02_RN31542EN16GLA0_Radio Network Planning Fundamentals

Radio Network Planning Fundamentals Slide 1

NokiaEDU Radio network planning fundamentals

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© Nokia Solutions and Networks 2016

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Module Objectives

At the end of the module you will be able to: • Explain basic radio propagation mechanisms • Explain fading phenomena • Calculate free space loss • Explain basic concepts related to Node B and UE performance

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Radio network planning fundamentals - Propagation mechanisms • Basics: deciBel (dB) • Radio channel

• Reflections • Diffractions

• Scattering

- Multipath & Fading - Propagation Slope & Different Environments

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deciBel (dB) – Definition Power

 P  dB  10 log   P 0 

P( dB)

[ P lin. ]  10

10

Voltages

 E  dB  20 log   E 0 

E(dB)

[ E lin. ]  10

20

 

P lin.~ E lin. ² / 2

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deciBel (dB) – Conversion UMTS Power Range -50 dBm = 10 nW -30 dBm = 1 nW -20 dBm = 10 mW -10 dBm = 100 nW -7 dBm = 200 nW -3 dBm = 500 nW 0 dBm = 1 mW +3 dBm = 2 mW +7 dBm = 5 mW +10 dBm = 10 mW +13 dBm = 20 mW +20 dBm = 100mW +30 dBm = 1 W +40 dBm = 10W +50 dBm = 100W

Calculations in dB (deciBel) - Logarithmic scale Always with respect to a reference - dBW = dB above Watt - dBm = dB above mWatt - dBi = dB above isotropic - dBd = dB above dipole - dBmV/m = dB above mV/m Rule-of-thumb: - +3dB - +7 dB - +10 dB - -3dB - -7 dB - -10 dB

= = = = = =

factor 2 factor 5 factor 10 factor 1/2 factor 1/5 factor 1/10

UMTS Power  Link Budget: • min. UE Power: -50 dBm* • max. UE Power: 21 dBm / 24 dBm (UE Power Class 4 / 3)* • max. Node B Power/cell typically: 40 - 46 dBm * 3GPP TS 25.101 8

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Radio Channel – Main Characteristics  Multipath Effects  RAKE Receiver  α (Orthogonality)

- Linear • In field strength - Reciprocal • UL & DL channel same (if in same frequency) - Dispersive • In time (echo, multipath propagation) • In spectrum (wideband channel)

: orthogonality factor

α

Time Dispersion / Multipath propagation Loss of Orthogonality in DL Transmission (Channelisation Codes only orthogonal

e d u t i l p m A

direct path

when synchronised)

echoes

• α location dependent (Multi-path effect) • value α = [0..1]; typically: - 0.4 - 0.9 (Macro Cells)

Delay time

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-

> 0.9 (Micro & Pico Cells)


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Propagation Mechanisms (1/2) Free-space propagation - Signal strength decreases exponentially with distance

D Reflection

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• Specular reflection amplitude A  phase f  polarisation 

a*A (a < 1) - f material dependent phase shift

• Diffuse reflection amplitude A  phase f  polarisation 

a *A (a < 1) random phase random

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specular reflection

diffuse reflection


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Propagation Mechanisms (2/2) Absorption -

A

Heavy amplitude attenuation Material dependant phase shifts Depolarisation

A - 5..30 dB

• Diffraction Wedge - model Knife edge Multiple knife edges

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Scattering – Macrocell Macro Cell - Scattering local to UE

Scattering local to BS

• causes fading • small delay & large angle spreads • Doppler spread  time varying effects

- Scattering local to BS

Scattering local to UE

• No additional Doppler spread • Small delay & angle spread

Remote scattering

- Remote scattering • • • •

Independent path fading No additional Doppler spread Large delay spread Large angle spread

Micro Cell • local scattering: Large angle spread • Low delay spread • Medium or high Doppler spread

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Radio network planning fundamentals - Propagation mechanisms - Multipath & Fading • Delay – Time dispersion • Angle – Angular Spread • Frequency – Doppler Spread • Fading – Slow & Fast

- Propagation Slope & Different Environments

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Multipath propagation: Delay – Time dispersion - Multipath: Different radio paths have different properties • Distance  Delay/Time • Direction  Angle • Direction & Receiver/Transmitter Movement  Frequency

1.

Multipath propagation

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- Multipath delays due to multipath propagation • 1 s 300 m path difference

- WCDMA: RAKE Receiver to combine multipath components • Components with delay separation > 1 chip (0.26 s = 78 m) can be separated & combined • Standardized delay profiles in 3GPP specs: - TU3 typical urban at 3 km/h (pedestrians) - TU50 typical urban at 50 km/h (cars) - HT100 hilly terrain (road vehicles, 100 km/h) - RA250 rural area (highways, up to 250 km/h)

P

Multipath delays due to multipath propagation • 1 s  300 m path difference • 1 chip  260.4 ns  78 m ( RAKE Receiver/Matched Filter)

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1. 2.

