Chapter 1(1) Ver 1.0 Radio Wave Propagation (02-1516)

8/16/2019 Chapter 1(1) Ver 1.0 Radio Wave Propagation (02-1516)

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BENT 3163TELECOMMUNICATION SYSTEM ENGINEERING

CHAPTER 1: RADIO WAVE PROPAGATION

Part 1

02 -2015/2016

1

Chapter Contents

• Introduction to Frequency Spectrum

• Introduction to radio wave propagation

• Mobile radio propagation:

• Large-scale path loss

• Prediction model:

• Free space / Plane earth

• Statistical• Okumura / Hata / Lee

• Small-scale fading & multipath

• Fading

• Large-scale/Small-scale

• Doppler Shift

• Rayleigh & Ricean Distributions

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References

Wireless Communication:

Principle and Practice 2

nd

Edition

Theodore S. Rappaport

Prentice Hall

Electronic Communication

Systems: Fundamentals through

Advanced, 5th EditionTomasi W.,

Prentice Hall

3

References

Wireless Communications 2nd

Edition

Andreas F. Molisch,

Wiley IEEE Press

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FREQUENCY SPECTRUM

• Communication between locations realised by:

• Converting information signal to electromagnetic energy

• Receiving station convert back to original form.

• Electromagnetic energy distributed throughout almost infinite

frequency ranges.

• The spectrum is divided into bands ( subsections).

• Each band have different name and boundary.

• Radio frequency (RF) spectrum divided into narrower bands.

ELECTROMAGNETIC FREQUENCY SPECTRUM

• Radio Spectrum (services) – provided by ITU



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ELECTROMAGNETIC FREQUENCY SPECTRUMBand

Number Frequency Range Designations Applications

2 30 Hz ~ 300 Hz ELF AC Power distribution, telemetry

3 0.3kHz ~ 3kHz VF Telephone

4 3 kHz ~ 30 kHz VLF Navigation, submarine comm.

5 30 kHz ~ 300 kHz LF Marine, aeronautical navigation

6 0.3 MHz ~ 3 MHz MF AM radio broadcasting

7 3 MHz ~ 30 MHz HF 2 – way radio, amateur radio, CB

8 30 MHz ~ 300 MHz VHF Mobile radio, TV/FM broadcasting

9 300 MHz ~ 3 GHz UHF TV, mobile phone, navigation system

10 3 GHz ~ 30 GHz SHF Microwave, satellite radio system11 30 GHz ~ 300 GHz EHF Specialised applications (& expensive)

12 0.3 THz ~ 3 THz Infrared Light Astronomy, heat –seeking system

FREQUENCY SPECTRUM

Radio waves:

Wavelength ratherthan frequency.

Wavelength:

The length that one

cycle of anelectromagnetic wave

occupies in space.

Low frequencies vs

high frequencies.



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FREQUENCY SPECTRUM

BANDWIDTH OF:

INFORMATION:

Difference between thehighest and lowest

frequencies contained in theinformation.

COMMUNICATIONCHANNEL:

Difference between thehighest and the lowest

frequencies that channelwill allow to pass through it

STANDARDS• To ensure no conflicts to spectrum (or frequency) allocations, users are

governed by these organisation standards:

STANDARDS

InternationalTelecommunication Union (ITU)

European Conference of Postaland TelecommunicationsAdministrations (CEPT)

EuropeanTelecommunicationsStandards Institute

(ETSI)

International Special Committee onRadio Interference (Comité

international spécial des perturbationsradioélectriques - CISPR)



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STANDARDS

• How about Malaysia?

