JOIN OUR iBwave USERGROUP ON LINKEDIN
WE WILL BE POSTING ANSWERS TO THE QUESTIONS WE RECEIVE DURING THE WEBINAR ON
iBwave’s In-Building Talks Webinar Series
PIM: IN-BUILDING SYSTEM DESIGN &
INSTALLATION STRATEGIES FOR LTE
SPECIAL GUEST:
JULY 17, 2013
• THE STANDARD for in-building network design and documentation
• LEADING TECHNOLOGY & FIRST MOVER in a dynamic and fast-growing wireless market
• 9-YEAR-OLD Canadian company – privately held
• PRESENCE in all Americas, Europe, Middle-East, Africa, Asia and Oceania
• TRUSTED BY 500+ CUSTOMERS in more than 80 countries
Phillip Chan Manager, InBuilding System Design
Rogers
ABOUT Rogers is a diversified Canadian communications and media company. They are one of Canada's largest provider of wireless voice and data communications services and one of Canada's leading providers of cable television, high speed internet and telephony services. Rogers is publicly traded on the Toronto Stock Exchange and on the New York Stock Exchange. www.rogers.com
John Beadles System Designer
Rogers
Marc Beranger Senior RF Interference Specialist
Rogers
IN-BUILDING SYSTEM DESIGN STRATEGIES FOR LTE
Phillip Chan, Manager, Wireless In-Building System Design
July 17, 2013
Introduction
PIM is a self-generated noise typically caused by defects in the antenna
system, and by interactions of antennas with nearby objects
This noise causes: Reduced capacity
Reduced coverage
Slower data speed
Dropped calls
Shorter battery life
In-building DAS systems All channels run on the same antennas and cables
Need for higher capacity, new technologies and DAS system sharing with
other operators result in potential PIM problems
Frequency planning to avoid PIM is no longer viable
This drives the requirement to minimize PIM noise
What is Passive Intermodulation?
Passive Intermodulation noise is the by product when radio signals mix
These products are combinations of sum and difference of the signals The center frequency of these resulting products are mathematically
predictable
However, as the number of signals increase, the number of products
increase significantly
PIM is not related to return loss, VSWR or insertion loss!!! It cannot be detected by sweeps
PIM Noise Products
0 MHz Increasing FrequencyTX BandRX Band
b-a
2nd
Order
2a-b
3rd
Order
2b-a
3rd
Order
2b-2a
4th Order
3b-3a
6th Order
3a-2b
5th Order
4a-3b
7th
Order 3b-2a
5th Order
4b-3a
7th
Order
Actual PIM product amplitude cannot be predicted Varies on a case by case basis
Decreases with the order of product
PIM product bandwidth is proportional to the order and the bandwidth
of the fundamental frequencies 3rd order BW is three times the bandwidth of the fundamental
5th order BW is five times the bandwidth of the fundamental
Common Sources of PIM
Poor connector assembly Improper installation Damaged connector face Loose connections due to under torque
Metallic particles contamination In the plenum cable In the connector assembly In the connector face
Damaged cable Cut or broken conductor Damage to plating
Damaged antenna Broken pigtail Damaged connector face
Antenna Interacting with environment Rusty bolt effect
Manufacturing defects Bad solder joints Poor choice of materials
Physical damage Improper torque applied Forced fit
Why is PIM important for LTE?
LTE system link budget is based on Resource Block (RB)
One RB = 180 kHz (12 Sub Carriers X 15 kHz each)
Thermal Noise of one RB = -121dBm
Assuming eNode B receiver Noise Figure = 2dB, receiver sensitivity = -
119dBm
Any PIM Noise generated in the DAS has to be significantly lower than -
119dBm to not degrade receiver sensitivity
Required PIM Noise << -119dBm
LTE Uplink SINR vs. Throughput
SINR (dB) 10MHz UL Through Put (Mbps)
0 4.1
1 4.8
2 5.6
3 6.5
4 7.4
5 8.5
6 9.5
7 10.7
8 11.8
9 13.0
10 14.2
11 15.4
12 16.6
13 17.7
14 18.8
15 19.7
16 20.5
17 21.2
18 21.8
19 22.2
20 22.4
High SINR required for LTE UL
Performance LTE UL data throughput is much more
superior than HSPA UL
Requires significant higher SINR than
HSPA
Any degradations in receiver sensitivity
impacts throughput
DAS system needs to have good PIM
performance to get full benefit of LTE
Note: the above table is based on simulation, and it is only for
illustration purposes.
Strategies to Meet LTE PIM Performance Requirement?
