Influences of haptic communication on a shared manual task

With the advent of new haptic feedback devices, researchers are giving serious consideration to the incorporation of haptic communication in collaborative virtual environments. For instance, haptic interactions based tools can be used for medical and related education whereby students can train in minimal invasive surgery using virtual reality before approaching human subjects. To design virtual environments that support haptic communication, a deeper understanding of humans′ haptic interactions is required. In this paper, human′s haptic collaboration is investigated. A collaborative virtual environment was designed to support performing a shared manual task. To evaluate this system, 60 medical students participated to an experimental study. Participants were asked to perform in dyads a needle insertion task after a training period. Results show that compared to conventional training methods, a visual-haptic training improves user′s collaborative performance. In addition, we found that haptic interaction influences the partners′ verbal communication when sharing haptic information. This indicates that the haptic communication training changes the nature of the users′ mental representations. Finally, we found that haptic interactions increased the sense of copresence in the virtual environment: haptic communication facilitates users′ collaboration in a shared manual task within a shared virtual environment. Design implications for including haptic communication in virtual environments are outlined.     

可靠组播协议中的差错控制机制

可靠组播研究是目前网络研究的活跃领域之一。已提出了大量的可靠组播协议。该文对多种可靠组播传输协议中的差错控制机制进行了分析与比较，并且讨论了应用和网络环境对差错控制机制的影响。     

POPEYE: providing collaborative services for ad hoc and spontaneous communities

Next generation collaborative systems will offer mobile users seamless and natural collaboration amongst a diversity of agents, within distributed, knowledge-rich and virtualized working environments. This ambitious goal faces numerous challenges from the underlying communication infrastructure to the high level application services, with the aim to provide services with the appropriate quality (such as persistence, synchronization, and security). Most currently available tools supporting collaboration address either rather traditional and rigid intra-organizational collaboration scenarios or, at the opposite, completely free and unstructured open communities’s interactions. Emerging dynamic, flexible and ad hoc collaboration schemes are hardly or not supported at all. The POPEYE framework offers collaborative services for applications that aim to enable spontaneous collaboration over P2P wireless ad hoc groups, where fixed infrastructure is not a prerequisite, where virtual communities can emerge spontaneously and share data with the appropriate quality of service for business applications (persistence, synchronization, security, etc.).     

Dynamicmultimedia protocol stacks

Fixed end-system protocols are unable to support the wide range of applications requirements on top of current networks without adding overhead in the form of unnecessary functionality for multiple combinations of application requirements and networks.This paper presents the Real-time Wide Area Network Dissemination Architecture Protocol (RWANDA), which dynamically configures multimedia protocol stacks to support a wide range of application requirements and to increase performance. It overcomes synchronous limitations by providing an asynchronous group communication model. Applications only pay for required quality of service (QoS) such as multicast, virtual synchrony and encrypted communication.In RWANDA, information sources use channels to disseminate information to a potentially large and changing set of channel subscribers. RWANDA recognises the differing media characteristics and transport requirements of multimedia by providing a protocol composition framework that extends to incorporate yet unsupported communication protocols, qualities of service and optimised multimedia stacks. RWANDA provides an asynchronous foundation necessary for developing a large-scale wide area network continuous media protocol.     

Hybrid client-server architecture and control techniques for collaborative product development using haptic interfaces

In this paper, a collaborative product development and prototyping framework is proposed by using distributed haptic interfaces along with deformable objects modeling. Collaborative Virtual Environment (CVE) is a promising technique for industrial product development and virtual prototyping. Network control problems such as network traffic and network delay in communication have greatly limited collaborative virtual environment applications. The problems become more difficult when high-update-rate haptic interfaces and computation intensive deformable objects modeling are integrated into CVEs for intuitive manipulation and enhanced realism. A hybrid network architecture is proposed to balance the computational burden of haptic rendering and deformable object simulation. Adaptive artificial time compensation is used to reduce the time discrepancy between the server and the client. Interpolation and extrapolation approaches are used to synchronize graphic and haptic data transmitted over the network. The proposed techniques can be used for collaborative product development, virtual assembly, remote product simulation and other collaborative virtual environments where both haptic interfaces and deformable object models are involved.     

