gnss-sdr/README

HOW TO BUILD GNSS-SDR
----------------------

This document describes how to set up the compilation environment and build GNSS-SDR. See also http://gnss-sdr.org/documentation/building-guide

Ubuntu 10.04, 10.10, 11.04 and 11.10
--------------------------------------

* Install GNU Radio:

- Downloading, building and installing GNU Radio and all its dependencies is not a simple task. We recommend to use Marcus Leech's build-gnuradio script, which automatically does all the work for you. In a terminal, do:

$ wget http://www.sbrac.org/files/build-gnuradio
$ chmod a+x build-gnuradio
$ ./build-gnuradio

This can take a while (up to two hours to complete, depending on your system), and installs the latest versions of UHD and GNU Radio in your system, including all their dependencies. In case you do not want to use the script and prefer to build and install GNU Radio manually from source, follow instructions in http://gnuradio.org/redmine/projects/gnuradio/wiki/BuildGuide

- Set up some system variables needed by the GNSS-SDR build system:

export PYTHONPATH=/usr/local/lib/python2.7/dist-packages
export GNURADIO_ROOT=/path/to/gnuradio
export LD_LIBRARY_PATH=/usr/local/lib

where /path/to/gnuradio is the folder in which you invoked build-gnuradio. In order to avoid defining these variables each time you enter a session, you may want to add these three lines to your $HOME/.bashrc file.

* Install other libraries used by GNSS-SDR:

- Download, compile, and install the Armadillo linear algebra library

$ wget http://sourceforge.net/projects/arma/files/armadillo-3.2.3.tar.gz
$ tar xvfz armadillo-3.2.3.tar.gz
$ cd armadillo-3.2.3
$ cmake .
$ make
$ sudo make install

The full stop separated from "cmake" by a space is important. CMake will figure out what other libraries are currently installed and will modify Armadillo's configuration correspondingly. CMake will also generate a run-time armadillo library, which is a combined alias for all the relevant libraries present on your system (eg. BLAS, LAPACK and ATLAS).

NOTE: ATLAS version 3.6 is know to cause random crashes and incorrect results under Ubuntu. The minimum recommended version is 3.8. It is a good idea to completely remove ATLAS 3.6 from your system, in case you have it, as it intercepts calls to BLAS and LAPACK. 

- Download, unzip, configure, build and install gperftools, a set of performance analysis tools:

$ wget http://gperftools.googlecode.com/files/gperftools-2.0.tar.gz 
$ tar xvfz gperftools-2.0.tar.gz 
$ cd gperftools-2.0
$ ./configure --enable-frame-pointers
$ make
$ sudo make install


- Download, unzip, configure, and build Google C++ Testing Framework (also known as Google Test):

$ wget http://googletest.googlecode.com/files/gtest-1.6.0.zip
$ unzip gtest-1.6.0.zip
$ cd gtest-1.6.0
$ ./configure
$ make

Please DO NOT install gtest (do not do "sudo make install"). Every user needs to compile his tests using the same compiler flags used to compile the installed Google Test libraries; otherwise he may run into undefined behaviors (i.e. the tests can behave strangely and may even crash for no obvious reasons). The reason is that C++ has this thing called the One-Definition Rule: if two C++ source files contain different definitions of the same class/function/variable, and you link them together, you violate the rule. The linker may or may not catch the error (in many cases it is not required by the C++ standard to catch the violation). If it does not, you get strange run-time behaviors that are unexpected and hard to debug. If you compile Google Test and your test code using different compiler flags, they may see different definitions of the same class/function/variable (e.g. due to the use of #if in Google Test). Therefore, for your sanity, we recommend to avoid installing pre-compiled Google Test libraries. Instead, each project should compile Google Test itself such that it can be sure that the same flags are used for both Google Test and the tests. The building system of GNSS-SDR does the compilation and linking of gtest its own tests; it is only required that you tell the system where the gtest folder that you downloaded resides. Just add to your $HOME/.bashrc file the following line:

export GTEST_DIR=/home/username/gtest-1.6.0

changing /home/username/gtest-1.6.0 by the actual directory where you downloaded gtest. 



