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The TDMA-based MAC Protocols for WSNs ----- EMACs and LMAC. EMACs: IEEE VTC 2004-Spring LMAC: INSS 2004. Wang, Sheng-Shih Feb. 21, 2005. Advantage of a TDMA based, energy-efficient, self-organizing MAC protocol for WSNs.

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the tdma based mac protocols for wsns emacs and lmac

The TDMA-based MAC Protocols for WSNs----- EMACs and LMAC

EMACs: IEEE VTC 2004-Spring

LMAC: INSS 2004

Wang, Sheng-Shih

Feb. 21, 2005

advantage of a tdma based energy efficient self organizing mac protocol for wsns

Advantage of a TDMA based, energy-efficient, self-organizing MAC protocol for WSNs

L. F. W. van Hoesel†, T. Nieberg†, H. J. Kip††, and P. J. M. Havinga†

† Department of Electrical Engineering, Mathematics and Computer Science

University of Twente, The Netherlands

†† Nedap N. V., Groenlo, The Netherlands

IEEE Vehicular Technology Conference(VTC2004-Spring)

european research project eyes
European Research Project EYES
  • Website: http://eyes.eu.org

Applications

Data Splitting

Connected active set formation

(Multipath) Routing

Clustering

EMACs

TDMA-based

Dynamic Topology

overview emacs
Overview --- EMACs

frame

frame

frame

frame

frame

time

timeslot

TC

DATA

CR

  • CR: Communication Request Section
  • TC: Traffic Control Section
  • DATA: Data Section
overview clustering cont d
Overview --- Clustering (cont’d)

anchor

bridge

nonmember

  • Both the anchor and bridge nodes are regarded as the active nodes
  • All active nodes comprise the connected dominating subset
emacs
EMACs
  • Main goal
    • Minimize energy consumption
  • Operation modes
    • Active
      • Forward messages to a destination
      • Accept data from passive nodes
    • Passive
      • Keep track of the active node
    • Dormant
      • Enter low power states
emacs frame structure
EMACs --- Frame Structure

frame

frame

frame

frame

frame

time slot

An active node autonomously picks its own time slot

CR

TC

DATA

  • CR: Communication Request Section
  • TC: Traffic Control Section
  • DATA: Data Section
emacs frame structure cont d
EMACs --- Frame Structure (cont’d)
  • Communication Request Section
    • An active node listens for incomingrequests from passive nodes
    • The passive node sends the request if any data
  • Traffic Control Section
    • An active node transmits a shortcontrolmessage
      • The possible acknowledgement to the request
      • Control and synchronization messages (e.g., slot schedule table)
    • The passive node listens the message from its active node
  • Data Section
    • Used for the actual transfer of data
emacs operation
EMACs --- Operation
  • Node A is an active node, while nodes B, C, and D are all passive nodes
  • Nodes B, C, and D are node A’s neighbors
  • Nodes B, C, and D intend to send packets to node A

A

C

B

D

emacs operation cont d
EMACs --- Operation (cont’d)
  • In CR section, nodes B, C, and D send their own requests to node A (via random backoff mechanism)

A

C

B

D

emacs operation cont d1
EMACs --- Operation (cont’d)
  • Suppose the transmission of node C is allowed
  • In TC section, node A broadcasts a control message (w/ ack. of the request, slot schedule table, etc)

A

C

B

D

emacs operation cont d2
EMACs --- Operation (cont’d)
  • In DATA section, node C transmits the data to node A (w/o any collision)

A

C

B

D

emacs operation cont d3
EMACs --- Operation (cont’d)
  • In CR section, nodes B and D send their own requests to node A (via random backoff mechanism)

A

C

B

D

emacs operation cont d4
EMACs --- Operation (cont’d)
  • Suppose the transmission of node B is allowed
  • In TC section, node A broadcasts a control message (w/ ack. of the request, slot schedule table, etc)

A

C

B

D

emacs operation cont d5
EMACs --- Operation (cont’d)
  • In DATA section, node B transmits the data to node A (w/o any collision)

A

C

B

D

emacs operation cont d6
EMACs --- Operation (cont’d)
  • In CR section, node D sends its own request to node A (via random backoff mechanism)

