Making Radios More Like Human Ears

®

Copyright© Intel Corporation 2000-2004

Making Radios More Like Human EarsMaking Radios More Like Human Ears

Jing Zhu, Xingang Guo, L. Lily Yang, Jing Zhu, Xingang Guo, L. Lily Yang, W. Steven ConnerW. Steven Conner

Intel Corp.Intel Corp.

Lakshman KrishnamurthyLakshman Krishnamurthy

Principal EngineerPrincipal Engineer

Intel Corp.Intel Corp.

• 2 •Communications TechnologyCommunications Technology

LabLab

Leveraging spatial reuse with enhanced physical carrier sensing Copyright© Intel Corporation 2000-2004

Three pointsThree points We can improve performance by making We can improve performance by making

radios like our earsradios like our ears And behaving like people – talk even though you And behaving like people – talk even though you

hear othershear others

Mesh can give more bandwidth – not lessMesh can give more bandwidth – not less

Stop working on routing and NS2!Stop working on routing and NS2!


LabLab


Problem overviewProblem overview Mesh networkMesh network

An ad-hoc group of nodes relaying each other’s trafficAn ad-hoc group of nodes relaying each other’s traffic

Logically flat hierarchy – AP mesh, station mesh, hybrid Logically flat hierarchy – AP mesh, station mesh, hybrid meshmesh

Spatial reuse – use the same channel at spatially Spatial reuse – use the same channel at spatially separated locationsseparated locations Enable simultaneous communications to improve overall Enable simultaneous communications to improve overall

network throughputnetwork throughput

Applicable to large-scale wireless networksApplicable to large-scale wireless networks

* Third party brands/names are property of their respective owners


LabLab


Physical carrier sensingPhysical carrier sensing 802.11 MAC based on CSMA/CA802.11 MAC based on CSMA/CA

CS (Carrier Sensing) to avoid interferenceCS (Carrier Sensing) to avoid interference

Carrier sensing – a station listens before transmitCarrier sensing – a station listens before transmit Listen – sample the radio energy (interference) in the airListen – sample the radio energy (interference) in the air

Carrier sensing thresholdCarrier sensing threshold Decide transmit or waitDecide transmit or wait Current devices – static, not independently tunableCurrent devices – static, not independently tunable

Make the threshold tunable, and network throughput Make the threshold tunable, and network throughput can be improved dramatically with properly tuned can be improved dramatically with properly tuned thresholdthreshold


LabLab


Network throughputNetwork throughput Large-scale 802.11 networks, in each channelLarge-scale 802.11 networks, in each channel

Link date rate – RLink date rate – R 11 Mbps 11 Mbps

# of simultaneous comm. – # of simultaneous comm. – NN 1010

X) .X) .

Network throughput (R*N)Network throughput (R*N) 110 Mbps 110 Mbps

““N” determined by spatial reuseN” determined by spatial reuse Reuse the same channel in separated locationReuse the same channel in separated location

Tuning CS threshold can leverage spatial reuse Tuning CS threshold can leverage spatial reuse


LabLab


Communication modelCommunication model Each data rate has its own requirement on channel Each data rate has its own requirement on channel

qualityquality SNIR thresholdSNIR threshold

Spatial reuseSpatial reuse Properly separateProperly separate

simultaneous comm.simultaneous comm.

Different rates willDifferent rates will

require differentrequire different

separation distancesseparation distances

CS threshold reflects separation distanceCS threshold reflects separation distance

0.00E+00

1.00E+06

2.00E+06

3.00E+06

4.00E+06

5.00E+06

6.00E+06

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

SNIR (dB)

On

e-H

op

Ca

pa

cit

y (

bp

s)

1 Mbps

2 Mbps

5.5 Mbps

11 Mbps


LabLab


A

B

TX

D

RX

Anatomy of interferenceAnatomy of interference

R I

X C


LabLab


Simulating chain networkSimulating chain network 90-node chain, 90-90-node chain, 90-

hop e2e pathhop e2e path Tx range tuned to Tx range tuned to

node distancenode distance Measure e2e Measure e2e

throughput while throughput while varying Pvarying Pcs_tcs_t

E2e throughput E2e throughput changes dramaticallychanges dramatically

Optimal POptimal Pcs_tcs_t depends depends on data rateon data rate


LabLab


Simulating grid networkSimulating grid network 10x10 grid, comm. w/ 10x10 grid, comm. w/

immediate neighborsimmediate neighbors Tx range tuned to node Tx range tuned to node

distancedistance Measure aggregate Measure aggregate

throughput while throughput while varying Pvarying Pcs_tcs_t

E2e throughput E2e throughput changes dramaticallychanges dramatically

Optimal POptimal Pcs_tcs_t NOT NOT depending on depending on propagation propagation environmentenvironment


LabLab


RTS/CTS?RTS/CTS? Protocol exchange may Protocol exchange may

fail when outside of Tx fail when outside of Tx rangerange

A

B

TX

D

RXR I

C

VCS failed to take VCS failed to take full advantage of full advantage of higher pathloss to higher pathloss to increase spatial increase spatial reusereuse


LabLab


ConclusionConclusion Properly tuned carrier sensing achieves optimal Properly tuned carrier sensing achieves optimal

spatial reusespatial reuse

Dramatically improves network throughputDramatically improves network throughput

Computational efficientComputational efficient

Complementary to RTS/CTSComplementary to RTS/CTS

Non-disruptive enhancement to 802.11 MACNon-disruptive enhancement to 802.11 MAC

Make the carrier sensing tunable in all 802.11 Make the carrier sensing tunable in all 802.11 devicesdevices


LabLab


Overview: Experimental evaluation of an 802.11b home mesh networkOverview: Experimental evaluation of an 802.11b home mesh network

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

B

C

D

A

70 71

72

73

74

7576

77

Experiments performed in 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.)


