Presence Of Co-channel Interference Research Articles

Performance Analysis of Uplink Non-Orthogonal Multiple Access in the Presence of Co-Channel Interference

In sixth generation (6 G) networks, a massive number of users and devices must be connected, necessitating flexible resource allocation. In this context, non-orthogonal multiple access (NOMA) has been proposed as a promising technique to enable mass connectivity. This study presents a performance analysis for the impact of co-channel interference (CCI) on uplink NOMA networks. More specifically, it is considered that CCI is introduced by randomly deployed terminals within the cellular coverage area, affecting the reception of the base station (BS) in the uplink. In this network, fading conditions follow the Rayleigh distribution and two cases are examined for the CCI statistics, i.e. independent and identically distributed, and independent but not identically distributed. A thorough performance analysis is conducted to derive the outage probability, ergodic rate, error probability, achievable sum-rate, and throughput expressions, highlighting the adverse effects of CCI on the uplink NOMA network. Furthermore, an asymptotic analysis is provided, shedding light on the derived analytical results. Towards improving the performance of uplink NOMA, power allocation is formulated as an optimization problem, and solved to derive the power allocation coefficient of the users. Our analytical and asymptotic derivations are verified through Monte-Carlo-based computer simulations and it is revealed that the proposed power allocation method achieves significant performance gains, facilitating uplink NOMA.

Wireless Communication System Performance in M2M Nakagami-m Fading Channel

In this paper, we investigate a wireless mobile communication system with a cooperative network operating over a mobile-to-mobile (M2M) fading channel in the presence of co-channel interference. Since there is no direct line of sight between the source (S) and the destination (D) due to various obstacles, the signal transmission takes place by using a relay (R). We modeled and represented the desired signal and co-channel interference by using the Nakagami-m fading distribution from the source (S) to the relay (R), as well as from the relay (R) to the destination (D). As the popularity of M2M communication has increased in 5G cellular networks, the performance analysis of the proposed system is of great importance. We derived closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-interference ratio (SIR) at the input of the destination station. Based on the cumulative distribution function (CDF), we also evaluated the outage probability (Pout) of the proposed communication system. In addition, we derived a closed-form approximate expression for the level crossing rate (LCR) by using the Laplace approximation formula for the three-fold integral. Validity of the derived theoretical results we approved by Monte Carlo simulations.

On Outage Analysis in Overlay CCRN with RF Energy Harvesting and Co-channel Interference

This paper studies the effect of co-channel interference (CCI) on energy harvesting (EH) from radio frequency (RF) signal and the performance of reliable communication. An overlay mode of cooperative cognitive radio network (CCRN) model is considered that may support one-way communication between primary users (PUs) and two-way communications between secondary users (SUs). Closed form PU and SU outage expressions are derived in presence of CCI at two SU nodes and multiple antennas at PU transmitter. The absolute impact of CCI on the performance of the proposed system is analysed with respect to various parameters like, transmission power, interference-to-noise-ratio (INR), power splitting factor, number of CCI sources and number of antennas. About 20% and 15% improvements are achieved for PU and SU outage using two antennas compared to single antenna system model.

On the second order statistics of the ratio of two Fisher-Snedecor random variables and its application to interference limited communications

The paper investigates the higher order statistics of the ratio of two Fisher-Snedecor F (FS-F) random variables (RVs) and its application to wireless communications in the presence of co-channel interference. Namely, the work provides novel expressions for probability density function (PDF), cumulative density function (CDF), level crossing rate (LCR) and average fade duration (AFD) of the ratio of two FS-F RVs. Numerical examples of the analytically derived statistical measures in terms of FS-F multi-path and shadowing parameters are shown and examined. Moreover, the impact of the number of interferes on the considered measures are further presented and examined.

Rate-Splitting Multiple Access for UAV-Based RIS-Enabled Interference-Limited Vehicular Communication System

Rate-splitting multiple access (RSMA) has emerged as a novel generalized multiple access technology which can control the interference in multi-user communication systems. Reconfigurable intelligent surface (RIS) has also been proven to improve the spectral efficiency in the next-generation (beyond 5 G (B5G) and 6 G) wireless communication networks. Thus, in this paper, we explore the RSMA scheme for RIS-enabled unmanned aerial vehicle (UAV) based multi-user vehicular communication network in the presence of co-channel interference. The communication between the UAV and the desired vehicle takes place through an RIS along with the direct link and is interfered by multiple interfering vehicles operating in the same spectrum. After deriving the approximate cumulative distribution function (CDF) of common and private stream signal-to-interference-plus-noise ratios (SINRs) at the desired vehicle in the interference limited scenario, we obtain an expression for the average outage probability (AOP) over the complete flying duration of the UAV. Furthermore, the optimum RSMA power allocation coefficients in each time slot of UAV flight duration are obtained by minimizing the Sum-AOP over all the desired vehicles. The performance of the proposed RSMA based RIS-aided vehicular communication network is compared with (a) RSMA based network without RIS and (b) non-orthogonal multiple access (NOMA) based RIS-aided counterpart. The numerical results reveal the superiority of RSMA over NOMA and the significance of deploying RIS in considered vehicular communication network. The analytical results are corroborated with Monte Carlo simulations.

