ano he se ice (see Figu e 5-12).
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Figu e 5-12. Exempla y ep esen a ion o he in e ela ion o ne wo k slicing enable s,
including SDN/NFV/SDR
The e will be added complexi y o in oduce and handle SDN/NFV/SDR p inciples (e.g.
in e aces/APIs, pe o mance moni o ing, secu i y issues). The e o e, i is s ill an open issue
how a i ualiza ion in he RAN can be cos -e icien ly in oduced while achie ing high
pe o mance wi hou ex ensi e usage o dedica ed econ igu able HW accele a o s (i.e.,
Physical NFs in con as o Vi ual NFs), which may limi lexibili y.
Especially he in e ela ion be ween logical and in as uc u e esou ces in he RAN and hei
e icien and as managemen and o ches a ion ia hype iso p inciples has o be u he
e alua ed (e.g. e-adjus men and/o e-con igu a ion o NF esou ces in case o o e load o
aul si ua ions). No el managemen schemes o AIV econ igu a ion (e.g. changing he
p ope ies o an AIV such as he ca ie bandwid h, ame nume ology e c. on he o de o
hou s) may be adop ed o mo e e icien use, o adap he ne wo k o he dynamic beha io o
he a ic and o globally maximize he capaci y. Acco dingly, he AIV econ igu a ion can shape
he o e all AI landscape and implies a modi ica ion o he a ailable se o esou ces on which
RM schemes will be ope a ing. The e o e, he unc ions wi hin agile RM amewo k, as de ailed
in Sec ion 6.2, need o ake in o accoun such AIV econ igu a ions. In ac , gi en a cell se in a
ce ain a ea, he a ic o di e en slices o se ices e.g. on a speci ied AIV may change om
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one sub-a ea o he o he acco ding o he day pe iod (e.g., in a s adium be o e, du ing and a e
an e en such as a oo ball ma ch o a conce ). I o en happens ha some a eas may be
conges ed (wi h high blocking pe cen ages) in some pa icula zones ( he so-called ho -spo s as
he s adium) in which he a ic is mo e consis en , while su ounding cells a e less loaded o
cha ac e ized by low blocking pe cen ages.
The AIV econ igu a ion managemen unc ionali y spans di e en AIVs and managing and
con olling he nodes inside he NW, wi h he goal o sel -adap ing owa ds an op imal mix o
suppo ed AIVs and equency bands. This unc ion could ac on he basis o some inpu
pa ame e s, such as he a ailable esou ces (spec um and HW), he a ic demand, he
capabili ies o he UEs wi hin he NW (suppo ed AIVs, equency bands, e c.), he eques ed
se ices (e.g., bandwid h and QoS), e c. In addi ion, his unc ionali y could exploi a
collabo a i e AIV econ igu a ion managemen scheme, whe e he decision making unc ions
a e sha ed among di e en NW nodes.
On hese basis, wo main di e en ypologies o econ igu a ion acco ding o he speci ic
con ex s can be pe o med: an in a-sys em econ igu a ion ha in ol es only one single AIV
and/o an in e -sys em econ igu a ion ha in ol es wo o mo e di e en AIVs. Fo example, an
in a-sys em econ igu a ion could be necessa y when he a ic on a speci ied AIV d as ically
changes om one sub-a ea o he o he (e.g. some cells may be conges ed while he
su ounding ones a e no ). On he o he side, he in e -sys em econ igu a ion could be needed
when di e en a ic loads a e expe ienced by each AIV, in o de o inc ease he pe cen age o
adio esou ces de o ed o he o e -loaded sys em while dec easing he ones used by he
o he s (supposed unde -loaded). I should be no ed ha in a-sys em and in e -sys em
econ igu a ions can be simul aneously pe o med. Figu e 5-13 depic s a gene ic scena io ha
includes bo h ypes o econ igu a ions and ha implica es modi ica ions o bo h ha dwa e and
adio esou ces o he in ol ed AIVs. Please no e once again ha he e m AIV econ igu a ion
he e e e s o he change o subs an ial pa ame e s o AIVs (e.g. change o channel bandwid h,
change o nume ology, ac i a ion o a no el AIV in a di e en equency band e c.), which is
expec ed o happen on a slowe ime scale (e.g. on he o de o hou s). A as ac i a ion /
deac i a ion o access poin s and mapping o adio esou ces wi hin a gi en AIV con igu a ion o
o e mul i-AIVs a e handled in he con ex o he agile RM amewo k p esen ed in Sec ion 6.2.
As an icipa ed, in o de o pe o m such ne wo k econ igu a ions, an app op ia e AIV
econ igu a ion managemen unc ionali y o span di e en AIVs, manage and con ol he nodes
inside he ne wo k, in o de o sel -adap owa ds an op imal mix o suppo ed AIVs and
equency bands, need o be in oduced a he logical CP le el. F om a high le el pe spec i e,
such AIV econ igu a ion managemen unc ionali y is de o ed o pe o m he ollowing ac ions:
 Moni o pe iodically he cu en ac i i y s a us o he cells ( o each suppo ed AIV), o
example, in e ms o measu emen o he numbe o he eques s and ejec s (i any)
om he di e en sys ems;
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6.1.4 Ene gy E icien Design and RAN Mode a ion in 5G
While i is o eseen ha a ic will inc ease massi ely in 5G ne wo ks, a key elemen o allow
sus ainabili y o u u e sys ems is ha he absolu e ene gy consump ion in cellula ne wo ks
should no inc ease as compa ed o oday. In essence, his means ha he o e all ene gy
e iciency (e.g. in bi s/Joule) will ha e o inc ease a a simila o e en highe pace han he
mobile da a a ic i sel .
The opic o ene gy consump ion in mobile ne wo ks has been al eady widely s udied in ecen
yea s [EARTH, 5GREEN], ha ing led o he a ailabili y o new ansmission nodes wi h mo e
e icien powe consump ion p o iles, ha a e able o scale be e hei powe usage based on
he ac ual amoun o a ic ha is se ed [MII16-D51]. As explained in Sec ion 6.1.3, he lean
design o he 5G common channels is one impo an enable o his. Also, mechanisms ha
enable as on/o swi ching o nodes al eady exis , allowing o u he educe he ene gy
consump ion o a node when i is no ansmi ing, exploi ing a “sleep mode” o “lock” s a e (see
also [WZZ15]).
The highe deg ee o lexibili y and o coo dina ion ha will be a ailable in 5G ne wo ks allow o
inc ease he sa ing o e ed by his kind o mechanism. Fo example, in [MII16-D51], an
app oach is in es iga ed ha exploi s as sleep mechanisms h ough a cen alized schedule ,
which le e ages on coo dina ion echniques such as Join T ansmission and Dynamic Poin
Selec ion / Blanking o u he educe ene gy consump ion when a ic is below i s peak. This
app oach can wo k on a e y sho ime scale, in he o de o milliseconds, wo king on
ins an aneous luc ua ion o he o e all a ic. In [MII16-D51] i is u he shown ha hanks o a
coo dina ed managemen o he a ailable ansmission nodes i is possible o ade-o he ex a
capaci y p esen in he ne wo k, and achie e highe ene gy sa ings when his addi ional
capaci y is no needed. I was e alua ed ha a powe consump ion educ ion o up o ~50%
could be eached, compa ed o a si ua ion whe e no coo dina ion be ween he ansmi ing
nodes is p esen . This coo dina ed app oach is in pa icula able o educe he powe
consump ion depending on he dynamic po ion o he ene gy consump ion p o ile o base
s a ions, i.e. he po ion ha depends on he amoun o adio esou ces used o ansmission.
On he o he hand, he s a ic po ion o he ene gy consump ion model, he one ha is always
p esen , e en when no a ic is se ed, canno be educed in his way. Tha po ion ep esen s
a undamen al limi on how much ene gy consump ion can be educed, as was al eady
highligh ed in he EARTH p ojec . In ha sense, he e is a limi on he e ec i eness ha can be
eached exploi ing only sleep modes, since he e has o be some signals ha a e always on o
make he CP o he sys em wo k p ope ly. This issue can be sol ed wi h no el app oaches
based on a lean design o he ne wo k.
