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1. Telecommunications Fundamental Lecture 1: Introduction www.soran.edu.iq Dr Muhammadamin Daneshwar

2. Objectives Learning Introduction Signals Composite Signals Bandwidth Analog Signal Digital Signal Contents:

3. On Completion, the student should able to: Understand the signal concept Understand the properties, advantages and disadvantages of Analog and Digital signals Understand the concept of important blocks of a basic diagram for digital communication systems. Objectives Learning

4. What does Communication mean? Introduction (Cont..)

5. Introduction (Cont..) Transfer the information signal from a source to a recipient via a channel or medium. Basic block diagram of a communication system

6. Introduction (Cont..) A data communications system has five components: Message: The information (Data) to be communicated. Popular forms of information include text, numbers, pictures, and so on. Transmitter(Sender) is the device that sends the data message. It can be a computer, telephone handset, video camera, and so on. Receiver is the device that receives the message. It can be a computer, telephone handset, television, and so on. Transmission Medium (Channel) is the physical path by which a message travels from sender to receiver. like: twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves. Protocol is a set of rules that govern data communications.

7. Signals Signals are the physical representation of data. Users of a communication system can only exchange data through the transmission of signals. The general function of a sine wave is: Signal parameters are the amplitude A , the frequency f , and the phase shift φ .

8. Signals (Cont..) Time domain representation of a signal A signal is represented by three way: A typical way to represent signals is the time domain .Here the amplitude A of a signal is shown versus time (time is mostly measured in seconds s, amplitudes can be measured in, e.g., volt V ).

9. Frequency domain representation of a signal Representations in the time domain are problematic if a signal consists of many different frequencies. In this case, a better representation of a signal is the frequency domain. Fourier transformations are a mathematical tool for translating from the time domain into the frequency domain and vice versa (using the inverse Fourier transformation). Signals (Cont..) Arbitrary periodic functions would have many peaks, known as the frequency spectrum of a signal. A tool to display frequencies is a spectrum analyzer .

10. Signals (Cont..)

11. Signals (Cont..) Composite Signals is made of many simple sine waves. needed to communicate data. A single-frequency sine wave is not useful in data communications (alarm signal), carry no information. The Bandwidth of a composite signal is the difference between the highest and the lowest frequencies contained in that signal. For example 1 , if a composite signal contains frequencies between 2000 and 5000, its bandwidth is 5000 - 2000, or 3000 Hz.

12. Signals (Cont..) Example 2 If a periodic signal is decomposed into five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz, what is its bandwidth? Draw the spectrum, assuming all components have a maximum amplitude of 10 V. Solution Let , be the highest frequency, the lowest frequency, and B the bandwidth. Then B = - = 900 - 100 = 800Hz   1

13. Signals (Cont..) The spectrum has only five spikes, at 100, 300, 500, 700, and 900 Hz 1

14. Analog Signal An analog signal is a continuous signal that contains time-varying physical quantity which convey some sort of information. Like: sound wave, pressure , or temperature . Continuous Infinite range of values They can be periodic (repeating) or non-periodic.

15. Hz   sec   Analog Signal (Cont..) The Frequency f is the number of cycles per second, measured in Hertz, Hz. The Period T is the time in seconds for one Cycle. The Amplitude is absolute value of a signal’s highest intensity, Normally in volts . The Phase is a Position of waveform relative to time zero, measured in ( degrees or radians ). [ 360° is 2 π rad; 1° is 2 π / 360 rad, and 1 rad is 360 /( 2 π ].

16. Analog Signal (Cont..)

17. Analog Signal (Cont..)

18. Infinite amount of data Easy processing. Uses less bandwidth . Advantages Analog Signal (Cont..)

19. Analog hardware is inflexible implementation and expensive. No error detection and correction capability. Sensitive to Noise. The effects of noise create signal loss and distortion. This is impossible to recover. Disadvantage s Analog Signal (Cont..)

20. Disadvantage s Analog Signal (Cont..)

21. Analog Signal (Cont..) Noise refers to unwanted electrical signals that are always present in electrical systems. The presence of noise superimposed on a signal tends to obscure or mask the signal; it limits the receiver`s ability to make correct symbol decisions, and thereby limits the rate of information transmission. Distortion: It is defined to be the change of shape in signal getting transmitted from one point to the other or from the source to the destinationInduced Noise.

22. Digital Signal Digital Signal is discrete-time signal generated by digital modulation convey discrete symbols that are usually interpreted as digits represent 0 and 1(binary signal). Discrete Finite range of values (0 and 1) They can be periodic (repeating) or non-periodic .

23. Introduction

24. Digital Signal (Cont..) Note; both bandwidths are infinite, but the periodic signal has discrete frequencies while the nonperiodic signal has continuous frequencies.

25. Digital Signal (Cont..) Bit interval ( instead of period): time required to send one bit = 1/ Bit rate. A digital signal is a composite signal having an infinite numbers of frequencies i.e. infinite bandwidth. Bit rate (instead of frequency): is used to describe the digital signal.

26. Digital Signal (Cont..)

27. Digital Signal (Cont..)

28. Digital Signal (Cont..) A digital circuits are more reliable and can be produced in lower cost and the digital hardware more flexible implementation. Signal can be transmitted over long distances. Less susceptible (very immune) to Noise and Interference. Advantages

29. Digital Signal (Cont..) Suffer from more attenuation(strength loss) Pulses become rounded and smaller, Leads to loss information Greater bandwidth is essential Systems and processing are more complex Disadvantage s

30. Digital Vs. Analog