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23 juin 2017

Post-Doc at IETR, Rennes - Analytical derivations and algorithms for PAPR reduction

Catégorie : Post-doctorant

Optimisation of novel PAPR reduction techniques and analytic evaluation of in-band and out-of-band distortions of multicarrier signals with non-linear amplification for Digital Video Broadcasting systems.

Beginning : 01/10/17

Duration : 1 to 2 years

Related Projects : FUI Convergence TV and Eurostar GreenTEA

Contact: Matthieu Crussière, matthieu.crussiere@insa-rennes.fr


The energy consumption of the broadcast and wireless communication networks is huge (in the order of several Megawatts for countries like France or Spain). Between 50 and 80 % of this consumption (depending on the type of service) is directly due to the amplification of the signals, because all modern transmission systems (including 4G cellular, digital terrestrial TV) are using multicarrier waveforms, which are characterized by a high Peak to Average Power Ratio (PAPR) leading to a low efficiency of the amplification systems. PAPR reduction techniques can be implemented in order to reduce this dynamic range and thus be able to use the non-linear amplifier at an operating point leading to better energy efficiency. However, non-linear amplification results in in-band distortions measured by the Error Vector Magnitude (EVM) and out-of-band distortions measured by Adjacent Channel Power Ratio (ACPR). Reducing the PAPR of the multicarrier signals in order to improve the efficiency of the power amplifiers and analysing the in-band and out-of-band distortions is then a high research topic with a vast potential for energy savings. This research work will be performed within the framework of the FUI “Convergence TV” project, which aims, among other things, at developing innovative solutions for reducing the energy consumption of television transmitters

This research project will therefore include two complementary aspects.

The first objective of this work based on simulations is to go beyond the state of the art by optimising PAPR reduction process using Tone Reservation technique. Efficient Tone Reservation based PAPR reduction algorithms have already been studied by the research team in a previous work. However, a lot of parameters must be optimized to reach the optimal performance/complexity/latency trade-off taking into account the detailed characteristics of the FGPGA, which is used for the final implementation. Then, the PAPR reduction algorithm selected and optimised for DVB-T2 will be combined with the pre-distortion module. In a second step, various tone reservation algorithms will be studied and applied to the new American ATSC3.0 standard. The PAPR reduction algorithms selected and optimised for ATSC3.0 will be combined with the pre-distortion module. Furthermore, the measurements of the performance of the complete system with a real test bench including DVB-T2 and ATSC3.0 generators with or without the selected optimized PAPR reduction algorithms, the digital pre-distortion module and high power amplifiers will be carried out. Combined with the use of new generation high efficiency power amplifiers, the results of the project will then be to optimise new modulators and new transmitters for Digital Terrestrial Television in compliance with the 2 second generation standards such as DVB-T2 and ATSC3.0, which cover about 70 % of the worldwide market. It is expected to obtain a reduction of 10% to 15% in energy consumption.

The second aspect of this research work deals with the analytic evaluation of the resulting in-band and out-of-band distortions of multicarrier signals after non-linear amplification by taking into account different PAPR reduction techniques and specifically the previous optimized Tone Reservation techniques. A previous work has already been carried out by our research team but with only simple clipping reduction PAPR techniques. Within this work, the novelty will be to generalize this approach by first analyzing the statistics of the signals after the implementation of Tone reservation PAPR reduction techniques taking into account pre-distortion techniques. Then in-band and out-of-band distortions will be analytically evaluated according to the characteristics of the power amplifier with or without memory effect and compared to simulation results. Besides, particular attention will be paid to the link and relative evolution of in-band and out-of-band distortions.

Finally, the study will be extended to the candidate filtered multicarrier waveforms for the 5th generation of cellular networks. It is worthwhile to note that these proposed theoretical analyses will be very useful for optimizing future transmitter efficiency and linearity of the power amplifier in the field of broadcasting applications for the deployment of DVB-T2 and ATSC3.0 transmitters as well as for LTE and future cellular networks.

Advanced and novel efficient solutions will be studied in order to publish in high scientific level journals and communicate in the best international conferences. This work will benefit from the strong experience of IETR concerning multicarrier modulation, PAPR reduction techniques, wireless technologies and associated signal processing in general. During the last 5 years, IETR has been working on those techniques for different applications as future cellular networks and Digital Video Broadcasting in European projects, and is today one of the rare academic partners involved in European projects in that field.


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