Performance Evaluation of the IEEE 802.16 MAC for QoS Support

Aemen Hassaan Lodhi05060021Multimedia Communications Project (Spring 2006-07)

Outline

IEEE 802.16 (WiMAX) Project Objective Simulation Environment Performance Metrics Experiments Carried out Discussion of results Conclusion

IEEE 802.16 (WiMAX)

Wireless MAN – provides network access to subscriber stations (SS) with radio base stations (BS)

Offers an alternative to cabled access networks – fiber optic links, coaxial cables using cable modems, DSL links

Supports nomadic and mobile clients on the go (IEEE 802.16 e, 2004)

MAC layer

Manage the resources of the link air-link in efficiently and provide Quality of Service (QoS) differentiation for different connections/streams

Supporting Point to Multipoint and Mesh network models

Performing Link Adaption & ARQ functions Transmission Scheduling Admission Control Link Initialization Fragmentation and Retransmission

Project Objective

Verify via simulation the ability of IEEE 802.16 MAC to handle different types of traffic having different QoS requirements

The response of the protocol to different types of traffic and environments

Simulations of IEEE 802.16 on NS-2

Simulation Environment

NS 2 Simulator PMP mode Time Division Multiple Access mode for

transmission from SSs to BS Downlink and Uplink subframes duplexed

using Frequency Division Duplex Full Duplex Subscriber Stations

Simulator environment

Simulator Environment

Problems with Chang Gung University’s WiMAX Module

Couldn’t support more than 11~12 nodes when actual simulations were carried out

Generated Segmentation faults Even though the transmissions from source

nodes were cut-off the Base station continued to send traffic to receiver nodes!!

Problems with Chang Gung University’s WiMAX Module

WiMAX module by NIST, USA

Number of Nodes (the simulator crashes after 24 nodes) Traffic (CBR, Poisson ON/OFF source, Pareto ON/OFF source

to model web traffic, Real Audio, any mix of the above.) Radio Propagation models (2-Ray ground model for open/sub-

urban areas and Shadowing model for urban areas) Mobility of nodes Packet Sizes A number of parameters at the physical layer e.g. modulation

schemes Does NOT offer choice of scheduling mechanism at the MAC

layer. Only Best Effort Scheduler is available

Traffic Models

Constant Bit Rate Pareto ON/OFF source to model web traffic Voice over IP traffic

– Followed the specs of ITU G7.11– 64Kbps during talk spurt (fixed)– Average length of talk spurt 352 ms– Average length of silence period 650 ms

Videoconference traffic could not be run

Performance Evaluation

Throughput for different types of traffic %age utilization of bandwidth vs. Input load Packet loss rate for different traffic streams Comparison of the response of IEEE 802.16

with Best Effort Scheduler to different traffic streams and different environments

Packet loss rate vs. Number of Nodes CBR stream, Stationary nodes, 2Ray Ground

Packet loss rate vs. Number of Nodes Pareto ON/OFF source, Stationary nodes, 2Ray Ground

Packet loss rate vs. Number of Nodes Pareto ON/OFF stream, Stationary nodes, 2Ray

No. of mobile nodes Packets Sent Packets Received

1 24 22

3 72 66

5 120 110

7 168 154

9 216 192

11 264 242

13 312 286

15 360 323

17 408 368

20 480 429

24 576 516

Packet loss rate vs. Number of Nodes CBR stream, Mobile nodes, 2Ray

Packet loss rate vs. Number of Nodes Pareto ON/OFF stream, Mobile nodes, 2Ray

Packet loss rate vs. Number of Nodes CBR stream, Stationary nodes, Shadowing

Packet loss rate vs. Number of Nodes Pareto On/Off stream, Mobile nodes, Shadowing

Packet loss rate vs. Number of Nodes VoIP Traffic, Stationary nodes, 2Ray

Packet loss rate vs. Number of Nodes Traffic Mix (CBR + VoIP + Web)

CBR Stationary vs. Mobile Nodes

CBR, 2Ray Ground vs. Shadowing

Pareto On/Off source, 2Ray vs. Shadowing

CBR vs. Pareto throughput

Throughput (Mbps) vs. Number of nodes

Percentage Utilization of Bandwidth vs. Number of Nodes

Conclusions

Though utilization is high the standard with its current specifications (70 Mbps) will maximize its throughput at about 80 nodes.

Without a proper classification of streams at the base station the streams with stringent QoS will suffer great loss

With TDD polling mechanism the nodes generating traffic with stringent QoS requirements suffer a great deal

Packet loss rate vs. Number of Nodes Traffic Mix (CBR + VoIP + Web)

References

1. Claudio Cicconetti, Alessandro Erta, Luciano Lenzini, and Enzo Mingozzi, ‘Performance Evaluation of the IEEE 802.16 MAC for QoS Support’, IEEE Transactions on Mobile Computing, VOL. 6, No. 1, January 2007

2. Jenhui Chen , Chih-Chieh Wang, Frank Chee-Da Tsai§, Chiang-Wei Chang, Syao-Syuan Liu, Jhenjhong Guo, Wei-Jen Lien, Jui-Hsiang Sum, and Chih-Hsin Hung, ‘The Design and Implementation of WiMAX Module for ns-2 Simulator’, ACM International Conference Proceeding Series, Proceeding from the 2006 workshop on ns-2: the IP network simulator

3. F.H.P. Fitzek and M. Reisslein, “MPEG4 and H.263 Video Traces for Network Performance Evaluation,” IEEE Network Magazine, vol. 15, no. 6, pp. 40-54 Nov. 2001.

4. NS-2 reference manual5. ITU G7.11 specifications

References

“Radio Propagation Models”, Chapter 17, NS Documentation

P.M. Fiorini, “Voice over IP (VoIP) for Enterprise Networks: Performance Implications & Traffic

Models”.