CPW-OFDM(Cyclic Postfix Windowing OFDM) for the B5G (Beyond 5th Generation) Waveform

Abstract

For the new radio waveform of the beyond 5G mobile system, the spectrum efficiency is the most important factor. Especially, OOB (out-of-band) power spectrum must be reduced to increase the spectrum efficiency and to save the frequency resources. Filtering is the one way to get the sharp OOB spectrum. So, f-OFDM (filtered orthogonal frequency division multiplexing), UFMC (universal filtered multicarrier) and FBMC (filter bank multicarrier) belong to the filtering method and were suggested as 5G new radio waveform. However, there are still some problems such as the very complicated process and some difficulty to the realization. The other approach is the windowing method. WOLA-OFDM (weighted overlap and add - orthogonal frequency division multiplexing) system is the most representative windowing method. However, the WOLA-OFDM system has inherently some serious problem. Due to the overlap process of the copied and added extensions, the left extension part will invade into the right part of the previous OFDM symbol because left extension and right extension of two consecutive OFDM symbols must be overlapped in order not to sacrifice the time resource. This is very serious data collision in the transmitter even before the transmission. So, in order to improve the WOLA-OFDM system and to solve this data collision problem of WOLA-OFDM between the consecutive OFDM symbols, we like to propose a CPW-OFDM (cyclic postfix windowing - orthogonal frequency division multiplexing). In this proposed CPW-OFDM system, the first part of the OFDM symbol is copied and added on the right-end of the OFDM, which is the cyclic postfix. Then, windowing is made on this cyclic postfix and already existing cyclic postfix. WOLA-OFDM has right and left extensions and windowing is performed on these 2 extensions, but the proposed CPW-OFDM has only one extension on the right side and windowing is perform and on this right extension and left part of CP(cyclic prefix). Therefore, there is no data collision in the proposed CPW-OFDM. CPW-OFDM system is an improved and simplified version of the WOLA-OFDM system. Simulations results show that the proposed CPW-OFDM system has comparable OOB spectrum reduction characteristics and can be designed by simple some modification from the conventional OFDM system.