Multiple Receiver Antennas Research Articles

Interference DOA estimation and suppression for GNSS receivers using fully augmentable arrays

Multiple antenna receivers have been proposed for interference nulling in Global Navigation Satellite Systems (GNSS). An open-loop anti-jam approach is considered and an interference direction-of-arrival (DOA) estimation technique using fully augmentable non-uniform linear arrays is introduced. The DOAs of incoming jammers are estimated utilising the minimum output power method applied to the GNSS receiver coarray and through two different approaches of spectrum sensing and polynomial rooting. Subsequently, the strong interferers are cancelled utilising a subspace projection approach, whereas the 30 dB despreading gain of GNSS receivers protects the satellite signals against weak jammers. Supporting simulation results demonstrate that DOA estimation based on polynomial rooting outperforms spectrum sensing and validate the effectiveness of the proposed anti-jam strategy.

Soft-Limited Polarity-Coincidence-Array Spectrum Sensing in the Presence of Non-Gaussian Noise

A new spectrum sensing scheme is proposed for detecting a primary signal corrupted by generalized Gaussian noise (GGN). It is assumed that the power of the primary signal is much smaller than noise power and that the secondary users (SUs) take advantage of multiple receiver antennas. The proposed scheme, which is referred to as soft-limited polarity coincidence array (SL-PCA), is characterized by a slope parameter that controls the operation of its limiter. It is shown that by optimizing the slope parameter, the proposed scheme outperforms its predecessor (i.e., PCA), as well as the well-known energy detection (ED) scheme in the presence of heavy-tailed GGN. It is also observed that the SL-PCA scheme can achieve superior performance with a single receiver antenna, whereas the PCA scheme cannot be used when the SUs are equipped with only one receiver antenna. Finally, the sensitivity of the proposed scheme to the slope parameter is investigated for several scenarios. It is observed that even when the slope parameter is not optimum, SL-PCA can still outperform the PCA and ED schemes, provided that the slope parameter is appropriately chosen.

MIMO-OFDM technique with IDMA scheme for underwater wireless communication

In this paper, we propose an efficient, scalable, adaptive MIMO-OFDM technique with IDMA scheme to mitigate the fading issues in underwater wireless communications. MIMO technique is defined as the technique containing multiple transmitter antennas and multiple receiver antennas. MIMO systems can provide a potentially very high capacity that, in many cases, grows approximately linear with the number of antennas. This technique increases the data rate, while OFDM saves the bandwidth and reduces fading. In this scheme, the entire signal orthogonally overlaps in a frequency domain that saves the bandwidth. IDMA scheme is based on interleaving technique. It distinguishes the users by chip level interleaving principle. IDMA scheme is better than any other available multiple access schemes available for underwater communication. We simulate the MIMO-OFDM with IDMA scheme to reduce the channel noise and fading issues. This scheme is able to serve as a primer for mitigating the fading issues in future underwater wireless communication.

Cell Coverage Extension With Orthogonal Random Precoding for Massive MIMO Systems

In this paper, we investigate a coverage extension scheme based on orthogonal random precoding (ORP) for the downlink of massive multiple-input multiple-output systems. In this scheme, a precoding matrix consisting of orthogonal vectors is employed at the transmitter to enhance the maximum signal-to-interference-plus-noise ratio of the user. To analyze and optimize the ORP scheme in terms of cell coverage, we derive the analytical expressions of the downlink coverage probability for two receiver structures, namely, the single-antenna receiver and multiple-antenna receiver with antenna selection. The simulation results show that the analytical expressions accurately capture the coverage behaviors of the systems employing the ORP scheme. It is also shown that the optimal coverage performance is achieved when a single precoding vector is used under the condition that the threshold of the signal-to-noise ratio of the coverage is greater than one. The performance of the ORP scheme is further analyzed when the different random precoder groups are utilized over multiple time slots to exploit precoding diversity. The numerical results show that the proposed ORP scheme over multiple time slots provides a substantial coverage gain over the space–time coding scheme despite its low feedback overhead.

Linear Degrees of Freedom of the MIMO X-Channel With Delayed CSIT

We study the degrees of freedom (DoFs) of the multiple-input multiple-output X-channel (MIMO XC) with delayed channel state information at the transmitters (delayed CSITs), assuming linear coding strategies at the transmitters. We present two results: 1) the linear sum DoF for MIMO XC with general antenna configurations and 2) the linear DoF region for MIMO XC with symmetric antennas. The converse for each result is based on developing a novel rank-ratio inequality that characterizes the maximum ratio between the dimensions of received linear subspaces at the two multiple-antenna receivers. The achievability of the linear sum DoF is based on a three-phase strategy, in which during the first two phases only the transmitter with fewer antennas exploits delayed CSIT in order to minimize the dimension of its signal at the unintended receiver. During the third phase, both transmitters use delayed CSIT to send linear combinations of past transmissions, such that each receiver receives a superposition of desired message data and known interference, thus simultaneously serving both receivers. We also derive other linear DoF outer bounds for the MIMO XC that, in addition to the outer bounds from the sum DoF converse and the proposed transmission strategy, allow us to characterize the linear DoF region for symmetric antenna configurations.

