Effects Of Physical Layer Impairments Research Articles

Robust QoT Assured Resource Allocation in Shared Backup Path Protection Based EONs

Survivability is mission-critical for elastic optical networks (EONs) as they are expected to carry an enormous amount of data. In this paper, we consider the problem of designing shared backup path protection (SBPP) based EON that facilitates the minimum quality-of-transmission (QoT) assured allocation against physical layer impairments (PLIs) under any single link/shared risk link group (SRLG) failure for static and dynamic traffic scenarios. In general, the effect of PLIs on lightpath varies based on the location of failure of a link as it introduces different active working and backup paths. To address these issues in the design of SBPP EON, we formulate a mixed integer linear programming (MILP) based robust optimization framework for static traffic with the objective of minimizing overall fragmentation. In this process, we use the efficient robust bitloading technique for spectrum allocation where each frequency slot of a request is assigned with different modulation format. In addition, we propose novel SBPP-impairment aware (SBPP-IA) algorithm considering the limitations of MILP for larger networks. For this purpose, we introduce a novel sorting technique named most congested working-least congested backup first (MCW-LCBF) to sort the given set of requests. Next, we employ our SBPP-IA algorithm for dynamic traffic scenario and compare it with existing algorithms in terms of different QoT parameters. Further, we guarantee the QoT of existing requests while allocating each new request without reserving any margin. We demonstrated through simulations that our study provides 33.94-41.02% more QoT guaranteed requests compared to existing ones at 70 Tbps traffic load.

Effect of transmission impairments in CO-OFDM based Elastic Optical Network design

Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) based Elastic Optical Network (EON) is one of the emerging technologies being considered for next generation high data rate optical network systems. Routing and Spectrum Allocation (RSA) is an important aspect of EON. Apart from spectral fragmentation created due to spectrum continuity and contiguity constraints of RSA, transmission impairments such as shot noise, amplified spontaneous emission (ASE), beat noise due to coherent detection, crosstalk in cross-connect (XC), nonlinear interference, and filter narrowing, limit the transmission reach of optical signals in EON. This paper focuses on the off-line joint optimization of delay-bandwidth product, fragmentation and link congestion for RSA in CO-OFDM EON while considering the effect of physical layer impairments. First, we formulate an optimal Mixed Integer Linear Programming (MILP) that achieves load-balancing in presence of transmission impairments and minimizes delay-bandwidth product along with fragmentation. We next propose a heuristic algorithm for large networks with two different demand ordering techniques. We show the benefits of our algorithm compared to the existing load-balancing algorithm.

A Cross-layer Traffic Grooming Algorithm in Joint Optimization of the IP over Elastic Optical Network

Abstract To fully utilize the existing optical network resource, the dynamic traffic grooming technology, which could efficiently multiplex many low-speed services arriving dynamically onto high-capacity optical channels, has been studied extensively and used widely. In this article, the problem of dynamic traffic grooming in joint optimization of IP over elastic optical network (EON) is studied. This problem consists of three sub-problems at two layers: the routing problem at the IP-layer (IPR), the routing, modulation level (RML), and the spectrum allocation (SA) problems at the optical layers. We proposed a novel topology-integration and adaptive-modulation based in cross-layer routing spectrum allocation (CL-RSA) algorithm, which follows a multi-cost approach that solves the IPR, the RML, and the SA problems jointly. The most important features of the proposed algorithm are merging physical topology with virtual topology and using the minimum-weight preferred method for route selection. Meanwhile, the effect of physical-layer impairments (PLI) on signal transmission is considered. In addition, the adaptive modulation scheme is used to allocate the spectrum resource. The simulation results show that the algorithm can effectively improve the spectrum resource utilization and reduce the network blocking probability compared to other algorithms in various network conditions, especially in the high load condition effectively.

Impairment-aware dynamic lightpath provisioning in mixed-line-rate networks

In Mixed-Line-Rate (MLR) networks, different line rates on different wavelengths can coexist on the same fiber. MLR brings flexibility to handle diverse demands by allowing each lightpath to be established end-to-end with different line rates, if necessary. However, advanced modulation techniques, which are required for high line rates, are highly susceptible to physical-layer impairments (PLIs), especially to the cross-phase modulation (XPM) induced by intensity-modulated channels.In this study, we investigate the impairment-aware lightpath provisioning problem for MLR networks. We consider a transparent optical network where we aim to maximize the number of established connections, while avoiding disrupting the existing lightpaths. We propose two different approaches: the first approach, Fixed Wavelength-Interval Allocation, takes PLIs into account implicitly, as signals for different line rates with different modulation formats are placed on channels over separate wavelength intervals. The second approach, Weighted Routing and Wavelength Assignment, handles the problem with a novel weight assignment scheme. We employ an auxiliary graph to capture the effects of PLIs on each channel with a weight-assignment scheme. Simulation results show that our approaches have better performance, in terms of bandwidth blocking ratio, utilization, and resource consumption with respect to the existing approaches.

Data-path selection mechanism based on physical layer impairments for WDM network

In optical networks, Physical Layer Impairments (PLIs) incurred by non-ideal optical transmission media accumulate along the optical path. The overall effect of PLIs determines the feasibility of the light-paths. It is important to understand the process that provide PLI information to the central manager and use this information efficiently to compute feasible routes and wavelengths. Based on the PLI impairments like fibre attenuation, Chromatic Dispersion (CD) and Polarisation Mode Dispersion (PMD), which reflects the Quality of service factors (Q-Factor); a centralised PLI-based routing algorithm is proposed for the selection of data-paths.

