Efficient Routings For Duty-Cycled Wireless Sensor Networks In Forest Environment Monitoring

Wireless Sensor Networks(WSNs)in forest environment monitoring need to be deployed for long term and in some areas where are hard for humans to arrive easily which brings challenge for energy of sensor nodes.In recent years,duty-cycled mechanism has achieved a promising approach of improving the energy efficiency of WSNs.Meanwhile,there are also some problems in duty cycle WSNs.Firstly,the dynamics of topology due to the nodes switching their states between working and sleeping improves the complexity and difficulty of routing decision.Secondly,transmission delay increases multiplied because of most packets having to wait for the forwarders awake before sending out.Facing these problems and the characteristic of WSNs in forest environment monitoring,the paper studies routing mechanism in depth as follows:(1)WSNs in forest environment monitoring are distributed in wide nature and more and more energy-Harvesting nodes are applied.For Energy-Harvesting Wireless Sensor Networks(EH-WSNs)which is also duty-cycled WSNs,network must restructure when the energy-harvesting nodes stop working to collecting energy,which seems gone from the network.Experiments show that loop is easier to form when the nodes have to find new forwarders because they can not find their previous ones.A new routing protocol named La-CTP is presented aiming to avoiding loopstotheutmost and unlocking loops if they have happened more effectively than CTP.By new rule of parent updating and an adaptive beacon timer adjusting scheme,La-CTP decreases the number of loops and beacons in networks so that increases the throughput and saving energy,which has been proved in experiments.(2)WSNs in forest environment monitoring need to collect various indicators using different sensor nodes with different work arrangement.In heterogeneous duty cycle wireless sensor networks,nodes have their own duty cycle and work schedule different from others according to their different tasks,positions and so on.The paper presents EOF,an opportunistic routing protocol for heterogeneously duty-cycled WSNs,which considers the forwarders' awake time and link quality to improve the network efficiency.EOF includes three points:a forwarding metric that can efficiently exploit the single-hop forwarding opportunity;a light forwarding coordination and a light link quality updating scheme.Experiments focus on the throughput,path delay,energy consumption,network coverage and hops.Compared to the state-of-the-art protocol,EOF can achieve better network performance with identical energy cost,especially when it is applied with significantly heterogeneous duty cycles.(3)For early warning in forest environment monitoring,such as fire alarm,Soil erosion monitoring,diseases and insect pests monitoring,has high demand for real-time data transmission and most of the nodes work in higher duty cycles than other networks.The paper presents S-APTEEN protocol which optimizes the data collecting scheme,ameliorates the selecting policy of cluster-head nodes,considers the transmission quality and energy balance in networks.Experiments show that S-APTEEN achieves better performance than APTEEN protocol.