Local Scattering Detection Around Relay on Multi-Hop MIMO Channels Using SDRs in Time Domain

Abstract

Multi-hop communication system using relay has been developed to bridge long distance separates the connection between transmitter-receiver. Proper knowledge of the conditions and scattering characteristics around the relay is important to evaluate the performance of Multi-Hop communication systems. The scattering characteristics could be illustrated from the physical parameters of the channel including transmission delay, double directional for departure and arrival angles (DOD and DOA), and complex amplitude. These parameters are estimated from I + jQ data measured and processed using Space Alternating Generalized Expectation-Maximization (SAGE) algorithm. In this paper, we would report double-directional measurements on the Multi-Hop MIMO channels in the time domain using software defined radio (SDR). By working in the time domain, the complexity of the mathematical calculations required in analyzing a system could be reduced. The analysis of delay time and the distance of signal propagating in a radio channel is easier to do in the time domain. The challenge lies in the temporal resolution that is closely related to the measuring instrument, here we choose SDR which has a sampling rate of 33.33 MHz for MIMO channel. It means that the measurement system could resolve two multipath component signals (MPCs) as long as they are equal to or greater than 60 ns. The results show the measurement system that has been built using SDRs in time domain could detect some MPCs in both indoor and outdoor-corridor environment. The data processing system has successfully estimated the physical parameters which have been validated through 2-D ray tracing. We could detect the scattering location, identified the local scattering around relay, and classified one of the scatterings as common local scattering (CLS).