Since real world communication channels are not error free, the coded data transmitted on them may be corrupted, and block based image coding systems are vulnerable to transmission impairment. So the best neighborh...Since real world communication channels are not error free, the coded data transmitted on them may be corrupted, and block based image coding systems are vulnerable to transmission impairment. So the best neighborhood match method using genetic algorithm is used to conceal the error blocks. Experimental results show that the searching space can be greatly reduced by using genetic algorithm compared with exhaustive searching method, and good image quality is achieved. The peak signal noise ratios(PSNRs) of the restored images are increased greatly.展开更多
在多输入输出(Multiple-Input Multiple-Output,MIMO)系统中提出一种块分组编码与VBLAST的联合编码方案,该方案对最先检测的2层数据流采用块分组编码,其余层采用垂直分层空时码(Vertical Bell Layered Space-Time Code,VBLAST)的编码方...在多输入输出(Multiple-Input Multiple-Output,MIMO)系统中提出一种块分组编码与VBLAST的联合编码方案,该方案对最先检测的2层数据流采用块分组编码,其余层采用垂直分层空时码(Vertical Bell Layered Space-Time Code,VBLAST)的编码方式,MIMO系统同时具有了空时分组码(Space Time Block Code,STBC)可以降低误码率的优点与VBLAST能够提高系统容量的优点。块分组编码将数据符号按层分块后交叉通过不同的天线对发射,数据流之间产生了一定交织效果,使编码获得了更好的分集增益,在接收端结合QR分解的最大似然解码算法进行解码。仿真结果表明该联合编码方案与传统的Alamouti编码和VBLAST的联合编码方案相比误码率性能有较大改善。展开更多
The closed-form solutions for error rates of Space-Time Block Code (STBC) Multiple Phase Shift Keying (MPSK) systems are derived in this paper. With characteristic function based method and the partial integration bas...The closed-form solutions for error rates of Space-Time Block Code (STBC) Multiple Phase Shift Keying (MPSK) systems are derived in this paper. With characteristic function based method and the partial integration based respectively, the exact expressions of error rates are obtained for (2,1) STBC with and without channel estimation error. Simulations show that the practical error rates accord with the theoretical ones, so closed-form error rates are accurate references for STBC performance evaluation. For the error of pilot assisted channel estimation, the performance of a (2,1) STBC system is deteriorated about 3dB.展开更多
针对当前加密图像可逆信息隐藏方法中存在的嵌入率低,标记图像直接解密后视觉质量差的问题,提出一种位平面分块编码的加密图像可逆信息隐藏方法。算法通过2D sine logistic混沌映射对图像分块加密,保留块内像素的相关性。将加密后的图...针对当前加密图像可逆信息隐藏方法中存在的嵌入率低,标记图像直接解密后视觉质量差的问题,提出一种位平面分块编码的加密图像可逆信息隐藏方法。算法通过2D sine logistic混沌映射对图像分块加密,保留块内像素的相关性。将加密后的图像块化分成8个位平面,在低阶位平面中,根据块平面内0元素和1元素的分布情况,进行编码压缩,利用压缩后块平面内生成冗余空间进行机密信息的嵌入,图像的其余位平面部分则保持不变。在接收端,接收者获取密钥后可以进行信息提取,图像解密和图像的无损恢复。利用标准图像库中图像进行仿真实验,结果表明:随着可嵌入低位平面数的增加,算法的嵌入容量逐渐增大,在低阶平面数取3时,该算法保持较高的嵌入率时,仍然使得直接解密后的图像仍具有较高的PSNR值。展开更多
文摘Since real world communication channels are not error free, the coded data transmitted on them may be corrupted, and block based image coding systems are vulnerable to transmission impairment. So the best neighborhood match method using genetic algorithm is used to conceal the error blocks. Experimental results show that the searching space can be greatly reduced by using genetic algorithm compared with exhaustive searching method, and good image quality is achieved. The peak signal noise ratios(PSNRs) of the restored images are increased greatly.
文摘在多输入输出(Multiple-Input Multiple-Output,MIMO)系统中提出一种块分组编码与VBLAST的联合编码方案,该方案对最先检测的2层数据流采用块分组编码,其余层采用垂直分层空时码(Vertical Bell Layered Space-Time Code,VBLAST)的编码方式,MIMO系统同时具有了空时分组码(Space Time Block Code,STBC)可以降低误码率的优点与VBLAST能够提高系统容量的优点。块分组编码将数据符号按层分块后交叉通过不同的天线对发射,数据流之间产生了一定交织效果,使编码获得了更好的分集增益,在接收端结合QR分解的最大似然解码算法进行解码。仿真结果表明该联合编码方案与传统的Alamouti编码和VBLAST的联合编码方案相比误码率性能有较大改善。
文摘The closed-form solutions for error rates of Space-Time Block Code (STBC) Multiple Phase Shift Keying (MPSK) systems are derived in this paper. With characteristic function based method and the partial integration based respectively, the exact expressions of error rates are obtained for (2,1) STBC with and without channel estimation error. Simulations show that the practical error rates accord with the theoretical ones, so closed-form error rates are accurate references for STBC performance evaluation. For the error of pilot assisted channel estimation, the performance of a (2,1) STBC system is deteriorated about 3dB.
文摘针对当前加密图像可逆信息隐藏方法中存在的嵌入率低,标记图像直接解密后视觉质量差的问题,提出一种位平面分块编码的加密图像可逆信息隐藏方法。算法通过2D sine logistic混沌映射对图像分块加密,保留块内像素的相关性。将加密后的图像块化分成8个位平面,在低阶位平面中,根据块平面内0元素和1元素的分布情况,进行编码压缩,利用压缩后块平面内生成冗余空间进行机密信息的嵌入,图像的其余位平面部分则保持不变。在接收端,接收者获取密钥后可以进行信息提取,图像解密和图像的无损恢复。利用标准图像库中图像进行仿真实验,结果表明:随着可嵌入低位平面数的增加,算法的嵌入容量逐渐增大,在低阶平面数取3时,该算法保持较高的嵌入率时,仍然使得直接解密后的图像仍具有较高的PSNR值。
