Bluetooth wireless technology is short-range and low cost wireless interface, which is optimized for mobile devices providing very low power consumption. However, a scope of Bluetooth application areas is not limited to mobile devices but expands to fixed equipment as well. Not only Bluetooth functions as cable replacement but also it can establish ad-hoc wireless network for voice and data simultaneously. Due to nature of 2.4 GHz ISM frequency band, Bluetooth is equipped with various data packets selection to minimize throughput degradation. Also, to secure connecting to the right target devices, Bluetooth includes authentication and encryption for communication links.

Developments in new frequency bands for wireless communications make a broadband channel for new services possible. Great effort has been made researching and developing broadband wireless communication in the 60-GHz millimeter-wave band since the early 1990s. In this paper, we design an ATM (asynchronous transfer mode)-based indoor millimeter-wave wireless local area network (WLAN) that supports multimedia transmissions and focus on the wireless access topic for implementation of wireless ATM. We propose an integrated multimedia transmission protocol, based on the MAC (medium access control) protocol, called RS-ISMA (reservation-based slotted idle signal multiple access). It supports CBR (constant bit rate), VBR (variable bit rate), ABR (available bit rate) and UBR (unspecified bit rate) transmissions and provides QoS (quality of service)-dependent adaptive retransmissions. An RS-ISMA-based prototype full-duplex indoor high-speed WLAN in the 60-GHz band was developed.

A blind technique for adaptive signal suppression in multipath DS-CDMA communication channels for the downlink is considered. Its performance is degraded when mismatch problem occurs when multipath components arrive with fractional-chip delays. In order to surmount this problem, Multiple Finger Expansion Optimal Filter (MFE-OF) was recently proposed to estimate the received desired signal subspace using fractionally delayed despreading fingers. However, MFE-OF requires much computational complexity for good performance. In this paper, a modification to the MFE-OF is introduced by utilizing decision-directed steering vector to reduce the number of fingers required by MFE-OF down to that of the conventional OMF-RAKE without much performance degradation. This modified receiver is called Decision-Directed Optimal Filter (DDOF). Computer simulation validates the effectiveness of the new receiver to increase the downlink capacity of DS-CDMA systems.

We present calculations of the linear-response conductance of a SiGe based single-electron transistor (SET). The conductance and the discrete charging of the quantum dot are calculated by free-energy minimization. The free-energy calculation takes the discrete level-spectrum as well as complex many-body interactions into account. The tunneling rates for tunneling through the source and lead barrier are calculated using Bardeen's transfer Hamiltonian formalism. The tunneling matrix elements are calculated for transitions between the zero-dimensional states in the quantum dot and the lowest subband in the one-dimensional constriction. We compare the results for the conductance peaks with those from calculations with a constant tunneling rate where the shape of the peaks is only due to energetic arguments.

Thin films of carbon (C)-sulfur (S) compound were formed by plasma CVD (PCVD) at the special chemical condition. The reactor has a parallel plate electrode system and was operated at a discharge frequency of 13.56 MHz with using a mixture gas of argon (Ar), methane (CH4) and SF6. The deposition was performed on a substrate placed on the grounded electrode. Atomic composition of the film was observed to depend on the gas mixture ratio. The sulfur atom density was increased up to 30% with using a mixture gas at a pressure of 0.1 Torr and at a flow rate of 20, 20 and 50 SCCM for Ar, CH4 and SF6, respectively. It was expected that the C-S compounds were deposited under the condition of F atom elimination by forming HF.

In this paper, the LVQ (Learning Vector Quantization) model and its variants are regarded as the clustering tools to discriminate the natural seismic events (earthquakes) from the artificial ones (nuclear explosions). The study is based on the six spectral features of the P-wave spectra computed from the short period teleseismic recordings. The conventional LVQ proposed by Kohenen and also the Fuzzy LVQ (FLVQ) models proposed by Sakuraba and Bezdek are all tested on a set of 26 earthquakes and 24 nuclear explosions using the leave-one-out testing strategy. The primary experimental results have shown that the shapes, the number and also the overlaps of the clusters play an important role in seismic classification. The results also showed how an improper feature space partitioning would strongly weaken both the clustering and recognition phases. To improve the numerical results, a new combined FLVQ algorithm is employed in this paper. The algorithm is composed of two nested sub-algorithms. The inner sub-algorithm tries to generate a well-defined fuzzy partitioning with the fuzzy reference vectors in the feature space. To achieve this goal, a cost function is defined as a function of the number, the shapes and also the overlaps of the fuzzy reference vectors. The update rule tries to minimize this cost function in a stepwise learning algorithm. On the other hand, the outer sub-algorithm tries to find an optimum value for the number of the clusters, in each step. For this optimization in the outer loop, we have used two different criteria. In the first criterion, the newly defined "fuzzy entropy" is used while in the second criterion, a performance index is employed by generalizing the Huntsberger formula for the learning rate, using the concept of fuzzy distance. The experimental results of the new model show a promising improvement in the error rate, an acceptable convergence time, and also more flexibility in boundary decision making.

All the existing scheduling algorithms order the instructions of the program in such a way that it can be executed in minimal time only for one fixed number of processors. In this paper we propose a new scheduling method, called Parallelism-Independent Scheduling Method, which enables the execution of the scheduled program on parallel computers with any degree of parallelism in near-optimal time. We propose three Parallelism-Independent algorithms, which have the following phases: obtaining a parallel schedule by using a list scheduling heuristics, optimization of the parallel schedule by rearranging the tasks in each level, so that they can be executed efficiently with different degrees of parallelism, serialization of the parallel schedule, and insertion of markers for the parallel execution limits. The three algorithms differ in their optimization phase. To prove the efficiency of our algorithms, we have made simulations with random directed acyclic graphs with different size and degree of parallelism. We compared the results in terms of schedule length to those obtained using the Critical Path Algorithm separately for each degree of parallelism.

Efficient content-based retrieval of complex images is a challenging task since the detected object may appear in various scale, rotation and orientation with a wide variety of background colors and forms. In this paper, we propose a novel representation of objects with multiple colors, the spatial neighborhood-adjacency graph(SNAG), which can serve as a basis for detecting object by color contents from the candidate image. The SNAG consists of a set of main-vertices and two sets of edges. Each main-vertex represents a single color region of multi-colored object, and edges are divided into two classes: Neighborhood edges representing neighborhood relationship between two main-vertices with similar color, and adjacency edges representing adjacency relationship between a main-vertex and another vertex with different color. By investigating whether SNAG of object image is an isomorphic subgraph of SNAG of a candidate image, we can determine whether the similar object exists in the candidate image. In addition, we have also applied the proposed approach to a range of different object detection problems involving complex background, and effectiveness has been proved.

For a wireless communication system to work effectively without interference, the electromagnetic environment needs to be controlled. We experimentally and analytically investigated the requirements for controlling the electrical field strength and delay spread so as to achieve the best communication without electromagnetic interference in selected regions for a 2.4-GHz-band wireless LAN system. To control the coverage, partitions were placed around desks in a test environment and covered on the inside with electromagnetic absorbing board from the top of the desks to the top of the partitions; four indoor environments that combined one of two wall-material types and one of two partition heights were used. The transmission loss and delay spread were measured, then calculated using ray tracing to verify the effectiveness of using ray-tracing calculation. The throughput and BER characteristics were measured for the same environments to clarify the requirements for controlling the coverage. We found that covered and uncovered regions could be created by using partitions with absorbing boards and that the delay spread must be less than 15 ns and the received-signal must be stronger than -75 dBm for a region to be covered. We verified that the delay spread can be calculated to within 5 ns and the received-signal level can be calculated to within 5 dB of the measured data by using ray tracing. Therefore, ray tracing can be used to design antenna positions and indoor environments where electromagnetic environments are controlled for 2.4-GHz-band wireless LAN systems.

