Device like this http://aldiga.com/english/A-100-USB-EDGE10.htm
contains Prolific 2303 chip.
Actually their site a bit outdated - I have AlDiga AL-11U
GSM/GPRS/EDGE modem and it works with pl2303 module after adding
corresponding product ID.
By default modem uses baud rate 460800. GSM chipset - SIMCom SIM600,
quad band 850/900/1800/1900 MHz