JP2012175637A - Reception device, reception system, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase in power consumption and reduce interference.SOLUTION: A control module 63 determines whether data addressed to another user has been transmitted or not. An interference removal module 65 removes interference from a channel estimation value and a reception signal. When it is determined that the data addressed to another user has been transmitted, a multiplexer 66 selects the channel estimation value and the reception signal from which interference has been removed, and supplies a demodulation module 67 with the selected channel estimation value and the reception signal. When it is determined that the data addressed to another user has not been transmitted, the multiplexer 66 selects a channel estimation value and a reception signal from which interference has not been removed, and supplies the demodulation module 67 with the selected channel estimation value and the reception signal. The present invention is applicable to a reception device.

Description

  The present invention relates to a receiving apparatus, a receiving method, and a program.

  In recent years, the development of communication technology has been remarkable, and a system for communicating a large amount of data at high speed is being realized. This applies not only to wired communication but also to wireless communication. In other words, with the spread of mobile terminals such as mobile phones, research and development of next-generation communication methods that enable high-speed communication of large volumes of data even wirelessly and use of multimedia data such as videos and voices on mobile terminals are being promoted. It is actively done.

  As a next-generation communication method, MIMO-OFDM (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing) such as LTE (Long Term Evolution) discussed in 3GPP (Third Generation Partnership Project) is attracting attention. . MIMO-OFDM enables high-speed, high-capacity communication by enabling user data to be spatially multiplexed by using multiple transmit / receive antennas in addition to the high frequency utilization efficiency that is the advantage of OFDM (Orthogonal Frequency Division Multiplexing). Can be realized. FIG. 7A is a diagram illustrating a configuration of a single-user MIMO (Multiple-Input Multiple-Output) communication system that spatially multiplexes and transmits user data. User data is transmitted from one transmitter 201 to one receiver 202.

  Further, as shown in FIG. 7B, the throughput of the entire system can be improved by spatially multiplexing data addressed to different users. In this case, each user data is transmitted from one transmitter 211 to each of the two receivers 212-1 and 212-2. Such a technique is called multi-user MIMO. LTE also supports multi-user MIMO and is defined as transmission mode 8.

  In LTE transmission mode 8, a beam is formed by controlling the directivity of a plurality of transmission antennas provided on the base station side, and this is transmitted toward a receiving terminal. The transmission mode 8 is also called dual layer beamforming. In the transmission mode 8, a maximum of two data (layers) can be transmitted simultaneously. In the case of single user MIMO, one or two layers are transmitted toward one receiving terminal. On the other hand, in the case of multi-user MIMO, one layer is transmitted to two receiving terminals. Whether to use single-user MIMO or multi-user MIMO is determined on the network side, and the receiving terminal cannot know whether data addressed to other users is being transmitted.

  The configuration of a general multiuser MIMO receiver will be described with reference to FIG.

  The general MIMO demodulator 231 shown in FIG. 8 includes a demapping unit 241, an interference canceller 242, and a demodulator 243.

  The MIMO demodulator 231 receives the channel estimation value and the received signal as inputs. First, the demapping unit 241 extracts resource elements necessary for demodulation from the channel estimation value and the received signal. Next, the interference removal unit 242 removes the influence of interference caused by data addressed to other users. Thereafter, the demodulation unit 243 performs channel equalization to obtain likelihood information.

  Conventionally, an orthogonal transformer performs orthogonal transformation on N time-series data extracted from received radio signals, and a multi-user detector transmits from each radio transmission device from the orthogonal-transformed time series data. The signal is extracted, the inverse orthogonal transformer performs inverse orthogonal transformation on the extracted transmission signal, the despreader performs despreading on the transmission signal subjected to inverse orthogonal transformation, and the rectangular filter circuit In some cases, Nw pieces of time-series data are extracted from the despread transmission signal by removing time-series data of Mh pieces at the front end and Mt pieces at the end (see, for example, Patent Document 1).

