Basic Propagation Principles of Radio Waves and Basic RF Knowledge

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Basic Principles of Radio Propagation and Basic RF Knowledge www.huawei.com

HUAWEI TECHNOLOGIES CO., LTD.

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Objectives Upon completion of this course, you will be able to:

 Get familiar with the propagation principles of

radio waves and make theoretical preparation for subsequent events such as link budget.  Understand the related knowledge about

antennas and the meanings of common counters.  Understand the basic RF knowledge, devices

and instruments that are often used in the wireless network planning and optimization.


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Contents

Chapter 1 Radio Wave Knowledge Chapter 2 Introduction to Antennas Chapter 3 Basic RF Knowledge

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Chapter 1 Radio Wave Knowledge



Section 1 Basic Principles



Section 2 Propagation Features



Section 3 Propagation Models



Section 4 Propagation Model Calibration


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Basic Principles — Wireless Spectrum Frequency 3-30Hz 30-300Hz 300-3000Hz 3-30KHz 30-300KHz 300-3000KHz 3-30MHz 30-300MHz 300-3000MHz 3-30GHz 30-300GHz

Classification

Designation

Extremely Low Frequency Voice Frequency Very-low Frequency Low Frequency Medium Frequency High Frequency Very High Frequency Ultra High Frequency Super High Frequency Extremely High Frequency

ELF VF VLF LF MF HF VHF UHF SHF EHF

300-3000GHz

Frequencies in different bands have different propagation features. HUAWEI TECHNOLOGIES CO., LTD.

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Basic Principles — Propagation of Radio Waves 

When radio waves are propagated in the space, the direction of the electric field changes regularly. This phenomenon is called the polarization of radio waves. The field direction of radio waves is called the polarization direction.  If the direction of the electric field is vertical to the ground, the waves are called vertically-polarized waves.

Dipole

 If the direction of the electric field is horizontal to the ground, the waves are called horizontally-polarized waves.

Magnetic field

Magnetic field

Electric field

Electric field

Electric field Propagation direction of waves


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Basic Principles — Propagation Path

Direct waves and ground-reflected waves (most common propagation path)

Mountain-diffraction waves (signal source of the shadow region) HUAWEI TECHNOLOGIES CO., LTD.

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Troposphere-reflected waves (great randomness in propagation)

Ionosphere-reflected waves (trans-horizon communication path) Page 7

Basic Principles — Propagation Path

1. Building-reflected waves 2. Diffraction waves 3. Direct waves 4. Ground-reflected waves


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










Section 4 Propagation Model

Calibration


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Radio Propagation Environment  The propagation of radio waves is affected by the terrain structures and

man-made environment. The radio propagation environment directly determines the selection of the propagation models. The main factors affecting the radio propagation environment are:  Natural terrain (mountains, hills, plains and water areas)  Number, distribution and material features of architectures

 Vegetation features in this region  Weather conditions  Conditions of natural and manual electromagnetic noises


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Terrain Classification Quasi-smooth terrain A quasi-smooth terrain refers to a terrain that has

T R

gently rolling surface and the rolling height is less than or equal to 20 m.

Irregular terrain According to the status, other terrains except the

T

quasi-smooth terrain can be classified into: hilly

R

terrain, isolated mountains, sloping terrain, mixed terrain of water and land. HUAWEI TECHNOLOGIES CO., LTD.

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Signal Fading Receive Power (dBm) –20

Fast fading Slow fading

–40

–60

10 HUAWEI TECHNOLOGIES CO., LTD.

20 HUAWEI Confidential

Distance (m)

30 Page 12

Signal Diversity Methods Against Fast Fading — Diversity  Time Diversity

 Symbol interleaving, error detection, error correcting codes and RAKE receiver technology  Space Diversity

 Adopt the main and diversity antenna to receive signals. The receive signals of the main and diversity antenna do not have the feature of fading at the same time. The capability provided by the receiver of the BTS for balancing signals of different delays within a certain period is also a form of space diversity.  Frequency Diversity

 The GSM network adopts the frequency hopping.  The CDMA network adopts the frequency spread technology.


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Extension of Radio Waves Delay  It is originated in the reflection and mainly refers to the shared-frequency

interference caused by the difference between the main signals of the receiver and other multi-path signals in terms of the transmission time in space.  Transmitting signals come from an object that is far from the receiver antenna.

