In the current digital mobile communication that is used in the micro cellular system, a Self-Organized Dynamic Channel Assignment (DCA) Method has been proposed to use frequencies effectively. However, its characteristics and operational matters have not been reported yet. This paper takes up the TDMA/TDD system used in the current PHS system and also evaluates the characteristics and operational matters of this method through the actual operational tests. In addition, this paper aims to propose a new DCA method in order to speed up the Channel Segregation and evaluates its effects through the actual operational tests.

This paper proposes and investigates optimum modulation assignment and band allocation scheme according to subband channel status for BST-OFDM system. The proposed system can adaptively optimize modulation assignment and band allocation according to the conditional parameter under independently fading subband channels. Specifically, in this paper only two optimization problems are treated in terms of modulation assignment. At first, an optimization criterion is a total Bit Error Rate (BER) subject to the constraint conditions of a desired total information bit rate under a fixed effective bandwidth. Another optimization problem is the maximization of a total information bit rate to satisfy a desired BER under a fixed effective bandwidth. Knowledge of the subband channel status is assumed to be updated by the feedback information from a receiver. This paper shows that the proposed system can overperform the conventional system in which all subbands employ the same modulation schemes in terms of BER. In addition, it is shown that the proposed system improves the overall information bit rate, which is not accomplishable in the conventional system.

Using moment generating function (MGF) of generalized selection combining (GSC) output signal-to-noise ratio (SNR), we derive closed-form expressions for average combined SNR at the output of GSC, which optimally combines the N largest out of L available diversity signals, over Nakagami-m fading channels for N = 2, 3 and L = 4. The Nakagami-m fading statistics on each diversity branch are assumed to be independent and identically distributed (i.i.d.). The average combined SNRs at the outputs of GSC receivers are also compared with the average combined SNRs at the outputs of conventional maximal ratio combining (MRC) and selection combining (SC).

A knowledge gap between network operators and system developers in Network Management System (NMS) construction has widened. This has been caused by an expansion of supported business processes and increasingly sophisticated network management functions. This gap makes system development costly and time consuming. Function development, led by operators, is a promising solution to the problems caused by the gap. This type of development should not require an operator to know how to develop NMS. Standard objects may be used to meet this requirement and save time and the cost of NMS construction. However, they are not sufficient to design functions supporting some tasks that are for providing custom services. In this paper, we propose a partial extension package, composed of several object classes. This package is attached to the standard objects to design a custom function. Information processing in a new function can be added, and easily modified, using this package. This package specifies states that invoke the information processing. It also includes objects that add new data without changing standard objects. It makes use of several design patterns in order to weaken coupling to the standard objects. We have applied this package to two programs. One plans maintenance tasks schedules, the other sets threshold values for quality of service. We made use of software metrics to measure their performance in terms of flexibility. The results show that the proposed package continues to make it possible to reuse the standard objects, and makes it easy to modify the behavior of a new function.

Precise and quick multi-beam forming including null control will be one of the key technologies for the future satellite communication systems utilizing SDMA (Space Division Multiple Access) and DOA (Direction of Arrival) estimation. In order to realize the precise multi-beam forming, calibration procedure is indispensable since there are several unavoidable factors that degrade the multi-beam patterns of the array. Particularly amplitude and phase imbalance between RF circuits needs to be calibrated frequently and quickly when the array system exists in changeable environment since the imbalance easily occurs due to thermal characteristics of each RF circuit. This paper proposes a simple and high-speed remote calibration scheme compensating for amplitude and phase imbalance among RF circuits of a transmitting adaptive array antenna onboard satellite. This calibration is conducted at a remote station such as a gateway station on the ground in the satellite communication system, by utilizing the received signal including the temporally multiplexed orthogonal codes transmitted from the array antenna onboard satellite. Since the calibration factors for all the antenna elements can be simultaneously obtained by the parallel digital signal processing, calibration time can be drastically reduced. The accuracy of this calibration is estimated by simulation. Simulation results show that the amplitude imbalance among RF circuits can be suppressed within the range from -0.5 dB to +0.25 dB for the initial imbalance ranging from -2 dB to +3.5 dB, phase imbalance can be suppressed within the range of -3 deg. to +3 deg. for the initial imbalance ranging from -120 or +180 deg. by this method. The amplitude and phase deviations among the elements can be suppressed within 0.36 dB and 2.5 degrees, respectively, in 80% of probability. Simulation results also show that this calibration method is valid under the relatively bad carrier-to-noise conditions such as -10 dB at the receiver. Good improvement of the multi-beam patterns by this calibration is shown under the low carrier-to-noise ratio condition.

