Adaptive Transmission Techniques Research Articles

Extended α-η-μ Fading Distribution: Statistical Properties and Applications

In this paper, the impact of the non-linearity of the propagation medium on the extended η-μ fading distribution is studied. In particular, the extended α-η-μ fading model in which the parameter α represents the non-linearity of the propagation environment is presented via providing the exact and asymptotic of the statistical properties, namely, the probability density function (PDF), cumulative distribution function (CDF), and generalized-moment generating function (G-MGF). To this effect, exact closed-form mathematically tractable expressions of the outage probability (OP), average symbol error probability (ASEP), amount of fading (AoF), channel quality estimation index (CQEI) and effective rate (ER) are obtained. The asymptotic behaviour at high average signal-to-noise (SNR) values is also analysed to gain further insights into the influence of the index α on the performance metrics of the wireless communication systems. Moreover, the average channel capacity (ACC) under different adaptive transmission techniques, such as, optimum rate and adaptation (ORA), capacity of the channel with inversion and fixed rate (CIFR), and truncated inversion and fixed rate (TIFR) are derived. The validation of the derived expressions is verified via comparing the numerical results with the Monte-Carlo simulations as well as some previous works for different scenarios.

On the performance of DF-based multi-hop system over α − κ − μ and α − κ − μ-extreme fading channels

Several emerging application scenarios for the multi-hop wireless networking have been introduced in 5G and beyond networks, to provide ultra-low latency and much higher data rate to the end users. In this work, an integrated performance evaluation of a decode-and-forward (DF) multi-hop wireless communication system is undertaken over the non-linear generalized α−κ−μ and α−κ−μ-Extreme fading models. Novel closed-form expressions for the amount of fading (AoF), channel capacity under various adaptive transmission techniques are derived. Additionally, decoding error probability for short packet communication is derived and analyzed. The provided expressions are very useful in designing the channel/link quality for practical multi-hop communication networks. The effects of the fading parameters and the number of hops on the system performance are demonstrated. The correctness of the proposed solutions has been corroborated by comparing them with Monte Carlo simulation results.

Scintillation due to atmospheric turbulence on optical GEO and MEO satellite links: Time series synthesizer for system level simulations

SummaryOptical satellite links have been proposed in order to cover the increasing capacity demand for satellite networks. The reliable design of the performance of optical satellite links is of utmost importance. In the present paper, an analytical methodology for the generation of time series of scintillation due to atmospheric turbulence of optical satellite links is proposed. Under cloud‐free line of sight, scintillation causes the degradation of link's quality. In order to design adaptive transmission techniques for scintillation compensation, an accurate channel model for time series synthesis is required. The proposed synthesizer is based on stochastic differential equations (SDEs) driven by fractional Brownian motion and generates log‐amplitude time series for plane and spherical waves affected by turbulence. The links are considered between Ground and Geostationary or Medium Earth Orbit satellites. The synthesizer is validated using the theoretical aspects of scintillation considering the first‐ and second‐order statistics. Additionally, the performance of the synthesizer for the case of Geostationary is validated with data from ARTEMIS optical satellite link experiment carried out by European Space Agency. The proposed synthesizer can be directly employed for the system performance of transmission techniques for optical satellite forward and reverse links taking into account the scintillation effects.

Capacity analysis of maximal ratio combining over Beaulieu-Xie fading

The present paper analyzes an L-branch maximal ratio combining (MRC) receiver over the Beaulieu-Xie (BX) fading channel. The expression of the probability density function (PDF) of the signal-to-noise ratio (SNR) of an MRC receiver in BX fading is derived by using the characteristic function approach. The obtained PDF is then utilized to calculate the various link-level and system-level parameters. This paper focuses on deriving closed-form expressions for different adaptive transmission techniques based on instantaneous channel state information in BX fading. The accuracy of our derived expressions is verified by comparing them with Monte Carlo simulations.

Performance of Resource Management Techniques for Weather-Impacted Satellite Networks

Signals transmitted via satellite networks at high frequency in the Ka,Q, andVbands are susceptible to degradation due to rain attenuation. Adaptive transmission techniques are usually employed to mitigate the effect of rain and improve users’ quality of service (QoS) but the effectiveness of these techniques hinges on the accuracy with which rain attenuation on the link is known. Commonly, most techniques rely on predicted attenuation along the link for selection of optimal transmission parameters. This paper proposes an efficient approach to predict the rain attenuation experienced by sources of multimedia connections in rain-impacted satellite networks. The proposed technique is based on three Markov models for widespread, shower, and thunderstorm rain events and predicts the attenuation experienced at different periods within the duration of a user’s connection. It relies on an adaptive modulation and coding (AMC) scheme to dynamically mitigate rain attenuation and a call admission control (CAC) policy to guarantee the satisfaction of users’ QoS requirements.

