Hydroacoustic Communication Research Articles

Attempts to increase communication rates with explosive acoustic sources for underwater communications

Abstract To meet the requirement of a higher speed rate for hydroacoustic communication, an innovative scheme is proposed to simulate an airgun sound source by superimposing two different frequency Ricker Wavelets to form a multi-wave Ricker Wavelet. On the receiver side, two bandpass filters are employed to recover the original information. First, the characteristics of a single Ricker Wavelet, a multi-wave Ricker Wavelet, and an airgun sound source were compared. We found that the multi-wave Ricker Wavelet has characteristics that are similar to the airgun sound source, which leads to the conclusion that using a multi-wave Ricker Wavelet is the best way to simulate the airgun sound source. Secondly, we proposed a method to simulate the airgun sound source for transmission by superposition of two multi-wave Ricker Wavelets of different frequencies, which was an innovative scheme capable of sending two bits of information in one code element duration, thus better meeting the demand for higher communication rates in hydroacoustic communication. Finally, we conducted simulation experiments to verify the validity of the above conclusions. The analysis and elaboration can provide a novel and efficient solution for the field of hydroacoustic communication.

Помехоустойчивость когерентного приема двоичных сигналов с огибающей вида приподнятый косинус в гидроакустическом канале связи

Goals: The main purpose of this work is to develop a methodology for determining the parameters of binary signals, at which the signals become relatively invariant to frequency distortions in the marine environment. The frequency distortion of the signals is caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. In accordance with this, the error probabilities of signal receivers with various types of manipulation are determined, which are optimal in the absence of distortion. Methods: The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content: The paper considered a model of a single-beam hydroacoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude -frequency response and a linear phase-frequency response. The error probabilities of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are determined. Coherent receivers optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment are considered as receivers. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters that are relatively invariant to frequency distortions in the marine environment are determined. Results: Expressions of the error probability of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of sending the signal, the carrier frequency and the initial phase of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, signal duration, for each type of signal, the boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed, a comparison is made with the case of signals with a sinusoidal envelope. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given. Expressions of the error probability of coherent receivers of binary signals with amplitude, frequency and phase manipulation with an envelope of the raised cosine type are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of sending the signal, the carrier frequency and the initial phase of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, signal duration, for each type of signal, the boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed, a comparison is made with the case of signals with a sinusoidal envelope. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given.

Practical Steps towards Establishing an Underwater Acoustic Network in the Context of the Marine Internet of Things

When several hydroacoustic modems operate simultaneously in an area of mutual coverage, collisions of data packets received from several sources may occur, which lead to information loss. With an increase in the number of simultaneously operating hydroacoustic modems, physical layer algorithms do not provide stable data transmission and the likelihood of collisions increases, which makes the operation of modems ineffective. To ensure effective operation in a hydroacoustic signal propagation environment and to reduce collisions when exchanging data between two modems that do not have the ability to operate synchronously and to reduce the access time to the signal propagation environment, methods of the medium access control layer using link layer protocols are required. Typically, this problem is solved using code separation of hydroacoustic channels. If you need to transfer over a network, this option will not work, since network transfer involves working on the basis of “broadcast” messages, particularly between data source and data sink that remain too far from each other, outside of their mutual audibility. In practical use, it is convenient to place these protocols into a software environment for developing specific user applications for solving network communication problems. This software framework allows for custom modification of existing network algorithms, as well as the inclusion of new network hydroacoustic communication algorithms. To build a predictive model, the DACAP, T-Lohi, Flooding, and ICRP protocols were used in this work. The implementation is performed in Erlang. The paper presents algorithms for implementing these protocols. A comparative analysis of network operation with and without protocols is provided. Efficiency of operation, i.e., data rates and probabilities of data delivery, was assessed.

