M-ary encoding pdf

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pulses, where each symbol has m finite states. Each symbol represents n bits of information . Vector-Space Representation of M-ary Signals. ? The digital source generates digital symbols for Input binary sequence is first differentially encoded and then modulation using a BPSK modulator. ? Differentially encoded During the course of my master's degree and PhD at IIT Madras, I had the opportunity to learn the fundamental concepts of digital communications from my instructors, Dr. V. G. K. Murthy, Dr. V. V. Rao, Dr. K. Rad- hakrishna Rao, Dr. Bhaskar Ramamurthi and Dr. Ashok Jhunjhunwalla. It is a pleasure to acknowledge their Quite often we have to send digital data through analog transmission media such as a telephone network. In such situations it is essential to convert digital data to analog signal. Basic approach is shown in Fig. 2.6.1. This conversion is accomplished with the help of special devices such as modem (modulator-demodulator) M-ary transmission. An M-ary transmission is a type of digital modulation where instead of transmitting one bit at a time, two or more bits are transmitted simultaneously. This type of transmission results in reduced channel bandwidth. However, sometimes, two quadrature carriers are used for modulation. FSK is a form of constant-amplitude angle modulation similar to standard frequency modulation (FM) except the modulating signal is a binary signal that varies between two discrete voltage levels rather than a continuously changing analog waveform. Reasons for Choosing Encoding Techniques. • Digital data, digital signal For binary signals (two voltage levels). • C = 2B. – With multilevel signaling (M-ary signalling). • C = 2B log2 M. • M = number of discrete signal or voltage levels. • N= number of bits . Selection of Encoding/Modulation Schemes. • Performance in an Modulation is the process of encoding information from a message source in a manner M-ary schemes increase the bandwidth efficiency but require If M > 2, each waveform carry log2(M) bits. This scheme is therefore more bandwidth efficient. It is called M-ary. ASK. – Exp: M = 4; log2(4)=2 bits/waveform. » A1 = 0; 00. Meixia Tao @ SJTU. Topics to be Covered. ? Binary digital modulation. ? M-ary digital modulation. ? Comparison study. Source. A/D converter. Source encoder. Channel encoder. Modulator. Channel. Detector. Channel decoder. Source decoder. D/A converter. User. Absent if source is digital. Noise. 2 2-2-2 M-ary Encoding. M-ary is a term derived from the word binary. M simply represents a digit that corresponds to the number of conditions, levels, or combinations possible for a given number of binary variables. For example, a digital signal with four possible conditions (voltage levels, frequencies, phases, and so on) is