Multiple Cochannel Interferers Research Articles

Second-Order Statistics for IRS-Assisted Multiuser Vehicular Network With Co-Channel Interference

In this paper, we consider a downlink multi-user vehicular communication network empowered by an intelligent reflecting surface (IRS) with the base station (BS) employing the orthogonal frequency division multiple access (OFDMA) scheme. The performance of the considered system is evaluated in terms of second-order statistics (SOS) in the presence of multiple co-channel interferers with varying powers and speeds. In particular, we develop the analytical expressions of level crossing rate (LCR) and average outage duration (AOD) of the received signal envelope at a desired vehicle by considering a generalized fading model as - distribution. The impact of various system and channel parameters such as number of reflecting elements, amplitude of reflection coefficients, number of interferers, Doppler frequencies of desired and interfering vehicles, and different channel fading environments has been shown on the LCR and AOD performances. Moreover, we derive an expression for asymptotic LCR under high transmit power conditions. It has been shown that the asymptotic LCR is independent of the threshold and transmit power. In addition, we consider a stop and wait automatic repeat request (SW-ARQ) protocol for reliable data packet transmission and derive the expressions for packet error rate (PER) and throughput by utilizing the finite-state Markov channel (FSMC) model. The optimal packet length is also determined which maximizes the throughput under SW-ARQ protocol. The impact of various system parameters is also shown on the PER and throughput performances.

Performance Analysis of Beacon-Assisted Wireless Powered Communications With Spatially Random Sensors

In this work, we present the performance evaluation of a power beacon-assisted wireless-powered communication system in the presence of multiple co-channel interferers. We consider and compare three distinct interference modeling scenarios, namely the totally induced interference is approximated by the Gamma distribution, interferers are distributed according to a Poisson point process and interferers are distributed according to a binomial point process. Analytical expressions for the outage probability and the ergodic capacity of the considered system under each interference scenario are derived. Furthermore, optimization problems are formulated to determine the optimum switching time maximizing the achieved ergodic capacity. Numerical results accompanied with Monte Carlo simulations are presented to corroborate the proposed theoretical analysis.

Investigation of RIS Enabled Mixed RF/VLC Relaying with Interference

The present research work aims at analyzing a variable gain amplify-and-forward (AF) relaying system with reconfigurable intelligent surface (RIS) systems to set-up a mixed communication system with visible light communication (VLC). The RIS and VLC forms of communication will hold utmost importance in the future generations of wireless communication. However, while implementation, various practical challenges are to be dealt with. One such challenge is the impact of interference on the reliability of the communication setup. To evaluate this, it has been assumed that the channel state information (CSI) aided amplify-and-forward (AF) relay node operates in the vicinity of multiple co-channel interferers (CCIs). For the considered system model, closed-form expressions have been derived for outage probability and bit error rate (BER) of the system. The formulation of symbol error rate (SER) has also been presented to generalize the findings. The analysis has been taken forward to showcase the impact of various system parameters such as number of elements in RIS, length and inclination angles of the VLC system along with number and strength of the interferers in system. It has been observed during investigation that the increment in the number of reflecting elements in the RIS has a major contribution in minimizing the signal degradation caused due to the multiple CCIs. Numerical results have been verified using the Monte-Carlo simulations.

Reconfigurable Intelligent Surface for Mixed FSO-RF Systems With Co-Channel Interference

Reconfigurable intelligent surface (RIS) is an emerging technology that can achieve reconfigurable radio propagation environments for beyond 5G/6G wireless systems by smartly tuning the signal reflection via a large number of low-cost passive reflecting elements. In this letter, we investigate the effect of co-channel interference (CCI) on RIS-based dual-hop mixed free-space optical (FSO)-radio frequency (RF) communication systems. The source node, equipped with multiple FSO apertures, transmits subcarrier intensity modulated symbols on the FSO link subjected to Gamma-Gamma (GG) distributed atmospheric turbulence with pointing errors (PEs). It is assumed that the relay-RIS and RIS-destination links follow Rayleigh distribution. The destination node is corrupted by multiple CCI (each following Rayleigh distribution). The performance of the considered system is evaluated by deriving novel closed-form expressions for the outage probability (OP) and bit error rate (BER). It is shown through numerical results that RIS-based dual-hop mixed FSO-RF system provide a significant performance enhancement in comparison to a traditional dual-hop mixed FSO-RF system even in presence of CCI.

