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Part5 Indoor Coverage Optimization

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HUAWEI TECHNOLOGIES CO., LTD. www.huawei.com HUAWEI Confidential Security Level: Indoor Coverage Optimization ISSUE1.0 Internal use only
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Page 1: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

HUAWEI Confidential

Security Level:

Indoor Coverage Optimization

ISSUE1.0

Internal use only

Page 2: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential Page 2

Contents

Chapter 1 Coverage Analysis

Chapter 2 Leakage Analysis

Chapter 3 Interference Analysis

Chapter 4 Handover Analysis

Page 3: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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 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.

Page 3

Page 4: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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 faulty 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.

Page 4

Page 5: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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 halls to increase signal coverage.

Page 5

Page 6: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Contents

Chapter 1 Coverage Analysis

Chapter 2 Leakage Analysis

Chapter 3 Interference Analysis

Chapter 4 Handover Analysis

Page 6

Page 7: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Page 7

Page 8: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Signal leakage drawing before the rectification

(The leakage proportion exceeds 3%.) Signal leakage drawing after the rectification

Omni-directional antenna

Directional antenna

Page 8

Page 9: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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 omni-

directional antennas (which are placed near the windows).

3. The problem can be solved by installing directional antennas on walls.

Directional ceiling mount antenna

The directional antennas must be installed close to

pillars or the outer walls to avoid signal leakage.

Page 9

Page 10: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Contents

Chapter 1 Coverage Analysis

Chapter 2 Leakage Analysis

Chapter 3 Interference Analysis

Chapter 4 Handover Analysis

Page 10

Page 11: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Page 11

Page 12: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

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.

Page 12

Page 13: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Uplink Interference Symptoms

User Experience

Access difficulty: The average access time is relatively long (longer than five seconds). The 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).

Page 13

Page 14: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Cause Analysis for Uplink Interference

Perform simulated loading by transmitting

idle 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:

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% a. BTS

b. Combiner

c. Downlink

LA d. Uplink LA

e. External interference

Interference channel:

1) a (transmitting)-b-a (receiving)

2) a (transmitting)-b-c-d-b-a

(receiving)

3) e-d-b-a (receiving)

DAS equivalent topology

Page 14

Page 15: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Cause Analysis for Uplink Interference

High RTWP

The RTWP is

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 a result, the transmitting signals interfere with receiving

band and self excitation occurs in the 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 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 leakage in connectors)

5. Inter-combiner interference in the DAS

6. External interference

During the interference troubleshooting, load 75% of the network downlink to simulate a high

load network scenario. In this way, you can check the project quality 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.

Page 15

Page 16: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Page 16

Page 17: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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

Page 17

Page 18: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Indoor and Outdoor Intra-Frequency Networking

Change the handover

region

F1

Indoor coverage ARFCN

F1

Outdoor macro BTS

coverage ARFCN

Intra-

frequ

ency

soft

hand

over

Advantages: The networking model saves the frequency resources, and 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.

Page 18

Page 19: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Indoor and Outdoor Inter-frequency Networking

Advantages: Indoor and outdoor layered coverage is implemented, intra-frequency interference is reduced, and QoS and cell

capacity is improved.

Disadvantages: More ARFCNs are required. Inter-frequency hard handover occurs, which leads to call drops more frequently

than soft handover.

Inter-frequency networking is applicable in high-rise buildings where wireless environment is relatively complicated.

Change the handover

position

F2

Dedicated ARFCN for indoor coverage

F1

Outdoor macro BTS

coverage ARFCN

Inter-

freque

ncy

hard

hando

ver

Page 19

Page 20: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Hybrid Networking

Advantages: The pilot pollution of high-rise buildings can be cleared in a reasonable 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.

Change the handover

region

F2

Inter-frequency ARFCN in

high-rise building coverage

F1

Outdoor macro BTS

coverage ARFCN

F1

Intra-frequency ARFCN in

low-rise building covrage

Intra-

freque

ncy

soft

hando

ver

Page 20

Page 21: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Pilot Pollution Control

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.

Indoor pollution

control principle:

Assisting the strong and

suppressing the poor

Generally, the indoor and outdoor intra-frequency coverage networking

mode is used. Therefore, the pilot pollution must be controlled.

The specific solutions are subject to the actual test results.

Indoor pilot

pollution caused

by outdoor

coverage

How to control

pilot pollution?

Page 21

Page 22: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

1. Optimize the macro BTSs on the live network to

enable one of the macro BTSs to dominate the indoor

coverage.

The coverage strength of multiple sectors

in the building is similar and no main pilot

exists, resulting in pilot pollution.

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

Page 22

Page 23: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

2. Introduce indoor coverage, and establish DAS.

Pilot Pollution Optimization for High-rise

Building Coverage

CELL 1

Limitation:

For some indoor regions, the

outdoor signal is strong and

cannot be suppressed by indoor

coverage.

Page 23

Page 24: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Pilot Pollution Optimization for High-rise

Building Coverage

3. Add outdoor sectors to dominate indoor coverage.

Antenna tilt

Page 24

Page 25: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

The antenna location is unreasonable.

The indoor coverage power is low.

Avoid signal leakage when strengthening coverage to prevent the

indoor coverage from affecting the outdoor coverage.

Optimize the neighboring list.

Multi-antenna and low-power design

4. Rectify unreasonable DAS.

Pilot Pollution Optimization for High-rise

Building Coverage

Install directional antennas

near the windows

Limitations:

• The rectification of antenna feeders is

complicated.

• The rectification is restricted by property owners.

• No all problems are solved.

Page 25

Page 26: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Contents

Chapter 1 Coverage Analysis

Chapter 2 Leakage Analysis

Chapter 3 Interference Analysis

Chapter 4 Handover Analysis

Page 26

Page 27: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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

Page 27

Page 28: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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.

Page 28

Page 29: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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)

Hall exit and

entrance

Elevator entrance and

staircase Parking slot exit

and entrance

Windows on

different floors

Where does

indoor handover

occur? Handover policy in

different scenarios

Page 29

Page 30: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Elevator Handover Setting

For scenarios where

coverage is divided

according to floors, unify the

coverage of elevators by

using high-rise cell or low-

rise cell coverage.

Elevator cell division

Cell 1

Cell 2

Outdoor cell

Elevator

Elevator

shaft

f1

f3

f1

Page 30

Page 31: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Elevator Handover Setting

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.

Elevator room handover

Page 31

Page 32: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Indoor and Outdoor Handover — Hall Exit/Entrance Handover

Change the

handover

region

Intra

-freq

ue

ncy s

oft

ha

nd

ove

r

Inte

r-freq

ue

ncy

hard

hand

over

Change the

handover position

Parameter optimization

handover region

The diameter of the indoor and outdoor

soft handover is about 3 m–5 m. The diameter of the indoor

and outdoor hard 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.

Page 32

Page 33: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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 inter-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.

Page 33

Page 34: Part5 Indoor Coverage Optimization

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

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, inter-

frequency hard handover enabling, and compressed mode threshold disabling.

Page 34 Coverage

Analysis

Page 35: Part5 Indoor Coverage Optimization

Thank you

www.huawei.com


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