Cramer-Rao bounds of SNR estimation for BPSK and QPSK signals over SIMO channels

In this paper, we derive Cramer-Rao lower bounds for the estimation of signal-to-noise ratio of BPSK and QPSK modulated signals over SIMO channels, when multiple antenna elements are deployed to receive the desired signal. The lower bounds are derived for non-data aided estimation where the transmitted symbols are unknown at the receiver, and compared to those for data-aided estimations (known symbols at the receiver). It is shown that there is a significant difference between the bounds for non-data-aided and data aided estimations at low SNR for only one antenna, but become smaller as the antenna number grows. It is assured for us to achieve a substantial performance improvement due to the optimal usage of the mutual information between the branches.