CN-122027407-A - OAM-OFDM multiplexing communication method based on MIMO equalization technology

CN122027407ACN 122027407 ACN122027407 ACN 122027407ACN-122027407-A

Abstract

The invention discloses an OAM-OFDM multiplexing communication method based on MIMO equalization technology, which comprises dividing data signals into multiple paths at a transmitting end, carrying out OFDM modulation and OAM mode multiplexing respectively, transmitting the data signals to a receiving end through an underwater sound channel, carrying out OFDM demodulation on the received signals by the receiving end under the condition that OAM demultiplexing is not needed, completing frequency domain channel estimation and interpolation based on pilot frequency subcarriers to construct an equivalent MIMO channel estimation matrix, carrying out linear equalization processing on the multiple paths of signals aiming at each OFDM subcarrier, and carrying out serial-parallel conversion and symbol demodulation on the equalized data to obtain a decoding result. The invention effectively eliminates the inter-mode crosstalk of OAM multiplexing caused by the multipath effect of the underwater acoustic channel, improves the communication rate and the bit error rate performance, avoids large-scale matrix inversion operation and reduces the calculation complexity.

Inventors

QU FENGZHONG
Qiao Yueyi
LI ZHIPENG
WEI YIRAN
HAN HAIBIN
BAI HUAJUN
WEI YAN
TU XINGBIN

Assignees

浙江大学

Dates

Publication Date: 20260512
Application Date: 20260410

Claims (10)

1. An OAM-OFDM multiplexing communication method based on MIMO equalization technology is characterized by comprising the following steps: The method comprises the steps that S1, a transmitting end sets data subcarriers, pilot subcarriers and null subcarriers according to a preset pilot configuration scheme, maps data signals to be transmitted to digital modulation symbols, and loads the digital modulation symbols to corresponding data subcarriers to form a transmitting symbol sequence; S2, carrying out OFDM modulation on the sending symbol sequence, and adding a cyclic prefix to obtain an OFDM signal; S3, OAM mode multiplexing is carried out on the OFDM signals to generate transmission signals, and the transmission signals are transmitted through a transmission transducer and transmitted to a receiving end through an underwater sound channel; s4, after the receiving end obtains the received signal, OFDM demodulation is carried out on the received signal under the condition of not carrying out OAM demultiplexing to obtain frequency domain data of each subcarrier; S5, extracting the corresponding equivalent MIMO channel estimation matrix for each OFDM subcarrier, and carrying out equalization processing on multipath signals under the subcarrier by utilizing linear equalization; s6, carrying out serial-parallel conversion recombination on the data after the equalization processing, and then carrying out symbol demodulation to obtain a final decoding result.
2. The OAM-OFDM multiplexing communication method as recited in claim 1, wherein S1 includes the sub-steps of: S1.1, dividing data to be transmitted into m paths of data streams by a transmitting end according to the dimension of OAM multiplexing, and respectively carrying out digital symbol modulation on each path of data; and S1.2, the transmitting end sets a data subcarrier, a pilot frequency subcarrier and a null subcarrier according to a preset pilot frequency configuration scheme, and loads the digital modulation symbol obtained in the S1.1 to the corresponding data subcarrier to form a transmitting symbol sequence.
3. The OAM-OFDM multiplexed communication method as recited in claim 2, wherein the digital symbol modulation uses any one of BPSK, QPSK, 8QAM, and 16QAM modulation methods.
4. The OAM-OFDM multiplexing communication method as recited in claim 1, wherein S4 includes the sub-steps of: S4.1, under the condition of full rank of an equivalent MIMO channel, OFDM demodulation is carried out on a received signal acquired by a receiving end under the condition of not carrying out OAM demultiplexing, and frequency domain received data corresponding to each subcarrier is obtained; s4.2, according to a pilot frequency configuration scheme preset by a transmitting end, performing frequency domain MIMO channel estimation on each pilot frequency subcarrier to obtain initial channel response from each path of transmitting signal to each path of receiving signal, and then adopting an interpolation method on subcarriers among pilots to obtain channel response of all data subcarriers, thereby constructing an MIMO channel estimation matrix corresponding to each subcarrier.
5. The OAM-OFDM multiplexing communication method based on the MIMO equalization technique according to claim 4, wherein the interpolation method is any one of polynomial interpolation and FFT interpolation.
6. The OAM-OFDM multiplexed communication method as recited in claim 1, wherein the linear equalization method uses any one of zero forcing equalization and minimum mean square error.
7. The OAM-OFDM multiplexing communication method as recited in claim 1, wherein S6 includes the sub-steps of: S6.1, splicing m symbols on each equalized subcarrier into m paths of symbols according to subcarrier sequence, then carrying out serial-parallel conversion recombination, and merging into 1 paths of symbols; And S6.2, performing symbol demodulation by adopting a symbol demodulation method corresponding to the symbol modulation mode in the S1, and restoring the received symbols into a bit data stream to obtain a final decoding result.
8. An OAM-OFDM multiplexing communication system based on MIMO equalization technology is characterized in that the system comprises a symbol modulation module, an OAM multiplexing module, a channel estimation module, an equalization module and a symbol demodulation module, wherein: the system comprises a symbol modulation module, a transmission symbol sequence, a cyclic prefix generation module, a transmission symbol sequence and a transmission symbol sequence, wherein the symbol modulation module is used for setting a data subcarrier, a pilot subcarrier and a null subcarrier according to a preset pilot frequency configuration scheme, mapping a data signal to be transmitted into a digital modulation symbol and loading the digital modulation symbol onto a corresponding data subcarrier to form the transmission symbol sequence; The OAM multiplexing module is used for carrying out OAM mode multiplexing on the OFDM signals to generate transmission signals; the channel estimation module is used for carrying out OFDM demodulation on the received signals acquired by the receiving end under the condition of not carrying out OAM demultiplexing to obtain frequency domain received data corresponding to each subcarrier; performing frequency domain MIMO channel estimation on each pilot frequency subcarrier according to a pilot frequency configuration scheme preset by a transmitting end to obtain initial channel response from each path of transmitting signals to each path of receiving signals; The equalization module is used for extracting the MIMO channel estimation matrix corresponding to each OFDM subcarrier and performing equalization processing on the multipath signals under the subcarrier by utilizing linear equalization; and the symbol demodulation module is used for carrying out serial-parallel conversion recombination on the data after the equalization processing, and then carrying out symbol demodulation to obtain a final decoding result.
9. An electronic device, comprising: one or more processors; storage means for storing one or more programs that, when executed by the electronic device, cause the electronic device to implement the OAM-OFDM multiplexing communication method based on the MIMO equalization technique of any one of claims 1 to 7.
10. A computer-readable storage medium, having stored thereon a program which, when executed by a processor, implements the MIMO equalization technique-based OAM-OFDM multiplexing communication method as recited in any one of claims 1 to 7.

