FiWi Access Networks Research Articles

A MPCP-Based Centralized Rate Control Method for Mobile Stations in FiWi Access Networks

Fiber Wireless (FiWi) access networks is widely used to connect users to the core network. The FiWi access networks consist of the edge router, the Passive Optical Networks (PONs), and the wireless networks. In this environment, the edge router, which is the terminal to the core network, can have heavy congestion. To cope with this problem, we propose a Multi Point Control Protocol (MPCP)-based centralized rate control method to centrally control the traffic rate at each Home GateWay (HGW) so as to avoid congestion at the edge router. In the proposed scheme, the transmission delay due to rate control overhead can be mitigated. The performance of the proposed scheme is verified by numerical analysis and computer simulations.

Comparison and Analysis of ONU Sleep Mechanism Based on OPNET for Green Fiber-Wireless Access Network

As one of promising "last mile" scheme for broadband access network, Fiber-Wireless (FiWi) access network has the advantages of high capacity, long distance, low cost etc because it is the integration of optical back-end and wireless front-end. At the same time, energy consumption of FiWi access network is an important factor that limits the development of networks. A number of ONU sleep states such as ONU power shedding state, ONU doze state, ONU deep sleep state and ONU fast sleep state have been proposed to obtain low-power ONU state, which indirectly reduce energy consumption of networks. However, these low-power states of ONU are born to coordinate to green Passive Optical Network (PON), of which the function of ONU is different from FiWi. In this paper, two low power ONU sleep mechanisms called Static ONU Sleep (SOS) mechanism and Dynamic ONU Sleep (DOS) mechanism, respectively, are proposed and embedded into FiWi access network. By simulation and analysis based on OPNET 14.5, this paper shows that the DOS mechanism has a better performance than SOS, and both of them can save energy of FiWi access network.

Maximum covering planning of survivable Fiber-Wireless access network considering network connectivity

Fiber-Wireless (FiWi) access network is now becoming a promising architecture for access networks. Survivability is one of the key issues in the planning of FiWi access network because many high-rate traffic flows may be interrupted in case of a single fiber failure, which can cause a huge traffic loss. In addition, the users need ubiquitous broadband access that can be provided by FiWi access network. In this paper, we propose the protection approach called Maximum Covering Planning with Survivability (MCPS), including Integer Linear Programming (ILP) solution and heuristic solution, for the planning of survivable FiWi access network against single distribution fiber failure. The proposed approach aims at maximum coverage under the constraints of network connectivity. When a distribution fiber is broken, the interrupted Optical Network Unit (ONU) can transmit traffic to its backup ONU through the wireless paths between them. Simulation results show the network coverage of clients for different number of ONUs in different urban areas, and demonstrate the relationship between network coverage and the cost represented by the number of WiFi routers.

Performance improvement for applying network virtualization in fiber-wireless (FiWi) access networks

Fiber-wireless (FiWi) access networks, which are a combination of fiber networks and wireless networks, have the advantages of both networks, such as high bandwidth, high security, low cost, and flexible access. However, with the increasing need for bandwidth and types of service from users, FiWi networks are still relatively incapable and ossified. To alleviate bandwidth tension and facilitate new service deployment, we attempt to apply network virtualization in FiWi networks, in which the network’s control plane and data plane are separated from each other. Based on a previously proposed hierarchical model and service model for FiWi network virtualization, the process of service implementation is described. The performances of the FiWi access networks applying network virtualization are analyzed in detail, including bandwidth for links, throughput for nodes, and multipath flow transmission. Simulation results show that the FiWi network with virtualization is superior to that without.

Fiber-wireless (FiWi) access network: Performance evaluation and scalability analysis of the physical layer

The fiber-wireless (FiWi) access network is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In this paper, the FiWi access network is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul with data rate of 2.5Gb/s and wireless fidelity-worldwide interoperability for microwave access (WiFi–WiMAX) technologies at the wireless front-end along a 50m–5km wireless links with data rate of 54–30Mb/s, respectively. The performance of the optical backhaul and the wireless front-end, in the proposed FiWi access network, has been evaluated in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR) of the physical (PHY) layer. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length of 24km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10−9.

