Beidou system is the world's first satellite navigation system to provide three-frequency signal service. GPS uses dual-frequency signals, which is Beidou's late-comer advantage. The use of dual-frequency signals can reduce the impact of ionospheric delay, and the use of three-frequency signals can build more complex models to eliminate higher-order errors of ionospheric delay. At the same time, the use of three-frequency signals can improve the efficiency of carrier phase ambiguity resolution, and theoretically also improve the carrier convergence speed. Because of this, the GPS system is also expanding into a three-frequency signal system.
Beidou-2 provides three public service signals of B1I, B2I and B3I in the three frequency bands of B1, B2 and B3. Among them, the center frequency of the B1 band is 1561.098MHz, B2 is 1207.14MHz, and B3 is 1268.52MHz.
Beidou-3 provides five public service signals B1I, B1C, B2a, B2b and B3I in the three frequency bands of B1, B2 and B3. The center frequency of the B1 band is 1575.42MHz, B2 is 1176.45MHz, and B3 is 1268.52MHz.
