Signal-to-interference-plus-noise Ratio Performance Research Articles

CAWE-ACNN Algorithm for Coprime Sensor Array Adaptive Beamforming.

This paper presents a robust adaptive beamforming algorithm based on an attention convolutional neural network (ACNN) for coprime sensor arrays, named the CAWE-ACNN algorithm. In the proposed algorithm, via a spatial and channel attention unit, an ACNN model is constructed to enhance the features contributing to beamforming weight vector estimation and to improve the signal-to-interference-plus-noise ratio (SINR) performance, respectively. Then, an interference-plus-noise covariance matrix reconstruction algorithm is used to obtain an appropriate label for the proposed ACNN model. By the calculated label and the sample signals received from the coprime sensor arrays, the ACNN is well-trained and capable of accurately and efficiently outputting the beamforming weight vector. The simulation results verify that the proposed algorithm achieves excellent SINR performance and high computation efficiency.

User-Centric Cluster Design and Analysis for Hybrid Sub-6GHz-mmWave-THz Dense Networks

The terahertz (THz) waves with enormous bandwidth can be used along with the existing sub-6GHz and millimeter wave (mmWave) bands to achieve the ever evolving ecosystem of applications that need to be supported by the modern wireless networks. This paper investigates a user-centric dynamic base station (BS) clustering design for a hybrid network where THz, mmWave, and sub-6GHz BSs coexist. Invoking the proposed clustering model, the BS cooperation within each band is made possible by considering long term channel variations and all the surrounding BSs within a cluster with tunable size. A typical user is associated with the best BS cluster, from either a sub-6GHz, mmWave or THz tier based on the maximum signal-to-interference-plus-noise-ratio (SINR) criterion or the maximum rate criterion. Using tools from stochastic geometry, we assess the performance of the proposed user-centric hybrid system in terms of SINR and rate coverage performances, while accounting for: band specific propagation models, directional beamfroming, and BSs random locations. The accuracy of the analytical results is validated with Monte-Carlo simulations. The obtained results recognize a clear coverage/rate trade-off where a high fraction of THz BSs improves the rate significantly but may degrade the coverage performance. Thus, with carefully planned networks, enabling user-centric BS cooperation for hybrid wireless systems can achieve ultra-high rates while maintaining sufficient coverage in sixth-generation (6G) networks.

Finite-Order Filter Designs of Source and Multiple Full-Duplex Relays for Cooperative Communications in Presence of Frequency- Selective Fading and Inter-Relay Interference

This paper considers the finite-order filter design problem for the source and multiple full-duplex (FD) relays in a cooperative communication system under frequency-selective fading channels. The goal is to optimize the source and relay filters such that the end-to-end signal-to-interference-plus-noise ratio (SINR) of minimum mean-squared error decision-feedback equalizer (MMSE-DFE) can be maximized. The resultant design problem is very difficult since we need to deal with self interference (SI), inter-relay interference (IRI), and inter-symbol interference (ISI) at the same time. Novel designs are then proposed to overcome the difficulty in this work. Transforming the signals into the frequency domain and using some optimization techniques, we first theoretically derive the power spectrum of the source filter and the spectrums of the relay filters. Then, the finite-order design is developed to approach the derived spectrums. Based on the weighted least-square (WLS) criterion, the Steiglitz-McBride method is exploited to obtain the filter coefficients in finite lengths. Numerical results demonstrated that complete removal of SI may not be a good strategy; preserving a certain amount of SI at each relay instead provides better SINR performance.

Performance Analysis of Massive Hybrid Directional Modulation With Mixed Phase Shifters

To reduce the signal-to-interference-plus-noise ratio (SINR) loss of analog directional modulation (DM) with finite radio frequency (RF) phase shifters (PSs), a hybrid analog and digital (HAD) DM with mixed PSs is proposed. Using the law of large numbers, the closed-form expressions of SINR performance loss (PL), secrecy rate (SR), and bit error rate (BER) are derived. In accordance with the closed-form expression of SINR loss, it is clear that the SINR PL at desired receiver (Bob) gradually decreases as the fraction <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\eta$</tex-math></inline-formula> of the low-resolution phase shifter decreases, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\eta$</tex-math></inline-formula> is defined as the ratio of the number of low-resolution shifters to the total number of shifters. The simulation results show that the SINR PL, SR PL, and BER gradually decrease as the number of quantization bits increases. When the fraction of low-resolution shifters is equal to 50%, 2 bits is sufficient for low-resolution shifters to achieve a SINR PL less than 0.5 dB and a negligible BER degradation. Also, when the number of quantization bits of low-resolution shifters is equal to 2, the SR PL is about 0.3 bits/s/Hz. Thus, compared with analog DM, the HAD DM structure strikes a good balance between PL and circuit cost.

