CDMA寻呼信道的容量分析

本文介绍了一种估算CDMA IS-95寻呼信道容量的方法,可用于指导无线网络的设计和规划.     

减少长短信寻呼量研究

本文对手机在接收长短信的时候需要多次寻呼响应才能完成长短信接收的情况进行了深入的研究,提出了优化短信中心的MT流程的方案.该方案可以很好的解决长短信多次寻呼问题,能有效降低寻呼总量,既不影响用户感受,也不影响设备性能,是值得采用的低成本高回报优化方式.     

阿朗CDMA软交换设备完全业务信道短信下发机制分析和实现

就阿朗CDMA核心软交换引入后的短信下发机制进行了分析,并提出更改阿朗设备核心网参数,控制短信MT全部从业务信道下发,以减小寻呼信道的负荷。通过追踪前后短信MT相关SMRG数据,比较MT在完全业务信道下发和部分通过寻呼信道下发的相关指标差异,从而确认参数修改对降低寻呼信道负荷的效果和其它短信相关性能所受影响。     

CDMA寻呼信道负荷的计算(下)

首先分析了寻呼信道的特性和帧结构；然后通过分析寻呼信道发送的各种消息的内容，对每个内容的长度进行了计算，并得出了每种消息相对于寻呼信道总容量的寻呼信道占用率；最后给出了在一定假设条件下，一个寻呼区域中BHCA值和寻呼信道负荷的关系。     

CDMA寻呼信道负荷的计算(上)

首先分析了寻呼信道的特性和帧结构；然后通过分析寻呼信道发送的各种消息的内容，对每个内容的长度进行了计算，并得出了每种消息相对于寻呼信道总容量的寻呼信道占用率；最后给出了在一定假设条件下，一个寻呼区域中BHCA值和寻呼信道负荷的关系。     

高峰期短信业务量对网络的影响及解决方法

文章结合现网无线侧短信传送占用信道类型及数据分析,分析CDMA网络高峰期短信业务量对网络指标的影响,并提出相关网优解决措施。     

CDMA网络承载短信群发业务的解决方案

针对cdma20001×、GSM、WCDMA等制式对短信群发业务的承载能力进行分析,提出在CDMA网络上高效率承载短信群发业务的端到端解决方案,并通过现网应用证明了该方案的可行性。     

CDMA网络短信寻呼成功率的提升策略

CDMA短信寻呼成功率是总部必须考核的指标之一,其得分直接影响到其他众多考核指标。以某市CDMA网络为例,统计分析寻呼成功率低的原因,提出了CDMA短信寻呼成功率的提升策略。测试验证结果表明：短信寻呼成功率上升明显。     

CDMA无线系统中的寻呼信道负荷与短消息承载之间的关系探讨

从寻呼信道的负荷计算和短信业务在寻呼信道上发送机制两个方面来阐述信道负荷与短信业务发送之间的关系;并以石家庄系统为例计算寻呼信道负荷,分析了短消息在寻呼信道上的发送算法。     

CDMA2000移动台的时隙工作模式与待机时间分析

介绍了CDMA2000移动台的时隙工作模式与实现,并讨论了时隙模式与待机时间的关系,同时对提高移动台待机时间进行了分析。     

Blind channel estimation for long code multiuser CDMA systems

In CDMA systems with long codes, the users' signatures change in each bit period, impeding the estimation of the time-invariant multipath parameters. In this paper, correlation-matching methods are employed to blindly estimate those multipath parameters. For given code sequences, the output correlation matrix (parameterized by the unknown channel coefficients) is compared with its instantaneous approximation. By minimizing the Frobenius norm of the resulting error matrix, the channel parameters can be estimated up to a complex scalar ambiguity. Both batch and adaptive algorithms are derived. Under the assumption of i.i.d. code sequences, identifiability up to a complex scalar ambiguity for each channel is guaranteed, and the asymptotic convergence of the proposed algorithm is established. Furthermore, step-size selection for the adaptive version is investigated. When only the code sequence of the user of interest is available, a single user receiver is also derived. Simulation results verify those claims and provide comparisons with other methods     

Diversity-assisted channel estimation and multiuser detection for downlink CDMA with long spreading codes

In downlink communication of a direct-sequence (DS) code-division multiple-access (CDMA) system, each user's short spreading codes are superimposed by base station's common long codes. This situation creates much difficulty in blind signal detection when multipath propagation occurs. However, when spatial/temporal diversity is available at the receiver, it is shown in this paper that subspace technique can be directly applied to estimate the common downlink multipath channel. Then, typical linear receivers, such as zero-forcing (ZF), minimum mean-square-error (MMSE) and RAKE receivers can be designed to detect the desired signal. Since the data covariance matrix is used but estimated from finite data samples, performance of both channel estimator and receivers gets perturbed. It is thus thoroughly and jointly analyzed by perturbation analysis. Justification of analysis and comparison of different receivers are also made through simulations.     

