Showing papers in "IEEE\/OSA Journal of Optical Communications and Networking in 2017"
TL;DR: FlexEthernet and FlexOTN will be put in place to allow network operators to optimize capacity in their optical transport networks without manual changes to the client hardware.
Abstract: In this paper, we discuss building blocks that enable the exploitation of optical capacities beyond 100 Gb∕s. Optical networks will benefit from more flexibility and agility in their network elements, especially from coherent transceivers. To achieve capacities of 400 Gb∕s and more, coherent transceivers will operate at higher symbol rates. This will be made possible with higher bandwidth components using new electro-optic technologies implemented with indium phosphide and silicon photonics. Digital signal processing will benefit from new algorithms. Multi-dimensional modulation, of which some formats are already in existence in current flexible coherent transceivers, will provide improved tolerance to noise and fiber nonlinearities. Constellation shaping will further improve these tolerances while allowing a finer granularity in the selection of capacity. Frequency-division multiplexing will also provide improved tolerance to the nonlinear characteristics of fibers. Algorithms with reduced computation complexity will allow the implementation, at speeds, of direct pre-compensation of nonlinear propagation effects. Advancement in forward error correction will shrink the performance gap with Shannon’s limit. At the network control and management level, new tools are being developed to achieve a more efficient utilization of networks. This will also allow for network virtualization, orchestration, and management. Finally, FlexEthernet and FlexOTN will be put in place to allow network operators to optimize capacity in their optical transport networks without manual changes to the client hardware.
123 citations
TL;DR: This study investigates whether CoE can meet delay and jitter requirements by performing FPGA-based Verilog experiments and simulations and shows that the proposed scheduling policy of CoE flows on Ethernet can reduce jitter when redundant Ethernet capacity is provided.
Abstract: Common Public Radio Interface (CPRI) is a successful industry cooperation defining the publicly available specification for the key internal interface of radio base stations between the radio equipment control (REC) and the radio equipment (RE) in the fronthaul of mobile networks. However, CPRI is expensive to deploy, consumes large bandwidth, and currently is statically configured. On the other hand, an Ethernet-based mobile fronthaul will be cost-efficient and more easily reconfigurable. Encapsulating CPRI over Ethernet (CoE) is an attractive solution, but stringent CPRI requirements such as delay and jitter are major challenges that need to be met to make CoE a reality. This study investigates whether CoE can meet delay and jitter requirements by performing FPGA-based Verilog experiments and simulations. Verilog experiments show that CoE encapsulation with fixed Ethernet frame size requires about tens of microseconds. Numerical experiments show that the proposed scheduling policy of CoE flows on Ethernet can reduce jitter when redundant Ethernet capacity is provided. The reduction in jitter can be as large as 1 μs, hence making Ethernet-based mobile fronthaul a credible technology.
105 citations
TL;DR: The results show that implementing network coding can produce savings up to 37% on the ring topology and 23% considering typical topologies, and the impact of varying the demand volumes on the network coding performance is studied.
Abstract: In this work we investigate the use of network coding in 1 + 1 survivable IP-over-wavelength-division-multiplexing (WDM) networks by encoding the protection paths of multiple flows with each other at intermediate nodes. We study the energy efficiency of this scheme through mixed-integer linear programming (MILP) and a heuristic with five operating options. We evaluate the MILP and the heuristics on typical and regular network topologies. Our results show that implementing network coding can produce savings up to 37% on the ring topology and 23% considering typical topologies. We also study the impact of varying the demand volumes on the network coding performance.
102 citations
TL;DR: A look beyond the capabilities of SDM as a means of boosting transmission capacity is taken and ideas and concepts on how to exploit the spatial dimension for improved efficiency and resource sharing in optical networks are discussed.
Abstract: Space division multiplexing (SDM) is mainly seen as a means to increase data throughput and handle exponential traffic growth in future optical networks. But its role is certainly more diverse. Research on SDM encourages device integration, brings newfunctionality to network elements, and helps optical networks to evolve. As a result, the number of individual components in future networks will decrease, which in turn will improve overall network reliability and reduce power consumption as well as operational expenditure. After reviewing the state-of-the-art in SDMfiber research and development with a particular focus on weakly coupled single-mode multi-core fibers, we take a look beyond the capabilities of SDM as a means of boosting transmission capacity and discuss ideas and concepts on howto exploit the spatial dimension for improved efficiency and resource sharing in optical networks.
74 citations
TL;DR: A matheuristic for dynamic optical routing is introduced, which can be implemented as an application into a software-defined mobile carrier network and used to solve off-line mixed-integer linear programming instances of an optical routing (and wavelength) assignment optimization problem.
Abstract: In general, humans follow a routine with highly predictable daily movements. For instance, we commute from home to work on a daily basis and visit a selected set of places for commercial and recreational purposes during the nights and weekends. The use of mobile phones increases when commuting via public transportation, during lunch breaks, and at night. Such regular behavior creates predictable spatiotemporal fluctuations of traffic patterns. In this paper, we introduce a matheuristic for dynamic optical routing, which can be implemented as an application into a software-defined mobile carrier network. We use machine learning to predict tidal traffic variations in a mobile metro-core network, which allows us to solve off-line mixed-integer linear programming instances of an optical routing (and wavelength) assignment optimization problem. The optimal results are used to favor near-optimal on-line routing decisions. Results demonstrate the effectiveness of our on-line methodology, with results that match almost perfectly the behavior of a network that performs optical routing reconfiguration with a perfect, oracle-like traffic prediction and the solution of an optimization problem.
