A Method of Selecting the Best Pilot Sequence to Suppress the Peak-to-Average Ratio of Underwater Acoustic Ofdm Signal

Abstract

The invention relates to a method for suppressing an underwater acoustic OFDM signal peak-average-ratio by selecting the optimal pilot frequency sequence. The method comprises: at a transmitting terminal, (1) loading an information sequence which is subjected to QPSK mapping and serial-to-parallel conversion onto an information subcarrier; and (2) establishing a pilot frequency sequence set by assembling Gold sequences, loading pilot frequency sequences in the set onto pilot frequency subcarriers respectively, then performing OFDM modulation, and selecting a transmitting signal with the smallest peak-average-ratio; and at the receiving terminal, through related operations, selecting a local pilot frequency sequence which has the highest relativity with a received pilot frequency sequence from the pilot frequency sequence set, then sequentially performing channel equalization, OFDM demodulation and QPSK demapping, and finally recovering information. Through adoption of the method, not only is the peak-average-ratio reduced, but also sideband information is eliminated, so that the accuracy of decoding is ensured.

Description

technical field [0001] The invention belongs to the technical field of underwater acoustic communication, in particular to a method for selecting the best pilot sequence to suppress the peak-to-average ratio of underwater acoustic OFDM signals. Background technique [0002] With the development of marine science and marine development, the research of underwater acoustic communication technology has been paid more and more attention, among which underwater acoustic OFDM communication technology has become a research hotspot. [0003] High-speed underwater acoustic communication is one of the important development directions of underwater acoustic communication. An important factor restricting the speed of underwater acoustic communication is the limitation of underwater acoustic channel bandwidth. The OFDM communication system modulates information on mutually orthogonal subcarriers in the time domain. Due to the orthogonality, although these subcarriers overlap each other i...

AI Technical Summary

Problems solved by technology

[0004] However, OFDM communication technology also has its own technical defects. The traditional OFDM technology has the defect that the ratio of peak power to average power (peak-to-average ratio) is relatively large.

This leads to high linearity requirements for the power amplifier at the transmitter end in the actual system implementation process

If the dynamic range of the amplifier cannot satisfy the change of the signal, it will cause distortion to the signal and change the spectrum of the superimposed signal, thus destroying the orthogonality between the sub-carrier signals and causing mutual interference, which will deteriorate the system performance. deterioration

[0005] There are many ways to reduce the peak-to-average ratio of OFDM signals: 1. Limiting technology, mainly including limiting method and companding method, this type of method can greatly reduce the peak-to-average ratio, but due to the nonlinearity of the original signal Transformation destroys the orthogonality between subcarriers, so it affects the correctness of decoding

2. Probabilistic technologies, mainly including Selective Mapping Method (SLM) and Partial Transmission Sequence Method (PTS). These methods have no effect on decoding accuracy, but will generate additional side information and reduce spectrum utilization.

3. Coding technology, mainly constructing complementary Golay sequence, Newman sequence, etc. This type of technology can greatly reduce the peak-to-average ratio, but at the cost of increasing coding redundancy and reducing spectrum utilization

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