Terahertz dynamic subarray hybrid beamforming method based on partial channel information

Abstract

A terahertz dynamic subarray hybrid beamforming method based on partial channel information, according to the starting angle and path loss amplitude of the propagation path between the transmitter and the receiver, a spectrum efficiency model including the switch state is constructed, the optimal switch state corresponding to the maximum value of the model is obtained by solving, and then the optimized digital beamforming matrix is ​​calculated, and finally the multi-select switch state is adjusted according to the optimal switch state matrix, and the digital signal processing weight is adjusted using the optimized digital beamforming matrix, so as to complete the beamforming process. The present invention utilizes the antenna phase orthogonality of the terahertz ultra-large-scale antenna array, and only requires a small number of channel parameters, namely the starting angle and path loss amplitude of the propagation path between the transmitter and the receiver, to achieve a spectrum efficiency similar to that of the existing method based on complete channel information, thereby greatly reducing the complexity of channel estimation and having similar spectrum efficiency.

Description

Technical Field

[0001] The invention relates to a technology in the field of communications, in particular to a terahertz dynamic subarray hybrid beamforming (RSD) method based on partial channel information. Background Art

[0002] Due to the huge number of antennas, high hardware complexity and power consumption in the existing terahertz ultra-large-scale multi-input and output systems, the existing pure digital beamforming architecture is no longer applicable. The hybrid beamforming architecture can achieve similar spectral efficiency as the pure digital beamforming architecture with lower hardware complexity. The existing hybrid beamforming architecture can be divided into fully connected architecture, subarray architecture, and dynamic subarray architecture according to the connection mode. Fully connected and subarray architectures are two widely studied hybrid beamforming architectures.

[0003] In a fully connected architecture, each RF link connects all antennas, so it has high spectral efficiency while consuming high power. Figure 1 As shown in (a), in the subarray architecture, each RF link only connects one subarray, so the power consumption is greatly reduced. However, at the same time, the spectrum efficiency of the subarray architecture is also low. Therefore, the energy efficiency (defined as the ratio of spectrum efficiency to power consumption) of both architectures is low. In order to improve energy efficiency, the existing improved dynamic subarray architecture is as follows: Figure 1 As shown in (b), due to the low power consumption of fixed phase shifters and switching devices, the dynamic subarray architecture has low power consumption and high spectral efficiency, thus achieving high energy efficiency. Summary of the invention

[0004] In view of the deficiency that the existing hybrid beamforming methods in the terahertz dynamic subarray architecture require complete channel information to perform beamforming, the present invention proposes a terahertz dynamic subarray hybrid beamforming method based on partial channel information. By utilizing the antenna phase orthogonality of the terahertz ultra-large-scale antenna array, only a small number of channel parameters, namely the starting angle and path loss amplitude of the propagation path between the transmitter and the receiver, are required to achieve a spectrum efficiency similar to that of the existing methods based on complete channel information, thereby greatly reducing the complexity of channel estimation and achieving similar spectrum efficiency.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a terahertz dynamic subarray hybrid beamforming method based on partial channel information. According to the starting angle and path loss amplitude of the propagation path between a transmitter and a receiver, a spectrum efficiency model including a switch state is constructed. The optimal switch state corresponding to the maximum value of the model is obtained by solving, and then an optimized digital beamforming matrix is ​​calculated. Finally, the multi-select switch state is adjusted according to the optimal switch state matrix, and the digital signal processing weight is adjusted using the optimized digital beamforming matrix, thereby completing the beamforming process.

[0007] The starting angle and path loss amplitude of the propagation path include: the transmitting array response matrix A t And the path loss amplitude diagonal matrix Λ, specifically: N t ×L-dimensional complex matrix A t , from the 1st column to the Lth column, they are the transmitting array response vectors corresponding to the departure angles of the 1st to the Lth paths, N t is the number of antennas at the transmitter end, L is the number of terahertz wave paths from the transmitter to the receiver; the L×L dimensional diagonal matrix Λ, whose diagonal elements are the amplitudes of the path losses from the 1st to the Lth paths respectively.

[0008] The switch state is: all N t The state matrix of the switches of the terahertz dynamic sub-array architecture antenna, S i With S 1：i-1 Represents the i-th row and the first i-1 rows of the matrix S, respectively, and the vector S i Only one element is 1, and the others are 0. The value 0 and 1 of each element represent the open and closed states of the switch.

