Estimation of CSI
Since the channel conditions vary, instantaneous CSI needs to be estimated on a short-term basis. A popular approach is so-called training sequence (or pilot sequence), where a known signal is transmitted and the channel matrix is estimated using the combined knowledge of the transmitted and received signal.
Let the training sequence be denoted, where the vector is transmitted over the channel as
By combining the received training signals for, the total training signalling becomes
with the training matrix and the noise matrix .
With this notation, channel estimation means that should be recovered from the knowledge of and .
Read more about this topic: Channel State Information
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