Optical Switching and Networking最新文献

Light-Fidelity (LiFi) is quickly emerging as the next-generation communication technology thanks to its unique benefits, such as available spectrum, high data rates, low implementation costs, and inherent beamforming capabilities. As a consequence, it is endorsed by the scientific literature as an appealing innovation for disclosing disruptive services. The wavefront of LiFi technology is very wide: in this manuscript, we focus our attention on the interplay with the Internet of Things. Essentially, LiFi can assist the IoT in interconnecting a massive number of heterogeneous devices by addressing the current Radio Frequency spectrum bottleneck. Moreover, by investigating LiFi and IoT individually, several surveys and review papers testify to the noteworthiness of both technologies. However, to the best of the authors’ knowledge, a comprehensive investigation of contributions where both of them interplay is missing. To fill this gap, this survey provides a thorough investigation of all the research areas in which LiFi key features might enhance the upcoming IoT networks. The evaluation of existing literature on LiFi adopted in the IoT domain can be valuable in identifying missing gaps arising from the interaction of these two technologies, as well as proficiently pinpointing future research directions.

In this paper, a self-adaptive anti-misalignment model for transceivers in hybrid radio frequency (RF) communication and visible light communication (VLC) vehicle-to-vehicle (V2V) network is firstly proposed to solve the transceiver misalignment (TM) between vehicles in adjacent lanes caused by vehicle states' changes. By the information on roads and the state of vehicles, traffic scenarios are divided into three categories: the static traffic scenario, the low-speed traffic scenario and the high-speed traffic scenario. By the vehicle behavior characteristics, the relationship between TMs and vehicle states in different traffic scenarios is established. By the relationship, the self-adaptive anti-misalignment model for transceivers is constructed. By the model, the TM can be predicted and the communication mode can be selected. By simulation, the effectiveness of the model is demonstrated. The simulation results show that the model has comparative advantages of preventing the VLC links' interruption and reducing communication modes’ handover numbers in different traffic scenarios.

For the purpose of improving the resources utilization efficiency and decrease network redundancy of electric power communication network (EPCN), the paper explores using failure independent path protection preconfigured cycle (FIPP p-Cycle) to provide backup paths for electric communication service and presents a protection algorithm of enhanced FIPP p-Cycle with traffic grooming (EFIPP-TG). Firstly, the multiplexing conditions of FIPP p-Cycle are analyzed specifically, and we propose a FIPP p-Cycle multiplexing algorithm to improve the utilization efficiency of backup resources. Then segment protection algorithm for working path is designed to decrease service blocking ratio as much as possible. In addition, by taking advantage of traffic grooming strategy, the routing paths of services are optimized, yielding effective decrease of network blocking probability. Simulation results from different topologies demonstrate that compared with traditional FIPP p-Cycle scheme, other p-Cycle based protection algorithms and shared backup path protection algorithm, the proposed EFIPP-TG algorithm can significantly reduce the redundancy and blocking probability of networks, shorten the length of backup path and hence improve the reliability of service and performance of network survivability.

A fast data synchronization method in optical inter-connected data center is proposed. The origin data are combined to fewer coded data to reduce the synchronization slots. The coded data are broadcast to other nodes. Each node decodes the coded data to recover its missing data. A coding strategy based on coding matrices is proposed for various data distribution. The parity-check matrices in error-control coding theory can be used as coding matrices. The synchronization slots are reduced by the proposed coding method, especially when the missing ratio is low. The slots can be further reduced when the coding field is extended to high-order galois fields.

In control-plane of optical packet forwarding engines (OPFEs), the group-membership query algorithm determines the egress through which a packet should be forwarded. To implement a high-performance multicast-enabled switch/router, a super-fast group-membership query algorithm is the key element within the PFEs which require the following essential properties: high link-bandwidth, high port-density, high forwarding speed, high scalability, and affordable cost. Current group-membership query approaches such as Bloom filter (BF) and Scalar-Pair Vectors Routing and Forwarding (SVRF) still suffer from serious weaknesses in terms of the space/time inefficiency, false-positive error, and low maintainability, etc. To accommodate these weaknesses, we propose an improved forwarding scheme–M-way Scaler-matrix and Vectors Routing and Forwarding (M-way SVRF) by re-examining the idea of the original SVRF. The M-way SVRF divides a ρ-bit port identifier into M-sub-blocks in the memory unit, thus element's keys belonging to distinct sub-blocks are able to reuse relatively smaller identical prime keys. Compared to previous works, simulation results show that the membership queries can be partitioned to leverage task parallelism, and better performance in the aspects of memory consumption and computational complexity, especially when the port-density of optical PFE is sufficiently high.

