005 wcdma rnp fundamental
TRANSCRIPT
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Internal
OWJ100001 WCDMARNP Fundamental
ISSUE 1.0
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Upon completion of this course, you will be able to:
Get familiar with principles of radio wave
propagation, and theoretically prepare for the
subsequent link budget.
Introduce the knowledge about antennas and the
meanings of typical indices.
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Chapter 2 AntennaChapter 2 Antenna
Chapter 3 RF BasicsChapter 3 RF Basics
Chapter 4 Symbol ExplanationChapter 4 Symbol Explanation
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Section 1 Basic Principles of Radio WaveSection 1 Basic Principles of Radio Wave
Section 2 Propagation Features of Radio WaveSection 2 Propagation Features of Radio Wave
SectionSection 3 Propagation Model of Radio Wave3 Propagation Model of Radio Wave
SectionSection 4 Correction of Propagation Model4 Correction of Propagation Model
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Radio Wave SpectrumRadio Wave Spectrum
The frequencies in each specific band present unique propagation features.300-3000GHz
EHFExtremely High
Frequency
30-300GHz
SHFSuper High Frequency3-30GHz
UHFUltra High Frequency300-3000MHz
VHFVery High Frequency30-300MHz
HFHigh Frequency3-30MHz
MFMedium Frequency300-3000KHz
LFLow Frequency30-300KHz
VLFVery-low Frequency3-30KHz
VFVoice Frequency300-3000Hz
ELFExtremely Low
Frequency
30-300Hz3-30Hz
DesignationClassificationFrequency
The radio waves are distributed in 3Hz ~ 3000GHz. This spectrum is divided
into 12 bands, as shown in the above table. The frequencies in each specific band
present unique propagation features: The lower the frequency is, the lower the
propagation loss will be, the farther the coverage distance will be, and the
stronger the diffraction capability will be. However, lower-band frequencyresources are stringent and the system capacity is limited, so they are primarily
applied to the systems of broadcast, television and paging. The higher-band
frequency resources are abundant and the system capacity is large; however, the
higher the frequency is, the higher the propagation loss will be, the shorter the
coverage distance will be, and the weaker the diffraction capability will be. In
addition, the higher the frequency is, the higher the technical difficulty will be,
and the higher the system cost will be. The band for purpose of the mobile
communication system should allow for both coverage effect and capacity.
Compared with other bands, the UHF band achieves a good tradeoff between thecoverage effect and the capacity, and is hence widely applied to the mobile
communication field. Nevertheless, with the increase of mobile communication
demand, more capacity is required. The mobile communication system is bound
to develop toward the high-frequency band.
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Propagation of Electromagnetic Wave
When the radio wave propagates in the air, the electric f ield direction
changes regularly. If the electric field direction of radio wave is vertical to theground, the radio wave is vertical polarization wave.
If the electric field direction of radio wave is parallel with the ground, the
radio wave is horizontal polarization wave
electric wave transmission direction
Electric FieldElectric Field
Magnetic FieldMagnetic Field
Electric Field
Dipole
Propagation of electromagnetic propagation takes on an energy propagation
mode. During the propagation, the electric field is vertical to the magnetic field,
both vertical to the propagation direction. Through interaction between the
electric field and the magnetic field, the energy is propagated to the distance, just
like propagation of water waves.
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Perpendicular incidence waveand ground refraction wave
(most common propagation modes)
Troposphere reflection wave
(the propagation is very random)
Mountain diffraction wave
(shadow area signal source)
Ionosphere refraction wave(beyond-the-horizon communication path)
Propagation Path
Radio wave can be propagated from the transmitting antenna to the receiving
antenna in many ways: perpendicular incidence wave or ground refraction wave,
diffraction wave, troposphere reflection wave, ionosphere reflection wave, as
shown in the diagram. As for radio wave, the most simple propagation mode
between the transmitter and the receiver is free space propagation. One isperpendicular incidence wave; the other is ground reflection wave. The result of
overlaying the perpendicular incidence wave and the reflection wave may
strengthen the signal, or weaken the signal, which is known as multi-path effect.
Diffraction wave is the main radio wave signal source for shadow areas such
building interior. The strength of the diffraction wave is much dependent of the
propagation environment. The higher the frequency is, the weaker the diffraction
signal will be. The troposphere reflection wave derives from the troposphere.
The heterogeneous media in the troposphere changes from time to time for
weather reasons. Its reflectance decreases with the increase of height. Thisslowly changing reflectance causes the radio wave to curve. The troposphere
mode is applicable to the wireless communication where the wavelength is less
than 10m (i.e., frequency is greater than 30MHz).Ionosphere reflection
propagation: When the wavelength of the radio wave is less than 1m (frequency
is greater than 300MHz), the ionosphere is the reflector. There may be one or
multiple hops in the radio wave reflected from the ionosphere, so this
propagation is applicable to long-distance communication. Like the troposphere,
the ionosphere also presents the continuous fluctuation feature.
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Building reflection waveBuilding reflection wave
Diffraction waveDiffraction wave
Direct waveDirect wave
Ground reflection waveGround reflection wave
Propagation Path
In a typical cellular mobile communication environment, a mobile station is
always far shorter than a BTS. The direct path between the transmitter and the
receiver is blocked by buildings or other objects. Therefore, the communication
between the cellular BTS and the mobile station is performed via many other
paths than the direct path. In the UHF band, the electromagnetic wave from thetransmitter to the receiver is primarily propagated by means of scattering,
namely, the electromagnetic wave is reflected from the building plane or
refracted from the man-made or natural objects.