Performance analysis of Mixed MUD-RF/Multi-aperture FSO Relay Communication System with Co-channel Interference

This paper discusses the performance of an improved dual-hop mixed radio frequency (RF) / free space optical (FSO) relay communication system in the present of multiple co-channel interferences (CCIs) at the relay node. Multi-user diversity(MUD) technology has been adopted to improve the RF link performance. In order to improve the performance of the FSO link, multi-aperture receiver scheme has been implemented. The multi-user RF link experiences Nakagami-m fading, while the FSO link is subjected to Exponentiated Weibull distributed atmospheric turbulence. Moreover, the CCIs at the relay node are assumed to undergo Nakagami-m fading. For this proposed system, the exact closed-form expression for the outage probability (OP) has been derived. To quickly understand the effects of different parameters on the system performance, the asymptotic expression for the case of high signal-to-noise (SNR) has been further presented. Results show that the diversity order of this proposed system is min (αβM/2,m 1 K), where M represents the number of receiver apertures; K denotes the number of users; α, β and m 1 are the channel parameters. Additionally, the effects of various parameters on system performance have been investigated. Finally, the numerical results have been validated by Monte-Carlo simulations.

Impact of RF I/Q Imbalance on Interference-Limited Mixed RF/FSO TWR Systems With Non-Zero Boresight Error

In this letter, we investigate a generic model assessing the effect of in-phase/quadrature-phase imbalance (IQI) on an asymmetric dual hop radio frequency/free space optical (RF/FSO) two-way relay (TWR) system in the presence of multiple co-channel interferers (CCIs) at the relay. The fading on the RF and FSO links have been modeled using K-distribution and double generalized Gamma (D-GG) turbulence model, respectively. The impact of non-zero boresight pointing error and type of optical demodulation schemes have been considered on the FSO link. To this end, a closed-form probability density function (PDF) has been derived for the FSO link undergoing D-GG irradiance with non-zero boresight pointing error. Furthermore, the exact and high signal-to-noise (SNR) asymptotic expression for outage probability have been presented. To gain insights into the throughput of the system, approximate and asymptotic expressions for the achievable sum rate (ASR) have been derived. The results show dependency of reliability and throughput offered on IQI at the RF front-end and strength of interference for the considered TWR system.

Mixed MUD-RF/FSO Two Way Dcode and Forward Relaying Networks in the Presence of Co-Channel Interference

In this research work, mixed radio frequency (RF)/free-space optical (FSO) decode-and-forward (DF) two-way relaying (TWR) system is investigated in the presence of interference. In order to improve the performance of the RF link, multiuser diversity (MUD) scheme has been implemented. The multiple RF users undergo Nakagami-m distributed fading. The atmospheric turbulence on the FSO link is assumed to follow the double generalized Gamma (D-GG) scintillation model. The model on the FSO link considers two kinds of optical detection schemes, i.e., intensity modulation/direct detection (IM/DD) and coherent demodulation scheme, and also includes the effect of pointing errors. Furthermore, multiple co-channel interferers (CCIs) at the relay node are assumed to undergo Nakagami-m fading. For the considered TWR system, exact closed-loop expressions for the outage probability and bit error rate (BER) have been derived. These exact closed-form expressions have been further simplified for the case of high signal-to-noise (SNR) to derive the asymptotic expressions for the outage probability and BER of the considered system. Finally, the analytical framework developed in the research work has been validated using numerical examples.

Link Selection in Buffer-Aided Cooperative Networks for Green IoT

In this paper, the link selection algorithm in buffer-aided cooperative networks with multiple co-channel interferers for green internet of things (IoT) is investigated. In the considered system, the relay node selects the better link from the first and the second hop with the help of buffers. We evaluate the effects of the system parameters by deriving the analytical analysis as well as the asymptotic results on the exact expressions of the outage probability. The impacts of system parameters, such as the predefined target rate, the priority-outage tradeoff parameter, the buffer length and the number of interferers are evaluated in different setup scenarios. Considerable performance gains can be obtained compared with the classical decode-and-forward relaying networks. Simulation results are provided to verify the theoretical analysis.

