阅读说明：本技术 发送装置、接收装置、基站、终端以及发送方法 (Transmission device, reception device, base station, terminal, and transmission method ) 是由 长谷川文大 平明德 于 2018-01-10 设计创作，主要内容包括：本申请提供一种发送装置、接收装置、基站、终端以及发送方法。本申请的发送装置(50)：在多个组ID、与所述组ID对应的1个以上的端口号、以及与所述端口号对应的1个以上的参照信号之间的关系上,该发送装置具有：发送部,其发送所述端口号；参照信号生成部,其使用与所述端口号对应的组ID生成作为参照信号使用的随机数,所述发送部对生成的所述参照信号进行发送。(The application provides a transmitting device, a receiving device, a base station, a terminal and a transmitting method. Transmission device (50) of the present application: the transmission device has, in a relationship among a plurality of group IDs, 1 or more port numbers corresponding to the group IDs, and 1 or more reference signals corresponding to the port numbers: a transmission unit that transmits the port number; and a reference signal generation unit that generates a random number used as a reference signal using a group ID corresponding to the port number, wherein the transmission unit transmits the generated reference signal.)

1. A transmission device, characterized in that in the relation among a plurality of group IDs, 1 or more port numbers corresponding to the group IDs, and 1 or more reference signals corresponding to the port numbers,

the transmission device includes:

a transmission unit that transmits the port number; and

a reference signal generation unit that generates a random number used as a reference signal using the group ID corresponding to the port number,

the transmission unit transmits the generated reference signal.

2. A receiving apparatus that receives a signal from the transmitting apparatus according to claim 1, the receiving apparatus comprising:

and a demodulation unit that generates a random number used as a reference signal using the group ID corresponding to the port number transmitted by the transmission device.

3. A base station having the transmission apparatus of claim 1.

4. A terminal having the receiving apparatus of claim 2.

5. A transmission method, in a relationship between a plurality of group IDs, 1 or more port numbers corresponding to the group IDs, and 1 or more reference signals corresponding to the port numbers, comprising:

the sending device sends the port number;

the transmitting device generating a random number used as a reference signal using a group ID corresponding to the port number; and

the transmission device transmits the generated reference signal.

Technical Field

The present invention relates to a transmission device, a reception device, a base station, a terminal, and a transmission method for transmitting a digital signal.

Background

In a digital communication system, frequency selectivity and time variation of a transmission path are caused by multipath fading caused by reflection of a transmission signal by a building or the like or doppler variation caused by movement of a communication apparatus. In a multipath environment where multipath fading occurs, a signal received by a communication apparatus is a signal in which a transmission symbol (transmission symbol) that has reached directly from the communication apparatus as a transmission source interferes with a symbol that has been reflected by a building or the like and then has arrived with a delay.

In order to obtain the best reception characteristics in a transmission path having Frequency selectivity, an OFDM (Orthogonal Frequency Division Multiplexing) transmission scheme, which is a multi-Carrier (MC) block transmission, is used (for example, see non-patent document 1 below).

Further, as a technique for improving communication capacity, there is a MIMO (Multiple Input Multiple Output) radio transmission system using a plurality of transmission/reception antennas. In MIMO communication, there are a scheme of multiplexing transmission layers in order to improve communication capacity and a scheme of multiplexing transmission layers in order to transmit signals to a plurality of users in parallel. The latter is called multi-user MIMO. In multi-user MIMO, a plurality of layers directed to a plurality of users are multiplexed on the transmission side.

Multi-layer multiplexing is typically implemented using precoding at the transmitting side. Precoding is performed using a transmission path estimation value of a transmission path from a transmitting side to a receiving side. Therefore, the communication device on the transmission side generates and transmits a signal into which a reference signal that can be used for transmission path estimation is inserted, so thatThe communication device on the receiving side can perform estimation of the transmission path and feedback to the transmitting side. The reference signal is also used for demodulating the multiplexed signal. Reference signals are of several kinds. In the standardization organization 3GPP (3)^rdGeneration Partner ship Project: third generation partnership project) also defines a plurality of Reference signals, one of which is DMRS (modulation Reference Signal: demodulation reference signal) is transmitted after being subjected to precoding processing. Therefore, the communication device on the receiving side can perform the precoding processing performed on the transmitting side using the DMRS and estimate the transmission path. DMRS is also referred to as a demodulation reference signal.

In addition, in general, in multi-user MIMO, individual reference signals are allocated to each layer and each user. In this case, the communication device on the receiving side can perform channel estimation on a layer to which a signal is transmitted by using a reference signal assigned to the layer, and can demodulate the received signal.

Prior art documents

Non-patent document

Non-patent document 1: w.y.zou and y.wu, "COFDM: an overview ", IEEE trans. on Broadcasting, vol.41, No.1, March 1995, pp.1-8.

Disclosure of Invention

Problems to be solved by the invention

However, there are problems as follows: since each user does not know the reference signal assigned to another user, when inter-user interference occurs, that is, when communication of a certain user is interfered by communication of another user, the interference cannot be removed.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a transmission device capable of improving communication quality.

Means for solving the problems

In order to solve the above problems and achieve the object, a transmission device according to the present invention is a transmission device having a plurality of group IDs, 1 or more port numbers corresponding to the group IDs, and 1 or more reference signals corresponding to the port numbers, the transmission device including: a transmission unit that transmits the port number; and a reference signal generation unit that generates a random number used as a reference signal using a group ID corresponding to the port number, wherein the transmission unit transmits the generated reference signal.

Effects of the invention

The transmission device of the present invention has the effect of improving communication quality.

Drawings

Fig. 1 is a diagram showing a configuration example of a wireless communication system according to embodiment 1.

Fig. 2 is a diagram showing a configuration example of a base station according to embodiment 1.

Fig. 3 is a sequence diagram showing an example of the operation of the wireless communication system according to embodiment 1.

Fig. 4 is a sequence diagram showing another operation example of the radio communication system according to embodiment 1.

Fig. 5 is a diagram showing an example of a table used when the base station of embodiment 1 notifies the terminal of the reference signal information.

Fig. 6 is a diagram showing an example of the configuration of a control channel in the case where the base station of embodiment 1 notifies the target terminal of reference signal information of an interfering terminal.

Fig. 7 is a diagram showing an example of the configuration of a control channel in a case where the base station according to embodiment 1 transmits reference signal information of a target terminal and reference signal information of an interfering terminal by dividing them into a plurality of symbols.

Fig. 8 is a diagram showing a configuration example of a receiving apparatus according to embodiment 1.

Fig. 9 is a flowchart showing an example of the operation of the base station according to embodiment 1.

Fig. 10 is a diagram showing a configuration example of a control circuit used when the components of the base station according to embodiment 1 are realized by software.

Fig. 11 is a diagram showing an example of a configuration of a dedicated circuit used when the components of the base station according to embodiment 1 are realized by dedicated hardware.

Fig. 12 is a sequence diagram showing an example of the operation of the wireless communication system according to embodiment 2.

Fig. 13 is a sequence diagram showing another example of the operation of the wireless communication system according to embodiment 2.

Fig. 14 is a diagram showing a configuration example of a receiving apparatus according to embodiment 2.

Fig. 15 is a flowchart showing an example of the operation of the base station according to embodiment 2.

Fig. 16 is a diagram showing a configuration example of a base station according to embodiment 3.

Fig. 17 is a diagram showing an example of a port mapping table stored in a base station and a terminal according to embodiment 3.

Fig. 18 is a diagram of a 1 st allocation example of reference signals in 1 resource block transmitted by the base station according to embodiment 3.

Fig. 19 is a diagram showing a 2 nd arrangement example of reference signals in 1 resource block transmitted by the base station of embodiment 3.

Fig. 20 is a diagram showing a first half of another example of a port mapping table stored in a base station and a terminal according to embodiment 3.

Fig. 21 is a diagram showing the second half of another example of the port mapping table stored in the base station and the terminal according to embodiment 3.

Fig. 22 shows a 3 rd arrangement example of reference signals in 1 resource block transmitted by the base station according to embodiment 3.

Fig. 23 is a diagram showing a 4 th arrangement example of reference signals in 1 resource block transmitted by the base station of embodiment 3.

Fig. 24 is a diagram showing an example 1 of a communication method between a base station and a terminal according to embodiment 3.

Fig. 25 is a diagram showing an example 2 of a communication method between a base station and a terminal according to embodiment 3.

Fig. 26 is a diagram showing a configuration example of a precoding unit provided in a base station according to embodiment 4.

Fig. 27 is a diagram showing another configuration example of a precoding unit provided in a base station according to embodiment 4.

Detailed Description

Hereinafter, a transmitting apparatus, a receiving apparatus, a base station, a terminal, and a transmitting method according to embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.

Embodiment 1.

Fig. 1 is a diagram showing a configuration example of a wireless communication system according to embodiment 1. The wireless communication system according to embodiment 1 includes a base station 1 and a plurality of terminals 2 (terminals 2)₁～2_n)。

The terminal 2 is a communication device called a User terminal or UE (User Equipment) and demodulates a signal received from the base station 1 using a reference signal described later. The transmission path from the base station 1 to the terminal 2 is called a downlink, and the transmission path from the terminal 2 to the base station 1 is called an uplink. In downlink communication, a base station 1 is a transmitting apparatus and a terminal 2 is a receiving apparatus. In uplink communication, the terminal 2 is a transmitting apparatus and the base station 1 is a receiving apparatus. In the wireless communication system according to the present embodiment, the OFDM scheme is used for downlink communication.

Fig. 2 is a diagram showing a configuration example of the base station 1 according to embodiment 1. The base station 1 includes a reception unit 11, a feedback information processing unit 12, a multiplexing control signal generation unit 13, a reference signal information management unit 14, a reference signal generation unit 15, a data signal generation unit 16, a multiplexing unit 17, a precoding unit 18, and a transmission unit 19. The multiplexing control signal generating unit 13, the reference signal information managing unit 14, the reference signal generating unit 15, the data signal generating unit 16, the multiplexing unit 17, the precoding unit 18, and the transmitting unit 19 constitute a transmitting apparatus 50. In the present embodiment, a radio communication system configured to multiplex a plurality of layers is assumed. The layer here corresponds to an information sequence including 1 or more of data, control signal, and reference signal. By transmitting a plurality of layers in a multiplexed manner, transmission with a large capacity can be realized. The multilayer multiplexing is performed by performing precoding and using MIMO (Multiple Input Multiple Output) transmission or the like. The reference signal generation unit 15, the data signal generation unit 16, and the multiplexing unit 17 shown in fig. 2 constitute a transmission signal generation unit that executes processing for an information sequence corresponding to the layer number i (layer # i). That is, the base station 1 includes a plurality of transmission signal generation units, and each transmission signal generation unit generates a transmission signal for each layer. In the present embodiment, the case where 1 layer is allocated to 1 terminal 2 has been described, but this is merely an example. A plurality of layers may be allocated to 1 terminal 2.

