Vector Perturbation Channel Inversion forSWIPT MU-MISO Systems

in IEEE Wireless Communications Letters (2022)

This letter investigates the employment of vector-perturbation (VP) precoding to convey simultaneously informa-tion and energy in multiple-user multiple-input single-output(MU-MISO) downlink channel. We ... [more ▼]

This letter investigates the employment of vector-perturbation (VP) precoding to convey simultaneously informa-tion and energy in multiple-user multiple-input single-output(MU-MISO) downlink channel. We show that the conventionalVP in addition to the information capacity benefits that providesto linear channel inversion techniques, it enhances the harvestedenergy at the receivers due to the extended symbol constellation.To further boost harvesting performance, a modified VP tech-nique (named VP-EH) is proposed that designs the VP integeroffsets such as to maximize the delivered power. The proposedscheme incorporates an integer least square problem to find theclosest lattice point to a point which is given by a Rayleighquotient optimization problem. Finally, a convex combinationbetween conventional VP and VP-EH is proposed to achieve atrade-off between maximizing information or energy. Theoreticaland simulations results validate that VP is a promising techniqueto simultaneously convey information and energy in MU-MISOsystems. [less ▲]

RF Precoding for Cognitive Radio Systems

in IEEE Wireless Communications Letters (2022), 11(9), 1845-1849

In this letter, a precoding framework in the radio-frequency (RF) domain is developed for the downlink of a multiuser multiple-input single-output underlay cognitive radio (CR) system. Firstly, a low ... [more ▼]

In this letter, a precoding framework in the radio-frequency (RF) domain is developed for the downlink of a multiuser multiple-input single-output underlay cognitive radio (CR) system. Firstly, a low hardware complexity analog multiantenna architecture is proposed for the system’s transmitter. The proposed analog architecture is based on a phase-shifting network driven by an variable gain amplifier and has low power consumption since it avoids the use of energy hungry components such as digital-to-analog converters (DACs). Secondly, a novel RF precoder for the design of the transmit signals is developed such that the performance of the CR system is optimized and the constraints related to both the system’s architecture and the employed underlay CR paradigm are satisfied. The corresponding nonconvex and difficult optimization problem is formulated and solved via a novel algorithmic solution based on the saddle point method. The convergence of the proposed algorithmic solution is theoretically studied. The proposed approach is shown to be much more energy efficient than existing approaches based on fully digital transceivers. [less ▲]

Outage Performance of Satellite Terrestrial Full-DuplexRelaying Networks with Co-Channel Interference

in IEEE Wireless Communications Letters (2022), 11(7), 1478-1482

This letter investigates the performance of thesatellite-terrestrial networks (STN), where a satellite tries totransmit information to a ground user through the help of mul-tiple decode-and-forward relays ... [more ▼]

This letter investigates the performance of thesatellite-terrestrial networks (STN), where a satellite tries totransmit information to a ground user through the help of mul-tiple decode-and-forward relays and the existence of co-channelinterference sources. In particular, the full-duplex technique andpartial relay selection are applied at the relay to increase the totalthroughput at the destination, enhance the system reliability, andreduce the complexity. In this context, the outage probability (OP)is computed in a closed-form expression. Numerical results areprovided to confirm the accuracy of the proposed mathematicalframework. Our findings illustrate that the outage performancecan be effectively enhanced by increasing either number of relaysor transmit power. [less ▲]

Coverage Probability of STAR-RIS-Assisted Massive MIMO Systems With Correlation and Phase Errors

in IEEE Wireless Communications Letters (2022)

An Enhanced Spectrum Reservation Framework for Heterogeneous Users in CR-Enabled IoT Networks

in IEEE Wireless Communications Letters (2021)

Fulfilling the diverse communication requirements of heterogeneous users is envisioned to be one of the key challenges in cognitive radio-enabled IoT networks. To this end, we propose a novel scheme ... [more ▼]

Fulfilling the diverse communication requirements of heterogeneous users is envisioned to be one of the key challenges in cognitive radio-enabled IoT networks. To this end, we propose a novel scheme focused on multi-tier prioritized and heterogeneous regime of users and reservation-based resources allocation. The proposed scheme manipulates the secondary users’ (SUs’) heterogeneity based on their priorities for improving their capacities and blocking probabilities. Besides, the scheme systematically deals with SUs’ dropping for bringing fairness in the service provisioning to SUs. Furthermore, the scheme allows primary users (PUs) to follow an organized approach when accessing channels for mitigating the number of handoffs. Additionally, we propose a dynamic channel reservation algorithm for PUs to enhance spectrum utilization. We leverage the continuous-time Markov chain for system modeling and consider channel failures for making the analysis more realistic. Results confirm the effectiveness of our scheme as compared to the state-of-the-art. [less ▲]

Secure Transmission in Massive MIMO System with Specular Component-based Beamforming and Artificial Noise over Ricean Fading Channel

in IEEE Wireless Communications Letters (2021), 10(11, Nov. 2021),

This paper investigates the secure transmission in a multi-user massive MIMO system over Ricean fading channel in the presence of a multi-antenna eavesdropper. In order to reduce the system complexity and ... [more ▼]

