A lattice reduction aided (LRA) minimum mean square error (MMSE) Tomlinson-Harashima pre-coding (THP) was proposed based on vertical Bell Labs layered space time (VBLAST) algorithm for multiple input multiple output (...A lattice reduction aided (LRA) minimum mean square error (MMSE) Tomlinson-Harashima pre-coding (THP) was proposed based on vertical Bell Labs layered space time (VBLAST) algorithm for multiple input multiple output (MIMO) systems. The extended channel was used to provide optimal tradeoff between residual interference and noise amplification. The processing based on lattice reduction method helps achieve maximal diversity order. The VBLAST algorithm was applied to get the optimal processing ordering for successive interference cancellation (SIC) at transmitter. Simulation results show that the proposed algorithm outperforms conventional THP and the LRA zero-forcing (ZF) THP with full diversity order.展开更多
The turbo equalization approach is studied for Orthogonal Frequency Division Multiplexing （OFDM） system with combined error control coding and linear precoding. While previous literatures employed linear precodcr of...The turbo equalization approach is studied for Orthogonal Frequency Division Multiplexing （OFDM） system with combined error control coding and linear precoding. While previous literatures employed linear precodcr of small size for complexity reasons, this paper proposes to use a linear precoder of size larger than or equal to the maximum length of the equivalent discrete-time channel in order to achieve full frequency diversity and reduce complexities of the error control coder/decoder. Also a low complexity Linear Minimum Mean Square Error （LMMSE） turbo equalizer is derived for the receiver. Through simulation and performance analysis, it is shown that the performance of the proposed scheme over frequency selective fading channel reaches the matched filter bound; compared with the same coded OFDM without linear precoding, the proposed scheme shows an Signal-to-Noise Ratio （SNR） improvement of at least 6dB at a bit error rate of 10 6 over a multipath channel with exponential power delay profile. Convergence behavior of the proposed scheme with turbo equalization using various type of linear precoder/transformer, various interleaver size and error control coder of various constraint length is also investigated.展开更多
In order to reduce the feedback load of multi-user orthogonal frequency division multiplexing （ OFDM ） -based wireless systems, a practiral limited bits feedback precoding algorithm is proposed with direct source-de...In order to reduce the feedback load of multi-user orthogonal frequency division multiplexing （ OFDM ） -based wireless systems, a practiral limited bits feedback precoding algorithm is proposed with direct source-destination link based on amplify-and- forward cooperative relay network under frequency selective fading channels. Using joint minimum mean square error（MMSE） filter, the receiving decoding matrix is designed for each user in the paper. Source precoding （beamforming） matrix is optimized with convex function of weight mean square error （MSE）. Relay precoding matrix is obtained under MSE decomposition and convex optimization. The precoding matrix index is fed back for clustered subcarrier of OFDM with limited feedback. Then using interpolation algorithm, all precoding matrices are achieved at base station （BS） and relay nodes. Simulations indicate the effectiveness of the proposed limited feedback joint precoding and beam_formlng design. The proposed method can improve bit error rate （BER） performance and obtain better sum-rate performance in contrast to existing algorithms. It displays the BER performance is close to that of the unquantified precoding feedback method.展开更多
针对LTE下行多输入多输出正交频分多址(MIMO-OFDM)系统中的天线间干扰和多径干扰问题,提出一种低复杂度的迭代均衡算法。该算法在接收端通过预编码矩阵将发射信号扩展到所有子载波上,从而减少部分子载波深衰落对扩展前原始发射信号的影...针对LTE下行多输入多输出正交频分多址(MIMO-OFDM)系统中的天线间干扰和多径干扰问题,提出一种低复杂度的迭代均衡算法。该算法在接收端通过预编码矩阵将发射信号扩展到所有子载波上,从而减少部分子载波深衰落对扩展前原始发射信号的影响。算法在接收端引入最小均方差误差排序QR分解(MMSE-SQRD)软干扰消除均衡算法,一方面避免传统基于最小均方误差(MMSE)并行软干扰消除均衡算法中矩阵求逆运算,进而降低了算法复杂度,另一方面利用信道排列,优先检测信噪比最大的传输符号进而提高检测准确性。同时通过预编码对重构信号进行预处理,进而缓解在迭代干扰消除过程中的误差传播。仿真结果表明:在4发4收场景下,误码率为10-5时,所提算法信噪比改善约0.7 d B。展开更多
基金The National Natural Science Foundation of China (No. 60772100) The Science and Technology Committee of Shanghai (No. 060215013)
文摘A lattice reduction aided (LRA) minimum mean square error (MMSE) Tomlinson-Harashima pre-coding (THP) was proposed based on vertical Bell Labs layered space time (VBLAST) algorithm for multiple input multiple output (MIMO) systems. The extended channel was used to provide optimal tradeoff between residual interference and noise amplification. The processing based on lattice reduction method helps achieve maximal diversity order. The VBLAST algorithm was applied to get the optimal processing ordering for successive interference cancellation (SIC) at transmitter. Simulation results show that the proposed algorithm outperforms conventional THP and the LRA zero-forcing (ZF) THP with full diversity order.