In the base station 1, the transmission signal generating unit of each layer generates a signal to be transmitted to each terminal 2, and transmits the signal to each terminal 2 via the precoding unit 18 and the transmitting unit 19. That is, in the transmission signal generating unit of each layer, the reference signal generating unit 15 generates a reference signal used when the terminal 2 performs signal reception processing such as channel estimation and demodulation. The data signal generation unit 16 generates a data signal to be transmitted to the terminal 2. The multiplexing unit 17 multiplexes the reference signal generated by the reference signal generating unit 15 and the data signal generated by the data signal generating unit 16. Multiplexing here means that, for example, a reference signal and a data signal are arranged in a specific region defined by time and frequency. When a control signal including reference signal information described later is input from the reference signal information management unit 14, the multiplexing unit 17 multiplexes the input control signal with the reference signal and the data signal.

The precoding unit 18 precodes the transmission signals generated by the transmission signal generating unit for each layer. The transmission unit 19 performs transmission processing such as multi-antenna transmission processing and waveform formation processing on the transmission signal precoded by the precoding unit 18. As an example of the waveform forming process, there is an OFDM process. In the OFDM processing, the transmitter 19 performs IDFT (Inverse Discrete fourier transform) processing and CP (Cyclic Prefix) addition.

The receiving unit 11 of the base station 1 receives the signal transmitted from the terminal 2, performs processing such as demodulation and decoding, and restores the information sequence transmitted by the terminal 2. The feedback information processing unit 12 decodes the information sequence transmitted in the uplink. In the uplink, if the transmission source is a terminal 2 which is not in communication, that is, a terminal 2 before the start of communication, information indicating a communication request or the like is transmitted to the base station 1, and if the transmission source is a terminal 2 which is in communication, information indicating the state of the transmission path or the like is transmitted to the base station 1. Examples of the state of the transmission path include the number of paths in a multiplex transmission path, transmission path information in multi-antenna communication, and the like. In addition, the transmission path in the multi-antenna communication can be represented by a complex matrix, and in this case, information corresponding to the transmission path information includes a maximum rank number, an eigenvector, an eigenvalue, and the like of the matrix.

The feedback information processing unit 12 decodes the information sequence received from the terminal 2, and extracts and outputs information indicating the state of the transmission path, that is, transmission path state information, to the multiplexing control signal generating unit 13 when the information sequence includes the information.

The multiplexing control signal generating unit 13 generates a control signal for generating a reference signal based on the channel state information. As described above, the transmission path state information corresponds to the maximum rank number of the transmission path matrix in the multi-antenna communication. The multiplexing control signal generation unit 13 determines the number of layers to be multiplexed based on the channel state information, and determines a reference signal to be used for each layer to be multiplexed. The multiplexing control signal generating unit 13 determines different reference signals as the reference signals used in each layer to be multiplexed. The multiplexing control signal generation unit 13 outputs a control signal for instructing the reference signal generation unit 15 for each layer to use a reference signal to be used, that is, a reference signal to be generated. In addition, the multiplexing control signal generating unit 13 may not output a control signal to the reference signal generating unit 15 of the layer not to be multiplexed. The multiplexing control signal generating unit 13 outputs reference signal information indicating the use in each layer to the reference signal information managing unit 14. The multiplexing control signal generating unit 13 outputs a control signal relating to the data signal generating operation to the data signal generating unit 16 of each layer. The control signal relating to the operation of generating the data signal is a signal instructing generation of the data signal. The multiplexing control signal generating unit 13 outputs a control signal instructing the data signal generating unit 16 of the layer to be multiplexed to generate the data signal. For example, when determining to multiplex the layer #1 and the layer #2, the multiplexing control signal generating unit 13 outputs a control signal instructing the data signal generating unit 16 of the layer #1 and the data signal generating unit 16 of the layer #2 to generate a data signal. The control signal for instructing generation of the data signal may include, in addition to information for instructing generation of the data signal, other information associated with generation of the data signal, such as information on the amount of generation of the data signal.

When receiving the reference signal information indicating the use in each layer from the multiplexing control signal generating unit 13, the reference signal information managing unit 14 holds the information. The reference signal information management unit 14 generates a control signal including the reference signal information transmitted to the terminal 2, and outputs the control signal to the multiplexing unit 17 of the layer that transmits the reference signal. For example, it is assumed that the reference signal information management unit 14 receives the reference signal used in the layer #1 and the reference signal information used in the layer #2 from the multiplexing control signal generation unit 13. In this case, the reference signal information management unit 14 generates a control signal including reference signal information used in the layer #1 and outputs the control signal to the multiplexing unit 17 of the layer #1, and generates a control signal including reference signal information used in the layer #2 and outputs the control signal to the multiplexing unit 17 of the layer # 2. When there is an interfering terminal with respect to a target terminal described later, the reference signal information management unit 14 generates a control signal including reference signal information to be transmitted to the target terminal and reference signal information to be transmitted to the interfering terminal, and outputs the generated control signal to the multiplexing unit 17 of the layer that transmits a signal to the target terminal. In the following description, the "reference signal transmitted to the target terminal" may be referred to as a "reference signal of the target terminal". In addition, the "reference signal transmitted to the interfering terminal" may be referred to as "reference signal of the interfering terminal". In addition, the reference signal transmitted to the target terminal is set as the 1 st reference signal, and the reference signal transmitted to the interfering terminal is set as the 2 nd reference signal. In this case, the reference signal information transmitted to the target terminal becomes the 1 st reference signal information, and the reference signal information transmitted to the interfering terminal becomes the 2 nd reference signal information.

When input to the multiplexing unit 17, the control signal output from the reference signal information management unit 14 to the multiplexing unit 17 is multiplexed together with the reference signal and the data signal, and then transmitted to the terminal 2 via the precoding unit 18 and the transmission unit 19. The transmission of the reference signal information to the terminal 2 may be performed by any method. Several examples are shown below.

The reference signal information can be transmitted from the base station 1 to the terminal 2 using an upper layer or a lower layer. As a case of using the higher Layer, for example, information transmission of RRC (Radio Resource Control) using Layer 3(Layer3) specified by 3GPP belongs to this case. That is, the base station 1 can include the reference signal information in the RRC message and transmit the reference signal information to the terminal 2. In addition, as a case of using a lower layer, the use of a PDCCH (Physical Downlink Control Channel) specified by 3GPP belongs to this case. When the PDCCH is used, the reference signal information is defined as parameter information, and the base station 1 includes the reference signal information as parameter information in the PDCCH and transmits the parameter information to the terminal 2. The PDCCH is a control channel for transmitting information of Layer 1(Layer 1). The base station 1 may transmit the reference signal information to the terminal 2 using mac ce (control element) transmitted in Layer 2(Layer2) in 3GPP, such as mac (medium Access control) Layer. Further, if the reference signal information is a parameter that does not change for a long time, the reference signal information may be transmitted from the base station 1 to the terminal 2 as a layer3 or layer2 control signal in 3 GPP. If the reference signal information is a parameter that changes in a short period of time, the reference signal information may be transmitted using a layer1 control signal in 3 GPP.

The reference signal information managed by the reference signal information management unit 14 differs depending on the method of generating the reference signal. An example of a method of generating a reference signal will be described. In the method specified by 3GPP LTE, a pn (pseudonoise) sequence is generated as a demodulation reference signal (DMRS) for downlink. The PN sequence generated as the DMRS is determined by the ID of each cell and the scrambling code ID. That is, in the 3gpp lt, PN sequences different from the IDs are generated and used. In this case, the reference signal information management unit 14 manages the cell ID and the scramble code ID as reference signal information.

The DMRS is mapped to Resource Elements (REs) of time and frequency corresponding to a designated port number. Here, the RE indicates a unit in frequency, and in 3GPP LTE, the RE of a group consisting of 12 subcarriers and 7 symbols is referred to as 1 Resource Block (RB). The 1 symbol in the downlink is an OFDM symbol. The scrambling code ID and the cell ID are transmitted by DCI (Downlink Control Information) included in the PDCCH or the like. Thus, a terminal in 3GPP LTE can understand, by decoding the PDCCH, the DMRS configuration, which is a PN sequence used for the DMRS and a port number, that is a generation method of the DMRS directed to the terminal. Therefore, the terminal can demodulate a data signal transmitted to the terminal using the DMRS allocated to the terminal.

However, in a conventional wireless communication system represented by 3GPP LTE, each terminal cannot know a reference signal transmitted to another terminal. Therefore, when each terminal receives a signal in a state of being interfered by a signal transmitted from the base station to another terminal, it is impossible to estimate an interference component contained in the received signal.

In contrast, in the wireless communication system according to the present embodiment, the base station 1 transmits reference signal information to be transmitted to other terminals to each terminal 2. Thus, each terminal 2 can know the reference signal transmitted to the other terminal, and can suppress the interference component included in the signal transmitted to the own terminal using the reference signal transmitted to the other terminal. In addition, when there is downlink communication of another terminal 2 that interferes with downlink communication of a certain terminal 2, the base station 1 transmits reference signal information transmitted to the interfering terminal 2. In the following description, for convenience, a terminal on the side of receiving interference is referred to as a "target terminal", and a terminal that causes interference to the target terminal is referred to as an "interfering terminal".

In order to notify the target terminal of the reference signal information transmitted to the interfering terminal, the base station 1 needs to know whether or not the target terminal is in a state of being interfered by another terminal 2. Thus, the base station 1 identifies the interfering terminal when receiving the notification from the target terminal, and transmits information on the interfering terminal, that is, reference signal information transmitted to the target terminal. Whether the terminal 2 needs to know the information about the interfering terminal is determined by whether the terminal 2 has the interference cancellation function. In order to effectively utilize communication resources and prevent malfunctions, it is preferable that the base station 1 not notify the terminal 2 having no interference cancellation function of information about an interfering terminal. In addition, although the efficiency may be reduced, reference signal information of all users transmitted simultaneously may be notified to all users in order to simplify the procedure.

