JP2018056812A - Base station device, terminal device and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: When MUST using a transmission power ratio which makes a distance between signal points remarkably short is introduced, an influence of EVM or the like is severely exerted, thereby heavily deteriorating a transmission characteristic.SOLUTION: MUST is performed using a transmission power ratio which makes a minimum value of a distance between signal points of constellation of MUST after electric power normalization equal to or larger than a minimum value of a distance between signal points of existing constellation of 256 QAM or the like.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a base station device, a terminal device, and a communication method.

With the recent spread of smartphones and tablet terminals, the demand for high-speed wireless transmission is increasing. The Third Generation Partnership Project (3GPP), one of the standardization organizations, is making specifications for LTE (Long Term Evolution). L up to Rel-11
In the TE downlink, QPSK (Quadrature Phase Shift Keying) is used as a modulation method.
), 16QAM (Quadrature Amplitude Modulation) and 64QAM are supported. In QPSK, it is possible to transmit 2 bits with one modulation symbol. In 16QAM, 4 bits can be transmitted with one modulation symbol. In 64QAM, 6 bits can be transmitted with one modulation symbol. That is, 16QAM has higher frequency utilization efficiency than QPSK. Furthermore, 64QAM has higher frequency utilization efficiency than 16QAM. Furthermore, in LTE Rel-12, 256QAM capable of transmitting 8 bits with one modulation symbol is introduced (Non-Patent Document 1).

In LTE Rel-14, examination of MUST (Multi-User Superposition Transmission) is being conducted (Non-Patent Document 2). In MUST, a base station device adds signals addressed to two terminal devices at an arbitrary transmission power ratio, and transmits the added signal to the two terminal devices. Here, the transmission power ratio is a ratio at which the base station distributes power used for data transmission in the downlink to a plurality of terminals. At this time, a terminal device that is far from the base station and has a low reception quality (a remote terminal device, a terminal device that does not require interference suppression or removal, a terminal for which MUST is not set, a legacy terminal) and a terminal that has a high reception quality near the base station Devices (neighboring terminal devices, terminal devices that require interference suppression or removal, and terminals for which MUST is set) are paired, a large power is allocated to the far terminal device, and the remaining power is allocated to the neighboring terminal device. Since the remote terminal device is dominated by noise, inter-cell interference and the like, even if a signal addressed to a nearby terminal device is included in the signal, the reception quality can be suppressed to a slight deterioration.

  On the other hand, for a nearby terminal device, a signal addressed to a remote terminal device causes large interference. However, by canceling or suppressing a signal addressed to a remote terminal device first, it is possible to demodulate a signal addressed to the local station. In this way, a base station multiplexes and transmits signals addressed to a plurality of terminal devices and separates them by a terminal device that is a receiver, whereby a plurality of terminal devices can communicate at the same frequency and at the same time. As a result, the communication opportunity of each terminal device can be increased, so that the throughput can be increased.

  If the base station apparatus can set a plurality of transmission power ratios, MUST can be applied to communication with terminal apparatuses in various environments. It has been proposed to reuse an existing LTE constellation (signal point) as a transmission power ratio candidate (Non-Patent Document 3, Non-Patent Document 4). For example, when 16QAM and QPSK are combined by MUST and transmitted, 64 points out of 256QAM signal points are used. Since there are many ways to select 64 points, many candidates for the transmission power ratio can be secured using the existing constellation.

“Physical layer procedures (Release 12)” 3GPP TS 36.213 v12.5.0 (2015-03) “Study on Downlink Multiuser Superposition Transmission (MUST) for LTE (Release 13)” 3GPP TR 36.859 v13.0.0 (2015-12) 3GPP, R1-166277, Qualcomm Incorporated, “Power ratio design for MUST” 3GPP, R1-167689, Nokia, Alcatel-Lucent Shanghai Bell, “MUST Case 1 and 2 transmission schemes”

  However, in 3GPP, it is necessary to consider how the influence of EVM (Error Vector Magnitude) and the like will be when a modulation scheme that shortens the distance between signal points is introduced. Therefore, when the transmission power ratio is adjusted, if the distance between signal points is remarkably shortened, the transmission power ratio may not be specified because it is greatly affected by EVM or the like. Alternatively, there is a possibility that MUST can be applied only to base station devices and terminal devices that support transmission and reception at that transmission power ratio.