Simultaneous remote haptic collaboration for assembling tasks

Stand-alone virtual environments (VEs) using haptic devices have proved useful for assembly/disassembly simulation of mechanical components. Nowadays, collaborative haptic virtual environments (CHVEs) are also emerging. A new peer-to-peer collaborative haptic assembly simulator (CHAS) has been developed whereby two users can simultaneously carry out assembly tasks using haptic devices. Two major challenges have been addressed: virtual scene synchronization (consistency) and the provision of a reliable and effective haptic feedback. A consistency-maintenance scheme has been designed to solve the challenge of achieving consistency. Results show that consistency is guaranteed. Furthermore, a force-smoothing algorithm has been developed which is shown to improve the quality of force feedback under adverse network conditions. A range of laboratory experiments and several real trials between Labein (Spain) and Queen’s University Belfast (Northern Ireland) have verified that CHAS can provide an adequate haptic interaction when both users perform remote assemblies (assembly of one user’s object with an object grasped by the other user). Moreover, when collisions between grasped objects occur (dependent collisions), the haptic feedback usually provides satisfactory haptic perception. Based on a qualitative study, it is shown that the haptic feedback obtained during remote assemblies with dependent collisions can continue to improve the sense of co-presence between users with regard to only visual feedback.     

可靠组播协议的比较研究

IP组播是在标准的IP技术上的一个扩展,由于它有效降低了网络带宽和服务器负载,所以在视频会议、分布式交互仿真、交互式协同应用和数据分发等领域得到广泛的应用。但是,其固有的不可靠、多副本和无序的缺点阻碍了它的进一步发展。于是,一系列可靠组播协议被提了出来。论文首先介绍了当前对可靠组播模型流行的分类方法,然后选取了当前有代表性的四个可靠组播协议,研究了它们的应用背景,工作机制,分析了它们各自的优点和不足。最后,文章分析了分布式会议控制对可靠组播的应用需求,并针对这一应用背景提出了一个新的层次化可靠组播通信模型。     

A taxonomy of multicast protocols for Internet applications

The continuous growth in applications that require communications among a group of hosts or simultaneous dissemination of data to multiple sites on the Internet has led to considerable interest in multicast communication. These applications have different quality of service requirements such as deadlines to response time and tolerance to data loss. Internet multicast protocols provide a spectrum of services to cater for the needs of a wide array of multicast applications. The design alternatives of a multicast protocol for a particular application may lead to different performance characteristics, for example higher utilization of network bandwidth vs lower protocol processing requirements. Therefore a framework is required to various design choices available to design multicast protocols and evaluate the performance tradeoffs associated with these alternatives. Motivated by such a need and by the evolution of multicast applications over the Internet, this article presents a taxonomy of multicast protocols and a common framework to evaluate their performance.     

Carpeno: interfacing remote collaborative virtual environments with table-top interaction

Creativity is enhanced by communication and collaboration. Thus, the increasing number of distributed creative tasks requires better support from computer-mediated communication and collaborative tools. In this paper we introduce “Carpeno”, a new system for facilitating intuitive face-to-face and remote collaboration on creative tasks. Normally the most popular and efficient way for people to collaborate is face-to-face, sitting around a table. Computer augmented surface environments, in particular interactive table-top environments, are increasingly used to support face-to-face meetings. They help co-located teams to develop new ideas by facilitating the presentation, manipulation, and exchange of shared digital documents displayed on the table-top surface. Users can see each other at the same time as the information they are talking about. In this way the task space and communication space can be brought together in a more natural and intuitive way. The discussion of digital content is redirected from a computer screen, back to a table where people can gather around. In contrast, collaborative virtual environments (CVE) are used to support remote collaboration. They frequently create familiar discussion scenarios for remote interlocutors by utilizing room metaphors. Here, virtual avatars and table metaphors are used, where the participants can get together and communicate with each other in a way that allows behaviour that is as close to face-to-face collaboration as possible. The Carpeno system described here combines table-top interaction with a CVE to support intuitive face-to-face and remote collaboration. This allows for simultaneous co-located and remote collaboration around a common, interactive table.

