Opportunistic Fair Scheduling for the Downlink of 802.16WirelessMetropolitan Area Networks

Mehri Mehrjoo, Mehrdad Dianati, Xuemin (Sherman) Shen,

and Kshirasagar Naik

Department of Electrical and Computer EngineeringUniversity of Waterloo, Ontario, Canada

The Third International Conference on Quality of Service inHeterogeneous Wired/Wireless Networks(QShine’06)

Outlines

Introduction Opportunistic Fair Scheduling

Scheme Simulation Conclusion

Introduction_802.16(1)

Defines two transmission mode Point-to-MultiPoint (PMP) mode Mesh mode

PMP mode is designed for high rate transmission service with support

of various QoS Require all SSs to be with clear LOS

Introduction_802.16(2)

Four service flows have been defined ： Unsolicited Grant Service (UGS) Real-time Polling Service (rtPS) Non-real-time Polling Service (nrtPS) Best Effort (BE) service

Opportunistic Fair Scheduling Scheme_motive

an optimal scheduling policy is to transmit to SSs with the best channel quality at the maximum achievable rates in each scheduling interval and cause unfairness

a fairness mechanism is deployed to assign bandwidth to each SS according to its history of transmission and average channel quality

Opportunistic Fair Scheduling Scheme_(1)

Assume that can achieve a transmission rate of Shannon’s upperbound and there are N nodes

average power gain of the

channel

allocated power to SSjRj is the allocated rate to SSj

The total power budget

of the BS

Opportunistic Fair Scheduling Scheme_(2)nonlinear optimization

Opportunistic Fair Scheduling Scheme_(3)utility function

is the weighted minimum average rate

is the weighted maximum average rate

is the weighted rate

is the rate allocation vector

Rj is the allocated rate to SSj

=

Opportunistic Fair Scheduling Scheme_(3)utility function

+ +

Opportunistic Fair Scheduling Scheme_(3)utility function

Opportunistic Fair Scheduling Scheme_(4)the fair of scheduling

Fair share weight, denoted by ( ) as follows:

Approximately utility fair allocation :

Simulation_(1)

Simulation_(2)

Simulation_(3)

Simulation_(4)Gini fairness index

If I=0 ,mean perfect fairness

and are the long term average transmissionrate and the fair share weight of SSk

Simulation_(4)

Simulation_(5)

Conclusion

A fairness enforcement mechanism can maintain long term fairness and smooth service delivery

It takes advantage of the temporary variations of a fading channel to improve the overall throughput