Downlink holographic multiple access method and device based on reconfigurable holographic metasurface

Abstract

The application discloses a downlink holographic multiple access method and device based on a reconfigurable holographic metasurface, which comprises the following steps: a receiver determines the position and direction of each transmitter according to the direction of an incident beam, and determines the channel parameters between a reconfigurable holographic metasurface and each transmitter, wherein the reconfigurable holographic metasurface is arranged in the receiver, and the reconfigurable holographic metasurface comprises a plurality of feed sources, a waveguide and a plurality of radiation units; a to-be-transmitted signal is encoded, and the encoded signal is transmitted to each feed source; based on the position, the direction and the channel parameters, a holographic pattern of a corresponding transmitter is constructed, then each feed source transmits a reference wave containing the encoded signal to excite the holographic pattern; and each radiation unit transmits a beam carrying the encoded signal to the corresponding transmitter based on the excited holographic pattern. The application not only realizes low-cost holographic multiple access, but also greatly reduces the volume of a holographic multiple access device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electricity, in particular to a downlink holographic multiple access method and device based on a reconfigurable holographic super surface. BACKGROUND

[0002] The next generation of wireless communication is expected to provide high-speed data services and support large-scale network access for a large number of mobile devices. This exponentially growing data transmission requirement has led to the emergence of large-scale multiple-input multiple-output (MIMO) technology and large-scale phased arrays. Large-scale MIMO systems based on spatial division multiple access (SDMA) can significantly improve system capacity by utilizing spatial diversity. However, the inherent limitations of phased arrays have seriously hindered the future development of large-scale MIMO systems, as the elements of phased arrays, such as phase shifters and high power consumption, are expensive. In addition, considering the trade-off between manufacturing difficulty and radiation performance, the element spacing of phased arrays is usually about half a wavelength. Therefore, it is difficult to implement large-scale MIMO systems in practical engineering due to the problem of excessive size of phased arrays.

[0003] Recently, with the rapid development of tunable metamaterials, the emergence of ultra-thin and lightweight reconfigurable holographic surfaces (RHS) provides a promising solution to overcome the shortcomings of phased arrays. RHS is composed of a large number of metamaterial radiation elements arranged compactly. According to the effective medium theory, the spacing between the elements is not more than one-quarter of the wavelength, and the feed of the RHS is embedded in the bottom of the waveguide to generate electromagnetic waves, which are also called reference waves, propagating along the waveguide. RHS can use metamaterial radiation elements to construct holograms according to the holographic interference principle, recording the interference between the target wave pointing to the receiver and the reference wave. In other words, a hologram corresponds to a desired wave direction. When the reference wave excites the hologram, each element can electrically control the radiation amplitude of the reference wave to produce a target beam.

[0004] Chinese patent application CN113098536A discloses a communication transmission system and a communication optimization method based on a reconfigurable holographic super surface, but it mainly considers amplitude optimization and does not consider the superposition characteristics of different holographic patterns corresponding to different incident beam directions. SUMMARY

[0005] Solve the problem that the traditional phased array antenna depends on the large volume, high cost and high power consumption of spatial division multiple access. The application provides a downlink holographic multiple access method and device based on a reconfigurable holographic super surface. In the holographic multiple access, the RHS superimposes all holograms corresponding to all receivers in different directions to generate a superimposed total hologram. Therefore, all transmitted data are mapped onto the superimposed hologram. When the reference wave excites the hologram, the signals sent to different receivers can be distinguished, that is, the RHS can generate multiple required directional beams pointing to different receivers. The application can effectively solve the above problems and greatly improve the total data rate of the communication system.

[0006] To achieve the above technical objectives, the technical scheme of the application includes:

[0007] A downlink holographic multiple access method based on a reconfigurable holographic super surface, comprising the following steps:

[0008] 1) The receiver determines the position and direction of each transmitter according to the incident beam direction, and determines the channel parameters between the reconfigurable holographic super surface and each transmitter, wherein the reconfigurable holographic super surface is arranged in the receiver, and the reconfigurable holographic super surface comprises a plurality of feed sources, a waveguide and a plurality of radiation units;

[0009] 2) The to-be-transmitted signal is encoded, and the encoded signal is transmitted to each feed source;

[0010] 3) Based on the position, direction and channel parameters, the holographic pattern of the corresponding transmitter is constructed, and each feed source transmits a reference wave containing the encoded signal to excite the holographic pattern;

[0011] 4) Each radiation unit transmits a beam carrying the encoded signal to the corresponding transmitter based on the excited holographic pattern.

[0012] Further, the receiver comprises a base station.

[0013] Further, the transmitter comprises an electronic device of a user.

