Transmit Antenna Selection Research Articles

TAS Strategies for Incremental Cognitive MIMO Relaying: New Results and Accurate Comparison

In this paper, we thoroughly elaborate on the impact different transmit-antenna selection (TAS) strategies induce in terms of the outage performance of incremental cognitive multiple-input multiple-output relaying systems employing receive maximum-ratio combining (MRC). Our setup consists of three multi-antenna secondary nodes: a transmitter, a receiver and a decode-and-forward relay node acting in a half-duplex incremental relaying mode whereas the primary transmitter and receiver are equipped with a single antenna. Only a statistical channel-state information is acquired by the secondary system transmitting nodes to adapt their transmit power. In this context, our contribution is fourfold. First, we focus on two TAS strategies that are driven by maximizing either the received signal-to-noise ratio (SNR) or signal-to-interference-plus-noise ratio (SINR), and extend their operating mode into an incremental relaying setup where MRC is carried jointly over both relaying hops. Second, given the inherited complexity, we proceed by the exact outage analysis of the direct (first-hop) transmission as a preliminary yet innovative step pertaining to the SINR-driven TAS strategy. Third, the end-to-end (second-hop) transmission outage performance is also evaluated although shown to entail an involved derivation roadmap for both TAS strategies. Fourth, we simplify our exact derivations by means of the asymptotic analysis which reveals that the detrimental effect of mutual interference on the secondary system is originated from the primary transmitter (i.e., co-channel interference) and not from the primary receiver (i.e., interference threshold). That is, even if the secondary system operates at a high tolerated amount of interference, an outage floor will still occur because the primary system will pump a high amount of co-channel interference in return. The SINR-driven TAS shows up as an optimal interference-aware strategy in this regard. It achieves the same diversity gain but a better coding gain compared to its SNR-driven counterpart. The correctness of our results is confirmed by Monte Carlo simulations and the actual outage gap between both TAS strategies is reflected.

Partial Cooperation Based on Dynamic Transmit Antennas for Two‐Hop Massive MIMO Systems

As the ever‐increasing attention to green communication, energy efficiency has become an imperative metric in the emerging massive multiple‐input multiple‐output (MIMO) systems. In order to maximize the energy efficiency, transmit antenna selection has been widely concerned by researchers. In this paper, we investigate the coded cooperation transmission for dynamic transmit antennas aided two‐hop massive MIMO systems. Explicitly, we propose a rate‐less codes aided cooperation scheme for reducing the implementation complexity in the broadcast phase, compared to the fixed‐rate coded cooperation scheme. Furthermore, we develop a partial cooperation scheme in the cooperative phase in order to avoid the low achievable rate caused by the full cooperation, especially when the source‐to‐relay (S‐R) channels are poor. Finally, the number of transmit antennas at the base station (BS) is optimized through theoretical analysis in a metric of maximizing the energy efficiency. Moreover, we also analyze the achievable error performance for different modulations. Our simulation results demonstrate the effectiveness of the proposed scheme.

Unified Performance Analysis of Transmit Antenna Selection With OSTBC and Imperfect CSI Over Nakagami- m Fading Channels

A unified error analysis of multi-antenna systems with orthogonal space-time block coding (OSTBC) using transmit antenna selection (TAS) over Nakagami- $m$ channels in the presence of feedback delay and channel estimation error is presented, where the number of transmit antennas is arbitrarily selected. For imperfect channel state information (CSI), the Nakagami- $m$ channel is modeled as the sum of Nakagami- $\hat{m}$ channel and independent Gaussian channel error. By this model, accurate and closed-form approximate bit error rate (BER) expressions of TAS-OSTBC for M-ary quadrature amplitude modulation and M-ary phase-shift keying are derived by using the moment generating function of received SNR. With the approximate BER formula, the number of antennas to be selected for transmission can be adapted by minimizing the BER of the system with imperfect CSI. The diversity and coding gains of TAS-OSTBC with $K$ receive antennas and $M$ antennas selected from $N$ transmit antennas for transmission are analyzed at high SNR. For noninteger $mK$ , the upper and lower bounds of the diversity gain for different CSI and estimation error scenarios are derived. But for integer $mK$ , the results indicate that the upper and lower bounds are equal achieving the full diversity order of $mKN$ for perfect CSI, zero diversity order and partial diversity order of $mMK$ for estimation error variance being fixed and being a decreasing function of average SNR, respectively. The coding gain is affected by $M$ , $N$ , $K$ , Nakagami parameter $m$ , code rate, modulation, and channel correlation coefficients. Simulation results verify the validity of the theoretical analysis and effectiveness of the adaptive antenna selection scheme.

