Rectangular Quadrature Amplitude Modulation Research Articles

A framework for Gaussian Q approximation with BSA and its application to RIS-assisted systems

This paper proposes a novel and improved Chiani approximation for the Gaussian Q-function by employing the backtracking search optimization algorithm (BSA). The proposed approximation includes only exponential terms which are comfortable for the mathematical functionality. Then, a wireless communication application of reconfigurable intelligent surface (RIS) structures, which are anticipated to play a crucial role in integrated sensing and communication (ISAC), has been presented. In the considered wireless communication scenario, the link between the source and RIS node is Nakagami-m fading, while the link between RIS node and the destination is Rayleigh fading. The received probability density function (PDF) expression of instantaneous signal to noise ratio for this system has been derived analytically. Using this derived PDF, the error expression (Pe) for the RIS-assisted communication system employing the rectangular quadrature amplitude modulation (RQAM) technique has been obtained with the assistance of the proposed improved Chiani approximation in this study. The obtained RQAM error figures are presented comparatively, and the results clearly show that the Pe expression by obtained the proposed approximation with BSA for the RIS-assisted communication system, which is an important aspect for ISAC, is in excellent agreement with computer simulations.

Performance analysis of rectangular quadrature amplitude modulation for multiple-input multiple-output dual-hop cooperative underwater visible light communication system

Performance analysis of rectangular quadrature amplitude modulation for multiple-input multiple-output dual-hop cooperative underwater visible light communication system

Performance analysis of energy harvesting‐enabled relay networks inκ‐μfading channels

AbstractIn this paper, we investigate the performance of an energy harvesting (EH)‐enabled multiple relay network operating over generalized‐fading channels. Our approach involves utilizing a partial relay selection strategy and employing an amplify and forward relay protocol for efficient EH from RF signals. Additionally, we integrate a selection combining scheme at the receiver to combine both direct and relaying path signals. In our research, we first obtain the exact closed‐form expression of the cumulative distribution function (CDF) for the system under investigation. Subsequently, we derive expressions for the outage probability (OP) and the moment generating function (MGF) using the derived CDF expression. Furthermore, with the assistance of a CDF‐based approach, we derive closed‐form expressions for the average symbol error rate (ASER) for coherent quadrature amplitude modulation (QAM) schemes, including rectangular QAM (RQAM) and hexagonal QAM (HQAM). We also analyze the ASER expression for non‐coherent frequency shift keying (NCFSK), leveraging the derived MGF expression. To gain valuable insights into the performance of EH‐enabled multiple relay networks, we assess the asymptotic expression of the OP. The outcomes indicate how the behavior of the system is affected by various factors such as time switching ratio, channel fading components, number of relays, and the distance between nodes. To corroborate the accuracy of the analytical findings, Monte Carlo simulations are executed.

Analyzing the Performance of TAS/MRC with Decode-and-Forward Relaying for Multihop Transmission over Fisher-Snedecor F Fading Channels

This study comprehensively assesses a decode-and-forward relaying system that employs Transmit Antenna Selection/Maximal Ratio Combining (TAS/MRC) for multi-hop communication across Fisher-Snedecor F fading channels. The study primarily focuses on the average symbol error rate (ASER) and outage probability (OP) while using cross QAM (XQAM) and rectangular quadrature amplitude modulation (RQAM). The proposed MIMO system effectively decreases the hardware complexity and cost of large antennas by implementing Transmit Antenna Selection (TAS) at the source and relay nodes and Maximum Ratio Combining (MRC) diversity at the destination and relays. Analytical formulations for OP (outage probability) and ASER (average symbol error rate) are derived using PDF (Probability Density Function)-based methods. Monte-Carlo simulations further validate these formulas. The investigation indicates that system performance is improved under conditions of lighter shadowing compared to moderate and extreme shadowing settings. Additionally, increasing the hop count amplifies the observed performance. Moreover, when the fading parameter increases, both the OP and ASER decrease. This study comprehensively examines the impact of many parameters, including m, p, L, R, and o, on the behaviour of the system under Fisher-Snedecor F fading. Based on the findings, the combination of shadowing and multipath fading significantly affects the system's performance, with both m and p significantly influencing this. When examining the Signal-to-Noise Ratio (SNR), a comparison between RQAM and XQAM demonstrates that XQAM is superior. The research uncovers crucial information for planning and executing the TAS/MRC-based MIMO multi-hop communication system. This technology possesses the capability to enhance the effectiveness of similar communication systems, as seen by the encouraging advancements in performance, especially in scenarios including signal attenuation.

