Routing scalability in multi-domain DWDM networks

This paper studies routing scalability in multi-domain DWDM networks. Although inter-domain provisioning has been well studied for packet/cell-switching networks, the wavelength dimension (along with wavelength conversion) poses many challenges in multi-domain DWDM settings. To address these concerns a detailed GMPLS-based hierarchical routing framework is proposed for multi-domain DWDM networks with wavelength conversion. This solution uses mesh topology abstraction schemes to hide domain-internal state. However related inter-domain routing loads can be significant here, growing by the square of the number of border nodes. To address these scalability limitations, improved inter-domain routing update strategies are also proposed and the associated performance of inter-domain lightpath RWA and signaling schemes studied.

Performance evaluation of p-cycle based protection methods for provisioning of dynamic multicast sessions in mesh WDM networks

Network survivability is crucial to both unicast and multicast traffic. Up to now, extensive research has been done on unicast traffic protection. Recently, due to the rapid growth of multicast applications, such as video-conferencing, high definition television (HDTV), distance learning, and multi-player on-line gaming, the problem of multicast traffic protection has started to draw more research interests. The preconfigured protection cycle (p-cycle) method proposed by Grover offers fast speed in restoration (because p-cycles are pre-cross-connected) and high efficiency in resource utilization (because p-cycles protect both on-cycle and straddling links). So far p-cycles based protection approaches have been intensively studied for unicast traffic protection, but have been rarely investigated for multicast traffic. We propose to apply p-cycles to dynamic protection provisioning of multicast traffic, and evaluate the blocking performance in comparison to other existing multicast protection schemes. We consider three different p-cycle based multicasting protection methods, namely dynamic p-cycle (DpC) design, p-cycle based protected working capacity envelope (PWCE) design, and hybrid DpC and PWCE design. We show that p-cycle-based multicast protection approaches offer much better blocking performance, as compared with other existing multicast protection schemes. The main reasons for the much better blocking performance are attributed to the facts that (i) the selection of p-cycles is independent of the routing of the multicast light trees, (ii) there are no path/segment disjoint constraints between the selected p-cycles and the multicast light trees to be protected, (iii) the selected p-cycles are the most efficient p-cycles.

Finite-state Markov Model for Lognormal,Chi-square (Central), Chi-square (Non-central), and <Emphasis Type="Italic">K</Emphasis>-distributions

This paper formulates a finite-state Markov channel model to represent received signal-to-noise (SNR) ratios having lognormal, K-distribution, chi-square (central) and chi-square (non-central) distributions in a slow fading channel. The range of the SNRs is partitioned into a finite number of states following earlier works in literature. Performance measures like level crossing rates, steady-state probabilities, transition probabilities, and state-time durations are derived, and numerical results are plotted and discussed for the FSMC models for all the distributions.

Locally reconfigurable p-cycle networks for dual-failure restoration

p-Cycle reconfiguration methods (for instance complete, incremental, or dynamic-repair) based on the first event adaptive restoration model provide a promising approach for improving the dual-failure restorability characteristics of static p-cycle methods based on the static preplanned restoration model. However, if the reconfiguration process triggered by the first failure is not completed before a second failure occurs, p-cycle reconfiguration methods fail to achieve 100% dual-failure restorability and reduce to the static p-cycle methods which do not take advantage of the spare capacity to be reconfigured. In this study, we propose to use a new restoration model designated as first event locally adaptive restoration model with a coordinated re-restoration effort. This model is aimed to limit the reconfiguration scope to a local p-cycle where the spare capacity is only reconfigured on its straddling links for reducing the reconfiguration overhead (i.e., the average number of reconfigured links during the reconfiguration time.) According to this model, a two-phase locally reconfigurable p-cycle method is proposed. Only the straddling links of the local p-cycle affected by the first failure are reconfigured in the first phase. The second phase is not initialized until the second failure really occurs in the affected local p-cycle. The second phase is to enable the dual-failure restorations with a coordinated re-restoration effort for the first failed link from its original end nodes for any damage that the second failure causes to previously deployed restoration paths. The objective of the proposed method is to maximize the dual-failure restorability within a limited reconfiguration scope. We evaluate the correlation between the normalized spare capacity cost and the dual-failure restorability. The results show that the proposed local reconfiguration heuristic method improves the average dual-failure restorability of the 9n17s and Cost 230 networks by 45.1% and 20.1%, respectively, relative to the static p-cycles method and achieves closely the optimal value obtained using integer linear programming (ILP). Additionally, the spare capacity cost of the proposed local reconfiguration method is smaller than that of previous p-cycle reconfiguration methods in the two test networks.

Restoration in wavelength-routed optical networks by means of ant colony optimization

Because of the distributed control of the network, the dynamic nature of the traffic and the unpredictability of a failure event, the flexibility and robustness of ant colony optimization (ACO) make it a suitable candidate for provisioning lightpaths in an optical network. In this work, we propose a fault-tolerant dynamic routing and wavelength assignment (RWA) algorithm based on the ACO framework, presenting its integration into the Generalized multi-protocol label switching (GMPLS) control plane. By simulating two different scenarios, we demonstrate the effectiveness of this algorithm when a single link or node failure occurs.