A High-Precision Positioning Method for Autonomous Underwater Vehicles with Communication Delays

In underwater navigation of autonomous underwater vehicles (AUVs), communication delays frequently occur, leading to a reduction in positioning accuracy. To mitigate this challenge, this work introduces a novel method for relative angle correction, aiming to reconstruct measurement information. Initially, Doppler measurement data are assimilated into the reconstruction of measurement equations to determine the relative angle between the AUV and the observatory. Subsequently, the obtained angle information is integrated into the Extended Kalman Filter (EKF) for the reconstruction of measurement equations. The proposed method effectively reduces positioning errors caused by hydroacoustic communication delays, consequently enhancing AUV positioning accuracy. The efficacy of the proposed method is demonstrated through a simulation study. Simulation results reveal that the incorporation of Doppler angle correction in the reconstructed measurement information method significantly decreases the localization error by approximately 50% compared to EKF and by around 20% compared to the method lacking angle correction.

Применение теоремы Гаусса–Маркова для эквализации гидроакустического канала передачи

Researchers in the field of modern hydroacoustics frequently encounter such problems as interference and noise in communication channels. Multipath propagation is an inevitable hydroacoustic communication problem arising in a sound channel due to reflections from the water surface and seabed. In general, this may decrease the overall communication quality. As a rule, noise cannot be completely eliminated, although its influence can be minimized. In this article, we describe a method for equalizing the hydroacoustic transmission channel using the Gauss–Markov theorem. This method can be used for reducing the multipath propagation effect and obtaining an unbiased estimate with minimal variance.

CONCEPTS OF THE DEVELOPMENT OF A CIVIL NETWORK SYSTEM OF UNDERWATER TRAFFIC CONTROL

The article examines the development of underwater space in the interests of maritime freighttransport as such, which increases the carrying capacity of existing sea transport routes, increasesenergy efficiency and reduces the risks of freight transport, provided there is no negative impact on themovement of the vehicle by wind, surface waves and drift currents. It is proposed to create anextensive system of cargo transportation in the underwater space as an alternative to conventionalshipping. The best underwater data exchange in terms of speed and volume of transmitted informationis provided by laser methods. In second place is radio communication in the microwave range and inthird place is the hydroacoustic communication channel. Thus, underwater data transmission based onlasers and radio waves is effective for data transmission only in conditions where the underwatertransport vessel moves in the near-surface layer of the ocean. In the future, hybrid data exchangesystems will be created under water, based on the physical principles of data transmission by radio,laser, hydroacoustic communication. Hybrid communication systems based on hydroacoustics andradar are not excluded. Keywords: Underwater space, underwater vehicles, hydroacoustic, navigation, cargotransportation.

Application of Incoherent Multi-Frequency Signals for Information Transmission in a Nonstationary Hydroacoustic Environment

A class of digital incoherent methods of information transmission based on multi-frequency signals for mobile underwater complexes is presented, which does not require regular and accurate estimation of channel parameters and is a priori resistant to various types of interference in nonstationary hydroacoustic communication channels, and is oriented to solving communication and navigation problems for underwater robotic complexes. The limitation of spectral efficiency of such multi-frequency systems of information transmission by the value of 0.5 bits/s/Hz in various frequency ranges, nonstationary hydrological conditions, with achievement of the maximum range at acceptable levels of error probability during information decoding is shown. The operability of the proposed class of multi-frequency multiplexing methods was confirmed by numerical and in situ sea experiments on the shelf at distances from 2.5 to 7 km with the mutual drifting of ships and with sea waves of up to 3 points.

