Approximate Expressions For Outage Probability Research Articles

Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surface Assisted NOMA Networks

Simultaneously transmitting/refracting and reflecting reconfigurable intelligent surface (STAR-RIS) has been introduced to achieve full coverage area. This paper investigate the performance of STAR-RIS assisted non-orthogonal multiple access (NOMA) networks over Rician fading channels, where the incidence signals sent by base station are reflected and transmitted to the nearby user and distant user, respectively. To evaluate the performance of STAR-RIS-NOMA networks, we derive new approximate expressions of outage probability and ergodic rate for a pair of users, in which the imperfect successive interference cancellation (ipSIC) and perfect SIC (pSIC) schemes are taken into consideration. Based on the asymptotic expressions, the diversity orders of the nearby user with ipSIC/pSIC and distant user are achieved carefully.The high signal-to-noise ratio slopes of ergodic rates for nearby user with pSIC and distant user are equal to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$one$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$zero$ </tex-math></inline-formula> , respectively. In addition, the system throughput of STAR-RIS-NOMA is discussed in delay-limited and delay-tolerant modes. Simulation results are provided to verify the accuracy of the theoretical analyses and demonstrate that: 1) The outage probability of STAR-RIS-NOMA outperforms that of STAR-RIS assisted orthogonal multiple access (OMA) and conventional cooperative communication systems; 2) With the increasing of reflecting 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> and Rician factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\kappa $ </tex-math></inline-formula> , the STAR-RIS-NOMA networks are capable of attaining the enhanced performance; and 3) The ergodic rates of STAR-RIS-NOMA are superior to that of STAR-RIS-OMA.

Uplink Multiple Access for Reconfigurable Intelligent Surface-Aided Wireless Systems

The integration of reconfigurable intelligent surface- (RIS-) aided wireless communication and multiple access is an attractive and promising scheme for next-generation wireless networks. In this research work, separate uplink RIS-aided nonorthogonal multiple access (NOMA) and uplink relay-assisted NOMA schemes are studied, where the RIS and relay devices are deployed to enhance the coverage of an obstructed single-antenna far user by assisting it to communicate with a single-antenna base station. In each scenario, both perfect successive interference cancellation (pSIC) and imperfect successive interference cancellation (ipSIC) operations are considered in the proposed multiple access network. To characterize the system performance, the associated residual interference caused by ipSIC and relay loop self-interference is characterized using the Rayleigh fading model; subsequently, new channel statistics are derived based on the Gauss-Laguerre polynomial. Consequently, the closed-form approximate outage probability expressions are derived for each scenario in the high signal-to-noise ratio (SNR) regime. To gain further insight, the system throughput in the delay-limited transmission is also obtained for each scenario. The formulated expressions are validated via Monte-Carlo simulations. Finally, the obtained simulation results demonstrate and validate the superiority of the RIS system over the relay device under several system parameters of interest despite the limitation of ipSIC.

Distributed Antenna-and-Relay Selection Schemes for MIMO Cooperative Relay Network

Relay selection, antenna selection, and link selection are three potent means to enrich network capacity in MIMO relaying networks. To reduce feedback overhead, in this paper, three distributed antenna-and-relay selection schemes are proposed for AF multiple-relay network, which is equipped with multiple antennas at nodes. Closed-form formulations of system outage probability are derived for these schemes, as well as the lower bounds and upper bounds. Furthermore, the approximate expressions of outage probability at high SNR regime are also derived, showing that the proposed optimal strategy can achieve full diversity order. In addition, link selection scheme can improve spectral efficiency since it saves one time slot when direct link is selected.

Outage Probability Analysis of Decode-and-Forward Two-Way Relaying System with Energy Harvesting Relay

In this paper, we evaluate a two-way relay system consisting of two terminals and an intermediate relay. In this model, two terminals do not have a direct link but exchange data with each other via the relay in three phases. The relay utilizes energy harvesting technology to collect energy from the received signals of two terminals in the first two phases and then uses the obtained energy for signal transmission in the third phase. Each node is equipped with a single antenna and operates under a half-duplex mode. All wireless channels are influenced by reversible independent flat Rayleigh fading. Using analytical methods, we provide the exact and approximate closed-form expressions of user outage probability and system outage probability. The approximate expressions of these outage probabilities are more explicit and straightforward, providing a better understanding of the influences of network parameters on the system quality. Monte-Carlo simulations are used to confirm the correctness of mathematical analyses.

