Performance enhancement of 6g millimeter wave links via RIS beamforming and CDL-based channel modeling.

Communication using millimeter waves offer large bandwidth, become one of the key components of future sixth-generation wireless (6G) network. However, high levels of path loss and blockage limit the reliability of these types of links and communication, especially in non-line-of-sight (NLOS) scenarios. Recently, a novel technology known as reconfigurable intelligent surfaces (RIS) has been developed to help reconfigure the wireless propagation environment through programmable electromagnetic reflection. This paper discusses how using realistic cluster-delayed-line (CDL) channel modelling can improve the performance of RIS-assisted millimeter-wave communication links. A cascaded base station (BS)-RIS-user equipment (UE) system using a propagation channel that has been modelled according to mobile radio channel characteristics from the 3GPP Technical Report (38.901) was simulated at a frequency of 28 GHz in order to study the multipath clustering, angular dispersion and delay spread effects that take place when propagating signals using a wireless or radio channel. An iterative RIS phase optimization algorithm was developed for maximizing the coherent signal power obtained by combining all of the reflected signals based on the available directional antennas operated by RIS hardware. We present performance evaluations of the RIS-assisted channel compared to performance evaluations of traditional direct based channel configurations of identical communications facilities based on analysis of communications efficiency, signal-to-noise ratio, coverage probability, energy efficiency and accuracy of localization. The results show that RIS-assisted beamforming greatly improves communication performance from direct established links. For instance, when using 200 RIS elements, spectral efficiency of communication increases from approximately 2 bps/Hz to greater than 8 bps/Hz and the SNR at the receiver will have improved by almost 40 dB when using RIS technology compared to direct-established links.