Maximum-ratio Combining/maximum-ratio Transmission Research Articles

Deep learning-based energy efficiency and power consumption modeling for optical massive MIMO systems

The fifth generation (5G) wireless communication system is considered a promising and recent research. Massive Multiple-Input Multiple-Output (MIMO) system has an influential role in improving game-changing enhancements in area throughput and energy efficiency (EE). EE refers to one of the easiest and most cost-effective ways to combat climate change, reduce energy costs for consumers, and improve the competitiveness of businesses. Deep Learning (DL) can significantly improve area throughput and EE. It plays a crucial role in the 5G wireless communication systems. Optical systems are not far from this system, which include the optical components which serve more accurately.To assess the overall power usage in up-link and down-link communications, a power dissipated model is introduced. The proposed model incorporates the overall power used by the base station (BS) power amplifier and circuit components as well as single antenna user equipment (UE). In this paper, EE and power consumption of massive MIMO systems are calculated based on Convolutional Neural Network hybrid with Long Short-Term Memory cell (CNNLSTM). This model is proposed to overcome the high complexity and over fitting by replacing the inner dense connections with convolution layers resulting in improved model performance. There are different linear processing schemes applied for detection and precoding, as Minimum Mean Squared Error (MMSE), Zero-Forcing (ZF), and Maximum Ratio Transmission/Maximum Ratio Combining (MRT/MRC). These schemes are applied to train our proposed CNNLSTM.It is observed the results are improved by 12.8% when using ZF (perfect CSI) and the system outperforms other schemes by 10%, 10.44% and 12.05% when using MRT, ZF (imperfect CSI), and MMSE, respectively, for the EE performance. The obtained results also reveal that an improvement of 7.5% is achieved when using MRT. It outperforms other schemes by 6.5%, 5% and 5%, respectively, when using ZF (perfect CSI), ZF (imperfect CSI), and MMSE for average power consumption per antenna using the CNNLSTM model. When using MRT, an improvement of 7.5% is achieved in the area throughput performance, and it outperformed the other schemes, ZF (perfect CSI), ZF (imperfect CSI) and MMSE, by 5.2%, 5% and 5.2%, respectively.

Analysis and Optimization of Massive Access to the IoT Relying on Multi-Pair Two-Way Massive MIMO Relay Systems

We investigate massive access in the Internet-of-Things (IoT) relying on multi-pair two-way amplify-and-forward (AF) relay systems using massive multiple-input multiple-output (MIMO). We utilize the approximate message passing (AMP) algorithm for joint device activity detection and channel estimation. Furthermore, we analyze the achievable rates for multiple pairs of active devices and derive the closed-form expressions for both maximum-ratio combining/maximum-ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT)-based beamforming schemes adopted at the relay. Moreover, to improve the achievable sum rates, we propose a low-complexity algorithm for optimizing the pilot length L. Our simulation results verify the accuracy of the closed-form expressions of the MRC/MRT and ZFR/ZFT scenarios. Finally, the proposed pilot-length optimization algorithm performs well in both the MRC/MRT and ZFR/ZFT scenarios.

Design and Analysis of Full-Duplex Massive Antenna Array Systems Based on Wireless Power Transfer

In this paper, we consider a wireless communication system, where a full-duplex hybrid access point (HAP) transmits to a set of cellular users (CUs) in the downlink channel, while receiving data from a set of energy-constrained communication devices like user equipments (UEs) in the uplink channel. The HAP has a massive antenna array, while all CUs and UEs nodes are equipped with single antenna each. Time switching protocol is adopted, where channel estimation, wireless power transfer, and information transfer between UEs, CUs and full-duplex HAP are performed in two phases. By adopting maximum ratio combining/maximum ratio transmission (MRC/MRT) and zero-forcing (ZF) processing at the HAP, the uplink and downlink achievable rate expressions in the large-antenna limit and approximate results that hold for any finite number of antennas are derived. Moreover, the optimum energy beamformer and time-split parameter at the HAP are found to maximize the downlink sum-rate under a constraint on uplink sum-rate. Our findings reveal that our proposed energy beamforming with ZF and MRC/MRT processing for information transfer achieves up to 47% and 14% average sum rate gains as compared with the suboptimum energy beamformer, respectively.

Massive MIMO Two-Way Relaying Systems With SWIPT in IoT Networks

In sixth-generation (6G) communication networks, ultrahigh-data rate and reliability are greatly vital for massive user connections and network sensors, such as Internet of Things (IoT) devices. Simultaneous wireless information and power transfer (SWIPT) has been evolved as an efficient strategy to enhance the reliability of wireless communication systems through prolonging the battery lifetime by harvesting energy from the received radio-frequency (RF) signals. Furthermore, cooperative relay sensors in IoT networks can extend the network coverage. In this article, we consider a massive multiple-input–multiple-output (MIMO) two-way relaying system, where the relay node splits the received RF signals into two power streams, one for information decoding (ID) and the other for energy harvesting (EH). Two classical and linear relay precodings, i.e., zero-forcing reception/zero-forcing transmission (ZFR/ZFT) and maximum-ratio combining/maximum-ratio transmission (MRC/MRT), are adopted to satisfy the requirements of high rate in this relay system. Different from prior work, the SWIPT technique and large-scale fading effects of MIMO channels are taken into account for deriving the asymptotic sum-rates of four prevalent power scaling cases when the number of relay antennas grows to infinity. Finally, the analytical results are evaluated by the presented simulation and numerical results.

Secrecy performance of massive MIMO relay‐aided downlink with multiuser transmission

In this study, the authors study secure multiuser transmission in a massive multiple-input multiple-output (MIMO) relaying system, where a base station sends its messages to multiusers via an amplify-and-forward relay station. Beamforming matrices of maximum ratio combining/maximum ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT) at relay are considered. The authors derive exact and asymptotic expressions for user rate and outage secrecy rate for a predetermined secure outage probability of eavesdropper links with channel state information imperfection. They have shown that ZFR/ZFT is a better choice than MRC/MRT from the perspectives of secrecy performance. Furthermore, the asymptotic analysis is proposed to show that almost the eavesdropper rates in all cases are degraded as a number of relay antennas goes to infinity, and simultaneously the transmit power at the base station and the relay can be scaled down significantly. Finally, numerical results provide more insightful validity of the proposed analysis.

Spectral- and Energy-Efficiency of Multi-Pair Two-Way Massive MIMO Relay Systems Experiencing Channel Aging

In this paper, we demonstrate the impact of channel aging on the spectral- and energy-efficiency performance of the multi-pair two-way massive MIMO relay (MTW-MMR) systems, where massive antennas are deployed at the relay and the amplify-and-forward (AF) protocol is operated. By assuming the maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing reception/ zero-forcing transmission (ZFR/ZFT) relaying processing, we analyze the spectral efficiency (SE) and energy efficiency (EE) of the MTW-MMR systems experiencing both imperfect channel estimation and channel aging based on the four proposed power-scaling schemes. Furthermore, we compare the performance of the full-duplex (FD)-assisted MTW-MMR systems with that of the half-duplex (HD)-assisted MTW-MMR systems, showing that the FD mode outperforms the HD mode with the interference level not exceeding −15 dB. Our studies show that channel aging may significantly degrade the achievable performance in terms of SE and EE. However, the inter-pair interference caused by the other user pairs and the self-interference can be effectively mitigated by the MRC/MRT processing or ZFR/ZFT processing at the relay.

Statistically Robust Beamforming Optimization for Multi-Antenna Full-Duplex DF Relaying

This paper studies robust beamforming optimization for full-duplex (FD) multi-antenna decode-and-forward (DF) relaying subject to stochastic channel state information (CSI) errors. By exploiting the statistics of CSI errors, we jointly optimize the receive and transmit beamformers of the FD relay to maximize the system achievable rate. Firstly, we prove that the original optimization problem can be equivalently transformed into a solvable convex feasibility check problem with second-order cone (SOC) constraints, whose globally optimal solution can be obtained in polynomial time. In order to reduce the computational complexity of the optimal beamforming, we further advocate a semi-closed form solution which achieves near-optimal performance. Afterwards, concerning a special case with spatially uncorrelated CSI errors, we develop a closed-form relay beamforming solution which reveals the optimality of the maximum ratio combining/maximum ratio transmission (MRC/MRT) strategy. Simulations are conducted to validate the effectiveness of the proposed robust FD relay beamforming designs.

