Low-cost super-large-scale MIMO communication system and method based on cylindrical direct-connection antenna array

Abstract

The invention discloses a low-cost super-large-scale MIMO (Multiple Input Multiple Output) communication system and method based on a cylindrical direct-connection antenna array. According to the system, low-cost antenna units (1) are uniformly and circularly arranged into a plurality of simple and uniform circular arrays (2), and then the simple and uniform circular arrays (2) are stacked along the side surface of a cylinder to form a cylindrical direct-connection antenna array. Each simple and uniform circular array is divided into two sub-arrays (3) with the same number of antennas, and the sub-array center antennas of different circular arrays point to different directions. The sub-arrays are connected to the radio frequency combiner (5) through the delay lines (4) with different lengths to form a path of signal output, and beams with matched orientations can be generated without analog or digital beam forming. Based on the selection matrix (6), the system can dynamically select the direct connection subarrays (3) and access a radio frequency link for baseband processing. According to the invention, the use of an expensive phase shifter is avoided, the implementation cost of ultra-large-scale MIMO is remarkably reduced, the spatial resolution and the communication performance are improved, and the problems of difficulty in implementation of dynamic beams and high cost in millimeter wave, terahertz and other high-frequency wireless communication systems are effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of 6G and future wireless communication systems and ultra-large-scale multiple-input multiple-output, multi-antenna technology, millimeter wave, terahertz, and specifically relates to a wireless communication system and method based on a cylindrical direct-connection antenna array without inter-array occlusion. BACKGROUND

[0002] Multiple-antenna or MIMO (multiple-input multiple-output) technology has always been the cornerstone of wireless communication evolution. From 4G (Fourth-Generation) to 5G (Fifth-Generation) mobile communication networks, multiple-antenna technology has developed from 8 antennas to 64 antennas, significantly improving spectral efficiency, reliability, and connection density. For the upcoming 6G (Sixth-Generation) mobile communication network, more ambitious goals need to be achieved, such as centimeter-level positioning accuracy, ultra-high connection density, and ultra-low latency on the order of 0.1-1 milliseconds. To achieve these goals, researchers are actively exploring various new multiple-antenna technologies, such as ultra-large-scale multiple-antenna technology, sparse multiple-antenna technology, and cell-free multiple-antenna technology.

[0003] In particular, for ultra-large-scale multiple-antenna technology, due to the extremely large number of antenna elements, ultra-large-scale multiple-antenna technology can achieve higher beamforming gain, better spectral efficiency, and more accurate sensing and positioning capabilities. With the growing trend of using higher frequency bands (such as millimeter waves and terahertz) to build 6G networks, the practical application of ultra-large-scale multiple-antenna technology faces many challenges, including high hardware costs due to expensive front-end RF (Radio Frequency) components, increasingly complex signal processing, and the difficulty of designing and manufacturing advanced components such as high-precision phase shifters. These factors collectively hinder the practical application of ultra-large-scale multiple-antenna technology. Therefore, it is crucial to develop innovative and cost-effective ultra-large-scale multiple-antenna array structures to reduce deployment difficulty.

[0004] Due to the high cost and high power consumption of RF links and front-end components, an effective strategy to implement the massive multi-antenna technology is to reduce the number of RF links or to use more efficient front-end components. For example, HBF (Hybrid Analog / Digital BeamForming), lens antenna array, movable antenna array or fluid antenna system, and reconfigurable three hybrid multi-antenna array have been intensively studied. However, for HBF and reconfigurable three hybrid multi-antenna technology, the number of phase shifters required will increase with the number of antennas, which is still a huge hardware cost and power consumption overhead for a massive multi-antenna technology system. In addition, HBF requires a complex control system to achieve precise and dynamic phase control, thereby additionally increasing the hardware complexity and power consumption. For lens antennas, it is difficult to integrate them with multi-antenna technology due to the large volume and high insertion loss of the dielectric lens. For movable antenna or fluid antenna array based on massive multi-antenna technology, it is extremely challenging to accurately estimate the CSI (Channel State Information). In addition, additional mechanical control devices need to be introduced, which will affect the cost-effectiveness, power consumption and response time.

