In this paper, we develop a new iterative turbo multiuser detector for direct sequence code-division multiple access (DS-CDMA) systems over unknown frequency-selective channels by decomposing the observation signal into a number of signal components. Virtual trellis model representing the ISI channel for each separating signal user is designed to generate extrinsic probability in term of BCJR algorithm for exchange with a single channel decoder as priori information. Minimum kullback-leibler (MKL) framework is derived to calculate numerical channel estimation and extrinsic probability. In comparison with other similar receiver, simulation results demonstrate that the proposed solution achieves the desirable performance.

The performances of a PCTH-based communication UWB system with diversiform modulation schemes are compared on the classic AWGN channel propagation and the realistic IEEE-UWB channel model. By employing different versions of modulation at the transmitters, the performances of an optimal receiver and a Rake receiver with various combining schemes are studied in this paper. The numerical results for several compared cases illustrate the tradeoff between transmitter diversity and receiver complexity. It is shown that the actual performance of the PAM-PCTH scheme can be better in both kinds of channel propagation. We also find that the PCTH-based UWB system with the Rake receiver has better performance than the conventional proposal for overcoming the multipath propagation effects in the UWB indoor environment.

Finite impulse response (FIR) filtering is the most computationally intensive operation in the channelizer of a wireless communication receiver. Higher order FIR channel filters are needed in the channelizer to meet the stringent adjacent channel attenuation specifications of wireless communications standards. The computational cost of FIR filters is dominated by the complexity of the coefficient multipliers. Even though many methods for reducing the complexity of filter multipliers have been proposed in literature, these works focused on lower order filters. This paper presents a coefficient-partitioning-based binary subexpression elimination method for realizing low power FIR filters. We show that the FIR filters implemented using proposed method consume less power and achieve speed improvement compared to existing filter implementations. Design examples of the channel filters employed in the Digital Advanced Mobile Phone System (D-AMPS) and Personal Digital Cellular (PDC) receivers show that the proposed method achieved 23% average reductions of full adder and power consumption and 23.3% reduction of delay over the best existing method. Synthesis results show that the proposed method offers average area reduction of 8% and power reduction of 22% over the best known method in literature.

In this paper, a new fractional sample rate conversion (SRC) scheme based on a direct insertion/cancellation scheme is proposed. This scheme is suitable for signals that are sampled at a high sample rate and converted to a lower sample rate. The direct insertion/cancellation scheme may achieve low-complexity and lower power consumption as compared to the other SRC techniques. However, the direct insertion/cancellation technique suffers from large aliasing and distortion. The aliasing from an adjacent channel interferes the desired signal and degrades the performance. Therefore, a modified direct insertion/cancellation scheme is proposed in order to realize high performance resampling.

In the design of Space Time Block Coding (STBC), for an arbitrary complex signal constellation with a size above 2 as well as a real signal matrix with a size above 8, it is difficult to acquire full code rate and full transmit diversity simultaneously. In this letter, an efficient selective receiver switching scheme is proposed for STBC with the full code rate and non-orthogonal design with the example of a 4-by-4 matrix. In the proposed scheme with the aid of beamforming, we divide the received signals into two groups according to the encoded matrix. By this way, we can eliminate the interference from the neighboring signals by more than half.

This paper presents a triple-band WCDMA direct conversion receiver (DCR) IC that needs a small number of off-chip components and control signals from digital baseband (DBB) IC. The DCR IC consists of 3 quadrature demodulators (QDEMs) with on-chip impedance matching circuit and an analog baseband block (ABB) that contains a low-pass filter (LPF) with fc automatic tuning circuit using no off-chip components and a linear-in-dB variable-gain amplifier (VGA) with on-chip analog high-pass filter (HPF). In order to make use of DBB control-free DC offset canceler, the DCR is designed to avoid large gain change under large interference that causes long transient response. In order to realize that characteristic without increasing quiescent current, the QDEM is used that employs class AB input stage and low-noise common mode feedback (CMFB) output stage. The DCR IC was fabricated in a SiGe BiCMOS process and occupies about 2.9 mm3.0 mm. The DCR needs SAW filters only for off-chip components and a gain control signal from DBB IC for AGC loop. The IIP3 of over -4.4 dBm for small signal input level and that of over +1.9 dBm for large signal input level are achieved. The gain compression of the desired signal is less than 0.3 dB for ACS Case-II condition.

We investigate the problem of joint transmitter and receiver power allocation with the minimax mean square error (MSE) criterion for uplink transmissions in a multi-carrier code division multiple access (MC-CDMA) system. The objective of power allocation is to minimize the maximum MSE among all users each of which has limited transmit power. This problem is a nonlinear optimization problem. Using the Lagrange multiplier method, we derive the Karush-Kuhn-Tucker (KKT) conditions which are necessary for a power allocation to be optimal. Numerical results indicate that, compared to the minimum total MSE criterion, the minimax MSE criterion yields a higher total MSE but provides a fairer treatment across the users. The advantages of the minimax MSE criterion are more evident when we consider the bit error rate (BER) estimates. Numerical results show that the minimax MSE criterion yields a lower maximum BER and a lower average BER. We also observe that, with the minimax MSE criterion, some users do not transmit at full power. For comparison, with the minimum total MSE criterion, all users transmit at full power. In addition, we investigate robust joint transmitter and receiver power allocation where the channel state information (CSI) is not perfect. The CSI error is assumed to be unknown but bounded by a deterministic value. This problem is formulated as a semidefinite programming (SDP) problem with bilinear matrix inequality (BMI) constraints. Numerical results show that, with imperfect CSI, the minimax MSE criterion also outperforms the minimum total MSE criterion in terms of the maximum and average BERs.

