Maximal Ratio Combining Research Articles

Use of NOMA for maritime communication networks with P-DF relaying channel

In this paper, a partial de-code-and-forward (P-DF) cooperative relaying network (CRN) with non-orthogonal multiple access (P-DF-CRN-NOMA) for maritime space communications is proposed. Without loss of generality, three kinds of relay forwarding protocols are studied to characterize the superiority of the proposed P-DF-CRN-NOMA scheme, where, after receptions from the coastal base station (BS), the island relay forwards the successful decoded symbols to the ship user to avoid the performance loss provided by the high decoding requirement in decode-and-forward (DF). To further improve the system performance, as well as for a fairness comparison, the maximum ratio combining (MRC) is utilized at the ship user. Specifically, to present the impact of the channel qualities, the scenarios of the weak and strong links that from the source to destination (S-D) are both considered. The closed-form expressions for the outage probability of the P-DF-CRN-NOMA are derived considering the three proposed forwarding cases. Qualitative numerical results corroborating our theoretical analysis, especially for the high signal-to-noise ratio (SNR), show that the proposed P-DF-CRN-NOMA scheme significantly improves the outage probability performance in comparison to the conventional CRN-NOMA schemes. Furthermore, for an increased S-D link, the corresponding outage probability performance will be also better for all the cases.

On the energy detection performance of multi‐antenna correlated receiver for vehicular communication using MGF approach

In this work, energy detection-based spectrum sensing for multiple antenna receiver under the effect of mobility is investigated by considering L number of correlated antenna branches. The authors consider the uniform, exponential and arbitrarily correlation among the antenna branches based on the spacing between them. The moment generating function (MGF) approach is applied to obtain the statistical knowledge of the received signal to noise ratio because the Laplace domain behaviour will help to derive the closed-form expressions using simple algebraic operations. They derived the closed-form expressions for the detection probability over Nakagami-m fading, in terms of Lauricella and Confluent Hypergeometric function for maximal ratio combining (MRC) and equal gain combining (EGC) diversity techniques under the effect of vehicle mobility. Monte-Carlo simulation is carried out to validate the derived analytical expressions. The results show that the degradation in detection performance due to fading correlation can be reduced by choosing the appropriate diversity scheme and by increasing the number of antennas. Furthermore, they also found that at high fading parameter ( m = 4 ) value, the low value of the probability of false alarm and highly correlated fading, MRC works better than EGC for high relative velocity.

Jointly designed quasi-cyclic LDPC-coded cooperation with diversity combining at receiver

This correspondence proposes a jointly-designed quasi-cyclic (QC) low-density parity-check (LDPC)-coded multi-relay cooperation with a destination node realized by multiple receive antennas. First, a deterministic approach is utilized to construct different classes of binary QC-LDPC codes with no length-4 cycles. Existing methods put some limitations in terms of code length and rate in order to provide high error-correction performance. Therefore, this article gives three classes of QC-LDPC codes based on a combinatoric design approach, known as cyclic difference packing (CDP), with flexibility in terms of code-length and rate selection. Second, the proposed CDP-based construction is utilized to jointly-design QC-LDPC codes for coded-relay cooperation. At the receiver, the destination node is realized by multiple receive antennas, where maximal-ratio combining (MRC) and sum-product algorithm (SPA)-based joint iterative decoding are utilized to decode the corrupted sequences coming from the source and relay nodes. Simulation results show that the proposed QC-LDPC coded-relay cooperations outperform their counterparts with a coding gain of about 0.25 dB at bit-error rate (BER) [Formula: see text] over a Rayleigh fading channel in the presence of additive white Gaussian noise. Furthermore, the extrinsic-information transfer (EXIT) chart analysis has been used to detect the convergence threshold of proposed jointly-designed QC-LDPC codes. Numerical analysis shows that the proposed jointly-designed QC-LDPC codes provide a better convergence as compared to their counterparts under the same conditions.