[0005] To solve the above problems, a new RAA (Ray Antenna Array) architecture has recently been proposed, which provides a promising solution to reduce hardware cost while improving system performance. The RAA architecture is composed of a large number of low-cost antenna elements arranged in a ray-like structure, where each ray corresponds to a directional sULA (simple Uniform Linear Array) with a carefully designed rotation angle. All antenna elements within each sULA are directly connected, so each sULA can form a main lobe of the beam consistent with its physical direction. With the help of RSN (Ray Selection Network), RAA can achieve uniform spatial resolution, enhanced beamforming gain, high-precision sensing performance, and very low hardware cost, but at the cost of larger array size. However, when multiple sULAs are deployed in different directions on the same 2D (Two-Dimensional) plane, the RAA architecture can be affected by signal blocking between different sULA arrays. Specifically, the beam generated by one sULA will propagate directly in front of it, and the adjacent sULA will be located in that direction, thereby physically blocking the transmitted signal. SUMMARY

[0006] The technical problem solved by the present application is: for the signal blocking problem in the RAA architecture in the background art, the present application proposes a low-cost ultra-large-scale MIMO communication system and method based on a cylindrical direct-connected antenna array, to solve the problems of difficult design and high cost of millimeter wave, terahertz wireless communication and perception system.

[0007] To solve the above technical problems, the present application proposes the following technical solutions:

[0008] Firstly, the present application proposes a cylindrical direct-connected antenna array, comprising:

[0009] A plurality of low-cost directional antenna units arranged in a cylindrical structure, forming N simple uniform circular arrays vertically stacked along the side surface of the cylindrical structure;

[0010] Each of the simple uniform circular arrays is divided into two subarrays containing the same number M of antenna units, and the pointing directions of the center antennas of the subarrays of different simple uniform circular arrays are different;

[0011] All M antenna units in each of the subarrays are directly connected to a radio frequency combiner through delay lines of different lengths, so that the subarray can form a beam in the direction in which the center antenna points, and output a combined signal from the radio frequency combiner;

[0012] A selection matrix with its input end connected to the output ends of all the radio frequency combiners, for selecting multiple signal outputs from the 2N subarray combined signals.

[0013] Further, the directional antenna units of the cylindrical direct-connected antenna array proposed by the present application are PCB antennas.

[0014] Further, the radius a of the simple uniform circular array of the cylindrical direct-connected antenna array proposed by the present application satisfies: a = Mλ / (2π), where λ is the wavelength of the working signal, and the spacing between adjacent antenna units in the same simple uniform circular array and the spacing between antenna units of vertically adjacent two simple uniform circular arrays are not less than half the wavelength.

[0015] Further, in each of the subarrays of the cylindrical direct-connected antenna array proposed by the present application, the length l of the delay line connected to the mth antenna unit is designed as: m

[0016]

[0017] wherein, a is the radius of the simple uniform circular array, λ is the wavelength of the working signal, and m = 1, 2,..., M.

[0018] ​Further, the cylindrical direct connection antenna array proposed in the application, in the N simple and uniform circular arrays vertically stacked, the rotation angle η of the subarray corresponding to the serial number satisfies n The difference Δη of the arithmetic sequence satisfies:

[0019] Δη = Wherein M is the number of antenna units contained in each subarray.

[0020] Further, the cylindrical direct connection antenna array proposed in the application, the selection matrix is composed of a plurality of radio frequency switches.

[0021] Further, the cylindrical direct connection antenna array proposed in the application, the selection matrix is configured to dynamically select the output signal corresponding to the subarray matching the current channel direction according to the obtained channel state information.

[0022] Meanwhile, the application provides a low-cost super large scale MIMO communication system based on the cylindrical direct connection antenna array, which works in the millimeter wave or terahertz frequency band, and comprises:

[0023] The cylindrical direct connection antenna array as described above;

[0024] A radio frequency link, the input end of which is connected with the cylindrical direct connection antenna array through the selection matrix, for receiving the signal selected by the selection matrix;

[0025] A baseband processing module, connected with the output end of the radio frequency link, for performing baseband signal processing on the received signal.

