Public Safety DAS Design

Sujeeva RanasingheSenior Principal, Engineering

Convergent Wireless Solutions, LLC303-483-3387

Agenda

IntroductionWhat 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

PassiveActive

Distributed Antenna System DesignDistributed Antenna System Codes

New FCC Regulations on Part 90 Signal Boosters/Repeaters/BDACurrent Public Safety DAS RF EnvironmentNew Public Safety DAS Standards Recommendations

In-Building and Outdoor Distributed Antenna Systems RF Engineer.

RF Engineer with 23 years experience15 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

Introduction

Most Public Safety Distributed Antenna Systems (DAS) are designedby the lowest bidder. These systems use subpar components that addnoise and interference to the uplink, potentially shutting sites down.

Jurisdictions should adopt or enforce the FCC Repeater Part 90 rulesof March, 2014 and establish new DAS design guidelines to ensureubiquitous Public Safety in-building coverage.

A DAS is a network of spatially separated antennas connected to atransport medium - coaxial, fiber optic or twisted pair cable or acombination of each – that provides wireless service within buildings andopen air venues (stadiums, fairgrounds etc.).

For the purpose of this presentation, we will only be discussing in-buildingDAS.

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 Safetyentities are supported.

Normally between 150 – 2700MHz.

What are Distributed Antenna Systems a.k.a. DAS?

Why is a DAS needed for Public Safety?

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 IssueInteroperability 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.

What are the benefits of a DAS for Public Safety?

Improved Coverage and Quality of Service95% of building covered for First Responder handsetsHigher DAQ of 4.0 or better

Improved ReliabilitySignificant reduction in call failure

Distributed Antenna Systems are a reliable and innovative solution to poor coverageinside buildings, large venues requiring capacity, and inconsistent RF environmentswhere it is difficult to improve coverage and quality.

DAS ConfigurationPassive

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 groups1. RF Source: Over-The-Air Repeater(s) and donor antenna system2. Passive Coaxial Cable Network and indoor antennas.

DAS ConfigurationPassive

DAS ConfigurationActive

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 frequenciesMulti-operator installation allows for efficient power sharing capabilitiesFlexible growth and expansion capabilityFour component groups:

RF SourceBTS 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.

DAS ConfigurationActive

Public Safety DAS Design

For Public Safety, design threshold is determined by one of two standardsbodies:- 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 whatextent.

For Public Safety, design threshold is typically -95dBm handset RSSI over 95% of coveragearea. Per NFPA-72 2010, critical areas (fire control rooms, EOCs, stairwells etc.) must have99% coverage.

Design Threshold

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

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 powerBuilding material – Low-E glass, heavy concrete, marble and steel are RF attenuatorsBody 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 countsupported by a DASAs 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

Public Safety DAS DesignComponents

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 FailureA/C FailureActive 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 frequenciesLow PIM Passive Components – cables, connectors, splitters and antennas

New FCC Repeater RulesReport 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 March1st, 2014.

Requires owners/users to:Obtain wireless service provider/operator consent to operate the device, andRegister the device with their serving wireless service provider prior tooperation

Within Part 90 are two classes:Class A, designed to transmit and receive one or more specific channels andeach passband CANNOT exceed 75kHz.Class B, designed to transmit and receive wideband frequencies and eachpassband exceeds 75kHz. These BDAs must be registered directly with theFCC before use.

A brief word about PIMWhat is it?

PIM or Passive Intermodulation occur when 2 or more transmitted frequencies (Downlink) combine togetherresulting in the sum and differences of those frequencies. This becomes an issue when it occurs within thereceive 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 Intermodulationf1 = 769MHzf2 = 860MHz

IM3 = 678MHz & 951MHz

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 PIMWhat causes it?

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 inDenver 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 instairwells and fire command centers requiring more DAS be designed and installed.

Current Public Safety DAS Environment

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 areagenerating some level of PIM overwhelming a high power donor siteuplink receive sensitivity.

Current Public Safety DAS Environment

Meeting coverage requirement alone is not enough. System quality must also beaddressed by DAS

Public Safety DAS Site Audits are necessary to ensure all Bi-directional Amplifiers complywith 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 specifiedConnectors, 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

Thank YouContact Information:Sujeeva Ranasinghe

Senior Principal, EngineeringConvergent Wireless Solutions

Sujeeva.Ranasinghe@cwslk.com303-483-3387