A quality-aware VoWLAN architecture and its quantitative evaluations

The deployment of wireless LAN and other communication media, such as 3G cellular, is proceeding rapidly. In the near future, multiple WLAN carriers, together with 3G cellular and other communication carriers, will provide their services in a complementary fashion. Furthermore, next-generation mobile phones, which may use voice and data services simultaneously, will connect these networks. In the present article we design and evaluate a new network architecture that ensures appropriate QoS for next-generation mobile phones. Through performance evaluations, we show that our architecture improves QoS for voice communication.     

卫星通信无线宽带接入技术研究

无线接入技术是无线通信系统的核心技术之一,也是实现卫星组网,提高航天信息系统效率的关键技术。基于对当前卫星移动通信系统和地面移动通信系统的无线接入技术的现状分析,指出卫星移动通信无线接入面临的六大问题和发展趋势;提出基于连接标识的面向连接的卫星移动通信无线接口技术方案。该方案实现复杂度低,灵活性高,适应多种物理层技术,扩展性强,并且针对每一个业务连接具有不同的QoS保证。     

Wireless communications in the twenty-first century: a perspective

Wireless communications are expected to be the dominant mode of access technology in the next century. Besides voice, a new range of services such as multimedia, high-speed data, etc. are being offered for delivery over wireless networks. Mobility will be seamless, realizing the concept of persons being in contact anywhere, at any time. Two developments are likely to have a substantial impact on the mobile communications systems deployed in the twenty-first century: the adoption of International Mobile Telecommunications-2000 and wireless asynchronous transfer mode (ATM). They are two different but cooperative approaches to providing high-speed wireless access. The limitations of the radio-frequency spectrum and radio channel propagation impose special constraints on the technologies of systems to be deployed. To make future mobile systems globally acceptable, standardization efforts are underway in the International Telecommunications Union and the ATM Forum. This paper reviews the international standardization efforts, the challenges to the technologies imposed by the radio spectrum limitations, radio channel propagation-induced distortions, and possible solutions. Evolution, migration, and architecture issues also are discussed     

卫星通信系统多优先级信道预留分配策略

随着通信系统的不断发展,对融合地面系统的天地一体化网络的研究越来越多,而卫星通信系统中,由于卫星高速移动等特性,不可避免需要对呼叫的接入切换进行研究。针对天地一体化信息网络需要支持多场景多业务情况下的通信需求,考虑不同呼叫优先级不同,对多优先级的多种呼叫业务进行考虑。根据信道预留的思想,对不同优先级接入与切换呼叫设定不同的可用信道数,优先级越高的呼叫,为其留更多的可用信道以确保其接入信道成功。同时,由于动态信道预留较固定信道预留能够更好地利用信道资源,最终考虑多优先级下的动态信道预留策略。对多优先级动态信道预留与多优先级固定信道预留策略进行仿真验证,发现动态预留方案得到的系统服务质量更好。对于单一策略,发现优先级越高的用户接入与切换呼叫接入信道失败率更低。     

Multiuser cross-layer resource allocation for video transmission over wireless networks

With the advancement of video-compression technology and the wide deployment of wireless networks, there is an increasing demand for wireless video communication services, and many design challenges remain to be overcome. In this article, we discuss how to dynamically allocate resources according to the changing environments and requirements, so as to improve the overall system performance and ensure individual quality of service (QoS). Specifically, we consider two aspects with regard to design issues: cross-layer design, which jointly optimizes resource utilization from the physical layer to the application layer, and multiuser diversity, which explores source and channel heterogeneity for different users. We study how to efficiently transmit multiple video streams, encoded by current and future video codecs, over resource-limited wireless networks such as 3G/4G cellular system and future wireless local/metropolitan area networks (WLANs/WMANs).     

Channel characteristics, planning and deployment of picocellularsystems at UHF: an overview

Cellular mobile radio communication systems are evolving towards the provision of high-capacity, high-quality voice and data services inside confined environments such as buildings. The systems deployed will provide capacity and coverage over small geographical areas such as an office floor, Such systems are referred to as being `picocellular' in the context of cellular mobile telephony. This paper provides an overview of the channel characteristics, planning and deployment of picocellular systems, which in general differ from those of macro- and microcellular systems     

毫米波视距MIMO安全通信技术研究

移动通信和信息社会的高速发展对宽带高速数据传输提出了较高的要求,而毫米波多输入多输出（multiple-input multiple-output,MIMO）技术成为实现高速安全数据传输的重要技术途径.考虑到一些特殊的需求和应用场景,比如对偏远地区的覆盖,构建应急通信系统,特别是军事宽带战术互联网,基于空中移动平台的毫米波MIMO技术成为当前研究的一个热点.本文充分调研国内外相关文献资料,阐述了毫米波视距（line-of-sight,LoS）MIMO信道建模、天线阵列优化、混合波束成形设计以及物理层安全等相关技术的当前进展、存在的挑战,并指出未来的研究方向,推动基于空中平台的毫米波MIMO系统的工程化应用.     