70 citations
TL;DR: A novel optical flat DCN architecture in which the number of interconnected ToRs scales as the square of the optical packet switches’ (OPS) port count (OPSquare) is proposed and investigated, which has a cost saving of 56% compared with H-LION for a 160,000-server DCN.
Abstract: Aiming at solving the scaling issues of bandwidth and latency in current hierarchical data center network (DCN) architectures, we propose and investigate a novel optical flat DCN architecture in which the number of interconnected ToRs scales as the square of the optical packet switches’ (OPS) port count (OPSquare). The proposed flat DCN architecture consists of two parallel interand intra-cluster networks that are built on a single-hop OPS with nanosecond time and wavelength switching for efficient statistical multiplexing operations. Fast optical flow control is implemented for solving packet contentions that may occur at the buffer-less optical switches. The performance of OPSquare DCN in terms of scalability, packet loss, latency, and throughput is assessed by a numerical simulation employing OMNeT++ under realistic data center (DC) traffic. The results report a server-to-server latency of less than 2 / s (including packet retransmission), a packet loss <10−5 at a load of 0.4, and aDC size of 10,240 servers with a ToR buffer size equal to 50 KB for all traffic patterns. Moreover, the cost and power consumption of the OPSquare DCN have been studied and compared with fat-tree DCN based on electrical switches and H-LION connected by an arrayed wave guide grating router (AWGR). The results indicate 23.8% and 39% cost and power savings, respectively, for the OPSquare DCN supporting 160,000 servers with respect to the fat-tree DCN. The OPSquare has a cost saving of 56% compared with H-LION for a 160,000-server DCN.
69 citations
TL;DR: A comprehensive investigation of both the illumination and communication coverages of an indoor MIMO-VLC system based on NHS-OFDM is presented and the analytical bit error rate expression of the system is derived.
Abstract: Visible light communication (VLC) using multiple-input multiple-output (MIMO) has great potential for future high-data-rate indoor wireless communications. Owing to the dual function of white light-emitting diodes (LEDs), i.e., illumination and communication functions, both the illumination and communication coverages need to be evaluated when implementing an indoor MIMO-VLC system. In this paper, we present a comprehensive investigation of both the illumination and communication coverages of an indoor MIMO-VLC system. Two techniques are applied in the MIMO-VLC system for communication coverage improvement, including a non-Hermitian symmetry orthogonal frequency division multiplexing (NHS-OFDM) modulation scheme and an imaging angle diversity receiver. A general indoor imaging MIMO-VLC system using NHS-OFDM is described and the analytical bit error rate expression of the system is derived. The impact of LED pairing on the communication coverage of an indoor imaging MIMO-VLC system based on NHS-OFDM is also analyzed.
62 citations
TL;DR: High-quality real-time video streaming over an underwater wireless optical communication (UWOC) link up to 5 m distance is experimentally demonstrated using phase-shift keying (PSK) modulation and quadrature amplitude modulation (QAM) schemes.
Abstract: We experimentally demonstrate high-quality real-time video streaming over an underwater wireless optical communication (UWOC) link up to 5 m distance using phase-shift keying (PSK) modulation and quadrature amplitude modulation (QAM) schemes. The communication system uses software defined platforms connected to a commercial TO-9 packaged pigtailed 520 nm directly modulated laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter and an avalanche photodiode (APD) module as the receiver. To simulate various underwater channels, we perform laboratory experiments on clear, coastal, harbor I, and harbor II ocean water types. The measured bit error rates of the received video streams are 1.0 × 10-9 for QPSK, 4-QAM, and 8-QAM and 9.9 × 10-9 for 8-PSK. We further evaluate the quality of the received live video images using structural similarity and achieve values of about 0.9 for the first three water types, and about 0.7 for harbor II. To the best of our knowledge, these results present the highest quality video streaming ever achieved in UWOC systems that resemble communication channels in real ocean water environments.
58 citations
TL;DR: Simulation results show that the reconfigurability of fronthaul can improve the CoMP service through elastic radio resource allocation and it is observed that MCG-LR achieves a lower inter-BBU CoMP ratio and lower BBU migration than BW-LR after lightpath (wavelength) reconfiguration.
