In this paper, we present a method to analyze the steady-state performance of a complex coefficient adaptive IIR notch filter which is useful for the rejection of multiple narrow-band interferences from broad-band signals in quadrature phase shift keying (QPSK) spread-spectrum communication systems. The adaptive notch filter based on the simplified gradient algorithm is considered. Analytical expressions have been developed for the conditional mean and variance of notch filter output. The signal-to-noise ratio improvement factor is also obtained from which the validity of the use of the notch filter can be concluded. Finally, the results of computer simulations are shown which confirm the theoretical predictions.

In this paper, we propose a new consolidation algorithm called the Selective Backward Resource Management (BRM) cell Feedback (SBF) algorithm. It achieves a fast response and low consolidation noise by selectively forwarding BRM cell from the most congested branch to the source instead of waiting from all branches. Mathematical models are derived to quantitatively characterize the performance, i.e. the response time and ACR of the source, of SBF and previously proposed algorithms. The interoperation of consolidation algorithms in point-to-multipoint available bit rate (ABR) is investigated. We address response time, consolidation noise and the effect of asymmetrical round trip delay (RTD) from branch point to destinations aspects. All combinations of four different consolidation algorithms are interoperated in both local/metropolitan area network (LAN/MAN) and wide area network (WAN) configuration. By a simulation method, we found that the consolidation algorithm used at the uppermost stream branch point, especially in WAN configuration, plays an important role in determining the performance of the network. However, consolidation algorithm used at the lower stream branch point affects the network performance insignificantly. Hence, in order to achieve a good and effective performance of the consolidation algorithms interoperated network, a fast response with low consolidation noise algorithm should be used at the uppermost stream branch point and a simple and easy to implement algorithm should be used at the lower stream branch point.

In this paper, a new family of interconnection networks which we call the Incrementally Extensible Twisted Cube (IETQ) is proposed. The topology of this network is a novel generalization of the twisted cube. It inherits all the merits but without the limitations owned by a twisted cube. First, this proposed IETQ is incrementally extensible and can be adapted for use in any number of nodes; therefore, this network is particularly well suited for the design of a distributed communication network with an arbitrary number of nodes. Second, the vertex connectivity of IETQ is n. Measured by this vertex connectivity, we demonstrate that this network is optimally fault-tolerant . And it is almost regular, because the difference between the maximum and minimum degree of any node in an IETQ is at most one. A shortestpath routing algorithm for IETQ is proposed to generate path for any given pair of vertices in the network. Third, comparing with most of the other competitors, the diameter of this IETQ network is only half in size. This low diameter helps to reduce the internode communication delay. Moreover, IETQ also possesses the property of a pancyclic network. This attractive property would enable us to map rings of any length into the proposed network.

It is known that MUSIC and ESPRIT algorithms can estimate simultaneously both the instantaneous Direction of Arrival (DOA) and the instantaneous Angular Spread (AS) in multiple scattering environments. These algorithms use the Extended Array Mode Vector (EAMV) with complex angle. The previous work evaluated the performance of those algorithms by comparing the estimated DOA and the estimated AS with the DOA and the AS given in the EAMV, which uses the first-order approximation. Thus, this evaluation method has not clearly reflected the estimation accuracy of MUSIC and ESPRIT. This paper presents the joint estimation performance of MUSIC and ESPRIT by introducing the criteria for evaluation. For this, the spatial signature (SS) is reconstructed from the estimates of the DOA and the AS, and compared to the true SS in the meaning of data fitting.

This letter is concerned with a performance analysis of a VPG DS/CDMA acquisition system employing a reference filter based on the statistical evaluation of the decision threshold. The probabilities of detection and false alarm are derived, and the mean acquisition time is evaluated as a measure of the system performance. From the results, it is shown that in the performance analysis of the parallel acquisition system with reference filtering, the statistical evaluation of the decision threshold seems more appropriate than the approximation of the decision threshold adopted in other acquisition schemes.

We consider equalizer initialization problems when the transmitted symbol rate is higher than the available channel bandwidth. In this case, the coefficients of an adaptive equalizer in the receiver can be updated only once per a predefined symbol period, requiring unacceptably long training time. The training time can be reduced significantly if the equalizer begins the training process from a properly initialized condition. In this letter, a fast initialization method is analytically designed for a minimum mean squared error (MMSE) type equalizer. Finally, the initialization performance is verified by computer simulation.

