DJFS: Providing Highly Reliable and High‐Performance File System with Small‐Sized NVRAM

File systems and applications try to implement their own update protocols to guarantee data consistency, which is one of the most crucial aspects of computing systems. However, we found that the storage devices are substantially under‐utilized when preserving data consistency because they generate massive storage write traffic with many disk cache flush operations and force‐unit‐access (FUA) commands. In this paper, we present DJFS (Delta‐Journaling File System) that provides both a high level of performance and data consistency for different applications. We made three technical contributions to achieve our goal. First, to remove all storage accesses with disk cache flush operations and FUA commands, DJFS uses small‐sized NVRAM for a file system journal. Second, to reduce the access latency and space requirements of NVRAM, DJFS attempts to journal compress the differences in the modified blocks. Finally, to relieve explicit checkpointing overhead, DJFS aggressively reflects the checkpoint transactions to file system area in the unit of the specified region. Our evaluation on TPC‐C SQLite benchmark shows that, using our novel optimization schemes, DJFS outperforms Ext4 by up to 64.2 times with only 128 MB of NVRAM.     

A distributed utility‐based scheduling for peer‐to‐peer video streaming over wireless networks

Interactive multimedia applications such as peer‐to‐peer (P2P) video services over the Internet have gained increasing popularity during the past few years. However, the adopted Internet‐based P2P overlay network architecture hides the underlying network topology, assuming that channel quality is always in perfect condition. Because of the time‐varying nature of wireless channels, this hardly meets the user‐perceived video quality requirement when used in wireless environments. Considering the tightly coupled relationship between P2P overlay networks and the underlying networks, we propose a distributed utility‐based scheduling algorithm on the basis of a quality‐driven cross‐layer design framework to jointly optimize the parameters of different network layers to achieve highly improved video quality for P2P video streaming services in wireless networks. In this paper, the quality‐driven P2P scheduling algorithm is formulated into a distributed utility‐based distortion‐delay optimization problem, where the expected video distortion is minimized under the constraint of a given packet playback deadline to select the optimal combination of system parameters residing in different network layers. Specifically, encoding behaviors, network congestion, Automatic Repeat Request/Query (ARQ), and modulation and coding are jointly considered. Then, we provide the algorithmic solution to the formulated problem. The distributed optimization running on each peer node adopted in the proposed scheduling algorithm greatly reduces the computational intensity. Extensive experimental results also demonstrate 4–14 dB quality enhancement in terms of peak signal‐to‐noise ratio by using the proposed scheduling algorithm. Copyright © 2015 John Wiley & Sons, Ltd.     

A multi‐agent self‐adaptative management framework

The self‐management vision, which has raised much interest in recent years, is only an operational aim that does not provide any solution in its definition on how to attain this management autonomy. The general contribution of this article suggests concepts, methods and mechanisms to conceive a self‐adaptative management framework, thus participating in this self‐management vision. This framework is composed of organizational aspects based on multi‐agent concepts, informational aspects based on different management ontologies and cooperative aspects based on specific agent behaviours which automate the accomplishment of management actions on the overall distributed environment. We have also implemented a prototype of this work to validate the feasibility of our approach and confirm the self‐adaptation capacities of the system. Copyright © 2008 John Wiley & Sons, Ltd.     

Mitigating file‐sharing misbehavior with movement synchronization to increase end‐to‐end availability for delay sensitive streams in vehicular P2P devices

When dealing with wireless connectivity in a mobile peer‐to‐peer (MP2P) environment, there are many concerns about the offered efficiency and availability of the requested resources and concerns about practicality considerations. These considerations deal with the movement and deployment of continuous connectivity. The intermittent connectivity is a major factor for object sharing misbehavior because it aggravates the connectivity and reliability. MP2P environments are in need of specialized placement algorithms where structured index‐centric solutions will be able to provide efficiency and object location determination over intermittent connectivity and communication. Replication of any requested object and redundancy face the requests' failures because they create severe duplications, and aggravate the capacity of the end‐to‐end path. This work proposes a framework that enables mitigation between the file sharing misbehavior in contrast to the movement synchronization, and it quantifies the parameters that affect the end‐to‐end efficient transmission by taking into consideration the synchronization between moving peers to assign the requested resources in the end‐to‐end path. Resilience metrics are introduced to enable reliability in cooperative file sharing procedure. The proposed scheme considers synchronization and assignment of the moving mobile Infostation peer with certain object indices to a certain vehicle via a synchronized cooperative scheme where the file sharing process is performed through the message ferry mobile peer. In addition, a resource assignment cooperation engine is developed taking into consideration the social cooperation model and the end‐to‐end capacity of the relay path. The proposed resource exchange apparatus for file chunks' migration is performed to enable delay sensitive streaming. The proposed model is evaluated through experimental simulation taking measures for the throughput and the reliability offered and for the robustness for sharing resources of any capacity in dynamically changing MP2P wireless environments under synchronized movements. Copyright © 2012 John Wiley & Sons, Ltd.     

