数据业务中公共控制信道的优化方法

近几年数据业务发展迅速,由于数据业务对GSM无线网络公共控制信道资源占用的快速增长,部分小区在业务忙时出现了公共控制信道的拥塞,从而导致该小区无线网络的寻呼性能及网络接入性能下降。湖州移动创新使用多种方法对公共控制信道进行了优化,缓解了公共控制信道的拥塞,并在高数据业务压力及高语音业务负荷之下依旧维持了较好的小区寻呼性能和网络接入性能。湖州移动现网的运营经验证明,这些优化方法是行之有效的。     

LTE-Advanced中eNodeB解调性能研究

提出基站解调性能要求的目标是估计实际网络如何运行,验证基站不同的损害因素,这些损害因素会对网络性能产生影响。这些影响因素包括RF和基带损害因素、接收机EVM(误差矢量幅度)时域和频域跟踪、频率估计等。对物理上行链路共享信道(PUSCH)、物理上行链路控制信道(PUCCH)和物理随机接入信道(PRACH)的基站解调性能要求进行了描述,给出了各类信道的基站测试集。     

CDMA2000系统反向信道的性能研究

基于扩频码分多址移动通信系统(SS-CDMA)条件下,分析了CDMA2000反向接入信道的性能参数,利用SystemView5.0对反向信道进行建模、仿真分析,结果显示了设计的CDMA2000系统反向信道模型的良好性能,表明了设计的信道模型合理。     

无线数据通信网中的信道接入协议研究

信道接入协议（MAC）是无线数据通信协议的重要组成部分。由于无线信道是一个开放、共享的信道，网络节点在通信过程中存在隐终端和暴露终端问题。基于目前无线通信常用的MAC协议存在的问题，着重分析了基于扩频码的信道接入协议，该协议利用扩频码的正变特性，使得网络中各节点可以同时占用信道而互不干扰，较好地解决了信道争用问题，提高了系统效率。同时指出，在选择MAC协议时，应根据无线网络的拓扑结构及特点灵活选择，以提高网络性能。     

CDMA网络接入失败的原因探讨

1 前言CDMA网络的接入过程比较复杂,涉及的参数比较多,接入失败比较常见,实际表现形式多,而且难以模拟,是引起用户各种投诉的重要原因,一直困扰着网络运维工作。本文对接入流程进行分析,重点探讨了接入过程中占比例较高的移动台试探失败和基站信道捕获失败原因,以便在CDMA网络日常的运维、优化和投诉处理中,可以针对性地定位问题、解决问题。2 接入流程分析按照cdma2000系列标准规定,当移动台有业务到达或收到基站的寻呼消息时,移动台进入接入系统状态(ACC-mode),其接入流程一般可分为5个不同阶段:(1)移动台接入试探,在接入信道发送…     

LTE物理随机接入信道规划

LTE接入技术与GSM、CDMA有很大不同,为确保LTE网络正常运行,物理随机接入信道需进行精细规划。介绍了LTE-FDD移动通信系统接入技术,物理接入信道相关参数,物理随机接入信道格式、容量、小区逻辑根序列码复用模式与小区覆盖距离之间关系,以及高速移动场景对接入前导循环位移的影响,总结出物理随机接入信道的规划方法。     

CDMA接入信道的容量分析

本文简要介绍了CDMA接入信道的特性,随后给出了接入信道容量的概念和计算方法,最后提出了优化接入信道容量的建议.     

