Technical Services

Telecom Test Solutiions

Tunnel Radio Communications System for the Baltimore Metro Subway

Tunnel Radio Communications System for the Baltimore Metro Subway


GL Communications developed design and technical specifications for the Baltimore Metro Subway to extend the system-wide radio communications in the tunnel and underground stations. Baltimore subway operated by Maryland Transit Administration (MTA) has a total of 14 stations over 15 miles long stretch with a significant underground portion consisting of dual-bore tunnels.

The new Tunnel Radio Communication (TRC) system provides seamless radio coverage to the transit and the public safety personnel of Baltimore City's Fire and Police operating in the underground portion on-board trains as well as in the station platforms and stairway exits to the surface for evacuation purpose in case of an emergency. GL's newly designed system captures the off-air RF signals from the existing above ground land mobile radio system, amplify and feeds them to leaky coaxial cables and point source antennas located throughout the underground that, then, would radiate the signal to radio users. Our engineers also insured that no single-point of failure existed.

GL's team of engineers provided:

Design Services

  • Redundant and physically diverse off-air feeds for the MTA's 490 MHz UHF and Baltimore City's 800 MHz trunked simulcast radio systems
  • Off-air interface provided by roof-top pick-up antennas and channelized Bi-Directional Amplifiers (BDA), thereby, eliminating the interference potential
  • Fiber-fed 490 MHz UHF and 800 MHz broadband BDAs
  • Off-air coverage extenders for stations below-grade aboveground stations
  • Network Monitoring System (NMS) for monitoring and control the BDAs
  • Detailed drawings and documentation for project implementation

Program Management

  • Procurement support for vendor proposals and review of contract award
  • Site surveys and inspections services
  • Technical review of the contractor's design documentation
  • Monitoring of link budget analysis and coverage performance requirements
  • Survey of clearance between the train envelop and cable installations within the tunnel and public areas for aesthetics
  • Review of existing cable specifications for RF-on-Fiber signal transport
  • Inspection of new fiber cable for RF distribution and alarm system
  • Verification of 490 MHz and 800 MHz BDAs layout and location selection
  • Development of tunnel interface requirements for Motorola's MOSCAD and monitor integration with overall Network Management System
  • Oversight of system testing and verification for acceptance and commissioning of 490 MHz and 800 MHz RF systems

Tunnel Radio Communications System