| Energy is a great concern in wireless networks. Therefore, when designing algorithms and protocols for wireless networks, energy must be considered and should be used efficiently. This dissertation studies how to efficiently conserve energy for different issues in wireless networks so that the network lifetime can be extended.; Broadcast is a mainly used communication method in wireless networks. The broadcast problem is to decide a transmission power for each host so that the source can broadcast to all other hosts either directly or indirectly through the relay hosts. In this dissertation, we solve this problem by constructing a broadcast tree with the purpose to balance the energy consumptions of all the nodes. We also propose a method to construct a strongly connected broadcast tree with bounded total energy consumption while the transmission latencies between the source and all other hosts are also bounded.; The topology control problem in wireless networks studies how to adjust the transmission power at each node in order to achieve a desired topological property. In this dissertation, we solve this problem by focusing on the network connectivity and try to find an energy-efficient way to maximize the network lifetime.; With a limited number of hosts actively participating in the routing tasks, both the total energy consumption and the communication can be reduced greatly. A virtual backbone based routing mechanism is then stimulated. In this dissertation, we approximate a virtual backbone by a Connected Dominating Set (CDS). The problem to find a minimum CDS is NP-hard and we propose several approximation algorithms for this problem.; Finally, we study the target coverage problem in sensor networks. It requires finding a small number of sensors that can cover some targets in the monitored area. In this dissertation, we study this problem by organizing the sensors into a maximal number of set covers that are activated successively to conserve energy and extend the network lifetime. Only the sensors from the current active set monitor the targets, all the other sensors are in a sleep mode. |
