7 umts rf optimization-36
DESCRIPTION
UMTS RF OptimizationTRANSCRIPT
UMTS RF Optimization
ZTE University
Content
UMTS Radio Transmission Theory
RF Optimization Policy
RF Adjustment and Network Simulation
Mobile Communication Environments
Low antenna of UE
Transmission paths are always influenced by terrains and man-made
environments; various terrains and complex buildings, forests and so on
make signals received as overlap of scattering signals and reflected
signals.
Mobility of UE
UE is always moves, or the peripheral environments change. This makes a
transmission path between a base station and an UE change all the time.
In addition, the difference of direction and speed of an UE relative to the
base station also causes changes of signal levels.
Signal levels change at random
Signal levels change with time and position; it can be described only with
probability distribution of random process.
Mobile Communication Environments
Waveguide effect exists in urban environment
Powerful signals can
observed in streets in the direction from the north to
the south No influence of the channel
effect is imposed in this area
Radiating direction N
Powerful signals can
observed in streets in the direction from the east to
the west
Transmitter Platitude direction
Effects of Street Waveguide
Mobile Communication Environments
Serious man-made noises
Man-made noises include noises in starting motor vehicles, power
line noises and industrial noises.
Serious Interference
Generally, there are co-frequency interference, adjacent-channel
interference, intermodulation interference, local to remote ratio
interference. co-frequency interference and adjacent-channel
interference are the main factors.
Types of Radio Wave Transmission
Types of radio wave transmission: Direct wave, reflected
wave, diffracted wave and scattering wave
B
A
d
D
LOS NLOS
RFD
+
Penetration through buildings/vehicles
Multi-path transmission
Types of Radio Wave Transmission
Sight distance and non-sight distance transmission, multi-path
environments of complex forms
Loss through buildings/vehicles
)()()( 0 trtmtr )()()( 0 drdmdr
Radio Signal Presentation Methods
A signal is a random value, so it must be characterized jointly by a
median and a transient value. An actually received signal is a median
overlapped with a transient value. The median is called slow fading
and the transient value is called quick fading.
m(x) is slow fading, or local average, or long-term fading.
r0(x) is quick fading, or Rayleigh fading, or short-term fading.
The two methods for presenting signal field strength are used in
different occasions: The signal presented in a time function is used for
studying signal fading; while a signal presented in a distance function
is used for studying transmission loss curve. Variation of the median
level of a received signal with time is far less than that with location.
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Statistical Features of Slow Fading
Definition of slow fading
It is the average of attenuated signals received, that is, average (or
field strength value or loss value) of signal levels attained in a
specified length L. The value of L is 40 wavelengths, with 36~50
signals for test.
Cause of slow fading
Slow fading is caused by changes of terrains and man-made
environments on transmission paths.
Probability density function and accumulation probability
distribution function of slow fading
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r
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rrP )exp(1)exp(
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Rdr
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rRrP
R
Statistical Features of Quick Fading
Definition of quick fading
It is the transient value of fading signals received.
Cause of quick fading
When transmission is reflected due to obstruction by scattering
objects (mainly buildings) or natural obstacles (mainly forests) in
the vicinity (within 50~100 wavelengths) of an UE, there will be
multi-path wave interference on the ground, leading to a standing
wave field. When the MS passes the standing wave field, the
received signals presents quick fading, and the field strength
fluctuates.
Probability density function and accumulation probability
distribution function of quick fading
Other Features of Signal Transmission
Time delay extended width
Related bandwidth
Inter-code Interference
……
Transmission Theory
Definition of Transmission Theory
For a radio link, the loss (or fading) value of power level of a signal
from the output end of a transmitting antenna through certain
transmission paths to the input end of the antenna. Usually, it is
expressed in dB .
Common Relations between Transmission Theory and
Distance
In mobile communication, the greater the transmission distance is,
the greater the transmission loss will be. Within 1~20 km, roughly
40dB/dec. dec is 10 times the distance; in case of greater distance,
it will be increased to 50~60dB/dec.
Common Types of Transmission Theory
Free Space Transmission Theory
Diffraction Loss
Reflection Loss
Building Penetration Loss
Human Body Loss
In-vehicle Loss
Vegetation Loss
f(n)=ST+RT=SR+n*/2
S
R
T Gap (0.577 time of the 1st Fresnel
radius)
Fresnel Region and Transmission clearance
Fresnel Region
An area between curves satisfying f(n) and f(n-1) is called the nth
Fresnel region. When N=1, it is called the 1st Fresnel region, an
ellipsoid; the 1st Fresnel region contains 1/2 of the transmitting energy.
In addition, tests and theories demonstrate that, if the gap is greater
than 0.577 time of the radius of the 1st Fresnel region, the loss will be
equal to the loss of the free space.
Transmission Gap
0.577 time of the 1st Fresnel radius.
Content
UMTS Radio Transmission Theory
RF Optimization Policy
RF Adjustment and Network Simulation
Single station
check
Base station group
optimization Whole network
optimization
Satisfy
the
ind
exes o
r no
t?
