视频信号处理器的并行结构综述及分类

本文先从并行性的角度提出了视频图像处理器结构的新分类方法.然后对视频图像处理器的并行结构进行了全面的综述,指出各类并行结构的特点和以及今后研究和发展的方向.     

Minimum Cross Correlation Spreading Codes

Multiple access interference (MAI) appears in Code Division Multiple Access (CDMA) systems when the communication channel is a multi-path channel and the spreading codes are not orthogonal. Orthogonality between spreading codes cannot be maintained at the CDMA receiver because the codes may be asynchronous due to channel delay and multi-path spread. The receiver cannot perfectly separate the different signals of the multiple access users, and the resultant MAI limits the capacity of CDMA systems. MAI is a function of the cross correlation property between used spreading codes. In this paper we focus on the cross correlation of the spreading codes, we propose a method to find spreading codes with minimum magnitude of cross correlation. Employing these codes will reduce the resultant MAI in the CDMA system; hence it will increase the system capacity. A great enhancement is shown by comparing found minimum cross correlation spreading codes (MCCSC) with Hadamard and Gold codes.

二维光纤码分多址通信系统

介绍了三种二维光纤码分多址（OCDMA）系统。分析表明,它们的性能都优于一维OCDMA。同时也比较了WDM＋OCDMA和多波长OCDMA系统的性能。     

一种新的CDMA系统空时分组码结构

本文提出了一种新的采用空时分组码的CDMA系统上行链路的结构。发射端每个用户对发送信号先进行扩频,再对扩频后的信号进行空时分组编码后送至发射天线。同时本文还相应提出了接收端对接收信号的处理方法。仿真结果表明,该结合空时分组码的CDMA系统的误码率优于一般CDMA系统的误码率。     

CDMA系统无线网络规划浅谈

从无线网络等方面探讨CDMA移动通信技术,从容量和覆盖角度探讨了CDMA无线网络中的关键问题--选择合适的蜂窝结构,最后根据湖北省移动网的特点估算了CDMA网络的容量.     

一种多跳无线网扩频码分配算法

在多跳分组无线网中使用码分多址(CDMA)技术可以明显地降低隐终端问题对网络造成的影响.码分配是多跳无线网中使用CDMA的基本问题.码分配的目的在于提高扩频码的空间重用、降低分组冲突以及反映网络的动态变化.本文提出了一种多跳无线网扩频码分配算法,证明了其正确性并与其它算法比较了复杂度.与以往的算法追求降低码的数目不同,本算法是假设扩频码的数目有一定的冗余,寻求算法的方便、快捷和低通信开销.     

A Novel Space-time Spreading Transmit Diversity Scheme for Wireless CDMA System

1　Introduction　Thefundamentalchallenge,whichmakesreliablewirelesstransmissiondifficult,isthetime varyingmulti pathfading .Theoretically ,themosteffectivetechniqueformitigatingmulti pathfadinginawire lesschannelistransmitterpowercontrol.ButinCDMAsystems,powercontrolislimitedbythetransmitterdynamicrangeandthenear fareffect.Diversityisanefficientandpracticaltechniquetocombattime varyingmulti pathfading .Andanten nadiversityiswidelyappliedtoreducetheeffectofmulti pathfading .Theclassicalappro…     

CDMA无线网络中的突发数据业务延时分析

本文对CDMA无线网络中的突发数据业务的延时性能进行了分析。与以往的工作相比，本文假设数据流量模型为Markov到达过程(而非简单的泊松过程)，并从理论上对系统延时性能进行了分析。本文首先为数据子系统建立了完整的Markov模型，并运用矩阵几何技术求解该Markov链；然后计算数据包延时的概率分布函数(而非简单的平均延时)。仿真结果表明系统建模和延时分析方法是正确的。     

Estimation of Implementation Losses in MAC Protocols for Wireless CDMA Networks

This paper presents an analysis of implementation losses in feedback channel state information (FCSI) based MAC protocols for the up-link (UL) of a centralized asynchronous CDMA packet radio system. Such protocol can be used in different segments (or domains) of the future wireless IP networks including WCDMA cellular networks, wireless LANs and Ad Hoc networks. The motivation behind these protocols is to control the channel access by statically or dynamically changing packet transmission permission probability (TPP), also referred to as persistence probability, depending on FCSI. This is supposed to keep the UL load under a certain threshold depending on the QoS requirements. As the main contribution of this paper, effects of the feedback delay, access delay, and imperfect channel sensing are taken into account simultaneously in the analysis. These effects are referred to as imperfections. For performance analysis the system sensitivity functions are introduced. These functions represent the relative performance losses due to the imperfections, which are also referred to as implementation losses. The tradeoff between throughput, outage probability and packet delay in the presence of imperfections is discussed based on numerical results for a number of queuing system models.     

