A Highly Reusable Code Assignment Approach with Modified Busy Tone Signaling for CDMA-Based Ad Hoc Networks

Medium access control (MAC) protocol is among the most active topics of research in ad hoc networks. With the CDMA-based MAC protocol the code allocation plays an important role and has significant impact on the protocol performance. In this paper, we propose a distributed CDMA code assignment protocol for the mobile ad hoc networks (MANETs). The protocol is mainly composed of (1) a modified busy tone signaling mechanism that protects on-going data transmission as well as distributes code usage information, and (2) a set of specially designed code selection rules that work by taking into consideration whether relevant nodes are in the transmitting or receiving state. By combining the two proposed schemes with the conventional request-to-send (RTS)/clear-to-send (CTS) dialogue and power control mechanism, our protocol is able to increase CDMA code reusability. The simulation results indicate that the proposed protocol indeed performs better than the static and dynamic code assignment methods (either with or without power control) in terms of successful transmission rate and successful code assignment rate. And instead of sending continuously, the proposed modified busy tone mechanism only issues busy tone signal in randomly selected cycles, which may save battery energy as compared to conventional busy tone implementations. Moreover, the proposed code selection rules and the modified busy tone signaling may also be integrated into existing MAC protocols, either separately or in combination.     

一种基于Gauss-Seidel方法的空时多用户检测算法

为了提高DS-CDMA系统的容量,提出了一种基于高斯-赛德尔(Gauss-Seidel)迭代算法的空时多用户检测算法.针对高斯-赛德尔迭代算法容易引起的误差扩散,改进算法同时从正反两个方向进行串行干扰消除,并借助最大似然序列准则进行判决,有效地抑制了误差扩散的影响.仿真结果表明,改进算法具有更快的收敛速度和更优的误码性能.     

CDMA无线网络向EV-DO升级方案分析

介绍了CDMA网络演进路线,以及现有的CDMA 1X网络向1XEV-DO网络平滑过渡的升级方式.针对现网扩容升级中存在的一些问题,建议CDMA网络EV-DO升级与基站搬迁结合起来,以减少无线网络的反复割接,有利于CDMA网络的长期发展.     

子空间方法盲多用户检测技术分析与探索

着重分析了基于子空间跟踪的盲线性多用户检测算法 ,并对其内部算法模块进行了仿真比较 ,最后对算法性能改善方法提出了自己的新思路     

MAX2206～MAX2208功率检测器在CDMA中的应用

本介绍了MAX2206～MAX2208功率检测器的应用和选择方法，以及分析了其功率检测器输出特性。     

最佳(F,K,1)光正交码的构造算法研究

(F ,K ,1)光正交码 (OOC’s)是适合于光码分多址 (OCDMA)通信的最佳地址码 ,但成功构造最佳 (F ,K ,1)光正交码十分困难。针对该问题 ,研究了一种构造算法 ,给出了构造该光正交码的具体算法及相应的计算机辅助设计方法。通过该方法可以容易地构造出最佳 (F ,K ,1)光正交码。     

A multi-criteria comparative analysis of different Rayleigh fading channel simulators

In this paper, an in-depth comparative analysis of the most accepted and approved Rayleigh fading channel simulators is presented. Our study addresses the three common methods for generating time-correlated Rayleigh fading processes: the inverse discrete Fourier transform (IDFT) method, the filtering white Gaussian noise (FWGN) method and the sum-of-sinusoids (SOS) method. Totally seven models, including the recently proposed models, are analyzed and compared with Clarke's reference model. We use four quantitative measures for judicious assessment of the quality of generated processes in terms of both first-order and second-order statistics. Additionally, these measures cover analysis in time domain as well as in frequency domain. An evaluation of the computational effort is also depicted. The simulation results suggest that the recently published Wang's model is very attractive and it outperforms all SOS-based models. We conclude that Zheng and Xiao's first model remains the best choice among Zheng and Xiao's family models. Several other important remarks and conclusions about the accuracy and the capability of the different Rayleigh fading simulators are driven from this study.     

基于领弹-从弹架构的无导引头导弹协同定位与制导方法

针对无导引头导弹在采用现有制导律时定位误差会产生较大脱靶量的问题,通过双领弹的领弹-从弹协同架构,设计了一种协同定位与制导策略,以实现无导引头导弹对静止目标的精确命中。基于扩展卡尔曼滤波,提出了一种无导引头导弹的协同定位方法。该协同定位方法与比例导引结合时存在终止时刻过载指令过大问题,因此设计一种新型变系数比例导引律,分析了变系数比例导引律的制导系数对脱靶量、终止时刻过载与最大过载的影响。仿真结果表明：采用所提出的协同定位方法可减小具有定位误差的无导引头导弹脱靶量,而采用变系数比例导引律可避免终止时刻过载指令过大。     

一种消除TD-SCDMA系统小区间干扰的方法

时分-同步码分多址(TD-SCDMA)系统采用的扩频码码长最大为16,当邻小区用户处于2小区边缘时会对本小区造成较大的干扰。针对上行链路提出了一种新的干扰消除方法:串行干扰消除-联合检测(SIC-JD)。该方法采用复杂低的SIC对上行链路中的小区间干扰进行消除,对于小区内干扰和残留的小区间干扰采用联合检测进行消除。3GPP case1信道下的仿真结果显示了此方法能够有效消除小区间和小区内干扰,提高接收机性能。     

含吸收型色散介质的光子晶体的腔极化激元研究

对色散介质层采用洛仑兹振子模型,通过考虑色散介质层两边的边界条件,可以严格得到表征色散介质层的转移矩阵.通过改变介质层的不同参数,详细研究了含吸收型色散介质的对称光子晶体的腔极化激元.研究发现吸收型色散微腔和增益型色散微腔在简正模耦合,无定型展宽效应和失谐效应方面都可以表现出大致相似的性质,但其在透射强度和耦合模频率飘移方面都有着明显的不同.最后对同时含有吸收型色散介质层和Kerr非线性层的一维对称光子晶体的光双稳行为进行了研究,发现其形成双稳态所需的阈值入射光强比仅含Kerr非线性层的阈值入射光强有所降低.