CN112865845B - Method and system for rapidly determining reflection coefficient of intelligent super surface - Google Patents

Method and system for rapidly determining reflection coefficient of intelligent super surface Download PDF

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CN112865845B
CN112865845B CN202110002114.XA CN202110002114A CN112865845B CN 112865845 B CN112865845 B CN 112865845B CN 202110002114 A CN202110002114 A CN 202110002114A CN 112865845 B CN112865845 B CN 112865845B
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reflection
angle
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CN112865845A (en
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尹海帆
李展鹏
曹琳
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0632—Channel quality parameters, e.g. channel quality indicator [CQI]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/02—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole
    • H01Q3/04—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical movement of antenna or antenna system as a whole for varying one co-ordinate of the orientation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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Abstract

The invention discloses a method and a system for rapidly determining an intelligent super-surface reflection coefficient, which belong to the technical field of wireless communication.A hierarchical scanning method is applied, a wave beam is from wide to narrow, the general range of a receiving antenna is determined by using the characteristic of wide wave beam coverage range, then a narrower wave beam is used for scanning in the direction covered by the wide wave beam in the first stage, and in a smaller scanning range, the wave beam with higher resolution ratio is used, and the precision of the wave beam aiming at the receiving antenna is higher; and determining an optimal angle, and calculating to obtain the reflection coefficient of each reflection unit. Therefore, the invention can have higher accuracy on the premise of ensuring low time complexity; meanwhile, the main beam of the reflected signal points to the direction of the user by changing the reflection coefficient of the RIS reflection unit without moving the position of the user.

Description

Method and system for rapidly determining reflection coefficient of intelligent super surface
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a method and a system for quickly determining an intelligent super-surface reflection coefficient.
Background
In the field of 5G wireless communication and even in the field of future 6G wireless communication, the millimeter wave technology is extremely important as a key technology, but the millimeter wave has a fatal defect, and the loss is serious when an obstacle is met, so that the communication effect is not ideal.
To solve this problem, the prior art adds a specially manufactured, low-cost, programmable Intelligent super Surface (RIS/Large Intelligent Surface/configurable Intelligent Surface/Software Defined Surface/measuring Surface/IRS/Intelligent reflection Surface/configurable metal-Surface/geographical MIMO, etc., hereinafter all expressed as RIS) to the wireless communication environment to assist communication. When there is a barrier between the AP (access point) or the Base Station (Base Station) and the User Equipment (UE), a signal may be reflected at the RIS by installing a RIS at a suitable position, so as to form a channel AP-RIS-UE, so that the AP and the UE can perform effective communication, as shown in fig. 1.
However, in most of the existing studies, the RIS reflection coefficient matrix is calculated based on the radio channel information (Ch) of AP-RIS or RIS-UEChannel State Information (CSI) with a complexity of at least O (N)2) Or higher. However, unlike the traditional Multiple Input Multiple Output (MIMO) technology, the RIS does not have a radio frequency link (RF-Chain) and cannot sense electromagnetic wave signals in the environment, so that the acquisition of the wireless channel information of the AP-RIS or RIS-UE is a difficult problem.
When the wireless channel information cannot be effectively acquired, the determination of the RIS reflection coefficient matrix can adopt an exhaustive search method. The exhaustive search method can find the optimal reflection coefficient (i.e. the phase shift and amplitude generated by the reflection unit), but the time complexity is too high, and if we quantize the reflection coefficient by n-bit and the number of the reflection units on the RIS is m, the time complexity is O (2)m*n) If the number of reflection units is large, too high time complexity cannot adapt to a rapidly changing channel, and the practicability of the method is limited.
Therefore, in most of the realized RIS, there is no good method to autonomously adjust the position of the main lobe of the reflected signal so that the main beam with the strongest energy points to the user direction. In order to maximize the received signal, the most conventional method is to adjust the position of the user to search for the best receiving position, which obviously lacks flexibility and has great uncertainty.
Disclosure of Invention
In view of the above defects or improvement requirements of the prior art, the present invention provides a method and a system for rapidly determining an intelligent super-surface reflection coefficient, thereby solving the technical problems that the time complexity is too high or the performance cannot meet the requirements in the process of calculating the RIS reflection coefficient in the prior art.
