Scalability of Wireless Networks

This paper investigates the existence of scalable protocols that can achieve the capacity limit of c/radicN per source-destination pair in a large wireless network of N nodes when the buffer space of each node does not grow with the size of the network N. It is shown that there is no end-to-end protocol capable of carrying out the limiting throughput of c/radicN with nodes that have constant buffer space. In other words, this limit is achievable only with devices whose buffers grow with the size of the network. On the other hand, the paper establishes that there exists a protocol which realizes a slightly smaller throughput of c/radicNlogN when devices have constant buffer space. Furthermore, it is shown that the required buffer space can be very small, capable of storing just a few packets. This is particularly important for wireless sensor networks where devices have limited resources. Finally, from a mathematical perspective, the paper furthers our understanding of the difficult problem of analyzing large queueing networks with finite buffers for which, in general, no explicit solutions are available     

Throughput Scalability of Wireless Hybrid Networks over a Random Geometric Graph

In this paper, we consider the transport capacity of ad hoc networks with a random flat topology under the present support of an infinite capacity infrastructure network. Such a network architecture allows ad hoc nodes to communicate with each other by purely using the remaining ad hoc nodes as their relays. In addition, ad hoc nodes can also utilize the existing infrastructure fully or partially by reaching any access point (or gateway) of the infrastructure network in a single or multi-hop fashion. Using the same tools as in [9], we show that the per source node capacity of Θ(W/log(N)) can be achieved in a random network scenario with the following assumptions: (i) The number of ad hoc nodes per access point is bounded above, (ii) each wireless node, including the access points, is able to transmit at W bits/sec using a fixed transmission range, and (iii) N ad hoc nodes, excluding the access points, constitute a connected topology graph. This is a significant improvement over the capacity of random ad hoc networks with no infrastructure support which is found as in [9]. We also show that even when less stringent requirements are imposed on topology connectivity, a per source node capacity figure that is arbitrarily close to Θ(1) cannot be obtained. Nevertheless, under these weak conditions, we can further improve per node throughput significantly. We also provide a limited extension on our results when the number of ad hoc nodes per access point is not bounded.Ulaş C. Kozat was born in 1975, in Adana, Turkey. He received his B.Sc. degree in Electrical and Electronics Engineering from Bilkent University, Ankara, Turkey and his M.Sc. in Electrical Engineering from The George Washington University, Washington D.C. in 1997 and 1999 respectively. He has received his Ph.D. degree in May 2004 from the Department of Electrical and Computer Engineering at University of Maryland, College Park. He has conducted research under the Institute for Systems Research (ISR) and Center for Hybrid and Satellite Networks (CSHCN) at the same university. He worked at HRL Laboratories and Telcordia Technologies Applied Research as a research intern. His current research interests primarily focus on wireless and hybrid networks that span multiple communication layers and networking technologies. Mathematical modelling, resource discovery and allocation, vertical integration of wireless systems and communication layers, performance analysis, architecture and protocol development are the main emphasis of his work. E-mail: kozat@isr.umd.eduLeandros Tassiulas (S′89, M′91) was born in 1965, in Katerini, Greece. He obtained the Diploma in Electrical Engineering from the Aristotelian University of Thessaloniki, Thessaloniki, Greece in 1987, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of Maryland, College Park in 1989 and 1991 respectively.He is Professor in the Dept. of Computer and Telecommunications Engineering, University of Thessaly, Greece and Research Professor in the Dept. of Electrical and Computer Eng and the Institute for Systems Research, University of Maryland College Park since 2001. He has held positions as Assistant Professor at Polytechnic University New York (1991–95), Assistant and Associate Professor University of Maryland College Park (1995–2001) and Professor University of Ioannina Greece (1999–2001).His research interests are in the field of computer and communication networks with emphasis on fundamental mathematical models, architectures and protocols of wireless systems, sensor networks, high-speed internet and satellite communications.Dr. Tassiulas received a National Science Foundation (NSF) Research Initiation Award in 1992, an NSF CAREER Award in 1995 an Office of Naval Research, Young Investigator Award in 1997 and a Bodosaki Foundation award in 1999 and the INFOCOM′94 best paper award. E-mail: leandros@isr.umd.edu     

The Performance Evaluation of Hybrid Localization Algorithm in Wireless Sensor Networks

As one of the key techniques in wireless sensor networks (WSN), localization algorithm has been a research hot topic and indispensable function in most wireless applications. In order to promote localization accuracy and efficiency, a lot of localization algorithms with different performances and computation complexities have been proposed. The paper discusses the drawbacks of some typical works on localization, and proposes a hybrid localization algorithm integrated with approximate point in triangle (APIT) and distance vector-hop (DV-HOP). To address the positioning accuracy and coverage rate, the objectives of this paper are three folds: firstly, adopting angle detection to determine the exact direction of unknown nodes. Then, the APIT algorithm is adopted over all unknown nodes within the triangle and its localization error is reduced from 14.7215 m in conventional APIT to 3.2348 m in the considered scenario. Finally, the DV-HOP algorithm is adopted with different weights for the nodes within the minimum hops, and localizes the rest unknown nodes in WSN with localization accuracy increased by 49%.     

