QoS-Guaranteed Scheduling and Resource Allocation Algorithm for IEEE 802.16 OFDMA System

1. QoS-Guaranteed Scheduling and Resource Allocation Algorithm for IEEE 802.16 OFDMA System ICC 2008 ICC 2008 Xinning Zhu1, Jiachuan Huo2, Xiaoxi Xu2, Chunxiu Xu2, Wei Ding1 School of Continuing Education1, School of Telecommunication Engineering2 Beijing University of Posts and Telecommunications

2. Outline • Introduction • System Module • Proposed Scheduling and Resource Allocation Algorithm • Simulation Results • Conclusions

3. Introduction • Five classes of scheduling services are defined in IEEE 802.16: • Unsolicited Grant Service (UGS) • Real-Time Polling Service (rtPS) • Extended rtPS (ertPS) • Non-Real-Time Polling Service (nrtPS) • Best Effort (BE)

4. Introduction • Efficient methods for QoS support in • IEEE 802.16 system • Deploying Wireless-OFDMA physical layer • In the OFDMA system, resources are scheduled in • Frequency • Time • Power domains

5. Introduction • A user scheduling priority function for each active user and update it dynamically depending on each • User’s subchannel quality • Quality deviation on subchannels • Its connection’s QoS satisfaction

6. FFT sizes 2048 1024 512 128 Total number of data subcarriers(Ndata) 1536 768 384 96 System Module • Adaptive Modulation and Coding (AMC) Single BS BS SS1 SS2 SSN N SS

7. System Module • Nine adjacent subcarriers form a bin which includes • 8 data subcarriers • 1 pilot subcarrier • An AMC slot is defined as • Nbinbins by Msymsymbols • Where Nbin × Msym= 6 • A basic allocation unit consists of • 48 data subcarriers

8. System Module • Whole bandwidth can be divided into • K = Ndata/Nbinsubchannels • A downlink subframe consists of • subsequent M OFDMA symbols • Where M is a multiple of Msym

9. System Module • Focus on the downlink scheduling problem • Assume that BS has knowledge of • All subchannels of all users in the system • Wireless channel is constant over an entire downlink OFDMA subframe • Do NOT consider UGS and ertPS • UGS and ertPS connections are given the highest priority and allocated fixed slots first

10. Subchannel k Priority User i ProposedScheduling and Resource Allocation Algorithm • A. Determination of Scheduling Priority Cidenotes the QoS satisfaction indicator of user i Sikis a variable reflecting current channel state

11. Quantifies the normalized channel quality ProposedScheduling and Resource Allocation Algorithm • A. Determination of Scheduling Priority bikdenotes the information bits that can be carried (as indicated in Table I) bimaxdenotes the maximum number of bits of user i on all subchannels bmaxeachsubcarrier can be loaded to at most bits per symbol when the most efficient AMC mode is selected

12. ProposedScheduling and Resource Allocation Algorithm bikdenotes the information bits that can be carried bimaxdenotes the maximum number of bits of user i on all subchannels

13. ProposedScheduling and Resource Allocation Algorithm • Maximum connection priority of user Cijdenotes the QoS priority of connection j, which belongs to user i

14. ProposedScheduling and Resource Allocation Algorithm

15. ProposedScheduling and Resource Allocation Algorithm • For rtPS connection j of user i, the QoS priority Cijis defined as βrtPS∈[0, 1] is the rtPS-class coefficient as defined in [4] Wijdenotes the longest packet waiting time of the connection j of user i Tijis the maximum latency which is negotiated when the connection j is established Tframe is the frame duration

16. ProposedScheduling and Resource Allocation Algorithm

17. ProposedScheduling and Resource Allocation Algorithm • For nrtPS connection j of user i, the QoS priority is defined as Qijdenotes the current number of bytes in the queue of connection j of user i ϕijis the queue thresholds set to obtain the fill level indicator of the queue using the ratio Qij /ϕij

18. ProposedScheduling and Resource Allocation Algorithm • B. Resource Allocation • Define the normalized channel quality deviation of subchannel k as follows bkmaxis the maximum number of bits that can be carried by one subcarrier in one OFDMA symbol on subchannel

19. ProposedScheduling and Resource Allocation Algorithm • B. Resource Allocation

20. ProposedScheduling and Resource Allocation Algorithm • The number of information bits should be sent can be expressed as • during the frame m + 1 for connection j of user i

21. ProposedScheduling and Resource Allocation Algorithm • The number of information bits allocated to rtPS connection j of user i is given by • The number of OFDMA symbols needed to carry Δij(m+ 1) information bits on subchannel k equals to Δ’ij(m+1) denotes the total bits of packets from the head of line to the finding packet ^

22. Simulation Results • A time-varying and frequency-selective channel model, ITUPedestrian A multi-path model, is used

23. Simulation Results • A. Case 1: Multiple users with multiple rtPS connections each Set the data buffer large enough that any packet drop will occur only when it fails to meet the latency requirement

24. Simulation Results

25. Simulation Results • B. Case 2: Multiple users with multiple nrtPSconnectionseach

26. Simulation Results

27. Simulation Results

28. Simulation Results • B. Case 3: Multiple users with one rtPS, one nrtPS and oneBE connection each

29. Simulation Results

30. Simulation Results

31. Conclusions • This paper developed an efficient scheduling and resource allocation algorithm • for multiple connections with diverse QoS requirements • which can be used in IEEE 802.16 OFDMA system • This paper scheduled • the user with the highest priority first • allocated the resource to the connection with the highest QoS priority

32. YOU THANK