IT2101: Communication Technology

2: Introduction

Program: BSCS I (January Semester – 2014)Lecturer: Rebecca Asiimwe

Phone Number:+256 712-997- 544 /0704 522 081

Email: rasiimwe@technology.ucu.ac.ug

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• This lecture is aimed at introducing students to communication technology and the key terms and concepts as used in this area of study.

• It will also introduce students to forms of communication; the past and present and also presents the key communications model upon which communication systems can be based.

Introduction

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• Communication:• Exchanging of information• A process of sending information from a sender to a

receiver through a channel or medium (channel= a Physical path or path way over which information can be conveyed).

• The activity of conveying meaningful information– Comes from a Latin word “Communo” which means “To Pass

along”

• Technically, a message is encoded on sending and is decoded by the receiving party to convey the desired meaning.

Definition and Overview of Key Terms:

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• When we communicate, we are sharing information. This sharing can be local or remote. Between individuals local communication usually occurs face to face while remote communication takes place over long distances.

• The term telecommunication which includes telephony, telegraphy and television means communication at a far distance. Tele is a Greek word meaning “far”.

• Communication between remote parties can be achieved through a process called networking that involves the connection of end devices (computers / phones), media and networking devices. Networks exist so that data may be sent from place to place.

Communication cont’d

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For communication to take place, there must be a sender, message and a recipient, however as we shall see later on, for communication to occur, other entities may come into play.

Communication can be made possible over vast distances because the recipient does not need to be present.

For communication to take place, participants (devices/people) need to have or communicate using a similar language and should follow protocol.

Communication cont’d

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LightSmoke signals

SoundDrumWhistleFireworks

PhysicalPersonal delivery

But these are limited by time and distance

Traditional Communication Methods

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• Electronic transmission of signals for

communications– Telephone and all its dimensions– Radio– Television– Through computer networks– Electronic mails (emails).– Fax etc

– These Lessen barriers of time and distance in a cost effective way

Current Communications

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• We’ve come a long way since the very first instances of verbal and written communication. From the early stages of speech, along with the primitive use of symbols and pictures to convey messages to one another, we’ve evolved into a communications powerhouse.

• Data has never been transferred faster and communication has thus never been more sophisticated than it is today.

Communication: Past to Present

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• From ancient writing techniques and newspapers, we’ve moved on to text messaging and email. From Morse code(an example is shown in subsequent slides) and telegraphs to telephones and radios, we now moved on to televisions, computers and cell phones.

• TV’s that utilized tubes with vacuum seals and boasted analog signals and black and white color are now Flat Screen LCD’s or Plasma’s that boast all digital High Definition Signals, thousands of lines of resolution and millions of color pixels.

Communication: Past to Present Cont’d

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• * Morse Code - (a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment.

• The International Morse Code encodes the Roman alphabet, the Arabic numerals and a small set of punctuation and procedural signals as standardized sequences of short and long signals called "dots" and "dashes" respectively.

Communication: Past to Present Cont’d

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• Dial up communication has been transformed to portable phones. From there they moved on to satellite communication cellular phones. Hand written symbols, numbers and letters went from being carried to being digitally transferred.

• We no longer have to wait for days to receive information as most of our data messages can be transferred in a matter of seconds over high speed broadband internet connections with computers that boast Gigabytes of Ram and Gigahertz of processor speed.

Communication: Past to Present Cont’d

• Visual Communication– Can be seen but not heard– Text i.e. Words, symbols,– Graphical i.e. Pictures, Images and

Photographs

• Audio Communication– Can be heard but not seen– Spoken language, buzzers, telephones,

radios, & doorbells

• Audiovisual– Can be seen and heard– Television, videos, & movies

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Forms of Communication

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• Audio

• Graphics

• Text and Numbers

• Audio-Visual

• Multimedia

Forms of Data and Information

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• Communication involves transmission of a signal by way of a medium from a sender to a receiver.

Overview of Communication

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• Communication involves:

• Data: – Raw facts about objects.• Information: – data with meaning. • Data communications involve the exchange of

data between two devices via some form of transmission medium such as a wire cable.

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• Refers to application of scientific knowledge for practical purposes.

• Involves the art, skill / craft of carrying out a task.

• Technology is assumed to be morally, culturally, and politically neutral

• Provides independent tools • Exists independent of local value systems • Can be used impartially to support different things

Technology

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It is a set of tools, both hardware and software that help us act and think better.

Technology includes all objects from pencil, paper to the latest electronic gadgets.

Electronic and computer technology helps us share information and knowledge quickly & efficiently. What was previously slow and tedious is now easier and more realistic

We can simply say: It is the application of knowledge through inventions and innovations to satisfy the ever changing needs of the society.

Technology Cont’d

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• Information Technology e.g. Computers, Scanners, Printers, Software, Modems, etc.

• Electrical Technology: E.g; Electricity (Hydro, thermal, solar panels, bulbs, Dams etc….

