对重大突发公共事件处置联合应急无线电管理指挥机构设置的研究

在考查重大突发公共事件处置对应急无线电管理工作迫切需求的基础上,着重讨论了重大突发公共事件应急无线电管理工作的相关概念,分析了应急无线电管理的特点和要求,并对重大突发公共事件应急无线电管理机构设置问题进行了研究。     

重大突发公共事件军地联合 应急无线电管理保障机制构想

在总结回顾“5．12”抗震救灾军地无线电管理部门联合保障航空专用频率工作的基础上,结合重大突发公共事件的特点,分析了目前军地联合应对重大突发公共事件的需求,对应对重大突发公共事件军地联合应急无线电管理保障的机制进行了研究与探讨。     

综合应急无线电指挥调度网的组建与实施

在总结回顾“5．12”抗震救灾应急通信组织情况的基础上,结合各种应急无线电通信手段的特点,针对目前重大突发公共事件事发区域内指挥调度与协同通信的不足,对综合应急指挥调度网的组建及拓扑进行了研究与探讨,并从实际应用层面对该网络的承建,运行提出了建议。     

论重大突发公共事件中的应急无线电管理工作

在总结应急无线电管理的地位和作用的基础上，提出了应对重大突发公共事件应急无线电管理工作的流程，并对应急无线电管理的主要工作进行了全面阐述。     

软件无线电中的信道化技术研究

软件无线电通信利用多频段和多模式的无线通信进行互连互通,具有极大的灵活性和适应性。文章围绕无线电接收机的信道化技术、带通采样理论等展开论述,利用CIC,HBF和FIR级联设计下变频抽取系统的实际方案作为论据,对基于软件无线电技术的信道化技术等展开论述,探讨软件无线电多速率信号等处理技术要点。     

基于动态控制信道的认知无线电网络MAC协议

在认知无线电网络中,MAC协议主要用于信道资源的感知、选择以及接入控制从而保证公平性和有效的资源共享。针对认知无线电网络基于控制信道的研究现状,文中在认知无线电网络分布式多信道MAC(CR-MMAC)协议的基础上,引入同步机制,不等待传输机制和不重申机制,提出一种基于动态公共控制信道的认知无线电网络MAC(CR-DCMAC)协议。它能够减少信道资源开支,降低控制信道上的控制分组量。仿真结果表明,CR-DCMAC协议能提高系统总吞吐量和空闲频谱资源的利用率,综合性能优于CR-MMAC协议。     

认知无线电路由信道选择研究

0引言 随着无线电与移动通信的快速发展,频谱资源变得越来越紧缺,为了提高频谱资源的利用率,2003年FCC报告提出了认知无线电的概念,致力于解决频谱稀缺的问题。在认知无线电网络里,频谱随着时间、空间是动态变化的,当前更多的研究集中于物理层和MAC（medium access cwntrol）层。     

认知无线电技术的信道交汇策略

随着网络技术的发展,无线设备的大量增加,为频谱资源的使用带来了极大的压力。频谱资源利用率低让网络发展进入了一个停滞期。但随着认知无线电技术的提出,与其在信道交汇中的应用,改变了网络频谱资源使用不均衡的现状,推动了网络技术的发展。本文对认知无线电技术与信道交汇的基本内涵分别进行了阐述,说明认知无线电技术与信道交汇之间的关系,进而提出了认知无线电技术的信道交汇策略,从调整信道算法、整合频谱资源、重构信道交汇方向等方面展开论述,旨在促进信道交汇,促进网络技术的发展。     

玉树抗震救灾无线电应急安全保障工作回顾与思考

本文介绍了青海省无线电管理机构在＂4·14＂玉树大地震后实施救灾无线电应急安全保障的步骤和方法,揭示了重大自然灾害无线电应急安全保障工作发挥的作用和重要意义,对如何提高应对突发事件无线电应急安全保障能力进行了探索和思考,为无线电管理部门开展无线电应急安全保障工作提供了参考和借鉴。     

数据链系统中无线电信道一体化组件的设计

主要介绍了数据链系统中微波一体化组件的各个组成部分,并概述各功能单元的基本结构及其关键技术,着重分析各个功能单元构成一体化组件的技术难点,给出数据链系统中形成一体化组件的设计思路。     

Analysis of GMSK with differential detection in land mobile radio channels

The effect of intersymbol interference (ISI) of Gaussian filtered minimum shift keying (GMSK) on the probability of error of one bit differential detection is analyzed theoretically in fast Rayleigh fading characterizing land mobile radio channels. A closed-form expression is derived for the probability of error as a function of the fading rate, IF filter bandwidth, signal-to-noise ratio (SNR) and ISI. Numerical results are presented for cases of practical interest to researchers and designers of cellular land mobile radio systems.     

Equalization of digital radio channels with large multipath delayfor cellular land mobile applications

A new maximum a posteriori (MAP) equalizer is proposed for digital radio links affected by large multipath delays. The “sparse” nature of the channel, where a few nonzero powerful taps are spaced by many negligible taps, is exploited to achieve a complexity proportional to the number of nonzero taps. When the channel is time-varying, an efficient nonlinear Kalman like channel estimator is employed to track only the nonzero taps     

Error-rate performance of digital FM with differential detection in land mobile radio channels

Error-rate performance of a digital FM with differential detection in the presence of both thermal Gaussian noise and cochannel interference is theoretically analyzed in the fast Rayleigh fading environment encountered in the typical UHF or microwave land mobile radio channels. The temporal correlation of the fades is included in the performance analysis. The error probability is presented by a simple closed form for the important situations where both effects of Gaussian noise and cochannel interference predominate in causing errors. Finally, a comparison with the other detection schemes, e.g., discriminator and coherent detections, is given.     

