Terahertz beamforming structure and method based on dynamic grouping subarray and true time delay

Abstract

The application discloses a terahertz beam forming structure and method based on dynamic grouping subarray and true time delay, relates to the field of high-frequency wireless broadband communication, and aims to solve the problem that the prior art cannot reduce system power consumption while ensuring high frequency spectrum efficiency by reducing the use of true time delay and phase shifters; the application comprises a terahertz beam forming structure and a terahertz beam forming method for solving structure parameters; the terahertz beam forming structure comprises an antenna divided into subarrays and radio frequency links connected with the subarrays; the radio frequency links and the subarrays are grouped; within the group, the radio frequency links and the subarrays are fully connected through true time delay and phase shifters; the application uses a dynamic grouping subarray structure to reduce the use of high-energy-consuming true time delay units, reduces system power consumption, maintains high frequency spectrum efficiency, and introduces a dynamic switch to realize real-time power consumption adjustment and meet the requirements of different communication scenarios.

Description

Technical Field

[0001] This invention relates to the field of high-frequency wireless broadband communication, specifically to a terahertz beamforming structure and method based on dynamic grouped subarrays and true time delay. Background Technology

[0002] The ultra-wide bandwidth of the terahertz band enables it to meet the ever-increasing demands for data transmission rates, and terahertz beamforming technology is one of the key technologies for sixth-generation mobile communication. However, when performing beamforming in the terahertz band, the combination of its large bandwidth and ultra-large-scale MIMO can lead to severe beam squint. Beam squint causes a significant decrease in the spectral efficiency of the wireless communication system.

[0003] Current methods for addressing beam squint involve replacing phase shifters with true time delay (TTD) in the analog radio frequency domain. However, TTD is a high-power analog component, and its widespread replacement of phase shifters significantly increases system power consumption, a critical limitation of current wireless communication systems. To reduce the use of TTD, one approach is to use TTD and phase shifters in tandem for beamforming; another is to use fixed true time delay (FTTD) instead of phase shifters to mitigate beam squint.

[0004] The antenna array is divided into multiple subarrays using a combination of true delay and phase shifters. Each RF link connects all subarrays via true delay and phase shifters. The analog signal in the RF link first passes through a power divider, splitting it into multiple paths. Taking one path as an example, the signal first passes through a true delay unit, then is further split into multiple paths by the power divider to correspond to the number of antennas in the subarray. The split signals then pass through phase shifters and are finally transmitted through the antennas. This structure and method can reduce the number of true delay units while maintaining high spectral efficiency. However, its effect on reducing the number of true delay units is limited, and it still results in significant system power consumption.

[0005] Another approach using fixed true delay (PDD) instead of phase shifters involves connecting multiple PDDs to each RF link, and then deploying a dynamic switching matrix between the PDDs and the antenna to perform beamforming in specific scenarios. The power consumption of PDDs is significantly lower than that of true delays, thus achieving high energy efficiency. However, since PDDs can only align the beam at a specific angle, the spectral efficiency of the system drops sharply when the beam angle changes. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention proposes to provide a terahertz beamforming structure and method based on dynamic grouped subarrays and true time delay, aiming to solve the problem that the prior art cannot reduce system power consumption while ensuring high spectral efficiency by reducing the use of true time delay and phase shifters.

[0007] The terahertz beamforming structure based on dynamic grouped subarrays and true time delay includes antennas divided into subarrays and radio frequency links connected to the subarrays. The radio frequency links and subarrays are grouped, and within each group, the radio frequency links and each subarray are fully connected through true time delay and phase shifters.

[0008] The terahertz beamforming method based on dynamic grouped subarrays and true time delay includes the following steps:

[0009] S1: Model the optimization problem based on the terahertz beamforming structure, including the phase shifter matrix, the switching matrix, and the true time delay matrix;

[0010] S2: Calculate the true delay and phase based on the channel state information and the principle of maximizing array gain, combined with the phase shifter matrix and the true delay matrix;

[0011] S3: Based on the principle that the array gain is independent of the position of the switches but proportional to the number of closed switches, the switch parameters are determined in conjunction with the switch matrix.

