Fast Rayleigh Fading Channels Research Articles

Bayesian iterative demodulation and decoding for LoRa modulation in fast Rayleigh fading channels

Bayesian iterative demodulation and decoding for LoRa modulation in fast Rayleigh fading channels

Reweighted Error Reducing Channel Estimator for QoS Enhancement in Wireless Nautical Radio Networks

Maritime explorations may suffer from unwanted situations such as delays, insecurity, congestions, and collisions, etc., which may arise from severe environmental conditions. Thus, there is a need to develop proper techniques that will improve the overall quality of service (QoS) of marine users. This work aims to address the limitations of wireless transmissions over maritime communication systems using channel estimation (CE) by designing and verifying the performances of two estimators named inter-symbol interference/average noise reduction (ISI/ANR) and reweighted error-reducing (RER) for aggrandizing the quality of nautical radio transmissions. To show that adopting accurate and stable CE methods can considerably increase the QoS requirements of marine networks, the performances of the proposed estimators are analysed in comparison to traditional methods under signal propagations assuming both line of sight (Rician) and Non-line of sight (Rayleigh) conditions. The adoption of a reweighting attractor in addition to the introduction of a variable leakage factor controlled log-sum penalty function to our proposed RER estimator provides additional stability for the estimation of oceanographic channels. Results obtained highlight that the proposed estimator demonstrates a performance gain of over 1 dB at a data rate of 100 bps under severe fading environments in comparison to the customary RLS technique. At an MSE of 10−2, the RER method under slow fading channels show a performance gain of about 1 dB when compared to the traditional RLS method while similarly showing superiority gain of about 0.6 dB over RLS method assuming fast fading Rayleigh channel conditions.

Rate Compatible Modulation for Non-Orthogonal Multiple Access

We propose a new Non-Orthogonal Multiple Access (NOMA) coding scheme based on the use of a Rate Compatible Modulation (RCM) encoder for each user. By properly designing the encoders and taking advantage of the additive nature of the Multiple Access Channel (MAC), the joint decoder from the inputs of all the users can be represented by a bipartite graph corresponding to a standard point-to-point RCM structure with certain constraints. Decoding is performed over this bipartite graph utilizing the sum-product algorithm. The proposed scheme allows the simultaneous transmission of a large number of uncorrelated users at high rates, while the decoding complexity is the same as that of standard point-to-point RCM schemes. When Rayleigh fast fading channels are considered, the BER vs SNR performance improves as the number of simultaneous users increases, as a result of the averaging effect.

Multiple relay‐based Reed–Muller network‐coded cooperation for wireless communication system

This research article proposes a multiple relay-based Reed–Muller network-coded cooperative (MR-RMNCC) scheme for wireless communication. In the MR-RMNCC scheme, Hadamard transform construction is adopted to build Reed–Muller (RM) codes that effectively achieve network coded-cooperation among multiple sources and multiple relays over slow and fast Rayleigh fading channels. In any network coded-cooperative system, a proper encoding strategy at the relay nodes is vital for achieving an optimum code construction at the destination node. Therefore, the authors have proposed an efficient message bit selection algorithm at relay-2 that optimally selects the message bits. The supremacy of the message bit selection algorithm is demonstrated by Monte–Carlo simulation. Furthermore, the performance bound for average error-probability is also derived for the MR-RMNCC scheme that validates its simulated bit-error-rate performance over a fast Rayleigh fading channel. At the destination node, the MR-RMNCC scheme is jointly decoded by two different decoding strategies, i.e. joint soft maximum likelihood decoding and joint majority logic decoding. Monte–Carlo simulations suggest that the MR-RMNCC scheme not only provides a significant bit-error-rate performance gain over its corresponding coded non-cooperative scheme but also to the existing state-of-the-art RM network-coded cooperative scheme under identical conditions.

A Novel Spatial CCK Modulation Design for Underwater Acoustic Communications

Underwater acoustic (UWA) channels exhibit double selectivity in both time and frequency domains, posing significant challenges to reliable UWA communications. This correspondence paper presents a novel spatial block coding scheme integrated with complementary code keying (CCK) modulation to exploit both spatial diversity and code diversity against doubly selective fading channels. The proposed spatial-CCK modulation utilizes multiple transmit transducers and extends the traditional CCK code set to improve receiver performance. We introduce novel code design criteria by considering maximum likelihood detection receivers under fast Rayleigh fading channel condition. Simulation and lake experiment results demonstrate substantial performance gain by the proposed spatial-CCK scheme over the conventional space–time codes without incurring additional high complexity cost for UWA channels.

