Socially-Aware Multi-phase Opportunistic Routing for Distributed Mobile Social Networks

The work presented in this paper focuses on opportunistic routing in distributed Mobile Social Networks (MSNs). It proposes a novel routing protocol called Socially-Aware Multi-Phase Opportunistic (SAMPhO), where the routing procedure for each message is carried out in multiple phases. From the various socially aware metrics considered, ego-betweenness and tie strength are selected to be utilized according to the conditions of the social environment. Previous research on the area suggests that different metrics are useful in different conditions. However, only recently steps towards this direction are taken. To evaluate the proposed hypothesis, a simulated delay tolerant MSN was introduced in the OMNeT++ environment using a framework, developed as part of this work. It is called Socially-Aware Opportunistic Routing System (SAORS) and its modular design facilitates further research in opportunistic networks. The routing mechanism is divided in three independent stages, with SAORS focusing on providing the necessary functionality for the first one. The simulation results drawn clearly demonstrate the scalability and improved performance of SAMPhO, especially in highly social scenarios. It is shown to be both more efficient and effective than previous algorithms, in terms of bandwidth and memory utilization, and delivery rates respectively. However, it relies greatly on the accuracy of the social tie detection, since the copy generation is very limited.     

On Bandwidth Allocation for Data Dissemination in Cellular Mobile Networks

Wireless bandwidth is a scarce resource in a cellular mobile network. As such, it is important to effectively allocate bandwidth to each cell such that the overall system performance is optimized. Channel allocation strategies have been extensively studied for voice communications in cellular networks. However, for data dissemination applications, studies on bandwidth allocation have thus far been limited to a single-cell environment. This paper investigates the problem of bandwidth allocation for data dissemination in a multi-cell environment, which, to the best of our knowledge, has not been investigated before. The performance objective is to minimize the overall expected access latency given the workload for each cell in a data dissemination system. Two heuristic techniques, called compact allocation and cluster-step allocation, are proposed to effectively allocate bandwidth for a cellular network. Simulation experiments are conducted to evaluate the performance of the proposed bandwidth allocation schemes. Experimental results show that the proposed schemes substantially outperform the uniform allocation and proportional allocation schemes.     

Multicast and Broadcast Multimedia Services in Mobile WiMAX Networks

Multicast and broadcast services in WiMAX are downlink point-to-multipoint access services optimized for transmission of a common set of multimedia data packets to a group of users. This capability enables low-cost delivery of large volumes of popular contents (e.g., for video/audio streaming and file sharing) in a mobile network. The MCBCS framework in WiMAX allows multicast/broadcast of data in a radio channel that is time shared with unicast services. In a single-frequency network, where MCBCS transmissions are synchronized or coordinated across BSs in the designated service area, the mobile stations can use macro-space diversity to improve achievable data rates and also maintain service continuity and power saving across cells with minimal interaction with the network.     

Signaling for Multimedia Conferencing in Stand-Alone Mobile Ad Hoc Networks

Mobile ad hoc networks (MANETs) are infrastructure-less and can be set up anywhere, anytime. They can host a wide range of applications in rescue operations, military, private, and commercial settings. Multimedia conferencing is the basis of a wealth of killer” applications that can be deployed in MANETs. Some examples are audio/video conferencing, multiplayer games, and online public debating. Signaling is the nerve center of multimedia conferences—it establishes, modifies, and tears down conferences. This paper focuses on signaling for multimedia conferences in MANETs. We review the state of the art and propose a novel architecture based on application-level clusters. Our validation employed SIP as the implementation technology and OPNET as our simulation tool. Our clusters are constructed dynamically and the nodes that act as cluster heads are elected based on their capabilities. The capabilities are published and discovered using a simple application-level protocol. The architectural principles and the clustering operations are discussed. Our SIP-based implementation is also presented along with the performance evaluation.     

Coupons: A Multilevel Incentive Scheme for Information Dissemination in Mobile Networks

Integrating mobile computing and localized user interaction into the Internet requires more than simply overcoming pure routing challenges. Apart from issues such as intermittent connectivity and unreliable nodes, the human factor is becoming increasingly important. To date, user behavior has only been considered in terms of mobility patterns and incentives for encouraging cooperation. Moreover, the focus has always been on systems that aim to enforce fairness by either bringing an indirect equilibrium or by punishing "misbehaving" users. The goal of this paper is therefore to present Coupons. Coupons is an idea to define, evaluate, and implement algorithms for the emerging class of social network and information sharing applications. Coupons is a system designed to allow users to opportunistically interact and share data through a wireless medium, to overcome highly variable Internet access through adaptive localized interaction, and to incorporate an incentive scheme to make the system usable and encourage participation.     