LabLab


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)

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77

Multi-Hop ESS Individual Node Throughput

5.179

2.679 2.686

1.8

0

1

2

3

4

5

6

Th

rou

gh

pu

t (M

bp

s)


70 (O)

73 (D)

75 (L)

77 (B)

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77

Individual Node ThroughputIndividual Node ThroughputNon-Mesh BSS Individual Node Throughput

Out of ra

nge

1.7X 3.1X Connected!


LabLab


Multi-Node ThroughputMulti-Node Throughput

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77Out o

f range

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

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77

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

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)

5.322

3.910 3.8803.284

1.3X 1.9X 2.1X


LabLab


Multi-Node Throughput cont.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

Th

rou

gh

pu

t (M

bp

s)

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

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77Out o

f range

1.719

3.709

2.1X


LabLab


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

0.776 0.792

2.721

0

0.5

1

1.5

2

2.5

3

Th

rou

gh

pu

t (M

bp

s)

LR to Den LR to LR Off to Off

75 (L) -> 73 (D)

75 (D) -> 76 (D)

71 (O) -> 72 (O)

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77Out o

f range

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77

Multi-Hop ESS Client-to-Client Throughput

1.886

2.716 2.721

0

0.5

1

1.5

2

2.5

3

Th

rou

gh

pu

t (M

bp

s)

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


LabLab


Network LatencyNetwork LatencyNon-Mesh BSS End-to-End Latency

4.06 4.16 3.88

0

1

2

3

4

5

6

7

8

9

Ro

un

d-T

rip

-Tim

e (

ms

)


70 (O)

73 (D)

75 (L)

77 (B)

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77Out o

f range

Multi-Hop ESS End-to-End Latency

4.18

6.34 6.06

8.34

0

1

2

3

4

5

6

7

8

9

Ro

un

d-T

rip

-Tim

e (

ms

)


70 (O)

73 (D)

75 (L)

77 (B)

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77 Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Upper Level

Office

Upper Level

Office

Lower Level

LivingRoom

Den

BackYard

Lower Level

LivingRoom

Den

BackYard

A

70 71

72

73

74

7576

77

A

70 71

72

73

74

7576

77

70 71

72

73

74

7576

77

• Highly dependent on implementation

~ 2ms increase per hop


LabLab


Shorter range radio hops offer higher throughput

Source: Intel CorporationSource: Intel Corporation

Theoretical Data Rates

0

10

20

30

40

50

60

70

80

90

100

0.00 10.00 20.00 30.00 40.00 50.00Distance (m)

Th

rou

gh

pu

t (M

bp

s) IEEE802.11a

IEEE 802.11gUWB


LabLab


Summary of home testbed ResultsSummary of home testbed Results

A multi-hop mesh is beneficial, even for a A multi-hop 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)


LabLab


Mesh test bed and PlatformsMesh test bed and Platforms•25-35 nodes

•Laptops and embbeded Xscale boards (PXA-255 and IXP425)

•Boards, software available for research

•Performance comparison of mesh and wireless network self organization


LabLab


Microsoft ResearchMicrosoft Research IntelIntel

Routing ProtocolRouting Protocol Median Throughput of Median Throughput of 100 TCP transfers100 TCP transfers

LQSR w/ shortest pathLQSR w/ shortest path

(No link quality metric)(No link quality metric)1155 Kbps1155 Kbps

LQSR w/ ETX LQSR w/ ETX

(MIT 2002)(MIT 2002)1379 Kbps1379 Kbps

LQSR w/ ETX++LQSR w/ ETX++

(MSR 2003)(MSR 2003)1601 Kbps1601 Kbps

AODV w/ link filteringAODV w/ link filtering

(Intel 2003)(Intel 2003)1460 Kbps1460 Kbps

Topology and Transmit power have significant impactTopology and Transmit power have significant impact

Routing ProtocolRouting Protocol Median Throughput Median Throughput of 100 TCP transfersof 100 TCP transfers

LQSR w/ shortest LQSR w/ shortest pathpath

(No link quality (No link quality metric)metric)

LQSR w/ ETX LQSR w/ ETX

(MIT 2002)(MIT 2002)

7334 Kbps7334 Kbps

1935 Kbps1935 Kbps

LQSR w/ ETX++LQSR w/ ETX++

(MSR 2003)(MSR 2003)

AODV w/ link filteringAODV w/ link filtering

(Intel 2003)(Intel 2003)

11709 Kbps11709 Kbps

2079 Kbps2079 Kbps

Need self-configuration algorithms


LabLab


802.11S MESH standardLowering the Barriers to 802.11 Mesh Deployment802.11S MESH standardLowering the Barriers to 802.11 Mesh Deployment

Standardize Multi-Hop ESS MeshStandardize Multi-Hop ESS Mesh Interoperability Interoperability Radio/Metric-Aware L2 Routing/SwitchingRadio/Metric-Aware L2 Routing/Switching SecuritySecurity Self-Configuration / ManagementSelf-Configuration / Management

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

interference)interference)

Major focus of new Mesh Major focus of new Mesh Task Group (802.11s)Task Group (802.11s)

Leverage 802.11i/k where Leverage 802.11i/k where possiblepossible

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 possibleLeverage 802.11e/n where possible Mesh-specific MAC enhancements Mesh-specific MAC enhancements

can be made in ESS Mesh TGcan be made in ESS Mesh TG

Parallel Efforts:


LabLab


Thank youThank you

Documents

Making Radios More Like Human Ears