Localization is one of the most important technologies in wireless sensor network, and mobile beacon assisted localization is a promising localization method. The mobile beacon trajectory planning is a basic and important problem in these methods. There are many obstacles in the real world, which obstruct the moving of mobile beacon. This paper focuses on the obstacle avoidance trajectory planning scheme. After partitioning the deployment area with fixed cell decomposition, the beacon trajectory are divided into global and local trajectory. The approximate shortest global trajectory is obtained by depth-first search, greedy strategy method and ant colony algorithm, while local trajectory is any existing trajectories. Simulation results show that this method can avoid obstacles in the network deployment area, and the smaller cell size leads to longer beacon trajectory and more localizable sensor nodes.

Only by means of XOR operation, a novel image encryption scheme is proposed based on a nonlinear chaotic map (NCM). There are two rounds in the proposed image encryption scheme. In each round of the scheme, the pixel gray values are modified from the first pixel to the last pixel firstly, and then the modified image is encrypted from the last pixel to the first pixel in the inverse order. In order to accelerate the encryption speed, every time NCM is iterated, n (n>3) bytes random numbers which are used to mask the plain-image can be gained. And to enhance the security, a small perturbation will be given to the parameters of the NCM based on the last obtained n bytes modified elements before next iteration. Experimental results and theory analysis show that the algorithm has a high security performance and a good efficiency.