Find out base station
group that do not
satisfy requirements
No
Common RF Optimization Process
Single Station Check
Confirm site information
Longitude and latitude, configuration, height above sea level, peripheral
environments and so on.
Confirm antenna feeder information
Antenna type, azimuth, down-tile angle and height.
Check antenna feeder link
Standing wave ratio, primary set and diversity RSSI check, primary set and
diversity lock balance.
Confirm system parameters
List of adjacent areas, overhead channel transmitting power, PN
configuration, switching parameters.
Check and test basic functions
Basic call process, soft switching, softer switching.
Check station coverage
Base Station Group Optimization
Spectrum scanning
Load-free test
Load test
Whole Network Optimization
Test on various radio indexes of the system
Analysis on test results
Confirm whole network adjustment scheme
Performance Test Indexes
Voice quality--FER
Call connection rate (call completion rate and paging
response rate)
Resource utilization—CPU utilization-
Switching completion rate
Call drop rate
Network coverage rate
Forward coverage
Pilot coverage
Service coverage
Backward coverage
Common RF Problems
Call Drop
Discontinuity
Access Failure
Call Drop Analysis
Forward coverage is not satisfactory (Ec/Io and Ec)
Improve the coverage of the points.
List of adjacent areas is not complete
Configuration of list of adjacent areas is not complete.
Interference
There is in-band interference source.
Pilot pollution is serious
Faults with base stations
Incorrect connection of antenna feeders, GPS fault causes
asynchrony between the time and the system, interruption of
transmission.
Hard switching takes place
Access Failure
Interference
Coverage over weak areas, blind zones or pilot pollution
areas makes it impossible for signaling interaction between
the base station and the mobile phone to be completed
during the access.
Mobile phone performance
RF Optimization Policy
Adjust the antenna down-tilt angle
Adjust the antenna directional angle
Adjust the antenna height
Change the antenna type
Appropriately adjust the base station transmitting power
Adjust the base station location
Increase the base stations
RF Optimization Policy
Antenna directional angle
During optimization, attention
should be paid to antenna
directional angle, as shown in
the figure on the right.
If the antenna coverage area is
a vast space of residence, and
the buildings are of the similar
structure, the antenna direction
shall be alongside the direction
of the buildings (as the red
arrow on the left); if the antenna
direction is the same as the
arrow on the right, the quality of
signals in the coverage area
may not be good.
RF Optimization Policy
RF Optimization Policy for Pilot Pollution
Adjust the antenna down-tilt angle, so as to reduce the coverage
area, and further reduce the number of pilots in the pilot pollution
area.
Appropriately reduce the transmitting power of the cell, so as to
reduce the signal strength to narrow the coverage area, and also
further reduce the number of pilots in the pilot pollution area.
If the two measures are of no use, we can increase base stations in
the pollution areas, so that there will be a master pilot signal, to
solve the pollution. But be careful in taking this measure, as it may
impose great influence on the entire network.
Content
UMTS Radio Transmission Theory
RF Optimization Policy
RF Adjustment and Network Simulation
Before Adjustment
The diagram on the right
shows part of the base
stations of the Guangzhou
MTNet Pilot Network.
Where, the directional
angle of the antenna in the
DiTuChuBanShe is 30°,
the mechanica down-tilt
angle is 6° and the
electronic down-tilt is 2 °.
Before Adjustment
This is a pilot
intensity simulation
diagram: We can
see that the pilot
intensity is quite
satisfactory as a
whole.
This is a pilot Ec/Io
simulation diagram:
We can see that the
pilot Ec/Io in the
middle (the yellow
part) of the diagram
is not so satisfactory.
Before Adjustment
This is a pilot pollution
simulation diagram: We
can see pilot pollution in
the lower middle (the
brown part) of the
diagram. Taking the pilot
Ec/Io simulation effect in
the previous diagram
into consideration, we
should perform RF
optimization here.
Before Adjustment
After Adjustment
Analysis shows that adjustment
of RF parameters in the
DiTuChuBanShe may improve
the current situation.
Adjust the mechanical down-tilt
of the antenna in the
DiTuChuBanShe as 0°, and
leave the electronic down-tilt
angle unchanged as 2 °.
Through this adjustment, the
pilot intensity of the
DiTuChuBanShe, where there
is pilot pollution, is improved,
and becomes the maste pilot,
so that pilot pollution is
improved and the pilot Ec/Io
here is enhanced.
This is the effect of
pilot intensity
simulation after
adjustment. We can
see that the pilot
intensity after
adjustment is much
improved than that
before adjustment.
After Adjustment
The effect of pilot
Ec/Io simulation
after adjustment.
We can also see
that the pilot Ec/Io
after adjustment is
much improved
than that before
adjustment.
After Adjustment
This is the effect of
pilot pollution
simulation after
adjustment. We can
see that big brown
part (with pilot
pollution) has been
greatly reduced.
This proves that the
RF adjustment has
fulfilled the
optimization aims.
After Adjustment