Provocation of verbal interaction of dolphins via a hydro-acoustic channel on the basis of cognitive empathy

The provocation of the hydroacoustic communication interaction of Tursiops truncatus dolphins based on cognitive empathy showed that they use packets of ultrashort pulses (USPs) in the process of “dialogue”. The duration of bursts varies from 40 ms to 3000 ms with modulation of the interval between USPs from ~1 to ~120 ms and pauses between bursts. The interval modulation pattern is structured using various modulation laws. The communication signals were obtained in an experiment with theparticipation of three animals, who knew the main task of sequential acoustic differentiation of two objective stimuli. The impetus for hydroacoustic interaction is the resolution of uncertainty when teaching the respondent the inverse differentiation problem. This generates emotional empathy in observers and provokes vocalization between individuals. The advantages and disadvantages of methodological methods of provoking hydroacoustic interaction are considered in detail, starting the process of cognitive empathy. In the method under consideration, echolocation and communication signals are spaced apart in time and space, which allows them to be uniquely identified.

A Survey of Localization Techniques for Underwater Wireless Sensor Networks

With the continuous development of marine resources, the position of Underwater Wireless Sensor Network (UWSN) is becoming more and more important, and UWSN needs to know the location of sensor nodes when completing tasks such as marine data collection, environmental monitoring, and aiding navigation, etc. Accurate sensor node location information is the key to effective acquisition of underwater data. The key to effective underwater data acquisition is accurate sensor node location information. Due to the influence of the environment, global positioning system (GPS) signals cannot be propagated underwater, so hydroacoustic communication becomes the best choice for node positioning. However, the unstable underwater environment brings a series of challenges to hydroacoustic communication, such as high channel bit error rate, low bandwidth, large propagation delay, and obvious multipath effect. According to the characteristics and challenges of hydroacoustic communication, this paper classifies the localization algorithms of underwater wireless sensor networks into (i) distance-based and distance-free localization algorithms, (ii) single-hop and multi-hop localization algorithms, and (iii) distributed and centralized localization algorithms.

Помехоустойчивость когерентного приема сигналов с многопозиционной фазовой манипуляцией и синусоидальной огибающей в гидроакустическом канале связи

Goals: The main purpose of this work is to develop a methodology for determining the parameters of signals with multi-position phase manipulation (M-PSK), in which the signals become relatively invariant to frequency distortions in the marine environment. The frequency distortion of the signals is caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. To do this, the error probabilities of the M-PSK signal receiver are determined, which is optimal in the absence of distortion. Methods: The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content: The paper considered a model of a single-beam hydroacoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude -frequency response and a linear phase-frequency response. The additive boundary of the error probability for coherent reception of M-PSK signals with a sinusoidal envelope is determined. As a receiver, a coherent receiver is considered, optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters that are relatively invariant to frequency distortions in the marine environment are determined. Results: Expressions are found for the upper bound of the error probability of coherent receivers of M-PSK signals with a sinusoidal envelope for M = 2, 4, 8, 16, 32. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of sending the signal, the carrier frequency and the number of phases of the signal, as well as on the communication range and the signal-to-noise ratio is determined. On the plane of the carrier frequency, the duration of sending the signal, for each type of signal, a boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed. A comparison is made with the case of receiving M-PSK signals with a rectangular envelope. It is shown that invariant signals with a sinusoidal envelope have a shorter duration than signals with a straight-angle envelope. In addition, the duration of signals with a sinusoidal envelope is significantly less dependent on the number of phases of the signal.

Analysis of the influence of the continental shelf slope in the South China Sea on sound propagation

Continental shelf slopes are widely found in transitional sea areas, which are the connecting part between shallow and deep seas. The sound propagation in this part has special effects. This paper takes the continental shelf slope sea area of the South China Sea (SCS) as the research object to analyze the influence of the shelf slope on sound propagation at different seasons. The seasonal difference in the three-dimensional sound ray trajectory and its corresponding transmission loss (TL) are mainly reflected in the case of a shallow sound source, which is caused by the difference in the sound speed field environment. Due to the presence of a strong surface sound channel in winter, the sound source at shallow depths can achieve long-distance propagation. As the strength of the surface sound channel becomes weaker, sound rays with large grazing angles can deflect across the surface sound channel towards the seabed, and sound energy leaks out of the surface sound channel. This part of the sound energy complements the area that the original sound energy can not reach, so the TL in this area is less than 90 dB. As for the slope enhancement effect, we verify it from the perspective of sound ray propagation, calculate the maximum distance between the sound ray and the shelf slope, and the mean absolute percentage error (MAPE) between the theoretical value and the actual value is 7.6%. The above results will have important implications for target detection and hydroacoustic communication in the sea area of continental shelf slopes.

