Orthogonal Chirp Division Multiplexing-Based Multi-Numerology Communications for 6G

Abstract

This paper deals with the capability of the orthogonal chirp division multiplexing (OCDM) modulation scheme to cope with multi-numerology concept in the context of next generations of communications. The OCDM-based multi-numerology transceiver is introduced, based on the discrete Fourier transform (DFT) modulation, leading to expressions of the signals in both time and frequency domains. Then, the inter-numerology interference (INI) is analytically derived. The case of filtered-OCDM is considered as well, allowing to both reduce the INI and to shape the power spectrum of the composite signal (i.e. the signal composed of unitary signals configured with different numerologies) according to strong constraints of low out-of-band emissions. The simulations results show the inherent robustness of OCDM against INI as the interference is spread over all subcarriers, whereas it is concentrated in particular subcarriers in OFDM. It results that the (filtered)-OCDM waveform largely outperforms the orthogonal frequency division multiplexing (OFDM) by more than 2 dB in term of bit error rate (BER) performance, without need for a guard-band between numerologies. Otherwise, the OFDM requires a guard-band between unitary signals to reach the BER performance of OCDM, to the cost of a spectral efficiency loss.

Keywords

• OCDM
• multi-numerology
• 6G
• OFDM