Mitigate PIM Problems
Apply DAS design strategies to mitigate PIM problems
Achieve PIM Performance Requirements Follow installation and testing procedures to improve DAS construction, and
to achieve PIM performance
Strive for Success and Doing it Better Apply real life experiences and learning from installation work
Enhance / revise design strategies, and installation and testing procedures
when applicable
Share knowledge and experiences with the industry, and get feedback from
other indoor DAS solution integrators and operators
Influence the industry to further develop DAS products and testing equipment
to facilitate “doing it better”
Types of DAS: Hi Power Active DAS 20W or more
Requires less number of remote
amplifiers
Noise Figure from the active DAS
components usually does not
require high UL attenuation to
mask the active DAS noise
Passive DAS PIM performance
is important
Types of DAS: Med Power Active DAS ~28dBm
Requires greater number of remote amplifiers than hi power active
DAS
Likely need more UL attenuation to mask the active DAS noise
Passive DAS PIM performance could be more relaxed due the
required UL attenuation
Types of DAS: Low Power Active DAS ~20dBm
Requires large number of remote amplifiers
Noise Figure from the active DAS components does require
high UL attenuation to mask the active DAS noise
Passive DAS PIM performance is usually not a concern due to the
high UL attenuation
Types of DAS: Passive DAS
Passive DAS PIM
performance is very
important!
Radio Base Station directly
drives the passive DAS
Why not only deploy Low Power Active DAS?
High UL attenuation required to mask active
DAS component noise may also have a
significant negative impact on the UL SINR
To maintain acceptable DL and UL path loss in-
balance, base station needs to be interfacing
the active DAS at much higher power. This
places a huge demand on the required power
handling and PIM performance of the radio base
station interface equipment
Low Power Active DAS Uplink SINR Calculation Passive DAS Uplink SINR Calculation
Downlink Overall Path Loss Downlink Overall Path Loss
RBS Output Power 35dBm RBS Output Power 35dBm
CPICH Output Power 25dBm CPICH Output Power 25dBm
DAS Losses 0.0dB DAS Losses 25.0dB
Remote Antenna ERP 10.0dBm Remote Antenna ERP 10.0dBm
Remote Antenna CPICH ERP 0.0dBm Remote Antenna CPICH ERP 0.0dBm
CPICH Threshold -75dBm CPICH Threshold -75dBm
Pathloss (Antenna to UE) 75.0dB Pathloss (UE to Antenna) 75.0dB
Overall Pathloss 100dB Overall Pathloss 100dB
Uplink Overall Path Loss Uplink Overall Path Loss
Pathloss (UE to Antenna) 75.0dB Pathloss (UE to Antenna) 75.0dB
DAS Losses 0.0dB DAS Losses 25.0dB
DAS UL Noise Figure 39.3dB 85 Remote units DAS UL Noise Figure 0.0dB
DAS UL Gain 0.0dB DAS UL Gain 0.0dB
Rx Sensitivity -119.0dBm Rx Sensitivity -119.0dBm
DAS Noise from Uplink -81.7dBm DAS Noise from Uplink N/A
Required Attenuation 43dB Required Attenuation N/A
DAS Noise Level after Attenuation -124.7dBm
DAS Noise Level after Attenuation N/A
Overall Uplink Pathloss 118dB Overall Uplink Pathloss 100dB
UL and DL Path Inbalance 18dB UL and DL Path Inbalance 0.0dB
DAS Uplink Noise Figure Calculation
Noise Figure per Remote 20dB For 1 Remote
Noise Figure ALL Sectors 39.3dB For 85 Remotes
Uplink Gain ALL Sectors 0.0dB
Uplink Noise Power -81.7dBm
Low Power Active DAS Uplink SINR Calculation Passive DAS Uplink SINR Calculation
UE Tx Level Total 23.0dBm UE Tx Level Total 23.0dBm
UE Tx Level per RB 6.0dBm UE Tx Level per Subcarrier 6.0dBm
Uplink Pathloss 118dB Uplink Pathloss 100dB
UE Rx Level at RBS per RB -112.0dBm UE Rx Level at RBS per RB -94.0dBm
Uplink RX Noise Level -118.0dBm Uplink RX Noise Level -119.0dBm
Uplink SINR per RB 6.0dB Uplink SINR per RB 25.0dB
Uplink Datarate 9.5 Mbps Uplink Datarate 22.4 Mbps
Common Denominator: Passive DAS
How do we achieve the LTE PIM performance requirement with
the passive DAS??