Ene gy e iciency in he con ex o join ansmission and ecep ion o dynamic TDD is also
in es iga ed as pa o [MII16-D51]. Dynamic TDD is conside ed a p omising solu ion o cope
wi h as - a ying a ic, especially in ul a-dense small cell deploymen s whe e a ic is d i en

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by only a ew ac i e UEs. Clea ly, h oughpu and ene gy e iciency a e in a ade-o
ela ionship, as any smalles inc ease in h oughpu equi es powe ing on sleeping BSs.
I is u he shown in [MII16-D51] ha a ne wo k ene gy e iciency u ili y can p o ide
compa a i ely good pe o mance inc ease in e ms o a e age UE h oughpu o an indoo
en i onmen , while a he same ime educing ene gy consump ion by keeping BSs ha p o ide
li le o no gain in sleep mode. The la ges pe o mance gains a e obse ed a low a ic load,
which is when he numbe o BSs ha can be selec ed o he join ansmission and ecep ion is
g ea es , and he gene a ed in e e ence o o he UEs is limi ed.
6.1.5 Na i e Relaying, Sel -backhauling and D2D Suppo in 5G
As men ioned in Sec ion 3.1, a key design equi emen o he 5G sys em is he na i e suppo o
elaying, sel -backhauling and D2D, as opposed o legacy sys ems like LTE-A, whe e hese
ea u es a e ei he in oduced as an ex ension o he o iginal design o ha e no ye been
in oduced. Such add-on app oach in many cases na u ally in ol e comp omises w. . . a
po en ially be e design. METIS-II is in es iga ing he ollowing communica ion scena ios ha
a e ela ed o elaying, sel -backhauling and D2D:
 G ouping o de ices in p oximi y wi h simila communica ion needs. Mul iple
de ices in p oximi y may be g ouped oge he based on hei mobili y, simila se ice
and communica ion cha ac e is ics (e.g., da a o be ansmi ed, packe delay
equi emen s). De ices in he same g oup may use unicas D2D communica ion o
one- o-many / one- o-all D2D communica ion. Besides, one o he g oup membe s,
based on ce ain c i e ia such as powe o p ocessing capabili ies, may be selec ed as
a g oup head o clus e head. This g oup head may hen use he PC5* in e ace wi h i s
di ec ly connec ed de ices o D2D disco e y and / o communica ion o collec ing
agg ega ing CP messages (e.g., RACH eques s). The in a-g oup communica ion may
ake place ei he ia a di e en in e ace e.g. IEEE 802.15 / Zigbee o IEEE 802.11 o
ia D2D communica ion o e a cellula AIV. The g oup head may use he Uu in e ace
o communica ion wi h he 5G-RAN. De ices in he same g oup can join ly access a
cellula sys em ins ead o indi idually doing so. This communica ion scena io could be
sol ed by ope a ing clus e heads as sel -backhauled access nodes (i.e. such ha
o he de ices in p oximi y would pe cei e hese as in as uc u e nodes and connec o
hem acco dingly), o by keeping clus e heads and o he de ices on he same
hie a chy le el and using pee - o-pee (o mul icas ) D2D communica ion among hese.
 Deep co e age ex ension o mMTC se ices. Deep co e age e e s o he case
whe e mMTC de ices a e deployed in loca ions whe e hey expe ience challenging
adio p opaga ion condi ions wi h a la ge pene a ion loss, e c. O en such de ices may
be senso nodes wi h no mobili y. In such scena ios, ce ain mMTC UEs wi h decen
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adio condi ions may be p e-con igu ed o dynamically selec ed o ac as elay UEs.
This helps o imp o e powe consump ion as well as inc ease o e all co e age a ea.
 D2D communica ion in he con ex o mobili y. Mobile de ices may disco e o he
de ices o in e es which a e in hei p oximi y, and es ablish D2D communica ion. A
pai o D2D de ices in p oximi y and wi h ongoing communica ion can be wi hin he
same base s a ion co e age bu due o hei mobili y, hey may mo e ou o co e age
o one base s a ion and in-co e age o ano he base s a ion. He e, he ocus is on
g oup mobili y and UE mobili y unde di e en in e -AIVs o in a-AIV scena ios.
 Wi eless sel -backhauling in e y dense 5G deploymen s. I is commonly
unde s ood ha o e y dense small cell deploymen s in 5G i may be economically
un easible o es ablish wi ed backhaul o each access node. Hence, wi eless in-band
backhauling should be na i ely suppo ed, enabling access nodes wi hou wi ed
backhaul o au onomously es ablish backhaul links using he same cellula echnology
as he wi eless access.
Since he enable s o elaying, sel -backhauling and D2D ha e many commonali ies, hese a e
he e ea ed in one sub-sec ion. METIS-II has been wo king on de eloping ollowing solu ions:
 Channel sounding among pai s o de ices. One key equi emen in he con ex o
D2D communica ions is he need o es ima e links be ween de ices. The METIS-II
assump ion is he e ha his should be done based on a euse o he same sounding
e e ence signals (SRS) ha a e also used o he cellula uplink. This is di e en o he
LTE Rel. 12 app oach, whe e dedica ed signals a e used o de ice disco e y. A key
challenge is hen ha a de ice can o cou se only send i s own SRS o ecei e he SRS
ansmi ed om ano he de ice a he same ime. Hence, i is equi ed o design SRS
mu ing pa e ns such ha de ices can es ima e he links o o he de ices in p oximi y
o e ime.
 Con ol signaling among de ices. Ano he di icul y is how o enable con ol signaling
be ween di ec ly communica ing de ices (e.g. ACK / NACK, channel quali y indica o ,
CQI, eedback e c.), in pa icula i his is expec ed o build upon he same con ol
channels as designed o cellula communica ions. I o ins ance he e a e ce ain
signals o eseen o uplink con ol signaling, and o he s o downlink con ol signaling,
hen i he uplink con ol signals a e eused o he con ol signaling be ween D2D pai s,
a de ice can only ansmi uplink con ol signals o ecei e hese om ano he de ice,
bu no bo h a he same ime. Solu ions a e he e o ei he again apply a mu ing pa e n
o he con ol signals, as in he case o channel sounding, o o elay con ol signals ia
an in as uc u e node.
 Coope a i e D2D communica ion is when D2D pai s a e u ilized as elays o acili a e
he ansmission be ween a cellula use (CU) and i s base-s a ion (BS) o imp o e
spec um e iciency. In his case, he PC5* in e ace is enhanced o suppo unicas D2D
communica ion and / o one- o-many / one- o-all D2D communica ion among pai s o
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de ices, whe e one o hese de ices can be he sou ce (DT o D2D T ansmi e ), while
o he de ices can be he des ina ion (DR o D2D Recei e ). Besides, such D2D de ices
acili a e cellula use ansmission by ac ing as elay de ices. A coope a i e
communica ion scheme as p oposed he e enables 5G RAN o dynamically allow
coope a i e D2D mode selec ion and communica ion, while a he same ime ensu ing
in e e ence mi iga ion e.g. in case o simul aneous D2D and CU o BS communica ion
o e he sha ed adio esou ces, e c. Mo e p ecisely, h ee ypes o coope a ion a e
conside ed, namely o e lay, unde lay and hyb id coope a ion [MII16-D61].
