| The heterogeneous wireless network is the development trend, which is an integratednetwork with different wireless access technologies. Because of the different characteristics ofthe wireless access technologies, they can complement each other to meet the diverse needs ofusers. Vertical handoff is an important issue to achieve heterogeneous wireless networks.First, this paper introduces the history of mobile communications and the future trends.Then, a vertical handoff algorithm is researched based on the movement aware acquired byprocessing the RSS samples. The RSS samples are handled by KALMAN filtering, the methodof least squares quadratic polynomial fitting and compensation to acquire current RSS and RSSrate and the residence time in base stations, which could be used for vertical handoff decision.The simulation results show that the proposed algorithm can reduce the number of handoffs andimprove the available bandwidth.Second, a GPS location information based movement aware vertical handoff algorithm isproposed. If the terminal speed is decomposed, the only component affecting the distancebetween the terminal and the base station is the speed component in the radius direction. Theuser residence time in base stations is more precisely estimated by this velocity component. Thesimulation results show that using the speed component in the radius direction to estimate theresidence time, the available bandwidth can be increased.Finally, a residence time based adaptive vertical handoff algorithm is proposed. In theanalysis of current vertical handoff decision algorithms based on MADM, the user movementinformation should be considered, such as the residence time in a base station. The proposedalgorithm adaptively adjusts the weight of residence time and combines user movementinformation and current MADM algorithms using SAW. The simulation results show that theproposed algorithm could decrease the handoff number and improve the user quality. |
