A de-embedding technique for the measurement of very small parasitic capacitances of package or small module interconnects is presented. At high frequencies small parasitic capacitances become important, and measurement probes can strongly affect measurement results. The present technique is based on additional measurements with only one tip of the probe touching one conductor, while the second tip is kept floating on the substrate. A necessary condition for its application is that the measured capacitance does not depend on the position of the floating probe tip. Measurements with inverted probe tip polarities are also used. In this way, the capacitances between probe tips and DUT can be estimated together with the parasitic capacitances of interest. Depending on the required accuracy, de-embedding of different orders have been introduced, which consider capacitance configurations of increasing complexity. The technique requires the solution of one or more systems of non-linear equations. In the present example the minimization of the norm of the residual of the system has been treated as a least squares problem, and has been solved numerically with MATLAB. The accuracy of the measurement can be also approximately estimated with the residual. As application example, a small module with power and ground planes has been considered. Two different probes have been used. Even though the stray capacitances of the probes are very different, the values of the extracted parasitic capacitances are in agreement with each other. The accuracy has been verified also with simulation results. To this purpose, a combination of known formulas from the literature, a 2D Finite Element Method (FEM) tool and a 3D Boundary Element Method (BEM) tool have been used. A high accuracy can be obtained, even when a strong capacitive coupling between probe ground and DUT is present. The technique can be applied also when only a subset of measurement results are available.

The crosstalks between a single-ended line and a differential pair in parallel are analyzed using telegrapher's equations for multi-conductor lines. The crosstalk from the single-ended trace to the differential pair is estimated at shunt-arm resistors in T or Π termination networks. The analysis is conducted by incorporating the termination conditions with the solution of the telegrapher's equations. The time-domain characteristics of the crosstalk are obtained by using the fast inverse Laplace transform. The measurements are conducted easily by using a single-ended digital oscilloscope since the crosstalk is evaluated on the shunt-arm resistors. Both the calculated and measured results are presented, and the characteristics of the crosstalk are also investigated qualitatively.

We propose a method of crosstalk analysis for two bent transmission lines with vias at both ends on a PCB using a circuit-concept approach in the quasi-static condition. In this condition, the electromagnetic fields can be approximately estimated by the quasi-static terms of the accurate Green's function in an inhomogeneous medium. Thus we obtain a circuit model in an ABCD matrix by taking account of the fields generated by a longitudinal line and a vertical via on a PCB. To verify the proposed approach, we conducted some experiments and compared our approach's results with measured results and a commercial electromagnetic solver's results.

A new radio-frequency (RF) radiated immunity/susceptibility test method using four-septum TEM cell is proposed. A rotating-EM field can be generated inside the cell by feeding four-different RF DSB-SC signals to four septa arranged in the cell. Since a polarization plane of the rotating-EM field rotates in a low speed, the immunity/susceptibility test for the EM field with various polarizations can be conducted more easily. In this paper, a technique for generating the rotating-EM field in the cell is investigated. The basic characteristics of the cell and the rotating-EM field by using the technique are clarified. To verify the validity of this test method, a RF radiated susceptibility of a printed circuit board is measured. The measured results are verified by comparing with the theoretical results based on modified telegrapher's equations.

This paper describes a capacitive voltage probe (CVP) that can measure a common-mode voltage on a cable without touching its conductor. This CVP has two coaxial electrodes: the inner electrode works as a voltage pickup and the outer one shields the inner electrode. These electrodes separate into two parts for clamping to the cable. Using a high input impedance circuit, this probe measures the common-mode voltage by detecting the voltage difference between the two electrodes. The probe characteristics are evaluated by measuring its linearity and frequency response. The results show that this probe has a dynamic range of 100 dB and flat frequency response from 10 kHz to 30 MHz. Deviations in sensitivity due to the position of the clamped cable in the inner electrode and to differences in the cable radius are evaluated theoretically and experimentally. The results indicate that the influence of the cable position can be calibrated. Finally, measured data obtained using both an impedance stabilizing network (ISN) and a CVP are compared to confirm the validity of the CVP. The results show that data measured by the CVP closely agreed with that obtained by the ISN. Therefore, the CVP is useful for EMC measurements to evaluate common-mode disturbances.