Design Strategies to Mitigate PIM Problems
Use PIM rated and proven DAS components See following slide for details
Keep transmit power low See following slide for details
Use simple and intuitive DAS vertical and horizontal topologies See following slides for details
Established DAS component naming convention Allow creation of automated testing spreadsheets based on component
naming
Standardized naming convention promotes common understanding of the
DAS for the designers, installers and field operation and maintenance staff
DAS System PIM and Return Loss Performance Targets
System Construction Targets 850MHz: System PIM ≤ -114dBm @ 2 X +25dBm
1900MHz: System PIM ≤ -127dBm @ 2 X +35dBm
System Return Loss ≥ 14dB
System Sharing Acceptance Targets 850MHz: System PIM ≤ -108dBm @ 2 X +25dBm
1900MHz: System PIM ≤ -121dBm @ 2 X +35dBm
System Return Loss ≥ 14dB
Difference in construction and acceptance targets allows margin to
ensure that the system will continue to meet the acceptance target as
the DAS ages
Use PIM Rated and Proven DAS Components
Use DIN connector as much as possible instead of N-Type Will be further discussed in an upcoming slide
Lab experiments Rusty bolt effect
Component testing
Manufacturer collaboration Connector design and installation
Multi-band combining solution
Installer feedback Part of establishing DAS component “proven” performance
Typical passive DAS RF Component PIM Specs Splitter, combiners, connectors, and cables ≤ -155dBc @ 2 X 43dBm
Indoor antennas are subjected to real life environment testing as the
manufacturer PIM spec is very different when testing in real life environment
DAS head end multi-band combining solution ≤ -162dBc @ 2 X 35dBm
Keep Transmit Power Low
Radio Base Station output power = 35dBm composite per channel Typical minimum passive component PIM spec is -150dBc @ 2 x 43dBm.
Assuming 2.5dB roll off, the PIM response at 2 X 35dBm is estimated to be -
127dBm
Lower power handling passive components could be used
Max power into the antenna = 15dBm composite per channel Significantly minimizes the rusty bolt effects when antenna interacts with its
environment
Typical design power is about 10dBm composite per channel, dependent on
size of coverage area and environment in terms of rusty bolt effect
Vertical Design – Organized by Floor
Organized vertically and horizontally
Construction and testing could be done on a per floor basis
Fault isolation on a per floor level can begin in the equipment room
1st Floor
2nd Floor
3rd Floor
4th Floor
5th Floor
6th Floor
Vertical Design – Not Organized by Floor
Not organized vertically or horizontally
Construction and testing cannot be done on a per floor level
Fault isolation will require a lot of test equipment movement, possible access issues
Difficult to maintain from a Field Operation and Maintenance point of view
1st Floor
2nd Floor
3rd Floor
4th Floor
5th Floor
6th Floor
Horizontal Design – Organized for Testing
Centralized location of splitter components
Can provide fault isolation to the branch level, depending on design
Minimizes the amount of test set movement, therefore less test labor time
Horizontal Design – Not Organized for Testing
Decentralized location of splitter components
Maximizes the amount of test set movement, therefore more test labor time
Many cascaded components increase the points of failure for the floor
DAS TEST PROCEDURES AND REPORTING
John Beadles, System Designer, Rogers Communications
July 17, 2013
Goals for Testing
Goals for Testing Thoroughly test and exercise new DAS systems before acceptance
Prove that the system is being constructed properly Prove that the system passes PIM at acceptance Provide evidence that it will continue to pass in the future Prevent hidden quality control problems from popping up at the last minute
Get projects done on schedule, on budget Make the projects predictable So that they can be controllable Then cost controls can be implemented
Challenges Local contractors have little prior PIM testing experience Some contractors have little or no cellular construction experience at all Contractors not typically experienced with handling a lot of test data Need to streamline the testing process
Make it flow as much as possible so that milestones can be met Make no assumptions about previous contractor experience
Test requirements need to be flexible enough to accommodate all project types
