This Thesis presents a GFSK Modem implementation on a DSP (Digital Signal Processor) platform applied to mobile communications. It is the beginning of a future implementation of a complete Software-radio setup. The project presents an analysis of the most used digital modulations in wireless communications, a detailed analysis of GFSK modulation based on Matlab simulations and the implementation in a TMS320C5416 Texas Instruments DSP. Within this Thesis, it is analyzed, simulated and implemented: a FSK continuous phase modulator, low pass and Gaussian filters, a non-coherent FSK demodulator and an IaD (Integrate and Dump) decision algorithm. Finally the analysis of the implementation at high rates with available ADC- DAC is presented together with the comparison between the simulated system and the implemented system.