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Wireless Systems
IK1330
Anders Västberg
[email protected]
08-790 44 55
IK1330 Wireless Systems
• TEN1: 4,5 hec.
– A part theory, B part problems
• LAB1: 3 hec.
– Three labs, propagation and planning, WLAN, measurements,
• Required reading:
– Stallings, W., Wireless Communications and Network, Pearson,
2005
• Course Webpage:
– http://www.kth.se/student/programkurser/kurshemsidor/ict/cos/IK1330/VT10-1
• Book Webpage:
– http://williamstallings.com/Wireless/Wireless2e.html
Stallings: Wireless
Communications and
Networks
[Stallings., 2005]
Radio Communication
• Radio or radio communication means any transmission,
emission, or reception of signs, signals, writing, images,
sounds or intelligence of any nature by means of
electromagnetic waves of frequencies lower than three
thousand gigacycles per second (3000 GHz) propagated
in space without artificial guide.
• Examples of radio communication systems:
–
–
–
–
–
–
Radio broadcasting.
TV broadcasting.
Satellite communication.
Mobile Cellular Telephony.
Wireless LAN.
Multimedia communication & Mobile Internet
[Slimane]
History
• 1864: Maxwell describes radio wave
mathematically
• 1888: Hertz generates radio waves
• 1890: Detection of radio waves
• 1896: Marconi makes the first radio transmission
• 1915: Radio tubes are invented
• 1948: Shannon’s law
• 1948: Transistor
• 1960: Communication Satellites
• 1981: Cellular technology
Classification of radio
spectrum
AM broadcasting, naviation, radio
beacons, distress frequencies.
Broadcasting TV, satelites, Personal
telephone systems, radar systems,
fixed and mobile satelite services
Fixed services, Fixed statelite
services, Mobile serivces, Remote
sensing
Frequency assaignments up 60 GHz
300-3000
Hz
3-30
kHz
30-300
kHz
300-3000
KHz
3-30
MHz
30-300
MHz
300-3000
MHz
3-30
GHz
30-300
GHz
Wavelength
1000
-100 km
100
-10 km
10
-1 km
1000
-100 m
100
-10 m
10
-1 m
100
-10 cm
10
-1 cm
10
-1 mm
Term
ELF
VLF
LF
MF
HF
VHF
UHF
SHF
EHF
Time and Frequency Normals,
Navigation, Underwater
Communication, Remote sensing
under ground, Maritme telegraphy
Broadcasting, TV, FM, Mobile
services for maritime, aeronautical
and land, Wireless microphones,
Meteor burst communicaiton
Fixed point to point communication,
Mobile maritime aeronautical, land
services, military communication,
amateur radio and broadcasting
Long distance communication (fixed
and marite), Broadcasting,
Naviagation, Radio beacons
Frequency
Application
The Radio Spectrum
• The frequency spectrum is a shared resource.
• Radio propagation does not recognize geopolitical
boundaries.
• International cooperation and regulations are required for
an efficient use of the radio spectrum.
• The International Telecommunication Union (ITU) is an
agency, within the UN, that takes care of this resource.
– Frequency assignment.
– Standardization.
– Coordination and planning of the international
telecommunication services.
Evolution of Wireless
Systems
[Stallings., 2005]
Evolution of Cellular
Systems
AMPS
USDC
IS-136
CDPD
GSM
GPRS
CDMA
IS-95
CDMAone
IS-95B
TD-SCDMA
ETACS
EDGE
WCDMA
NMT
1G
2G
2.5G
CDMA2000
3G
[Slimane]
Radio Communication
• Three main problems:
– The path loss
– Noise
– Sharing the radio spectrum
Communication Systems
Source of
information
Message
signal
Transmitter
Transmitted signal
Channel
Estimate of
message
signal
Received signal
Receiver
Information
sink
[Ahlin et. al., 2006]
Analog Communication
System
Source of
information
Signal
Processing
Modulator
RF-Stage
Channel
Information
sink
Signal
Processing
Demodulator
RF-Stage
[Slimane]
Digital Communication
System
Source of
Information
Source
Encoder
Channel
Encoder
Digital
Modulator
Modulator
RF-Stage
Channel
Information
Sink
Source
Decoder
Channel
Decoder
Digital
Demodulator
Demodulator
RF-Stage
[Slimane]
decibels
•
The bel is a logarithmic unit of power ratios. One bel corresponds to an
increase of power by a factor of 10 relative to some reference power, Pref.
P[ bel ]
•




The bel is a large unit, so that decibel (dB) is almost always used:
P[ dB ]
•
 P
 log 10 
P
 ref
 P
 10 log 10 
P
 ref




The above equation may also be used to express a ratio of voltages (or
field strengths) provided that they appear across the same impedance (or
in a medium with the same wave impedance):
V[ dB]
 V
 20 log 10 
V
 ref




[Saunders, 1999]
decibels
Unit
Reference Power
Application
dBW
1W
Absolute power
dBm
1 mW
Absolute power
P [dbW] = P [dBm] - 30
dBmV
1 mV
Absolute voltage, typically at the input
terminals of a receiver
dB
any
Gain or loss of a network
dBmV/m
1 mV/m
Electric field strength
dBi
Power radiated by and isotropic
reference antenna
Gain of an antenna
dBd
Power radiated by a half-wave
dipole
Gain of an antenna
0 dBd = 2.15 dBi
[Saunders, 1999]