[0026] On the other hand, the application also proposes a communication method based on the super large scale MIMO communication system, comprising the following steps:

[0027] S1. Each subarray of the cylindrical direct connection antenna array forms a beam in a specific direction where the center antenna of the subarray points to, through the internal delay lines of different lengths, and combines all the signals received or to be transmitted by the antenna units into one output;

[0028] S2. The selection matrix dynamically selects one or more signals from the multiple signals output by all the subarrays according to the channel state information obtained by the system;

[0029] S3. The signal selected by the selection matrix is transmitted to the baseband processing module through the radio frequency link for subsequent processing.

[0030] The application adopts the above technical means, compared with the prior art, has the following technical effects:

[0031] The application proposes a novel "simple uniform circular array", the design of delay lines with different lengths and selection matrix. Through delay lines with different lengths, each subarray of the "simple uniform circular array" can form a beam matching the direction of the center antenna without relying on analog or digital beamforming technology.

[0032] The selection matrix dynamically connects a large number of subarrays to a small number of radio frequency links for subsequent baseband processing, avoids using expensive phase shifters, significantly reduces the implementation cost of super large MIMO, and improves spatial resolution and communication performance. Benefiting from the three-dimensional multi-layer stacking structure of the cylindrical direct connection antenna array, the application can effectively avoid physical obstruction between arrays, improve spatial resolution and communication performance, and effectively solve the problems of dynamic beam implementation difficulty and high cost in high-frequency wireless communication systems such as millimeter wave and terahertz. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram of a cylindrical direct connection antenna array architecture.

[0034] Figure 2 is a schematic diagram of "simple uniform circular array" and its subarray.

[0035] Figure 3 is a subarray response diagram using delay lines with different lengths.

[0036] Figure 4 is a schematic diagram of the beam pattern of the cylindrical direct connection antenna array.

[0037] Figure legend: 1-antenna element, 2-simple uniform circular array, 3-subarray, 4-delay line, 5-radio frequency combiner, 6-selection matrix, 7-radio frequency switch. DETAILED DESCRIPTION

[0038] In order to better understand the purpose, structure and function of the application, the application of a low-cost super large MIMO communication system and method based on a cylindrical direct connection antenna array is further described in detail below in combination with the drawings.

[0039] The application adopts low-cost antenna elements arranged in a uniform circular shape as a plurality of "simple uniform circular arrays", and then stacked along the side of the cylinder to form a cylindrical direct connection antenna array. Each "simple uniform circular array" is divided into two subarrays with the same number of antennas, and the center antennas of the subarrays of different circular arrays face different directions. Each subarray is directly connected to a radio frequency combiner through a delay line with different lengths to form a signal output. The selection matrix uses a plurality of radio frequency switches and an optimized algorithm to dynamically select the output signal of the appropriate subarray to access the radio frequency link for subsequent baseband processing.

[0040] The cylindrical direct-connected antenna array architecture is composed of multiple directional antenna units, and the directional antenna units form a "simple uniform circular array" according to an optimally designed radius to satisfy that the distance between the antenna units is not less than half a wavelength; and multiple "simple uniform circular arrays" are stacked to form the cylindrical direct-connected antenna array through an optimally designed vertical distance to satisfy that the distance between two vertically adjacent "simple uniform circular arrays" is not less than half a wavelength.

[0041] The cylindrical direct-connected antenna array architecture designs the rotation angle of the simple uniform circular array at an equal-angle interval, and the angle interval is set as the beam width from the peak point to the first valley point of the main lobe of the subarray to minimize the interference between the vertically adjacent subarrays.

[0042] In the cylindrical direct-connected antenna array architecture, all the antenna units of the subarray of each "simple uniform circular array" are directly connected to a radio frequency combiner through delay lines of different lengths, combined as an output signal, and connected to a selection matrix through a radio frequency line.

[0043] The selection matrix is composed of multiple radio frequency switches, and an appropriate subarray output signal is dynamically selected through a designed optimization algorithm using the obtained channel state information and connected to a radio frequency link for baseband signal processing.

[0044] Figure 2 A schematic diagram of the "simple uniform circular array" and its subarray is given. Each simple uniform circular array 2 is composed of directional antenna units 1, and each of the two subarrays contains directional antenna units 1. The radius of the "simple uniform circular array" is designed as: where is the signal wavelength.