Interference-Limited Mixed MUD-RF/FSO Two-Way Cooperative Networks Over Double Generalized Gamma Turbulence Channels

In this letter, the performance of multiuser-radio frequency/free space optics (RF/FSO) two-way relay network in the presence of interference is investigated. The FSO link accounts for pointing errors and both types of detection techniques, i.e., intensity modulation/direct detection as well as coherent demodulation, which is modeled as double generalized gamma (D-GG) turbulence channel. On the other hand, the multiple users on the RF link are assumed to undergo Nakagami-m fading. Multiple co-channel interferers (CCIs) which corrupt the signal at relay node are modeled using Nakagami-m distribution. Specifically, the exact closed-form expressions for the outage probability (OP) of the overall system are derived. Moreover, the closed form expression for the achievable sum-rate (ASR) of the considered system is presented. In order to simplify the results, the asymptotic approximations of the OP and ASR are derived in terms of elementary functions. The results presented in the letter are validated by the Monte Carlo simulations.

Performance analysis of mixed RF/FSO system with CCI

In this study, the performance of the mixed radio-frequency (RF)/free-space optical (FSO) system with co-channel interference (CCI) is investigated. The RF links are modelled as Rayleigh fading, whereas FSO links follow M-distribution with pointing errors. Assume the amplify-and-forward relay is corrupted by multiple CCIs, and both fixed and variable gain relay schemes are considered. Novel expressions for the end-to-end outage probability (OP), symbol error rate (SER) and outage capacity in different cases are presented and analysed. Numerical results demonstrate the existence of OP and SER floors in the presence of CCIs, which implies system performance is dominant by RF links, and interference is the main factor affecting the system performance. Additionally, the fixed gain scheme provides a performance enhancement compared with the variable gain scheme in the authors' system.

Average symbol error rate for integrated satellite-terrestrial cooperative transmission with interference

As an indispensable method of constructing ubiquitous communication network, satellite communication technology has received significant attention in both industrial and academic areas recently. In this paper we investigate the performance of an integrated satellite-terrestrial cooperative network in the presence of co-channel interference, which consists of a satellite source having a single antenna, a terrestrial relay equipped with multiple antennas to assist satellite signal transmission, and a single-antenna user corrupted by multiple co-channel interference. On the assumption that the user receives the signals from direct link and relaying link with decode-and-forward protocol, the output signal-to-interference-plus-noise ratio of the user with the maximal ratio combining scheme is firstly obtained. Then, according to the Meijer-G function, we derive the moment generating function of the destination and the relay, where the satellite links are assumed to experience Shadowing-Rician fading while the terrestrial links undergo Rayleigh fading, and the analytical average symbol error rate expression for the considered system is obtained. Finally, the simulation results demonstrate the effectiveness of the theoretical analysis and reveal theinfluences of antenna number, interference number, and modulation schemes on the system performance. Therefore, our work provides useful guidelines for the engineers in designing the integrated satellite-terrestrial cooperative networks for future satellite mobile communication.

Hop-by-Hop ZF Beamforming for MIMO Full-Duplex Relaying With Co-Channel Interference

In this paper, a comprehensive design and analysis of multiple-input multiple-output (MIMO) full-duplex (FD) relaying systems in a multi-cell environment is investigated, where a multi-antenna amplify-and-forward FD relay station serves multiple half-duplex (HD) multi-antenna users. The pivotal obstacles of loopback self-interference (LI) and multiple co-channel interferers (CCI) at the relay and destination when employing FD relaying in cellular networks are addressed. In contrast to the HD relaying mode, the CCI in the FD relaying mode is predicted to double since the uplink and downlink communications are simultaneously scheduled via the same channel. In this paper, the optimal layout of transmit (receive) precoding (decoding) weight vectors which maximizes the overall signal-to-interference-plus-noise ratio is constructed by a suitable optimization problem, and then a closed-form sub-optimal formula based on null space projection is presented. The proposed hop-by-hop rank-1 zero-forcing (ZF) beamforming vectors are based on added ZF constraints used to suppress the LI and CCI channels at the relay and destination, i.e., the source and relay perform transmit ZF beamforming, while the relay and destination employ receive ZF combining. To this end, unified accurate expressions for the outage probability and ergodic capacity are derived in closed form. In addition, simpler tight lower bound formulas for the outage probability and ergodic capacity are presented. Moreover, the asymptotic approximations for outage probability are considered to gain insights into system behavior in terms of the diversity order and array gain. Numerical and simulation results show the accuracy of the presented exact analytical expressions and the tightness of the lower bound expressions. The case of hop-by-hop maximum-ratio transmission/maximal-ratio combining beamforming is included for comparison purposes. Furthermore, our results show that while multi-antenna terminals improve the system performance, the detrimental effect of CCI on FD relaying is clearly seen. Therefore, our findings unveil that MIMO FD relaying could significantly improve the system performance compared to its conventional MIMO HD relaying counterpart.

