Random Waterfilling in a Clustered Multiuser OFDM System

In this paper, a random waterfilling power allocation is proposed for performance enhancement in clustered multiuser orthogonal frequency division multiplexing (OFDM) systems in a low SNR regime. The proposed random waterfilling increases the multiuser diversity gain so that it achieves higher throughput than static equal power allocation. The relative gain over static equal power allocation increases as the received SNR decreases. Based on an upper bound on the normalized capacity of the proposed random waterfilling derived in this paper, it is shown that the capacity grows with number of users K like O(log2K-1/¿2K-1).