Refer to the specific Wiki to setup the GSM configuration for your gateway:
Wirnet Product Line (iBTS, iFemtoCell): http://wikikerlink.fr/wirnet-productline/doku.php?id=wiki:network_mana:backhaul#cellular_configuration
Wirnet iBTS (before FW v4.0): http://wikikerlink.fr/wirnet-ibts/doku.php?id=wiki:backhaul_3.3.3#cellular_configuration
Wirnet iFemtoCell (before FW v4.0): http://wikikerlink.fr/wirnet-ifemtocell/doku.php?id=wirnet-ifemtocell:network_3.4.4#gsm_configuration
Wirnet Station: http://wikikerlink.fr/lora-station/doku.php?id=wiki:station#g_gprs_modem_management