An example of a method of the base station 1 determining an interfering terminal with respect to a target terminal will be described. The method of identifying the interfering terminal is not limited to the following example. In the present embodiment, the reference signal information management unit 14 is configured to identify an interfering terminal with respect to a target terminal. That is, the reference signal information management unit 14 functions as a determination unit that determines an interfering terminal that is a terminal that is likely to perform communication that interferes with communication with a target terminal that is a terminal to which a data signal is transmitted.

(1) Method for determining interference terminal according to distance between terminals

The base station 1 can grasp the positional relationship of each terminal 2 by feeding back the positional information to each terminal 2. The positional information is, for example, latitude and longitude information, and the terminal 2 obtains the positional information by using a GPS (Global Positioning System) or the like. In general, it is difficult to consider spatial separation of terminals at a short distance, and interference occurs. The base station 1 calculates the distance between the target terminal and the other terminal 2, and determines the terminal 2 whose distance is equal to or less than a threshold value as an interfering terminal.

(2) Method for determining interfering terminal according to information of beam captured by terminal

The base station 1 which performs communication using narrow beams periodically performs beam scanning on the entire cell area in order to detect the occurrence of a new user. At this time, since a beam is irradiated to a predetermined position, the base station 1 knows the beam received by each terminal 2 at the maximum power, and can thereby know the approximate position of each terminal 2. The base station 1 can grasp the positional relationship of each terminal 2 by causing each terminal 2 to feed back information of a beam having the maximum reception power. The information of the fed-back beam is set as the identification information of the beam. In addition to the identification information of the beam, the reception power may also be fed back. The base station 1 determines that the terminal 2 is an interfering terminal, and the terminal 2 is a beam closer to the beam where the target terminal is located. When the base station 1 and each terminal 2 establish time synchronization, the information fed back from the terminal 2 to the base station 1 may be information of the time at which the maximum value of the received power of the beam is detected. In this case, the base station 1 compares the time when the target terminal detects the maximum value of the received power with the time when the other terminal 2 detects the maximum value of the received power, and determines that the terminal 2 whose time difference is equal to or smaller than the threshold value is an interfering terminal.

(3) Method for determining interfering terminal according to spatial correlation

The transmission path Information (CSI) between the base station 1 and the terminal 2 is important Information for beamforming. The base station 1 can generally acquire the propagation path information by using an uplink known signal that uses Reciprocity (reliability) or reversibility of the propagation path, or by explicit feedback from the terminal 2. As an explicit feedback example, a plurality of transmission path matrices, eigenvectors, and eigenvalues are considered. The reversibility of the transmission path means that it is possible to use an environment in which the transmission paths of the uplink and the downlink are the same. When the reversibility of the propagation path is established, the base station 1 can know the propagation path of the downlink by performing propagation path estimation using the reference signal transmitted in the uplink, and therefore, it is not necessary to receive feedback of the propagation path information of the downlink from the terminal 2. The base station 1 can calculate spatial correlation between the target terminal and the other terminals 2 from the transmission path information. The base station 1 determines that the terminal 2 having a high spatial correlation with the target terminal is an interfering terminal.

In addition, a case is assumed where a plurality of interfering terminals exist with respect to the target terminal. In this case, the base station 1 may set different unit thresholds for the distance, the correlation value, and the like, treat the terminal 2 having a distance lower than the threshold or the terminal 2 having a correlation value higher than the threshold as an interfering terminal, and transmit the reference signal information of each interfering terminal to the target terminal.

Since the number of interfering terminals from which the terminal 2 can remove interference is limited, the base station 1 transmits reference signal information of the number of terminals that can be handled to the target terminal. In this case, if the base station 1 identifies the interfering terminals according to the method (1), the number of terminals that can be processed by the target terminal is sequentially selected as the interfering terminals from the terminal closer to the base station in the order from the near to the far. Similarly, if the base station 1 determines the interfering terminal according to the method (3), the number of terminals that can be processed by the target terminal is selected as the interfering terminals in the order of the correlation value from the terminal with the higher correlation value to the terminal with the lower correlation value. The base station 1 transmits the reference signal information of the selected interfering terminal to the target terminal.

Fig. 3 is a sequence diagram showing an example of the operation of the wireless communication system according to embodiment 1. In fig. 3, the terminals 2 other than the target terminal are 1, but 2 or more terminals may be used. The target terminal is any one terminal 2 among the plurality of terminals 2. In the wireless communication system according to embodiment 1, first, all the terminals 2 including the target terminal notify the base station 1 of the propagation path information (step S11), and the base station 1 stores the propagation path information notified from each terminal 2 (step S12). The base station 1 then transmits the reception notification to the target terminal (step S13). For example, when receiving a notification of the propagation path information from a terminal 2 other than the target terminal, the base station 1 transmits a reception notification to the target terminal. Note that the reception notification is transmitted when the transmission path information is configured to be occasionally notified from each terminal 2. When the transmission path information is periodically notified from each terminal 2, it is not necessary to transmit a reception notification from the base station 1 to the target terminal. Then, the target terminal transmits a request for reference signal information of the interfering terminal to the base station 1 (step S14), and the base station 1 which has received the request searches for the interfering terminal, that is, determines which terminal among the terminals 2 other than the target terminal corresponds to the interfering terminal (step S15). The base station 1 determines the interfering terminal using any one of the above-described methods (1) to (3) or another method. After identifying the interfering terminal, the base station 1 notifies the target terminal of the reference signal information of the interfering terminal (step S16). When the interfering terminal is not present, the base station 1 does not perform step S16. The target terminal removes, from the received signal, the interference component received by the communication between the base station 1 and the interfering terminal, based on the reference signal information received from the base station 1. The target terminal may perform step S14, i.e., request reference signal information of the interfering terminal, when a predetermined condition is satisfied, such as when the frequency of occurrence of reception errors reaches a predetermined value. Note that step S15 is omitted to simplify the flow, and reference signal information of all users whose signals are transmitted simultaneously may be notified to all users.

Here, all the terminals 2 of the wireless communication system can be target terminals. Therefore, after storing the propagation path information in step S12, the base station 1 transmits a reception notification to all the terminals 2 in communication. Then, upon receiving the request for the reference signal information of the interfering terminal, the base station 1 executes steps S15 and S16 for the terminal 2 that is the transmission source of the request.

Fig. 3 shows a procedure in which the base station 1 transmits reference signal information of an interfering terminal in response to a request from a target terminal. Although the notification is not performed periodically in the procedure of fig. 3, the base station 1 may perform the notification periodically. In this case, the procedure is as shown in fig. 4. Fig. 4 is a sequence diagram showing another operation example of the wireless communication system according to embodiment 1. In the sequence shown in fig. 4, after steps S11 to S13 shown in fig. 3 are executed, the target terminal transmits a periodic notification request of the reference signal information of the interfering terminal to the base station 1 (step S14 a). The base station 1 having received the request in step S14a executes the above-described steps S15 and S16, retrieves the interfering terminal, and notifies the reference signal information of the interfering terminal to the target terminal. Then, the base station 1 periodically performs steps S15 and S16. That is, the base station 1 repeatedly performs steps S15 and S16 in such a manner that steps S15 and S16 are performed every time a fixed time equivalent to the notification interval shown in fig. 4 elapses. The regular execution of steps S15 and S16 may be ended after a predetermined time elapses or after a predetermined number of times of repeated execution, or may be ended after receiving an end request from the target terminal. Further, the base station 1 may end the regular execution of steps S15 and S16 in a case where the signal from the target terminal is no longer received. Although not shown in fig. 4, the base station 1 receives the notification of the propagation path information from all the terminals 2 including the target terminal in each fixed period.

The periodic notification request of the target terminal transmitted from the target terminal in step S14a may include information on an interval at which the base station 1 notifies the reference signal information of the interfering terminal. The periodic notification request from the destination terminal may include information for notifying the release of the periodic notification or information on the number of times the periodic notification is performed.

The reference signal information notified to the target terminal by the base station 1 is the generation information of the reference signal used by the interfering terminal in the reception process and the position of the reference signal. The generated information is information associated with the content, which is the structure of the reference signal.

In 3GPP LTE, when a base station notifies a terminal to be communicated of reference signal information used for data reception processing, the base station uses the number of a DCI table specified by 3 GPP. Therefore, when the base station 1 is a base station of 3GPP LTE, the base station 1 may notify the reference signal information of the interfering terminal to each target terminal using the number of the DCI table.

Fig. 5 is a diagram showing an example of a table used when the base station 1 of embodiment 1 notifies the terminal 2 of the reference signal information. The table shown in fig. 5 is a DCI table used to notify the DMRS specified in document "3 GPP TS 36.212 V14.0.0".

In the transmission of the reference signal information using the DCI table shown in fig. 5, a Value is selected from "Value" which is an option in the left column or the right column according to the number of codewords used, and the selected Value is transmitted through the PDCCH. For example, when layer2 multiplexing is performed in case of 2 codeword transmission, onlyTo select "1" from the right column, the base station 1 notifies the terminal 2 that the transmission and scrambling code ID are 1, that is, n, using port numbers 7 and 8_SCID1 for the case of a corresponding DMRS. In this case, the terminal 2 knows that the n-sum is inserted at the positions corresponding to the port numbers 7 and 8_SCIDThe DMRS of the mode corresponding to 1 can demodulate a signal transmitted from the base station 1. In the DCI table shown in fig. 5, OCC represents Orthogonal Code (Orthogonal Code is superimposed on symbol) and Orthogonal Code multiplied by DMRS for layer separation. Since OCCs corresponding to port numbers 7 and 8 are determined in advance, the corresponding OCCs can be generated as long as the port numbers are known on the receiving side.

Fig. 6 shows an example of the configuration of a PDCCH when the base station 1 notifies the target terminal of reference signal information of an interfering terminal by using the DCI table number. As shown in fig. 6, the PDCCH includes a "target terminal value" as a value of the DCI table as reference signal information of a target terminal, and includes an "interfering terminal value" as a value of the DCI table as reference signal information of an interfering terminal. The reference signal information of the target terminal is the 1 st reference signal information, and the reference signal information of the interfering terminal is the 2 nd reference signal information. In fig. 6, description of other information included in the PDCCH is omitted. Furthermore, the value of the target terminal and the value of the interfering terminal need not be configured continuously. The information included in the PDCCH can be error correction coded.