This paper investigates the secure transmission in a multi-user massive MIMO system over Ricean fading channel in the presence of a multi-antenna eavesdropper. In order to reduce the system complexity and the channel estimation overhead, a low-complexity beamforming (BF) scheme using only the specular component is presented. Moreover, the generation of artificial noise (AN) is employed at the base station (BS) for additional security enhancement. Specifically, a tractable closedform lower bound for the achievable ergodic secrecy rate is derived. Furthermore, the optimal power allocation factor is obtained based on the asymptotic analysis to maximize the achievable ergodic secrecy rate. The analytical results reveal that the ergodic secrecy rate improves with the increase of Ricean K- factor and converges to a specific constant when increasing the number of antennas. The performance of the proposed scheme is evaluated through comprehensive simulations. [less ▲]

Coverage Probability of Distributed IRS Systems Under Spatially Correlated Channels

in IEEE Wireless Communications Letters (2021)

This paper suggests the use of multiple distributed intelligent reflecting surfaces (IRSs) towards a smarter control of the propagation environment. Notably, we also take into account the inevitable ... [more ▼]

This paper suggests the use of multiple distributed intelligent reflecting surfaces (IRSs) towards a smarter control of the propagation environment. Notably, we also take into account the inevitable correlated Rayleigh fading in IRS-assisted systems. In particular, in a single-input and single-output (SISO) system, we consider and compare two insightful scenarios, namely, a finite number of large IRSs and a large number of finite size IRSs to show which implementation method is more advantageous. In this direction, we derive the coverage probability in closed-form for both cases contingent on statistical channel state information (CSI) by using the deterministic equivalent (DE) analysis. Next, we obtain the optimal coverage probability. Among others, numerical results reveal that the addition of more surfaces outperforms the design scheme of adding more elements per surface. Moreover, in the case of uncorrelated Rayleigh fading, statistical CSI-based IRS systems do not allow the optimization of the coverage probability. [less ▲]

Coverage Probability of Double-IRS Assisted Communication Systems

in IEEE Wireless Communications Letters (2021), 10(8), 1722-1726

In this paper, we derive the coverage probability of a double-intelligent reflecting surface (IRS) assisted wireless network and study the impact of multiplicative beamforming gain and correlated Rayleigh ... [more ▼]

In this paper, we derive the coverage probability of a double-intelligent reflecting surface (IRS) assisted wireless network and study the impact of multiplicative beamforming gain and correlated Rayleigh fading. In particular, we derive a novel closed-form expression of the coverage probability of a single-input single-output (SISO) system assisted by two large IRSs while being dependent on the corresponding arbitrary reflecting beamforming matrices (RBMs) and large-scale statistics in terms of correlation matrices. Taking advantage of th large-scale statistics, we achieve to perform optimization of the RBM of both IRSs at every several coherence intervals rather at each interval. This property, based on statistical channel state information (CSI), is of paramount importance in multi-IRS assisted networks, which are accompanied with increased computational complexity during their RBM optimization. Numerical results validate the tightness of the analytical results even for small IRSs and reveal insightful properties. [less ▲]

Resource Allocation for Energy Efficiency in OFDMA-Enabled WPCN

in IEEE Wireless Communications Letters (2020), 9(12), 2049-2053

This letter considers a wireless powered communication network (WPCN), where an energy-constrained device directly uses harvested energy from a power transfer source to transmit independent signals to ... [more ▼]

This letter considers a wireless powered communication network (WPCN), where an energy-constrained device directly uses harvested energy from a power transfer source to transmit independent signals to multiple Internet of Things (IoT) users using orthogonal frequency division multiple access (OFDMA). Our goal is to maximize the system energy efficiency (EE) by jointly optimizing the duration of energy harvesting (EH), subcarrier and power allocation. The formulated problem is a mixed integer nonlinear programming (MINLP) problem due to the presence of binary assignment variables, and thus it is very challenging to solve it directly. By leveraging Dinkelbach method, a very efficient iterative algorithm with closed-form solutions in each iteration is developed, where its convergence is guaranteed. Numerical results show that the proposed algorithm obtains a fast convergence and outperforms baseline algorithms. Notably, they also reveal that the power source should transmit its maximum allowable power to obtain the optimal EE performance. [less ▲]

Deep Channel Learning For Large Intelligent Surfaces Aided mm-Wave Massive MIMO Systems

in IEEE Wireless Communications Letters (2020), 9(Sept. 2020), 1447-1451

This letter presents the first work introducing a deep learning (DL) framework for channel estimation in large intelligent surface (LIS) assisted massive MIMO (multiple-input multiple-output) systems. A ... [more ▼]

This letter presents the first work introducing a deep learning (DL) framework for channel estimation in large intelligent surface (LIS) assisted massive MIMO (multiple-input multiple-output) systems. A twin convolutional neural network (CNN) architecture is designed and it is fed with the received pilot signals to estimate both direct and cascaded channels. In a multi-user scenario, each user has access to the CNN to estimate its own channel. The performance of the proposed DL approach is evaluated and compared with state-of-the-art DL-based techniques and its superior performance is demonstrated. [less ▲]