Interesting to see that this femto from Samsung has a GPS device in it, which is used to "geo lock" it to an operator's licenced territory.
I presume this is particularly relevant for countries like the US where there are regional operators. For markets elsewhere with nationwide licences, I guess that the IP address of the broadband connection should be sufficient to ensure customers don't put the device in a suitcase and try & plug it in somewhere the provider isn't permitted to operate.
Interesting to see the real-world practicalities starting to come out, though. I suspect there's going to be a range of issues around security/authentication for femtocells that are only now being recognised.
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Thursday, April 05, 2007
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Dean - a GPS in a femto - which is designed to sit INDOORS! Don't believe all the press releases you get!
GPS can work indoors. And also in this case the femto isn't as power-constrained as a battery-powered device, and can therefore keep monitoring GPS signals 24x7. Could be some form of assisted GPS too, I guess.
First, you are absolutely correct: secirity, authentication, provisioning are all critical - and are there are a number of "subtle but important" issues. Making sure that subscribers to a "home service" do not just put the femto in a suitcase for freecalls all the time are a good example.
As such, most carriers and OEMs are planning on such "geo-locking" in their systems.
Secondly, GPS is a possibility. Indoor coverage is not too bad: especially as you only need "slow" tracking (the house is unlikely to move down a motorway: any movement is a worry). That said, coverage in US is probably better than, say, Korean towerblocks.
However, there are alternatives. One of the obvious is just locking the femto to a specific DSLAM or CMTS: if it is moved you must call the carrier to reset it. (Yes, I know this opens up a load of other issues... We are back to "subtle but important - and good examples of why creating a scalable service is much more than just building a modem!).
Finally, though, is a different point. Basestations need very accurate timing: a few parts-per-billion, accurate over the life of the BS. In normal use that is from a stratum clock locked over PDH (T1 link), a rubidium OCXO -- or a "proper" GPS timing reference. There are a number of ways of doing this - but if you can rely on coverage (see above, reasonable in USA), then why not kill two birds with one stone?
Rupert Baines, picoChip
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