In addition, the reference signal information of the target terminal and the reference signal information of the interfering terminal may be transmitted by dividing them into a plurality of symbols. When such information is transmitted through the PDCCH, for example, reference signal information corresponding to a target terminal is included in the PDCCH used for the first transmission, and reference signal information of an interfering terminal is included in the PDCCH used for the next transmission. The PDCCH configuration in this case is shown in fig. 7, for example.

Next, a receiving terminal according to the present embodiment will be explained. Fig. 8 is a diagram showing a configuration example of a receiving apparatus according to embodiment 1. The receiving apparatus 3 shown in fig. 8 constitutes the terminal 2 shown in fig. 1, and receives a signal transmitted from the base station 1.

The reception device 3 includes a reception processing unit 31, a demodulation unit 32, and a control signal demodulation unit 33. The reception processing unit 31 performs reception processing corresponding to the applied modulation scheme on the received signal. For example, when the modulation scheme is OFDM, the reception processing unit 31 outputs the control signal to the control signal demodulation unit 33 and outputs the data signal to the demodulation unit 32 after performing processing such as CP removal and frequency domain conversion processing.

The control signal demodulation unit 33 demodulates the control signal, and restores the reference signal information of the target terminal and the reference signal information of the interfering terminal. The control signal demodulation unit 33 outputs the restored information to the demodulation unit 32.

The demodulation unit 32 performs channel estimation or demodulation processing for each layer. In this case, the demodulation unit 32 uses the reference signal information of the target terminal and the reference signal information of the interfering terminal, which are input from the control signal demodulation unit 33. The reference signal information of the target terminal is the 1 st reference signal information, and the reference signal information of the interfering terminal is the 2 nd reference signal information. As described above, the reference signal of the target terminal is a reference signal used for demodulation of a signal transmitted to the own device, and the reference signal of the interfering terminal is a reference signal used for processing for removing an interference component included in the received signal. Therefore, the demodulation unit 32 demodulates the data signal based on the 1 st reference signal information, and removes the interference component included in the data signal based on the 2 nd reference signal information. Specifically, in the demodulation processing for each layer, the demodulation unit 32 first generates a reference signal for the target terminal from the reference signal information of the target terminal, and further generates a reference signal for the interfering terminal from the reference signal information of the interfering terminal. The demodulation unit 32 demodulates the data signal using the reference signal directed to the target terminal, estimates an interference wave from the interfering terminal from the reference signal directed to the interfering terminal, and removes an interference component included in the data signal using the estimated interference wave. The removal of the interfering component can be performed by an IRC (Interference Rejection Combining) method or the like.

In the example shown in fig. 8, the demodulation unit 32 for demodulating the data signal and the control signal demodulation unit 33 for demodulating the control signal are configured independently of each other, but they may be integrated as a single unit. For example, the demodulation unit 32 may demodulate both the data signal and the control signal. In this case, the demodulation unit 32 first demodulates the control signal to acquire the reference signal information of the target terminal and the reference signal information of the interfering terminal. Then, a reference signal to be transmitted to the target terminal and a reference signal to be transmitted to the interfering terminal are generated using the reference signal information obtained by demodulating the control signal, and the data signal is demodulated using the generated reference signals.

Fig. 9 is a flowchart showing an operation example of the base station 1 according to embodiment 1, and shows an operation example of a case where reference signal information of an interfering terminal is transmitted to a target terminal.

As shown in fig. 9, the base station 1 first receives transmission path information from the terminal 2 (step S1). In step S1, the base station 1 receives the transmission path information from all the terminals 2. The base station 1 then determines an interfering terminal of the target terminal (step S2). In step S2, the base station 1 determines an interfering terminal when each terminal 2 is a target terminal, with respect to all terminals 2. That is, the base station 1 determines its interfering terminal for each terminal 2. The base station 1 then notifies the target terminal of the reference signal information of the interfering terminal (step S3). Normally, there are a plurality of target terminals, and the base station 1 transmits reference signal information of the interfering terminal to each of the plurality of target terminals in step S3.

As described above, in the radio communication system according to the present embodiment, when receiving the propagation path information from each terminal 2, the base station 1 determines an interfering terminal according to the case where each terminal 2 is a target terminal, and specifies an interfering terminal with respect to the target terminal. The base station 1 then notifies each terminal 2 of reference signal information of the interfering terminal, that is, reference signal information transmitted to the interfering terminal. Thus, the terminal 2 can calculate the interference component included in the received signal from the reference signal information of the interfering terminal, and can remove the interference component from the received signal. Therefore, the communication quality can be improved.

Next, a hardware configuration of the base station 1 of the present embodiment will be explained. Each of the components constituting the base station 1 shown in fig. 2 is formed of a circuit. Each of the components constituting the base station 1 shown in fig. 2 may be realized as a dedicated circuit, or may be realized by a circuit using a processor.

Among the components of the base station 1 shown in fig. 2, components realized by software are realized by a control circuit shown in fig. 10, for example. Fig. 10 is a diagram showing a configuration example of a control circuit 100 used when the components of the base station 1 according to embodiment 1 are realized by software. As shown in fig. 10, the control circuit 100 includes: an input unit 101 as a receiving unit that receives data input from the outside; a processor 102; a memory 103; and an output unit 104 as a transmission unit for transmitting data to the outside. The input unit 101 is an interface circuit that receives data input from the outside of the control circuit 100 and supplies the data to the processor 102, and the output unit 104 is an interface circuit that transmits data from the processor 102 or the memory 103 to the outside of the control circuit 100. When at least a part of the components shown in fig. 2 is implemented by the control circuit 100 shown in fig. 10, the components are implemented by reading and executing programs corresponding to the components implemented by software, which are stored in the memory 103, by the processor 102. The memory 103 is also used as a temporary memory in each process executed by the processor 102.

The Processor 102 is a CPU (Central Processing Unit, also referred to as a Central Processing Unit, Processing device, arithmetic device, microprocessor, microcomputer, Processor, DSP (Digital Signal Processor)), or the like. Examples of the Memory 103 include nonvolatile or volatile semiconductor memories such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash Memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), and the like, a magnetic Disk, a flexible Disk, an optical Disk, a compact Disk, a mini Disk, and a DVD (Digital Versatile Disk).

Among the components of the base station 1, components realized as dedicated circuits are realized by, for example, a circuit shown in fig. 11. Fig. 11 is a diagram showing an example of the configuration of a dedicated circuit 100a used when the components of the base station 1 according to embodiment 1 are realized by dedicated hardware. As shown in fig. 11, the dedicated circuit 100a may be a circuit in which the processor 102 of the control circuit 100 shown in fig. 10 is replaced with a processing circuit 105. The processing Circuit 105 is, for example, a single Circuit, a composite Circuit, a program processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

The terminal 2 may be implemented by the same hardware. Note that the base station and the terminal described in embodiment 2 can be implemented by the same hardware.

Embodiment 2.

In embodiment 1, the base station 1 transmits reference signal information of an interfering terminal to a target terminal, and the target terminal removes an interference component contained in a received signal based on the reference signal information of the interfering terminal. In this case, if there are a plurality of interfering terminals, the amount of control signals increases, and the amount of data that can be transmitted decreases. Therefore, it is preferable to minimize the transmission amount of the control signal.

Therefore, in the present embodiment, a base station capable of transmitting reference signal information of a plurality of interfering terminals to a target terminal while suppressing the transmission amount of a control signal will be described. The configuration of the wireless communication system is the same as that of embodiment 1. The configuration of the base station is also the same as that of embodiment 1. In this embodiment, a portion different from embodiment 1 will be described. For convenience of explanation, the base station of embodiment 2 is referred to as a base station 1a, separately from the base station 1 of embodiment 1. Similarly, the terminal of embodiment 2 is referred to as a terminal 2 a.

The base station 1a according to embodiment 2 groups a target terminal and an interfering terminal, and transmits information described below to the target terminal as information on a reference signal of the interfering terminal. The base station 1a may generate different reference signals for each terminal in units of groups. That is, the base station 1a operates to transmit different reference signals to terminals belonging to the same group, and may transmit the same reference signal to terminals belonging to different groups. In 3GPP, although it is specified that the initial value of the DMRS serving as the reference signal differs depending on the cell ID, a group ID smaller than the cell ID may be defined and the initial value of the DMRS may be made different for each group ID. When the base station 1a according to embodiment 2 generates the DMRS as the reference signal, the base station may use a group ID instead of the cell ID.

The base station 1a also generates a group based on the propagation path information acquired from each terminal 2 a. The reference for generating a group is to group terminals 2a interfering with the target terminal, i.e., interfering terminals, into the same group using the position information or the correlation information described in embodiment 1.

The group formation method will be explained. The base station 1a sets different unit thresholds for the distance between the target terminal and the other terminal 2a or the related information calculated from the position information, for example. Then, a terminal 2a whose distance is shorter than the threshold value and a terminal 2 having a correlation value higher than the threshold value are set as terminals 2a of the same group as the target terminal. The cell is a unit within the determined range, and the group determined by the base station 1a is adaptively generated, and therefore is a unit different from the cell.

When the reference signal information of the interfering terminal is notified to the target terminal, the base station 1a notifies the target terminal of the group ID and the number of group members as the reference signal information of the interfering terminal. The number of group members is the number of terminals 2a included in the group of the notified group ID. The group generation is performed by, for example, the reference signal information management unit 14. In this case, the reference signal information management unit 14 of the base station 1a functions as a group creation unit in addition to the function of the reference signal information management unit 14 of the base station 1 according to embodiment 1.

When receiving the notification of the group ID and the number of group members, the target terminal strongly searches for candidate DMRSs that can be considered based on the notified group ID and the number of group members, and estimates interference received from the interfering terminal. As described above, the DMRS is determined by the cell ID and the scrambling code ID, but the target terminal may generate the DMRS using the group ID to which the notification is received instead of the cell ID. The scrambling code ID is not notified from the base station 1a, and the scrambling code ID used is selected from a plurality of patterns defined in advance. Therefore, the target terminal combines all the scrambling code IDs and the group IDs to generate all the DMRSs that can be considered, and estimates the interference received from the interfering terminal. In addition, since the position where the DMRS is inserted is determined, the target terminal determines the DMRS to be used for estimation of interference received from the interfering terminal, based on the correlation between the signal received at the insertion position of the DMRS and each of the DMRSs generated as described above. At this time, the target terminal determines the same number of DMRSs as the number of group members to be notified.