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Section 1 Basic Principles of Radio WaveSection 1 Basic Principles of Radio Wave
Section 2 Propagation Features of Radio WaveSection 2 Propagation Features of Radio Wave
SectionSection 3 Propagation Model of Radio Wave3 Propagation Model of Radio Wave
SectionSection 4 Correction of Propagation Model4 Correction of Propagation Model
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Radio Propagation Environment
Radio wave propagation is affected by topographic structure and
man-made environment. The radio propagation environment directly
decides the selection of propagation models. Main factors that affect
environment are:
Natural landform (mountain, hill, plains, water area)
Quantity, layout and material features of man-made buildings
Natural and man-made electromagnetic noise conditions
Weather conditions
Vegetation features of the region
The radio wave is largely affected by the topography and man-made
environment. The natural landforms such as mountains and hills as well as man-
made buildings affect the propagation features of radio waves. Weather and time
conditions also affect propagation of radio wave. For example, the ionosphere is
relatively stable at night, so the shortwave radio is well received.
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Quasi-smooth landformThe landform with a slightly rugged surface and
the surface height difference is less than 20m
Irregular landform
The landforms apart from quasi-smooth landform
are divided to: hill landform, isolated hills, slant
landform, and land & water combined landform.
R
T
T
R
Landform Categories
The quasi-smooth landform refers to the landform with a slightly rugged surface,
and the surface height difference is less than 20m. The average surface height
difference is slight. The Okumura propagation model defines the roughness
height as the difference between 10% and 90% of the landform roughness in
10km in front of the mobile station antenna. CCIR defines it as the differencebetween the height over 90% and the height over 10% of landform height at
10~50 km in front of the receiver. Other landforms than abovementioned are
called irregular landforms.
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distance (m)
Receiving power (dBm)
10 20 30
-20
-40
-60
slow fading
fast fading
Signal Fading
Slow fading: In case shadow effect is caused by obstacles, and the receiving
signal strength decreases but the field strength mid-value changes slowly with
the change of the topography, the strength decrease is called slow fading orshadow fading. The field strength mid-value of slow fading takes on alogarithmic normal distribution, and is related to location/locale. The fading
speed is dependent on the speed of the mobile station.
Fast fading: In case the amplitude and phase of the combined wave change
sharply with the motion of the mobile station, the change is called fast fading.The spatial distribution of deep fading points is similar to interval of half of
wavelength. Since its field strength takes on Rayleigh distribution, the fading is
also called Rayleigh fading. The amplitude, phase and angle of the fading are
random.
Fast fading is subdivided into the following three categories:
Time-selective fading: In case the user moves quickly and causes Doppler effect
on the frequency domain, and thus results in frequency diffusion, time-selectivefading will occur.
Space-selective fading: The fading features vary between different places and
different transmission paths.
Frequency-selective fading: The fading features vary between different
frequencies, which results in delay diffusion and frequency-selective fading.
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In order to mitigate the influence of fast fading on wireless communication,
typical methods are: space diversity, frequency diversity, and time diversity.
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Signal Diversity
Measures against fast fading --- Diversity
Time diversity
Space diversity
Frequency diversity
To resist such kind of fast fading, the BTS adopts the time diversify, space
diversity (polarization diversity), and frequency diversity.
Time diversity uses the methods of symbol interleaving, error check and error
correction code. Each code has different anti-fading features.
Space diversity uses the main/diversity antenna receiving. The BTS receiverhandles the signals received by the main and diversity antennas respectively,
typically in a maximum likelihood method. This main/diversity receiving effect
is guaranteed by the irrelevance of main antenna receiving and diversity antenna
receiving. Here irrelevance means the signals received by the main antenna andthe signals received by the diversity antenna do not have the feature of
simultaneous attenuation. This requires the interval between the main antenna
and the diversity antenna in case of space diversity to be greater than 10 times of
the radio signal wavelength (for GSM, the antenna interval should be greater
than 4m in a distance of 900m, and greater than 2m in a distance of 1800m).
Alternatively, the polarization diversity method should be used to ensure that
signals received by the main and diversity antennas do not have the same
attenuation features. As for mobile stations (mobile phones), only one antenna
exists, so this space diversity function is not supported. The BTS receiver scapability of balancing the signals of different delays in a certain time range
(time window) is also a mode of space diversity. In case of soft switch in the
CDMA communication, the mobile station contacts multiple BTSs concurrently,
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and selects the best signals from them, which is also a mode of space
diversity.
Frequency diversity is performed primarily by means of spreading. In the
GSM communication, it simply uses the frequency hopping to obtain the
frequency hop gain; in the CDMA communication, since every channelworks at a broad band (WCDMA has a band of 5MHz), the communication
itself is a kind of spreading communication.
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SolutionRAKE technologyRAKE technology
Radio Wave Delay Extension
Deriving from reflection, it refers to the co-frequency interference caused
by the time difference in the space transmission of main signals and
other multi-path signals received by the receiver.
The transmitting signals come from the objects far away from the
receiving antenna.
Radio wave delay extensionAnother type of frequency-selective fading. The
spatial distribution of deep fading points is similar to interval of half of a
wavelength (17cm for 900MHz, 8cm for 1800/1900MHz). If the mobile station
antenna is located at this deep fading point at this time (when the mobile user in
a car resides in this deep fading point in case of a red light, we call it read lightproblem), the voice quality is very poor, and relevant technologies should be
used to resolve it, e.g., the Rake technology in CDMA system.
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T
R
Diffraction Loss
The electromagnetic wave diffuses aroundat the diffraction point.
The diffraction wave covers all directions
except the obstacle.
The diffusion loss is most severe
When analyzing the transmission loss in the mountains or the built-up
downtowns, we usually need to analyze the diffraction loss and penetration loss.
Diffraction loss is a measure for the obstacle height and the antenna height. The
obstacle height must be compared with the propagation wavelength. The
diffraction loss generated by the height of the same obstacle for the longwavelength is less than that for short wavelength. Diffraction loss is caused the
electromagnetic wave being scattered around at the diffraction point, and the
diffraction wave covers all directions except the obstacle. This diffusion loss is
most severe, and the calculation formula is complicated and varies with different
diffraction constants.