In this research, the performance degradation of the digital electronic equipment under electromagnetic (EM) disturbance was studied in order to investigate the interference of intra-equipment. To develop the evaluation method of the performance degradation, some communication indexes were measured under EM disturbance. From some experimental results, it is known that the performance degradation of the electronic equipment was estimated by the degradation of "through-put," one of the communication performance indexes. For further investigation of the interference of intra-equipment, the near EM field from a PCB of the electronic equipment and its performance degradation under EM disturbance were measured and compared. From the measured results, the relationship between near field measurement and performance degradation could be obtained in some extent. These facts enable us that the weak area under the EM disturbance application on PCB can be foreseen by measuring the near field emission from the equipment and vise versa.

With the rapid progress of electronic and information technology, an expectation for the realization of body area network (BAN) has risen. However, on-body transmission characteristics are greatly dependent on the frequency, and a high-speed transmission is difficult due to the remarkable signal attenuation at higher frequencies. In this study, we proposed a pulse transmission system with the frequencies at dozens of mega-hertzes. The system was based on an impulse radio (IR) scheme with bi-phase modulation. By using the frequency-dependent finite difference time domain (FD²TD) method, we investigated the on-body transmission characteristics and derived a path loss expression. Based on the transmission characteristics, we also investigated the influences of white Gaussian noises and other narrow-band interferences on the communication link budget and bit error rate (BER) performance. The results have shown the feasibility of the proposed on-body IR communication system.

As the basic study of the electromagnetic interference (EMI) problem at the circuit elements, the near magnetic field distributions above resistors for the termination of a transmission line are measured to reveal the profile of radiation. Five kinds of resistors and two types of resistance values are sampled. The results showed that the variation of the near magnetic field distribution above the transmission line is effected largely by the reactance of the resistor at the high frequency. These results are the basis for the design of the structure of the component.

The peak SAR values of two-element array antennas for mobile handsets in the vicinity of a spherical phantom of a human head are evaluated numerically as a function of the distance between the array antenna and the head phantom when the two elements of a two-element array antenna are either co-phase voltage-fed or reverse-phase voltage-fed. It is found that relation between the worst case of the SAR and the phase difference of array elements strongly depends on the distance. When part of the head phantom is located in the reactive near-field region of the array antenna, although the co-phase feed SAR value is slightly smaller than the reverse-phase feed SAR value, the SAR value is practically independent of the phase difference, but when the head is completely outside the reactive near-field region, the co-phase feed SAR value is larger than the reverse-phase feed SAR value.

We measured the complex permittivities of whole blood and blood plasma in quasi millimeter and millimeter wave bands using a coaxial probe method. The validity of these measurements was confirmed by comparing with those of a different measurement method, i.e., a dielectric tube method. It is shown that the complex permittivities of the blood samples are similar to those of water in quasi millimeter and millimeter wave bands. Furthermore, the temperature dependences of the complex permittivities of the samples were measured.

In this paper, we propose tight performance upper bounds for convolutional codes terminated with an input sequence of finite length. To obtain the upper bounds, a generalized weight enumerator of single error event is defined to represent the relation between the Hamming distance of the coded output and the Hamming distance of the selected input bits of a terminated convolutional code. In the generalized weight enumerator of single error event, codewords composed of multiple error events are not counted to provide tighter performance upper bounds. The upper bounds on frame error rate (FER) and average bit error rate (BER) of selected bits are computed from the generalized weight enumerators of single error event. A simple method is presented to compute the weight enumerator of a terminated convolutional code based on a modified trellis diagram.

