Optimal Rate Adaptation Research Articles

Different Power Adaptive Transmission Schemes Over Alternate Rician Shadowed Fading Channels

The two-sided bimodality property of Alternate Rician Shadowed (ARS) fading channels makes it a suitable fading model for body-centric wireless communication. The ARS fading model consists of two fluctuating specular components in which only one is active at a time. To provide excellent spectral efficiency with higher quality of service, system transmitter employs an adaptive transmission scheme. This paper derives the exact closed-form expressions of the ARS fading channels capacity. Various adaptive transmission schemes such as channel inversion with a fixed-rate, truncated channel inversion with a fixed-rate, and optimal rate adaptation are considered. A comparison of these schemes is also highlighted. Performance expressions such as binary bit error rate for various coherent and non-coherent modulation schemes and the outage probability are also derived. The derived results are plotted and analyzed for varying fading parameters of the ARS channel. Finally, the results of all performance metrics are verified with Monte-Carlo simulation results.

Optimal Joint Power and Rate Adaptation for Awareness and Congestion Control in Vehicular Networks

To support inter-vehicular applications, vehicles broadcast beacons with information about their state. Congestion may occur when the load on the channel due to beaconing can prevent the transmission of other types of messages. In this paper, we propose a distributed algorithm for optimal joint adaptation of transmit power and beaconing rate for congestion and awareness control. Our approach is based on a network utility formulation of the congestion control problem, which allows us to induce a desired fairness notion and set different priorities for vehicles. We formulate the general problem but, since it is not convex, we assume Rayleigh fading and derive an algorithm, called PRAIOS, that solves the optimization problem in a decentralized way with convergence guarantees. Our results, validated with realistic simulations in both static and dynamic scenarios and compared with other proposals, show that PRAIOS quickly converges to close to optimal allocations, while keeping the maximum beaconing load at the desired level. They also show that it can control the load when the fading is not Rayleigh. Applications can dynamically set their requirements as constraints, that are enforced by the algorithm while complying with the maximum load, which allows seamless integration of operational requirements into the control framework.

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.

Capacity Analysis of Channel Inversion Using Space-Time Block Coding with Transmit Power Control

In this paper, we analyze channel inversion with transmit diversity in terms of capacity and bit error rates in correlated fading. We obtain the Shannon capacity of Rayleigh fading channel under channel inversion using spatially correlated dual branch orthogonal space-time block coding, in comparison with the optimal power and rate adaptation policy, and provide a simple fixed-rate power adaptation policy to invert the Rayleigh fading into additive white Gaussian noise channel, and obtain the bit error rates using binary phase-shift keying modulation with/without channel inversion. It is found that the correlation generally causes a loss in capacity, which becomes more distinct with channel inversion relative to the optimal power and rate adaptation policy, especially when power correlation is greater than 0.5, and hinders otherwise possible full inversion. Transmit power truncation introduces power gain over full inversion, which manifests itself as an increase in capacity and a decrease in bit error probability. This gain increases with decreasing truncation level of the allowed peak transmit power. Inverting with truncation, a gain of about 19 dB in signal-to-noise ratio is obtained over classical single-antenna transmission without inversion. This gain may be further increased by a combination of truncation and correlation levels, as the correlation surprisingly turns to advantage when the normalized permitted peak-power is below 2 dB. However, the gain is normally accompanied by lower throughput or bandwidth expansion for a fixed data rate due to outage.

