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Mobile edge computing is popular for providing services with low latency and high privacy. It becomes more powerful by leveraging the widely deployed Small cell Base Stations (SBS) with zooming cells for energy-efficient service placement. However, the literature ignores the joint optimization of SBS power control and service placement. The Quality of Services (QoS) guarantee is also challenging, taking into account the component dependency and parallelization in multi-component services and the resource slicing for separated service deployment. Moreover, prior works assume the same amount of allocated resources of links on a placed path for service edge allocation, leading to the ossification of resource allocation and inevitable resource fragments. Towards the above challenges, this paper addresses the energy-efficient and flexible service placement in cell zooming enabled Mobile Edge Cloud (MEC) networks. The delay of multi-component services is constructed depending on the allocated resource slice. Besides, the joint optimization of service placement and SBS power control is formulated and transformed into a Mixed Integer Linear Programming (MILP). More importantly, the equivalent bandwidth for an edge allocation is defined and analyzed to obtain flexible edge placement with minimum resource cost. Leveraging the results of MILP, an Energy-efficient Service placement algorithm based on equivalent Bandwidth in Cell zooming enabled MEC networks (ESBC) is proposed to improve the probability of successful service placement with QoS guarantee by optimizing the delay distribution among components and edges and reducing resource fragments. Finally, simulation results validate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The exponential growth of the demand for broadband services has imposed great challenges on the design of spectrum-efficient optical transmission system in Passive Optical Network (PON). Recently, an innovative Orthogonal Frequency Division Multiplexing (OFDM) scheme, called Polar-OFDM (P-OFDM), has emerged as a promising solution to boost the spectral efficiency of optical transmission in PON. However, the traditional P-OFDM does not yet perform best in spectral efficiency as it only uses half of the total subcarriers. In this paper, we verify a promising complementation between Polarization Multiplexing (POLMUX) and P-OFDM aiming at higher spectral efficiency. We then propose the full-subcarriers P-OFDM by loading data on the even-indexed subcarriers of X polarization and the odd-indexed subcarriers of Y polarization, respectively. Thus, all of the subcarriers will be utilized for effective data transmission, which can double the spectral efficiency. More importantly, because the subcarriers are interlaced on different polarizations, the cross-polarization interference can be significantly mitigated, which enables the independent channel estimation and equalization at the receiver to recover the data carried on each polarization. Our evaluation results demonstrate that the proposed system realizes the double spectral efficiency of the traditional P-OFDM with reasonable Bit Error Rate (BER) performance loss. [ABSTRACT FROM AUTHOR]

While some long noncoding RNAs (lncRNAs) might promote nasopharyngeal carcinoma (NPC) initiation and progression, the involved molecular mechanisms remain largely unclear. Here, we discovered the novel LncRNA, prostate cancer associated transcript 7 (PCAT7), which was overexpressed and associated with worse prognosis in NPC. Decreased PCAT7 expression was found to significantly suppress tumor cell proliferation in vitro, and inhibited tumor growth and reduced the expression of proliferation antigen Ki-67 in vivo. Rescue assay was performed to further confirm that PCAT7 contributed to the progression of NPC through regulating miR-134-5p/ELF2 signal pathway. These results indicated that PCAT7 might contribute to the tumor progression in NPC by functioning as a ceRNA to sponge miR-134-5p. [ABSTRACT FROM AUTHOR]

