Satellite communication systems for domestic/business services

This paper is composed of two parts. The first part addresses some topics associated to the implementation of FDMA/TDM systems for ‘business’ services applications, operating at K_a band. A modular regenerative and processing satellite repeater, each module capable of handling up to 16 up-link carriers in the 2 Mb/s range is considered. Available coding techniques were reviewed; concatenated codes seem highly interesting because of the high coding gains achievable with two simpler co-decoding processes in series, and also because they lead to an implementation wherein the internal coder is installed on board the satellite, while the external one is installed in the user terminals. The problem of keeping stable the up-link carriers in the satellite demodulators is discussed and a compensation method is proposed. Finally, simulation results of co-decoding and carrier extraction performance are illustrated. The second part concerns the implementation of a multifrequency TDMA system. This is a hybrid system whereby the access for up-links uses time and frequency slots in a time-frequency map. The adoption of a clock synchronous network allows a frame for which no preamble and guard time are inserted between the burst. The error contributions and the performance of the clock synchronous network are assessed. A solution to the problem of fast phase/frequency estimation is proposed. For a clock synchronous network fast algorithms suitable for frequency demultiplexing and detecting of the FDM signal could be adopted; a modular solution to the implementation of the demultiplexer and detector is proposed based on the use of an optimized matched filter; a multistage scheme minimizes the number of multiplications.     

Satellite direct broadcast

A brief history and commentary on the development of satellite direct broadcast (direct broadcast satellite, or DBS) to small user terminals is given, and the interrelations among the technical, economic, and political aspects are discussed. The fundamental technical problems in the transmission of video and audio directly to small user terminals are reviewed at a basic level, and points of particular interest relating to DBS are highlighted. The effects of improved transmission systems using multiplexed analog components and of high-definition television are related to the satellite transmission problems. The conflicting requirements of performance, compatibility with existing equipment, competition with other means of transmission, and vested political interests are pointed out. A reasonably complete summary of existing programs, both true DBS and near DBS, is given     

Splitting schedules for Internet broadcast communication

The broadcast disk provides an effective way to transmit information from a server to many clients. Work has been done to schedule the broadcast of information in a way that minimizes the expected waiting time of the clients. Much of this work has treated the information as indivisible blocks. We look at splitting items into smaller pieces that need not be broadcast consecutively. This allows us to have better schedules with lower expected waiting times. We look at the case of two items of the same length, each split into two halves, and show how to achieve optimal performance. We prove the surprising result that there are only two possible types of optimal cyclic schedules for items 1, and 2. These start with 1122 and 122122. For example, with demand probabilities p₁= 0.08 and p₂= 0.92, the best order to use in broadcasting the halves of items 1 and 2 is a cyclic schedule with cycle 122122222. We also look at items of different lengths and show that much of the analysis remains the same, resulting in a similar set of optimal schedules     

Frequency planning for broadcast services in Europe

The regular lattice theory is a powerful tool to achieve an efficient use of the frequency spectrum when assigning frequencies or channels to broadcast transmitters. In this paper the basis of the theory is explained, and it is shown how it can be implemented in planning broadcasting transmitter networks for AM or FM sound and television. Physical laws and local considerations will, of course, influence the design of networks and some practical examples are given to make clear how they have been taken into account. The theory will be useful not only in building or remodeling actual transmitter networks, but also with the aim of optimizing technical parameters such as channel spacing, transmitter characteristics, etc. In this later case computerized method will be efficient. Regular lattices have been of some help in former ITU planning conferences, and will certainly be of assistance to experts in charge of achieving good plans in the future conferences of the years to come.     

SDN-based mobile packet core for multicast and broadcast services

Wireless Networks - The current mobile packet core network is evolving to cope with the pressure of the mobile traffic explosion and the advent of new services. Software-defined networking (SDN) is...     

手机电视业务标准——DVB-H

DVB-H标准是目前手机电视业务创建过程中普遍关注的一个热点话题,具有广泛的内涵。本文讨论了DVB-H的多协议封装前向纠错、时间分片、4K模式和深度符号交织、传输参数信令等关键技术,并分析了手机电视的几种运营模式,最后总结了DVB-H标准存在的问题以及发展前景。     

Determination of minimum cost interference between services sharing the same frequency bands

The optimum value of interference between two radio communication systems sharing the same frequency band is the level that minimises the total cost, including capital costs and annual costs;it should therefore be used in system design. The maximum permissible value of interference is the value corresponding to a significant increase in minimum total cost as the interference-controlling parameters are varied. The paper describes a procedure to determine these values and achieve the partitioning of the performance objectives specified by Ccir among the various noise and interference sources. The method is applied to mutual interference between an Fdm-Fm terrestrial radio-relay system and an Scpc/psk/4 øsatellite earth station.     

