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

2. Overview 802 sees the value of higher rates at 2.4 GHz
Month 2000
doc.: IEEE /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

3. CCK-OFDM Proposal Use .11b preamble with 802.11a waveform
Month 2000
doc.: IEEE /304
May 2001
CCK-OFDM Proposal
Use .11b preamble with a waveform
Optional: Use pure a
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

4. Overview of Performance Issue
Month 2000
doc.: IEEE /304
May 2001
Overview of Performance Issue
OFDM has an advantage against interference
PBCC proposal submission IEEE /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

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

6. TI’s Range Curve IEEE 802.11-01/282
May 2001
TI’s Range Curve IEEE /282
Path Loss Model
After 8m, assumes indoor path loss exponent of 3.3:
Lpath = – 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

7. 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

8. 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

9. 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 = – 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

10. 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

11. 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 g
Webster & Halford, Intersil