%*********************BINARY?PHASE?SHIFT?KEYING?*******************
%
%?Simulation?of?BPSK?system?in?presence?of?Additive?White?Guassian?Noise
%?and?Rayleigh?fading?and?Dopper?shift?and?using?SPREAD?SPECTRUM?TECH
%
%******************DIRECT?SEQUENCE?SPREAD?SEQUENCE******************
clear?all
clc

f_data=1;??????????%?DATA?FREQUENCY
f_chip=11;?????????%?LENGTH?OF?CHIP?SEQUENCE
fc=220;????????????%?RELATIVE?CARRIER?FREQUENCY
fs=fc*3;???????????%?SAMPLING?FREQUENCY
N=fs/f_chip;???????%?CODING?RATE
data_length=1000;??
M=2;???????????????%?BINARY?LEVEL?CODING

matches=0;
errors=0;
count=1;

SNRpbit=0;
SNR=SNRpbit;
rand（‘state‘12345）;????%?INITIALISATION?‘SEED‘
randn（‘state‘54321）;

numplot=100;

msg_unspread=randsrc（data_length1[0:M-1]）;?%?GENERATION?OF?RANDOM?DATA?


PN_sequence=randsrc（111[0:1]）;?????????????%?GENERATION?OF?PN?SEQUENCE

%?GENERATION?OF?SPREADED?MESSAGE
j=1;
for?i?=?1:data_length
????for?k?=?j:j+f_chip
????????msg_orig（k）?=?msg_unspread（i）;
????end;
????msg_orig（j:（j+f_chip-1））?=?xor（msg_orig（j:（j+f_chip-1））‘PN_sequence（1:f_chip））;
????j?=?f_chip*i+1;????
end;

len_of_orig=length（msg_orig）;


%?MODULATING?THE?SPREAD?MESSAGE?
msg_tx=dmod（msg_origfcf_chipfs‘psk‘M）;
len_of_tx=length（msg_tx）;


%?%?RAYLEIGH?COEFFICIENTS
%?magT=abs（T）;
%?
%?%?ADDING?RAYLEGH?FADING?COEFFICIENTS
%????k=1;
%????for?i=1:len_of_tx
%???????msg_tx（1i）=msg_tx（1i）*10*magT（1k）;
%???????if（mod（ik））
%??????????k=k+300;
%???????end?;
%????end;????

%?PERFORMANCE?ANALYSIS?FOR?VARYING?SNR‘S

for?SNRpbit=0:1:7
??
????SNR=SNRpbit;
????rand（‘state‘12345）;
????randn（‘state‘54321）;

???%?ADDING?AWGN?TO?THE?SIGNAL?
????msg_rx_data=awgn（msg_txSNR-10*log10（N）‘measured‘‘dB‘）;?
????
????%?plot（tmsg_rx（1:length（t））‘b-‘）;
????msg_rx=?msg_rx_data?;
???????
????
????msg_rx=msg_tx;
???%?DEMODULATING?THE?RECEIVED?SIGNAL
????msg_demod=ddemod（msg_rxfcf_chipfs‘psk‘M）;

???%?CORRELATING?WITH?THE?PN?SEQUENCE?
????j=1;
????for?i?=?1:data_length
??????msg_demod（j:（j+f_chip-1））?=?xor（msg_demod（j:（j+f_chip-1））‘PN_sequence（1:f_chip））;
??????j?=?f_chip*i+1;????
????end;

???%?DESPREADING?THE?RECEIVED?SIGNAL
????j=1;
????for?i?=?1:data_length
??????sum=0;
??????for?k?=?j:j+f_chip
????????sum=sum+msg_demod（k）;
??????end;
??????if?（sum?>=7）
????????msg_demod_rec（i）=1;
??????else
????????msg_demod_rec（i）=0;
??????end;????
????j?=?f_chip*i+1;????
????end;
?
???%?CALCULATION?OF?ERRORS
?
???for?i=1:data_length;
?????if?（msg_demod_rec（1i）==?msg_unspread（i1））
???????????matches=matches+1;
?????else
???????????errors=errors+1;
?????end?;
???end;?????
?
??%?BER_ray（count）=errors/data_length;
??BER_awgn（count）=errors/data_length;
??%BER_theo（count）=0.07*erfc（SNR^0.5）;
????count=count+1;
????errors=0;
????
end;???????

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件????????698??2003-05-14?20:38??read_me.txt

?????文件???????2855??2006-05-04?19:40??bpsk_spread.m

?????文件???????1485??2003-04-28?15:10??jakesmodel.m

-----------?---------??----------?-----??----

?????????????????5038????????????????????3