Summary of conclusions of the 1992 World Administrative RadioConference

The major decisions made at the conference are briefly described. Additional frequency bands for shortwave (HF) radio broadcasting were agreed upon. Frequency allocations were made to support a number of US proposals, to provide advanced mobile radio services using low Earth orbit satellites. Allocations for land based mobile services adopted at WARC '92, in the range 1700 to 2600 MHz, are meant to foster improved mobile services that can be used worldwide. An allocation was also made to support commercial telephone service between passengers flying on aircraft and individuals on the ground. Allocations were made for sound broadcasting from satellites, as well as for providing a means to accommodate a complementary terrestrial-based digital audio broadcasting service. New frequency allocations to support space activities were agreed upon, and an allocation was made to the fixed satellite service in the band 13.75 to 14.0 GHz     

WARC Allocations and Some of their Impacts on Japan and in Asia

This paper describes certain decisions made at the World Administrative Radio Conference (WARC) held in September 1979 which will have great impact on the utilization of radio in Japan and throughout Asia and Oceania. This paper concentrates on the table of frequency allocations adopted at the conference. It also outlines some of the problems expected at the forthcoming WARC for high-frequency broadcasting (WARC-HFBC) and on the space services planning conferences.     

An Introduction to the RARC '83 Plan for DBS Systems in the Western Hemisphere

The 1983 Regional Administrative Radio Conference (RARC '83), sponsored by the International Telecommunication Union (ITU), adopted a plan that assigns to each country in ITU Region 2 (the western hemisphere) the frequencies and orbital positions it can use for direct broadcasting satellite (DBS) systems in the 12.2-12.7 GHz band. An earlier ITU conference, the 1977 World Administrative Radio Conference (WARC '77), had already made such a plan for countries of ITU Region 1 (Africa, Europe, the Soviet Union, and Mongolia) and Region 3 (the rest of Asia, Australia, and the southwest Pacific) in the 11.7-12.5 and 11.7-12.2 GHz bands, respectively. In addition to orbital positions and frequencies, both plans specify the satellite polarization, coverage, and maximum radiated power to be used by each country. This paper describes the RARC '83 Plan and compares some of its features to those of the WARC '77 Plan. The reference system parameters used for planning at RARC '83 and WARC '77 are summarized and discussed briefly. The RARC '83 Plan itself is described in terms of the satellite coverage areas; the channelization of the band; and the specific orbital position, frequency, and polarization assignments provided. Further details about the assignments in the plan and an assessment of their impact on the development of DBS systems in Region 2 are also included.     

How WARC '92 will affect mobile services

The US proposals to, and the decisions of, the 1992 World Administrative Radio Conference (WARC '92) that relate to mobile and mobile-satellite services are described. Mobile-satellite service (MSS) issues addressed at WARC '92 include new allocations for low Earth-orbit (LEO) satellite operations, new MSS spectrum allocations, and modifications to current allocations used to support mobile-satellite operations. Allocation issues on the agenda of WARC '92 that related to the terrestrial mobile services include allocations for mobile services between 1 and 3 GHz, allocations for aeronautical public correspondence, and designation of frequency bands for future public land mobile telecommunications services. A number of proposals which were put forward by the US to support MSS allocations and operations that did not explicitly require allocations to the MSS are discussed     

DVB-T Network Planning: A Case Study for Greece

Terrestrial digital video broadcasting (DVB-T) network planning is the main interest of this article, along with a case study for Greece. The basic principles and the guidelines of the DVB-T planning process are presented, in conjunction with their application to the establishment of the Greek DVB-T allotment plan. The procedures described in this article were followed by the authors during the International Telecommunication Union (ITU) DVB-T planning project that concluded with the ITU's Regional Radiocommunication Conference 2006 (RRC-06), and the Geneva (GE-06) frequency plan for terrestrial digital radio broadcasting.     

