Average SER Performance of Distributed Antenna Systems Over Shadowed Generalized-Gamma Channels for Different Modulation Schemes

Distributed antenna systems (DAS) play a key role in future wireless communications. Despite the increasing previous research work, the channel models of DAS lack generality. This paper presents a holistic and generic channel model, which incorporates path loss, lognormal shadowing, and generalized-gamma fast fading into consideration. This overarching composite channel model encompasses well-known composite channel models as special cases. A probabilistic system outage model is attained by selective transmission scheme in terms of the proposed channel model and the distribution of mobile stations in the cell. Experimental results substantiate that the theoretical model provides sufficient precision for evaluating the outage performance of DAS.

Based on selective transmission (ST) and maximal ratio combining (MRC) schemes, this paper focuses on the analysis of downlink system capacity in distributed antenna systems (DAS) over composite channels. Firstly, this paper establishes a composite channel model which takes path loss, lognormal shadowing and Rayleigh fading into account. Then, the probability density function (PDF) of the output signal to-noise ratio (SNR) is derived after MRC at the receiver. Moreover, the distribution of the output SNR is approximated by a lognormal distribution. After that, by making use of ST scheme, an approximate expression of the capacity for a mobile station (MS) over a given position is derived. Further, considering the distribution of MSs in the system, a closed-form expression of the system capacity is obtained. Numerical results show that the closed-form expression can provide sufficient precision for evaluating the system capacity performance of DAS.

A paradigm for multiple-input multiple-output (MIMO) channel modeling demands diversity technique to compensate the effects of fading and shadowing. In this paper, error performance of MIMO system is analyzed with orthogonal space time block code (OSTBC) and maximal ratio combining (MRC) techniques over Weibull-gamma (WG) fading channel. WG distribution forms a composite channel model which is used to determine the effects of multipath as well as shadowing. In this scenario, exact analytical expressions for symbol error rate (SER) are computed for MIMO systems using OSTBC and MRC. Consequently, the effects of fading severity by varying shape parameters are also shown by simulation and analytical results.

In this paper, we present a novel framework for deriving closed-form exact expressions for the symbol error rate (SER) of α-μ fading channels, assuming single-branch and equalgain combining and maximal-ratio combining receivers and considering most of the commonly used modulation schemes. The proposed framework is based on Mellin transform, and the SER expressions are given in terms of the univariate and multivariate Fox H-functions, which have recently been extensively used in the literature. The proposed framework has the following advantages over previous frameworks: First, it is straightforward and general; therefore, it allows the derivation of the exact SER expressions for cases untreated before in the literature. Second, it enables direct derivation for the asymptotic expressions of the SER for high average signal-to-noise ratios (SNRs). To validate the obtained expressions, we compare the results of the special case of the Nakagami-m fading channel with those reported in the literature. Furthermore, Monte Carlo simulations are conducted, and their results are shown to perfectly match the analytic expressions. Finally, the obtained asymptotic expressions for all the studied modulation schemes and diversity receivers are shown to match the behavior of their corresponding exact values for a wide range of SNR values that are of practical interest.

We examine the multi-input multi-output (MIMO) channel capacity where one side of the link constitutes a largely spaced antenna array, e.g. distributed antenna system (DAS), which prompts the need to model the channel that has both microscopic and macroscopic fading. Specifically, we consider a MIMO system comprising M antennas co-located at one side of the link and N largely separated ports each with L antennas colocated within a port at the other, named as generalized distributed antenna system (GDAS). We assume independent macroscopic and microscopic fading between ports and common macroscopic but independent microscopic fading at each antenna in a port. Using a simple composite fading channel model, a Rayleigh-lognormal composite fading, the influence of the macroscopic diversity as well as the microscopic diversity on the channel capacity, especially the outage capacity, of the MIMO GDAS is investigated for both the uplink and the downlink.

On the maximal-ratio combining of FSO and RF links over generalized distributions and its applications in hybrid FSO/RF systems

Performance study of wavelength diversity serial relay OFDM FSO system over exponentiated Weibull channels

This paper investigates a hybrid framework that combines free space optics (FSO) and terahertz (THz) technologies for a backhaul network. In this hybrid configuration, the FSO and THz systems are empowered by reconfigurable intelligent surface (RIS) and are combined at the receiver using either maximal ratio combining (MRC) or selection combining (SC). The performance of the RIS-assisted hybrid FSO/THz system is evaluated under multiple impairments for FSO and THz links. The exact closed-form expressions for probability density function (PDF), cumulative distribution function (CDF), and moment-generating function (MGF) of the output signal-to-noise ratio (SNR) of both RIS-assisted FSO and THz links are derived. Leveraging these SNR statistics, we compute the outage probability and the average symbol error rate (SER) of the proposed hybrid FSO/THz system with MRC and SC schemes. Additionally, this paper conducts an asymptotic analysis at high SNR levels, yielding asymptotic expressions for outage and average SER, which not only reduce computational complexity but also provide insights into the system’s diversity gain. In the numerical results, the performance of the proposed hybrid FSO/THz system is compared against other state-of-the-art wireless systems, including direct link FSO without RIS, RIS-aided FSO, and the hybrid FSO/THz systems without RIS using diversity combining techniques.