Performance of single empirical orthogonal function regression method in global sound speed profile inversion and sound field prediction

The sound speed profile (SSP) reflects the change in sound speed from the surface to the bottom of the seawater, which will have an important influence on underwater acoustic detection and communication. Depending on the inversion of sea surface data sets measured by satellite to obtain near-real-time and high-precision SSPs has become a research hotspot. In this paper, based on the Argo data and the sea surface data sets, we use the single empirical orthogonal function regression (sEOF-r) method to inverse the global SSPs and evaluate the performance of this method. There are also differences in the performance of inversed results at different sites and in different months at the global scale of the ocean. The eddy kinetic energy (EKE) affects the accuracy of inversion, we propose to add the EKE into the inversion formula at the same time to further optimize the inversed results and improve the accuracy, the global average inversion error after optimization reduces by 20%. Finally, we verify the effectiveness of the optimized method from the perspective of sound field prediction. In most cases, the correlation coefficient of the transmission loss (TL) calculated through the inversion SSP and Argo-SSP exceeds 0.7 and the error is controlled below 6 dB, which will have important implications for the actual sound field prediction and hydroacoustic communication.

Analysis of Influence of the Seamount in the South China Sea on Sound Propagation

The influence of seamounts on sound propagation is very important, and it is also a research hotspot for hydroacoustic. This paper uses the BELLHOP ray model to analyze the influence of seamounts in the South China Sea on sound propagation, it is found that the blocking of seamounts has a greater impact on the spatial distribution of the transmission loss. When forward propagation, the distribution of the transmission loss is mainly influenced by seamounts, and its temporal variation is not obvious. When the sound source is relatively far away from the first seamount, the first seamount does not have a great influence on the distribution of the transmission loss. When backward propagation, the transmission loss increases rapidly after passing through the first seamount. Most of the sound energy is blocked due to the higher height of the first seamount. In addition, the impact of the undulating bottom on the front of seamounts on sound propagation should also not be ignored during backward propagation. The seamount determines the most important characteristics of the transmission loss distribution, while the undulating bottom has a certain degree of influence on the distribution characteristics of some specific regions. The above results have important applications for target detection and hydroacoustic communication in the area of seamounts.

Multi-AUV Formation Predictive Control Based on CNN-LSTM under Communication Constraints

For the problem of hydroacoustic communication constraints in multi-AUV leader follower formation, this paper designs a formation control method combining CNN-LSTM prediction and backstepping sliding mode control. First, a feedback linearization method is used to transform the AUV nonlinear model into a second-order integral model; then, the influence of hydroacoustic communication constraints on the multi-AUV formation control problem is analyzed, and a sliding window-based formation prediction control strategy is designed; for the characteristics of AUV motion trajectory with certain temporal order, the CNN-LSTM prediction model is selected to predict the trajectory state of the leader follower and compensate the effect of communication delay on formation control, and combine the backstepping method and sliding mode control to design the formation controller. Finally, the simulation experimental results show that the proposed CNN-LSTM prediction and backstepping sliding mode control can improve the effect of hydroacoustic communication constraints on formation control.

