Mean Squared Error (hsid_mse)

The purpose of this module is to complete the MSE computation between the captured HSP and a reference signature from the spectral library. The data input width is 32 bits, meaning that two consecutive bands are introduced simultaneously for both the captured HSP and the reference signature. The figure below shows how the beginnings and ends of each HSP are delimited. Each reference signature is associated with an identifier (hsp_ref) corresponding to its position in the spectral library.

Since the data input provides two consecutive bands, processing can be performed in parallel using two instances of the hsid_sq_df_acc module. The intermediate accumulated results obtained from both instances are added together and finally divided by the number of bands in the HSP. The dataflow of the hsid_mse module is illustrated in the following figure.

For an HSP of n bands, the latency of this module is \(\frac{n}{2} + 4 + (K + 1)\) cycles: \(\frac{n}{2}\) cycles for transferring the band_packs, plus four cycles to complete the hsid_sq_df_acc pipeline and the final accumulator, and \(K + 1\) cycles to perform the division yielding a K-bit result within the hsid_mse module. Both HSP and reference signature must contain more than \(4 (K + 1)\) bands to avoid issues with hsid_divider as this module is not pipelined.

The figure below shows an example waveform illustrating the computation of the MSE for two consecutive reference signatures using the hsid_divider module with a divider of 5 bits.