Solution


Balance and RAKE Technologies

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Diffraction Loss  Electromagnetic waves spread around the diffracted point.  Diffracted waves cover all directions except obstacles.  The diffraction loss is the most serious type of loss.  The calculation formula is complicated and changes with the constants.

T R


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Penetration Loss (1)  Indoor signals depend on the penetration loss of the building.  The penetration loss of signals near the window is greatly

different from the penetration loss of signals in the center of the building.  Materials of the building affect the penetration loss.  The incidence angle of electromagnetic waves affects the

penetration loss. w1 ¦ Å0¦ Ì 0

d D

w2

¦ Å¦ Ì

¦ Å0¦ Ì 0

E2

¦È ¦È E1 W dBm

X dBm

Penetration loss = X – W = B dB


Reflection and refraction of electromagnetic waves penetrating the wall

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Penetration Loss (2)  The obstacle diffraction loss or penetration loss is:

 Loss caused by the obstacle of a partition: 5–20 dB  Loss caused by the obstacle of a floor: > 20 dB  Indoor loss (which is a function of the floor height, –1.9 dB/floor)  Loss caused by furniture and other barriers: 2–15 dB

 Loss caused by thick glass: 6–10 dB  Penetration loss caused by a railway compartment: 15–30 dB  Penetration loss caused by an elevator: about 30 dB  Penetration loss caused by thick leaves: 10 dB

T

R


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










Section 4 Propagation Model Calibration


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Common Propagation Models  Propagation model in the free space  Okumura/Hata model  COST231-Hata model

 COST231 Walfish-Ikegami model  Keenan-Motley model  Computer-aided calculation model


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Propagation Model in the Free Space

Lo = 91.48 + 20lgd, for f = 900 MHz Lo = 97.98 + 20lgd, for f = 1900 MHz Lo = 99 + 20lgd, for f = 2100 MHz  The propagation model in the free space applies to the radio

environment that has isotropic propagation medium (such as vacuum). It is a theoretical model. This environment does not exist in reality, but the air medium is similar to the isotropic medium.


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Okumura-Hata Model Application scope: Frequency range f: 150 MHz to1500 MHz Height of BTS antenna Hb: 30 m to 200 m Height of mobile station Hm: 1 m to 10 m Distance d: 1 km to 20 km



Applicable to the macro cell model



Applicable to the scenario when the height of BTS is higher than the surrounding buildings



Not applicable to prediction within 1 km



Not applicable to cases that the frequency is higher than 1500 MHz


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COST 231-Hata Model Application scope:

Frequency range f: 1500 MHz to 2000 MHz Height of BTS antenna Hb: 30 m to 200 m Height of mobile station Hm: 1 m to10 m Distance d: 1 km to 20 km



Applicable to the Macro cell model



Height of BTS antenna is higher than surrounding buildings



Not applicable to forecast within 1 km



Not applicable if the frequency is higher than 2000 MHz or lower than 1500 MHz


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COST 231 Walfish-Ikegami Model Application scope: Frequency range f: 800 MHz to 2000 MHz Height of BTS antenna Hbase: 4 m to 50 m Height of mobile station Hmobile: 1 m to 3 m Distance d: 0.02–5 km Height of buildings Hroof (m) Width of roads w (m) Spacing between buildings b Street direction relative to the direction of direct waves a (º) 

Applicable to the environment in the city, macro cell or micro cell



Not applicable to the suburb or country environment HUAWEI TECHNOLOGIES CO., LTD.

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Radio Propagation Model Model of ASSET Planning Software Ploss = K1 + K2lgd + K3 (Hms) + K4lg (Hms) + K5lg (Heff) + K6lg (Heff) lg(d) + K7 + Kclutter

Path loss: path loss (dB) K1: constant related to the frequency K2: constant of distance fading K3, K4: calibration coefficient of the height of mobile station K5, K6: calibration coefficient of the height of BTS antenna K7: calibration coefficient of diffraction Kclutter: calibration coefficient of features d: distance between the BTS and the mobile station (km) Hms, Heff: effective height of the mobile station and BTS antenna (m)


