Receiver Structure Research Articles

RF Transceiver for the Multi-Mode Radar Applications.

In this work, a multi-mode radar transceiver supporting pulse, FMCW and CW modes was designed as an integrated circuit. The radars mainly detect the targets move by using the Doppler frequency which is significantly affected by flicker noise of the receiver from several Hz to several kHz. Due to this flicker noise, the long-range detection performance of the radars is greatly reduced, and the accuracy of range to the target and velocity is also deteriorated. Therefore, we propose a transmitter that suppresses LO leakage in consideration of long-range detection, target distance, velocity, and noise figure. We also propose a receiver structure that suppresses DC offset due to image signal and LO leakage. The design was conducted with TSMC 65 nm CMOS process, and the designed and fabricated circuit consumes a current of 265 mA at 1.2 V supply voltage. The proposed transmitter confirms the LO leakage suppression of 37 dB at 24 GHz. The proposed receiver improves the noise figure by about 20 dB at 100 Hz by applying a double conversion architecture and an image rejection, and it illustrates a DC rejection of 30 dB. Afterwards, the operation of the pulse, FMCW, and CW modes of the designed radar in integrated circuit was confirmed through experiment using a test PCB.

Two approaches to multiuser detection over fading channels

In this paper, two different receiver structures to multiuser detection that are appropriate for the code-division multiple-access systems with antenna arrays in fading channels are investigated and compared. We analyze and compare the performance of the two different multiuser detection structures for uplink or downlink channels. The number of elements of receiving antenna array may be limited in the downlink channel due to the small size of receivers. We assume a synchronous system, but it can be easily extended to an asynchronous system. The first approach is based on the distributed decorrelator where the signal decorrelation is performed by each receiving antenna element independently and decorrelated outputs are combined according to the maximum ratio. The second approach is the central decorrelator where the signal decorrelation is performed once collectively on the outputs from all elements of receiving antenna array. Both decorrelators provide the same performance in the additive white Gaussian noise channels. The distributed decorrelator provides the better performance in flat fading channels. We employ the decorrelator to demonstrate our results. The results discussed in the present paper can be extended to other configurations such as the blind adaptive space-time multiuser detection.

SCMA System Design With Index Modulation via Codebook Assignment

Sparse code multiple access (SCMA) is a promising non-orthogonal multiple access (NOMA) scheme for massive machine-type communications for 5G-and-beyond communication systems. Innovative use of orthogonal frequency division multiplexing with index modulation (OFDM-IM) takes advantage of using tone indices in data transmission. In this study, we propose a novel multiplexing and multiple access scheme, namely SCMA based on OFDM-IM (SCMA-IM). SCMA-IM method can be implemented in uplink NOMA systems in an efficient way with similar computational complexity as SCMA. In this method constellation differences and diversity are obtained via SCMA codebooks (CBs) and the employment of CBs is transferred to index modulation (IM). Performance improvement is achieved via CBs so that the number of data bits carried by indices increases more than one bit with different constellations, and also with the number of CBs assigned. In order to determine the indices used in IM, the receiver structure is simplified by the message passing algorithm and log-likelihood ratio detection process used in SCMA receivers without indexing the receiver. Thus, a new NOMA scheme is obtained by coding with IM. Bit error rate performance of the system is studied for 150% and 200% overloading factors.

Research on Throughout with SWIPT in Two-Way Relay System Under Power Splitting Receiver

We consider the Simultaneous Wireless Information and Power Transfer strategy optimization in the two-way transmission relay system under Power Splitting (PS) receiver. In such case, we propose two operational strategies for two-way transmission under PS receiver structure, (1) Delay-Limited-Relay strategy (PS-LDR) and (2) Delay-Tolerated-Relay strategy (PS-TDR). PS-LDR strategy is that both sending node and receiving node need synchronization of information transmission, so communication systems have higher Signal Noise Ratio (SNR) threshold for channels, or communication may break down. In order to explore the performance of PS-LDR strategy, we use outage probability to calculate the analytical expression of the actual maximum throughput (AMT). PS-TDR strategy allows that the information received by the receiving node delays with the information sent by the sending node. Communication system in PS-TDR strategy has lower SNR threshold than that in PS-LDR strategy. The analytical expression of the AMT is calculated by the ergodic capacity in PS-TDR strategy. The influences of system parameters on the optimal throughput in two strategies are discussed.

