Communications
• Communication means conveying information• Usually categorized by the types of information
• Person-to-person• Telephone• Mobile phone• SMS• CB radio• Radio• Remote control
• Free TV• Cable TV• Newspaper• Letter• Email• WWW
Communications – Classifications
• Delivery time• Slow → non-electronic
• Newspaper, letter
• Fast → electronic• TV, telephone
• The scope of this course is limited to fast delivery time, electronic communications
Communications – Classifications
• Medium• Copper wire
• Telephone
• Waveguide or fiber optics• Cable TV
• Free space• Mobile phone
• Information type• Voice
• Mobile phone
• Video• TV
• Data• Email, WWW
Communications – Classifications
• Information flow• Simplex
• TV, SMS
• Half duplex• CB radio
• Full duplex• Telephone
• Full duplex exists only in physical system, but not in application level
• Information distribution• Unicast → one-to-one
• Telephone
• Multicast → one-to-many• Cable TV
• Broadcast → one-to-all• Free TV, radio
• Sometimes broadcast is considered as a special case of multicast
Communications – Model
• Source• Generate data to be transmitted• Voice, audio, video, text, digital data, etc.
• Transmitter• Convert data into transmittable signals• Can be viewed as 2 separate tasks• Input transducer
• Translate information into electric signal• Microphone, for example
• Transmitter• Modulation, filtering, encoding, transmitting, etc.
Communications – Model
• Receiver• Convert received signal into data• Can also be viewed as 2 separate tasks• Receiver
• Filtering, amplifying, demodulating, decoding, etc.
• Output transducer• Revert to the original information format• Loudspeaker, for example
• Destination• Take incoming data
Communications – Model
• Transmission system• Carry signals• Twisted pair, coax, fiber, air, etc.
• Goal is to minimize |m' − m|• In a two-way communication system, both the
transmitter and the receiver are implemented within one physical unit
Communications – Networking
• Point-to-point communication system• Link-level issues
• Signaling, bit rate, medium, connector types, filtering, amplification, equalization, synchronization, error control, flow control, etc.
• Addressing, connection establishing, switching, routing are non-issues
A B
Communications – Networking
• Communication network• Network issues such as addressing and routing are
essential
12
3
45
6
7
8
Networks
• Point-to-point communication usually not practical• Devices are too far apart• Large set of devices would need impractical number of
connections
• Solution is communication networks• Wide area networks• Local area networks
Networks – WAN
• Wide area networks• Large geographical area• Crossing public rights of way• Rely in part on common carrier circuits• Alternative technologies
• Circuit switching• Packet switching
Networks – WAN
• Circuit switching• Dedicated communications path established for the duration
of the conversation• Telephone networks
• Packet switching• Data sent out of sequence• Small chunks of data at a time
• Packets
• Packets passed from node to node between source and destination
• Used for terminal to computer and computer to computer communications
Networks – LAN
• Local area networks• Smaller scope
• Building or small campus
• Usually owned by same organization as attached devices
• Very high data rate
Networks – MAN
• Metropolitan area networks• Middle ground between LAN and WAN• Private or public networks• High speed• Large area
Networks – Wireless
• Wireless LAN• Wi-Fi
• Wireless WAN• Cellular systems
• Personal area networks• System interconnection• Bluetooth
Networks – Trends
• Traditional communication networks• Voice Telephone and cellular networks• Video Cable and satellite TV networks• Data Computer networks• Communication revolution
• Digital age• Driven by innovations in digital communication, signal
processing, computer, IC, optics and wireless technology
Networks – Trends
• New generation of communication networks• Voice Telephone and cellular networks• Video Cable and satellite TV networks• Data Computer networks• Use of Internet• Integrated service with differentiated QoS
CE 4228 – Outline
• Signals & bandwidth• Transmission systems
• Transmission media• Transmission signals• Multiplexing
• Data link control• LANs• WANs
• Protocol architecture• OSI• TCP/IP