A New Hybrid Diversity Combining Scheme for Mobile Radio Communication Systems over Nakagami Fading Chanel

Diversity combining is a technique in wireless network that uses multiple antenna system to improve the quality of radio signal. Mobile radio system suffers multipath propagation due to signal obstruction in the channel. A new hybridized diversity combining scheme consisting of Equal Gain Combining (EGC) and Maximal Ratio Combining (MRC) was proposed in this paper. Theperformance of the hybrid model was evaluated using Outage Probability (Pout) and Processing time (Pt) at different Signal-to-Noise Ratio (SNR) and Signal Paths (L=2,3) for 4-QAM and 8-QAM Modulation Schemes. A mathematical expression for the hybrid EGC-MRC was realized using the Probability Density Function (PDF) of the Nakagami fading channel. MATLAB R2015b software was used for the model simulation. The result shows that hybrid EGC-MRC outperforms the standalone EGC and MRC schemes by having lower Pout and Pt values. Hence, hybrid EGC-MRC exhibits enhanced potentials to mitigate multipath propagation at reduced system complexity.

PERFORMANCE ANALYSIS AND EVALUATION OF MASSIVE MIMO SYSTEM

This article examines the performance of massive MIMO uplink system over Rician fading channel. The performance is estimated regarding spectral efficiency versus number of base station antennas utilizing three plans of linear detection, maximum-ratio-combining (MRC), zero forcing receiver (ZF), and minimum mean-square error receiver (MMSE). The simulation results reveal that the spectral efficiency increments altogether with expanding the quantity of base station antennas. Additionally, the spectral efficiency with MMSE is superior to that with ZF, and the last is superior to that with MRC. Furthermore, the spectral efficiency diminishes with expanding the fading parameter.

Hybrid Power Line/Wireless Systems: An Optimal Power Allocation Perspective

This paper investigates optimal power allocation in hybrid power line/wireless systems (HPWS). By adopting maximal-ratio combining (MRC) for the signals received from different channels, power allocation problems under sum power and sum power-channel constraints are formulated. These power constraints impose distinct bounds on the transmission power and, as a consequence, constitute different optimization problems. Therefore, two power allocation algorithms, which aim to maximize the achievable data rate in HPWS, are obtained. Furthermore, mathematical analyses show that data communication must employ only one medium per subchannel as the sum power constraint and frequency-selective channels are taken into account. Also, with high probability, the sum power-channel constraint results in the same conclusion with respect to the sole use of one medium per subchannel when the channels are frequency selective. In other words, MRC and selection-combining yield the same performance in terms of achievable data rate. Numerical analyses evaluate the proposed power allocation algorithms for exploiting the diversity between power line and wireless media by comparing them to alternative algorithms reported in the literature, especially when the total transmission power belongs to a practical range, and the attained results confirm their effectiveness and validate their usage in practical scenarios.

Analysis of Uplink Cell-Free Massive MIMO System With Mixed-ADC/DAC Receiver

A generalized uplink cell-free massive multi-input multi-output (MIMO) system assuming access points (APs) are paired with mixed-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) is investigated in this article. Specifically, the mixed-ADC/DAC architecture sacrifices part of performance gains and advocates a few low-precision ADCs/DACs to reduce the power consumption. Based on this antenna structure, we derive closed-form achievable rate expressions for maximal ratio combining (MRC) receiver filters by drawing support from the additive quantization noise model (AQNM) and analyze the impacts of the key design parameters, i.e., the number of total antenna arrays, the precision of coarse ADCs/DACs, the proportion of ideal ADCs/DACs in the mixed ADCs/DACs structure, and the power control strategy. In addition, the energy efficiency (EE) of the considered mixed-ADC/DAC architecture is also explored by recalling a generic power consumption model. Aside from this, to guarantee uniformly good service wherever users are geographically located, a max–min fairness power optimization algorithm is proposed, which can be determined by solving a geometric programming problem. Numerical simulations validate our theoretical analyses and examine the effectiveness of the proposed algorithm.

Performance Analysis of Cognitive Relay-Assisted Ambient Backscatter with MRC over Nakagami-m Fading Channels

This study presents ambient backscatter communication (AmBC) network as a concept of "modulation in the air" that has drawn growing interest by both academia and industry recently. In particular, we investigate and analyze an AmBC system relying on cognitive radio, where the primary destination is equipped with multiple antennas and maximum ratio combining (MRC). A wireless powered relay is necessary to serve both primary and secondary destinations. Benefiting from the surrounding radio frequency (RF) source, the relay can support the backscattering signal. To facilitate the performance analysis of received nodes, this study presents exact closed-form expressions of the outage probability. For comparison, the outage and throughput performance of these nodes are considered in numerical simulation. Taking advantage of the AmBC technology, the impact of the backscatter ratio on system performance is carefully studied considering various other parameters. Simulation results demonstrate the exactness of the derived outage probabilities and show that the optimal throughput performance can be achieved at specific parameters.

