Reconfigurable intelligent surface auxiliary communication system visual area detection method

Abstract

The invention discloses a method for detecting a visual area of a reconfigurable intelligent surface-assisted communication system, which comprises the following steps of: setting phases of all elements of an RIS (Reconfigurable Information System) to be 0 degree in a 0-th time slot, and receiving a signal sent from user equipment by a base station; the RIS elements are equally grouped, the phases of the elements in each group are sequentially set to be 180 degrees in the later time slot, meanwhile, the phases of the elements in other groups are kept to be 0 degree, and the base station receives signals sent by the user equipment in the time slots; sequentially subtracting the signals received in the 0th time slot from the signals received in the later time slots, obtaining the power of the difference signals, comparing the power with a threshold value, judging completely shielded groups, and forming an initial visible area; and detecting inwards from the boundary of the initial visual area to form a final visual area. According to the invention, accurate visual area detection is realized with low complexity and measurement overhead.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technologies, and particularly relates to a method for detecting a visible area of a reconfigurable intelligent surface-assisted communication system. Background Art

[0002] Reconfigurable intelligent surfaces (RISs) are considered to be one of the most promising solutions to meet the technical requirements of sixth-generation mobile communication systems and have sparked extensive discussions in recent years. An RIS is a surface composed of a large number of passive reflection units, which is placed between a base station and user equipment to provide a supplementary link. It can effectively improve the transmission performance and expand the coverage area. Compared with traditional relay systems, RISs have the advantages of low cost, low power consumption, and easy deployment.

[0003] To fully exploit the potential of RISs, it is necessary to estimate the channels in and out of the RISs and obtain accurate channel state information, which is crucial for achieving the passive beamforming gain of RISs. However, most of the current studies on RIS-assisted channel estimation assume ideal propagation conditions and ignore the near-field effect caused by the extremely large scale of RISs and the shadow effect of the channel between the RISs and user equipment caused by environmental obstacles. Under the influence of the shadow effect, only a part of the RIS elements may be able to receive and manipulate the electromagnetic wave signals sent by user equipment. We call this part of the RIS elements visible to the user equipment the visible area of the user equipment. Only by accurately estimating the visible area of each user equipment can the accuracy of subsequent channel estimation and user positioning be ensured, and the advantages of RISs can be maximally utilized.

[0004] Previously, some RIS-assisted channel estimation works have considered the visible area of user equipment, but their visible area detection depends on the rough channel estimation results. As the scale of RISs increases, the number of training signals required for channel estimation also increases. In a multi-user environment or under more complex signal processing requirements, the complexity of channel estimation may increase sharply. There are also works that have proposed a low-complexity RIS fault element diagnosis method. However, it requires pre-measuring thresholds using a fault-free RIS in a laboratory environment, which is difficult to implement in a real environment. In addition, when the scale of RISs is large, detecting all RIS elements one by one requires a considerable detection overhead.

[0005] In summary, how to accurately detect the visible area of user equipment with low complexity and detection overhead, so as to ensure that subsequent RIS-assisted channel estimation has high accuracy and low complexity, has become a difficult problem faced by RIS-assisted communication systems. Summary of the Invention

[0006] Technical problem: To solve the above problems, the present invention provides a method for detecting the visible area of a RIS-assisted communication system, aiming to achieve relatively accurate visible area detection with relatively low complexity and measurement overhead, so as to ensure high accuracy and low complexity of subsequent RIS-assisted channel estimation.

[0007] Technical solution: A method for detecting the visible area of a RIS-assisted communication system according to the present invention includes the following steps:

[0008] A method for detecting the visible area of a reconfigurable intelligent surface-assisted communication system, the method includes the following steps:

[0009] Step 1: In the 0th time slot, set the phases of all elements of the RIS to 0°, and the base station receives the signals sent from the user equipment.

[0010] Step 2: Divide all elements of the RIS into L groups evenly. In the lth time slot, set the phases of all elements in the lth group to 180°, and keep the phases of the elements in other groups unchanged at 0°. The base station receives the signals sent from the user equipment in these time slots, where l = 1, …, L.

[0011] Step 3: Subtract the signals received in Step 1 from the signals received in Step 2 in turn, obtain the powers of these difference signals, and compare them with a threshold. If the power of the difference signal exceeds the threshold, it is determined that the RIS elements in this group are completely blocked, otherwise it is considered that this group is not completely blocked; according to this judgment result, exclude the completely blocked groups to form an initial visible area.

[0012] Step 4: Detect from the boundary of the initial visible area inward to form the final visible area.

