Connectedness oriented communication denotes a mode of communication in which the activities of communication are more important than the contents of communication. It is targeted at maintaining and enhancing human social relationships. As our lifestyles and societies are shifting along with the progress of Information Technology, communication media that are connectedness oriented will play an important role. In this paper we propose a media called FaintPop, which is an example of such new media that are suitable for connectedness oriented communication. It is a communication media designed for a community, with which the sense of connectedness can be shared among members. Furthermore, it provides a general overview of the communication activities occurring in the community. We discuss several principles and points in designing the media, especially about the interaction of the users. Results and findings from the experiment using the media are reported.

A fully differential direct conversion receiver IC for W-CDMA is presented. The receiver IC consists of an LNA, a quadrature demodulator, low-pass filters (LPFs), and variable gain amplifiers (VGAs). In order to suppress DC offset, which is the most important issue in a direct conversion system, an active harmonic mixer is applied to the quadrature demodulator. Furthermore, a receiving system, including the LNA and an RF filter, adopts a differential architecture to reduce local signal leakage, which generates DC offset. Performance of the entire receiving system was evaluated and DC offset in steady state was measured at only 40 mV. Moreover, DC offset variation at the LNA gain change, which has the largest affect on the receiving performance, was limited to 70 mV, which is less than -10 dB compared to desired signal strength. It was confirmed by computer simulation that the DC offset variation at the LNA gain change did not degrade bit error rate (BER) performance at all.

We propose a neural-sensing LSI with a bi-directional wireless interface, which is capable of detecting 5-channel neural signals in a living animal. The proposed sensing LSI consists of a multiplexer with 5-channels selectable from 10 channels, a chopper amplifier using a new direct-chopper-input scheme, a programmable multi-mode analog-to-digital converter (ADC), and a wireless-transmitter/receiver with BPSK modulation signals. The test-chip was implemented by mixed-signal 0.35-µm CMOS technology. We measured the test chip and confirmed basic operations of these blocks. The chopper-amplifier achieved 66-dB DC gain, bandwidth of 400 kHz, and 4-µV noise with power dissipation of 6-mW with a 3-V supply. We observed real nerve signals in a living cricket using the proposed chopper amplifier. ADC achieved 52-ksps operation with power dissipation of 0.43-mW at 3-V supply. The wireless transmitter achieved 1-Mbps data transmission at a distance of 1-m with 1.5-mW power dissipation at 3-V supply.

Compressed video bitstream is sensitive to errors that may degrade the reconstructed images severely even the bit error rate is small. One approach to combat the impact of error is error concealment at the decoder without increasing the bit rate and changing the encoder. We propose motion vector based error concealment algorithms to recover the motion vector per pixel instead of that per block according to the relation of neighboring motion vectors. The displacement per pixel can be estimated more accurately by using the tendency of neighboring motion vectors. Besides, we use not only the relation among motion vectors, but also the pixels. The pixels of the error block are divided into different parts according to their consistency with neighboring blocks and the displacement at each pixel of these parts is interpolated by relative motion vectors. From simulation results, the proposed motion vector based methods provide better reconstruction quality for damaged images than other methods.

In this paper we propose a parallel and distributed computation of genetic local search with irregular topology in distributed environments. The scheme we propose in this paper is implemented with a tree topology established on an irregular network where each computing element carries out genetic local search on its own chromosome set and communicates with its parent when the best solution of each generation is updated. We evaluate the proposed algorithm by a simulation system implemented on a PC-cluster. We test our algorithm on four types topologies: star, line, balanced binary tree and sided binary tree, and investigate the influence of communication topology and delay on the evolution process.

In 1960, the famous computer pioneer J.C.R. Licklider described a vision for human-computer interaction that he called "man-computer symbiosis. " Licklider predicted the development of computer software that would allow people "to think in interaction with a computer in the same way that you think with a colleague whose competence supplements your own. " More than 40 years later, one rarely encounters any computer application that comes close to capturing Licklider's notion of human-like communication and collaboration. We echo Licklider by arguing that true symbiotic interaction requires at least the following three elements: a complementary and effective division of labor between human and machine; an explicit representation in the computer of the user's abilities, intentions, and beliefs; and the utilization of nonverbal communication modalities. We illustrate this argument with various research prototypes currently under development at Mitsubishi Electric Research Laboratories (USA).

We have been developing new cycling environments by using knowledge sharing and speech communication. We have offered multimodal knowledge contents to share knowledge on safe and exciting cycling. We accumulated 140 contents, focused on issues such as riding techniques, trouble shootings, and preparations on cycling. We have also offered a new way of speech communication using an ad-hoc wireless LAN technology for safe cycling. Group cycling requires frequent communication to lead the group safely. Speech communication achieves spontaneous communication between group members without looking around or speaking loudly. Experimental result through actual cycling has shown the effectiveness of sharing multimodal knowledge contents and speech communication. Our new developed environment has an advantage of increasing multimodal knowledge through the accumulation of personal experiences of actual cycling.

