A case for variable-range transmission power control in wireless multihop networks

We study the impact of individual variable-range transmission power control on the physical and network connectivity, network capacity and power savings of wireless multihop networks such as ad hoc and sensor networks. First, using previous work by Steele (1988) and Gupta (2000) we derive an asymptotic expression for the average traffic carrying capacity of nodes in a multihop network where nodes can individually control the transmission range they use. For the case of a path attenuation factor α = 2 we show that this capacity remains constant even when more nodes are added to the network. Second, we show that the ratio between the minimum transmission range levels obtained using common-range and variable-range based routing protocols is approximately 2. This is an important result because it suggests that traditional routing protocols based on common-range transmission can only achieve about half the traffic carrying capacity of variable-range power control approaches. In addition, common-range approaches consume ∼ (1 $2/(2^α)) % more transmission power. Second, we derive a model that approximates the signaling overhead of a routing protocol as a function of the transmission range and node mobility for both route discovery and route maintenance. We show how routing protocols based on common-range transmission power limit the capacity available to mobile nodes. The results presented in the paper highlight the need to design future wireless network protocols (e.g., routing protocols) for wireless ad hoc and sensor networks based, not on common-range which is prevalent today, but on variable-range power control.