Lecture Computer networks 1 - Lecture 2: Communication media has contents: Theoretical basis for data communication, guided transmission media, wireless transmission, digital subscriber lines,... and other contents.
Trang 1Computer Networks 1
(Mạng Máy Tính 1)
Lectured by: Dr Phạm Trần Vũ
Trang 2Lecture 2: Communication Media
Reference :
Chapter 2 - “Computer Networks”,
Andrew S Tanenbaum, 4th Edition, Prentice Hall, 2003.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 3Theoretical basis for data communication
Wireless transmission
Digital subscriber lines
Internet over TV cables
Trang 5Fourier Series
Trang 6Bandwidth
Signals lose power during transmission
Different transmission facilities diminish different
Fourier components with different amounts ->
distortion of signals
Usually, high frequency components will be
diminished
Bandwidth : range of frequencies can be
transmitted without being strongly attenuated
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 7Bandwidth-Limited Signals (1)
A binary signal and its root-mean-square Fourier amplitudes.
(b) – (c) Successive approximations to the original signal.
Trang 8Bandwidth-Limited Signals (2)
the original signal.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 9Bandwidth-Limited Signals (3)
Relation between data rate and harmonics for a voice
telephone line
Trang 11Twisted Pair
(a) Category 3 UTP.
(b) Category 5 UTP.
Trang 12Coaxial Cable
A coaxial cable.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 13Fiber Optics
(a) Three examples of a light ray from inside a silica fiber
impinging on the air/silica boundary at different angles.
(b) Light trapped by total internal reflection.
Trang 15Fiber Cables
(a) Side view of a single fiber.
(b) End view of a sheath with three fibers.
Trang 16Fiber Optic Networks
A fiber optic ring with active repeaters.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 17Fiber Optic Networks (2)
A passive star connection in a fiber optics network.
Trang 19The Electromagnetic Spectrum
The electromagnetic spectrum and its uses for
communication.
Trang 20Radio Transmission
(a) In the VLF, LF, and MF bands, radio waves follow the
curvature of the earth.
(b) In the HF band, they bounce off the ionosphere.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 21Lightwave Transmission
A bidirectional system with two lasers is pictured here.
Trang 22Communication Satellites
• Geostationary Satellites
• Medium-Earth Orbit Satellites
• Low-Earth Orbit Satellites
• Satellites versus Fiber
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 23Communication Satellites
Communication satellites and some of their properties,
including altitude above the earth, round-trip delay time
Trang 24Communication Satellites (2)
The principal satellite bands.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 25Modems, ADSL, and Wireless
Trang 27Digital Subscriber Lines - ADSL
Bandwidth versus distanced over category 3 UTP for DSL.
Trang 28Digital Subscriber Lines – ADSL (2)
Operation of ADSL using discrete multitone modulation.
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 29Digital Subscriber Lines (3)
A typical ADSL equipment configuration.
Trang 30Internet over Cable
Cable television
CuuDuongThanCong.com https://fb.com/tailieudientucntt
Trang 31Internet over Cable (2)
The fixed telephone system.
Trang 32Spectrum Allocation
Frequency allocation in a typical cable
TV system used for Internet access
CuuDuongThanCong.com https://fb.com/tailieudientucntt