Hybrid Optical-wireless Networks Research Articles

A hybrid optical-wireless network for decimetre-level terrestrial positioning.

Global navigation satellite systems (GNSS) are widely used for navigation and time distribution1-3, features that are indispensable for critical infrastructure such as mobile communication networks, as well as emerging technologies such as automated driving and sustainable energy grids3,4. Although GNSS can provide centimetre-level precision, GNSS receivers are prone to many-metre errors owing to multipath propagation and an obstructed view of the sky, which occur particularly in urban areas where accurate positioning is most needed1,5,6. Moreover, the vulnerabilities of GNSS, combined with the lack of a back-up system, pose a severe risk to GNSS-dependent technologies7. Here we demonstrate a terrestrial positioning system that is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronized at the subnanosecond level through a fibre-optic Ethernet network8. Using optical and wireless transmission schemes similar to those encountered in mobile communication networks, and exploiting spectrally efficient virtual wideband signals, the detrimental effects of multipath propagation are mitigated9, thus enabling robust decimetre-level positioning and subnanosecond timing in a multipath-prone outdoor environment. This work provides a glimpse of a future in which telecommunication networks provide not only connectivity but also GNSS-independent timing and positioning services with unprecedented accuracy and reliability.

Hybrid Medium Access Control Protocol for Radio-Over-Fiber Networks

The oncoming Internet-of-things (IoT) applications and smart machine-to-machine (M2M) communication lead to an enormous increase in network traffic. To meet the escalating demands of these time-critical applications, we need a hybrid optical-wireless network, for which the radio-over-fiber (RoF) technology is a promising candidate. These networks need to support the stringent delay requirements of the above applications for a large number of mobile users. However, the existing user registration and identification approaches for these networks are not efficient for a high user density and cannot keep the overall mean delay within the permissible limit for such applications. In this article, we present a hybrid medium access control (MAC) protocol for the RoF network, for which we propose hybrid user identification and neighbor-aware hybrid user identification algorithms for high user density. Further, the MAC protocol uses a gated polling method for data transfer. Moreover, we propose an analytical delay model for the hybrid MAC protocol, which gives overall end-to-end mean delay considering user identification and data transfer. We verify it with the results obtained from the simulations. Finally, we evaluate the mean delay and packet loss rate of the proposed algorithms by varying the network load, user density, and fiber length and benchmark the performance of the proposed algorithm with the state-of-the-art (SoA).

Self-configuration and self-optimization process with taguchi method in hybrid optical wireless network

<p>In this paper, an alternative improvement is proposed which is the adaptive wireless access networks-based optical backhaul convergence that will greatly promote to use the existing resource of MANET (mobile ad hoc network). However, these characteristics itself acts as a drawback to the MANET applications such as the random distribution of nodes and continuously changing topology. MiNiTab statistical software was used to model the effect of the parameter variation to predict the field quality through the design of experiments while OMNeT++ network simulation was created to visualize the effect of QoS performance study in response with varying speed scenario. The result shows that the proposed ESCMDR scheme can obtain robustness and outperformed compared to the non-Taguchi previous study when it is used in random waypoint mobility model in any speed of sources. The work is based on Packet Delivery Ratio (PDR) and Packet Loss Probability (PLP) metric under the varying speed scenario. It results in better QoS network PDR of 28.9% improvement, with 83.56% improvement on average PLP. The paper shows that the MANET QoS performance constrained can be addressed with the self-configured data rate of integrated optimization with Taguchi method on AODV-UU (Adhoc On Demand Distance Vector-Uppsala University) routing technique.</p>

Multi-domain SDN controller federation in hybrid FiWi-MANET networks

Traditionally, mobile ad hoc networks (MANET) and hybrid optical-wireless networks, also known as fiber-wireless (FiWi), have been considered disjointly and independently, with no synergic management solutions. The former has primarily focused on dispatching packets among mobile nodes in infrastructure-less and very dynamic environments, the latter on offering high-bandwidth and low-latency access to cellular-equipped mobile nodes. The recent advancements and penetration of software-defined networking (SDN) techniques have stimulated the adoption of SDN-based flexible monitoring and control also for the MANET and FiWi domains. In this perspective, the paper originally proposes a model and an architecture that loosely federate MANET and FiWi domains based on the interaction of MANET and FiWi controllers: the primary idea is that our MANET and FiWi federated controllers can seldom exchange monitoring data and control hints the one with the other, thus mutually enhancing their capability of packet management over hybrid FiWi-MANET networks. Our model is applied to several relevant use cases to practically point out the benefits of the proposal in terms of both load balancing and fairness improvements.

Quality Management of Surveillance Multimedia Streams Via Federated SDN Controllers in Fiwi-Iot Integrated Deployment Environments

Traditionally, hybrid optical-wireless networks (Fiber-Wireless - FiWi domain) and last-mile Internet of Things edge networks (Edge IoT domain) have been considered independently, with no synergic management solutions. On the one hand, FiWi has primarily focused on high-bandwidth and low-latency access to cellular-equipped nodes. On the other hand, Edge IoT has mainly aimed at effective dispatching of sensor/actuator data among (possibly opportunistic) nodes, by using direct peer-to-peer and base station (BS)-assisted Internet communications. The paper originally proposes a model and an architecture that loosely federate FiWi and Edge IoT domains based on the interaction of FiWi and Edge IoT software defined networking controllers: the primary idea is that our federated controllers can seldom exchange monitoring data and control hints the one with the other, thus mutually enhancing their capability of end-to-end quality-aware packet management. To show the applicability and the effectiveness of the approach, our original proposal is applied to the notable example of multimedia stream provisioning from surveillance cameras deployed in the Edge IoT domain to both an infrastructure-side server and spontaneously interconnected mobile smartphones; our solution is able to tune the BS behavior of the FiWi domain and to reroute/prioritize traffic in the Edge IoT domain, with the final goal to reduce latency. In addition, the reported application case shows the capability of our solution of joint and coordinated exploitation of resources in FiWi and Edge IoT domains, with performance results that highlight its benefits in terms of efficiency and responsiveness.

