![]() The following table summarizes the parameters transmitted by FNAV and INAV messages. This scheme allows reducing the bit error ratio in the increased data rates.Īs referred, the FEC coded symbols are transmitted interleaved within the page and because of that the navigation data can only be decoded when the complete interleaving FEC coded part is received. Block Interleaving on the resulting frames: provides robustness to the FEC decoding algorithm since in presence of a burst of erroneous bits it is converted into small errors in several pages.Tail Bits (sequence of zeros) to allow Viterbi decoding A one-half rate Forward Error Correction (FEC).A Cyclic Redundancy Check (CRC) with error detection capabilities after recovery of the received data.Three levels of error coding are applied to the Galileo Message Data Stream: The size of this field is different in each navigation message. In addition both navigation messages transmit a CRC data field in order to detect corrupted data. The page starts with a Synchronisation Word (SW) followed by the interleaving FEC (Forward Error Correction) coded navigation data and ends with tail bits for the FEC decoding. Medium rate (Ephemeris, Clock Correction): sub-frame. ![]() ![]() Fast rate (for urgent data, such as integrity): page.This arrangement allows accomplishing the three different main categories of data to be transmitted at different rates: The general structure of the navigation messages are common but the number of sub-frames and pages as well as the duration of each page are not the same, as represented in the following table. ![]()
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