[0012] S4: Calculate the final analog domain precoding matrix and digital domain precoding matrix based on the calculated true delay, phase, and switching parameters.

[0013] Preferably, the optimization problem modeling based on the terahertz beamforming structure in S1 includes: assuming the number of transmitting antennas is... The number of receiving antennas is The spacing between the antennas is The number of RF links is The number of carriers is The system bandwidth is The center frequency is Assuming there are sender and receiver ends. The path has a sending angle and an arrival angle of 1 / 2. and The equivalent send angle and arrival angle are defined as follows: and Considering the beam squint effect, the corresponding array vector at the transmitting end can be expressed as:

[0014]

[0015] in, ;

[0016] The channel matrix between the transmitter and receiver can be represented as:

[0017]

[0018] in,

[0019]

[0020] This reflects the characteristics of terahertz channels, including free space loss, reflection loss, and molecular absorption loss. and These are the median absorption coefficient and the transmission distance, respectively; the signal received at the receiver can be modeled as:

[0021]

[0022] in It is the equivalent analog domain precoding matrix, which is the phase shifter matrix. True delay matrix and switch matrix The Hadama product; It transmits signals. It's noise; This is the precoding matrix for the digital field.

[0023] Preferably, the phase shifter matrix, switching matrix, and true delay matrix are represented as follows:

[0024] Based on the proposed structure, the phase shifter matrix is ​​a block diagonal matrix, which can be represented as:

[0025]

[0026] in yes dimension, It refers to the number of subarray antennas. It is the true delay of the RF link connection. This represents the number of RF links within the group; the block matrix on the diagonal can be further expressed as:

[0027]

[0028] in, yes dimensional vector;

[0029] Similarly, the switching matrix and the true delay matrix can be expressed as follows:

[0030]

[0031] and

[0032]

[0033] Further

[0034]

[0035] and

[0036]

[0037] in, and , This corresponds to the value of the true delay unit.

[0038] Preferably, the system spectral efficiency is set to:

[0039]

[0040] in, Noise power;

[0041] Based on the aforementioned calculations, the optimization problem can ultimately be modeled as follows:

[0042]

[0043] in, For system power consumption, This represents the upper limit of power consumption in a specific communication scenario. This refers to the transmission power.

[0044] Preferably, S2 includes:

[0045] The steering vector at the sending end is represented as:

[0046]

[0047] Assuming the phase shifter is guided in a specific direction Then an auxiliary phase shift vector is introduced. This achieves better performance, and the phase shifter vector can then be expressed as...

[0048]

[0049] For simplicity, the corresponding vector of the transmitter array, i.e., formula (1), is written in the form of a subarray.

[0050]

[0051] in, The number of subarrays;

[0052]

[0053] The system array gain can be expressed as,

[0054]

[0055] Substitute (13) and (15) into (17).

[0056]

[0057] Based on the properties of the Dirichlet function, an optimal solution to the above equation can be expressed as:

[0058]

[0059] in For true delay, and These are the phase shifter parameters; from this, the true time delay matrix and the phase shifter matrix are obtained.

[0060] Preferably, step S3 includes: determining the switch matrix in the following manner:

[0061] a) Randomly select from different RF links One switch;

[0062] b) Disconnect these switches individually and calculate the spectral efficiency;

[0063] c) Select the switch that has the least impact on spectral efficiency to turn off;

[0064] d) Repeat step ac until the power constraint is met;

[0065] By using step ad, the switch with the least impact on spectral efficiency was selected as the switch parameter.

[0066] Preferably, S4 includes: based on the calculated true time delay, phase, and switching parameters, according to formulas (5), (7), and (10) and The final analog domain precoding matrix and digital domain precoding matrix are obtained.

[0067] The beneficial effects of this invention include:

[0068] This invention proposes a terahertz beamforming structure based on dynamic grouped subarrays and true time delay. This structure greatly reduces the use of true time delay and phase shifters, reducing system power consumption while ensuring high spectral efficiency. In addition, to further reduce power consumption and meet the power consumption requirements of different communication scenarios, a dynamic switching matrix is ​​introduced to achieve real-time power consumption adjustment to meet the needs of different communication scenarios.

