SMS and GPRS are certainly not new, but I haven’t seen much discussion comparing/contrasting them, so I thought I would briefly summarize what I know about them here.

Location tracking devices that use one of the various cellular wireless networks will generally employ either SMS, GPRS, or sometimes both for communications.

SMS is best known as the communication approach used by teens around the world for “texting.”

GPRS provides the same IP communications protocols as the Internet on the cellular wireless networks — HTTP, TCP, UDP, etc.

There are some interesting trade-offs between these two communications methods.

SMS has limited message size, no more than about 160 bytes after headers, but this may not be a problem for most applications applications where the device simply sends location and a few other data items. Most service plans charge by the message, favoring infrequent (for example, once-per-day) reporting scenarios. But SMS messaging has more robust coverage and will continue to work on the fringe of rural coverage and other weak-signal scenarios when GPRS will not.

GPRS has many advantages: It supports standard IP protocols, so the same tools and infrastructure that have been built to support the Internet can be used in your GPRS-based solution. Also, lots of people are familiar with these technologies, so the pool of technical talent is large. Since most service plans charge “by the byte,” GPRS is probably a better choice for higher-frequency reporting scenarios (for example, hourly or whenever the device moves a certain distance). Typically, developers have more options to optimize and reduce cost with GPRS than they do with SMS.

The funny thing is that most carriers and most radios support both, but not all service plans and technical support for these options are equal. So, not only must you make the right technical choice based on the inherent merits of SMS and GPRS, you need to be sure your carrier supports your choice well.

I have begun investigating OpenDMTP which is “Open Device Monitoring and Tracking Protocol”. I have long been a strong supporter of open standards and protocols even though I haven’t been able to do much to further that cause in the last year or two, so the idea of an open standard for GPS tracking applications is certainly exciting to me. I am currently looking into the possibility of offering a OpenDMTP Foundation product. Don’t hesitate to contact us if this may be of interest to you.