Base station and communication method

Abstract

This base station comprises: a channel generation unit that receives information indicating an estimated channel matrix from the base station, generates, on the basis of the estimated channel matrix, a precoding matrix and a post-coding matrix by solving an optimization problem which applies sparse regularization, and transmits the precoding matrix and the post-coding matrix to the base station and a terminal; and a signal transmission / reception unit that transmits, to the base station, a signal changed on the basis of the precoding matrix and the post-coding matrix.

Description

Base stations and communication methods

[0001] The present invention relates to a base station and a communication method in a wireless communication system.

[0002] The 3rd Generation Partnership Project (3GPP) is exploring wireless communication methods known as 5G or NR (New Radio) (hereinafter referred to as "NR") in order to achieve even greater system capacity, even faster data transmission speeds, and even lower latency in the wireless section. In order to meet the requirements of achieving a throughput of 10 Gbps or more while keeping the latency in the wireless section below 1 ms, various wireless technologies and network architectures are being considered (for example, Non-Patent Documents 1 and 2).

[0003] Furthermore, various requirements are being considered for the next generation of 6G. These requirements include, for example, ultra-broadband communication, mission-critical communication, ultra-massive connection, universal coverage, intelligent connection, and ubiquitous sensing.

[0004] To meet these requirements, the new concept aims for extensibility (e.g., making it more effective for future use), ease of operation, customizability (e.g., making it easier to operate), and sustainability (e.g., cost reduction, a more robust configuration, and resilience). Furthermore, guaranteed communication, ensuring a minimum level of performance at all times, is being considered.

[0005] 3GPP TS 38.300 V18.3.0 (2024-09)3GPP TS 38.401 V18.3.0 (2024-09)

[0006] Various wireless relay technologies have been devised to simplify wireless base station networks. In mobile communication networks, fronthaul or backhaul relay between base stations may be performed wirelessly instead of via wire. For example, a mobile communication network may be configured using multiple land mobile relay stations. On the other hand, MIMO (Multiple Input Multiple Output) has been devised as a technology to improve communication channel capacity.

[0007] In MIMO communication, when using multiple distributed transmitters or transmitting antennas, it is necessary to wirelessly transmit signals to each transmitter or transmitting antenna, raising concerns about communication volume congestion. Therefore, a method is needed to reduce the amount of information transmitted wirelessly by limiting the signals transmitted to each transmitter or transmitting antenna.

[0008] This invention has been made in view of the above points, and aims to reduce the amount of communication involved in wireless relay in mobile communication systems.

[0009] According to the disclosed technology, a base station is provided that includes a channel generation unit that receives information indicating an estimated channel matrix from a base station, generates a precoding matrix and a postcoding matrix by solving an optimization problem applying sparse regularization based on the estimated channel matrix, and transmits them to the base station and a terminal, and a signal transmission / reception unit that transmits a modified signal based on the precoding matrix and postcoding matrix to the base station.

[0010] According to the disclosed technology, it is possible to reduce the amount of data transmitted for wireless relay in mobile communication systems.

[0011] This figure shows an example configuration of a wireless communication system in an embodiment of the present invention. This figure illustrates an example of MIMO communication (1). This figure illustrates an example of MIMO communication (2). This figure shows an example of the functional configuration of a base station 10 in an embodiment of the present invention. This figure shows an example of the functional configuration of a base station 11 in an embodiment of the present invention. This figure shows an example of the functional configuration of a terminal 20 in an embodiment of the present invention. This figure shows an example of the functional configuration of a system in an embodiment of the present invention. This is a flowchart illustrating an example of the operation of a system in an embodiment of the present invention. This figure illustrates an example of a V matrix (1) in an embodiment of the present invention. This figure illustrates an example of a V matrix (2) in an embodiment of the present invention. This figure illustrates an example of a U matrix in an embodiment of the present invention. This figure shows an example of the hardware configuration of a base station 10, base station 11, or terminal 20 in an embodiment of the present invention. This figure shows an example of the configuration of a vehicle 2001 in an embodiment of the present invention.

[0012] Embodiments of the present invention will be described below with reference to the drawings. Note that the embodiments described below are examples, and the embodiments to which the present invention is applied are not limited to those described below.

[0013] In the operation of the wireless communication system according to the embodiments of the present invention, existing technologies may be used as appropriate. However, such existing technologies include, for example, existing LTE, but are not limited to existing LTE. Furthermore, the term "LTE" as used herein has a broad meaning that includes LTE-Advanced and LTE-Advanced and later technologies (e.g., NR), unless otherwise specified.

[0014] Furthermore, in the embodiments of the present invention described below, terms such as SS (Synchronization signal), PSS (Primary SS), SSS (Secondary SS), PBCH (Physical broadcast channel), PRACH (Physical random access channel), PDCCH (Physical Downlink Control Channel), PDSCH (Physical Downlink Shared Channel), PUCCH (Physical Uplink Control Channel), and PUSCH (Physical Uplink Shared Channel), which are used in existing LTE systems, will be used. This is for convenience of description, and similar signals, functions, etc., may be called by other names. Also, the above terms in NR correspond to NR-SS, NR-PSS, NR-SSS, NR-PBCH, NR-PRACH, etc. However, even if a signal is used in NR, it is not necessarily explicitly stated as "NR-".

[0015] Furthermore, in the embodiments of the present invention, the duplex system may be a TDD (Time Division Duplex) system, an FDD (Frequency Division Duplex) system, or any other system (for example, a Flexible Duplex).

