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Improving Wireless Link Throughput via Interleaved FEC

Explore the integration of FEC and Interleaving at the Bluetooth link layer to optimize throughput in the presence of burst errors. Simulated in DM mode with Hamming code. Evaluate performance against DH mode and without FEC.

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Improving Wireless Link Throughput via Interleaved FEC

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  1. Improving Wireless Link Throughput via Interleaved FEC Ling-Jyh Chen, Tony Sun, M. Y. Sanadidi, Mario Gerla Computer Science Department, University of California at Los Angeles

  2. Improving Wireless Link Throughput via Interleaved FEC Background Dealing with packet losses: • End-to-end • ARQ: Retransmission in TCP • FEC: Robust Audio Tool (RAT) [14] • Partial Correctness: Interleaving as inVideo transfer protocols [RFC 2354] • Link Layer Level • ARQ: as in HDLC, or Bluetooth link layer protocol • FEC:as in 802.11a and Bluetooth ISCC 2004

  3. Improving Wireless Link Throughput via Interleaved FEC Background • Problems: • ARQ does not perform well for high error rates • FEC works if errors are not bursty • Interleaving introduces latency • Our Proposal: I-FEC • combines FEC and Interleaving at Bluetooth link layer for high-rate bursty errors ISCC 2004

  4. Improving Wireless Link Throughput via Interleaved FEC Background • In Bluetooth DM mode, FEC uses a (15, 10) Hamming code • Each block of 10 information bits is encoded into a 15 bit codeword • Capable of correcting single bit error in each block ISCC 2004

  5. Improving Wireless Link Throughput via Interleaved FEC Gilbert-Elliott Burst Error Model ISCC 2004

  6. Improving Wireless Link Throughput via Interleaved FEC Burst Error Length At high Pbb, burst length are too long; do not expect FEC to work ISCC 2004

  7. Improving Wireless Link Throughput via Interleaved FEC Packet Error Rate after FEC Pgb = 0.0005 • When Pbb is high, FEC does not help much! ISCC 2004

  8. Improving Wireless Link Throughput via Interleaved FEC Proposed Approach: I-FEC • Inherits both the robustness to random errors from FEC and the survivability to burst errors from Interleaving • Simulated I-FEC in Bluetooth, and to Bluetooth DH (no FEC coding) and DM (FEC coding) modes ISCC 2004

  9. Improving Wireless Link Throughput via Interleaved FEC Proposed Approach: I-FEC • Bluetooth DM mode (FECed already!) (b) I-FEC • The FEC overhead is the same as DM mode • The latency caused by interleaving is negligible, since I-FEC interleaves data in bit level within one link layer packet, instead of packet level cross different packets ISCC 2004

  10. Improving Wireless Link Throughput via Interleaved FEC Evaluation • Comparison of I-FEC, DH, and DM mode packets using 5-timeslot Bluetooth packets. • PER with different Pgb and Pbb (using Monte Carlo Simulation) • TCP Throughput with different Pgb and Pbb (using NS2 simulator) • Simulation Topology: (a) one hop (b) two hops ISCC 2004

  11. Improving Wireless Link Throughput via Interleaved FEC Packet Error Rates (1 hop) Pgb = 0.0005 Pbb = 0.2 ISCC 2004

  12. Improving Wireless Link Throughput via Interleaved FEC TCP Performance Pbb = 0.2 Pbb = 0.2 ISCC 2004

  13. Improving Wireless Link Throughput via Interleaved FEC TCP Performance Pgb = 0.0003 Pgb = 0.0003 ISCC 2004

  14. Improving Wireless Link Throughput via Interleaved FEC Conclusion • I-FEC, a hybrid approach incorporating the robustness of FEC coding to random errors and the survivability of interleaving to burst errors • I-FEC is simple and applicable to other link technologies, as long as FEC is already there ISCC 2004

  15. Improving Wireless Link Throughput via Interleaved FEC T h a n k s ISCC 2004

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