Admission control algorithms for cellular systems

This paper evaluates call admission control algorithms for a cellular or mi crocellular system. Algorithms are evaluated based on two Quality of Servic e (QoS) metrics: the new call blocking probability. which is the probabilit y that a new call is denied access to the system, and the forced-terminatio n probability, which is the probability that a call that has been admitted will be terminated prior to the call's completion. Three novel algorithms a re presented: the Weighted Sum Scheme, the Probability Index Scheme, and th e Hybrid Control Scheme. The weighted sum scheme uses the weighted sum of t he number of calls underway in various cells when making the admission deci sion. The probability index scheme computes a probability index, which refl ects the forced-termination probability of a new call arrival, and admits t hose calls with low probability indexes. The hybrid control scheme combines these two approaches. These novel algorithms are compared with three known algorithms: the Reservation Scheme in which a specific number of channels are reserved in each cell for handoffs, the Linear Weighting Scheme in whic h the admission decision depends on the total number of calls underway in a group of cells, and the Distributed Admission Control Scheme in which the admission decision depends on the projected overload probabilities in the c ell at which the new call arrives and adjacent cells. We show that the Hybr id Control Scheme yields the best performance. particularly during periods when load differs from the expected level. We also show that the simple Res ervation Scheme performs remarkably well, often superior to more complex sc hemes that have been proposed.