Abdallah Shami

Dynamic Wavelength and Bandwidth Allocation in Hybrid TDM/WDM EPON Networks

We discuss a wavelength-division-multiplexed-based passive-optical-network (PON) architecture that allows for incremental upgrade from single-channel time-division multiple-access PONs in order to provide higher bandwidth in the access network. Various dynamic-wavelength and bandwidth-allocation algorithms (DWBAs) for wave-division multiplexed PON are presented; they exploit both interchannel and intrachannel statistical multiplexing in order to achieve better performance, especially when the load on various channels is not symmetric. Three variants of the DWBA are presented, and their performance is compared. While the first variant incurs larger idle times (and, hence, poor performance), the other two algorithms achieve better but different performance with critical dissimilarities. Our analysis also focuses on the fair assignment of excessive bandwidth in the upstream direction to highly loaded optical network units. We compare the performance of DWBA to another algorithm that relies on static-channel allocation. Furthermore, a study is presented wherein the number of wavelengths increases, and a comparison with interleaved polling with adaptive cycle time is shown. We use extensive simulations throughout this paper

NFV: state of the art, challenges, and implementation in next generation mobile networks (vEPC)

As mobile network users look forward to the connectivity speeds of 5G networks, service providers are facing challenges in complying with connectivity demands without substantial financial investments. Network function virtualization (NFV) is introduced as a new methodology that offers a way out of this bottleneck. NFV is poised to change the core structure of telecommunications infrastructure to be more cost-efficient. In this article, we introduce an NFV framework, and discuss the challenges and requirements of its use in mobile networks. In particular, an NFV framework in the virtual environment is proposed. Moreover, in order to reduce signaling traffic and achieve better performance, this article proposes a criterion to bundle multiple functions of a virtualized evolved packet core in a single physical device or a group of adjacent devices. The analysis shows that the proposed grouping can reduce the network control traffic by 70 percent.

Software defined networking: State of the art and research challenges

Network usage and demands are growing at a rapid pace, while the network administrators are facing difficulties in tracking the frequent users’ access of the network. Consequently, managing the infrastructure supporting these demands has become a complicated and time-consuming task. Networks are also in a flux state, they are not only expanding but require reconfigurations to meet the business needs. Software defined networking (SDN) and network function virtualization (NFV) technologies have emerged as promising solutions that change the cost profile and agility of internet protocol (IP) networks. Conceptually, SDN separates the network control logic from its underlying hardware, enabling network administrators to exert more control over network functioning and providing a unified global view of the network. However, SDN and NFV can be merged and have the potential to mitigate the challenges of legacy networks. In this paper, our aim is to describe the benefits of using SDN in a multitude of environments such as in data centers, data center networks, and Network as Service offerings. We also present the various challenges facing SDN, from scalability to reliability and security concerns, and discuss existing solutions to these challenges.

Jitter performance in ethernet passive optical networks

Ethernet passive optical networks (EPONs) have emerged as one of the most promising access network technologies. Propelled by rapid price declines in fiber optics and Ethernet components, these architectures combine the latest in optical and electronic advances and are poised to become the dominant means of delivering gigabit broadband connectivity to homes over a unified single platform. As this technology matures, related quality of service (QoS) issues are becoming a key concern. This paper proposes a novel dynamic scheduling algorithm, termed hybrid granting protocol (HGP), to support different QoS in EPON. Specifically, the proposed dynamic scheduling algorithm minimizes packet delay and jitter for delay and delay-variation sensitive traffic (e.g., voice transmissions) by allocating bandwidth in a grant-before-report (GBR) fashion. This considerably improves their performance without degrading QoS guarantees for other service types. Detailed simulation experiments are presented to validate the effectiveness of the proposed algorithm.

On the fairness of dynamic bandwidth allocation schemes in Ethernet passive optical networks

Ethernet passive optical networks (EPONs) technology has emerged as a promising candidate for next-generation broadband access networks. As this technology evolves, the development of efficient dynamic bandwidth allocation (DBA) algorithms has become a key concern. This paper devises and presents the principle and implementation issues of a new robust DBA scheme. This proposed scheme consistently maintains a robust fairness mechanism in the DBA operation. With the better maintained fairness mechanism, network performance is improved; specifically average packet delay and upstream link utilization, as well as inter-ONU statistical bandwidth multiplexing. Detailed simulation experiments are presented to study the performance and to validate the effectiveness of the proposed algorithm.

