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Handover procedures in a Bluetooth network

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

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Handover procedures in a Bluetooth network

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  1. 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

  2. Outline of the contents • Bluetooth basic • Handover algorithms • Table-based handover (TBH) • On-demand handover (ODH) • Simulation model • Experimental results • Conclusions and future work COST273 TD (02)-146

  3. 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) COST273 TD (02)-146

  4. slave2 slave3 master slave1 master active slave parked slave standby 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 COST273 TD (02)-146

  5. f(2k) f(2k+1) f(2k+2) master t slave t 625 ms FH & 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 COST273 TD (02)-146

  6. 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 COST273 TD (02)-146

  7. Next in the line… • Bluetooth basic • Handover algorithms • Table based handover (TBH) • On-demand handover (ODH) • Simulation model • Experimental results • Conclusions and future work COST273 TD (02)-146

  8. Pure-Bluetooth Handover • Scope: • Seamless transfer of slave connection from the originmaster 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 COST273 TD (02)-146

  9. 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 COST273 TD (02)-146

  10. 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 COST273 TD (02)-146

  11. PROS Fast and simple Does not require any coordination Does not require the knowledge of the network topology CONS No control on the choice of the new master (the first paging) Failure in case of paging collisions PROS Allows the slave to choose the best master after receiving several paging from different masters Paging is collision-free CONS Needs coordination among masters Can take a long time for scanning the paging table Pros and Cons On-demand (ODH) Table-based (TBH) COST273 TD (02)-146

  12. Next in the line… • Bluetooth basic • Handover algorithms • Table-based handover (TBH) • On-demand handover (ODH) • Simulation model • Experimental results • Conclusions and future work COST273 TD (02)-146

  13. 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 COST273 TD (02)-146

  14. Model 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 COST273 TD (02)-146

  15. Next in the line… • Bluetooth basic • Handover algorithms • Table-based handover (TBH) • On-demand handover (ODH) • Simulation model • Experimental results • Conclusions and future work COST273 TD (02)-146

  16. TBH-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 COST273 TD (02)-146

  17. ODH-time statistic • 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

  18. Sniff-time • Simulation parameters • Scatternet with 3 masters • 3 devices per piconet • Variable Sniff time • Results • Handover-time grows linearly with the Sniff-time COST273 TD (02)-146

  19. 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 COST273 TD (02)-146

  20. Next in the line… • Bluetooth basic • Handover algorithms • Table-based handover (TBH) • On-demand handover (ODH) • Simulation model • Experimental results • Conclusions and future work COST273 TD (02)-146

  21. Final 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 COST273 TD (02)-146

  22. 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 COST273 TD (02)-146

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