Retrieval Delay Research Articles

Achieve Adaptive Data Storage and Retrieval Using Mobile Sinks in Wireless Sensor Networks

In WSNs (Wireless Sensor Networks), data storage and retrieval is a challenging problem because of the limited resource and the short communication radius of the sensor nodes. Most of the existed schemes choose one or more static sensor nodes or Sinks to act as the rendezvous nodes, which can be seen as the connectors between the data producers and the data consumers. However, those schemes cannot avoid both the “hot spot” problem and the “bottleneck” problem, which refer to the much higher load balance of the sensor nodes around the rendezvous nodes. Moreover, most of the existing schemes never consider the dynamic nature of WSNs, which leads to the lack of adaptability. In this paper, we propose a novel dynamic-optimization-based framework named SRMSN using mobile Sinks to solve such a problem. SRMSN utilizes two heuristic methods, which are based on the virtual-grid-division technology and the diversity-factor-analysis technology, to determine the optimal target locations of the mobile Sinks in each time interval when each Sink node stay at a certain position and the optimal length of each of the time intervals adaptively, aiming at improving the adaptability and the efficiency of WSNs on data storage and retrieval. Simulation results show that SRMSN can reduce and balance the energy consumption greatly as well as decrease the average delay of data storage and retrieval in comparison with the state-of-the-art scheme on data storage and retrieval in WSNs.

Dynamic Interest Transmission Approach for Improving Link Failure Resiliency in Content Centric Network

Information centric network (ICN) is becoming a prevailing design for future Internet to provide data objects to end customers. One crucial problem in ICN is to design routing and forwarding strategy so that traffic can be transmitted efficiently even with the dynamics of network link. In this paper, we consider content centric network (CCN), which is one of the promising candidate architecture design for ICN. Particularly, we consider the scalable CCN with name mapping system, which improves scalability by using router Identifier as name prefix to forward interests. We address the issue of improving link failure resiliency for CCN by designing a dynamic interest transmission approach. We propose the link failure resilient interest transmission algorithm (LFRIT) to enhance link failure resiliency by considering both network traffic and link status information. Additionally, we propose the advanced design of LFRIT (A-LFRIT), which calculates and updates the forwarding table centrally for link updates to further improve network robustness. Numerous simulations are conducted to evaluate the proposed approach under realistic network topologies with respect to packet loss, latency, and network link utilization. Simulation results demonstrate that the packet loss probability and data retrieval delay of A-LFRIT can reduce to 50% of the basic CCN and multi-repository single path approaches.

The Benefits of Hybrid Caching in Gauss–Poisson D2D Networks

Device caching has recently been proposed as an efficient way to offload traffic from congested cellular networks. However, previous works usually ignore the fact that, in practice, the user device may not be willing to help others due to the limited battery capacity. In this paper, we introduce cooperation among the device-to-device (D2D) transmitters and propose two novel hybrid caching strategies—single-point caching combined with two-point cooperative caching with joint transmission (SPC-CCJT) or multi-stream transmission (SPC-CCMT)—aiming at saving the energy cost of content deliverers. Using tools from stochastic geometry, we propose an analytical framework of the hybrid caching strategies by modeling the locations of the D2D transmitters as a Gauss–Poisson process (GPP) to accurately capture the clustering and cooperative behaviors. First, we consider a probabilistic caching placement and optimize the caching distribution to maximize the cache hit probability. Second, to compare the performance between different content delivery strategies, we derive the success probability and per-user capacity for SPC, CCJT, and CCMT, respectively. These results are then applied to evaluate the offloading gain and the distribution of the content retrieval delay for SPC-CCJT and SPC-CCMT in the GPP-based D2D networks. It turns out that significant offloading gain and delay improvement can be achieved by hybrid caching with cooperation while the energy cost of each cooperator is kept low.

Efficient caching strategy in content‐centric networking for vehicular ad‐hoc network applications

Recently, content-centric networking (CCN) has been proposed as a promising solution for content distribution in vehicular ad-hoc networks (VANETs) owing to its named-data routing and in-network caching characteristics. In this network, the caching strategies are performed in the intermediate nodes, and even in the vehicular storage space. However, the typically existing caching strategies have indicated the low stored contents efficiency due to the peculiarities of VANET environment, like cache redundancy, high mobility, rapidly changing topology, and limited vehicular storage space. In this study, the authors proposed an efficient caching strategy in vehicle-to-vehicle scenario through CCN, which considers the requirements of different types of applications, the crucial features of data, and the peculiarities of the vehicular network (e.g. content popularity, cache occupancy, the stability link of the vehicles, and user's preference). Each vehicle makes its caching decision independently to improve the cache space and efficient use of the stored contents corresponding to the requirements of different application types. Simulation results validate that the proposed strategy outperforms other caching strategies in terms of reducing data retrieval delay, increasing cache hit ratio, and improving the cache performance on the vehicles.

