An Eeciency Limit of Cellular Mobile Systems

In order to limit hando blocking probability, in cellular systems admission control can be applied to new call requests and resources reserved for future hando attempts. Such resource reservation strategies have been widely studied in the literature. The denial of new call attempts, however, impacts system throughput creating a trade-o with hando performance. The contribution of this paper is an analytical investigation of this trade-o . In particular, we study the impact of hando on a cellular system's e ciency which we de ne as the system's throughput normalized by the theoretically optimal throughput at zero user mobility. As a reference case, we rst determine the e ciency of a hypothetical system with deterministic advance reservation. Next, we consider systems with statistical reservation and calculate the maximum achievable e ciency, under the set of possible local admission control strategies subject to a hard constraint on the probability of call failure due to hando blocking. Local admission control strategies are investigated because they represent e cient, yet simple strategies that lend themselves to easy implementation. We note that trunk reservation is a special case of local policies. We relate the calculated e ciency bound to call and mobility characteristics and show that the achievable e ciency decreases with decreasing cell size and with the increasing proportion of multimedia calls, both of which are recognized trends today.