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UMTS, a third-generation mobile communications system, has the feature of a high rate in the wireless link and is expected to provide various services. When the rate of the wireless link is raised, it is expected that the communications configuration will be expanded to one in which multiple terminals share a radio bearer through a mobile node, rather than the communications configuration in which each mobile terminal occupies a radio bearer. UMTS manages packet communications via the PDP context. A mechanism is established in which the QoS is controlled for each bearer, which is defined for each PDP context. However, the communications configuration in which multiple users on a bearer communicate with different counterparts with various QoS conditions is not considered. This paper proposes to integrate packet communications from multiple terminals of a UMTS network on a radio bearer with QoS control. By integrating the radio bearer, the handover processing load can be reduced. It is also shown that the proposed QoS control is effective in reducing transport delay. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(5): 28–38, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20163 [ABSTRACT FROM AUTHOR]

In cellular communication systems, every call is carried through a base station, and when the communication path to the base station is obstructed by buildings or other obstacles, the communication may not be established. It is expected that ad hoc relaying of such an obstructed call will increase the performance of the network as a whole. This paper discusses how to theoretically analyze the communication traffic performance of a cellular system with ad hoc networking and shows that the network performance can be increased even with relatively small range of relaying capability of terminals. This paper also shows by simulation that multihop relaying does not give significantly greater performance improvement than that by two-hop relaying. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(11): 1–10, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10135 [ABSTRACT FROM AUTHOR]

This paper discusses the communication traffic characteristics of Dynamic Channel Assignment (DCA) in cellular mobile communication systems. In general, it is difficult theoretically to analyze the communication traffic characteristics of DCA. This paper proposes an approximate method called clique packing, for analyzing the blocking probability performance of an idealized DCA. For calculating the blocking probability of clique packing, an approximate formula is derived which is based on the Erlang B formula and is in a simple form. It is shown that the numerical results of the approximate method agree with computer simulation results. An approximate analytical method for calculation of the blocking rate el practical DCA methods such as the first-available method also is proposed. To calculate the blocking rate of the practical DCA methods, the simple formula for clique packing is used after modeling the practical DCA methods as clique packing. It is shown that the modeling is appropriate. This modeling enables the blocking rate of the practical DCA methods to be calculated by using the approximate formula for clique packing. [ABSTRACT FROM AUTHOR]

In cellular mobile communication, the same channel is shared by a number of cells. Up to now, the model has been considered where the same channel is used with a sufficient separation, so that the radiowave interference is sufficiently small for any call generated in the cell. Recently, on the other hand, a model has been proposed where the same channel is assigned independently of the specified cell separation, as long as the carrier-interference ratio is above a certain value. Although the assignment algorithm has been discussed for the traditional model, no report has been made on the detailed assignment procedure for the new model. With such a situation as the background, this paper proposes an application of Hopfield's neural net as an approach to the channel assignment in the new model and derives the energy function. Several results of computer simulation are shown where the proposed neural net is applied to the mobile communication model. It is not always true that the neural net produces the optimal solution, but it is interesting that an unexpected improvement of the channel utilization is observed in the communication traffic as far as the result of computer simulation is concerned. [ABSTRACT FROM AUTHOR]