Reed–Muller Network Coded-Cooperation With Joint Decoding

This letter proposes a Reed–Muller network coded-cooperative (RMNCC) scheme with the joint decoding. The Kronecker product (KP) construction is utilized to construct RM codes. The KP construction is effectively employed to accomplish network coded-cooperation between two users. An asymptotic error performance bound is presented to validate the average BER performance of the RMNCC scheme over fast Rayleigh fading channel. Monte Carlo simulated results for the RMNCC scheme agree with the analytical framework at higher SNR. Furthermore, a joint bit selection algorithm for the optimum selection of information bits at the relay node is also proposed, which results in an improved BER performance.

Turbo Coded OFDM Combined with MIMO Antennas Based on Matched Interleaver for Coded-Cooperative Wireless Communication

A turbo coded cooperative orthogonal frequency division multiplexing (OFDM) with multiple-input multiple-output (MIMO) antennas scheme is considered, and its performance over a fast Rayleigh fading channel is evaluated. The turbo coded OFDM incorporates MIMO (2 × 2) Alamouti space-time block code. The interleaver design, and its placement always plays a vital role in the performance of a turbo coded cooperation scheme. Therefore, a code-matched interleaver (CMI) is selected as an optimum choice of interleaver and is placed at the relay node. The performance of the CMI is evaluated in a turbo coded OFDM system over an additive white Gaussian noise (AWGN) channel. Moreover, the performance of the CMI is also evaluated in the turbo coded OFDM system with MIMO antennas over a fast Rayleigh fading channel. The modulation schemes chosen are Binary Phase shift keying (BPSK), Quadrature phase shift keying (QPSK) and 16-Quadrature amplitude modulation (16QAM). Soft-demodulators are employed along with joint iterative soft-input soft-output (SISO) turbo decoder at the destination node. Monte Carlo simulated results reveal that the turbo coded cooperative OFDM system with MIMO antennas scheme incorporates coding gain, diversity gain and cooperation gain successfully over the direct transmission scheme under identical conditions.

Progressive Pseudo-analog Transmission for Mobile Video Streaming

We propose a progressive pseudo-analog video transmission scheme that simultaneously handles SNR and bandwidth variations with graceful quality degradation for mobile video streaming. With the inherited SNR-adaptability from pseudo-analog transmission, the proposed progressive solution acquires bandwidth adaptability through an innovative scheduling algorithm with optimal power allocation. The basic idea is to aggressively transmit or retransmit important coefficients so that distortion is minimized at the receiver after each received packet. We derive the closed-form expression of reduced distortion for each packet under given transmission power and known channel conditions, and show that the optimal solution can be obtained with a water-filling algorithm. We also illustrate through analyses and simulations that a near-optimal solution can be found through approximation when only statistical channel information is available. Simulations show that our solution approaches the performance upper bound of pseudo-analog transmission in an additive white Gaussian noise channel and significantly outperforms existing pseudo-analog solutions in a fast Rayleigh fading channel. Trace-driven emulations are also carried out to demonstrate the advantage of the proposed solution over the state-of-the-art digital and pseudo-analog solutions under a real dramatically varying wireless environment.

Iterative Detection and Decoding Algorithms for MIMO Systems in Block-Fading Channels Using LDPC Codes

We propose iterative detection and decoding (IDD) algorithms with low-density parity-check (LDPC) codes for multiple-input multiple-output (MIMO) systems operating in block-fading and fast Rayleigh fading channels. Soft-input-soft-output minimum-mean-square-error (MMSE) receivers with successive interference cancellation are considered. In particular, we devise a novel strategy to improve the bit error rate (BER) performance of IDD schemes, which takes into account the soft a posteriori output of the decoder in a block-fading channel when root-check LDPC codes are used. A MIMO IDD receiver with soft information processing that exploits the code structure and the behavior of the log-likelihood ratios is also developed. Moreover, we present a scheduling algorithm for decoding LDPC codes in block-fading channels. Simulations show that the proposed techniques result in significant gains in terms of BER for both block-fading and fast-fading channels.

On the Ergodic Secret-Key Agreement Over Spatially Correlated Multiple-Antenna Channels With Public Discussion

We consider secret-key agreement with public discussion over multiple-input multiple-output (MIMO) Rayleigh fast-fading channels under correlated environment. We assume that transmit, legitimate receiver, and eavesdropper antennas are correlated. The legitimate receiver and the eavesdropper are assumed to have perfect channel knowledge while the transmitter has only knowledge of the correlation matrices. First, we derive the expression of the secret-key capacity under the considered setup. We prove that the optimal transmit strategy achieving the secret-key capacity consists in transmitting independent Gaussian signals along the eingenvectors of the transmit correlation matrix. The powers allocated to each channel mode are determined as the solution to a numerical optimization problem. A necessary and sufficient condition for beamforming (i.e., transmitting along the strongest channel mode) to be capacity-achieving is derived. Moreover, we analyze the impact of correlation matrices on the system performance. Finally, we study the system’s performance in the two extreme power regimes. In the high-power regime, we provide closed-form expressions of the gain/loss due to correlation. In the low signal-to-noise ratio (SNR) regime, we investigate the energy efficiency of the system by determining the minimum energy required for sharing a secret-key bit and the wideband slope while highlighting the impact of correlation matrices.

