A-1

1
The Physical Layer

• Our goals
• Transmission media
• Magnetic media
• Twisted Pair(TP) UTP (unshielded), STP(shielded)
• Coaxial cable (Baseband/digital,
  Broadband/analogy)
• Optical Fiber (Single mode, multimode
  graded-index, step-index)
• Satellite/Wireless (Microwave, Radio)
• Modulation technologies
• Analogy FM,AM,PM,
• Digital ASK, FSK, PSK, QPSK, QAM,
• Digital Signal Encoding RZ, NRZ, Manchester,
  4B/5B,..
• Digital Hierarchy PDH, SDH, T1, E1,

2
Twisted Pair

• With better stability
• Transmission distance 100m (without repeater)
• Connector RJ-45(Internet), RJ-11 (phone)
• 10Baase-T, 100Base-T, 1000Base-T(Ethernet)
• Categories

Category 1 MTR 2Mbps, voice
Category 2 MTR 4Mbps, voice
Category 3 MTR 16Mbps, used by 10BaseT
Category 4 MTR 20Mbps, used by Token Ring
Category 5 MTR 100Mbps, used by 100BaseTx
Category 6 MTR 2.4Gbps, used by 1000BaseT
3
Twisted Pair UTP STP
4
Coaxial Cabel

• Immune to magneticwave interference
• RG-58
• Broadband Coaxial Cable impedance 75?, analogy
  transmission, higher bandwidth
• Baseband Coaxial Cable impedance 50?, digital
  transmission, lower bandwidth
• T-type BNC connector
• Used by 10Base2 (Thin Ethernet), 10Base5 (Thick
  Ethernet)

5
Optical Fiber

• Multimode Fiber
• LED emitting, with dispersion, shorter
  transmission distance
• Step-Index
• Graded-Index

• Advantages
• Immune to inference
• Long transmission distance
• High security
• High bandwidth, gt 1 Gbps
• High stability
• Low loss
• Single Mode Fiber
• LX SC connector
• Laser emitting, longer transmission distance

6
Optical Fiber
7
Satellite

• A large repeater
• GEOGeostationary Earth Orbit(36000km)
• MEOMedium-Earth Orbit
• LEOLow-Earth Orbit
• Large coverage
• High economic efficiency
• Everywhere can see the sky can communicate

8
Data Communication System
9
Modulation Technologies

• Analogy Modulation
• AM (Amplitude Modulation)
• FM (Frequency Modulation)
• 
  where
• 
  
• PM (Phase Modulation)
• Digital Modulation
• ASK, FSK, PSK, BPSK, QPSK
• QAM

10
Digitize TechnologyPCM
Sampling Nyquist Theorem Voice 8kHz sampling
rate
11
PCMQuantization
12
Computation of Digital Data Volume
What data volume of a song in the audio CD?
13
Digital Signal Encoding
14
Digital HierarchyPDH

• PDH (Plesiochronous Digital Hierarchy)
• Northern American Standards T1(DS1), T2(DS2),
  T3(DS3),
• DS1

DS0 DS1(T1) DS2(T2) DS3(T3)
Rate 64kbps 1.544Mbps 6.312Mbps 44.736Mbps
15
Digital HierarchyPDH

• PDH (Plesiochronous Digital Hierarchy)
• European Standards E1, E2, E3,
• E1

E1 E2 E3
Rate 2.048Mbps 8.448Mbps 139.264Mbps
16
Digital HierarchySDH
0
0
17
Digital HierarchySDH
STS-1 (Synchronous Transport Signal-1) STM-1
(Synchronous Transfer Mode-1) SPE (Synchronous
Payload Envelope)
SONET Frame Format
18
Digital HierarchySDH
SDH Frame Format