1. Range & Rate of CCK-OFDM
November 2001
Range & Rate of CCK-OFDM
Steve Halford
Jim Zyren
Mark Webster
Intersil Corporation
Palm Bay, FL
S.Halford, Intersil Corporation

2. Does PBCC-22 add value to CCK-OFDM?
November 2001
Does PBCC-22 add value to CCK-OFDM?
NO!
Incomplete comparisons made in r1
Ignores optional modes of CCK-OFDM (18 Mbps)
Uses unexplained modes of PBCC (49 & 66 Mbps)
Incorrect noise bandwidth values used in r1
r1: Penalized OFDM by > 7 dB
Corrected in r2 but never presented
S.Halford, Intersil Corporation

3. May 2000
doc.: IEEE /xxx
November 2001
Range Calculations
Note that PBCC and CCK/Barker use a single carrier so the number of subcarriers is equal to one.
For comparison -- only these values will differ between CCK, OFDM, and PBCC
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

4. Path Loss Model Selected ITU-RP.1238 model Model
May 2000
doc.: IEEE /xxx
November 2001
Path Loss Model
Selected ITU-RP.1238 model
See Doc r1 or Doc r0
Model used by r2 assumes 8m of free space propagation
Seems unreasonable for W-LAN environment
Model selection has minor impact on conclusions
Model
The loss exponent of 3.6 (36) was selected to make CCK-11 range match the Intersil measured range of 120 feet (36 meters) at 5 % PER.
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

5. Range Equation Simplified
November 2001
Range Equation Simplified
Distance (in m) as a function of SNR required to meet a given packet error rate
S.Halford, Intersil Corporation

6. SNR per subcarrier (at MF output)
May 2000
doc.: IEEE /xxx
November 2001
SNR as a function of PER
Waveform
Data Rate
(Mbps)
SNR per subcarrier (at MF output)
in dB
SNR(.01)
1% PER
SNR(.05)
5% PER
SNR(.10)
10% PER
Barker 1
11.1
10.5
10.25 2
15.9
15.3
14.7
CCK
5.5
5.7
5.0
4.8 11
8.6
8.0
7.0
PBCC
1.9
1.5
1.2
4.4
4.1 22
9.0
8.5
8.3
OFDM 6
0.8
0.6 9
3.8
3.4
3.1 12
3.5 18
6.4
6.1 24
10.1
9.4
9.1 36
13.1
12.7
12.4 48
17.7
16.9
16.5 54
19.0
18.3
18..0
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

7. Throughput Calculations
November 2001
Throughput Calculations
Use Maximum Sustainable Throughput (Rmax) as basis
Defined by (see also )
Consider the following case
IEEE b short preamble with 1000 byte packets
Acknowledgement packets of 14 bytes at same rate as data
No access backoff (DIFS only between ACK & subsequent packets)
Modify the throughput to account for re-transmissions
Same procedure as followed by r2
Adjusts the throughput based on average # of retransmissions for a given
Same formula for all waveforms
S.Halford, Intersil Corporation

8. Throughput with Re-transmission
May 2000
doc.: IEEE /xxx
November 2001
Throughput with Re-transmission
Waveform
Data Rate
(Mbps)
Throughput (Mbps)
Rmax
R(0)
1% PER
R(.01)
5% PER
R(.05)
10% PER
R(.10)
Barker 1
0.96
0.95
0.91
0.86 2
1.86
1.84
1.76
1.67
CCK/PBCC
5.5
4.63
4.59
4.40
4.17 11
8.09
8.00
7.68
7.28
PBCC 22
12.89
12.76
12.24
11.60
OFDM 6
4.87
4.82
4.62
4.38 9
6.69
6.62
6.35
6.02 12
8.26
8.18
7.85
7.44 18
10.75
10.65
10.22
9.68 24
12.66
12.53
12.03
11.39 36
15.50
15.35
14.73
13.95 48
17.39
17.22
16.52
15.65 54
18.02
17.84
17.11
16.22
Sources: IEEE Document r0
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

9. TGg Range & Rate for PER = 0.05
May 2000
doc.: IEEE /xxx
November 2001
TGg Range & Rate for PER = 0.05
Waveform
Rate
Range
(meters)
Throughput
(Mbps)
CCK 11 35
7.5
PBCC 22 34
12.0
OFDM 18
10.0 24 29 36 23
14.5 48
16.5 54 16
17.0
Sources: IEEE Document r0
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

10. TGg Range & Rate for PER = 0.05
May 2000
doc.: IEEE /xxx
November 2001
TGg Range & Rate for PER = 0.05
In theory, a W-LAN system with PBCC-22 might get 2 Mbps higher throughput for this 5 meter region. For all other regions, CCK-OFDM has equivalent or superior throughput
Sources: IEEE Document r0
S.Halford, Intersil Corporation
M. Webster and K. Halford, Intersil Corp

11. Conclusions from Range vs. Rate
November 2001
Conclusions from Range vs. Rate
CCK-OFDM offers superior throughput for nearly all ranges
PBCC proposal offers a small throughput advantage over a very limited range under ideal conditions
Optional a mode offers vastly superior throughput for the 2.4 GHz band
Much better than the extended (>22 Mbps) PBCC
This is undisputed!
See r0 & r2
PBCC team recognized this advantage & added the same optional mode
S.Halford, Intersil Corporation

12. Would adding PBCC-22 as Tx-only requirement make sense?
November 2001
Would adding PBCC-22 as Tx-only requirement make sense?
No!
MAC issues
How to handle broadcast?
Market confusion due to adding a third waveform
Violates the spirit of the PAR req’ment for single high rate waveform
No real throughput improvement in PBCC-22 mode
Burden the standard with unnecessary IP
Scramble sequence has no demonstrated value
Questions remain about other codes with same performance
Increased complexity to any TGg product
Add gates (& IP) in order to transmit PBCC-22
More modes to test and debug
S.Halford, Intersil Corporation