This paper considers combining receptions with multiple receive antennas for space time coded MPSK signals over correlated Rayleigh fading channels. For the system with dual-antenna at receiver, a new transform is proposed, which can convert the correlated fading signals into uncorrelated ones. With the results obtained by using the proposed transform, the equivalent selective combining (SC) reception and maximum likelihood (ML) reception are presented. Theoretical analysis shows that ML reception has better performance than SC reception in terms of bit error rate. For the system with triple antenna at receiver, the simulation results are presented by using Monte Carlo method. All the results show that compared to using a receive antenna, a considerable signal to noise ratio gain can be obtained by using multiple receive antennas when the correlation coefficients among the receive antennas is not too high.

A novel power spectral density accumulation (PSDA) method for estimating the bandwidth of the clutter spectra is proposed, based on a priori knowledge of the shape of the clutter spectra. The comparison of the complexity and the performance between the PSDA method and the general ones is presented. It is shown that the PSDA method is effective for the short-time clutter data in the practical application.

Gallager has defined an ensemble of regular low density parity check (LDPC) codes for deriving the ensemble performance of regular LDPC codes. The ensemble is called the Gallager ensemble. In this paper, we define a new ensemble of LDPC codes, called extended Gallager ensemble, which is a natural extension of the Gallager ensemble. It is shown that an extended Gallager ensemble has potential to achieve larger typical minimum distance ratio than that of the original Gallager ensemble. In particular, the extended Gallager ensembles based on the Hamming and extended Hamming codes have typical minimum distance ratio which is very close to the asymptotic Gilbert-Varshamov bound. Furthermore, decoding performance of an instance of an extended Gallager ensemble, called an extended LDPC code, has been examined by simulation. The results show good block error performance of extended LDPC codes.

This letter investigates sidelobe levels of a two-bit digital phased array composed of a small number of elements. Among several phase shifter designs applicable to phased arrays, a two-bit design needs the least number of circuit elements so that the development and manufacturing need the lowest cost. Now the following questions arise. Is a two-bit phased array practical? How low can its sidelobe level be reduced? To answer the questions, three methods are tried to reduce the sidelobe level of a uniformly-excited linear array of isotropic elements. The methods are the quadratic-phase feed method, the partially randomizing method of periodic phase errors, and the genetic algorithm (GA) approach. Among the methods, the quadratic-phase feed method provides the lowest sidelobe level around -12.5 dB - -13.2 dB in the steering angles from 0 to 48 degrees for a 21-element, half-wavelength spacing array, and -11.2 dB - -13.0 dB in the steering angles from 0 to 30 degrees for an 11-element, 0.6-wavelength spacing array. Although it depends on the system requirement, these values would be acceptable in some applications, hence a two-bit phased array designed properly may be practical in an actual system.

A new test structure, which has a 0.5 µm line and space polysilicon pattern of which center is aligned on the MOSFET's gate center, is proposed for hot-carrier-induced photoemission analysis in subquarter micron devices. The photoemission-intensity profiles were measured using the photoemission microscope with a liquid N2 cooled CCD imager. We successfully measured a peak position of photoemission intensity from the center of MOSFET's gate with a spatial resolution sufficiently less than 24 nm at the microscope magnification of 1000. The test structure is useful to study the photoemission effects in semiconductor devices.

In this paper, we propose a new approach to the adaptive MLSE receiver, which is based on the delay estimation of the paths in the fading channel. The path delays are estimated by using the known training sequence, and based on this estimation the proposed MLSE tracks not the T-spaced equivalent channel but the variations of each path in the frequency-selective channel directly. It will be shown through computer simulations that the proposed MLSE can improve the performance of the conventional MLSE receivers, when the number of paths is small.

This paper addresses a classic question about whether transmit power control (TPC) can increase the spectrum efficiency of a TDMA system and an FDMA cellular system as in the case of a DS-CDMA cellular system. Two types of TPC schemes are considered; one is slow TPC that regulates the distance dependent path loss and shadowing loss, while the other is fast TPC that regulates multipath fading as well as path loss and shadowing loss. In addition to TPC, antenna diversity reception is considered. The allowable interference rise factor χ, which is defined as the interference plus background noise-to-background noise power ratio, is introduced. The simple expressions for the signal-to-interference plus background noise power ratio (SINR) at the diversity combiner output using maximal-ratio combining (MRC) are derived to obtain the reuse distance by computer simulations. The impact of joint use of TPC and antenna diversity reception on the spectrum efficiency is discussed. It is found that the joint use of fast TPC and antenna diversity is advantageous and larger spectrum efficiency can be achieved than with no TPC. On the other hand, the use of slow TPC is found advantageous only for small values of standard deviation of shadowing loss; however, the improvement in the spectrum efficiency is quite small.

