A Fast Handoff Scheme For IP over Bluetooth Sang-Hsu Chung, Hyunsoo Yoon, and Jung-Wan Cho Department of Electrical Engineering & Computer Science Divison of Computer Science Korea Advanced Institute of Science and Technology International Conference on Parallel Processing Workshops, 2002 (ICPPW’02) Speaker : Chung-Hsien Hsu

2003/01/28Chung-Hsien Hsu2 Outline  Introduction  Communication establishment  Handoff Scheme  Simulation analysis  Conclusions

2003/01/28Chung-Hsien Hsu3 Introduction  BLUEPAC ( BLUEtooth Public ACcess ) It is a kind of the indoor network and its structure is similar to that of cellular network. It is a kind of the indoor network and its structure is similar to that of cellular network. It is designed to support IP over Bluetooth. It is designed to support IP over Bluetooth. Providing users to access to the public network such as the Internet. Providing users to access to the public network such as the Internet. It can be installed in a public area such as train stations, airports, and supermarkets. It can be installed in a public area such as train stations, airports, and supermarkets.

2003/01/28Chung-Hsien Hsu4 Introduction (cont.) Fixed Bluetooth Device Assume the scan interval of a base station is 1.28 sec

2003/01/28Chung-Hsien Hsu5 Introduction (cont.)  Scan Interval The frequency synchronization delay is proportional to the scan interval of the receiver. The frequency synchronization delay is proportional to the scan interval of the receiver. Bluetooth specification defined three scan intervals: Bluetooth specification defined three scan intervals: 10 ms ( continuous scan )10 ms ( continuous scan ) 1.28 sec1.28 sec 2.56 sec2.56 sec Receiver Scan Interval 16 slots Time

2003/01/28Chung-Hsien Hsu6 Introduction (cont.)  Motive: Short range of Bluetooth arises frequent handoffs. Short range of Bluetooth arises frequent handoffs. Slow handoffs might result in the degradation of the network performance. Slow handoffs might result in the degradation of the network performance.  The proposed scheme is motivated by the need for a fast handoff in BLUEPAC.

2003/01/28Chung-Hsien Hsu7 Connection establishment  The frequency synchronization between two devices Inquiry procedure : Inquiry procedure : To obtain the device’s clock and address information.To obtain the device’s clock and address information. Page procedure : Page procedure : To establish a connection to other device.To establish a connection to other device.

2003/01/28Chung-Hsien Hsu8 Inquiry Access Code Frequency Hop Synchronization Device Access Code Inquiry Procedure Page Procedure

2003/01/28Chung-Hsien Hsu9 T inquiry = 2 * frequency synchronization delay + random backoff delay T page = frequency synchronization delay

2003/01/28Chung-Hsien Hsu10 Handoff Scheme  Fundamental idea: Base station controller assists a mobile device to establish a connection to new base stations by giving their addresses and clocks. Base station controller assists a mobile device to establish a connection to new base stations by giving their addresses and clocks. A mobile device during a handoff has no need for inquiring the new base station. A mobile device during a handoff has no need for inquiring the new base station.

2003/01/28Chung-Hsien Hsu11 Mobile device Old BS New BS1 New BS2 BSC Request msg for neighboring BS info Request msg for clock and device addr Clock and addr Communication Handoff detected Handoff request Scan request Start to scan Start to scan Ack DAC Measure signal str. DAC FHS Measure signal str. & choose the best

2003/01/28Chung-Hsien Hsu12 Mobile device Old BS New BS1 New BS2 BSC DAC New connection established Communication tear-down Ack Handoff completed If # of slaves in existing piconet <7 Master / slave switch request Ack End to scan

2003/01/28Chung-Hsien Hsu13 Simulation analysis  Two network topologies for the simulation. Mobile devices move to a free direction at speed of 1m/s. Mobile devices move to a specific direction at speed of 1m/s.

2003/01/28Chung-Hsien Hsu14 Simulation analysis (cont.)  Handoff delay : The delay from when a mobile device detects handoff till when a mobile device establishes a connection to new base station. The delay from when a mobile device detects handoff till when a mobile device establishes a connection to new base station.  Overhead : The ratio of the required time during handoffs and the total simulation time. The ratio of the required time during handoffs and the total simulation time.

2003/01/28Chung-Hsien Hsu15 Simulation analysis (cont.)  Assume The handoff message is higher priority than data. The handoff message is higher priority than data.  Comparison: Daid’s scheme [4] Daid’s scheme [4] The plain inquiry-page procedure. The plain inquiry-page procedure.

2003/01/28Chung-Hsien Hsu16 Simulation analysis (cont.)

2003/01/28Chung-Hsien Hsu17 Simulation analysis (cont.)

2003/01/28Chung-Hsien Hsu18 Conclusions  Presented a new scheme for improving the handoff performance in BLUEPAC.  In order to reduce handoff delay, the inquiry procedure should be invoked as small times as possible.  Base station controller stations aggressively assist a mobile device, the mobile device has no need to inquiry the new base stations.  The proposed scheme significantly reduced the handoff delay and imposed the very light overhead on the base station.

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