- Download, unzip, configure, build and install Google's gflags package, a commandline flags processing module for C++:

$ wget http://google-gflags.googlecode.com/files/gflags-2.0.zip
$ unzip gflags-2.0.zip
$ cd gflags-2.0
$ ./configure
$ make
$ sudo make install

- Download, unzip, configure, build and install glog, a Google's library that implements application-level logging:

$ wget http://google-glog.googlecode.com/files/glog-0.3.2.tar.gz 
$ tar xvfz glog-0.3.2.tar.gz 
$ cd  glog-0.3.2
$ ./configure
$ make
$ sudo make install

- Install Subversion

$ sudo apt-get install subversion

* Check out the latest version of GNSS-SDR

$ svn co http://gnss-sdr.svn.sourceforge.net/svnroot/gnss-sdr gnss-sdr

* Build GNSS-SDR

- Go to GNSS-SDR's root directory and compile the program:

$ cd gnss-sdr/trunk
$ bjam

If everything went fine, a executable will be found at gnss-sdr/trunk/install/gnss-sdr

- You can also build the release version (an optimized, faster executable) by typing:

$ bjam release




Mac OS X 1.6.8 (Snow Leopard) 
------------------------------
NOTE: Currently the GCC toolchain is broken. We are working towards the use of LLVM/Clang.

* If you have still not installed Apple's Developer Tools Xcode, do it now from  http://developer.apple.com/technologies/tools/ (it's free)

* Install Macports from  http://www.macports.org/install.php We recommend to install directly the <20>dmg<6D> disk images for Snow Leopart. GNSS-SDR has not been tested with Leopard or Tiger.

* Install some tools:

$ sudo port install doxygen graphviz subversion orc


* With your favorite text editor, create a $HOME/user-config.jam file and specify that you want to use the darwin toolset (Apple's version of the GCC toolchain) and doxygen:

using darwin ;
using doxygen ;

* Install GNU Radio and UHD driver:

$ git clone git://code.ettus.com/ettus/uhd.git
$ cd uhd
$ mkdir build
$ cd build
$ cmake ../
$ make
$ sudo make install
$ cd..
$ git clone git://gnuradio.org/gnuradio
$ cd gnuradio
$ mkdir build
$ cd build 
$ cmake ../
$ make
$ sudo make install


* Set some variables:

export DYLD_LIBRARY_PATH=/usr/local/lib
export GNURADIO_ROOT=/path/to/gnuradio

where /path/to/gnuradio is the root folder where the source code of GNU Radio was downloaded. 

In order to avoid defining these variables each time you enter a session, you may want to add these two lines to your $HOME/.bash_profile file.

* Create symbolic links in order to be able to use GNU Radio libraries from /usr/local/lib

$ sudo ln -s /usr/local/include/gnuradio /opt/local/include/gnuradio
$ sudo ln -s /usr/local/lib/libgnuradio-uhd.dylib /opt/local/lib/libgnuradio-uhd.dylib
$ sudo ln -s /usr/local/lib/libgnuradio-core.dylib /opt/local/lib/libgnuradio-core.dylib
$ sudo ln -s /usr/local/lib/libvolk.dylib /opt/local/lib/libvolk.dylib

- Download, compile, and install the Armadillo linear algebra library

$ wget http://sourceforge.net/projects/arma/files/armadillo-2.4.3.tar.gz
$ tar xvfz armadillo-2.4.3.tar.gz
$ cd armadillo-2.4.3
$ cmake .
$ make
$ sudo make install

    The full stop separated from "cmake" by a space is important. CMake will figure out what other libraries are currently installed and will modify Armadillo's configuration correspondingly. CMake will also generate a run-time armadillo library, which is a combined alias for all the relevant libraries present on your system. The "Accelerate" framework is used for accessing BLAS and LAPACK functions.

- Install Google's performance analysis tools, google-perftools:

$ sudo port install google-perftools
$ sudo ln -s /opt/local/lib/libprofiler.dylib /usr/local/lib/libprofiler.dylib 
$ sudo ln -s /opt/local/lib/libtcmalloc.dylib /usr/local/lib/libtcmalloc.dylib

- Download, unzip, configure, and build Google C++ Testing Framework (also known as Google Test):

$ wget http://googletest.googlecode.com/files/gtest-1.6.0.zip
$ unzip gtest-1.6.0.zip
$ cd gtest-1.6.0
$ ./configure
$ make

Please DO NOT install gtest (do not do "sudo make install"). Every user needs to compile his tests using the same compiler flags used to compile the installed Google Test libraries; otherwise he may run into undefined behaviors (i.e. the tests can behave strangely and may even crash for no obvious reasons). The reason is that C++ has this thing called the One-Definition Rule: if two C++ source files contain different definitions of the same class/function/variable, and you link them together, you violate the rule. The linker may or may not catch the error (in many cases it is not required by the C++ standard to catch the violation). If it does not, you get strange run-time behaviors that are unexpected and hard to debug. If you compile Google Test and your test code using different compiler flags, they may see different definitions of the same class/function/variable (e.g. due to the use of #if in Google Test). Therefore, for your sanity, we recommend to avoid installing pre-compiled Google Test libraries. Instead, each project should compile Google Test itself such that it can be sure that the same flags are used for both Google Test and the tests. The building system of GNSS-SDR does the compilation and linking of gtest its own tests; it is only required that you tell the system where the gtest folder that you downloaded resides. Just add to your $HOME/.bash_profile file the following line:

export GTEST_DIR=/Users/username/gtest-1.6.0

changing /Users/username/gtest-1.6.0 by the actual directory where you unziped gtest. 

