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Indoor Coverage Optimization ISSUE1.0 www.huawei.com
HUAWEI TECHNOLOGIES CO., LTD.
HUAWEI Confidential
Contents
Chapter 1 Coverage Analysis Chapter 2 Leakage Analysis Analysis Chapter 3 Interference Analysis
Chapter 4 Handover Analysis Analysis
Coverage Problems
Signal coverage hole
It is the coverage area where the pilot signal power is lower than the lowest access threshold of a cell phone. Signals are blind in the following areas: elevator shafts, tunnels, underground garages, basements, or huge buildings.
Coverage hole (poor coverage)
It is the coverage area where the pilot signal power is higher than the lowest access threshold of a cell phone but fails to meet the lowest requirements of the full coverage services.
Cross-boundary coverage
The coverage of a certain BTS exceeds the planned. Scattered dominant areas meeting the requirements for full coverage services are formed in the coverage areas of other BTSs.
Coverage hole
Coverage Analysis Coverage problems are common and easy to be addressed during the optimization. Generally, causes of and solutions to poor coverage are as follows: Cause:
2G and 3G communication systems share the same DAS. A few areas of the 2G communication system are not
covered. Solution: Strengthen coverage in the areas. Cause:
The designed power of an antenna port is low.
Solution: Increase the TX power per carrier or the power distribution rate of a pilot channel. Alternatively, you can add the main equipment. Cause:
The shielding of elevator materials is strong.
Solution: Increase the TX power at the antenna ports approximately or add antennas. Cause:
The indoor distributed antenna system (DAS) is faulty. Signal coverage under the antennas is poor.
Solution: Perform troubleshooting in the DAS. Cause:
The active equipment is faul ty or encounters power failures.
Solution: Query the real-time alarm about the main equipment on the M2000. Cause:
The parameter settings are incorrect. As a result, the indoor signals cannot be attached to the indoor cells in time.
Solution: Optimize the parameter settings.
Examples for Poor Coverage Analysis Problem description: The causes of poor coverage in the areas enclosed in red in the following figure are as follows: –
The enclosing wall of the house is not well-built.
–
Part of the outer wall is made of glass.
–
The coverage of indoor antennas fails to meet the requirements.
–
Outdoor signals leak to indoor cells.
Solution: Add antennas to the elevator elevator halls to increase signal coverage. coverage.
Contents Chapter 1 Coverage Analysis Chapter 2 Leakage Analysis Analysis Chapter 3 Interference Analysis
Chapter 4 Handover Analysis Analysis
Leakage The common means to improve indoor effect is to add antennas or increase antenna port power. The side effects of these means are signal leakage and rise of network noise floor. In this case, the signal leakage must be controlled to avoid interference of indoor signals to outdoor ones. Common methods to control signal leakage: 1. Decrease the TX power per carrier or distribution rate of carrier power. It is just a stop gap. 2. Adjust the tributary antenna power or add attenuators on antenna ports. 3. Use panel antennas or directional ceiling mount antennas to implement directional coverage. 4. Adopt the coverage principle of multi-antenna and low power.
Examples for Leakage Analysis 1. Unreasonable DAS design: signal leakage caused by unreasonable antenna types
Problem Description: Signal leakage occurred in a building somewhere, resulting in severe interference to outdoor signals. Operating Process: 1. According to the on-site test, the signals have leaked to the road. When vehicles pass by, handover call drops easily occur. 2. A test performed in the building suggests that the leakage is caused by improper positioning of omni -directional antennas (which are placed near the windows). 3. The problem can be solved by replacing the omni-directional antennas with directional ones.
Directional antenna Omni-directional antenna
Signal leakage drawing before the rectification (The leakage proportion exceeds 3%.)
Signal leakage drawing after the rectification
Examples for Leakage Analysis (Continued) 1. Improper construction: signal leakage caused by the improper installation of directional antennas (Directional antennas must be installed on the walls.)
Problem Description: Signal leakage occurred in a building somewhere, resulting in severe interference to outdoor signals.
Operating Process: 1. According to the on-site test, the signals have leaked to the road. When vehicles pass by, handover call drops easily occur. 2. A test performed in the building suggests that the leakage is caused by improper positioning of omnidirectional antennas (which are placed near the windows). 3. The problem can be solved by installing directional antennas on walls.
The directional antennas must be installed close to pillars or the outer walls to avoid signal leakage.
