Signal capturing:

Hardware: USRP1 + DBSRX daughterboard (Rev 4.5) + Antenna Novatel GPS-600. The USRP1 uses its internal 64 MHz onboard reference for deriving the sampling clock.

Date: July 26th, 2012
Time: 13:31:49 (UTC)
Location: Roof of the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), (40.396764 N, 3.713379 E), located at the Parc Mediterrani de la Tecnologia, Av. Carl Friedrich Gauss, 7, 08860 Castelldefels, Barcelona, Spain.

Signal capture utility: we used the Universal Hardware Driver (UHD). 
UHD driver capture to file example located in uhd/host/build/examples/$.rx_samples_to_file

File sink:
In order to avoid buffer overflows the target destination for the capture file was a 4 GB RAM unit (in a system equipped with 8 GB of RAM). The linux command used to setup the RAM drive was:
$ mkdir /tmp/ram
$ mount -t tmpfs -o size=4G tmpfs /tmp/ram

The command for capturing data was:

$ ./rx_samples_to_file --file /tmp/ram/usrpcap1.dat --type short --freq 1575420000 --gain 50 --rate 8000000 --nsamps 800000000

This captures samples in interleaved (I&Q) short format (signed 16-bits, or 2 bytes), which is still not implemented in GNSS-SDR. Thus, the file was converted to gr_complex using a simple script in GNU Radio Companion.

===== MATLAB Results using plot_acq_grid_gsoc.m ===========================================================================================

Settings:

sampling_freq_Hz = 4000000
Doppler_max_Hz = 9875
Doppler_min_Hz = -10000
Doppler_step_Hz = 125

Results:

PRN 11

POSITIVE ACQUISITION
maximum_correlation_peak = 23.0285
delay_error_sps = 13873
Doppler_error_Hz = -9500
noise_floor = 1.8919
Gain_dbs = 10.8538

PRN 12

POSITIVE ACQUISITION
maximum_correlation_peak = 16.5534
delay_error_sps =  10583
Doppler_error_Hz = -7250
noise_floor = 1.9020
Gain_dbs = 9.3968