To achieve the above object, in one aspect, the present invention provides a method for rapidly determining an intelligent super-surface reflection coefficient, comprising the steps of:
(1) given the initial angle of the main lobe of the RIS reflection signal, selecting partial reflection units on the RIS and activating the partial reflection units; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle;
(2) changing the angle of the main lobe of the RIS reflected signal to enable the RIS to scan by using beams in different directions and receive data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal intensity, thereby determining a first angle range;
(4) activating more reflection units, performing the steps (2) and (3) in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
(5) and calculating the reflection coefficient of each reflection unit based on the optimal angle.
Further, still include:
(1) giving an initial pitch angle of a main lobe of a RIS reflection signal, selecting a partial reflection unit on the RIS, and activating the partial reflection unit; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated;
(2) changing the azimuth angle of the main lobe of the RIS reflected signal, enabling the RIS to scan by using beams in different directions and receiving data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal intensity, thereby determining a first azimuth angle range;
(4) activating more reflection units, performing steps (2) and (3) in the first azimuth angle range, and determining a second azimuth angle range; until all the reflection units are activated, thereby determining an optimal azimuth angle;
(5) giving an initial azimuth angle of a main lobe of a RIS reflection signal, and determining an optimal pitch angle in the same manner as the steps (1) to (4);
(6) and calculating the reflection coefficient of each reflection unit based on the optimal azimuth angle and the optimal pitch angle.
Further, the reflection unit is inactivated, which means that the reflection unit is in a substantially non-reflective state or a transmitted electromagnetic wave state.
Further, the reflection unit is activated by applying a voltage signal or an optical signal or a pressure signal.
Further, the reflection coefficient of the reflection unit is changed by applying a voltage signal or an optical signal or a pressure signal.
Further, the data fed back by the user is an indicator of the received signal strength of the user, including CQI, SNR, SINR, RSRP, RSRQ, and RSSI.
Further, the user performs a feedback after each scan, which is compared by the RIS; or, the RIS sends an instruction to the user to instruct the user to perform continuous scanning in the future K time sequences, and after the continuous scanning, the user compares the instruction to determine a beam direction with the maximum received signal intensity and feeds the beam direction back to the RIS.
Further, in the step (6), the reflection coefficient of each reflection unit is calculated based on the optimal azimuth and the optimal pitch angle and the steering vector of the RIS array.
In another aspect, the present invention provides a system for rapidly determining an intelligent super-surface reflection coefficient, comprising:
the optimal angle determining module is used for giving an initial angle of a main lobe of an RIS reflected signal, selecting a part of reflecting units on the RIS and activating the reflecting units; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle; changing the angle of the main lobe of the RIS reflected signal to enable the RIS to scan by using beams in different directions and receive data fed back by a user; comparing the data fed back after each scanning to determine a beam direction with the maximum received signal intensity, thereby determining a first angle range; activating more reflection units, changing the angle of the main lobe of the RIS reflection signal in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
and the reflection coefficient calculation module is used for calculating the reflection coefficient of each reflection unit based on the optimal angle.
Further, the reflection unit is inactivated, which means that the reflection unit is in a substantially non-reflective state or a transmitted electromagnetic wave state.
Further, the reflection unit is activated by applying a voltage signal or an optical signal or a pressure signal.
Further, the reflection coefficient of the reflection unit is changed by applying a voltage signal or an optical signal or a pressure signal.
Further, the data fed back by the user is an indicator of the received signal strength of the user, including CQI, SNR, SINR, RSRP, RSRQ, and RSSI.
Further, the user performs a feedback after each scan, which is compared by the RIS; or, the RIS sends an instruction to the user to instruct the user to perform continuous scanning in the future K time sequences, and after the continuous scanning, the user compares the instruction to determine a beam direction with the maximum received signal intensity and feeds the beam direction back to the RIS.