Organized so that connector damage caused by testing is minimized
Types of Tests
PIM Testing Proves that the system is free of defects that would cause self-generated
noise back into the receivers
Return Loss Testing Ensures that the TX power doesn’t get reflected back toward the transmitter
Prevents early transmitter failure
Ensures that RF power actually contributes to coverage
Insertion Loss Testing Verifies that the correct power tappers are installed
Verifies that the power tappers facing the correct direction
Ensures that each antenna will see the correct TX power
Distance to Fault Testing Provides individual cable lengths
Finds damaged cables
Helps prove that the contractor is building the system as designed
Test Procedure (Antenna & Individual Cable)
Pre-Install Antenna Testing PIM Test Ensures that the environment around the antenna won’t contribute to failing
PIM at the antenna
Post Install Antenna Testing PIM Test Return Loss Test Ensures that the antenna performs properly in the installed position, and that
the antenna VSWR won’t prevent the antenna from covering the area properly
Individual Cable Testing PIM Test Return Loss Test Distance to fault Ensures that each cable meets a standard quality spec Helps remove the cables as a source of problems when debugging other
issues Ensures that the cable is close to the length the system designer intended
Pre- and Post- Install Antenna Testing
Pre-Install antenna testing uses an antenna on a stick to verify the PIM
environment in the area around which the antenna will be mounted
Post-Install antenna testing proves the antenna at that particular location
These tests have been a key to getting good antenna performance
System, Floor, Branch Level Components
Syst
emC
om
bin
er
Rad
ioR
adio
Rad
io
Floor 1
Floor 2
Floor 3
Floor 4
Floor 5
Floor 6
System Combiner Level Components
System Level Components
(multiple floors)
Floor Level Components(1 per floor)
Branch Level Components(multiple per floor, feeds antennas, no
more than 5 antennas per branch)
Riser Room
Test Procedure (Branches)
Branch Construction Test PIM test set attached to the entry point of the branch Low PIM terminations in place of antennas Test pass level -150 dBc @ 2x 43dBm when all jumpers and combiners are
attached. This test proves that the branch cabling is defect free
Branch Insertion Loss Test Signal generator attached to the entry point of the branch Power measurement taken at the output of each antenna jumper and is
compared to a predicted value. This test detects improperly installed power splitters and tappers. Also finds contractor “modifications” Antennas attached to each jumper after each test is complete
Branch Antenna PIM Test PIM test set attached to the entry point of the branch. Test is taken with all antennas attached PIM test power is set to the system design power at that point
Minimizes environmental PIM between the antennas and their surroundings
Pass/fail is set to a dBm value based on receiver threshold, construction margin
Branch Construction & Testing
PIM Tester
S49-1 S49-2 S49-3C49-103
C4
9-1
04
C4
9-1
05
C49-101FloorFeeder
C49-102
C4
9-1
06
C4
9-1
07
S49-1 S49-2 S49-3C49-103
C4
9-1
04
C4
9-1
05
C49-101FloorFeeder
C49-102
C4
9-1
06
C4
9-1
07
Signal Generator
PIM Tester
S49-1 S49-2 S49-3C49-103
C4
9-1
04
C4
9-1
05
C49-101FloorFeeder
C49-102
C4
9-1
06
C4
9-1
07
Branch constructed and terminated
with low PIM loads. Construction PIM
test performed.
Branch Antenna PIM test performed
with all antennas attached. If it
passes, testing is complete on this
branch and no other disconnects are
allowed.
Stepwise insertion loss testing
performed at each antenna
connector, then the antenna is
attached. Power
Meter
Floor / Branch Organization
Each floor organized into a floor combiner network with multiple branches
Each branch, and the floor divider network, are tested as a unit
Minimizes the number of expensive low PIM test terminations that the
contractor must purchase
SPT G2-3-3
SPT G2-3-8
SPT G2-3-12 SPT G2-3-5SPT G2-3-4 SPT G2-3-7 SPT G2-3-9 SPT G2-3-1
SPT G2-3-6 SPT G2-3-2
SPT G2-3-10 SPT G2-3-11
C G2_3-25
C G
2_3
-21
C G
2_3
-22
C G
2_3
-23
C G
2_3
-54
C G
2_3
-86
C G
2_3
-85
C G
2_3
-24
C G
2_3
-83
C G
2_3
-28
C G
2_3
-32
C G
2_3
-36
C G
2_3
-37
C G
2_3
-35
C G
2_3
-34
C G
2_3
-31
C G
2_3
-55
C G
2_3
-56
C G
2_3
-29
C G2_3-82 C G2_3-26
C G
2_3
-27
C G2_3-33 C G2_3-28
ANT G2_3-11
ANT G2_3-6 ANT G2_3-8 ANT G2_3-13 ANT G2_3-14 ANT G2_3-1