Coding for radio channels

The conventional remedy to time and/or frequency variability of radio channels is diversity. Redundant coding is a kind of diversity, as each coded symbol can be recovered from other symbols. Only linear binary block codes are considered. Any binary random variable can be represented by its algebraic value,a real number whose sign indicates its most likely value and whose absolute value measures the probability of this value. The algebraic value of a received binary symbol is itself a random variable, whose distribution obeys a particular constraint. The algebraic value associated with the maximum likelihood decision on a binary symbol, given a set of independent received replicas of it, and that associated with the sum modulo 2 of binary random variables are also considered. The symbol-by-symbol decoding is then analysed in the case of threshold decoding, then in the general case. An approximate bound on the decoding error probability for additive Gaussian noise and coherent demodulation is used to assess the advantage of coding when unequalenergy symbols are received, according to a deterministic or a Rayleigh distribution. Simulation results are given for the Hamming (15,11) code. Coding affords a significant advantage provided the channel is good enough, while conventional diversity always provides gain.     

An experimental investigation of the active-idle pattern of speech over land mobile radio telephone channels

Two methods of speech detection at the syllabic level of voice traffic over land mobile radio telephone channels are presented. Both methods are based on the periodic comparison of the audio signal level with a threshold and provide an ON-OFF pattern of active-idle periods on the channel at a rate equal to 100 to 200 samples per second. One method is entirely digital whereas the other method uses an analog detector followed by digital processing. Results of the analysis show that during a conversation more than 50 percent of the time the channel is idle, with an average duration of the silences larger than 300 ms. These results and those concerning other parameters of interest indicate that even during a conversation many useful idle periods do occur. These silences could indeed be exploited by making them available to additional users and hence improve both the efficiency of the channels and their congestion.     

Error rate performance of binary DPSK system with multiple co-channel interference in land mobile radio channels

The error rate performance of a binary differentially encoded phase-shift keying (DPSK) system in the presence of both thermal noise and multiple co-channel interferers is theoretically analyzed in the fast Rayleigh fading environment encountered in the typical UHF or microwave land mobile radio channels. The main objective is to show the additional degradation of an error rate of a binary DPSK system when undesired multiple co-channel M-ary DPSK interferers are virtually generated in a practical land mobile radio channel. The error probabilities are presented by a simple closed form as a function of noise correlation, interferer correlation, the number of interferers, M-ary modulating phase of interferer, Doppler frequency, carrier-to-noise (CNR) and carrier-to-interference (CIR) average power ratios.     

Achievable rates in cognitive radio channels

Cognitive radio promises a low-cost, highly flexible alternative to the classic single-frequency band, single-protocol wireless device. By sensing and adapting to its environment, such a device is able to fill voids in the wireless spectrum and can dramatically increase spectral efficiency. In this paper, the cognitive radio channel is defined as a two-sender, two-receiver interference channel in which sender 2 obtains the encoded message sender 1 plans to transmit. We consider two cases: in the genie-aided cognitive radio channel, sender 2 is noncausally presented the data to be transmitted by sender 1 while in the causal cognitive radio channel, the data is obtained causally. The cognitive radio at sender 2 may then choose to transmit simultaneously over the same channel, as opposed to waiting for an idle channel as is traditional for a cognitive radio. Our main result is the development of an achievable region which combines Gel'fand-Pinkser coding with an achievable region construction for the interference channel. In the additive Gaussian noise case, this resembles dirty-paper coding, a technique used in the computation of the capacity of the Gaussian multiple-input multiple-output (MIMO) broadcast channel. Numerical evaluation of the region in the Gaussian noise case is performed, and compared to an inner bound, the interference channel, and an outer bound, a modified Gaussian MIMO broadcast channel. Results are also extended to the case in which the message is causally obtained.     

Estimation of time-varying digital radio channels

In the design of block-oriented digital communication systems that must operate over time-dispersive channels, it is usually assumed that the channel is constant over the duration of a data block, even if the channel fades. The authors study the degradation in receiver performance caused by actual interblock channel variation. For tractability, attention is restricted to the case in which the channel variations are not tracked using decision-directed adaptation. The results suggest that unless the system parameters are carefully chosen, the constant-channel assumption is far from accurate. The quantitative results also offer a measure of the rate of channel time-variations, and give guidelines for deciding when those variations can be considered slow. These guidelines can be used as first-order evaluators of important system design decisions, such as total block size, training overhead, and data rate, for particular channel conditions     

广播电视传输覆盖网与无线电技术应用探究

科学技术的发展对广电事业产生了积极影响,保证了广电信号良好的传输状况。为了丰富广播电视传输方面的技术内涵,提高节目播出质量,需要对与之相关的覆盖物与无线电技术应用进行充分考虑,确保广播电视信号传输有效性,在技术层面上为其高效传输及潜在应用价值提升等提供有效保障。文章将对广播电视传输覆盖网与无线电技术应用进行系统阐述。