Successful development of cloud computing paradigm necessitates accurate performance evaluation data centers. As exact modeling centers is not feasible due to the nature and diversity user requests, we describe a novel approximate analytical model for server farms solve it obtain estimation complete probability distribution request response time other important indicators. The allows operators determine relationship between number servers input buffer size, on one side, indicators such as...

As modern vehicles and distributed fog services advance apace, vehicular (VFSs) are being expected to span across multiple geo-distributed datacenters, which inevitably leads cross-datacenter authentication. Traditional authentication models not suitable for the scenario of high-speed moving accessing VFS, because these either ignored user privacy or delay requirement driving vehicles. This paper proposes a blockchain-assisted lightweight anonymous (BLA) mechanism is provisioned BLA can...

This article investigates a hierarchical aerial computing system, where both high-altitude platforms (HAPs) and unmanned vehicles (UAVs) provision computation services for ground devices (GDs). Different from the existing works which ignored UAV task offloading to HAPs suffered long transmission delay between GDs, in our UAVs are responsible collecting tasks generated by GDs. Considering limited resources constrained coverage, need cooperatively allocate their (including spectrum, caching,...

The performance of an IEEE 802.15.4 compliant network operating in the beacon enabled mode with both downlink and uplink traffic is analyzed through discrete time Markov chains theory M/G/1 queues. model considers acknowledged transmissions includes impact different parameters such as packet arrival rate, size, inactive period between beacons, number stations. We investigate nonsaturation region outline conditions under which abruptly goes to saturation. analysis stability queues shows that...

Accurate performance evaluation of cloud computing resources is a necessary prerequisite for ensuring that quality service parameters remain within agreed limits. In this paper, we employ both the analytical and simulation modeling to addresses complexity systems. Analytical model comprised distinct functional submodels, results which are combined in an iterative manner obtain solution with required accuracy. Our models incorporate important features centers such as batch arrival user...

In this paper, we propose an analytical performance model that addresses the complexity of cloud centers through distinct stochastic submodels, results which are integrated to obtain overall solution. Our incorporates important aspects such as pool management, compound requests (i.e., a set submitted by one user simultaneously), resource virtualization and realistic servicing steps. manner, not only detailed assessment center performance, but also clear insights into equilibrium arrangement...

We present an anonymous authentication and verification scheme for the IEEE Wireless Access in Vehicular Communications (WAVE)-based vehicular ad hoc networks (VANETs). Our contribution includes message efficient prioritized strategy periodic road safety messages. A variation of elliptic curve digital signature algorithm (ECDSA) is used combination with identity-based (ID-based) signature, where current position information on a vehicle utilized as ID corresponding vehicle. This waives need...

Deep Neural Networks (DNNs) have been gaining state-of-the-art achievement compared with many traditional Machine Learning (ML) models in diverse fields. However, adversarial examples challenge the further deployment and application of DNNs. Analysis has carried out for studying reasons DNNs' vulnerability to perturbation focused on model architecture. No research done investigating impact optimization algorithms (namely, optimizers DNNs) employed training DNN models' sensitivity examples....

The consensus algorithm is an essential ingredient of any blockchain system. Many different mechanisms, such as practical Byzantine fault tolerance (PBFT), Proof-of-Work (PoW), Proof-of-Stake (PoS), and their many derivatives, have been proposed over the years, but complementary problems performance resilience to malicious behavior nodes yet be resolved in a satisfactory manner. In this work, we propose mechanism that integrates PoS with PBFT, which can effectively deal dishonest nodes, both...

Due to lack of an appropriate wireless technology which satisfies all the requirements Wireless Body Area Networks (WBANs) IEEE 802.15.6 Task Group introduced communication standard optimized for low power devices and operation on, in or around human body. In this work we develop analytical model performance evaluation 802.15.6-based WBAN under saturation condition error prone channel. We backoff procedure as specified employing a probabilistic approach. validate results with simulation...

In this paper, we evaluate the performance of cloud centers with high degree virtualization and Poisson batch task arrivals. To end, develop an analytical model validate it independent simulation model. Task service times are modeled a general probability distribution, but also accounts for deterioration due to workload at each node. The allows calculation important indicators such as mean response time, waiting time in queue, queue length, blocking probability, immediate service,...

