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Self Organization and Energy Efficient TDMA MAC Protocol by Wake Up for Wireless Sensor Networks

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Assign time slots to the sensors within each TDMA-W frame ... More than one node intends to send data ... Data packet may only contain the destination information ... – PowerPoint PPT presentation

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Title: Self Organization and Energy Efficient TDMA MAC Protocol by Wake Up for Wireless Sensor Networks


1
Self Organization and Energy Efficient TDMA MAC
Protocol by Wake Up for Wireless Sensor Networks
  • Zhihui Chen and Ashfag Khokhar
  • ECE/CS University of Illinois at Chicago
  • IEEE SECON 2004
  • Presented by Jeffrey

2
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

3
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

4
Wireless Sensor Networks (WSNs) Are Unique
  • Traffic rate is very low
  • Typical communication frequency is at minutes or
    hours level
  • Sensor networks are battery powered and
    recharging is usually unavailable
  • Energy is an extremely expensive resource

5
Wireless Sensor Networks (WSNs) Are Unique
  • Sensor nodes are generally stationary after their
    deployment
  • Sensor nodes coordinate with each other to
    implement a certain function
  • Traffic is not randomly generated as those in
    mobile ad hoc networks

6
Previous Energy-Efficient MAC Protocols for WSNs
  • An Energy-Efficient MAC Protocol for Wireless
    Sensor Networks
  • W. Ye, J. Heidemann and D. Estrin
  • IEEE INFOCOM 02
  • S-MAC (10 S-MAC)

7
Previous Energy-Efficient MAC Protocols for WSNs
  • An Adaptive Energy-Efficient MAC Protocol for
    Wireless Sensor Networks
  • T. Dam and K. Langendoen
  • ACM SENSYS 03
  • T-MAC

8
Concentrate traffic to fixed periods?
  • Increases contention probability
  • Incurs unnecessary retransmissions
  • S-MAC proposes to perform RTS/CTS handshake
    procedure
  • Duty rate or portion of listening period of S-MAC
    should be carefully chosen
  • T-MAC adapts duty cycle to the traffic rate

9
Previous Energy-Efficient MAC Protocols for WSNs
  • Energy-Efficient, Collision-Free Medium Access
    Control for Wireless Sensor Networks
  • V. Rajendran, K. Obraczka and J.J.
    Garcia-Luna-Aceves
  • ACM SENSYS 03
  • TRAMA

10
Scheduling
  • Data transmissions are scheduled in advance to
    avoid contention
  • TDMA-W
  • TDMA-Wakeup
  • Each node is assigned two slots
  • Transmission/Send slot (s-slot)
  • Wakeup slot (w-slot)

11
(No Transcript)
12
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

13
Channel and Traffic Assumption
  • Ideal physical layer
  • The only reason for packet loss is transmission
    contention
  • No packet loss due to noise
  • Three types of traffic pattern
  • One-to-all broadcast
  • All-to-one reduction
  • One-hop random traffic

14
Channel and Traffic Assumption
  • A TDMA-W frame lasts for Tframe seconds
  • Tframe is known to all nodes and is preset before
    deployment
  • A TDMA-W frame is divided into slots
  • Each node is assigned one slot for transmission
    and one slot for wakeup
  • Networks are synchronized

15
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

16
Self-Organization
  • Assign time slots to the sensors within each
    TDMA-W frame
  • Assume sensor networks has data rate of 1 Mbps
  • Transmission of a 512 byte packet occupies the
    channel for about 3.9 ms
  • Assume a TDMA-W frame of 1 second divided into
    256 slots
  • Each slot is of 3.9 ms
  • Capable of communicating 512 bytes

17
Self-Organization Scheme
  • Each node randomly selects a slot with uniform
    probability among all slots to be its s-slot
  • During its selected s-slot, each node broadcasts
  • Its node ID
  • Its s-slot number
  • Its one-hop neighbors IDs and their s-slot
    assignments
  • Slot number of any s-slot during which this node
    has identified a collision

18
Self-Organization Scheme
  • When a node is not transmitting, it turns on its
    receiver circuit and listens to the traffic from
    neighbors
  • The node should record all the information being
    broadcast by all its neighbors
  • Their s-slot assignments and their node IDs
  • The slot number of any slot being broadcast as a
    collision-prone slot

19
Self-Organization Scheme
  • If a node determines that
  • it is involved in a collision
  • or finds out that one of its two-hop neighbors
    has the same s-slot
  • It then randomly selects an unused slot and go to
    step 2

20
Self-Organization Scheme
  • If
  • no new nodes are joining in
  • or s-slot assignments are not changing
  • or no collisions are detected for a certain
    period
  • It implies all neighbor nodes are found and all
    the s-slots are final

21
Self-Organization Scheme
  • Each node broadcasts the s-slot selections of
    their two-hop neighbors.
  • Each node identifies an unused slot or any s-slot
    being used by the nodes beyond its two-hop
    neighbors and declares it as its w-slot
  • Note that w-slots need not be unique
  • Each node broadcasts its w-slot and the
    self-organization is complete

