architecture - What are the best practices for building an SMS server

Question

I am trying to build a system in which I have terminal nodes capable of sending/receiving SMS messages over a GSM network. I now need to construct a server solution which would send SMS messages acting as a gateway between a webserver holding my business logic and the clients (nodes). The communication is both ways. I've read something about complete SMS server solutions (that act as a GSM gateway, possibly), but they turn out to be too expensive. I've thought about attaching a mobile phone to my server (and then using some APIs), but it may be that my server will go to a data-center whereby I cannot attach anything in this way. I do not expect to have too many messages (like 100 per day/both ways). And I do not plan to have too many clients too (less than 100). Here I'm asking for a general system solution (e.g. best practice).

Answer 1

There are three basic alternatives for building such an SMS server:

1) Attach mobile phones or USB GSM sticks to the server and use these for SMS communicaton. Limitations are

• Limited volumes (however your 100 SMS/day should be fine).

• Possibly rather unreliable due to consumer hardware (e.g. phone/stick firmware is not built for 24x7 operation, you may need to reset devices regularly; most mobile phones require a battery in order to function, batteries wear out).

• Possibly not placable in data centers, due to RF rules and mobile network coverage.

• Mobile number scheme limited to SIM MSISDN.

2) Connect the SMS to a network operators SMS gateway. Network operators use these exactly for this scenario: bulk SMS communication. These are proprietary and usually talk an "easier" to digest message transport protocol. Limitations:

• You are bound to the network operator, connection-wise and protocol-wise.

• Possibly delays in communication since the gateway might do store-and-forward.

• Depending on pricing scheme might make sense only for high volumes.

3) Connect the SMS server to the mobile operators SS7 network, adding it as a network element. Limitations:

• Complex implementation. Requires dedicated hardware (an SS7 interface card) and drivers to be programmed.

• Requires non-trivial network integration with network operator including extensive testing.

• Requires an E1/T1 line (or bigger, or SIGTRAN) for connection this is typically a data center thing, but not available in every data center.

• Expensive, in terms of pricing scheme and operation.

Assuming I understand your requirements, for your case I would go for option 1) and place the SMS server where it has good coverage, i.e. not necessarily in the data center. Sell it as a head-end for the server infrastructure. If putting it in the data center is a must, then go to option 2) and check out your mobile network operators SMS wholesale offerings.