This letter describes a new method of carrier jiter cancelling which can be implemented with quite a simple hardware for high-speed data modem. The proposed carrier jitter canceller is a kind of transversal filters that comprises sevral band pass filters, whereby the phase jitter can be efficiently cancelled with no more than 4 taps comparing to the conventional pure transversal type carrier jitter cancellers without band pass filters which need much more taps.

Trellis-Coded Modulation (TCM) schemes become popular in digital transmission systems to improve error performance. However, demodulation of Trellis-Coded signal is rather difficult. Because TCM schemes need many signal points compared with the uncoded schemes. This leads to a comparatively high probability of cycle slips. In addition, large loop delay caused by decoding can not be avoided when decision feed back type demodulators are used. This paper proposes a novel demodulation method for TCM signal using block demodulation. The block demodulation scheme is a kind of off-line demodulation, which has many advantages. The Viterbi decoder in the proposed block demodulator is used not only for Viterbi decoding but also for carrier estimation. Such a combined processing is done twice for high performance. In addition, a block demodulation scheme is not affected by processing delay. Therefore in the proposed system, carrier estimation becomes accurate, and Viterbi decoding also becomes correct. As a result, it can get coding gains which cannot be obtained by conventional block demodulation methods. And the proposed system can demodulate not only PSK signal but also QAM signal. The performance of the proposed demodulator is confirmed by computer simulation.

A complete theory for the analysis of narrowband binary FM with limiter-discriminator detection in a fast Rayleigh as well as a Rician fading channel is presented. Error rate results which are in close agreement with experimental measurements are obtained for both cases and compared against the nonfaded benchmark. The use of digital FM and other modulation schemes in a fading environment is also discussed in relation to the nonfaded benchmark. It is suggested that DQPSK with its high spectral efficiency is suitable for land-based cellular mobile communications while binary FM with limiter-discriminator detection is appropriate for satellite-based mobile radio systems.

This paper discusses lossless encoding methods of compressing two-dimensional black and white images for the efficient communication of such images. All the models concerned are adaptive in the sense that we assume no prior knowledge of statistical properties of any input and that the image is serially scanned and encoded in one pass. In the adaptive strategy, each picture element (pel) is encoded based on the time-variant coding parameters, which are empirically estimated from the already encoded pels in the present image. Since the coding parameters depend on the conditioning neighboring pels, modeling involves a pel-by-pel determination of conditioning neighboring pels. Two approximate solutions of how to select the conditioning pels are given, both of which are based on Rissanen's MDL criterion. Although no rigorous theory to account for the performance has been established, the experimental study demonstrates that one of them is superior in compression performance to any adaptive model utilizing a fixed number of conditioning pels. In this paper, an efficient implementation of models by means of an arithmetic code is also presented.

Efficient spectrum utilization is a constant theme in radio systems. Cellular mobile radio is one solution and by making the cell radius quite small, e.g. microcell, the channel capacity increases. However, in microcells, handovers are frequent and the optimum control algorithm is not yet known except for some indication of decentralization. On the other hand, mobile packet radio networks provide communication between mobile users via mobile repeaters. For network survivability against topology changes, distributed control is suggested. This paper focuses on these controls, reviewing the basic issues and research results.

In this paper, we consider an extended form of the optimum sub-band interpolation for a family of band limited signals. It is assumed that this family of signals is a certain subset of the set of the signals whose Fourier spectrums have weighted L2 norms smaller than a given positive number. We use the sample values of the output signals of the finite number of linear systems excited, at the same time, by a band limited signal to be restored approximately. The proposed method minimizes the measure of error which is equal to the envelope of the approximation errors in the frequency domain. It is proved that the presented method is the optimum, in a certain sense, among all the linear and the nonlinear approximations using the same sample values of the signal.

By combining rubber with carbon and ferrite in an appropriate weight ratio, the material which has both dielectric and magnetic losses, suitable for an electromagnetic-wave absorber, is obtained. The dispersion characteristics of complex relative permittivity and permeability of this material are measured, and equations of both permittivity and permeability are derived in RF frequencies. By using these dispersion equations, we can easily simulate applications using this kind of material as an electromagnetic wave absorvber.

