Dynamic spectrum access in open spectrum wireless networks

One of the reasons for the limitation of bandwidth in current generation wireless networks is the spectrum policy of the Federal Communications Commission (FCC). But, with the spectrum policy reform, open spectrum wireless networks, and spectrum agile radios are set to drive next general wireless networks. In this paper, we investigate continuous-time Markov models for dynamic spectrum access in open spectrum wireless networks. Both queueing and no queueing cases are considered. Analytical results are derived based on the Markov models. A random access protocol is proposed that is shown to achieve airtime fairness. A distributed version of this protocol that uses only local information is also proposed based on homo egualis anthropological model. Inequality aversion by the radio systems to achieve fairness is captured by this model. These protocols are then extended to spectrum agile radios. Extensive simulation results are presented to compare the performances of fixed versus agile radios.     

On the design of self-organized cellular wireless networks

It has been observed that complex networks such as the Internet, World Wide Web, social networks, and biological systems are self-organizing in nature and exhibit some common properties such as the power law degree distribution. Recently, two models (i.e., small world and scale-free network models) have been proposed and successfully used to describe the nature of such networks. In this article we investigate whether these concepts can also be applied to cellular wireless networks, which typically do not exhibit self-organizing or scalability properties due to the limited range of the wireless nodes. Our ultimate goal is to design robust, reliable, scalable, and efficiently utilized wireless networks via self-organizing mechanisms.     

Mobility management in next-generation wireless systems

This paper describes current and proposed protocols for mobility management for public land mobile network (PLMN)-based networks, mobile Internet protocol (IP) wireless asynchronous transfer mode (ATM) and satellite networks. The integration of these networks will be discussed in the context of the next evolutionary step of wireless communication networks. First, a review is provided of location management algorithms for personal communication systems (PCS) implemented over a PLMN network. The latest protocol changes for location registration and handoff are investigated for mobile IP followed by a discussion of proposed protocols for wireless ATM and satellite networks. Finally, an outline of open problems to be addressed by the next generation of wireless network service is discussed     

基于特征根优化的无线网络控制系统故障检测滤波器设计

为提高无线传感器执行器网络(WSANs)的可靠性,本文提出了一种面向WSANs的故障检测滤波器的优化设计方法.针对无线网络固有的较大的数据包传输延迟,本文将该传输延迟对网络控制系统的影响建模为一种外部噪音,创造性地提出了基于特征根分解和扰动频率估计的优化算法,以滤除网络传输延迟导致的噪音.该方法只需在有限个频率点对目标函数进行优化,且避免了马尔科夫转移矩阵难以获得的难题.最后,通过MATLAB/NS2的混合仿真验证了该设计的有效性.     

无线传感器网络中数据链路层和网络层设计

作为无线通信网络的一个新的研究热点,无线传感器网络正以其独有的特点和全新的应用而得到人们的广泛关注.本文简要介绍无线传感器网络的体系结构、节点构成和协议层次.分类阐述了几种典型的数据链路层和网络层的设计方案和设计思想.数据链路层中MAC协议可分为两大类:基于竞争的MAC协议和基于预约的MAC协议;网络层的路由算法也分为两大类:平面路由协议和分级路由协议.最后提出一些研究构想.     

Broadband wireless access

This article reviews the technologies and potential markets, applications, and architectures for broadband wireless access. The emergence of wireless communications for cellular systems is presented, together with its projected future evolution to mobile wideband systems. The field of broadband access systems, services, and network architectures is also covered, and then systems for broadband wireless communications for indoor local area networks and outdoor public fixed access networks are discussed. Broadband wireless access systems are emerging as a new and growing area of telecommunications, since the ability to provide access without extensive installation of copper or fiber infrastructures make wireless technology well suited for broadband services. Finally, some of the key enabling technologies, such as adaptive antennas and video compression, and the future architectural directions of broadband wireless networks are presented     

