邻近信息约束下的随机异构无线传感器网络节点调度算法

针对高密度部署的随机异构传感器网络内部存在的覆盖冗余问题,该文提出一种随机异构无线传感器网络的节点调度算法(NSSH)。在网络原型拓扑的支撑下构建Delaunary三角剖分,规划出节点进行本地化调度的局部工作子集。通过折中与邻近节点的空外接圆半径,完成对感知半径的独立配置;引入几何线、面概念,利用重叠面积和有效约束圆弧完成对灰、黑色节点的分类识别,使得节点仅依赖本地及邻居信息进行半径调整和冗余休眠。仿真结果表明,NSSH能以低复杂度的代价,近似追平贪婪算法的去冗余性能,并表现出了对网络规模、异构跨度和参数配置的低敏感性。     

A Markovian Approach to Radio Access Technology Selection in Heterogeneous Multiaccess/Multiservice Wireless Networks

This paper addresses the problem of Radio Access Technology (RAT) selection in heterogeneous multi-access/multi-service scenarios. For such purpose, a Markov model is proposed to compare the performance of various RAT selection policies within these scenarios. The novelty of the approach resides in the embedded definition of the aforementioned RAT selection policies within the Markov chain. In addition, the model also considers the constraints imposed by those users with terminals that only support a subset of all the available RATs (i.e. multi-mode terminal capabilities). Furthermore, several performance metrics may be measured to evaluate the behaviour of the proposed RAT selection policies under varying offered traffic conditions. In order to illustrate the validation and suitability of the proposed model, some examples of operative radio access networks are provided, including the GSM/EDGE Radio Access Network (GERAN) and the UMTS Radio Access Network (UTRAN), as well as several service-based, load-balancing and terminal-driven RAT selection strategies. The flexibility exhibited by the presented model enables to extend these RAT selection policies to others responding to diverse criteria. The model is successfully validated by means of comparing the Markov model results with those of system-level simulations.     

An End-To-End Approach for Transparent Mobility Across Heterogeneous Wireless Networks

With the advent of a myriad of wireless networking technologies, a mobile host today can potentially be equipped with multiple wireless interfaces that have access to different wireless networks. It is widely perceived that future generation wireless networks will exhibit a similar trend in supporting a large variety of heterogeneous wireless access technologies that a mobile host can choose from. In this paper, we consider such a multi-homed mobile host and propose an end-to-end solution that enables the seamless use of heterogeneous wireless access technologies. The unique features of the proposed solution include: (i) a purely end-to-end approach to handle host mobility that requires no support from the underlying network infrastructure, (ii) seamless vertical handoffs when the mobile host migrates from one access network to another, (iii) ability to support different congestion control schemes for a live connection traversing different interfaces, and (iv) effective bandwidth aggregation when the mobile host has simultaneous access to multiple networks. We present the design and details of the proposed approach, and evaluate its performance through simulations and real-life field experiments.     

Stochastic Geometry and Random Graphs for the Analysis and Design of Wireless Networks

Wireless networks are fundamentally limited by the intensity of the received signals and by their interference. Since both of these quantities depend on the spatial location of the nodes, mathematical techniques have been developed in the last decade to provide communication-theoretic results accounting for the network?s geometrical configuration. Often, the location of the nodes in the network can be modeled as random, following for example a Poisson point process. In this case, different techniques based on stochastic geometry and the theory of random geometric graphs ? including point process theory, percolation theory, and probabilistic combinatorics ? have led to results on the connectivity, the capacity, the outage probability, and other fundamental limits of wireless networks. This tutorial article surveys some of these techniques, discusses their application to model wireless networks, and presents some of the main results that have appeared in the literature. It also serves as an introduction to the field for the other papers in this special issue.     

Location-Aided Handover in Heterogeneous Wireless Networks

The concept of being always online, regardless of the time and place, has been one of the hot topics in the commercial and scientific forums during the last years. The term itself is not solidly defined, however it is often used to refer to user's ability to get the same services via changing variety of underlying networks. In order to really work, this kind of multiaccess in heterogeneous networks still requires research, technological achievements and even compromises. The key to successfully implement the multiaccess is vertical handover that allows the application services to be seamlessly transferred between different networks.     

A Queue-Based Approach to Power Control in Wireless Communication Networks

In modern wireless communication systems, power control plays a fundamental role for efficient resource utilization, in particular in the systems where the users share the same bandwidth at the same time. In such systems, in fact, many users transmit over the same radio channel using the same frequency band and time slots so that the signal of an individual user becomes interference for the other users. Hence the transmission power levels need to be smartly manipulated so as to achieve an adequate quality of service for as many users as possible and, thus, an efficient network utilization. Conventional power control algorithms adopt the Signal-to-Interference-plus-Noise Ratio (SINR) as controlled variable and neglect the important effects of the manipulated control variables (transmission powers) and of the retransmission mechanism on the queueing dynamics. In this paper, we pursue a different queue-based approach which takes into account the queueing dynamics and adopts the queue size as controlled variable. In particular, a novel queue-based power control algorithm with low on-line computational burden is proposed and its performance is evaluated both theoretically and via simulation experiments.     

Enabling Intelligent Handovers in Heterogeneous Wireless Networks

In the future Wireless Internet, mobile nodes will be able to choose between providers offering competing services at a much finer granularity than we find today. Rather than months, service contracts may span hours or minutes. Connectivity, however, is just one of many possible services. Providers will begin to offer network and application-level services targeted at improving the overall wireless experience of the user. Determining the best path through the various networks will require accurate information describing which services are being offered by each provider. In this paper, we model the process of propagating this information as an instance of a distributed, hierarchical cache. Access routers actively discover and collect information about the immediate network neighborhood on behalf of mobile nodes. Mobiles fill their own caches through queries to their local access routers, and then employ the cached information to make informed, intelligent handover decisions. Through simulation, we show that high cache hit rates at the mobile node can be achieved even when the discovery process at the access router is incomplete. In comparison to static and centralized approaches, our dynamic approach requires less configuration and maintenance, avoids single points of failure, and provides a scalable solution that spans administrative domains. Robert C. Chalmers received his B.S. in Computer Science from the California State Polytechnic University, Pomona in 1997, and his M.S. in 2003 from the University of California in Santa Barbara. He is currently a Ph.D. candidate at the University of California in Santa Barbara where his main research interests focus around leveraging intelligence within the network. Particularly, he has studied multicast and its effect on resource utilization, as well as how to provide services for small, mobile devices in edge networks. He was awarded the Ericsson Fellowship in 2001 and is currently a Eugene Cota-Robles Fellow. Govind Krishnamurthi received an M.S. (Electrical Engineering) and Ph.D. degree (Computer Engineering) from the University of Washington and the Iowa State University, in 1997 and 1999 respectively. He spent the summer of 1995 as an intern at Bellcore, Morristown, NJ. He is a recipient of the Research Excellence Award from the Iowa State University for his Ph.D. thesis. Since the summer of 1999 he has been a Senior Research Engineer at the Nokia Research Center, Boston, MA. He has authored several publications and holds 3 patents. His current interests deal with QoS, location based services and security issues in IP based wireless networks. Kevin C. Almeroth earned his Ph.D. in Computer Science from the Georgia Institute of Technology in 1997. He is currently an associate professor at the University of California in Santa Barbara where his main research interests include computer networks and protocols, multicast communication, large-scale multimedia systems, and performance evaluation. At UCSB, Dr. Almeroth is a founding member of the Media Arts and Technology Program (MATP), Associate Director of the Center for Information Technology and Society (CITS), and on the Executive Committee for the University of California Digital Media Innovation (DiMI) program. In the research community, Dr. Almeroth is on the Editorial Board of IEEE Network, has co-chaired NGC 2000, Global Internet 2001, NOSSDAV 2002, and MMNS 2002; has served as tutorial chair for several conferences, and has been on the program committee of numerous conferences. Dr. Almeroth is serving as the chair of the Internet2 Working Group on Multicast, and is a member of the IETF Multicast Directorate (MADDOGS). He is also serving on the advisory boards of several startups including Occam Networks, NCast, Hidden Footprint, and the Santa Barbara Technology Incubator.     

A Kerberized Architecture for Fast Re-authentication in Heterogeneous Wireless Networks

In this paper we present an architecture for fast re-authentication, based on the use of the Kerberos protocol, which allows the reduction in the latency introduced for an authentication process based on the Extensible Authentication Protocol (EAP) when providing network access in mobile networks. The architecture supports two modes of operation, proactive and reactive, to reduce the latency added for the authentication processes which is required when a mobile user changes network points of attachment. Moreover, we provide implementation details on a representative wireless testbed and obtain experimental results from the testbed. Those results are used for simulations to evaluate the performance of the proposed architecture for different deployment scenarios and parameters. We also provide a mathematical analysis to compute authentication delay and validate the simulation results. Performance comparison based on the experiment, simulation and analysis show that the proposed architecture can reduce the authentication delay, compared to other alternatives in typical deployment scenarios.     

Terminal-Controlled Mobility Management in Heterogeneous Wireless Networks

The coexistence of multiple access technologies deployed by different operators is fundamental for future fourth-generation mobile networks. In spite of this heterogeneity, seamless interoperator/intersystem mobility is a mandatory requirement. In this article we present a seamless mobility management approach that does not require changes to existing network infrastructure. The novelty of the proposed approach is that mobility management is fully controlled by the terminal, and network selection is user-centric, power-saving, cost-aware, and performance-aware. Total mobility management, including interface management, handover decision, and execution, is also detailed     

一种无线传感器网络异构分簇模型的簇头调度方案

将无线传感器网络划分成簇会有效利用系统资源,近来提出的基于异构分簇模型的无线传感器网络,是指网络中存在多种不同能力的节点,能力强的节点自动成为簇头,这种网络避免了复杂的簇头选举过程并有效降低了普通节点的硬件复杂性和成本。但是,固定簇头的方法会削弱系统的负载均衡以及健壮性。为了解决这个问题,提出了一种基于自适应退避策略的簇头调度方案,该方案通过适当增加冗余度实现传感节点的k覆盖,增强了网络的健壮性。同时,依赖于地理信息和剩余电池能量信息,簇头节点通过自主周期性睡眠来保证系统负载的均衡分配,延长网络生存期。     

A Flexible QoS-aware Service Gateway for Heterogeneous Wireless Networks

The integration of different types of wireless access networks, or heterogeneous wireless networks (HWN), is emerging. This article investigates in particular how a combination of UMTS (Universal Mobile Telecommunications System) cellular networks, wireless LAN ad hoc networks, and DVB-H (digital video broadcasting - handheld) broadcasting networks, called UWD networks for short, is constructed and managed to provide users with QoS-aware services. Given the complexity of the UWD networks, a novel policy-based service gateway is proposed. As a software framework sitting over and communicating with the UWD network, this UWD service gateway makes network management decision by reasoning over a set of predefined policies that describe the behaviors of the UWD network. Network variables such as bandwidth, delay, and mobility in policies are fuzzified using fuzzy control theory to make the service gateway (as well as the whole UWD network) more flexible and robust. Both the prototype implementation and the evaluation results indicate the feasibility and effectiveness of the system     

A Practical Approach to Energy Efficient Communications in Mobile Wireless Networks

Energy efficiency and capacity maximization are two of the most challenging issues to be addressed by current and future cellular networks. Significant research effort has been placed recently in reducing the total energy consumption while maintaining or improving capacity either by introducing more efficient hardware components or by developing innovative software techniques. In this paper we investigate a novel networking paradigm to address the aforementioned problems. By capitalizing on the inherent delay tolerance of Internet type services, we argue that significant energy savings can be achieved by postponing the communication of information for a later time instance with better networking conditions. We device decentralized algorithms for the proposed postponement schemes and show the superior performance of implementing such schemes over the traditional cellular operation.     

A Cross-layer Approach to Channel Assignment in Wireless Ad Hoc Networks

To improve the capacity of wireless ad hoc networks by exploiting multiple available channels, we propose a distributed channel assignment protocol that is based on a cross-layer approach. By combining channel assignment with routing protocols, the proposed channel assignment protocol is shown to require fewer channels and exhibit lower communication, computation, and storage complexity than existing channel assignment schemes. A multi-channel MAC (MC-MAC) protocol that works with the proposed channel assignment protocol is also presented. We prove the correctness of the proposed channel assignment protocol. In addition, through a performance study, we show that the proposed protocol can substantially increase throughput and reduce delay in wireless ad hoc networks, compared to the IEEE 802.11 MAC protocol and an existing multi-channel scheme.

A Mobile-Directory Approach to Service Discovery in Wireless Ad Hoc Networks

We present the Service Directory Placement Algorithm (SDPA), a directory-placement scheme that leverages the performance of existing service discovery protocols over wireless ad-hoc networks. SDPA promotes the deployment of a nomadic service directory, whose current location in the network varies according to the dynamics of service-discovery queries driven by the users' applications and partial knowledge of the network's topology. SDPA is based on a heuristic approach, whose performance is optimized by formulating the directory-placement problem as a Semi-Markov Decision Process solved by means of a reinforcement-learning technique known as Q-Learning. Performance evaluations obtained through computer simulations of networks with up to 45 hosts moving at pedestrian walking speeds equal to or slower than 2 m/s reveal average bandwidth savings close to 50% over a default broadcast approach for service discovery once an efficient directory-placement policy is found.     

A Packet Scheduling Approach to QoS Support in Multihop Wireless Networks

Providing packet-level quality of service (QoS) is critical to support both rate-sensitive and delay-sensitive applications in bandwidth-constrained, shared-channel, multihop wireless networks. Packet scheduling has been a very popular paradigm to ensure minimum throughput and bounded delay access for packet flows. This work describes a packet scheduling approach to QoS provisioning in multihop wireless networks. Besides minimum throughput and delay bounds for each flow, our scheduling disciplines seek to achieve fair and maximum allocation of the shared wireless channel bandwidth. However, these two criteria can potentially be in conflict in a generic-topology multihop wireless network where a single logical channel is shared among multiple contending flows and spatial reuse of the channel bandwidth is possible. In this paper, we propose a new scheduling model that addresses this conflict. The main results of this paper are the following: (a) a two-tier service model that provides a minimum fair allocation of the channel bandwidth for each packet flow and additionally maximizes spatial reuse of bandwidth, (b) an ideal centralized packet scheduling algorithm that realizes the above service model, and (c) a practical distributed backoff-based channel contention mechanism that approximates the ideal service within the framework of the CSMA/CA protocol.     

An Efficient Approach for Big Data Aggregation Mechanism in Heterogeneous Wireless Connected Sensor Networks

Recently and due to the impressive growth in the amounts of transmitted data over the heterogeneous sensor networks and the emerged related technologies especially the Internet of Things in which the number of the connected devices and the data consumption are remarkably growing, big data has emerged as a widely recognized trend and is increasingly being talked about. The term big data is not only about the volume of data, but also refers to the high speed of transmission and the wide variety of information that is difficult to collect, store and process using the available classical technologies. Although the generated data by the individual sensors may not appear to be significant, all the data generated through the many sensors in the connected sensor networks are able to produce large volumes of data. Big data management imposes additional constraints on the wireless sensor networks and especially on the data aggregation process, which represents one of the essential paradigms in wireless sensor networks. Data aggregation process can represent a solution to the problem of big data by allowing data from different sources to be combined to eliminate the redundant ones and consequently reduce the amounts of data and the consumption of the available resources in the network. The main objective of this work is to propose a new approach for supporting big data in the data aggregation process in heterogeneous wireless sensor networks. The proposed approach aims to reduce the data aggregation cost in terms of energy consumption by balancing the data loads on the heterogeneous nodes. The proposal is improved by integrating the feedback control closed loop to reinforce the balance of the data aggregation load on the nodes, maintaining therefore an optimal delay and aggregation time.

     

A Unified Approach to QoS-Guaranteed Scheduling for Channel-Adaptive Wireless Networks

Scheduling amounts to allocating optimally channel, rate and power resources to multiple connections with diverse quality-of-service (QoS) requirements. It constitutes a throughput-critical task at the medium access control layer of today's wireless networks that has been tackled by seemingly unrelated information-theoretic and protocol design approaches. Capitalizing on convex optimization and stochastic approximation tools, the present paper develops a unified framework for channel-aware QoS-guaranteed scheduling protocols for use in adaptive wireless networks whereby multiple terminals are linked through orthogonal fading channels to an access point, and transmissions are (opportunistically) adjusted to the intended channel. The unification encompasses downlink and uplink with time-division or frequency-division duplex operation; full and quantized channel state information comprising a few bits communicated over a limited-rate feedback channel; different types of traffic (best effort, non-real-time, real-time); uniform and optimal power loading; off-line optimal scheduling schemes benchmarking fundamentally achievable rate limits; as well as on-line scheduling algorithms capable of dynamically learning the intended channel statistics and converging to the optimal benchmarks from any initial value. The take-home message offers an important cross-layer design guideline: judiciously developed, yet surprisingly simple, channel-adaptive, on-line schedulers can approach information-theoretic rate limits with QoS guarantees.     

LTE-U与Wi-Fi异构网络下的公平共存方案

本文首先对LTE-U技术进行概述并对其在5GHz非授权频谱上与Wi-Fi进行对比,凸显其优势所在.同时表明与现有Wi-Fi技术共存问题是LTE-U发展的最大瓶颈,并提出三种解决方案,以使LTE-U突破共存瓶颈,在Wi-Fi和LTE-U网络公平共存场景下的,使得系统性能得到了进一步提升.