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Nishihara, Kazuharu,Okada, Hiraku,Yamazato, Takaya,Katayama, Masaaki 통신위성우주산업연구회 2003 Joint Conference on Satellite Communications Vol.2003 No.-
To increase the channel efficiency, most of the Low Earth-Orbital satellite (LEOs) systems use the multibeam antenna and reuse the available channels. But in such systems, a beam handover occurs very frequently and a dropping probability becomes very high compared with the one beam systems. In this paper, we propose the nondropping handover and channel allocation scheme in the above LEOs systems. In the proposed scheme, we allocate an extra idle channel for a new call. Because of the predictable change of channel reuse distances, each user can always use the same channel as before. Furthermore, we proposed some cost functions used by channel selection and channel reassignment. For comparison, we show the lower bound of blocking probability by maximal complete dependent set (MCDS). We confirm that the proposed channel selection scheme improves the system performance by computer simulation.
A Study on Cluster Lifetime in Multi-HopWireless Sensor Networks with Cooperative MISO Scheme
Huang, Zheng,Okada, Hiraku,Kobayashi, Kentaro,Katayama, Masaaki The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.4
As for cluster-based wireless sensor networks (WSNs), cluster lifetime is one of the most important subjects in recent researches. Besides reducing the energy consumptions of the clusters, it is necessary to make the clusters achieve equal lifetimes so that the whole network can survive longer. In this paper, we focus on the cluster lifetimes in multi-hop WSNs with cooperative multi-input single-output scheme. With a simplified model of multi-hop WSNs, we change the transmission schemes, the sizes and transmission distances of clusters to investigate their effects on the cluster lifetimes. Furthermore, linear and uniform data aggregations are considered in our model. As a result, we analyze the cluster lifetimes in different situations and discuss the requirements on the sizes and transmission distances of clusters for equal lifetimes.
A Study on Cluster Lifetime in Multi-HopWireless Sensor Networks with Cooperative MISO Scheme
Zheng Huang,Hiraku Okada,Kentaro Kobayashi,Masaaki Katayama 한국통신학회 2012 Journal of communications and networks Vol.14 No.4
As for cluster-based wireless sensor networks (WSNs),cluster lifetime is one of the most important subjects in recent researches. Besides reducing the energy consumptions of the clusters,it is necessary to make the clusters achieve equal lifetimes so that the whole network can survive longer. In this paper, we focus on the cluster lifetimes in multi-hop WSNs with cooperative multiinput single-output scheme. With a simplified model of multi-hop WSNs, we change the transmission schemes, the sizes and transmission distances of clusters to investigate their effects on the cluster lifetimes. Furthermore, linear and uniform data aggregations are considered in our model. As a result, we analyze the cluster lifetimes in different situations and discuss the requirements on the sizes and transmission distances of clusters for equal lifetimes.
New Error Correcting Scheme for Hard Detected QAM Signal
Yamaoka, Tomaya,Yamazato, Takaya,Okada, Hiraku,Katayama, Masaaki,Ogawa, Akira 통신위성우주산업연구회 2004 Joint Conference on Satellite Communications Vol.2004 No.-
In order to achieve high speed satellite communication, we propose a new R=m-2/m error correcting scheme for hard detected $2^m$-QAM signal, where we consider m $\geq$ 6. The main focus of the paper is to improve the performance even in the case of hard-detection. As results, we found that our proposed error=correcting scheme achieves good error performance despite the hard detection and the high coding rate.