An Efficient Multi-channel Management
Protocol for Wireless Body Area Networks
Wangjong Lee*, Seung Hyong Rhee*, Youjin Kim** and Hyungsoo Lee**
* Kwangwoon University, Korea,
** Electronics and Telecommunications Research Institute, Korea
International Conference on Information Networking (ICOIN), 2009
Computer Systems Lab Group Meeting
Presented by: Zakhia Abichar
April 15, 2010
Application: Nike+
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2 nodes: sensor & receiving device
Sensor inserted into shoes
Sensor measures distance
Transmits in wireless to on-body
device; upload to computer
• Track progress; train on a program
Receiving device options
Wireless-enabled iPod
Cost: $19 (sensor-only)
Wireless-enabled iPod
Cost: $29 (sensor +
wireless receiver)
Sensor
Sensor insertion
Nike Sportband
Cost: $78 (sensor +
Sportband)
Track progress
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Application: Adidas miCoach
• System: miCoach pacer (cost: $139)
• 3-nodes system:
– Sensor measure the speed
– HRM measure the heart rate
– Pacer gathers the information via
wireless
HRM: Heart
Rate Monitor
• Pacer gives audio feedback: speed
up, slow down
Pacer
– Based on HRM & training goal
• Wireless standard used ANT+
• Also available: miCoach ZONE
– HRM + sport-like device (Cost: $69)
– Monitor hear-rate while exercising
Sensor
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Wireless Body Area Networks
• They are also called WBAN
• Can be considered a successor of WPAN
(Wireless Personal Area Network)
• WBAN have a range of 3 meters (9.8 ft)
• Medical or non-medical according to use
• In 2.4 GHz ISM band and 400 MHz band of
MICS
– ISM: Industrial Scientific Medical, used for Wi-Fi
– MICS: Medical Implanted Communication Service
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Technical Topic
• We need a protocol to reduce the interference in the
MICS band
– Interference between MICS systems
– or between MICS and primary systems
• There is a an LBT (Listen-Before-Talk) protocol defined
• LBT isn’t good for non-collision and emergency traffic
• This paper proposes an efficient way of multi-channel
management
– The channel is reserved
– Channel aggregation makes a single wide channel and satisfies
various traffic types
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Outline
• Preliminary material
• Proposed scheme
• Simulation results
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Preliminaries
• IEEE working to make WBAN standards through Task
Group 802.15.6
• ITU-R issued Recommendation SA.1346 for MICS devices
401
ITU-R: International
Telecom. Union Radiocommunication
402
403
404
METAIDS
MICS
405
406
MHz
METAIDS:
Meteorological Aids
SA.1346:
• MICS devices should limit to -16 dBm in a bandwidth of 300 kHz to
prevent interference with METAIDS
• Channel spacing of 25 kHz with channel aggregation up to 300 kHz
• Also, there is LBT specs
• MICS use low power, concluded there’s no interference with METAIDS
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Distributed and Beacon-Enabled MAC Protocol
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This is the proposed scheme
MICS band consists of 10 channels with 300 kHz bandwidth
1 channel is the control channel. The other 9 are data
The control and data channels are not fixed
Outbody device allocates the channels to inbody devices through the
control channel
• Outbody device continuously sends a beacon frame on the control
channel
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Channel Assignment
• Outbody device initiates communication with inbody devices
• It also senses the channels to set up a control channel
• MICS devices are secondary users; transmit/received when METAIDS
devices are silent
• They should coexist with other MICS; using LBT protocol
• Outbody device selects one channel as the control channel after sensing
• It also assigns a channel number to each channel except the control
channel
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Channel Assignment
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On control channel, a beacon superframe consists of 9 beacon slots
Each beacon slot maps to a data channel
A beacon in the 1st slot means the 1st channel is reserved
No beacon in the nth means the nth channel is not reserved
Inbody devices listen to control channel to know what channel to use
Inbody devices then send a data packet to the outbody device on the
reserved channel
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Supporting Sleep State
• Inbody devices have 2 modes: wake mode & sleep mode
• There is a duty cycle: wake/sleep
• At wake up, inbody device listens to control channel
– If there is a channel allocated for it, it talks to outbody device
– During this time, a beacon is sent on the control to indicate the data
channel is busy
– At end of communication, inbody device sleeps. Outbody device stops the
beacon for the sleeping device
– If there was no data channel for it at wake up, inbody device sleeps
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Channel Aggregation
• MICS frequency band has narrow channels
• This limits traffic types that need high bandwidth
• Outbody device can allocate aggregated data channels
– by transmitting the same beacon in adjacent beacon slots
– the channels are combined in a single wideband channel
• This scheme prevents a waste of resource by using channel guards
• It also reduces transmission failure caused by narrow channel
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Single MAC for 2 PHYs
• Two PHYs for WBAN: ISM (2.4 GHz) and MICS (400 MHz)
• Use ISM for outbody communication and MICS for inbody
communication
• Like MICS, ISM band is divided into non-overlapping channels
– the same proposed scheme can be used
• WBAN device has two PHY layers and one MAC layer
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Simulation Results
• Simulation with ns-2, CMU wireless extension and MAC
modules developed by Intel (refs.)
• Topology: 2 inbody devices communicating with 1
outbody device
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Throughput of Proposed Scheme and LBT
• In proposed scheme, control channel is overhead
• In LBT, sensing before transmission is overhead
– sensing time is varied in simulation
Listening Time = 0.05 ms
Listening Time = 0.1 ms
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Throughput with Channel Aggregation
• First case is one aggregate channel of 900 kHz
• Second case is 3 separate channels of 300 kHz each
• Aggregation increases the throughput
Channel: 1 x 900 kHz
Channel: 3 x 300 kHz
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