The lattice-reduction （LR） has been developed to im- prove the performance of the zero-forcing （ZF） precoder in multiple input multiple output （MIMO） systems. Under the assumptions of uncorrelated flat fading ch...The lattice-reduction （LR） has been developed to im- prove the performance of the zero-forcing （ZF） precoder in multiple input multiple output （MIMO） systems. Under the assumptions of uncorrelated flat fading channel model and perfect channel state information at the transmitter （CSIT）, an LR-aided ZF precoder is able to collect the full transmit diversity. With the complex Lenstra- Lenstra-Lov^sz （LLL） algorithm and limited feedforward structure, an LR-aided linear minimum-mean-square-error （LMMSE） pre- coder for spatial correlated MIMO channels and imperfect CSIT is proposed to achieve lower bit error rate （BER）. Assuming a time division duplexing （TDD） MIMO system, correlated block flat fad- ing channel and LMMSE uplink channel estimator, it is proved that the proposed LR-aided LMMSE precoder can also obtain the full transmit diversity through an analytical approach. Furthermore, the simulation results show that with the quadrature phase shift keying （QPSK） modulation at the transmitter, the uncoded and coded BERs of the LR-aided LMMSE precoder are lower than that of the traditional LMMSE precoder respectively when Eb-No is greater than 10 dB and 12 dB at all correlation coefficients.展开更多
This paper discusses the blind carrier frequency offset （CFO） estimation for orthogonal frequency division multiplexing （OFDM） systems by utilizing trilinear decomposition and genera- lized preceding. Firstly, the...This paper discusses the blind carrier frequency offset （CFO） estimation for orthogonal frequency division multiplexing （OFDM） systems by utilizing trilinear decomposition and genera- lized preceding. Firstly, the generalized precoding is employed to obtain multiple covariance matrices which are requisite for the trilinear model, and then a novel CFO estimation algorithm is proposed for the OFDM system. Compared with both the joint diagonalizer and estimation of signal parameters via rotational invariant technique （ESPRIT）, the proposed algorithm enjoys a better CFO estimation performance. Furthermore, the proposed algorithm can work well without virtual carriers. Simulation results illustrate the performance of this algorithm,展开更多
正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术在时延-多普勒域调制信息,为高移动场景下的通信提供了一种稳健的解决方案。然而,与其他多载波技术类似,OTFS也面临高峰均功率比(Peak-to-Average Power Ratio,PAPR)问题,可...正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术在时延-多普勒域调制信息,为高移动场景下的通信提供了一种稳健的解决方案。然而,与其他多载波技术类似,OTFS也面临高峰均功率比(Peak-to-Average Power Ratio,PAPR)问题,可能导致信号失真和性能下降。为此,提出一种矩阵维度可调的扩展预编码方案,将预编码矩阵统一表示为周期展开变换矩阵和能量守恒矩阵的乘积,通过调整矩阵维度,在略微增加复杂度的情况下,灵活降低信号PAPR。此外,讨论了扩展预编码OTFS的感知性能,推导了其在连续时延-多普勒域的输入输出关系,并基于时延-多普勒域处理的两阶段搜索感知算法,进行了距离和速度估计。仿真结果表明,所提出的扩展预编码方案在一定的多普勒索引和时延索引下,至少能够降低3 dB的PAPR,并能实现比传统OTFS更优的误码率性能,同时能得到毫米级的距离估计精度和分米每秒级的速度估计精度。展开更多
Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal freque...Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal frequency-division multiplexing （OFDM） systems. A redundant linear frequency-domain precoder is applied to each pair of blocks before they enter the OFDM system. Because of the introduced structure, the frequency-selective channel can be identified at the receiver based on autocorrelation operations, singular value decomposition （SVD）, and by resolving the scalar ambiguity. The proposed channel estimation method has low computational complexity and requires no prior statistical information on channel or noise. And the proposed blind method has high spectral efficiency owing to exploiting no training sequence. Computer simulations confirm that this proposed blind channel estimation method can identify the frequency-selective channels perfectly and obtain a good performance.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars (60725105)the National Basic Research Program of China (2009CB320404)+4 种基金the Program for Changjiang Scholars and Innovative Research Team in University (IRT0852)the 111 Project(B08038)the National Natural Science Foundation of China (60702057)the Special Research Fund of State Key Laboratory (ISN1102003)the National Science and Technology Major Project (2011ZX03001-007-01)
