Research On Adaptive Modulation And Demodulation Technology In Millimeter Wave High Speed Communication

The arrival of the 5G era means that communication systems will get higher throughput and lower latency.As an important technology of 5G communication,millimeter wave communication link brings great progress to the communication system,but it also has the problem of being vulnerable to atmospheric absorption and rain attenuation in the meantime.Different modulation methods of baseband signal directly affect the performance of communication link.By changing communication parameters according to channel conditions,adaptive modulation and coding(AMC)technology can improve the reliability and throughput of the communication system,and reduce the negative impact of millimeter-wave loss on the communication process.The key to AMC technology is the determination of the mode switching threshold and the accuracy of receiver synchronization and Signal-to-Noise Ratio(SNR)estimation algorithms.In the common adaptive modulation and coding design,due to problems in the frame format,receiver synchronization algorithms and signal-to-noise ratio estimation algorithms,the receiver's adaptive accuracy has a large deviation.To solve these problems,this thesis mainly handles the following tasks:Firstly,design a single carrier(SC)frame format.According to IEEE 802.11 ad standard protocol,the short training field and channel estimation field are constructed by using Gray sequence to realize each synchronization algorithm of receiver more efficiently.The header field and data field are designed to store adaptive modulation signaling information and effective data respectively.Secondly,simplify the computational complexity of some algorithms,optimize the frame synchronization judgment conditions and propose an efficient demapping algorithm.The receiver synchronization process includes burst frame detection,frame synchronization,phase tracking,SNR estimation and demapping,etc.This article simplifies the calculation process of some of the above algorithms,and proposes a frame synchronization judgment conditions to increase the system's tolerance to noise,the efficient demapping algorithm in each mode is also designed.In addition,the FPGA design and optimization method of each algorithm on the hardware is given.Thirdly,build the adaptive link,clarify adaptive switching thresholds,and save SNR estimation expenses.The design reuses the channel estimation sequence as auxiliary data for SNR estimation to reduce sequence expenses and compares estimated parameters and mode switching thresholds in real time,automatically switches to the appropriate communication mode to coordinates the operation of the entire transmitter/receiver.