Scalability Technologies for Wireless Mesh Networks

The continuous increase of data transmission density in wireless mobile communications has posed a challenge to the system performance of Wireless Mesh Networks (WMNs ). There is a rule for wireless Ad hoc networks that the average node capacity decreases while the number of nodes increases , so it is hard to establish a large - scale wireless Mesh network. Network scalability is very important for enhancing the adaptive networking capability of the wireless Mesh network. This article discusses key scalability technologies for Mesh Base Stations (BSs ) and Mesh Mobile Stations (MSs ), such as channel allocation, intelligent routing , multi- antenna , node classification, Quality of Service (QoS) differentiation and cooperative transmission.     

无线Mesh网络可扩展性相关技术

无线移动通信中传输的数据密度持续增长对无线Mesh网络的系统性能提出了挑战。在无线自组织网络中,由于存在随着节点数目的增加而平均节点容量逐步降低的规律,因此无线Mesh网络的大规模组网难以实施。无线Mesh网络可扩展性对于增强无线Mesh网络的自适应组网能力至关重要,因此,文章对在Mesh基站和Mesh移动台上采用的与可扩展性相关的关键技术,如信道分配技术、智能路由技术、多天线技术、节点分类和QoS分级技术、协作传输技术等,进行了探讨。     

Mobility Modeling and Performance Evaluation of Heterogeneous Wireless Networks

The future-generation wireless systems will combine heterogeneous wireless access technologies to provide mobile users with seamless access to a diverse set of applications and services. The heterogeneity in this inter-technology roaming paradigm magnifies the mobility impact on system performance and user perceived service quality, necessitating novel mobility modeling and analysis approaches for performance evaluation. In this paper, we present and compare three mobility models in two-tier integrated heterogeneous wireless systems, the independence model as a naive extension of the traditional cell residence time modeling techniques for homogeneous cellular networks, the basic Coxian model which takes into consideration the correlation between the residence time within different access technologies, and the extended-Coxian model for further improved estimation accuracy. We propose a general stochastic performance analysis framework based on application session models derived from these mobility models, applying it to a 3G-WLAN integrated system as an example. Our numerical and simulation results demonstrate the general superiority of Coxian-based mobility modeling over the independence model. Furthermore, using the proposed modeling and analysis methods, we investigate the impact of different parameters on system performance metrics such as network utilization time, handoff rates, and forced termination probability, for a wide range of user applications.     

Mobility Management for Hierarchical Wireless Networks

In this paper, we consider the mobility management in large, hierarchically organized multihop wireless networks. The examples of such networks range from battlefield networks, emergency disaster relief and law enforcement etc. We present a novel network addressing architecture to accommodate mobility using a Home Agent concept akin to mobile IP. We distinguish between the physical routing hierarchy (dictated by geographical relationships between nodes) and logical hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). The performance of the mobility management scheme is investigated through simulation.     

Performance Evaluation of Scheduling Approaches for Wireless Sensor Networks

Wireless Personal Communications - The design of wireless sensor networks (WSN) is still a hot topic either for industry or academia. Many research teams work on various issues as communication...     

Performance Evaluation of CANCAR Algorithm in Realistic Wireless Mesh Networks

Wireless Personal Communications - A new technique for designing compact, notched filter is presented in this paper. The proposed approach is based on the design and optimization of micro strip...     

Performance Evaluation of Routing Protocols for Ad Hoc Wireless Networks

A mobile ad hoc network is a collection of autonomous mobile nodes that communicate with each other over wireless links. Such networks are expected to play an increasingly important role in future civilian and military settings, being useful for providing communication support where no fixed infrastructure exists or the deployment of a fixed infrastructure is not economically profitable and movement of communicating parties is possible. However, since there is no stationary infrastructure such as base stations, mobile hosts need to operate as routers in order to maintain the information about the network connectivity. Therefore, a number of routing protocols have been proposed for ad hoc wireless networks. In this paper, we study and compare the performance of the following routing protocols AODV, PAODV (preemptive AODV), CBRP, DSR, and DSDV. A variety of workload and scenarios, as characterized by mobility, load and size of the ad hoc network were simulated. Our results indicate that despite its improvement in reducing route request packets, CBRP has a higher overhead than DSR because of its periodic hello messages while AODV's end-to-end packet delay is the shortest when compared to DSR and CBRP. PAODV has shown little improvements over AODV.     

