PRECISIO a multi-constellation, multi-frequency software receiver. William Roberts, NSL ENC GNSS October 2010 Braunschweig

Transcription

1 PRECISIO a multi-constellation, multi-frequency software receiver William Roberts, NSL ENC GNSS October 2010 Braunschweig

2 Develop a GNSS receiver... to meet the challenges of today s users Sufficiently high-end to meet the needs of users. Multi-constellation capable. Multi-frequency capable. Upgradeable and flexible for new GNSS signals and services that is designed to Provide differentiators over other solutions. Be scalable to a user production product and potential further markets. that will be tested and validated In operational environments ensuring it meets users requirements for fixed infrastructure receivers Slide 2

3 Adopting a SDR approach Delivers several key benefits to users and operators Future proof equipment against the uncertainty in GNSS signals and services. Reconfigurable and upgradeable equipment that can take advantage of future signals and services as they becomes available. Longer lifetime for installed equipment. Allowing for dynamic reconfiguration to an always-optimal processing chain in constrained environments. Dramatically reduced receiver costs. Potential for shared infrastructure for disparate markets and operations. Slide 3

4 The Precisio Team Slide 4

5 Slide 5

6 Slide 6

7 Authors 1 William Roberts, Michele Bavaro, Mark Dumville 2 Enrique Domínguez Tijero, Manuel Toledo-López 3 Stefano Vaccaro, 4 Fabrice Legrand 5 Stuart Mitchell, Andy Sage, Daniel Kominak 6 Chris Hill, Terry Moore 1 Nottingham Scientific Ltd, Loxley House, Tottle Road, Nottingham NG2 1RT, UK 2 GMV Aerospace and Defence SA, Isaac Newton, 11 P.T.M. Tres Cantos, Madrid, Spain 4 M3 Systems, 26 rue du soleil levant, Lavernose, France 3 JAST SA, PSE-C, Lausanne, CH-1015, Switzerland 5 Helios, 29 Hercules Way, Aerospace Boulevard, AeroPark, Farnborough, GU14 6UU, UK 6 IESSG, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK Slide 7

8 Project Structure and Timeline WP1 User Analysis WP2 Tech. Research WP3 Req. Consol. WP4 Design WP5 Development WP6 Validation & Trials WP7 Implementation Plan WP8 Dissemination & Awareness WP9 Coordination & Support to GSA WP10 Management T 0 Project Duration T m Now Slide 8

9 Capturing the User Requirements Market analysis Indentify and characterise market segments Supply chain and purchasing analysis Current and emerging applications D1: User Requirements and User Segment Analysis Document Recent reports Internal project knowledge Target stakeholders for consultation Market 1: Application 1A Initial Initial Initial user user user requirements requirements requirements User requirements consultation Classify critical functionality for competitive advantage Technical (GNSS) user requirements Non-GNSS requirements Slide 9

10 Market Analysis to User Requirements Market segments National reference networks International public infrastructure Global commercial service networks GNSS infrastructure Maritime DGNSS Meteorology Metrology networks Interference monitoring Ionospheric monitoring (TEC) Ionospheric monitoring (Scintillation) Payload/signal validation tool Survey Rail Automotive Consultation Market analysis Market characterisation: Users and Applications Competitive environment Market Evolution Purchasing behaviour Receiver technology: Technical & commercial priorities Current issues/limitations Implications and needs for a SDR Specific requirements GNSS requirements Non GNSS requirements Slide 10

11 Precisio Product Rollout End of project prototype +6 months +12 months +18 months Slide 11

12 Subset of User requirements Track code, phase, doppler observables for all in view satellites for all received frequencies in all GNSS (GPS, Glonass, Galileo, Compass) includes GPS L2C & L2P Upgradable to all future GNSS (on publication of ICD) Compass, Glonass CDMA, Galileo PRS, CS Receive WAAS, EGNOS and MSAS 72 channels 220 for 2 nd generation 20Hz to 100Hz sampling frequency No smoothing is applied to the observables as standard phase smoothing optional Carrier/code phase 0.2/20 mm rms Receiver hardware delay extremely stable Synchronize with GPS time < ± 1 ms Timing accuracy should be 1ns or better Support RTCM, RTCM-HP, BINEX, RINEX v3, NMEA and 1pps outputs Remote operation, configuration, and diagnostics Inc acquisition and tracking settings Choke ring or multi-element antenna as multipath mitigation system Phase centre repeatability +/- 0.5mm in the horizontal and +/- 1mm in the vertical The receiver MTBF > hours Rx availability > % Low cost Slide 12