 D2D disco e y and communica ion. In a D2D disco e y p ocedu e, a BS pe o ms he
D2D pai ing algo i hm by analyzing dynamically collec ed con ex in o ma ion. A e
ecei ing BS con i ma ion, a elay UE sends a disco e y eply message oge he wi h a
e e ence signal o he emo e UE. The emo e UE may espond wi h an ACK o NACK
based on i s calcula ed RSRP o he D2D link. In a D2D communica ion p ocedu e, a
emo e UE ansmi s i s da a packe o he co esponding elay UE wi h which i has
been pai ed in he D2D disco e y p ocedu e. A andom access p ocedu e and D2D link
con igu a ion p ocedu e migh occu in his s ep based on whe he he uplink a ic om
he emo e UE is pe iodic o no . A e wa ds, he elay UE will o wa d he success ully
ecei ed packe s o he se ing BS. The p oposed D2D disco e y and D2D
communica ion p ocedu es a e suppo ed in idle as well as connec ed inac i e s a e. I is
only necessa y o a elay UE o en e RRC ac i e s a e i he elay UE needs o o wa d
he esul o a disco e y p ocedu e o a da a packe o a emo e UE o he BS. The
equi ed con igu a ion in o ma ion o suppo D2D ope a ion is ca ied by D2D link
sys em in o ma ion blocks and downlink con ol in o ma ion om physical downlink
con ol channel (PDCCH). Mo eo e , when pai ed D2D UEs s ay in connec ed inac i e
s a e, ce ain con ex in o ma ion ela ed o he D2D link can be kep in bo h elay UE
and emo e UE(s), in o de o educe bo h signaling load and powe consump ion.
 Sel -backhauling. A basic unc ional equi emen o sel -backhauling is he need o be
able o align he ansmissions on backhaul and access links om he pe spec i e o a
sel -backhauled en i y. I , o ins ance, a sel -backhauled node uses one anscei e o
bo h access and backhaul, i mus be possible o mul iplex he con ol signaling on he
backhaul and access links in ime, meaning ha bo h he backhaul and access link mus
be able o be con igu ed o use ce ain mu ing pa e ns w. . . con ol signaling. I a sel -
backhauled node has sepa a e anscei e s a ailable o backhaul and access, his hal -
duplex cons ain would o cou se be elaxed, bu i may s ill be necessa y ha he node
synch onizes he usage o ansmission and ecep ion on he backhaul and access links
(i.e. i may no ansmi con ol signals on he backhaul link while i is ecei ing con ol
signals on he access link, due o po en ially oo la ge c oss-in e e ence).
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6.2 Func ions ela ed o Agile T a ic S ee ing and
Resou ce Managemen
The di e se se o equi emen s om he wide ange o se ices and he need o a sus ainable
5G sys em (e.g., in e ms o low ene gy consump ion, high lexibili y, and abili y o suppo new
businesses) necessi a e e icien and e ec i e RM schemes ha wo k on an ex ended ealm o
esou ces [MII16-D51]. To his end, METIS-II is de eloping an agile RM amewo k ha
holis ically conside s he no el and di e en ia ing aspec s o 5G sys ems wi h espec o
p e ious gene a ions o mobile communica ion s anda ds, speci ically in e ms o di e se and
challenging se ices and use cases, exis ence o mul iple AIVs, dynamic adio opologies (e.g.,
nomadic nodes), and no el communica ion modes (e.g., D2D). In wha ollows, a ious
unc ional conside a ions wi hin his amewo k a e b ie ly highligh ed. De ails can be ound in
[MII16-D51].
6.2.1 Mul i-AIV Resou ce Mapping
To ensu e ha he QoS equi emen s o he a ic lows a e ul illed conside ing he ela i e
unp edic abili y o he adio links (especially on he highe equency bands), he con en ional
a ic s ee ing mechanisms need o be ex ended owa ds a mul i-AIV dynamic a ic s ee ing
amewo k, which is no only elying on ha d hando e s bu exploi ing mul i-connec i i y and
enabling a ic low adap a ion on a as e and possibly synch onous ime scale. Such a
amewo k needs o ake eal- ime eedback om he mul iple AIVs cu en ly se ing he UE, in
o de o adjus he a ic lows on a as ime scale.
One possible implemen a ion o such amewo k is o apply hie a chical con ol unc ionali ies in
he RAN. In pa icula , as illus a ed in Figu e 6-2 (le ), he ‘ou e loop’ RAN a ic s ee ing
unc ionali y (AN-O) has a global 5G RAN iew, in o de o enable be e a ic s ee ing wi hin
each AIV. The QoS policies a e sen om he CN o he AN-O laye , whe e he a ic
agg ega ion is assumed o happen. Thus, he dynamic a ic s ee ing amewo k is hen
implemen ed in he ou e laye , in o de o do a as a ic e- ou ing o he a ious AIVs in he
‘inne loop’ RAN (AN-I) laye . The AN-I laye is ope a ed wi h an op imal amoun o ac i e links
engaged in mul i-connec i i y wi h he 5G UE, in o de o achie e he QoS a ge s o he se ice
lows. He e, he s ee ing is assumed o happen based on eal- ime eedback (pe -TTI o
pe iodically o e a ew TTIs) om he AN-I laye s. Due o he ela i e un eliabili y o he in ol ed
links, he eedback is equi ed eal- ime, in o de o do a as a ic e ou ing in case a link
ailu e is de ec ed. Cu en LTE adio link ailu e de ec ion and eco e y mechanisms would ake
se e al seconds in o de o e-es ablish he adio bea e , and since his is unaccep able o
high-p io i y, high- eliabili y a ic, he dynamic a ic s ee ing amewo k will ensu e ha he
QoS policies ecei ed om he CN a e success ully en o ced by a oiding adio esou ce
ese a ion due o he RLFs.
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In e ms o he physical deploymen scena ios as discussed in Sec ion 5.5.1, mul i-AIV dynamic
a ic s ee ing concep s a e especially sui able o cloud-based deploymen s. In his ega d, he
po en ial op ions o a lexible p o ocol spli be ween he 5G adio on end and cen alized
p ocessing a e shown in Figu e 6-2, based on [3GPP16-160043] wi h an open xHaul* assumed
o be p esen be ween he adio access poin (local AN-I laye ) and he cloud RAN (assumed o
be he local AN-O laye ). He e, spli A could be conside ed simila o he LTE-A dual
connec i i y ea u e. Op ion-B conside s he RLC PDUs being anspo ed o e he xHaul*
in e ace o mul iple AN-I nodes and deli e ed o he UE which hen does he combining. Op ion-
C could be conside ed simila o he ca ie agg ega ion ea u e in LTE, whe e he MAC PDUs
a e deli e ed o he UE using mul iple LTE RRHs. F om he dynamic a ic s ee ing amewo k
pe spec i e, i he spli is done a he MAC laye (op ion C) o lowe , hen he e a e po en ially
no new impac s pe cei ed on he xHaul*, since he AN-O laye would be ecei ing eal- ime
eedback o scheduling he physical esou ces. Ye , i he spli is done a a highe laye ,
(op ions A and B), wi h as a ic e- ou ing done o e he mul iple AIVs, hen new RAN
measu emen in o ma ion elemen s should be de ined o be anspo ed o e he xHaul*, in
o de o enable he en isioned a ic s ee ing. The eedback in his case should be op imized o
a oid any signi ican addi ional signalling load o e he xHaul* in e ace. In a nu shell, in 5G, due
o he s ingen se ice equi emen s and due o he ela i e unp edic abili y o he adio links
(especially on he highe equency bands), i is desi able ha a ic s ee ing is en o ced in he
lowe laye s o he p o ocol s ack, o e.g., in he RLC o MAC laye s.
Figu e 6-2. Se ice low deli e y mechanism conside ed using he p oposed dynamic
a ic s ee ing amewo k (le ), and unc ionali ies co e ed by AN-O and AN-I o
di e en example unc ion spli op ions ( igh ) [MII16-D51].
