Slot allocation in a CDMA/TDD cellular network, which decomposes a frame into uplink and downlink slots, is a multi-dimensional optimization problem involving all the cells in the system due to interference between cells. However, the complexity of the problem makes it computationally too expensive to solve simultaneously for all the cells in a system of reasonable size. In this paper, we propose a novel predictive and distributed slot allocation scheme for transporting multimedia traffic over CDMA/TDD cellular networks with multiple cells, designed to maximize a general utility function that is (strictly) concave increasing. We formulate the utility-maximizing slot allocation problem as a nonlinear integer programming problem, and provide a solution that can be realized efficiently in a distributed manner. Also, we derive sufficient conditions for a real-number solution to be optimal and develop an efficient algorithm to find a near-optimal integer solution. The effectiveness of the integer solution is demonstrated by showing that its gap with the optimal solution is small. We show by experiments that the proposed predictive method has a sufficient accuracy when there are many active users in cells. Extensive simulation results show that the proposed distributed slot allocation method performs very well in comparison to an existing method.

Since the digital video broadcast-return channel via satellite (DVB-RCS) standard was released in 2000, developing an interactive satellite multimedia (ISM) network has become a hot issue. In order to provide high-speed multimedia services using a DVB-RCS system, it is important to efficiently and dynamically assign the timeslots to a number of terminals according to their various demands. Also, it is imperative to improve the degradation of link quality due to rain-fade attenuation in Ka-band satellite communications. As a result, multirate superframe structures should be implemented for a relatively low data rate at the cost of stable connection to terminals in rain-fade regions and a relatively high data rate to terminals in clear-sky regions. Timeslot scheduling in this environment is studied in this paper. We mathematically formulate the timeslot assignment problem as a nonlinear integer programming problem and develop an efficient real-time solution algorithm. Extensive simulation results show that our algorithm successfully finds a feasible solution with optimality gap less than 0.05% within about 5 ms at Pentium III PC. We believe that our algorithm can be utilized as a guideline in developing real-time timeslot assignment algorithms for ISM networks.

The CDMA/shared-TDD system is a highly attractive solution to support the next generation cellular mobile systems which provide unbalanced multimedia services. In this paper, we analyze the interference for downlink, uplink, and crossed timeslots in a multicell CDMA/shared-TDD system. We also mathematically formulate optimal timeslots and channel allocation problem, which is to maximize the system capacity under the given traffic unbalance. Computational experiments show that the capacity of the CDMA/shared-TDD system is larger than that of the pure CDMA/TDD system.

In this paper, we suggest a new dynamic channel assignment scheme with two types of channel allocation strategies, and perform an analysis on the handoff probabilities of handoff and new calls. Our scheme is compared with other existing schemes in terms of three types of blocking probabilities-new call blocking probability, handover blocking probability, and network blocking probability. Simulation results show that our scheme significantly reduces those blocking probabilities over the existing schemes. Furthermore, our scheme has much smaller number of reallocations than other schemes.