[0045] Starting from one end, the index of the antenna units in a subarray 3 is defined as . For a subarray, the included angle of the central antenna unit (the th antenna unit) relative to the reference direction is defined as the rotation angle of the subarray. Therefore, for a subarray with a rotation angle of , the rotation angle of each antenna unit in the subarray relative to the reference direction is:

[0046]

[0047] Let the angle of arrival of a far-field uniform plane wave signal in space be , where is the horizontal angle, and is the elevation angle. Therefore, the steering vector of the subarray with a rotation angle of can be represented as:

[0048]

[0049] wherein is the relative angle of arrival of the th antenna element, is the antenna element radiation pattern vector, which can be expressed as:

[0050]

[0051] wherein is the directional antenna element radiation pattern, is the antenna element relative elevation angle. In order to make the rotation angle of the subarray of be able to form a beam towards the direction, as shown in the figure, the present application introduces different lengths of delay lines 4 to change the radiation phase of the Figure 2 antenna elements 1 in the subarray 3, so that they are coherently superimposed in the direction to form a high-gain beam. The phase shift vector of the th antenna element is defined as:

[0052]

[0053] which is the phase shift introduced by the delay line, m = 1, 2,... M. Considering that the distance of the arrival signal source from the cylindrical direct antenna array is much larger than the size of the cylindrical direct antenna array, in the design, . Therefore, the phase shift can be written as:

[0054] ,

[0055] which is only related to the index of the antenna element.

[0056] Further, the length of the delay line of the th antenna element is defined as , and the length of the delay line optimized in the present application is :

[0057]

[0058] wherein .

[0059] Therefore, the rotation angle of the subarray of is the response of the direct connection to the radio frequency combiner through the delay line of different lengths:

[0060]

[0061] wherein .

[0062] The beam width of the sub-array in the horizontal direction angle is , which is the distance between the first valley point of the positive and negative directions obtained by the estimation of the 0-order Bessel function.

[0063] Figure 1 The schematic diagram of the architecture design of the cylindrical direct-connected antenna array is given. The cylindrical direct-connected antenna array is composed of directional antenna units, which are arranged into “simple uniform circular arrays”, that is, a total of sub-arrays. In the order from low to high, each “simple uniform circular array” is numbered as . For the “simple uniform circular array”, the rotation angles of its two sub-arrays can be written as and , respectively, indicating that its rotation angle is forward rotation or reverse rotation relative to the reference direction. The orientation of the center antenna unit of a sub-array of the “simple uniform circular array” numbered is defined as the reference direction, that is, and . Therefore the response of the sub-array can be written as: .

[0064] Based on the channel state information, the cylindrical direct-connected antenna array dynamically selects appropriate signals from the signals obtained by the sub-arrays, where is the number of radio frequency links. The selection matrix can be mathematically expressed as , which satisfies and , where and . Then connect the selected output ports to the radio frequency links for further baseband signal processing. In order to reduce the interference between the sub-arrays as much as possible, the present application designs the rotation angles of two vertically adjacent sub-arrays, that is, the relationship between and and and is:

[0065]

[0066] That is, the valley point of the main lobe of a sub-array and the peak point of the next vertically adjacent sub-array are aligned.

[0067] Rotation angle of each subarray , The design is as follows:

[0068]

[0069] according to The design of the rotation angle of each subarray, in order to achieve 360° omnidirectional coverage communication, requires a certain number of "simple uniform circular arrays". for:

[0070]

[0071] Design the distance between two adjacent "simple uniform circular arrays" in the vertical direction. The height of the cylindrical direct-connected antenna array can be obtained as follows: .

[0072] The technical solution of the present invention will be further described in detail below with reference to two embodiments:

[0073] Example 1: For a "simple uniform circular array", where the rotation angle is ? The number of antenna elements in the subarray is set to Furthermore, the radiation pattern of the directional antenna element conforms to the antenna model specified in the 3GPP 38.901 protocol. The response to the horizontal angle is as follows Figure 3 As shown, the subarray achieves the condition that the horizontal angle is 0 if and only if the delay lines of different lengths are used. The signals are coherently superimposed at the same time.

