Of late, I've listened to numerous conversations about M2M being the next 'big way' for cellular carriers to leverage their legacy network assets. Pundits are even predicting that connected M2M devices will balloon to 50 billion over the next 10 years. (More on that at a later date). And with high-bandwidth consumer applications making the transition over to 4G and LTE, it is logical that 3G technology stands out as a proper means to support the glut of connected devices coming online, from home metering and home automation to telehealth and municipal applications that manage water, waste and traffic.
By and large, 3G offers many advantages. Over the lifetime of a device, the lower cost of 3G airtime generally offsets the initial higher cost of 3G modules. It also carries more cache, with multimedia capabilities, etc.
However, there are plenty of times when 2G technologies are appropriate — even preferable — for your M2M application, for a variety of cost, power and form factor reasons. The key questions to ask are, "How long will this device be in service?" and "How data-rich is the application?" In other words, will the device transmit a continuous stream of time-sensitive data or is it more of the garden variety, merely transmitting short bursts of data on an intermittent or exception basis.
As rule of thumb, if the device's life-cycle is projected in the 3-5 year range, go 2G. Examples include tracking devices for the buy here/pay here automotive market, where the device is expected to be in service for the length of a 3-year lease. In such a scenario, a 3G communications module could rise to 15 percent of the total cost of ownership, while 2G is typically less than 5 percent.
If the lifecycle is any longer, or the application is particularly data intensive, meaning it will consume considerable amounts of data, then 3G is the better choice (assuming coverage is the same, which isn't always the case). Since electric meters have a 7-15 year expected lifespan, utility companies won't — and rightly shouldn't — consider anything less than 3G. Or consider a feature-rich fleet management application that transmits real-time driver behavior, vehicle diagnostics and other information. It creates so much network traffic that the cost of a 3G module shrinks down to 2 percent of the TCO.
The only real surprise we've found is that in-car infotainment and navigation systems for consumers use a remarkable small amount of data, on average. They also have a designed obsolescence component to them. When one thinks 'consumer,' one automatically tends to think 3G, but in this case 2G may still be a viable option.
There is one caveat, of course. We need to collectively keep tabs on the cost differential between 2G and 3G modules. When these reach parity, M2M will transition over time into an all 3G world.