[0069] Meanwhile, this invention designs a terahertz beamforming method based on dynamic grouped subarrays and true time delay to calculate various parameters of the proposed structure, including digital domain precoding matrix, switching matrix, phase shifter matrix and true time delay matrix parameters. The computational complexity of solving the parameters is low. According to the characteristics of the proposed structure, the algorithm maximizes the system spectral efficiency while maintaining high energy efficiency under the constraint of power consumption limit. Attached Figure Description

[0070] Figure 1 This is a diagram of the terahertz beamforming structure based on dynamic grouping subarrays and true time delay involved in Embodiment 1 of the present invention.

[0071] Figure 2 This is a comparison chart of the spectral efficiency of the present invention and other methods involved in Example 1.

[0072] Figure 3 This is a comparison chart of the energy efficiency of the present invention and other methods involved in Example 1.

[0073] Figure 4 This is a comparative graph of the spectral efficiency and energy efficiency of the present invention as described in Example 1. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0075] Example 1

[0076] The following is in conjunction with the appendix Figure 1-4 Specific embodiments of the present invention will be described in detail;

[0077] Terahertz beamforming structures based on dynamic grouped subarrays and true time delay, such as Figure 1As shown, the system includes antennas divided into subarrays and radio frequency (RF) links connected to the subarrays. The RF links and subarrays are grouped, and within each group, the RF links and each subarray are fully connected via true delay and phase shifters. This structure significantly reduces the use of true delay and phase shifters, lowering system power consumption while maintaining high spectral efficiency. Furthermore, to further reduce power consumption and meet the power consumption requirements of different communication scenarios, a dynamic switching network is introduced between the RF links and subarrays. By setting different system power consumption thresholds, the corresponding number of closed switches is determined, enabling customized requirements for different scenarios.

[0078] The terahertz beamforming method based on dynamic grouped subarrays and true time delay includes the following steps:

[0079] S1: Modeling an optimization problem based on the terahertz beamforming structure, including the phase shifter matrix, switching matrix, and true time delay matrix, specifically:

[0080] The optimization problem modeling in S1 based on the terahertz beamforming structure includes: assuming the number of transmitting antennas is... The number of receiving antennas is The spacing between the antennas is The number of RF links is The number of carriers is The system bandwidth is The center frequency is Assuming there are sender and receiver ends. The path has a sending angle and an arrival angle of 1 / 2. and The equivalent send angle and arrival angle are defined as follows: and Considering the beam squint effect, the corresponding array vector at the transmitting end can be expressed as:

[0081]

[0082] in, ;

[0083] The channel matrix between the transmitter and receiver can be represented as:

[0084]

[0085] in,

[0086]

[0087] This reflects the characteristics of terahertz channels, including free space loss, reflection loss, and molecular absorption loss. and These are the median absorption coefficient and the transmission distance, respectively; the signal received at the receiver can be modeled as:

[0088]

[0089] in It is the equivalent analog domain precoding matrix, which is the phase shifter matrix. True delay matrix and switch matrix The Hadama product; It transmits signals. It's noise; This is the precoding matrix for the digital field.

[0090] The phase shifter matrix, switching matrix, and true delay matrix are represented as follows:

[0091] Based on the proposed structure, the phase shifter matrix is ​​a block diagonal matrix, which can be represented as:

[0092]

[0093] in yes dimension, It refers to the number of subarray antennas. It is the true delay of the RF link connection. This represents the number of RF links within the group; the block matrix on the diagonal can be further expressed as:

[0094]

[0095] in, yes dimensional vector;

[0096] Similarly, the switching matrix and the true delay matrix can be expressed as follows:

[0097]

[0098] and

[0099]

[0100] Further

[0101]

[0102] and

[0103]

[0104] in, and , This corresponds to the value of the true delay unit.

