Transmit Antenna Selection/maximal-ratio Combining Research Articles

Outage performance analysis of antenna selection schemes in UAV-assisted networks

In this paper, we investigate the performance of various antenna selection (AS) techniques in an unmanned aerial vehicle (UAV)-assisted relay communication system, wherein a UAV is deployed as a flying relay to establish and sustain a communication link between source and destination nodes. The AS schemes under study encompass transmit antenna selection/maximal ratio combining (TAS/MRC), joint transmit and receive antenna selection (JTRAS), and maximum ratio transmission/receive antenna selection (MRT/RAS). We present a unified outage probability (OP) performance analysis of AS techniques in UAV relay networks. We initially derive a closed-form expression for the OP under Nakagami-m fading channels. Subsequently, an asymptotic expression elucidating the array and diversity gain is derived to offer deeper insights into the performance of the studied system. Finally, Monte Carlo simulations are conducted to validate the theoretical results.

Analyzing the Performance of TAS/MRC with Decode-and-Forward Relaying for Multihop Transmission over Fisher-Snedecor F Fading Channels

This study comprehensively assesses a decode-and-forward relaying system that employs Transmit Antenna Selection/Maximal Ratio Combining (TAS/MRC) for multi-hop communication across Fisher-Snedecor F fading channels. The study primarily focuses on the average symbol error rate (ASER) and outage probability (OP) while using cross QAM (XQAM) and rectangular quadrature amplitude modulation (RQAM). The proposed MIMO system effectively decreases the hardware complexity and cost of large antennas by implementing Transmit Antenna Selection (TAS) at the source and relay nodes and Maximum Ratio Combining (MRC) diversity at the destination and relays. Analytical formulations for OP (outage probability) and ASER (average symbol error rate) are derived using PDF (Probability Density Function)-based methods. Monte-Carlo simulations further validate these formulas. The investigation indicates that system performance is improved under conditions of lighter shadowing compared to moderate and extreme shadowing settings. Additionally, increasing the hop count amplifies the observed performance. Moreover, when the fading parameter increases, both the OP and ASER decrease. This study comprehensively examines the impact of many parameters, including m, p, L, R, and o, on the behaviour of the system under Fisher-Snedecor F fading. Based on the findings, the combination of shadowing and multipath fading significantly affects the system's performance, with both m and p significantly influencing this. When examining the Signal-to-Noise Ratio (SNR), a comparison between RQAM and XQAM demonstrates that XQAM is superior. The research uncovers crucial information for planning and executing the TAS/MRC-based MIMO multi-hop communication system. This technology possesses the capability to enhance the effectiveness of similar communication systems, as seen by the encouraging advancements in performance, especially in scenarios including signal attenuation.

Performance of TAS/MRC in NOMA energy harvesting relay networks

This paper investigates the outage probability (OP) performance for multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA) based energy harvesting (EH) relaying network. The base station communicates multiple users with the assistance of EH-relay. The optimal transmit antenna selection/maximal ratio combining (TAS/MRC) and sub-optimal majority-based TAS (TAS-maj)/MRC are employed in the first and second hops, respectively. We first derive the signal-to-interference-and-noise ratio (SINR) expressions. Then, the derived SINR expressions are used to obtain expressions of OP for each user in closed form in Nakagami-m fading channels. We finally verify the exactness of the theoretical analysis with the numerical results through Monte Carlo simulations. The results show that the outage performance improves considerably with the increased number of transmit and/or receive antennas and the enhanced channel conditions. Furthermore, regardless of the antenna’s configurations, the optimal position of the EH-based relay has to be close to the base station, while the optimal power division ratios for users vary. Moreover, the proposed TAS/MRC scheme is superior to the previous schemes, such as max–max–max and max–min–max-based MRC.

Secrecy performance of transmit antenna selection for underlay MIMO cognitive radio relay networks with energy harvesting

In this paper, the secrecy performance in a MIMO cognitive radio (CR) relay network with energy harvesting (EH) and transmit antenna selection/maximal ratio combining (TAS/MRC) is invstigated, where the DF relaying protocol and multiple colluding passive eavesdroppers are considered. To improve the security of wireless transmission, two antenna selection schemes are proposed, namely, the optimal transmit antenna selection (OTAS) scheme and suboptimal transmit antenna selection (STAS) scheme. For the purpose of comparison, the space-time transmission (STT) scheme is introduced as a baseline. The exact and asymptotic closed-form secrecy outage probability (SOP) expressions for OTAS, STAS and STT schemes are derived over Rayleigh fading channels. An extension of the TAS framework to an artificial noise (AN) aided MIMO network is further presented and an AN aided transmit antenna selection (AN-TAS) scheme is proposed, in which the unselected antennas at R are used to emit AN for interfering with Es. Numerical results show that the OTAS and STAS schemes perform better than STT scheme in terms of SOP. Meanwhile, the SOP of AN-TAS scheme is much smaller than that of OTAS, STAS and STT schemes in the high SNR region, indicating the benefit of applying AN in MIMO network.

