Luca Valcarenghi

Sleep Mode for Energy Saving PONs: Advantages and Drawbacks

A common approach to reduce energy consumption in communication networks is to allow network elements to switch to sleep mode. While this technique has been widely utilized in wireless networks, recent studies have proposed to exploit sleep mode in wired networks to conserve energy as well. This paper focuses on some feasible implementations of sleep mode in passive optical networks (PONs). In particular, ONU sleep mode is considered. The paper first outlines the ONU wake-up process using current time division multiplexing (TDM) PON protocols. Current and novel optical network unit (ONU) architectures that selectively switch-off some elements are then described. Their advantages in terms of energy savings are analytically computed under different traffic scenarios. Using the proposed architectures, analytical results show more than 50% energy saving under realistic TDM traffic. Finally, possible drawbacks in terms of new scheduling challenges are also discussed and potential solutions are presented.

Challenges and requirements for introducing impairment-awareness into the management and control planes of ASON/GMPLS WDM networks

The absence of electrical regenerators in transparent WDM networks significantly contributes to reduce the overall network cost. In transparent WDM networks, a proper resource allocation requires that the presence of physical impairments in routing and wavelength assignment (RWA) and lightpath provisioning be taken into account. In this article a centralized, a hybrid centralized-distributed and two distributed approaches that integrate information about most relevant physical impairments in RWA and lightpath provisioning are presented and assessed. Both centralized and hybrid approaches perform a centralized path computation at the management-plane level, utilizing physical impairment information, while the lightpath provisioning is done by the management plane or the control plane, respectively. The distributed approaches fall entirely within the scope of the ASON/GMPLS control plane. For these two approaches, we provide functional requirements, architectural functional blocks, and protocol extensions for implementing either an impairment-aware real-time RWA, or a lightpath provisioning based on impairment-aware signaling.

Energy efficiency in passive optical networks: where, when, and how?

This article provides an overview of current efforts in reducing energy consumption in passive optical access networks. Both ITU-T and IEEE standardized PONs are considered. The current solutions proposed by standardization authorities, industry, and academia are classified based on the layer they address in the standardized architectures: physical layer, data link layer, and hybrid. Then, the article provides answers to major questions, such as where, when, and how to reduce PON energy consumption in TDM PONs by means of a quantitative evaluation. Results show that to reduce energy consumption, ONUs must be provided with physical devices that are not only power-efficient but also provide improved services (e.g., fast synchronization) to upper layers. For this latter purpose, novel physical ONU architectures are proposed to speed up the synchronization process and enable effective data link layer solutions. Finally, the feasibility of switching ONUs to low power mode in idle slots is assessed through a testbed implementation.

Enhancing GMPLS Signaling Protocol for Encompassing Quality of Transmission (QoT) in All-Optical Networks

In this paper, quality of transmission (QoT)-aware lightpath provisioning schemes for transparent optical networks are proposed and assessed. The main idea is to overcome lightpath blocking due to excessive physical impairments (i.e., unacceptable QoT) by means of successive lightpath set up attempts performed by generalized multiprotocol label switching (GMPLS) signaling protocol along alternate routes. The schemes are enabled by the introduction into current GMPLS signaling protocol [i.e., resource reservation protocol with traffic engineering (RSVP-TE)] of extensions which encompass the QoT parameters that characterize the optical layer. Differently from previous approaches, the proposed GMPLS-based schemes are still distributed but they do not imply the introduction of additional extensions into the routing protocol (e.g., OSPF-TE). The QoT-aware provisioning schemes are first validated by simulations performed on a WDM mesh network. Results show that only few successive set up attempts are required to complete the lightpath establishment. In addition, an experimental demonstration where the proposed RSVP-TE extensions are implemented in the control plane of a transparent metro network is reported showing that impairment-aware lightpath provisioning is achieved on a time scale of few milliseconds.

