Year

2013

Degree Name

Master of Engineering - Research

Department

School of Electrical, Computer and Telecommunications Engineering

Abstract

As communications technology continues its rapid transition from analogue to digital, more functions of modern radio systems are implemented in software, rather than hardware, leading toward the software defined radio architecture. Software defined radio (SDR) is a promising technique for multi-type, high speed wireless communication system with low requirements on capability of hardware devices, low development cost and facilitation of the development process. SDR is an emerging and developing technique, thus it has not been matured yet.

In this project, a SDR testbed has been built to evaluate the practical error performance of Orthogonal Frequency Division Multiplexing (OFDM) based systems in different propagation conditions with different system configurations. In particular, the testbed has been built based on the GNU Radio Software platform and version-2 Universal Software Radio Peripheral (USRP2) devices.

Theoretical simulation results show that OFDM provides good error performance and high data rate transmission, compared to single carrier transmission techniques. However, the implementation of OFDM with SDR in actual hardware, as well as the verification of its performance in various realistic propagation conditions with different system configurations, has been almost unexplored. Evaluation of practical performance of OFDM systems is very important from practical points of view, including but not being limited to, the deep understanding of the effects of synchronisation and channel estimation techniques to the error performance and the awareness of what the realistic limitations of hardware and SDR are. Therefore, this project aims at evaluating the error performance of practical OFDM systems in various experimental environments, including typical laboratory rooms and corridors. The performance of OFDM with different digital modulation schemes is also evaluated in this project. The error performances of the implementation are then compared to the theoretical performances to confirm the effects of synchronisation and channel estimation processes and the limitations of hardware and SDR.

Outcomes of this project include the testbed which has been successfully built with SDR in the USRP2 hardware modules, a detailed technical documentation on how an OFDM system can be implemented with SDR and USRP2, a family of error performance curves of the implemented OFDM system with different modulation schemes in different propagation environments, in depth analyses of synchronisation and channel estimation processes and their effects to the experimental performances, and analyses of the realistic limitations of SDR and USRP2. These outcomes are significant, bearing in mind that SDR is an emerging-but-yet-mature technique.

The successful development of the OFDM testbed with SDR and USRP2 opens various opportunities to research further other advanced signal processing techniques for OFDM-based systems, such as the improved synchronisation and channel estimation techniques, the techniques to reduce the well known Peak-to-Average Power Ratio (PAPR) issue, and the emerging Multiple-Input Multiple-Output (MIMO) technique. These research directions will be our future works.

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