Description

OAM-OFDM multiplexing communication method based on MIMO equalization technology Technical Field The invention relates to the field of underwater acoustic communication, in particular to an OAM-OFDM multiplexing communication method based on MIMO equalization technology. Background The underwater acoustic communication channel has limited frequency spectrum resources, and the traditional low-rate underwater acoustic communication mode has difficulty in meeting the current requirements on underwater communication speed and bandwidth. With the increasing demand for efficient underwater acoustic communication technology, high-speed underwater acoustic communication based on multiplexing communication technology such as orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) is an important research direction in the field of underwater communication. The OFDM technology improves the spectral efficiency of a channel by transmitting data on a plurality of subcarriers, and has become an effective means to alleviate the problem of bandwidth limitation of an underwater acoustic channel. On this basis, orbital angular momentum (Orbital Angular Momentum, OAM) technology is an emerging multiplexing technology due to its unique helical wavefront and phase structure. The modes of the OAM acoustic beam have orthogonality, so that simultaneous transmission of multiple paths of data streams can be realized by using different OAM modes as new communication dimensions, and the transmission rate and capacity of a communication system are effectively improved. By combining OAM multiplexing with an OFDM modulation technology, the spectrum utilization efficiency of underwater acoustic communication can be improved to a greater extent, so that the information transmission rate is improved. However, in a practical underwater acoustic communication environment, multipath effects are a common problem. As the signal propagates in water along a plurality of different paths, the propagation time of each path is different, thereby forming a plurality of signal components of different delays. Superposition of these signal components can cause distortion of the OAM phase distribution, which in turn leads to energy crosstalk between different OAM modes. For such crosstalk, the conventional signal processing method generally cannot effectively separate each OAM mode in the demultiplexing process, so that the receiving end cannot accurately recover the data stream of each channel, which results in information loss or interference. Disclosure of Invention Aiming at the defects existing in the prior art, the invention introduces a Multiple-Input Multiple-Output (MIMO) equalization technology, and provides an OAM-OFDM multiplexing communication method based on the MIMO equalization technology, which can effectively compensate crosstalk between OAM modes by directly carrying out equalization processing on received and transmitted data streams without carrying out OAM demultiplexing, and remarkably enhances the multipath interference resistance of an OAM-OFDM multiplexing communication system, thereby improving the overall information transmission rate, the communication quality and the reliability of the system. The aim of the invention is achieved by the following technical scheme: An OAM-OFDM multiplexing communication method based on MIMO equalization technology comprises the following steps: The method comprises the steps that S1, a transmitting end sets data subcarriers, pilot subcarriers and null subcarriers according to a preset pilot configuration scheme, maps data signals to be transmitted to digital modulation symbols, and loads the digital modulation symbols to corresponding data subcarriers to form a transmitting symbol sequence; S2, carrying out OFDM modulation on the sending symbol sequence, and adding a cyclic prefix to obtain an OFDM signal; s3, OAM mode multiplexing is carried out on the OFDM signals to generate transmission signals, and the transmission signals are transmitted through a transmission transducer and transmitted to a receiving end through an underwater sound channel; s4, after the receiving end obtains the received signal, OFDM demodulation is carried out on the received signal under the condition of not carrying out OAM demultiplexing to obtain frequency domain data of each subcarrier; S5, extracting the corresponding equivalent MIMO channel estimation matrix for each OFDM subcarrier, and carrying out equalization processing on multipath signals under the subcarrier by utilizing linear equalization; s6, carrying out serial-parallel conversion recombination on the data after the equalization processing, and then carrying out symbol demodulation to obtain a final decoding result. Further, S1 comprises the following sub-steps: S1.1, dividing data to be transmitted into m paths of data streams by a transmitting end according to the dimension of OAM multiplexing, and respectively c