To solve the problems of synchronization error accumulation and unbalanced energy consumption in multi-hop wireless sensor networks, a cluster-based and energy-balanced time synchronization algorithm for wireless sensor networks was proposed. Based on hierarchical clustering topology, cluster heads in adjacent layers adopted pairwise broadcast mechanism instead of bidirectional pair-wire synchronization mechanism to reduce communication overhead and the synchronization error of transmission delay. Cluster members synchronized the cluster head using the combination of bidirectional pair-wise synchronization and reference broadcast synchronization. In addition, the response node was selected according to residual energy to balance energy consumption of cluster nodes. The performance of synchronization precision and energy consumption of the proposed algorithm and traditional algorithm were analyzed by theoretical analysis and simulation. The results show that the new algorithm not only ensures high synchronization accuracy, but also reduces communication overhead and balances network node energy consumption to lengthen the cycle life of the network.
As a kind of pure location routing algorithm in Wireless Multimedia Sensor Network (WMSN), Two Phase Geographic Greedy Forwarding (TPGF) helps to select the next-hop node which is of nearest distance to the destination from neighbor ones. In some cases, the distance between the next-hop node and the destination node could be farther than that of the current node and the destination node; At the same time, by numbering the nodes, TPGF solves the problem of hole and satisfies the Quality of Service (QoS) requirements. In line with the strategy of selecting the next-hop node farther than the current node, action-angle variables and DATF (Direction-Angle Greedy Forwarding) algorithm were introduced to guarantee and optimize the process of selecting the bound nodes. The simulation result indicates that DATF algorithm shows better performance than TPGF in both energy consumption and end-to-end transmission delay and also has a significant effect on solving the problem of hole.