Slide 1

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Performance of an 802.11 Home Network Mesh Testbed

September 15, 2003

W. Steven Conner

Intel Corporation

(w.steven.conner@intel.com)

Slide 2

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

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

Slide 3

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Overview: 802.11 Mesh ArchitecturesInfrastructure Mode ESSInfrastructure Mode ESSwith WDS Backhaulwith WDS Backhaul

WDS Links

Ad Hoc Links

Peer-to-Peer MeshPeer-to-Peer Mesh(Ad Hoc Mode)(Ad Hoc Mode)

Ad Hoc Links

Ad Hoc or WDS Links

Hybrid Infrastructure/Hybrid Infrastructure/Ad Hoc MeshAd Hoc Mesh

Slide 4

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Overview: 802.11 ESS Mesh

Mesh is not limited to highly mobile networks Mesh is not limited to highly mobile networks with no infrastructurewith no infrastructure

Also has application in many fixed-infrastructure Also has application in many fixed-infrastructure environmentsenvironments Extended range and coverage, without requiring Extended range and coverage, without requiring

additional wires (convenient deployment, cost)additional wires (convenient deployment, cost)

Enhanced redundancy, reliabilityEnhanced redundancy, reliability

Potential throughput improvementPotential throughput improvement

Example networks where ESS Mesh is useful:Example networks where ESS Mesh is useful: Home networks, hotspot networks, etc.Home networks, hotspot networks, etc.

Slide 5

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

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Question: Does it Make Sense to Deploy a Wireless ESS Mesh for a Home Network?

B

C

D

A

70 71

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Slide 6

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Overview: Experimental evaluation of an 802.11b home mesh network

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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.)

Slide 7

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Testbed ConfigurationsConfiguration 1Configuration 1 Traditional 1-hop BSSTraditional 1-hop BSS

802.11b, auto-rate, 15mW802.11b, auto-rate, 15mW

BSS emulated with ad-hoc BSS emulated with ad-hoc modemode

All clients communicate All clients communicate directly with AP-directly with AP-AA

Configuration 2Configuration 2 Multi-hop ESS MeshMulti-hop ESS Mesh

802.11b, 11Mbps, 15mW802.11b, 11Mbps, 15mW

ESS emulated with ad-hoc modeESS emulated with ad-hoc mode- Centrally configured minimum-airtime-Centrally configured minimum-airtime-

metric routing (zero overhead)metric routing (zero overhead)

Clients communicate with best AP Clients communicate with best AP to join wireless ESS meshto join wireless ESS mesh

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70 71

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Slide 8

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

5.182

1.5720.85

00

1

2

3

4

5

6

Th

rou

gh

pu

t (M

bp

s)

Office Living Room Den Backyard

70 (O)

73 (D)

75 (L)

77 (B)

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Multi-Hop ESS Individual Node Throughput

5.179

2.679 2.686

1.8

0

1

2

3

4

5

6

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rou

gh

pu

t (M

bp

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Office Living Room Den Backyard

70 (O)

73 (D)

75 (L)

77 (B)

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A

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Individual Node ThroughputNon-Mesh BSS Individual Node Throughput

Out of ra

nge

1.7X 3.1X Connected!

Slide 9

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Multi-Node Throughput

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Non-Mesh BSS Aggregate Throughput

1.772

1.798

1.768

0.91

0.992

0.976

0.684

0.646

0.664

0.522

0.494

0.504

0

1

2

3

4

5

6

Ag

gre

ga

te T

hro

ug

hp

ut

(Mb

ps

)

3Office 2Office,1Den 1Office,2Den 3Den

70 (O)

71 (O)

72 (O)

73 (D)

75 (D)

76 (D)

5.338

2.878

1.9941.520

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Multi-Hop ESS Aggregate Throughput

1.775

1.795

1.7525

1.304

1.336

1.27

1.338

1.314

1.228

1.45

1.048

0.786

0

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2

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6

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gre

ga

te T

hro

ug

hp

ut

(Mb

ps

)

3Office 2Office,1Den 1Office,2Den 3Den

70 (O)

71 (O)

72 (O)

73 (D)

75 (D)

76 (D)

5.322

3.910 3.8803.284

1.3X 1.9X 2.1X

Slide 10

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Multi-Node Throughput cont.

