请教几个名词翻译signalling stack, baseband, cellular modem

是关于Symbian手机通信方面书中的：
1. The signalling stack (also referred to as the ‘baseband’ or ‘cellular
modem’) is provided by the manufacturer of the device, so Symbian OS
contains a series of adaptation layers to allow standard Symbian OS APIs
to be adapted to the specific signalling stack in use.
2.另外，handset是不是就是 手机 啊？
the first non-Nokia S60 handset--the Siemens SX1.
this version of the OS also went into a series of sophisticated handsets rel
eased by Fujitsu for the DoCoMo network in Japan.
This is a connection from the handset to the GGSN, and provides access to th
e network
attached to the GGSN.
非常感谢！

第一个基本上就是指硬件吧，Symbian OS提供的那个adaption layer可以理解为硬件抽象层，如果你有做硬件或者驱动的经历，应该比较好理解
第二个基本上就是指手机