SER performance investigation of a MPPM relay-aided FSO system with three decision thresholds over EW fading channel considering pointing errors

The symbol error rate (SER) performance of a multi-hop parallel free-space optical (FSO) communication system with multiple pulse position modulation (MPPM) scheme considering three different decision threshold schemes, fixed decision threshold (FDT), optimized decision threshold (ODT), and dynamic decision threshold (DDT) has been investigated over exponentiated Weibull (EW) atmospheric turbulence channel combiningthe impact of the fading induced by pointing errors. On the basis of the decode-and-forward (DF) protocol, the cumulative distribution function (CDF) and probability density function (PDF) in terms of the Meijer’ s G-function for this considered FSO communication system are derived with the max–min criterion as the best path selection scheme. After that, the closed-form SER expressions for three threshold schemes are obtained by Gauss–Laguerre quadrature function and then confirmed by Monte Carlo (MC) simulation. The SER performance is further analyzed systematically under different turbulence conditions, receiver aperture sizes, jitter variances, and structure parameters (R and C) for three decision threshold schemes. The results show that pointing errors will deteriorate the system performance, while the multi-hop parallel transmission can improve the SER performance and expand the communication range. Furthermore, ODT and DDT schemes can significantly overcome the effect of the error floor of FDT scheme. This work benefits the development of the MPPM based relay-aided FSO system.

A Joint TOA and DOA Acquisition and Tracking Approach for Positioning With LTE Signals

A receiver structure is proposed to jointly estimate the time-of-arrival (TOA) and azimuth and elevation angles of direction-of-arrival (DOA) from received cellular long-term evolution (LTE) signals. In the proposed receiver, a matrix pencil (MP) algorithm is used in the acquisition stage to obtain a coarse estimate of the TOA and DOA. Then, a tracking loop is proposed to refine the estimates and jointly track the TOA and DOA changes. The performance of the acquisition and tracking stages are evaluated in the presence of noise and multipath. Simulation results are provided to validate the analytical results. The Cramér-Rao lower bounds (CRLBs) of the TOA and DOA estimates are derived to compare the performance of the proposed acquisition and tracking approaches with the best-case performance. It is shown that the proposed approach has lower complexity compared to the MP algorithm. Finally, experimental results are provided with real LTE signals, showing a reduction of 93%, 57%, and 31% in the standard deviation of TOA, azimuth, and elevation angles' estimation errors, respectively, using the proposed receiver compared to the MP algorithm.

Simple Design on Nanoscale Receivers Using CNT Cantilevers

To develop nanoscale sensors with future potential, a nanoscale receiver utilizing the nanomechanical vibration of a cantilever composed of a carbon nanotube, had been proposed for detecting the digital information carried by wireless signals. The introduced receiver includes two essential parts: a phase detector and demodulator, which employ a reference signal and carrier signal, respectively. Additional components such as electrical circuits and oscillators are required to excite these signals, increasing the sensor size. This study presents a design method for simplifying the receiver structure to contribute to sensor miniaturization. This study theoretically derives a tractable form that can describe the performance of the introduced receiver. This form enables the determination of a simple receiver structure with performance enhancement from a mathematical perspective. Using the proposed method, either the reference wave or carrier signal can be excluded from the receiver, simplifying its structure. The results are demonstrated through a numerical simulation.

Enhanced Uplink Coverage for 5G NR: Frequency-Domain Spectral Shaping With Spectral Extension

This paper describes and investigates a novel concept of frequency-domain spectral shaping (FDSS) with spectral extension for the uplink (UL) coverage enhancement in 5G New Radio (NR), building on discrete Fourier transform spread orthogonal frequency-domain multiplexing (DFT-s-OFDM). The considered FDSS concept is shown to have large potential for reducing the peak-to-average-power ratio (PAPR) of the signal, which directly impacts the feasible maximum transmit power under practical nonlinear power amplifiers (PAs) while still meeting the radio frequency (RF) emission requirements imposed by the regulations. To this end, the FDSS scheme with spectral extension is formulated, defining filter windows that fit to the 5G NR spectral flatness requirements. The PAPR reduction capabilities and the corresponding maximum achievable transmit powers are evaluated for a variety of bandwidth allocations in the supported 5G NR frequency ranges 1 and 2 (FR1 and FR2) and compared to those of the currently supported waveforms in 5G NR, particularly π/2-BPSK with FDSS without spectral extension and QPSK without FDSS. Furthermore, an efficient receiver structure capable of reducing the noise enhancement in the equalization phase is proposed. Finally, by evaluating the link-level performance, together with the transmit power gain, the overall coverage enhancement gains of the method are analyzed and provided. The obtained results show that the spectrally-extended FDSS method is a very efficient solution to improve the 5G NR UL coverage clearly outperforming the state-of-the-art, while being also simple in terms of computational complexity such that the method is implementation feasible in practical 5G NR terminals.