  The present invention has been made in view of the above problems, and an object of the present invention is to perform MUST using a transmission power ratio candidate composed only of an allowable transmission power ratio even when there is an influence of EVM or the like. A base station device, a terminal device, and a communication method thereof are provided.

  In order to solve the above-described problems, each configuration of the base station and the terminal according to the present invention is as follows.

  (1) In order to solve the above problem, a base station apparatus according to one aspect of the present invention combines a signal addressed to a first terminal apparatus and a signal addressed to a second terminal apparatus at a predetermined transmission power ratio. A transmission power ratio in which a distance between signal points of modulation symbols in the signal generated by the combination is equal to or longer than a predetermined value is set to the predetermined transmission power ratio. The transmission power ratio storage unit having one or more as candidates, the transmission power ratio selection unit for selecting one from the one or more transmission power ratios of the transmission power ratio storage unit, and the transmission power ratio selection unit selected A transmission power setting unit that changes the power of the modulation symbol based on the transmission power ratio.

  (2) In order to solve the above problem, the base station apparatus according to one aspect of the present invention is characterized in that the predetermined value is a shortest distance among signal point distances of a predetermined QAM modulation symbol. And

  (3) In order to solve the above problem, the base station apparatus according to one aspect of the present invention is characterized in that the predetermined QAM modulation symbol is 256 QAM.

  (4) In order to solve the above problem, the base station apparatus according to one aspect of the present invention is configured such that the distance between the signal points of the modulation symbols in the signal generated by the combining is between the signal points in the same quadrant. Distance.

  (5) In order to solve the above problem, the base station apparatus according to one aspect of the present invention is configured such that the distance between the signal points of the modulation symbol in the signal generated by the synthesis is the distance between the signal points in different quadrants. It is.

(6) In order to solve the above problem, a terminal device according to an aspect of the present invention combines a signal addressed to the terminal device and a signal addressed to a terminal device other than the terminal device at a predetermined transmission power ratio. A terminal device for receiving a signal, wherein a transmission power ratio in which a distance between modulation symbol signal points in a signal generated by the synthesis is the same or longer than a predetermined value is a candidate for the predetermined transmission power ratio A transmission power ratio storage unit having one or a plurality of transmission power ratios, a transmission power ratio notification unit for notifying information indicating one of the transmission power ratios of the one or more transmission power ratios of the transmission power ratio storage unit, and the transmission power A demodulation unit that performs demodulation using information indicating the transmission power ratio notified from the ratio notification unit.

  (7) In order to solve the above problem, a communication method according to one aspect of the present invention combines a signal addressed to a first terminal device and a signal addressed to a second terminal device at a predetermined transmission power ratio. A transmission method of a base station apparatus to transmit, a transmission power ratio selection step of selecting one from one or a plurality of transmission power ratios possessed by a transmission power ratio storage unit, and the transmission power selected in the transmission power ratio selection step A transmission power setting step of changing the power of the modulation symbol based on the ratio, and the transmission power ratio storage unit compares a distance between signal points of the modulation symbol in the signal generated by the combination with a predetermined value. And having one or a plurality of transmission power ratios that are the same or longer as candidates for the predetermined transmission power ratio.

  (8) In order to solve the above-described problem, a communication method according to one aspect of the present invention combines a signal addressed to the terminal device and a signal addressed to a terminal device other than the terminal device at a predetermined transmission power ratio. A communication method of a terminal device that receives a signal, a transmission power ratio notifying step of notifying a demodulation unit of information indicating one of a transmission power ratio of one or a plurality of transmission power ratios held by a transmission power ratio storage unit; A demodulation step of performing demodulation using information indicating the transmission power ratio in the demodulation unit, wherein the transmission power ratio storage unit has a predetermined distance between modulation symbol signal points in the signal generated by the combining One or a plurality of transmission power ratios that are equal to or longer than the value of the predetermined transmission power ratio are provided as candidates for the predetermined transmission power ratio.

  According to the present invention, it is possible to apply MUST that uses a transmission power ratio that minimizes the influence of EVM or the like.

