The Wireless Sensor Network MAC
Edgar H. Callaway · 2005
Wireless sensor networks usually employ performance metrics that are different from those of more conventional data networks, emphasizing low power consumption and low cost rather than data throughput or channel efficiency. Since power is consumed every time a networked device accesses the channel (either transmitting or receiving), the method by which the device accesses the channel can have a large effect on its power consumption, and therefore the valuation of the wireless sensor network as a whole. Should the channel access method require specialized or additional hardware (e.g., a second transceiver, or more processor memory), the cost incurred can similarly affect network valuation. The OSI stack places the responsibility for channel access in the medium access control (MAC) sublayer of the data link layer, the second layer of the stack. This chapter discusses the function of the MAC sublayer, identifies some of the problems that are addressed (or avoided) in a good MAC design, and reviews the relationships between the performance goals of the network and tradeoffs that can be made in selecting and designing a MAC protocol. The chapter then reviews the major categories of MAC protocols used in data networks of all types, describe a selection of MAC protocols designed for wireless sensor networks, and concludes with a look at directions for future research.