I'll put on hold a moment the debate of "do unlimited data plans really exist?" and get back to cellular data access to telemetry devices. Today (and perhaps forever) cellular data access only makes sense if you have your data access well defined and under-control. If you poll X words of data every Y minutes, you will be able to select a monthly data plan that fits within a planned budget. If you connect to remote equipment for limited diagnostic maintenance and you understand that the cellular overage charges could cost you X dollars per hour, you will be able to manage your monthly bills. However, if you approach cellular data access to telemetry devices by saying you need to poll as much data as fast as you can, then this is NOT the correct technology for you. You are better to look at the various long-range Ethernet line-of-sight radios.
So back to the question of "do unlimited data plans really exist?" Hmm, unlimited - sounds nice, doesn't it. Yet an Internet search for "+unlimited +internet +cancelled" shows a growing collection of frustrated people with DSL or cable broadband, wireless PDAs, voice-over-ip (VoIP), and cellular plans who have had their "unlimited services" cancelled because they (ta-da) moved too much data. It seems unlimited doesn't really mean unlimited. I could provide links to such information, but the sites tends to be full of wild ranting language, plus I don't want to single out just a few companies. Do the search above and you'll find examples for any type of service you desire.
While I can empathize with the ranters who've found out that unlimited just means "without a predefined limit", as a network professional I understand the basis for these service cancellations. It would be nice if the marketing hype-sters could be honest enough to stop using the term "unlimited", but then no user would sign up for an honest broadband service stupid enough to define limits when competitors are shouting about "unlimited plans".
All IP-based broadband systems consist of a series of hops or links, each with a predefined maximum data throughput. All commercial broadband services try to handle as many customers as they can sign up. Therefore the performance a user sees is merely a function of how many other users are active at that instant, how much data they are trying to push through at that instant, and what is the limiting throughput of the system bottlenecks. As a business person seeking to make money, would you prefer to keep 100 users paying $80 monthly to each move 100MB of data per month (10,000MB/month), or prefer to keep the one user paying $80 monthly to move 10GB (10,000MB) of data per month? While this is an extreme example, as soon as a few of the 100MB/month users complain to the broadband service about their high-speed internet seeming pretty slow speed, the solution is obvious to the business-minded. Canceling the "unlimited service" of the one user moving 10,000MB/month will effectively double the performance of the other 100 users with no added expenses and a mere loss of $80 per month of income. Failing to cancel the "unlimited service" of the one heavy user risks causing 10 or 20 of the other 100 light users to change services with a potential monthly income loss of hundreds or even thousands of dollars. I am not saying this is honest to cancel "unlimited service" based on high usage. I am just saying it is understandable and makes business sense.
How is this cancellation legal? Easy - just read the huge terms of service contract you agree to when you sign up for unlimited data service. To generalize some typical clauses in an unlimited cellular service plan:
- You agree to only use it for internet web browsing and email checking
- You agree to not download or upload files
- You agree to not use streaming media or peer-to-peer file sharing
- You agree to not run any application servers or data services
- You agree to not use the service as a replacement for a wired data circuit
- You agree to not use the service as a backup for a wired data circuit
- You agree that the service provider can cancel the service without notice if your usage impacts the operation of the service or other users of the service
In other words, you agree to use the cellular data service as a typical consumer with a notebook PC or PDA who spends at most an hour or two daily accessing the internet. I hope by now you can see how difficult it will be to fool any cellular service provider for long that your telemetry data system was just a normal consumer.