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Abstract: Long-Reach Passive Optical Network (LR-PON) is known as a promising and economical solution for Next-Generation PON (NG-PON). Survivability is one of the key issues in the planning of LR-PON because massive high-rate traffic flows may be interrupted in case of network component failure. However, the survivability issue for LR-PON is addressed in little works. More importantly, most of the previous works focus on single distribution fiber failure and remain untouched the simultaneous failure of multiple distribution fibers, which is a possible failure scenario in LR-PON. In this paper, we focus on the survivability of LR-PON against single Shared-Risk Link Group (SRLG) failure. A reliability model is proposed to represent the disconnection probability of the ONUs. Based on this reliability model, we propose a novel Backup Fibers Protection (BFP) scheme. In the BFP scheme, we deal with the optimization problem of allocating backup capacity and deploying backup fibers. Under the constraint of reliability requirement, our objective is to fully protect all traffic demand in the network with the minimum deployment cost of backup fibers. Both ILP-based approach and heuristic approach are proposed to solve the optimization problem in the BFP scheme. To the best of our knowledge, this paper is the first work regarding the survivability of LR-PON against single SRLG failure. Through extensive simulation, we investigate the performance of BFP and demonstrate its effectiveness in different scenarios. [Copyright &y& Elsevier]

Survivability is one of the key issues in fiber-wireless (FiWi) access networks, since network component failure may cause huge data loss. Especially in the scenario of segment failure, all optical network units (ONUs) lose their connections with the optical line terminal. Previous works focus on the protection of FiWi against segment failure by deploying backup fibers among the backup ONUs in different segments. However, these works consider only single segment failure. They also ignore the issue of traffic recovery efficiency. More importantly, they underutilize the backup fibers and ignore optimizing the selection of backup ONUs. Therefore, these works usually require a considerable deployment cost for backup fibers. To conquer these challenges, we propose an efficient protection scheme called cluster-based protection (CBP) in this paper. In CBP, we first partition the segments in the network into clusters in order to reduce the overhead for the management of traffic recovery. Then, we select one of the ONUs in each segment as the backup ONU and deploy backup fibers among the backup ONUs of different segments in the same cluster. Under a constraint on the maximum number of segments in each cluster, the CBP scheme aims to protect FiWi against the simultaneous failures of multiple segments with a minimum deployment cost for backup fibers. We propose both an integer-linear-programming-based approach and a heuristic approach to solve the joint optimization problem in CBP of selecting backup ONUs, clustering segments, and deploying backup fibers. To the best of our knowledge, this paper is the first work regarding the survivability of FiWi against the simultaneous failures of multiple segments. Through extensive simulation, we demonstrate that our CBP scheme outperforms the previous works significantly in terms of survivability enhancement and cost savings. [ABSTRACT FROM PUBLISHER]

Abstract: Survivability is one of the key issues in Fiber-Wireless (FiWi) access network because network component failures may cause huge data loss, especially when the failures in optical back-end. According to the failure severity, we categorize the failures in optical back-end into two levels, that is, Optical-Network-Unit (ONU)-level failure and segment-level failure. In this paper, instead of the expensive fiber duplication approach traditionally, we propose a novel protection approach for FiWi against ONU-level failure by assigning each ONU several alternate ONUs in the same segment and against the segment-level failure by deploying backup fibers among different segments. On one hand, we optimize the assignment of alternate ONUs, aiming to maximize the amount of protected traffic and minimize the number of wireless hops. On the other hand, we optimize the deployment of backup fibers, aiming to maximize the amount of protected traffic and minimize the length of backup fibers. We mathematically formulate these two objectives as Maximum Protection and Minimum Hops Number (MPMHN) problem and the Maximum Protection and Minimum backup Fibers Length (MPMFL) problem, respectively. An efficient algorithm called Auxiliary Graph based Protection (AGP) is proposed to solve the MPMHN and MPMFL problems. In the simulation, we investigate the performance of AGP in various scenarios and demonstrate the cost-efficiency of the proposed protection approach. [Copyright &y& Elsevier]

