JP6316204B2 - Base station apparatus, radio communication system, radio communication method, and integrated circuit - Google Patents

Description

  The present invention relates to a base station apparatus, a wireless communication system, a wireless communication method, and an integrated circuit.

  Multiple input multiple output (MIMO) technology that performs radio transmission using multiple transmission / reception antennas is attracting attention as a technology that can significantly improve frequency utilization efficiency. In cellular systems and wireless LAN systems, etc. It has been put into practical use. The amount of improvement in frequency utilization efficiency by the MIMO technology is proportional to the number of transmission / reception antennas. However, there is a limit to the number of receiving antennas that can be arranged in a terminal device that is a receiving device. Thus, a plurality of terminal devices that are simultaneously connected are regarded as a virtual large-scale antenna array, and a downlink multi-user MIMO (Multi-User MIMO) that spatially multiplexes transmission signals from the base station device (transmitting device) to each terminal device. : MU-MIMO) is effective in improving the frequency utilization efficiency.

  In MU-MIMO, transmission signals addressed to each terminal device (user) that are spatially multiplexed are received by the terminal device as inter-user interference (IUI). End up. Here, if the base station device knows the state of the propagation path from each transmitting antenna of the base station device to each receiving antenna of each terminal device, the IUI is suppressed during reception at the terminal device without imposing a heavy load on the terminal device. Several methods that can generate a transmission signal that can be generated have been proposed (Non-Patent Document 1).

For example, there is a method of performing transmission after precoding the transmission signal in the base station apparatus so that reception can be performed in a state where the IUI is suppressed at the time of reception at the terminal apparatus. As an example, from a propagation path matrix H having a complex propagation path gain between each transmission antenna and each reception antenna of each terminal device, which is obtained from information (Channel State Information: CSI) representing propagation path state, Using the inverse matrix H ⁻¹ (or pseudo inverse matrix H ^† = H ^H (HH ^H ) ⁻¹ : superscript H represents Hermitian conjugate) as a weight matrix (linear filter) W, the transmission signal is weighted. Weight-matrix (linear filter) W = H ^H (which is obtained by Zero-forcing (ZF) precoding for multiplying the transmission signal by W = H ⁻¹ or Minimum Mean Square Error (MMSE) norm. HH H ⁺ αI) -1 ^(I is a unit matrix, alpha is such MMSE precoding weighting the transmission signal in representing a normalization factor), linear pre precoding a transmit signal by a linear processing Over loading (Linear Precoding: LP) there is. For example, in a cellular system such as LTE (Long Term Evolution) and LTE-Advanced, and a wireless LAN system such as IEEE802.11ac, a linear filter calculated based on propagation path information notified from each terminal device is used as a base station. Linear precoding (linear beamforming) is employed in which the transmission signal is pre-multiplied by the device to suppress IUI.

  On the other hand, in recent years, wireless LANs are rapidly spreading due to the growing demand for high-speed wireless communication networks in offices or homes. The next-generation wireless LAN is being developed in IEEE TGac (IEEE Institute of Electrical and Electronics Engineers, Inc.) 802.11 TGac, aiming to achieve a throughput of 1 Gbps or higher, with a channel frequency band of 80 MHz or higher. Expansion and introduction of the MU-MIMO have been studied (Non-Patent Document 2).

Spencer et al., "An Introduction to the Multi-User MIMO Downlink", IEEE Communication Magazine, Vol. 42, Issue 10, p. 60-67, October 2004 `` IEEE P802.11 Wireless LANs Specification Framework for TGac '', IEEE 802.11-09 / 0992r21, January 2011

  However, with the widespread use of wireless LANs, a plurality of wireless LAN access points (base station apparatuses) share the same frequency channel, and an environment in which respective service areas (cells) overlap each other tends to occur. Therefore, a decrease in cell throughput is a problem.

  The present invention has been made in view of such circumstances, and in the overlapping cell environment as described above, the base station apparatus autonomously suppresses the interference given to the terminal apparatus of the neighboring cell and improves the throughput. It is an object of the present invention to provide a base station device, a wireless communication system, a wireless communication method, and an integrated circuit that can be made to be performed.

  In order to achieve the above object, the present invention takes the following measures. That is, the base station apparatus according to the present invention includes a radio reception unit that receives a first radio frame that is a radio frame transmitted by a terminal device in a neighboring cell, and the peripheral signal based on a reception signal of the first radio frame. A channel estimation unit for estimating a channel state between the terminal device of the cell and the base station device, and precoding for transmission data addressed to the terminal device of the own cell based on the estimation result of the channel state A precoding unit for performing transmission and a wireless transmission unit for transmitting the transmission data subjected to the precoding.

  The radio communication system of the present invention includes a base station device and a terminal device, and the base station device receives a radio frame transmitted by a terminal device in a neighboring cell, and based on a received signal of the radio frame. , Estimating the propagation path state between the terminal device of the neighboring cell and the base station apparatus, and based on the estimation result of the propagation path state, so that the null is directed to the terminal device of the corresponding neighboring cell, The transmission data addressed to the terminal device of the own cell is precoded and transmitted.

  The radio communication system of the present invention includes a base station device and a terminal device, and the base station device receives a radio frame transmitted by a terminal device in a neighboring cell, and based on a received signal of the radio frame. The propagation path between the terminal apparatus of the own cell and the terminal apparatus of the own cell notified from the terminal apparatus of the own cell, which is estimated from the state of the propagation path between the terminal apparatus of the neighboring cell and the own base station apparatus Receiving propagation path information based on the state, and based on the propagation path information notified from one or more terminal apparatuses of the own cell and the estimation result of the propagation path state, addressed to the terminal apparatus of the one or more own cells The one or more own cells so as to suppress inter-user interference when transmitting transmission data by spatial multiplexing and simultaneously transmitting the data, and so that a null is directed to a terminal device of a neighboring cell corresponding to the estimation result of the propagation path state Data sent to the terminal device And transmitting performing precoding by.

  The radio communication method of the present invention is a radio communication method for performing communication between a base station device and a terminal device, wherein the base station device receives a radio frame transmitted by a terminal device in a neighboring cell. And a step of estimating a propagation path state between the terminal device of the neighboring cell and the own base station apparatus based on the received signal of the radio frame, and a corresponding peripheral based on the estimation result of the propagation path state Precoding the transmission data addressed to the terminal device of the own cell and transmitting the signal subjected to the precoding so that null is directed to the terminal device of the cell. And

  The radio communication method of the present invention is a radio communication method for performing communication between a base station device and a terminal device, wherein the base station device receives a radio frame transmitted by a terminal device in a neighboring cell. And a step of estimating a propagation path state between the terminal device of the neighboring cell and the own base station device based on the received signal of the radio frame, and the own base station device notified from the terminal device of the own cell Receiving the propagation path information based on the propagation path state between the mobile terminal and the terminal device of the own cell, the propagation path information notified from one or more terminal apparatuses of the own cell, and the estimation result of the propagation path state Based on the above, it is possible to suppress interference between users when the transmission data addressed to the terminal device of the one or more own cells is spatially multiplexed and simultaneously transmitted, and the terminal device of the neighboring cell corresponding to the estimation result of the propagation path state Is null The memorial and a step of performing precoding on transmission data addressed to the terminal device the one or more of the own cell, and transmitting a signal subjected to the precoding, characterized in that it has a.

