Multicarrier systems, such as MB-OFDM system, have shown better performance measures when system parameters (power, bits) are optimized, simultaneously, over different frequencies with respect to channel gain factor. In this paper, the parameter allocation problem in a multi-band OFDM (MB-OFDM) system for ultra-wide band is described considering UWB spectrum that is divided into bands that are 528 MHz wide. Within each sub-band, the bits and power are allocated in an optimized way. A Genetic Algorithm is designed that takes into account the problem of parameter allocation (power, bits) to different sub-bands in MB-OFDM scheme. The proposed solution tends to converge after a specific number of generations depending upon the number of bits allocated to each sub-carrier that in turn is dependent on channel gain.