Blue oo h Low Ene gy senso ne wo ks o ailway
applica ions
Ángela He nández, An onio Valdo inos
A agon Ins i u e o Enginee ing Resea ch (I3A)
Uni e si y o Za agoza
Za agoza, Spain
Da id Pe ez-Diaz-de-Ce io, Jose Luis Valenzuela
Signal Theo y and Communica ions Depa men
Uni e si a Poli ècnica de Ca alunya
Cas ellde els, Spain
Abs ac — This pape analyzes he iabili y o Blue oo h Low
Ene gy (BLE) as he enabling echnology in ailway scena ios o
allow senso da a ansmission om g ound o ain. This
p oposal is based on using he b oadcas ing capabili ies
in oduced by he Blue oo h speci ica ions since 4.0. The las
e sion, 5.0, ex ends he ange he speed and he b oadcas
capaci y. Howe e , due o i s ecen publica ion i is ha d o ind
eal de ices wi h i implemen ed in he ma ke . The p oposed
schema has been alida ed by means o expe imen al
measu emen s using 4.2.
Keywo ds— BLE; ehicula ne wo ks; ene gy consump ion;
ailway communica ions
I. INTRODUCTION
In he las ew yea s, In e ne o he Things (IoT) has
expe imen ed a echnological leap in senso applica ions. The
new wi eless s anda ds allow o ansmi mo e in o ma ion wi h
less ene gy consump ion and wi h mo e eliabili y. Hund eds o
senso s and in o ma ion sys ems can be in eg a ed in he ailway
o con inuously moni o hei pa ame e s c ea ing in elligen
anspo sys ems. The use o wi ed and wi eless elemen s o
sensing and ailway communica ions in ailway lines has many
challenges. Ene gy consump ion, eliabili y and delay a e he
main pa ame e s which limi he use o au onomous senso s.
The Eu opean Rail T a ic Managemen Sys em (ERTMS)
[1] o Communica ions-Based T ain Con ol (CBTC) [2] ha e
been implemen ed o imp o e he in e ope abili y o sys ems
and o c ea e a s anda d o ain con ol and command sys ems.
Ne e heless, hese sys ems lack o lexibili y o ins all he
senso s in de e mined condi ions. The main objec i e o his
wo k is o in es iga e he easibili y o using Blue oo h Low
Ene gy (BLE) wi eless echnologies o ain communica ion
scena ios and hei u u e in eg a ion in he ailway
communica ions sys ems. Many di e en senso s (Fig. 1) could
make use o BLE as i s enabling echnology: ailway wo ke
p o ec ion sys ems, collision a oidance, me eo ological senso s,
ack moni o ing sys ems, ain de ec ion mechanisms,
pan og aph and ca ena y senso s, e c.
Gene ally, Blue oo h is uled ou as a sui able echnology o
ehicula communica ions. The e is a much ex ended hough
which says ha Blue oo h is limi ed o a e y sho ange and
equi es a conside ably amoun o ime o s ablish a connec ion
and ansmi da a. In [3], i was al eady demons a ed ha
classic Blue oo h could be employed o ailway communica ion
sys ems. Howe e , he in e nal ope a ion and he oles o he
employed de ices is comple ely di e en when using BLE. In
[3], he classic Blue oo h senso s equi ed o be cons an ly
scanning o he a i al o he con oy, which was gene a ing
emo e name eques s. When he senso ecei ed his eques i
answe ed wi h he s o ed da a. This mechanism, al hough iable,
consumes a huge amoun o ene gy on he senso side. Wi h he
in oduc ion o BLE, we p opose o swi ch he oles and he
place he scanne inside he ain engine. Thus, he powe
consump ion o he senso s will be educed d as ically.
Fig. 1. Example o a ailway scena io senso deploymen
So, in his pape , we will demons a e ha BLE is
app op ia e o his kind o communica ions imp o ing he
pe o mance ob ained by classic Blue oo h in e ms o da a
ecep ion la ency and ene gy consump ion wi h a simila ange.
II. BLE OVERVIEW
The BLE speci ica ion de ines a comple e wi eless
a chi ec u e in ended o enable low-powe communica ions.
BLE de ines 40 b oadcas and connec ion channels in he
Indus ial Scien i ic Medical (ISM) 2.4 GHz band wi h a
physical da a a e o 1 Mbps.
