6.1 ISI and zero-ISI condition Let H()be the Fourier transform of h(t)and R,=1/T be the symbol rate. Nyquist zero-ISI theorem: xn=co[n川台 ∑H(f-kR)=const. As shown in fig,the condition requires the summation yields a flat spectrum. Foris periodic with Zero-ISI condition:the overall communication Rs,we pay attention to the interval system has to be designed such that h() of(-R/2,+R,/2). satisfies the following. &=wn=a5-日 n=0 n≠0 where c is an arbitray non-zero constant. -R R UESTC-Digital transmission thro BLAWGN channels Prof李晓峰 13