Fiber-wireless Networks Research Articles

Distributed cooperative computation offloading in multi-access edge computing fiber–wireless networks

Novel 5G applications will require the processing of large amounts of computation-intensive, delay-sensitive tasks. Mobile devices, however, are subject to limited hardware resources (e.g., battery life, CPU, and storage) and therefore may fall short of satisfying the stringent latency requirements of complex tasks. To fill the gap between the increasing demands of computation-intensive, delay-sensitive tasks driven by emerging 5G applications and the availability of limited resources on smart mobile devices, we introduce our proposed architecture of multi-access computing (MEC) enabled Fiber–Wireless (FiWi) LTE enhanced HetNets, enabling the coexistence and cooperation between conventional (remote) cloud and MEC servers. After presenting our analytical framework to evaluate the energy-delay performance, we propose our distributed cooperative offloading strategy with the objective of minimizing the average response time for mobile users.

An Analytical Cost-Optimal Cloudlet Placement Framework over Fiber-Wireless Networks with Quasi-Convex Latency Constraint

To meet the low-latency constraints arising from future smart mobile devices, Internet-of-Things, and 5G applications, major interest is currently given to the integration of centralized cloud computing and distributed edge computing infrastructures to deliver higher performance and reliability to edge devices in accessing mobile cloud services. The three-tier network architecture arising from cloud, cloudlet, and edge-devices can handle miscellaneous latency requirements for both latency-sensitive and latency-tolerant applications more efficiently than conventional two-tier networks. In this paper, we primarily focus on the static cloudlet network planning problem and propose an analytical hybrid cost-optimization framework for optimal cloudlet placement. We formulate this problem as a convex optimization problem and solve by using Karush-Kuhn-Tucker (KKT) conditions, and show that this framework can be evaluated without any scalability issues observed with integer programming based frameworks for large datasets. Moreover, we derive user-friendly closed form expressions that provide a first-hand estimation of cloudlet deployment cost depending on a few important network parameters like split-ratio, population density, and network bandwidth. Finally, we also show that the optimal solution of this analytical framework can be considered as a tight lower bound of the optimal solutions of integer programming based frameworks and makes a better cloudlet installation cost estimation compared to other existing frameworks.

Fi-Wi Architecture and Survivability

In the present scenario, internet users are increasing rapidly thus there is need of high-speed internet connectivity. Since Passive Optical Network (PON) provides higher bandwidth but it is costly. Similarly wireless access network provide high scalability, rapid deployment, comparatively low cost and due to channel interference, its bandwidth is restricted. Therefore, the solution to get high-speed internet at lower cost is Hybrid Fiber wireless networks. Hybrid Fiber wireless networks have the merits of both i.e. PON and Wireless Mesh Network (WMN). Survivability is one of the important issues in Fiber Wireless Networks because failure of components or single segment can cause huge reduction of data. Present work is an overview of various kinds of failure of hybrid fiber wireless networks and protection mechanisms to prevent these failures. In this work we will discuss various issues related to survivability of Hybrid Fiber wireless (Fi-Wi) networks.

40 Gbps Laguerre-Gaussian and Hermite-Gaussian Optical Mode Division Multiplexing for Radio over Fiber System

Abstract Radio over Fiber technology is utilizing the high capacity of optical fiber system and wireless mobility network. In this work, we proposed two different optical propagation modes namely Laguerre-Gaussian (LG) and Hermite-Gaussian (HG) setting to (0.1), (0.2) mode types generated by a special CW laser source at varying wavelength from 800 nm to 1150 nm with 50 nm spacing channel Mode division Multiplexing (MDM) technique. These wavelengths transmitted×5Gb/s data modulated on PSK modulator having 100 GHz radio frequency subcarrier over 5 km Parabolic-Index Multimode Fiber link. Q factor value and eye diagram used to evaluate system performance which showed the maximum Q factor value found at 800 nm channel 1 equal to 12.0113 for both LG 0 1 and HG 0.1. While the maximum Q factor appears at 800 nm channel 1 equal to 8.49756 for LG 0,2 and 3.56785 at 1000 nm channel 5 for HG 0.2.

Optimal Deployment of FiWi Networks Using Heuristic Method for Integration Microgrids with Smart Metering.