Energy harvesting (EH) wireless communications have become more and more popular due to its capability of effectively reducing the battery replacement time. In this paper, we focus on decode-and-forward-based cooperative wireless communications with an EH relay. The stochastic characteristics of the harvestable energy and the wireless channel make it difficult to optimally manage the energy harvested at the relay for better communication performance. We formulate such a problem as an optimization by minimizing the long-term average symbol error rate (SER) subject to a battery constraint. Based on the Lyapunov optimization theory, we utilize the virtual queue technique and transform the optimization problem into a drift-plus-penalty minimization. Then, we conduct theoretic analysis of the optimal energy strategy derived by the proposed scheme. Specifically, we show the convexity of the drift-plus-penalty minimization problem, and prove that the virtual queue is bounded and the battery constraint is always satisfied. We also show that the proposed optimal energy management strategy is limited by an upper bound that is independent of the operation time index, derive the closed-form expression for the asymptotical average SER, and analyze the corresponding diversity order and EH gain. Finally, simulation results using the real solar irradiance data show that the proposed algorithm can achieve much better performance in terms of both average SER and diversity order, compared with the Markov decision process-based method.

Performance analysis of multiple relay cooperative communication over generalized κ–μ and η–μ fading channels

Recently, visible light communication (VLC) technology has attracted great attention in both academia and industry. In this paper, a spatial modulation (SM) based multiple-input multiple-output (MIMO) VLC system with input-dependent noise is investigated. Based on the input-dependent noise, the theoretical symbol error rate (SER) expression is obtained. The SER performance of SM-based MIMO VLC system is analyzed for both input-dependent noise and input-independent noise cases. Considering the trade-off between SER and transmission rate, the successful transmission rate indicator is formulated, which is the product of SER and transmission rate. An optimization problem, whose goal is to maximize the successful transmission rate, is proposed to optimize the modulation order. Simulation results show the effectiveness of the obtained SER expression. Simulations also indicate that the system with larger input-dependent noise tends to have smaller modulation order in order to maximize the successful transmission rate.

Analytical expressions for symbol error rate (SER) of M-ary dual ring star shaped quadrature amplitude modulation (QAM), when corrupted by additive white Gaussian noise (AWGN), have been derived. Utilizing the result for AWGN channel, SER expressions for various frequency non-selective slow fading channels (e.g. Rayleigh, Rician, and Nakagami-m) are also found. The results obtained are in the form of summation of single integrals which can be easily calculated through numerical methods. More importantly, compared to the erroneous results published earlier, the derived expressions are accurate. Extensive Monte Carlo simulations were performed to validate the analytical framework. The inadequacy of Gray's approximation for calculation of bit error rate (BER) has also been pointed out.

Recently, energy detection (ED) has been investigated in massive single-input multiple-output (SIMO) systems, where transmit symbols can be decoded by averaging the received power across all receive antennas. In this paper, we concentrate on the performance of non-coherent massive SIMO in the presence of antenna correlation. Specifically, closed-form expressions of symbol error rate (SER) and achievable rate are derived. Furthermore, asymptotic behaviors of SER and achievable rate in regimes of a large number of receive antennas, high antenna correlation and large signal-to-noise ratio (SNR) are investigated. Interestingly, the results show that antenna correlation poses a great impact to SER, but has little effect on the achievable rate. Numerical results are presented to verify our analytical results.

We apply amplitude corrections to a truncated Bessel beam that has propagated through turbulent atmosphere modelled by random phase screens. These corrections are realized via transmitting an unmodulated beam in parallel to the one carrying the 4 amplitude shift keying (ASK) modulated message signal. On the receiver side, the amplitude corrections are obtained by dividing the intensity of the unmodulated beam by its free space equivalence. The corrections are then used to restore the amplitude distortions of the beam carrying the 4ASK modulated message signal and in the determination of decision boundaries for the received 4ASK symbols. The success of the system is visually inspected by comparing the received intensity profiles before and after the application of corrections. Furthermore, simulation analysis of symbol error rate (SER) is made, where the proposed set-up is found to be quite insensitive to wavelength difference between the unmodulated and modulated beams. On the other hand, the difference in the structure constant values of these two beams seems to have profound effect on system performance.

In this paper we give the performance of MQAM OFDM based WLAN in presence of single and multiple channels Zigbee interference. An analytical model for getting symbol error rate (SER) in presence of single and multiple channel Zigbee interference in AWGN and Rayleigh fading channel for MQAM OFDM system is given. Simulation results are compared with analytical symbol error rate (SER) of the MQAM-OFDM system. For analysis we have modeled the Zigbee interference using the power spectral density (PSD) of OQPSK modulation and finding the average interference power for each sub-carrier of the OFDM system. Then we have averaged the SER over all WLAN sub-carriers. Simulations closely match with the analytical models. It is seen from simulation and analytical results that performance of WLAN is severely affected by Zigbee interference. Symbol error rate (SER) for 16QAM and 64QAM OFDM system is of order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> for SIR (signal to interference ratio) of 20dB and 30dB respectively in presence of single Zigbee interferer inside the WLAN frequency band for Rayleigh fading channel. For SIR values more than 30dB and 40dB the SER approaches the SER without interference for 16QAM and 64QAM OFDM system respectively.