A Code-Orthogonal PMCW Transmission Scheme for Improving Communications Performance in JCAS Systems

Abstract

Joint communications and sensing (JCAS) is regarded as a major technology building block in 6G networks. The combination of communications and radar sensing systems benefits from saved hardware costs, reduced energy consumption, and less spectrum occupation. Phase-modulated continuous waveform (PMCW) is regarded as an attractive candidate waveform for future automotive JCAS systems due to its perfect anti-interference properties and radar sensing performance. However, PMCW-based JCAS systems usually suffer from extremely low data rates and undesirable communications reliability in dynamic environments, limiting their applicability in traffic scenarios, where the propagation channel may suffer from a high Doppler shift and spread and a large data throughput is expected. To overcome the shortcomings, in this work, a novel PMCW approach with simultaneously transmitted pilot and data sequences, named code-orthogonal PMCW (CO-PMCW), is introduced. The presented CO-PMCW approach benefits from significantly improved data rate and robustness in dynamic environments. Regarding the differences in system architecture between PMCW and CO-PMCW, the authors verified the advantages and investigated the potential side effects of the CO-PMCW system. The properties including the interference between the pilot and data, influence on transmission power, behavior in multipath fading channels, etc. are measured. The result shows that the presented CO-PMCW approach significantly improves the communications performance with slightly influenced radar properties. Based on the simulation result, the application feasibility and scenarios of the CO-PMCW-based JCAS system are analyzed.

Keywords

• 77 GHz
• channel fading
• Doppler effect
• integrated sensing and communications (ISAC)
• joint communications and sensing (JCAS)
• JCRS