The unpredictable increase in electrical demand affects the quality of the energy throughout the network. A solution to the problem is the increase of distributed generation units, which burn fossil fuels. While this is an immediate solution to the problem, the ecosystem is affected by the emission of CO2. A promising solution is the integration of Distributed Renewable Energy Sources (DRES) with the conventional electrical system, thus introducing the concept of Smart Microgrids (SMG). These SMGs require a safe, reliable and technically planned two-way communication system. This paper presents a heuristic based on planning capable of providing a bidirectional communication that is near optimal. The model follows the structure of a hybrid Fiber-Wireless (FiWi) network with the purpose of obtaining information of electrical parameters that help us to manage the use of energy by integrating conventional electrical system with SMG. The optimization model is based on clustering techniques, through the construction of balanced conglomerates. The method is used for the development of the clusters along with the Nearest-Neighbor Spanning Tree algorithm (N-NST). Additionally, the Optimal Delay Balancing (ODB) model will be used to minimize the end to end delay of each grouping. In addition, the heuristic observes real design parameters such as: capacity and coverage. Using the Dijkstra algorithm, the routes are built following the shortest path. Therefore, this paper presents a heuristic able to plan the deployment of Smart Meters (SMs) through a tree-like hierarchical topology for the integration of SMG at the lowest cost.

Improving Animal-Human Cohabitation with Machine Learning in Fiber-Wireless Networks

In this paper, we investigate an animal-human cohabitation problem with the help of machine learning and fiber-wireless (FiWi) access networks integrating cloud and edge (fog) computing. We propose an early warning system which detects wild animals near the road/rail with the help of wireless sensor networks and alerts passing vehicles of possible animal crossing. Additionally, we show that animals’ detection at the earliest and the related processing, if possible, at sensors would reduce the energy consumption of edge devices and the end-to-end delay in notifying vehicles, as compared to the scenarios where raw sensed data needs to be transferred up the base stations or the cloud. At the same time, machine learning helps in classification of captured images at edge devices, and in predicting different time-varying traffic profiles— distinguished by latency and bandwidth requirements—at base stations, including animal appearance events at sensors, and allocating bandwidth in FiWi access networks accordingly. We compare three scenarios of processing data at sensor nodes, base stations and a hybrid case of processing sensed data at either sensors or at base stations, and showed that dynamic allocation of bandwidth in FiWi access networks and processing data at its origin lead to lowering the congestion of network traffic at base stations and reducing the average end-to-end delay.

Multi‐stage resource allocation in hybrid 25G‐EPON and LTE‐Advanced Pro FiWi networks for 5G systems

The 5G vision is not restricted solely to the wireless domain and its challenging requirements cannot be fulfilled without the efficient integration of cutting-edge technologies in all portions of the telecommunications infrastructure. The promoted architectures for next generation telecommunications systems involve high capacity network domains, which operate flexibly and seamlessly to offer full quality of experience to all types of subscribers. The proliferation of highly demanding multimedia services and the features of modern communication devices necessitate the development of end-to-end schemes which can efficiently distribute large amount of network resources anywhere and whenever needed. This study introduces a new resource allocation scheme for cutting-edge fibre-wireless networks is introduced that can be applied in the fronthaul portion of 5G-enabled architectures. The adopted technologies are the forthcoming 25G-Ethernet Passive Optical Network (EPON) for the optical domain and the 5G-ready long-term evolution -Advanced Pro for the wireless domain. The proposed scheme performs allocation decisions based on the outcome of an adjustable multi-stage optimisation problem. The optimisation factors are directly related to the major considerations in bandwidth distribution, namely priority-based traffic differentiation, power awareness, and fairness provision. The conducted evaluations prove that this approach is able to ensure high efficiency in network operations.

Collaborative Computation Offloading for Multiaccess Edge Computing Over Fiber–Wireless Networks

By offloading the computation tasks of the mobile devices (MDs) to the edge server, mobile-edge computing (MEC) provides a new paradigm to meet the increasing computation demands from mobile applications. However, existing mobile-edge computation offloading (MECO) research only took the resource allocation between the MDs and the MEC servers into consideration, and ignored the huge computation resources in the centralized cloud computing center. Moreover, current MEC hosted networks mostly adopt the networking technology integrating cellular and backbone networks, which have the shortcomings of single access mode, high congestion, high latency, and high energy consumption. Toward this end, we introduce hybrid fiber-wireless (FiWi) networks to provide supports for the coexistence of centralized cloud and multiaccess edge computing, and present an architecture by adopting the FiWi access networks. The problem of cloud-MEC collaborative computation offloading is studied, and two schemes are proposed as our solutions, i.e., an approximation collaborative computation offloading scheme, and a game-theoretic collaborative computation offloading scheme. Numerical results corroborate that our solutions not only achieve better offloading performance than the available MECO schemes but also scale well with the increasing number of computation tasks.

