Diseño e implementación de técnicas de sincronización, estimación e igualación de canal para plc

Resumo

Power Line communications (PLC) systems have experienced an increasing research interest in recent years: there are already some commercial proposals for multimedia connectivity in homes, and they are playing an important role in the development of smart energy distribution networks (Smart Grids). At the same time, they have implied a change in the current society, being one of the most important means to provide broadband support for data transmission. The fact of being a medium with a very low installation cost, since they use the existing electrical network in most of the indoor public environments (buildings, households, industrial factories, etc.), is one of its main advantages. The PLC channel has certain particularities, such as the strong selective frequency fading, the longer effective channel length, as well as the characterization of the channel noise into background noise and into three types of impulsive noise. The IEEE 1901-2010 standard proposes the use of Wavelet-OFDM as a medium access technique. This technique allows to improve the spectral efficiency of the system by better defining the subcarriers in frequency and, therefore, it reduces emissions outside the emission band. Wavelet-OFDM introduces a filtering for each subcarrier after the DCT-IV, known as a prototype filter. This filtering makes consecutive symbols overlap in the time domain. The first objective of the thesis is to propose a robust algorithm of temporal synchronization in broadband PLC systems, using the Wavelet-OFDM as medium access technique. This algorithm proposes the use of complementary sets of multilevel sequences as pilot symbols, due to their optimal correlation properties, making it possible to perform a precise synchronization in the receiver. Secondly, possible methods of equalization and channel estimation are analyzed to compensate the effects introduced in the PLC transmission. This requires the study of various transmission techniques, such as the insertion of a cyclic prefix and zeropadding, to select the one that best fits the specifications. As before for synchronism, the proposed algorithms for estimation and channel equalization are based on the use of Zadoff-Chu sequences as pilot symbols in the preambles of the PLC transmission. Finally, an efficient architecture based on FPGAs (Field-Programmable Gate Arrays) is presented for the real-time implementation of the proposed synchronization algorithm, together with the ones proposed for the estimation and equalization of the channel, which can be integrated into a hypothetical PLC receiver that uses WaveletOFDM as medium access technique