Simulation studies of the effects of user mobility on the handoff performance of mobile communications

The performance of soft handoffs of code division multiple access (CDMA) mobile communication systems is determined by several factors. Due to the importance of handoffs in mobile communications, several handoff methods have been proposed and evaluated through computer simulations. However, the credibility of simulation results depends on the objectivity of the assumptions made by the simulations. This paper presents a new soft handoff method that controls handoff drop timer based on a mobile station’s speed, and compares it with the current method of CDMA systems. A computer program has been developed to simulate the handoff methods under a variety of conditions. The simulation results showed that the new method is much more efficient for mobile stations that are free in their moving direction and space than for those restricted in their moving direction and space. In addition, the results showed that even the same handoff method may produce different simulation results depending on whether a service area is modeled as two-dimensional space or three-dimensional space. These results indicate the importance of suitable models of user mobility, especially the movement types and space allowed for mobile stations, which have been neglected in simulation studies of mobile communications.