This paper proposes to design, develop and implement a fast and markerless mobile augmented reality system to achieve the registration for, the visualization of, and the interaction with machines in indoor smart factories with Industry 4.0 vision. A lightweight deep-learning image detection module based on MobileNets running on mobile devices is used to detect/recognize different machines and different portions of machines. Internet of Things (IoT) networking allows machines and sensors in machines to report data, such as machine settings and machine states, to the cloud-side server. Thus, augmented information associated with a machine portion can be derived from the server and superimposed with the portion image shown on the device display. Furthermore, interaction methods based on touch gestures and distance calculation are also implemented. A prototype system is developed and tested in a mechanical workshop for the purpose of validation and evaluation. The system is shown to achieve high detection accuracy, intuitive visualization, and unique interaction modes.

This paper proposes a tree-based RFID tag anti-collision protocol, called the silence coding query tree (SCQT) protocol, based on a novel coding scheme, namely the silence coding, to speed up tag identification. The proposed protocol can identify multiple tags at a time even at the appearance of tag signal collisions. Simulation results show that the SCQT protocol significantly outperforms other related tree-based protocols in terms of the number of cycles to identify tags.

In these years, the traffic is rapidly increasing in mobile communication networks. The increasing traffic seriously consumes the bandwidth of the core network. The 3GPP proposes a series of traffic offloading solutions in the Long Term Evolution-Advanced (LTE-A) system in which part of traffic from the core network is migrated to the Internet. Two traffic offloading methods are designed for the Home eNodeB (HeNB) networks: (1) Local IP Access (LIPA), which provides User Equipments (UEs) with the ability to communicate with other objects (e.g., UEs and servers) located in the same local HeNB network via HeNB without accessing the core network, and (2) Selected IP Traffic Offload at Local Network (SIPTO@LN), which provides UEs with the ability to connect to the Internet via HeNB without going to the core network. Several studies tried to improve 3GPP traffic offloading methods; however, those methods have no or little support of mobility. In this paper, we propose two methods to offload the traffic in Local HeNB Network (LHN) with better mobility support than existing methods. The first method, Local Access Traffic Offload (LATO), enhances the LIPA function by providing UEs with the ability to hand over into and out of the LHN. The second method, Global Access Traffic Offload (GATO), enhances the SIPTO function by providing UEs with the ability to hand over between the LHNs.

This paper extends the well-known Dijkstra's shortest path algorithm to consider not only the edge weights but also the node weights for a graph derived from the underlying SDN topology. We use Pyretic to implement the extended Dijkstra's algorithm and compare it with the original Dijkstra's algorithm and the unit-weighted Dijkstra's algorithm under the Abilene network topology in terms of end-to-end latency with the Mininet tool. As shown by the comparisons, the extended Dijkstra's algorithm outperforms the other algorithms.

This paper studies a Disk Covering Tour Problem (DCTP) for reducing the energy consumption of a mobile robot's movement to provide services for sensor nodes in a wireless sensor network (WSN). Given a set of locations of sensor nodes and a starting location of mobile robot, the DCTP is to find a minimum cost tour of a sequence of tour stops for the mobile robot to serve sensor nodes by keeping every sensor node within a specified distance of a tour stop. We propose an algorithm, called Decreasing k-means (Dk-means), to find an approximate solution to the DCTP. The idea is to select a minimum number of disks or circles of a fixed radius to cover all sensor nodes, and then to find a minimum cost tour passing all disk centers. The simulation results show the proposed algorithm outperforms the related CSP (Covering Salesman Problem) algorithm and the QiF algorithm.

Anti-Collision is one of the most important problems of the RFID technology. In this paper, we propose an Efficient Query Tree (EQT) protocol to improve both the Query Tree (QT) protocol and the Collision Tree (CT) protocol. The main idea of the EQT protocol is to reduce as much as possible the timeslots used to transmit bits between the reader and tags, so that the time of tag identification procedure is shortened and the energy consumption is lessened. In the EQT protocol, the timeslots structure, the query and responses between the reader and tags are carefully redesigned to allow tags to transmit fewer bits. We analyze and simulate the EQT protocol and compare it with the QT and the CT protocols. The simulation results show the EQT protocol outperforms the other two protocols in terms of the tag identification time.

