9/18/2003 UCAN @ MOBICOM'03 1

UCAN: A Unified Cellular and Ad-Hoc Network

Architecture

Haiyun LuoRamachandran Ramjee

Prasun Sinha, Li Erran Li, Songwu Lu

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Wireless WAN v.s. LAN

1xEV-DO (HDR) Large coverage Low data rate Infrastructure

only IEEE 802.11

Small coverage High data rate Ad-hoc capable

BaseStation

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Wireless WAN v.s. LAN Observations:

Commercial applications need availability assurance – only through WAN infrastructure

Low data-rate (depending on location) client reduces WAN T’put

Goal: Cost-effective way to improve WAN channel

utilization, while maintaining fairness Solution:

A new network paradigm to improve WAN T’put through opportunistic use of ad-hoc LAN

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Motivation: Experiment

Verizon WirelessCDMA2000-1X

Dual interfaces Verizon Wireless

CDMA2000-1X 144Kbps

802.11b 11Mbps Destination Laptop

Locate in Lab Room w/ Poor CDMA2000-1X Channel

Relay Computer Locate in Lab

Corridor w/ Good CDMA2000-1X Ch’l

Destinationin Lab Room

Relay inLab Corridor

BaseStation

802.11b

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Results

Average T’put No-relay

51.6Kbps Relay 93.9Kbps

Max T’put No-relay

95Kbps Relay 130Kbps

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Outline UCAN Device UCAN Architecture

Base-station assisted routing Incentive provisioning

Simulation evaluation Conclusion, future work

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UCAN Device

Dual interfaces: both 3G WAN and 802.11 LAN Laptops with 3G wireless modem and 802.11

card GTRAN Wireless ‘DotSurfer 5000 Wireless

Modem” 802.11b and CDMA2000-1X in a single client card

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UCAN Architecture

low data-rate

high data-rate

Poor WANChannel

Good WANChannel

802.11b

RelayProxy

BaseStation

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Issues

high data-rate

PoorChannel

GoodChannel802.11

RelayProxy

Routing Node mobility HDR channel

dynamics Scheduling Incentives

WAN operator Proxy & relay

1xEV-DOBase

Station

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Routing Proxy discovery, proxy and route

maintenance On-demand and greedy proxy discovery Base station assisted error recovery

Design principles Leverage always-available HDR links Frugal use of HDR links (downlink and

uplink) Client push v.s. base station pull

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On-demand Proxy Discovery

BSC

A B E

J

F

1. RtRequest Flooding with Limited Range (2 hops) --- Client Downlink Quality (A:2)

C

B E

F

D

2. Proxy Candidates D, E, F, inform BS

F

E

D3. Base station chooses E as Proxy --- Proxy table:

E2

2

6 10

5

8

7

12

1

12

2

2Dst. Proxy

A E

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Greedy Proxy Discovery

BSC

A B E

D

F1. RtRequest Unicast with Range Limit (2 hops) --- A’s Downlink Quality included

2. Base station assigns E as proxy --- Proxy table:

E2

2

6 10

5

8

7

42

1

12

2

2Dst. Proxy

A E

0. Maintains one-hop neighboring devices’ downlink channel qual

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UCAN Proxy Discovery On-demand

Best proxy within certain range Flooded RTREQ message Multiple Proxy Application messages on HDR

uplink Greedy

Proactive neighborhood maintenance Unicast RTREQ propagation Single Proxy Application message

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Route Maintenance

BSC

A E

J

1. If B moves away

3. Base station assigns D as proxy --- Proxy table:D

2

2

B6 10

5

82

Dst. Proxy

A D

2. E reports error to Base station3. Base station proxy table:

Dst. Proxy

A A

B6B6B6B6

Dst. Proxy

A E

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Route Maintenance Proxy downlink channel degradation:

Periodical piggyback in data packets Skip the proxy with degraded channel data rate

Any case: Route failure detection and recovery (1 single

message) Recovery from mobile client (receiver-initiated) HDR base station assisted (fast, efficient,

reliable)

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Providing Incentives WAN operators

Increased channel utilization through ad-hoc relay

Increased channel diversity through HDR base station scheduling

No extra equipment cost Clients actively receiving

Increased throughput of their own flows through HDR base station scheduling

Idle clients ?

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Incentives for Relay Clients

PoorChannel

GoodChannel802.11

RelayProxy

Refined PF scheduling Use destination’s own

channel rate Make entire path

available at base station Simplified loop

detection Further increased

channel diversity Award all relay clients

BaseStation

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Simulation

NAM Snapshot

Destination

Destination

Relay

Relay

Proxy

Proxy

NS-2 simulation HDR downlink TDMA

channel w/ slow and Rayleigh fast fading

Proxy discovery and path maintenance

HDR scheduling Mobile clients of

different densities Multiple FTP/TCP,

CBR/UDP flows

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Simulation Summary Throughput gain

Single flow w/ 3-hop relay: up to 50% gains with average 1 neighbor, 210% throughput gain with average 4 neighbors

Up to 60% aggregate throughput gain in five flow case w/ 3-hop relay – PF scheduling

Resilient to node mobility, sensitive to node density

Greedy proxy discovery: 50% higher energy consumption on 802.11b interfaces

On-demand proxy discovery: Up to 7 times higher overhead on HDR uplink

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Related Work Multi-hop cellular

A-GSM, ODMA, MCN: reduce power consumption

MADF: tradeoff between channel utilization and complexity

iCAR: pre-deployed, dedicated, stationary relay devices

Routing for p2p traffic in MANET DSDV, DSR, AODV, TORA, GPSR, LANMAR, LAR

Cooperation enforcement (Hubaux et al)

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UCAN Architectural Benefits Integration of two complementary wireless

data technologies Cellular networks

Improved channel utilization and network throughput w/o additional equipment cost

Ad-hoc networks Improved connectivity through more efficient

and reliable routing Incentives for commercial application scenarios Other resources in managed WAN infrastructure:

key management, time sync, localization …

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Summary A new network paradigm of unified and

cellular ad-hoc architecture Opportunistic use of ad-hoc relay to improve

wireless WAN throughput Routing, scheduling and incentive provisioning Simulation evaluation

Design space for Wireless WAN LAN Collaboration

Future work: uplink proxy, multicast, flooding, QoS for p2p traffic