Bandwidth Adaptation Algorithms for Adaptive Multimedia Services in Mobile Cellular Networks

The fluctuation of available link bandwidth in mobilecellular networks motivates the study of adaptive multimediaservices, where the bandwidth of an ongoing multimedia call can bedynamically adjusted. We analyze the diverse objectives of theadaptive multimedia framework and propose two bandwidth adaptationalgorithms (BAAs) that can satisfy these objectives. The firstalgorithm, BAA-RA, takes into consideration revenue and``anti-adaptation' where anti-adaptation means that a user feelsuncomfortable whenever the bandwidth of the user's call ischanged. This algorithm achieves near-optimal total revenue withmuch less complexity compared to an optimal BAA. The secondalgorithm, BAA-RF, considers revenue and fairness, and aims at themaximum revenue generation while satisfying the fairnessconstraint defined herein. Comprehensive simulation experimentsshow that the difference of the total revenue of BAA-RA and thatof an optimal BAA is negligible. Also, numerical results revealthat there is a conflicting relationship between anti-adaptationand fairness.     

未来移动多媒体网络之间无缝切换的挑战

第三代移动通信系统的主要目标是提供多媒体业务,在移动多媒体通信系统中的切换问题非常重要,本文介绍了多媒体业务的特点,移动多媒体业务切换的特殊要求,不同网络间的切换协议。重点介绍了基于IP网络的移动多媒体网络之间无缝切换的各种水平切换和垂直切换方式以及无线TCP的优化。     

QoS Provisioning in Wireless/Mobile Multimedia Networks Using an Adaptive Framework

Recently there is a growing interest in the adaptive multimedia networking where the bandwidth of an ongoing multimedia call can be dynamically adjusted. In the wireless/mobile multimedia networks using the adaptive framework, the existing QoS provisioning focused on the call blocking probability and the forced termination probability should be modified. We, therefore, redefine a QoS parameter – the cell overload probability – from the viewpoint of the adaptive multimedia networking. Then, we propose a distributed call admission control (CAC) algorithm that guarantees the upper bound of the cell overload probability. Also, a bandwidth adaptation algorithm which seeks to minimize the cell overload probability is also presented. Simulation experiments are carried out to verify the performance of the proposed CAC algorithm. Furthermore, the performance of the adaptive wireless/mobile network is compared to that of the existing non-adaptive wireless/mobile networks. As a further step in QoS provisioning, we propose another QoS parameter, the degradation period ratio, and discuss analytically how the CAC algorithm guarantees the upper bound of the degradation period ratio.     

A Call Admission Control Mechanism Using Mobility Graph in Mobile Multimedia Networks

One of the important issues in providing efficient multimedia traffic on a mobile computing environment is to guarantee the mobile host (client) with consistent QoS (Quality of Service). However, the QoS negotiated between the client and the network in one cell may not be honored due to client mobility, causing hand-offs between cells. In this paper, a call admission control mechanism is proposed to provide a consistent QoS guarantee for multimedia traffic on a mobile computing environment. Each cell can reserve fractional bandwidth for hand-off calls to its adjacent cells. It is important to determine the right amount of bandwidth reserved for hand-off calls because the blocking probability of new calls may increase if the amount of reserved bandwidth is more than necessary. An adaptive bandwidth reservation based on a mobility graph and a 2-tier cell structure is proposed to determine the amount of bandwidth to be reserved in the cell and to control dynamically its amount according to network conditions. We also propose a call admission control based on this bandwidth reservation and ``next-cell prediction' scheme using a mobility graph. In order to evaluate the performance of our call admission control mechanism, we measure metrics such as blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of existing mechanisms such as NR-CAT2, FR-CAT2, and AR-CAT2.     

Layer 7 Multimedia Proxy Handoff Using Anycast/Multicast in Mobile Networks

Proxies can improve the quality of service (QoS) of clients in the three-tier networking architecture. However, it is more complicated to apply the server-proxy-client networking architecture to mobile networks for multimedia streaming because mobile clients possess the "keeping moving" characteristic. Therefore, the three-tier architecture in mobile networks must take user mobility into consideration, i.e., mobile clients should be able to switch to a proxy dynamically. In this paper, application-layer proxy handoff (APH) is defined to have applications be executed smoothly when mobile clients move in the server-proxy-client architecture. First, APH employs application-layer anycast to select one of the candidate proxies as the next proxy based on 1) the network condition between the mobile client and each candidate proxy and 2) the load balance among the candidate proxies. Second, APH utilizes IPv6 multicast to switch the session from the original proxy to the next proxy smoothly and to forward the available cache unsent in the original proxy to the next proxy for keeping the original session continuous     