Satellite radio interface and radio resource management strategy for the delivery of multicast/broadcast services via an integrated satellite-terrestrial system

A variety of hybrid systems combining third-generation mobile communication networks with broadcast systems have been proposed for the delivery of multimedia broadcast multicast services (MBMS) to mobile users. The article discusses one of these alternatives, which involves the use of a geostationary satellite component for MBMS delivery. In particular, it proposes a radio access scheme for the satellite component of the system that features maximum commonalities with the standardized T-UMTS WCDMA-based interface. The ultimate advantages of this approach are more efficient delivery of MBMS as far as the mobile network operator is concerned. The required adaptations at the interface layers are described, and the radio resource management strategy that fulfills the particular requirements of the satellite system is presented.     

Hybrid ARQ schemes for point-to-multipoint communication overnonstationary broadcast channels

Hybrid automatic-repeat-request (ARQ) error control schemes make use of both error detection and error correction in order to achieve high throughput and low undetected error probabilities on two way channels. Two hybrid ARQ schemes, termed hybrid go-back-N (HGB- N) and hybrid selective-repeat (HSR), are proposed for point-to-multipoint communications over broadcast channels. Both schemes incorporate a concatenated code for error correction and error detection. The performance study of the hybrid schemes is based on a two-state Markov model of a burst noise channel. An analytic solution is derived for the throughput efficiency of the HSR scheme, while approximations and computer simulation are used to evaluate the throughput efficiency of the HGB-N scheme. It is shown that the schemes perform considerably better than the corresponding pure ARQ schemes in which a block code is used for error detection only, especially in environments with a large number of receivers and large channel roundtrip delays, such as satellite broadcast links     

基于NR的5G多播/广播关键技术

交互式网络电视(internet protocol television,IPTV)、群组通信等应用具有明显的多播/广播业务特征,5G蜂窝移动通信系统需要高效支持这类应用数据的传输。首先,按照多播/广播业务数据从5G核心网经由基站到终端的不同传输方式分析了5G多播/广播系统的基本架构;然后,从无线空口协议栈、物理层与高层协议增强、业务过程与业务连续性等方面对5G多播/广播无线传输技术进行了详细分析;最后,对5G多播/广播技术的后续演进方向进行了展望。     

Satellite systems for personal communication networks

The paper addresses some issues related to Satellite Personal Communication Networks (S‐PCNs). The role of satellite communications in that scenario is discussed, and some characteristics of S‐PCNs are identified. In addition, the problem of the integration of S‐PCNs with the Universal Mobile Telecommunication System (UMTS) is considered. In this respect an original methodology for accomplishing such integration is proposed; such methodology aims at avoiding complex protocol conversions at the interfaces between the terrestrial and the satellite segment. The paper is partly based upon the work performed by the authors in the framework of the European Community INSURED Project “INtegrated Satellite UMTS Real Environment Demonstrator”. This revised version was published online in June 2006 with corrections to the Cover Date.     

An integrated network/storage architecture for sharing high-quality broadcast TV contents

With the advent of personal video recorders (PVRs), the way people watch TV is rapidly changing. By recording or time-shifting live TV programs into the embedded-disk storage of a PVR, people can watch what they want independent of the broadcasting schedule. Furthermore, peer-to-peer networking technology provides an additional TV content distribution channel to unidirectional broadcasting. However, due to the current limited broadband bandwidth, it is difficult to support high-quality TV content streaming between PVRs on the Internet. In this article we propose novel integrated network/storage architecture to provide the streaming of high-quality broadcast TV contents over fast network connections. To take full advantage of our system resources, we also develop efficient sharing schemes such as matching of a communication pair and channel assignment for extensive time-shifting.     

数字音频广播服务综述

1901年12月，马可尼(G．Marconi)用莫尔斯(Mors)电码第一次成功地完成了相距约2900km的两地间的无线电通信实验。这次通信实质上用的是数字无线电技术，因为莫尔斯电码是数字量。但由于以数字电子计算机为基础的数字技术当时尚未诞生，从第一座无线电台开始服务的1922年到20世纪80年代末、90年代初，60多年时间内模拟无线电技术一直统治着无线电广播领域。     

Scheduling data broadcast in asymmetric communication environments

With the increasing popularity of portable wireless computers, mechanisms to efficiently transmit information to wireless clients are of significant interest. The environment under consideration is asymmetric in that the information server has much more bandwidth available, as compared to the clients. In such environments, often it is not possible (or not desirable) for the clients to send explicit requests to the server. It has been proposed that in such systems the server should broadcast the data periodically. One challenge in implementing this solution is to determine the schedule for broadcasting the data, such that the wait encountered by the clients is minimized. A broadcast schedule determines what is broadcast by the server and when. In this paper, we present algorithms for determining broadcast schedules that minimize the wait time. Broadcast scheduling algorithms for environments subject to errors, and systems where different clients may listen to different number of broadcast channels are also considered. Performance evaluation results are presented to demonstrate that our algorithms perform well.     

