Optical Switching and Networking最新文献

In this paper, the joint problem of user association and power allocation for non-orthogonal multiple access (NOMA)-visible light communication (VLC) systems is investigated. First, a novel intelligent user association (UA) method for multi-user NOMA-VLC is proposed to improve the multiplexing efficiency. Second, a new adaptive optimal power allocation scheme based on the UA method is presented and three corresponding mathematical optimization problems are established, aiming to optimize the system throughput while each user's illumination requirement, quality of service demand, eye safety, and transmission power limit are satisfied simultaneously. Third, for the error propagation at the NOMA receiver, the perfect and imperfect interference cancellations are considered in the established power allocation models. Finally, the numerical results demonstrate the superiority of the proposed scheme on the VLC network capacity under perfect and imperfect interference cancellation. Furthermore, it is also found that the proposed scheme could achieve higher system throughput by modifying users' field-of-views (FOVs).

The rise of traffic intensive services and applications is pushing the limits of conventional single band Wavelength Division Multiplexing (WDM) optical networks. As an answer to this challenge, new data plane technologies are being investigated. Multi-band optical networks have raised as a very interesting candidate due to the potential increased capacity they offer thanks to the exploitation of multiple bands of the optical spectrum. Considering the whole telecom ecosystem, multi-band optical networks will coexist with other technological segments (e.g., Radio Access Network (RAN)) with the aim of provisioning services across the end-to-end infrastructure. With the advent of 5G and beyond 5G (B5G) architectures, novel provisioning paradigms are taking preponderance, such as the case of network slicing, which represents a radical paradigm change with respect to legacy business and provisioning models. As such, proper solutions for supporting network slice provisioning and runtime maintenance at the data plane are required. With this in mind, in this paper we present a control and orchestration architecture for the configuration and maintenance of network slices in multi-band optical networks, in support of B5G end-to-end services. Indeed, quality assurance and maintenance at all levels is seen as a cornerstone in B5G architectures. Thus, proper mechanisms adapted to the nature of the underlying sliceable multi-band data plane are required to ensure the quality of deployed slices. In this regard, we also present a novel band-adaptive protection scheme which takes advantage of the properties of the multi-band data plane so as to enhance the robustness of slices against quality degradations. We showcase the provisioning and maintenance of multi-band optical network slices by means of an experimental demonstration in a real testbed deployed at our premises. In addition, we evaluate the performance of the proposed band-adaptive protection scheme for slice quality assurance in front of other strategies by means of extensive simulation analysis in larger network scenarios.

The paper presents a Q-learning based dynamic routing algorithm for C+L band elastic optical networks (EONs) considering fiber impairments such as cross-phase modulation (XPM), self-phase modulation (SPM), amplified spontaneous emission (ASE), and inter-channel stimulated Raman scattering (ISRS). The effect of fragmentation is considered in the Q-learning process in addition to considering constraints related to spectrum continuity, contiguity, and non-overlapping. Three classical spectrum allocation strategies, first-fit, last-fit, and exact-fit are used after the Q-learning routing algorithm. The proposed routing, modulation, and spectrum allocation (RMSA) approach is shown to have a lower blocking probability compared with using K-shortest path routing combined with the three classical spectrum allocation strategies.

Wavelength division multiplexingtime division multiplexing passive optical network (WDM/TDM-PON) is the attractive candidate for PON bandwidth sharing among multiple service providers, featuring massive bandwidth and longer reach. This infrastructure reduces the overall cost of the Fiber-to-the-premises (FTTP) services and offers relatively lower tariffs for the end customers. The dynamic bandwidth and wavelength allocation (DBWA) process in such PON networks ensure the fair sharing of the available bandwidth resources among the virtual network operators ($\mathrm{vNOs}$). The earlier reported DBWA schemes with multiple $\mathrm{vNOs}$ have not efficiently utilized the unused and residual upstream bandwidth. This study presents a novel load adaptive merging algorithm (LAMA) for converting various individual virtual bandwidth maps($\mathrm{vBWmaps}$) into a single physical bandwidth map ($\mathrm{phyBWMap})$. The LAMA scheme modifies the existing strict priority scheme called the Priority-Based Merging Algorithm (PBMA) scheme and improves the performance of the merging engine by allocating the $\mathrm{phyBWMap}$ in a load adaptive manner to the $\mathrm{vNOs}$ in the multi-tenant PON architecture. The proposed algorithm is compared with PBMA in terms of throughput efficiency, upstream delay, and capacity utilization under self-similar and Poison traffic scenarios. The results show that the proposed scheme offers higher bandwidth utilization resulting in increased throughput with lower upstream delays in the multi-tenant PON environment.

Flexible Ethernet (FlexE)-over-WDM is one of the promising technologies of 5G transport networks that aims to provide a variety of Ethernet MAC rates over large capacity wavelength channels. Ultra-reliable communication is a key scenario of 5G, which poses a big challenge to the transport networks. To achieve ultra-reliability, frame replication and elimination for reliability (FRER) was proposed by IEEE. 802.1CB to provide redundant transmission in layer 2. However, previous studies of FRER considered to replicate MAC frames at source node and eliminate them at the destination, which may cause a waste of network resources, especially for the services that require different reliabilities in a condition of network with different packet loss rates of link and node. To this end, we propose a novel redundant routing scheme, called segment FRER (S-FRER), to balance the reliability and network efficiency. And a FlexE group allocation scheme is coming with S-FRER to assign the Flexible Ethernet channels along the path. Two heuristic algorithms, which are end-to-end FRER (E-FRER) and ordinal FRER (O-FRER), are compared with S-FRER. Simulation results show that S-FRER can satisfy diverse reliability requirements of services, and the resource redundancy and equipment cost are condensed.We further take the resource utilization efficiency as the optimization goal, and propose a FlexE Group allocation strategy based on segmented frame repetition and elimination to realize the resource redistribution of service flows on redundant routes. The experimental results verify the effectiveness of the scheme in terms of resource utilization efficiency.

