Quasi-orthogonal Space Time Block Code (STBC) was designed to provide full transmission rate when using more than two antennas. However, it cannot have a full diversity gain because of the interference resulted from its quasi orthogonality property. In order to achieve full diversity from quasi-orthogonal STBC, the interference can be removed by a Simple Correlation Canceling (SCC) algorithm which improves a system performance significantly. However, the SCC algorithm has a disadvantage that produces noise enhancement, thereby resulting in performance degradation. Accordingly, without increasing an extra system complexity, an unequal power allocation scheme in a transmitter is proposed to achieve a better system performance than the conventional STBC system using the SCC algorithm. Also, the unequal power allocation scheme enables a receiver to use a simple decoding procedure that does not produce noise enhancement.

A Huffman sequence has a zero-sidelobe aperiodic autocorrelation function except at both shift ends. This paper presents orthogonal sets of the zero correlation zone (ZCZ) Huffman sequences and the application to a quasi-synchronous CDMA system with interferences suppressed. The sequences with low or large peak values are constructed on the basis of sequence spectra corresponding to multiple convolution of elementary sequences, and include the ZCZ sequences. The CDMA system is constructed from the ZCZ sequences, and suppresses intersymbol and interchannel interferences.

Several research fields have to deal with very large classification problems, e.g. handwritten character recognition and speech recognition. Many works have proposed methods to address problems with large number of samples, but few works have been done concerning problems with large numbers of classes. CombNET-II was one of the first methods proposed for such a kind of task. It consists of a sequential clustering VQ based gating network (stem network) and several Multilayer Perceptron (MLP) based expert classifiers (branch networks). With the objectives of increasing the classification accuracy and providing a more flexible model, this paper proposes a new model based on the CombNET-II structure, the CombNET-III. The new model, intended for, but not limited to, problems with large number of classes, replaces the branch networks MLP with multiclass Support Vector Machines (SVM). It also introduces a new probabilistic framework that outputs posterior class probabilities, enabling the model to be applied in different scenarios (e.g. together with Hidden Markov Models). These changes permit the use of a larger number of smaller clusters, which reduce the complexity of the final classifiers. Moreover, the use of binary SVM with probabilistic outputs and a probabilistic decoding scheme permit the use of a pairwise output encoding on the branch networks, which reduces the computational complexity of the training stage. The experimental results show that the proposed model outperforms both the previous model CombNET-II and a single multiclass SVM, while presenting considerably smaller complexity than the latter. It is also confirmed that CombNET-III classification accuracy scales better with the increasing number of clusters, in comparison with CombNET-II.

A compact open-loop resonator bandpass filter is presented to suppress the spurious passband using compensated compact microstrip resonant cell (C-CMRC) feeding structure. Based on the inherently compact and stopband characteristics of the C-CMRC feeding, the proposed filters shows a better spurious rejection performance than the only open-loop resonator filter. The suppression is -57.4 dB, -49.5 dB, and -43.9 dB at the 2nd, 3rd and 4th harmonic signal separately. All the performance of proposed filters have been verified by the measured results.

A novel structure for a frequency-independent steerable composite right/left-handed (CRLH) leaky wave (LW) antenna in the millimeter-wave band is proposed. This has the advantages of wide beam scanning and low profile, and is a suitable structure for mass-production. The proposed antenna has features wherein a movable dielectric slab is placed above the CRLH LW antenna, and the radiation angle can be steered by changing the distance between the slab and the antenna using compact actuators. Moreover, slots are added to the antenna to control the aperture amplitude distribution of the array antenna in order to enhance aperture efficiency. A prototype CRLH LW antenna has been fabricated with these slots, and backward-to-forward beam scanning characteristics at 76 GHz have been demonstrated successfully by measurement. A wide scanning angle from 73 to 114 deg. has been achieved experimentally. The aperture efficiency is 25.3%.

A test structure to separately measure sheet resistances of highly-doped-drain (HDD) and lightly-doped-drain (LDD) in LDD-type CMOSFETs with various gate spaces S having sub-100 nm sidewalls was proposed. From the reciprocal of source/drain-resistance R-1 versus S characteristics, the sheet resistance ρH of the high-conductive-region (HCR) corresponding to HDD and the approximate width WLC of the low-conductive-region (LCR) corresponding to LDD could be estimated. Both of ρH and WLC for p- and n-MOS devices were scarcely dependent on the gate voltage. The sidewall-width difference of 40 nm could be sufficiently detected by using the test structure with the S pitch of about 60 nm. The R-1 versus S characteristics showed the unstable resistance variations in the narrow S region less than 0.3 µm, which corresponded to the minimum S for the process used for the test device fabrication and suggested that various micro-loading effects seriously affected on the characteristics.