Vehicular Networks Under Nakagami-m Fading Channels: Outage Probability and Ergodic Achievable Rate

Vehicular networks are regarded as an effective solution for the traffic management and road safety. In this paper, the performance of the vehicular networks is investigated under Nakagami-m fading channels. The vehicular communication is considered to reuse the same time-frequency with another vehicular communication link, so that both interference and noise produce an effect on each vehicle and infrastructure. Firstly, we derive the closed-form expressions for the outage probability of vehicular links and particularly examine two special cases, that is, high SNR case and weak interference case. For both cases, approximate expressions for outage probability are provided in closed form. Then, we derive lower and upper bounds of ergoidic achievable rate, which are evident to be sufficiently tight to the Monte-Carlo simulated results. Based on these results, we further analyze the high SNR and weak interference scenarios and the asymptotic expressions of ergoidic achievable rate are also presented. All the analytical results are applicable for arbitrary locations, transmit power, as well as channel parameters. Finally, we propose the power optimization which aims at maximizing the ergodic achievable rate and guaranteeing the outage performance. Numerical results validate our analytical results via Monte Carlo simulations.

Joint relay selection and power allocation protocol for two-way relaying system

The Joint Relay Selection and Power Allocation (JRSPA) for Amplify-and-Forward (AF) relaying (JRSPA-AF) combines Power Allocation (PA) and Relay Selection (RS) very well in Two-Way Relaying (TWR) system. In order to explore the system performance of JRSPA-AF protocol, the outage probability and Diversity-Multiplexing Trade-off (DMT) of JRSPA-AF protocol are analysed. One upper bound, two lower bounds and approximate expressions of outage probability along with the DMT are derived. Based on this, the idea of JRSPA is introduced into Decode-and-Forward (DF) relaying TWR system, and the JRSPA-DF protocol is proposed. Moreover, the exact expressions of outage probability and DMT for JRSPA-DF are derived. Simulations are developed to validate the analytical results, the results show that the approximation outage probability of JRSPA-AF can be used well to evaluate system outage probability over the entire transmission SNR region, and the analysis results of outage probability of JRSPA-DF are consistent with its simulation results. In addition, the simulation results indicate that JRSPA-DF can achieve lower outage probability than JRSPA-AF and other protocols.

Joint relay selection and power allocation protocol for two-way relaying system

The Joint Relay Selection and Power Allocation (JRSPA) for Amplify-and-Forward (AF) relaying (JRSPA-AF) combines Power Allocation (PA) and Relay Selection (RS) very well in Two-Way Relaying (TWR) system. In order to explore the system performance of JRSPA-AF protocol, the outage probability and Diversity-Multiplexing Trade-off (DMT) of JRSPA-AF protocol are analysed. One upper bound, two lower bounds and approximate expressions of outage probability along with the DMT are derived. Based on this, the idea of JRSPA is introduced into Decode-and-Forward (DF) relaying TWR system, and the JRSPA-DF protocol is proposed. Moreover, the exact expressions of outage probability and DMT for JRSPA-DF are derived. Simulations are developed to validate the analytical results, the results show that the approximation outage probability of JRSPA-AF can be used well to evaluate system outage probability over the entire transmission SNR region, and the analysis results of outage probability of JRSPA-DF are consistent with its simulation results. In addition, the simulation results indicate that JRSPA-DF can achieve lower outage probability than JRSPA-AF and other protocols.

Performance of Secondary Network With Primary Beamforming-Assisted Energy Harvesting Transmitters

In this paper, we consider a novel energy-harvesting (EH) cognitive radio framework in which the primary source beamforms excess available energy to an EH secondary transmitter (ST) so as to enable it to share the spectrum. In the first phase of transmission, the multi-antenna primary source optimally beamforms symbols to its decode and forward relay while beamforming all excess energy to a selected EH ST. In the second phase while the relay transmits symbols to a selected primary receiver, the EH ST transmits symbols using underlay principles to its secondary receiver. Assuming peak interference constraints at the STs, we derive approximate expressions for outage probability and ergodic rate of the secondary link with the optimal beamformer . Using asymptotic expressions for outage and ergodic rate, we derive useful insights into performance of the system. We show that diversity equal to the number of secondary transmitters is achieved by the considered system. Computer simulations confirm accuracy of the derived expressions.

