Matakuliah : H0484/Jaringan Komputer
Tahun
: 2007
Transmisi Data
Pertemuan 04
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• Menjelaskan transmisi data
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Outline Materi
• Media
• Gangguan
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Coaxial Cable
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Coaxial Cable Applications
• Television distribution
– Antenna to TV
– Cable TV + Cable Modem
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Optical Fiber
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Optical Fiber Transmission Modes
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Optical Fiber - Characteristic
• Greater capacity (Data rates of hundreds
of Gbps)
• Smaller size & weight
• Lower attenuation
• Electromagnetic isolation
• Greater repeater spacing
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Spektrum untuk Communication
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Transmission Frequencies
• 2GHz to 40GHz
– Microwave
– Highly directional
– Point to point
– Satellite
• 30MHz to 1GHz
– Omnidirectional
– Broadcast radio
• 3 x 1011 to 2 x 1014
– Infrared
– Local
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Bands
Band
Range
Propagation
Application
VLF
3–30 KHz
Ground
Long-range radio navigation
LF
30–300 KHz
Ground
Radio beacons and
navigational locators
MF
300 KHz–3 MHz
Sky
AM radio
HF
3–30 MHz
Sky
Citizens band (CB),
ship/aircraft communication
VHF
30–300 MHz
Sky and
line-of-sight
VHF TV,
FM radio
UHF
300 MHz–3 GHz
Line-of-sight
UHF TV, cellular phones,
paging, satellite
SHF
3–30 GHz
Line-of-sight
Satellite communication
EHF
30–300 GHz
Line-of-sight
Long-range radio navigation
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Wireless Propagation
Signal travels along three routes
– Ground wave
• Follows contour of earth (up to 2MHz, AM radio)
– Sky wave
• Amateur radio, BBC world service, Voice of America
• Signal reflected from ionosphere layer of upper
atmosphere (actually refracted)
– Line of sight
• Above 30Mhz
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Satellite Point to Point Link
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Satellite Broadcast Link
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Transmission Impairments
• Signal received may differ from signal transmitted
– Analog - degradation of signal quality
– Digital - bit errors
• Caused by
– Attenuation and attenuation distortion
– Delay distortion
– Noise
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Attenuation
• Signal strength falls off with distance
• Depends on medium
• Received signal strength:
– must be enough to be detected
– must be sufficiently higher than noise to be
received without error
• Attenuation is an increasing function of frequency
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Noise
• Additional signals inserted between transmitter and
receiver
• Thermal
– Due to thermal agitation of electrons
– Uniformly distributed
– White noise
• Intermodulation
– Signals that are the sum and difference of original
frequencies sharing a medium
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Noise
• Crosstalk
– A signal from one line is picked up by another
• Impulse
– Irregular pulses or spikes
• External electromagnetic interference
• Short duration
• High amplitude
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