The GALILEO GPS Software Receiver Company Software Receiver

-The GALILEO & GPS Software Receiver Company Software Receiver Technology 30 -September-2004 Tampere University of Technology Glenn Mac. Gougan glenn@nordnav. com +46 703113880 Copyright © 2004 Nord. Nav Technologies AB

Nord. Nav Technologies AB • Unique Competence Ø GPS & GALILEO Ø Real-time Software Receiver Technology • Headquarter in Luleå, Sweden Ø Luleå University of Technology Ø Office in Stockholm • Developing and licensing real-time GPS & GALILEO software receivers Copyright © 2004 Nord. Nav Technologies AB

Agenda • GNSS Receiver Technology – Traditional GNSS Receiver Technology – Software Radio Technology – Software GNSS Receiver Technology • Demonstration – Nord. Nav-R 30 Software GPS Receiver – New Features • GPS and Galileo • Conclusion Copyright © 2004 Nord. Nav Technologies AB

GNSS Receiver – 3 Steps • Search phase (acquisition) t 0 Start GPS 0 -2 sec Acq t 1 Tracking 1. 2 -6 sec No t 2 No TOW decoded ? Yes Ephemeris decoded ? 18 -30 sec No Yes 4 satellites ? Yes Pos Fix – Satellite, Carrier Frequency, Code phase • Track satellites (tracking) – Adjust local replica signal using two coupled loops • Code - Delay-Lock-Loop • Carrier - Phase-Lock-Loop – Decode Data message • Navigation computation (navigation) – ”Triangulate” position • Distance to satellites known and their precise position – X, Y, Z, Velocity and Time t 3 Copyright © 2004 Nord. Nav Technologies AB

Traditional GNSS Receiver Architecture • Block diagram of a typical GNSS receiver Antenna Baseband ASIC Analog RF Front End ASIC AGC N 2 RF Pre Amp (LNA) Down Converter Reference Oscillator Frequency Synthesizer User Interface Analog IF Low Speed Comm Link A/D Converter Digital IF Digital Receiver Channel 1 Power Supply Navigation Processing Acquisition Tracking Microprocessor Copyright © 2004 Nord. Nav Technologies AB

• Software Radio The software radio concept is built upon two basic principles 1. Move the analog-to-digital converter (ADC) as close to the antenna as possible 2. Process the resulting samples using a programmable processor Antenna Amplification Analog filtering low Programmable element Available Processing Rate high ASIC Analog to digital Conversion (ADC) FPGA Microprocessor (Assembly Language) Level of Flexibility low Microprocessor (High Level Language) Microprocessor (Simulation Tool) high Copyright © 2004 Nord. Nav Technologies AB

Software Radio: Myths & Truths • Current technology simply does not meet the needs for the ”ideal” software radio – High-end analog-to-digital converter (ADC) examples • Maxim MAX 104: 8 Bits; 1. 0 Gsps; 2. 2 GHz Analog Input BW • Analog Devices: AD 6645: 14 Bits; 0. 105 Gsps; 0. 200 GHz Analog Input BW – High performance processor element examples • Intel Pentium IV Processor @ 3. 4 GHz clock • Xilinx Virtex II Pro FPGA (up to four embedded Power. PC 405 processors) • Impractical to sample wide spectrum and digitally filter, decimate, and process bands/signals of interest – It is possible to construct multiple front ends and use software to process the output of each – It is possible to have a single front end and use software to provide an efficient, flexible, and dynamic signal processing solution • Such an ”ideal” radio would not be cost-effective Copyright © 2004 Nord. Nav Technologies AB

Software GNSS Receiver: Feasibility & Comments • The typical GPS receiver design, with a combination of hardware and software signal processing, is well engineered design – The high speed signal processing deals with a samples on the order of 4 -20 Msps, while the low speed programmable processor deals with pre-processed samples on the order of 1 Ksps • Current technology allow for the implementation of a real time GNSS software receiver – Flexible signal processing • Possible to use for new signals and the • Hybrid GPS/Galileo receivers – Potenial low-cost alternative for system integrators – Bandwidth of the signals [sampling frequency] the most important parameter • Moore’s law can be interpreted to show processing power has and continues to increase exponentially since the 1970’s – so tradeoff changes perspective Copyright © 2004 Nord. Nav Technologies AB