In the RFID system, when two or more tags respond their IDs to the reader simultaneously, wireless signal collision occurs and no tag can be identified successfully by the reader. How to reduce such collisions in order to speed up the identification performance is thus important. There are many anti-collision protocols proposed to solve the tag collision problem. They can be categorized into two classes: ALOHA-based and tree-based protocols. The query tree (QT) protocol is a famous tree-based protocol having many advantages. It is stateless and uses no on-tag memory to keep protocol states, it is a plain protocol and uses no special techniques, such as bit-tracking, ID-revising, and re-identification. In this paper, we propose a stateless and plain tree based anti-collision protocol, called PRQT, by using tag ID partial responses to speed up tag identification. We also conduct simulation experiments for PRQT and compare it with QT in terms of the number of iterations to identify tags. As we will show, the PRQT protocol uses less numbers of iterations to identify tags than the QT protocol.

With low Peak-to-Average Power Ratio (PAPR), Single Carrier ¡V Frequency Division Multiple Access (SCFDMA) is adopted by 3GPP to be the uplink access method of the LTE system. SC-FDMA allocates continuous Resource Blocks (RBs) to each subscriber to reduce PAPR. However, the continuous RB allocation degrades the flexibility in resource allocation. How to efficiently allocate radio resource in the SCFDMA scheme has been a critical issue. This paper proposes a scheduling algorithm concerning user satisfaction in LTE uplink radio resource allocation. The proposed algorithm is a generalization and an improvement of the well-known Mean Enhanced Greedy (MEG) scheduling algorithm. The simulation results show that the proposed algorithm achieves not only higher user satisfaction degree but also better fairness between subscribers than the MEG scheduling algorithm and a related algorithm, called the Recursive Maximum Expansion (RME) algorithm, no matter the desired uplink transmission rates among subscribers are the same or not.

In this paper, we propose a peer-to-peer voice communication scheme, called immersive voice communication (IVC), to provide MMOG players with the immersive experience to hear the voice of neighbor players within the area of interest (AOI). IVC uses a relation model to classify neighbors of a player into the listener and the over hearer, in which the latter consumes much less bandwidth than the former to reduce the traffic load. IVC also adopts the network coordinate system (NCS) to reduce the voice transmission latency and construct an adaptive k-ary tree (AK-tree) to utilize the bandwidth completely. Furthermore, IVC prioritizes voice data and uses voice masking mechanism to reduce the network traffic. As shown by the simulation results, the proposed scheme outperforms other related schemes.

In this paper, we propose a synchronous multihop architecture (SYMA) for wireless ad hoc multiplayer games. In SYMA, devices are assumed to have one-hop neighbor device information, as well as timers synchronized with good accuracy. A player, called game initiator, broadcasts an invitation message to invite other players to join a new game. A joining player issues a message along with its neighborhood information, including the expected transmission time (ETT) for each neighbor node, to reply to the invitation so that the initiator can derive the topology of the participating players. The initiator applies Floyd-Warshall shortest path algorithm, taking the topology and ETT values as input to construct the shortest path spanning tree rooted at each player (or node). It then calculates the expected broadcast time (EBT) for each tree, which is useful to estimate the time for the root node of a tree to broadcast a game state to all tree nodes. Finally, the tree with the smallest EBT is selected as the communication tree and its root is designated as the coordinator, which collects time stamped actions of each player, executes the game logic, and then broadcasts the new game state. By exploiting synchronized timers, the game state consistency is guaranteed, and each node can be scheduled to send/receive game messages without causing collisions.

With the increase of network bandwidth and the advance of 3D graphics technology, networked virtual environments (NVEs) have become popular recently. Early SIMNET and currently booming massively multiplayer online games (MMOGs), such as Second Life (SE) and World of War craft (WoW), are examples of NVEs. Because NVE users, interests or habits may be similar, avatars, or the representative of NVE users, may have similar behavior patterns, which leads to similar motion paths in the NVE. This paper proposes two NVE avatar path clustering algorithms, namely, Average Distance of Corresponding Points-Density Clustering (ADCP-DC) and Longest Common Subsequence-Density Clustering (LCSS-DC). Given avatar paths, both algorithms will produce a collection of path clusters and their representative paths (RPs), which can be used to analyze avatar behaviors for improving NVE design. We take SE user trace data as input of the algorithms to demonstrate their applicability. We also show how to adjust algorithm parameters to obtain high-quality path clustering in terms of silhouette coefficient and cluster coverage.

