中文摘要：

在OFDM系统中应用白适应比特分配能够优化系统的性能。在传输速率固定的前提下，对动态比特和功率分配的优化问题进行分析后．提出了一种新的基于预分配的自适应比特分配算法。该算法由预分配和迭代分配两个过程组成。在预分配过程中．信道状态较好的子载波将被优先考虑，然后通过迭代分配进一步将总发射功率降低。仿真结果表明，该算法是一种最优的比特和功率分配算法。与传统的等比特分配方案相比，该算法能够显著提高系统的性能。

英文摘要：

After an overview of existing bit and power allocation algorithms, a new adaptive allocation algorithm is proposed for the OFDM system based on pre-allocation. The algorithm is consisted of pre-allocation and iterative allocation. Firstly the bits and corresponding power are allocated to the sub-carriers in better channel condition, and then the transmit power is minimized with an iterative procedure. Simulation results show that the proposed algorithm is an optimal algorithm and it can clearly improve system performance compared with the traditional equal bit allocation algorithm.