A DAS is a network of antennas connected by cable that provides wireless coverage inside buildings. DAS are needed for public safety to improve coverage and reliability for first responders. The benefits of a public safety DAS include 95% building coverage, high quality of service, and improved reliability. Proper DAS design is important to ensure adequate coverage levels are met based on standards from NFPA and IFC. Components like filtered repeaters, backup power, and antennas supporting all public safety frequencies are important. New FCC rules require registration of bi-directional amplifiers used on public safety networks.

1. Public Safety DAS Design
Sujeeva Ranasinghe
Senior Principal, Engineering
Convergent Wireless Solutions, LLC
303-483-3387

2. Agenda
Introduction
What is a Distributed Antenna System (DAS)?
Why are Distributed Antenna Systems needed for Public Safety communications?
What are the benefits of a DAS for Public Safety?
Distributed Antenna System Configurations
Passive
Active
Distributed Antenna System Design
Distributed Antenna System Codes
New FCC Regulations on Part 90 Signal Boosters/Repeaters/BDA
Current Public Safety DAS RF Environment
New Public Safety DAS Standards Recommendations

3. In-Building and Outdoor Distributed Antenna Systems RF Engineer.
RF Engineer with 23 years experience
15 years DAS design, installation and commissioning experience.
10 years Public Safety DAS
Licensed in 2014 by Denver Fire Department to work on Public Safety DAS.
Certified for multiple OEMs including Solid Technologies, Commscope, Advanced RF, Corning
Mobile Access, Teko Telecom and TE Connectivity.
Multiple Verticals – Healthcare, Education, Office/Multi-Tenant High Rise, Public Venues,
Industrial, Government/Military, Transit Hubs and Hospitality.
Introduction

4. Introduction
Most Public Safety Distributed Antenna Systems (DAS) are designed
by the lowest bidder. These systems use subpar components that add
noise and interference to the uplink, potentially shutting sites down.
Jurisdictions should adopt or enforce the FCC Repeater Part 90 rules
of March, 2014 and establish new DAS design guidelines to ensure
ubiquitous Public Safety in-building coverage.

5. A DAS is a network of spatially separated antennas connected to a
transport medium - coaxial, fiber optic or twisted pair cable or a
combination of each – that provides wireless service within buildings and
open air venues (stadiums, fairgrounds etc.).
For the purpose of this presentation, we will only be discussing in-building
DAS.
A DAS can be driven by a direct connection to Base Transceiver Stations
(BTS), Over-The-Air Repeaters or a combination of both.
All frequencies used by Wireless Service Providers (WSP) and Public Safety
entities are supported.
Normally between 150 – 2700MHz.
What are Distributed Antenna Systems a.k.a. DAS?

6. Why is a DAS needed for Public Safety?

7. Why is a DAS needed for Public Safety?
First Responder Safety – to have the ability to transmit and receive communications during
high stress situations with a high degree of reliability and quality.
Address a critical Officer Safety Issue
Interoperability with local public safety agencies
While in-building radio coverage has been an issue especially in large metro areas for years
9/11 brought the issue to the fore front.
The 9/11 commission issued a report that was very critical of public safety radio systems
where they pertain to in building use.
In an attempt to improve in building coverage several standards bodies drafted ordinances
that set specific criteria for Public Safety DAS systems (PSDAS) for in-building first
responder radio coverage.
Those two standards bodies are National Fire Protection Agency (NFPA) and International
Codes Councils International Fire Code (IFC). Both these bodies develop building codes.

8. What are the benefits of a DAS for Public Safety?
Improved Coverage and Quality of Service
95% of building covered for First Responder handsets
Higher DAQ of 4.0 or better
Improved Reliability
Significant reduction in call failure
Distributed Antenna Systems are a reliable and innovative solution to poor coverage
inside buildings, large venues requiring capacity, and inconsistent RF environments
where it is difficult to improve coverage and quality.

9. DAS Configuration
Passive
Passive DAS – coaxial cable and passive elements used to distribute RF signals
Driven by Over-The-Air Repeater(s)
Ideal solution for smaller venues < 150,000 ft2
Limited growth or expansion capability
Noise and interference prone
Two component groups
1. RF Source: Over-The-Air Repeater(s) and donor antenna system
2. Passive Coaxial Cable Network and indoor antennas.

