Abdallah Khreishah

Cross-layer optimization for wireless multihop networks with pairwise intersession network coding

For wireless multi-hop networks with unicast sessions, most coding opportunities involve only two or three sessions as coding across many sessions requires greater transmission power to broadcast the coded symbol to many receivers, which enhances interference. This work shows that with a new flow-based characterization of pairwise intersession network coding (coding across two unicast sessions), an optimal joint coding, scheduling, and rate-control scheme can be devised and implemented using only the binary XOR operation. The new scheduling/rate-control scheme demonstrates provably graceful throughput degradation with imperfect scheduling, which facilitates the design tradeoff between the throughput optimality and computational complexity of different scheduling schemes. Our results show that pairwise intersession network coding improves the throughput of non-coding solutions regardless of whether perfect/imperfect scheduling is used. Both the deterministic and stochastic packet arrivals and departures are considered. This work shows a striking resemblance between pairwise intersession network coding and non-coded solutions, and thus advocates extensions of non-coding wisdoms to their network coding counterpart.

Cloud Computing Security: A Survey

Cloud computing is an emerging technology paradigm that migrates current technological and computing concepts into utility-like solutions similar to electricity and water systems. Clouds bring out a wide range of benefits including configurable computing resources, economic savings, and service flexibility. However, security and privacy concerns are shown to be the primary obstacles to a wide adoption of clouds. The new concepts that clouds introduce, such as multi-tenancy, resource sharing and outsourcing, create new challenges to the security community. Addressing these challenges requires, in addition to the ability to cultivate and tune the security measures developed for traditional computing systems, proposing new security policies, models, and protocols to address the unique cloud security challenges. In this work, we provide a comprehensive study of cloud computing security and privacy concerns. We identify cloud vulnerabilities, classify known security threats and attacks, and present the state-of-the-art practices to control the vulnerabilities, neutralize the threats, and calibrate the attacks. Additionally, we investigate and identify the limitations of the current solutions and provide insights of the future security perspectives. Finally, we provide a cloud security framework in which we present the various lines of defense and identify the dependency levels among them. We identify 28 cloud security threats which we classify into five categories. We also present nine general cloud attacks along with various attack incidents, and provide effectiveness analysis of the proposed countermeasures.

Coexistence of WiFi and LiFi toward 5G: concepts, opportunities, and challenges

Smart phones, tablets, and the rise of the Internet of Things are driving an insatiable demand for wireless capacity. This demand requires networking and Internet infrastructures to evolve to meet the needs of current and future multimedia applications. Wireless HetNets will play an important role toward the goal of using a diverse spectrum to provide high quality-of-service, especially in indoor environments where most data are consumed. An additional tier in the wireless HetNets concept is envisioned using indoor gigabit small-cells to offer additional wireless capacity where it is needed the most. The use of light as a new mobile access medium is considered promising. In this article, we describe the general characteristics of WiFi and VLC (or LiFi) and demonstrate a practical framework for both technologies to coexist. We explore the existing research activity in this area and articulate current and future research challenges based on our experience in building a proof-of-concept prototype VLC HetNet.

Toward better horizontal integration among IoT services

Several divergent application protocols have been proposed for Internet of Things (IoT) solutions including CoAP, REST, XMPP, AMQP, MQTT, DDS, and others. Each protocol focuses on a specific aspect of IoT communications. The lack of a protocol that can handle the vertical market requirements of IoT applications including machine-to-machine, machine-to-server, and server-to-server communications has resulted in a fragmented market between many protocols. In turn, this fragmentation is a main hindrance in the development of new services that require the integration of multiple IoT services to unlock new capabilities and provide horizontal integration among services. In this work, after articulating the major shortcomings of the current IoT protocols, we outline a rule-based intelligent gateway that bridges the gap between existing IoT protocols to enable the efficient integration of horizontal IoT services. While this intelligent gateway enhances the gloomy picture of protocol fragmentation in the context of IoT, it does not address the root cause of this fragmentation, which lies in the inability of the current protocols to offer a wide range of QoS guarantees. To offer a solution that stems the root cause of this protocol fragmentation issue, we propose a generic IoT protocol that is flexible enough to address the IoT vertical market requirements. In this regard, we enhance the baseline MQTT protocol by allowing it to support rich QoS features by exploiting a mix of IP multicasting, intelligent broker queuing management, and traffic analytics techniques. Our initial evaluation of the lightweight enhanced MQTT protocol reveals significant improvement over the baseline protocol in terms of the delay performance.

Scalable Cloudlet-based Mobile Computing Model☆

Abstract Mobile Cloud Computing (MCC) has been introduced as a feasible solution to the inherited limitations of mobile computing. These limitations include battery lifetime, processing power and storage capacity. By using MCC, the processing and the storage of intensive mobile device jobs will take place in the cloud system and the results will be returned to the mobile device. This reduces the required power and time for completing such intensive jobs. However, connecting mobile devices with the cloud, suffers from the high network latency and the huge transmission power consumption especially when using 3G/LTE connections. On the other hand, multimedia applications are the most common applications in todays mobile devices; such applications require high computing resources. In this paper, a Cloudlet-based MCC system is introduced, aiming at reducing the power consumption and the network delay of multimedia applications while using MCC. The MCC concepts with the proposed Cloudlet framework are integrated and a new scalable framework for the MCC model is proposed. Our practical experimental results using multimedia applications show that using the proposed model reduces the power consumption of the mobile devices as well as reducing the communication latency when the mobile device requests a job to be performed remotely while satisfying the high quality of service requirements.

