Direct-sequence code-division multiple access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability are encountered. To track and ...Direct-sequence code-division multiple access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability are encountered. To track and compensate the channel distortion, a decentralized hypothesis-feedback equalization (HFE) algorithm based on chip-rate update has been used[1]. But due to multiple access interference (MAI), its performance suffers degradation. For this reason, successive interference cancellation hypothesis-feedback equalization (SIC-HFE) algorithm is proposed, which combines the capabilities of HFE to track the time-varying channel and SIC implemented by cross-over feedback filters to cancel out the MAI effects between users. Simulation and experiment results show that the proposed algorithm can significantly improve the performance of asynchronous multiuser CDMA underwater communication system.展开更多
Multiple access interference (MAI) and near-far problem are two major obstacles in DS-CDMA systems. Combining wavelet neural networks and two matched filters, the novel multiuser detector, which is based on multiple v...Multiple access interference (MAI) and near-far problem are two major obstacles in DS-CDMA systems. Combining wavelet neural networks and two matched filters, the novel multiuser detector, which is based on multiple variable function estimation wavelet networks over single path asynchronous channel and space-time channel respectively is presented. Excellent localization characteristics of wavelet functions in both time and frequency domains allowed hierarchical multiple resolution learning of input-output data mapping. The ma thematic frame of the neural networks and error back ward propagation algorithm are introduced. The complexity of the multiuser detector only depends on that of wavelet networks. With numerical simulations and performance analysis, it indicates that the multiuser detector has excellent performance in eliminating MAI and near-far resistance.展开更多
The structure and performance of space-time multiuser detection receiver at base stations of WCDMA system is analyzed, in which smart antenna is employed. WCDMA uplink signal model is established in this paper. Space-...The structure and performance of space-time multiuser detection receiver at base stations of WCDMA system is analyzed, in which smart antenna is employed. WCDMA uplink signal model is established in this paper. Space-time multiuser receiver presented in this paper combines 2D-RAKE with parallel interference cancellation (PIC), and the improved parallel interference cancellation methods are given. A novel space-time multiuser detection scheme, 2DRAKE-GPPIC is proposed. This scheme employs smart antenna to suppress unexpected DOA (Direction Of Arrival) signal, uses RAKE receiver to combine different delays of expected signal, and utilizes grouped partial parallel interference cancellation (GPPIC) algorithm to suppress further the interference signal in the main lobe of array antennas. The simulation results reveal that the scheme of space-time multiuser detection presented in this paper has better performance for WCDMA system.展开更多
Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochann...Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.展开更多
基于透镜天线阵列的毫米波大规模MIMO系统,可以在不损失性能的情况下,有效减少所需的射频链数。为了解决现有波束空间信道中的功率泄露和多用户干扰问题,提出了一种联合QR分解和波束增益对准(beam gain alignment,BGA)的混合预编码方案...基于透镜天线阵列的毫米波大规模MIMO系统,可以在不损失性能的情况下,有效减少所需的射频链数。为了解决现有波束空间信道中的功率泄露和多用户干扰问题,提出了一种联合QR分解和波束增益对准(beam gain alignment,BGA)的混合预编码方案。首先,设计了一种移相网络(phase shift network,PSN)结构,使得波束空间MIMO中的每个射频链能够选择多个波束来收集泄露功率。其次,对波束信道矩阵进行QR分解,以可达和速率为目标,按照递增顺序逐一选择合适的波束,直至选出最优波束选择矩阵。最后利用波束增益对准策略设计模拟预编码,为了消除系统中的多用户干扰,设计了一种使信道对角化的数字预编码器。仿真结果表明,所提算法有着更低的复杂度以及更高的可达和速率及能量效率。展开更多