10. DAS Configuration
Passive

11. DAS Configuration
Active
Active DAS – active fiber optic conversion and transport added to coaxial cable
and passive elements to distribute wireless service.
Driven by Base Transceiver Stations (BTS) and/or Over-The-Air Repeater(s)
Ideal solution for larger venues > 150,000 ft2
A single system a.k.a. Neutral Host supports multiple operators and frequencies
Multi-operator installation allows for efficient power sharing capabilities
Flexible growth and expansion capability
Four component groups:
RF Source
BTS locally situated or connected via RF-Over-Fiber from remote location.
OTA Repeater locally situated
Head-End : Input RF signal filtering and conditioning.
Use of DAS Interface Trays are highly recommended to condition the input RF signal to the necessary power levels.
Optical Distribution: Convert filtered and conditioned RF signal to IR and transport over fiber to Remote
Units.
Passive Coaxial Cable Network and indoor antennas.

12. DAS Configuration
Active

13. Public Safety DAS Design
For Public Safety, design threshold is determined by one of two standards
bodies:
- National Fire Protection Agency (NFPA) and
- International Codes Councils International Fire Code (IFC).
Both these bodies develop building codes.
The codes are NFPA-72 2010 and the IFC 2012 510 respectively
It is up to the local Authority Having Jurisdiction (AHJ) which they adopt and to what
extent.
For Public Safety, design threshold is typically -95dBm handset RSSI over 95% of coverage
area. Per NFPA-72 2010, critical areas (fire control rooms, EOCs, stairwells etc.) must have
99% coverage.
Design Threshold

14. IFC 2012 Section 510 NFPA 72 2010 Chapter 24
Installation: Optional/Mandatory Mandatory Mandatory
New, Existing Buildings Both Both
Building type specification Not specific Not specific
Optional "automatic activation" Not specific Not specific
NEMA 4 enclosures Yes Yes
12 or 24 Hour back‐up power 24 24
Signal Strength -95 dBm -95 dBm
Must correct interference Yes Yes
Requires permits Yes Yes
Coverage 95% 99% Critical areas 90% other
Antenna isolation between donor and DAS antennas Not Specific 15db
Analog and digital modulation Not Specific Yes
Propagation delay specification provided Not Specific Yes
Component pre approval Not Specific Yes
ALL PS band devices need pre‐approval Yes Not Specific
FCC Certified equipment only Yes Yes
External filters prohibited Yes Yes
Add/Change required frequencies Yes Yes
Alarms (all "supervised" type circuits)
Antenna malfunction Not Specific Yes
Signal booster failure Yes Yes
Loss of AC power Yes Yes
Battery charger fail Yes Yes
70% battery capacity used. Not Specific Yes
Dedicated external alarm panel Not Specific Yes
Audible trouble alarm Optional No
Transmit alarms to central station Yes Not Specific
Grid type coverage test procedure Yes Yes
Minimum DAQ value per square No 3
Minimum RF level per square -95 dBm -95 dBm
Test records retained Yes Yes
Acceptance test required Yes Yes
Annual tests required Not Specific Yes
AHJ provides technical info Yes Yes
Compliance to FCC Rules required Yes Yes
Mandatory service contract No No
Personnel Requirements
FCC general radio operator license Yes No
Factory trained on equipment used Yes Yes
Public Safety DAS Codes

15. Public Safety DAS Design
Ideally design for the worst case scenario
Accurate Link Budgets for both Downlink and Uplink paths are essential
Design for required signal threshold depends on multiple factors:
BDA or remote unit output power
Building material – Low-E glass, heavy concrete, marble and steel are RF attenuators
Body loss (typically about 3.0 dB)
Fade margin (typically about 5.5dB)
Portable radio receive sensitivity (typically about -116dBm)
Coaxial cable and passive element loss.
Properly tuned propagation model using CW Testing and Prediction Tool
Power sharing and number of channels among like frequencies also a limiting factor.
Multiple agencies using the same 700 and 800MHz channels contribute to total channel count
supported by a DAS
As the number of channels increases, the output power of Repeater or Remote Unit reduces
Every time the number of channels double, the output power reduces by half.
Design Methodology

