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

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. Outline. Introduction Channel and Traffic Assumption TDMA-W: Details

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

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  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 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 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 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 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 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) 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 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 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 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) NTU NSLAB

  11. 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 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 NTU NSLAB

  14. Channel and Traffic Assumption • A TDMA-W frame lasts for Tframeseconds • Tframeis 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 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 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 NTU NSLAB

  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 NTU NSLAB

  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 NTU NSLAB

  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 NTU NSLAB

  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 NTU NSLAB

  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 NTU NSLAB

  22. Can Detect Any Two-hop Collisions 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 NTU NSLAB

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

  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 NTU NSLAB

  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 NTU NSLAB

  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 NTU NSLAB

  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 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 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 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 NTU NSLAB

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

  34. Average Delay 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 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 NTU NSLAB

  37. Simulation Results of Self-Organization Protocol 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 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 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 NTU NSLAB

  41. Power Consumption of One-Hop Random Traffic NTU NSLAB

  42. Delay of Random One-Hop Traffic NTU NSLAB

  43. Delay of All to One Reduction Operation Traffic 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 NTU NSLAB

  45. Conclusion • Efficient protocolsTDMA-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 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 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 NTU NSLAB

  48. Thank you very much for your attention! NTU NSLAB

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