© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
TOWARDS STATISTICAL CLIENT PREDICTION – ANALYSIS OF USER
BEHAVIOUR IN DISTRIBUTED INTERACTIVE MEDIA
Aa on McCoy*, Declan Delaney^, D . Seamus McLoone* and D . Tomás Wa d*
*Depa men o Elec onic Enginee ing, ^Depa men o Compu e Science
Na ional Uni e si y o I eland Maynoo h
Maynoo h, Co. Kilda e
I eland
E-mail: [email protected]
KEYWORDS
Dis ibu ed in e ac i e media, To que game engine, Time-
se ies da a analysis, Beha iou al modeling, S a is ical clien
p edic ion, Ne wo ked mul iplaye games, Dead- eckoning.
ABSTRACT
Dis ibu ed in e ac i e media such as ne wo ked mul iplaye
compu e games o e use s he oppo uni y o in e ac and
sha e expe iences wi hin a i ual en i onmen . Mo e o en
han no , hese in e ac ions a e equi ed o be pe o med in
eal- ime, a cons ain which poses p oblems gi en he
unde lying ne wo k capabili ies used o ansmi in o ma ion.
In hese eal- ime dis ibu ed sys ems, he amoun o
in o ma ion ha needs o be sha ed be ween pa icipan s in
o de o main ain comple e game-s a e ideli y is oo la ge.
As a esul , ade-o s mus be made o e wha in o ma ion
equi emen s a e necessa y o main ain a le el o consis ency
ha will p o ide adequa e quali y o in e ac ion o he use s.
One possible solu ion o his p oblem is he use o s a is ical
modeling echniques ha a emp o cap u e he indi idual
beha iou o sys em use s. These models can hen be used o
p edic he likely u u e beha iou o he use s, hus
educing he sha ed in o ma ion equi emen s. In his pape
we p esen some p elimina y analysis o he beha iou o
use s wi hin a dis ibu ed in e ac i e applica ion, wi h a goal
owa ds u u e wo k o a emp ing o de elop and inco po a e
s a is ical models o use beha iou o he pu pose desc ibed
abo e.
INTRODUCTION
Dis ibu ed in e ac i e media (DIM) such as ne wo ked
mul iplaye games a e p one o quali y-o -in e ac ion and
scalabili y p oblems as a consequence o non-ideal
communica ion in as uc u e cha ac e is ics such as ne wo k
la ency and bandwid h. This well-known p oblem is
gene ally deal wi h h ough ca e ul en i y s a e upda e
p ocedu es ha il e he game-s a e based on c i e ia such as
clien ele ancy o s a e changes. An example o he o me
is a ea-o -in e es echniques (Singhal 1999) while examples
o he la e a e del a-comp ession (Van Hook e al. 1994)
and dead- eckoning (IEEE 1993). In addi ion QoS
echniques a e some imes used o ensu e ha all pa icipa ing
clien s a e gi en su icien ne wo k esou ces o mee quali y-
o -in e ac ion c i e ia (In e ne 2 2004). The communica ion
o game s a e changes is he key issue in all o he abo e and
he games indus y-s anda d echniques a e based chie ly on
a ian s o dead- eckoning, which is an example o an en i y
s a e ex apola ion mechanism. Ra he han upda ing en i ies
o e he ne wo k once pe simula ion loop (which we will
e e o as he game loop) all clien s in he DIM main ain a
local model, usually a linea ex apola ion, o en i y
dynamics. This model is only upda ed when he clien
esponsible o he en i y de e mines ha he di e ence
be ween he ue en i y s a e and ha o he model as used by
all o he clien s has de ia ed by some p e-de ined h eshold
amoun . Only his upda e hen needs o be ansmi ed o all
he pa icipa ing clien s hence educing he numbe o
packe s equi ed o main ain a ole able ideli y ac oss he
DIM.
