%%.......??2006.12.12........%%
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%基于隱導頻的定時同步???首先仿真各種定時同步算法?
%?仿真噪聲對?定時矩陣的影響?幅度的衰減
%?基本結論??在高斯信道下??park算法很好性能??在多徑信道下?sca和minn算法性能變化不大
%?多徑信道下一個主要問題就是如何設定判決門限
%?如果首徑最強?那么可以準確的定時?否則將在最強徑位置
%?定時同整數倍頻偏之間具有一致性
%??目標?同時兼顧估計精度?和檢測性能?
%%?同park算法進行?MSE（et）比較???注意限制條件為有限多徑
%?單獨設置?Nv測試?SCA算法的?MSE（et）
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clear?all;?
close?all;
clc;
fprintf（‘***********???It?is?running????************?\n‘）;
fprintf（‘***OFDM改進導頻定時算法***\n‘）;
%%--------------------------%%
Nframe=1;
N=1024;
Ng=256;????
%?%?SNRdB=5;??????????????????????????????%（0）
Ns=N+Ng;
v=2.8;?????????????????????????????????%（1）????研究頻偏對定時的影響
phase_begin=0;
P=N/4;??
L_est=32;???????????????????????????????%估計最大信道長度

?%h=[-0.3752?+?0.2211i???0.7139?-?0.1112i?0.2895?+?0.3627i???0.0118?+?0.1712i?-0.0001?+?0.0886i??-0.0167?+?0.0208i?-0.1435?+?0.0143i??-0.0183?+?0.0966i??-0.0148?-?0.0278i??-0.0019?+?0.0591i];
?%?h=[0.2833?-?0.4372i??-0.3360?+?0.4070i??-0.1657?-?0.1047i?-0.0052?-?0.0967i??-0.3599?-?0.2275i??-0.0721?+?0.0937i??0.2035?+?0.2520i???0.2091?-?0.0880i??-0.0821?+?0.1364i?0.0801?-?0.1370i];
?%h=[-0.2415?-?0.2726i???0.1209?+?0.4102i?0.0849?+?0.3239i???0.0706?-?0.0794i?0.0645?+?0.4963i???0.0699?-?0.2956i?0.0655?+?0.0727i???0.2799?-?0.1807i?0.2156?-?0.0677i??-0.0499?+?0.2103i];
????????????????????????
%-----------通用時域CAZAC序列產生-----------%??
???N1=P;???????????????????????????????????????%%對應序列周期P
???r=1/1;??????????????????????????????????
???k=0:N1-1;
???ct=exp（j*pi*r.*（k.^2）/N1）;??????????????????
???ct_sym=ct（N1+1-[1:N1]）;
???%--?m序列?用于ren?方法--%
???mgen=[1?1?0?0?1?1?1?1?1?1??];???????????????%%特定于N=1024
???PN=[m_sequence（mgen）?-1];
???
???mgen_half=[1?1?1?0?0?0?1?1?1];??????????????%%特定于N=512
???PN_half=[m_sequence（mgen_half）?-1];??
???
???mgen_128=[1?0?0?0?0?0?1];??????????????????????%%特定于128=N/2/L_est
???PN_128=[m_sequence（mgen_128）?-1];
???
???mgen_64=[1?1?1?0?0?1];??????????????????????%%特定于64=N/2/L_est
???PN_64=[m_sequence（mgen_64）?-1];
???
???mgen_32=[1?1?0?1?1];????????????????????????%%特定于32=N/2/L_est
???PN_32=[m_sequence（mgen_32）?-1];
???
???mgen_16=[1?0?0?1?];????????????????????????%%特定于16=N/2/L_est
???PN_16=[m_sequence（mgen_16）?-1];
???
???N2=2*P;
???k=0:N2-1;
???r2=1;
???ct1=exp（j*pi*r2.*（k.^2）/N2）;
???ct1_sym=ct1（N2+1-[1:N2]）;
???
???N4=N/2/L_est;
???k=0:N4-1;
???r4=1;
???ct_wls=exp（j*pi*r4.*（k.^2）/N4）;
???
???%%?序列補零擴展到N/2?同時產生擴展的差分序列
???PN_diff=PN_16;
???ct_matrix（11:N4）=ct_wls*sqrt（L_est）;
???PN_matrix（11:N4）=PN_diff;
???ct_matrix（[2:L_est]1:N4）=zeros（L_est-1N4）;
???PN_matrix（[2:L_est]1:N4）=zeros（L_est-1N4）;
???ct_wl=reshape（ct_matrix1N4*L_est）;
???PN_wl=reshape（PN_matrix1N4*L_est）;
???%?A?Robust?Joint?Estimator?for?OFDM?Timing?and?Frequency?Offsets?based?on?PN?Codes
???%?SY方法用于ct1序列（兩個相同CAZAC）
%-----------------------------------%
%數據QPSK調制??導頻CAZAC序列
%----------------------------------
tic;
step1=1;
start=10