An efficient in‐network caching decision algorithm for Internet of things

SummaryRecently, content‐centric networking (CCN) has become one of the important technologies for enabling the future networks. Along with its recognized potentialities as a content retrieval and dissemination solution, CCN has been also recently considered as a promising architecture for the Internet of things (IoT), because of 2 main features such as named‐based routing and in‐network caching. However, IoT is characterized by challenging features: small storage capacity of resource‐constrained devices due to cost and limitation of energy and especially transient data that impose stringent requirements on the information freshness. As a consequence, the intrinsic caching mechanisms existing in CCN approach do not well suit IoT domains; hence, providing a specific caching policy at intermediate nodes is a very challenging task. This paper proposes an effective multiattribute in‐network caching decision algorithm that performs a caching strategy in CCN‐IoT network by considering a set of crucial attributes including the content store size, hop count, particularly key temporal properties like data freshness, and the node energy level. Simulation results proved that our proposed approach outperforms 2 cache management schemes (probabilistic least recently used and AlwaysCache–first in first out in terms of improving total hit rate, reducing data retrieval delay, and enhancing content reusability in IoT environment).

Cache Freshness in Named Data Networking for the Internet of Things

The Information-Centric Networking (ICN) paradigm is shaping the foreseen future Internet architecture by focusing on the data itself rather than its hosting location. It is a shift from a host-centric communication model to a content-centric model supporting among others unique and location-independent content names, in-network caching and name-based routing. By leveraging the easy data access, and reducing both the retrieval delay and the load on the data producer, the ICN can be a viable framework to support the Internet of Things (IoT), interconnecting billions of heterogeneous constrained objects. Among several ICN architectures, the Named Data Networking (NDN) is considered as a suitable ICN architecture for IoT systems. However, its default caching approach lacks a data freshness mechanism, while IoT data are transient and frequently updated by the producer which imposes stringent requirements in terms of information freshness. Furthermore, IoT devices are usually resource-constrained with harsh limitations on energy, memory and processing power. We propose in this paper a caching strategy and a novel cache freshness mechanism to monitor the validity of cached contents in an IoT environment while minimizing the caching process cost. We compared our solution to several relevant schemes using the ccnSim simulator. Our solution exhibits the best system performances in terms of hop reduction ratio, server hit reduction ratio and response latency, yet it provides the lowest cache cost and significantly improves the content validity.

Analysis of User Content Retrieval Delay Based on the Matern Hard‐Core Point Process of Type II

The content retrieval delay is an important performance metric for enhancing user experience in wireless networks. In this paper, by modeling the locations of the base stations (BSs) as the Matern hard‐core point process of type II (MHP), we analyze the content retrieval delay for a typical cache‐enabled device in wireless networks under the most popular content policy. Since it is intractable to get the size distribution of a Voronoi cell in the MHP model, we propose an approximate formula based on the empirical result in the Poisson point process and derive the cellular load which denotes the number of the user devices connected to a randomly chosen BS. Since the probability generating functional for MHP does not exist, we also propose approximate methods for the coverage probability of the MHP model. At last, we derive the cumulative distribution function of the content retrieval delay. Simulation results validate the accuracy of our analytical conclusions for user content retrieval delay.

Achieving Content-Oriented Anonymity with CRISP

As a popular realization of Information-Centric Network (ICN), Named Data Networking (NDN) greatly improves the efficiency of Internet content-distribution. A feature of NDN is that it improves privacy, as no addresses are needed for either the content consumer or publisher. However, NDN packets contain content names, and hence a well-motivated adversary can still deduce what content the user is requesting once it can link the packets and users. How to provide privacy in NDN, given its unique data retrieval mode, is an open problem. In this paper, we explore a specific content-oriented anonymity model called content-user unlinkability , which breaks the relationship between the content and the requesting user. We argue that achieving content-user unlinkability efficiently is a non-trivial task, since existing tunnel-based approaches will largely dismiss content caching of NDN, resulting in large content retrieval delay. To this end, we propose CRISP, namely C ooperative R andom I ntere S t P ropagation. In CRISP, routers cooperate to form full-meshed groups, within which content requests are randomly propagated before they are forwarded to content producers. We show CRISP can achieve probable content-user unlinkability with probabilistic models. Extensive simulations demonstrate that CRISP outperforms existing solutions including ANDANA and Crowds, in terms of both content retrieval latency and data throughput.

