Transcript A Fast Handoff Scheme For IP over Bluetooth

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
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Introduction
Communication establishment
Handoff Scheme
Simulation analysis
Conclusions
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Introduction
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BLUEPAC ( BLUEtooth Public ACcess )
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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.
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Introduction (cont.)
Assume the scan interval
of a base station is 1.28 sec
Fixed Bluetooth Device
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Introduction (cont.)
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Scan Interval
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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
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Introduction (cont.)
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Motive:
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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.
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Connection establishment
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The frequency synchronization between two
devices
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Inquiry procedure :
• To obtain the device’s clock and address information.
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Page procedure :
• To establish a connection to other device.
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Inquiry Access Code
Inquiry
Procedure
Page
Procedure
Frequency Hop Synchronization
Device Access Code
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Tinquiry = 2 * frequency synchronization delay + random backoff delay
Tpage = frequency synchronization delay
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Handoff Scheme
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Fundamental idea:
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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.
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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
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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
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Simulation analysis
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Two network topologies for the simulation.
Mobile devices move to a free
direction at speed of 1m/s.
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Mobile devices move to a specific
direction at speed of 1m/s.
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Simulation analysis (cont.)
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Handoff delay :
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The delay from when a mobile device detects handoff
till when a mobile device establishes a connection to
new base station.
Overhead :
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The ratio of the required time during handoffs and the
total simulation time.
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Simulation analysis (cont.)
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Assume
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The handoff message is higher priority than data.
Comparison:
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Daid’s scheme [4]
The plain inquiry-page procedure.
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Simulation analysis (cont.)
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Simulation analysis (cont.)
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Conclusions
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Presented a new scheme for improving the handoff
performance in BLUEPAC.
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In order to reduce handoff delay, the inquiry procedure
should be invoked as small times as possible.
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Base station controller stations aggressively assist a
mobile device, the mobile device has no need to inquiry
the new base stations.
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The proposed scheme significantly reduced the handoff
delay and imposed the very light overhead on the base
station.
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End