Abstract: The fifth generation of mobile communication is characterized by ultra-dense cellular networks, where massive small cells are deployed in hot spots to increase the network capacity As a promising technology in the small-cell scenario, coordinated multipoint (CoMP) is proposed to improve cell-edge user throughput by converting inter-cell interference into useful signals In this paper, we study how reconfigurable fronthaul enabled by optical networks can help improve the CoMP service According to the baseband unit (BBU) that serves the purposes of coordination, we classify the CoMP service into intra-BBU CoMP and inter-BBU CoMP Inter-BBU CoMP will cause data exchange between the BBUs, which requires backhaul to support a large bandwidth and low latency Our proposal is to associate coordinated RRHs with a single BBU to reduce the data exchange To achieve this goal, we propose two heuristic algorithms: a minimum-cut graph-based lightpath reconfiguration (MCG-LR) and a BBU weightbased lightpath reconfiguration (BW-LR) The two algorithms are emulated on a time and wavelength division multiplexing passive optical network-based fronthaul under different cell conditions The simulation results show that the reconfigurability of fronthaul can improve the CoMP service through elastic radio resource allocation In addition, we can observe that MCG-LR achieves a lower inter-BBU CoMP ratio and lower BBU migration than BW-LR after lightpath (wavelength) reconfiguration
56 citations
TL;DR: In this article, the performance of a space shift keying (SSK) scheme in a free-space optical (FSO) communication system under indoor and outdoor conditions is analyzed. And the analytical bit error rate (BER) of an indoor N t χ 1 FSO-SSK system experiencing a deterministic channel is derived.
Abstract: In this paper, we study the performance of a space shift keying (SSK) scheme in a free-space optical (FSO) communication system under indoor and outdoor conditions. For the outdoor N t χ 1 FSO-SSK system, where N t is the number of transmitters (Txs), a novel closed-form mathematical expression for the probability density function (pdf) of the difference between two weighted gamma-gamma random variables is derived. Using this pdf, a new analytical expression is obtained for the tight upper bound of the average bit error rate (ABER) of this system. We also study the analytical bit error rate (BER) of an indoor N t χ 1 FSO-SSK system experiencing a deterministic channel. For this system, optimized values of transmit power weights are obtained by minimizing the analytical BER; it is observed that the optimized nonuniform power distribution is better than the uniform power distribution. However, for the outdoor FSO-SSK system, the best error performance can be achieved by employing uniform transmit power. An asymptotic BER analysis of uniformly weighted general outdoor FSO-SSK with an arbitrary number of Tx and receiver (Rx) apertures is also performed. Furthermore, the analytical coding gain and diversity order of the considered system are found based on the derived analytical BER expression. An interesting result observed from the coding gain analysis is that the performance of the outdoor FSO-SSK system remains unaltered from a moderate to a strong atmospheric turbulence regime, which makes the considered system nearly independent of turbulence. In addition, it is found by simulation and analysis that the considered system performs more poorly under the weak turbulence regime as compared to the other (strong and moderate) turbulence regimes. Our analysis also shows that the diversity order of the outdoor FSO-SSK system is N r /2, where N r is the number of Rx apertures, irrespective of the number of optical sources and turbulence conditions. In addition, it is observed that the performance of the FSO-SSK system degrades with an increasing number of optical sources under both indoor and outdoor conditions. Therefore, a trade-off between spectral efficiency and ABER is observed.
51 citations
TL;DR: This paper proposes the integration of QKD systems with well-known protocols and methodologies to secure the network’s control plane in an SDN and NFV environment and experimentally demonstrates a workflow whereQKD keys are used together with classically generated keys to encrypt communications between cloud and SDN platforms for setting up a service via secure shell.
Abstract: Today's networks are quickly evolving toward more dynamic and flexible infrastructures and architectures. This software-based evolution has seen its peak with the development of the software-defined networking (SDN) and network functions virtualization (NFV) paradigms. These new concepts allow operators to automate the setup of services, thus reducing costs in deploying and operating the required infrastructure. On the other hand, these novel paradigms expose new vulnerabilities, as critical information travels through the infrastructure fromcentral offices, down to remote data centers and network devices. Quantum key distribution (QKD) is a state-of-the-art technology that can be seen as a source of symmetric keys in two separated domains. It is immune to any algorithmic cryptanalysis and is thus suitable for long-term security. This technology is based on the laws of physics, which forbids us from copying the quantum states exchanged between two endpoints from which a secret key can be extracted. Thus, even though it has some limitations, a correct implementation can deliver keys of the highest security. In this paper, we propose the integration of QKDsystems with well-known protocols and methodologies to secure the network’s control plane in an SDN and NFV environment. Furthermore, we experimentally demonstrate a workflow where QKD keys are used together with classically generated keys to encrypt communications between cloud and SDN platforms for setting up a service via secure shell, while showcasing the applicability to other cryptographic protocols.
TL;DR: A proportional-integral-derivative (PID) controller integrated with a neural network (NN) is proposed to ensure quality of service (QoS) bandwidth requirements in passive optical networks (PONs) for the first time an approach that implements aNN to tune a PID to deal with QoS in PONs.
