CSE-525 (Winter 2004)
Topic #14: Energy Efficient MAC
Nilesh Jain
[2] An Energy Efficient MAC Protocol for Wireless LANs by E. Jung and N. Vaidya
[3] Energy efficient communications in ad hoc networks using directional antennas by A. Spyropoulos and C. Raghavendra
Summary: All three paper talks about the energy conservation in MAC protocol, each paper presents a approach to optimize power in MAC, they have optimized this by keeping certain area or application in mind, they are not generic solution.
Paper #1: Author talks about modification in contention based protocol (CSMA/CA) for sensor network, because conventional MAC is fit for energy limited networks. He points out 4 major source of energy inefficiency i.e. Collision, Overhearing, Control packet overhead and Idle listing; to overcome from these limitation he proposed Periodic listing and sleep, Message passing, and to reduce control overhead synchronization in listing cycle. Author doesn't mentioned anything about synchronization of listen cycle of initially disjoint group of node. His work shows considerable amount of energy saving, by loosing some per hop fairness and latency, but that is acceptable if application fairness and latency is maintained in senor applications. Avenues for future work include, more analysis on energy consumption and latency and effect of topological change.
Paper #2: This paper talks about modification in Power Save Mechanism (PSM) in Distributed Coordinating Function (DCF) in IEEE 802.11. Author point out that having fixed ATIM window, is not good for all condition and hence lead to more power consumption or performance degradation, so purposed a dynamic ATIM window size setting, based on network traffic condition. Author does simulation based on proposed increment and decrement rules for ATIM window size, and result show improvement in power saving using D-PSM.
Paper #3: Author talks about Energy efficient routing and scheduling algorithm in ad hoc network where each node has single directional antenna. He devised a algorithm for finding shortest cost path to be energy efficient using topology consisting of all possible link in the network, then calculate the amount of traffic that has go over each link and maximum time each link can be up, and finally schedule node’s transmissions, trying to minimize the total time it takes for all possible Tx-Rx pairs to communicate with each other. Avenues for future work include multicasting and broadcasting and there scheduling algorithm.
Discussion: In class we discuss about how node will align, if they have different sleep schedule. It is similar to the issue mentioned in the second paper, about aligning of beacon interval of initially disjoint networks. Author doesn't mentioned any thing about this in the paper.
Presentation: Slides