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=c6[n台 ∑H(f-kR)=cosi. Observation: Zero-ISI condition:the overall communication =y(nT)=>agh(nT-kT)+v(-) system has to be designed such that h() 0 0 ..+a2h(2T)+ah()+a,h(0) satisfies the following. n=0 +ah(-T)+amh(-2T)+... v(nT =ah00+汉+，9mn） 0 &=lwn=a5-6 n≠0 where c is an arbitray non-zero constant. UESTC-Digital transmission thro BLAWGN channels Prof李晓峰 12