  The integrated circuit of the present invention is an integrated circuit that is mounted on a base station device to cause the base station device to perform a plurality of functions, and has a function of receiving a radio frame transmitted by a terminal device in a peripheral cell. And a function of estimating the propagation path state between the terminal device of the neighboring cell and the own base station apparatus based on the received signal of the radio frame, and a corresponding peripheral based on the estimation result of the propagation path state A series of functions including a function of performing precoding on transmission data addressed to a terminal apparatus of the own cell and a function of transmitting a signal subjected to the precoding so that null is directed to the terminal apparatus of the cell. And making the base station apparatus exhibit it.

  The integrated circuit of the present invention is an integrated circuit that is mounted on a base station device to cause the base station device to perform a plurality of functions, and has a function of receiving a radio frame transmitted by a terminal device in a peripheral cell. And a function of estimating a propagation path state between the terminal device of the neighboring cell and the own base station device based on the received signal of the radio frame, and the own base station device notified from the terminal device of the own cell A function of receiving propagation path information based on a propagation path state between the terminal apparatus of the own cell and the propagation path information notified from one or more terminal apparatuses of the own cell, and an estimation result of the propagation path state Based on the above, it is possible to suppress interference between users when the transmission data addressed to the terminal device of the one or more own cells is spatially multiplexed and simultaneously transmitted, and the terminal device of the neighboring cell corresponding to the estimation result of the propagation path state Against the null Thus, the base station apparatus exhibits a series of functions of a function of performing precoding on transmission data addressed to the terminal device of the one or more own cells and a function of transmitting the signal subjected to the precoding. It is characterized by making it.

  In an overlapping cell environment with a plurality of base station devices, the base station device can autonomously perform communication while suppressing interference with terminal devices in neighboring cells, and throughput can be improved.

It is a schematic block diagram which shows the structural example of the radio | wireless communications system of this invention. It is a functional block diagram which shows the example of 1 structure of the base station apparatus 100 of this invention. It is a functional block diagram which shows the example of 1 structure of the terminal device 300 of this invention. It is a time chart which shows an example of transmission / reception of the radio | wireless frame between the base station apparatus which concerns on the 1st Embodiment of this invention, and a terminal device. It is a flowchart which shows an example of the flow of the process which the base station apparatus estimates the propagation path state between the base station apparatus and terminal device of a periphery cell based on the 1st Embodiment of this invention. It is a flowchart which shows an example of the flow of the transmission process of the base station apparatus which concerns on the 1st Embodiment of this invention. It is a time chart which shows an example of transmission / reception of the radio | wireless frame between the base station apparatus which concerns on the 2nd Embodiment of this invention, and a terminal device. It is a flowchart which shows an example of the flow of the transmission process of the base station apparatus which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements are denoted by the same numbers. The attached drawings show specific embodiments and implementation examples based on the principle of the present invention, but these are for understanding the present invention and are not intended to limit the present invention. Not used.
(First embodiment)
FIG. 1 is a diagram showing a schematic configuration example of a wireless communication system of the present invention. As shown in the example of FIG. 1, in the wireless communication system according to the present embodiment, two base station apparatuses (base station apparatus 100-1 and base station apparatus 100-2 are collectively referred to as base station apparatus 100-1). And a plurality of terminal devices 300-1 to 300-6 that are connected to and communicate with at least one of these base station devices (these terminal devices are also collectively referred to as the terminal device 300). Is present.

  A terminal device 300-1, a terminal device 300-2, and a terminal device 300-3 are connected to the base station device 100-1, and a terminal device 300-4, a terminal device 300-5, And the terminal device 300-6 is connected. Further, the base station device 100-1 and the base station device 100-2 share the same frequency channel, and the base station device 100-1 is a service area of the cell (area surrounded by a dotted line in FIG. 1) and the base station apparatus 100-1. The cell of the station device 100-2 (the region surrounded by the alternate long and short dash line in FIG. 1) constitutes an environment (overlap cell) partially overlapping.

  In the example of FIG. 1, the radio signals transmitted from the base station apparatus 100-2 configuring the neighboring cell are transmitted to the terminal apparatus 300-1 and the terminal apparatus 300-3 connected to the base station apparatus 100-1 (noise). The radio signal transmitted by the terminal device 300-1 and the terminal device 300-3 is received by the base station device 100-2 of the neighboring cell. Similarly, the terminal device 300-4 connected to the base station device 100-2 has a wireless signal transmitted by the base station device 100-1 that constitutes a neighboring cell (with sufficient power that cannot be regarded as noise). The radio signal transmitted by the terminal device 300-4 is received by the base station device 100-1 of the neighboring cell.

  In the wireless LAN system, a group composed of one base station device and one or more terminal devices connected to the base station device is called a BSS (Basic Service Set), and an area in which the BSS forms a wireless communication network. Corresponds to a cell. An environment in which the cells share the same frequency channel and overlap is called an OBSS (Overlapping BSS) environment.

  Under such an OBSS environment, a base station apparatus or a terminal apparatus of one cell is transmitting a radio signal, or within a channel use time (Transmission Opportunity: TXOP) set by them, Since the terminal device cannot communicate, the cell throughput is greatly deteriorated.

  In the present embodiment, the base station device 100-2 has a propagation path from the base station device 100-1 of the neighboring cell to the terminal device 300 (a part or all of the terminal devices 300-1 to 300-3) in the cell. Monitor the communication process when requesting notification of information. The base station apparatus 100-2 estimates a propagation path state between the terminal apparatus 300 of the neighboring cell and the own base station apparatus 100-2 during the monitoring of the communication process. Based on the propagation path estimation result, the base station apparatus 100-2 pre-codes the transmission signal to the terminal apparatus 300 in its own cell so that the signal does not reach the terminal apparatus 300 in the neighboring cell, and then performs radio transmission. Send a signal.

  Note that, as the propagation path information, channel state information (a complex propagation path gain between each antenna of the base station apparatus 100 and each antenna of each terminal apparatus 300, a covariance value thereof, or a value calculated or converted therefrom) The case where channel state information (CSI) is used will be described as an example. However, the present invention is not limited to this. For example, an index (Precoding Matrix Indicator: PMI) of a desired precoding matrix obtained from the channel state may be used.

  FIG. 2 is a functional block diagram showing a configuration example of the base station apparatus 100 of the present invention. The configuration example of the base station apparatus 100 in FIG. 2 includes M antennas. 2 corresponds to base station apparatus 100-1 and base station apparatus 100-2 in FIG.

  The base station apparatus 100 includes an error correction coding unit 201, a modulation unit 202, a reference signal multiplexing unit 203, a precoding unit 204, an IFFT unit 205, a GI insertion unit 206, a wireless transmission unit 207, an antenna unit 208, and a wireless reception unit 209. GI removal section 210, FFT section 211, reference signal separation section 212, propagation path estimation section 213, equalization section 214, demodulation section 215, error correction decoding section 216, and upper layer 217.

  The error correction coding unit 201 receives a control data sequence, a maximum of M (M streams) user data sequences addressed to the terminal device 300, a broadcast data sequence, or a multicast data sequence, which are input from the upper layer 217. Error correction coding is performed on each of the maximum M transmission data sequences to generate a transmission data encoded sequence. Furthermore, the error correction coding unit 201 may perform bit puncturing (puncturing, rate matching) in accordance with the coding rate designation from the upper layer 217 or the like. When the coding rate is not specified, the error correction coding unit 201 may perform bit puncturing at a predetermined coding rate. Further, error correction coding section 201 may perform interleaving on the coded sequence of transmission data after bit puncturing.

  Modulation section 202 modulates each of the maximum M transmission data encoded sequences output from error correction encoding section 201, and generates a modulation symbol sequence of the transmission data. Note that the modulation unit 202 preferably performs modulation in accordance with the designation of the modulation method from the upper layer 217 or the like. When there is no designation of the modulation method, the modulation unit 202 preferably performs modulation using a predetermined modulation method.

