Audio streaming over bluetooth scatternet using adaptive link layer
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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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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

Outlines

  • Background

  • Adaptive Automatic Retransmission ReQuest (ARQ) Retransmission Timeout (RTO)

  • Previous Research

  • Related work

  • Implementations

  • Simulations

  • Conclusion

  • Future Work


Background

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


Background cont d

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.


An adaptive arq rto

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


Previous research

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


Previous research cont d

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


Previous research cont d1

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


Previous research cont d2

Previous Research (cont’d)

  • Adaptive ARQ RTO Results

    • Enhance the streaming audio quality remarkably

    • Robust solution for real-time/streaming data over wireless network.


Related work

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


Implementations

Implementations

  • Blueware:

    • Developed by MIT

    • Bluetooth simulator as an extension to NS

    • Various Scatternet formation and link scheduling schemes.


Implementations cont d

Implementations (cont’d)

Applications

L2CAP

LMP

Host Controller Interface

Bluetooth Baseband

Bluetooth Radio

Bluetooth Stack


Implementations cont d1

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


Implementations cont d original method

Implementations (cont’d)Original Method

Application L2CAPL2CAP HCI/LC ReceiverLayer QueueLayer Layer

Partial RTT

RTT

RTT < RTO


Implementations cont d original method1

Implementations (cont’d)Original Method

Application L2CAPL2CAP HCI/LC ReceiverLayer QueueLayer Layer

Partial RTT

HCI_FLUSH

RTT

Partial RTT > RTO


Implementations cont d next packet drop

Implementations (cont’d) Next Packet Drop

Application L2CAPHCI/LCReceiverLayer LayerLayer

RTT1

RTT1 < RTO

RTT2


Implementations cont d next packet drop1

Implementations (cont’d) Next Packet Drop

Application L2CAPHCI/LCReceiverLayer LayerLayer

RTT1

RTT2

RTT1 > RTO

RTT2 < RTO


Implementations cont d flow control

Implementations (cont’d)Flow Control

Application L2CAPL2CAP HCI/LC ReceiverLayer QueueLayer Layer

RTT

RTT < RTO


Implementations cont d flow control1

Implementations (cont’d)Flow Control

Application L2CAPL2CAP HCI/LC ReceiverLayer QueueLayer Layer

RTT

RTT > RTO


Audio streaming over bluetooth scatternet using adaptive link layer

Implementations (cont’d)Flow Control

Application L2CAPL2CAP HCI/LC ReceiverLayer QueueLayer Layer

RTT

RTT < RTO

Drop

Queue size = 5


Implementations cont d2

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


Implementations cont d3

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.


Implementations cont d4

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


Experiment results

Experiment Results

Adaptive RTO


Experiment results cont d

Experiment Results (cont’d)

  • Throughput of Next packet drop (2nodes)


Experiment results cont d1

Experiment Results (cont’d)

  • Delay of Next packet drop (2nodes)


Experiment results cont d2

Experiment Results (cont’d)

  • Throughput of Flow control (2nodes)


Experiment results cont d3

Experiment Results (cont’d)

  • Delay of Flow control (2nodes)


Experiment results cont d4

Experiment Results (cont’d)

  • Packet Success Rate with 2 Nodes


Experiment results cont d5

Experiment Results (cont’d)

  • Packet Success Rate with 3 Nodes


Experiment results cont d6

Experiment Results (cont’d)

  • Packet Success Rate with 5 Nodes


Experiment results cont d7

Experiment Results (cont’d)

  • Fairness

    • Topology

    • Fairness in 2 flows topology

    • Unfairness in 3 flows topology

2 flows

3 flows


Audio streaming over bluetooth scatternet using adaptive link layer

Experiment Results (cont’d)

2 Flows (Adaptive RTO : Next packet drop)


Audio streaming over bluetooth scatternet using adaptive link layer

Experiment Results (cont’d)

3 Flows (Adaptive RTO : Next packet drop)


Audio streaming over bluetooth scatternet using adaptive link layer

Experiment Results (cont’d)

3 Flows (No RTO)


Audio streaming over bluetooth scatternet using adaptive link layer

Experiment Results (cont’d)

Success Rate of Random Error vs. Burst Error


Conclusion

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


Future work

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


Future work cont d

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


References

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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