Such a echnique ob iously helps educe bandwid h
equi emen s and he e o e aids in scalabili y. Mo e sub ly i
also aids in he educ ion o communica ion la ency, one o
he key ac o s in main aining a high quali y o in e ac ion o
he use . This is appa en i we look a he indi idual
componen s which make up la ency in dis ibu ed in e ac i e
media o any pa icula link be ween wo pa icipa ing
clien s i and j :
ij
ij
ij
cij O
B
K++=Τ
τ
(1)
whe e K ep esen s he gene a ion a e o s a e in o ma ion
du ing he global gameloop in bi s pe second and B is he
bandwid h o he link o he pa icula clien in ques ion. τc
ep esen s he physical p opaga ion delay. O ep esen s all
o he p ocessing o e heads. Ob iously h ough an inc ease in
link bandwid h o a educ ion in K he la ency can be
educed. I is h ough such in o ma ion a e educ ion
echniques such as in dead- eckoning ha la ency p oblems
can be deal wi h in DIM.
Recen ly in an a emp o u he imp o e he powe o en i y
s a e upda e mechanisms using he concep o s a e
ex apola ion, a echnique known as he hyb id model
app oach has been p oposed (Delaney e al. 2003). This
concep is e y powe ul and ye qui e simple. In his
pa adigm en i y s a e a e ex apola ed based on a
combina ion o low o de sho e m ex apola ion and longe
e m s a is ical in e ence. Essen ially he echnique elies on
ex apola ing s a e changes based on p e ious examples o
s a e beha iou in simila ci cums ances. In he absence o
good in o ma ion on ypical s a e changes o an en i y, he
model is swi ched o simple low o de ex apola ion as in
dead- eckoning. By swi ching be ween he wo models,
hence he e m hyb id model, en i y s a es can be
ex apola ed u he han cu en ly possible unde dead-
eckoning and o he en i y s a e ex apola ion schemes.
Fu he , in he absence o good s a is ical in o ma ion, long-
© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
e m heu is ic models can be used in lieu as p o ided by he
DIM designe . Consequen ly he echnique has supe io
pe o mance o dead- eckoning alone as demons a ed in
(Delaney e al. 2003). Howe e o he echnique o ealize
i s po en ial in he ield o DIM i is impe a i e ha
echniques and me hods should be de eloped o i s o all
ecognize, and second o all ep esen , such s a is ical
models. All wo k in his a ea so a has concen a ed on
demons a ing he concep o ixed s a is ical spa ial models
ha na u ally a ise ou o s a ic na iga ion asks in ypical
DIAs (Ma shall 2004). We a e cu en ly s udying he
possibili y o au oma ic ecogni ion o s a is ically simila
beha iou among en i y dynamics in impo an classes o
DIM.
In a p e ious pape we ha e shown ha pa e ns o beha iou
eme ge o human-human in e ac ion in such DIM (McCoy
2004). Howe e , in an a emp o b idge he mo e solid
s a is ical ca ego iza ion ha a ose ou o ixed spa ial
models wi h such pa e ns, an in e media e s udy has been
conduc ed in which he eac i e coupling be ween human
agen s has been loosened h ough he in es iga ion o
in e ac ion be ween human use s and ini e-s a e machine-
d i en agen s (BOTS). This pape epo s on wo k done on
his a ea so a in explo ing such human use beha iou in
hese mul iplaye compu e games. I is hoped ha h ough
he analysis o such beha iou ha ca ego iza ion can be
de e mined wi h he goal in mind ha s a is ically simila
pa e ns o beha iou can be ecognized and ul ima ely
exploi ed o p edic u u e beha iou in o de o p e-emp
games a e changes ahead o ime and so educe la ency
p oblems in such DIM h ough bo h upda e packe a e
educ ion and pe haps p e-emp i e ansmission.
TEST ENVIRONMENT AND TEST SCENARIOS
We use he To que Game Engine om Ga ageGames
(Ma shall 2004) o cons uc simple es en i onmen s and
es scena ios. This allows us o pe o m expe imen s in a
ela i ely con olled manne , and p o ides us wi h he abili y
o eco ding in o ma ion. Du ing a use ’s in e ac ion wi hin
he es en i onmen , a ious da a is ime-s amped and
collec ed in a log ile o subsequen analysis. Fi s ly, 3-
dimensional posi ional da a o each use is eco ded a
egula sampling in e als (a he a e o a leas 1 He z, bu
usually highe ), allowing us o econs uc a use ’s posi ional
s a e o e ime wi h espec o ha o ano he use and any
e en s ha occu . This posi ional da a is ep esen ed as ime-
se ies da ase s o analysis, examples o which can be seen in
he esul s and da a analysis sec ion. Secondly, di ec
in e ace con ol in e ac ions (i.e. keyboa d and mouse bu on
p esses) pe o med by he use o con ol hei playe
onsc een a e ime-s amped and eco ded whene e hey
occu ( his consis s o p ima ily mo emen and weapon i ing
ins uc ions). This allows us o econs uc a use ’s con ol
sequence o ac ions wi h espec o any e en s ha occu .
Gi en he limi ed complexi y o ou es en i onmen
desc ibed below, he only e en s which we a e conce ned
wi h he e a e bo h weapon i ing e en s and disabled e en s
(whe e one use is disabled by weapons i e om ano he ),
and hese a e eco ded and ime-s amped when hey occu .
The es en i onmen ha we used o he expe imen s
epo ed in his pape is a simple enclosed en i onmen
consis ing o se e al building and owe like s uc u es along
wi h se s o ees and ocks. These p o ide some isual
s imula ion o he use s and also helps obscu e hei iew in
ce ain a eas, o cing hem o mo e abou . The expe imen s
a e pe o med in he s yle o a Fi s -Pe son Shoo e (FPS)
game, whe eby use s in e ac wi h he en i onmen as hough
hey we e looking h ough he eyes o hei playe (see Figu e
1). FPS games a e one o he mos popula gen es o games
cu en ly in he ma ke , and hei ne wo ked mul iplaye
capabili ies make hem on ob ious choice o esea ch in o
dis ibu ed in e ac i e sys ems in gene al.
Figu e 1: In-game sc eensho o he es en i onmen .
Tes Scena io 1
This was a simple es scena io se up wi h he in en ion o
analyzing he beha iou o a use owa ds a pseudo-dynamic
goal. A he beginning o he game, he use is spawned
andomly inside one o he buildings. In addi ion, a compu e
con olled opponen ( ypically e e ed o as a ‘bo ’) is
spawned andomly a one o he p ede ined pa hnodes ha
we e placed be o ehand h oughou he en i onmen . These
pa hnodes join oge he o o m a pa h ne wo k, and his pa h
ne wo k is a e sed by he bo pa hnode-by-pa hnode (a
ep esen a ion o his pa h ne wo k can be seen below in
Figu e 2). The bo is se on a looping un so ha all i does is
cons an ly ollow he pa h o e and o e again – no a i icial
‘ hinking’ o eac ing occu s o he bo . The goal o he use
in his case is o disable he bo a speci ied numbe o imes
using hei weapon be o e he speci ied ime-limi uns ou .
The use is encou aged o sco e as high as possible o e a
numbe o uns such ha mo e ypical ocused beha iou is
exhibi ed a he han ca e ee wande ing h ough he
en i onmen . This is so as o eplica e he ypical condi ions
unde which FPS games ope a e. Typical beha ou ial
pa e ns we would expec o see should be a ge seeking,
pu sui and i ing ac ion. Such classes o beha iou a e use ul
labels (albei no always clea ly dis inguishable) and ha e
been applied wi h some success in ou p e ious wo k
(McCoy 2004).
© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
Figu e 2: Pa h ne wo k used o na iga ion by he bo .
