1 y-mac: an energy-efficient multi-channel mac protocol for dense wireless sensor networks youngmin...
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1
Y-MAC: An Energy-efficient Multi-channel MAC Protocol for Dense Wireless Sensor Networks
Youngmin Kim, Hyojeong Shin, and Hojung Cha
International Conference on Information Processing in Sensor Networks 2008
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Outline
Introduction The Y-MAC Implementation Evaluation Conclusions
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Introduction
Propose a light-weight channel hopping mechanism
When a traffic burst occurs, a receiver and potential senders hop to other channels
Each node is guaranteed to receive at least one message on the base channel
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The Y-MAC protocol
Y-MAC is a TDMA-based multi-channel MAC protocol
If each node has an exclusive send time slot, it results in idle listening and overhearing
Scheduling receivers is more energy efficient and contention among senders is eliminated
5
Frame architecture
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Control Message
The sink node periodically broadcasts control messages to initiate the network
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Initial Time synchronization Nodes periodically broadcast the information
required for time synchronization It consists
time remaining to the start of the next frame and the sequence number originated from the
sink node Once a node receives that, it sets its time
remaining to the next frame equal to sender
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Network partition detection If a node considered to be detached from the
network not received control messages with fresh
sequence numbers for a certain time If a node detects a network partition
it goes into the sleep mode to save energy and wakeup periodically to received control
messages When it fail to rejoin network, sleep interval
will double
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Time Slot Assignment
A
B
C
E
DB
C
C
B
B
DC
A
A
C
D
E
E
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Time Slot Retrieval
A node is removed from networks, or run out of battery its control message has not arrived during a
predefined time the time slot that has been used by that node
must be released for the future use neighboring nodes update their slot allocation
vectors
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Medium Access Design
A node wishing to send a packet sets a random backoff value on contention window
Receiver wakes up at the end of the contention window to receive the data
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Channel Hopping Mechanism 1/2
DATA
ACK
Notify message
A B C D Channel polling
A B C D
A -> B
A -> B
D -> C
Contention window
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Channel Hopping Mechanism 2/2
A B C D
A B C D
C -> B D -> C
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Implementation
Implemented in RETOS operating system on TmoteSky Motes
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Experimental Setup
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Single-Hop Environments
1 packet per 10 seconds
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Single-Hop Environments
1 packet per second
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Multi-Hop Environments
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Conclusion
Proposed a multi-channel MAC protocol for wireless sensor networks
Implemented it in the RETOS operating system running on TMoteSky motes
Also proposed a light-weight channel hopping mechanism
Enables multiple node pairs to communicate simultaneously on multiple channels
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~THE END~
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