[0016] Furthermore, in the embodiments of the present invention, "configuring" wireless parameters may mean that predetermined values ​​are pre-configured, or that wireless parameters notified from the base station 10 or terminal 20 are configured.

[0017] Figure 1 shows an example of the configuration of a wireless communication system in an embodiment of the present invention. The wireless communication system in the embodiment of the present invention includes a base station 10 and a terminal 20, as shown in Figure 1. Figure 1 shows one base station 10 and one terminal 20, but this is an example, and there may be multiple base stations 10 and terminals 20.

[0018] Base station 10 is a communication device that provides one or more cells and communicates wirelessly with terminal 20. The physical resources of the wireless signal are defined in the time domain and the frequency domain. The time domain may be defined by the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols, and the frequency domain may be defined by the number of subcarriers or resource blocks. Base station 10 transmits synchronization signals and system information to terminal 20. Synchronization signals are, for example, NR-PSS and NR-SSS. System information is transmitted, for example, in NR-PBCH and is also called broadcast information. Synchronization signals and system information may also be called SSB (SS / PBCH block). As shown in Figure 1, base station 10 transmits control signals or data to terminal 20 via DL (Downlink) and receives control signals or data from terminal 20 via UL (Uplink). Both base station 10 and terminal 20 are capable of transmitting and receiving signals using beamforming. Furthermore, both the base station 10 and the terminal 20 can apply MIMO (Multiple Input Multiple Output) communication to DL or UL. Also, both the base station 10 and the terminal 20 may communicate via Carrier Aggregation (CA) through secondary cells (SCell) and primary cells (PCell). Additionally, the terminal 20 may communicate via Dual Connectivity (DC) through the primary cell of base station 10 and the primary secondary cell group cell (PSCell) of another base station 10.

[0019] Terminal 20 is a communication device equipped with wireless communication capabilities, such as a smartphone, mobile phone, tablet, wearable device, or M2M (Machine-to-Machine) communication module. As shown in Figure 1, Terminal 20 receives control signals or data from the base station 10 via DL and transmits control signals or data to the base station 10 via UL, thereby utilizing various communication services provided by the wireless communication system. Terminal 20 also receives various reference signals transmitted from the base station 10 and performs propagation path quality measurement based on the reception results of said reference signals.

[0020] Furthermore, various requirements are being considered for the next generation of 6G. For example, these requirements may include ultra-broadband communication, mission-critical communication, ultra-massive connection, universal coverage, intelligent connection, and ubiquitous sensing.

[0021] Furthermore, these requirements may include ultra-high-speed communication, large-capacity communication, ultra-wide coverage, ultra-low power consumption, cost reduction, ultra-low latency, ultra-high reliability communication, ultra-high connectivity, and sensing.

[0022] To meet these requirements, the new concept aims for extensibility (e.g., making it more effective for future use), ease of operation, customizability (e.g., making it easier to operate), and sustainability (e.g., cost reduction, a more robust configuration, and resilience). Furthermore, guaranteed communication, ensuring a minimum level of performance at all times, is being considered.

[0023] To simplify wireless base station networks, various wireless relay technologies have been devised. In mobile communication networks, fronthaul or backhaul relay between base stations may be performed wirelessly instead of via wire. For example, a mobile communication network may be configured using multiple land mobile relay stations. On the other hand, MIMO (Multiple Input Multiple Output) has been devised as a technology to improve communication channel capacity.

[0024] In MIMO communication, when using multiple distributed transmitters or transmitting antennas, it is necessary to wirelessly transmit signals to each transmitter or transmitting antenna, raising concerns about communication volume congestion. Therefore, a method is needed to reduce the amount of information transmitted wirelessly by limiting the signals transmitted to each transmitter or transmitting antenna.

[0025] Figure 2 is a diagram illustrating an example of MIMO communication (1). Figure 2 shows an example of a dense information transmission network in which streams #1, #2 and #3 are transmitted from all RUs #1, #2, #3, #4, #5, #6, #7 and #8 to antennas #1, #2, #3 and #4 of the UE.

[0026] Figure 3 is a diagram illustrating an example of MIMO communication (2). In Figure 3, stream #1 is transmitted from RU #4 to antennas #1, #2, #3 and #4 of the UE. Stream #2 is transmitted from RU #1 and RU #8 to antennas #1, #2, #3 and #4 of the UE. Stream #2 is transmitted from RU #2, RU #5 and RU #8 to antennas #1, #2, #3 and #4 of the UE. As described above, Figure 3 shows an example of a sparse information transmission network. A sparse information transmission network can reduce the amount of information transmitted wirelessly compared to the dense information transmission network shown in Figure 4.

[0027] Next, a functional configuration example of the base stations 10, 11, and the terminal 20 that execute the processes and operations described in the embodiments of the present invention will be described. The base stations 10, 11, and the terminal 20 include functions for executing the examples. However, each of the base stations 10, 11, and the terminal 20 may be provided with only some of the functions in the examples.

[0028] <Base Station 10> Figure 4 is a diagram showing an example of the functional configuration of the base station 10 in the embodiment of the present invention. As shown in Figure 4, the base station 10 has a signal transmission / reception unit 101 and a channel generation unit 102. The base station 10 shown in Figure 4 may be a DU, an RU, or a CU. The functional configuration shown in Figure 4 is merely an example. As long as the operations according to the embodiments of the present invention can be executed, the functional divisions and the names of the functional units may be anything.

