Measurement and Analytical Study of the Correlation Properties of Subchannel Fading for Noncontiguous Carrier Aggregation

The new multichannel/multicarrier technologies can potentially support much higher data rates in mobile multiple-access environments, such as carrier aggregation (CA) defined in the fourth-generation Long-Term Evolution Advanced enhancement. The correlation properties of noncontiguous subchannels are critical for the performance of CA, including cell coverage, frequency diversity, and channel state estimation. This paper has studied the correlation of the large-scale fading (LSF) and small-scale fading (SSF) of arbitrarily separated subchannels by realistic channel measurement and analytical modeling. We first obtain the subchannel correlation from the ultrawideband (UWB) channel measurement. This new approach avoids probing multiple subchannels simultaneously with channel sounders, which would be prohibitively complicated. The cross correlation of two distinct subchannels and the autocorrelation of a single subchannel are evaluated. Second, a new propagation model for the Nakagami-m fading in a multipath environment is proposed. The frequency-domain level crossing rate (FD-LCR) is defined and derived based on the propagation model. Then, a Markov chain for the frequency fading of the wideband channel is established, which can generate the correlated gain/power of subchannels in a wide bandwidth. Therefore, this model can be used as a fast simulator of CA over correlated subchannels. Finally, the cross correlation coefficients (CCCs) between two Nakagami-m fading subchannels obtained from the measurement and the proposed Markov model are compared with the analytical results in the literature. This paper provides important insights into the fading correlation of the multicarrier channels and can be applied to the design and simulation of indoor/outdoor multicarrier communications.