Technical information about GSM
For technical support and advanced users
v4.20 - DD / COM One - December 2000
2. Transparent mode, non transparent mode (= RLP), and UDI
3. Compression done by PC Card through GSM network
5. Connection and carrier : information's returned by S95
6. GSM modes : connections traces samples
6.1 Non Transparent (RLP, default PC Card mode)
6.2 Transparent only (not recommended)
6.3 Transparent + compression V42bis and errors correction
6.4 Transparent + compression MNP5 and errors correction
6.6 UDI transparent (not recommended)
This document applies to these PC Cards :
- MC218 (COM One Communication Card, 3 in 1).
- MC220 (COM One Platinium Card, 4 in 1).
- MC222 (COM One Platinium Card, 2 in 1).
- MC223 (COM One Platinium Card, 3 in 1).
- GSM Only (COM One GSM/PCN/DCS Mobile Data PC Card).
Most of the information's of this document are true for OEM products too.
Standard |
Max speed in Bits per second |
Kb/s (Kilo bytes per second) |
V34 (analog) |
33 600 |
3,28 |
GSM |
9 600 |
0,93 |
HSCSD |
57 600 |
5,62 |
GPRS |
150 000 |
14,6 |
|
Transparent AT+CBST=x,x,0 |
Non transparent AT+CBST=x,x,1 |
Fax |
UDI AT+CBST=[65 to 71],x,x (we recommend 71) |
Possible |
Possible |
Not available |
Non UDI AT+CBST=[<65],x,x (we recommend 7) |
Possible |
Possible |
Not available |
UDI = Unrestricted Digital Information.
RLP = Radio Link Protocol.
You can get more information's about AT +CBST into the reference manual.
- By default we use the non transparent mode (= RLP). String is : "AT +CBST=7,0,1"
- For some rare numbers the string "AT +CBST=71,0,1" may be recommended. The GSM network moves the connection to a digital link to the digital telecom network, and avoid the analog usual way through 2 analogs modems.
- If you know the server is using an ISDN TA (V120). You can use the string: "AT +CBST=71,0,1". You may get a fast connect (5 seconds instead of 20 for analog). Some people call it "V110" but this has nothing to do with the ISDN V110 protocol. We prefer to name this mode "UDI".
- You can receive calls from an ISDN TA in UDI mode. But your GSM data subscription must validated for UDI (ex: France Telecom Itineris need this).
- In PSTN and/or without the GSM cable plugged, MC218 ignore the AT +CBST command but MC22x return "ERROR".
- "AT \N0" is a fast command to set transparent mode. "AT \N2" for RLP. But we recomment to use the command "AT +CBST…", it is more clear.
- In some areas of France, the SFR network requires the "AT+CBST=7,0,1" to be sent a second time (this command is already sent by default).
- Minitel : AT+CBST=71,0,1 (note
that this is *not* the analog V23 mode, it's a digital mode).
Minitel GSM speed is 9600 bps instead of the 1200/75 bps analog mode.
Only France Telecom Itineris enable access to UDI (Minitel ...). SFR don't
provide UDI service.
|
MC218 |
MC220, MC222, MC223 |
GSM Only card |
Transparent mode |
Not possible |
Yes |
Yes |
UDI |
Not possible |
Not possible * |
Not possible * |
Non Transparent mode |
Not possible |
Not possible * |
Not possible * |
* : Not supported by networks yet.
MNP4 + V42bis |
MNP4 + MNP5 |
AT \N5 %C2 |
AT \N5 %C1 |
These commands automatically switch to the right mode (transparent). The opposite command could be : AT+CBST=7,0,1.
We recommend using MNP4 + V42bis instead of MNP4 + MNP5.
Downloading from an internet connection by FTP a HTML file (40415 bytes).
- PSTN 31200 bps no compression (%C0) : 3173 bytes / sec.
- PSTN 31200 bps MNP4 + V42bis : 8252 bytes / sec.
- Cellular 9600 bps RLP : 937 bytes / sec.
- Cellular 9600 bps MNP4 + V42bis : 1800 bytes / sec.
With compression mode, the error correction is activated only after been connected with the modem. That's why if any little GSM network error occurs during the negotiation, the connection can fail ("NO CARRIER").
GSM Mode |
Without compression |
With compression |
Transparent mode |
No errors correction |
Yes done by the PC Card |
UDI |
Yes, done by the network |
Not possible |
Non Transparent mode |
Yes, done by the network |
Yes by V42 bis |
This register can be set to various values, and is very useful to get more information's about the connection (for GSM and PSTN modes only).
AT S95=1
OK
atdt0556693080
CONNECT 9600
ATS95=44
OK
atdt0556693080
CARRIER 9600 <- DCE speed (connection)
PROTOCOL: RLP
COMPRESSION: NONE
CONNECT 115200 <- DTE speed (junction)
ATS95=45
OK
atdt0556693080
CARRIER 9600 <- Line speed
PROTOCOL: RLP
COMPRESSION: NONE
CONNECT 9600 <- Line speed
atS95=44
at+CBST=7,0,1
OK
atd0556788382
CARRIER 9600
PROTOCOL: RLP
COMPRESSION: NONE
CONNECT 115200
atS95=44
OK
at+CBST=7,0,0
OK
atd0556788382 (COM One BBS, modem 33600)
CARRIER 9600
PROTOCOL: NONE
COMPRESSION: NONE
CONNECT 115200
ats95=44
OK
at+CBST=7,0,0
OK
at\N5%C2
OK
atd0556788382
CARRIER 9600
PROTOCOL: ALT
COMPRESSION: V.42BIS
CONNECT 115200
OK
at&f&wz
OK
ats95=44
ok
at\N5%C1
OK
atd0147282288
CARRIER 9600
PROTOCOL: ALT
COMPRESSION: CLASS 5
CONNECT 115200
ats95=44
OK
at+CBST=71,0,1
OK
atd3611 (this is the French Videotex number (GSM Minitel))
CARRIER 9600
PROTOCOL: RLP
COMPRESSION: NONE
CONNECT 115200
ATS95=44
OK
at+CBST=71,0,0
OK
atd3611
CARRIER 9600
PROTOCOL: NONE
CONNECT 115200
Here's the fax modes supported by our products when used into GSM modes :
|
MC218 |
MC220, MC222, MC223 |
GSM Only card |
Fax class 1 |
Supported |
Supported |
Supported |
Fax class 2 |
Not supported |
Supported |
Supported |
We recommend using Fax class 1 (fax process done by the application).
When sending fax onto GSM network the PC Cards use the "transparent" mode. This mean the fax quality can be bad (ex: some lines missing), if the GSM network quality is very bad.
The standard ETSI GSM 04.08 only allow dialling number of 20 digits maximum.
- GSM dialling does not support the comma (,) nor any pause when dialling a number.
Note: Most of our firmwares ignore this command.
- GSM dialling does not support the "^". Calling tone does not exist for GSM.
Note: Most of our firmwares ignore this command.
- In GSM mode you can't dial a voice server then switch to data mode.
Example:
Analog support "ATD0836701313,*,,2,,231,#" (this dial a voice fax server).
But GSM does *not* support this kind of dialling.
You can get the update of this document by writing to "support@com1.fr" (mention in the email the version you already have).
Visit our Web site for more information's about our products : http://www.com1.fr