This paper presents a ZCZ code which are combinedly used for spreading sequences and a synchronization symbol in quasi-synchronous CDMA systems using PSK, ASK or BFSK. Furthermore a simple matched filter is presented, which simultaneously calculates correlations with any sequences in the ZCZ code.

With development of wireless communication technologies, users are no longer satisfied with only a single service provided per time. They are willing to enjoy multiple services simultaneously. Therefore scheduling multiple services per user becomes quite important usability issue in the area of resource management. In this paper, the multiple-service scheduling problem is firstly formulated as an integrated optimization problem based on a utility function in homogeneous service systems. Due to its NP-hard characteristic, a set of low-complexity sub-optimal algorithms is therefore proposed and used to schedule resources for multiple services per user at the downlink of Orthogonal Frequency Division Multiplexing (OFDM) systems. The proposed algorithms are capable to effectively and efficiently distribute assigned resources among multiple services for one user. Moreover the utility of our algorithms is further extended from homogeneous service systems to heterogeneous service systems. And full exploitation of multi-user diversity gain is achieved while guaranteeing quality of service (QoS). The simulation results show that the proposed algorithm outperforms traditional algorithm in terms of system best effort service throughput and fairness criterion.

In this paper, we emphasize the need for data cleansing when clustering large-scale transaction databases and propose a new data cleansing method that improves clustering quality and performance. We evaluate our data cleansing method through a series of experiments. As a result, the clustering quality and performance were significantly improved by up to 165% and 330%, respectively.

In this paper, newly-found properties of the pseudo-ternary maximum-length shift register sequences (pseudo-ternary M-sequences) are described. In particular, the balance properties, the run-length distribution, the cross-correlation properties, and the decimation relationships are shown. The pseudo-ternary M-sequence is obtained by subtracting the one-chip shifted version from the {+1,-1}-valued M-sequence. Moreover, in this paper, performances of the direct sequence spread spectrum (DS/SS) system using the pseudo-ternary M-sequence are analyzed. In the performance evaluation, tracking error performance (jitter) and bit error rate (BER) performance that takes the jitter into account in DS/SS system with a pseudo-ternary M-sequence non-coherent DLL are evaluated. Using the pseudo-ternary M-sequence instead of the conventional M-sequences can improve the tracking error performance about 2.8 [dB]. Moreover, BER of the DS/SS system using the pseudo-ternary M-sequence is superior about 0.8 [dB] to that using the {+1,-1}-valued M-sequence.

This paper addresses the issue of Unconditional or Stochastic Maximum likelihood (SML) estimation of directions-of-arrival (DOA) finding using sensors with arbitrary array configuration. The conventional SML estimation is formulated without an important condition that the covariance matrix of signal components must be non-negative definite. An likelihood function can not be evaluated exactly for all possible sets of directions. First, this paper reveals that the conventional SML has three problems due to the lack of the condition. 1) Solutions in the noise-free case are not unique. 2) Global solution in the noisy case becomes ambiguous occasionally. 3) There exist situations that any local solution does not satisfy the condition of the non-negative definiteness. We propose an exact formulation of the SML estimation of DOA to evaluate an likelihood function exactly for any possible set of directions. The proposed formulation can be utilized without any theoretical difficulty. The three problems of the conventional SML are solved by the proposed exact SML estimation. Furthermore we show a local search technique in the conventional SML has a good chance to find an optimal or suboptimal DOA although the suboptimal solutions violate the condition of the non-negative definiteness. Finally some simulation results are shown to demonstrate good estimation properties of the exact SML estimation.

Two-dimensional (2D) communication is a novel physical communication form that utilizes the surface as a communication medium to provide both data and power transmission service to the sensor devices placed on the surface's top. In previous works, we developed 2D communication systems that utilize separated channels for data and power transmission. Though this assignment of different channels can achieve strong network performance, the sensor devices must be equipped with two or more interfaces to simultaneously receive the power and data signals, which significantly complicates and enlarges those devices. Moreover, when a channel is used for the power supply, it not only continually monopolizes the wireless frequency resource, it is also likely to cause interference with the other signal source in the case of the input power continually being sent out above a certain level. In this paper, we develop a novel 2D communication sensor system by using a single-carrier frequency for both power and data transmission, equipped with the wireless module for the two together in a compact body. To enable a sensor node that concurrently receives energy and data communication, we propose an enhancement scheme based on the IEEE802.15.4 MAC protocol standard. Through both computer simulation and actual measurement of the output power, we evaluate the performance of power supply and data transmission over the developed 2D communication sensor system.

