一种新的空时2D-RAKE接收机

提出一种新的空时2D-RAKE接收机算法,它将波束形成技术与RAKE相结合。此中波束形成算法在干扰方向上完全陷零,其权重仅与阵列天线的导向矢量有关,与接收信号无关。仿真实验表明,这种空时2D-RAKE接收机与传统2D-RAKE接收机相比,具有较好的性能,而且该算法对噪声具有鲁棒性。这种2D-RAKE接收机与并行干扰抵消(PIC)算法相结合的空时多用户检测的仿真结果表明,多级检测的误码率曲线与第一级重合,采用这种2D- RAKE能够完全消除多址干扰和多径干扰。     

宽带CDMA中的多用户检测技术研究

研究了多用户检测技术在宽带 CD-MA系统中的应用。比较系统地介绍了最佳多用户检测和次最佳多用户检测接收机的原理 ,对多级串行和并行干扰抵消算法进行了仿真 ,并给出了结论 :从复杂度和误码性能两方面综合考虑 ,干扰抵消接收机的抵消级数选为 3级时 ,接收机的性能最优。     

一种空时盲自适应RAKE接收机

多址干扰是直扩码分多址系统中的一个主要问题.多用户检测技术和阵列天线已成为解决这一问题的两种主要方法,将这两种方法结合起来的空时处理能大大提高系统的容量和性能.本文提出了一种空时盲自适应RAKE接收机.研究结果表明,该接收机具有较强的抑制多址干扰和克服"远-近"效应的能力,且能快速收敛.     

CDMA系统中2-D RAKE接收机的性能研究

CDMA系统中,信号在无线信道中传输,由于多用户同时同频传输和多径衰落的存在,导致多址干扰(MAD和符号间干扰(ISI),使系统接收机的性能下降.空时接收机(2-D RAKE)能够有效地抑制MAI和对抗多径衰落,这里介绍了几种接收机的工作特点,并对各种空时接收机进行了详细的分析和比较.     

空时多用户检测器的级联结构

探讨了一种级联结构的空时多用户检测器。它可认为是改进的(或优化的)2D—RAKE接收机或改进的CMOE盲多用户检测器。其结构类似ST2D—RAKE接收机，但能充分利用所需用户的扩频码信息。用优化的方法生成解扩序列，从而大大改善了性能。     

一种新的用于DS/CDMA系统的多级盲空时多用户接收机

本文讨论的接收机是用于DS/CDMA系统的多级自适应阵列和串行干扰消除联合接收机(AA-SIC),介绍的接收机同时使用了空域和时域处理以及多用户联合检测技术.一般的联合接收机要使用RAKE单元,本文所讨论的接收机没有使用RAKE单元,而利用智能天线的自适应算法能起到分集接收的功能,不仅能抑制多址干扰信号,而且构成简便,计算时间较短,有利于实际应用.     

DS-CDMA系统新的空时并联结构 及二维自适应DBF算法

针对直接序列扩频码分多址(DS-CDMA)移动通信接收系统,本文提出了一种新的空时二维信号处理结构,这是一种"智能天线与瑞克(RAKE)接收机的并联连接"(PI-SA&RR)结构.基于PI-SA&RR结构,提出了空时二维自适应数字波束形成(ST2-DADBF)算法.与"二维RAKE接收机"(2-DRR)相比,ST2-DADBF算法不需要对延时-波达方向(DOA)进行估计就能够获得最优空-时域联合输出.与"导频符号辅助相干自适应天线阵列分集接收机"(PSA-CAAADR)相比,ST2-DADBF算法能够使智能天线和RAKE接收机联合参与自适应算法,不需要对RAKE分支信道参数进行估计,是一种真正的二维自适应算法.针对多用户移动通信系统,同时考虑到信道的时延扩展和空间角度弥散的影响,本文给出了一种接收信号的通用模型,基于该模型对ST2-DADBF算法进行了计算仿真.仿真结果表明,ST2-DADBF算法能够在空时二维域中捕获感兴趣用户的各个多径分量,并将这些多径分量同步相干合成,同时抑制其它用户在时域和空域形成的干扰,因而可获得良好的误码率(BER)性能.     