It is a schematic block diagram which shows the structure of the radio | wireless communications system which concerns on this embodiment. It is a figure which shows the transmitter structural example of the base station apparatus which concerns on this embodiment. It is a figure which shows an example of the allocation subset of the signal point which concerns on this embodiment. It is a figure which shows an example of the constellation of the signal point allocation based on the signal point arrangement | positioning of 256QAM in the near-terminal modulation order 2 which concerns on this embodiment. It is a figure which shows another example of the allocation subset of the signal point in this embodiment which concerns on this embodiment. It is a figure which shows an example of the allocation subset of the signal point which concerns on 2nd Embodiment. It is a figure which shows an example of the allocation subset of the signal point which concerns on 3rd Embodiment. It is a figure which shows the constellation by the last line of FIG. 7 which concerns on this embodiment. . It is a figure which shows the receiver structural example of the terminal device which concerns on 1st this embodiment.

Terminal equipment includes user equipment (User Equipment: UE), mobile station (Mobile Station: MS, Mobile
Terminal: MT), mobile station device, mobile terminal, subscriber unit, subscriber station, wireless terminal, mobile device, node, device, remote station, remote terminal, wireless communication device, wireless communication device, user agent, access terminal A mobile type or a fixed type user end device such as the above is generically referred to. The base station apparatus is a generic term for any node at the end of the network that communicates with a terminal such as a node B (NodeB), an enhanced node B (eNodeB), a base station, or an access point (Access Point: AP). Note that the base station apparatus is an RRH (Remote Radio
Head, a device having an outdoor-type radio unit smaller than the base station device, and Remote Radio Unit (also referred to as RRU) (also referred to as remote antenna and distributed antenna). The RRH can be said to be a special form of the base station apparatus. For example, the RRH has only a signal processing unit, and can be said to be a base station apparatus in which parameters used in the RRH are set by another base station apparatus and scheduling is determined.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a schematic block diagram illustrating a configuration of a wireless communication system according to the present embodiment. The system includes a base station apparatus 101, a nearby terminal apparatus 102 (first terminal apparatus), and a remote terminal apparatus 103 (second terminal apparatus). In FIG. 1, it is assumed that the near terminal apparatus 102 is close to the base station apparatus and has high reception quality, and the far terminal apparatus 103 is far from the base station apparatus, and the reception quality is lower than that of the far terminal apparatus 102. Note that the number of antenna ports configured in each device may be one or plural. Here, the antenna port indicates not a physical antenna but a logical antenna that can be recognized by a communication device.

  FIG. 2 is a diagram illustrating a transmitter configuration example of the base station apparatus 101 according to the present embodiment. FIG. 2 shows only blocks (processing units) necessary for describing the embodiment of the present invention.

  An encoded bit sequence (code word) obtained by encoding data addressed to the nearby terminal apparatus 102 is input to the scrambling section 200-1, and an encoded bit sequence (code word) encoded data addressed to the far terminal apparatus 103 is Are input to the scrambling unit 200-2. In the scrambling unit, scrambling unique to the terminal device is applied. The outputs of scrambling section 200-1 and scrambling section 200-2 are input to modulation section 201-1 and modulation section 201-2, respectively. The modulation unit 201-1 and the modulation unit 201-2 perform processing for converting the input bit string into modulation symbols (QPSK modulation symbol, QAM modulation symbol) such as QPSK and 64QAM. Here, in the present embodiment, the explanation is made on the assumption that the modulation scheme of the far terminal apparatus 103 is always limited to QPSK, but the present invention is not limited to this, and a modulation scheme such as 16QAM or 64QAM may be used. . Note that the modulation unit 201-1 that modulates the neighboring terminal apparatus 102 is not limited to QPSK, and a modulation scheme such as 16QAM or 64QAM is applied.

