A study of precoding schemes for OFDM systems


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2008

Student: FATMA SELCEN ÇAKAR

Co-Supervisor: ALİ ÖZGÜR YILMAZ, ÇAĞATAY CANDAN

Abstract:

We examine the effect of precoding on OFDM systems. The precoding operation, which is also known as constellation rotation, leads to a gain in diversity order for fading channels. In this thesis, we examine the effect of precoding for different receivers such as Maximum Likelihood (ML), Minimum Mean Squared Error (MMSE), and Zero Forcing (ZF) receivers. The diversity gain due to precoding comes at no cost of bandwidth expansion or power increase. Therefore it is an attractive and practical alternative. We also examine the precoding gain, when some reduction of rate is tolerable and compare the performance of rate reduced system with the uncoded system with the system which is coded by rateless unitary precoders, and with the hard-decision decoded BCH coded coded system.