Null-Interference

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Improved QO-STBC OFDM System Using Null Interference Elimination

Journal Title, Volume, Page: 
International Journal of Computer Science and Applications 01/2013; 4(8)
Year of Publication: 
2013
Authors: 
Kelvin Anoh
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
Raed Abd-Alhameed
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
Yousef Dama
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
Current Affiliation: 
Department of Telecommunication Engineering, Faculty of Engineering and Information Technology, An-Najah National University, Nablus. Palestine
Steve Jones
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
T. S. Ghazaany
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
J. Rodrigues
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
K. N. Voudouris
Mobile and Satellite Communications Research Centre, University of Bradford, UK BD7 1DP
Preferred Abstract (Original): 
ABSTRACT
The quasi-orthogonal space time block coding (QO-STBC) over orthogonal frequency division multiplexing (OFDM) is investigated. Traditionally, QO-STBC does not achieve full diversity since the detection matrix of QO-STBC scheme is not a diagonal matrix. In STBC, the decoding matrix is a diagonal matrix which enables linear decoding whereas the decoding matrix in traditional QO-STBC does not enable linear decoding. In this paper it is shown that there are some interfering terms in terms of non-diagonal elements that result from the decoding process which limit the linear decoding. As a result, interference from the application of the QO-STBC decoding matrix depletes the performance of the scheme such that full diversity is not attained. A method of eliminating this interference in QO-STBC is investigated by nulling the interfering terms towards full diversity for an OFDM system. It was found that the interference reduction technique permits circa 2dB BER performance gain in QO-STBC. The theoretical and simulation results are presented, for both traditional QOSTBC and interference-free QO-STBC applying OFDM.
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