Josep Solé Pareta

A survey on physical layer impairments aware routing and wavelength assignment algorithms in optical networks

Optical networks are moving from opaque and translucent architectures towards all-optical (transparent) architectures. In translucent architectures a small amount of regeneration (e.g. optical-electronic-optical conversion) is available in the network. The incorporation of the physical impairments in the routing and wavelength assignment (RWA) problem in transparent optical networks has recently received some attention from the research communities. This work compiles a comprehensive survey of the proposed algorithms that address this issue. The physical layer impairments and related classification in optical networks are initially presented followed by physical layer impairments (PLI) constrained and aware RWA algorithms. Algorithmic approach, current PLI-RWA proposals, impact of wavelength conversion on these algorithms, protection and resilience considerations, and proposed extensions to control planes are covered in this work. Further research topics are presented in this study.

PHLAME: A Physical Layer Aware MAC protocol for Electromagnetic nanonetworks in the Terahertz Band

Nanotechnology is enabling the development of integrated devices just a few hundred nanometers in size. Communication among these nano-devices will boost the applications of nanotechnology in the biomedical, environmental and military fields. Within the communication alternatives at the nanoscale, the state of the art in nanomaterial research points to the Terahertz band (0.1–10 THz) as the frequency range of operation of graphene-based electromagnetic (EM) nano-transceivers. This frequency band supports very large transmission bit-rates and enables simple communication mechanisms suited to the limited capabilities of nano-devices. Due to an expectedly very large number of nano-devices sharing the same channel, it is necessary to develop new Medium Access Control (MAC) protocols which will be able to capture the peculiarities of nanonetworks in the Terahertz band. In this paper, PHLAME, a physical layer aware MAC protocol for electromagnetic nanonetworks, is introduced. This protocol is built on top of a novel communication scheme based on the exchange of femtosecond-long pulses spread in time, and exploits the benefits of novel low-weight channel coding schemes. In the PHLAME protocol, the transmitting and receiving nano-devices jointly select the communication parameters that minimize the interference in the nanonetwork and maximize the probability of successfully decoding the received information. The performance of the protocol is analyzed in terms of energy consumption, delay and achievable throughput, by taking also into account the energy limitations of nano-devices. The results show that, despite its simplicity, the PHLAME protocol is able to support densely populated nanonetworks by exploiting the peculiarities of the Terahertz band.

PHLAME: A physical layer aware MAC protocol for electromagnetic nanonetworks

Nanotechnology is enabling the development of integrated devices just a few hundred nanometers in size. Communication among these nano-devices will boost the applications of nanotechnology in the biomedical, environmental and military fields. Within the communication alternatives at the nanoscale, the state of the art in nanomaterial research points to the Terahertz band (0.1–10 THz) as the frequency range of operation of graphene-based electromagnetic (EM) nano-transceivers. This frequency band supports very large transmission bit-rates and enables simple communication mechanisms suited to the limited capabilities of nano-devices. Due to an expectedly very large number of nano-devices sharing the same channel, it is necessary to develop new Medium Access Control (MAC) protocols which will be able to capture the peculiarities of nanonetworks in the Terahertz band. In this paper, PHLAME, a physical layer aware MAC protocol for electromagnetic nanonetworks, is introduced. This protocol is built on top of a novel communication scheme based on the exchange of femtosecond-long pulses spread in time, and exploits the benefits of novel low-weight channel coding schemes. In the PHLAME protocol, the transmitting and receiving nano-devices jointly select the communication parameters that minimize the interference in the nanonetwork and maximize the probability of successfully decoding the received information. The performance of the protocol is analyzed in terms of energy consumption, delay and achievable throughput, by taking also into account the energy limitations of nano-devices. The results show that, despite its simplicity, the PHLAME protocol is able to support densely populated nanonetworks by exploiting the peculiarities of the Terahertz band.

An offline impairment aware RWA algorithm with dedicated path protection consideration

We present excellent performance results for a novel offline physical layer impairment aware routing and wavelength assignment algorithm for various transparent all-optical networks, while considering dedicated path protection.

Optical slot size dimensioning in IP/MPLS over OPS networks

Current optical technology allows an easy implementation of synchronous, time-slotted optical networks. In contrast, traffic in electrical domain (for instance IP) mainly consists of asynchronous, variable length packets. Therefore a packet format adaptation process is needed between electrical and optical domains, the optical slot size being in this process a crucial parameter, which strongly influences the bandwidth utilisation and determines the overall network performance. In this paper we address the problem of designing this adaptation layer and of dimensioning the optical slot size in IP/MPLS over optical packet switched networks. Three different optical packet formats, namely fixed-length packet, slotted variable-length packet, and fixed-length packet with traffic aggregation are discussed. To find the optimum size, the efficiency of such formats are evaluated by simulations.

Modelling and Performance Evaluation of a Translucent OBS Network Architecture

Most research works in optical burst switching (OBS) networks do not take into account the impact of physical layer impairments (PLIs) either by considering fully transparent (i.e., using optical 3R regeneration) or opaque (i.e., electrical 3R regeneration) networks. However, both solutions are not feasible for different reasons. In this paper, we propose a novel translucent OBS network architecture which aims at bridging the gap between the transparent and opaque solutions. In order to evaluate its performance, two different joint regenerator placement and routing heuristics are provided. Simulation results show that our translucent network model achieves performance results as good as those obtained with an opaque solution but with considerably less regenerators.

Self-organized server farms for energy savings

Server farms are an increasingly important source of energy consumption, and ICT services will be deeply impacted by architectures allowing significant power savings. Self-supervision and self-adaptability are key requirements for future network and service platform. This paper describes some algorithms, based on a self-organization approach, for energy savings in server farms.

Novel contention resolution technique for QoS support in connection-oriented optical packet switching

This paper considers an optical packet-switched node with limited buffer capabilities and subject to asynchronous, variable-length packets and connection-oriented operation. In such a scenario, we address the problem of providing QoS. While existing solutions focus on applying some form of resources reservation on top of the contention resolution algorithm, here we propose a novel method: given a set of K categories of service to be provided in the network, K different contention resolution algorithms are implemented to cope with the requirements of such service categories. In this paper, we define three different OPS service categories based on three different contention resolution algorithms, we design an ad-hoc pool of fiber delay lines for such a scheme, and evaluate its performance by simulation. The obtained results indicate the merits of our method which opens up future interesting developments for a whole network scenario studies.

A Unified Model for Bandwidth Adaptation in Next Generation Transport Networks

In this paper we propose a unified model for dynamic bandwidth adaptation in future transport networks. It acts as an umbrella for both next generation SONET/SDH (NG-SONET/SDH) and even more general, networks with a GMPLS control plane. We adapt bandwidth in discrete steps by exploiting features of virtual concatenation and bundled links, respectively. Applying our model, we demonstrate its advantage in providing improved service quality in comparison to a scheduled provisioning scheme. We evaluate the adaptation granularity to provide a required quality of service for typical IP network traffic behavior in the access network. Furthermore we quantify in depth the impact of increasing access bandwidth at the network edge on signaling load in a transport network.

Feedback Based Load Balancing, Deflection Routing and Admission Control in OBS Networks

The Optical Burst Switching (OBS) paradigm allows statistical multiplexing directly at the optical layer. Thus, OBS networks are suited to carry traffic demands varying in either the short or long term. Due to the lack of buffering, burst contention due to short term variations can only be mitigated through deflection routing. For longer term variations, higher order mechanisms such as dynamic flow-balancing or flow shaping are generally proposed. In this paper, a unified scheme, based on a feedback mechanism combined with deflection routing and admission control is introduced to handle all types of traffic variations. The use of only one single scheme simplifies the architecture of OBS networks and enhances its flexibility. The validity of our technique is supported by simulation results.