[0014] Further, the channel parameters include the distance and path loss factor between the receiver and the transmitter.

[0015] Further, the pre-encoded signal is transmitted to each feed source by the following steps:

[0016] 1) The to-be-transmitted signal is pre-encoded;

[0017] 2) The pre-encoded signal is up-converted to the carrier frequency band on the RF chain to obtain the encoded signal;

[0018] 3) The encoded signal is transmitted to each feed source through the RF chain.

[0019] Further, the precoding method comprises a zero-forcing receiving processing method.

[0020] Further, the holographic pattern wherein L is the number of transmitters, K is the number of feeds, a l,k is the amplitude ratio of the beam from transmitter l pointing to feed k, is the propagation vector of the incident wave propagating in free space, k s is the propagation vector of the incident wave propagating in the reconfigurable holographic metasurface, r n is the position vector of the nthradiating unit, is the phase of the incident beam when propagating from the nthradiating unit to the kthfeed.

[0021] Further, a l,k The value setting method comprises: according to the communication scene, the channel condition, and the different requirements of the receiver on the quality of service, a corresponding mathematical method is used for solving.

[0022] Further, when the transmitting beam is only to one transmitter, the holographic pattern constructed wherein is the propagation vector of the incident wave propagating in free space, k s is the propagation vector of the incident wave propagating in the reconfigurable holographic metasurface, r n is the position vector of the nthradiating unit, is the phase of the incident beam when propagating from the nthradiating unit to the kthfeed.

[0023] A storage medium, the storage medium has a computer program stored therein, wherein the computer program is set to execute the above method when running.

[0024] An electronic device comprising a memory and a processor, wherein the memory stores a program for executing the above method.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] On the one hand, since all the components required for manufacturing the RHS are mass-produced commercial off-the-shelf parts, the overall manufacturing and hardware cost of the holographic multiple access is very low compared with the phased array antenna for implementing the traditional spatial division multiple access which relies on a large number of phase shifters and power amplifiers. On the other hand, the spacing between the radiating units of the RHS is smaller than that of the phased array. When the physical size of the RHS and the phased array is the same, the number of radiating units in the RHS is much more than that of the phased array, so the holographic multiple access wireless communication system has great potential in improving the capacity and supporting large-scale connection. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1is a specific structural schematic diagram of RHS.

[0028] Figure 2 is a flow chart of the method of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only specific embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The downlink holographic multiple access device of the present application comprises:

[0031] (1) a beam pointing determination module for determining the position of the receiver;

[0032] (2) a channel estimation module for the transmitter to determine the channel parameters between the transmitter and the receiver, including the distance between the transceiver, the road loss factor, etc.;

[0033] (3) a precoding module for the transmitter to preprocess the transmitted signal to eliminate the interference between the signals sent to different receivers;

[0034] (4) a holographic multiple access module, which uses a reconfigurable holographic super surface to construct a holographic pattern, and maps the transmitted signal onto the holographic pattern, after the precoding module transmits the transmitted signal to the holographic multiple access module, the signal excites the holographic pattern on the reconfigurable holographic super surface, and a beam pointing to each receiver direction is generated.

[0035] As shown in Figure 1 The reconfigurable holographic surface (RHS) is composed of a feed, a waveguide, and a metamaterial radiation unit, wherein the feed is embedded at the bottom of the super surface to emit electromagnetic waves (also called reference waves) carrying the transmitted signal, the electromagnetic waves directly hit the waveguide and propagate along the waveguide, and the super surface uses the radiation amplitude of the metamaterial radiation unit to construct a holographic pattern, when the reference wave carrying the transmitted signal excites the holographic pattern on the reconfigurable holographic super surface, each radiation unit will control the radiation amplitude of the reference wave at the unit according to the current phase of the reference wave, thereby generating a corresponding directional target beam.

[0036] The downlink holographic multiple access method of the present application comprises:

[0037] (1) single-beam directional holographic pattern construction:

[0038] Consider a RHS composed of N radiating elements, the radiation amplitude of each radiating element is between [0, 1], and the target beam direction of the RHS is i.e. the direction of the target receiver is The holographic pattern is constructed by the radiation amplitude of each radiating element. In order to construct the corresponding holographic pattern, for each feed, the radiation amplitude of each radiating element should be

[0039]

[0040] where is the propagation vector of the target wave propagating in free space, k s is the propagation vector of the reference wave propagating on the surface of the RHS, r n is the position vector of the nth radiating element; is the phase of the target beam on the nth radiating element, is the phase of the reference wave propagating from the kth feed to the nth radiating element; (a) indicates that when the phase of the reference wave on a certain element is close to the phase of the target wave on the element, more energy will be radiated to the free space to form the target beam, and when the phase of the reference wave on a certain element is far from the phase of the target wave on the element, less energy will be radiated to the free space to avoid forming beams in other directions.