IPv6-based dynamic coordinated call admission control mechanism over integrated wireless networks

Many wireless access systems have been developed recently to support users mobility and ubiquitous communication. Nevertheless, these systems always work independently and cannot simultaneously serve users properly. In this paper, we aim to integrate IPv6-based wireless access systems and propose a coordinated call admission control mechanism to utilize the total bandwidth of these systems to minimize the call blocking probabilities, especially the handoff call dropping probabilities. First, we propose an integrated hierarchical wireless architecture over IPv6-based networks to combine the wireless access systems including cellular systems (second-generation, General Packet Radio Service, or third-generation), IEEE 802.11 a/b/g WLAN, and Bluetooth. In the proposed architecture, mobile user can request a call with quality-of-service (QoS) requirements by any wireless network interfaces that can be accessed. When the proposed coordinated call admission control (CCAC) mechanism receives a request, it takes the QoS requirements of the incoming call and the available and reserved bandwidth of this wireless system into consideration to accept or reject this request. Besides, the mechanism can coordinate with other wireless systems dynamically to adjust the bandwidth reserved for handoff calls at each wireless system in this architecture so as to reduce the call blocking probabilities. Once the call is admitted, the mobile user is able to access heterogeneous wireless access networks via multiple interfaces simultaneously. Finally, we evaluate this system to show that the CCAC on the proposed architecture outperforms other mechanisms proposed before.     

Efficient dynamic authentication for mobile satellite communication systems without verification table

The mobile satellite system is an important wireless communication system widely used nowadays. The issue of protecting the transmission security in low‐earth‐orbit satellite networks thus becomes more and more critical. It is known that several authentication schemes for satellite communication systems have been proposed to deal with the issue. However, previous protocols either employ complicated public key computation or have to maintain a verification table. In this paper, the author will introduce a new dynamic authentication protocol for mobile satellite communication systems without using a verification table. The comparison results will also show that the proposed scheme has lower computational costs. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of Ethernet Powerlink Wireless Extensions Based on the IEEE 802.11 WLAN

The industrial communication scenario is experiencing the introduction of wireless networks at all levels of factory automation systems. The benefits deriving from such an innovation are manifold, even if wireless systems cannot be thought as a complete replacement of wired networks. Rather, they will be even more used in the near future to realize hybrid (wired/wireless) configurations. In particular, it is envisaged that wireless networks may be employed to implement extensions of (possibly already installed) wired systems. In this paper we consider wireless extensions of Ethernet Powerlink, a very popular Real-Time Ethernet network, implemented by means of the IEEE 802.11 WLAN. Specifically, we focus on a widespread network configuration and address two types of extensions based on, respectively, bridge and gateway devices. In the second part of the paper we provide an analysis of the hybrid networks aimed at evaluating the most relevant performance indexes. Since the reliability of wireless networks may represent a critical aspect, the analysis is carried out taking into account the presence of interference as well as fading in the wireless segment. The results we show, obtained from a theoretical analysis and validated by numerical simulations, allow to get some useful insights on the overall performance of the hybrid networks.      

Network architecture and medium access control for deploying third generation (3G) wireless systems over CATV networks

We propose a novel and cost‐effective approach for the deployment of third generation (3G) wireless systems over hybrid fiber coaxial (HFC) CATV networks. The main goal is to facilitate 3G deployment over the existing CATV plant and reduce the large cost required for building a dedicated last mile infrastructure for 3G access networks. Our proposal reduces the last mile cost by sharing the existing CATV network and using the standard equipment and protocols of data‐over‐cable systems interface specifications (DOCSIS). This allows rapid deployment of 3G wireless systems, facilitates convergence of wireless and wireline networks and paves the way towards all IP wireless networks. Enhancements to the DOCSIS medium access control (MAC) protocol must be implemented in order to support Quality of Service (QoS) guarantees for 3G data and signaling traffic. This paper presents the proposed 3G over CATV network architecture and DOCSIS medium access control (MAC) enhancements for enabling the support of QoS guarantees for 3G data and signaling traffic. The proposed MAC enhancements can reduce the access delay for delay‐sensitive traffic by 30 to 40% over existing DOCSIS MAC without compromising QoS guarantees for other traffic classes, or the DOCSIS channel utilization. Copyright © 2004 John Wiley & Sons, Ltd.     