Resource allocation in a network-based cloud computing environment: design challenges

Cloud computing is a utility computing paradigm that has become a solid base for a wide array of enterprise and end-user applications. Providers offer varying service portfolios that differ in resource configurations and provided services. A comprehensive solution for resource allocation is fundamental to any cloud computing service provider. Any resource allocation model has to consider computational resources as well as network resources to accurately reflect practical demands. Another aspect that should be considered while provisioning resources is energy consumption. This aspect is getting more attention from industrial and government parties. Calls for the support of green clouds are gaining momentum. With that in mind, resource allocation algorithms aim to accomplish the task of scheduling virtual machines on the servers residing in data centers and consequently scheduling network resources while complying with the problem constraints. Several external and internal factors that affect the performance of resource allocation models are introduced in this article. These factors are discussed in detail, and research gaps are pointed out. Design challenges are discussed with the aim of providing a reference to be used when designing a comprehensive energy-aware resource allocation model for cloud computing data centers.

Intra-ONU bandwidth scheduling in Ethernet passive optical networks

Quality-of-service (QoS) support in Ethernet passive optical networks (EPON) is a crucial concern. However, most studies have only focused on optical line terminal (OLT) capacity allocation amongst multiple optical network units (ONU), and the further issue of intra-ONU allocation remains open. In this work a novel decentralized intra-ONU solution is presented using virtual-time schedulers. Results confirm good performance for a wide range of input traffic classes and loads.

Energy-Aware Resource Allocation Strategies for LTE Uplink with Synchronous HARQ Constraints

In this paper, we propose a framework for energy efficient resource allocation in multiuser localized SC-FDMA with synchronous HARQ constraints. Resource allocation is formulated as a two-stage problem where resources are allocated in both time and frequency. The impact of retransmissions on the time-frequency problem segmentation is handled through the use of a novel block scheduling interval specifically designed for synchronous HARQ to ensure uplink users do not experience ARQ blocking. Using this framework, we formulate the optimal margin adaptive allocation problem, and based on its structure, we propose two suboptimal approaches to minimize average power allocation required for resource allocation while attempting to reduce complexity. Results are presented for computational complexity and average power allocation relative to system complexity and data rate, and comparisons are made between the proposed optimal and suboptimal approaches.

Evaluation of communication technologies for IEC 61850 based distribution automation system with distributed energy resources

This paper presents the study of different communication systems between IEC 61850 based distribution substation and distributed energy resources (DERs). Communication networks have been simulated for a typical distribution automation system (DAS) with DERs using OPNET software. The simulation study shows the performance of wired and wireless communication systems for different messages, such as GOOSE and measured (metered) values between DAS and DERs. A laboratory set-up has been implemented using commercial relay and communication devices for evaluating the performance of GOOSE messages, using wired and wireless physical medium. Finally, simulation and laboratory results are discussed in detail.

A Comprehensive Investigation of Wireless LAN for IEC 61850–Based Smart Distribution Substation Applications

Todays power grid is facing many challenges due to increasing load growth, aging of existing power infrastructures, high penetration of renewable, and lack of fast monitoring and control. Utilizing recent developments in Information and Communication Technologies (ICT) at the power-distribution level, various smart-grid applications can be realized to achieve reliable, efficient, and green power. Interoperable exchange of information is already standardized in the globally accepted smart-grid standard, IEC 61850, over the local area networks (LANs). Due to low installation cost, sufficient data rates, and ease of deployment, the industrial wireless LAN technologies are gaining interest among power utilities, especially for less critical smart distribution network applications. Extensive work is carried out to examine the wireless LAN (WLAN) technology within a power distribution substation. The first phase of the work is initiated with the radio noise interference measurements at 27.6- and 13.8-kV distribution substations, including circuit breaker switching operations. For a detailed investigation, the hardware prototypes of WLAN-enabled IEC 61850 devices are developed using industrial embedded systems, and the performance of smart distribution substation monitoring, control, and protection applications is analyzed for various scenarios using a round trip-time of IEC 61850 application messages. Finally, to examine the real-world field performance, the developed prototype devices are installed in the switchyard and control room of 27.6 power distribution substation, and testing results of various applications are discussed.