The interaction between the human eye and electromagnetic (EM) waves in the ISM (industrial, scientific, and medical) frequency bands is investigated with the use of the finite-difference time-domain (FDTD) method. In order to assess possible health hazards, the specific absorption rates (SARs) are calculated and compared with the recommended safety standards. In particular, we calculate temperature rises in the human eye to assess the possibility of microwave-induced cataract formation. The results show that the maximum values of averaged SARs are less than the standard levels. In addition, we observed what is called the 'hot spot' in the region of eye humor at 2.4 GHz but not at 900 MHz and 5.8 GHz. Furthermore, the maximum temperature rise due to the incident EM power density of 5.0 mW/cm2, which is the MPE (maximum permissible exposure) limit for controlled environments, has been found to be at most 0.26 at 5.8 GHz, which is small compared with the threshold temperature rise 3.0 for cataract formation.

Design of wireless communications systems with a transmission rate of 6 and 10 Mbit/s is presented for the 2.4 GHz Japanese ISM band, in which a spread spectrum technique named "CFO-SS (Carrier Frequency Offset-Spread Spectrum)" scheme is employed. In the CFO-SS system, a single PN code is commonly assigned to all the synchronized multiplexed carriers, and the frequency separation between carriers is determined by the transmission rate of each carrier. To realize the CFO-SS system, a timing acquisition and tracking scheme, an important part of the design, is presented first. Next, bit and packet error performance is investigated under severe multipath environments with/without a RAKE receiver. Degradation by channel bandwidth limitations, frequency inaccuracy of the hardware and co-channel interference (CCI) is also investigated by computer simulation. Simulation results presented confirmed sufficient performance of the CFO-SS system for wireless LAN systems using the 2.4 GHz ISM band.

In this paper, we will present a study of the time-dependence effect in alumite perpendicular media at different thicknesses. Important parameters of the time-dependence effect such as magnetic viscosity and activation volume are investigated. Viscosity as a function of applied field (viscosity curve) exhibits a short plateau at a low field and then decreases monotonously with increasing field. After correcting for the demagnetizing field, the shape of the intrinsic viscosity curves changes to the well-known shape of the viscosity curve of in-plane media, i. e. , they have a peak near Hc. The intrinsic viscosity curves obtained from the experiments were fitted to an analytical model by Chantrell et al., from which, we found that the effective switching volumes obtained by fitting are much smaller than the column volumes, indicating that the reversal mechanism is incoherent.

Wireless communication systems are affected by several factors in the indoor environment. The complexity of this environment, however, has hampered the development of methods for analyzing it. Reported here is our investigation of the relationship between the propagation characteristics and performance of a 2.4-GHz ISM-band wireless LAN in various indoor environments. Our objective was to develop guidelines for designing ideal indoor environments for wireless LANs. A booth constructed of a ceiling, floor, and wall materials that could be changed was used for our investigation. The transmission loss and delay spread were measured for four environments; they were calculated by using a ray-tracing method to verify the effectiveness of the ray tracing calculation. The throughput and BER characteristics were measured for the same environments. The following results were obtained. (1) The transmission loss and delay spread could be estimated by using this ray tracing method because the deviations between the calculated and measured data were within 5 dB for the transmission loss and within 10 ns for the delay spread. (2) Reflections from the walls caused a serious interference problem: throughput was 0.0 at more than 30% of the positions along the center line of the booth when the walls were constructed of high-reflection-coefficient material. (3) The throughput and BER were closely correlated with the delay spread; the number of positions meeting a certain throughput was estimated by the method based on the delay spread calculated using the ray tracing method. It was within 10% of the number measured. The results obtained can be used to design ideal indoor environments for 2.4-GHz ISM-band LAN systems.

This paper presents two competitive learning methods with the objective of avoiding the initial dependency of weight (reference) vectors. The first is termed the refractory and competitive learning algorithm. The algorithm has a refractory period: Once the cell has fired, a winner unit corresponding to the cell is not selected until a certain amount of time has passed. Thus, a specific unit does not become a winner in the early stage of processing. The second is termed the creative and competitive learning algorithm. The algorithm is presented as follows: First, only one output unit is prepared at the initial stage, and a weight vector according to the unit is updated under the competitive learning. Next, output units are created sequentially to a prespecified number based on the criterion of the partition error, and competitive learning is carried out until the ternimation condition is satisfied. Finally, we discuss algorithms which have little dependence on the initial values and compare them with the proposed algorithms. Experimental results are presented in order to show that the proposed methods are effective in the case of average distortion.

