Residual Hardware Impairments Research Articles

Cooperative NOMA in cognitive radio networks: A study on imperfect CSI, SIC and hardware impairments over Nakagami-m fading channel

This paper proposes a cooperative uplink–downlink non orthogonal multiple access (NOMA) in an overlay cognitive radio network (CR). We examine the impact of imperfect channel state information (impCSI), imperfect successive interference cancellation (impSIC) and residual hardware impairments (RHI) on the cooperative cognitive radio network over Nakagami-m fading channels. We derive the exact outage probabilities of primary user (PU) and multicast secondary users (SUs) under perfect/imperfect conditions for fixed and adaptive power allocations. We show that the use of multiple relays enhances the diversity order, but with fixed power allocation in perfect/imperfect case and adaptive power allocation in imperfect case both suffer from an error floor, which reduces the diversity order to zero. On the other hand, the adaptive power allocation for the perfect case achieves full diversity gain. We validate the analytical results with Monte Carlo simulations and demonstrate the diversity gains of the considered schemes.

On the physical layer security performance of full‐duplex cooperative NOMA system with multiple eavesdroppers, imperfect SIC and hardware imperfections

AbstractIn this letter, we propose a control jammer‐assisted framework for improving the physical layer security (PLS) of full‐duplex (FD) ‐ cooperative non‐orthogonal multiple access (FD‐CNOMA) network. We derive analytical expressions for the secrecy outage probabilities (SOPs) of the users for the jammer‐assisted and the no‐jammer scenarios, considering multiple non‐colluding eavesdroppers, residual hardware impairments and imperfect successive interference cancellation conditions. It is demonstrated that the proposed jammer‐assisted framework provides significant reduction of the SOPs experienced by the downlink users in FD‐CNOMA network.

Securing NOMA 6G Communications Leveraging Intelligent Omni-Surfaces Under Residual Hardware Impairments

Securing NOMA 6G Communications Leveraging Intelligent Omni-Surfaces Under Residual Hardware Impairments

Impact of Residual Hardware Impairments on Joint Transmission-CoMP-Cooperative NOMA Networks

Impact of Residual Hardware Impairments on Joint Transmission-CoMP-Cooperative NOMA Networks

Sensing-Communication Coexistence vs. Integration

The design options of sensing-communication coexistence (SCC) vs. integrated sensing and communications (ISAC) relying on non-orthogonal downlink transmission (NO-DLT) and transmit antenna selection are investigated. To be practical, both realistic residual hardware impairments (RHI) and imperfect successive interference cancellation are considered. The performance of the SCC and ISAC NO-DLT frameworks is characterized by deriving both the exact and the asymptotic outage probabilities (OPs) as well as the probability of successful target detection (PoD). Our numerical results demonstrate the accuracy of the theoretical analysis and confirm that: 1) The ISAC NO-DLT framework is superior to the SCC NO-DLT framework both in terms of its OP and PoD; 2) The realistic RHI degrades the S&C performance of both the SCC and ISAC NO-DLT frameworks.

Performance Analysis of Ambient Backscatter NOMA Systems

This paper analyzed the performance of an ambient-backscatter-(AmBC)-assisted non-orthogonal multiple access (NOMA) system, where a backscatter device (BD) broadcasts its signal to numerous users. More specifically, the realistic assumptions of imperfect successive interference cancellation (ipSIC) and residual hardware impairments (RHIs) for AmBC–NOMA systems were taken into consideration. We further derived the closed-form and asymptotic expressions of outage probability for the BD and the d-th user. Based on the asymptotic expressions, the diversity orders of the BD and the d-th user were obtained in the high SNR regime. Furthermore, throughput and energy efficiency are further discussed for AmBC-assisted orthogonal multiple access (OMA) systems in the delay-limited transmission model. The numerical results revealed that: (i) AmBC–NOMA systems have the ability to achieve better outage behavior than AmBC–OMA; (ii) due to the existence of the backscatter link, the error floors of outage probability for the BD and the d-th user appear at a high signal-to-noise ratio; (iii) AmBC–NOMA systems are able to achieve higher energy efficiency and throughput than AmBC–OMA systems.

