# Advanced Physical-Layer Technologies for Beyond 5G Wireless Communication Networks
## 3 Brief Review of Technical Papers
Evolutionary algorithms for the joint computation of RF/digital precoders increase the SE of a partially connected hybrid precoding architecture. The paper titled Evolutionary-Algorithm-Based Capacity Maximization of 5G/B5G Hybrid Precoding Systems [17] considered the problem of spectrally efficient precoder design and presented an evolutionary-algorithm-based hybrid precoding strategy for partially connected antenna arrays in mmWave-massive MIMO systems. The proposed artificial bee-colony-based precoding scheme provided the highest achievable rates and outperformed benchmark evolutionary algorithms in terms of SE. The 5G IoT-enabled smart-home environment detects human activities by manipulating data collected from numerous sensors and using appropriate deep-learning algorithms. The detection of expected or unexpected behavior events indicating human activity is a challenging task in the activity-detection paradigm. In addition, sensor energy resources are continuously depleted for the ubiquitous and extensive monitoring of activities. The paper titled Scheduling Sensor Duty Cycling Based on Event Detection Using Bidirectional Long Short-Term Memory and Reinforcement Learning [18] presented an energy- and event-aware sensor duty cycling (EEA-SDC) scheme. In the proposed scheme, the event of a resident's activities in a smart home was modeled as a time-sequence information problem, and the bidirectional long short-term memory (LSTM) model was used to predict expected future events and allocate the predictive sensors. Moreover, a monitor sensor within a cluster of hibernate sensors using the Jaccard similarity index was used to detect the unexpected events. The performance of the proposed scheme was optimized by employing a Q-learning algorithm by tracking missed or undetected events. Different users in multiuser 5G MIMO networks can experience distinct spatial channel correlations. The paper titled Statistical Beamforming for Massive MIMO Systems with Distinct Spatial Correlations [19] presented a novel statistical beamforming (SBF) method called partial-nulling-based SBF (PN-SBF) to serve several users experiencing distinct spatial channel correlations. The massive MIMO system with the two user groups was considered, i.e., the first group experienced low spatial channel correlation, and the second group experienced high spatial channel correlation. A prebeamforming matrix based on the zero-forcing-based design principle was constructed to eliminate intergroup interference from the low- to the high-correlation group. Furthermore, postbeamforming vectors were designed to maximize the signal-to-leakage-and-noise ratio to solve intragroup interference. Simulation results indicated that the proposed PN-SBF scheme performed better than conventional SBF schemes did in terms of the ergodic sum rate in a massive MIMO system with distinct spatial correlations. RF energy harvesting is a promising solution for EE in 5G systems [20]. In the paper titled Outage Probability and Ergodic Capacity of a Two-User NOMA Relaying System with an Energy Harvesting Full-Duplex Relay and Its Interference at the Near User [21], the authors considered the two-user downlink NOMA relay system in which a full-duplex and energy-harvesting-enabled relay assisted communications between the base station and a far user over flat, independent, and nonidentically Rayleigh fading channels. The paper provided insights into the impact of interuser interference at the relay and self-interference cancellation coefficient on the outage probabilities and ergodic capacities. Furthermore, the optimal value of the power-division ratio was determined. Numerical results indicated that the decoding signal-to-interference-plus-noise ratio decreased when the relay harvested more energy; consequently, outage-probability performance and ergodic capacity at the far user were reduced. Using the proposed numerical method, an appropriate power-division ratio satisfying the quality-of-service requirements at the far user was determined.