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Penetration Loss
Penetration loss caused by obstructions:
XdBmWdBm
Penetration loss =X-W=B dBPenetration loss =X-W=B dB
Indoor penetration loss refers to the difference between the average signal
strength outside the building and the average signal strength of one layer of the
building.
Penetration loss represents the capability of the signal penetrating the building.
The buildings of different structures affect the signals significantly. The
penetration loss generated by the long wavelength is greater than that generated
by the short wavelength of the same building. The incidence angle of the
electromagnetic wave also affects the penetration loss considerably.
Typical Penetration loss:
Wall obstruction : 5~20dB
Floor obstruction : >20dB
Indoor loss value is the function of the floor number : -1.9dB/floor
Obstruction of furniture and other obstacles: 2~15dB
Thick glass : 6~10dB
Penetration loss of train carriage is 15~30dB
Penetration loss of lift is : 30dB
Dense tree leaves loss : 10dB
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Section 1 Basic Principles of Radio WaveSection 1 Basic Principles of Radio Wave
SectionSection 2 Propagation Features of Radio Wave2 Propagation Features of Radio Wave
Section 3 Propagation Model of Radio WaveSection 3 Propagation Model of Radio Wave
SectionSection 4 Correction of Propagation Model4 Correction of Propagation Model
Propagation model is very important. It is the foundation of the mobile
communication planning. The propagation model of radio wave is a process of
using the actual measurement and computers to develop curves from the
measured results in different regions and ultimately outline the propagation
formula of the radio wave in different topographic conditions. For example, theOkumura model introduced below is an empiric formula obtained by the
Japanese Okumura from measurement of tens of thousands of curves in Tokyo. It
is now widely recognized and accepted, plays important roles in guiding the
construction of communication networks. This session deals with the typical
propagation models currently available.
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Propagation model is used for predicting the medium value of path loss. The formula
can be simplified under if the heights of UE and base station are given
where: is the distance between UE and base station, and is the frequency
Propagation environment affect the model, and the main factors are :
Natural terrain, such as mountain, hill, plain, water land, etc;
Man-made building (height, distribution and material);
Vegetation;
Weather;
External noise
),( fdfPathLoss =
d f
Propagation model
If the heights of UE and BTS are given and ignore the environment affect, the
path loss is just related with the distance between UE and BTS and radio
frequency.
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Lo=91.48+20lgd, for f=900MHz
Lo=97.98+20lgd, for f=1900MHz
Free Air Space Model
Free space propagation model is applicable to the wireless
environment with isotropic propagation media (e.g., vacuum),
and is a theoretic model.
This environment does not exist in real life
Free space means an infinite space full of even, linear, isotropic ideal media, and
is an ideal situation. For example, the radio wave propagation of satellite is very
similar to the propagation condition of free space. As seen from the above
formula, once the distance is doubled, the loss will increase by 6dB. If the
frequency is doubled, as shown in the above example, the 1900MHz loss will be6dB more than the 900MHz loss.
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Ploss= L0+10lgd -20lghb - 20lghm
Path loss gradient , usually is 4
hb BTS antenna height
hm mobile station height
L0 parameters related to frequencyR
T
Flat Landform Propagation Model
In the flat landform propagation model, in addition to the frequency and distance,
we also consider the heights of the UE and BTS. Once the BTS antenna height is
doubled, the path loss will be compensated for by 6dB.
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Application ScopeApplication Scope
CharacteristicCharacteristic
Frequency range f:150~1500MHz
BTS antenna height Hb:30~200m
Mobile station height Hm:1~10m
Distance d:1~20km
Macro cell model
The BTS antenna is taller than the surrounding buildings
Predication is not applicable in 1km
Not applicable to the circumstance where the frequency is above
1500MHz
Okumura-Hata Model
The Okumura-Hata model is commonly used in the planning software. It is
applicable to the micro cell that covers more than 1km below 1500MHz. In
1960s, Okumura and his men used a broad range of frequencies, heights of
several fixed stations and heights of several mobile stations to measure the signal
strength in all kinds of irregular landforms and environments, and developed aseries of curves, then set up a model by fitting the curves to obtain the empiric
formula of propagation model. This model has been widely used across the globe,
and is applicable to areas outside Tokyo by use of the correction factor.
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Application ScopeApplication Scope
Frequency range f:1505~2000MHz
BTS antenna height Hb:30~200m
Mobile station height Hm:1~10m
Distance d:1~20km
CharacteristicCharacteristic
Macro cell model
The BTS antenna is taller than the surrounding buildings
Predication is not applicable in 1km
Not applicable to the circumstance where the frequency is above2000MHz or below 1500MHz
COST 231-Hata Model
The COST231 model is applicable 1500-2000MHz, and is not accurate within
1km. The COST231-hata model is based on the test results of Okumura, and
works out the suggested formula by analyzing the propagation curve of higher
bands.