Joint CCI Mitigation and Power Control for MC-DS-CDMA in LEO Satellite Networks

We investigate a novel downlink multicarrier direct-sequence code division multiple access (MC-DS-CDMA) resource allocation scheme in the context of low earth orbit (LEO) satellite-ground integrated networks (SGINs). In contrast to the existing MC-DS-CDMA works which mainly focus on delay-tolerant services in terrestrial networks, we consider the heterogeneous delay traffic and take the unique characteristics of LEO satellite systems into account. Specifically, we exploit the channel information, the delay requirement, the buffer state, and the visible time of users to construct a utility function and formulate the resource allocation optimization problem in presence of co-channel interferences (CCI) in LEO satellite-ground heterogeneous systems. We transform the original nonconvex optimization problem into two convex ones and use the Lagrange dual decomposition method to derive the solution. We also design an efficient algorithm dynamically scheduling subcarriers, codes, and transmission power of MC-DS-CDMA. The simulation results confirm the superiority of our work in terms of lower average delay and higher overall throughput.

Performance Evaluation of Reconfigurable Intelligent Surface against Distributed Antenna System at the Cell Edge

In small spaces in which typical cell towers cannot be constructed, distributed antenna systems (DASs) are the preferable approach for increasing network coverage, as they are a superior solution for congested, high-volume areas. However, due to their high cost and complexity in backhaul routing, reconfigurable intelligent surfaces (RISs) are a promising solution to overcome the major drawbacks of DAS systems while improving network coverage. Thus, this work investigated a correlation of execution in an RIS-aided system cell framework and DAS-aided system cell framework where a simple and precise structure for the performance measurement of area spectral efficiency (ASE) and energy efficiency (EE) under realistic channel presumptions was introduced. The analysis started with the downlink ergodic capacity with regards to the RIS framework and DAS framework under a generalized Nakagami-m fading channel with the presence of path-loss attenuation and interference from co-channel base stations (BSs), and was simplified further by utilizing a moment-generating function (MGF)-based approach. From the computed expression, the effects of traffic activity, EE and ASE were derived and analyzed for both systems in the presence of co-channel interference. The results were then verified by comparing them with Monte Carlo simulations, and the findings show that the two outcomes generally match. Based on these, it is demonstrated that the ASE performance of the RIS-assisted system in various traffic activity conditions outperforms the DAS-aided system; however, in high signal-to-noise (SNR) regions with full traffic activity, the ASEs are highest for both systems; by only 0.005 bits/s/Hz/km2.

Multi-UAV deployment for NOMA-enabled wireless networks based on IMOGWO algorithm

In this article, we address the multi-unmanned aerial vehicle (UAV) deployment problem in the presence of co-channel interference (CCI) for non-orthogonal multiple access (NOMA) enabled wireless networks. Considering UAV as aerial base station for downlink communication, we aim to maximize the energy efficiency and coverage rate by jointly optimizing the power allocation of users and the locations of UAVs. Initially, the ground users are divided into clusters by K-means clustering, where each UAV serves a cluster. Then, the clusters are further divided into multiple sub-clusters, each having a pair of near and far users. Orthogonal multiple access (OMA) is applied among sub-clusters, and NOMA is applied to intra sub-cluster users. Lastly, to tackle the formulated multi-objective non-convex problem, we propose an improved multi-objective grey wolf optimizer (IMOGWO) to maintain an optimal trade-off between energy efficiency and coverage rate. Simulation results demonstrate that the proposed algorithm outperforms the benchmarks.

Effect of Node Mobility on MU-MIMO Transmissions in Mobile Ad Hoc Networks

In this paper, we investigate the expected outage probability and expected throughput of a multi-user multiple-input multiple-output (MU-MIMO) transmission in mobile ad hoc networks (MANET) in the presence of co-channel interference and unpredictable inter-beam interference. In order to achieve multi-user diversity gain, the receiving nodes are required to report measured channel information to the transmitting node. During the time gap between channel measurement and data transmission, the channel may change with the location of moving nodes. The unpredictable behavior may cause a mismatch between the weight of beams and the instantaneous channel and the inter-beam interference in the data transmission phase. In order to obtain the closed form expected outage probability, we categorize the behavior of nodes according to whether the inter-beam interference exists or not and the number of received interference beams. The probability of each category and the closed form outage probability of an instantaneous MU-MIMO transmission of each category are derived. Additionally, the expected throughput of an MU-MIMO transmission which changes with the number of receiving nodes is obtained, and the optimal value of receiving nodes to maximize the expected throughput is discussed. Numeric results show the unpredictable inter-beam interference degrades the outage probability performance. Reducing the duration of the time gap could improve the expected outage probability and expected throughput.