Performance improvement of space diversity technique using space time block coding for time varying channels in wireless environment

Performance improvement of space diversity technique using space time block coding for time varying channels in wireless environment

Adaptive time-switching and power-Splitting protocols for energy harvesting sensor networks with multiple relays

In the conventional energy-harvesting (EH) relaying protocols based on time switching (TS) and power splitting (PS), the system performance depends on the parameters such as TS and PS ratios. In order to achieve the optimum performance, these parameters need to be optimized. In the distributed cooperative networks, where relay operates independently, the optimization of PS and TS ratios becomes cumbersome and challenging. In this work, we overcome this issue by proposing two relaying protocols referred to as adaptive time-switching (ATS) and adaptive time-switching adaptive power-splitting (ATS-APS) protocols. In the proposed protocols, the relay can dynamically optimize their respective TS and PS ratios according to their local channel condition among relays, i.e., without any external help from the source or destination, which makes the proposed protocols promising for the distributed relaying network. Through rigorous numerical analysis, we show that the proposed protocols can outperform the conventional approach. We also derive mathematical expressions for the outage probability and the effective transmission rate in the framework of decode-and-forward (DF) relaying with partial relay selection (PRS) scheme based on various diversity combining techniques including maximum ratio combining (MRC), selection combining (SC), and selective relaying (SR). Through numerical analysis, we demonstrate that the proposed adaptive SR technique, where the source receives assistance from the relay only if the source-to-destination link is in deep fading, can achieve better performance than the other techniques compared here in terms of the achievable effective transmission rate. All the theoretical results developed are confirmed by numerical simulations.

Interpretation of AF-DF protocols for FitureMulti Layer-IDMA

In this article, we investigate the bit error rate (BER) performance in a cooperative relay communication system for multilateral IDMA (ML-IDMA) using the maximum ratio combination (MRC) technique. ). ). We investigate the effect of the number of lines on performance and find the average error rate in bits of the AF relay scheme (Amplify and Forward) using the signal-to-noise ratio (SNR) of the relay connection in closed form. The proposed system for evaluating ML-IDMA performance is provided with a different number of layers and a different number of relays in an ML-IDMA cooperative environment. The simulation results show that the BER performance of a 4-relay IDMA double layer system (K = 2) is approximately 4 dB. In addition, the bandwidth saving is 50%. Ultimately, BER performance deteriorates as the number of layers increases and the proposed system increases bandwidth by approximately 1/K.

Fairness-Aware Intragroup Cooperative Transmission in Wireless Powered Communication Networks

This article investigates fairness-aware transmission in a wireless powered communication network (WPCN), in which a group of adjacent users receive radio frequency energy and then cooperatively transmit information to a remote access point (AP) by using the harvested energy with time division multiple access (TDMA) scheme. Considering the constraints of practical energy harvesting electric circuits, a non-linear energy harvesting model is adopted in this paper. To guarantee both throughput fairness and signal-to-noise-ratio (SNR) fairness among users in the group, we propose a cooperative transmission protocol which contains three phases: wireless energy transmission (WET) phase, single information transmission phase and cooperative information transmission phase. Each user harvests wireless energy in WET phase, and then divides the harvested energy into two parts to be used in the rest two phases. In single information transmission phase, each user broadcasts its information to the AP and all the other users. In cooperative information transmission phase, all the users transmit information jointly to the AP. At the AP, the same signals in cooperative information transmission phase are combined with these in single information transmission phase by using maximum ratio combining (MRC) method. The common SNR of the received signals at the AP from all the users is achieved in both single information transmission phase and cooperative information transmission phase. Furthermore, the throughput fairness is achieved by common SNR and equal time allocation for information transmission at each user. Besides, we optimize the max-min throughput by joint WET time and harvested energy allocation. The optimal time allocation ratio and harvested energy allocation ratio are derived in closed forms. The cooperative diversity gain is achieved and numerical results demonstrate that the proposed protocol has low complexity and high reliability. Moreover, it also achieves a higher minimum throughput and is more energy-efficient in harsh transmission condition than other transmission protocols in the literature.

