Omar Carvalho Branquinho

Analysis of performance degradation in Radio-over-Fiber systems based on IEEE 802.16 protocol

In order to the increasing demand for wireless connectivity and large coverage, Radio-over-Fiber (RoF) infrastructure has been suggested as a cost-effective solution for the provisioning of bandwidth in small cell size. In this article, we present an analysis of the use of RoF technology in IEEE 802.16 networks. The propagation delay introduced by the fiber length impacts the tuning of MAC and physical layers parameters. For an effective tuning, we present a comprehensive study of the performance degradation of WiMAX networks employing RoF infrastructure. Results were obtained using analytical models and simulations. Results indicate the viability of RoF scenarios with degradation bounded to 20% at physical layer when using fiber links with maximum length of 115 Km and degradation bounded to 20 % at application layer for fiber length up to 80 Km.

Mobility Impact on IEEE 802.15.4 Network through a Simulation Platform

The IEEE 802.15.4 network standard is being used as a suitable solution for wireless sensor networks in many environments and areas of expertise. They differ from other types of wireless networks because of its specific features. This work intends to analyse the mobility impact on IEEE 802.15.4 networks. For this reason it was developed a simulation platform with the requirements necessary to evaluate and compare environments with and without mobility. The results show that the mobility of elements in the scenarios evaluated caused signal degradation at short distances, but improvement in the rate of transmission for distances between 30 and 40 meters, as well as at distances greater than 60 meters. This is due to the fact that at intermediate distances the network presents high rate of collisions, making the technique CSMA/CA improve network performance in environments with more variability of the signal.

MAC protocols for wireless sensor networks over radio-over-fiber links

In this paper, two Medium Access Control (MAC) protocols exclusively tailored to WSNs over RoF (RWSNs) namely SPP-MAC (Scheduled Priority Polling Medium Access Control) (polling-based) and HMARS (Hybrid Medium Access Control for Hybrid Radio-over-Fiber Wireless Sensor Network Architecture) (hybrid-based) are proposed. They deal with the main problems in RWSNs i.e. the delay imposed by optical fiber and the existence of two collision domains: the wireless and the fiber optical links. The performance of these two protocols evince their effectiveness for the connection of WSNs by RoF links.

Optimization of the Use of Radio Resource of Radio-Over-Fiber Access Networks

In this paper, we introduce a radio resource optimization model for Radio-over-Fiber (RoF) access networks. We propose a mixed integer programming model to minimize the network cost while providing service to all mobile users. The proposed architecture arranges cells in a multi-layer fashion, with cells in each layer providing different coverage radius. The optimization algorithm performs dynamic cell splitting to improve network capacity in congested areas and cell merging in areas with low demand to save resources. The computational demand of the proposed model increases proportionally to the number of layers of RAUs in the infrastructure. Results indicate that two layers of RAUs give the best trade-off between network cost reduction and computational demand.

Radio Resource Allocation and GreenOperation for Mobile Access Networks Basedon Radio-over-Fiber

This paper proposes an architecture for mobile wireless networks based on Radio-over-Fiber (RoF) technology. The architecture organizes cells in a multi-tier fashion, with different tiers covering areas with different radii lengths. Proposed optimization algorithm splits cells to improve network capacity in congested areas and merges cells when the demand is low. The evaluation of the effectiveness of the proposed model considered three distinct objectives: minimization of the number of base stations used, maximization of the number of users served, and minimization of network energy consumption. The combination of the first two objectives was also evaluated. Three algorithms based on linear relaxation techniques are introduced for rapid computation of the near-optimum solutions. The proposed architecture is shown to lead to network infrastructures that save costs and energy and yet provide service to a large number of users.

Investigation of noise sources in Radio-over-Fiber systems for Wi-Fi applications

This work presents a experimental and analytical evaluation of Radio-over-Fiber (RoF) systems applied in Wi-Fi networks operating at 2.4 GHz. The performance metrics used were Packet Error Rate (PER), throughput and Relative Signal Strength Indication (RSSI). We used two different commercial RoF systems and verified the impact of each system on these networks. It was observed that Wi-Fi technology can be successfully applied with RoF technology to provide a remote employment up to 3 km from central office.

LatinCon04 - Analysis of Performance Degradation in Radio-Over-Fiber Systems Based on IEEE 802.16 Protocol

In order to the increasing demand for wireless connectivity and large coverage, Radio-over-Fiber (RoF) infrastructure has been suggested as a cost-effective solution for the provisioning of bandwidth in small cell size. In this article, we present an analysis of the use of RoF technology in IEEE 802.16 networks. The propagation delay introduced by the fiber length impacts the tuning of MAC and physical layers parameters. For an effective tuning, we present a comprehensive study of the performance degradation of WiMAX networks employing RoF infrastructure. Results were obtained using analytical models and simulations. Results indicate the viability of RoF scenarios with degradation bounded to 20% at physical layer when using fiber links with maximum length of 115 Km and degradation bounded to 20% at application layer for fiber length up to 80 km.

Protocols for Wireless Sensors Networks Connected by Radio-Over-Fiber Links

Radio-over-fiber (RoF) technology has been employed in network infrastructure due to its large capacity, low attenuation, and low operational costs, as well as due to the possibility of enlarging network coverage. This paper introduces a new approach for the interconnection of wireless sensor network (WSN) by employing RoF links, specifically wireless sensor network based on radio-over-fiber (WSN-RoF). The main contribution of this paper is the introduction of an architecture for the interconnection of WSN and two medium access control (MAC) protocols exclusively tailored to WSN-RoF architecture: scheduling of polling priority MAC and dynamic hybrid MAC for WSNs based on RoF access infrastructure. Both protocols deal with the main problems in WSN-RoF, i.e., the round-trip propagation delay in optical fiber links and the existence of two distinct collision domains: one wireless and the other optical. The performance of these two protocols shows their effectiveness in the interconnection of WSN through RoF links. Results of experiments demonstrate the benefits of using RoF links for the backhaul of WSN.

Fast algorithms for resource allocation in Radio-over-fiber access networks

This article presents algorithms for the optimization of radio resources and proposes an optimization model that can be implemented in dynamic mobile networks based on RoF. The algorithms are based on linear relaxation technique for integer linear programming (ILP) problems. The formulation models a multi-tier structure of antennas with increasing radius. Considering this antenna structure the optimizer performs dynamic cell merging and cell splitting in the coverage area for saving resources and yet improving network availability. Both the integer and the relaxation formulations showed similar results for all the experiments, but the time of processing required by the relaxation algorithms was much shorter than that required by the integer algorithm for large instances of the problem, which highlights the advantages of relaxation techniques under time constraints.

Radio over Fiber system applied to IEEE 802.15.4 standard

We have experimentally applied the Radio over Fiber (RoF) technology to a Wireless Sensor Network (WSN) based on IEEE 802.15.4 standard. Numerical simulations and experimental results demonstrate a successful implementation of a RoF technology operating at 2.4 GHz band over at least 160 km of a geographically-distributed optical network.