Deep Learning-Based Timing Offset Estimation for Deep-Sea Vertical Underwater Acoustic Communications

This study proposes a novel receiver structure for underwater vertical acoustic communication in which the bias in the correlation-based estimation for the timing offset is learned and then estimated by a deep neural network (DNN) to an accuracy that renders subsequent use of equalizers unnecessary. For a duration of 7 s, 15 timing offsets of the linear frequency modulation (LFM) signals obtained by the correlation were fed into the DNN. The model was based on the Pierson–Moskowitz (PM) random surface height model with a moderate wind speed and was further verified under various wind speeds and experimental waveforms. This receiver, embedded with the DNN model, demonstrated lower complexity and better performance than the adaptive equalizer-based receiver. The 5000 m depth deep-sea experimental data show the superiority of the proposed combination of DNN-based synchronization and the time-invariant equalizer.

BER Analysis of Integrated WFRFT-OTFS Waveform Framework Over Static Multipath Channels

Orthogonal time frequency space (OTFS) modulation has been proposed to achieve outstanding performances over delay-Doppler channels in comparison with orthogonal frequency division multiplexing (OFDM) systems. Particularly, transmitter and receiver structures of OTFS are same as those of asymmetric OFDM (A-OFDM) waveforms, and OTFS is simplified as A-OFDM over static multipath channels. In this letter, we propose an integrated waveform framework based on weighted-type fractional Fourier transform (WFRFT) with two-dimensional adjustable parameters and strong scalability, called as WFRFT-OTFS, which can be reduced to OTFS, A-OFDM, hybrid carrier (HC), OFDM and other waveforms. Basically, theoretical BER expressions of integrated WFRFT-OTFS framework over multipath channels with zero forcing (ZF) and minimum mean square error (MMSE) receivers are derived through fusing different waveform components and verified by simulation results.

A New Non-Orthogonal Transceiver for Asynchronous Grant-Free Transmission Systems

The grant-free non-orthogonal multiple access (GF-NOMA) system, in which users autonomously transmit uplink data signals without carrying out a complicated random access process, offers significant advantages for increasing the efficiency of resource usage with low signaling overhead. In the proposed GF-NOMA system, since the collision resolution process is omitted and resources are not pre-assigned to users, multiple users may use same resource, without the base station (BS) being able to identify these collided users. In addition, in the absence of the UL synchronization procedure generally performed in the random access process, multiple users’ signals are received asynchronously. To solve these problems, we have developed a new transceiver structure for the GF-NOMA system consisting of a secondary preamble and a multiuser-multisymbol (MUMS) detector. The purpose of the secondary preamble is to successfully detect user access and estimate channel information even when no collision resolution process is being performed. The MUMS receiver is then proposed as a way to effectively mitigate the severe interference caused by the asynchronous transmission. Simulation results show that the proposed preamble structure and the receiver structure are superior to the conventional schemes. Furthermore, we show that the GF-NOMA system with the proposed transceiver structure achieves much better performance than other GF-NOMA systems in terms of reliability and successfully detected bits.

PAPR reduction scheme for optical OFDM techniques

Abstract In both optical wireless and optical fiber communication, orthogonal frequency division multiplexing (OFDM) plays an important role in data transmission. In the similar context, DC-coupled optical (DCO) OFDM and asymmetrically clipped optical (ACO) OFDM are discussed. DCO-OFDM has better peak to average power ratio (PAPR) but bit error rate (BER) performance is poor; however, in case of ACO-OFDM, PAPR is poor but BER performance is good. Moreover, DCO-OFDM is more power hungry; therefore, ACO-OFDM is considered as a preferred choice. Recently, asymmetrically clipped DC-biased optical (ADO)-OFDM is proposed, which shows good PAPR and BER performance. Clipping and µ-law companding techniques are discussed for PAPR reduction. The mathematical model is developed for all the three methods for received signal while considering clipping and companding noises along with channel noise. It is found that ADO-OFDM is better choice in comparison to DCO and ACO-OFDM. However, in case of ADO-OFDM, receiver structure is more complex.

Transceiver Design for GFDM with Hexagonal Time–Frequency Allocation Using the Polyphase Decomposition

Generalized frequency division multiplexing (GFDM) is a waveform for the next-generation communication systems to succeed in the drawbacks of orthogonal frequency division multiplexing (OFDM). The symbols of users are transmitted with the time- and frequency-shifted versions of a prototype filter. According to filtering operation, the computational complexity and processing load are high for the devices that suffer from energy consumption. The communication systems are required to support the new generation devices that need low energy consumption and low latency issues. Motivated by such demands of the next-generation communication system, we propose a novel GFDM waveform that we call hexagonal GFDM. The contributions of the hexagonal GFDM are that it: (i) supports short transmission time based on its hexagonal time–frequency allocations; and (ii) provides low latency communication with low computational complexity manner. Furthermore, we design a transmitter and receiver structure in a less complicated way with mathematical derivation by using polyphase decomposition and Fourier transform (FT) transformation. The proposed systems are realized analytically and investigated over Rayleigh fading channel model through computer simulations.

