The performance of the proposed ZPN-OFDM transmission scheme was evaluated by simulations. Two different types of channels are used. One is a simulated channel where one channel tap is generated based on a multipath fading channel with maximum tap delay L ch 32 . The other is a measured underwater acoustic channel adopted from an experimental data collection in the ASCOT01 experiment conducted off the coast of New England in June 2001, as reported in  and is truncated to have an order L ch 128 . In the ASCOT01 experiment, the source is deployed at a depth of 103 meters and four meters above the bottom. Receiving elements with 16 vertical vector sensor arrays is used as a receiver, covering a depth of 30-90 meters. Approximately 10 km was the source-receiver range. Every 120 seconds, the transmitter transmits a probe signal. It is repeated each period of 160 minutes to study the channels. The data bandwidth was 500 Hz with 3550 Hz carrier frequency. A linear frequency modulated (LFM) was used as a probe signal. The received signal is on a large time scale of 120 seconds, and the 16 channels can be acquired with 78 estimates using matched filtering . We investigate the performance of the proposed communication system by testing uncoded and coded bit error rate (BER) performance. In all simulation experiments, the OFDM data sub-carrier number N data 1024 and QPSK modulations are employed. To generate data symbols, random information bits are generated and modulated directly by QPSK modulation in the uncoded case. However, in the coded case the random information bits are first encoded by a rate-1/2 convolutional encoder with generator polynomial [65,57] . Then, the encoded bits are interleaved by a block interleaver of depth 8 prior to QPSK modulation.
sampling frequency. Through these relations one can easily compute the CFO value. For the sake of comparison, we have run the simulations for different OFDM systems. Table I shows our proposed MUSIC based method estimations. Besides, we summarize the OFDM system parameters and SNR value of our first scenario in this table. In this simulation, OFDM symbol duration is 75ms. As we can see from Table I, the estimated values and the real values are very close to each other. Figure 1 shows the pseudo- spectrum according to the contents of Table 1. This figure exhibits the results of the MUSIC-based method for the first scenario.
We consider one more important case that arises when feedback taps are involved. It is known that in general, equalizers with feedback (DFEs) perform better than their linear counterparts . In many cases, using a DFE is necessary to achieve reasonable performance. However, DFEs are subject to a catastrophic failure mode. This has been noted in  and  in the context of Multiuser CDMA systems and in  for underwatercommunicationsystems, although, to the best of our knowledge, it has not been analyzed in detail. We now discuss how it occurs due to errors in the adaptation process, and demonstrate that our analysis procedure can indeed predict it.
significant if the acoustics are used in shallow water because turbidity, ambient noise and manmade noise in shallow water have bigger affection on the acoustic waves. In addition acoustic signals have limited bandwidth and low propagation velocity. Consequently, electromagnetic signals can be used for communication between sensor motes and especially in shallow water environment. In this project, the performance of using EM communication in underwater WSN deployed in the shallow water environment is studied. Theoretical and practical investigation will be conducted.
The technology is ideal for wireless docking, data links with kiosks and mobile displays, medium-range beaming, data Showers and optical cellular networks. Users will be able to enjoy a wireless RF-free user environment with data rates that can transfer a 2-hour HDTV video in less than 30 seconds and wirelessly link their bus-connected heavy- lifting peripheral cabinets located elsewhere in the room. For communication purpose light wave carry data in a fast manner, but in radio wave the data transfer rate is slow. So for that reason we are looking for light wave communication.
It has been approached in  to develop a sufficiently robust acoustic link allowing the transmission of differ- ent information using Reed Solomon coder and conven- tional coding to protect data transmission over underwa- ter acoustic channel. Where underwater acoustic link is designed to transmit different kinds of data as text, im- ages and speech signal, blind spatial-temporal equalizer is used to reduce different underwater acoustic perturba- tions. To improve the underwater acoustic link perform- ance and obtain a higher code rate, Reed Solomon Block Turbo Codes (RS BTC) has been introduced and tested in real conditions, with the aim to decrease the BER. A dif- ferential coding has been used to solve the phase ambi- guities. Channels block coders algorithm applies to trans- mission of constant data. Where Block codes are FEC codes that enable a limited number of errors to be de- tected and corrected without retransmission. Block codes has been used to improve the performance of a commu- nications system when other means of improvement (such increasing transmitter power or using a stronger modulator) are impractical .
transmitter to communicate with the onshore sink (os-sink) or to a surface sink (s-sink).Sensors can be connected to uw-sinks via direct links or through multi-hop paths. In the former case, each sensor directly sends the gathered data to the selected uw-sink. This is the simplest way to network sensors, but it may not be the most energy efﬁcient, since the sink may be far from the node and the power necessary to transmit may decay with powers greater than two of the distance. Furthermore, direct links are very likely to reduce the network throughput because of increased acoustic interference due to high transmission power. In case of multi-hop paths, as in terrestrial sensor networks , the data produced by a source sensor is relayed by intermediate sensors until it reaches the uw-sink. This results in energy savings and increased network capacity but increases the complexity of the routing functionality as well. In fact, every network device usually takes part in a collaborative process whose objective is to diffuse topology information such that efﬁcient and loop free routing decisions can be made at each intermediate node. This process involves signaling and computation. Since, as discussed above, energy and capacity are precious resources in underwater environments, in UWASNs the objective is to deliver event features by exploiting multi-hop paths and minimizing the signaling overhead necessary to construct underwater paths at the same time.
