Q－CDMA系统新的网络结构

本文介绍了新提出的Ｑ－ＣＤＭＡ系统网络结构，重点介绍了其基站系统的组成，包括Ａ－ｂｉｓ和Ａ接口协议及新颖的ＩＰＩ（网络互联分组接口）网络，并进行了分析。     

BSS transition optimizations and analysis for VoIP over WLAN

Voice over IP (VoIP) is emerging as a critical application for IEEE 802.11 Wireless Local Area Networks (WLANs). However, the limited range of the IEEE 802.11 radio forces frequent transitions from one access point to another. Moreover, the introduction of IEEE 802.11i security and IEEE 802.11e Quality of Service (QoS) has increased the average transition time from ms to seconds, leaving mobile users with the unenviable dilemma of choosing good security and QoS while sacrificing real-time performance, or gaining acceptable real-time performance at the expense of security and QoS. Thus, optimizations to device transitioning that will provide an acceptable balance of latency, security, and QoS are needed to enable VoIP. This paper analyzes WLANs MAC layer transition procedure and optimizations being considered by IEEE 802.11 Working Group to improve transition times while retaining good security and QoS. The transition time improvements proposed in this paper are achieved through discovery phase optimizations and transition phase optimizations. The selective scanning and smart AP selection algorithms are designed to optimize the discovery phase to enable the mobile device to better exploit its ambient radio resource environment. The transition phase optimization seeks to accelerate device transition without compromising security. The paper then identifies security flaws in the current design and proposes simple corrections. Finally, experiment results for transition optimization are explained that demonstrate a significant increase in transition efficiency.     

Partially Constrained Blind Source Separation for Localization of Unknown Sources Exploiting Non-homogeneity of the Head Tissues

A new brain source localization technique using electroencephalograms (EEGs) is investigated in this paper. The information which describes the location of certain known sources is used as the constraint within the proposed blind source separation (BSS) algorithm and leads to a solution to the ill-posed inverse problem of source localization. Non-homogeneity of the head tissues, on the other hand, is exploited by introducing a realistic model of the mixing system. This model is used to better identify the location of the unknown sources within the brain from projection of the separated independent components on to the scalp. A separate procedure is employed to highlight the rhythmic EEG sources such as Alpha rhythm as the known sources. The performance of the scheme is shown on real EEG measurements and compared with that of “conventional dipole fitting algorithm”.

基于独立分量分析的正交空时分组编码盲检测方案

通过在不同天线发射的信号之间引入时域和空域信息,正交空时分组编码(OSTBC)可以获得发射分集增益,而且可以在不牺牲带宽的情况下获得更高的编码增益。但是其译码却需要精确的信道状态信息(CSI),因此,信道信息估计的准确性严重影响系统的性能。基于独立分量分析(ICA)的盲源分离(BSS)技术可以在不进行信道估计的情况下对发射信号实现有效检测。通过利用OSTBC的正交特性,提出了2种基于ICA的盲检测方案,同时,一些基于信道估计的检测算法也被用来进行性能比较。瑞利衰落信道下的仿真结果表明,2种新方案均具有较好的系统适应性和误码率性能。     

一种强混响环境下的盲语音分离算法

强混响环境下语音信号的频域盲分离问题是盲源分离领域的一个难点,主要是因为混合系统的脉冲响应时间过长,甚至超过信号的非平稳时间,导致算法性能下降。本文针对这个问题提出了一种解决方法,在用一个短时傅立叶变换将时域卷积混合信号转化为频域的过程,再在时频域上使用另一个短时傅立叶变换,将信号变换到调制谱域,这样较长的脉冲响应就被转化为调制谱域上的瞬时混合形式,而瞬时混合情形则采用独立向量分析(IVA)算法来避免排序模糊性问题。计算机仿真实验证实了该算法在强混响环境下优于传统频域盲分离算法。      

基于步长自适应的独立向量分析卷积盲分离算法

独立向量分析(IVA)是解决频域卷积盲分离排序模糊性最好的方法之一,但存在迭代次数较多、运算时间较长、分离效果易受分离矩阵初值影响的局限性。该文提出一种基于步长自适应的IVA卷积盲分离算法,该算法使用特征矩阵联合近似对角化(JADE)算法对分离矩阵进行初始化,并对步长参数进行了自适应优化。JADE初始化能够使分离矩阵具有合理的初值,避免局部收敛的情况;步长的自适应优化能够显著提升算法的收敛速度。仿真结果表明,该算法进一步提升了分离性能,并显著缩短了运算时间。     

业务支撑系统网络化体系的研究

提升业务支撑能力,在竞争激烈的市场抢占业务发展制高点,已成为目前通信业界关注的重点问题。本文针对全网一体化运营需求,结合新一代网络体系架构,研究业务支撑系统网络化部署方案,介绍了网络化体系应用模式及实施方案,为全网一体化运营提供参考。     

浅析BSS对全业务运营的支撑

从全业务运营策略入手,阐述了全业务支撑重点需求,通过对现有BSS技术架构的分析,提出了全业务运营支撑技术方案。     

一种充分利用变量结构的解卷积 混合盲源分离新方法

 针对卷积混合盲源分离问题,提出一种基于接收信号不同延时下自相关矩阵组的联合块内对角化方法.为了求解表征联合块内对角化近似程度的基于最小二乘的三二次代价函数,给出基于梯度下降法的三迭代算法.该算法在充分利用混迭矩阵的块Toeplitz结构和源信号相关矩阵的块内对角化结构的基础上,交替估计代价函数中的三组待定参数,搜索代价函数最小点,从而得到混迭矩阵的估计,实现信道的盲均衡和源信号的盲分离.分析了三迭代算法的收敛性能,证明即使存在估计误差时,该算法依然全局渐进收敛.仿真结果表明,与其他经典的两步算法相比,提出的一步算法能够更好地估计混迭矩阵并恢复出源信号,有效地解决了卷积混合盲源分离问题.