Non-orthogonal waveforms (NOW)
thesisposted on 28.03.2022, 13:04 by Billy Conditsis
This project looks at a new interface to be developed by using non-orthogonal waveforms as opposed to orthogonal waveforms. It focuses on the particular non-orthogonal waveform called Generalised Frequency Division Multiplexing (GFDM), which consists of subcarrier filtered multicarrier modulation using circular convolution. This is important as the upcoming consumer environment is not well suited for orthogonality. this document reports the idea of abandoning synchronism and orthogonality altogether, thereby leading to possible problems such as crosstalk or interference, and tests if these impairmants may be optimised by a suitable transceiver structure and transmission technique. The way way in which this transmission technique will be optimised is by the comparison of various filtered GFDM signals through simulations using Matlab software. These simulations represent future proposed transmission examples and highlight the benefits of using specific GFDM filters over OFDM. The main problem to be analysed is Out of Band (OOB) emissions in each of the filters. Comarisons of different parameters in the filters, such as the roll-off factor and subcarrier/subsymbols are manipulated to illustrate positive as well as negative effects. This has allowed an optimal solution to the problem at hand. This optimal solution is revealed using a prototype XIA 4th order filter using full roll-off and maximum subsymbols. In doing so, the performance of the GFDM signal is increased via less interference. Overall, a clearer understanding of the proposed waveform is presented and recommended.