03-150323115803-conversion-gate01 (1)
TRANSCRIPT
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4G LTE – Drivetest and Cove
Different Between TD-LTE & FD-LTE
Item LTE-TDD LTE-FDD
Duplex mode TDD FDD
Frame structure Type 2 Type 1
UL and DL Ratio 7 types of UL and DL ratio, flexible All subframes can be allocated only fo
downlink.
RRU Noise Figure
A T/R converter is required. The T/R
converter will bring about the insertion
loss of 2~2.5 dB .
A duplexer is required and the duple
about the insertion loss of 1
BeamformingSupported (exchangeability based on
uplink and downlink channel)
Not supported (no exchangeability ba
and downlink channels)
MIMO Mode Modes 1 –8 are supported. Mode 1 –6 are supported
Network InterferenceStrict synchronization is required in the
whole network.Synchronization requirement is n
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4G LTE – Drivetest and Cove
Drive Test Peripheral
Notebook
GPS
LTE
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4G LTE – Drivetest and Coverage Analysis| Page 4
ReferenceSignal Received
Power (RSRP)
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4G LTE – Drivetest and Cove
LTE RS Power Allocation• RS Power for 20 MHz @ 10W/port
RS = 40dBm – 10*log(12*100) + 10*log(1+1)
= 12.2 dBm
• RS Power for 10 MHz @ 5W/portRS = 37dBm – 10*log(12*50) + 10*log(1+1)
= 12.2 dBm
RS Power for 10 MHz @ 10W/port
RS = 40dBm – 10*log(12*50) + 10*log(1+1)= 15.2 dBm
With the same total power, coverage LTE
10 Mhz is larger than with LTE 20 MHz
RS Power for 10 MHz @ 10W/
RS = 40dBm – 10*log(12*50) = 15.2 dBm
With the same total power, co
10 Mhz is larger than with LTE
Impact on Radio Netw
Performance: A larger
results in a larger incr
ReferenceSignalPwr, b
estimation performan
PDSCH demodulation
but it also leads to low
power of the PDSCH (
increases
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4G LTE – Drivetest and Cove
LTE RS Power Allocation
• Power Boosting for RS
PB =1 by default
• RS Power for 20MHz
= 43 – 10*log(100*12) + 10*log10(PB+1) = 15.2dBm
Bandwidth 10M
15M
20M
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4G LTE – Drivetest and Cove
RS Power Overhead Comparison with CPICH
Type A Symbol: without RS REsType B Symbol: with RS REs
• RS power per RE is 15.2dBm (0.033W) for 20MHz
• Total RS power in 20MHz for Type B Symbol is 0.033*2 (RS REs/ RB) * 100 RBs = 6.6W
• Total RS power in 20MHz for Type A Symbol is 0
• Only two symbols carry RS within 0.5ms and hence the RS power overhead is about over 1 timeslot
LTE RS power overhead is about 9.4% which is similar to 10% CPICH
of UMTS
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4G LTE – Drivetest and Cove
RxLev, RSRP and RSCP ComparisonItems GSM UMTS LTE
(e)NodeB power per Tx (dBm) 43 43 43
Bandwidth (MHz) 0.2 5 20
Number of RB N/A N/A 100
BCCH Power/ CPICH power
/RS power per RE (dBm) 43 33 15.2
CL (dB) 120 120 120
Rx Lev/RSCP/RSRP (dBm) -77 -87 -104.8
Received RS signal strength
over whole bandwidth
-81.8
RSRP is the recei
over 15KHz band
bandwidth of RS
RSRP of LTE is much smaller than RSCP of UMTS under same radi
Only 1/6 REs is used
within one RB and h
power is 10*log10(
than RSRP
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4G LTE – Drivetest and Covera
Factors Influencing LTE Coverage
Some other factors such as site height, BPL, TMA, coverage probability,…
TX Power
MIMO Radio Condition
Frequency
BandData RateICIC
RB NuFactors Affecting LTELink Budget
MCSCell Load
InterferenceMargin LTE Standard
LTE
Specific
ICIC:Inter Cel
k d l
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4G LTE – Drivetest and Covera
Weak Coverage and Coverage Holes
The signal quality in cells is poorer than the optimization baseline
As a result, UEs cannot be registered with the network or accessed s
cannot meet QoS requirements.
If there is no network coverage or coverage levels are excessively low in an area, the area is
coverage area. The receive level of a UE is less than its minimum access level (RXLEV_Adownlink receive levels in a weak coverage area are unstable. In this situation, the UE is d
network. After entering a weak coverage area, UEs in connected mode cannot be handed
cell, and even service drops occur because of low levels and signal quality.
