RIS equipment, communication system based on equipment and communication protocol

Abstract

The invention discloses RIS equipment, a communication system based on the equipment and a communication protocol, which are applied to the field of RIS-assisted backscatter communication, and the RIS equipment does not need an additional RIS control link to carry out RIS management and setting, and can directly communicate with a backscatter reader-writer sharing the same backscatter communication technology. The RIS equipment is realized by adopting a traditional antenna array technology, an antenna unit port is connected to a multi-beam forming network, and the network synthesizes a static or reconfigurable high-gain beam, so that high-gain operation can be carried out in a wider angle direction by utilizing the whole array surface; and the multi-beam forming network port is connected to the energy collection circuit and the backscatter communication equipment to realize communication with the base station / backscatter reader-writer.

Description

Technical Field

[0001] The invention belongs to the field of RIS-assisted backscattering communication, and in particular relates to a RIS device. Background Art

[0002] Reconfigurable Intelligence Surface (RIS) is a new technology that aims to improve the performance of modern communication systems; in fact, RIS are large flat reflective surfaces that can be installed in indoor / outdoor environments to provide channel reconfigurability by intelligently controlling RF signal reflections. In the future vision of the sixth generation (6G) of wireless communications, RIS will be widely installed for communication, positioning, energy sustainability, etc.

[0003] The prior art with publication number CN 116569496 A relates to beam control of a multi-antenna device. The device receives an activation signal and outputs signals with different phase shifts. Each of the multiple antenna elements on the device receives a phase shift signal from a related phase shifter and outputs a beam based on the phase shift signal received by the related phase shifter.

[0004] The prior art with announcement number CN 221202564 U proposes a 1-bit multifunctional intelligent reflector, which includes multiple intelligent reflector units (including an upper structure, an amplifying layer and a bottom structure). By changing the bias voltage of the varactor diode, the phase and amplitude can be adjusted; the amplifying circuit is combined with the RIS unit of the above design to realize the signal amplification function, thereby realizing the multifunctional RIS.

[0005] An energy harvesting system for a multifunctional RIS-assisted communication system is proposed in the prior art with the announcement number CN 221151028 U. Energy harvesting enables RIS components to operate autonomously and continuously without the need for a continuous external power source or battery, which is critical for applications that utilize energy from ambient sources such as radio frequency signals to operate uninterruptedly.

[0006] The prior art with announcement number CN 221010109 U proposes a multifunctional reconfigurable smart plane device, including: a RIS reflection unit, a RIS transmission unit, a power amplifier circuit, a power distribution circuit, a reflection phase adjustment circuit, a transmission phase adjustment circuit and a control module, which realizes full spatial coverage, converts the multiplicative fading of the cascaded channel into additive fading, and reduces the number of units required for the RIS architecture.

[0007] The prior art with publication number CN 118157813 A discloses an intelligent metasurface control method and related devices, which adopts a dynamic design for the structure of the control signaling and uses control signals of different lengths for different weight adjustment methods in the RIS array, effectively reducing the control signaling overhead and improving communication efficiency.

[0008] In the background technology, the base station communicates with the RIS through an additional control channel, and sends signaling to the RIS based on channel estimation, thereby controlling the signal transmission to the terminal. The additional control channel not only requires additional hardware resources, but also requires a more complex communication protocol, which must integrate the RIS control channel and the BS terminal communication technology. Summary of the invention

[0009] To solve the above technical problems, the RIS device adopted by the present invention can be reconfigured without an additional control link.

[0010] One of the technical solutions adopted by the present invention is: a RIS device for RIS-assisted backscatter communication, including an array composed of a plurality of RIS units, the structure of each RIS unit including: a patch antenna, a reconfigurable phase reflection load, and an antenna load; and also including a metal through hole set on the patch antenna; the patch antenna transmits the electromagnetic wave energy that hits the surface of the patch antenna to the antenna load through the metal through hole, and the reconfigurable phase reflection load is connected in parallel with the antenna load.

[0011] Two orthogonal metal through holes are arranged on the patch antenna.

[0012] The second technical solution adopted by the present invention is: a communication system based on RIS equipment, including the above-mentioned RIS equipment, a base station BS, and a receiver; the BS signal sent by the base station BS is incident on the RIS equipment, and the RIS equipment reflects the incident BS signal to the receiver.

[0013] The third technical solution adopted by the present invention is: a RIS-assisted backscatter communication protocol, based on the above-mentioned communication system, comprising the following steps:

[0014] S1, initially all RIS units are configured in the absorbing state;

[0015] S2, all RIS units perform energy collection;

[0016] S3, perform the traditional backscatter tag identification process; all RIS communication units that receive the 'query command' reply to the base station BS during the identification process;

[0017] S4. The RIS unit selected by the base station is configured to be in a reflective state.