[0029] The signal transmission / reception unit 101 changes the transmission / reception signal based on the generation results of the precoding matrices U and V that can set the number of streams, received from the channel generation unit 102. The signal transmission / reception unit 101 transmits and receives signals with the signal transmission / reception unit 111 of the base station 11.

[0030] The channel generation unit 102 generates the post-coding matrix U and the precoding matrix V from the block channel estimation matrix H received from the channel estimation unit 112 of the base station 11. ｋ

[0031] Figure 5 is a diagram showing an example of the functional configuration of the base station 11 in the embodiment of the present invention. As shown in Figure 5, the base station 11 has a signal transmission / reception unit 111, a channel estimation unit 112, a weight matrix multiplication unit 113, and an antenna group 114. The base station 11 shown in Figure 5 may be a DU, an RU, or a CU. The functional configuration shown in Figure 5 is merely an example. As long as the operations according to the embodiments of the present invention can be executed, the functional divisions and the names of the functional units may be anything.

[0032] The signal transceiver unit 111 transmits and receives signals with the signal transceiver unit 101 of the base station 10. Also, the signal transceiver unit 111 transmits and receives signals with the weight matrix multiplication unit 113.

[0033] The channel estimation unit 112 transmits the block channel matrix Hk, which estimates the channel between the antenna group 114 and the antenna group 203 of the terminal 20, to the channel generation unit 102 of the base station 10.

[0034] The weight matrix multiplication unit 113 executes the transmission and reception processing of the MIMO signal with the terminal 20 based on the precoding matrix V received from the channel generation unit 102 of the base station 10.

[0035] The antenna group 114 transmits and receives MIMO signals with the antenna group 203 of the terminal 20.

[0036] <Terminal 20> Fig. 6 is a diagram showing an example of the functional configuration of the terminal 20 in the embodiment of the present invention. As shown in Fig. 6, the terminal 20 includes a signal transceiver unit 201, a weight matrix multiplication unit 202, and an antenna group 203. The functional configuration shown in Fig. 6 is merely an example. As long as the operations according to the embodiment of the present invention can be executed, the functional classification and the names of the functional units can be anything.

[0037] The signal transceiver unit 201 transmits and receives signals with the signal transceiver unit 111 of the base station 11. Also, the signal transceiver unit 201 transmits and receives signals with the weight matrix multiplication unit 202.

[0038] The weight matrix multiplication unit 202 executes the transmission and reception processing of the MIMO signal with the base station 11 based on the postcoding matrix U received from the channel generation unit 102 of the base station 10.

[0039] The antenna group 203 transmits and receives MIMO signals with the antenna group 114 of the base station 11.

[0040] Fig. 7 is a diagram showing an example of the functional configuration of the system in the embodiment of the present invention. As shown in Fig. 7, the base station 1 has the functional configuration of the base station 10, and the base stations 2-1, 2-2, and 2-3 have the functional configuration of the base station 20.

[0041] The signal transmission / reception unit 101 of base station 1 is connected to the signal transmission / reception units 111 of base stations 2-1, 2-2, and 2-3. The signal transmission / reception unit 101 modifies the transmission and reception signals based on the generation results of a precoding matrix V and a postcoding matrix U, which can set the number of streams, received from the channel generation unit 102.

[0042] The channel generation unit 102 of base station 1 generates a precoding matrix V and a postcoding matrix U from the block channel estimation matrix Hk received from the channel estimation units 112 of base stations 2-1, 2-2, and 2-3.

[0043] The signal transmission / reception units 111 of base stations 2-1, 2-2, and 2-3 transmit and receive signals with the signal transmission / reception unit 101 of base station 1. The signal transmission / reception units 111 also transmit and receive signals with the weight matrix multiplication unit 113.

[0044] The channel estimation units 112 of base stations 2-1, 2-2, and 2-3 transmit a block channel matrix Hk, which estimates the channel between the antenna group 114 and the terminal antenna group 203, to the channel generation unit 102 of base station 1.

[0045] The weight matrix multiplication units 113 of base stations 2-1, 2-2, and 2-3 perform MIMO signal transmission and reception processing based on the precoding matrix V received from the channel generation unit 102 of base station 1.

[0046] The terminal's signal transmission / reception unit 201 transmits and receives signals with the signal transmission / reception units 111 of base stations 2-1, 2-2, and 2-3. The terminal's signal transmission / reception unit 201 also transmits and receives signals with the weight matrix multiplication unit 202.

[0047] The terminal's weight matrix multiplication unit 202 performs MIMO signal transmission and reception processing with base stations 2-1, 2-2, and 2-3 based on the postcoding matrix U received from the base station 10's channel generation unit 102.

[0048] The following steps 1) through 4) may be performed.

[0049] Step 1) Each lower-level node (designated as the k-th node) on the network executes channel estimation with the destination terminal. Let the estimated channel matrix be H ｋ and denote it as such.

[0050] Step 2) Each lower-level node transmits the information of H ｋ to the upper-level node.

[0051] Step 3) The upper-level node calculates the combined H = [H ｋ , ···, H １ , ···, H ｋ , ···] and calculates the precoding matrix V and the postcoding matrix U from H. Here, a sparse regularization term regarding V may be added to obtain a sparse solution of V (most components are 0).