JP 2009-71448 A

  However, in multi-user MIMO, since data addressed to other users interferes with data addressed to the user, a technique for reducing / removing interference on the receiving side is required. This complicates the receiver circuit and increases power consumption. Further, as in LTE transmission mode 8, the receiver may not be notified that data addressed to other users is being transmitted. In this case, it is necessary for the receiver to always remove the interference even when only the data addressed to itself, and the interference cancellation technology that degrades the demodulation result of the data addressed to itself is used when there is no interference. Cannot be used. In other words, even if the interference removal capability is high, an interference removal technique in which the presence or absence of interference affects the demodulation result cannot be used.

  Therefore, an object of the present invention is to solve the above-described problems, that is, to provide a receiving apparatus, a receiving method, and a program that can suppress an increase in power consumption and reduce interference.

  In order to solve the above problems, one aspect of the receiving apparatus of the present invention is a receiving apparatus that receives a signal transmitted by spatially multiplexing data addressed to a user and data addressed to another user. A plurality of channel estimation values and reception depending on a determination means for determining whether data addressed to another user is transmitted and a determination result of whether data addressed to another user is transmitted. A selection means for selecting a predetermined channel estimation value and a received signal from the signals is provided.

  In addition to the above-described configuration, one aspect of the reception apparatus of the present invention is an interference removal that removes interference from a channel estimation value and a received signal when it is determined that data addressed to another user is transmitted. And when the selection means determines that the data addressed to another user is being transmitted, the channel estimation value from which the interference is removed by the interference removal means and the received signal are selected, and the other user is selected. When it is determined that the addressed data is not transmitted, the channel estimation value and the received signal from which the interference is not removed are selected by the interference removing unit.

  Furthermore, in addition to the above-described configuration, one aspect of the receiving apparatus of the present invention is highly effective in removing interference when it is determined that data addressed to other users greater than a predetermined threshold is being transmitted. Interference is removed from the channel estimation value and the received signal by the interference cancellation method, and it is determined that the number of data addressed to other users equal to or less than the threshold is transmitted, or the data addressed to other users is transmitted If it is determined that there is no interference canceling method with a low interference canceling effect, it further has interference canceling means for canceling interference from the channel estimation value and the received signal, and the selecting means is directed to other users whose number is greater than the threshold. If it is determined that the data is transmitted, the channel estimation value and the received signal from which the interference is removed by the interference removal method having a high interference removal effect are selected, and the data addressed to other users equal to or less than the threshold value is selected. Sent If it is determined that the data addressed to the other user is not transmitted, the channel estimation value from which the interference is removed by the interference cancellation method having a low interference cancellation effect and the received signal are obtained. It is supposed to be selected.

  Further, according to one aspect of the receiving apparatus of the present invention, in addition to the above-described configuration, the determination unit determines whether data addressed to another user is transmitted based on signal power of data addressed to the other user. It is supposed to be.

  Furthermore, according to one aspect of the reception apparatus of the present invention, in addition to the above-described configuration, the determination unit determines whether data addressed to another user is transmitted based on noise interference power.

  Further, according to one aspect of the receiving apparatus of the present invention, in addition to the above-described configuration, the determining unit determines whether or not data addressed to another user is transmitted by SNR (Signal-to-Noise Ratio). It is supposed to be.

  Furthermore, one aspect of the receiving apparatus of the present invention is to receive a signal transmitted by a MIMO-OFDM (Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplexing) scheme in addition to the above-described configuration. Yes.

  In addition to the above-described configuration, one aspect of the receiving apparatus of the present invention is configured to receive a transmitted signal by an LTE (Long Term Evolution) scheme.

  Also, one aspect of the receiving method of the present invention is a receiving method for receiving a signal transmitted by spatially multiplexing data addressed to a user and data addressed to another user. In accordance with a determination step for determining whether or not data is transmitted, and a result of determination whether or not data addressed to other users is transmitted, among a plurality of channel estimation values and received signals, A selection step of selecting a predetermined channel estimation value and a received signal is included.

  Further, according to one aspect of the program of the present invention, a computer that controls a receiving device that receives a signal in which data addressed to a user and data addressed to another user are spatially multiplexed is transmitted to another user. A determination step for determining whether or not data addressed is transmitted and a result of determination on whether or not data addressed to another user is transmitted from a plurality of channel estimation values and received signals. , A process including a selection step of selecting a predetermined channel estimation value and a received signal is performed.