This paper proposes a new parameter estimation method for the MIMO-OFDM MAP receiver with spatial-temporal filters. The proposed method employs eigenvalue decomposition (EVD) so as to attain precise estimates especially under interference-limited conditions in MIMO-OFDM mobile communications. Recursive EVD is introduced to reduce the computational complexity compared to the nonrecursive EVD. The spatial-temporal prewhitening is placed prior to FFT because this arrangement is superior to that of conventional prewhitening posterior to FFT in accuracy of the parameter estimation. In order to improve tracking capability to fast fading, the proposed scheme applies a decision-directed algorithm to the parameter estimation by using log-likelihood ratios of coded bits. Computer simulations demonstrate that the proposed scheme can track fast fading and reduce the complexity to 18 percents of the conventional one, and that the spatial-temporal filtering prior to FFT outperforms the conventional one posterior to FFT.

In this paper, sampling rate selection diversity (SRSD) scheme for Direct-Sequence/Spread-Spectrum (DS/SS) is proposed. In DS/SS communication systems, oversampling may be employed to increase the signal-to-noise ratio (SNR). However, oversampling enlarges the power consumption because signal processing of the receiver has to be carried out at a higher clock rate. Higher sampling rate does not always maximize the SNR. In the proposed SRSD scheme, the power consumption can be reduced by selecting the optimum sampling rate depending on the characteristics of the channel. The proposed SRSD scheme can also reduce the BER more than the conventional oversampling scheme under certain channel conditions.

In this letter, we introduce a new adaptive beamforming assisted receiver based on minimizing the approximate negentropy (NEGMIN) of the estimation error. We consider the approximate negentropy by using a nonpolynomial expansion of the estimation error as a new performance criterion to improve the performance of adaptive beamforming receivers based on the minimizing minimum mean squared error (MMSE) criteria. Negentropy includes higher order statistical information and its minimization provides improved converge, performance, and accuracy compared to traditional methods such as MMSE in terms of bit error rate (BER).

In this paper, a non-data aided minimum mean square error (MMSE) receiver with enhanced multiple access interference (MAI) suppression is proposed for direct-sequence code-division multiple-access (DS-CDMA) systems over a multipath fading channel. The design of the proposed receiver is via the following procedure: First, an adaptive correlator is constructed based on the linearly constrained minimum variance (LCMV) criterion to collect each multipath signal and suppress MAI blindly. A maximum ratio combiner is then utilized to coherently combine the correlator outputs. With a set of judicious chosen weight vectors, effective diversity combining can successfully suppress MAI and the desired signals can be effectively retained. Finally, further performance improvement against the finite data sample effect is achieved using a decision-aided scheme in which the channel response is obtained by the decision data and incorporated with the MMSE method to compute the refined weight vector. Performance analysis based on the output signal-to-interference-plus-noise ratio (SINR) is done to examine the efficacy of the proposed non-data aided MMSE receiver, which can offer the similar results as those of the MMSE receiver with the channel estimation correctly obtained beforehand. Computer simulation results then confirm correctness of the analysis results and demonstrate that the proposed blind receiver can successfully resist MAI as well as the finite data sample effect, and significantly outperform than the conventional blind receivers.

Multicast delivery in heterogeneous wireless networks requires careful coordination, in order to take full advantage of the resources such an interworking network environment can offer. Effective coordination, however, may require interworking signaling from coordinating network entities to receivers of a multicast service. Scalable delivery of such signaling is of great importance, since a large number of receivers may be interested in a multicast service. This paper therefore investigates the use of a multicast signaling channel (MSCH) to carry such interworking signaling in a scalable manner. Applications of interworking signaling for multicast service delivery in heterogeneous wireless networks are presented, motivating the need for an MSCH. Then a comparative study is performed analysing potential benefits of employing an MSCH for signaling message delivery compared to conventional unicast signaling. The analysis reveals that the benefits of the MSCH depend mainly on the selection of an appropriate signaling network to carry the MSCH and also on efficient addressing of a subset of receivers within the MSCH. Based on the findings, guidelines for the selection of a suitable signaling network are provided. Furthermore a novel approach is proposed that allows efficient addressing of a subset of receivers within a multicast group. The approach minimizes the required signaling load on the MSCH by reducing the size of the required addressing information. This is achieved by an aggregation of receivers with common context information. To demonstrate the concept, a prototype of the MSCH has been developed and is presented in the paper.