针对超宽带定位系统在多用户和弱信号环境下接收端易出现码间串扰(inter symbol interference,ISI)和多用户干扰(multiuser interference,MUI)等问题,提出一种基于修正最小均方误差估计(minimum mean square error estimation,MMSE)的...针对超宽带定位系统在多用户和弱信号环境下接收端易出现码间串扰(inter symbol interference,ISI)和多用户干扰(multiuser interference,MUI)等问题,提出一种基于修正最小均方误差估计(minimum mean square error estimation,MMSE)的自适应迭代算法进行超宽带(ultra-wideband,UWB)脉冲设计。该算法选取修正Hermite多项式(modefied Hermite polynomial,MHP)作为脉冲设计基函数。通过分析MHP的时频特性对最小均方误差估计准则下组合脉冲的各阶MHP系数进行修正,在此基础上根据组合脉冲功率谱密度与美国联邦通讯委员会(federal communications commission,FCC)辐射掩蔽之间的拟合程度设计自适应算法,对组合脉冲进行自适应调整实现脉冲设计。仿真结果表明该方案获得的脉冲有较高功率利用率,同时在多用户接入和弱信号检测方面也具备很强的适用性。展开更多
基金National Natural Science Foundation of China (60572098)
文摘Direct-sequence code-division multiple access (CDMA) is considered for multiuser communication network in underwater acoustic channel, where extended multipath and rapid time-variability are encountered. To track and compensate the channel distortion, a decentralized hypothesis-feedback equalization (HFE) algorithm based on chip-rate update has been used[1]. But due to multiple access interference (MAI), its performance suffers degradation. For this reason, successive interference cancellation hypothesis-feedback equalization (SIC-HFE) algorithm is proposed, which combines the capabilities of HFE to track the time-varying channel and SIC implemented by cross-over feedback filters to cancel out the MAI effects between users. Simulation and experiment results show that the proposed algorithm can significantly improve the performance of asynchronous multiuser CDMA underwater communication system.
基金This project was supported by the National Natural Science Foundation of China (60073053 60133010).
文摘Multiple access interference (MAI) and near-far problem are two major obstacles in DS-CDMA systems. Combining wavelet neural networks and two matched filters, the novel multiuser detector, which is based on multiple variable function estimation wavelet networks over single path asynchronous channel and space-time channel respectively is presented. Excellent localization characteristics of wavelet functions in both time and frequency domains allowed hierarchical multiple resolution learning of input-output data mapping. The ma thematic frame of the neural networks and error back ward propagation algorithm are introduced. The complexity of the multiuser detector only depends on that of wavelet networks. With numerical simulations and performance analysis, it indicates that the multiuser detector has excellent performance in eliminating MAI and near-far resistance.
文摘The structure and performance of space-time multiuser detection receiver at base stations of WCDMA system is analyzed, in which smart antenna is employed. WCDMA uplink signal model is established in this paper. Space-time multiuser receiver presented in this paper combines 2D-RAKE with parallel interference cancellation (PIC), and the improved parallel interference cancellation methods are given. A novel space-time multiuser detection scheme, 2DRAKE-GPPIC is proposed. This scheme employs smart antenna to suppress unexpected DOA (Direction Of Arrival) signal, uses RAKE receiver to combine different delays of expected signal, and utilizes grouped partial parallel interference cancellation (GPPIC) algorithm to suppress further the interference signal in the main lobe of array antennas. The simulation results reveal that the scheme of space-time multiuser detection presented in this paper has better performance for WCDMA system.
基金the National Natural Science Foundation of China (60372055)National Doctoral Foundation of China (20030698027).
文摘Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.
文摘基于透镜天线阵列的毫米波大规模MIMO系统,可以在不损失性能的情况下,有效减少所需的射频链数。为了解决现有波束空间信道中的功率泄露和多用户干扰问题,提出了一种联合QR分解和波束增益对准(beam gain alignment,BGA)的混合预编码方案。首先,设计了一种移相网络(phase shift network,PSN)结构,使得波束空间MIMO中的每个射频链能够选择多个波束来收集泄露功率。其次,对波束信道矩阵进行QR分解,以可达和速率为目标,按照递增顺序逐一选择合适的波束,直至选出最优波束选择矩阵。最后利用波束增益对准策略设计模拟预编码,为了消除系统中的多用户干扰,设计了一种使信道对角化的数字预编码器。仿真结果表明,所提算法有着更低的复杂度以及更高的可达和速率及能量效率。