Performance Analysis of Energy Harvesting Multi-Antenna Relay Networks With Different Antenna Selection Schemes

In this paper, we investigate the performance of three transmit antenna selection (TAS) schemes for an energy harvesting decode-and-forward relay cooperative network. In the network, the energy-limited relay first harvests the energy from the received signal with the power-splitting scheme, and then utilizes the harvested energy to forward the received signal to the destination. Specifically, exact analytical expressions for the outage probability of the considered network with three TAS schemes are derived for evaluating the impact of key parameters on the outage performance. In order to deeply extract insights, we further present tractable asymptotic outage probabilities for three TAS schemes to characterize the diversity order and coding gain in high signal-to-noise ratio regimes, respectively. In addition, we also analyze the impact of feedback delays on the performance of the optimal TAS scheme, which is quantified by the reduction of diversity order and coding gain. Numerical results sustained by Monte Carlo simulations demonstrate that: 1) the second suboptimal TAS schemes achieve a comparable performance as the optimal TAS scheme with the reduced implementation cost; 2) the relay location has a great impact on the outage performance and the optimal power-splitting ratio; and 3) the feedback delay plays a critical role in determining the diversity order achieved by the considered system.

Secrecy Performance of Wireless Powered Communication Networks With Multiple Eavesdroppers and Outdated CSI

In this paper, we present a comprehensive secrecy performance analysis of wireless powered communication networks with multiple eavesdroppers, where an energy-limited information source with multiple antennas harvests the radio frequency energy from a dedicated power beacon (PB) before transmission. To exploit the benefits of multiple antennas at source, two popular multi-antenna transmission schemes, i.e., maximal ratio transmission and transmit antenna selection, are investigated for two intercepting ways at Eves, i.e., non-colluding and colluding scenarios, respectively. Specifically, adopting the time-switching protocol at PB, we derive exact closed-form expressions of the secrecy outage probability and the average secrecy rate for both two transmission schemes taking into account the outdated channel state information. Furthermore, in order to deeply extract insights on the system design, we further present tractable asymptotic secrecy outage probability and ergodic secrecy capacity at high signal-to-noise ratio regimes, which easily enable us to obtain the secrecy diversity order and coding gain of two transmission schemes, respectively. From our analysis, several important concluding remarks are obtained as follows: 1) full secrecy diversity order can be achieved by both two transmission schemes with no feedback delay, however, it reduces to one in the presence of feedback delay; 2) as the number of eavesdroppers increases, the secrecy performance gap between non-colluding and colluding scenarios becomes large; and 3) maximal ratio transmission (MRT) scheme always outperforms transmit antenna selection (TAS) scheme with no feedback delay. However, TAS scheme achieves a similar performance as MRT scheme or even better in moderate and even serious feedback delay conditions.

On Secrecy Outage Probability and Average Secrecy Rate of Large‐Scale Cellular Networks

We investigate the secrecy performance in large‐scale cellular networks, where both Base Stations (BSs) and eavesdroppers follow independent and different homogeneous Poisson point processes (PPPs). Based on the distances between the BS and user, the intended user selects the nearest BS as serving BS to transmit the confidential information. We first derive closed‐formed expressions of secrecy outage probability and average secrecy rate of a single‐antenna system for both noncooperative and cooperative eavesdroppers scenarios. Then, to further improve the secrecy performance through additional spatial degrees of freedom, the above analyses generalize to the multiantenna scenario, where BSs employ the transmit antenna selection (TAS) scheme. Finally, the results show the small‐scale fading has a considerable effect on the secrecy performance in certain density of eavesdroppers and small path loss exponent environment, and when the interference caused by BS is considered, the secrecy performance will be reduced. Moreover, the gap of secrecy performance between noncooperative and cooperative eavesdroppers cases is nearly invariable as the number of antennas increases.

