Roberto Petroccia

CARP: A Channel-aware routing protocol for underwater acoustic wireless networks

The paper concerns the definition and performance evaluation of a new multi-hop routing protocol for underwater wireless sensor networks. Our solution, termed CARP for Channel-aware Routing Protocol, exploits link quality information for data forwarding, in that nodes are selected as relays if they exhibit recent history of successful transmissions to their neighbors. CARP avoids loops and can successfully route around connectivity voids and shadow zones by using simple topology information, such as hop count. The protocol is also designed to take advantage of power control for selecting robust links. The performance of CARP has been compared with that of two other protocols for underwater routing, namely, the Focused Beam Routing (FBR) and a flooding-based solution (EFlood). Metrics of interest include packet delivery ratio, end-to-end packet latency and energy consumption, which have been investigated through ns2-based simulations and experiments at sea. The in-field trials have been conducted at two European locations, namely, a Norwegian fjord and the Mediterranean Sea. The tests in the Mediterranean Sea have been performed jointly with the NATO Science and Technology Organization Centre for Maritime Research and Experimentation (STO CMRE), under a collaboration agreement between the University of Roma and CMRE. 1 Our results show that CARP robust mechanism for relay selection doubles the packet delivery

The SUNSET framework for simulation, emulation and at-sea testing of underwater wireless sensor networks

The Sapienza University Networking framework for underwater Simulation Emulation and real-life Testing (SUNSET) is a toolkit for the implementation and testing of protocols for underwater sensor networks. SUNSET enables a radical new way of performing experimental research on underwater communications. It allows protocol designers and implementors to easily realize their solutions and to evaluate their performance through simulation, in-lab emulation and trials at sea in a direct and transparent way, and independently of specific underwater hardware platforms. SUNSET provides a complete toolchain of pre-deployment and deployment time tools able to identify risks, malfunctioning and under-performing solutions before incurring the expense of going to sea. Novel underwater systems can therefore be rapidly and easily investigated. Heterogeneous underwater communication technologies from different vendors can be used, allowing the evaluation of the impact of different combinations of hardware and software on the overall system performance. Using SUNSET, underwater devices can be reconfigured and controlled remotely in real time, using acoustic links. This allows the performance investigation of underwater systems under different settings and configurations and significantly reduces the cost and complexity of at-sea trials. This paper describes the architectural concept of SUNSET and presents some exemplary results of its use in the field. The SUNSET framework has been extensively validated during more than fifteen at-sea experimental campaigns in the past four years. Several of these have been conducted jointly with the NATO STO Centre for Maritime Research and Experimentation (CMRE) under a collaboration between the University of Rome and CMRE.

A comparative performance evaluation of MAC protocols for underwater sensor networks

A propagation-delay-aware MAC protocol, based on carrier sensing multiple access, is proposed. The design aims at maximizing the bandwidth utilization by keeping track of neighboring transmissions to avoid collisions, thus enabling interleaved packet transmission between different pairs of users. The performance is compared to several representative MAC protocols: the standard and slotted ALOHA, and three protocols designed specifically for the underwater acoustic environment, APCAP [1], DACAP [2] and T-Lohi [3]. Simulation results identify network settings (traffic load, node density, single/multi-hop topologies) in which each protocol offers the best performance.

Optimized Packet Size Selection in Underwater Wireless Sensor Network Communications

In this paper, we investigate the effect of packet size selection on the performance of media access control (MAC) protocols for underwater wireless sensor networks, namely, carrier sense multiple access (CSMA) and the distance-aware collision avoidance protocol (DACAP). Our comparative analysis, conducted via ns-2 simulations, considers scenarios with varying, nonzero bit error rate (BER) and interference. We investigate metrics such as throughput efficiency (the ratio between the delivered bit rate and the offered bit rate), end-to-end packet latency, measured “per meter” to allow for different sizes of deployment areas, and the energy consumed to correctly deliver an information bit to the network collection point. Our results show the dependence of these metrics on the packet size, indicating the existence of an optimum. The optimum packet size is found to depend on the protocol characteristics, the bit rate, and the BER. For each protocol and scenario considered, we determine the packet size that optimizes throughput performance, and we show its effect on the normalized packet latency and on energy consumption.

Choosing the packet size in multi-hop underwater networks

Two MAC layer protocols are considered for multi-hop underwater acoustic networks: Pure CSMA, suitably configured to perform over a long-delay channel, and the Distance-Aware Collision Avoidance Protocol (DACAP), a protocol specifically designed for collision avoidance via a distributed coordination function à la IEEE 802.11. We investigate the impact of packet size on the performance of these two protocols. A comparative analysis, conducted via ns-2 simulations, quantifies throughput efficiency, end-to-end delay and energy-per-bit consumption as functions of the packet size. The results clearly indicate the existence of an optimal packet size for each scenario. The optimal packet size depends on the protocol characteristics, on the offered load, and is heavily influenced by the bit error rate. The results also reveal performance sensitivity to the choice of the packet size for the different protocols (CSMA and DACAP), emphasizing how a wrong selection of the packet size can result in a higher cost to performance.