空时CDMA多用户信号检测

本文利用最小均方误差(MMSE)和最大似然(ML)准则,推导了空时CDMA多用户检测算法,分析了空时多用户检测与单用户检测的关系,并提出一种空时CDMA多用户检测接收机结构.计算机仿真结果说明了本文提出的空时CDMA多用户检测算法,与单用户检测方法相比其误码性能有相当的改进.     

频率选择性衰落信道下DS-CDMA系统发射分集技术

本文研究多径频率选择性衰落信道下,DS-CDMA系统开环发射分集技术.提出了一种将线性多用户检测与发射分集相结合的新方法,该方法能在克服信道衰落的同时抑制多址干扰和码间串扰.针对两种不同的扩频码分配方式,本文分别给出了盲和半盲的信道估计和检测算法.仿真结果表明,本文所提方法的性能优于基于空时分组码的RAKE接收机,特别是存在远近效应时性能改善更大.     

一种低复杂度的空时多用户迭代检测方案

该文针对已有的对多用户空时编码系统的研究大都集中在多用户STTC和STBC方案, 提出一种联合Turbo-BLAST的多用户空时方案。在接收端,针对传统的基于符号干扰抵消(Symbol-Level Cancellation, SLC)与检测的迭代接收机复杂度仍然较高的前提下,提出一种低复杂度的基于比特级干扰抵消(Bit-Level Cancellation, BLC)的迭代检测方案。该方案在检测部分将M-QAM调制符号分解成为一系列的BPSK符号的线性组合,采用比特级的干扰抵消。理论分析和仿真结果表明,该文提出的方案在保持BLAST高频谱效率的同时,与传统检测方案相比,在不降低系统性能的前提下,计算复杂度得到了很大程度的降低。     

一种有效的智能天线波束成形技术

提出了一种新的智能天线算法,这种算法结合了多用户联合检测技术和RAKE接收技术,具有较小的运算量和良好的误码率性能,仿真的结果也证明了这是一种可行的方法,特别是在大的用户数目的情况下,智能天线的性能要远远好于一般的阵列天线的性能。     

WCDMA系统中连续干扰抵消方法实现研究

本文研究了 WCDMA系统中连续干扰抵消的实现方法。在分析连续干扰抵消的基本原理和 RAKE接收机的基础上 ,结合 WCDMA系统发送原理 ,经过仿真给出了连续干扰抵消法在 WCDMA系统中低复杂度的实现方法     

基于多种调制方式的空时OFDM系统多用户检测技术

建立了基于空时分组码的多输入多输出(MIMO)-正交频分复用(OFDM)系统模型,研究了基于最小均方误差的串行干扰消除(MMSE-SIC)多用户检测算法,通过优化排序迭代结构,使得接收算法具有较好的性能.仿真结果表明,该算法在误码率方面能够取得优于常规线性MMSE算法的性能,而且得出星座图中映射点间距也影响着检测算法的性能,随着间距的缩小,误码概率会上升.     

STBC块传输系统中的一种新型分集合并算法

该文在二发一收的空时分组码(STBC)单载波块传输系统中,提出一种空时和多径分集合并接收算法。通过基于STBC的单载波频域均衡(STBC-SC-FDE)算法得到对发送信号的估计,以此和信道状态信息(CSI)分离接收信号中的各多径分量,对各多径分量分别采用STBC合并,最后再将各多径分量的合并输出结果按照最大比(MRC)的方式进行合并,从而实现空时二维RAKE接收。该算法在较低的计算复杂度情况下,可以同时获得发射分集和多径分集,Monte Carlo仿真验证了该算法的性能。     

On the usefulness of outer-loop power control with successive interference cancellation