ANT G2_3-7 ANT G2_3-2 ANT G2_3-5
ANT G2_3-12 ANT G2_3-15 ANT G2_3-9 ANT G2_3-3ANT G2_3-14ANT G2_3-10
PIM Tester
Branch 1
Branch 2
Branch 3Branch 4
Branch 5
Floor Divider Network
Test Procedure (Floor & System Level)
Floor Testing Insertion Loss Test
Return Loss Test
PIM Test
These tests, from the first unique floor level cable, ensures that all cables
and passive devices, are installed correctly and functioning properly
System (Sector) Testing Insertion Loss Test
Return Loss Test
PIM Test
Ensures that the entire system, with the exception of the combiner, is
working and that all system level cables and passive components are
installed correctly and functioning properly
System Combiner Testing PIM Test (Each Input)
Verifies that the combiner and assorted inputs are working
Project Acceptance
Performed by Rogers Personnel Maximum accountability
Eliminates communications problems with the contractor
System level PIM test Or performed by contractor while being observed by Rogers auditor
System level return loss test Or performed by contractor while being observed by Rogers auditor
Coverage testing Verify that all antennas are covering properly
Finds accidental system disconnects
Delivery of all test results from contractor Reviewed & approved by the system designer
Contractor Deliverables
Completed test spreadsheet All values must pass
Or have variances accepted by Rogers
PIM test measurements Screen shots (compiled into PDF)
Return loss measurements Screen shots (compiled into PDF)
Data file (.DAT, .VNA)
Distance to fault measurements Screen shots (compiled into PDF)
Data file (.DAT, .VNA)
Photographs Pre, post antenna location
Floor diagram markups
Automated Test Spreadsheet
Custom Developed by Rogers Identifies each test required from the contractor Used by project manager to cost out the testing Used by the contractor to define test parameters, collect test data Used by the system designer for QC monitoring, acceptance
Created by the system designer, custom for each project
Loaded by importing iBwave reports using Excel macros iBwave Link Budget Report
Provides insertion loss at any point Used to test power at each test point
iBwave Cable Routing Report Provides the cable lengths, connection points Used to calculate branch, system topology
Custom excel macro Generates one worksheet per test type Recalculates test powers based on desired test frequency Generates custom PIM test powers depending on design power Generates predicted insertion losses for branch, floor and system level tests Provides logic for pass/fail color coding for each test
Each worksheet contains: Sector, floor and Test Point ID Test powers Pass levels Predicted line lengths Insertion losses
From iBwave to the Automated Test Spreadsheet
iBwave Cable Routing Report
iBwave Link Budget Report Rogers Automated Test Spreadsheet
iBwave
Import
Examples of Antenna & Cable Worksheets
Post-install Antenna Worksheet
RF Cable Worksheet
Pre-install Antenna Worksheet
Test
Cable Attn
(dB)
Test Pwr
(dBm)
Test Pim
(dBm)
Pass
Level
(dBm)
1 Ground Floor AP-A-01A 16 -114 5 21 -136.1 -119
1 Ground Floor AP-A-01B 15 -114 5 20 -139.2 -119
1 Ground Floor AP-A-02A 15 -114 5 20 -134.1 -119
1 Ground Floor AP-A-02B 15 -114 5 20 -128.5 -119
1 Ground Floor AP-A-03A 15 -114 5 20 -130.6 -119
Antenna Placement Test
Sector Floor Test IDDesign
Pwr (dBm)
850 PIM
Pass
Level
(dBm)
850 Mhz PIM Test
Sweep-RL (dB)
Test
Cable Attn
(dB)
Test Pwr
(dBm)
Test Pim
(dBm)
Pass
Level
(dBm)
Test
Cable Attn
(dB)
Test Pwr
(dBm)
Test Pim
(dBc)
Pass Level
(dBm)698-2700 mHz
1 Ground Floor A-01A 16 15 -114 -127 5 21 -129.5 -119 5 20 -133.7 -132 15.23
1 Ground Floor A-01B 15 15 -114 -127 5 20 -121.9 -119 5 20 -133.9 -132 17.74
1 Ground Floor A-02A 15 15 -114 -127 5 20 -124.2 -119 5 20 -133.7 -132 13.11
1 Ground Floor A-02B 15 15 -114 -127 5 20 -131.1 -119 5 20 -135 -132 17.45
1 Ground Floor A-03A 15 15 -114 -127 5 20 -132.8 -119 5 20 -133.8 -132 17.77
Sector
Installed Antenna Test Installed Antenna Test
Floor Test ID
Design
Pwr 850
(dBm)
Design
Pwr 2100
(dBm)
850 PIM
Pass
Level
(dBm)
2100 PIM
Pass
Level
(dBm)
850 Mhz PIM Test 2100 MHz PIM Test
850 MHz (2x43 dBm) 2100 MHz (2x 43 dBm) Design Plan Cable Predicted IL (dB) Measured IL (dB)
Sector Floor RF-Cable-ID Return Loss (dB) Length (meters) High Pim (dBc) High Pim (dBc) Length (meters) 2110 MHz 2110 MHz
1 Ground Floor C1-44 34.20 2.63 -162.4 -155.7 10.00 1.6 0.46
