A polyphase-filter-based FFT for DFT calculation in LTE uplink

In LTE uplink, a DFT with 34 possible lengths is performed. The traditional method directly transforms the sequences with different lengths by using the mixed-radix FFT which is not appropriate to apply on the DSP processor only supplying radix-2 butterfly hardware especially. In this paper, we resample the arbitrary-length input sequence so that a 2ⁿ-point FFT can be applied by using the polyphase filter. Theoretical analysis demonstrates the equivalence of the proposed polyphase-filter-based FFT (PF-FFT) and the original DFT. Moreover, the PF-FFT also keeps low complexity and good fixed-point performance.