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Application ScopeApplication Scope
Frequency range : 800~2000MHz
BTS antenna height Hbase : 4~50m
Mobile station height Hmobile : 1~3m
Distance d : 0.02~5km
CharacteristicCharacteristic
Urban environment, macro cell or micro cell
Not applicable to suburban or rural environment
COST 231 Walfish-Ikegami Model
The COST231 propagation model team of the European Research Committee
puts forward the following two suggested models: One is based on the Hata
model, and works out the frequency coverage extends from 1500MHz to
2000MHz by using some correction items. However, in all the test environments,
the BTS is taller than the surrounding buildings, so it is not appropriate to extendthe valid range to the circumstance where the BTS antenna is lower than the
surrounding buildings. This model is applicable to large-cell macro cell. In the
micro cell, the BTS antenna is lower than the roof, so the Committee created
the COST-Walfish-Ikegami model according to the results of Walfishs
calculation of the urban environment, the Ikegamis corrective function for
handling the street direction and the test data. This model is tested in a German
city Mannheim, and more improvements are found to be made. When using the
model, some parameters that describe the urban environment features may be
required: Building height Hroof (m) Pavement width w (m) Building interval b(m) Street direction against the perpendicular incidence wave direction ( )
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K1
Propagation path loss constant value
K2 log(d) correction factor D
Distatnce between receiver and transmitter (m);K3
log(HTxeff) correction factor;
HTxeff Transmitter antenna height (m);
K4 Diffraction loss correction factor;K5
log(HTxeff)log(D) correction factor;
K6
Correction factor; Receiver antenna height (m);
Kclutter: clutter correction factor;
( )
( ) ( ) ( ) ( )clutterfKHKHDKlossnDiffractioKHKDKKPathLoss
clutterRxeffTxeff
Txeff
+++
+++=
65
4321
loglog
loglog
RxeffHRxeff
H
Experimental formulaExperimental formula
ExplanationExplanation
Standard Propagation
Using the multiplier factor configured by customer, the propagation model can
be made by order totally. It can support using different K1 and K2 according to
distance and LOS or NLOS. It also can use different diffraction loss algorithm
and effective BTS height algorithm. One optional amendment condition is that
U-net can amend the path loss of hilly terrains environments under it is LOSbetween transmitter and receiver.
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
SectionSection 1 Basic Principles of Radio Wave1 Basic Principles of Radio Wave
SectionSection 2 Propagation Features of Radio Wave2 Propagation Features of Radio Wave
SectionSection 3 Propagation model of Radio Wave3 Propagation model of Radio Wave
Section 4 Correction of Propagation ModelSection 4 Correction of Propagation Model
Propagation model of radio wave have close relation with concrete terrain and
clutter. Usually, classical theoretical analysis of propagation model have biggish
error. So, in practice, we use test statistics method, namely, using a great deal
test data to amend the classical model. Here we use the CW test.
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Basic Principles and Procedures
Error compliant with
requirements?
Target propagation environment
CW data collection
Measured propagation path loss
Selected propagated environment
parameter setting
Forecast propagation path loss
Comparison
End
Due to difference of propagation environment, the propagation model parameters
must be corrected based on measured values, so as to embody the radio wave
propagation features of the actual environment. Generally, we use the
Continuous Wave (CW) test method to measure the propagation path loss in the
actual environment. By comparing the actual value with the forecast value, weadjust the parameters in the model. The process recurs until the error meets the
requirements.
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5m
Criteria for selecting a site:
The antenna height is greater than 20m.
The antenna is at least 5m taller than the nearest obstacle
Site Selection
If the antenna is taller than the nearest obstacle by 5m or more, the data in GSM
will be inherited, as defined according to the first Fresnel zone. This condition is
sufficiently compliant with the WCDMA requirements.
Obstacle here means the tallest building on the roof of the antenna. The
building serving as a site should be taller than the average height of the
surrounding buildings
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Transmitting subsystems
transmitting antenna, feeder, high-frequency signal source, antenna bracket
Omni-Antenna
Transmitter
Antenna
bracket
Feeder
Test Platform
After the test platform is set up, switch on the signal source to transmit the RF
signal, and begin drive test. To perform the CW test, it is necessary to select an
appropriate site for transmitting the RF signal. In case of CW test data handling,
it is necessary to be aware of the EIRP of the test BTS, and record the data of
signal gain attributable to each part, including signal source transmitting power,RF cable loss, transmitting antenna gain, and receiving antenna gain.
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Receiving subsystem
Test receiver, GPS receiver, test software, portable
PositioningSystem
Data Acquisition System
GPS-Antenna Antenna
Receiver
Test Platform
After the test platform is set up, switch on the signal source to transmit the RF
signal, and begin drive test. To perform the CW test, it is necessary to select an
appropriate site for transmitting the RF signal.In case of CW test data handling,
it is necessary to be aware of the EIRP of the test BTS, and record the data of
signal gain attributable to each part, including signal source transmitting power,RF cable loss, transmitting antenna gain, and receiving antenna gain.
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Rules of selecting a test path:
Landform: the test path must consider all main landforms in the region.
Height: If the landform is very rugged, the test path must consider the
landforms of different heights in the region.
Distance: The test path must consider the positions differently away
from the site in the region.
Direction: The test points on the lengthways path must be identical with
that on the widthways path.
Length: The total length of the distance in one CW test should be
greater than 60km.
Number of test points: The more the test points are, the better (>10000
points, >4 hours as a minimum)
Test Path
The distance corrected in the CW test primarily falls within the impact range of
this cell, so the test distance is not necessarily more than twice of the cell radius.
The total length of the test distance in a CW test should be greater than
60km.Generally, the number of test points for each site is more than 10000, or
the test duration is more than 4 hours. According to the sampling rate of 1point/6m after smoothing the sampling data, it takes at least 60km as a test
distance for 10000 sampling points.
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Rules of selecting a test path:
Test Path
Overlaying: The test path of different test sites can be preferably overlapped to
increase the reliability of the model
Obstacles: When the antenna signals are obstructed by one side of the building,
do not run to the shadow area behind this side of building
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The sampling law is meets the Richard Law :40 wavelengths, 50
sampling points
Upper limit of drive speed: Vmax=0.8/Tsample
The test results obtained in exceptional circumstances must be
removed from the sampling data.
Sampling point with too high fading (more than 30dB) ;
In a tunnel
Under a viaduct
If using a directional antenna for CW test, the test path is selected
from the main lobe coverage area.
