A Grouping Method of Bit Loading for Real-Time OFDM-Based Wireless Networks

A Grouping method of bit and power allocation in orthogonal frequency division multiplex (OFDM) system is presented in this paper. The complexity of BABGS algorithm, as bit allocation based on grouping subcarriers (BABGS), is lower than suboptimal algorithms. This algorithm aims to minimize the total transmitted power under the constraint of bit error rate (BER) and total bit rate, so it is based on margin adaptive (MA) principle. The structure of the proposed algorithm includes two stages. In the first stage, the subcarriers are divided into several groups according to the channel characteristics and the initial bits are assigned to per subcarrier in each group at the same time. The second stage is to adjust bits of each subcarrier in order to minimize the total transmission power. Compared with the Nader algorithms, this algorithm is reduced computing complexity by 20% and suitable to be utilized in deep fading frequency selected channel of the real-time systems. And its performance is still close to suboptimal algorithms.