A USRP2-based reconfigurable multi-constellation multi-frequency GNSS software receiver front end

Abstract

We present a multi-constellation multi-band GNSS software receiver front end based on USRP2, a general purpose radio platform. When integrated with appropriate daughter boards, the USRP2 can be used to collect raw intermediate frequency (IF) data covering the entire GNSS family of signals. In this study, C?? classbased software receiver processing functions were developed to process the IF data for GPS L1, L2C, and L5 and GLONASS L1 and L2 signals collected by the USRP2 front end. The front end performance is evaluated against the outputs of a high end custom front end driven by the same local oscillator and two commercial receivers, all using the same real signal sources. The results show that for GPS signals, the USRP2 front end typically generates carrier-to-noise ratio (C/N 0 ) at 1-3 and 1-2 dB below that of the high end front end and a NovAtel receiver, respectively. For GLONASS signals, the USRP2 C/N 0 outputs are comparable to those of a Septentrio receiver. The carrier phase noise from the USRP2 outputs is similar to those of the benchmarking devices. These results demonstrate that the USRP2 is a suitable front end for applications, such as ionosphere scintillation studies.

Design of a robust receiver architecture for scintillation monitoring

“…To avoid affecting the scintillation indices computation the receiver architecture should be able to minimize the thermal noise, the oscillator phase noise and interference effects on the carrier phase and signal amplitude estimates [7].…”

GPS navigation data bit decoding error during strong equatorial scintillation

“…Figure 3 depicts the reconfigurable multi-GNSS SDR data collection system used in this campaign, which contains five RF front-ends each configured to collect signals within one frequency band: GPS L1/Galileo E1, GPS L2C, GPSL5/ Galileo E5a, GLONASS L1, and BeiDou B1 signals (Peng and Morton 2011). All front-ends share the same wideband antenna input and are driven by the same low phase noise OCXO with zero IF and 4-bit resolution.…”

Implementation and Performance Analysis of Multi-GNSS Signal Collection System using Single USRP

“…The USRP used in this study was NI-USRP 2940R (National The USRP has the internal oscillator of 10 MHz whose accuracy is 2.5 ppm (part per million). However, a Doppler error can be generated up to 4000 Hz at the L1 band signals if replica signals are created and down converted with the 2.5 ppm oscillator (Peng & Morton 2013). This problem increases a loop error of signal tracking thereby causing a performance degradation of receivers such as data error rate and navigation accuracy.…”

“…As examples of typical technologies, direct RF conversion technology (Akos et al 1999) that samples RF signals directly and a technique that utilizes a general purpose front-end can be found. Among them, the USRP (Universal Software Radio Peripheral) developed by Ettus is one of the widely known general purpose front-ends (Peng & Morton 2013). If the USRP is utilized, a Local oscillator (LO) frequency of mixer, gain of amplifier, and a sampling rate of ADC can be set to preferred values so a single piece of hardware can cope with various signals.…”

“…Because of this advantage, the USRP has been much utilized in studies on SDR. For example, Purdue University (Thompson et al 2012) and Virginia Tech (Peng & Morton 2013) also utilized USRP in studies on GNSS SDR.…”