Drive Test
Sampling distance: The distance between adjacent sampling points should be-
/4 so as to eliminate the impact of Raylaigh fading. Suppose the sampling
frequency of the drive test equipment is: 1000HzThe 2G band bearer wavelength
is: 0.15m (50 sampling points are required per 6m)Upper limit of drive speed:
0.8*0.15*1000=120m/s
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The test data needs to be processed before being
able to be identified by the planning software. The
processing procedure is :
Data filtering
Data dispersion
Geographic averaging
Format conversion
Test Data Processing
The CW test data obtained after reasonable design are basis of our model
correction, and are input of the first step. The reasonableness of the CW test data
directly affects the correctness of the correction result. However, even the design
is reasonable, the measured data is not perfect, and needs further processing.
Typical processing steps include: Data filtering, data dispersion, geographical
averaging, and format conversion. In the actual test, some test data may beinconsistent with the model correction requirements. In order to avoid such data
from affecting the model correction result adversely, such data should be filtered.
1. Since we need to know the accurate position of each test point in the model
correction, for the data obtained from measuring the places where GPS cannot
position accurately should be filtered. Such circumstances include: 1) under a
viaduct; 2) in a tunnel; 3) in the narrow street with tall buildings on both sides; 4)
in the narrow street covered by dense tree leaves. 2. Generally, we regard the
distance 0.1R~2R away from the antenna is reasonable, where R is the forecast
cell radius. The signal strength distribution and the propagation distance do not
form a strict linear relationship. If too near, the test data will be less, and average
distribution will be impossible. 3. If the receiving signal is too weak,exceptional value point may occur, because the receiver is located at the critical
status of resolving the signal at this time, and its value is vulnerable to influence
of transient fluctuation. To prevent the deeply faded signals from being filtered,
we use the homocentric circle technology to filter out circular rings at the test
point lower than-121dbm, e.g., above 20% of the site ring. That is because the
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receiver speed is far greater than the GPS signal collection speed, and will result
in multiple test data at one location point. Suppose the vehicle runs at equal
speeds, such data should be distributed to the two fixed points on average, which
is a process of data dispersion. The main function of geographic averaging is to
eliminate the influence of fast fading and slow fading.
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Questions
Which band of radio wave is used for the mobile communication system?
What are the two modes of signal fading in the radio propagation
environment? What are their characteristics and reasons of generation?
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Summary
This chapter deals with radio wave. The learning points
include:
Propagation path of radio wave
Loss and dispersion characteristics of radio wave,
and main compensation solutions
Typical radio wave models, main parameters
involved
Methods of correcting radio propagation models
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Chapter 2 AntennaChapter 2 Antenna
Chapter 3 RF BasicsChapter 3 RF Basics
Chapter 4 Symbol ExplanationChapter 4 Symbol Explanation
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Positions and Functions of Antenna
Lightning protectiondevice
main feeder(7/8)
Feederclip
Cablingrack
Grounding device
3-connector seal componentinsulation sealing tape, PVC
insulation tape
Antenna adjustment bracket
GSM/CDMAplate-shape
antenna
radio mast (50~114mm)
Outdoorfeeder
Indoor superflexible feeder
Feeder cablingwindow
main deviceof BTS
BTS antenna & feeder system diagramBTS antenna & feeder system diagram
Positions and functions of antenna: In the radio communication system, antenna
is an interface between the transceiver and the outside communication media.
An antenna may both emit and receive radio waves; it converts the high-
frequency current to electromagnetic wave when transmitting; and converts the
electromagnetic wave to high-frequency current when receiving. Other parts ofthe antenna & feeder are shown in the diagram.
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omni antenna
Antenna
Connector
Dipole
Feed network
Antenna
Connector
Feed network
Dipole
Directional antenna
Feed network
Working Principles of Mobile Antenna
The BTS antenna in mobile communication system is antenna array
consist of a lot of basic dipole units. The dipole unit is half wave dipole
that the length of dipole is half wave of electromagnetic wave. The feed
network usually use equal power network.
For directional antenna, there is a metal flat at the back of dipole units as
a reflection plane to increase the antenna gain.
The tie-in of antenna usually is DIN type (7/16''). Usually it is at the bottom
of antenna, sometimes at the back of antenna.
Structurally, the dipole units and feed network are covered by antenna
casing to protect the antenna. Usually, the antenna casing is made by
PVC material or tempered glass, and the loss for electromagnetic wave is less
and the strength is better.
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Categorize by emission direction
Directional antenna omni antenna
Categories of Antenna
By emission direction, antennas are categorized into directional antenna and
omni antenna.
Directional antenna usually is used in urban area, and omni antenna is used in
rural area for wide coverage.
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Plate-shape antenna Cap-shape antenna
Whip-shape Paraboloid antenna
Categorize by appearanceCategorize by appearance
Categories of Antenna
The installed antennas can be categorized into plate-shape antenna, cap-shape
antenna, whip-shape, and paraboloid antenna. As shown in the above diagram,
the cap-shape antenna is generally used in indoor distribution system, while the
paraboloid antenna is mainly used for satellite communication and radar.
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Omni antennaUni-polarization
Directional antennaDual polarization
Directional antenna
Categorize by polarization modeCategorize by polarization mode
Categories of Antenna
By polarization mode, antennas are categorized into: vertical polarization
antenna (or unipolarization antenna), cross polarization antenna (or dual
polarization antenna). The foregoing two polarization modes are both line
polarization mode. Circle polarization and oval antenna are usually not used in
GSM. Unipolarization antennas are mostly vertical polarization antennas. Thepolarization direction of their dipole unit is in the vertical direction. Dual
polarization antennas are mostly 45-degree slant polarization antennas. Their
dipole unit is a dipole that crosses the leftward tilt 45-degree polarization and
rightward tilt 45-degree polarization, as shown in the above diagram. The dual
polarization antennas are equivalent to two unipolarization antennas combined
into one. Use of dual polarization antennas can reduce the number of antennas on
the tower, and reduce the workload of installation, hence reduces the system cost,
so they are popularly applied now.
