TDMA数字移动通信系统无线干扰技术研究

采用TDMA技术体制的数字移动通信系统,其系统架构和工作方式类似,因此对其干扰方式也基本相同。针对军用TDMA数字移动通信系统,以典型的GSM数字移动通信系统为研究对象,对灵巧式和欺骗式干扰技术进行了研究。     

多天线OFDM系统信道估计算法的改进

提出一种针对多天线OFDM系统中基于LS准则的信道估计的改进方法。该方法使用梳状训练序列估计出一半的信道频率响应,然后利用抛物线插值对剩余一半进行估计。分析和仿真表明该信道估计算法可以抵抗信道的严重频率选择性衰落。     

一种应用遗传算法的阵列天线共址干扰抑制技术

针对有限大平台部署多种传感器导致的严重的自干扰问题,提出了一种应用遗传算法实现的阵列天线共址干扰抑制技术。首先针对同平台上的阵列天线和其他天线建立了辐射和接收模型,然后将辐射特性和接收机抗干扰特性分别抽象为最优化问题的目标函数和约束条件,最后通过遗传算法进行最优化求解。该技术在不同辐射角度时能抑制共址干扰,具有一定的工程实用价值。     

STC-OFDM系统中基于扩展贝叶斯滤波的鲁棒共信道干扰抑制算法研究

空时编码正交频分复用(STC-OFDM)系统易受共信道干扰(CCI)影响,利用波束成形可以抑制共信道干扰的影响。然而,目前存在的一些方法都是基于期望信号波达方向(DOA)的精确估计的。实际上,当期望信号的波达方向存在误差时,这些波束成形器的性能将明显下降。为此,该文提出了基于扩展贝叶斯滤波的鲁棒波束成形算法来提高当期望信号的波达方向存在误差时的系统性能。在这一算法中,每一个期望信号的波达方向被看成一个由若干离散样点组成的随机变量。利用贝叶斯公式对这些样点的后验概率进行估计,当有样点的后验概率低于一定的门限值时,对这些样点进行重采样,使有效样点的数目保持恒定。最后,波束成形器的最优权值由这些样点的后验概率加权获取。仿真结果表明,该文算法对抑制多径信道中STC-OFDM系统的共信道干扰具有很强的鲁棒性。     

基于入射夹角的自适应阵列干扰抑制性能评估方法

在一定的干扰损耗下,提出基于干扰与信号的入射夹角的最小值反映自适应阵列干扰抑制性能的评估方法。多个干扰与信号的入射关系难以衡量,因而提出逐个增加干扰的方法实现多个干扰情况下的基于入射夹角的性能评估。以4元阵为例,验证了评估方法的有效性和可实现性。     

任意平面阵列的干扰抑制

本文提出一种任意平面阵列抑制干扰的方法.对任意平面阵列的接收信号进行多次正交变换,然后对变换后信号的自相关矩阵求平均值,所得矩阵应用最大信号与干扰加噪声功率比准则求得抑制干扰的权值.计算机模拟实验表明,该方法能有效抑制干扰且对干扰信号之间的相关特性没有要求.     

频率复用系统同信道干扰抑制因子的研究

本文对频率复胳系统同信道干扰抑制因子提出了解析和统计两种求解方法，并利用统计求解结果，证明了解析求解法在实际情形中应用的可行性。     

OFDM系统中一种实用的干扰抑制信道估计算法

针对OFDM系统中IS信道估计在噪声消除和干扰抑制上的不足,提出一种干扰抑制信道估计算法.算法利用OFDM信号的时频二维特性,在LS信道估计基础上通过3次FFT/IFFT实现信道噪声消除和窄带干扰抑制,算法复杂度低,具有较好的工程可行性.算法仿真结果表明,这种干扰抑制的信道估计性能比传统LS信道估计在多径信道下的性能提升3 dB以上,在有窄带干扰的场景下系统性能损失在1.5 dB以内.     

