In multi-monitoring-task mobile sensor networks,different monitored objects have different requirements for real-time transmission.To satisfy those requirements,a multi-layered real-time data routing protocol (MRDR) was proposed to satisfy the requirements of both soft real-time and hard real-time monitoring.In MRDR,a layer mechanism was introduced into mobile sensor networks and the network was divided into layers with equal width.For ordinary event messages with higher delay tolerance,MRDR could enable messages to be forwarded to the sink at as low energy consumption as possible.For emergent event messages with lower delay tolerance,MRDR could send messages to the sink by multi-hop real-time transmission.At the same time,for the problem of energy holes in hard real-time routing,a backward mechanism was proposed to enable emergent event messages avoiding node holes and finally be transmitted to the sink.At last,to reduce message redundancy,message queue management was designed and the principle for discarding messages was presented when the queue was full.To evaluate the performance,simulation was carried out to compare MRDR and other three algorithms in terms of network lifetime, average delivery ratio and average delay.The result proved the efficiency of MRDR.In different network environments,MRDR could effectively be applied to multi-monitoring-task mobile sensor networks and satisfy different requirements of different real-time transmissions.
