1. Proposed 802.11 MAC Extensions for 11n/s/p
May 2006
Proposed MAC Extensions for 11n/s/p
Date:
Authors:
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M. Benveniste (Avaya Labs)

2. Proposed Multi-Purpose 802.11 MAC Extensions
May 2006
Proposed Multi-Purpose MAC Extensions
Mathilde Benveniste
Background:
M. Benveniste (Avaya Labs)

3. May 2006
Introduction
Extension of the MAC protocol to allow parallel use of multiple channels by a set of wireless devices can boost aggregate throughput beyond what an enhanced link protocol can
The CCC MAC
Achieves shorter delays and higher BSS/mesh aggregate throughput through the parallel use of multiple channels
Facilitates multiple-radio device operation for higher node throughput, to avoid bottlenecks at traffic concentration points
Observes CCA and virtual carrier sense on all channels used
Both existing and new link technologies (11/11b/ 11g/11a/11n) can be used together with CCC
M. Benveniste (Avaya Labs)

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

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

6. Basic protocol description
May 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
Devices reserve time on data channels by exchanging CC-RTS/CC-CTS on the control channel
CC-RTS/CC-CTS indicate channel being reserved and reservation duration
A dedicated radio (receiver) monitors reservations on control channel
Control channel may carry data
Control channel can serve data channels of diverse PHYs (11b/a/g/n)
Data Channels
Data radio transmits/receives data on one of multiple data channels, and monitors data channel when not transmitting
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
CC-Ack useful for multiple-radio devices
M. Benveniste (Avaya Labs)

7. CCC MAC protocol May 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. Backward-compatibility and co-existence with independent devices
1 Summary description of CCC features
May 2006
Backward-compatibility and co-existence with independent devices
CCC observes CCA and virtual carrier sense
CCA
Transmission on the control and data channel follows CSMA/CA rules
Virtual carrier sense
A NAV is maintained for each of the channels used
Each NAV is updated by
CC-RTS/CC-CTS transmitted on control channel
RTS/CTS and other NAV-setting frames on data channel
NAV-setting information is collected by both the control radio and the data radio(s)
A device has the control radio constantly tuned to the control channel and a data radio tuned to a data channel, collecting NAV information continually
The data radio must be tuned to a data channel for at least a time period (TBD) prior to initiating its reservation, to enable NAV synchronization
M. Benveniste (Avaya Labs)

9. May 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
Data traffic on
the control channel
Data traffic on
the data channel AP
HDTV
Legacy APs and
legacy stations
co-exist with
CCC stations
Desktop
3 channels in use CC
(control channel) DC
(data channels)
Laptop
Printer
Camcorder
M. Benveniste (Avaya Labs)

10. on both data and control channel on both data and control channel
May 2006
Multi-channel multi-radio BSS/mesh under CCC MAC Example: Some handheld devices have 1 radio AP and other devices have 1.5 (2) radios
PVR
WiFi phone
Dual WiFi/cell
camera phone
PDA
MP3 Player
AP communicates
on both data and control channel
DLS transmissions
on both data and control channel
HDTV AP
Desktop
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. WLAN traffic load concentration calls for multi-radio devices
May 2006
WLAN traffic load concentration calls for multi-radio devices
Infrastructure APs concentrate BSS traffic
A multi-radio AP will accommodate high aggregate BSS throughput to/from DS
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)

12. Adjacent Channel Interference
May 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
Using ‘non-adjacent’ channels only to avoid ACI lowers efficiency of channel use
Low channel re-use since only a few channels can be used in the mesh
M. Benveniste (Avaya Labs)

13. CCC solution to ACI problem
1 Summary description of CCC features
May 2006
CCC solution to ACI problem
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 device 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 device is transmitting on
Acknowledgements between end points involved in adjacent-channel transmissions must be sent on the control channel
M. Benveniste (Avaya Labs)

14. 802.11n – CCC in High Throughput
May 2006
802.11n – CCC in High Throughput
HT will provide high link and high aggregate network throughput
CCC enables
Use of multiple-radio devices to increase link throughput; the control channel can be used simultaneously with another channel
Any combination of multiple channels can be used by different streams (including DLS) in BSS to increase aggregate throughput, even beyond what’s possible with current TGn proposal
If added as an optional feature, CCC imposes no requirements on non-CCC devices
M. Benveniste (Avaya Labs)

15. 802.11s – CCC in ESS Mesh (Extended Service Set Mesh)
May 2006
802.11s – CCC in ESS Mesh (Extended Service Set Mesh)
ESS Mesh – Wireless distribution system for multiple APs and for extension of coverage
The traffic of multiple APs is conveyed along wireless backbone
CCC capabilities
Multiple-channel access – high aggregate throughput based on availability
Multiple-radio devices – high link throughput, to avert bottlenecks near portal
CCA and virtual carrier sense capability for co-existence with independent and legacy devices
Current 11s proposal lacks the following:
No multi-radio capability
Virtual carrier sense is not always observed (not backward compatible)
M. Benveniste (Avaya Labs)

16. 802.11p – CCC in WAVE (Wireless Access in Vehicular Environment)
May 2006
802.11p – CCC in WAVE (Wireless Access in Vehicular Environment)
WAVE – Communications between roadside APs and vehicles and between vehicles
Very short latencies
Some applications must complete multiple data exchanges within 4 to 50ms
CCC enables
Quick short reservation on control channel – high priority access
Choice of one of many data channels to perform the data exchange
Un-tethered multicast/broadcast capability
Efficient use of available channels for maximum throughput
M. Benveniste (Avaya Labs)

17. 1 Summary description of CCC features
May 2006
Summary
With the CCC MAC, communicating wireless devices 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) – a ‘must’ for wireless backhaul meshes
CCC can be used with any mix of PHY channels, including 11n
If used with 11n channels, CCC multiplies the throughput increase beyond what is attainable by 11n alone (e.g. for multimedia applications)
Several task groups will benefit from the adoption of CCC as an optional MAC extension: TGn, TGs, and TGp
Implementation of CCC as an option poses no requirements on non-CCC devices
CCC is backward compatible with existing devices
CCC devices can co-exist with non-CCC and independent (in different BSSs or non-mesh) devices
M. Benveniste (Avaya Labs)

18. 1 Summary description of CCC features
May 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)