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Audio Streaming over Bluetooth Scatternet: using Adaptive Link Layer

Audio Streaming over Bluetooth Scatternet: using Adaptive Link Layer. Team members: Sewook Jung, Jungsoo Lim, Soon Young Oh Tutor: Ling-Jyh Chen Professor Mario Gerla CS218 – Fall 2003. Outlines. Background Adaptive Automatic Retransmission ReQuest (ARQ) Retransmission Timeout (RTO)

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Audio Streaming over Bluetooth Scatternet: using Adaptive Link Layer

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  1. Audio Streaming over Bluetooth Scatternet: using Adaptive Link Layer Team members: Sewook Jung, Jungsoo Lim, Soon Young Oh Tutor: Ling-Jyh Chen Professor Mario Gerla CS218 – Fall 2003

  2. Outlines • Background • Adaptive Automatic Retransmission ReQuest (ARQ) Retransmission Timeout (RTO) • Previous Research • Related work • Implementations • Simulations • Conclusion • Future Work

  3. Background • Multimedia contents are prosperous • Eg. MP3 audio • Wireless Personal Area Network (PAN) needs to support multimedia • The varying nature of the wireless link can make streaming over wireless a challenging problem • Packets are arrived to client with a consistent rate

  4. Background (cont’d) • ARQ mechanism • Packets being dropped/delayed in bad link • Beneficial to non-real-time traffic • Need modifications for real-time/streaming traffic • ARQ retransmission limit • Too high • Packets are severely delayed • Streaming audio/video quality is degraded • Too low • large number of packets are dropped at the link layer • Also causes poor audio quality.

  5. An Adaptive ARQ RTO • Original Bluetooth • stop-and-wait ARQ scheme at link layer • packet is retransmitted until receives ACK or retransmission timeout (RTO) is exceeded. • In most current Bluetooth chipsets • the default RTO is infinite • To provide reliable link. • Infinite RTO degrades real-time streaming audio/video quality

  6. Previous Research • Fixed ARQ RTO • Use a fixed finite RTO • Impossible to accommodate all different link qualities with one fixed value. • Adaptive ARQ RTO • Adjust RTO by measurement of previous RTT • Improvement on average delay time and the packet success rate RTT increase -- decrease ARQ RTO RTT decrease -- increase ARQ RTO

  7. Previous Research (cont’d) The RTO equation SRTT’ = (1- ) X SRTT +  X RTT (1)  X RTO; if RTT < SRTT (2) RTO’ =  X RTO; if RTT > SRTT RTO; if previous packet is dropped SRTT = smooth RTT,  = 1.1 β= 0.9  = 0.25

  8. Previous Research (cont’d) • Set the upper bound and lower bound for ARQ RTO • RTOmin = 2 X Tpackets (= 6*625ms in DH5) • RTOmax = Tpackets X Max(Available Buffer X 75%, 2) Tpacket = time interval between first packet fragments and last fragments’ ACK Available buffer = (system maximum input buffer – used buffer)/packet size

  9. Previous Research (cont’d) • Adaptive ARQ RTO Results • Enhance the streaming audio quality remarkably • Robust solution for real-time/streaming data over wireless network.

  10. Related work • TCP-Friendly Rate Control (TFRC): equation based TCP rate control • Video Transport Protocol (VTP): sender adjust the sending rate based on estimated eligible rate • RAP: End-to-end Rate Based Control: mimics TCP’s AIMD behavior • RCS: A Rate Control Scheme: source probes the connection with dummy packets, and adjust sending rate

  11. Implementations • Blueware: • Developed by MIT • Bluetooth simulator as an extension to NS • Various Scatternet formation and link scheduling schemes.

  12. Implementations (cont’d) Applications L2CAP LMP Host Controller Interface Bluetooth Baseband Bluetooth Radio Bluetooth Stack

  13. Implementations (cont’d) Topology formation • Manipulate the topology formation • Set position of nodes manually • Original Blueware has only random topology formation The examples of topology formations: 2 hops 3 hops 1 hop 2 flows 3 flows

  14. Implementations (cont’d)Original Method Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer Partial RTT RTT RTT < RTO

  15. Implementations (cont’d)Original Method Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer Partial RTT HCI_FLUSH RTT Partial RTT > RTO

  16. Implementations (cont’d) Next Packet Drop Application L2CAP HCI/LC Receiver Layer Layer Layer RTT1 RTT1 < RTO RTT2

  17. Implementations (cont’d) Next Packet Drop Application L2CAP HCI/LC Receiver Layer Layer Layer RTT1 RTT2 RTT1 > RTO RTT2 < RTO

