Communication systems
Dr. Bahawodin Baha
School of Engineering
University of Brighton, UK
July 2007
Block diagram of a Communication System
Carrier
Transmitted
signal
Transmitter
Information to
be transmitted
(Baseband signal)
Received
signal
Channel
Receiver
Recovery of
information
COMMUNICATION SYSTEMS
• Provide electronic exchange of multimedia data,
Voice, data, video, music, email, web pages, etc.
• Communication Systems of today Radio and TV
broadcasting, Public Switched Telephone Network
(voice, fax, modem)
– Cellular Phones
– Computer networks (LANs, WANs, and the
Internet)
– Satellite systems (pagers, voice/data, movie
broadcasts)
– Bluetooth
• Provide electronic exchange of multimedia
information
• The information to be transmitted is electromagnetic
wave or electrical signal may represent: multimedia
data, Voice, data, video, music, email, web pages,
etc.
• The frequency bandwidth occupied by the
information signal is called the baseband, and the
signal is often referred to as the baseband signal.
• Channel – is the medium by which the transmitted
signal is propagated:
• Various layers of atmosphere, cable for telephone or
date link, cable TV or
• Electrical signals are converted to a corresponding
light signal that is propagated through a fiber optic
channel
Electromagnetic Spectrum
Based on these conditions, the radio spectrum is divided into the
following sub bands:
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Extra Low Frequency (ELF)
300 – 3000 Hz (l =1000 – 100km)
Very Low Frequency (VLF)
3 – 30 kHz (l = 100 – 10 km)
Applications: mining, underwater communication (submarine), Sonar
Low Frequency (LF)
30 – 300 kHz (l = 10 – 1 km)
Applications: broadcasting, radio navigation
Medium Frequency (MF)
300 – 3000 kHz (l = 1000 – 100 m)
Applications: AM radio broadcasting (550 – 1600 kHz)
High Frequency (HF)
3 – 30 MHz (l = 100 – 10 m)
Applications: Broadcasting over large areas, amateur radio (ham), citizens band (CB) radio.
Very High Frequency (VHF)
30 – 300 MHz (l = 10 – 1 m)
Applications: TV, FM radio (88 –1108 MHz ), radio beacons for air traffic control
Ultra High Frequency (UHF)
300 – 3000 MHz (l = 1 m – 10 cm)
Applications: broadcasting, satellite (TV) broadcasting, all (1G to 3G) land mobile telephones, cordless telephones,
some air traffic control.
Super High Frequency (SHF)
3 – 30 GHz (l = 10 – 1 cm)
Applications: Satellite service for telephony and TV, mobile services in the future
Extremely High Frequency (EHF)
30 – 300 GHz (l = 10 – 1 mm)
Applications: communications at short distances (within Line-Of-Sight), broadcast satellite for HDTV (for satellite
communication between satellites in space, not space to earth).
Communication theories
• Communication systems send and receive
information electronically over
communication channels
• Modulation
• Demodulation
• Amplification
• Filtering
• Signal detection
• Digital Signal Processing, DSP
Wireless Communication
• Objectives:
• Multimedia wireless Communications at any Time and
Anywhere
• Brief history
• Ancient Systems: Smoke Signals, Carrier Pigeons
• Radio invented in the 1880s by Marconi
• Many sophisticated military radio systems were developed
during and after WW2
• Cellular has enjoyed exponential growth since 1988, with more
than 1 billion users worldwide today
• Ignited the recent wireless revolution, 1980-2003
• Growth rate tapering off
• Is there a future for wireless?
Design Challenges
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Hardware Design
Precise components
Small, lightweight, low power
Cheap
High frequency operations
System Design
Converting and transferring information
High data rates
Robust to noise and interference
Supports many users
Network Design
Connectivity and high speed
Energy and delay constrains
Main Points
• Introduction to Communication
Systems
• Block diagram of a Communication
System
• Electromagnetic spectrum
• Main theories
• Wireless and mobile Communications
• Design challenges include hardware,
system and network issues
The END
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