On the Double-Generalized Gamma Statistics and Their Application to the Performance Analysis of V2V Communications

Important statistical properties of the double-generalized Gamma (dGG) distribution are studied in this paper. The dGG distribution is suitable for modeling non-homogeneous double-scattering radio propagation fading conditions, which can be frequently observed in vehicle-to-vehicle (V2V) communications. In this context, important statistical metrics for the bivariate dGG distribution, such as the joint probability density function, cumulative distribution function, and the moments, are derived for the first time, while simplified expressions for the corresponding marginal statistical metrics are presented. Moreover, the second-order statistics of this distribution are also analytically studied. The derived analytical framework has been employed to analyze the performance of a transmit antenna selection system operating in V2V communication channels modeled by the dGG distribution. In this scenario, the impact of outdated channel state information (CSI) to the system’s performance is investigated in terms of various metrics, including the level crossing rate and the average fade duration. Furthermore, simplified asymptotic closed-form expressions for the outage probability have been derived to examine the achievable diversity and coding gains. Based on our analysis, insightful discussions are provided. It is shown that the diversity gain is independent from the number of transmit antennas when the available CSI becomes outdated.

Outage Performance for IDF Relaying Mobile Cooperative Networks

Cooperative communication has emerged as a key technique in fifth generation (5G) mobile wireless networks. In this paper, with incremental decode-and-forward (IDF) relaying and transmit antenna selection (TAS), we investigate the outage probability (OP) performance of mobile cooperative networks. Exact closed-form expressions for OP with optimal TAS are derived. These expressions are used to evaluate the impact of power allocation on OP performance. Then we verify the mathematical derivations using Monte Carlo simulations. The OP performance is influenced by power-allocation parameter.

Cooperative Communications With Wireless Energy Harvesting Over Nakagami- $m$ Fading Channels

In this paper, a dual-hop decode-to-forward cooperative system is considered where multiple relays are with finite energy storage and can harvest energy from the destination. In our analysis, the relays are spatially randomly located with invoking stochastic geometry. In an effort to improve spectral efficiency, an optimal source-relay link scheme is employed. Assuming Nakagami- $m$ fading, two different scenarios are considered: 1) the single-antenna source with perfect channel state information (CSI) and 2) the multiple-antenna source with transmit antenna selection and imperfect CSI. In both scenarios, the destination node is equipped with a single transmit antenna to forward power via frequency radio signal to the relay candidates. For improving the system performance, multiple antennas at the destination are considered to process the multiple copies of the received signal from the best relay. For characterizing the performance of the proposed scenarios, exact closed-form analytical expressions for the outage probability are derived. To obtain further insights, we carry out diversity gain analysis by adopting asymptotic relative diversity. We also derive the exact closed-form analytical expression for the system throughput. Finally, simulation results are presented to corroborate the proposed analysis and to show that: 1) the system performance is improved by enlarging the area of the circle and the density of the relays and 2) the energy storage size has impacts on the performance of considered networks, which determines the maximal transmit power at relays.

Secrecy Performance of Imperfect One Bit Feedback Based Alamouti MISO System

We study the secrecy performance of one bit imperfect feedback-based diagonal precoder for Alamouti multiple-input single-output (MISO) system in the presence of a single antenna equipped eavesdropper. An error-tolerant weighting (ETW) scheme is employed for transmit power allocation. The exact and asymptotic closed-form expressions of the secrecy outage probability (SOP) of the considered MISO system are derived with the ETW scheme. Also, the SOPs of uniform power allocation (UPA) scheme and best transmit antenna selection (BTAS) scheme with erroneous feedback are derived. Analysis shows that the proposed ETW scheme provides a significant secrecy performance gain in comparison to UPA scheme and remains insensitive to feedback error, unlike the BTAS scheme.

Antenna Selection for Energy Efficient MISO Systems

This letter studies the mathematical property of the energy-efficiency (EE) function for multiple-input single-output systems with transmit antenna selection. We prove that the monotonicity of the function is guaranteed if the system signal-to-noise ratio satisfies a sufficient condition, which is quite feasible in practice. Based on this property, an algorithm with low complexity is proposed to find the maximum EE. The monotonicity of the function and the advantage of the proposed algorithm are confirmed by numerical results.

