Showing papers in "IEEE\/OSA Journal of Optical Communications and Networking in 2015"
TL;DR: An overview is given of currently available optical fronthaul technologies, and of recently started activities toward more efficient and scalable solutions, and an outlook is given into which 5G specific service characteristics may further impact future backhaul, midhaul, and fr onthaul networks.
Abstract: Centralized processing is expected to bring about substantial benefits for wireless networks both on the technical side and on the economic side. While this concept is considered an important part of future radio access network architectures, it is more and more recognized that the current approach to fronthauling by employing the Common Public Radio Interface protocol will be inefficient for large-scale network deployments in many respects, and particularly for the new radio network generation 5G. In this paper, an overview is given of currently available optical fronthaul technologies, and of recently started activities toward more efficient and scalable solutions, and finally an outlook is given into which 5G specific service characteristics may further impact future backhaul, midhaul, and fronthaul networks.
187 citations
TL;DR: In this work, the performance and the capacity analysis of a fixed-gain amplify-and-forward (AF)-based dual-hop asymmetric radio frequency-free space optical (RF-FSO) communication system is performed and the effects of fading, turbulence, and pointing error are studied on the outage probability, average BER, and the channel capacity.
Abstract: In this work, the performance and the capacity analysis of a fixed-gain amplify-and-forward (AF)-based dual-hop asymmetric radio frequency–free space optical (RF–FSO) communication system is performed. The RF link experiences Nakagami-m fading and the FSO link experiences Gamma–Gamma turbulence. For this mixed RF–FSO cooperative system, novel and finite power series-based mathematical expressions for the cumulative distribution function, probability density function, and moment generating function of the end-to-end signal-to-noise ratio are derived. Using these channel statistics new finite power series-based analytical expressions are obtained for the outage probability, the average bit error rate (BER) for various binary and M-ary modulation techniques, and the average channel capacity of the considered system. The same analysis is also performed for the scenario when the FSO link undergoes significant pointing errors along with the Gamma–Gamma distributed turbulence. As a special case analytical expressions for the outage probability, BER, and channel capacity are also presented for a dual-hop asymmetric RF–FSO system where the RF link is Rayleigh distributed. Simulation results validate the proposed mathematical analysis. The effects of fading, turbulence, and pointing error are studied on the outage probability, average BER, and the channel capacity.
186 citations
TL;DR: The hybrid WiFi-VLC system is proposed, which outperforms the conventional WiFi for crowded environments in terms of throughput and Web page loading time, and the further improved performance of the aggregated system when considering the blocking duration and the distance between the access point and the user device is demonstrated.
Abstract: Visible light communication (VLC) has wide unlicensed bandwidth, enables communication in radiofrequency-sensitive environments, realizes energy-efficient data transmission, and has the potential to boost the capacity ofwireless access networks through spatial reuse. On the other hand, WiFi provides more coverage than VLC and does not suffer from the likelihood of blockage due to the line-of-sight requirement of VLC. In order to take the advantages of both WiFi and VLC, we propose and implement two heterogeneous systems with Internet access. One is the hybrid WiFi–VLC system, utilizing a unidirectional VLC channel as the downlink and reserving the WiFi backchannel as the uplink. The asymmetric solution resolves the optical uplink challenges and benefits from the full-duplex communication based on VLC. To further enhance the robustness and increase throughput, the other system is presented, in which we aggregate WiFi and VLC in parallel by leveraging the bonding technique in the Linux operating system. We also theoretically prove the superiority of the aggregated system in terms of average system delay. Online experiment results reveal that the hybrid system outperforms the conventional WiFi for crowded environments in terms of throughput and Web page loading time, and also demonstrate the further improved performance of the aggregated system when considering the blocking duration and the distance between the access point and the user device.
129 citations
TL;DR: This paper proposes and evaluates mobile VLC systems that operate at 10 Gbps and achieves significant improvements in the SNR over other systems in the worst case scenario in the considered real indoor environment.
Abstract: Over the past decade, visible light communication (VLC) systems have typically operated between 50 Mbps and 3.4 Gbps. In this paper, we propose and evaluate mobile VLC systems that operate at 10 Gbps. The enhancements in channel bandwidth and data rate are achieved by the introduction of laser diodes (LDs), angle diversity receivers (ADR), imaging receivers, relay nodes, and delay adaptation techniques. We propose three mobile VLC systems: an ADR relay assisted LD-VLC, an imaging relay assisted LD-VLC (IMGR-LD), and select-the-best imaging relay assisted LD-VLC. The ADR and imaging receiver are proposed for the VLC system to mitigate the intersymbol interference, maximize the signal-to-noise ratio (SNR), and reduce the impact of multipath dispersion due to mobility. The combination of IMGR-LD with a delay adaptation technique adds a degree of freedom to the link design, which results in a VLC system that has the ability to provide high data rates under mobility. The proposed IMGR-LD system achieves significant improvements in the SNR over other systems in the worst case scenario in the considered real indoor environment.