• Nuclear technology : Focuses on the powerful reactions of atomic nuclei. Has caused a lot of public concern especially because of the nuclear weapons. Other applications include nuclear medicine (e.g Radiation to view unborn babies in the womb)

Some types of Technology

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• Other types of technology include Biotechnology and Communications technology

• Communications technology: The “Technology” that helps us to communicate better (Remember Technology definition here)

• Telephones, Fax, Microphones, E-mail, Internet, etc. We will view Communications Technology as a sub set of ICT.

Some types of Technology cont’d

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• Communication technology involves a range of technologies used for gathering, storing, retrieving, processing, analyzing, and transmitting information. This includes personal computers, mobile phones, the network hardware, communication middleware as well as necessary software e.t.c.

• It encompasses the practices and components by which information is shared and processed.

• Involves communication systems and the technologies behind them - how they are designed, constructed and maintained.

Information & Communication Technology

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• Therefore ICT in general consists of all technical means used to handle information and aid communication.

• It consists of IT as well as telephony, broadcast media, all types of audio and video processing and transmission and network based control plus monitoring functions.

Information & Communication Technology

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What are some types of communication systems that are

known to you?

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• Cable TV systems

• Networks

• Phonographs

• Broadcasting systems

• Rader systems

• Telegraphs and telefax

• Telephone

Examples of Communication Systems

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• Just in time (JIT) Communication

• Communicate with anybody anytime and anywhere.

• Access, gather, store and retrieve any data and information worldwide, e.g. concerning newspapers and libraries, art and politics, commerce and technology information , working and learning materials.

Capabilities of Information and Communication Technologies

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• Make any business transactions within seconds: shifting huge amounts of money about; selling, buying, moving goods worldwide; “remote control” of machines and people across and between continents, etc.

• And many more

Capabilities of Information and Communication Technologies

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• The effectiveness of communication systems depends on four fundamental characteristics.

• Delivery – the system must deliver data to the correct destination

• Accuracy – the data must be delivered accurately• Timeliness – the system must deliver data in a timely

manner, data delivered late may end up being useless.• Jitter – Especially in delivery of audio or video packets

(jitter refers to the variation in packet arrival time).

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• Communication between two devices can be simplex, half-duplex, or Full-duplex.

• Simplex mode: The communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive e.g. Keyboards and traditional monitors. The keyboard can only introduce input; the monitor can only accept output.

• The simplex mode can use the entire capacity of the channel to send data in one direction

Forms of Data Flow in Communication

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• In half-duplex mode, each station can both transmit and receive, but not at the same time:

• When one device is sending, the other can only receive, and vice versa.

• The half-duplex mode is like a one-lane road with traffic allowed in both directions. I.e. When cars are travelling in one direction, cars going the other way must wait.

• The entire capacity of a channel is taken over by whichever of the two devices is transmitting at the time. Walkie-talkies and CB (citizens band) radios are both half-duplex systems.

Data Flow cont’d

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• In full-duplex mode, (duplex), both stations can transmit and receive simultaneously/ at the same time.

Signals are transmitted in both directions at the same time and share the capacity of the link. This sharing can occur in two ways: Either the link must contain two physically separate transmission paths, one for sending and the other for receiving; or the capacity of the channel is divided between signals travelling in both directions. E.g telephone network.

• Used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions.

Data Flow cont’d

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Data Flow-Illustration

DIGITAL VS ANALOG

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• Data – Raw facts about objects

• Signals– Electric or electromagnetic representations of data– Signaling- Physical propagation of the signal along a

suitable medium.

• Transmission– Communication of data by propagation and processing

of signals which can either be analog or digital.

Analog And Digital Data Transmission

signals

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Analog signal

Varies in a

smooth way

over time

Digital signal

Maintains a

Constant level

then changes

to another

constant level

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• Analog comes from “analogous” which means similar or equivalent.– Analog data takes on continuous values within the

some interval– e.g. sound, video are continuously varying patterns of

intensity. Most data collected by sensors such as temperature and pressure are continuous.

• Analog data is represented as continuous waveforms e.g. audio tapes

• Analog involves a process of taking an audio or video signal (in most cases, the human voice) and translating it into electronic pulses.

Analog Technology

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• In an analog tape recorder, a signal is taken straight from the microphone and laid onto tape.

• The wave from the microphone is an analog wave.

Example

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Analog Signals

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• Analog signal transmitted without regard to content.

(i.e., the signals may represent analog data or

digital data).

• Loss of signal strength over distance (Attenuation).

• Use amplifiers to boost the signal.

• But also amplifies noise.

Analog Transmission Characteristics

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• Digital comes from the Latin word “digitus” which refers to fingers (counting of fingers).

– Digital data takes on discrete values e.g. text, integers

• Digital is similar to digit which is used to describe whole numbers, from 0 to 9.

• A digital system uses discrete numbers or values for data storage, transmission and input as opposed to an analog system that processes continuous streams of data

Digital Communications Technology

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• Digital involves breaking the signal into a binary format where the audio or video data is represented by a series of "1"s and "0"s.