Architectures and Algorithms for Radio-Over-Fiber Networks

To serve futuristic applications, wireless access with a wired-like connectivity is required. To accomplish this goal, we propose a design for a flexible radio-over-fiber (RoF) network, where we optimize the RoF network for the right choice of subcarrier modulation scheme. Then we propose a mobile interleaved polling (MIP) and a wavelength allocation algorithm, and benchmark the performance of the polling mechanism with the simple polling that has been proposed in the literature. Using a simulation environment, we evaluate the packet latency of the MAC protocol with different user densities, user loads, and cell sizes. Based on these results, we give general design recommendations for an RoF network.

Collaborative Mobile Edge Computation Offloading for IoT over Fiber-Wireless Networks

Mobile edge computing is envisioned to be a promising paradigm to address the conflict between computationally intensive IoT applications and resource-constrained lightweight mobile devices. However, most existing research on mobile edge computation offloading has only taken the resource allocation between the mobile devices and the MEC servers into consideration, ignoring the huge computation resources in the centralized cloud computing center. To make full use of the centralized cloud and distributed MEC resources, designing a collaborative computation offloading mechanism becomes particularly important. Note that current MEC hosted networks, which mostly adopt the networking technology integrating cellular and core networks, face new challenges of single networking mode, long latency, poor reliability, high congestion, and high energy consumption. Hybrid fiber-wireless networks integrating both low-latency fiber optic and flexible wireless technologies should be a promising solution. Toward this end, we provide in this article a generic fiber-wireless architecture with coexistence of centralized cloud and distributed MEC for IoT connectivity. The problem of cloud-MEC collaborative computation offloading is defined, and a game-theoretic collaborative computation offloading scheme is proposed as our solution. Numerical results corroborate that our proposed scheme can achieve high energy efficiency and scales well as the number of mobile devices increases.

FiWi network throughput-delay modeling with traffic intensity control and local bandwidth allocation

Fiber-Wireless (FiWi) networks typically combine an optical access network with a wireless access network so as to build on the respective strengths of the optical and wireless network technologies. Prior analytical throughput-delay studies of FiWi networks have typically considered heavy-loaded traffic models, i.e., constantly backlogged source nodes. In contrast, in this paper we present a more general comprehensive FiWi network throughput-delay analysis that encompasses Poisson (non-heavy) as well as heavy-loaded input traffic models. In addition, our analysis covers bandwidth assignments of wireless channels both at the hop distance level and at the node level, as well as a queuing model of dynamic bandwidth allocation in the optical access network. Our analysis provides insightful guidelines for setting the channel access probabilities for source traffic and relay traffic in FiWi networks. Our numerical evaluations demonstrate that prior studies which considered only heavy traffic loads gave misleading results for the delay performance of well-known access probability assignments. We correct and clarify these misleading results with our more general analysis for non-heavy traffic.

Non-Saturation Delay Analysis of Medium Transparent MAC Protocol for 60 GHz Fiber-Wireless Towards 5G mmWave Networks

In this paper, we demonstrate an analytical model for computing the end-to-end packet delay of a converged optical/wireless 60 GHz Radio-over-Fiber (RoF) network operating under the medium-transparent MAC (MT-MAC) protocol. For the calculation of the cycle times, this model considers the protocol time consumed for contention and data exchange over both optical and wireless media, a feature of the MT-MAC that effectively enables it to provide direct and seamless interaction between the RoF Central Office and the end users. This new analytical model enables us to conduct an extensive delay performance analysis of the various performance aspects of hybrid RoF networks operating under the fixed service paradigm, such as various optical capacity availability scenarios, varying load conditions, optical network ranges, transmission window lengths, and data packet sizes. The derived theoretical results present an excellent match with the respective simulation findings, providing sub millisecond latency values for a plethora of network conditions, confirming that the MT-MAC scheme can effectively be incorporated into the upcoming mm-wave 5G era.

