March 2006
doc.: IEEE 802.11-06/0408r1
802.11 MAC Extensions for Increasing
Aggregate WLAN Throughput
Date: 2006-03-08
Authors:
Name
Company
Address
Phone
email
Mathilde
Benveniste
Avaya Labs
233 Mt Airy Road
Basking Ridge, NJ
07920
973 7616105
[email protected]
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Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
802.11 MAC Extensions for Increasing
Aggregate WLAN Throughput
Mathilde Benveniste
[email protected]
Background: http://pubs.research.avayalabs.com/pdfs/CCC_High_throughput_MAC.pdf
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
Multi-channel BSS/mesh
Dual WiFi/cell
camera phone
DVD Player
WiFi
phone
HDTV
PDA
MP3 Player
AP
Desktop
Multimedia
games
Laptop
Camcorder
Submission
Printer
Camera
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
Description of Common Control Channel
(CCC) MAC Protocol
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
CCC MAC protocol
CC
DC 1
DC 2
DC 3
TXOP
TXOP
TXOP
TXOP
time
Radio
Frequency
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
Multi-channel BSS under CCC MAC
Example: AP, WiFi phone and PDA have 1 radio
All other devices have 1.5 (2) radios
PDA
DVD Player
WiFi
phone
HDTV
AP
Legacy APs and
Desktop
legacy non-AP stations
can co-exist with
CCC stations
3 channels in use
CC
(control channel)
DC
Laptop
Camcorder
Printer
(data channels)
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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 =30x
Load =15x
Portal
Mesh AP
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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
Dual WiFi/cell
camera phone
PVR
WiFi
phone
HDTV
PDA
MP3 Player
AP
Multi-radio CCC AP
serves CCC
Multimedia
games
and legacy stations
4 channels in use
on multiple channels
CC
(control channel)
DC
(data channels)
Submission
Desktop
Laptop
Camcorder
Printer
Camera
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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 multiradio MPs in the mesh
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
Proposed Solution
1. The control and data channels are selected so that the
control channel is not adjacent to any of the data channels
2. 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
–
–
–
Submission
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 adjacentchannel transmissions must be sent on the control channel
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
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
–
•
CCC is backward compatible with existing 802.11 devices
–
•
•
High-throughput devices (APs or mesh portals) can communicate with low
throughput devices without loss of capacity
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
Submission
M. Benveniste (Avaya Labs)
March 2006
doc.: IEEE 802.11-06/0408r1
References
1.
2.
3.
4.
M. Benveniste, "CCC Mesh MAC Protocol," IEEE 802.11s Document, DCN
802.11-05/0610r1, June 2005, https://802wirelessworld.com
M. Benveniste, "CCC MAC Protocol Framework and Optional Features," IEEE
802.11s Document, DCN 802.11-05/0880r0, September 2005,
https://802wirelessworld.com
M. Benveniste and Z. Tao, "Performance Evaluation of a MAC Protocol for
802.11s Mesh Networks," 2006 IEEE Sarnoff Symposium, Princeton, NJ,
March 2006, www.research.avayalabs.com/user/benveniste
M. Benveniste, “Avoiding Adjacent Channel Interference with Multi-Radio
Mesh Points,” IEEE 802.11s Document, DCN 802.11-05/1123r0, November
2005, https://802wirelessworld.com
Submission
M. Benveniste (Avaya Labs)