WLAN的TX代码第二篇：20M信号HT-MF格式的帧头LLTF和HTLTF演示

幻始现终 · 发表于 2014-4-11 15:30:41

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本帖最后由幻始现终于 2014-4-11 15:54 编辑

接着第一篇的帧结构，LSTF部分后面的是LLTF部分，这个部分包含2个OFDM符号，其结构如下图所示

这2个symbol主要是用来细频偏估计、细同步和信道估计，其频域的子载波如下

pilotPatten = [zeros(1,6) 1,1,-1,-1,1,1,-1,1,-1,1,1,1,1,1,1,-1,-1,1,1,-1,1,-1,1,1,1,1,0,
1,-1,-1,1,1,-1,1,-1,1,-1,-1,-1,-1,-1,1,1,-1,-1,1,-1,1,-1,1,1,1,1 zeros(1,5)];

我们假定MCS=1只有一个数据流，但采用了STBC=1,这样就是2个天线的发射分集，TX=2，其主代码如下

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% description: This function is main function of 802.11n
% author:
% date: 2014 02 19
% call function list:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear;clc;close all;
global vecTx;
vecTx.format = 'HT_MF';
vecTx.non_HT_modulation = 'OFDM';
vecTx.L_length = 4095;
vecTx.L_dataRate = 6; %
vecTx.L_sigValid = 1;
vecTx.MCS = 1;
vecTx.CH_bandWidth = '20MHz'; % '20MHz' or '40MHz'
vecTx.CH_offset = 'CH_OFF_20'; % 'CH_OFF_20' 'CH_OFF_40' 'CH_OFF_20U'or 'CH_OFF_20L'
vecTx.length = 65535;
vecTx.smoothing = 1;
vecTx.sounding = 0;
vecTx.aggregation = 0;
vecTx.STBC = 1;
vecTx.FEC_coding = 0; % 0:BCC or 1:LDPC
vecTx.GI_type = 0; % 0:long GI or 1:short GI
vecTx.Ness = 0; % Num_exten_S
vecTx.Ntx = 2;
vecTx.expension_MAT = 'COMPRESSED_SV';
vecTx.expension_MAT_type= 0; % 1:expension_MAT is present 0:not present
vecTx.SPMmode = 'DM'
% system configuration
vecTx = ParameterMCS(vecTx);
%% LLTF
LLTF = LLTF_Gen;
figure;plot(real(LLTF)');title('LLTF-real');legend('real-tx1','real-tx2');
figure;plot(imag(LLTF)');title('LLTF-imag');legend('imag-tx1','imag-tx2');
figure;plot(abs(fftshift(fft(LLTF(1,:),64))));title('LLTF-freWave');
%% HTLTF
HTLTF = HTLTF_Gen;
figure;plot(real(HTLTF)');title('HTLTF-real');legend('real-tx1','real-tx2');
figure;plot(imag(HTLTF)');title('HTLTF-imag');legend('imag-tx1','imag-tx2');
figure;plot(abs(fftshift(fft(HTLTF(1,:),64))));title('HTLTF-freWave');