Joint Sensing and Reception Design of SIMO Hybrid Cognitive Radio Systems

In this paper, the problem of joint design of spectrum sensing (SS) and receive beamforming, with reference to a cognitive radio (CR) system, is considered. The aim of the proposed design is the maximization of the achievable average uplink rate of a secondary user, subject to an outage-based quality-of-service constraint for primary communication. A hybrid CR system approach is studied, according to which the system either operates as an interweave (i.e., opportunistic) or as an underlay (i.e., spectrum sharing) CR system, based on SS results. A realistic channel state information framework is assumed, according to which the direct channel links are known by the multiple antenna receivers, while merely statistical (covariance) information is available for the interference links. A new closed-form approximation is derived for the outage probability of primary communication, and the problem of rate-optimal selection of SS parameters and receive beamformers is addressed for hybrid, interweave, and underlay CR systems. It is proved that our proposed system design outperforms both underlay and interweave CR systems for a range of system scenarios.

Multistream Multiuser Coordinated Beamforming for Cellular Networks With Multiple Receive Antennas

Multicell coordinated beamforming (CB) can mitigate intercell interference (ICI). However, existing work on CB focuses on systems that maximize overall throughput. This paper considers CB for systems with multiple receive antennas and further extends the CB to multiuser and multistream transmission. We consider fairness and pay close attention to cell-edge users. CB that maximizes the harmonic sum of signal-to-interference-plus-noise ratio (SINR) can be derived into a low-complexity algorithm that favors cell-edge users. Two iterative algorithms are developed. From the simulation results, the proposed algorithms can provide a better fifth-percentile user throughput compared with the CB algorithms minimizing mean square error, maximizing uplink SINR, and maximizing weighted sum rate. Furthermore, the computational complexity of the proposed algorithms is significantly lower than that maximizing the minimum SINR of users.

Spectral Efficiency Scaling Laws in Dense Random Wireless Networks With Multiple Receive Antennas

This paper considers large random wireless networks, where transmit-and-receive node pairs communicate within a certain range while sharing a common spectrum. By modeling the spatial locations of nodes as a Poisson point process, analytical expressions for the ergodic spectral efficiency of a typical node pair are derived as a function of the channel state information available at a receiver (CSIR) in terms of relevant system parameters: the density of communication links, the number of receive antennas, the path loss exponent, and the operating signal-to-noise ratio. One key finding is that when the receiver only exploits CSIR for the direct link, the sum spectral efficiency increases linearly with the density, provided the number of receive antennas increases as a certain superlinear function of the density. When each receiver exploits CSIR for a set of dominant interfering links in addition to that of the direct link, the sum spectral efficiency increases linearly with both the density and the path loss exponent if the number of antennas is a linear function of the density. This observation demonstrates that having CSIR for dominant interfering links provides an order gain in the scaling law. It is also shown that this linear scaling holds for direct CSIR when incorporating the effect of the receive antenna correlation, provided that the rank of the spatial correlation matrix scales superlinearly with the density. These scaling laws are derived from integral representations of the distribution of the signal to interference and noise ratio, which are of independent interest and which in turn derived from stochastic geometry and more precisely from the theory of shot noise fields. Simulation results back the scaling laws and the integral representations.

On Adjacent Channel Interference Mitigation for Rotating MIMO Receivers

Virtually rotating antennas, which rotate once or several times during a symbol interval, have been considered in recent years as a compact (in volume) alternative for achieving additional degrees of freedom compared to standard multiple antenna receivers. Antenna rotation effectively induces bandwidth expansion at the receiver, which in turn increases the effective dimensionality, and may potentially allow for spatial multiplexing. However, in a licensed spectrum such bandwidth expansion also introduces interference from signals transmitted in adjacent frequency bands. This paper investigates to what extent such adjacent channel interference can be mitigated by appropriate signal processing. The potentially achievable throughput of systems employing multiple virtually rotating antennas is examined analytically in a multiuser setting, while considering the large system limit, and employing random matrix theory tools. The analysis focuses on the linear minimum mean-square error (MMSE) receiver, and a receiver that optimally decodes the transmissions of desired users, while being unaware of the codebooks of interferers. The achievable throughput is compared to the corresponding throughputs of standard multiple antenna receivers employing the same number of physical active antenna elements. Conditions for virtually rotating antennas to be beneficial are identified, which when met are shown to lead to significant performance enhancement over standard multiple antenna receivers.

