Focusing on the problem of encountering the moving obstacle for the water quality monitoring platform in the autonomous navigation,a new dynamic obstacle avoidance method based on the obstacle motion prediction model and the velocity obstacle avoidance model was proposed. Firstly, the ultrasonic ranging module and image acquisition module were used to measure the distance and the azimuth angle between the obstacle and the platform, and then the obstacle's speed and direction were calculated using the coordinate transformation method. Secondly, obstacle motion prediction model was built based on maximum likelihood estimation method, and obstacle speed and direction of the next sampling instant were obtained by this model. Finally, the platform's course angle of the next sampling instant was calculated using the velocity obstacle avoidance model. The experimental results prove that the proposed obstacle avoidance method can plan out a more realistic and optimal path. Compared with the obstacle avoidance method without the obstacle motion prediction model, the proposed obstacle avoidance method could improve the success rate of obstacle avoidance.

Next Generation Network (NGN) is an integrative network which uses different radio access technologies. In this converged network environment, vertical handoff between different wireless access technologies becomes an important research topic. However, most of vertical handoff algorithms do not think about the actual demands of network and the mobility of user, but taking network properties as the standards of judgment. In order to solve the problem above, a speed adaptive vertical handoff algorithm based on application requirements was proposed, which used the speed factor and network propertise matrix to compensate for the quality loss of wireless link caused by mobility, which adaptively adjusted the weights of network properties that the application needs and supported node to make effective decisions. This algorithm realized vertical handoff with adaptive speed which better served the application and . Simulation results show that the proposed algorithm can overcome the ping-pang effect effectively and it has higher packet throughput in comparison with the other vertical handoff algorithms.