Asterisk GSM

Overview

Asterisk uses the Libwat to interface with the Sangoma W400 GSM cards.

 Installation

Download the following System requirements
-> Prerequisites

• Note: if you do not install the above requirements the installation will fail

Dahdi Installation

1. Download the latest Dahdi sources from

asterisk.org:
     example:

 wget http://downloads.asterisk.org/pub/telephony/dahdi-linux-complete/releases/dahdi-linux-complete-2.5.0.2.+2.5.0.2.tar.gz

1. Untar and install dahdi

tar xfz dahdi-linux-complete-2.5.0.2+2.5.0.2.tar.gz
cd dahdi-linux-complete-2.5.0.2+2.5.0.2
make && make install

Wanpipe Installation

Installation

LibWAT Installation

1. Download the latest LibWAT:

wget ftp://ftp.sangoma.com/linux/libwat/libwat-2.1-current.tgz

1. Untar & Compile & Install

tar xfz libwat-2.1-current.tgz
cd libwat-X.X.X/build
cmake ..
make
make install

Asterisk LibWAT Patching

Currently, libwat requires a patched version of Asterisk to work. Libwat Asterisk patches can be found in the libwat-X.X.X/asterisk directory.

Autoconf

You will need autoconf 2.60 or later to be able to patch Asterisk.

Copy patches to asterisk source directory. Make sure to use the patch version that matches your version of asterisk:

cd libwat-1.X.X/asterisk
cp asterisk-<your specific asterisk patch> /usr/src/asterisk-<verison>

To patch your Asterisk Installation:

cd asterisk-<version>
patch -p 1 < asterisk-<version>.patch

Re-configure and re-compile your Asterisk:

./bootstrap
./configure
make clean
make
make install

Configuration

Use the wancfg_dahdi script to generate your configuration files

wancfg_dahdi

Asterisk GSM Advanced Configuration options

Sending and Receiving SMS with Asterisk

1. Sending/Receiving SMS using Asterisk CLI

2. Sending/Receiving SMS using Asterisk Management Interface

Sending SMS using Asterisk CLI

Syntax:

wat send sms <span> <number> <message>

Example: 

CLI> wat send sms 1 6474024628 "Hello World"

Receiving SMS using Asterisk CLI

When a SMS is received, it will printed in the Asterisk CLI and the logs.

-- Span 1: SMS received Hello World

Debugging

It is recommended to enable Asterisk full debugging while the LibWAT library is still in beta phase to facilitate debugging.

Instructions on how to enable Asterisk Full Debug Logging

Enable debug configuration in chan_dahdi.conf

In chan_dahdi.conf in the Channel section create a variable called:

wat_debug=

Below are the possible options to use for wat_debug:

all

uart_raw

uart_dump
call_state
span_state
at_parse
at_handle
sms_encode
sms_decode

For example: wat_debug=all

any combination of the above separated by commas will work.

Most of the time I'd stick to "all" when debugging a problem and only use the others if you've been asked to.

 You can also enable UART (serial interface) debugging to see which AT commands are sent and received at the driver level:

wanpipemon -i w1g1 -c gude

All UART communications will be dumped to the driver logs (ie: /var/log/messages)

To disable UART debugging:

wanpipemon -i w1g1 -c gudd

(gude - GSM uart debug enable)
(gudd - GSM uart debug disable) 

Troubleshooting

1. Confirm that SIM cards are inserted

wanrouter status

GSM modules that do not have a SIM card connected will have status: Disconnected 

 2. Checking network registration

From the Asterisk CLI:

CLI> wat show spans

WAT span 1: Up ("+16472673394")
WAT span 2: Down
WAT span 3: Down
WAT span 4: Down

Devices that have registered to the network successfully, will have status: Up. If the subscriber number (own number) is available, it will be displayed beside that span ("+16472673394 " in our case). 

3. Checking Signal Quality 

From the Asterisk CLI:

CLI> wat show span 1

1. It is recommended to have a signal strength higher that (-80) dBM (a value between -50 dBM and -80 dBM) to avoid dropped calls.

2. Having a high Signal BER (Bit Error Rate) may affect audio quality.

3. The first time the GSM modules are started in a location, it may take up to 6 minutes for a GSM signal to be detected. This is because the GSM chip is iterating through each of the 4 GSM bands to search for a signal. Once a signal is detected, the band is memorized, and subsequent starts will take only  a couple seconds.

3. Enable Asterisk command line debugging

Aside from the driver debugging of the serial line (which sends and receives AT commands, responses and notifications), Asterisk can also print AT debugging information to the screen, which is easier to correlate to call events within Asterisk.

If you have the latest libwat release + Asterisk patch, there is a way to enable debugging from the command line:

Even when wat debugging is enabled, you still have to enable regular Asterisk debugging settings:

 /etc/asterisk/logger.conf

When changing this file you must either restart asterisk or execute "logger reload". Note that if you restart Asterisk the debugging options (verbose, debug, wat all) enabled thru the command line will be lost. Therefore you want to do thelogger.conf changes first.

Please verify the have latest libwat and Asterisk patch, if they do not have it the command "wat debug all" won't be available.