116 citations
TL;DR: In this paper, energy-efficient traffic grooming in IP-over-elastic optical networks with a sliceable optical transponder is studied, and three bandwidth-variable transponders (BVTs) based on their sliceability are investigated.
Abstract: The sliceable optical transponder, which can transmit/receive multiple optical flows, was recently proposed to improve a transponder's flexibility. The upper-layer traffic can be offloaded onto an optical layer with “just-enough transponder” resources. Traffic grooming evolves as the optical transponder shifts from fixed to sliceable. “Optical-layer grooming” enabled by a sliceable optical transponder can reduce the number of power-consumption components (e.g., IP ports and optical transponders). In this paper, energy-efficient traffic grooming in IP-over-elastic optical networks with a sliceable optical transponder is studied. Three bandwidth-variable transponders (BVTs) based on their sliceability, namely, non-sliceable BVTs, fully sliceable BVTs, and partially sliceable BVTs, are investigated. For each transponder, we develop energy-minimized traffic grooming integer linear programming (ILP) models and corresponding heuristic algorithms. Comprehensive comparisons are performed among the three types of transponders, and two interesting observations emerge. First, we find that significant power savings can be achieved by using a sliceable optical transponder. Second, we find that power savings do not keep improving linearly while transponder sliceability is increasing, and traditional electrical-layer grooming is still required to work together with optical-layer grooming to reduce power consumption.
98 citations
TL;DR: The proposed scheme is able to save about 50% of the signaling cost of the VHO process without an obvious loss in system performance and is adaptable to different scenarios.
Abstract: Visible light communication (VLC) is a promising complementary technology to its radio frequency (RF) counterpart. Heterogeneous VLC-WiFi systems offer a solution for future indoor communications that combines VLC to support high data rate transmission and RF to support reliable connectivity. In such heterogeneous systems, vertical handover (VHO) is critical for improving the system performance. This paper investigates an efficient VHO scheme. We formulate it as a Markov decision process problem and adopt a dynamic approach to obtain a tradeoff between the switching cost and the delay requirement. The proposed scheme determines whether to perform VHO given the queue length and the condition of the optical wireless channel (available or unavailable). The simulation results demonstrate that the proposed scheme is able to save about 50% of the signaling cost of the VHO process without an obvious loss in system performance. Moreover, the proposed scheme is adaptable to different scenarios.
90 citations
TL;DR: This work proposes virtualizing the tenant SDN control functions of a VTN and moving them into the cloud, and experimentally assess and evaluate the first SDN/NFV orchestration architecture in a multipartner testbed to dynamically deploy independent SDN controller instances for each instantiatedVTN and to provide the required connectivity within minutes.
Abstract: Software-defined networking (SDN) and network function virtualization (NFV) have emerged as the most promising candidates for improving network function and protocol programmability and dynamic adjustment of network resources. On the one hand, SDN is responsible for providing an abstraction of network resources through well-defined application programming interfaces. This abstraction enables SDN to perform network virtualization, that is, to slice the physical infrastructure and create multiple coexisting application-specific virtual tenant networks (VTNs) with specific quality-of-service and service-levelagreement requirements, independent of the underlying optical transport technology and network protocols. On the other hand, the notion of NFV relates to deploying network functions that are typically deployed in specialized and dedicated hardware, as software instances [called virtual network functions (VNFs)] running on commodity servers (e.g., in data centers) through software virtualization techniques. Despite all the attention that has been given to virtualizing IP functions (e.g., firewall; authentication, authorization, and accounting) or Long-Term Evolution control functions (e.g., mobility management entity, serving gateway, and packet data network gateway), some transport control functions can also be virtualized and moved to the cloud as a VNF. In this work we propose virtualizing the tenant SDN control functions of a VTN and moving them into the cloud. The control of a VTN is a key requirement associated with network virtualization, since it allows the dynamic programming (i.e., direct control and configuration) of the virtual resources allocated to the VTN. We experimentally assess and evaluate the first SDN/NFV orchestration architecture in a multipartner testbed to dynamically deploy independent SDN controller instances for each instantiated VTN and to provide the required connectivity within minutes.