Abstract: In this paper, a proportional-integral-derivative (PID) controller integrated with a neural network (NN) is proposed to ensure quality of service (QoS) bandwidth requirements in passive optical networks (PONs). To the best of our knowledge, this is the first time an approach that implements aNNto tune a PID to dealwithQoS in PONs is used. In contrast to other tuning techniques such as Ziegler– Nichols or genetic algorithms (GA), our proposal allows a real-time adjustment of the tuning parameters according to the network conditions. Thus, the new algorithm provides an online control of the tuning process unlike the ZN and GA techniques, whose tuning parameters are calculated offline. The algorithm, called neural network service level PID (NNSPID), guarantees minimum bandwidth levels to users depending on their service level agreement, and it is compared with a tuning technique based on genetic algorithms (GASPID). The simulation study demonstrates that NN-SPID continuously adapts the tuning parameters, achieving lower fluctuations than GA-SPID in the allocation process. As a consequence, it provides a more stable response than GA-SPID since it needs to launch the GA to obtain new tuning values. Furthermore, NN-SPID guarantees the minimum bandwidth levels faster than GA-SPID. Finally, NN-SPID is more robust than GA-SPID under real-time changes of the guaranteed bandwidth levels, as GA-SPID shows high fluctuations in the allocated bandwidth, especially just after any change is made.
TL;DR: A dynamic wavelength and bandwidth allocation (DWBA) algorithm for NG-EPON to schedule upstream wavelength channels while providing a low average packet delay and catering frame resequencing problem is proposed.
Abstract: Recently, the IEEE 802.3ca Task Force has been working to standardize the next-generation Ethernet passive optical network (NG-EPON) to fulfill future bandwidth demands. NG-EPON allows an optical network unit (ONU) transmission to be scheduled on multiple wavelength channels simultaneously. This will increase network capacity up to 100 Gb/s, along with flexibility, as any of the channels can be allocated from the four wavelength channels, each having a capacity of 25 Gb/s. However, it also raises many technical aspects to be considered while deciding on an optimum scheduling strategy for NG-EPON (100G-EPON) architecture. This paper proposes a dynamic wavelength and bandwidth allocation (DWBA) algorithm for NG-EPON to schedule upstream wavelength channels while providing a low average packet delay and catering frame resequencing problem. An online scheduling framework with gated service grant sizing policy has been demonstrated in this work. The proposed DWBA algorithm’s performance is evaluated in comparison with legacy interleaved polling with an adaptive cycle time (modified- IPACT) and recently proposed water-filling algorithmbased DWBA (WF-DBA) algorithms. Simulation results confirmed the validity of the proposed DWBA algorithm.
TL;DR: This paper addresses the resource assignment problem in QKD-enabled optical networks by proposed and verified by the integer linear programming formulation and a heuristic algorithm and indicates that there is a trade-off between security levels and security-level types and resource utilization.
Abstract: Data transmission with optical fiber is vulnerable to eavesdropping. Moreover, conventional key distribution technology suffers from increasing computational power and upgraded attack algorithms. To address these issues, quantum key distribution (QKD), a quantum technology that secures secret information (such as a cryptographic key) exchange between two parties, can be used to guarantee secure data transmission. Integrating QKD into existing wavelength division multiplexing optical networks has been verified through a series of experiments, which contribute to ensuring network security and saving fiber resources. This paper addresses the resource assignment problem in QKD-enabled optical networks. First, a QKD-enabled optical network architecture is introduced. A small fraction of wavelength channels are segmented into multiple time slots with optical time division multiplexing technology to construct quantum key channels (QKChs) and measuring-basis channels, and then the remaining wavelengths can construct traditional data channels. Second, a static routing, wavelength, and time-slot assignment (RWTA) strategy is proposed and verified by the integer linear programming formulation and a heuristic algorithm. In the RWTA, QKChs are assigned for service requests according to the security levels specified by relevant key-updating periods. Thus, the secret keys for data encryption can update periodically to enhance security. Simulation results indicate that there is a trade-off between security (i.e., security levels and security-level types) and resource utilization.
TL;DR: An optimized DBA known as optimized round-robin (optimized-RR) that support front-hauling over XG-PONs is proposed that shows significant improvement in upstream delay and utilization as well as lower packet loss and jitter forFront-haul uplink traffic transmitted via XG -PON in virtualized C-RAN architecture.
Abstract: Time division multiplexing passive optical network (TDM-PON) technologies are viewed as an attractive solution for flexible and cost-efficient mobile front-haul for cloud radio access network (C-RAN) architecture. However, it is a challenge for TDM-PONs to meet the strict latency requirement of mobile front-haul in C-RAN because they use a dynamic bandwidth allocation (DBA) mechanism to manage upstream traffic. The latency issue of TDM-PON based mobile front-haul has been extensively investigated in the literature with particular focus on IEEE TDM-PON (e.g., 10G-EPON). However, ITU TDM-PONs such as XG-PON and XGS-PON have not yet even been explored in the context of mobile front-haul. To cover this gap, we first evaluate the performance of two recently proposed XG-PON-standard-compliant DBAs, namely, group-assured GIANT (gGIANT) and round-robin DBA (RR-DBA), over simulated mobile front-haul traffic. We conclude based on our evaluation that neither RR-DBA nor gGIANT satisfies the delay required for mobile front-haul. Therefore, we propose an optimized DBA known as optimized round-robin (optimized-RR) that support front-hauling over XG-PONs. The performance evaluation of our optimized DBA against gGIANT and RR-DBA shows significant improvement in upstream delay and utilization as well as lower packet loss and jitter for front-haul uplink traffic transmitted via XG-PON in virtualized C-RAN architecture.
