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用于宽带无线通信的空时频编码OFDM技术 总被引:2,自引:1,他引:2
为进一步改善频率选择性衰落信道下的空时编码系统性能,提出了一种系统误码性能更为优越、功率效率更高的空时频编码OFDM(COFDM)技术.该技术采用子载波分组与线性预编码方案,通过适当的子载波分组,可以保证系统获得最大的分集增益,并使系统编译码的的复杂程度大为降低;同时将空时格栅码(STTC)与空时分组码(STBC)相结合,使得系统在获得最大分集增益的前提下,具有良好的编码增益;最后引入功率配置来进一步改善系统误码率性能和提高功率效率.仿真结果表明,该方案具有良好的系统误码率性能和较高的功率效率. 相似文献
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针对OFDM系统中FFT处理器的设计要求 ,提出了并行蝶算单元算法和双蝶算单元算法 ,并给出了基于这两种算法的一种高效FFT处理器的实现方案。该方案利用蝶算单元中旋转因子产生特性 ,将乘法运算与加法运算并行处理 ,从而有效地提高了FFT处理器的运算速度 ,同时减小了其硬件资源耗用量。本文给出了相应的算法描述和结构框图 相似文献
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Differential unitary space-time modulation (DUSTM), which obtains full transmit diversity in slowly fiat-fading channels without channel state iufonnation, has generated significant interests recently. To combat frequency-selective fading, DUSTM has been applied to each subcarrier of an OFDM system and DUSTM-OFDM system was proposed. Both DUSTM and DUSTM-OFDM, however, are designed for slowly fading channels and suffer performance deterioration in fast fading channels. In this paper, two novel differential unitary space-time modulation schemes are proposed for fast fading channels. For fast fiat-fading channels, a subatrix interleaved DUSTM (SMI-DUSTM) scheme is proposed, in which matrix-segmentation and sub-matrix based interleaving are introduced into DUSTM system. For fast frequency-selective fading channels, a differential unitary space-frequency modulation (DUSFM) scheme is proposed, in which existing unitary space-time codes are employed across transmit antennas and OFDM subcarriers simultaneouslv and differential modulation is performed between two adjacent OFDM blocks. Compared with DUSTM and DUSTM-OFDM schemes, SMI-DUSTM and DUSFM-OFDM are more robust to fast channel fading with low decoding complexity, which is demonstrated by performance analysis and simulation resuits. 相似文献
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一、玉米播种期杂草的防治
1.阿特拉津.可于玉米播种前、播后苗前进行土壤处理,也可在苗后玉米3~4叶期、禾本科杂草1~2叶期、阔叶杂草3~4叶期进行茎叶处理.用40%阿特拉津悬浮剂150~200毫升/亩,粘土地和有机质含量高的土壤要适当加大剂量. 相似文献
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纹枯病是小麦生产上的一种常见病害,每年均有不同程度发生.但2007年该病在许昌市的发生程度是近年来最为严重的一年,主要表现在:病株率高,侵茎率高,造成部分地块甚至出现枯孕穗和白穗.为此,笔者对2007年许昌市小麦纹枯病发生情况进行了调查,对其重发原因进行分析,并探讨了防治对策. 相似文献
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1.阿特拉津。可于玉米播种前、播后苗前进行土壤处理。也可在苗后玉米3—4叶期、禾本科杂草1—2叶期、阔叶杂草3—4叶期进行茎叶处理。用40%阿特拉津悬浮剂150~200毫升/亩,粘土地和有机质含量高的土壤要适当加大剂量。 相似文献