Achievable rates for full-duplex massive MIMO systems with low-resolution ADCs/DACs under imperfect CSI environment

We investigate the uplink and downlink achievable rates of full-duplex (FD) massive multi-input multi-output (MIMO) systems with low-resolution analog-digital converters/digital-to-analog converters (ADCs/DACs), where maximum ratio combining/maximum ratio transmission (MRC/MRT) processing are adopted and imperfect channel state information (CSI) is assumed. In this paper, the quantization noise is encapsulated as an additive quantization noise model (AQNM). Then, employing the minimum mean-square error (MMSE) channel estimator, approximate expressions of the uplink and downlink achievable rates are derived, based on the analysis of the quantization error, loop interference (LI), and the inter-user interference (IUI). It is shown that the interference and noise can be eliminated by applying power scaling law properly and increasing the number of antennas. Moreover, given the number of antennas, it is found that the uplink and downlink approximate achievable rates will converge to a constant when the number of quantization bit tends to infinity. Therefore, the system performance that can be improved by increasing ADC/DAC resolution is limited, implying that it is reasonable to adopt low-resolution ADCs/DACs in FD massive MIMO systems.

Hybrid Processing Design for Multipair Massive MIMO Relaying With Channel Spatial Correlation

Massive multiple-input multiple-output (MIMO) avails of simple transceiver design which can tackle many drawbacks of relay systems in terms of complicated signal processing, latency, and noise amplification. However, the cost and circuit complexity of having one radio frequency (RF) chain dedicated to each antenna element are prohibitive in practice. In this paper, we address this critical issue in amplify-and-forward (AF) relay systems using a hybrid analog and digital (A/D) transceiver structure. More specifically, leveraging the channel long-term properties, we design the analog beamformer which aims to minimize the channel estimation error and remain invariant over a long timescale. Then, the beamforming is completed by simple digital signal processing, i.e., maximum ratio combining/maximum ratio transmission (MRC/MRT) or zero forcing (ZF) in the baseband domain. We present analytical bounds on the achievable spectral efficiency taking into account the spatial correlation and imperfect channel state information at the relay station. Our analytical results reveal that the hybrid A/D structure with ZF digital processor exploits spatial correlation and offers a higher spectral efficiency compared to the hybrid A/D structure with MRC/MRT scheme. Our numerical results show that the hybrid A/D beamforming design captures nearly 95% of the spectral efficiency of a fully digital AF relaying topology even by removing half of the RF chains. It is also shown that the hybrid A/D structure is robust to coarse quantization, and even with 2-bit resolution, the system can achieve more than 93% of the spectral efficiency offered by the same hybrid A/D topology with infinite resolution phase shifters.

Uplink/Downlink Rate Analysis and Impact of Power Allocation for Full-Duplex Cloud-RANs

This paper considers a cloud radio access network, where full-duplex (FD) users communicate with remote radio heads (RRHs) that are spatially distributed. We consider all participate RRH association (ARA) and single nearest RRH association (SRA) policies with optimal, maximum ratio combining/maximal ratio transmission (MRT), and zero-forcing/MRT (ZF/MRT) processing schemes and derive analytical expressions useful to compare the average uplink/downlink (UL/DL) sum rate among association schemes as a function of the number of RRHs antennas and UL/DL RRH density. We also study a dense network setting with multiple FD users and derive exact expressions for the average UL/DL rates, where a user-centric clustering technique is adopted and each user is served by its nearest UL and DL RRHs. Furthermore, by maximizing the instantaneous sum rate, we develop an optimum power allocation scheme for the single-user case. We observe that ARA results in a rate region that is strongly biased toward the UL or DL, but using SRA results in a more balanced rate region. Moreover, SRA policy with ZF/MRT processing achieves up to 32% and 42% average sum rate gains as compared with the HD SRA and FD ARA counterparts, respectively.

