This article provides an up-to-date survey of hybrid fiber-wireless (FiWi) access networks that leverage on the respective strengths of optical and wireless. A definitive objective of Fiber-Wireless (FiWi) systems is the meeting of different optical and wireless innovations under a solitary base keeping in mind the end. Survey Smoothly Fiber-Wireless (FiWi) Accessing Wireless Networks: Convergence and Challenges. Naseer Hwaidi Alkhazaali, Raed Abduljabbar Aljiznawi.
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Not only do the required tunable transmitters add to the complexity and cost of each ONU but also might optical amplifiers become necessary to compensate for the coupling and insertion losses of the inserted combiner netorks AWG, thereby violating the unpowered nature of PONs and cost-sensitivity of access networks in general.
Each receiving ONU determines to discard or forward the traffic according to the location of the destination mesh client.
A given ingress wireless router computes a path to a gateway, if the traffic is DTS-sensitive. Availability is the probability that a connection will be found in the operating state at a random time in the future. Each optical terminal is equipped with a thin film filter TFFwhich lets pass only the corresponding wavelength channel of a given optical terminal. The delay along different paths may be different and may vary over time. The external buffers can store DTS-insensitive data packets when the links are congested and forward them to the server when the links to the gateways become less congested.
The presented simulation results show that under different network sizes the proposed tabu search heuristic outperforms random and fixed ONU placement schemes in terms of achievable network throughput, especially for an increasing number of ONUs. Bringing fiber all the way to buildings gives rise to FTTB networks. In Section 3we review the state of the art of FiWi broadband access networks, while recent progress is described in Section 4.
When migrating from macro-only to HetNet environments, mobility management becomes more challenging due to increased interference and decreased femto cell radius. According to [ 92 ], there is a clear trend toward including additional mobility enhancements in future LTE releases to ensure a smooth migration from traditional network controlled to user equipment UE assisted mobility as a remedy for reducing signaling overhead via fiber interconnections between macrocells and small cells.
However, these data packets may arrive at the OLT out of order due to the fact that each path in general has a different delay. In this section, we describe a number of algorithms that help solve important FiWi network planning problems related to the optimal placement of ONUs, mitigation of the detrimental impact of wireless interferences for peer-to-peer communications between wireless end-users, and architectural modifications for the support of direct inter-ONU communications.
However, for FiWi access networks with a larger number of nodes and higher traffic loads, heuristics are needed to solve the problem. View at Scopus P. FiWi access networks are instrumental in strengthening our information society while avoiding its digital divide. In , we recently described a variety of advanced techniques to render FiWi broadband access networks dependableincluding optical coding based fiber fault monitoring techniques, localized optical redundancy strategies, wireless extensions, and availability-aware routing algorithms, in order to improve their reliability, availability, and survivability as well security and safety.
Furthermore, broadband increases competitiveness and flexibility in the economy by the increased diffusion of information at lower cost and by improving market access to increasingly larger markets. A metropolitan area FiWi network architecture called optical burst wireless mesh architecture OBWMAwhich interconnects multiple WMNs at the user access side through an optical burst switching OBS core network, was proposed in [ 63 — 65 ].
Fiber-wireless (FiWi) access networks: A survey – Semantic Scholar
To fiqi this optimization problem, the authors applied a tabu search based heuristic, a widely used metaheuristic algorithm for solving combinatorial problems. Beside economic and regulatory issues, the new key challenges arising in femtocell deployments are i interference coordination, ii cell association and biasing, iii mobility and soft handover, and iv self-organizing networks SONs [ 89 ].
In a wireless front-end with multiple-radio mesh nodes, it is important to assign the wireless channels efficiently such that contention is reduced. The simulation and experimental work in [ 68 ] has shed some light on the tradeoff between energy saving and QoS support in FiWi access networks.
In the downstream direction, data packets are routed from the CO to the wireless gateways through the optical backhaul and are then forwarded to the MCNs by wireless mesh routers. With the advent of high-speed IEEE FTTCab is also used by cable network operators to build hybrid fiber-coax HFC networks, where the drop lines are realized through coax cables instead of twisted pairs.
However, with increasing peer-to-peer traffic the interferences in the wireless mesh front-end increase and the throughput of WMNs decreases dramatically. Equipping some of the wireless mesh routers with an additional radio does not lead to an increased maximum throughput due to the fact that the bottleneck links remain the same; however, it helps reduce the average delay of the network to some extent.
A number of different remodulation schemes have been proposed and investigated, for example, differentiated phase-shift keying DPSK for downstream and on-off-keying OOK for upstream, optical carrier suppression OCS for downstream and reused for upstream, or PM for downstream and directly modulated semiconductor optical amplifier SOA for upstream. Skip to search form Skip to main content. Access network Wireless mesh network. Historical recurrence of once-in-a-half-century bubble and golden age prosperities [ 88 ].
For each successful perturbation, wireless end-users are reassigned to their nearest ONU. See our FAQ for additional information. Toward this end, the proposed heuristic deploys the wireless access points or base stations uniformly, determines their transmission radius, and assigns channels to them such that the carrier-to-interference ratio does not drop below a certain threshold.
Fiber-wireless (FiWi) access networks: A survey
Whenever the wireless link conditions change, a WiMAX subscriber station sends a bandwidth request message to its accsss ODU to update its service requirements. In the proposed architecture, low-complexity RAUs are connected via analog RoF links to a central processing unit CUwhich performs joint signal processing and resource management.
The CO is responsible for managing the transmission of information between mobile client nodes MCNs and their associated APs as well as acting as a gateway to other networks.
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. Multipath routing and its implications have been studied in greater detail in [ 54 ].
Finally, paving all the way to the home with optical fiber leads to FTTH networks, which come in two flavors: This major difference between optical fiber and wireless links should also be taken into account in the design of integrated routing algorithms for FiWi access networks.
In the WMN, a certain percentage of the link capacity is allocated to each traffic class at every mesh node and either traffic class is allowed to exceed its allocated bandwidth flber-wireless if the other traffic class has not reached its fibber-wireless bandwidth.
Advances in Optics
Another important trend is the convergence of mobile cellular networks and WSNs in order to support machine-to-machine M2M communications. According to [ 17 ], external intensity and phase modulation schemes are the most practical solutions for all-optical RF generation due to their low cost, simplicity, and long-distance transmission performance.
More specifically, the OLT is equipped with an array of fixed-tuned transmitters and an array of fixed-tuned receivers, each operating on a different dedicated wavelength fiber-wireldss, for transmitting and receiving data to and fiber-wirelesx the ONUs.