CDMA手机测试浅析

介绍了CDMA手机的测试标准,并详细介绍了CDMA手机的测试内容和方法。     

GSM与CDMA手机辐射的测试

众所周各,由于CDMA(IS-95)系统中采用快速的反向功率控制、软切换、语音激活等技术,以及IS-95规范对于机最大发射功率的限制,使CDMA手机存通信过程中辐射功率很小面亨有“绿色手机”的美誉。但最近有一些报导对“绿色手机”提出了质疑,认为GSM手机与CDMA手机幅射相当,其基本观点是GSM手机只有八分之一的时间产生幅射,因此GSM手机与CDMA手机的SAR值(人体单位质量吸收的射频功率)大体相当。     

CDMA手机秘籍

一、摩托罗拉系列CDMA手机编程方法1.摩托罗拉7762、8167手机编程方法(1)开机按一次“FCN”键,然后输入00~(**)83786633; (2)按“STO”键,然后输入#55#; (3)按“*”键翻阅,分别输入相应内容共计26项,每项内容如下:01项:00013;02项:100000;03项:75500XXXXX;04项:106;05项:10;06项:000000;07项:123;08项:4;09项:000000;10项:000000;11～14     

CDMA移动电话测试指标及维修

1 概述 CDMA通信体制与目前常用的FDMA和TDMA不同,它通过采用Hadama矩阵排列算法得到不同的扩频码来区分不同的用户（多址连接）。当发/收两端的扩频码不匹配时,在接收端收到的是噪声;当发/收两端的扩频码相匹配时,接收机通过相关接收可获得相关峰,然后就可以解调出有用的信息来。从理论上来说,全球的CDMA用户可以共享同一时间资源、同一频率资源。例如:中国联通的CDMA用户可以在同一时间共用CH283信道（前向信道即BS发的频率为:878.49MHz,反向信道即手机发的频率为:833.49MHz）。但实际上,由于互相关性足够好的扩频码数量有限,故在CDMA通信体制中还要用到其他的信道,例如CH384、CH777等等。CDMA通信的理论基础可以用非常著名的Shanon公式来说明:     

具有干扰估计和双硬件限幅器的光CDMA直接检测接收机

提出了一种应用干扰估计和双硬件限幅器的光CDMA的直接检测技术。在提出的系统中,当硬件限幅器的输出为“0”时,系统的输出为“0”;当硬件限幅器的输出为“1”时,系统估计这个“1”到底是干扰还是传输的信号。仿真结果表明,该系统有效地减小了多用户干扰的影响。     

多址干扰对CDMA系统的影响及干扰抑制措施

对CDMA通信系统的容量进行了理论分析,并使用SPW(Signal Processing Worksystem)软件对CDMA系统的多址性能进行了仿真,表明了多址干扰对CDMA通信系统的影响。然后,分析了几种现有抑制多址干扰的方法的性能。     

CDMA干扰的测试定位与处理

在无线蜂窝通信系统中，不同的频段分配给不同的通信系统导致系统间产生干扰，同时由于各系统采用不同的复用方法来提高频谱效率，以增加系统容量，同时带来了同／邻频干扰。另外，系统还存在由于电波传播的多径效应造成的干扰等。无线干扰信号会给基站覆盖区域内的移动通信带来许多问题，如掉话、通话质量差、信道拥塞等。主要介绍CDMA中可能出现的各种干扰及对这些干扰的定位和处理方法。     

无线干扰的测试和定位

本文重点针对CDHA网络环境，介绍了在无线通信中产生各种干扰的可能成因，并讨论了对这些干扰的测试、定位和处理的方法。     

Proposal of an interference cancellation receiver with lowcomplexity for DS/CDMA mobile communication systems

The main targets of any direct-sequence code division multiple-access (DS/CDMA) mobile communication system are to overcome the multipath fading influences as well as the near/far effect and to increase the capacity. Many optimal and suboptimal detection approaches have been proposed and analyzed in the literature. Unfortunately, most of them share the drawback of requiring a complex implementation and do not represent a practical solution. This paper proposes a simple interference cancellation receiver for applications in DS/CDMA uplink communications. This receiver allows users to overcome the near/far effect and to enhance the system capacity. Differently from previous methods, the interference cancellation is performed on a one-shot basis. The performance of the proposed interference cancellation receiver is derived through computer simulations. However, a suitable analytical approach is also presented in the appendix in order to evaluate the bit error rate (BER) performance in the particular case of synchronous users and the transmission channel being affected only by additive white Gaussian noise (AWGN). The good behavior of the proposed approach is demonstrated by means of comparisons in terms of the BER performance and implementation complexity with the classical RAKE receiver and different multiuser receivers previously proposed in the literature on this subject     

Base-station antenna array receiver with interference cancellationfor wideband CDMA

The authors present a combining technique of adaptive array antenna and multiple access interference (MAI) cancellation for increasing system capacity in wideband code division multiple access (W-CDMA) systems. From the simulation results, an improvement in system performance proportional to the number of antennas is observed and additional improvement is obtained due to the interference cancellation     

A CDMA interference canceling receiver with an adaptive blind array

Interference cancelling receivers have been suggested as low complexity multiuser receivers for code division multiple access (CDMA) systems. A multi-element interference cancelling receiver is proposed, and it is demonstrated that using spatial information about the users will improve the performance of the receiver. Two blind algorithms are suggested to adaptively combine the outputs of the antenna elements. The performances of these algorithms are compared, and it is shown that without requiring any additional information, the receiver can spatially discriminate between the users and improve the error performance     

Direct-detection optical CDMA receiver with interference estimation and double optical hardlimiters

This paper proposes a new channel interference cancellation technique using interference estimation and double optical hardlimiters (DHLs) for direct-detection optical code-division multiple-access systems. In the proposed system, when the output of the DHL is "0", the proposed system outputs "0". When the output of the DHL is "1", the proposed system reconstructs the interference and estimates whether the output "1" is owing to the interference or the transmitted signal. It is shown that the proposed system is effective to reduce the effects of the channel interference. Moreover, it is shown that the proposed system can improve the error floor of the systems with DHL.     

