The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper aims at studying underwater acoustic OFDM communication systems interfering with each others in the same channel. We propose a decentralized spectrum sharing method that minimizes the total power consumed while satisfying a constraint related to their information rate. The considered systems are supposed noncooperative, i.e. unable to communicate with each others so that they cannot agree...
This work presents experimental results for single carrier underwater communication systems using widely linear frequency domain equalization. The underwater channel models were obtained from a stochastic replay-based channel simulator, which was fed with data from channel measurements conducted in the harbor of Brest (France). It was seen that when symbols from improper constellations are considered...
Intersymbol interference (ISI) cancellation over frequency-selective underwater acoustic channel (UAC) is usually performed efficiently using iterative equalization. To this aim, an interleaver is required between the error correction scheme and the modulation scheme, and the longer the interleaver block length the better the performance. However, in the case of time-varying UAC, the length of the...
Noncooperative underwater acoustic (UWA) communication systems are prone to interfere with each other since the limited resource offered by the channel is not regulated by any standard. Mutual inteferences can significantly degrade the performances of such systems and it is necessary to find policies allowing UWA devices to access the same physical resource. In this paper, we consider noncooperative...
Due to the absence of spectrum regulation and limited bandwidth, underwater acoustic (UA) systems are prone to interfere with each other. To limit this interference, a decentralized power allocation strategy is proposed for multiple OFDM UA links sharing the same physical resource. These links are supposed to be noncooperative and aim at selfishly maximizing their own information rate. Each link is...
Stochastic replay is a channel simulation method that generates random time-varying impulse responses (TVIRs) from data collected at sea. Most existing replay-based simulators only consider single-input single-output transmissions. In this paper, a single-input multiple-output (SIMO) stochastic replay-based simulator is presented. It is shown to keep temporal, inter-tap as well as spatial correlations...
Deep space communication systems operate in the presence of high atmospheric attenuation and the capacity of the on-board energy generator is limited which produces a very low signal to noise ratio (SNR) at the reception. In order to satisfy the required transmission quality of deep space mission in terms of power and spectral efficiency, a coherent demodulation is mandatory. Coherent demodulation...
A real demand for underwater acoustic (UWA) communications exists in oceanography, ocean exploration and undersea navigation. A new Doppler resilient digital communication, based on quadratic frequency modulations (QFM) is presented. The binary information is transmitted using two orthogonal QFM chirps. This signal modulation is suitable for low-data-rate communication such as telemetry. The first...
This paper lays the foundation of an underwater acoustic channel simulation methodology that is halfway between parametric modeling and stochastic replay of at-sea measurements of channel impulse responses. The motivation behind this approach is to extend the scope of use of replay-based methods by allowing some parameterization of the channel properties while complying with some level of realism...
Development and deployment of underwater acoustic (UWA) sensor networks have emerged as an efficient solution for many applications related to marine environment e.g., scientific, industrial, and military operations. The main tasks to execute are remote sensing and monitoring. Grid topology with multihop relaying is very useful, since it allows a wide area coverage as well as long distance data transmission...
Decision feedback equalizer (DFE) uses the past decisions in the feedback filter to mitigate the intersymbol interference (ISI). For the underwater acoustic channel, the impulse response often covers tens to hundreds of symbols, requiring at least tens of taps in the feedback filter. The error propagation easily occurs when the signal to noise ratio (SNR) decreases. In order to improve the DFE performance,...
The use of orthogonal frequency division multiplexing (OFDM) based underwater acoustic (UWA) modems has raised a growing interest within the scientific community. This is motivated mainly by the relative simple implementation of the OFDM system and its capability to transmit efficiently over long time spread channels. This paper describes the modem developed in the context of COMET project, which...
Orthogonal frequency division multiplexing (OFDM) systems combat inter-symbol interferences (ISI) using cyclic prefix (CP) or the equivalent guard interval (GI) in case of zero-padded (ZP) OFDM. Nevertheless, inter-carrier interferences (ICI) due to the synchronization mismatches for instance, remain a strong disadvantage. Pulse-shaping is one of the solutions introduced in narrow band context. In...
One of the challenges faced by future networks is to integrate heterogeneous segments whose protocols are optimized for very different conditions. This work provides an overview of project COMPOUND, which tackles problems in this class to interface an underwater acoustic network comprising both static and mobile nodes to the Internet. The main goal is to create value and foster new applications in...
We propose a self-reconfiguring constant modulus algorithm (CMA) using a constrained mode followed by an unconstrained mode for solving the singularity issue of CMA equalizers in polarization-division-multiplexed coherent receivers.
In this paper, frequency-domain equalization approach is proposed to deal with the intersymbol interference in underwater acoustic communications. To track the time-varying underwater acoustic channel, an adaptive algorithm is considered using overlap-and-save method. This technique makes it possible to remove the overhead due to the transmission of cyclic prefix over each block of data, such as in...
In this paper, we focus on the adaptive identification of sparse SIMO channels in a blind context. More specifically, we propose different adaptive implementations of the sparse cross relation (SCR) method then we compare and analyse their performances in terms of convergence rate, estimation accuracy and robustness. The SCR method proceeds as follows: at first a blind approach based on the cross-relation...
TRIDENT project was launched a few years ago by GESMA (Groupe d'Etudes Sous-Marines de l'Atlantique) in collaboration with TELECOM Bretagne. First objectives were to develop a multiple rate underwater acoustic link for images, speech signal, text and data transmission. This link was designed to provide a wireless communication to AUVs. Recently the platform was extended to low bit rate speech transmission...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.