Telecommunications aspects of intelligent buildings

The role of the telecommunications systems in intelligent building telecommunication technology is described, focusing on trends in Japan. The capabilities of private branch exchanges (PBXs) are examined, local area networks (LANs) are considered, and possible architectures for a backbone network are described. The building wiring issue is addressed, stressing the need for a topology accommodating ISDN and all branch LAN needs. The interfacing of the telecommunications systems with the building automation and office automation systems is briefly discussed     

A group-based security scheme for wireless sensor networks

In recent years, wireless sensor networks have been a very popular research topic, offering a treasure trove of systems, networking, hardware, security, and application-related problems. Distributed nature and their deployment in remote areas, these networks are vulnerable to numerous security threats that can adversely affect their proper functioning. The problem is more critical if its purpose is for some mission-critical applications such as in a tactical battlefield. This paper presents a security scheme for group-based distributed wireless sensor networks. Our first goal is to devise a group-based secure wireless sensor network. We exploit the multi-line version of matrix key distribution technique and Gaussian distribution to achieve this goal. Secondly, security mechanisms are proposed for such a group-based network architecture in which sensed data collected at numerous, inexpensive sensor nodes are filtered by local processing on its way through more capable and compromise-tolerant reporting nodes. We address the upstream requirement that reporting nodes authenticate data produced by sensors before aggregating and the downstream requirement that sensors authenticates commands disseminated from reporting nodes. Security analysis is presented to quantify the strength of the proposed scheme against security threats. Through simulations, we validate the analytical results.     

A Comprehensive Tutorial on Localization: Algorithms and Performance Analysis Tools

This tutorial offers a comprehensive view of technological solutions and theoretical fundamentals of localization and tracking (LT) systems for wireless networks. We start with a brief classification of the most common types of LT systems, e.g. active versus passive technologies, centralized versus distributed solutions and so forth. To continue, we categorize the LT techniques based on the elementary types of position-related information, namely, connectivity, angle, distance and power-profile. The attention is then turned to the difference between active and passive LT systems, highlighting the evolution of the localization techniques. Motivated by the interests of industry and academia on distance-based active localization system, a deep review of the most common algorithms used in these systems is provided. Non-Bayesian and Bayesian techniques will be tackled and compared with numerical simulations. To list some of the proposed approaches, we mention the multidimensional scaling (MDS), the semidefinite programming (SDP) and the Kalman filter (KF) methods. To conclude the tutorial, we address the fundamental limits of the accuracy of range-based positioning. Based on the unifying framework proposed by Abel, we derive the closed-form expressions for the Cramér?CRao lower bound (CRLB), the Battacharyya Bound (BB), the Hammersley?CChapmann?CRobbins Bound (HCRB) and the Abel Hybrid Bound (AHB) in a source localization scenario. We show a comparison of the aforementioned bounds with respect to a Maximum-Likelihood estimator and explore the difference between random and regular (equi-spaced anchors) network topologies. Finally, extensions to cooperative scenarios are also discussed in connection with the concept of information-coupling existing in multitarget networks.     

A Mathematical Theory of Network Interference and Its Applications

In this paper, we introduce a mathematical framework for the characterization of network interference in wireless systems. We consider a network in which the interferers are scattered according to a spatial Poisson process and are operating asynchronously in a wireless environment subject to path loss, shadowing, and multipath fading. We start by determining the statistical distribution of the aggregate network interference. We then investigate four applications of the proposed model: 1) interference in cognitive radio networks; 2) interference in wireless packet networks; 3) spectrum of the aggregate radio-frequency emission of wireless networks; and 4) coexistence between ultrawideband and narrowband systems. Our framework accounts for all the essential physical parameters that affect network interference, such as the wireless propagation effects, the transmission technology, the spatial density of interferers, and the transmitted power of the interferers.      

