Space radio services and WARC-MOB-87

A recent conference of the ITU has agreed upon worldwide frequency allocations near 1600 MHz for communication by satellite with mobile stations on land, and has permitted the use of some aeronautical mobile-satellite frequency bands for passengers' in-flight telephone calls to the ground. Frequencies for systems for locating mobile stations by radio, using satellites, were allocated.     

Europe prepares for WRC-95: mobile satellite service issues

European preparations for World Radiocommunication Conferences are coordinated within the European regional posts and telecommunications organization known as the CEPT. The basic objective of the European proposals is to achieve an even playing field for the introduction of competitive mobile satellite services that can provide global services from the earliest feasible common date. Europe believes the additional allocations made at the 1992 conference are sufficient for the foreseeable future, especially now that there is an opportunity every two years to make additional allocations should the need be proven. What must be agreed upon, however, are the allocations for the feeder links to the mobile satellite service to complement the 1992 allocations for service links. Europe also need to consider the technical constraints that were placed on the use of these service links at the 1992 conference. Of particular concern to Europe, is the most unsatisfactory conclusion in 1992 on the date of availability of the 2 GHz mobile satellite service allocations. The article describes the European proposals on these mobile satellite issues     

Provisions for High Frequency Future Use

An area of widespread interest at the 1979 World Administrative Radio Conference (WARC-79) was concerned with allocation proposals related to the modification of the high-frequency (HF) (4-27.5 MHz) portion of the spectrum. From a wide range of proposals, the Conference adopted allocation provisions that reduced the exclusive fixed-service bands by two-thirds, made significant allocations to the broadcasting and maritime-mobile services, and provided somewhat lesser spectrum provisions for the amateur service. Shared use of fixed bands by the mobile service was greatly increased. Few changes were made to aeronautical service allocations. Provisions were planned to remove an unused fixed-service assignment from the International Telecommunication Union (ITU) Master Frequency Register, and to provide special assistance to Less Developed Countries (LDC's) to enable them to better meet their fixed requirements. A conservative schedule of changes, through 1994, was adopted, including several specialized planning conferences to assist in optimizing the use of HF bands. With continued national needs and improved technology being developed and adopted by the ITU member countries, systems in all authorized HF services will be widely used to meet requirements of the world community for a long time to come.     

Broadcasting

Three major allocation issues involving the broadcasting and broadcasting-satellite services that will be discussed at the 1992 World Administrative Radio Conference (WARC-92) are examined. They are expansion of frequencies for conventional high-frequency (shortwave) broadcasting, new frequencies for both satellite and terrestrial digital audio (radio) broadcasting to handheld and automobile receivers, and new frequencies for studio-quality high-definition television broadcasting from satellites. The bands that are viable candidates for these services are discussed     

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     

Mobile communications

An important issue facing the 1992 World Administrative Radio Conference, namely, determining how to provide additional spectrum for both existing and entirely new mobile services, is examined. At least six types of mobile systems will be seeking new or expanded allocations; three involve satellites and three rely on primarily terrestrial techniques. All but one will be forced to compete for allocations in the same crowded 1-3 GHz frequency range. The various allocation proposals are discussed     

CD by radio-digital radio broadcasting

Engineers have been looking at ways of broadcasting a digital radio service to the general public, which would ideally have the following features: sound quality comparable with that of the CD; reliable reception to all listeners in the coverage area; capability of offering coverage of all listeners; capability of fixed, mobile and portable reception using simple low grains antennas; simple push-button programme selection-no tuning; frequency efficiency, so that many services can be provided in any spectrum available; and capability of operation from terrestrial transmitters and/or satellite. The author describes the requirements of a digital audio broadcasting system regarding intersymbol interference and then discusses COFDM, coded-orthogonal frequency division multiplex. The author also discusses low-bit-rate sound, terrestrial transmission, satellite broadcasting, receivers, frequency allocation and system testing     

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     

The maritime radio spectrum future

Future satisfaction of the electromagnetic spectrum needs of the maritime mobile service is dependent on the translation of those needs to frequency allocations. In September 1979, over 100 countries will consider all of the spectrum, and make changes to meet perceived needs of radio services, including maritime needs up to the year 2000. This conference, the World Administrative Radio Conference 1979, will have a significant impact on future maritime radio operations. Issues, procedures, competing requirements, are explored to enable a better understanding of the regulatory process for frequency allocations.     

