Relay Diversity Techniques for OFDM and MC-CDMA

The future of mobile and personal communications requires a system<br/>that can support a large number of users and has the ability to provide<br/>high-speed services. Meeting this demand is challenging since wireless<br/>communications are subject to these four major constraints: complex<br/>fading channels, a scarce usable radio spectrum, and limitations on<br/>the power and size of the mobile terminals. Space-time codes, such<br/>as the Alamouti/space-time block coding (STBC) and cyclic delay<br/>diversity (CDD) can provide diversity and coding gains in multipleinput<br/>multiple-output (MIMO) systems over fading channels.<br/>However in an ad-hoc network, nodes are often constrained in hardware<br/>complexity and size, which makes MIMO systems impractical for<br/>certain applications. Cooperative relay diversity schemes have been<br/>introduced in an eort to overcome these limitations. Cooperative<br/>techniques allow a collection of communication nodes to cooperate<br/>with to relay signals amongst each other, eectively creating a virtual<br/>antenna array, which combat multipath fading in wireless channels.<br/>This thesis investigates relay diversity techniques in cooperative communications,<br/>namely the distributed space-time block coding (DSTBC)<br/>and relay cyclic delay diversity (RCDD) for OFDM and MC-CDMA<br/>systems. The performance analysis of the wireless relay networks under<br/>dierent protocols and fading channels are investigated. We derived<br/>the formulas for the symbol error rate (SER) of the investigated<br/>schemes in fading channels.<br/>Finally, a novel hybrid relay diversity (HRD) is presented for OFDMbased<br/>system. This new relay structure addresses the issue of achieving<br/>a full spatial and multipath diversity by developing a hybrid for<br/>CDD and STBC. Simulation on the system performance of HRD<br/>shows the superiority of the technique compared to standalone DSTBC<br/>and RCDD.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

King's College London

Year dc:date.issued

2012

Author dc:creator

• Abdul Razak, Nur Idora

Advisors dc:contributor.advisor

• Said, Fatin
• Aghvami, Abdol-Hamid

Language dc:language

eng

Identifier

oai:kclpure.kcl.ac.uk:studenttheses/7aff62f9-7af4-47f5-b4bc-d91377988f5a

OAI identifier oai:identifier

oai:kclpure.kcl.ac.uk:studenttheses/7aff62f9-7af4-47f5-b4bc-d91377988f5a