Abstract
To solve the problem of the high peak-to-average power ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) for the underwater acoustic communication system, the paper offers a method of reducing PAPR which combines the amplitude limiting and the improved nonlinear transformation. Traditional amplitude limiting technique can reduce PAPR in OFDM system effectively, at the cost of reducing the bit error rate (BER). However the companding transformation has far less computation complexity than SLM or PTS technologies and can improve the BER performance compared to the amplitude limiting technique simultaneously. The paper combines these two kinds of techniques, takes full use of advantages of the two method, and puts forward a low-complexity scheme choosing parameters that are more appropriate to the underwater acoustic field, with the result of improved BER performance even in lower SNR. Both simulation and experiment results show that the new method which combines clipping and companding transformation can effectively reduce the PAPR in the underwater acoustic OFDM communication system and improve the BER performance simultaneously.
Highlights
The main research direction of underwater acoustic communication includes high-speed underwater acoustic communication at near distance and low-speed acoustic communication at remote distance [1,2,3]
The paper is based on this point, according to [7], aiming at the underwater acoustic channel’s time-varying and multipath to improve the performance of the underwater acoustic Orthogonal Frequency Division Multiplexing (OFDM) communication system, choosing parameters that are suitable for the underwater acoustic channel and the parameters can adjust according to the requirements of the application, achieving a compromise between the SNR and bit error rate (BER), and the effectiveness of the arithmetic is proved in the simulation of multipath fading underwater acoustic channel and the water tank experiment
The technique to decrease peak-to-average power ratio (PAPR) is at the cost of increasing power, increasing BER, decreasing the data rate, and adding computational complexity
Summary
The main research direction of underwater acoustic communication includes high-speed underwater acoustic communication at near distance and low-speed acoustic communication at remote distance [1,2,3]. OFDM has the defect of high PAPR, which will restrict the linear dynamic range of transmitter’s power amplifier and generate clipping distortion which in turn influences the BER performance of the whole system. It will reduce the accuracy of A/D and D/A convertor and even break the subcarrier’s orthogonality in OFDM system [7]. In signal predisposition technique, clipping is the simplest way to realize and is widely used in previous underwater acoustic OFDM communication It is a kind of nonlinear process, which will bring serious in-band interference and out-band noise. The paper is based on this point, according to [7], aiming at the underwater acoustic channel’s time-varying and multipath to improve the performance of the underwater acoustic OFDM communication system, choosing parameters that are suitable for the underwater acoustic channel and the parameters can adjust according to the requirements of the application, achieving a compromise between the SNR and BER, and the effectiveness of the arithmetic is proved in the simulation of multipath fading underwater acoustic channel and the water tank experiment
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