[0018] Beneficial effects of the invention: The present invention provides a RIS device that can be reconfigured without an additional control link, analogous to the current implementation of the latest RIS-assisted backscatter communication; the RIS device proposed by the present invention includes an electromagnetic RF signal absorption / reflection surface, which is implemented by multiple high-efficiency antenna units with reconfigurable behavior to absorb the incident RF signal power, act as a traditional antenna and enable the RIS control unit to process RIS reconstruction protocol control messages, and use the reconfigurable reflection phase capability of each unit to reflect the incident RF signal to a specific direction. The antenna elements are connected to a multi-beamforming network that simultaneously synthesizes static or reconfigurable orthogonal high-gain beams and transmits signals received / transmitted from different directions (multi-beamforming ports) to the RIS communication unit (backscatter device), thereby enabling communication between the base station / backscatter reader and RIS, and reconfiguring the reflection behavior of each RIS unit according to the requirements of the base station;

[0019] Another aspect of the invention relates to the possibility of utilizing a large RIS surface and a multi-beamforming network to achieve efficient energy harvesting, which can be used to obtain full or partial energy self-sustainability of the RIS device; to achieve this function, the RIS antenna unit elements are not directly connected to the RIS communication unit, but the receive / transmit signals are distributed to the energy harvesting circuit and the RIS communication unit through an RF switch or a non-uniform power divider;

[0020] Finally, an extended acquisition-transfer protocol is also part of the present invention, which includes RIS full / partial power-up, RIS reconfiguration, final and additional power-up to support reflective mode, and RIS operation towards a specific reflective direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A RIS-assisted backscatter communication scenario is shown;

[0022] Figure 2 The schematic diagram of the connection of the reconfigurable reflective phase load using MOS transistors and transmission lines of different lengths and the absorption circuit is shown;

[0023] Figure 3 The detailed absorption structure is shown, including a multi-beamforming network, a time-division or power-division multiplexing circuit, an energy harvesting circuit, a RIS communication unit, and a RIS control unit;

[0024] Figure 4 A schematic diagram of a RIS sink circuit for a dual orthogonal implementation is shown;

[0025] Figure 5 A flow chart illustrating an extended acquisition-transmission protocol is shown.

[0026] Explanation of reference numerals: 1 is a RIS structure, 2 is a RIS unit, 3 is a base station BS, 4 is a receiver, 5 is a direct communication path, 6 is a RIS reflected beam, 7 is a BS signal, 8 is a RIS control unit, 9 is a patch antenna, 10 is a reconfigurable phase reflection load, 11 is a metal through hole, 12 is a dual orthogonal polarization unit cell, 13 is a MOS transistor, 14 is a short-circuited transmission line, 15 is a bias voltage, 16 is a reflection phase, 17 is a MOS transistor bias signal, 18 is an environment, 19 is a RIS reconstruction, 20 is a multi-beam forming network, and 21 is a RIS The antenna port of unit 2, 22 is a high gain beam, 23 is an RF switch or power divider, 24 is an input port of the multi-beam forming network 20, 25 is an energy collection circuit, 26 is a RIS communication unit, 27 is a conventional backscatter communication receiver, 28 is an orthogonal polarization signal, 29 is a circular polarization signal, 30 is a first power-on time period, 31 is a traditional backscatter tag identification process, 32 is a query for available tags, 33 is a verification of RIS, 34 is a reflection state, 35 is a RIS auxiliary inventory, 36 is an additional power-on operation, and 37 is an identification of other RIS. DETAILED DESCRIPTION

[0027] To facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further explained below with reference to the accompanying drawings.

[0028] Assumptions Figure 1 The RIS structure 1 in the example is composed of a planar (or conformal) array of N×M RIS units 2, the general size of which is d x ×d y , d x ,d y Respectively represent the length and width of the RIS unit 2. When the direct communication path 5 is blocked or the receiver cannot receive, it is necessary to enable backscatter communication between the base station BS 3 (backscatter reader) and the receiver 4 (backscatter tag). The reflection behavior of each RIS unit 2 of the RIS structure 1 is timely reconfigured to synthesize the RIS reflection beam 6 towards the receiver direction, reflect the incident BS signal 7, and maximize the 'base station-reflector-receiver' power link budget. The RIS-assisted 'base station-reflector-receiver' receiver communication channel is bidirectional, which can realize base station-receiver backscatter communication and data exchange.

