Recently, the small set of nonbinary Kasami sequences was presented and their correlation properties were clarified by Liu and Komo. The family of nonbinary Kasami sequences has the same periodic maximum nontrivial correlation as the family of Kumar-Moreno sequences, but smaller family size. In this paper, first it is shown that each of the nonbinary Kasami sequences is unbalanced. Secondly, a new family of nonbinary sequences obtained from modified Kasami sequences is proposed, and it is shown that the new family has the same maximum nontrivial correlation as the family of nonbinary Kasami sequences and consists of the balanced nonbinary sequences.

Fiber-optic passive double star (PDS) network is described as an access network for microcellular radio communication systems. The intrinsic characteristics of the PDS network, reduction in the optical fiber count and flexible access capability, are examined. A unit cell structure is introduced which enables the PDS network to be effectively incorporated into the access portion of microcellular radio communication systems. The reduced total fiber length in the unit cell structure based on the PDS network is discussed in comparison with the conventional architecture. Calculations show that there is an optimum splitting ratio that minimizes the total fiber length. When the microcell radius and service area radius are 100m and 10km, respectively, the total fiber length of the PDS network is reduced to only about 9% of that of the conventional single star (SS) network for a splitting ratio of 34. Resource sharing and handover between microcells in a unit cell are performed by using the dynamic channel allocation function of the PDS system. Substantial performance improvement for loaded traffic can be obtained by resource sharing. When the splitting ratio is 32, the available traffic of a base station (BS) increases from 0.9 [erl/BS] to 3.4 [erl/BS] by adopting dynamic channel allocation for the lost call probability of 0.01.

This paper tends to analyze the trends of the research in logic synthesis. The first part is devoted to an expertise of the efficiency of factorization methods developed during the last decade and to the proposal of dedicated methods for complex logic blocks. The second part shows the importance of Binary Decision Diagrams as representation of Boolean functions. Their use in the technology mapping phase of multiplexor-based FPGAs in an industrial tool is taken as illustration.

A fiber-optic transmission system for linking radio base stations to the mobile communication center is developed, and its performance is evaluated. The introduction of this system yields two main improvements: optimum zone allocation to increase radio frequency utilization efficiency and the elimination of service quality issues such as dead zones and traffic imbalance. Being optical, the system suffers from the interferometric noise and distortion created by multiple reflections within the fiber. Moreover, because system response is much different from that of optical CATV systems, we clarify the optical parameter selection criteria and hypothetical return loss model for an embedded fiber infrastructure. An optical multiplexing method is also introduced that reduces the quantity of fiber and connectors, as well as splicing and cable installation costs. A new ternary optical multiplexing architecture combined with a cost-effective self-tuning type WDM technique and a high isolation type circulator are proposed for the 1.3µm wavelength region. The performance of low distortion high power common amplifiers is measured with the aim of reducing the size and weight of back-up batteries, and to improve the packaging density of the typical base station.

Test pattern generation is getting much harder as the circuit size becomes larger. One problem is that it tends to take much time and another one is that it is difficult to detect redundant faults. Aiming to cope with these problem, an enhanced unique sensitization technique is proposed in this paper. This powerful global implication reduces the number of backtracks with reasonable computational time. And a fast test pattern generator featuring this unique sensitization demonstrates its performance using large benchmark circuits with over ten thousands of gates. It takes only a minute to detect all testable faults and to identify all redundant faults of 20,000 gates circuit on a workstation.

Markov chain models are used to derive the average stationary throughput and delay performance of Idle-Signal Casting Multiple Access (ICMA), with and without Failure Detection (/FD), protocols which are suitable for use in mobile packet radio local area networks, where propagation impairments are prevalent. The models consider the effects of pure Rayleigh fading on channel access and packet transmission. Numerical results, validated by computer simulations, are obtained that enable a quantitative study of the performance of the protocols. It is found that the performance of the ICMA/FD protocol is affected more significantly by fading on the base-to-mobile channel than is the performance of the ICMA protocol. In addition, performance improves with larger packet sizes eventhough such packets are more vulnerable to failure due to fading.

In this paper, a new method of synthesizing multi-level logic circuits directly from binary decision diagrams (BDDs) is proposed. In the simple multiplexer implementation, the depth of the synthesized circuit was always O (n), where n is the number of input variables. The new synthesis method attempts to reduce the depth of circuits. The depth of the synthesized circuits is O (log n log w) where w is the maximum width of given BDDs. The synthesized circuits are 2-rail-input 2-rail-output logic circuits. The circuits have good testability; it is proved that the circuits are robustly path-delay fault testable and also totally self-checking for single stuck-at faults.