Spectral Efficiency of One-Bit Sigma-Delta Massive MIMO

We examine the uplink spectral efficiency of a massive MIMO base station employing a one-bit Sigma-Delta sampling scheme implemented in the spatial rather than the temporal domain. Using spatial rather than temporal oversampling, and feedback of the quantization error between adjacent antennas, the method shapes the spatial spectrum of the quantization noise away from an angular sector where the signals of interest are assumed to lie. It is shown that, while a direct Bussgang analysis of the Sigma-Delta approach is not suitable, an alternative equivalent linear model can be formulated to facilitate an analysis of the system performance. The theoretical properties of the spatial quantization noise power spectrum are derived for the Sigma-Delta array, as well as an expression for the spectral efficiency of maximum ratio combining (MRC). Simulations verify the theoretical results and illustrate the significant performance gains offered by the Sigma-Delta approach for both MRC and zero-forcing receivers.

Performance Analysis in Double-Rayleigh Channels with Diversity Combining Techniques

In this paper, we provide a performance analysis of communication systems over Rayleigh-product channels with two popular diversity combining techniques, namely maximal ratio combining (MRC) and selection combining (SC). We first derive new closed-form expressions for the exact cumulative distribution function (CDF) and probability density function (PDF) of the post-processing signal-to-noise ratio (SNR) for these two schemes. Secondly, we present the first-order asymptotic expansions for these CDF and PDF functions. Performance of MRC and SC techniques, in terms of outage probability, average symbol error rate (SER) and ergodic capacity, is derived using the exact expressions of CDF and PDF. Furthermore, we present new expressions for key metrics characterizing the system performance at the high and low SNR regimes. Thanks to the asymptotic CDF and PDF expressions, we compute the average SER in the high SNR regime and derive the diversity order and array gain parameters. In addition, we provide simple expressions for the ergodic capacity in the asymptotic low and high SNR regimes. Monte-Carlo simulations are conducted and their results agree well with the analytical results.

Security Enhancement via Antenna Selection in MIMOME Channels With Discrete Inputs

Transmit antenna selection (TAS) is an emerging technology in physical layer security. To provide new insights into the achievable secrecy performance of TAS in practical communication systems, this paper investigates the average secrecy rate (ASR) and secrecy outage probability (SOP) under practical modulation schemes in TAS aided multiple-input multiple-output multiple-antenna eavesdropper (MIMOME) wiretap channels over Rayleigh fading. Particularly, this research concentrates more on the square $M$ -ary quadrature amplitude modulation ( $M$ -QAM). Furthermore, in the considered MIMOME channel, a single antenna is selected to transmit the secret message, and selection combining (SC) or maximal-ratio combining (MRC) is utilized at the legitimate receiver and the eavesdropper. Based on this system model, novel expressions for the ASR and SOP are formulated to characterize the secrecy performance of the finite-alphabet driven MIMOME channel. Besides exact analysis, an asymptotic analysis is performed using the considered performance metrics in high signal-to-noise ratio (SNR) regime. Theoretical analyses suggest that the asymptotic ASR and SOP converge to finite constants in high SNR regime due to the discrete constellation constraint, and we find that the asymptotic behaviour of discrete inputs differs from that of Gaussian inputs. Furthermore, we derive concise expressions to characterize the rate of convergence (ROC) of the ASR and SOP, respectively. To unveil more system design insights, we discuss the relationship between the ROC and several important system parameters such as the antenna number and the modulation order.

Analysis of MRT/MRC diversity techniques to enhance the detection performance for MIMO signals in full-duplex wireless relay networks with transceiver hardware impairment

In this paper, we investigate the detection performance for MIMO signals in a wireless full-duplex (FD) relaying network, in which the diversity techniques, including maximal ratio transmission (MRT) at source and maximal ratio combining (MRC) at destination, are applied. Especially, we rigorously study the impact of hardware impairment (HI) at all nodes and the residual self-interference (RSI) at the FD relay (FDR), which have not mentioned in previous works. Here, the closed-form expressions of key performance factors such as outage probability (OP), throughput, and symbol error rate (SER) of the considered MIMO-FDR system with HI are derived mathematically. All analytical expressions are validated by Monte Carlo simulations. Numerical results demonstrate a strong impact of HI on OP, throughput, and SER of the MIMO-FDR system in comparison with the ideal (ID) MIMO-FDR system, especially at high data rate. The combination of HI and RSI prevents OP and SER of the MIMO-FDR system from going lower than some error floors even at high signal-to-noise ratio (SNR) regime. However, by using MRT/MRC techniques with larger number of transmit antennas at source than the number of receive antennas at destination, the OP and SER performance in HI condition can be significantly improved.

