THE MULTIPLE-CALL HAND-OFF PROBLEM IN HIGH-CAPACITY CELLULAR COMMUNICATIONS-SYSTEMS

As cellular portable and vehicular communications proliferate, some mobile platforms may support multiple calls simultaneously. Examples include buses, trains, taxicabs, aircraft, and boats. A cell boundary crossing by such a vehicle can concurrently generate multiple hand-off attempts. The same issue arises in other mobile network contexts such as naval communications, or spaceborne surveillance where mobile platforms each supporting a multiplicity of semi-autonomous sensors and/or communications links, maintain network connectivity through a nearby gateway. In this paper, an analytical model is developed which characterizes the hand-off problem in an environment where mobile platforms can support multiple independent calls. A suitable vector state representation is identified which casts the problem as a multidimensional birth-death process. An iterative method is used to find implicit hand-off parameters for systems in statistical equilibrium. Theoretical performance characteristics that show blocking, hand-off failure, and forced termination probabilities as functions of communications traffic are determined.