Further, based on the optimal azimuth angle and the optimal pitch angle, and the steering vector of the RIS array, the reflection coefficient of each reflection unit is calculated.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) the invention uses the method of the hierarchical scanning, the wave beam is from wide to narrow, utilize the wide characteristic of the wide beam coverage range at first, confirm the rough range of the receiving antenna, then scan with narrower wave beam in the direction covered by the wide beam in the first stage, in the smaller scanning range, use the wave beam with higher resolution, the wave beam will be higher to the precision of the receiving antenna too; and determining an optimal azimuth angle and an optimal pitch angle, and further calculating to obtain the reflection coefficient of each reflection unit. Therefore, the invention can have higher accuracy on the premise of ensuring low time complexity; meanwhile, the main beam of the reflected signal is enabled to point to the position of the user by changing the reflection coefficient of the RIS reflection unit, and the position of the user does not need to be moved.
(2) The method has strong universality, can be suitable for various RIS arrays such as square arrays, circular arrays and the like, has low time complexity of O (n) level and good performance, and has overall performance superior to that of a codebook exhaustive search method.
Drawings
Fig. 1 is a wireless communication system architecture diagram of an existing RIS;
FIG. 2 is a uniform rectangular area array model provided by the present invention;
FIG. 3 is a flow chart of a method for rapidly determining the reflection coefficient of an intelligent super-surface provided by the present invention;
fig. 4-1 to fig. 4-3 are respectively a beam pattern under the optimal condition, a beam pattern corresponding to the optimal codeword obtained by exhaustive search of a two-dimensional DFT codebook, and a beam pattern corresponding to the reflection coefficient obtained by calculation using the present invention, when not quantized;
fig. 5-1 to fig. 5-3 are respectively a beam pattern under the best condition, a beam pattern corresponding to the best codeword obtained by exhaustive search of a two-dimensional DFT codebook, and a beam pattern corresponding to a reflection coefficient obtained by calculation using the present invention when 1-bit quantization is performed;
fig. 6-1 to 6-4 show beam patterns corresponding to azimuth angles θ of-90 °, -30 °,30 °, and 90 ° when 4 rows of reflecting elements are activated, respectively;
fig. 7-1 to 7-4 show beam patterns corresponding to azimuth angles θ of 30 °,50 °,70 °, and 90 ° when 8 rows of reflecting units are activated, respectively;
fig. 8-1 to 8-3 show beam patterns corresponding to azimuth angles θ of 30 °,40 °, and 50 ° when 16 rows of reflection units are activated, respectively;
fig. 9-1 to 9-3 show beam patterns corresponding to azimuth angles θ of 40 °,45 °, and 50 ° when 32 rows of reflecting units are activated, respectively;
fig. 10-1 to 10-6 show beam patterns corresponding to azimuth angles θ of 45 °,46 °,47 °,48 °,49 °, and 50 ° when 64 rows of reflecting elements are activated, respectively.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The plane array model researched by the invention consists of M × N structural units, wherein M is the row number of the reflection units in the RIS array, and N is the column number of the reflection units in the RIS array. As shown in fig. 2, the antenna elements in the y-axis and z-axis are uniformly arranged, dyRepresenting the spacing between the elements of the y-axis, dzRepresenting the spacing between the z-axis antenna elements. In the model, a signal source is set as a far-field narrow-band signal, so that incident waves are equivalent to plane waves when reaching an antenna, and a pitch angle and an azimuth angle are respectively used
Figure BDA0002881878910000061
And theta. The antenna unit at an original point is taken as a reference point, a point P (x, y, z) in space is taken as an observation point, and a projection point of the observation point on an xoy plane is taken as P1(x, y, 0) whose projection of the unit vector in the direction of signal propagation onto the x, y, z axis is represented as:
Figure BDA0002881878910000062
therefore, the phase difference of the uniform linear arrays along the y-axis direction and the z-axis direction is respectively as follows:
Figure BDA0002881878910000071
Figure BDA0002881878910000072
therefore, the steering vectors of the uniform linear arrays in the directions of the y axis and the z axis are respectively as follows:
Figure BDA0002881878910000073
Figure BDA0002881878910000074
the steering vector of the whole planar array is:
Figure BDA0002881878910000075
the RIS array has M × N reflection units that can be independently controlled. When the RIS array is used for auxiliary communication, the relation of the transmitting and receiving signals is as follows:
Y＝GTQHX+N
wherein, Y is a user receiving signal, X is an AP transmitting signal, N is a noise signal, Q is a reflection coefficient matrix, G is an AP-IRS channel, and H is an IRS-UE channel.