90 citations
TL;DR: Simulation results show that the proposed FDAPA-Holograms system can reduce the time required to identify the optimum hologram position from 64 ms taken by a classic adaptive hologram to about 14 ms, and the fast search algorithm introduced that is based on a D&C algorithm reduces the computation time required.
Abstract: In this paper, we introduce a new adaptive optical wireless system that employs a finite vocabulary of stored holograms. We propose a fast delay, angle, and power adaptive holograms (FDAPA-Holograms) approach based on a divide and conquer (D&C) methodology and evaluate it with angle diversity receivers in a mobile optical wireless system. The ultimate goal is to increase the signal-to-noise ratio (SNR), reduce the effect of intersymbol interference, and eliminate the need to calculate the hologram at each transmitter and receiver location. A significant improvement is achieved in the presence of demanding background illumination noise, receiver noise, multipath propagation, mobility, and shadowing typical in a realistic indoor environment. The combination of beam delay, angle, and power adaptation offers additional degrees of freedom in the link design, resulting in a system that is able to achieve higher data rates (5 Gb/s). At a higher data rate of 5 Gb/s and under eye safety regulations, the proposed FDAPA-Holograms system offers around 13 dB SNR with full mobility in a realistic environment where shadowing exists. The fast search algorithm introduced that is based on a D&C algorithm reduces the computation time required to identify the optimum hologram. Simulation results show that the proposed system, FDAPA-Holograms, can reduce the time required to identify the optimum hologram position from 64 ms taken by a classic adaptive hologram to about 14 ms.
81 citations
TL;DR: Novel techniques are presented for disaster-aware datacenter placement and content management in cloud networks that can mitigate loss by avoiding placement in given disaster-vulnerable locations and reducing network resource usage and satisfying quality-of-service requirements.
Abstract: Recent targeted attacks and natural disasters have made disaster-resilient cloud network design an important issue. Network operators are investigating proactive and reactive measures to prevent huge data loss and service disruptions in case of a disaster. We present novel techniques for disaster-aware datacenter placement and content management in cloud networks that can mitigate such loss by avoiding placement in given disaster-vulnerable locations. We first solve a static disaster-aware datacenter and content placement problem by adopting an integer linear program with the objective to minimize risk, defined as expected loss of content. It is a measure of how much, in terms of cost or penalty, a network operator may lose probabilistically due to possible disasters in a cloud network. We also show how a service provider's budget constraint can affect disaster-aware placement design. Since disaster scenarios, content popularity, and/or importance are always changing in time, content placement should rapidly adapt to these changes. We propose a disaster-aware dynamic content-management algorithm that can adjust the existing placement based on dynamic settings. Besides reducing the overall risk and making the network disaster-aware, reducing network resource usage and satisfying quality-of-service requirements can also be achieved in this approach. We also provide a cost analysis of employing a dynamic disaster-aware placement design in the network based on real-world cloud pricing.
71 citations
TL;DR: An inter-domain protocol to facilitate FA-RSA in multi-domain SD-EONs with the cooperation of multiple OpenFlow controllers is designed and implemented and the experimental results indicate that the OpenFlow-controlled DF systems perform well and can improve the performance of SD- EONs effectively.
Abstract: Spectrum fragmentation limits the efficiency of spectrum utilization in elastic optical networks (EONs). This paper studies how to take advantage of the centralized network control and management provided by software-defined EONs (SD-EONs) for realizing OpenFlow-assisted implementation of online defragmentation (DF). We first discuss the overall system design and OpenFlow protocol extensions to support efficient online DF and conduct DF experiments with routing and spectrum assignment (RSA) reconfigurations in a single-domain SD-EON. Then, we propose to realize fragmentation-aware RSA (FA-RSA) in multi-domain SD-EONs with the cooperation of multiple OpenFlow controllers. In order to provision inter-domain lightpaths with restricted domain visibility on intradomain resource utilization, we design and implement an inter-domain protocol to facilitate FA-RSA in multi-domain SD-EONs and demonstrate controlling the spectrum fragmentation on inter-domain links with FA-RSA. Our experimental results indicate that the OpenFlow-controlled DF systems perform well and can improve the performance of SD-EONs effectively.
67 citations
TL;DR: This paper investigates the problem of joint defragmentation (DF) for the spectrum and IT resources in EO-DCIs by reoptimizing the allocations of multidimensional resources jointly with complexity-controlled network reconfigurations.