Multiuser detection (MUD) performance can be significantly better than the conventional matched filter receiver in CDMA systems. Further, since optimal MUD is exponentially complex, research has mainly focused on suboptimal approaches such as successive interference cancellation (SIC). SIC requires a geometric distribution of received powers to achieve equal performance for all received signals. We propose a power control scheme for SIC to achieve this profile (or the profile corresponding to any desired and achievable set of error rates) based on frame-error rate (FER) or bit-error rate (BER). Specifically, we derive the relationship between received power and BER for linear SIC and show that for unlimited mobile powers, a deterministic distributed BER-based outer-loop power control drives the received powers to the optimal power profile. The convergence of the deterministic BER-based algorithm is examined in the absence of inner loop power control errors. The simulated performance of a stochastic version of this algorithm is examined using instantaneous FER measurements. The stochastic algorithm is shown to provide unbiased estimates of the true power updates and converge to the optimal power vector provided the mobiles have unlimited power. We consider power limits for specific mobiles and find that individual mobile limits do not affect the performance of other signals. We examine the impact of system loading, multiple FER targets, error correction, and inner loop power control error on the performance of the algorithm.     

Successive Interference Cancelers for Multimedia Multicode DS-CDMA Systems Over Frequency-Selective Fading Channels

Noncoherent and coherent multicode direct-sequence code-division multiple access (DS-CDMA) systems with successive interference cancellation (SIC) for multimedia reverse links over frequency-selective fading channels are studied. Followed by a RAKE receiver, the SIC scheme is applied for combating the multiple access interference. The bit error rate (BER) using the SIC technique over Nakagami-m fading channels is derived. Simulation results show that the multicode DS-CDMA system with SIC has demonstrated better performance than that without SIC under the multipath fading environment, while their corresponding numerical results from performance analyses are also provided for verifications. Furthermore, the coherent receiver could achieve a more satisfactory BER than the noncoherent counterpart at the expense of synchronization.     

MBER Space-Time Decision Feedback Equalization Assisted Multiuser Detection for Multiple Antenna Aided SDMA Systems

This paper proposes a space-time decision feedback equalization (ST-DFE) assisted multiuser detection (MUD) scheme for multiple receiver antenna aided space division multiple access systems. A minimum bit error rate (MBER) design is invoked for the MUD, which is shown to be capable of improving the achievable bit error rate performance and enhancing the attainable system capacity over that of the standard minimum mean square error (MMSE) design. An adaptive implementation of the MBER ST-DFE assisted MUD is proposed using a stochastic gradient-based least bit error rate algorithm, which is demonstrated to consistently outperform the classical least mean square (LMS) algorithm, while achieving a lower computational complexity than the LMS algorithm for the binary signalling scheme. Our simulation results demonstrate that the MBER ST-DFE assisted MUD is more robust to channel estimation errors as well as to potential error propagation imposed by decision feedback errors, compared to the MMSE ST-DFE assisted MUD.     

A research of UWB rake receiver based on novel RLS adaptive algorithm

A modified RAKE receiver based on novel Recursive Least Squares （RLS） adaptive algorithm is proposed. The receiver uses L-fingered correlators, which are composed of RLS adaptive filters, to enhance the performance of multipath receiving. It can also track the amplitude of the received signal to form a real-time amplitude estimation which is correlated with the power of excess delay bin. The simulation results based on the IEEE UltraWide Band （UWB） channel models （CMI to CM4） show that the novel RLS algorithm can alter the attenuation estimation with the finger＇s power delay profile, and RAKE receiver with few fingers can be employed to get high performance.     

Multistage MMSE PIC Space–Time Receiver With Non-Mutually Exclusive Grouping

The arrival of new data services for wireless mobile communications requires an efficient use of the available bandwidth. Interference-limited cellular systems based on code-division multiple access (CDMA) can benefit from multiuser detection (MUD) and beamforming with antenna array to reduce multiple-access interference. Group-based techniques have been proposed to reduce the complexity of space-time MUD and have been shown to provide a performance-complexity tradeoff between matched filtering and full MUD. In this paper, the intergroup interference, which is a limiting factor in group-based systems, is reduced using multistage parallel interference cancellation after group-based minimum mean square error (MMSE) linear filtering. In addition, the extra resources that are available at the receiver are exploited by sharing users among groups. The proposed receiver is shown to converge, as the number of stages increases, to the full space-time MMSE linear MUD filter. The results show that the new approach provides bit error rate (BER) performance close to the full MUD receiver at a fraction of the complexity.