Multiple-Input Multiple-Output (MIMO) techniques are promising in wireless communication systems for its high spectral efficiency. Sphere Detector (SD) is favoured in MIMO detection to achieve Maximum-Likelihood (ML) ...Multiple-Input Multiple-Output (MIMO) techniques are promising in wireless communication systems for its high spectral efficiency. Sphere Detector (SD) is favoured in MIMO detection to achieve Maximum-Likelihood (ML) performance. In this paper, we proposed a new SD method for MIMO-Orthogonal Frequency Division Multiplexing (OFDM) systems based on IEEE802.11n, which uses Singular Value Decomposition (SVD) in complex domain to reduce the computation complexity. Furthermore, a new Schnorr-Euchner (SE) enumeration algorithm is also discussed in detail. The computer simulation result shows that the computational complexity and the number of visited nodes can be reduced significantly compared with conventional SD detectors with the same Bit Error Rate (BER) performance.展开更多
A list sphere detector can use a smaller list than commonly believed by employing an appropriate soft output approximation method. Its effect on the ＂quality＂ of detector＇s soft output value is evaluated by measuri...A list sphere detector can use a smaller list than commonly believed by employing an appropriate soft output approximation method. Its effect on the ＂quality＂ of detector＇s soft output value is evaluated by measuring mutual information under ergodic channel. The result shows a length 40 list is adequate for a 4×4 16QAM MIMO system without system-level iteration. For the ergodic channel, the gain of a sphere detector over the linear MMSE detector is dependent on channel coding rate, which answers an important question when sphere detector should he used in system level design. All these theoretical results are then verified by Monte Carlo simulation.展开更多
针对中波红外辐射测量定标的需求,提出了将微型积分球与中红外探测器集成在低温环境中。验证比对了几种用于制作积分球内腔表面的材料样品,通过宽光谱反射率、特征光谱反射率、双向反射分布函数(bidirectional reflectance distribution...针对中波红外辐射测量定标的需求,提出了将微型积分球与中红外探测器集成在低温环境中。验证比对了几种用于制作积分球内腔表面的材料样品,通过宽光谱反射率、特征光谱反射率、双向反射分布函数(bidirectional reflectance distribution function,BRDF),以及用激光共聚焦显微镜、扫描电子显微镜(scanning electron microscope,SEM)等进行微观表面形貌的测量,获得了适用于制作中红外积分球的内腔表面制作工艺。BRDF测试结果显示,制作的内腔表面接近朗伯反射表面。测试了积分球探测器样品的光谱与电学性能,经过表面粗糙化处理并蒸镀金属反射膜,样品的光谱波段适应性好,光强衰减比为0.0674,经计算,积分球内腔壁的反射率为96.4%;同时,低温积分球的引入,使探测器芯片的噪声由3.5×10^(-12)A·Hz^(-1/2)降低至1.0×10^(-12)A·Hz^(-1/2)。展开更多
随着核技术在各领域的应用推广,中子屏蔽材料得到越来越广泛的应用,而目前国内外还没有测试中子屏蔽性能的统一标准。为了探索一种简单可行、能够在较宽中子能量范围内测试材料屏蔽性能的方法,本文对3He正比计数管、计数管外包镉及计数...随着核技术在各领域的应用推广,中子屏蔽材料得到越来越广泛的应用,而目前国内外还没有测试中子屏蔽性能的统一标准。为了探索一种简单可行、能够在较宽中子能量范围内测试材料屏蔽性能的方法,本文对3He正比计数管、计数管外包镉及计数管外包不同直径的聚乙烯(Polyethylene,PE)慢化球共12个模型进行了MCNP(Monte Carlo N Particle Transport Code)模拟计算,得到一种慢化球探测器组合测试方法,使测试能够在1×10-5-1.25 Me V能量范围内有较一致的响应。利用这种方法测试了2 cm和4 cm厚PE对252Cf中子的透射率,与多球谱仪解谱法得到的结果在±1.0%内相吻合,对几种材料的测试结果也符合不同类型材料对中子的屏蔽规律,证实了这种简易组合测试方法的可行性。展开更多
超奈奎斯特（Faster Than Nyquist,FTN）信号是一种很有前途的无线通信技术,它能够在不影响频谱效率的情况下提高无线通信系统的数据传输速率。然而,FTN会存在符号间干扰（inter-symbol interference,ISI）,这样会使FTN的增益受损。为...超奈奎斯特（Faster Than Nyquist,FTN）信号是一种很有前途的无线通信技术,它能够在不影响频谱效率的情况下提高无线通信系统的数据传输速率。然而,FTN会存在符号间干扰（inter-symbol interference,ISI）,这样会使FTN的增益受损。为了抑制ISI带来的影响,本文使用一个鲁棒的带有Sphere Detector（SD）的判决反馈均衡器（Decision Feedback Equalizer,DFE）去处理FTN导致的ISI。它能大大降低系统的误码率并实现最大似然（Maximum Likelihood,ML）检测。通过仿真实验,结果表明,提出的算法性能更接近香农极限,相比传统的DFE,误码率会有1~2 d B的优势。展开更多
本文阐述了单球中子谱仪的原理,介绍了基于单慢化球和19对6Li-7Li闪烁体探测器构成的单球中子谱仪的结构及解谱方法,使用蒙特卡罗中子输运程序模拟了单球中子谱仪的中子响应函数。计算结果表明,该谱仪具有较好的空间对称性,能根据谱仪...本文阐述了单球中子谱仪的原理,介绍了基于单慢化球和19对6Li-7Li闪烁体探测器构成的单球中子谱仪的结构及解谱方法,使用蒙特卡罗中子输运程序模拟了单球中子谱仪的中子响应函数。计算结果表明,该谱仪具有较好的空间对称性,能根据谱仪中各探测器的计数对源的大致方位进行判断;模拟了单球谱仪在241Am-Be源照射下各探测器的计数,使用Unfolding with Maxed and Gravel (UMG)解谱程序在不同解谱算法以及初始谱的情况下对模拟数据进行解谱计算,在使用最大熵散发以及与源项相同的预置谱的情况下,解谱结果最为准确,验证了响应函数的准确性。展开更多
文摘Multiple-Input Multiple-Output (MIMO) techniques are promising in wireless communication systems for its high spectral efficiency. Sphere Detector (SD) is favoured in MIMO detection to achieve Maximum-Likelihood (ML) performance. In this paper, we proposed a new SD method for MIMO-Orthogonal Frequency Division Multiplexing (OFDM) systems based on IEEE802.11n, which uses Singular Value Decomposition (SVD) in complex domain to reduce the computation complexity. Furthermore, a new Schnorr-Euchner (SE) enumeration algorithm is also discussed in detail. The computer simulation result shows that the computational complexity and the number of visited nodes can be reduced significantly compared with conventional SD detectors with the same Bit Error Rate (BER) performance.
