Imperfectly synchronized cooperative network using distributed space-frequency coding.

In distributed multiple-input-multiple-output (MIMO) systems, imperfect synchronization causes a unique problem in a coded cooperative diversity system. In the presence of a fractional-symbol delay between the signals transmitted from different relay nodes, the channels become highly dispersive even at a flat-fading environment. Existing methods solve such problem based on time-domain approaches where adaptive equalization is required at the receivers for combining the information transmitted from distributed sources. In this paper, we propose the use of OFDM-based approaches using distributed space-frequency codes. The proposed schemes are insensitive to fractionalsymbol delays and lead to higher data rate transmission and simplified implementation. In addition, the proposed schemes permit the use of relatively simple amplify-andforward algorithm in multi-hop wireless networks without delay accumulations. The proposed methods remove the time delay in each relaying hop by reconstructing the prefix and, as such, improve the spectral efficiency, while keeping a simplified relaying structure.

Main Author:	Zhang, Yimin.
Other Authors:	Wang, Genyuan., Amin, Moeness G.
Language:	English
Published:	2005
Online Access:	http://ezproxy.villanova.edu/login?url=https://digital.library.villanova.edu/Item/vudl:173351