Spectral Efficiency Evaluation for Selection Combining Diversity Schemes under Worst Case of Fading Scenario

The results of spectral efficiencies for optimum rate adaptation with constant power (ORA) and channel inversion with fixed rate (CIFR) schemes over uncorrelated diversity branch with Selection Combining (SC) available so far in literature are applicable only for m?1.This paper derived closed-form expressions for the spectral efficiency of dual-branch SC over uncorrelated Nakagami-0.5(m&lt;1) fading channels. This spectral efficiency is evaluated under ORA and CIFR schemes. Since, the spectral efficiency expression under ORA scheme contains an infinite series, hence bounds on the errors resulting from truncating the infinite series have been derived The corresponding expressions for Nakagami-0.5 fading are called expressions under worst fading condition with severe fading. Finally, numerical results are presented, which are then compared to the spectral efficiency results which have been previously published for ORA and CIFR schemes. It has been observed that by employing SC, spectral efficiency improves under ORA, but does not improve under CIFR

Average spectral efficiency of multi-pulse position with adaptive transmissions and aperture averaging over atmospheric turbulence

Abstract The analysis of average spectral efficiency (ASE) of multi-pulse position modulation (MPPM) scheme with optimal rate adaptation (ORA) and channel inversion with fixed rate (CIFR) adaptation schemes over the gamma–gamma free space optical (FSO) channel has been carried out in this paper. The performance of the adaptation schemes has been analyzed in terms of the average channel capacity and has been further scrutinized under the aperture averaging effects in moderate and strong atmospheric turbulence. For the first time, closed form expressions for MPPM with ORA and CIFR transmitter adaptation schemes have been derived in terms of Meijer’s G functions. Using the derived expressions, the performance of the two adaptation policies have been compared for different transmitter power and varying FSO length, MPPM modulation order and aperture averaging. The analysis results revealed that generally, ORA performs better than CIFR under the considered turbulence strength, modulation order and aperture averaging. However, aperture averaging offers more gain in ASE in strong turbulence than moderate turbulence for both ORA and CIFR. Furthermore, the results revealed that aperture averaging effects offers much more gain in ASE when used with CIFR than ORA.

Capacity analysis of shadowed Beaulieu-Xie fading channels

In this paper, we provide a capacity analysis for the shadowed Beaulieu-Xie (SBX) fading model, under different transmission policies. From this analysis, we derive new expressions for the channel capacity per unit bandwidth considering four adaptive transmission schemes, namely: constant power with optimal rate adaptation (ORA); optimal power and rate adaptation (OPRA); channel inversion with fixed rate (CIFR) and truncated CIFR (TCIFR). We obtain asymptotic expressions for the channel capacity. A unified ergodic capacity analysis is presented for the maximum-ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SC) diversity receivers. We present capacity curves for different parameters that characterize the channel.

On power adaptation schemes in aerial-terrestrial communications

This paper mainly studies the transmission capacity performance of an aerial-terrestrial communication system, in which an unmanned aerial vehicle (S) delivers information bits to a terrestrial receiver (D) by adaptively controlling its transmit power according to the instantaneous channel state information. In this work, three adaptive transmission schemes, i.e., optimal simultaneous power and rate adaptation, optimal rate adaptation with constant transmit power and truncated channel inversion with fixed rate, are considered at S. Closed-form expressions for the ergodic capacity (EC) under these adaptive transmission schemes are derived, while considering the randomness of the location of D. Furthermore, some insights are obtained by deriving asymptotic expressions for the EC. Finally, numerical results are proposed to compare the performance of these considered power adaption methods, as well as to confirm the accuracy of the proposed analytical models.

BER and channel capacity analysis of wireless system over $${\kappa -\mu /}$$inverse gamma and $${\eta -\mu /}$$inverse gamma composite fading model

The $${\kappa -\mu /}$$ Inverse Gamma (KMIG) and $${\eta -\mu /}$$ Inverse Gamma (EMIG) are recently introduced composite fading distributions for the precise design of the wireless systems, where multipath fading and shadowing occur concomitantly. Further, these composite fading models are competent to be employed in the performance investigation of the digital communication system as their mathematical formulations are quite tractable. Average symbol error probability (SEP) and channel capacity analysis are important parameters to investigate the performance of a digital communication system. The applicability of these fading models is illustrated by analysing the performance matrices of the digital communication channels in the present work. Various performance matrices such as the average SEP, the channel capacity under different adaptive schemes namely, optimum rate adaptation (ORA), channel inversion with fixed rate (CIFR) and truncated CIFR are derived. The asymptotic analysis of KMIG and EMIG composite fading models over average SEP performance matrices with coding gain and diversity gain is also carried out in this work. The simplified high and low signal-to-noise-ratio solutions to channel capacity are also provided as a by-product. In addition, approximate analysis to ORA and CIFR capacity are provided under realistic environmental conditions. The accuracy of the derived numerical formulations is validated with the use of Monte–Carlo simulation. The results of present work will be advantageous in the modelling and designing of popular wireless services such as vehicle-to-vehicle communication, wearable communication and wireless power transfer related technologies.

