By On December 15, 2016
定位
Galileo, GNSS, GPS

With the Declaration of Galileo Initial Services being available (15th December 2016), Galileo officially moves from a testing phase to the provision of live services. For the first time ever, users around the world can be guided using the positioning, navigation and timing information provided by Galileo’s global satellite constellation.

By Andy Walker On October 10, 2011
定位
CNAV, Modernized GPS, Multi-GNSS, Galileo, GLONASS

CNAV is the name for the civilian navigation message that will be carried by the modernized GPS system. And while the CNAV message will carry similar data to the existing NAV message, its structure will be completely different, with a packetised format that will increase message bandwidth to allow for greater information density and pave the way for future system expansion. To this end, the system is designed to support 63 satellites, compared with 32 for the L1 NAV message. Each packe...

By Andy Walker On May 31, 2011
定位
BOCM, BOC modulation, Galileo

Binary offset carrier modulation (or BOCM) is a split-spectrum modulation scheme used by the Galileo navigation satellite system. BOCM is a square subcarrier modulation. A signal is multiplied by a rectangular subcarrier of a frequency that is equal to or higher than the CDMA rate. Following this subcarrier multiplication, the spectrum of the signal is divided into two parts. The purpose for using BOC modulation in Galileo is to reduce interference with BPSK-modulated signals such as C...