[0052] Step 4) The upper-level node sends V (or its block matrix V ｋ ) and U to the lower-level nodes, and the lower-level nodes execute MIMO communication based on U and V.

[0053] For example, more specifically, when generating the precoding matrix V and the postcoding matrix U, DU may collect the channel matrices between each RU-UE, and solve the singular value decomposition of the collected channel matrices as a sparse optimization problem on the Stiefel manifold.

[0054] FIG. 8 is a flowchart for explaining an example of the operation of the system in an embodiment of the present invention. In step S101, the channel matrix is acquired. RU#k estimates the channel matrix H ｋ ∈ C Ｍ between its own device and the UE, and transmits the estimated values H ｋ ~ to the upper-level node (e.g., DU) respectively.

[0055] In step S102, DU calculates the overall estimated channel H~ = [H １ ~, ···, H Ｎ ~] ∈ C Ｍ×Ｎ . M is the number of antennas of the UE, and N is the number of RUs.

[0056] In step S103, we formulate the problem as a sparse optimization problem on a Stiefel manifold (⊂ Riemann manifold) to find U and V. For example, we may find U and V by solving the following equation.

[0057] minimize f(U,V)=-tr(U Ｈ HVN) + λf ｓｐａｒｃｅ (V), (U,V)∈St(M,L)×St(N,L)

[0058] St(n,p) is a Stiefel variety, and n,p ∈ Z ＋ , St(n,p)={U∈C ｎ×ｐ | U Ｈ U=I ｐ}

[0059] L is the number of streams. N is given by N = diag(μ １ , μ ２ , ..., μ Ｌ ), μ １ >μ ２ >...>μ Ｌ > 0. f ｓｐａｒｃｅ (V) is a sparse regularization term, for example, f ｓｐａｒｃｅ (V) = Σ|V ｉｊ | is the regularization parameter. λ > 0 is the regularization parameter.

[0060] The above -tr(U Ｈ HVN corresponds to singular value decomposition. λf ｓｐａｒｃｅ (V) corresponds to sparse regularization.

[0061] Figure 9 is a diagram illustrating an example (1) of the V matrix in an embodiment of the present invention. The V matrix may be calculated as shown in Figure 9. In the V matrix of Figure 9, stream #1 is transmitted from RU #3, stream #2 is transmitted from RU #1 and RU #6, stream #3 is transmitted from RU #2, RU #4 and RU #6, and stream #4 is not transmitted.

[0062] In step S104, the DU transmits the obtained (U,V) to each RU and UE. Each RU and UE performs MIMO transmission based on (U,V).

[0063] Figure 10 is a diagram illustrating an example (2) of the V matrix in an embodiment of the present invention. Figure 10 shows an example of communication between multiple RUs, each having multiple antennas, and a single UE, each having multiple antennas. As shown in Figure 10, it is sufficient for the matrix to be sparse on a RU-by-RU basis, rather than on a RU-antenna basis, so the sparse regularization term in step S103 may be replaced with equation 1.

[0064]

[0065] max | V in Math 1 ｉｊ |, j∈J(RU#k) is V for j belonging to the k-th RU ｉｊ It corresponds to the maximum value.

[0066] In the V matrix of Figure 10, which is sparse on a RU basis, stream #1 is transmitted from antennas #1 and #2 of RU #1, stream #2 is transmitted from antennas #3 and #4 of RU #2, stream #3 is transmitted from antennas #1 and #2 of RU #1 and antennas #3 and #4 of RU #2, and stream #4 is not transmitted.

[0067] Figure 11 is a diagram illustrating an example of a U matrix in an embodiment of the present invention. Figure 11 shows an example of communication between multiple RUs having multiple antennas and multiple UEs having multiple antennas. When multiple UEs are assumed, orthogonality between the UEs is required. Therefore, the orthogonality determination term shown in Equation 2 may be added to or multiplied by the sparse regularization term in step S103 above.

[0068]

[0069] In the mutually orthogonal U-matrix of Figure 11 between different UEs, stream #1 is transmitted to antenna #1-antenna #4 of UE #1, stream #2 is transmitted to antenna #5-antenna #8 of UE #2, stream #3 is transmitted to antenna #1-antenna #4 of UE #1, and stream #4 is not transmitted.

[0070] As demonstrated in the above embodiment, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced.

[0071] In other words, it is possible to reduce the amount of communication involved in wireless relay in mobile communication systems.

[0072] The block diagrams (Figures 4, 5, and 6) used in the description of the above embodiments show functional units. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically coupled, or it may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wired or wireless connections). A functional block may also be realized by combining software with the one or more of the above devices.

[0073] Functions include, but are not limited to, judgment, decision, judgment, calculation, calculation, processing, derivation, investigation, exploration, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, assumption, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating (mapping), and assigning. For example, a functional block (configuration part) that enables transmission is called a transmitting unit or transmitter. In all cases, as mentioned above, the method of implementation is not particularly limited.

[0074] For example, the base stations 10 and 11, terminal 20, etc. in one embodiment of the present disclosure may function as computers that process the wireless communication method of the present disclosure. Figure 12 is a diagram showing an example of the hardware configuration of the base stations 10 and 11 and terminal 20 according to one embodiment of the present disclosure. The above-mentioned base stations 10 and terminal 20 may be physically configured as computer devices including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0075] In the following explanation, the term "device" can be read as "circuit," "device," "unit," etc. The hardware configuration of base station 10, base station 11, and terminal 20 may include one or more of the devices shown in the figure, or it may be configured without some of the devices.

