Spectrally overlaid narrow-band and wide-band CDMA systems

A spectral overlay of a narrow-band code-division multiple access (CDMA) system and a wide-band CDMA system is proposed. The achievable joint capacity of the overlaid system is examined and the capacity tradeoffs between the two CDMA systems are given in a closed form     

宽窄CDMA信号共享频谱卫星系统性能分析

有效利用频谱资源是世界各国普遍关心的问题。通过合理配置宽带与窄带CDMA信号频率，使得宽带CDMA信号和窄带CDMA信号共享频谱，从而提高频谱的利用效率，并使系统容量有较大幅度地提高。对系统性能进行了分析和仿真计算，得出了结论。     

Multiservice/multirate pure CDMA for mobile communications

Future mobile communication systems should be able to support a wide range of services with different bit rates. Spread-spectrum code-division multiple-access (CDMA) techniques have attracted much attention to be employed in such a system. Different techniques of CDMA could be used to map low-, medium-, and high-bit rates data into the same allocated bandwidth, including pure or wide-band CDMA, FDM/FH/CDMA, TDM/TH/CDMA, or a hybrid of these techniques. This paper investigates multirate pure CDMA using multiuser interference statistics derived for both Gaussian and Rayleigh fading channels. Approximation of multiuser/multipath interference, in general, helps in the theoretical approach to error performance evaluation and, in particular, is quite useful for simulation approach in a fading channel. Some results of a multirate pure CDMA system with two services (low- and high-bit rates), for both BPSK and DPSK modulation schemes, are presented and compared     

TD-SCDMA系统导频污染分析

在TD-SCDMA系统中,由于PCCPCH作用的导频污染会导致很多网络问题,如呼叫接通率低、掉话率上升及高BLER等,也会由于干扰的增加导致系统容量的下降,所以在TD-SCDMA系统的网络规划和网络优化中需要重点考虑导频污染的影响。介绍了TD-SCDMA系统中存在导频污染的判断标准,分析了TD-SCDMA系统的导频污染产生的原因及其对网络造成的影响,根据试验网的实际优化工作,由实例验证了针对导频污染的优化方法。     

宽带CDMA数字中频接收机

本文建立了宽带CDMA的阻塞模型,在此基础上,提出一种数字中接收机的实现方案,并对主要电路的性能要求作了分析,给出了关键器件设计与实现的方法。     

某电信运营商CDMA无线网络安全评估探讨

针对目前CDMA无线网络中存在大量运行风险的情况,通过建立无线网络安全评估指标体系,对某电信运营商的CDMA无线网络现状进行分析,指出网络出现的问题和隐患,从而评估无线网络的安全性,并最终提出了降低网络安全风险的措施和方法。     

MISO CDMA transmission with simplified receiver for wirelesscommunication handsets

The next-generation wireless personal and mobile communication systems are expected to accommodate not only high-quality voice services, but also a broad range of other multirate services. Of the various multiaccess techniques, wide-band code-division multiple access (CDMA) has been regarded as an important part of the third-generation wireless communication systems because of its high frequency utilization efficiency and suitability for handling multimedia and multirate services. In this paper, we consider a system with a simplified receiver structure for direct-sequence CDMA (DS/CDMA) wireless communication handsets, in which improved performance is demonstrated when compared to a conventional DS/CDMA system with a RAKE receiver at the mobile station. We arrive at this system by finding the optimal solution to a general multiple-input single-output (MISO) DS/CDMA smart antenna system. We find that this solution reduces to a pre-RAKE with space transmit diversity system under the assumption that a simple one-finger matched filter is used at the receiver. This system combines the advantages of pre-RAKE diversity and transmit antenna diversity. It is shown that significant system performance and capacity improvements are possible. The numerical results also reveal that this system is not too sensitive to channel estimation errors     

A CDMA overlay system using frequency-diversity spread spectrum

The frequency bands currently used by existing narrow-band users might be shared with a code-division multiple-access (CDMA) spread-spectrum (SS) overlay system. Thus, the spectral efficiency is improved, providing more capacity for future personal communications services. Since both narrow- and wide-band signals interfere with each other, an SS modulation scheme with a good resistance to narrow-hand interference results in an increased number of acceptable overlay users. We study a frequency-diversity SS modulation scheme for which optimal detection in the presence of narrow-band interference is easy to implement. The acceptable number of overlay users is evaluated and compared to that of conventional direct-sequence SS (DS-SS) modulation schemes with and without interference rejection filters. The proposed system also presents the following advantage: by suppressing transmission of replicas where narrow-band signals (NBSs) are present, the mutual interference can be avoided completely     

Capacity unbalance between uplink and downlink in spectrallyoverlaid narrow-band and wide-band CDMA mobile systems

In this paper, we discuss capacity unbalance between uplink (mobile-to-base) and downlink (base-to-mobile) in future code division multiple access (CDMA) radio networks where both narrow-band and wide-band CDMA systems are coexisted. Since the two links are not operated in an identical condition, their capacities are unequal and either of the links determines the whole system capacity. The purpose of this paper is to examine which link limits the system capacity and what are the limiting factors. To facilitate the examination, “transmission capacity” and “connection capacity” are defined, and simplified formulas are presented to compute those capacities, respectively for uplink and downlink. Signal quality required for each link, effectiveness of power control, spatial distribution of mobile users and other-cell as well as same-cell user interference are usually determining the limiting link. Besides, the traffic unbalance between the links imposed by specific service applications and the network evolution scenarios are also shown to be very influencing factors     

CDMA无线侧网络拥塞问题分析和解决

本文通过对引起CDMA无线侧网络拥塞的各种情况进行分析总结,结合现网运行中所出现的案例,就如何解决CDMA网络拥塞做探讨。     

CDMA无线网络工程规划分析

本文主要介绍了CDMA无线网络的关键技术和工程规划流程.首先说明了CDMA无线网络在通信系统中的重要地位,接着从传播模型的校正、链路预算、容量和干扰分析等方面阐述CDMA网络的关键性问题,最后,详细介绍了CDMA无线网络工程规划的流程,并且,通过仿真得出了符合要求的覆盖效果.     

