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以易于工程实现的Log-MAP算法为基础,深入研究了两种不同的外信息使用方式:Berrou方案及Robertson方案,指出两种外信息使用方式具有统一性,不同的是迭代译码过程中对外信息使用权重的处理;在相同约束条件下对基于两种外信息使用方式的Turbo码性能进行蒙特卡罗仿真,结果表明Robertson方案从整体上要略优于Berrou方案。 相似文献
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Lipu Zhou Zhidong Deng 《清华大学学报》2014,(3):314-322
In this paper,we propose a new algorithm to establish the data association between a camera and a 2-D Light Detection And Ranging sensor (LIDAR).In contrast to the previous works,where data association is established by calibrating the intrinsic parameters of the camera and the extrinsic parameters of the camera and the LIDAR,we formulate the map between laser points and pixels as a 2-D homography.The line-point correspondence is employed to construct geometric constraint on the homography matrix.This enables checkerboard to be not essential and any object with straight boundary can be an effective target.The calculation of the 2-D homography matrix consists of a linear least-squares solution of a homogeneous system followed by a nonlinear minimization of the geometric error in the image plane.Since the measurement quality impacts on the accuracy of the result,we investigate the equivalent constraint and show that placing the calibration target nearby the 2-D LIDAR will provide sufficient constraints to calculate the 2-D homography matrix.Simulation and experimental results validate that the proposed algorithm is robust and accurate.Compared with the previous works,which require two calibration processes and special calibration targets such as checkerboard,our method is more flexible and easier to perform. 相似文献
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The 16-ary quadrature amplitude modulation (16QAM) is a high spectral efficient scheme for high-speed transmission systems. To remove the phase ambiguity in the coherent detection system, differential-encoded 16QAM (DE-16QAM) is usually used, however, it will cause performance degradation about 3 dB as compared to the conventional 16QAM. To overcome the performance loss, a serial concatenated system with outer low density parity check (LDPC) codes and inner DE-16QAM is proposed. At the receiver, joint iterative differential demodulation and decoding (ID) is carried out to approach the maximum likelihood performance. Moreover, a genetic evolution algorithm based on the extrinsic information transfer chart is proposed to optimize the degree distribution of the outer LDPC codes. Both theoretical analyses and simulation results indicate that this algorithm not only compensates the performance loss, but also obtains a significant performance gain, which is up to 1 dB as compared to the conventional non-DE-16QAM. 相似文献
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绝对光纤珐珀应变传感器 (AEFPI)已经在工程结构监测中得到了应用。对传统 AEFPI的算法进行了分析 ,并提出了一种改进算法 ,仿真的结果证明了传统算法只是该算法的一种特例 ,而该算法在不改变任何硬件的情况下 ,能够显著的降低测量系统的测量误差 相似文献
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通过对解空间的分布,发现摄像机外部姿态参数中旋转矩阵的解分布于一半径固定的超球面上,且此超球面的维数可由方程组的系数矩阵确定。据此提出了在全空间中求取全解的搜索策略。实验表明,用本算法所得到的结果与理论分析相吻合,能够较好地解决参数求取过程中的完全解问题。 相似文献
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大尺寸三维激光测量系统标定方法 总被引:1,自引:0,他引:1
研究了一种基于平面几何射影变换原理的三维激光测量系统标定方法. 根据测量系统中激光扫描平面的旋转特点,基于平面射影变换中直线不变的映射关系建立了标定对象表面被测点在不同参考系之间变换的约束关系,并采用封闭运动链思想定义系统参考系空间刚体变换关系,将系统标定问题转化为世界坐标系下系统内参数矩阵和外参数矩阵的求解. 通过空间变换关系得到上述2个矩阵的解,实现系统的标定. 该方法标定装置简单、速度快、稳定性好,能够满足实际工程应用中的需求. 相似文献
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基于对数似然比的BP译码算法与标准BP译码算法相比,降低了一定的运算量,但仍具有较高的计算复杂度,硬件实现时需要消耗较高的资源。针对此问题,提出了一种变量节点动态更新选择的对数似然比BP译码算法,根据每一次迭代后变量节点外信息的收敛情况及校验方程的满足情况,动态地选择置信度最低的部分节点参与更新,其他置信度较高的节点则不进行更新。仿真结果显示,该算法译码性能与对数似然比BP译码算法相比,在0.5码率,10-4误码率时,1 024码长有0.1dB的性能损失,2 048码长性能损失仅有0.07dB,但从第4次迭代开始归一化运算量至少降低了50%。 相似文献
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用整个系统的角动量守恒条件代替切向动量守恒条件,将星风吸积与盘吸积两种质量吸积一起来,考虑双星系统的轨道偏心率e的二次以上的高次项,重新推导了吸积质量及轨道参量变化方程。 相似文献
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