Recent advances in consensus protocols for blockchain: a survey

Wireless Networks - As the core of a blockchain system, the consensus mechanism not only helps to maintain the consistency of node data, but also gets involved in the issuance of tokens and...     

UP2P: a peer-to-peer overlay architecture for ubiquitous communications and networking

Approaches to building an intelligent consumerfriendly network have evolved over time from centralized switch-based to router- and serverbased Internet architectures. We propose to drive this evolution further with a new highly scalable architecture that provides features to users derived from the computational and networking capabilities of very large populations of sophisticated terminals. This architecture relies on emerging peer-to-peer overlay technology. We describe a peer-to-peer overlay design that addresses requirements crucial for consumer applications, including overlay federation, peer heterogeneity, peer mobility, and service discovery. In addition, we introduce the concept of an overlay operator and describe the requirements for managed overlays. We have designed and implemented both a middleware and a peer-topeer platform that illustrates these concepts.     

Weighted voting on the blockchain: Improving consensus in proof of stake protocols

Proof of stake (PoS) protocols rely on voting mechanisms to reach consensus on the current state. If an enhanced majority of staking nodes, also called validators, agree on a proposed block, then this block is appended to the blockchain. Yet these protocols remain vulnerable to faults caused by validators who abstain either accidentally or maliciously. To protect against such faults while retaining the PoS selection and reward allocation schemes, we study weighted voting in validator committees. We formalize the block creation process and introduce validators' voting profiles which we update by a multiplicative weights algorithm relative to validators' voting behavior and aggregate blockchain rewards. Using this framework, we leverage weighted majority voting rules that optimize collective decision making to show, both numerically and analytically, that the consensus mechanism is more robust if validators' votes are appropriately scaled. We raise potential issues and limitations of weighted voting in trustless, decentralized networks and relate our results to the design of current PoS protocols.     

RBFT:基于Raft集群的拜占庭容错共识机制

针对现有联盟链共识机制因可拓展性不足,无法在支持大规模网络的同时满足低时延、高吞吐量和安全性的问题,采用网络分片的思想,提出一种适用于联盟链的带有监督节点的两级共识机制——RBFT.首先对网络节点进行分组,组内采用改进的Raft机制进行共识,然后由每个组内选出的领导者组成网络委员会,网络委员会内部采用PBFT机制进行共...     

Information transmission based on network coding over wireless networks: a survey

Network coding (NC) for wireless local area network has received a lot of attention from researchers. It replaces the traditional methods of video erasure protection. The principal of NC is to combine several packets together before their transmission. Thus, NC is able to provide higher throughput, reliability and efficient transmission. Up to now, many works have been done to ensure the advantages and the robustness of NC against the packet loss and link failures. The performance gains of NC are successfully processed not only for data to increase throughput, but also for video streaming over wireless networks. In this context, this paper surveys and discusses the most popular approaches based on NC of both data and video transmission over wireless network (static or dynamic). Strength and limitations for robust video streaming and data transmission are deeply discussed.     

Smart grid sensor data collection,communication, and networking: a tutorial

The smart grid is an innovative energy network that will improve the conventional electrical grid network to be more reliable, cooperative, responsive, and economical. Within the context of the new capabilities, advanced data sensing, communication, and networking technology will play a significant role in shaping the future of the smart grid. The smart grid will require a flexible and efficient framework to ensure the collection of timely and accurate information from various locations in power grid to provide continuous and reliable operation. This article presents a tutorial on the sensor data collection, communications, and networking issues for the smart grid. First, the applications of data sensing in the smart grid are reviewed. Then, the requirements for data sensing and collection, the corresponding sensors and actuators, and the communication and networking architecture are discussed. The communication technologies and the data communication network architecture and protocols for the smart grid are described. Next, different emerging techniques for data sensing, communications, and sensor data networking are reviewed. The issues related to security of data sensing and communications in the smart grid are then discussed. To this end, the standardization activities and use cases related to data sensing and communications in the smart grid are summarized. Finally, several open issues and challenges are outlined. Copyright © 2012 John Wiley & Sons, Ltd.     

