1. 802.11 MAC Extensions for Increasing Aggregate WLAN Throughput
March 2006
MAC Extensions for Increasing Aggregate WLAN Throughput
Date:
Authors:
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M. Benveniste (Avaya Labs)

2. 802.11 MAC Extensions for Increasing Aggregate WLAN Throughput
March 2006
MAC Extensions for Increasing Aggregate WLAN Throughput
Mathilde Benveniste
Background:
M. Benveniste (Avaya Labs)

3. March 2006
Introduction
A MAC protocol that allows parallel use of multiple channels can boost WLAN aggregate throughput beyond what a link protocol can
The CCC MAC achieves higher BSS/mesh aggregate throughput through the parallel use of multiple channels
Multiple-radio stations enable higher throughput at traffic concentration points
Both existing and new link technologies (11/11b/ 11g/11a/11n) can be used with CCC
M. Benveniste (Avaya Labs)

4. Multi-channel BSS/mesh
March 2006
Multi-channel BSS/mesh AP
WiFi phone
HDTV
Camcorder
Desktop
PDA
Laptop
Printer
Dual WiFi/cell
camera phone
Multimedia
games
MP3 Player
DVD Player
Camera
M. Benveniste (Avaya Labs)

5. Description of Common Control Channel (CCC) MAC Protocol
March 2006
Description of Common Control Channel (CCC) MAC Protocol
M. Benveniste (Avaya Labs)

6. Basic protocol description
March 2006
Basic protocol description
One control and multiple data channels are available for use in a BSS or mesh
CCC works with 1, 1.5, … or n radios
Control Channel
Stations reserve time on data channels by exchanging CC-RTS/CC-CTS on the control channel
CC-RTS/CC-CTS indicate channel being reserved
A dedicated radio (receiver) monitors reservations on control channel
Control channel may carry data
Control channel can serve data channels of diverse PHYs (11a/g/n)
Data Channels
Data radio transmits/receives data on one of multiple data channels
A device may have multiple data radios for higher node throughput
Acknowledgements
Acknowledgements may be sent on same channel as data or on control channel
Needed for multiple-radio devices
M. Benveniste (Avaya Labs)

7. CCC MAC protocol March 2006 TXOP TXOP TXOP TXOP time Radio Frequency
CC-RTS
CC-CTS
CC-RTS
CC-CTS
CC-RTS
CC-CTS
CC-RTS
CC-CTS
DC 2
DC 1 CC
DC 3
TXOP
TXOP
TXOP
TXOP
time
Radio
Frequency
M. Benveniste (Avaya Labs)

8. legacy non-AP stations
March 2006
Multi-channel BSS under CCC MAC Example: AP, WiFi phone and PDA have 1 radio All other devices have 1.5 (2) radios
DVD Player
WiFi phone
PDA AP
HDTV
Legacy APs and
legacy non-AP stations
can co-exist with
CCC stations
Desktop
3 channels in use CC
(control channel) DC
(data channels)
Laptop
Printer
Camcorder
M. Benveniste (Avaya Labs)

9. WLAN traffic load concentration calls for multi-radio stations
March 2006
WLAN traffic load concentration calls for multi-radio stations
Infrastructure APs concentrate BSS traffic
A multi-radio AP will accommodate high aggregate BSS throughput
For meshes, load increases (geometrically) with the number of mesh APs (hops) as paths converge toward the portal
The total load through the portal is the sum of the loads offered at the mesh APs
Multi-radio devices are needed closer to the portal of a mesh and at APs with heavy traffic loads
Load =x
Load =3x
Load =7x
Load =15x
Portal
Load =30x
Mesh AP
M. Benveniste (Avaya Labs)

10. March 2006
Multi-channel multi-radio BSS/mesh under CCC MAC Example: WiFi phone and PDA have 1 radio AP has 2.5 (3) radios; all other devices have 1.5 (2) radios
PVR
WiFi phone
Dual WiFi/cell
camera phone
PDA
MP3 Player
HDTV AP
Desktop
Multi-radio CCC AP
serves CCC
and legacy stations
on multiple channels
Multimedia
games
4 channels in use
CC (control channel) DC
(data channels)
Laptop
Printer
Camcorder
Camera
M. Benveniste (Avaya Labs)

11. Adjacent Channel Interference
March 2006
Adjacent Channel Interference
Multi-radio devices can suffer adjacent channel interference (ACI) while transmitting and receiving simultaneously on adjacent channels
The number of available non-adjacent data channels is small
The available unlicensed RF spectrum has several segments of channels: one in 2.4 GHz range and 3 (or 4) in the 5 GHz range
Channels from different segments would not cause one another ACI
Avoiding ACI by using only ‘non-adjacent’ channels lowers efficiency of channel use
Low channel re-use – only a few channels can be used by multi-radio MPs in the mesh
M. Benveniste (Avaya Labs)

12. 1 Summary description of CCC features
March 2006
Proposed Solution
The control and data channels are selected so that the control channel is not adjacent to any of the data channels
Data channels may be adjacent to one another, as long as there is no simultaneous transmission and reception by the same device on adjacent channels
A transmission is delayed if a station is receiving and there is no non-adjacent channel available
A reservation is declined if the request is for a channel adjacent to the one the station is transmitting on
Acknowledgements between end points involved in adjacent-channel transmissions must be sent on the control channel
M. Benveniste (Avaya Labs)

13. 1 Summary description of CCC features
March 2006
Summary
With the CCC MAC, stations in a BSS or mesh points can access in parallel a pool of channels, not just one channel
At nodes of high traffic concentration, a device can operate on multiple radios at once without ACI
Few radios can leverage the full capacity of a channel pool
High-throughput devices (APs or mesh portals) can communicate with low throughput devices without loss of capacity
CCC is backward compatible with existing devices
CCC stations can co-exist with legacy APs and non-AP stations
CCC can be used with any mix of PHY channels, including 11n
CCC used with 11n channels multiplies the throughput increase beyond what is attainable by 11n alone
M. Benveniste (Avaya Labs)

14. 1 Summary description of CCC features
March 2006
References
M. Benveniste, "CCC Mesh MAC Protocol," IEEE s Document, DCN /0610r1, June 2005,
M. Benveniste, "CCC MAC Protocol Framework and Optional Features," IEEE s Document, DCN /0880r0, September 2005,
M. Benveniste and Z. Tao, "Performance Evaluation of a MAC Protocol for s Mesh Networks," 2006 IEEE Sarnoff Symposium, Princeton, NJ, March 2006,
M. Benveniste, “Avoiding Adjacent Channel Interference with Multi-Radio Mesh Points,” IEEE s Document, DCN /1123r0, November 2005,
M. Benveniste (Avaya Labs)