Power Scaling Laws of Massive MIMO Full-Duplex Relaying With Hardware Impairments

This paper considers a massive MIMO full-duplex relaying (FDR) system, in which multiple single-antenna sources simultaneously communicate with multiple single-antenna destinations using a single relay that is equipped with $N_{\mathrm {tx}}$ transmit antennas and $N_{\mathrm {rx}}$ receive antennas. Under the practical scenario of imperfect channel-state information, the relay processes the received signals by means of maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing (ZF) processing, and employs either the decode-and-forward (DF) or amplify-and-forward (AF) scheme. Considering hardware impairments, closed-form expressions of the lower bounds on the sum spectral efficiencies for DF and AF schemes are derived for both the MRC/MRT and ZF processing methods. Based on the obtained expressions, various power scaling laws are established to show the relationships among the transmit powers of the sources, relay, and pilots in order to maintain a desirable quality of service when $N_{\mathrm {tx}}$ and $N_{\mathrm {rx}}$ go to infinity but with a fixed ratio. In particular, it is found that the massive MIMO FDR systems under consideration are not affected by the loop interference, can save power, and improve the rate performance when the three transmit powers are scaled down to ${1/ {N_{\mathrm {rx}}^{a}}}$ , ${1 / {N_{\mathrm {tx}}^{b}}}$ , and ${1 / {N_{\mathrm {rx}}^{c}}}$ , respectively, where $a + c = 1$ , $b + c , and $b > 0$ . Numerical results corroborate the accuracy of the closed-form expressions and show that, when the loop interference level is small, using low-quality hardware at the relay and high-quality hardware at the sources and the destinations is a good design choice in the practical design of low-cost massive MIMO FDR systems.

Performance Analysis for Training-Based Multipair Two-Way Full-Duplex Relaying With Massive Antennas

This paper considers a multi-pair two-way amplify-and-forward relaying system, where multiple pairs of full-duplex users are served via a full-duplex relay with massive antennas, and the relay adopts maximum-ratio combining/maximum-ratio transmission (MRC/MRT) processing. The orthogonal pilot scheme and the least square method are firstly exploited to estimate the channel state information (CSI). When the number of relay antennas is finite, we derive an approximate sum rate expression which is shown to be a good predictor of the ergodic sum rate, especially in large number of antennas. Then the corresponding achievable rate expression is obtained by adopting another pilot scheme which estimates the composite CSI for each user pair to reduce the pilot overhead of channel estimation. We analyze the achievable rates of the two pilot schemes and then show the relative merits of the two methods. Furthermore, power allocation strategies for users and the relay are proposed based on sum rate maximization and max-min fairness criterion, respectively. Finally, numerical results verify the accuracy of the analytical results and show the performance gains achieved by the proposed power allocation.

On the energy/spectral efficiency of multi-user full-duplex massive MIMO systems with power control

In this paper, we consider a multi-user full-duplex (FD) massive multiple-input multiple-output (MIMO) system. The FD base station (BS) is equipped with large-scale antenna arrays, while each FD user is equipped with two antennas (one for transmission and the other one for reception). We assume that the channel state information (CSI) is imperfect, and no instantaneous CSI of loop interference (LI) channel is obtained. On the basis of low-complexity uplink beamforming and downlink precoding techniques, i.e. maximum-ratio combining/maximum-ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT), the asymptotic expressions of signal-to-interference-plus-noise ratio (SINR) of uplink and downlink are derived respectively when the number of antennas of the BS tends to infinity. Based on the asymptotic SINR expressions, we first analyse the spectral efficiency (SE) performance assuming that the generalized power scaling scenario is adopted. Through the theoretical derivation, it is shown that the detrimental impact of the LI can be eliminated by the very large number of antennas at the BS if the power scaling scenario is appropriately applied, as well as the interference caused by the imperfect channel estimation, the multi-user interference (MUI) and inter-user interference (IUI). Then, we propose power allocation (PA) scenarios to maximize the energy efficiency (EE) and the sum SE with the constraint of maximum powers at the BS and users. The simulation results verify the accuracy of the asymptotic method, we also validate the effectiveness of the EE and the sum SE maximization PA algorithms. We show that adopting the PA scheme to maximize the sum SE can make the multi-user FD massive MIMO system outperform the half-duplex (HD) counterpart regardless of the level of LI.