We address the problem of routing and wavelength assignment (RWA) considering differentiated reliability (DiR) in WDM mesh networks. The backup resource can be shared by the primary lightpaths. However, both the primary-backup sharing and the different levels of fault tolerance requirement have never been considered together in the literature. In the paper, we consider the dynamic character of the link availability, which is caused by primary-backup sharing. Moreover, the priority of traffic is considered in the paper. The paper focuses on routing under dynamic availability of wavelength resource while the requested reliability of traffic has to be met, using the modified shortest path algorithm. A layered availability model is established based on wavelength layered graph model. Using this model, we propose a new algorithm called dynamic layered availability (DLA) algorithm. We evaluate the performance of the proposed algorithm on the NSFNET.

We propose a service differentiation scheme for optical burst switching (OBS) with the scheduling algorithm Horizon. In the proposed scheme, in addition to the latest horizon used in the conventional Horizon, we introduce the second latest horizon and use them for reservation preemption. Burst priority order is perfectly guaranteed according to the burst class information informed by its control packet if the arrival time of the burst is later than the second latest horizon and earlier than the latest horizon. Since the extra offset time is no longer needed for service differentiation, the burst blocking probability and the data latency will be reduced. We assume a multi-hop network with ring topology where bursts traverse five intermediate nodes, and evaluate the performance in terms of the end-to-end and hop-by-hop burst blocking probabilities. Simulation results show that the proposed scheme can achieve service differentiation with smaller blocking probability than the extra-offset-time-based scheme with Horizon. Furthermore, we show that the proposed scheme preserves service differentiation even in multi-hop environments.

When we consider user's convenience for electronic transactions, it might be desirable to generate a digital signature using biometrics. However, it is not easy nor practicable in today's communications environment because of inaccurate measuring and potential hill-climbing attacks with regard to biometrics, unless specific hardware storage is provided for manipulating signature keys or biometric templates securely. In this paper, we study a simple practical method for biometrics based digital signature generation without such restriction. It is based on the existing tools in software in our proposed model where a general digital signature such as RSA can be applied without losing its security. This is not a cryptography paper but rather written from the practical perspectives.

A proactive cluster-based distance vector routing protocol based on DSDV protocol is proposed for mobile ad hoc networks. A network is divided into a number of clusters, each cluster having a clusterhead that directly connects the other nodes in the same cluster. Each clusterhead broadcasts update request (UREQ) messages at reqular intervals or in an event driven manner to its neighbor clusterheads. In this way, clusterheads update their own global routing tables that give a path among all clusterheads. In this process, multiple local paths from source clusterhead to its neighbor clusterheads are established as well. A node having a packet to send forwards the packet to its own clusterhead. The clusterhead determines next clusterhead with respect to the destination clusterhead by looking up its own global routing table. Then, the packet is delivered to the next clusterhead along a local path. The advantages of this protocol are threefold. The size of a global routing table is small since it has entries only for clusterheads. A UREQ message travels up from the initiating clusterhead to neighbor clusterheads. Hence, the convergence range of a update request is at least nine times as wide as that of DSDV or CGSR, increasing the correctness of routing. Lastly, a technique to bypass clusterheads, whenever possible, on the fly during packet transmission is presented, to reduce route length as well as to prevent clusterheads from becoming congested. Simulation results show that PCDV outperforms some key protocols of the same category greatly.

This paper presents a novel technique to compensate intermodulation distortion of a self-heterodyne direct conversion OFDM system in multipath propagation environments. A self-heterodyne direct conversion system has an advantage that simple receivers can be built that are completely immune to any phase noise or frequency offset. This system, however, has a disadvantage that the nonlinear square-law detector at the receiver of the self-heterodyne direct conversion system gives rise to second order intermodulation distortion. In this study, channel estimation is performed using a training sequence and then the predistortion coefficients with regard to estimated channel parameters are derived to compensate the receiver nonlinearity. Transmit power distribution is employed to overcome multipath fading channels as well. Computer simulation demonstrates that the proposed approach improves the BER performance of the self-heterodyne direct conversion OFDM system in a multipath fading channel. This scheme gives advantage to multi-carrier systems that are much more sensitive to frequency and phase error than single-carrier systems.

