In this letter, a prerake combining scheme for signal detection in ultra-wideband (UWB) multiple input single output (MISO) systems with a hybrid pulse amplitude and position modulation (PAPM) is analytically examined. For a UWB MISO system, the analytical BER performance of a prerake combining scheme with PAPM is presented in a log-normal multipath fading channel. The analytical BERs are observed to match well the simulated results for the set of parameters chosen. The prerake diversity combining UWB systems, which can significantly reduce the complexity of the receiver side compared to the rake diversity systems, improve the error performance as the number of transmit antennas increases.

The probability of making mistakes on the decoded signals at the relay has been used for the maximum-likelihood (ML) decision at the receiver in the decode-and-forward (DF) relay network. It is well known that deriving the probability is relatively easy for the uncoded single-antenna transmission with M-pulse amplitude modulation (PAM). However, in the multiplexing multiple-input multiple-output (MIMO) transmission, the multi-dimensional decision region is getting too complicated to derive the probability. In this paper, a high-performance near-ML decoder is devised by applying a well-known pairwise error probability (PEP) of two paired-signals at the relay in the MIMO DF relay network. It also proves that the near-ML decoder can achieve the maximum diversity of MSMD+MR min (MS,MD), where MS, MR, and MD are the number of antennas at the source, relay, and destination, respectively. The simulation results show that 1) the near-ML decoder achieves the diversity we derived and 2) the bit error probability of the near-ML decoder is almost the same as that of the ML decoder.

Recently proposed full-rate quasi-orthogonal space-time block codes (QSTBCs) with power scaling is able to achieve full-diversity through linearly combining two adequately power scaled orthogonal space-time block codes (OSTBCs). While in our initial work we numerically derived the optimal value of the power scaling factor to achieve full-diversity, our goal in this letter is to analytically derive the optimal power scaling, especially for square lattice constellations (e.g., 4-QAM, 16-QAM, etc.) by maximizing the coding gain.

In this paper, the joint optimization issue of the cooperative precoder design is investigated for the transmission from the cooperative multi-point system to one mobile terminal. Based on the mean squared error minimization criterion, the problem is established for the cooperative precoder design. Unfortunately, this problem cannot be solved due to the block diagonal structure of the whole precoding matrix resulting from the fact that there is no data exchange among multiple base stations. In order to tackle this difficulty, the original problem is converted into an equivalent problem by stacking all of the nonzero entries in the block diagonal matrix into a long column vector. With the equivalent problem, the optimum solution is obtained in a closed-form expression by using the Lagrangian multiplier method. Numerical simulations illustrate the effectiveness of the proposed scheme in terms of bit error rate and spectral efficiency.

An efficient pruning method is proposed for the infinity-norm sphere decoding based on Schnorr-Euchner enumeration in multiple-input multiple-output spatial multiplexing systems. The proposed method is based on the characteristics of the infinity norm, and utilizes the information of the layer at which the infinity-norm value is selected in order to decide unnecessary sub-trees that can be pruned without affecting error-rate performance. Compared to conventional pruning, the proposed pruning decreases the average number of tree-visits by up to 37.16% in 44 16-QAM systems and 33.75% in 66 64-QAM systems.

The processor-sharing (PS) rule arises as a natural paradigm in a variety of practical situations, including time-shared computer systems. Although there has been much work on Poisson-input queueing analysis for the PS rule, there have been few results for renewal-input GI/G/1 (PS) systems. We consider the GI/G/1 (PS) system to provide develop a two-moment approximation for the mean performance measures. We derive the relationship between the mean unfinished work and the conditional mean sojourn time for the GI/G/1 (PS) system. Using this relationship, we derive approximate formulas for the mean conditional sojourn time, mean sojourn time, and the mean number of customers in the GI/G/1 (PS) system. Numerical examples are presented to compare the approximation with exact and simulated results. We show that the proposed approximate formulas have good accuracy.

We consider a stabilization problem of a class of input-delayed nonlinear systems that have not only feedforward, but also some non-feedforward nonlinearity. While there are some existing results that deal with input-delayed non-feedforward nonlinear systems, they often assume a small input delay. It has been often the case that for a large input delay, the results are limited to only feedforward systems. In this letter, combined with the LMI approach in [3] and the reduction method in [5], we show that some feedforward and non-feedforward systems with a large delay in the input can be stabilized via the proposed controller.

