A Tradeoff between Energy and Bandwidth Efficiency in Wireless Networks

In this paper, we study the bandwidth efficiency and energy efficiency of wireless ad hoc networks in which the energy supply of nodes and bandwidth are the primary resource constraints. For bandwidth efficiency, we consider the total number of channel uses between source and destination node. Also, energy consumption of the receiver in order to process each coded bit is considered as well as the wasted energy of a nonideal amplifier in the transmitter. With the location of relaying nodes, we investigate the impact on bandwidth efficiency and energy efficiency for both common rate and common power Schemes. All nodes in a network operate in half-duplex mode, hence more channel uses are required in a multihop transmission. This leads to a loss in bandwidth efficiency but a potential gain in energy efficiency because each node can save its transmitting power. We investigate this tradeoff between energy efficiency and bandwidth efficiency of the network similar in nature to that found by Shannon for a single link. We also develop performance characterizations in terms of transport efficiency, which combines bandwidth efficiency and energy efficiency into a single metric. It is shown that equidistant relaying cases perform better than non-equidistant relaying cases for either common rate or common power schemes. For non-equidistant relaying cases, it is also shown that common power schemes achieve a higher bandwidth efficiency than do common rate schemes, whereas energy efficiency depends on the received signal-to-noise ratio at the destination node.