Computer networking in the People's Republic of China: a tripreport

The authors were part of an eighteen-member international delegation of data communications professionals that recently visited the People's Republic of China. This report on computer networking in China is based on their visits to four universities and 11 government organizations in four different cities. They discuss computer systems, telecommunications systems, and data communication in China     

Imp Raft: a consensus algorithm based on Raft and storage compression consensus for IoT scenario

In order to meet various challenges in the Internet of things (IoT), such as identity authentication, privacy preservation of distributed data and network security, the integration of blockchain and IoT became a new trend in recent years. As the key supporting technology of blockchain, the consensus algorithm is a hotspot of distributed system research. At present, the research direction of the consensus algorithm is mainly focused on improving throughput and reducing delay. However, when blockchain is applied to IoT scenario, the storage capacity of lightweight IoT devices is limited, and the normal operations of blockchain system cannot be guaranteed. To solve this problem, an improved version of Raft (Imp Raft) based on Raft and the storage compression consensus (SCC) algorithm is proposed, where initialization process and compression process are added into the flow of Raft. Moreover, the data validation process aims to ensure that blockchain data cannot be tampered with. It is obtained from experiments and analysis that the new proposed algorithm can effectively reduce the size of the blockchain and the storage burden of lightweight IoT devices.     

Survey on mobile social networking in proximity (MSNP): approaches,challenges and architecture

Recently, mobile social networks (MSN) have gained tremendous attention, which free users from face-to-monitor life, while still can share information and stay in touch with their friends on the go. However most MSN applications regard mobile terminals just as entry points to existing social networks, in which centralized servers (for storage and processing of all application/context data) and continual Internet connectivity are prerequisites for mobile users to exploit MSN services, even though they are within proximity area (like campus, event spot, and community, etc.), and can directly exchange data through various wireless technologies (e.g., Bluetooth, WiFi Direct, etc.). In this paper, we focus on mobile social networking in proximity (MSNP), which is explicitly defined in our paper as: MSNP is wireless peer-to-peer (P2P) network of spontaneously and opportunistically connected nodes, and uses geo-proximity as the primary filter in determining who is discoverable on the social network. In this paper, first, primary support approaches related to MSNP available in literature, are summarized and compared, including MSN, mobile P2P and opportunistic networks. And then, we offer the special characteristics of MSNP, open issues and potential solutions. A networking technologies and platform independent architecture is proposed for developing MSNP applications, and proof-of-concept implementation of WiFi direct based MSNP application is also provided. Our primary goal is to identify the characteristics, technical challenges and potential solutions for future MSNP applications, capable to flexibly adapt to different application domains and deployment requirements.     

通信、网络、计算融合的天地一体化信息网络体系架构研究

随着人类活动范围从大陆向海洋、太空的不断扩展,世界各国纷纷开始布局全球无缝覆盖、连接无处不在的天地一体化信息网络建设。天地一体化信息网络是天基网络与地面网络的深度融合,不是简单的地面向空间的拓展与叠加。从融合的角度出发,首先梳理了地面互联网、移动通信网、天基信息网络发展现状以及存在的问题与挑战;然后总结分析了天地一体化信息网络体系架构研究现状以及新型网络架构向云化、智能化发展的趋势;最后提出了通信、网络、计算融合的天地一体化信息网络的体系架构,并从物理架构、功能架构、物理与功能架构映射等多个维度进行了阐述,提出了一体化信息通信系统、一体化网络系统、一体化信息系统的3层功能架构模型,以期为后续天地一体化信息网络的研究、建设和标准化提供有价值的建议和参考。     

Multilevel inverters: a survey of topologies, controls, and applications

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. This paper presents the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor), and cascaded multicell with separate DC sources. Emerging topologies like asymmetric hybrid cells and soft-switched multilevel inverters are also discussed. This paper also presents the most relevant control and modulation methods developed for this family of converters: multilevel sinusoidal pulsewidth modulation, multilevel selective harmonic elimination, and space-vector modulation. Special attention is dedicated to the latest and more relevant applications of these converters such as laminators, conveyor belts, and unified power-flow controllers. The need of an active front end at the input side for those inverters supplying regenerative loads is also discussed, and the circuit topology options are also presented. Finally, the peripherally developing areas such as high-voltage high-power devices and optical sensors and other opportunities for future development are addressed.     