[0074] Example 2: The relevant parameters in this example are: the number of antennas in each subarray is set to... The directional antenna element's radiation mode conforms to the antenna model specified in 3GPP 38.901 protocol, and has a total of A simple uniform circular array, with an operating frequency of [frequency missing]. GHz. Figure 4 This is the beam diagram of the cylindrical direct-connect antenna array in this embodiment. From Figure 4 It can be observed that the cylindrical direct-connect antenna array architecture can achieve efficient beamforming without relying on analog or digital beamforming. Furthermore, the cylindrical direct-connect antenna array architecture performs uniform sampling in the angular domain space through multiple subarrays, and still has a main lobe of the same width at non-central angular positions, thereby improving spatial resolution and achieving full spatial coverage.

[0075] Those skilled in the art will understand that the present application is not limited to the above-mentioned specific embodiments, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be defined by the protection scope defined in the claims.

Claims

1. A cylindrical direct-connect antenna array, characterized in that, include: Multiple low-cost directional antenna elements (1) are arranged in a cylindrical structure to form N simple uniform circular arrays (2) stacked vertically along the side of the cylindrical structure. Each of the simple uniform circular arrays (2) is divided into two subarrays (3) containing the same number of M antenna elements, and the central antennas of the subarrays (3) of different simple uniform circular arrays (2) have different pointing directions. All M antenna elements (1) in each subarray (3) are directly connected to a radio frequency combiner (5) through delay lines (4) of different lengths, so that the subarray (3) can form a beam in the direction pointed to by its central antenna and output a combined signal by the radio frequency combiner (5). The selection matrix (6), whose input is connected to the output of all the radio frequency combiners (5), is used to select multiple signal outputs from the combined signals of the 2N subarrays.

2. The cylindrical direct-connect antenna array according to claim 1, characterized in that, The directional antenna unit (1) is a PCB antenna.

3. The cylindrical direct-connect antenna array according to claim 1, characterized in that, The radius a of the simple uniform circular array (2) satisfies: a = Mλ / (2π), where λ is the wavelength of the working signal, and the spacing between adjacent antenna elements (1) in the same simple uniform circular array (2) and the spacing between antenna elements between two vertically adjacent simple uniform circular arrays (2) are not less than half a wavelength.

4. The cylindrical direct-connect antenna array according to claim 1, characterized in that, In each of the subarrays (3), the length l of the delay line (4) connected to the m-th antenna element is... m Designed as follows: in, , where a is the radius of the simple uniform circular array (2), λ is the wavelength of the working signal, and m=1,2,...,M.

5. The cylindrical direct-connect antenna array according to claim 1, characterized in that, In N simple uniform circular arrays (2) stacked vertically, the subarray (3) with the corresponding index has a rotation angle η n The sequence is set according to an arithmetic progression, and the common difference Δη of the arithmetic progression satisfies: Δη = , where M is the number of antenna elements contained in each subarray (3).

6. The cylindrical direct-connect antenna array according to claim 1, characterized in that, The selection matrix (6) is composed of multiple radio frequency switches (7).

7. The cylindrical direct-connect antenna array according to claim 1, characterized in that, The selection matrix (6) is configured to dynamically select the output signal corresponding to the subarray (3) that matches the current channel direction based on the acquired channel state information.

8. A low-cost, ultra-large-scale MIMO communication system based on a cylindrical direct-connected antenna array, characterized in that, include: Cylindrical direct-connect antenna array as described in any one of claims 1 to 7; The radio frequency link, whose input end is connected to the cylindrical direct-connect antenna array through the selection matrix (6), is used to receive the signal selected by the selection matrix (6); The baseband processing module is connected to the output of the radio frequency link and is used to perform baseband signal processing on the received signals.

9. The ultra-large-scale MIMO communication system according to claim 8, characterized in that, The system operates in the millimeter wave or terahertz frequency band.

10. A communication method based on the ultra-large-scale MIMO communication system of claim 8 or 9, characterized in that, Includes the following steps: S1. Each subarray (3) of the cylindrical direct-connected antenna array forms a beam in a specific direction pointed to by its central antenna through delay lines (4) of different lengths inside, and combines the signals received or to be transmitted by all antenna elements into one output. S2. The selection matrix (6) dynamically selects one or more signals from the multiple signals output by all subarrays (3) based on the channel state information obtained by the system. S3. The signal selected by the selection matrix (6) is transmitted to the baseband processing module through the radio frequency link for subsequent processing.

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