Analytical performance of CBOC-modulated Galileo E1 signal using sine BOC(1,1) receiver for mass-market applications

Abstract

Composite Binary Offset Carrier (CBOC) modulation has been selected for the future Galileo signals to be used in mass-market applications. CBOC consists of a superposition of two sine Binary Offset Carrier (BOC) waveforms: a sine BOC(1,1) and a sine BOC(6,1) component. CBOC modulation has higher spectral components than BPSK modulation currently used in GPS, and therefore would require a wider bandwidth than what is currently used in mass-market GPS receivers in order to achieve the full performance. Fortunately, CBOC signals can be processed with a sine BOC(1,1) receiver, with lower bandwidth and sampling frequency needs. This paper analyzes how much deterioration (if any) in terms of tracking accuracy (i.e., code tracking error variance and robustness to multipath) occurs when we process a CBOC signal with a reference sine BOC(1,1) receiver (instead of processing it with a CBOC receiver). The analysis focuses especially on narrowband receiver cases (i.e., front-end double-sided bandwidth lower or equal to 5 MHz), which are the cases of interest in mass-market applications. Analytical closed-form expressions of signal Power Spectral Densities (PSD) are derived by taking into account the rate differences of the two components of CBOC signal, and tracking results are analyzed in terms of tracking error variances and multipath error envelopes.