Wireless Information and Power Transfer in MIMO Virtual Full-Duplex Relaying System

Interrelay interference (IRI) is known to degrade the performance of virtual full-duplex (FD) relaying schemes. Although interference avoidance and cancelation strategies have been proposed in the existing literature, most studies reflect the traditional information theoretical viewpoint of interference as a degrading factor on information decoding (ID). However, from energy harvesting (EH) perspective, the IRI could be beneficial. This motivates the study of simultaneous wireless information and power transfer in decode-and-forward multiple input multiple output virtual FD relaying system, where the IRI serves as an additional source of energy to the relay. To manage the degrading effect of the IRI on the ID receiver, transmit antenna selection is proposed at the relay. In addition, precoding matrices that optimize the ID and EH receivers are jointly designed. The simulated results show that although IRI could be a degrading factor from the information viewpoint, it can be properly managed and exploited for EH at the relay while maintaining the end-to-end data rate. In addition, the results show that the end-to-end information rate and harvested energy can be simultaneously achieved using the proposed precoders.

On the error probability of Alamouti scheme with transmit antenna selection for CPM‐MIMO systems

Up to now, some related results on the upper bounds of error probability have been concluded for some linear modulations with orthogonal space–time block codes in multiple-input and multiple-output (MIMO) systems. For instance, the performance of MIMO systems with antenna selection (AS) has been investigated widely, whereas in non-linear modulations, i.e. continuous phase modulation (CPM), there are few relevant literatures found to this date. With this motivation, this study derives upper bound of the error probability of Alamouti scheme with transmit AS (TAS) in CPM-MIMO systems. First, a new form of signal matrix for CPM-MIMO system is given. Then, the pair wise probability conditioned on fading channel statistics is written availably by computing the difference of signal matrix. Moreover, the probability distribution function is obtained by employing order statistics theory. Furthermore, the tight upper bounds of the frame error rate are derived. Finally, simulated results verify the accuracy of the theoretical analysis.

Transmit Antenna Selection Schemes for Quadrature Spatial Modulation

The objective of this paper is to investigate the application of transmit antenna selection (TAS) to quadrature spatial modulation (QSM). The application of optimal Euclidean distance based antenna selection (EDAS) to QSM (EDAS-QSM) is first proposed. EDAS-QSM requires an exhaustive search, which imposes a significantly high computational complexity. In this regard, a reduced-complexity algorithm for the computation of EDAS-QSM is proposed. Finally, several low-complexity, sub-optimal TAS techniques for QSM are investigated. The decision metrics of these schemes are based on channel amplitude, antenna correlation, Euclidean distance or a combination thereof. Monte Carlo simulation results demonstrate the effectiveness of the proposed schemes, while the computational complexity of each is analysed. The trade-off between error performance and computational complexity is discussed for each of the schemes.

Secure Transmission Via TAS/RAS in MIMO Wiretap Channels

In the multiple-input multiple-output (MIMO) system, the transmit antenna is selected by transmitting antenna selection (TAS)/receiver using receiver antenna selection (RAS). Consider the actual transmission situation: the transmitter cannot get the channel information of the eavesdropper’s channel. The main channel between the transmitter and the receiver is selected, and an antenna with the largest instantaneous signal- to-noise ratio (SNR) is selected for transmission. RAS is adopted at the receiving end. The main channel and the eavesdropper’s channel are independent and distributed Rayleigh channel. In this paper, we derive closed-form expressions of probability and safety outage probability for TAS/RAS. Various numerical results are presented that corroborate the analysis.

Improving performance of the asynchronous cooperative relay networks with maximum ratio combining and transmit antenna selection technique

In this paper, a new amplify and forward (AF) asynchronous cooperative relay networks using maximum ratio combining (MRC) and transmit antenna selection (TAS) technique is considered. In order to obtain a maximal received diversity gain, the received signal vectors of all antennas of the each relay node are jointly combined by MRC technique in the first phase. Then, only one the selected antenna of each relay will amplify and retransmit the resulting MRC signal vectors to the destination node in the second transmission step of network. The proposed scheme not only offers to reduce the interference components induced by inter-symbol interference (ISI) among the relay nodes, but also can effectively remove them with employment near-optimum detection (NOD) at the destination node as compared with the previous distributed close loop extended-orthogonal space time block code (DCL EO-STBC) scheme. The analysis and simulation results confirm that the new scheme outperforms the previous cooperative relay networks in both synchronous and asynchronous conditions. Moreover, the proposed scheme allows to reduce the requirement of the Radio-Frequency (RF) chains at the relay nodes and is extended to general multi-antenna relay network without decreasing transmission rate.