Abstract: With its agile spectrum management in the optical layer, the flexible-grid elastic optical network can become a promising physical infrastructure to efficiently support the highly dynamic traffic in future datacenter interconnections (DCIs). While the resulting elastic optical DCIs (EO-DCIs) need to serve requests that not only require bandwidth resources on fiber links but also require multidimensional IT resources in the DCs, multidimensional resource fragmentation can occur during dynamic network operations and deteriorate the network performance. To address this issue, this paper investigates the problem of joint defragmentation (DF) for the spectrum and IT resources in EO-DCIs. Specifically, we reoptimize the allocations of multidimensional resources jointly with complexity-controlled network reconfigurations. For the DFoperation, we first study the request selection process and propose a joint selection strategy that can perform the spectrum- and IT-oriented selections adaptively according to the network status. Then, we formulate a mixed integer linear programming model and design several heuristics to tackle the problem of network reconfiguration in the joint DF. The proposed algorithms are evaluated with extensive simulations. Simulation results demonstrate that the proposed joint DF algorithms can significantly reduce the blocking probability in EO-DCIs by consolidating the spectrum and IT resource usages effectively.
TL;DR: A network optimization method, exploiting the correlation between sites and single-site availabilities, is proposed and the cloud data are used to find several optimal OGS networks and to simulate the networks' availabilities and temporal behaviors.
Abstract: Space-to-ground optical data links enable higher data rates, require less electrical power, and allow more compact system designs than their corresponding RF counterparts. They may be applied to, for example, downlink Earth observation data from low Earth orbit satellites, or as so-called feeder links for data transmission to geostationary telecommunication or multimedia satellites. However, optical space-to-ground links suffer from limited availability due to cloud blockage. The application of optical ground station (OGS) diversity and thus a network of OGS is required to overcome this limitation. In this paper, we report on OGS networks and the calculation of combined network availabilities. Five years of cloud data gathered by a Meteostat Second Generation satellite have been evaluated. Single- and joint-site statistics as well as correlation between OGS sites are introduced. In order to effectively reduce computational effort, a network optimization method, exploiting the correlation between sites and single-site availabilities, is proposed. Furthermore, the cloud data are used to find several optimal OGS networks and to simulate the networks' availabilities and temporal behaviors. Optimal German, European, and intercontinental networks are identified. With the increasing number of stations, the German network converges to an availability of 84.7%, and the European network to around 99.9%. The intercontinental network even reached an availability of 100% for nine or more stations during the considered time span.
TL;DR: A dynamic restoration scheme for EONs based on the SDN framework is proposed that contemporarily exploits centralized path computation and node configuration to avoid contentions during the recovery procedure with the final aim of minimizing the recovery time.
Abstract: Optical transport networks typically deploy dynamic restoration mechanisms in order to automatically recover optical connections disrupted by network failures. Elastic optical networks (EONs), currently emerging as the next-generation technology to be adopted in optical transport, introduce new challenges for traditional generic multiprotocol label-switching (GMPLS)-based restoration that may seriously impact the achievable recovery time. At the same time, the software-defined networking (SDN) framework is emerging as an alternative control plane. It is therefore important to investigate possible benefits provided by SDN in the implementation of restoration mechanisms for EONs. This paper proposes a dynamic restoration scheme for EONs based on the SDN framework. The proposed scheme contemporarily exploits centralized path computation and node configuration to avoid contentions during the recovery procedure with the final aim of minimizing the recovery time. The performance of the proposed scheme is evaluated by means of simulations in terms of recovery time and restoration blocking probability and compared against three reference schemes based on GMPLS and SDN.
TL;DR: This work designs two node mapping strategies: one is sequential selection using efficient weights defined by the availability information, while the other uses auxiliary graphs to transform the problem into a classical problem in graph theory, i.e., the maximum-weight maximum clique.
Abstract: In this work, we study the availability-aware survivable virtual network embedding (A-SVNE) problem in optical interdatacenter networks that use wavelength-division multiplexing. With A-SVNE, we try to satisfy the availability requirement of each virtual component (i.e., a virtual link or a virtual node) in a virtual network. We first analyze the availability of a virtual component based on the availabilities of the substrate link(s) and node(s). Then, we formulate an integer linear programming model for the A-SVNE problem and propose several time-efficient heuristics. Specifically, we design two node mapping strategies: one is sequential selection using efficient weights defined by the availability information, while the other uses auxiliary graphs to transform the problem into a classical problem in graph theory, i.e., the maximum-weight maximum clique. Finally, we use extensive simulations to compare the proposed A-SVNE algorithms with existing ones in terms of the blocking probability, availability gap, and penalty due to service-level agreement violations, and the results indicate that our algorithms perform better.