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Smart antennaSmart antenna
Smart directional antenna Smart omni-antennaSmart directional antenna
Categories of Antenna
Smart antenna techniques are already used in many wireless systems, but UMTS
is the first system where they are considered already in the system specification
phase. Smart antennas are especially attractive in WCDMA networks, as they
could be used to reduce the intracell interference levels considerably.
Interference is one of the most important and difficult issues in the WCDMA airinterface, and any improvement in the interference level management will bring
increased capacity.
Generally, a smart antenna is an antenna structure consisting of more than one
physical antenna element, and a signal processing unit that controls these
elements and combines or distributes the signals among these elements. Note
that the antenna elements are not smart as such, but the smartness of the device
lies in the controlling signal processing unit.
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Electric down tilt AntennaElectric down tilt Antenna
Electrical down tilt Antenna
Categories of Antenna
The main parts of electric down tilt antenna:
1. RCU (Remote Control Unit)
2. SBT (Smart Bias-Tee)
3. BT (Bias-Tee)
4. STMA (Smart TMA)
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Electric Indices of Antenna
Electric performances include: working band, gain, polarization mode, lobe
width, preset tilt angle, down tilt mode, down tilt angle adjustment range, front
and back suppression ratios, side lobe suppression ratio, zero point filling, echo
loss, power capacity, impedance, third order inter-modulation.
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Top view side view
directional antenna direction diagramomni antenna direction diagram
Symmetric halfSymmetric half--wave dipolewave dipole
Antenna Direction Diagram
Direction ability of antenna refers to the capability of the antenna emitting
electromagnetic waves toward a certain direction. For a receiving antenna, the
direction ability means the capability of the antenna receiving radio waves from
different directions. The characteristic curve of direction ability of antenna is
generally represented in a direction diagram.
Direction diagram is used for describing the capability of the antenna
receiving/emitting electromagnetic waves in different directions of the air.
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dBi
dBd
2.15dB
Antenna Gain
Gain means a ratio of the power density generated by the antenna at a certain
point in the maximum emission direction to the power density generated by the
ideal point source antenna at the same point. Gain reflects the capability of the
antenna emitting the radio waves in a certain direction in a centralized way.
Generally, the higher of the antenna gain is, the narrower the lobe width will be,and more centralized the energy emitted by the antenna will be. The unit of
antenna gain is dBi or dBd. dBi uses the ideal point source antenna gain as a
reference, and dBd uses the half-wave dipole antenna gain as a reference. The
difference of values represented by the two kinds of unit is 2.15 dB. For example,
if the antenna gain is 11dBi, it can be said as 8.85dBd, as shown in the above
diagram. dBi is defined as the energy centralization capability of the actual
direction antenna (including omni antenna) relative to the isotropic antenna,
where irepresents Isotropic.dBd is defined as the energy centralization
capability of the actual direction antenna (including omni antenna) relative to thehalf-wave dipole antenna, where drepresents Dipole.
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Antenna Pattern
Antenna pattern
It is a three-dimensional solid pattern. It show the theoretic pattern of one
directional antenna.
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Antenna Pattern
Side lobe
Zero point filling
Main lobe
Max value
Zero point filling
Vertical pattern
Back lobe
horizontal half-power
angles
Horizontal pattern
Front to back
ratio
Beam width is one of the key indices of antenna. It consists of horizontal half-
power angle and vertical half-power angle. Horizontal half-power angle/vertical
half-power angle is defined as beam width between the two points where the
power is reduced by half (3dB) in the horizontal/vertical directional relative to
the maximum emission direction. Typical horizontal half-power angles of BTS
antenna are 360, 210, 120, 90, 65, 60, 45 and 33. Typical
vertical half-power angles of BTS antenna are 6.5, 13, 25 and 78. The
front/back suppression ratio means the ratio of signal emission strength of the
antenna in the main lobe direction and in the side lobe direction, and the
difference between the side lobe level and the maximum beam within backward
18030. Generally, the front/back ratio of antenna falls within 18~45dB.
For dense urban areas, the antenna with great front/back suppression ratio is
preferred. Zero point filling: When the BTS antenna vertical plane adopts the
shaped-beam design, in order to make the emission level in the service are more
even, the first zero point of the lower side lobe should be filled, rather thanleaving an obvious zero depth. High-gain antennas have narrow vertical half-
power angles, so especially need the zero point filling technology to improve the
nearby coverage. Generally, if the zero depth is -26dB greater than the main
beam, it indicates that the antenna has zero point filling. Some suppliers adopt
percentage notation. For example, when an antenna zero point filling is 10%.
The relationship between the
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two notation methods is:
Y dB=20log(X%/100%)
For example, zero point filling 10%, namely, X=10; using dB to notate it:
Y=20log(10%/100%)=-20dBUpper side lobe suppression: For the cellular
system based on minor cell system, in order to improve the frequency
multiplexing and reduce the co-frequency interference between adjacent cells,
the BTS antenna lobe shaping should lower the side lobe aimed at the
interference area, and increase the D/U value. The first side lobe level should be
less than18dB. For the BTS antenna based on major cell system, this
requirement is not imposed.
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Electric down tiltElectric down tilt
Mechanical down tiltMechanical down til t
Mechanical Down Tilt and Electric Down Tilt
Three kinds of methods and their combinations are usually used for antenna
beam downtilt: Mechanical downtilt, preset electricity downtilt and electrically
controlled downtilt (for electrically controlled antennas). During adjustment of
the electrically controlled antenna downtilt angle, the antenna itself will not
move, but the phase of the antenna dipole is adjusted through electricity signalsto change the field intensity so that the antenna emission energy deviates from
the zero-degree direction. The filed intensity of the antenna is increased or
decreased in each direction so that there will be little change in the antenna
pattern after the downtilt angle is changed. The horizontal semi-power width is
unrelated with the downtilt angle. However, during mechanical adjustment of the
downtilt angle, the antenna itself will be moved. It is necessary to change the
downtilt angle by adjusting the location of the back support of the antenna.