Online Social Networks (OSNs) are more and more popular recently, people may through them interact with each other for the purpose of social intercourse. The client/server OSN architecture brings about the bottleneck of bandwidth and computation. It leads to the scalability problem and the communication latency increases as users grows. This paper proposes a bandwidth- and latency-aware peer-to-peer (P2P) instant friend cast scheme for every user (or peer) in OSNs to construct a friend cast tree (FCT) to send instant messages to all of its friends. A lightweight server is responsible for only easy tasks, such as logining and maintaining peer information, to facilitate the tree construction. A peer logins to the server to obtain the list of friends and their Vivaldi coordinates, which are computed by every peer in a distributed way to estimate the latency between peers. The proposed scheme also uses Available Out-Degree Estimation (AODE) to evaluate the proper out-degree of a peer, and then uses Degree-Adapted Greedy Tree Algorithm (DATGA) to construct FCT. The scheme is simulated and compared with other relevant ones to show its advantages.

In this paper, we present an authentication scheme for group-based peer-to-peer 3D streaming that takes advantage of secure group communication to reduce computation overheads of authentication. Users of the same interest first form a group, and one of the users is then elected to be the trusted leader, who is to download 3D contents, to verify their authenticity and integrity, and to send group members a checksum value for each 3D content piece via group secure channels. By the encrypted checksum values, a group member can authenticate 3D contents downloaded from any source. Since checksum is cheap to compute, much computation is saved. We have evaluated the computation saving of the proposed scheme for the case of progressive meshes based on the hash chain signature 3D streaming authentication scheme. We have also evaluated the rendering quality when embedding hash chain signatures into the least significant bits (LSBs) of the mesh data to make the signatures imperceptible.

Broadcasting is one of the most important operations in the wireless network for disseminating information throughout the entire network. Flooding is a simple mechanism to realize broadcasting, but it has high redundancy of retransmissions, leading to low transmission efficiency. Many broadcast protocols have been proposed for pursuing optimized transmission efficiency for wireless networks hypothetically deployed on the 2-dimesional (2D) plane. In the real world, wireless networks are deployed in the 3D space. In this paper, we derive the upper bound of 3D transmission efficiency and propose a 3D broadcast protocol with optimized transmission efficiency by partitioning the 3D space into multi-layer hexagonal prisms of a hexagon ring pattern in each layer. As we will show, the transmission efficiency of the proposed protocol can reach 1/¿, which is better than those of other polyhedron-filling approaches using cubes, hexagon prisms, rhombic dodecahedrons, and truncated octahedrons.

The Wireless Sensor and Actor Network (WSAN) is an extension of the wireless sensor network (WSN). Besides resource-limited sensor nodes, WSANs have resource-rich nodes, called actors, of higher capabilities to perform powerful actions. In this paper, we focus on target surveillance systems built atop WSANs to monitor critical targets. Since sensor nodes are usually equipped with limited energy sources and are likely to be influenced by unpredictable failures occurring in the harsh sensor field, we need to seriously take fault-tolerance and energy-efficiency into consideration. Hence, we develop an optimal path planning (OPP) scheme to construct a maximum number of node-disjoint paths to deliver targetspsila event notification with minimum energy consumption. We also evaluate OPP performance by simulations and compare it with a related scheme to show its advantages.

In this paper, we propose a distributed event contour tracking (DECT) algorithm for multi-sink wireless sensor networks. We focus on the convex-shaped area event, which has a large effect region and may trigger many sensors at the same time. An area event may change its shape or move with time. Wild animal migration, army march, gas diffusion and chemical pollution are typical examples of area events. DECT utilizes near optimal regular hexagonal-based deployment to achieve energy efficiency and to track the area event contour. It finds out all sensor nodes on the event contour and collects their reporting data for tracking the event. DECT takes advantage of multiple sinks to forward data; it divides the event contour into several segments in a distributed way, and nodes in every segment will select a specific sink for transmitting reporting data. So, data traffic is dispersed and the chance of congestion and the packet dropping rate are thus reduced. We also perform simulation experiments for DECT and compare the simulated results with related ones to show the advantages of DECT.

