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An Adaptive TDMA Slot Assignment Protocol in Ad Hoc Sensor Networks

An Adaptive TDMA Slot Assignment Protocol in Ad Hoc Sensor Networks. Akimitsu Kanzaki, Takahiro Hara and Shojiro Nishio ACM Symposium on Applied Computing, 2005 (ACM SAC’05). Outline. Introduction Related Work USAP(Unifying Slot Assignment Protocol) USAP-MA(USAP-Multiple Access)

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An Adaptive TDMA Slot Assignment Protocol in Ad Hoc Sensor Networks

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  1. An Adaptive TDMA Slot Assignment Protocolin Ad Hoc Sensor Networks Akimitsu Kanzaki, Takahiro Hara and Shojiro Nishio ACM Symposium on Applied Computing, 2005 (ACM SAC’05)

  2. Outline • Introduction • Related Work • USAP(Unifying Slot Assignment Protocol) • USAP-MA(USAP-Multiple Access) • ASAP(Asaptive Slot Assignment Protocol) • E-ASAP (Extend ASAP) • Simulation Results • Conclusion

  3. Introduction • Motivation • E-ASAP prevents the excessive increase of unassigned slots • By minimizing each node’s frame length.

  4. The first slot in each frame is reserved to transmit control packet Related Work- USAP(Unifying Slot Assignment Protocol) MILCOM’96 N frames=Cycle M slots

  5. Related Work- USAP(Unifying Slot Assignment Protocol) MILCOM’96 • When a new node joins the network • It firstly collects NMOPs by listening the network channel for a cycle • It recognizes the slot assignments in its contention area. • Disadvantage of USAP • N(frame) and M(slot) should be large enough • The channel utilization usually becomes low • Due to a large number of unassigned slots.

  6. Related Work- USAP-MA(USAP-Multiple Access) MILCOM’99 Double frame length Frame Length= 8 Frame Length= 4 Frame Length= 8 Frame Length= 4

  7. Frame Length= 8 Frame Length= 4 Related Work- USAP-MA(USAP-Multiple Access) MILCOM’99 • Advantage of USAP-MA • USAP-MA improves the channel utilization • By reducing unassigned slots with consideration of the number of nodes and the network topology. • Disadvantage of USAP-MA • The channel utilization is still low • Unassigned slots in the later part if frame when frame length is double • USAP-MA does not offer • When and how to change the frame length • How to select a slot assigned to a new node

  8. Related Work-ASAP(Asaptive Slot Assignment Protocol) AINA 2003 • Set the frame length for a new node • Base on the number of nodes in its contention area • Minimize the number of unassigned slots to improve the channel utilization • Packet Format • Transmit mode • Data packet (DAT) • Contain the information on the frame length and slots assigned to the sender • Maximum frame length of the sender and its neighbor

  9. REQ A 1 B 3 C INF New node Related Work-ASAP(Asaptive Slot Assignment Protocol) AINA 2003 • Packet Format • Control mode • Request packet (REQ) • Arequests the information on the frame length and assigned slots of all nodes in its contention area. • Information packet (INF) • Contain the information on the frame length of Band slots assigned to the sender andC • Suggestion packet (SUG) • A sends to its neighbors to announce the frame length and its assigned slot. • Reply packet (REP) • Btransmits to confirm of receiving SUG

  10. SUG A 1 B 3 C REP New node Related Work-ASAP(Asaptive Slot Assignment Protocol) AINA 2003 • Packet Format • Control mode • Request packet (REQ) • Arequests the information on the frame length and assigned slots of all nodes in its contention area. • Information packet (INF) • Contain the information on the frame length of Band slots assigned to the sender andC • Suggestion packet (SUG) • A sends to its neighbors to announce the frame length and its assigned slot. • Reply packet (REP) • Btransmits to confirm of receiving SUG

  11. Related Work-ASAP(Asaptive Slot Assignment Protocol) AINA 2003 • Setting the frame length and grasping slot assignment • After collecting INFs from all neighbors, new node sets its frame length. • New node adopts the maximum frame length among all nodes in the contention area Frame Length= 4 Frame Length= 8

  12. Related Work-ASAP(Asaptive Slot Assignment Protocol) • Selecting an assigned slot • Getting an unassigned slot (GU) • Releasing multiple assigned slots (RMA) • Doubling the frame (DF) Double

  13. Related Work-ASAP(Asaptive Slot Assignment Protocol) • Disadvantage of ASAP • Frame length in the whole network tends to increase • Frame length of a new node is set as the maximum frame length among nodes in its contention area.

  14. E-ASAP (Extend ASAP) • Each node assigns a slot to itself in the frame of the minimum length Frame Length= 8 6 d 1 i h c 1 2 g j 3 4 f 5 Frame Length= 4

  15. E-ASAP (Extend ASAP) h 1 hop 2 hop Information held by node h in E-ASAP

  16. Unassigned slot Multiple slots a b a b d c a b e E-ASAP (Extend ASAP)-Slot Assignment • Steps: • New node collects INFstransmitted by its neighbors • Try to assign a slot to itself in the minimum frame length of 4 slots • New node searches a slot • Getting an unassigned slot (GU) • If the first slot is not assigned to any neighbors, and some unassigned slots are found. • Releasing multiple assigned slots (RMA) • If the first slot is not assigned to any neighbors and all the other slots are assigned to other nodes in its contention area • Doubling the frame (DF) • If no slot is available in the current frame length, new node doubles the frame and tries again to assign a slot • RMA and GU

  17. 2/4 2/8 , 6/8 3/4 1/4 3/4 Double 0/4 E-ASAP (Extend ASAP) a c d b 1/8 e New node b GU RMA New node

  18. conflict E-ASAP (Extend ASAP)-Detecting of conflict c 1 d 3 2 3 5 e a f g 4 4 b New node

  19. E-ASAP (Extend ASAP)-Solution to solve conflict • Deleting a conflicting slot • Divide the assignment Delete slot 3 of a Divide slots

  20. E-ASAP (Extend ASAP)-Solution to solve conflict • Doubling the frame and dividing the assignment Double Frame Length= 8 Frame Length= 4 Frame Length= 8

  21. E-ASAP (Extend ASAP)-Releasing Slot Assignment • When a node exits from the network • It releases slots assigned to itself, and its neighbors detect the exit • After reconfiguring the slot assignment information • The neighbors of the exiting node temporarily release their own assigned slots • And search for slots that can be assigned to themselves by Getting an unassigned slot (GU) • If a neighbor finds a slot which can assign to itself in the shorter frame than the current one • It updates its own assignment • Each neighbor updates its own assignment transmits in its contention area.

  22. E-ASAP (Extend ASAP)-Simulation • Simulation Environment • Each node in the network does not move. • Initially 2 nodes, and this number increases one by one until 50 nodes are present. • The number of nodes then decreases one by one in the reverse order • ASAP and E-ASAP • New node listens to the channel for 128 slots for collecting information • USAP: frame length 50 slots

  23. E-ASAP (Extend ASAP)-Simulation Average channel utilization

  24. E-ASAP (Extend ASAP)-Simulation Control traffic

  25. E-ASAP (Extend ASAP)-Simulation Setting delay (control mode changes to transmit mode)

  26. E-ASAP (Extend ASAP)-Conclusion • E-ASAP is a TDMA slot assignment protocol • To improve the channel utilization. • To decreases the number of unassigned slots • Efficiently assign slots to nodes • When a node appears and disappears from the network • Future Work • To consider a frame format to accommodate the movement of nodes. • To extend E-ASAP to adapt the change of network environment • Such as traffic load

  27. Thanks for Your Listening

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