System Design and Calibration for Wideband Channel Sounding With Multiple Frequency Bands

This paper presents a multiple frequency bands-switching scheme for wideband channel sounding, which is able to extend the overall sounding bandwidth without changing operation bandwidth of the hardware. It is especially suitable for low mobility and high data-rate scenarios (e.g., indoor hot spot) in the fifth generation mobile communication systems. With this scheme, a channel sounder is developed on a software-defined radio platform that employs an orthogonal frequency division multiplexing signal at 5.6 GHz. In each sounding cycle, ten concatenated frequency bands (20 MHz bandwidth) are covered to acquire an equivalent measurement over a 200-MHz bandwidth, corresponding to 5-ns time delay resolution. The key challenges and solutions for hardware system calibration, including amplitude and phase compensation on different frequency bands, are detailed to ensure the accuracy of measurement results. Next, the spurious free dynamic range of channel impulse response is modeled and verified for this sounding scheme. Finally, to explore the massive multiple-input-multiple-output channel characteristics in indoor scenarios, a virtual large antenna array is built based on the wideband sounder.