Streaming Stored Video Over Multi-Channel Wireless Systems: Scheduler Performance Evaluation Ms. Sahar Ebadinezhad Mr. Keivan Bahmani (presenter) Assoc. Prof. Dr. Doğu Arifler Assoc. Prof. Dr. Erhan A. İnce Eastern Mediterranean University 9/20/2018

Outline : Introduction OFDMA-Based Systems Schedulers Multi-User, Multi-Channel Wireless Systems MPEG-4 Traffic Model and LRD Performance Evaluation Conclusions Future Work References

4G and OFDMA WiMaX LTE

IEEE 802.16e Frame 9/20/2018

Multi-user Concept in OFDMA OFDM Symbol n+1 OFDM Symbol n OFDM Symbol n+2 Subchannels 9/20/2018

Scheduling Disciplines: Frequency Selective Scheduling (User Diversity) Frequency Diverse Scheduling (Frequency Diversity) 9/20/2018

Multi-User, Multi-Channel Wireless Systems 𝑄 𝑖 𝑡+1 = 𝑄 𝑖 𝑡 − 𝑗=1 𝐾 𝑋 𝑖𝑗 (𝑡)𝑌 𝑖𝑗 (𝑡) + + 𝐴 𝑖 (𝑡) 𝑎 + =max⁡(𝑎,0) 𝑖 𝑌 𝑖𝑗 𝑡 ≤1 9/20/2018

i.i.d ON-OFF random variable Wireless Channel i.i.d ON-OFF random variable in each time slot to model fading [2] 9/20/2018

Frequency Selective Scheduling: Evaluated Algorithms: Round Robin Scheduling (RR) Maximum-Throughput Scheduling (MT) Maximum-Weight Scheduling (MW) 9/20/2018

Round Robin (RR) Channel-unaware Fairest low complexity 9/20/2018

Maximum-Throughput (MT) Channel-aware Allocating each subchannel Maximizing the over the air throughput Starving users with bad channel 9/20/2018

Maximum-weight Scheduling: The allocation is made by selection of the user with the largest weight. Weight =( 𝑋 𝑖𝑗 (𝑡) 𝑄 𝑖 (𝑡)) 𝑋 𝑖𝑗 𝑡 : 𝑎𝑐ℎ𝑖𝑒𝑣𝑎𝑏𝑙𝑒 𝑑𝑎𝑡𝑎 𝑟𝑎𝑡𝑒 𝑜𝑛 𝑗𝑡ℎ 𝑠𝑢𝑏𝑐ℎ𝑎𝑛𝑛𝑒𝑙 for i th user 𝑄 𝑖 𝑡 : queue length of i th user 9/20/2018

Synthetic Video Traffic : MPEG-4 Traffic with IBBPBBPBBPBB GOP and 25 frame/sec Exhibiting Long-Range Dependence (LRD) Predominant video format for YouTube over Wireless Mobile Networks ( Itag 17 )[5] 9/20/2018

Synthetic Video Traffic : Scene Length Geometric (p=0.098) I-frame Size Lognormal(μ=9.65, σ=0.44) P-frame Size Lognormal(μ=8.90, σ=0.68) B-frame Size Lognormal(μ=8.59, σ=0.69) AR(2) model parameters [4] 𝑎 1 =0.39, 𝑎 2 =0.15, σ 𝑒 =4.36 9/20/2018

Stability comparison among RR, MT, MW Schedulers (K=20, q=0.5, R=50 bytes/slot.) 9/20/2018

Effect of channel (K=20, N=4, R=50 bytes/slot .) Note that for the channel on-probability in the range between 0.5-0.7 there is a big difference between channel-aware and channel-unaware schedulers. 9/20/2018

Effect of Traffic Shaping Max-Weight scheduler, Changing Inter-arrival time from 40-ms to 10-ms (K=20, N=4, q=0.5, R=50 bytes/slot.) 9/20/2018

Conclusion: Performance of three scheduling algorithms (RR, MT, MW) has been evaluated for streaming stored video over multi-user, multi-channel wireless systems. Adapting a traffic shaping mechanism in the source video server can greatly decrease the amount of lost bytes and I-frames in a finite buffer size scenario. When the system is unstable with 5 users, the buffer occupancy with ON/OFF sources is about 1 megabyte (MB) less than that with MPEG sources For channel on-probabilities in the range between 0.5-0.7 using a channel-aware scheduler will provide much lower mean queue length in comparison to a that of channel-unaware schedulers. 9/20/2018

Future work A more realistic channel can be adapted to make the results more appropriate for use in practice. More complex scheduling algorithm such as SSG can be evaluated under the same condition. 9/20/2018

Thank you for your attention 9/20/2018

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