• Spectrum allocations are controlled by MCMC (Malaysian Communications &

Multimedia Commission)

• All radio wave use for communication are govern by standards

Broadcasting

Spectrum Frequency (MHz)

Medium and Short Wave < 30

Band I 47 ~ 68

Band II 87.5 ~ 108

Band III 174 ~ 230

Band IV & V 470 ~ 806

L Band 1452 ~ 1492

STANDARDS• GSM 900 ( source from MCMC )

Mobile

Communication

Band TELCO Frequency (MHz)

Lower

Maxis 800 ~ 886

Digi 886 ~888

Celcom888 ~ 890

890 ~ 905

Upper

Maxis 925 ~ 931

Digi 931 ~ 933

Celcom933 ~ 935

935 ~ 950

Maxis 950 ~ 960



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STANDARDS

• GSM 1800 ( source from MCMC )

Mobile

Communication


Lower

Maxis 1710 ~ 1735

Celcom 1735 ~ 1760

Digi 1760 ~ 1785

Upper

Maxis 1805 ~ 1830

Celcom 1830 ~ 1855

Digi 1885 ~ 1880

STANDARDS• IMT2000 – FDD ( source from MCMC )

International

MobileTele –

communication


Lower

U Mobile 1920 ~ 1935

UMTS 1935 ~ 1950

Celcom 1950 ~ 1965

Digi 1965 ~ 1980

Reserved 1980 ~ 2010

Upper

U Mobile 2010 ~ 2125

UMTS 2125 ~ 2140

Celcom 2140 ~2155

Digi 2155 ~ 2170

Reserved 2170 ~ 2200



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STANDARDS

• IMT2000 – TDD ( source from MCMC )

International

Mobile

Telecommunication

TELCO Frequency (MHz)

U Mobile 1915 ~ 1920

Digi 2010 ~ 2015

UMTS 2015 ~ 2020

Celcom 2020 ~ 2025

Introduction to Radio Wave Propagation

• Electromagnetic wave propagation can be generally attributed to:

• Reflection

• Diffraction

• Scattering

• Reflection occurs when a propagating electromagnetic wave

impinges upon an object which has very large dimensions whencompared to the wavelength, e.g., buildings, walls.

• Diffraction occurs when the radio path between the transmitterand receiver is obstructed by a surface that has sharp edges.

• Scattering occurs when the medium through which the wavetravels consists of objects with dimensions that are smallcompared to the wavelength.

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• Most cellular radio systems operate in urban areas

• No direct line-of-sight

• Observing the power at a separation of several km, a steady decrease

in power is observed, this is simple attenuation

• High-rise buildings causes severe diffraction loss

• Multipath fading due to different paths of varying lengths

•

Caused by multiple reflections from various objects• Strength of the wave decrease as the distance between Tx & Rx increases

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Propagation Model

• Propagation model – predicting average received signal

strength at a given distance from the transmitter

• Large-scale propagation models predict the mean signal

strength for an arbitrary T-R separation distance.

• Useful in estimating radio coverage area of a transmitter

• Characterize signal strength over large T-R separation distances

(several hundreds or thousands of meters)

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Propagation Model

• Small-scale propagation models characterize the rapid

fluctuations of the received signal strength over very short

travel distance or short time duration.

• Also known as fading models

• As a MS moves over very small distances, the instantaneous

received signal strength may fluctuate rapidly giving rise to

small-scale fading• Because received signal is a sum of many contributions from different

directions with different phases

• Random phases cause the sum varying widely (ex: Rayleigh fading

distribution)

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Types of Radio Propagation Model

Prediction

•Calculation of the path loss (attenuation)

•Exact prediction is possible only for simpler cases,

•Example: Free space propagation or the Plane-earth model.

Statistical methods (empirical)

•Based on measured and averaged losses along typical classes of radio links.

•Example: Young, COST-231 Okumura-Hata, Lee, etc.

•Based on large collections of data collected for the specific scenario.

•For any model, the collection of data has to be sufficiently large to provide enough likeliness (orenough scope) to all kind of situations that can happen in that specific scenario.

Deterministic methods

•Based on the physical laws of wave propagation

•Example: Ray tracing

•Expected to produce more accurate and reliable predictions of the path loss than the empiricalmethods but more expensive in computational effort and depend on the detailed and accuratedescription of all objects in the propagation space, such as buildings, roofs, windows, doors, andwalls.

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Free Space Propagation Model

• The free space propagation model is used to predict received

signal strength when the transmitter and receiver have a

clear line-of-sight path between them.