1 Ground Floor C1-40 30.66 0.31 -158.9 -165.90 2.00 0.6 0.08
1 Ground Floor C1-48 35.85 0.50 -164.3 -162.5 2.00 0.6 0.12
1 Ground Floor C1-39 32.55 4.96 -158.3 -151.1 5.00 1.0 0.66
1 Ground Floor C1-42 29.18 0.01 -156.9 -157.7 2.00 0.6 0.16
1 Ground Floor C1-43 33.26 6.87 -151.8 -167.9 5.00 1.0 0.87
1 Ground Floor C1-46 35.52 1.00 -158 -164.5 2.00 0.6 0.19
1 Ground Floor C1-47 37.96 0.06 -158.3 -158.4 2.00 0.6 0.12
Sweep Test (1710-2155 MHz)
Test ID specifies the
particular antenna. The
“AP” prefix is used to
separate PIM test
screen shots
Test ID specifies the
cable
Examples of Branch Worksheets
Branch Construction PIM Worksheet
Branch Antenna PIM Worksheet
Branch Insertion Loss Worksheet
850 MHz (2x43 dBm) 2100 MHz (2x 43 dBm)
Sector Floor Test ID High Pim (dBc) High Pim (dBc)
1 Ground Floor BP-C1-9 -153.2 -150.9
1 Ground Floor BP-C1-19 -158.2 -153.3
1 Ground Floor BP-C1-10 -160 -165.3
1 Ground Floor BP-C1-23 -171 -166.1
1 Ground Floor BP-C1-27 -167.5 -165.4
1 Ground Floor BP-C1-40 -170.9 -154.3
1 Ground Floor BP-C1-28 -162.1 -165.6
1 Ground Floor BP-C1-46 -158.3 -152.5
Measured
Insertion
Loss (dB)
Predicted
Insertion
Loss (dB)
Sector Floor Test ID 2110 MHz 2110 MHz
1 Ground Floor BI-C1-9-C1-6 12.32 11.55
1 Ground Floor BI-C1-19-C1-20 12.40 11.55
1 Ground Floor BI-C1-9-C1-50 12.56 12.12
1 Ground Floor BI-C1-19-C1-11 12.06 12.31
1 Ground Floor BI-C1-9-C1-49 10.22 10.37
1 Ground Floor BI-C1-19-C1-26 9.90 10.57
Sector Floor Test ID
Test
Power
(dBm)
Test PIM
(dBm)
Pass
Level
(dBm)
Test
Power
(dBm)
Test PIM
(dBm)
Pass
Level
(dBm)
1 Ground Floor BAP-C1-9 15 -131.2 -114 26 -133.6 -127
1 Ground Floor BAP-C1-19 15 -130.3 -114 26 -127.4 -127
1 Ground Floor BAP-C1-10 15 -130.4 -114 23 -128.1 -127
1 Ground Floor BAP-C1-23 15 -129.9 -114 23 -127 -127
1 Ground Floor BAP-C1-27 15 -98.2 -114 15 -100.2 -127
1 Ground Floor BAP-C1-40 15 -129.8 -114 15 -121.8 -127
850 MHz PIM Test 2100 MHz PIM Test
Test ID specifies the
jumper entering the
branch, exiting the
jumper facing an
antenna
Test ID specifies the
jumper entering that
branch. All antenna
jumpers are terminated
with low PIM loads.
Test ID specifies the
jumper entering that
branch. All antennas
are installed at this
point.
Examples of Floor Worksheets
Measured Insertion Loss (dB) Predicted Insertion Loss (dB)
Sector Floor Test ID 2110 MHz 2110 MHz
1 Ground Floor FI-C1-4-C1-9 2.26 2.32
1 Ground Floor FI-C1-54-C1-19 2.25 2.32
1 Ground Floor FI-C1-4-C1-10 4.94 5.32
1 Ground Floor FI-C1-54-C1-23 4.98 5.32
1 Ground Floor FI-C1-33-C1-27 3.72 4.58
1 Ground Floor FI-C1-44-C1-40 3.72 4.58
1 Ground Floor FI-C1-33-C1-28 3.78 4.58
1 Ground Floor FI-C1-44-C1-46 3.78 4.58
Floor Insertion Loss Worksheet
Return Loss
Sweep-Return
Loss(dB)PIM
Sector Floor Test ID
698-2700 mHz Test IDTest Pwr
(dBm)
Test PIM
(dBm)
Pass
Level
(dBm)
Test Pwr
(dBm)
Test PIM
(dBm)
Pass
Level
(dBm)
1 Ground Floor FR-C1-4 13.74 FAP-C1-4 15 -130.9 -114 28 -130.1 -127
1 Ground Floor FR-C1-54 13.81 FAP-C1-54 15 -129.8 -114 28 -131.5 -127
1 Ground Floor FR-C1-33 11.67 FAP-C1-33 15 -108.1 -114 15 -112.8 -127
1 Ground Floor FR-C1-44 14.84 FAP-C1-44 15 -100.1 -114 15 -127.3 -127
850 MHz PIM Test 2100 MHz PIM Test
Floor PIM & RL Worksheet
Test ID specifies the
first single jumper
entering that floor
Test ID specifies the
input as the jumper
entering that floor and
the output of each
power splitter facing the
individual branches
Examples of System Worksheets
Return Loss Sweep-RL (dB)
Sector
Floor Test IDTest Pwr
(dBm)Test PIM
(dBm)
Pass
Level
(dBm)
Test Pwr
(dBm)
Test PIM
(dBm)
Pass
Level
(dBm) Test ID
698-2700 mHz
1 Ground Floor SCP- 1-1900-1A 25 -114 35 -130.6 -127 SCR- 1-1900-1A 18.35
1 Ground Floor SCP- 1-1900-1B 25 -114 35 -127 SCR- 1-1900-1B 17.58
1 Ground Floor SCP- 1-2100-1A 25 -114 35 -127 SCR- 1-2100-1A 18.74
1 Ground Floor SCP- 1-2100-1B 25 -114 35 -130.8 -127 SCR- 1-2100-1B 18.71
1 Ground Floor SCP- 1-850-1A 25 -133.9 -114 35 -127 SCR- 1-850-1A 17.7
1 Ground Floor SCP- 1-850-1B 25 -122 -114 35 -127 SCR- 1-850-1B 17.74
850 MHz PIM Test 1900 and/or 2100 MHz PIM Test
System Insertion Loss Worksheet
System PIM & Return Loss Worksheet
System Combiner Worksheet
Test ID specifies each
input port on the system
level combiner
Test ID specifies the
jumper coming out of
the system combiner,
facing the DAS network
Test ID specifies the
input as the jumper
coming out of the
system combiner and
the output of the power
splitter facing the floor
That’s a Lot of Testing!