I is expec ed ha he AN-O can p o ide a uni ied and agg ega ed iew o he a ious AIVs and
esou ces a i s disposal i i is implemen ed as an AIV-agnos ic con e gence o abs ac ion
laye . A key ques ion in his espec is which a ic s ee ing and RM unc ionali ies can be

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designed as AIV-agnos ic, and which should be AIV-speci ic, and a which le el in he p o ocol
s ack he ansi ion should happen. He e, AIV-agnos ic implies ha he co esponding RM
unc ionali y could emain agnos ic o he design o he physical laye design o he AIVs ha a e
in ol ed and, hus, can ope a e in an AIV-o e a ching manne . Fu he mo e, he abs ac ion
models and RM amewo k should also acili a e achie ing an edgeless use expe ience in
dynamic opology se ings. A con e gence o abs ac ion laye can p o ide a uni ied and
agg ega ed iew o he a ious AIVs and esou ces a disposal, which shall be analyzed
oge he wi h he associa ed a chi ec u e and in e ace implica ions.
Some MAC o synch onous con ol unc ions migh be mos sui ably implemen ed as AIV-
agnos ic o AIV-o e a ching, such as logical channel p io i iza ion, (de-)mul iplexing o logical
channels, queue managemen , eedback con ol o highe laye s, AIV-speci ic con igu a ion
con ol unc ions, and an adap a ion laye owa ds highe laye s (e.g., o educe dependencies
o RLC pa ame e s on adio). The schedule , howe e , can be designed wi h di e en deg ees
o AIV-agnos ic e sus AIV-speci ic unc ionali ies. Two examples a e desc ibed in he sequel
and shown in Figu e 6-3.
Figu e 6-3. Example o AIV-agnos ic RM wi h in eg a ed (le ) o coo dina ed MAC
ins ances o mul iple AIVs ( igh ) [MII16-D51].
Example 1 o AIV-agnos ic RM: In eg a ed MAC laye o mul iple AIVs
In his op ion, a single MAC en i y would handle di e en AIVs wi h speci ic MAC laye unc ions
o sublaye s which can handle he adio-awa e pa o each. The common o AIV-agnos ic laye
o he MAC pe o ms he con olling ole o con igu ing di e en adio speci ic en i ies. The
schedule in his iew is common ac oss all adio in e aces and con igu es pa ame e s ac oss
all o hem. MAC-H (High) as a common laye is en isioned o encapsula e he in e ace wi h
highe laye s and he common con ol/coo dina ion unc ions.
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Example 2 o AIV-agnos ic RM: Coo dina ed MAC ins ances o mul iple AIVs
In his logical iew, sepa a e ins ances o adio agnos ic MAC a e ins an ia ed o each AIV.
The e a e sepa a e adio schedule s o each o he AIVs coo dina ed by a cen al schedule
en i y. This p o ides he lexibili y o ha e independen ly op imized scheduling algo i hms o
indi idual AIVs o use cases. Each adio schedule could be handling a sepa a e AIV o a
speci ic a ic ype. Indi idual MAC ins ances would coo dina e o p o ide a uni ied amewo k,
wi h indi idual schedule s coo dina ing o unde a join o e all schedule /coo dina o .
I is wo h no ing ha ha i is s ill being esea ched o which ex en he abo e concep s a e
pu ely implemen a ion-speci ic, o whe he hese would equi e s anda diza ion, o ins ance,
due o he need o in oduce changes on he Uu in e ace.
On his basis, a lexible scheduling amewo k ha is able o simul aneously accommoda e
use s wi h e y di e en se ice equi emen s is in es iga ed [MII16-D51]. The design aims a
ull lexibili y in he sense ha i does no equi e sepa a ion and ese a ion o esou ces o
di e en se ices, adap ing dynamically o he a ic demands wi h maximum esou ce
e iciency. Fo ins ance, he a ge ed lexibili y can be ob ained ia a lexible ame s uc u e wi h
a iable TTI size suppo . The de eloped aspec s shall na i ely suppo D2D and sel -
backhauling, as de ailed in Sec ion 6.1.5.
The amewo k o mul i-AIV esou ce mapping can inco po a e no only no el AIVs, bu also he
in e wo king be ween legacy and no el AIVs. In his ega d, one example implemen a ion is
p o ided conside ing in e wo king be ween LTE and no el 5G AIVs.
Pa icula ly in ea ly 5G deploymen s, when no el AIVs may no ye be able o p o ide ull
co e age, a igh e in e wo king wi h LTE and no el AIVs may be c ucial in o de o ensu e ul a-
high eliabili y and ex eme bi a es in a 5G sys em [MII16-D51]. One possible mechanism o
enable igh e in e wo king is LTE Rel. 12 dual connec i i y [3GPP13-36842], which ypically
ope a es on a slow ime scale, i.e., in an asynch onous manne . Ne e heless, conside ing he
s ingen 5G equi emen s, e.g., eliabili y and sho delay, he e is an u ge o enable such igh
in e wo king mechanisms on a as e ime-scale, i.e., in a synch onous manne . In he ollowing,
wo concep s, namely, as UP swi ching and dual connec i i y a e highligh ed. Bo h concep s
may bene i om possibly new UE measu emen s pe AIV (LTE and 5G) in o de o make an
op imal scheduling decision, p e e ably on milliseconds basis i he backhaul o e X2* allows o
his. One possible way o achie e his is o s anda dize new UE measu emen s simila o no mal
LTE hando e measu emen s bu on a as e ime-scale. Mo eo e , adding and dele ing a new
CP connec ion in dual connec i i y o a use mus be e y as and ligh weigh in e ms o
signaling o suppo ul a- eliabili y equi emen s.
The i s concep is a as UP swi ch a he (common) PDCP laye , see Figu e 6-4. A i s , i is
assumed ha he con ol plane is using “dual connec i i y” wi h LTE and 5G, while he UP is
swi ched a PDCP le el o ei he LTE o 5G. I he CP is connec ed o bo h he LTE node and
he 5G node, no signaling is equi ed and he UP swi ch may be almos ins an aneous. The as
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UP swi ch can be based on no mal hando e measu emen s such as RSRP. Howe e , possibly
new kind o UE measu emen s is necessa y o e icien ly op imize he pe o mance o he as
UP swi ch. A d awback o ha ing mul iple lows o he CP is he inc eased o e head.
The second concep ela es o he case when bo h UP and CP a e connec ed o LTE and 5G
(simila o “dual connec i i y” in LTE) and he UP da a is agg ega ed (o spli ) a PDCP laye ,
see Figu e 6-4. I is wo h no ing ha an al e na i e o he dual connec i i y solu ion is o use he
MAC laye o agg ega ion, as in ca ie agg ega ion o LTE. In his case, he schedule can
hen use esou ces in an op imal way based on he measu emen in o ma ion abou all ca ie s
(i.e., bo h LTE and 5G ca ie s). The measu emen s and signaling o suppo his should also be
possible o de elop o he dual connec i i y solu ion (s ill using PDCP as agg ega ion / spli
laye ).
Figu e 6-4. Tigh in e wo king op ions be ween LTE-A e olu ion and no el 5G AIVs: Fas
UP swi ching and dual connec i i y (downlink example) [MII16-D51].
6.2.2 Resou ce Managemen o Ne wo k Slices
METIS-II in ends o de elop a RAN design ha ul ils NGMN’s ision o he o e all na i e SDN /
NFV-based 5G a chi ec u e (So wa e De ined Ne wo king / Ne wo k Func ion Vi ualiza ion), as
desc ibed in he NGMN 5G Whi e Pape [NGM15-WP], which is based on he idea o
decoupling he so wa e om he ha dwa e pla o m o he ne wo k as well as o decouple CP
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and UP. The a chi ec u e ision includes a new concep which is desc ibed as E2E ne wo k
slicing. Based on he idea, i will be possible o un mul iple logical ne wo ks as i ually
independen business ope a ions on a common physical in as uc u e. Thus, he RAN needs o
suppo di e en ly la o ed ypes o i ual ne wo ks (i.e. slice ins ances) on he same ha dwa e
pla o m wi h each i ual ne wo k op imized o UCs wi h po en ially con adic ing KPIs. 3GPP
has s a ed ha by now i has o be explo ed i and which new unc ionali y in he RAN pa is
needed o suppo he slicing concep [3GPP15-22891]. Wi h espec o he esou ce abs ac ion
amewo k he slicing concep plays an impo an ole. The esponsible en i y needs enough
in o ma ion abou he cu en ly ins an ia ed slices om he CN side o alloca e a ailable
esou ces. I can be a new cen alized logical elemen (e.g. an access agnos ic Slice Enable as
depic ed in Figu e 6-5). Al e na i ely, i is possible o inco po a e he ea u es o RM o ne wo k
slices in o he AN-O in oduced in he p e ious sec ion. The alloca ion o esou ces is supposed
o happen in a way ha he QoS equi emen s o he di e en se ices as well as he de ined
se ice le el ag eemen (SLA) o a speci ic slice a e conside ed, as illus a ed in Figu e 6-5.
B ie ly, RM o ne wo k slices is a no el RM s a egy, which enables he sha ing o a common
RAN (consis ing o mul iple AIVs) by mul iple ne wo k slices. This includes an abs ac ion o
RAN esou ces o pe o m in e -slice RM wi h coo dina ion o esou ce usage by di e en AIVs
and o e ing a single con ol poin o mobile ne wo k. Fo mo e in o ma ion, in e es ed eade s
a e e e ed o [MII16-D51].
Figu e 6-5. Sha ing o a common RAN by mul iple ne wo k slices.
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Al hough he RAN based paging seems o minimize CN in ol emen in he paging p ocedu e, i
is done a he cos o added RAN complexi y and a highe signaling load on he X2* in e ace.
RAN based paging in oduces he need o o wa ding he no i ica ion o incoming da a as well
as o wa ding he ac ual UP da a om he las se ing cell o he cu en se ing cell. By limi ing
he RAN acking a ea o a single UE-cen ic node would simpli y he in e -node in e aces bu
would also limi he a ea wi hin which UE-based cell eselec ions a e allowed. Fu he de ails
can be ound in [MII16-D61].
6.3.4 Mobili y Managemen
In LTE, he mobili y p ocedu e in RRC Idle s a e is UE-based and op imized o powe sa ing
and minimized signaling while in RRC Connec ed s a e mobili y is ne wo k based and op imized
o se ice con inui y. METIS-II belie es he same app oach should be applied o 5G as well, i.e.
mobili y p ocedu es should be indi idually op imized o RRC Connec ed and RRC Connec ed
Inac i e s a e, handling ac i e da a ansmission and low ac i i y pe iods, espec i ely. Mobili y
p ocedu es o RRC Idle s a e may be needed mainly o aul managemen due o adio link
ailu es and in some allback p ocedu es whe e he de- egis e ed UE needs o pe o m PLMN
selec ion and e-a ach o he ne wo k.
How o pe o m he hando e p ocedu e o handle o e y s ic equi emen s is o majo
impo ance in 5G. Fo la ency-c i ical use cases i is impo an o minimize he se ice
in e up ion due o mobili y e en s o bo h ideal and non-ideal backhaul scena ios. I he
equi emen o in e up ion ime is down o 0 ms, hen make-be o e-b eak mobili y e en s a e
equi ed implying hando e s using dual/mul i-connec i i y. Howe e , he in e up ion ime
equi emen in 5G migh no be he same o all use cases. The e o e, we p opose bo h b eak-
be o e-make and make-be o e-b eak hando e p ocedu es o be conside ed in 5G. The b eak-
be o e-make p ocedu e migh be a na u al consequence o single connec i i y, whe eas, he
make-be o e-b eak hando e is a na u al consequence and use case o mul i-connec i i y.
The beam o ming mobili y design should suppo a as swi ching / acking o he
communica ion beam o comba apid changes in link quali y. The design should be able o
exploi he a ailabili y o mul iple o e lapping beams used o he communica ion wi h a single
UE. Fu he , he beam managemen should ha e a minimum impac o he RRC laye . One
solu ion o ul ill hese equi emen s is he idea o clus e -se based mobili y, which is a se o
nodes ha he UE can de ec and which a e p epa ed in ad ance o a as e- ou ing o he
signaling and use da a. Mo e de ails on his can be ound in [MII16-D61].
Mobili y wi h he use o massi e beam o ming causes new challenges o 5G a highe ca ie
equencies. Due o he lean design o he DL e e ence symbols, he epo ed mobili y
measu emen s o he DL may ca y limi ed measu emen in o ma ion o ne wo k hando e
p ocedu es. One app oach o o e come he limi a ion is o use he UL measu emen s o
mobili y. Fo he UL measu emen s, METIS-II p oposes a new scheme whe e each UE (a leas

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UEs in RRC Connec ed) di ec ionally b oadcas s a sounding e e ence signal (SRS) in a ime-
a ying di ec ion ha con inuously sweeps he angula space. Each po en ial se ing cell scans
all i s angula di ec ions and moni o s he s eng h o he ecei ed SRS along wi h i s a iance o
cap u e be e he dynamics o he channel. In o de o ake ad an age o he UL measu emen s
o mobili y, he neighbo ing cells needs o exchange he UL measu emen in o ma ion, hus
inc easing he signaling load on he X2* in e ace.
In LTE, he acking a ea managemen needed o loca e UEs in RRC Idle s a e is cen alized o
he Mobili y Managemen En i y. To allow o always-connec ed UEs in 5G, he loca ion acking
could be dis ibu ed and done in he RAN, since he mobili y ancho and S1* in e ace
connec ion o CN is a ailable also du ing he low ac i i y pe iods. In his case, he UEs in RRC
Connec ed Inac i e s a e do no c ea e loca ion upda e signaling owa ds a CN when eselec ing
a new cell du ing a low ac i i y pe iod.
To minimize he need o S1* pa h swi ching and UE con ex ans e s in he RAN due o cell
eselec ions du ing RRC Connec ed Inac i e s a e, he S1* pa h(s) can emain e mina ed in he
las se ing node whe e he UE was las ime in RRC Connec ed s a e. The las se ing node
akes he ole o mobili y ancho , which allows keeping he CP and he UP connec ions
unmodi ied and ac i e owa ds he CN. The UE pe o ms cell eselec ion and may in o m he
ne wo k abou he new cell iden i y, bu he ne wo k may decide no o pe o m he las se ing
node change. Ins ead, he las se ing node can es ablish a bi-di ec ional X2* unnel which is
used o ans e ing he UP da a om he mobili y ancho o he se ing node. Some low
la ency use cases may equi e swi ching he S1* connec ion o he op imal node immedia ely
when he UE eselec s o a new cell o co e age a ea which is ela ed o he node cu en ly
e mina ing he S1* connec ion. The e o e, o some URLLC 5G use cases, he mobili y du ing
Connec ed Inac i e s a e may cause equen S1* in e ace pa h swi ching. Fu he discussion
can be ound in [MII16-D61].
6.4 Summa y
The p e ious sec ions p o ided a b ie summa y on key unc ional design conside a ions om
METIS-II, which a e being de eloped and e alua ed in WP4 [MII16-D41], WP5 [MII16-D51], and
WP6 [MII16-D61]. Table 6-2 summa izes hese unc ional design conside a ions o 5G, and
highligh s hei key bene i s, he di e ences o LTE-A e olu ion, and he main implica ions on
he o e all 5G RAN design.
The key unc ional conside a ions mo e owa ds se e al di ec ions and bene i he ne wo k in
a ious ways. In b ie , he bene i s include be e co e age and capaci y (i.e., beam-cen ic
design, elaying and sel -backhauling, in e e ence managemen , mul i-AIV in e wo king),
inc eased ene gy e iciency (i.e., lean design, ene gy e icien RAN mode a ion, op imized UE
con ex measu emen ), and inc eased lexibili y (i.e., AIV con igu a ion, a ic s ee ing, slicing,
e c.). Addi ionally, signaling o e head is educed using e icien and op imized mobili y
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managemen , a new RRC s a e model, and op imized ini ial access. Apa om he educ ion o
he signaling o e head, he no el unc ionali ies also inc ease he eliabili y and educe he
la ency.