[0009] The spectrum efficiency model including the switch state refers to: Among them: A i =c 1：i-1 S 1：i-1 F, B i =C i S i F, C i With C 1：i-1 represent the i-th column and the first i-1 columns of the matrix c, respectively. The superscript H is the conjugate transpose of the matrix. L is the L×L dimensional identity matrix. F is L t Q×L t dimensional block diagonal matrix, divided into L t Each block consists of the same Q×1-dimensional complex vector, in which the amplitude of each element is 1 and the phase is 0, 2π / Q, ..., 2π(Q-1) / Q. When i=1, A1=0; Nr is the number of antennas at the receiver, is the communication noise power.

[0010] The optimal switch state, i.e., the switch matrix S, is obtained by: starting from i=1, respectively making S i Each element in is 1, and the other elements are 0. Calculate the spectrum efficiency model and take the S that maximizes the model. i As the result, let i=i+1 and calculate S by the above process. i , until i = N t , we can get the switch matrix S.

[0011] The optimized digital beamforming matrix is ​​obtained by: firstly calculating the matrix H e = The singular value decomposition of ACSF obtains the right singular value matrix V, and then the digital beamforming matrix D is set to the first N of the matrix V s Column, where N s is the number of transmitted data streams. The digital beamforming matrix D is normalized so that Equal to the transmitter transmission power.

[0012] Technical Effects

[0013] Compared with the prior art, the present invention only requires the departure angle and path loss amplitude information of the electromagnetic wave propagation path between the communication transmitter and the receiver, without the arrival angle and path loss phase information, which is 50% less than the complete channel information required by the prior art method, and can greatly reduce the difficulty of obtaining channel information. At the same time, the spectrum efficiency of the beamforming RSD method in the present invention is similar to that of the prior art method that requires complete channel information, which can reach 97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the prior art;

[0015] In the figure: (a) subarray architecture, (b) dynamic subarray architecture;

[0016] Figure 2 is a flow chart of the beamforming RSD method of the present invention;

[0017] Figure 3 to Figure 5 It is a schematic diagram of the effect of the embodiment;

[0018] Figure 3[1] is the algorithm disclosed in the literature L. Yan, C. Han, N. Yang, and J. Yuan, "Dynamic-subarray with quantized-and fixed-phase shifters for terahertz hybrid beamforming," in Proc. IEEE Globecom., Dec. 2020, pp. 1-6.; [2] is the algorithm disclosed in the literature F. Sohrabi and W. Yu, "Hybrid analog and digital beamforming for mwave OFDM large-scale antenna arrays," IEEE J. Sel. Areas Commun., vol. 35, no. 7, pp. 1432–1443, Jul. 2017.; [3] is the algorithm disclosed in the literature H. Li, M. Li, Q. Liu, and A. L.

[0019] Swindlehurst, “Dynamic hybrid beamforming with low-resolution PSs for wideband mmwave MIMO-OFDM systems,” IEEE J. Sel. Areas Commun., vol. 38, no. 9, pp. 2168–2181, Sep. 2020.; [4] The algorithm disclosed in the literature X. Gao, L. Dai, S. Han, C. - LI, and R. W. Heath, “Energy-efficient hybrid analog and digital precoding for mmwave MIMO systems with large antenna arrays,” IEEE J. Sel. Areas Commun., vol. 34, no. 4, pp. 998–1009, Apr. 2016. DETAILED DESCRIPTION

[0020] like Figure 1 (b) with Figure 2As shown, this embodiment involves a terahertz dynamic subarray hybrid beamforming system based on partial channel information, including: a plurality of parallel transmitting end RF chains, a plurality of fixed phase shifter units arranged at the output end of each RF chain, a multi-selection switch connected to the output end of the fixed phase shifter unit, and a plurality of amplifiers and transmitting antennas connected to the multi-selection switch, wherein: the RF chain performs digital-to-analog conversion, up-conversion, amplification and filtering processing according to the signal after the communication baseband digital signal processing and outputs the high-frequency signal, the fixed phase shifter unit performs phase shift processing according to the input high-frequency signal and outputs the phase-shifted high-frequency signal, the multi-selection switch connects the corresponding fixed phase shifter unit and the amplifier unit according to the switch matrix S obtained by the RSD method, the amplifier performs signal amplification processing according to the antenna input information and outputs the power-amplified high-frequency signal to the transmitting antenna, and the digital signal processing part is set according to the digital beamforming matrix obtained by the RSD method.