Squared and rectangular QAM compatible decoder for spectrally efficient frequency division multiplexing optical systems

Squared and rectangular QAM compatible decoder for spectrally efficient frequency division multiplexing optical systems

Performance evaluation of L‐maximal ratio combining diversity with estimation error for Shadowed Beaulieu‐Xie fading channels

SummaryTo provide the increasing demand for wireless technologies, high capacity with lower latency is vital. New emerging technologies like 5G, millimeter wave, THz, and so forth are able to characterize such complex fading and shadowed environments. Spatial diversity is one of the techniques to minimize fading in the wireless communication channel. The performance of the wireless communication system can be further optimized by using estimators at the receivers. The influence of imperfect channel estimation on the performance over shadowed Beaulieu‐Xie (SBX) fading channels with L‐maximal ratio combining (MRC) diversity is studied. The probability density function (PDF) of the received output signal‐to‐noise ratio (SNR) with L‐MRC over SBX fading channels is derived. Further PDF of the received output SNR, outage probability, and average bit error rate (ABER) using the derived PDF is evaluated for L‐MRC diversity with channel estimation error over SBX fading channels. ABER expression for Gray‐coded rectangular quadrature amplitude modulation over the SBX channel is also evaluated. The study also includes how the system performs under the effect of different shadowing and fading parameters.

Average bit error probability performance of intelligent reflecting surface‐aided wireless communications over Hoyt fading

SummaryIn this article, the performance of a wireless communication system with an intelligent reflecting surface (IRS) panel installed between the transmitter and receiver is studied. The channel is considered to be the Hoyt faded and additive white Gaussian noise. Closed‐form expressions for average bit error probability (ABEP) for both coherent Gray‐coded rectangular quadrature amplitude modulation and non‐coherent modulation schemes are presented. We apply the moment‐generating function‐based method for the derivation. In addition, asymptotic ABEP expressions are also obtained. Using asymptotic ABEP expressions, we obtained diversity order which is a function of the number of IRS elements. The effect of the number of IRS elements and fading parameters on the ABEP is studied. The ABEP performance improves with an increase in the number of reflecting elements but degrades with an increase in the fading severity. The accuracy of each analytical ABEP expression is verified by the simulation of the system considered herewith.

On the performance of energy harvesting‐assisted Nth best relay cooperative networks in Nakagami‐m fading

SummaryWe study the energy harvesting (EH)‐assisted system model based on the performance of a dual‐hop cooperative communication system that is subjected to Nakagami‐ fading. Through the partial relay selection method, the selection of th best relay (BR) is performed among amplify and forward (AF) relays, which can harvest energy from radio frequency signals. At the receiver, the selection combining scheme is considered to select between the signals of th best relaying path and the direct path. For this considered system, we compute the closed‐form expressions of outage probability (OP) and the average symbol error rate (ASER) for higher order quadrature amplitude modulation (QAM) techniques, especially for rectangular QAM, cross QAM, and hexagonal QAM. Further, a new moment‐generating function expression is obtained which is used to derive the ASER expression related to the generalized non‐coherent modulation technique. We also give the asymptotic expression of OP to find out the diversity order. Furthermore, we study the effect of fading parameters, th BR, and other factors on system behavior. Finally, we verify the derived expressions with Monte Carlo simulations.

