Abstract: The even slight Frequency Offset（FO） in Multicarrier Code Division Multiple Access（MC-CDMA） systems will destroy the orthogonality among subcarriers and degrade the system performance seriously.Therefore，FO should be estimated and compensated.It is a multi-dimensional and global search when FO is estimated based on maximum likelihood principle，and the computational complexity is high.In this paper，a frequency offset estimation based on PSO algorithm for uplink MC-CDMA systems is presented，which reduces the computational complexity.The simulation results show that the frequency offset estimation method based on PSO for MC-CDMA systems has better performance and the mean square error is less than frequency offset estimation based on virtual carriers.

Key words: multicarrier code division multiple access, frequency offset estimation, particle swarm, virtual carriers

摘要： 多载波码分多址（MC-CDMA）系统的微小载频偏移将破坏子载波之间的正交性，恶化系统性能，因此需要载频偏移估计和补偿；各个载频偏移的最大似然估计是个多维的全局搜索过程，计算复杂。提出一种MC-CDMA系统上行链路的基于粒子群算法的多用户频偏估计算法，降低了频偏估计方法的计算复杂度。仿真结果表明，基于粒子群算法的MC-CDMA系统多用户频偏估计方法的估计性能好，其均方误差小于基于虚拟子载波的多用户频偏估计的均方误差。

关键词: 多载波码分多址, 频偏估计, 粒子群, 虚拟子载波