Design and Analysis of Bit-Interleaved Coded Modulation With Pseudorandom Sequence

In this paper, we design and analyze an improved bit-interleaved coded modulation (CM) scheme with a pseudorandom sequence (BICM-P). For the proposed scheme, the pseudorandom sequence is introduced into a systematic encoder at the transmitter and serves as side information at the receiver. With this design, the receiver can enjoy the benefit of increased Hamming distance when applying this side information at the receiver. In particular, we present a new constellation mapping principle to take advantage of the side information in the modulator, which leads to different signal constellations for the information bits and the parity-check bits. We then analytically derive the constellation-constrained capacity for BICM-P and quantify its gain as a nonlinear function associated with the two constellations. For the practical use of BICM-P, this paper indicates that the side information makes the regular low-density parity-check (LDPC) code irregular. Accordingly, the density evolution analysis tool is developed to design and optimize the regular LDPC code for BICM-P. The performance of LDPC-coded BICM-P on additive white Gaussian noise (AWGN) channels and fast Rayleigh fading channels is analyzed using extensive simulations. We observe that, at high code rates $(\geqslant \mbox{1}/\mbox{2})$ , LDPC-coded BICM-P has a substantial gain (0.1117–0.6558 dB) compared with LDPC-coded BICM on the AWGN channel. The performance gains will become more significant (0.7541–2.3481 dB) on the fast Rayleigh fading channel.

Performance Analysis of No Reference Image quality based on Human Perception

In this work, a No-Reference objective image quality assessment based on NRDPF-IQA metric and classification based metric are tested using LIVE database, which consisting of Gaussian white noise, Gaussian blur, Rayleigh fast fading channel, JPEG compressed images, JPEG2000 images. We plot the Spearman’s Rank Order Correlation Coefficient [SROCC] between each of these features and human DMOS from the LIVE-IQA database using our proposed method to ascertain how well the features correlate with human judgement quality. The analysis of the testing and training is done by SVM model. The proposed method shows better results compared with the earlier methods. Finally, the results are generated by using MATLAB. DOI: http://dx.doi.org/10.11591/ijece.v4i6.6783

Performance Analysis of PAPR and LS Estimation in OFDM Systems

The inherent feature of the highly efficient spectrum usage has made Orthogonal Frequency Division Multiplexing (OFDM) preferable for Communication Standards. This study evaluated the performance of a Least Square (LS) estimator for a comb-type pilot insertion scheme over a fast fading Rayleigh channel. A High Peak-to-Average Power Ratio (PAPR) is one of the major downsides of the OFDM. The effects of an increase in the number of subcarriers on PAPR and the performance of the LS Estimator were studied. Increasing the number of subcarriers while keeping the pilots overhead constant resulted in improved performance of the LS estimator but the PAPR increased with increasing number of subcarriers. Therefore some trade-off between the number of subcarriers and the performance of the OFDM system is needed. The Mean Square Error (MSE) expression was also derived for the LS estimator in the case of a comb-type pilot arrangement. The MSE expression clearly explains the effects of the number of subcarriers on the performance of the LS estimator.

PERFORMANCE ANALYSIS OF ML AND MMSE DECODING USING GRADIENT BASED ALGORITHM

Discrete-time all-analog-processing joint source-channel coding with Maximum Likelihood (ML) and Minimum Mean Square Error (MMSE) detections are employed in fast fading Rayleigh channel. Co-operative communication achieves spatial diversity using single antenna devices. Spatial diversity improves the performance of analog joint source-channel coding in wireless fading channels. In the case of discrete time processing signals ML decoding is unstable when compared to MMSE. Thus gradient based algorithm is proposed to reduce the complexity of the ML decoding. This algorithm quantizes the discrete processing signals into a continuous process. It also increases the capacity and cost of the channels thus making it suitable for the multiple input multiple output (MIMO) systems.