When 5G meets ICN: An ICN-based caching approach for mobile video in 5G networks

The dramatic increasing demand for video from mobile users (MU) has imposed huge pressure on cellular networks. By using the millimeter wave (mmWave) technique, the fifth generation (5G) networks can provide rich bandwidth to satisfy the requirements for high quality mobile video and alleviate the traffic pressure. However, the shorter transmission range of mmWave leads mobile users in 5G network suffer frequent handoffs and long connection delays which degrades the Quality of Experience (QoE) for mobile video users. How to improve QoE for mobile video users has become a crucial challenge.Information-centric-networking (ICN) is a promising paradigm to mitigate this challenge as its in-network caching can bring videos closer to users, which can reduce network traffic and video retrieval delay significantly. In this paper, we propose an ICN-based caching approach that considers both the mobility of users and the popularity of videos. While user mobility has rarely been considered in existing works, in this paper, user mobility is exploited to reduce the retrieval delay caused by frequent handoffs. Videos can be retrieved from the router which is directly connected to the base station (BS) instead of the original content provider when a handoff happens. Consequently, the retrieval delay caused by frequent handoffs can be significantly reduced. Simulations results show that our ICN-based approach outperforms the traditional IP-based RAN caching and the cooperation-driven ICN-based caching scheme (CDIC) in terms of retrieval delay and network traffic deduction.

D2D-Aware Device Caching in mmWave-Cellular Networks

In this paper, we propose a novel policy for device caching that facilitates popular content exchange through high-rate device-to-device (D2D) millimeter-wave (mmWave) communication. The D2D-aware caching policy splits the cacheable content into two content groups and distributes it randomly to the user equipment devices, with the goal to enable D2D connections. By exploiting the high bandwidth availability and directionality of mmWaves, we ensure high rates for the D2D transmissions, while mitigating the co-channel interference that limits the throughput gains of the D2D communication in the sub-6-GHz bands. Furthermore, based on a stochastic-geometry modeling of the network topology, we analytically derive the offloading gain that is achieved by the proposed policy and the distribution of the content retrieval delay considering both half- and full-duplex modes for the D2D communication. The accuracy of the proposed analytical framework is validated through Monte Carlo simulations. In addition, for a wide range of a content popularity indicator, the results show that the proposed policy achieves higher offloading and lower content-retrieval delays than existing state-of-the-art approaches.

Industrial Internet of things at work: a case study analysis in robotic‐aided environmental monitoring

Nowadays, Internet of things (IoT) and robotic systems are key drivers of technological innovation trends. Leveraging the advantages of both technologies, IoT-aided robotic systems can disclose a disruptive potential of opportunities The present contribution provides an experimental analysis of an IoT-aided robotic system for environmental monitoring. To this end, an experimental testbed has been developed. It is composed of: (i) an IoT device connected to (ii) an unmanned aerial vehicle (UAV) which executes a patrolling mission within a specified area, where (iii) an IoT network has been deployed to sense environmental data. An extensive experimental campaign has been carried out to scavenge pros and cons of adopted technologies. The key results of the authors analysis show that: (i) the UAV does not incur any significant overhead due to onboard IoT equipment and (ii) the overall quality of service expressed in terms of network joining time, data retrieval delay and packet loss ratio satisfies the mission requirements. These results enable further development in larger-scale environment.

Optimal Device-Aware Caching

Caches in Content-Centric Networks (CCN) are increasingly adopting flash memory based storage. The current flash cache technology stores all files with the largest possible “expiry date,” i.e., the files are written in the memory so that they are retained for as long as possible. This, however, does not leverage the CCN data characteristics where content is typically short-lived and has a distinct popularity profile. Writing files in a cache using the longest retention time damages the memory device thus reducing its lifetime. However, writing using a small retention time can increase the content retrieval delay, since, at the time a file is requested, the file may already have been expired from the memory. This motivates us to consider a joint optimization wherein we obtain optimal policies for jointly minimizing the content retrieval delay (which is a network-centric objective) and the flash damage (which is a device-centric objective). Caching decisions now not only involve what to cache but also for how long to cache each file. We design provably optimal policies and numerically compare them against prior policies.

