Multiple Receiver Antennas Research Articles

A Slotted Pilot-Based Unsourced Random Access Scheme With a Multiple-Antenna Receiver

A Slotted Pilot-Based Unsourced Random Access Scheme With a Multiple-Antenna Receiver

Orthogonal Space-Time Block Coding for Double Scattering V2V Links with LOS and Ground Reflections

This work presents the performance analysis of space-time block codes (STBCs) for vehicle-to-vehicle (V2V) fast-fading channels in scenarios with modified line-of-sight (LOS). The objective is to investigate how the V2V MIMO (multiple-input multiple-output) system performance is influenced by two important impairments: deterministic ground reflections and an increased Doppler frequency (time-variant channels). STBCs of various coding rates (using an approximation model) are evaluated by assuming antenna elements distributed over the surface of two contiguous vehicles. A multi-ray model is used to study the multiple constructive/destructive interference patterns of the transmitted/received signals by all pairs of Tx–Rx antenna links considering ground reflections. A double scattering model is used to include the effects of stochastic channel components that depend on the Doppler frequency. The results show that STBCs are capable of counteracting fades produced by destructive self-interference components across a range of inter-vehicle distances and for a range of Doppler frequency values. Notably, the effectiveness of STBCs in deep fades is shown to outperform schemes with exclusive receive diversity, despite the interference created by the loss of orthogonality in time-varying channels with a moderate increase of Doppler frequency (mainly due to higher vehicle speeds, higher frequency or shorter time slots). Higher-order STBCs with rate losses are also evaluated using an approximation model, showing interesting gains even for low coding rate performance, particularly when accompanied by a multiple antenna receiver. Overall, these results can shed light on how to exploit transmit diversity in time-varying vehicular channels with modified LOS.

Spread Unsourced Random Access With an Iterative MIMO Receiver

This work is dedicated to the unsourced random access (URA) with multiple-antenna receiver. We utilize a preamble-payload packet format where the preamble, selected from a pool shared between all active users, serves as a temporary activity detection identifier. The payload carries the main portion of the message data which is encoded for error correction, permuted, and scrambled. The compressed-sensing (CS) preamble receiver that estimates the active preambles and the respective user channels is followed by a payload receiver which performs several iterations of data and channel estimation and parallel interference cancellation. Our numerical and analytic results demonstrate that the presented system outperforms the related work in terms of the achievable numbers of active users and signal-to-noise ratios (SNR)s supported by the system.

DL-Based Physical Tamper Attack Detection in OFDM Systems with Multiple Receiver Antennas: A Performance-Complexity Trade-Off.

This paper proposes two deep-learning (DL)-based approaches to a physical tamper attack detection problem in orthogonal frequency division multiplexing (OFDM) systems with multiple receiver antennas based on channel state information (CSI) estimates. The physical tamper attack is considered as the unwanted change of antenna orientation at the transmitter or receiver. Approaching the tamper attack scenario as a semi-supervised anomaly detection problem, the algorithms are trained solely based on tamper-attack-free measurements, while operating in general scenarios that may include physical tamper attacks. Two major challenges in the algorithm design are environmental changes, e.g., moving persons, that are not due to an attack and evaluating the trade-off between detection performance and complexity. Our experimental results from two different environments, comprising an office and a hall, show the proper detection performances of the proposed methods with different complexity levels. The optimal proposed method achieves a 93.32% true positive rate and a 10% false positive rate with a suitable level of complexity.

Design Switchable Precoded Space-Time Parallel Two-Path OFDM Systems

A 2x2 space-time (ST) orthogonal frequency division multiplexing (OFDM) system is proposed with parallel cancellation (PC) two-path transmission to form a 2x2 STPC system. The 2x2 STPC-OFDM systems mitigate the inter-carrier interference (ICI) in the mobile channels with a better BER than that of a 2x2 ST-OFDM system. The design is switchable between two operation modes: either high data rate with ST-OFDM or high reliability with STPC in mobile fading channels having lower bit error rate (BER). Furthermore, a generalized STPC architecture is designed with multiple receiver antennas. It offers higher diversity order and better BER. Two orthogonal transforms, such as Zadoff-Chu transform (ZCT) and Walsh–Hadamard transform (WHT), are employed as the precoder to enhance the BER further. Although the proposed STPC-OFDM systems require two-path transmission with the cost of reducing bandwidth efficiency, simulations show that the proposed 2x2 STPC-OFDM systems are robust to various channel environments and have a better BER performance for fair data rate comparison with 2x2 ST-OFDM.