13 Subset of User requirements Track code, phase, doppler observables for all in view satellites for all received frequencies in all GNSS (GPS, Glonass, Galileo, Compass) includes GPS L2C & L2P Upgradable to all future GNSS (on publication of ICD) Compass, Glonass CDMA, Galileo PRS, CS Receive WAAS, EGNOS and MSAS 72 channels 220 for 2 nd generation 20Hz to 100Hz sampling frequency No smoothing is applied to the observables as standard phase smoothing optional Carrier/code phase 0.2/20 mm rms Capable, Flexible, Transparent, High quality, Reconfigurable, Stable, Useful, Low cost Receiver hardware delay extremely stable Synchronize with GPS time < ± 1 ms Timing accuracy should be 1ns or better Support RTCM, RTCM-HP, BINEX, RINEX v3, NMEA and 1pps outputs Remote operation, configuration, and diagnostics Inc acquisition and tracking settings Choke ring or multi-element antenna as multipath mitigation system Phase centre repeatability +/- 0.5mm in the horizontal and +/- 1mm in the vertical The receiver MTBF > hours Rx availability > % Low cost Slide 13

14 Functional Blocks of a GNSS Rx Output Example Applications Interference detection Antenna beamforming Push to fix applications Multipath detection Signal Quality Monitoring Professional applications GNSS augmentations Mobiles, car navigation, LBS, tracking, etc Slide 14

15 Hardware Rx implemented using ASICs Hardware GNSS Rx Comments Sub-component outputs available internally (eg used for multipath/interference mitigation) Limited outputs Limited applications Slide 15

16 Validated COTS Designed and Developed in PRECISIO SDR Rx on processor/fpga SDR RF Front End Software Defined Radio GNSS Rx Comments Outputs available for different applications Flexible RF settings Flexible correlation and acquisition & tracking functions/routines Slide 16

17 Antenna Considerations Selection criteria Radiation pattern properties Amplitude: multipath rejection Phase: phase centre variation, errors Polarization: multipath rejection, G/T Form factor Weight, encumbrance Height, standard radomes Interface: 1 or 2 ports Other antenna properties Bandwidth Efficiency User acceptance Slide 17

18 Antenna Radiating elements Different candidates have been evaluated and traded-off against main requirements Turnstile, Dipoles Spiral, Conical Helix, Quadrifilar Helix Patches Trade-off results suggest patches or planar elements like spirals offer the highest performance, flexibility and integratability with multipath mitigation strategy (Choke rings, array) Slide 18

19 Multipath rejection features Multipath rejection techniques Vertical array Phase-cancelling configurations Reactive ground planes Absorbing ground planes Digital beamforming Passive structures (e.g chocke rings) have been selected as the most suitable multipath rejection technique. Slide 19

20 RF Front End Design Capture all GNSS Frequencies & Digitise to suitable resolution Maintain a reasonable form factor, power consumption, & cost Lower RNSS Band ( MHz) High RNSS Band ( MHz) Slide 20

21 Architectural solutions (limited to COTS) Multi-channel super-heterodyne Multi-channel homodyne (direct conversion) Multiple narrow band F/Es are difficult to tune equally Power consumption an issue Not many COTS components would do E5 AltBOC Chaotic RF and digital design hard to maintain Slide 21

22 Preferred RF FE solution Direct band-pass sampling front-end ADVANTAGES One RF chain for all GNSS frequencies Very elegant solution Commercially feasible now RF board, Isolates & amplifies GNSS frequencies DISADVANTAGES Need high gain at RF Needs very careful filtering of the signal Slide 22 Digital Board, ADC and digital band tuning