Weakcoverage
Coverage holes
R l i W k C P bl
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4G LTE – Drivetest and Covera
Resolving Weak Coverage Problems
Analyze geographical environments and
check the receive levels of adjacent
eNodeBs.
Analyze the EIRP of each sector based on
parameter configurations and ensure
EIRPs can reach maximum values if
possible.
Increase pilot power.
Adjust antenna azimuths and tilts,
increase antenna height, and use high-gain
antennas.
Deploy new eNodeBs if coverage hole
problems cannot be resolved by
adjusting antennas.
Increase coverage by adjacent eNodeBs
to achieve large coverage overlapping
between two eNodeBs and ensure a
moderate handover area.
Note: Increasing coverage may lead to
co-channel and adjacent-channel
interference.
Use RRUs, ind
leaky feeders, a
resolve the pro
elevator shafts
garages or bas
buildings.
Analyze the im
terrains on cov
Case: Searching for a Weak Coverage Area by Using a Scanner or Performing Drive Tests
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4G LTE – Drivetest and Covera
Case: Searching for a Weak Coverage Area by Using a Scanner or Performing Drive Tests
UEs
Perform drive tests in zero-load environments to obtain
the distribution of signals on
test routes. Then, find a
weak coverage area based
on the distribution, as
shown in the figure.
Adjust RF parameters of the
eNodeB covering the area.
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R l i P bl ith L k f D i
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4G LTE – Drivetest and Covera
Resolving Problems with Lack of a Dominan
…
Adjust engineering
parameters of a cell that can
optimally cover the area as
required.
Determine cells covering an
area without a dominant cell
during network planning, and
adjust antenna tilts and
azimuths to increase coverage
by a cell with strong signals
and decrease coverage of
other cells with weak signals.
C S hi f A With t C ll
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4G LTE – Drivetest and Covera
Case: Searching for an Area Without a Dominant Cell
Symptom
UEs frequently perform cell reselections or
handovers between identical cells.
Analysis
Analysis can be based on signaling procedures andPCI distribution.
According to PCI distribution shown in the figure,
PCIs alternate in two or more colors if there is no
dominant cell.
Solution
According to the coverage plan, cell 337 is a
dominant cell covering the area and cell 49 also hasstrong signals. To ensure handovers between cells 337
and 49 at crossroads, increase tilts in cell 49.
1.P
La
do
ce
Cross Co erage
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4G LTE – Drivetest and Covera
Cross Coverage
Cross coverage means that the coverage scope of an eNodeB exceeds the planned on
discontinuous dominant areas in the coverage scope of other eNodeBs. For example
much higher than the average height of surrounding buildings, its transmit signals p
roads and form dominant coverage in the coverage scope of other eNodeBs. This is
If a call is connected to an island that is far away from an eNodeB but is still served b
around the island are not configured as neighboring cells of the current cell when ce
are configured, call drops may occur immediately once UEs leave the island. If neigh
configured but the island is excessively small, call drops may also occur because UE
handed over. In addition, cross coverage occurs on two sides of a bay because a shotwo sides. Therefore, eNodeBs on two sides of a bay must be specifically designed.
Cross
coverage
Resolving Cross Coverage Problems
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4G LTE – Drivetest and Covera
Resolving Cross Coverage Problems
…
Adjust antenna tilts or replace
antennas with large-tilt antennaswhile ensuring proper antenna
azimuths. Tilt adjustment is the
most effective approach to control
coverage. Tilts are classified into
electrical tilts and mechanical tilts.
Electrical tilts are preferentially
adjusted if possible.
Adjust antenna azimuths properly
so that the direction of the mainlobe slightly obliques from the
direction of a street. This reduces
excessively far coverage by electric
waves because of reflection from
buildings on two sides of the street.
Decrease th
a high site.Decrease tr
carriers whe
not affected.
Case: Cross Coverage Caused by Improper Tilt Settings
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4G LTE – Drivetest and Covera
Case: Cross Coverage Caused by Improper Tilt Settings
Symptom
As shown in the upper right figure, cross coverage
occurs in a cell whose PCI is 288. Therefore, the cell
interferes with other cells, which increases the
probability of service drops.
Analysis
The most possible cause for cross coverage is
excessively antenna height or improper tilt settings.
According to a check on the current engineering
parameter settings, the tilt is set to an excessively
small value. Therefore, it is recommended that the tilt
be increased.
Solution
Adjust the tilt of cell 288 from 3 to 6. As shown in the
lower right figure, cross coverage of cell 288 is
significantly reduced after the tilt is adjusted.
Case: Inverse Connections Involved in the Antenna System
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4G LTE – Drivetest and Covera
Case: Inverse Connections Involved in the Antenna System
SymptomThe RSRPs of cells 0 and 2 at the Expo Village site are low and
high respectively in the red area shown in the figure. The signalquality of cells 0 and 2 is satisfactory in the areas covered bycells 2 and 0 respectively.