A Matrix-Inverse-Free Implementation of the MU-MIMO WMMSE Beamforming Algorithm

The WMMSE beamforming algorithm is a popular approach to address the NP-hard weighted sum rate (WSR) maximization beamforming problem. Although it efficiently finds a local optimum, it requires matrix inverses, eigendecompositions, and bisection searches, operations that are problematic for real-time implementation. In our previous work, we considered the MU-MISO case with single-antenna receivers and effectively replaced such operations by resorting to a first-order method. Here, we consider the more general and challenging MU-MIMO case with multiple-antenna receivers. Our earlier approach does not generalize to this scenario and cannot be applied to replace all the hard-to-parallelize operations that appear in the MU-MIMO case. Thus, we propose to leverage a reformulation of the auxiliary WMMSE function given by Hu et al. By applying gradient descent and Schulz iterations, we formulate the first variant of the WMMSE algorithm applicable to the MU-MIMO case that is free from matrix inverses and other serial operations and hence amenable to both real-time implementation and deep unfolding. From a theoretical viewpoint, we establish its convergence to a stationary point of the WSR maximization problem. From a practical viewpoint, we show that in a deep-unfolding-based implementation, the matrix-inverse-free WMMSE algorithm attains, within a fixed number of iterations, a WSR comparable to the original WMMSE algorithm truncated to the same number of iterations, yet with significant implementation advantages in terms of parallelizability and real-time execution.

Multiuser Opportunistic Beamforming Systems With Multiple Receive Antennas in Nakagami-$m$ Fading Channels

Multiuser Opportunistic Beamforming Systems With Multiple Receive Antennas in Nakagami-$m$ Fading Channels

Generalization of Index-Modulation: Breaking the Conventional Limits on Spectral and Energy Efficiencies

In the context of orthogonal frequency-division multiplexing with index modulation (OFDM-IM), this paper first presents an improved index modulation (IIM) technique to address the well-known low spectral efficiency problem of IM techniques in general and OFDM-IM in particular. OFDM-IIM is realized by deriving the minimum required number of subcarriers per group, and the minimum number of active subcarriers in each group, of the conventional OFDM-IM technique. It is proven that OFDM-IIM can deliver higher spectral and energy efficiencies than classical OFDM and OFDM-IM. The gains come at the expense of increased detection complexity. Therefore, a proposal of OFDM with generalized IM (OFDM-GIM) technique is presented, where a variable number of subcarriers per group are allowed to be activated. Two variants of OFDM-GIM are designed based on the activation pattern of the subcarriers: the first achieves superior spectral efficiency with reduced detection complexity as compared to OFDM-IIM, and the second is tailored for low data rate communications with higher energy efficiency requirements. Besides optimal maximum likelihood detection, a less-complex sub-optimal detector is proposed. A closed-form expression for the bit error rate (BER) of OFDM-IIM and the two variants of OFDM-GIM is derived, considering transmissions over Nakagami fading channels and multiple-antenna reception. Finally, OFDM-IIM and OFDM-GIM are compared with state-of-the-art techniques to validate their superiority in terms of BER, achievable rate, and energy efficiency.