Centralized vs. distributed approaches for encompassing physical impairments in transparent optical networks

Transparent optical mesh networks are an appealing solution to provide cost-effective high bandwidth connections eliminating the need of expensive intermediate electronic regenerators. However, the implementation of transparent optical networks requires to take into account physical impairment information for effective lightpath set-up. In this paper, we present two distributed solutions to encompass physical impairments based on enhancements of the GMPLS protocol suite. Specifically, both GMPLS routing protocol and signaling protocol extensions are presented and discussed. An alternative centralized approach based on an impairment-aware Path Computation Element (PCE) is also proposed. The distributed routing approach exhibits convergence limitations, while the distributed signaling approach is scalable and effective. The latter is then compared against the centralized PCE approach through simulations considering both a metro network and a more complex WDM network scenario. In addition, experimental implementations of the two approaches are presented. Results show the trade-off of the two approaches, demonstrating the general good performance in terms of lightpath set up time for both approaches.

Implementing a Path Computation Element (PCE) to encompass physical impairments in transparent networks

A PCE implementation is presented and evaluated in single-area, multi-area, and multi-layer networks. The proposed implementation provides not only efficient bandwidth utilization with good scalability performance but it allows also to encompass physical impairment constraints.

Challenges for 5G transport networks

5G mobile communications is seen as the enabler for the networked society where connectivity will be available anywhere and anytime to anyone and anything. The details of 5G are the subject to ongoing research and debate, mostly focused on understanding radio technologies that can enable the 5G vision. So far, less work has been dedicated to the challenges that 5G will pose to the transport network. This paper provides a first analysis of the key challenges to 5G transport in terms of capacity, flexibility and costs, for example. Different use cases are discussed as well as technology options and control plane concepts.

GMPLS-controlled dynamic translucent optical networks

The evolution of optical technologies has paved the way to the migration from opaque optical networks (i.e., networks in which the optical signal is electronically regenerated at each node) to transparent (i.e., all-optical) networks. Translucent optical networks (i.e., optical networks with sparse opto-electronic regeneration) enable the exploitation of the benefits of both opaque and transparent networks while providing a suitable solution for dynamic connections. Translucent optical networks with dynamic connections can be controlled by the GMPLS protocol suite. This article discusses the enhancements that the GMPLS suite requires for the control of dynamic translucent optical networks with quality of transmission guarantees. Such enhancements concern QoT-awareness and regenerator-awareness and can be achieved by collecting and disseminating the information on QoT and regenerator availability, respectively, and by efficiently leveraging such information for traffic engineering purposes. More specifically, the article proposes two distributed approaches, based on the routing protocol and the signaling protocol, for disseminating regenerator information in the GMPLS control plane. Moreover, three strategies are introduced to efficiently and dynamically designate the regeneration node(s) along the connection route. Routing and signaling approaches are compared in terms of blocking probability, setup time, and control plane load during provisioning and restoration.

An advanced smart management system for electric vehicle recharge

Recent studies about climate change are mandating a drastic reduction of green house gas (GHG) emissions. Solutions include the utilization of renewable energy sources (e.g., wind, solar energy) and the increased utilization of hybrid and electric vehicles (EVs). In this scenario ICT can play a significant role by fostering the smart utilization of current energy and transportation infrastructures (smart grid and smart cities). This paper presents a new ICT infrastructure to enable the intelligent exploitation of distributed energy resources in order to minimize the EV charging times while optimizing the efficiency of the electrical infrastructure. The proposed system is based on a distributed communication infrastructure (both wired and wireless) aimed at collecting/emitting bidirectional energy dispatching opportunities for electric vehicles. The envisaged system seamlessly interconnects emerging self-organizing wireless technologies (i.e., VANETs and Wireless Mesh Networks), with legacy wired communication technologies, to guarantee a fast rollout of the EV charging service with minimum investments in communication infrastructures. The performance of the proposed solution is evaluated in terms of its sustainability by analyzing the quality of the charging service as perceived by the users, and the capability of the charging infrastructure to meet the charging requests in a timely manner.

Label preference schemes in GMPLS controlled networks

The GMPLS assumption that all available labels are equal is reasonable in electronic networks but not always true in WDM optical networks where labels correspond to physical wavelengths. In this paper we present two schemes for collecting the preference for specific labels during GMPLS signaling. For this purpose a new use of the Suggested Label object is proposed, and a novel object called Suggested Vector is introduced. The approach is validated through simulations showing significant wavelength converter usage reduction in a WDM optical network