A Medium Access Control Protocol Based on Interference Cancellation Graph for AUV-Assisted Internet of Underwater Things

With the booming development of marine exploration technology, new studies such as the oceanix city, smart coastal city, and underwater smart cities have been proposed, and the Internet of Underwater Things (IoUT) has received a lot of attention. Data collection is an important application of the IoUT. The common method is to collect data by traversing the network using underwater intelligent devices, such as Autonomous Underwater Vehicles (AUVs). However, traditional data collection methods focus more on issues, such as path planning or the task assignment of AUVs. It is commonly known that the MAC protocol plays a crucial role in data transmission, which is designed to solve the competition issue for shared channels. However, the research on MAC is very challenging owing to the characteristics of hydroacoustic communication, e.g., the low bandwidth, high error rate, and long transmission latency. Hence, this paper proposes a MAC protocol based on an Interference Cancellation Graph (ICG-MAC) for AUV-assisted IoUT. It ensures that AUVs can join the network for data transmission immediately after arriving at the target area and they do not interfere with the normal work of other sensor nodes. Firstly, the target area to be reached by an AUV for data collection is defined according to the node degree and residual energy; then the interference model between neighboring nodes is analyzed and an Interference Cancellation Graphx is established, based on which the time slots are allocated for sensor nodes; and finally, the AUV moves to the target area for conflict-free data collection. The simulation results show that the proposed algorithm outperforms the comparison algorithms in terms of the network throughput and energy consumption. With the assistance of an AUV, better network connectivity and higher network traffic can be obtained.

Research on a stacked high-sensitivity hydroacoustic transducer

PurposeIsland attack and defense, emergency rescue, scientific research, civilian fisheries and other fields are inseparable from timely, high-quality underwater communications. However light and other electromagnetic waves are severely attenuated in water, acoustic is currently the only energy carrier that can transmit signals over long distances in water. However, the complex water environment and serious interference bring serious challenges to underwater activities using underwater acoustic sensors-hydroacoustic transducers. Thus, this paper aims to develop a class of high reception sensitivity hydroacoustic transducer structures to provide research and utilization ideas for related scholars.Design/methodology/approachThe electromechanical coupling coefficient is improved by converting the thickness vibration mode of the piezoelectric ceramic into the longitudinal vibration mode of the piezoelectric pillars array, and no polymer is added between the piezoelectric pillars array to reduce lateral coupling as well as internal friction, which can thus reduce the energy losses. Radial stacking in parallel can also enhance the charge generated through the positive piezoelectric effect. The optimal parameters of the structure are determined by equivalent circuit method and finite element analysis, and a hydroacoustic transducer of this structure is fabricated finally.FindingsAccording to the standard test procedure, the hydroacoustic transducer was tested in water. The tests show that the conductance curve of the stacked high-sensitivity hydroacoustic transducer tested in the air is in good agreement with the simulation results. The resonant frequency is about 118 kHz, and the receiver sensitivity is −166 dB. The stacked material hydroacoustic transducer is in the high-frequency range and has a much higher sensitivity (−166 dB) than many types of hydroacoustic transducers fabricated by piezoelectric ceramic (less than −200 dB).Research limitations/implicationsAlthough the stacked high-sensitivity hydroacoustic transducer that the authors have fabricated has a performance improvement, it has a limitation. The hollow design of the pillar arrays increases the reception stress on each pillar, and the imposed pressure comes from water also increases simultaneously, so the depth of water that the stacked high-sensitivity hydroacoustic transducer can operate in may be slightly shallower than that made of a pure piezoelectric ceramic block or a piezoelectric ceramic material with polymer added. This will be a problem to be solved in a future deployment.Practical implicationsWhether it is marine scientific research or in various fields such as civil recreation and fishing, hydroacoustic communication and necessary underwater exploration are indispensable for acoustic waves. The hydroacoustic transducer is the sensor that sends and receives sound waves, so a lot of water equipment, such as yachts, sonar buoys, and so on, cannot be separated from the hydroacoustic transducer. In addition, the complexity of the water environment also requires a good performance of the hydroacoustic transducer to facilitate the convenience and effectiveness of subsequent signal processing. Therefore, hydroacoustic transducers have great market and commercial value.Social implicationsHydroacoustic transducers are not only of great commercial value but also have a significant impact on the military as well as on people’s livelihood. As we all know, in the area of submarine communication and underwater exploration, sonar is the main force. The performance of the hydroacoustic transducer directly affects the performance of the hydroacoustic signal processing system, and ultimately directly determines the success or failure of the mission. In addition, the large-scale replacement of hydroacoustic transducers on equipment requires the concerted efforts of a large number of practitioners, such as material scientists, structural scientists, mathematicians and so on. Therefore, the rise of hydroacoustic transducers has given rise to a large number of learning positions as well as employment positions.Originality/valueTo enhance the reception sensitivity of the hydroacoustic transducer, the authors have optimized the existing hydroacoustic transducer materials and structures to propose a stacked sensitive element, which can effectively enhance the electromechanical conversion coefficient of the piezoelectric material. Furthermore, the authors have manufactured a hydroacoustic transducer using the proposed stacked sensitive element. The test results of the hydroacoustic transducer also show that the designed stacked sensitive element is of great help to enhance the reception sensitivity of the hydroacoustic transducer.