The sound speed profile of the selected region has been obtained from the provided data base of the World Ocean Atlas at 1-degree resolution, extended at the depth up to 5500 meters. The high-resolution sound speed profile can be obtained by using the cubic- spline interpolation in MATLAB. The environmental (ENV) files are generated which contain information about maximum floor depth, source (transmitter) depth and collector (receiver) depth, range of communication and the number of beams that need to be transmitted. The ENV files are further useful in finding out the channel frequency response and impulse response with the help of Bellhop ray tracing algorithm.
For WBAN UWB systems, it was anticipated in Section 2.7.2 that the radio propagation channel will exhibit some new and interesting characteristics such as antenna near-field and body-proximity eﬀects. All these phenomena are very char- acteristic to the around-the-body propagation channel, thus a suitable character- ization and modeling is required for them. The far-field propagation equations derived in Section 2.2 can be applied under certain conditions with respect to the positions of the transmitter and receiver antennas on the body and antenna types. Nevertheless, the solution for the de-embeding problem combined with double- directional measurements is not practical in typical WBAN scenarios where small devices are used. Similar, the scattering amplitudes in the theoretical expression for the UWB channel presented in Section 2.3 become very di ﬃ cult to evaluate for the dynamic (nonstationary) around-the-body propagation channel. Further- more, the dynamic near-field e ﬀ ects due to the body proximity cannot be derived and included analytically. In order to identify and separate the influence of the environment on the measured radio channel, di ﬀ erent user and body-phantom positions can be measured. The data can then be analyzed in order to determine the channel impulse-response variability caused by the body phantom or human user only.
EM (Electromagnetic) techniques enable efficient wireless communications in different media with different material absorptions. A wide range of novel and important applications in such challenged environments can be realized based on the EM communication mechanism. The main challenge in this area is the realization of efficient and reliable links to establish multi-hop communication and efficiently disseminate data for seamless operation. However, the hostile environments do not allow the direct usage of most, if not all, existing wireless communication and networking solutions, mainly because of the extremely high path loss, small communication range, and high dynamics of the EM waves when penetrating the different medium. In this paper, the propagation based on EM waves in the 315/433 MHz band through a solid: soil, coal, oil sand, and liquids: water, salty water, and crude oil medium is analyzed in order to explore its applicability. The developed model evaluates the total path loss, the transmission characteristics, and bit error rate. The propagation characteristics are investigated through simulation. The theoretical analysis and the simulation results prove the feasibility of wireless communication in the 315/433 MHz band in these environments and highlight several important aspects in this field.
Andre Goalic et al, A highdata rate acoustic link has been developed by the GESMA. The Main objective of this project was to create an acoustic communication link between anAWV(Autonomous Underwater Vehicle) and a surface vessel. This acoustic link must be sufficiently robust and improve underwater vehicles autonomy. The first years of this project were devoted to upstream studies .The goal was to choose the best solution able to deal with different perturbations generated by underwater acoustic channelAn equalizer developed and patented by the ENST Bretagne stood for a very good solution for thisapplication .An acoustic link was then developed to validate the whole communication between source dataemitter and receiver. Transmission part aswell asreception stage (hydrophones, amplifier) were designed by ORCA Instrumentation (SERCEL), a French company specialized in underwater acoustics modems. The receiver platform was developed by ENST Bretagne. The spatio-temporal equalizer called SOC-MI-DFE (Self Optimized Configuration Multiple Input Decision Feedback Equalizer) constitutes the receiver core. Some experiments were carried out in 2002 and 2003 to show some images, dataandtext transmissions. From now, GESMA plans to extend TRIDENT possibilities to low bit rate speech digital transmission. Existing andcommercial products are mostly based on analog communications; Digital transmission is expected to provide improved reliability. Duringour fistsea-trail, digitized speech by code excited linear predictive coding (CELP) clearly shown a better listening quality.
Sensors can be connected to uw-sinks via direct links or through multi-hop paths. In the former case, each sensor directly sends the gathered data to the selected uw-sink. This is the simplest way to network sensors, but it may not be the most energy efficient, since the sink may be far from the node and the power necessary to transmit may decay with powers greater than two of the distance. Furthermore, direct links are very likely to reduce the network throughput because of increased acoustic interference due to high transmission power. In case of multi-hop paths, as in terrestrial sensor networks , the data produced by a source sensor is relayed by intermediate sensors until it reaches the uw-sink. This results in energy savings and increased network capacity but increases the complexity of the routing functionality as well. In fact, every network device usually takes part in a collaborative process whose objective is to diffuse topology information such that efficient and loop free routing decisions can be made at each intermediate node. This process involves signaling and computation. Since, as discussed above, energy and capacity are precious resources in underwater environments, in UW- ASNs the objective is to deliver event features by exploiting multi-hop paths and minimizing the signaling overhead nec- essary to construct underwater paths at the same time.