基金National Natural Science Foundation ofChina(No.60332030)
文摘A list sphere detector can use a smaller list than commonly believed by employing an appropriate soft output approximation method. Its effect on the ＂quality＂ of detector＇s soft output value is evaluated by measuring mutual information under ergodic channel. The result shows a length 40 list is adequate for a 4×4 16QAM MIMO system without system-level iteration. For the ergodic channel, the gain of a sphere detector over the linear MMSE detector is dependent on channel coding rate, which answers an important question when sphere detector should he used in system level design. All these theoretical results are then verified by Monte Carlo simulation.
文摘针对中波红外辐射测量定标的需求,提出了将微型积分球与中红外探测器集成在低温环境中。验证比对了几种用于制作积分球内腔表面的材料样品,通过宽光谱反射率、特征光谱反射率、双向反射分布函数(bidirectional reflectance distribution function,BRDF),以及用激光共聚焦显微镜、扫描电子显微镜(scanning electron microscope,SEM)等进行微观表面形貌的测量,获得了适用于制作中红外积分球的内腔表面制作工艺。BRDF测试结果显示,制作的内腔表面接近朗伯反射表面。测试了积分球探测器样品的光谱与电学性能,经过表面粗糙化处理并蒸镀金属反射膜,样品的光谱波段适应性好,光强衰减比为0.0674,经计算,积分球内腔壁的反射率为96.4%;同时,低温积分球的引入,使探测器芯片的噪声由3.5×10^(-12)A·Hz^(-1/2)降低至1.0×10^(-12)A·Hz^(-1/2)。
文摘随着核技术在各领域的应用推广,中子屏蔽材料得到越来越广泛的应用,而目前国内外还没有测试中子屏蔽性能的统一标准。为了探索一种简单可行、能够在较宽中子能量范围内测试材料屏蔽性能的方法,本文对3He正比计数管、计数管外包镉及计数管外包不同直径的聚乙烯(Polyethylene,PE)慢化球共12个模型进行了MCNP(Monte Carlo N Particle Transport Code)模拟计算,得到一种慢化球探测器组合测试方法,使测试能够在1×10-5-1.25 Me V能量范围内有较一致的响应。利用这种方法测试了2 cm和4 cm厚PE对252Cf中子的透射率,与多球谱仪解谱法得到的结果在±1.0%内相吻合,对几种材料的测试结果也符合不同类型材料对中子的屏蔽规律,证实了这种简易组合测试方法的可行性。
文摘超奈奎斯特（Faster Than Nyquist,FTN）信号是一种很有前途的无线通信技术,它能够在不影响频谱效率的情况下提高无线通信系统的数据传输速率。然而,FTN会存在符号间干扰（inter-symbol interference,ISI）,这样会使FTN的增益受损。为了抑制ISI带来的影响,本文使用一个鲁棒的带有Sphere Detector（SD）的判决反馈均衡器（Decision Feedback Equalizer,DFE）去处理FTN导致的ISI。它能大大降低系统的误码率并实现最大似然（Maximum Likelihood,ML）检测。通过仿真实验,结果表明,提出的算法性能更接近香农极限,相比传统的DFE,误码率会有1~2 d B的优势。
文摘本文阐述了单球中子谱仪的原理,介绍了基于单慢化球和19对6Li-7Li闪烁体探测器构成的单球中子谱仪的结构及解谱方法,使用蒙特卡罗中子输运程序模拟了单球中子谱仪的中子响应函数。计算结果表明,该谱仪具有较好的空间对称性,能根据谱仪中各探测器的计数对源的大致方位进行判断;模拟了单球谱仪在241Am-Be源照射下各探测器的计数,使用Unfolding with Maxed and Gravel (UMG)解谱程序在不同解谱算法以及初始谱的情况下对模拟数据进行解谱计算,在使用最大熵散发以及与源项相同的预置谱的情况下,解谱结果最为准确,验证了响应函数的准确性。