FiWi Access Networks Based on Next-Generation PON and Gigabit-Class WLAN Technologies: A Capacity and Delay Analysis

Current Gigabit-class passive optical networks (PONs) evolve into next-generation PONs, whereby high-speed Gb/s time division multiplexing (TDM) and long-reach wavelength-broadcasting/routing wavelength division multiplexing (WDM) PONs are promising near-term candidates. On the other hand, next-generation wireless local area networks (WLANs) based on frame aggregation techniques will leverage physical-layer enhancements, giving rise to Gigabit-class very high throughput (VHT) WLANs. In this paper, we develop an analytical framework for evaluating the capacity and delay performance of a wide range of routing algorithms in converged fiber-wireless (FiWi) broadband access networks based on different next-generation PONs and a Gigabit-class multiradio multichannel WLAN-mesh front end. Our framework is very flexible and incorporates arbitrary frame size distributions, traffic matrices, optical/wireless propagation delays, data rates, and fiber faults. We verify the accuracy of our probabilistic analysis by means of simulation for the wireless and wireless-optical-wireless operation modes of various FiWi network architectures under peer-to-peer, upstream, uniform, and nonuniform traffic scenarios. The results indicate that our proposed optimized FiWi routing algorithm (OFRA) outperforms minimum (wireless) hop and delay routing in terms of throughput for balanced and unbalanced traffic loads, at the expense of a slightly increased mean delay at small to medium traffic loads.

Fiber-Wireless (FiWi) Broadband Access Networks in an Age of Convergence: Past, Present, and Future

After describing the beginnings and state of the art of integrated fiber-wireless (FiWi) broadband access networks in great detail, we briefly review recent progress and point to various ongoing research activities, including the design of energy-efficient “green” FiWi access networks, advanced survivability techniques, and integration of wireless and fiber optic sensors, towards realizing adaptable, dependable, and ecoconscious future-proof broadband access networks based on both wireless and shared passive fiber media. Furthermore, we discuss service, application, business, and operation related aspects, which motivate access technology to move into a substantially different direction in the long run than continued capacity provisioning. Given that most 4G cellular mobile network researches so far have been focusing on the achievable performance gains in the wireless front-end only without looking into the details of backhaul implementations and possible backhaul bottlenecks, we identify open key research challenges for FiWi broadband access networks. We explore ways of how they can be deployed across relevant economic sectors other than telecommunications per se, taking major paradigm shifts such as the Third Industrial Revolution, Energy Internet, smart grid, and explosion of mobile data traffic in today’s cellular networks into account.

Deployment of survivable fiber-wireless access for converged optical and data center networks

As a promising solution for the bandwidth bottleneck of Data Center (DC) network, the converged optical and DC networks have gained an increasing popularity due to their advantages in rich bandwidth and high reliability. Although the converged optical and DC networks bring the opportunity for high-speed transmission of DC traffic, they also impose more severe challenge on the survivability design, because the network component failure will cause greater data loss. Some works focus on the survivability of core network for the convergence of optical and DC networks and remain less touched on that of access network. In fact, access network plays an important role in the reliable transmission of the traffic between end-users and DC, which accounts for considerable portion of all DC traffic. However, since the vulnerability to component failure, the traditional Passive Optical Network (PON) may no longer satisfy the higher survivability requirement. As an emerging broadband access technology, Fiber-Wireless (FiWi) may be a preferable candidate for the survivable access of converged optical and DC networks. In FiWi access network, the Wireless Mesh Network (WMN) at front-end can protect the Passive Optical Network (PON) at back-end by wirelessly rerouting. This paper focuses on the deployment of survivable FiWi access network against single distribution fiber failure, which is a typical failure scenario in optical access network. We propose a new protection approach called Wireless Rerouting with Backup Radios (WRBR) for the deployment of survivable FiWi access network. In WRBR, we deal with the optimization of wireless routers placement and backup radios configuration. Both Integer Linear Programming (ILP) and heuristic approach are proposed, aiming to minimize the deployment cost. Simulation results demonstrate the advantage of WRBR in saving deployment cost of FiWi access for converged optical and DC networks over the previous works.

