In this thesis, we follow the standard proposal IEEE 802.12.3a to implement the MB-OFDM UWB system in C programming language. We also analyze the system performance in the multipath fading channel, the IEEE 802.15.3a channel standard. Four different conditions of frequency and timing synchronization are considered. Since the entire system consists of two subsystems: (a) the channel coding with the bit-interleaving and (b) OFDM modulation, the analysis is proceeded in two stages. First, we consider the performance of the only OFDM subsystem. Degradation ratio and average bit error probability are the two metrics used to evaluate the performance. Secondly, we provide the performance bound of the entire UWB system. The performance analysis provides a good understanding of the system behavior in the IEEE 802.15.3a channel standard under various synchronization conditions. The knowledge about the performance of the MB-OFDM UWB system defines our main contribution to the area of wireless communications.