  The outputs of modulation section 201-1 and modulation section 201-2 are input to transmission power setting section 202-1 and transmission power setting section 202-2, respectively. Transmission power setting sections 202-1 and 202-2 set transmission power according to the transmission power ratio input from transmission power ratio selection section 209. For example, when 0.8 (or information indicating 0.8) is input to the transmission power setting unit 202-1 as the transmission power ratio from the transmission power ratio selection unit 209, a signal input from the modulation unit 201-1 A signal obtained by multiplying the power of the signal by 0.8 is input to the signal synthesis unit 203. Note that when the terminal apparatus 101 and the terminal apparatus 102 apply SU-MIMO, that is, use a plurality of layers, the same transmission power ratio may be used for each layer, or different values may be set. Details of the transmission power ratio selection unit 209 will be described later.

Outputs of transmission power setting section 202-1 and transmission power setting section 202-2 are input to signal synthesis section 203. The signal combining unit 203 generates a signal obtained by combining (adding) the outputs from the transmission power setting unit 202-1 and the transmission power setting unit 202-2. Here, at the time of synthesis, instead of simply performing synthesis, transmission power setting is performed according to the output of the modulation unit 201-2 related to the remote terminal apparatus so that the combined signal satisfies Gray coding (labeling). Processing such as combining may be performed after the sign of the output from the unit 202-1 is inverted. 2, the modulation unit 201-1 and the modulation unit 201-2, the transmission power setting unit 202-1 and the transmission power setting unit 202-2, and the signal synthesis unit 203 are configured independently, but are not necessarily configured independently. There is no need to do this, and processing may be performed in one block.

  The output of the signal synthesis unit 203 is input to the layer mapping unit 204. In the layer mapping unit 204, when the base station apparatus includes a plurality of transmission antennas, a process of allocating the codeword of each terminal apparatus to the transmission antenna is applied. The output of the layer mapping unit 204 is input to the precoding unit 205. The precoding unit 205 performs precoding for transmitting each layer from a plurality of antenna ports. The output of the precoding unit 205 is input to the resource element mapping unit 206. Resource element mapping section 206 arranges the signal input from precoding section 205 in an arbitrary resource element (subcarrier). The subcarrier group used by the neighboring terminal device 102 and the subcarrier group used by the far terminal device 103 do not need to match, and the far terminal device 103 and the neighboring terminal device 102 that perform transmission of different bandwidths perform MUST. May be. Note that which resource element is used is determined by an input from a scheduling unit (not shown).

The output of the resource element mapping unit 206 is input to the OFDM signal generation unit 207. In the OFDM signal generation unit 207, IFFT (Inverse Fast Fourier Transform) is applied to the input from the resource element mapping unit 206, and CP (Cyclic Prefix) is applied.
) Is added. Further, processing such as D / A conversion, filtering, and up-conversion is applied, and transmission is performed from the antenna 208.