阵列天线抑制同频干扰研究

同频干扰~([1][2])因其频率重叠性,不能采用一般的频域滤波器来抑制同频干扰。文章以抑制无线通信中同频干扰为目的,引入了阵列天线~[3],结合阵列信号处理中的数字波束形成技术,采用空域滤波的方法~[4]实现同频干扰的抑制。文章分析了阵列信号接收模型,在阵列模型的基础上论述了数字波束形成中抑制同频干扰的两种零陷技术——最大信干噪比(MSINR)准则和线性约束最小方差(LCMV)准则。最后通过MATLAB仿真,验证了这两种方法在抑制同频干扰时的有效性。     

基于正交复合波形设计的宽带雷达共信道干扰消除方法研究

多部雷达信号间的共信道干扰是目前雷达传感网等面临的电磁兼容问题。适合于窄带雷达运用的传统捷变频与编码分集等方法无法有效解决高分辨宽带雷达共信道干扰问题。文中提出了一种波形与时间双分集的复合设计方法,通过多元码脉冲位置编码、伪随机序列阵脉冲压缩和脉冲积累的复合体制,为较好解决宽带雷达间的共信道干扰提供了 一种解决途径。仿真结果表明在共信道信干比大于-30dB 的前提下,所提出的设计波形具有明显的干扰抑制能力,计算结果验证了该设计的可行性与高效性。     

GSM公共信道中FCCH的同频分离与捕获

针对GSM侦察设备升空后，截获和分析GSM信号时存在的严重的同频干扰问题。首先分析了GSM系统公共信道中频率校正信道（FCCH）的结构，然后根据其特点，提出了几种捕获和克服同频FCCH的方法，并进行了仿真验证。结果表明提出的方法能够有效克服GSM空中FCCH同频干扰，并且可以准确地捕获FCCH。     

存在同信道干扰和多用户分集的多蜂窝系统性能分析

考虑存在来自其他蜂窝的不同功率同信道干扰的多用户上行链路,分析了基站采用多用户调度和最大比合并接收时的系统性能.在期望信号和干扰信号分别为Nakgami-m和Rayleigh时,运用基于概率密度函数的性能分析法推导了系统中断概率和平均误符号率(ASER)的闭合表达式.仿真结论显示,系统中断概率和ASER的解析曲线与数值仿真结果一致,系统性能随着天线数和用户数的增大而提升,多天线和多用户分集增益明显,干扰功率有较大差异时系统中断概率性能有所下降.     

消除手机中的耳机爆破音和TDMA噪声

本文介绍手机模拟音频设计中经常会遇到的耳机爆破音和TDMA噪声产生机理,并介绍如何通过选择合适的耳机驱动器来消除爆破音和TDMA噪声.     

Cochannel Interference in Cellular Fixed Broadband Access Systems with Directional Antennas

The Cellular Fixed Broadband Access System for LMCS (Local Multipoint Communication Services) is aiming to provide broadband services to fixed subscribers through wireless access. A representative LMCS scenario involves a cellular system design with the entire allocated bandwidth being used in each cell and with a highly directional antenna employed at the subscriber. The LMCS system designs rely on assumed information regarding radio propagation phenomena in the anticipated coverage areas. The research reported here, therefore, has the objective of verifying such information by theoretical modeling and simulation. Simulation and analysis have been used to study the effects of a number of factors on the system performance and interference characteristics of such a LMCS system. The investigated factors include beamwidth and gain ratio of directional antennas, sectorization of hub antennas, propagation exponent, lognormal shadowing, site diversity and transmitter power control. Both models of LOS (line of sight) and NLOS (non-line of sight) have been investigated in this work. The simulation results demonstrate that highly directional antennas at the subscribers can dramatically improve the system performance for both uplink and downlink. The system design with frequency reuse of one is examined, and it is confirmed that an outage of 0.9% for a NLOS system could be achieved by using narrow beam antennas of 3 degrees with site diversity and power control techniques employed. Under the condition of LOS available for the desired links, the outage can be expected to be as low as 0.3%.     