We introduce automatic procedures for generating and verifying sufficient correctness properties of synchronous processors. The targeted circuits are synchronous array processors designed from localized, highly regular data dependency graphs (DDGs). The specification, in the form of a DDG, is viewed as a maximally parallel circuit. The implementation, on the other hand, is a (partially) serialized circuit. Since these circuits are not equivalent from an automata-theoretic viewpoint, we define the correctness of the implementation against the specification to mean that a certain relation (called the β-relation) holds between the two. We use a compositional approach to decouple the verification of the control circuitry from that of the data path, thereby gaining efficiency. An array processor in isolation may not have a definite flow of control, because control may reside in the data stream. Therefore, for the purpose of verification, we construct an auxiliary machine, which keeps a timing reference and generates control signals abstracted from a typical data stream. Sufficient correctness conditions are expressed as past-tense computation tree logic (CTL) formulae and verified by CTL model-checking procedures. Experimental results of the verification of a matrix multiplication array and a Gaussian elimination array are presented.

System and chip synthesis must evaluate candidate Register-Transfer (RT) architectures with respect to finished physical designs. Current RT level cost measures, however, are highly simplified and do not reflect the real physical disign. Complete physical design, on the other hand, is quite costly, and infeasible to be iterated many times. In order to establish a more realistic assessment of layout effects, we propose a new layout model which efficiently accounts for the effects of wiring and floorplanning on the area and performance of RT level designs, before the physical design process. Benchmarking has shown that our model is quite accurate.

This paper describes an overview of wireless communications based on fiber-radio technologies from the viewpoint of system applications, particularly in the area of microcell radio systems. Feasible fiber-radio networks design are detailed in order to increase system performance and cost effectiveness. The benefits of the evolving fiber-radio microcell system are discussed with a spectral delivery scheme to meet traffic demands. Foreseeable electronic and optic technologies are reviewed in light of the key parameters to optimize the overall system. This strategy will play a role in broadband and flexible networks.

Corresponding to the development of B-ISDN, integrated services for data, voice, etc. are imperatively required for the so called third generation wireless communication networks. In this paper, I-ISMA (Idle Signal Multiple Access for Integrated services) is proposed to transmit integrated voice and data traffic from dispersed terminals to a base station. In the system, data packets and the first packets of talkspurts of conversational speeches are transmitted using ISMA protocol over a shared channel while subsequent packets of talkspurts are sent with time reservation technique. The channel capacity of I-ISMA is evaluated and compared with that of PRMA. The region in which I-ISMA has larger capacity than PRMA is figured out. Generally speaking, I-ISMA has larger capacity than PRMA when the duration for transmitting and detecting an idle signal is not too long and the channel is not too congested by the reserved voice transmissions. When we concern real time voice transmission, delay is one of the most important performance measures. Only is a qualitative discussion on delay performance given here. The quantitative evaluation is obtained by the dynamic analysis in our succeeding paper.

A quantum interconnection scheme by controlling the Coulomb interaction between ballistic electrons is proposed in which 2DEG (2 dimensional electron gas) plays the role of an interconnection medium. This concept brings up new possibilities for the interconnection approach in various fields such as parallel processing, telecommunications switching, and quantum functional devices. Cross-over interconnection, address collision, and address selection in a quantum information network system were analyzed as the first step. The obtained results have shown that the interconnection probability can be controlled by the velocity and timing of the ballistic electron emission from the emitter electrode. The proposed interconnection scheme is expected to open up a new field of quantum effect integrated circuits in the 21st century.

This paper proposes a new subscriber distribution method called FTTA (Fiber To The Area), which uses millimeter-wave radio band to connect subscribers with base station and optical fiber to connect base station with control station in order to obtain broad-band transmission. Usually two main causes of signal degradation, i.e., rainfall attenuation on radio channel and intermodulation distortion on optical channel are considered in this system. Taking into considerations of these two factors, we analyze the available capacity of FTTA system for various 22nQAM modulation levels. The analysis clarifies that there exists an optimum modulation level that can maxize the available capacity, and AGC circuit in the base station is useful to compensate the rainfall attenuation. It is shown that 18.0Gbps is available under the optimum modulation method of the 64QAM with AGC and 12.0Gbps under the 16QAM without AGC when 20 carriers are used.

