Abstract: To the ultrawideband systems (OFDMUWB) based on orthogonal frequency division multiplexing, an adaptive bit allocation algorithm is proposed to combat the frequency selective fading of ultrawideband channels. Under the constraints of data transmitting rate and uniform power spectrum density, the bit allocation is transformed into an optimization problem, whose target function is bit error rate. The bit allocation algorithm is presented in details. Simulation results suggest that the proposed algorithm can effectively boost the system performance.

Key words: OFDM, bit allocation, uniform power spectrum density , UWB