Mobile communication services have become popular due to the rapid popularization of cellular mobile telephones. In order to offer services to an increasing number of users and to upgrade services, the development of Third-Generation Mobile Telecommunication is required. Our proposed system utilizing W-CDMA enables high-speed variable data communications, uninterrupted hand-over between communication zones, doubling of subscriber capacity and reduction of operation costs. Various actions are being taken internationally toward the establishment of a global standard for the Third-Generation Mobile Telecommunication System, aiming at its practical application around AD 2000. The W-CDMA system has been adopted as the standard for Japan. We are developing experimental W-CDMA system equipment. For this development, many Field Programmable Gate Array (FPGA) devices and Digital Signal Processors (DSP) have been used to meet the changes of equipment specifications and system evaluation parameters. By developing customized Large-scale Integrated circuit (LSI) devices and high-speed DSP, a small-size portable phone and a compact visual phone have been realized. Also, high-density mounting of the signal processing parts has been done in the Base Transceiver Station (BTS). In the development of a Mobile Communication Controller Simulator (MCC-SIM), the developmental period has been shortened by using our ATM switching system (AD8700) and generic-use PBX (Pana EXA) in the proposed system. In this paper, the features of the W-CDMA system and the outline of the newly developed experimental equipment have been described.

In this paper we present a Quality of Service (QoS) management architecture for distributed multimedia applications in heterogeneous communication environments of wired and wireless networks. Gaps in network performance such as bandwidths and error rates between wired and wireless networks, as well as gaps in terminal performance in media handling between desktop computers and handheld computers, bring about heterogeneities. Furthermore, even performance gaps among various desktop computers cause heterogeneities. As a result of these heterogeneities in network and terminal performances and various user preferences, the QoS requirement from each receiver is different. Therefore, mechanisms that adjust and satisfy each QoS requirement are needed. We propose a proxy server called Communication Coordination Server (CCS), which intermediates a video server and a receiver and manages the QoS coordination. The CCS performs QoS admission, adjustment, and allocation mechanisms to satisfy the user's QoS requirement. Then transcoding is used to realize the allocated QoS, and it decodes the input video stream from the video server and encodes it within the CCS. A QoS mapping mechanism that translates application-level QoS into resource-level QoS is needed for the QoS admission. We also propose a new QoS mapping mechanism using spline functions that enables a continuous QoS translation. We have built a CCS prototype in our laboratory testbed, and have verified that the CCS can resolve the heterogeneities between the server and receiver by the QoS adjustment mechanism of the transcoding and the QoS admission.

The constant modulus algorithm (CMA) of the adaptive array has been developed for suppressing the co-channel interference and the intersymbol interference in mobile communications. In this paper a novel CMA for the hybrid of the adaptive array and equalizer (HAE) is proposed to combat the problems of insufficient degrees of freedom and mainbeam multipath interferers. The HAE with CMA utilizes the constant modulus property for the output signal of the HAE to adjust the weight vectors of the array and equalizer simultaneously. The co-channel interferers can be canceled by the array and the multipath interferers can be removed by the array or the equalizer following the array in the HAE. Therefore, the array in the HAE with CMA may need less number of elements than that required by the CMA array which cancels both the co-channel interferers and multipath interferers. Besides, the presence of the mainbeam multipath interferers, which may seriously degrade the performance of the CMA array, has much less effect on the HAE with CMA since it can be suppressed by the equalizer instead of the array. Simulation results are presented to demonstrate the merits of the CMA for the HAE.

This paper describes the effectiveness of compact semiconductor optical amplifiers (SOAs) in the photonic transport system (PTS). Such amplifiers are small enough to permit high-density packaging. SOAs, having unsaturated signal gain of 10 dB and saturation output power of 10 dBm, can improve the Q-value by 3 over the SOA input power range of 10 dB. Within this range, the signal transport distance can be expanded from 360 km to 600 km by placing SOAs on individual optical channels in a PTS even though the amplified spontaneous emission (ASE) generated by individual SOAs is combined with the optical signals and delivered to the same output fiber. This result indicates that it is useful to employ compact SOAs in the PTS for enlarging the distances between nodes.