Hybrid Fiber-Wireless Network: An Optimization Framework for Survivable Deployment

Abstract—Hybrid fiber-wireless (FiWi) networks, which benefit from high bandwidth and ubiquitous access of optical and wireless networks, have been identified as a promising technology candidate for next-generation broadband access. As various component/fiber failures may occur in hybrid FiWi networks, thus affecting huge numbers of end users, survivability has become one of the key important deployment considerations in such networks. This paper focuses on developing optimal network planning strategies to achieve survivable hybrid FiWi networks. In particular, to address the additional cost involved in deploying backup fibers in previously proposed redundancy strategies against distribution fiber failures, we propose the use of wireless routing through the ubiquitous wireless coverage of end users in a hybrid FiWi network. We present an optimization framework to optimally plan and deploy a survivable hybrid FiWi network, where traffic from an affected optical network unit (ONU) can be effectively rerouted to backup ONUs through wireless connections in the event of a distribution fiber failure. However, focusing only on the resilience of a network without considering its cost, and ignoring the resultant capacity, latency, and coverage under normal and protection operating conditions, is impractical. Our proposed framework therefore ensures maximum end-user coverage whilst satisfying survivability, connectivity, delay, and capacity constraints of the network, by optimizing the placement of passive optical splitters, ONUs, and wireless routers in conjunction with fiber and wireless connections. Moreover, we demonstrate the feasibility of our framework in the context of an urban deployment under different deployment scenarios. In particular, our results provide insight into how survivable FiWi networks can be deployed without compromising on the latency, coverage, and capacity requirements of such networks.

A 60-GHz 4-Gb/s Fully Integrated NRZ-to-QPSK Fiber-Wireless Modulator

A fully integrated optical-to-wireless modulator for low-cost fiber-optical backhaul links is presented in this paper. In the receiver, a CMOS photodetector with a bandwidth of 0.5 GHz is integrated to perform optical-to-electrical conversion. A gain-boosted inverter based transimpedance amplifier achieves a high gain-bandwidth product without using inductive peaking. The two-stage equalizer compensates the photodetector bandwidth and extends the operation data rate to 4 Gb/s. The wireless modulator directly up-converts and modulates the baseband I/Q NRZ data to a QPSK signal centered at 60 GHz. Realized in 65-nm CMOS, the optical front-end achieves -3-dBm optical input sensitivity at 4 Gb/s with $10^{\mathrm {-12}}$ BER. The modulator produces -7.2-dBm output power with -12-dB EVM at a bit efficiency of 19.6 pJ/b. This design demonstrates that a small form factor and low cost optical-to-millimeter-wave modulator can be realized to support future fiber-wireless networks.

38-GHz Millimeter Wave Beam Steered Fiber Wireless Systems for 5G Indoor Coverage: Architectures, Devices, and Links

Millimeter wave (mm-wave) beam steering is a key technique for the next generation (5G) wireless communication. The 28 and 38-GHz bands are widely considered as the candidates for 5G. In the context of indoor coverage, fiber-wireless systems with multiple simplified remote antenna sites are attractive to avoid the indoor coverage problem caused by the high wall penetration loss of mm-wave signals. To allow enough antenna gain at the mm-wave bands, radio beam steering (and beamforming) is desired. Combining fiber-wireless system with remotely controlled photonic mm-wave beam steering can bring significant advances in terms of energy efficiency and cost. In this paper, we explore two kinds of indoor fiber-wireless network architectures for such mm-wave beam steering. Then, we discuss and investigate the key enabling device, which is an arrayed waveguide grating feedback loop (AWG-loop). Based on the AWG-loop, we further design two fiber-wireless links to accommodate the two network architectures. Both links with bit rates from 50 Mb/s to 8 Gb/s per spatial channel are experimentally demonstrated with a 38-GHz carrier frequency. The advanced reversely modulated optical transmitter and half-cycled 16 quadrature amplitude modulation (QAM-16) are employed to realize a simplified mm-wave beam steered fiber-wireless link with the record-breaking 16-b/s/Hz (4 spatial channels× 4 bits/s/Hz) spatial-spectral efficiency in its kind.

Fiber-wireless for smart grid: A survey

Smart grid allows two-way communication between power utility companies and their customers while having the ability to sense along the transmission lines. However, the downside is such, when the smart devices are transmitting data simultaneously, it results in network congestion. Fiber wireless (FiWi) network is one of the best congestion solutions for smart grid up to date. In this paper, a survey of current literature on FiWi for smart grid will be reviewed and a testbed to test the protocols and algorithms for FiWi in smart grid will be proposed. The results of number of packets received and delay vs packet transmitted obtained via the testbed are compared with the results obtained via simulation and they show that they are in line with each other, validating the accuracy of the testbed.

