Ad hoc物理层关键问题的探讨

A d hoc网络一般都是基于无线通信的,同样需要解决衰落、多径干扰、功率控制等无线通信经常遇到的问题。本文针对A d hoc网络中物理层的若干关键问题进行了探讨,包括选择和参考的标准,M IMO、OFDM、UW B、软件无线电等与物理层有关的新技术以及物理层模型对其他层的影响。     

IEEE 802.15.4: a developing standard for low-power low-costwireless personal area networks

A low-rate wireless personal area network, or LR-WPAN, is a network designed for low-cost very-low-power short-range wireless communications. Until now, the main focus in the wireless industry has been on communications. Until now, the main focus in the wireless industry has been on communication with higher data throughput, leaving out a set of applications requiring simple wireless connectivity with relaxed throughput and latency requirements. LR-WPANs will connect devices that previously have not been networked and allow applications that cannot use current wireless specifications, including applications in fields such as industrial, agricultural, vehicular, residential, medical sensors and actuators. TaskGroup 4 of the IEEE 802.14 Wireless personal Area Network working group is currently working to define a wireless communication standard for LR-WPANs. This article discusses the technical considerations and system requirements necessary when implementing a low-cost low-power wireless personal area network and provides an overview of the unique applications such a technology will enable     

Handover approaches for seamless mobility management in next generation wireless networks

Next generation wireless networks (NGWN) will be an integration of heterogeneous wireless access networks that will interwork over an IP‐based infrastructure. This all‐IP vision has led to the development of handover mechanisms to support seamless mobility for active network services among the different interworking wireless networks in order to ensure network access ubiquity in NGWN. These handover mechanisms need to ensure that mobile devices continue to receive ongoing communication without any noticeable disruption during handover events among the heterogeneous networks. This paper gives a qualitative and quantitative review of current handover approaches of IP mobility management protocols for NGWN with an objective to introduce a new way of further optimizing the handover performance. In particular, the paper focuses on handover approaches of mobile IPv6 (MIPv6) based mobility management protocols. Thus, the need, benefits, and limitations of these handover approaches are explored. Thereafter, dynamic handover coordination is introduced as a new viable solution that exploits the benefits and mitigates the limitations of these handover approaches hence improving handover performance in terms of handover delay, packet loss, and signaling overhead. Copyright © 2011 John Wiley & Sons, Ltd.     

第四代移动通信系统的调制技术

现有通信系统的调制技术限制了信号速率的进一步提高,即将推出的第四代(4G)移动通信系统需要更优良的调制技术。正交频分复用(OFDM)技术是很受欢迎的高速率无线通信技术,结合OFDM的调制技术将在4G系统中得到广泛应用。文中概要介绍了4G系统的特点及关键技术,然后系统介绍了OFDM多载波原理,最后重点介绍了多载波码分多址(MC-CDMA)和正交频分复用时分多址(OFDM-TDMA)两种多载波调制(MCM)技术。     

面向未来无线通信系统的小蜂窝网络综述

为了满足人们日益增长的数据流量需求,未来无线通信系统将向更小的小区部署迁移。小蜂窝网络是下一代无线通信系统的关键技术,也是适应未来更加复杂通信环境的有效途径。首先介绍了小蜂窝网络的基本概念,论述了其主要的技术特点和独特的应用优势,分析了其在未来无线通信系统中与其他各种技术可能的融合场景并讨论了对应的特点和存在的难题;然后概述了小蜂窝网络技术发展过程中所面临的主要挑战,分析了目前主要的研究成果和解决方案;最后,结合下一代无线通信的关键技术,如大规模多输入多输出通信、毫米波通信、D2D(Device-to-Device)通信和认知无线电技术等,总结了小蜂窝网络的应用现状并分析了其市场和发展前景。     

A Discussion About Some of the Principles/Practices of Wireless Communication Under a Maxwellian Framework