Analysis After installation and commissioning are complete, the RSRP in
the direction of the main lobe in cell 0 is low. After cell 0 is
disabled and cell 2 is enabled, the RSRP in cell 2 is normal andthe SINR is higher than that tested in cell 0. Therefore, thisproblem may occur because the antenna systems in the twocells are connected inversely. Test results are as expected afteroptical fibers on the baseband board are swapped.
SolutionSwap optical fibers on the baseband board or adjust feeders and
antennas properly. It is recommended that optical fibers on thebaseband board be swapped because this operation can beperformed in the equipment room.
SuggestionsNetwork planning personnel must participate in installation.
Alternatively, customer service personnel have detailed network
planning materials and strictly supervise project constructors forinstallation. After installation is complete, labels must beattached and installation materials must be filed.
Imbalance Between Uplink and Downlink
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4G LTE – Drivetest and Covera
Imbalance Between Uplink and Downlink
When UE transmit power is less than eNodeB transmit power, UEs in idle mode may
successfully register in cells. However, the eNodeB cannot receive uplink signals
when UEs perform random access or upload data. In this situation, the uplink cov
the downlink coverage distance. Imbalance between uplink and downlink involves
coverage. In limited uplink coverage, UE transmit power reaches its maximum but
requirement for uplink BLERs. In limited downlink coverage, the downlink DCH tra
its maximum but still cannot meet the requirement for the downlink BLER. Imbala
downlink leads to service drops. The most common cause is limited uplink covera
Imbalance
between
uplink and
downlink
Uplink coverage areaDownlink coverage area
coverage area
Resolving Problems with Imbalance Between Uplink and Downlink
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4G LTE – Drivetest and Covera
Resolving Problems with Imbalance Between Uplink and Downlink
…
If no performance data is available for RF
optimization, trace a single user in the OMC
equipment room to obtain uplink measurement
reports on the Uu interface, and then analyze the
measurement reports and drive test files.
If performance data is available, check each
carrier in each cell for imbalance between uplink
and downlink based on uplink and downlink
balance measurements.
If uplink interference leads to imbalance
uplink and downlink, monitor eNodeB ala
check for interference.
Check whether equipment works proper
whether alarms are generated if imbalanc
uplink and downlink is caused by other fa
example, uplink and downlink gains of rep
trunk amplifiers are set incorrectly, the an
system for receive diversity is faulty when
and transmission are separated, or power
are faulty. If equipment works properly or
generated, take measures such as replace
isolation, and adjustment.
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4G LTE –
Drivetest and Coverage Analysis| Page 23
Signal to Noise& Interference
Ratio (SINR)
Traditional Frequency Planning
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4G LTE – Drivetest and Covera
Traditional Frequency Planning
1
1
Advantage
Higher spectrum efficiency
Disadvantage Lower cell edge throughput due to serious interference
Suitable Scenario Lacking frequency resource Capacity requirement scenarios, such as dense urban and urban areas during network
initial stage
1*3*1 Frequency Planning
Advantage Lower interference and larger coverage radius
Disadvantage Lower spectrum efficiency
Suitable Scenario Abundant frequency resource or inconsecutive spectrum scenarios large coverage
scenarios.
1*3*3 Frequency Planning
Interference and Capacity Comparison 1*3*3
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4G LTE – Drivetest and Covera
Interference and Capacity Comparison 1 3 3
The downlink service channel SINR of ×3×
and ×3×3
0
0.2
0.4
0.6
0.8
1
-10 0 10 20 30 40
SINR
C D F
1×3×1 1×3×3
SINR distribution comparison Average sector capacity compariso
1*3*3 with low interference because of more frequency resource.
1*3*3 with high sector capacity because of low interference.
More frequency resource required for 1*3*3
1*3*3 10MHz channel (30MHz) compare with 1*3*1 10MHz channel (
SINR
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4G LTE – Drivetest and Covera
SINRThe SINR is not specifically defined in 3GPP specifications. A common formula is as follow
SINR = S/(I + N)
S: indicates the power of measured usable signals. Reference signals (RS) and physica
channels (PDSCHs) are mainly involved.
I: indicates the power of measured signals or channel interference signals from other cesystem and from inter-RAT cells.
N: indicates background noise, which is related to measurement bandwidths and receive
coefficients.
Empirical SINR at the edge of a cell:
The SINR is greater than -3 dB in 99% areas in Norway.
The SINR is greater than -3 dB in 99.25% areas in the Huayang field in Chengdu.
