May 2001 doc IEEE 802 11 01304 Issues
- Slides: 11
May 2001 doc. : IEEE 802. 11 -01/304 Issues with 33 Mbps PBCC Mark Webster Steve Halford Submission 1 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Overview • A 33 Mbps PBCC mode has been proposed by TI (IEEE 802. 11 -00/386). • IEEE 802. 11 -00/386 did not delve into receiver implementation issues. • This presentation examines some receiver issues associated with 33 Mbps PBCC. Submission 2 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 33 Mbps PBCC Uses PSK Symbol-Rate Switching 11 MHz Rate 16. 5 MHz Rate Packet Structure Submission 3 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Switch Transmit Pulse Shapes Nyquist Filter • 11 MHz sym rate: 81. 8% • 16. 5 MHz sym rate: 21. 2% Zero Crossing Change Ref: IEEE 802. 11 -00/386 p. 17 Submission 4 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Switch-Over Behavior 6 d. B Peak-to. Average Power Ref: IEEE 802. 11 -00/386 p. 20 Submission 6 d. B Peak-to. Average Power 5 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 High-Level Receiver Architecture for 802. 11 b Non-trivial Complexity CIR Estimator ADC Calculate WMF and Equalizer Settings WMF (or CMF) Equalizer Channel Matched Filter or Whitened Matched Filter Submission 6 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Channel Impulse Response (CIR) Estimation for 802. 11 b Packet Structure 1 & 2 Mbps Barker Preamble Estimate Channel Impulse Response Submission Header Payload Compute WMF and Equalizer Use WMF and Equalizer 7 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 (CIR) Estimation Problem for 33 Mbps PBCC Symbol Rate Change and Transmit Pulse change!? 1 & 2 Mbps Barker Preamble Estimate Channel Impulse Response Submission Header CIR Estimate Is No Longer Valid Payload Compute WMF and Equalizer Use WMF and Equalizer 8 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Solution 1: Add Re-sync Overhead Symbol Rate Change and Transmit Pulse change Reuse circuitry or Additional circuitry required? 1 & 2 Mbps Barker Preamble Estimate Channel Impulse Response Submission Header Compute Use WMF and Equalizer Sync Estimate Compute Channel WMF and Impulse Equalizer Response 9 Payload Use WMF and Equalizer Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Solution 2: Force Same CIR? Potential Drawbacks • No longer Nyquist for one of the two symbol rates • Lose AWGN and multipath performance over 33 Mbps(? ) • Must still re-design WMF and Equalizer at rate change Small Switch Buffer 1 & 2 Mbps Barker Preamble Estimate Channel Impulse Response Submission Header Payload Use 2 nd WMF and Equalizer Compute 1 st Use 1 st WMF and Equalizer Compute 2 nd WMF and Equalizer 10 Webster & Halford, Intersil
May 2001 doc. : IEEE 802. 11 -01/304 Conclusions • We have identified CIR estimation issues associated with the 33 Mbps PBCC mode. • Two potential solutions were identified, with various advantages and disadvantages. • More work is needed to find the best resolution of these issues. Submission 11 Webster & Halford, Intersil
