Digital Communications: Message Formatting and PCM Techniques, Slides of Digital Communication Systems

Download Digital Communications: Message Formatting and PCM Techniques and more Slides Digital Communication Systems in PDF only on Docsity! 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 1 EE4723 : Digital Communications II Week 3: Message Formating A review of PCM, DPCM and ADPCM Delta Modulation Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 2 Formatting Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 5 Example 1:  In ASCII alphabets, numbers, and symbols are encoded using a 7-bit code  A total of 27 = 128 different characters can be represented using a 7-bit unique ASCII code (see ASCII Table, Fig. 2.3) Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 6 Figure The basic elements of a PCM system. Pulse Code Modulation Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 7 Encoding Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 10 Consider a finite-duration impulse response (FIR) discrete-time filter which consists of three blocks : 1. Set of p ( p: prediction order) unit-delay elements (z-1) 2. Set of multipliers with coefficients w1,w2,…wp 3. Set of adders (  ) Linear Prediction Coding (LPC) Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 11 Differential Pulse-Code Modulation (DPCM) Usually PCM has the sampling rate higher than the Nyquist rate. The encode signal contains redundant information. DPCM can efficiently remove this redundancy. 32 Kbps for PCM Quality Docsity.com 2/23/2012 Muhammad Ali Jinnah University, Islamabad Digital Communications EE3723 12 Delta Modulation (DM) Docsity.com