Figure BDA0002881878910000076
aAP-RISIs the channel amplitude, phi, of the AP-RISAP-RISIs the phase of the channel and is,
Figure BDA0002881878910000077
represents the steering vector of the AP-RIS.
Figure BDA0002881878910000078
aRIS-UEIs the channel amplitude, phi, of the RIS-UERIS-UEIs the phase of the channel and is,
Figure BDA0002881878910000079
a steering vector representing a UE-RIS.
The reflection coefficient matrix is obtained by calculating after the RIS collects the information of the transmitting channel and the receiving channel and the phase shift of the reflection unit, and the RIS reflection coefficient matrix Q belongs to CM×MAnd (3) solving:
Q＝argmax{|GTQH|2}
wherein,
Figure BDA0002881878910000081
it should be noted that the phases of the RIS reflector unitThe shift parameters sometimes need to be discretized/quantized. In this case, the RIS reflection coefficient matrix Q calculated as described above needs to further calculate a suitable solution in the case of dispersion/quantization
Figure BDA0002881878910000082
Similarly, the nearest quantized/discrete value of each parameter in Q can be found out respectively, so as to obtain the reflection coefficient matrix under quantized/discrete condition
Figure BDA0002881878910000083
Changing equivalent channel G using reflection coefficient matrix QTThe strength of QH. In order to reduce the computational complexity, we can adopt a bit quantization manner to simplify the computation process of Q, and the more the number of bits is, the finer the quantization is.
Generally, as the RIS includes more reflective elements, the narrower the beam it reflects, and the more concentrated the energy. In the process of reflecting the electromagnetic wave by the reflecting unit, the main lobe has the maximum and most stable signal intensity. However, when we scan the beam, we need to quickly determine the angle range where the user is located, and avoid exhaustive search. Therefore, the scheme of the invention comprises the following steps: in the early stage, a wide-angle beam is used for scanning, an angle range covering the UE is determined after user feedback, and then a narrower beam is used for scanning in the angle range. The narrower the wave beam, the higher the resolution and the higher the scanning precision, and on the basis, a more accurate angle range is determined, the wave beam width is continuously narrowed, the scanning angle range is also continuously narrowed, and finally, the main lobe of the electromagnetic wave reflected by the RIS points to the direction of the user.
Method of generating a wide beam: the phase positions of partial reflection units can be adjusted to enable the partial reflection units not to basically reflect electromagnetic waves, and the rest reflection units can continue to work, so that wider beams can be generated to scan, and the effect of accurately positioning and quickly shaping the beams is achieved.
Referring to fig. 3, a flowchart of a method for rapidly determining an intelligent super-surface reflection coefficient provided by the present invention includes the following steps:
(1) given an initial angle of a main lobe of a RIS reflection signal, selecting a partial reflection unit on the RIS and activating the partial reflection unit; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle;
(2) changing the angle of the main lobe of the RIS reflected signal, enabling the RIS to scan by using beams in different directions and receiving data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal strength, thereby determining a first angle range;
(4) activating more reflection units, performing the steps (2) and (3) in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
(5) and calculating the reflection coefficient of each reflection unit based on the optimal angle.
It should be noted that the scanning may be performed by pitch angle scanning first, backward azimuth angle scanning first, or azimuth angle scanning first, pitch angle scanning last, or two-angle joint scanning, or by scanning obliquely after rotating the coordinate system.
The following specifically describes the operation steps of the present invention, taking azimuth angle scanning first and pitch angle scanning second as an example, and includes:
(1) giving an initial pitch angle of a main lobe of a RIS reflection signal, selecting a partial reflection unit on the RIS, and activating the partial reflection unit; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated;
(2) changing the azimuth angle of the main lobe of the RIS reflected signal, enabling the RIS to scan by using beams in different directions and receiving data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal intensity, thereby determining a first azimuth angle range;
(4) activating more reflection units, performing steps (2) and (3) in the first azimuth angle range, and determining a second azimuth angle range; until all the reflection units are activated, thereby determining an optimal azimuth angle;
(5) giving an initial azimuth angle of a main lobe of a RIS reflection signal, and determining an optimal pitch angle in the same manner as the steps (1) to (4);
(6) and calculating the reflection coefficient of each reflection unit based on the optimal azimuth angle and the optimal pitch angle.