TL;DR: An auxiliary graph model is proposed to address multilayer virtual network mapping in a dynamic traffic scenario and can be achieved by adjusting weights of the edges of the auxiliary graph, which depends on the purposes of the network operators.
Abstract: Network virtualization is meant to improve the efficiency of network infrastructure by sharing a physical substrate network among multiple virtual networks. Virtual network embedding (VNE) determines how to map a virtual network request onto a physical substrate. In this paper, we first overview three possible underlying substrates for interdatacenter networks, namely an electrical-layer-based substrate, an optical-layer-based substrate, and a multilayer-based (optical and electrical layer) substrate. Then, the corresponding VNE problems for the three physical substrates are discussed. The work presented focuses on VNE over a multilayer optical network; a key problem is how to map a virtual network request onto either an electrical or optical substrate. We propose an auxiliary graph model to address multilayer virtual network mapping in a dynamic traffic scenario. Different node-mapping and link-mapping policies can be achieved by adjusting weights of the edges of the auxiliary graph, which depends on the purposes of the network operators.
TL;DR: In this article, the performance of a multicarrier code-division multiple access (MC-CDMA) system using intensity modulation/direct detection scheme suitable for an indoor visible light communication (VLC) environment was evaluated.
Abstract: In this paper, we present a design methodology with implementational insight and evaluate the performance of a multicarrier code-division multiple access (MC-CDMA) system using intensity modulation/direct detection scheme suitable for an indoor visible light communication (VLC) environment. The proposed system is a CDMA system based on an orthogonal frequency division multiplexing (OFDM) platform. To overcome the light-dimming issue, we use a newly proposed methodology, namely, polarity reversed optical OFDM (PRO-OFDM). A unipolar signal is either added to the minimum current or subtracted from the maximum current in the LED linear current range to provide various amounts of dimming. The CDMA part employs Hadamard sequences to provide synchronous resource sharing. Combining the robustness of orthogonal modulation with the flexibility of CDMA schemes makes the proposed system a viable candidate for future indoor wireless communications such as VLC. The performance of the proposed MC-CDMA is evaluated, and mathematical formulations for the proposed system are derived. For example, closed-form equations for the signal-to-interference-plus-noise ratio and bit error rate (BER) performance are obtained. Furthermore, the analytical formulations are used in numerical analysis to verify the BER performance achieved in simulation results.
TL;DR: The joint resource allocation in flexible-grid networks based on a nonlinear physical layer impairment model is studied to assign resources and guarantee the signal quality for every channel and the maximum spectrum usage is shown to be insensitive to the ordering of channels.
Abstract: In this paper, we study the joint resource allocation in flexible-grid networks based on a nonlinear physical layer impairment model. An optimization problem is formulated to assign resources and guarantee the signal quality for every channel. Compared with the resource allocation in a fixed-grid wavelength-division multiplexing scenario, our method achieves significant bandwidth reduction and transmission distance extension in flexible- grid networks. The maximum spectrum usage is shown to be insensitive to the ordering of channels. We also analyze the relation between modulation formats and transmission distance based on the results of the proposed method. Finally, we demonstrate the performance and scalability of the proposed algorithm in ring networks.
TL;DR: Experimental results validate the successful setup of virtual network slices for intra-data center interconnect and quality of service (QoS) guarantee for high-priority application flows and enable the implementation and experimental validation of load balancing algorithms to improve the QoS performance.
Abstract: Optical packet switching (OPS) can enhance the performance of data center networks (DCNs)by providing fast and large-capacity switching capability. Benefiting from the software-defined networking (SDN) control plane, which could update the look-up-table (LUT) of the OPS, virtual DCNs can be flexibly created and reconfigured. In this work, we have implemented and assessed an SDN-based control framework for an OPS node, where the OpenFlow protocol has been extended in support of the OPS switching paradigm. Application flows are switched by the OPS at submicrosecond hardware speed, decoupled from the slower (millisecond timescale) SDN control operation. By the DCN infrastructure provider, the virtual networks become directly programmable with the abstraction of the underlying OPS node. Experimental results validate the successful setup of virtual network slices for intra-data center interconnect and quality of service (QoS) guarantee for high-priority application flows. Data plane resources are efficiently shared by exploiting statistical multiplexing. In addition, the capability of exposing per-port OPS traffic statistics information to the SDN controller enables the implementation and experimental validation of load balancing algorithms to improve the QoS performance.