In this paper the authors propose a method for designing the Virtual Private Network (VPN) that guarantees a strict Quality of Service (QoS) over IP networks. The assumed QoS metric is PLP (Packet Loss Probability), and it is guaranteed probabilistically by the provision of an appropriate equivalent bandwidth. We consider two network architectures for constructing VPN, the customer pipe scheme and the Hose scheme, and we present an analytic model to compute the amount of the required bandwidth for the two schemes. Finally, we investigate the validity of the proposition via numerical experiments.

This letter treats computational complexity of bounded asymmetric choice (AC) net. AC net is a subclass of Petri net that properly includes the class of well-known extended free choice net. It is shown that satisfiability problem of Boolean expressions is polynomial time reducible to liveness problem of bounded AC nets. This implies that the problem is NP-hard.

This paper deals with a cellular system based on Code Division Multiple Access (CDMA) and investigates the performance of Signal-to-Interference (SIR)-based Closed Loop-Power Control (CLPC) schemes taking into account errors on the feedback channel that conveys the power control command from the base station to the mobile terminals. We have evaluated both the distribution of the received power at the base station and the optimum control step size that minimizes the Control Error (CE) standard deviation, a useful measure of the CLPC performance. The impact of interference variations has been deeply investigated for different mobility scenarios and for different feedback channel error conditions.

M-convex functions have various desirable properties as convexity in discrete optimization. We can find a global minimum of an M-convex function by a greedy algorithm, i.e., so-called descent algorithms work for the minimization. In this paper, we apply a scaling technique to a greedy algorithm and propose an efficient algorithm for the minimization of an M-convex function. Computational results are also reported.

This paper describes a kind of 3D graphics geometry processor architecture for high performance/cost 3D graphics, its application to a real chip, and the results of performance evaluation. In order to establish the high speed geometry processing, dedicated hardware is introduced for accelerating special operations, such as power calculations, clip tests, and program address generation. The dedicated hardware consists of a modified floating-point multiplier in a four-parallel SIMD processing core, a clip test unit, and an internal program address generation scheme optimized to geometry processing mode. Special instructions corresponding to the dedicated schemes are also defined and added. The parallelism of the SIMD core is adjusted to a geometry data structure. Employing dedicated hardware and software significantly accelerates these complicated operations deriving from geometry algorithms. The collaboration of the hardware design and the software design considerably reduces instruction step counts for complex processing. Two kinds of program are dealt with in the proposed architecture. One is a special case program containing few conditional jump instructions, and the other is a general case program combining many program routines. The proposed program address generation scheme provides the automatic selection of a program optimized to each geometry processing mode. By this program address generation scheme and the program types, the frequency of the conditional jump operations, that usually disturb a pipeline operation, are minimized under practical use. Additionally, the programmable design and this program address generation scheme facilitate the load balancing of the geometry calculations with the CPU. A programmable geometry processor was fabricated by using 0.35 µm CMOS process as an application of this architecture. One point three million transistors are integrated in a 11.84 12.07 mm2 die. The increase of the gate counts for all the dedicated hardware is a total of 24 K gates and is approximately only a 7.4% increase of the total gate count. This chip operates at 150 MHz, and achieves the processing performance of 5.8 M vertex/sec. The result shows that the proposed programmable architecture (ESIMD: Enhanced SIMD) is 2.3 times more cost effective than a programmable geometry LSI reported previously.

In this paper, we present the division algorithm (DA) for the computation of b=c/a over GF(2m) in two aspects. First, we derive a new formulation for the discrete-time Wiener-Hopf equation (DTWHE) Ab = c in GF(2) over any basis. Symmetry of the matrix A is observed on some special bases and a three-step procedure is developed to solve the symmetric DTWHE. Secondly, we extend a variant of Stein's binary algorithm and propose a novel iterative division algorithm EB*. Owing to its structural simplicity, this algorithm can be mapped onto a systolic array with high speed and low area complexity.

Most conventional studies on self-stabilization have been indifferent to the vulnerability under convergence. This paper investigates how mutual exclusion property can be achieved in self-stabilizing rings even for illegitimate configurations. We present a new method which uses a state with a large state space to detect faults. If some faults are detected, every process is reset and not given a privilege. Even if the reset values are different between processes, our protocol mimics the behavior of Dijkstra's unidirectional K-state protocol. Then we have a fast and safe mutual exclusion protocol. Simulation study also examines its performance.