Directional ceiling mount antenna
Contents
Chapter 1 Coverage Analysis Chapter 2 Leakage Analysis Analysis Chapter 3 Interference Analysis
Chapter 4 Handover Analysis Analysis
Uplink Interference and Downlink Interference
Uplink interference: The received total wideband power (RTWP) of a NodeB rises. If power control is performed, the UE TX power raises; leading to the interference with neighbor cells. If the RTWP is high, the quality of UE uplink deteriorates, and even call drops occur.
Downlink interference: UE background noise rises. The signal-interference ratio (SIR) is decreased. The block error rate (BLER) is relatively large. Power is continuously increased due to power control and the communication quality deteriorates. Call drops occur if the downlink power reaches the upper power threshold.
Uplink Interference (RTWP)
In the WCDMA network, the best way to detect uplink interference is to view the average RTWP of the network running counters. c ounters.
When the network runs properly, the RTWP is about 105.5 dBm when the cells have –
no load. If the average RTWP is about
95 dBm (10 dB RTWP rise compared with the RTWP
–
when a cell has no load) in certain cells, uplink interference occurs in the cells. If the average RTWP is about
85 dBm (20 dB RTWP rise compared with the RTWP
–
when a cell has no load) in certain cells, severe uplink interference occurs in the cells.
Uplink Interference Symptoms
User Experience
Access difficulty: The average access time is relatively long (longer (longer than five seconds). The system system is even inaccessible when the uplink interference is severe. Low voice quality: Voice intermittence, noise, mute, single access, and even call drops may occur.
Symptoms on UEs
The TX power of UEs is continuously high. Signals are displayed on the UEs, but users cannot make phone calls. UEs cannot access the network after a period (about 20 seconds) of attempts. As a result, they go offline and begin to search for the network again.
OMC traffic statistics
The average RTWP of carriers is relatively high (higher than 95 dBm). –
Cause Analysis for Uplink Interference e. External interference Perform simulated loading by transmitting idle Brust. Brust. Change the power level and frequency combination, and view the interference region to locate the interference source. Main causes of uplink interference are as follows:
c. Downlink LA
d. Uplink LA
1) Line amplifier (LA) (uplink and downlink) 70 80% –
2) Combiner
5% to 10%
3) External interference
< 1%
4) BTS intermodulation (IMD)
1% to 2%
5) Connector
5 10%
b. Combiner
–
a. BTS
Interference channel: 1) a (transmitting)-b-a (transmitting)-b-a (receiving) 2) a (transmitting)-b-c-d-b-a (transmitting)-b-c-d-b-a (receiving) 3) e-d-b-a (receiving)
DAS equivalent topology
Cause Analysis for Uplink Interference
During the interference troubleshooting, load 75% of the network downlink to simulate a high load network scenario. In this way, way, you can check the project quality effectively. effectively.
In the 2G communication system, the biggest challenges are LA and repeater. In the 3G (WCDMA/TDMA) system, in addition to the passive DAS, the main equipment used in the network is BBU+RRU. Therefore, the uplink interference proportion of 3G indoor coverage is greatly reduced compared with that of 2G indoor coverage.
The RTWP is High RTWP
higher than 95 dBm in a certain period or for a long time. –
1. Interference caused by the main equipment faults (The receiver is faulty. As faulty. As a result, the transmitting transmitting signals interfere with receiving receiving band and self excitation occurs in t he receiver .) .) 2. If LAs are used, the possible causes of uplink interference are as follows: 1) Some LAs in the DAS are running properly. 2) Too Too many LAs are used in the DAS. 3. The multi-band combiner isolation is insufficient. 4. Poor engineering quality (unqualified jumper connectors: damaged jumper and water water leakage in connectors) connectors) 5. Inter-combiner interference in the DAS 6. External interference
Uplink Interference Troubleshooting 1. Check whether LAs are available in the DAS drawing. If yes, follow step 2. If no, go to step 3. 2. Power off the LAs one by one, and trace the NodeB RTWP in real time. If the RTWP is recovered normally when an LA is powered off, the uplink interference is caused by the LA. Adjust the uplink and downlink gain of the LA to check whether the RTWP is normal. If no, replace the LA. 3. If no LA is used and the coverage is implemented in the BBU+RRU mode, locate the problem by checking the RRU one by one. Power off an RRU, connect the RRU to a load. Check the interference band to see whether the inference occurs on the main equipment or in the DAS. If the main equipment is interfered with, change the RRUs. If the interference occurs in the DAS, disconnect the trunk and branch nodes in the DAS routes. If the RTWP is recovered normally when a node is disconnected, the interference is caused by the node and the following ones. In this case, check the connectors, feeders, and components of the branch cable to locate the interference until the interference is located (according to the preceding troubleshooting experience, the interference is caused by the connectors near the NodeB or the connection states of antenna connectors). 4. If no problem is found in the connection of LAs, connectors, and feeders, check whether spurious GSM signal interference occurs at the combination points of the CDMA/GSM/WCDMA networks. 5. If the preceding problems are not found, check whether external interference exists by using the troubleshooting methods of external interference.