Recently wireless sensor networks (WSN) has risen as one of the advanced candidate technologies in order to provide more efficient structure health monitoring (SHM) solution in construction sites. In this paper, we proposed WSN monitoring framework in building sites based on 3D visualization and Augmented Reality (AR) in mobile devices. The proposed system applies 3D visualization and AR technology to camera-enabled mobile devices in WSN environment in order to gather much more information than before. Based on the proposed system, we made an experiment to validate the effectiveness of 3D and AR mode using collected data in IEEE 802.15.4-based WSN.

In wireless sensor networks (WSNs), geographic routing algorithms can enhance the network capacity. However, in real WSNs, it is difficult for each node to know its physical location accurately. Geographic routing with location errors may produce serious problems such as disconnected links and data transmission delays. In this letter, we present an efficient location error compensation algorithm for the geographic routing. The proposed algorithm efficiently detects and corrects the location errors and significantly enhances the network performance of geographic routing in the presence of location errors.

Recently, novel full-diversity full-rate quasi-orthogonal space-time block codes (QSTBCs) with power scaling and double-symbol maximum likelihood (ML) decoding was proposed. Specifically, the codes can achieve full-diversity through linearly combining two adequately power scaled orthogonal space-time block codes (OSTBCs). In this letter, we derive expressions for mutual information and post-processing signal-to-noise ratio (SNR) for a system with four transmit antennas. By exploiting these formulas, we propose three transmit antenna grouping (TAG) methods for a closed-loop system with low-rate feedback information. The TAG methods make it possible to provide an excellent error-rate performance even with a low-complexity zero-forcing (ZF) detection, especially in spatially correlated fading channels.

A novel approach for fast traffic classification for the high speed networks is proposed, which bases on the protocol behavior statistical features. The packet size and a new parameter named "Estimated Protocol Processing Time" are collected from the real data flows. Then a set of joint probability distributions is obtained to describe the protocol behaviors and classify the traffic. Comparing the parameters of an unknown flow with the pre-obtained joint distributions, we can judge which application protocol the unknown flow belongs to. Distinct from other methods based on traditional inter-arrival time, we use the "Estimated Protocol Processing Time" to reduce the location dependence and time dependence and obtain better results than traditional traffic classification method. Since there is no need for character string searching and parallel feature for hardware implementation with pipeline-mode data processing, the proposed approach can be easily deployed in the hardware for real-time classification in the high speed networks.

This paper proposes a stabilized multichannel random access protocol based on slotted ALOHA for relay deployed cellular networks. To ensure the stability of random access, the proposed protocol dynamically controls the number of random access channels in a BS and a RS and the retransmission probability of the random access packets under heavy load conditions. A mathematical formula is also developed that derives an optimal partition ratio of the shared random access channels between a base station and a relay station without and with capture effect. Numerical results show that the proposed protocol can guarantee the required utilization and delay even in high offered load, which otherwise can cause bistable problem of slotted ALOHA.

An algorithm is formulated for reconstructing a dielectric cylinder with the use of the T-matrix and the singular value decomposition (SVD) and is discussed through numerical examples under noisy conditions. The algorithm consists of two stages. At the first stage the measured data of scattered waves is transformed into the T-matrix. At the second stage we reconstruct the cylinder from the T-matrix. The singular value decomposition is applied in order to separate the radiating and the nonradiating currents, and the radiating current is directly obtained from the T-matrix. The nonradiating current and the object are reconstructed by decreasing a residual error of the current in the least square approximation, where linear equations are solved repeatedly. Some techniques are used in order to reduce the calculation time and to reduce the effects of noise. Numerical examples show us that the presented approach is simple and numerically feasible, and enables us to reconstruct a large object in a short time.

Recently, privacy preservation has become one of the key issues in data mining. In many data mining applications, computing frequencies of values or tuples of values in a data set is a fundamental operation repeatedly used. Within the context of privacy preserving data mining, several privacy preserving frequency mining solutions have been proposed. These solutions are crucial steps in many privacy preserving data mining tasks. Each solution was provided for a particular distributed data scenario. In this paper, we consider privacy preserving frequency mining in a so-called 2-part fully distributed setting. In this scenario, the dataset is distributed across a large number of users in which each record is owned by two different users, one user only knows the values for a subset of attributes, while the other knows the values for the remaining attributes. A miner aims to compute the frequencies of values or tuples of values while preserving each user's privacy. Some solutions based on randomization techniques can address this problem, but suffer from the tradeoff between privacy and accuracy. We develop a cryptographic protocol for privacy preserving frequency mining, which ensures each user's privacy without loss of accuracy. The experimental results show that our protocol is efficient as well.