We propose an optical packet switch (OPS) using a hybrid buffer structure for the contention resolution of asynchronous variable length packets. The hybrid buffer consists of a fiber delay line (FDL) buffer as the prime buffer and a shared electronic buffer as the supplementary buffer. For the performance evaluation, a modified void filling scheduling algorithm that can be applied to the OPS was proposed. Simulation results show that the use of the electronic buffer together with the FDL buffer significantly reduce the number of FDLs required for contention resolution and considerably lower packet loss.

As various mobile communication systems have developed, dramatically integrated wireless network, where users can communicate seamlessly via several wireless access systems, have become expected. At present, there are many studies of integrated wireless network, but no study of a network design method. Therefore, in this paper, we discuss a network design method for integrated wireless networks. Because of the handover procedure, the network design where adjacent base stations are connected to the same router, regardless of radio system type, is simply considered. However, in such a design, where mobile users crowd into a particular area and users' access to the base stations located there increases, the load of these accesses is centralized to the single router. To overcome this problem, we propose a new network design wherein the base stations of heterogeneous wireless communication systems, the service areas of which overlap, are connected to a different router. In the proposed network design, although users' accesses are concentrated on the base stations located in a particular area, users in that area can be assigned bandwidth of several upper links according to the access conditions of the base stations in neighboring areas. Finally, we show the excellent performance of the proposed design by simulation experiments.

General closed-form expressions are derived and analyzed for the exact bit error rate (BER) performance of the arbitrary rectangular Gray coded QAM signal in conjunction with maximal-ratio combining (MRC) diversity on frequency non-selective slow m-distributed Nakagami fading channel. The analyses consider four channel models, independent and identical, independent and nonidentical, identical but correlated, and arbitrary correlated fading. Numerical results demonstrate error performance improvement with the use of MRC diversity reception. The new expressions presented here are suitable for evaluating various cases of practical interest on wireless communication channels.

IP multicast is seen as an efficient way of encouraging multimedia services such as Internet TV and Videoconferencing because it can deliver packets to multiple users while efficiently using network resources. Source Specific Multicast (SSM) is suggested as the IP multicast routing protocol and it can construct multicast trees efficiently. However it increases multicast forwarding table entries and fails to handle source mobility. This paper proposes the Unicast Extension Multicast Protocol (UMP) to solve these problems. In the protocol, only the routers that act as branching points keep multicast forwarding table entries, and packets are delivered between these routers using IP unicast. This prevents the multicast forwarding table entries from burdening other non-branch routers. Additionally, UMP supports source mobility by using the recursive join messages to prevent the creation of redundant paths while supporting source mobility.

In a telecommunication network system, a scheme for reforwarding call-terminating setup messages (SETUP messages) is used to guard against their loss. We have developed a method for evaluating the loss probability of these reforwarding schemes. We started with a stochastic model in which the messages are reforwarded after a constant time span from the time that the first messages have been forwarded. This model corresponds to the finite-capacity BPP/M/1/m model. We showed a method for calculating the "timeout" probability. We then added an approximate method for calculating the loss probability. Finally, using the proposed methods, we clarified the existence of the best reforwarding timelag.

In this paper, an adaptive transmission scheme considering the stay time in a spot mobile access system is proposed. The proposed adaptive transmission scheme selects the modulation format according to the user's stay time in the spot communication zone and the types of data requested by each user. In the proposed system, when the stay time of a user is short, high-speed modulation is selected for this user. When the stay time of a user is long, a more reliable modulation format is selected. The computer simulation results show that the proposed transmission scheme without any channel estimation can achieve the same or better performance than when using the modulation format fixedly when the carrier-to-noise ratio changes rapidly.

Band Division MC-CDM (BD-MC-CDM) has been proposed for high quality wireless communications and has been investigated in terms of link level performance. In this paper, we investigate frequency band and time slot selection technique from the viewpoint of system level performance in order to realize the efficient BD-MC-CDM system under cellular environments. Then a downlink frequency band and time slot selection scheme is proposed for cellular BD-MC-CDM systems. The proposed scheme selects transmission frequency band according to the signal-to-interference ratio (SIR) estimated by using the pilot signal at mobile stations and also selects transmission time slot by using the SIR threshold. Simulation results show that the proposed scheme improves the downlink throughput but degrades delay performance and it has a trade off between throughput and delay performance. By selecting suitable control parameters, the proposed scheme achieves the throughput improvement without sacrificing the delay performance.

