Investigation of FBMC systems

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Dr. Kollár Zsolt
Department of Broadband Infocommunications and Electromagnetic Theory

In wireless communications cognitive radio systems are gaining more and more attention. The digital switchover of the TV broadcasting will result in frequency whitespaces (TVWS). Numerous researches focus on the spectrally efficient usage of these frequencies. There is a big opportunity to use multicarrier modulations in these bands.

The most widely used OFDM (Orthogonal Frequency Division Multiplexing) based systems have poor spectral properties regarding ACLR (Adjacent Channel Leakage Ratio) and thus spectral efficiency. However FBMC (Filterbank Multicarrier), which also belongs to the family of multicarrier modulation schemes, has much better spectral parameters. The performance (e.g. nonlinear distortion of amplifiers, DAC limits etc.) of the currently applied wireless data transmission circuits sets limitations for spectral and data transmission parameters of the system. The effects of nonlinear distortion have a big impact on ACLR. In case of multicarrier modulation schemes the signal's high PAPR (Peak-to-Average Power Ratio) is one of the main reasons for distortions. With the aid of signal processing methods PAPR can be reduced preserving the original ACLR so improving the parameters of the realized data transmission system.

In my work I simulate the non-ideal component's effects on the signals and the PAPR reducing schemes. With the help of USRP2 (Universal Software Radio Peripheral) developed by Ettus Research I verify the simulation results with measurements. Based on the measurement results I can verify that the methods also work in real-life environment.


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