TL;DR: The filtering-induced tradeoffs among upstream transmission capacity, filter design flexibility, and filter DSP complexity are examined, based on which optimum filter design guidelines are identified for various application scenarios.
Abstract: Digital filter multiple access (DFMA) passive optical networks (PONs) are, for the first time to our knowledge, proposed and extensively investigated, where digital signal processing (DSP)-enabled, software-reconfigurable, digital orthogonal filtering is employed in each individual optical network unit (ONU) and the optical line terminal to enable all ONUs to dynamically share the transmission medium under the control of the centralized software-defined controller and the transceiver-embedded DSP controllers. The DFMA PONs fully support software-defined networking with the network control further extended to the physical layer. As digital filtering is the fundamental process at the heart of the proposed DFMA PONs, the filtering-induced tradeoffs among upstream transmission capacity, filter design flexibility, and filter DSP complexity are examined, based on which optimum filter design guidelines are identified for various application scenarios. Furthermore, the performance characteristics of the DFMA PONs are also numerically explored in terms of maximum achievable upstream transmission capacity, differential ONU launch power dynamic range, and ONU count-dependent minimum received optical power.
TL;DR: Three promising sets of OGSs in the vicinity of existing ingress and egress points of a selected pan-European optical fiber network are reported, optimized for reaching at least 99.9% feeder link availability while minimizing the overall cost of the system.
Abstract: High-data-rate space-to-ground optical links are anticipated to be an alternative to radio-frequency spectrum congestion for the next generation of high-throughput geostationary satellites. An affordable site diversity system based on several optical ground stations (OGSs) and an optical fiber network is necessary to overcome cloud obstruction of the feeder link. In this paper, we report three promising sets of OGSs in the vicinity of existing ingress and egress points of a selected pan-European optical fiber network. These OGS networks are optimized for reaching at least 99.9% feeder link availability while minimizing the overall cost of the system. For the first time, the optical fiber network between OGSs is optimized using existing high-data-rate fiber links to limit its expense. The resulting cost estimates for each OGS network highlight the need to define a new cost model considering optical feeder link specificity. In addition, the link availability is simulated using a 2 year cloud mask data bank, taking into consideration practical cloud blockage forecasting duration and assuming optical transmission through thin ice clouds.
TL;DR: This paper proposes an auxiliary-graph-based algorithm, namely, parallel VI mapping (PAR), to offer dedicated protection against any single physical node or link failure, and demonstrates that the PAR algorithm can significantly reduce the VI request blocking probability and improve the traffic-carrying capacity of the networks, compared to the baseline sequential VI mapping approaches.
Abstract: Efficiently mapping multiple virtual infrastructures (VIs) onto the same physical substrate with survivability is one of the fundamental challenges related to network virtualization in transport software-defined networks (T-SDNs). In this paper, we study the survivable VI mapping problem in T-SDNs with the objective of minimizing the VI request blocking probability. In particular, we address the subproblems of modulation selection and spectrum allocation in the process of provisioning optical channels to support virtual links, taking into consideration the optical layer constraints such as the transmission reach constraint and the spectral continuity constraint. We propose an auxiliary-graph-based algorithm, namely, parallel VI mapping (PAR), to offer dedicated protection against any single physical node or link failure. More specifically, the PAR algorithm can jointly optimize the assignments of mapping the primary and backup VIs by adopting the modified Suurballe algorithm to find the shortest pair of node-disjoint paths for each virtual link. Through extensive simulations, we demonstrate that the PAR algorithm can significantly reduce the VI request blocking probability and improve the traffic-carrying capacity of the networks, compared to the baseline sequential VI mapping approaches.
TL;DR: Simulation results prove that the proposed RSA schemes can reduce the computational complexity significantly and provide network accommodation that is comparable to and traffic blocking probability that is similar to existing dynamic RSA schemes.