Signal Quality (SINR is mainly involved)
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4G LTE – Drivetest and Covera
Signal Quality (SINR is mainly involved)
Frequency
plan
③ Site
selection
④ Antenna
height
⑤ A
az⑥ A
Cell layout
Resolving Signal Quality Problems Caused by Improper Parameter Sett
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4G LTE – Drivetest and Covera
g g Q y y p p
Change and optimize frequencies based on drive test and
performance measurement data.
Optimizing
frequencies
Adjust antenna azimuths and tilts to change the distribution of signinterfered area by increasing the level of a dominant sector and dec
other sectors.
Adjusting the
antenna
system
Increase power of a cell and decrease power of other cells to form
cell.
Decrease RS power to reduce coverage if the antenna pattern is
of a large antenna tilt.
Power adjustment and antenna system adjustment can be used t
Adding dominant
coverage
Adjusting power
Case: Adjusting Antenna Azimuths and Tilts to Reduce Inte
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4G LTE – Drivetest and Covera
Case: Adjusting Antenna A imuths and Tilts to Reduce Inte
SymptomCross coverage occurs at sites 1, 2, 3, 7, 8, 9, 10, 11, and 12, and co-channel i
in many areas. Analysis
According to the analysis of engineering parameters and drive test data, cell decoverage areas. Coverage by each cell can be reduced by adjusting antenna
SolutionChange the tilt in cell 28 from 2 degrees to 4 degrees so that the direction poindemonstration route. Change the tilt in cell 33 from 3 degrees to 6 degrees so points to the Wanke Pavilion. Change the tilt in cells 50 and 51 from 3 degreesthat the direction points to the Communication Pavilion. Decrease the transmit3 dB to reduce its interference to overhead footpaths near China Pavilion.
SINR before optimization in Puxi SINR after
Poor signal
quality before
optimization
Case: Changing PCIs of Intra-frequency Cells to Reduce Int
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4G LTE – Drivetest and Covera
g g q y
Symptom
Near Japan Pavilion, UEs access a cell whose PCI is 3 and SINRs are low. UEs are about 200
eNodeB. This problem may be caused by co-channel interference.
Analysis
This problem is not caused by co-channel interference because no neighboring cell has the sam
current cell. Cell 6 interferes with cell 3. SINRs increase after cell 6 is disabled. In theory, stagg
reduce interference.
Solution
Change PCI 6 to PCI 8. Test results show that SINRs increase by about 10 dB.
SINR when cell 6 is enabled SINR when cell 6 is disabled SINR w
Case: Handover Failure Caused by Severe Interference
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4G LTE – Drivetest and Covera
y
Symptom
During a test, handovers from PCI 281 to PCI 279 fail.
Analysis
Cell 281 is a source cell and is interfered by cells 279 and 178. Delivered handover co
fail and cannot be received correctly by UEs. Cell 279 is a target cell for handover, and
not adjusted preferentially because the signal strength in the handover area can ensur
after handovers. Therefore, cell 178 must be adjusted to reduce its interference to cell
Solution
Adjust antenna tilts to decrease coverage by cell 178.
SINR Improvement
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4G LTE – Drivetest and Covera
SINR Improvement AFTER ACPINITIAL PLAN
In the inner city of Jakarta where ZTE antenna configuration taken
into the initial planning show there are so much SINR around 0~5
(dB). After do the ACP Optimization the SINR much improve with
much blue color (SINR >=15 dB)
Initial Plan
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4G LTE – Drivetest and Covera
Initial Plan
After ACP
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4G LTE – Drivetest and Covera
Radio Parameter @ GENEX Probe
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4G LTE – Drivetest and Covera
@
PCI (Physical Cell Identifier)
Value range : 0 – 839, cross-chec
feeder problem when conductin
RSRP (Reference Signal Receive P
-70 dBm to -90 dBm
-91 dBm to -110 dBm →
-110 dBm to -130 dBm →
SINR (Signal to Interference+No 16 dB to 30 dB → Goo
1 dB to 15 dB → Norm
-10 dB to 0 dB → Bad
Radio Parameter @ GENEX Probe…cont
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4G LTE – Drivetest and Covera
Modulation Coding Scheme
64 QAM → Good
16 QAM → Normal
QPSK → Bad
Neighboring cell Downlink EARFCN
@
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Signal quality overview plot (Serving PCI)
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4G LTE – Drivetest and Covera
RNO-1
Signal quality overview plot (RSRP)
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4G LTE –
Drivetest and Covera
Signal quality overview plot (SINR)
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4G LTE –
Drivetest and Covera
Signal quality overview plot (DL Throughput)
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4G LTE –
Drivetest and Covera
Signal quality overview plot (UL Throughput)
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4G LTE –
Drivetest and Covera
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