
I'm here to answer your questions about cellular tech - sherifhanna
Hi - I work for Qualcomm. I noticed some recent threads where 4G and 5G technologies were discussed. The comments indicated to me that there&#x27;s a lot of misconceptions about how cellular technologies work, and the relationship between device capabilities and networks.<p>If you want, I&#x27;m available to answer any questions you may have. I promise to stick with the technology and not veer towards marketing. I&#x27;m much more interested in fostering a better understanding of the technology itself.
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Bigrio
When I authenticate with a tower, given that roaming exists, what/who is my
phone authenticating against?

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sherifhanna
Against a pre-authorized list of networks, identified by their PLMN (public
land mobile network) IDs stored in the SIM card, and cryptographic keys that
the network uses to prove that it really is the network that's authorized in
the SIM card. There are two network functions inside the core 4G network
responsible for authenticating users, checking what services they're
authorized to access, and handling them as they move across towers or roam
into/out of range of the network. More here:
[http://www.3gpp.org/technologies/keywords-
acronyms/100-the-e...](http://www.3gpp.org/technologies/keywords-
acronyms/100-the-evolved-packet-core)