MOFA: a model for fault and availability in complex services

Asset allocation to optimize reliability and availability (R&A) has been studied in the literature. However, these concepts have not been investigated in combination with degraded performance in realistic reliability-models. Some reliability models, techniques, and tools allow modeling of degradable performance. However, they are mainly used in evaluating R&A of given systems; they do not consider the inverse problem of determining the system parameters that would maximize the R&A. This paper provides a realistic reliability model for complex services; the model can be used to study the asset allocation problem in degradable complex services. This paper uses a simple model to describe the failure characteristics of the system parts. This model provides: (1) an infrastructure for defining R&A in a flexible way, and (2) a way of defining at what level of availability it is worth offering the service, and at what level of failure of resources the system should be declared faulty. This model is then used to `allocate optimally the available assets' to `implement a service that is tailored to the availability needs of the user and the situation'. The model is applied to a realistic example of a complex service, viz. a multimedia communication service     

Will IEEE 802.15.4 make ubiquitous networking a reality?: a discussion on a potential low power, low bit rate standard

The new IEEE standard 802.15.4 shows promise to bring ubiquitous networking into our lives, at least technically. Unlike other standards targeting high- or moderate-data-rate applications, IEEE 802.15.4 is a global standard designed for low-data-rate, low power consumption, and low-cost applications. This so-called enabling standard brings many simple, originally standalone devices into networks, and thus not only open the door to an enormous number of new applications, but also add values to many other existing applications. In this article we first present a few application scenarios to show the potential extent to which the new standard can affect our lives, and then give an overview of the standard, focusing on its feasibility and functions in establishing ubiquitous networks. We also outline some quantitative results from our experiments so as to have a better view of the standard.     

Completing the convergence puzzle: a survey and a roadmap

Convergence has more than ever been a central issue for fixed and mobile operators throughout the world and is considered to be the next big step in the evolution of telecommunication networks. Convergence opens new market opportunities and competition among network operators and above all offers enhanced user experience. Multimode handsets and the proliferation of terminals and access technologies are generating increasing demands for solutions that enable convergence, seamless handover, and transparent service delivery across heterogeneous access networks. Different strategies are available for operators, depending on the services they intend to deliver to their customers, from basic commercial convergence limited to unified billing for Fixed/Mobile/Internet up to in-dept network convergence covering new applications and services. This article surveys different technologies which offer seamless handover and converged access to mobile voice, video, and data services. It provides first the different network parts involved in defining the operator global convergence strategy and then surveys different technologies which achieve this step-by-step convergence. We present the main features of these technologies and discuss their limitations and potentials to enable convergence in heterogeneous networks. We also provide a personal stance as to the emergence of these technologies and our vision towards the long term converged telecommunication networks.     

Could-based vehicular networks: a taxonomy,survey, and conceptual hybrid architecture

Wireless Networks - In recent times, vehicular network research has attracted the attention of both researchers and the industry partly due to its potential applications in efficient traffic...     

军械器材管理中RFID与WSN的组网研究

提出了一种将RFID和WSN技术融合,利用ZigBee组网来实现军械器材管理的设计方法。将ZigBee技术用于RFID和WSN系统中,可提高系统的数据完整性和可靠性及组网的便捷性。研究采用CC2431为ZigBee节点主控芯片的设计方案,并设计出ZigBee的硬件节点。     

Cross-layer design: a survey and the road ahead

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.     

Detecting, diagnosing, and tolerating faults in SRAM-based field programmable gate arrays: a survey

Topics related to the faults in SRAM-based field programmable gate arrays (FPGAs) have been intensively studied in recent research studies. These topics include FPGA fault detection, FPGA fault diagnosis, FPGA defect tolerance, and FPGA fault tolerance. This paper provides a guided tour to the approaches related to these topics. These include techniques, which are applied to the FPGA and others which have been recently introduced and can be applied to today's FPGAs.