Performance of IRS-Aided FD Two-Way Communication Network With Imperfect SIC

Intelligent reflecting surface (IRS) is a promising technology to deploy reconfigurable and cost-effective next-generation wireless communication systems. In this work, we investigate the performance of an IRS-aided two-way communication network over Rayleigh fading channels, where downlink and uplink transmission between the base station and the user equipment is established in full-duplex mode. We take into account the impact of residual self-interference (RSI), which results from imperfect self-interference cancellation. We derive the analytical expressions of outage probability (OP), asymptotic OP, and obtain diversity order of the system. We also derive ergodic capacity in terms of the Meijer-G function. Further, we derive the analytical expressions of average symbol error rate (ASER) for general order rectangular quadrature amplitude modulation (QAM), cross QAM, and hexagonal QAM. We highlight the impact of reflecting elements, RSI, and other system parameters on the performance of the considered network and also compare the ASER of various QAM constellations. Finally, Monte-Carlo simulations validate the derived analytical expressions.

Improved Chernoff Bound of Gaussian Q-function with ABC algorithm and its QAM applications to DB SC and MRC systems over Beaulieu–Xie channels

In this study, we propose an improved upper bound for the Gaussian Q function by using artificial bee colony algorithm. Then, we investigate the performance of the dual-branch (DB) selection combining (SC) and maximal ratio combining (MRC) systems over the Beaulieu–Xie fading channels. The probability density functions of the instantaneous signal to noise ratio for the considered systems are obtained. Employing the proposed upper bound, we derive closed-form expressions of the error probability for the quadrature amplitude modulation (QAM) techniques such as rectangular QAM (RQAM), cross QAM (XQAM), and hexagonal QAM (HQAM). Furthermore, the asymptotic error probability expressions for the DB SC system are also obtained to simplify the analyses. The effects of some key parameters in the systems are shown in the results. Comparisons of the different modulation types and the different upper bound approaches for the Gaussian Q function are presented. Finally, it has been shown that the upper bound approximation presented in this study can be widely used for many communication applications.

On the Performance of Square, Rectangular, Star, and Hexagonal QAM for Backscatter Systems

Applications on wireless sensing and internet of things (IoT) require communication systems based on low power with high data rates. Thus, backscatter communication plays an important role in the new emerging IoT communications. In the literature, several works have been reported about backscatter modulators with high-order modulation formats. However, only the square quadrature amplitude modulation (S-QAM) scheme is considered, although it is not optimal in the sense of power efficiency. In this letter, the performance of two dimensional (2-D) signal constellations is evaluated, namely rectangular QAM, star QAM, and hexagonal QAM, in terms of the symbol error rate, in backscatter systems context. A power consumption analysis is presented for these modulation schemes. To provide the symbols of the aforementioned constellations, a practical high-order backscatter modulator, corroborated by measurement campaigns, is implemented. Several SER curves are also presented in this work.

On the ASER performance of RF energy harvesting multiple relay networks

We present the average symbol error rate (ASER) of quadrature amplitude modulation (QAM) for radio frequency energy harvesting assisted dual-hop multiple amplify-and-forward (AF) relay network. In this relaying network, partial relay selection scheme is employed to select best relay among multiple relays, while selection combining is considered at destination to combine the signals coming from the direct path and the relaying path. In particular, we derive the exact ASER expressions of rectangular QAM (RQAM), hexagonal QAM and cross QAM schemes for the considered systems over independent and non-identically distributed Nakagami-m fading channels using cumulative distribution function method. Moreover, the asymptotic ASER expression of RQAM is determined to examine the system’s diversity order. Further, to verify the correctness of derived expressions, numerically evaluated results are compared with Monte Carlo simulations. Furthermore, the effects of fading parameter, number of relay, time switching ratio, and large scale fading are studied on the ASER performance.

Performance of rectangular QAM/FSO communication systems in the anisotropic non-Kolmogorov ground-to-satellite uplink

Quadrature amplitude modulation (QAM) is an exciting technology to accomplish a high communication data rate without increasing the system bandwidth, which can undoubtedly greatly improve the performance of free-space optical (FSO) communication systems. With the increase of experimental and theoretical results about atmospheric turbulence, scientists have confirmed that the anisotropy and non-Kolmogorov property cannot be ignored for atmospheric turbulence. In this paper, utilizing the new anisotropic non-Kolmogorov (ANK) turbulence spectrum models for the satellite links that are applicable to both vertical and slant links, we derive the average bit error rate (BER) expression of rectangular QAM for a Gaussian-beam transmission through the weak ANK ground-to-satellite uplink under the influences of both scintillation and beam wander. Numerical results display that, when the zenith angle is less than a certain angle, the average BER of the ground-to-satellite uplink decays with the enhancement of the anisotropic factor, but while the zenith angle is greater than the certain angle, the contrary trend will occur. Our work will benefit the design optimization of QAM/FSO communication systems in ANK satellite links.