Hybrid Optical Wireless Network for Future SAGO-Integrated Communication Based on FSO/VLC Heterogeneous Interconnection

Free-space optics (FSO) and visible light communication (VLC) share the same optical wireless features, such as high data rate, license free, energy efficient, flexible access, and high degree of security. A hybrid optical wireless network based on FSO/VLC heterogeneous interconnection is presented here for future space-air-ground-ocean-integrated communication architecture, especially in the radio-frequency-sensitive (RF) or security-required environments. The functional modules of the hybrid network coordinator are defined, along with the implementation and deployment details. Three fundamental network-layer mechanisms are designed in the coordinator including user identification and localization, user mobility and handoff control, and routing and traffic management. An experimental platform is built to evaluate the transmission performance of the presented hybrid network, and a complete data aggregation/transmission/distribution procedure based on heterogeneous interconnection is first realized, which includes two-segment 1.0-m 450-Mb/s orthogonal-frequency-division-multiplexing-based VLC transmissions interconnected by one-segment 430-m 0.96-Gb/s on-off keying (OOK)-based nonturbulent FSO transmission, with the bit error rate under the forward-error-correction limit (3.8 × 10−3 ). The VLC transmission performances under three speed levels and FSO transmission performances under five typical air-quality conditions are experimentally demonstrated, which validate the feasibility of the proposed hybrid optical wireless network.

DIANA: A Machine Learning Mechanism for Adjusting the TDD Uplink-Downlink Configuration in XG-PON-LTE Systems

Modern broadband hybrid optical-wireless access networks have gained the attention of academia and industry due to their strategic advantages (cost-efficiency, huge bandwidth, flexibility, and mobility). At the same time, the proliferation of Software Defined Networking (SDN) enables the efficient reconfiguration of the underlying network components dynamically using SDN controllers. Hence, effective traffic-aware schemes are feasible in dynamically determining suitable configuration parameters for advancing the network performance. To this end, a novel machine learning mechanism is proposed for an SDN-enabled hybrid optical-wireless network. The proposed architecture consists of a 10-gigabit-capable passive optical network (XG-PON) in the network backhaul and multiple Long Term Evolution (LTE) radio access networks in the fronthaul. The proposed mechanism receives traffic-aware knowledge from the SDN controllers and applies an adjustment on the uplink-downlink configuration in the LTE radio communication. This traffic-aware mechanism is capable of determining the most suitable configuration based on the traffic dynamics in the whole hybrid network. The introduced scheme is evaluated in a realistic environment using real traffic traces such as Voice over IP (VoIP), real-time video, and streaming video. According to the obtained numerical results, the proposed mechanism offers significant improvements in the network performance in terms of latency and jitter.

Traffic-prediction-assisted dynamic bandwidth assignment for hybrid optical wireless networks

Hybrid optical-wireless networks provide the inexpensive broadband bandwidth, vital for modern applications, as well as mobility, and scalability required for an access network. However, in order to provide satisfactory Quality of Service (QoS) on such a non-homogeneous network, innovative designs are required. This paper proposes a novel scheduling mechanism to significantly improve the delay guarantee, while maintaining high-level throughput, by predicting the incoming traffic to optical network units (ONU). The proposed scheduler managed to exploit the available information in hybrid optical-wireless networks, to enhance the ONU scheduler. This results in accurate prediction of incoming traffic, which leads to intelligent and traffic-aware, scheduling and dynamic bandwidth assignment (DBA). Based on the proposed architecture, two DBA algorithms are proposed and their performance is evaluated by extensive simulations. Moreover, the maximum throughput of such network is analyzed. The results show that by using the proposed algorithms, the delay bound of delay-sensitive traffic classes can be decreased by a factor of two, without any adverse effect on the throughput.

Integrated resource management framework in hybrid optical wireless networks

The interworking between optical networks and wireless networks is a promising evolution approach for fixed mobile convergence networks, which can exploit and combine their complementary characteristics. Efficient utilisation of available bandwidth over hybrid optical wireless networks is a critical issue, especially for multimedia applications with high data rates and stringent quality of service (QoS) requirements. The authors present a resource management framework in a hybrid Ethernet passive optical network (EPON) and worldwide interoperability for microwave access network. First, the authors formulate and study the problem of sharing resource allocation information between optical and wireless domains. The existing signalling protocol in EPON is modified and enhanced. Secondly, a novel integrated admission control scheme is proposed. Simulations conducted using the optimised network evaluation tool modeller show that the proposed system achieves significant improvements in terms of user QoS guarantee and network resource utilisation.

Investigation on a microring laser coupled with phase-section bus waveguide as a tunable transmitter for application in future optical/wireless hybrid networks

In this paper, semiconductor microring lasers with integrated phase sections in the bus waveguide are numerically evaluated, using a dynamic multimode laser model, and investigated as low-cost, integrated, potential tunable directly modulated transmitters for future hybrid optical–wireless networks. The effect of optical feedback through bus waveguide is revealed as a promising mechanism for improving nonlinear distortion. Additionally, tunability is achieved with the aid of phase-tuning. The underlying laser dynamics beyond this behavior are analyzed.