Abstract: Fiber-Wireless (FiWi) broadband access network is a promising “last mile” access technology, because it integrates wireless and optical access technologies in terms of their respective merits, such as high capacity and stable transmission from optical access technology, and easy deployment and flexibility from wireless access technology. Since FiWi is expected to carry a large amount of traffic, numerous traffic flows may be interrupted by the failure of network components. Thus, survivability in FiWi is a key issue aiming at reliable and robust service. However, the redundant deployment of backup resource required for survivability usually causes huge energy consumption, which aggravates the global warming and accelerates the incoming of energy crisis. Thus, the energy-saving issue should be considered when it comes to survivability design. In this paper, we focus on the green survivability in FiWi, which is an innovative concept and remains untouched in the previous works to our best knowledge. We first review and discuss some challenging issues about survivability and energy-saving in FiWi, and then we propose some instructive solutions for its green survivability design. Therefore, our work in this paper will provide the technical references and research motivations for the energy-efficient and survivable FiWi development in the future. [Copyright &y& Elsevier]

Traditional Wavelength-Division-Multiplexing (WDM) optical networks, which allocate spectrum resource in a fixed grid, may lead to inefficient resource utilization, low flexibility and high energy consumption. Therefore, by introducing the Orthogonal Frequency Division Multiplexing (OFDM) technology to the spectrum elastic optical networks could utilize spectrum resources efficiently. This paper established a power consumption model in spectrum elastic optical networks. Both dedicated and shared path protection were studied with static traffic demand under 6 different modulation modes. Considering the energy consumption of the network, a Routing and Modulation Level Spectrum Allocation (RMLSA) algorithm is proposed. In this algorithm, power saving can be achieved by dynamically adapting the number of bandwidth variable-transponders according to the chosen modulation level. Furthermore the paper proposed Spectrum Efficient RMLSA (SERMLSA) to make a trade-off between the energy consumption and the fragmentation. Based on the SERMLSA algorithm, we also proposed Allowing n fragments spectrum efficient RMLSA (AnSERMLSA) algorithm which allowed the fragments in certain limitation to save more energy. Simulation results showed that, in terms of energy saving and spectrum utilization, the proposed SERMLSA and AnSERMLSA heuristic algorithms reflected good performances in energy saving and defragmentation. [ABSTRACT FROM AUTHOR]

Abstract: Survivability is an important issue to ensure the service continuity in optical network. At the same time, with the granularity of traffic demands ranging from sub-wavelength-level to wavelength-level, traffic demands need to be aggregated and carried over the network in order to utilize resources effectively. Therefore, multi-granularity grooming is proposed to save the cost and reduce the number of switching ports in Optical-Cross Connects (OXCs). However, current works mostly addressed the survivable wavelength or waveband grooming. Therefore, in this paper, we propose three heuristic algorithms called Multi-granularity Dedicated Protection Grooming (MDPG), Multi-granularity Shared Protection Grooming (MSPG) and Multi-granularity Mixed Protection Grooming (MMPG), respectively. All of them are performed based on the Survivable Multi-granularity Integrated Auxiliary Graph (SMIAG) that includes one Wavelength Integrated Auxiliary Graph (WIAG) for wavelength protection and one waveBand Integrated Auxiliary Graph (BIAG) for waveband protection. Numerical results show that MMPG has the lowest average port-cost, the best resource utilization ratio and the lowest blocking probability among these three algorithms. Compared with MDPG, MSPG has lower average port-cost, better resource utilization ratio and lower blocking probability. [Copyright &y& Elsevier]

Abstract: With the network size increasing, the optical backbone is divided into multiple domains and each domain has its own network operator and management policy. At the same time, the failures in optical network may lead to a huge data loss since each wavelength carries a lot of traffic. Therefore, the survivability in multi-domain optical network is very important. However, existing survivable algorithms can achieve only the unilateral optimization for profit of either users or network operators. Then, they cannot well find the double-win optimal solution with considering economic factors for both users and network operators. Thus, in this paper we develop the multi-domain network model with involving multiple Quality of Service (QoS) parameters. After presenting the link evaluation approach based on fuzzy mathematics, we propose the game model to find the optimal solution to maximize the user’s utility, the network operator’s utility, and the joint utility of user and network operator. Since the problem of finding double-win optimal solution is NP-complete, we propose two new hybrid protection algorithms, Intra-domain Sub-path Protection (ISP) algorithm and Inter-domain End-to-end Protection (IEP) algorithm. In ISP and IEP, the hybrid protection means that the intelligent algorithm based on Bacterial Colony Optimization (BCO) and the heuristic algorithm are used to solve the survivability in intra-domain routing and inter-domain routing, respectively. Simulation results show that ISP and IEP have the similar comprehensive utility. In addition, ISP has better resource utilization efficiency, lower blocking probability, and higher network operator’s utility, while IEP has better user’s utility. [Copyright &y& Elsevier]