[0041] (2) Holographic multiple access scheme:

[0042] Holographic multiple access uses the superposition of the above single-beam holographic pattern to map all transmitted signals to a total holographic pattern, so that signals to different receivers can be distinguished, i.e. through the overall holographic pattern, the RHS can generate multiple desired directional beams pointing to users. Specifically, the holographic pattern of the RHS can be calculated as the weighted sum of the radiation amplitude distribution of each target beam corresponding element.

[0043] Let the receivers be represented as {1, 2, …, L}, and the direction of receiver l relative to the RHS be represented as Then the holographic pattern M, i.e. the normalized radiation amplitude of each radiating element, can be represented as:

[0044]

[0045] where a l,k is the amplitude ratio of the beam from feed k to receiver l, satisfying a l,k The specific value of a can be calculated by computer using corresponding mathematical methods according to the communication scenario, channel condition, and different requirements of the receiver for service quality, so that the capacity of the communication system is maximized.

[0046] (3) The overall communication flow of downlink holographic multiple access is shown as follows: Figure 2

[0047] Step 1: The transmitter (e.g. base station) determines the position and direction of each receiver by using a beam pointing module;

[0048] Step 2: The transmitter determines the channel parameters between the RHS and each receiver (e.g. user) by using a channel estimation module;

[0049] Step 3: The transmitter pre-encodes the signals to be transmitted to different receivers at a pre-encoding module, and the processing mode includes but is not limited to a zero-forcing pre-encoding scheme, so as to eliminate the interference between different signals;

[0050] Step 4: After the pre-encoding, the signals are up-converted to the carrier frequency band through the RF chain, and then the signals after frequency conversion are transmitted into each feed source of the RHS through the RF chain. Each feed source emits a corresponding reference wave, and the RHS constructs a corresponding holographic pattern according to the formula (*), and the reference wave excites the holographic pattern, thereby generating the required beam pointing to each receiver and carrying the corresponding signal, thereby completing the downlink holographic multiple access communication.

[0051] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A downlink holographic multiple access method based on a reconfigurable holographic metasurface, comprising the following steps: 1) The transmitter determines the position and orientation of each receiver and determines the channel parameters between the reconfigurable holographic metasurface and each receiver. The reconfigurable holographic metasurface is set in the transmitter and includes: several feed sources, a waveguide and several radiating elements. 2) Encode the signal to be propagated and transmit the encoded signal to each feed source; 3) Based on the position, direction and channel parameters, after constructing the holographic pattern of the corresponding transmitter, each feed source transmits a reference wave containing the coded signal to excite the holographic pattern; 4) Each radiating element transmits a beam carrying a coded signal to the corresponding receiver based on the excited holographic pattern.

2. The method as described in claim 1, characterized in that, The transmitter includes a base station; the receiver includes a user's electronic device.

3. The method as described in claim 1, characterized in that, Channel parameters include the distance between the receiver and the transmitter and the path loss factor.

4. The method as described in claim 1, characterized in that, The precoded signal is transmitted to each feed source through the following steps: 1) Pre-encode the signal to be propagated; 2) The precoded signal is up-converted to the carrier frequency band via the RF chain to obtain the coded signal; 3) The encoded signal is transmitted to each feed source via the RF chain.

5. The method as described in claim 4, characterized in that, Precoding methods include: zero-forcing precoding schemes.

6. The method as described in claim 1, characterized in that, Holographic patterns Where L represents the number of receivers and K represents the number of feedhorns. Let a be the orientation of the receiver l relative to the reconfigurable holographic metasurface. l,k For the amplitude ratio of the beam pointing from the feed k to the receiver l, satisfying Let k be the propagation vector of the target wave in free space. s Let r be the propagation vector of the reference wave propagating on the reconfigurable holographic metasurface. n The position vector of the nth radiating element The phase of the reference wave emitted by feed k when it propagates to the nth radiating element.

7. The method as described in claim 1, characterized in that, The holographic pattern constructed when a beam carrying a coded signal is transmitted to only one receiver. in Let k be the propagation vector of the target wave in free space. s Let r be the propagation vector of the reference wave propagating on the reconfigurable holographic metasurface. n The position vector of the nth radiating element The phase of the reference wave emitted by feed k when it propagates to the nth radiating element.

8. A storage medium storing a computer program, wherein, The computer program is configured to execute any of the methods described in claims 1-7 at runtime.

9. An electronic device comprising a memory and a processor, the memory storing a computer program, the processor being configured to run the computer program to perform the method as claimed in any one of claims 1-7.

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