Galileo Dual-Channel CBOC Receiver Processing under Limited Hardware Assumption

Composite Binary Offset Carrier (CBOC) modulation is currently proposed for future Open Service (OS) Galileo signals in E1 frequency band. CBOC consists of a weighted sum or difference of two sine Binary Offset Carrier (BOC) waveforms: a sine BOC(1,1) and a sine BOC(6,1) component. The transmitted OS signal has both data and pilot channels. Data and pilot channels use slightly different modulation, namely CBOC(+) (i.e., weighted sum of BOC(1,1) and BOC(6,1)) and CBOC(-) (i.e., weighted difference of those). At the receiver side, depending on the number of channels available, several approaches are possible: processing either data or pilot, or processing both channels with any of the BOC(1,1) and BOC(6,1) components, or with a weighted or time-multiplexed combination of those. Therefore, a significant number of receiver processing variants is possible. The focus here is on the architectures having a limited hardware available, when we assume that only two channels per satellite and per E1 Open Service signal are used at the receiver and when we have one-bit processing only. This allows us to either process both data and pilot channels with a single sine-BOC(1,1) reference, or to process only the data channel with both BOC(1,1) and BOC(6,1) components, and then combine them with appropriate weights. The question we address here is which of these two variants is better in terms of performance. The novelty of our solution comes from an analytical approach of this problematic and from the comparison of the two architectures in terms of tracking performance at various bandwidths. Our analysis focuses both on narrowband receiver cases (i.e., low frontend receiver bandwidts, of interest in mass-market applications), and on wideband receiver cases (more suitable for professonal receivers). The tracking results are analyzed in terms of tracking error variances and multipath error envelopes.