Delivering interactive services via a digital TV infrastructure

This article discusses an architecture for interactive service delivery to the home via the digital television (DTV) infrastructure in systems with and without return channels. This approach relies on a broadcast computing model adapted to suit the DTV environment. The model works even with low-cost user terminals, such as the basic DTV set-top boxes with limited computational and graphics capability and no local disk storage     

Joint VSB terrestrial digital TV indoor reception project

The reliability and efficacy of indoor reception of 8VSB digital terrestrial television (DTV) in four major U.S. cities was studied in an initial field measurement survey program and a subsequent data capture and processing program. Measurements from the initial survey identified problem sites for reliable DTV reception using currently available 2nd generation DTV receivers. Subsequent field dual channel data captures made at the identified problem sites provided data for testing and verification of new antenna diversity receiver algorithms destined for future generation DTV receivers. From data captures at selected problem sites of sufficient signal strength, but where currently available 2nd generation DTV receivers failed, it was found that in 70% of the cases DTV reception performance was satisfactory when using new antenna diversity receiver algorithms. These measurements and data captures corroborate the claim that the VSB DTV indoor reception problem may be less severe than implied from surveys using less advanced current 2nd generation receivers with a single antenna. For sites with severe multipath, 8VSB DTV reception could be potentially superior to NTSC, which would experience an unwatchable picture.     

面向多维数字媒体的访问控制机制

在多维数字媒体场景中,用户期望利用环境、时态等因素实现访问权限的自我约束。针对该需求,综合环境、时态、角色定义授权属性,提出面向多维数字媒体的访问控制机制,该机制定义用户—授权属性分配关系和授权属性—访问权限分配关系,根据用户的ID、属性信息、所处环境和时态、角色,用户—授权属性分配关系为用户分配相应授权属性;根据用户所赋予的授权属性,授权属性—访问权限分配关系为用户分配相应访问权限。引入约束条件,用户通过设置约束条件进行访问权限的自我约束,实现访问权限随环境、时态、角色等因素的变化而动态缩减。使用Z符号对该机制进行形式化描述,通过实例分析验证其可行性,与现有工作的比较表明所提机制支持最小权限、职责分离、数据抽象等安全原则,支持访问权限的动态缩减。     

DTV standards and transition: A comparative policy analysis

China recently has emerged as a serious player in setting ICT standards, as evidenced by its presence in major conferences on standardization with the International Telecommunications Union. While the ATSC standard contributed to the successful completion of the DTV transition in the US, China’s home-grown DTV standard bears little, to date, on its relative success in converting one third of its cable households to digital service. In light of these differing outcomes, this paper identifies and compares the strategies behind the quest for national DTV standards by retracing the key policy initiatives in China and the US. Our analysis suggests that protectionist impulses shaping distinct standards for the US (Grand Alliance), China, and other regions dampen prospects for a global standard in DTV. However, the US has been more successful at maintaining the kind of balance between industry and governmental policy that is critical to maintaining technological innovation and a competitive marketplace.     

Investigation into the interference potential of spread-spectrum clock generation to broadband digital communications

Since its inception, spread-spectrum clocks have been a valuable technology for the purposes of EMI reduction and EMC compliance. This study evaluates the interference potential of spread spectrum clocks to broadband digital communications such as high definition television (HDTV). This is accomplished by comparing the spread spectrum clock interference susceptibility of digital television (DTV) receivers to the interference susceptibility of analog television receivers. This study shows that DTV receivers are more immune to the same level of interference than existing analog television receivers by 16 dB. Since industry has shown that analog television has had negligible interference from information technology equipment, including spread spectrum clocks, then the digital systems should have even less.     

Canadian digital terrestrial television system technical parameters

On November 8, 1997, Canada formally adopted the ATSC Digital Television Standard for terrestrial transmission as defined in document A/53 of the Advanced Television Systems Committee of the USA and as modified by the FCC document MM Docket No. 87-268. This paper discusses the Canadian digital terrestrial television system technical parameters for implementation and frequency planning: interference protection ratios, reference system parameters, and radio frequency emission masks, as well as their design methodology. First, the Canadian terrestrial DTV design guidelines are presented, followed by the introduction of DTV reference receiving system set up and the parameter selection of the interference protection ratios. Last, the design methodology of the emission masks is discussed     

一种快速提取位同步的全数字锁相环

本文提出了一种快速提取位同步的全数字锁相环方案。该方案通过对同步区、反相区以及快慢区的切换,有效地克服了同步时间与量化相位误差的矛盾。具有同步建立时间短、保持时间长、且同步精度高、抗干扰能力强等优点。     

Using object multiplex technique in data broadcast on digital CATV channel

Data broadcast is a new kind of value-add service of DTV broadcasting and some data broadcast protocols have already been established. However, these protocols only describe the method for locating files in data streams, and a method for distribution of a large collection of files in one or more data streams is not provided. Research on this problem mainly focuses on how to decrease the wait time and some methods of allocating files on multiple streams based on access probability are proposed, but how to assign the file with a reasonable bandwidth is ignored. In this paper, we introduced an object multiplex algorithm to optimize the allocation of objects on a DTV channel. This method assigns different bandwidth statistically to a different object according to its size and access probability. In this method, both download time and wait time are considered. It adopts a modified virtual clock (VC) scheduling algorithm to multiplex files accurately and smoothly.     

