| With the increasing demand of wireless communication,the hybrid automatic repeat request technology is introduced into Wi-Fi in the proposal of IEEE 802.11 be standard,which is a new generation of Wi-Fi protocol,to improve the adaptive ability of Wi-Fi link and improve the throughput.At present,there are some research proposals aimed at introducing hybrid automatic repeat request technology into Wi-Fi,but none of them have been adopted by IEEE 802.11 standard organization,so there still have research value.In this thesis,the selection of retransmission unit and the inherent characteristics of low-density parity check matrix are studied.In this thesis,the hybrid automatic repeat request technology based on low density parity code in Wi-Fi is studied in depth.Firstly,the Wi-Fi protocol is studied,and the data frame composing process,data frame coding and modulation process and data frame feedback process in the protocol are investigated,and the related link level simulation platform is built,through the realization and simulation of the related algorithm in the platform,the physical characteristics are statistically analyzed,and its advantages and disadvantages are analyzed.Then,the hybrid automatic repeat request mechanism is introduced in IEEE 802.11 be to improve the system communication throughput.Based on current automatic repeat request mechanism,a codeword block based hybrid automatic repeat request scheme is proposed.A codeword block consisting of a number of code words is employed as retransmission unit in our proposal,at both the transmitter and receiver,the encoding and decoding of data frames could be completed according to predefined rules,and neither additional signaling nor additional information including the amount of retransmitted messages and their coordinates are required.Furthermore,using codeword block as retransmission unit improves the parity-check resolution,and hence potentially avoid some redundant retransmission.The simulation results show that in major fraction of the considered SNR region,our proposal achieves an energy gain around 1.5 to 2dB compared with the performance of the state-of-the-art existed hybrid automatic repeat request proposals for 802.11 be.Finally,the low-density parity check matrix in Wi-Fi is studied,and a hybrid automatic repeat request strategy based on degree distribution and cycle length is proposed,according to the degree distribution and cycle length characteristics of low-density parity check matrix of each code length and code rate,the algorithm will priority retransmit the higher degree bits in the code word,and the bits that need to be removed in the process of matching orthogonal frequency division multiplexing symbols are selected from the cycle length.Based on this method,the retransmission bits corresponding to each check matrix are fixed,without additional signaling indicating retransmission information and without wasting the ability of orthogonal frequency division multiplexing symbols to carry information.Simulation results show that the hybrid automatic request retransmission scheme based on degree distribution and cycle length can reduce the packet error rate and improve the throughput compared with the existing mainstream standard proposals in the middle and low signal to noise ratio region. |