Hydroacoustic communication channel capacity

Objectives . Capacity, describing the maximum rate of information transmission, is an important characteristic of any communication channel. The main purpose of this work isto determine the capacity of a hydroacoustic communication channel with constrained average intensity of the transmitted signal. An additional aim consists in finding the optimal spectrum of a transmitted signal and calculate its boundary frequencies. A model of a single-path channel was considered, which is characteristic of the deep sea with the receiver or transmitter placed at a sufficient depth. Methods . Concepts of applied hydroacoustics, the theory of random processes, and information theory were used. Results . An expression for gain in a hydroacoustic communication channel has been obtained. A novel expression derived for the spectral level of sea noise caused by sea surface waves is based on piecewise linear approximation of the curves of the spectral levels of noise obtained from four sources: turbulence, shipping, sea waves, and the thermal noise of the sea. Dependencies of the hydroacoustic channel capacity on communication distance, intensity of the transmitted signal, and sea state, are characterized. The definition of the optimal spectrum itself is determined along with the lower and upper boundary frequencies of the optimal spectrum of the transmitted signal. The dependence of the bandwidth usage on the intensity of the input signal at various communication distances has been investigated. Conclusions . On the basis of the Francois–Garrison attenuation coefficient, channel capacity was correlated with the parameters of the marine environment: temperature, salinity, and pH in the study area. At a given intensity of the input signal, channel capacity was shown to decrease significantly with increasing distance and sea wave intensity. It is also shown that the width of the optimal spectrum decreases with increasing distance. Sea wave noise was noted to affect significantly the shape of the optimal spectrum and its boundary frequencies. The possibility of cases where bandwidth usage increases with increasing distance at a given input signal intensity cannot be ruled out.

Помехоустойчивость когерентного приема сигналов с многопозиционной фазовой манипуляцией и прямоугольной огибающей в гидроакустическом канале связи

The main purpose of this work is to develop a methodology for determining the parameters of M-PSK signals, in which the signals become relatively invariant to frequent distortions in the marine environment. The frequency distortions of the signals are caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. To do this, the error probabilities of the receiver of M-PSK signals determined, which is optimal in the absence of distortion. Methods. The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content. The paper considered a model of a single-beam hydroacoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude - frequency response and a linear phase-frequency response. The additive boundary of the probability of error in the coherent reception of M-PSK signals with a rectangular envelope is determined. As a receiver, a coherent receiver is considered, optimal by the criterion of maximum similarity under the action of white Gaussian noise and the absence of distortion in the marine environment. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters that are relatively invariant to frequency distortions in the marine environment are determined. Results. Expressions are found for the upper bound of the probability of error of coherent signal receivers of M-PSK signals with a rectangular envelope for M = 2, 4, 8, 16, 32. A logarithmic measure of the relative increase in the probability of error compared to the case of the absence of distortions is introduced. The functional dependence of this measure is determined on the duration of sending the signal, the carrier frequency and the number of phases of the signal, as well as on the communication range and the signal-to-noise ratio. On the plane of the carrier frequency, the duration of the signal, for each type of signal, the boundary of the region above which the signals are relatively invariant to frequency distortions in the marine environment is constructed. For the communication range R = 3 km and the carrier frequency f0 = 30 kHz, the minimum values of the duration of invariant signals are given.