Unlike classical Blue oo h, BLE de ines h ee special
channels (37, 38 and 39), called ad e ising channels used o
he p ocess o disco e ing, ini ia ing a connec ion and
b oadcas ing da a. In his wo k, we used non-connec able
undi ec ed ad e ising, which is one o he di e en ad e ising
e en s p oposed by he s anda d. Thus, he ad e ise
pe iodically gene a es e en s, which consis o a sequence o
packe s in he h ee ad e ising channels. The pe iod be ween
hese e en s is de e mined by he ad e ising in e al pa ame e
(Tad In e al) plus a andom pe iod be ween 0 and 10 ms
(τ andomDelay) o a oid consecu i e collisions among di e en
ad e ise s.
This wo k has been suppo ed in pa by he MINECO/FEDER unde he
p ojec s TEC2014-58341-C4-2-R and TEC2014-60258-C2-2-R.
The o al packe size is 47 by es, whe e he payload is
a iable om eigh o 39 aw by es. Howe e , in ou
expe imen s, he payload consis s o a wo-by e heade plus he
ADV add ess, a h ee-by e lags ield o allow he eading o he
ad e ising by s anda d mobile applica ions and he use da a
i sel anging om 1 o 26 by es plus wo by es o leng h and
ype o da a.
III. EXPERIMENTAL PERFORMANCE OF BLE
To e alua e he sui abili y o BLE o g ound o ain
communica ions we analyzed i s ange, he da a ecep ion delay,
i s pe o mance on high densi y senso ne wo ks and he ene gy
consump ion.
A. Range
I is widely belie ed ha Blue oo h has a limi ed ange o
ens o me e s. E en he Blue oo h SIG has ecen ly published a
whi e pape o demys i y his ac [4]. The eal e ec i e ange is
condi ioned by he ansmi ed powe , dis ance, p opaga ion
condi ions, he an ennae and he ecei e sensi i i y.
Ne e heless, a quick e alua ion could be done using he ee
space p opaga ion model [5] o wi h simple measu es [3]. In
equa ion 1, PR is he ecei ed powe in Wa s, λ is he
elec omagne ic wa eleng h (0.125 m), G is he an enna gain, d
is dis ance be ween ansmi e and ecei e . The subsc ip s T
and R deno e each one o hem, espec i ely. Using he
maximum equi alen iso opically adia ed powe (EIRP) in he
2.4 GHz band, 100 mW, combined bo h wi h high sensi i i y
ecei e s (−93 dBm) and 3 dBi ecei e an enna, Blue oo h can
heo e ically allow anges up o nea i e kilome e s:
𝑃𝑃𝑅𝑅=𝑃𝑃𝑇𝑇·𝐺𝐺𝑇𝑇·𝐺𝐺𝑅𝑅·�𝜆𝜆
4𝜋𝜋𝑑𝑑�2 (1)
Howe e , in p ac ice, we ha e measu ed ha due o o he
impai men s, e.g., he p esence o obs acles o he e ec o he
g ound, wea he condi ions, he losses in oduced by bo h he
an enna cable and he connec o s, e c., he ange is limi ed o
abou wo kilome e s.
B. Da a ecep ion delay and high densi y senso ne wo ks
Ano he ac ha should be e u ed is ha Blue oo h
in oduces oo much delay on he connec ion and da a
ansmission which makes i un iable o ehicula
communica ions whe e high speed mo ing nodes a e in ol ed.
Wi h his objec i e in mind, we designed a senso ne wo k
wi h up o 15 de ices ( om wo o 14 ad e ise s and one
scanne ) and we measu ed he mean ime be ween consecu i e
ad e isemen s coming om he same de ice. We made hese
measu emen s o h ee use payloads (1, 10 and 26 by es) and
h ee di e en ad e ising in e als (100, 300 and 500 ms). The
esul s a e depic ed in Fig. 2. The e, we can app ecia e ha o a
couple o de ices, he da a can be ob ained in he expec ed alue
o Tad In e al + τ andomDelay.
We can ex ac mo e conclusions om his igu e. Fo
example, when he numbe o de ices inc eases, he collisions
and, he e o e, he non-de ec ions also inc ease. Ne e heless,
hey keep on a sus ainable a e. The packe size also has a small
impac on he esul s, he la ge he packe , he mo e p obable
a e he collisions. And, hus, he da a ecep ion ge s sligh ly
delayed.