Capacity and amount of fading analysis for SIMO communications over η–μ and λ–μ fading channels

This study evaluates the performance of single-input multiple-output (SIMO) wireless networks or dual-branch (DB) SIMO scenarios over the η–μ and the λ–μ fading links. First, the probability density functions (PDFs) of the instantaneous signal to noise ratio for a DB SIMO system in the η–μ and the λ–μ fading conditions. Then, the closed-form expressions of the effective rate (ER or effective capacity) for a SIMO network are derived. In addition to this, asymptotic ER expressions for the considered SIMO network are proposed. The analytical capacity expressions with different transmission policies such as optimal rate adaptation with constant transmit power, optimal simultaneous power and rate adaptation, channel inversion with fixed-rate (CIFR), and truncated channel inversion with fixed-rate are obtained for the SIMO network. Furthermore, the capacity expressions with CIFR policy for DB SIMO communications over the η–μ and the λ–μ fading channels are derived by using the proposed PDFs. Finally, the amount of fading expressions for SIMO networks over the η–μ and the λ–μ fading links are proposed by employing the elementary functions. The proposed analytical expressions provide to establish different radio propagation scenarios by adjusting η, λ or μ parameter. To confirm the accuracy of our analysis, the proposed analytical expressions are verified via exact simulations.

Statistical Delay and Error-Rate Bounded QoS Provisioning for mURLLC Over 6G CF M-MIMO Mobile Networks in the Finite Blocklength Regime

In supporting the new 6G standard traffic services-massive ultra-reliable low-latency communications (mURLLC), several advanced techniques, including statistical delay-bounded quality-of-service (QoS) provisioning theory and finite blocklength coding (FBC), have been developed to upper-bound both delay and error-rate for time-sensitive multimedia applications. On the other hand, cell-free (CF) massive multi-input multioutput (m-MIMO), where a large number of distributed access points (APs) jointly serve a massive number of mobile devices using the same time-frequency resources, has emerged as one of the 6G key promising techniques to significantly improve various QoS performances for supporting mURLLC. However, it is challenging to statistically guarantee stringent mURLLC QoS-requirements for transmitting multimedia traffics over CF m-MIMO and FBC based 6G wireless networks. To overcome these problems, we develop analytical models to precisely characterize the delay and error-rate bounded QoS performances while considering non-vanishing decode-error probability for CF m-MIMO based schemes. In particular, we develop FBC based system models and apply the Mellin transform to characterize arrival/service processes for our proposed CF m-MIMO modeling schemes. Then, we formulate and solve the delay violation probability minimization problem and obtain the closed-form solution of the optimal rate adaptation policy for each mobile user over 6G CF m-MIMO mobile wireless networks in the finite blocklength regime. Our simulation results validate and evaluate our proposed schemes for statistical delay and error-rate bounded QoS provisioning.