A novel hybrid forwarding strategy for content delivery in wireless information-centric networks

Information-centric networking (ICN) is a promising solution for content delivery in multi-hop wireless networks. In these environments, the ICN forwarding strategies typically rely on broadcasting, which facilitates content distribution by taking advantage of the shared medium, but brings about undesirable side effects. To avoid the broadcast-related issues of packet redundancy and unreliability due its unacknowledged mode, a few recent proposals advocated unicasting as the communication mode to resort to, once the content provider has been discovered. However, unicasting may suffer from connectivity breakages due to node mobility and harsh propagation conditions, and, generally, limits the data sharing capability of the wireless medium.In this paper, we design a robust ICN-based forwarding strategy, called Ad Hoc Dynamic Unicast (ADU), that wisely harnesses unicast and broadcast primitives on top of IEEE 802.11-based wireless networks. ADU relies on unicasting for content dissemination after the provider discovery, and promptly falls back to broadcast to find a new content provider in case of a link failure notified by the Medium Access Control (MAC) layer. Extensive simulations in two different multi-hop wireless scenarios, i.e., mobile and vehicular ad hoc networks, under different load settings, assess the ADU performance against benchmark ICN forwarding schemes, representative of broadcast-based and unicast-based solutions. Results show that ADU outperforms them in all circumstances, proving its better responsiveness to link failures, which guarantees a shorter content retrieval delay and a lower message overhead and energy consumption.

Delay-Tolerant Forwarding Strategy for Named Data Networking in Vehicular Environment

Named data networking (NDN) has been considered as a promising networking architecture for vehicular ad-hoc networks (VANETs). However, interest forwarding in NDN suffers severe issues in vehicular environment. Broadcast storms result in much packet loss and huge transmission overhead. Also, link disconnection caused by highly dynamic topology leads to low packet delivery ratio and extreme long delay in data retrieval. Thus, an efficient NDN forwarding strategy to retrieve data is urgently required. In this paper, we propose the density-aware delay-tolerant (DADT) interest forwarding strategy to retrieve traffic data in vehicular NDN. DADT specifically addresses data retrieval during network disruptions using delay tolerant networking (DTN). It makes retransmission decisions based on directional network density. Also, DADT mitigates broadcast storms by using a rebroadcast deferring timer. We compared DADT against other strategies through simulation and the results show that it can achieve a higher satisfaction ratio while maintaining low transmission overhead.

Selective Placement of Caches for Hash-Based Off-Path Caching in ICN

In-network caching has evidently emerged as an indispensable core functionality of ICN. Of the various types of caching techniques, off-path caching turns out to be a potential technique. With a view to improve the performance of hash-based off-path caching, the aim of the paper is to ensure profitable, economic and selective placement of caches such that the final cache allocation tends to reduce simultaneously average retrieval delay and maximum internal link-stress. To achieve the same, we propose simple yet elegant heuristic algorithm to strategically identify and exclude the bad node-positions for placement of caches. More specifically, for a given topology, the algorithm computes cost (in terms of delay) for all the nodes and prepares a cost based descending ordered list of nodes. Further, iteratively, increasing number of nodes, in sequence, from the cost-based ordered list of nodes are debarred from caching thereby resulting in family of solutions. A solution represents a selective cache allocation map corresponding to the number of debarred nodes. Moreover, every iterative solution reduces average retrieval delay and seeks opportunistic reduction in maximum internal linkstress. Comparing the solutions graphically would enable network operators to finally select (as per desire) one cache allocation map for a given network topology for hash-based off-path caching. In a way, the selected cache allocation map for the considered topology implies that it is better to place the caches at the core of the network as compared to edge.

Proactive Caching for Mobile Video Streaming in Millimeter Wave 5G Networks

Mobile video streaming is fundamental to advanced applications in the fifth generation (5G) networks. Millimeter wave (mmWave) communication represents a leading 5G technology, which provides rich bandwidth and, therefore, great potentials for high-quality mobile video streaming. However, mobile video streaming in mmWave 5G networks faces fundamental challenges due to mmWave antenna directivity and high user mobility. As such, users typically have short connection durations and frequent handoffs, making video streaming suffer from long handoff delays and connection latency. In this paper, we tackle the issues by developing a caching-based mmWave framework, which precaches video contents at the base station for handoff users and thus significantly reduces the connection and retrieval delays. As a result, high-mobility users with frequent handoffs can enjoy continuous high-quality video streaming. Specifically, we model the proposed system as a cache management problem and attain optimal video streaming quality by using Markov decision process to dynamically allocate proper cache memory space of each base station to mobile users. A cell-by-cell decomposition method is proposed to solve the dynamic programming problem with significantly reduced computational complexity. Using extensive simulations, we demonstrate that the proposed solution can effectively maintain high-quality mobile video streaming for high-mobility 5G users moving among mmWave small cells with directional antenna.

