On the role of future high-frequency BFWA systems in broadband communication networks

Frequencies above 25 GHz represent a great opportunity for BFWA systems because of the extraordinary bandwidths available. But standards for high-frequency BFWA published so far have not been able to unleash this potential. We believe this is due to the fact that the performance characteristics have been shaped considering these systems in isolation. This has brought on a mismatch between what these systems can offer and what is really needed. Most of today's broadband networks focus on data communication. In this article, we focus on how to make high-frequency BFWA systems fit better into the architecture required for fulfilling the "broadband for all" vision (i.e., including more video streaming and transfer). By modifying and extending the standards to fulfill the performance requirements implied, high-frequency BFWA systems can play an important role in future high-capacity broadband networks with flexible resource allocation     

HDTV制式与HDTV

本文对世界三大HDTV制式——日本MUSE、西欧HD-MAC和美国多种与NTSC兼容共存HDTV制式中具有代表性的制式,从原理和技术性能上进行了讨论比较,其中主要有MUSE、N-MUSE、NCM-6、NCM-9、D-MAC/packet、D_2-MAC/packet、HDS/NA、HDS/NA-6、SC-HDTV等。并根据今后HDTV发展方向给出了目前国际上与现有电视制式兼容共存的几种途径,以及判断一种HDTV制式优劣的标准。     

Coexistence of broadband power line communication systems

es and the radiation field are finally determined.     

宽带无线通信网络中频谱效率的计算方法

频谱效率是无线通信网络的一个重要参数，它描述了位速率与带宽之间的相互关系。从多角度对频谱效率进行分析，给出了一套实用的有效的频谱效率计算方法。     

The role of vsat systems in broadband networks and intelligent networks

The scope of this paper is to present the status and the preliminary results of the research activities that Telespazio is carrying out with the aim at identifying the role of the VSAT systems in the advanced telecommunications services, which will be dominant in the second half of nineties and beyond. The first part of the paper is devoted to an overview of the evolution trend of the terrestrial networks. The main body of the paper presents the results of our investigations on the application of VSAT systems in two fields: broadband networks and intelligent networks. Background information has been intentionally added for the easier comprehension of the topics presented in the paper. A list of acronyms appears as an Appendix.     

Adaptive point-to-point communication approach for subscriber stations in broadband wireless networks

The point-to-multipoint (PMP) mode is considered the well-adopted transmission type that is supported by the IEEE 802.16 standard. The base station (BS) is served as the centralized coordinator to control and forward packets for the subscriber stations (SSs) within the network. In the case that two SSs intend to conduct packet transmission, it is required for the packets to be rerouted to the BS before arriving at the destination SS. The communication bandwidth is apparently wasted due to the rerouting processes. In this paper, an adaptive point-to-point communication (APC) approach is proposed to achieve direct communication between SSs within the PMP mode of the IEEE 802.16 standard. The BS is coordinating and arranging specific time intervals for the two SSs that are actively involved in packet transmission. Based on channel conditions among the BS and the SSs, the packet transmission operation is switched between direct communication and indirect communication in the APC approach. Both the architectural design and analytical modeling of the proposed scheme are conducted in this paper. The effectiveness of the proposed APC approach in terms of user throughput and its corresponding overhead can be observed via both the analytical and simulation results.     

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     

Design considerations for broadband indoor infrared wireless communication systems

Recently there has been a growing interest in using infrared light for broadband indoor wireless communications. There are two major limitations for establishing a wideband infrared communications link. The first and most important limit is the power requirements of such a link. The second important impairment is the intersymbol interference caused by multipath dispersion. In this paper we address the issue of designing an optimized transmission system to provide the best power efficiency for an infrared link. Important parameters that should be considered for this design and some examples of efficient link designs are discussed. The suggested designs can improve the power efficiency of an indoor infrared link up to 4 to 8 dBo while providing a smaller rms delay spread, more robustness to shadowing and a more uniform distribution of power. Characteristics of the indoor infrared channel depends upon the directions of the receiver. This dependency can be used in designing a direction diversity receiver to decrease the rms delay spread of the received signal and to reduce the effects of noise by using proper combining techniques. We discuss the effects of receiver direction and field-of-view on the channel parameters and suggest a configuration for a direction diversity receiver.     

Design of broadband transimpedance amplifier for optical communication systems

This paper describes the design and analysis of broadband transimpedance amplifiers (TIAs) based on Regulated Cascode (RGC) configuration. The focus is to deal with bandwidth restriction occurring in optical receivers coming from TIA input parasitic capacitances. Despite the conventional method for broadband RGC TIA design that a ladder matching network is employed to isolate the input capacitance of TIA and the photodiode capacitance, the proposed TIA eliminates the effects of these parasitic components by absorbing them in a T-matching network. The conventional broadband RGC TIA is analyzed and the disadvantages of the ladder matching network is demonstrated in a TIA design example. The proposed RGC TIA is simulated on 0.18-μm standard RF CMOS process. The simulation results presented show that the Gain-Bandwidth product (GBW) is extended by a larger factor compared to that of the conventional broadband RGC TIA while the biasing conditions and the value of the photodiode capacitance are considered the same.     

