Next generation of mobile communication systems? goal is to impeccably integrate an extensive variety of communication services such as high speed data, video and multimedia traffic on top of voice signals. The purpose of this work is to assemble realistic communication systems based on Software Defined Radio kits. Two projects were implemented using the Ettus Universal Radio Peripheral (USRP); an Orthogonal Frequency Division Multiplexing (OFDM) communication system and a GSM Base Transceiver Station (BTS). The reliability and performance of the implemented OFDM system was deliberated by modeling a number of factors such as different operating frequencies, various distances and gains. Several Bit Error Rate (BER) and power level graphs were demonstrated. For GSM BTS emulation, successful call between two phones was brought to life in the new network created by the base station, furthermore, a jamming experiment was employed to deteriorate or even drop a call. Aside from these two practical applications, a Partial Transmit Sequence based OFDM system was implemented to significantly reduce the Peak-To-Average Power Ratio. Different encoding algorithms were used to decrease the BER.