1. 4 Channel Special Committee Report
March 2002
May 2002
4 Channel Special Committee Report
Anuj Batra
Kofi Anim-Appiah
Richard Williams
Matthew B. Shoemake
Texas Instruments
A. Batra et al., Texas Instruments
A. Batra et al., Texas Instruments

2. Motivation for 4 Channels
May 2002
Motivation for 4 Channels
To increase capacity and spectral efficiency in the 2.4 GHz ISM band.
To increase the number of simultaneous users that can be supported in a given network/area.
To make network planning in enterprise environments easier.
A. Batra et al., Texas Instruments

3. Summary of 4 Channel Proposal (1)
May 2002
Summary of 4 Channel Proposal (1)
Define CHNL_ID = 0 to correspond to a center frequency of 2407 MHz.
Allow the use of CHNL_ID = 12 in North American.
North American Channel Selection: optional 4 channel scheme.
Channel 4 and 8 are already IEEE b channels.
A. Batra et al., Texas Instruments

4. Summary of 4 Channel Proposal (2)
May 2002
Summary of 4 Channel Proposal (2)
European Channel Selection: optional 4 channel scheme.
Channels 1 and 13 are approximately the same distance from the forbidden bands.
No additional channels are need for this scheme. Channels 1 – 13 are already defined in IEEE b standard.
In Europe and Asia, 4 non-overlapping channels can be implemented today!
A. Batra et al., Texas Instruments

5. Ad-Hoc Conference Calls
May 2002
Ad-Hoc Conference Calls
Two conference calls were held (second call was a replay of the first call).
Generally, the group agreed that increasing the number of channels, and therefore the overall capacity, was a good idea.
Concerns voiced by the group:
PA backoff required for the outer channels (0 and 12).
Effects of adjacent channel interference.
Is this proposal strictly for g devices.
What happens when b device roams into BSS supporting 4 channel option.
Will aggregate throughput for 4 channels be substantially higher than aggregate throughput for 3 channels.
A. Batra et al., Texas Instruments

6. Addressing the Concerns (1)
May 2002
Addressing the Concerns (1)
PA Backoff: Moving from channel 0 to channel 1 requires an additional 3 to 4 dB of PA backoff.
This could reduce total transmit power for current designs.
However, as power amplifiers become more linear, this should not be an issue.
ACI: Steve Halford agreed to look at this issue.
There will be a presentation on this issue at this meeting.
It was decided by the group that this proposal should be specifically targeted for IEEE g devices.
No resolution on how to handle legacy devices roaming into BSS using 4 channel option.
Possibly deny service for devices that don’t support 4 channels option. Need to add capability bits to exchange informational elements.
A. Batra et al., Texas Instruments

7. Addressing the Concerns (2)
May 2002
Addressing the Concerns (2)
Consider the following experiment using legacy devices.
Baseline:
25 MHz channel spacing.
AP1 is on channel 6.
(Adhoc1, Adhoc2) on channels (1,11).
Streamed UDP data on adhoc networks.
Used Chariot to measure throughput from AP1 to STA1.
Measured throughput at 3 distances.
Experiment:
20 MHz channel spacing.
AP1 is on channel 5.
(Adhoc1, Adhoc2) on channels (1,9).
A. Batra et al., Texas Instruments

8. Addressing the Concerns (3)
May 2002
Addressing the Concerns (3)
Experimental Results: AP1 STA 1 Throughput
d (ft)
No adjacent channels
20 MHz Spacing
25 MHz Spacing
1 Adjacent Channel
2 Adjacent Channels 8
4.8 30
4.6
4.5 40
4.0
3.9
3.6
A. Batra et al., Texas Instruments

9. Addressing the Concerns (4)
May 2002
Addressing the Concerns (4)
In general, it is difficult to extrapolate the aggregate throughput. It really depends on the layout of the cells.
Three non-overlapping channels:
Device associated with channel 6 will experience interference from 2 adjacent channels.
Devices associated with channels 1 and 11 will experience interference from 1 adjacent channel.
Assumes worst location when STA is located at the boundary of two cells.
A. Batra et al., Texas Instruments

10. Addressing the Concerns (5)
May 2002
Addressing the Concerns (5)
Four non-overlapping channels:
Again, assumes worst location when STA is located uniformly at the boundary of two cells.
Devices associated with channels 0 and 12 will experience interference from 1 adjacent channel with prob = 2/3 and no interference with prob = 1/3.
Devices associated with channels 4 and 8 will experience interference from 1 adjacent channel with prob = 2/3 and from 2 adjacent channels with prob = 1/3.
Use the throughput measured on the inner channels (channel 6 for baseline, and channel 5 for experiment) for the outer channels.
This value is correct for Europe and Asia because outer channel is 1 (normal channel), but may be optimistic for North America because outer channel is 0 (proposed new channel).
A. Batra et al., Texas Instruments

11. Addressing the Concerns (6)
May 2002
Addressing the Concerns (6)
Experimental Results: AP1 STA 1 Throughput
From this experiment, we see that the extrapolated aggregate throughput for 4 channel option is approximately 29% to 33% greater than that for 3 channels.
d (ft)
No adjacent channels
20 MHz Spacing
25 MHz Spacing
1 Adjacent Channel
2 Adjacent Channels
4-channel aggregate throughput *
3-channel aggregate throughput * 8
4.8
19.2
14.4 30
4.6
4.5
18.3
13.7 40
4.0
3.9
3.6
15.5
12.0
* Extrapolated values are calculate using the discussion on previous two slides.
A. Batra et al., Texas Instruments

12. May 2002
Possible Resolution
In Europe and Asia it is possible to use 4 non-overlapping today.
To allow for 4 non-overlapping channels in North American, we need to do the following:
Minimum changes required:
Define CHNL_ID = 0 to correspond to a center frequency of 2407 MHz.
Changes needed to specify operation:
Allow support for CHNL_ID = 0 and CHNL_ID = 12 in North America.
Add informative text on how to select the 4 non-overlapping channels for North America and Europe.
Add informative text on how to handle legacy devices joining networks using the 4 channels.
Add necessary informational elements and possibly denial codes.
A. Batra et al., Texas Instruments

13. Conclusion Held conference calls to discuss 4 channel proposal.
May 2002
Conclusion
Held conference calls to discuss 4 channel proposal.
Group agreed that increasing the number of channels from 3 to 4 was a good idea.
Group also voiced concerns with the proposal.
This presentation attempted to address many of these concerns.
Presented possible resolutions.
A. Batra et al., Texas Instruments

14. May 2002
Motion
Move to add definition of CHNL_ID = 0 to correspond to center frequency of 2407 MHz in the IEEE g draft.
A. Batra et al., Texas Instruments