Presence Of Multiple Co-channel 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.

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.

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.

The Performance of Wireless Powered MIMO Relaying With Energy Beamforming

This paper analyzes the performance of energy-constrained dual-hop amplify-and-forward relaying systems with multi-antenna nodes in the presence of multiple co-channel interferers at the destination. To maximize the overall signal-to-interference-plus-noise ratio, as well as the harvested energy so as to mitigate the severe effects of fading and enable long-distance wireless power transfer, hop-by-hop information and energy beamforming is proposed where the transmitted signal is steered along the strongest eigenmode of each hop. The wirelessly powered relay scavenges energy from the source information radio frequency signal through energy beamforming, where both the time-switching receiver and power-splitting receiver are considered, and then uses the harvested energy to forward the source message to the destination. To this end, tight lower and upper bound expressions for the outage probability and ergodic capacity are presented in closed form. These are employed to investigate the throughput of the delay-constrained and delay-tolerant transmission modes. In addition, the asymptotic high signal-to-noise ratio outage probability and ergodic capacity approximations are derived, where the achievable diversity order is also presented. Numerical results sustained by Monte Carlo simulations show the tightness of the proposed analytical expressions. The impact of various parameters, such as energy harvesting time, power-splitting ratio, source transmit power, and the number of antennas on the system throughput, is also considered.

Outage Equivalence of Opportunistic Relaying and Selection Cooperation in Presence of Co-Channel Interference

In this paper, we investigate two different relay selection schemes, opportunistic relaying (OR) and selection cooperation (SC), for decode-and-forward (DF)-based relay networks consisting of a source, multiple relays, and a destination in the presence of multiple co-channel interferers, where each terminal has a single antenna and operates in a half-duplex mode. For the network, we first extend the conventional OR and SC to relay networks with the direct-path and multiple co-channel interferers, and obtain the exact and closed-form outage probability of the OR. Then, we show that the SC is equivalent to the OR in terms of outage performance for relay networks with the direct-path and multiple co-channel interferers. Finally, we show that the SC and OR are outage-optimal under the aggregate power consumption constraint at the relays for relay networks with the direct-path and multiple co-channel interferers.

Performance analysis of two‐way decode‐and‐forward relaying in the presence of co‐channel interferences

This study investigates the performance of two-way decode-and-forward (DF) relaying networks, considering transmissions over independent but not necessarily identically distributed (i.n.i.d.) Rayleigh fading channels, in the presence of multiple co-channel interferers at both the relay and end-source nodes. Both asymmetrical and symmetrical cases, of whether the channels from source terminals to the relay are identically distributed or not, are considered. Specifically, closed-form expressions for the cumulative distribution function of the equivalent signal-to-interference-plus-noise ratio (SINR) in different cases are derived, based on which the exact symbol error probability (SEP) and the systems’ achievable rate are derived and analysed. Based on the analytic results, the authors study the impacts of system parameters, such as interference power and number of interferers on the performance of the system. Furthermore, the system behavior at high signal-to-noise ratio (SNR) values is studied via deriving the asymptotic SEP. The results of this study are attested through Monte Carlo simulations.

Performance Analysis of TAS/MRC in MIMO Relay Systems With Outdated CSI and Co-Channel Interference

In this paper, we investigate the impact of outdated channel state information (CSI) and multiple co-channel interferers (CCI) on the performance of transmit antenna selection/receiver maximal-ratio combining (TAS/MRC) in a dual-hop amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay network. The tight lower bound and asymptotic expressions for the outage probability are derived. The diversity order of the system with/without outdated CSI in the presence of multiple CCI is further discussed. Numerical and simulation results are presented to validate our analysis and to demonstrate the effect of outdated CSI and multiple CCI on the system performance.