[0029] Figure 1The behavior of each RIS unit 2 is controlled by a RIS control unit 8. Each RIS unit 2 of the array is designed to exhibit high efficiency and good impedance matching over a wide angle range, and to operate in reflection and absorption modes by integrating a conventional patch antenna 9 and a reconfigurable phase reflective load 10. The patch antenna 9 transfers the electromagnetic wave energy that strikes the antenna surface to the antenna load through a metal through-hole 11, and the reconfigurable phase reflective load 10 is connected in parallel with the antenna load. Due to the simple unit structure, a dual orthogonal polarization patch antenna with two orthogonal metal through-holes (realizing a dual orthogonal polarization unit cell 12) can also be easily realized, thereby realizing dual orthogonal polarization RIS operation.

[0030] The reconfigurable phase reflection load 10 can be realized by connecting the drains of a plurality of low on-resistance MOS transistors 13 in parallel, such as Figure 2 As shown, the sources of the MOS transistors are connected to short-circuited transmission lines 14 with different lengths; when a bias 15 is applied to the gate of a MOS transistor, the patch antenna 9 is short-circuited, synthesizing an EM wave relative reflection phase 16 proportional to the length of the connected short-circuited transmission line 14. The number of MOS transistors Q determines the possible Q reconfigurable reflection phase states of each RIS unit 2. The MOS transistor bias signal 17 is controlled by the RIS control unit 8, and the RIS control unit 8 determines the reconfigurable reflection phase state of each RIS unit 2 according to the direction of the incident EM wave BS signal 7 and the desired RIS reflected beam 6 direction, let φ mn is the reflection phase of the mth and nth unit cells, which is defined according to [W.Tang et al., “Wireless communications with reconfigurable intelligent surface: path loss modeling and experimental measurements,” IEEE Trans. Wireless Comm., vol. 20, no. 1, pp. 421-439, Jan. 2021], φ mn is defined as:

[0031]

[0032] Among them, the direction of the base station incident EM wave BS signal 7 is The direction of RIS reflected beam 6 is λ is the wavelength of the RF signal, which is closest to φ mn The reflection phase is the reconfigurable reflection phase of the unit.

[0033] The reconfigurable phase reflective load 10 can also be implemented in other forms, such as using a single MOS transistor 13, whose source is connected to a short-circuited variable phase shifter with a discrete / continuous phase adjustment mechanism. On the contrary, in the absorption state, that is, without the MOS transistor 13 bias, the patch antenna 9 is used as a conventional antenna to receive / transmit signals. This characteristic can be used to collect the EM energy present in the environment 18, which helps to meet the energy requirements of the proposed RIS device, and to achieve communication with the base station BS, which is necessary for RIS reconstruction 19 and avoids the need for an auxiliary control link in conventional RIS devices.

[0034] In order to utilize the entire planar array surface for high gain operation in a wider angle direction, and to improve both the received energy (improvement of rectification efficiency determined by the latest microwave rectification performance) and the 'base station-reflector-receiver' communication distance, the output port of a multiple beam forming network (MBFN) 20 such as a Butler matrix or a Rotman lens is connected to the antenna port 21 of the RIS unit 2, such as Figure 3 As shown, a single antenna array is used to synthesize multiple orthogonal static (or reconfigurable in the case of a reconfigurable MBFN 20) high gain beams 22. A time division multiplexing or power division multiplexing method, i.e., an RF switch or power divider 23, can be used to connect the input port 24 of the MBFN 20 to the energy harvesting circuit 25 and the RIS communication unit (RIS BD) 26. In the case of backscatter communication, the RIS communication unit 26 can act as a conventional backscatter communication receiver 27, which implements backscatter communication protocol command reception and processing as well as backscatter modulation. The RIS communication unit 26 is controlled by a RIS control unit 8 (which can be implemented on the same MCU / FPGA unit used for RIS communication unit 26 protocol command reception and processing), which is responsible for reconfiguration of the behavior of the RIS unit 2. For dual orthogonal polarization cells 12, the Figure 3 The structure in is doubled to process two orthogonal polarization signals 28 (such as Figure 4 As shown), or dual orthogonal polarization signals can be combined to process a single specific polarization configuration, such as a circular polarization (CP) signal 29.

