| The network layer of wireless sensor network (WSN) forms the transmission path based on data-centric concept. As the node energy and resources are limited, the design of routing protocol should meet energy-efficient, low latency, load balancing and other special requirements which are hot issues in current WSN research. Three routing protocols are respectively proposed for load balance in large scale sensor networks:(1) Energy-efficient Double-sink Routing Protocol (EDRP)EDRP constructs the sensor network in two-sink mode. In order to avoid the data transmission concentrating on a single path, the residual power comparison scheme is proposed based on minimum cost forwarding algorithm (MCFA) which utilizes the cost field to carry out each node's nearest and sub-nearest sink node that reside in different group, so the nodes afterwards can select different path to the sink. Then the nodes resolve the next hop by comparing the residual energy of downstream nodes and dynamically select a next hop node that has a higher residual energy, so the transmission path is gradually established to nearest or sub-nearest sink. EDRP is designed for use in applications which have the sink nodes distributed in centered regions.(2) Grid Shift Routing Protocol (GSRP)GSRP partitions the network into grids which have equal side length, the adjacent dissemination nodes of grid communicates under a preset direction. The sink would only do the local flooding to fetch desired information if needed. GSRP utilizes the grid shift scheme to improve the situation that most energy tunneled on the dissemination nodes located on a single transmission path. This scheme introduces a grid shifting scheme to periodically alter the grid structure, so the dissemination nodes of grid can work alternately at different time, thus the load for the dissemination nodes in a single transmission path is balanced. GSRP is designed for use in latency-sensitive applications with mobile sink.(3) Hierarchical Chain-based Routing Protocol (HCRP)To effectively overcome the problem of excessive energy consumption due to the increase in distance between adjacent nodes, HCRP partitions the network into grid regions and each region forms a chain structure based on greedy algorithm in hierarchical iteration, thus the hierarchical chain structure is established. HCRP enhances the utilization of idle nodes by merging the adjacent grids region into an integral one and ensure the equilibrium quantity of nodes in each grid region by further splitting of grid region, so energy consumption is effectively balanced. HCRP is designed for use in applications which deploys the nodes in non-uniform density and performs under persistent queries.In order to verify the validity and feasibility of the three protocols, the OMNeT++ simulation platform is used to evaluate the performance of the three routing protocols and comparison is respectively made. Simulation results show that compare with GRAB, EDRP increases network lifetime by about 30%, decreases the latency to 75%, exceeds about 30% at most in terms of residual energy saved in each round. Compare with TTDD, GSRP increases network lifetime by about 40%, decreases the latency to 70%, exceeds about 20% at most in terms of residual energy saved in each round. Compare with COSEN, HCRP increases network lifetime by about 20%, decreases the latency to 75%, exceeds about 15% at most in terms of residual energy saved in each round. Therefore, the three protocols proposed could achieve load balance under different situations which could also give low latency and longer network lifetime. |
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