A Game-Theoretic Framework for Landmark-Based Image Segmentation

A novel game-theoretic framework for landmark-based image segmentation is presented. Landmark detection is formulated as a game, in which landmarks are players, landmark candidate points are strategies, and likelihoods that candidate points represent landmarks are payoffs, determined according to the similarity of image intensities and spatial relationships between the candidate points in the target image and their corresponding landmarks in images from the training set. The solution of the formulated game-theoretic problem is the equilibrium of candidate points that represent landmarks in the target image and is obtained by a novel iterative scheme that solves the segmentation problem in polynomial time. The object boundaries are finally extracted by applying dynamic programming to the optimal path searching problem between the obtained adjacent landmarks. The performance of the proposed framework was evaluated for segmentation of lung fields from chest radiographs and heart ventricles from cardiac magnetic resonance cross sections. The comparison to other landmark-based segmentation techniques shows that the results obtained by the proposed game-theoretic framework are highly accurate and precise in terms of mean boundary distance and area overlap. Moreover, the framework overcomes several shortcomings of the existing techniques, such as sensitivity to initialization and convergence to local optima.     

A Noncooperative Game-Theoretic Framework for Radio Resource Management in 4G Heterogeneous Wireless Access Networks

Fourth generation (4G) wireless networks will provide high-bandwidth connectivity with quality-of-service (QoS) support to mobile users in a seamless manner. In such a scenario, a mobile user will be able to connect to different wireless access networks such as a wireless metropolitan area network (WMAN), a cellular network, and a wireless local area network (WLAN) simultaneously. We present a game-theoretic framework for radio resource management (that is, bandwidth allocation and admission control) in such a heterogeneous wireless access environment. First, a noncooperative game is used to obtain the bandwidth allocations to a service area from the different access networks available in that service area (on a long-term basis). The Nash equilibrium for this game gives the optimal allocation which maximizes the utilities of all the connections in the network (that is, in all of the service areas). Second, based on the obtained bandwidth allocation, to prioritize vertical and horizontal handoff connections over new connections, a bargaining game is formulated to obtain the capacity reservation thresholds so that the connection-level QoS requirements can be satisfied for the different types of connections (on a long-term basis). Third, we formulate a noncooperative game to obtain the amount of bandwidth allocated to an arriving connection (in a service area) by the different access networks (on a short-term basis). Based on the allocated bandwidth and the capacity reservation thresholds, an admission control is used to limit the number of ongoing connections so that the QoS performances are maintained at the target level for the different types of connections.     

Medium Access Control for ATM-to-CDMA Interface

An integrated medium access control framework for a direct sequence code-division multiple access (CDMA) radio access to an asynchronous transfer mode (ATM) network is considered. The system accommodates multimedia services such as voice and data. The inherently high error rate associated with the multipath fading channel is partly overcome by the introduction of a data link control layer employing one- and two-dimensional CRC codes for error detection/correction in voice and data packets, respectively. Analysis and simulations show promising average delay and error probability performance, as well as low coding redundancy. Two-dimensional CRC, particularly in conjunction with automatic repeat request (ARQ), outperforms convolutional coding with much less overhead and processing requirement at the ATM-CDMA interface.     

DQCA：一种新的城域网介质访问控制协议

本文提出一种新的城域网介质访问控制协议－ＤＱＣＡ。在大文件传输时ＤＱＣＡ网络经过一个暂态过程后可达到公平的稳态。而这个暂态过程比ＤＱＤＢ短得多，而且网络无带宽浪费。ＤＱＣＡ城域网的带宽分配十分灵活。计算机仿真显示了ＤＱＣＡ良好的介质访问特性。     

M－DQCA：可调信道访问光波网介质访问控制协议

本文提出了一种可调信道访问光波网以及适合于该网的介质访问控制协议Ｍ－ＤＱＣＡ，利用波分复用技术将双总线光波网分成多个并行信道，用一个信道专门传输等时业务和请求信息，使网络管理得到简化；利用时隙重用技术，提高了网络的吞吐量；拥塞控制方法与多跳网相比简单得多，各用户只需根据本站缓存的情况来控制输入业务的流量。计算机仿真表明，Ｍ－ＤＱＣＡ光波网具有很好的性能。     

跨域访问控制策略合成的可视化框架

The rapid increase in resource sharing across domains in the cloud computing environment makes the task of managing inter-domain access control policy integration difficult for the security administrators. Although a number of policy integration and security analysis mechanisms have been developed, few focus on enabling the average ad-ministrator by providing an intuitive cognitive sense about the integrated policies, which considerably undermines the usability factor. In this paper we propose a visualization framework for inter-domain access control policy integration, which integrates Role Based Access Control (RBAC) policies on the basis of role-mapping and then visualizes the integrated result. The role mapping algorithm in the framework considers the hybrid role hierarchy. It can not only satisfy the security constraints of non-cyclic inheritance and separation of duty but also make visualization easier. The framework uses role-permission trees and semantic substrates to visualize the integrated policies. Through the interactive policy query visualization, the average administrator can gain an intuitive understanding of the policy integration result.     

A Framework to Enforce Access Control, Usage Control and Obligations

In this paper, we define a core language to express access control, usage control and obligation policies and we specify a policy controller in charge of evaluating such policies. This policy language can be used to specify security requirements of many applications such as drm (Digital Right Management), P2P or Web Service applications. It is used to express both contextual permissions and obligations. In our formalism, a permission is associated with two conditions: The “start condition” that must be true just when the access request is evaluated (access control) and the “ongoing condition” that must be always satisfied while the access is in progress (usage control). Moreover, we introduce the concept of cancellation actions to authorize users to cancel access in progress. Obligations are mandatory access that users must perform. An obligation is associated with two conditions as well: The “raise condition” to trigger the obligation and the “deadline condition” to determine when the obligation is violated. Moreover, we introduce the concept of non-persistent obligation where the raise condition must be true until the corresponding request is received or the deadline expires, otherwise the corresponding access is no longer mandatory.     

移动Ad Hoc网络MAC协议综述

移动AdHoc网络(MANET)是移动节点自组织网络,由于特殊的应用环境成为现今研究的热点。文章对MANET物理信道的特点作了描述并对其MAC协议进行了归类和详细介绍,同时分析了各种协议的优缺点,最后对整个领域及未来的研究方向作了简要的总结和说明。     

SYN-MAC: A Distributed Medium Access Control Protocol for Synchronized Wireless Networks

In this paper, we propose a novel medium access control (MAC) protocol, called SYN-MAC (for SYNchronized MAC), based on a binary countdown approach tailored for wireless networks. SYN-MAC has several attractive features such as simplicity, robustness, high efficiency, fairness, and quality of service capability. We evaluate SYN-MAC in terms of collision probability, system throughput, and packet delay, via both analysis and simulation. Our results show that, with properly chosen parameters, SYN-MAC can achieve a very low collision probability, packet delay tolerance, and extremely high channel efficiency (of > 90%) under a wide range of traffic load. As a result, SYN-MAC may serve as an alternative to IEEE 802.11 for the wireless stations in synchronized networks.This work is supported in part by National Science Foundation CAREER Award under Award Number CNS-0347686, by U.S. Department of Energy (DoE) under Award Number DE-FG02-04ER46136, and by Board of Regents, State of Louisiana under Contract Number No. DOE/LEQSF(2004-07)-ULL and LEQSF(2003-06)-RD-A-37. Part of this work was presented in the student poster session of IEEE International Conference on Network Protocols (ICNP) 2003, Atlanta, GA.Hongyi Wu is currently a tenure-track Assistant Professor in the Center for Advanced Computer Studies (CACS), University of Louisiana (UL) at Lafayette. He received his Ph.D. degree in computer science and M.S. degree in electrical engineering from State University of New York (SUNY) at Buffalo in 2002 and 2000, respectively. He received his B.S. degree in scientific instruments from Zhejiang University in 1996. His research interests include wireless mobile ad hoc networks, wireless sensor networks, next generation cellular systems, and integrated heterogeneous wireless systems. He has served as symposium chair, session chair, and technical committee member of several IEEE conferences, and a guest editor of ACM MONET special issue on Integration of Heterogeneous Wireless Technologies. He has published more than two dozens of technical papers in leading journals and conference proceedings.Anant P. Utgikar (S’03) graduated with B.Tech. in Electrical Engineering from IIT—Bombay in 2001. He received M.S. in Computer Engineering from Univ. of Louisiana at Lafayette (UL Lafayette) in 2003. Presently he is working towards Ph.D. at UL Lafayette. His research interests include computer networking, logic design, software, simulation, mobile computing and distributed systems. His contributions to network simulator NS2 were ranked in top-5 of over 240,000 pages by Google. He has won many programming competitions, IEEE, IEE technical paper presentation contests as undergraduate and High School Science-Math Olympiads in India. He was honored by Govt. of India for outstanding performance at national level in XII-th. He has authored a book chapter on Reservation Based MAC protocols. He has published in IEEE ICNP’03, IEEE SiPS’03 and IEEE CAMP’03. He was invited with travel grant to NS2 workshop’02 at USC/ISI, ICNP’03 and SiPS’03. He has been in organizing team of IEEE CAMP 2003 and CyberSecurity Workshop 2003. He has served as Reviewer for IEEE-VTC and ACM-MONET. He has held positions of Student Government Senator and Secretary, Graduate Students Organization at UL Lafayette. He has contributed as volunteer to National Science-Technology-Math ESTME Week organised by NSF and DoE, USA.Nian-Feng Tzeng received the Ph.D. degree in Computer Science from the University of Illinois at Urbana-Champaign. Since 1987, he has been with Center for Advanced Computer Studies, the University of Louisiana at Lafayette, where he is currently a professor. His current research interest is in the areas of computer communications and networks, high-performance computer systems, parallel and distributed processing and fault-tolerant computing. He was on the editorial board of the IEEE Transactions on Parallel and Distributed Systems, 1998–2001, and on the editorial board of the IEEE Transactions on Computers, 1994–1998. He served as a Distinguished Visitor of the IEEE Computer Society, 1994–1997, and was the Chair of Technical Committee on Distributed Processing, the IEEE Computer Society, from 1999 till 2002. He has been on the technical program committees of various conferences and will serve as the Technical Program Chair of the 10th International Conference on Parallel and Distributed Systems, July 2004.Dr. Tzeng is the recipient of the outstanding paper award of the 10th International Conference on Distributed Computing Systems, May 1990. He received the University Foundation Distinguished Professor Award in 1997.     

一种提供时延QoS保障的无线网络MAC协议

本文从提高系统工作效率的角度出发,提出了一种基于无争用集中控制的忙队列周期查询(BQPO)控制协议.该协议为时延QoS要求较高的无线终端提供了稳定可靠的保障,通过系统建模分析获得了系统的信息分组平均等待时间的解析结果.仿真实验结果表明理论分析和仿真实验的一致性与合理性,与PCF控制方式相比,BQPO协议具有更好的稳定性和时延QoS保障.     

基于QoS的无线ATM网的MAC协议

首先介绍了传统OSI模型中介质接入控制（MediumAccessControl,MAC）协议及其在有线本地网中的应用。接着针对无线ATM网的特．或对两种基于服务质量（Quakity—of－Service，QoS）的MAC协议进行了详细的阐述。最后指出了它们相对于传统的MAC协议的优越性。     

宽带GEO卫星网络媒体接入控制协议

宽带地球同步轨道（GEO）卫星通信网络中对媒体接入控制协议设计的目的就是在保障用户服务质量的同时提高系统资源利用率。概述了宽带GEO卫星网络的特点,总结了影响媒体接入控制协议性能的主要因素,重点对两种多址接入方案进行分析：基于混合式自适应分配机制的媒体接入控制协议和基于地面请求策略的动态分配多址接入协议。结果表明,提高网络性能的最佳方法是将有效的地面请求策略与合理的资源分配方式相结合。最后,对下一步的研究方向提出了建议。     

Enabling Distributed Medium Access Control for Impulse-Based Ultrawideband Radios

Impulse-based ultrawideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to multipath effects, subcentimeter ranging ability, simple hardware, and low radiated power. Large distributed networks, such as ad hoc and sensor networks, often implement distributed medium access control (MAC) protocols based on carrier sense multiple access (CSMA). In CSMA, narrowband systems check for medium activity before transmitting by checking for in-band energy around a carrier frequency. I-UWB systems lack a carrier, and the narrow pulses, low radiated power, harsh channel conditions, and strict Federal Communications Commission power limits present challenges in detecting medium activity. We propose a pulse sensor for I-UWB systems that overcomes the challenges of quickly, reliably, and efficiently identifying medium activity. The pulse sensor enables distributed MAC protocols for I-UWB radios that are analogous to CSMA for narrowband radios. Simulations show that the proposed pulse sensor architecture is practical for I-UWB radios     

A Novel Medium Access Control for Ad hoc Networks Based on OFDM System

1IntroductionIn Ad hoc networks , the nodes share the wirelesschannel under the control of media access control proto-col . Currently,there are two types of MAC protocolsproposedfor Ad hoc networks . The first is hand-shak-ing protocol such as IEEE 802 .11 MAC protocol[1 ~4]and MACAW[5], which controls the access procedureby exchanging the control packets among the activenodes . The secondis busy-tone protocol that introducesadditional busy tone signal to control the medium ac-cess . S…     

A Medium Access Control Protocol for Voice/Data Integrated Wireless CDMA Systems

In this paper, a medium access control protocol is proposed for integrated voice and data services in wireless local networks. Uplink channels for the proposed protocol are composed of time slots with multiple spreading codes per slot based on slotted code division multiple access (CDMA) systems. The proposed protocol uses spreading code sensing and reservation schemes. This protocol gives higher access priority to delay‐sensitive voice traffic than to data traffic. The voice terminal reserves an available spreading code to transmit multiple voice packets during a talkspurt. On the other hand, the data terminal transmits a packet without making a reservation over one of the available spreading codes that are not used by voice terminals. In this protocol, voice packets do not come into collision with data packets. The numerical results show that this protocol can increase the system capacity for voice service by applying the reservation scheme. The performance for data traffic will decrease in the case of high voice traffic load because of its low access priority. But it shows that the data traffic performance can be increased in proportion to the number of spreading codes.     

A Detailed Review of Multi-Channel Medium Access Control Protocols for Wireless Sensor Networks

Most applications of Wireless Sensor Networks (WSNs) assume the presence of single-channel Medium Access Control (MAC) protocols. In the usual dense deployment of the sensor networks, single-channel MAC protocols may be deficient because of radio collisions and limited bandwidth. Hence, using multiple channels can significantly improve the performance of WSN. Recent developments in sensor technology, as seen in Crossbow’s MICAz Mote, Rockwell’s WINS nodes and IEEE 802.15.4 Zigbee, have enabled support for multi-channel communications. Several multi-channel MAC protocols with different objectives have been proposed for WSNs in literature. This paper surveys and classifies the state-of-the-art multi-channel MAC protocols that are proposed for WSNs. It first outlines the sensor network properties that are crucial for designing a MAC protocol. It subsequently reviews the existent challenges to design a good multi-channel MAC protocol for the sensor networks. Then, several multi-channel MAC protocols specifically proposed for the WSNs are inspected in detail and compared with each other. Finally, some open issues in this area are outlined for future research.