802.11 MAC Extensions for Increasing Aggregate WLAN Throughput

1. 802.11 MAC Extensions for Increasing Aggregate WLAN Throughput Mathilde Benveniste benveniste@ieee.org Background:http://pubs.research.avayalabs.com/pdfs/CCC_High_throughput_MAC.pdf M. Benveniste (Avaya Labs)

2. 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)

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

4. Description of Common Control Channel (CCC) MAC Protocol M. Benveniste (Avaya Labs)

5. 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)

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

7. AP WiFi phone Multi-channel BSS under CCC MACExample: AP, WiFi phone and PDA have 1 radio All other devices have 1.5 (2) radios PDA DVD Player 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)

8. Load =x Load =3x Load =7x Load =15x Load =30x Portal Mesh AP 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 M. Benveniste (Avaya Labs)

9. AP WiFi phone Multi-channel multi-radio BSS/mesh under CCC MACExample: 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 PDA DVD Player MP3 Player HDTV Desktop Multi-radio CCC AP serves CCC and legacy stations Multimedia games 4 channels in use CC (control channel) DC (data channels) Laptop Printer Camcorder Camera M. Benveniste (Avaya Labs)

10. 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 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)

11. 1 Summary description of CCC features 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)

12. 1 Summary description of CCC features 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 802.11 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)

13. 1 Summary description of CCC features References • 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 M. Benveniste (Avaya Labs)