Eurofix

Description

EUROFIX, A DELFT UNIVERSITY CONCEPT to integrate GPS and Loran-C. Eurofix time-modulates the Loran-C pulses, producing a reliable data link out to a range of about 1,000 km.

The Eurofix modulation scheme uses the last six pulses of the standard LORAN pulse group (Figure 9). These pulses are Pulse Position Modulated (PPMPulse Position Modulation) by ±1 μs. There are 729 possible modulation patterns. To minimize the impacts to users, the PPMPulse Position Modulation encoding uses 128 of a possible 141 balanced patterns to represent seven bits of data per Group Repetition Interval (GRI). The data rate is 70 to 175 bits per second, based on the GRI, and uses forward error correction (Reed-Solomon encoding) [8]. The Eurofix message length is fixed at 210 bits with consisting of 30 seven-bit words (GRIs). Seventy bits are used to represent the application data, while the remaining 140 bits are used for the forward error correction. The 70 bits of application data are structured such that four bits indicate the message type, 52 bits contain the application data, and there are 14 Cyclic Redundancy Check (CRC) bits. There are 16 possible message types that can be broadcast using Eurofix with Message Type 6 providing the UTC data [9].