Doppler mitigation method based on smart reflective surfaces

Abstract

The application relates to a Doppler suppression method based on an intelligent reflecting surface, which comprises the following steps: a baseband single pilot signal p(t) with a sending time length of MT s is broadcast by a sending end; N phases are randomly generated, and the reflecting coefficients of corresponding RIS units are configured as the single pilot signal p(t) sent by the sending end passes through a wireless channel with the RIS with the configured coefficients; a signal y i (t) is received by a receiving end; the signal y i (t) received by the receiving end is sampled at a period T s to obtain r i (m) = y i (mT s ), and corresponding operation is performed; and finally, optimal Doppler suppression reflecting coefficients of the RIS are configured. This scheme effectively improves the ability of the RIS to suppress the influence of the Doppler effect on system performance, and greatly improves the reliability of vehicle networking communication after the RIS is introduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Doppler suppression in a vehicle-to-everything environment, and in particular to a Doppler suppression method based on an intelligent reflecting surface. BACKGROUND

[0002] A reconfigurable intelligent surface (RIS) is an artificial electromagnetic surface structure with programmable electromagnetic properties, developed from metamaterial technology. Traditional metamaterials can achieve unique physical phenomena such as electromagnetic black holes and electromagnetic cloaking, but they are described by equivalent medium parameters, which are single-function and fixed analog metamaterials. In recent years, the rapidly developing RIS technology has the characteristics of real-time programmable electromagnetic properties. Real-time programmable is a revolutionary technological leap, which allows the super surface to change its electromagnetic properties, thereby realizing various functions that traditional metamaterials cannot achieve.

[0003] V2X is the abbreviation of Vehicle to Everything communication, which involves wireless communication and coordination between vehicles and their environment. Through the use of low-latency communication and information sharing, V2X technology aims to help today's drivers and future autonomous systems coordinate more economically, efficiently, and safely. With the development of China's economy and the improvement of technological level, cars have become a part of people's daily life. At present, China has become the world's largest car producer and seller. The rapid growth of household vehicles and other vehicles has brought convenience to people's lives, but it has also inevitably led to traffic congestion, frequent traffic accidents, parking difficulties and a series of social problems. At the same time, people have put forward new requirements for the safe driving of vehicles, traffic management, information exchange between vehicles (such as collision warning, danger warning, traffic congestion detection, and information sharing), and other services. These needs have driven the rapid development of vehicle wireless communication networks. With the widespread application of intelligent transportation systems, the demand for increasing the sensing range of sensors beyond the scope of individual vehicles is more urgent than ever. The purpose of V2X research and standardization is to enable vehicles to communicate with each other and connect with road infrastructure, that is, to achieve the purpose of intelligent transportation through effective coordination of people, vehicles, and roads, which not only enhances the intelligent level of vehicles, but also greatly relieves urban road traffic pressure.

[0004] At present, with the progress and deployment of vehicle-to-everything technology, due to the higher frequency band used by vehicle-to-everything and the faster speed of vehicles, the signal is greatly affected by the Doppler effect when vehicle-to-everything communication is performed, thereby reducing the reliability of vehicle-to-everything communication. SUMMARY

[0005] To solve the above problems, the application provides a Doppler suppression method based on a smart reflective surface.

[0006] To achieve the above purpose, the application designs a Doppler suppression method based on a smart reflective surface, which is performed according to the following steps:

[0007] Step 1: a baseband single-tone pilot signal p(t) with a sending time length of T is broadcast by a sending end , wherein , and is a sampling period, and M is the number of sampling points of the length of the baseband single-tone pilot signal p(t);

[0008] Step 2: N phases are randomly generated, and the reflection coefficients of the respective units of the RIS are configured as , wherein is the complex phase of the reflection coefficient of the nth reflection unit of the RIS randomly generated for the ith time, 1≤n≤N, and N is the number of reflection units of the RIS;

[0009] Step 3: the single-tone pilot signal p(t) sent is subjected to a wireless channel with the RIS having a configured coefficient , and the signal received by the receiving end is ;