Analysis and modelling of broadcast services for TDMA wireless ad hoc networks

MAC protocols designed to provide QoS in wireless ad hoc networks need to be able to reserve and control resources efficiently. To this purpose, TDMA-based networks often lie in a frame subdivision that consists of a broadcast control phase and an information phase. In the control phase, each active terminal broadcasts signalling information required to handle the access to the data resources. Analysis and modelling of the broadcast service is carried out, which allows an efficient frame dimensioning in this scenario     

On a reliable data communication broadcast system

This paper describes the design and implementation of a 3 KHz band HF data broadcast communication system, using a quantized frequency modulation, adaptive lattice equalizer together with forward error correcting code (FEC) to obtain a high link reliability and low error rate. A frequency diversity approach is also used in the selection of the timely best carrier frequency, and a microcomputer is implemented into the system for automatic best carrier acquisition, data transmission and clock synchronization, with minimum operator's attention. Extensive field experiments were conducted and experimental results indicate that the system can achieve, for daytime operation, a link reliability of 87–98%, with a probability of error between 10^?4 to 10^?5, depending upon data rate (50, 75bps) and FECs used. For night time operation, the link reliability reduces to from 65–93% with a probability of error down in the order of 10^?3.     

Equal resource sharing scheduling for PCS data services

For high speed mobile communication applications, the data rate can be increased by using multiple channels (or time slots) instead of one channel. To reduce the high blocking rate of multiple channels assignment, flexible resource allocation strategies have been proposed. This paper proposes the Equal Resource Sharing Allocation scheme (ERSA scheme) for flexible resource allocation. The ERSA scheme dynamically averages the allocated resource to the call requests based on the number of calls in a base station. The scheme accommodates the maximum number of requests while providing acceptable quality to the admitted requests. We developed an analytic model to investigate the performance of ERSA, and conducted simulation experiments to validate the analytic model. We define satisfaction indication SI as the performance measurement of the resource allocation algorithm. The experiment results indicate that the ERSA scheme outperforms other resource allocation algorithms proposed in our previous study.     

卫星通信与卫星互联网

由于受技术进步、全球竞争、互联网等因素的影响,卫星通信的产业格局和服务形式正在发生结构性的变化。这些变化主要表现在以下几个方面：一、休斯、吉莱特、劳拉、洛克希德马丁等传统卫星制造商纷纷从上游制造行业进入到下游运营服务行业;Intelsat、Panamsat、Inmarsat这些卫星运营公司已从传统电信市场扩展到互联网市场;SES Astra、Eutelsat、Panamsat等公司从基本的转发器租赁服务进入到提供卫星网络服务等增值服务;各类运营商已从话音、数据等单一服务转向多媒体、互联网等综合服务,同时将服务范围从局部地区延伸到全球,而且…     

广播通信融合网络能效分析

针对广播通信融合网络的性能分析问题,提出了一种新的系统模型及能效分析方法。从用户请求业务角度出发,将请求的业务分类为热门与非热门业务。并基于随机空间网络模型,将融合网络中的蜂窝基站与用户建模为2个独立的空间泊松点过程（PPP）随机分布,而广播大塔位于服务区域中心。通过考虑广播网的覆盖范围及蜂窝网的中断概率推导出广播与通信融合网络下系统的能量效率（EE）闭合表达式,进一步讨论热门业务概率对融合网络能效的影响。仿真结果表明,基于讨论的融合系统模型,并考虑了通用场景下的基站和用户密度,当热门业务超过总业务的 后,融合网络能效相比于单蜂窝网络有显著提高。这种新的系统模型及能效分析方法为后期分析融合网络总体性能奠定了基础。     

无线局域网中基于可靠广播的文件共享

文件共享作为人们工作学习中最有效的方式之一,但是在网络状况不好甚至是没有网络的时候用户想要共享文件是不能实现的,针对此问题,提出了一个在移动终端上实现的文件共享系统。在本系统中,用户可以自行组织成网络进行文件共享,不必考虑外部的网络环境,通过底层使用Ad Hoc网络,在网络内部使用UDP广播,可实现各节点快速的文件共享。通过无线局域网内部的文件共享实验,证实了该系统的性能不会因为网络中节点数目的增加而下降;通过移动终端节点和服务器节点文件共享的实验,证实不能连接到服务器的节点也可以和服务器实现文件共享,而且与每个节点都要主动和服务器共享文件的情况相比,提高了文件共享的效率。