Abstract: Empowered by multirate transmission and bandwidth-variable switching technology, elastic optical networks (EONs) enhance spectrum utilization efficiency and increase network capacity to satisfy the rapid growth of Internet traffic. Routing and spectrum allocation (RSA) is one of the key elements in realizing EONs. However, previous RSA schemes with superior performance have had the drawback of high computational complexity. In this work, we focus on achieving superior RSA performance with reduced computational complexity. We first propose a dynamic network resource evaluation method that takes into account both the distribution of traffic bandwidth and the spectrum blocks’ carrying capability. Based on this, we introduce traffic-based fragmentation-aware concepts into the RSA steps. In the routing step, we propose a lowcomplexity fragmentation-aware load-balanced shortest path routing scheme and a modified fragmentation-aware load-balanced k-shortest-path routing scheme. In the spectrum allocation step, we propose an efficient traffic-based fragmentation-aware spectrum allocation scheme. Simulation results prove that the proposed RSA schemes can reduce the computational complexity significantly and provide network accommodation that is comparable to and traffic blocking probability that is similar to existing dynamic RSA schemes.
TL;DR: A multiple access scheme based on block encoding time division multiplexing (TDM) that provides a better performance than the conventional TDM and is more applicable to the accurate positioning of a moving device.
Abstract: In view of the application of a visible light positioning system in a public indoor environment with numerous light emitting diodes (LEDs), a long delay is one of the main factors that limits the performance of the positioning systemwith a moving device. To solve this problem, a multiple access scheme based on block encoding time division multiplexing (TDM) is proposed in this paper. In our scheme, nine LEDs compose one block to reduce the system delay. Meanwhile, in order to reduce intercell interference, an extended binary coded decimal code is used to encode signals transmitted by LEDs. The feasibility and performance of the scheme is demonstrated by simulations. The results show that the proposed TDMscheme provides a better performance than the conventional TDM and is more applicable to the accurate positioning of a moving device.
TL;DR: In this paper, a link-based mixed-integer linear programming (MILP) formulation is proposed to solve the optimal resource allocation problem in elastic optical networks. But the authors also show that the suboptimal recursive solution speeds up the calculation and makes the running time more predictable, compared to the optimal MILP.
Abstract: Compared to legacy wavelength division multiplexing networks, elastic optical networks (EONs) have added flexibility to network deployment and management. EONs can include previously available functionality, such as signal regeneration and wavelength conversion, as well as new features such as finer-granularity spectrum assignment and modulation conversion. Yet each added feature adds to the cost of the network. In order to quantify the potential benefit of each functionality, we present a link-based mixed-integer linear programming (MILP) formulation to solve the optimal resource allocation problem. We then propose a recursive model in order to either augment existing network deployments (spectrum and regenerators) or speed up the resource allocation computation time for larger networks with higher traffic demand requirements than can be solved using an MILP. We show through simulation that systems equipped with signal regenerators or wavelength converters require a notably smaller total bandwidth, depending on the topology of the network. We also show that the suboptimal recursive solution speeds up the calculation and makes the running time more predictable, compared to the optimal MILP.
TL;DR: This demonstration verifies the feasibility of implementing a compact high-capacity wavelength division multiplexing interconnect on a chip, which also enables many new advanced optic network functionalities on aChip scale.
Abstract: Optical interconnects have the potential to realize a scalable intra- and inter-chip communication infrastructure. They can meet the large bandwidth capacity and stringent latency requirements in a power-efficient fashion. Integration of photonics on silicon provides a path to a low-cost and highly scalable platform for this application. Here, we report an intra-chip 10 × 10 Gb/s optical link based on a large-scale silicon photonic integrated circuit with 72 functional elements. Furthermore, the optical circuit is reconfigurable as a 10 × 10 switch or a broadcasting network. This demonstration verifies the feasibility of implementing a compact high-capacity wavelength division multiplexing interconnect on a chip, which also enables many new advanced optic network functionalities on a chip scale.
TL;DR: Experimental results showed that the CPRI over TDM-PON meet the requirements of a mobile front-haul using CPRI by the implemented delay jitter reduction and low-latency bandwidth allocation techniques.
Abstract: In this paper, we experimentally and numerically evaluate the performance of a common public radio interface (CPRI) over a time division multiplexed passive optical network (TDM-PON) system for accommodating densely deployed small cells in centralized-radio-accessnetwork- based future radio access. A prototype of the CPRI over TDM-PON is developed by using Ethernet-based TDM-PON. Experimental results showed that its synchronization accuracy and latency meet the requirements of a mobile front-haul using CPRI by the implemented delay jitter reduction and low-latency bandwidth allocation techniques. An in-phase and quadrature (IQ) data compression technique is also implemented on the system to enable a higher accommodation of remote radio heads. Experiments confirmed that the compression technique meets open radio equipment interface standards in terms of latency and signal quality degradation. Numerical results showed that the technique with a 0.45 compression ratio increases the number of supportable remote radio heads from 3 to 7 for a mobile front-haul with a 100 μs latency limitation.
