Abstract
In wireless networks, reducing aggregate transmit power and in many cases, having even power distribution increase the network lifetime. Conventional direct transmission (DTX) scheme results in high aggregate transmit power and uneven power distribution. In this paper, we consider location-aware cooperation-based schemes namely immediate-neighbor cooperation (INC), maximal cooperation (NIAX), and wireless network cocast (WNC) that achieve spatial diversity to reduce aggregate transmit power and even power distribution. INC utilizes two-user cooperative communication, resulting in good reduction of aggregate transmit power and low transmission delay; however, power distribution is still uneven. MAX utilizes multi-node cooperative communication, providing incremental diversity to achieve even power distribution and substantial reduction in aggregate transmit power. Transmission delay in MAX, however, grows quadratically with network sizes. As a result, the novel WNC is proposed to achieve incremental diversity as in MAX and low transmission delay as in INC. In WNC, mobile units acting as relays form unique linearly-coded signals from overheard signals and transmit them to the destination, where a multiuser detector jointly detects the symbols from all received signals. Performance evaluation in uniformly distributed networks shows that INC, MAX, and WNC substantially reduce aggregate transmit power while MAX and WNC also provide even power distribution.