or vector s data rate that could be received e g cqi such feedback would typically be based on observation of periodically transmitted reference symbols designed for this purpose i e csi rs and estimates of interference the feedback may be broadband e g covering the entire carrier bandwidth or frequency selective covering parts of the carrier bandwidth spatially white meaning that the interference level is substantially spread all around the secondary station spatially localized meaning that the interference level is only high at some locations around the secondary station uniform in the frequency domain frequency selective constant in the time domain or time varying the secondary station could determine appropriate assumptions itself by observation of the signals at its antenna outputs then if the interference is spatially localised the secondary station may be able optimize receiver processing i e selection of antenna weights in order to mitigate the effect of the interference and maximise sinr otherwise the secondary station should apply mrc maximum ratio combining calculation of antenna weights would be based on an estimate the spatial signature of the interference at the secondary station these weights could be applied to reception of data transmissions as well as reporting the channel quality e g cqi if the interference is frequency selective or time varying e g with an identifiable pattern this would lead to higher cqi values corresponding to parts of the spectrum with lower estimated interference one problem with using only the secondary station measurements is that interference environment in any future subframes may be different to that derived from past history note that in practice the spatial characteristics of the interference may be more complex for example.