Tieline Technologies

GSM Support

Broadcast Tech Note 002: GSM Troubleshooting


This Tech Note explains some troubleshooting procedures for using Tieline codecs over GSM
connections. For more detailed information on GSM connections, please see the GSM section in
the main user manual for the codec you are operating.


(Please note: Even though some codecs accept two GSM modules, only one can be used in your
codec. If you wish to connect using two GSM connections, you must use the RS 232 connection
on the codec and attach a GSM-compatible cell-phone such as the Nokia® 6310 or 6310i).

GSM Transparent and Non-transparent Data Modes

If you are using a GSM connection, we recommend you ensure that your SIM card has been set
to send data in non-transparent mode. Check this with your telco when you order your data
service. (Some cell-phone networks only provide non-transparent data capabilities). When
transparent mode is used, the bit error rate could be as high as 1/1000. This will lead to dropouts
in audio.

When data is sent in transparent mode you require sustained data flow to transfer data reliably.
This is network dependent and if the network is unreliable there may be some loss of data
packets, more bit errors (1/1000) and therefore dropouts in audio.

In non-transparent data mode, Radio Link Protocol (RTP) is used, providing better error
correction and less bit errors (1/100,000,000). Data is buffered when it is being sent and
received from a GSM module or cell-phone in this mode. This mode is more reliable for a data
call and Tieline GSM modules only support the sending of non-transparent data. We also
recommend that you use non-transparent data mode when you use a Nokia® 6310i cell-phone.

If your SIM card is set to transparent mode you will be unable to receive any calls to your cell-
phone or GSM module. Contact your telco to check if your SIM card has been set to non-
transparent data mode and get them to switch it if it hasn't.

GSM Troubleshooting Tips

Following are some troubleshooting tips if you are having trouble with your codec's GSM
connection:

  1. Use the balanced inputs and outputs on your codec where possible to minimize the likelihood of cell-phone interference.
  2. Attach the male to female antenna adaptor to your GSM module. This adapter is provided with the antenna kit when you purchase a GSM module from Tieline. If you don't use the adapter, connections could be unreliable and audio problems may be introduced.
  3. If you are dialing from the landline connected codec, check that you are dialing the special GSM data number and not the standard GSM voice number. You may have topurchase this data number from your telco. Most telco's have a data number that is
    separate to the standard voice number. You can get the data number by calling your telco
    and requesting it.
  4. If you are having problems with dialing from the landline side, but you are successful
    dialing from your cell-phone to the landline connected codec, it could be that your GSM
    data number has been set up in ‘Transparent' mode. Ring up your telco and change over
    to ‘Non-transparent' mode.
  5. Please check that your GSM signal strength is high enough to make a successful call. This
    is indicated numerically on your codec's LCD from 0-9. Try to achieve reception as close
    to 9 as possible. For the best reception, place your antenna as high as possible and attach
    the magnetic base to a steel surface for a ground plane. (If you are using a cell-phone
    check its reception signal strength is acceptable.)
  6. If you encounter audio drop-outs try increasing the pre-buffer second setting. You only
    need to adjust this setting if the GSM connected codec is having problems receiving
    audio. Program signals will be delayed by the amount of time set in this menu. If you are
    still getting program drop-outs after adjusting this setting, it could be due to network
    congestion. Hang up the connection and try to reconnect in a short while. (Please note: If
    you adjust this while you are connected, the settings will only take effect when you next try
    to connect. In other words, you must hang up and redial the connection.)
  7. If you are still having trouble connecting, check your configuration settings are correct on
    both codecs. Configuration procedures follow for the different connection types.


Configuring GSM Connections Using a GSM Module

If you are dialing out from a codec via a GSM module, then you will need to follow these
steps to configure the GSM codec connection successfully.

  • First, press SOFTKEY 4 to access the Menu submenus;
  • Next, scroll to and select the Configuration submenu;
  • Next, scroll to and select the GSM Setup menu;
  • Then scroll to and select GSM Module 1;
  • Next you need to set the GSM Bitrate. Auto is the setting you should select;
  • Then set the Wireless Network menu from either GSM/CSD or GSM/HSCSD;
  • Then set the Pre-Buffer Secs. Initially set this to 0; and
  • Finally, set the Codec Type (Algorithm) from either Music, Other or Voice G3 (use Voice G3 if you are connecting in CSD mode and select either Voice G3 or Music if you are connecting via HSCSD. Both codecs must be set to use the same algorithm.

Configuring GSM Connections via the RS 232 Serial Port

If you are connecting via the RS 232 port on the rear of the codec then you will need to
follow these steps to configure your codec and connect successfully.

  • First connect your phone to the RS232 port on the rear of the codec;
  • Secondly, press SOFTKEY 4 to access the Menu submenus;
  • Next, scroll to and select the Configuration submenu;
  • Next, scroll to and select the GSM Setup menu;
  • Then scroll to and select the Ext Cellphone menu and select Enable;
  • Next you need to set the GSM Bitrate. Auto is the setting you should select;
  • Then set the Wireless Network menu from either GSM/CSD or GSM/HSCSD ;
  • Then set the Pre-Buffer Secs. Initially set this to 0; and
  • Finally, set the Codec Type (Algorithm) from either Music, Other or Voice G3 (use  Voice G3 if you are connecting in CSD mode and select either Voice G3 or Music if  you are connecting via HSCSD. Both codecs must be set to use the same algorithm.

Important note for GSM cell phone users:

If you are using codec firmware version 0.7.80 or higher, and you are using the serial port on
the rear of the codec to connect (using either a Nokia® 6310 or 6310i cell phone), it will be
configured automatically for GSM use. If you are using a firmware version lower than 0.7.80,
you must configure the serial port using the following instructions. (Please note: Load the
GSM profile you will be using first, or an error message may appear on the codec when you
try to change the serial port setting.)
To set the codec for GSM serial port operation press Softkey 4 to access the [Menu] screen
and then scroll using the MS to [Configuration] and select this option. Then scroll using the
MS to the [Advanced Menu] and select this. Select [Serial Port Mode] with the MS and then
select [GSM] with the MS. GSM^ should then appear on the main menu screen as a
connection option. If it doesn't appear on the main menu screen, power the codec down and
then power it up and it should appear.)
This feature can also be set in ToolBox software via the Serial Port Mode drop-down menu in
the Global Unit Settings TAB menu.

Configuring a POTS Landline Codec for GSM Connections

If you are dialing a GSM connected codec via a POTS landline connection, then you will
need to follow these steps to configure the POTS landline connection successfully.

  • First, press SOFTKEY 4 to access the Menu submenus;
  • Next, scroll to and select the Configuration submenu;
  • Next, scroll to and select the GSM Setup menu;
  • Then scroll to and select the Landline POTS connection;
  • In the GSM Landline Mode menu that opens select Enable;
  • Next you need to set the GSM Landline Bitrate. 9600 is the setting you should select for CSD. If you are sure that your GSM network has HSCSD available, and it has been enabled on your SIM card, select 28800;
  • Then set the Pre-Buffer Secs. Initially set this to 0.; and
  • Finally, set the Codec Type (Algorithm) from either Music, Other or Voice G3 (use Voice G3 if you are connecting in CSD mode and select either Voice G3 or Music if you are connecting via HSCSD. Both codecs must be set to use the same algorithm.