Exploring the accuracy of capturing snapshots in large‐scale P2P IPTV systems

With the growing maturity of peer‐to‐peer (P2P) technology, Internet protocol television (IPTV) applications based on that gained great success commercially and have attracted more and more attentions from both industry and academia. Currently, the active measurement method based on crawler technology is the most popular and effective one to study P2P IPTV systems. Existing measurement results revealed that accuracy of captured overlay snapshots depends on the crawling speed of crawler system. In order to capture more accurate overlay snapshots of P2P IPTV system, we developed a very fast and efficient distributed crawler system using the distributed architecture and peer degree‐rank mechanism. In this paper, we first introduce the architectures of PPTV channel‐list resource distribution and the whole system, which is the most popular and largest instance of P2P IPTV applications nowadays. Subsequently, this paper evaluates the crawling results of two dedicated crawlers capturing from peer‐list servers and ordinary peers, respectively. Finally, we propose a fast and accurate dedicated crawler system based on distributed architecture and peer degree rank for PPTV. The experiment results show that the performance of our distributed crawler system is much better than other existing crawler systems. Specifically, our distributed crawler can track a very popular channel with about 7200 online users in 30 s. It is also reasonable to believe that our distributed crawler system can capture complete overlay snapshots. To the best of our knowledge, our study work is the first to explore capturing accurate overlay snapshots of large‐scale P2P IPTV applications. Our crawler system can provide a good solution for capturing more accurate overlay snapshots of PPTV system and can also be used to help researchers to design crawler systems for other P2P IPTV systems. Copyright © 2015 John Wiley & Sons, Ltd.     

A survey and comparison on overlay‐underlay mapping techniques in peer‐to‐peer overlay networks

Peer‐to‐peer (P2P) overlay networks were developed initially for file sharing such as Napster and Gnutella; but later, they have become popular for content sharing, media streaming, telephony applications, etc. Underlay‐unawareness in P2P systems can result in suboptimal peer selection for overlay routing and hence poor performance. In this paper, we present a comprehensive survey of the research work carried out to solve the overlay‐underlay mapping problems up till now. The majority of underlay‐aware proposals for peer selection focus on finding the shortest overlay routes by selecting nearest nodes according to proximity information. Another class of approaches is based on passive or active probing for provision of underlay information to P2P applications. Some other optimizations propose use of P2P middleware to extract, process, and refine underlay information and provide it to P2P overlay applications. Another class of approaches strive to use ISPs or third parties to provide underlay information to P2P overlay applications according to their requirements. We have made a state‐of‐the‐art review and comparison for addressing the overlay‐underlay mismatch in terms of their operation, merits, limitations, and future directions.     

Location‐based distributed caching for device‐to‐device communications underlaying cellular networks

Device‐to‐device (D2D) communications have been viewed as a promising data offloading solution in cellular networks because of the explosive growth of multimedia applications. Because of the nature of distributed device location, distributed caching becomes an important function of D2D communications. By taking advantage of the caching capacity of the device, in this work, we explore the device storage and file frequent reuse to realize distributed content dissemination, that is, storing contents in mobile devices (named helpers). Specifically, we first investigate the average and lower bound of helper amount by dividing the network into small areas where the nodes are within each other's communication radius. Then, optimal helper amount is derived based on average helper amount and network topology. Subsequently, a location‐based distributed helper selection scheme for distributed caching is proposed based on the given optimal helper amount. In particular, nodes are selected as helpers according to their locations and degrees, and contents are placed in the manner for maximizing total user utility. Extensive simulation results demonstrate the factors that affect the optimal helper amount and the total user utility. Copyright © 2015 John Wiley & Sons, Ltd.     

Distributed key management scheme for peer‐to‐peer live streaming services

Live media streaming over peer‐to‐peer (P2P) network structures is commonplace nowadays. However, with the large number of users in a typical P2P system, it is impractical to use the central server to process the key information update requests of all the users Accordingly, the present study proposes a distributed key management scheme in which the server is only required to transmit the key update information to a limited number of users. To further reduce the load on the server, the update information is distributed using a hop‐by‐hop approach. An effective method is proposed for protecting the key update information as it is propagated through the network. In addition, a technique is presented for ensuring the security of the certificates used in the system It is shown that the distributed key management scheme and authentication procedure ensure an efficient and secure P2P live streaming performance even in the event of high churn rates. Copyright © 2012 John Wiley & Sons, Ltd.     