The roles of sensory modalities in collaborative virtual environments (CVEs)

This study was conducted to assess the effects of sensorial modalities on user performance, perception, and behavior in collaborative virtual environments (CVEs). Participants played a CVE game, air hockey, together with a remote partner under different sensory modality conditions, depending on the type of sensory feedback provided: visual-only (V), visual–haptic (V + H), and visual–haptic–audio feedback (V + H + A). Three types of measurements were used as dependent variables: (1) task performance measured as playing time, (2) user perception including the sense of presence, the sense of togetherness, and perceived collaboration, and (3) behavior measurement including the amount of force applied and the mallet deviation. Results of the study indicated that the task performance, perception, and user behavior in CVEs can be affected due to supported sensory modalities. Therefore, the multiple sensory information types that are required to perform the task at hand should be provided to effectively support collaboration between people in CVEs. The outcomes of this research should have a broad impact on multimodal user interaction, including research on physiological, psychophysical, and psychological mechanisms underlying human perception on multisensory feedback in CVEs.     

支持Internet实时多媒体应用的Overlay技术研究

目前出现的大规模（large-scale）的多媒体应用对Internet提出了新的挑战。传统的IP组播（IP multicast,IPM）由于实现技术的复杂性,很难在Internet上推广。相反,基于叠加网络（overlay network,ON）的解决方案则受到各方面的关注。本文针对大规模实时多媒体应用需求,通过建立评价参数模型对ON协议进行研究。尤其时overlay组播（overlay multicast,OM）的QoS控制、可靠性以及可伸缩性机制进行了分析。与IPM相比,OM虽然有性能代价（performance penalty）问题,但是OM能方便、灵活地利用多种高层的功能实现,基于hop-by-hop方式有效地提供E2E（end—to-end）的可靠性和QoS保障,并且较好地支持TCP-friendliness,具有良好的可伸缩性。此外,0M的基础网络（infrastructure／underlay network）无关性,也使其容易在Internet中进行配置。以上特性使得OM成为支持Internet上大规模实时多媒体应用的最具前景的技术．     

Island Multicast: Combining IP Multicast With Overlay Data Distribution

Traditional overlay protocols use unicast connections to form delivery trees. While it can achieve global multicast across the Internet, it is not as efficient as IP multicast. In this paper, we integrate IP multicast into overlay data distribution to improve delivery efficiency. We investigate island multicast where unicast connections are used to connect multicast domains and IP multicast is used within multicast domains. We first explore a centralized island multicast protocol (termed CIM), which relies on a central server to construct a delivery tree. We then study a distributed protocol (termed DIM), where hosts can distributedly join islands and form a delivery tree. We study the key issues in both protocols. We also discuss how to apply these protocols to media streaming applications. We have evaluated both protocols on Internet-like topologies. We have also implemented a prototype for CIM and tested it on PlanetLab. The results show that our approaches can significantly im prove network performance as compared to pure overlay protocols. Our study shows that it is important to consider local multicast capability when designing overlay protocols.     

Provably secure and efficient identification and key agreement protocol with user anonymity

Many authentication and key agreement protocols were proposed for protecting communicated messages. In previous protocols, if the user?s identity is transmitted in plaintext, an adversary can tap the communications and employ it to launch some attacks. In most protocols with user anonymity, they focus on satisfaction of several security requirements. From a client?s point of view, those protocols are not admired since the cost of storage, computation and communication is high. In pervasive computing, a client usually uses a limited-resource device to access multiple servers. The storage and computation are very important issues especially in this kind of environments. Also, for a convenience of designing protocol, most protocols use timestamps to prevent the replay attack. As we know, the serious time synchronization problem exists in timestamp-based protocols. Finally, most protocols do not have formal proofs for the security. In this paper, we propose a secure and efficient identification and key agreement protocol with user anonymity based on the difficulty of cracking the elliptic curve Diffie–Hellman assumption. In addition, we also propose an augmented protocol for providing the explicit mutual authentication. Compared with the related protocols, the proposed protocols? computation cost is lower and the key length is shorter. Therefore, our protocols are suitable even for applications in low power computing environments. Finally, we formally prove the security of the proposed protocols by employing the random oracle model.     