The use of directional antenna and polarization diversity techniques has been reported to achieve good MIMO performance. Low-profile, small structures are required to configure the MIMO antenna with these techniques. First, we assume downlink transmission in indoor MIMO systems and present the design guidelines for the radiation pattern to obtain large channel capacity by the ray-tracing method. We then propose a uni-directional, dual-polarized MIMO antenna with a thickness of 0.24λ based on the design guidelines. The proposed antenna consists of dipole antennas mounted horizontally to the ground plane and cavity backed slot antennas for vertical polarization. We apply the proposed antenna to 2 2 MIMO transmission and demonstrate the effectiveness of channel capacity enhancement in an actual environment. The improvement factor is revealed to be +16.2% with place averaged value compared to sleeve antenna configuration.

Design of high gain and high efficiency antennas is one of the key challenges in antenna engineering and especially in millimeter wave communication systems. Various types of planar waveguide arrays with series-fed traveling wave operation have been developed in Tokyo Tech with the special focus upon efficiency enhancement as well as reduction of fabrication cost. In this review, four kinds of single layer waveguide arrays characterized with the series fed travelling wave operation are surveyed first. To cope with the bandwidth narrowing effects due to long line effects associated with the series fed operation, authors have introduced partially corporate feed embedded in the single layer waveguide. They further extended the study to cover fully corporate feed arrays with multiple layer waveguide as well; a new fabrication technique of diffusion bonding of laminated thin plates has the potential to realize the low cost mass production of multi-layer structures for the millimeter wave application. Secondly, the novel methods for loss evaluation of copper plate substrate are established for the design of post-wall waveguide arrays where dielectric loss and conductor loss is determined in wide range of millimeter wave band, by using the Whispering gallery mode resonator. This enables us to design the planar arrays with the loss taken into account. Finally, the planar arrays are now applied to two kinds of systems in the Tokyo Tech millimeter wave project; the indoor short range file-transfer systems and the outdoor communication systems for the medium range backhaul links. The latter has been field-tested in the model network built in Tokyo Tech Ookayama campus. Early stage progress of the project including unique propagation data is also reported.

This letter considers power-controlled transmission from directional antennas in mmWave wireless personal area network (WPAN) systems. The attributes of these systems are studied; these include the number of concurrent transmissions and the power consumption with different system parameters, such as the antenna's beamwidth and radiating efficiency. Numerical results are presented to show that the power controlled transmission enables more concurrent transmissions than the non-power controlled transmission. The results also show that the number of concurrent transmissions increases as the beamwidth and the path loss component become smaller and the antenna's radiating efficiency increases. In addition, the power controlled system generally uses less power than the non-power controlled transmission set up; the overall analysis is verified by simulation.

This manuscript introduces a pointing interface for a tabletop display with a reflex in eye-hand coordination. The reflex is a natural response to inconsistency between kinetic information of a mouse and visual feedback of the mouse cursor. The reflex yields information on which side the user sees the screen from, so that the screen coordinates are aligned with the user's position.

This paper presents a calibration scheme for delay mismatch between envelope and phase in the OFDM polar transmitter. An asynchronous delay detection method is proposed to avoid using a complicated signal processing algorithm or synchronous elements which need high clocking rates for detecting small delay mismatch. This scheme uses buffer delay chains to estimate the mismatch and then the estimated delay values are asynchronously stored in registers. It is verified that the proposed scheme well suites application to the OFDM polar transmitter through SPW, Matlab and HDL simulations. It achieves the margin of about 20 dB at 20 MHz offset, 10 dB at 40 MHz offset in terms of spectral limit specified in WLAN standard.

The exact time complexity of Hsu and Huan's self-stabilizing maximal matching algorithm is provided. It is n2 + n - 2 if the number of nodes n is even and n2 + n - if n is odd.

A new linearly tapered slot antenna (LTSA) with defected sides is proposed in this letter. Both sides are defected with half-dumbbell shape slots that may alter the surface current intensities on both sides. As the half-dumbbell size is increased, the 3-dB beamwidth of the proposed antenna is 4° and 6° lower in the E/H-plane, respectively, than these of the LTSA without defects. Accordingly, the measured gain is improved by up to 3.75 dB and the first side lobe level is lowered by about -10.8 dB and -5.8 dB in the E/H-planes, respectively.