The paper argues that a radical shift in the market for communications services is emerging, driven by the mass availability of cheap bandwidth, computing and global mobility combined with the pervasive rise of Internet based data services. At the same time, the Operation Support Systems (OSS's*) that are essential in order to create business value from these technologies are lagging behind market need. The authors argue for a re-think of the humble management system into a complete software wrap-around of the network to deliver a value creation platform - as different from yesterday's OSS as the bakelite telephone is from today's tri-band mobile handsets. This software will be based on product standards, not paper ones and will require a major shift of gears from the position of today. This value creation platform will be built from advanced, component based software delivered through a very different market model to that of today. Much of this technology exists; we simply need critical mass behind a common approach. The discussion in this paper represents the personal views of the authors and does not necessarily represent the views of any organisation.

In this paper, we propose a preemptive priority handoff scheme for integrated voice/data cellular mobile systems. In our scheme, calls are divided into three different classes: handoff voice calls, originating voice calls, and data calls. In each cell of the system there is a queue only for data calls. Priority is given to handoff voice calls over the other two kinds of calls. That is, the right to preempt the service of data is given to a handoff voice call if on arrival it finds no idle channels. The interrupted data call returns to the queue. The system is modeled by a two-dimensional Markov chain. We apply the Successive Over-Relaxation (SOR) method to obtain the equilibrium state probabilities. Blocking and forced termination probabilities for voice calls are obtained. Moreover, average queue length and average transmission delay of data calls are evaluated. The results are compared with another handoff scheme for integrated voice/data cellular mobile systems where some numbers of channels are reserved for voice handoff calls. It is shown that, when the data traffic is not very light, the new scheme can provide lower blocking probability for originating voice calls, lower forced termination probability for ongoing voice calls, and shorter average queue length and less average transmission delay for data calls.

Feature interaction detection determines whether interactions occur or not between the new and existing telecommunication services. Most of conventional detection methods on state transition model utilize an exhaustive search. The exhaustive search is fundamentally very powerful in the sense that all interactions are exactly detected. However, it may suffer from the state explosion problem due to the exponential growth of the number of states in the model when the number of users and the number of features increase. In order to cope with this problem, we propose a new detection method using a state reduction technique. By means of a symmetric relation, called permutation symmetry, we succeed in reducing the size of the model while preserving the necessary information for the interaction detection. Experimental evaluation shows that, for practical interaction detection with three users, the proposed method achieves about 80% reduction in space and time, and is more scalable than the conventional ones especially for the increase of the number of users in the service.

This paper reports on the development of an eyeglass-type infrared-controlled telephone communication interface for the disabled. This system is comprised of four major components: A) a headset; B) an infrared transmitting module; C) an infrared receiving/signal-processing module; and D) a main controller, the Intel-8951 microprocessor. The headset with a tongue-touch panel, a wireless earphone, and a wireless microphone. The infrared transmitting module utilizes a tongue touch panel via tongue-touch circuitry which is converted to an infrared beam and a low power laser (<0.1 mW) beam. The infrared receiving/signal-processing module, receives the infrared beam and fine tunes the unstable infrared beam into standard pulses which are used as control signals. The main controller is responsible for detecting the input signals from the infrared receiving/signal-processing module and verifying these signals with the mapping table in its memory. After the signal is verified, it is released to control the keys of the telephone interface. This design concept was mainly based on the idea that the use of an infrared remote module fastened to the eyeglasses could allow the convenient control of the dialing motion on the keys of a telephone's dialing-pad which are all modified with infrared receiving/signal-processing modules. The disabled are competent for some of work, such as a telephone operator. The increase of opportunity to do a job for the disabled would help them live independently.