Encrypted data sharing with multi-owner based on digital rights management in online social networks简

The online social networks（OSNs） offer attractive means for social interactions and data sharing, as well as raise a number of security and privacy issues. Although current solutions propose to encrypt data before sharing, the access control of encrypted data has become a challenging task. Moreover, multiple owners may enforce different access policy to the same data because of their different privacy concerns. A digital rights management（DRM） scheme is proposed for encrypted data in OSNs. In order to protect users＇ sensitive data, the scheme allows users outsource encrypted data to the OSNs service provider for sharing and customize the access policy of their data based on ciphertext-policy attribute-based encryption. Furthermore, the scheme presents a multiparty access control model based on identity-based broadcast encryption and ciphertext-policy attribute-based proxy re-encryption, which enables multiple owners, such as tagged users who appear in a single data, customize the access policy collaboratively, and also allows the disseminators update the access policy if their attributes satisfy the existing access policy. Security analysis and comparison indicate that the proposed scheme is secure and efficient.     

同密条件接收系统软件适配层的设计与实现

提出了一种数字电视同密条件接收系统在终端设备上移植的方法,它具备简单、易用,可复用性高等特点.该方法从DVB标准出发,综合多个条件系统工作流程,接口函数以及硬件平台驱动层的差异,通过软件适配层建立了统一的数据接口,可支持多种同密条件接收系统的应用移植要求.     

Broadband access using subcarrier multiplexing and asymmetric digital subscriber lines

A broadband access system using subcarrier multiplexing on optical fibre and asymmetric digital subscriber lines (ADSL) or very high‐speed digital subscriber lines (VDSL) on unshielded twisted‐pair is proposed to provide broadband access. In this hybrid‐fibre/twisted‐pair (HFTP) system, the digital multiplexing/demultiplexing process is moved back to the central office by using subcarrier multiplexing for fibre transmission. Instead of installing in remote node, ADSL/VDSL transceivers are installed at the central office to greatly reduce the remote node complexity. The local node simply down‐converts the subcarrier multiplexed ADSL/VDSL signal to the baseband, suitable to send directly into the twisted‐pair. The reduction of complexity could result in a lower initial installation cost, especially for a low service penetration rate. Copyright © 2000 John Wiley & Sons, Ltd.     

A primer for digital television RF facility design and construction

With the release of the FCC's (Federal Communications Commission) Sixth Further Notice of Proposed Rulemaking, many television broadcasters are concerned about the design and reconstruction considerations for digital television (DTV). This paper discusses some of these considerations and reviews some of the basic design criteria for a digital television transmission system     

Design and Implementation of an End-to-End System for DTV Multicasting to Home Over Broadband IP Access Network

This paper describes design and implementation of an end-to-end system which implements digital television (DTV) multicasting to the home over broadband IP access network. We have developed a DTV-IP gateway for introducing DTV programs from broadcasting network into IP network with special considerations of the challenges, which consist of different service models and different protocols when deploying DTV services between the traditional satellite, cable or terrestrial network and the broadband IP network. According to different application scenario, the DTV-IP gateway can output two types of streams: CBR (constant bit-rate) transport stream (TS) over IP and VBR (variable bit-rate) TS over IP. Moreover, we have proposed a method to auto-regenerate the standard CBR TS from VBR TS over IP for the standard set-top-box (STB) with consideration of timing synchronization. This end-to-end system has been verified to work well in the broadband IP access network environment.     

高级数字电视广播系统传输方案

作为高清晰度电视总体组在数字电视传输技术研究方面的组成部分，介绍一种由浙江大学、上海交通大学和西安电子科技大学共同提出并开发的高级数字电视广播系统（Advanced Digital Television Broadcasting System,ADTB)的传输方案。该方案在功能和性能上超越现有的国外数字电视标准，能够在使用民用级调谐器的前提下，实现大容量广播数据的稳定的无线固定、便携和移动接收，支持单频网络和同频道转发，包含高效的数字有线广播传输模式，易于兼容国外标准。这是我国数字电视广播标准理想的侯选方案之一。     

The U.S. Digital Television Standard and its Impact on VLSI

The U.S. is in the final stages of establishing a Digital Television (DTV) transmission standard for digital terrestrial broadcasting in both HDTV and SDTV formats. The Grand Alliance prototype hardware has been extensively tested in both laboratory and field conditions and has exhibited outstanding performance. As of this writing, the Grand Alliance system has been officially recommended by industry to the FCC as the U.S. standard and final approval is expected from the FCC by the middle of 1996. The U.S. DTV standard will create a new market for digital consumer electronics products based on the standard, including DTV receivers, VCRs, camcorders and Personal Computer interface cards that will employ VLSI circuits to cost-effectively implement the products.     

