Modulation Schemes for the Eurofix Datalink

Modulation Schemes for the Eurofix Datalink

Offermans, G.W.A.

Breeuwer, E.J. (mentor)
Weber, J.H. (mentor)

Electrical Engineering, Mathematics and Computer Science

Telecommunicatie- en Verkeersbegeleidingssystemen

1994-09

In the Eurofix system DGPS corrections are transmitted using the Loran-C signal as a datalink by time shifting the Loran-C pulses. The performance of the datalink, however, is bounded by restrictions of both the Loran-C system and the DGPS system. First, the normal Loran-C performance should not degrade noticeably due to the extra data modulation. Second, the DGPS corrections should be regularly updated with a low message error probability. The use of error correcting code reduces the effective data rate but is necessary to achieve a low message error probability In this report the properties of the Loran-C datalink are discussed and possible modulation schemes for the Loran-C datalink are derived. The design of the modulation schemes is restricted by the balancing requirement imposed by the normal Loran-C performance. The degradation of the normal Loran-C performance is simulated as a function of the signal-to-noise ratio for the different balanced modulation schemes. The balancing requirement reduces the data channel capacity significantly. Also, the normal Loran-C receiver is not guaranteed a bias-free tracking signal with balanced modulation as the Loran-C performance degradation depends on the alignment of the receiver window with respect to the balancing block. Therefore, simulations have been done to investigate whether unbalanced data transmission yields tolerable Loran-C performance degradation. A coding scheme based on nearly balanced modulation yields great improvement in the properties of the data channel. The normal Loran-C performance degradation is comparable with the degradation due to balanced modulation.

Eurofix
Loran-C data channel
low data rate DGPS channel
cross-rate interference

http://resolver.tudelft.nl/uuid:e0f4ecbd-2cbb-421a-a5e2-cf1472e2a1ee

Student theses

master thesis

(c) 1994 G.W.A. Offermans