A variety of real-time multicast applications such as video conferences, remote lectures, and video-on-demand have become in commonplace with the expansion of broadband Internet services. Due to nontrivial problems in the IP multicast technology, the peer-to-peer multicast technology (P2P-multicast) has emerged as a practical implementation, although its network resource utilization is less efficient. A multihome network has the potential of alleviating this inefficiency by providing flexibility in communication path selections for each host with multiple gateways to the Internet. This paper has first formulated the P2P-multicast routing problem in the multihome network, and has proved the NP-completeness of its decision problem. Then, a two-stage heuristic algorithm called P2PMM_router has been presented for this P2P Multicast Multihome-network routing problem. The first stage constructs an initial multicast routing tree from an optimum spanning tree by Prim algorithm, through satisfying the constraints. The second stage improves the tree by repeating partial modifications and constraint satisfactions. The extensive simulation results using random network instances support the effectiveness of our P2PMM_router.

In this paper, we propose a simple and accurate transfer function model of the power amplifiers for mobile communications. Detail analysis yields a generalized model for AM/AM characteristics in classes AB, B, and C. The analysis includes the effect of drain current variation with input level variation. This model introduces a loadline variation ratio to indicate the change of drain current and to represent the operation classes in a small signal region. Further discussion leads to simplified approximate equations for the AM/AM characteristics, and the estimation procedures for the simplified model parameters. Using the derived procedures, an efficient power amplifier employing pseudomorphic high electron mobility transistor (PHEMT) is fabricated for the 2 GHz band. Finally, the various characteristics given by the model, simulator and measurements are compared and found to agree well in the range of 20 dB below the saturated output level. The model is very effective for characterizing the power amplifiers that are used in linear compensation techniques such as predistortion methods, due to its severe nonlinearity of AM/AM and AM/PM characteristics.

The rapid spread of cellular phones in recent years has facilitated not only voice communication but also Internet access via the cellular phone system, and in addition, subscriber demand has led to a diversification in the services provided. One service in high demand is the seamless use of cellular phones in both public and private wireless network areas. In the data world, there is already such an application in the form of public and private use of wireless LAN. However, an increase in the number of users would require the realization of low-cost, easy-to-install very small base stations (VSBS) that use the frequency band efficiently in order to allow private use of ordinary cellular phones. To bring such VSBS into effect, a technology that autonomously selects frequencies which do not interfere with the public communication system from out of the publicly used frequency band is essential for turning such VSBS into reality. This paper proposes a frequency selection algorithm that actively uses cellular phone features such as frequency selection and received signal level measurement, and discusses the results of verification experiments.

An IIR digital low pass filter with flat monotonic passband, equiripple stopband and narrower transition bandwidth than that of Inverse Chebyshev digital filters of the same order is designed. The requisite equiripple stopband is realized by designing the filter in Deczkeys' w-plane. The characteristic functions are designed so as to have a root of multiplicity n at ω = 0 to ensure the n degree of flatness of the passband, and to have a pair of complex conjugate roots with coordinates constrained such that the magnitude response of the passband attenuates monotonically. The freedom in the coordinate of the complex conjugate roots is exploited to minimize the transition bandwidth. The equations are derived that give the minimum transition bandwidth of the proposed filter, which is considerably narrower than that of Inverse Chebyshev filters. It is showen through practical numerical examples that the order of the proposed filter is as low as half that of the Inverse Chebyshev filter satisfying the same specification.

This paper describes a full-CMOS single-chip Bluetooth LSI fabricated using a 0.18 µm CMOS, triple-well, quad-metal technology. The chip integrates radio and baseband, which is compliant with Bluetooth Core Specification version 1.1. A direct modulation transmitter and a low-IF receiver architecture are employed for the low-power and low-cost implementation. To reduce the power consumption of the digital blocks, it uses a clock gating technique during the active modes and a power manager during the low power modes. The maximum power consumption is 75 mW for the transmission, 120 mW for the reception and 30 µW for the low power mode operation. These values are low enough for mobile applications. Sensitivity of -80 dBm has been achieved and the transmitter can deliver up to 4 dBm.

This paper presents time slot assignment algorithms applicable to uplink of space division multiple access (SDMA)/time division multiple access (TDMA) systems with adaptive antennas. In the time slot assignment process for a new terminal in a cell, we consider not only the signal quality of the new terminal but also that of active terminals in the same cell. Intra-cell hand over is performed for an active terminal when its signal quality deteriorates. We evaluate the blocking and forced termination probabilities for pure TDMA systems, sectorized systems, and SDMA/TDMA systems in cellular environments by computer simulations. The simulation results show that the SDMA/TDMA systems have much better performance than the pure TDMA and sectorized systems.