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Reliable MAC Layer in IEEE 802.11Wireless Networks

Reliable MAC Layer in IEEE 802.11Wireless Networks. Min-Te Sun, Lifei Huang, Anish Arora, Ten-Hwang Lai Presented by Md Tareq Adnan. Outline. Existing Multicast MAC Protocols Problems with Existing Multicast MAC Protocols Batch Mode Multicast MAC protocol, BMMM

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Reliable MAC Layer in IEEE 802.11Wireless Networks

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  1. Reliable MAC Layer in IEEE 802.11Wireless Networks Min-Te Sun, Lifei Huang, Anish Arora, Ten-Hwang Lai Presented by Md Tareq Adnan CSE 6590 - High Performance Computer Networks

  2. Outline • Existing Multicast MAC Protocols • Problems with Existing Multicast MAC Protocols • Batch Mode Multicast MAC protocol, BMMM • Location Aware Multicast MAC protocol, LAMM • Performance Evaluation based on Simulation CSE 6590 - High Performance Computer Networks

  3. IEEE 802.11 multicast/broadcast Protocol • IEEE 802.11 multicast/broadcast protocol is based CSMA/CA • Increased probability of lost frames due to interference or collisions • MAC-level recovery on multicast frame CSE 6590 - High Performance Computer Networks

  4. Solution to unreliable IEEE 802.11 multicast/broadcast protocol • Batch Mode Multicast MAC protocol, BMMM • Reduces the number of contention phases • Reduces the time required for a multicast/broadcast • Location Aware Multicast MAC protocol, LAMM • Uses node Geo location • Further improve upon BMMM. CSE 6590 - High Performance Computer Networks

  5. Overview on CSMA/CA • A node before transmit listens to the medium • Backoff timer • Contention phase • Hidden terminal problem • Distributed Coordination Function (DCF) MAC protocol CSE 6590 - High Performance Computer Networks

  6. Existing Multicast MAC Protocols and Problems cont… • In IEEE 802.11 • RTS/CTS / ACK is not used for broadcast/multicast • Protocol in [19] • Introduce RTS/CTS handshake • WAIT_FOR_CTS • WAIT_FOR_DATA • Problems • Collision of CTS frames • Short inter-frame spacing (SIFS) • Direct Sequence (DS) capture ability • Contention window [0,w] CSE 6590 - High Performance Computer Networks

  7. Existing Multicast MAC Protocols and Problems cont… • Broadcast Support Multiple Access (BSMA) • Introduce NAK Frame • WAIT_FOR_NAK • Problem • Collision of NAK Frame CSE 6590 - High Performance Computer Networks

  8. Existing Multicast MAC Protocols and Problems cont… • Broadcast Medium Window (BMW) • Each broadcast is treated as multiple unicast requests • Each node maintains three lists • NEIGHBOR • SEND BUFFER • RECEIVER BUFFER • Problems • Requires at least n contention phases for each multicast • Long time for multicast process lead to time out CSE 6590 - High Performance Computer Networks

  9. BMMM reduces multicast time compared with BMW Reduces n contention phases into one CSE 6590 - High Performance Computer Networks

  10. BMMM Provides Simple Coordination • Prevent neighbors from passing contention phase • RTS frame tells to transmit CTS sequentially • RAK frame tells to transmit ACK sequentially CSE 6590 - High Performance Computer Networks

  11. Why use BMMM • Greatly reduces the number of contention phases • No modification on control frame format • Co-exist with IEEE 802.11 protocols CSE 6590 - High Performance Computer Networks

  12. Batch Mode Multicast MAC Protocol(BMMM) CSE 6590 - High Performance Computer Networks

  13. Location Aware Multicast MAC Protocol(LAMM) • GPS location information • A subset S’ of S will be a cover set if A(S)=A(S’). 1. Sender receives an ACK from every node in S’ Receiver guaranteed to receive data frame without collision CSE 6590 - High Performance Computer Networks

  14. Location Aware Multicast MAC Protocol(LAMM) 2. Minimum cover set of S can be computed in O(n^4/3) time 3. Every receiver is guaranteed to receive the data frame without collision if the transmission area of a node is completely covered by the transmission areas of a set of nodes CSE 6590 - High Performance Computer Networks

  15. Cover Angle • If two nodes are at the same location, cover angle is [0,360] • If two nodes are R away, cover angle is Ø • Transmission area of p, A(p) is completely covered by C CSE 6590 - High Performance Computer Networks

  16. Why use LAMM • LAMM protocol is refinement of the BMMM protocol • US FCC has requested all wireless service carriers to provide 911 calls CSE 6590 - High Performance Computer Networks

  17. Expected number of contentionphases before data sent CSE 6590 - High Performance Computer Networks

  18. Successful Delivery Rate CSE 6590 - High Performance Computer Networks

  19. Successful Delivery Rate CSE 6590 - High Performance Computer Networks

  20. Average Number of ContentionPhases CSE 6590 - High Performance Computer Networks

  21. Average Message Completion Time CSE 6590 - High Performance Computer Networks

  22. A Pointer to Future Work • Focus was to resolve the hidden terminal problem for multicast • Has not addressed the exposed terminal problem CSE 6590 - High Performance Computer Networks

  23. Thank You CSE 6590 - High Performance Computer Networks

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