QoS provisioning in GEO satellite with onboard processing using predictor algorithms

Recently, IP satellite networks have attracted considerable interest as a technology to deliver high-bandwidth IP-based multimedia services to nationwide areas. In particular, IP satellite networks seem to be one of the most promising technologies for connecting users in rural areas, where a wired high-speed network (e.g., xDSL) is not foreseen to be used. However, one of the main problems arising here is to guarantee specific quality of service constraints in order to have good performance for each traffic class. Among various QoS approaches used in the Internet, recently the DiffServ technique has become the most promising solution, mainly for its scalability with respect to the IntServ approach. Moreover, in satellite communication systems, DiffServ computational capabilities are placed at the edge points, reducing the implementation complexity of the satellite onboard equipment. This article deals with the problem of QoS provisioning for packet traffic by considering some resource allocation schemes, including bandwidth allocation techniques and priority-driven onboard switching algorithms. As to the first aim, the proposed technique takes advantage of proper statistical traffic modeling to predict future bandwidth requests. This approach takes into consideration DiffServ-based traffic management to guarantee QoS priority among different users. Moreover, the satellite onboard switching problem has been addressed by considering a suitable implementation of the DiffServ policy based on a cellular neural network.     

第三代移动通信中的服务质量及技术挑战

第三代移动通信(3G)系统将Internet和移动通信相结合，使得移动通信中业务的数量和种类得到前所未有的增长。各种实时和多媒体业务的不断涌现，要求提供端到端的服务质量(QoS)保证。与Internet相比，3G系统中的QoS具有自身的特点，给3G系统QoS的实现带来更大的技术挑战。本文总结了这一领域近年来众多的研究成果，对实现3G系统中的QoS所面临的挑战进行分析，指出了几种技术解决途径，提出了无线接口的QoS实现框架，最后展望了3G的未来及支持QoS的技术发展方向。     

Priority-determined multiclass handoff scheme with guaranteed mobile QoS in wireless multimedia networks

The provision of multiclass services is gaining wide acceptance and will be more ubiquitous in future wireless and mobile systems. The crucial issue is to provide the guaranteed mobile quality of service (QoS) for arriving multiclass calls. In multimedia cellular networks, we should not only minimize the dropping rate of handoff calls, but also control the blocking rate of new calls at an acceptable level. This paper proposes a novel multiclass call-admission-control mechanism that is based on a dynamic reservation pool for handoff requests. In this paper, we propose the concept of servicing multiclass connections based on priority determination through the combined analysis of mobile movement information and the desired QoS requirements of multimedia traffic. A practical framework is provided to determine the occurrence time of handoff-request reservations. In our simulation experiments, three kinds of timers are introduced for controlling the progress of discrete events. Our simulation results show that the individual QoS criteria of multiclass traffic such as the handoff call-dropping probability can be achieved within a targeted objective and the new-call-blocking probability is constrained to be below a given level. The proposed scheme is applicable to channel allocation of multiclass calls over high-speed wireless multimedia networks.     

A Cross-System Approach for Multimedia Services with IP Multicast in 4G Networks

The increased demand for multimedia services by mobile end users in recent years have driven both Broadcast and Wireless Network operators to develop new systems and architectures for the deployment of such services. The proposed solutions are nonetheless limited either in terms of QoS or Capabilities to deliver new interactive services. This paper highlights strengths and drawbacks of the existing technologies in terms of QoS, Security and Mobility. In order to fill the gap between current solutions we propose a new architecture that builds itself on the synergies created by a heterogeneous network made of existing delivering technologies, such as 3GPP/MBMS and DVB, where services can be delivered to end-users in the most appropriate way for end-users and operators alike. A prototype implementation is further described.     

Advanced cellular Internet service (ACIS)

The public's desire for mobile communications and computing, as evidenced by the popularity of cellular phones and laptop computers combined with the explosive demand for Internet access suggest a very promising future for wireless data services. The key to realizing this potential is the development and deployment of high-performance radio systems. In this article we describe a basic service concept, advanced cellular Internet service (ACIS), and the technologies for achieving reliable high-speed transmission to wide-area mobile and portable cellular subscribers with very high spectrum efficiency. Such a wireless service, optimized to meet the needs of a client-server model for information retrieval and Web browsing, and combined with evolutionary enhancements in second-generation technologies, can provide an attractive option for third-generation systems. The radio link design combines OFDM with transmit and receive antenna diversity and Reed-Solomon coding to overcome the link budget and dispersive fading limitations of the cellular mobile radio environment. For access, a dynamic packet assignment algorithm is proposed which combines rapid interference measurements, priority ordering, and a staggered frame assignment schedule to provide spectrum efficiencies of two-to-four times existing approaches     