On the Multiplexing of Data and Metadata for Ultra-Reliable Low-Latency Communications in 5G

This paper addresses the problem of downlink radio resource management for ultra-reliable low-latency communications (URLLC) in fifth generation (5G) systems. To support low-latency communications, we study performance of two multiplexing schemes namely in-resource control signalling and joint encoding of data and metadata . In the former, the metadata and data are separately encoded and the metadata is sent at the beginning of transmission time prior to the data. Thus, it benefits from a low-complexity receiver structure to decode the data block. The latter takes advantages of transmitting a larger blocklength to enhance the reliability and improve spectrum efficiency by jointly encoding data and metadata as a single codeword. Dealing with small URLLC payloads, the overhead and error of sending metadata are not negligible and have a significant impact on the system performance in terms of resource usage the reliability of transmission. For each scheme, we derive expressions for the outage probability and resource usage by taking into account impacts of the finite blocklength payloads, overhead and error of sending metadata, and probability of error in uplink feedback channel. We propose a novel framework for joint data and metadata link adaptation to minimize the average number of allocated resources, while ensuring the stringent URLLC quality of service requirements. An optimization problem is formulated for each scheme that is mixed-integer non-convex problem, difficult to solve in polynomial time. Solutions based on successive convex optimization are proposed. Numerical evaluations show that the proposed algorithms perform close to the optimal solution and demonstrate remarkable gains of up to $\mathbf {27\%}$ improvement in resource usage. Finally, we present sensitivity analysis of the results for various network parameters.

Parametric design optimization of e-compressor NVH using blocked forces and substructuring

The combination of frequency based substructuring (FBS) and blocked force Transfer Path Analysis (TPA) allows to perform parametric NVH design optimizations. Blocked forces are not dependent on one specific receiver structure, in contrast to interface forces of classical TPA. Blocked forces can therefore be used as a source description in design optimization. For optimizing the assembly, different substructures are virtually coupled to each other, where each substructure is described by the most appropriate modeling approach. Frequency based substructuring (FBS) allows coupling analytical, numerical or experimental models to each other. The transfer functions of the final assembly can thus be simulated by FBS. Numerical models are used for substructures which can be simulated with high accuracy. These are parametrized for optimization. Experimental substructure models are used for substructures that are hard to simulate accurately.The application example is an electric climate compressor. Its excitation is characterized by means of blocked forces. The assembly consists of: a) a FEM model of the receiver, b) experimental models of different rubber isolators, c) a parametrized FEM model for the compressor support, and d) an analytical rigid body model for the compressor itself. The rubber isolator choice and the FEM model of the support, are iteratively optimized for minimal structure borne noise. Virtually coupling the substructures, and applying the compressors blocked forces to the assembly, makes it possible to simulate the resulting loudness for different design parameters. We discuss the formulation of an objective function and the applicability of different optimization algorithms on a minimal example first. Then we apply a genetic optimization algorithm to the objective function for the compressor design. The simulated predictions for the optimal parameters are validated with measurements on the physically built up design, including auralization of the results.

Exploiting dynamic sparsity for time reversal underwater acoustic communication under rapidly time varying channels

Underwater acoustic (UWA) communication encounters significant difficulties posed by the simultaneous presence of multipath and time variations. It has been recognized that, under the assumption that channel keeps static within the processing windows, time reversal (TR) processing approach is capable of mitigating multipath via the spatial–temporal focusing. However, for a rapidly time-varying UWA channel, the replica channel impulse response in time reversal processor need to be updated frequently to avoid performance degradation, which leads to huge computational complexity and significant overhead. Consider that after time reversal processing the resulting time-reversed channel response exhibits much more slow time variations compared to the original channel impulse response, previously Kalman filtering has been adopted to track the time-reversed channel response to alleviate the requirement of frequent channel update. Under the framework of dynamic compressed sensing (DCS), in this paper the time-reversed channel is formulated as a sparse set consisting of constant and slowly time-varying supports to derive the Kalman Filtered Compressed Sensing (KF-CS) channel estimation algorithm for time reversal communication. Based on the receiver structure by coupling the KF-CS estimator driven time reversal processor with a single channel decision-feedback equalizer (TR-DCS-DFE), shallow water experimental results with field data are provided to demonstrate the effectiveness of the proposed algorithm, compared to the classic time reversal communication scheme.