00.2230.2110.1980.2340.2910.2790.283

0.398

0.461

0.457

0.408

0.412

0.517

0.522

0.534

0

0.5

1

1.5

2

2.5

3

3.5

4

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Non-Mesh BSS Multi-Hop ESS

70 (O)

71 (O)

72 (O)

73 (D)

74 (D)

75 (L)

76 (L)

77 (B)

Aggregate Throughput with 8 Clients

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1.719

3.709

2.1X

Slide 11

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Client-to-Client ThroughputNon-Mesh BSS Client-to-Client Throughput

0.776 0.792

2.721

0

0.5

1

1.5

2

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3

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LR to Den LR to LR Off to Off

75 (L) -> 73 (D)

75 (D) -> 76 (D)

71 (O) -> 72 (O)

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Multi-Hop ESS Client-to-Client Throughput

1.886

2.716 2.721

0

0.5

1

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3

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LR to Den LR to LR Off to Off

75 (L) -> 73 (D)

75 (D) -> 76 (D)

71 (O) -> 72 (O)

2.4X 3.4X

• Note: Direct client-to-client links can help here as well

Slide 12

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Network LatencyNon-Mesh BSS End-to-End Latency

4.06 4.16 3.88

0

1

2

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7

8

9

Ro

un

d-T

rip

-Tim

e (

ms

)

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73 (D)

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Multi-Hop ESS End-to-End Latency

4.18

6.34 6.06

8.34

0

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8

9

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un

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ms

)

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• Highly dependent on implementation

~ 2ms increase per hop

Slide 13

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Summary of Testbed Results A multi-hop ESS mesh is beneficial, even for a A multi-hop ESS mesh is beneficial, even for a

relatively small-scale home networkrelatively small-scale home network Multi-hop topologies:Multi-hop topologies:

Can be built with standard 802.11 hardware Can be built with standard 802.11 hardware Can improve network performance in comparison Can improve network performance in comparison

to traditional 1-hop BSS networksto traditional 1-hop BSS networks These experiments used 1 radio on each AP/router; multi-radio per These experiments used 1 radio on each AP/router; multi-radio per

AP/router would allow even better performance (multi-channel)AP/router would allow even better performance (multi-channel)

Question: If mesh networking with 802.11 Question: If mesh networking with 802.11 works today, why do we need additional works today, why do we need additional standards support?standards support?

Slide 14

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

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

Slide 15

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Making Mesh WorkKey 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

Slide 16

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Research indicates 802.11 MAC performance needs to be optimized for large scale mesh networks

A few notable examples:A few notable examples:

RTS/CTS does not correctly solve hidden terminal problem in a RTS/CTS does not correctly solve hidden terminal problem in a meshmesh

Tends to either sacrifice spatial reuse or allow excessive interferenceTends to either sacrifice spatial reuse or allow excessive interference11

RTS/CTS fails to achieve good schedule in a multi-hop chainRTS/CTS fails to achieve good schedule in a multi-hop chain RTS/CTS scheduling along a chain can cause serious TCP fairness RTS/CTS scheduling along a chain can cause serious TCP fairness

problems and backoff inefficienciesproblems and backoff inefficiencies22

RTS/CTS does not efficiently schedule transmissions in a multi-hop chainRTS/CTS does not efficiently schedule transmissions in a multi-hop chain33

[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.

Slide 17

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Enabling Mesh Usage Models Before MAC Enhancements:Before MAC Enhancements:

Home NetworkHome Network

Small OfficeSmall Office

Small HotspotSmall Hotspot

MAC Enhancements Necessary:MAC Enhancements Necessary: EnterpriseEnterprise

Large ConferenceLarge Conference

High Performance Home Network High Performance Home Network Power-users, A/VPower-users, A/V Multi-hop scheduling/scalability

are significant issuesMulti-hop scheduling/scalability are significant issues

Slide 18

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Lowering the Barriers to 802.11 Mesh Deployment

Standardize Multi-Hop ESS (AP Mesh)Standardize Multi-Hop ESS (AP Mesh) Radio/Metric-Aware L2 Routing Radio/Metric-Aware L2 Routing Interoperability Interoperability SecuritySecurity Configuration / ManagementConfiguration / Management