When the downtilt angle is very large, although the coverage distance in the
main lobe direction changes obviously, yet signals in the direction perpendicularto the main lobe almost keep not change, the antenna pattern deforms seriously,
and the horizontal beam width becomes greater as the downtilt angle is increased.
A preset downtilt antenna is similar to an electrically controlled antenna in
working principle, but a preset angle can not be adjusted.
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The advantages of an electrically controlled antenna are as follows: When the
downtilt angle is very large, the coverage distance in the main lobe direction will
be shortened obviously and the antenna pattern will not remarkably change, so
the interference can be reduced. On the other hand, mechanical downtilt may
deform the pattern. The larger the angle is, the more serious the deformation is.
Hence it is difficult to control the interference.
In addition, electrically controlled downtilt and the mechanical downtilt have
different influence on the back lobe. Electrically controlled downtilt allows
further control of the influence on the back lobe, while mechanical downtilt
enlarges the influence on the back lobe.
If the mechanical downtilt angle is very large, the emission signals of the
antenna will propagate to high buildings in backward direction through the back
lobe, thus resulting in additional interference.
In addition, during network optimization, management and maintenance, when
we need to adjust the downtilt angle of an electrically controlled antenna, it is
unnecessary to shut down the entire system. So we can monitor the adjustment of
the antenna downtilt angle using special test equipment for mobile
communication, so as to ensure the optimum value of the downtilt angle value of
the antenna.
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Questions
How are antennas categorized by emission direction, and by appearance?
What are electric indices of antenna?
What are mechanical indices of antenna?
Into which types does the distributed antenna system break down?
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Summary
Working principles of antenna
Categories of antenna
Electric indices of antenna
Mechanical indices of antenna
New technologies of antenna
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Chapter 2 AntennaChapter 2 Antenna
Chapter 3 RF BasicsChapter 3 RF Basics
Chapter 4 Symbol ExplanationChapter 4 Symbol Explanation
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Absolute power(dBm)
The absolute power of RF signals is notated by dBm and dBW.
Their conversion relationships with mW and W are: e.g., the signal
power is x W, its size notated by dBm is:
For example, 1W=30dBm=0dBW.
Relative power(dB)
It is the logarithmic notation of the ratio of any two powers
For example If , so P1 is 3dB greater than P2
Introduction to Power Unit
=
mw
mwPWdBmp
1
1000*lg10)(
=
mWP
mwPdBp
2
1lg10)(
wP 21 = wP 12 =
Most spectrum analyzers use the dB notation to display the measurement results.
dB is so popularly used because it can use the logarithmic mode to compress the
signal level that changes in a wide range. For example, 1V signal and 10uV
signal can appear on the monitor whose dynamic range is 100dB, while the
linear scale cannot display the two signals simultaneously in a clear picture.Therefore, dB is determines the power ratio and voltage ratio in the logarithmic
mode. In this case, the multiplication operation changes to convenient addition
operation. It is typically used in calculating the gain and loss in the electronic
systems.
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Noise
Noise means the unpredictable interference signal that occur during the
signal processing (the point frequency interference is not counted as noise)
Noise figure
Noise figure is used for measuring the processing capability of the RF
component for small signals, and is usually defined as: output SNR divided
by unit input SNR.
NF
Si
Ni
So
No
Noise-Related Concepts
Typical noises are: external sky and electric noise, vehicle start-up noise, heat
noise from inside systems, scattered noise of transistor during operation,
intermodulation product of signal and noise.
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Noise figure formula of cascaded network
G1 NF1 G2 NF2 Gn NFn
Noise-Related Concepts
1211
21
...
1...
1
++
+=
n
ntotal
GGG
NF
G
NFNFNF
As seen from the above formula, in the system noise, the noise figure of the
level-1 component imposes the greatest influence, the noise figure of level-2
component imposes less influence, and so on. This explains why the cascaded
noise figure is reduced after installing the tower amplifier. Usually, the NF of
TMA is 1.5 . The NF of the level-1 component of BTS is 2.2 .
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Receiving Sensitivity
Receiving sensitivity
Expressed with power:
Smin=10log(KTB)+ Ft +(S/N), unit: dBm
K is a Boltzmann constant, unit: J/K (joule /K) , K=1.38066*10-19 J/K
T represents absolute temperature, unit: K
B represents signal bandwidth, unit: Hz
Ft represents noise figure, unit: dB
(S/N) represents required signal-to-noise ratio, unit: dB
If B=1Hz, 10log(KTB)=-174dBm/Hz
Receiving sensitivity refers to the minimum receiving signal strength under a
certain signal-to-noise ratio. It is an index that reflects the receiving capability of
the equipment.
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Tower Mounted Amplifier
Enlarge uplink signal, but its a loss
for downlink
Duplexer
Sharing antenna for receiving and
transmitting
Sharing antenna for multi-system
RF Components
The core of a TMA is a low noise amplifier, which can be used to solve a limited
uplink coverage problem and increase the uplink coverage area. For uplink, the gain
is around 13dB. For downlink, the loss is around 0.3dB.
Duplexer : A device that permits the simultaneous use of a transmitter and a
receiver in connection with a common element such as an antenna system.
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Splitter
Coupler
RF Components
Both couplers and power splitters are components for power distribution. The
difference is: a power splitter is for equal power distribution, while a coupler is for
non-equal power distribution. Therefore, couplers and power splitters are used in
different applications. In general, to distribute power to different antennas within the
same storey, a power splitter is used; to distribute power from the trunk to
tributaries of different stories, a coupler is used.