Beamforming Design for Full-Duplex SWIPT with Co-Channel Interference in Wireless Sensor Systems.

The simultaneous wireless information and power transfer (SWIPT) technique has been regarded as an appealing approach to prolong the lifetime of wireless sensor networks. However, co-channel interferences with SWIPT in wireless networks have not been investigated from a green communication perspective. In this paper, joint transmit and receive beamforming design for a full-duplex multiple-input multiple-output amplify-and-forward relay system with simultaneous wireless information and power transfer in WSNs is investigated. Multiple co-channel interferers are considered at the relay and destination sensor nodes. To minimize the mean-squared-error of the system, joint source and relay beamforming optimization is proposed while guaranteeing the transmit power constraints and destination’s energy harvesting constraint. An iterative algorithm based on alternating optimization with successive convex approximation which converges to a local optimum is proposed to solve the non-convex problem. Moreover, a low-complexity scheme is derived to reduce the computational complexity. Simulations for MSE versus iterations and MSE versus signal-to-noise ratio (SNR) demonstrate the convergence and good performance of the proposed schemes.

SSC Reception over Kappa-Mu Shadowed Fading Channels in the Presence of Multiple Rayleigh Interferers

Modelling of complex wireless transmission scenario over fading channels in the presence of multiple co-channel (CCI) interferers will be presented in this paper. Propagation environment will be modelled with general kappa-mu shadowed model, which can be reduced to other well-known model as its singularities. Probability density function (PDF) and cumulative distribution function (CDF) of resulting signal-to-interference (SIR) ratio statistics at the reception will be derived in the rapidly converging infinite-series expressions form. Obtained expressions will be further used for evaluation of standard wireless performance criterions, outage probability (OP) and average bit error rate (ABER) and their analysis in the function of transmission parameters. Finally, possible performance improvement will be considered for the case of possible application of switch-and-stay (SSC) diversity reception technique.DOI: http://dx.doi.org/10.5755/j01.eie.24.2.20640

Performance analysis of energy harvesting AF relay systems over Nakagami-[formula omitted] fading channels with co-channel interferences

In this paper, we present performance analysis for an energy harvesting amplify-and-forward relay system with multiple co-channel interferences (CCIs) at the relay and destination, over Nakagami-m fading Channels. Specifically, exact and asymptotic closed-form expressions are derived for outage probability of the considered relay system. In addition, we also obtain an efficient numerical expression for the ergodic throughput by exploiting Gauss–Chebychev quadrature formula. Finally, the optimal time ratio for maximizing the system’s ergodic throughput is studied numerically. The theoretical derivations are validated through Monte Carlo simulations. Through the asymptotic analysis, we show that the system diversity order is determined by the smaller channel fading severity parameters of the dual-hop desired transmission links, regardless of the fading channel parameters of CCIs.

Effects of multiple co-channel interferers on the performance of amplify-and-forward relaying with optimum combining, multiple relays and multiple antennas

Cooperative relaying is a method used mainly to improve cellular networks in terms of diversity gain and coverage extension. However, its performance is gravely affected by the co-channel interference (CCI), especially when a high channel reuse is needed. Optimum combining (OC) is the combining technique that maximizes the signal-to-interference-plus-noise-ratio (SINR) and eliminates the CCI, achieving the best diversity gain. In the present paper, the performance analysis of cooperative amplify-and-forward relaying by using OC is extended for a scenario with multiple co-channel interferers, multiple-antenna relays and multiple antenna-destination. Also, the techniques of multiple relay transmission (MRT) and relay selection with transmit antenna selection (RS-TAS) are evaluated and compared. An approximation of the SINR and the diversity gain are obtained for both transmission techniques. The moment-generating function (MGF) of SINR is derived in order to obtain the average bit-error rate (BER) of the system. Analytical results are validated using Monte-Carlo simulations, which shows that the proposed scenario combats the CCI in a non obvious way and obtains diversity gain in both transmission techniques. Moreover, the MRT technique cancels a greater number of interferers than RS-TAS, while RS-TAS achieves better spectral efficiency and obtains better performance for small number of interferers.

