Hideaki Tani

On the effectiveness of integrating WiMAX and Wi-Fi

In this paper, we give a quantitative evaluation on the effect of integrating WiMAX and Wi-Fi, as compared to the case of separate WiMAX and Wi-Fi systems, with respect to the system capacity under QoS constraint. We focus particularly on the VoIP traffic aspects of the system. Based on this capacity evaluation, a cost analysis is further presented. We also propose and analyse a resource management scheme on Wi-Fi to WiMAX handover.

Intelligent SIP system for mobile Internet

This paper proposes a scalable network service execution system that executes a Parlay application while taking advantage of the session initiation protocol (SIP). By adopting a decentralized architecture which distributes the Parlay service logic execution environment (SLEE) to user terminals and support server, scalability as a system is improved. In this system, the objects comprising the Parlay applications are downloaded to the corresponding SLEE and the objects communicate with each other as necessary to run the entire application. It is therefore possible to realize a scalable application execution environment that is highly compatible with SIP as well as inheriting Parlay softwares accumulated assets.

A Lightweight Application-Layer Signaling Protocol

The session Initiation Protocol (SIP) is a widely used application-layer control protocol. The processing load of the SIP protocol is reportedly seen as one of the potential problems which may limit the range of its application although it has a number of advantages. Many research efforts have been made and have come up with various compression algorithms to reduce the packet size in order not to waste scarce bandwidth especially for wireless access networks. However, they increase the processing load at the same time. We propose a lightweight application-layer signaling protocol (lightweight-SIP) which reduces network bandwidth without sacrificing CPU performance by introducing a gateway which translates SIP into the proposed protocol. The gateway works as a cache for static and lengthy header fields of SIP messages. We expect the proposed protocol to be used by low-spec devices such as sensor nodes, less-expensive surveillance cameras and wearable computers so that it could reduce the energy consumption and lengthening the battery life or loosen requirements for the hardware specs.

Comparison of Data-Searching Algorithms for a Real-Time Information-Delivery System

The number of content-generation devices is expected to increase explosively in the near future thanks to evolution in the field of input/output devices and Consumer Generated Media (CGM) tools. Users will simultaneously wear communicating sensor devices wherever they are, whenever they need them,and whatever they are doing. Under such circumstances, various contents will be generated,updated by the devices and moved much more frequently than they are now. We propose an architecture for a real-time information-delivery system that enables users to quickly discover the freshest, most accurate content. We compared three types of well-known data searching algorithms, i.e., in DNS-like static-tree method, Web crawler method,and Chord method, which can be used in servers in existing systems to retrieve the metadata on the content.We first developed a simulator and evaluated the algorithms to assess the methods to find which generation, update, and movement of content occurred more frequently. We discovered that the Web crawler method and Chord method both offered roughly the same correct answer rate. However, the number of messages increased dramatically with the Web crawler method when the content-update interval shortened.The average search time also increased with the Chord method as the number of user nodes increased.

Capacity analysis and resource management of an integrated WiMAX & Wi-Fi access system for VoIP

In this paper, we give a quantitative evaluation on the effect of integrating WiMAX and Wi-Fi, as compared to the case of separate WiMAX and Wi-Fi systems, on the system capacity with QoS being considered. We focus particularly on the VoIP traffic aspects of the system. Based on this capacity evaluation, a cost analysis is further presented. We also propose and analyze a resource management scheme on Wi-Fi to WiMAX handover.