Target Scattering Coefficients Estimation in Cognitive Radar under Temporally Correlated Target and Multiple Receive Antennas Scenario

Target Scattering Coefficients Estimation in Cognitive Radar under Temporally Correlated Target and Multiple Receive Antennas Scenario

단일주파수방송망 구축을 위한 클라우드 전송 시스템에서의 다중 안테나 수신 성능 분석

본 논문은 클라우드 전송 시스템의 수신 성능을 향상시키기 위해 다중 수신 안테나를 적용하는 단일주파수방송망 기반의 차세대 지상파 방송 기술에 대하여 연구하였다. 다중 수신 안테나를 채용함으로써 단일주파수방송망 경계지역에서의 방송 신호 수신이 분산 MIMO(Multi Input Multi Output) 시스템으로 모델링을 하였고, MIMO 수신기의 간섭 제거 효과로 단일 안테나 수신기를 적용하는 것보다 인접 방송 권역 간섭을 감소시킬 수 있다. 모의실험을 통해 클라우드 전송 시스템에 다중 안테나 수신기를 적용하면 단일주파수방송망 경계지역에서의 수신 성능 개선이 이루어짐을 확인하였다. In this paper, we propose a study for the next generation terrestrial broadcasting technology based on SFN(Single Frequency Networks), which applies multiple receiving antenna to improve receiving performance of cloud transmission system. By applying multiple receiving antenna, the received broadcast signals at the boundary of different SFN broadcasting area could be modelled by distributed MIMO system. Due to the interference cancellation effect of the MIMO detector, the proposed scheme could suppress the adjacent area interference more efficiently compared to the single receiving antenna case. Simulation results show that receiving performance can be improved dramatically in overlapping area of SFN by applying multiple antenna receivers in cloud transmission system.

Simulation of MIMO System with STBC in Simulink and MATLAB

The space-time block coding (STBC) makes use of a high algebraic structure to provide diversity gain. Paper shows that the multiple receiver antennas increase the diversity, which results in high SNR. The two illustrative examples of Multiple Input Multiple Output (MIMO) system in wireless network using STBC are presented. Firstly, paper compares the case of single user while incorporating multiple receiving antennas. Secondly, paper compares the case of multiple users while incorporating multiple receiving antennas. The simulation results after experimental testing are in good agreement. General Terms Wireless communications, MIMO system, Space-time block coding (STBC).

Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment

This study presents a simple and powerful technique for multichannel measurements of the density profile in laboratory plasmas by microwave interferometry. This technique uses electromechanical microwave switches to temporally switch the connection between multiple receiver antennas and one phase-detection circuit. Using this method, the phase information detected at different positions is rearranged into a time series that can be acquired from a minimum number of data acquisition channels (e.g., two channels in the case of quadrature detection). Our successfully developed multichannel microwave interferometer that uses the antenna switching method was applied to measure the radial electron density profiles in a magnetized plasma experiment. The advantage of the proposed method is its compactness and scalability to multidimensional measurement systems at low cost.

A GPU implementation of an iterative receiver for energy saving MIMO ID-BICM systems

Iterative detection and decoding in communication systems with multiple transmitter and receiver antennas suffer from a significant increase in the computational cost and energy consumption. Nowadays, application of specific high-performance computing techniques for signal processing in communication systems is receiving considerable attention. In this paper, we present an accelerated and efficient iterative receiver, which has been implemented following two strategies. First, we reduce the computational cost using parallelized algorithms executed on graphics processing unit. In addition, our receiver allows the selection between two types of detectors with different complexity and performance. The selection can be done to fulfill a given compromise between bit error rate and power consumption.

Limited Feedback for Cooperative Multicell MIMO Systems with Multiple Receive Antennas

Limited Feedback for Cooperative Multicell MIMO Systems with Multiple Receive Antennas

Receiver-Based Recovery of Clipped OFDM Signals for PAPR Reduction: A Bayesian Approach

Clipping is one of the simplest peak-to-average power ratio reduction schemes for orthogonal frequency division multiplexing (OFDM). Deliberately clipping the transmission signal degrades system performance, and clipping mitigation is required at the receiver for information restoration. In this paper, we acknowledge the sparse nature of the clipping signal and propose a low-complexity Bayesian clipping estimation scheme. The proposed scheme utilizes a priori information about the sparsity rate and noise variance for enhanced recovery. At the same time, the proposed scheme is robust against inaccurate estimates of the clipping signal statistics. The undistorted phase property of the clipped signal, as well as the clipping likelihood, is utilized for enhanced reconstruction. Furthermore, motivated by the nature of modern OFDM-based communication systems, we extend our clipping reconstruction approach to multiple antenna receivers and multi-user OFDM.We also address the problem of channel estimation from pilots contaminated by the clipping distortion. Numerical findings are presented that depict favorable results for the proposed scheme compared to the established sparse reconstruction schemes.