On the Energy Efficient Multiple Pair Communications in Two-Way Massive MIMO Relaying Networks with Imperfect CSI

Multiple-pair two-way communication in massive multiple-input multiple-output (MIMO) relay network is studied in this article wherein K single antenna source nodes exchange their messages to the corresponding K single antenna destination nodes with the help of one relay provisioned with N(N >> K) antenna array. And the energy efficient two-way multiple-pair communication in Massive MIMO relay network through the precoding design at relay is addressed. It is shown hat, even with the imperfect channel state information at the relay, the maximum ratio combining-maximum ratio transmission (MRC/MRT) precoding and the zero-forcing reception zero-forcing transmission (ZFR/ZFT) precoding at relay can be employed to mitigate inter-pair interference. The asymptotic signal to interference plus noise ratio (SINR) analysis of four power-scaling schemes in the regime of very large number of antenna at relay shows that, the inter-pair interference can be eliminated, the effect of the small-scale fading can be averaged out; the total transmit power consumption can be reduced for a better energy efficient multiple-pair communication when the number of antenna at relay is large enough. Moreover, when the transmit power at relay is sufficient, both the MRC/MRT and the ZFR/ZFT based relaying strategy can effectively cope with the channel state information (CSI) error. Simulation results are presented to validate our analysis.

Effect of low‐resolution ADCs and loop interference on multi‐user full‐duplex massive MIMO amplify‐and‐forward relaying systems

This paper focuses on a multi-user full-duplex massive multiple-input multiple-output amplify-and-forward relaying system with low-resolution analogue-to-digital convertors (ADCs). By modelling the loop-interference and quantisation noise as additive noise, we perform the analyses of the achievable spectral efficiency (SE) by considering the two canonical processing schemes, maximum ratio combining/maximal ratio transmission (MRC/MRT) and zero-forcing receive/zero-forcing transmission (ZFR/ZFT), respectively. Specially, we first obtain the tractable closed-form expressions of the achievable SE. Then, we present the asymptotic analyses under three different power-scaling scenarios. Comparison analysis shows that the low-resolution quantisers impose more performance loss on ZFR/ZFT schemes than MRC/MRT ones. At the same time, it is found that with different power-scaling schemes, the systems have different capabilities to restrict the effect of loop interference and low-resolution ADCs. Specially, the impact of both the loop-interference and quantisers on achievable SE can be restricted effectively only under the power-scaling scenario where the relay's transmission power is scaled down with the number of transmit antennas and the sources’ transmission power is fixed. For the power-scaling case where the transmission powers of both relay and sources are scaled down simultaneously with the number of antennas, only the effect of the loop interference can be restricted, but the one of low-resolution quantisers remains.

On the Spectral and Energy Efficiency of Full-Duplex Small-Cell Wireless Systems With Massive MIMO

The achievable rate of full-duplex (FD) small-cell systems with massive multiple-input multiple-output (MIMO), in which a low-power base station (BS) equipped with large antenna arrays sends/receives data to and from multiple half-duplex (HD) users at the same time on the same frequency, is investigated. The BS uses imperfect channel state information (CSI) obtained from received pilots, nonideal hardware, and a linear transmitter and receiver, i.e., zero-forcing (ZF) or maximum-ratio transmission/maximum-ratio combining (MRT/MRC), to process the signals. The approximate closed-form expressions of the achievable rate for both the ZF and MRT/MRC processing are derived and used to analyze the effect of the number of antennas and the hardware imperfection on the self-interference (SI), which is a bottleneck of the FD systems. To maximize the spectral efficiency (SE) and the energy efficiency (EE) of this system, two nonconvex power-allocation optimization problems are formulated and solved by utilizing the sequential convex approximation technique and the fractional programming technique. Two iterative algorithms are proposed with proved local convergence. Numerical results illustrate that the analytical approximation of achievable rate matches well with the Monte Carlo simulation. It is also shown that the ZF processing has greater ability to suppress SI, compared with MRT/MRC processing. The proposed power-allocation algorithms are shown to increase the SE and EE significantly, compared with the uniform power-allocation scheme when the BS is equipped with moderately large antenna arrays.

