Ground Reference Prototype- Real Time Platform

The GRP-RTP is part of the Ground Reference Prototype. The GRP provides a functioning ground station for use by NEXCOM avionic vendors to assist with avionic radio testing.

The GRP consists of this Real Time Platform, a Software Control Platform (SCP), and two Multimode Digital Radios (MDRs). The purpose of the RTP is to provide real-time voice and messaging functions for the GRP.  The GRP-RTP has been developed for the NEXCOM Group (ACB-560) of the Federal Aviation Administration’s William J. Hughes Technical Center to support the NEXCOM development activities.

The GRP-RTP contains two primary modules housed in a VME-style chassis. The Octal T1 Module (OTM) is a multi-port T1 interface module that generates NEXCOM system timing and performs message translation/routing functions. The Voice Channel Module (VCM) is a voice processing module that encodes and decodes ground controller voice according to the ATC-10B algorithm. The OTM and VCM modules communicate over a 24-slot Time Division Multiplexed (TDM) bus.

The SCP and RTP subsystems function as a standalone NEXCOM Prototype Radio Interface Unit (PRIU). The SCP functions as the primary controller for the entire GRP system. It configures all GRP subsystem components and generates/processes all ground station messages. The RTP performs time critical functions such as voice encoding/decoding, NEXCOM timing channel generation, precisely timed message transmission and time stamping of MDR receive messages. The MDRs perform radio frequency (RF) transmission and reception for the GRP.

There are three major user interfaces for the GRP including Ground Controller Headset Interface, SCP Control Interface and the RF Interface. The RTP is supplied with a compatible headset assembly. The headset includes a microphone, stereo headphones, and a PTT switch. The SCP Control Interface and RF Interfaces are described in other GRP ground station documentation. There are two major internal subsystem interfaces including SCP-RTP subsystem interface and RTP-MDR subsystem interface. The SCP-RTP subsystem interface supports MDR data/voice/control messages and RTP voice/control messages. The RTP-MDR subsystem interface provides control for the radios.

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