Spatial channel characterisation of FDD wireless links

For smart antenna deployments in frequency division duplex (FDD) applications the downlink weight vector can be derived from the uplink steering vector. However, this assumes a degree of correlation between these channels. It is shown here that de-correlation between uplink and downlink power azimuth spectrums (PAS) is significant for frequency offsets as small as 5 MHz in urban environments, with this increasing to 15 MHz when long term averaging is applied. Results reported here are computed from measured data taken within the UMTS (Universal Mobile Telecommunications System) frequency band for a cluttered urban environment.