Here, the transmission power ratio selection unit 209 will be described. The transmission power ratio selection unit 209 selects a predetermined transmission power ratio from one or a plurality of transmission power ratio candidates (or information on the transmission power ratio) input from the transmission power ratio storage unit 210. The selected transmission power ratio is input to transmission power setting section 202-1 and transmission power setting section 202-2. The selected transmission power ratio may be notified to the terminal device 102 dynamically or semi-dynamically using a DCI (Downlink Control Information) format, or using RRC (Radio Resource Control) signaling or the like. And may be notified statically or semi-statically. Further, when the terminal apparatus 101 performs transmission using a plurality of layers, a different transmission power ratio may be set for each layer and each may be notified. Note that the transmission power ratio is not necessarily notified to the terminal device, and the terminal device 101 may estimate the transmission power ratio by blind detection. Note that the transmission power ratio stored in the transmission power ratio storage unit 210 may be determined in advance by the system, or may be rewritten by communication in an upper layer such as RRC (Radio Resource Control) signaling.
In the present embodiment, one or a plurality of transmission power ratios are determined using some points of the constellation based on the LTE constellation of 16QAM, 64QAM, and 256QAM. FIG. 3 is an example of a signal point allocation subset according to the present embodiment. The LTE constellation in the table indicates which of the LTE constellations is used to generate the MUST signal point. The neighboring terminal modulation order indicates the modulation multi-level number, 2 indicates QPSK, 4 indicates 16 QAM, and 6 indicates 64 QAM. The transmission power ratio storage unit 210 selects one or a plurality of transmission power ratios from the transmission power ratio candidates shown in FIG. 3 according to the modulation multi-level number (modulation order) of the terminal apparatus 101 and inputs the selected transmission power ratio to the transmission power ratio selection unit 209. To do. The far terminal power ratio indicates the power allocated to the far terminal when the total power is 1. The normalized power ratio indicates the transmission power ratio between the distant terminal and the nearby terminal. Since the expected power uses only a part of the basic LTE constellation, there is a possibility that the transmission power may be increased or decreased as compared with the basic LTE constellation. When the expected power is positive, it indicates that the power is larger than that of the LTE constellation. Next, the allocation subset of signal points in the table will be described. The squares in the figure show assignments within a quadrant with the underlying LTE constellation. For example, in FIG. 3, the twelfth row from the top (seventh from the bottom) is the second from the left and the fifth from the left among the eight values in each quadrant (that is, the right) The fourth signal point is used. The signal points used are the same for the Q axis as well as the I axis. FIG. 4 is a diagram showing an example of a signal point assignment constellation based on the 256QAM signal point arrangement in the vicinity terminal modulation order 2 according to the present embodiment. FIG. 4 shows the signal point arrangement indicated by the twelfth row from the top in FIG. When the transmission power ratio selection unit selects the signal point arrangement indicated by the twelfth row from the top, one of the 16 candidate points indicated by the black dots in FIG. 4 is used according to the transmission data. Transmission takes place. In this case, the transmission power ratio of the nearby terminal is 100/109, that is, 91.743%, and the transmission power ratio of the remote terminal is 9/109, that is, 8.2569%. However, when only a part of 256QAM signal points is used for transmission, there is a possibility that the average transmission power changes as compared with transmission by 256QAM. This is described in the expected power column. In the case of the signal point arrangement indicated by the twelfth row from the top, it is shown that 1.0801 dB power is increased as compared with general 256QAM transmission. When the average transmission power increases, the burden on the power amplifier increases, so it is necessary to perform power normalization so that the average transmission power is constant regardless of the transmission power ratio.

  FIG. 5 is a diagram showing another example of the signal point allocation subset in the present embodiment. In FIG. 5, only the transmission power ratio that increases the signal point by normalization is set as a candidate for the transmission power ratio so that the average transmission power does not vary depending on the selected transmission power ratio with respect to the combined constellation. FIG. 5 uses only the transmission power ratio as a candidate in FIG. 3 in which the expected power is the same as or lower than the normal 16QAM, 64QAM, and 256QAM (that is, the expected power column is zero or a negative value). As a result, in FIG. 5, the number of transmission power ratio candidates is limited from the number of candidates in FIG.

  Next, the terminal apparatus 102 that receives the signal transmitted by the base station apparatus 101 will be described. FIG. 9 is a diagram illustrating a receiver configuration example of the base station apparatus 102 according to the present embodiment. FIG. 9 shows only blocks (processing units) necessary for describing the embodiment of the present invention. A signal transmitted from the base station apparatus 101 is received by the receiving antenna 901. An OFDM signal receiving unit 902 performs down conversion, A / D conversion, CP removal, FFT application, and the like on the signal received by the receiving antenna. The output of the OFDM signal receiving unit 902 is input to the resource element demapping unit 903. The resource element demapping unit 903 extracts resource elements used for communication with the terminal apparatus 102 based on scheduling information input from a scheduling unit (not shown). The output of the resource element demapping unit 903 is input to the signal detection unit 904. In the signal detection unit 904, processing for compensating for the influence of the propagation path is applied. When there are a plurality of receiving antennas 901, only a signal addressed to the terminal apparatus 102 is detected by applying spatial filtering or MLD. The output of the signal detection unit 904 is input to the layer demapping unit 905. In the layer demapping unit 905, when the signal transmitted from the terminal apparatus 102 is composed of a plurality of layers (streams), conversion into a code word is performed. The output of the layer demapping unit 905 is input to the demodulation unit 906. The demodulator 906 performs a process of calculating a bit sequence LLR (Log Likelihood Ratio) from the input received signal sequence. When the signal addressed to the terminal apparatus 102 and the signal addressed to the terminal apparatus 103 are multiplexed using MUST, the LLR of the signal addressed to the terminal apparatus 102 is transmitted using the transmission power ratio notified from the transmission power ratio notification unit 908. Is calculated. For the calculation, reception processing based on MLD may be applied, or a codeword level or symbol level canceller may be used. The bit LLR sequence output from the demodulation unit 906 is input to the descrambling unit 907. The descrambling unit 907 releases the scrambling unique to the terminal device. Processing such as decoding is applied to the encoded bit string output from the descrambling unit 907 in the receiving apparatus.

