Table 2.
Comparison of recent research works regarding IS on THz wireless communication channel modeling in terms of performance evaluation, system model, design objective, and optimization technique.
| Reference | Performance Evaluation | System Model | Design Objective | Optimization Techniques |
|---|---|---|---|---|
| [29] | Path gain and capacity | D–band indoor downlink | Maximize signal reflection and restore LoS link between the transmitter and receiver blocked by obstacles | Antenna theory |
| [30] | Adaptively selecting step size | Indoor MIMO downlink | Spectral efficiency with phase shift adjust | Taylor expansion aided gradient descent |
| [31] | Path loss | THz systems downlink | Expression that determines the optimal phase shift | Electromagnetic theory |
| [32] | Path loss | MIMO | Power gain and energy efficiency | Beamforming |
| [33] | Beam pattern and quantization error | mMIMO | Channel estimation and transmission solutions with hybrid beamforming architectures | Geometric channel model and IAP-SP for CSI acquisition. |
| [34] | NMSE | Indoor MIMO systems | Channel estimation | Beam training |
| [35] | NMSE | MIMO | Channel estimation | IAP-SP scheme |
| [36] | SNR feedback | MISO downlink | Minimization transmit power while maximizing the system achievable rate | Beamforming optimization based on statistical CSI and genetic algorithms |
| [37] | Success rate and beamforming gain ratio | mmWave/THz downlink | Perfectly aligned transmitter-receiver channel | Efficient beam training with cascade channel |
| [38] | Secrecy rate | mmWave/THz systems | Optimal discrete phase shifts to maximize the secrecy rate | SDP-based method and the element-wise BCD method |
| [39] | Secrecy rate | MISO downlink | Secure operation with secrecy rate maximization | Active beamformer and passive reflecting phase shifters |
| [41] | Path loss | Not detailed | Intensity for the electric field reflected by RISs in the short and long transmission distance regimes | General scalar theory of diffraction and the Huygens-Fresnel principle |
| [42] | SNR | Not detailed | Improve the average receive SNR | Beamforming |
| [50] | SNR, SNDR, small-scale amplitude fading, OP, and ergodic capacity | THz system | Exact PDF and CDF expressions of end-to-end SNR and SNDR of the system | FTR distribution and multivariate Fox’s H-function |
| [51] | Path loss and beam pattern | THz systems | Beamfocusing | Beamforming with physical optics channel model |
| [52] | Beam pattern | THz massive MIMO systems (downlink and uplink) | Beamforming design and channel estimation performance | Beamforming with physical channel model |
| [53] | SNR, ergodic capacity and OP | THz indoor systems downlink | Receiver beam misalignment and restore the transmitter/receiver connection blocked by obstacles | Electromagnetic theory |
| [54] | UAV trajectory, phase shift, THz band allocation and power control | UAV systems downlink | To maintain reliable THz communication and minimize average rate of users | SCA |
| [129] | Energy-efficient, SNR, latency and success rate | 3-D indoor THz wireless communication | Minimizes latency using ray tracing techniques to find the best THz signal propagation path | Ray searching and beam-selecting |
| [130] | Achievable rate, phase compensation and normalized array gain | IS-aided THz system | Achievable rate maximization for distributed IS-assisted THz communications | Analog beamforming, digital beamforming vector |
| [131] | Phase shifts, ergodic net throughput, blocking probability | CF mMIMO | Channel estimation and unblock links | OP and fading spatial correlation with increased element numbers |
| [128] | Misalignment fading | THz inter-satellite links | Compensation for the high path loss associated with high carrier frequencies and to improve SNR | Antenna theory |
| [132] | Coverage area and sum rate | mmWave or THz indoor communication | Placement optimization to maximize the long-term sum rate and then optimization of transmit beamforming and reflecting procedure in real time | Antenna theory and deep learning |
| [133] | BER and modulation speed | Full-wave simulation | Eliminate on-chip signal attenuation and inter-symbol interference | Binary IS optimization algorithm |