Dependable Fiber-Wireless (FiWi) Access Networks and Their Role in a Sustainable Third Industrial Revolution Economy

According to the Organisation for Economic Co-operation and Development (OECD), broadband access networks enable the emergence of new business models, processes, inventions, as well as improved goods and services. In fact, broadband access is viewed as a so-called general purpose technology (GPT) that has the potential to fundamentally change how and where economic activity is organized. In this paper, we focus on the implications of the emerging Third Industrial Revolution (TIR) economy, which goes well beyond current austerity measures, and has recently been officially endorsed by the European Commission as the economic growth roadmap toward a competitive low carbon society by 2050. This roadmap has been receiving an increasing amount of attention by other key players, e.g., the Government of China most recently. More specifically, we describe a variety of advanced techniques to render converged bimodal fiber-wireless (FiWi) broadband access networks dependable, including optical coding based fiber fault monitoring techniques, localized optical redundancy strategies, wireless extensions, and availability-aware routing algorithms, to improve their reliability, availability, survivability, security, and safety. Next, we elaborate on how the resultant dependent FiWi access networks can be exploited to enhance the dependability of other critical infrastructures of our society, most notably the future smart power grid and its envisioned electric transportation, by means of probabilistic analysis, co-simulation, and experimental demonstration.

Cooperative QoS Control Scheme Based on Scheduling Information in FiWi Access Network

Fiber-wireless (FiWi) access networks comprising wireless local area networks (WLANs) and passive optical networks (PONs) have attracted much attention recently for future cyber-physical systems (CPSs). Because of the explosive growth of smart devices such as smart phones and sensors, the number of such devices has also grown phenomenally that require real time communication demanding quality of service (QoS)-centric applications for CPSs, such as smart grid, medical, and traffic control systems, which construct smart society. To deal with such situations, the FiWi access networks may be a suitable choice since they are capable of providing both wide bandwidth and flexibility. However, combining the WLAN and PON in FiWi that are inherently different networking technologies leads to inefficient data transmission in the point of junction of the WLAN and PON. Therefore, the QoS of real time communication degrades significantly. In this paper, we address this problem involving QoS degradation in the FiWi networks, and propose a QoS control scheme, which is based on cooperation between the WLAN and PON. Through computer-based simulations, we demonstrate that our proposed scheme can significantly improve the QoS performance of the FiWi access networks for CPSs.

Energy efficient routing algorithm for fiber-wireless access networks: A network formation game approach

New multimedia services and ubiquitous networking pose great challenges on existing access network infrastructures. To cope with such requirements new access technologies, such as the fiber-wireless (FiWi), are being developed. Together with the emergence of new access networks, efforts are being made to reduce the amount of energy required to provide services. Indeed, this issue plays an increasingly important role. Here we propose an energy efficient routing algorithm for FiWi access networks. The main idea is to exploit the multipath capabilities of the wireless mesh front end of FiWi access networks to create energy efficient routes that optimize the sleeping and active periods of all ONUs and wireless nodes. To achieve this goal, an energy efficient network model based on network formation game theory is used. This model allows several network formation processes to be compared in regard to the energy efficiency of the routes they generate. Our results reveal that the farsighted network formation process establishes the most energy efficient routes, meaning that the choices done by this formation process were the best ones. However, this farsighted process is computationally expensive. For this reason a heuristic algorithm is developed, which explores the most energy efficient choices taken by the network formation processes, and farsighted process in particular. Results show that the proposed heuristic is able to obtain results close to the farsighted process.

