mickposter nuim
TRANSCRIPT
IEEE 802.11 WLAN Capacity and Optimization forMultiplayer Network Games
Hanghang QiHamilton Institute, National University of
Ireland, Maynooth, [email protected]
David MaloneHamilton Institute, National University of
Ireland, Maynooth, [email protected]
Dmitri BotvichTSSG, Waterford Institute of Technology,
1 Problem define:network game within an WLAN
. . .
AP
CC C
S
λc λc λc
n
n(λc + λs)
nλs
Figure 1: How many players can play a good game within a 802.11WLAN?
2 Network games trafficWe did many experiments in our 4 PCs wireless game network testbed and gotthe game traffic in packet transmission level. The key characteristics are shownin Fig. 2
0 0.02 0.04 0.06 0.08 0.1 0.120
2000
4000
6000
8000
10000
12000
14000AtoS
interarrival time (s)
(a) Client to Server
0 0.02 0.04 0.06 0.08 0.1 0.120
50
100
150
200
250
300
350
400
450
500StoA
interarrival time (s)
(b) Server to Client
0 50 100 150 2000
500
1000
1500
2000
2500
3000
3500
4000
4500
5000AtoS
packet size (bytes)
(c) Client to Server
0 50 100 150 2000
100
200
300
400
500
600
700StoA
packet size (bytes)
(d) Server to Client
Figure 2: Quake 4 game traffic characteristics
3 802.11 network model and performanceIEEE 802.11 MAC DCF uses a CSMA/CA with exponential backoff schemewhich can be modelled with a 2-D Markov Chain.
... ... ... ...
... ... ... ...
0,0e 0,w0−1e1−q 1−q 1−q
0,1e 0,2e ...
0,0 0,w0−1
i−1,0
i,wi−1
0,1 0,2 ...1 1 1
1 1 1
1 1 1m,wm−1
i,0 i,1 i,2 ...
m,0 m,1 m,2 ...
...
1−p
1−p
1−p
1−p
q q q q
Figure 3: Markov chain model of 802.11 MAC
The Bianchi’s 2-D Markov chain model together with the traffic arrivalmodel are used to calculate the throughput, delay and jitter. Then Frank’s em-pirical mapping model is used to get Mean Opinion Score (MOS)from delayand jitter.
0 5 10 15 20 25 30 350
0.2
0.4
0.6
0.8
1
Number of stations
Thr
ough
put e
ffici
ency
stationsgame serverAP
(a) Throughput efficiency
0 5 10 15 20 25 30 350
0.002
0.004
0.006
0.008
0.01
0.012
0.014
Number of stations
Del
ay (
s)
stationsAPgame server
(b) Delay
0 5 10 15 20 25 30 350
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
Number of stationsJi
tter
(s)
stations
AP
game server
(c) Jitter
0 5 10 15 20 25 30 351.5
2
2.5
3
3.5
4
4.5
Number of stations
MO
S
DCF
(d) Mean Opinion Score
Figure 4: Performance of a basic 802.11 DCF network
4 AP and Server with larger TXOP nLarger TXOP, one of the 802.11e parameters, are given to AP and Server as nincreases (n is the number of clients; normal client’s TXOP is 1) to give APand Server larger transmission opportunity, the network performance can beimproved for the games.
0 5 10 15 20 25 30 350.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Number of stations
Thr
ough
put e
ffici
ency
game serverstationsAP
(a) Throughput efficiency
0 5 10 15 20 25 30 350
0.005
0.01
0.015
0.02
Number of stations
Del
ay (
s)game serverstationsAP
(b) Delay
0 5 10 15 20 25 30 350
0.01
0.02
0.03
0.04
0.05
Number of stations
Jitte
r (s
)
game serverstationsAP
(c) Jitter
0 5 10 15 20 25 30 351.5
2
2.5
3
3.5
4
4.5
Number of stations
MO
S
TXOP
(d) MOS
Figure 5: AP and Server priority with TXOP
5 ConclusionsOur analytical model suggests that a basic DCF 802.11b WLAN can supportmaximum 10 players of Quake 4. By using 11e parameter TXOP to give APand Game Server higher priority to access the channel, the network perfor-mance can be improved to 15 players.
References[Bianchi, 2000] Bianchi, G. (2000). Performance analysis of the ieee 802.11
distributed coordination function.Selected Areas in Communications, IEEEJournal on, 18(3):535–547.
[Cricenti and Branch, 2007] Cricenti, A. and Branch, P. (2007). Arma(1,1)modeling of quake4 server to client game traffic. InNetGames ’07, NY,USA. ACM.
[Wattimena et al., 2006] Wattimena, A. F., Kooij, R. E., van Vugt, J. M., andAhmed, O. K. (2006). Predicting the perceived quality of a first personshooter: the quake iv g-model. InNetGames ’06, NY, USA. ACM.