State management is a basic requirement for multiuser virtual environments (VEs) such as massively multiplayer online games (MMOGs). Current MMOGs rely on centralized server-clusters that possess inherent scalability bottlenecks and are expensive to adopt and deploy. In this paper, we propose Voronoi state management (VSM) to maintain object states for peer-to-peer-based virtual worlds. By dynamically partitioning the VE with Voronoi diagrams and aggregating game states of overloaded nodes onto superpeers, VSM supports existing consistency control to enable scalable, load balanced, and fault tolerant VE state management. As both client and server-side resources are utilized collaboratively, VSM also integrates both client-server and peer-to-peer VE designs in a unified approach.

In this paper, we propose an asynchronous duty cycle adjustment MAC protocol, called ADCA, for the wireless sensor network (WSN). ADCA is a sleep/wakeup schedule-based protocol to reduce power consumption without lowering network throughput or lengthening transmission delay. It is asynchronous; it allows each node in the WSN to set its own sleep/wakeup schedule independently. The media access is thus staggered and collisions are reduced. According to the statuses of previous transmissions, ADCA adjusts the duty cycle length for shortening transmission delay and increasing throughput. Simulation results show that ADCA outperforms related ones in terms of energy saving, network throughput and transmission delay.

How to secure data communication is an important problem in wireless sensor networks (WSNs). General solutions to the problem are to encrypt the packet payload with symmetric keys. But those solutions only prevent the packet content from being snooped or tampered. Adversaries still can learn network topology by the traffic analysis attack. In this paper, we propose an anonymous path routing (APR) protocol for WSNs. In APR, data are encrypted by pair-wise keys and transmitted with anonyms between neighboring sensor nodes and anonyms between the source and destination nodes of a multi-hop communication path. The encryption prevents adversaries from disclosing the data, and the anonymous communication prevents adversaries from observing the relation of the packets for further attacks. We implement APR on the MICAz platform to evaluate its overheads for demonstrating its applicability in practical WSNs.

Peer-to-Peer (P2P) networks have been proposed as one promising approach to provide better scalability for Networked Virtual Environment (NVE) systems, but P2P-NVE also increases the probability of cheating by allowing users to manage the states of objects. In this paper, we propose Delaunay State Management (DSM), a P2P-NVE state management scheme that divides the whole virtual world into many triangular regions by Delaunay triangulation. In DSM, each region is managed by three super-peers, whose collective decisions determine how states will change. Assuming that at most one of the three super-peers is malicious, effective anti-cheating can be provided. Additionally, we also describe how DSM provides the essential features for a state management system, such as consistency, load-balancing, and fault-tolerance. Finally, we discuss some of DSM's potential applications.

We propose the design of Plug, an application to find and keep contacts with friends within many inter-connected 3D virtual worlds. Users use an instant messenger (IM)-like interface to converse with friends and find new contacts, using a virtual representation of the user's self. It consists of three parts: a plug is an automatous agent / avatar situated at a user's computer that reflects and mimics its owner's behaviors and interests; a plugspace is a virtual environment that can be inter-connected, with scales ranging from a room to an entire virtual universe; and plugtalk is a set of packet formats and protocols that allow plugspaces to inter-connect, and individual plugs to navigate. Plug utilizes standards whenever possible, and is designed to be scalable, extensible, and customizable for various uses such as distance learning, virtual shopping, or online gaming. By combining the looks of 3D virtual worlds and the accessibility of IMs, we envision Plug as a step towards common virtual world experiences sharable by all Internet users.

Interactive 3D content on Internet has yet become popular due to its typically large volume and the limited network bandwidth. Progressive content transmission, or 3D streaming, thus is necessary to enable real-time content interactions. However, the heavy data and processing requirements of 3D streaming challenge the scalability of client-server delivery methods. We propose the use of peer-to-peer (P2P) networks for 3D streaming, and argue that due to the non-linear access patterns of 3D content, P2P 3D streaming is a new class of applications apart from existing media streaming and requires new investigations. We also present FLoD, the first P2P 3D streaming framework that allows clients of 3D virtual globe or virtual environment (VE) applications to obtain relevant data from other clients while minimizing server resource usage. To demonstrate how FLoD applies to real-world scenarios, we build a prototype system that adapts JPEG 2000-based 3D mesh streaming for P2P delivery. Experiments show that server-side bandwidth usage can thus be reduced, while simulations indicate that P2P 3D streaming is fundamentally more scalable than client-server approaches.