Cluster-Based Protection for Survivable Fiber-Wireless Access Networks

Survivability is one of the key issues in fiber-wireless (FiWi) access networks, since network component failure may cause huge data loss. Especially in the scenario of segment failure, all optical network units (ONUs) lose their connections with the optical line terminal. Previous works focus on the protection of FiWi against segment failure by deploying backup fibers among the backup ONUs in different segments. However, these works consider only single segment failure. They also ignore the issue of traffic recovery efficiency. More importantly, they underutilize the backup fibers and ignore optimizing the selection of backup ONUs. Therefore, these works usually require a considerable deployment cost for backup fibers. To conquer these challenges, we propose an efficient protection scheme called cluster-based protection (CBP) in this paper. In CBP, we first partition the segments in the network into clusters in order to reduce the overhead for the management of traffic recovery. Then, we select one of the ONUs in each segment as the backup ONU and deploy backup fibers among the backup ONUs of different segments in the same cluster. Under a constraint on the maximum number of segments in each cluster, the CBP scheme aims to protect FiWi against the simultaneous failures of multiple segments with a minimum deployment cost for backup fibers. We propose both an integer-linear-programming-based approach and a heuristic approach to solve the joint optimization problem in CBP of selecting backup ONUs, clustering segments, and deploying backup fibers. To the best of our knowledge, this paper is the first work regarding the survivability of FiWi against the simultaneous failures of multiple segments. Through extensive simulation, we demonstrate that our CBP scheme outperforms the previous works significantly in terms of survivability enhancement and cost savings.

The power of smartphones

Smartphones have been shipped with multiple wireless network interfaces to meet their diverse communication and networking demands. However, as smartphones increasingly rely on wireless network connections to realize more functions, the demand of energy has been significantly increased, which has become the limit for people to explore smartphones’ real power. In this paper, we first review typical smartphone computing systems, energy consumption of smartphone, and state-of-the-art techniques of energy saving for smartphones. Then, we propose a location-assisted Wi-Fi discovery scheme, which discovers the nearest Wi-Fi network access points (APs) using the user’s location information. This allows the user to switch to the Wi-Fi interface in an intelligent manner when he/she arrives at the nearest Wi-Fi network AP. Thus, we can meet the user’s bandwidth needs and provide the best connectivity. Additionally, it avoids the long periods in idle state and greatly reduces the number of unnecessary Wi-Fi scans on the mobile device. Our experiments and simulations demonstrate that our scheme effectively saves energy for smartphones integrated with Wi-Fi and cellular interfaces.

Placement of ONUs and Wireless Routers in Fiber-Wireless Access Network with Survivability Constraints

Survivability is one of the key issues in Fiber-Wireless (FiWi) access network since a single network component failure may cause enormous data loss. This paper focuses on survivability of citywide FiWi access network and proposes a scheme using Integer Linear Programming (ILP) to tolerate the failures of distribution fiber and WiFi routers considering coverage problem. Simulation shows good performance of this scheme. When WiFi routers and ONUs are places in suitable potential sites, the maximal coverage of uses and survivability of FiWi access network are realized.

Load Adaptive and Fault Tolerant Framework for Energy Saving in Fiber–Wireless Access Networks

Energy saving (ES) in telecommunication networks is an important criterion when planning access networks. In fiber-wireless (FiWi) access networks the ES potential is high, when compared with other architectures, because different routes and optical access points can be used by routers at the wireless section. Although some proposals to increase energy efficiency in these architectures have been presented, these are not approaches that can adapt to variations in traffic load or distribution of traffic across the network. Here we fill this gap and propose a load adaptive and fault tolerant framework for ES in FiWi access networks. This framework allows optical network units (ONUs) to enter long-standing sleep mode under low traffic conditions, reducing energy waste, permitting fast reaction to ONU or fiber failures, and allowing quality of service (QoS) to be kept at a certain level. Results show that significant ES can be achieved under low to medium traffic loads while maintaining QoS and fault tolerance.

Energy-efficient rings mechanism for greening multisegment fiber-wireless access networks

Through integrating advantages of optical and wireless communications, the Fiber-Wireless (FiWi) has become a promising solution for the “last-mile” broadband access. In particular, greening FiWi has attained extensive attention, because the access network is a main energy contributor in the whole infrastructure. However, prior solutions of greening FiWi shut down or sleep unused/minimally used optical network units for a single segment, where we deploy only one optical linear terminal. We propose a green mechanism referred to as energy-efficient ring (EER) for multisegment FiWi access networks. We utilize an integer linear programming model and a generic algorithm to generate clusters, each having the shortest distance of fully connected segments of its own. Leveraging the backtracking method for each cluster, we then connect segments through fiber links, and the shortest distance fiber ring is constructed. Finally, we sleep low load segments and forward affected traffic to other active segments on the same fiber ring by our sleeping scheme. Experimental results show that our EER mechanism significantly reduces the energy consumption at the slightly additional cost of deploying fiber links.

