Gary W. Atkinson

Power Trends in Communication Networks

Power trends in communication networks are analyzed using a transaction-based model. Traffic models are developed for North America and used to evaluate the relative power trends of wireline networks and mobile networks through 2020. An ideal case for aggressive network-efficiency improvement measures is evaluated within this framework and shown to lead to roughly unchanged consumption over the next decade. Implications for future technology requirements are discussed.

In-network caching effect on optimal energy consumption in content-centric networking

In content-centric networking (CCN), the in-network caching feature provides several attractive advantages such as low dissemination latency and network transport load reduction. Thus, CCN requires less transport energy but additional energy to provide a caching capability at every content router. In this paper, we investigate the minimum energy consumption that CCN can achieve with optimal cache locations by considering different caching hardware technologies, number of downloads per hour, and content popularity. We first set up an energy consumption model for CCN and then formulate linear and nonlinear programming problems to minimize total energy consumption of CCN. Also, a genetic algorithm (GA) approach is proposed to find energy-efficient cache locations. Using reported energy efficiency of computational hardware and network equipment, we show CCN yield greater energy savings for very popular content and small-sized catalog, compared to conventional CDN. Our results also indicate that two aspects of the memory technology, energy-proportional caching and sufficient memory capacity, are critical to the overall energy efficiency gain of CCN.

SeDAX: A Scalable, Resilient, and Secure Platform for Smart Grid Communications

Smart Grid applications are imposing challenging requirements of security and reliability on the N-way communication infrastructure being designed to support multiple grid applications. These challenges stem from the increasing incorporation of distributed renewable energy sources on to the grid, the rising deployment of electric vehicles, and active consumer participation into power grid operations, all of which communicate with the utility control center with varying degrees of priority and security. To address these challenging requirements, we propose SeDAX, a SEcure Data-centric Application eXtensible platform for Smart Grid applications. SeDAX implements scalable, resilient and secure data delivery and data sharing in a wide area network. The platform can scalably handle high volumes of data generated by both applications and sensors. The SeDAX architecture has as its basis a Delaunay Triangulation (DT) network. The properties of the DT graph are leveraged to scalably support secure data-centric (or information-centric) group communication. The primary goals of this platform are to support communication resilience and data availability. The key functional blocks of the SeDAX platform are: (1) a geographic hash forwarding algorithm that operates over the DT graph (DT-GHF), and (2) a DT-based data replication scheme. The forwarding and replication schemes are scalable and cost effective in terms of communication overhead and memory. We describe the design details of the SeDAX platform and present empirical results on the performance of SeDAX as compared with other geometric-based alternatives such as Geographic Hash Table (GHT) forwarding and Content Addressable Networking (CAN). The operation of SeDAX is illustrated in the context of implementing demand response, a known Smart Grid application.

Evaluating the energy benefit of dynamic optical bypass for content delivery

We evaluate the energy efficiency of dynamic optical bypass for decentralized content delivery networks (CDNs). We build energy models based on the energy consumption of current network equipment and devices and analyze the energy tradeoff among key networking resources. Our results show that, due to the under-utilization associated with signaling and reconfiguration overhead, a CDN with dynamic optical bypass achieves the largest savings in delivering very large files (100 Gb (gigabit) and above) with high download rate (a few hundred downloads per hour). We also derive a threshold for a file size, which is approximately the bandwidth-overhead product scaled by the ratio between the power density of WDM equipment and routers: CλT°pwdmd/pr1d. We show that, only for the delivery of content of sizes larger than this size threshold, a CDN with dynamic optical bypass is more energy efficient than CDN without bypass.