[0010] Step 4: the signal received by the receiving end is sampled at a period of T to obtain , and the following operation is performed:

[0011]

[0012] , wherein R is the discrete Fourier transform of r, and k is the discrete frequency domain index;

[0013] Step 5: the following processing is performed on :

[0014]

[0015]

[0016] , wherein is a threshold value , and the complex number modulo operation is represented by

[0017] Step 6: the ith equivalent Doppler spread is calculated ;

[0018] Step 7: it is judged whether is less than the equivalent Doppler spread threshold ; if the condition is met, then ​and go to step 9; if the condition is not satisfied, go to step 8;

[0019] Step 8: judge whether i is greater than the maximum number of iterations I, if the condition is satisfied, calculate: and go to step 9; otherwise, i = i + 1, go to step 2;

[0020] Step 9: configure the optimal Doppler suppression reflection coefficient of the RIS as .

[0021] Preferably, the single-tone pilot signal in step 1 is , wherein is the carrier frequency, .

[0022] Preferably, the reflection coefficient of each unit of the corresponding RIS in step 2 is configured as , wherein is the complex phase of the reflection coefficient of the nth reflection unit in the RIS randomly generated for the ith time, and .

[0023] Preferably, in step 4:

[0024]

[0025] , wherein .

[0026] Preferably, the threshold value in step 5 is , which can be set as:

[0027]

[0028] , wherein is an adjustable proportion coefficient, and the value range is represents the complex modulus operation.

[0029] Preferably, in step 7, judge whether is less than the equivalent Doppler spread threshold value ; wherein is the maximum mobile speed supported by the system, is the carrier wavelength, is an adjustable proportion coefficient, and .

[0030] The present application provides a Doppler suppression method based on intelligent reflecting surface, which uses a single-tone pilot signal to estimate the optimal Doppler suppression reflection coefficient of the RIS, effectively improves the ability of the RIS to suppress the influence of the Doppler effect on the system performance, and greatly improves the reliability of the vehicle networking communication after introducing the RIS. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a flow chart of a method for Doppler suppression based on a smart reflective surface according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present application will be described hereinafter with reference to the accompanying drawings, in which the preferred embodiments of the present application are shown. It should be understood, however, that the preferred embodiments described herein are intended to illustrate the general principles of the present application and are not intended to limit the present application to such preferred embodiments.

[0033] Embodiment 1.

[0034] As shown in Figure 1, the embodiment describes a method for Doppler suppression based on a smart reflective surface, which is characterized by the following steps: Figure 1

[0035] Step 1: The sending end broadcasts a baseband single-tone pilot signal p(t) with a sending time length of T , where T is the sampling period, and M is the number of sampling points of the length of the baseband single-tone pilot signal p(t).

[0036] Step 2: Randomly generate N phases and configure the reflection coefficients of the respective units of the RIS as , where is the complex phase of the reflection coefficient of the nth reflection unit of the RIS randomly generated for the ith time, 1≤n≤N, and N is the number of reflection units of the RIS.

[0037] Step 3: The sent single-tone pilot signal p(t) passes through the wireless channel with the RIS having the configured coefficient , and the signal received by the receiving end is .

[0038] Step 4: The signal received by the receiving end is sampled at a period of T to obtain , and the following operation is performed:

[0039]

[0040] where R is the discrete Fourier transform of r, and k is the discrete frequency domain index.

[0041] Step 5: The following processing is performed on :

[0042]

[0043]

[0044] where is a threshold value , and the complex number modulo operation is represented by mod.​​

[0045] Step 6: Calculate the ith equivalent Doppler spread ;

[0046] Step 7: Determine whether is less than the equivalent Doppler spread threshold ; if the condition is true, then , and go to Step 9; if the condition is not true, go to Step 8;

[0047] Step 8: Determine whether i is greater than the maximum iteration number I, if the condition is true, then calculate: , and go to Step 9; otherwise, i = i + 1, and go to Step 2;

[0048] Step 9: Configure the optimal Doppler suppression reflection coefficient of the RIS as .