In 2001, the DEMETER micro-satellite will be launched to perform Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions. Its main scientific objective is related to the investigation of the ionospheric perturbations due to the seismic and volcanic activity. A system allowing an onboard identification and characterization of spatially and temporally coherent structures associated with the measurement of one or several electromagnetic wave field components is used. It is based on neural networks. The choice and training of the neural network are done on the ground from available waveforms. The parameters of the neural network system are then transmitted to the satellite. This reconfiguration process can be repeated whenever necessary during the space mission. Details about the functioning and coding optimization for DSP implementation is presented. The first function of this system which will be performed on the satellite DEMETER is the real-time identification and characterization of whistler phenomena. An application to the analysis of such phenomena observed in data from the AUREOL-3 satellite is exposed.

This paper proposes a new design method of nonlinear filtering and fixed-point smoothing algorithms in discrete-time stochastic systems. The observed value consists of nonlinearly modulated signal and additive white Gaussian observation noise. The filtering and fixed-point smoothing algorithms are designed based on the same idea as the extended Kalman filter derived based on the recursive least-squares Kalman filter in linear discrete-time stochastic systems. The proposed filter and fixed-point smoother necessitate the information of the autocovariance function of the signal, the variance of the observation noise, the nonlinear observation function and its differentiated one with respect to the signal. The estimation accuracy of the proposed extended filter is compared with the extended maximum a posteriori (MAP) filter theoretically. Also, the current estimators are compared in estimation accuracy with the extended MAP estimators, the extended Kalman estimators and the Kalman neuro computing method numerically.

A GaAs linear power amplifier operating with a single 3-V supply has been developed for 5.8-GHz ISM band applications. Two kinds of refractory WNx/W self-aligned gate MESFETs, a P-pocket MESFET and an asymmetric MESFET with a buried p-layer (BP- MESFET ) have been compared in terms of DC characteristics, small signal characteristics and power performances at 5.8 GHz. To obtain both high gain and high efficiency in the case of single 3-V supply operation at 5.8 GHz, we used a highly efficient and linear P-pocket MESFET for the output-stage power FET and a high-gain asymmetric MESFET with a buried p-layer (BP- MESFET ) for the driver-stage FET. The bias condition for 1-mm output-stage P-pocket MESFET was set near class-AB, so as to obtain sufficient output power with high PAE. The two-stage power amplifier MMIC module which can include all matching and biasing circuits, has been designed and fabricated. The amplifier exhibits a high power gain of 17.9 dB and a high power-added efficiency of 25.7% with a sufficient output power of 18.7 dBm at the 1-dB compression point. This self-aligned gate GaAs MESFET technology is promising for near-future 5.8-GHz applications, because of such good power performance and good mass-producibility.

We propose a learning algorithm for self-organizing neural networks to form a topology preserving map from an input manifold whose topology may dynamically change. Experimental results show that the network using the proposed algorithm can rapidly adjust itself to represent the topology of nonstationary input distributions.

The ATM Forum specifies several fairness criteria, thus the scheduling mechanisms should allocate enough bandwidth to each connection to achieve one of such fairness criteria. However, two fairness criteria (MCR plus equal share, maximum of MCR or Max-Min share) cannot be achieved by conventional scheduling mechanisms. In this letter, we have developed new scheduling mechanisms that achieve these fairness criteria. We also present simulation results to show that our mechanisms can allocate bandwidth fairly.

This research presents a novel analytic model to predict the instruction execution rate of superscalar processors using the queuing model with finite-buffer size and synchronous operation mode. The proposed model is also able to analyze the performance relationship between cache and pipeline. The proposed model takes into account various kinds of architectural parameters such as instruction-level parallelism, branch probability, the accuracy of branch prediction, cache miss, and etc. To prove the correctness of the model, we performed extensive simulations and compared the results with the analytic model. Simulation results showed that the proposed model can estimate the average execution rate accurately within 10% error in most cases. The proposed model can explain the causes of performance bottleneck which cannot be uncovered by the simulation method only. The model is also able to show the effect of the cache miss on the performance of out-of-order issue superscalar processors, which can provide an valuable information in designing a balanced system.