无线信道接入技术中冲突解决算法的研究

中首先简要说明信道接入技术在无线网络中的地位和作用；然后对当前无线网络中使用较流行的一些信道接入协议进行有针对性的分类；最后，鉴于日益发展的数据业务，主要对随机信道接入协议进行详细的阐述，将其分为随机接入算法和冲突解决算法两部分，并介绍了它们各自当前的一些主流技术。在冲突解决算法中主要从基于协议的算法以及基于信号处理的技术这两个方向进行分析比较。后体现了信号处理技术和网络技术相互融合的趋势。     

CDMA接入信道容量的计算

文章通过对接入信道对反向链路的干扰分析得出了接入信道所允许的利用率，并且在一定假设条件下计算出了现网中一个扇区的接入信道的实际利用率和短消息数，以及呼叫模型及载波数的关系，文章还对CDMA2000的接入控制过程进行了分析，并与IS-95在接入信道方面进行了详细的对比。     

对CDMA系统的干扰方法分析

对CDMA下行信道和上行信道进行干扰,实现干扰CDMA系统的目的.重点分析了对CDMA下行信道的干扰方法和对CDMA上行信道的干扰方法,包括对下行信道的非相干压制式干扰、对下行公共信道的相干伪码扩频干扰和基于伪基站的欺骗式干扰,以及对上行信道非相干式压制式干扰和对接入信道的欺骗式干扰,归纳得到各种干扰方法的原理、优缺点、对侦察的需求及其适用范围.     

A detailed study of a CDMA based approach to enhance ad hoc network performance

Random access schemes operate typically on a contention based common channel, which brings problems with increasing traffic load. These problems are emphasized in a multi-hop wireless ad hoc network environment. Efficient collision avoidance methods are needed, but they also tend to decrease the spatial capacity of the network. With CDMA (Code Division Multiple Access), it is possible to make multiple simultaneous co-located successful transmissions and thus increase network capacity within the limits of multiple access interference (MAI). Bi-code channel access (BCCA) is a method to apply CDMA in ad hoc networking, providing also a common access channel for network connectivity maintenance and self-configuration. With BCCA, collisions are rare, and thus, more straightforward medium access control (MAC) methods can be used. A MAC solution designed especially for BCCA (BC-MAC) and ad hoc networking increases the efficiency of the channel usage. As BCCA is based on receiver code CDMA, the spreading code of the next hop node is needed. A novel network layer spreading code distribution (NSCD) method is proposed for this purpose. The spreading codes are distributed within routing protocol control packets at the route establishment phase.A detailed study on the performance behavior of different methods is provided. Also, interesting aspects considering the ad hoc network operation are discussed. Instead of the widely used unrealistic cut propagation model, a propagation model with realistic MAI calculation is used in this study. It is shown that the use of NSCD increases the network control load only slightly, and that the performance is practically the same as it is with the assumption of known spreading codes. BCCA with its dedicated MAC and NSCD clearly outperforms commonly used methods (like IEEE 802.11) and yet is easy to implement, robust for design parameters under different conditions while maintaining the original idea of ad hoc networking.     

Uplink channel assignment with balanced load for code division multiple access cellular systems

In a code division multiple access (CDMA) wireless communication system, each mobile handset must be power controlled such that the power received at the base station is roughly the same. Otherwise, the interferences between mobile handsets will degrade the performance and increase the error rate. When a mobile handset uses channels from the neighbouring cells, it will raise its power to meet the threshold of signal strength. This will also increase the interference in the home cell. Therefore, we do not want a mobile handset to use channels from other cells blindly. In this paper, we propose an uplink channel assignment method based on the directed retry concept for CDMA cellular systems. The purpose is to achieve load balancing between neighbouring cells and at the same time controlling the interference levels at the base stations such that it will not affect the performance. Furthermore, priorities are given to handoff calls when assigning channels. Copyright © 2002 John Wiley & Sons, Ltd.     

