Department of Information Engineering University of Padova, Italy COST273 Sep. 19-20, 2002 Lisboa TD (02)-146 Handover procedures in a Bluetooth network.

Department of Information Engineering

University of Padova, Italy

COST273 Sep. 19-20, 2002 LisboaCOST273 Sep. 19-20, 2002 Lisboa TD (02)-146TD (02)-146

Handover procedures in a Handover procedures in a Bluetooth networkBluetooth network

Roberto Corvaja

{corvaja, zanella}@dei.unipd.it

, Andrea Zanella

Sep. 19-20, 2002 COST273 TD (02)-146 2

Outline of the contentsOutline of the contents

Bluetooth basic Handover algorithms

Table-based handover (TBH) On-demand handover (ODH)

Simulation model Experimental results Conclusions and future work

Sep. 19-20, 2002 COST273 TD (02)-146 3

Bluetooth TechnologyBluetooth Technology

What is Bluetooth? A wireless technology

Proposed as cable replacement for portable electronic devices, BT provides short-range low-power point-to-(multi)point wireless connectivity

A global industry standard in the making Initially developed by Ericsson, now BT is promoted by an

industry alliance called Special Interest Group (SIG)

Sep. 19-20, 2002 COST273 TD (02)-146 4

Bluetooth piconetBluetooth piconet

Two up to eight Bluetooth units sharing the same channel form a piconet

In each piconet, a unit acts as master, the others act as slaves

Channel access is based on a centralized polling scheme

active slavemaster

parked slavestandby

slave1

slave2

slave3

master

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FH & TDDFH & TDD

Each piconet is associated to frequency hopping (FH) channel The pseudo-random FH sequence is imposed by the master Time is divided into consecutive time-slots of 625 s Each slot corresponds to a different hop frequency

Full-duplex is supported by Time-division-duplex (TDD) Master-to-slave (downlink) transmissions start on odd slots Slave-to-Master (uplink) transmissions start on even slots

625 s

t

t

master

slave

f(2k) f(2k+1) f(2k+2)

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Bluetooth scatternetsBluetooth scatternets Piconets can be interconnected by Inter-piconet Units (IPUs) IPUs may act as gateways, forwarding traffic among adjacent

piconets IPUs must time-division their presence among the piconets Time division can be realized by using SNIFF mode

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Next in the line…Next in the line…

Bluetooth basic Handover algorithms

Table based handover (TBH) On-demand handover (ODH)


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Pure-Bluetooth Pure-Bluetooth HandoverHandover

Scope: Seamless transfer of slave connection from the origin

master to the target master

Hybrid networks (wired/wireless) Make use of the wired connection between masters

Pure-Bluetooth network Make use of standard Inquiry/Page/Scan modes

Handover-time can be of the order of seconds

Make use of accurate Page/Scan modes Devices are acquainted with slave’s clock & BT address The accurate paging reduces the time to the order of

milliseconds

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Table-based handoverTable-based handover The slave issues an handover-request to its origin master and enters

the page-scan mode The origin master forwards the request to the other masters and

acquaints them with the slave’s parameters The masters start paging on the basis of a paging-table

Only one master at a time is allowed to page the slave The slave just listens but DOES NOT reply to any page

Once the paging-table has been scanned, the slave can choose the best master and synchronize to it

The sequence of masters (table) has to be repeated once more to allow the synchronization between the slave and the chosen master

The new master that takes the slave in its piconet, finally, signals the end of the procedure to the origin master

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On-demand handoverOn-demand handover

The slave issues an handover-request to its origin

master and enters the page-scan mode

The origin master forwards the request to the other

masters and acquaints them with the slave’s

parameters

The target masters begin an accurate page of the slave

The slave replies to the first page packet it gets

The corresponding master connects the slave

The new master issues an handover-complete message

The other masters stop paging

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Pros and ConsPros and Cons

PROSPROS

Fast and simple

Does not require any

coordination

Does not require the

knowledge of the network

topology

CONSCONS

No control on the choice of the

new master (the first paging)

Failure in case of paging

collisions

PROSPROS

Allows the slave to choose the

best master after receiving

several paging from different

masters

Paging is collision-free

CONSCONS

Needs coordination among

masters

Can take a long time for

scanning the paging table

On-demand (ODH)On-demand (ODH)Table-based (TBH)Table-based (TBH)

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Bluetooth basic

Handover algorithms Table-based handover (TBH) On-demand handover (ODH)


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Simulation platform Simulation platform Simulator Tool: OPNET Modeler Ver. 8.0 The simulator does support

Baseband protocols Frequency Hopping, Paging, Inquiry, Scan

Link manager (LM) protocol Link layer control and adaptation protocol

(L2CAP) Connection setup/release, Sniff Mode

Handover for Bluetooth slaves

The simulator does not support Multi-slot data packets Handover for master and gateway units

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Model assumptionsModel assumptions

Pre-formed Scatternet Roles of master/slave/gateway are pre-assigned

Pure Round Robin polling strategy Nodes have the same priority and get polled in cyclic order

2 piconets per gateway A gateway spends equal time in each one of its piconet

Sniff mechanism is used to support inter-piconet switching

Gateways are not coordinated

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Bluetooth basic



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TBH-time statisticTBH-time statistic

Simulation parameters Scatternet with 3 masters

3 and 5 devices per piconet

Sniff time N=10 slots

2 table-scanning repetitions

12 paging slots per master

Results Handover time less than 100

slots

Small dispersion

Limited impact of the # of slaves

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ODH-time statisticODH-time statistic


3 and 5 devices per piconet


Results Handover time less than 25

slots

Limited impact of the # of

slaves

Handover time better than TBH

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Sniff-timeSniff-time


3 devices per piconet

Variable Sniff time

Results Handover-time grows

linearly with the Sniff-time

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Number of devicesNumber of devices

Simulation parameters

Scatternet with 3 masters


Variable number of devices

Results

Handover-time is only

marginally dependent on the

number of devices per

piconet

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Bluetooth basic



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Final RemarksFinal Remarks Handover can be supported by an accurate paging Impact on the handover time

Sniff time: strong impact Number of devices per piconet: weak impact

Table-based handover Handover takes less than 100 slots Choice of optimum master is possible Exchange of information and coordination is required

On-demand handover Handover takes less than 25 slots Choice of optimum master is NOT possible No coordination is required

Sep. 19-20, 2002 COST273 TD (02)-146 22

Future workFuture work

Next in the line… Simulator enhancements

Multi-slot packets

Physical channel characterization

Implementation of dynamic scatternet formation

algorithms

Integration of handover and routing procedures

Mathematical analysis of the scatternet capacity

Department of Information Engineering University of Padova, Italy COST273 Sep. 19-20, 2002 Lisboa TD (02)-146 Handover procedures in a Bluetooth network.

Documents

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bluetooth scatternetspiconets