Iterative Algorithms for Performance Evaluation of Wireless Networks with Guard Channels

Analytical and modeling work performed since the late eighties have led to nonlinear equations that relate important parameters used for performance evaluation of wireless networks. These nonlinear equations have no closed-form solution and iterative algorithms are used to find numerical solutions. However, iterative algorithms that are not designed to detect and overcome nonconvergence situations may fail to converge. We present an iterative algorithm that numerically solves six dependent nonlinear equations. The algorithm always converges and obtains values of blocking probability, p _b , and forced termination probability, p _ft , at any desired level of accuracy. We then used this algorithm to numerically show that for a given pair of values of p _b and p _ft , there is an optimal number of guard channels that supports a maximal new-call arrival rate.     

应用于分级复用系统的全光网波长分配算法

研究了全光网中采用分级复用系统的波长分配问题,充分考虑到分级复用系统在降低整个网络成本上的重要意义,以最小化光纤数量和波长路径为优化目标,提出一种启发式波长分配算法。     

移动无线传感网能量时延约束的自适应路由及性能评估

 针对间歇性连通的移动无线传感网提出一种能量时延约束的自适应路由协议(EDCA),EDCA由初始化阶段、转发决策阶段、转发阶段和等待阶段组成,传感器节点根据目标时延实时判断是否转发副本,并选择剩余能量多的节点进行副本转发.EDCA对平均时延和网络负载具有控制力,对网络环境变化具有自适应能力,能够有效延长网络生命周期.     

Hybrid FGWO Based FLCs Modeling for Performance Enhancement in Wireless Body Area Networks

Wireless Personal Communications - The progression over wireless technologies paves the way for the emergence of wireless body area networks (WBAN) towards several motivating applications....     

基于不对称方式的无线接入网络体系结构及性能仿真

首先介绍基于不对称方式的无线接入网络和3GPP定义的4类通信业务模式,然后搭建了基于MATLAB无线通信仿真系统并对不对称方式和传统方式两种无线接入网络配置情况进行系统仿真,同时通过4类通信业务条件下的仿真结果评估无线接入网和核心网络的性能表现,最后根据软件仿真结果给出仿真数据分析和结论。     

Performance Analysis of Hybrid Optimization Algorithm for Virtual Head Selection in Wireless Sensor Networks

Wireless Personal Communications - In today's world, wireless sensor network is an unavoidable technology especially for Internet of Things applications. But the nodes limited resource...     

基于无线信号不规则性的无线传感网层次型拓扑控制算法

构建层次型拓扑结构是延长网络生存时间的有效方法。该文将拓扑构建过程分为由簇成员组成的感知层和由簇头组成的平面数据转发层,建立了基于无线信号不规则性的网络能耗模型以及节点成簇稳定性模型,提出了基于无线信号不规则性的层次型拓扑控制(WSIBTC)算法。WSIBTC算法根据节点平均有效传输距离将监测区域划分为多个子区域,由成簇稳定性和节点在簇中的位置决定最终簇头,簇头间形成平面拓扑结构,延长网络生存时间。分析和仿真结果表明由WSIBTC算法得到的网络拓扑大幅度地提升了网络生存时间。     

Trust-Assisted Handover Approach in Hybrid Wireless Networks

In Next-Generation (NG) hybrid wireless networks, Mobile-Controlled Handover (MCHO) is expected to be employed as the handover control mechanism, in contrast to Network-Controlled Handover (NCHO) used in homogeneous wireless networks. As more independent network operators get involved in providing Internet access, roaming mobile users would have to deal with complex trust relationships between heterogeneous network domains. The state-of-the-art handover approaches just take into account Quality of Service (QoS), but ignore the complexities arising from the coexistence of multiple network operators in the NG networks. The existence of a complex trust relationship between networks may lead to unnecessary handover attempts in service roaming. In this regard, this paper introduces a novel approach of dynamically retrieving network trust information, and using it in MCHO. We show how network trust information can be utilised to obtain a 35% reduction in handover delay, meanwhile retain QoS in a handover. The proposed scheme does not need bulk storage in mobile handsets, and can react to changes to network topology and trust relationships dynamically. Analytical results are provided to demonstrate how roaming mobile users make more intelligent and reliable handover if implementing the proposed handover approach in a multi-operator and multi-technology environment.     

能量有效的多级无线传感网络数据采集方法

The majority of the energy consumption by the sensors is the energy requirement for data transmission in Wireless Sensor Networks (WSNs). Therefore, introducing mobile collectors to collect data instead of multi-hop data relay is essential. However, for many proposed data gathering approaches, long data delay is the main problem. Hence, the problem of how to decrease the energy consumption and the data delay needs to be solved. In this paper, a low delay data collection mechanism using multiple mobile collectors is proposed. First, a self-organization clustering algorithm is designed. Second, sensor nodes are organized into three-level clusters. Then a collection strategy based on the hierarchical structure is proposed, which includes two rules to dispatch mobile collectors rationally. Simulation results show that the proposed mechanism is superior to other existing approaches in terms of the reduction in energy expenditure and the decrease in data delay.