Design of an off-axis freeform diversity receiver to improve SINR performance of a multi-cell VLC system

This paper introduces a novel and promising design of a freeform diversity receiver (FDR) to reduce the inter-channel interference (ICI) of multi-cell visible light communication (VLC) system. Based on the potential of rotationally non-symmetric freeform optics, we have established the design of an off-axis VLC receiver front-end. In this study, we have performed the detailed design of the freeform surface profiles and have analysed the corresponding fabrication tolerances. Nonetheless, the communication performance of the VLC system using the proposed design has been evaluated with the help of Monte-Carlo based ray-tracing technique. Results show that the system with the proposed FDR significantly outperforms the existing state-of-the-art multi-cell VLC receivers in terms of signal-to-interference-plus-noise ratio (SINR). The spatial SINR ranges from 98 dB to 137 dB while 120.5 dB average SINR is attained over the communication floor. This compact size receiver (15.12 mm × 15.12 mm × 6.76 mm) with substantial wireless reception reliability has prospective future applications in the emerging field of visible light communication and its counterpart Li-Fi.

Adaptive Beamforming With Software-Defined-Radio Arrays

Digital beamforming is the holy grail of antenna array technologies, however implementing digital beamforming into practical antenna arrays has been slow due to hardware complexity and cost. We propose a relatively inexpensive new approach to digital beamforming using software defined radios. Using this system, we carried out experiments on adaptive interference cancellation. We present detailed description of the beamformer system along with the developed control software and experimentally verify the beamformer performance. Our results show that in high-interference and high-multipath environments, where carrier frequency offsets cannot be measured, conventional interference cancellation algorithms fail. We propose two new robust solutions to this problem and compare the results with multiple techniques, including the minimum variance distortionless response beamformer, which outputs the highest possible signal-to-interference-plus-noise-ratio (SINR). We experimentally demonstrate that both our approaches work well in the face of these types of signal corruptions and are capable of interference cancellation without degrading SINR or other system performance factors, and without the need for transmitter and receiver synchronization.

A Fair SINR Performance Comparison of FBMC/OQAM and FBMC/QAM Multicarrier Communication Systems in the Discrete-Time Framework

In the last couple of decades, multicarrier modulations have witnessed a considerable interest in wireless communication networks due to their ability to fight against multipath fading and offer multiple access with flexible resource sharing. One of the well known multicarrier modulation systems is filter-bank multi-carrier with an offset quadrature amplitude modulation (FBMC/OQAM), which was proposed as a powerful solution during the standardization of 5G. In this paper, we derive a closed-form expression of the signal to interference plus noise ratio (SINR) for FBMC/OQAM systems in the discrete-time context, for arbitrary wide sense stationary uncorrelated scattering (WSSUS) channels as well as transmitter (Tx) and receiver (Rx) waveforms. We quantify the potential gains in SINR brought by FBMC/OQAM, which exclusively operates on critical lattice density, with respect to FBMC/QAM, which have the flexibility to operate on critical or non-critical lattice densities. For completeness, we compare the performance of FBMC/OQAM in the discrete-time context, sweeping the discrete space of waveforms supports, with that of FBMC/OQAM in the continuous-time context, using the Hermite functions, and show how they perform similarly. Simulation results prove that FBMC/OQAM optimization algorithm, performing with the ping-pong optimized pulse shaping (POPS) paradigm, converges rapidly to excellent SINR values, even with small supports durations, in discrete-time context, which is equivalent to a reduced number of Hermite functions, in the continuous-time context.

Fault detection and location in power distribution systems: The usefulness of the HS-OFDM scheme for time-domain reflectometry

This study discusses key characteristics and benefits of using time-domain reflectometry (TDR) systems based on the Hermitian symmetric orthogonal frequency-division multiplexing (HS-OFDM) scheme for fault detection and location in power distribution networks. In this context, a system model with power line modems injecting signals and capturing reflections in a power distribution network is outlined. Next, two reflectogram processing approaches, namely digital pulse compression and channel estimation, are examined. Also, the effects of different parametrizations and multiple access schemes on the performance of the HS-OFDM-based TDR system are addressed. Numerical results confirm that HS-OFDM-based TDR systems making using of channel estimation outperforms their counterparts based on pulse compression. The frequency range for narrowband power line communication provides fair range resolution and maximum unambiguous range values. Also, it is seen that the use of frequency-division multiple access schemes implies different signal-to-interference-plus-noise ratio (SINR) performance among different power line modems (PLMs) connected to a power distribution network. Time-division and code-division multiple access schemes, on the other hand, provide fair SINR performance among the PLMs at the cost of obtaining a small number of reflectograms during a time interval.