  According to one aspect of the present invention, it is possible to provide a reception device, a reception method, and a program that can suppress an increase in power consumption and further reduce interference.

It is a figure explaining a transmitter and a receiver. 2 is a block diagram illustrating a configuration of a transmission device 10. FIG. 3 is a block diagram showing a configuration of a receiving device 20. FIG. 3 is a block diagram illustrating an example of a configuration of a MIMO demodulation unit 46. FIG. It is a flowchart explaining the process of interference removal. It is a block diagram which shows the structural example of the hardware of a computer. It is a figure which shows the structure of the communication system of single user MIMO and multiuser MIMO. It is a block diagram explaining the structure of the receiver of a general multiuser MIMO.

  Hereinafter, a receiving apparatus according to an embodiment of the present invention that employs multi-user MIMO in 3GPP LTE transmission mode 8 will be described with reference to FIGS.

  FIG. 1 is a diagram illustrating a transmission device and a reception device. One transmitter 10 transmits user data to either of the two receivers 20-1 and 20-2 via the antenna 11, or each of the two receivers 20-1 and 20-2. Each user data is transmitted. The receiving device 20-1 receives user data addressed to the user of the receiving device 20-1 via the receiving antenna 21-1. The reception device 20-2 receives user data addressed to the user of the reception device 20-2 via the reception antenna 21-2.

  Hereinafter, when there is no need to individually distinguish the receiving device 20-1 or 20-2, the receiving device 20-1 or 20-2 is simply referred to as the receiving device 20. Hereinafter, when it is not necessary to individually distinguish the receiving antennas 21-1 or 21-2, they are simply referred to as the receiving antennas 21.

  FIG. 2 is a block diagram illustrating a configuration of the transmission device 10. The transmission device 10 is a general LTE transmission device.

  The transmission apparatus 10 includes a channel encoding unit 31, a MIMO modulation unit 32, an IFFT (Inverse Fast Fourier Transform) processing unit 33, a CP (Cyclic Prefix) addition unit 34, a D / A (Digital / Analog) conversion unit 35, and a transmission An antenna 11 is provided.

  In the transmission device 10, transmission data addressed to each user is first subjected to error detection coding / error correction coding by the channel coding unit 31. The MIMO modulation unit 32 performs symbol mapping and weight control for forming the directivity of the transmission antenna. Next, the IFFT processing unit 33 converts the symbol into a time domain signal. The CP adding unit 34 adds a CP to the head of the OFDM symbol in order to prevent the influence of intersymbol interference due to multipath. The OFDM symbol to which the CP is added is transmitted from the transmission antenna 11 after being converted from a digital signal to an analog signal by the D / A converter 35.

  FIG. 3 is a block diagram illustrating a configuration of the receiving device 20. The receiving apparatus 20 includes a receiving antenna 21, an A / D (Analog / Digital) conversion unit 41, an FFT timing detection unit 42, a CP removal unit 43, an FFT (Fast Fourier Transform) processing unit 44, a channel estimation unit 45, and a MIMO demodulation unit. 46 and a channel decoding unit 47.

  In the reception device 20, the reception signal received by the reception antenna 21 is converted from an analog signal to a digital signal by the A / D conversion unit 41. The digital signal is input to the FFT timing detection unit 42 and the CP removal unit 43. The FFT timing detection unit 42 detects the start timing of the OFDM symbol and supplies FFT timing information indicating the start timing of the OFDM symbol to the CP removal unit 43.

  The CP removal unit 43 removes the CP added to the head from the OFDM symbol based on the FFT timing information detected by the FFT timing detection unit 42. The FFT processing unit 44 converts a time-domain signal wave into each subcarrier component.