23 Prototype RF FE solution GNSS Antenna GNSS ch1 digital downconverter GNSS ch2 FIFO buffer FPGA parallel LVDS Interface partner FPGA RF chain ADC digital downconverter FIFO buffer GNSS ch1 GNSS chn GNSS ch2 Serialiser GB Eth adapter digital downconverter FIFO buffer GNSS chn Validation I/F SDR Receiver Slide 23

24 Digital Board RF board FE Spectrum Response 1 st iteration had poor outof-band rejection 2 nd iteration dual band filters have good response, with minimal noise folding in the digital domain. Marketable low cost product, available now Slide 24

25 The Software Receiver Digital signal processing complexity analysis : High level of complexity due to : The capability to process all GNSS signals : complexity of the baseband signal processing vs. signal modulation schemes Optimal processing architectures for BOC, MBOC and ALTBOC signal processing High level of performance and robustness : Interference robustness and mitigation capabilities Multipath effect mitigation capabilities Precise positioning capabilities Autonomous integrity capabilities Hybridization with external sensors capabilities Complete re-configurability and upgradability capabilities Support of standard interfaces Slide 25

26 Architecture options General purpose microprocessor-based architecture Pros: Generic platform, standard C/C++ source codes Cons: Limited performances in term of integration capabilities (amount of channels, advanced signal processing techniques), limited input signal bandwidth) DSP-based architecture Pros: improved signal processing performances Cons: device-dedicated C source codes, limited performances in term of integration capabilities (amount of channels) FPGA-based architecture Pros: high integration capability (amount of channels), high input signal bandwidth, Cons: limited performances of VHDL-based or integrated processors Mixed Proc-DSP-FPGA architecture Preferred solution for high performance and high integration capability for the targeted multi-constellation and multi-frequency receiver Slide 26

27 Mixed Proc-DSP-FPGA architecture Mother board: Microprocessor implementing : PVT, enhanced processing applications, HMI, communication drivers, data formatting functions for I/O standard FLASH memory implementing : the executable code, the PRN and secondary codes sequences, the default configuration parameters of the receiver Storage Signal Processing boards: FPGA implementing : pre-processing functions, correlators, FFT-coprocessor for acquisition Microprocessor (ASIC or FPGA implemented) implementing : extended correlation processes tracking loops; data and navigation message demodulation functions raw measurements formatting Slide 27

28 Precisio Validation Precisio target market: GNSS infrastructures and services The project prototype will be validated Within existing GNSS networks Signals in space, simulated signals magicgnss will be used as the receiver validation platform A web application for GNSS data processing, featuring high precision and integrity Calculates precise user coordinates, clock and tropospheric delay, etc Calculate suser receiver integrity Oriented to precision applications Will Precisio deliver performances comparable with the hardware receiver devices currently deployed in international GNSS networks? Slide /09/24 Page 28 PRECISIO PROTOTYPE VALIDATION

29 Tested within 4 Networks 1. UK, British Isles continuous GNSS Facility - BIGF. 2. UK, RTK reference network.. 3. Spain, IGS Network within the IGS Real Time Pilot Project) 4. UK, alongside a COMPASS tracking station (dependent on ICD) Slide /09/24 Page 29 PRECISIO PROTOTYPE VALIDATION

30 In Summary User requirements identified Initial target markets National reference networks, international public infrastructure, meteorological services Requirements: capable, flexible, transparent, high quality, reconfigurable, stable, useful... & low cost (meets IGS Super Rx) Antenna, RF Front End and SDR Rx are currently at the design stage RF Front End following a iterative design process Prototype will be validated in real-world networks (IGS, UK national/regional, COMPASS*) using simulated signals Using test/initial transmissions Slide 30

31 Workshop Announcement Workshop on State of the Art SDR GNSS Technologies 2-day event, April, 2011 Hosted by GRACE, sponsored by industry & EC projects Day 1 Invited speakers, technology specialists Day 2 EC project presentations Technology demonstrations throughout Using GPS + Galileo full constellation simulator Dynamic positioning test track Signal log and replay devices Slide 31

32 Thank you