CSC 242 Introduction to
Telecommunications Systems
Dr. Ehsan MunirDepartment of Computer ScienceCOMSATS Institute of Information Technology
Lecture # 1
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What is CommunicationWhat is Communication When we communicate we share
information Local Communication
Face to face Remote Communication
Over distance
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DATA COMMUNICATIONSDATA COMMUNICATIONS
Data communicationsData communications are the exchange of data between are the exchange of data between two devices via some form of transmission medium such two devices via some form of transmission medium such as a wire cable. The word data refers to information as a wire cable. The word data refers to information presented in whatever form is agreed upon by the parties presented in whatever form is agreed upon by the parties creating and using the data. creating and using the data.
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Data Communication System For data communication to occur,
communicating devices must be a part of a system made up of some specific kind of hardware and software. This system is known as “DC System”
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Factors Effecting DC System Delivery
Deliver data to correct destination Accuracy
Deliver data accurately Timeliness
Deliver data in a timely manner Jitter
Variation in packet arrival time
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Data Flow Simplex
Transmission in one direction. Example Television
Half duplex Either direction, but only one way at a time.
Example Walkie-talkies Full duplex
Both directions at the same time. Example Phones.
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What is Telecommunication Tele is Greek word, meaning “far off” Webster calls it communications at a
distance The IEEE Standard Dictionary defines
telecommunications as the transmission of signals over long distance,
Science of communicating over distance
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Networks A network is a set of devices (nodes)
connected by communication links. A node can be a computer, printer, or
any other device capable of sending and/or receiving data generated by other nodes on the network.
A link is a communication pathway that transfers data from one device to another
Topology: Arrangement of nodes in a network specify topology.
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Network Criteria Performance
Throughput: Number of bits transmitted in one second
Delay: How long it takes a bit of data to travel in network
Reliability Robustness : ability of the network to
perform its function in the face of attack (node failure)
Security Unauthorized access viruses
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Bus Topology Single cable connect all computers Each computer has connector to shared
cable Cable must end with a terminator Advantages
Ease of installation Inexpensive Works well for small networks
Disadvantages Cable break, whole network down Limited number of devices can be attached
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Star Topology All computers attach to central point The devices are not directly linked to
one another Advantages
Ease of installation Inexpensive (less than mesh) Robustness
Disadvantages Hub fails, whole network down Costly than bus
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Mesh Topology Each device connected to every other
device Advantages
Robustness Can carry more data
Disadvantages Expensive Difficult to install Difficult to manage
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Ring Topology Each device connected to two devices
(immediate neighbors) The signal is passed along the ring in
one direction Advantages
Easy to install and reconfigure Inexpensive (less than mesh)
Disadvantages Break in a ring disables the whole network Unidirectional
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Types of Networks Local Area Network (LAN)
Links the nodes in a single office, building or campus
Wide Area Network (WAN) Links the nodes in states, countries or in the
whole world Metropolitan Area Network (MAN)
Between LAN and WAN Links the nodes in a town or city
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Protocols Protocol defines:
What is communicated How, it is communicated When, it is communicated
Elements of a protocol Syntax Semantics Timing