Performance Analysis and Optimization of IRS-Aided Covert Communication With Hardware Impairments

Residual hardware impairments widely exist in transceivers and intelligent reflecting surface (IRS) in practical systems, which lead to serious signal distortion, causing performance loss and covert transmission challenging. In this paper, we study the robust transmission design for an IRS-aided covert communication system in the presence of transceiver and IRS hardware impairments. To maximize the signal-to-noise ratio at the legitimate receiver and satisfy the covertness requirement, the transmit power at the source and the reflection coefficients at the IRS are jointly optimized. Since the optimization variables are coupled, an alternating optimization algorithm is proposed to solve the optimization problem. Specifically, in each iteration, the analytical expression of the optimal transmit power is obtained, and the penalty successive convex approximation algorithm is adopted to obtain the optimal reflection coefficients. Numerical results show the performance loss caused by hardware impairments. Besides, by comparing the values of Kullback-Leibler divergence, results also illustrate that the proposed transmission scheme is more robust to the hardware impairments, as the nonrobust designed parameters can not satisfy the covert constraint.

System Outage Performance of SWIPT Enabled Full-Duplex Two-Way Relaying With Residual Hardware Impairments and Self-Interference

This article investigates the joint impact of residual hardware impairments (RHIs) and residual self-interference (RSI) at all transceivers on the system outage performance for a simultaneous wireless information and power transfer (SWIPT) enabled full-duplex two-way decode-and-forward (DF) relay network. Considering a time switching scheme at the relay node, we derive the system outage probability in a closed-form, and further identify the overall system ceiling (OSC) effect caused by only RHIs. More specifically, when the data rate exceeds the OSC threshold determined by the RHIs level, the communication of the entire network ceases no matter what the signal-to-noise ratio is. In addition, we derive the achievable diversity gain of the considered network, and demonstrate that the diversity gain always equals zero due to the existence of RHIs and RSI. Finally, numerical simulations are provided to study the influence of multifarious network parameters on the system outage performance and the performance gap between the DF and amplify-and-forward strategies.

Intelligent-Reflecting-Surface-Aided Bidirectional Full-Duplex Communication System With Imperfect Self-Interference Cancellation and Hardware Impairments

In this article, we combine two new technologies [full-duplex (FD) transmission and intelligent reflecting surface (IRS)] in a wireless communication system for investigation. Specifically, we evaluate the performance of an IRS-aided bidirectional FD communication system in a practical scenario where imperfect self-interference (SI) cancellation and hardware impairments (HIs) are taken into consideration. We successfully derive the closed-form expressions of ergodic capacity (EC) and symbol error rate (SER) of the IRS-aided FD-HI system over Rayleigh fading channels. We confirm the correctness of the derived expressions via Monte-Carlo simulations. To clarify the effects of residual SI and HIs, we compare the performance of the IRS-aided FD-HI system with that of the IRS-aided FD-ideal hardware (ID), half-duplex (HD)-HI, and HD-ID systems. Numerical results clarify a strong impact of residual SI and HIs on the EC and SER of the IRS-aided FD-HI system. Thus, the EC and SER of the IRS-aided FD-HI system go to the saturated values in a high signal-to-noise regime even with a large number of reflecting elements in the IRS. Therefore, depending on the residual SI and HI levels as well as the requirements about the EC and SER in practice, we can use appropriately the transmit power of terminals and number of reflecting elements in the IRS for enhancing the performance and saving the energy consumption of the IRS-aided FD-HI system.

Effective capacity analysis of NOMA with transceiver hardware and SIC imperfections

In this paper, we study the performance of the non-orthogonal multiple access (NOMA) networks. By considering two practical factors of residual hardware impairments (RHIs) and imperfect serial interference cancellation (ipSIC), we adopt effective capacity as a metric to characterize the effects of latency on the performance of NOMA networks and derive the analytical expressions of the effective capacity for the near user (NU) and the far user (FU). For further insights, we provide asymptotic analysis by invoking high signal-to-noise ratio (SNR) slope and high SNR power offset. Numerous analytical and simulated results have shown that: (1) The effective capacities of NU and FU are positively proportional to the SNR at low SNR, while at high SNR, the effective capacities approach to the constants; (2) Comparing the two users of the considered NOMA network, the effective capacity of NU shows pronounced advantages under the requirements of low quality of service. (3) RHIs are detrimental to the effective capacities of both NU and FU, especially for the high SNR regime. (4) The effective capacity of NU is limited by ipSIC.

Enhancing Secrecy Performance for STAR-RIS NOMA Networks

Simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) is becoming a prospective technology in realizing extremely low power transmission and seamless coverage for the sixth generation (6G) wireless communication era. Motivated by this, we study the secrecy performance of the STAR-RIS assisted non-orthogonal multiple access (NOMA) networks. To be more practical, we assume that all nodes suffer from residual hardware impairments (RHIs). To characterize the performance of the considered network, the analytical expressions of the secrecy outage probability (SOP) for NOMA users over the Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> fading channels are derived. Meanwhile, the asymptotic behaviors of SOP at high signal-to-noise ratio (SNR) are also studied. The numerical results show that: 1) The existence of the RHIs reduces the secrecy performance of the network under consideration. 2) The increase in the number of configurable elements <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> will improve the system secrecy performance.