A Feasible Commercial Software GNSS Receiver Architecture Antenna Analog RF Front End Microprocessor/DSP AGC N 2 Pre Amp (LNA) Down Converter Reference Oscillator Frequency Synthesizer Analog IF A/D Converter Digital IF Navigation Processing Digital Baseband Channel 1 Acquisition Tracking • Downconversion is used – ADC is situated after the IF stage - Ideally programmable bandwidth & frequency band • Signal processing function after IF stage are realized in software increased flexibility Copyright © 2004 Nord. Nav Technologies AB

Two product lines: • PC-based GNSS Receiver : Nord. Nav-Rxx – – Specialized customer applications High end receiver End customers in R & D R 25/R 30 being shipped now! Automotive General DSP or Microprocessor • Embedded Receiver : Nord. Nav-Exx Family – Single point fixes/continuous tracking – Designed for a DSP/Embedded processors – Extremely cost effective (re-use existing processing power in mobile terminal) Mobile Terminals Exx SW Nord. Nav Soft GPS Copyright © 2004 Nord. Nav Technologies AB

Nord. Nav-RXX characteristics • Complete receivers targeted towards R&D and Test & Verification market segments – Desktop research – Desktop verification • Specialized customer applications • Designed to run on an PC platform • Multiple sensor integration (GPS/INS/dead reckoning), interference investigations, antenna arrays/beamforming etc. • Record raw IF samples & replay samples Copyright © 2004 Nord. Nav Technologies AB

Nord. Nav-RXX Architecture Microprocessor GPS Antenna USBv 2 Data Acqusition Interface IF Samples Engine RF Multibit L 1 Front End Hard drive User App. Sample. Streamer GUI Correlator Engine Acqusition & Tracking API Navigation Receiver GUI Copyright © 2004 Nord. Nav Technologies AB

Nord. Nav-R 30 Demonstration • Receiver will be run on Pentium 1. 7 GHz Notebook PC – Replay a recorded datafile from Stockholm • Unique features briefly demonstrated – – – 24 channels (typically 14 -16 realtime depending on configuration) Configurable parameters Add multiple correlators – New feature! Tracking loop framework – Updated framework Signal Injection – example study interference effects Copyright © 2004 Nord. Nav Technologies AB

Baseband Configuration Copyright © 2004 Nord. Nav Technologies AB

Receiver GUI Examples Horizontal scatter plot Monitor AGC level Monitor the antenna frequency spectrum Copyright © 2004 Nord. Nav Technologies AB

Real-Time GUI Correlator Plot • Add multiple correlator pairs • Each channel can be individually configured • User can set the tracking pairs & spacing Copyright © 2004 Nord. Nav Technologies AB

Impact of Tracking Loop Parameters 10 Hz PLL 20 Hz PLL Copyright © 2004 Nord. Nav Technologies AB

External Tracking Loop Framework 1(2) • The user can implement its own discriminators for code & carrier • Implement its own code and carrier tracking loop • Excellent for ”aiding” of tracking loops by for example IMU Nord. Nav R 30 GUI Nord. Nav R 30 API Nord. Nav R 30 Receiver Visual C Framework • User implemented code - dll • Example implementation included Close. Loops API Close. Loops. dll Copyright © 2004 Nord. Nav Technologies AB

External Tracking Loop Framework 2(2) Updated and added functionality • Updated values every navigation update rate (not every ms as the accumulators): – Satellite positions – Receiver position & velocity • Indicator to tell the receiver to NOT try and extract data – For low C/No studies Copyright © 2004 Nord. Nav Technologies AB

