19.Wo Na01 e1 1 Umts Rf Optimization-36
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Transcript of 19.Wo Na01 e1 1 Umts Rf Optimization-36
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.
)2
)(exp(21)( 2
2
myyP
LdymyLyP )
2)(exp(
21)( 2
2
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
)exp(2)( 2
2
2 rr
r
rrP )exp(1)exp(2)( 2
2
0 2
2
2 rRdr
rr
r
rRrPR
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 indexes or not?
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
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.
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.
After Adjustment
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.
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
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.