A blockwise loading algorithm for the adaptive modulation technique in OFDM systems

Abstract

The OFDM transmission technique has the inherent flexibility to adapt the modulation scheme on each subcarrier according to the reception quality, i.e. the signal-to-noise ratio (SNR) on a subcarrier. The allocation of bits to subcarriers is performed by so-called loading algorithms. In this paper, a new and rather simple loading algorithm is introduced which shows comparable performance and lower computational complexity compared to the well-known algorithm of Chow et al. (1995). In the proposed algorithm, subcarriers are clustered in blocks, which are allocated the same modulation scheme. This way, the signalling overhead can be reduced in comparison with standard subcarrier bit loading algorithms.