Performance of Indoor VLC System Under Random Placement of LEDs With Nonimaging and Imaging Receiver

This article analyzes the performance of multiple-input-multiple-output indoor visible light communication (VLC) system by randomly deploying the light-emitting-diodes (LEDs) using Matern hardcore point process (MHCP). Furthermore, photodetectors (PDs) with two different field of view (FOVs) have been utilized for an imaging as well as nonimaging receiver structures. It is a widely known fact that in a conventional VLC system, signal-to-noise ratio (SNR) profile inside the room varies with respect to the LED placement and the PDs position. Consequently, the proposed work attempts to achieve uniform SNR across the room, by utilizing MHCP based LED placement at the transmitter, and a nonimaging receiver with four PDs using 1-FOV, 2-FOV, and imaging receiver configurations. Simulation results show that random deployment of LED using MHCP configuration results in a more uniform SNR profile inside the room as compared to regular LED deployment schemes. Furthermore, three different power allocation schemes for LEDs namely equal power, distance-based power, and an optimal power allocation are proposed. For the different power allocation schemes, the average SNR and the variance of the received optical power (OP) inside the room are derived and compared. In addition, the closed-form expression for the bit-error-rate (BER) probability is derived for the proposed MHCP configuration using <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> - <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> keying as a modulation scheme. Results show improvement in BER performance with the OP allocation in comparison to other power allocation schemes both for imaging and nonimaging receiver configuration.

A Fast and General Method to Calculate Mutual Inductance for EV Dynamic Wireless Charging System

For the electric vehicle (EV) dynamic wireless charging system, mutual inductance is an important factor affecting the output power. In this article, a fast and general method to calculate mutual inductance is proposed. This method can calculate the mutual inductance of magnetic couplers with different receiver structures and receiver positons by only one simulation, and it can also provide a theoretical guidance for the receiver design. Calculation models for different receiver structures are established, and the mutual inductance calculation-coefficients are proposed to describe the functional relationships between mutual inductance and receiver's parameters. Based on the concept of mutual inductance calculation-coefficients, the surface-integral in the conventional analytical calculation method can be simplified to be the product of these coefficients and magnetic flux density's amplitude, and then the calculation difficulty of the mutual inductance can be reduced. Finally, a prototype was built for experimental verification. The experiment results show that the max error between the measured mutual inductance and the calculated result is only 1.56%, which verifies the feasibility and the accuracy of the proposed calculation method.

Design and Analysis of Probabilistic Shaping in Color Shift Keying Modulation Schemes

In this article, we analyze the performance of probabilistic shaping (PS) color shift keying (CSK) modulated visible light communication (VLC) systems. Specifically, we have considered three variants of CSK with respect to receiver structure, namely CSK with one photodetector (PD), CSK with three PDs, and CSK with one avalanche PD. For shaping the CSK input symbols, four different source distributions are considered viz., uniform, exponential, Maxwell–Boltzmann, and Pareto. The article comprises of developing algorithms to obtain the optimum probability order for maximizing the received signal-to-noise ratio (SNR) gain. The proposed systems have been analyzed for computational complexity. Furthermore, the closed-form expressions for symbol error rate (SER) have been derived for the proposed PS-CSK schemes. It has been observed that proposed PS-CSK schemes provide different SNR gain for different source distributions at a given SER. The results show that PS based on Pareto distribution gives the best performance gain at unity achievable information rate among all considered source distributions.

Integrated receiver with high misalignment tolerance used in dynamic wireless charging

Misalignments between the transmitter and receiver coils would in some cases lead to a significant decline in transmission power and efficiency in the wireless power transfer system. This study presents an integrated two-layer receiver to improve the tolerance of horizontal misalignment. On the lower layer of the integrated receiver, two coplanar spiral coils, which are decoupled and work as the auxiliary repeater, are designed to help keep a stable power transmission between transmitter coils on the track and the main receiver coil on the upper layer. Then, the optimisation model based on the Bayesian algorithm is established for the proposed receiver structure and some key parameters are optimised. A sensor-coil-based positioning approach is also proposed to achieve on–off control of the transmitter coils. The simulation results show that the system based on the optimised integrated receiver has a stable output power with a variation lower than 13.17%. Two 300 W dynamic charging prototypes based on the integrated receiver and conventional spiral receiver, respectively, have been developed to verify the effectiveness of the proposed design and the optimisation method. The experimental results match well with the simulation results.