There has been a lot of coverage lately of Vodafone Australia’s decision to start charging data in 1MB increments on prepaid plans, a lot of it incorrect, misinformed etc. Other providers also do this such as Prepaid Optus 3G & Kogan. So let’s try and explain it a bit

The 1MB increments refer to data sessions from your mobile device. On most smartphone platforms a push notification service will remain constantly connected in the background meaning you always have a data session open, so sending a 50KB email will not result in consuming 1MB. If you have ActiveSync email this is also maintains a constant connection to the Exchange server, waiting to be notified of new emails

When the data session closes your data for that session will be rounded up to the nearest MB. So if in that session you’ve consumed 10.6MB, this will be counted as 11MB, if you’ve consumed 0.1MB this will count as 1MB

The thing you should be more concerned about is coverage. because your smart phone maintains a push notification data session at all times, if you lose coverage your data session will end, when you get coverage again your phone will establish another data session to maintain the push notification connection.

Imagine for a moment you catch a train around the CityCircle in Sydney and you leave your phone in your pocket and you don’t use any apps at all, here is what your data consumption will look like, for arguments sake let’s say it’s an iPhone running iOS 6. You’ll turn your iPhone on at Central and travel around the City Circle then turn your phone off at Central again

• You turn your iPhone on at Central and do nothing, it connects to the Apple Push Notification Service (APNS) and consumes 50KB in the process
• You get the train to Town Hall, on the way you lose coverage so the data session is closed, you are now charged 1MB
• You get to Town Hall where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• The train continues to Wynyard and the coverage drops out so your data session is ended, you are now charged 1MB
• You get to Wynyard where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• The train continues to Circular Quay and the coverage drops out so your data session is ended, you are now charged 1MB
• You get to Circular Quay where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• The train continues to St James and the coverage drops out so your data session is ended, you are now charged 1MB
• You get to St James where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• The train continues to Museum and the coverage drops out so your data session is ended, you are now charged 1MB
• You get to Museum where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• The train continues to Central and the coverage drops out so your data session is ended, you are now charged 1MB
• You get to Central where coverage comes back, your iPhone connects to the APNS and consumes 50KB in the process
• You turn your phone off, your data session has ended so you are charged 1MB

So as you can see just this little hypothetical trip without even opening an app has consumed 7MB on your bill but you actually only consumed 0.35MB from the network. Now just image your daily routine and every time your phone disconnects from a network and your data session is ended. When you get in a lift, walk to the centre of a building where there is no coverage, blackspots when driving, blackspots on the train network or even just turning your phone off and on or into airplane mode and out again to solve a technical issue.

If you are lucky there may be a timeout grace period on the providers side of the network, so that in fact losing coverage for a specified time won’t end the data session but there isn’t much information about this from the carriers that are now charging like this.