Radio Astronomy and Spectrum Management: The Impact of WARC-79

As a valid use of the radio spectrum and an official radio service, radio astronomy was very much a part of the 1979 World Administrative Radio Conference (WARC-79). The allocation of frequency bands is vitally important for the sustained health of the science. WARC-79 provided first the impetus for astronomers, worldwide, to examine the allocation requirements of radio astronomy and then the opportunity to communicate those needs to the regulatory community. The characteristics of radio astronomy, the criteria for interference-free operation, possibilities for sharing with other radio services, and the need for frequency-band allocations are discussed because all bear directly on an evaluation of the Conference. The Final Acts of WARC-79 are examined from the viewpoint of their impact on radio astronomy.     

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.     

A framework for investigating radio resource management algorithms in TD-SCDMA systems

TDD-CDMA, globally recognized as the basis for Chinese 3G, is designed for symmetrical and asymmetrical 3G mobile services. As a time-division duplexing system, TD-SCDMA works in unpaired frequency allocations, supporting the flexible allocation of uplink/downlink slots in one carrier, and adapting to the different system loads between uplink and downlink. Dynamic time slot allocations make it more spectrally efficient than paired uplink/downlink carriers. Consequently, TD-SCDMA can make full use of the radio spectrum through optimal adaptive radio resource allocation. In order to support peak rates of 5 Mb/s or higher, the TD-SCDMA standard is enhanced via high-speed downlink packet access (HSDPA) mode. In this article the properties and strategies of radio resource management (RRM) are introduced, and the differences in admission control, power control, handover, load control, dynamic channel allocation, and adaptive HSDPA techniques between TDD-CDMA and the conventional FDD-CDMA system are analyzed. Some advanced strategies and architectures for TDD-CDMA RRM algorithms are presented. Since uplink multi-user detection (MUD) and smart antenna (SA) techniques are adopted in TD-SCDMA, the RRM algorithms based on MUD and SA are investigated further. In addition, these advanced RRM algorithms are characterized by an OPNET-based dynamical system-level simulator.     

The Impact of WARC-79 on Space Applications

Prior to the 1979 World Administrative Radio Conference (WARC-79), no frequency bands were allocated for remotesensing measurements. Actions taken by the WARC insure that frequencies will be available for such use, and that operations can be conducted without harmful interference on a worldwide basis for the benefit of all nations. Allocations employed for transfer of scientific data from spacecraft in all regions of space from near-Earth orbit to deep-space planetary ranges were significantly improved. New global allocations for Earth exploration-satellites will permit worldwide acquisition of Earth exploration data both via direct transmission and via relay satellites. New allocations for meteorological satellite data transmission will permit wide-band applications such as direct reception of highresolution picture data by users. Satellite-aided search and rescue systems will benefit from WARC decisions to allocate frequencies exclusively for emergency radiobeacon systems using space techniques. Bands to provide links between the satellite and Earth were designated for distress and safety operations. Time and frequency services with accuracies in the 10- to 50-ps range, needed to meet future system requirements for precise time and frequency information, will be possible because of WARC actions to allocate frequency bands with suitable bandwidth for these services. The search for communications from extraterrestrial intelligence was afforded a degree of protection near several spectral lines of basic physical interest.     

U.S. Perspectives on the New Allocations Table

One of the major activities at the 1979 World Administrative Radio Conference (WARC-79) was revision of the International Table of Frequency Allocations. This paper gives an overview of significant ways in which these international allocations were changed. Revisions to the U.S. national allocations are still in process; however, some comments on the national allocation table are offered.     

