Capacity of Sparse Multipath Channels in the Ultra-Wideband Regime

—This paper studies the ergodic capacity of time- and frequency-selective multipath fading channels in the ultrawideband (UWB) regime when training signals are used for channel estimation at the receiver. Motivated by recent measurement results on UWB channels, we propose a model for sparse multipath channels. A key implication of sparsity is that the independent degrees of freedom in the channel scale sublinearly with the signal space dimension (product of signaling duration and bandwidth). Sparsity is captured by the number of resolvable paths in delay and Doppler. Our analysis is based on a training and communication scheme that employs signaling over orthogonal short-time Fourier (STF) basis functions. STF signaling naturally relates sparsity in delay-Doppler to coherence in time and frequency. We study the impact of multipath sparsity on two fundamental metrics of spectral efficiency in the wideband/low-SNR limit introduced by Verdu: first- and second-order optimality conditio...

• Type: Journal
• Year: 2007
• Where: CORR
• Authors: Vasanthan Raghavan, Gautham Hariharan, Akbar M. Sayeed
• Keywords: CORR 2007, Education, Multipath Sparsity, Sparse Multipath Channels, Sparsity