  Reference signal multiplexing section 203 multiplexes a symbol sequence of a reference signal (pilot signal, training signal, preamble signal) with a modulation symbol sequence of transmission data output from modulation section 202. In this reference signal symbol sequence, the terminal device 300 estimates a propagation path state between each antenna of the base station device 100 and the antenna of the terminal device 300 (or each antenna when the terminal device 300 includes a plurality of antennas). It is a symbol sequence of a known signal used for The reference signal symbol sequence is preferably multiplexed such that the terminal device 300 receives the reference signals transmitted from the respective antennas of the base station apparatus 100 in a form that can be separately identified. For example, the reference signal symbol sequence may be multiplexed with the transmission data sequence by time division, may be multiplexed by frequency division such as division by subcarriers, or may be multiplexed by code division. The reference signal multiplexing unit 203 may further multiplex another reference signal symbol sequence for OFDM symbol synchronization, radio frame synchronization, and the like.

  The precoding unit 204 performs precoding on the transmission data sequence output from the reference signal multiplexing unit 203 and multiplexed with the reference signal symbol sequence based on the precoding filter information input from the higher layer 217, A precoded symbol sequence transmitted from each antenna of the antenna unit 208 is generated. In this embodiment, a case where linear precoding is used as the precoding method will be described as an example, but non-linear precoding may be used. Details of the precoding will be described later.

  The IFFT unit 205 performs frequency-time conversion such as Inverse Fast Fourier Transform (IFFT) on the post-precoding symbol sequence for each antenna output from the precoding unit 204, to a time domain signal. Convert.

  The GI insertion unit 206 inserts a guard interval (GI) into the time domain signal output from the IFFT unit 205.

  The radio transmission unit 207 converts the signal output from the GI insertion unit 206 into an analog signal, up-converts the signal to a radio signal, and transmits the radio signal through the antenna unit 208.

  The radio reception unit 209 down-converts the radio signal received through the antenna unit 208 into a baseband signal, converts it to a digital signal, and outputs it.

  The GI removal unit 210 removes the guard period from the signal output from the wireless reception unit 209.

  The FFT unit 211 performs time-frequency conversion such as Fast Fourier Transform (FFT) on the signal from the GI removal unit 210 from which the guard period has been removed, and outputs a received symbol sequence for each antenna. To do.

  The reference signal demultiplexing unit 212 demultiplexes the reference signal symbol sequence from the received symbol sequence for each antenna output from the FFT unit 211 and inputs it to the propagation path estimation unit 213, and modulates the received data that is the remaining received symbol sequence The symbol series is input to the equalization unit 214.

  Based on the reference signal symbol sequence output from reference signal demultiplexing section 212, propagation path estimating section 213 and each base station of the transmitting apparatus (terminal apparatus 300 or base station apparatus 100 in the neighboring cell) that transmitted this signal A propagation path state and reception quality with each antenna of the station apparatus are estimated, and a propagation path state estimation result and a reception quality estimation result are output.

  Based on the propagation path state estimation result output from propagation path estimation section 213, equalization section 214 equalizes (propagation path compensation) the modulation symbol sequence of the received data output from reference signal separation section 212. Further, when the received signal is a MIMO signal, the equalization unit 214 performs MIMO signal detection based on the propagation path state estimation result output from the propagation path estimation unit 213.

  Demodulation section 215 performs demodulation processing on the modulated symbol sequence of the received data after equalization output from equalization section 214, and outputs a received data encoded sequence. Note that the demodulation unit 215 preferably performs demodulation in accordance with the designation of the modulation scheme from the upper layer 217 or the like, and preferably performs demodulation using a predetermined modulation scheme if no modulation scheme is designated.

  Error correction decoding section 216 performs error correction decoding on the received data encoded sequence output from demodulation section 215, and outputs a received data sequence. When bit puncturing is performed in the transmission apparatus, prior to error correction decoding, bit depuncturing (depuncturing and rate) is performed on the received data coded sequence in accordance with the coding rate designation from the higher layer 217 or the like. Matching). When bit puncturing is performed in the transmission apparatus and no coding rate is specified, the error correction decoding unit 216 preferably performs bit depuncturing at a predetermined coding rate. When interleaving processing is performed in the transmission apparatus, error correction decoding section 216 performs deinterleaving on the received data encoded sequence prior to error correction decoding and bit depuncturing.

  The upper layer 217 generates a transmission data sequence and a precoding filter. Further, the upper layer 217 processes the received data sequence to acquire the user data sequence, the control data sequence, the propagation path information notified by the terminal device 300, and the like, and the acquired propagation path information is the propagation path information storage unit. Store in 218. The upper layer 217 also specifies a terminal ID for designating the terminal device 300 such as a transmission source or a transmission destination of the signal from the received data series of signals transmitted from the base station device 100 of the neighboring cell and the terminal device 300 of the neighboring cell. The terminal ID acquisition part 220 is acquired and memorize | stored. Further, the upper layer 217 outputs the propagation path state estimation result and the reception quality estimation result between the terminal apparatus 300 in the neighboring cell and the base station apparatus 100 in the neighboring cell, which are output from the propagation path estimation unit 213, as a propagation path estimation. The result is stored in the result storage unit 219. The upper layer 217 identifies the terminal device 300 of the neighboring cell stored in the terminal ID acquisition unit 220 when storing the propagation path state estimation result and the reception quality estimation result with the terminal device 300 of the neighboring cell. Together with the terminal ID to be stored. Further, the upper layer 217 controls the operation of each of the above parts.

  FIG. 3 is a functional block diagram showing a configuration example of the terminal device 300 of the present invention. The configuration example of the terminal device 300 in FIG. 3 includes one antenna. Note that the terminal device 300 in FIG. 3 corresponds to the terminal devices 300-1 to 300-6 in FIG.

  The terminal device 300 includes an antenna unit 301, a radio reception unit 302, a GI removal unit 303, an FFT unit 304, a reference signal separation unit 305, a channel estimation unit 306, an equalization unit 307, a demodulation unit 308, and an error correction decoding unit 309. , Error correction coding section 310, modulation section 311, reference signal multiplexing section 312, IFFT section 313, GI insertion section 314, radio transmission section 315, and higher layer 316.

  The radio reception unit 302 down-converts a radio signal received through the antenna unit 301 into a baseband signal, converts it to a digital signal, and outputs the digital signal.

  The GI removal unit 303 removes the guard period from the signal output from the wireless reception unit 302.

  The FFT unit 304 performs time-frequency transform such as Fast Fourier Transform (FFT) on the signal from the GI removal unit 303 from which the guard period is removed, and outputs a received symbol sequence.

  The reference signal separation unit 305 separates the reference signal symbol sequence from the reception symbol sequence output from the FFT unit 304 and inputs the reference signal symbol sequence to the propagation path estimation unit 306, and receives the modulation symbol sequence of the received data that is the remaining reception symbol sequence. Input to the equalization unit 307.

  Based on the reference signal symbol sequence output from reference signal demultiplexing section 305, propagation path estimating section 306 determines between each antenna of the transmitting apparatus (base station apparatus 100) that transmitted this signal and the antenna of its own terminal apparatus. A propagation path state is estimated and a propagation path state estimation result is output.

  Based on the propagation path state estimation result output from propagation path estimation section 306, equalization section 307 equalizes (channel propagation compensation) the modulation symbol sequence of the received data output from reference signal separation section 305.