Replication schemes for peer‐to‐peer content in wireless mesh networks with infrastructure support

Many mobile devices (e.g., smart phones, PDAs, portable computers) and wireless routers (e.g., WiFi access points) nowadays are equipped with ad hoc transmission mode. In a dense environment such as a college/office campus, this creates the possibility of forming a wireless mesh network (WMN) in which mobile users communicate with each other through multiple wireless hops. This allows mobile users to exchange (share) files over the free access WMN rather than a carrier frequency such as 3G and WiMax. We consider a peer‐to‐peer (P2P) content sharing setting in a WMN, wherein the mesh network operator over‐provision a number of mesh routers in the network with additional storage capacity and P2P‐aware devices that are programmed to cache and store P2P content. Those mesh routers act as caches and participants in P2P content sharing. The aim of this setting is to both reduce the cost of communications between peers within the WMN (i.e., reduce bandwidth and energy that P2P traffic consumes in the network), and enhance the performance of P2P content sharing (i.e., reduce the average P2P content download delay). Our main contribution in this paper is an optimum P2P content replication strategy at the participating mesh routers. In particular, we determine the optimum number of replicas for every P2P file such that the average access cost of all files in the network is minimized. We propose a centralized algorithm that enables the participating mesh routers to implement the optimal strategy. We further propose a distributed (low cost) algorithm for P2P content replication at the participating mesh routers, and show that the distributed algorithm mimics the optimal strategy very well. The analytical and simulation results show that our replication strategy significantly reduces the average overall cost of accessing P2P files in the WMN as compared with other commonly used replication strategies. Copyright © 2013 John Wiley & Sons, Ltd.     

Metal‐Organic‐Framework‐Based Vaccine Platforms for Enhanced Systemic Immune and Memory Response

Nanoparticulate delivery platforms have shown promising advantages for vaccines in many aspects. However, their application was limited so far by lengthy synthetic protocols, the requirement of specific modification of antigen, and by the low efficiency in inducing antigen‐specific cytotoxic T‐lymphocyte responses. This study demonstrates for the first time the construction of metal‐organic‐framework (MOF) based vaccines by encapsulating ovalbumin (OVA) and attaching the cytosine‐phosphate‐guanine oligodeoxynucleotides (CpG ODNs) in/on zeolitic imidazolate framework‐8 (ZIF‐8) nanoparticles. The pH responsive decomposition feature enables the system to release the protein antigens and CpG ODNs in the same antigen presenting cells more efficiently. More importantly, in addition to the induction of a potent immune memory response, both in vitro and in vivo experiments show that the vaccines can induce strong humoral and cellular immunity. These findings suggest that the MOF‐based vaccine platforms can be used to produce effective vaccines against a range of ailments, which will facilitate the application of MOFs in biomedical areas.     

Optimal rate and power allocation under quality‐of‐service requirements for wireless multihop networks

In wireless networks, real‐time applications have strict QoS requirements for packet delay, packet loss, and reliability. However, most existing work has not considered these QoS metrics when allocating wireless resources so that the QoS requirements of real‐time applications may not be satisfied. To overcome this shortcoming, a rate and power allocation framework incorporating these QoS metrics is first proposed for slow‐fading systems. Second, two distributed algorithms are developed to solve this optimization framework although it is nonconvex and nonseparable. Third, an improved framework is proposed to deal with the rate and power allocation with QoS requirements for fast‐fading systems. It is shown that the fast‐fading state of the network does not need to be considered in this improved framework, and it can be solved using algorithms that are similar to those for the framework of slow‐fading systems. In the end, simulations show that our algorithms converge closely to the globally optimal solution. By comparison with an existing model, simulations also verify the validity of our frameworks on dealing with the rate and power allocation with QoS requirements. Copyright © 2012 John Wiley & Sons, Ltd.     