[0013] Further, in Step 2, all elements of the RIS are divided into L groups evenly, where the number of groups γ is the minimum ratio covered by the visible area, where represents rounding up.

[0014] Further, Step 3 is specifically:

[0015] Step 3.1: Subtract the signals received in the 0th time slot from the signals received in the lth time slot in turn, and obtain the powers of these L difference signals, where l = 1, …, L.

[0016] Step 3.2: Measure the noise power of the current environment. The threshold can be set according to multiples of the noise power. To better adapt to different transmit power ranges, especially when the transmit power of the user equipment usually ranges from 10 dBm to 30 dBm, the threshold should be dynamically adjusted between 6 times and 16 times. When the transmit power is low, the threshold can be appropriately set to 6 times the noise power to optimize performance and system stability. When the transmit power is high, a slightly higher multiple can be selected to meet specific system requirements. This adjustment mechanism aims to flexibly adjust the threshold according to changes in environmental noise and transmit power, thereby ensuring the best performance of the system under various conditions;

[0017] Step 3.3: Compare the L differential signal powers obtained in Step 3.1 with the threshold set in Step 3.2, and record the group index numbers corresponding to all differential signals with powers smaller than the threshold. All components in the groups corresponding to these index numbers are judged to be completely blocked. According to different situations of the group index numbers and the number of components in the group, calculate the boundary index of the blocked area, and then calculate the initial visible area.

[0018] Further, Step 4 is specifically as follows:

[0019] Step 4.1: Detect components one by one from the front boundary of the initial visible area backward. That is, in each time slot, set the phase of the component to be detected to 180°, and keep the phases of the remaining components unchanged at 0°. The base station receives the signal sent from the user equipment in this time slot, subtract the received signal in this time slot from the signal received in Step 1 to obtain the differential signal power, and then compare this differential signal power with the threshold set in Step 3.2. If it is less than the threshold, it is judged that the component is blocked; if it is greater than the threshold, it is judged that the component is in the visible area. Perform the same one-by-one component detection process on the components after the front boundary as described above until a component in the visible area is detected, and then stop detecting backward;

[0020] Step 4.2: Detect from the rear boundary of the initial visible area forward. The detection method is the same as that described in Step 4.1 until a component in the visible area is detected, and then stop detecting forward;

[0021] Step 4.3: The front boundary obtained in Step 4.1 and the rear boundary obtained in Step 4.2 are the final boundaries of the visible area detection.

[0022] Further, the specific steps for calculating the initial visible area in Step 3.3 are as follows: The front boundary n up and the rear boundary n down are calculated according to the following four situations:

[0023] Situation 1: The recorded group indexes are the first few groups; according to the maximum value t in the recorded indexesmax , the initial boundary can be denoted as

[0024] Case 2: The recorded packet indices are the last few packets; according to the minimum value t in the recorded indices min , the initial boundary can be denoted as

[0025] Case 3: The recorded packet indices are the first few packets and the last few packets; according to the maximum value t and the minimum value t in the recorded indices max and the minimum value t min , the initial boundary can be denoted as

[0026] Case 4: No packet index is recorded; the initial boundary can be denoted as

[0027] where a is the number of components in each packet; N is the number of reflection units;

[0028] The boundary of the initial visible region can be determined by recording packet indices smaller than the threshold.

[0029] The method for detecting the visible region of a RIS-assisted communication system according to the present invention has the following advantages:

[0030] 1. Most of the existing visible region detection schemes for RIS-assisted communication systems are based on rough channel estimation. The proposed scheme in the present invention utilizes the continuity of the visible region and develops a method for detecting the visible region of a RIS-assisted communication system by grouping, which can accurately detect the visible region of the user equipment with relatively low complexity and measurement overhead.

[0031] 2. Due to the power accumulation effect brought by reversing the components in one packet at a time in the grouping strategy of the proposed scheme in the present invention, compared with the method of detecting one by one, the detection accuracy of the visible region in the case of poor signal-to-noise ratio conditions can be improved. Description of the Drawings

[0032] Figure 1 It is a diagram of the initial visible region and the initial occlusion distribution in the case of grouping for a RIS-assisted communication system provided by an embodiment of the present invention;

[0033] Figure 2 It is a flowchart of the visible region detection algorithm for a RIS-assisted communication system provided by an embodiment of the present invention. Detailed Embodiment

[0034] In the following description, specific values such as the number of RIS components and the number of groups are proposed for the purpose of illustration rather than limitation, so as to thoroughly understand the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details.

