摘要 : There is a growing consensus among broadcasters that the key difference between digital and analog television will be the new level of interactivity that digital broadcasting will allow. In 1999 the digital video broadcasting (DVB... 展开 There is a growing consensus among broadcasters that the key difference between digital and analog television will be the new level of interactivity that digital broadcasting will allow. In 1999 the digital video broadcasting (DVB) project mandated work within an Ad-hoc Group (AHG) group (DVB-RCCL) to develop a wireless terrestrial return channel technology (to be known as DVB-TRC, digital video broadcasting return channel terrestrial). In parallel with this the European Union agreed in 2000 to fund an accompanying measure project known as WITNESS (Wireless Interactive Terrestrial Network Systems and Services) in order to verify and validate technical issues relating to operation of such a system. These issues include identification and allocation of suitable spectrum, set top box (STB) development work, and technical field trials in Ireland and France to allow investigation of system performance. The objective of the work is to aid the DVB-TRC subgroup in specifying this new system, and to build a wider consensus among the many stakeholders on the important issues related to this subject. This paper aims to introduce the technologies, and some of the organizations involved in this field of study, and to describe some of the socio-economic drivers behind these activities 收起