Signal detection with co-channel interference using deep learning

Signal detection using deep learning is a challenging and promising research topic. Several learning-based signal detectors have been proposed to produce significant results. However, most of them have ignored interference in their designs. In this paper, we evaluate the performance of learning-based signal detectors in the presence of co-channel interference under different channel conditions. Specifically, fully connected deep neural network (FCDNN) and convolutional neural network (CNN) are examined as the data-driven signal detector for blind signal detection without knowledge of the channel state information. Several important system parameters, including signal-to-interference ratio, number of interferences and type of interference, are considered. Numerical results show that FCDNN and CNN-based detectors have better performance and robustness to different SIRs conditions than traditional detectors in the presence of interference and FCDNN performs better than CNN when SIR is small and the order of interference modulation is high.

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.

Investigation on energy harvesting enabled device-to-device networks in presence of co-channel interference

Energy harvesting from ambient radio-frequency (RF) sources has been a novel approach for extending the lifetime of wireless networks. In this paper, a cooperative device-to-device (D2D) system with the aid of energy-constrained relay is considered. The relays are assumed to be able to harvest energy from information signal and co-channel interference (CCI) signals broadcasted by nearby traditional cellular users and forward the source’s signal to its desired destination (D2D user) utilizing amplify-andforward (AF) relaying protocol. Time switching protocol (TSR) and power splitting protocol (PSR) are proposed to assist energy harvesting and information processing at the relay. The proposed approaches are applied in a model with three nodes including the source (D2D user), the relay and the destination (D2D user), the system throughput is investigated in terms of the ergodic capacity and the outage capacity, where the analytical results are obtained approximately. Our numerical results verify the our derivations, and also points out the impact of CCI on system performance. Finally, this investigation provide fundamental design guidelines for selecting hardware of energy harvesting circuits that satisfies the requirements of a practical cooperative D2D system.

Three-dimensional wireless ad hoc networks with random nodes distribution

ABSTRACT This paper proposes a model for three-dimensional (3-D) wireless ad hoc networks with randomly distributed nodes and unknown node locations. In this model, the nodes are assumed to be randomly distributed in a cubic torus. The distances between neighbouring nodes (hop lengths) and the distance between thesource and destination nodes (route length) are assumed to be random. In the first part of this paper, exact analytical expressions are derived for the cumulative distribution function (CDF) and the probability density function (PDF) of the hop and route lengths.Then, these distributions are used to find the average hop length,route length and number of hops analytically and numerically. The performance of the system is studied in terms of the average route bit error rate (BER) and the optimal transmit power needed to achieve a given threshold BER to maintain network connectivity. Moreover, the performance of decode-and-forward (DF) relaying scheme over Rayleigh fading channels in the presence of cochannelinterference (CCI) is studied. It is assumed that CCI is modelled as the sum of independent-not-identically distributed Rayleigh variates.

Multi-UAV Deployment for Throughput Maximization in the Presence of Co-Channel Interference

Over the past few years, there has been a growing interest in using unmanned aerial vehicles (UAVs) for high-rate wireless communication systems due to their highly flexible deployment and maneuverability. The aim of this article is to propose a 3-D multi-UAV deployment approach to provide Quality-of-Service (QoS) requirements for different types of user distributions in the presence of co-channel interference by maximizing the minimum achievable system throughput for all of the ground users. The proposed approach is divided into two separate algorithms. In the first algorithm, by using the mean-shift technique and prior knowledge of users’ positions provided by the global positioning system (GPS), it has been shown that one can simultaneously find $xy$ coordinates of UAVs, which are associated with the maximum of users’ density and schedule users to UAVs. Once the $xy$ -Cartesian coordinates of UAVs are determined, UAVs’ altitudes and transmit powers are separately optimized. Since these problems are nonconvex optimizations, the successive convex optimization technique has been applied to approximate their nonconvex constraints. In the second algorithm, the block coordinate descent technique is leveraged to jointly optimize UAVs altitudes and transmit powers by tightening the bounds obtained for approximations. It is then proven that the suggested algorithm is guaranteed to converge. The computational complexity of the proposed placement approach is derived. Numerical experiments are carried out to evaluate the performance of our technique and show its superiority to conventional benchmarks.

