Design of Algorithm for Multicarrier Modulation to Improve Transmission Performance of Inductive Cou

Design of Algorithm for Multicarrier Modulation to Improve Transmission Performance of Inductive Coupling Temperature–Salinity–Depth Chain

Abstract: The inductive coupling temperature–salinity–depth chain uses seawater as a medium, where the transmission of electrical signals has multipath effect in infinite seawater. When the transmission frequency is increased, multipath delay spreads, inter code crosstalk, and selective fading of the received signals will be enhanced.

In this letter, the finite-element simulation and numerical calculation are used to determine the key parameters, such as the number of paths, time delay, and channel attenuation factor. A multipath mathematical model of a long-distance inductively coupled channel based on electric current communication is established. Finally, an algorithm for multicarrier modulation, suitable for the channel, is proposed. The simulation results show that the proposed algorithm for multicarrier modulation can effectively resist multipath fading and improve system transmission performance.

Existing system: ASK and DPSK are the most widely used single carrier modulation techniques for inductively coupled transmission, but the data transmission rate is limited in long

range deepsea measurements. With the increase of the transmission rate, multipath effect is the key issue affecting the reliability of signal transmission. Therefore, this letter proposes an algorithm for multicarrier modulation, which can effectively resist multipath fading. Simulation results show that the BER is significantly reduced in the low SNR range by using our algorithm for multicarrier modulation.

To further optimize the algorithm, parameters such zero padding, PAPR, and channel capacity are analyzed and discussed in this letter.

Proposed system: The underwater electric current communication method differs from the conventional acoustic method. Electric noise level in undersea environment is low, and electric current does not reflect in a conductor as its transmission rate is much higher than underwater acoustic speed. These advantages allow the current field method to meet the need for high data and short range underwater communications with little propagation delay, and a induced electric dipole model is established.

Meanwhile, electric current method is known to be useful for long range inductively coupled temperature-salinity-deep communication system. However, with the increase of transmission distance and frequency, the multipath fading effect of current signal transmission performance in infinite waters will be enhanced. The distribution of sensor nodes in inductively coupled transmission underwater are relatively static, so a multipath channel model of long distance linear time-invariant FIR filter based on inductively coupled electric current communication is established in this letter.

Advantages: With signal frequency, time-varying multipath propagation, and low speed of sound underwater (1500 m/s). Channel modeling is established in accordance with the physical nature of propagation. For example, a linear time-invariant filter modeling used in slow time-varying coherent multipath channels, and a timevarying modeling is established in explicit Doppler shift modeling.

Research in this field is currently active on using MIMO acoustic communication channels. The underwater electric current communication method differs from the conventional acoustic method. Electric noise level in undersea environment is low,

and electric current does not reflect in a conductor as its transmission rate is much higher than underwater acoustic speed.

Disadvantages: These advantages allow the current field method to meet the need for high data and short range underwater communications with little propagation delay, and a induced electric dipole model is established Meanwhile, electric current method is known to be useful for long range inductively coupled temperature-salinity-deep communication system.

However, with the increase of transmission distance and frequency, the multipath fading effect of current signal transmission performance in infinite waters will be enhanced. The distribution of sensor nodes in inductively coupled transmission underwater are relatively static, so a multipath channel model of long distance linear time-invariant FIR filter based on inductively coupled electric current communication is established in this letter.

Modules: DEEP-SEA environmental monitoring technology : DEEP-SEA environmental monitoring technology is of great importance to the marine environment, as it enables acquisition of marine parameters and environmental factors. Inductively coupled temperature-salinity-deep chain is an important instrument for ocean depth monitoring. Based on the electromagnetic coupling principle, seawater and steel cable are used as transmission channels for long-distance underwater non-contact communication. The ocean is a time and spatially varying propagation environment, whose characteristics pose significant challenges to the development of effective underwater wireless communication.

Such communication can be challenging due to multipath propagation, time variations of the channel, small bandwidth, and strong signal attenuation.

Compared with optical and electromagnetic, acoustic and electric current communications are the primary forms of wireless underwater communications over long ranges. Acoustic propagation is characterized by three major factors.

Channel modeling:

Channel modeling is established in accordance with the physical nature of propagation. For example, a linear time-invariant filter modeling used in slow time-varying coherent multipath channels, and a time-varying modeling is established in explicit Doppler shift modeling. Research in this field is currently active on using MIMO acoustic communication channels. The underwater electric current communication method differs from the conventional acoustic method.

Electric noise level in undersea environment is low, and electric current does not reflect in a conductor as its transmission rate is much higher than underwater acoustic speed. These advantages allow the current field method to meet the need for high data and short range underwater communications with little propagation delay, and a induced electric dipole model is established. Meanwhile, electric current method is known to be useful for long range inductively coupled temperature-salinity-deep communication system. However, with the increase of transmission distance and frequency, the multipath fading effect of current signal transmission performance in infinite waters will be enhanced. The distribution of sensor nodes in inductively coupled transmission underwater are relatively static, so a multipath channel model of long distance linear time-invariant FIR filter based on inductively coupled electric current communication is established in this letter.

Multipath: In section II, it is discussed that multipath channel has frequency selectivity. With the increase of frequency, the attenuation and aliasing of multipath channels worsen. In order to verify that the algorithm for multicarrier modulation could reduce multipath, this letter compares and analyzes the BER using ASK, DPSK and algorithm for multicarrier modulation. The signal x(m) is set as a 640-bit binary number. The transmitting signal passes through the multipath channel model and the final signal x(k) is determined according to the judgment threshold after demodulation on the receiving end. To further improve the performance of algorithm for multicarrier modulation, the methods of reducing PAPR and channel capacity under different mapping modes are compared.