Movable safety zone scheme in urban fiber-optic microcellular systems

We consider a urban fiber-optic microcellular environment in which a cigar-shaped cell consists of several microzones with their own antenna sites connected to a central station through optical fibers. To increase the efficiency of radio resources and to reduce unnecessary handoff calls between microzones, we propose a movable safety zone scheme in which each communicating user has his own safety zone not permitting cochannel reuse. His safety zone also can move if his cochannel interference is not met as he moves to an adjacent microzone. Considering user mobility characteristics and urban microcell shapes, we analyze and evaluate the proposed system in terms of intercell/intracell handoff rate, call blocking probability, and channel reuse parameter. The proposed system can handle the traffic capacity of about 12 erlangs for 7 traffic channels under the call blocking probability of 1%, and generates a negligibly small number of intracell handoffs compared with intercell handoffs.