Analog Devices recently opened a new partitioning option for wireless chip set designers with a transceiver that integrates the ADCs and DACs and delivers a digital signal to the baseband chip.
The traditional solution is to put ADCs and DACs on the baseband chip and communicate with the transceiver using analog signaling. Although ADI positioned this concept as partitioning for WiMAX, the idea is useful for other wireless technologies. See Smart Partitioning of WiMAX Radios.
An additional argument for adopting this system partitioning is a bit more forward looking. As process nodes go to finer and finer geometries, it is going to be harder and harder the build 10- or 12-bit ADCs what is essentially a digital device.
When you have a 1-V supply, dividing the analog signal into, say, 10 segments makes for a pretty dicy proposition.
So it's best, in the long term if not the short term, to put those functions on the RF devices where the supply in 3V or 5V and we know how to handle them.