1. Alantro Communications
May 2000
Spread Spectrum and b
Chris Heegard
Alantro Communications
141 Stony Circle
(707)
May 8, 2000
Chris Heegard, Alantro Communications

2. IEEE 802.11b is not Spread Spectrum*
May 2000
IEEE b is not Spread Spectrum*
This is a scientific statement
Not political (e.g., the FCC rules)
The blocklength (8) of CCK does not relate to gain (6 dB ???)
The scrambling period (256) of PBCC does not relate to gain (24 dB ???)
*for rates above 2Mbps
Chris Heegard, Alantro Communications

3. Definitions W - Bandwidth (Hz) R - Data Rate (bps = bits*Hz)
May 2000
Definitions
W - Bandwidth (Hz)
R - Data Rate (bps = bits*Hz)
“Spectral efficiency” (bits)
Spreading Ratio
Relates the # of dimensions used by a waveform set to the bandwidth occupancy of the set
Waveform complexity (Hz)
Chris Heegard, Alantro Communications

4. What is Spread Spectrum?
May 2000
What is Spread Spectrum?
No:
Yes:
IEEE802.11b:
1-Barker Barker
5.5-CCK CCK
5.5-PBCC PBCC
22-AC
Note: The value of r assumes no excess bandwidth
Chris Heegard, Alantro Communications

5. Why not High Rate and Spread Spectrum
May 2000
Why not High Rate and Spread Spectrum
Shannon Theory tells us why…
Chris Heegard, Alantro Communications

6. Shannon Theory with Spreading
May 2000
Shannon Theory with Spreading
Chris Heegard, Alantro Communications

7. May 2000
Spreading at Low Rate
Chris Heegard, Alantro Communications

8. May 2000
Spreading at High Rate
Chris Heegard, Alantro Communications