Majo di e ences compa ed o LTE-A include se ice-o ien ed designs (e.g., a ge ed
enume a ions o he AIVs o ce ain se ices, op imized andom access allowing o se ice
p io i iza ion, a se ice- ailo ed RRC s a e ansi ion handling), all o which p o ide he basis o
ne wo k slicing in 5G. Addi ionally, he no el ne wo k design, con a y o ha o LTE-A, may
enable he sys em in o ma ion dis ibu ion and he e e ence signals ansmission only when
needed. Fu he mo e, compa ed o LTE-A, op imized RM echniques a e being inco po a ed o
p o iding e icien a ic s ee ing and in e e ence managemen , whe eas ce ain unc ionali ies
such as D2D and sel -backhauling, which in p e ious deploymen s ha e been added on in
ma u e phases o he LTE-A, a e na i ely in eg a ed in he 5G sys em. Finally, he UE
measu emen s, and mobili y managemen will in 5G ocus on he new needs wi h mul iple AIVs
a ailable, and an ex ensi e use o beam o ming.
Table 6-2. Summa y on key unc ional design conside a ions o 5G.
5G Func ional
Design Pa adigm
Key bene i s
Key di e ence o LTE-
A e olu ion
Implica ion on o e all RAN
design
Beam-cen ic
Design
Be e co e age,
capaci y and da a
a es in highe bands
Na ow beams
possibly swep ins ead
o omni-di ec ional
cells
Majo ; all con ol signals
beam o med; all mobili y
and ini ial access p ocedu es
need na i e beam-cen ic
design
Lean and Fu u e-
p oo Design
Ene gy e iciency and
u u e-p oo ness,
po en ially also
imp o ed C-plane
scalabili y
Re e ence signals no
always on, no ull
band, no all
sub ames
Signi ican ly mo e
con igu able e e ence
signals and mobili y p oc.
Ene gy E icien
Design and RAN
Mode a ion in 5G
Reduc ion in o e all
ne wo k ene gy
consump ion wi h
good h oughpu
ade-o
Exploi a ion o
coo dina ion schemes
o a ain high ene gy
e iciency bo h in FDD
and dynamic TDD
sys ems le e aging on
he imp o ed powe
consump ion models
o 5G nodes
New in o ma ion elemen s
o e he X2* in e ace o
indica e he load and
in e e ence in o ma ion on
a TTI-le el; new in o ma ion
elemen s o e X2* o
indica e he ype and le el
o coope a ion; a cen alized
en i y o coo dina ed
scheduling
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Na i e Relaying,
Sel -backhauling
and D2D suppo
in 5G
E icien suppo o
5G se ices ha can
bene i , e.g., om
capaci y, esou ce
euse, powe
consump ion and
co e age gains
o e ed by hese
echnologies
Na i e in eg a ion
since he beginning o
5G sys em design
(e.g., in e ms o CP
unc ionali ies, ame
s uc u es, e c.) a he
han an add-on
ea u e on op o an
al eady ma u e sys em
like LTE
CP and UP unc ionali ies
anging om PHY o highe
laye s should conside
na i e D2D and sel -
backhauling suppo
Mul i-AIV Resou ce Mapping
Dynamic
T a ic
S ee ing
Holis ic and agile RM;
highe o e all
eliabili y;
T a ic s ee ing
pe o med on
compa a i ely a
lowe p o ocol s ack
laye ; dynamic a ic
s ee ing ins ead o
hando e
New con ol in o ma ion
elemen s and s ee ing
op ions be ween p o ocol
laye s needed, poss. impac
on Uu
AIV
abs ac ion
and AIV-
agnos ic
unc ionali y
E icien and lean RM
wi h mul iple AIVs
and dynamic
opologies
Mul iple AIVs and
dynamic opologies in
5G equi e an e icien
way o deal wi h hem
om RM pe spec i e
Spli be ween AIV-speci ic
s. AIV-agnos ic
unc ionali ies; message
exchange o e X2* o
edgeless use expe ience
Flexible
ame
s uc u e
wi h a iable
TTI size
Simul aneous
suppo o use s wi h
e y di e en se ice
equi emen s
TTI size ailo ed pe
use and pe
scheduling ins ance
acco ding o da a a e,
la ency, eliabili y and
co e age needs
PHY suppo o lexible
ame s uc u e wi h
a iable TTI size
RM o Ne wo k
Slicing
Possibili y o sha e a
common RAN o
mul iple businesses
and se ices wi h
di e ging
equi emen s
Ne wo k Slicing is a
new ea u e which is
no pa o LTE-A
New RM concep s equi ed
o implemen slice awa e
esou ce assignmen ;
possible new en i y ha
pe o ms slice-o e a ching
RM
Mul i-AIV
In e wo king on
Fas Time Scale
Tigh in e wo king
inc eases use bi -
a e and connec ion
eliabili y
A oidance o in e -
RAT ha d hando e
which causes a
ansmission
in e up ion; also as
PDCP le el
agg ega ion/swi ch
be ween AIVs, i.e. LTE-
Fas addi ion and dele ion o
a new CP connec ion in dual
connec i i y o a UE along
wi h ligh weigh signaling o
suppo ul a- eliabili y;
new signaling o AIV quali y
me ic; me ics o enabling
bo h load balancing and
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A and 5G
a ic s ee ing be ween LTE
and 5G bene icial, bu
equi e new meas. o e X2*
RAN Enable s o
In e e ence
Managemen
Highe cell-edge use
h oughpu , la ge
capaci y and be e
co e age
Ad anced coope a i e
in e e ence mgm .
echniques a ge ed a
dynamic opologies
and dense
deploymen s, o
ins ance wi h lexible
UL/DL TDD
RAN impac is mos ly
cha ac e ized by he need
o signaling and p ocedu es
o e he wi ed o wi eless
backhaul using X2* in e ace
o suppo he exchange o
in o ma ion among
coope a ing BSs
No el UE
Measu emen
Con ex in 5G
Reduced o e head,
enhanced ene gy
e iciency
Func ional ex ensions
and changes in he UE
measu emen con ex
New in o ma ion and
con igu a ions in he UE
measu emen con ex ;
Op ion ha a UE may
main ain mul iple
measu emen con ex s
A No el RRC S a e
Model
Reduced UE powe
dissemina ion, C-
plane la ency and
CN/RAN signalling,
esp. sui able o
bu s y connec i i y
and massi e access
UEs a e always
connec ed om a CN
pe spec i e;
signi ican ly la ge
possibili ies o
se ice-spec.
con igu a ion
Con ex e ching needs o be
speci ied and suppo ed.
No el mobili y p ocedu es
o new s a e o be de ined
Se ice
P io i iza ion a
Ini ial Access
Se ice
di e en ia ion
al eady a i s
access; lowe la ency
o mission-c i ical
se ices
Di e en le els o
se ice p io i iza ion
o di e se se s o
delay equi emen s
wi hou ese ing
esou ces o ce ain
se ice classes
New MAC p ocedu es
equi ed o RACH o enable
se ice p io i iza ion;
signalling o highe laye s
Mobili y
Managemen
Mobili y wi h e y
low in e up ion
delays and e icien
beam- o ming
mobili y
Suppo o ex eme
low in e up ion
hando e and
unc ions o handle
massi e beam- o ming
Majo ; beam o ming
mobili y equi es new se o
measu emen s and
signalling; new mobili y
p ocedu es o handle low
in e up ion delay HO
RAN-based Paging
Reduced CN/RAN
signalling, educed C-
plane la ency
In LTE paging is a CN
unc ion, which is now
mo ed in o he RAN
En i e e-design o paging
unc ionali y, signalling e c.,
change o usage o CN/RAN
in e ace
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7 Key RAN Design Ques ions
Add essed
In he METIS-II p ojec p oposal and desc ip ion o wo k, he pa ne s had posed 11 key 5G
RAN design ques ions seen o be mos impo an o be add essed du ing he cou se o he
p ojec . Table 7-1 below now p o ides a sho summa y on he s a us o he wo k w. . . hese
key ques ions, and he in o ma ion whe e he eade can ind de ails on he wo k. In case ce ain
key RAN design ques ions could no ye be ully answe ed, i is b ie ly lis ed when hese will be
ackled, and in which u u e epo o deli e able a inal answe will be p o ided. I is wo h
no ing ha , as shown in Figu e 1-3, a ious deli e ables in he i s yea o he p ojec co e he
d a conside a ions (i.e., D2.2, D4.1, D5.1, and D6.1), while he inal conside a ions will be
p o ided owa ds he end o he p ojec (i.e., D2.4, D4.2, D5.2, and D6.2).
