Résumé: This paper focuses on how to assign channels for initial and handoff calls. All the previous schemes give priority to handoff calls by queuing handoff calls, reserving some channels for handoff calls, or subrating existing calls for handoff calls. In this paper, we queue both initial and handoff calls. We get the idea of queuing both initial and handoff calls from derivations of the optimal value for an approximation to the call-completion probability. Our goal is to have higher call-completion probability and still keep forced-termination probability low. Then we propose four schemes: the SFTT, SPTT, DFTS, and DPTS. The four proposed schemes, along with the NPS and FIFO schemes, are simulated and compared. For the SFTT scheme, we also simulate different average timeouts for initial calls. All four proposed schemes are shown to have better call-completion probabilities than the NPS and FIFO schemes. We find that giving priority to handoff calls over initial calls would not yield better call-completion probabilities in general. The proportions between handoff and initial calls will influence the call-completion probability. Call-completion probabilities can be improved by implementing a priority scheme, which serves the waiting call with the least remaining time first. The implementation of the statistical multiplexing also has the effect of increasing the call-completion probabilities when the average new-call arrival rates are high. However, both the priority scheme and statistical multiplexing might also have the effects of increasing the forced-termination probabilities. The average values of timeouts for initial calls and handoff calls are another main factor for influencing the call-completion probabilities. When the mean new-call arrival rates are not very high, the longer average timeouts for initial calls also increase the chance of initial calls being served and thus have higher call-completion probabilities.

Langue: Anglais