KR102165835B1 - Method for tracking beam via particle filter in mmWave communication and base station thereof - Google Patents

Abstract

According to an embodiment of the present invention, disclosed is a beam tracking method based on a millimeter wave communication particle filter. The beam tracking method comprises: a reference signal receiving step of receiving a reference signal from a mobile terminal moving from a first point to a second point through a communication network established with a base station at the first point after time elapses from the first point to the second point; a mobility estimating step of estimating mobility of the mobile terminal from a first time point to a second time point based on a particle filter by using the reference signal received by the base station as a measurement model at the second time point; and a communication network reconstruction step of establishing a new communication network between the base station and the mobile terminal at the second point based on the estimated mobility, and the base station transmitting preset data to the mobile terminal.

Description

Millimeter wave communication particle filter-based beam tracking method, and a base station implementing the method {Method for tracking beam via particle filter in mmWave communication and base station thereof}

The present invention is an invention of a particle filter-based beam tracking method and a base station implementing the method. More specifically, in implementing millimeter wave communication, a path loss phenomenon due to high frequencies is minimized based on a particle filter. The present invention relates to a possible beam tracking method and a base station implementing the method.

The fifth generation (5G) mobile communication requires high data traffic technology requirements such as high efficiency spectrum, improved coverage, and large-scale connectivity. One of the major candidates for solving these 5G technology requirements is millimeter wave communications. The millimeter wave frequency range is 30GH to 300GHz, and 28GHz, 30GHz, 60GHz and E bands are mainly used.

The millimeter wave has a wavelength of about millimeters and has been traditionally assigned and used for military purposes. In particular, military satellite communications in the 12~45GHz band, vehicle-mounted military radar electronic warfare weapons in the 3~95GHz band, and missile tracking devices have been studied based on millimeter wave communication systems. The reason millimeter wave communication is an appropriate communication system for military use is that the frequency band is wide, so there is little fear of being eavesdropped and a lot of information can be exchanged at once.

However, the millimeter wave communication can secure high data traffic with a high frequency and a wide frequency band, but a serious path loss due to high frequencies is pointed out as a problem. As a method for solving this problem, a beamforming technology using a large array antenna is drawing attention.

The main difference between millimeter-wave communication and traditional communication systems is that they use a large array antenna, which provides the necessary beamforming techniques for channel estimation and beam alignment.

A large array antenna can obtain a high beamforming gain, but as the number of array antennas increases, the beam width becomes narrow and it is difficult to align the beam pairs. In particular, millimeter-wave communication is applied to mobile systems such as cellular systems, vehicle-to-infrastructure (V2I), and vehicle-to-vehicle (V2V) communication, and in this case, beam ratio alignment due to mobility is a very serious problem. To solve this problem, real-time beam rearrangement through beam tracking has been proposed, and a new beam tracking scheme is required to reduce beam alignment overhead.

1.Korea Patent Publication No. 10-2019-0016959 (published on February 19, 2019) 2. Korean Patent Publication No. 10-2013-0094177 (published on August 23, 2013) 3. Korean Patent Registration No. 10-1248150 (2013.04.02 announcement)

Analysis of Radar Cross Section of the Tank and Its Application at Millimeter Wave W-Band (released on September 30, 2017)

The technical problem to be solved by the present invention is to provide a particle filter-based beam tracking method capable of reducing beam alignment overhead and minimizing path loss as a beam realignment method through real-time beam tracking.

The method according to an embodiment of the present invention for solving the above technical problem is a base station from the first point to the mobile terminal moving from the first point to the second point after time elapses from the first point to the second point. A reference signal receiving step of receiving a reference signal through the established communication network; A mobility estimating step of estimating mobility of the mobile terminal from a first time point to a second time point based on a particle filter by using the reference signal received by the base station as a measurement model at a second time point; And a communication network reconstruction step of establishing a new communication network between the base station and the mobile terminal at the second point on the basis of the estimated mobility, and transmitting preset data to the mobile terminal by the base station.

The base station according to another embodiment of the present invention for solving the above technical problem, from the first point to the second point from the mobile terminal moved from the first point to the second point in time, A receiving unit for receiving a reference signal through the established communication network; A control unit for estimating mobility of the mobile terminal from a first time point to a second time point based on a particle filter by using the received reference signal as a measurement model at a second time point; And a transmitter configured to establish a new communication network with the mobile terminal at the second point on the basis of the estimated mobility and transmit preset data to the mobile terminal.

