%?File:?c15_bwa.m
%?Software?given?here?is?to?accompany?the?textbook:?W.H.?Tranter?
%?K.S.?Shanmugan?T.S.?Rappaport?and?K.S.?Kosbar?Principles?of?
%?Communication?Systems?Simulation?with?Wireless?Applications?
%?Prentice?Hall?PTR?2004.
%
function?[p?pye?b]?=?c15_bwa（iterationsstatesout）;
len?=?length（out）;
p?=?input（‘Enter?the?initial?state?transition?matrix?P?>?‘）;
pye?=?input（‘Enter?the?initial?state?probability?vector?pye?>?‘）;
b?=?input（‘Enter?the?initial?output?symbol?probability?matrix?B?>?‘）?;
alpha=zeros（lenstates）;?beta=zeros（lenstates）;
eta=zeros（statesstates）;?gamma=zeros（1states）;?scale=zeros（len1）;
loglikelihood?=?zeros（1iterations）;
iplot?=?1;							%?likelihood?plot?if?1
%
p									%?display?initial?p
pye									%?display?initial?pye
%
pye_rec?=?zeros（states1）;
pye_rec（:1）?=?pye‘;
sum_gamma?=?0;
sum_eta?=?0;
%
for?cycle?=?1:iterations
???cycle		????????????????????%?display?iteration?index
???%
???%?????alpha?generation?
???%
???alpha（1:）?=?pye.*b（1:）;
???scale（1）?=?sum（alpha（1:））;
???alpha（1:）?=?alpha（1:）/scale（1）;
???for?t?=?2:len
???????alpha（t:）?=?（alpha（t-1:）*p）.*b（out（t）+1:）;
???????scale（t）?=?sum（alpha（t:））;
???????alpha（t:）?=?alpha（t:）/scale（t）;
???end
???%
???%?????beta?generation?
???%
???beta（len:）?=?1/scale（len）;
???for?t?=?len-1:-1:1
???????beta（t:）?=?（beta（t+1:）.*b（out（t+1）+1:））*（p‘）/scale（t）;
???end
???%
???%?????eta?generation?
???%
???sum_eta?=?zeros（states）;
???for?t?=?1:len-1
??????for?i?=?1:states
?????????eta（i:）?=?（（alpha（ti）*（p（i:）.*（b（out（t+1）+1:）））.*beta（t+1:）））...
????????????/sum（alpha（t:）.*beta（t:））;
???????end
???????sum_eta??=?sum_eta?+?eta;
???end
???%?
???%?????gamma?generation?
???%
???gamma_sum?=?zeros（1states）;
???for?t?=?1:len
??????gamma_sum?=?gamma_sum?+?alpha（t:）.*beta（t:）;
???end
???%?
???%		calculate?and?display?the?log_likelihood?function
???%
???loglikelihood?=?sum（log10（scale））;
???log_likelihood（cycle）?=?loglikelihood;
???loglikelihood									%?display?result
???%
???%?????Re-estimation?of?the?intial?state?probability?vector?pye????????
???%??
???pye（1:）?=?alpha（1:）.*beta（1:）/sum（alpha（1:）.*beta（1:））;
???%
???pye							%?display?pye
???%
???pye_rec（:cycle+1）?=?pye‘;	%?Save?for?plot?illustrating?convergence	
???%
???%?????Re-estimation?of?the?state?transition?matrix?P
???%
???for?i?=?1:states
??????for?j?=?1:states
?????????p_estimate（ij）?=?sum_eta（ij）/（gamma_sum（i）-alpha（leni）.*beta（leni）...
????????????/（sum（alpha（len:）.*beta（len:））））;
??????end
??????p_estimate（i:）?=?p_estimate（i:）/sum（p_estimate（i:））;
???end
???%
???p?=?p_estimate				%?display?p
???%
???%?????Re-estimation?of?output?symbol?probability?matrix?B
???%
???out_0?=?find（out?==?0）;
???out_1?=?find（out?==?1）;
???sum_0?=?zeros（1states）;
???sum_1?=?zeros（1states）;
???for?i?=?1:length（out_0）
??????sum_0?=?sum_0?+?alpha（out_0（i）:）.*beta（out_0（i）:）...
?????????/sum（alpha（

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2004-08-04?15:22??Chapter_15\
?????文件????????3667??2004-08-02?13:29??Chapter_15\c15_bwa.m
?????文件????????1773??2004-08-02?13:29??Chapter_15\c15_errvector.m
?????文件????????1612??2004-08-02?13:29??Chapter_15\c15_hmm2.m
?????文件????????1011??2004-08-02?13:29??Chapter_15\c15_hmmtest.m
?????文件?????????804??2004-08-02?13:29??Chapter_15\c15_intervals1.m
?????文件????????2215??2004-08-02?13:29??Chapter_15\c15_intervals2.m
?????文件?????????702??2004-08-02?13:29??Chapter_15\c15_MMtransient.m
?????文件????????1170??2004-08-02?13:29??Chapter_15\c15_seglength.m
?????文件????????5243??2004-08-02?13:29??Chapter_15\c15_semiMarkov.m