  Demodulation section 308 performs demodulation processing on the modulated symbol sequence of the received data after equalization output from equalization section 307, and outputs a received data encoded sequence. Note that the demodulation unit 308 preferably performs demodulation in accordance with the designation of the modulation method from the upper layer 316 or the like. When there is no designation of the modulation method, it is preferable to perform demodulation using a predetermined modulation method.

  Error correction decoding section 309 performs error correction decoding on the received data encoded sequence output from demodulation section 308, and outputs a received data sequence. When bit puncturing is performed in the transmission apparatus, prior to error correction decoding, bit depuncturing (depuncturing and rate) is performed on the received data coded sequence according to the coding rate designation from the higher layer 316 or the like. Matching). When bit puncturing is performed in the transmission device and no coding rate is specified, the error correction decoding unit 309 preferably performs bit depuncturing at a predetermined coding rate. When interleaving processing is performed in the transmission apparatus, error correction decoding section 309 performs deinterleaving on the received data encoded sequence prior to error correction decoding and bit depuncturing.

  Error correction encoding section 310 performs error correction encoding on the control data sequence input from upper layer 316 and transmission data sequences such as a user data sequence addressed to base station apparatus 100 and a data sequence of propagation path information, respectively. To generate an encoded sequence of transmission data. Further, the error correction coding unit 310 may perform bit puncturing (puncturing, rate matching) in accordance with the coding rate designation from the upper layer 316 or the like. When the coding rate is not specified, the error correction coding unit 310 may perform bit puncturing at a predetermined coding rate. Further, error correction coding section 310 may perform interleaving on the coded sequence of transmission data after bit puncturing.

  Modulating section 311 modulates each of the transmission data encoded sequences output from error correction encoding section 310 to generate a modulation symbol sequence of the transmission data. Note that the modulation unit 311 preferably performs modulation in accordance with the designation of the modulation method from the upper layer 316 or the like. When there is no designation of the modulation method, the modulation unit 311 preferably performs modulation using a predetermined modulation method.

  Reference signal multiplexing section 312 multiplexes a symbol sequence of a reference signal (pilot signal, training signal, preamble signal) with a modulation symbol sequence of transmission data output from modulation section 311. This reference signal symbol sequence is a symbol sequence of a known signal used by base station apparatus 100 to estimate a propagation path state between the antenna of terminal apparatus 300 and each antenna of base station apparatus 100. The reference signal multiplexing unit 312 may further multiplex another reference signal symbol sequence for OFDM symbol synchronization, radio frame synchronization, or the like.

  The IFFT unit 313 performs frequency time conversion such as inverse fast Fourier transform (IFFT) on the transmission data sequence output from the reference signal multiplexing unit 312 and multiplexed with the reference signal symbol sequence, Convert to domain signal.

  The GI insertion unit 314 inserts a guard interval (GI) into the time domain signal output from the IFFT unit 313.

  The wireless transmission unit 315 converts the signal output from the GI insertion unit 314 into an analog signal, up-converts the signal into a wireless signal, and transmits the signal through the antenna unit 301.

  The upper layer 316 performs generation of transmission data sequences, reconfiguration of received data sequences, processing of control data, generation of propagation path information from propagation path state estimation results, and the like, and further controls the operation of each unit.

  4 shows a base station apparatus 100-1 (base station apparatus in a neighboring cell) and a base station apparatus 100-2 (base station apparatus in its own cell) and terminal apparatuses 300-1 to 300-3 ( It is a time chart which shows an example of transmission / reception of the radio | wireless frame between the terminal device of a periphery cell) and terminal device 300-4-300-6 (terminal device of a self-cell).

  In FIG. 4, a series of sequences (sequence SEQ <b> 1) led by the base station device 100-1 in the neighboring cell to request and collect propagation path information from the terminal devices 300-1 to 300-3 belonging to the neighboring cell. ) Is observed, the base station device 100-2 estimates the propagation path state between the base station device 100-1 in the neighboring cell and the terminal devices 300-1 to 300-3 in the neighboring cell. An example is shown. When the base station device 100-2 transmits a radio frame to the terminal devices 300-4 to 300-6 belonging to the own cell, the base station device 100-2 and the base station device 100-1 of the neighboring cell based on the estimated propagation path state A signal subjected to precoding is transmitted so that the signal does not reach the terminal devices 300-1 to 300-3 in the neighboring cells.

  For example, when the base station apparatus 100-1 intends to perform MU-MIMO transmission to a plurality of terminal apparatuses 300-1 to 300-3 in its own cell, the base station apparatus 100-1 In order to know the propagation path state between each of the terminal devices 300-1 to 300-3, a propagation path information request sequence such as the sequence SEQ1 in FIG. 4 is executed.

  First, at the start of the propagation path information request sequence, the base station apparatus 100-1 (in a neighboring cell) designates one or more terminal apparatuses that request notification of propagation path information as target terminal apparatuses, and sets each terminal apparatus. A frame for notifying each target terminal device of information such as the number of streams (MIMO rank number) of propagation path information requesting notification, for example, an NDPA (Null Data Packet Announcement) frame is transmitted (frame F401). The NDPA frame includes information of an identification number (Association ID: AID), a MAC (Media Access Control) address, or both of the terminal device designated as the target terminal device (hereinafter, the information is collectively referred to as “the ID”). Called terminal ID). In the NDPA frame, a terminal device that first notifies (feeds back) propagation path information to the base station device 100-1 among the target terminal devices is specified by the terminal ID. FIG. 4 illustrates an example in which three terminal devices 300-1 to 300-3 are designated as target terminal devices. Further, the NDPA frame may include a sequence number for identifying the propagation path information request sequence.

  In the example of the wireless communication system in the present embodiment shown in FIG. 1, the NDPA frame F401 transmitted from the base station apparatus 100-1 is also received by the base station apparatus 100-2. The base station device 100-2 receives the NDPA frame F401, and the base station device 100-1 first transmits the channel ID to the terminal ID of the target terminal device that is requesting the notification of the channel information. The information (terminal ID) of the target terminal device fed back to -1 is acquired and stored. Note that the base station device 100-2 may store only the terminal ID of the target terminal device that first notifies the base station device 100-1 of the propagation path information. Furthermore, the base station apparatus 100-2 may store a sequence number included in the NDPA frame.

  Subsequently, the base station apparatus 100-1 includes a frame (sounding frame) including a reference signal for each target terminal apparatus to estimate a propagation path state with the base station apparatus 100-1, for example, NDP (Null Data Packet). ) A frame is transmitted (frame F402). The NDP frame includes a reference signal transmitted for each antenna of the base station apparatus 100-1, and each target terminal apparatus that has received the NDP frame receives the base station based on the received signal of each reference signal. Propagation path information that estimates the propagation path state between each antenna of the apparatus 100-1 and one or more antennas of the terminal apparatus and represents the propagation path state for the number of streams specified in the previously received NDPA frame F401. Is generated.

  The NDP frame F402 transmitted by the base station device 100-1 is also received by the base station device 100-2 in the same manner as the NDPA frame F401. The base station apparatus 100-2 receives the NDP frame F401, estimates the propagation path state and reception quality between each antenna of the base station apparatus 100-1 and each antenna of the own base station apparatus, and transmits the propagation path. The state estimation result and the reception quality estimation result are stored. The reception quality includes received signal power, signal power to noise power ratio (SNR), signal power to interference plus noise power ratio (SINR), and carrier power to signal power. It is preferable to estimate the noise power ratio (Carrier to Noise power Ratio: CNR) or carrier power to interference plus noise power ratio (CINR), but is not limited thereto. Below, the case where reception signal power is estimated as reception quality is demonstrated as an example. Further, the base station apparatus 100-2 may store the sequence number acquired from the NDPA frame together with the propagation path state estimation result and the reception quality estimation result.