[0035] As shown Figure 1 in the figure, a method for detecting the visible area of a RIS-assisted communication system according to the present invention includes the following steps:

[0036] Step 1: In the 0th time slot, set the phases of all elements of the RIS to 0°, and the base station receives the signal sent from the user equipment;

[0037] Step 2: Divide the RIS elements into L groups evenly. In the lth (l = 1, …, L) time slot, set the phases of all elements in the lth group to 180°, and keep the phases of the elements in other groups unchanged at 0°. The base station receives the signals sent from the user equipment in these time slots;

[0038] Step 3: Subtract the signal received in Step 1 from the signal received in Step 2 in sequence, obtain the power of these difference signals, and compare it with the threshold. If the power of the difference signal exceeds the threshold, it is determined that the RIS elements in this group are completely blocked; otherwise, it is considered that this group is not completely blocked. According to this judgment result, exclude the completely blocked groups to form an initial visible area;

[0039] Step 4: Detect from the boundary of the initial visible area inward to form the final visible area.

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will be described in detail with reference to the accompanying drawings. A method for detecting the visible area of a RIS-assisted communication system provided by an embodiment of the present invention, where the base station and the RIS are both uniform linear arrays, and are respectively equipped with M antennas and N = 2 Q (Q >> 1) reflection units. The signal sent by the single-antenna user equipment is reflected by the RIS and then received by the base station.

[0041] The present invention models the visible area of the user equipment as a continuous element subset of the RIS, and assumes that the size of the visible area is not less than γN, where 0 < γ < 1 represents the minimum coverage rate.

[0042] Step 1. In the 0th time slot, set the phases of all elements of the RIS to 0°. The base station receives the signal y0 sent from the user equipment;

[0043] Step 2. Divide the RIS elements into L groups evenly. In the lth (l = 1, …, L) time slot, set the phases of all elements in the lth group to 180°, and keep the phases of the elements in other groups unchanged at 0°. The base station receives the signals sent from the user equipment in these time slots. The specific steps are as follows:

[0044] 2.1) Evenly divide all elements of the RIS into L = 2 q groups, where q satisfies The smallest integer. Ensure that all components in at least one group are within the visible area, and the number of components a in each group is 2 Q-q As large as possible to ensure effective reduction of measurement overhead;

[0045] 2.2) In the t = 1,..., L time slots, sequentially set the phase of each component in each group to 180°, and keep the phases of the components in the remaining groups unchanged at 0°. The base station receives the signal y sent from the user equipment in the t-th time slot t .

[0046] Step 3: Sequentially subtract the signal received in Step 1 from the signal received in Step 2, calculate the power of these difference signals, and compare with the threshold to determine the completely blocked groups and form the initial visible area. The specific steps are as follows:

[0047] 3.1) Sequentially subtract y0 from y t to obtain the difference signal Δ t = y0 - y t , and calculate the power P t of Δ t ;

[0048] 3.2) Measure the noise power σ 2 of the current environment. When the transmission power is large, set the threshold to 16σ 2 . At this time, as long as there is one component in the group within the visible area, P t is very likely to be much larger than 16σ 2 ; when the transmission power is small, the threshold can be appropriately reduced, such as set to 8σ 2 , to ensure fairness in the judgment of the visible area and the blocked area;

[0049] 3.3) Compare P t with the threshold set in 3.2), and record the group indexes of all groups smaller than the threshold. All components in the groups corresponding to these indexes are judged to be completely blocked. Calculate the boundary index of the blocked area according to the group index and the number of components in the group, and then calculate the initial visible area. Specifically, the front boundary n up and the rear boundary n down of the initial visible area can be calculated according to the following four cases:

[0050] Case 1: The recorded group indexes are the first few groups. According to the maximum value t max in the recorded indexes, the initial boundary can be recorded as

[0051] Case 2: The recorded group indexes are the last few groups. According to the minimum value t min in the recorded indexes, the initial boundary can be recorded as

[0052] Case 3: The recorded grouping indexes are the first several groups and the last several groups. According to the maximum value t max and the minimum value t min , the initial boundary can be recorded as

[0053] Case 4: No grouping index is recorded. The initial boundary can be recorded as

[0054] The calculation processes of these four cases reflect the technical innovation points of the present invention, that is, the boundary of the initial visible area can be accurately determined by recording the grouping indexes smaller than the specific threshold. At this time, there may still be some components in the obtained visible area that are blocked, such as Figure 1 as shown

[0055] Step 4: Detect inward from the boundary of the initial visible area to form the final visible area. The specific steps are as follows:

