SONAR Systems and Underwater Signal Processing

One of the most significant problems in many application areas is to extract the required signal from background noise.
Background noise is random, the occurrence of signal and the behaviour of signal are also random. Therefore, it is
practical to deal with the signal extraction problem using methods based on probability theory and statistical
estimation. That is to say that signal detection and parameter estimation problems are statistical hypothesis testing
problems in mathematical statistics. In this paper, signal and noise environment is encountered in active sonar system for
target detection. The optimum receiver is presented for range-Doppler-shift processing in a background-noise-limited
environment using linear frequency modulation pulse. FFT based implementation for target detection of active sonar
system using MATLAB has been shown here.

Cartographie du couvert vegetal marin du golfe de gabes et mise en place d'un reseau de surveillance du de Posidonia oceanica. La cartographie a ete realise a travers 4800 stations d'observations directes par plongee au scaphandre autonome, apnee et ROV et camera sous marine, le recours au sonar a balayage lateral (swatch bathymetry) et l'imagerie satellitaire a permis de couvrir la totalite du golfe de la Chebba au nord a la frontiere Tuniso-Libyenne au sud, et du littoral a lisobathe -50m. La superfice couverte par nos travaux est estimee a 3.407.600 hectares, dont 1.152.900 ha sont occupes par la Posidonie soit 34% de cette aire prospectee, occupant ainsi la superficie la plus inportante de medietrranee. Pour assurere le suivi de cet importante biocenose marine littorale, nous avons balises 39 stations allant de -0.5 m a -36.7 m de profondeur. Sur une periode de 12 mois, ces 39 stations ont montre dans l'ensemble une regression de faible ampleur.

In this paper, a simulation framework that can be utilized during the simulation and algorithm selection phases of active sonar system development for surface and subsurface platforms, are described. HAVELSAN will have the capability to develop techniques and perform the performance analysis of
different methods that can be used in different areas like target detection sonars, torpedo sonars and mine hunting sonars with this simulation framework.

Цифровое формирование характеристики направленности гидроакустической антенны гидролокатора подводного робота во временной области Обработка гидроакустической информации выполняется во временной или спектральной области, причем последняя распространена очень широко. В любом случае предусматривается формирование характеристик направленности антенных устройств и моделирование алгоритмов обработки входных сигналов. Возможны два подхода к отработке алгоритмов. Первый состоит в обработке сигналов по выходам каналов антенны, и тогда необходимо вычислять и имитировать сигналы и помехи на выходах каналов антенны в соответствии с расчетными характеристиками направленности каналов и заданным распределением источников и параметров сигналов и помех. Второй состоит в генерации сигналов и помех в элементах антенной решетки, получении на выходах каналов процессов со свойствами, заданными на уровне элементов, и обработке суммарных сигналов во временной области. Приводятся формулы сигналов и помех для антенны мобильного подводного робота. направленность, гидроакустическая антенна, моделирование сигналов и помех, временная область, частотная область, формирование каналов антенны Digital forming of sonar antenna direction in time domain Hydroacoustic data processing is being performed in time or spectral domain, the spectral domain is being distributed more widely. In any case, there can be created formation characteristics of the antenna devices and modeling algorithms for processing input signals. There are two possible approaches to working out the algorithms. The first is to process the signals to the outputs of channels the antenna, and then you need to calculate and simulate the signal and interference at the antenna output channels in accordance with the calculated directional characteristics of channels and a given source distribution and the parameters of the signals and noise. The second is to generate signals and noise in the elements array, receiving the outputs of channel processes with the properties given on the item level, and the total processing of signals in time domain. The formulas of signals and interference antenna mobile underwater robot are included in this note.

This paper deals with the problem of estimating the directions of arrival (DOA) of multiple source signals from a single
observation vector of an array data. In particular, four estimation algorithms based on the theory of compressed sensing
(CS), i.e., the classical ℓ1 minimization (or Least Absolute Shrinkage and Selection Operator, LASSO), the fast smooth ℓ0
minimization, and the Sparse Iterative Covariance-Based Estimator, SPICE and the Iterative Adaptive Approach for
Amplitude and Phase Estimation, IAA-APES algorithms, are analyzed, and their statistical properties are investigated
and compared with the classical Fourier beamformer (FB) in different simulated scenarios. We show that unlike
the classical FB, a CS-based beamformer (CSB) has some desirable properties typical of the adaptive algorithms
(e.g., Capon and MUSIC) even in the single snapshot case. Particular attention is devoted to the super-resolution
property. Theoretical arguments and simulation analysis provide evidence that a CS-based beamformer can achieve
resolution beyond the classical Rayleigh limit. Finally, the theoretical findings are validated by processing a real sonar
dataset.

