The blocking probabilities of n64Kb/s multi-slot calls are generally much higher than that of single slot calls. In order to improve these blocking probabilities of multi-slot calls, we propose a scheme to limit the number of time slots to be searched for lower rate calls. We analyze the performance of our scheme in a double-buffered time-space-time switching network which accommodates multi-slot calls as well as single-slot calls. The proposed method yields the reduced blocking probabilities of multi-slot calls, the increased traffic handling capacity and the reduced CPU processing load, compared with those of the conventional methods.

An adaptive channel access control method for CDMA/PRMA protocol is proposed. The proposed method utilizes a load and backlog based access control. Dynamic optimal channel loads by which the required packet loss probability can be satisfied are obtained. The number of contending terminals is also estimated more accurately, using statistical characteristics of source models. Permission probability is then calculated based on the dynamic optimal channel load and the estimated number of contending terminals such that the mean channel load (the mean number of packets transmitted in each time slot) can be maintained at the optimal channel load. By maintaining the mean channel load at the dynamic optimal channel load, the radio channel can be very effectively utilized, satisfying the required packet loss probability. A backlog based data transmission using a mixed mode of contention and reservation mode is also proposed to reduce redundant contention and corruption. Simulations are carried out in an isolated cell environment and a cellular environment. The simulation results show that the system capacity can be improved significantly by the proposed method compared with the conventional permission control methods.

Traditional soft-handoff algorithms are based on the static threshold handoff algorithm recommended in the IS-95 standard. They are characterized by two parameters, an add threshold Tadd and a drop threshold Tdrop. These two parameters are assumed to have some constant values irrespective of the received signal strength of the pilot in the active set. To improve the performance of the soft-handoff, a dynamic threshold concept was proposed in previous work, where Tadd and Tdrop are dynamically determined according to the received signal strength of the pilot channel in the active set. In this study, previous work of the dynamic threshold algorithm is extended by including additional handoff criteria based on absolute signal strength and/or drop timer. Some functional forms with two new parameters, called boundary thresholds, and slope constant are proposed to dynamically determine Tadd and Tdrop. The dynamic threshold algorithms are compared with static ones in four different cases. Computer simulations show that the dynamic threshold algorithms outperform the static algorithms. We can see that the performance improvements differ from case to case. For example, when a pure dynamic threshold algorithm is compared with a pure static one (case 1), the decrease in the number of active set is about 13.7%. When the absolute threshold and the drop timer are also included in the handoff decision criteria (case 4), however, the decrease is only about 6.2%.