A rigorous and simple method is proposed for analyzing guided modes of metallic electromagnetic crystal waveguides. The method is a combination of generalized reflection and transmission matrices and the mode-matching technique. Fast convergence, low computer cost, and high calculating precision are main advantages of the proposed method. This method can easily avoid the relative convergence phenomena than a classical mode-matching method, and the proposed formulation is very suitable to analyzing multilayered problems with very low computer cost. The existence of H-polarized modes in metallic electromagnetic crystal waveguides has been verified.

In this paper, a parallel combinatory spread spectrum (PC/SS) system using a constant amplitude signaling scheme is proposed. The amplitude of the transmitted signal from multicode transmission systems such as PC/SS systems have a large dynamic range which requires that amplifiers have a wide linearity in the transmitter. From a view point of power efficiency, however, it is reasonable to use non-linear amplifiers rather than linear ones. In that case, the bit error rate performance must degrade because of non-linear distortion. The proposed system can avoid influence of the non-linear amplifiers by making the transmitted signal have a constant amplitude. The bit error rate performance and the data transmission rate performance are investigated. They prove that the proposed system is an attractive candidate among the constant amplitude signaling systems.

This paper introduces a novel MIMO (Multiple Input Multiple Output) communication system having orthogonal dual polarization diversity branches. We have designed a dual polarized circular patch antenna which has two orthogonal polarization ports such as vertical polarization (V) and horizontal polarization (H) on its metal surface. This design makes it works as two independent antennas in multipath environments. By using two dual polarized antennas at both the transmitter and receiver, we designed a dual-polarization 44 MIMO experiment system. This system can be used to investigate the performance of various MIMO transmission methods as well as the performance of adaptive algorithms in indoor multipath environments. To investigate the performance of our experiment system, we carried out a number of MIMO transmission experiments such as space-time-coded transmission having two parallel streams and MIMO eigenmode transmission. We will show the results of those experiments and discuss the advantages of using polarization diversity in MIMO communication system for next generation broadband wireless communication.

We propose a wave analysis method for probe-fed Radial Line Planar Antennas (RLPAs) which yields an approximate solution for the aperture field distribution and scattering by loaded probes. Damping of electric power in the radial line due to radiation by antenna elements is included. The method can accommodate the effect of all conductors, including the terminating wall, by introducing the concept of equivalent posts. We have found good correspondence between the measured and calculated values of the aperture field distribution. The proposed method is effective for general geometries of probe-fed RLPAs.

Some signal design methods for the approximately synchronized CDMA systems based on complete complementary codes have been proposed. It has been shown that estimating the multipath channels and applying the convolution of the spread signals can increase both the information transmission rate and frequency usage efficiency. There are some variations of such signal design methods using complete complementary codes. The efficiency of the communication systems and information transmission rate depend upon the applied signal design method and the modulation scheme. In this paper, we consider two of these signal design methods. We analyze the bit error rate (BER) performances for both methods through some numerical simulations under the single cell scenario. Numerical results show the BER properties under some modulation schemes such as BPSK, QPSK and 16QAM. Some discussions on the relation between the BER performance and the information transmission rate are also included.

Eigenvalue equations and expressions of EM fields for volume modes in an anisotropic single-negative slab with tensor material parameters is presented. By the comparison with the eigenvalue equation of surface modes along single-negative slab with negative scalar permeability, the validity of the present study is confirmed. We have also made clear which elements of the material parameter tensors affect existence of TE and TM modes in the slab. Taking the dispersion of material parameters into consideration, we demonstrate in detail that TE modes propagate in a slab with one negative element of the permeability tensor numerically. These TE modes turn out to be the magnetostatic waves (MSWs), which is the first demonstration of the MSW in a nonmagnetic material.