A decentralized MAC protocol for opportunistic spectrum access in cognitive wireless networks

Cognitive MAC protocols are designed to efficiently utilize the scarce spectral resources without affecting the performance characteristics of primary users. The use of spectrum opportunities can often require stochastic approaches due to difficulty in predicting their appearance. Infrastructure based coordinated access techniques are not viable for many applications and spectrum bands, especially in the case of wireless local area and sensor networks. In this article, we describe CogMAC, a decentralized cognitive MAC protocol, which is based on the multichannel preamble reservation scheme. The protocol dynamically selects an available communication channel using a distributed channel selection scheme and allows nodes to be completely asynchronous to each other. CogMAC does not require a common control channel or a cooperative infrastructure. The MAC design addresses practical issues such as network dynamics and traffic awareness. We have carried out the performance evaluation of our CogMAC protocol on Wireless Open Access Research Platform (WARP) SDR testbed. Experimental results indicate that our protocol is able to achieve reliable data communication by opportunistically utilizing the available spectrum holes even in harshly interfering environments.     

Tele-immersive collaborative virtual environment for intuitive interpretation

The purpose of tele-immersive collaboration is to enable people in separate locations to work together effectively by the Virtual Reality (VR) technology facilitating the human intuitive insight and interpretation. Consequently, it is important to cogitate with figures and characters as well as voice communication in Collaborative Virtual Environment (CVE). In this paper, we constructed tele-immersive CVE with annotation capability and free-hand drawing of characters and figures into Immersive Projection Technology (IPT) environment. In addition, participants from remote sites connected over a Wide Area Network (WAN) were enabled to interact with each other by sharing annotations via a PDA application. Moreover, we developed applications for scientific visualization and, for intellectual work based on KJ Method inside a tele-immersive CVE. From these results, we are able to maintain essential information for thinking by making annotation on IPT environment, and have proved the system can support intuitive understanding in remote collaborative work. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

基于逻辑环的可靠多播协议

随着计算机网络的发展,计算机支持的协同工作（CSCW）受到了越来越多的研究,而多播作为协同应用的一个重要组成部分,在视频会议,协同编著方面发挥着越来越重要的作用。文章总结了可靠协议中需要解决的问题、它们的实现方式,在此基础上提出了一种可靠多播协议的实现算法。该协议比较好地解决了确认的爆炸问题,同时具有很大的灵活性,能够适应不同的应用需求。     

两种可靠多播协议(SRM和TORM)的差错修复性能比较

主人林差错修复的角度，比较了两种可靠多播协议，SRM／Adaptive和TORM协议，在两种典型的网络拓扑下，分析和采用软件模拟的方法比较这两种协议随着节点数 链路丢失率的变化对数据修复延迟和重复请求包数的影响，并实际实验了基于TORM协议开发的应用软件SameView，软件模拟结果说明SRM对于大规模的实时交互应用是很不适合的，它的数据修复延迟会变的很大，分布不稳定，并且重复数据请求也会很多，TORM在软件模拟和实际应用中都表现 较好的性能，由于具有很多特性，比如流量和拥塞控制，局部恢复等，因此TORM对于大规模的实时交互应用是比较适合的。     

可靠多播技术研究

组播是一人发送多人接收的技术,但它是不可靠的。这些年出现了许多可靠多播协议,论文先评价了两种可靠组播协议优缺点,同时引入了第三种组播协议——异步分层编码协议,并全面介绍了异步分层编码的协议框架和一些实现方法,最后给出了异步分层编码协议在DVB网络上的一个应用。     

可靠多播协议的性能分析与研究

介绍了当前几种可靠多播协议,并对它们的性能参数进行分析研究。研究表明,基于超立方体的CubeFullDist和CimCube在可靠多播传输中有明显的优势。而ComCube更在结构的维护与稳定性等方面取得了进一步的发展,具有独特的优越性。