In this paper, we investigate the performance of networks built from single-channel devices that use wireless access in vehicular environment protocols. We consider several traffic combinations, each which presents a mix classes, over control and service channels. Our results show time switching between channels causes synchronization backoff processes, increases frame collision probability, particular for small sizes contention windows. also evaluate impact interruption process by inactive...

We have developed an analytical model for a non-saturated IEEE 802.15.6 wireless body area network (WBAN) operating under error-prone channel. The most suitable vehicle improving performance was found to be the choice of access phase lengths based on traffic loads different user priorities (UPs). It also that deployment exclusive (EAP) is not necessary in typical WBAN; fact, short and random phases (EAP RAP, respectively) lead inefficient use available bandwidth. four (out eight available)...

A VANET that uses IEEE 802.11p EDCA mechanism is susceptible to a synchronization-based DDoS attack due periodicity of transmissions and small contention window sizes. To make things worse, neither the sender nor receivers periodic broadcasts will be aware since broadcast communications in do not have acknowledgements. In this paper, we analyze prospect attacks on vehicular propose mitigation techniques avoid such an attack.

The articles in this special section focus on vehicular cloud computing platforms (CVCC). As a platform, connected (CVCC), which seamlessly combines and VANETs, has been recently proposed to accelerate the adoption of extends traditional infrastructure consisting majority stationary nodes edge vehicles. CVCC is mobile paradigm that consists in-motion vehicles cooperating with each other achieve bunch practical applications, such as collaborative package delivery information dissemination....

The Unmanned Aerial Vehicles (UAVs) play a significant role to alleviate the negative impacts of disasters by providing essential assistance rescue and evacuation operations in affected areas. Then, reliability UAV connections accuracy exchanged information are critical parameters. In this paper, we propose networking security architecture for disaster surveillance system. scheme involves two-tier cluster network based on IEEE 802.11ah, which can provide traffic isolation between tiers....

Vehicular fog computing (VFC) complements vehicular cloud as a promising solution for accommodating the surge of mobile traffic and reducing latency. This paper considers service (VFS) provided by (VF), which is formed on-the-fly integrating storage resources parked vehicles. VF dynamicity, due to vehicles' random arrivals departures, poses number challenges reliable secure VFS provision client We propose novel mechanism consists construction method access ensure reliability security without...

IEEE 802.11ah protocol is specifically designed to provide network connectivity a large number of energy efficient heterogeneous quality service (QoS) Internet things (IoT) devices. Restricted access window (RAW) mechanism the an innovative feature that aims at reducing medium contention by slotting beacon interval and allowing limited nodes contend in specific slot. In this paper, we evaluate important control (MAC) layer performance metrics differentiated QoS IoT RAW mechanism. Our...

This work proposes Practical Byzantine Fault Tolerance (PBFT) ordering service needed for block formation in permissioned blockchain environments. Contrary to current PBFT implementations that only provide a single point of entry the service, we allow each node act as an and conducts consensus process including new record distributed ledger. To ensure atomicity insertion ledger, have developed bandwidth reservation protocol uses modification CSMA/CA regulate access broadcast medium formed by...

In this paper, we provide a comprehensive analytical model for Bitcoin's blockchain distribution network. Components of the are derived from recent measurements and business analysis reports. We data algorithm using branching processes in network with random node connectivity. Then, apply Jackson to entire which individual nodes operate as priority M/G/1 queuing systems. Data arrival is modeled non-homogeneous Poisson process where rate delivery protocol. Within performance results, present...

Selfish mining strategy allows miners to gain unfair advantage and excess revenue in Bitcoin network, but it also disrupts the normal operation of network. In this work, we analyze impact selfish behavior on network through a number performance indicators such as connectivity, block arrival rate, node response time, delivery time for honest blocks, respectively. We discuss probability unintentional well intentional forks. have found that is noticeable, extreme cases, disproportional or their...

This paper investigates a dual-unmanned aerial vehicle (UAV) aided communication system to improve the security of between ground devices and UAVs. Different from existing works which ignored mobility just considered one-way UAVs, we allow be mobile consider bi-directional ground-UAV security. Specifically, one UAV server communicates with devices, other jammer is invoked confuse eavesdroppers. Our objective maximize worst-case average secrecy rate by joint optimization trajectory sender...