wireless systems ik1330 anders västberg [email protected] 08-790 44 55
TRANSCRIPT
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/program-kurser/kurshemsidor/ict/cos/I
K1330/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
Application
Tim
e a
nd
Fre
qu
en
cy No
rma
ls, Na
viga
tion
, Un
de
rwa
ter C
om
mu
nica
tion
, Re
mo
te se
nsin
g u
nd
er g
rou
nd
, Ma
ritme
tele
gra
ph
y
Lo
ng
dista
nce
com
mu
nica
tion
(fixed
an
d m
arite
), Bro
ad
castin
g, N
avia
ga
tion
, Ra
dio
be
aco
ns
AM
bro
ad
castin
g, n
avia
tion
, rad
io b
ea
con
s, distre
ss freq
ue
ncie
s.
Fixe
d p
oin
t to p
oin
t com
mu
nica
tion
, Mo
bile
ma
ritime
ae
ron
au
tical, la
nd
service
s, milita
ry com
mu
nica
tion
, am
ate
ur ra
dio
an
d
bro
ad
castin
g
Bro
ad
castin
g, T
V, F
M, M
ob
ile se
rvices fo
r ma
ritime
, ae
ron
au
tical a
nd
lan
d, W
irele
ss micro
ph
on
es, M
ete
or b
urst co
mm
un
icaito
n
Bro
ad
castin
g T
V, sa
telite
s, Pe
rson
al te
lep
ho
ne
system
s, rad
ar syste
ms, fixe
d a
nd
mo
bile
sate
lite se
rvices
Fixe
d se
rvices, F
ixed
state
lite se
rvices, M
ob
ile se
rivces, R
em
ote
sen
sing
Fre
qu
en
cy assa
ign
me
nts u
p 6
0 G
Hz
Frequency300-3000 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
Wavelength1000
-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
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
[Slimane]
AMPS
ETACS
NMT
GSM GPRS EDGE
USDCIS-136
CDPD TD-SCDMA
WCDMA
CDMAIS-95
CDMAoneIS-95B
CDMA2000
1G 2.5G2G 3G
Radio Communication
• Three main problems:– The path loss– Noise– Sharing the radio spectrum
Communication Systems
Source of information
Informationsink
Transmitter
Channel
Receiver
Message signal
Estimate of message
signal
Transmitted signal
Received signal
[Ahlin et. al., 2006]
Analog Communication System
Source of information
Signal Processing
Modulator RF-Stage
Channel
RF-StageInformation
sinkSignal
ProcessingDemodulator
[Slimane]
Digital Communication System
Source of Information
SourceEncoder
Modulator RF-Stage
Channel
RF-StageInformation
SinkSource
DecoderDemodulator
ChannelEncoder
DigitalModulator
ChannelDecoder
DigitalDemodulator
[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.
refbel P
PP 10][ log
refdB P
PP 10][ log10
• The bel is a large unit, so that decibel (dB) is almost always used:
• 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):
refdB V
VV 10][ log20
[Saunders, 1999]
decibels
Unit Reference Power Application
dBW 1 W Absolute power
dBm 1 mW Absolute power
P [dbW] = P [dBm] - 30
dBV 1 V Absolute voltage, typically at the input terminals of a receiver
dB any Gain or loss of a network
dBV/m 1 V/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]