SUNSET version 2.0: enhanced framework for simulation, emulation and real-life testing of underwater wireless sensor networks

We describe the newest design and development of the Sapienza University Networking framework for underwater Simulation Emulation and real-life Testing (SUNSET), a powerful toolkit for implementation and testing of novel protocol solutions for underwater sensor networks. SUNSET enables testing and enhancement of underwater solutions using a controlled simulation environment. The very simulation code can be then transparently ported to various real hardware and underwater platforms for protocol emulation and actual in field testing. SUNSET was the first open source framework for seamless simulation, emulation and actual at sea testing of novel underwater systems. The first SUNSET was presented in 2011 [1], improved in 2012 [2] and freely released to the research community in May 2012. Since then, SUNSET has been significantly improved and validated through several trials at sea. New modules have been created and the functionalities of existing ones have been extended and enhanced. The new SUNSET version 2.0 has been recently released to the community (October 2013 [3]). This paper discusses in details the SUNSET 2.0 features and modules, and report about the latest in field tests where SUNSET 2.0 has been used.

Investigation of Underwater Acoustic Networking Enabling the Cooperative Operation of Multiple Heterogeneous Vehicles

In this paper, the authors investigate the creation of an underwater acoustic network to support marine operations based on static and mobile nodes. Each underwater device combines communication, networking, and sensing capabilities and cooperates with the other devices in coordinated missions. The proposed system is built upon the SUNSET framework, providing acoustic communications and networking capabilities to autonomous underwater vehicles, autonomous surface vessels, and moored systems, using underwater acoustic modems. Specific solutions have been developed and tested to control the underwater nodes acoustically and to instruct the vehicles on keeping a given formation using acoustic links. One of the novelties of our approach has been the development and utilization of a realistic simulation infrastructure to provide a very accurate representation of all the dynamic systems involved in the network, modeling the vehicle dynamics, the acoustic channel, and the communication messages. This infrastructure has been extensively used to investigate and validate the proposed solutions under different environmental conditions before the actual deployment of devices. Several experiments were then conducted in the laboratory and in the field. The experimental results have confirmed the effectiveness of the proposed solutions and the reliability of the proposed simulation framework in estimating system performance.

ROME: Routing Over Mobile Elements in WSNs

In this paper we present ROME, a geographic routing protocol for wireless sensor networks (WSNs) with mobile nodes. ROME design is suited to deal with communication problems in WSN scenarios with high network dynamics, such as nodal addition, nodal removal and node mobility. In addition, it retains desirable properties of protocols for static WSNs such as using cross-layer techniques for performance optimization, dealing with asynchronous nodal duty cycles, and being able to deal with connectivity dead ends. We define the protocol in details and provide detailed simulation-based performance evaluation of ROME. In scenarios with static and mobile nodes together, our ns2-based experiments show that ROME performs remarkably well with respect to metrics such as packet delivery ratio, energy consumption and end-to-end packet latency.

Implementation of an underwater acoustic network using multiple heterogeneous vehicles

In this paper we investigate the creation of an heterogeneous underwater network with static and mobile assets cooperating together in coordinated missions using acoustic links. Each underwater device combines communication, networking, and sensing capabilities, and cooperates with the other devices to accomplish a given task. The flexibility and capability of the proposed system allows to overcome the limitations of commercial solutions currently available in the market which typically focus on point to point communications. SUNSET framework has been used to provide acoustic communication and networking capabilities to AUVs, ASVs and moored systems developed by the Oceans Systems Group, at the University of Porto, in Portugal. New solutions have been developed and tested allowing to combine together acoustic data transmission and ranging estimation, to control the underwater nodes acoustically and to instruct the vehicles on keeping a given formation using acoustic links. To validate the proposed approach several experiments with increasing complexity have been conducted at the laboratory and in the field. The experimental results confirm the validity, efficiency and reliability of the proposed solution opening to several possibilities for future developments.

Energy efficient interference-aware routing and scheduling in underwater sensor networks

Underwater Wireless Sensor Networks (UWSNs) are emerging as a key enabling technology for a wide range of applications in the marine environment. Although there are significant efforts to find viable alternatives, acoustics are still the main technology in use for underwater communications. The use of acoustic transmissions in water, however, introduces several challenges such as variable and long propagation delays, low data rate, significant fluctuations in terms of link reliability over time and long interference range. Furthermore, sensor nodes are usually powered by batteries whose replacement can introduce high cost and complexity. The objective of this paper is to design a cross-layer heuristic solution for an efficient use of the scarce resources of Underwater Acoustic Sensor Networks (UASNs), such as bandwidth and energy. We propose a class of scheduling and routing policies, supporting the use of power control, to achieve reliable, low power, interference aware communications.