Radio frequency (RF) spectrum is highly occupied and adding further broadband channels to fulfill the exiting user requirements has become difficult. Optical free-space communication can be regarded a possible alternative as it offers several potential advantages such as reliable connectivity, secure link, higher data rates, and large bandwidth. Consequently, free-space optical (FSO) communication system which is the most dominant optical wireless technology has become more attractive in current era to deploy additional broadband channels, and it can support bandwidth-hungry services. FSO has appealing benefits such as easy deployment, inherited secure communication, higher data rate, non-interfering link, and licensed-free large spectrum. FSO communication links are also susceptible to several meteorological situations including smog, fog, scintillation, smoke, snow, and dust. A critical research question is to ensure connectivity under these adverse circumstances. FSO communication is severally hampered by link attenuation, atmospheric turbulence, and line-of-sight (LOS) demands. To overcome these challenges, relay nodes can be employed to improve coverage area and error rate of FSO communication system. However, relay nodes cannot overcome pointing errors in FSO communication due to various critical factors such as building sway. To enhance the availability of FSO systems, a redundant backup RF link to form a hybrid network is a viable solution. The coexistence of both RF and optical system is proposed to tackle challenges as mentioned before and attain benefits of both spectrums. A hybrid FSO/RF technology is promising as it can substantially enhance the availability and reliability than individual channels and offers unique solution to high-throughput wireless connectivity, comparable data rates, and insensitivity to weather conditions. This hybridization approach can help both channels to jointly recover the deficiencies of each technology and secure efficient data transmission with highly variable channel conditions. The immediate switching in hybrid FSO/RF systems can enable suboptimal usage of FSO network. In this study, we examine switching techniques, routing protocols, channel models, and modulation schemes. We outline several projects discussed in literature and examine various application scenarios. Finally, we discuss potential challenges, physical layer security issues and associated practical solutions.

Free space optical (FSO) communication refers to the information transmission technology based on the propagation of optical signals in space. FSO communication requires that the transmitter and receiver directly see each other. High-altitude platforms (HAPs) have been proposed for carrying FSO transceivers in the stratosphere. A multihop HAP network with FSO links can relay traffic between ground FSO nodes. In this study, we propose an end-to-end switching model for forwarding traffic between massive pairs of ground FSO nodes over a HAP network. A protection mechanism is employed for improving the communication survivability in the presence of clouds, which may break the line of sight (LoS) between HAPs and ground nodes. We propose an algorithm to identify a set of necessary HAPs and to design the HAP network topology in integrating the protection mechanism. The design aims to a network with the minimal equipment cost. The results demonstrate that, even though networks with survivable capacity use more resources, they are not necessary much more expensive than those without survivability in terms of equipment, i.e., HAPs and FSO devices, and in terms of wavelength resource utilization.

10-Gigabit passive optical network (XG-PON) has emerged as an effective architecture to meet today's growing demand for bandwidth in the family of next-generation passive optical networks (NG-PON). It supports various quality of services such as voice, video live streaming, network browsing, etc., where these services demand bandwidth, which is limited. To overcome this limitation, bandwidth management schemes are employed by central authorities such as optical line terminals (OLT). Several dynamic bandwidth allocation (DBA) schemes exist for XG-PON in the literature, but these lack in detailed information about XG-PON and a comparison of various DBA schemes in one place. Therefore, this paper presents a detailed architecture of XG-PON and comprehensively reviews the existing dynamic bandwidth allocation schemes for the XG-PON system. This paper further identifies and implements majorly adopted bandwidth allocation schemes such as GIANT, X-GIANT, IACG, and EBU using a pre-existing module of XG-PON in the network simulator 3 (NS-3) simulation framework. The results have been obtained in two phases having different traffic scenarios, where, in phase 1, the load of all ONUs has been increased simultaneously, and in phase 2, the load of only one ONU has been increased. The obtained results have been analysed in terms of various network performance metrics. Hence, this paper reviews the available DBA schemes and provides a comprehensive analysis of the identified important DBA schemes.

Multicasting is inevitable in the advent of the age of online video streaming. Light trail, the unidirectional optical bus, enhances multicasting by facilitating sub wavelength granularity. Splitting a light trail into segments increases the bandwidth utilization. To remove the overburden of the auxiliary graph of the existing works lead the motivation of the proposed heuristic algorithm known as Dynamic Multicast Traffic Grooming and Split Light Trail Assignment (DMTG-SLTA), which further aims to reduce the blocking probability and other network resources while satisfying the dynamic connection requests. Simulation results are verified though numerical analysis and compared to the existing well known algorithms, thereby concluding the proposed work to be successful only after minimizing its computational complexity.

Fault management has long been an indispensable component for controlling and managing telecommunication networks. To prevent huge data losses, it is necessary to develop a fast and efficient fault localization mechanism. In this work, we study the problem of multi-failure localization in transparent optical networks. In this context, a correlation-based approach is introduced to exploit the quality of transmission of acquired lightpaths to localize the faulty links. The proposed search-based framework can be implemented by leveraging any search algorithm. One may utilize the exhaustive search method to localize faulty links more accurately, but at the cost of taking more time. On the other hand, one may utilize intelligent search methods with the aim of reducing the required time for localization at the expense of accuracy. However, we propose to use both of the search approaches together. In this way, faulty links are first localized by the intelligent search methods to reroute and restore the failed traffic as fast as possible to prevent further loss of data. To this aim, a genetic algorithm (GA) is proposed to search among the suspected links. Subsequently, exhaustive search method can be utilized to localize failures more accurately without time constraint and then send technicians to the right site to recover the faulty links. The obtained results reveal that the proposed GA approach achieves overall high localization accuracy (98.6%–100%) that is insignificantly affected as the traffic load decreases. Dual and triple-failure incidents are localized within 42–80 ms and 596–2180 ms, respectively. It is shown that the mean time required for localizing failures using the GA search algorithm is significantly lower than exhaustive search approach by several orders of magnitude. Hence, the proposed GA-based fault localization algorithm can reduce the average time required to restore the traffic in case of failures, applicable for the restoration applications.