  In the NDPA frame F401, the target terminal device that is first designated to feed back the propagation path information to the base station device 100-1, for example, in the case of FIG. 4, the terminal device 300-1 generates the propagation generated based on the NDPA frame F402. A frame including the path information, for example, an SND FB (Sounding Feedback) frame is transmitted to the base station apparatus 100-1 (frame F403).

  The base station device 100-1 receives the SND FB frame F403 transmitted from the terminal device 300-1, and acquires the propagation path information notified from the terminal device 300-1.

  In the example of the wireless communication system in the present embodiment illustrated in FIG. 1, the SND FB frame F403 transmitted from the terminal device 300-1 is also received by the base station device 100-2. Base station apparatus 100-2 receives SND FB frame F403, and based on a reference signal included in SND FB frame F403, a propagation path between the antenna of terminal apparatus 300-1 and each antenna of the own base station apparatus Estimate state and reception quality. The base station apparatus 100-2 acquires the propagation path state estimation result together with the terminal ID of the target terminal apparatus (terminal apparatus 300-1) that is obtained from the NDPA frame F401 and first feeds back the propagation path information to the base station apparatus 100-1. And the reception quality estimation result are stored in the propagation path estimation result storage unit 219. As the terminal ID, a sender address (Transmitter Address: TA) included in the SND FB frame F403 may be acquired and used. If the channel state estimation result and the reception quality estimation result are already stored in the channel estimation result storage unit 219 together with the terminal ID, the storage is updated with the newly estimated result (hereinafter referred to as SND FB). The same processing is performed when receiving a frame). Further, the base station apparatus 100-2 may store the sequence number acquired from the NDPA frame together with the propagation path state estimation result and the reception quality estimation result.

  The base station apparatus 100-1 then sends a frame requesting feedback of the propagation path information to the target terminal apparatus to which the propagation path information is fed back next, for example, the terminal apparatus 300-2 in the case of FIG. 4, for example, FB Poll (Feedback Poll) frame is transmitted (frame F404).

  The base station device 100-2 receives the FB Poll frame F404, and acquires the terminal ID of the target terminal device (terminal device 300-2) from which the base station device 100-1 requests feedback of propagation path information.

  The terminal device 300-2 receives the FB Poll frame F404 from the base station device 100-1, and directs the SND FB frame including the propagation path information generated based on the NDP frame F402 toward the base station device 100-1. Transmit (frame F405).

  The base station apparatus 100-1 receives the SND FB frame F405 transmitted from the terminal apparatus 300-2, and acquires the propagation path information notified from the terminal apparatus 300-2.

  In the example of the wireless communication system in the present embodiment illustrated in FIG. 1, the SND FB frame F405 transmitted by the terminal device 300-2 is not received by the base station device 100-2. For this reason, the base station apparatus 100-2 discards the terminal ID acquired from the FB Poll frame F404 when the SND FB frame F405 cannot be received within a specified time after the FB Poll frame F404 ends.

  The base station apparatus 100-1 transmits an FB Poll frame requesting the feedback of the propagation path information to the target terminal apparatus to which the propagation path information is fed back next, for example, the terminal apparatus 300-3 in the case of FIG. Frame F406).

  The base station apparatus 100-2 receives the FB Poll frame F406, and acquires the terminal ID of the target terminal apparatus (terminal apparatus 300-3) for which the base station apparatus 100-1 requests feedback of propagation path information.

  The terminal device 300-3 receives the FB Poll frame F406 from the base station device 100-1, and directs the SND FB frame including the propagation path information generated based on the NDP frame F402 to the base station device 100-1. Transmit (frame F407).

  The base station device 100-1 receives the SND FB frame F407 transmitted from the terminal device 300-3, and acquires the propagation path information notified from the terminal device 300-3.

  In the example of the wireless communication system in the present embodiment illustrated in FIG. 1, the SND FB frame F407 transmitted from the terminal device 300-3 is also received by the base station device 100-2. Base station apparatus 100-2 receives SND FB frame F407, and based on a reference signal included in SND FB frame F407, a propagation path between the antenna of terminal apparatus 300-3 and each antenna of the own base station apparatus Estimate state and reception quality. The base station apparatus 100-2 stores the propagation path state estimation result and the reception quality estimation result in the propagation path estimation result storage unit 219 together with the terminal ID acquired from the FB Poll frame F406. As the terminal ID, the sender address included in the SND FB frame F407 may be acquired and used. Further, the base station apparatus 100-2 may store the sequence number acquired from the NDPA frame together with the propagation path state estimation result and the reception quality estimation result.

  As a result, the base station apparatus 100-2 associates the terminal state 300-1 and the terminal apparatus 300 with the propagation path state estimation result, the reception quality estimation result, and the terminal ID with the base station apparatus 100-1. -3, the propagation path state estimation result and the reception quality estimation result are stored in the propagation path estimation result storage unit 219. The base station apparatus 100-2 may further store the sequence numbers in association with each other.

  The base station device 100-2 transmits the transmission data addressed to the terminal device 300-4 of its own cell to the stored base station device 100-1, the terminal device 300-1, and the terminal device 300-3. Based on the propagation path state estimation result, precoding is performed so that nulls are directed to them (frame F408).

  The terminal device 300-4 receives the frame F408.

  Similarly, the base station apparatus 100-2, with respect to transmission data addressed to the terminal apparatus 300-5 of its own cell, the base station apparatus 100-1 and terminal apparatus 300- stored in the propagation path estimation result storage unit 219. 1 and the terminal apparatus 300-3, based on the propagation path state estimation result, pre-coding is performed so that nulls are directed to them (frame F409).

  The terminal device 300-5 receives the frame F409.

  In the example of FIG. 4, when the base station device 100-2 transmits data to the terminal device of its own cell, the base station device 100-2 receives all the base stations of the neighboring cells that have received signals. Although the case where the precoding which directs null so that a transmission signal does not reach with respect to the station apparatus 100-1, the terminal device 300-1, and the terminal device 300-3 was shown was shown, it is not restricted to this.

  For example, since the number of nulls exceeding the degree of freedom of the antenna cannot be generated, the base station apparatus 100-2 has a high reception quality estimation result stored in the propagation path estimation result storage unit 219 (the reception signal power is high). In order from the highest), the base station apparatus or terminal apparatus in the neighboring cell may be selected up to the maximum number of antenna degrees of freedom, and precoding may be performed in which nulls are directed toward the base station apparatus or terminal apparatus in the selected neighboring cell. In this way, by selecting a destination to which nulls are directed in descending order of the reception quality estimation result, a signal transmitted by the base station device 100-2 may be received greatly for base station devices and terminal devices in neighboring cells. Thus, null can be preferentially directed, and inter-cell interference with respect to neighboring cells can be efficiently suppressed.

  As another example, the base station device 100-2 is configured to increase the number of base station devices and terminal devices of neighboring cells to the maximum in order from the latest sequence number of the propagation channel information request sequence stored in the propagation channel estimation result storage unit 219. It is also possible to select up to the number of degrees of freedom and perform precoding that directs nulls to the base station apparatus and terminal apparatus of the selected neighboring cell. In this way, by selecting a destination where nulls are directed in order from the newest sequence number, it is possible to preferentially direct nulls to base station devices and terminal devices of neighboring cells that are likely to be communicating, Inter-cell interference with neighboring cells can be efficiently suppressed.