Error Rate Analysis of Different Modulation Schemes Over Shadowed Beaulieu-Xie Fading Channels

ABSTRACT A new composite model called shadowed Beaulieu-Xie (BX) is used in terahertz and millimeter-wave wireless communication systems. This model characterizes an environment with an arbitrary number of non-line-of-sight and line-of-sight signals. In this paper, an analysis of the average bit error rate (ABER) is done. The analysis is carried out for different coherent and non-coherent modulation techniques. The mathematical expressions of ABER are obtained using the probability density function of the output signal to noise ratio of the shadowed BX fading channel. A new closed-form ABER expression for gray-coded rectangular quadrature amplitude modulation over the shadowed BX channel is also evaluated. The effects of fading and shadowing parameters on the modulation techniques are analyzed and compared.

Performance analysis of vertical multihop cooperative underwater visible light communication system with imperfect channel state information

Visible light communication (VLC) has gained attention due to its ability to provide a high data rate in underwater communication. We consider an underwater VLC (UWVLC) system and vertical propagation through the column of water with L layers (channels) and M relays between the transmitter and the receiver. We consider the real-time adverse effects of depth-dependent weak turbulence and path loss. We model each of the L channels with a log-normal distribution, where its statistical parameters mean and variance are functions of the parameters representing the adverse effects of the turbulence. For this concatenated L layered UWVLC, using Gauss–Hermite integral technique, we derive closed-form expressions of outage probability and average symbol error probability taking square quadrature amplitude modulation and rectangular quadrature amplitude modulation modulations with different configurations and assuming imperfect channel state information available at the receiver for detection. We have observed that there is a drastic degradation in the performance as the depth (distance between the transmitter and the receiver) is increased. However, the severity can be alleviated by installing multiple relays between the transmitter and the receiver.

Performance of UAV-Assisted Multiuser Terrestrial-Satellite Communication System Over Mixed FSO/RF Channels

In this letter, performance of a multiantenna multiuser unmanned aerial vehicle (UAV)-assisted terrestrial-satellite communication system over mixed free space optics (FSO)/radiofrequency (RF) channels is analyzed. Downlink transmission from the satellite to the UAV is completed through FSO link which follows gamma–gamma distribution with pointing error impairments. Both the heterodyne detection and intensity modulation direct detection techniques are considered at the FSO receiver. To avail the antenna diversity, multiple transmit antennas are considered at the UAV. Selective decode-and-forward scheme is assumed at the UAV and opportunistic user scheduling is performed while considering the practical constraints of outdated channel state information (CSI) during the user selection and transmission phase. The RF links are assumed to follow Nakagami-m distribution due to its versatile nature. In this context, for the performance analysis, analytical expressions of outage probability, asymptotic outage probability, ergodic capacity, effective capacity, and generalized average symbol-error-rate expressions of various quadrature amplitude modulation (QAM) schemes such as hexagonal-QAM, cross-QAM, and rectangular QAM are derived. A comparison of various modulation schemes is presented. Further, the impact of pointing error, number of antennas, delay constraint, fading severity, and imperfect CSI are highlighted on the system performance. Finally, all the analytical results are verified through the Monte–Carlo simulations.

Modeling and Analyzing Trellis-Coded Modulation on Power Line Communication Systems

Power Line channels present a very harsh environment for high speed data transfer which degrades the data transmission. Using proper channel coding can enhance the data transmission over PLC systems. The purpose of using channel coding is to encode the information transmitted over communication channel in such a way that in presence of other interferences and noise, the error can be detected and possibly corrected. This paper investigates the Bit Error Rate (BER) performance of PLC systems based on Orthogonal Frequency Division Multiplexing (OFDM), in presence of Middleton class A noise, and applying Trellis Coded Modulation (TCM) / Rectangular Quadrature Amplitude Modulation (QAM) TCM as a channel coding. Simulations are undertaken in Matlab 2013b. The obtained results illustrates that although trellis codes produce improvements in the SNR in presence of Additive white Gaussian noise (AWGN), they do not perform well with multipath power line channel and Middleton class A noise. Therefore the Rectangular QAM TCM has been used to enhance the results.

