数字化中波同步广播单频网的音频时延分析

随着广播电视技术的高速发展,广播电视信号的传输已经全部实现了数字化,数字化的音频在数字化传输途径中所产生的音频时延有很大的不同.介绍了组成中波同步广播单频网要素,针对单频网中同步发射台音频信号的各种传输途径,阐述数字化音频的各种传输方式,并具体分析每种传输方式所引起的音频信号时延.     

相位制中波同步广播单频组网及测试分析

中波同步广播单频网技术能够在一定程度上缓解频率频谱资源紧张的问题,并消除同频干扰.本文在简要介绍精密相位制中波同步广播技术理论的基础上,将重点对前期开展的基于这种高精密度相位制同步组网测试工作进行阐述.     

中波载频同步广播的数字化设计与改造

介绍中波载频同步广播的基本原理和技术要求规范,结合目前中波载频同步广播的现状,分析实现中波载频同步广播的条件,利用当前最流行的数字化技术,设计中波载频同步广播的技术方案,并进行具体的实施。     

基于DDS技术的中波同步广播激励器的应用

本文通过对DDS技术的叙述,重点介绍利用基于DDS技术的数字化中波同步激励器,阐述中波同步广播激励器在我台实际中的应用,从而提升了中波同步广播发射的运行质量。     

中波同步广播技术在内蒙古电台覆盖中的应用

本文重点分析了同频相干区干扰问题的要素和实现中波同步广播单频覆盖要遵循的技术原则,简单对中波单频网技术在内蒙古电台农村牧区广播扩大覆盖项目中的应用进行了介绍。     

基于精密相位制同步广播技术构建大规模中波单频覆盖网

内蒙古人民广播电台,基于精密相位制同步广播技术,构建了我国最大规模的中波同步广播单频网,用于全自治区的"农村牧区广播"频率的中波无线覆盖。目前,中波广播仍然是我国广大农村地区广播的重要覆盖手段,采用先进的精密相位制同步广播技术,在大幅度改善覆盖效果的同时,可以高效释放中波频率资源,实现"单频"组网覆盖,为开办更多的广播节目频率创造了条件,具有重要意义。     

单频网数字电视广播的时间同步系统设计

提出在数字电视广播单频网中进行的一种TS流时间同步的方法,该方法在DVB标准ETSI TS 101 191的基础上引入GPS绝对时间,采用27 MHz作为同步对时时钟,简化了系统设计,并使得延迟时间不再局限于1 s的限制,总延迟时间可根据设备内存的大小任意设置.根据该方法研究的设备已经用于实践之中.     

相位制中波同步广播技术及组网实践探讨

随着我国中波广播发射台频率复用度越来越高、发射功率越来越大,中波广播可用场强被不断提高,服务区逐渐缩小,对中波广播节目的覆盖质量造成了一定程度的影响.同步广播是模拟广播的单频网技术,是向数字音频广播过渡时期的必然产物,它可以缓解频率复用度高的问题,有效节约频谱资源,抑制同频干扰,扩大广播有效覆盖范围,提高广播收听质量,是我国中波广播网覆盖规划的重要技术措施.     

地面数字电视广播单频网的应用

作为数字广播电视的一种无线电发射台,单频网的出现大大地节约了频率资源,提高了频谱的利用率,就地面电视广播数字化的发展以及单频网的有关问题进行了论述。     

基于DVB-T的单频广播网络

１引言随着社会发展，高质量、实时、移动的视音频以及数据广播市场需求越来越多。在这种需求下，如何实现这些业务的传输一直是人们比较关心的问题。通常情况下，是用类似于蜂窝结构的多频网络（MFN）来实现。如图１a所示，它采用多个发射机来广播相同的业务，每个发射机用不同的频率。接收机在不同的小区中移动时，换用不同的接收频率。这样做缺点多，一是频率资源浪费较严重；二是在各个频率之间有相互干扰；三是在小区之间切换时会有间断。如采用如图１b所示的单频网络（SFN）实现则可克服这些缺点。单频网络是指所有网络内的发射机…     

Analysis of an advanced satellite digital audio broadcasting systemand complementary terrestrial gap-filler single frequency network

Digital audio broadcasting (DAB) to mobile and fixed users exploiting the latest advances in compression coding, and transmission techniques represents an appealing application for future satellite systems. This paper introduces coded quasi-orthogonal code division multiplexing (CQO-CDM) as a transmission technique for digital audio broadcasting. The proposed technique performs well over both the L-band satellite fading channel and the terrestrial gap-filler type of transmission. Preliminary link budgets based on extensive computer simulation results are provided. Numerical results show that remarkable overall capacity can be achieved by using a constellation of satellites in highly elliptical orbit (HEO) complemented by a terrestrial gap-filler network. A variety of transmission rates and hence broadcasting services can be realized with the proposed transmission technique. It is shown that a geostationary orbit (GEO) satellite can provide limited service availability to the mobile user, but can also be used for experimental purposes     