• satellite communication

• microwave line-of-sight radio link

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TransmitterDistance, d

Receiver

ht

hr



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• Friis free space equation

L are usually due to transmission line attenuation, filter losses and antenna losses

L = 1 indicates no loss in the system hardware

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• The gain of the antenna:

• Ae: effective aperture (related to the physical size of the antenna)

• The wavelength, λ is related to the carrier frequency by:

• f : carrier frequency in Hertz

• ωc : carrier frequency (radians/second)

• c : speed of light (meters/s)

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• Example 1:

• If Pt = 10W, Gt = 0dB, Gr = 0dB and f c = 900 MHz, find Pr in

Watts at a free space distance of 1 km.

•Example 2:

• Assume a receiver is located 10 km from a 50 W transmitter.

The carrier frequency is 6 GHz and free space propagation is

assumed, Gt = 1 and Gr = 1. Find the power at the receiver.

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Free Space Path Loss

• Loss in signal strength of an electromagnetic wave

• resulting from a line-of-sight path through free space (usually air)

• with no obstacles nearby to cause reflection or diffraction.

• It does not include factors such as:

• the gain of the antennas used at the transmitter and receiver

• any loss associated with hardware imperfections

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FSPL =

FSPL (dB) = 32.4 + 20 + 20

f c: carrier frequency in MHz

d : distance in km



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FSPL = 32.4 + 20 + 20 [dB]

= + + − − [dBm]

= + − − [dBm]

= + [dBm]

P r : power received

P t : power transmitted

Gr : gain at mobile station

Gt : gain at base station

L s: path loss

Lm: medium loss (urban/suburban/rural area)

Effective isotropic radiated power -maximum radiated power available fromtransmitter in the direction of maximum

antenna gain as compared to an isotropicradiator


• The power received at any distance, d can be calculated from

knowledge of a reference power, P r (d 0 ) measured at some

reference distance, d 0

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2

0

0

d

d d P d P

r r

0d P r

d

d

mW

d P d P

r

r

00 log201

log10dBm

in Watts



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• Example 3:

• If a transmitter produces 50 W of power, express the

transmit power in units of dBm and dBW. If 50 W is applied

to a unity gain antenna with a 900 MHz carrier frequency,

find the received power in dBm at a free space distance of

100 m from the antenna.

• What is Pr(10 km)? Assume unity gain for the receiver

antenna.

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Carrier to Noise Ratio (C/N or CNR)

= CNR = Cdbm – Ndbm [dB]

C = carrier signal power or Pr

N = minimum signal level

= kTBF

k = Boltzmann constant, 1.38x10-23

T = temperature [K]

B = bandwidth of system, eg: GSM ,B = 200kHz

F = noise factor

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In telecommunications, the C/N is the SNR of a modulated signal.

CNR is defined as the ratio of the received modulated carrier signal power, C

to the received noise power, N after the receive filters



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Carrier to Noise Ratio (C/N or CNR)

Example 4:

• Suppose you received license to operate at a GSM1800

transmitting 5W into a 10 dB gain antenna. Your portable

receiver having an antenna gain of 2 dB. The total medium

loss is 10 dB. Calculate:

i. Power received at portable Rx located 1km away

ii. Minimum signal level, N if 5 dB noise figure

iii. C/N

iv. whether the portable receiver can be used at a distance of 5 km

from RBS

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Plane Earth Propagation Model

• Considers both direct path and a ground reflected

propagation path between Tx and Rx

• Also known as two-way ground reflection model

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=

ℎℎ

[watt]

= + + + 20 ℎℎ

[dBm]


Example 5:

• Consider a GSM system with 50 W of EIRP transmitting from

a RBS. Gain of the mobile antenna is 2dB. Calculate:

i. power receive in watt that would be available at the mobile unit at a

distance of 5 km from RBS for plane earth condition. Assume the

height of antenna at RBS equal to 200m and at the mobile unit equal

to 3m

ii. C/N if NF = 2dB

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Chapter 1(1) Ver 1.0 Radio Wave Propagation (02-1516)

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Transcript of Chapter 1(1) Ver 1.0 Radio Wave Propagation (02-1516)