1 / 23

TCP over Bluetooth multihop:

TCP over Bluetooth multihop:. hardware implementation and performance modeling. Tutor: Rohit Kapoor. Member: Ling-Jyh Chen WeiChih Kuo. Outline. Motivation Development Evaluations Discussion Future work References. Motivation. Why TCP over Bluetooth

lydia
Download Presentation

TCP over Bluetooth multihop:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. TCP over Bluetooth multihop: hardware implementation and performance modeling Tutor: Rohit Kapoor Member: Ling-Jyh ChenWeiChih Kuo

  2. Outline • Motivation • Development • Evaluations • Discussion • Future work • References

  3. Motivation • Why TCP over Bluetooth • Bluetooth is expected to become a ubiquitous solution for providing short range, low power, low cost wireless connectivity • A lot of data applications need TCP or UDP to transmit packets • Evaluation the performance of TCP over bluetooth in a real implementation

  4. Bluetooth • a short-range radio technology operating in the unlicensed 2.4GHz ISM frequency band • Frequency Hopping: 1600 hops per second • Piconet & Scatternet Cordless headset Cell phone Cordless headset Cordless headset Cell phone Cell phone

  5. DM1 DH1 DM3 DH3 2/3 FEC DM5 DH5 No FEC Bluetooth Data Packet Type Asymmetric Symmetric Asymmetric Symmetric

  6. Applications IP SDP RFCOMM Control Data Audio L2CAP Link Manager Baseband RF Development • Hardware • Ericsson Bluetooth Application Tool Kit • Software • Microsoft Visual C++ 6.0 • Ericsson Bluetooth Stack

  7. Application Programming Interface Application Application COM Server interface Windows COM Server HOST STACKby Ericsson serial interface (COM/USB) Desktop System Description

  8. Some Features and limitations • Features • Support point-to-multipoint connection • Well-designed API • Limitations • COM Server is not reliable • The stack will crash if we fill the memory buffer too often=>Andus Chan, et al., “Bluetooth Evaluation Project”, http://www.ece.uvic.ca/499/2001a/group19/BT_evaluation_report.pdf

  9. TCP – Retransmission Timeout • RFC 1122 • Jacobson's algorithm for computing the smoothed round- trip ("RTT") time incorporates a simple measure of the variance • Karn's algorithm for selecting RTT measurements ensures that ambiguous round-trip times will not corrupt the calculation of the smoothed round-trip time

  10. TCP Tahoe Initialize: State <-- Slow Start; Case of: ACK received in Slow Start: cwnd <-- cwnd +1; /* “exponential ” increase of cwnd */ If cwnd > Threshold Then State= Congestion Avoidance; ACK received in Congestion Avoidance: If # Acks received = cwnd Then cwnd <-- cwnd +1; /* “linear” increase of cwnd */ Timeout: Threshold <-- cwnd/2; cwnd <-- 1; State <-- Slow Start;

  11. TCP Reno Initialize: State <-- Slow Start; Case of: ACK received in Slow Start: cwnd <-- cwnd +1; If cwnd > Threshold Then State= Congestion Avoidance; ACK received in Congestion Avoidance: cwnd <-- cwnd +1/cwnd; Timeout: Threshold <-- cwnd/2; cwnd <-- 1; State <-- Slow Start; 3 duplicate ACKs: Threshold <-- cwnd/2; cwnd <-- Threshold; State <-- Slow Start;

  12. TCP Westwood • When three duplicate ACKs are detected: • Set ssthresh = BSE*RTT/Packet_Size • If (cwin > ssthresh) Set cwin=ssthresh • When a TIMEOUT expires: • Set ssthresh=BSE*RTT/Packet_Size and cwin=1 Note: RTT = min round trip delay since connection set up

  13. Evaluations • Point to point • Packet size vs Throughput • TCP- Tahoe/Reno/Westwood • Congestion window & RTO • Multihop (not yet)

  14. 1. Packet size vs Throughput • Using TCP Tahoe with different packet size (200bytes ~ 30000bytes) in each connection mode • Ericsson’s COM server will crash if we fill the buffer too often, i.e. with high transmit rate or with small packet size

  15. 1. Packet size vs Throughput

  16. 2. TCP- Tahoe/Reno/Westwood

  17. 2. TCP- Tahoe/Reno/Westwood

  18. 3. Congestion window & RTO

  19. 3. Congestion window & RTO

  20. 3. Congestion window & RTO

  21. Discussion • Our implementation performs well and much close to the maximum throughput • Throughput increases as the packet size increases, and decreases after exceeding a certain amount • Without 3 duplicate ACKs, TCP Tahoe/Reno/Westwood performs almost the same

  22. Future work • Multihop in the same piconet • Multihop across scatternet • Multiple data flows • Connection with interference

  23. References • The Bluetooth Specification v1.1http://www.bluetooth.com • Ericsson Bluetooth Development Kithttp://www.comtec.teleca.se/ • J. C. Haartsen, "The Bluetooth radio system", IEEE Personal Communications , Volume: 7 Issue: 1 , Feb. 2000, Page(s): 28 –36 • M. Gerla, et al., “TCP westwood: congestion window control using bandwidth estimation”, GLOBECOM '01. IEEE , Volume: 3 , 2001, Page(s): 1698 –1702 • B. Braden, ed., "Requirements for Internet Hosts - Communication Layers," RFC 1122, Oct. 1989. • W. R. Stevens, "TCP/IP Illustrated, Volume 1: The Protocols", Addison-Wesley, 1994.

More Related