Yes it is! But it is necessary to ensure that all the parts of the DAS are working and will
continue to work
Can’t some of the testing be eliminated? Sure, but eliminating any part increases risk
Some problems may not be found until system turn-up or later Can the contractor find and fix problems in a timely fashion?
Do they have previous experience? Are their construction and test crews experienced? Does the contractor have personnel turnover issues?
What is the added cost of finding problems late? Scheduled access restrictions Cost of security, cleaning crews, elevator access Contract requirements Customer, property manager relationships
What is the cost of a PIM problem found later in the system life cycle? After other operators are added? Maintenance cost?
May be possible to reduce some testing As confidence in contractor competence increases As DAS components become more resistant to PIM Antenna environmental PIM not likely to ever go away
REAL WORLD DAS PIM TESTING
Marc Beranger, Sr. RF Interference Specialist, Radio Engineering
July 17, 2013
In-Building DAS Construction Testing
Real World PIM Challenges Highlight some of the issues we have had through nearly two years of
developing our design and test procedures.
“Build then Test” VS “Test as we Build” Will provide reasons why we approach testing the way we do
DAS Performance Achievements Examine the progress we have made to date
DAS Specific Test Equipment Focus on PIM testing equipment and the requirements necessary to properly
test DAS systems
Real World PIM Challenges - Components
PIM Rated Components Splitters, Tappers, Antennas
All must be PIM rated
Combiners near the radio may need better PIM specs due to LTE noise
requirements Typical: -150 dBc @ 2x 43 dBm (-107 dBm)
Our spec: -162 dBc @ 2x 35 dBm (-127 dBm)
Connectors Some field installable connectors work well on foam filled outdoor cable
But can fail dynamic PIM because of differences in conductor thickness
Factory Jumper Cables Have been known to fail dynamic PIM
Be prepared to do quality control checks on all components, because
manufacturing accidents do happen
Real World PIM Challenges - Training
Contractor Training and Feedback Rogers provides mandatory contractor training, including:
Connector installation training (supplied by the connector vendor)
Overview of PIM relating to DAS
Lessons learned from previous projects
Review of test procedures and deliverables
Review of test data collection
Hands on training in pre-install antenna location procedure
Rogers constantly updates this training based on feedback from contractors
Real World PIM Challenges – Connector Assembly
Proper Installation and assembly of connectors and cabling Plenum cable is hollow. Metal particles can fall inside and create PIM. During earlier
projects we have had to replace almost all cable on several floors to clear PIM
Hack saws and files MUST NOT be used! PVC pipe cutter provides a clean cut.
Clean cable ends during with isopropyl alcohol during cable prep
Cover unterminated cable ends with plastic caps or electrical tape
Bad flares, ragged cuts, plating damage can result in poor PIM
Real World PIM Challenges - Contamination
Metal wears off the threads during each connection and stick to the threads or conducting
surfaces. If this metal gets in between the conducting surfaces, PIM noise can be created.
Clean with alcohol before each connector mating.
Clean any protective caps for adapters
CLEAN ALL CONNECTORS ALL THE TIME!!
Using a swab and a stick, wipe between the inner and outer connector
Next wipe the insulator and metal surfaces
Using the clean side of the swap, use your finger to wipe the tops of the
inner and outer conductor
Real World PIM Challenges – Cleaning
Real World PIM Challenges – Connector Torque
Connectors must be correctly torqued to pass PIM
Undertorque results in unstable connections, causing failures
Overtorque can result in damage to connectors, causing failures
Experience shows that good PIM performance with N connectors is possible using slight overtorque.
7-16 DIN connectors are strongly recommended wherever possible
Test cables and adapters must be monitored for torque related damage
This connector is ok Broken
Broken
Broken
Real World PIM Challenges - Connector Stress
The system to the right was
secured to the wall with
cable clamps, drywall
anchors
These connectors would
fail PIM erratically
The system was
redesigned with secured
power dividers and stress
relief loops
PIM issues were
dramatically reduced
Real World Challenges - “Rusty Bolt” PIM Noise
PIM Noise can be created by RF interaction between the antenna and conductive objects in the environment outside the antenna system. PIM sources can be both below and above the antenna.
This is unpredictable but using general guidelines and the antenna pre-install procedure, we can find antenna locations that limit the impact of environmental PIM
850 MHz frequencies tends to be more reactive then AWS/PCS frequencies within the environment. This is reflected in our system level test specs AWS/PCS -127 dBm at a test power of 2x35 dBm 850 -114 dBm at a test power of 2x25 dBm
POTENTIAL PIM SOURCES Electrical cabling
Ceiling mounting hardwareLighting control devices
ABOVE ANTENNA
BELOW ANTENNAPOTENTIAL PIM SOURCES
Suspended lighting or pipingMetal on metal contact points
Mounting Surface
Various sources of “Rusty Bolt PIM”
Suspect components Ballast in fluorescent lights DC power supplies in LED lights Steel hardware Heat Sensors
Keep antennas at least 1 metre away
Generally an open concrete ceiling has better environmental PIM response than a suspended ceiling
Case Study-Foil backed insulation & Steel Studs
PIM noise observed in antennas mounted on walls with foil backed insulation
Remove insulation from behind antennas
Install antennas between steel studs where possible.
Relocate occurred on most of the floors where the antenna was positioned in this location
FRONT VIEW BACK VIEW
Case Study-RF Absorber Material
Can be helpful when PIM source is above the antenna.
If you lower your antenna during pre-install PIM testing and the PIM improves then your prime PIM source is likely above the antenna.
This is not a solution for all situations but it is one more tool in the toolkit.
Expensive!
“Build then Test” vs. “Test while Building”
“Build then Test” (then fix as required) Advantages
Faster, cheaper to construct, if number of defects is small (unlikely with PIM)
Disadvantages Large number of defects can dramatically slow fault finding (likely) If fault finding not built in to schedule, likely to result in schedule, cost overruns Schedule overruns likely due to probable high number of PIM failures Uncaught contamination issues led to whole floors of cables being replaced
“Test while Building” Advantages
Contractor has immediate quality control feedback Operator can monitor contractor quality Assurance that construction is correct before moving on in restricted access situations Finds common defect types early
Environmental PIM Manufacturer defects Technique errors Faulty equipment
Disadvantages Slower, more costly to construct (but built into project)
DAS Performance Achievements
Pool of contractors that build and test our DAS systems increasing Now contractors that had no previous DAS experience being successful
Continue to monitor existing contractors to improve performance and
incorporate their feedback in testing procedures.
The most recent acceptance audits are now completed in one visit. Initially we struggled to meet acceptance specifications, with many return
visits.
Typical low PIM DAS construction effort of a single floor of an office
initially took up to 2 weeks to test and install, now we can do this in less
than a week. 8-12 antennas, 20,000 sq. ft.
DAS Specific Test Equipment Recommendations
PIM Interaction between the antennas and the environment drives design requirements for lower TX power per antenna Non linear response prevents testing of antennas using scaled power, PIM results PIM testing needs to be done at system design powers, PIM acceptance values need to be related to receiver thresholds Drives a need for PIM test eqpt with lower test powers, better sensitivity, lower residual PIM
Test reporting is a key to successful PIM quality control PIM testing of macro site PIM testing may generate tens of reports a week DAS PIM testing may generate hundreds of reports a week, for weeks at a time To improve productivity, PIM test eqpt needs better ways to manage reports Test spreadsheet already defines test IDs, test parameters Allowing upload of test spreadsheet into PIM test set would eliminate a lot of operator data
entry Ethernet capable, remote operation?
Test equipment connections Test equipment uses N, DIN connectors Connectors wear with each connect / disconnect cycle, require cleaning each time DAS testing has hundreds of connect / disconnect cycles a week, for weeks at a time Need a better, non-threaded on test equipment for time savings
Hands-on, DAS specific training needed from PIM test set manufacturers Must include in-building environmental antenna effects
DAS Specific Test Equipment Recommendations
Ideal PIM Test Set Test Power Range
+43 dBm to +20 dBm in 1 dB increments (minimum)
+43 dBm to +10 dBm in 1 dB increments (desired)
+43 dBm (20w) power needed to for component acceptance testing
Adjustable low power needed to avoid environmental interaction with antennas
Sensitivity, Residual PIM -170 dBc (-127 dBm) @ 2x43 dBm
-157 dBc (-137 dBm) @ 2x20 dBm (minimum)
-147 dBc (-137 dBm) @ 2x10 dBm (desired)
Networkability Run PIM test sets with multiple frequency bands from one terminal
Automatic download to test results to one terminal
Ability to upload test point definition Preset test ID, test powers, frequencies, pass levels
Eliminate extra operator data entry
Thank You!
JOIN OUR iBwave USERGROUP ON LINKEDIN
WE WILL BE POSTING ANSWERS TO THE QUESTIONS WE RECEIVE DURING THE WEBINAR ON
Thank you! www.ibwave.com
PRESENTERS: Phillip Chan Marc Beranger John Beadles www.rogers.com