nally developed for offering phone services to mobile subscribers. The wireless cellular communicationsystems with first-generation (1G) of analogue stage used frequency division multiple access (FDMA) scheme. Due to rapid advances in technologies it has led to the second-generation (2G) of digital stage with time division mul- tiple access (TDMA) and code division multiple access (CDMA) schemes, and now it has stepped into the third- generation (3G). High data rate transmission and burst data traffic which would be the dominant portion of traf- fic load resolved in 4G generation with IDMA Scheme. The next generation mobile communicationsystems, i.e. fourth-generation (4G) is required (you can refer to IMT-advanced requirements) to support multiple services in different types of environments. 4G is being developed to facilitate the QoS (quality of service) and required data rate such as wireless broadband access, multimedia messaging service (MMS), video chat, and mobile TV. This paper also focuses the light on various multiple access techniques proposed in 4G communication sys- tems.
The ACOUSTIC model refers to the communication with the sound waves. In under- water environment, communicating medium can be either radio, optical or sound (acoustic) waves. But the non-acoustic waves are electromagnetic waves which suffer from high propagation losses as well as scattering problems. These non-acoustic waves do not travel long distances in underwater environment. Radio waves require high transmission power as well as long antennas to communicate and Optical waves suffer from high signal attenuation so it can travel short ranges only. Hence sound is the best communicating medium for underwater networks. Till now and in near future also, the acoustic waves can be seen as the best communication medium for wireless net- works in UWSNs.
The towing of an underwater object by means of a cable attached to a ship is an important problem in underwater technology. An underwater towed body is generally at the mercy of hydrodynamic and hydrostatic forces, which controls its motion through water. These forces affect the depth characteristics of the towed body giving specific configuration to the towline. This work consists of the development of a finite element program for the dynamic analysis of underwater towed cable and its tow characteristic
Underwater Wireless Sensor Networks (UWSNs) is a collection of organized and distributed wireless communication networks that comprises of enormous number of sensor nodes in underwater. The emerging wireless charging technology is a promising alternative to address the power constraint problem in sensor networks. Comparing to existing approaches, this technology can replenish energy in a more controllable manner and does not require accurate location of or physical alignment to sensor nodes. However, little work has been reported on designing and implementing a wireless charging system for sensor networks. In this paper, we design such a system, build a proof-of-concept prototype, conduct experiments on the prototype to evaluate its feasibility and performance in small-scale networks, and conduct extensive simulations to study its performance in large-scale networks. The proposed system can utilize the wireless charging technology effectively to prolong the network lifetime through delivering energy by a robot to where it is needed.
This paper investigates how to increase communication distance of underwater wireless optical communication system. In order to analyze the communication distance of UWOC, the performance of optical transmitter and receiver, underwater channel characterization and modulation schemes were discussed. The communication link model was established based the on Beer-Lambert Law. The suitable transmitter power and the maximum communication were achieved in order to achieve communication rate to 1Mbits/s and bit error rate to 10 -6 .This paper not only provides comprehensive understanding of
A low cost and low power acoustic modem has been designed in paper to have better short range communication. The tests are performed with transducers for an in- air communication. The efficient functioning of the proposed new design modem has been proved by the successful transmission and reception of data with low latency.  provides a comparative study of three dispersion comparison fiber model as pre, post and symmetrical which involves the concept of compensation fiber of Bragg grating under 40Gbps single channel optical fiber transmission system. Three modulation schemes duo- binary coding, modified duo-binary and carrier suppressed return to zero are simulated and analyzed in terms of Q- factor and bit error rate for each set up by range of CW laser power. The simulation of optical system based on optisystem-10. In paper , a DC-biased optical OFDM and asymmetrically clipped OFDM are considered for underwater optical wireless communication. This produces a half-way symmetry time signal at the output modulator by assigning the subcarriers. This assigns data. This DC based OFDM assigns data evenly to all possible subcarriers in order to increase the data rate. This paper considers a practical LED model to study the performance in terms of average electrical OFDM signal power versus bit error ratio in the presence of AWGN.
Abstract: The formal transfer of GNSS under water is not possible. It probably makes sense to talk only about the transformation of GPS into LPS, that is, in the Local Position System. However, the basic methods that are used to solve the problem of Spoofing Detection above water can be used under water. It should be understood that engineering problems are significantly different, since the nature of the propagation of acoustic waves in water and electromagnetic waves in the atmosphere are fundamentally different. In this article, we will limit the navigation with acoustically passive receiver. The receiver “listens” to the buoys and solves the problem of finding its own position based on the coordinates of the buoys (such systems are called GNSS-like Underwater Positioning Systems or GNSS-like UPS). Depending on the scale of system service areas, GNSS-like UPS are divided into global, regional, zonal and local system. In this article, we will limit ourselves to considering only local GNSS-like UPS. The acoustic signal generator transmits a signal simulation of several satellites. If the level of the simulated signal exceeds the signal strength of real satellites, the receiver of UPS will “capture” the fake signal and calculate the false position based on it.