Signal to interference plus noise ratio improvement of a multi‐cell indoor visible light communication system through optimal parameter selection complying lighting constraints

AbstractTo achieve improved communication and illumination performances of a multi‐cell indoor visible light communication system, the selection of transmitter configuration and receiver's field of view (FoV) play a critical role. Based on multiple criteria decision modeling, a design‐centric methodology is proposed in this paper to determine the optimal transmitter configuration and receiver's FoV under lighting constraints. These optimal parameter selections are instrumental to obtain a highly uncorrelated channel, thus significantly mitigate both co‐channel interference from the neighboring transmitter and intersymbol interference due to multipath reflection. The implication for the optimum selection is explored using two communication and two lighting (Eavg, UO) performance indicating metrics. For a typical indoor scenario, three different transmitter arrangements with varying half‐power beam‐width are considered as alternatives. Furthermore, the signal to interference plus noise ratio (SINR) is tested over the communication floor (CF) by a simple receiver structure with a single photodiode. Incorporating the optimal transmitter configuration and receiver's FoV, 36.13 dB average SINR and 345 lx average horizontal illuminance is achieved. Analytically obtained SINR is also validated using a commercial ray tracing optical software for different positions over the CF. In comparison with the state of the art non‐optimal and sub‐optimal solutions, the proposed scheme, without real‐time computational complexity exhibits noteworthy improvement in SINR performance at expense of a trivial drop in overall uniformity of horizontal illuminance.

Data Aided MSE-Optimal Time Varying Channel Tracking in Massive MIMO Systems

The temporal variations in the wireless propagation channel, referred to as channel aging, cause a mismatch between the estimated channel and the channel state at the time of data detection. This mismatch has been shown to severely impair the performance of massive MIMO systems. In this paper, we present data aided MSE-optimal channel tracking algorithms to decode the received symbols and update the channel estimates at the base station (BS) and the UEs. These algorithms combine ideas from Kalman filtering for channel tracking and deterministic equivalent analysis for symbol estimation. In the uplink case, we first develop a minimum mean squared error (MMSE) data estimator and the MSE-optimal channel predictor based on the Kalman filtering algorithm. We analytically show that the updated channel estimate obtained from the estimates of the data symbols leads to significantly larger signal to interference-plus-noise ratio (SINR), and hence achievable rate, compared to that obtained from the channel estimate based on pilot symbols. Following this, in the downlink case, we develop an algorithm to track the effective channel at the UEs and analyze its MSE, SINR and achievable rate performance. We show that tracking the effective downlink channel mitigates the effects of channel aging and leads to improved performance. However, since the beamforming matrices at the BS are not updated, downlink channel tracking is not as effective as uplink channel tracking. Finally, via Monte Carlo simulations, we validate our derived results, and demonstrate the gains achievable by tracking the time-varying channels in massive MIMO systems.

Optimality Conditions of Performance-Guaranteed Power Minimization in MIMO Networks: A Distributed Algorithm and Its Feasibility

A distributed approach is proposed to the problem of signal-to-interference-plus-noise-ratio (SINR)-guaranteed power minimization (SGPM) for multicell multiuser (MCMU) multiple-input multiple-output (MIMO) systems. Unlike prior SGPM approaches, the proposed technique is based on solving necessary and sufficient optimality conditions, which are derived by decomposing the original problem into forward and backward (FB) subproblems, while ensuring the strong duality of each subproblem. The proposed distributed SGPM algorithm makes use of FB adaptation and Jacobi recursion, respectively, for iterative filter design and power allocation. A sufficient condition for the feasibility of the proposed distributed algorithm is analyzed, based on the matrix inverse-positive theory. Unlike the existing fully distributed FB filter update algorithms, the proposed approach guarantees target SINR performance as well as its convergence to a stationary point. Simulation results illustrate the enhanced power efficiency with the performance guarantees of the proposed method compared to the existing distributed techniques.