[0049] Preferably, the single-tone pilot signal in Step 1 is , wherein is the carrier frequency, .

[0050] Preferably, the reflection coefficient of each unit of the corresponding RIS in Step 2 is configured as , wherein is the complex phase of the reflection coefficient of the nth reflection unit in the RIS randomly generated for the ith time, and .

[0051] Preferably, in Step 4, the following is performed:

[0052]

[0053] , wherein .

[0054] Preferably, the threshold value in Step 5 is , which can be set as:

[0055]

[0056] , wherein is an adjustable proportionality coefficient, and the value range is represents the complex modulus operation.

[0057] Preferably, in Step 7, it is determined whether is less than the equivalent Doppler spread threshold value ; wherein is the maximum mobile speed supported by the system, is the carrier wavelength, is an adjustable proportionality coefficient, and .

[0058] The embodiment provides a Doppler suppression method based on an intelligent reflecting surface, an optimal Doppler suppression reflection coefficient of the RIS is estimated by using a single pilot signal, the ability of the RIS to suppress the influence of the Doppler effect on system performance is effectively improved, and the reliability of vehicle networking communication after the RIS is introduced is greatly improved.

[0059] In the description of the present application, it should be pointed out that the terms "vertical", "upper", "lower", "horizontal" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0060] In the description of the present application, it should be pointed out that unless otherwise specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above-mentioned terms in the present application can be understood according to the specific circumstances.

[0061] Finally, it should be pointed out that: the above-mentioned only for the preferred embodiments of the present application, and does not limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for Doppler mitigation based on smart retro-reflective surfaces, characterized by The following steps are performed: Step 1: the sending end broadcasts a baseband single-tone pilot signal with a sending time length of , wherein , and is a sampling period, and M is the number of sampling points of the length of the baseband single-tone pilot signal p(t). Step 2: Randomly generate N phases and configure the reflection coefficients of the respective RIS units as where is the complex phase of the reflection coefficient of the nthreflection unit of the RIS for the ithrandom generation, 1≤n≤N, N is the number of reflection units of the RIS; Step 3: The transmitted single-tone pilot signal p(t) passes through the wireless channel with RIS with configured coefficients , and the received signal at the receiver is ; Step 4: Operation on the signal received by the receiving end with a period sampling, obtaining and performing the following operation: where R is a discrete Fourier transform of r, and k is a discrete frequency domain index; Step 5: To a solution of was treated as follows: wherein is a threshold value denotes a complex modulo operation; Step 6: Calculate the ith equivalent Doppler spread ; Step 7: Determine if is less than or equal to the equivalent Doppler spread threshold ; if so, then and go to Step 9; If the condition is not true, go to step 8; Step 8: Determine if i is greater than the maximum number of iterations I. If so, calculate: and go to Step 9; otherwise, i = i + 1 and go to Step 2. Step 9: Configure the optimal Doppler suppression reflection coefficient of the RIS as .

2. The method of claim 1, wherein the single tone pilot signal in step 1 is wherein is the carrier frequency, .

3. The Doppler suppression method based on a smart reflective surface according to claim 1, characterized in that: configuring the reflection coefficients of the respective RIS units in step 2 to wherein is the complex phase of the reflection coefficient of the n-th reflection unit in the i-th randomly generated RIS, and .

4. The Doppler suppression method based on a smart reflective surface according to claim 1, characterized in that: As described in step 4: wherein .

5. The method of claim 1, wherein the method is based on a smart reflective surface. The threshold value described in step 5 may be set to: wherein is an adjustable proportionality coefficient, with a value range of .

6. The method of claim 1, wherein the method is based on a smart reflective surface. the equivalent Doppler spread threshold value described in step 7 ; wherein is the maximum mobile speed supported by the system, is the carrier wavelength, is the adjustable scaling factor, and .

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