一种用于无线传感器网的协作接收方案

无线传感器网中,能量效率是系统设计首要考虑的因素.基于提高无线传感器网能量效率的目的,本文提出了一种简单的协作接收方案并分析了其能量效率,理论分析及仿真结果表明,当通信距离大于某一门限值时采用该接收方案可以有效提高无线传感器网的能量效率.     

Mobility support across hybrid IP-based wireless environment: review of concepts, solutions, and related issues

The 4G or Beyond 3G wireless networks is consist of IP-based heterogeneous access networks from 3G cellular, WiFi, WiMAX to other emerging access technologies such as mesh networks. The key objective of designing the next generation wireless networks is to support of mobile subscribers. To support the mobile host in the hybrid wireless access technologies, many solutions based on network protocol stack have been proposed in the literature. In this article, after review of mobility concepts, a special attention is given to some of the mobility management methods as well as handover techniques across various wireless access networks. We have also compared the major mobility protocols in each layer for their features. Finally, some of the open issues that needed to be addressed in mobility management protocol in the next generation wireless networks are outlined.     

Implementation and performance evaluation for mobility managementof a wireless PBX network

As wireless technology advances, wireless products are integrated with enterprise networking to offer cordless terminal mobility. Most corporations have deployed wireless PBXs at the departmental level. However, the mobility management mechanism that integrates these facilities at the corporation level may not be available. This paper describes a mobility management mechanism for an enterprise wireless telephone network. We show how, to modify the call model of the private branch exchange (PBX) to accommodate mobility management for an enterprise network. Our design was implemented on a commercial PBX product called Jupiter. An analytical model is proposed to evaluate the performance of the implemented system. Our study shows that with a large number of WPBXs and long Internet message delays, the misrouting probability can be limited to within 1%. This performance result is considered satisfactory     

Cross-Layer Scheduling and Power Control Combined With Adaptive Modulation for Wireless Ad Hoc Networks

Efficient resource management is a major challenge in the operation of wireless systems, especially energy-constrained ad hoc networks. In this paper, we propose a cross-layer optimization framework to jointly design the scheduling and power control in wireless ad hoc networks. We study the system performance by combining scheduling, power control, and adaptive modulation. Specifically, the transmitted power and constellation size are dynamically adapted based on the packet arrival, quality of service (QoS) requirements, power limits, and channel conditions. A key feature of the proposed method is that it facilitates a distributed implementation, which is desirable in wireless ad hoc networks. The performance of our proposed methodology will be investigated in ad hoc networks supporting unicast as well as multicast traffic. Simulation results will show that the proposed scheme achieves significant gains in both the single-hop throughput and power efficiency compared with the existing method, which implements the scheduling through a central controller, and adopts power control with fixed modulation     

Dynamic spectrum allocation in composite reconfigurable wireless networks

Future wireless systems are expected to be characterized by increasing convergence between networks and further development of reconfigurable radio systems. In parallel with this, demand for radio spectrum from these systems will increase, as users take advantage of high quality multimedia services. This article aims to investigate and review the possibilities for the dynamic allocation of spectrum to different radio networks operating in a composite reconfigurable wireless system. The article first looks into the current interest of regulators in this area, before describing some possible schemes to implement dynamic spectrum allocation and showing some example performance results. Following this, the technical requirements that a DSA system would have, in terms of reconfigurable system implementation, are discussed.     

Telecommunications

The author discusses advances and changes in: Internet; multichannel optical fibre networks using erbium-doped fibre amplifiers and wavelength division multiplexing; HDTV; digital radio; satellites for mobile voice telephony; the auction of wireless telephony licences; and unlicensed personal communication systems