MIMO-OFDM系统中自适应比特和功率分配

Adaptive bit and power allocation for MIMO-OFDM systems

高速多媒体业务的发展要求无线通信能够提供更高的数据速率和服务质量。为了提高系统容量和性能,M IMO技术、OFDM技术以及自适应传输技术得到了广泛的研究。在完全已知信道状态信息假设前提下,提出了一种针对单用户M IMO-OFDM系统的自适应传输方案。该方案基于子载波上预编码优化设计,在多入多出信道的特征子信道中进行功率注水和动态比特分配,能在满足平均功率约束和给定误比特率条件下最大化系统传输速率。仿真结果表明,所提算法与贪婪算法相比,具有较快的收敛速度,同时其性能在不同的误比特率要求和时延扩展条件下,都优于传统的波束成形和正交空时编码方案。

To meet the demand of transmission of high data multimedia, there has emerged considerable interest recently in orthogonal frequency division multiplexing （OFDM）, multiple-input multiple-output （MIMO） and adaptive transmission technologies to enhance system performance and capacity. The adap- tive transmit strategy was addressed for single-user MIMO-OFDM systems with instantaneous channel state information at transmitter. Based on optimal precodlng design at every subcarrier and water-filling distribution of power over the eigen subchannels, an algorithm was proposed for bit allocation, which can maximize the transmit data rate subject to average transmit power constraints and the given BER require- ment. The simulation results show that the proposed algorithm has the faster convergence rate than the Greedy algorithm, and outperforms conventional beamforming and orthogonal space-time block coding schemes in terms of spectral efficiency under different BER requirements and delay spread.