Transparent network-assisted flow mobility for multimedia applications in IMS environments

Cellular network operators are striving to solve the problem caused by the increasing volume of traffic over their networks. Given the proliferation of multi-interface devices, offloading part of the traffic to available access networks (e.g., WiFi or 3G access networks, even from other operators) seems to be a promising alternative. Here, we propose an IMS-compatible solution for flow mobility between access networks that exhibits two key features: flow mobility is transparent to both local applications at mobile nodes and their communication peers (e.g., multimedia content servers), and mobility operations are assisted by the network, so the home network supports the terminal in the process of access network discovery, and provides the terminal with policies that meet visited and home operators¿ roaming agreements while optimizing the use of their networks. The proposed solution has been validated using a real IMS testbed with Ethernet and WiFi access networks, where the mobility of UDP and TCP flows has been tested.

Energy-Efficient Rings: A Green Mechanism for Multi-Segment Fiber-Wireless Access Networks

In this paper, we propose a novel green mechanism called Energy-Efficient Ring (EER) for multi-segment Fiber-Wireless (FiWi) access networks. We first utilize clustering scheme to generate clusters each with the shortest distance of fully connected segments in it. Leveraging backtracking method, we then connect segments in each cluster through fiber links and the shortest fiber ring is constructed in each cluster. Finally, we sleep low load segments and forward affected traffic to other active segments on the same fiber ring. Experimental results show that EER significantly reduces the energy consumptions at the slightly additional cost of deploying fiber links.

VMP: A MAC Protocol for EPON-Based Video-Dominated FiWi Access Networks

Optical and wireless network technologies are expected to converge in the near to midterm, giving rise to bimodal fiber-wireless (FiWi) broadband access networks. In triple-play (voice, video, and data) service scenarios for such FiWi access networks, video traffic will likely dominate due to the widely predicted increase in video network services and the high traffic volume of compressed video compared to voice and data services. In this paper, we introduce and evaluate a comprehensive video MAC protocol (VMP) to efficiently deliver prerecorded video downstream to wireless consumers over a FiWi network in the presence of voice and data upstream and downstream traffic. VMP consists of three main novel components: (i) frame fragmentation in conjunction with hierarchical frame aggregation for efficient MAC frame transport over the integrated optical and wireless network segments, (ii) multi-polling medium access control for upstream voice and data packets and acknowledgements for downstream video packets, and (iii) prefetching of video frames over the optical and wireless network segments in conjunction with hybrid reservation/contention-based medium access. Our simulation results indicate that VMP achieves significant improvements in throughput-delay performance for all three traffic types as well as reductions in the playback starvation probability for video traffic compared to existing state-of-the-art MAC mechanisms.

Design of QoS-Aware Energy-Efficient Fiber–Wireless Access Networks

Energy-efficient network design has recently become a very important topic because of the energy cost increases in service providers’ infrastructures. This is of particular importance in access networks because of the growing demand for digital traffic by end users. Here we address the challenge of reducing the energy consumption of fiber–wireless (FiWi) access networks, which use both optical and radio frequency technologies to provide high bandwidth and ubiquity for end-user applications, while keeping delay under a threshold. Our goal is to find optimal sleep mode schedulings that allow energy consumption to be reduced while keeping packet delay acceptable. For this purpose a mathematical formalization and an algorithm are developed. The results show that the proposed approach is able to reduce the average packet delay, with negligible energy cost increases, in many scenarios, besides being computationally efficient and scalable. The proposed approach may, therefore, serve as a basis for planning and design of quality-of-service-aware energy-efficient FiWi access networks.