Specifically, the reflection unit is activated by applying a voltage signal or an optical signal or a pressure signal.
Specifically, the reflection coefficient of the reflection unit is changed by applying a voltage signal or an optical signal or a pressure signal.
Specifically, the data fed back by the UE is an indicator of the received signal strength of the UE, and includes CQI, SNR, SINR, RSRP, RSRQ, RSSI, and the like.
Specifically, the UE may perform feedback once after each scan, compared by the RIS. Or an instruction can be sent to the UE by the RIS to inform the UE that the RIS can carry out continuous scanning in K time sequences in the future, and after the continuous scanning, the UE compares and determines the optimal scanning beam and feeds back to inform the RIS which reflection coefficient matrix the signal is strongest.
Specifically, the reflection coefficient of each reflection unit is calculated based on the optimal azimuth angle and the optimal pitch angle, and the steering vector of the RIS array.
Furthermore, based on the reflection coefficient of each reflection unit, the main beam of the reflection signal is enabled to point to the user direction by changing the reflection coefficient of the RIS reflection unit, and the effective communication between the wireless AP and the UE can be realized without changing the position of the UE.
In another aspect, the present invention provides a system for rapidly determining an intelligent super-surface reflection coefficient, comprising:
the optimal angle determining module is used for giving an initial angle of a main lobe of an RIS reflected signal, selecting a part of reflecting units on the RIS and activating the reflecting units; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle; changing the angle of the main lobe of the RIS reflected signal to enable the RIS to scan by using beams in different directions and receive data fed back by a user; comparing the data fed back after each scanning to determine a beam direction with the maximum received signal intensity, thereby determining a first angle range; activating more reflection units, changing the angle of the main lobe of the RIS reflection signal in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
and the reflection coefficient calculation module is used for calculating the reflection coefficient of each reflection unit based on the optimal angle.
The division of the modules in the system for rapidly determining the reflection coefficient of the intelligent super surface is only used for illustration, and in other embodiments, the system for rapidly determining the reflection coefficient of the intelligent super surface can be divided into different modules as required to complete all or part of the functions of the system.
The present invention is further described below in a specific application scenario.
1. Preconditions and associated presets
(1) There is a communication system consisting of an AP, a UE, and a passive RIS. The relevant parameters of AP and RIS are known, including the distribution of RIS reflecting units, etc.
(2) The size of the RIS reflection array is M × N, and the intervals of the reflection units are respectively Dy、Dz。
(3) The reflection coefficient of the reflection unit has n-bit quantization.
2. The concrete steps
(1) Setting a model initial value: frequency, velocity, wavelength, reflective element spacing, initial pitch angle, and azimuth angle.
(2) The broad beam is used to determine the approximate orientation of the receiving antenna.
(3) And (3) increasing the number of units of the electromagnetic wave capable of being reflected, and scanning in the azimuth range determined in the step (2).
(4) Beam scanning: when beam scanning is carried out, the receiving antenna needs to feed back corresponding data to the RIS controller in time after receiving signals.
3. Setting simulation parameters
RIS: 20 rows, 64 columns, 1280 total reflection units, 4 control units per column, and one control unit per columnControlling 5 reflection units; distance d between reflecting unitsz＝dy＝0.262λ。
Spatial position: establishing a coordinate system by taking the lower left corner unit of the RIS as a coordinate origin (0, 0, 0), wherein the RIS is positioned on a yoz plane, the reflecting units in the y direction and the z direction are uniformly distributed, and the distance is DyAnd Dz。
Emission source: frequency f is 5.5GHz and wave speed v is 3 × 108m/s, normal incidence.
Far field model: plane waves arrive at the RIS.
A receiving antenna: lying in the xoy plane, the azimuth angle is 45 °.