Outage analysis of TAS/MRC in dual hop full-duplex MIMO relay networks with co-channel interferences

In this paper, we investigate the outage performance of transmit antenna selection (TAS) and maximal-ratio combining (MRC) in dual hop full-duplex (FD) amplify-and-forward (AF) relay network over Rayleigh fading channels. In the analysis, Rayleigh faded multiple co-channel interferers (CCIs) are also taken into account at the relay. In the network, source and destination are equipped with multiple antennas, and relay is equipped with one receive and one transmit antennas, respectively and source-destination link is not available. While the TAS is applied at the source without considering residual self-interference (RSI) effect, received signals at the destination are combined based on the MRC technique. For the analysis, we consider three approaches at the relay. In the first, we consider the received signal at the relay is corrupted by faded RSI and noise, in the second one, the RSI is considered as non-fading. In the last one, the noise is neglected. In all cases, the relay suffers from multiple Rayleigh faded CCIs. Outage probability (OP) expression related to all the cases is derived and obtained in single integral forms in case of the faded/non-fading RSI and in closed form in case of the noise neglected approach. Moreover, we also find asymptotic OPs and conduct effective diversity order analysis. The analytical results are verified by the Monte Carlo simulations. Results show that TAS decreases error floor at high signal-to-noise ratio (SNR) region and MRC provides diversity gain at low SNR region. In addition, approaches II and III are good approximations to approach I at low and high SNR regions, respectively.

Optimal Beamforming for Dual-Hop MIMO AF Relay Networks With Cochannel Interferences

In this paper, we investigate a beamforming (BF) scheme for a dual-hop multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay network in the presence of multiple cochannel interferences (CCIs) at both the relay and the destination nodes. In order to maximize the signal-to-interference-plus-noise ratio at the destination node, the optimal BF weights for the relay network in the presence of CCIs are derived. A tight lower bound on the outage probability (OP) is derived in a closed form by assuming that multiple CCIs have equal power at the relay and destination nodes. Through computer simulations, it is shown that the proposed BF scheme can outperform the existing schemes. Furthermore, the impacts of antenna configurations, CCIs, and power allocation on the outage performance of the MIMO AF relay systems have been demonstrated with simulations.

SRT analysis of relay selection in the presence of multiple co‐channel interferers

In this study, a cooperative wireless network is studied based on physical-layer security, where multiple co-channel interferers exist at relays, the destination and eavesdropper. Under the influence of multiple co-channel interferers, the tradeoff between the security and reliability of wireless communications against eavesdropping attacks is analysed in terms of the intercept probability (IP) and the outage probability (OP). The exact closed-form expressions for the IP and OP are derived for the direct transmission (DT) and the relay selection (RS) schemes over Rayleigh fading channels. The theoretical analysis is validated by numerical results. It is shown that the increase of the number of relays and (or) the number of co-channel interferers can efficiently improve the security-reliability tradeoff (SRT). Moreover, the RS strategy can achieve a higher SRT performance compared with the DT strategy.

Performance Analysis of Dual-Hop MIMO AF Relaying Network With Multiple Interferences

In this paper, we investigate the performance of a dual-hop multiple-input–multiple-output (MIMO) amplify-and-forward (AF) relay network, where the source, relay, and destination are all equipped with multiple antennas. By using maximum ratio transmission (MRT) at the transmitter and maximum ratio combining (MRC) at the receiver, we first obtain the output signal-to-interference-plus-noise ratio (SINR) of the dual-hop AF relay system, considering multiple cochannel interferences (CCIs), as well as noise at the relay. Then, we derive an exact closed-form expression for the outage probability (OP), and the asymptotic result of OP at high SNR, which can be used to calculate the array gain and diversity order. Finally, computer simulations are conducted to validate the performance analysis. Our new analytical expressions not only provide a fast and efficient method to evaluate the system performance but enable us to gain valuable insights into the effects of key parameters on the MIMO AF relaying network performance that benefits from implementing multiple antennas at each of the three nodes as well.