The number of terminals included in each group, i.e., the maximum number of group members, may be fixed. In this case, the base station 1a may notify only the group ID and not the number of group members. The maximum number of terminals in 1 group can be notified from the base station 1a to the terminal 2a via an upper layer or the like, or a preset value can be continuously used. Further, the maximum number of containers in 1 group may be specified by the specification, and the specified value is used.

Further, the base station 1a may generate a group by assigning a unique number to each terminal in the group, and then may transmit the number assigned to each terminal 2a in the group to the target terminal in addition to the group ID. Hereinafter, the number assigned to the terminal is set as the group member ID. The group member ID may be a value unique to each group, or may be a common value between different groups. When assigning a group member ID to each terminal, the base station 1a generates a reference signal to be transmitted to each terminal using the group ID and the group member ID assigned to each terminal.

Here, a method of generating a DMRS in conventional 3GPP LTE will be described. The initial value for generating the random number required for generating the PN sequence used as the DMRS is defined in the document "3 GPP TS 36.212 V14.0.0" and is expressed by the following equation (1).

[ mathematical formula 1]

In the formula (1), n_SCIDIs 0 or 1, and is transmitted from the base station 1a to the terminal 2a using DCI. n is_SCIDReferred to as the scrambling code ID. The cell ID received from the upper layer is set to the value expressed by equation (2).

[ mathematical formula 2]

In this way, in the existing 3GPP LTE, a scrambling code ID and a cell ID are used in generating a DMRS.

In contrast, in the radio communication system according to the present embodiment, the above-described group ID is used instead of the cell ID shown in equation (2) when the DMRS is generated. The group ID may be adaptively set. When the group ID is adaptively set, the set value of the group ID is transmitted from the base station 1a to the terminal 2a using the PDCCH. Further, the group member ID may also be used as n of the numerical expression (1)_SCID. That is, when the DMRS is generated, the group member ID may be used instead of the conventional scrambling ID. The initialization of the PN sequence when generating the DMRS is not limited to the method according to equation (1). Other methods may be utilized for initialization.

Fig. 12 is a sequence diagram showing an example of the operation of the wireless communication system according to embodiment 2. In fig. 12, 1 terminal 2a other than the target terminal is shown, but 2 or more terminals may be used. The target terminal is any one terminal 2a among the plurality of terminals 2 a.

In the wireless communication system according to embodiment 2, the base station 1a collects and stores the propagation path information from each terminal 2a (steps S11 and S12), and transmits a reception notification to the destination terminal (step S13). Then, the base station 1a receives a request for reference signal information of the interfering terminal from the target terminal (step S14). The processing in steps S11 to S14 is the same as the processing in steps S11 to S14 of fig. 3 described in embodiment 1. The base station 1a that has received the request for the reference signal information of the interfering terminal generates a group including the target terminal, that is, a group including the target terminal and the interfering terminal, by the above-described method (step S21). Next, the base station 1a notifies the target terminal of the generated group ID of the group and information of the group members (step S22). The information of the group members is the number of group members, i.e. the number of interfering terminals. In addition, when the maximum value of the number of group members is determined, the information of the group members may not be transmitted.

In fig. 12, a sequence in which the base station 1a transmits a group ID or the like to the target terminal according to a request from the target terminal is shown. The sequence in fig. 12 is an aperiodic report, but the base station 1a may periodically perform the report. In this case, the procedure is as shown in fig. 13. Fig. 13 is a sequence diagram showing another example of the operation of the wireless communication system according to embodiment 2. In the sequence shown in fig. 13, after steps S11 to S13 shown in fig. 12 are executed, the target terminal transmits a request for periodic notification of reference signal information of the interfering terminal to the base station 1a (step S14 a). The processing in steps S11 to S13 and S14a is the same as the processing in steps S11 to S13 and S14a in fig. 4 described in embodiment 1. The base station 1a that has received the request in step S14a performs the above-described steps S21 and S22, generates a group, and notifies the target terminal of the group ID and the like. Then, the base station 1a periodically performs steps S21 and S22. That is, the base station 1a repeatedly performs steps S21 and S22 in such a manner that steps S21 and S22 are performed every time a fixed time equivalent to the notification interval shown in fig. 13 elapses. The regular execution of steps S21 and S22 may be ended when a predetermined time has elapsed or when a predetermined number of times has been repeatedly executed, or when an end request is received from the target terminal. Further, the base station 1a may end the regular execution of steps S21 and S22 in a case where the signal from the target terminal is no longer received. Although not shown in fig. 13, the base station 1a receives the notification of the propagation path information from all the terminals 2a including the target terminal in each fixed period.

Fig. 14 is a diagram showing a configuration example of a receiving apparatus 3a according to embodiment 2. In the receiving apparatus 3a shown in fig. 14, the demodulating unit 32 and the control signal demodulating unit 33 of the receiving apparatus 3 described in embodiment 1 are referred to as a demodulating unit 32a and a control signal demodulating unit 33 a.

The demodulation unit 32a performs channel estimation or demodulation processing for each layer, as in the demodulation unit 32 of the reception device 1 according to embodiment 3. In this case, the demodulation unit 32a uses the reference signal information of the target terminal, the group ID, and the number of group members. In the demodulation processing for each layer, the demodulation unit 32a first generates a reference signal to be transmitted to the target terminal based on the reference signal information of the target terminal, and also generates a reference signal to each interfering terminal based on the group ID and the number of group members. The demodulation unit 32a demodulates the data signal using the reference signal directed to the target terminal, estimates the interference wave from each interference terminal from the reference signal directed to each interference terminal, and removes the interference component included in the data signal using the estimated interference wave. The removal of the interfering component is performed by the IRC method or the like.

Fig. 15 is a flowchart showing an operation example of the base station 1a according to embodiment 2, and shows an operation example in the case where the group ID and the information on the group members are transmitted to the target terminal as the reference signal information of the interfering terminal.

As shown in fig. 15, the base station 1a first receives transmission path information from the terminal 2a (step S1). In step S1, the base station 1a receives the transmission path information from all the terminals 2 a. The base station 1a then generates a group of the target terminal and the interfering terminal (step S4). In step S4, the base station 1a generates a target terminal and an interfering terminal group for each terminal 2a as a target terminal, for all terminals 2 a. That is, the base station 1a generates a group for each terminal 2 a. The base station 1a then notifies the target terminal of the group ID and the number of group members (step S5). In general, there are a plurality of target terminals, and the base station 1a transmits the group ID and the number of group members to each of the plurality of target terminals in step S5.

As described above, in the radio communication system according to the present embodiment, when receiving the propagation path information from each terminal 2a, the base station 1a determines an interfering terminal for each case when the terminal 2a is a target terminal, and generates a group consisting of the target terminal and the interfering terminal. Next, the base station 1a notifies each terminal 2a of the group ID and the number of group members, which are reference signal information of the interfering terminal. In this way, the terminal 2a can calculate the interference component included in the received signal from the reference signal information of the interfering terminal and can remove the interference component from the received signal. Therefore, the communication quality can be improved. Further, it is possible to prevent an increase in the amount of control signals in the case where there are a plurality of interfering terminals.

Embodiment 3.

In embodiment 2 described above, a radio communication system in which a target terminal and an interfering terminal are grouped, and the target terminal reduces interference received by the interfering terminal belonging to the same group as the own terminal is described. In embodiment 2, a configuration in which a base station of a wireless communication system notifies a target terminal of a reference signal of an interfering terminal using a group ID and the number of group members, and a configuration in which a base station of a wireless communication system notifies a target terminal of a reference signal of an interfering terminal using a group ID, the number of group members, and the group member ID have been described. In contrast, in the wireless communication system according to the present embodiment, the base station notifies the destination terminal of the reference signal of the destination terminal by using the port number. The configuration of the wireless communication system is the same as that of embodiment 1 (see fig. 1).

Fig. 16 is a diagram showing a configuration example of a base station according to embodiment 3. In fig. 16, the same components as those of the base station 1 (see fig. 2) according to embodiment 1 are denoted by the same reference numerals. In the base station 1b according to embodiment 3, the transmission device 50 of the base station 1 according to embodiment 1 is referred to as a transmission device 50 b. The transmission device 50b is configured by using the reference signal information management unit 14 of the transmission device 50 as the reference signal information management unit 14b and adding the control unit 41. The terminal according to embodiment 3 is referred to as a terminal 2 b. The base station 1b groups the terminals 2b in the same manner as the base station 1a of embodiment 2.

The reference signal information management unit 14b generates a control signal including reference signal information to be transmitted to the terminal 2b, similarly to the reference signal information management unit 14 described in embodiment 1. The reference signal information included in the control signal generated by the reference signal information management unit 14b is information indicating a port number described later. The reference signal is a DMRS as in embodiments 1 and 2.

The control unit 41 generates a control signal indicating the type of precoding, and outputs the control signal to the precoding unit 18. The control unit 41 generates a control signal indicating linear precoding or a control signal indicating nonlinear precoding. When the control signal input from the control unit 41 instructs linear precoding, the precoding unit 18 performs linear precoding, that is, precoding using linear processing on the transmission signal. When the control signal input from the control unit 41 indicates nonlinear precoding, the precoding unit 18 performs nonlinear precoding on the transmission signal, that is, performs precoding using nonlinear processing. Examples of non-linear Precoding are VP (Vector Perturbation), THP (Tomlinson Harashima Precoding: Thomlinson Harashima Precoding), etc. When the control signal input from the control unit 41 instructs both linear precoding and nonlinear precoding, the precoding unit 18 performs both linear precoding and nonlinear precoding on the transmission signal.

The base station 1b of the present embodiment stores a port mapping table shown in fig. 17, and notifies a reference signal transmitted to a target terminal to the target terminal using the port mapping table. The port mapping table contains an index, a port number corresponding to the index, the number of CDM (Code Division Multiplexing) groups that do not contain data, and the number of DMRS symbols used. The DMRS symbols are reference signal symbols. The CDM group is described later. When notifying the reference signal to the target terminal, the base station 1b generates a control signal including an index of the port mapping table as reference signal information, and transmits the control signal to the target terminal. As shown in fig. 17, the index of the port mapping table corresponds to the port number or the like, and the index is information indicating the port number. The base station 1b notifies the target terminal of the index of the port mapping table using, for example, the DCI described above.

