Performance analysis of a Galileo weak signal acquisition algorithm

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					         Performance analysis of a Galileo weak signal
                   acquisition algorithm
   Soon Lim, Deok Won Lim, Dong-Hwan Hwang, Sang Jeong Lee, Department of Electronics Engineering, Chungnam
                                               National University, Korea
                                Seung Wook Moon, Hanyang Navicom Co. Ltd, Korea
          Chansik Park, School of Electrical and Computer Engineering, Chungbuk National University, Korea

                                                              however, the PIT can be long while it causes the square
INTRODUCTION
                                                              loss. This squaring loss makes the noise power level
Galileo system developed by EU will provide various
                                                              higher [3]. For compensating this phenomenon, modified
services such as civil navigation, governmental, and
                                                              non-coherent integration was proposed [3]. By using
commercial service. These new signals are planned to
                                                              modified non-coherent integrator instead of non-coherent
provide data-less signals, called the pilot signal. The
                                                              integration, the square loss will be mitigated and the
processing of weak signal becomes easier using the pilot
                                                              performance advance is expected.
signal so that the signal acquisition in the environments
such as indoor situation can be easier. In this paper, the
embodiment of an algorithm that uses the Galileo pilot        PERFORMANCE ANALYSIS
signals for weak signal acquisition is given, and             Through the experiment, the performance of the modified
performance evaluation will be presented.                     non-coherent integration and coherent integration is
                                                              analyzed. The effect of the integration time in both the
                                                              coherent integration and the non-coherent integration is
GALILEO SIGNAL STRUCTURE
                                                              given. And the detection probability and the mean
Galileo system has three frequency bands, E1, E5, and E6.
                                                              acquisition time are also analyzed.
The Galileo E1 signal has a 1575.42MHz center
frequency and uses the BOC (Binary Offset Carrier)
modulation. This signal will provide OS (Open Service),       CONCLUSIONS
CS (Commercial Service), and SOL (Safety of Life)             This paper analyzed the performance of a weak signal
service. The Galileo E5 signal has an 1191.795 MHz            acquisition algorithm adopting both the modified non-
center frequency and applies the Alternative BOC              coherent integration and the coherent integration. And the
modulation. The E5 signal is also planned to provide OS,      proper integration time for the Galileo pilot signal has
CS, SOL service. The E6 signal has a 1278.75MHz center        been provided.
frequency and uses the BPSK modulation. This signal
will provide only CS [1]. These three signals have two
                                                              REFERENCES
channels of signal: data channel that includes the
navigation data and pilot channel that has no navigation      [1] Galileo Open Service Signal In Space Interface
data. The pilot channel of GPS L2C, L5 and Galileo are            Control Document (OS SIS ICD), European Space
dataless so that no bit transition occurs and it makes a          Agency/Galileo Joint Undertaking, 2006.
reception of weak signal easier [2].                          [2] C. Botteron, G. W lchli, G. Zamuner, M. Frei, D.
                                                                  Manetti, F. Chastellain, P. A. Farine, “A flexible
                                                                  Galileo E1 Receiver Platform for the Validation of
INTEGRATION TECHNIQUES                                            Low Power and Rapid Acquisition Schemes,” ION
The typical method of acquiring weak GNSS signal is to            GNSS 19th International Technical Meeting of the
adopt both the non-coherent integration and the coherent          Satellite Division, September 2006, Fort Worth, TX.
integration. The increase of the integration time will        [3] Fernando M. G. Sousa, Fernando D. Nunes, Jose M.
provide the higher correlation value, so the probability of       N. Leitao, “Partial Correlation Technique for the
weak signal detection becomes higher. But increasing the          Acquisition of Weak GPS/Galileo Signals,” ION
integration time means the long acquisition time. In this         61st Annual Meeting/The MITRE Corporation &
case, the bit transition of the navigation data during the        Draper Laboratory, June 2005, Cambridge, MA.
PIT is also concerned [3]. Using the pilot channel is a
solution of the PIT limitation problem, but applying the
longer coherent integration will cause the more decreased
tracking performance because of the dynamic stress. Non-
coherent integration could complement the defect of
coherent integration. Using non-coherent integration,