On the performance of a relay assisted hybrid RF-NLOS UVC system with imperfect channel estimation

Non-line-of-sight (NLOS) ultraviolet communication (UVC) is emerging as an attractive optical wireless communication technology that enables wireless connectivity in radio-frequency (RF) prohibited areas with no LOS availability. NLOS UVC, however, suffers from a very high path loss, thereby restricting its usage to smaller link distances. In this paper, we address the challenge of providing long-distance wireless connectivity to RF prohibited areas by mixing NLOS UVC with RF communication using a decode-and-forward relay. The RF link is modeled using Rayleigh distribution, and the NLOS UV link is modeled using lognormal distribution under weak turbulence conditions. A framework for analytical expressions of the outage probability and probability density function (PDF) of the end-to-end signal-to-noise ratio is presented by considering the practical scenario of imperfect channel state information (CSI) at the receiver. Subsequently, a PDF based novel closed-form analytical expression of the average symbol error rate is deduced for spectrally efficient higher-order modulation schemes, including rectangular quadrature modulation (RQAM), square QAM (SQAM), cross-QAM (XQAM), and hexagonal QAM (HQAM). Numerical investigations are conducted, and the impact of CSI imperfections on the system performance is evaluated. It is shown that the RF link is more vulnerable to channel estimation error (CEE) than the NLOS UV link. Further, it is illustrated that for constellation sizes greater than four, HQAM always performs better than the RQAM, SQAM, and XQAM schemes, irrespective of the amount of CEE present. Furthermore, it is shown that an elevation angle of 70° or less in the NLOS UVC link results in better outage performance. Correctness of the derived analytical expressions is supported through extensive Monte Carlo simulations.

ASER Analysis of Hybrid Receiver Based SWIPT Two-Way Relay Network

In this paper, we investigate the performance of a hybrid receiver-based simultaneous wireless information and power transfer (SWIPT) two-way relay network over Nakagami- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> faded channels. A hybrid receiver is adopted at the relay node that utilizes both the time switching (TS) and power splitting (PS) protocols for energy harvesting and information transmission. Amplify-and-forward relaying protocol is utilized at the relay node to process the information in half-duplex mode. In the considered network, impact of a practical non-linear power amplifier (NLPA) at the relay node is considered. Selection combining is performed at the destination node to utilize the direct-link and relay assisted signals. For the considered system, the analytical expressions of outage probability (OP) and asymptotic OP are derived over Nakagami- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> faded channels for both the integer and non-integer value of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> . The analytical expression of the system throughput and energy efficiency of the considered network are also derived. Further, the analytical expression of ergodic capacity is derived in terms of the Meijer-G function. By utilizing a cumulative distribution function based approach, analytical expressions of average symbol error rate (ASER) for general order hexagonal quadrature amplitude modulation (QAM), general order rectangular QAM, and 32-cross QAM schemes are derived. For different QAM constellations, a comparative ASER analysis is also illustrated. Furthermore, the impact of TS factor, PS ratio, energy conversion efficiency, NLPA, and threshold data-rates on the considered network is also highlighted. Finally, Monte-Carlo simulations are performed for validation of the derived analytical expressions.

Power Allocation for Reliable SIC Detection of Rectangular QAM-based NOMA Systems

This paper considers the power allocation for non-orthogonal multiple access (NOMA) users to enable using the successive interference cancellation (SIC) while providing reliable error performance. The derived closed-form expressions are applicable for arbitrary number of NOMA users each of which has a square or rectangular quadrature amplitude modulation (QAM) constellation with arbitrary order. The obtained numerical results show that power assignment process at the transmitter for the superposition process and at the receiver for the SIC process should be performed meticulously because the power difference between the weakest and strongest users can be tremendous when the number of users or the modulation orders increase. Moreover, the derived expressions can be used to reduce the computational complexity that is required to obtain the optimal power coefficients using brute force methods by significantly reducing the search space.