混叠频分/码分多址(O-FCDMA)系统框架

Overlapped frequency/code division multiple access(O-FCDMA)system framework

针对Ku频段甚小口径天线终端(VSAT)多点回传应用中面临的频谱利用效率和功率谱密度约束的矛盾,提出一种混叠频分/码分多址(O-FCDMA)系统框架。每个用户采用不同的序列扩频并分别调制到存在频谱混叠的不同子载波上,在保持较低接收机复杂度的同时提高频谱利用效率。仿真表明:部分混叠的O-FCDMA方案可以有效降低多用户干扰(MAI),其性能接近最优的基于置信传播(BP)多用户联合迭代检测译码的直接扩频码分多址(DS-CDMA)系统的,并优于混合频分/码分多址(H-FCDMA)系统的,逼近单用户无干扰时的性能,而且对传统基于匹配滤波的DS-CDMA系统具有更好的兼容性,更易于工程实现。

An overlapped frequency/code division multiple access（OFCDMA）system framework was developed with the equivalent isotropic radiated power（EIRP）mask restraint to improve the spectral efficiency of multiple access systems for very small aperture terminals（VSATs）in the reverse link at the Ku band.Each user＇s information bits are spread by different sequences and then modulated on different subcarriers,with adjacent spectra partially overlapping.The system reduces the receiver complexity and improves the spectral efficiency.Simulations show that the reduced multiple access interference（MAI）improves the O-FCDMA system performance so that it outperforms the hybrid frequency/code division multiple access（H-FCDMA）system and approximates the optimal performance achieved by the belief propagation（BP）based joint iterative detection and decoding algorithm in direct-sequence code division multiple access（DS-CDMA）systems,with similar performance to single user systems.Moreover,the O-FCDMA system has a good compatibility with conventional DS-CDMA systems,so it can be easily implemented.