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High energy consumption in Ethernet Passive Optical Networks (EPONs) has caused intense research on energy-saving methods in recent years. The most common method for EPON energy saving is to cause optical network units (ONUs) to sleep which are idle or low loaded. With the popularity of multimedia applications, the ONUs carry not only unicast traffic but also more and more multicast traffic. However, existing studies mainly focus on ONUs that support only unicast traffic. The many differences between multicast traffic and unicast traffic make it necessary to design novel energy-saving methods. This paper proposes a multicast-traffic-oriented energy-saving algorithm for EPONs, called the energy-saving algorithm for multicast traffic (ESMT). To save as much energy as possible, the proposed algorithm uses a hybrid sleep mode (composed of a deep sleep state and an independent sleep mode) in which not only can ONU enter a deep sleep state, but also the ONU transmitter and receiver can sleep independently. Simulation results show that the proposed algorithm, which is oriented to multicast traffic in EPONs, is more energy efficient than other algorithms. [ABSTRACT FROM AUTHOR]

Abstract: Since optical network carries a lot of traffic, survivability is very important to ensure the service continuity against network failures. Recently, multicast services become more popular to meet the huge multimedia demand in network, so that multicast survivability in optical network has got more attention. However, multicast survivability may lead to more energy consumption due to more redundant backup resources allocated. Since greening network is particularly important with the energy crisis keeping growing, green multicast survivability in optical network is a challenging issue. This paper focuses on the green multicast grooming protection problem in optical network and designs two auxiliary graphs that includes a virtual topology graph and an integrated graph to address the survivable multicast grooming, routing and wavelength assignment. Based on the auxiliary graphs, this paper proposes an efficient heuristic called green multicast grooming algorithm based on spanning path dedicated protection (GMG-SPDP), in which the network reliability and the energy efficiency are jointly taken into account. Simulation results show that, compared to other algorithms, the proposed GMG-SPDP not only has lower blocking probability and higher bandwidth utilization ratio, but also saves more energy. [Copyright &y& Elsevier]

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: In passive optical network (PON), the existing energy-saving algorithms are implemented only with one kind of PON. However, as far as Ethernet PON (EPON), good performances cannot be reached simultaneously in both 10G-EPON and 1G-EPON. Although 10G-EPON can provide higher throughput and lower delay than 1G-EPON, it consumes more energy. Currently, there are four types of optical network unit (ONU) sleep modes which are specified by ITU-T. If transmitter and receiver can be turned off independently without upstream traffic or downstream traffic, additional energy can be saved. Therefore, in this paper, to obtain high throughput and low delay with low energy consumption, we propose a new energy saving mechanism based on double-sleep-state and dynamic double-threshold receiver selection (EDDS) with the combination of 1G-EPON and 10G-EPON techniques. In EDDS, ONU's receiver not only can be switched between 1Gbps receiver and 10Gbps receiver according to the downstream traffic, but also can be put into sleep state independently when possible. Hereby, EDDS can provide higher throughput and lower delay than 1G-EPON while consume less energy than 10G-EPON. To support EDDS, new structures for optical line terminal (OLT) and ONU are introduced. Simulation results show that EDDS achieves better performances than the traditional schemes. [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]