A quadrature demodulator (QDEMOD) for WCDMA direct-conversion receiver using a common-base input stage is reported. A common-base input stage is robust to parasitic elements and is suitable for integrating on-chip matching circuits to realize small and low-cost RF front-end modules. However, a common-mode blocker signal, such as the transmitter (TX) leakage signal, degrades the noise performance due to DC current increase and intermodulation distortion of the TX leakage signal and noise. We propose a QDEMOD with a common-base input stage capable of suppressing the TX leakage signal using symmetrical inductors. The QDEMOD was fabricated using SiGe BiCMOS process with fT of 75 GHz. The measured results show that the NF degradation does not occur until the TX leakage signal input is larger than -10 dBm.

The linearity and noise required by GSM and UMTS receivers make the design of a CMOS mixer for these applications so challenging. A new technique for IP2 improvement in Zero-IF active mixers is presented in this paper. This inductor-less technique is based on canceling the parasitic capacitor of common source node of the switching transistors and synthesizing resistive impedance. Using this technique, a reconfigurable down converter mixer works from 900 MHz to 2.4 GHz is designed supporting GSM, DCS, PCS, UMTS and IEEE802.11 b-g standards. The mixer IIP2 is higher than 71 dBm in GSM and UMTS bands. The mixer conversion gain is higher that 12 dB in all frequency bands. The design is done in 65 nm CMOS technology and consumes 10 mA from a 1.2 V supply. The design meets the performance required for all mentioned standards, while its area and power is comparable with high performance single band mixers.

Spatial multiplexing (SM) offers a linear increase in transmission rate without bandwidth expansion or power increase. In SM systems, the LMMSE receiver establishes a good tradeoff between the complexity and performance. The performance of the LMMSE receiver would be degraded by MIMO channel estimation errors. This letter focus on obtaining the asymptotic convergence of output interference power and SIR performance for the LMMSE receiver with channel uncertainty. Exactly matched simulation results verify the validity of analysis in the large-system assumption. Furthermore, we find that the analytical results are also valid in the sense of average results for limited-scale system in spite of the asymptotic assumption used in derivation.

The performance of a new APSK receiver is analyzed using numerical simulation. The proposed receiver eliminates the penalty caused by SPM-induced phase-shift of optical pulses by employing three sub-modules and an amplitude-pattern controlled switch for each DPSK tributary. The interplay between SPM, IXPM, and XPM determines the performance of the proposed receiver for single-channel and WDM transmission.

We report on a subsystem of electromagnetic wave radiation and propagation estimation using high-Tc superconducting (HTS) receiving filters for S band. The subsystem, comprised of HTS filters, a rubidium standard signal generator (Rb SSG), a global positioning system (GPS) unit, etc., was used to evaluate the electromagnetic-wave (EMW) intensities, frequencies, the frequency interferences and the ground positions where the EM are measured. The developed subsystem showed high frequency selectivity for S band by using the HTS filters. Furthermore, we verified that the subsystem with the HTS filters operated on the moving car.

Iterative receivers, which perform MMSE detection and decoding iteratively, can provide significant performance improvement compared with noniterative method. However, due to the high computational cost and numerical instability, conventional MMSE detection using a priori information can not be implemented in hardware. In this letter, we propose a newly-built iterative receiver which is division-free and numerically stable, and then we analyze the results of a fixed-point simulation and present the hardware implementation architecture.

This paper proposes a two-dimensional self-matching receiver for Free Space Optics (FSO) communication system using chaotic spatial synchronization. This system is able to obtain the information of two-dimensional code from received pattern. This paper considers that proposed system is applied to two applications. The first application is image transmission. This paper shows that applying proposed system to image transmission enables to restore the desired image, which doesn't require strict alignment of receiver, and evaluates transmission optical power. The second application is Code Division Multiplexing (CDM). This paper shows that applying proposed system to CDM system enables to demodulate desired digital signals regardless of the uncertainty of received position. Moreover, the required transmission optical power and bit error rate performance are obtained by computer simulation.

Diseases of the gastro-intestinal tract are becoming more prevalent. New techniques and devices, such as the wireless capsule endoscope and the telemetry capsule, that are able to measure the various signals of the digestive organs (temperature, pH, and pressure), have been developed for the observation of the digestive organs. In these capsule devices, there are no methods of moving and grasping them. In order to make a swift diagnosis and to give proper medication, it is necessary to control the moving speed of the capsule. This paper presents a wireless system for the control of movements of an electrical stimulus capsule. This includes an electrical stimulus capsule which can be swallowed and an external transmitting control system. A receiver, a receiving antenna (small multi-loop), a transmitter, and a transmitting antenna (monopole) were designed and fabricated taking into consideration the MPE, power consumption, system size, signal-to-noise ratio and the modulation method. The wireless system, which was designed and implemented for the control of movements of the electrical stimulus capsule, was verified by in-vitro experiments which were performed on the small intestines of a pig. As a result, we found that when the small intestines are contracted by electrical stimuli, the capsule can move to the opposite direction, which means that the capsule can go up or down in the small intestines.