Abstract
Wireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS conditions. In our method, we used multiple frequency-shift keying (MFSK) modulation, sending a single bit on two carriers, and diversity combining. The method was tested in laboratory conditions which simulated underwater signal propagation during the penetration of the wreck. The propagation conditions were investigated by determining the impulse responses at selected measurement points using the correlation method. Additionally, for comparison, the data transmission quality was determined by the bit error rate (BER) under the same conditions using direct sequence spread spectrum (DSSS) and binary phase shift keying (BPSK) modulation. The obtained results confirmed the usefulness of the application of the developed method for wireless data transmission in a hydroacoustic channel under NLOS conditions.
Highlights
The most important are the multipath propagation leading to intersymbol interference and the Doppler effect which, due to the relatively low speed of sound propagation in the water environment, is hundreds of thousands of times stronger than that it is in the case of radio communication [2]
The presented estimates clearly visible that, as thetoset receivingvalue, hydrophones is moved the created corridor, normalized with respect theofmaximum separately for eachinmeasurement point. It conditions at the first measuring point, and NLOSinconditions in is clearly visible are that,present as the set of receiving hydrophones is moved the createdprevail corridor, the subsequent points. It can be determined on the basis of the appearance time of the LOS conditions are present at the first measuring point, and NLOS conditions prevail in peak of the estimation impulse response,oni.e., measurement the the subsequent points
Comparing the obtained bit error rate (BER) error rates with the results presented in Figure 12, the proposed method based on multiple frequency-shift keying (MFSK) is much better than the traditional direct sequence spread spectrum (DSSS)
Summary
The propagation of a sound wave in water is accompanied by many unfavorable phenomena that affect the overall quality of transmission expressed by the range of data transmission, bit error rate or bit rate. Among these phenomena, the most important are the multipath propagation leading to intersymbol interference and the Doppler effect which, due to the relatively low speed of sound propagation in the water environment, is hundreds of thousands of times stronger than that it is in the case of radio communication [2]. Serious difficulties exist in obtaining relatively fast (about kilobits) and reliable (BER about 10−3 )
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