A beamspace-time interference cancelling CDMA receiver for sectoredcommunications in a multipath environment

A beamspace-time (BT) receiver is proposed for interference suppression and multipath diversity reception in sectored wireless code division multiple access communications. The scheme involves two stages. First, a set of adaptive space-time diversity processors, in the form of beamformer-correlator pairs, is constructed which provides effective suppression of unwanted interference and reception of signals from a prescribed space-time region. Second, the output data obtained by these processors are maximum ratio combined to capture the signal multipath components coherently. The proposed BT receiver is blind in that no training signal is required. The only information required is the signature sequence, timing and a rough estimate of the angle of arrival of the signal for selecting the sector of interest     

Channel estimation and interference suppression for uplink CDMA mobile communication systems

Wireless communications for mobile telephone and data transmission is currently undergoing very rapid development. Code division multiple‐access (CDMA) implemented with direct sequence spread spectrum signaling is among the most promising multiplexing technologies for cellular telecommunications services. In this paper, jointly period inserted pilot symbols assisted recursive (PIPSAR) channel estimation and interference suppression techniques are proposed for uplink CDMA mobile communication systems. The uplink CDMA mobile communication system model is described in the form of space‐time domain through antenna array and multipath expression. Interference suppression is achieved by using adaptive minimum mean squared error (MMSE) digital filters that span several successive received chip oversampling vectors of a symbol interval. PIPSAR techniques are used to estimate channel parameters. The correlation between the successive periods is considered to further improve the performance of the proposed scheme. Analysis and simulations are used to evaluate the performance of the proposed scheme. Copyright © 2004 John Wiley & Sons, Ltd.     

A novel CDMA multiuser interference cancellation receiver withreference symbol aided estimation of channel parameters

A novel multistage successive interference cancellation scheme is proposed which operates on the reverse code-division multiple-access (CDMA) link using binary phase shift keying (BPSK) modulation, coherent detection and reference symbols to obtain channel estimates. The results of a single cell multiuser investigation demonstrate increased traffic capacity. However, this increase is initially very moderate due to corruption of the channel estimates by interference from symbols not yet demodulated and cancelled. A modification in the transmitted signal structure addressing this problem is proposed. The results of a single cell analysis of the modified cancellation scheme demonstrate that the system's traffic capacity reaches approximately 80% of that of a multistage successive interference cancelling receiver operating with the perfect knowledge of channel parameters. A subsequent multicell investigation shows that for a hexagonal cell geometry with a path loss exponent of four and without any forward error correction (FEC) coding or cell sectorization, the system capacity compares very favorably with that of the IS-95 system, which employs powerful error control coding. Capacities with other path loss exponents and cell geometries are also investigated. The results show a substantial traffic capacity increase over that of a comparable receiver without interference cancellation     

基于Matlab的CDMA RAKE接收机性能仿真

CDMA移动通信系统中,受到建筑物和地形地貌的影响,通信环境十分复杂,通信系统的通信质量受到严重影响。CDMA系统采用RAKE接收技术,它可以在时间上分辨出细微的多径信号,这样便把多径信号加以利用,克服了多径衰落带来的影响,达到增强接收效果的目的。在对RAKE接收机基础理论进行分析的基础上,采用Matlab仿真软件对不同用户状态下的RAKE接收机性能进行仿真,并对最大比合并、等增益合并、选择式合并这三种合并方式进行比较,给出仿真结果及误码率性能参数。然后,针对CDMA系统中RAKE接收机的性能进行建模仿真,仿真结果表明,CDMA系统中采用RAKE接收机起到了抗多径干扰、提高系统性能的目的。     

Performance evaluation of Passive Optical CDMA Networks using a linear parallel interference receiver in imperfect power cases

In this paper, we propose a transmission and reception block diagram to cancel interference in the case of multiuser Optical Code Division Multiple Access. We evaluate the performances of Passive Optical Networks using different transmitted powers. To highlight the problem and analyze imperfect power, we propose a new approach based on technical issues of two transmitter groups. These groups correspond to high and low multiple access interference issued from different power classes. A compensation factor is added to the linear parallel interference cancelation structure to improve channel propagation errors. Transmission errors are evaluated analytically and by simulation, considering synchronous and asynchronous cases. The error probabilities of the proposed optical code division multiple access system are estimated using Gaussian approximation. We show that the optimization of the compensation factor gives better performances in terms of bit error rate than other classical receivers. It also shows that this approach on the one hand, overcomes the problem of multiple services in a network source optical code division multiple access and on the other hand, it avoids the imperfect power effects for different users.     

Evaluation of a DS/CDMA multiuser receiver employing a hybrid formof interference cancellation in Rayleigh-fading channels

This paper assesses the performance of a multiuser detection DS/CDMA receiver based on a hybrid scheme of successive interference cancellation (SIC) and parallel interference cancellation (PIC). Two configurations of the proposed hybrid IC are presented and compared with existing SIC and PIC schemes. The performance criteria used for comparison are complexity, delay, power control requirements, and average bit-error rate (BER) performance obtained by simulation in Rayleigh-fading channels with additive white Gaussian noise (AWGN). The suggested hybrid IC combines good average BER performance, short delay, acceptable complexity, and also operates under slow power control