Rui Prior

Energy analysis of routing protocols for underwater wireless sensor networks

Underwater wireless sensor networks consist of a certain number of sensors and vehicles that interact to collect data and perform collaborative tasks. Designing energy-efficient routing protocols for this type of networks is essential and challenging because sensor nodes are powered by batteries, which are difficult to replace or recharge, and because underwater communications are severely affected by network dynamics, large propagation delays and high error probability of acoustic channels. The goal of this paper is to analyze the total energy consumption in underwater acoustic sensor networks considering two different scenarios: shallow water and deep water. We propose different basic functioning principles for routing protocols in underwater wireless sensor networks (relaying, direct transmission and clustering) and analyze the total energy consumption for each case, establishing a comparison between them.

A Distributed Clustering Scheme for Underwater Wireless Sensor Networks

Underwater wireless sensor networks (UWSNs) pose many challenges due to the intrinsic properties of underwater environments such as large propagation delays, node mobility and limited bandwidth capacity of acoustic channels. In this paper we present DUCS (distributed underwater clustering scheme), a new GPS-free routing protocol for UWSNs that does not use flooding techniques, minimizes the proactive routing message exchange and uses data aggregation to eliminate redundant information. Besides, DUCS assumes random node mobility and compensates the high propagation delays of the underwater medium using a continually adjusted timing advance combined with guard time values to minimize data loss and maintain communication quality. The simulations carried out demonstrate the effectiveness of the proposed scheme.

Improving AODV with preemptive local route repair

This paper proposes an extension to the AODV protocol, denoted preemptive local route repair (PLRR), that aims to avoid route failures by preemptively local repairing routes when a link break is about to occur. This protocol extension resorts to AODV layer 3 connectivity information with new mobility extensions. Our proposal is to enhance nodes information concerning link stability to its neighbours resorting to HELLO messages. These messages are appended with a mobility extension containing the nodes position, motion vector and an associated timestamp. This mobility information will be used to predict the instant a link between two neighbours will break. Our proposal does not need to take into account the sender and destination location information, as other location-aided routing protocols. In this proposal, location and mobility information needs to be propagated only between neighbours. This proposal aims at improving the AODV quality of service capabilities by minimizing route failures.

Heterogeneous Signaling Framework for End-to-End QoS Support in Next Generation Networks

Next generation wireless communication systems aim to handle diverse types of services across different types of access technologies in a seamless way. This paper proposes a next generation network architecture and evaluates possible associated signaling strategies, focusing in network-level QoS support aspects. The scenarios handled cover terminal-initiated signaling, network controlled signaling, and application-provider controlled signaling. Possible message sequence charts associated with these scenarios are presented and discussed. The paper compares the relative merits of each approach and concludes that the optimum QoS signaling solution depends on the QoS models that will be used, which are directly related to the business models chosen by the operators.

Network Coding Protocols for Smart Grid Communications

We propose a robust network coding protocol for enhancing the reliability and speed of data gathering in smart grids. At the heart of our protocol lies the idea of tunable sparse network coding, which adopts the transmission of sparsely coded packets at the beginning of the transmission process but then switches to a denser coding structure towards the end. Our systematic mechanism maintains the sparse structure during the recombination of packets at the intermediate nodes. The performance of our protocol is compared by means of simulations of IEEE reference grids against standard master-slave protocols used in real systems. Our results show that network coding achieves 100% reliability, even for hostile network conditions, while gathering data 10 times faster than standard master-slave schemes.

Design and Analysis of a GPS-free Routing Protocol for Underwater Wireless Sensor Networks in Deep Water

In this paper we present DUCS (distributed underwater clustering scheme), a new GPS-free clustering scheme specifically designed for underwater wireless sensor networks. DUCS is adapted to the intrinsic properties of underwater environments, such as long propagation delays, low data rates and difficulty of synchronization. DUCS minimizes the proactive routing message exchange, and compensates the high propagation delays of the underwater medium using a continually adjusted timing advance combined with guard time values to minimize data loss and maintain communication quality. The simulations carried out in deep water demonstrate the effectiveness of the proposed scheme in these environments.

Systematic network coding for packet loss concealment in broadcast distribution

This paper describes a system for the distribution of content over multicast and broadcast media that uses network coding techniques for concealing packet losses from the applications, improving the received Quality of Service. We propose a systematic network code designed for this purpose, analyze the performance of the code, comparing it with a standard approach based on random linear network coding, and provide experimental results obtained in an implemented prototype of the system.

An Adaptive Gateway Discovery Algorithm to support QoS When Providing Internet Access to Mobile Ad Hoc Networks

When a node in an ad hoc network wants Internet access, it needs to obtain information about the available gateways and it should select the most appropriate of them. In this work we propose a new gateway discovery scheme suitable for real-time applications that adjusts the frequency of gateway advertisements dynamically. This adjustment is related to the percentage of real-time sources that have quality of service problems because of excessive end-to-end delays. The optimal values for the configuration parameters (time interval and threshold) of the proposed adaptive gateway discovery mechanism for the selected network conditions have been studied with the aid of simulations. The scalability of the proposed scheme with respect to mobility as well as the impact of best-effort traffic load have been analyzed. Simulation results indicate that the proposed scheme significantly improves the average end-to-end delay, jitter and packet delivery ratio of real-time flows; the routing overhead is also reduced and there is no starvation of best-effort traffic.

SIP and MIPv6: Cross-Layer Mobility

Terminal mobility may be handled at different layers. Though the MIPv6 protocol is the strongest candidate for handling mobility in next generation networks, mobility management facilities are also provided by SIP, the most widely deployed and researched protocol for session control. When jointly used, this duplication of functions leads to inefficiencies in session setup signaling, particularly if coupled with end-to-end resource reservation for the media flows. This paper analyses these inefficiencies and proposes an integrated approach that minimizes the session setup delay. The gains of the proposal are demonstrated both by a delay analysis and by simulation results.

Efficient Reservation-Based QoS Architecture

This paper describes a new architecture that provides end-to-end QoS support, and analyses its performance in terms of QoS guarantees and scalability of the solution. This architecture introduces a scalable per-flow signalling model, using several techniques and algorithms developed in order to minimise the computational complexity. A label switching mechanism and an efficient timer implementation were developed with the goal of reducing the signalling processing overhead at each router. The underlying architecture is based on DiffServ and the resource reservation is performed for aggregates of flows at both core and access networks. The performance results presented in this paper show that this architecture is able to support both IntServ service models in high speed networks, minimizing the processing load in each network element.