Each terminal 2b of the present embodiment also stores a port mapping table shown in fig. 17. When receiving a control signal including an index of the port mapping table from the base station 1b, each terminal 2b grasps the port number assigned to the terminal from the received index. Each terminal 2b also specifies a reference signal to be transmitted from the base station 1b to the terminal, based on the port number assigned to the terminal. Each terminal 2b specifies a reference signal to be transmitted from the base station 1b to another terminal belonging to the same group as the own terminal, based on the port number assigned to the own terminal. Note that, in the index 6, 9, 10, 11, and 30, data is not transmitted in a group other than the group of the assigned ports. That is, SU-MIMO (Single User MIMO: Single User multiple input multiple output) transmission is assumed in indexes 6, 9, 10, 11, and 30.

Fig. 18 and 19 are diagrams showing an example of the arrangement of reference signals in 1 resource block transmitted from the base station 1b to the terminal 2b in embodiment 3.

In the examples shown in fig. 18 and 19, the number of CDM groups is 2. That is, the number of CDM groups is the number of reference signal sequences included in 1 resource block. Each CDM group performs frequency multiplexing. 1 reference signal sequence is assigned to 1 of a group of terminals 2b configured to include a target terminal and an interfering terminal.

In the examples shown in fig. 18 and 19, when the number of reference signal symbols included in 1 resource block is 1 and 2, the number of ports included in each CDM group is different. The port corresponds to the reference signal sequence, and if the terminal 2b knows the port number corresponding to the reference signal sequence allocated to the terminal itself and the number of DMRS symbols, it knows the reference signals that can be allocated to each terminal 2b constituting 1 group. The number of port numbers and DMRS symbols is information indicating candidates of reference signals allocated to each terminal 2b constituting 1 group. Thus, the target terminal can grasp the reference signal that may be assigned to the interfering terminal belonging to the same group as the own terminal if the target terminal knows the reference signal assigned to the own terminal. The target terminal generates all reference signals that are likely to be allocated to the interfering terminal and estimates the interference received from the interfering terminal.

The explanation returns to the examples shown in fig. 18 and 19. FIG. 18 is set upThe example of the arrangement of the reference signal in the case of 1 symbol shows an example in the case where the number of reference signal symbols included in 1 resource block is 1. In the case of the arrangement shown in fig. 18, 1 group corresponds to 2 ports, and as an example of the arrangement, it is considered to use the arrangement in a case where the group of the terminal 2b is configured by 1 target terminal and 1 or less interfering terminals. Fig. 19 shows an example of the arrangement of reference signals when 2 symbols are set, and shows an example in which 2 reference signal symbols are included in 1 resource block. In the case of the arrangement shown in fig. 19, 1 group corresponds to 4 ports, and as an example of use of the arrangement, it is considered that the arrangement is used when the group of the terminal 2b is configured by 1 target terminal and 3 or less interfering terminals. The reference signals are frequency-multiplexed in an orthogonal state by multiplying the reference signals by the OCC. Here, for simplicity of explanation, let the number of reference signal symbols included in 1 resource block be X, let the group index of the CDM group included in 1 resource block be Y, and describe the CDM group as "group X-Y". In the example shown in fig. 18, ports 0 and 1 are included in group 1-0, and ports 2 and 3 are included in group 1-1. In the example shown in fig. 19, the group 2-0 includes the ports 0, 1, 4, and 5, and the group 2-1 includes the ports 2, 3, 6, and 7. When the position of the reference signal is expressed by coordinates (frequency, time), in the example shown in fig. 18, the reference signal of the terminal corresponding to the group 1-0 is arranged at the coordinates (0, 2), (2, 2), (4, 2), (6, 2), (8, 2), (10, 2). Let the reference signal arranged at these coordinates be q₀、q₁、q₂、q₃、q₄、q₅When the reference signals of 2 ports are multiplexed, the reference signal + q corresponding to the port 0 is arranged at coordinates (0, 2), (2, 2), (4, 2), (6, 2), (8, 2), and (10, 2)₀、+q₁、+q₂、+q₃、+q₄、+q₅And a reference signal + q corresponding to port 1₀、-q₁、+q₂、-q₃、+q₄、-q₅. Since each reference signal is code-multiplexed by the OCC, even if a plurality of reference signals are arranged at the same frequency and time, that is, at the same coordinate, the reference signals are kept at the same frequency and timeWhich proves orthogonality.

In addition, the resource element transmitting the reference signal may be used to transmit data instead of the reference signal. In addition, the above-mentioned "CDM group containing no data" refers to the following CDM group: data is transmitted using the resource elements transmitting the reference signals instead of the reference signals. When the reference signal is transmitted in all resource elements in which the reference signal is transmitted, the "number of CDM groups not including data" is "2". For example, the number of DMRS symbols is 1, and when reference signals are transmitted using all resource elements (frequencies 0 to 11) having a time of 2 in the configuration example shown in fig. 18, the number of CDM groups that do not include data is 2. In addition, the number of DMRS symbols is 1, and when a reference signal is transmitted using resource elements having frequencies of 1, 3, 5, 7, 9, and 11 among the resource elements having a time of 2 in the configuration example shown in fig. 18, the number of CDM groups that do not include data is 1.

When the base station 1b notifies the destination terminal of the index 26 when the port mapping table shown in fig. 17 is used, the destination terminal determines that the reference signals corresponding to the port numbers 0, 1, and 4 are allocated to the own terminal, and can transmit the rank of 3, that is, can perform 3-layer multiplexed data transmission. At this time, the port number corresponding to communication that may cause interference with communication corresponding to the port numbers {0, 1, 4} assigned to the target terminal is the port number 5 belonging to the same group. However, since there is no means for notifying the target terminal from the base station 1b whether or not the reference signal corresponding to the port number 5 is allocated to another terminal, that is, whether or not there is an interfering terminal, it is not clear whether or not there is an interfering terminal for the target terminal.

When the base station 1b notifies the destination terminal of the index 20, the destination terminal determines that the reference signal corresponding to the port number {0, 1} has been allocated to the own terminal. However, the destination terminal cannot know whether or not one or both of the reference signal corresponding to port number 4 and the reference signal corresponding to port number 5, which belong to the same CDM group as port numbers {0 and 1} are allocated to other terminals, based on the notified index 20. Therefore, the base station 1b may notify the destination terminal notified of the index 20 of a port number corresponding to the reference signal allocated to the interfering terminal (hereinafter, referred to as "interfering port number") among the port numbers 4 and 5. The notification of the interference port number is performed using DCI, for example, as in the index.

However, if the foregoing method is adopted, it is necessary to transmit the interference port number according to each index notified to the target terminal. Therefore, the types of signal information become various, overhead increases, and an enormous number of bits are required for control information. Therefore, the base station 1b can notify the target terminal of the number of ports (hereinafter referred to as "interference ports") corresponding to the reference signal allocated to the interference terminal, instead of the interference port number. For example, when the target terminal is notified of the index 20, the target terminal is assigned ports 0 and 1 (see fig. 17). Further, the ports 4 and 5 may become interference ports (refer to fig. 19). In this case, the number of interference ports may be any one of 0, 1, and 2. By notifying the number of interference ports from the base station 1b to the target terminal, it is clear whether or not the interference from the interfering terminal needs to be removed, and the target terminal can perform interference removal without depending on the numerical value of each index.

Further, the reference signal information management unit 14b that generates a control signal including an index indicating a port number may notify the presence of a non-interference port from the upper layer by using a flag indicating whether or not there is an interference port in each group. For example, in the upper layer, the reference signal information management unit 14b may be notified of whether or not an interference port corresponding to a port assigned to a target terminal exists in a GROUP using a flag such as INTRA _ GROUP _ INT. The name INTRA _ GROUP _ INT of the parameter is an example, and any name may be used as long as it is a parameter for notifying the interference state in the GROUP. When INTRA _ GROUP _ INT is used as a parameter, for example, when INTRA _ GROUP _ INT is 0, it indicates that the presence of an interference port is not notified. That is, when INTRA _ GROUP _ INT is 0, the number of interference ports is 0. In the case where the interference port does not exist, the number of interference ports is not notified, whereby signal overhead for the terminal can be reduced. The case of INTRA _ GROUP _ INT ═ 1 indicates the case where there is an interfering port in the GROUP. For example, when the target terminal is notified of the port numbers 0 and 1 using the index 20 shown in fig. 17, the reference signal information management unit 14b can notify the target terminal of the number of interfering ports by notifying the target terminal of INTRA _ GROUP _ INT 1 from the upper layer. In this case, if the parameter indicating the number of interfering PORTs is N _ INT _ PORT, N _ INT _ PORT is {1, 2 }. That is, the reference signal information management unit 14b notifies the target terminal of N _ INT _ PORT 1 or N _ INT _ PORT 2.

When the reference signal information management unit 14b notifies the target terminal of the PORT numbers 4 and 5 using the index 22 shown in fig. 17, it is possible to notify the target terminal of the N _ INT _ PORT 2. When notified that the N _ INT _ PORT is 2, the target terminal makes the PORTs of PORT numbers 0 and 1 in the same group as PORT numbers 4 and 5 an interfering PORT.

In addition, in the case of notifying the target terminal of 12 as the index shown in fig. 17, port 0 is allocated to the target terminal, and ports 1, 4, and 5 may be interfering ports. In this case, the number of PORTs N _ INT _ PORT generating interference is any one of 1, 2, and 3. When the PORT numbers are set in ascending order for each terminal, if N _ INT _ PORT is set to 2, PORT 1 and PORT 4 become interfering PORTs. When N _ INT _ PORT is set to 1, PORT 1 becomes an interfering PORT.

There may be 1 or more interfering terminals. In the presence of interfering terminals, the base station 1b may notify the target terminal of the number of interfering terminals. By using the above-described notification of the N _ INT _ PORT and the notification of the number of interfering terminals at the same time, more detailed information can be transmitted. A parameter indicating the number of interfering terminals is set to N _ INT _ UE. For example, when the index of fig. 17 is notified as 12 and port 0 is set for the target terminal, the number of interfering terminals is 0, 1, 2, or 3. If the port numbers are set in ascending order for each terminal, port 1 is set for the interfering terminal when the number of interfering terminals is 1, that is, when N _ INT _ UE is 1. When N _ INT _ PORT is 3 and N _ INT _ UE is 3, PORTs 1, 2, and 3 are set for 3 interfering terminals, respectively.