This paper proposes a frequency diversity scheme using only even-numbered samples for single-carrier transmission with frequency-domain equalization (SC-FDE). In the proposed scheme, a periodical frequency spectrum generated by using only even-numbered samples in the time domain provides the frequency redundancy, which is utilized for frequency diversity. Moreover, in order to avoid the data rate reduction due to the decrease in the samples within one block, the high-level modulation is applied to each sample and the transmitting power of each sample can be doubled for the equivalent power transmission instead. Computer simulation results show that the proposed scheme provides a steeper BER curve than the typical SC-FDE over frequency selective fading channels, while the typical SC-FDE is more favorable than the proposed scheme over flat fading channels. Moreover, the proposed scheme still retains its characteristic even when channel estimation and channel coding are additionally taken into account.

The paper describes a low complexity tree-structure based user scheduling algorithm in an up-link transmission of MLD-based multi-user multiple-input multiple-output (MIMO) wireless systems. An M-branch selection algorithm, which selects M most-possible best branches at each step, is proposed to maximize the whole system sum-rate capacity. To achieve the maximum capacity in multi-user MIMO systems, antennas configuration and user selection are preformed simultaneously. Then according to the selected number of antennas for each user, different transmission schemes are also adopted. Both the theoretical analysis and simulation results show that the proposed algorithms obtain near optimal performance with far low complexity than the full search procedure.

This paper proposes a suboptimal algorithm for the maximum likelihood detection (MLD) in multiple-input multiple-output (MIMO) communications. The proposed algorithm regards transmitted signals as continuous variables in the same way as a common method for the discrete optimization problem, and then searches for candidates of the transmitted signals in the direction of a modified gradient vector of the metric. The vector is almost proportional to the direction of the noise enhancement, from which zero-forcing (ZF) or minimum mean square error (MMSE) algorithms suffer. This method sets the initial guess to the solution by ZF or MMSE algorithms, which can be recursively calculated. Also, the proposed algorithm has the same complexity order as that of conventional suboptimal algorithms. Computer simulations demonstrate that it is much superior in BER performance to the conventional ones.

To improve the channel estimation accuracy of multiple-input multiple-output (MIMO) multiplexing, we previously proposed iterative QR-decomposition with M-algorithm (QRD-M) with decision directed channel estimation. In this paper, to keep the computational complexity low while further improving the transmission performance, we will modify previously proposed iterative QRD-M by incorporating cyclic redundancy check (CRC) coding. In the proposed method, transmitted signals are ranked according to their results of CRC decoding and the received signal-to-interference plus noise power ratio (SINR). In the modified M-algorithm, since the results of Turbo decoding and CRC decoding are used to generate the surviving symbol replica, the accuracy of signal detection in the following steps can be improved. Furthermore, based on the results of CRC decoding, iterative process can be terminated before reaching the maximum allowable number of iterations. Computer simulation results show that the loss in the required average received signal energy per bit-to-noise power spectrum density ratio E_b/N₀ for average packet error rate (PER) = 10^-2 is only about 0.4 dB from maximum likelihood detection (Full MLD) with ideal channel estimation.

This paper proposes an OFDM mobile radio packet system that employs a new protocol of automatic repeat request (ARQ) for nonlinear multiuser detection (MUD) with log likelihood ratio combining (LC) on the appropriate bits. The conventional metric combining (MC) MUD separates collided packets by using nonlinear MUD, accumulates the Euclidian distance metrics of the received subcarrier symbols in the packets, and then achieves throughput improvement. However, when MC-MUD detects a packet error, it makes user terminals retransmit the same packets so as to reproduce the collision of the same packets. The proposed LC-MUD scheme simplifies the ARQ protocol and requires no reproduction of the same packet collision. The computer simulations demonstrate the superior throughput of LC-MUD to that of MC-MUD, and further improvement due to adaptive modulation and coding (AMC) optimized for the nonlinear MUD in LC-MUD.

