1. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 1 Performance of an 802.11 Home Network Mesh Testbed September 15, 2003 W. Steven Conner Intel Corporation (w.steven.conner@intel.com)

2. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 2 Outline   Overview of 802.11 ESS Mesh   Performance evaluation of a wireless home network testbed   Lowering the barriers to 802.11 mesh deployment   Recommendation to start 802.11 Mesh SG/TG   Summary

3. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 3 Overview: 802.11 Mesh Architectures Infrastructure Mode ESS with WDS Backhaul WDS Links Ad Hoc Links Peer-to-Peer Mesh (Ad Hoc Mode) Ad Hoc Links Ad Hoc or WDS Links Hybrid Infrastructure/ Ad Hoc Mesh

4. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 4 Overview: 802.11 ESS Mesh  Mesh is not limited to highly mobile networks with no infrastructure  Also has application in many fixed-infrastructure environments  Extended range and coverage, without requiring additional wires (convenient deployment, cost)  Enhanced redundancy, reliability  Potential throughput improvement  Example networks where ESS Mesh is useful:  Home networks, hotspot networks, etc.

5. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 5 Upper Level Office Lower Level Living Room Den Back Yard Question: Does it Make Sense to Deploy a Wireless ESS Mesh for a Home Network? B C D A 70 71 72 73 74 75 76 77

6. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 6 Overview: Experimental evaluation of an 802.11b home mesh network Upper Level Office Lower Level Living Room Den Back Yard B C D A 70 71 72 73 74 75 76 77   Experiments performed in my house (~2000 sq. ft.) in Hillsboro, OR (August, 2003)   Topology: 8 Client Laptops and 4 AP routers   In a real home network scenario, some of the laptops would likely be replaced by other 802.11 enabled devices (e.g., DVRs, media servers, stereo systems, etc.)   Traffic: Experiments assume network traffic is not limited to Internet surfing on a broadband link   Clients share significant amount of data within the home (e.g., A/V content sharing, photo storage, data backup, etc.)

7. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 7 Testbed Configurations Configuration 1  Traditional 1-hop BSS  802.11b, auto-rate, 15mW  BSS emulated with ad-hoc mode  All clients communicate directly with AP-A Configuration 2  Multi-hop ESS Mesh  802.11b, 11Mbps, 15mW  ESS emulated with ad-hoc mode - Centrally configured minimum-airtime- metric routing (zero overhead)  Clients communicate with best AP to join wireless ESS mesh Out of range

8. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 8 5.182 1.572 0.85 0 0 1 2 3 4 5 6 Throughput (Mbps) OfficeLiving Room DenBackyard 70 (O) 73 (D) 75 (L) 77 (B) Multi-Hop ESS Individual Node Throughput 5.179 2.679 2.686 1.8 0 1 2 3 4 5 6 Throughput (Mbps) OfficeLiving Room DenBackyard 70 (O) 73 (D) 75 (L) 77 (B) Individual Node Throughput Non-Mesh BSS Individual Node Throughput Out of range 1.7X  3.1X  Connected!

9. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 9 Multi-Node Throughput Out of range Non-Mesh BSS Aggregate Throughput 5.338 2.878 1.994 1.520 Multi-Hop ESS Aggregate Throughput 5.322 3.910 3.880 3.284 1.3X  1.9X  2.1X 

10. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 10 Multi-Node Throughput cont. Aggregate Throughput with 8 Clients Out of range 1.719 3.709 2.1X 

11. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 11 Client-to-Client Throughput Non-Mesh BSS Client-to-Client Throughput Out of range Multi-Hop ESS Client-to-Client Throughput 2.4X  3.4X  Note: Direct client-to-client links can help here as well

12. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 12 Network Latency Non-Mesh BSS End-to-End Latency Out of range Multi-Hop ESS End-to-End Latency Highly dependent on implementation ~ 2ms increase per hop

13. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 13 Summary of Testbed Results  A multi-hop ESS mesh is beneficial, even for a relatively small-scale home network  Multi-hop topologies:  Can be built with standard 802.11 hardware  Can improve network performance in comparison to traditional 1-hop BSS networks  These experiments used 1 radio on each AP/router; multi-radio per AP/router would allow even better performance (multi-channel)  Question: If mesh networking with 802.11 works today, why do we need additional standards support?

14. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 14 Barriers to 802.11 Mesh Deployment   Interoperability   Security   Configuration / Management   Should require minimal effort to deploy   Lack of hooks for statistics/control   Radio and metric-aware routing   MAC Performance

15. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 15 Making Mesh Work Key areas for IEEE Standardization:   Interoperability   Standardizing over-the-air messaging for mesh   Routing: –L2 mesh subnet for wireless backhaul –Radio and metric-aware path selection (hop-count is not sufficient!)   Security:   To make it possible to secure a mesh, routers should be able to trust each other   Leverage/extend 802.11i for mesh   Improving Configuration / Management   Should require minimal effort to deploy (beyond router introduction)   Statistics and control hooks need to be exposed between MAC and “mesh layer”   Leverage/extend 802.11k for mesh

16. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 16 Research indicates 802.11 MAC performance needs to be optimized for large scale mesh networks A few notable examples:  RTS/CTS does not correctly solve hidden terminal problem in a mesh  Tends to either sacrifice spatial reuse or allow excessive interference 1  RTS/CTS fails to achieve good schedule in a multi-hop chain  RTS/CTS scheduling along a chain can cause serious TCP fairness problems and backoff inefficiencies 2  RTS/CTS does not efficiently schedule transmissions in a multi- hop chain 3 [1] Kaixin Xu, M. Gerla, and Sang Bae, "How effective is the IEEE 802.11 RTS/CTS handshake in ad hoc networks?" IEEE Globecom'02, 2002, pp. 72 -76. [2] Shugong Xu and Tarek Saadawi – “Does the IEEE 802.11 MAC Protocol Work Well in Multihop Wireless Ad Hoc Networks?” IEEE Communications Magazine, June 2001, pp 130-137. [3] J. Li, C. Blake, D. S. De Couto, H. I. Lee, and R. Morris. Capacity of ad hoc wireless networks. In Proceedings of ACM MOBICOM, pages 61--69, July 2001.

17. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 17 Enabling Mesh Usage Models  Before MAC Enhancements:  Home Network  Small Office  Small Hotspot  MAC Enhancements Necessary:  Enterprise  Large Conference  High Performance Home Network  Power-users, A/V Multi-hop scheduling/scalability are significant issues

18. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 18 Lowering the Barriers to 802.11 Mesh Deployment  Standardize Multi-Hop ESS (AP Mesh)  Radio/Metric-Aware L2 Routing  Interoperability  Security  Configuration / Management  Enhance MAC Performance for Mesh  Scalability  Scheduling (managing collisions/ interference) New 802.11 Mesh Study/Task Group  Leverage 802.11i/k where possible Influence current/ future MAC enhancement efforts to improve scalability for mesh  Leverage 802.11e/n where possible Proposed Parallel Efforts:

19. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 19 Recommendation to WNG for Starting a Mesh Study/Task Group  Scope: Develop an Infrastructure-Mode 802.11 ESS AP Mesh that Appears as a Broadcast Ethernet to Higher Layer Protocols  Scale: Up to 255 devices (APs and Clients)  Security: Include support for trusted set of routers controlled by single entity  Routing: Include support for both broadcast and radio/metric- aware unicast routing  Multiple-radios: Include support for optional multiple-radios per router  Usage Models: Initially focus on home and small- scale hotspot networks

20. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 20 Backup

21. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 21 Is IEEE the Right Place to Create a Mesh Standard?  IETF/IRTF MANET groups have been working on L3 mesh standards for years  But… radio awareness is out-of-scope, significantly limiting opportunity for efficient use of the wireless channel  Major focus on large scale and high mobility (hard problems!) has significantly prolonged the standards process  IEEE 802.11 is a reasonable place to create a L2 mesh subnet standard  Allows tight integration with MAC (radio awareness)  Has the advantage of creating a mesh that looks like an ethernet to IP applications  Improved hooks/statistics for supporting a L2 mesh can also be used to improve L3 mesh implementations  IETF L3 mesh network can be used to interconnect multiple IEEE L2 mesh subnets  There is recent precedent for standardizing mesh support in IEEE  802.16a already has explicit mesh support Yes, we need improved standard support for mesh in 802.11!

22. Doc.: IEEE 11-03-0712-01-0wng Submission September 2003 Intel Corporation Slide 22 Fixing the 802.11 MAC for Mesh  We know there are issues with the current 802.11 MAC, but what about 802.11e?  EDCF should improve fairness and efficiency  TXOPs  Block ACK  Direct links between clients  Multiple queues allow traffic prioritization  What are the implications for mesh?  Improving MAC in IEEE:  Option 1: Start a new study group/task group focused on MAC support for mesh  Option 2: Piggyback on current/future non-mesh MAC enhancement efforts (e.g., 802.11n)