When N _ INT _ PORT is 3 and N _ INT _ UE is 2, the interfering terminal is 2 stations, and the target terminal that has received the notification of N _ INT _ PORT 3 and N _ INT _ UE 2 knows that 2 PORTs are set for 1 station of the interfering terminal and 1 PORT is set for the other 1 station. In this case, the base station 1b notifies the target terminal of 12 as the index of fig. 17, and the port setting state for the 2 nd interfering terminal is a state in which the 1 st interfering terminal is set with the port 1 and the 2 nd and 3 are set with the 2 nd interfering terminals, or a state in which the 1 st interfering terminal is set with the port 1 and 2 and the 2 nd interfering terminal is set with the port 3. The target terminal performs interference removal in consideration of these two setting states.

In addition, the N _ INT _ PORT is notified through the DCI described above. The INTRA _ GROUP _ INT is notified using the RRC described above or the like. The number of interference ports and the number of interference terminals may be notified in an upper layer such as RRC. When the notification is performed by the upper layer, the value cannot be updated frequently, and therefore the maximum interference port number or the maximum interference terminal number may be notified.

The port mapping table shown in fig. 17 corresponds to the arrangement of the reference signals shown in fig. 18 and 19, but the port mapping tables shown in fig. 20 and 21 may be used instead. The port mapping tables shown in fig. 20 and 21 correspond to the configurations of the reference signals shown in fig. 22 and 23. Fig. 20 and 21 show 1 port mapping table, fig. 20 shows port mapping tables corresponding to indexes 0 to 31 in the first half, and fig. 21 shows port mapping tables corresponding to indexes 32 to 63 in the second half. When the 1 st mapping table, which is the port mapping table shown in fig. 17, and the 2 nd mapping table, which is the port mapping table shown in fig. 20 and 21, are used, the type of port mapping is notified from the base station 1b to the target terminal by the upper layer. For example, the 1 st mapping table is set to configuration _1, and the 2 nd mapping table is set to configuration _ 2. Then, a parameter such as DMRS _ CONFIG _ NUM is prepared in the upper layer, configuration _1 is indicated from the base station 1b to the target terminal by using DMRS _ CONFIG _ NUM of 0, and configuration _2 is indicated from the base station 1b to the target terminal by using DMRS _ CONFIG _ NUM of 1.

In addition, in DMRS sequences that are sequences of reference signals arranged in 1 resource block, a signal pattern differs for each DMRS. In addition, the DMRS sequence may be generated using a scrambling code ID. For example, although the DMRS sequence is generated using a PN sequence generator, an initial value of the PN sequence generator may be set according to the following equation (3) and may be changed by a symbol index.

[ mathematical formula 3]

In the formula (3), n_sIndicating the slot number within the frame, l indicating the symbol number within the slot, n_SCIDThe value is set as a scrambling code ID of 0 or 1, and is different depending on the scrambling code ID for a parameter expressed by the following equation (4). The parameter expressed by the equation (4) may be set differently for each terminal 2 b.

[ mathematical formula 4]

When the base station 1b generates a DMRS sequence using a PN sequence generator, the base station may set an initial value of the PN sequence generator according to equation (3) to generate a DMRS sequence of 1 OFDM symbol.

When generating DMRS sequences to be transmitted to terminals 2b belonging to the same group, the base station 1b may set the parameters expressed by equation (4) to the same values or to different values. When the parameters expressed by equation (4) are set to the same value, the target terminal can generate a DMRS sequence of the interfering terminal using the parameters provided to the target terminal. Further, the base station 1b may notify the target terminal of the scrambling code ID used by the interfering terminal together with the interfering port number.

The base station 1b may also generate the DMRS using a predetermined scheme. That is, the DMRS may be generated by using an existing cell ID or the like without using the group ID or the like. In this case, the OCC may be applied for each port. By such a generation method, the generation of DMRS sequences independent of port mapping and group ID can be achieved.

The base station 1b notifies the target terminal of the information on the reference signal of each terminal 2b belonging to the same group by using the port mapping table, but may notify the target terminal of the information on the reference signal of the terminal 2b belonging to another group. The transmission signals transmitted from the base station 1b to the terminal 2b are assigned to different frequencies for each group and multiplexed at the same time. However, when the transmission path varies within the OFDM signal, interference may occur between REs. In this case, the target terminal may be interfered with by the terminal 2b of another group, that is, an interfering terminal with respect to the target terminal may exist in a group different from the group to which the target terminal belongs. Therefore, the base station 1b can suppress the occurrence of interference between the target terminals by notifying the target terminals of the information on the reference signals of the terminals 2b belonging to the other group. As a result, the communication quality can be improved.

As is apparent from the structure of the port mapping table shown in fig. 17 and the like, the target terminal receives notification of the number of CDM groups containing no data from base station 1 b. Therefore, the target terminal can grasp whether or not the reference signal is assigned to the terminal belonging to the other group. However, even if the target terminal knows that the reference signal is assigned to the terminal belonging to another group, it cannot know which port the terminal 2b corresponding to is the interfering terminal. Therefore, in order to represent the inter-group interference, I _ N _ INT _ PORT and I _ N _ INT _ UE are defined, and the base station 1b uses these to notify the target terminal of the reference signal of the interfering terminal of another group. I _ N _ INT _ PORT is the number of interfering PORTs of different groups, i.e., the number of PORTs allocated to interfering terminals belonging to different groups. I _ N _ INT _ UE is the number of interfering terminals belonging to different groups. For example, when the target terminal is notified from the base station 1b with an index of 4 using the port map shown in fig. 17 and the arrangement of the reference signal shown in fig. 18 and 19, it means that the number of CDM groups containing no data is 2, and there are terminals 2b receiving data from the base station 1b in each of the 2 groups. Further, the number of ports corresponding to each group is 2. Therefore, I _ N _ INT _ PORT ═ {1, 2}, and I _ N _ INT _ UE ═ 1, 2 }. That is, the number of interfering ports of different groups is 1 or 2, and the number of interfering terminals belonging to different groups is 1 or 2. The parameter INTER _ GROUP _ INT notified from the upper layer is defined, and if the INTER _ GROUP _ INT is in a state of 1, interference from a different GROUP is notified, and if the INTER _ GROUP _ INT is 0, interference from a different GROUP is not notified.

In the present embodiment, the case where the number of CDM groups is 2, that is, the case where the terminals 2b receiving data from the base station 1b are divided into 2 groups has been described, but this is merely an example. The number of CDM groups may also be 3. When the number of CDM groups is 3 and the target terminal receives interference from the terminal 2b in another group, the base station 1b notifies the target terminal of another group to which the terminal 2b causing interference to the target terminal belongs (hereinafter, referred to as "interference group"). For example, the base station 1b notifies the target terminal of the interference GROUP by using parameters such as INTER _ GROUP _ INT _0 indicating the presence of the interference GROUP 0 and INTER _ GROUP _ INT _1 indicating the presence of the interference GROUP 1. For example, let INTER _ GROUP _ INT _0 ═ 1 denote the presence of interference GROUP 0, INTER _ GROUP _ INT _0 ═ 0 denote the absence of interference GROUP 0, INTER _ GROUP _ INT _1 ═ 1 denote the presence of interference GROUP 1, and INTER _ GROUP _ INT _1 ═ 0 denote the absence of interference GROUP 1. Then, in the following, correspondence between an interference group with respect to a target terminal and other groups in the case where 3 CDM groups are set as group 2-0, group 2-1, and group 2-2 is defined. Is predefined as: when the target terminal exists in the group 2-0, the interference group 0 with respect to the target terminal corresponds to the "group 2-1", the interference group 1 corresponds to the "group 2-2", when the target terminal exists in the group 2-1, the interference group 0 with respect to the target terminal corresponds to the "group 2-0", the interference group 1 corresponds to the "group 2-2", when the target terminal exists in the group 2-2, the interference group 0 with respect to the target terminal corresponds to the "group 2-0", and the interference group 1 corresponds to the "group 2-1". For example, when the target terminal in the GROUP 2-0 receives interference from the terminal in the GROUP 2-1 and does not receive interference from the terminal in the GROUP 2-2, the base station 1b notifies the target terminal in the GROUP 2-0 of INTER _ GROUP _ INT _0 being 1 and INTER _ GROUP _ INT _1 being 0. When the target terminal existing in the GROUP 2-1 receives interference from the terminal of the GROUP 2-0 and interference from the terminal of the GROUP 2-2, the base station 1b notifies the target terminal existing in the GROUP 2-1 of INTER _ GROUP _ INT _0 being 1 and INTER _ GROUP _ INT _1 being 1. When the target terminal existing in the GROUP 2-2 is not interfered by the terminal of the GROUP 2-0 and is interfered by the terminal of the GROUP 2-1, the base station 1b notifies the target terminal existing in the GROUP 2-2 of INTER _ GROUP _ INT _0 ═ 0 and INTER _ GROUP _ INT _1 ═ 1. Similarly, parameters such as I _ N _ INT _ PORT _0 and I _ N _ INT _ PORT _1 indicating whether or not each PORT assigned to the terminal of each group corresponds to an interference PORT, and parameters such as I _ N _ INT _ UE _0 and I _ N _ INT _ UE _1 indicating whether or not the terminal 2b corresponds to an interference terminal are defined, and each parameter is associated with the PORT in advance, and the base station 1b notifies the target terminal of the interference terminal and the interference PORT in the interference group using these parameters.

In the present embodiment, the description has been given of the operation of notifying the target terminal of the interfering terminal when the 1 base station communicates with the target terminal, that is, the interference notification corresponding to the 1 base station. However, it is also possible to perform interference notification when a plurality of base stations communicate with a target terminal, and to notify the target terminal of a plurality of SU-MIMO port numbers from the base stations. In addition, the port number for SU-MIMO is specified in the port mapping table according to the specification and the like. As shown in fig. 24, when the terminal 2b communicates with the base station 1b-1 and the base station 1b-2, the terminal 2b can measure the interference received by the communication between the terminal 2b and each base station from the communication with another base station by knowing in advance that different SU-MIMO port numbers are notified from the base station 1b-1 and the base station 1 b-2. Further, as shown in fig. 25, when the target terminal 2-1 and the interfering terminal 2-2 exist, the target terminal 2-1 can remove interference received from communications between the base stations 1b-1 and 1b-2 and the interfering terminal 2-2 as long as the target terminal 2-1 grasps DMRS port information notified to the interfering terminal 2-2. Interference measurement can be easily performed by specifying CDM groups or port information to be set for each terminal when a plurality of base stations perform transmission in advance in the specification. For example, in the case where the index of the port mapping table shown in fig. 20 is 23, a mode in which 1 port is used at a time from among 2 ports of group 1-0 and 2 ports of group 1-1 shown in fig. 22 may be used for a plurality of base station communications. Further, an index indicating a combination of port numbers 1 and 3 may be used. Note that the index number in the port mapping table shown in fig. 17 and a part of the index number in the port mapping tables shown in fig. 20 and 21 may be used for communication among a plurality of base stations.

