The correlation properties of subchannel fading for non-continuous carrier aggregation based on indoor ultra-wideband measurement

The new multichannel/multicarrier technologies have drawn great attention recently to support high data rate in mobile multiple-access environments, such as the carrier aggregation (CA) as a part of 4G LTE-Advanced enhancement. On the way to the development of multicarrier technologies, there is a considerable need to understand and utilize the correlation properties of distinct subchannels, which, however, has not been reported in the literature. Based on the extensive indoor ultra-wideband (UWB) channel measurement, this paper develops a new approach to analyze the correlation of the large and small-scale fading of arbitrarily separated subchannels. The approach avoids the high complexity and cost of the conventionally probing the multiple subchannels simultaneously using channel sounders which would be too complicated to implement. We first propose a modified CLEAN algorithm to reliably extract channel impulse responses (CIRs) from the measured pulse response waveforms with substantially varying noise floor. Then the cross-correlation of the fading of two distinct subchannels, the autocorrelation of the fading of a single subchannel and the correlation of the multipath profile over a small area are analyzed. The study has revealed how significantly the channel response would change when the receiver travels from room to room or just over a distance of dozen of wavelength, and how two separated subchannels are correlated. In our view, the acquired new insights on subchannel correlations could provide guidelines for efficient designs and performance predictions of multicarrier communication systems.