HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile

controlled handoffs

D. Forsberg, J.T. Malinen, J.K. Malinen, H.H. Kari

TSE-Institute

Telecommunications and Software Engineering

Laboratory of Information Processing Science

Helsinki University of Technology

Finland

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Presentation overviewIntroduction

Wireless Mediapoli

Dynamics - HUT Mobile IP

Motivation

Criteria

Improving communication availability with Mobile IP

Policy based mobility agent selection and detection with prioritization

Signal quality awareness

Two phase handoff

Signal quality awareness802.11 link layer modes

Policies and configurability

Two phase, forward and mobile controlled soft handoff

Enables glitchless handoffs

Transparent to the mobile user

TestsHandoff times

Packet loss per location update

Configurable monitor testing

Data throughput

Conclusions

Future workDynamic and automatic policy

configurations

Dynamic advertising of access network services and capabilities

Questions?

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Introduction

• communication availability problem– CA is readiness for usage– we solved the problem under signal quality based handoff

management with Mobile IP in WLAN

• developed system is currently in use and evolving – Wireless Mediapoli

http://www.mediapoli.com/wireless

– Dynamics - HUT Mobile IPhttp://www.cs.hut.fi/Research/Dynamics/

• this presentation assumes that you are familiar with basic mobile IP

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Motivation• clients require mobility in the Internet• wireless mobile computers and portable digital

assisstants (PDA) are becoming more common• increased use of multimedia content with mobile

computers (mp3 streams, real video and audio etc.)– Mobile computers are powerful enough and WLANs have

enough bandwidth to deliver the content

• mobile users want to roam between different link layer technologies– Our environment is built on top of 802.11 and Ethernet

• user wants to control the communication parameters– The user may want to use different service providers based

on his needs and current resources

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Criteria

• mobility should not affect the data transmission• tolerance for congestion• efficiency• the mobile node should use the mobility agent that

offers the best communication availability– the word best may not mean the same between two

different mobile users (cost, bandwidth, services etc.)

• independence of the underlying radio technology– roaming between different wireless networks

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Improving communication availability with Mobile IP

policy based mobility agent selection and detection with prioritization

- MN can hear possibly many MAs- priority modification techniques

two phase, soft handoff

signal quality awareness- every available MA gets its own priority based on the signal quality (SNR) value

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Signal quality awareness

• comparisons and selections are based on dynamic node priorities

• the signal quality can be seen as a meaningful distance for the mobile node between the access point and mobile node– Meaningful in the sense that the communication

availability is highly dependant on the signal strength in the communication path

• priorities are based on signal quality values received from the mobility agents– In our system the mobility agent is running in an access

point and thus the advertisements have different signal quality source

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Policies and configurability

• policy is a set of rules that affect the node selection process in the mobile node

• four different policies implemented: – default-policy: uses signal quality history and threshold

when selecting or comparing the current mobility agent – newest-FA: the mobile node selects the most recently

detected mobility agent– eager-switching: neither signal quality history nor

threshold is used during mobility agent selection– early-expire: the mobile node expires the mobility agent

from the list of available mobility agents more eagerly

HELSINKI UNIVERSITY OF TECHNOLOGY

• configuration of parameters fine tune the handoff procedures and policies– average length: number of signal quality values taken into

the priority calculation. Average is calculated.– threshold: mobile node will not change the current mobility

agent if the signal quality difference is below the threshold– min-balance: do not use threshold if the signal quality goes

below this level– expirepercent: degrade the mobility agent priority with this

percentage if the advertisement from the mobility agent is old enough

• policies and configuration variables together form a adjustable environment for mobile users

Increasing communication availability with signal-based mobile controlled handoffs

Policies and configurability

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Hierarchical Mobile IP

CN HAInternet

Home Network

WLAN

FA5

FA2

HFA1

FA1

FA3 FA6

Mobile NodeMobile NodeMobile Node

FA4

SFA

FA4FA3

FA1 Foreign Network

FA4

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Two phase, forward and mobile controlled soft handoff

• enables glitchless handoffs• transparent to the mobile user

MN sends location update request to the new FA

SFA changes the downstream route and sends the location update request reply

MN receives the reply and changes the upstream route to the new FA

every FA between the LFA and the SFA prepares the downstream route for the MN

every FA between the SFA and the LFA prepares the upstream route for the MN

phase I phase II

1. 2. 3.