Integration of satellite and terrestrial systems in future multimedia communications

In this article we examine the role of satellite communications in future telecommunication networks and service provision. Lessons from the past indicate that satellites are successful as a result of their wide area coverage or speed to market for new services. Niche areas such as coverage of air and sea will persist, but for land masses convergence of fixed, mobile, and broadcasting will dictate that the only way forward for satellites is in an integrated format with terrestrial systems. We outline future ways forward for satellites, and discuss the research challenges and technology advances needed to facilitate this integrated approach.     

Multimedia goes mobile in broadcast networks

In digital broadcasting systems, like Eureka 147 DAB, it is possible to separate the actual service from the transmission system. Such a separation enables the distribution of any type of digital data to stationary, portable, or mobile terminals. However, a radio channel for mobile reception has certain characteristics to which existing multimedia services must adapt. We present a multimedia system model for digital broadcasting. We also discuss implementing this model within the broadcasting framework     

Regulatory Procedures and WARC-79

There are two major elements of a General World Administrative Radio Conference such as WARC-79. One is to review and revise allocations of radio frequencies to functional services such as fixed, mobile, satellite, and radionavigation. The other major element is the detailed radio regulations concerning use of these allocations by member Administrations. These regulations combine technical, economic, geopolitical, and other considerations into a framework which attempts to satisfy the perceived requirements of all Administrations. This aspect of WARC79 is the subject of this paper. As will be seen, some substantial changes in regulations were made at the Conference, especially those concerning HF assignments and use. Other changes are implicit in the Resolutions for future conferences which were adopted at WARC-79. The key to success in framing effective and acceptable allocations, and regulations, is cooperation. In this respect, WARC-79 was not much different from preceding conferences, despite contrary misgivings.     

数字移动电视单频网的建设

数字移动电视广播系统是我国广播电视综合覆盖体系中的重要组成部分,单频网(SFN)是目前地面数字电视广播系统覆盖最好的方法之一。介绍数字移动电视单频网建设中的一些经验和心得,包括合理指配单频网数字台站、选择合适的单频网传输模式、单频网时延的合理设置等。     

Improving mobile network performance with two queueing buffer allocations of priority-based queueing scheme

As current mobile core network systems are expected to evolve into all-IP networks, packet switching will be a prerequisite for all mobile applications. Next-generation mobile networks, as envisioned by ITU-T, are packet-based networks capable of providing consistent and ubiquitous service to end users, independent of the network, access technology, and device used. This study discusses the differentiated packet forwarding performance of four major types of mobile network traffic under the proposed mobile network priority-based queueing (MPQ) scheme with two queueing buffer allocations, namely dynamic queueing buffer (DQB) allocation and overflow queueing buffer (OQB) allocation. As different queueing buffer allocations are adopted to store arriving packets in DQB and OQB, the MPQ scheme shows different packet forwarding performance under these two methods. In this study, we use ns2 (Network Simulator version 2) as the simulation platform to simulate several scenarios. The simulation results show that the MPQ scheme is able to support differentiated packet forwarding behavior for mobile traffic with both DQB and OQB allocations in a mobile core network. Some issues were identified in the MPQ scheme with both DQB and OQB allocation, which will need to be addressed.     

Dynamic bandwidth allocation in DVB-T networks providing IP services

The combination of high capacity, signal robustness, and worldwide acceptance have made digital terrestrial broadcasting (DVB-T) one of today's more promising technologies, while newly adopted standards support the integration of digital television programs and data services within a single multiplex, offered to both stationary and mobile end users. The paper addresses the issue of optimal bit rate allocation among DTV and IP services within the DVB-T multiplex, and demonstrates a novel configuration providing real-time sharing of the available bandwidth via an algorithm based on service hierarchy and perceptual quality assessment. The architecture and performance of a fully functional DVB-T testbed developed on this concept is also presented.