Signal Combiner 1(4) • Allows to inject a simulated signal into real GPS samples prior receiver processing • Possibility to study the effect interference signals and jamming scenarios • The user can implement any signal structure, even GPS signals which the receiver can track – Simulated file : each sample stored as signed char (byte) Copyright © 2004 Nord. Nav Technologies AB

Signal Combiner 2(4) GPS Signal Stored GPS samples Sample Streamer Antenna Front end Stored external signal samples Example : Simulated CW, Noise A/D Multiplication factor R 30 Software Receiver Signal Combiner Copyright © 2004 Nord. Nav Technologies AB

Signal Combiner 3(4) >> cw_gen(5 e 5, 1 e 6, 0. 05, 'cw_500 k. Hz. sim') Included example signal generation scripts CW tone noise Copyright © 2004 Nord. Nav Technologies AB

Signal Combiner 3(4) Example of GPS L 1 frequency spectrum with a injected 20 d. B CW tone (sinusoid) at 500 KHz off L 1 frequency Copyright © 2004 Nord. Nav Technologies AB

New features in this software release • • Fault Detection and isolation Improved Dynamic performance Velocity output Troposphere (same as WAAS model) 2 -D navigation (height fixing) Almanac Configuration per channel basis – Correlators (spacing and numbers) – Tracking loop parameters – Acquisition parameters • External Tracking Loop Framework updated Copyright © 2004 Nord. Nav Technologies AB

Fault Detection Example (severe multipath reflection) Normal Processing – R 30 With Reference Fault Detection Receiver Processing – R 30 Copyright © 2004 Nord. Nav Technologies AB

Next Major Software Release • SBAS – Support for WAAS/EGNOS • Scheduled IF recording • Improved Sensitivity • External Position API • Next Major Software release – Galileo L 1 (software IF signal generator & processing) Copyright © 2004 Nord. Nav Technologies AB

Galileo • Galileo – European ”GPS”. Designed to be independent but compatible with GPS – Same frequency band as GPS – Different signal structure • Operational 2008 [2010] – Civil system Great asset for all users with hybrid GPS/Galileo receivers! • Increase service availability drastically! • Five different service categories – Open Service (OS) - Free of charge! – Safety of Life (So. L), Commercial services (CS), Search and Rescue (SAR), Public Regulated Service (PRS) Copyright © 2004 Nord. Nav Technologies AB

GNSS Frequency Spectrum Modernized GPS and Glonass signals not included Copyright © 2004 Nord. Nav Technologies AB

GPS Signals Carrier at 1575. 42 MHz (L 1) 1227. 60 MHz (L 2) 19 cm (L 1) Code at 1. 023 Mcps (C/A) 10. 23 Mcps (P(Y)) 300 m (CA) Navigation Data at 50 bps 6000 km Copyright © 2004 Nord. Nav Technologies AB

Galileo – Open Service Signal L 1 Band, BOC(n, m) Copyright © 2004 Nord. Nav Technologies AB

GPS and Galileo Sharing L 1 Spectrum : C/A and BOC(1, 1) GPS C/A Galileo BOC(1, 1) (data bearing signal) • Code length 1023 chips • 1. 023 MHz chipping rate (1 ms period time) • 50 Hz data rate (20 code periods per data bit) • ~90 % of signal power within ~2 MHz bandwidth • Code length 8184 chips • 1. 023 Mhz base frequency (8 ms period time) • 125 Hz data rate (1 code period per data bit) • ~85 % of signal power within ~4 Mhz bandwidth ~4 MHz BW Copyright © 2004 Nord. Nav Technologies AB

Conclusion • ”Ideal Software Receiver” is still a dream – Current technology do not allow for such designs • However for bandlimited signals, such as GPS/GNSS, software receiver are commercially feasible – Downconversion front end used – Process digital IF samples in software • Software receivers are receiving market acceptance – Technology not only for research in a laboratory • Although fantastic for this purpose! – More and more feasible as alternative to traditional Rx – Multi-channnel receivers exists today • Important technology for Galileo – Hybrid GPS/Galileo L 1 receiver for mass market Copyright © 2004 Nord. Nav Technologies AB