• In digital technology, the wave is sampled at some interval, and then turned into numbers that are stored in the digital device.

• On a CD, the sampling rate is 44,000 samples per second. So on a CD, there are 44,000 numbers stored per second of music.

Digital cont’d

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• Concerned with content• Integrity endangered by noise, attenuation etc.• Repeaters used

– Repeater receives signal– Extracts bit pattern and recovers pattern– Retransmits new signal– Attenuation is overcome– Noise is not amplified

Digital Transmission

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• You have both an audio cassette and a CD and you want to play track Number 4 “Cornerstone” by Hillsong.

• How would you get to that track?

An example to Illustrate the difference

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• The audio cassette uses Analog format and therefore stores continuous streams of data.

• To get to your favourite song, you need to forward through to the song.

• Using a CD which is a digital device that stores discrete data, you will only need to select the number of your favourite song.

Example cont’d

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• Digital signals are usually used for digital data and analog signals for analog data

• But we can use an analog signal to carry digital data and this can be possible through the use of a modem that converts a series of binary voltage pulses into an analog signal by encoding the digital data onto a carrier frequency.

Data and Signals

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• In an operation very similar to that performed by a modem, analog data can be represented by digital signals.

• The device that performs this function for voice data is a codec (coder-decoder). In essence the codec takes the analog signal that directly represents the voice data and approximates that signal by a bit stream. At the receiving end the bit stream is used to reconstruct the analog data.

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• Digital technology– Low cost LSI/VLSI technology (Large scale

integration caused a drop in cost and size of digital circuitry)

• Data integrity– Repeaters rather than amplifiers are used so the

effects of noise and other impairments are not cumulative. Signals can be propagated for longer distances and over lower quality lines while maintaining integrity.

Advantages of Digital Transmission

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• Capacity utilization

– High bandwidth links economical– High degree of multiplexing needed to utilize capacity is easily

achieved with digital techniques

• Security & Privacy

– Encryption-A digital bit stream is easier to encrypt than an analog stream (=more secure).

• Integration

– Can treat analog and digital data similarly and economies of scale and convenience can be achieved by integrating voice, video and digital data. (Integrating voice, video and data is simpler with digital transmission than with analog transmission)

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• The digital divide• Financial- e.g. initial costs – like backbone.• Availability- like the internet, DVDs• Capacity to understand- Only technocrats• Obsolescence- A new computer is out of date as

soon as you’ve bought it.• Fragile- eg CDs, Digital cameras, any gadget with

a touch screen, etc.• Can easily be corrupted.

Cons of Digital Transmission

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• An ADC is an electronic device that converts an input of (continuous) analog signals like voltage(or current or electronic impulse) into discrete digital numbers or digital signals.

• Digital-to-analog converter(DAC)• Device for converting a digital (usually binary)

code to an analog signal (current, voltage or electric impulse).

Analog-to-Digital converter (ADC)

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The ADC captures an analog wave/electric voltage on an audio line and represents it as a digital number that can be sent to a computer. By capturing the voltage thousands of times per second, you can get a very good approximation to the original audio signal. Each dot in the figure above represents one audio sample.

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• Digital information can be stored in a variety of different formats like

– DVD (Digital Versatile Disk)– VCD (Video Compact Disk)– CD (Compact Disk)– Computer Hard disk.– etc

Digital data storage

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Modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted.

Converting a digital signal to an analog signal.• For most of radio and telecommunication today, the

carrier is alternating current (AC) in a given range of frequencies. The goal is to produce an information bearing modulated waveform best suited to the given communication task.

Converting an analog signal to a digital signal is known as Demodulation

Modulation

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Analog inputFiltered Analog input

Digitized input

Digitized output

Analog output-unfiltered

Analog output

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• Is an electronic device that converts a computer’s digital signals into specific frequencies to travel over telephone or cable television lines.

• At the destination, the receiving modem demodulates the frequencies back into digital data.

• Computers use modems to communicate with one another over the internet.

Modem: Modulator-demodulator

• Amplitude modulation (AM)

• In AM transmission, the carrier signal is modulated so that its amplitude varies with the changing amplitudes of the modulating signal. The frequency and phase of the carrier remain the same; only the amplitude changes to follow variations in the information.

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Key types of Modulation

• In FM transmission, the frequency of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal. The peak amplitude and phase of the carrier signal remain constant, but as the amplitude of the information signal changes, the frequency of the carrier changes correspondingly.

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Frequency Modulation (FM)

• In PM transmission, the phase of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal.

• The peak amplitude and frequency of the carrier signal remain constant, but as the amplitude of the information signal changes, the phase of the carrier changes correspondingly.

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Phase Modulation (PM)

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1. Define: • Communication, technology and Communication

Technology

2. Justify the use of digital communications and explain the cons of using this method.

3. Differentiate between analog and digital signals

4. Research about and discuss:• Computer network classifications.• Building blocks for a computer network.

Lecture Review Questions

Q & A