Enhance MAC Performance for MeshEnhance MAC Performance for Mesh ScalabilityScalability Scheduling (managing collisions/ Scheduling (managing collisions/

interference)interference)

New 802.11 Mesh New 802.11 Mesh Study/Task GroupStudy/Task Group

Leverage 802.11i/k Leverage 802.11i/k where possiblewhere possible

Influence Influence current/ future MAC current/ future MAC enhancement efforts to improve enhancement efforts to improve scalability for meshscalability for mesh

Leverage 802.11e/n where Leverage 802.11e/n where possiblepossible

Proposed Parallel Efforts:

Slide 19

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Recommendation to WNG for Starting a Mesh Study/Task Group Scope: Develop an Infrastructure-Mode 802.11 ESS Scope: Develop an Infrastructure-Mode 802.11 ESS

AP Mesh that Appears as a Broadcast Ethernet to AP Mesh that Appears as a Broadcast Ethernet to Higher Layer ProtocolsHigher Layer Protocols Scale: Up to 255 devices (APs and Clients)Scale: Up to 255 devices (APs and Clients)

Security: Include support for trusted set of routers controlled by Security: Include support for trusted set of routers controlled by single entitysingle entity

Routing: Include support for both broadcast and radio/metric-Routing: Include support for both broadcast and radio/metric-aware unicast routingaware unicast routing

Multiple-radios: Include support for optional multiple-radios per Multiple-radios: Include support for optional multiple-radios per routerrouter

Usage Models: Initially focus on home and small-Usage Models: Initially focus on home and small-scale hotspot networksscale hotspot networks

Slide 20

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Backup

Slide 21

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Is IEEE the Right Place to Create a Mesh Standard?

IETF/IRTF MANET groups have been working on L3 mesh standards for IETF/IRTF MANET groups have been working on L3 mesh standards for yearsyears

But… radio awareness is out-of-scope, significantly limiting opportunity for efficient use But… radio awareness is out-of-scope, significantly limiting opportunity for efficient use of the wireless channelof the wireless channel

Major focus on large scale and high mobility (hard problems!) has significantly Major focus on large scale and high mobility (hard problems!) has significantly prolonged the standards processprolonged the standards process

IEEE 802.11 is a reasonable place to create a L2 mesh subnet standardIEEE 802.11 is a reasonable place to create a L2 mesh subnet standard Allows tight integration with MAC (radio awareness)Allows tight integration with MAC (radio awareness) Has the advantage of creating a mesh that looks like an ethernet to IP applicationsHas 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 Improved hooks/statistics for supporting a L2 mesh can also be used to improve L3

mesh implementationsmesh implementations IETF L3 mesh network can be used to interconnect multiple IEEE L2 mesh subnetsIETF L3 mesh network can be used to interconnect multiple IEEE L2 mesh subnets

There is recent precedent for standardizing mesh support in IEEEThere is recent precedent for standardizing mesh support in IEEE 802.16a already has explicit mesh support802.16a already has explicit mesh support

Yes, we need improved standard support for mesh in 802.11!Yes, we need improved standard support for mesh in 802.11!

Slide 22

Doc.: IEEE 11-03-0712-01-0wng

Submission

September 2003

Intel Corporation

Fixing the 802.11 MAC for Mesh We know there are issues with the current 802.11 We know there are issues with the current 802.11

MAC, but what about 802.11e?MAC, but what about 802.11e? EDCF should improve fairness and efficiencyEDCF should improve fairness and efficiency

TXOPsTXOPs

Block ACKBlock ACK

Direct links between clientsDirect links between clients

Multiple queues allow traffic prioritizationMultiple queues allow traffic prioritization

What are the implications for mesh?What are the implications for mesh?

Improving MAC in IEEE:Improving MAC in IEEE: Option 1: Start a new study group/task group focused on MAC Option 1: Start a new study group/task group focused on MAC

support for meshsupport for mesh

Option 2: Piggyback on current/future non-mesh MAC Option 2: Piggyback on current/future non-mesh MAC enhancement efforts (e.g., 802.11n)enhancement efforts (e.g., 802.11n)