Communications and entertainment onboard a high-speed public transport system

This article discusses architectural design at the conceptual/functional level of communication and entertainment services onboard a high-speed public transport system, such as a high-speed train, a transoceanic cruise ship, or even a mid- to long-range airplane. Existing commercial mobile communication services, such as AMPS and GSM, are inaccessible to passengers onboard these public transport systems. A hierarchical architecture is laid out to provide passengers with communication and entertainment services. Within this framework, the transport system itself becomes an entity of a mobile network whose connection with the infrastructure networks may be interfaced through either a land terrestrial microwave or a satellite communication system. The entire architecture is further divided into the mobile subsystem, the radio transport, and the land backbone network. Potential research topics are outlined.     

未来移动通信系统及其关键技术

文中介绍了未来移动通信系统的特点和网络架构。讨论了未来移动通信物理层的正交频分复用技术（OFDM）、多入多出系统（MIMO）、认知无线电技术、软件无线电技术以及自适应调制与编码技术等传输的关键技术以及相应的网络结构和协议。最后对未来移动通信系统的发展进行了一定的展望,即未来移动通信系统应该具有高教据率、高频谱利用率、低发射功率、灵活业务支撑能力等特点。     

卫星移动通信信道特性与模型研究

从多径效应、阴影效应、多普勒效应和电离层闪烁等方面具体分析了卫星移动通信信道传输特性,并从单状态统计模型和多状态统计模型两方面详细介绍了瑞利信道模型、莱斯信道模型、对数正态衰落信道模型、Loo模型、Corazza模型、Lutz两状态信道模型和五状态M arkov信道模型,最后对未来卫星移动通信信道模型研究做了展望。     

宽带无线网络中的纠错编码

随着高速多媒体业务的迅速发展,如何提高第三代移动通信系统（3G）以及新一代移动通信系统（Beyond3G）的性能和容量愈发受到人们的重视。在业务无线接入时的服务质量（QoS）问题上,高效的纠错编码是必不可少且行之有效的解决方法之一。文中简要回顾了纠错码在前两代移动通信中的应用,并着重介绍了目前的研究热点——Turbo码和LDPC码的研究现状及发展前景。     

国外卫星移动通信新进展与发展趋势

在地面移动通信迅猛发展的新形势下,提供相似业务的卫星移动通信的发展动态和趋势值得关注.首先介绍了国外卫星移动通信市场发展动态,然后分别介绍了静止轨道、中轨道和低轨道三类卫星移动通信系统的最新进展,其中静止轨道卫星移动通信发展最好,中低轨道卫星移动通信系统发展相对不景气;最后探讨了卫星移动通信的发展趋势,指出通过星地集成...     

PERFORMANCE STUDY OF AN INTEGRATED SATELLITE/TERRESTRIAL MOBILE COMMUNICATION SYSTEM

Terrestrial cellular networks and mobile satellite systems are expected to converge towards a future integrated satellite/terrestrial mobile communication network. Besides a system globalization, the integration of terrestrial and satellite mobile systems will lead to the unloading of the fixed part of the mobile network. This paper proposes an integrated satellite/terrestrial mobile communication system and evaluates its performance in terms of the blocking probability for new call attempts, the call dropping probability and the probability of unsuccessful call. This communication system was simulated and its performence compared with that of a stand-alone terrestrial mobile system. In the terrestrial part of the system we have considered fixed channel allocation (FCA) and dynamic channel allocation (DCA) techniques. Satellite channels can have equal or lower priority compared to terrestrial channels. The improvement of the system performance by means of satellite-to-terrestrial handovers was also estimated.     

新一代超密集异构蜂窝无线网络研究

近年来,随着移动互联网的蓬勃发展和智能终端的快速普及,对无缝网络覆盖和高速数据传输要求日趋增强,超密集异构蜂窝无线网络通过减小小区半径,增加低功率节点数量进行超密集组网,提高无线资源利用率和频谱效率,因而引起了国内外研究学者的广泛关注。然而,超密集异构蜂窝无线网络中愈发密集的网络部署也带来了各种严峻的问题,包括超密集异构蜂窝无线网络中的系统干扰问题、无线信息的安全传输问题、以及网络运营的能量供给问题等。为此,本文首先简单介绍了超密集异构蜂窝无线网络架构,接着从干扰管理、物理层安全和能量效率等方面,深入分析了超密集异构蜂窝无线网络中的关键技术和当前挑战,最后,进一步展望了超密集异构蜂窝无线网络的未来发展。