Table 7-1. S a us o he METIS-II wo k on answe ing key 5G RAN design ques ions.
No
Key RAN Design Aspec / Ques ion
1
Wha is he gene al spec um usage o eseen o 5G?
A b ie summa y on he gene al spec um usage o eseen o 5G is gi en in Sec ion
4.1.1. Mo e de ails can be ound in [MII16-D31].
2
Gi en he a ious cha ac e is ics o di e en spec um bands, which band should
be used o wha ype o se ice, ai in e ace and how much spec um needs o be
made a ailable o mobile communica ions in he di e en bands?
A b ie summa y on which band should be used o wha ype o se ice is gi en in
Sec ion 4.1.1, wi h mo e de ails in [MII16-D31]. Ini ial conside a ions on spec um needs
in di e en bands a e gi en in [MII16-R31]. A mo e de ailed spec um demand analysis
will be p o ided in deli e able D3.2, o be published June 2017. The ques ion o which
bands should be used o which se ice was addi ionally co e ed in [MII15-R41, MII16-
D41], by de e mining which o e all se (s) o AIVs, e.g. ope a ing in di e en spec um
bands and / o ailo ed owa ds ce ain se ices, will be mos sui able o add ess he
o e all 5G equi emen s space.
3
Which ai in e ace a ian s a e expec ed o be in oduced in he con ex o 5G, and
which a e o be e ol ed om exis ing s anda ds?
A p elimina y answe o his ques ion is gi en in [MII15-R41], whe e i is explained why
legacy echnology and i s likely e olu ion will no be able o mee many o he 5G
equi emen s. The epo u he desc ibes speci ic physical laye componen s and
selec ed AIVs building upon hese componen s, mee ing some o many o he 5G
equi emen s and con ibu ing o he METIS-II o e all AI design goals. This wo k is u he
ex ended in [MII16-D41], whe e o e all AI p oposals being conside ed o 5G a e
desc ibed in de ail, as well as hei ela ionship wi h exis ing s anda ds. A u he

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assessmen and down-selec ion o sui able AIVs and possible o e all AI amewo ks is
ongoing and will be documen ed in D4.2, o be published in Ap il 2017.
4
How many di e en no el and legacy ai in e ace a ian s should di e en de ices
suppo ? Which o ms o concu en connec i i y (e.g. mul i-s anda d and mul i-
cell connec i i y, concu en de ice- o-de ice and de ice- o-in as uc u e
connec i i y) will be equi ed in 5G?
A commonali y analysis o di e en METIS-II AI p oposals was ca ied ou in [MII16-D41].
Following his analysis, an ini ial assessmen was pe o med o he AI p oposals (g ouped
a ound subjacen wa e o m echnologies) using he ha moniza ion KPIs concei ed wi hin
METIS-II, whe e a ious o ms o AI agg ega ion we e iden i ied and hei ea u es
discussed. This has laid he ounda ion o unde s anding he impac on de ice
complexi y and whe he a de ice should be able o se e mul iple AIVs simul aneously,
as well as whe he a de ice should be able o conduc a ansmission o he in as uc u e
and o ano he de ice simul aneously, again in he con ex o use plane design. These
in es iga ions will be con inued owa ds D4.2, o be published in Ap il 2017.
Fu he , he s a ed ques ions ha e been ouched om he pe spec i e o which o m o
mul i-connec i i y o concu en de ice- o-de ice and de ice-in as uc u e connec i i y is
ac ually bene icial in he con ex o holis ic RM. Fu he mo e, possible implica ions on he
de ice complexi y ha e been aken in o accoun o he in es iga ion on po en ial UE
con ex ex ensions, as desc ibed in Sec ion 6.2.4. Fu he de ails on d a conside a ions
in his di ec ion a e cap u ed in [MII16-D51].
5
How igh ly a e no el ai in e ace a ian s expec ed o be in eg a ed wi h each
o he and wi h legacy echnologies (e.g. LTE e olu ion and Wi-Fi), o which ex en
should hey be ha monized o ha e common unc ionali y in he p o ocol s ack,
and on which le el should di e en ansmission o ms be agg ega ed?
The METIS-II pa ne s ha e concluded ha he in eg a ion among LTE-A e olu ion and
no el AIVs, o he in eg a ion among mul iple no el AIVs, should be possible on RAN
le el [MII16-D61]. In his espec , speci ic en isioned o ms o UP agg ega ion and CP
in eg a ion ha e been desc ibed in de ail in Sec ion 5.4. Rega ding ha moniza ion, he
gene al iew is ha among no el AIVs, a la ge ex en o p o ocol s ack unc ion
ha moniza ion should be s i ed o (i.e. a leas a ha monized MAC and highe laye s)
[MII16-D41]. Among LTE-A e olu ion and no el AIVs, ha moniza ion has o be ca e ully
aded agains possible backwa ds-compa ibili y cons ain s imposed owa ds 5G
echnology. He e, i is assumed ha a leas he PDCP laye and abo e could ollow a
common e olu ion, as s a ed in Sec ion 5.4. These in e media e conside a ions a e
expec ed o be concluded in D4.2, D5.2, D6.2 and D2.4 h oughou Ap il – June 2017.
6
How can one e icien ly handle in e e ence in an ul a dense en i onmen ? Wha
kind o in o ma ion is equi ed, a wha ime scale and how as he sys em mus
eac ?
This ques ion is s ill being in es iga ed. Va ious TeCs cons i u ing he Agile RM
F amewo k o METIS-II a e a ge ing in e e ence managemen as i s exempli ied in
[MII15-R51]. I is emphasized he e ha he way o handling in e e ence depends on he
ope a ional scena io and use case. Fo example, when a cen alized RAN app oach can
be implemen ed, i is possible o design a cen alized in e e ence managemen sys em
exploi ing de ailed channel s a e in o ma ion (CSI) and ope a ing on a e y sho (e.g., 1
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ms) ime ame. The CSI may be ed back om he use s o one o mo e access poin s
(which migh be ela ed o di e en AIVs) dynamically. The applicabili y o he a ailable
in o ma ion and he ela ed imescales o in o ma ion exchange and ne wo k
con igu a ion upda es a e being in es iga ed and ha e been documen ed in [MII16-D51].
Fu he mo e, he concep o lean design o common signals educes he amoun o
in e e ence, which is an impo an enable o he 5G sys em o handle ul a-dense
en i onmen s. This has been summa ized in Sec ion 6.1.3 and is de ailed in [MII16-D61].
7
Wha will be conside ed as “ esou ce” in a 5G sys em? How can we manage hese
esou ces e ec i ely in o de o achie e he 5G KPIs?
As cap u ed in [MII16-D51], i is expec ed ha in 5G he no ion o a esou ce may be
expanded beyond classical adio esou ces o also include u he dimensions o
spec um esou ces (e.g. unlicensed bands, spec um sha ing), ansmission poin s along
wi h adio equency (RF) equipmen and hei so capabili ies, such as p ocessing
esou ces, s o age and memo y esou ces, anspo ne wo k esou ces and ene gy.
Wi h espec o how his ex ended no ion o esou ce will be managed e icien ly,
p elimina y conside a ions ha e been p esen ed in [MII16-D51] and summa ized he e in
Sec ion 6.2. A conclusion on his opic is expec ed o be p o ided in D5.2 in May 2017.