Benchmarking the interactions among barriers in third-party logistics implementation: An ISM approach

Purpose – The purpose of this paper is to analyze the interaction among some of the major barriers that may hinder the implementation of third-party logistics (TPL) in manufacturing industries. Design/methodology/approach – This paper uses an interpretive structural modeling (ISM) methodology to analyze the interactions among the barriers. Findings – It is beneficial for the management of any firm to be aware of significant barriers and to diagnose those that could be integral to the organizations future survival. Many works have focused on identifying barriers for TPL implementation, but a model for such barriers is lacking. This paper attempts to develop a model for the barriers using an ISM methodology and analyzes the mutual interactions among the barriers. The model differentiates between the barriers so that driving barriers, which can intensify other barriers, and dependent barriers are identified separately. Originality/value – In this research, eight barriers are considered. Interactions between...

Network Coding Techniques for Wireless and Sensor Networks

Network coding is a technique where relay nodes mix packets using mathematical operations, which can increase the throughput. Network coding was first proposed for wired networks to solve the bottleneck in a single multicast session problem and to increase the throughput. However, the broadcast nature of wireless networks and the diversity of the links make network coding more attractive in wireless networks. Network coding can be classified as either inter or intra-session. Inter-session network coding allows the packets from different sessions (sources) to be mixed to increase the throughput. In contrast, intra-session network coding, which can be used to address the packet loss problem, uses the diversity of the wireless links and mixes packets from the same sessions. In this chapter, we survey the recent works on network coding in both general wireless networks and wireless sensor networks. We present various network coding techniques, their assumptions, applications, as well as an overview of the proposed methods.

Distributed network coding-based opportunistic routing for multicast

In this paper, we tackle the network coding-based opportunistic routing problem for multicast. We present the factors that affect the performance of the multicast protocols. Then, we formulate the problem as an optimization problem. Using the duality approach, we show that a distributed solution can be used to achieve the optimal solution. The distributed solution consists of two phases. In the first phase, the most reliable broadcasting tree is formed based on the ETX metric. In the second phase, a credit assignment algorithm is run at each node to determine the number of coded packets that the node has to send. The distributed algorithm adapts to the changes in the channel conditions and does not require explicit knowledge of the properties of the network. To reduce the number of feedback messages, and to resolve the problem of delayed feedback, we also perform network coding on the feedback messages. We evaluate our algorithm using simulations which show that in some realistic cases the throughput achieved by our algorithm can be double or triple that of the state-of-the-art.

An Indoor Hybrid WiFi-VLC Internet Access System

Visible light communications (VLC) is emerging as a new alternative to the use of the existing and increasingly crowded radio frequency (RF) spectrum. VLC is unlicensed, has wide bandwidth, supports new levels of security due to the opacity of walls, and can be combined to provide both lighting and data communications for little net increase in energy cost. As part of a lighting system, VLC is ideal as a downlink technology in which data are delivered from overhead luminaries to receivers in the lighting field. However, realizing a symmetric optical channel is problematic because most receivers, such as mobile devices, are ill-suited for an optical uplink due to glare, device orientation, energy constraints. In this paper we propose and implement a hybrid solution in which the uplink challenge is resolved by the use of an asymmetric RF-VLC combination. VLC is used as a downlink, RF is used as an uplink, and the hybrid solution realizes full duplex communication without performance glare or throughput degradation expected in an all-VLC-based approach. Our proposed approach utilizes a software defined VLC platform (SDVLC) to implement the unidirectional optical wireless channel and a WiFi link as the back-channel. Experiments with the implemented prototype reveal that the integrated system outperforms conventional WiFi for crowded (congested) multiuser environments in term of throughput, and demonstrate functional access to full-duplex interactive applications such as web browsing with HTTP.

Optimization Based Rate Control for Communication Networks with Inter-Session Network Coding

In this paper we develop a distributed rate control algorithm for multiple-unicast-sessions when network coding is allowed. Building on our recent flow-based characterization of network coding, we formulate the problem as a convex optimization problem. The formulation exploits pairwise coding possibilities between any pair of sessions, where the objective function is the sum of the utilities based on the rates supported by each session. With some manipulation on the Lagrangian of the formulated problem, a distributed algorithm is developed with no interaction between intermediate nodes, and each source having the freedom to choose its own utility function. The only information required by the source is the weighted sum of the queue length updates of each link, which can be piggy-backed on the acknowledgment messages. In addition to the optimal rate control algorithm, we propose a decentralized pairwise random coding scheme (PRC) that is optimal when a sufficiently large finite field is used for network coding. The convergence of the rate control algorithm is proved analytically and verified by extensive simulations. Simulations also demonstrate the advantage of our algorithm over the state-of-the-art in terms of throughput and fairness.