Digitizing radio-over-fiber transceiver based on optical tunable encoder and optical codewords

Radio over fiber (RoF) is a very attractive and promising technology for wireless access networks, because of several advantages such as providing huge bandwidth, inherent immunity to electromagnetic interference and reduced power consumption. The analog RoF networks cannot be used for the transmission of radio signals over long lengths of fiber due to the distortions induced by dispersion and nonlinearity of the optical link. The digitized RoF communication presents an interesting alternative to circumvent the limitations of ARoF networks. In this paper, we propose an all-optical DRoF (Digital RoF) scheme based on the optical encoding technique and optical codewords instead of modulation techniques. The proposed scheme is composed of an all-optical sampler, an all-optical thresholder and an all-optical encoder. The proposed all-optical DRoF design is simulated by implementing its three main components using the simulation platform, Optisystem. We have also studied the capacity of the proposed encoding architecture in terms of the maximum number of chips that can be supported. Furthermore, ARoF, DRoF and the proposed all-optical DRoF systems are compared based on the minimum bit error rate, the maximum quality factor, and the complexity and implementation cost.

Optical Physical-Layer Digital Network Coding for 2.5-Gb/s RoF-Based FiWi Networks

We demonstrate the first digital optical physical-layer network coding (OPNC) scheme for 2.5-Gb/s ON/OFF keyed (OOK) subcarrier modulated (SCM) signals suitable for the application in fiber-wireless networks. The proposed OPNC scheme employs all optical XOR logic gates that rely on cross-phase modulation-based Semiconductor Optical Amplifier (SOA) Mach–Zehnder interferometers to perform encoding and decoding operations. The proposed encoding and decoding scheme is targeting deployment at the central office and the clients site at the remote antenna units, respectively. Proof of concept verification is experimentally demonstrated for 2.5-Gb/s OOK-SCM data using a 10-GHz subcarrier. Both synchronous and asynchronous operations are evaluated, achieving error free operation.

Dominant handover algorithms for vehicular Radio-over-Fiber networks at 60 GHz: A performance evaluation study

In mobile picocellular network topologies a critical issue is the handover procedure in conjunction with the provided quality of service, due to the limited overlapping areas between adjacent cells. In vehicular picocellular networks handovers are more frequent and render quality of service metrics–such as packet loss rate, delay and jitter–even more critical, since the afore-mentioned limitation is combined with the high velocities of mobile end-users.The paper focuses on presenting the dominant handover algorithms in vehicular Radio-over-Fiber (RoF) networks at 60 GHz, i.e., the Traditional Handover Algorithm (THO), the Virtual Cellular Zone (VCZ), the Moving Extended Cell (MEC) and the Moving Extended N-Cells (MENC), respectively. Furthermore, we present a performance evaluation study on the provided quality of service for all the afore-mentioned handover algorithms. Specifically, for all four handover algorithms the corresponding theoretical mathematical models regarding packet losses are analyzed. Moreover, a simulation study is realized, in order to verify the theoretical results and to present algorithms’ effect on additional quality of service indicators, i.e., delay and jitter. The presented results of our performance evaluation study could be a valuable tool to network operators that plan to provide bandwidth-voracious services by deploying vehicular RoF network at 60 GHz.

Phase-shifted Brillouin dynamic gratings using single pump phase-modulation: proof of concept.

Two novel phase-shifted Brillouin dynamic gratings (PS-BDGs) are proposed using single pump phase-modulation (SPPM) in a polarization maintaining fiber (PMF) for the first time to our knowledge. Firstly, based on the stimulated Brillouin scattering (SBS), a transient PS-BDG with a 3-dB bandwidth of 354MHz is written by a 2-ns pump1 pulse and a 100-ps pump2 pulse, where the phase of pump1 pulse is shifted with π from its middle point through phase modulation. Then, with a high repetition rate of 250MHz for both pump pulses, an enhanced PS-BDG with a deep notch depth is obtained and its notch frequency can be easily tuned by changing the phase shift. We demonstrate a proof-of-concept experiment of the transient PS-BDG and show the notch frequency changing by tuning the phase shift. The proposed PS-BDGs have important potential applications in microwave photonics, all-optical signal processing and RoF (radio-over-fiber) networks.