%0 Journal Article %1 Ledvina2005 %A Ledvina, B. M. %A Psiaki, M. L. %A Powell, S. P. %A Kintner, P. M. %D 2005 %J Proc. of the 18th ION GNSS Conf. %K GPS, multipleFrequency, satnav softwareReceiver %P 1-16 %T A 12-Channel Real-Time GPS L1 Software Receiver %X A GPS receiver has been developed that runs 12 tracking channels in real-time using a software correlator. This work is part of an effort to develop a flexible receiver that can use new GPS signals as they become available without the need for new correlator hardware. The receiver consists of an RF front-end, a system of shift registers, a digital data acquisition (DAQ) card, and software that runs on a 1.73 GHz PC. The commercial RF front-end down converts the signal into a 2-bit digital data stream at 5.714 MHz. The shift registers parallelize the magnitude and sign data bit streams into separate words, which the DAQ reads into the PC's memory using direct memory access. The PC performs base-band mixing and PRN code correlations in a manner that directly simulates a hardware digital correlator. It also performs the usual signal tracking and navigation functions, under the control of a real-time Linux operating system. The software correlator receives frequency commands for simulated carrier and code NCOs and, in effect, uses these to reconstruct carrier and code replicas which it mixes with the input data stream. The resulting signals are summed to produce the standard in-phase and quadrature, prompt and early-minus-late accumulations. These, along with the phases of the 2 NCOs, are sent back to the part of the code that executes the tracking loops and the navigation functions. The contributions of this work are a set of special high-speed algorithms for doing the correlations in software. They make use of bit-wise parallelism so that a single C-code command (partially) processes 32 samples at a time. This system has been tested using a roof-mounted antenna. When operating with 12 channels, the entire re ceiver uses less than 50% of the capacity of the 1.73 GHz processor and navigates to an accuracy of 10 meters.

@article{Ledvina2005, abstract = {A GPS receiver has been developed that runs 12 tracking channels in real-time using a software correlator. This work is part of an effort to develop a flexible receiver that can use new GPS signals as they become available without the need for new correlator hardware. The receiver consists of an RF front-end, a system of shift registers, a digital data acquisition (DAQ) card, and software that runs on a 1.73 GHz PC. The commercial RF front-end down converts the signal into a 2-bit digital data stream at 5.714 MHz. The shift registers parallelize the magnitude and sign data bit streams into separate words, which the DAQ reads into the PC's memory using direct memory access. The PC performs base-band mixing and PRN code correlations in a manner that directly simulates a hardware digital correlator. It also performs the usual signal tracking and navigation functions, under the control of a real-time Linux operating system. The software correlator receives frequency commands for simulated carrier and code NCOs and, in effect, uses these to reconstruct carrier and code replicas which it mixes with the input data stream. The resulting signals are summed to produce the standard in-phase and quadrature, prompt and early-minus-late accumulations. These, along with the phases of the 2 NCOs, are sent back to the part of the code that executes the tracking loops and the navigation functions. The contributions of this work are a set of special high-speed algorithms for doing the correlations in software. They make use of bit-wise parallelism so that a single C-code command (partially) processes 32 samples at a time. This system has been tested using a roof-mounted antenna. When operating with 12 channels, the entire re ceiver uses less than 50% of the capacity of the 1.73 GHz processor and navigates to an accuracy of 10 meters.}, added-at = {2011-05-30T10:41:10.000+0200}, author = {Ledvina, B. M. and Psiaki, M. L. and Powell, S. P. and Kintner, P. M.}, biburl = {https://www.bibsonomy.org/bibtex/23431f6a6b2db756209b120d139156bea/bmuth}, groups = {private}, interhash = {2e80b96065dc8330d64153889e0bdbf1}, intrahash = {3431f6a6b2db756209b120d139156bea}, journal = {Proc. of the 18th ION GNSS Conf.}, keywords = {GPS, multipleFrequency, satnav softwareReceiver}, owner = {bmuth}, pages = {1-16}, timestamp = {2014-08-11T22:37:44.000+0200}, title = {{A 12-Channel Real-Time GPS L1 Software Receiver}}, username = {bmuth}, year = 2005 }