Energy efficient robust scheduling of periodic sensor packets for discrete rate based wireless networked control systems

Wireless networked control systems (WNCSs) require the design of a robust scheduling algorithm that meets the stringent timing and reliability requirements of control systems, despite the limited battery resources of sensor nodes and adverse properties of wireless communication for delay and packet errors. In this article, we propose a robust delay and energy constrained scheduling algorithm based on the exploitation of the mostly pre-known periodic data generation nature of sensor nodes in control systems. We first formulate the joint optimization of scheduling, power control and rate adaptation for discrete rate transmission model, in which only a finite set of transmission rates are supported, as a Mixed-Integer Non-linear Programming problem and prove its NP-hardness. Next, we propose an optimal polynomial-time power control and rate adaptation algorithm for minimizing the transmission time of a node subset. We then design a novel polynomial-time heuristic scheduling algorithm based on first determining the concurrently transmitting node subsets and then distributing them uniformly over time by a modified Karmarkar-Karp algorithm. We demonstrate the superior performance of the proposed scheduling algorithm in terms of robustness, delay and runtime on the Low-Rate Wireless Personal Area Network (LR-WPAN) simulation platform, which we developed in network simulator-3 (ns3).

Capacity analysis of free space optical communication system under atmospheric turbulence

In this paper, the analytical channel capacity of the free space optical (FSO) system under weak, moderate and strong turbulence is derived. The FSO channel statistics follows the log-normal distribution under weak turbulence and follows the Gamma–Gamma distribution under moderate and strong turbulence. The three generally used adaptive transmission schemes in FSO communication system are as follows (1) optimal simultaneous power and rate adaptation, (2) optimal rate adaptation with constant transmit power, and (3) truncated channel inversion with a fixed rate. The closed-form approximations for the average ergodic channel capacity for these adaptive transmission schemes under different atmospheric turbulence without any pointing error are derived. Simulation results depict the excellent agreement of the proposed analytical models with the Monte Carlo simulation.

Capacity of Adaptive Transmission Schemes over FTRF Channels

The study of channel capacity is essential to assure the quality of service and to measure spectral efficiency for designing a wireless system. In this paper, a simple probability density function (PDF) expression for fluctuating two ray fading (FTRF) channels is developed. Capacity analysis for various adaptive transmission schemes such as channel inversion with fixed-rate, the truncated channel inversion with fixed-rate, and optimal rate adaptation are evaluated using the PDF expression. The FTRF channel is the best statistical model of fifth-generation millimeter-wave communication. A comparison of the capacity among the adaption schemes over the FTRF channel is also presented.

Effective Capacity of $L_p$ -Norm Diversity Receivers Over Generalized Fading Channels Under Adaptive Transmission Schemes

This paper presents novel moment generating function (MGF)- and characteristic function (CHF)-based frameworks for the EC performance analysis of a generic L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity combining scheme under adaptive transmission policies. The considered system operates over generalized fading channels, a maximum delay constraint and under various channel state information (CSI) conditions. Depending upon the operational CSI, four policies are studied, namely: i) Constant power with optimal rate adaptation (ORA); ii) Optimal power and rate adaptation (OPRA); iii) Channel inversion with fixed rate (CIFR); and iv) Truncated CIFR (TIFR). The L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity is a generic diversity structure which includes as special cases various well-known diversity schemes, such as equal gain combining (EGC), maximal ratio combining (MRC) and amplify-and-forward (AF) relaying. Under the ORA and OPRA policies, we derive single integral expressions for evaluating the EC of L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> -norm diversity reception directly from the MGF or the incomplete MGF of the Signal-to-Noise-Ratio (SNR) at the receiver, respectively. For the EC performance evaluation of the EGC and AF relaying systems operating under the OPRA policy, a CHF-based approach, which is computationally more efficient as compared to the MGF-based approach, is further presented. It is shown that the EC for the CIFR and TIFR policies can be directly evaluated from the MGF or the CHF of the SNR at the receiver, respectively. For the ORA policy, a novel analytical approach for the asymptotic EC performance analysis is also developed and evaluated, revealing how important system operation parameters affect the overall system performance. The mathematical formalism is validated with selected numerical and equivalent simulation performance evaluation results, thus confirming the correctness of the proposed analytical methodology.

