How are mobile telephony networks like LTE (4G) and HSPA (3G) encrypted? between what parts is the communication encrypted? who has access to the keys? is symmetric or asymmetric encryption used? is it similar to TLS?
Generally the 4G and 3G networks are not used to make phonecalls or send/recieve texts, those are still pushed to the CDMA and GSM networks and 3/4G are used to connect your device to the internet. The encryption will depend on the company deploying it as well as the device user, because you can setup secure connections to an encrypted VPN or even route through a home proxy. I know my android phone has these features and has retained them through multiple updates. I can only suggest that you call your service provider and ask them how it works.
I suspect that @Jay Looney is correct; for authoritative answers, contact the service provider. (who will report you to DHS and DMCA).
Blackhat description of attacks on HSPA includes a brief overview and architecture, that may address the portion of the question re: what parts are encrypted. This resource also includes the following sentence,
I found one source that asserts that the answer is Feistel encryption, but it doesn't address the key management issue. I continue to believe that is something that only the vendor can answer, and I'm willing to bet they won't.
Agilent provides some internal details, but I think that is more specific than you want. It may be useful as context/example.
You could always take a course in the subject for a mere $1500.