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K Parameter

Reference Value

K1

152/1800 M Urban

K2

44.90

K3

–2.55

K4

0.00

K5

–13.82

K6

–6.55

K7

–0.80

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Radio Propagation Model Model of U-net Planning Software Ploss = K1 + K2logd + K3log (Heff) + K4Diffraction + K5log (d) log (Heff) + K6 (Hmeff) + Kclutterf (clutter) + K (hill, los) K Parameter

Reference Value

K1

–52.92

K2

68.6

K3

5.83

K4

1

K5

–6.55

K6

0

Path loss: path loss (dB) K1: offset constant K2: constant of distance fading K3: calibration coefficient of the height of BTS antenna K4: multiplier of diffraction calculation (must be a positive number) K5: multiplier of log (HTxeff) log(d) K6: calibration coefficient of the height of mobile station Kclutter: calibration coefficient of features K(hill, los): calibration factor of mountain area (Nlos = 0) d: distance between the BTS and the mobile station (m) Hmeffs, Heff: valid height of the mobile station and BTS antenna (m)


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










Section 4 Propagation Model

Calibration


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Model Calibration  The meaning of model calibration is as follows:

 The propagation model is a basis for the cell planning of a mobile network. Whether the cell planning is proper and whether the carriers can meet user requirements with economical and reasonable investment all depend on the accuracy of the propagation model. Therefore, the propagation model calibration is required to obtain the radio propagation model that fits the practical environment in this region, improve the predicted coverage accuracy and lay a good foundation for the network planning.


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Basic Principles and Process of Model Calibration Target propagation environment

Propagation model selection

Parameter configuration

CW data collection

Forecast of propagation

Measurement of propagation path loss

Path loss

Comparison

Does the error meet the demand?

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Location Selection of the BTS  The rules for selecting the location of the BTS are as follows:

 a. The antenna is higher than 20 m.  b. The antenna is at least 5 m higher than the nearest obstacles.

5m

 c. The obstacle here refers to the highest building on the roof where the antenna is located. The building selected as the location of the BTS is required to be higher than the average height of the surrounding buildings.


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Test Platform The transmitting subsystem includes the transmitting antenna, feeder,

high-frequency signal source, and antenna support. The receiving subsystem includes the test receiver, GPS receiver, test

software, and portable computer.

Transmitting antenna

Signal source

RF cable 1

High frequency signal source

Power amplifier

RF cable 2

Receiving antenna

Power supply


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Receiving antenna

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Portable computer

Test Path 

Principle of Selecting the Test Path  Terrain: The test path must cover all major terrains in the region.  Height: If great differences of terrains exist in this region, the test path must cover terrains in different height.  Distance: The test path must take positions in different distance from the BTS into account.  Direction: Test points in vertical and horizontal paths must keep consistent.  Length: The total length of a CW test must be longer than 60 km.  Point: The test points are the more the better. (Requirement: > 10000 points, > 4 hours)  Overlap: Test paths of different BTSs can be overlapped to strengthen the reliability.  Obstacle: When antenna signals are blocked by one side of the floor, the test path cannot pass the shadow region.


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Drive Test  Samples are compliant with the Lee's Criteria: 40

wavelengths and 50 samples.  The maximum speed is: Vmax = 0.8λ/Tsample  In abnormal cases, test results must be removed from

the sampling data.  Samples with too high fading (over 30 dB)  In the tunnel  Under the viaduct  …  If the directional antenna is taken the CW test, the test

path is selected from regions covered by the major lobe.


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Test Data Processing  Test data can be identified by the planning software only after

being processed. The processing procedure is as follows:  Data filtering  Data discrete  Geographic binning  Format conversion


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Preparations  Install the network planning software.

 U-net is powerful planning and optimization software. Model calibration is only one of the function modules.  The items are created.

 In the U-net, all tasks, such as planning, optimization and model calibration are performed on the basis of items.  The antenna patterns are exported.

 The antenna pattern varies with specific manufacturer. Export the correct one.  Build the model and import the data.


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Model Calibration

Filtering Configuration  Distance Filter:

 Recommendation: The data is filtered in the range of r < 150 m or r > 3 km  Signal Strength Filter:

 Recommendation: The data is filtered in the range of Signal > –40 dBm or Signal < – 121 dBm  Clutter Filter:

 Recommendation: The clutters are filtered where the number of test points are smaller than 300.


