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Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach. Ling-Jyh Chen, Rohit Kapoor, Kevin Lee, M. Y. Sanadidi, Mario Gerla. Department of Computer Science, University of California at Los Angeles. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach. Outline.

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Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach


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    1. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Ling-Jyh Chen, Rohit Kapoor, Kevin Lee, M. Y. Sanadidi, Mario Gerla Department of Computer Science, University of California at Los Angeles

    2. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Outline • Introduction • Background and related work • Proposed approach • Implementation and experiment results • Conclusion MNSA 2004

    3. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Introduction • Wireless PAN is becoming popular nowadays. • Digital media, such as audio/video streaming, is becoming more desired than before. • The varying nature of the wireless link makes audio streaming over wireless become a challenging problem. • A well-designed solution should minimize the packet loss rate and delay of perceived streaming data. MNSA 2004

    4. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Bluetooth Overview • The “enabler” of Personal Area Network (PAN) • Low power, low cost, and smaller chips MNSA 2004

    5. Best-effort Streaming adapt sending rate Real-time Streaming adapt sending rate and stream quality Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Streaming Overview SCP VTP RAP Helix TEAR Microsoft TFRC All of the upper layer streaming protocols has no ideas about link layer behavior. MNSA 2004

    6. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Link Layer Enhancements • Three potential solutions [RFC 3366]: • Retransmission (e.g. ARQ) • Redundancy (e.g. FEC) • Interleaving • Challenges • User-perceived streaming quality • Random errors vs bursty errors MNSA 2004

    7. Decrease delay Increase reliability Retransmission timeout High Low More packets will be dropped, and the streaming quality will become poor Enlarge the delay, and degrade the streaming quality Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Retransmission - ARQ • Stop-and-wait ARQ: retransmit a packet until either the acknowledgement of a successful reception is received or the retransmission timeout is exceeded. MNSA 2004

    8. An Example:Bluetooth DM mode The FEC coding scheme used in DM mode is a (15, 10) shortened Hamming code, in which each block of 10 information bits is encoded into a 15 bit codeword, and it is capable of correcting single bit error in each block. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Redundancy - FEC MNSA 2004

    9. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Error Model • Wireless errors are usually bursty in occurrences. Burst Error Model (aka Gilbert-Elliott model) MNSA 2004

    10. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Wireless Channel Model (cont.) Retransmissions are still required when burst errors are present!! MNSA 2004

    11. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Related Work • S. Krishnamachari et al proposed to adaptively change the maximum number of MAC layer retransmissions and FEC encoding level in the application layer by using the estimated MAC layer link quality (SNR). • However, the link quality prediction may not be appropriate due to the dynamics of wireless networks. MNSA 2004

    12. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Proposed Approach • Adaptive ARQ Timeout in Bluetooth • Problem: The deployed stop and wait ARQ is harmful to real-time streaming audio over Bluetooth, especially in the error prone environment. • Aim: to reduce the audio packet delay and loss rate • Ideas: • If we spent too much time on sending packet n, then we should decrease RTO on packet n+1 • If we save some time on sending packet n, then we should increase RTO on packet n+1 • If we drop at least two of the last 5 packets, then we should reset RTO MNSA 2004

    13. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach RTO Update Equation • Initialization • Update • Reset MNSA 2004

    14. Audio Client Audio Server RTP Packet BNEP BNEP BlueZ L2CAP L2CAP HCI HCI BluetoothDevice Baseband Baseband Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Implementation 128kbps MP380 ms/RTP packet Average DelayRTP Packet Loss Rate RTP Packet BufferFlush Timeout Packets RTP Packet RTTLink Quality DH5 packet MNSA 2004

    15. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Measure Link Quality • Get_Link_Quality function call (in BT spec.) • Get_Link_Quality: This command returns the value of the Link Quality. It returns a number between 0 and 255, with the higher value representing a better channel. Each Bluetooth module vendor will determine how to measure the link quality • For CSR Bluetooth Chipsets If BER (Bit Error Rate) = 0, LQ (Link Quality) = 255 If BER <= 40/40000, LQ = 255 – BER * 40000 If 40/40000<BER <= 4000/40000, LQ = 215 – ((BER / 32) * 40000) If 4000/40000<BER <= 40000/40000, LQ=105– ((BER / 256)* 40000) MNSA 2004

    16. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Experiments MNSA 2004

    17. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach MNSA 2004

    18. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach MNSA 2004

    19. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach MNSA 2004

    20. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Conclusion • Such cross-layer optimization can significantly improve application performance in PAN. • Our proposed approach is simple and applicable to other wireless technologies. MNSA 2004

    21. Audio Streaming over Bluetooth: An Adaptive ARQ Timeout Approach Thank You!! MNSA 2004