[0076] Each function in base station 10, base station 11, and terminal 20 is realized by loading predetermined software (programs) onto hardware such as the processor 1001 and storage device 1002, which allows the processor 1001 to perform calculations, control communication by the communication device 1004, and control at least one of the reading and writing of data in the storage device 1002 and auxiliary storage device 1003.

[0077] The processor 1001 controls the entire computer, for example, by running an operating system. The processor 1001 may consist of a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic units, registers, etc. For example, the control unit and the like described above may be implemented by the processor 1001.

[0078] Furthermore, the processor 1001 reads programs (program code), software modules, or data from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002, and executes various processes accordingly. The program used is one that causes the computer to execute at least a part of the operations described in the above embodiment. For example, the control unit of the base station 10 shown in Figure 2 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Also, for example, the control unit of the terminal 20 shown in Figure 3 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Although the above-described processes have been explained as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The program may also be transmitted from the network via a telecommunications line.

[0079] The storage device 1002 is a computer-readable recording medium and may consist of at least one of the following: ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc. The storage device 1002 may also be called a register, cache, main memory, etc. The storage device 1002 can store executable programs (program code), software modules, etc., for implementing a communication method according to one embodiment of the present disclosure.

[0080] The auxiliary storage device 1003 is a computer-readable recording medium and may consist of at least one of the following: an optical disc such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital multipurpose disk, a Blu-ray® disk), a smart card, flash memory (e.g., a card, a stick, a key drive), a floppy® disk, a magnetic strip, etc. The above-mentioned storage medium may also be a database, server, or other suitable medium that includes at least one of the storage device 1002 and the auxiliary storage device 1003.

[0081] The communication device 1004 is hardware (transmitting / receiving device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as a network device, network controller, network card, communication module, etc. The communication device 1004 may be configured to include, for example, a high-frequency switch, duplexer, filter, frequency synthesizer, etc., in order to implement at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, the transmitting and receiving antenna, amplifier section, transmitting and receiving section, transmission path interface, etc., may be implemented by the communication device 1004. The transmitting and receiving section may be implemented in a physically or logically separated manner, with a transmitting section and a receiving section.

[0082] The input device 1005 is an input device that accepts input from an external source (e.g., a keyboard, mouse, microphone, switch, button, sensor, etc.). The output device 1006 is an output device that outputs to an external source (e.g., a display, speaker, LED lamp, etc.). The input device 1005 and the output device 1006 may be configured as an integrated unit (e.g., a touch panel).

[0083] Furthermore, each device, such as the processor 1001 and the storage device 1002, is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or different buses may be configured for each device.

[0084] Furthermore, base stations 10, 11, and terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and some or all of each functional block may be realized by such hardware. For example, the processor 1001 may be implemented using at least one of these hardware components.

[0085] Figure 13 shows an example of the configuration of vehicle 2001. As shown in Figure 13, vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in this disclosure may be applied to a communication device mounted on vehicle 2001, for example, to the communication module 2013.

[0086] The drive unit 2002 consists of, for example, an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel, which is operated by the user.

[0087] The electronic control unit 2010 consists of a microprocessor 2031, memory (ROM, RAM) 2032, and communication ports (IO ports) 2033. Signals from various sensors 2021 to 2029 installed in the vehicle 2001 are input to the electronic control unit 2010. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0088] Signals from various sensors 2021 to 2029 include current signals from current sensor 2021 for sensing motor current, front or rear wheel rotation speed signals acquired by rotation speed sensor 2022, front or rear wheel air pressure signals acquired by air pressure sensor 2023, vehicle speed signals acquired by vehicle speed sensor 2024, acceleration signals acquired by acceleration sensor 2025, accelerator pedal depression signals acquired by accelerator pedal sensor 2029, brake pedal depression signals acquired by brake pedal sensor 2026, shift lever operation signals acquired by shift lever sensor 2027, and detection signals acquired by object detection sensor 2028 for detecting obstacles, vehicles, pedestrians, etc.

[0089] The Information Service Unit 2012 consists of various devices for providing (outputting) various types of information such as driving information, traffic information, and entertainment information, including a car navigation system, audio system, speakers, television, and radio, and one or more ECUs that control these devices. The Information Service Unit 2012 uses information acquired from external devices via a communication module 2013, etc., to provide various multimedia information and multimedia services to the occupants of the vehicle 2001. The Information Service Unit 2012 may include input devices that accept input from the outside (e.g., keyboard, mouse, microphone, switch, button, sensor, touch panel, etc.) and output devices that perform output to the outside (e.g., display, speaker, LED lamp, touch panel, etc.).

[0090] The driver assistance system unit 2030 consists of various devices that provide functions to prevent accidents or reduce the driver's workload, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System)), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. The driver assistance system unit 2030 also transmits and receives various information via the communication module 2013 to realize driver assistance functions or autonomous driving functions.

[0091] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via its communication port. For example, the communication module 2013 sends and receives data via the communication port 2033 between the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, the microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021-29 provided in the vehicle 2001.

[0092] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with external devices. For example, it can send and receive various types of information with external devices via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station or a mobile station.

[0093] The communication module 2013 may transmit at least one of the following to an external device via wireless communication: signals from the various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on said signals, and information based on input from an external source (user) obtained via the information service unit 2012. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc., may also be called input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include the information based on the above input.

