Low power rendezvous in embedded wireless networks

In the future, wireless networking will be embedded into a wide variety of common, everyday objects. In many embedded networking situations, the communicating nodes will be very small and battery powered. For this reason, it is crucial that power consumption is as low as possible. A technique for reducing power consumption is to place nodes into a sleep mode whenever possible, and have them occasionally awaken to interact with other nodes. This type of action is referred to as a node rendezvous, and can be used in a variety of different ways. We consider power-efficient service rendezvous in embedded wireless networks with external triggering. We first define two basic rendezvous mechanisms, namely, server beaconing and client beaconing. We show that server beaconing is preferred when the client arrival rate is below a parameter dependent threshold. Above this level, the use of client beaconing results in lower power consumption. We also consider a hybrid technique whereby server nodes independently select the beaconing mode so that the total power consumption is reduced over a wide range of system parameter values. The operation of the client nodes is transparent to this selection. We also introduce the use of adaptive server beaconing. In a static server beaconing system, the optimum beaconing rate is an increasing function of the client loading level. It is shown that by adapting the server beacon rate in an intelligent way, the total power consumption can be greatly reduced over a large range of traffic loading conditions. A very simple method is introduced for performing this adaptation. Several other innovations are discussed which can be used to reduce power consumption in embedded networks. We investigate the use of an AC mains-powered rendezvous server for power reduction, and we discuss a distributed power reduction technique referred to as client beacon proxying. It is shown that by performing rendezvous in an intelligent manner, the total power consumption may be greatly reduced in many situations.