Opportunistic ISAC for Rain Microphysical Parameters Estimation Using LOS-MIMO Systems

The line-of-sight multiple-input multiple-output (LOS-MIMO) has emerged as a potential solution for increasing spectral efficiency in dense urban microwave links, given limited spectrum resources. Phase variation and power attenuation may introduce uncertainty to the channel estimation, affecting channel capacity and the performance of interference cancellation by zero-forcing receivers. This paper investigates the impact of this uncertainty in the presence of rain. Commercial backhaul links (CMLs) in cellular networks are not only essential for data transmission but have also proven useful for rainfall monitoring. They are now emerging as a new opportunistic integrated sensing and communication (OISAC) application for weather sensing. This paper also studies the use of LOS-MIMO backhaul technology for rain rate estimation. The availability of multiple data streams allows the number of rain estimation values to increase linearly with the minimum number of transmit and receive antennas in the MIMO link, Additionally, the potential for LOS-MIMO microwave links to retrieve parameters related to rain drop size distribution based on measurement data is also explored. This new backhaul solution shows great potential to be used for near-ground environmental monitoring and weather prediction studies, particularly with the advent of the big data era.