Crest factor reduction techniques for OFDM telecommunication systems

Two popular Crest Factor Reduction techniques applicable to OFDM signals have been studied and implemented within this project. To provide adequate background, a brief description of OFDM communication systems is included in the first sections, and the problem of high Peak to Average Power Ratio in multi-carrier transmission schemes is presented. An overview of the most relevant Crest Factor Reduction techniques is performed, and the Clipping and Filtering and Peak Windowing algorithms are selected as implementation candidates due to their protocol agnostic nature. Several implementation architectures have been discussed, and the most computationally efficient one has been used to implement both algorithms within srsRAN, an open source, full software radio implementation of an LTE network with all of its components. In order to provide a comprehensive evaluation of the developed algorithms, an extensive measurement campaign has been designed and carried out, comprised of synthetic testing, as well as experimental physical signal measurements in a laboratory setting, and an outdoor measurement campaign. To speed up the measurement process, an automated measurement system has been designed in MATLAB, which remotely operates a signal analyser to perform spectrum and statistical power measurements, as well as IQ sample collection of the generated LTE signals. This measurement system has been used to carry out unwanted emissions tests following the LTE conformance testing procedures, which are also discussed within this document. For the outdoor measurements, an LTE single cell network has been deployed using a software radio transceiver and an LTE phone, with the aim of assessing the end to end quality of service improvements provided by the developed algorithms. The gathered results illustrate that the implemented Crest Factor Reduction techniques can provide significant network performance gains in situations with limited available transmission power. Additional gains provided by these techniques include increased efficiency in the operation of power amplification stages, and reduced network deployment costs. Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura