An industrial Internet-of-things URLLC system via cross-layer design for anti-jamming

The classical OFDM multicarrier waveforms for transmission are adopted by the existing 5G/B5G URLLC standard (3GPP R17-18), and less attention is paid to the anti-interference strategy of URLLC-OFDM multicarrier transmission due to its operation in the licensed frequency band. In the future, unlicensed frequency bands will host most heterogeneous multi-QoS services for IIoT, resulting in complex wireless communication links. The stringent requirements of high reliability and low latency for IIoT information transmission can not be fully met by the existing URLLC-OFDM waveforms. Firstly, the more robust Sub-FH technique was applied to OFDMA based on subcarrier-configurable OFDMA (i.e., Sub-FH/OFDMA) to improve the signal transmission reliability. Additionally, the Sub-FH/OFDMA waveforms were incorporated into a scheduling strategy with mini-slots as the basic unit. Hamming coding + mini-slot hopping HARQ were utilized by this scheduling strategy to effectively reduce the amount of retransmissions, which aim to enhance the real-time transmission among IIoT nodes. The theoretical relationship between BER/BLER and transmission delay was derived and compromises were made. Simulation results demonstrate that the scheme can ensure stable transmission quality of IIoT nodes despite external electromagnetic interference and internal multi-user interference, achieving a transmission delay of milliseconds when the target BLER is 10^-5. A feasible solution for the future practical application of B5G/6G communication in complex IIoT scenarios is provided through the cross-layer design of waveform design and MAC slot scheduling in this paper.