Large Scale Antenna Selection and Precoding for Interference Exploitation

We propose several low-complexity transmit antenna selection (TAS) and precoding schemes for massive multi-input multi-output (M-MIMO). It is well established that large antenna arrays in M-MIMO lead to particularly high hardware overheads as they require an equally large number of radio-frequency chains, and antenna selection is envisaged as a solution to reducing this hardware complexity. Accordingly, in the proposed schemes, both hardware and computational complexity of M-MIMO systems are addressed by jointly optimizing TAS and precoding. We first introduce a mixed-integer programming approach that simultaneously identifies the transmitting antennas subset and solves the precoding problem, by employing a unified metric based on constructive interference (CI) concept. We then propose three sub-optimal techniques that allow a reduction of the computational complexity required to solve the joint optimization. Our analyses and results prove that the proposed joint TAS and precoding schemes based on CI exploitation are able to outperform the state-of-the-art, while providing a favorable performance-complexity tradeoff.

Reliable Virtual Full-Duplex Relaying in the Presence of Interrelay Interference

Interrelay interference (IRI) is known to limit the performance of virtual full-duplex (VFD) relaying schemes. Available interference cancelation schemes are unable to simultaneously improve the diversity and maintain the multiplexing gain of VFD relaying schemes in multiple antennas scenarios. In this paper, we propose a technique to improve the reliability of multiantenna VFD relaying scheme, while maintaining the multiplexing gain in the presence of IRI. In the proposed scheme, the source and interrelay channels are concatenated and their signals are jointly decoded at the relay. A superposition of the decoded messages is forwarded to the destination. To reduce the effect of IRI on the receiving relay, two suboptimal relay transmit antenna selection schemes, namely, random antenna selection and maximum capacity antenna selection, are investigated. The system capacity and outage probability bounds of the proposed scheme are derived in closed form. The diversity and multiplexing tradeoff is also characterized. The analytical and numerical results show that the proposed scheme can achieve full diversity and maintain the multiplexing gain of the full-duplex relaying scheme. Also, the proposed scheme can outperform conventional VFD relaying scheme in terms of reliability even in the presence of IRI.

Secrecy outage performance of transmit antenna selection for cognitive radio systems

In this study, the authors investigate the employment of transmit antenna selection (TAS) against eavesdropping in cognitive radio systems, where a cognitive source (CS) node transmits to a cognitive destination (CD) node in the face of an eavesdropper, each equipped with multiple antennas. The authors derive a closed-form expression of secrecy outage probability for the proposed TAS scheme. For the purpose of comparison, the authors also study the random antenna selection (RAS) as a baseline. Moreover, the secrecy diversity orders of TAS and RAS are analysed to provide an intuitive insight into the effect of the number of antennas on the secrecy outage performance. It is of interest to observe that the secrecy diversity order of TAS is the product of number of transmit antennas at CS and receive antennas at CD and the secrecy diversity order achieved by RAS scheme is the number of receive antennas at CD, which both have nothing to do with the number of antennas at eavesdropper. Finally, the simulation results validate the authors’ theoretical results and the proposed TAS outperforms the conventional RAS in terms of secrecy outage probability.

Analysis of Correlated MRC With Transmit Antenna Selection Under $\eta$–$\mu$ Fading

A wireless link considering correlated maximal ratio combining and transmit antenna selection under the general $\eta$ – $\mu$ fading is analyzed. Exact and asymptotic expressions for the cumulative distributing function (CDF) and probability density function (PDF) are derived. These new results are used to evaluate the outage capacity and the asymptotic average bit error rate for different binary modulations. The obtained theoretical results are validated through Monte Carlo simulations.