Routing In Bluetooth
Download
Report
Transcript Routing In Bluetooth
Department of Information Engineering
University of Padova, Italy
Handover procedures in a
Bluetooth network
Roberto Corvaja , Andrea Zanella
{corvaja, zanella}@dei.unipd.it
COST273 Sep. 19-20, 2002 Lisboa
TD (02)-146
Outline 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
2
Bluetooth 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
3
Bluetooth 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
Sep. 19-20, 2002
COST273 TD (02)-146
slave2
slave3
master
slave1
master
active slave
parked slave
standby
4
FH & TDD
f(2k)
f(2k+1)
f(2k+2)
master
t
slave
t
625 s
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
Sep. 19-20, 2002
COST273 TD (02)-146
5
Bluetooth 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
Sep. 19-20, 2002
COST273 TD (02)-146
6
Next in the line…
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
7
Pure-Bluetooth Handover
Scope:
Hybrid networks (wired/wireless)
Seamless transfer of slave connection from the origin master to
the target master
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
Sep. 19-20, 2002
COST273 TD (02)-146
8
Table-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
Sep. 19-20, 2002
COST273 TD (02)-146
9
On-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
Sep. 19-20, 2002
COST273 TD (02)-146
10
Pros and Cons
On-demand (ODH)
Table-based (TBH)
PROS
Allows the slave to choose the best
Fast and simple
master after receiving several
Does not require any coordination
Does not require the knowledge of
paging from different masters
PROS
Paging is collision-free
CONS
Needs coordination among masters
Can take a long time for scanning
the paging table
Sep. 19-20, 2002
the network topology
CONS
No control on the choice of the new
master (the first paging)
Failure in case of paging collisions
COST273 TD (02)-146
11
Next in the line…
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
12
Simulation platform
Simulator Tool: OPNET Modeler Ver. 8.0
The simulator does support
Baseband protocols
Link manager (LM) protocol
Link layer control and adaptation protocol (L2CAP)
Frequency Hopping, Paging, Inquiry, Scan
Connection setup/release, Sniff Mode
Handover for Bluetooth slaves
The simulator does not support
Multi-slot data packets
Handover for master and gateway units
Sep. 19-20, 2002
COST273 TD (02)-146
13
Model assumptions
Pre-formed Scatternet
Pure Round Robin polling strategy
Roles of master/slave/gateway are pre-assigned
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
Sep. 19-20, 2002
COST273 TD (02)-146
14
Next in the line…
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
15
TBH-time statistic
Sep. 19-20, 2002
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
COST273 TD (02)-146
16
ODH-time statistic
Sep. 19-20, 2002
Simulation parameters
Scatternet with 3 masters
3 and 5 devices per piconet
Sniff time N=10 slots
Results
Handover time less than 25 slots
Limited impact of the # of slaves
Handover time better than TBH
COST273 TD (02)-146
17
Sniff-time
Simulation parameters
Scatternet with 3 masters
3 devices per piconet
Variable Sniff time
Results
Handover-time grows linearly
with the Sniff-time
Sep. 19-20, 2002
COST273 TD (02)-146
18
Number of devices
Simulation parameters
Scatternet with 3 masters
Sniff time N=100 slots
Variable number of devices
Results
Handover-time is only
marginally dependent on the
number of devices per piconet
Sep. 19-20, 2002
COST273 TD (02)-146
19
Next in the line…
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
20
Final Remarks
Handover can be supported by an accurate paging
Impact on the handover time
Table-based handover
Sniff time: strong impact
Number of devices per piconet: weak impact
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
21
Future 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
Sep. 19-20, 2002
COST273 TD (02)-146
22