Efficient QoS Provisioning for Adaptive Multimedia in Mobile Communication Networks by Reinforcement Learning

The scarcity and large fluctuations of link bandwidth in wireless networks have motivated the development of adaptive multimedia services in mobile communication networks, where it is possible to increase or decrease the bandwidth of individual ongoing flows. This paper studies the issues of quality of service (QoS) provisioning in such systems. In particular, call admission control and bandwidth adaptation are formulated as a constrained Markov decision problem. The rapid growth in the number of states and the difficulty in estimating state transition probabilities in practical systems make it very difficult to employ classical methods to find the optimal policy. We present a novel approach that uses a form of discounted reward reinforcement learning known as Q-learning to solve QoS provisioning for wireless adaptive multimedia. Q-learning does not require the explicit state transition model to solve the Markov decision problem; therefore more general and realistic assumptions can be applied to the underlying system model for this approach than in previous schemes. Moreover, the proposed scheme can efficiently handle the large state space and action set of the wireless adaptive multimedia QoS provisioning problem. Handoff dropping probability and average allocated bandwidth are considered as QoS constraints in our model and can be guaranteed simultaneously. Simulation results demonstrate the effectiveness of the proposed scheme in adaptive multimedia mobile communication networks. This work is based in part on a paper presented at BroadNet's 04, San Jose, CA, Oct. 2004. Fei Yu received the M.S. degree in Computer Engineering from Beijing University of Posts and Telecommunications, P.R. China, in 1998, and the Ph.D. degree in Electrical Engineering from the University of British Columbia (UBC), Canada, in 2003. From 1998 to 1999, Dr. Yu was a system engineer at China Telecom, P.R. China, working on the planning, design and performance analysis of national SS7 and GSM networks. From 2002 to 2004, He was a research and development engineer at Ericsson Mobile Platforms, Sweden, where he worked on dual-mode UMTS/GPRS handsets. He is currently a postdoctoral research fellow at UBC. His research interests are quality of service, cross-layer design and mobility management in wireless networks. Vincent W.S. Wong (S'94-M'00) received the B.Sc. (with distinction) degree from the University of Manitoba, Winnipeg, MB, Canada, in 1994, the M.A.Sc. degree from the University of Waterloo, Waterloo, ON, Canada, in 1996, and the Ph.D. degree from the University of British Columbia (UBC), Vancouver, BC, Canada, in 2000, all in electrical engineering. From 2000 to 2001, he was a Systems Engineer at PMC-Sierra, Inc., Burnaby, BC. Since 2002, he has been with the Department of Electrical and Computer Engineering, UBC, where he is currently an Assistant Professor. His research interests are in wireless communications and networking. Dr. Wong received the Natural Science and Engineering Research Council (NSERC) postgraduate scholarship and the Fessenden Postgraduate Scholarship from Communications Research Centre, Industry Canada, during his graduate studies. Victor C.M. Leung received the B.A.Sc. (Hons.) degree in electrical engineering from the University of British Columbia (U.B.C.) in 1977, and was awarded the APEBC Gold Medal as the head of the graduating class in the Faculty of Applied Science. He attended graduate school at U.B.C. on a Natural Sciences and Engineering Research Council Postgraduate Scholarship and obtained the Ph.D. degree in electrical engineering in 1981. From 1981 to 1987, Dr. Leung was a Senior Member of Technical Staff at Microtel Pacific Research Ltd. (later renamed MPR Teltech Ltd.), specializing in the planning, design and analysis of satellite communication systems. He also held a part-time position as Visiting Assistant Professor at Simon Fraser University in 1986 and 1987. In 1988, he was a Lecturer in the Department of Electronics at the Chinese University of Hong Kong. He joined the Department of Electrical Engineering at U.B.C. in 1989, where he is a Professor, Associate Head of Graduate Affairs, holder of the TELUS Mobility Industrial Research Chair in Advanced Telecommunications Engineering, and a member of the Institute for Computing, Information and Cognitive Systems. His research interests are in the areas of architectural and protocol design and performance analysis for computer and telecommunication networks, with applications in satellite, mobile, personal communications and high speed networks. Dr. Leung is a Fellow of IEEE and a voting member of ACM. He is an editor of the IEEE Transactions on Wireless Communications, and an associate editor of the IEEE Transactions on Vehicular Technology. He has served on the technical program committees of numerous conferences, and is serving as the Technical Program Vice-Chair of IEEE WCNC 2005.     

