This is an explanation of the init strings in wvdial.conf for Huawei/E220 :

ATDT

A command string should start with "AT" or "at", except for the commands "A/" and "+++". At or aT are invalid

After issuing ATDT, the modem will attempt to establish a connection.

ATZ

ATZ Resetting the modem

After the command ATZ has been issued, a pause of two seconds should be respected before entering the next commands

ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0

Several commands can be given in one command string.

ATE0V1&D2&C1S0=0+IFC=2,2

directions: from DTE to modem (<by_ta> option) and from modem to DTE (<by_te>):

+CGDCONT

 AT+CGDCONT=1,"IP","ac.vodafone.es"; 

It is a ETSI GSM 07.07 command for GPRS. GSM 07.07 "AT command set for GSM Mobile Equipment (ME)" describes the Main AT commands to communicate via a serial interface with the GSM subsystem of the phone (see http://www.ctiforum.com/standard/standard/etsi/0707.pdf ). Note that the descendant of this specification is 3GPP TS 27.007 - AT command set for User Equipment (UE) ( http://www.3gpp.org/ftp/Specs/html-info/27007.htm ).

+CGDCONT defines the Packet Data Protocol (PDP) Context

AT+CGDCONT[=
[<cid>
[,<PDP_type>
[,<APN>
[,<PDP_addr>
[,<d_comp>
[,<h_comp>
[,<pd1>
[,…[,pdN]]]]]]]]]]

Set command specifies PDP context parameter values for a PDP context
identified by the (local) context identification parameter, <cid>
Parameters:

<cid> - (PDP Context Identifier) numeric parameter which specifies a
particular PDP context definition.
1..max - where the value of max is returned by the Test command

<PDP_type> - (Packet Data Protocol type) a string parameter which
specifies the type of packet data protocol
"IP" - Internet Protocol
"PPP" - Point to Point Protocol

<APN> - (Access Point Name) a string parameter which is a logical name
that is used to select the GGSN or the external packet data
network. If the value is null or omitted, then the subscription value
will be requested.

<PDP_addr> - a string parameter that identifies the terminal in the address
space applicable to the PDP. The allocated address may be
read using the +CGPADDR command.

<d_comp> - numeric parameter that controls PDP data compression
0 - off (default if value is omitted)
1 - on

<h_comp> - numeric parameter that controls PDP header compression
0 - off (default if value is omitted)
1 - on
<pd1>, …, <pdN> - zero to N string parameters whose meanings are
specific to the <PDP_type>

Note: a special form of the Set command, +CGDCONT=<cid>, causes the
values for context number <cid> to become undefined.

Note: issuing AT+CGDCONT<CR> is the same as issuing the Read command

AT+CGDCONT? is a read command, it returns the current settings for each defined context.
AT+CGDCONT=? is a test command, it returns values supported as a compound value.

The requirement of an APN is Telco dependent. A lot of them use the same APN for all users and apply a default through the tower or something like that, others use a specific one. I.e., Three in the UK needs you to set the APN as three.co.uk. For the others, a lot of them you can just plug and go without requiring any APN at all. The requirement of an APN is more an exception than the rule.

Phone

The Initiative for GPRS Connections proposed the use of the phone number *99#.

When the modem sees the number *99#, it is going to attempt the call. Assuming that the GPRS context is correct (and the server exists at the IP address and port specified) a TCP socket will be opened between the modem and the server application and the modem will return the string "CONNECT".

Stupid mode

When wvdial is in Stupid Mode, it does not attempt to interpret any prompts from the terminal server. It starts pppd immediately after the modem connects. Apparently there are ISP's that actually give you a login prompt, but work only if you start PPP, rather than logging in. Go figure.

See also


CategoryNetworking

DialupModemHowto/Huawei/E220/wvdial.conf (last edited 2008-07-24 17:11:11 by localhost)