Tes Scena io 2
This es scena io was se up wi h he in en ion o analyzing
he use ’s beha iou owa ds a bo ha had limi ed eac i e
capabili ies owa ds hei own ac ions, namely he abili y o
i e i ’s own weapon and damage he use . I was se up in
exac ly he same manne as desc ibed o es scena io 1,
wi h he excep ion ha he bo is gi en a senso ield ha can
be used o de ec he p esence o he use . I he use comes
wi hin he bo ’s senso ield and wi hin di ec line-o -sigh
(LOS) o he bo , he bo is ins uc ed o i e i ’s weapon in
he di ec ion o he use . I he use goes ou o LOS o he
bo o ou o i ’s senso ield adius, hen he bo is ins uc ed
o s op i ing i ’s weapon. The mo emen capabili y o he
bo is ixed as in es scena io 1, meaning ha i ne e
de ia es i ’s posi ion o o he pa h ne wo k on which i
na iga es h ough he en i onmen , ega dless o whe he i is
cu en ly i ing i ’s weapon a he use o no . Again, he goal
o he use in his case is o disable he bo a speci ied
numbe o imes be o e he ime-limi is eached. Unlike es
scena io 1 howe e , i was now possible o he bo o win
he game by disabling he use he speci ied numbe o imes.
The mo i a ion o his es scena io is o de e mine i any
esul an de ensi e o e asi e beha iou can be ecognized in
addi ion o hose beha iou s s a ed o he p e ious scena io.
RESULTS AND DATA ANALYSIS
In his sec ion, we shall p esen a speci ic selec ion o esul s
aken om da a ha was collec ed o use s o a ying
‘expe ise’ wi h ega d o no only his pa icula es
en i onmen , bu also wi h compu e games in gene al and
FPS speci ic games. Each use was asked o play a numbe o
successi e games in each es scena io, and hey we e gi en a
speci ic sco e ha hey had o each o comple e he game.
Tes Scena io 1
Figu es 3-5 below p esen s a e da a o e ime o se e al
di e en use s o a ying abili y. In each igu e, he i s 3
subplo s p esen posi ional da a o he use (Playe 1) and
he bo (Playe 2), and a e b oken in o x, y and z coo dina es
and plo ed sepa a ely. O e laid on each o hese a e solid
e ical lines ep esen ing each poin in ime whe e he use
disabled he bo , and hese lines allow us o segmen he da a
in o pa i ions. The inal subplo wi hin each igu e uses solid
e ical lines o ep esen each poin in ime whe e he use
i ed hei weapon. In Figu es 9-11, we ha e plo ed he
ela i e posi ion o he use wi h espec o he bo (i.e. aking
he bo ’s posi ion as he o igin o each ime-s ep). Each o
he da a pa i ions a e plo ed indi idually, wi h a da k ci cle
ep esen ing he s a ing posi ion o he use , and a da k ‘x’
ma king hei end posi ion (i.e. when hey disabled he bo ).
F om isual inspec ion o Figu e 3 (no ice use ), we can see
se e al a eas whe e he posi ional da a o he use and he bo
seem o co ela e highly, wi h one essen ially ‘ ollowing’ he
o he one. This co esponds o a pu sui s a egy, whe e he
use has ound he bo and is now pu suing hem wi h he
in en ion o disabling hem ( om ime 50 o 100 o
ins ance). I is in e es ing o no e ha his is less p onounced
in he da a o he ad anced and expe use . The p ima y
eason o his is ha hese use s end o wai in a cen al a ea
and le he bo come o hem a he han engage in pu sui ,
due o he ac ha hey o en quickly lea n he ixed
mo emen pa e n o he bo along he pa h ne wo k. As a
esul , hei mo emen pa e ns end o display signi ican ly
less a ia ion han ha o he no ice use . Also, hey end o
ake less ime disabling he bo han less expe ienced use s.
This is e iden om he shoo ing e en s seen in each igu e,
whe e we see ha he no ice use ends o i e hei weapon
in la ge sp eads, while he mo e ad anced use s i e sho e ,
accu a e bu s s ha end o disable he bo quickly, as
e idenced by he co ela ion be ween he shoo ing e en s and
disabled e en s. Ob iously i he bo had lea ning beha iou
o was con olled by ano he expe use such a ixed s a egy
would only p o ide sho - e m esul s, as Playe 2 would
soon adap o deal wi h his. Indeed i is his cons an
in e play be ween a ious s a egies in he human-human
case ha makes such online games bo h enjoyable o he
use and di icul o p edic o esea che s (McCoy 2004).
