There are about 90 million high performance mobile phones used in Japan. We are now planning to develop new applications of mobile phone to support children and elder and disabled people who are out of scope of major mobile phone application based on their requirements. We have a responsibility to extend the application filed of mobile phone as a leading country of ubiquitous life. This paper discusses possibilities to realize mobile ad hoc networks using Bluetooth functions equipped on a mobile phone. Hierarchical mobile ad hoc networks using Bluetooth in a mobile phone are firstly developed as a test platform. The test platform proves the possibility of developing mobile ad hoc network by mobile phone built-in Bluetooth functions. We demonstrate their capabilities by showing results of implementing game applications on the test platform. The paper also describes some example applications using mobile ad hoc network technologies, which include a location tracking system for children on the way to a school and an alarm system for hearing impaired people

Telecommunications are powerful tools to reduce loss of life and property damage during disasters. Especially, for the people with disabilities, information provided through their own telecommunication devices is indispensable to move to a place of refuge safely and rapidly. In this paper, we propose the wireless system to send information on disasters to people with disabilities (especially deaf people) and to identify their location at the refuge when they are evacuated. The system consists of cellular phone, web server and electronic display, which are concatenated by Short Message Service (SMS) and Bluetooth. By using these devices and public network services, the system provides a function to send appropriate information to people with disabilities rapidly. The system provides the network platform to share information about their whereabouts with related persons. Finally, we summarize results from demonstration of our system to the deaf people experienced large earthquake.

We study formulating the ubiquitous cloud (UC) model proposed by Murakami at KDDI [4]. Based on the analysis for Ad Hoc wireless network by Gupta and Kumar [3], we rearrange their setting to an appropriate one for the UC, and then give an evaluation of network capacity called transport capacity. The evaluation takes the form similar to [3], when transmission bit rates are equal in each layer. Also, as a model of the node part in the network, we propose applying a birth-death process in M/M/1 queue, in order to describe the connection and disconnection of the nodes to the network.

Proposes some reversible variable length codes (RVLCs) which can be decoded instantaneously both in the forward and backward directions and have high transmission efficiency. These codes can be used, for example, in the backward reconstruction of video signals from the data last received when some signal is lost midway in the transmission. Schemes for a symmetrical RVLC requiring only a single code table and for an asymmetrical RVLC having short average code length are introduced. They compare favorably with other reversible codes such as B2 codes in several aspects.>

An efficient technique for obtaining a variable length code (VLC) resistant to synchronization loss due to channel errors is proposed. Bit errors in the channel lead to incorrect decoding of a VLC and result in error states for continuous codewords. In this paper first a precise value is found for assessing the ability of a VLC to recover synchronization from the error states. Next a new transformation for converting a code into another of the same efficiency (equivalent transformation) is introduced, and several VLCs with an identical efficiency are compared through estimation of synchronization recovery in order to find an error-resistant VLC. Based on the equivalent transformation, an efficient method for finding an error-resistant VLC with high recovery performance from among multiple VLCs is described.>

This paper describes a 15/30 Mbit/s TV codec with a new approach to high-efficiency coding for TV signals, i.e., median adaptive prediction. The 15/30 Mbit/s codec, commonly applicable to NTSC, PAL, and SECAM (525/60 and 625/50) systems, uses adaptive prediction incorporating a motion-compensated interframe, an interfield, and an intrafield predictor. Its performance for digital transmission is presented. This universal codec is designed, based on CCIR recommendations concerning digital TV coding parameters for studios (Rec. 601) and general principles on long-distance digital TV transmission (Rec. 604). A field trial of 15 Mbit/s digital TV transmission using this codec between earth stations with a 30 m diameter antenna and a 5 m diameter antenna is reported.

As a high efficiency coding method for TV signals, variable length coding, such as Huffman coding, is extremely effective. However, when this variable length coding is applied to an actual TV codec which requires high-speed real-time processing, maximum word length will be limited for the hardware configuration. This correspondence describes an algorithm for the construction of a modified Huffman code with limited maximum word length by means of a "top-down" procedure meeting this requirement instead of the conventional "bottom-up" algorithm.

This paper describes the results of theoretical studies made on performance of various kinds of intrafield two-dimensional transform codings (Hadamard, cosine, and slant) for carrier chrominance signals, by introducing a new measure (transform coefficients of zero variance) for such coding performances. In addition, a comparative study of the performance of these transform codings is performed for different sampling frequencies(2f_{sc}, 3f_{sc}, 4f_{sc})with the same transmission rate, taking into account the tradeoff between the number of bits assigned to a picture element at each sampling frequency and the autocorrelation between adjacent picture elements.

Since DPCM and transform coding are two fundamental approaches to high-efficiency (bit reduction) coding, it is important to clarify the basic coding characteristics of these approaches and the differences between them in order to utilize the high-efficiency coding method effectively. It is important to compare them not only from the standpoint of coding performance as optimized coding schemes based on the statistics of the input picture signal, but also from that of the robustness of coding performance for the variation of picture statistics to be coded. This paper theoretically compares the robustness of the coding performance of DPCM having a two-dimensional predictor with that of a two-dimensional Hadamard transform coding in an intrafield coding method of the NTSC composite signal. The comparison provides theoretical evidence that transform coding is more stable than DPCM, and this tendency is marked at lower bit rates such as 1 or 2 bits/pel, while DPCM has a higher coding performance for pictures with high autocorrelation.

Since differential-pulse-code modulation (DPCM) and orthogonal transform coding (OTC) are the most fundamental methods of high-efficiency coding (bit-reduction method), it is important to clarify the basic coding characteristics of these methods and the difference between them in order to utilize the bit-reduction method effectively. This paper theoretically as well as experimentally compares the coding efficiency of a DPCM having a two-dimensional predictor with that of a two-dimensional Hadamard transform coding method (HTC) in the intrafield coding of the NTSC composite signal. The comparison evidenced that the distinctive difference in coding characteristics between DPCM and HTC depends greatly on the power level of carrier chrominance signals. That is, it is confirmed theoretically and experimentally that the coding efficiency of the HTC is far lower than that of the DPCM in the case of a signal having a high power level carrier chrominance signal such as a color-bar signal.

This paper proposes a new approach to the composite coding of the NTSC color TV signal, i.e., an interfield-intrafield adaptive prediction. First, concerning prediction efficiency for various moving pictures, an advantage of this coding scheme over interframe coding is clarified theoretically and experimentally. This adaptive prediction gives very good and stable performance for still to violently moving pictures. A 30 Mbit/s. codec, based on this idea, and its performance are presented. Field transmission testing through an INTELSAT satellite using this codec is also described. The picture quality is satisfactory for practically all the pictures expected in broadcast TV programs, and it is subjectively estimated to be a little better than that of the half-transponder FM transmission now employed in the INTELSAT system.