Optimal SWIPT in RIS-Aided MIMO Networks

The use of simultaneous wireless information and power transfer (SWIPT) is a key enabler of achieving convenience and prolonging the energy supply lifetime of wireless networks. To address the low efficiencies of far-field power transfer, a reconfigurable intelligent surface (RIS) is adopted to enhance the energy harvesting (EH) performance, which can construct a favorable wireless propagation environment. In this paper, we consider an RIS-assisted SWIPT system with wireless transfer from the access point (AP) to multiple-antenna receivers, which include information receivers (IRs) and energy receivers (ERs). First, we formulate the problem of maximizing the minimum rates of the IRs as a nonconvex constrained optimization problem. For ideal and nonideal channels, we propose two different solutions. Second, we simplify the objective function and decompose the problem into several subproblems by using sorting and iterative optimization algorithms. Moreover, under optimal boundary and Karush-Kuhn-Tucker (KKT) conditions, we successfully solve this problem. The simulation results illustrate a promising approach for wireless communication by comparing ideal RIS and unsatisfactory situations with no RIS cases under various conditions.

A phase-difference-of-arrival assisted ultra-wideband positioning method for elderly care

Ultra-wideband (UWB) is a promising mean for elderly care in line-of-sight (LOS) environments. One major limitation of UWB-based localization is the non-line-of-sight (NLOS) for signals caused by severe environments, resulting in dramatic performance degradation. Although many NLOS identification and compensation methods in presence of complex indoor environments have been proposed, they are only applicable to specific environments or require enough LOS BSs to detect NLOS measurements. To address these issues comprehensively, we propose a phase-difference-of-arrival (PDOA) assisted UWB positioning method (PDOA-UWB) for elderly care in this paper, which consists of three steps: (1) coarse localization, calculated from PDOA measurements at multiple receiver antennas of UWB base stations (BSs), (2) LOS BSs selection, and (3) fine localization through a convex regression estimator. Our method is simple and effective and can be used in various practical environments without prior information about the NLOS error. Overall experimental results verify that PDOA-UWB can achieve better positioning accuracy than existing methods in severe NLOS environments.

Generative Adversarial Network in the Air: Deep Adversarial Learning for Wireless Signal Spoofing

The spoofing attack is critical to bypass physical-layer signal authentication. This paper presents a deep learning-based spoofing attack to generate synthetic wireless signals that cannot be statistically distinguished from intended transmissions. The adversary is modeled as a pair of a transmitter and a receiver that build the generator and discriminator of the generative adversarial network, respectively, by playing a minimax game over the air. The adversary transmitter trains a deep neural network to generate the best spoofing signals and fool the best defense trained as another deep neural network at the adversary receiver. Each node (defender or adversary) may have multiple transmitter or receiver antennas. Signals are spoofed by jointly capturing waveform, channel, and radio hardware effects that are inherent to wireless signals under attack. Compared with spoofing attacks using random or replayed signals, the proposed attack increases the probability of misclassifying spoofing signals as intended signals for different network topology and mobility patterns. The adversary transmitter can increase the spoofing attack success by using multiple antennas, while the attack success decreases when the defender receiver uses multiple antennas. For practical deployment, the attack implementation on embedded platforms demonstrates the low latency of generating or classifying spoofing signals.

On the energy detection performance of multi‐antenna correlated receiver for vehicular communication using MGF approach

In this work, energy detection-based spectrum sensing for multiple antenna receiver under the effect of mobility is investigated by considering L number of correlated antenna branches. The authors consider the uniform, exponential and arbitrarily correlation among the antenna branches based on the spacing between them. The moment generating function (MGF) approach is applied to obtain the statistical knowledge of the received signal to noise ratio because the Laplace domain behaviour will help to derive the closed-form expressions using simple algebraic operations. They derived the closed-form expressions for the detection probability over Nakagami-m fading, in terms of Lauricella and Confluent Hypergeometric function for maximal ratio combining (MRC) and equal gain combining (EGC) diversity techniques under the effect of vehicle mobility. Monte-Carlo simulation is carried out to validate the derived analytical expressions. The results show that the degradation in detection performance due to fading correlation can be reduced by choosing the appropriate diversity scheme and by increasing the number of antennas. Furthermore, they also found that at high fading parameter ( m = 4 ) value, the low value of the probability of false alarm and highly correlated fading, MRC works better than EGC for high relative velocity.