[0094] The communication module 2013 receives various information (traffic information, signal information, inter-vehicle information, etc.) transmitted from an external device and displays it on the information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may also be called an output unit, which outputs information (for example, outputs information to devices such as displays and speakers based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from the external device in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021-2029, etc., provided in the vehicle 2001.

[0095] (Summary of Embodiments) As described above, according to embodiments of the present invention, a base station is provided which includes a channel generation unit that receives information indicating an estimated channel matrix from a base station, generates a precoding matrix and a postcoding matrix by solving an optimization problem to which sparse regularization is applied based on the estimated channel matrix, and transmits them to the base station and a terminal, and a signal transmission / reception unit that transmits a signal modified based on the precoding matrix and postcoding matrix to the base station.

[0096] With the above configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced. In other words, the amount of communication related to wireless relay in a mobile communication system can be reduced.

[0097] The signal transmission / reception unit may transmit a signal to the base station with at least the number of streams changed based on the precoding matrix and postcoding matrix. With this configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced.

[0098] The channel generation unit may generate the precoding matrix and postcoding matrix by solving an optimization problem that applies sparse regularization to the overall estimated channel based on multiple estimated channel matrices received from multiple base stations. With this configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced.

[0099] The channel generation unit may generate the precoding matrix by solving an optimization problem that applies sparse regularization, which is sparse at the base station level. With this configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced.

[0100] The channel generation unit may generate the postcoding matrix so that it is orthogonal on a terminal-by-terminal basis. With this configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced.

[0101] Furthermore, according to an embodiment of the present invention, a communication method is provided in which a base station performs the following steps: receiving information indicating an estimated channel matrix from a base station, generating a precoding matrix and a postcoding matrix by solving an optimization problem to which sparse regularization is applied based on the estimated channel matrix, and transmitting them to the base station and a terminal; and transmitting a signal modified based on the precoding matrix and postcoding matrix to the base station.

[0102] With the above configuration, by using a sparse solution as the precoding matrix, the combination of lower nodes and streams used can be limited, and the amount of communication between upper and lower nodes can be significantly reduced. In other words, the amount of communication related to wireless relay in a mobile communication system can be reduced.

[0103] (Supplement to Embodiments) Embodiments of the present invention have been described above, but the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, substitutions, etc. Specific numerical examples have been used to facilitate understanding of the invention, but unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention, and matters described in two or more items may be combined as needed, and matters described in one item may be applied to matters described in another item (as long as they do not contradict each other). The boundaries of functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries of physical parts. The operation of multiple functional units may be physically performed by one part, or the operation of one functional unit may be physically performed by multiple parts. The processing procedures described in the embodiments may be rearranged as long as they do not contradict each other. For the convenience of explaining the processing, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be realized in hardware, software, or a combination thereof. The software operated by the processor of the base station 10 according to an embodiment of the present invention and the software operated by the processor of the terminal 20 according to an embodiment of the present invention may be stored in any suitable storage medium such as random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or other appropriate storage medium.

[0104] Furthermore, notification of information is not limited to the embodiments described herein and may be carried out by other means. For example, notification of information may be carried out by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), upper layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling), broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals, or combinations thereof. Also, RRC signaling may be called RRC messages, and may be, for example, RRC Connection Setup messages, RRC Connection Reconfiguration messages, etc.

[0105] Each aspect / embodiment described in this disclosure may be applied to at least one of the following systems: LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), FRA (Future Radio Access), NR (new Radio), W-CDMA®, GSM®, CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi®), IEEE 802.16 (WiMAX®), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth®, and other appropriate systems, as well as next-generation systems extended based thereon. Furthermore, multiple systems may be applied in combination (for example, a combination of at least one of LTE and LTE-A with 5G).

[0106] The processing procedures, sequences, flowcharts, etc., of each aspect / embodiment described herein may be reordered, provided they are consistent with each other. For example, the methods described herein present various step elements in an exemplary order and are not limited to that specific order.

[0107] In this specification, specific operations performed by the base station 10 may, in some cases, be performed by its upper node. In a network consisting of one or more network nodes having a base station 10, it is clear that various operations performed for communication with the terminal 20 can be performed by the base station 10 and at least one of the other network nodes (for example, an MME or S-GW, but not limited to these). Although the above example illustrates the case where there is one other network node besides the base station 10, the other network node may be a combination of multiple other network nodes (for example, an MME and an S-GW).

[0108] The information or signals described in this disclosure may be output from a higher layer (or lower layer) to a lower layer (or higher layer). They may also be input and output via multiple network nodes.

[0109] Input and output information may be stored in a specific location (e.g., memory) or managed using a management table. Input and output information may be overwritten, updated, or appended to. Output information may be deleted. Input information may be transmitted to other devices.

[0110] The determination in this disclosure may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a numerical comparison (for example, a comparison with a predetermined value).

[0111] Software should be broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, and so on, whether they are called software, firmware, middleware, microcode, hardware description languages, or by any other name.

[0112] Furthermore, software, instructions, information, etc., may be transmitted and received via a transmission medium. For example, if software is transmitted from a website, server, or other remote source using at least one of wired technology (such as coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL)) and wireless technology (such as infrared or microwave), then at least one of these wired and wireless technologies is included in the definition of a transmission medium.

[0113] The information, signals, etc. described in this disclosure may be represented using any of the various different techniques. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0114] In addition, terms used in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of the channel and symbol may be a signal (signaling). Also, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, cell, frequency carrier, etc.

