Filipe Ribeiro

PACE: Simple multi-hop scheduling for single-radio 802.11-based Stub Wireless Mesh Networks

IEEE 802.11-based Stub Wireless Mesh Networks (WMNs) are a cost-effective and flexible solution to extend wired network infrastructures. Yet, they suffer from two major problems: inefficiency and unfairness. A number of approaches have been proposed to tackle these problems, but they are too restrictive, highly complex, or require time synchronization and modifications to the IEEE 802.11 MAC. PACE is a simple multi-hop scheduling mechanism for Stub WMNs overlaid on the IEEE 802.11 MAC that jointly addresses the inefficiency and unfairness problems. It limits transmissions to a single mesh node at each time and ensures that each node has the opportunity to transmit a packet in each network-wide transmission round. Simulation results demonstrate that PACE can achieve optimal network capacity utilization and greatly outperforms state of the art CSMA/CA-based solutions as far as goodput, delay, and fairness are concerned.

Novel ns-3 model enabling simulation of electromagnetic wireless underground networks

Wireless Underground Networks (WUNs) have applications such as agriculture, border surveillance, maintenance of playing fields, and infrastructure monitoring. When designing a sensor network for one of these applications some of the sensors (communication nodes) will be buried underground, which means the propagation medium will be the soil or hybrid (air plus soil) in case of one of the nodes is aboveground. Thus, new models have to be implemented in existing simulators, in order to enable the proper simulation of these communications scenarios. This paper presents a new model, named underground model, and discusses its integration into the ns-3 simulator. The underground model enables the simulation of WUNs, including network topologies with underground and aboveground nodes. The accuracy of the underground model is shown for two frequency bands by comparing simulations results with experimental results.

A ns-3 based simulator of TCP/IP Wireless Underground Networks

Wireless Underground Networks (WUNs) include communications links between buried nodes and between buried and aboveground nodes. WUNs have many applications, such as border surveillance, agriculture monitoring, and infrastructure monitoring. Recent studies have shown that they are feasible and have deployment advantages over wired networks. Yet, so far WUNs evaluations have been done using testbeds only, and a tool enabling simulations on TCP/IP WUNs is lacking. We propose a simulator of TCP/IP wireless underground networks based on ns-3. The simulator was validated against experimental results for 433 MHz and 2.4 GHz frequency bands. The results show its accuracy for most of the communications scenarios.

Experimental Evidence for Azeotrope Formation from Protic Ionic Liquids

Herein, we present experimental evidence that protic ionic liquids (PILs), derived from 1 : 1 liquid mixtures of the organic superbases 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with carboxylic acids, form azeotropic mixtures with acid/base molar fractions different from 1 : 1. The ability of the carboxylic acids to form strong hydrogen bonds with the PIL ion pair leads to an azeotropic composition richer in the acid component. The results show that the azeotropic composition is ruled by the extent of acid-base equilibrium and the relative volatility of the neutral species in the PIL medium. The PILs show marked negative deviations from Raoults Law with the stronger superbase (DBU) leading to an azeotropic composition closer to the equimolar 1 : 1 ratio.

Stub Wireless Multi-hop Networks using self-configurable Wi-Fi Basic Service Set Cascading

The increasing trend in wireless Internet access has been boosted by IEEE 802.11. However, the application scenarios are still limited by its short radio range. Stub Wireless Multi-hop Networks (WMNs) are a robust, flexible, and cost-effective solution to the problem. Yet, typically, they are formed by single radio mesh nodes and suffer from hidden node, unfairness, and scalability problems. We propose a simple multi-radio, multi-channel WMN solution, named Wi-Fi network Infrastructure eXtension - Dual-Radio (WiFIX-DR), to overcome these problems. WiFIX-DR reuses IEEE 802.11 built-in mechanisms and beacons to form a Stub WMN as a set of self-configurable interconnected Basic Service Sets (BSSs). Experimental results show the improved scalability enabled by the proposed solution when compared to single-radio WMNs.

A traffic-aware solution for green Wireless Video Sensor Networks

The growth of the IP cameras market, due to their low price and high availability, is making Wireless Video Sensor Networks (WVSNs) attractive. In a mesh, multi-hop video surveillance scenario Wi-Fi is the enabling technology for WVSNs, due to its flexibility and low cost. However, WVSNs still suffer from bad performance, throughput unfairness, and energy inefficiency. Previously, we proposed FM-WiFIX+, a holistic solution to address the problem. FM-WiFIX+ uses FM radio to signal when a video sensor should turn its IEEE 802.11 interface OFF, thus saving energy. Herein, we present a new traffic-aware version of FM-WiFIX+. The results obtained through numerical, simulation, and experimental evaluation demonstrate that the new version can achieve savings in energy consumption up to 84 %, while maintaining the levels of performance and throughput fairness.