In multi-user networked virtual environments such as Second Life, 3D streaming techniques have been used to progressively download and render 3D objects and terrain, so that a full download or prior installation is not necessary. As existing client-server architectures may not scale easily, 3D streaming based on peer-to-peer (P2P) delivery is recently proposed to allow users to acquire 3D content from other users instead of the server. However, discovering the peers who possess relevant data and have enough bandwidth to answer data requests is non-trivial. A naive query-response approach thus may be inefficient and could incur unnecessary latency and message overhead. In this paper, we propose a peer selection strategy for P2P-based 3D streaming, where peers exchange information on content availability incrementally with neighbors. Requestors can thus discover suppliers quickly and avoid time-consuming queries. A multi-level area of interest (AOI) request is also adopted to avoid request contention due to concentrated requests. Simulation results show that our strategies achieve better system scalability and streaming performance than a naive query-response approach.

Presents the introductory welcome message from the conference proceedings. May include the conference officers' congratulations to all involved with the conference event and publication of the proceedings record.

In recent years, massively multiplayer online games (MMOGs) have become more and more popular. Many techniques have been proposed to enhance the experience of using MMOGs, such as realistic graphics, vivid animations, and player communication tools, etc. However, in most MMOGs, communication between players is still based on text, which is unnatural and inconvenient. In this paper, we propose the concept of AOI voice chatting for MMOGs. The term AOI stands for the area of interest; a player in the MMOG only pays attention to his/her AOI. By AOI voice chatting, a player can easily chat by voice with other plays in the AOI. This improves the way players communicate with one another and provides a more realistic virtual environment. We also propose two peer-to-peer schemes, namely QuadCast and SectorCast, to achieve efficient AOI voice chatting for MMOGs. We perform simulation experiments to show that the proposed schemes have reasonable end-to-end delay and affordable bandwidth consumption.

We show that subsets of Cohorts coteries proposed in [J.-R. Jiang et al., (1997)] are nondominated (ND) k-coteries, which are candidates to achieve the highest availability when utilized to solve the distributed k-mutual exclusion problem and the distributed h-out of-k mutual exclusion problem.

We investigate the power mode management problem for an IEEE 802.11-based mobile ad hoc network (MANET) that allows mobile hosts to tune to the power-saving (PS) mode. We adopt an asynchronous approach proposed in [Y. C. Tseng et al., (2002)] and correlate this problem to the quorum system concept. We identify a rotation closure property for quorum systems. It is shown that any quorum system that satisfies this property can be translated to an asynchronous power-saving protocol for MANETs. We derive a lower bound for quorum sizes for any quorum system that satisfies the rotation closure property. We identify a group of quorum systems that are optimal or near optimal in terms of quorum sizes, which can be translated to efficient asynchronous power-saving protocols. We also propose a new e-torus quorum system, which can be translated to an adaptive protocol that allows designers to trade hosts' neighbor sensibility for power efficiency.

We propose a structure named Cohorts to solve the problem of the access control of multiple entries to a critical section. Our solution is formalized as forming quorums in a k-coterie. It is resilient to node failures and/or network partitioning, invokes constant expected message cost and has comparably high availability.

A k-coterie is a family of sets (called quorums) in which any (k+1) quorums contain at least a pair of quorums intersecting each other. K-coteries can be used to develop distributed k-mutual exclusion algorithms that are resilient to node and/or communication link failures. A k-coterie is said to dominate another k-coterie if and only if every quorum in the latter is a super set of some quorum in the former. Obviously the dominating one has more chance than the dominated one for a quorum to be formed successfully in an error-prone environment. Thus, we should always concentrate on nondominated k-coteries that no k-coterie can dominate. We introduce a theorem for checking the nondomination of k-coteries, define a class of special nondominated k-coteries-strongly nondominated (SND) k-coteries, and propose two operations to generate new SND k-coteries from known SND k-coteries.

The authors extend the concept of coterie into k-coterie for k entries to a critical section. A structure named Cohorts is proposed to construct quorums in a k-coterie. The solution is resilient to node failures and/or network partitioning and has a low communication cost. The Cohorts structure is further improved to increase the availabilities of 1-entry critical sections.>