It is necessary for anyone to be able to extract embedded index data without specific keys or secret information when index data are embedded into digital contents. In this paper, we propose a new data hiding technique for embedding index data into color images using wavelet transform. In our method, we prevent image quality from degrading by utilizing not specific keys but features of wavelet transform. The method extracts index data without specific keys and is tolerant of edge-enhancement, gamma correction, brightness conversion and lossy image compression such as JPEG compression.

A signaling system for a single-track railroad has been specified in CafeOBJ. In this paper, we describe the specification of arbitrary two adjacent stations connected by a single line that is called a two-station system. The system consists of two stations, a railroad line (between the stations) that is also divided into some contiguous sections, signals and trains. Each object has been specified in terms of their behavior, and by composing the specifications with projection operations the whole specification has been described. A safety property that more than one train never enter a same section simultaneously has also been verified with CafeOBJ.

In this paper, we propose an approach to test pattern generation for Speed-Independent (SI) asynchronous control circuits. Test patterns are generated based on a specified sequence, which is derived from the specification of a target circuit in the form of a Signal Transition Graph (STG). Since the sequence represents the behavior of a circuit only with stable states, the state space of the circuit can be represented as reduced one. A product machine, which consists of a fault-free circuit and a faulty circuit, is constructed and then the specified sequence is applied sequentially to the product machine. A fault is detected when the product machine produces inconsistency, i.e., output values of a fault-free circuit and a faulty circuit are different, and the sequentially applied part of the sequence becomes a test pattern to detect the fault. We also propose a test generation method using an undetectable fault identification as well as the specified sequence. Since the reduced state space is a subset of that of a gate level implementation, test patterns based on a specification cannot detect some faults. The proposed method identifies those faults with a circuit topology in advance. BDD is used to implement the proposed methods efficiently, since the proposed methods have a lot of state sets and set operations. Experimental results show that the test generation using a specification achieves high fault coverage over single stuck-at fault model for several synthesized SI circuits. The proposed test generation using a circuit topology as well as a specification decreases execution time for test generation with negligible cost retaining high fault coverage.

Access control plays an important role in the area of information security, which guarantees that any access to data is authorized. Hierarchical access control is a special access control model in distributed environment, in which each user protects his local data using a secret key; moreover, for any two related users ui and uj, ui can access uj's data if, and only if, ui's priority is higher than uj. Therefore, there should be a way for ui to obtain the secret key of uj if ui's priority is higher than uj. This paper presents an efficient solution to the problem. A special kind of function called secure filter is used as the building block of the proposed solution. In the solution, an authorized user can acquire correct keys efficiently and securely via secure filters. The proposed solution is also well-performed while inserting/deleting users, injecting/removing relations, and changing secret keys. Especially, only deleting users and removing relations will change some keys in the system, other operations can be performed freely without affecting other keys in the system; only secure filters need to be modified in these cases.

This paper presents a genetic algorithm for designing at minimum cost a two-connected network topology such that the shortest cycle (referred to as a ring) to which each edge belongs does not exceed a given maximum number of hops. The genetic algorithm introduces a solution representation in which constraints such as connectivity and ring constraints are easily encoded. Furthermore, a problem specific crossover operator that ensures solutions generated through genetic evolution are all feasible is also proposed. Hence, both checking of the constraints and repair mechanism can be avoided thus resulting in increased efficiency. Experimental evaluation shows the effectiveness of the proposed GA.

A new IDDQ testable design method is proposed for static CMOS PLA circuits. A testable PLA circuit of NOR-NOR type is designed using this method. It is shown that all bridging faults in NOR planes of the testable designed PLA circuit can be detected by IDDQ testing with 4 sets of test input vectors. The test input vectors are independent of the logical functions to be realized in the PLA circuit. PLA circuits are designed using this method so that the quiescent supply current generated when they are tested will be zero. Thus, high resolution of IDDQ tests for the PLA circuits can be obtained by using the testable design method. Results of IDDQ tests of PLA circuits designed using this testable design method confirm not that the expected output can be generated from the circuits but that the circuits are fabricated without bridging faults in NOR planes. Since bridging faults often occur in state-of-the-art IC fabrication, the testable design is indispensable for realizing highly reliable logic systems.

Our aim is to develop an intuitive sound designing interface for non-expert users. We propose editing sound by sound, which means using vocal mimicking as a "master" to transform the pitch and amplitude envelope. Our technique allows any user to easily and intuitively design sound because it requires no knowledge of acoustic features.