22
Can Detect Any Two-hop Collisions
23
Undetectable One Hop Collision
  • To solve this problem
  • Let a node go to the listening mode in its
    assigned s-slot with a probability

24
Deadlock
  • To listen during s-slot with a probability
  • To set a collision counter

25
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

26
TDMA-W Channel Access Protocol
  • Each node maintains a pair of counters for every
    neighbors
  • Outgoing counters
  • Incoming counters
  • These counters are preset to an initial value
  • If no outgoing data is sent to a node in a TDMA-W
    frame
  • The node decrements the corresponding outgoing
    counter by one
  • Otherwise it resets the counter to the initial
    value

27
TDMA-W Channel Access Protocol
  • If no incoming data is received from a
    neighboring node in a TDMA-W frame
  • The node decrements the corresponding incoming
    counter by one
  • If the counter is less than or equal to zero,
    the node stop listening to that slot starting
    from next TDMA-W frame

28
TDMA-W Channel Access Protocol
  • If a outgoing data transmission request arrives
  • The node first checks the outgoing counter
  • If the counter is greater than zero, then the
    link is considered active and the packet can be
    sent out during the s-slot
  • If the counter is less than or equal to zero, a
    wakeup packet is sent out during the w-slot of
    the destination node prior to the data
    transmission

29
TDMA-W Channel Access Protocol
  • If a node receives a wakeup packet in its w-slot
  • It turns itself on during the s-slot
    corresponding to the source node ID contained in
    the wakeup packet
  • If a collision is detected in the w-slot
  • More than one node intends to send data
  • The node then searches all its neighbors for
    incoming traffic

30
Packet Content
  • Wakeup packet contains only the source and the
    destination information
  • Data packet may only contain the destination
    information
  • Omit source ID since the source ID is determined
    by the s-slot

31
Broadcast
  • If a data packet is to be broadcast to multiple
    nodes
  • The destination address contains a special
    identifier to mark it as a broadcast message
  • Before sending a broadcast data packet
  • The node should wakeup all its neighbors that
    intend to receive this packet
  • In the case when multiple users share the same
    w-slot
  • The destination field of the wakeup message
    should also be set to a broadcast address

32
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

33
Performance Analysis of TDMA-W
  • Let us fix the position of the w-slot

34
Average Delay
35
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

36
Deployment of Sensor Nodes
  • Nodes are deployed randomly in a 500x500 sq. ft.
    area
  • Communication range is 100 feet for all nodes
  • Assume an IEEE 802.11 basic rate of 1 Mbps as the
    physical layer transmission rate
  • Slot length is set to be 4 ms
  • Long enough for transmitting a 512-byte packet
  • Tframe is set to one second
  • A TDMA-W frame has 250 slots

37
Simulation Results of Self-Organization Protocol
38
Power Consumption
  • Power consumption
  • Transmission Receiving/Listening Sleeping
  • 1.83 1 0.001
  • 10 S-MAC
  • Use RTS/CTS frames to reserve channel for
    node-to-node traffic
  • Use ACK packet to acknowledge the successful
    transmission
  • If data or ACK packet is corrupted by collision,
    the data packet is retransmitted

39
Power Consumption
  • The network is synchronized
  • All the nodes become active at the same time
  • All data packets are fixed to be 256 bytes in
    length
  • Control packets (RTS, CTS, ACK in S-MAC and
    Wakeup packet in TDMA-W) are about 20 bytes in
    length
  • Assume energy consumption for a control packet is
    1/10 of a data packet

40
Power Consumption
  • Initial value for counters is set to 3
  • Transmission buffer length is set to 50 packets
  • Both TDMA-W and S-MAC are run for 10 minutes

41
Power Consumption of One-Hop Random Traffic
42
Delay of Random One-Hop Traffic
43
Delay of All to One Reduction Operation Traffic
44
Outline
  • Introduction
  • Channel and Traffic Assumption
  • TDMA-W Details
  • Self-Organization
  • TDMA-W Channel Access Protocol
  • Performance Analysis of TDMA-W
  • Simulation Results
  • Conclusion

45
Conclusion
  • Efficient protocols TDMA-W for self-organization
    and channel access control in wireless sensor
    networks are proposed
  • Proposed protocols were verified using extensive
    simulations
  • Proposed protocols only consume 1.5 to 15 power
    of 10 S-MAC
  • 6 to 67 times better than 10 S-MAC

46
Conclusion
  • Proposed scheme responds to the event with a
    delay comparable to S-MAC for one-hop traffic
  • Proposed protocol is collision free for data
    traffic so reliable transmission is guaranteed
    for all types of traffic

47
Comments
  • Strength
  • Great improvement in the power consumption
  • Weakness
  • Verify results by using simulation (MATLAB) with
    not so practical assumptions
  • Delay could be significant
  • Scalability would be poor
  • Large overhead in memory

48
  • Thank you very much for your attention!
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