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Model Calibration Parameter Calibration


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Model Calibration  Analysis of Calibration Results

 The accuracy of the obtained model must be analyzed after the calibration.  The accuracy of the model refers to the fitness between the resulted models and the practical test environment. Normally it is assessed by the value of RMS Error.

 In the best cases, the RMS Error is less than 8, indicating that the resulting models fit the practical environment. In practical model calibration, it is recommended to make RMS Error close to this goal.


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Questions  Which band of the radio waves does the mobile

telecommunication system use?  What are the propagation methods of radio waves?  Which are the two forms of the signal fading in the

propagation environment of radio waves? What are the features and causes reasons of the two forms?  What are the major forms of signal propagation loss in

the propagation environment of radio waves?  What are the common propagation models? What are

their application environments?


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Summary  This chapter describes related knowledge of radio waves, including:

 Propagation paths of radio waves  Losses and dispersion features of radio waves and main compensation scheme  Common models of radio waves and involved parameters  Calibration methods of propagation models of radio waves


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Contents


Chapter 2 Introduction to the Antenna Chapter 3 Basic RF Knowledge

Training.huawei.com


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Chapter 2 Introduction to the Antenna

 Section 1 Working Principle  Section 2 Classification  Section 3 Electrical Specifications  Section 4 Mechanical Specifications  Section 5 New Technologies


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Position and Function Antenna Feeder System of BTS 1. Modulation support of antenna Holding pole (50–114 mm) 3. Sealing connector Insulation sealing tape, PVC insulation tape

GSM/CDMA panel antenna

4. Grounding device

Master feeder (7/8) 9. Super-flexible feeder

2. Outdoor feeder

8. Lighting protector 6. Cable tray

5. Feeder fixing clip 7. Feeder through window


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Main device of BTS

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Working Principle




When a wire carries the alternating current, electromagnetic radiation is formed. The ability of radiation is related to the length and shape of the wire.



If two wires are closely located, and the electromotive forces generated by the wires are offset, the radiation is weak.



If the two wires are opened, the current of these two wires is on the same direction. The electromotive forces generated are in the same direction. Therefore, the radiation is strong.



When the length of the wire is much shorter than the wavelength, current of the wire is low and the radiation is weak.



When the length of the wire can be increased to the wavelength, current of the wire is greatly enhanced. Therefore a stronger radiation is formed.



Normally the straight wire that can generate remarkable radiation is called dipole.



The dipole where the length of both supporting poles is 1/4 wavelength is called half-wave dipole.

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Working Principle of Mobile Antenna Unit dipole

Unit dipole

Feed network Feed network Feed network

Wireless connector

Wireless connector

Directional antenna HUAWEI TECHNOLOGIES CO., LTD.

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Omni-directional antenna Page 44

Classification of Antennas (1) The antennas can be divided into the following types according to the radiation direction.

Directional antenna HUAWEI TECHNOLOGIES CO., LTD.

Omni-directional antenna

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Classification of Antennas (2) The antennas can be divided into the following types according to different appearances:

Cap antenna

Panel antenna

Whip antenna

Paraboloidal antenna


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Classification of Antennas (3) The antennas can be divided into the following types according to the polarization directions.

Omni-directional antenna HUAWEI TECHNOLOGIES CO., LTD.

Single-polarized directional antenna HUAWEI Confidential

Dual-polarized directional antenna Page 47

Major Electrical Specifications of Antenna


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Antenna Pattern Pattern of Symmetric Half-Wave Dipole Top view

Side view

Directional Antenna Pattern Omni-directional Antenna Pattern


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Antenna Gain

2.15 dB

dBi and dBd


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Other Major Electrical Specifications of Antenna 

Beamwidth, front-to-back suppression ratio, null filling, and upper side lobe suppression


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Mechanical Tilt and Electrical Tilt Mechanical tilt

Electrical tilt


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Major Electrical Specifications of Antenna Antenna SWR

Forward: 10 W 50 ohms

80 ohms Back: 0.5 W


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9.5 W

Major Electrical Specifications of Antenna

 Reasons for Passive Intermodulation

 Magnetic materials exist.  The joint is not connected tightly.  The metals of different materials are contacted.  The contact surfaces of same type of

f1 f2 f3 f4 f2–f1 f3–f2 f4–f3 f3–f1 f4–f2 f4–f1

materials are not smooth.