Помехоустойчивость когерентного приема двоичных сигналов с прямоугольной огибающей в гидроакустическом канале связи

Goals. The main purpose of this work is to develop a methodology for determining the parameters of binary signals, at which the signals become relatively invariant to frequency distortions in the marine environment. The frequency distortion of the signals is caused by the uneven frequency response of the attenuation of the marine environment. The main part of this technique is to assess the effect of frequency distortion of signals on the noise immunity of reception. In accordance with this, the error probabilities of signal receivers with various types of manipulation are determined, which are optimal in the absence of errors. Methods. The provisions of applied hydroacoustics, the theory of random processes and the theory of transmission of discrete messages are used. The main content. The paper considered a model of a single-beam hydro-acoustic communication channel, characteristic of the deep sea, when the receiver or transmitter is located in the depths of the sea. The transmission coefficient of the channel is used as a transmission coefficient with a Gaussian amplitude-frequency characteristic and a linear phase-frequency characteristic. The error probabilities of coherent binary signal receivers with amplitude, frequency and phase manipulation with a rectangular envelope are determined. Coherent receivers optimal by the criterion of maximum likelihood under the action of white Gaussian noise and the absence of distortion in the marine environment are considered as receivers. A logarithmic measure of increasing the probability of error is introduced, which characterizes the deterioration of noise immunity due to frequency distortions in the channel. For some typical cases, the values of signal parameters are determined that are relatively in-variant to frequency distortions in the marine environment. Results. Expressions of the error probability of coherent binary signal receivers with amplitude, frequency and phase manipulation with a rectangular envelope are found. A logarithmic measure of the relative increase in the probability of error compared to the case of no distortion is introduced. The functional dependence of this measure on the duration of the signal transmission, the carrier frequency and the initial phase of the signal, as well as on the communication distance and the signal-to-noise ratio is determined. On the plane of the carrier frequency, the duration of the signal, for each type of signal, a boundary of the region is constructed, above which the signals are relatively invariant to frequency distortions in the marine environment. For communication ranges R = 1.5 km and 3 km and typical carrier frequencies, the minimum values of the duration of invariant signals are given.

ТЕХНОЛОГИИ РАЗВИТИЯ МОРСКИХ ИНТЕГРИРОВАННЫХ СИСТЕМ СВЯЗИ

The goal is to improve the quality of information interaction of objects by increasing the reliability of message delivery to recipients and bandwidth through the integration of networks using various signals and physical channels. A search for new technical solutions for the creation of integrated (hybrid) communication technologies aimed at expanding the possibilities for creating adaptive, self organizing, resistant to destabilizing factors communication systems with an increased quality of services provided in vast areas was carried out. The method of solving the tasks is based on the analysis of development trends and forecasting the requirements for integrated mobile communication systems. The novelty lies in the development and evaluation of options for building the structures of integrated communication systems, represented by diverse, complementary subsystems using various methods of channel separation, including in physical environments, as well as algorithms for their operation. Key findings. A set of technologies for the development of coastal integrated communication systems has been developed: the structure of the system based on a hybrid mesh topology; the basic form of the carrier signal with controlled parameters depending on the physical channel; the principle of control of orthogonal signals in adjacent channels of switching and relay nodes, as well as between network nodes; hydroacoustic communication method. Hydroacoustic communication for coastal areas is a potential for increasing the number of simultaneously used information channels per unit of the volume of interaction of vital objects and makes it possible to connect satellite, air, surface, underwater and bottom subsystems of telecommunications. The con ducted studies have shown the stability of the proposed methods in conditions of excess of interference over the signal.