And (3) quantification: for each reflection coefficient qn,nA 1-bit quantization is performed.
The channel amplitude a is 1.
For Q ═ argmax { | GTQH|2G is a total 1-column vector, a reflection coefficient matrix Q (the phase shift of each element in Q is opposite to that of the corresponding guide vector element) with different directions can be generated by the reflection signal guide vector, and the reflection coefficient amplitude | Qn,n|＝1。
4. Simulation result
The best case is calculated from the known UE pitch and azimuth angles, in which case the RIS can provide the maximum gain.
Fig. 4-1 to 4-3 are beam patterns under the best condition, beam patterns corresponding to the best codewords obtained by exhaustive search of a two-dimensional DFT codebook, and beam patterns corresponding to reflection coefficients calculated by the present invention, when not quantized.
Fig. 5-1 to 5-3 show the beam pattern under the best condition, the beam pattern corresponding to the best codeword obtained by exhaustive search of the two-dimensional DFT codebook, and the beam pattern corresponding to the reflection coefficient obtained by calculation using the present invention, when quantizing 1-bit.
(1) Unquantized
(11) Firstly, 4 rows of reflection units are activated, and the azimuth angle theta is-90 degrees, -30 degrees, 90 degrees and the pitch angle are taken
Figure BDA0002881878910000121
Calculating the reflection coefficientThe matrix Q, the scan back view is shown in fig. 6-1 to 6-4.
(12) From (11), it can be determined that the receiving antenna is located between 30 ° and 90 °, the activated reflection units are increased to 8 columns, and then the azimuth angle θ is taken to be 30 °,50 °,70 °,90 °, and the scanning rear direction is as shown in fig. 7-1 to 7-4.
(13) From (12), it can be determined that the receiving antenna is located between 30 ° and 50 °, the activated reflection units are increased to 16 columns, and then the azimuth angle θ is taken to be 30 °,40 °,50 °, and the scanning rear direction is as shown in fig. 8-1 to 8-3.
(14) From (13), it can be determined that the receiving antenna is located between 40 ° and 50 °, the number of activated reflection units is increased to 32 columns, and then the azimuth angle θ is taken to be 40 °,45 °,50 °, and the scanning direction is as shown in fig. 9-1 to 9-3.
(15) It can be judged from (14) that the receiving antenna is located between 45 ° and 50 °, the activated reflection units are increased to 64 columns, and then the azimuth angle θ is 45 °,46 °,47 °,48 °,49 °,50 °, and the scanning rear direction is as shown in fig. 10-1 to fig. 10-6.
(16) From (15), it can be known that the signal strength of the receiving antenna is maximum when θ is 45 °, and therefore it can be determined that the azimuth angle of the receiving antenna is located near the direction of θ being 45 ° or the azimuth angle is 45 °.
(2)1-bit quantization
(21) After quantization, the beams are symmetric in two angular ranges of-90, 0 and 0, 90, so that only the 0, 90 scanning is required. The number of activated reflection elements is 8 columns, and the azimuth angle θ is 0 °,10 °,20 °,30 °,40 °,50 °,60 °,70 °,80 °,90 °.
(22) When the scanning result of (21) can judge that the intensity of the receiving antenna signal is maximum in the angle range [30 degrees and 50 degrees ], the number of activated reflecting units is increased to 16 columns, and the azimuth angle theta is taken to be 30 degrees, 35 degrees, 40 degrees, 45 degrees and 50 degrees.
(23) When the scanning result of (22) can judge that the intensity of the receiving antenna signal is maximum in the angle range [40 degrees and 50 degrees ], the activated reflection units are increased to 32 columns, and the azimuth angle theta is taken to be 40 degrees, 42.5 degrees, 45 degrees, 47.5 degrees and 50 degrees.
(24) When the scanning result of (23) can judge that the intensity of the receiving antenna signal is maximum in the angle range [42.5 °,47.5 ° ], the number of activated reflection units is increased to 64 columns, and the azimuth angle θ is 42.5 °,43 °,44 °,45 °,46 °,47 °,47.5 °.