Adaptive Generalized Sidelobe Canceler Beamforming With Time-Varying Direction-of-Arrival Estimation for Arrayed Sensors

Adaptive generalized sidelobe cancelers (GSCs) have been widely used to enhance the desired signal and instantaneously suppress interference signal and noise. However, the GSC beamforming method must know the direction of arrival (DOA) of the desired signal in advance. In this paper, we consider the case of a sensor array application in free-field air in which the target signal source is moving, leading to a time-varying DOA problem. Through analysis of the GSC output error signal, we propose an effective method for estimating the time-varying DOA for a GSC. The new method avoids the intensive complexity requirements of conventional DOA estimation algorithms such as the multiple signal classification algorithm and estimation of signal parameters via rotational invariant techniques. In addition, the convergence performance of adaptive GSC algorithms suffers from an error signal in the presence of the desired signal. A simple augmented Kalman filter (AKF) is employed to calculate the beamformer’s weighting coefficients, removing the influence of the desired signal from the GSC output to improve the convergence performance. A simulation evaluation of the signal-to-interference-plus-noise ratio (SINR) revealed that the AKF algorithm combined with the new DOA tracking method has a better convergence rate and SINR performance than other adaptive GSC algorithms of similar complexity such as the standard Kalman filter and recursive least squares.

Low-Complexity Joint Transmit and Receive Beamforming for MIMO Radar With Multi-Targets

We consider the joint design of transmit and receive beamforming for multiple-input multiple-output (MIMO) systems in the presence of multiple targets and interferences. The objective is to maximize the minimum receiver output signal-to-interference-plus-noise-ratio (SINR) of the targets with constraints on the total and, respectively, per-antenna transmission power. The problem can be solved by an iterative bisection search (IBS) based method, which is, however, computationally intensive since it requires solving a feasibility problem multiple times for each update of the transmit beamformer. We propose a new method that bypasses the iterative feasibility checking by employing an SINR approximation. An analytical proof, which ensures the convergence of the proposed method, is provided. Numerical results show that the proposed method attains a similar SINR performance as the IBS based method but at a significantly lower computational complexity.

Waveform Optimization of Compressed Sensing Radar without Signal Recovery

Radar signal processing mainly focuses on target detection, classification, estimation, filtering, and so on. Compressed sensing radar (CSR) technology can potentially provide additional tools to simultaneously reduce computational complexity and effectively solve inference problems. CSR allows direct compressive signal processing without the need to reconstruct the signal. This study aimed to solve the problem of CSR detection without signal recovery by optimizing the transmit waveform. Therefore, a waveform optimization method was introduced to improve the output signal-to-interference-plus-noise ratio (SINR) in the case where the target signal is corrupted by colored interference and noise having known statistical characteristics. Two different target models are discussed: deterministic and random. In the case of a deterministic target, the optimum transmit waveform is derived by maximizing the SINR and a suboptimum solution is also presented. In the case of random target, an iterative waveform optimization method is proposed to maximize the output SINR. This approach ensures that SINR performance is improved in each iteration step. The performance of these methods is illustrated by computer simulation.

Interference cancellation in co‐located MIMO radars using waveform optimisation in signal dependent clutter

In this study, two iterative design algorithms for multiple-input multiple-output (MIMO) radars with co-located antennas with point targets are proposed. In these algorithms, by joint design of the receiver filter and transmit waveform using linear combination of orthogonal waveforms, the authors aim to maximise the signal-to-interference plus-noise ratio (SINR) in the presence of signal dependent interference. In the first proposed algorithm, in each iteration, transmit waveforms and receive filter are designed in closed form to decrease the computational complexity. In the second method, by adding constant envelope criteria, the final waveform would be a linear combination of orthogonal waveforms and because of using a constant envelope, combining coefficients have equal magnitudes and different phases. Therefore, it is more practical for hardware implementation in comparison to the first proposed method. Simulation results show that both proposed methods have better SINR performances compared with other methods proposed in MIMO radar literature. The outperformance of the second proposed method with respect to phased arrays shows that by only using phase shifted combination of orthogonal waveforms, better performance in comparison to phased array radars can be achieved.