If couplers and power splitters are used in coordination, the transmit power of the
signal source can be distributed as evenly as possible to various antenna ports of the
system, namely, the transmit power of each antenna in the entire distribution system
is almost the same.
During power splitter selection, priority should be given to 1/2 power splitters, not
1/4 power splitters. When using a 1/3 power splitter, make sure that the power
splitter is not too close to the antenna, and the feeder cable connecting them should
be over 20m long.
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Tx/Rx
Trunk
Trunk
Splitter
Trunk
Coupler
Splitter
Splitter
Splitter
Splitt
er
Splitter
Coupler
Coupler
Splitter
Splitter
Distribution System
In the tunnel/subway/indoor, if we cover it just by outdoor NodeBs, because of the
blocking of the obstacle, the QoS will be very bad, even cause call drop. In addition,
in large building, we usually use micro cell system to cover it. But the indoor
environment is different with outdoor and it is hard to use one fixed antenna to
cover the whole building because of the blocking of the wall and other obstacle. The
indoor distribution system (IDS) can solve these problems and increase the coverage
of the micro NodeB. So the IDS is necessary in some buildings.
In general, when selecting feeder cable types, select 7/8" cable for the trunk, and
1/2" common cables or super flexible cable for tributaries. During the trunk cabling
process, if the curvature radius does not meet the requirement, the trunk can be
disconnected at corners, and a section of 1/2" super flexible cable can be used for
cabling around the corners.
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Summary
Definition about dBm, dB
Noise-Related Concepts
Receiving Sensitivity
RF Components
SummarySummary
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Chapter 1 Radio Wave IntroductionChapter 1 Radio Wave Introduction
Chapter 2 AntennaChapter 2 Antenna
Chapter 3 RF BasicsChapter 3 RF Basics
Chapter 4 Symbol ExplanationChapter 4 Symbol Explanation
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Ec
Average energy per Chip
Not considered individually, but used for Ec/Io
Pilot Ec is measured by the UE (for HO) or the Pilot scanner, in the form
of Received Signal Code Power (RSCP)
For CPICH Ec:
Depends on power and path loss.
Constant for a given power and path loss. Ec is not dependent on
load
For DPCH Ec:
Depends on power and path loss
Symbol Explanation
The same could be said for the Dedicated Channel as for the pilot. The Ec
remains constant for a given power and path loss. The main difference between
the pilot and the DCH is that the DCH is power controlled.
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Eb
Average energy per information bit for the PCCPCH, SCCPCH, and DPCH, at the
UE antenna connector.
Typically not considered individually, but used for Eb/Nt
Depends on channel power (can be variable), path loss, and spreading gain (Gp)
Constant for a given bit rate, channel power, and path loss
Can be estimated form Ec and processing gain
Speech 12.2kbps example
Ec = -80 dBm
12.2kbps data rate => Processing gain = 24.98 dB
Eb~ -80 + 24.98 = -55.02 dBm
Symbol Explanation
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Io
The total received power spectral density, including signal and
interference, as measured at the UE antenna connector.
Similar to UTRA carrier Receive Strength Signal Indicator (RSSI), at
least for practical consideration (SC scanner)
RSSI in W or dBm
Io in W/Hz or dBm/Hz
Measured by the UE (for HO) or Pilot scanner in the form of RSSI
Depends on All channel power, All cells, and path loss
Depends on same-cell and other cell loading
Depends on external interferences
Symbol Explanation
This is different form other Io definitions: other users interferences
Io = total receive power per-channel receive power
This latest definition of Io is more in line with the ISCP (Interference Signal
Code Power) defined in the standard
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No common RF definition Thermal noise density
Typically not considered individually, but used for Eb/No
Can be calculated
No = KT
K is the Bolzman constant, 1.38*10^-23
T is the temperature, 290 K
No = 174 dBm/Hz under typical conditions
Typically the bandwidth noise and the receiver noise figure are also considered
No = KTBNF, where NF is noise figure
To avoid confusion, NF should be used when referring to thermal noise
Symbol Explanation
For a WCDMA system, the bandwidth is 3.84Mcps. For WCDMA, the typical
noise figure is 3dB Uplink (NodeB, but Huaweis NodeB is 2.2 dB in RND) and
7 dB downlink (UE). These figures should always be checked against the vendor
specification, because implementation affects them
Based on the previous formula, this gives the total noise power (noise floor) as
Uplink: -174+66+3= -105dBm (RTWP value without subscriber)
Downlink: -174+66+7= -101dBm
These values are not the receiver sensitivity but the power measured at the
reference point, in the absence of signal. As WCDMA allows the extraction ofsignals below the noise floor, the sensitivity can not be deducted from these
values.
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No for WCDMA system Total one-sided noise power spectral density due to all noise sources
Typically not considered individually, but used for Eb/No
Defined this way, No and Io are substituted for one another:
On the uplink the substitution is valid
On the downlink, differentiating between Noise and Interference is more
challenging
Symbol Explanation
Originally, Eb/No meant simply bit energy divided by noise spectral density.
However, over time the expression Eb/No has acquired an additional meaning.
One reason is the fact that in CDMA the interference spectral density is added to
the noise spectral density, since the interference is noise, due, for example, to
spreading. Thus, No can usually be replaced by Io, interference plus noisedensity.
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RTWP
Received Total Wide Bandwidth power
To describe uplink interference level
When uplink load increase 50%, RTWP value will increase 3dB
RSSI
Received Signal Strength Indicator
To describe downlink interference level at UE side
Symbol Explanation
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RSCP
Revived Signal Code Power (Ec)
Ec/Io = RSCP/RSSI, to describe downlink CPICH quality
ISCP
Interference Signal Code Power; can be estimated by:
ISCP = RSSI RSCP
Symbol Explanation
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Summary
Ec, Eb, Io and No
RTWP, RSSI, RSCP and ISCP
SummarySummary
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