Multi-Stream FFT Architectures for a Distributed MIMO Large Intelligent Surfaces Testbed

A modern communication testbed based on distributed multiple-input multiple-output (MIMO) is constructed at Lund University. This testbed uses 16 -antenna panels as a base for the distributed MIMO system. As the mixers in these panels are fully digital, there is a rational relationship between the sample frequency and the clock frequency of the field-programmable gate-array that performs the digital baseband processing. This rational relationship, combined with the multiple data streams in the panel, makes for an interesting design challenge when implementing high-utilization circuits. Three unique 16 multi-stream fast Fourier transform architectures tailored toward this particular distributed MIMO testbed are presented. The proposed architectures take the rational relationship between clock frequency and sample frequency into consideration and achieve ${9 6 . 2 5 \% - 1 0 0 \%}$ butterfly utilization in the multi-stream FFT.