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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 Outline Introduction Communication establishment Handoff Scheme Simulation analysis Conclusions 2003/01/28 Chung-Hsien Hsu 2 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 designed to support IP over Bluetooth. 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. 2003/01/28 Chung-Hsien Hsu 3 Introduction (cont.) Assume the scan interval of a base station is 1.28 sec Fixed Bluetooth Device 2003/01/28 Chung-Hsien Hsu 4 Introduction (cont.) Scan Interval The frequency synchronization delay is proportional to the scan interval of the receiver. Bluetooth specification defined three scan intervals: • 10 ms ( continuous scan ) • 1.28 sec • 2.56 sec 16 slots Receiver Time Scan Interval 2003/01/28 Chung-Hsien Hsu 5 Introduction (cont.) Motive: Short range of Bluetooth arises frequent handoffs. 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. 2003/01/28 Chung-Hsien Hsu 6 Connection establishment The frequency synchronization between two devices Inquiry procedure : • To obtain the device’s clock and address information. Page procedure : • To establish a connection to other device. 2003/01/28 Chung-Hsien Hsu 7 Inquiry Access Code Inquiry Procedure Page Procedure Frequency Hop Synchronization Device Access Code 2003/01/28 Chung-Hsien Hsu 8 Tinquiry = 2 * frequency synchronization delay + random backoff delay Tpage = frequency synchronization delay 2003/01/28 Chung-Hsien Hsu 9 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. A mobile device during a handoff has no need for inquiring the new base station. 2003/01/28 Chung-Hsien Hsu 10 Mobile device Old BS New BS1 BSC New BS2 Request msg for neighboring BS info Request msg for clock and device addr Clock and addr Clock and addr Clock and addr Communication Handoff detected Handoff request Scan request Ack Ack DAC Measure signal str. Measure signal str. & choose the best Ack Start to scan Start to scan DAC DAC DAC FHS 2003/01/28 Chung-Hsien Hsu 11 Mobile device Old BS BSC New BS1 New BS2 DAC New connection established Communication tear-down End to scan Ack Handoff completed Master / slave switch request If # of slaves in existing piconet <7 Ack 2003/01/28 Chung-Hsien Hsu 12 Simulation analysis Two network topologies for the simulation. Mobile devices move to a free direction at speed of 1m/s. 2003/01/28 Chung-Hsien Hsu Mobile devices move to a specific direction at speed of 1m/s. 13 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. Overhead : The ratio of the required time during handoffs and the total simulation time. 2003/01/28 Chung-Hsien Hsu 14 Simulation analysis (cont.) Assume The handoff message is higher priority than data. Comparison: Daid’s scheme [4] The plain inquiry-page procedure. 2003/01/28 Chung-Hsien Hsu 15 Simulation analysis (cont.) 2003/01/28 Chung-Hsien Hsu 16 Simulation analysis (cont.) 2003/01/28 Chung-Hsien Hsu 17 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. 2003/01/28 Chung-Hsien Hsu 18 End