Outage Performance of Relaying with Directional Antennas in the Presence of Co-Channel Interferences at Relays

Relaying with directional antennas helps enhance the link reliability and extend the communication range for millimeter wave 60GHz communication system, particularly in the presence of multiple co-channel interferences (CCIs). In this letter, the outage performance of decode-and-forward (DnF) and amplify-and-forward (AnF) relaying schemes with directional antennas are analyzed and compared. Our derived exact and closed-form expressions using Moschopoulos's gamma series in the presence of multiple CCIs with dissimilar Nakagami fading channels at relays offer more accurate analytic result with practically computational efficiency. Numerical results show that relaying with directional antennas, in the forms of uniformly spaced linear antenna arrays, helps improve the system performance significantly in the presence of CCIs.

Outage Performance of Two Hop AF Relaying Systems with Co-Channel Interferers over Nakagami-m Fading

This letter investigates the outage performance of dual-hop amplify-and-forward (AF) cooperative networks in the presence of multiple co-channel interferers at both the relay and destination nodes and subject to non-identically distributed Nakagami-m fading. A simple, easy-to-compute, highly accurate closed-form approximate expression for the end-to-end outage probability is derived. Such expression is written in terms of finite sums of the product of Meijer's G-functions, and is evaluated instantaneously regardless of the number of interferers, drastically contrasting with the intricacy and computational inefficiency inherent to the exact formulation. The tightness of our proposed methodology is attested through Monte Carlo simulation results.

Outage Performance and Average Symbol Error Rate of M-QAM for Maximum Ratio Combining with Multiple Interferers

In this paper, we investigate the performance of maximum ratio combining (MRC) in the presence of multiple cochannel interferences over a flat Rayleigh fading channel. Closed-form expressions of signal-to-interference-plus-noise ratio (SINR), outage probability, and average symbol error rate (SER) of quadrature amplitude modulation (QAM) with M-ary signaling are obtained for unequal-power interference-to-noise ratio (INR). We also provide an upper-bound for the average SER using moment generating function (MGF) of the SINR. Moreover, we quantify the array gain loss between pure MRC (MRC system in the absence of CCI) and MRC system in the presence of CCI. Finally, we verify our analytical results by numerical simulations.

Effects of Spatial Correlation on MIMO Adaptive Antenna System With Optimum Combining

In this paper, we investigate the effects of the spatial fading correlation on the performance of a multiple-input multiple-output (MIMO) adaptive antenna system with optimum combining (OC) in the presence of multiple cochannel interferers over a correlated Rayleigh fading channel. Based on the Khatri's distribution functions of quadratic forms in complex Gaussian random matrices, we develop a unified determinant representation of those joint eigenvalue distributions. Taking into account the spatial correlation among the antenna elements at the transmitter or receiver, we derive the closed-form formulas for the probability density function and outage probability of the maximum output signal-to-interference ratio (SIR) in an interference-limited MIMO-OC system. Furthermore, the average output SIR and error probability are also investigated. From numerical examples, we show that a new theoretical approach gives a simple and accurate way to assess the performance of the MIMO-OC system over arbitrarily correlated fading channels

Performance Comparison of Different Selection Combining Algorithms in Presence of Co-Channel Interference

In this paper, we present a unified approach for the computation of the outage probability, the level crossing rate (LCR), and the average outage duration (AOD) of selection combining (SC) in the presence of multiple cochannel interferences and under both minimum signal-to-interference ratio (SIR) and desired signal power constraints. We consider three selection algorithms, namely: 1) the best signal power algorithm; 2) the best SIR algorithm; and 3) the best total power (desired plus interference) algorithm. As a specific application example, we analyze the three algorithms for a low-complexity dual-branch SC receiver subject to multiple interferers over Rayleigh fading channels. When applicable, the new results are compared to those previously reported in the literature dealing with the outage probability, AOD, and LCR of 1) interference-limited systems and 2) power-limited systems. Numerical examples show that the minimum desired signal power constraint induces a floor to the outage probability, AOD, and LCR performance measures. They also show that the best SIR algorithm provides the best outage probability and AOD performance for low average SIR. On the other hand, the best signal power algorithm and the best S+I algorithm outperform the best SIR algorithm for high average SIR. It is also shown that the best SIR algorithm tends to have more outage level crossings.

