There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Computer communications

This paper reviews advanced optical burst switching (OBS) and optical packet switching (OPS) technologies and discusses their roles in the future photonic Internet. Discussions include optoelectronic and optical systems technologies as well as systems integration into viable network elements (OBS and OPS routers). Optical label switching (OLS) offers a unified multiple-service platform with effective and agile utilization of the available optical bandwidth in support of voice, data, and multimedia services on the Internet Protocol. In particular, OLS routers with wavelength routing switching fabrics and parallel optical labeling allow forwarding of asynchronously arriving variable-length packets, bursts, and circuits. By exploiting contention resolution in wavelength, time, and space domains, the OLS routers can achieve high throughput without resorting to a store-and-forward method associated with large buffer requirements. Testbed demonstrations employing OLS edge routers show high-performance networking in support of multimedia and data communications applications over the photonic Internet with optical packets and bursts switched directly at the optical layer

Optical Packet and Burst Switching Technologies for the Future Photonic Internet

Cognitive radio (CR) has emerged as a promising technology to exploit the unused portions of spectrum in an opportunistic manner. The fixed spectrum allocation of governmental agencies results in unused portions of spectrum, which are called "spectrum holes" or "white spaces". CR technology overcomes this issue, allowing devices to sense the spectrum for unused portions and use the most suitable ones, according to some pre-defined criteria. Spectrum assignment is a key mechanism that limits the interference between CR devices and licensed users, enabling a more efficient usage of the wireless spectrum. Interference is a key factor that limits the performance in wireless networks. The scope of this work is to give an overview of the problem of spectrum assignment in cognitive radio networks, presenting the state-of-the-art proposals that have appeared in the literature, analyzing the criteria for selecting the most suitable portion of the spectrum and showing the most common approaches and techniques used to solve the spectrum assignment problem. Finally, an analysis of the techniques and approaches is presented, discussing also the open issues for future research in this area.

Spectrum Assignment in Cognitive Radio Networks: A Comprehensive Survey

Enhancing Adult Motivation to Learn

Three-phase time-aware energy minimization with DVFS and unrolling for Chip Multiprocessors

In this paper, we present a new online algorithm for dynamically routing bandwidth guaranteed label switched paths (LSPs). LSP set-up requests are represented in terms of a pair of ingress and egress routers as well as its bandwidth requirement, and arrive one by one. There is no a priori knowledge regarding future LSP set-up requests and their characteristics. Our proposed algorithm considers not only the importance of critical links, but also the degree of their importance to routing possible future LSP set-up requests by characterizing their normalized bandwidth contribution to routing future LSP demands. Moreover, link residual bandwidth information, i.e., the link's capability of routing future LSPs, is also incorporated. Simulation results show that our proposed algorithm performs better than the best known bandwidth guaranteed routing algorithm, the minimum interference routing algorithm, in terms of LSP rejection rate under both static and dynamic LSP set-up request arrivals.

http://suraj.lums.edu.pk/~te/cspf/cspf27.pdf

A new bandwidth guaranteed routing algorithm for MPLS traffic engineering

In this paper, we propose a general scheduled traffic model, sliding scheduled traffic model. In this model, the setup time t/sub s/ of a demand whose holding time is T time units is not known in advance. Rather t/sub s/ is allowed to begin in a pre-specified time window [l,T] subject to the constraint that l/spl les/t/sub s//spl les/r-T. We then consider two problems: (1) how to properly place a demand within its associated time window to reduce overlapping in time among a set of demands; and (2) route and assign wavelengths (RWA) to a set of demands under the proposed sliding scheduled traffic model in mesh reconfigurable WDM optical networks without wavelength conversion. In addition, we consider how to rearrange a demand by negotiating a new setup time that minimizes the demand schedule change in case that the demand is blocked. To maximize temporal resource reuse, we propose a demand time conflict reduction algorithm to solve the first problem. Two algorithms, window based RWA algorithm and traffic matrix based RWA algorithm, are then proposed for the second problem. We compare the proposed RWA algorithms against a customized tabu search scheme. Simulation results show that the proposed demand time conflict reduction algorithm can resolve well over 50% of time conflicts and the space-time RWA algorithms are effective in satisfying demand requirements and minimizing total network resources used, d.

On service provisioning under a scheduled traffic model in reconfigurable WDM optical networks

Bandwidth degradation QoS provisioning for adaptive multimedia in wireless/mobile networks

We consider the grooming of multicast traffic in WDM optical mesh networks with sparse nodal light splitting capability. Given multicast routing trees for individual multicast sessions, the multicast traffic grooming problem is NP-hard. Moreover, constructing an optimal multicast routing tree in WDM optical mesh networks is also an NP-hard problem. We formulate the problem of multicast traffic grooming in WDM optical mesh networks as an integer linear program. We propose a heuristic algorithm for constructing multicast routing trees and a first-fit algorithm for traffic grooming, assuming wavelength conversion capability in the network nodes. By intelligently grooming several multicast sessions with fractional wavelength bandwidth requirements onto a single wavelength, we demonstrate that our algorithms achieve a significant reduction in the maximum number of wavelengths required in a link as well as in the total number of wavelength links needed.

Bin Wang

Papers

Three-phase time-aware energy minimization with DVFS and unrolling for Chip Multiprocessors

A new bandwidth guaranteed routing algorithm for MPLS traffic engineering

On service provisioning under a scheduled traffic model in reconfigurable WDM optical networks

Bandwidth degradation QoS provisioning for adaptive multimedia in wireless/mobile networks

Multicast traffic grooming in WDM optical mesh networks