Efficient Fast-Convolution-Based Waveform Processing for 5G Physical Layer

Abstract

This paper investigates the application of fastconvolution (FC) filtering schemes for flexible and effective waveform generation and processing in 5th generation (5G) systems. FC based filtering is presented as a generic multimode waveform processing engine while, following the progress of 5G new radio (NR) standardization in 3rd Generation Partnership Project (3GPP), the main focus is on efficient generation and processing of subband-filtered cyclic prefix orthogonal frequencydivision multiplexing (CP-OFDM) signals. First, a matrix model for analyzing FC filter processing responses is presented and used for designing optimized multiplexing of filtered groups of CP-OFDM physical resource blocks (PRBs) in a spectrally welllocalized manner, i.e., with narrow guardbands. Subband filtering is able to suppress interference leakage between adjacent subbands, thus supporting independent waveform parametrization and different numerologies for different groups of PRBs, as well as asynchronous multiuser operation in uplink. These are central ingredients in the 5G waveform developments, particularly at sub-6 GHz bands. The FC filter optimization criterion is passband error vector magnitude minimization subject to a given subband band-limitation constraint. Optimized designs with different guardband widths, PRB group sizes, and essential design parameters are compared in terms of interference levels and implementation complexity. Finally, extensive coded 5G radio link simulation results are presented to compare the proposed approach with other subband-filtered CP-OFDM schemes and time-domain windowing methods, considering cases with different numerologies or asynchronous transmissions in adjacent subbands. Also the feasibility of using independent transmitter and receiver processing for CP-OFDM spectrum control is demonstrated.

PAPR Reduction With Mixed-Numerology OFDM

“…However, as will be shown in this paper, such approach does not facilitate efficient PAPR reduction of the aggregated signal combining multiple BWPs. Additionally, in CP-OFDM systems supporting different numerologies, inter-numerology interference (INI) is introduced [1], [3]. Therefore, the mixed-numerology signal structure and possible increase of INI should be considered when designing and developing the PAPR reduction algorithms.…”

“…Filtered OFDM is another effective approach for INI mitigation, and fast-convolution filtered OFDM (FC-F-OFDM) [3] is a computationally efficient and very flexible frequencydomain method for mixed-numerology systems, like 5G NR. In this paper, an effective PAPR reduction scheme is proposed by embedding properly tailored ICEF-like processing into the FC filtering.…”

Transparent Tx and Rx Waveform Processing for 5G New Radio Mobile Communications

“…In this section, the considered system parameterization is given, example performance results for different combinations of Tx and Rx units are provided and evaluated in terms of the achievable radio link BLER, and in the end a complexity comparison between evaluated waveform processing solutions is provided. The considered waveform processing solutions are fast convolution based subband filtered CP-OFDM (FC-F-OFDM) [10], filtered CP-OFDM (f-OFDM) [11], and windowed overlap-and-add (WOLA) processed CP-OFDM [7]. In all cases, the assumed reference Tx-Rx radio link performance for DL or UL is also given as a baseline.…”

“…FC-F-OFDM [10], is an efficient and flexible subband or BWP filtering scheme that allows computationally efficient implementation of steep subband, BWP or channel filters. The filter design is based on optimized frequency domain windows allowing to balance the required minimum stopband attenuation, transition bandwidth, and EVM performance.…”

Filtered multitone multicarrier modulation with partially overlapping sub-channels

“…The high level of spectral side lobes makes it necessary to have wide guardbands between asynchronous multiplexes, and OFDM sidelobe control has gained a lot of attention since early 2000's [4]. Recently, in the 5G context, this issue has gained more interest and the strong candidate waveforms include filtered OFDM schemes [5], [6], [3], [7].…”