다중 수신안테나로 구성된 RF 무선 전력 카메라 시스템 구현

카메라 기기들의 급속한 보급과 데이터 전송 기술의 발전으로 영상의 촬영 및 전송이 쉽게 가능하나 전력 공급시 내장형 배터리나 유선 방식을 사용하여 지속적인 동작이 어려운 문제점을 가지고 있다. 따라서 본 연구에서는 RF 무선전력전송(WPT: Wireless Power Transfer) 시스템에 적용할 수 있는 무선 카메라 시스템을 제안하며, 다중 수신 안테나로 구성된 5.8 GHz 수신단 회로 및 제어와 유지보수 없이 지속해서 동작 가능한 능동형 무선 카메라 시스템 설계를 주제로 연구한다. 본 논문에서 제안하는 시스템의 수신단은 ADS(Advanced Design System)를 통해 시뮬레이션 후 제작되었으며, 테스트베드 제작을 통해 WPT 기반의 지속적인 동작이 가능함을 검증하고 시스템 성능을 확인하였다.

Evaluation of EAR Spaced Antenna Performance Using Multiple Receiving Antennas Orientations

AbstractEquatorial Atmosphere Radar (EAR) is a very high frequency (VHF) Doppler radar with an active phased array antenna system operating at 47 MHz. It had originally been equipped with a single receiving channel system since its establishment in 2001 at the equator in Kototabang, West Sumatra, Indonesia (0.20°S, 100.32°E). Recent progress has enabled the implementation of a spaced antenna (SA) method on the EAR through the development of a multichannel receiver using Universal Software Radio Peripheral (USRP) and GNU Radio. However, this approach exhibits limited height observation and horizontal wind estimation accuracy. Here, we present comparison and analysis of EAR SA performance with five different orientations, taking into consideration the size of the receiving antennas and their separation distance. Experiments with the chosen configurations were carried out between April and September 2019, and the horizontal wind profiles were estimated using full correlation analysis (FCA) and compared with the EAR standard data. In addition, FCA with the least squares method is carried out for all configurations with the aim of improving the estimation accuracy. Based on the results, the configuration with the largest aperture shows a clear advantage over the other four configurations but with limited improvement in terms of maximum observable height.

Detecting Hazardous Spatial Gradients at Satellite Acquisition in GBAS

In this article, we develop a ground monitor capable of detecting anomalous signal-in-space spatial gradients for rising, newly acquired, and reacquired satellites in the ground-based augmentation system using either single or dual frequency. These gradients can be caused by satellite orbit ephemeris faults and ionospheric fronts. The monitor utilizes differential code and carrier phase measurements across multiple reference receiver antennas as the basis for detection. We show that the new monitor significantly improves performance over existing detection algorithms and is capable of meeting Category III precision approach and landing requirements.

On secure system performance over SISO, MISO and MIMO-NOMA wireless networks equipped a multiple antenna based on TAS protocol

This study examined how to improve system performance by equipping multiple antennae at a base station (BS) and all terminal users/mobile devices instead of a single antenna as in previous studies. Experimental investigations based on three NOMA down-link models involved (1) a single-input-single-output (SISO) scenario in which a single antenna was equipped at a BS and for all users, (2) a multi-input-single-output (MISO) scenario in which multiple transmitter antennae were equipped at a BS and a single receiver antenna for all users and (3) a multi-input-multi-output (MIMO) scenario in which multiple transmitter antennae were equipped at a BS and multiple receiver antenna for all users. This study investigated and compared the outage probability (OP) and system throughput assuming all users were over Rayleigh fading channels. The individual scenarios also each had an eavesdropper. Secure system performance of the individual scenarios was therefore also investigated. In order to detect data from superimposed signals, successive interference cancellation (SIC) was deployed for users, taking into account perfect, imperfect and fully imperfect SICs. The results of analysis of users in these three scenarios were obtained in an approximate closed form by using the Gaussian-Chebyshev quadrature method. However, the clearly and accurately presented results obtained using Monte Carlo simulations prove and verify that the MIMO-NOMA scenario equipped with multiple antennae significantly improved system performance.

