This paper proposes Steepest Decreasing Constant Modulus Algorithm （SDCMA） detection in frequency dornain for MultiCarrier Direct Sequence-Code Division Multiple Access （MC DS-CDMA） systems. The proposed algorithm...This paper proposes Steepest Decreasing Constant Modulus Algorithm （SDCMA） detection in frequency dornain for MultiCarrier Direct Sequence-Code Division Multiple Access （MC DS-CDMA） systems. The proposed algorithm is used to equalize independent ladings of all subcarriers. At the same time we compare the SDCMA blind detection with subspace-based Minimum Mean-Squared Error （MMSE） detection. The simulation results show that the pertbrmance of SDCMA blind detection is superior to that of subspace-based MMSE detection and the complexity of the former is much lower than that of the latter.展开更多
本文首先建立了采用TR-STBC发送分集的MIMO MC DS-CDMA系统模型,然后在此基础上,研究了SDCMA盲均衡在该系统中的应用,最后进行了仿真和分析。结论是对采用TR-STBC方案的MIMO MC DS-CDMA系统进行常模盲均衡,算法简单,较易实现,但当多址...本文首先建立了采用TR-STBC发送分集的MIMO MC DS-CDMA系统模型,然后在此基础上,研究了SDCMA盲均衡在该系统中的应用,最后进行了仿真和分析。结论是对采用TR-STBC方案的MIMO MC DS-CDMA系统进行常模盲均衡,算法简单,较易实现,但当多址干扰较大时,仅采用此均衡方法不能较好地改善系统性能,还需要进一步采用其他方法来减小或消除多址干扰。展开更多
We consider the uplink of a multiuser, multiple-input multiple-output (MIMO), frequency-time-domain spread, multi- carrier (MC), direct sequence code division multiple access (DS-CDMA) system. As other CDMA-like syste...We consider the uplink of a multiuser, multiple-input multiple-output (MIMO), frequency-time-domain spread, multi- carrier (MC), direct sequence code division multiple access (DS-CDMA) system. As other CDMA-like systems, the multiple access interference (MAI) effect still exists in such an MC DS-CDMA system. To mitigate the MAI effect, we propose user-based and group-based layered detection schemes. Specifically, to enable a trade-off between the performance and the computational complexity, the schemes only use one user's/group's soft decisions for user-based/ group-based layered detection. The results of simulations demonstrate that the proposed schemes outperform existing approaches, and their computational complexity is modest.展开更多
增益(Gain)校正有助于消除MC-ICP-MS不同高阻放大器之间的阻值差异,进而提高同位素分析的精度和准确度,但有关Gain的偏移和校正频率对同位素测试的影响和作用原理还缺乏系统认识。本研究结合本实验室Neptune Plus MC-ICP-MS的Gain校正数...增益(Gain)校正有助于消除MC-ICP-MS不同高阻放大器之间的阻值差异,进而提高同位素分析的精度和准确度,但有关Gain的偏移和校正频率对同位素测试的影响和作用原理还缺乏系统认识。本研究结合本实验室Neptune Plus MC-ICP-MS的Gain校正数据,以实际测试的汞同位素数据为例,评估了放大器Gain校正系数偏移对同位素测试的影响。结果显示,当测试标样和样品的校正系数偏移幅度一致时,汞同位素测试结果基本无变化;当偏移幅度存在明显差异且单一放大器校正系数的相对偏移幅度超过–0.070‰~0.058‰时,汞同位素的测试结果大于分析误差。Gain校正系数单日的相对变化幅度(–0.028‰~0.028‰)可保证汞同位素测试结果小于分析误差,但长期的偏移却会导致汞同位素变化远超分析误差。此外,仪器的硬件、温度和真空度等也是Gain校正系数变化的重要影响因素,因此建议定期维护仪器,并每日进行Gain校正,以保证测试结果的稳定和准确。展开更多
基金Supported by the National Natural Science Foundation of China (No.60472104).
文摘This paper proposes Steepest Decreasing Constant Modulus Algorithm （SDCMA） detection in frequency dornain for MultiCarrier Direct Sequence-Code Division Multiple Access （MC DS-CDMA） systems. The proposed algorithm is used to equalize independent ladings of all subcarriers. At the same time we compare the SDCMA blind detection with subspace-based Minimum Mean-Squared Error （MMSE） detection. The simulation results show that the pertbrmance of SDCMA blind detection is superior to that of subspace-based MMSE detection and the complexity of the former is much lower than that of the latter.
文摘本文首先建立了采用TR-STBC发送分集的MIMO MC DS-CDMA系统模型,然后在此基础上,研究了SDCMA盲均衡在该系统中的应用,最后进行了仿真和分析。结论是对采用TR-STBC方案的MIMO MC DS-CDMA系统进行常模盲均衡,算法简单,较易实现,但当多址干扰较大时,仅采用此均衡方法不能较好地改善系统性能,还需要进一步采用其他方法来减小或消除多址干扰。
文摘We consider the uplink of a multiuser, multiple-input multiple-output (MIMO), frequency-time-domain spread, multi- carrier (MC), direct sequence code division multiple access (DS-CDMA) system. As other CDMA-like systems, the multiple access interference (MAI) effect still exists in such an MC DS-CDMA system. To mitigate the MAI effect, we propose user-based and group-based layered detection schemes. Specifically, to enable a trade-off between the performance and the computational complexity, the schemes only use one user's/group's soft decisions for user-based/ group-based layered detection. The results of simulations demonstrate that the proposed schemes outperform existing approaches, and their computational complexity is modest.
文摘增益(Gain)校正有助于消除MC-ICP-MS不同高阻放大器之间的阻值差异,进而提高同位素分析的精度和准确度,但有关Gain的偏移和校正频率对同位素测试的影响和作用原理还缺乏系统认识。本研究结合本实验室Neptune Plus MC-ICP-MS的Gain校正数据,以实际测试的汞同位素数据为例,评估了放大器Gain校正系数偏移对同位素测试的影响。结果显示,当测试标样和样品的校正系数偏移幅度一致时,汞同位素测试结果基本无变化;当偏移幅度存在明显差异且单一放大器校正系数的相对偏移幅度超过–0.070‰~0.058‰时,汞同位素的测试结果大于分析误差。Gain校正系数单日的相对变化幅度(–0.028‰~0.028‰)可保证汞同位素测试结果小于分析误差,但长期的偏移却会导致汞同位素变化远超分析误差。此外,仪器的硬件、温度和真空度等也是Gain校正系数变化的重要影响因素,因此建议定期维护仪器,并每日进行Gain校正,以保证测试结果的稳定和准确。