(25) From the scanning result in (24), it can be known that the signal strength of the receiving antenna is the greatest when θ is 45 °, and therefore it can be determined that the azimuth angle of the receiving antenna is located near the direction of θ being 45 ° or the azimuth angle is 45 °.
Therefore, the invention has higher accuracy on the premise of ensuring low time complexity.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A method for rapidly determining the reflection coefficient of an intelligent super-surface, comprising the steps of:
(1) given the initial angle of the main lobe of the RIS reflection signal, selecting partial reflection units on the RIS and activating the partial reflection units; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle;
(2) changing the angle of the main lobe of the RIS reflected signal to enable the RIS to scan by using beams in different directions and receive data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal intensity, thereby determining a first angle range;
(4) activating more reflection units, performing the steps (2) and (3) in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
(5) and calculating the reflection coefficient of each reflection unit based on the optimal angle.
2. A method as claimed in claim 1, characterized in that the reflection unit is activated by means of the application of a voltage signal or an optical signal or a pressure signal.
3. The method of claim 1, wherein the reflection coefficient of the reflection unit is changed by applying a voltage signal or an optical signal or a pressure signal.
4. The method of claim 1, wherein the data fed back by the user is an indicator of received signal strength of the user, including CQI, SNR, SINR, RSRP, RSRQ, RSSI.
5. The method of claim 1, wherein the user performs feedback after each scan, and the RIS compares the feedback to determine a beam direction having the greatest received signal strength; or,
the RIS sends an instruction to the user to instruct the user to carry out continuous scanning in the future K time sequences, and after the continuous scanning, the user compares the instruction to determine a beam direction with the maximum received signal intensity and feeds the beam direction back to the RIS.
6. The method according to claim 1, wherein in the step (5), the reflection coefficient of each reflection unit is calculated based on the optimal angle and a steering vector of the RIS array.
7. A method for rapidly determining the reflection coefficient of an intelligent super-surface, comprising the steps of:
(1) giving an initial pitch angle of a main lobe of a RIS reflection signal, selecting a partial reflection unit on the RIS, and activating the partial reflection unit; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated;
(2) changing the azimuth angle of the main lobe of the RIS reflected signal, enabling the RIS to scan by using beams in different directions and receiving data fed back by a user;
(3) comparing the data fed back after each scanning in the step (2) to determine a beam direction with the maximum received signal intensity, thereby determining a first azimuth angle range;
(4) activating more reflection units, performing steps (2) and (3) in the first azimuth angle range, and determining a second azimuth angle range; until all the reflection units are activated, thereby determining an optimal azimuth angle;
(5) giving an initial azimuth angle of a main lobe of a RIS reflection signal, and determining an optimal pitch angle in the same manner as the steps (1) to (4);
(6) and calculating the reflection coefficient of each reflection unit based on the optimal azimuth angle and the optimal pitch angle.
8. A system for rapidly determining intelligent super-surface reflection coefficients, comprising:
the optimal angle determining module is used for giving an initial angle of a main lobe of an RIS reflected signal, selecting a part of reflecting units on the RIS and activating the reflecting units; each reflecting unit can reflect the electromagnetic signals emitted to the reflecting unit after being activated; the angles include a pitch angle and an azimuth angle; changing the angle of the main lobe of the RIS reflected signal to enable the RIS to scan by using beams in different directions and receive data fed back by a user; comparing the data fed back after each scanning to determine a beam direction with the maximum received signal intensity, thereby determining a first angle range; activating more reflection units, changing the angle of the main lobe of the RIS reflection signal in the first angle range, and determining a second angle range; until all the reflection units are activated, thereby determining an optimal angle;
and the reflection coefficient calculation module is used for calculating the reflection coefficient of each reflection unit based on the optimal angle.
9. The system of claim 8, wherein the user performs feedback after each scan, compared by the RIS, to determine a beam direction in which the received signal strength is greatest; or,
the RIS sends an instruction to the user to instruct the user to carry out continuous scanning in the future K time sequences, and after the continuous scanning, the user compares the instruction to determine a beam direction with the maximum received signal intensity and feeds the beam direction back to the RIS.
10. The system of claim 8, wherein the reflection coefficient of each reflection unit is calculated based on the optimal angle and a steering vector of the RIS array.
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