The transmission power ratio notifying unit 908 uses one or a plurality of transmission power ratios stored in the transmission power ratio storage unit 909 and information on the transmission power ratio notified from the base station apparatus 101 by DCI or the like. Is input to the demodulator 906. Here, the transmission power ratio stored in the transmission power storage unit 909 is selected based on the same criteria as the transmission power ratio storage unit 210 in FIG. 2 and is shared by the base station apparatus 101 and the terminal apparatus 102. When not notified from the base station apparatus, the transmission power ratio is estimated by blind detection. When performing blind detection, it may be assumed that only the transmission power ratio stored in the transmission power storage unit 909 is used in the base station apparatus 101.

Thus, the transmission power ratio storage unit 210 stores only transmission power ratios that can be set from signal point arrangements that are a subset of the existing LTE constellation. Furthermore, in the normalization so that the average signal transmission power does not change from that of the existing constellation, only the transmission power ratio that is the normalization for increasing the power is selected as a candidate for the subset of signal points. As a result, the transmission power ratio that is shorter than the signal point distance of the existing modulation scheme is not used as a candidate, so that the existing apparatus can apply MUST without causing significant degradation.
[Second Embodiment]
In the first embodiment, when a transmission power ratio that constitutes a signal point using only a subset of an existing constellation is used as a transmission power ratio candidate in MUST, the average transmission of a set of signal points consisting only of the subset It has been explained that only transmission power ratios whose power is smaller than the average transmission power of the existing modulation scheme are candidates. However, if the transmission power ratio is limited only when the expected transmission power is smaller than the transmission power of the existing modulation scheme, the transmission power ratio candidates may be too narrowed. Therefore, in the present embodiment, a method for increasing the number of transmission power ratio candidates from the first embodiment while considering only the transmission power ratio in consideration of the influence of EVM or the like will be described.

  When generating a MUST constellation using a subset of an existing constellation, it is necessary to perform normalization as described in the first embodiment. Therefore, transmission is performed at a signal point different from the existing constellation by normalization. For this reason, a signal having a distance between signal points different from that of the existing constellation is generated. The influence of EVM or the like becomes more susceptible as the distance between signal points becomes smaller. Therefore, if the distance between signal points is shorter than the distance between signal points of 256QAM that has already been introduced, the impact on specification and introduction is reduced.

  FIG. 6 is a diagram showing an example of a signal point allocation subset according to the present embodiment. In FIG. 6, the distance between the shortest signal points in the quadrant after normalization is added to the table of FIG. Here, the shortest signal point distance is the shortest signal point distance among the candidate signal points in the quadrant. Here, the distance from the shortest signal point of LTE is 16QAM, the fifth from the top is 64QAM of LTE, and the tenth from the top is 256QAM of LTE. Here, as shown in the sixth from the top, there is one in which the shortest signal point distance is shorter than the existing constellation (256QAM).

  The transmission power ratio storage unit 210 according to the present embodiment excludes a constellation in which the shortest signal point distance is shorter than an existing constellation from among MUST constellation candidates that use a subset of the existing constellation. Only a constellation in which the distance between the shortest signal points is the same as or longer than the existing constellation is taken as a candidate. For example, in the table of FIG. 6, the sixth candidate from the top is excluded from the candidates because the shortest signal point distance is shorter than the shortest signal point distance of 256QAM.

As described above, the transmission power ratio storage unit 210 according to the present embodiment removes the MUST constellation having a signal point distance shorter than the shortest signal point distance of the existing constellation from the transmission power ratio candidates. Thus, it is possible to introduce a MUST that reduces the influence on the power amplifier and the like.
[Third Embodiment]
In the second embodiment, the method of performing MUST using a transmission power ratio such that the shortest signal point distance in the quadrant is equal to or less than the LTE 256QAM signal point distance is described. However, the distance between signal points needs to consider not only the distance between signal points in a quadrant but also the distance between signal points in other quadrants. In the present embodiment, a method for selecting a transmission power ratio of MUST in consideration of the distance between signal points between quadrants will be described.