[0035] The communication between the base station BS 3 and the RIS structure 1 is carried out via Figure 5The communication protocol described is managed, obviously supported by backscatter communication technology. Initially, all RIS units 2 are configured in an absorbing state (no MOS transistor 13 is biased); depending on the implementation of the energy harvesting / RIS communication unit multiplexing method 23, energy harvesting can be performed continuously during the RIS absorption state (power division multiplexing) or only during a dedicated first power-on period 30 (time division multiplexing) until sufficient energy is stored. After energy harvesting (for the latter case), a traditional backscatter tag identification process 31 is performed to query all available tags 32 and verify the presence of RIS 33, i.e. receive replies from RIS communication units 26. All RIS communication units 26 that can receive the 'query command' reply to the base station BS 3 during the identification process 31. In principle, only the RIS communication units 26 connected to the MBFN port associated with the high-gain beam in the direction of the base station BS3 should reply to the 'query command', providing information about the RIS device; however, in practice, multiple RIS communication units 26 can respond to the command when the received power on adjacent beam channels is large enough to activate the RIS communication unit 26. Regardless, the base station BS 3 can identify the RIS communication unit 26 that responds with the greatest power, or simply communicate with multiple RIS communication units 26. Once the available RIS communication unit 26 responds, the base station BS 3 can decide whether to use the RIS function to extend coverage and find a more distant or blocked receiver. In this case, the base station BS 3 requires the RIS unit 2 to operate in the reflective state 34 for a period of time (T RIS ), and the RIS control unit 8 configures the RIS unit reflection phase 16 according to the location of the base station BS 3 (i.e. the beam direction of the RIS communication unit communicating with the BS) to reflect the BS signal to a specific direction. The base station BS 3 performs a RIS assisted query 35, associates the discovered tag ID with a specific RIS reflected beam direction and searches for the receiver 4; at time T RIS Afterwards, the base station BS 3 can communicate with the identified RIS communication unit 26 again (if necessary, this may include an additional power-on operation 36), requiring the signal to be reflected in a different direction for other inventories, or in a direction that has been selected, in order to communicate and / or exchange data with the tags that have been found. During the RIS-assisted inventory 35, it may be possible to identify RIS communication units of other RIS 37; in this case, a longer T may be required. RIS time to RIS, thereby enabling reconfiguration of other RIS and conducting inventory operations with dual / multiple cascaded RIS.

[0036] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the scope of protection of the present invention is not limited to such specific statements and embodiments. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A RIS device for RIS-assisted backscatter communication, characterized in that: The invention comprises an array composed of several RIS units, each of which comprises a patch antenna, a reconfigurable phase reflection load and an antenna load; and also comprises a metal through hole arranged on the patch antenna; the patch antenna transmits the electromagnetic wave energy striking the surface of the patch antenna to the antenna load through the metal through hole, and the reconfigurable phase reflection load is connected in parallel with the antenna load.

2. A RIS device for RIS-assisted backscatter communication according to claim 1, characterized in that: Two orthogonal metal through holes are arranged on the patch antenna.

3. A RIS device for RIS-assisted backscatter communication according to claim 1 or 2, characterized in that: Also includes: A multi-beam forming network, an RF switch or a power divider, an energy harvesting circuit and a RIS communication unit; one end of the multi-beam forming network is connected to the antenna port of the RIS unit, and the other end of the multi-beam forming network is connected to the energy harvesting circuit and the RIS communication unit through the RF switch or the power divider.

4. A RIS device for RIS-assisted backscatter communication according to claim 3, characterized in that: The reconfigurable phase reflection load includes a plurality of MOS transistors with parallel drains, short-circuit transmission lines of different lengths connected to the sources of the MOS transistors, the drains of the MOS transistors are connected to the metal through holes on the corresponding patch antennas, and the gates of the MOS transistors are connected to the bias voltage.

5. The RIS device for RIS-assisted backscatter communication according to claim 4, characterized in that: The reconfigurable phase reflection load comprises a single MOS transistor, a source of which is connected to a short-circuit variable phase shifter with a discrete / continuous phase adjustment mechanism, a drain of which is connected to a metal through hole on a corresponding patch antenna, and a gate of which is connected to a bias voltage.

6. The RIS device for RIS-assisted backscatter communication according to claim 3, characterized in that: When a bias is applied to the gate of the MOS transistor in the RIS unit, the drain and source channels are turned on, and the RIS unit works in a reflective state.

7. A RIS device for RIS-assisted backscatter communication according to claim 6, characterized in that: When no bias is applied to the gate of the MOS transistor in the RIS cell, the RIS cell operates in an absorption state.

8. The RIS device for RIS-assisted backscatter communication according to claim 3, characterized in that: Also includes: The RIS control unit is used to control the bias signal of the gate of the MOS transistor and is also used to determine the reconfigurable reflection phase state of each RIS unit according to the direction of the incident BS signal and the required reflection direction.

9. A communication system based on RIS equipment, characterized in that: The invention comprises the RIS device as claimed in claim 8, a base station BS, and a backscatter tag; a BS signal sent by the base station BS is incident on the RIS device, and the RIS device reflects the incident BS signal to the backscatter tag.

10. A RIS-assisted backscatter communication protocol, characterized in that: The communication system according to claim 9 comprises the following steps: S1, initially all RIS units are configured in the absorbing state; S2, all RIS units perform energy collection; S3, perform the traditional backscatter tag identification process; all RIS communication units that receive the 'query command' reply to the base station BS during the identification process; S4. The RIS unit selected by the base station is configured to be in a reflective state.

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