TL;DR: Results show that this scheme can realize all-optical encryption and decryption by using key-stream generators at high speed up to 250 Gb/s.
Abstract: We propose a scheme to realize high-speed all-optical encryption and decryption using key-stream generators and optical XOR gates utilizing the ultrafast two-photon absorption (TPA)-induced phase change in semiconductor optical amplifiers (SOAs). The key used for encryption and decryption is a high-speed all-optical pseudorandom bit sequence which is generated by a linear feedback shift register (LFSR) together with optical XOR and AND gates. The input intensities to the SOA are high enough so that the fast TPA-induced phase change is larger than the regular induced phase change. We also designed and investigated three more secure key-stream generators, i.e., a three LFSR cascaded design generator, an alternating step generator, and a shrinking generator. Results show that this scheme can realize all-optical encryption and decryption by using key-stream generators at high speed up to 250 Gb/s.
TL;DR: The status of standardization activities on the black link (BL) and corresponding alien wavelength concepts are reviewed and relevant work on control and management plane interoperability comprising generalized multi-protocol label switching and transport software defined networking aspects is presented.
Abstract: This paper aims to review the status of standardization activities on the black link (BL) and corresponding alien wavelength concepts. It discusses experimental work on filterless optical networks conducted within a dedicated Deutsche Telekom project. The general prospects and existing challenges concerning elastic extensions of the BL are also assessed. Furthermore, we present relevant work on control and management plane interoperability comprising generalized multi-protocol label switching and transport software defined networking aspects. In the second part of the article, we report on the latest dual-vendor experiments on data plane interoperability in terms of digital signal processing technology for next generation 1.28 Tb/s PM-16QAM super-channels. Finally, we present a network reachability analysis based on the widely used Gaussian noise model in the context of data plane interoperability. This analysis estimates the network-wide impact of the single-vendor versus the dual-vendor approach.
TL;DR: It is found that a cascade of linear filters can be combined into a single, truncated, linear, adaptive filter with negligible impact on receiver sensitivity, and by utilizing a multiplier-free tap weight update algorithm, the overall complexity of a digital coherent receiver can be significantly reduced, making it attractive for use in an ONU.
Abstract: Coherent receivers offer a potential solution for implementing a high-capacity, long-reach (up to 100 km) passive optical network (LR-PON), due mainly to their high sensitivity, frequency selectivity, and bandwidth efficiency. When using coherent receivers, received signals can be post-processed digitally to mitigate the specific impairments found in access networks and, additionally, relax the optical complexity requirements of the coherent receiver. However, the digital signal processing must itself be low complexity in order to minimize the overall complexity and power consumption of the optical network unit (ONU). This paper focuses on the impact of reduced complexity equalization algorithms on receiver sensitivity in a LR-PON. It is found that a cascade of linear filters can be combined into a single, truncated, linear, adaptive filter with negligible impact on receiver sensitivity. Additionally, by utilizing a multiplier-free tap weight update algorithm, the overall complexity of a digital coherent receiver can be significantly reduced, making it attractive for use in an ONU. Matched filtering, chromatic dispersion compensation, and polarization tracking are all performed by the adaptive equalizer. The performance of this low-complexity, multiplier-free equalizer is experimentally verified for 3 GBd polarization division multiplexed quadrature phase shift keying (12 Gbit/s) in both a back-to-back configuration and transmission over 100 km standard single-mode fiber.
TL;DR: This paper thoroughly analyzes the carrier sensing multiple access with collision avoidance (CSMA/CA) mechanism of the MAC protocol of this standard and Simulation results match the analytic ones very closely, which proves the validity of the proposed model.
Abstract: IEEE 802.15.7 is a physical and MAC layer standard for visible-light communication. This paper thoroughly analyzes the carrier sensing multiple access with collision avoidance (CSMA/CA) mechanism of the MAC protocol of this standard. The nodal behavior of the CSMA/CA mechanism is modeled using a Markov chain. Performance parameters are derived for saturated traffic in a star topology network. The derived performance metrics of the network include throughput, transmission probability, collision probability, packet discard probability, delay, and power consumption. Furthermore in order to improve the obtained analytic results, a semi-analytic approach is developed. To verify the obtained results, CSMA/CA is completely simulated in a MATLAB environment, and network parameters are derived and compared with analytic models. Simulation results match the analytic ones very closely, which proves the validity of the proposed model.