In mobile communication systems using Dynamic Channel Assignment, channels are possible to be rearranged so that blocking probability can be made low. The smaller the number of cells where channels are rearranged, the smaller the load on the base stations in the cells. Also, we can reduce the deterioration of communication quality caused by reassingning a new channel to a call instead of the channel already assigned. In this paper, we consider not only how to rearrange channels but also which channel should be rearranged and assigned to a new call in rearrangement, and propose very simple but effective methods for rearrangement. The ways to select a candidate channel to be rearranged and assigned to a new call in the new methods make the number of cells where a channel is rearranged smaller. We also examine the relations between characteristics and the number of cells where a channel is rearranged. Using computer simulation results, the properties of the new rearrangement methods are compared with those of the traditional methods.

This paper describes a forward subchannel control of multi-carrier scheme intended to compensate for phase/amplitude distortions under frequency selective fading. The forward subchannel control scheme is used for a Time Division Duplex (TDD) multi-carrier system on up-link. The forward subchannel control scheme provides forward subchannel control of phase/amplitude variation and subchannel assignment control. These controls are applied before transmission of an up-link signal. The forward control parameters are estimated by a preamble down-link signal. Simulation results clarify that the BER performance with the forward subchannel control scheme shows a superiority of more than one order at the condition of 22 dB of Eb/N0 and 400 Hz of fading frequency.

We introduce the distance between two edges in a graph (nondirected graph) as the minimum number of edges in a tieset with the two edges. Using the distance between edges we define the eccentricity ετ (ej) of an edge ej. A finite nonempty set J of positive integers (no repetitions) is an eccentric set if there exists a graph G with edge set E such that ετ (ej) J for all ei E and each positive integer in J is ετ (ej) for some ej E. In this paper, we give necessary and sufficient conditions for a set J to be eccentric.

A recent trend in routing research is the use of overlay routing to improve end-to-end QoS without changing the network-level architecture. The key of this technology is to find an alternative route that can avoid congested routes, using an overlay network. Developing cost-efficient overlay routing in terms of calculation cost and information distribution cost needed to find an alternative route is important for deploying QoS-aware overlay routing. Thus, this paper evaluates how effective overlay routing can be when the number of alternative route candidates is limited to reduce costs. Evaluation results using actual measurement data indicate that overlay routing is still effective even if alternative route candidates are limited to 1/4 of all possible alternative routes. We also discuss an overlay routing algorithm to enable us to find an appropriate route under the constraint that the number of alternative route candidates is limited.

This paper describes communication traffic characteristics in cellular systems employing the concept of reuse partitioning and Dynamic Channel Assignment. Such systems hava a problem of the spatial unbalance of blocking probability. The objective of this paper is overcoming this problem. To accomplish this objective, we use a method for analyzing communication traffic characteristics. We also show results on traffic characteristics in the systems.