SINR and Rate Meta Distributions for HCNs With Joint Spectrum Allocation and Offloading

This paper focuses on the meta distributions of the signal-to-interference-plus-noise ratio (SINR) and user-perceived rate in heterogeneous cellular networks (HCNs) with multiple tiers of base stations. On the one hand, it is desirable to offload users to small cells to alleviate the congestion in macrocells; on the other hand, such offloading would in turn cause an SINR degradation of the offloaded users, which needs to be mitigated through interference avoidance based on resource partitioning. Thus, in consideration of both aspects, we provide a general framework for modeling and analyzing joint spectrum allocation and offloading in an HCN using the $K$ -tier homogeneous-independent Poisson model. With it, we derive the per-tier and overall moments of the conditional SINR and rate distribution given the point process, based on which the exact meta distributions are given. We show that the conventional SINR or rate performance evaluated at the typical user (averaging over all tiers and links in the HCN), by itself, is insufficient, and a much sharper version provided by the meta distribution is required in conjunction with the expected value to give a thorough assessment of the benefits of joint resource partitioning and offloading in HCNs.

Constant modulus waveform design for high frequency radar using optimal filter

This paper design waveform for high frequency radar to optimize its performances in co-channel interference/colored noise environment. Considering that radar applies the optimal filter for range processing, a novel objective function accounting for both Signal to Interference plus Noise Ratio (SINR) and Integrated Sidelobes Level (ISL) is introduced and the constant modulus constraint on the probing waveform is forced. To resolve the resulting non-convex quartic optimization problem, an efficient iterative algorithm based on Majorization-Minimization (MM) and Pattern Search (PS) is proposed. In each iteration, the proposed algorithm produces a multi-dimension quadratic majorized problem and then splits it into multiple one-dimension problems with closed-form solutions. Simulation results show that the SINR and ISL performances of designed waveform can be flexibly adjusted. Besides, the convergence speed and stability of the proposed algorithm are more satisfactory than the other methods.

Efficient low‐PAR radar waveform design method based on the alternating direction method of multipliers for multiple missions

This study addresses the low-peak-to-average power ratio (PAR) radar waveform design problem to optimise the detection and estimation performance simultaneously in the presence of signal-dependent clutter. The aim is to realise an effective trade-off between maximising the output signal-to-interference-plus-noise ratio (SINR) and mutual information (MI) under a low-PAR constraint. In the existing method, this problem is solved via convex optimisation, but the high computational complexity of this method limits its application. Motivated by the decomposability and superior convergence of the alternating direction method of multipliers, the authors propose an efficient method to obtain the optimal waveform by converting the original non-convex problem into simpler convex sub-problems that can be solved efficiently. The simulation results illustrate that the optimal waveform can be obtained efficiently within the given low-PAR range and that the synthesised waveform can provide a reasonable trade-off between the detection and estimation performances. Compared with the existing method, the proposed method has reduced computational complexity without SINR and MI performance degradations.

Performance Analysis of Directional Modulation With Finite-Quantized RF Phase Shifters in Analog Beamforming Structure

The radio frequency (RF) phase shifter with finite quantization bits in analog beamforming (AB) structure forms quantization error (QE) and causes a performance loss of received signal to interference plus noise ratio (SINR) at the receiver (called Bob). By using the law of large numbers in probability theory, the closed-form expression of SINR performance loss is derived to be inversely proportional to the square of sinc (or sin(x)/x) function. Here, a phase alignment method is applied in directional modulation transmitter with AB structure. Also, the secrecy rate (SR) expression is derived with QE. From numerical simulation results, we find that the SINR performance loss gradually decreases as the number L of quantization bits increases. This loss is less than 0.3dB when L is larger than or equal to 3. As L exceeds 5, the SINR performance loss at Bob can be approximately trivial. Similarly, SR performance loss gradually reduces as L increases. In particular, the SR performance loss is about 0.1 bits/s/Hz for L=3 at signal-to-noise ratio of 15dB.

Interference mitigation and capacity enhancement using constraint field of view ADR in downlink VLC channel

The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio-frequency wireless connections with high-speed ones. Visible light communication (VLC) is a promising license free indoor wireless technology that could offer high-speed connections. However, both co-channel interference (CCI) from more neighbour transmitters and inter-symbol interferences (ISI) from multipath reflections limit the performance of VLC downlink channel. In this study, a constraint field of view angular diversity receiver (CFOV-ADR) is proposed to mitigate these limitations. By optimising the photodetector's (PD) field of view (FOV) angle, the line of sight CCI could be totally eliminated and the ISI could be significantly reduced. The optimal range for FOV angle is calculated in a typical indoor scenario. Furthermore, the zero-forcing (ZF) algorithm is applied to the conventional ADR (ADR-ZF) which can significantly eliminate the ISI components. The received optical signal-to-interference-plus-noise ratio (SINR) is tested at various room positions. The simulation results show that the proposed CFOV-ADR can achieve higher SINR performance than single receiver, conventional ADR, and ADR-ZF at all positions and orientations.