TRANSMISI BASE-BAND oleh :Budi Prasetya Modul #11 TT3213 SISTEM KOMUNIKASI 1 TRANSMISI BASE-BAND oleh :Budi Prasetya Program Studi S1 Teknik Telekomunikasi Departemen Teknik Elektro - Sekolah Tinggi Teknologi Telkom Bandung – 2008

Review Probabilitas dan Statistik Gaussian/Normal Normal Distribution: Completely characterized by mean () and variance (2) pN(y) N1(=0,1) N2(=0,2) 2 > 1 Modul 11 - Siskom I - Base Band Transmission

Gaussian: Rapidly Dropping Tail Probability! Modul 11 - Siskom I - Base Band Transmission

Review Probabilitas dan Statistik pN(y) Gaussian/Normal Normal Distribution: Completely characterized by mean (=0) and variance (2=1) Q-function: one-sided tail of normal pdf erfc(): two-sided tail. So: N(=0,=1) p(y>z)= z Modul 11 - Siskom I - Base Band Transmission

Standardize the Normal Distribution Standardized Normal Distribution One table! Modul 11 - Siskom I - Base Band Transmission

Modul 11 - Siskom I - Base Band Transmission Example P(X  8) Normal Distribution Standardized Normal Distribution .1179 .5000 .3821 Shaded area exaggerated PERTANYAAN ! Luas daerah yang diarsir = 0.3821 = Q(??); ?? = 0.3 Modul 11 - Siskom I - Base Band Transmission

Q-function: Tail of Normal Distribution Q(z) = P(Z > z) = 1 – P[Z < z] Modul 11 - Siskom I - Base Band Transmission

Modul 11 - Siskom I - Base Band Transmission Tabel Q-function Modul 11 - Siskom I - Base Band Transmission

Baseband Digital Transmission Link Modul 11 - Siskom I - Base Band Transmission

Modul 11 - Siskom I - Base Band Transmission Sinyal Terima + AWGN original message d(t) received wave y(t)=d(t)+n(t) Modul 11 - Siskom I - Base Band Transmission

Modul 11 - Siskom I - Base Band Transmission AWGN n(t) = gaussian noise dengan zero-mean σ = standar deviasi = tegangan effektive noise Modul 11 - Siskom I - Base Band Transmission

Gangguan Noise Terhadap Sinyal Digital Modul 11 - Siskom I - Base Band Transmission

Determining Decision Threshold -A V =Theshold The comparator implements decision rule: Choose Ho (ak=0) if Y<V Choose H1 (ak=1) if Y>V Average error error probability: Transmitted ‘0’ but detected as ‘1’ Channel noise is Gaussian with the pdf: Modul 11 - Siskom I - Base Band Transmission

Error rate and Q-function V =Theshold V threshold = 0 This can be expressed by using the Q-function by Modul 11 - Siskom I - Base Band Transmission

Baseband Binary Error Rate in Terms of Pulse Shape and S/N setting V=0 yields then for polar, rectangular NRZ [-A,A] bits Probability of occurrence Signal power: Noise power: Energy Bit to Noise Spectral Density Ratio Note that (BW pulse shapping filter) Modul 11 - Siskom I - Base Band Transmission

Modul 11 - Siskom I - Base Band Transmission When p0 = p1 =1/2, the value of V that minimizes the probability of error is V = 0. Modul 11 - Siskom I - Base Band Transmission