Unraveling the Mystery of PTC Communications for Commuter Rail

David Thurston, PhD, P.E., FIRSE

Atkins, Vice President – Rail and Transit

Pittsburgh, Pennsylvania

Agenda1) PTC Basics2) I-ETMS Operation 3) Interoperability4) RF and MMC’s Role in I-ETMS5) Spectrum and PTC 220’s Role in

I-ETMS6) Ground Based Networks and WSRS

What is PTC? Positive Train Control (PTC)

Is a predictive collision avoidance system that provides a warning to train operators and then intervenes and stops a train before a collision or overspend movement occurs. The primary purpose is to prevent incidents caused by single-point human failures by proactively stopping the train.

1) Train-to-Train Collisions

2) Over Speed Derailments

3) Work Zone Incursions

4) Movement Through a Switch improperly Lined

What is PTC?

PTC System Overview

Initialization

Track DatabaseSpeed Restrictions

Work ZonesTrain Consist

Movement Authorities

Braking Curve

Warning Curve

Predictive Braking

Physical features

• Work Zones• Signals

• TSR• Authorizations

Established Points

On-Board

Wayside

Computer Aided Dispatch & Back Office Server

Location Reports/ Authorities

Signal Status

BaseStation

CommunicationNetwork GPS

As a Communications Based Signal System, connectivity is the key to successful operation.

PTC System Overview

InteroperabilityThe Interoperability Requirement

drives many issues for I-ETMS.• Host is defined as the railroad in “operational control”, not the “owner”.

• “Tenant” must agree to conditions imposed by the Host.

I-ETMS Example of InteroperabilityRailroad #1

Dispatcher (BO) Railroad #3 Dispatcher(BO)

Railroad #2 Dispatcher (BO)

Communications System Responsibilities

Railroads• System Integration• Messaging Hardware• Interoffice Network• System Deployment• Wayside Status Relay

Service• Network Management • Key Exchange• Configuration

Management• Access Control –Role Authentication

• GBN Installation

PTC 220 LLC.• RF Design of 220 MHz

Network

Suppliers• GBN Equipment• Local Secure Key storage

• Other (depending on Asset capabilities)

MeteorComm RF and ITCM

• Radio Designs • ITCM • ICD & Protocols for SMS

• Secure File Distribution

• Access Control

RF and MMC’s Role in I-ETMSMeans of Connectivity

The wireless options for ITCM Connectivity:1) Narrow-band 220 MHz networks (low

data through-put and high coverage). This network is intended to have full coverage of the railroad and is primarily used in continuous communications between the base stations and locomotives and wayside locations and locomotive.

2) Broad-band networks (WiFi, high data through-put and low coverage). Broad-band networks are primarily targeted for initial bulk data downloads.

3) Broad-band networks (Cellular, high data through-put and intermittent coverage). These links are intended to be a back up to the 220 MHz.

RF and MMC’s Role in I-ETMSMeans of Connectivity

• Four Class I railroads formed a consortium to develop the I-ETMS infrastructure, and…….1. MeteorComm (owns and develops the shared

standard radio platform and Messaging Architecture)

2. PTC 220 MHz LLC (owns the shared nationwide frequencies), and

3. ITC Standards Committee

Base Radio

Locomotive Radio

MeteorComm’s Role in PTC Communications

MeteorComm is not an Integrator, they Provide certain IP and Proprietary Products that are essential to I-ETMS Operation.The License fees paid to MeteorComm through their ELUA are based on actual costs associate with the maintenance, administration and development of their Products.

MeteorComm’s Role in PTC Communications

MMC’s Other Function - Interoperable Train Control Messaging (ITCM)

ITCM performs several tasks;• Message Control and Routing• Essentially the “Internet” of ITC• Proprietary Software owned, controlled and licensed by MeteorComm

• Considered part of the BO Segment, but components exist in Locomotive and Wayside Segments as well.

ITCM and Federation Federated Cloud

(Two suppliers, redundant networks)

Railroad #1Back Office

server

Base StationsCellular WiFi

Railroad #1Back Office

server

Base StationsCellular WiFi

Railroad #1Back Office

server

Base StationsCellular WiFi

Railroad #4Train

• Base stations and WiFi installation, once Federated, will generate traffic for any captured train. Non Federated sites that captures a train will cause undesired operation.

• Once Federated, Anyone can and will use it.

Implication of Federation and RF

Spectrum and PTC 220’s Role in I-ETMS

•Similar to MeteorComm, PTC 220 LLC. is wholly owned by Class 1 Railroads (and for largely the same reasons. •However, their mission involves other key areas of interoperability, RF Design and Spectrum Management.

PTC 220 LLC

1. frequency management, coordination and acquisition,

2. Spectrum,

3. RF Design for coverage, 4. Cell topology,5. simulation, 6. Additional comms –

cellular and WiFi

•Their license fees associated with their ELUA account for the purchase of Spectrum, design of RF coverage (with the associated tools), and frequency coordination. All of this is required to be interoperable. Specific areas we will look at include:

Spectrum:

PTC 220 LLC

I-ETMS Spectrum • 7 frequencies each for 75 Watt base stations.

• 7 frequencies that are power restricted.• For a total of 14 frequencies.

– 1 is the Common channel (Nationwide)– 6 75 Watt are called a Primary Local Channel (nation wide)

– 7 Local Channels

Managing a Nationwide NetworkMentum Planet Hosted Server Application is used for the RF design and FCC License Coordination. All Base and Field radios are contained in the database. Coverage maps are generated to determine base placement that is coordinated with slot planning.

RF Design Coverage

1 2 3 54 20…

WIU TIME SLOTS

3-SEC

600-mS DURATION

…

…

…

F-Frame is used to support WIU status messages. The F-Frame is divided into “slots” for each Wayside Interface Unit assigned to the Base station.

Each base radio has an assigned local channel frequency that it controls for use in its area to communicate with remote radios.

Channel Management and wayside slot planning

Ground Based Networks and Their Role in I-ETMS

Wayside Status Relay Service (WSRS)

• Is a subscription based message relaying application that consumes Wayside Status Messages (WSMs) and then sends those WSMs to interested parties.

• A separate application running on the ITCM Server (not supplied by MeteorComm).

On-Board

Wayside

Computer Aided Dispatch & Back Office Server

Location Reports/ Authorities

Signal Status

BaseStation

CommunicationNetwork GPS

WSRS provides for alternate message delivery, and is used in several I-ETMS systems today.

PTC System Overview

Signal Status

• I-ETMS Interoperability requires common Host and Tenant RF Links and Messaging,

• 220 MHz radio network is the Prime data channel with Cell and WiFi as Backup,

• 220 coverage spectrum, radios and ITCM are all proprietary.

• WSRS is a separate consideration

Conclusions