In this letter, a novel adaptive total variation (ATV) model is proposed for image inpainting. The classical TV model is a partial differential equation (PDE)-based technique. While the TV model can preserve the image edges well, it has some drawbacks, such as staircase effect in the inpainted image and slow convergence rate. By analyzing the diffusion mechanism of TV model and introducing a new edge detection operator named difference curvature, we propose a novel ATV inpainting model. The proposed ATV model can diffuse the image information smoothly and quickly, namely, this model not only eliminates the staircase effect but also accelerates the convergence rate. Experimental results demonstrate the effectiveness of the proposed scheme.

In this paper, a differential input/output linear MOS transconductor using an adaptively biasing technique is proposed. The proposed transconductor based on a differential pair is linearized by employing an adaptively biasing circuit. The linear characteristic of the individual differential output currents are obtained by introducing the adaptively biased currents to terminate the differential output terminals. Using the proposed technique, the common-mode rejection ration (CMRR) becomes high. Simulation results show that the proposed technique is effective for improvement of the linearity and other performances.

In this letter, we consider a control problem of a chain of integrators with a delay in the input under measurement feedback. While there are several control results for our considered system, they have not dealt with any of measurement feedback problems. Our proposed controller is coupled with a low-pass filter such that it can attenuate the sensor noise effect and reduce the ultimate bounds of the controlled systems states. Our result shows that the proposed method has clear benefit over the existing results.

A bootstrapped analog switch with constant on-resistance is proposed for the successive approximation (SA) analog-to-digital converters (ADCs) that have many input-sampling switches. The initialization circuit, which is composed of a short pulse generator and a transmission gate, improves the linearity of the proposed bootstrapped analog switch by reducing the effect of the capacitive load. To evaluate the proposed bootstrapped analog switch, the 10-bit 1 MS/s CMOS SA ADC with a rail-to-rail differential input signal was designed by using a 0.18 µm CMOS process with 1.0 V supply voltage. The proposed bootstrapped analog switch reduced the maximum VGS variation of the conventional bootstrapped analog switch by 67%. It also enhanced the signal to noise-distortion ratio of the SA ADC by 4.8 dB when the capacitance of its gate node is 100 fF, and this improvement was maximized when the capacitance of its gate node increases.

In this paper, we report the fabrication and device characteristics of InP/InGaAs double heterojunction bipolar transistors (DHBTs) with buried SiO2 wires. The SiO2 wires were buried in the collector and subcollector layers by metalorganic chemical vapor deposition toward reduction of the base-collector capacitance under the base electrode. A current gain of 22 was obtained at an emitter current density of 1.25 MA/cm2 for a DHBT with an emitter width of 400 nm. The DC characteristics of DHBTs with buried SiO2 wires were the same as those of DHBTs without buried SiO2 wires on the same substrate. A current gain cutoff frequency (fT) of 213 GHz and a maximum oscillation frequency (fmax) of 100 GHz were obtained at an emitter current density of 725 kA/cm2.

A resource allocation scheme for multi-access MIMO-OFDM systems in uplink was developed to improve power and spectrum efficiency in the frequency and the space domains [1]. The scheme requires a multi-user detector in the receiver and assumes identical spatial crosscorrelation across all subcarriers for any pair of spatially separable users. However, the multi-user detection device may not exist in the receiver and the identical spatial crosscorrelation assumption may not be valid in some operational scenarios. The paper develops a scheme to remedy these problems for multi-access MIMO-OFDM systems without using multi-user detection techniques and the assumption. The proposed scheme aims at minimizing the total user transmit power while satisfying the required data rate, the maximum transmit power constraint, and the bit error rate of each user. The simulation results are presented to demonstrate the efficacy of the proposed algorithm.

A balanced push-push frequency doubler has been demonstrated in 0.25-µm SOI (Silicon on Insulator) SiGe BiCMOS technology operating from 22 GHz to 29 GHz with high fundamental frequency suppression and high conversion gain. A series LC resonator circuit is connected in parallel with the differential outputs of the doubler core circuit. The LC resonator is effective to improve the fundamental frequency suppression. In addition, the LC resonator works as a matching circuit between the output of the doubler core and the input of the output buffer amplifier, which increases the conversion gain of the whole circuit. A measured fundamental frequency suppression of greater than 46 dBc is achieved at an input power of -10 dBm in the output frequency band of 22-29 GHz. Moreover, maximum fundamental frequency suppression of 66 dBc is achieved at an input frequency of 13 GHz and an input power of -10 dBm. The frequency doubler works at a supply voltage of 3.3 V.

