Hajime Matsumura

Top of worlds: method for improving motivation to participate in sensing services

We propose a method for improving motivation to participate in sensing services by presenting rankings in multidimensional hierarchical sets. We call this method Top of Worlds. Because previously proposed methods only rank a user among all other users, many have little chance of being ranked in the top group, resulting in little motivation to continue. Top of Worlds creates many sets with varying granularity to increase the chance of many users being ranked in the top group and presents these rankings in those sets. Through an experiment, we partially confirmed the validity of Top of Worlds.

Transmission System For Multimedia Services In Satellite Broadcasting Channels

In Japan, a new digital satellite broadcasting service is scheduled to start in the year 2000. The technical standard for the transmission system was established in 1998. The system provides an information bit rate of 52 Mbps, which is sufficient for broadcasting true HDTV programs. It can handle multiple MPEG2 transport streams. The system supports multiple modulation schemes such as trellis coded 8PSK(TC8PSK), QPSK and BPSK. These modulation schemes can be selected and/or used simultaneously. Accordingly, broadcasters sharing one satellite channel can select modulation schemes suitable for their own services independently from each other. The configuration and characteristics of the system are described.

UBI-Tree: Indexing Method for Schema-Less Search

We propose an indexing method called UBI-Tree for improving the efficiency of a new type of data search called schema-less search. Schema-less search is a multi-dimensional range search from a wide variety of data, such as sensor data, collected through participatory sensing. Such data have different types and number of dimensions because a participant uses various devices. Therefore, applications must search for their target data within the sensor data in a cross-schema manner. UBI-Tree is a tree-structured index based on R-Tree. The insert algorithm classifies various data into nodes according to newly introduced scores to estimate the inefficiency of classification. The score can uniformly represent the difference in the types of dimensions between data as well as the difference in dimension values. By classifying data that have a similar dimension set into the same node, UBI-Tree suppresses the curse of dimensionality and makes schema-less searches efficient. The validity of UBI-Tree was evaluated through experiments.

Maximum transmission bit rate for satellite ISDB and its application in a satellite broadcasting plan

ISDB (integrated service digital broadcasting) is investigated as a flexible broadcast system for the future. This paper discusses a transmission system for satellite digital broadcasting, based on this concept. The purpose is to provide inputs for the reconsideration of the 12-GHz satellite broadcast plan presently promoted by ITU-R. As the first step, we propose a method of determining the optimal parameters of the transmission system. A new parameter is defined, namely, the normalized EIRP, combining EIRP of the satellite and the transmission bandwidth. Then the relations among the service availability, the transmission capacity, and the transmission system, which is the key to the satellite broadcast system, can be derived in general form. Assuming the use of QPSK + convolutional code, as well as TCM8PSK, the actual satellite channel model is defined. Detailed investigations are made by simulation, and the transmission system that maximizes the transmission rate is determined, along with the normalized transmission rate. The following results are obtained. In the case of such a satellite with a high EIRP, as currently in the Japanese broadcast satellites, TCM8PSK is better when the worstcase monthly availability is less than 99.7 percent; and QPSK + convolutional code is better when an availability above 99.9 percent is required. For a satellite with a low EIRP, QPSK + convolutional code is better.

Distributed Sampling Storage for Statistical Analysis of Massive Sensor Data

Cyber-physical systems interconnect the cyber world with the physical world in which sensors are massively networked to monitor the physical world. Various services are expected to be able to use sensor data reflecting the physical world with information technology. Given this expectation, it is important to simultaneously provide timely access to massive data and reduce storage costs. We propose a data storage scheme for storing and querying massive sensor data. This scheme is scalable by adopting a distributed architecture, fault-tolerant even without costly data replication, and enables users to efficiently select multi-scale random data samples for statistical analysis. We implemented a prototype system based on our scheme and evaluated its sampling performance. The results show that the prototype system exhibits lower latency than a conventional distributed storage system.

A 21-GHz-band Advanced Satellite Broadcasting System

A previously proposed variable equivalent isotropic radiated power (e.i.r.p.) satellite system, which uses phased array antenna technology to increase the radiated power only in areas of heavy rainfall, has now been conceptually applied to the future 21-GHz-band broadcasting satellite system. Using various parameter values for the antenna, we evaluated the radiation patterns that result when forming a nationwide beam in the shape of the Japanese landmass, for various antenna aperture diameters and numbers of spot beams. We confirmed the feasibility of our proposed phased array system by computer simulation. We then calculated the values of the major parameters, such as the antenna weight required for estimating the satellite bus. We also clarified the satellite scale in terms of required mass at launch and subsequently proposed different scales. As a result, we demonstrated that a 21- GHz-band broadcasting satellite system can be realized with a phased array antenna in terms of satellite buses and rocket systems.