Design and analysis of underwater communication

Underwater communication processes will introduce in sending and receiving messages of below the water. To observes the effectiveness of communication over sea water through free space optics. The transmitter and receiver data rate will vary depending on the level of various aspects of the sea. Underwater communication is crucial for the military and commercial purpose.

Underwater communications are being utilized to explore the activity of the ocean, especially how they respond to any seismic activity, like tsunamis, seaquakes, and earthquakes, for disaster prevention. Path losses are different for types of water and different communication ranges are simulated. The communication range and bit error rate performance for such channel are also evaluated. Underwater optical wireless communication in the wavelength band of 400nm-600nm is modeled. It analyzed these links in Opti system.

I. INTRODUCTION

Optical wireless communication comes under the form of optical communication in which ultraviolet light or unguided visible infrared light is used to carry the signal. Optical wireless communication operates in the visible light between the range of (390-750nm) are commonly referred as visible light communication. The major advantages of optical wireless communication are minimized communication and computational cost. The main concept of optical wireless communication is it is allowed to transmitting over long distances and it withstanding capacity of high bandwidth and high data rate.

The underwater scattering channel for underwater optical wireless communication is modeled by ray tracing techniques [1]. reported the broadband characteristics of the OUWC channel in different water condition. Acoustic waves are traditionally for constructing corresponding long-range wireless submerged links. Recently evolved single carrier and multicarrier mod techniques have extremely upgraded traditional modulation equivalent parts, based on communication range and data rate.

Their data are in the range of tens 10 kbps [2-4]. The underwater investigation has been one of the most stunning topics to worldwide researchers because of immense unfamiliar underwater resources which will be very difficult for the shortage of natural resources [3]. Even so optical underwater communication is without subject to a tremendous challenge since the optical beam will impaired extremely by the absorption and scatter of water molecular and suspend particles, just as chlorophyll.

Water dissolved salt and mineral, etc. The multiple scattering of the light will increment the path loss broaden the impulse the path replication, which cause the ISI. When transmission long data rates are over long distances [5] optical underwater communication which utilizes the light transmission window of water in the 400nm-600nm (blue/green) wavelength band, changed to be a congruous solution for the authentic time high rate communication up to 1Gbps in meters [6].

II. UNDERWATER COMMUNICATION

For the design of underwater communication is attracting attention due to their important underwater applications. Normally underwater communication plays a major role in investigating, (i) changes of climate, (ii) monitoring biological, (iii) biogeochemical, (iv) ecological changes of the sea. Free space optics requires a clear line-of-sight between transmitter and receiver in optical conditions can cover a distance of several kilometers, even if a quality of services (QOS) suitable for communication can be achieved only at smaller link ranges. The frequency and wavelength are inversely proportional, that is taken for this model is,
= f ∝1/w……. (1)
The wavelength and frequency of light are closely related the increase the frequency and then smaller the wavelength because every light waves progress through a vacuum at the equal speed. Waves in higher frequency have smaller wavelength and lower frequency have higher wavelength’s and it’s water variations in the ranges of the area of water. The frequency ranges of light can be calculated by using the following expression,
Frequency, f = c/λ…… (2)
Where c represents the speed of light .that means, it specifies a velocity of light and its range is 3.0×10^8 m/s and λ stands for wavelength.

Underwater communication is intricate due to elements such as multipath propagation, time variations of the channel, smaller bandwidth and robust signal attenuation, especially over long ranges. Seawater has widely varying optical properties depending on the location, time delay, organic and inorganic content, as well as temporal variations such as turmoil and surface motion. To design an optical link it is important to perceive their properties. underwater optical wireless communication is a quickly improving the area of research, the contrast to acoustic optical wireless communication has been proposed as the best replacement in order to overcome the restrictions in underwater acoustic communication. e underwater optical wireless communication simulation results of the path loss versus communication distance based on absorption, scattering, and extinction coefficient for the three types of Water, (i) clean ocean water, (ii) coastal water, (iii) turbid harbor water. In order to distinguish the channel in broadband spectrum, the scattering and absorption effects, generally distance dependent, should be well represented. Corresponding to [1], the wavelength dependent absorption coefficient of ocean water can be expressed as,
a(λ) =aw(λ)+ac0(λ) (Cc/Cc0)0.602+af0Cfexp(-kfλ)
+ah0Chexp(-khλ)