A novel design technique for two-dimensional (2-D) waveguide slot arrays is proposed in this paper that combines a full-wave method of moments (MoM) analysis and an equivalent circuit with the explicit restraint of input matching. The admittance and slot spacing are determined first in an equivalent circuit to realize the desired distribution of power dissipation and phase, with the explicit restraint of input matching. Secondly by applying a full-wave MoM analysis to the finite 2-D array, slot parameters are iteratively determined to realize the active admittance designed above where slot mutual coupling and wall thickness are fully taken into account. The admittance, treated as the key parameter in the equivalent circuit corresponds to the power dissipation of the slots but not to the slot voltage, which is directly synthesized from the radiation pattern. The initial value of the power dissipation is assumed to be proportional to the square of the amplitude of the desired slot voltage. This assumption leads to a feedback procedure, because the resultant slot voltage distribution generally differs from the desired ones due to the effect of non-uniformity in the characteristic impedance on slot apertures. This slot voltage error is used to renew the initial distribution of power dissipation in the equivalent circuit. Generally, only one feedback cycle is needed. Two 2427-element arrays with uniform and Taylor distributions were designed and fabricated at 25.3 GHz. The measured overall reflections for both antennas were suppressed below -18 dB over the 24.3-26.3 GHz frequency range. High aperture efficiencies of 86.8% and 55.1% were realized for the antennas with uniform and Taylor distributions, the latter of which has very low sidelobes below -33 dB in both the E- and H-planes.

In this letter, an improved channel estimator for MIMO-SCBT systems is proposed. Pilot blocks are constructed using quadriphase complementary sequences (QCSs) which enable both one-sided (OSD) and two-sided (TSD) channel estimation (CE). And OSD-CE and TSD-CE are combined to provide improved performance in frequency-selective fast and slow fading channels and to maintain low-complexity implementations. Simulation results demonstrate the performance merits of the proposed scheme.

This paper proposes a multiple-input multiple-output (MIMO) precoding scheme for the down link of single user (SU) cooperative base station (BS) systems. The proposed precoding scheme mitigates the performance degradation caused by large inter-BS path-loss imbalance and large intra-BS antenna correlation by controlling two parameters. The proposed precoding scheme multiplexes the multiple layers by adjusting the amplitude of each layer, and then decreases the occurrence probability of the small absolute value of the log likelihood ratio (LLR), and so reduces the bit error rate (BER). Link level simulation results show that the proposed precoding scheme decreases the required signal-to-noise ratio (SNR) of BER = 0.001 by 5.5 dB, 2.2 dB, and 0.7 dB in the case of QPSK and coding rate 1/1, 3/4, and 1/2 respectively. The proposed precoding scheme is also evaluated in terms of spectrum efficiency using rank adaptation and adaptive modulation, showing that it improves the spectrum efficiency when the SNR per a receiver antenna is higher than 4 dB.

In this paper, a new framework to characterize the tradeoff between diversity and multiplexing gains of Multi Input Multi Output (MIMO) wireless systems at finite Signal to Noise Ratios (SNRs) is presented. By suitable definitions of non-asymptotic diversity and multiplexing gains, we extract a useful tool to investigate the performance of space-time schemes at finite SNRs. Exact results on the diversity-multiplexing tradeoff (DMT) are derived for Multi Input Single Output (MISO), Single Input Multi Output (SIMO), and 22 MIMO channels. We show that our outcomes coincide with the Zheng and Tse's results at high SNRs. When the new definitions of non-asymptotic diversity and multiplexing gains are used, the resulted DMT converges to its asymptotic value at realistic SNRs. Furthermore, using these definitions enables the diversity gain to represent the outage probability with reasonable accuracy.

In this letter, we propose a novel frequency-domain equalization (FDE) scheme for single-carrier multiple-input multiple-output (MIMO) systems over time-varying channels. Based on frequency-domain decision-feedback equalization (FD-DFE), we design a feedforward filter with constraint such that the equalization can be easily realized segment-by-segment with the help of the overlap-save (OLS) method. Since the segment length and block length can be designed independently, our proposal sets relatively short segment length to obtain good performance in time-varying environments, and very long block length to achieve high spectral efficiency. Furthermore, we present two scenarios in the design of filters for MIMO systems.

In this letter, we analyze the average symbol error rate (SER) performance for multiple-input multiple-output (MIMO) wireless communication links with transmit beamforming and maximum ratio combining (MRC), known as MIMO-MRC, in the presence of multiple interferers in Rayleigh fading channels. An upper bound and an approximation of the average SER for M-ary signaling and an exact average SER for some modulation formats are evaluated. Moreover, an exact closed-form expression of the average SER in an interference-limited environment is derived. The analytical results are confirmed by numerical simulations.