  Further, the channel estimation unit 45 obtains a channel estimation value of each subcarrier using a known reference signal multiplexed and transmitted with the data symbol. The distortion of the signal received in the channel is compensated (channel equalization) in the MIMO demodulator 46 by multiplying the received signal of each subcarrier by the complex conjugate of the channel estimation value. Further, channel estimates of other users are used for interference cancellation. The received signal is subjected to interference removal and signal separation of user data of other users by the MIMO demodulator 46, and then converted into likelihood information. The channel decoding unit 47 performs error correction decoding and error detection to obtain received data.

  FIG. 4 is a block diagram illustrating an example of the configuration of the MIMO demodulator 46. The MIMO demodulation unit 46 includes a demapping unit 61, a signal power estimation unit 62, a control unit 63, a demultiplexer 64, an interference removal unit 65, a multiplexer 66, and a demodulation unit 67.

  The MIMO demodulator 46 is given a channel estimation value and a received signal as inputs. First, the demapping unit 61 extracts a resource element necessary for demodulation from the channel estimation value and the received signal.

  The demapping unit 61 supplies other users' channel estimation values to the signal power estimation unit 62. The signal power estimation unit 62 calculates signal power from the channel estimation values of other users. The signal power estimation unit 62 supplies the calculated signal power estimation value to the control unit 63. The control unit 63 determines the presence / absence of another user from the estimated value of the signal power of the channel estimation value of the other user. For example, the control unit 63 determines that there is interference from other users when the signal power is equal to or greater than a predetermined threshold, that is, there is another user, and if there is less than the threshold, there is no interference from other users. That is, it is determined that there is no other user. In other words, the control unit 63 determines whether data addressed to another user is being transmitted.

  Thereafter, the control unit 63 controls the demultiplexer 64 and the multiplexer 66 according to the determination result of the presence / absence of another user. Under the control of the control unit 63, the demultiplexer 64 supplies the channel estimation value and the received signal to the interference removal unit 65 when there is interference of user data of other users. In this case, after interference cancellation is performed from the channel estimation value and the received signal in the interference canceling unit 65, the channel estimation value and the received signal are input to the multiplexer 66. When there is no interference of user data of other users, the channel estimation value and the received signal are directly supplied to the multiplexer 66 as they are (without eliminating interference).

  The multiplexer 66 selects a channel estimation value and a received signal to be input to the demodulation unit 67 under the control of the control unit 63.

  Thereafter, the demodulator 67 performs channel equalization to obtain likelihood information.

  FIG. 5 is a flowchart for explaining interference removal processing. In step S <b> 11, the demapping unit 61 extracts the channel estimation value of another user, the channel estimation value of the user of the reception device 20, and the reception signal.

  In step S12, the signal power estimation unit 62 calculates the signal power from the channel estimation value of the other user. In step S13, the control unit 63 determines whether or not there is another user from the estimated value of the signal power of the channel estimation value of the other user. That is, in step S13, the control unit 63 determines whether data addressed to another user is being transmitted.

  If it is determined in step S13 that data addressed to another user is being transmitted, the procedure proceeds to step S14, and the control unit 63 controls the demultiplexer 64 to interfere with the channel estimation value and the received signal. The interference removing unit 65 removes interference from the channel estimation value and the received signal. As a method of interference cancellation, PIC (parallel interference cancellation canceller), SIC (sequential interference cancellation canceller), SQRD (QR decomposition method with sorting), MLD (maximum likelihood determination method), or the like can be adopted. The channel estimation value from which the interference is removed and the received signal are supplied to the multiplexer 66, and after step S14, the procedure proceeds to step S15.

  If it is determined in step S13 that data addressed to another user has not been transmitted, there is no interference of user data of the other user, so the control unit 63 controls the demultiplexer 64 to receive the channel estimation value and the reception. The signal is supplied to the multiplexer 66 as it is (without eliminating interference), the procedure of step S14 is skipped, and the procedure proceeds to step S15.

  In step S <b> 15, when it is determined that data addressed to another user is transmitted, the control unit 63 controls the multiplexer 66 so that the interference supplied to the multiplexer 66 from the interference removal unit 65 is removed. The selected channel estimation value and the received signal are selected, and the selected channel estimation value and the received signal are supplied to the demodulator 67. In addition, when it is determined that the data addressed to another user is not transmitted, the control unit 63 controls the multiplexer 66 so that the channel supplied from the demultiplexer 64 to the multiplexer 66 from which interference is not removed. The estimated value and the received signal are selected, and the selected channel estimated value and the received signal are supplied to the demodulator 67.

