CCK-OFDM Closing Remarks Month 2000 doc.: IEEE 802.11-00/304 May 2001 CCK-OFDM Closing Remarks Mark Webster Steve Halford Jim Zyren Webster & Halford, Intersil John Doe, His Company

Overview 802 sees the value of higher rates at 2.4 GHz Month 2000 doc.: IEEE 802.11-00/304 May 2001 Overview 802 sees the value of higher rates at 2.4 GHz FCC barriers are down Want backward compatibility Both proposals recognize value of OFDM Issue is how to best get there We feel it is CCK-OFDM not CCK-PBCC-OFDM Webster & Halford, Intersil John Doe, His Company

CCK-OFDM Proposal Use .11b preamble with 802.11a waveform Month 2000 doc.: IEEE 802.11-00/304 May 2001 CCK-OFDM Proposal Use .11b preamble with 802.11a waveform Optional: Use pure 802.11a Similar to the current use of short preamble Natural way to: Provide higher data rates Provide backward compatibility Provide convergence with .11a Webster & Halford, Intersil John Doe, His Company

Overview of Performance Issue Month 2000 doc.: IEEE 802.11-00/304 May 2001 Overview of Performance Issue OFDM has an advantage against interference PBCC proposal submission IEEE 802.11-01/286r1) shows a huge range advantage for PBCC over OFDM. We disagree with that conclusion. In a real world environment, OFDM has a range & throughput advantage Webster & Halford, Intersil John Doe, His Company

TI’s Range Curve IEEE 802.11-01/282 May 2001 TI’s Range Curve IEEE 802.11-01/282 Does this make Sense? 150 meters PBCC versus 83 meters OFDM 6 Mbps OFDM 5.5 Mbps PBCC Webster & Halford, Intersil

TI’s Range Curve IEEE 802.11-01/282 May 2001 TI’s Range Curve IEEE 802.11-01/282 Path Loss Model After 8m, assumes indoor path loss exponent of 3.3: Lpath = –37.7 + 10 log(4 p r3.3 / l) dB, r > 8m Working Backwards from this range ratio: 33 log10 ( 150 / 83 ) = 8.5 dB Advantage ???????? is shown for 5.5 Mbps PBCC versus 6 Mbps OFDM How can this be? Webster & Halford, Intersil

May 2001 OFDM PBCC FEC Codes OFDM uses the industry standard convolution code for 6 and 12 Mbps. PBCC uses a code which is equivalent to the industry standard at 5.5 and 11 Mbps. Both codes have the same AWGN performance for BPSK and QPSK in Eb/No. Webster & Halford, Intersil

OFDM Performance at 5.5 and 11 Mbps May 2001 OFDM Performance at 5.5 and 11 Mbps OFDM has an extra loss pilot tone loss of 10*log10(52/48)=0.347 dB OFDM has an extra guard interval loss of 10*log10(80/64)=0.969 dB OFDM has a pilot tone plus guard interval loss of 1.32 dB at 6 and 12 Mbps compared to PBCC at 5.5 and 11 Mbps Webster & Halford, Intersil

Range Difference for 1.32 dB May 2001 Range Difference for 1.32 dB Path Loss Model After 8m, assumes indoor path loss exponent of 3.3: Lpath = –37.7 + 10 log(4 p r3.3 / l) dB, r > 8m Manipulating above equation gives: 1.32 dB = 33 log10( R2/R1), where R2 is PBCC range and R1 is the OFDM range in meters. Solution: R2 = 1.09 R1 Difference translates to a 9% theoretical range advantage at 5.5 and 11 Mbps in AWGN versus OFDM at 6 and 12 Mbps. Webster & Halford, Intersil

May 2001 Conclusions on Range At best, a minimal theoretical range advantage in AWGN. AWGN is not the limiting factor What is limiting factor ? -- Multipath In a real multipath environment OFDM will have the advantage in range and throughput. Webster & Halford, Intersil

Conclusions CCK-OFDM meets the PAR requirements May 2001 Conclusions CCK-OFDM meets the PAR requirements CCK-OFDM offers a natural route to OFDM at 2.4 GHz CCK-OFDM has lower complexity CCK-OFDM is a multi-company solution CCK-OFDM is the best solution for 802.11g Webster & Halford, Intersil