带内全双工水声通信残余自干扰实时抵消技术研究

带内全双工水声通信(In-Band Full Duplex Underwater Acoustic Communication,IBFD-UWAC)因其频谱利用率可达传统半双工模式的两倍,已成为水声通信领域的研究热点之一。由于本地发射强功率自干扰信号会导致通信系统误码率性能无法达到正常需求,因此自干扰抵消(Self-interference Cancellation,SIC)技术成为IBFD-UWAC中的核心问题。针对经过模拟SIC或空间自干扰抑制后的残余干扰信号问题,文章利用硬件在环(Hardware In-Loop,HIL)仿真,基于Simulink^® Desktop Real-time平台,实现了实时SIC,并利用瞬时状态误差判断期望信号到达情况,提出一种基于期望信号到达阈值的改进Sigmoid函数可变步长最小均方(Improved Sigmoid function based Variable Step Size,LMS,ISVS-LMS)算法,该算法大大降低了期望信号对SIC过程带来的影响。分析、仿真及实验表明：该方法可实现实时带内全双工水声通信的自干扰抵消,且算法的收敛速度以及稳态效果均有显著提升。     

不完全SIC下CR-NOMA系统的功率分配算法

在不完全连续干扰消除(SIC)条件下,对认知无线电-非正交多址混合系统中的次用户总传输速率进行研究,提出一种基于参数变换和KKT条件的功率分配算法.采用非正交多址方式使次用户接入授权信道,在主次用户服务质量、最大发射功率等约束条件下,通过参数变换对原约束条件进行改写设计新的优化问题,并利用KKT条件求解最优功率分配因子...     

A new chip‐level linear SOR‐SIC multiuser detector for long‐code systems

In this work, we introduce a new chip‐level linear modified‐SIC multi‐user structure that is asymptotically equivalent to successive over‐relaxation (SOR) iteration, which is known to outperform the conventional Gauss–Seidel iteration by an order of magnitude in terms of convergence speed. The main advantage of this scheme is that it uses directly the spreading codes and not the cross‐correlation coefficients and thus reduces significantly the overall computational complexity. This is critical for the design of low‐complexity multiuser detectors for long‐code CDMA systems such as IS95 and UMTS. We use a matrix algebraic approach to show the equivalence of the proposed scheme to linear matrix filtering. This allows obtaining an analytical expression for both the bit‐error rate (BER) and the asymptotic multiuser efficiency (AME). Moreover, we study the convergence behavior of the proposed scheme and prove that it converges if the relaxation factor is within the interval ]0, 2[. Simulation results are in excellent agreement with theory. Copyright © 2008 John Wiley & Sons, Ltd.     

基于动态分组的球形译码算法

在MIMO信号检测中,采用最大似然算法可以使系统的误码率最低,但最大似然算法要搜索整个信号空间,计算速度相当慢。球形译码算法性能最接近最大似然算法,它通过减少需要比较的信号点可大大降低计算量。提出了动态分组的球形译码算法,对传统球形译码算法进行了改进。仿真结果表明,所提算法可以根据M IMO系统的需要进行动态调整,可在小信噪比时降低误码率,大信噪比时提高译码速率。     

双选择信道中的时间偏移广义频分复用通信

当信道存在时间-频率双选择性时,严重的子载波间干扰和子符号间干扰将导致广义频分复用(GFDM)系统性能显著下降。为此,该文提出一种时间偏移GFDM系统(TO-GFDM),通过对传统GFDM系统的原型滤波器进行时间偏移,来提高双选择信道下GFDM系统的性能。该文推导了GFDM信号在双选择信道中的平均信干比公式,并提出基于...     

On fast preprocessing schemes for the real‐valued spatially multiplexed MIMO detectors

Multiple‐input and multiple‐output detectors may rely on the complex and real signal models, yielding complex detectors for quadrature amplitude modulated signals and real detectors for pulse amplitude modulated signals, respectively. It is well‐known that the complex and real maximum likelihood detectors are equivalent. But relying on both the conventional real and pairwise real models, we show in this paper that some of the suboptimal real detectors are equivalent to their counterpart complex detectors, whereas some are not. The equivalence between the complex and pairwise real detectors also leads us to develop fast preprocessing algorithms for the real ordered successive interference cancelation and tree search detectors. Finally, we show that the preprocessing computations required by the equivalent suboptimal complex and pairwise real detectors are of the same complexity. When some practical preprocessing criteria are used, the real detectors may not detect the PAM signals in the pairwise manner. Such non‐pairwise real detectors outperform their counterpart complex detectors at the cost of higher preprocessing complexity. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of the Linear GSIC Multiuser Detector Using a Matrix Iterative Approach

In this work, we use a new approach that relies on the theory of matrix iterative analysis to study the convergence behavior of the linear group-wise successive interference cancellation (GSIC) detector. Particularly, we show that the linear GSIC detector is in fact a realization of a modified block successive over-relaxation (BSOR) iterative method where the relaxation factor is a matrix instead of scalar. Consequently, to study the convergence behavior of the GSIC detector, we propose two new corollaries that extend the famous work of Kahan (Varga, Matrix iterative analysis, 2000) to the case where the relaxation factor is a matrix instead of a scalar. Using the two new corollaries we develop two new conditions of convergence for the linear GSIC detector. Simulation results are in excellent agreement with theory.

改进的增加时间分集的OFDM系统

在现有文献的基础上提出了一种改进的增加时间分集的OFDM系统,在原来的系统中增加了空时编码。在接收端,采用一种低复杂度的MMSE信道均衡算法使得系统的空间分集和时间分集得以有效地利用。仿真结果表明,这种结构可以提高系统在高速移动信道环境下的误码率性能和稳定性。     

Turbo均衡在移动通信中的研究

为消除符号间的干扰，Douillard．et．a1提出了turbo均衡这种迭代均衡和解码的方法。在Prokis’B信道下，对Turbo均衡的性能进行仿真，采用基于MMSE的线性均衡(MMSE—LE)和判决反馈均衡(MMSE—DFE)算法，以及appMMSE—LE／SIC算法，通过性能仿真，对不同算法、不同的迭代次数对系统性能的影响进行比较。结果表明:appMMSE—LE／SIC算法在复杂性几乎没有增加的情况下，性能提高了很多。