Generalized Cochannel Outage Analysis with DTX in PCS Channels

Spectrum limitations are often a deterrent for swift growth of cellular radio systems. Therefore, different technologies have been explored to enhance the Radio Frequency (RF) capacity as well as to improve the communication quality. Recent technologies suggest the use of Discontinuous Transmission (DTX) as a mean to achieve these goals. In this paper, we analyze and quantify the performance improvement which result from implementing DTX in microcellular systems. The performance criteria is chosen to be the outage probability of de signal to interference ratio. Closed form expressions are derived for outage probabilities for systems using discontinuous transmission. Results are obtained for generalized Nakagami(n)/Nakagami(m) channels as well as for Ricean/Nakagami(m) environments. Moreover, since DTX effectiveness depend on voice patterns, modified expressions are developed for average outage probabilities which take into consideration different voice activity factors.     

时分多址(TDMA)通信系统频率源的研制

频率合成器是现代电子系统的重要组成部分 ,在通信、雷达、电子对抗、导航、广播电视、遥测遥控、仪器仪表等许多领域都得到广泛的应用。在雷达等通信设备中 ,它为发射机的调制器提供载频信号 ,也为接收机或发射机的混频器提供稳定可靠的本振源。该锁相频率合成器体积小、成本低、通用性强、使用灵活方便 ,频率控制可以通过硬件 (面板 )实现 ,也可以通过软件写入 ,工作频带 :3 80～ 4 40 MHz,频率步进 1 .2 5 MHz,输出功率≥7d Bm,相位噪声≥ -95 d Bc/Hz/1 0 k Hz。该频率合成器双路输出 ,收、发双工工作 ,已成功地用于时分多址 (TD-MA)通信网中     

A Variable Slot Length TDMA Protocol for Personal Communication Systems

We present a new TDMA-based scheme intended for carrying traffic withdiverse QoS requirements in mobile environments, e.g.,Personal Communication Systems (PCS).In contrast to mostother TDMA protocols for mobile applications, instead oftrying to fit the offered traffic to the slot size, our solution adaptsthe slot size to the offered traffic.This feature is combined with a dynamic and responsive bandwidth scheduler.As demonstrated by our performance studies, the proposedscheme is more flexible and incurs lower bandwidth overhead than otherTDMA-based solutions.     

A Blind Adaptive QR-Based Lattice Multi-Channel Filter for Cellular Base-Station TDMA Transceivers with Antenna Arrays

A new adaptive algorithm for blind interference rejection and multipath mitigation is studied and applied to antenna array processing in TDMA cellular communication systems. It is shown how the estimation of multiple signals from different sources by means of a multi-sensor receiver can be formulated as a multi-channel deconvolution problem. The proposed method is based on High-Order Statistics (HOS) processing of the baseband vector samples at the antenna array output. The similarity between the cumulant-based solution and the standard multi-variable Least Squares solution is exploited to derive an efficient adaptive algorithm based on the vector lattice architecture. The algorithm is numerically stable, considerably less complex than other existing multi-channel methods using HOS processing and exhibits rapid convergence with respect to blind array processing algorithms using simple gradient-based minimization procedures.     

Carrier Planning Issues for TDMA Personal Communication System

Radio spectrum is the most valuable resource for wireless communication, thus high spectrum utilization is mostly desired to increase system economy. With an efficient frequency allocation method and an effective handoff procedure, a personal communication system can be operated with minimal number of carriers while maintaining an acceptable level of system performance, and thereby leading to a better spectrum utilization. In this paper, we study the effect of different channel selection criteria for handoff procedure on carrier planning problem with Block Oriented Network Simulator (BONeS). The results show that the C/I-based channel selection criterion leads to the best performance, and the minimal numbers of carriers required by Personal Access Communications System (PACS) are 16, 13, 10 carriers for propagation environments with path-loss exponent 2.76, 3, 4, respectively.