Author: Aamir Mahmood Supervisor: Prof. Riku Jäntti
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Transcript of Author: Aamir Mahmood Supervisor: Prof. Riku Jäntti
Performance Evaluation of WLAN for Mutual Interaction between Unicast and
Multicast Communication Session
Author: Aamir Mahmood
Supervisor: Prof. Riku Jäntti
Wireless Local Area Networks
IEEE802.11 family of standards Maturity of standard, low cost infrastructure, operation
in unlicensed band Simple standalone infrastructure Extensions to existing networks (WiMax, TETRA) Providing access for high speed data and multimedia
services
Growing interest in outdoor operation of IEEE802.11
WLAN for Real-Time Services
Primary objective - asynchronous (data) services Case: A realistic network with multiple wireless
technologies complementing each other Requirement: Support for data and real-time services Challenges:
Uncontrolled and unreliable propagation environment Stringent Quality of Service (QoS) requirements Performance and scalability constraints of MAC algorithm
Thesis Contribution
WLAN evaluation by simulations under mutual interaction of unicast and multicast real-time sessions
Extending the isolating study of unicast and multicast sessions
Evaluation Steps: Designing a prototype for simulator verification (PHY and MAC
parameters, backoff time distribution, collision probability)
Mobility with a proposed model
Optimal size of WLAN cell, suitable for unicast and multicast sessions under TWO-RAY propagation model
Test bed and Simulator
Test environment concerns Modifications in system parameters Reliability and reproducibility of the results
Test bed Open Source Components: operating system, WLAN adaptor drivers,
real-time traffic emulation software, traffic monitoring and sniffing
Simulator Qualnet 4.0 – Reliable and comprehensive modeling / simulation Signal reception model IEEE 802.11 PHY layer Propagation model IEEE 802.11 MAC layer
Prototype Design for Simulator Verification - I
Monitoring Station
Node 1
Node 2
Var. Attenuator 40 dB
Access Point (AP)
30 dB
30 dB
RF Cable
Ethernet Cable
Maximum aggregate throughput
for two nodes with UDP flooding
Constant propagation environment
Measure the collision probability Two nodes sharing the equal
throughput
Testbed vs Simulation Throughput - II
100 300 500 700 900 1100 1300 14721
2
3
4
5
6
6.71
UDP Payload
Thr
ough
put (
Mbp
s)
simulatortestbed
100 300 500 700 900 1100 1300 14720.6
0.7
0.9
1.1
1.3
1.5
1.71
UDP Payload
Thr
ough
put (
Mbp
s)
simulatortestbed
@11Mbps @2Mbps
Collision Probability - III
Nodes Simulated collision probability
Simulated average backoff
Analytical average backoff
2 0.0318 16.0603 16.0423
3 0.0605 16.8147 16.5878
4 0.0867 17.1745 17.1213
6 0.1439 18.2225 18.2999
8 0.1818 19.1257 18.9628
1 (1 )(1 (2 ) 1 (2 1)( ).
1 2(1 2 ) 2 2
m m m m m
avg k
W p p p W p pW
p p
*H.L. Vu and T Sakurai, “Collision probability in saturated IEEE 802.11 networks”, ATNAC Australian Telecommunication Networks and Applications Conference 2006
*
Group Mobility
The proposed mutual interaction of unicast and multicast sessions is well-suited for simultaneous one-to-one and group communication
The performance for the proposed joint flows is evaluated under a proposed group mobility model
The model maps the mobility of public safety cooperative activities
Proposed Mobility Model
The deployment of users towards a randomly selected hotspot area belonging to the cell
Uniform initial distribution Speed of the user is proportional
to the distance from the destination in the hotspot
The destination location of a user in hotspot is also uniformly distributed
Statistical Analysis - I
0 0.5 1 1.5 20
0.005
0.01
0.015
Distance (units)
Vel
ocity
(uni
ts/s
)
0.005 0.006 0.007 0.008 0.009 0.01 0.011 0.012 0.013 0.014 0.0150
20
40
60
80
100
120
140
160
180
Velocity (units/s)
Velocity as a function of distance between the initial and final position
PDF of initial speed distribution
Rc = 1 units, Ro = 0.1 units, Vmin = 0.005 units/sec
Vmax = 0.015 units/sec
Statistical Analysis - II
20 40 60 80 100 1200
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.01
Simulation time (s)
Inst
an
tan
eo
us
ne
two
rk s
pe
ed
(u
nits
/s)
Ro=0.1
Ro=0.5
-1-0.5
00.5
1
-1
-0.5
0
0.5
10
0.2
0.4
0.6
0.8
xy
pd
f
Instantaneous network speed as a function of the simulation time
Spatial distribution of the nodes
Mutual Interaction of Unicast and Multicast Communication Session
Scenario Single multicast VoIP session in the downlink direction Increasing number of unicast VoIP session in the uplink direction Effect of adding one unicast video feed in addition to the uplink VoIPs
Performance measurement How does the performance of multicast session is degraded and vice
versa?
Metrics Packet Deliver Ratio PDR
PHY and MAC parameters, traffic emulation VoIP: CBR G.711 with 10ms payload size (92 bytes/packet) Video: CBR 30ms payload size (360Kbps)
Simulation Setup
Cell radiuses2Mbps:Target SNR = 6dB Cell Radius =300m
11Mbps:Target SNR = 10dB Cell Radius =240m
Probability of hidden nodes
Carrier sensing range (534m)
Hidden node probability 3%
0 1 2 3 4 5 6 7 8 9 100
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
SNR (dB)
PE
R
2Mbps11Mbps
0 20 40 60 80 100 120 1400
0.005
0.01
0.015
0.02
0.025
0.03
Packet Delivery Ratio (PDR)
2 3 4 5 60.84
0.86
0.88
0.9
0.92
0.94
No. of unicast voice sessions
Mul
ticas
t voi
ce P
DR
11Mbps11Mbps - 1 video
2 3 4 5 60.84
0.86
0.88
0.9
0.92
0.94
No. of unicast voice sessions
Mul
ticas
t voi
ce P
DR
2Mbps2Mbps - 1 video
Delay
2 3 4 5 60
2
4
6
8
10
12
No. of unicast voice sessions
Mul
ticas
t voi
ce d
elay
(mse
c)
11Mbps 2 Mbps11Mbps - 1 video 2 Mbps - 1 video
2 3 4 5 60
2
4
6
8
10
12
No. of unicast voice sessions
Uni
cast
voi
ce d
elay
(ms)
11Mbps 2 Mbps11Mbps - 1 video 2 Mbps - 1 video
Final remarks
The degradation in performance can be concluded as For multicast session it is the low PDR For unicast sessions it is the increasing average delay
Future Work It is expected that the degradation would be severe in the presence
of fading It will be more appropriate to model the traffic instead of considering
the CBR type of traffic DCF vs PCF
The End
Questions?
Thank You!