Judging methods of the third order intermodulation


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Major Mechanical Specifications of Antenna  Input port of antenna

 Antenna weight  Wind load  Operating temperature  Humidity requirement  Lightening protection  Tri-proof capability


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Coaxial Distributed Antenna System 3

3

Power splitter

6

0.5

3 Power splitter

Power splitter

3

10

10

3 Power splitter

Power splitter

3

Coupler

Coupler

0.5

3 Power splitter

Power splitter

Bi-directional amplifier


Equal power assignment

3 Power splitter


Tx/Rx

1.3 Coupler

Power splitter

3 Power splitter

3 Power splitter

3

Tx/Rx Unequal power assignment

Figure 3.1: Coaxial cable distributed system HUAWEI TECHNOLOGIES CO., LTD.

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Fiber Feeding Distributed Antenna System  It applies to the scenario with large coverage and long

Power splitter Power splitter Power splitter

Optical remote unit

Optical main unit

TRx

Optical remote unit

Optical remote unit

transmission distance.

Figure 3.3: Fiber distributed system HUAWEI TECHNOLOGIES CO., LTD.

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Intelligent Antenna System


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Intelligent Antenna System Two algorithms

Switched beams HUAWEI TECHNOLOGIES CO., LTD.

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Adaptive beams Page 59

Questions

 What are the antenna categories based on the signal

radiation direction and appearance?  What are the major electrical specifications of the antennas?  What are the major mechanical specifications of the antennas?

 What are the categories of distributed antenna systems

(DASs)?


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Summary

This chapter describes the following points:  Principle of Antenna  Major Electrical Specifications of Antenna  Major Mechanical Specifications of Antenna

 New Technologies of Antenna


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Contents

Chapter 1 Radio Wave Knowledge Chapter 2 Introduction to the Antenna

Chapter 3 Basic RF Knowledge

Training.huawei.com


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Introduction to the Unit of Power Expression of dB Indicating the Absolute Power

The absolute power of RF signals is indicated by using dBm or dBW. The conversion relationship between dBm/dBW and mW/W is as follows: For example, the signal power is x W and the value indicated by using dBm is:

pdBm  10

X 1000mW  log 1mW  log

pdBW  10  log log

XW 1W 

For example: 1 W = 30 dBm = 0 dBw Expression of dB Indicating the Relative Power

It is the logarithmic form of the ratio between any two power values. dBc is the logarithmic form of the ratio between the frequency output power and the carrier output power. HUAWEI TECHNOLOGIES CO., LTD.

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Related Concepts of Noise  Noise

 Noises refer to the interference signals that cannot be predicted during signal processing and cannot be predicted precisely. (Frequency interference does not belong to the noise.)  Noise factor

 The noise coefficient is used to measure the capability of an RF component to process low signals. The noise coefficient is defined as: unit input SNR/output SNR, as shown in the following figure.

Linear system

NF

Pno G Pni

Si NF

Ni So No


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Related Concepts of Noise 

Noise Factor Formula of Cascaded Network:

G1, NF1

NFtotal NF1

G2, NF2

NF2


G1

1 ...

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Gn, NFn

NFn

1

G1 G2 ... Gn 1

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Digital Modulation Data

Amplitude keying

Shift-frequency keying

Phase shift keying


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Application of Modulation Technologies


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Spurious Radiation

 Spurious Radiation

 Spurious radiation refers to the signals that are sent by the transmitter beyond the spectrum stated in the transmitting template. The spurious radiation includes harmonic components, parasitic radiations, crossmodulation products, intermodulation products of transmitters. The spurious radiation interferes with the wireless communication system. This specification aims to improve the system electromagnetic compatibility so that the system can co-exist with other systems (such as WCDMA) and ensures the normal operation of the system itself.


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RF Specifications of the Downlink Channel  Adjacent Channel Leakage Ratio (ACLR)

ACLR is used to measure the out-band radiation feature of transmitters. It is the ratio between the power of an adjacent and the power of the main channel, expressed in dBc, as shown in the following figure. Protection band

Main channel


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Adjacent channel

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Receiving Sensitivity  Receiving Sensitivity

Expressed using the power, Smin = 10log (KTB) + Ft + (S/N). The unit is: dBm. K is the Boltzmann constant and the unit is: J/K (Joule/K).

