Cellular communications systems that are integrated into mobile battle units present more complex handoff problems than traditional cellular systems, because the access points are moving along with the users. The authors present a new handoff decision algorithm that takes into account the ratio of the used capacity to total capacity of the access points, in addition to traditional inputs such as received signal strength, and the velocities of mobiles relative to access points. The authors’ algorithm can be tuned (by setting the handoff threshold) to address the trade-off between minimizing the number of handoffs and minimizing the call blocking rate. The authors evaluate their algorithm using simulations of various tactical scenarios.

The paper begins with a survey of prior work, listing common algorithms, and their advantages and disadvantages. This is followed by a description of virtual cell layout (VCL)-based mobile communications systems. VCL is the basis of the simulations used in the evaluation. In a VCL system, the battlefield is tessellated with regular hexagons, and radio resources (for example, carrier frequencies) are assigned to cells. The authors’ algorithm is then described in detail.

The algorithm was evaluated using the Computer Aided Exercises Interacted Tactical Communications Simulation system, developed at Bogazici University. The authors describe the scenarios used, and provide the values of various model parameters of the simulator. Performance, as measured by number of blocked calls and number of handoffs, was compared to that of three algorithms that used only received signal strength as input. The results are presented in ten charts, each accompanied by discussion.