Research and Performance Analysis of Constant-Envelope Multiplex for BD B2 Signals

AltBOC (15, 10) is proposed to be the modulation mode of BD B2 global signals, which combines lower and upper lobes with four signals. The modulation makes users able to receive and process one lobe separately, or process two lobes coherently to achieve higher accuracy of position and navigation. AltBOC could also fulfill compatibility among BD, Galileo E5, and GPS L5. There have been lots of researches of B2 signals’ solutions currently, but most of these only considered four signals with the same modulation mode and chip rate, which makes the choice of signals inflexible. Thus, we present two kinds of conditions that B2 signals have different modulation methods and chip rate, and three kinds of constant-envelope multiplex plans based on it to realize AltBOC modulation: non-symmetrical AltBOC, TD-AltBOC, and binary TD-AltBOC. The multiplex plans are simulated and multiplex efficiency of each one is given. Also the ranging accuracy, anti-multipath resistant, and anti-interference performance is shown to compare the three signals with the multiplex signals of B2 signals which are modulated as AltBOC (15, 10). Analysis results show the signals of the three multiplex plans have similar ranging accuracy, anti-multipath resistant, and anti-interference performance with the AltBOC (15, 10) signals. TD-AltBOC has the highest multiplex efficiency that is 100 % among the three plans. The multiplex schemes we present are able to combine signals with different modulation methods and chip rate as AltBOC modulation, which can achieve the same navigation performance to AltBOC (15, 10) signals and high multiplex efficiency, and these schemes could be new solutions for BD B2 signals.