Communication system Lecture 1 Bahria University 1 Course

Communication system Lecture 1 Bahria University 1

Course Schedule • Lectures: – – 11: 30 to 1: 30 (8 B) 2: 30 to 3: 30 (8 B) 11: 30 to 12: 30 (8 A) 2: 30 to 4: 30 (8 A) • Assignments: • Project/ Research Case study: • Quizzes: Bahria University 2

Recommended Books • Modern Digital and analog communication systems by B. P Lathi • Communication systems by Simon hykin • Digital communications, by John. G. Proakis. • Digital communications by Bernard sklar Bahria University 3

Course Outline 1. 2. 3. 4. 5. 6. Introduction to communication system Signal and systems Amplitude modulation Angle modulation Antennas and Wave propagation Digital communications Bahria University 4

Marks Distribution Mid-Term Quizzes Assignments Project Final Exam 20% 10% 5% 15% 50% Bahria University 5

The Real Aim Basic Parts of a Communication System Bahria University 6

A Communications Model Input Transducer mtx(t) Transmitter ptx(t) wired / wireless Transmission Medium prx(t) s(t) Receiver mrx(t) Output Transducer r(t) Noise n(t) s(t) – Input signal; audio, video, image, data etc. mtx(t) – Modulating signal; input signal that has been converted to electrical signal. ptx(t) – Modulated signal transmit by the transmitter. n(t) – Noise signal. prx(t) – Modulated signal receive by the receiver. mrx(t) – Modulating signal at the receiver. Bahria University r(t) – Output signal. 7

Conti…. Bahria University 8

Elements of Communication system • Transmitter: The transmitter is a collection of electronic components and circuits designed to convert the information into a signal suitable for transmission over a given communications medium. Bahria University 9

Conti…. . • Communication Channel: The communication channel is a medium by which the electronic signal is sent from one place to another. • Receiver: The receiver is another collection of electronic components and circuit that accept the transmitted message from the channel and convert it back into a form of understandable by humans. Bahria University 10

Transmission Medium (Guided) Twisted pair – Unshielded Twisted Pair (UTP) – Shielded Twisted Pair (STP) Coaxial Fiber Optic Bahria University 11

Wireless channel capacity Bahria University 12

WHAT IS BASEBAND ? Without any shift in the range of frequencies of the signal The signal is in its original form, not changed by modulation. Baseband is the original information that is to be Sent. It starts from zero and to some specific frequency Bahria University 13

What is Passband • After modulation, the original baseband signal is moved to a range of frequency which far more higher than the baseband signal • So it’s a range of frequency shifted after modulation Bahria University 14

What is Modulation MODULATION IS THE PROCESS OF CHANGING SOME PROPERTYOF THE INFORMATION SOURCES INTO SUITABLE FORM FOR TRANSMISSION THROUGH THE PHISICAL MEDIUM/CHANNEL “Process of coverting baseband signal into passband signal is called modulation” It is performed in the Transmitter by a device called Modulator. Bahria University 15

Classification of Communication system • There are two types or two ways to classify the communication system. 1. Simplex 2. Duplex Bahria University 16

Simplex • In simplex communication information travels in only one direction. • Example: • Radio and TV broadcasting. • Telemetry system of the satellite. Bahria University 17

Duplex • The bulk of electronic communications, however is two way. Example: • Telephone system • Cellular radio • This sort of communication comes in the category of Full duplex communications. Bahria University 18

Conti…. . • Another form of the two way communications is where only one party transmits at a time. This is known as half duplex. • Example: • Radar System Bahria University 19

Analog signals • Another way to categorize communication is by the types of intelligent signals transmitted. • There are two types of signals, Analog and Digital. • Analog signal is a continuously varying voltage or current. A typical analog signal is a sine wave tone. Bahria University 20

Digital Signals • The other type of the transmitted signal falls under the broad category of digital. • The earliest forms of both wire and radio communications used a type of on/off digital code. • Data used in computer is also digital where binary codes representing numbers, letters and special symbols are transmitted by wire or radio. Bahria University 21

Seven Bit Ascii Bahria University 22

Multiplexing • Multiplexing is the process of transmitting two or more signals simultaneously over the same channel, using TDM and FDM. Bahria University 23

Channel Accessing Techniques • There are three types for channel accessing, 1. FDMA 2. TDMA 3. CDMA Bahria University 24

FDMA Bahria University 25

TDMA Bahria University 26

CDMA Bahria University 27

Frequency Spectrum Bahria University 28

Overview of the communication systems • • • Modulation and detection Channel coding Source coding Analog to digital conversion Modern emerging technologies Bahria University 29