A Family of Solutions Based on the srx-10, a SW Defined Multi-Constellation GNSS Receiver

Teresa Ferreira, Manuel Toledo, Jose Maria López Almansa

Abstract: The srx-10 is a hosted software defined radio (SDR) multi-constellation GNSS receiver developed by GMV and capable to track GPS, GLONASS, Galileo and SBAS signals in the L1 band. Based on the flexibility of srx-10 and the availability of the srx-10FE radio frequency Front End we provide a range of solutions, from a fully hosted receiver to a multi-antenna system as well as the srx-10i, a solution for interference monitoring in the aeronautical domain. As a fully hosted solution, a general purpose CPU can host all software defined receiver functions for signal acquisition and tracking, real-time raw measurement generation (pseudo range, Doppler, carrier phase and C/N0), and real time position, velocity and time determination. Furthermore, srx-10 is able to work in A-GNSS mode, providing great navigation performances with extended ephemeris that can be supplied by GMV’s magicGNSS service. srx-10 has been developed to target mass-market applications. It is optimized to run on low cost CPU platforms, as those available on consumer or specialized mobility devices, from smartphones or tablets to automotive OBU’s. srx-10 versions ported to Pentium, Atom, XScale and ARM9 processors are available. With this approach, GMV’s product aims to offer GPS, GLONASS and Galileo reception, and SBAS augmentation with almost zero marginal production costs. User devices for personnel location and telematics applications will therefore be able to slash their BOM cost compared to conventional hardware receivers or partially hosted hardware receivers. Key benefits offered by GMV’s software receiver are its enormous flexibility and upgradeability. Since it is a fully hosted solution, there is no need to change any HW; this makes it much easier to phase in new features and market receiver customizations. In the case of automotive OEMs this feature will allow remote in-factory upgrading of telematics devices to include the latest available GNSS services. Extensive test campaigns carried out with these low cost CPUs in urban and non-urban scenarios are providing performances similar to those offered by conventional world class mass-market receivers. The latest versions of srx-10 incorporate advanced signal processing techniques to deliver high-quality carrier phase measurements suitable for accurate positioning based on RTK and PPP. As Front End for this software receiver, GMV has developed the srx-10FE, which is connected to the host processor through a USB port that allows real-time communication. The srx-10FE allows the user to configure many front-end parameters. In particular, RF bandwidth and sampling frequency can be configured, which allows adapting the front-end to the computational capabilities of the host processor and to the specific application. srx-10FE allows external clock connectivity in order to use several front-ends with a common shared clock, which can be very useful for multiple-antenna applications. As example of this capability, GMV has available a L1 GPS/GLONASS 3 antennae device, specialized in the assessment of the angle of arrival (AOA) of GNSS signals in urban environments. As part of this family of solutions, srx-10i is a complete GPS/Galileo spectrum monitoring, interference detection and analysis system in the L1/E1 bands fully developed by GMV following the ICAO 8071 recommendations. Unintentional interferences can emanate from telecommunication and electronic systems such as FM/TV transmitter harmonics, AM transmitters, maritime/military communications and mobile phone networks. Intentional interferences can emanate from jamming devices and GPS Repeaters. The system has been designed to fulfill the need of spectrum monitoring whenever GPS (and Galileo in the future) is used in support of the operation of critical infrastructures such as airports. The benefits offered by the system are an uninterrupted, automatic operation for continuous monitoring of disruption events due to interference in the GPS/Galileo L1/E1 bands and the identification and characterization of the interference sources. Based on a software receiver, this solution provides an optimum cost that enables a deployment in multiple points in the area to be monitored. This real-time interference detection system based on srx-10i is currently installed at 8 major airports in Spain where GPS/SBAS approach procedures are being deployed. To complement the srx-10 family of GNSS Receiver solutions and in order to support the assessment of innovative GNSS signal processing techniques, GMV has available the “grslab” signal generator, which can generate up to 20 GPS or Galileo signals, in base-band or in intermediate frequency, including civilian GPS signals (L1 C/A and P codes, L2 CM and CL codes and L5), and Galileo (E1, E5 and E6). The generated modulations included are BPSK, QPSK, THM (Tricode Hexaphase Modulation), CASM (Coherent Adaptive Subcarrier Modulation), BOC (Binary Offset Carrier) and AltBOC (Alternate BOC). The tool offers the possibility of generating single channels within each navigation signal. That is, for example, in case of Galileo E1, one can generate independently the A, B and C channels, but also the multiplexed version using the CASM or THM modulation schemes. This is especially useful in the early stages of receiver prototyping. In summary, due to its flexibility and modular design, the srx-10 is ideal to develop specialized GNSS solutions with special receiver requirements. Furthermore, complemented with the “grslab” signal generator, it is an ideal engineering tool to prototype and test innovative signal processing techniques and to perform engineering trade-offs among different options.
Published in: Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014)
September 8 - 12, 2014
Tampa Convention Center
Tampa, Florida
Pages: 285 - 306
Cite this article: Ferreira, Teresa, Toledo, Manuel, Almansa, Jose Maria López, "A Family of Solutions Based on the srx-10, a SW Defined Multi-Constellation GNSS Receiver," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 285-306.
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