MAPK‐Targeted Drug Delivered by a pH‐Sensitive MSNP Nanocarrier Synergizes with PD‐1 Blockade in Melanoma without T‐Cell Suppression

The combination of BRAF/MEK‐targeted therapy with immune checkpoint blockade is regarded as a promising regimen for patients with metastatic melanoma due to their complementary advantages. However, MEK‐inhibitor‐induced T‐cell toxicity impedes effective cooperation. In this experiment, a pH‐responsive on‐demand controlled release mesoporous silica nanoparticles (MSNPs) system is designed. Fluorescein‐isothiocyanate‐loaded MSNP can be specifically delivered into tumor cells rather than T‐cells. MEK‐inhibitor‐loaded MSNP avoids proliferative and functional inhibitions of T‐cells, while preserving growth suppression of tumor cells in vitro. In an in vivo model, MSNP encapsulation reverses the MEK‐inhibitor‐induced suppression of activated CD8⁺ T‐cells, and enhances the secretion of INF‐γ and IL‐2. The combination of BRAF inhibitor plus MSNP‐loaded MEK inhibitor and anti‐PD‐1 antibody synergistically inhibits tumor growth via promoting robust immune‐related antitumor response. This work provides a novel and generalized framework for combining T‐cell‐impaired targeted therapy and immune checkpoint blockade by using a nanoparticle‐based delivery system.     

Cross‐Layer Resource Allocation in Multi‐interface Multi‐channel Wireless Multi‐hop Networks

In this paper, an analytical framework is proposed for the optimization of network performance through joint congestion control, channel allocation, rate allocation, power control, scheduling, and routing with the consideration of fairness in multi‐channel wireless multi‐hop networks. More specifically, the framework models the network by a generalized network utility maximization (NUM) problem under an elastic link data rate and power constraints. Using the dual decomposition technique, the NUM problem is decomposed into four subproblems — flow control; next‐hop routing; rate allocation and scheduling; power control; and channel allocation — and finally solved by a low‐complexity distributed method. Simulation results show that the proposed distributed algorithm significantly improves the network throughput and energy efficiency compared with previous algorithms.     

Extending P2PMesh: topology‐aware schemes for efficient peer‐to‐peer data sharing in wireless mesh networks

Wireless mesh networks (WMNs) have emerged as a promising technology that provides low‐cost broadband access to the Internet for fixed and mobile wireless end users. An orthogonal evolution in computer networking has been the rise of peer‐to‐peer (P2P) applications such as P2P data sharing. It is of interest to enable effective P2P data sharing in this type of networks. Conventional P2P data sharing systems are not cognizant of the underlying network topology and therefore suffer from inefficiency. We argue for dual‐layer mesh network architecture with support from wireless mesh routers for P2P applications. The main contribution of this paper is P2PMesh: a topology‐aware system that provides combined architecture and efficient schemes for enabling efficient P2P data sharing in WMNs. The P2PMesh architecture utilizes three schemes: (i) an efficient content lookup that mitigates traffic load imbalance at mesh routers; (ii) an efficient establishment of download paths; and (iii) a data transfer protocol for multi‐hop wireless networks with limited capacity. We note here that the path establishment and data transfer schemes are specific to P2P traffic and that other traffic would use routes determined by the default routing protocol in the WMN. Simulation results suggest that P2PMesh has the potential to improve the performance of P2P applications in a wireless multi‐hop setting; specifically, we focused on data sharing, but other P2P applications can also be supported by this approach. Copyright © 2011 John Wiley & Sons, Ltd.     

Satellite‐based vessel Automatic Identification System: A feasibility and performance analysis

The Automatic Identification System (AIS) is a VHF communication system that provides identification/location information to vessels and shore stations by exchanging data such as position, identification, course, speed, etc. Recently, the interest in detecting and tracking ships at distances from coastlines larger than what can be accomplished by normal terrestrial VHF communications has grown, driven by requirements of long‐range applications such as better handling of hazardous cargo, improved security and countering illegal operations. This paper presents an extension of AIS to a long‐range positioning reporting through a constellation of LEO satellites. It outlines technical challenges like the high rate of message collisions from ships in the field of view of a satellite. Technical solutions are proposed at system and sub‐system level to address these challenges. A computer‐based system simulator is used to assess the system performance and carry out a high‐level system sizing. Results show that a relatively small constellation of LEO satellites can guarantee good ship position detection probability as well as a reporting time interval of a few hours. System performance aspects to be addressed in future work are the possible impact of terrestrial mobile communications interference as well as variations of the estimated traffic data. Copyright © 2009 John Wiley & Sons, Ltd.     

