2.4 GHz data transmission, multiple channels. Is external oscillator needed?

Hi!
I want to implement an audio transmission system. As a reference i use
802.11g, but my design is much simpler because my goal is 1.4 Mbps
throughput (excl. all overheads). I am using USPR + RFX2400. My goal is
to implement as much as possible on hardware. At the moment I am
thinking about how to implement the channel hopping (i plan to have 16
channels), and I can’t find much detailed information about how
multiple-channel systems usually work. Do i need a separate external
oscillator (something like Chrystal) or can I generate all the clocks I
need on FPGA? As I understand, the same upsampling/downsampling hardware
is used, and the channel frequency is specified by small frequency
difference at the baseband, is it correct? If you know any good source
where I can read about multiple channel systems in detail - link will be
appreciated!

Thank you for your answer!

Andrey