TL;DR: A comparison with analog MFH reveals that the proposed digitalMFH based on delta-sigma modulation can offer improved resilience against noise and nonlinear impairments, and it increases the fronthaul capacity by four times compared with the conventional CPRI-based digital MFH without significant EVM penalty.
Abstract: We first experimentally demonstrated a digital mobile fronthaul (MFH) architecture using delta-sigma modulation as the new digitization interface to replace the conventional common public radio interface (CPRI). Both one-bit and two-bit delta-sigma modulations were demonstrated, and the digitized signals were transmitted over on-off keying (OOK) or 4-level pulse-amplitude-modulation (PAM4) optical intensity modulation-direct detection (IM-DD) links. 32 LTE component carriers (CCs) were digitized and transmitted over a 25-km single-λ 10-Gbaud OOK/PAM4 link, so that 32 LTE carrier aggregation (CA) specified by 3GPP release 13 can be supported. Compared with the conventional digitization interface based on CPRI, the fronthaul capacity is increased by four times. Error vector magnitude (EVM) less than 5% or 2.1% for all LTE CCs was obtained using one-bit and two-bit delta-sigma modulators, so that high-order modulations (256QAM/1024QAM) can be supported. As a waveform-agnostic digitization interface, delta-sigma modulation can digitize not only 4G-LTE but also 5G waveforms, and its 5G compatibility was verified by filter-bank-multicarrier (FBMC) signals. The tolerance to bit error ratio (BER) of the proposed delta-sigma modulation-based digital MFH was evaluated, and no significant EVM degradation was observed for BER up to 3 χ 10−5. A comparison with analog MFH reveals that the proposed digital MFH based on delta-sigma modulation can offer improved resilience against noise and nonlinear impairments, and it increases the fronthaul capacity by four times compared with the conventional CPRI-based digital MFH without significant EVM penalty.
TL;DR: In this paper, the authors developed a power-consumption model and a novel dynamic bandwidth and wavelength allocation (DBWA) scheme for transmission scheduling in wavelength-agile passive optical network (WA-PON).
Abstract: Recently, the IEEE 802.3 Ethernet Working Group has classified three architectures for the nextgeneration Ethernet passive optical network (NG-EPON). They are called single-scheduling domain (SSD) PON, multi-scheduling domain (MSD) PON, and wavelength-agile (WA) PON, and they differ based on how a group of optical network units (ONUs) share awavelength. Existing dynamic bandwidth and wavelength allocation (DBWA) schemes for conventional EPON can be applied to MSD-PON and SSDPON, but not WA-PON. This is because WA-PON is a new architecture with full flexibility where a flexible number of wavelengths can be assigned to one ONU, and multiple ONUs can transmit at the same time. In this work, we develop a mathematical model and a novel DBWA scheme for transmission scheduling in WA-PON. However, as WA-PON incurs penalties in terms of delay and power consumption when an ONU activates its transmissions on new wavelengths, a trade-off between energy saving and data-transfer latency reduction needs to be carefully addressed when performing transmission scheduling. So, we develop a power-consumption model and modify the proposed DBWA scheme to enhance the energy efficiency ofWA-PON. Finally, we conduct simulation experiments for performance evaluation of the three PON architectures in terms of latency and packet loss ratio.We quantitatively investigate the influence of various parameters, such as the number of ONU transceivers and ONU buffer size, onWA-PON latency and packet loss ratio, and we evaluate the energy efficiency gain of the modified DBWA scheme.
TL;DR: The architecture modeling results show the vast potential for cost and power savings that node consolidation can bring, but the architecture also recognizes the limits of long-reach transmission for low-latency 5G services and proposes ways to address such shortcomings in future projects.
Abstract: This paper reports on the architectural, protocol, physical layer, and integrated testbed demonstrations carried out by the DISCUS FP7 consortium in the area of access–metro network convergence Our architecture modeling results show the vast potential for cost and power savings that node consolidation can bring The architecture, however, also recognizes the limits of long-reach transmission for low-latency 5G services and proposes ways to address such shortcomings in future projects The testbed results, which have been conducted end-toend, across access–metro and core, and have targeted all the layers of the network from the application down to the physical layer, show the practical feasibility of the concepts proposed in the project
TL;DR: In this article, the bit error rate (BER) performance of a free space optical (FSO) communication system was evaluated in the presence of amplified spontaneous emission (ASE) noise under weak, moderate to strong, and very strong atmospheric turbulence regimes and PEs.
Abstract: The performance of a free space optical (FSO) communication system is significantly affected by various atmospheric turbulence conditions and pointing errors (PEs) apart from the additive noise, which is assumed to be Gaussian Optical pre-amplifiers are an essential component of FSO systems for improving the receiver sensitivity However, optical pre-amplification results in amplified spontaneous emission (ASE), which dominates the receiver thermal and shot noises The square law photodetection process at the receiver in a FSO system necessitates the consideration of chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in the literature In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on–off keying modulation in the presence of ASE noise under weak, moderate to strong, and very strong atmospheric turbulence regimes and PEs We also derive asymptotic BER expressions for the considered FSO system for large values of the signal-to-noise ratio in terms of simple elementary functions Further insight into the system is provided by performing a diversity analysis
TL;DR: In this paper, the performance of a hybrid M-ary quadrature amplitude modulation multi-pulse pulse position modulation (hybrid QAM-MPPM) technique was investigated in both turbulence-free and gamma-gamma freespace optical (FSO) channels.
