Evaluating an Energy Efficient MAC Protocol for Wireless Sensor Network

Wireless sensor networks (WSN) are a trend of the past few years. The availability of micro-sensors; low power, yet reasonably efficient wireless communication equipments; embedded systems; distributed computation techniques and improved small-scale energy supplies have made this emerging technological vision possible. The study of energy-efficient wireless devices focuses mainly on the following aspects: design of low-power consuming hardware, reduction of the computational complexity to reduce the power consumption by CPU/memory, diminishment of communication-related power consumption. Broadly speaking, communication-related power consumption also includes computation-related power consumption. But in this paper I focus on the power consumed by pure communication operations. Generally, a wireless node in sensor network resides in one of the following states: transmit, receive and standby, where most of the energy is consumed in the transmission state and least in standby state. So the optimization of transmission power is of ultimate importance. The optimization can be carried out at any layer of the protocol stack. For example, at the physical layer an adjustable transmission range can be implemented based on the distance from the next hop to allow the wireless node to use the minimum energy to transmit packets. This not only preserves the energy but also reduces the interference. At data link layer an efficient sleeping scheme is able to further diminish the power consumption when nodes are idle. At network layer there exist several energy-efficient routing protocols being capable of using energy more efficiently. In addition, load balancing, that implies to use the energy more evenly and thus prevents certain nodes from being overused is also an important consideration.