Tor Arne Reinen

Linking Acoustic Communications and Network Performance: Integration and Experimentation of an Underwater Acoustic Network

Underwater acoustic networks (UANs) are an emerging technology for a number of oceanic applications, ranging from oceanographic data collection to surveillance applications. However, their reliable usage in the field is still an open research problem, due to the challenges posed by the oceanic environment. The UAN project, a European-Union-funded initiative, moved along these lines, and it was one of the first cases of successful deployment of a mobile underwater sensor network integrated within a wide-area network, which included above water and underwater sensors. This contribution, together with a description of the underwater network, aims at evaluating the communication performance, and correlating the variation of the acoustic channel to the behavior of the entire network stack. Results are given based on the data collected during the UAN11 (May 2011, Trondheim Fjord area, Norway) sea trial. During the experimental activities, the network was in operation for five continuous days and was composed of up to four Fixed NOdes (FNOs), two autonomous underwater vehicles (AUVs), and one mobile node mounted on the supporting research vessel. Results from the experimentation at sea are reported in terms of channel impulse response (CIR) and signal-to-interference-plus-noise ratio (SINR) as measured by the acoustic modems during the sea tests. The performance of the upper network levels is measured in terms of round trip time (RTT) and probability of packet loss (PL). The analysis shows how the communication performance was dominated by variations in signal-to-noise ratio, and how this impacted the behavior of the whole network. Qualitative explanation of communication performance variations can be accounted, at least in the UAN11 experiment, by standard computation of the CIR and transmission loss estimate.

Underwater acoustic network performance: Results from the UAN11 sea trial

An underwater acoustic network (UAN) represents a communication infrastructure that can offer the necessary flexibility for continuous monitoring and surveillance of critical infrastructures located by the sea. Given the current limitation of acoustic-based communication methods, a robust implementation of UANs is still an open research field. The FP7 UAN project moved along these lines, and it was one of the first cases of successful deployment of a mobile underwater sensor network integrated within a wide-area network, which included above water and underwater sensors. This contribution gives details on the UAN network structure and equipment. It reports statistics on the performance of the system as collected during the project final sea trial, which was held in Trondheim, Norway, in May 2011. The UAN network was in operation for five continuous days and was composed of up to four fixed nodes, two autonomous underwater vehicles and one mobile node mounted on the supporting research vessel. Results from the experimentation at sea are reported in terms of channel impulse response and signal to noise plus interference ratio as measured by the acoustic modems during the sea tests. The performance of the upper network levels are measured in terms of round trip time and probability of packet loss. Finally, the experimental results have been compared with those obtained in simulation using the BELLHOP acoustic code, fed with the environmental data gathered during the sea trial.

Underwater Wireless Sensor Network

The NNN-UTS project (Nordområdenes Nye Nervesystem – Undervanns Trådløst Sensornettverk) has aimed to develop wireless network technology for underwater sensor networks, employing acoustic communication to realize wireless functionality in water. Research and development has been carried out in 2006-2009. A final sea test/demonstration of the system was carried out at Breiangen in the Oslo fjord, on December 3-4 2009. The result is a fully operative network system available for water depths down to 4000m.

Underwater Acoustic Networks: The FP7 UAN Project

Abstract The EU-funded project UAN - Underwater Acoustic Network aims at conceiving, developing and testing at sea an innovative and operational concept for integrating in a unique communication system submerged, surface and aerial sensors with the objective of protecting off-shore and coastline critical infrastructures. A crucial aspect of the project consisted in the use of autonomous underwater vehicles (AUVs) as mobile nodes in the underwater acoustic communication network. In particular, AUVs have the role of adapting the network geometry to the variation of the acoustic channel. This paper reports on the project concept and vision as well as on the progress of its various development phases. The recent at-sea successes that have been demonstrated within the UAN framework are detailed and results of the final UAN project demonstration, UAN11, held in the May of 2011, are reported. The UAN network was in operation for five continuous days with up to five nodes, of which three of them were mobile nodes.

The Trondheim harbour: Acoustic propagation measurements and communication capacity

This paper presents results from a propagation measurement campaign carried out in the Trondheim harbour during the period from June to November 2007. Two vertically mounted transducers operating at a carrier frequency of 38 kHz permitted both single-input/single-output (SISO) and multiple-input/multiple-output (MIMO) channel measurements. The upper transducers at both sides were mounted around 2 meters from the sea surface. The sound velocity profile measurements showed large variations in the upper layers of the water column during the campaign period. Due to the fixed mechanical transducer constructions, the observed Doppler spread was low. The Delay spread however varied from 0.5 ms in the summer up to 9 ms in November. The calculated spatial multiplexing capacity within a 3 kHz bandwidth of the MIMO topology gave a factor in the order of 1.8 capacity improvement compared to derived SISO capabilities. The reference SISO propagation channels used in the calculations were one of the estimated elements of the corresponding MIMO channel matrices. Channel state information (CSI) at the transmitter maximises the capacity, particularly at low signal to noise (SNR) rations. Simulations comparing capacities achieved with and without transmitter CSI are shown. The results show that for the observed channels, spatial multiplexing MIMO capacity outperforms SISO and verified that CSI is beneficial at decreasing SNR values.