Low-Power FPGA-Implementation of <Emphasis Type="Italic">atan</Emphasis>(<Emphasis Type="Italic">Y</Emphasis>/<Emphasis Type="Italic">X</Emphasis>) Using Look-Up Table Methods for Communication Applications

This paper presents an architecture for the computation of the atan(Y/X) operation suitable for broadband communication applications where a throughput of 20 MHz is required. The architecture takes advantage of embedded hard-cores of the FPGA device to achieve lower power consumption with respect to an atan(Y/X) operator based on CORDIC algorithm or conventional LUT-based methods. The proposed architecture can compute the atan(Y/X) with a latency of two clock cycles and its power consumption is 49% lower than a CORDIC or 46% lower than multipartite approach.

New traffic grooming approaches in optical networks under restricted shared protection

In this paper, two traffic grooming approaches based on alternate path routing are proposed to accommodate a greater number of connections in optical networks. In the first approach (called as Source_SWG), the connections of same source and different destinations along a path are groomed in a wavelength channel, whereas in the second approach (called as Des_SWG), the connections of the same destination and different sources along a path are groomed in a wavelength channel. These approaches are compared with existing heuristic traffic grooming algorithms based on fixed routing. It is found that both the approaches provide less wavelengths than the existing heuristic traffic grooming algorithms for establishment of all the connections present in the network. The comparative studies of these approaches are also made under restricted shared protection. It is seen that in case of Source_SWG, the number of wavelengths required for establishment of all the connections present in the network is less than that for Des_SWG.

Improvement of Location Accuracy by Adding Nodes to Ad-Hoc Networks

We discuss the effect of adding nodes on the location accuracy of Ad-Hoc networks. All results are obtained by analyzing the Cramér-Rao Lower bound. We show that for planar network the additional node must have at least 3 connections in order to have any effect on the existing nodes accuracy. Further, we identify the nodes whose accuracy will be improved. Finally, we show that the accuracy cannot be improved without limit by adding more and more nodes to an existing network.

MGFs for Rayleigh Random Variables

Expressions are given for the moment generating functions of the Rayleigh and generalized Rayleigh distributions.

Reducing vulnerability of shared-path protection subject to double-link failures in WDM mesh networks

Shared-path protection (SPP) is a capacity- efficient mechanism to provide 100% single-link failure protection in WDM mesh networks. After the first link failure, however, if reconfiguration is unavailable, a second link failure may lead to tremendous service interruption. Vulnerability of a link is the percentage of links that are vulnerable to the arbitrary second link failure after the link failed and network vulnerability is defined as the average vulnerability of links in the network. In this article, we present three policies that can reduce network vulnerability by reducing backup sharing in shared-path protection. The first policy tries to restrict the times of sharing a wavelength-link by connections. The second policy tries to avoid backup sharing on highly vulnerable links. The third policy tries to avoid backup sharing on highly vulnerable wavelength-links. Algorithms to implement these policies based on a similar framework are presented. Numerical results suggest that there is a trade-off between capacity efficiency and network vulnerability in all the three policies. The third policy can deliver a better performance in terms of blocking probability and network vulnerability.

Error Probability for <Emphasis Type="Italic">L</Emphasis>-branch Coherent BPSK Equal Gain Combiners over Generalized Rayleigh Fading Channels

In this paper, a closed-form expression for the probability of error in a coherent BPSK system over Generalized Rayleigh fading channels is derived. An L-branch equal gain combining diversity scheme is used. Theoretical results for the probability of error are plotted for various values of the number of degrees of freedom (n) and diversity order (L). A simulation is performed and the simulated results are found to match very well with the theoretical results.

Successively Structured Gaussian Two-terminal Source Coding

Multiterminal source coding refers to separate encoding and joint decoding of multiple correlated sources. Joint decoding requires all the messages to be decoded simultaneously which is exponentially more complex than a sequence of single-message decodings. Inspired by previous work on successive coding, we apply the successive Wyner-Ziv coding, which is inherently a low complexity approach of obtaining a prescribed distortion, to the two-terminal source coding scheme. First, we consider 1-helper problem where one source provides partial side information to the decoder to help the reconstruction of the main source. Our results show that the successive coding strategy is an optimal strategy in the sense of achieving the rate-distortion function. By developing connections between source encoding and data fusion steps, it is shown that the whole rate-distortion region for the 2-terminal source coding problem is achievable using the successive coding strategy. Comparing the performance of the sequential coding with the performance of the successive coding, we show that there is no sum-rate loss when the side information is not available at the encoder. This result is of special interest in some applications such as video coding where there are processing and storage constraints at the encoder. Finally, we provide an achievable rate-distortion region for the m-terminal source coding.

