Haruya Miyajima

All-SIP Mobility: Session Continuity on Handover in Heterogeneous Access Environment

Given the high performance of recent access networks and mobile terminals, it has become feasible for mobile nodes to support multiple ongoing sessions while they are moving. However, in the heterogeneous access network environment, the IP addresses of mobile nodes are forced to change when they switch networks. In this paper, we introduce a simple network platform on which inter-network handover can be efficiently realized. We then propose the SIP-MIP controlled mobility architecture, which prevents QoS degradation of real-time sessions while keeping TCP connections alive. We also propose the all-SIP mobility architecture; it literally uses only SIP components to maintain both TCP and UDP sessions. The proposed architecture eliminates the cost issue and residual drawbacks of using MIP. In addition, both architectures require little or no modification on the server side, which makes them more cost effective and easier to deploy on existing infrastructure.

Field Evaluations on a Prototype System of Cooperative Multi-Cell MIMO Transmission for Asynchronous Inter-Site Base Station Networks

For next generation cellular mobile communication systems, cooperative multi-cell MIMO transmission (cooperative MIMO) technologies, in which multiple base stations (BSs) coordinate their wireless transmission, have recently been receiving considerable attention due to their potential cell-boundary throughput improvement. However, there are few studies that provide field evaluation of cooperative MIMO in real radio-propagation environments. To evaluate cooperative MIMO in a real field, BSs located at different sites should be synchronized to each other with high accuracy in asynchronous inter-site BS networks. We develop a prototype of an experimental system by using a GPS (Global Positioning System)-based inter-BS synchronous controller. We conduct field experiments on two cooperative MIMO transmission schemes: (i) cooperative MIMO-SDM based on space division multiplexing and (ii) Cooperative MIMO-SFBC based on space frequency block coding. We confirm that cooperative MIMO technologies improve the cell-boundary throughput in real radio-propagation environments. This paper describes the developed field experimental system and its field evaluation results. It also shows the effectiveness of cooperative MIMO wireless transmission at the cell-boundary.

Fast Authentication Based on Heuristic Movement Prediction for Seamless Handover in Wireless Access Environment

With the explosive proliferation of WLANs (wireless local area networks), their inter-working with other existing wireless mobile networks, such as 3G cellular networks, is being actively promoted by carriers to achieve ubiquitous broadband communication. Fast authentication is essential to achieve seamless handover in such an environment. Existing fast authentication proposals are too complicated to be easily deployed in the current commercial WLAN service. Therefore, we introduce three proposals: a heuristic movement prediction algorithm based on existing service logs, a simple area-based pre-authentication method, and a temporary authentication scheme. With these proposals, we can provide a seamless communication environment that consists of currently deployed cellular networks, public WLAN networks, and other kinds of wireless access networks.

An implementation of enhanced all-SIP mobility

In recent years, adding mobility technology to heterogeneous access networks has become important due to the growth and diversification of broadband access networks. For the simple and easily realization of seamless mobility in heterogeneous access networks, our previous paper proposed the All-SIP mobility architecture; it uses only SIP components in order to maintain both TCP and UDP communication sessions in heterogeneous access networks, but it was limited to only a few major TCP applications. This paper presents the enhanced All-SIP (eAll-SIP) mobility architecture which utilizes UDP encapsulation to suit all TCP applications; evaluation results of a prototype system including application programs are presented.

A Prototype System for Evaluating Multi-Cell Cooperative Transmission in Asynchronous Mobile Radio Networks

Mobile communication services are now expected to support the speeds offered by fixed lines. To fill this demand, a critical goal is to improve user throughput performance especially at the cell-edge, even in the LTE (Long Term Evolution)-Advanced system. Multi-cell cooperative transmission is a promising technology and has been extensively studied. This technology requires highly accurate synchronization between multiple BSs. However, the future mobile network will consist of asynchronous networks (e.g., those controlled by IP protocols) and stable synchronization is not possible with existing techniques. We have been studying synchronization schemes for asynchronous networks to realize multi-cell cooperative transmission. In this paper, we present a prototype of a multi-cell cooperative transmission system that combines our synchronization scheme with radio equipment. Experiments confirm its synchronization accuracy, and the resulting wireless transmission performance in the field evaluation indicates our synchronization scheme provides a practical and effective approach.

A Balloon-Based Wireless Relay System for Disaster Response

When a disaster occurs, various initiatives are often carried out to rapidly restore mobile communication to service areas where communication failures have occurred. As one such initiative, we have developed a balloon-based wireless relay system in which a non- regenerative wireless repeater is installed on a balloon. Through our experimentation, we confirmed that coverage within a 5 km radius was successfully achieved. In this paper, we present an overview of our balloon-based wireless relay system and the means to its deployment.