FEASIBILITY OF DFT-S-OFDM IN 6G CELLULAR DOWNLINK

Since the beginning of the first mobile communication systems during early 1980s the cellular industry has been developing extremely rapidly. Approximately every ten years a new generation of cellphone network technology is introduced. The motivation behind development is of course the unquenchable need for more reliable and faster connections between devices. One of the key areas of improvement have always been the enhancement of something that already existed in the older generation technology. Simultaneously something completely new is always introduced when the requirements for the next generation are drafted.
The most common parameters that are constantly being improved from generation to generation are spectrum efficiency, mobility, latency, reliability, user experienced data, security and peak data rate. However, the sustainability and energy efficiency are aspects that have strongly risen into consideration lately in the mobile network industry as well as others. This can be observed from the IMT-2030 (International Mobile Telecommunications2030) standard that sets the technical reference for 6G, issued by ITU-R (International Telecommunication Union Radiocommunication Sector). It is noteworthy that in IMT2020 (technical reference for 5G) the requirement of energy efficiency was to be equal to that of 4G. Also in IMT Advanced (technical reference for 4G) the sustainability or energy efficiency was not mentioned at all.
In the context of these new interests towards sustainability, the main goal of this thesis is to study whether energy efficiency could be improved by using DFT-s-OFDM (Discrete Fourier Transform-spread-Orthogonal Frequency Division Multiplexing) waveform instead or alongside of OFDM in 6G downlink communications in base stations. The proposed waveform is well studied and its most important properties of low PAPR (Peak to average power ratio) and thus larger coverage are well known, but the effects of utilizing DFT-s-OFDM in regards to energy efficiency remains, to the most part, unclear.
The thesis is structured as follows. First, a brief overview of evolution of mobile communication system generations (from 1G to 4G) is given, focusing mostly on physical layer aspects. Then chapter 2 proceeds to introduce multicarrier modulation basics and a comparison is made to its more traditional counterpart, single carrier modulation. The comparison is made by analyzing their strongest and weakest features in terms of performance in data transmission. The following chapter 3 focuses solely on imperfect analog electronics in transceivers and their effects on signal quality. Then a performance comparison between DFT-s-OFDM and CP-OFDM is made based on theory, and the simulation results presented in chapter 4. The thesis ends by drawing conclusions about the simulation results.