Time-Dependent Bit Error Rate Analysis for Smart Utility Networks in the Presence of WLAN Interferers

The smart grid (SG) modernizes the aging power grid by using two-way reliable communications dedicated to adaptive energy management. To achieve this goal, smart utility networks (SUNs) are used to efficiently connect the SG devices. However, the SUNs are designed to work on unlicensed frequency bands and are very sensitive to interferences from other networks operating in the same band, such as wireless local area networks (WLANs). Therefore, in this paper, the effect of the WLAN interferers on the SUN transmission is investigated and we show that by detecting the initial transmission offset of each WLAN transceiver using energy sensing, the activity of the interferers can be predicted with high accuracy. Furthermore, we prove that the SUN data bit error rate is time dependent and that each SUN bit has a different bit error rate expression depending on its time offset. These expressions are derived analytically and verified by Monte Carlo simulations. In fact, these expressions can be used by the SUN devices to enhance their communication links in the presence of WLAN devices by using adaptive transmission techniques to avoid the interference.

Dual-Hop Cooperative Relaying with Beamforming Under Adaptive Transmission in κ–μ Shadowed Fading Environments

In this paper, we analyze the performance of a dual-hop cooperative decode-and-forward (DF) relaying system with beamforming under different adaptive transmission techniques over κ − μ shadowed fading channels. We consider multiple antennas at the source and destination, and communication takes place via a single antenna relay. The published work in the literature emphasized the performance analysis of dual-hop DF relaying systems, in conjunction with different adaptive transmission techniques for classical fading channels. However, in a real scenario, shadowing of the line-of-sight (LoS) signal is caused by complete or partially blockage of the LoS by environmental factors such as trees, buildings, mountains, etc., therefore, transmission links may suffer from fading as well as shadowing, either concurrently or separately. Hence, the κ − μ shadowed fading model was introduced to emulate such general channel conditions. The κ − μ shadowed fading model is a general fading model that can perfectly model the fading and shadowing effects of the wireless channel in a LoS propagation environment, and it includes some classical fading models as special cases, such as κ − μ , Rician, Rician-shadowed, Nakagami- m ^ , One-sided Gaussian, and Rayleigh fading. In this work, we derive the outage probability and average capacity expressions in an analytical form for different adaptive transmission techniques: (1) optimal power and rate adaptation (OPRA); (2) optimal rate adaptation and constant transmit power (ORA); (3) channel inversion with a fixed rate (CIFR); and (4) truncated channel inversion with a fixed rate (TIFR). We evaluate the system performance for different arrangements of antennas and for different fading and shadowing parameters. The obtained analytical expressions are verified through extensive Monte Carlo simulations.

Adaptive Transmission in Spectrum Sharing Systems With Alamouti OSTBC Under Spatially Correlated Channels

This paper presents a performance analysis for adaptive transmission techniques in a spectrum sharing system in which a primary user (PU) and a secondary user (SU) employ an Alamouti orthogonal space-time block coding (OSTBC) system under correlated antennas over Rayleigh fading channels. The considered adaptive transmission techniques include practical rate-adaptive modulation techniques and classical adaptive transmission techniques, namely, optimal power and rate adaptation (opra), constant transmit power with optimal rate adaptation (ora), and channel inversion with fixed rate (cifr). Closed-form expressions are derived for the following performance metrics: the average spectral efficiency, the outage probability, the average channel capacity, and the average bit error rate (BER) of the system. Using numerical evaluation results, the impacts of antenna correlation on the performance of each adaptive technique in different cases and under various parameters are evaluated. These results provide comprehensive and useful insights about the performance of the considered system under various adaptive transmission techniques.

On the Capacity of Joint Fading and Two-Path Shadowing Channels

The ergodic and outage channel capacity of different optimal and suboptimal combinations of transmit power and modulation rate adaptation strategies over a joint fading and two-path shadowing (JFTS) fading/shadowing channel is studied in this paper. Analytically tractable expressions for channel capacity are obtained, assuming perfect channel side information (CSI) at the receiver and/or the transmitter with negligible feedback delay. Furthermore, the impacts of the JFTS parameters on the channel capacity achieved by these adaptive transmission techniques are determined.

Experimental demonstration of an adaptive orthogonal frequency division multiplexing visible light communication system

We propose and experimentally demonstrate a simple visible light communication system by combining an adaptive transmission technique with orthogonal frequency division multiplexing. In the adaptive transmission scheme, power allocation is performed in such a way as to maximize the channel capacity under electric power constraints, and adaptive modulation is then introduced to achieve the maximum data rate given a target bit error rate. Experimental results show that spectrum efficiency can be greatly improved through this adaptive transmission technique.