Error probability and channel capacity analysis of wireless system over inverse gamma shadowed fading channel with selection diversity

SummaryIn this paper, we present an analytical framework to analyse the error probability and the channel capacity of the inverse gamma (I‐Gamma) shadowed fading channel. First, the work discusses the utility of the I‐Gamma over log‐normal (LN) and gamma fading models where the closeness of I‐Gamma with other existing shadowing models is carried out. Utilising the probability density function (PDF) of the I‐Gamma shadowed fading channel, various metrics of the communication system, namely, the average symbol error probability (SEP), the channel capacity under optimal rate adaptation (ORA), channel inversion with fixed rate (CIFR), and truncated CIFR (TIFR) are derived. Further, the work is extended to derive a novel selection combining (SC) PDF, and the analytical results for the SEP and the channel capacity of SC diversity are presented. Furthermore, we also provide simpler asymptotic expressions for the average SEP. In addition, the simplified high and low signal‐to‐noise‐ratio (SNR) solutions to channel capacity are also provided. The derived mathematical formulations have been endorsed by comparing with Monte Carlo simulations.

Comparison of adaptive algorithms for free space optical transmission in Málaga atmospheric turbulence channel with pointing errors

In this study, the authors investigate average capacity of free space optics communication over Málaga atmospheric turbulence channel with pointing errors and path loss, for intensity modulated/direct detection (IM/DD) and heterodyne detection. Various algorithms which use adaptive transmission with both types of detection are considered, such as: optimal rate adaption (ORA), optimal power and rate adaption (OPRA), channel inversion with fixed rate (CIFR) and truncated channel inversion with fixed rate (TIFR). Analytical closed-form expressions for channel capacities of ORA, OPRA and TIFR adaptive transmission are presented, and the authors prove that CIFR transmission is not feasible in the strict sense for the conditions considered. Obtained analytical results are numerically evaluated and graphically presented for different strengths of atmospheric turbulence (in weak, moderate and strong turbulence regime) for both types of detection (IM/DD and heterodyne), and for considered algorithms of adaptive transmission (ORA, OPRA and TIFR). The authors have developed expressions suitable for approximating high signal-to-noise ratio channel capacity, and they graphically present and compare the asymptotic approximations with the obtained analytical results for different strengths of turbulence for both types of detection. Also, obtained analytical results were confirmed by Monte-Carlo simulations, and graphically compared for different strengths of turbulence regimes.

Asymptotic capacity analysis under different adaptive transmission for TAS/MRC MIMO scheme subject to Weibull fading channels

This paper investigates a unified average channel capacity (ACC) analysis under different adaptive transmission of multiple-input multiple-output (MIMO) system, combining single transmit antenna selection (TAS) and maximal-ratio combining (MRC) receiver operating under independent flat Weibull multipath fading channels (WFCs). Based on a tight approximate probability density function expression of the signal-to-noise ratio (SNR) at the considered receiver output, we derive new accurate closed-form expressions of ACC for TAS/MRC system employing several rate adaptation techniques, namely optimal rate adaptation, optimal simultaneous power and rate adaptation, channel inversion with fixed rate (CIFR), truncated CIFR (TCIFR), and continuous power TCIFR (CTCIFR). Further, asymptotic expressions, in both high and low-SNR regimes, are investigated. The results show high accuracy for significant values of Lt×Lr TAS/MRC system. Indeed, the smaller Lt×Lr, the better the PDF’s accuracy, therefore, the better are the capacities. Numerical outcomes have been assessed by utilizing Mathematica and Matlab Software and corroborated via Monte-Carlo simulations.

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.

Different Power Adaption Methods on Fluctuating Two-Ray Fading Channels

In this letter, we consider a typical scenario where the transmitter employs different power adaption methods, including the optimal rate and power algorithm, optimal rate adaption, channel inversion and truncated channel inversion, to enhance the ergodic capacity (EC) with an average transmit power constraint over fluctuating two-way fading channels. In particular, we derive exact closed-form expressions for the EC under different power adaption methods, as well as corresponding asymptotic formulas for the EC valid in the high signal-to-noise ratio (SNR) region. Finally, we compare the performance of the EC under different power adaption methods, and this also validates the accuracy of our derived expressions for the exact and asymptotic EC.