Traffic handling capability of a broadband indoor wireless networkusing CDMA multiple access

CDMA (code division multiple access) may be an attractive technique for wireless access to broadband services because of its multiple access simplicity and other appealing features. In order to investigate the traffic handling capabilities of a future network providing a variety of integrated services, this paper presents a study of a broadband indoor wireless network supporting high-speed traffic using CDMA multiple access. The results are obtained through the simulation of an indoor environment and the traffic capabilities of the wireless access to broadband 155.5 MHz ATM-SONET networks using the mm-wave band. A distributed system architecture is employed and the system performance is measured in terms of call blocking probability and dropping probability, the impacts of the base station density, traffic load, average holding time, and variable traffic sources on the system performance are examined. The improvement of system performance by implementing various techniques such as handoff, admission control, power control and sectorization are also investigated     

无线多址信道中的协作模型研究

在无线多址信道环境下,为了充分利用协作分集技术提高系统的传输速率和通信质量,引入了多址接入中继信道（MARC）模型。通过加入一个专门的中继节点,MARC模型中的发送节点类似操作在普通的多址信道下,从而使得现有的系统可平滑过渡到协作系统,实用性强。把MARC模型应用在直序扩频CDMA系统中,在Rayleigh信道下对其误码率进行仿真,结果表明,采用MARC模型的协作网络能获得显著的性能增益。     

A New Approach for Performance Evaluation of TCP over Interference-Limited Wireless Channels

A new metric for performance evaluation of transport control protocol(TCP) over wireless channels based on the interference-limited characteristics of code division multiple address(CDMA) system is proposed. According to the new metric, the performance of TCP over CDMA correlated channel for different protocol parameters and different versions is investigated. The results show that appropriate selection of protocol parameters and packet error rate(PER) operation point can improve significantly the capacity of packet-switched CDMA-based network.     

Reverse link performance of wireless local loop CDMA networks

We study the effect of directional subscriber antennas on the reverse link performance of a power-controlled code-division multiple access (CDMA) network in wireless local loop deployments. We investigate the capacity gain that is attained in wireless local loop (WLL) CDMA over mobile cellular systems and its variation as a function of the channel statistics. We also determine the overhead that soft handoff and directional subscriber antennas impose on the WLL system capacity     

CDMA随机多址接入技术研究

CDMA作为一种多址接入技术在无线网络中已广为应用,在多码CDMA和单码CDMA研究的基础上,构造了多码CDMA和单码CDMA在无线分组数据网络中的随机多址接入模型,并且分析了两种系统的吞吐率特性和归一化时延特性。结果证明单码CDMA和多码CDMA具有相同的多址接入性能。     

cdma 1X VPDN行业应用无线信道资源优化探讨

通过对"机器到机器"行业应用的cdma 1X VPDN的接入方式的分析,指出行业无线终端接入cdma 1X无线广域网可能导致对cdma1X无线信道高占用、低效率的影响,及cdma1X无线网络资源造成的压力的弊端所在;提出了通过无线信道休眠和唤醒机制的cdma1X VPDN行业应用无线信道资源优化方案。     

A CDMA wireless packet network for voice-data transmissions

This letter investigates the possibility of integrating voice and data communications in a CDMA wireless packet network to provide access to a base station over a common short-range radio uplink channel for many spatially dispersed voice and data user terminals. Speech activity detection is assumed for voice communications to temporarily devote codes unused by voice user terminals during silence periods to data transmissions. The network proposed exhibits a good performance both in terms of quality of voice communications which is independent of data transmissions and maximum data traffic load supported with bounded delay     

Broadband CDMA techniques

A very high-speed wireless access of 100 Mb/s to 1 Gb/s is required for fourth-generation mobile communications systems. However, for such high-speed data transmissions, the channel is severely frequency-selective due to the presence of many interfering paths with different time delays. A promising wireless access technique that can overcome the channel frequency-selectivity and even take advantage of this selectivity to improve the transmission performance is CDMA. There may be two approaches in CDMA technique: direct sequence CDMA and multicarrier CDMA. A lot of attention is paid to MC-CDMA. However, recently it has been revealed that DS-CDMA can achieve good performance comparable to MC-CDMA if proper frequency domain equalization is adopted. This article discusses their similarities and performances. A major transmission mode in 4G systems is packet-based. Automatic repeat request combined with channel coding is a very important technique. Recent research activity on this technique is also introduced.