Wimax standards and Security The Wimax

TABLE 4.2
QoS Scheduling Simulation
Light Traffic (λ = 2) Heavy Traffic (λ = 5)

	Comp. Jobs	Avg. bandwidth (bps)	Comp. Jobs	Avg. bandwidth (bps)
UGS	469	512	1164	512
rtPS	471	512	1197	510
nrtPS	505	512	1264	453
BE	494	512	677	15
100

80

%
60
40
20
0
Number of SSs = 100,  = 2, 10 min run


FIGURE 4.10
Simulation of channel utilization (light traffic).

• 
  Request profiles: equally distributed for UGS (25%), rtPS (25%), nrtPS(25%), and BE (25%).
  
• 
  
  ×
  Bandwidth per request: 8 64 Kbps. For UGS it is 100% MSTR. For rtPS/nrtPS it is 50% MSTR and 50% MRTR. For BE it is all MSTR. We ran the simulation for both fixed bandwidth and exponentially distributed bandwidth. The results presented are based on fixed bandwidth for ease of analysis.
  
• 
  Average data size per request: 250 KB (exponential distribution).
  
• 
  Simulation run: 10–20 min.
  

The results of the simulation are illustrated in Table 4.2, Figure 4.10 (light traffic), and Figure 4.11 (heavy traffic). We observe that during the light traffic load, each traffic class receives almost the same bandwidth allocation. During


100
90
80
70
60

%
50
40
30
20
10
0
Number of SSs = 100,  = 5, 10 min simulation run


FIGURE 4.11
Simulation of channel utilization (heavy traffic).

the heavy load, only the UGS class is able to maintain the same performance level. For rtPS and nrtPS, they maintain the level of MRTR. The BE class receives very little bandwidth allocation from the BS. This simulation results conform to the expected behavior of WiMAX QoS, and are consistent with other studies in the literature [12,13].

4. 
   Conclusions
   

This chapter presents the concept and requirements of QoS as specified in the IEEE 802.16 standard, along with an architecture to implement QoS in a sim- ulation model. As presented in this chapter, the QoS requirements specified in IEEE 802.16 are similar to ATM QoS, and the QoS procedure is based on poll/grant that is similar to PCF of 802.11. The support of QoS is essential for BWA because service providers can use it to offer differentiated services. The IEEE 802.16 standard does not provide the details of admission control and QoS scheduling, and this chapter fills the gap to implement a solution for it. Another contribution of this chapter is the development of a simulation model. The results from simulation conform to the expected behavior of QoS as specified in IEEE 802.16 and are consistent with other studies.

4. 
   Acknowledgments
   

This research project is partially supported by the Quality Instruction Council (QIC) grant of DePaul University. The author would like to thank ISP, Inc.

at British Columbia, Canada for its generous donation of a high-capability Linux server that is used for the simulation of this project.

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5

Propagation and Performance