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Reliable MAC Layer in IEEE 802.11Wireless Networks

This presentation discusses existing multicast MAC protocols, their problems, and introduces the Batch Mode Multicast MAC protocol (BMMM) and the Location Aware Multicast MAC protocol (LAMM). It also evaluates their performance through simulation.

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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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