[0021] like Figure 3 As shown, after MATLAB engineering simulation experiments, in the terahertz dynamic subarray architecture with a communication frequency of 0.3 THz, a communication distance of 40m, a bandwidth of 30GHz, and a transmission power of 20dBm, the experimental data that can be obtained are: Based on the partial channel information in the present invention, the RSD beamforming algorithm can achieve an energy efficiency of 0.47 bits / s / Hz / W and a spectrum efficiency of 23.2 bits / s / Hz. Compared with the prior art (L. Yan, C. Han, N. Yang, and J. Yuan, "Dynamic-subarray with quantized-and fixed-phase shifters for terahertz hybrid beamforming," in Proc. IEEE Globe com., Dec. 2020, pp. 1–6.), it is necessary to know all the channel information, that is, the amplitude diagonal matrix Λ of the path loss and the transmit array response matrix A t , the path loss phase diagonal matrix ψ, the receiving array response matrix A r Compared with the method, the RSD method only requires 50% of the channel information, namely, matrix Λ, matrix A t , and can achieve 97% energy efficiency and spectrum efficiency. Since only 50% channel information is required, the RSD method can greatly reduce the complexity of the system's channel estimation. Compared with other architectures in the existing literature, such as FC, DC, and AoSA architectures, the terahertz dynamic subarray architecture using the RSD method can achieve more than 1.67 times the energy efficiency.

[0022] like Figure 4 and Figure 5As shown, under the conditions of 0.3THz communication frequency and 30GHz bandwidth, by changing the transmission power and communication distance, the RSD method of the present invention can achieve a spectrum efficiency similar to that of the prior art, and only requires 50% of the channel information, which can greatly reduce the channel estimation complexity of the system.

[0023] Compared with the prior art, this method can reduce the complexity of channel estimation and achieve 97% of the spectrum efficiency of existing methods based on complete channel information. Under the conditions of 0.3THz communication frequency, 40m communication distance, and 30GHz bandwidth, the terahertz dynamic subarray hybrid beamforming method based on partial channel information can achieve a spectrum efficiency of 23.2bits / s / Hz. Compared with the existing terahertz dynamic subarray hybrid beamforming method based on complete channel information, under different transmission power and communication distance, the method proposed in the present invention can achieve 97% spectrum efficiency and greatly reduce the complexity of channel estimation.

[0024] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A terahertz dynamic subarray hybrid beamforming method based on partial channel information, characterized in that: According to the starting angle and path loss amplitude of the propagation path between the transmitter and the receiver, a spectrum efficiency model including the switch state is constructed. The optimal switch state corresponding to the maximum value of the model is obtained by solving it, and then the optimized digital beamforming matrix is ​​calculated. Finally, the multi-select switch state is adjusted according to the optimal switch state matrix, and the digital signal processing weight is adjusted using the optimized digital beamforming matrix, thereby completing the beamforming process. The starting angle and path loss amplitude of the propagation path include: the transmitting array response matrix A t And the path loss amplitude diagonal matrix Λ, specifically: N t ×L-dimensional complex matrix A t , from the 1st column to the Lth column, they are the transmitting array response vectors corresponding to the departure angles of the 1st to the Lth paths, N t is the number of antennas at the transmitter end, L is the number of terahertz wave paths from the transmitter to the receiver; L×L-dimensional diagonal matrix Λ, whose diagonal elements are the amplitudes of the path losses from the 1st to the Lth paths respectively; The switch state is: all N t The state matrix of the switches of the terahertz dynamic sub-array architecture antenna, S i With S 1:i-1 Represents the i-th row and the first i-1 rows of the matrix S, respectively, and the vector S i Only one element is 1, and the others are all 0. The value 0 and 1 of each element represent the open and closed states of the switch. The spectrum efficiency model including the switch state refers to: Among them: A i =C 1:i-1 S 1:i-1 F, B i =C i S i F, C i With C 1：i-1 represent the i-th column and the first i-1 columns of the matrix C respectively, The superscript H is the conjugate transpose of the matrix, I L is the L×L dimensional identity matrix, F is L t Q×L t dimensional block diagonal matrix, divided into L t blocks, each block consists of the same Q×1-dimensional complex vector, the amplitude of each element in the vector is 1, and the phase is 0, 2π / Q, ..., 2π(Q-1) / Q, when i=1, A1=0; N r is the number of antennas at the receiver end, is the communication noise power; The optimal switch state, i.e., the switch matrix S, is obtained by: starting from i=1, respectively making S i Each element in is 1, and the other elements are 0. Calculate the spectrum efficiency model and take the S that maximizes the model. i As the result, let i=i+1 and calculate S by the above process. i , until i = N t , we can get the switch matrix S; The optimized digital beamforming matrix is ​​obtained by: firstly calculating the matrix H e = ΛCSF, and then let the digital beamforming matrix D be the first N of the matrix V. s The digital beamforming matrix D is normalized so that Equal to the transmitter transmission power.

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