This paper describes the application of Trellis Coded Modulation (TCM) to multi-state QAM. The proposed strategy of increasing coding gain is based on the classical approach of error correction coding, in which redundant bits are added at the cost of bandwidth expansion. It is shown that symbol-rate-increased TCM is superior to the conventional TCM as the modulation state increases in number. Transparency to phase rotations is also considered. A pair of linear codes transparent to 180phase rotation is applied to the in-phase and the quadrature channels in a symbol-rate-increased manner. The tranparent code search has found a new encoder for 64-state convolutional code which has the same minimum squared distance but a smaller Nfree than the Ungerboeck nontransparent code. As an example, the new TCM approach to 256 QAM digital radio-relay systems is discussed from the fundamental system design poin of view. As a result, it has been shown that STM-1 (155.520 Mbit/s) signals can be transmitted within a 30 MHz bandwidth in spite of bandwidth expansion and a flat fade margin improvement of more than 5 dB is obtained.

The cell discard process and the requirements for cell loss compensation methods in ATM (Asynchronous Transfer Mode)-based networks are discussed. In addition to the average cell loss rate, the probability distribution of consecutive cell discard length is slso investigated using computer simaulation of cell multiplexing. Average cell loss rate characteristics show the difficulty of reducing the cell loss rate only by increasing buffer size when cell arrival is bursty. The probability distribution of consecutive cell discard length indicates that cells are consecutively discarded even if cell arrival is less-bursty and the link utilization factor is not large. A simple mathematical model which represents the cell discard process is also derived. Estimation of cell loss compensation effect based on the obtained cell discard process model is presented. It shows that a cell loss compensation method which can only compensate for the isolated cell losses provides a cell loss rate reduction factor of only around 1/2 to 1/5 even if the input signals are not bursty. Therefore, consecutive cell loss compensation is necessary to efficiently reduce cell loss probability regardless of the burstiness of the input cell arrival.

The TAT system compresses the bandwidth of picture signals into about 1/2 by using variable subsampling with 2 or 3 subsampling modes. In this paper, a new variable subsampling scheme with many modes is proposed for higher compression. We call it the pyramidal TAT. In the proposed scheme, the basic 2-modes TAT is applied to the pyramidal representation of the picture. The pyramid used here is the complementary pyramid we proposed before. Variable subsampling with very many modes is easily done and a wide range of compression ratios are achieved with the pyramidal TAT. It is effective at compression ratios higher than 2 : 1 compared to the conventional TAT system.

Havihg modified and extended the routing algorithm used in our previously proposed Bidirectional Shuffle Ring Network (BSRN), we here provide some adaptive routing algorithms that can relieve the congestion caused by bottlenecks when nonuniform traffic exists. As to preserve the transmission order of cells associated with a message which may otherwise arrive at the destination out of sequence if they are forwarded along different routing paths, two control schemes are also devised. The BSRN proves to be highly reliable and robust since countermeasures against node or link failure can also easily be realized.

Communication theory has much contributed for establishing an efficient, reliable and secure communication (storage) system. Various mathematical theories have provided another theoretical backgrounds to develope practical coding techniques. In this paper we discuss Communication theories, practical coding techniques and their applications.

In this paper, we propose the adaptive cutoff priority for a multiple server finite-capacity buffer system with two kinds of arrival streams to reduce loss probabilities of both kinds of arrivals. The number of reserved" servers for high priority customers is adaptively decreased by using the adaptive cutoff priority, when the number of waiting customers of low priority is increased. We first derive the state probabilities which are the function of both the number of customers in the queue and the number of customers in service, so that it is possible to present general expressions for the loss probability and the average queueing time. Next, the numerical calculation is carried out and it is found that not only the loss probability of each arrival but slso the total loss probability are reduced by using more than two thresholds and selecting the treshold values appropriately. It is shown that the computer simulated results agree with the theoretical results.

To reduce the computational complexity due to the long tap structure of filters used for subband coding, a new structure of filter banks is proposed. Applying the concept of hierarchical coding to the perfect reconstruction condition in a one-dimensional analysis/synthesis system, which is represented as a matrix operation in z-transform domain, our approach realizes perfect reconstruction with short length FIR filters and reduction of the number of filters by half compared with the conventional approaches. Moreover, it is expanded to two-dimensional case, where both a separable structure and a non-separable one are considered.