There has been a plethora of papers dealing with wireless communication that use techniques, which when viewed from the perspective of a Maxwellian framework raise more questions than they answer. By Maxwellian framework we imply not only the relevance of electromagnetics in studying communication systems but also the proper interpretation of an ensemble processing in mathematical physics which was first introduced by Maxwell to study the behavior of an aggregate of molecules rather than the property of individuals. Initially, most of the modern signal processing techniques was developed for scalar acoustic problems. However, with the advent of wireless, these same techniques are being applied to the vector electromagnetics problem, which is fundamentally different in concept with respect to the scalar acoustic problem. The objective is to discuss some of these concerns associated with some of the current modeling methodologies particularly related to propagation modeling and antenna diversity. A goal is to initiate a dialog about the scientific merits of these new applications. One of the points to be made is that an incorrect use of probability theory can often lead to erroneous conclusions that directly contradict the principles of physics. A few examples are presented to initiate this dialog, mainly the applicability of scalar techniques to the vector wireless problem, including a proper interpretation of the Shannon channel capacity theorem. A methodology is also presented to illustrate how a simple multiple-input-multiple-output system can be based on the principles of reciprocity. Integration of the electromagnetic principles in some of the current methodologies of signal processing and communications theory may lead to a better system     

Compact-Modeling Solutions For Nanoscale Double-Gate and Gate-All-Around MOSFETs

Compact-modeling principles and solutions for nanoscale double-gate and gate-all-around MOSFETs are explained. The main challenges of compact modeling for these devices are addressed, and different approaches for describing the electrostatics, the transport mechanisms, and the high-frequency behavior are explained. Several approximations used to derive analytical solutions of Poisson's equation for doped and undoped devices are discussed, and the need for self-consistency with SchrÖdinger's equation and with the current continuity equation resulting from the transport models is addressed. Several techniques to extend the compact modeling to the high-frequency regime and to study the RF performance, including noise, are presented and discussed.     

A review of industrial wireless networks in the context of Industry 4.0

There have been many recent advances in wireless communication technologies, particularly in the area of wireless sensor networks, which have undergone rapid development and been successfully applied in the consumer electronics market. Therefore, wireless networks (WNs) have been attracting more attention from academic communities and other domains. From an industrial perspective, WNs present many advantages including flexibility, low cost, easy deployment and so on. Therefore, WNs can play a vital role in the Industry 4.0 framework, and can be used for smart factories and intelligent manufacturing systems. In this paper, we present an overview of industrial WNs (IWNs), discuss IWN features and related techniques, and then provide a new architecture based on quality of service and quality of data for IWNs. We also propose some applications for IWNs and IWN standards. Then, we will use a case from our previous achievements to explain how to design an IWN under Industry 4.0. Finally, we highlight some of the design challenges and open issues that still need to be addressed to make IWNs truly ubiquitous for a wide range of applications.     

MIMO-OFDM同步门限值方法

正交频分复用技术(OFDM)由于其对抗多径能力强和频谱利用率高而被视为下一代无线通信的核心技术。多输入输出(MIMO)技术和OFDM技术已经或者即将应用于各种高速宽带通信系统中,对于MIMO-OFDM系统关键技术的研究至关重要。MIMO-OFDM与SISO-OFDM相似,对定时同步错误和频率偏移敏感,定时和频率不同步都可能会破坏帧结构,因此准确的符号定时和精确的载波频偏估计是系统正常工作的前提。本中首先用CAZAC序列构建出共轭交错结构作为训练序列,然后应用门限值方法改进定时同步估计并基于交错结构进行载波频率偏移估计,最后结合仿真结果确定影响门限值性能的参数值。仿真数据显示,在多径信道条件下,该方法可以使得系统的误码率相对传统方法得到进一步减小,有效地提高同步性能。      

Teletraffic considerations for widespread deployment of PCS

To offer personal communication services (PCS) to large segments of the population, sophisticated digital radio access techniques and extensive use of “Advanced Intelligent Network” services of public wireline networks will be required. To accommodate wireless access on such a wide scale, a broad range of challenging new teletraffic problems will need to be solved. In this article the authors give a brief, high-level overview of some of the important teletraffic issues that they believe will need to be addressed to support widespread deployment of PCS. Much more work is needed in order to refine our understanding of these issues, to prioritize specific problems, and to solve them. The purpose of this article is not to provide an exhaustive list of all PCS teletraffic issues, but rather to stimulate discussion of these problems     

A Solution of Secure Communication in the Current and Future Mobile Network

1　Introduction　The mobile network is making people s lives more conve nient. Using mobile terminals people can talk to anyone atany time and at any places. And we want more. People willask if I can send short messages to Tom without others beingable to obtain their meanings. When I use my mobile phonetransferring my credit card, can anyone filch my credit cardpassword? Can I safely using my mobile phone to exchangestock? And so on…　Unfortunately, the answer is no nowadays. People canno…     

The Future of Integrated Circuits: A Survey of Nanoelectronics

While most of the electronics industry is dependent on the ever-decreasing size of lithographic transistors, this scaling cannot continue indefinitely. Nanoelectronics (circuits built with components on the scale of 10 nm) seem to be the most promising successor to lithographic based ICs. Molecular-scale devices including diodes, bistable switches, carbon nanotubes, and nanowires have been fabricated and characterized in chemistry labs. Techniques for self-assembling these devices into different architectures have also been demonstrated and used to build small-scale prototypes. While these devices and assembly techniques will lead to nanoscale electronics, they also have the drawback of being prone to defects and transient faults. Fault-tolerance techniques will be crucial to the use of nanoelectronics. Lastly, changes to the software tools that support the fabrication and use of ICs will be needed to extend them to support nanoelectronics. This paper introduces nanoelectronics and reviews the current progress made in research in the areas of technologies, architectures, fault tolerance, and software tools.     

A routing framework for energy harvesting wireless nanosensor networks in the Terahertz Band

Wireless NanoSensor Networks (WNSNs) will allow novel intelligent nanomaterial-based sensors, or nanosensors, to detect new types of events at the nanoscale in a distributed fashion over extended areas. Two main characteristics are expected to guide the design of WNSNs architectures and protocols, namely, their Terahertz Band wireless communication and their nanoscale energy harvesting process. In this paper, a routing framework for WNSNs is proposed to optimize the use of the harvested energy to guarantee the perpetual operation of the WNSN while, at the same time, increasing the overall network throughput. The proposed routing framework, which is based on a previously proposed medium access control protocol for the joint throughput and lifetime optimization in WNSNs, uses a hierarchical cluster-based architecture that offloads the network operation complexity from the individual nanosensors towards the cluster heads, or nano-controllers. This framework is based on the evaluation of the probability of saving energy through a multi-hop transmission, the tuning of the transmission power of each nanosensor for throughput and hop distance optimization, and the selection of the next hop nanosensor on the basis of their available energy and current load. The performance of this framework is also numerically evaluated in terms of energy, capacity, and delay, and compared to that of the single-hop communication for the same WNSN scenario. The results show how the energy per bit consumption and the achievable throughput can be jointly maximized by exploiting the peculiarities of this networking paradigm.     

High-speed integrated transceivers for optical wireless

Optical wireless LANs have the potential to provide bandwidths far in excess of those available with current or planned RF networks. There are several approaches to implementing optical wireless systems, but these usually involve the integration of optical, optoelectronic, and electrical components in order to create transceivers. Such systems are necessarily complex, and the widespread use of optical wireless is likely to be dependent on the ability to fabricate the required transceiver components at low cost. A number of UK universities are currently involved in a project to demonstrate integrated optical wireless subsystems that can provide line-of-sight in-building communications at 155 Mb/s and above. The system uses two-dimensional arrays of novel microcavity LED emitters and arrays of detectors integrated with custom CMOS integrated circuits to implement tracking transceiver components. In this article we set out the basic approaches that can be used for in-building optical wireless communication and argue the need for an integrated and scalable approach to the fabrication of transceivers. Our work aimed at implementing these components, including experimental results and potential future directions, is then discussed.     