Channel capacity of TAS/MRC system with adaptive transmission and channel estimation errors

This correspondence presents the impact of channel estimation error (CEE) on the channel capacity analysis of multiple-input multiple-output (MIMO) system employing transmit antenna selection and maximal ratio combining (TAS/MRC) under adaptive transmission (ADT) techniques over frequency-flat Rayleigh fading channels. In this paper, we evaluated exact closed-form expressions of channel capacity for TAS/MRC system with CEE under different variable power and variable rate adaptation techniques: (i) optimal power and rate adaptation (opra) (ii) constant power with rate adaptation (cpra) (iii) channel inversion with fixed rate (cifr). The channel state information (CSI) consisting of the signal-to-noise ratio (SNR) level is estimated by the decoder and fed back to the transmitter. Further, the ADT schemes can be operated frame by frame, hence permitting for distinct compromises among the attainable capacity and the corresponding implementation complexity. Numerical outcomes illustrate the impact of CEE on the link capacity and outline the performance characteristics among the distinctive adaptation techniques.

Adaptive transmission in amplify‐and‐forward cooperative communications using orthogonal space–time block codes under spatially correlated antennas

This study analyses the impact of antenna correlation on orthogonal space–time block coding in amplify-and-forward cooperative relay networks in conjunction with different adaptive transmission techniques over Rayleigh fading channels. Closed-form expressions are derived for the cumulative distribution function, and probability distribution function of the total signal-to-noise ratio. For each considered adaptive transmission technique, the authors derive closed-form expressions for the average channel capacity, outage probability, average spectral efficiency and the average bit error rate of the system. Using numerical evaluations, the performances for different cases are compared in order to evaluate and quantify the effects of spatial correlation on the system performance.

On the channel capacity of SSC diversity system in η–μ and κ–μ fading environments

This paper deals with the capacity analysis of a dual-branch switch and stay combining (SSC) system operating over η–μ and κ–μ fading channels. In particular, expressions for the channel capacity of these two generalized fading distributions are derived under three adaptive transmission techniques, namely the optimal rate adaptation with constant power, channel inversion with fixed rate and truncated channel inversion with fixed rate. Some of the final capacity expressions contain infinite series, and thus we truncate those series and derive upper bounds on truncation errors. Closed form expressions for the optimum adaptive switching thresholds are also obtained. Corresponding expressions for Nakagami-m, Rician fading, and Nakagami-q fading are obtained here as special cases of η–μ and κ–μ fading. Numerical and simulation results are presented here for illustration purposes.

Adaptive-Transmission Channel Capacity of Maximal-Ratio Combining with Antenna Selection in Nakagami-m Fading channels

This correspondence presents the channel capacity analysis of maximal-ratio combining with transmit antenna selection (TAS/MRC) in frequency-flat Nakagami-m fading channel with variable power and rate allocation techniques. In this paper, we evaluated exact closed-form expressions of channel capacity for TAS/MRC under different adaptive transmission techniques (1) optimal simultaneous power and rate allocation (opra) (2) optimal rate allocation with constant transmit power (ora) (3) channel inversion with fixed rate (cifr) and (4) truncated version of (cifr). An exact closed-form expression for channel capacity has been derived in uncorrelated Nakagami-m fading channels with single infinite series of tabulated function while the fading index is a real value. Numerical results illustrate the impact of fading severity on the channel capacity and outline the performance characteristics between the distinctive allocation schemes.

Spectrum Efficiency Evaluation of SM MC-CDM with ZF USIC Under Different Adaptive Transmission Techniques

In this paper, closed form expressions for capacities per unit bandwidth for Spatially Multiplexed Multicarrier-Code Division Multiplexing with Zero Forcing Unified Successive Interference Cancellation detection are derived for optimal power and rate adaptation, optimal rate adaptation with constant transmit power, channel inversion with fixed rate, and truncated channel inversion adaptation policies, taking into account the effect of perfect channel estimation at the receiver. Optimal power and rate adaptation policy provides the highest capacity over other adaptation policies. Truncated channel inversion policy suffers a large capacity penalty relative to the optimal power adaptation policy. However, the capacity penalty for the truncated channel inversion policy is lower compared to channel inversion with fixed rate policy. Furthermore, we derive analytical results for (1) capacity statistics, (2) Complementary Cumulative Distribution Function, and (3) Probability Density Function.