Modified MMSE Estimator based on Non-Linearly Spaced Pilots for OFDM Systems

This paper proposes a Modified Minimum Mean Square Error (M-MMSE) estimator for an Orthogonal Frequency Division Multiplexing (OFDM) System over fast fading Rayleigh channel. The proposed M-MMSE estimator considered the effects of the efficient placement of pilots based on the channel energy distribution. The pilot symbols were placed in a non-linear manner according to the density of the channel energy. Comparative analysis of the MMSE estimator for a comb-type pilot arrangement and M-MMSE estimator for the proposed pilot insertion scheme revealed significant performance improvement of the M-MMSE estimator over the MMSE estimator.

Performance Comparison of SER and SNR using different states of PSK in presence of various noises

To enhance the data rates of next generation wireless communication operating in frequency selective fading environments, the combination of orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) is proved to produce improved results. To analyze this combination, various changes in baseband signal processing are required which includes time and frequency synchronization, channel estimation and diversity gain. In this paper, a noise interference reduction technique for the improvement of high data rate in traditional space time coding technique (STTC) has been proposed. These codes generate the points of the constellation with the same probability. Therefore, the systematic search for good codes can be reduced to in this class. Finally, the performance of proposed techniques 2-state, 4-state and 16-state codes is evaluated by simulation and described by the Symbol Error Rate (SER) over fast Rayleigh fading channels with AWGN floor. Reduced noise based estimation schemes are widely favored as their implementation is relatively simple and most current wireless standards already provide for their use. Training sequences for multiple transmit antennas require properties of zero (or very low) cross correlation between sequences transmitted from different transmit antennas. Keywords: STTC; Symbol Error Rate; Signal to Noise Ratio; Orthogonal frequency division multiplexing.

Optimization of Power Allocation and Relay Placement for Decode-and-Forward ARQ Relaying

In this letter, we investigate the power allocation and relay placement for decode-and-forward (DF) automatic repeat request (ARQ) relaying over fast Rayleigh fading channels, where the channel gains are constant during each ARQ transmission round and change independently from round to round. Specifically, when the relay decodes correctly, the source and the relay send the Alamouti space-time block coded (STBC) signals to the destination. The maximum number of ARQ rounds is represented by L, and an outage event occurs when the destination decodes the packet unsuccessfully after L ARQ rounds. Based on these assumptions, we derive the asymptotically tight approximation of outage probability in the high signal-to-noise ratio (SNR) regime. Furthermore, three optimization problems are formulated to minimize the obtained asymptotic outage probability, namely, optimization of the power allocation at the source and the relay with fixed relay placement, optimization of the relay placement with fixed power allocation, and joint optimization of the power allocation and relay placement. It is shown that joint optimization obtains the best outage performance.

Non-Coherent Detection for Two-Way AF Cooperative Communications in Fast Rayleigh Fading Channels

Two-way cooperative communications are considered to improve the throughput of conventional one-way cooperative communications. For fast Rayleigh fading channels, we propose optimal and suboptimal non-coherent detectors for on-off keying (OOK) and frequency-shift keying (FSK) modulated two-way amplify-and-forward (AF) cooperative communications in this paper. In the proposed system, the relaying node combines the received signals from two nodes, amplifies them and retransmits the conjugate of the combined and amplified signals to the above-mentioned nodes. At the receivers of above-mentioned nodes, the optimal non-coherent detection is employed which is based on maximum likelihood rule. Since it involves integration operation, the optimal detector is simplified to a suboptimal detector which omits the real component of the relayed signal over the frequency which includes interference. The simulation results have shown that compared with the optimal detector, the proposed suboptimal detector reduces the receiver complexity at the expense of acceptable performance degradation. Furthermore, we have analytically studied the bit-error-rate performance upper and lower bounds of proposed non-coherent FSK modulated two-way AF cooperative communications.

Optimal Spectrum Sensing in Fast Fading Rayleigh Channel for Cognitive Radio

In this paper, we propose an optimal spectrum detector for fast fading Rayleigh channel when primary user pilot signal are known to the cognitive radio and the statistical properties of the fading channel either are known or can be estimated sufficiently accurate at cognitive radio. We also analyze the performance of the proposed detector by obtaining closed form expressions. Comparing with other detectors numerically shows the performance gain of our proposed detector.

Game-Theoretic Approach for Primary-Secondary User Power Control Under Fast Flat Fading Channels

Power control is an important concern in cognitive radio networks in which secondary users compete to access spectrum allocated to primary users. However, most existing studies have ignored the impact of primary users and only considered the interactions between secondary users. Hence in this study a realistic primary-secondary game-theoretic scheme is proposed in which primary users are rewarded for sharing their spectrum. The proposed model is analyzed for Rician and Rayleigh fast flat fading channels. In addition, closed-form expressions are also derived for the average utility functions and the existence of a unique Nash equilibrium is also shown. Finally, detailed simulation results are presented to verify the realistic performance of the scheme under those new channel conditions.