文摘The lattice-reduction （LR） has been developed to im- prove the performance of the zero-forcing （ZF） precoder in multiple input multiple output （MIMO） systems. Under the assumptions of uncorrelated flat fading channel model and perfect channel state information at the transmitter （CSIT）, an LR-aided ZF precoder is able to collect the full transmit diversity. With the complex Lenstra- Lenstra-Lov^sz （LLL） algorithm and limited feedforward structure, an LR-aided linear minimum-mean-square-error （LMMSE） pre- coder for spatial correlated MIMO channels and imperfect CSIT is proposed to achieve lower bit error rate （BER）. Assuming a time division duplexing （TDD） MIMO system, correlated block flat fad- ing channel and LMMSE uplink channel estimator, it is proved that the proposed LR-aided LMMSE precoder can also obtain the full transmit diversity through an analytical approach. Furthermore, the simulation results show that with the quadrature phase shift keying （QPSK） modulation at the transmitter, the uncoded and coded BERs of the LR-aided LMMSE precoder are lower than that of the traditional LMMSE precoder respectively when Eb-No is greater than 10 dB and 12 dB at all correlation coefficients.
基金supported by the National Natural Science Foundation of China (60801052)the Aeronautical Science Foundation of China(2009ZC52036)+1 种基金Nanjing University of Aeronautics and Astronautics Research Funding (NS2012010 NP2011036)
文摘This paper discusses the blind carrier frequency offset （CFO） estimation for orthogonal frequency division multiplexing （OFDM） systems by utilizing trilinear decomposition and genera- lized preceding. Firstly, the generalized precoding is employed to obtain multiple covariance matrices which are requisite for the trilinear model, and then a novel CFO estimation algorithm is proposed for the OFDM system. Compared with both the joint diagonalizer and estimation of signal parameters via rotational invariant technique （ESPRIT）, the proposed algorithm enjoys a better CFO estimation performance. Furthermore, the proposed algorithm can work well without virtual carriers. Simulation results illustrate the performance of this algorithm,
文摘正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术在时延-多普勒域调制信息,为高移动场景下的通信提供了一种稳健的解决方案。然而,与其他多载波技术类似,OTFS也面临高峰均功率比(Peak-to-Average Power Ratio,PAPR)问题,可能导致信号失真和性能下降。为此,提出一种矩阵维度可调的扩展预编码方案,将预编码矩阵统一表示为周期展开变换矩阵和能量守恒矩阵的乘积,通过调整矩阵维度,在略微增加复杂度的情况下,灵活降低信号PAPR。此外,讨论了扩展预编码OTFS的感知性能,推导了其在连续时延-多普勒域的输入输出关系,并基于时延-多普勒域处理的两阶段搜索感知算法,进行了距离和速度估计。仿真结果表明,所提出的扩展预编码方案在一定的多普勒索引和时延索引下,至少能够降低3 dB的PAPR,并能实现比传统OTFS更优的误码率性能,同时能得到毫米级的距离估计精度和分米每秒级的速度估计精度。
基金This project was supported by the National Natural Science Foundation of China (60572157)National Hi-Tech Research and Development Program (863) of China (2003AA123310).
文摘Considering that channel estimation can play a crucial role in coherent detection of the information symbols in each data block, a blind channel estimation approach is proposed for redundant precoded orthogonal frequency-division multiplexing （OFDM） systems. A redundant linear frequency-domain precoder is applied to each pair of blocks before they enter the OFDM system. Because of the introduced structure, the frequency-selective channel can be identified at the receiver based on autocorrelation operations, singular value decomposition （SVD）, and by resolving the scalar ambiguity. The proposed channel estimation method has low computational complexity and requires no prior statistical information on channel or noise. And the proposed blind method has high spectral efficiency owing to exploiting no training sequence. Computer simulations confirm that this proposed blind channel estimation method can identify the frequency-selective channels perfectly and obtain a good performance.