基金Supported by the National High Technology ResearchDevelopment Program of China (863 Program)(No.2001AA 123014)
文摘The turbo equalization approach is studied for Orthogonal Frequency Division Multiplexing （OFDM） system with combined error control coding and linear precoding. While previous literatures employed linear precodcr of small size for complexity reasons, this paper proposes to use a linear precoder of size larger than or equal to the maximum length of the equivalent discrete-time channel in order to achieve full frequency diversity and reduce complexities of the error control coder/decoder. Also a low complexity Linear Minimum Mean Square Error （LMMSE） turbo equalizer is derived for the receiver. Through simulation and performance analysis, it is shown that the performance of the proposed scheme over frequency selective fading channel reaches the matched filter bound; compared with the same coded OFDM without linear precoding, the proposed scheme shows an Signal-to-Noise Ratio （SNR） improvement of at least 6dB at a bit error rate of 10 6 over a multipath channel with exponential power delay profile. Convergence behavior of the proposed scheme with turbo equalization using various type of linear precoder/transformer, various interleaver size and error control coder of various constraint length is also investigated.
基金National Natural Science Foundation of China-Guangdong，Guangdong-Hong Kong Key Projects of Science and Technology,China，University-Industry Key Project of Department of Education of Guangdong Province,China，National Natural Science Foundation of China
文摘In order to reduce the feedback load of multi-user orthogonal frequency division multiplexing （ OFDM ） -based wireless systems, a practiral limited bits feedback precoding algorithm is proposed with direct source-destination link based on amplify-and- forward cooperative relay network under frequency selective fading channels. Using joint minimum mean square error（MMSE） filter, the receiving decoding matrix is designed for each user in the paper. Source precoding （beamforming） matrix is optimized with convex function of weight mean square error （MSE）. Relay precoding matrix is obtained under MSE decomposition and convex optimization. The precoding matrix index is fed back for clustered subcarrier of OFDM with limited feedback. Then using interpolation algorithm, all precoding matrices are achieved at base station （BS） and relay nodes. Simulations indicate the effectiveness of the proposed limited feedback joint precoding and beam_formlng design. The proposed method can improve bit error rate （BER） performance and obtain better sum-rate performance in contrast to existing algorithms. It displays the BER performance is close to that of the unquantified precoding feedback method.
文摘针对LTE下行多输入多输出正交频分多址(MIMO-OFDM)系统中的天线间干扰和多径干扰问题,提出一种低复杂度的迭代均衡算法。该算法在接收端通过预编码矩阵将发射信号扩展到所有子载波上,从而减少部分子载波深衰落对扩展前原始发射信号的影响。算法在接收端引入最小均方差误差排序QR分解(MMSE-SQRD)软干扰消除均衡算法,一方面避免传统基于最小均方误差(MMSE)并行软干扰消除均衡算法中矩阵求逆运算,进而降低了算法复杂度,另一方面利用信道排列,优先检测信噪比最大的传输符号进而提高检测准确性。同时通过预编码对重构信号进行预处理,进而缓解在迭代干扰消除过程中的误差传播。仿真结果表明:在4发4收场景下,误码率为10-5时,所提算法信噪比改善约0.7 d B。