As described above, in the radio communication system according to the present embodiment, the base station 1b generates a set of a target terminal and an interfering terminal, as in the base station 1a according to embodiment 2. The base station 1b notifies the target terminal of the reference signal information transmitted to the target terminal and the reference signal information transmitted to the interfering terminal, using the port mapping tables stored in both the base station 1b and the terminals. This can provide the same effects as those of embodiment 2. In addition, since the base station 1b notifies the target terminal of the reference signal information transmitted to the target terminal and the reference signal information transmitted to the interfering terminal by notifying the index number of the port mapping table, the amount of control information transmitted to the target terminal can be suppressed.

Embodiment 4.

In the present embodiment, the precoding unit 18 of the base station 1b described in embodiment 3 will be described.

In recent years, application of nonlinear precoding for precoding by performing nonlinear processing on a transmission signal has been studied. The nonlinear precoding is processing performed on signals transmitted to a plurality of terminals, respectively, and each terminal to which the nonlinear-processed signal is transmitted needs to know a reference signal transmitted to another terminal when demodulating a data signal addressed to the terminal. That is, each terminal communicating with the base station 1b that notifies the reference signal information using the port number needs to know the port number assigned to the other terminal. Therefore, when the precoding unit 18 performs nonlinear precoding, the base station 1b notifies the target terminal of the port number assigned to the interfering terminal. In embodiment 3, the base station 1b notifies the target terminal of the port number assigned to the target terminal by notifying the index of the port mapping table by DCI. In contrast, when the base station 1b according to embodiment 4 notifies the target terminal of the index of the port mapping table by using DCI and notifies the port number assigned to the target terminal, the base station also notifies the port number assigned to the interfering terminal. For example, NLP _ INTF _ PORT _0 is defined as a parameter for notifying a PORT number allocated to an interfering terminal, and an interfering PORT number, which is a PORT number allocated to the interfering terminal, is notified by setting the value of the index of the PORT mapping table to the parameter and being transmitted to the target terminal by the base station 1 b. For example, when the base station 1b allocates the PORT numbers 0 and 1 corresponding to the index 20 of the PORT mapping table shown in fig. 17 to the target terminal and allocates the PORT numbers 4 and 5 corresponding to the index 22 to the interfering terminal, the base station notifies the target terminal of NLP _ INTF _ PORT _0 being 22 in addition to the index corresponding to the PORT number allocated to the target terminal.

Here, although the case of performing nonlinear precoding for 2 terminals is described, nonlinear precoding may be performed for 3 or more terminals. In the case of 3 terminals as objects, in addition to the above-described NLP _ INTF _ PORT _0, NLP _ INTF _ PORT _1 is defined, and the base station 1b sets indexes corresponding to PORT numbers allocated to 2 interfering terminals among indexes of the PORT mapping table to NLP _ INTF _ PORT _0 and NLP _ INTF _ PORT _ 1. For example, when the base station 1b allocates the PORT numbers 0 and 1 corresponding to the index 20 of the PORT mapping table shown in fig. 17 to the target terminal, and allocates the PORT number 4 corresponding to the index 16 and the PORT number 5 corresponding to the index 17 to the remaining 2 interfering terminals, NLP _ INTF _ PORT _0 is 16 and NLP _ INTF _ PORT _1 is 17, respectively.

In the above description, an example in which a parameter such as NLP _ INTF _ PORT _0 that notifies an interference PORT number is defined and used has been described, but the PORT mapping table shown in fig. 17 and the PORT mapping tables shown in fig. 20 and 21 may include an interference PORT number. In this case, the base station 1b can notify the target terminal of the port number and the interference port number allocated to the target terminal using 1 index.

Further, the reference signal information management unit 14b may notify the upper layer of the presence or absence of the nonlinear precoding by using a flag indicating whether or not the nonlinear precoding is performed, wherein the reference signal information management unit 14b generates a control signal including an index indicating a port number. For example, the presence or absence of the nonlinear precoding may be notified to the reference signal information management unit 14b by using a FLAG such as NLP _ FLAG in the upper layer. When the flag is set, the reference signal information management unit 14b generates a control signal including an index indicating the port number assigned to the interfering terminal.

In the above description, a method of notifying the interfering port number when the base station 1b transmits to the terminal 2b a signal on which only the nonlinear precoding is performed is shown, and next, a method of notifying the interfering port number to the terminal 2b by the base station 1b when transmitting a signal on which the nonlinear precoding and the linear precoding are performed is described.

For example, in the case of the configuration using the reference signal shown in fig. 19, assuming that port 0 is allocated to terminal 2b-1, port 1 is allocated to terminal 2b-2, port 4 is allocated to terminal 2b-3, and port 6 is allocated to terminal 2b-4, the 1 st group consisting of terminal 2b-1 and terminal 2b-2 and the 2 nd group consisting of terminal 2b-3 and terminal 2b-4 are separated by linear precoding, and terminal 2b-1 and terminal 2b-2 are nonlinearly precoded. In this case, interference occurs between 2 groups separated by linear precoding. When the target terminal is terminal 2b-1, base station 1b notifies terminal 2b-1 of the information on the port number assigned to terminal 2b-2 as described in the present embodiment. Then, the base station 1b notifies the terminals 2b-3 and 2b-4 that the terminals are interfering terminals by setting N _ INT _ UE and N _ INT _ PORT to 2 and transmitting the settings to the target terminal. In this example, both the nonlinear precoding and the linear precoding are used, and the base station 1b notifies the interfering terminal and the target terminal of the use of both the nonlinear precoding and the linear precoding by using parameters of an upper layer or the like.

It is assumed that a data signal transmitted using a PDSCH (Physical Downlink Shared Channel) is nonlinearly precoded, and a DMRS is linearly precoded. If DMRS is non-linearly precoded, the phase and amplitude of DMRS symbols are distorted, and transmission path estimation using DMRS cannot be performed on the receiving side. Therefore, when the base station 1b performs both linear precoding and nonlinear precoding, the precoding section 18 of the base station 1b is configured to have a signal processing section for performing linear precoding and a signal processing section for performing nonlinear precoding. Then, the precoding section 18 performs linear precoding or nonlinear precoding in accordance with an instruction from the control section 41.

Fig. 26 is a diagram showing an example of a precoding unit included in the base station according to embodiment 4. The precoding section 18 shown in fig. 26 includes a 1-time precoding section 181 and a 2-time precoding section 182. In the precoding section 18 shown in fig. 26, one of the 1 st-order precoding section 181 and the 2 nd-order precoding section 182 performs linear precoding, and the other performs nonlinear precoding. For example, the 1-time precoding unit 181 performs linear precoding, and the 2-time precoding unit 182 performs nonlinear precoding. The 1-time precoding unit 181 may perform nonlinear precoding and the 2-time precoding unit 182 may perform linear precoding. In the case of the configuration in which the 1-time precoding unit 181 performs linear precoding and the 2-time precoding unit 182 performs nonlinear precoding, the control unit 41 instructs the 1-time precoding unit 181 to perform precoding and instructs the 2-time precoding unit 182 not to perform precoding when the target of precoding is a reference signal. Further, when the target of precoding is a data signal, the control unit 41 instructs the 1-time precoding unit 181 not to perform precoding and instructs the 2-time precoding unit 182 to perform precoding. When the base station 1b notifies the terminal 2b of the precoding scheme to be used, parameters indicating the precoding scheme may be defined and notified by using the above-described RRC or the like. The base station 1b may also perform control for switching the precoding scheme using the MAC-CE, DCI, or the like described above. In addition, in the case of data transmission, both of 1-time precoding and 2-time precoding may be performed.

The configuration of the precoding unit 18 may be as shown in fig. 27. Fig. 27 is a diagram showing another example of a precoding unit provided in a base station according to embodiment 4. The precoding section 18 shown in fig. 27 includes a 1 st precoding section 183, a 2 nd precoding section 184, and a selection section 185. One of the 1 st precoding section 183 and the 2 nd precoding section 184 performs linear precoding, and the other performs nonlinear precoding. For example, the 1 st precoding section 183 performs linear precoding, and the 2 nd precoding section 184 performs nonlinear precoding. In this case, when a reference signal is input, the selection unit 185 outputs the reference signal to the 1 st pre-coding unit 183 to cause the 1 st pre-coding unit 183 to perform linear pre-coding, and when a data signal is input, inputs the data signal to the 2 nd pre-coding unit 184 to cause the 2 nd pre-coding unit 184 to perform nonlinear pre-coding. The 1 st precoding section 183 may be a precoder having a structure in which a linear precoder and a nonlinear precoder are coupled as shown in fig. 26, and the 2 nd precoding section 184 may be a linear precoder.

As described above, in the wireless communication system according to the present embodiment, the base station 1b includes the precoding unit 18 capable of performing linear precoding and nonlinear precoding, and notifies the target terminal of the interference port number when transmitting a signal obtained by performing nonlinear precoding. According to the base station 1b of the present embodiment, the terminal 2b can estimate a transmission path using a reference signal generated by nonlinear precoding.

The configuration described in the above embodiment is an example of the contents of the present invention, and may be combined with another known technique, and it goes without saying that a part of the configuration may be omitted or modified within a range not departing from the gist of the present invention.

Description of the reference symbols

1. 1b, 1b-1, 1 b-2: a base station; 2₁、2₂、…、2_n2-1, 2-2: a terminal; 3. 3 a: a receiving device; 11: a receiving section; 12: a feedback information processing unit; 13: a multiplex control signal generating section; 14: a reference signal information management unit; 15: a reference signal generation unit; 16: a data signal generating section; 17: a multiplexing unit; 18: a pre-coding unit; 19: sendingA section; 31: a reception processing unit; 32. 32 a: a demodulation unit; 33. 33 a: a control signal demodulation unit; 41: a control unit; 50. 50 b: a transmitting device; 181: a 1-time precoding unit; 182: a 2-time precoding unit; 183: a 1 st pre-encoding unit; 184: a 2 nd pre-encoding section; 185: a selection unit.