Secrecy outage analysis of imperfect MRC in SWIPT systems with a random eavesdropper

In this paper, we investigate the secrecy performance of simultaneous wireless information and power transfer (SWIPT) systems in terms of the secrecy outage probability (SOP), where multi-antenna diversity is employed to combat deep fading. In this investigated system, there are three nodes, namely, a source, a destination and an eavesdropper, and the destination and the eavesdropper are equipped with multiple antennas and adopt a maximal ratio combining (MRC) strategy. To reflect real-world conditions, MRC with Gaussian errors is also considered due to the imperfect channel state estimation. The eavesdropper, which is randomly distributed within a 2-dimensional disk area, harvests energy from the transmitted signals from the source to the destination and wiretaps the information from the received signals by using an energy-splitting strategy. Furthermore, we derive the closed-form expression of the SOP, along with the corresponding asymptotic SOP, to show the diversity order and array gain in the high signal-to-noise ratio region of the source−destination link. To obtain some valuable insights, we also perform some extensions in the case of perfect channel state estimation, including for large-scale antenna analysis, reliability–security tradeoff, multiple eavesdroppers and random locations modeled by a Gaussian distribution. Monte-Carlo simulations are presented to validate the correctness of our derived expressions.

Low Complexity Angular-Domain Detection for the Uplink of Multi-User mmWave Massive MIMO Systems

To compromise between the system performance and hardware cost, millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems have been regarded as an enabling technology for the fifth generation of mobile communication systems (5G). This paper considers a low-complexity angular-domain compressing based detection (ACD) for uplink multi-user mmWave massive MIMO systems, which involves hybrid analog and digital processing. In analog processing, we perform angular-domain compression on the received signal by exploiting the sparsity of the mmWave channel to reduce the dimension of the signal space. In digital processing, the proposed ACD scheme works well with zero forcing (ZF)/maximum ratio combining (MRC)/minimum mean square error (MMSE) detection schemes. The performance analysis of the proposed ACD scheme is provided in terms of achievable rates, energy efficiency and computational complexity. Simulations are carried out and it shows that compared with existing works, the proposed ACD scheme not only reduces the computational complexity by more than 50 % , but also improves the system’s achievable rates and energy efficiency.

Cooperative maximum-ratio transmission with multi-antenna relay nodes for tactical mobile ad-hoc networks

Abstract In this paper, we propose a cooperative maximum-ratio transmission (C-MRT) technique with multi-antenna relay nodes for tactical mobile ad-hoc networks (MANETs) where both the location and the number of antennas of relay nodes are arbitrary. Each relay node is assumed to know both the wireless channel coefficient from the source node to itself and the wireless channel from itself to the destination node, which is known as local channel state information (CSI) assumption. Maximum-ratio combining (MRC) and MRT techniques are used for beamforming the transmit and receive signals of the relay node, respectively. In addition, we mathematically analyze the overall outage probability of the proposed technique with moment generating function (MGF). It is shown that the mathematical analysis on the overall outage probability of the proposed C-MRT technique is matched well with the simulation results especially in high transmit power regimes. It is also observed that the proposed technique outperforms other schemes such as phase steering (PS) and optimal relay selection (ORS) in terms of outage probability.

Joint Pilot and Payload Power Allocation for Massive-MIMO-Enabled URLLC IIoT Networks

The Fourth Industrial Revolution (Industrial 4.0) is coming, and this revolution will fundamentally enhance the way the factories manufacture products. The conventional wired lines connecting central controller to robots or actuators will be replaced by wireless communication networks due to its low cost of maintenance and high deployment flexibility. However, some critical industrial applications require ultra-high reliability and low latency communication (URLLC). In this paper, we advocate the adoption of massive multiple-input multiple output (MIMO) to support the wireless transmission for industrial applications as it can provide deterministic communications similar as wired lines thanks to its channel hardening effects. To reduce the latency, the channel blocklength for packet transmission is finite, and suffers from transmission rate degradation and decoding error probability. Thus, conventional resource allocation for massive MIMO transmission based on Shannon capacity assuming the infinite channel blocklength is no longer optimal. We first derive the closed-form expression of lower bound (LB) of achievable uplink data rate for massive MIMO system with imperfect channel state information (CSI) for both maximum-ratio combining (MRC) and zero-forcing (ZF) receivers. Then, we propose novel low-complexity algorithms to solve the achievable data rate maximization problems by jointly optimizing the pilot and payload transmission power for both MRC and ZF. Simulation results confirm the rapid convergence speed and performance advantage over the existing benchmark algorithms.