A

C

B

D

emacs operation cont d7
EMACs --- Operation (cont’d)
  • Suppose the transmission of node D is allowed
  • In TC section, node A broadcasts a control message (w/ ack. of the request, slot schedule table, etc)

A

C

B

D

emacs operation cont d8
EMACs --- Operation (cont’d)
  • In DATA section, node D transmits the data to node A (w/o any collision)

A

C

B

D

emacs operation cont d9
Schedule

Challenges

Request collision

Time slot selection

Node role determination

EMACs --- Operation (cont’d)

A

B

C

D

transmitting/receiving state

power-saving state

request collision
Request Collision
  • The node will not receive any acknowledgement from the active node
  • The node sends the request in the next active node’s time slot
time slot selection
Time Slot Selection
  • The active node sends the time schedule table in the TC
    • The table contains the assignment of time slots occupied by the active node and its one-hop neighbors
  • The information is encoded by a number of bits
  • A node can pick an unused time slot for itself
time slot selection cont d
Time Slot Selection (cont’d)

The occupied time slots for

0010110…

?

(OR bit sets)

6

0110110…

1111110…

3

1001110…

5

0111100…

?

5

free time slot

4

2

1

1001100…

4

?

7

1101100…

1110100…

0101100…

node role determination
Node Role Determination
  • Based on passive clustering
  • The anchor (cluster head) and bridge (gateway node) are regarded as the activenodes
  • The nonmember (ordinary node) is regarded as the passivenode
simulation
Simulation
  • Simulator: OMNet++
  • Routing protocol: DSR
  • Network environment
    • Number of nodes: 46
    • Number of data sources: 5 (5-byte length data)
    • Number of the sink: 1
    • Size: 5 by 5 times the transmission range of a node
  • Network types
    • Static
    • Dynamic
      • Random waypoint model
simulation static network
Simulation --- Static Network

EMACs is able to prolong the lifetime with 30% to 55% compared to SMAC

simulation dynamic network
Simulation --- Dynamic Network

EMACs is able to extend the lifetime with a factor of 2.2 to 2.7 compared to SMAC

question
Question
  • Source
    • Frequent transceiver state switch
  • Results
    • Increase energy consumption
    • Increase latency
  • Solution
    • LMAC
a lightweight medium access protocol lmac for wireless sensor networks

A Lightweight Medium Access Protocol (LMAC) for Wireless Sensor Networks

L. F. W. van Hoesel and P. J. M. Havinga

† Department of Electrical Engineering, Mathematics and Computer Science

University of Twente, The Netherlands

International Workshop on Networked Sensing Systems (INSS 2004)

frame structure
Frame Structure

frame

frame

frame

frame

frame

timeslot

TC

DATA

  • TC: Traffic Control Section
  • DATA: Data Section
operation
Operation
  • All nodes should be awake in all TCs
  • A node always transmits a control message in its own TC, all neighbors should receive the control message
    • A node is addressed: listen to the data section
    • A node is not addressed: switch off transceiver, and wake up at the next time slot
    • Control message: 12 bytes
simulation static network1
Simulation --- Static Network

LMAC reduces preamble transmissions and transceiver state switches

summary
Summary
  • EMACs vs. LMAC
    • Active vs. passive
  • Advantages of EMACs/LAMC (compared to SMAC)
    • Energy conservation (mainly about idlelistening)
    • Delivery ratio
  • Drawbacks of EMACs/LMAC (compared to SMAC)
    • High latency
energy efficient medium access control

Energy-Efficient Medium Access Control

Koen Langendoen and Gertjan Halkes

Delft University of Technology

Book Chapter in the Embedded Systems Handbook

R. Zurawski (editor), CRC press, to appear in Aug. 2005

simulation result latency
Simulation Result --- Latency

Average delay for one hop

transmission is half the length

of a frame

Adaptive listening mechanism

(messages can travel about

2 hops during one active period)

conclusion
Conclusion
  • EMACs and LMAC are robust in the dynamic network
  • TDMA-based protocol
    • Less energy consumption due to free of idle listening
    • Incur high latency
    • Overhead of schedule computing and distribution through the network limit the applications