001 WCDMA RNP Fundamental
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Transcript of 001 WCDMA RNP Fundamental
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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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
ChapterChapter 22 AntennaAntenna
ChapterChapter 3 RF Basics3 RF Basics
ChapterChapter 44 SymbolSymbol ExplanationExplanation
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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
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 frequency resources 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 agood tradeoff between the coverage 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 freespace propagation. One is perpendicular 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 fromtime to time for weather reasons. Its reflectance decreases with the
increase of height. This slowly 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
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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 the transmitter 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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
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 shortwaveradio 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 difference between 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 thereceiving signal strength decreases but the field strength mid-valuechanges slowly with the change of the topography, the strength decreaseis called slow fading or shadow fading. The field strength mid-value ofslow fading takes on a logarithmic normal distribution, and is related to
location/locale. The fading speed is dependent on the speed of the mobilestation.
Fast fading: In case the amplitude and phase of the combined wavechange sharply with the motion of the mobile station, the change is calledfast fading. The spatial distribution of deep fading points is similar tointerval of half of wavelength. Since its field strength takes on Rayleighdistribution, 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 causesDoppler effect on the frequency domain, and thus results in frequencydiffusion, time-selective fading will occur.
Space-selective fading: The fading features vary between different placesand different transmission paths.
Frequency-selective fading: The fading features vary between differentfrequencies, which results in delay diffusion and frequency-selectivefading.
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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
and the 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 receivers
capability 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 light problem), 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 ofthe same obstacle for the long wavelength 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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
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 topographicconditions. For example, the Okumura 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 aboveexample, the 1900MHz loss will be 6dB 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 andenvironments, and developed a series 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 extend the 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 environmentfeatures 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 hillyterrains environments under it is LOS between transmitter and receiver.
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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
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 theactual value with the forecast value, we adjust 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 tothe sampling rate of 1 point/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 be inconsistent 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 deeplyfaded 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, andwill result in multiple test data at one location point. Suppose the vehicleruns at equal speeds, such data should be distributed to the two fixedpoints on average, which is a process of data dispersion. The mainfunction of geographic averaging is to eliminate the influence of fastfading 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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
ChapterChapter 22 AntennaAntenna
ChapterChapter 3 RF Basics3 RF Basics
ChapterChapter 44 SymbolSymbol ExplanationExplanation
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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 of the 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 polarizationantennas. The polarization 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 importantand difficult issues in the WCDMA air interface, 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 i represents Isotropic.dBd is defined as the energycentralization capability of the actual direction antenna (including omni
antenna) relative to the half-wave dipole antenna, where d represents
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 theservice are more even, the first zero point of the lower side lobe should be
filled, rather than leaving 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 than 18dB. 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 signals to 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 directionperpendicular to 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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
ChapterChapter 22 AntennaAntenna
ChapterChapter 3 RF Basics3 RF Basics
ChapterChapter 44 SymbolSymbol ExplanationExplanation
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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 signalssimultaneously 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, inter-modulation 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 BTSis 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 powerfrom 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 thewall 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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ChapterChapter 1 Radio1 Radio WaveWave IntroductionIntroduction
ChapterChapter 22 AntennaAntenna
ChapterChapter 3 RF Basics3 RF Basics
ChapterChapter 44 SymbolSymbol ExplanationExplanation
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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 of signals 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 canusually be replaced by Io, interference plus noise density.
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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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