Minimum Necessary Transmission Range Assignments for Network Connectivity

Networks of portable devices are very popular due to the technological evolution in the area of electronics. The devices are becoming smaller, more compact and getting more processing power and flexible communication capabilities. Furthermore, portable devices constitute the core of sensor networks, which is one of the more attractive areas of research. The portability that makes these devices popular, however, creates the inherent limitation of finite energy. If the energy of a critical node is depleted then the network gets disconnected. Such a phenomenon is usually referred to as the termination of the network lifetime. For prolonging the network lifetime we need to preserve and utilize the finite energy of the node in the most efficient way. Efficient utilization of energy requires the elimination of unnecessary energy usage wherever possible. For a portable - communication enabled - device, a significant part of energy is consumed for communications and more specifically for transmissions. As the transmission power is directly related to the transmission range achieved, we focus on optimizing the transmission range assignments; to reduce the corresponding energy consumed while sufficient network connectivity is preserved. In a typical 100 node network, for example, we show that lowering the transmission range of all nodes can reduce the power over 30% while still keeping all nodes reachable from all other nodes. Furthermore, by adjusting each node's range individually, we reduce transmit power another 30%. The developed heuristics are very efficient in this matter, as it is highlighted by their performance evaluation.