Source-Matched Spreading Codes for Optical CDMA

Puncturing is studied as a physical layer mechanism for efficiently transmitting datastreams containing bits of unequal priority via wavelength-time optical code-division multiple access. Puncturing increases system capacity, while ensuring that important bits are received with low bit-error rate     

Minimum Autocorrelation Spreading Codes

Intersymbol Interference (ISI) always appears when the communication channel is a multi-path channel. Many methods are used to reduce the effect of ISI. In this paper we focus on the autocorrelation property of the spreading codes and the role it plays in minimizing the ISI effect, where we obtain the spreading codes with minimum autocorrelation property. The results of comparing the average autocorrelation of the obtained codes with that of the well known Hadamard codes show a great enhancement in the performance, where for example, for codes of length 8 a gain of 408% was achieved at one shift, and for codes of length 16 a gain of 530% was achieved at one shift. Ahmad I. Amayrah was born in Amman in 1976. He received his Master of Science in Electrical Engineering from University of Jordan in 2003. He works as a lecturer in Al-Balqaa' University Abdallah K. Farraj was born in Amman in 1977. He earned his Bachelor of Science and Master of Science degrees in Electrical Engineering from University of Jordan, Amman, Jordan. He is currently working towards a PhD degree at the Department of Electrical and Computer Engineering, Texas A&M University. He is a fellow of the Graduate Teaching Academy, Texas A&M University, and he was awarded the Fulbright Scholarship for the 2005–2006 and 2006–2007 academic years.     

Providing Real-Time Service in CDMA Wireless Networks

Medium Access Control (MAC) protocol design plays a very important role in the design of wireless networks. In this paper, we propose a new MAC protocol to provide real-time service for a CDMA wireless network. This protocol has been designed based on the distributed queuing random access protocol for CDMA wireless networks (DQRAP/CDMA). As real-time scheduling schemes have been introduced into the protocol design, the new protocol has an ability to accommodate real-time traffic in the CDMA wireless networks. A series of simulation experiments have been carried out to evaluate the performance of the proposed protocol. The results reveal that the proposed protocol can efficiently provide real-time service to the traffic composed of time constrained messages in the CDMA wireless networks.     

KM序列用作RAKE型CDMA系统扩频码的分析

本文提出将KM 序列用作RAKE型CDMA系统的扩频码.基于一个RAKE接收机模型,分析了CDMA系统性能并提出了适于作RAKE型CDMA系统扩频码的PN序列的特性.接着,分析了KM 序列作RAKE型CDMA系统扩频码的优劣.最后,运用计算机仿真,比较了m序列和KM 序列的互相关特性以及在相干接收机和RAKE接收机下,这两种序列和Gold序列对应的系统平均误码率,从而证实了KM 序列作为扩频码的可行性.     

光码分多址系统关键技术及其应用

阐述了光码分多址(OCDMA)系统的关键技术,分析了影响系统性能的几个主要问题,指出了OCDMA在光纤宽带接入,高速光纤局域网和ATM交换网等领域的应用前景。     

Complete Complementary Orthogonal (CCO) Code-Based CDMA Using Natural Mapping QAM Constellations

In this short paper we propose a CCO code-based CDMA system that uses a natural mapping QAM scheme, in order to conserve both bandwidth and average transmitted power. We also suggest a design approach to obtain an optimal QAM mapping to further improve system performance. This is in contrast to the original CCO code-based system which used PAM transmission over twice as many channels. Here we present preliminary results for the 2-user case and the downlink.     

全光网中的光码分多址(OCDMA)技术及其应用发展

介绍了OCDMA的系统结构和关键技术,将OCDMA技术与现有的光时分复用(OTDM)和波分复用(WDM)技术进行了详细的比较,指出了各自的优缺点,在此基础上对OCDMA技术的应用作了分析和展望.     

典型场景的CDMA网络无线解决方案

本文针对CDMA网络的特征,结合作者的实际工程经验,详细介绍CDMA网络在6类典型场景下的无线解决方案,为更科学、准确的完成无线网络规划方案提供参考.     

采用喷泉码的无线协同多眺信息累积广播协议

为提高无线多跳广播的能量效率,提出了采用喷泉码的协同多跳信息累积广播胁议:令注水速率最大的节点进行发送,其发送功率由传输速率和注水速率决定.当有接收节点成功接收时,再由更新后注水速率最大的节点发送.各发送节点采用不同的喷泉码进行编码,使接收节点获得复用增益,并且节点可以接收可靠传输范围以外的信息并进行累积直至成功译码....     

CDMA2000基带信号发生器的FPGA+DSP实现

提出了基带信号发生器中CDMA2000无线传输技术的下行链路基带处理方案，给出了其数字基带处理原理框图，并详细介绍了设计过程中涉及的各种CDMA关键技术及其软硬件实施方案。     

An Evaluation Model for Integrated Services on Wireless Broadband CDMA Networks

This paper proposes a performance evaluation approach for integrated voice and data services on a broadband code division multiple access (CDMA) network. For random access schemes, the dynamic behavior of a CDMA channel infers that we must be cautious with a performance judgment. We must be especially careful when choosing a mathematical model that has to include the effect of dynamic error rates. The approach shown in this paper is to employ a Poisson error model that takes the occurrence of errors as a Poisson process with the occurring rate dependent on the channel traffic. Based on this assumption, we developed a continuous-time Markov chain model to evaluate the throughput and delay performance. This approach can certainly apply to the evaluation of many integrated services protocols.