Robust Recursive <Emphasis Type="Italic">H</Emphasis><Subscript>∞</Subscript> DOA Estimation Using Spatial Forward Linear Predictor

This letter deals with robust direction of arrival (DOA) estimation based on the recursive H _∞ algorithm for the forward linear predictor. This recursive H _∞ criterion is different from traditional H ₂ estimation criterions which minimize the squared prediction error. The forward linear predictor with recursive H _∞ algorithm is a worst case optimization approach, which minimizes the total effect of the worst disturbances on the prediction error. Some computer simulation examples are provided for illustrating the effectiveness of the proposed method.

On capacity planning for the GMPLS network control plane

This article presents capacity planning rules for the control plane of all-optical networks featuring GMPLS and RSVP-TE as a connection setup protocol. As per RSVP standard, a refresh message mechanism is incorporated to RSVP such that the state is periodically refreshed on a link per link basis. We provide analytical expressions for the bandwidth and buffer sizes to be provided such that no flows are torn down due to lack of refresh messages. Our findings show that small buffers (several KBytes) suffice to sustain the signaling load for as much as 400 RSVP flows per link, with the simplest RSVP refresh mechanism (neither using link bundling nor acknowledgments). On the other hand, we also find the packet drop probability per link for a given network topology for the case that the flow survival probability is larger than a given threshold. We provide numerical examples based on the COST 239 european network topology and real RSVP traffic traces from early-commercial switching equipment.

New results for path-based shared protection and link-based Hamiltonian cycle protection in survivable WDM networks

In this paper, we study the path-based shared protection (PBSP) and the link-based Hamiltonian cycle protection (LBHCP) schemes for tolerating single-link failures in survivable wavelength-division-multiplexing networks. Although previous work indicated that PBSP can perform better than link-based shared protection including the case of LBHCP, from theoretical analysis and simulation results in this paper, we can clearly see that this indication of previous work is not suitable for LBHCP since it can have a better resource utilization ratio and a faster recovery time than PBSP. Therefore, the new result of this paper is a modification for the previous inaccurate idea and it also can well guide future work of researchers.

Delay-dependent H ∞ control for 2-D discrete state delay systems in the second FM model

This paper is concerned with the problem of delay-dependent H _∞ control for two-dimensional (2-D) discrete state delay systems described by the second Fornasini and Marchesini (FM) state-space model. Based on a summation inequality, a sufficient condition to have a delay-dependent H _∞ noise attenuation for this 2-D system is given in terms of linear matrix inequalities (LMIs). A delay-dependent optimal state feedback H _∞ controller is obtained by solving an LMI optimization problem. Finally, a simulation example of thermal processes is given to illustrate the effectiveness of the proposed result.

Layered Access Control Schemes on Watermarked Scalable Media

Intellectual Property (IP) protection is a critical element in multimedia transmission and delivery systems. Conventional IP protection on multimedia data can be categorized into encryption and watermarking. In this paper, a structure to perform layered access control on scalable media by combining encryption and robust watermarking is proposed, implemented, and verified. By taking advantages of the nature of both encryption and watermarking, copyrights of multimedia contents can be well protected and at the same time, multiple-grade services can be provided. In the summated examples, we assume a scalable transmission scheme over the broadcasting environment and use it to test the effectiveness of proposed method. When the embedded watermark is extracted with high confidence, the key to decrypt the next layer can be perfectly recovered. Then, the media contents are reconstructed and the copyrights are assured. The application examples also demonstrate the practicality of the proposed system.

Hardware Organization to Achieve High-Speed Elliptic Curve Cryptography for Mobile Devices

Elliptic curve cryptography (ECC) is recognized as a fast cryptography system and has many applications in security systems. In this paper, a novel sharing scheme is proposed to significantly reduce the number of field multiplications and the usage of lookup tables, providing high speed operations for both hardware and software realizations.

An Expression for the Average Quantization Error

The quantization error for MIMO (multiple-input multiple-output) downlink channels is known to be the minimum of independent and identically distributed beta random variables. In this note, an exact expression is derived for the average quantization error. Computational issues relating to its correctness, usage and approximations are discussed.

The Criterions with LCR and AFD of Dual-Branch SC Diversity over Specified Wireless Radio Fading Channels

In this paper we proposed the results of average LCR (level crossing rate) and AFD (average fading duration) criterions applied to evaluate the performance of dual-branch SC (selection combining) reception in the specified fading channels characterized as statistical distributions with correlated-Rayleigh and correlated-Rice models. Moreover, in order to unify and clarify the criterions of performance formulas with average LCR and AFD for SC diversity over different kinds of fading models, include such as Rayleigh, Rice, Nakagami-m, and Weibull distributions etc., almost all of the ever researched and published results from discussing about the LCR and AFD of SC diversity are comprehensively collected in this report. On the other hand, for the purpose of comparison, there are a large number of LCR and AFD performance formulas for SC diversity and the generalized fading statistic models are extracted and tabulated together, in which the cases of correlated and independent proprieties between diversity branches are taken into consideration too (some of the formulas are illustrated by the assumption of dual-branch SC diversity).