WR-OFDM system and OOB spectrum comparison

The most important figure-of-merit for the 5G waveform is the spectrum efficiency. Especially, OOB (out-of-band) spectrum must be reduced to increase the spectrum efficiency and decrease the guard band between the channels. In the filtering methods, UFMC (universal filtered multi-carrier) and FBMC (filter bank multi-carrier) were suggested for the new waveform for 5G mobile communication system. Similar to OFDM system, they are based on the multi-carrier, but they have sharper OOB spectrum. Due to the very complicated process and some serious difficulty to the realization, windowing method has been enlightened. In the windowing method, WOLA-OFDM (weighted overlap and add — orthogonal frequency division multiplexing) system is the most famous and representative windowing method among the many possible conventional windowing methods. However, the WOLA-OFDM system has serious problems. Due to the copy and addition processes, time resource will be slightly sacrificed and the other is that the left part of the copied and added parts will invade into the right part of the previous OFDM symbol. This is very serious data damage even before the transmission. In this paper, we like to suggest a WR (windowing and restructuring)-OFDM system that shows competitive OOB spectrum characteristics and is designed by simple some modification of the conventional OFDM system. Basically this is similar to the conventional OFDM system, but windowing process has to be included after the CP (cyclic prefix) addition stage. By adding this windowing process, we can get the desirable OOB (Out-Of-Band) spectrum characteristics that are very important to save the frequency resources and competitively similar shape to the OOB spectra of FBMC and UFMC system. From the simulation results, it is confirmed that OOB power spectrum of WR-OFDM is quite comparable with the existing waveforms.