16. Public Safety DAS Design
Components
Channelized digital filtered Repeaters that allows band selectivity
Supports all Public Safety frequencies
Web based GUI to allow for remote monitoring from a NOC or EOC
Network Monitoring system with real-time alarming output to monitor:
Amplifier Failure
A/C Failure
Active Component Failure
NEMA 4 Compliant Housing
12-Hour UPS/Battery Back-up for all active components
Multi-frequency antennas supporting all PS frequencies instead of WSP frequencies
Low PIM Passive Components – cables, connectors, splitters and antennas

17. New FCC Repeater Rules
Report and Order FCC 13-21.
http://wireless.fcc.gov/signal-boosters/part-90 boosters/index.html
Part 90 specifically refers to Public Safety Bi-Directional Amplifiers since March
1st, 2014.
Requires owners/users to:
Obtain wireless service provider/operator consent to operate the device, and
Register the device with their serving wireless service provider prior to
operation
Within Part 90 are two classes:
Class A, designed to transmit and receive one or more specific channels and
each passband CANNOT exceed 75kHz.
Class B, designed to transmit and receive wideband frequencies and each
passband exceeds 75kHz. These BDAs must be registered directly with the
FCC before use.

18. A brief word about PIM
What is it?
PIM or Passive Intermodulation occur when 2 or more transmitted frequencies (Downlink) combine together
resulting in the sum and differences of those frequencies. This becomes an issue when it occurs within the
receive band (Uplink) at a level high enough to interfere with the desired signals.
f1 f2
2f1- f2 2f2- f1
3f1- 2f2 3f2- 2f1
4f1- 3f2 4f2- 3f1
f2- f1 f2+ f1
Interference Interference
3rd
3rd5th
5th7th
7th
Example of 3rd Order Intermodulation
f1 = 769MHz
f2 = 860MHz
IM3 = 678MHz & 951MHz

19. PIM can be caused by any nonlinearity in the RF path.
Possible sources include poor connections, damaged cable or water infiltration.
Weather-proof those donor antenna runs!
In some cases, PIM can also be caused by objects outside the path, such as machinery, metal conduit/cable trays,
or site equipment.
RF producing machinery, elevator equipment and certain medical devices are known PIM generators.
In fact, there are so many possible sources, PIM is sometimes known as “the rusty bolt effect.”
Indoor antennas with grounded backplanes, connectors touching cable trays etc.
A brief word about PIM
What causes it?

20. Public Safety DAS is cost driven, often designed and installed by the lowest bidder.
Legacy Public Safety DAS still operate BDAs not approved under Part 90.
Majority of Public Safety DAS are passive.
Increasing number of new construction is being LEED certified – 325 buildings in
Denver alone between 2012-2014.
http://www.usgbc.org/articles/usgbc-releases-top-10-states-leed-green-
building-capita-nation
Low-E glass in LEED certified buildings is attenuating Public Safety signals in
stairwells and fire command centers requiring more DAS be designed and installed.
Current Public Safety DAS Environment

21. The more passive components in a DAS – splitters, couplers, combiners,
jumper cables and connectors, the higher probability of PIM.
Imagine multiple Public Safety DAS installed in a major metro area
generating some level of PIM overwhelming a high power donor site
uplink receive sensitivity.
Current Public Safety DAS Environment

22. Meeting coverage requirement alone is not enough. System quality must also be
addressed by DAS
Public Safety DAS Site Audits are necessary to ensure all Bi-directional Amplifiers comply
with Part 90 and are Class A.
Maximum composite output power of channelized repeaters to be 30dBm.
PIM increases along with channel power
Low PIM rated components rated to at least -153 dBc specified
Connectors, Splitters, Hybrid Combiners, Jumpers and Antennas.
Mandatory PIM testing to be part of system design and installation.
Public Safety DAS design and testing parameters have to be widened to include PIM.
Reducing PIM will improve DAQ to 4.0 or better.
Acceptance testing should include mobile to mobile testing.
Adjacent high-power operator DAS PIM tested.
Public Safety DAS Recommendation

23. Thank You
Contact Information:
Sujeeva Ranasinghe
Senior Principal, Engineering
Convergent Wireless Solutions
Sujeeva.Ranasinghe@cwslk.com
303-483-3387