An embodiment of the present invention may provide a computer-readable recording medium storing a program for executing the method.

According to the present invention, when a beam misalignment occurs due to a movement of a mobile terminal in millimeter wave communication, it is possible to quickly and accurately perform beam rearrangement to reduce overhead and mitigate serious path loss.

1 is a diagram collectively showing an entire communication system according to the present invention.
2 is a block diagram illustrating an example of a base station for implementing the present invention.
3 is a block diagram showing an example of a mobile terminal for implementing the present invention.
4 is a flowchart illustrating an example of a particle filter-based beam tracking process according to the present invention.
5 is a flowchart schematically illustrating an example of a process in which a controller tracks a beam based on a particle filter.

As for terms used in the embodiments, general terms that are currently widely used as possible are selected while considering functions in the present invention, but this may vary according to the intention or precedent of a technician working in the field, the emergence of new technologies, and the like. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, the meaning of the terms will be described in detail in the description of the corresponding invention. Therefore, the terms used in the present invention should be defined based on the meaning of the term and the overall contents of the present invention, not a simple name of the term.

When a part of the specification is said to "include" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated. In addition, terms such as "... unit" and "... module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various forms and is not limited to the embodiments described herein.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

In addition, although the present disclosure describes embodiments using terms used in some communication standards (eg, 3GPP), this is only an example for description. Various embodiments of the present disclosure may be easily modified and applied to other communication systems.

This patent proposes a particle filter-based beam tracking algorithm. The relative motion of the transmitter and receiver is modeled by position, velocity, and acceleration.

Relative motility changes over time and this is represented by a nonlinear model. Every hour, the transmitter transmits pilot signals to the receiver, and the received signal is used as an observation model. The receiving end estimates the relative motion state using a particle filter, converts it into angle of departure and angle of arrival information, rearranges the beam, and performs beam tracking.

1 is a diagram collectively showing an entire communication system according to the present invention.

Referring to FIG. 1, it can be seen that the entire communication system according to the present invention includes a base station 110, a mobile terminal 120 at a first point of view, and a mobile terminal 130 at a second point of view. Each of the configurations disclosed in FIG. 1 is a representative representation of nodes using a radio channel in a wireless communication system. Although only one base station is shown in FIG. 1, one communication system according to the present invention includes one. The above base stations may be further included.

First, the base station 110 is a network infrastructure that provides wireless access to mobile terminals 120 and 130.

The mobile terminal 120 at the first point of view has mobility 140 and at the second point of view refers to a terminal having mobility 140 that moves to a second point where the mobile terminal 130 at the second point of view is located. The mobile terminal 130 at the second point of view refers to a mobile terminal when the mobile terminal 120 at the first point of view, located at the first point at the first point of time, has moved to the second point. That is, in the overall communication system according to the present invention, the terminal communicating with the base station 110 is a mobile terminal having mobility 140, and for convenience of explanation, a first point at a first point of view and a second point at the second point of time It is assumed to be located in

In this case, the mobility 140 can be expressed as a dynamic model between the mobile terminal 120 at the first point of view and the mobile terminal 130 at the second point of view, and the dynamic model is linear and non-linear. linear) function has a mixed form.

In addition, at the first point of view, the base station 110 communicates with the mobile terminal 120 at the first point of view while maintaining beam alignments 111 and 121, and at the second point of view, the base station 110 Through the mobile terminal 130 and the particle filter of the beam realignment (beam realignment) (112, 131) and maintain the communication connection.

As a specific example of the mobile terminal, a tank equipped with millimeter wave communication equipment, a helicopter (helicopter or chopper), a mobile radar unit, etc. may be a mobile terminal in the present invention.

2 is a block diagram illustrating an example of a base station for implementing the present invention.

Referring to FIG. 2, it can be seen that the base station 110 includes a wireless communication unit 210, a backhaul communication unit 220, a storage unit 230 and a control unit 240.

The wireless communication unit 210 performs functions for transmitting and receiving signals through a wireless channel, and is specified as a transmitter, a receiver, or a transceiver, or is considered to include a transmitter and a receiver.

The backhaul communication unit 220 provides an interface for performing communication with other nodes in the network.

The storage unit 230 stores data such as program and setting information for the operation of the base station 110.

The controller 240 controls overall operations of the base station 110 such as generating a signal or processing a signal while referring to data stored in the storage unit 230.

As an embodiment, the control unit 240 may implement a particle filter-based beam tracking method according to the present invention while controlling a transmitting unit and a receiving unit included in the wireless communication unit 210.

3 is a block diagram showing an example of a mobile terminal for implementing the present invention.

Referring to FIG. 3, it can be seen that the mobile terminal 130 at a second point of view includes a wireless communication unit 310, a storage unit 320, and a control unit 330.

The wireless communication unit 210 performs functions for transmitting and receiving signals through a wireless channel, and is specified as a transmitter, a receiver, or a transceiver, or is considered to include a transmitter and a receiver.

The storage unit 230 stores data such as program and setting information for the operation of the base station 110.

The controller 240 controls overall operations of the mobile terminal 130 at the second point of view, such as generating a signal or processing a signal while referring to data stored in the storage unit 230.

Hereinafter, a process of implementing the particle filter-based beam tracking method by the control unit 240 will be comprehensively described, and then, in detail, the steps to implement the beam tracking method will be described with reference to FIGS. 4 to 5. In addition, in the following, for convenience of description, it will be described with reference to FIG. 1.

The receiver receives the reference signal from the mobile terminal that has moved from the first point to the second point through the communication network established at the first point after time elapses from the first point to the second point.

The controller 240 estimates the mobility of the mobile terminal from the first point of view to the second point of view based on the particle filter by using the received reference signal as a measurement model of the second point of view.

The transmitter establishes a new communication network with the mobile terminal at the second point based on the mobility estimated by the control unit, and transmits preset data to the mobile terminal.

4 is a flowchart illustrating an example of a particle filter-based beam tracking process according to the present invention.

First, a state vector x, which is a value for tracking a beam through a particle filter, may be defined as in Equation 1.

In Equation 1, x and y are the relative positions between the base station 110 and the mobile terminal 130 at the second time point, and x', y'are the relative speeds between the base station 110 and the mobile terminal 130 at the second time point. , x", y" denote relative accelerations between the base station 110 and the mobile terminal 130 at the second point of view, respectively. In addition, in Equation 1, τ is a variable added to improve the reliability of the entire beam tracking result, and means the inclination of the mobile terminal 130 at the second point in time. That is, not only the relative position, relative speed, and relative acceleration between the base station 110 and the mobile terminal 130 at the second time point are estimated through the particle filter, but also the inclination of the mobile terminal is estimated, and the correct launch angle (transmission of the base station The beam angle) and the angle of arrival (the angle of the receiving beam of the mobile terminal) can be obtained.

In step 401, the mobile terminal 120 at the first point of view moves from the first point to the second point according to the mobility 140. Here, mobility may be expressed as in Equation 2.

In Equation 2, x _k is the motion state vector of the terminal 130 at time k, x _k-1 is the motion state vector of the mobile terminal 120 at the first time point k-1, and v _k-1 is Gaussian noise vector and function f _k added in the mobility 140 denote linear and nonlinear dynamic functions at time k, respectively.

In step 401, the mobile terminal 130 at the second time point transmits a reference signal to the base station 110. The reference signal is transmitted to the base station through a communication network using the beam pairs 111 and 121 at the first time point.

Subsequently, in step 402, the base station 402 estimates the mobility 140 of the terminal through the particle filter using the received signal as a measurement model.

The signal received by the base station 110 and the motion state vector have the same relationship as in Equation 3.

In Equation 3, z _k is the measurement model at the second time point _k , x _k is the motion state vector of the mobile terminal 130 at the second time point k, and n _k is the measurement model. Gaussian noise vector and function h _k denote relational expressions between linear and nonlinear measurement models and motion state vectors, respectively.

As described above, the control unit 240 of the base station 110 estimates the mobility of the mobile terminal based on the received reference signal using the measurement model, and tracks the beam based on the particle filter.

5 is a flowchart schematically illustrating an example of a process in which a controller tracks a beam based on a particle filter.