Secure Cognitive MIMO Wiretap Networks With Different Antenna Transmission Schemes

This paper investigates a secure transmission in the multiple-input multiple-output (MIMO) cognitive wiretap networks, where a secondary transmitter (Alice) sends data to a secondary receiver (Bob) in the presence of an eavesdropper (Eve). In order to solve the problems of inter channel interference and inter antenna synchronization encountered by traditional MIMO technologies, the antenna transmission scheme is adopted at the transmitter. As a comparison, we design two different antenna transmission schemes, namely transmit antenna selection maximal-ratio combining (TAS-MRC) scheme and differential spatial modulation maximal-ratio combining (DSM-MRC) scheme, respectively. Moreover, due to outdated channel state information (CSI) of the interference link from Alice to the primary user (PU), we propose power control mechanism to protect the quality of service (QoS) of PU. Furthermore, the closed-form for the secrecy outage probability and the secrecy throughput with TAS-MRC and DSM-MRC schemes are derived to evaluate the secrecy performance, respectively. What's more, we explore the security diversity gain and coding gain based on the asymptotic secrecy outage probability. As the results, it demonstrates that DSM-MRC requires less CSI and is convenient for modulation and demodulation, but sacrifices some secrecy performance gains between two proposed schemes.

Improving the Security and Spectrum Efficiency in Overlay Cognitive Full-Duplex Wireless Networks

In this paper, we design a new collaboration interference (CI) transmission scheme for overlay cognitive full-duplex wireless wiretap networks, where a full-duplex secondary user utilizes the licensed spectrum to transmit the secondary information and uses the secondary signal as a special noise to help and protect the secure transmission of primary information in the presence of multiple passive eavesdroppers, simultaneously. Specifically, the full-duplex secondary user firstly uses the joint transmit antenna selection/maximal ratio combining (TAS/MRC) scheme to transmit the secondary information and receive the primary information at the same time. Then, the full-duplex secondary user utilizes a new interactive zero forcing beamforming (IZFB) algorithm to transmit the primary and secondary information without mutual interference simultaneously. For comprehensively analyzing the secure performance of the primary transmission, two eavesdropping modes, i.e., non-colluding eavesdropping (NCE) and colluding eavesdropping (CE) are considered. Based on the two modes, we derived the exact and asymptotic closed-form expressions for secrecy outage probability (SOP) of the primary transmission. Furthermore, the effective throughput of secondary transmission is also derived. The results demonstrate that the proposed CI-based transmission scheme can simultaneously improve the secrecy performance of primary transmission and throughput of secondary transmission, and can further achieve better spectrum-and-energy efficiency than traditional overlay transmission.

Impact of Feedback Errors on the Security of MIMO Wiretap Systems with Antenna Selection

This paper analyzes the impact of feedback errors on the security performances of multiple-input multiple-output (MIMO) wiretap channels. For the legitimate MIMO system, two schemes are considered: (1) transmit antenna selection/maximal ratio combining (TAS/MRC) and (2) transmit antenna selection/receive antenna selection (TAS/RAS). The eavesdropper uses either MRC or RAS techniques. We assume that both legitimate and eavesdropper receivers have the knowledge of their own channel state information. Furthermore, we consider that the index of the transmit antenna with the strongest signal-to-noise ratio is fed back from Bob to Alice. We derive closed-form expressions for the exact secrecy outage probability (SOP) and the probability of strictly positive secrecy capacity in Nakagami-m flat fading. In order to obtain the secrecy diversity order and the secrecy array gain, an asymptotic SOP expression is also derived.

Secure Transmission in Cognitive MIMO Relaying Networks With Outdated Channel State Information

In this paper, we introduce transmit antenna selection/maximal-ratio combining (TAS/MRC) scheme in dual-hop randomize-and-forward (RaF) cognitive multiple-input multiple-output (MIMO) wiretap networks with outdated channel state information (CSI). In this network, the secondary transmitter adopts the TAS scheme to choose the antenna with the maximal received signal-to-noise ratio (SNR), while the secondary receiver and the eavesdropper adopt the MRC scheme to combine the received signals. To thoroughly assess the secrecy performance achieved by the TAS/MRC scheme and the impact of outdated CSI on the secrecy performance, we derive a new closed-form expression for the secrecy outage probability of dual-hop RaF cognitive MIMO wiretap networks. In order to achieve more insights on the application of TAS/MRC scheme, we further present tractable asymptotic secrecy outage probability at high SNR regimes under two distinct scenarios. From our analysis, several important concluding remarks are obtained as follows: 1) the RaF relaying strategy achieves better secrecy performance than that of the decode-and-forward relaying strategy for dual-hop cognitive MIMO wiretap networks; 2) outdated CSI decreases the secrecy diversity gain of the TAS/MRC scheme from ${N_{{R}}}\min \left ({ {{N_{{A}}},{N_{{B}}}} }\right )$ to $\min \left ({ {{N_{{R}}},{N_{{B}}}} }\right )$ ; and 3) although TAS/MRC scheme cannot attain full secrecy diversity gain for the considered system with outdated CSI, it still can achieve an extra secrecy coding gain compared with the random antenna selection/MRC scheme.

