The output feedback consensus problem of lower triangular nonlinear systems under a directed network with a switching topology is studied. It is assumed that every possible network topology contains a directed spanning tree. The proposed design method utilizes a high gain approach to compensate for triangular nonlinearity and to remove the restriction imposed on dwell time. Compared to the previous research, it is shown that the proposed control method can achieve the output feedback consensus of lower triangular nonlinear systems even in the presence of an arbitrarily small average dwell time. A numerical example is given to illustrate the effectiveness of the proposed design method.

In this paper, an adaptive resource allocation scheme for video stream based on video stream character and user mobility in wireless LAN is proposed. The proposed adaptive allocation scheme allocates the time slots according to the kind of the real-time or non real-time video stream, the required bit rate of video stream and user's mobility by each user. In the proposed system, when user requests the non real-time video stream and its dwell time is smaller than the service time of the video source, more time slots are allocated to the user. When user requests the non real-time video stream and its dwell time is larger than the service time of the source video, or when user requests the real-time video stream, minimum amount of the required time slots are allocated. The computer simulation results show that the proposed allocation scheme can achieve the better performance than the conventional allocation schemes which allocate the time slots only considering the required bit rate or user's dwell time.

This paper proposes an analytical model to demonstrate the benefit of data service in wireless networks using dynamic multi-channel scheme with channel de-allocation. The performance of a system providing buffers to voice calls to reduce the raised voice blocking probability caused by data contention is investigated. The effect of the cell dwell time and overlap area with adjacent cells on system performance are studied. All free channels are allocated to data users dynamically. For those data users using more than one channel, channels would be de-allocated for new requests, voice or data. Buffers are provided for voice calls to reduce the voice blocking probability caused by data packets contention. Handoff calls are given priority to be queued in the front of the buffer instead of providing guard channels to reduce their dropping probability. Meanwhile, the reneging time for new calls and the handoff dwell time for handoff calls are considered in our analysis to obtain an appropriate amount of buffer to voice. To compensate the blocking probability in data, guard channels are provided for data traffic. Numerical results show that the dynamic multi-channel scheme with possible de-allocation, compared with the single channel scheme, can enhance data traffic performance significantly in terms of the mean transmission time and blocking probability. A system providing an appropriate amount of buffer to voice traffic and giving priority to queued handoff calls can indeed reduce new call blocking probability and handoff call dropping probability. In addition, the proposed scheme can reduce the incomplete transmission probability of data packets.

In DS-CDMA (Direct Sequence-Code Division Multiple Access) mobile systems, soft handoff is recognized as reducing interference and increasing reverse link capacity, whereas from the radio channel resource viewpoint, soft handoff can make the system performance deteriorate significantly. This paper focuses on using the channel resources of soft handoff in a limited field environment for evaluating the performance of DS-CDMA mobile systems. Our traffic model is based on the mobile traffic environment with region overlap among multiple cells. The soft handoff rates are estimated by the mobility of mobiles, and simulation results show good agreement with the traffic model. The channel holding time distribution of the soft handoff traffic model, which does not have a closed-form solution, is derived by a numerical integration method. Computer simulations show promising results based on the non-closed-form application. We analyze the performance of DS-CDMA mobile systems with the proposed traffic model to see the effect of the soft handoff region on blocking probability. From the result, when the soft handoff region is extended with the given channels, both the handoff rate and the mean channel holding time are increased and these make the blocking probability increase a great deal. To maintain the required blocking probability as before, additional channel resources should be supplied according to the extended region. It is our belief that the proposed traffic model and the performance analysis presented in this paper are practically acceptable.

This paper discusses self-similarity in cell dwell time of a mobile terminal, the discovery of which was described in our previous paper, and its effects on teletraffic of mobile communication networks. We have evaluated various teletraffic statistics, such as cell dwell time and channel occupancy time, of a mobile terminal based on measurements of motion for various types of vehicles. Those results show that cell dwell time follows a long-tailed log-normal distribution rather than the exponential distribution that has been used for modeling. Here, we first elaborate on self-similarity in cell dwell time of various vehicles. We then evaluate self-similarity in channel occupancy time. For future mobile multimedia communication systems employing a micro-cell configuration, it is anticipated that data communication will be the main form of communication and that call holding time will be long. For such cases, we have shown that channel occupancy time will be greatly affected by the cell dwell time of the mobile terminal, and that self-similarity, a characteristic that is not seen in conventional systems, will consequently appear. We have also found that hand-off frequently fails as self-similarity in cell dwell time of a mobile terminal becomes stronger.

In evaluating the teletraffic of mobile communication networks, it is important to model the motion of terminals. In the previous migration model, mobility characteristics of terminals, such as cell dwell time, have been expressed by a single probability distribution. In this paper, we discuss the modeling of the cell dwell time of terminals in each cell. Using measured data we show that cell dwell time differs from cell to cell and follows log-normal distributions rather than conventional exponential distributions.

Teletraffic characteristics of a mobile packet communication network, which supports mobile Internet, were quantitatively evaluated by using a terminal migration model in which the cell dwell time possesses self-similarity. I used a migration model in which the migration speed of the terminal is determined by the density of the dwell terminals in a cell (determined from measured vehicular mobility characteristics). The transmission rates per terminal in a cell were estimated as teletraffic on the mobile packet communication networks using this migration model. I found that when there is self-similarity in the terminal cell dwell time, communicating terminals may be concentrated in the cell and restricted for an indefinite period of time to using only a narrow bandwidth.

In this paper, we propose a simple and accurate method to derive the dwell time distribution of a mobile in a cell by a numerical integration approach. In practical applications, only a few traffic models have a known closed-form solution, most of the models can not be solved in closed form. Therefore a simulation or approximating method has to be used to solve the problems. To validate the accuracy of the proposed method, we apply it to a typical hard handoff traffic model with known closed-form solution and the goodness-of-fit is measured. We also apply this method to a soft handoff traffic model, which does not have a closed-form solution. Computer simulations show promising results based on the non-closed-form application.