Channel sounding

Channel sounding is a technique that evaluates the radio environment for wireless communication, especially MIMO systems. Because of the effect of terrain and obstacles, wireless signals propagate in multiple paths (the multipath effect). To minimize or use the multipath effect, engineers use channel sounding to process the multidimensional spatial-temporal signal and estimate channel characteristics. This helps simulate and design wireless systems. Channel sounding is a technique that evaluates the radio environment for wireless communication, especially MIMO systems. Because of the effect of terrain and obstacles, wireless signals propagate in multiple paths (the multipath effect). To minimize or use the multipath effect, engineers use channel sounding to process the multidimensional spatial-temporal signal and estimate channel characteristics. This helps simulate and design wireless systems. Mobile radio communication performance is significantly affected by the radio propagation environment. Blocking by buildings and natural obstacles creates multiple paths between the transmitter and the receiver, with different time variances, phases and attenuations. In a single-input, single-output (SISO) system, multiple propagation paths can create problems for signal optimization. However, based on the development of multiple input, multiple output (MIMO) systems, it can enhance channel capacity and improve QoS. In order to evaluate effectiveness of these multiple antenna systems, a measurement of the radio environment is needed. Channel sounding is such a technique that can estimate the channel characteristics for the simulation and design of antenna arrays. In a multipath system, the wireless channel is frequency dependent, time dependent, and position dependent. Therefore, the following parameters describe the channel: To characterize the propagation path between each transmitter element and each receiver element, engineers transmit a broadband multi-tone test signal. The transmitter's continuous periodic test sequence arrives at the receiver, and is correlated with the original sequence. This impulse-like auto correlation function is called channel impulse response (CIR). By obtaining the transfer function of CIR, we can make an estimation of the channel environment and improve the performance. Based on multiple antennas at both transmitters and receivers, a MIMO vector channel sounder can effectively collect the propagation direction at both ends of the connection and significantly improve resolution of the multiple path parameters.