Energy efficient wireless communication network design is an important and challenging problem. It is always necessary especially in the field of wireless communication networks to have a network to serve our purpose without the loss of energy. The problem lies in developing a design methodology that integrates various aspects of a wireless communication network from the device layer, such as antennas and amplifier design, all the way to the network and application layers. We present a generic simulation-based design methodology that achieves global optimization for such networks and that is suitable for many kinds of mobile systems. We point out some important connections between the different layers in the design procedure. Some preliminary results of the application of this design methodology to a situational awareness mobile wireless network are given. These results illustrate the trade-off between performance and energy consumption in the operation of these networks
To highlight the trade-offs between performance and energy consumption at individual components, consider the design and operation of an amplifier. The amplifier boosts the power of the desired signal so that the antenna can radiate sufficient power for reliable communications. However, typical power amplifiers have maximum efficiency in converting DC power into RF power when the amplifier is driven into saturation. In this region of operation, the amplifier voltage transfer function is nonlinear. Because of this non linearity, the amplifier generates unwanted signals (so called intermodulation products) in the band of the desired signal and in adjacent bands. When the amplifier drive level is reduced significantly (large back off) the amplifier voltage transfer characteristic becomes approximately linear. In this case it does not generate intermodulation products. However, with large back off the amplifier is not able to efficiently convert DC power into RF power. Thus, there is considerable wasting of power at low drive levels, but at high drive levels more interfering signal are generated.
To highlight the coupling among the design of individual components of a wireless system, consider packet routing in a wireless network that contain no base station (i.e. an ad hoc network). For simplicity consider a network with nodes A, B and C shown in figure. If Node A wants to transmit a message to Node C, it has two options. Transmit with power sufficient to reach Node C in a single transmission, or transmit first from A to B with smaller power, and then B to C. since the received signal power typically decays with distance as d4, there is significantly smaller power loss due to propagation in the second option because d^4ac>d^4ab+d^4bc.however even though Node A transmits with smaller output power, it does not necessarily proportionally decreases the amount of actually consumed because of the amplifier’s effect discussed above.
Furthermore, besides the energy required for packet transmission, there are energy requirements for packet reception and information decoding. The probability of packet error reception that is achieved depends on energy allocated to the receiver. Consequently, there is a coupling among amplifier design, coding and modulation design, and decoding design as well as routing protocol.
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