利用调制引入循环平稳的CDMA盲信道估计

针对CDMA系统给出了一种新颖的盲辨识方法.它利用了恒模复序列调制产生的循环平稳性,其特色是,在接收机上可以根据循环统计量的支撑的不同,将各个用户的二阶循环统计量分离开来,每个用户形成自己的小规模子空间.采用已成熟的子空间方法,可以识别出不同的用户各自的片率传输信道,以便于均衡和检测.文中给出了自己的信道可辨识性的条件和证明,提出了辨识算法,并对算法进行了模拟.方法简单明了,适合于CDMA上行链路信道.     

Fuzzy decorrelating detector for non-Gaussian CDMA channel

A fuzzy decorrelating detector for CDMA non-Gaussian channels is proposed. The proposed scheme combines a linear decorrelator with a nonlinear preprocessor based on fuzzy logic and rank ordering that is incorporated to combat impulsive noise. Simulation results show that the proposed technique is very robust in combating impulsive noise.     

CDMA系统中接入信道配置方式的研究

CDMA接入方式对无线网络性能有很大影响。随着用户的不断增加，基站信道负荷也越来越高，部分基站的接入信道负荷超过80％。接入信道负荷过高，影响了无线网络的接入性能。简单介绍了CDMA移动通信系统反向信道及接入信道的工作原理，并据此在VC6．0环境下建立了计算机仿真平台，研究接入参数的设置对接入过程的时延、通过量、信道利用率等性能的影响，分析接入尝试对系统产生的额外干扰。通过分析，提出了改善的接入参数设置方法。     

基于一阶统计量的CDMA信道估计方法

本文是基于一阶统计量的CDMA信道估计方法研究,导出了信道估计和方差运算表达式,进行了估计器性能及峰均功率比分析.算法对信道没有特殊要求、运算简单且没有信息速率的损失.仿真结果验证了其有效性.     

Structured multiuser channel estimation for block-synchronousDS/CDMA

Uplink channel estimation for a block-synchronous chip-asynchronous DS/CDMA system as proposed for the time-division duplex option of third-generation cellular systems is considered. Training midambles are employed for joint channel estimation of all users. The standard unstructured approach based on modeling the effective user channels as unknown FIR filters is compared with two structured methods that exploit a priori knowledge about the user channels such as the maximum delay-spread, the transmit chip-shaping pulse and the path delays. Since these are usually unknown, a low-complexity estimator for the path delays of all users is derived from a maximum-likelihood approach. For all channel estimators, optimal sets of training sequences based on perfect root-of-unity sequences are found. For these optimal sets, it is shown that the reduction in channel estimation mean-squared error of the structured estimator versus the unstructured estimator is exactly the ratio of the number of structured parameters to unstructured parameters. Simulation results show that structured channel estimation provide advantages up to 4 dB in terms of output signal-to-interference plus noise ratio with respect to unstructured estimation, for linear RINSE detection. In contrast, for conventional single-user matched filtering, unstructured estimation proves to be sufficiently good     

CDMA2000导频辅助的信道估计方法研究

文章分析了非连续导频情况下CDMA2000反向信道结构，针对CDMA2000反向信道中导频信道与功控子信道时分复用情况，研究了四种信道估计方法，分别是重复使用、判断校正及其改进方法、最小二乘插值。最后用COSSAP软件对这四种方法的性能进行了比较，仿真结果表明改进的判别校正和最小二乘插值方法能有效的估计出插入功控比特导频情况下的信道参数。     

On multipath channel estimation for CDMA systems using multiplesensors

This paper focuses on the design of a multiuser receiver structure for the reverse link of a code-division multiple-access communication system, in the presence of multipath effects and using an antenna array at the base station receiver. The algorithm presented solves the complex multidimensional problem of channel estimation in this complex scenario using a maximum-likelihood approach. This channel estimation technique requires the transmission of a training sequence or feedback of detected data. Once a composite channel-impulse response of each user is estimated, it is directly used in the detection process instead of first extracting the individual channel parameters, such as path delays and attenuation factors. The paper presents a framework that facilitates a computationally efficient solution to the combined problem of channel estimation and detection in a scenario involving multiple users, multiple paths, and multiple sensors at the receiver     

The long and short of channel length

In this article, the powerful shift-and-ratio method proposed by Taur of IBM Corp. [1992] is used to accurately determine effective channel length and mobility of deep-submicron devices. We show that the extracted low field mobility of a short-channel device as a function of gate voltage is consistent with that of a long-channel device. Since in the BSIM3v3.2 industrial standard model a universal low field mobility is used for devices of various sizes, the shift-and-ratio method is particularly suitable for determining accurate effective channel length that leads to a consistent mobility value