An error-correcting coding scheme for teletext and othertransparent data broadcasting

Nonprimitive and primitive Reed-Solomon (RS) codes (and product codes based on them) that can provide a very low bit error rate (BER) for the transparent data broadcasting feature of North American broadcast Teletext Specification (NABTS) are described. Transparent data consist of 8-b bytes, each without a parity-check bit, as contrasted with nontransparent data, which consist of 8 bit bytes, each of which has a parity-check bit in every byte. Specific applications for transparent error-coding codes constructed from RS codes in broadcast teletext broadcasting are discussed. Nonprimitive RS codes designed for nontransparent data broadcasting by NABTS teletext are derived, and powerful product forms of shortened nonprimitive Reed-Solomon codes are described     

Planning aspects of satellite and terrestrial digital sound broadcasting

DAB is one of the most promising sound broadcasting techniques for the future. It will soon start terrestrial operations, and later on will be used for satellite broadcasting. The Eureka 147 DAB system is based on a set of well-demonstrated techniques, in particular the MUSICAM coding, adopted by MPEG, and OFDM modulation. It allows great spectrum efficiency, profiting from the single frequency network concept, one of the most interesting characteristics of the system. However, frequency problems remain a difficulty, as DAB must either examine the possibility of entering existing heavily used frequency bands or wait until the new frequency bands allocated by WARC 92 become fully available. For terrestrial broadcasting, most interested operators, broadcasters and manufacturers are convinced that appropriate solutions will be found and that DAB will start operational services from about 1996. In Europe, a CEPT planning conference will address the matter in 1995. Satellite broadcasting may come later. Short wave broadcasters examine possibilities to replace short waves, the quality of which is so poor, by digital satellite broadcasting. From the frequency spectrum point of view, this raises the difficulty of sharing frequency allocations with terrestrial applications.     

Asynchronous and reliable on-demand media broadcast

We discuss wireless broadcasting of multimedia streams within a framework that allows asynchronous media access. Receivers subscribe at any time to the ongoing broadcast session, but are still able to display the media stream from the beginning. A fully scalable broadcasting scheme is presented where the media stream is appropriately segmented, and segments are protected by fountain codes. Erasure-based decoding as well as soft decoding is discussed. Asynchronous data reception and full reliability are achieved at the same time. Depending on its receiving conditions, the receiver adapts its initial playout delay to guarantee high reliability of successful playout.     

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     

Jamming to the HF broadcasting service

The Institute for Telecommunication Sciences has been actively involved in an internationally coordinated monitoring program to determine the location of emitters of harmful interference (jamming) to the high-frequency (HF) broadcast service. four monitoring programs were undertaken between October 1984 and June 1986. The procedures that have been used and the results that have been obtained are summarized. The locations of the emitters that cause jamming to the HF broadcast service are shown and selected characteristics of the jamming environment are described. The degree to which jamming that is directed to certain broadcasters adversely impacts the performance of other broadcast services that operate on the same or adjacent channels as the targeted broadcaster is examined     

Some ionospheric factors affecting the coverage of an HF/VHF direct broadcasting satellite service

A study has been undertaken to assess the effects of the ionosphere on the performance of a direct broadcasting satellite service operating in the high frequency (HF) band. Results relating to two issues of performance are presented: 1) determining under what conditions a frequency allocated to the broadcasting service can be expected to reach the surface of the earth from a satellite and 2) the loss of signal strength due to passage through the ionosphere, it was found that if high frequency broadcast services are to be provided on a worldwide basis using satellite platforms, the satellites need to be optimally configured for the intended service area. Also, a 3 dB loss of signal strength is expected due to ionospheric absorption.     

Energy and Spatial Reuse Efficient Network-Wide Real-Time Data Broadcasting in Mobile Ad Hoc Networks

In this paper, we present NB-TRACE, which is an energy-efficient network-wide voice broadcasting architecture for mobile ad hoc networks. In the NB-TRACE architecture, the network is organized into overlapping clusters through a distributed algorithm, where the clusterheads create a nonconnected dominating set. Channel access is regulated through a distributed TDMA scheme maintained by the clusterheads. The first group of packets of a broadcast session is broadcast through flooding, where each data rebroadcast is preceded by an acknowledgment to the upstream node. Nodes that do not get an acknowledgment for a predetermined time, except the clusterheads, cease to rebroadcast, which prunes the redundant retransmissions. The connected dominating set formed through this basic algorithm is broken in time due to node mobility. The network responds to the broken links through multiple mechanisms to ensure the maintenance of the connected dominating set. We compare NB-TRACE with four network layer broadcast routing algorithms (Flooding, Gossiping, Counter-based broadcasting, and Distance-based broadcasting) and three medium access control protocols (IEEE 802.11, SMAC, and MH-TRACE) through extensive ns-2 simulations. Our results show that NB-TRACE outperforms other network/MAC layer combinations in minimizing energy dissipation and optimizing spatial reuse, while producing competitive QoS performance.     