Geodemographic classifications, the digital divide and understanding customer take-up of new technologies

The imperatives of social cohesion make it necessary to consider the highly variable characteristics of users alongside the design and implementation of IT networks and services. In this context much has been written on the so-called ‘digital divide’ in society. Recent ESRC-funded research at UCL has illustrated how it is simplistic to think of the impacts of new information and communication technologies (ICTs) in terms of a single, or even small number of, ‘digital divides’. As developments in what has been termed the ‘e-society’ reach wider and more generalised audiences, so it becomes appropriate to think of digital media as having wider-ranging but differentiated impacts upon consumer transactions, information gathering and citizen participation. This paper describes the development of a detailed, nationwide household classification based on levels of awareness of different ICTs, levels of use of ICTs, and their perceived impacts upon human capital formation and the quality of life. It illustrates how geodemographic classification makes it possible to provide context for detailed case studies, and hence identify how policy might best improve both the quality and degree of society’s access to ICTs. We have provided a more detailed overview of the methodology elsewhere [1, 2] and here we also illustrate how the classification may be used to investigate a range of regional and sub-regional policy issues. A particularly innovative aspect of this classification is the Web resource hosted at www.spatial-literacy.org/esocietyprofiler. This site makes it possible to look at the classification system, aggregated to unit postcodes, across Great Britain. Users can look at national distributions for each of the groups and types in the classification, and offer feedback as to whether the classification appears to work for any locality.     

Explaining caste-based digital divide in India

With the increasing importance of information and communication technologies in access to basic services like education and health, the question of digital divide based on caste assumes importance in India where large socioeconomic disparities persist between different caste groups. Studies on caste-based digital inequality are still scanty in India. Using nationally representative survey data, this paper analyzes the first-level digital divide (ownership of computer and access to the Internet) and the second-level digital divide (individuals skills to use computer and the Internet) between the disadvantaged caste groups and Others. Further, this paper identifies the caste-based differences in socioeconomic factors that contribute to the digital divide between these groups using a non-linear decomposition method. The results show that there exists large first-level and second-level digital divide between the disadvantaged caste groups and Others in India. The non-linear decomposition results indicate that caste-based digital divide in India is rooted in historical socioeconomic deprivation of disadvantaged caste groups. More than half of the caste-based digital gap is attributable to differences in educational attainment and income between the disadvantaged caste groups and Others. Findings of this study highlight the urgent need for addressing educational and income inequality between the different caste groups in India in order to bridge the digital divide.     

Bridging the digital divide among low income urban communities. Leveraging use of Community Technology Centers

To fully leverage the availability of the internet services in Kenya, all the citizens need to be able to access and use the internet and related services. The availability of 4G networks, cyber cafés and fiber connectivity in most residential areas of Nairobi has allowed many Nairobi residents to be part of its information-based society. But, as with the other existing social inequalities in Nairobi, many people residing in the city’s low-income areas lack access to the internet. This has a negative impact on the residents’ prospects as the governments and businesses are increasingly delivering their services online. Using a pre-tested questionnaire, data were collected from five hundred and fifty respondents on their internet access and digital literacy skills among the residents of the Mathare Slum. From the survey, the study found existence of limited digital literacy skills and lack of internet access among the residents of the Mathare Slum. The study then used the Community Technology Centers (CTCs) intervention approach to narrowing the digital divide by setting up a CTC in the Mathare Slum to offer free community internet access and digital literacy skills training. Eight cohorts, each of eighteen residents, were offered free digital literacy training for five weeks and free unlimited internet access for four months. The study then evaluated the trainees’ internet usage continuance intentions after four months of continued use of the internet at the CTC. The results indicate that perceived enjoyment, perceived usefulness, internet self-efficacy, and confirmation of expectations all significantly influence the participants’ satisfaction with use of the internet. The results also show that continuance intentions of the participants from low income household to continue using internet beyond the CTC can be predicted by perceived service cost, satisfaction, internet self-efficacy and perceived usefulness. The study demonstrates the effectiveness of CTCs as an intervention approach and a replicable model that can be used to bridge the urban digital divide among low income urban communities for the development of an all-inclusive information-based society. Implications and recommendations for policy, practice and research are provided.     

数字电视地面广播信道的均衡技术

作为数字电视地面广播的一种关键技术,均衡技术可以有效去除符号间干扰,保证视频流的优质传输,尤其确保了大容量、高速可靠移动接收的实现。本文对目前单载波和多载波传输方案中的均衡原理进行了描述,分析了现有方案的不足,并结合盲均衡提出了数字电视均衡技术的发展前景。