Installation on RaspberryPi 3

Prerequisites

What will we need

We would need Raspberry Pi 3, which has 64-bit ARMv7 processor. Please note that gr-gsm cannot be installed on Raspberry Pi 1 (we tested Model B), since it has ARMv6 processor. Some GNU Radio components are not supported on ARMv6 architecture.

On RPi we will install Debian based Linux operating system Raspbian Jessie (we used version from 2016-03-18).

Update software on Raspberry Pi

First we need to change default password with the command passwd. After that we need to install new updates:

sudo apt-get upgrade```

## Expand space on a SD card and set-up the device
Next step is to expand space on a SD card. We invoke the tool to do that with `sudo raspi-config`. In menu we select _Expand space_. We also need to set timezone, in which country we will use Wi-fi, keyboard settings (under _Internationalisation Options_). **Do not change language settings!** If system language is not English, some strange errors in Python start to appear.

Now we need to reboot the machine with `sudo reboot`.

## Update firmware on Raspberry Pi
Right after that we need to update Raspberry firmware with command `sudo rpi-update`. When this is finished, we need to stop the machine with `sudo shutdown -h now` and physically plug off the power. After some seconds we power it up again.

## Secure the device
Now it is good time to setup firewall, enable NTP client, change hostname... maybe we also want to set up VNC console. We assume you are able to secure the device, for some quick steps, you can see [this guide](https://pravokator.si/index.php/2016/03/30/raspberry-pi-priprava/) (in slovenian, [english translation via Google Translate is also available)](https://translate.google.com/translate?sl=sl&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=https%3A%2F%2Fpravokator.si%2Findex.php%2F2016%2F03%2F30%2Fraspberry-pi-priprava%2F&edit-text=&act=url)).

**Do not skip this step, security is important.**

## Increase swap space
Sometimes you will need more memory for compiling. You can "add" new memory with increasing swap space. Open the configuration file:
`sudo nano /etc/dphys-swapfile`
... and look for default value in Raspbian, which is:
`CONF_SWAPSIZE=100`
Change it to:
`CONF_SWAPSIZE=1024`
After that you need to stop and start the service that manages the swapfile on Rasbian:
```sudo /etc/init.d/dphys-swapfile stop
sudo /etc/init.d/dphys-swapfile start```

Now can then verify the amount of memory and swap space by issuing the following command:
`free -m`

## Install screen
Since compiling can take a long time, it may also be a good idea to install screen: `sudo apt-get install screen`.

# Installation of software needed for gr-gsm

## Install Kalibrate
First, we will install Kalibrate:
```sudo apt-get install libtool autoconf automake libfftw3-dev librtlsdr0 librtlsdr-dev libusb-1.0-0 libusb-1.0-0-dev
git clone https://github.com/asdil12/kalibrate-rtl.git
cd kalibrate-rtl
git checkout arm_memory
./bootstrap
./configure
make
sudo make install```

## Set access to USB devices
Plug in the RTL-SDR device and check it's ID with `lsusb` command. You will see something like this:
`Bus 001 Device 004: ID **0bda:2832** Realtek Semiconductor Corp. RTL2832U DVB-T`
`Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter`
`Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. `
`Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub`

In our case ID of the RTL.SDR device is **0bda:2832**. Now we open a rules file:
`sudo nano /etc/udev/rules.d/20.rtlsdr.rules`
...and add this line to it:
`SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2832", GROUP="adm", MODE="0666", SYMLINK+="rtl_sdr"`
If you are using several RTL-SDR devices, you can add several lines to this file.

Now we need to reboot our Raspberry Pi:
`sudo reboot`

## Calibrate RTL-SDR device
Now we can invoke the command to calibrate our RTL-SDR device for GSM frequency band (actually to compute the average absolute error in PPM):
`kal -s GSM900`

We get the result similar to this:
`Found 1 device(s):`
  `0:  Generic RTL2832U`

`Using device 0: Generic RTL2832U`
`Found Rafael Micro R820T tuner`
`Exact sample rate is: 270833.002142 Hz`
`kal: Scanning for GSM-900 base stations.`
`GSM-900:`
	`chan: 1 (935.2MHz - 33.430kHz)	power: 55085.23`
	`chan: 3 (935.6MHz - 34.130kHz)	power: 63242.36`
	`chan: 5 (936.0MHz - 33.970kHz)	power: 41270.82`
...
...
	`chan: 112 (957.4MHz - 32.934kHz)	power: 498930.07`
	`chan: 116 (958.2MHz - 31.859kHz)	power: 88039.44`
	`chan: 124 (959.8MHz - 32.429kHz)	power: 247404.23`

The strongest signal in our case is on channel 112. So we run calibration on this channel:
`kal -c 112`
... and get the result like this:
`Found 1 device(s):`
  `0:  Generic RTL2832U`

`Using device 0: Generic RTL2832U`
`Found Rafael Micro R820T tuner`
`Exact sample rate is: 270833.002142 Hz`
`kal: Calculating clock frequency offset.`
`Using GSM-900 channel 112 (957.4MHz)`
`average		[min, max]	(range, stddev)`
`- 34.368kHz		[-34376, -34357]	(20, 4.697051)`
`overruns: 0`
`not found: 0`
`average absolute error: 35.897 ppm`

So our average absolute error is 36 PPM (35.897 PPM).

## Install GNU Radio
Now we need to install GNU Radio, which is quite simple:
`sudo apt-get install gnuradio gnuradio-dev`
 
## Install libosmocore
We need to compile libosmocore...
`sudo apt-get install cmake `
`sudo apt-get install build-essential libtool shtool autoconf automake git-core pkg-config make gcc`
`sudo apt-get install libpcsclite-dev libtalloc-dev`
`git clone git://git.osmocom.org/libosmocore.git`
`cd libosmocore/`
`autoreconf -i`
`./configure`
`make`
`sudo make install`
`sudo ldconfig -i`
`cd`

## ...and install some other things
sudo apt-get install gr-osmosdr rtl-sdr
sudo apt-get install libboost-dev
sudo apt-get install osmo-sdr libosmosdr-dev
sudo apt-get install libusb-1.0.0 libusb-dev
sudo apt-get install libboost-all-dev libcppunit-dev swig doxygen liblog4cpp5-dev python-scipy

# Install gr-gsm
Now we are ready for the final step:
`git clone https://github.com/ptrkrysik/gr-gsm.git`
`cd gr-gsm`
`mkdir build`
`cd build`
`cmake ..`
`make`
`sudo make install`
`sudo ldconfig`

Finally, we create the ~/.gnuradio/config.conf config file with `nano ~/.gnuradio/config.conf`. We add this two lines to it (in that GNU Radio can find custom blocks of gr-gsm):
`[grc]`
`local_blocks_path=/usr/local/share/gnuradio/grc/blocks`

# Usage
Now we can run GSM scanner with:
`grgsm_scanner -p 36`
Please note, that we used parameter -p 36 - it is our average absolute error in PPM.

We can also use GSM Live Monitor (grgsm_livemon), but we need a GUI or VNC console.