First, in step 501, a plurality of particles are distributed according to the dynamic function described in Equation 2, and may be expressed as Equation 4.

In Equation 3, x _k ⁱ is the motion state vector of the i th particle at the second time point k, and x _k-1 ⁱ is the motion state vector of the mobile terminal 130 at the first time point k-1 , v _k-1 ⁱ is a Gaussian noise vector added from the mobility of the i-th particle at the first time point k-1, and the function f _k refers to the linear and nonlinear dynamic functions at the first time point k. do.

In step 502, the control unit 240 of the base station 110 estimates the motion state of the mobile terminal 130 at the second point in time. The control unit 240 calculates the weight of each particle, and the sum of the weight of each particle and the motion state vector product becomes a motion vector of the terminal estimated. The weight of each particle can be expressed as in Equation 5 by multiplying the weight of the first point of view by a likelihood function.

In Equation 4, w ⁱ _k is the weight of the i-th particle at the second point of time k, w ⁱ _k-1 is the weight of the i-th particle at the first point of time k-1, and function L is the likelihood function , zk denotes the measurement model at the second point in time k, and x _k ⁱ denotes the motion state vector of the i-th particle at the second point in time k, respectively.

At this time, the motion state vector of the mobile terminal 130 at the second point in time may be expressed as Equation 6 in the form of a sum of the product of the weight of each particle and the motion state vector.

는 제2시점인 시간 k에서의 이동식단말(130)의 운동상태벡터의 추정값, wⁱ _k는 제2시점인 시간 k에서의 i번째 입자의 가중치, x_k ⁱ는 제2시점인 시간 k에서의 i번째 입자의 운동상태벡터, N은 총 입자의 수를 각각 의미한다.In Equation 6

Is the estimated value of the motion state vector of the mobile terminal 130 at the second time point _k , w ⁱ _k is the weight of the i-th particle at the second time point _k , and x _k ⁱ is the second time point at time k. The motion state vector of the i-th particle of, N denotes the total number of particles, respectively.

The control unit 240 of the base station 110 converts the motion state of the mobile terminal 130 into angle information in step 503 and uses it for beam steering.

Equation 7 is an example of an equation used by the base station 110 to steer and rearrange a beam.

는 제2시점인 시간 k에서 기지국(110)과 이동식단말(130) 사이의 발사각(angle of departure) 및 입사각(angle of arrival),

는 제2시점인 시간 k에서의 이동식단말(130)의 운동상태벡터의 추정값, 함수 g_k는 시간 k에서 운동 상태와 각도 정보의 관계식을 각각 의미한다.

Is the angle of departure and angle of arrival between the base station 110 and the mobile terminal 130 at the second time point k,

Denotes the estimated value of the motion state vector of the mobile terminal 130 at the second time point k, and the function g _k denotes a relational expression between the motion state and angle information at time k.

In step 504, the control unit 240 of the base station 110 converts the motion state of the mobile terminal 130 into angle information through Equation 7 and rearranges the beams.

Hereinafter, FIG. 4 will be described next.

In step 403, the control unit 240 of the base station 110, when it is confirmed that the optimal beam alignment is set through the process as shown in FIG. 5, the new data is transferred to the established beam pairs 112 and 131 to the mobile terminal 130. Will be sent to.

According to the present invention, it is possible to rearrange the beams with a minimum overhead in the mobility scenario as described above, and by optimizing the alignment of the beams, path loss can be minimized, and efficient millimeter wave communication is possible.

In particular, the present invention is an invention devised based on millimeter-wave communication, and is equipped with millimeter-wave communication equipment while having mobility, such as a tank, helicopter, and mechanized infantry, by minimizing path loss. The efficiency of supporting mobile terminals performing missions can be significantly improved.

In particular, according to the present invention, by adding the estimated value of the slope of the mobile terminal at the second point of view as a parameter to the state vector x estimated through the particle filter, even the mobility of the slope of the mobile terminal is considered. Can be further improved.

The embodiment according to the present invention described above may be implemented in the form of a computer program that can be executed through various components on a computer, and such a computer program may be recorded in a computer-readable medium. In this case, the medium is a magnetic medium such as a hard disk, a floppy disk, and a magnetic tape, an optical recording medium such as a CD-ROM and a DVD, a magneto-optical medium such as a floptical disk, and a ROM. A hardware device specially configured to store and execute program instructions, such as, RAM, flash memory, and the like.