Channel impulse response 3. 4.

t


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Delay Spread • Typical values

Environment

Delay Spread (s)

Macrocellular, urban

0.5-3

Macrocellular, suburban

0.5

Macrocellular, rural

0.1-0.2

Macrocellular, HT

3-10

Microcellular

< 0.1

Indoor

0.01...0.1

Remember: • Loss of DL Synchronisation / Orthogonality Factor α • 1 chip  260.4 ns  78 m

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Angle – Angular Spread - Angular spread arises due to multipath, both from local scatterers near the mobile & near the base station and remote scatterers - Angular spread is a function of base station location, distance & environment - Angular Spread has an effect mainly on the performance of diversity reception & adaptive antennas Macrocell Antenna

• •

5 - 10 degrees in macrocellular environment >> 10 degrees in microcellular environment

MacrocellularEnvironment = Macrocell Coverage Area

• < 360 degrees in indoor environment Angular spread:

• function of BS location, distance & environment

Microcell Antenna

• has an effect mainly on the performance of diversity reception & adaptive antenna  typical no sectorisation in Micro- & Pico Cells

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MicrocellularEnvironment = Microcell Coverage Area


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Frequency – Doppler Spread - Doppler Effect: with a moving transmitter or receiver, the frequency observed by the receiver will change • Rise if the distance on the radio path is decreasing • Fall if the distance in the radio path is increasing

- The difference between the highest and the lowest frequency shift is called Doppler spread

f d 

v 



v c f

v :

Speed of receiver (m/s) c : Speed of light (3*10^8 m/s) f : Frequency (Hz)

f rec = f source (1-2)/1;  = v/c

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Fading Fading describes the variation of the total pathloss ( signal level) when receiver/transmitter moves in the cell coverage area +20 dB Fading is commonly categorised to two categories based on the phenomena causing it: • Slow fading: Caused by shadowing due to obstacles • Fast fading: Caused by multipath propagation

Power

Fast Fading Slow fading*

mean value

• Time-selective fading: Short delay + - 20 dB Doppler • Frequency-selective fading: Long delay • Space-selective fading: Large angle

2 sec

4 sec

6 sec

time

* or Lognormal Fading

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In wireless communications systems, the transmitted signal typically propagates via several different paths from the transmitter to the receiver. This can be caused, e.g., by reflections of the radio waves from the surrounding buildings or other obstacles, and is typically called multipath propagation. Each of the multipath components have generally different relative propagation delays and attenuations which, when summing up in the receiver, results in filtering type of effect on the received signal where different frequencies of the modulated waveform are experiencing different attenuations and/or phase changes. This is typically termed frequency-selective fading. Another important characteristics is related to the relative mobility of the transmitter and receiver, or some other time-varying behavior in the propagation environment. In effect, this causes the overall radio channel to be time-variant meaning time-varying delays and attenuations for the individual multipath components. This phenomenon is generally termed time-varying or time-selective fading.

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Slow Fading – Gaussian Distribution - Measurement campaigns have shown t hat Slow Fading follows Gaussian distribution • Received signal strength in dB scale (e.g. dBm, dBW)

- Gaussian distribution is described by mean value m, standard deviation • 68% of values are within m ± • 95% of values are within m ±2

- Gaussian distribution used in planning margin calculations Compensation of Slow Fading in UMTS • Rel. 99 & HSUPA: by Fast Power Control & SHO • HSDPA: by Fast Link Adaptation

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Fast Fading - Different signal paths interfere and affect the received signal • Rice Fading – the dominant (usually LOS) path exist

Compensation of Fast Fading in UMTS • Rel. 99 & HSUPA: by Fast Power Control • HSDPA: by Fast Link Adaptation • Rayleigh Fading – no dominant path exist

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Fast Fading – Rayleigh Distribution - It can be theretically shown that fast fading follows Rayleigh Distribution when there is no single dominant multipath component • Applicable to fast fading in obstructed paths • Valid for signal level in linear scale (e.g. mW, W) level (dB) +10

0 -10 -20 -30

0

1

2

3

4

5m

920 MHz v = 20 km/h

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Fast Fading – Rician Distribution - Fast fading follows Rician distribution when there is a dominant multipath component, for example line-of-sight component combined with in-direct components • Sliding transition between Gaussian and Rayleigh • “Rice-factor” K = r/A: direct / indirect signal energy K=0 K >>1

 

Rayleigh Gaussian K=0 (Rayleigh)

K=1 K=5

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Radio network planning fundamentals - Propagation mechanisms - Multipath & Fading - Propagation Slope & Different Environments • Free Space Loss • Received power with antenna gain • Propagation slope • Propagation Model – Idea

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Free Space Loss - Free space loss proportional to 1/d 2 • Simplified case: isotropic antenna

• Which part of total radiated power is found within surface A? • Power density S

= P/A = P / 4 d 2

 Received power within surface A´ :

P´ = P/A * A´

• Received power reduces with square of distance

d

Surface A = 4 * d 2

A´ = 4*A

A´´ = 16*A

A

assume surface A´= 1m2

d 2d 4d

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Received power with antenna gain P s

S

- Power density at the receiving end



4 d

- Effective receiver antenna area

Aeff

- Received power

P r

2

 2 



4

G s

G R

    G s Gr   P s  4 d 

P r

2

Aeff S

P s

P r

As

Ar

Gs

Gr

d

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Antenna gain is normally given by how much the given antenna is better than a dipole antenna (dBd) or an isotropic (fully omnidirectional) antenna (dBi)

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Propagation slope - The received power equation can be formulated as



P r P s G s Gr C d





Propagation Models: Statistical Path Loss

- Where

    C   4   

• C is a constant •

2

is the slope factor - 2 for free space

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-

4 for plane, smooth, perfectly conducting terrain

-

3-3.4 for irregular terrain

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Propagation Model – Idea A propagation Model is a function:

L F (d ) 

d = Distance from the BTS Antenna L = Path Loss to the distance d L = (Ptx – Prx) in dB

- Such a function should be able to estimate the Path Loss (signal level) for the different distances in the cell area For the Cell Radius R:

L Max F ( R) 

Lmax is the maximum allowed Path Loss (  minimum allowed Signal Level) at the cell edge (  Cell Radius R)

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Thank You !

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02_RN31542EN16GLA0_Radio Network Planning Fundamentals

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