Direct Tracking of Co-Channel Moving Sources With Different Cyclic Frequencies

Mobile source tracking is an important topic in the field of radio monitoring. A direct position determination method based on particle filtering is proposed in this letter for tracking multiple co-channel mobile transmitters. The co-channel signals, which have different symbol rates, overlap in both the time and frequency domains but can be distinguished in the cyclic frequency domain. We determine the positions of mobile targets directly from different cyclic cross-spectrum slices without time difference of arrival (TDOA) measurements. The particle filtering technique is employed to improve the accuracy in estimating motion states. Simulation results are given to demonstrate that the proposed algorithm outperforms other mobile tracking algorithms in the presence of co-channel interference.

A Direct Localization Method in the Presence of Cochannel Interference and Multipath Fading

Cochannel signals separation is an important topic in the field of radio monitoring. A direct geolocation method based on random spatial spectrum is proposed in this paper for multiple cochannel sources in the multipath wireless environment. A random spatial spectrum function is constructed based on a set of position particles. The cochannel signals are transformed to the spatial spectrum, which can significantly suppress the multipath components. A spatial sparse method based on clustering is then proposed to separate the sources in the spatial domain. Simulation results are given to demonstrate that the proposed algorithm outperforms other localization algorithms and approaches the Cramér Rao lower bound (CRLB) of the considered problem.

On performance of multihop energy harvesting CRN in the presence of co-channel interferers

ABSTRACT In this paper, the performance of a multihop cognitive radio network is investigated in the presence of co-channel interference (CCI) which affects the primary receiver and secondary receiver nodes. A deterministic expression for the maximum allowable transmit power of the secondary nodes is derived based on the tolerable outage probability of the primary network. The system considers radio frequency energy harvesting at the secondary source and intermediate secondary nodes from the primary user transmitter as well as from the various CCIs present around the nodes. We analyse secondary outage probability and derive a closed-form analytical expression for secondary outage probability. We present the impact of PU-TX transmit power and efficiency of harvester circuit on the secondary outage probability. The optimum number of intermediate relays is indicated for several number of CCIs which minimises outage probability of secondary network.

Effect of Co-channel Interference on Two-Way Untrustworthy Relay Selection

This study investigates the impact of co-channel interference on two-way untrustworthy relay selection over Rayleigh fading environment. The investigation considers that two source terminals make information exchange over J number of full-duplex based amplify-and-forward bi-directional untrustworthy relay in the presence of co-channel interference. In addition, limited number of friendly jammers generate artificial interference/noise signals to mitigate information leakage. So as to minimize the system overhead and also enhancing secrecy performance, the relay selection is made by means of max–min criteria, which is based on maximizing the minimum secrecy rate over the relay terminals. The system model fundamental performance limits are measured by means of secrecy outage probability, secrecy achievable sum rate, intercept probability, and secrecy throughput analysis metrics. According to Monte-Carlo based simulations and numerical results, the max–min based selection strategy achieves cooperative diversity order, which is equal to total number of possible paths, in high signal-to-noise ratio regimes. Results also reveal that the co-channel interference dominates the process of the information exchange and degrades the achievable cooperative diversity order from J to 0 and leads system coding gain losses on free-interference cases in high signal-to-noise ratio regimes.

Interference mitigation and capacity enhancement of cognitive radio networks using modified greedy algorithm/channel assignment and power allocation techniques

Cognitive radio (CR) concept is turning out as a prominent approach used in the wireless communication network for increasing spectrum efficiency by opportunistically and mutually sharing the spectrum of contemporary networks. CR can bear high traffic loads during emergencies and major disasters by overcoming the limitations like lack of network capacity. The fundamental issues pertaining the implementation of CR network (CRN) are the presence of co-channel interference and adjacent channel interference among CR users; and most importantly interference to primary users. Effective interference mitigation and management in CRN will make it more robust in easing the additional stress because of very high traffic loads during an intense emergency and disaster scenarios. In this study, an approach has been taken to minimise interference among secondary nodes by employing interference index as interference minimisation key which in turn maximises the system capacity. To validate the results, the authors thoroughly used an existing distributed greedy algorithm, which, on the introduction of interference index, furnished a gain of 60% in the CR network capacity. Further, a trade-off analysis between the interference index and channel leakage ratio is presented with an interference bound of 10 dBm, which may form the basis of interference management in CRN.

A Quantitative Analysis of Spectrum Efficiency of Various Diversity Combining Schemes in the Presence of Co-channel Interference

A Quantitative Analysis of Spectrum Efficiency of Various Diversity Combining Schemes in the Presence of Co-channel Interference