[0105] Set the system spectral efficiency to:

[0106]

[0107] in, Noise power;

[0108] Based on the aforementioned calculations, the optimization problem can ultimately be modeled as follows:

[0109]

[0110] in, For system power consumption, This represents the upper limit of power consumption in a specific communication scenario. Let be the transmit power; the goal of the solution is to maximize the spectral efficiency of the system under the condition of satisfying a specific power constraint; in order to solve the non-convex optimization problem (12), it is divided into two sub-problems, and the following two steps are designed to solve the sub-problems.

[0111] S2: Based on channel state information and the principle of maximizing array gain, combined with the phase shifter matrix and the true delay matrix, calculate the true delay and phase. Specifically:

[0112] The steering vector at the sending end is represented as:

[0113]

[0114] Assuming the phase shifter is guided in a specific direction Then an auxiliary phase shift vector is introduced. This achieves better performance, and the phase shifter vector can then be expressed as...

[0115]

[0116] For simplicity, the corresponding vector of the transmitter array, i.e., formula (1), is written in the form of a subarray.

[0117]

[0118] in, The number of subarrays;

[0119]

[0120] The system array gain can be expressed as,

[0121]

[0122] Substitute (13) and (15) into (17).

[0123]

[0124] Based on the properties of the Dirichlet function, an optimal solution to the above equation can be expressed as:

[0125]

[0126] in For true delay, and These are the phase shifter parameters; from this, the true time delay matrix and the phase shifter matrix are obtained.

[0127] S3: Based on the principle that the array gain is independent of the switch position but proportional to the number of closed switches, the switch parameters are determined using the switch matrix. Specifically, the switch matrix is ​​determined as follows:

[0128] a) Randomly select from different RF links One switch;

[0129] b) Disconnect these switches individually and calculate the spectral efficiency;

[0130] c) Select the switch that has the least impact on spectral efficiency to turn off;

[0131] d) Repeat step ac until the power constraint is met;

[0132] Through step ad, we selected those switches that had the least impact on spectral efficiency; disconnecting these switches can further reduce power consumption and improve energy efficiency; since these switches have little impact on spectral efficiency, disconnecting them results in limited performance degradation.

[0133] S4: Based on the calculated true time delay, phase, and switching parameters, according to formulas (5), (7), and (10) and The final analog domain precoding matrix and digital domain precoding matrix are obtained.

[0134] To verify the effectiveness of the proposed method, this embodiment will compare it with several other methods; Optimal-FullDigital represents the performance upper bound, TDD-aided and DPP are the previously mentioned methods of true delay and phase shift coordination, DS-FTTD is the fixed true delay method, FC-WBF is the width beamforming method, and FC-OMP is the orthogonal matched pursuit beamforming method; Proposed 1 and Proposed 2 are the structures and methods proposed in this invention; the difference is that Proposed 1 uses the switch selection algorithm in step 3, while Proposed 2 defaults to all switches being closed; the comparison between the two can demonstrate the effectiveness of step 3 in improving energy efficiency; specifically, such as Figure 2-4 As shown, where:

[0135] Figure 2 This is a comparison chart of the spectral efficiency of the present invention and other methods; the horizontal axis represents the received signal-to-noise ratio (SNR), and the vertical axis represents the spectral efficiency. The spectral efficiency curves of the proposed structure, Proposed 1 and Proposed 2, show better performance compared to other methods.

[0136] Figure 3 This is a comparison graph of the energy efficiency of the present invention and other methods; the horizontal axis is the number of transmitting antennas, and the vertical axis is the energy efficiency; it can be seen that the curve Proposed 1 of the present invention achieves the best energy efficiency; this also verifies the effectiveness of step 3.

[0137] Figure 4 This is a comparative graph of the spectral efficiency and energy efficiency of the present invention; the horizontal axis represents spectral efficiency and the vertical axis represents energy efficiency. As can be seen from the graph, the method proposed in this invention is located in the upper right corner of the graph, indicating that the present invention can take into account both energy efficiency and spectral efficiency, thereby achieving better performance.

[0138] Example 2

[0139] The difference between this embodiment and Embodiment 1 is that the terahertz beamforming method based on dynamic grouped subarrays and true time delay does not include the switch selection part in step 3.

