Thursday, April 10, 2008

Telemetry and 3G

Telstra is spruiking the wonders of telemetry over the 3G network.

It's an interesting thought, although not quite bleeding-edge. After all, telemetry over cellular networks has been with us for a while - even if it's hard to find in carriers' financial reports.

The reason it's hard to locate in the financials is, of course, because the telemetry market is so small that it doesn't warrant a break-out line item of its own.

There's a good reason for this: telemetry is a misfit with the way carriers like to market their mobile networks. The best mobile subscriber is the one that generates lots of billable events (calls, SMSs, MMSs, browsing and so on).

Why do you think prepaid dollars have a use-by date? The last thing any carrier wants is to have someone buy $50 of prepaid minutes and leave them sitting there for a year. Among other things, the expiry of pre-paid minutes is designed to encourage people to make calls. Bundled free calls with post-paid mobiles share the same aim (in social engineering terms, anyhow): if you habituate the user to make lots of calls, there's a good chance they'll keep happily racking up billable calls after their free calls are consumed.

The telemetry SIM might stay quiet for days - which is why, for the small amount of hoopla Telstra generated with its "telemetry over 3G" story, this kind of application remains "white noise" in carrier financias.

That's quite reasonable. Take a weather station, for example: it's sufficient for the device to collect its data and return that data to base by making a few of extremely brief calls each day. There may only be a hundred kilobytes to transfer with each call, after all (temperature samples, humidity samples, rainfall totals).

It's the same with many telemetry applications. Even with continuous data collection, you don't need continuous data transfer, unless there's an exception. If you're monitoring remote equipment, you don't need "up to the second" updates that simply say "two o'clock and all's well".

What you want is something which says "here's the data" at a specified period, but which can call for help if something goes wrong. And that's what most cellular telemetry does today - which means that compared to a human user, telemetry is very frugal in its use of the communications channel.

What Telstra wants is to create demand for telemetry applications that are more talkative: hence the focus on video streaming and live remote control in its telemetry press release. The ideal is to encourage applications that use the data channel as much as possible.

Another small point. Telstra made much of the usefulness of telemetry in remote locations. This is perfectly true: if you're monitoring a device that's 50 km from the homestead, you want to avoid travelling to the device wherever possible.

But who is Telstra kidding? For all of its claims that the mobile network covers 98% of Australia's population, the geographical coverage is a different matter.

So here's your quiz starter for ten points: is remote equipment likely to be close to the population centre?

As an idea, remote telemetry for the rural sector is wonderful - but only if the device is in the mobile footprint.

No comments: