Apparatus and method for wireless communication including beam training

Abstract

An apparatus and method for wireless communication including beam training are provided. In the wireless communication method, beam training phases are alternated with data transmission phases. The method includes: estimating a first channel based on signals received using one or more first training beams in a first beam training phase; and calculating a first data beam for a first data transmission phase from the one or more first training beams based on the estimated first channel and a first objective function corresponding to the estimated first channel in the first beam training phase, the first data transmission phase being after the first beam training phase.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2019-0043298 filed on April 12, 2019, and Korean Patent Application No. 10-2019-0074120 filed on June 21, 2019, in the Korean Intellectual Property Office, the disclosure of each of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to wireless communications, and more particularly, to apparatus and methods for wireless communications including beam training. Background Art

[0004] Wide frequency bands may require high throughput for wireless communications. For such broadband communications, a millimeter wave (mmWave) band of, for example, at least about 24 GHz may be used. Signals in high frequency bands like mmWave may be easily attenuated, and therefore, beamforming may be used to ensure service coverage. Beam training may be performed to align the beams of the transmitter and receiver before transmission of the payload, and may be repeated due to variable wireless communication environments. Therefore, the quality of wireless communications may depend on the accuracy and efficiency of beam training. Summary of the invention

[0005] On the one hand, an apparatus and method for effectively determining an optimal beam in wireless communication are provided.

[0006] According to an aspect of an example embodiment, there is provided a wireless communication apparatus, comprising: an antenna array; a transceiver configured to provide a signal to the antenna array to form a data beam, and configured to process a signal received through the antenna array using the data beam; and a controller configured to calculate the data beam in a beam training phase, and to control transmission according to the calculated data beam in a data transmission phase, wherein in the beam training phase, the controller is configured to estimate a channel using at least one first training beam, and calculate the data beam from the at least one first training beam based on the estimated channel and based on an objective function corresponding to the estimated channel.

[0007] According to another aspect of an example embodiment, a wireless communication method is provided, wherein a beam training phase alternates with a data transmission phase, the wireless communication method comprising: in a first beam training phase, estimating a first channel based on a signal received using at least one first training beam; and in the first beam training phase, calculating a first data beam for a first data transmission phase from the at least one first training beam based on the estimated first channel and a first objective function corresponding to the estimated first channel, the first data transmission following the first beam training phase.

[0008] According to another aspect of the example embodiment, a wireless communication method is provided, wherein a beam training phase alternates with a data transmission phase, the wireless communication method comprising: in a first beam training phase, calculating a first data beam for a first data transmission phase from at least one first training beam, the first data transmission phase being after the first beam training phase; in a second beam training phase after the first data transmission phase, determining at least one second training beam based on the first data beam; and in a second beam training phase, calculating a second data beam for a second data transmission phase from the at least one second training beam, the second data transmission phase being after the second beam training phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a block diagram of a wireless communication system according to an example embodiment;

[0011] Figure 2 is a timing diagram illustrating a wireless communication method according to an example embodiment;

[0012] Figure 3A and 3B is a diagram illustrating changes in training beams due to beam training according to an example embodiment;

[0013] Figure 4 is a flow chart of a wireless communication method according to an example embodiment;

[0014] Figure 5 is a diagram illustrating changes in a training beam and a data beam in a wireless communication method according to an example embodiment;

[0015] Figure 6 is a flow chart of a wireless communication method according to an example embodiment;

[0016] Figure 7 is a flow chart of a wireless communication method according to an example embodiment;

[0017] Figure 8 is a flow chart of a wireless communication method according to an example embodiment;

[0018] Fig. 9 is a diagram illustrating an operation of selecting a training beam according to an example embodiment;

[0019] Fig.10 is a flow chart of a wireless communication method according to an example embodiment;

[0020] Fig.11is a flow chart of a wireless communication method according to an example embodiment; and

[0021] Fig. 12A and 12B is a block diagram of an example of a beam controller according to an example embodiment. DETAILED DESCRIPTION

[0022] As used herein, the terms “first” and “second” may use corresponding components regardless of importance or order, and are used to distinguish one component from another without limiting the components.

[0023] Figure 1 is a block diagram of a wireless communication system 1 according to an example embodiment. Figure 1 As shown, the wireless communication system 1 may include a base station 200 and a user equipment 100 .

[0024] As non-limiting examples, the wireless communication system 1 may include a fifth generation wireless (5G) system, a long term evolution (LTE) system, an LTE advanced system, a code division multiple access (CDMA) system, or a global system for mobile communications (GSM) system using a cellular network, a wireless personal area network (WPAN) system, or other arbitrary wireless communication systems. Hereinafter, reference will be made mainly to a wireless communication system using a cellular network in the following description, but example embodiments are not limited thereto.

[0025] The user equipment 100 may be fixed or mobile like a wireless communication device, and may refer to any device that can transmit and receive data and / or control information to and from the base station 200 through wireless communication. For example, the user equipment 100 may be referred to as a terminal, a terminal device, a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, or a portable device. Figure 1 , the user equipment 100 may include a plurality of antennas 120 , a precoder 140 , a transceiver 160 , and a signal processor 180 .

[0026] The base station 200 may generally refer to a fixed station that communicates with a user equipment and / or another base station and can exchange data and control information with the user equipment and / or another base station. The base station 200 may also be referred to as a network access device. For example, the base station 200 may be referred to as a node B, an evolved node B (eNB), a next generation node B (gNB), a sector, a site, a base transceiver system (BTS), an access point (AP), a relay node, a remote radio head (RRH), a radio unit (RU) or a small cell. In this specification, in a broad sense, a base station or a cell may be interpreted as referring to a partial area or function, which is covered by a base station controller (BSC) in CDMA, a node B in broadband CDMA (WCDMA), an eNB in ​​LTE, a gNB or a sector (or site) in 5G, etc., and may include various coverage areas, such as giant cells, macro cells, micro cells, micro cells, micro cells, micro cells, relay nodes, RRHs, RUs, and small cellular communication ranges.

[0027] The user equipment 100 and the base station 200 may perform wireless communication using beamforming, and the wireless communication system 1 may define the requirements of the user equipment 100 and the base station 200 for beamforming. For example, the wireless communication system 1 may use the millimeter wave band to increase throughput, and may use beamforming to overcome the path loss of the millimeter wave. For wireless communication using beamforming, beam alignment of the user equipment 100 and the base station 200 may be required, and the user equipment 100 and the base station 200 may perform beam training for beam alignment. For example, Figure 1 As shown, the base station 200 may repeatedly transmit information (e.g., one symbol) using a transmission beam 20 during beam training, and the user equipment 100 may receive the symbol using a different reception beam 10. The user equipment 100 may determine a data beam to be used for wireless communication with the base station 200 based on the reception beam 10, and may provide information about the data beam to the base station 200, which may be used for wireless communication, i.e., transmitting and / or receiving a payload between the user equipment 100 and the base station 200. In this specification, a beam used in beam training may be referred to as a training beam, and a beam used for transmitting and / or receiving a payload as a result of beam training may be referred to as a data beam.

[0028] Since the wireless communication environment between the user equipment 100 and the base station 200 changes due to the mobility of the user equipment 100, obstacles near at least some of the multiple antennas 120, etc., beam training may be frequently performed. Therefore, it may be advantageous to quickly determine the optimal data beam through beam training in the wireless communication system 1. As described below with reference to the accompanying drawings, according to various exemplary embodiments, the data beam may not be limited to a predetermined training beam, but may be calculated from at least one training beam in the beam training stage. For example, at least one training beam may be used to estimate the channel between the user equipment 100 and the base station 200, and the optimal data beam calculated based on the estimated channel may be used for wireless communication. The data beam may also be used to determine at least one training beam corresponding to a higher resolution in a subsequent level (further described below), so that the optimal data beam providing high efficiency (e.g., beamforming gain) may be used for wireless communication. In the following, although the description of the exemplary embodiments will focus on the operation of the user equipment 100 determining the training beam and calculating the data beam, it should be understood that according to other exemplary embodiments, the base station 200 may determine the training beam and calculate the data beam in the same or similar manner.

[0029] The user equipment 100 may include multiple antennas 120 for beamforming, and the multiple antennas 120 may be referred to as antenna arrays. In some embodiments, the multiple antennas 120 may include multiple subarrays that form multiple beams respectively. In some embodiments, the subarrays may collectively refer to the element antennas included therein and the components (e.g., phase shifters) of the precoder 140 corresponding to the element antennas. The subarrays may receive radio frequency (RF) signals from the RF links included in the transceiver 160, or send RF signals to the RF chains. When the number of subarrays is different from the number of RF chains in the transceiver 160, switches and / or multiplexers may be arranged between the subarrays and the RF chains. In this specification, it is assumed that the number of subarrays and RF chains is K (where K is an integer greater than 1), and therefore is the same as each other, but the embodiments are not limited thereto. In some embodiments, the multiple antennas 120 may be used for spatial diversity, polarization diversity, spatial multiplexing, and the like.

[0030] The precoder 140 may provide a signal for forming a beam to the plurality of antennas 120 according to the control signal CTRL. In some embodiments, the precoder 140 may include a plurality of phase shifters and / or amplifiers, such as a power amplifier or a low noise amplifier, that receive the control signal CTRL, and may be referred to as an analog precoder. Figure 1As shown, in the transmission mode, the precoder 140 can receive the first RF signal RF_1 to the Kth RF signal RF_K from the transceiver 160, amplify the first RF signal RF_1 to the Kth RF signal RF_K according to the control signal CTRL, and / or adjust the phase of the first RF signal RF_1 to the Kth RF signal RF_K according to the control signal CTRL. In the reception mode, the precoder 140 can generate the first RF signal RF_1 to the Kth RF signal RF_K by amplifying the signal received through the multiple antennas 120 according to the control signal CTRL and / or by adjusting the phase of the signal received through the multiple antennas 120 according to the control signal CTRL.

[0031] The transceiver 160 may include a first RF chain 161_1 to a Kth RF chain 161_K, and in some embodiments, the transceiver 160 may be referred to as an RF integrated circuit (RFIC). An RF chain may refer to a path for independently processing an RF signal, and may include, for example, an amplifier, a filter, and / or a mixer. In some embodiments, the RF chain may further include an analog-to-digital converter (ADC) and / or a digital-to-analog converter (DAC). In some embodiments, the transceiver 160 may include a switch and / or a multiplexer, and the RF chain may be reconfigured by the switch and / or the multiplexer. The first RF chain 161_1 to the Kth RF chain 161_K may generate the first RF signal RF_1 to the Kth RF signal RF_K respectively in the transmit mode by processing the first baseband signal BB_1 to the Kth baseband signal BB_K respectively, and may generate the first baseband signal BB_1 to the Kth baseband signal BB_K respectively in the receive mode by processing the first RF signal RF_1 to the Kth RF signal RF_K respectively.

[0032] The signal processor 180 may provide the first baseband signal BB_1 to the K-th baseband signal BB_K to the transceiver 160, and receive the first baseband signal BB_1 to the K-th baseband signal BB_K from the transceiver 160. The signal processor 180 may be referred to as a communication processor, a baseband processor, etc., and may include logic hardware designed by logic synthesis, and / or may include a central processing unit having a core and software including a series of instructions executed by the core. Figure 1 As shown, the signal processor 180 may include a data processor 182 and a beam controller 184 .

[0033] The data processor 182 may generate transmission data including information to be provided to the base station 200, and may generate first baseband signals BB_1 to K-th baseband signals BB_K (or digital signals corresponding to the first baseband signals BB_1 to K-th baseband signals BB_K) from the transmission data. In addition, the data processor 182 may generate reception data including information provided by the base station 200 from the first baseband signals BB_1 to K-th baseband signals BB_K (or digital signals corresponding to the first baseband signals BB_1 to K-th baseband signals BB_K). For example, the data processor 182 may include an encoder, a decoder, a modulator and / or a demodulator. In some embodiments, the data processor 182 may include a precoder for beamforming, i.e., a digital precoder. Therefore, the data processor 182 may receive beamforming information from the beam controller 184 and perform precoding based on the beamforming information.

[0034] The beam controller 184 may perform a wireless communication method according to an example embodiment, and may define beamforming information for a beam formed by a plurality of antennas 120. For example, the beam controller 184 may define beamforming information for a training beam in a beam training phase, and generate a control signal CTRL according to the beamforming information. In addition, the beam controller 184 may define beamforming information for a data beam in a data transmission phase, and generate a control signal CTRL according to the beamforming information. In some embodiments, when the data processor 182 includes a digital precoder, the beam controller 184 may provide the beamforming information to the digital precoder. In the present specification, defining beamforming information may simply refer to defining a beam corresponding to the beamforming information, and calculating and determining beamforming information may simply refer to calculating and determining a beam corresponding to the beamforming information. In the present specification, the beam controller 184 may be simply referred to as a controller.

[0035] Figure 2 is a timing diagram illustrating a wireless communication method according to an example embodiment. In some embodiments, Figure 2 The wireless communication method can be Figure 1 The user equipment 100 shown in FIG. 1 is executed. Figure 2 describe Figure 1 .

[0036] In some embodiments, beam training phases are alternated with data transmission phases. Figure 2As shown, the beam training phase and the data transmission phase may be sequentially performed in level "s", and the beam training phase and the data transmission phase may be sequentially performed in the next level (i.e., level "s+1") (where "s" is an integer greater than 0). A pair of the beam training phase and the data transmission phase may be referred to as a single level, where the data transmission phase uses the data beam defined in the beam training phase. Figure 3A and 3B As described, the various beam training phases in consecutive levels may be connected to each other. It will be noted that, despite the name, the user equipment 100 may operate in a reception mode using a data beam in a data transmission phase.

[0037] refer to Figure 2 , can be used in the beam training phase at level "s" s training beams to perform beam training, where M s is an integer greater than 0. In some embodiments, the base station 200 may use the transmission beam 20 (which is fixed) to send the known training symbol M s In some embodiments, the transmission beam 20 may be a fixed transmission beam, and the base station 200 may send a known training symbol M s For example, the base station 200 may use a fixed transmission beam 20 to transmit a unit symbol channel state information reference signal (CSI-RS) resource through an orthogonal frequency division multiplexing (OFDM) symbol. The user equipment 100 (or the beam controller 184) may use M s A training beam is used to receive known training symbols to combine the received signals, and a data beam can be defined based on the received results. The training beam matrix To determine M s For example, the definition of the mth training beam (where 1≤m≤M) can be given by Formula 1. s )

[0038]

[0039] in y may be the training beam vector of the kth subarray in level “s” (where 1≤k≤K).

[0040] The codebook CB of level "s" can be s To define M sThe codebook may include a predefined training beam matrix corresponding to the training beams that can be formed by the plurality of antennas 120, and / or information defining such a training beam matrix. For example, the codebook may include predefined beam vectors corresponding to the beams that can be formed by the subarrays, respectively. In some embodiments, as described below with reference to 3A and 3B, the codebook may define training beams having patterns that at least partially overlap with each other at a level.

[0041] The user equipment 100 may include a plurality of codebooks corresponding to a plurality of levels, respectively. Figure 3A and 3B As described above, a codebook corresponding to a higher level among the multiple levels may have a higher resolution than a codebook corresponding to a lower level among the multiple levels. For example, the codebook CB for level "s+1" s+1 It is possible to have a codebook CB for level "s" s Higher resolution, and therefore, by the codebook CB for level “s+1” s+1 The training beams defined by the codebook CB for level “s” s Compared to the training beam defined by the invention, a pattern (e.g., a main lobe) may have a reduced width and a stronger orientation. Beam training may be performed via a hierarchical search using codebooks having different resolutions. Therefore, according to various example embodiments, beam training may be performed more efficiently than in the case of an exhaustive search where all beam pairs are checked. In this specification, the entire level (or height) of the hierarchical search may be denoted by S, where 1≤s≤S. ​​In this specification, codebooks having different resolutions may be collectively referred to as multi-resolution codebooks.

[0042] In some embodiments, the training beams may be defined by uniformly or non-uniformly quantizing the region in which the channel directions are available. In some embodiments, the region in which the channel directions are available may be quantized based on the statistical properties of the channel directions. The directions quantized in level "s" may be given by Formula 2:

[0043]

[0044] Among them, G s The resolution of the codebook may depend on the performance of the precoder 140 (or the performance of the digital precoder when a digital precoder is included), and for example, on the resolution of the phase shifter. As described above, as the level increases, training beams with higher resolution may be defined by the codebook. For example, G s+1 Can be better than G s (i.e., G s+1 >G s). The training beam set, which includes a training beam matrix defining training beams corresponding to the quantized directions in level "s", can be given by Formula 3:

[0045]

[0046] Wherein the vector a is an array response vector and may include values ​​corresponding to given directions as elements. In this specification, it may be said that a training beam group includes training beams.

[0047] In some embodiments, the data beam used in the data transmission phase may be calculated from at least one training beam used in the beam training phase in the same level as the data transmission phase. For example, the training beam matrix Calculate the data beam matrix in The data beam matrix defines the data beams used in the data transmission phase in level "s", Defines the M used in the beam training phase at level "s" s Similarly, the M used in the beam training phase in level “s+1” can be defined. s+1 The training beam matrix of training beams , calculate the data beam matrix defining the data beams used in the data transmission phase in level "s+1" In some embodiments, the beam controller 184 may use at least one training beam to estimate the channel between the user equipment 100 and the base station 200, and calculate the data beam from the training beam based on the estimated channel. Therefore, according to various example embodiments, the data beam may not be limited to the training beam defined by the multi-resolution codebook, and may provide a satisfactory beamforming gain. Figure 6 An example of a method of computing a data beam from at least one training beam is described.

[0048] In some embodiments, at least one training beam used in the beam training phase may be determined from data beams used in the data transmission phase in the previous level. For example, the at least one training beam used in the beam training phase may be determined based on a data beam matrix defining data beams used in the data transmission phase in level "s". From the codebook CB for level “s+1” s+1 In the training beam matrix defined, select the M used in the beam training phase in level "s+1" s+1 The training beam matrix of training beams As described above, data beams not limited to training beams can be used, and since the training beams in the subsequent level are selected from the data beams used in the previous level, the accuracy of hierarchical search can be improved. As a result, the accuracy and efficiency of beam training can be improved. Figure 8 An example of a method of determining a training beam based on a data beam of a previous level is described.

[0049] Figure 3A and 3B is a diagram illustrating changes in a training beam due to beam training according to an example embodiment. In detail, Figure 3A and 3B The angular range of the training beams in each level is shown, ranging from 0 to π angle of incidence (AOA). Figure 3A and 3B Two training beams are used, namely, M s =2, and 1≤s≤4. Figure 1 describe Figure 3A and 3B , repeated descriptions will be omitted.

[0050] refer to Figure 3A , when a channel between the user equipment 100 and the base station 200 is formed in one direction, the training beam can be gradually aligned in the direction as the level increases. Figure 3A As shown, the beam matrix can be trained To define two training beams in the first level L1, and the training beam matrix To define two training beams in the second level L2, and the training beam matrix To define two training beams in the third level L3, and the training beam matrix To define two training beams in the fourth level L4. As the level increases, ie, as "s" increases, the angular range of the training beam may decrease, ie, the training beam may have a pattern with decreasing width, and the training beam may be aligned in the direction of the channel.

[0051] In some embodiments, the training beams in a level may have patterns that at least partially overlap each other. For example, although the training beam matrix in the first level L1 The defined training beams may have patterns that do not overlap with each other, but two training beams in each of the second level L2, the third level L3, and the fourth level L4 may have patterns that at least partially overlap with each other. As described above, when the training beams that overlap with each other are selected, high-resolution beam alignment can be achieved even in a relatively low level.

[0052] refer to Figure 3B When a channel is formed between the user equipment 100 and the base station 200 in at least two directions, the training beam may be gradually aligned in these directions. Figure 3B As shown, as the level increases, that is, as "s" increases, the angular range of the training beam may be reduced, and the training beams in one level may be aligned in different directions, respectively.

[0053] Figure 4 is a flow chart of a wireless communication method according to an exemplary embodiment. Figure 2 As described, beam training phases alternate with data transmission phases, and Figure 4 The flowchart of FIG. 1 shows an example of the operation of repeating the beam training phase and the data transmission phase until the final data beam is determined. In some embodiments, the operation of Figure 4 For example, Figure 4 In the embodiment, operation S600 may be followed by operation S200. Figure 4 As shown, operation S200 may be performed in the beam training phase, and operations S400, S600, and S800 may be performed in the data transmission phase. Figure 4 Different, operation S800 can be performed in the beam training phase. In some embodiments, Figure 1 The beam controller 184 in the Figure 4 The method may be referred to as a method of operating the beam controller 184.

[0054] The following will refer to Figure 1 describe Figure 4 .

[0055] In operation S200, a data beam may be calculated from at least one training beam. For example, the beam controller 184 may calculate the data beam based on at least one training beam, and thus the data beam may not be limited to the training beam defined by the codebook. In some embodiments, the beam controller 184 may define an objective function based on the estimated channel, and may calculate a data beam that maximizes the objective function. Figure 6 An example of operation S200 is described.

[0056] The precoder may be set in operation S400. For example, the beam controller 184 may provide a control signal CTRL to the precoder 140 so that the data beam calculated in operation S200 is generated in the beam training phase. In some embodiments, as described above with reference to Figure 1 As described above, when the data processor 182 includes a digital precoder, the beam controller 184 may also set the digital precoder. Therefore, a data beam may be formed by the plurality of antennas 120, and data transmission and reception may be performed using the data beam.

[0057] The beamforming gain may be compared with a first threshold value THR1, and in operation S600 it may be determined whether the beamforming gain is greater than the first threshold value THR1. The beamforming gain is a measure indicating the efficiency obtained by the current data beam. A data beam that gives a higher beamforming gain may be considered more suitable and may be referred to as a beam gain. For example, the beamforming gain may be defined based on the received power obtained from the data beam. The first threshold value THR1 may indicate a beamforming gain for satisfactory wireless communication. Therefore, when the beamforming gain is higher than the first threshold value THR1, the current data beam may be maintained. However, when the beamforming gain is equal to or less than the first threshold value THR1, an operation of defining a new data beam will be performed. When the beamforming gain is equal to or less than the first threshold value THR1, operation S800 may be performed.

[0058] In operation S800, at least one training beam may be determined based on the data beam. For example, the beam controller 184 may select at least one from a plurality of training beams defined by the codebook CB based on the data beam used in the data transmission phase. In some embodiments, the beam controller 184 may select at least one training beam that may provide performance most similar to that of the data beam. Figure 8 An example of operation S800 is described.

[0059] Figure 5 is a diagram illustrating changes in training beams and data beams in a wireless communication method according to an example embodiment. In detail, Figure 5 The angular range of the training beam and the data beam in each level ranging from 0 to π AOA is shown. Figure 5 Two training beams are used, namely, M s =2, 1≤s≤4. Figure 1 and 4 describe Figure 5 .

[0060] refer to Figure 5 , as the level increases, that is, as “s” increases, the angular ranges of the training beam and the data beam may be reduced, and the training beam and the data beam may be gradually aligned in the direction of forming the channel. For example, in the first level L1, the training beam matrix may be Define two training beams, and can be obtained from the training beam matrix The data beam matrix calculated in To define the data beam. In the second level L2, the training beam matrix Define two training beams, the training beam matrix is ​​based on the data beam matrix in the first level L1 selected and can be determined by the data beam matrix Define the data beam, the data beam matrix is ​​derived from the training beam matrix In the third level L3, the training beam matrix Define two training beams, the training beam matrix is ​​based on the data beam matrix in the second level L2 selected and can be determined by the data beam matrix Define the data beam, the data beam matrix is ​​derived from the training beam matrix In the fourth level L4, the training beam matrix Define two training beams, the training beam matrix is ​​based on the data beam matrix in the third level L3 selected and can be determined by the data beam matrix Define the data beam, the data beam matrix is ​​derived from the training beam matrix Calculated in .

[0061] Figure 6 is a flow chart of a wireless communication method according to an example embodiment. In detail, Figure 6 The flowchart shows Figure 4 As shown in the above reference Figure 4 As mentioned above, it can be obtained from Figure 6 The data beam is calculated from at least one training beam in operation S200'. Figure 6 As shown, operation S200' may include operations S220 and S240. In the following, it is assumed that operation S200' is performed in the beam training phase in level "s". In some embodiments, Figure 1 The beam controller 184 in Figure 6 Operation S200'. Figure 1 describe Figure 6 .

[0062] refer to Figure 6 In operation S220, the channel may be estimated based on the signal received using at least one training beam. For example, the beam controller 184 may estimate the channel based on the signal received using M s The signal received by the training beam is used to estimate the channel. s The training beams are composed of the training beam matrices at level “s” Definition. The following will refer to Figure 7 An example of operation S220 is described.

[0063] In operation S240, a data beam may be calculated based on the estimated channel and an objective function. For example, the beam controller 184 may derive an objective function based on the estimated channel, and may calculate a data beam that maximizes the objective function. The objective function may be defined differently to evaluate the efficiency of beamforming. For example, the objective function may be defined based on a signal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio (SINR), a channel capacity, and an energy efficiency corresponding to the estimated channel, or a combination of at least two selected therefrom.

[0064] When the matrix corresponding to the training beam of the kth (where 1≤k≤K) subarray is defined as The data beam matrix defining the data beams in level “s” can be given by Equation 4:

[0065]

[0066] Where C is the coefficient matrix, defined as C = diag(c 1 ,…,c K ), and c k can be a vector for the kth subarray and can be defined as When the channel matrix indicating the channel estimated in operation S220 is When , the objective function R indicating the channel capacity or spectrum efficiency can be given by Formula 5:

[0067]

[0068] where γ can be defined by the received power and the transmit beam matrix, and the following will refer to Figure 7 Therefore, the coefficient matrix C that maximizes the objective function can be derived using the following formula 6: opt , and the data beam matrix that ultimately defines the data beams in level “s” can be given by Formula 7

[0069]

[0070]

[0071] Figure 7 is a flow chart of a wireless communication method according to an example embodiment. In detail, Figure 7 The flow chart shows Figure 6 As shown in the above reference Figure 6 As stated in Figure 7 In operation S220', the channel may be estimated based on a signal received using at least one training beam. Figure 7As shown, operation S220' may include operations S222 and S224. In the following, it is assumed that operation S220' is performed in the beam training phase in level "s". In some embodiments, Figure 1 The beam controller 184 performs Figure 7 Operation S220'. Figure 1 and 6 describe Figure 7 .

[0072] refer to Figure 7 , the M transmitted by receiving can be collected in operation S222 s When the training beam matrix defining the mth training beam is used, When receiving a signal, the received signal can be given by formula 8:

[0073]

[0074] Where P is the received power, H is the channel matrix, F is the transmission beam matrix used by the base station 200, "x" is the transmission signal, and is the channel noise. The training beam matrix can be given by formula 1 Therefore, the signal received in the beam training phase in level "s" can be given by Formula 9:

[0075]

[0076] In operation S224, a combined channel matrix may be generated based on the at least one training beam and the measurement value. When the measurement value is collected using Formula 9 in operation S222, the combined channel matrix indicating the estimated channel is It can be defined as formula 10:

[0077]

[0078] As mentioned above Figure 6 As described, the combined channel matrix The objective function is derived, and the data beam matrix that maximizes the objective function can be calculated For example, the objective function R may be defined as in Formula 5 which represents the channel capacity or spectrum efficiency. gNB ×N D The matrix and the channel noise in Equation 8 is a variance When the Gaussian noise is , then γ in Formula 5 can be defined as

[0079] Figure 8is a flowchart of a wireless communication method according to an example embodiment, Fig. 9 is a diagram illustrating an operation of selecting a training beam according to an example embodiment. In detail, Figure 8 The flowchart shows Figure 4 In the example of operation S800, Fig. 9 The diagram shows Figure 8 In the following, it is assumed that the beam training phase in level "s" is performed. Figure 8 Methods and Fig. 9 In some embodiments, the Figure 1 The beam controller 184 performs Figure 8 Methods and Fig. 9 The following will refer to Figure 1 and 4 describe Figure 8 and 9 .

[0080] refer to Figure 8 , as referenced above Figure 4 As mentioned above, it can be Figure 8 In operation S800′, at least one training beam is determined based on the data beam. Figure 8 As shown, operation S800' may include operations S820 and S840, and operation S820 may include operations S822 and S824.

[0081] In operation S820, the similarity between the data beam and the plurality of training beams defined in the codebook may be determined. For example, the beam controller 184 may calculate the similarity between the data beam in level "s" and the codebook CB in level "s+1". s+1 The similarity between multiple training beams defined by Figure 8 As shown, operation S820 may include operations S822 and S824. In some embodiments, both operations S822 and S824 may be performed, and the similarity may be generated by combining (e.g., performing a weighted sum on) the respective results of operation S822 (i.e., the error) and the results of operation S824 (i.e., the correlation). In some embodiments, only operation S822 may be performed, and it may be determined that the lower the error between the training beam and the data beam, the greater the similarity between them. In some embodiments, only operation S824 may be performed, and it may be determined that the higher the correlation between the training beam and the data beam, the higher the similarity between them.

[0082] The error between the data beam and each training beam may be calculated in operation S822. For example, the beam controller 184 may calculate the codebook CB in level "s+1" s+1 The multiple training beam matrices defined in (i.e., training beam group B(s+1) elements of ) with the data beam matrix at level "s" In some embodiments, the training beam set B can be calculated (s+1) The elements of the data beam matrix The root mean square error (RMSE) between them.

[0083] The correlation between the training beam matrix and the data beam may be calculated in operation S824. For example, the beam controller 184 may calculate the codebook CB in level "s+1" s+1 The training beam matrix defined in (i.e., training beam group B (s+1) elements of ) with the data beam matrix at level "s" The correlation between them.

[0084] In operation S840, at least one training beam may be selected from the training beams defined in the codebook. For example, the beam controller 184 may select at least one training beam from the codebook CB based on the similarity determined in operation S820. s+1 The training beam matrix defined in (i.e., training beam group B (s+1) Select M from the elements s+1 training beam matrices. Fig. 9 , training beam group B (s+1) The elements of M can be sorted in descending order of the determined similarity, and the training beam matrix M that gives the highest similarity can be selected. s+1 Training beam matrix In some embodiments, as shown below Fig.11 As described, M s+1 Can be different from M s .

[0085] In some embodiments, when calculating the training beam set B (s+1) When the RMSE between the elements of and the data beam matrix is ​​calculated, the RMSE can be sorted in ascending order and the M including the training beam matrix that gives the lowest RMSE can be selected using Formula 11 s+1 Training beam matrix

[0086]

[0087] where v is G s+1 ×1 vector, and ‖v‖ 0 =M s+1 It can be indicated that v includes non-zero M s+1 In some embodiments, when calculating the training beam set B (s+1)When the correlation between the elements of and the data beam matrix is ​​determined, the correlations can be sorted in descending order, and the M including the training beam matrix that gives the highest correlation can be selected. s+1 Training beam matrix

[0088] Fig.10 is a flow chart of a wireless communication method according to an example embodiment. In detail, Fig.10 is a flow chart of a method for determining a level in a hierarchical search for beam training. In some embodiments, Fig.10 Operation S810 may include Figure 8 In operation S800', and can be Figure 8 The operation S820 is performed before. Fig.10 As shown, operation S810 may include a plurality of operations S811, S813, S815, S817, and S819. In the following, it is assumed that operation S810 is performed in the beam training phase in level "s". Figure 1 The beam controller 184 in the Fig.10 The following will refer to operation S810. Figure 1 and 9 describe Fig.10 .

[0089] refer to Fig.10 , the beamforming gain can be obtained in operation S811. Figure 4 As described, beamforming gain may be defined as a metric indicating the efficiency obtained by a data beam, and a data beam giving a higher beamforming gain may be considered more suitable.

[0090] It may be determined in operation S813 whether the beamforming gain has increased. For example, the beam controller 184 may determine whether the beamforming gain obtained in the current level (i.e., level "s") has increased over the beamforming gain obtained in the previous level, and may recognize that the hierarchical search has been satisfactorily performed when the beamforming gain has increased. In some embodiments, the beam controller 184 may determine that the beamforming gain has increased when the beamforming gain in the current level increases from the beamforming gain in the previous level by at least a threshold ratio (e.g., a ratio greater than 1) or increases by at least a threshold magnitude. The threshold ratio may be predefined, and the threshold magnitude may be predefined. As Fig.10 As shown, when the beamforming gain increases (operation S813, yes), operation S815 may be performed. Otherwise, when the beamforming gain does not increase (operation S813, no), operation S817 may be performed.

[0091] When it is determined in operation S813 that the beamforming gain increases (operation S813, yes), a codebook CB of level "s+1" may be selected in operation S815. s+1 As mentioned above Figure 2 As described above, the codebook corresponding to a higher level may have a higher resolution, and the beam controller 184 may select the codebook CB of level "s+1" when the beamforming gain increases. s+1 , which is higher than the current level, i.e., level "s", to form a data beam with a higher orientation.

[0092] When it is determined in operation S813 that the beamforming gain has not increased (operation S813, no), it may be determined in operation S817 whether the beamforming gain has decreased. For example, the beamforming controller 184 may determine whether the beamforming gain obtained in the current level (i.e., level "s") is less than the beamforming gain obtained in the previous level, and may identify that it is not appropriate to use a codebook with a higher resolution when the beamforming gain decreases. In some embodiments, the beamforming controller 184 may determine that the beamforming gain has decreased when the beamforming gain of the current level decreases from the beamforming gain of the previous level by at most a threshold ratio (e.g., a ratio less than 1) or by at least a threshold size. The threshold ratio may be predefined, and the threshold size may be predefined. As Fig.10 As shown, when the beamforming gain decreases (operation S817, yes), operation S819 may be performed. Otherwise, when the beamforming gain does not decrease (operation S817, no), it may be determined that the beamforming gain is substantially maintained, and the codebook of the current level (ie, level "s") may be reused.

[0093] When it is determined in operation S817 that the beamforming gain is reduced (operation S817, yes), a codebook CB of level "s-1" may be selected in operation S819. s-1 As mentioned above Figure 2 As described, the codebook corresponding to the lower level may have a lower resolution, and the beam controller 184 may select a codebook CB of level "s-1" lower than the current level (ie, level "s") when the beamforming gain decreases. s-1 , to search for directions that form channels over a wider range.

[0094] Fig.11 is a flow chart of a wireless communication method according to an example embodiment. In detail, Fig.11 is a flow chart of a method for adaptively adjusting a beam training phase. In some embodiments, Fig.11 Operation S500 may be included in Figure 4 In the wireless communication method, and can be Figure 4 The operation S400 and the operation S600 are performed between the steps of FIG. Fig.11 As shown, Fig.11 The operation S500 may include operations S510, S530, S550, S570, and S590. Hereinafter, it is assumed that the operation S500 is performed in the data transmission phase in level "s". In some embodiments, Fig.11 The operation S500 may be performed by Figure 1 The beam controller 184 performs the following. Figure 1 and 4 describe Fig.11 .

[0095] refer to Fig.11 , the beamforming gain can be obtained in operation S510. Figure 4 As described, the beamforming gain may be a metric value defined as indicating the efficiency obtained by the data beam, and a data beam that gives a higher beamforming gain may be considered more suitable. As described below, the beam training phase may be reduced or extended based on the beamforming gain. For example, when the beam training phase in level "s+1" is reduced compared to the beam training phase in level "s", the number of training beams used in the beam training phase may be reduced (i.e., M s+1 <M s In contrast, when the beam training phase in level “s+1” is extended compared to the beam training phase in level “s”, the number of training beams used in the beam training phase may increase (ie, M s+1 >M s ).

[0096] In operation S530, the beamforming gain may be compared with a second threshold value THR2, and it may be determined whether the beamforming gain is greater than the second threshold value THR2. The second threshold value THR2 may indicate sufficient beamforming gain to allow a subsequent beam training phase to be reduced. In some embodiments, the second threshold value THR2 may be greater than Figure 4 Therefore, when the beamforming gain is greater than the second threshold THR2 (operation S530, yes), the subsequent beam training stage can be reduced. Fig.11 As shown, when the beamforming gain is greater than the second threshold THR2 (operation S530, yes), operation S550 may be performed. Otherwise, when the beamforming gain is not greater than the second threshold THR2 (operation S530, no), operation S570 may be performed.

[0097] When it is determined that the beamforming gain is greater than the second threshold THR2 (operation S530, yes), M may be requested in operation S550. s+1 For example, the beam controller 184 may request the base station 200 to reduce M s+1The beam controller 184 can provide information to the data processor 182 so that for M s+1 The request for the reduction of M is included in the transmission data. In some embodiments, the beam controller 184 may include M in the request. s+1 The base station 200 may reduce the stage in which known symbols for beam training are transmitted in level "s+1" in response to the request.

[0098] Otherwise, when it is determined that the beamforming gain is not greater than the second threshold THR2 (operation S530, No), the beamforming gain may be compared with a third threshold THR3 in operation S570, and it may be determined whether the beamforming gain is less than the third threshold THR3. The third threshold THR3 may indicate an insufficient beamforming gain that requires expansion of a subsequent beam training phase. In some embodiments, the third threshold THR3 may be less than Figure 4 Therefore, when the beamforming gain is less than the third threshold THR3 (operation S570, yes), the subsequent beam training phase can be extended. Fig.11 As shown, when the beamforming gain is not less than the third threshold THR3 (operation S570, No), operation S500 may end. Therefore, the number of training beams used in the beam training phase in level "s+1" may be the same as the number of training beams used in the beam training phase in level "s" (i.e., M s+1 =M s Otherwise, when the beamforming gain is less than the third threshold THR3 (operation S570, yes), operation S590 may be performed.

[0099] In operation S590, M may be requested. s+1 For example, the beam controller 184 may request the base station 200 to increase M s+1 The beam controller 184 may provide information to the data processor 182 so that for M s+1 The request for the increase of M is included in the transmission data. In some embodiments, the beam controller 184 may include M in the request. s+1 The base station 200 may extend the stage in which known symbols for beam training are transmitted in level "s+1" in response to the request.

[0100] Fig. 12A and 12B is a block diagram of an example of a beam controller according to an example embodiment. In detail, Fig. 12A and 12B The block diagram shows Figure 1As described above with reference to the accompanying drawings, Fig. 12A The beam controller 300 and Fig. 12B The beam controller 400 may perform at least one operation included in the wireless communication method according to the exemplary embodiment. Hereinafter, redundant description will be omitted.

[0101] refer to Fig. 12A , the beam controller 300 may include a precoding controller 302, a channel estimator 304, a beam calculator 306, and a beam selector 308 as logic hardware components designed by logic synthesis. The precoding controller 302 may generate a control signal CTRL for controlling the precoder 140 according to the training beam matrix or the data beam matrix. In some embodiments, when the data processor 182 includes a digital precoder, the precoding controller 302 may control the digital precoder. The channel estimator 304 may estimate the channel based on a signal received using at least one training beam in a beam training phase. For example, the channel estimator 304 may generate a channel matrix As described above with reference to Formulas 8, 9, and 10. The beam calculator 306 may calculate a data beam, i.e., a data beam matrix, based on the estimated channel and the objective function, and may provide the data beam matrix to the precoding controller 302. The beam selector 308 may select at least one training beam from a plurality of training beams defined in the codebook. For example, the beam selector 308 may calculate the similarity between the data beam and the training beam, select at least one training beam based on the similarity, and provide the training beam matrix corresponding to the selected training beam to the precoding controller 302.

[0102] refer to Fig. 12B , the beam controller 400 may include a processor 410 and a memory 420. The processor 410 may be a central processing unit and may include at least one core, and the memory 420 may include a series of instructions or programs, each of which is executed by the processor 410. As non-limiting examples, the memory 420 may include a volatile memory such as a dynamic random access memory (DRAM) or a static RAM (SRAM), or a non-volatile memory such as a flash memory or an electrically erasable programmable read-only memory (EEPROM). Fig. 12B As shown, the memory 420 may include a precoding controller 422, a channel estimator 424, a beam calculator 426, and a beam selector 428 as software modules executed by the processor 410. The processor 410 may access the memory 420 and execute the stored software modules to execute the precoding controller 422, the channel estimator 424, the beam calculator 426, and the beam selector 428 respectively. Fig. 12AThe operations of the precoding controller 302, channel estimator 304, beam calculator 306 and beam selector 308 correspond to those in FIG.

[0103] In some embodiments, the system may be formed by combining logical hardware and software modules. Figure 1 For example, the beam controller 184 may include a precoding controller implemented by logic hardware, a processor, and a memory including a channel estimator, a beam calculator, and a beam selector as software modules.

[0104] While the inventive concept has been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A wireless communication device, comprising: Antenna arrays; a transceiver configured to provide signals to the antenna array to form a data beam and configured to process signals received by the antenna array using the data beam; as well as a controller configured to calculate a data beam in a beam training phase and control transmission according to the calculated data beam in a data transmission phase, wherein the controller is configured to estimate a channel using at least one first training beam during a beam training phase, and to calculate a data beam from the at least one first training beam based on the estimated channel and based on an objective function corresponding to the estimated channel, The controller is further configured to determine, based on the calculated data beam, at least one second training beam to be used in a subsequent beam training phase after the data transmission phase.

2. The wireless communication device according to claim 1, in, The objective function is based on at least one of an estimated signal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio (SINR), a channel capacity, or an energy efficiency of the channel.

3. The wireless communication device according to claim 1, in, The controller is configured to determine the at least one second training beam based on a calculated error and / or correlation between the data beam and the at least one second training beam.

4. The wireless communication device according to claim 1, in, The controller is also configured to collect measurement values ​​generated from a signal received using the at least one first training beam, the received signal being sequentially transmitted M times using the same transmission beam, and to generate a combined channel matrix based on the at least one first training beam and the measurement values, where M is an integer greater than 1.

5. The wireless communication device according to claim 4, in, The controller is further configured to obtain a beamforming gain in a data transmission phase, and generate transmission data including information on an increase or decrease in M ​​based on the beamforming gain.

6. A wireless communication method, wherein: The beam training phase is alternated with the data transmission phase, and the wireless communication method includes: In a first beam training phase, estimating a first channel based on a signal received using at least one first training beam; In a first beam training phase, calculating a first data beam for a first data transmission phase from the at least one first training beam based on the estimated first channel and a first objective function corresponding to the estimated first channel, the first data transmission phase being subsequent to the first beam training phase; and In a second beam training phase after the first data transmission phase, at least one second training beam is determined based on the first data beam.

7. The wireless communication method according to claim 6, wherein: Estimating the first channel includes: collecting measurements generated from a signal received using the at least one first training beam, the received signal being sequentially transmitted M times using the same transmission beam, where M is an integer greater than 1; and Based on the measurements and the at least one first training beam, a combined channel matrix is ​​generated.

8. The wireless communication method according to claim 7, further comprising: Obtaining a beamforming gain for a first data beam in a first data transmission phase; as well as Transmission data including information on increase or decrease of M is generated based on the beamforming gain in the first data transmission stage.

9. The wireless communication method according to claim 6, in, The first objective function is based on at least one of an estimated signal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio (SINR), a channel capacity, or an energy efficiency of the first channel.

10. The wireless communication method according to claim 6, further comprising: In a first beam training phase, the at least one first training beam is selected from the training beams defined in the first codebook, Wherein, determining the at least one second training beam comprises selecting the at least one second training beam from training beams defined in a second codebook, wherein the training beams defined in the second codebook have a higher resolution than the training beams defined in the first codebook.

11. The wireless communication method according to claim 6, further comprising: In a first beam training phase, selecting the at least one first training beam from training beams defined in a first codebook; as well as In a first data transmission phase, a beamforming gain for a first data beam is obtained. Wherein, determining the at least one second training beam comprises: selecting a codebook from among a first codebook, a second codebook having a higher resolution than the first codebook, and a third codebook having a lower resolution than the first codebook based on the beamforming gain; and The at least one second training beam is selected from the training beams defined in the selected codebook.

12. The wireless communication method according to claim 6, in, Determining the at least one second training beam includes selecting the at least one second training beam based on an error and / or a correlation between the first data beam and the at least one second training beam.

13. The wireless communication method according to claim 6, in, The at least one second training beam includes training beams respectively having patterns that at least partially overlap with each other.

14. The wireless communication method according to claim 6, further comprising: In a second beam training phase, estimating a second channel based on a signal received using the at least one second training beam; as well as In a second beam training phase, a second data beam for a second data transmission phase is calculated from the at least one second training beam based on the estimated second channel and a second objective function corresponding to the estimated second channel, the second data transmission phase being subsequent to the second beam training phase.

15. A wireless communication method, wherein: The beam training phase is alternated with the data transmission phase, and the wireless communication method includes: In a first beam training phase, a first data beam for a first data transmission phase is calculated from at least one first training beam, the first data transmission phase being after the first beam training phase; In a second beam training phase after the first data transmission phase, determining at least one second training beam based on the first data beam; and In a second beam training phase, a second data beam for a second data transmission phase is calculated from the at least one second training beam, the second data transmission phase following the second beam training phase.

16. The wireless communication method according to claim 15, further comprising In a first beam training phase, the at least one first training beam is selected from training beams defined in a first codebook, in, Determining the at least one second training beam includes selecting the at least one second training beam from training beams defined in a second codebook, wherein the training beams defined in the second codebook have a higher resolution than the training beams defined in the first codebook.

17. The wireless communication method according to claim 15, in, Determining the at least one second training beam includes selecting the at least one second training beam based on an error and / or a correlation between the first data beam and the at least one second training beam.

18. The wireless communication method according to claim 15, in, The at least one second training beam includes training beams respectively having patterns that at least partially overlap with each other.

19. The wireless communication method according to claim 15, further comprising In a first beam training phase, estimating a channel based on a signal received using the at least one first training beam, in, Calculating the first data beam includes calculating the first data beam based on the estimated channel and an objective function corresponding to the estimated channel.

20. The wireless communication method according to claim 19, in, Channel estimation includes: collecting measurements generated from a signal received using the at least one first training beam, the received signal being sequentially transmitted M times using the same transmission beam, where M is an integer greater than 1; and A combined channel matrix is ​​generated based on the measurements and the at least one first training beam.

21. The wireless communication method according to claim 20, further comprising: In a first data transmission phase, obtaining a beamforming gain for a first data beam; as well as In the first data transmission stage, transmission data including information on increase or decrease of M is generated based on the beamforming gain.

22. The wireless communication method according to claim 19, in, The objective function is based on at least one of an estimated signal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio (SINR), a channel capacity, or an energy efficiency of the channel.

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