Light fidelity (LiFi) is a wireless optical communication (WOC) technology that holds the key to solving the challenges of 5th and higher generation mobile networks. LiFi is a two-way wireless communication technology that enables high-speed transmission on both up and down links simultaneously. Today, researchers and manufacturers consider LiFi technology as an essential solution for radio frequency (RF) spectrum limitation due to growing demand of Internet users. In addition, integration of various communication technologies such as wireless fidelity (WiFi) and LiFi can help to overcome the traffic restriction challenge caused by the growing demand of Internet users. Although LiFi provides high-speed data transfer capability, it has some weaknesses such as coverage. So, hybrid WiFi/LiFi network can uses fast data transfer from LiFi and wide coverage from WiFi. Their integration can complement the shortcomings of each of these technologies and increases the network performance. In this work, while describing LiFi theory, the recent studies in this field are presented. Theoretical and practical concepts of LiFi-based indoor networks, issues such as network structures, cell deployment models, modulation techniques, multiple access schemes, criteria for measuring network performance, and scenario-based architectures for implementing a real LiFi-based indoor network based on up-to-date equipment manufactured by some LiFi manufacturers are discussed in detail.

In space division multiplexing-elastic optical networks (SDM-EONs), crosstalk and fragmentation are the significant factors determining overall resource utilization. Crosstalk and fragmentation management spectral resource allocation schemes can enhance the overall resource utilization in SDM-EONs. This paper proposes three crosstalk and fragmentation management bi-directional resource allocation schemes for multi-core SDM-EONs to suppress inter-core crosstalk and network fragmentation. A spatial resource partitioning method is presented to mitigate inter-core crosstalk, and this paper adopts a k-shortest path routing method to suppress fragmentation while spectral resource allocation. To the best of our knowledge, there is no such scheme that handles both crosstalk and fragmentation together while allocating spectral resources in a counter-propagating manner for multi-core fiber (MCF) SDM-EONs. The estimated result shows that the proposed scheme outperforms the traditional co-propagation method and enhances existing resource utilization by reducing blocked requests.

In a long-reach passive optical network (LR-PON), protection for optical network units (ONUs) against their distribution fiber (DF) failures is highly desirable to ensure uninterrupted Internet access to the associated users. In the distribution section of the LR-PON, shared-risk link groups (SRLGs) are formed by DFs due to sharing fiber cables and conduits. Most of the existing SRLG-aware DF protection schemes require residual bandwidth with ONUs. Therefore, they fail to provide protection to all ONUs under high reliability requirements (RRs) and result to be very cost-inefficient as well. We first propose a SRLG-aware reliability framework to compute the connection reliability of every ONU and joint reliability of every ONU-ONU pair and ONU-node pair. Thereafter, we propose two different SRLG-aware nonresidual bandwidth based partial protection schemes and their compatible architectures to provide partial DF protection to ONUs against SRLG failures to satisfy the given RR. Following the proposed schemes, we formulate two different integer linear programming (ILP) based optimization problems to set up backup connections by using backup DFs and other backup optical resources with the minimum protection cost. The proposed ILP-based protection planning models restrict the backup DF lengths to bound the propagation delay to satisfy the strict delay requirement for real-time applications. Since the proposed ILP-based models turn out to be computationally intractable for large network problems, we also propose two heuristic schemes that provide comparable results to that of the ILP-based models. We evaluate the performance of the proposed partial protection schemes with reference to the protection cost and total length of backup DFs (TLBDF). The exhaustive simulation results show that the proposed partial protection schemes not only satisfy high RRs, but also require a much lower protection cost, TLBDF, and optical power margin in comparison to the existing SRLG-aware protection schemes.

Benchmarking is commonly used in research fields, such as computer architecture design and machine learning, as a powerful paradigm for rigorously assessing, comparing, and developing novel technologies. However, the data centre network (DCN) community lacks a standard open-access and reproducible traffic generation framework for benchmark workload generation. Driving factors behind this include the proprietary nature of traffic traces, the limited detail and quantity of open-access network-level data sets, the high cost of real world experimentation, and the poor reproducibility and fidelity of synthetically generated traffic. This is curtailing the community's understanding of existing systems and hindering the ability with which novel technologies, such as optical DCNs, can be developed, compared, and tested.

We present TrafPy; an open-access framework for generating both realistic and custom DCN traffic traces. TrafPy is compatible with any simulation, emulation, or experimentation environment, and can be used for standardised benchmarking and for investigating the properties and limitations of network systems such as schedulers, switches, routers, and resource managers. We give an overview of the TrafPy traffic generation framework, and provide a brief demonstration of its efficacy through an investigation into the sensitivity of some canonical scheduling algorithms to varying traffic trace characteristics in the context of optical DCNs. TrafPy is open-sourced via GitHub and all data associated with this manuscript via RDR.