Abstract: The performance of a hybrid M-ary quadrature amplitude modulation multi-pulse pulse-position modulation (hybrid QAM-MPPM) technique is investigated in both turbulence-free and gamma-gamma freespace optical (FSO) channels. Both the spectral efficiency and asymptotic power efficiency of the hybrid QAM-MPPM are estimated and compared to traditional QAM and MPPM techniques. The bit error rate (BER) of intensity-modulation direct-detection (IM-DD) systems adopting the hybrid technique is investigated over turbulence-free FSO channels. Upper-bound expressions for the average BER and outage probability are derived for FSO systems by adopting a hybrid QAM-MPPM scheme over gamma-gamma turbulent channels. In addition, the performance of a Reed-Solomon coded hybrid QAM-MPPM is considered. The obtained expressions are used to numerically investigate the performance of the hybrid technique. Our results reveal that, under the conditions of comparable data rates, the same bandwidth, and the same energy per bit, FSO systems adopting the hybrid technique outperform those adopting traditional MPPM, QAM, and on-off keying (OOK) techniques by 1.5, 0.4, and 3 dB, respectively, in the case of turbulence-free channels. Moreover, the new technique shows a better BER performance under different turbulence levels when compared with traditional MPPM and QAM techniques in turbulent FSO communication channels. Also, it shows an improvement in outage probability compared to MPPM, QAM, and OOK over gamma-gamma FSO channels.
TL;DR: Two original procedures based on segment routing are proposed for dynamic traffic recovery and traffic engineering in multi-domain networks to significantly simplify the network operation with respect to traditional Internet Protocol (IP)/MPLS procedures.
Abstract: Segment routing is an emerging traffic engineering technique relying on Multi-protocol Label-Switched (MPLS) label stacking to steer traffic using the source-routing paradigm. Traffic flows are enforced through a given path by applying a specifically designed stack of labels (i.e., the segment list). Each packet is then forwarded along the shortest path toward the network element represented by the top label. Unlike traditional MPLS networks, segment routing maintains a per-flow state only at the ingress node; no signaling protocol is required to establish new flows or change the routing of active flows. Thus, control plane scalability is greatly improved. Several segment routing use cases have recently been proposed. As an example, it can be effectively used to dynamically steer traffic flows on paths characterized by low latency values. However, this may suffer from some potential issues. Indeed, deployed MPLS equipment typically supports a limited number of stacked labels. Therefore, it is important to define the proper procedures to minimize the required segment list depth. This work is focused on two relevant segment routing use cases: dynamic traffic recovery and traffic engineering in multi-domain networks. Indeed, in both use cases, the utilization of segment routing can significantly simplify the network operation with respect to traditional Internet Protocol (IP)/MPLS procedures. Thus, two original procedures based on segment routing are proposed for the aforementioned use cases. Both procedures are evaluated including a simulative analysis of the segment list depth. Moreover, an experimental demonstration is performed in a multi-layer test bed exploiting a software-defined-networking-based implementation of segment routing.
TL;DR: Two survivable schemes are proposed that enable network energy savings through sleep mode operation without having to compromise on failure detection time and provide enhanced connection availability and power savings at less than 0.2% incremental network cost.
Abstract: So much has been promised by the fifth generation (5G), the revolution of mobile communications that allows for flexible, speedy, and efficient delivery of unlimited data and information sharing between people located anywhere and at any time. The road toward making 5G a reality, however, requires concerted efforts in designing both the underlying infrastructure and the enabling technologies to simultaneously satisfy not only capacity but also reliability, low latency, synchronization, security, and energy consumption requirements. In that respect, the transport segment of a 5G network, i.e., the backhaul network of mobile base stations (BSs) or fronthaul of remote radio units (RRUs), must not be overlooked. Further, any future design of a resilient 5G transport network must also consider the potential exploitation of switching on and off network resources such as RRUs and BSs to improve energy efficiency. At present, there are few inroads on 5G transport networks that provide resilience during sleep mode operation. Therefore, the focus of this work is aimed specifically at providing solutions to enhance both the survivability and power savings of mobile transport networks that implement sleep mode operation. We develop our solutions around a dense wavelength-division multiplexed (DWDM) optical ring transport network that has been previously proven to be energy efficient as a 5G transport network. Further, we propose two survivable schemes that exploit the inherent resiliency of the ring network. In conjunction with cw monitoring signals and highly sensitive monitoring modules, these schemes facilitate for the first time continuous monitoring of the network at all times, even during idle periods of transmission when transceivers are sleeping. That is, our proposed schemes enable network energy savings through sleep mode operation without having to compromise on failure detection time. Compared to a conventional ring architecture, our survivable schemes provide enhanced connection availability and power savings at less than 0.2% incremental network cost. Based on performance evaluations for brownfield, duct reuse, and greenfield deployments, we provide guidance on the most suitable scheme for each considered scenario, thus driving the future choices of mobile network operators.