An improved Max-Log-Map (MLM) turbo equalization algorithm called Scaled Max-Log-Map (SMLM) iterative equalization is presented. Simulations show that the scheme can dramatically outperform the MLM besides it is insensitive to SNR mismatch. Unfortunately, its performance is still much worse than that of Log-Map (LM) with exact SNR over high-loss channels. Accordingly, we also propose a new SNR estimation algorithm based on the reliability values of soft output extrinsic information of SMLM decoder. Using the new scheme, we obtain good performance close to that of LM with ideal knowledge of SNR.

Recently, the superimposed pilot channel estimation has attracted attention for wireless communications, where the pilot symbol sequence is superimposed on a data symbol sequence and transmitted together, and thus there is no drop in information rate. In the superimposed pilot channel estimation, the receiver correlates the received symbol sequence with the pilot symbol sequence, and obtains the channel estimate. However, the correlation between the pilot symbol sequence and the data symbol sequence deteriorates the channel estimation accuracy. In particular, the channel estimation accuracy of the superimposed pilot channel estimation scheme is significantly deteriorated in MIMO systems, because the pilot symbol power of each transmit antenna to the total transmit power of all transmit antennas becomes smaller as the number of transmit antennas increases. On the other hand, it has been well known that the SAGE algorithm is an effective method for channel estimation and data detection. This algorithm is particularly effective in MIMO systems, because the operation of this algorithm can cancel the interference from other transmit antennas. In this paper, we evaluate the performance of the SAGE algorithm for channel estimation and data detection using superimposed pilot channel estimation in MIMO systems. From the results of computer simulations, we show that the system using the SAGE algorithm with superimposed training can achieve the good BER performances by using the SAGE algorithm with iteration.

Since Smart Antenna technology has powerful spatial processing ability; it is regarded as a promising approach to enhancing the data rates and capacity of wireless LAN systems. In this paper, a small size, practical switched-beam antenna system, well suited for domestic in-home networking in the 2.4 GHz band, is designed and tested. The system has the configuration of regular nine-prism, and nine 1/4 wavelength rectangular patches are symmetrically distributed on the nine sides of the prism. The switching process is based on control of the microstrip used to feed the patch radiators, by placing PIN diodes at the microstrip feeding lines. The antenna array can generate nine beams with a gain of 11 dB. All the beams generated by the system are cophasal excited and have a 40°beamwidth. Compared to the uniform array, the system can guarantee the consistency of every beam and is preferable in shape.

MIMO systems using a space division multiplexing (SDM) technique in which each transmit antenna sends an independent signal substream have been studied as one of the successful applications to increase data rates in wireless communications. The throughput of a MIMO channel can be maximized by using an eigenbeam-SDM (E-SDM) technique, and this paper investigates the practical performance of 22 and 44 MIMO E-SDM based on indoor measurements. The channel capacity and bit error rate obtained in various uniform linear array configurations are evaluated and are compared with the corresponding values for conventional SDM. Analysis results show that the bit error rate performance of E-SDM is better than that of SDM and that E-SDM gives better performance in line-of-sight (LOS) conditions than in non-LOS ones. They also show that the performance of E-SDM in LOS conditions depends very much on the array configuration.

UWB pulse radars enable us to measure a target location with high range-resolution, and so are applicable for measurement systems for robots and automobile. We have already proposed a robust and fast imaging algorithm with an envelope of circles, which is suitable for these applications. In this method, we determine time delays from received signals with the matched filter for a transmitted waveform. However, scattered waveforms are different from transmitted one depending on the target shape. Therefore, the resolution of the target edges deteriorates due to these waveform distortions. In this paper, a high-resolution imaging algorithm for convex targets is proposed by iteration of the shape and waveform estimation. We show application examples with numerical simulations and experiments, and confirm its capability to detect edges of an object.