[0140] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A terahertz beamforming method based on dynamic grouped subarrays and true time delay, characterized in that, Includes the following steps: S1: Model the optimization problem based on the terahertz beamforming structure, including the phase shifter matrix, the switching matrix, and the true time delay matrix; The optimization problem modeling in S1 based on the terahertz beamforming structure includes: assuming the number of transmitting antennas is... The number of receiving antennas is The spacing between the antennas is The number of RF links is The number of carriers is The system bandwidth is The center frequency is Assuming there are sender and receiver ends. The path has a sending angle and an arrival angle of 1 / 2. and The equivalent send angle and arrival angle are defined as follows: and Considering the beam squint effect, the corresponding array vector at the transmitting end can be expressed as: in, ; The channel matrix between the transmitter and receiver can be represented as: in, This reflects the characteristics of terahertz channels, including free space loss, reflection loss, and molecular absorption loss. and These are the median absorption coefficient and the transmission distance, respectively; the signal received at the receiver can be modeled as: in It is the equivalent analog domain precoding matrix, which is the phase shifter matrix. True delay matrix and switch matrix The Hadama product; It transmits signals. It's noise; For the digital field precoding matrix; The phase shifter matrix, switching matrix, and true delay matrix are represented as follows: Based on the proposed structure, the phase shifter matrix is ​​a block diagonal matrix, which can be represented as: in yes dimension, It refers to the number of sub-array antennas. It is the true delay of the RF link connection. This represents the number of RF links within the group; the block matrix on the diagonal can be further expressed as: in, yes dimensional vector; Similarly, the switching matrix and the true delay matrix can be expressed as follows: and Further and in, and , This corresponds to the value of the true delay unit; S2: Calculate the true delay and phase based on the channel state information and the principle of maximizing array gain, combined with the phase shifter matrix and the true delay matrix; S3: Based on the principle that the array gain is independent of the position of the switches but proportional to the number of closed switches, the switch parameters are determined in conjunction with the switch matrix. S4: Calculate the final analog domain precoding matrix and digital domain precoding matrix based on the calculated true delay, phase, and switching parameters.

2. The terahertz beamforming method based on dynamic grouped subarrays and true time delay according to claim 1, characterized in that, Set the system spectral efficiency to: in, Noise power; Based on the aforementioned calculations, the optimization problem can be modeled as follows: in, For system power consumption, This represents the upper limit of power consumption in a specific communication scenario. This refers to the transmission power.

3. The terahertz beamforming method based on dynamic grouped subarrays and true time delay according to claim 2, characterized in that, S2 includes: The steering vector at the sending end is represented as: Assuming the phase shifter is guided in a specific direction Then an auxiliary phase shift vector is introduced. This achieves better performance, and the phase shifter vector can then be expressed as... For simplicity, the corresponding vector of the transmitter array, i.e., formula (1), is written in the form of a subarray. in, The number of subarrays; The system array gain can be expressed as, Substitute (13) and (15) into (17). Based on the properties of the Dirichlet function, an optimal solution to the above equation can be expressed as: in For true delay, and These are the phase shifter parameters; from this, the true time delay matrix and the phase shifter matrix are obtained.

4. The terahertz beamforming method based on dynamic grouped subarrays and true time delay according to claim 3, characterized in that, S3 includes determining the switch matrix in the following manner: a) Randomly select from different RF links One switch; b) Disconnect these switches individually and calculate the spectral efficiency; c) Select the switch that has the least impact on spectral efficiency to disconnect; d) Repeat step ac until the power constraint is met; By using step ad, the switch with the least impact on spectral efficiency is selected as the switch parameter.

5. The terahertz beamforming method based on dynamic grouped subarrays and true time delay according to claim 4, characterized in that, The S4 includes: based on the calculated true time delay, phase, and switching parameters, according to formulas (5), (7), and (10) and The final analog domain precoding matrix and digital domain precoding matrix are obtained.

6. A terahertz beamforming structure based on dynamic grouped subarrays and true time delay, used to implement the method as described in any one of claims 1-5, characterized in that, It includes antennas divided into subarrays and radio frequency links connected to the subarrays. The radio frequency links and subarrays are grouped together. Within each group, the radio frequency links and each subarray are fully connected through true delay and phase shifters.

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