2005/8/2NTU NSLAB1 Self Organization and Energy Efficient TDMA MAC Protocol by Wake Up for...
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Transcript of 2005/8/2NTU NSLAB1 Self Organization and Energy Efficient TDMA MAC Protocol by Wake Up for...
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2005/8/2 NTU NSLAB 1
Self Organization and Energy Efficient TDMA MAC Protocol by Wake Up for
Wireless Sensor Networks
Zhihui Chen and Ashfag KhokharECE/CS University of Illinois at Chicago
IEEE SECON 2004
Presented by Jeffrey
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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)
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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)
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2005/8/2 NTU NSLAB 11
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1 ZZZ ZZZ ListenWake
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Send ZZZ ZZZ ZZZ ZZZ ZZZ Listen ZZZ ZZZ ZZZ
2 ZZZ ZZZ ZZZ
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Nd3ZZZ Send ZZZ ZZZ ZZZ ZZZ ZZZ Listen ZZZ ZZZ
3 ZZZ ZZZ
Wakeup
Nd4Listen Listen Listen Send ZZZ ZZZ ZZZ ZZZ Listen ZZZ ZZZ
4 ZZZ ZZZ ListenWake
up Nd6
ZZZ ZZZ Listen Send ZZZ ZZZ Listen ZZZ ZZZ ZZZ
5 ZZZ ZZZ ListenWake
up Nd6
ZZZ ZZZ ZZZ ZZZ Send ZZZ Listen ZZZ ZZZ ZZZ
6 ZZZ ZZZ ZZZ Listen ZZZ ZZZ ZZZ Listen Listen ZZZ ZZZ Listen ZZZ ZZZ
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 17
Self-Organization Scheme
1. Each node randomly selects a slot with uniform probability among all slots to be its s-slot
2. 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
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2005/8/2 NTU NSLAB 18
Self-Organization Scheme
3. 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
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2005/8/2 NTU NSLAB 19
Self-Organization Scheme
4. 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
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2005/8/2 NTU NSLAB 20
Self-Organization Scheme
5. 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
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2005/8/2 NTU NSLAB 21
Self-Organization Scheme
6. 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
7. Each node broadcasts its w-slot and the self-organization is complete
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2005/8/2 NTU NSLAB 22
Can Detect Any Two-hop Collisions
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 24
Deadlock
• To listen during s-slot with a probability• To set a collision counter
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 26
TDMA-W Channel Access Protocol
1. Each node maintains a pair of counters for every neighbors
– Outgoing counters – Incoming counters– These counters are preset to an initial value
2. 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
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2005/8/2 NTU NSLAB 27
TDMA-W Channel Access Protocol
3. 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
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2005/8/2 NTU NSLAB 28
TDMA-W Channel Access Protocol
4. 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
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2005/8/2 NTU NSLAB 29
TDMA-W Channel Access Protocol
5. 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 33
Performance Analysis of TDMA-W
• Let us fix the position of the w-slot
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2005/8/2 NTU NSLAB 34
Average Delay
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 37
Simulation Results of Self-Organization Protocol
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 41
Power Consumption of One-Hop Random Traffic
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2005/8/2 NTU NSLAB 42
Delay of Random One-Hop Traffic
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2005/8/2 NTU NSLAB 43
Delay of All to One Reduction Operation Traffic
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 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
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2005/8/2 NTU NSLAB 48
Thank you very much for your attention!