Performance Analysis of Polar Codes Over Fox’s H-Fading Channels With RHI and IQI Impairments

This study examined the error probability performance of polar codes across Fox’s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -fading (FHF) channels while taking into account in-phase and quadrature-phase imbalance (IQI), as well as residual hardware impairments (RHI). This fading model generalizes most of the commonly used fading and turbulence models where Málaga- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {M}$ </tex-math></inline-formula> turbulence is taken into account as a specific case of FHF in this paper. Specifically, an upper bound on block error probability (BLER) for the successive cancellation (SC) decoding method of polar codes is derived in terms of the Fox’s <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -function. According to numerical results, by lengthening polar codes and changing the properties of fading channels, it is possible to decrease the impact of system impairments on the error probability performance.

Mixed Coded RF/FSO EH-Based Communication System Subject to Multiuser Interference and Residual Hardware Impairments

Mixed Coded RF/FSO EH-Based Communication System Subject to Multiuser Interference and Residual Hardware Impairments

Performance Analysis of I/Q Imbalance With Hardware Impairments Over Hyper Fox’s H-Fading Channels

Impairments baseband model in-phase and quadrature-phase Imbalance (IQI) and Residual hardware impairments (RHI) are two key factors degrading the performance of wireless communication systems (WCSs), particularly when high-frequency bands are employed, as in 5G systems and beyond. The impact of either IQI or RHI on the performance of various WCSs has been investigated exclusively in a separate way. To fill this gap, in this paper, the joint effect of both IQI and RHI on the performance of a WCS subject to Hyper Fox’s H-fading (HFHF) channel, is investigated. Such a fading model generalizes most, if not all, of well-known fading and turbulence models. To this end, closed-form expressions for the outage probability (OP), Average channel capacity (ACC) under constant power with optimum rate adaptation (ORA) policy, and average symbol error probability (ASEP) for both coherent and non-coherent modulation schemes are derived. Specifically, all the analytical expressions are derived for three different scenarios: (i) ideal Tx and Rx impaired, (ii) Tx impaired and ideal Rx, and (iii) both Tx and Rx are impaired. Further, asymptotic expressions for OP, ACC under ORA policy, and ASEP are obtained, based on which, insightful discussions on the IQI and RHI impacts are made. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha -\mu $ </tex-math></inline-formula> and Málaga <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {M}$ </tex-math></inline-formula> turbulence with pointing error distribution models have been considered as particular cases of the HFHF distribution. The analytical derivations, endorsed by simulation results, demonstrate that the RF impairments’ effects should be seriously taken into account in the design of next-generation wireless technologies.

Uavnoma: A UAV-NOMA Network Model under Non-Ideal Conditions

Uavnoma is a set of Python functions and a front-end script for modeling, studying, and analyzing the communication system composed by an unmanned aerial vehicle (UAV) and two ground users. We assume that the UAV acts as an aerial base station to serve the users according to non-orthogonal multiple access (NOMA) principles. For more practical insights, residual hardware impairments (RHI) and imperfect successive interference cancellation (ipSIC) are considered. More specifically, <strong>uavnoma</strong> allows the modelers to study and visualize the system performance in terms of achievable rate and outage probability. Additionally, the package produces figures and tables showcasing results from the specified performance metrics.

Performance analysis of ABCom NOMA systems for 6G with generalized hardware impairments

With the continuous emergence of new smart applications, the number of smart devices is increasing exponentially. Therefore, it is a great challenge to meet the rising network demands for the sixth generation (6G) communication. To solve the above problem, non-orthogonal multiple access (NOMA) and ambient backscatter communication (AmBC) technologies are introduced. However, deploying a large number of low cost components, all nodes are prone to hardware non-ideal, and the system performance is limited by the imperfect factors of in-phase and quadrature-phase imbalance (IQI) and residual hardware impairments (RHIs). Motivated by this, this paper considers an AmBC-NOMA communication system with both IQI and RHIs. In particular, we derive the analytic expressions for outage probability (OP) and ergodic rate (ER) of each node for the cases of ideal and non-ideal conditions. In order to get further insights, we analyze the asymptotic behavior of OPs and ERs at high signal-to-noise ratios (SNRs). The comparison of theoretical analysis and Monte Carlo simulation show that: (1) IQI and RHIs have negative impacts on the effectiveness and reliability of the system; (2) As the transmit SNR increases, the OP of each node converges to a non-zero constant, resulting in the diversity order approaches zero; (3) The ER of Uf is less affected by these two non-ideal factors; (4) RHIs have a greater impact on the ER of Un than Uf.