Ano he poin o in e es is he co ela ion o he dis ance
be ween use and bo , he i ing e en s o he use , and he
bo being disabled. In mos cases, we can see he posi ions
con e ging close oge he igh be o e he bo is disabled,
indica ing he use mo ing close owa ds he bo . This is
pa icula ly e iden om inspec ion o Figu es 9-11, whe e
we can see he con e gence o he use ’s ajec o ies ela i e
o he bo (whe e each ajec o y s a s as a da k ci cle and
wo ks i s way owa ds a da k ‘x’ ma ke ). This ag ees wi h
ou in ui i e no ion ha in o de o disable he bo quicke ,
we should ge close o hem (pa icula ly in his case whe e
he bo does no i e back). We also no ice he a iance in he
ajec o ies ha appea unde di e en ci cums ances. Fo
ins ance, long-winding ajec o ies ypically ep esen some
andom o wande ing ype beha iou o a use , whe eas
sho e mo e con e gen ajec o ies would o en ep esen
a ack- ype beha iou . O in e es a e he ajec o ies ha
appea o bo h di e ge and subsequen ly con e ge a he
sha ply. These o en ep esen cases whe e a use has
engaged he bo bu no disabled i , and ha ing lea ned he
bo s p edic able mo emen s a egy, chooses no o pu sue i
bu ins ead chooses o wai in a sui able a ea o ambush.
© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
Figu e 3: S a e da a o e ime o a no ice use .
Figu e 4: S a e da a o e ime o an ad anced use .
Figu e 5: S a e da a o e ime o an expe use .
Figu e 6: S a e da a o e ime o a no ice use .
Figu e 7: S a e da a o e ime o an ad anced use .
Figu e 8: S a e da a o e ime o an expe use .
© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
Figu e 9: T ajec o y o no ice use ela i e o bo .
Figu e 10: T ajec o y o ad anced use ela i e o bo .
Figu e 11: T ajec o y o expe use ela i e o bo .
Figu e 12: T ajec o y o no ice use ela i e o bo .
Figu e 13: T ajec o y o ad anced use ela i e o bo .
Figu e 14: T ajec o y o expe use ela i e o bo .
Tes Scena io 2
Figu es 6-8 below p esen s a e da a o e ime o use s o
a ying le el o abili y as in he p e ious sec ion. Howe e ,
he e we ha e chosen o omi he z posi ional da a subplo in
a ou o a subplo showing he 3-dimensional Euclidean
dis ance be ween he use and he bo a each ime s ep. As
be o e, he i s wo subplo s o each igu e ep esen he x
and y posi ional da a o bo h he use and he bo , o e laid
wi h disabled e en s o bo h (unlike he las sec ion, which
only showed disabled e en s o he bo ). Finally, he las
subplo shows shoo ing e en s o bo h use and bo (whe e
he shoo ing e en s o he use a e abo e he cen e line and
he shoo ing e en s o he bo a e below he cen e line).
Figu es 12-14 p esen plo s o he use ’s posi ion ela i e o
he bo o each imes ep, as de ailed in he p e ious sec ion.
