The global bandwidth shortage in the wireless communication sector has motivated the study and exploration of wireless access technology known as massive Multiple-Input Multiple-Output (MIMO). Massive MIMO is one of the key enabling technology for next-generation networks, which groups together antennas at both transmitter and the receiver to provide high spectral and energy efficiency using relatively simple processing. Obtaining a better understating of the massive MIMO system to overcome the fundamental issues of this technology is vital for the successful deployment of 5G—and beyond—networks to realize various applications of the intelligent sensing system. In this paper, we present a comprehensive overview of the key enabling technologies required for 5G and 6G networks, highlighting the massive MIMO systems. We discuss all the fundamental challenges related to pilot contamination, channel estimation, precoding, user scheduling, energy efficiency, and signal detection in a massive MIMO system and discuss some state-of-the-art mitigation techniques. We outline recent trends such as terahertz communication, ultra massive MIMO (UM-MIMO), visible light communication (VLC), machine learning, and deep learning for massive MIMO systems. Additionally, we discuss crucial open research issues that direct future research in massive MIMO systems for 5G and beyond networks.

Massive MIMO Systems for 5G and Beyond Networks-Overview, Recent Trends, Challenges, and Future Research Direction.

Research on two-dimensional designer optical structures, or metasurfaces, has mainly focused on controlling the wavefronts of light propagating in free space. Here, we show that gradient metasurface structures consisting of phased arrays of plasmonic or dielectric nanoantennas can be used to control guided waves via strong optical scattering at subwavelength intervals. Based on this design principle, we experimentally demonstrate waveguide mode converters, polarization rotators and waveguide devices supporting asymmetric optical power transmission. We also demonstrate all-dielectric on-chip polarization rotators based on phased arrays of Mie resonators with negligible insertion losses. Our gradient metasurfaces can enable small-footprint, broadband and low-loss photonic integrated devices.

Controlling propagation and coupling of waveguide modes using phase-gradient metasurfaces

This work investigates the impact of imperfect statistical information in the uplink of massive MIMO systems. In particular, we first show why covariance information is needed and then propose two schemes for covariance matrix estimation. A lower bound on the spectral efficiency (SE) of any combining scheme is derived, under imperfect covariance knowledge, and a closed-form expression is computed for maximum-ratio combin- ing. We show that having covariance information is not critical, but that it is relatively easy to acquire it and to achieve SE close to the ideal case of having perfect statistical information.

Massive MIMO with Imperfect Channel Covariance Information

The Precipitation Radar (PR), the first space-borne precipitation radar onboard the Tropical Rainfall Measuring Mission (TRMM) satellite, could observe three-dimensional precipitation in global tropical regions and acquire continuous rainfall information with moderate temporal and high spatial resolutions. TRMM PR had carried out 17 years of observations and ended collecting data in April, 2015. So far, comprehensive and abundant research results related to the application of PR data have been analyzed in the current literature, but overall precipitation features are not yet identified, a gap that this review intends to fill. Studies on comparisons with ground-based radars and rain gauges are first introduced to summarize the reliability of PR observations or estimates. Then, this paper focuses on general precipitation features abstracted from about 130 studies, from 2000 to 2018, regarding lightning analysis, latent heat retrieval, and rainfall observation by PR data. Finally, we describe the existing problems and limitations as well as the future prospects of the space-borne precipitation radar data.

Studies of General Precipitation Features with TRMM PR Data: An Extensive Overview

Observation of bright-band height data from TRMM-PR for satellite communication in South Africa

Comparison and analysis of the regularized zero forcing (RZF) precoder, Sherman-Morrison-Woodbury (SMW)-based precoder, rapid numerical algorithms (RNA)-based precoder and the truncated polynomial expansion (TPE)-based precoder are compared and analyzed for massive multiple-input multiple-output (MIMO) wireless system in a downlink scenario. The achievable data rates and signal-to-noise ratio (SNR) were investigated. The simulated outcome agrees with the theory of massive MIMO system. Also the RZF precoder, RNA-based precoder and the SMW-based precoder perform better in comparison to TPE-based precoder under good CSI quality and low ratio of transmit to receive antennas.

Comparison and analysis of massive MIMO linear precoding schemes in the downlink

Frees Space Optical (FSO) communication is a kind of communication that uses open medium to transmit laser light and carry data between the transmitter and receiver This type of communication system is affected by the effect of weather parameters when transmitting laser light source in the air A number of studies have been conducted to evaluate the effect of the attenuation coefficient on the laser beam at different wavelength This study focuses the evaluation of the attenuation coefficient of the laser beam at (750, 785, 950 and 1550) nm wavelength at different visibility of 50km and below At it has shown when transmitting light beam at distances from 500m to 50km the light beams will be attenuated the same The other study done by this paper was on the influences of weather condition in the receiver optical power, the link margin and the data transfer rate and the result shows that the weather conditions affect them differently

Multiple Wavelength Propagation in Free Space Optical Wireless Channel

In this paper, 4-year precipitation data obtained from Tropical Rain Measuring Mission-Precipitation Radar (TRMM-PR) satellite were processed and used to determine the distribution of rain height based on 00C isotherm height over Durban in South Africa. The results show that there is a strong variation of bright-band height over the years of observation and will mostly lie between 3639 m and 4197 m above mean sea level. The observed rain height lies between 4517 m and 4803 m. Comparison of the observed results show that the International Telecommunication Union — Recommendation (ITU-R) P.839 recommended values were underestimated. Thus, the specific attenuation values are determined using ITU-R P.618 by incorporating the determined rain height for the location of Durban. It is noticed that the differences between the estimated attenuation based on the measured rain height and the established ITU-R rain height can be as high as 8 dB at Ka band. Thus, recommending using the physical information about rain height derived from the local databases to improve in the rain attenuation prediction accuracy for this region.

Analysis of bright-band height data from TRMM-PR for satellite communication in Durban, South Africa

Rain height is one of the significant parameters for prediction of rain attenuation for Earth-space telecommunication links, especially those operating at frequencies above 10 GHz. This study examines Three-parameter Dagum distribution of the rain height over Durban, South Africa. 5-year data were used to study the monthly, seasonal, and annual variations using the parameters estimated by the maximum likelihood of the distribution. The performance estimation of the distribution was determined using the statistical goodness of fit. Three-parameter Dagum distribution shows an appropriate distribution for the modeling of rain height over Durban with the Root Mean Square Error of 0.26. Also, the shape and scale parameters for the distribution show a wide variation. The probability exceedance of time for 0.01% indicates the high probability of rain attenuation at higher frequencies.

https://google.iopscience.iop.org/article/10.1088/1757-899X/321/1/012006/pdf

O. Sokoya

Papers

Observation of bright-band height data from TRMM-PR for satellite communication in South Africa

Comparison and analysis of massive MIMO linear precoding schemes in the downlink

Multiple Wavelength Propagation in Free Space Optical Wireless Channel

Analysis of bright-band height data from TRMM-PR for satellite communication in Durban, South Africa

Distribution of rain height over subtropical region: Durban, South Africa for satellite communication systems