Likelihood-Based Modulation Classification for Multiple-Antenna Receiver

Likelihood-based algorithms for the classification of linear digital modulations are systematically investigated for a multiple receive antennas configuration. Existing modulation classification (MC) algorithms are first extended to the case of multiple receive antennas and then a critical problem is identified that the overall performance of the multiple antenna systems is dominated by the worst channel estimate of a particular antenna. To address the performance degradation issue, we propose a new MC algorithm by optimally combining the log likelihood functions (LLFs). Furthermore, to analyze the upper-bound performance of the existing and the proposed MC algorithms, the exact Cramer-Rao Lower Bound (CRLB) expressions of non-data-aided joint estimates of amplitude, phase, and noise variance are derived for general rectangular quadrature amplitude modulation (QAM). Numerical results demonstrate the accuracy of the CRLB expressions and verify that the results reported in the literature for quadrature phase-shift keying (QPSK) and 16-QAM are special cases of our derived expressions. Also, it is demonstrated that the probability of correct classification of the new algorithm approaches the theoretical bounds and a substantial performance improvement is achieved compared to the existing MC algorithm.

Performance Analysis of MIMO OFDM System by using LS and MMSE Techniques

In today’s world, high speed is an important factor to be considered in wireless communication systems. This is because high speed is required for access of video, images, and many others multimedia application. One way to achieve high data rate is OFDM. Orthogonal Frequency Division Multiplexing (OFDM) is a technique which transmitted data parallel and this data are orthogonal to each other, hence result high data rate in wireless transmission as large no. of data is transmitted at same time. Another way is MIMO system. To increase the diversity gain or to enhance the system capacity on time-variant and frequency-selective channels, OFDM may be combining with multiple transmitter antenna and receiver antenna, this resulting MIMO OFDM system. MIMO-OFDM, a new wireless 4G technologies, has capability of enhance data rate transmission and robustness against multi-path fading. In this paper, two techniques Least Square (LS) and Minimum Mean Square Error (MMSE) are used to analysis the performance of MIMO OFDM System also used to reduce BER.

Hierarchical modulated quadrature amplitude modulation with signal space diversity and maximal ratio combining reception in Nakagami‐ m fading channels

This study combines hierarchical modulation with signal space diversity (SSD) to present an unequal error protection scheme with improved bit-error rate (BER) performance for single as well as multiple antenna reception by employing maximal ratio combing in Nakagami- m fading channels. The optimal rotation angles for different constellation priority parameter α are derived. A theoretical BER expression in Nakagami- m fading channels using the nearest neighbour approximation approach is also derived. This is confirmed as a valid performance approximation for single and multiple antenna reception through simulations. The resultant scheme produces improved BER performance for both important and less important data without consuming any additional power than a non-SSD system at the cost of increased complexity at detection. Specifically, performance gains of up to 18 and 17 dB at a BER of 1 × 10 -5 for base and refinement bits, respectively, are observed for single receive antenna with Nakagami m = 1. A further improvement of roughly 3 dB at a BER of 1 × 10 -6 for base bits at N = 3 receiver antennas is found as hierarchy is increased. Although the gain is observed to decrease as m increases, a gain of 14 dB at 1 × 10 -6 for α = 4 is achieved even as m increases from m = 1 to m = 3.

A multiple antenna wireless testbed for the validation of DoA estimation algorithms

In this paper, a wireless testbed with a multiple antenna receiver is described. It comprises a rotating four-element antenna array connected to a quad radio frequency (RF) front-end, and a channel acquisition board equipped with a field programmable gate array (FPGA). The algorithms can be implemented directly on the FPGA, but they can also be tested via simulation, e.g., with Matlab, since the acquired data can be transferred from the board memory to a personal computer (PC). Moreover, the algorithm implementation on the FPGA can be done by exploiting the System Generator for DSP Xilinx tool that allows the algorithm synthesis from a Simulink block diagram. These features make the testbed useful for rapid prototyping. In particular, the presence of the rotating antenna array enables the analysis of direction of arrival (DoA) estimation techniques. We report the main results from the experimental measures conducted to characterize the hardware non idealities. We then describe a DoA estimation algorithm that has been used to compare real and simulated results. It is shown that the results are in good agreement with the simulations, also when the effect of non isotropic antenna gains and/or phase noise originated from non co-phased RF front-ends becomes considerable.