TL;DR: This work investigates the performance of asymmetric radio frequency (RF) and free-space optical (FSO) dual-hop cognitive amplify-and-forward relay networks where RF links are subject to independent and nonidentically distributed Nakagami-m fading.
Abstract: We investigate the performance of asymmetric radio frequency (RF) and free-space optical (FSO) dual-hop cognitive amplify-and-forward relay networks where RF links are subject to independent and nonidentically distributed Nakagami-m fading We consider that the RF link transmitter and receiver are secondary users of an underlay cognitive network Specifically, the transmit power conditions of the proposed spectrum-sharing network are governed by either the combined power constraint of the interference on the primary network and the maximum transmission power at the secondary network, or the single power constraint of the interference on the primary network Also, we consider a double generalized gamma fading channel with pointing error and both heterodyne and intensity modulation/direct detection methods in the FSO link The closed-form and asymptotic expressions of outage probability for this system are calculated for fixed gain and channel-state-informationassisted relaying techniques It is demonstrated that the diversity order is a function of the fading severity of the RF link, turbulence parameters of the FSO link, and pointing error, regardless of the interference channel parameter of the primary user However, the coding gain is impressed by the interference link parameter and RF-FSO links parameters The diversity-multiplexing trade-off analysis is done for this network, where we show that this trade-off is independent of the primary network
TL;DR: This paper proposes a novel technique for solving the routing and spectrum allocation problem, called delayed spectrum allocation (DSA), which improves resource allocation efficiency for scheduled demands and lowers call blocking.
Abstract: In response to bandwidth-hungry applications, the field of elastic optical networks (EONs) has emerged. In this paper, we investigate the provisioning and allocation problem in EONs, which presents a number of new and exciting challenges not otherwise present in optical networking solutions.We propose a novel technique for solving the routing and spectrum allocation problem, which improves resource allocation efficiency for scheduled demands. This approach, called delayed spectrum allocation (DSA), promises network resources to each demand upon request for scheduling, but delays the selection and allocation of those specific resources until immediately before the transmission begins. Through extensive simulations, we are able to conclude that the DSA improves resource consumption efficiency and lowers call blocking. We also evaluate demands with flexible reservation windows such that a range of acceptable start times can be specified by the user. This flexibility is found to significantly increase the performance improvement of the DSA with little additional delay.
TL;DR: This work derives bounds on the variance of OWC interference under the constraints of an OWC channel, and evaluates the accuracy of assuming that interference follows a Gaussian distribution.
Abstract: The emerging field of optical wireless communications (OWC) offers exceptional promise as a technology for next-generation wireless networks. High data rate capabilities and ultra-dense access point deployment will allow OWC to supplement traditional RF technologies and remove congestion from the crowded RF spectrum. When implementing OWC via intensity modulation with direct detection (IM/DD), peak optical power emission constrains the instantaneous optical power. Average optical power is also constrained by eye safety regulations and illumination requirements of infrared and visible light communication (VLC) systems, respectively. These constraints differ from the conventional electrical power constraint of RF and wireline systems. Accordingly, performance metrics such as signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) have been redefined in relation to the optical channel constraints in order to provide fair comparison across OWC implementations. In densely deployed networks, interference has a significant effect on system performance. Two key properties simplify the analysis of RF networks: 1) the relationship between electrical power and interference variance is modulation agnostic and 2) many interferers are typically assumed. The former allows SINR to be defined in terms of the channel constraint and the latter allows the aggregate disturbance from interference-plus-noise to be modeled as an additive Gaussian random component. In OWC networks, the optical power constraints relate to interference variance in a modulation specific manner, and the highly directional optical channel creates instances where a small set of interferers dominate the aggregate disturbance. In this work, we first derive bounds on the variance of OWC interference under the constraints of an OWC channel. We then evaluate the accuracy of assuming that interference follows a Gaussian distribution. Finally, we show results of a study in a testbed environment with 15 VLC-enabled LED luminaires in order to empirically evaluate OWC interference characteristics.
TL;DR: A spatial multiplexing scheme with M transceivers to increase the data rate of a free-space optical (FSO) system and derives the analytical expressions for spectral efficiency of both spatialmultiplexing and diversity configurations to facilitate performance analysis.
Abstract: In this paper, we employ a spatial multiplexing scheme with M transceivers to increase the data rate of a free-space optical (FSO) system. In our proposed scheme, each transmitter sends independent information toward the center of its related receiver aperture. We analyze the performance of the proposed scheme in terms of average achievable rate. To compare the performance of our proposed scheme with its spatial diversity FSO system counter-part, we define a case in which M transmitters send the same information. To facilitate performance analysis, we also derive the analytical expressions for spectral efficiency of both spatial multiplexing and diversity configurations, which reduces the (M + 2)-dimensional integration of spatial multiplexing and (M2 + 2)-dimensional integration of spatial diversity FSO systems to a two-dimensional integration in both configurations. The adequacies of our analytical results are thoroughly confirmed by numerical simulations.
