Efficient tracking of joint Galileo OS data and pilot components

The Galileo E1 OS signal is transmitted with code-multiplexed data (E1B) and pilot (E1C) components. Their coherent addition results in a 3 dB gain. However, the modulated data symbols and the secondary code of the pilot component requires either addition after correlation with symbol-transition correction or the use of multiple correlators. Consequently, joint tracking of these components is both resource-intensive and complicated. This paper presents a joint correlator design which is processing efficient as it exploits the code similarities between the two components. It separates processing into two smaller correlations with one of the correlation outputs is selected for further processing. This method requires approximately half the number of operations compared to other joint tracking methods. As the presented correlator has to choose one of two correlator outputs, the incorrect selection of the output is analyzed and verified with simulations. Further, a global navigation satellite system (GNSS) software-defined radio (SDR) implementation verifies the functionality of this method. In conclusion, this presented combined correlation method is an efficient implementation that exploits the full signal power from its code-multiplexed data and pilot components.