Adaptive array antennas, which control their own patterns by means of feed-back or feed-forward control, are effective tools for gain enhancement and interference suppression. However, when applying them to mobile terminals, the problems of hardware complexity and power consumption need to be taken into consideration. One solution is the use of analog device-based adaptive array antennas, such as Reactively Steered Adaptive Array (RESAA) antennas and phased array antennas, which have the attractive characteristics of low cost and power consumption. In this paper, we propose an adaptive beamforming method based on a one-dimension search algorithm for phased array antennas with Micro Electro Mechanical Systems (MEMS) phase shifters, taking into consideration their slow operating speed due to mechanical structure of the devices. Furthermore, a smoothing processing is introduced to prevent the effect of noise and a multi-resolution alogrithm is proposed to help the system form beams more quickly and stably. Numerical results based on the IEEE 802.11a Wireless Local Area Network (WLAN) standard show that the proposed method has good interference suppression and gain enhancement capabilities in multipath fading channels.

This letter presents a new gossip-based ad hoc service discovery protocol that uses a novel decentralized, peer-to-peer mechanism to provide mobile devices with the ability to advertise and discover services in an efficient way. Our performance study shows that the proposed protocol appropriately addresses the need of proximal service discovery over a dynamic wireless medium.

The diffraction of a transverse magnetic (TM) plane wave by a perfectly conductive surface made up of a periodic array of rectangular grooves is studied by the modal expansion method. It is found theoretically that the reflection coefficient approaches -1 but no diffraction takes place when the angle of incidence reaches a low grazing limit. Such singular behavior is shown analytically to hold for any finite values of the period, groove depth and groove width and is then demonstrated by numerical examples.

In this article, the empirical mode decomposition (EMD) is introduced to the problem of signal detection in underwater sound. EMD is a new method pioneered by Huang et al. for non-linear and non-stationary signal analysis. Based on the EMD, any input data can be decomposed into a small number of intrinsic mode functions (IMFs) which can serve as the basis of non-stationary data for they are complete, almost orthogonal, local and adaptive. Another useful tool for processing transient signals is discrete wavelet transform (DWT). In this paper, these IMFs are applied to determine when the particular signals appear. From the computer simulation, based on the receiver operating characteristics (ROC), a performance comparison shows that this proposed EMD-based detector is better than the DWT-based method.

This letter proposes non-pilot-aided symbol timing and carrier frequency estimation methods in a multicarrier transmission system. To do this, multicarrier system uses a frequency diversity scheme over two consecutive data symbols with the combination of a cyclic time shift. Using the multicarrier signal equipped with frequency diversity, however, time and frequency are accurately estimated without any training symbol.

Barker sequences have been used in many existing communications and ranging systems. Unfortunately, the longest known biphase and quadriphase Barker sequences are of lengths 13 and 15, respectively. In this paper, we introduce the so-called quasi-Barker sequences which achieve the minimum peak sidelobe level one within a certain window centered at the mainlobe. As our key results, all the best biphase and quadriphase quasi-Barker sequences of lengths up to 36 and 21, respectively, were obtained by an efficient computer search. These sequences may provide better multipath resistance and tracking accuracy in ranging applications.

Sequence set with Three Zero Correlation Zones (T-ZCZ) can efficiently mitigate the Multiple Access Interference (MAI) and Inter Symbol Interference (ISI) caused by multi-path in CDMA system. In this paper, an algorithm for generating T-ZCZ sequence set is presented. Moreover, in order to study the restrictions among the parameters such as the length of the sequence, the number of the sequences and the length of the T-ZCZ etc., the corresponding theoretical bound is investigated and proved. Additionally, the performance of T-ZCZ sequence in MC-CDMA system is evaluated to confirm the capability of interference cancellation as well as system capacity improvement.

Binary sequences with two-level periodic autocorrelation correspond directly to cyclic (v, k, λ)-designs. When v = 4t-1, k = 2t -1 and λ = t-1, for some positive integer t, the sequence (or design) is called a cyclic Hadamard sequence (or design). For all known examples, v is either a prime number, a product of twin primes, or one less than a power of 2. Except when v = 2k-1, all known examples are based on quadratic residues (using the Legendre symbol when v is prime, and the Jacobi symbol when v = p(p+2) where both p and p+2 are prime); or sextic residues (when v is a prime of the form 4a2 + 27). However, when v = 2k-1, many constructions are now known, including m-sequences (corresponding to Singer difference sets), quadratic and sextic residue sequences (when 2k-1 is prime), GMW sequences and their generalizations (when k is composite), certain term-by-term sums of three and of five m-sequences and more general sums of trace terms, several constructions based on hyper-ovals in finite geometries (found by Segre, by Glynn, and by Maschietti), and the result of performing the Welch-Gong transformation on some of the foregoing.