TL;DR: This work first formulate this problem as an integer linear programming model, then design an efficient heuristic named the “congestion-aware local fast reroute” (CALFR), which enables fast recovery while avoiding link congestion in the post-recovery network.
Abstract: Although a restoration approach derives a reroute path when failure occurs and greatly reduces forwarding rules in switches compared with a protection approach, software-defined networks (SDNs) induce a long failure recovery process because of frequent flow operations between the SDN controller and switches. Accordingly, it is indispensable to design a new resilience approach to balance failure recovery time and forwarding rule occupation. To this end, we leverage flexible flow aggregation in fast reroute to solve this problem. In the proposed approach, each disrupted traffic flow is reassigned to a local reroute path for the purpose of congestion avoidance. Thus, all traffic flows assigned to the same local reroute path are aggregated into a new “big” flow, and the number of reconfigured forwarding rules in the restoration process is greatly reduced. We first formulate this problem as an integer linear programming model, then design an efficient heuristic named the “congestion-aware local fast reroute” (CALFR). Extensive emulation results show that CALFR enables fast recovery while avoiding link congestion in the post-recovery network.
TL;DR: A novel dynamic RSA method to reduce spectrum fragmentation and control the service level of IR and AR requests in terms of bandwidth blocking probability (BBP) in EONs considering the multiplexing effect of spatial channels is proposed.
Abstract: Numerous studies have investigated elastic optical networks (EONs) with the aim of expanding the transmission capacities of core networks. To achieve this goal, it is necessary to solve the spectrum resource wastage problem caused by spectrum fragmentation. Moreover, due to the potentially high traffic demands in future networks, it is important to handle requests that need to be reserved immediately (immediate reservation, IR) as well as those that can be reserved in advance (advance reservation, AR). In networks that support the coexistence of IR and AR requests, IR service degradation by AR requests is a challenging issue because AR requests tend to reserve future resources, which causes a lack of current resources to meet IR requests. Therefore, we address the problem of spectrum fragmentation and the service-level control of IR and AR requests by routing and spectrum allocation (RSA). First, we summarize related research into EONs and resource- allocation methods for IR and AR requests. Next, we propose a novel dynamic RSA method to reduce spectrum fragmentation and control the service level of IR and AR requests in terms of bandwidth blocking probability (BBP) in EONs considering the multiplexing effect of spatial channels. Finally, we evaluate the proposed method based on computer simulations and our results demonstrate that the proposed method can improve the BBP for the entire traffic flow by reducing spectrum fragmentation, as well as the service control of AR requests and IR requests under various network conditions.
TL;DR: In this paper, the authors define a 5G radio deployment scenario for fixed wireless access (FWA) that can meet the service requirements of future fixed broadband access and analyze different transport requirements imposed by different radio access network (RAN) split options.
Abstract: With the advent of 5G, fixed wireless access (FWA) has emerged as a promising candidate for rolling out fixed broadband services. By means of radio simulations, we define a 5G radio deployment scenario for FWA that can meet the service requirements of future fixed broadband access. Different transport requirements imposed by different radio access network (RAN) split options are considered and a broad range of optical transport technologies/systems to support the FWA scenario is analyzed. For higher-layer RAN split options, we find that conventional 10G passive optical networks (XG-PONs) and coarse wavelength-division multiplexing (CWDM) technologies are the most cost effective. CWDM provides improved support for low-latency services while XG-PON facilitates future migration to fiber to the home. For lower-layer RAN splits, point-to-point (PtP) fiber or PtP-WDM is required. In the considered scenario, CWDM and PtP technologies are found to be the most cost effective.
TL;DR: Simulation results show that the reconfiguration schemes with holding-time awareness can be effectively utilized to reduce the spectrum fragmentation and, hence, result in better resource utilization and overall lower connection blocking probability.
Abstract: Elastic optical networks are prone to spectrum fragmentation, resulting in poor resource utilization and often higher blocking probability. To overcome the spectrum fragmentation, a defragmentation (DF) of the spectrum can be applied by reconfiguring some or all active connections. However, reconfiguration is generally not desirable, as it can interrupt the services of the existing connections. In this paper, we propose two novel connection reconfiguration schemes to efficiently address spectrum DF: (i) a reactive–disruptive scheme and (ii) a proactive– non-disruptive scheme. Both schemes utilize the information of holding times of the existing connections in order to reduce fragmentation and thus improve resource utilization and minimize connection blocking. The reactive– disruptive reconfiguration scheme tries to allocate an incoming connection, which could not be accepted otherwise, by reconfiguring some existing connections. The proactive–non-disruptive reconfiguration method, on the other hand, allows us to reconfigure only such connections, which can be shifted without crossing over the spectrum of other connections. This paves the way for a non-disruptive DF when setting up a new connection, which is a desirable feature. Simulation results show that the reconfiguration schemes with holding-time awareness can be effectively utilized to reduce the spectrum fragmentation and, hence, result in better resource utilization and overall lower connection blocking probability.