srsRAN_4G VS OpenBTS-UMTS

srsRAN is both. It includes the source for user equipment in its "srsue" directory.

Use cases are partly captured by the list of customers across the bottom of the srsRAN home page (https://www.srsran.com/). It's great for any company/research group smaller than a multinational base station manufacturer, at which size the big players don't want to talk to you.

I thought you were kidding me...

here is the letter Q in PHICH:

https://github.com/srsran/srsRAN_4G/blob/master/lib/src/phy/...

as the sibling comment states, q is the reQuest

Yes, for example there is srsue in https://github.com/srsran/srsRAN_4G (the predecessor of the stack used in TFA)

软件套件：https://github.com/srsran/srsRAN

The most popular open source LTE stack is srsLTE (now called srsRAN). https://github.com/srsran/srsRAN

- Literally building a mini cellphone network with something like OpenBTS or updated variant. I don't even know if this is legal and would probably electrocute myself or crash planes, but the idea of software defined radio is interesting. I remember reading a comment somewhere from a developer building an analog phone to cell convertor. They said if you could convert analog signal to cellphone/vice versa, it's theoretically possible to convert it to anything you want.