Double-directional outdoor MIMO channel measurement at 2.4 GHz using SDR

Wireless communication offers greater mobility to users but also susceptible to disruption because of many scatterers result multipath fading. Proper knowledge about the conditions and characteristics of scatterers around communication channel is very important to evaluate the performance of communication systems. By measuring the double directional we could have knowledge about the direction of radio wave propagation. It could lead us to predict the scattering point which dissipating the radio wave. This paper reports the measurement system build on software defined radio (SDR) platforms at 2.4 GHz band and the preliminary measurement results of the MIMO channel at outdoor environment. Space Alternating Generalized Expectation-Maximization (SAGE) algorithm is used to estimate the parameters of the channel, i.e., delay, double directional (DOD and DOA), and complex amplitude of multipath component signals (MPCs) to observe scattering mechanism around MIMO communication link. The 2×2 MIMO channel measurements were performed at the courtyard of Robotics building at Institut Teknologi Sepuluh Nopember (ITS). Our measurement system use a sampling rate of 33.33 MHz, so it is only capable of separating two multipath component signals that have interval delay greater than or equal to it's delay resolution which is 60 ns. Using SAGE we estimate the parameters of MPCs. Then we verify the obtained parameters value using simple ray tracing. The results show that there are three MPCs with different delay. They are a LOS component, a signal component scattered by the surface of the ground, and a signal component scattered by Robotics building. Therefore, for this measurement we conclude that there are two scattering objects which are ITS Robotics building and the land surface.