Power Allocation for Multi-Pair Massive MIMO Two-Way AF Relaying With Linear Processing

In this paper, we consider a multi-pair two-way amplify-and-forward relaying system where multiple sources exchange information via a relay node equipped with large-scale antenna arrays. Given that channel estimation is non-ideal, and that the relay employs either maximum-ratio combining/maximum-ratio transmission (MRC/MRT) or zero-forcing reception/zero-forcing transmission (ZFR/ZFT) beamforming, we derive two corresponding closed-form lower bound expressions for the ergodic achievable rate of each pair sources. The closed-form expressions enable us to design an optimal power allocation (OPA) scheme that maximizes the sum spectral efficiency under certain practical constraints. As the antenna array size tends to infinity and the signal-to-noise ratios become very large, asymptotically OPA schemes in simple closed-form are derived. The capacity lower bounds are verified to be accurate predictors of the system performance by simulations, and the proposed OPA outperforms equal power allocation (EPA). It is also found that in the asymptotic regime, when MRC/MRT is used at the relay and the link end-to-end large-scale fading factors among all pairs are equal, the optimal power allocated to a user is inverse to the large-scale fading factor of the channel from the user to the relay, while OPA approaches EPA when ZFR/ZFT is adopted.

Spectral and Energy Efficiency of Multipair Two-Way Full-Duplex Relay Systems With Massive MIMO

In this paper, we consider a multipair amplify-and-forward two-way relay channel, where multiple pairs of full-duplex users exchange information through a full-duplex relay with massive antennas. For improving the energy efficiency, four typical power-scaling schemes are proposed based on the maximum-ratio combining/maximum-ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT) at the relay. When the number of relay antennas tends to infinity, we quantify the asymptotic spectral efficiencies and energy efficiencies for the proposed power-scaling schemes. We show that the loop interference can be reduced by decreasing the transmit power under massive relay antennas. Besides, the inter-pair interference and inter-user interference in such systems can also be eliminated in large number of antennas. Moreover, we analytically compare the performance between MRC/MRT and ZFR/ZFT, and describe the impact of the number of user pairs on the spectral efficiency. We also evaluate the energy efficiency performance based on the practical power consumption model, and depict the impact of the relay antenna number on the energy efficiencies for the proposed schemes. Furthermore, we provide the available regions where full-duplex systems can outperform half-duplex systems. Finally, we show that the proposed schemes achieve good performance tradeoffs between the spectral efficiency and the energy efficiency.

Transceiver Optimization for Full-Duplex Massive MIMO AF Relaying With Direct Link

This paper focuses on the end-to-end signal-to-noise ratio (SNR) maximization for full-duplex massive multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay systems in the presence of direct link. First, we rigorously prove the asymptotic optimality of the maximum-ratio combining/maximum-ratio transmission (MRC/MRT) relaying strategy by taking into account the massive MIMO setup. Then, concerning the equivalent optimization problem with respect to source beamformer, we advocate a two-tier iterative algorithm relying on bi-section search, which guarantees a globally optimal solution. As a byproduct of this approach, we show that the optimal source beamformer has an interesting generalized channel matching structure associated with both source-relay and source-destination links. In addition to the optimal design, we devise a high SNR approximation-based suboptimal scheme, which admits a closed-form solution. Simulation results verify the advantage of our full-duplex relaying designs, and also demonstrate a negligible performance gap between the proposed optimal and suboptimal methods.

Wireless Information and Power Transfer in Relay Systems With Multiple Antennas and Interference

In this paper, an energy harvesting dual-hop relaying system without/with the presence of co-channel interference (CCI) is investigated. Specifically, the energy constrained multi-antenna relay node is powered by either the information signal of the source or via the signal receiving from both the source and interferer. In particular, we first study the outage probability and ergodic capacity of an interference free system, and then extend the analysis to an interfering environment. To exploit the benefit of multiple antennas, three different linear processing schemes are investigated, namely, 1) Maximum ratio combining/maximal ratio transmission (MRC/MRT), 2) Zero-forcing/MRT (ZF/MRT) and 3) Minimum mean-square error/MRT (MMSE/MRT). For all schemes, both the systems outage probability and ergodic capacity are studied, and the achievable diversity order is also presented. In addition, the optimal power splitting ratio minimizing the outage probability is characterized. Our results show that the implementation of multiple antennas increases the energy harvesting capability, hence, significantly improves the systems performance. Moreover, it is demonstrated that the CCI could be potentially exploited to substantially boost the performance, while the choice of a linear processing scheme plays a critical role in determining how much gain could be extracted from the CCI.