Security Performance Analysis of Relay Networks Based on κ - μ Shadowed Channels with RHIs and CEEs

This paper mainly describes the transmission reliability and physical layer security of multiantenna decode-and-forward relay networks over the κ - μ shadowed fading distribution. We consider the existence of residual hardware impairments (RHIs) and channel estimation errors (CEEs) at the same time. Firstly, we give the network model. On this basis, we analyze the reliability and security by deriving the exact expressions of outage probability (OP) and intercept probability (IP). To further verify and investigate the theoretical derivation, the approximate analysis of OP is obtained under the high signal-to-noise ratio. In addition, we also use an optimized antenna selection technology at the transmitter to improve the security performance. Finally, through the comparative study of theoretical simulation and Monte Carlo simulation results, the factors affecting network transmission and security are acquired. The interesting conclusion is that both RHIs and CEEs can increase OP and decrease IP; that is to say, the existence of RHIs and CEEs can reduce reliability and enhance security.

Uplink NOMA Short-Packet Communications With Residual Hardware Impairments and Channel Estimation Errors

In this paper, we study an uplink non-orthogonal multiple access (NOMA) wireless system with short-packet communications (SPC) in the presence of channel estimation errors and residual transceiver hardware impairments. Two NOMA decoding schemes are considered, namely fixed-order decoding (i.e., mean-power based decoding) and dynamic-order decoding (i.e., instantaneous-power based decoding). We first derive the closed-form exact and asymptotic expressions of the cumulative distribution functions (CDF) of the signal-to-interference-plus-noise ratio (SINR) associated with the two decoding schemes. Based on this, we analyze the average block error-rate (BLER) achieved in the finite block-length regime. Next, we formulate maximum throughput optimization problems with respect to the length of the packet. This problem is shown to be quasi-concave, which facilitates the finding of the optimal block-length via a search algorithm. Analytical comparisons between the NOMA-SPC system and its OMA-SPC counterpart are also performed. Simulation results are provided to validate the analysis.

Throughput fairness in cognitive backscatter networks with residual hardware impairments and a nonlinear EH model

This paper is to design a throughput fairness-aware resource allocation scheme for a cognitive backscatter network (CBN), where multiple backscatter devices (BDs) take turns to modulate information on the primary signals and backscatter the modulated signals to a cooperative receiver, while harvesting energy to sustain their operations. The nonlinear energy harvesting circuits at the BDs and the residual hardware impairments at the transceivers are considered to better reflect the properties of the practical energy harvesters and transceivers, respectively. To ensure the throughput fairness among BDs, we formulate an optimization problem to maximize the minimum throughput of BDs by jointly optimizing the transmit power of the primary transmitter, the backscattering time and reflection coefficient for each BD, subject to the primary user’s quality of service and BDs’ energy-causality constraints. We introduce the variable slack and decoupling methods to transform the formulated non-convex problem, and propose an iterative algorithm based on the block coordinate descent technique to solve the transformed problem. We also investigate a special CBN with a single BD and derive the optimal solution in the closed form to maximize the BD’s throughput. Numerical results validate the quick convergence of the proposed iterative algorithm and that the proposed scheme ensures much fairness than the existing schemes.

Robust Max-Min Energy Efficiency for RIS-Aided HetNets With Distortion Noises

The energy efficiency (EE) of femtocells is always limited by the surrounding radio environments in heterogeneous networks (HetNets), such as walls and obstacles. In this paper, we propose to deploy reconfigurable intelligent surfaces (RISs) to improve the EE of femtocells. However, perfect channel state information is more difficult to obtain due to the passive characteristics of RISs and non-cooperative relationship between different tiers. Besides, the low-cost transceivers and reflecting units suffer nontrivial hardware impairments (HWIs) due to the hardware limitations of practical systems. To this end, we investigate a realistic robust beamforming design based on max-min fairness for an RIS-aided HetNet under channel uncertainties and residual HWIs. The joint optimization of transmit beamforming vectors of femto base stations (FBSs) and the phase-shift matrices of RISs is formulated as a non-convex problem to maximize the minimum EE of the femtocell subject to the constraints of the maximum transmit power of FBSs, the quality of service of users, and unit modulus phase-shift constraints of RISs. We develop an iterative block coordinate descent-based algorithm which exploits the semi-definite relaxation, the S-procedure, and the singular value decomposition method. Simulation results reveal that the proposed algorithm outperforms existing algorithms in terms of fairness, EE, and outage probability.