This paper proposes a Kalman filter algorithm for simultaneous estimation of absolute ionospheric delay and DCB(differential code bias). It is well known that the two quantities are mixed in GNSS measurements causing rank-deficiency problem. In case of GPS, only one receiver DCB is considered. In case of GLONASS, satellite and receiver DCBs for each frequency number should be considered since GLONASS ephemeris do not provides satellite DCB information and each GLONASS satellite utilizes different L1 and L2 frequency bands to implement the FDMA(Frequency Division Multiple Access) principle. In this paper, GLONASS DCBs are modeled as a combination of center-frequency dependent DCB and offset-frequency dependent DCB which is propotinal to the frequency number. Experimental results based on real GLONASS measurements demonstrate the feasibility of the proposed method.

Keywords: ionospheric delay, DCB (differential code bias), estimation