Optimal layer division for low latency in DHT‐based hierarchical P2P network

Hierarchical architecture can significantly reduce the workload overheads and facilitate effective search in peer‐to‐peer (P2P) network by dividing the peers into two layers: a supernode layer and an ordinary node layer. System scalability is therefore improved, which is critical to the deployment of P2P applications, particularly for the P2P‐based Voice over Internet Protocol systems. However, the lack of appropriate size ratio of the supernode layer to the ordinary node layer makes the system search performance far from being optimal. To address the problem, the goal of this paper is to find the optimal layer ratio, such that lookup latency is minimized, subject to the capacity constraint of supernodes. With this particular objective, this paper first formulates a search delay model for the distributed hash table (DHT)‐based layered P2P architecture, taking account of two main sources of latency: DHT routing and queuing delay at the supernode. Then the optimal ratio between supernodes and ordinary nodes is found with the analytical model. Simulation and numerical results show that the obtained solution can improve the performance of a two‐layer P2P system in terms of lookup latency. Copyright © 2016 John Wiley & Sons, Ltd.     

Cooperative Q‐learning techniques for distributed online power allocation in femtocell networks

In this paper, we address the problem of distributed interference management of femtocells that share the same frequency band with macrocells using distributed multi‐agent Q‐learning. We formulate and solve two problems representing two different Q‐learning algorithms, namely, femto‐based distributed and sub‐carrier‐based distributed power controls using Q‐learning (FBDPC‐Q and SBDPC‐Q). FBDPC‐Q is a multi‐agent algorithm that works on a global basis, for example, deals with the aggregate macrocell and femtocell capacities. Its complexity increases exponentially with the number of sub‐carriers in the system. Also, it does not take into consideration the sub‐carrier macrocell capacity as a constraint. To overcome these problems, SBDPC‐Q is proposed, which is a multi‐agent algorithm that works on a sub‐carrier basis, for example, sub‐carrier macrocell and femtocell capacities. Each of FBDPC‐Q and SBDPC‐Q works in three different learning paradigms: independent (IL), cooperative (CL), and weighted cooperative (WCL). IL is considered the simplest form for applying Q‐learning in multi‐agent scenarios, where all the femtocells learn independently. CL and WCL are the proposed schemes in which femtocells share partial information during the learning process in order to strike a balance between practical relevance and performance. We prove the convergence of the CL paradigm when used in the FBDPC‐Q algorithm. We show via simulations that the CL paradigm outperforms the IL paradigm in terms of the aggregate femtocell capacity, especially in networks with large number of femtocells and large number of power levels. In addition, we propose WCL to address the CL limitations. Finally, we evaluate the robustness and scalability of both FBDPC‐Q and SBDPC‐Q, against several typical dynamics of plausible wireless scenarios (fading, path loss, random activity of femtocells, etc.). We show that the CL paradigm is the most scalable to large number of femtocells and robust to the network dynamics compared with the IL and WCL paradigms. Copyright © 2014 John Wiley & Sons, Ltd.     

iPTT: peer‐to‐peer push‐to‐talk for VoIP

This paper proposes iPTT, a peer‐to‐peer (P2P) Push‐to‐Talk (PTT) service for Voice over IP (VoIP). In iPTT, a distributed and mobile‐operator independent network architecture is presented to accelerate the deployment of the PTT service. Based on the serverless architecture, we develop two mechanisms, that is, flooding‐based floor control mechanism (FFC) and tree‐based floor control mechanism (TFC), for real‐time talk‐burst determination. The determination algorithms and the corresponding message flows for these two mechanisms are designed to show the feasibility of FFC and TFC. The performance of FFC and TFC is investigated through our analytical and simulation models in terms of the determination latency and the number of floor‐control message exchanges. Copyright © 2008 John Wiley & Sons, Ltd.     

基于分片、松耦合的分布式文件系统的设计与实现

文章介绍为CGSP^＊（China Grid Support Platform）身定制的一个基于分片的、松耦合的分布式文件系统。与现存的分布式文件系统相比，本系统有以下特点：（1）将资源层与管理层完全分离；（2）基于分片而不是整个文件进行管理；（3）数据资源和用户虚拟空间都纳入WSRF框架。以上几点都是针对网格海量数据密集型应用而设计的：     

A cyclic redundancy check‐based non‐coherent receiver for automatic identification system signals

A non‐coherent receiver for automatic identification system (AIS) signals is proposed in this paper. The proposed receiver is based on the Viterbi algorithm with cyclic redundancy check (CRC) trellis. It takes bit stuffing into consideration and is designed to simultaneously demodulate decode and correct the received messages. The complexity of the proposed receiver has been reduced with state‐complexity reduction. Simulations prove that the proposed receiver outperforms those AIS receivers without CRC trellis error correction in terms of BER and packet error rate. Copyright © 2015 John Wiley & Sons, Ltd.