Minimal cost coverage planning for single frequency networks

OFDM based single frequency networks (SFNs) have been standardized for terrestrial broadcasting systems, for digital audio broadcasting (DAB) as well as for digital video broadcasting (DVB). Due to the multipath tolerance of the OFDM scheme, the receiver is able to combine signals coming from several transmitters, despite of the varying propagation delays, i.e., heavy artificial multipath propagation. In order to take full advantage of the diversity gain provided by the SFN architecture, proper network design is required. We focus on the cost efficient design of an SFN providing broadcasting services over a predefined service area with requirements both on the received signal quality and on the allowable interference level experienced by existing services in the same spectrum. We formulate the problem as a discrete optimization problem, where the network design parameters such as power, antenna heights and transmitter locations are the decision variables. The general stochastic optimisation algorithm simulated annealing has been adapted for solving the above problem. The novelty of our method is that cost factors and interference constraints are embedded in the optimisation procedure. Through numerical examples we demonstrate that significant reduction in network cost can be achieved by our approach     

On the outage probability in local/regional single frequency broadcasting networks

A receiver in an ODFM based broadcasting system allows all transmitters in a radio network to simultaneously broadcast the same information in the same frequency block. This procedure generates an artificial multipath environment at the receiver. Since the receiver is designed to overcome these problems, such a Single Frequency Network (SFN) provides good coverage and frequency economy in national applications. However, the efficiency in local SFN has been questioned. The network planning of local SFNs is a mixture of conventional frequency reuse planning and planning to avoid excessive propagation delays caused by the artificial delay spread. In this paper we propose some rules of thumb to be considered in the design of local SFNs. The coverage properties in SFNs are strongly dependent on the transmitter density which determines the degree of diversity of receiving signals from several transmitters. Results indicate that required coverage can be attained in local networks using three OFDM frequency blocks, provided that seven transmitters are used to cover each regional service area. The results also indicate that the duration of the guard interval between two consecutive OFDM signals has to be chosen with some care dependent on the size of the service area. Furthermore, we show that there exists an optimal antenna height for a given coverage area and guard interval.     

The future of high frequency broadcasting

Since the end of World War II, the number of daily frequency hours used by high-frequency (HF) broadcasting (also known as shortwave and band 7, 3-30 MHz) has tripled. Approximately 35000 daily frequency hours are carried in an HF spectrum that can barely accommodate half that amount. As a consequence, congestion is severe, and interference levels intolerably high. Attempts to remedy this situation by planning the high-frequency bands date back to 1947, but, thus far, they have not been successful. International planning conferences in 1984 and 1987 have shown a possibility for agreement; another conference is tentatively scheduled for 1992. Some broadcasters have attempted to solve their congestion problems by moving out-of-band, sometimes expanding their services int bands allocated to other services, such as amateur radio, fixed, aeronautical, and mobile. It is feared this trend will continue. The attempts that have been made to plan the HF bands in an effort to alleviate congestion are described and the outlook for the remainder of the 20th century is discussed     

CMMB单频网接收端网络监测点选择的分析

本文首先从理论和实际两个方面综合分析了单频网发射端可能出现的故障,通过仿真软件模拟发射端各类型故障,观察接收端相应发生的变化和产生不良接收的区域,从而在应用中通过接收端的实际情况判断发射端是否出现故障,以及出现故障的种类。     

Gravel coverage rate measurement in synchronous chip seal based on deep convolutional neural network

Synchronous chip seal is an advanced road constructing technology, and the gravel coverage rate is an important indicator of the construction quality. In this paper, a novel approach for gravel coverage rate measurement is proposed based on deep learning. Convolutional neural network (CNN) is used to segment the image of ground covered with gravels, and the gravel coverage rate is computed by the percentage of gravel pixels in the segmented image. The gravel coverage rate dataset for model training and testing is built. The performance of fully convolutional neural network (FCN) and U-Net model in the dataset is tested. A better model named GravelNet is constructed based on U-Net. The scaled exponential linear unit (SELU) is employed in the GravelNet to replace the popular combination of rectified linear unit (ReLU) and batch normalization (BN). Data augmentation and alpha dropout are performed to reduce overfitting. The experimental results demonstrate the effectiveness and accuracy of our proposed method. Our trained GravelNet achieves the mean gravel coverage rate error of 0.35% on test dataset.     

局域网视频广播接收器的设计

描述了一个局域网视频广播接收器的设计。发送端以计算机按UDP/IP的方式向局域网中发送视频广播，在接收端利用FPGA器件设计的接收器对广播进行接收、缓冲、格式转换，以电视作为显示终端，并介绍了在FPGA器件中所设计的各个模块。     

Satellite broadcasting of time and frequency signals

The authors discuss the advantages of broadcasting time from a satellite over the more traditional ground based methods such as short wave and low frequency standard time and frequency broadcasts. The authors describe several one way satellite time services currently operational and discuss, in particular, a broadcast service using the Indian domestic satellite INSAT. The signal format, transmitting and receiving setups, and the methods for satellite position prediction are described in detail for the INSAT broadcast. Some typical results of time and frequency calibration are also discussed     

单频网组网优化方法及复杂度分析

首先介绍了单频网覆盖的判定准则,其次针对地面数字电视广播单频网的组网优化问题,提出了一种基于遗传算法的优化方法,并分析了算法的复杂度,着重探究算法参数对算法性能的影响,从而确保在得到最佳优化结果的同时付出最小的代价.