超宽带及其在无线个域网中的应用

近年来,超宽带(UWB)无线通信成为短距离、高速无线网络最热门的物理层技术之一。介绍了超宽带无线通信技术的概念及其信号传输过程中使用的关键技术,包括脉冲成形技术、调制技术以及接收技术,给出了超宽带无线传输系统的基本模型,最后分析了该技术在无线多媒体个域网中的应用。     

Spread spectrum techniques in wireless communication

Spread spectrum communication techniques including in-time and frequency domains for direct sequence, frequency hopping, and time hopping are currently used in a large number of wireless applications. This article provides an overview of these techniques. Results of laboratory tests of a ZigBee network are presented, and experimental results are compared with theoretical expectations. Part 2 of this paper will present an application we developed for a wireless distributed measurement sensing and actuating system for water quality assessment.     

Misbehavior Detection in Industrial Wireless Networks: Challenges and Directions

In communications, there has been a paradigm shift toward the widespread adoption of wireless technologies in recent years. This evolution to—often ad-hoc—wireless communication has led to significant benefits in terms of flexibility and mobility. However, alongside these benefits, arise new attack vectors, which cannot be mitigated by traditional security measures. Especially in scenarios where traditional, proactive cryptographic techniques cannot be deployed or have been compromised, reactive mechanisms are necessary to detect intrusions. In this paper, we discuss new directions and future challenges in detecting insider attacks for the exemplary application domain of industrial wireless networks, an enabling technology for current smart factory trends. First, we review existing work on intrusion detection in mobile ad-hoc networks with a focus on physical-layer-based detection mechanisms. Second, we conduct a proof-of-concept study of insider detection in industrial wireless networks using real-world measurements from an industrial facility. Based on the study, we point out new directions for future research.     

无线光互连技术发展综述

人们对无线宽带通信技术的需求在近些年稳步增长.无线电波频谱的带宽限制和频带拥堵,通过微波无线网络的发展已经有了明显的改善.然而,无线光互连技术才能使得数据传输带宽达到理想的要求.作为许多无线通讯系统的最终方案,无线光互连也被选择为长期的解决策略.并且,无线光互连的大量优势还没有得到完全的发掘,许多基础性和应用性的研究还需要在实验层面和商业应用层面加以深入.国外,Gb/s的无线光传输已经在实验室中得到了验证,然而,可用的室内无线光互连系统也仅仅达到了155Mb/s的速度.下面将着重从收发系统、性能及安全性方面对无线光互连技术作一概况阐述.     

Moving Query Monitoring in Spatial Network Environments

Moving queries over mobile objects are an important type of query in moving object database systems. In recent years, there have been quite a few works in this area. Due to the high frequency in location updates and the expensive cost of continuous query processing, server computation capacity and wireless communication bandwidth are the two limiting factors for large-scale deployment of moving object database systems. Many techniques have been proposed to address the server bottleneck including one using distributed servers. To address both scalability factors, distributed query processing techniques have been considered. These schemes enable moving objects to participate in query processing to substantially reduce the demand on server computation, and wireless communications associated with location updates. Most of these techniques, however, assume an open-space environment. Since Euclidean distance is different from network distance, techniques designed specifically for an open space cannot be easily adapted for a spatial network. In this paper, we present a distributed framework which can answer moving query over moving objects in a spatial network. To illustrate the effectiveness of the proposed framework, we study two representative moving queries, namely, moving range queries and moving k-nearest-neighbor queries. Detailed algorithms and communication mechanisms are presented. The simulation studies indicate that the proposed technique can significantly reduce server workload and wireless communication cost.     

基于4G/LTE网络的无人作战平台视频传输系统设计

无人作战平台在执行任务时,需要进行无线视频传输。然而目前广泛使用的移动通讯技术在传输视频数据时,对视频质量有很大的限制。为了满足作战指挥人员获取高清视频的需要,运用4G/LTE构建无人作战平台视频传输系统无疑是好的选择。该系统在无人作战平台控制、参加抢险救灾和战场监控等方面将会有广阔的应用前景。