In order to fix a bug or install a new application, disseminating a code to specific target sensors is an important management task in wireless sensor networks. In order to disseminate a code to specific target sensors in an energy efficient manner, it is required to select the minimum required number of forwarders with a small number of control messages. In this paper, we propose an energy efficient target specific code dissemination scheme with a forwarder selection algorithm. The proposed scheme consists of two steps, (i) a forwarder selection algorithm with a control message suppression, (ii) unnecessary forwarders reduction with a sleep mechanism. In order to select the minimum required forwarders with a small number of control messages, we propose an algorithm to select a forwarder where more target sensors are reachable, through a single control message by leveraging overhearing of control messages. In addition, in order to reduce the number of forwarders, we propose a sleep mechanism to put unnecessary forwarders to sleep where any target sensor is not reachable. A performance analysis has shown that the number of control messages of the proposed scheme is always theoretically smaller than that of a previously published forwarder selection scheme under the same condition. In addition, we have shown that the proposed scheme reduces the energy consumption compared with the previous scheme.

The video streaming service over Wireless Mesh Networks (WMNs) is an attractive feature for live streaming and video conversation when disaster occurs. The path construction with the conventional metrics e.g., throughput, latency, or packet loss rate, suffers from the repeated waiting time due to the CSMA/CA since paths are concentrated on nodes with good metric. As a consequence, it brings about throughput fluctuation of video streaming service. We propose two metrics that reflect on the magnitude of CSMA/CA interference around a node in order to select a path that the throughput of video streaming session will get stable. The first metric is calculated from the number of received Request To Send (RTS)/Clear To Send (CTS) frames. Since the number of RTS/CTS reflects on the frequency of the packet transmission around a node, a source node can chooses a path which does not make a node waiting for constant time due to the CSMA/CA on the existing path that might use streaming service. The second metric uses the number of neighbor nodes and we set the larger metric value as more nodes exist. The idea comes from the fact that a node which has few neighbor nodes does not much interfere other established paths. The proposed metrics can be easily installed into Hybrid Wireless Mesh Protocol (HWMP) which is a de facto standard path selection protocol defined in IEEE802.11s. We show that the proposed metrics can achieve lower rate of throughput fluctuation than that of conventional metric by using the networks simulator Qualnet.

Reliability is the key factor in realizing high QoS performances of telecommunications networks, and effective reliability design gives great impact on their resource managements. Therefore, highly effective reliability design technologies have been studied and we have already obtained such highly effective technologies using reliability measure `end-to-end reliability'. However, we claimed that end-to-end reliability was proposed for designing telecommunications networks in advanced countries. It is doubtful this is also effective in developing country such as Africa, India, and Indonesia, because of the following reason. Telecommunications networks in developing countries are often constructed over a long period of years and the structure of network varies according to investment strength and level of regional development. Further, in countries with major and smaller islands, the reliability of transmission facilities also varies. To design this kind of network from reliability point of view, end-to-end reliability is not suitable because it never considers the regional differences in a country. Exactly saying, we have to evaluate reliability considering factors of distribution of economic activities, progress process of network facilities, and disparity of reliability at inter-regional level caused by geometric reason; but end-to-end reliability never considers these factors. Therefore, we need the new reliability measure to be used for evaluating telecommunications networks in developing countries Now this paper proposes the new reliability measure `one-to-all reliability' so that it can evaluate reliability considering regional differences in a country. This reliability expresses the individual reliability of each region in a whole network, Based on this new reliability measure, experimental evaluations taking samples from networks in Indonesia, as a typical developing country, have been conducted. We focus on Indonesia's next-generation networks, which are currently in progress as the government project, and we evaluate one-to-all reliability of them.

In this paper, we propose a simple competitive PSO for finding plural solutions. In the proposed PSO, particles are divided into groups corresponding to the required number of solutions. Each group simultaneously searches solutions having a priority search region. This region affects to prohibit that different groups search the same solutions. The proposed PSO can effectively find desired plural acceptable solutions with a high accuracy and with a low computation cost, and can easily control combinations of these solutions by adjusting a parameter. Also, the proposed PSO is applied to a problem in wireless sensor networks (WSNs). The simulation results show that obtained results can contribute to prolonging lifetime of WSNs.

Wireless sensor networks (WSNs) have attracted significant interests of many researchers because they have great potential as a means of obtaining information of various environments remotely. WSNs have their wide range of applications, such as natural environmental monitoring in forest regions and environmental control in office buildings. In WSNs, hundreds or thousands of micro-sensor nodes with such resource limitation as battery capacity, memory, CPU, and communication capacity are deployed without control in a region and used to monitor and gather sensor information of environments. Therefore, scalable and efficient network control and/or data gathering scheme for saving energy consumption of each sensor node is needed to prolong WSN lifetime. In this paper, assuming that sensor nodes synchronize to intermittently communicate with each other only when they are active for realizing the long-term employment of WSNs, we propose a new synchronization scheme for gathering sensor information using chaotic pulse-coupled neural networks (CPCNN). We evaluate the proposed scheme using computer simulation and discuss its development potential. In simulation experiment, the proposed scheme is compared with previous synchronization scheme based on a pulse-coupled oscillator model to verify its effectiveness.

The conventional go-back-NARQ is modified so as to be applicable to point-to-multipoint communication by using a control block that indicates the occurrence of retransmission to all the receivers. This paper also presents a "tandem error control scheme," in which the up-link and the down-links use separate go-back-NARQ's. The throughput efficiency of the tandem go-back-NARQ is analyzed. Specifically, the mathematical formula for the throughput efficiency is obtained for cases in which there is a single receiver. The throughput efficiencies of these schemes are also evaluated by simulation.

Phase-locked loops have been used in various parts of telecommunication systems because of their wide applicability to bit synchronization and FM- and PM-demodulation, etc. Several types of digital phase-locked loops (DPLL's) have also been studied due to the increased reliability and decreased cost of integrated digital circuitry. DPLL's of the type employing binary quantized phase detection and discrete phase adjustments have been utilized for detection of a binary signal or suppression of phase jitter in data-transmission techniques. Unfortunately the width of the locking-range and the ability to suppress phase jitter are contrary to each other, and furthermore, the capacity for jitter suppression rapidly lowers as the frequency of input signal deviates from a free-running frequency of the loop. To improve these vicious properties, a DPLL employing a new type of sequential loop filter is proposed in this paper. The sequential filter controls the properties of itself asymmetrically, depending on the input and output phase distributions to keep the output phase at the center of input phase distribution. The loop performance is analyzed theoretically, experimentally, and by computer simulation in the presence of random Gaussian phase jitter. It is shown that the loop has satisfactory performance as a DPLL used for phase jitter suppression.