Performances of Transmit Antenna Selection, Receive Antenna Selection, and Maximal-Ratio-Combining-Based Hybrid Techniques in the Presence of Feedback Errors

In this paper, performances of joint transmit and receive antenna selection (JTRAS), transmit antenna selection/maximal ratio combining (TAS/MRC), and transmit antenna selection/receive antenna selection (TAS/RAS) techniques are examined in a unified manner in the (42) presence of feedback errors. Exact and closed-form outage probability, moments, moment-generating function, ergodic capacity, and symbol error probability (SEP) expressions are derived for flat Nakagami-m fading channels. In addition, to obtain diversity order and array gain of the investigated techniques in the presence of feedback errors, asymptotic outage probability and SEP expressions are also derived. Analytical results are validated by Monte Carlo simulations. Results show that the diversity order is significantly reduced in the presence of feedback errors, whereas all the systems provide full diversity order for a perfect feedback channel.

Adaptive Power Allocation for Effective Capacity of TAS-MRC Systems

In this paper, the effective capacity of transmit antenna selection-maximal ratio combining (TAS-MRC) systems is studied. By considering constant power allocation, a closed-form expression for the effective capacity is derived. While for variable power allocation, restricted by the average power, optimal power allocation scheme and associated effective capacity is given. Adaptive modulation is used for both constant and variable power allocation, and the superiority of variable power allocation versus constant power allocation is demonstrated by the computer simulations.

Positive Effect of Severe Nakagami-mFading on the Performance of Multiuser TAS/MRC Systems with High Selection Gain

This paper investigates the positive effect of severe Nakagami-mfading on the performance of multiuser transmit antenna selection/maximal-ratio combining (TAS/MRC) systems with high selection gain. Both amount of fading (AF) and symbol error rate (SER) ofM-QAM are derived as closed-form expressions for integerm. For arbitrarym, the AF and the SER are expressible as a single infinite series of Gamma function and Gauss hypergeometric function, respectively. The analytical results lead to the following observations. First, the SER performance can demonstrate the positive effect of severe Nakagami-mfading on multiuser TAS/MRC systems with high selection gain. Second, the AF performance only exhibits the negative impact of severe fading regardless of high selection gain. Last, the benefit of severe fading to the system performance diminishes at high signal-to-noise ratio (SNR).

Performance Evaluation of Actual Multielement Antenna Systems Under Transmit Antenna Selection/Maximal Ratio Combining

In this letter, the performance of actual multielement antenna (MEA) systems under the transmit antenna selection/maximal ratio combining (TAS/MRC) technique is evaluated. An alternative version of an efficient, recently developed, stochastic electromagnetic methodology is employed to investigate the TAS/MRC performance of five MEA systems operating in the 5.2-GHz ISM band. The MEA systems are comprised two up to six printed antennas, and their performance is evaluated through the diversity gain (DG) at 1% outage probability level. Interestingly, DG degradation is revealed when the number of receiving antennas is six.

Concise Performance Analysis of Maximal Ratio Combining with Transmit Antenna Selection in Nakagami-m Fading Channels

This letter presents structurally simpler symbol error rate (SER) expressions for Transmit Antenna Selection/Maximal-Ratio Combining (TAS/MRC) scheme in independent Nakagami-m fading channels in a comparison with those in the literature. First, the SER is derived as a single infinite series of simple functions for arbitrary m. For integer m, the SER can be attained as a closed-form expression with a double finite series. Moreover, simple asymptotic SER expressions suggest that the TAS/MRC scheme can achieve a full diversity order at high SNR. Numerical and simulation results verify the conciseness of the derived expressions.

Outage probability of multiuser transmit antenna selection/maximal-ratio combining systems over arbitrary Nakagami-m fading channels

The outage probability of multiuser diversity (MUD) in transmit antenna selection/maximal-ratio combining (TAS/MRC) systems is derived as an exact closed expression in independent and identically distributed (i.i.d.) Nakagami-m channels with an integer fading parameter. For a non-integer fading parameter, the exact outage probability is derived as a single infinite series of incomplete Gamma function. At high signal-to-noise ratios (SNRs), the analytical results deduce that the multiuser TAS/MRC systems can achieve a full diversity order equal to the product of the fading parameter, number of users, number of transmit antennas and number of receive antennas. The advantage of the total diversity gain becomes more pronounced on a severe fading channel. The achieved results provide an analytical framework for the assessment of multiuser TAS/MRC systems. All the derived expressions are verified by Monte Carlo simulations.

Outage Capacity Analysis of TAS/MRC Systems over Arbitrary Nakagami-m Fading Channels

A simple closed-form approximation for the outage capacity of Transmit Antenna Selection/Maximal-Ratio Combining (TAS/MRC) systems over independent and identically distributed (i.i.d) Nakagami-m fading channels is derived while the fading index is a positive integer. When the Nakagami-m fading index is not an integer, the approximate outage capacity is derived as a single infinite series of Gamma function. Computer simulations verify the accuracy of the approximate results.