Cost effectiveness of joint multilayer protection in packet-over-optical networks

The recent advances in generalized multiprotocol label switching/multiprotocol label switching (GMPLS/MPLS) and extensive study and understanding of packet-over-optical network architecture have made it possible to manage the resources of the packet network and underlying optical transport network in an interoperable manner. This opens up the possibility for coordinated actions across the two networking layers. In this context, we propose and evaluate a novel joint protection scheme for future packet-over-optical networks. There are two aspects that make the proposed joint scheme novel and, furthermore, cost effective: 1) It captures the best tradeoff between the finer grooming granularity of the packet layer and the cheaper port cost of the optical layer, and 2) it reuses network resources from both the primary paths and paths that exist for link failure protection by the optical layer. To examine the proposed approach, a mixed-integer optimization model was developed. In particular, we observe that overlaying joint packet-optical router protection with transport-layer link protection permits strong synergy of protection capacity reuse. Indeed, our case studies show that the proposed joint packet-optical router protection is low- or no-cost when it is overlaid on an existing transport-layer protection scheme.

Persistent channel power deviations in constant gain amplified long-chain ROADM networks

Numerical simulations of the evolution of the channel power response to power adjustments in constant gain amplified degree-2 ROADM networks demonstrate novel persistent and periodic distant-dependent power deviation patterns.

GridDataBus: Information-centric platform for scalable secure resilient phasor-data sharing

The advent of new Smart Grid applications such as electric vehicles and renewable energy sources are imposing challenging requirements on the stability and operation of the grid. This challenge is critical in the areas of supply-demand balance and power quality assurance. To address this challenge, phasor measurement units (PMUs) are being deployed to monitor grid operations. A major impediment to the widespread use of this PMU technology is a lack of secure, scalable, and resilient data sharing infrastructure. Applying information-centric networking concepts we have designed GridDataBus (GDB), a secure data sharing bus. Through evaluation, we show the scalability and performance of GDB in terms of data access latency.

Optical transparency and network energy efficiency

Communication networks have been identified as an important enabling technology for realizing dramatic reductions in energy consumption across many sectors of our society, including electric power delivery (smart grids), transportation (tele-presence and traffic management), and building controls. Recent reports indicate that by 2020 information and communication technologies could offset their own carbon footprint by five-fold through savings realized in other areas [1]. This benefit presupposes the sustainable growth of communication networks, even as the Internet continues to expand exponentially. Historically optical networks have benefited from exponential increases in transmission capacity and interface speeds. However, recent studies have demonstrated that spectral efficiencies of optical transmission systems are approaching channel capacity limits [2], indicating that efficiency improvements through bandwidth increase may be limited. This brings focus to network energy efficiency, measured as the power of the network equipment per unit bandwidth delivered to the user, as an important dimension for continued efficiency improvements. Optical transparency enables efficient use of network resources through optimized wavelength routing and switching. Some of this translates directly into reduced electronic processing and consequently reduced energy consumption. Nevertheless, there are further opportunities for power reductions including re-use of stranded resources through reconfiguration, dynamically varying capacity to follow traffic fluctuations over time, and changing network configuration to take maximum advantage of available renewable energy resources. In this work we build transaction-based network models [3] to examine the relative benefit and potential opportunities for improving overall network energy efficiency. These models include projected traffic growth through 2020 for different network services. The relative impact of optical technology efficiency measures is included to understand benefits to the overall network efficiency.

A min-max theorem for plane bipartite graphs

We consider a partitioning problem, defined for bipartite and 2-connected plane graphs, where each node should be covered exactly once by either an edge or by a cycle surrounding a face. The objective is to maximize the number of face boundaries in the partition. This problem arises in mathematical chemistry in the computation of the Clar number of hexagonal systems. In this paper we establish that a certain minimum weight covering problem of faces by cuts is a strong dual of the partitioning problem. Our proof relies on network flow and linear programming duality arguments, and settles a conjecture formulated by Hansen and Zheng in the context of hexagonal systems [P. Hansen, M. Zheng, Upper Bounds for the Clar Number of Benzenoid Hydrocarbons, Journal of the Chemical Society, Faraday Transactions 88 (1992) 1621-1625].

Cross-Layer Aware Software Defined Networking in an IP Over Optical Transport Network

We demonstrate possible applications for software-defined networking in a transport network using carrier-grade routers and optical transmission equipment. The cross-layer applications dynamically respond to traffic conditions and optical impairments