  The physical layer of 5G cellular communications systems is designed to
achieve better flexibility in an effort to support diverse services and user
requirements. OFDM waveform parameters are enriched with flexible
multi-numerology structures. This paper describes the differences between Long
Term Evolution (LTE) systems and new radio (NR) from the flexibility
perspective. Research opportunities for multi-numerology systems are presented
in a structured manner. Finally, inter-numerology interference (INI) results as
a function of guard allocation and multi-numerology parameters are obtained
through simulation.