Detecting edge directions and estimating the exact value of a missing line are currently active research areas in deinterlacing processing. This paper proposes a spatial domain fuzzy rule that is based on an interpolation algorithm, which is suitable to the region with high motion or scene change. The algorithm utilizes fuzzy theory to find the most accurate edge direction with which to interpolate missing pixels. The proposed fuzzy direction oriented interpolator operates by identifying small pixel variations in seven orientations (0°, 45°, -45°, 63°, -63°, 72°, and -72°), while using rules to infer the edge direction. The Bayesian network model selects the most suitable deinterlacing method among three deinterlacing methods and it successively builds approximations of the deinterlaced sequence, by evaluating three methods in each condition. Detection and interpolation results are presented. Experimental results show that the proposed algorithm provides a significant improvement over other existing deinterlacing methods. The proposed algorithm is not only for speed, but also effective for reducing deinterlacing artifacts.

This paper proposes effective energy feature normalization methods for robust speech recognition in noisy environments. We first develop an energy subtraction method and a modified method for the Log-energy Dynamic Range Normalization (ERN) using inverse function. We then present the hybrid method combining the energy subtraction and the modified ERN. Using Aurora2.0 database for representative evaluations, a significant performance improvement over the ERN method is demonstrated.

We propose a digital carrier recovery loop employing both a frequency detector and a phase detector for M-ary phase shift keying (MPSK) systems. A new frequency error correction function is also derived to increase the acquisition range. It is shown through computer simulation that the proposed scheme can reduce the acquisition time at large frequency offsets, unlike the existing ones.

We propose a simple and scalable scheduler called Elapsing Time-based Priority (ETP) scheduler for the optical burst switch (OBS) control channel; it eliminates the requirements of global synchronization and core-state information. This scheduler reduces edge-to-edge delays of burst control packets and total latencies of data bursts.

An adaptive tri-threshold dynamic call admission control scheme for wideband mobile cellular networks is proposed. The relationship between the Channel Utilization and the Weighted Handover Dropping Probability versus traffic loadings are investigated. This scheme supports voice, data and multimedia services with differentiated QoS.

In this letter, we first analyze the delay of the WLAN discovery scheme specified for 3GPP and WLAN interworking networks. Theoretical analysis indicates that the delay of the discovery scheme given by 3GPP increases linearly with the number of WLAN channels needed to be scanned. To reduce the discovery delay, we then propose an effective WLAN discovery scheme utilizing the cellular network to aid in the broadcasting the information of WLANs. Thus the number of WLAN channels required to be scanned for users is greatly reduced. The effectiveness of the proposed scheme is demonstrated by analysis and simulation.

We present a computationally efficient sequential detection scheme using a modified Fano algorithm (MFA) for V-BLAST systems. The proposed algorithm consists of the following three steps: initialization, tree searching, and optimal selection. In the first step, the proposed detection scheme chooses several candidate symbols at the tree level of one. Based on these symbols, the MFA then finds the remaining transmitted symbols from the second tree level in the original tree structure. Finally, an optimal symbol sequence is decided among the most likely candidate sequences searched in the previous step. Computer simulation shows that the proposed scheme yields significant saving in complexity with very small performance degradation compared with that of sphere detection (SD).

The performance of M-ary code shift keying (CSK) in multipath fading channels is analyzed in this letter. In conventional spread spectrum (SS) systems, which employ a single spreading code, the interference due to the delay signal depends on the auto-correlation property of the spreading code. In CSK, since one code is selected from a code set that contains multiple codes, the effect of the delay signal differs from that for conventional SS systems. Analytical results reveal that, in the multipath fading channel, the error rate of CSK depends on the cross-correlation property with the other codes in addition to the auto-correlation of transmitted code.

In this letter, we investigate the application of Tomlinson-Harashima precoding (THP) in the downlink of multiuser multiple-input multiple-output (MIMO) systems, where multiple antennas are located at all the transceivers. Based on the criterion of maximum system sum-capacity, a per-layer optimization scheme is proposed, in which the subchannel ordering and transceiver filters design are generated. In the proposed scheme, the successive character of THP can be fully exploited, so that both the minimum cost of interference suppression and the maximum power and diversity gains can be implemented, and hence, the system sum-capacity can be improved effectively.