[0115] The terms “system” and “network” as used in this disclosure are interchangeable.

[0116] Furthermore, the information, parameters, etc., described in this disclosure may be expressed using absolute values, relative values ​​from a given value, or other corresponding information. For example, wireless resources may be indicated by an index.

[0117] The names used for the parameters described above are not restrictive in any way. Furthermore, the formulas and other expressions using these parameters may differ from those expressly disclosed in this disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name, and therefore, the various names assigned to these various channels and information elements are not restrictive in any way.

[0118] In this disclosure, terms such as "Base Station (BS)", "wireless base station", "base station equipment", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "transmission / reception point", "cell", "sector", "cell group", "carrier", and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0119] A base station can accommodate one or more (e.g., three) cells. If a base station accommodates multiple cells, the entire coverage area of ​​the base station can be divided into multiple smaller areas, each of which may also be provided with communication services by a base station subsystem (e.g., a Remote Radio Head (RRH)). The terms “cell” or “sector” refer to part or all of the coverage area of ​​at least one of the base station and / or base station subsystems that provide communication services in that coverage.

[0120] In this disclosure, the transmission of information by a base station to a terminal may be interpreted as the base station instructing the terminal to perform control or operation based on the information.

[0121] In this disclosure, terms such as "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" may be used interchangeably.

[0122] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or several other appropriate terms.

[0123] At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may also be a device mounted on a mobile body, the mobile body itself, etc. The mobile body refers to a movable object, and its speed of movement is arbitrary. This also includes the case when the mobile body is stationary. The mobile body includes, but is not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcarts, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and items mounted on them. The mobile body may also be a mobile body that moves autonomously based on operation commands. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile body (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). Furthermore, at least one of the base station and the mobile station may include devices that do not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0124] Furthermore, the term "base station" in this disclosure may be interpreted as "user terminal." For example, the various aspects / embodiments of this disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, the terminals 20 may have the functions that the base station 10 has. Also, terms such as "uplink" and "downlink" may be interpreted as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, uplink channel, downlink channel, etc., may be interpreted as side channel.

[0125] Similarly, the term "user terminal" in this disclosure may be replaced with "base station." In this case, the base station may be configured to have the same functions as the user terminal described above.

[0126] As used in this disclosure, the terms “determining” and “determining” may encompass a wide variety of actions. “Determining” may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, or inquiring (e.g., searching in a table, database, or other data structure), or ascertaining. “Determining” may also include receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, or accessing (e.g., accessing data in memory). Furthermore, "judgment" and "decision" can include considering something as having been "judged" or "decided" after resolving, selecting, choosing, establishing, comparing, etc. In other words, "judgment" and "decision" can include considering something as having been "judged" or "decided" after some action. Also, "judgment (decision)" can be reinterpreted as "assuming," "expecting," or "considering."

[0127] The terms “connected,” “coupled,” or any variation thereof, mean any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are “connected” or “coupled” with each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, “connection” may be reinterpreted as “access.” As used in this disclosure, two elements may be considered to be “connected” or “coupled” with each other using at least one of one or more wires, cables, and printed electrical connections, and, in some non-limiting and non-exclusive examples, electromagnetic energy having wavelengths in the radio frequency domain, microwave domain, and optical (both visible and invisible) domain.

[0128] The reference signal can also be abbreviated as RS (Reference Signal), and may be called a pilot depending on the applicable standard.

[0129] In this disclosure, the phrase "based on" does not mean "based solely on" unless otherwise specified. In other words, the phrase "based on" means both "based solely on" and "based at least on."

[0130] Any reference to elements using the designations “first,” “second,” etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Accordingly, references to the first and second elements do not imply that only two elements may be employed, or that the first element must precede the second element in any way.

[0131] In the configuration of each of the above devices, "means" may be replaced with "part," "circuit," "device," etc.

[0132] Where the terms “include,” “including,” and variations thereof are used in this disclosure, these terms are intended to be inclusive, as is the term “comprising.” Furthermore, the term “or” as used in this disclosure is not intended to mean exclusive OR.

[0133] A wireless frame may consist of one or more frames in the time domain. Each of these frames in the time domain may be called a subframe. A subframe may further consist of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0134] Numerical logic may be communication parameters applied to at least one of the transmission and reception of a signal or channel. Numerical logic may include, for example, at least one of the following: subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame configuration, specific filtering processes performed by the transceiver in the frequency domain, and specific windowing processes performed by the transceiver in the time domain.

[0135] A slot may consist of one or more symbols in the time domain (such as OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, etc.). A slot may also be a time unit based on neurologic.

[0136] A slot may include multiple minislots. Each minislot may consist of one or more symbols in the time domain. Minislots may also be called subslots. Minislots may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called a PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called a PDSCH (or PUSCH) mapping type B.

[0137] Wireless frames, subframes, slots, minislots, and symbols all represent units of time when transmitting a signal. Different names may be used for each of these terms.

[0138] For example, one subframe may be called a Transmission Time Interval (TTI), multiple consecutive subframes may be called a TTI, or one slot or one minislot may be called a TTI. In other words, at least one of a subframe and a TTI may be a subframe in existing LTE (1 ms), a period shorter than 1 ms (e.g., 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

[0139] Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, the base station schedules each terminal 20 to allocate wireless resources (such as the frequency bandwidth and transmission power available to each terminal 20) in TTI units. However, the definition of TTI is not limited to this.