IGBDD: Intelligent Grid Based Data Dissemination Protocol for Mobile Sink in Wireless Sensor Networks

Lifetime and energy efficiency are important factors in the design of wireless sensor network. A critical issue during data collection is the formation of energy holes near the sink. Sensors which are located near the sink have to participate in relaying data on behalf of other sensors and thus their energy will be depleted very quickly. Mobile sink movement yields the significant performance gained by decreasing the amount of energy consumption. In this paper, we propose an Intelligent Grid Based Data Disseminating protocol for mobile sink in wireless sensor networks. We have utilized a virtual grid as the protocol’s substructure. In our proposed method, cell heads (CHs) will be selected based on the locations of virtual cross points (CPs) and CPs selection is needless to transfer any required data between neighbor nodes. We have optimized CPs selection using linear programming technique in order to increase network lifetime. By selecting the CHs based on our proposed algorithm, data will be disseminated toward the sink. Our data dissemination protocol is simple and has low overhead to construct and maintain. Also, we have presented a new method for sink location update which leads to the least cost in data transfer. Simulation results illustrate that by utilizing hierarchical functionality and selecting appropriate CPs and consequently selecting CHs, energy consumption will be decreased in comparison with other presented methods which directly lead to network lifetime increment. Also by determining an optimal cell size, packet delivery rate will be improved noticeably.     

Mobile Multimedia Services

Mobile multimedia has been a goal for technologists and the mobile industry alike for some time, but now many components are coming together to make mobile multimedia a reality — mobile data networks, devices with colour screens, multimedia content, etc. This paper reviews the vision for mobile multimedia and describes a roadmap for its deployment, beginning in the here and now with SMS-based services and culminating in 3G services complemented by wireless LAN hot-spots. Since mobile technology alone cannot realise mobile multimedia, later sections of this paper also consider the importance of appropriate business models, value chains and billing. Some challenges to mobile multimedia are also discussed and some potential solutions and developments that may help to overcome them. This revised version was published online in July 2006 with corrections to the Cover Date.     

移动互联网助推移动视讯发展

随着移动互联网的飞速发展,移动网络速度不断提升,智能终端成本持续下降,移动互联网为多媒体视讯发展带来新的增长契机——移动视讯。结合移动应用、位置定位、传感器件等智能终端技术,移动视讯在监控、会话、会议、消息等方面得到广泛应用。同时,移动互联网催生了包括微视频、富媒体广告在内的多种新颖移动视讯形式。移动互联网在提升移动视讯服务质量的同时,在应用的深度和广度上也极大程度地推动移动视讯的发展。但是受限于移动智能终端的特点和无线数据信道的稳定性差,移动视讯也存在诸多问题。本文首先阐述移动视讯技术需求和移动互联网特点优势,进而介绍移动互联网在移动视讯中典型应用,最后分析移动视讯存在的问题。     

个人移动视频浅析

个人移动视频通讯（Mobile video Communications MVC）一直被认为是3G移动网络潜在的”杀手级应用（killerapplications）“之一。然而,市场和技术方面的局限性使得很多人对该应用的推广提出了质疑。Wainhouse Research针对这些焦点问题开展了深度研究。以下为该报告的摘录，着重阐述了一些关键性研究成果。     

Cost Based Data Dissemination in Satellite Networks

We consider the problem of data dissemination in a broadcast network. In contrast to previously studied models, broadcasting is among peers, rather than client server. Such a model represents, for example, satellite communication among widely distributed nodes, sensor networks, and mobile ad hoc networks. We introduce a cost model for data dissemination in peer to peer broadcast networks. The model quantifies the tradeoff between the inconsistency of the data, and its transmission cost; the transmission cost may be given in terms of dollars, energy, or bandwidth. Using the model we first determine the parameters for which eager (i.e. consistent) replication has a lower cost than lazy (i.e. inconsistent) replication. Then we introduce a lazy broadcast policy and compare it with several naive or traditional approaches to solving the problem.     

SDN技术及其在移动通信网中的应用

提出移动分组域网关控制面进一步分离以及面向用户和业务的智能路由两种在移动核心网引入软件定义网络(SDN)技术的思路,对移动分组域架构的演进展开了进一步思考;分析了数据中心内部和跨数据中心网络中可能的SDN应用场景,预测了SDN短期应用的可能性;分析了网络服务虚拟化的应用场景和关键技术.     

Dynamic Information Dissemination to Mobile Users

We present the dynamic channel model, an information push model for data dissemination to mobile users. This is a set of extensions to the conceptual models developed for information channels that capture mobility-specific requirements. Dynamic channels are used for filtering and setting update order priorities for the information that users intend to monitor, which depends on their location and changes as they roam. The dynamic channel model was implemented in Ubidata, a software framework for the construction of systems for information dissemination to mobile users.