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Transcript

  • 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
    • RTO min = 2 X T packets (= 6*625ms in DH5)
    • RTO max = T packets X Max(Available Buffer X 75%, 2)
    • T packet = 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 Bluetooth Radio Host Controller Interface Bluetooth Baseband LMP 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:
    1 hop 2 hops 3 hops 2 flows 3 flows
  • 14. Implementations (cont’d) Original Method Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT < RTO RTT Partial RTT
  • 15. Implementations (cont’d) Original Method Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer Partial RTT > RTO RTT Partial RTT HCI_FLUSH
  • 16. Implementations (cont’d) Next Packet Drop Application L2CAP HCI/LC Receiver Layer Layer Layer RTT1 < RTO RTT1 RTT2
  • 17. Implementations (cont’d) Next Packet Drop Application L2CAP HCI/LC Receiver Layer Layer Layer RTT1 > RTO RTT2 < RTO RTT1 RTT2
  • 18. Implementations (cont’d) Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT < RTO RTT
  • 19. Implementations (cont’d) Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT > RTO RTT
  • 20. Implementations (cont’d) Flow Control Application L2CAP L2CAP HCI/LC Receiver Layer Queue Layer Layer RTT < RTO Drop Queue size = 5 RTT
  • 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. Implementations (cont’d) Burst Error transition diagram Bit error rate: Pgg: 1-BER Pgb: BER Pbb: 0.9 Pbg: 0.1 Good Bad Pbg Pgb Pbb Pgg
  • 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 – T packets ( = 6 *625ms in DH5)
        • RTO = RTO - jitter
          • RTT > T packets RTO decrease
          • RTT < T packets 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, &quot; The Bluetooth Radio System ,&quot; 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, &quot; Audio Streaming over Bluetooth : An Adaptive ARQ Timeout Approach ,&quot;
    • Reza Rejaie, Mark Handley, Deborah Estrin, &quot; RAP: An End-to-end Rate-based Congestion Control Mechanism for Realtime Streams in the Internet ,&quot; In Proceedings of IEEE INFOCOM 1999.
    • G. Holland, and N. Vaidya,&quot; Analysis of TCP performance over mobile ad hoc networks ,&quot; In Proceedings of ACM Mobicom'99, Seattle, Washington, 1999.
    • Balk, D. Maggiorini, M. Gerla, and M. Y. Sanadidi, &quot; Adaptive MPEG-4 Video Streaming with Bandwidth Estimation , &quot;, UCLA.
    • J. Tang, G. Morabito, I. F. Akyildiz, and M. Johnson, &quot; RCS: A Rate Control Scheme for Real-Time Traffic in Networks with High Bandwidth-Delay Products and High Bit Error Rates ,&quot; In Proceedings of Infocom 2001, Anchorage, AK, 2001.

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