A simple, yet effective geometric method is presented to construct the signature sequences for multicarrier code-division multiple access (MC-CDMA) systems. By minimizing the correlation of the effective signature vectors, the signature sequences are recursively determined via projection onto a properly constructed subspace. Conducted simulations verify the effectiveness of the method.

A carrier frequency synchronization scheme is proposed for orthogonal frequency-division multiplexing (OFDM) systems in the presence of phase noise (PHN). In the proposed scheme, carrier frequency synchronization is performed based on the maximum-likelihood (ML) algorithm using an OFDM preamble symbol. The proposed scheme is compared with conventional methods. Simulation results are presented to illustrate the effectiveness of the proposed scheme in the presence of PHN.

Orthogonal frequency division multiplexing (OFDM) has been adopted in the physical layer of WLAN systems such as IEEE802.11a. In this letter, an efficient preamble structure is proposed to improve the frequency synchronization performance of OFDM-based WLAN systems. The novel preamble effectively multiplexes two different symbols, and the frequency-offset estimation can efficiently utilize the preamble for better estimation performance. Simulation results indicate that using the proposed preamble structure, the frequency synchronization performance can significantly be improved in OFDM-based WLAN systems.

A method for searching minimum Euclidean distances of respective substreams for different modulation orders of M-ary quadrature amplitude modulation signals in multiple-input and multiple-output systems is described. A channel matrix is cyclically-sorted sequentially and QR-decomposed. Using upper triangular matrices obtained by QR decomposition, minimum Euclidean distances are searched over trellis diagrams consisting of symbol-difference lattice points by computationally efficient multiple trellis-search algorithms. The simulation results demonstrate that per-substream minimum Euclidean distances can be detected with a high correct-estimation probability by path-re-searching controls over different modulation orders.

In this letter, the effect of a propagation delay resulting from the use of an OFDM system with a transparent mobile multi-hop relay (MMR) is initially analyzed. Then, a least square (LS) channel estimation technique for the OFDM system with throughput enhancement (TE) MMR or cooperative MMR is proposed. It is demonstrated by computer simulation that the proposed LS channel estimation technique for OFDM systems with transparent MMR is superior to the conventional technique in terms of mean square error (MSE) and bit error rate (BER).

In order to improve the antenna gain, a composite right/left-handed (CRLH) leaky-wave (LW) antenna composed of symmetrical unit cells with short stubs terminated by vertical vias is designed. The use of symmetrical unit cells suppresses the cross-polarization of radiation to less than 23 dB. By comparing the measured radiation characteristics to that of a conventional CRLH LW antenna without short stub in the X-band, it is shown that the presented CRLH LW antenna with 51 unit cells offers a narrower beam and the antenna gain improves 4.1, 2.2 and 3.1 dB in the backward, broadside and forward directions of radiation, respectively.

This letter proposes a new bandpass shielding enclosure (BPSE) for modern handheld communication devices. This enclosure is characterized by high transmittance at the specified wireless signal band and high shielding effectiveness (SE) outside this band. In addition, it has little influence on the impedance-matching bandwidth and antenna patterns of an internal antenna embedded inside the device. A prototype was created, simulated and measured. The simulated and measured results demonstrate the promising performance of this newly proposed shielding enclosure.

We propose a periodic binary sequence that compress a pulse to a width of severel chips. In the region of relatively small compression ratios, many periodic binary sequences exist for which Peak Side Lobe Levels (PSLs) are smaller than that those of conventional codes such as m-sequences.

In this paper, we propose a predictive block-constrained trellis-coded quantization (BC-TCQ) to quantize cepstral coefficients for distributed speech recognition. For prediction of the cepstral coefficients, the first order auto-regressive (AR) predictor is used. To quantize the prediction error signal effectively, we use the BC-TCQ. The quantization is compared to the split vector quantizers used in the ETSI standard, and is shown to lower cepstral distance and bit rates.