Introduction to Line Coding Schemes
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Line coding schemes are used to convert digital data into electrical signals for transmission over channels. This document outlines various line coding techniques such as NRZ, Manchester, and Differential Manchester coding. It discusses properties of good line coding schemes, including low transmission bandwidth, power efficiency, transparency, clock synchronization, error handling, and prevention of baseline wandering. Line coding is important for digital transmission in applications such as local and wide area networks, pulse shaping, and telephonic transmission.
Introduction to Line Coding Schemes
- 1. Line Coding Schemes Digital Transmission: D/D Conversion CMS-A-CC-4-8 Lockdown Talk Series: DCNIT-LDTalks-2 Arunabha Saha Department of Computer Science, Vidyasagar College University of Calcutta April 2020
- 2. Outline Introduction to Line Coding Classification of line coding schemes Properties of line coding Applications
- 3. Line coding(1) What is Line coding..?? The process of converting binary(digital) data into digital signals
- 4. Line coding(2) Also known as Baseband transmission Baseband signals(or lowpass) , which includes the frequencies close to 0 in comparison with the highest frequency It uses baseband channel(or lowpass) to transfer the low frequencies; e.g. serial cable, LAN. The output of a multiplexer is coded into electrical pulses or waveforms for the purpose of transmission ovr the channel. This process is called line coding1 . 1 Modern Digital and Analog Communication Systems, 3e, B.P. Lathi, OUP, 1998
- 5. Types of line coding NRZ, NRZ-L, NRZ-I, RZ, Manchester, Differential Manchester
- 6. Properties of line coding(1) Transmission bandwidth: as small as possible Power efficiency: for any given bandwidth B and detection error probability e, transmitted power need to be as small as possible Transparency: the digital signal should be transmitted correctly, irrespective of the pattern of 0’s and 1’s in input stream. Clock synchronization: both sender and receiver need to be synchronized to avoid any kind of misinterpretation
- 7. Properties....(2) Error handling: error should be detected and corrected properly Baseline wandering: In decoding a digital signal, the receiver calculates a running average of the received signal power. This average is called the baseline. The incoming signal power is evaluated against this baseline to determine the value of the data element. A long string of 0s or 1s can result a drift in the baseline (baseline wandering) and introduce errors in decoded output. A good line coding scheme needs to prevent baseline wandering.
- 8. Properties....(3) Signal element vs data element: define r = # of data elements # of signal elements ; r need to be well defined. Data element = blue line, signal element = magenta line
- 9. Applications Data transmission over LAN and WAN. Pulse shaping and relocation without modulation or filtering. e.g. in telephonic transmission, the transfer characteristics highly attenuated bellow 300 Hz. References Modern Digital and Analog Communication Systems, 3e, Lathi,B.P. (1998), OUP. Computer Networks, 5e, Tanenbaum, A. S.; Wetherall, D.J. (2011), Prentice Hall.
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