And the wavelength dependent scattering coefficient of ocean water can be expressed as,
b(λ) =bw(λ)+bs0(λ) Cs+bl0(λ) Cl The path loss versus communication ranges for the different types of water, such as clean water, coastal water, harbor water in three wavelength’s (480nm, 530nm, 570nm).we can see that the path loss in the harbor water is much higher than the coastal water and clean water because of the coastal water and clean water because of the absorption and scatter effects of suspended particles.

III. RESULT DESCRIPTION

Here we analyzed the quality factor, bit error rate, path loss, data rate, eye diagram in the proposed model. The absorption and scattering coefficients can be used to calculate the Path Loss. The most common figure of merit for digital links is the bit error rate, which commonly is abbreviated as BER. The BER is defined as the ratio of the number of bit errors is occurring over a particular time interval to the total number of bits sent during that interval; that is, BER = NE/NT. Figure (1) shows the basic link diagram of three types of waters.

The eye diagram technique is easy but robust measurement techniques for accessing the data handling capability of a digital transmission system. This method has been used greatly for assessing the performance of free space. The eye model measurements are making in the time domain and let on the consequence of waveform distortion to be shown immediately on the display the standard BER test performance. Figure 2 shows the eye diagram of clean water, the eye is closed because of noise. The maximum amplitude level is 3 µv only. When water profundity increases the attenuation and the scattering parameter range also increased.

IV. CONCLUSION

The goal of this paper is to propose an underwater communication with a high bit rate using optical wireless communication, which is modeled by free space optic. We can see from the result that as the distance increase in the output gets more distorted. For the measure of the quality factor, bit error rate, path loss, data transmission rate is considered. We achieved the maximum quality factor of clean water is 828. 499at the power of 30mw. So there is a possibility to increase the quality factor to reduce the bit error rate compared to coastal and harbor water.

REFERENCE
[1]Weihao Liu, Difan Zou, Peilin Wang, Zhengyuan, and Liuqing Yang, “Wavelength-dependent channel characterization for underwater optical wireless communication,” IEEE Journal of Oceanic Engineering, vol. 33, no. 2, pp. 198–209, 2008.
[2] X. Cheng, F. Qu, and L. Yang, “Single carrier FDMA over underwater acoustic channels,” in Proceedings of CHINACOM Conference, Harbin, China, August 17-19, 2011, pp. 1052– 1057.
[3] I. Vasilescu, C. Detweiler and D. Rus, “Aqua Nodes: an underwater sensor network,” Proceedings of the second workshop on Underwater Networks, 2007, pp. 85-88.
[4] X. Cheng, M. Wen, X. Cheng, L. Yang, and Z. Xu, “Effective self-cancellation of intercarrier interference for OFDM underwater acoustic communications,” Proc. of The 8th ACM International Conference on Underwater Networks & Systems, Taiwan, November 11-13, 2013.
[5] F. Hanson and S. Radic, “High bandwidth underwater optical communication,” Appl. Opt., Jan. 2008, vol. 47, no. 2, pp. 277– 283.
[6] D. Anguita, D. Brizzolara, and G. Parodi, “Building an underwater wireless sensor network based on optical communication: Research challenges and current results,” in Int. Conf. on Sensor Technologies and Applications (SENSORCOMM), Athens, Greece, Aug. 2009, pp. 476–479.
[7] C. D. Mobley, Light and Water: Radiative Transfer in Natural Waters. Academic Press, June 1994.
[8] V. I. Haltrin, “Chlorophyll-based model of seawater optical properties, ” Appl. Opt., vol. 38, no. 33, pp. 6826–6832, 1999.