- Download, unzip, configure, build and install Google's gflags package, a commandline flags processing module for C++:

$ wget http://google-gflags.googlecode.com/files/gflags-1.7.tar.gz
$ tar xvfz gflags-1.7.tar.gz
$ cd gflags-1.7
$ ./configure
$ make
$ sudo make install

- Download, unzip, configure, build and install glog, a Google's library that implements application-level logging:

$ wget http://google-glog.googlecode.com/files/glog-0.3.1-1.tar.gz 
$ tar xvfz glog-0.3.1-1.tar.gz 
$ cd  glog-0.3.1
$ ./configure
$ make
$ sudo make install

* Check the repository for the latest version of GNSS-SDR:

- Check out the latest version of GNSS-SDR

$ svn co http://gnss-sdr.svn.sourceforge.net/svnroot/gnss-sdr gnss-sdr

* Build GNSS-SDR

- Go to GNSS-SDR's root directory and compile the program:

$ cd gnss-sdr/trunk
$ bjam

If everything went fine, a executable will be found at gnss-sdr/trunk/install/gnss-sdr

NOTE: During compilation, you might see a harmless message g++: unrecognized option '-no-cpp-precomp'. You can safely ignore it, and even change darwin toolset configuration to remove it: for OS X 10.6.8 I changed /opt/local/share/boost-build/tools/tools/darwin.jam at line 58 like this

#flags darwin.compile OPTIONS : -no-cpp-precomp ;
flags darwin.compile OPTIONS : -std=c++0x ;

- You can also build the release version (an optimized, faster executable) by typing:

$ bjam release


GETTING STARTED
---------------


1. After building the code, you will find the gnss-sdr executable file in ./install directory. 

2. At this moment, the real-time connection with the RF front-ends (USRPs or USB GNSS dongles) is not implemented yet. You need to work in post-processing mode. This means that you have to provide a captured GNSS signal file.
    
    2.1. The signal file can be easily recorded using the GNU Radio file sink in gr_complex<float> mode.

    2.2. You will need a GPS active antenna and a suitable USRP daughter board to receive GPS L1 C/A signals. GNSS-SDR require to have at least 2 MHz of bandwidth in 1.57542 GHz. (remember to enable the DC bias with the daughter board jumper).
We use the DBSRX to do the task, but you can try the newer ETTUS daughter boards as well. 

    2.3. The easiest way to capture a signal file is to use the GNU Radio Companion GUI. Only two blocks are needed: an USRP signal source connected to complex float file sink. You need to tune the USRP central frequency and decimation factor using USRP signal source properties box. We suggest using a decimation factor of 20 if you use the USRP2. This will give you 100/20= 5 MSPS which will be enough to receive GPS L1 C/A signals. The front-end gain should also be configured. In our test with the DBSRX we obtained good results with G=50

    2.4. Capture at least 80 seconds of signal in an open sky conditions (at this moment, the acquisition is not very sensitive..). During the process, be aware of USRP driver buffer underuns messages. If your hard disk is not fast enough to write data at this speed you can capture to a virtual RAM drive. 80 seconds of signal at 5 MSPS occupies less than 3 Gbytes using gr_complex<float>.

3. You are ready to configure the receiver to use your captured file among other parameters:

    3.1. The configuration file reside in ./conf/gnss-sdr.conf
    3.2. You need to modify at least the following settings:
        3.2.1. SignalSource.filename= (absolute or relative route to your GNSS signal captured file)
        3.2.2. GNSS-SDR.internal_fs_hz=(captured file sampling rate in Hz)
        3.2.3. SignalSource.sampling_frequency=(captured file sampling rate in Hz)
        3.2.4. SignalConditioner.sample_freq_in=(captured file sampling rate in Hz)
        3.2.5. SignalConditioner.sample_freq_out=(captured file sampling rate in Hz)
        3.2.6. TelemetryDecoder.fs_in=(captured file sampling rate in Hz)

    3.3. The configuration file has in-line documentation, you can try to tune the number of channels and several receiver parameters.

4. Run the receiver from the install directory. The program reports the current status in text mode, directly to the terminal window. If all goes well, and GNSS-SDR is able to successfully track an decode at least 4 satellites, you will get a PVT fix. The program will write a Google Earth KML file and RINEX (yet experimental) files in the install directory. Among the console output, GNSS-SDR also writes log files in /tmp/.