Capacity of orthogonal space–time block codes in spatially correlated MIMO Weibull fading channel under various adaptive transmission techniques

The effect of spatial correlation on channel capacity of orthogonal space---time block codes (OSTBCs) over multiple-input multiple-output Weibull fading under different adaptive transmission scheme is studied. In this paper, we have derive the moment generating function of the OSTBC received signal-to-noise ratio for integer Weibull parameter $$\beta $$s, considering spatial fading correlation. Utilizing the exact expression of the MGF, the probability density function has been simply achieved, thus enabling the exact evaluation of OSTBC capacity under distinct power and rate allocation schemes. Numerical outcomes illustrate the effect of fading severity $$\left( \beta \right) $$s and fading correlation on the channel capacity and outline the performance differences among the distinctive adaptation schemes. It can be observed that OSTBC system with $$opra$$opra outperform the system with $$tifr$$tifr adaptive scheme.

장거리 무선 링크의 가용도 보장을 위한 적응전송 기법

In Microwave Radio Link, it is necessary to consider the radio fading to consistently assure the radio link of the high quality as the distance. If the fixed modulation is used for the microwave radio link, it is difficult to keep the high availability of link for the case of the long distance. Adaptive Modulation(AM) provide good quality on microwave link, but the application of the only-AM is not enough to provide the availability assurance due to the fluctuating characteristics of link capacity. Our previous study has proposed the improvement method of transmission in association with the distance, however the previous method needed to make up for the common application. There was no suggestion of a mathematical formula with a variable. In this paper, we propose an optimized Adaptive Transmission Techniques with calculating formula of the priority traffic transmission capacity based on AM in consideration of the fade margin for the availability assurance as the distance and the comparison of the channel bandwidth for Long-distance Radio Link.

Adaptive Long-Range Prediction of Three-State LMS Channel Model

In order to provide the accurate real-time knowledge of future channel state information for the adaptive transmission of narrowband land mobile satellite (LMS) communication systems, an adaptive long-range prediction (ALRP) method, suitable for a three-state LMS channel model at S-band, is proposed. The very slow shadowing conditions' variations of satellite propagation channel can be described as a three-state Gilbert---Elliot channel model based on Markov chain. The channel state of future long-range is predicted based on weighting prediction while the parameters of linear auto-regression model are updated using an iterative adaptive tracking algorithm. The future channel fading series are predicted by the latest observations within current channel state. Simulation results show that the proposed method can be used to predict the future long-range channel state and fading series of three-state Gilbert---Elliot channel model accurately; and it is observed from the mean square error results that the prediction performance of the ALRP method is much more accurate than that of long-range prediction method. Moreover, the method has advantage of real-time and low-complexity which will make the adaptive transmission techniques feasible for LMS channel models.

Adaptive Transmission Schemes for MISO Spectrum Sharing Systems: Tradeoffs and Performance Analysis

In this paper, we propose a number of adaptive transmission techniques in order to improve the performance of the secondary link in a spectrum sharing system. We first introduce the concept of minimum-selection maximum ratio transmission (MS-MRT) as an adaptive variation of the existing MRT (MRT) technique. While in MRT all available antennas are used for transmission, MS-MRT uses the minimum subset of antennas verifying both the interference constraint (IC) to the primary user and the bit error rate (BER) requirements. Similar to MRT, MS-MRT assumes that perfect channel state information (CSI) is available at the secondary transmitter (ST), which makes this scheme challenging from a practical point of view. To overcome this challenge, we propose another transmission technique based on orthogonal space-time block codes with transmit antenna selection (TAS). This technique uses the full-rate full-diversity Alamouti scheme in order to maximize the secondary's transmission rate. The performance of these techniques is analyzed in terms of the average spectral efficiency (ASE), average number of transmit antennas, average delay, average BER, and outage performance. In order to give the motivation behind these analytical results, the tradeoffs offered by the proposed schemes are summarized and then demonstrated through several numerical examples.

Aerial-terrestrial communications: terrestrial cooperation and energy-efficient transmissions to aerial base stations

Hybrid aerial-terrestrial communication networks based on low-altitude platforms are expected to meet optimally the urgent communication needs of emergency relief and recovery operations for tackling large-scale natural disasters. The energy-efficient operation of such networks is important given that the entire network infrastructure, including the battery-operated ground terminals, exhibits requirements to operate under power-constrained situations. In this paper, we discuss the design and evaluation of an adaptive cooperative scheme intended to extend the survivability of the battery-operated aerial-terrestrial communication links. We propose and evaluate a real-time adaptive cooperative transmission strategy for dynamic selection between direct and cooperative links based on the channel conditions for improved energy efficiency. We show that the cooperation between mobile terrestrial terminals on the ground could improve energy efficiency in the uplink, depending on the temporal behavior of the terrestrial and aerial uplink channels. The corresponding delay in having cooperative (relay-based) communications with relay selection is also addressed. The simulation analysis corroborates that the adaptive transmission technique improves overall energy efficiency of the network whilst maintaining low latency, enabling real-time applications.