NowSMS and Multitech CDMA Modem

Posted by on Oct 15, 2008 in Support Blog

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NowSMS is primarily used for sending and receiving SMS and MMS messages in GSM environments.

In GSM environments, there have been long established standards for special “AT commands” used for sending and receiving SMS messages using a GSM modem interface.

We sometimes get questions about using NowSMS with operators that use CDMA technology. This question comes up most frequently in North America, where Verizon and Sprint are major mobile operators using CDMA technology, while AT&T and T-Mobile use GSM technology.

When we talk about GSM modems, we use the terminology GSM modem as a generic term to refer to any modem that supports one or more of the protocols in the GSM evolutionary family, including the 2.5G technologies GPRS and EDGE, as well as the 3G technologies WCDMA, UMTS, HSDPA and HSUPA.

The GSM modem standards were originally defined in ETSI GSM 07.05 and ETSI GSM 07.07. They have evolved and been further enhanced for 3G environments that are an evolution of GSM, and are published in 3GPP TS 23.005 and 3GPP TS 23.007.

Unfortunately, similar standards were never devoloped for CDMA environments, including CDMA2000 and EVDO which are the 3G evoluationary paths for CDMA.

However, there are some CDMA devices that provide some support for the AT commands defined for GSM modems. One such family of devices that we encounter somewhat frequently is the Multitech MultiModem CDMA (http://multitech.com/PRODUCTS/Families/MultiModemCDMA/).

NowSMS automatically detects that these modems can be used for sending and receiving text messages (they cannot be used for sending any binary SMS message types). However, a bug in recent firmware versions of these modems causes problems for NowSMS. The problem typically manifests itself with NowSMS reporting “ERROR – Error waiting for response from modem (1)”. This problem is caused by a bug in the modem’s implementation of one of the important AT commands for sending/receiving SMS.

Until this modem bug is fixed, we have added a configuration setting in NowSMS v2008.09.09 and later.

If you experience the error “Error waiting for response from modem (1)” with a Multitech CDMA modem, try editing SMSGW.INI, and under the [Modem – driver name] section header, add ModemSendWorkaround=Yes.

An update for NowSMS that includes this work-around can currently be downloaded at http://www.nowsms.com/download/nowsmsupdate.zip.

Note that NowSMS can only be used to send and receive text SMS messages with this CDMA modem. It might be possible to also send MMS messages … if anyone with a Multiech Multimodem CDMA device is interested in exploring this, please visit us on the NowSMS Discussion Board at http://www.nowsms.com/messages.

For comments and further discussion, please click here to visit the NowSMS Technical Forums (Discussion Board)...