[0140] TTI may be a transmission time unit for channel-encoded data packets (transport blocks), code blocks, code words, etc., or it may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the actual time interval (e.g., number of symbols) in which the transport block, code block, code word, etc. are mapped may be shorter than the TTI.

[0141] Furthermore, if one slot or one mini-slot is referred to as a TTI, then one or more TTIs (i.e., one or more slots or one or more mini-slots) may constitute the minimum time unit for scheduling. In addition, the number of slots (number of mini-slots) that constitute this minimum time unit for scheduling may be controlled.

[0142] A TTI with a time length of 1 ms may be called a normal TTI, a long TTI, a normal subframe, a long subframe, a slot, etc. A TTI shorter than a normal TTI may be called a shortened TTI, a short TTI, a partial or fractional TTI, a shortened subframe, a short subframe, a mini slot, a sub slot, a slot, etc.

[0143] Furthermore, long TTIs (e.g., normal TTIs, subframes, etc.) may be interpreted as TTIs with a time length exceeding 1 ms, and short TTIs (e.g., shortened TTIs, etc.) may be interpreted as TTIs with a TTI length less than that of a long TTI but 1 ms or more.

[0144] A resource block (RB) is a resource allocation unit in the time domain and frequency domain, and in the frequency domain, it may contain one or more consecutive subcarriers. The number of subcarriers in an RB may be the same regardless of the neurology, for example, 12. The number of subcarriers in an RB may be determined based on the neurology.

[0145] Furthermore, the time domain of the RB may contain one or more symbols and may be the length of one slot, one minislot, one subframe, or one TTI. One TTI, one subframe, etc., may each consist of one or more resource blocks.

[0146] One or more RBs may also be called a Physical RB (PRB), Sub-Carrier Group (SCG), Resource Element Group (REG), PRB pair, RB pair, etc.

[0147] Furthermore, a resource block may consist of one or more resource elements (REs). For example, one RE may be a radio resource area comprising one subcarrier and one symbol.

[0148] A Bandwidth Part (BWP), also known as a partial bandwidth, may represent a subset of consecutive common resource blocks (RBs) for a particular neurology in a given carrier. These common RBs may be identified by an index of the RBs relative to a common reference point of the carrier. The PRBs may be defined and numbered within a given BWP.

[0149] A BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be set within a single carrier for a UE.

[0150] At least one of the configured BWPs may be active, and the UE does not need to assume that it will transmit or receive a predetermined signal / channel outside of the active BWP. In this disclosure, terms such as "cell" and "carrier" may be read as "BWP".

[0151] The structures described above, such as wireless frames, subframes, slots, minislots, and symbols, are merely illustrative. For example, the number of subframes included in a wireless frame, the number of slots per subframe or wireless frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, and the number of symbols, symbol length, and cyclic prefix (CP) length within a TTI can be varied in various ways.

[0152] In this disclosure, if articles are added through translation, such as a, an, and the in English, this disclosure may include the fact that the noun following these articles is plural.

[0153] In this disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "combine" may be interpreted similarly to "different."

[0154] Each aspect / embodiment described in this disclosure may be used individually, in combination, or switched between as needed during implementation. Furthermore, notification of specific information (e.g., notification that "X is") is not limited to explicit notification, but may also be implicit (e.g., by not providing such notification).

[0155] Although the present disclosure has been described in detail above, it will be clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the intent and scope of the present disclosure as defined by the claims. Therefore, the descriptions in the present disclosure are illustrative and not intended to be restrictive in any way.

[0156] 10 Base station 101 Signal transmission / reception unit 102 Channel generation unit 11 Base station 111 Signal transmission / reception unit 112 Channel estimation unit 113 Weight matrix multiplication unit 114 Antenna group 20 Terminal 201 Signal transmission / reception unit 202 Weight matrix multiplication unit 203 Antenna group 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Front wheel 2008 Rear wheel 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 Rotation speed sensor 2023 Air pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driver assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (I / O port)

Claims

1. A base station having a channel generation unit that receives information indicating an estimated channel matrix from a base station, generates a precoding matrix and a postcoding matrix by solving an optimization problem applying sparse regularization based on the estimated channel matrix, and transmits them to the base station and a terminal; and a signal transmission / reception unit that transmits a modified signal based on the precoding matrix and postcoding matrix to the base station.

2. The base station according to claim 1, wherein the signal transmitting / receiving unit transmits a signal to the base station with at least the number of streams changed based on the precoding matrix and the postcoding matrix.

3. The base station according to claim 1, wherein the channel generation unit generates a precoding matrix and a postcoding matrix by solving an optimization problem to which sparse regularization is applied, based on an overall estimated channel based on a plurality of estimated channel matrices received from a plurality of base stations.

4. The base station according to claim 1, wherein the channel generation unit generates the precoding matrix by solving an optimization problem that applies sparse regularization, which is sparse on a per-base station basis.

5. The base station according to claim 1, wherein the channel generation unit generates postcoding matrices so that they are orthogonal on a terminal-by-terminal basis.

6. A communication method in which a base station performs the following steps: receiving information indicating an estimated channel matrix from a base station, generating a precoding matrix and a postcoding matrix by solving an optimization problem applying sparse regularization based on the estimated channel matrix, and transmitting them to the base station and a terminal; and transmitting a modified signal based on the precoding matrix and postcoding matrix to the base station.

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