F om inspec ion o he plo s, we can see ha in gene al he
dis ance be ween he use and he bo ends o con e ge
be o e a disabled e en occu s, implying he use mo ing
close o he bo in an a emp o inc ease hei chances o
disabling i . This is again e iden om he plo s o use
ajec o ies ela i e o he bo (Figu es 12-14), whe e we can
see he con e gence o he ajec o ies (al hough in he case
o he expe use , i is less p onounced). These disabled
e en s p o ide na u al pa i ions o he da a due o he
andom espawning o a playe wi hin he en i onmen a e
hey a e disabled, leading o jumps in he posi ional s a e
( andom espawning is a e y common sys em used in FPS
game in gene al). In he case o he no ice use (Figu e 6),

© IJIGS/Uni e si y o Wol e hamp on/EUROSIS
we end o see less o he pu sui s a egy ha was so
p ominen o es scena io 1 (Figu e 3). This is qui e e iden
om he subplo showing shoo ing e en s, whe e we see
bu s s o i ing sp ead apa , indica ing mo e apid
engagemen s be ween use and bo a he han p olonged
pu suing. Pa o he eason o his is ha because he bo
now has he abili y o i e back, use s a e much mo e
cau ious abou how hey app oach he bo , and o en like o
hide behind co e and a emp o ‘ambush’ he bo as i
na iga es along i ’s pa h ne wo k. I is in e es ing o no e he
a ia ion in dis ance be ween use and bo o he case o he
expe use , whe e we can see an ex ended pe iod o ime
( om 50 seconds onwa ds) du ing which dis ance con e ged
bu subsequen ly di e ged, coupled wi h a easonably high
deg ee o shoo ing e en s. This would indica e ha he use
engaged he bo and subsequen ly b oke o hei a ack, bu
did no engage he bo in di ec pu sui . Ra he , ha ing
lea ned he bo ’s mo emen pa e n, hey mos likely wai ed
o he bo o e u n on i s cou se and hen e-engage i , a
which poin hey inally disabled he bo . This is consis en
wi h he esul s shown in Figu e 14, whe e we can obse e
he di e gence o he use ’s ajec o ies coupled wi h he
subsequen con e gence, indica ing a sec ion o ime ha
mos likely in ol ed mul iple pe iods o in e ac ion be ween
use and bo . Also e iden is he ac ha he end poin s o
he expe use ’s ajec o ies (ma ked by da k ‘x’ poin s)
ha e a highe sp ead as opposed o bo h he no ice and
ad anced use s (Figu es 12 and 13 espec i ely) – his would
indica e g ea e accu acy on he pa o he expe use a
disabling he bo wi h his weapon.
CONCLUSION
F om he esul s al eady shown o a numbe o use s i is
clea ha ce ain pa e ns o beha iou do eme ge. In bo h
es scena ios i is ha co ela ed dynamical beha iou can
occu indica ing ha he espec i e en i y s a es canno be
s a is ically independen . In in ui i e e ms his means o
example ha i he a ge playe changes eloci y
d ama ically i is o en he case ha he pu suing playe will
do likewise. This a he ob ious obse a ion could be
exploi ed in en i y s a e ex apola ion h ough p edic ing such
changes whe e he con en ional pa adigm o dead- eckoning
would ha e had o ansmi a packe indica ing a eloci y
change. I may e en be possible o p eemp shoo ing e en s
which con en ional echniques ha e no possibili y o
p edic ing. In ano he s ep owa ds modeling he human-
human in e ac ion ha is so impo an in DIM ano he
in e media e s ep will be aken in which he bo can exhibi
mo e human-like beha iou . This can be as simple as a
hun ing and pu sui beha iou whe e he bo ha ing spo ed
Playe 1 will a emp o close he dis ance be o e a emp ing
o disable he opponen . Such beha iou should elici mo e
in e es ing de ensi e o e asi e beha iou in he human use
ha will be impo an o analyze. Fu he analysis along
hese lines should yield insigh , ools and esul s ha will
allow be e and mo e comp ehensi e analysis o human
use s in e ac ing in he same en i onmen s. Consequen ly i
will be possible o make be e guesses abou wha such use s
may do nex and hence achie e quali y o in e ac ion and
scalabili y bene i s o he dis ibu ed case.
ACKNOWLEDGEMENT
This ma e ial is based upon wo ks suppo ed by En e p ise
I eland unde g an no. SC/2002/129/.
REFERENCES
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BIOGRAPHY
Aa on McCoy ecei ed his B.Sc. deg ee om he Na ional
Uni e si y o I eland, Maynoo h in 2002, specializing in
compu e science and heo e ical physics. His main a eas o
in e es a e dis ibu ed sys ems, ne wo ked i ual
en i onmen s and he use o a i icial in elligence in
in e ac i e games. He is cu en ly s udying o his PhD a
NUI Maynoo h in he a ea o use modeling in Dis ibu ed
In e ac i e Applica ions.