Example 04 - Simulation with channel impulse response files

This example shows the simulation of a channel impulse response (CIR) with SNACS. In this example we use the simple CIR file which was generated in Example 03.

We can use the same SNACS configuration file structure as in Example 02 we only have to insert the "snChannel" module and provide the correct CIR file name:

                {       Type = "snChannel";
                        file = "../../examples/example_04/snacs_cir_moving_los_v01.h5";
                        interpolation_type = "SINC";
                        interpolation_bandwidth = 10.23e6;
                },              

The same signal is defined for both signal generation and tracking. The complete configuration file for the simulation example is given below.

You can start it by running

cd snacs/trunk/release
./SNACS-release -f ../../examples/example_04/example_04_gps.cfg 

This is a screenshot of the running simulation:

SNACS screenshot of example 04

You can use the MATLAB script plot_snacs_results_example04.m to plot the results:

SNACS simulation result of Example 04

This is the complete configuration file for the simulation example:

/*
 *   Example configuration file for
 *
 *   SNACS - The Satellite Navigation Radio Channel Simulator
 *
 *   example_04_gps.cfg
 *
 *   Demonstration of a SNACS simulation with GPS signal generation 
 *   and the channel impulse response file which was generated in Example 03.
 *
 *   Copyright (C) 2010  F. M. Schubert
 *
 */
 
Simulation:
{
        sampling_frequency = 40e6; // Hz
        c0 = 2.99e8;
        length = 5.0; // s
        
        conc_buf_length = 0.001; // in s
        buffers_per_concbuf = 2;
        
        result_directory = "/tmp/snacs-result_example04";
        append_date_to_outdir = false;

        SNBlocks = (
                {       Type = "snSignalGenerate";
                        start = 0.0001;
                        signal = {
                                inphase = {
                                        code = "C/A";
                                        prn = 1;
                                        modulation = "BPSK(n)";
                                        n = 1.0;
                                        data_type = "none";
                                };
                        };
                },

                {       Type = "snChannel";
                        file = "../../examples/example_03/snacs_cir_moving_los_v01.h5";
                        interpolation_type = "SINC";
                        interpolation_bandwidth = 10.23e6;
                },              

                {       Type = "snADC";
                        intermediate_frequency = 15e6; // Hz
                        adc_enable = true;
                        adc_bits = 4;           
                        vga_enable = true;
                        vga_lowest_amplification_dB = -6.0;
                        vga_highest_amplification_dB = 42.5;
                },

                {       Type = "snSDRStandard";

                        signal = {
                                inphase = {
                                        code = "C/A";
                                        prn = 1;
                                        modulation = "BPSK(n)";
                                        n = 1.0;
                                        data_type = "none";
                                };
                        };

                        intermediate_frequency = 15e6; // Hz
                        aquisition_enable = true;
                        
                        Aquisition:     
                        {       
                                plot_3d = true;
                                length = 1e-3;
                                aq_freq_band = 10000.0; // Hz
                                aq_freq_step = 250.0; // Hz
                                threshold = 2.5;
                        };              

                        tracking_enable = true;
                        Tracking:
                        {
                                DLL:
                                {
                                        discriminator_type = "EML";
                                        correlation_length = 0.001; 
                                        early_late_spacing = 1.0;
                                        damping_ratio = 0.707;
                                        noise_bandwidth = 5.0;

                                        corr_func_samples = 13; // amount of additional samples on correlation function
                                        corr_func_start = -1.5; // start here with additional corr func samples in chips
                                        corr_func_dist = 0.25; // distance between corr func samples in chips
                        
                                        write_corr_func = false;
                                };
                                PLL:
                                {
                                        damping_ratio = 0.707;
                                        noise_bandwidth = 25.0;
                                };
                        };
                }

        ); // end SNBlocks
}; // end Simulation

Plotting:
{
        UpdateInterval = 500; // ms
        PlotXSize = 300L; // pixel to be plottet. format: long (L) 
        plot_buffer_length = 0.0001; // s 
};