In this letter, the bit error probability of a hybrid DS/SFH-SS (Direct-Sequence/Slow-Frequency-Hopped Spread-Spectrum) system is derived for a Nakagami fading channel in the presence of multiple tone jamming. At a low JSR (jamming-to-signal power ratio), a pure DS-SS system can achieve lower bit error probability than a hybrid DS/SFH-SS system. But at a high JSR, a hybrid DS/SFH-SS system is shown to be superior to a pure DS-SS system. Especially, the worst case performance of a hybrid DS/SFH-SS system is almost equal to that of a pure DS-SS system.

To realize S-band mobile satellite communications and broadcasting systems, the onboard mission system and equipment were designed for the Japanese Engineering Test Satellite VIII. The system performs voice communications using handheld terminals, high-speed data communications, and multimedia broadcasting through a geostationary satellite. To enhance system efficiency and flexibility, the onboard mission system features phased-array-fed reflector antennas with large antenna diameter and baseband switching through onboard processors. Configurations and performance of the subsystems and key onboard equipment, large deployable reflectors, feed arrays, beam forming networks and onboard processors, are presented. The S-band mobile systems and onboard equipment will be verified through in-orbit experiments scheduled for 2002.

A T-user uniquely decodable (UD) code {C1,C2,,CT} over an integer set {0,1,,k} with arbitrary code length is developed for a multiple-access adder channel (MAAC). Each of the T users is equipped with two codewords, one of which is zero vector. The T-user UD code is used to identify users through the MAAC. It is shown that a T(f+g+1)-user UD code with code length f+g+1 can be arranged from two given T(f)-user and T(g)-user UD codes. This idea makes it possible to construct recursively a T-user UD code for an arbitrary code length n and a positive integer k. The T-user UD code includes the Jevticode.

In this paper, we study the link capacity assignment problem in packet-switched networks (CA problem) focusing on the case where link cost function is a piecewise linear concave function. This type of cost function arises in many communication network design problems such as those arising from developments in communication transmission technologies. It is already known that the method of link set assignment is applicable for solving the CA problem with piecewise linear convex cost function. That is, each link in the network is assigned to one of a group of specific sets, and checked for link set contradiction. By extending the method of link set assignment to the case of piecewise linear concave cost function, an important characteristic of the optimal solution of the CA problem is derived. Based on this characteristic, the non-differentiable link cost function can be treated as a differentiable function, and a heuristic algorithm derived from the Lagrange multiplier method is then proposed. Although it is difficult to determine the global optimum of the CA problem due to its non-convexity, it is shown by numerical results that the solution obtained from the proposed algorithm is very close to the global optimum. Moreover, the computation time is linearly dependent on the number of links in the problem. These performances show that the proposed algorithm is very efficient in solving the CA problem, even in the case of large-scale networks.

The relationships between lattice orientation of the electron-beam evaporated MgO layer used as protecting layer for ac plasma displays (ac-PDPs) and the discharge characteristics of color ac-PDPs were investigated by the measurements of ion-induced secondary electron emission. It is proved that values of γi for MgO are large in the order of (220) orientation, (200) orientation, and (111) orientation, that is, γi(220) > γi(200) > γi(111). The values of φ for different lattice orientation are obtained by the measurements of thermionic emission and photo emission. The aging measurements for testing panels with the different lattice orientation of MgO layer revealed that performance of those panels are excellent in the order of (220), (200), and (111). In particular, luminance and luminous efficiency become larger in the order of (220), (200), and (111). It is pointed out that the degree of longevity, sustaining voltage, and memory margin for ac-PDPs with protecting materials as MgO are estimated by the measurements of γi.

The minimum mean-squared error (MMSE) linear detector has been proposed to successfully suppress the multiple access interference and mitigate the near-far problem in direct-sequence code-division multiple access communication systems. In the presence of unknown or time-varying channel parameters, the MMSE linear detector can be implemented by the blind Griffiths' algorithm, which uses the desired signal vector instead of a training sequence of symbols for initial adaptation. In this paper, a variable step-size (VSS) Griffiths' algorithm is proposed for accelerating the convergence speed, especially in the presence of strong interference. Numerical results show that the convergence properties of the VSS Griffiths' algorithm are robust against the wide eigenvalue-spread problem of the correlation matrix associated with the received signal vector compared to the Griffiths' algorithm using a fixed step-size.