OCDD/CDMA: a new DS/CDMA with orthonormal code diversity detection

The paper presents a new spread spectrum communication system called orthonormal code diversity detection (OCDD)/CDMA system based on the novel concept of orthonormal-basis diversity which is a generalization of the existing spread spectrum diversity concepts such as path diversity and frequency diversity. The OCDD/CDMA system is similar to the conventional DS/CDMA system in the transmitter structure, but is different in the receiver structure as it employs the extended orthonormal basis-function set which is the union of the Walsh basis-functions multiplied by the PN sequences and, optionally, their delayed replicas. The received signal is matched to the extended basis functions, and the matched signal components are combined together after individual channel compensation. The proposed OCDD/CDMA system exhibits the bit error performance which is much improved over the conventional DS/CDMA system using maximal ratio combing. In addition, it is robust to the chip timing error, which becomes more crucial in the future DS/CDMA systems having a higher data rate and smaller chip interval. From the simulation results, we confirm that the OCDD/CDMA system is a unique spread spectrum communication technique that can effectively increase the diversity utilization in the slowly fading channel, overcoming the inherent problems in the DS/CDMA and OFDM/CDMA systems     

CDMA邻区优化研究

由于CDMA网络是一个自干扰系统,邻区设置的好坏不仅会影响切换成功率、掉话率等网络指标,甚至还会影响CDMA网络的系统容量。所以说好的邻区设置是保证CDMA1X网络性能的基本要求。     

IMT—2000CDMA宏小区蜂窝无线网络的仿真

ＩＭＴ－２０００ＣＤＭＡ宏小区蜂窝无线网络的仿真,是为评估当前在第三代移动通信系统中较具实力的Ｗ－ＣＤＭＡ和ｃｄｍａ２０００技术而开发的。仿真包括链路级和系统仿真两部分,主要分析研究、验证了评估了两种ＣＤＭＡ无线传输技术的性能以及ＣＤＭＡ无线网络的频谱效率／系统容量。     

CDMA系统中天线系统的调整

在CDMA系统中天线系统的调整对CDMA系统整体性能都会产生影响，本分析了天线系统的干扰和天线系统对小区覆盖的影响，讨论了天线系统的调整在CDMA无线网络优化过程中的应用。     

A dynamic CDMA network for multicore systems

Code-division multiple-access (CDMA) is a data transmission method based on the spreading code technology, wherein multiple data streams share the same physical medium with no interference. A novel architecture for on-chip communication networks based on this approach is devised. The proposed design allows sharing coding resources among network?s users through the use of dynamic assignment of spreading codes. Data transmission latency is reduced by adopting a parallel structure for the coding/decoding circuitry. A 14-node CDMA network based on the proposed architecture is synthesised using 65 nm ST technology library. Performance analysis reveals that the proposed approach achieves significantly lower data packet latency compared to both conventional CDMA and packet switched network-on-chip implementations. Large area and power savings compared to existing approaches are also obtained.     

干扰消除技术在CDMA网络中的应用

CDMA网络中存在前反向的多址干扰,降低了前反向容量。为了减少多址干扰对前反向容量的影响,对多址干扰产生的原因和机理进行深入分析,详细介绍了多用户检测技术和干扰消除技术。通过对造成干扰的所有用户信号信息进行检测,根据多址干扰信号的结构特征进行干扰消除和信号恢复,从而改善各个信号的信噪比,提高CDMA系统的前反向容量。重点介绍了准线性干扰消除技术QLIC（Quasi-Linear Interference Cancellation）和反向干扰消除技术RLIC（Reverse Link Interference Cancellation）的基本原理,分别对QLIC技术和RLIC技术的容量增益进行了理论推导,并计算了QLIC和RLIC对CDMA网络容量提升的程度。QLIC和RLIC是现有CDMA网络容量提升的重要技术手段,能够为运营商进行技术升级和网络部署提供重要参考。     

Capacity evaluation of packet-switched CDMA system

In this letter, an extended definition for packet-switched CDMA system capacity based on the protocol stack characteristics is proposed. According to the extended definition, the capacity of the packet-switched CDMA system for different ARQ protocols and different channel models is investigated. The results show that, compared with the traditional definition, the extended definition is more appropriate for describing the packet-switched CDMA network capacity     

CDMA无线网络测试及其方法

CDMA无线网络测试是网络工程验收、网络优化、网络评估的前提和依据。文章就CDMA无线网络测试的主要内容和方法进行了详细的介绍,包括基站的测试、呼叫质量CQT测试、移动情况下系统性能DT测试的各项指标及方法。     

CDMA2000系统信令监测方案设计

提出一套可行的CDMA2000网络信令监测仪总体硬软件设计方案,能为CDMA2000系统接入网设备制造商和网络运营商工程开通与验收测试、故障定位、日常维护、网络优化和性能分析等提供必备的检测手段与检测依据。