  The demodulator 67 equalizes the channel based on the channel estimation value and the received signal supplied from the multiplexer 66, obtains likelihood information, and ends the interference removal processing.

  Thus, in a wireless communication system using multi-user MIMO, when it is unknown whether data addressed to other users is transmitted, the presence or absence of other users is estimated by measuring the signal power of other users, An appropriate reception method is selected according to the presence or absence of other users.

  For example, when there is no interference from other users, a normal single user reception method is used, and when there is interference from other users, a reception method having an interference removal function is used. By switching the reception method according to the presence / absence of other users, it is not necessary to perform unnecessary interference removal in the case of single user MIMO, and thus power consumption in the receiving device 20 can be expected to be reduced. Further, since interference removal is performed only when there is interference from another user, it is possible to select an interference removal technique without considering the case of no interference.

  As described above, by switching the reception method according to the presence / absence of other users, it is not necessary to remove unnecessary interference in the case of single-user MIMO, so that reduction in power consumption of the receiver can be expected. Further, since interference removal is performed only when there is interference from another user, it is possible to select an interference removal technique without considering the case where there is no interference.

  In the description so far, as an example, a receiving apparatus that performs interference removal when another user exists is described as an example, but the present invention is not limited to this.

  For example, as in the conventional method, interference removal may always be performed, and an interference removal method may be selected according to the presence or absence of other users. More specifically, when there are a plurality of other users, if the number of other users that cause interference is larger than a predetermined threshold, the interference removal method having a high interference removal effect is selected, and the number of other users that cause interference. If is less than or equal to the threshold value, an interference removal method having a low interference removal effect may be selected.

  Furthermore, as an example, it has been described that the presence / absence of another user is estimated by measuring the signal power of the other user. However, the present invention is not limited to this.

  For example, the presence or absence of other users may be determined by estimating noise interference power or SNR (Signal-to-Noise Ratio) instead of signal power.

  In addition, although the above explanation has been given taking LTE as an example being discussed in 3GPP as an example, it is not necessarily limited thereto. The present invention can be similarly applied to other MIMO-OFDM systems using multi-user MIMO and other wireless communication systems.

  Thus, in a wireless communication system using multi-user MIMO, when it is unknown whether data addressed to other users is being transmitted, the presence or absence of other users is estimated by measuring the signal power of other users, An optimal reception method can be selected according to the presence or absence of other users.

  The receiving device 20 can be a receiving device of a communication device such as a mobile phone, a data communication card, a PHS (Personal Handyphone System), a PDA (Personal Data Assistance, Personal Digital Assistants), a smartphone, or a wireless base station.

  The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software executes various functions by installing a computer incorporated in dedicated hardware or various programs. For example, it is installed from a program recording medium in a general-purpose personal computer or the like.

  FIG. 6 is a block diagram illustrating a hardware configuration example of a computer that executes the above-described series of processing by a program.

  In a computer, a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, and a RAM (Random Access Memory) 103 are connected to each other via a bus 104.

  An input / output interface 105 is further connected to the bus 104. The input / output interface 105 includes an input unit 106 including a keyboard, a mouse, and a microphone, an output unit 107 including a display and a speaker, a storage unit 108 including a hard disk and nonvolatile memory, and a communication unit 109 including a network interface. A drive 110 for driving a removable medium 111 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory is connected.

  In the computer configured as described above, the CPU 101 loads, for example, the program stored in the storage unit 108 to the RAM 103 via the input / output interface 105 and the bus 104 and executes the program. Is performed.