8
On which ime scale should ce ain 5G adio access ne wo k unc ionali y (e.g.
adio RM, adio esou ce con ol, mobili y) ope a e, and consequen ly, how should
he necessa y unc ionali ies be bes abs ac ed, g ouped and ackled in
s anda diza ion and implemen a ion?
The gene al end is ha , in 5G, many unc ionali ies a e expec ed o be handled on a
as e ime scale han in legacy sys ems. Fo ins ance, i is en isioned in METIS-II o
enable mobili y and mul i-connec i i y among LTE-A e olu ion and no el AIVs on RAN
le el, inhe en ly allowing o a as e se up o new mul i-connec i i y cons ella ions and
swi ching among hese, see Sec ion 5.4.2. Fu he , i is en isioned ha a ic s ee ing
among di e en AI echnologies, which was so a done ia ha d hando e , is pe o med
on lowe p o ocol s ack laye s and consequen ly on a much as e ime scale, as de ailed
in Sec ion 6.2.1. Addi ionally, aking in o accoun he o e all AI consis ing o mul iple
AIVs, he unc ionali ies, e.g., ela ed o RM, may be g ouped in e ms o in a-AIV
schemes and AIV-o e a ching schemes, see Sec ion 6.2 and [MII16-D51]. The mos
sui able ime scale o p ocedu es ela ed o RRC s a e handling, mobili y and sys em
access is in es iga ed and documen ed in [MII16-D61]. No e ha he a o emen ioned
aspec s a e ini ial conside a ions, and will be concluded and u he de ailed in D5.2, D6.2
and D2.4, o appea in he ime ame Ap il – June 2017.
9
How will he concep s om dynamic spec um managemen in e wo k wi h he
con ol plane a chi ec u e (new ne wo k elemen s and in e aces o his pu pose
and/o some le el o in eg a ion o he con ol plane design)?
The dynamic spec um managemen is o p o ide he in o ma ion on which pa s o he
spec um a e cu en ly accessible o he 5G sys em also ela ed o he loca ion and
a ailable in as uc u e. Also, as i is no expec ed ha all adio nodes a e equipped by
same RF pa s and an enna ypes, access node and de ice capabili ies a e also ele an .
The “Holis ic Spec um Managemen A chi ec u e”, which will be pa o METIS-II
deli e able D3.2 o be a ailable in June 2017, is going o conside hese aspec s.
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10
Wha will be he ne wo k elemen s and in e aces in he 5G sys em a chi ec u e
and, assuming hese, how would hese in e aces look like, i.e. which
unc ionali ies will hey ha e, which p og ammabili y le el will be adop ed, wha
le el o openness, wha le el o abs ac ion, e c.?
METIS-II has al eady s a ed o in es iga e he equi emen s o he o e all 5G logical
a chi ec u e and, mo e speci ically o he RAN con ol plane. An impo an assump ion
aken in METIS-II is he logical spli be ween he RAN and CN (and Se ice Laye )
unc ions, see Sec ion 5.2. In his espec , he p ojec has designed a new connec ed
s a e op imized o inac i i y pe iods be ween small packe ansmissions, and RAN-
based paging solu ions o add ess densi ied deploymen s, bo h app oaches implying a
shi o unc ionali y om CN o RAN, see Sec ion 6.3 and [MII16-D61].
Rega ding in a-RAN in e aces, i is assumed ha an e ol ed X2* in e ace be ween
access nodes will be equi ed, o a ious easons de ailed in Sec ion 5.3. I is expec ed
ha his in e ace will also be c ucial o agile in e e ence managemen in 5G, as lis ed in
Sec ion 6.2.3 and desc ibed in u he de ail in [MII16-D51]. Rega ding possible unc ion
spli s in he RAN o di e en physical deploymen s, a ious op ions ha e been discussed
in Sec ion 5.5. This opic is expec ed o be concluded in D2.4 in June 2017.
The p e e ed le el o p og ammabili y is s ill unde in es iga ion. Fo he RAN, i may be
assumed as a baseline ( o compa ison pu poses) he cu en p og ammabili y le els
enabled by Ope a ions, Adminis a ion and Main enance (OAM) in e aces whe e
cen alized (OSS-based) SON is one example o how o p og am and con ol RAN
ea u es. Ne e heless, i is an icipa ed ha ex ensions o such capabili ies will be
in es iga ed o achie e a mo e lexible and adap able con ol plane unc ionali y. Fo ha
pu pose, p og ammabili y equi emen s will be p oposed and solu ions de i ed in D6.2, o
appea in June 2017.
11
Wha ype o con ol and use plane unc ionali ies should be cen alized o
dis ibu ed depending on he 5G use cases associa ed o hem? Ou o hese
unc ionali ies, wha a e he mos p omising candida es o be implemen ed as
i ual ne wo k unc ions?
P elimina y conside a ions on he cen aliza ion and dis ibu ion o ne wo k unc ions
ha e been p o ided in Sec ion 5.5, o ins ance p oposing speci ic unc ion spli s be ween
physical ne wo k en i ies o di e en deploymen scena ios. A use-case / physical
a chi ec u e speci ic p oposal o unc ion spli s will be p o ided in D2.4 in June 2017.
The deg ee o cen aliza ion and he associa ed bene i s also cons i u e an impo an
aspec o he RM unc ionali ies wi hin he agile RM amewo k, which conside s bo h
cen alized and dis ibu ed con ol unc ions. The wo k wi hin he agile RM amewo k
may also impac he mechanics o CP / UP spli . I is, as well, seen impo an o enable
RM o ne wo k slices, which adds an addi ional dimension in e ms o business
equi emen s. In his di ec ion, ini ial conside a ions ha e been p o ided in Sec ions 6.2.1
and 6.2.2, wi h u he de ails in [MII16-D51].
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8 Summa y and Ou look
This deli e able has cap u ed he d a 5G RAN design conside a ions a he mid-poin o he
METIS-II p ojec . I has p o ided an insigh in o he cu en METIS-II iew on he 5G ai in e ace
(AI), which is expec ed o be composed o mul iple AI a ian s (AIVs), including bo h e ol ed
legacy echnology such as LTE-A, as well as no el AIVs, o ins ance ailo ed o di e en
se ices and bands. The documen has u he mo e summa ized he key consensus ound so
a on he o e all 5G a chi ec u e, o ins ance he iew on a logical CN / RAN spli , on he
ne wo k in e aces allowing o in eg a e new AIVs wi h e ol ed LTE-A, he likely mapping o
logical o physical a chi ec u e o di e en deploymen s, and a chi ec u al enable s o ne wo k
slicing. In a dedica ed chap e , he eade has u he ob ained an o e iew on a ious
unc ional design conside a ions o he METIS-II p ojec , wi h a b ie summa y o he key
expec ed bene i s and implica ions on he o e all RAN design.
As could be seen om Chap e 7, he METIS-II pa ne s ha e al eady ob ained a good common
unde s anding o he 5G RAN design, and ha e been able o p o ide p elimina y answe s on
mos o he key RAN design ques ions ha we e posed a he beginning o he p ojec . In he
emainde o he p ojec , i is now impo an o p o ide mo e echnical de ails o he de eloped
solu ions, and in pa icula p o ide nume ical e alua ions o be able o quan i y he bene i s o
he conside ed schemes when pu in conjunc ion, and o see whe he he de eloped concep s
ul ill he o e all 5G needs as s a ed in [MII16-D11]. I u he has o be c oss-checked ha he
METIS-II solu ions a e capable o scale o any equi emen ex emes, adap o any o he
conside ed use cases, and wo k wi h any o he physical deploymen a chi ec u es de ined in
Sec ion 5.5. All hese aspec s will be cap u ed in inal deli e ables owa ds he end o he
p ojec , acco ding o he imeline depic ed in Sec ion 1.1.