基于协同机理的下一代宽带无线通信系统

介绍了协同技术基本原理,基于协同技术的先进性,提出了下一代宽带无线通信系统的异构性和泛在性等要求可以通过协同技术得到保证。介绍了一种基于协同机理的下一代宽带无线通信系统的网络结构,并详细介绍了其中的关键支撑技术。     

宽带卫星通信系统中强干扰抵消方法

在强干扰环境下,星上信道化器的关键部件模数转换器(ADC)会发生数据溢出,严重影响星上载荷转发性能。为此,提出了一种基于抵消思路的宽带卫星通信系统中强干扰抑制方法。该方法首先在数字域对强干扰进行检测、提取和相位幅度调整,然后在模拟域进行强干扰抵消,最后通过检测反馈保证抵消效果。给出了数字域提取滤波器的基本设计方法和实现步骤,并且结合工程实际,采用数学形态学滤波方法消除卫星宽频带噪底起伏带来的影响。研究与仿真结果表明,该方法能对强干扰进行有效抑制。     

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.     

宽带卫星通信系统技术发展及应用前景

一、宽带热──虚火,还是务实？ 宽带卫星通信是整个宽带通信系统的一部分,因此,应先看看当前宽带通信的情况如何。 近几年来,“宽带”成为通信领域的头号热点。宽带传输、宽带交换、宽带无线、宽带接入、宽带卫星……都向宽带靠拢,不讲宽带就不时髦,就没有吸引力。有几本知名杂志也改了名,如美国的《Satellite Communications》（卫星通信）改为《Satellite Broadband》（卫星宽带）;原《世界有线电视信息》改名为《世界宽带网络》。 而今年以来,各种媒体对宽带通信的报道不能说是“铺天盖地”,也差不多是“连篇累牍”。然而,…     

移动通信系统中宽带功放线性化设计与仿真

自适应数字预失真技术能够解决宽带高峰均比信号经过功放产生的非线性失真问题.主要介绍了自适应数字预失真的结构、预失真器的数学模型及相关的自适应算法.仿真结果表明采用自适应数字预失真技术能够显著地改善功放输出信号的带外频谱失真,是一种有效、灵活的技术.     

Granulated broadband networks

A new ATM platform concept can accelerate the introduction of broadband services with enhanced integration of existing narrowband services-including POTS. In order to reduce initial costs for broadband services, an ATM-based platform must be constructed for various services. In particular, existing public switched telephone network (PSTN) services can be economically accommodated in ATM-based broadband networks, and the costly part of the network could be shared by dominant PSTN services. This article proposes a granulated broadband network (GBN) concept as an intermediate platform for achieving broadband aspects of ISDN (B-ISDN)     

Probabilistic fault localization in communication systems using belief networks

We apply Bayesian reasoning techniques to perform fault localization in complex communication systems while using dynamic, ambiguous, uncertain, or incorrect information about the system structure and state. We introduce adaptations of two Bayesian reasoning techniques for polytrees, iterative belief updating, and iterative most probable explanation. We show that these approximate schemes can be applied to belief networks of arbitrary shape and overcome the inherent exponential complexity associated with exact Bayesian reasoning. We show through simulation that our approximate schemes are almost optimally accurate, can identify multiple simultaneous faults in an event driven manner, and incorporate both positive and negative information into the reasoning process. We show that fault localization through iterative belief updating is resilient to noise in the observed symptoms and prove that Bayesian reasoning can now be used in practice to provide effective fault localization.     

Traffic models in broadband networks

Traffic models are at the heart of any performance evaluation of telecommunications networks. An accurate estimation of network performance is critical for the success of broadband networks. Such networks need to guarantee an acceptable quality of service (QoS) level to the users. Therefore, traffic models need to be accurate and able to capture the statistical characteristics of the actual traffic. We survey and examine traffic models that are currently used in the literature. Traditional short-range and non-traditional long-range dependent traffic models are presented. The number of parameters needed, parameter estimation, analytical tractability, and ability of traffic models to capture marginal distribution and auto-correlation structure of the actual traffic are discussed     

Testing HDTV terrestrial broadcasting systems

The Advanced Television Test Center (ATTC) is a private sector, nonprofit organization created to undertake full, fair, and impartial testing of the various advanced television (ATV) systems that have been proposed as the United States terrestrial broadcast standard. Cable Television Laboratories (CableLabs) organized by the cable television industry operates, in cooperation with ATTC, a state-of-the-art laboratory testing facility capable of thoroughly evaluating the proposed ATV systems when transmitted by cable TV, including both coaxial cable and fiber-optic transmission. Presently there are six systems scheduled for test by the ATTC and CableLabs. The systems and their scheduled test dates are shown. One of the systems is an enhanced NTSC compatible system and the other five are high-definition television (HDTV) simulcast systems. Four of the simulcast systems are digital. Both objective and subjective tests of all six systems are discussed     

High‐resolution compressive channel estimation for broadband wireless communication systems

Broadband channel is often characterized by a sparse multipath channel where dominant multipath taps are widely separated in time, thereby resulting in a large delay spread. Accurate channel estimation can be done by sampling received signal with analog‐to‐digital converter (ADC) at Nyquist rate and then estimating all channel taps with high resolution. However, these Nyquist sampling‐based methods have two main disadvantages: (i) demand of the high‐speed ADC, which already exceeds the capability of current ADC, and (ii) low spectral efficiency. To solve these challenges, compressive channel estimation methods have been proposed. Unfortunately, those channel estimators are vulnerable to low resolution in low‐speed ADC sampling systems. In this paper, we propose a high‐resolution compressive channel estimation method, which is based on sampling by using multiple low‐speed ADCs. Unlike the traditional methods on compressive channel estimation, our proposed method can approximately achieve the performance of lower bound. At the same time, the proposed method can reduce communication cost and improve spectral efficiency. Numerical simulations confirm our proposed method by using low‐speed ADC sampling. Copyright © 2012 John Wiley & Sons, Ltd.