Self-Powered Wireless Two-Way Relaying Networks: Model and Throughput Performance with Three Practical Schemes

In this paper, we analyse the throughput performance for two, three and four time slot transmission schemes, (2TS, 3TS and 4TS) for two-way amplify-and-forward relaying networks, in which we use RF signal for the energy harvesting (EH) enabled relay node to assist the exchange of information. Most importantly, we derive expression for delay-limited throughput and the approximate expressions for outage probability, and we also compare these results in case of EH and non-EH. Additionally, the trade-off between the distance allocation between source to relay, and relay to destination is comprehensively investigated, in which the large scale path loss is considered to obtain the optimal throughput. Thanks to the numerical results, we consider a scenario in each scheme, where the throughput of 2TS is higher regardless of values of power splitting coefficients compared to other two schemes. Numerical results provide an interesting trade-off between the considered EH parameters in the system design, and reveal the improvement of bandwidth and power efficiency. The proposed schemes confirm that the appropriate placement of nodes can help achieve low outage probability and optimal throughput.

Full-duplex distributed switch-and-stay networks with wireless energy harvesting: design and outage analysis

Distributed switch and stay combining (DSSC) has been considered as an effective technique to achieve spatial diversity in a distributed manner with low processing complexity. In this paper, we incorporate DSSC into a full-duplex dual hop relaying system, where two energy-constrained relay nodes assist the information transmission from the source to the destination using energy wirelessly harvested from the source. By applying DSSC at the destination, this efficient technique not only improves performance of full-duplex relaying systems and increases the system diversity but also reduces the implementation and hardware complexity at the destination. We obtain tight approximate expression for outage probability in the case of using decode-and-forward (DF) relaying protocol and analytical expression for outage probability in the case of using amplify-and-forward (AF) relaying protocol. Numerical results show that our DSSC full-duplex relaying with wireless information and power transfer (WIPT) system achieves the full spatial diversity and has a better performance in terms of outage probability than that of the DSSC half-duplex relaying and conventional full-duplex relaying with WIPT system.

A User Grouping Based Opportunistic Network Coding Scheme for Multi-user Multi-relay Uplink Transmissions

In this paper, we study a User Grouping based Opportunistic Network Coding (UG-ONC) scheme for multi-user multi-relay uplink transmission scenario. In traditional opportunistic network coding (ONC) schemes, the use of network coding is often determined by the state of relays, i.e., buffer, packets waiting time, packets' successful decoding. However, whether the use of network coding is beneficial to the users is not considered. In our proposed UG-ONC scheme, whether network coding is adopted is not only determined by the state of relays, but also by the link quality between users and base station, that is, determined by the state of users. We consider two information-theoretic metrics, i.e., outage probability and throughput, to evaluate the validity and reliability of the UG-ONC scheme. And the approximate expressions of outage probability and throughput are derived. To further examine the performance of the scheme, we compare UG-ONC scheme with an existent network coding scheme. Monte Carlo simulations are presented to validate our analysis. The results show that our proposed UG-ONC scheme achieves considerable gains over the traditional network coding scheme. Our proposed UG-ONC scheme gives a new thought for designing opportunistic network coding.

Approximate Outage Probability and Capacity for &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\kappa$&lt;/tex-math&gt;&lt;/inline-formula&gt;- &lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\mu$&lt;/tex-math&gt;&lt;/inline-formula&gt; Shadowed Fading

Recently, a generalization of $\kappa$ - $\mu$ fading and Rician shadowed fading, i.e, $\kappa$ - $\mu$ shadowed fading has been proposed. In this work, we derive approximate expressions for outage probability and channel capacity when the signal of interest and interferers both experience $\kappa$ - $\mu$ shadowed fading with arbitrary parameters. The expressions are expressed in terms of well known hypergeometric function, which can be easily evaluated numerically. Finally, simulation results are provided which shows that our approximation is fairly tight.

