A simplified convolutional decoder for galileo os: performance evaluation with a galileo mass-market receiver in live scenario

Abstract

The Galileo E1 Open Service signal broadcasts a navigation message containing 120 bits of information per page on the signal component E1B. This raw navigation message is ½ convolutional encoded with a Forward Error Correcting (FEC) Code. The encoded symbols are interleaved within a block interleaver size of 240 symbols and broadcast every second. The resulting data rate is 250 symbol/second. The user receiver, after the detection of the synchronization pattern and the deinterleaving of the symbols, decodes the page symbols into data bits commonly by using a Viterbi Algorithm (VA) [1]. VA performs an iterative search to realise maximum-likelihood decoding. Implementing a Viterbi Decoder (VD) for mass-market and commercial applications could be demanding. In communication application, a VD may consume more than onethird of power consumption of the whole baseband processing [2]. Thus, designing an optimized VD to reduce the power consumption, especially for mobile and mass market applications, is an important topic. This paper presents the results of a new decoder called State Transparent Convolutional (STC) [4]. The analyses are carried out in simulated scenarios and on-field tests and the computational load of the VD and STC decoder as function of the C/N0 and elevation angle will be investigated. Results show a great benefit in term of complexity reduction when STS is applied in decoding the Galileo Open Service Navigation messages.