Parameter representations for baseband processing of 2G and 3G mobile communications systems

The international standard for third generation (3G) mobile communications IMT-2000 includes five different air interfaces. It is desirable that all interfaces can operate everywhere in order to reach a global roaming, however this may be not feasible. Furthermore a backward compatibility to the second generation (2G) mobile systems such as GSM, IS-136 and IS-95 is required. So at least the hand-helds should be able to perform the main 2G and 3G air interfaces to operate in the available systems. A parametrized structure for the base band processing is proposed in this paper, which guarantees small handsets, the possibility of updating and of seamless system handover, e.g. between UTRA and GSM. Since the baseband functions will be implemented on reconfigurable hardware like DSPs and FPGAs, it can bee viewed as a software radio or software defined radio. The way of parameterization is explained in detail by the example of a common modulator in this paper. Also some implementation aspects of the MAP-algorithm used for channel decoding and equalization are discussed.