Download presentation
Presentation is loading. Please wait.
1
doc.: IEEE 802.11-00/304 Mark Webster Steve Halford
Month 2000 doc.: IEEE /304 May 2001 Issues with 33 Mbps PBCC Mark Webster Steve Halford Webster & Halford, Intersil John Doe, His Company
2
Month 2000 doc.: IEEE /304 May 2001 Overview A 33 Mbps PBCC mode has been proposed by TI (IEEE /386). IEEE /386 did not delve into receiver implementation issues. This presentation examines some receiver issues associated with 33 Mbps PBCC. Webster & Halford, Intersil John Doe, His Company
3
33 Mbps PBCC Uses PSK Symbol-Rate Switching
May 2001 33 Mbps PBCC Uses PSK Symbol-Rate Switching 11 MHz Rate 16.5 MHz Rate Packet Structure Webster & Halford, Intersil
4
Switch Transmit Pulse Shapes
Month 2000 doc.: IEEE /304 May 2001 Switch Transmit Pulse Shapes Nyquist Filter 11 MHz sym rate: 81.8% 16.5 MHz sym rate: 21.2% Zero Crossing Change Ref: IEEE /386 p. 17 Webster & Halford, Intersil John Doe, His Company
5
Switch-Over Behavior 6 dB Peak-to- Average Power 6 dB Peak-to- Average
May 2001 Switch-Over Behavior 6 dB Peak-to- Average Power Ref: IEEE /386 p. 20 6 dB Peak-to- Average Power Webster & Halford, Intersil
6
High-Level Receiver Architecture for 802.11b
May 2001 High-Level Receiver Architecture for b Non-trivial Complexity CIR Estimator Calculate WMF and Equalizer Settings WMF (or CMF) ADC Equalizer Channel Matched Filter or Whitened Matched Filter Webster & Halford, Intersil
7
Channel Impulse Response (CIR) Estimation for 802.11b
May 2001 Channel Impulse Response (CIR) Estimation for b 802.11b Packet Structure 1 & 2 Mbps Barker Preamble Header Payload Estimate Channel Impulse Response Compute WMF and Equalizer Use WMF and Equalizer Webster & Halford, Intersil
8
(CIR) Estimation Problem for 33 Mbps PBCC
May 2001 (CIR) Estimation Problem for 33 Mbps PBCC Symbol Rate Change and Transmit Pulse change!? CIR Estimate Is No Longer Valid 1 & 2 Mbps Barker Preamble Header Payload Estimate Channel Impulse Response Compute WMF and Equalizer Use WMF and Equalizer Webster & Halford, Intersil
9
Solution 1: Add Re-sync Overhead
May 2001 Solution 1: Add Re-sync Overhead Symbol Rate Change and Transmit Pulse change Reuse circuitry or Additional circuitry required? 1 & 2 Mbps Barker Preamble Header Sync Payload Estimate Channel Impulse Response Use WMF and Equalizer Estimate Channel Impulse Response Compute WMF and Equalizer Compute WMF and Equalizer Use WMF and Equalizer Webster & Halford, Intersil
10
Solution 2: Force Same CIR?
May 2001 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 Header Payload Estimate Channel Impulse Response Use 2nd WMF and Equalizer Compute 1st WMF and Equalizer Use 1st WMF and Equalizer Compute 2nd WMF and Equalizer Webster & Halford, Intersil
11
May 2001 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. Webster & Halford, Intersil
Similar presentations