Improving broadcast performance by traffic isolation in wireless ad hoc networks

In this paper we propose a new broadcasting algorithm. In the proposed method we significantly reduce the broadcast overhead and also improve the broadcast delivery ratio in mobile networks. A novel traffic isolation method has been used which reduces the control message exchange. The proposed broadcasting method is based on a clustering method called ‘stability‐based clustering algorithm’ which had been proposed before. The broadcasting traffic is divided into internal (flow inside a cluster) and external traffic (flow among the clusters). For internal flooding traffic, cluster‐heads and gateways are responsible for re‐broadcasting but for external type, border nodes may perform the forwarding function as well. This simplifies the gateway selection method through the local selection of gateway nodes by its cluster head. Therefore, a cluster head selects gateway in its own cluster without any knowledge of other clusters. Considering the effect of mobility and node density, simulations have been conducted in a number of wireless environments. Simulation results show the broadcast coverage is close to 100% at different node speeds. Moreover, we study the broadcast parameters in light and dense networks and show improvement of the overhead and the number of forward nodes in comparison to other broadcasting methods. Copyright © 2005 John Wiley & Sons, Ltd.     

海门市数字电视前端平台监测系统的设计与实现

数字电视前端平台建设中,系统监测部分的设计和建设在整个平台建设中显得越来越重要。数字电视平台的监测主要分为播出质量的监管、播出信道的监测和播出数据流的监测3个部分。结合海门数字电视前端平台的特点,对海门数字电视前端播出平台监测部分的设计内容作了介绍,为数字电视前端平台建设提供参考。     

HDTV broadcasting systems

A brief overview of HDTV broadcasting in the USA, Japan, and Europe is given. The requirements for HDTV broadcast systems are examined. The issue of compatibility is discussed. Standardization activities for HDTV broadcasting are described. The Japanese MUSE (multiple sub-Nyquist sampling encoding) system and the European HD-MAC (high-definition multiplexed analog components) systems are examined with respect to their technical basis, underlying principle, and coding/decoding     

High definition television systems

High definition television (HDTV) services will play the most important role in the digital television systems for the future. HDTV is already broadcast daily in Japan and advanced television (ATV) standards will soon be established in the US. The hardware systems for two HDTV systems, the 1125/60 and 1250/50 systems, have already been developed. Their outlines are described in the paper. Signal processing of HDTV is mainly carried out by digital methods on both the studio and receiver sides. The principles of processing are the same as for conventional television but the higher clock frequency and larger quantity of information require more sophisticated hardware. Digital signal processing methods are the key technology in HDTV broadcasting systems regardless of whether modulation is analog or digital. Some broadcasting systems are already practical use while others, are experimental. The author discusses these systems. The aim of the article is to present a global scope of the HDTV technology     

Service, system, and technology considerations for space-basedinternational radio broadcasting used in the conduct of public diplomacy

It is argued that the technology and operating characteristics of a space-based international radio broadcasting system designed to meet the service needs of the world's governments in the conduct of public diplomacy in an effective and efficient fashion now can be clearly seen. It is concluded that the international public diplomacy radio broadcasting community now should position itself to assist in seeing that the kind of system and service it needs is forthcoming. For instance, it should see the appropriate frequency allocations, preferably at L-band, are made available at the WARC '92 conference. In addition, generally, it should position itself to see that it makes the transition from surface-based software to space-based UHF in a sensible, paced and prudent fashion     

Provision of continuous VCR functions in interactive broadcast VoD systems

Video broadcasting is one of the feasible solutions to implement a large-scale video-on-demand (VoD) system. Nevertheless, it is still an open issue for the provision of continuous VCR functions in a delay insensitive broadcast VoD system. In this paper, we propose to jointly optimize an active buffer management scheme with contingency channels to support the VCR functions in an efficient protocol called partitioned broadcasting. We develop a greedy channel management scheme by exploiting the property of the broadcasting protocol such that the system bandwidth capacity can be fully utilized. Incorporating the channel management scheme with the partitioned video broadcast, the VoD system not only provides delay insensitive services but also handles all the interactive requests. Extensive simulation results demonstrate that the partitioned broadcasting system outperforms the traditional system based on the staggered broadcasting protocols. It is found that 20 broadcasting channels and 10 contingency channels are sufficient to support on average 720 customers for a single video with less that one second start-up delay and all types of VCR functions.