Optical communication systems using quantum state control have received much attentions. For this quantum state control communication, however, one of the most serious problems is the effect of transmission loss which degrades the advantage of the quantum state controlled signal. In optical long transmission communications, in general, transmission loss is large so that the advantage using quantum state controlled signal is hardly lost and performance of quantum state control communications is almost equal to that of conventional communications. So it is necessaty for a new application of quantum state control to overcome the standard quantum limitation which is achieved by the conventional coherent communication system. In this paper, we propose a realization of a new optical communication system with received quantum state controller, so called Received Quantum State Control (RQSC) system, in order to cope with transmission loss problem. This system can provide the advantage of quantum state control regardless of amount of transmission loss. Particularly, it is shown that the system can overcome the standard quantum limitation which corresponds to the limitation achieved by conventional BPSK homodyne system using coherent state signal. This corresponds to Quantum Receiver" of the broad sense in Helstrom's receiver theory.

A new method to measure the effective radiated power (ERP) of transmitters is proposed. The effects of nearby reflecting objects, which introduce measurement error, are canceled by the in-phase synthetic method, and therefore, this proposed measurement method is practicable even in a small test site. Theoretical formula is derived and error is evaluated using a simulation technique. Experimental results prove the validity of this method. Its application to anrtenna gain measurement, as well as the ERP measurement of communications equipment, is also presented.

A necessary and sufficient condition of the ergodicity for a class of Gaussian periodically correlated stochastic processes is given in this paper. Periodically correlated processes are also called cyclostationary processes in wide sense, and these are mainly studied as models of signal processes in the communication theory and as models of time series of practical data of stochastic phenomena in some periodical environment. On the line of Boyles and Gardner's study(10) on cycloergodicity of certain class of nonstationary processes of discrete time parameter, we reformulate such ergodicity of cyclostationary processes in strict sense in continuous time parameter case, and prove a ergodic theorem. Futhermore, we apply it to Gaussian periodically correlated process, and discuss almost sure limiting behavior of a sample periodogram of the process.

It is shown that significant accumulation of alignment jitter can result if there exists any delay difference between signal and timing paths in respective regenerators in a chain. This phenomenon of extra alignment jitter accumulation is analyzed by using Chapman model. Dependence of accumulation on timing extrator Q and delay difference is predicted through the theoretical analyses. Results of computer simulation are found to be in good agreement with theory. It is also revealed by the simulation that additional accumulation can be entailed, which is explained in terms of jitter fine structures. Methods for alleviating extraaccumulations and desigh considerations for time cross hair budget are also discussed.

The use of hypercube multiprocessor computer for solving large-scale linear programming problems with parallel simplex method is presented. The inherent parallelisms involved in each step of the sequential simplex method are investigated and we show how the topological properties of hypercube are effectively applied in the proposed algorithm. The analysis shows that an O(P) speedup with respect to the total running time required by sequential implementations of the simplex method is achieved by using P2p processors of p-dimensional hypercube.

A novel carrier recovery method for preambleless demodulation is proposed. The salient feature of this demodulation method is the carrier recovery in the frequency domain for a low rate burst PSK signal by digital signal processing. Firstly, the received signal is transformed to a frequency domain signal by FFT technique. The power spectrum of the received signal is searched to find its center frequency by the 1st estimator, and the frequency offset of the received carrier and excessive noise are removed. Then, the signal is frequency-multiplied to extract the carrier component. The precise frequency and phase of the carrier component are estimated by the 2nd estimator in the frequency domaim. Filtering, clock timing recovery, and data decision are also realized by digital signal processing. The carrier recovery in the frequency domain enable to accomplish coherent demodulation at a very low received C/N irrespective of the amount of carrier frequency offset. For a 600 bit/s BPSK burst signal, less than 0.5 dB degradation of bit error rate performance is achieved at the received C/N of 2 dB with frequency offset of as large as 2 kHz. The performance of carrier recovery is also analyzed through the error probability of q-ary FSK. In the frequency domain, the power spectra can be considered as the output of narrow bandwidth filters for a q-FSK demodulator. Thus the detection performance of the carrier component can be estimated through that of q-FSK, where the q would be the number of spectrum within the modulated bandwidth. The error rate performance in carrier detection obtained by a computer simulation is congruent with that caculated for q-FSK demodulation.