An analytic traffic model is presented to estimate the soft handoff rate in DS-CDMA cellular systems. The model is based on the fact that a mobile in soft handoff call is connected to two cell sites when it is in an overlapped region. The handoff rate is estimated by the mobility of mobiles, which is a function of the size and shape of cell area, and the call density and speed of mobiles in the area. Simulation results show good agreement with the analytical model.

Recent technology innovations have increased the study on wireless LAN (Local Area Network). Also, improved computing power of end user has needed the distributed communication environment. However, conventional access protocols (TDMA, CSMA/CA and CDMA) have some problems such as the degradation of channel utilization, necessity of control station and code reuse. Therefore, we propose new multiple access scheme, Hybrid Reservation CDMA based on our previous work, DR-CDMA. Proposed method for distributed/central wireless LAN architecture provides, distributed channel access mechanism, code reuse method and internetworking method with conventional wire-based LAN. In proposed mechanism, efficient channel utilization could be obtained by minimizing overhead. Also, variable length frame from upper layer could be transmitted without segmentation. Moreover, nodes are serviced based on priority. In view of management, insertion of new node could be done easily in proposed HR-CDMA in proposed method due to its variable length property which can encapsulate conventional LAN frame. According to computer simulation, it has been shown that performances of proposed method are better than those of reservation TDMA bitmap protocol with respect to delay and throughput characteristics in the distributed environments as well as interworking environments between wire and wireless LAN.

In this paper, we propose a handoff scheme with two-level priority for the reservation of handoff request calls in mobile cellular radio systems. We assume two types of mobile subscribers with different distributions of moving speed, that is, users with low average moving speed (e.g., pedestrians) and high average moving speed (e.g., people in moving cars). A fixed number of channels in each cell are reserved exclusively for handoff request calls. Out of these number of channels, some are reserved exclusively for the high speed handoff request calls. The remaining channels are shared by both the originating and handoff request calls. In the proposed scheme, both kinds of handoff request calls make their own queues. The system is modeled by a three-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking probabilities of calls, forced termination probabilities and average queue length of handoff calls of each type are evaluated. We can make the forced termination probabilities of handoff request calls smaller than the blocking probability of originating calls. Moreover, we can make the forced termination probability of high speed handoff request calls smaller than that of the low speed ones. Necessary queue size for the two kinds of handoff request calls are also estimated.

This paper presents the computer simulation results on frequency reuse efficiency and soft handoff statistics in the CDMA forward link according to path loss and cell loading. The soft handoff threshold effect on the handoff statistics is also evaluated. The frequency reuse efficiency is not a fixed value but varying as function of distance from the home cell, path loss slopes, and cell loading. The total soft handoff pecentile ranges from 0.0 to 64.9 according to cell loading, even if path loss slope is constant.

In this paper, we evaluate the performance of handoff schemes in microcellular personal communication systems (PCS) which cater to both pedestrian and vehicular users. Various performance parameters, including blocking of new calls,channel utilization, handoff blocking and call termination probabilities for each user type are evaluated. We study different queuing disciplines for handoff calls and their impact on system performance. We also study the tradeoff in handoff blocking and call termination probabilities between user types as the handoff traffic carried by the system from each user type is varied.

In a cellular system for mobile communications, every service area is divided into a number of cells for utilizing the frequency spectrum efficiently. Service areas for such systems are two dimensional, however, the analysis of the characteristics of the communication traffic for the areas are quite complicated, since the motion of the vehicles in the area can not be predicted precisely. For making the analysis easily, the areas are assumed to be band-shaped like a highway. Furthermore, in the analysis, the traffic offered to a cell is assumed to be stationary. In actual systems, the density of vehicles and the offered communication traffic is not stationary, so that many differences exist between the analysis and the actual systems. This paper presents an analysis method using state equations. The equations represent the transient characteristics of mobile communication traffic when a band-shaped service area is assumed. The transition is made by accidents or congestion, and causes the rapid offered traffic change in a communication system. In the method, numerical analysis is made under the consideration of "handoff" operation. The operation consists of surrendering the channel used in the previous cell and reassigning a new channel when the vehicle crosses the cell boundary. The analytical results are compared with the simulations, and the two results show good agreement. The method presented in this paper can be used for designing the switching system when the offered traffic changes rapidly due to accidents or congestion.