Guest Editorial: IJSCN Special Issue on ASMS2008

This Special Issue of the Wiley International Journal of Satellite Communications and Networking hosts aselection of papers from the fourth Advanced Satellite Mobile Systems (ASMS) Conference, held inBologna, Italy, on 26–28 August 2008. The conference was organized through a joint effort of theUniversity of Bologna, the Institute of Communications and Navigation of DLR (German AerospaceCenter) and the ISI (Integral SatCom Initiative) European Technology Platform, in cooperation with theSatellite Communications Network of Excellence (SatNEx) and the sISI Specific Support Action,supported by the European Commission FP6 and FP7 programmes, respectively.The ASMS conference has become a recognized event for industry and research institutions to exchangeup-to-date information about recent advances and emerging technologies in the field of mobile satellitecommunication systems. In addition, following the successful path opened by the 2006 edition, the scope ofthe conference has been widened to include broadband and broadcast satellite systems. This is veryimportant not only because the major part of the satcom market belongs to broadcasting and broadbandaccess operators but also fundamentally because the convergence of broadcast, mobile and fixed satellitecommunications is essential to offer seamless connectivity anywhere at anytime, which is recognized as thekey element for the successful deployment of future satellite systems.This Issue collects the extendedversions of eight of the best papers presented at the ASMS 2008 Conference. The papers have been selectedwith the aim of providing an insight in the developments and findings in this exciting field. The first papershows that Low Density Parity Check (LDPC) codes can tightly approach the performance of idealmaximum distance separable codes over memoryless erasure channels, under Maximum Likelihood (ML)decoding [1]. The decoding complexity of ML decoding can be kept low thanks to a class of decodingalgorithms which exploit the sparseness of the parity-check matrix to reduce the complexity of Gaussianelimination. The second paper includes a review and characterization of possible data link technologies foraeronautical communications covering a vast range of terrestrial (direct air-to-ground) and satellite-basedsolutions, with the final goal to identify suitable candidates for a future integrated aeronautical networkbased on IPv6 protocol, supporting both cockpit and cabin communications [2]. A new method to enableIPsec authentication and integrity services at the network layer is proposed in the thirdpaper [3]. Target scenarios include satellite multicast for large-scale delivery of data and video content.In these scenarios, a cross-layer architecture can mitigate the effects of physical layer impairments andlarge latency. Stemming from the three-state land mobile satellite channel model used for physical layersimulation in the course of the DVB-SH standardization process, an improved model is proposed in thefourth paper [4]. The new model includes two major modifications: a reduction in the number of states and

A cross‐layer framework for IPsec over satellite links

AbstractThe traditional modular OSI‐layered architecture has served a major role in the development of a variety of protocols. However, as physical layer impairments become complex and time varying, a dynamic cross‐layer design can enable better performance. A Cross‐Layer Architecture (CLA) is proposed to improve performance of error‐tolerant applications running over UDP‐Lite. This approach to implementation introduces new challenges in protocol design, as well as in the area of security, where the study proposes a new method to enable IP security (IPsec) authentication and integrity services at the network layer. Target scenarios include satellite multicast for large‐scale delivery of data and video content. In this scenario, CLA can mitigate the effects of physical layer impairments and high latency. Numerical analysis has shown that a link design employing header compression and cross‐layer signalling may protect protocol headers and can reduce the probability of packet discard. To evaluate the feasibility of the CLA, these methods have been implemented as an extension to the IPsec protocol, named Cross‐Layer IPsec (CL‐IPsec). A satellite emulation platform was used to validate the implementation of CL‐IPsec and to evaluate the overall performance improvement resulting from the proposed CLA. Copyright © 2010 John Wiley & Sons, Ltd.

Static Lightpath Establishment in Multilayer Traffic Engineering Under Physical Layer Impairments

This paper investigates the lightpath establishment problem in the optical layer, which arises in multilayer traffic engineering. The static version of the problem is considered, in which the set of requested lightpaths is known initially, and the objective is to set up as many of these lightpaths as possible by assigning the physical layer resources efficiently. In establishing the lightpaths, physical layer impairments are also considered, such that the bit error rates of all established lightpaths should remain within acceptable limits. A heuristic algorithm, called ROLE, is proposed for the solution of this problem. An integer linear programming (ILP) formulation for the static lightpath establishment with physical layer impairments is also developed, which considers the aggregated effect of physical layer impairments. This formulation is used as a performance benchmark for ROLE on smaller-size networks. It also provides upper bounds even when the ILP model cannot be solved to optimality. The performance of ROLE is close to the optimum solutions for all studied problem sets, for which the optimum solution can be obtained. ROLE significantly outperforms previously proposed algorithms in terms of the number of lightpaths established. The effect of switch cross-talk ratio on the problem solution is also investigated.

Effect of physical layer impairments on SUM and AND detection strategies for 2-D optical CDMA

The effect of physical layer impairments on the error performance of two-dimensional wavelength hopping/time spreading optical code-division multiple-access (OCDMA) systems is investigated for SUM and AND detection strategies. Relative intensity noise of the optical source, the signal-dependent shot noise, optical beat noise, and thermal noise at the receiver, fundamental issues in the design of OCDMA systems, are included in the bit-error-rate analysis. The analysis indicates that the SUM detection scheme is more robust in a noisy environment.