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

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

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 802.11b channels. A. Batra et al., Texas Instruments

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 802.11b standard. In Europe and Asia, 4 non-overlapping channels can be implemented today! A. Batra et al., Texas Instruments

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 802.11g devices. What happens when 802.11b 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

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 802.11g 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

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

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

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

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

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

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

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

May 2002 Motion Move to add definition of CHNL_ID = 0 to correspond to center frequency of 2407 MHz in the IEEE 802.11g draft. A. Batra et al., Texas Instruments