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New OFDM SERVICE Field Format for .11e MAC FEC

New OFDM SERVICE Field Format for .11e MAC FEC. Sunghyun Choi Philips Research USA Briarcliff Manor, New York sunghyun.choi@philips.com. 802.11a PPDU Format. Both SERVICE and PSDU are transmitted at the rate specified by RATE field. The Facts.

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New OFDM SERVICE Field Format for .11e MAC FEC

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  1. New OFDM SERVICE Field Formatfor .11e MAC FEC Sunghyun Choi Philips Research USA Briarcliff Manor, New York sunghyun.choi@philips.com Sunghyun Choi, PHILIPS

  2. 802.11a PPDU Format • Both SERVICE and PSDU are transmitted at the rate specified by RATE field. Sunghyun Choi, PHILIPS

  3. The Facts • 802.11a SERVICE field is modulated/encoded at the same scheme as the MPDU. • A garbled SERVICE field will make the whole frame useless as it is used for the scrambler initialization. • This is perfectly fine today as a single bit error in a MAC frame will result in the FCS error anyway!!! Sunghyun Choi, PHILIPS

  4. 802.11e MAC-Level FEC • An MPDU can be encode by (224,208) RS code for more reliable transmission Sunghyun Choi, PHILIPS

  5. Problem Statement • 802.11e will have a MAC-level FEC based on RS coding (Ref. 802.11e/D2.0a) • When the MPDU is encoded by the MAC-level FEC, the error performance in the SERVICE field can be the bottleneck. • This was noted by Bob O’Hara, and others within TGe. • The same problem will happen to 802.11g. • Note: .11b does not have such a problem. Sunghyun Choi, PHILIPS

  6. Proposed PPDU Format • The SERVICE field is transmitted at 6 Mbps by occupying a single OFDM symbol. Sunghyun Choi, PHILIPS

  7. New Format Usage • The new format is specified via “New SERVICE” bit in the SIGNAL field; the bit is currently reserved. • New SERVICE = 0: the original SERVICE format • New SERVICE = 1: the proposed SERVICE format • The new format can be used only for the RS-coded 802.11e QoS data frames in a selectable manner. • New format will consume more bandwidth for other frames usually. Sunghyun Choi, PHILIPS

  8. 12 Mbps 24 Mbps 6 Mbps Performance Comparison (w/ 10 RS blocks for MSDU) Sunghyun Choi, PHILIPS

  9. Comments • The results shows that .11e RS coding can be useful, but can be more useful with the proposed new SERVICE field format. • Don’t rely on the absolute error probability values as this is based on a simple analysis. • However, the relative performance differences among different options should be valid. • For 6 Mbps, the new format performance remains the same as the old one’s. Sunghyun Choi, PHILIPS

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