Fiber-Wireless (FiWi) access network is now becoming a promising architecture for access networks. Survivability is one of the key issues in the planning of FiWi access network because many high-rate traffic flows may be interrupted in case of a single fiber failure, which can cause a huge traffic loss. In addition, the users need ubiquitous broadband access that can be provided by FiWi access network. In this paper, we propose the protection approach called Maximum Covering Planning with Survivability (MCPS), including Integer Linear Programming (ILP) solution and heuristic solution, for the planning of survivable FiWi access network against single distribution fiber failure. The proposed approach aims at maximum coverage under the constraints of network connectivity. When a distribution fiber is broken, the interrupted Optical Network Unit (ONU) can transmit traffic to its backup ONU through the wireless paths between them. Simulation results show the network coverage of clients for different number of ONUs in different urban areas, and demonstrate the relationship between network coverage and the cost represented by the number of WiFi routers. [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: Fiber-wireless (FiWi) access network is a promising access technology because it integrates the merits of optical and wireless access networks. In FiWi network, the placement of optical network units (ONUs) is one of the key issues for the network deployment since the ONU acts as the interface between wireless front-end and optical back-end. Some works have been carried out to investigate the ONU placement in FiWi. However, most of these works consider only the Internet traffic and ignore the effect of peer-to-peer (P2P) traffic on the ONU placement. Furthermore, all of these works remain untouched on the issue of load balancing among different ONUs. In this paper, we propose a novel ONU placement algorithm called load balanced ONU placement (LBOP) with the consideration of both Internet traffic and P2P traffic. According to the LBOP algorithm, with the objective of minimizing the number of ONUs, we first place the ONUs one-by-one in a greedy manner under the constraints of wireless hop number for both types of traffic. Then, for the purpose of load balancing, we implement the load transferring among different ONUs by coordinating the sets of their subordinate wireless routers. Simulation results demonstrate that the proposed LBOP algorithm is more effective in reducing the number of ONUs and achieving the load balancing than previous works. [Copyright &y& Elsevier]

Abstract: With increasing network sizes, the energy consumption of Passive Optical Networks (PONs) has grown significantly. Therefore, it is important to design effective energy-saving schemes in PONs. Generally, energy-saving schemes have focused on sleeping the low-loaded Optical Network Units (ONUs), which tends to bring large packet delays. Further, the traditional ONU sleep modes are not capable of sleeping the transmitter and receiver independently, though they are not required to transmit or receive packets. Clearly, this approach contributes to wasted energy. Thus, in this paper, we propose an Energy-Saving scheme that is based on downstream Packet Scheduling (ESPS) in Ethernet PON (EPON). First, we design both an algorithm and a rule for downstream packet scheduling at the inter- and intra-ONU levels, respectively, to reduce the downstream packet delay. After that, we propose a hybrid sleep mode that contains not only ONU deep sleep mode but also independent sleep modes for the transmitter and the receiver. This ensures that the energy consumed by the ONUs is minimal. To realize the hybrid sleep mode, a modified GATE control message is designed that involves 10 time points for sleep processes. In ESPS, the 10 time points are calculated according to the allocated bandwidths in both the upstream and the downstream. The simulation results show that ESPS outperforms traditional Upstream Centric Scheduling (UCS) scheme in terms of energy consumption and the average delay for both real-time and non-real-time packets downstream. The simulation results also show that the average energy consumption of each ONU in larger-sized networks is less than that in smaller-sized networks; hence, our ESPS is better suited for larger-sized networks. [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: 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]

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]

Highlights: [•] Our work has considered the QoS factors and constructed a reward function to model the QoS properties. [•] Our work has considered MT’s velocity, network access cost and switching cost for vertical handoff decision. [•] We have applied G1 and entropy methods to calculate the weight of each QoS factor in the reward function. [•] By taking the MT’s velocity into consideration, our work can avoid unnecessary handoffs. [ABSTRACT FROM AUTHOR]

With the development of WDM techniques and cloud computing, incorporating the optical backbone into data centers has received extensive attention. Virtual network (VN) planning has been proposed for this new networking paradigm by taking advantage of network virtualization. VN planning is essentially a united virtualization of optical and server resources in a collaborative manner. In this article, we first elaborate the advantages and problems of existing VN planning schemes through a comprehensive survey. Next, we provide a VN planning scheme. The simulation results demonstrate the effectiveness of our strategy, particularly in the context of power outage and evolving recovery. Finally, the future opportunities and challenges are also discussed. [ABSTRACT FROM PUBLISHER]

