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Infocommunication systems Infokommunikációs rendszerek Lecture 3. előadás Radio transmission Rádiós átvitel. Takács György. Radio transmission media. Frequency bands and wave propagation modes Terrestrial radio connection Satellite communication In door radio connection.

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slide1

Infocommunication systems Infokommunikációs rendszerekLecture 3. előadásRadio transmissionRádiós átvitel

Takács György

Komm. rendsz. 3. előadás 2012. szept. 24.

radio transmission media
Radio transmission media
  • Frequency bands and wave propagation modes
  • Terrestrial radio connection
  • Satellite communication
  • In door radio connection

Komm. rendsz. 3. előadás 2012. szept. 24.

media characteristics
Media characteristics
  • Transmission parameters (path loss, delay, fading, radio interferences)
  • Reliability and availability - equipment and propagation parameters (lightning, snow, rain, fog, smoke)
  • Openness – interferences - privacy

Komm. rendsz. 3. előadás 2012. szept. 24.

is radio communication a technical issue 1
Is radio communication a technical issue (1)?
  • Radio communications use open and common media. Using a radio frequency means consuming. So management of radio frequency is inevitable.
  • Using a radio frequency means a kind of environment pollution! Frequency police?
  • Radio frequencies are limited resources. The „good” frequencies are already consumed. Frequency fees! ORTT.
  • Propagation of radio waves do not consider political borders! Frequency management is a typical international process. (CCIR, ITU-R)

Komm. rendsz. 3. előadás 2012. szept. 24.

is radio communication a technical issue 2
Is radio communication a technical issue (2)?
  • Radio frequencies have considerable physiological effect!
  • Antennas are considered as special constructions. Local municipalities regulate construction rules and issue building licences.
  • Satellite positions are limited resources too. The „good” positions are consumed.
  • Differential equations of electromagnetic wave propagation are quite simple – in the case of plane wave and free space. Solutions in real geographic situations (among hills, valleys, buildings or especially inside buildings) are extremely difficult.

Komm. rendsz. 3. előadás 2012. szept. 24.

frequency bands and wave propagation modes
Frequency bands and wave propagation modes
  • LF (30-300kHz)
  • MF (300-3000kHz)
  • HF (3-30 MHz)
  • VHF (30-300 MHz)
  • UHF (300-3000MHz)
  • SHF (centimetric waves, 3-30GHz)
  • EHF (millimetric waves, 30-300GHz)

Komm. rendsz. 3. előadás 2012. szept. 24.

propagation modes and antennas
Propagation modes and antennas

LF

MF

Komm. rendsz. 3. előadás 2012. szept. 24.

propagation modes and antennas1
Propagation modes and antennas

HF

Komm. rendsz. 3. előadás 2012. szept. 24.

propagation modes and antennas2
Propagation modes and antennas

UHF

VHF

SHF

EHF

Komm. rendsz. 3. előadás 2012. szept. 24.

slide16

in free space (ε0,µ0):

plane-wave solution

1. electric and magnetic field vectors are perpendicular

2. ratio of their amplitudes is a constant and called as

free-space wave impedance

Komm. rendsz. 3. előadás 2012. szept. 24.

slide17

characteristic impedance

Reflection coefficient

Komm. rendsz. 3. előadás 2012. szept. 24.

free space radio link los
Free space radio link (LOS)

PT transmitted power

Ae effective area of antenna

G gain of antenna

λ wavelength

d distance

Komm. rendsz. 3. előadás 2012. szept. 24.

example by gsm mobile system
Example by GSM mobile system

Pr=kPT/d2

d=30m

Base station

P=50W

Pr=k×0,0555

d=3cm

P=5W

Pr=k×5555

100000×

Komm. rendsz. 3. előadás 2012. szept. 24.

polarization
Polarization:
  • Property of a radiated electromagnetic wave describing the time varying direction and relative magnitude of the electric-field vector
  • In general the field is elliptically polarized
  • Linear and circular polarizations are special cases

Komm. rendsz. 3. előadás 2012. szept. 24.

reflection
Reflection
  • The amplitude, phase and polarization of the reflected wave is determined by the material parameters of the medias and the surface irregularity.

Komm. rendsz. 3. előadás 2012. szept. 24.

propagation with direct and reflected waves and reflected only waves
Propagation with direct and reflected waves and reflected only waves

Komm. rendsz. 3. előadás 2012. szept. 24.

slide27

RADIO FOR MOBILES

SENDER

RECEIVER

Without FADING

Komm. rendsz. 3. előadás 2012. szept. 24.

good frequencies bandwidth issues
„Good” frequencies? Bandwidth issues?
  • Low attenuation (loss)
  • High bandwidth
  • Beaming – circular characteristic
  • Cheap or free
  • No interference
  • Exclusive usage
  • „Good” frequencies are not existing -- Only compromise of limitations

Komm. rendsz. 3. előadás 2012. szept. 24.

radio link types
Radio link types
  • Point-point connections
  • Point multipoint connections
  • Cellular systems

Komm. rendsz. 3. előadás 2012. szept. 24.

slide40

Optically visible

loop

The surface of the earth

30-50 km because the spherical earth

Terrestrial microwave connections

Komm. rendsz. 3. előadás 2012. szept. 24.

slide43

Centrifugal force

Mass of the satellite, kg

Mass of the earth

Gravitational constant

Speed of the satellite, m/s

Gravitation force

Geostationary satellite characteristics

Komm. rendsz. 3. előadás 2012. szept. 24.

cellular systems
in a cluster each cell has a separate frequency

a is the area of one cell

A is the cluster area

R is the cell diameter

D is the distance between clusters (the distance between cells with identical frequencies)

K is the number of the cluster cells

Cellular systems

Komm. rendsz. 3. előadás 2012. szept. 24.

examples for generating clusters
Examples for generating clusters

Komm. rendsz. 3. előadás 2012. szept. 24.

frequency reuse pattern for k 4
Frequency reuse pattern for K=4

Komm. rendsz. 3. előadás 2012. szept. 24.

frequency reuse pattern for k 7
Frequency reuse pattern for K=7

Komm. rendsz. 3. előadás 2012. szept. 24.

frequency reuse pattern for k 19
Frequency reuse pattern for K=19

Komm. rendsz. 3. előadás 2012. szept. 24.

slide66
K=?

Komm. rendsz. 3. előadás 2012. szept. 24.

increasing capacity in cellular systems
Increasing capacity in cellular systems
  • Adding new channels
  • Frequency borrowing
  • Cell splitting
  • Cell sectoring
  • Microcells

Komm. rendsz. 3. előadás 2012. szept. 24.

sectoring
Sectoring

Komm. rendsz. 3. előadás 2012. szept. 24.

in door wireless connections
In-door wireless connections

Komm. rendsz. 3. előadás 2012. szept. 24.

slide70

A vezetéknélküli adathálózat bázisállomásainak helye elő van készítve minden folyosón

Komm. rendsz. 3. előadás 2012. szept. 24.

interferences
Interferences

Komm. rendsz. 3. előadás 2012. szept. 24.