K  1.38066 1019J/K T indicates the absolute temperature and the unit is: ºK. B indicates the signal bandwidth and the unit is: Hz. Ft indicates the noise factor of the system and the unit is: dB. (S/N) indicates the SNR required in the modulation and the unit is: dB. If B = 1 Hz, 10log (KTB) = –174 dBm/Hz


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Blocking Index of the Receiver  Blocking

 The blocking index is used to assess the antiinterference ability of the receiver. It describes the situation in which the individual tone or modulating signal interference exists outside the receiving channel, but the interference signals are not in the adjacent channel or the spurious response frequency. The specific index depends on different systems. The blocking index requires that the receiver must have high third order cut-off frequency (large linear dynamic range) at its front end and the intermediate frequency filter has good selectivity.


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Filter Filter A

A

fc

fc Passband

Transtive band Stopband

F

Stopband

Low pass filter

Transtive band

Passband

F

High pass filter

A

A

f1

f2 F Stopband Transtive Passband Transtive Stopband band band Bandpass filter


f1

f2 F Passband Transtive Stopband Transtive Passband band band

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Bandstop filter

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Combiner  Functions of the Combining and Dividing Unit

 Make transmitting signals and receiving signals share the antenna and reduce the number of antenna feeders.  Complete the duplex mode of transmitting and receiving signals, combining and filtering of the transmitting signals.  Complete the filtering, low noise amplification and dividing of the receive signals.

 Provide the function of TMA feeder: including three modules, namely CDU, SCU and EDU.


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Combining Distribution Unit (CDU)

Tx1 Tx2 Tx_Comb Tx_Dup Rx1 Rx2 Rx3 Rx4 HL_out Rx5 Rx6 Rx7 Rx8 HL_in RxD_out


Tx/Rx_ANT Combiner

Duplex

Power splitter Amplified division Power splitter Filter

RxD

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Combiner

TX1

TX2

Combiner

TX3 TX4

TX- Comb


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Combiner

Simple Combining Unit (SCU)

Enhance Duplexer Unit (EDU)

Tx1

Rx1 Rx2

Rx1 Rx2

Power splitter

Power splitter

Tx/Rx_ANT1

Duplex

Tx/Rx_ANT2

Amplified division

Amplified division

Tx2


Duplex

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Loss Comparison Among All Combining and Dividing Units Combination methods

Typical value of the transmitting insertion loss (dB)

Price comparison (per carrier)

CDU

Two in one Level 1 3 dB bridge

4.5

Medium

SCU

Four in one Level 2 3 dB bridge

6.8

Low

Four in one Level 2 3 dB bridge

8

Low

1

Medium

1

High

SCU+CDU

EDU Dual-CDU (not passing the combiner) Dual-CDU (passing the combiner)


Failure Dual duplexer method Failure Dual-CDU method Combination Dual-CDU method

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4.5

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Medium

Common RF Components

Power splitter

Combiner HUAWEI TECHNOLOGIES CO., LTD.

Coupler

Line amplifier

Attenuator

Power amplifier HUAWEI Confidential

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Common RF Devices

Frequency meter

Field strength meter

Signal source HUAWEI TECHNOLOGIES CO., LTD.

Test cell phone

Integrated tester

SWR tester

Portable spectrum analyzer

Power meter HUAWEI Confidential

Spectrum analyzer Page 79

Questions

 What are the common forms to express the units of the

absolute power? What is the conversion relationship?  What is the definition of the noise factors? Can you write the

formula of the cascaded noise factors?  What is the spurious emission? What is the adjacent leakage?  Can you write the formula of sensitivity?  Can you list several modulation methods? Which one does

GSM use?


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Summary

 This chapter describes the common and basic concepts of RF,

including:  Concepts of power  Concepts of noise  Concepts and categories of modulation  Divergence channel specifications such as the spurious

emission and adjacent leakage  Sensitivity index of the receiving channel  Common RF components


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Summary of the Course

After completing this course, you should be able to learn:  Propagation principles, environment, features, models, and model

calibration of radio waves  Working principle, classification, electrical and mechanical features of

antenna  Basic concepts of RF and common RF components


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Basic Propagation Principles of Radio Waves and Basic RF Knowledge

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