Downlink Interference
For a certain network, the primary task is to solve the coverage problem, and then improve the quality. The prerequisite for improving signal quality is to control the network interference. For the WCDMA network, the main method to control the downlink interference is to solve the pilot pollution.
Common networking models in indoor coverage:
1. Indoor and outdoor intra-frequency networking 2. Indoor and outdoor inter-frequency networking 3. Hybrid networking: high-rise indoor and outdoor inter-frequency networking/low-rise indoor and outdoor intra-frequency networking
Indoor and Outdoor Intra-Frequency Networking Indoor coverage ARFCN F1 Intrafrequ ency soft hand over
Outdoor macro BTS coverage ARFCN F1
Change the handover region
Advantages: The networking model saves the frequency frequency resources, and reserves reserves more space for WCDMA capacity expansion. In addition, the successful rate for indoor and outdoor soft handover is relatively high, and call drop is not easy to occur during the handover. Disadvantages: Indoor and outdoor interference is not easy to control, and the available capacity is smaller than that in the indoor and outdoor inter-frequency networking mode.
Intra-frequency networking is applicable in low-rise buildings where the wireless environment is relatively simple.
Indoor and Outdoor Inter-frequency Networking Dedicated ARFCN for indoor coverage
F2 Interfreque ncy hard hando ver
Outdoor macro BTS coverage ARFCN F1
Change the handover position
Advantages: Indoor and outdoor layered coverage coverage is implemented, implemented, intra-frequency interference is reduced, and QoS and cell capacity is improved. Disadvantages: More ARFCNs ARFCNs are required. Inter-frequency hard handover occurs, which leads to call drops more frequently than soft handover. handover.
Inter-frequency networking is applicable in high-rise buildings w here wireless environment is relatively complicated.
Hybrid Networking Inter-frequency ARFCN ARFCN in high-rise building coverage
F2
Outdoor macro BTS coverage ARFCN F1
Intrafreque ncy soft hando ver
F1
Intra-frequency ARFCN in low-rise building covrage Change the handover region
Advantages: The pilot pollution of high-rise buildings can be cleared in a reasonable way way,, and the network can be adjusted flexibly. Disadvantages: Hard handover exists in the buildings. Call drops may occur if the handover parameters and handover regions are unreasonable.
For high-rise buildings with a large number of users, plan more than two cell coverage areas, and use the hybrid networking mode.
Pilot Pollution Control Generally, the indoor and outdoor intra-frequency coverage networking Generally, mode is used. Therefore, the pilot pollution must be controlled. How to control pilot pollution?
Indoor pollution control principle:
Assisting the strong and suppressing the poor
Indoor pilot pollution caused by outdoor coverage
Methods of pilot pollution control: 1. If the indoor coverage is established, properly enhance the indoor signal strength on the precondition of leakage free. The pilot pollution can be controlled by introducing a strong main pilot. 2. If the indoor neighboring wireless environment is complicated, you are recommended to use the inter-frequency coverage solution to control the pilot pollution effectively. effectively.
The specific solutions are subject to the actual test results.
Pilot Pollution Optimization for High-rise Building Coverage 1. Optimize the macro BTSs on the live network to The coverage strength of multiple sectors in the building is similar and no main pilot exists, resulting in pilot pollution.
enable one of the macro BTSs to dominate the indoor coverage.
Common optimization methods •
Antenna adjustment
•
Power adjustment
•
Changing the antenna feeder setting
Limitations: •
•
•
The pilot pollution cannot be controlled completely Heavy workload is involved The outdoor coverage is involved. Therefore, the adjustment is difficult.
Pilot Pollution Optimization for High-rise Building Coverage 2. Introduce indoor coverage, and establish DAS.
CELL 1
Limitation: For some indoor regions, the outdoor signal is strong and cannot be suppressed by indoor coverage.
Pilot Pollution Optimization for High-rise Building Coverage 3. Add outdoor sectors to dominate indoor coverage.
DAS cannot be established in certain important buildings because of the investment and property problems.
For ordinary buildings and the bottom of high-rise buildings, the problem can be solved by BTS signal penetration.