  The program executed by the computer (CPU 101) is, for example, a magnetic disk (including a flexible disk), an optical disk (CD-ROM (Compact Disc-Read Only Memory), DVD (Digital Versatile Disc), etc.), a magneto-optical disk, or a semiconductor. The program is recorded on a removable medium 111 that is a package medium including a memory or the like, or is provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  The program can be installed in the computer by loading the removable medium 111 in the drive 110 and storing it in the storage unit 108 via the input / output interface 105. Further, the program can be installed in a computer by being received by the communication unit 109 via a wired or wireless transmission medium and stored in the storage unit 108. In addition, the program can be installed in the computer in advance by storing the program in the ROM 102 or the storage unit 108 in advance.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  The embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 20 ... Receiver, 46 ... MIMO demodulation part, 61 ... Demapping part, 62 ... Signal power estimation part, 63 ... Control part, 64 ... Demultiplexer, 65 ... Interference removal part, 66 ... Multiplexer, 67 ... Demodulation part, 101 ... CPU, 102 ... ROM, 103 ... RAM, 108 ... storage unit, 109 ... communication unit, 111 ... removable media

Claims (10)

In a receiving apparatus that receives a signal transmitted by spatially multiplexing data addressed to a user and data addressed to another user,
Determination means for determining whether data addressed to another user is transmitted;
Selection means for selecting a predetermined channel estimation value and a received signal from a plurality of channel estimation values and a received signal according to a result of the determination as to whether or not data addressed to another user is transmitted. A receiving device comprising: The receiving device according to claim 1,
When it is determined that data addressed to another user is being transmitted, the apparatus further includes an interference removing unit that removes interference from the channel estimation value and the received signal.
When it is determined that data addressed to another user is transmitted, the selection means selects the channel estimation value from which interference has been removed by the interference cancellation means and the received signal, and When it is determined that data is not transmitted, the channel estimation value from which interference is not removed by the interference removal unit and the received signal are selected. The receiving device according to claim 1,
When it is determined that data destined for other users greater than a predetermined threshold is being transmitted, interference is removed from the channel estimation value and the received signal by an interference cancellation method that is highly effective in interference cancellation, When it is determined that data destined for another user equal to or less than the threshold is transmitted, or when it is determined that data destined for another user is not transmitted, an interference canceling method with low interference canceling effect Further comprising interference removing means for removing interference from the channel estimation value and the received signal,
When it is determined that the data addressed to other users more than the threshold is transmitted, the selection unit is configured to receive the channel estimation value from which interference has been removed by an interference removal method having a high interference removal effect and the reception. When it is determined that data destined for other users equal to or less than the threshold is transmitted, or when it is determined that data destined for another user is not transmitted, interference cancellation is performed. The receiving apparatus, wherein the channel estimation value from which interference is removed by an interference cancellation method having a low effect and the received signal are selected. The receiving apparatus according to any one of claims 1 to 3,
The determination unit determines whether or not data addressed to another user is transmitted based on signal power of data addressed to another user. The receiving apparatus according to any one of claims 1 to 3,
The determination unit determines whether data addressed to another user is transmitted based on noise interference power. The receiving apparatus according to any one of claims 1 to 3,
The receiving means determines whether or not data addressed to another user is being transmitted by SNR (Signal-to-Noise Ratio). The receiving apparatus according to any one of claims 1 to 6,
MIMO-OFDM (Multiple-Input Multiple-Output-Orthogonal Frequency Division
A receiving apparatus that receives a transmitted signal by a multiplexing method. The receiving apparatus according to any one of claims 1 to 6,
A receiving device that receives a transmitted signal by LTE (Long Term Evolution). In a receiving method for receiving a signal transmitted by spatially multiplexing data addressed to a user and data addressed to another user,
A determination step of determining whether data addressed to another user is being transmitted;
A selection step of selecting a predetermined channel estimation value and a received signal from a plurality of channel estimation values and a received signal according to a result of determination of whether or not data addressed to another user is transmitted. A reception method characterized by including. A computer that controls a receiving device that receives a signal transmitted by spatially multiplexing data addressed to a user and data addressed to another user,
A determination step of determining whether data addressed to another user is being transmitted;
A selection step of selecting a predetermined channel estimation value and a received signal from a plurality of channel estimation values and a received signal according to a result of determination of whether or not data addressed to another user is transmitted. A program that causes a process to be included.

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