  In addition, by combining the above two examples, the base station apparatus 100-2 determines the reception quality estimation results stored in the propagation path estimation result storage unit 219 in descending order of the reception quality estimation results (the reception signal power is high), and the propagation path information request. Select the base station device and terminal device of the neighboring cell by the number of degrees of freedom of the antenna in the order of the sequence number of the sequence, and perform precoding that directs null to the base station device and terminal device of the selected neighboring cell. May be. In this case, there is a possibility that the signal transmitted by the base station apparatus 100-2 is received greatly, and null is preferentially given to the base station apparatus or terminal apparatus of the neighboring cell that is likely to be communicating. Therefore, it is possible to efficiently suppress inter-cell interference with respect to neighboring cells.

  The case has been described above where one base station apparatus 100-2 performs precoding that directs nulls to the base station apparatus 100-1 and the terminal apparatuses 300-1 to 300-3 in the neighboring cells. Similarly, the base station device 100-1 estimates the propagation path state between the base station device 100-2 and the terminal devices 300-4 to 300-6 that are neighboring cells for the base station device 100-1, Precoding may be performed in which nulls are directed to these.

  FIG. 5 is a flowchart illustrating an example of a process flow in which the base station device 100 according to the present embodiment estimates the propagation path state between the base station device and the terminal device of the neighboring cell in the sequence SEQ1.

  When the base station apparatus 100 detects the NDPA frame transmitted from the base station apparatus of the neighboring cell (Yes in step S501), the base station apparatus 100 receives this and proceeds to step S502. When the NDPA frame is not detected (in step S501) No) returns to step S501.

  From the received NDPA frame transmitted from the base station apparatus of the neighboring cell, the base station apparatus 100 firstly feeds back the terminal ID of the target terminal apparatus for which the base station apparatus of the neighboring cell is requesting feedback of propagation path information. The terminal ID of the target terminal device designated to perform the process is acquired (step S502).

  The base station device 100 receives the NDP frame transmitted from the base station device of the neighboring cell, and based on the reference signal included in the received NDP frame, between the base station device of the neighboring cell and the own base station device A propagation path state and reception quality are estimated (step S503).

  When the base station apparatus 100 detects the SND FB frame transmitted from the terminal apparatus of the neighboring cell (Yes in step S504), the base station apparatus 100 receives this and proceeds to step S505, and the SND FB frame is not detected within the specified time. In the case (No in step S504), the process proceeds to step S506.

  Based on the reference signal included in the SND FB frame transmitted from the terminal device of the received neighboring cell, the base station device 100 estimates the propagation path state and the reception quality between the terminal device and the base station device. To do. And if it is the SND FB frame immediately after the NDP frame, the propagation path state estimation result and the reception quality estimation together with the terminal ID of the target terminal device designated to perform feedback first designated in the NDPA frame Remember the result. In addition, when the FB Poll frame is detected in Step S506, which will be described later, and it is the SND FB frame immediately after the terminal ID is acquired in Step S507, the propagation path state estimation result and the terminal ID acquired from the FB Poll frame are The reception quality estimation result is stored (step S505).

  When the base station apparatus 100 detects the FB Poll frame transmitted from the base station apparatus of the neighboring cell (Yes in step S506), the base station apparatus 100 receives this and proceeds to step S507, and when the FB Poll frame is not detected (step S507). No in S506) ends this flow.

  The base station device 100 acquires the terminal ID of the target terminal device for which the base station device of the neighboring cell is requesting feedback of the propagation path information from the received FB Poll frame transmitted from the base station device of the neighboring cell, The process returns to step S504 (step S507).

  Based on the above flow, the base station device 100 observes a series of sequences led by the base station device of the neighboring cell to request and collect propagation path information from the terminal devices belonging to the neighboring cell. Accordingly, it is possible to efficiently estimate the propagation path state between the base station apparatus and the terminal apparatus of the neighboring cell and the own base station apparatus.

  In addition, the estimation of the propagation path state between the base station apparatus and the terminal apparatus of the neighboring cell and the own base station apparatus is not limited to the method based on the observation of the sequence. For example, the base station apparatus 100 Various frames communicated between the cell base station apparatus and the terminal apparatus are individually observed, and propagation between the base station apparatus of the cell and the base station apparatus or terminal apparatus of the neighboring cell is performed based on each frame. The road condition may be estimated. In this case, the terminal ID of the terminal device in the neighboring cell may be obtained from the sender address included in each frame.

  FIG. 6 is a flowchart illustrating an example of a flow of transmission processing when the base station device 100 according to the present embodiment transmits data to the terminal device of the own cell.

  The base station apparatus 100 selects a terminal apparatus that transmits data based on the data storage status in the transmission buffer, QoS (Quality of Service) information of the transmission data, etc., from the terminal apparatuses of the own cell (step) S601).

  Base station apparatus 100 selects a base station apparatus or a terminal apparatus of a neighboring cell that stores a propagation path state estimation result, with the number of degrees of freedom of the base station apparatus as the upper limit number (step S602). At this time, base station apparatus 100 is based on the order in which the stored reception quality estimation result is high (the reception signal power is high), the sequence number of the stored channel information request sequence is the newest, or a combination thereof. However, it is preferable to select a base station apparatus or a terminal apparatus of a neighboring cell, but the present invention is not limited to this. Also, base station apparatus 100 groups terminal apparatuses of a plurality of neighboring cells determined to have strong correlation of propagation paths from the propagation path state estimation result, and selects one terminal apparatus as a representative from each group You may do it. At this time, the degree of antenna freedom is only required to direct null toward the selected representative terminal device. As a result of precoding described later, almost all the terminal devices in each group to which the selected representative terminal device belongs are null. Can be directed.

  Based on the stored propagation path state estimation result of the base station apparatus or terminal device of the selected neighboring cell, the base station apparatus 100 causes the null to be directed toward the base station apparatus or terminal device of the selected neighboring cell. A simple precoding filter is calculated (step S603).

  The base station apparatus 100 generates a transmission signal by multiplying the transmission data addressed to the terminal apparatus of the own cell selected in step S601 by the precoding filter calculated in step S603, and transmits the transmission signal (step S604). At this time, the reference signal and control information included in the frame to be transmitted may be precoded by multiplying the precoding filter.

As described above, according to the present embodiment, it becomes possible to perform precoding such that each base station apparatus autonomously suppresses inter-cell interference to neighboring cells, and the configuration of a plurality of base station apparatuses Cell throughput in an OBSS environment in which some or all of the cells to be overlapped can be improved.
(Second Embodiment)
Similarly to the first embodiment, the wireless communication system according to the present embodiment includes two base station devices, the base station device 100-1 and the base station device 100-2, which are connected to the base station device 100-1. Terminal device 300-1, terminal device 300-2, and terminal device 300-3, and terminal device 300-4, terminal device 300-5, and terminal device 300- connected to the base station device 100-2 1 will be described as an example.

  The configurations of the base station apparatus 100 and the terminal apparatus 300 in the present embodiment are the same as those in FIG. 2 and FIG. 3 in the first embodiment, and the base station apparatus 100-2 transmits data to the terminal apparatus of its own cell. However, another difference is that precoding is performed using propagation path information acquired from the terminal device of the own cell. Hereinafter, description of the same parts as those of the first embodiment will be omitted, and different parts will be described.

  FIG. 7 shows a base station device 100-1 (base station device in a neighboring cell) and a base station device 100-2 (base station device in its own cell) and terminal devices 300-1 to 300-3 ( It is a time chart which shows an example of transmission / reception of the radio | wireless frame between the terminal device of a periphery cell) and terminal device 300-4-300-6 (terminal device of a self-cell). In the example of FIG. 7, an example is shown in which the base station apparatus 100-2 transmits each transmission data addressed to the terminal apparatuses 300-4 to 300-6 by spatial multiplexing using MU-MIMO.

