ï»¿ï»¿**Article details**

**Title: **Coherence Time of Wideband and Ultra-Wideband Channels

**Author(s): ***Ioana-Alina Iordache* *Ana-Maria Piștea*

**Abstract: **Wideband (WB) and ultra-wideband (UWB) systems combined with multiple-input multiple-output (MIMO) technology increase both the systems performances and the complexity of the channel models required to evaluate their capabilities. Because in real scenarios waves propagate non-isotropically, the accuracy of the channel model is increased if non-isotropic propagation is considered. The channel bandwidth is the key term in the evaluation process of these systems because large bandwidths introduce frequency selectivity, a unique phenomenon to WB and UWB systems with more complexity in the latter case. This is due to the fact that unlike WB technology in which the propagating signal is the only affected parameter by the frequency selectivity, in the UWB case this phenomenon also affects the antenna radiation pattern (ARP). In this paper, we have developed a novel channel model based on the statistical analysis of two-dimensional cross-correlation functions (CCF)s of WB/UWB MIMO channel.

**Keywords: **wideband, ultra-wideband, coherent channel, propagation environment, bandwidth, frequency, UWB signals, frequency selectivity.

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