Computer Networks
Module 2
Data Communication Fundamentals
Version 2 CSE IIT, Kharagpur
Lesson 1
Data and Signal
Version 2 CSE IIT, Kharagpur
Specific Instructional Objectives
At the end of this lesson the students will be able to: • • • • • • • • • Explain what is data Distinguish between Analog and Digital signal Explain the difference between time and Frequency domain representation of signal Specify the bandwidth of a signal Specify the Sources of impairment Explain Attenuation and Unit of Attenuation Explain Data Rate Limits and Nyquist Bit Rate Distinguish between Bit Rate and Baud Rate Identify Noise Sources
2.1.1 Introduction
A simplified model of a data communication system is shown in Fig. 2.1.1. Here there are five basic components: • Source: Source is where the data is originated. Typically it is a computer, but it can be any other electronic equipment such as telephone handset, video camera, etc, which can generate data for transmission to some destination. The data to be sent is represented by x(t).
COMMUNICATION MEDIUM
Figure 2.1.1 Simplified model of a data communication system • Transmitter: As data cannot be sent in its native form, it is necessary to convert it into signal. This is performed with the help of a transmitter such as modem. The signal that is sent by the transmitter is represented by s(t).
Version 2 CSE IIT, Kharagpur
•
Communication Medium: The signal can be sent to the receiver through a communication medium, which could be a simple twisted-pair of wire, a coaxial cable, optical fiber or wireless communication system. It may be noted that the signal that comes out of the communication medium is s’(t), which is different from s(t) that was sent by the transmitter. This is due to various impairments that the signal suffers as it passes through the communication medium. Receiver: The receiver receives the signal s’(t) and converts it back to data d’(t) before forwarding to the destination. The data that the
Data Communication Fundamentals
Version 2 CSE IIT, Kharagpur
Lesson 1
Data and Signal
Version 2 CSE IIT, Kharagpur
Specific Instructional Objectives
At the end of this lesson the students will be able to: • • • • • • • • • Explain what is data Distinguish between Analog and Digital signal Explain the difference between time and Frequency domain representation of signal Specify the bandwidth of a signal Specify the Sources of impairment Explain Attenuation and Unit of Attenuation Explain Data Rate Limits and Nyquist Bit Rate Distinguish between Bit Rate and Baud Rate Identify Noise Sources
2.1.1 Introduction
A simplified model of a data communication system is shown in Fig. 2.1.1. Here there are five basic components: • Source: Source is where the data is originated. Typically it is a computer, but it can be any other electronic equipment such as telephone handset, video camera, etc, which can generate data for transmission to some destination. The data to be sent is represented by x(t).
COMMUNICATION MEDIUM
Figure 2.1.1 Simplified model of a data communication system • Transmitter: As data cannot be sent in its native form, it is necessary to convert it into signal. This is performed with the help of a transmitter such as modem. The signal that is sent by the transmitter is represented by s(t).
Version 2 CSE IIT, Kharagpur
•
Communication Medium: The signal can be sent to the receiver through a communication medium, which could be a simple twisted-pair of wire, a coaxial cable, optical fiber or wireless communication system. It may be noted that the signal that comes out of the communication medium is s’(t), which is different from s(t) that was sent by the transmitter. This is due to various impairments that the signal suffers as it passes through the communication medium. Receiver: The receiver receives the signal s’(t) and converts it back to data d’(t) before forwarding to the destination. The data that the