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Tests

• tests – handoff times– packet loss per location update– configurable monitor testing– data throughput

• forced location updates• handoff latency measured in the MN• data throughput measured with netperf

– maximum TCP throughput and paced UDP streams (about 1.4 Mbps)

HELSINKI UNIVERSITY OF TECHNOLOGY

HACN

HFA

FA2

FA3

FA13

FA29 FA14

FA32

FA15

FA1

Location update latencies for some transitions

FA11 FA12

FA13

FA31

OLD FA

NEW FA

Average in ms

FA11 FA12 19,1FA13 FA14 30,4FA31 FA32 41,4

Increasing communication availability with signal-based mobile controlled handoffs Handoff times in hierarchy

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs Configurable monitor testing

Setting 1 Setting 2Threshold 50 1

Min-balance 10 13Old-FA-factor 50 50

Worst-min-time 50 50Worst-max-time 10 10Average-length 1 3

Early-expire OFF OFFNewest-FA OFF OFF

Eager-switching ON OFF

Plain MIP Setting 1 Setting 2Lost Packets 2179 66 117

Location updates 8 63 9

• lost packets and location updates measurement with different settings of the monitor

• testbed emulated with signal quality environment recorder/replayer

• packet dropping based on low signal quality levels

HELSINKI UNIVERSITY OF TECHNOLOGY

HACN

HFA

FA12

FA3

FA31

FA29 FA14

FA32

FA15

FA11

FA3FA3FA13 Data stream CN --> MN

OLD FA

NEW FA

Lost packets/ update

FA11 FA31 0,00FA31 FA29 0,00FA29 FA32 0,00FA31 FA13 0,00FA12 FA15 0,00FA15 FA31 0,03FA32 FA11 0,07FA13 FA12 0,10

OLD FA

NEW FA

Lost packets/ update

FA11 FA31 0,27FA31 FA29 0,27FA29 FA32 0,00FA31 FA13 0,15FA12 FA15 0,14FA15 FA31 0,00FA32 FA11 0,00FA13 FA12 0,00

Data stream MN --> CN

Increasing communication availability with signal-based mobile controlled handoffs Lost packets/ location update

Data stream:

100kB/s, 1kB packets

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0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

0,1 1,0 10,0 100,0

locupds/s

Mb

ps

TCP

UDP

Increasing communication availability with signal-based mobile controlled handoffs Data throughput

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Conclusions

• the mobile user can change the policy and handoff parameters dynamically without disturbing the communication sessions

• the solution is not dependent on the handoff management below the network layer

• with soft handoffs neither buffering nor multicasting is required to achieve seamless handoffs

• the prioritiy-based FA comparison is feasible because it is not bound to the signal quality values and, thus, not only to the WLANs

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Conclusions

• the tests showed that hierarchical Mobile IP with signa quality awareness and two-phase handoff supports micro mobility

• signal quality awareness is a simple way to improve the communication availability without extending mobility protocol

• signal quality awareness is a simple way to improve the communication availability without extending mobility protocols

HELSINKI UNIVERSITY OF TECHNOLOGY

Increasing communication availability with signal-based mobile controlled handoffs

Future work

• scalability with multiple mobile nodes under the same FA hierarchy and an HA should be analysed

• hard handoff management is required whenchannel switching occurs in an ad hoc mode WLAN. Its use with the presented system should be evaluated.

• dynamic parameters in tha FA and agent advertisements to support mobility agent selection in the MN should be studied.

HELSINKI UNIVERSITY OF TECHNOLOGY

D. Forsberg, J.T. Malinen, J.K. Malinen, H.H. Kari

Email{dforsber, jtm, jkmaline, hhk}@cs.hut.fi

WWW

http://www.cs.hut.fi/Research/Dynamics/

Increasing communication availability with signal-based mobile controlled handoffs

Questions?