FIG. 7 is a diagram showing an example of an allocation subset of signal points according to the present embodiment. FIG. 7 shows the distance between the shortest signal points between the quadrants after normalization instead of the distance between the shortest signal points in the quadrant of the table of FIG. In addition, in order to clarify the effect of the present embodiment, the last row candidate is changed to another candidate among the candidates in the table of FIG. FIG. 8 is a diagram showing the signal point arrangement indicated by the last row in FIG.
The normalization shortest signal point distance of 256QAM is 0.076696 as described in the 10th line from the top of the table. When the inter-quadrant signal point distance is shorter than this value, the EVM of 256QAM is less than that of 256QAM. Will be affected. Therefore, such a transmission power ratio needs to be deleted.

  The transmission power ratio storage unit 210 according to the present embodiment is a candidate for a constellation in which the shortest signal point distance between quadrants is shorter than the existing constellation among MUST constellation candidates using a subset of the existing constellation. Remove from. For example, in the table of FIG. 7, the last row candidate is excluded from the candidates because the shortest signal point distance between quadrants is shorter than 0.76696, which is the shortest signal point distance of 256QAM.

  As described above, the transmission power ratio storage unit 210 according to the present embodiment excludes the MUST constellation having the inter-quadrant signal point distance shorter than the shortest signal point distance of the existing constellation from the transmission power ratio candidates. . As a result, it is possible to introduce a MUST that reduces the influence on the power amplifier and the like. In the above description, candidates for the shortest signal point distance between quadrants that are shorter than the shortest signal point distance of the existing LTE constellation are excluded from the transmission power ratios as candidates. Combination with the second embodiment is also possible. That is, the transmission power ratio storage unit 210 selects (sets) the transmission power ratio of the MUST so that the distance between the shortest signal points within the quadrant and between the quadrants is longer than the shortest signal point distance of the existing LTE constellation. It is also possible.

  The program that operates in the apparatus related to the present invention may be a program that controls the central processing unit (CPU) and the like to function the computer so as to realize the functions of the above-described embodiments related to the present invention. A program or information handled by the program is temporarily read into a volatile memory such as a random access memory (RAM) during processing, or stored in a nonvolatile memory such as a flash memory or a hard disk drive (HDD). In response, the CPU reads and corrects / writes.

A part of the apparatus in the above-described embodiment may be realized by a computer. In that case, a program for realizing the functions of the embodiments may be recorded on a computer-readable recording medium. You may implement | achieve by making a computer system read the program recorded on this recording medium, and executing it. The “computer system” here is a computer system built in the apparatus, and includes hardware such as an operating system and peripheral devices. The “computer-readable recording medium” may be any of a semiconductor recording medium, an optical recording medium, a magnetic recording medium, and the like.

  “Computer-readable recording medium” means a program that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client may be included, which holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  In addition, each functional block or various features of the apparatus used in the above-described embodiments may be implemented or executed by an electric circuit, that is, typically an integrated circuit or a plurality of integrated circuits. Electrical circuits designed to perform the functions described herein can be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or others Programmable logic devices, discrete gate or transistor logic, discrete hardware components, or a combination thereof. A general purpose processor may be a microprocessor or a conventional processor, controller, microcontroller, or state machine. The electric circuit described above may be configured by a digital circuit or an analog circuit. In addition, when an integrated circuit technology appears to replace the current integrated circuit due to the advancement of semiconductor technology, an integrated circuit based on the technology can be used.

  In addition, this invention is not limited to the above-mentioned embodiment. In the embodiment, an example of an apparatus has been described. However, the present invention is not limited to this, and a stationary or non-movable electronic device installed indoors or outdoors, such as an AV device, a kitchen device, It can be applied to terminal devices or communication devices such as cleaning / washing equipment, air conditioning equipment, office equipment, vending machines, and other daily life equipment.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention. The present invention can be modified in various ways within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention. It is. Moreover, it is the element described in each said embodiment, and the structure which substituted the element which has the same effect is also contained.