  In FIG. 7, first, similar to the sequence SEQ1 of FIG. 4, the propagation path information is requested from the terminal devices 300-1 to 300-3 belonging to the peripheral cell led by the base station apparatus 100-1 of the peripheral cell. A series of propagation path information request sequences for performing collection are executed. As a result, the base station device 100-2 associates the terminal state 300-1 and the terminal device 300- with the propagation path state estimation result, the reception quality estimation result, and the terminal ID with the base station device 100-1. 3, the propagation path state estimation result and the reception quality estimation result are stored in the propagation path estimation result storage unit 219. The base station apparatus 100-2 may further store the sequence numbers in association with each other.

  Subsequently, a series of channel information request sequences (sequence SEQ2) led by the base station device 100-2 to request and collect channel information from the terminal devices 300-4 to 300-6 belonging to the cell. Is executed.

  The base station apparatus 100-2 designates a plurality of terminal apparatuses that request notification of propagation path information as target terminal apparatuses at the start of the propagation path information request sequence, and a stream of propagation path information that requests notification from each terminal apparatus. A frame for notifying each target terminal device of information such as the number (the number of MIMO ranks), for example, an NDPA frame is transmitted (frame F701). FIG. 7 illustrates an example in which three terminal devices 300-4 to 300-6 are designated as target terminal devices.

  The base station apparatus 100-2 transmits a frame (sounding frame) including a reference signal for estimating a propagation path state between each target terminal apparatus and the base station apparatus 100-2, for example, an NDP frame (frame F702). ). The NDP frame includes a reference signal transmitted for each antenna of the base station apparatus 100-2, and each target terminal apparatus that has received the NDP frame F702 receives a base signal based on the received signal of each reference signal. A propagation path state between each antenna of the station apparatus 100-2 and one or more antennas of the own terminal apparatus is estimated, and a propagation path representing the propagation path states for the number of streams specified in the previously received NDPA frame F701. Generate information.

  The target terminal device first designated to feed back the propagation path information to the base station device 100-2 in the NDPA frame F701, for example, the terminal device 300-4 in the case of FIG. 7, generates the propagation generated based on the NDP frame F702. A frame including the path information, for example, an SND FB frame is transmitted to the base station apparatus 100-2 (frame F703).

  The base station apparatus 100-2 receives the SND FB frame F703 transmitted from the terminal apparatus 300-4, acquires the propagation path information notified from the terminal apparatus 300-4, and stores it in the propagation path information storage unit 218. .

  The base station apparatus 100-2 sends a frame requesting feedback of the propagation path information to the target terminal apparatus to which the propagation path information is fed back next, for example, the terminal apparatus 300-5 in the case of FIG. Transmit (frame F704).

  The terminal device 300-5 receives the FB Poll frame F704 from the base station device 100-2, and sends the SND FB frame including the propagation path information generated based on the NDP frame F702 to the base station device 100-2. Transmit (frame F705).

  The base station apparatus 100-2 receives the SND FB frame F705 transmitted from the terminal apparatus 300-5, acquires the propagation path information notified from the terminal apparatus 300-5, and stores it in the propagation path information storage unit 218. .

  The base station apparatus 100-2 transmits an FB Poll frame for requesting feedback of the propagation path information to the target terminal apparatus to which the propagation path information is fed back next, for example, the terminal apparatus 300-6 in the case of FIG. Frame F706).

  The terminal device 300-6 receives the FB Poll frame F706 from the base station device 100-2, and sends the SND FB frame including the propagation path information generated based on the NDP frame F702 to the base station device 100-2. Transmit (frame F707).

  The base station apparatus 100-2 receives the SND FB frame F707 transmitted from the terminal apparatus 300-6, acquires the propagation path information notified from the terminal apparatus 300-6, and stores it in the propagation path information storage unit 218. .

  As a result, the base station apparatus 100-2 enters a state in which the propagation path information fed back from the terminal apparatuses 300-4 to 300-6 is stored in the propagation path information storage unit 218.

  The base station device 100-2 stores the channel information fed back from the terminal devices 300-4 to 300-6 stored in the channel information storage unit 218 and the channel estimation result storage unit 219, respectively. Based on the propagation path state estimation results among the base station device 100-1, the terminal device 300-1, and the terminal device 300-3, the base station device 100-1, the terminal device 300-1, and the terminal device 300-3 On the other hand, with respect to each transmission data addressed to terminal apparatuses 300-4 to 300-6, nulls are directed and inter-user interference is suppressed with respect to terminal apparatuses 300-4 to 300-6. Then, precoding is performed and a MU-MIMO signal is transmitted (frame F708).

  Each of the terminal devices 300-4 to 300-6 receives the frame F708.

  In the example of FIG. 7, the base station apparatus 100-2 can receive a signal at the base station apparatus 100-2 when data is spatially multiplexed with MU-MIMO and transmitted to the terminal apparatus of the own cell. In addition, a case has been shown in which precoding is performed in which nulls are directed so that a transmission signal does not reach the base station apparatus 100-1, the terminal apparatus 300-1, and the terminal apparatus 300-3 of the neighboring cells. It is not limited.

  For example, since the number of nulls exceeding the degree of freedom of the antenna cannot be generated, the base station device 100-2 allows the user to transmit data to a plurality of terminal devices in the own cell by spatial multiplexing using MU-MIMO. The reception quality estimation result stored in the propagation path estimation result storage unit 219 is high (the reception signal power is high) up to the number of extra antenna degrees of freedom excluding the antenna degrees of freedom necessary for suppressing inter-interference. ) In order, precoding may be performed in which base station apparatuses and terminal apparatuses in neighboring cells are selected, and nulls are directed toward the base station apparatus and terminal apparatuses in the selected neighboring cells. In this way, by selecting a destination to which nulls are directed in descending order of the reception quality estimation result, a signal transmitted by the base station device 100-2 may be received greatly for base station devices and terminal devices in neighboring cells. Thus, null can be preferentially directed, and inter-cell interference with respect to neighboring cells can be efficiently suppressed.

  As another example, the base station apparatus 100-2 sets the maximum number of base station apparatuses and terminal apparatuses in the neighboring cells in order from the newest sequence number of the propagation path information request sequence stored in the propagation path estimation result storage unit 219. It is also possible to select up to the number of extra antenna degrees of freedom and perform precoding in which nulls are directed to the base station apparatus and terminal apparatus of the selected neighboring cell. In this way, by selecting a destination where nulls are directed in order from the newest sequence number, it is possible to preferentially direct nulls to base station devices and terminal devices of neighboring cells that are likely to be communicating, Inter-cell interference with neighboring cells can be efficiently suppressed.

  In addition, by combining the above two examples, the base station apparatus 100-2 determines the reception quality estimation results stored in the propagation path estimation result storage unit 219 in descending order of the reception quality estimation results (the reception signal power is high), and the propagation path information request. In order from the newest sequence number of the sequence, select the base station apparatus and terminal apparatus of the neighboring cell by the number of the above-mentioned excess antenna degrees of freedom, and direct null toward the base station apparatus and terminal apparatus of the selected neighboring cell. Precoding may be performed. In this case, there is a possibility that the signal transmitted by the base station apparatus 100-2 is received greatly, and null is preferentially given to the base station apparatus or terminal apparatus of the neighboring cell that is likely to be communicating. Therefore, it is possible to efficiently suppress inter-cell interference with respect to neighboring cells.