Meanwhile, the computer program may be specially designed and configured for the present invention, or may be known and usable to those skilled in the computer software field. Examples of the computer program may include not only machine language codes produced by a compiler but also high-level language codes that can be executed by a computer using an interpreter or the like.

The specific implementations described in the present invention are examples, and do not limit the scope of the present invention in any way. For brevity of the specification, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection or connection members of the lines between the components shown in the drawings exemplarily represent functional connections and/or physical or circuit connections, and in an actual device, various functional connections that can be replaced or additionally It may be referred to as a connection, or circuit connections. In addition, if there is no specific mention such as “essential” or “importantly”, it may not be an essential component for the application of the present invention.

In the specification of the present invention (especially in the claims), the use of the term “above” and a similar reference term may correspond to both the singular and the plural. In addition, when a range is described in the present invention, the invention to which an individual value falling within the range is applied (unless otherwise stated), and each individual value constituting the range is described in the detailed description of the invention. Same as Finally, if there is no explicit order or contrary to the steps constituting the method according to the present invention, the steps may be performed in a suitable order. The present invention is not necessarily limited according to the order of description of the steps. The use of all examples or illustrative terms (for example, etc.) in the present invention is merely for describing the present invention in detail, and the scope of the present invention is limited by the above examples or illustrative terms unless limited by the claims. It does not become. In addition, those skilled in the art can recognize that various modifications, combinations, and changes may be configured according to design conditions and factors within the scope of the appended claims or their equivalents.

Claims (9)

A reference signal receiving step of receiving a reference signal from a mobile terminal moving from a first point to a second point through a communication network established with a base station at the first point after time elapses from the first point to the second point;
A mobility estimating step of estimating mobility of the mobile terminal from a first point of time to a second point of time based on a millimeter wave communication particle filter by using the received reference signal as a measurement model at a second point of view; And
A communication network reconstruction step of establishing a new communication network between the base station and the mobile terminal at the second point based on the estimated mobility, and transmitting preset data to the mobile terminal by the base station,
The reference signal is
Including information in consideration of a relative position, a relative speed, a relative acceleration between the base station and the mobile terminal at the second time point, and an estimated slope value that estimates a slope of the mobile terminal,
The mobility estimation step,
By defining a state vector including a total of 7 vector components up to two components of a relative position between the base station and the mobile terminal, two components of a relative speed, two components of a relative acceleration, and a slope of the mobile terminal, the particle filter Millimeter wave communication particle filter-based beam tracking method, characterized in that estimating the mobility of the mobile terminal on the basis of. The method of claim 1,
The communication network,
Millimeter wave communication particle filter-based beam tracking method, characterized in that by using a beam pair (beam pair) built on the basis of the array antenna supporting a preset frequency. delete delete A computer-readable recording medium storing a program for executing the method according to any one of claims 1 and 2. A receiver configured to receive a reference signal from a mobile terminal that has moved from a first point to a second point through a communication network established at the first point after time elapses from the first point to the second point;
A control unit for estimating mobility of the mobile terminal from a first point to a second point based on a millimeter wave communication particle filter using the received reference signal as a measurement model for a second point of view; And
And a transmitter configured to establish a new communication network with the mobile terminal at the second point based on the estimated mobility, and transmit preset data to the mobile terminal,
The reference signal is
Including information in consideration of a relative position, a relative speed, a relative acceleration, and an estimated slope value that estimates a slope of the mobile terminal between the base station and the mobile terminal at the second time point,
The control unit,
By defining a state vector including a total of 7 vector components up to two components of a relative position between the base station and the mobile terminal, two components of a relative speed, two components of a relative acceleration, and a slope of the mobile terminal, the particle filter Base station implementing the millimeter wave communication particle filter-based beam tracking method, characterized in that estimating the mobility of the mobile terminal based on. The method of claim 6,
The communication network,
A base station implementing a beam tracking method based on a millimeter wave communication particle filter, characterized in that by using a beam pair built on an array antenna supporting a preset frequency. delete delete

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