Bit-Error Probability for Optimum Combining of Binary Signals in the Presence of Interference and Noise

We derive an exact bit-error probability (BEP) expression for coherent detection of binary signals with optimum combining in wireless systems in the presence of multiple cochannel interferers and thermal noise. A flat Rayleigh fading environment with space diversity, uncorrelated equal-power interferers, and additive white Gaussian noise is considered. The approach is to use the chain rule of conditional expectation together with the joint probability density function (pdf) of the eigenvalues of the interference correlation matrix. This joint pdf is related to the Vandermonde determinant. Let N/sub A/ denote the number of antennas and N/sub I/ the number of interferers. We consider both the cases of an overloaded system, in which N/sub I//spl ges/N/sub A/, and an underloaded system, in which N/sub I/<N/sub A/. Using averaging techniques that make use of the properties of the Vandermonde determinant, we obtain in each of the two cases a closed-form BEP expression as a finite sum, and the only special function that this expression contains is the Gaussian Q-function. This makes it a powerful tool for analysis and computation.

Bounds and approximations for optimum combining of signals in the presence of multiple cochannel interferers and thermal noise

We derive an upper bound and investigate some approximations on the symbol error probability (SEP) for coherent detection of M-ary phase-shift keying, using an array of antennas with optimum combining in wireless systems in the presence of multiple uncorrelated equal-power cochannel interferers and thermal noise in a Rayleigh fading environment. Our results are general and valid for an arbitrary number of antenna elements as well as an arbitrary number of interferers. In particular, the exact SEP is derived for an arbitrary number of antennas and interferers; the computational complexity of the exact solution depends on the minimum number of antennas and interferers. Moreover, closed-form approximations are provided for the cases of dual optimum combining with an arbitrary number of interferers, and of two interferers with an arbitrary number of antenna elements. We show that our bounds and approximations are close to Monte Carlo simulation results for all cases considered in this paper.

Performance of generalized selection combining for mobile radio communications with mixed cochannel interferers

The performance of generalized selection combining (GSC) space diversity for mobile radio systems in the presence of multiple cochannel interferers is studied. Two cochannel interference models are considered: (1) L cochannel interferers consisting of L-N Nakagami-m (1960) interferers and N Rayleigh interferers and (2) L cochannel interferers in which each interferer follows Nakagami-m distribution for a fraction of time and Rayleigh distribution for the remaining of time. The fading parameters of the Nakagami-m interferers are limited to integer values only. The desired signal is assumed to be Rayleigh faded. Also, all the desired signals and the cochannel interferers received on each branch are independent of each other. Closed-form expressions are derived for the probability density functions (PDFs) of the instantaneous signal-to-interference power ratio (SIR) at the output of the GSC for the two cochannel interference models. Using these SIR PDFs, closed-form expression for evaluating the outage probability and the average bit error probability (BEP) are subsequently derived. A differential phase-shift keying scheme is considered in the derivation. Numerical results showing the influences of various system parameters on the outage probability and the average BEP are then presented.

Detection in the presence of spherically symmetric random vectors

A random n -vector X=(X_{1}, \cdots , X_{n}) is said to be spherically symmetric (SS) if its joint characteristic function (CF) can be expressed as a function of the quadratic form u \rho u \prime , where u = (u_{1}, \cdots , u_{n}) and \rho is an n \times n positive definite matrix. The investigation in this paper is concerned with the properties of such vectors and some detection problems involving them. We first prove a theorem characterizing the form of SS random vectors X and use it to find the form of the probability density functions (pdf's) of X and of X + N , where N \sim {\cal N (0, \sigma^{2}I) is an independent Gaussian vector and I is the identity matrix. Applying these results we look at the problem of detecting a known signal vector in the presence of X + N when \rho =I . For the k -ary detection problem we present two conditions under which the minimum distance receiver is optimum. Lastly, we discuss an application of our findings to the problem of coherent detection of binary phase-shift keyed (PSK) signals in the presence of multiple co-channel interferences and white Gaussian noise.