The exploration of oceans and sea beds is being made increasingly possible through the development of Autonomous Underwater Vehicles (AUVs). This is an activity that concerns the marine community and it must confront the existence of notable challenges. However, an automatic detecting and tracking system is the first and foremost element for an AUV or an aqueous surveillance network. In this paper a method of Kalman filter was presented to solve the problems of objects track in sonar images. Region of object was extracted by threshold segment and morphology process, and the features of invariant moment and area were analysed. Results show that the method presented has the advantages of good robustness, high accuracy and real-time characteristic, and it is efficient in underwater target track based on sonar images and also suited for the purpose of Obstacle avoidance for the AUV to operate in the constrained underwater environment.

ABSTRACT The narrow subcarrier spacing and wide bandwidth arrangement in the LTE downlink produce a vulnerability to sample clock mismatch between the transmitting and receiving data converters. Without high precision sampling clock frequencies, a high level of inter-carrier interference (ICI) is introduced, yielding undesirable performance. In this article, a method to jointly estimate and correct sampling frequency mismatch is proposed. The proposed method uses information already known to the receiver, operates strictly in the time domain and does not require the aid of pilot symbols or other frequency domain information. The method allows clocks with lower precision to be used with minimal performance degradation. Results are presented using MATLAB simulation as well as an FPGA hardware implementation.

Abstract As displays become less expensive and are incorporated into more and more devices, there has been an increased focus on image resizing techniques to fill an image to an arbitrary screen size. Traditional methods such as cropping or resampling can ...

In the near future, small electronic hand-held devices will be equipped with digital cameras capable of acquiring high resolution images (HDTV) at real-time rates, resulting in video streams of dozens of megabytes per second. The real-time video decoding and especially encoding of such streams with AVC/ H.264 or SVC standards require a huge amount of computing power that, in the case of a hand-held device, has to be delivered under the constraint of low power dissipation. In this paper we present a Multi-Processor System-on-Chip dedicated for high performance, low-power video coding applications using Network-on-Chip (NoC) as communication infrastructure. Extensive experiments have established the power dissipation models of individual NoC components, i.e. network interfaces, routers and wires. Based on these models and the NoC topology, we build the power model of the complete NoC. For three different implementation scenarios of the AVC/H.264 simple profile encoder we derive the power dissipation of the NoC for image resolutions up to HDTV at rate of 30 frames per second. The results obtained show that for the same application mapping scenario (worst case), moving from CIF to HDTV resolution will result in a 35% increase of the total power dissipation. Finally, for HDTV resolution, the difference in power dissipation between the worst (21 mW) and the best case application mapping scenario is 26%.

Advanced bit manipulation operations are not efficiently supported by commodity word-oriented microprocessors. Programming tricks are typically devised to shorten the long sequence of instructions needed to emulate these complicated bit operations. As these bit manipulation operations are relevant to applications that are becoming increasingly important, we propose direct support for them in microprocessors. In particular, we propose fast bit gather (or parallel extract), bit scatter (or parallel deposit) and bit permutation instructions (including group, butterfly and inverse butterfly). We show that all these instructions can be implemented efficiently using both the fast butterfly and inverse butterfly network datapaths. Specifically, we show that parallel deposit can be mapped onto a butterfly circuit and parallel extract can be mapped onto an inverse butterfly circuit. We define static, dynamic and loop invariant versions of the instructions, with static versions utilizing a much simpler functional unit. We show how a hardware decoder can be implemented for the dynamic and loop-invariant versions to generate, dynamically, the control signals for the butterfly and inverse butterfly datapaths. The simplest functional unit we propose is smaller and faster than an ALU. We also show that these instructions yield significant speedups over a basic RISC architecture for a variety of different application kernels taken from applications domains including bioinformatics, steganography, coding, compression and random number generation.

An audio fingerprint is a compact content-based signature that summarizes an audio recording. Audio Fingerprinting technologies have attracted attention since they allow the identification of audio independently of its format and without the need of meta-data or watermark embedding. Other uses of fingerprinting include: integrity verification, watermark support and content-based audio retrieval. The different approaches to fingerprinting have been described with different rationales and terminology: Pattern matching, Multimedia (Music) Information Retrieval or Cryptography (Robust Hashing). In this paper, we review different techniques describing its functional blocks as parts of a common, unified framework.