Offset Spatial Modulation With Multiple Receive Antennas

Recently, a class of novel spatial modulation (SM) schemes, termed offset spatial modulation (OSM), were developed to reduce the radio frequency (RF) switching frequency, in the context of multiple-input single-output (MISO) transmission. In this paper, the structure of original OSM is extended to adapt multiple-input multiple-output (MIMO) systems by introducing multiple receive antennas (MRA). The detailed system design is presented and further developed for offset space shift keying (OSSK). Furthermore, the theoretical bounds of bit-error rate (BER) performance for the proposed OSM-MRA and OSSK-MRA systems are both quantified. It is demonstrated that the proposed OSM-MRA and OSSK-MRA systems outperform their counterparts including conventional OSM and OSSK with improved spectral efficiency.

Intelligent Reflecting Surface Assisted Secure Wireless Communications With Multiple- Transmit and Multiple-Receive Antennas

In this paper, we propose intelligent reflecting surfaces (IRS) assisted secure wireless communications with multi-input and multi-output antennas (IRS-MIMOME). The considered scenario is an access point (AP) equipped with multiple antennas communicates with a multi-antenna enabled legitimate user in the downlink at the present of an eavesdropper configured with multiple antennas. Particularly, the joint optimization of the transmit covariance matrix at the AP and the reflecting coefficients at the IRS to maximize the secrecy rate for the IRS-MIMOME system is investigated, with two different assumptions on the phase shifting capabilities at the IRS, i.e., the IRS has the continuous reflecting coefficients and the IRS has the discrete reflecting coefficients. For the former case, due to the non-convexity of the formulated problem, an alternating optimization (AO)-based algorithm is proposed, i.e., for given the reflecting coefficients at the IRS, the successive convex approximation (SCA)-based algorithm is used to solve the transmit covariance matrix optimization, while given the transmit covariance matrix at the AP, alternative optimization is used again in individually optimizing of each reflecting coefficient at the IRS with other fixed reflecting coefficients. For the individual reflecting coefficient optimization, the closed-form or an interval of the optimal solution is provided. Then, the proposed algorithm is extended to the discrete reflecting coefficient model at the IRS. Finally, some numerical simulations have been done to demonstrate that the proposed algorithm outperforms other benchmark schemes.

다중 수신안테나 기반 WAVE 통신시스템의 PER 성능향상을 위한 채널 추정 기법

본 논문에서는 다중 수신안테나 기반 IEEE802.11p WAVE (Wireless Access Vehicular Environment) 시스템에서 PER (Packet Error Rate) 성능 향상을 위한 새로운 채널 추정 기법을 제안한다. 제안 기법은 채널 상관값 기반 OFDM 데이터 심볼을 복원한 후 이를 데이터 파일럿으로 구성하여 MRC (Maximal Ratio Combining)를 기반으로 각 안테나 별 채널값을 업데이트함으로써 수신 다이버시티 이득을 극대화한다. 모의실험 결과 기존 채널 추정 기법 대비 PER 10SUP-3/SUP에서 2dB 이상의 SNR (Signal to Noise Ratio) 성능 이득을 얻는 것을 확인할 수 있다.

On the Optimal CSI Feedback Rate of Downlink MIMO Systems Using Multiple Receive Antennas in Cellular Networks

A downlink cellular network is considered, in which multiple-antenna base stations (BSs) are distributed following a homogeneous Poisson point process. Each BS serves a single user equipped with multiple-receive antennas. The partial channel state information is achieved at the transmitter using a limited feedback. The singular-value-decomposition-based precoding is performed for the downlink spatial multiplexing. In this letter, the optimal number of feedback bits that maximizes the net spectral efficiency is investigated. The net spectral efficiency is defined to measure the net profit achieved by using limited-feedback-based spatial multiplexing. By extending previous studies, the effect of using multiple-receive antennas on the optimal number is investigated. Specifically, the scaling rate of the optimal number is newly obtained for more than one receive antenna.