We demonstrate all-optical clock recovery at 160 Gbit/s by injection locking of a 10 GHz mode-locked laser diode. Effective locking in a range of 10 MHz is observed for average input powers around -10 dBm. The timing jitter is analyzed for data rates between 10 Gbit/s and 160 Gbit/s. Beyond 40 Gbit/s, the high frequency timing jitter of the slave laser becomes of prime importance and has to be taken into account since it degrades the performance of a subsequent receiver. Increasing power penalties are found, especially beyond 80 Gbit/s.

We consider methods for threshold RSA decryption among distributed agencies without any dealer or trusted party. The first solution is a combination of two techniques by [9] and [7] . It demonstrates the feasibility of combining the distributed key generation and the RSA secure function application. The second solution is another approach making the distributed key distribution simpler and alleviating a burden of each shareholder in comparison with the first scheme. The latter scheme is newly developed technique based on [9] and further inspired by Simmons' protocol-failure of RSA (we believe that it is very interesting that a "protocol failure attack" be turned into a constructive method). Our comparison between these two schemes indicates a new measure of the performance of a distributed cryptographic protocol that consists of multiple stages.

Multi-level divide-and-conquer (MDC) is a generalized divide-and-conquer technique, which consists of more than one division step organized hierarchically. In this paper, we investigate the paradigm of the MDC and show that it is an efficient technique for designing parallel algorithms. The following parallel algorithms are used for studying the MDC: finding the convex hull of discs, finding the upper envelope of line segments, finding the farthest neighbors of a convex polygon and finding all the row maxima of a totally monotone matrix. The third and the fourth algorithms are newly presented. Our discussion is based on the EREW PRAM, but the methods discussed here can be applied to any parallel computation models.

This paper conducts performance evaluation and performs simulation for a code division multiple access (CDMA) system when channel bands of multiple neighboring CDMA/DSSS are overlapped in time domain. It is assumed that all systems adopt direct-sequence spread-spectrum (DSSS) technique and are BPSK modulated by the different carrier frequencies. Automatic power control (APC) is also applied in the interfered system such that the receiver gets the same power from all users. Without loss generality, an additive white Gaussian noise (AWGN) channel is also assumed during analysis. In this paper, the analytic solution of the signal to noise ratio (SNR) is first derived in which both CDMA systems are modulated by different carrier frequencies. We have the results by simulation with Δ f = 0 and Δ f = 1 MHz, respectively. This analysis is good for general cases; and the results show an excellent computational performance. In particular, the result is very close to Pursley's result, when the systems have the same code length with no carrier difference.

We investigated the characteristics of optical duobinary signals in achieving high fiber input power transmission focusing on the idea of optimum residual dispersion equalization. We confirm through calculations and experiments that setting the total link dispersion at a non-zero value allows high fiber launched power (+18 dBm) and large dispersion tolerance (350 ps/nm) at 10 Gbit/s. We demonstrate repeaterless 250-km single mode fiber (SMF) transmission with a 10-Gbit/s optical duobinary signal. We also demonstrate high-speed complete optical duobinary coding and transmit synchronous digital hierarchy (SDH) frames over optical duobinary signals for the first time.

We investigated the characteristics of optical duobinary signals in achieving high fiber input power transmission focusing on the idea of optimum residual dispersion equalization. We confirm through calculations and experiments that setting the total link dispersion at a non-zero value allows high fiber launched power (+18 dBm) and large dispersion tolerance (350 ps/nm) at 10 Gbit/s. We demonstrate repeaterless 250-km single mode fiber (SMF) transmission with a 10-Gbit/s optical duobinary signal. We also demonstrate high-speed complete optical duobinary coding and transmit synchronous digital hierarchy (SDH) frames over optical duobinary signals for the first time.

In this paper, we consider the net assignment problem in the logic emulation system. This problem is also known as the board-level-routing problem. There are field programmable logic arrays (FPGAs) and crossbars on an emulator board. Each FPGA is connected to each crossbar. Connection requests between FPGAs are called nets, and FPGAs are interconnected through crossbars. We are required to assign each net to the suitable crossbar. This problem is known to be NP-complete in general. A polynomial time algorithm is known for a certain restricted case, in which we treat only 2-terminal nets. In this paper we propose a new polynomial time algorithm for this case.

We improve the algorithm to obtain the min-cut graph of a hyper-graph and show an application to the sub-network extraction problem. The min-cut graph is a directed acyclic graph whose directed cuts correspond one-to-one to the min-cuts of the hyper-graph. While the known approach trades the exactness of the min-cut graph for some speed improvement, our proposed algorithm gives an exact one without substantial computation overhead. By using the exact min-cut graph, an exhaustive algorithm finds an optimal sub-circuit that is extracted by a min-cut from the circuit. By experiments with the industrial data, the proposing method showed a performance enough for practical use.