Inter-Numerology Interference for Beyond 5G

Fifth generation (5G) radio access technology (RAT) is designed to flexibly serve multiple services with extremely diverse requirements. One of the steps taken toward fulfilling this vision of 5G-RAT is the introduction of multi-numerology concept, where multiple frame structures with different subcarrier spacings coexist in one frequency band. Though efficient in providing the required flexibility, this approach introduces a new kind of interference into the system known as inter-numerology interference (INI). In this study, a novel cyclic prefix (CP) insertion technique (referred to as common CP) for multi-numerology system is mathematically analyzed in terms of the INI problem and its extensive comparison with the conventional CP configuration (referred to as individual CP) standardized for the 5G multi-numerology systems is presented. An in-depth discussion of various critical issues concerning multi-numerology system such as frequency domain multiplexing, time domain symbol alignment, and orthogonality between subcarriers of different numerologies is presented in the light of both, individual and common CP configurations. The analyses reveal that common CP has an advantage of restructuring the INI pattern in the system in a manner that paves the way for developing better techniques of avoiding or minimizing INI in the future generations.