[0056] 4.1) Detect each component one by one backward from the front boundary n down of the initial visible area, that is, set the phase of the component to be detected to 180° in each time slot, and keep the phases of the remaining components unchanged at 0°. The base station receives the signal sent from the user equipment in this time slot, subtracts the received signal in this time slot from the signal y0 received in step 1 to obtain the difference signal power, and then compares the difference signal power with the threshold set in 3.2). If it is less than the threshold, it is determined that the component is blocked; if it is greater than the threshold, it is determined that the component is in the visible area; successively perform the above detection on the components after the front boundary until a component in the visible area is detected, and stop the detection continuing backward;

[0057] 4.2) Detect each component one by one forward from the rear boundary n up of the initial visible area. The detection method is the same as that described in 4.1), until a component in the visible area is detected, and stop the detection continuing forward;

[0058] 4.3) The final boundary of the visible area detection can be obtained from the front boundary obtained in 4.1) and the rear boundary obtained in 4.2).

[0059] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system, characterized in that: The method comprises the following steps: Step 1: In the 0th time slot, the phases of all elements of the RIS are set to 0°, and the base station receives the signal sent from the user equipment; Step 2: The RIS elements are divided into L groups. In the lth time slot, the phases of all elements in the lth group are set to 180°, and the phases of elements in other groups remain unchanged at 0°. The base station receives the signals sent from the user equipment in these time slots, where l = 1, ..., L. Step 3: Subtract the signal received in step 1 from the signal received in step 2 in turn to obtain the power of these difference signals and compare them with the threshold. If the power of the difference signal exceeds the threshold, it is determined that the RIS element of the group is completely blocked, otherwise it is considered that the group is not completely blocked. According to the judgment result, the completely blocked group is excluded to form an initial visible area. Step 4: Detect inward from the boundary of the initial visible area to form the final visible area.

2. The method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system according to claim 1, characterized in that: In step 2, all components of the RIS are divided into L groups, where the number of groups is γ is the minimum coverage ratio of the visible area, where Represents round up.

3. The method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system according to claim 1, characterized in that: The step 3 is specifically as follows: Step 3.1, sequentially subtract the signal received at the 0th time slot from the signal received at the lth time slot to obtain the power of the L difference signals, where l = 1, ..., L; Step 3.2, measure the noise power of the current environment, and set the threshold according to the multiple of the noise power; Step 3.3, compare the L difference signal powers obtained in step 3.1 with the threshold set in step 3.2, and record the group index numbers corresponding to all difference signals with powers smaller than the threshold. All elements in the groups corresponding to these index numbers are judged to be completely blocked. According to the different situations of the group index number and the number of elements in the group, the boundary index of the blocked area is calculated, and then the initial visible area is calculated.

4. The method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system according to claim 3, characterized in that: In step 3.2, the threshold is dynamically adjusted between 6 and 16 times the noise power.

5. The method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system according to claim 3, characterized in that: The step 4 is specifically as follows: Step 4.1, detect each element backward from the front boundary of the initial visible area, that is, set the phase of the detected element to 180° in each time slot, and keep the phase of other elements at 0° unchanged, and the base station receives the signal sent from the user equipment in the time slot, and subtracts the signal received in step 1 from the received signal in the time slot to obtain the difference signal power, and then compares the difference signal power with the threshold set in step 3.

2. If it is less than the threshold, it is determined that the element is blocked, and if it is greater than the threshold, it is determined that the element is in the visible area; the same element-by-element detection process as above is performed on the elements behind the front boundary in turn, until an element in the visible area is detected, and stop continuing to detect backward; Step 4.2, detect from the rear boundary of the initial visible area forward, the detection method is the same as that described in step 4.1, until a component is detected in the visible area, and stop detecting forward; The front boundary obtained in step 4.3 and step 4.1 and the rear boundary obtained in step 4.2 are the final boundaries of the visible area detection.

6. The method for detecting visible area of ​​a reconfigurable intelligent surface-assisted communication system according to claim 3, characterized in that: The initial visible area calculated in step 3.3 specifically includes the following steps: the front boundary n of the initial visible area up and the rear boundary n down The calculation is based on the following four situations: Case 1: The recorded group index is the first few groups; according to the maximum value t in the recorded index max , the initial boundary can be recorded as Case 2: The recorded group index is the last few groups; according to the minimum value t in the recorded index min , the initial boundary can be recorded as Case 3: The recorded group indexes are the first and last groups; according to the maximum value t in the recorded index max and the minimum value t min , the initial boundary can be recorded as Case 4: No grouping index is recorded; the initial boundary can be recorded as Where a is the number of elements in each group; N is the number of reflection units; The boundary of the initial visible area can be determined by grouping index records that are smaller than the threshold.

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