Scalable Numerology for Effective Asynchronous and Orthogonal Signal Waveforms Using FF-OFDM Scheme

Abstract

Wireless systems are often affected by distortions at the physical layer, which hinder reliable performance. A key challenge is the limited ability to suppress interference at the receiver, preventing the achievement of the asynchronous and orthogonal signal waveforms required for efficient utilization of Fifth Generation New Radio (5G NR) resources. Poor asynchronicity and orthogonality primarily result from Adjacent Channel Interference (ACI), Inter-Symbol Interference (ISI), and Inter-Channel Interference (ICI). This work addresses these challenges using the Feedback Filtered Orthogonal Frequency Division Multiplexing (FF-OFDM) channel access technique. Simulation results at 60 kHz Subcarrier Spacing (SCS) show that Hann--Kaiser-based FF-OFDM achieves superior mitigation of ICI (-47.0 dBm) and ISI (-39.0 dBm) compared to Hann-Chebyshev-based FF-OFDM (-45.2 dBm and -37.2 dBm, respectively). Conversely, Hann-Chebyshev-based FF-OFDM provides better ACI suppression (-27.5 dBm) than Hann-Kaiser-based FF-OFDM (-25.4 dBm). Similar trends were observed at 120 kHz SCS, where Hann-Kaiser-based FF-OFDM consistently produced more orthogonal signal waveforms, while Hann--Chebyshev-based FF-OFDM yielded safer asynchronous signal waveforms. The conventional and modified F-OFDM models were used as benchmarks for evaluating and validating these results.