This is the device in the iPhone that manages all the functions which require an antenna. The GSM phone, as well as the WiFi and bluetooth are all under the control of the baseband processor. The baseband processor has its own RAM and NOR flash resources, separate from the ARM core resources. The baseband processor is a resource to the OS.
Baseband Files of 1.1.1 to 1.1.4
For 04.04.05_G (1.1.4)
For 04.03.13_G (1.1.3)
For 04.02.13_G (1.1.2)
For 04.01.13_G (1.1.1)