In this paper we propose a novel dynamic subcarrier assignment algorithm for the downlink of an OFDMA system. In conventional schemes, subcarriers are assigned to the active users independently of the actual channel conditions. On the other hand, in a frequency-selective fading environment the users are characterized by different channel responses on each subcarrier. Thus, it makes sense to look for an efficient subcarrier allocation algorithm that fully exploits the inherent multiuser diversity and dynamically assigns a set of subcarriers to each user according to some optimality criterion. The proposed algorithm is based on a mini/max approach and aims at minimizing the error probability of the user with the most attenuated allocated subcarrier. Simulation indicate that the resulting scheme can achieve large improvements with respect to other existing alternatives in terms of either error probability or power consumption.
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