Abstract
Spectrum limitations for navigation systems require that the various navigation signals broadcast by the Galileo system must be combined and must utilize bandwidth-efficient modulations. At the L1 band, one of the most important questions is how to combine all the Open Service signals and the Public Regulated Service signal at the payload level, while maintaining good performance at reception. The Interplex modulation, a particular phase-shifted-keyed/phase modulation (PSK/PM), was chosen to transmit these signals because it is a constant-envelope modulation, thereby allowing the use of saturated power amplifiers with limited signal distortion. The Interplex modulation was also taken as baseline at the E6 band to transmit the three channels and the services associated on the same carrier frequency. At the E5 band, the modulation must combine two different services on a same constant envelope composite signal, while keeping the simplicity of a BOC implementation. The constant envelope Alternate Binary Offset Carrier (ALTBOC) modulation was chosen as the solution to transmit the Galileo E5 band signal. The main objective of this paper is to study these Galileo modulations. After the introduction, the E5 band signals are described, followed by the Alternate BOC modulation which has been chosen to transmit them. The second part describes the general formulation of the Interplex modulation and its key parameters for an optimal multiplexing of the Galileo L1 band signals. Since the Galileo Open Service signals at the L1 band are still not yet completely specified, different test cases are considered and their impact on the resulting choice for the Interplex modulation parameters is exposed.
Similar content being viewed by others
References
Avila-Rodriguez J-A, Wallner S, Hein GW, Rebeyrol E, Julien O, Macabiau C, Ries L, Delatour A, Lestarquit L, Issler J-L (2006) CBOC—an implementation of MBOC. CNES workshop on Galileo signals 2006, Toulouse
Butman S, Timor U (1972) Interplex—an efficient multichannel PSK/PM telemetry system. IEEE Trans Commun 20(3, Part 2):415–419
Galileo Joint Undertaking (2005) L1 band part of Galileo signal in space ICD. http://www.galileoju.com
Hein GW, Avila-Rodriguez JA, Ries L, Lestarquit L, Issler J-L, Godet J, Pratt T (2005) A candidate for the Galileo L1 OS optimized signal. ION GNSS 2005, Long Beach
Hein GW, Ávila-Rodríguez JA, Wallner S, Pratt AR, Owen J, Issler J-L, Betz JW, Hegarty CJ, Lt Lenahan S, Rushanan JJ, Kraay AL, Stansell TA (2006) MBOC: the new optimized spreading modulation recommended for GALILEO L1 OS and GPS L1C. ION IEEE/PLANS 2006, San Diego
Issler J-L, Ries L, Lestarquit L, Nouvel O, Jeandel O (2003) Spectral measurements of GNSS satellite signals need for wide transmitted bands. ION GPS/GNSS 2003, Portland
Julien O, Macabiau C, Issler J-L, Ries L (2006) 1-Bit processing of CBOC signals. CNES workshop on Galileo signals 2006, Toulouse
Rebeyrol E, Macabiau C, Lestarquit L, Ries L, Issler J-L, Boucheret M-L, Bousquet M (2005) BOC power spectrum densities. ION NTM 2005, San Diego
Rebeyrol E, Macabiau C, Ries L, Issler J-L, Boucheret M-L, Bousquet M (2006) Interplex modulation for navigation systems at L1 band. ION NTM 2006, Monterey
Ries L, Legrand F, Lestarquit L, Vigneau W, Issler J-L (2003) Tracking and multipath performance of assessments of BOC signals using a bit-level signal processing simulator. ION GPS/GNSS 2003, Portland
Sleewaegen J-M, De Wilde W, Hollreiser M (2005) Galileo ALTBOC receiver. Septentrio
Soellner M, Erhard P (2003) Comparison of AWGN code tracking accuracy for Alternative-BOC, Complex-LOC and Complex-BOC modulation options in Galileo E5-Band. GNSS Conference 2003, Graz
Wallner S, Hein GW, Pany T, Avila-Rodriguez J-A, Posfay A (2005) Interference computation between GPS and Galileo. ION GNSS 2005, Long Beach