Network Connectivity Solutions

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GSM-to-Serial solutions (G2S)

 

 

The GSM-to-Serial solutions are used when the communications reach for an existing device with a serial interface is it to be extended with a wireless dial-in or dial-out connection. For example for out-in-the-field installations, when no wired PSTN connection is available. Or for situations where the end-user does not allow use of the local PSTN network or independence of local infra-structure is wanted. (e.g. for security or availability reasons)

Another typical solution is a SMS-to-GPRS convertor, which uses GPRS as a means for transport of data which is normally transferred using SMS.

 

Solution example 1: Replacing wired PSTN solution with wireless GSM solution (dial-in)

 

Original configuration: An existing configuration that includes a PC and a serial device. The OEM device is connected to a Hayes compatible modem, and communicates with the modem using AT commands. (V25)

The user on the PC uses a PSTN to dial in on the device and perform interactive operations on the device.

The end-to-end connection between PC and device can be a PPP connection carrying TCP/IP packets. It may also be a OEM specific serial protocol.

 

 

 

Wanted: The wired PSTN connection is to be replaced by a wireless GSM connection. So that access to the OEM device is possible if the OEM device is installed at (out-in-the-field) locations where no PSTN is available.

Optionally: direct access to device via public internet.

 

Solution

 

 

Or when direct access via the public internet is wanted:

(solution requires GPRS)

 

 

The NCS0402 performs the modem emulation and optionally emulates a dial-in PPP server at the OEM device side. At the GSM side it performs the SIM card handling, the serial-to-GSM conversion (either GSM data or GPRS) and IP network address translation. (NAT)

 

Direct access to the device using the public internet is only an option when GPRS is used at the GSM side. Note also that there is a dependency for this on the GSM provider that is used, click here for more information.

 

 

Solution example 2: Replacing wired PSTN solution with wireless GSM solution (dial-out)

 

Original configuration: An existing configuration that includes a central server and a serial device that periodically uses a PSTN to dial in on the server to report status information or to upload gathered measurement data.

The OEM device is connected to a Hayes compatible modem, and communicates with the modem using AT commands. (V25)

The end-to-end connection between server and device is a regular PPP connection carrying TCP/IP packets.

 

 

Wanted: The wired PSTN connection is to be replaced by a wireless GSM connection.

This enables the OEM device to access the central server even if the OEM device is installed at (out-in-the-field) locations where no PSTN is available. Optionally: direct access to device using public internet.

 

Solution

 

 

Or when direct access via the public internet is wanted:

(solution requires GPRS)

 

 

The NCS0402 performs the modem emulation and emulates a dial-out PPP server at the OEM device side. At the GSM side it performs the SIM card handling, the serial-to-GSM conversion (either GSM data or GPRS) and IP network address translation. (NAT)

 

Direct access to the device using the public internet is only an option when GPRS is used at the GSM side. Note that there is a dependency for this on the GSM provider that is used, click here for more information.

 

 

Solution example 3: Replacing wired serial network with wireless GSM network

 

Original configuration: This solution is similar to the previous example. The only difference is that the device supports only direct connections to a serial IP network (e.g. SLIP/PPP), so no PSTN modem is used.

 

 

Wanted: The wired serial connection is to be replaced by a wireless GSM connection. So the OEM device can access the central server even if the OEM device is installed at (out-in-the-field) locations where no PSTN is available.

Optionally: direct access to device using public internet.

 

Solution

 

 

Or when direct access via the public internet is wanted:

(solution requires GPRS)

 

 

The role of the NCS0402 is similar to that in the previous G2S solution example. The major difference is that modem emulation is not used.

 

Direct access to the device using the public internet is only an option when GPRS is used at the GSM side. Note also that there is a dependency for this on the GSM provider that is used, click here for more information.

 

 

Solution example 4: SMS-to-GPRS converter (SMS concentrator)

 

Original configuration: A serial OEM device that supports transmitting SMS messages using a GSM modem and the GSM 07.05 standard. The device periodically sends SMS messages with status information or measurement data to a central server. A central server retrieves the SMS messages (and a bulk of other messages from other OEM devices) using an internet connection with the GSM server of the GSM provider.

 

 

Wanted: Usage of GPRS to transfer the data instead of SMS. Saves on operational costs as the costs per transferred data byte for SMS are much higher than the costs for GPRS.

This solution is economically viable for those applications that send at least 100 or more SMS messages per month.

 

Solution

 

 

The NCS0402 intercepts the GSM 07.05 modem commands that are issued by the device and translates them into GPRS data. (e.g. in email optional packaging one or more SMS messages in one email message) The data then is transmitted to the central server either directly (if it can act as a SMTP server) or indirectly (email is sent to an external e-mail account that is read by the central server - central server acts as automated POP3 client)

Translation is in the other direction is also possible. In that case the NCS0402 polls a POP3 mail server for incoming email and translates the e-mail messages into GSM 07.05 commands to simulate SMS reception.

Other conversions are also possible. (e.g. SMS-to-telnet, or SMS-to-FTP)

 

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Last updated:07-jan-2013