Redundancy is introduced by sampling a bandlimited signal at a higher rate than the Nyquist rate. In the cases of erasures due to fading or jamming, the samples are discarded. Therefore, what we get at the output of the receiver is a set if nonuniform samples obtained from a uniform sampling process with missing samples. As long as the rate of nonuniform samples is higher than the Nyquist rate, the original signal can be recovered with no errors. The sampling theorem can be shown to be equivalent to the fundamental theorem of information theory. This oversampling technique is also equivalent to a convolutional code of infinite constraint length is the Field of real numbers. A DSP implementation of this technique is through the use of a Discrete Fourier Transform (DFT), which happens to be equivalent to block codes in the field of real numbers. An iterative decoder has been proposed for erasure and impulsive noise, which also works with moderate amount of additive random noise. The iterative method is very simple and efficient consisting of modules of Fast Fourier Transforms (FFT) and Inverse FFT's. We also suggest a non-linear iterative method which converges faster than the successive approximation. This iterative decoder can be implemented in a feedback configuration. Besides FFT, other discrete transforms such as Discrete Cosine Transform, Discrete Sine Transform, Discrete Hartley Transform, and Discrete Wavelet Transform are used. The results are comparable to FFT with the advantage of working in the field of real numbers.

Gamma(γ)-ray irradiation effects have been investigated on three types of low-noise HEMTs, AlGaAs/GaAs conventional HEMT (conv. HEMT), AlGaAs/InGaAs pseudomorphic HEMT (P-HEMT) and InAlAs/InGaAs/InP HEMT (InP-based HEMT). The dose of irradiated γ-rays ranges from 1105 to 1108 rad. DC and RF characteristics of each type of HEMT are measured before and after irradiation and the parameter changes are investigated. For conv. HEMT and P-HEMT, no degradation of DC parameter is observed up to 108 rad, while noise figure (NF) at 12 GHz remains constant up to 107 rad and degrades by 0.1 dB at 108 rad. The InP-based HEMT shows IDSS and gm increase by about 10% at a dose of 108 rad and its NF at 18 GHz lowers gradually with the radiation dose. It has been found that the radiation hardness is greater than 107 rad for all types of HEMTs and over a hundred years of life can be expected against γ-ray irradiation in the space environment.

This paper summarizes basic system design for an optical fiber feeder for microcellular mobile communication systems. The optical feeder enables compact and low cost base stations, easy radio channel control and flexible mobile communication systems. Basic transmission characteristics are investigated through optical transmission experiments. By using these results, feeder performance is estimated and optimal system parameters are designed.

Reducing communication complexity is a viable approach to multilevel logic synthesis. A communication complexity based approach was proposed previously. In the previous works, only disjoint input decomposition was considered. However, for certain types of circuits, the circuit size can be reduced by using overlapped decomposition. In this paper, we consider overlapped decompositions. Some design issues for overlapped decompositions such as detecting globals" and deriving subfunctions are addressed. Moreover, the Decomposition Don't Cares (DDC) is considered for improving the decomposed results. By using these techniques together, the area and delay of circuits can be further minimized.

Acceleration techniques have been incorporated into the generalized method of characteristics (GMC) to perform transient analysis of uniform transmission lines, for the special case when the transmission lines are driven by digital signals. These techinques have been proved to improve the simulation speed to a great extent when the analysis is carried out using iterative waveform relaxation method. It has been identified that the load impedance connected to the transmission line has a bearing on the efficiency of one of these acceleration techniques. Examples of an RLCG line terminated with linear loads as well as nonlinear loads are given to illustrate the advantage of incorporating these acceleration techniques.

Fiber-optic microcellular system has been studied actively as an excellent system for solving the equipment cost problems in microcellular systems. However, the occurrence of intermodulation distortion (IMD) arising from the nonlinearity of the laser diode used for E/O conversion which degrades the transmission quality is a serious problem in this system. In this paper, we propose a new frequency switching/IM3 reduction method, which dynamically reassigns the carrier frequencies to minimize the carrier to IMD power ratio under the hostile environment with time-varying received carrier strength, and analyze the performance improvements by the proposed method. The improvements obtained both for the worst value of the overall CNR and for the overall CNR in a specific user are numerically made clear. It is also shown that if the interval between frequency reassignings is set less than one second, a sufficient improvement in the overall CNR is achievable.

We have achieved the room temperature cw lasing operation of GaInAsP/InP surface emitting lasers for the first time. By employing a buried heterostructure with 1.3 µm range active region and a MgO/Si heat sink mirror, cw operation was obtained up to 14 with the threshold current of 22 mA.