Inter-vehicle communication has aroused much interest because of its goal of reducing traffic accidents. In a non-platooning situation, where vehicles travel freely, multiple hop (MH) inter-vehicle communication has not yet been examined. In this paper a simple MH broadcast protocol is proposed, and shown to be effective. The effect of several parameters important to a MH network, such as maximum number of hops and data rate, are investigated. Multiple hop is shown to be superior to the conventional single hop (SH) system using non-platoon inter-vehicle communication.

Multimedia communications over mobile networks suffer from fluctuating channel degradation. Conventional error handling schemes consist of the first stage error correction decoding in wireless interface and the second stage error correction decoding in multimedia demultiplexer, where the second stage decoding result is not used to improve the first stage decoding performance. To meet the requirements of more powerful error protection, we propose iterative soft-input/soft-output error correction decoding in multimedia communications, where the likelihood output generated by the error correction decoding in multimedia demultiplexer is fed back to the decoding in wireless interface and the decoding procedure is iterated. The performances were evaluated by MPEG-4 video transmission simulation over mobile channels.

In order to guarantee pairwise independence of codewords in an ensemble of convolutional codes it is necessary to consider time-varying codes. However, Seguin has shown that the pairwise independence property is not strictly necessary when applying the random coding argument and on this basis he derives a new random coding bound for rate 1/n fixed convolutional codes. In this paper we show that a similar random coding bound can be obtained for rate k/n fixed convolutional codes.

In this paper, we show that the principle of quantum cryptography can be applied not only to a key distribution scheme but also to a data transmission scheme. We propose a secure data transmission scheme in which an eavesdropping can be detected based on sharing the bases Alice (the sender) and Bob (the receiver) have. We also show properties of this scheme.

In this paper, we focus on regularity and set-valued functions. Regularity was first introduced by S. C. Kleene in the propositional operations of his ternary logic. Then, M. Mukaidono investigated some properties of ternary functions, which can be represented by regular operations. He called such ternary functions "regular ternary logic functions". Regular ternary logic functions are useful for representing and analyzing ambiguities such as transient states or initial states in binary logic circuits that Boolean functions cannot cope with. Furthermore, they are also applied to studies of fail-safe systems for binary logic circuits. In this paper, we will discuss an extension of regular ternary logic functions into r-valued set-valued functions, which are defined as mappings on a set of nonempty subsets of the r-valued set {0, 1, . . . , r-1}. First, the paper will show a method by which operations on the r-valued set {0, 1, . . . , r-1} can be expanded into operations on the set of nonempty subsets of {0, 1, . . . , r-1}. These operations will be called regular since this method is identical with the way that Kleene expanded operations of binary logic into his ternary logic. Finally, explicit expressions of set-valued functions monotonic in subset will be presented.

An ultra-fast optoelectronic decision circuit using resonant tunneling diodes (RTD's) and a uni-traveling-carrier photodiode (UTC-PD) is proposed. The circuit employs two cascaded RTD's for ultra-fast logic operation and one UTC-PD that offers a direct optical input interface. This novel configuration is suitable for ultra-fast decision operation. Two types of decision circuits are introduced: a positive-logic type and a negative-logic type. Operations of these circuits were simulated using SPICE with precisely investigated RTD and UTC-PD models. In terms of circuit speed, 40-Gbit/s decision and 80-Gbit/s demultiplexing were expected. Furthermore, the superiority of the negative-logic type in terms of the circuit operating margin and the relationship between input peak photocurrent and effective logic swing were clarified by SPICE simulations. In order to confirm the basic functions of the circuits and the accuracy of the simulations, circuits were fabricated by monolithically integrating InP-based RTD's and UTC-PD's. The circuits successfully exhibited 40-Gbit/s decision operation and 80-Gbit/s demultiplexing operation with less than 10-mW power dissipation. The superiority of the negative-logic type circuit for the circuit operation was confirmed, and the relationship between the input peak photocurrent and the effective logic swing was as predicted.