机构地区: 北京邮电大学电信工程学院信息与通信工程学院
出 处: 《北京邮电大学学报》 2003年第3期17-21,共5页
摘 要: 研究了正交频分复用(OFDM)系统在精确已知信道状态信息和不精确的信道状态信息环境下的自适应调制,并对它们的性能进行了计算机仿真分析.结果表明,信道估计不精确和延迟均对自适应调制OFDM系统的性能有很大影响,尤其是延时的影响.为了减小其影响,提出了利用多个以前的信道估计值来确定每个子信道所传输的比特数.仿真结果表明,该方法能有效地提高自适应调制OFDM系统的性能. One way to improve the performance of OFDM system is to use adaptive modulation. However, accurate channel state information (CSI) is required at the transmitter to achieve the benefits. Imperfect CSI arises from noisy channel estimates, which may also be outdated due to a delay in getting the CSI to the transmitter. Adaptive OFDM with both perfect and imperfect CSI is studied. Performance results are provided for this system with imperfect CSI.