Radio architectures employing DSP techniques

Wireless communications is evolving in different directions from several starting points. In virtually all cases, evolution has proceeded from analogue systems to digital systems having more capability to cope with the radio environment and at a lower cost. The synergy between digital radio communications and VLSI is revolutionising the design of wireless terminals. More and more these terminals look like dedicated computers capable of executing digital signal processing (DSP) algorithms of extremely high complexity. On the one side, these algorithms are interfaced with the radio channel via the RF analogue front end and antenna of the terminal. On the other side with the user through a microphone, speaker and keyboard. In nearly all cases, the RF subsystem also contains a frequency synthesiser which is again a dedicated digital hardware. The evolution of these terminals is characterised by the disappearance of analogue signal processing components and subsystems and their replacement in the software domain by DSP code which runs on highly optimised hardware for maths. At the same time the DSP number crunching heart of the terminals is going faster, stronger, smaller and cheaper. One should expect that this type of evolution may continue until a point where the analogue hardware will be minimum dealing with signal amplification at RF frequencies, conversion to, and from, near baseband and interfacing via a discrete time analogue circuitry to the DSP domain