数字基带传输模型（单极性归零码）

OFDM(正交频率调制)实现多载波调制基本思想是将带宽信道分解成许多并行的窄子信道，是每个子信道的想干带宽，从而实现平稳衰落。搭建了完整的OFDM信道链路系统，运用三种不同的信道估计方法(LS信道估计、DFT信道估计、Improved-DFT信道估计)，并对AWGN理想信道和衰落信道误码情况进行了仿真和比较。(OFDM (Orthogonal Frequency Modulation) multicarrier modulation basic idea bandwidth channel is decomposed into a number of parallel narrow subchannels, each subchannel wanted bandwidth, in order to achieve a smooth fading. Build a complete OFDM channel link system, the use of three kinds of different channel estimated method (LS channel estimated, to the DFT letter Tao estimates, Improved-the DFT letter Road estimated), and AWGN ideal letter Road and fading channel bit error situation conducted a simulation and comparison .)

产生16QAM基带信号，成型滤波通过AWG信道，接收端得到误码率和星座图。(The 16QAM baseband signal is generated, the shaping filtering is passed through the AWG channel, and the receiving end obtains the BER and constellation diagram.)

1962年Gallager提出LDPC的博士论文，堪称经典(1962 Gallager LDPC proposed doctoral dissertation, a classic)

v2v信道建模，参数依据论文《Deep reinforcement learning based resource allocation in V2V communications》(V2V channel modelling, parameters are based on published paper Deep reinforcement learning based resource allocation in V2V communications)

在实际的调谐解调电路中，采用的是非相干载波解调，本振信号与发射端的载波信号存在频率偏差和相位抖动，因而解调出来的模拟I、Q基带信号是带有载波误差的信号。这样的模拟基带信号即使采用定时准确的时钟进行取样判决，得到的数字信号也不是原来发射端的调制信号，误差的积累将导致抽样判决后的误码率增大，因此数字QPSK解调电路要对载波误差进行补偿，减少非相干载波解调带来的影响。(In the actual tuning and demodulating circuit, non-coherent carrier demodulation is adopted, and the frequency deviation and phase jitter of the local oscillator signal and the carrier signal of the transmitting end are present, and thus the demodulated analog I and Q baseband signals are signals with carrier error.)

说明：  各种polar编译码函数，包括SC译码，BP译码，SCL译码以及循环检测编码(Various polar encoding and decoding functions, including SC decoding, BP decoding, SCL decoding and cyclic detection coding)

用于描述通讯中常用的RS编码原理，以及MATLBA仿真实例(Used to describe communication RS coding theory, and simulation MATLBA instance)

ekf implmentation for ofdm

说明：  在matlab环境下,仿真基于循环平稳特征检测的频谱感知,(Spectral sensing based on cyclic stationary feature detection)

说明：  IEC-61850标准分析完整中文版（自用）(IEC-61850 standard analysis)