I have an streaming video (cctv) application that requires a constant HSDPA connection.
Normally the SL808xT module works very well, but in areas of high signal strength with multiple base stations it regularly loses it’s connection to the mobile network and has to reconnect. This can happen as regularly as every two minutes and the disconnect/reconnect cycle can go on for hours. The device is in a static location and not moving.
The problem only seems to exist where there are multiple base stations. If there is just one base station, even at very high signal strength levels, the connection is never dropped.
I’ve searched through the logs and done all sorts of testing but I cannot see any reason why the device drops from the network in these situations. I can modify the application to automatically re-establish the data connection once the connection to the mobile operator is restored, but the regularly drops in data connection is making the application unusable.
Has anyone experiencing a similar problem, or can anyone suggest some options to stop the connection being lost? I’ve been trying to figure this out for weeks.
1: Connection is fine, using one base station:
2014/01/27;17:39:09:708;002;ATI;1;AT+CREG?<CR>
2014/01/27;17:39:09:708;004;ATI;1;<CR><LF>+CREG: 2,1,"002F","00C64698",2<CR><LF>
2014/01/27;17:39:09:708;006;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:12:703;002;ATI;1;AT+CREG?<CR>
2014/01/27;17:39:12:703;004;ATI;1;<CR><LF>+CREG: 2,1,"002F","00C64698",2<CR><LF>
2014/01/27;17:39:12:703;006;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:15:714;001;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:15:730;001;ATI;1;AT+CREG?<CR>
2014/01/27;17:39:15:730;003;ATI;1;<CR><LF>+CREG: 2,1,"002F","00C64698",2<CR><LF>
2014/01/27;17:39:15:730;005;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:18:740;001;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:18:740;002;ATI;1;AT+CREG?<CR>
2014/01/27;17:39:18:740;004;ATI;1;<CR><LF>+CREG: 2,1,"002F","00C64698",2<CR><LF>
2014/01/27;17:39:18:740;006;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:19:364;001;ATI;2;Rec V24_AT_CMD_IND_EXTENDED
2014/01/27;17:39:19:364;002;ATI;2;Rec AT_APPLI_SEND_RSP_EXTERNAL
2: Connection suddenly drops, apparently for no reason:
2014/01/27;17:39:21:439;001;L3RR;3;+CREG: 0
2014/01/27;17:39:21:439;002;L3RR;3;+CGREG: 0
2014/01/27;17:39:21:439;003;ATI;2;Rec I_MMT_MM_SERVICE_IND
2014/01/27;17:39:21:455;001;ATI;1;<CR><LF>+WIND: 8<CR><LF>
2014/01/27;17:39:21:455;003;ATI;1;<CR><LF>+CREG: 2<CR><LF>
2014/01/27;17:39:21:470;001;ATI;2;Rec MMT_GM_SERVICE_IND
2014/01/27;17:39:21:470;002;ATI;1;<CR><LF>+CGEV: ME DETACH<CR><LF>
2014/01/27;17:39:21:470;004;ATI;1;<CR><LF>+CGREG: 0<CR><LF>
2014/01/27;17:39:21:470;006;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:21:470;007;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:21:470;032;ADL;16;[ADL port] IsAvailable(80) : 1
2014/01/27;17:39:21:486;001;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:21:486;002;ATI;1;AT+CGACT=0,1<CR>
2014/01/27;17:39:21:486;004;ADL;31;[ADL] GPRS unsubs 107B5595 : 0
2014/01/27;17:39:21:486;005;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:22:874;001;L3RR;3;+CGREG: 0
2014/01/27;17:39:22:890;001;ATI;2;Rec I_MMT_MM_SERVICE_IND
2014/01/27;17:39:23:296;001;ATI;1;<CR><LF>+WIND: 7<CR><LF>
2014/01/27;17:39:23:296;003;ATI;1;<CR><LF>+CREG: 1,"002F","00C63F5F",2<CR><LF>
2014/01/27;17:39:23:311;001;ATI;2;Rec MMT_GM_SERVICE_IND
2014/01/27;17:39:23:311;002;ATI;2;Rec MMT_GM_SERVICE_IND
2014/01/27;17:39:23:311;003;ATI;1;<CR><LF>+CGREG: 1,"002F","00C63F5F",2<CR><LF>
2014/01/27;17:39:23:311;005;ATI;2;Rec MMT_SESSION_RELEASE_RSP
2014/01/27;17:39:23:311;006;ATI;1;<CR><LF>+CGEV: ME DEACT "IP", "10.19.32.19",1<CR><LF>
2014/01/27;17:39:23:311;008;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:23:311;010;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:23:311;011;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:23:311;012;ATI;2;Rec AT_APPLI_SEND_UNS_EXTERNAL
2014/01/27;17:39:23:311;013;ATI;2;Rec AT_APPLI_SEND_COMMAND
3: Device registers back onto home network, on a different base station (not sure if that’s relevant):
2014/01/27;17:39:23:311;014;ATI;1;AT+CREG?<CR>
2014/01/27;17:39:23:311;016;ATI;1;<CR><LF>+CREG: 2,1,"002F","00C63F5F",2<CR><LF>
2014/01/27;17:39:23:311;018;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:23:311;020;ADL;4;(Gprs) Registered on GSM network.
2014/01/27;17:39:23:311;021;ADL;4;(Gprs) SIM initialised, going online
2014/01/27;17:39:23:311;022;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:23:311;023;ATI;1;AT+CGDCONT?<CR>
2014/01/27;17:39:23:311;025;ATI;1;<CR><LF>+CGDCONT: 1,"IP","apn.com",,0,1<CR><LF>
2014/01/27;17:39:23:327;001;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:23:327;003;ADL;1;OpenAndStartBearer()
2014/01/27;17:39:23:327;004;NET;11;GPRS-USER gprs0 open: -> DISCONNECTED
2014/01/27;17:39:23:327;005;ADL;1;apn.com
2014/01/27;17:39:23:327;008;ADL;31;[ADL] Gprs subs 107B5595 : 0
2014/01/27;17:39:23:327;009;ADL;16;[ADL port] IsAvailable(80) : 1
2014/01/27;17:39:23:327;010;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:23:327;011;ATI;1;AT+CGDCONT=1,"IP","apn.com",,0,1<CR>
2014/01/27;17:39:23:327;013;ATI;1;<CR><LF>OK<CR><LF>
2014/01/27;17:39:23:327;015;ADL;31;[ADL] Gprs setup 1 : 0
2014/01/27;17:39:23:327;016;ADL;16;[ADL port] IsAvailable(80) : 1
2014/01/27;17:39:23:327;017;ATI;2;Rec AT_APPLI_SEND_COMMAND
2014/01/27;17:39:23:327;018;ATI;1;AT+CGACT=1,1<CR>