(a) Tad In e al = 100 ms
(b) Tad In e al = 300 ms
(c) Tad In e al = 500 ms
Fig. 2. Mean ime be ween consecu i e de ec ions
So, he delay un il we ecei e a packe depends no only on
Tad In e al, bu also on he numbe o elemen s o he senso
ne wo k. Fig. 3 depic s he p obabili y densi y unc ion o
ecei ing an ad e isemen in a wo s case scena io wi h 25 eal
ad e ise s using a Tad In e al o 100ms and ansmi ing 26-by e
use da a packe s. The e, we can see ha i he scanne could
emain unde he co e age a ea o a leas 600 ms i will ecei e
da a om all he ad e ise s o he senso ne wo k.
Fig. 3. P obabili y densi y unc ion o ecei ing an ad e isemen (25 nodes)
To complemen hese measu emen s, we designed an
expe imen whe e he BLE scanne was placed in a ca a 120
km/h and hen i came in o he p oximi ies o a small senso
ne wo k composed o i e de ices. The ad e ise s used a
Tad In e al o 100ms. Fig. 4 depic s he esul s ob ained. Each
poin in he igu e ep esen s he ecei ed signal s eng h
indica o (RSSI) o each ecei ed ad e isemen . As can be seen,
a his speed, he mobile node akes nea en seconds o a i e o
he poin nea es he senso s since i ecei es he i s
ad e isemen . Thus, combining hese esul s wi h he
p e iously ob ained in Fig. 3, he mobile has enough ime o
ecei e he da a om all he senso s and e en i would be
possible o educe he ad e ising in e al o sa e ene gy.
Fig. 4. RSSI o he ecei ed packe s wi h a high speed mobile node
C. Ene gy consump ion
Finally, one key aspec o discuss when alking abou BLE
is he ene gy consump ion. Classic Blue oo h ene gy
consump ion is in he mA o de o magni ude, o example, he
SPBT3.0DP2 chipse om STMic oelec onics has a cu en
consump ion in inqui y and page scan mode o 9 mA [6].
On he o he hand, o he p oposed sys em wi h BLE, he
a e age cu en consump ion o he di e en employed
pa ame e s is shown in Table I. I can be no iced ha he wi eless
senso de ices need up o 500 imes less ene gy using BLE.
IV. CONCLUSIONS
In his wo k we conduc ed and discussed se e al eal
expe imen s o demons a e ha Blue oo h is sui able o g ound
o ain connec i i y in ailway communica ions. The p esen ed
wo k alida es ha Blue oo h Low Ene gy can be used as a
wi eless long ange sys em, and i is possible o ansmi da a o
high speed mo ing ecei e s.
We assumed ha a 26-by e use da a packe can ca y
enough in o ma ion o ailway senso applica ions and, hus,
he ad e ising p ocedu e is p oposed agains o he connec ion
mechanisms. Using his p ocedu e, a message o up o 26 by es
can be ansmi ed in a e age a ound 100 ms wi h a e y low
ene gy consump ion. On he o he hand, i has been
demons a ed ha his da a exchange can be comple ed wi hin
wide co e age a eas, up o wo kilome e s, wi h s anda d and
comme cial de ices equipped wi h omnidi ec ional an ennas.
Al hough he p esen ed esul s we e pe o med in nea
op imal condi ions such as line o sigh , we ha e e i ied ha
Blue oo h sys ems also ope a e p ope ly ansmi ing wi h a
leaky eede o in bad wea he condi ions. Mo eo e , Blue oo h
echnology can use mesh ne wo k p o ocols ha can ex end da a
ansmission o e ens o kilome e s. The esul s p esen ed in
his pape a e ob ained using eal deploymen s. So, we can
conclude ha Blue oo h is a iable wi eless echnology o
designing senso s used in complex ailway communica ions.
TABLE I. AVERAGE CURRENT CONSUMPTION
Ad e ising
in e al (ms)
Use da a
payload
(by es)
Redbea
Nano (
µ
A)
Cyp ess
PSoC4-A BLE
(µA)
100 1 17.3 235
100 10 18.5 268
100 26 20 327
300 1 10.4 79.24
300 10 10.8 90.32
300 26 11.5 110
500 1 9.1 48
500 10 9.2 54
500 26 9.5 66
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