A common mechanism behind distractor-response and response-effect binding?

Short-term bindings between responses and events in the environment ensure efficient behavioral control. This notion holds true for two particular types of binding: bindings between responses and response-irrelevant distractor stimuli that are present at the time of responding, and also for bindings between responses and the effects they cause. Although both types of binding have been extensively studied in the past, little is known about their interrelation. In three experiments, we analyzed both types of binding processes in a distractor-response binding design and in a response-effect binding design, which yielded two central findings: (1) Distractor-response binding and response-effect binding effects were observed not only in their native, but also in the corresponding "non-native" design, and (2) a manipulation of retrieval delay affected both types of bindings in a similar way. We suggest that a general and unselective mechanism is responsible for integrating own responses with a large variety of stimuli.

Client–server games and their equilibria in peer-to-peer networks

In peer-to-peer networks, each peer acts simultaneously as client and server, by issuing and satisfying content requests respectively. In this work, we use concepts from non-cooperative game theory to model the interaction of autonomous peers. The client strategy set consists of feasible request load splits towards servers, while the server strategy set is formed out of possible service disciplines on received requests. The performance metric of interest is the average retrieval delay of content requests.First, we assume preassigned fixed server policies (FIFO and priority) and study the emerging client request load splitting game. Peers are either egotistic (i.e. interested only in optimizing their own delay) or altruistic ones that also take into account delay incurred to other peers. We consider best response updates to model iterative peer interaction. For egotistic peers, we show that the sequence of best responses always converges to the unique Nash Equilibrium Point (NEP). For altruistic peers best response updates converge to one of the multiple NEPs exist, with each one being a global optimum for the FIFO case and a local optimum for any other service strategy profile. We also consider mixed swarms consisting of both egotistic and (partially-) altruistic peers and show an interesting transition from one to multiple NEPs. Next, we include service strategies in the peer strategy set. Though with its service policy a peer cannot directly affect its delay, it can affect the resulting NEP. We devise two-level game models, where, at a first level, a peer selects its favorable service rule and then peers play a client load splitting game.

Potential brain death organ donors - challenges and prospects: A single center retrospective review

Organ donation after brain death (BD) is a major source for obtaining transplantable organs for patients with end-stage organ disease (ESOD). This retrospective, descriptive study was carried out on all potential BD patients admitted in different intensive care units (ICUs) of the Hamad medical Corporation (HMC), Doha, Qatar during a period from January 2011 to April 2012. Our aim was to evaluate various demographic criteria and challenges of organ donation among potential BD organ donors and plan a strategy to improve the rate of organ donation in Qatar. Various aspects of BD patients in the ICUs and their possible effects on organ donation were studied. The time intervals analyzed to determine the possible causes of delay of organ retrieval were: time of diagnosing fixed dilated pupils in the ICU, to performing the first BD test, then to the second BD test, to family approach, to organ retrieval and/or circulatory death (CD) without organ retrieval. There were a total of 116 potential BD organ donors of whom 96 (82.75%) were males and 20 (17.25%) were females. Brain hemorrhage and head injury contributed to 37 (31.9%) and 32 (27.6%) BD cases, respectively. Time interval between diagnosing fixed dilated pupil and performing the first test of BD was delayed >24 h in 79% of the cases and between the first and second BD tests was >6 h in 70.8% of the cases. This delay is not compatible with the Hamad Medical Corporation (HMC) policy for BD diagnosis and resulted in a low number of organs retrieved. BD organ donation, a potential source for organs to save patients with ESOD has several pitfalls and every effort should be made to increase the awareness of the public as well as medical personnel to optimize donation efficacy.

A Proposed Model for Web Proxy Caching Techniques to Improve Computer Networks Performance

one of the most important techniques for improving the performance of web based applications is web proxy caching Technique. It is used for several purposes such as reduce network traffic, server load, and user perceived retrieval delays by replicating popular content on proxy caches that are strategically placed within the network. The use of web proxy caching is important and useful in the government organizations that provides services to citizens and has many branches all over the country where it is beneficial to improve the efficiency of the computer networks performance, especially remote areas which suffer from the problem of poor network communication. Using of proxy caches provides all users in the government computer networks by reducing the amount of redundant traffic that circulates through the network. It also provides them by getting quicker access to documents that are cached. In addition, there are a lot of benefits we can obtain from the using of proxy caches but we will address them later. In this research, we will use web proxy caching to provide all of the above benefits that we are mentioned above and to overcome on the problem of poor network communication in ENR (Egyptian National Railways). We are going to use a scheme to achieve the integration of forward web proxy caching and reverse proxy caching.