mobiquitous 2004kimaya sanzgiri leveraging mobility to improve quality of service in mobile networks...

MobiQuitous 2004 Kimaya Sanzgiri

Leveraging Mobility to Improve

Quality of Service in Mobile Networks

Kimaya Sanzgiri and Elizabeth Belding-Royer

Department of Computer Science

University of California, Santa Barbara


Introduction

• Current Trends• Popularity of multimedia applications• Popularity of mobile networking• Support for multimedia content on mobile

devices

• Need for support of multimedia applications in mobile networks• Resource availability and QoS


Introduction

• Providing QoS support in mobile networks is difficult• Shared medium access

• Resource availability influenced by neighbors

• Mobility and dynamic topology• Neighborhood may change continuously


Introduction

• Several previously proposed QoS solutions• Basic idea

• Get QoS requirements from application• Query network to see whether satisfactory path is

available at user’s current location• If yes, make path available to application• If no, application is denied route

• Approach similar to wired networks


Motivation

• Mobile networks have special characteristics• Flexible connectivity• Resource availability influenced by

neighbors• Mobility

• Can these be leveraged to improve quality of service?


Observation

• Cellular networks have poor connectivity in some areas

• Users wander around observing signal strength bars on display

• Change of location often improves connectivity


Example from Cellular Networks

User

Base Station

I can’t hear clearly… the

signal is poor!

Maybe I should change my location…

User

Can you hear me

now?

User

Can you hear me

now?User

Aha! The signal is

great here!


Extending the Idea

• Lets apply the same idea to multihop mobile networks…


Changing Location in a Multihop Mobile Network

I want to see a

movie…

Network says: You don’t have enough

bandwidth

Maybe I should

change my location…

Aha!


Extending the Idea Further

• Build intelligence into network

• Network automatically guides user to new location

• Let us revisit our example…


Network-Suggested Location Change

I want to see a

movie…

Network says: You can’t watch the movie in your current location, but you

can if you move to location (x,y)

Aha!


Proposed Idea

• Leverage user mobility to improve service

• Network suggests new location• Beneficial to user

• Improved quality of service

• Beneficial to network• Spatial re-distribution of users• Efficient medium usage


Application Scenarios

• Applicable to networks with low to moderate mobility• Students on a campus• Users at a conference• Geography researchers in the field

• Not necessarily applicable to all ad hoc networks• Cars on a freeway


Implementation

• QoS-Aware AODV used as base QoS routing protocol

• Extended to leverage mobility

• Note that:• Idea is independent of routing mechanism• Other QoS protocols can be similarly

extended


QoS-Aware AODV (Q-AODV)

• RREQ specifies resource requirements

• Intermediate nodes check whether sufficient resources are available• If yes, forward the RREQ• If no, drop the RREQ

• Only destination may reply

• RREP specifies resource availability


Q-AODV Example

R

TP

V

QS DRREQ

RREP


Mobility-Enhanced Q-AODV (MQ-AODV)

• Extends Q-AODV to leverage mobility• RREQ broadcast at high power by

source• RREQ directly reaches more nodes• All recipients become candidates to

directly offer route to source• If necessary, source can move towards

node that offers best route


AODV Operation in Example Network

C

X

WV

U

T

S

R

QP

Y

Z

Congested Region

RegularTransmission

Range

RREQRREP


Q-AODV Operation in Example Network

C

X

WV

U

T

S

R

QP

Y

Z

Congested Region

RegularTransmission

Range


MQ-AODV Operation in Example Network

C

X

WV

U

T

S

R

QP

Y

Z

Congested Region

IncreasedTransmission

Range

RREQRREP


MQ-AODV Details

• Assumptions• Geographical location known• Transmission power adjustable• No obstacles

• User defines movement zone • Movement zone and regular

transmission range together define potential neighbor set


MQ-AODV Details

• RREQ broadcast by source at increased power• Should reach farthest potential neighbor• Contains location information of source

• First hop (potential neighbor) saves location information

• Regular route discovery procedure followed thereafter (at regular power)


MQ-AODV Details

• Destination sends RREP• Each intermediate node checks whether

it is the last hop• The last hop

• Adds its own location information to RREP• Looks up saved location information of

source• Increases transmission power if necessary


MQ-AODV Details

• On receiving RREP, source checks location information of last hop

• If necessary, source moves closer to last hop


MQ-AODV Limitations

• Movement distance limited by maximum transmission power

• Obstacles not considered

• Possibility of multiple users moving to same location


Protocol Evaluation

• Simulation-based (NS-2)

• 50 nodes in 1000m x 1000m area

• Regular transmission range = 250m

• MQ-AODV movement zone radius = 150m

• Between 2 and 10 application sessions (64 kbps, 180 seconds each)


Application Model

• Client-server-based streaming media application

• Implemented by modifying CBR• Client initiates session by sending

request to server• Server streams data at specified rate• Retry interval between 10 and 20

seconds


Mobility Pattern

• Graded mobility• 20 nodes static • Remaining nodes move based on

random waypoint• 10 nodes between 0 and 5 m/s• 10 nodes between 5 and 10 m/s• 10 nodes between 10 and 20 m/s

• Client and server nodes static


Performance Metrics

• Packet delivery fraction

• Number of data packets received

• End-to-end delay

• Fraction of received packets with unacceptable end-to-end delay (> 400ms)

• Routing load


Packet Delivery Fraction


Received Data Packets


End-to-End Delay


Delayed Packets


Routing Load


Performance Results

• MQ-AODV gives better packet delivery fraction, throughput, end-to-end delay and routing load as compared to Q-AODV

• AODV performs poorly due to lack of admission control


Conclusion

• Leveraging mobility does improve quality of service

• Future work:• Address limitations of MQ-AODV• Extend other QoS routing protocols


Thank You!

Questions/Comments?

mobiquitous 2004kimaya sanzgiri leveraging mobility to improve quality of service in mobile networks...

Documents

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displaychange of location

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