AGAL

A

Seamless

Handoff Protocol

Between

Ad-hoc

802.11 and

GSM/GPRS

AGAL

A

Seamless

Handoff Protocol

Between

Ad-hoc

802.11 and

GSM/GPRS

Shilpi GautamChris Haagen

Martin Nicholes

EEC273 W04Project Presentation

March 22, 2004

OverviewOverview

•Motivation•Previous Work•Our Approach•Methodology•Evaluation•Summary•Future Work•References

MotivationMotivation

•GSM/GPRS users desire an alternative higher bandwidth link to each other

•GPRS bandwidth is expensive

•GSM/GPRS Providersbecome burdened with growing increase in users

Related WorkRelated Work

• UCANUsing AdHoc to find higher bandwidth downlink

• ICARUsing Adhoc as a relay station for load balancing

• WiFi BridgeContinuity between WLAN and GPRS

• Other work all related to connecting GPRS/GSM to WLAN

Our ApproachOur Approach

• AGAL: Ad-hoc to GPRS/GSM Alternate Link

• Mobile host session over GPRS/GSM

• Ad-hoc node detected

• ALRequest transmitted over Adhoc

• ALReply received from target MH

• Alternate Link created

• Alternate Link tear down on failing 802.11 MAC signal (ALDelete is sent)

• TCP adjustment to help with vertical handoff

OSI Protocol StackOSI Protocol Stack

AGAL Protocol AGAL Protocol

ALREQALREPLYALDEL

MethodologyMethodology

• Simulate using NS-2

• AGAL implemented in routing layer

• Scenario (all 802.11 signaling)

• 3 MHs: 2 involved in FTP, 1 is “base station”

• 2 MHs move toward each other, triggering AGAL

• AGAL creates alternate link

• Alternate link deleted based on simulator time

• Graph of throughput was verified

• Graph of TCP trace was verified

• 8 runs with unique random seeds

Evaluation Evaluation

•GSM/GPRS bandwidth approx. 35Kbits/s

•Ad-hoc bandwidth approx. 700Kbits/s

•Successful switch between GSM/GPRS to ad-hoc

ThroughputThroughput

TCP TraceTCP Trace

TCP Trace

0

500

1000

1500

2000

2500

3000

3500

4000

10 30 50 70 90 110 130 150 170 190

Time (s)

Segment Number

TCP Segments

TCP ACKS

TCP Trace

0

500

1000

1500

2000

2500

3000

3500

4000

10 30 50 70 90 110 130 150 170 190

Time (s)

Segment Number

TCP Segments

TCP ACKS

Vertical HandoffVertical Handoff

TCP Trace

125

145

165

185

205

225

245

46 48 50 52 54 56 58

Time (s)

Segment Number

Node 0 TCP Rx

Node 0 ACK Rx

AGAL Events

TCP Trace

125

145

165

185

205

225

245

46 48 50 52 54 56 58

Time (s)

Segment Number

Node 0 TCP Rx

Node 0 ACK Rx

AGAL Events

TCP Trace

3260

3270

3280

3290

3300

3310

3320

89.5 90 90.5 91 91.5 92 92.5 93 93.5 94

Time (s)

Segment Number

Node 0 TCP Tx

Node 0 ACK Rx

AGAL Events

TCP Trace

3260

3270

3280

3290

3300

3310

3320

89.5 90 90.5 91 91.5 92 92.5 93 93.5 94

Time (s)

Segment Number

Node 0 TCP Tx

Node 0 ACK Rx

AGAL Events

Demonstration

SummarySummary

•Seamless handoff from GPRS/GSM to ad-hoc 802.11

•Expected bandwidth increase of the ad-hoc connection

•Movement of traffic to free ad-hoc alternate link

Future WorkFuture Work

•Implement AGAL on testbed system

•Two multihomed mobile hosts and a base station

•Explore interesting applications of protocol

•Enhance authentication for increased security

•Improve scalability of AGAL

ReferencesReferencesA. Calvagna, G. Morabito, A. La Corte. “WiFi bridge: wireless mobility framework supporting session continuity,” Proceedings of the First IEEE International Conference on Pervasive Computing and Communications, 2003.

Haiyun Luo, Ramachandran Ramjee, Prasun Sinha, Li (Erran) Li, Songwu Lu, “Cellular and hybrid networks: UCAN: a unified cellular and ad-hoc network Architecture,” Proceedings of the 9th annual international conference on Mobile computing and networking, September 2003

R. Chakravorty, J. Cartwright, and I. Pratt. “Practical Experience with TCP over GPRS”. Proc. of GLOBECOM, 2002. Vol. 2, pp. 1678-1682.

M. Ye, Y. Liu, and H. Zhang. “The Mobile IP handoff between hybrid networks”. The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2002. Vol. 1, pp. 265-269.

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