LINE CODING SCHEMES

Ali Nawaz Ranjha REG ID: CIIT/DDP-FA10-BTE-008/LHR

Jawad Ali REG ID: CIIT/DDP-FA10-BTE-022/LHR

Saad Hameed REG ID: CIIT/DDP-FA10-BTE-046/LHR

Usman Naseer REG ID: CIIT/DDP-FA10-BTE-053/LHR

Submitted to

Sir Saad Aslam

Department of Electrical Engineering

COMSATS-LANCASTER Dual Degree Program

COMSATS INSTITUTE OF INFORMATION TECHNOLOGY

LAHORE – PAKISTAN

PRESENTATION LAYOUT

• Introduction

• Mathematical and Block Diagrams

• Applications

• Conclusion

INTRODUCTION

What is line Coding?

• In a digital communications system, an information signal must be formatted so that it is represented by digital symbols (usually binary digits or bits).

• In baseband digital transmission, the electrical waveforms used are pulses and this conversion from digital data to digital waveforms is known as line coding.

INTRODUCTION (cont.)

Why line Coding?

• To transmit information over the channel.

INTRODUCTION (cont.)

Types of line coding

DESIRABLE PROPERTIES

• Transmission bandwidth should be as small as possible.

• For given bandwidth and specified detection error rate ,the transmitted power should be as low as possible.

• Error detection and correction capability should be as high as possible. Bipolar scheme only detects errors.

• Zero power spectral density at dc null so that A.C coupling can be used for transmission.

MATHEMATICAL AND BLOCK DIAGRAMS

MATHEMATICAL AND BLOCK DIAGRAMS (cont.)

Polar:-

MATHEMATICAL AND BLOCK DIAGRAMS (cont.)

Uni-Polar:-

MATHEMATICAL AND BLOCK DIAGRAMS (cont.)

Bi-Polar:-

MATHEMATICAL AND BLOCK DIAGRAMS (cont.)

APPLICATIONS

• LAN’s (Local Area Networks)

• Scrambling and Descrambling

• Error Detection

PROS AND CONS

Polar :-

• The essential bandwidth of the signal is 2 Rb. Not bandwidth efficient.

• No error-detection or error-correction capability.

• Non-zero PSD at dc( ω = 0).This will rule out the use of ac coupling in transmission.

• Most efficient scheme from the power requirement viewpoint for a given power, the detection-error probability for a polar scheme is the smallest possible.

• Transparent(Bit pattern does not affect the accuracy of timing information).

PROS AND CONS (cont.)

Uni-Polar :-

• For a given transmitted power, it is less immune to noise interference. Noise immunity difference of amplitudes representing binary 0 and 1.If a pulse of amplitude 1 or –1, as only one pulse is used so less noise immunity.

• Not transparent.

• No error detection capability & non-zero PSD at DC NULL.

PROS AND CONS (cont.)

Bi-Polar :-

• Spectrum has a dc dull.

• Bandwidth is not excessive.

• It has single-error-detection capability. Since, a single detection error a violation of the alternation pulse rule.

• Requires twice as much power as a polar signaling.

Distinction between A, -A, 0 vs. Distinction between A/2, -A/2

• Not transparent

CONCLUSION

In terms of the desirable properties of line codes, the most efficient line code is Bi-polar as it has

1). Single Error Correction Capability

2). Zero power spectral density at DC NULL

3). Less transmission bandwidth is required in case of bipolar compared to the cases of polar and unipolar. Typically, Rb hertz as compared to 2Rb hertz.

REFERENCES

• Prof. Murat Torlak, “Digital Transmission”, Telecom. Switching &Transmission,http://www.utdallas.edu/~torlak/courses/ee4367/lectures/CodingI.pdf

• Jrahhal, “codigoslinea” http://fetweb.ju.edu.jo/staff/EE/jrahhal/PDF/codigoslinea.pd

• Dr. Shi, “Line Codes” ,Chapter 7, New Jersey Institute of Technology

• Honary, Bahram, “Cryptography and Coding”, 8th IMA International Conference Cirencester, UK, December 17-19, 2001

• Morais, “Fixed Broadband Wireless Communications: Principles And Practical Applications”, Pearson Education India