Cooperative Distributed Beamforming With Outdated CSI and Channel Estimation Errors

This paper investigates the effect of imperfect channel state information (CSI) on the outage performance of cooperative distributed beamforming (DBF). The acquisition of perfect CSI is disturbed by outdated CSI and channel estimation errors. Decode-and-forward relays are considered with individual power constraints at each relay. Considering a training-and-feedback strategy to acquire CSI, a closed-form approximate expression for outage probability and the achievable diversity gain are first provided under Rayleigh fading channels. Numerical observations verify that the approximation is very tight. It is shown that outdated CSI seriously degrades the performance, and therefore, the outage probability is bounded and no diversity is achieved. Conversely, channel estimation errors cause slight performance degradation, and full diversity order is still achievable. However, even when CSI is outdated, it is shown that the asymptotic outage decreases as the number of relays $K$ increases, where the logarithm of the outage probability decreases at the rate of $K\log K$ . This paper shows that, when the destination re-estimates the current CSI for decoding, the effect of outdated CSI is greatly mitigated and consequently achieves a diversity gain of one. To re-estimate the current CSI with small overhead, the beamformed training sequence (BFTS) strategy is proposed, in which a new closed-form formula for minimum-mean-square-error estimation is presented using Gaussian approximation. Numerical results verify that the outage performance with the proposed BFTS scheme is close to that of a perfect estimation. A closed-form outage expression of DBF with the proposed BFTS scheme is also presented under an assumption of high-signal-to-noise ratio (SNR), but the expression is very tight even in low-to-moderate SNR regimes.

Outage Performance of Cooperative Systems Under IQ Imbalance

In this contribution, we investigate the outage performance of OFDM-based Decode and Forward (DF), Amplify and Forward (AF) and Controlled DF (CDF) cooperative systems under IQ Imbalance (IQI). In particular, tractable and compact approximate outage probability expressions are derived and the effect of the different IQI parameters is analyzed for different SNR ranges. Furthermore, by localizing the error floor in terms of IQI and SNR for each technique, we demonstrate when it is more beneficial to invest in increasing the transmission power or in compensating the imbalance. Moreover, we prove that the IQI compensation should be concentrated in the relay for some techniques and in the destination for some others. A comparative study between AF, DF, CDF and direct link transmission techniques is also conducted for different IQI parameters, SNR ranges, transmission rates and relay's position. Hence, this work may create a paradigm for future studies of more effective adaptive IQI compensation techniques that concentrate the compensation on the right IQI, SNR ranges, transceivers depending on the used transmission technique.

Performance analysis of network coding for multicast relay system over Nakagami-m fading channels

The outage probability performance of network coding for multicast relay system is analyzed in Nakagami-m fading channels. Two transmission strategies, i.e., complex field network coding (CFNC) and amplify-and-forward network coding (AFNC), are applied in the system, and the approximate expressions of outage probability are derived at high SNR and the conclusion is reached that the system diversity gains of two transmission strategies are both 2m, as is verified by numerical simulations. Simulation results also show that CFNC can outperform both AFNC and direct transmission without relay in the performances of system outage probability, sum rate and symbol error ratio.

Cooperative transmission in wireless networks using incremental opportunistic relaying strategy

In this study, the authors develop a novel cooperative transmission scheme – distributed opportunistic incremental decode and forward (DOIDF) that employs the incremental relaying (IR) strategy in opportunistic relaying (OR) protocols. By exploiting limited feedback from the destination, the proposed scheme starts the OR plan only when outage event happens in direct transmission (DT). The outage probability of DOIDF is derived in detail, and the results show that DOIDF can achieve the same space diversity order as multiple input single output (MISO) and single input multiple output (SIMO) systems, which is the upper limit of cooperative diversity. By analysing and comparing the approximate expression of outage probability of various protocols in high-signal-to-noise ratio (SNR) regime, the concept of system overhead factor (SOF), which reveals the effects of channel allocation in cooperative protocols on system performance, is proposed. Subsequent analysis and simulation results show that DOIDF outperforms corresponding OR schemes in outage probability, spectral efficiency and SNR gain over DT.