IEEE 802.11be: Performance of Chase Combining HARQ Protocol with LDPC over Channels with Doppler Spread and Feedback Delay

This paper analyses the performance of Chase Combining Hybrid Automatic Repeat Request (CC-HARQ) protocol in the novel 2024 IEEE 802.11 be physical layer (PHY) when it is implemented Low-Density Parity-Check (LDPC) codes over Doppler channels for the following transceiver architectures: downlink transmit beamforming (DL TxBF), DL multi-user multiple-input multiple-output (DL MU-MIMO), and uplink MU-MIMO. Simulation results indicate that the performance gains due to the implementation of CC-HARQ with LDPC codes vary between 2 to 4 dB with only one retransmission, where the achievable gains depend on PHY layer set-up and channel modelling. We also have observed that the performance of DL MU-MUMO transceivers presents a great sensibility with the decrease of precoding accuracy due to the joint effects of Doppler spread and channel state information feedback delay. Finally, we have concluded that the implementation of 802.11be PHY with 4096-QAM is possible with practical signal-to-noise ratio (SNR) when it is implemented TxBF transceivers even without implementing HARQ protocols. In this set-up, the implementation of CC-HARQ scheme with only one retransmission allows power gains between 3 to 4 dB, increasing the usage of 4096-QAM.