Haruki Izumikawa

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In sparse mobile networks, opportunistic access can be used to forward data in a so-called "store-carry-forward" manner using DelaylDisruption Tolerant Networking (DTN) techniques. In such environments, it is not always the case that a mobile terminal is within the communication range of other mobile terminals. Therefore, the terminal must first perform the(More)
The growing popularity of mobile data communication has been leading a growing lack of radio resource on a cellular network. Therefore, to avoid the data traffic from exceeding the capacity limit of a cellular base station (BS), cellular operators have been trying to install cellular femto cells (local BSs) or wireless LAN access points (APs) in(More)
TCP is a popular Internet protocol for reliable end-to-end data delivery, but it cannot be directly applied to wireless networks in which packet loss may be induced by higher BER or handover than congestion. TCP assumes that such packet loss is caused by network congestion and initiates congestion control procedures. In this paper, we present a novel(More)
We present a robust cellular network (RoCNet) that combines a cellular and an opportunistic networks for spatial uplink mobile data offloading, which focuses on the spatial difference of the traffic load among areas (e.g., business district and residential area in the daytime). RoCNet realizes the spatial data offload by leveraging the store-carry-forward(More)
It is necessary to select an appropriate access network out of the several available as well as perform vertical handover, which can be considered to be one of the key features of IMT-Advanced. We now have a dual-mode mobile terminal (MT) which can connect to both wireless LAN (WLAN) and cellular NWs, featuring a high transmission rate and wide coverage(More)
This paper describes an approach to authentication during han­ d�r. lin order to reduce the authentication delay, infonna­ tion is shared between users and the network using two hash-chains. IIIsers who are likely to change networks are are an expiration time. Therefore, in order to apply the new approach to a real etlll ironment, we propose 'pre-auth' type(More)
TCP is a popular internet protocol for reliable end-to-end data delivery, but it cannot be applied to wireless networks in which packet loss may be induced by higher BER or handover than congestion. It assumes that such packet loss is caused by network congestion and initiates congestion control procedures. In this paper, we present a novel protocol using(More)