  18. Implementations (cont’d)Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT RTT < RTO

  19. Implementations (cont’d)Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT RTT > RTO

  20. Implementations (cont’d)Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT RTT < RTO Drop Queue size = 5

  21. Implementations (cont’d) • Generating Packet Error • Blueware supports packet error rate (PER) instead of bit error rate (BER) • DH5 mode is used for all RTP packets where packet size is 2712 bits and a packet length is five Bluetooth slots • PER is defined as P = 1 – (1 – b)s b = bit error rate, s = packet size

  22. Implementations (cont’d) • Generating Packet Error (Cont’d) • Burst Errors • once the error starts, the probability of having an error in the next bit is extraordinarily high such as 90%. • If the burst error occurs in the middle of the packet, it may not affect the next packet. • However, if it occurs at the end of the packet, there is a great probability of affecting the next packet.

  23. Pbg Pgg Pbb Pgb Good Bad Implementations (cont’d) Burst Error transition diagram Bit error rate: Pgg: 1-BER Pgb: BER Pbb: 0.9 Pbg: 0.1

  24. Experiment Results Adaptive RTO

  25. Experiment Results (cont’d) • Throughput of Next packet drop (2nodes)

  26. Experiment Results (cont’d) • Delay of Next packet drop (2nodes)

  27. Experiment Results (cont’d) • Throughput of Flow control (2nodes)

  28. Experiment Results (cont’d) • Delay of Flow control (2nodes)

  29. Experiment Results (cont’d) • Packet Success Rate with 2 Nodes

  30. Experiment Results (cont’d) • Packet Success Rate with 3 Nodes

  31. Experiment Results (cont’d) • Packet Success Rate with 5 Nodes

  32. Experiment Results (cont’d) • Fairness • Topology • Fairness in 2 flows topology • Unfairness in 3 flows topology 2 flows 3 flows

  33. Experiment Results (cont’d) 2 Flows (Adaptive RTO : Next packet drop)

  34. Experiment Results (cont’d) 3 Flows (Adaptive RTO : Next packet drop)

  35. Experiment Results (cont’d) 3 Flows (No RTO)

  36. Experiment Results (cont’d) Success Rate of Random Error vs. Burst Error

  37. Conclusion • Success rates were about the same among next packet drop, flow control, and fixed RTO approach • Next packet drop method improved average delay, but throughput suffered • Flow control method did not improve throughput nor delay • Unfairness detected in 3 flow topology • Negligible difference in experiment results between the bit error model and the burst error model

  38. Future Work • Intelligent HCI_FLUSH • Previous HCI_FLUSH deletes packets based on connection_handle • All packets contain • connection_handle information • HCI packet header or baseband header • cid information • L2CAP header • Remove packets which have specific connection_handle or cid • Intelligent RTO • Adjust RTO based on jitter • New RTO equation: • jitter = RTT – Tpackets ( = 6 *625ms in DH5) • RTO = RTO - jitter • RTT > Tpackets RTO decrease • RTT < Tpackets RTO increase

  39. Future Work (cont’d) • Combination of Adaptive Packet Type (APT) and Adaptive RTO • Combine adaptive RTO scheme with adaptive packet type (i.e. DH5, DH3, DH1, DM5, DM3, DM1) • Choose the best packet type for different BER ranges • Implement the functionality to the Bluetooth LC layer • Optimal packet type can be selected dynamically

  40. References • J.C. Haartsen, " The Bluetooth Radio System," IEEE Personal Communications Magazine, Feb. 2000. • NS2 Simulator: http://www.isi.edu/nsnam/ns/ • L.-J. Chen, R. Kapoor, K. Lee, M. Y. Sanadidi, M. Gerla, " Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach," • Reza Rejaie, Mark Handley, Deborah Estrin, " RAP: An End-to-end Rate-based Congestion Control Mechanism for Realtime Streams in the Internet," In Proceedings of IEEE INFOCOM 1999. • G. Holland, and N. Vaidya," Analysis of TCP performance over mobile ad hoc networks ," In Proceedings of ACM Mobicom'99, Seattle, Washington, 1999. • Balk, D. Maggiorini, M. Gerla, and M. Y. Sanadidi, " Adaptive MPEG-4 Video Streaming with Bandwidth Estimation, ", UCLA. • J. Tang, G. Morabito, I. F. Akyildiz, and M. Johnson, "RCS: A Rate Control Scheme for Real-Time Traffic in Networks with High Bandwidth-Delay Products and High Bit Error Rates," In Proceedings of Infocom 2001, Anchorage, AK, 2001.

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