Fast Compression of OFDM Channel State Information with Constant Frequency Sinusoidal Approximation

We propose CSIApx, a very fast and lightweight method to compress the Channel State Information (CSI) of Wi-Fi networks. CSIApx approximates the CSI vector as the linear combination of a small number of base sinusoids on constant frequencies, and uses the complex coefficients of the base sinusoids as the compressed CSI. While it is well- known that the CSI vector can be represented as the linear combination of sinusoids, fixing the frequencies of the base sinusoids is the key novelty of CSIApx, which is guided by our mathematical finding that almost any sinusoid can be approximated by the same set of base sinusoids with small bounded error. CSIApx enjoys very low computation complexity, because the key steps in the compression can be pre-computed. We extensively test CSIApx with both experimental and synthesized Wi-Fi channel data, and the results confirm that CSIApx can achieve very good compression ratio with little loss of accuracy.