Interference is difficult to control.
Antenna tilt
Pilot Pollution Optimization for High-rise Building Coverage 4. Rectify unreasonable DAS.
The antenna location is unreasonable.
The indoor coverage power is low.
Avoid signal leakage when strengthening coverage coverage to prevent the indoor coverage from affecting the outdoor coverage.
Optimize the neighboring list.
Multi-antenna and low-power design
Limitations: The rectification of antenna feeders is complicated. The rectification is restricted by property owners. No all problems are solved. •
Install directional antennas near the windows
• •
Contents
Chapter 1 Coverage Analysis Chapter 2 Leakage Analysis Analysis Chapter 3 Interference Analysis
Chapter 4 Handover Analysis Analysis
Handover Analysis
Indoor coverage: In a good DAS, the coverage is strong, the uplink and downlink
interference is solved, and the signal leakage is controlled. The follow-up operation is to combine the indoor coverage and outdoor coverage.
Two problems involved: Cell
reselection in idle state
Handover
in busy state
Cell Reselection
Cell resident principle
To make the indoor coverage absorb traffic efficiently, indoor users must reside indoor. Set the cell reselection offset, ConnQoffset1sn and
ConnQoffset2sn. By doing this, the users can preferentially select the indoor coverage. The parameter cannot be set too large; otherwise, the outdoor users will hold the indoor signals, leading to the call failure. Therefore, the parameter configuration must be adjusted according to the actual situations.
Handover Analysis Two aspects are involved in handover:
Handover among cells (especially elevator handover)
Indoor and outdoor handover (hall exit and entrance handover and parking lot handover)
Where does indoor handover occur?
Handover policy in different scenarios
Windows on different floors Elevator entrance and staircase
Hall exit and entrance
Parking slot exit and entrance
Elevator Handover Setting
Elevator
cell division Elevator shaft Cell 2
For scenarios where coverage is divided according to floors, unify the coverage of elevators by using high-rise cell or lowrise cell coverage.
f3
Outdoor cell
f1
Elevator
f1 Cell 1
Elevator Handover Setting Elevator
room handover
Elevator coverage technology: Use the panel antennas in a reasonable way and implement split-level coverage. Implement split-level coverage by using panel antennas to enable the uniform coverage of signals. Set the handover region in the elevator room and expand the handover region. In addition, to improve the success rate of the handover, especially in the inter-frequency coverage scenarios, the 2D/2F event threshold must be improved, and the handover must be triggered as quickly as possible. The handover region must be expanded to the elevator rooms.
Indoor and Outdoor Handover — Hall Exit/Entrance Handover
h I n a t n r d a o f r v e e q r u e n c y s o f t
Parameter optimization handover region
h I n a t r e d r h f r a e n q d u o e v n e c r y
Change the handover region The diameter of the indoor and outdoor soft handover is about 3 m 5 m. –
Configure the handover region of the hall entrance three to five meters away from the doorway by adjusting parameter settings. Do not configure the handover region on the streets or the trunks.
Change the handover position
The diameter of the indoor and outdoor hard handover is about 3 m 5 m. –
Handover Analysis 1. Call drops caused by indoor and outdoor handover: In an indoor and outdoor transition handover region (the building entrance), when the indoor and outdoor cells are intra-frequency or inter-frequency neighboring cells, call drops may occur. The success rate of inter-frequency hard handover is lower than that of the inter-frequency soft handover. Therefore, the call drop rate increases.
Solutions: For intra-frequency neighboring cells, install antennas near the windows to ensure the inward coverage; therefore, the reasonable handover regions are set. For i nter-frequency neighboring cells, adjust the handover parameters and set the size of handover regions. Missing configuration of neighboring cells is a fundamental problem in neighboring optimization. For intra-frequency networking, call drops easily occur when the configuration of neighboring cells is missed. Therefore, neighboring cell check is significant in intra-frequency high-rise coverage. For inter-frequency networking, configure a single neighboring cell in high-rise coverage to suppress ping-pong handover and hold users indoor.
Handover Analysis
2. Call drops when going into or getting out the elevators In a DAS, one floor or several floors are a cell. Cells in and out of an elevator may not be the same. In this case, soft handover occurs when you get in or out of the elevator. Especially when the door is closed, call drops may occur when the handover cannot be performed in time.
Solutions: Optimize the handover parameters in cells to improve the success rate of the soft handover and the latency. Main parameters involved in the software handover are threshold, hysteresis, triggering time latency, interfrequency hard handover enabling, and compressed mode threshold disabling.
Coverage
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