CHIRP-OFDM system frequency domain diversity receiving method

Abstract

The invention discloses a CHIRP-OFDM (orthogonal frequency division multiplexing) system frequency domain diversity receiving method which comprises the following steps; at an emitting end, modulating data after serial-parallel conversion to a frequency spectrum, carrying out inverse discrete Fourier transform so as to obtain a group of time domain signals, carrying out spread spectrum modulation on the time domain signals by taking chirp signals as carrier waves, and determining a frequency modulation slope; at a receiving end, removing cyclic prefixes of received serial signals, carrying out despread modulation on the signals, and conjugating the frequency modulation slope and the emitting end in a same way of taking determined chirp signals as carrier waves; carrying out the inverse discrete Fourier transform to obtain a frequency domain frequency spectrum, carrying out phase compensation on each spectrum line of multi-path signals, and overlying with each direct signal spectrum line, so as to enable all spectrum lines to be added in a same-phase way, and realize diversity reception and further recover signal sending; and carrying out digital demodulation so as to obtain data output. The method can effectively overcome frequency selective fading in channels and improves the system performance.

Description

technical field [0001] The invention relates to a communication technology in the fields of underwater acoustic communication, signal detection and the like. Background technique [0002] The multi-path effect in the underwater acoustic channel makes the channel transfer function have the form of a comb filter, that is, there are fading and enhancement intervals of the frequency point. When the signal frequency component is in the fading interval of the frequency point, the signal energy is weakened or even Disappearance seriously affects the transmission of information, especially for single-frequency signals such as sinusoidal signals. If broadband signals are used, even if the energy of some frequency components is affected, the overall normal transmission of the signal can still be guaranteed. [0003] The traditional OFDM system uses a sinusoidal signal as a carrier, and modulates effective information onto mutually orthogonal sinusoidal signals by mapping methods such ...

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Problems solved by technology

[0004] However, most underwater acoustic channels are frequency-selective fading channels. When the sub-channel is in deep fading, this method of channel equalization will also fail to work, and the performance of the system will be severely inhibited.

[0005] Spread spectrum communication can resist channel fading and multipath interference, and has the advantages of long transmission distance, high reliability and low interception, but the transmission data rate is not high

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