  The present invention is suitable for use in a base station device, a terminal device, and a communication method thereof.

DESCRIPTION OF SYMBOLS 101 ... Base station apparatus, 102, 103 ... Terminal apparatus, 200-1, 200-2 ... Scrambling part, 201-1, 201-2 ... Modulation part, 202-1, 202- 2 ... Transmission power setting unit, 203 ... Signal combining unit, 204 ... Layer mapping unit, 205 ... Precoding unit, 206 ... Resource element mapping unit, 207 ... OFDM signal generation unit , 208 ... Transmission antenna, 209 ... Transmission power ratio selection unit, 210 ... Transmission power storage unit, 901 ... Reception antenna, 902 ... OFDM demodulation unit, 903 ... Resource element demapping 904... Signal detection unit 905... Layer demapping unit 906... Demodulation unit 907. Descrambling unit 908. Tough, 909 ... transmission power ratio storage unit

Claims (8)

A base station apparatus that synthesizes and transmits a signal addressed to the first terminal apparatus and a signal addressed to the second terminal apparatus at a predetermined transmission power ratio,
Transmission power ratio storage having one or more transmission power ratios as candidates for the predetermined transmission power ratio, in which the distance between signal points of modulation symbols in the signal generated by the synthesis is the same or longer than a predetermined value And
A transmission power ratio selection unit that selects one from one or more transmission power ratios of the transmission power ratio storage unit;
A transmission power setting unit that changes the power of the modulation symbol based on the transmission power ratio selected by the transmission power ratio selection unit;
A base station apparatus comprising:   The base station apparatus according to claim 1, wherein the predetermined value is a shortest distance among signal point distances of a predetermined QAM modulation symbol.   The base station apparatus according to claim 2, wherein the predetermined QAM modulation symbol is 256QAM.   The base station apparatus according to claim 1, wherein a distance between signal points of modulation symbols in the signal generated by the combination is a distance between signal points in the same quadrant.   The base station apparatus according to claim 1, wherein a distance between signal points of modulation symbols in the signal generated by the combining is a distance between signal points in different quadrants. A terminal device that receives a signal obtained by combining a signal addressed to the terminal device and a signal addressed to a terminal device other than the terminal device at a predetermined transmission power ratio,
A transmission power ratio storage unit having one or a plurality of transmission power ratios as candidates for the predetermined transmission power ratio, in which the distance between modulation symbol signal points in the signal generated by the synthesis is the same or longer than a predetermined value When,
A transmission power ratio notifying unit for notifying information indicating a transmission power ratio of one or a plurality of transmission power ratios of the transmission power ratio storage unit;
A demodulation unit that performs demodulation using information indicating the transmission power ratio notified from the transmission power ratio notification unit;
A terminal device comprising: A communication method of a base station apparatus for combining a signal addressed to a first terminal apparatus and a signal addressed to a second terminal apparatus at a predetermined transmission power ratio and transmitting the synthesized signal,
A transmission power ratio selection step of selecting one from one or a plurality of transmission power ratios possessed by the transmission power ratio storage unit;
A transmission power setting step of changing the power of the modulation symbol based on the transmission power ratio selected in the transmission power ratio selection step;
The transmission power ratio storage unit uses, as a candidate for the predetermined transmission power ratio, a transmission power ratio in which a distance between signal points of modulation symbols in the signal generated by the synthesis is the same or longer than a predetermined value. A communication method characterized by having one or more. A communication method for a terminal device that receives a signal obtained by combining a signal addressed to the terminal device and a signal addressed to a terminal device other than the terminal device at a predetermined transmission power ratio,
A transmission power ratio notifying step for notifying the demodulator of information indicating one of the transmission power ratios of the transmission power ratio storage unit or one of a plurality of transmission power ratios;
A demodulation step of performing demodulation using information indicating the transmission power ratio in the demodulation unit,
The transmission power ratio storage unit uses, as a candidate for the predetermined transmission power ratio, a transmission power ratio in which a distance between modulation symbol signal points in a signal generated by the synthesis is the same or longer than a predetermined value. Or a communication method characterized by having a plurality.

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