1. 2012 session 1 TELE3118: Network Technologies Week 1: Physical Layer
Some slides have been taken from:
Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition. Jim Kurose, Keith Ross. Addison-Wesley, July All material copyright J.F Kurose and K.W. Ross, All Rights Reserved.
Computer Networks, 4th edition. Andrew S. Tanenbaum. Prentice-Hall, 2003.
Physical Layer

2. Outline Theoretical basis Physical media Modulation Multiplexing
Fourier analysis and bandwidth-limited signals
Physical media
Guided (copper, fibre)
Unguided (wireless)
Modulation
Multiplexing
Physical Layer

3. Bandwidth-Limited Signals
(a) binary signal and its root-mean-square Fourier amplitudes.
(b) – (c) Successive approximations to the original signal.
Physical Layer

4. Bandwidth-Limited Signals (2)
(d) – (e) Successive approximations to the original signal.
Physical Layer

5. Physical Media Bit: propagates between transmitter/rcvr pairs
physical link: what lies between transmitter & receiver
guided media:
signals propagate in solid media: copper, fiber, coax
unguided media:
signals propagate freely, e.g., radio
Physical Layer

6. Twisted Pair two insulated copper wires
Category 3: phone wires, 10 Mbps Ethernet
Category 5: 100Mbps Ethernet
Physical Layer

7. Coaxial Cable two concentric copper conductors bidirectional baseband:
single channel on cable
legacy Ethernet
broadband:
multiple channel on cable
HFC
Physical Layer

8. Fiber Optic Cable glass fiber carrying light pulses, each pulse a bit
high-speed operation:
high-speed point-to-point transmission (e.g., 10 Gps)
low error rate: repeaters spaced far apart; immune to electromagnetic noise
Physical Layer

9. Optical Transmission
Physical Layer

10. Fiber Cables (a) Side view of a single fiber.
(b) End view of a sheath with three fibers.
Physical Layer

11. Wireless Wireless link types:
terrestrial microwave
e.g. up to 45 Mbps channels
LAN (e.g., Wifi)
2Mbps, 11Mbps
wide-area (e.g., cellular)
e.g. 3G: hundreds of kbps
satellite
up to 50Mbps channel (or multiple smaller channels)
signal carried in electromagnetic spectrum
no physical “wire”
bidirectional
propagation environment effects:
reflection
obstruction by objects
interference
Physical Layer

12. The Electromagnetic Spectrum
Physical Layer

13. Radio 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.
Physical Layer

14. Free-Space Optics
Convection currents can interfere with laser communication systems.
Physical Layer

15. Communication Satellites
Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.
Physical Layer

16. Low-Earth Orbit Satellites: Iridium
(a) The Iridium satellites from six necklaces around the earth.
(b) 1628 moving cells cover the earth.
Physical Layer

17. Modulation / Demodulation
(a) A binary signal
(b) Amplitude modulation
(c) Frequency modulation
(d) Phase modulation
Physical Layer

18. Modems (a) Quadrature Phase-Shift Keying: QPSK
(b) Quadrature Amplitude Modulation: QAM-16
(c) QAM-64
Baud-rate: symbols/sec
Bit-rate = baud-rate x bits/symbol
Physical Layer

19. Frequency Division Multiplexing
(a) The original bandwidths.
(b) The bandwidths raised in frequency.
(b) The multiplexed channel.
Physical Layer

20. Time Division Multiplexing
The T1 carrier (1.544 Mbps).
Physical Layer

21. Wavelength Division Multiplexing
Physical Layer