A spectrally efficient method for subcarrier and bit allocation in OFDMA

In this paper we propose and evaluate a new method for assigning subcarriers, constellation sizes and power to the users in an OFDMA system. The proposed scheme considers user-individual bit rate and power constraints, maximum constellation sizes and a spectral power density (PSD) mask. The algorithm minimizes the total used bandwidth by reserving as many subcarriers as possible for future users. By applying this algorithm in a WLAN environment we found that only very few additional transmit power is required in order to reserve a significant amount of subcarriers, even when compared to the best-known power-minimizing algorithm. The computational complexity of the algorithm is very low, which makes it suitable for practical implementation.