Abstract: Since atmosphere deeply influences the beams propagated in space-to-ground optical communications, it is important to study its effects on the beam transmission in the atmospheric channel. In this paper, we analyze the impacts of atmospheric channel with the theory of free space optical communication. First, we investigate the atmospheric attenuation of different beams through the mathematical models. Then, we analyze the effects of atmospheric turbulence on the signal transmission by the atmospheric refractive index structure constant. In addition, we simulate the atmospheric transmittance with different zenith angles, beams, heights and rainfall. The results show that the wavelength, atmospheric turbulence, zenith angle, height and rainfall have important impacts on the signal transmission of space-to-ground optical communications. This demonstrates much theoretical significance on the wavelength selection, height settings of the optical ground station as well as angle selection of transmitter. [Copyright &y& Elsevier]

Abstract: Saving the electrical requirements of network operators around the world makes power costs show a continuously decreasing trend. However, reducing the power costs is not only one way of gaining the marginal profit, a network operator also needs providing high-level quality of service (QoS), as well as employs effective strategies of pricing and hybrid grooming (i.e., integration of traffic grooming with an optical bypass) to make more users wish to pay the expense for their applications. In the final, users enjoy their services meanwhile operators obtain high profit in a power-efficient way, i.e., “double-win”. Accordingly, we propose the fast sub-optimal heuristics including Single-hop and Power-efficient Grooming algorithm based on Game theory (SPG2) as well as Multi-hop and Power-efficient Grooming algorithm based on Game theory (MPG2). Simulation results demonstrate that, compared with SPG2, MPG2 has the better comprehensive performance of both power efficiency and double-win between user and network operator in IP over WDM networks. [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: Optical communication technology shows promising prospects to fulfill the large bandwidth requirements of future deep-space exploration. This paper mainly studies the link design of Moon-to-Earth optical communication based on the telescope array receiver. Firstly, we analyze and design the telescope array model. An array of relatively small-sized telescope combined to form a larger synthesized aperture is a viable and efficient alternative to a large monolithic telescope. Moreover, this array structure also saves the total costs of the telescopes. In addition, we present an end-to-end system analysis to provide the expected signal and background photons as a function of the Moon–Earth distance. Then, we describe the work on the link design of the Moon-to-Earth optical communication. This primarily includes the received power, the antenna gain, the space loss, the atmospheric loss, and so on. We also provide an approximation calculation to the channel capacity, the data rate, the bit error ratio (BER) and signal-to-noise ratio (SNR). This demonstrates much theoretical significance on the actual Moon-to-Earth optical communication. [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: 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]

The emerging 5G applications and the connectivity of billions of devices have driven the investigation of multi-domain heterogeneous converged optical networks. To support emerging applications with their diverse quality of service requirements, network slicing has been proposed as a promising technology. Network virtualization is an enabler for network slicing, where the physical network can be partitioned into different configurable slices in the multi-domain heterogeneous converged optical networks. An efficient resource allocation mechanism for multiple virtual networks in network virtualization is one of the main challenges referred as virtual network embedding (VNE). This paper is a survey on the state-of-the-art works for the VNE problem towards multi-domain heterogeneous converged optical networks, providing the discussion on future research issues and challenges. In this paper, we describe VNE in multi-domain heterogeneous converged optical networks with enabling network orchestration technologies and analyze the literature about VNE algorithms with various network considerations for each network domain. The basic VNE problem with various motivations and performance metrics for general scenarios is discussed. A VNE algorithm taxonomy is presented and discussed by classifying the major VNE algorithms into three categories according to existing literature. We analyze and compare the attributes of algorithms such as node and link embedding methods, objectives, and network architecture, which can give a selection or baseline for future work of VNE. Finally, we explore some broader perspectives in future research issues and challenges on 5G scenario, field trail deployment, and machine learning-based algorithms. [ABSTRACT FROM AUTHOR]