  In the above, when one base station apparatus 100-2 transmits data addressed to a plurality of terminal apparatuses in its own cell by spatial multiplexing using MU-MIMO, the base station of the neighboring cell while suppressing inter-user interference The case where the precoding which directs null with respect to the apparatus 100-1 and the terminal devices 300-1 to 300-3 was demonstrated was demonstrated. Similarly, the base station device 100-1 estimates the propagation path state between the base station device 100-2 and the terminal devices 300-4 to 300-6 that are neighboring cells for the base station device 100-1, When data addressed to a plurality of terminal devices in its own cell is spatially multiplexed by MU-MIMO and transmitted, while suppressing interference between users, the base station device 100-2 and terminal devices 300-4 to 300- in the neighboring cell Precoding in which null is directed to 6 may be performed.

  FIG. 8 is a flowchart illustrating an example of a flow of transmission processing when the base station apparatus according to the present embodiment transmits data to the terminal apparatus of the own cell.

  The base station apparatus 100 selects a plurality of terminal apparatuses that transmit data from the terminal apparatuses of its own cell based on the data accumulation status in the transmission buffer, the QoS (Quality of Service) information of the transmission data, and the like ( Step S801).

  The base station apparatus 100 transmits a sounding frame for estimating a propagation path state between each antenna of the base station apparatus and one or more antennas of the terminal apparatus to the plurality of terminal apparatuses selected in step S801. Then, each terminal apparatus is fed back and acquired propagation path information based on the propagation path state estimation result (step S802).

  The base station apparatus 100 removes excess antenna freedom, excluding the degree of freedom of antennas necessary to suppress inter-user interference when data is spatially multiplexed with MU-MIMO and transmitted to a plurality of terminal apparatuses in its own cell. Using the degree as the upper limit number, the base station apparatus or terminal apparatus of the neighboring cell storing the propagation path state estimation result is selected (step S803). At this time, base station apparatus 100 is based on the order in which the stored reception quality estimation result is high (the reception signal power is high), the sequence number of the stored channel information request sequence is the newest, or a combination thereof. However, it is preferable to select a base station apparatus or a terminal apparatus of a neighboring cell, but the present invention is not limited to this. Also, base station apparatus 100 groups terminal apparatuses of a plurality of neighboring cells determined to have strong correlation of propagation paths from the propagation path state estimation result, and selects one terminal apparatus as a representative from each group You may do it. At this time, the degree of antenna freedom is only required to direct null toward the selected representative terminal device. As a result of precoding described later, almost all the terminal devices in each group to which the selected representative terminal device belongs are null. Can be directed.

  The base station apparatus 100 is based on the stored propagation path information fed back from the terminal apparatus of its own cell and the propagation path state estimation results of the base station apparatus and the terminal apparatus of the neighboring cell. Or a precoding filter such that a null is directed toward the terminal device and a signal is received with the inter-user interference suppressed for a plurality of terminal devices in the own cell (step S804).

  The base station apparatus 100 generates a transmission signal by multiplying the transmission data addressed to a plurality of terminal apparatuses in the own cell selected in Step S801 by the precoding filter calculated in Step S804, and transmits the transmission signal (Step S805). . At this time, the reference signal and control information included in the frame to be transmitted may be precoded by multiplying the precoding filter.

  As described above, according to the present embodiment, when each base station apparatus spatially multiplexes and transmits data to a plurality of terminal apparatuses in its own cell by MU-MIMO, it is provided between cells that autonomously give to neighboring cells. Precoding that suppresses interference can be performed, and cell throughput in an OBSS environment in which some or all of the cells constituting a plurality of base station apparatuses overlap can be improved.

  In each of the above embodiments, the frame transmission timing, the OFDM symbol timing, and the like are assumed to be asynchronous between the base station apparatus 100-1 and the base station apparatus 100-2, but the present invention is not limited to this. For example, when the base station device 100-2 receives a frame transmitted by the base station device 100-1 of the neighboring cell, for example, the NDPA frame F401 or the NDP frame F402, based on the timing of the frame or the OFDM symbol, It is also possible to adjust the frame transmission timing and OFDM symbol timing when the base station apparatus transmits a frame so that these timings are synchronized with the base station apparatus 100-1.

  In each of the above embodiments, it is assumed that the precoding filter is calculated based on the propagation path state estimation result for each OFDM subcarrier. However, the present invention is not limited to this, and a plurality of subcarriers are used. May be subbanded (grouped) together, and a precoding filter may be calculated for each subband. Further, one subband may be formed by all subcarriers in the OFDM band. In addition, when one subband is comprised by all the subcarriers, it is not necessary to take timing synchronization between base station apparatuses.

  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 the design and the like within the scope of the present invention are also within the scope of the claims. include.

  In addition, this invention is not limited to the above-mentioned embodiment. The terminal device 300 of the present invention is not limited to application to a terminal device such as a wireless LAN system, but is a stationary or non-movable electronic device installed indoors or outdoors, such as an AV device, a kitchen device, etc. Needless to say, the present invention can be applied to cleaning / washing equipment, air conditioning equipment, office equipment, vending machines, and other daily life equipment.

  The program that operates in the base station apparatus 100 and the terminal apparatus 300 related to the present invention is a program (a program that causes a computer to function) that controls the CPU and the like so as to realize the functions of the above-described embodiments related to the present invention. Information handled by these devices is temporarily stored in the RAM at the time of processing, then stored in various ROMs and HDDs, read out by the CPU as necessary, and corrected and written. As a recording medium for storing the program, a semiconductor medium (for example, ROM, nonvolatile memory card, etc.), an optical recording medium (for example, DVD, MO, MD, CD, BD, etc.), a magnetic recording medium (for example, magnetic tape, Any of a flexible disk etc. may be sufficient. In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also based on the instructions of the program, the processing is performed in cooperation with the operating system or other application programs. The functions of the invention may be realized.

  In the case of distribution in the market, the program can be stored and distributed in a portable recording medium, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is also included in the present invention. Moreover, you may implement | achieve part or all of the base station apparatus 100 and the terminal device 300 in embodiment mentioned above as LSI which is typically an integrated circuit. Each functional block of the base station apparatus 100 and the terminal apparatus 300 may be individually made into a processor, or a part or all of them may be integrated into a processor. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

[Summary]
(1) In order to achieve the above object, the present invention takes the following measures. That is, the base station apparatus according to the present invention includes a radio reception unit that receives a first radio frame that is a radio frame transmitted by a terminal device in a neighboring cell, and the peripheral signal based on a reception signal of the first radio frame. A channel estimation unit for estimating a channel state between the terminal device of the cell and the base station device, and precoding for transmission data addressed to the terminal device of the own cell based on the estimation result of the channel state A precoding unit for performing transmission and a wireless transmission unit for transmitting the transmission data subjected to the precoding.

  (2) Moreover, the base station apparatus of this invention memorize | stores the terminal ID acquisition part which acquires terminal ID which identifies the terminal device of the said surrounding cell from the said 1st radio | wireless frame, and the estimation result of the said propagation path state. A propagation path estimation result storage unit that stores the propagation path state estimation result in association with the acquired terminal ID, and the precoding unit includes at least the propagation path Based on one or more propagation path state estimation results selected from a path estimation result storage unit, precoding is performed on transmission data addressed to a terminal device of the own cell.

  (3) Moreover, in the base station apparatus of the present invention, the radio reception unit further receives a second radio frame that is a radio frame transmitted by a base station apparatus of a neighboring cell, and the terminal ID acquisition unit A terminal ID for identifying a terminal device of the neighboring cell is acquired from at least one of the first radio frame and the second radio frame.

  (4) Moreover, the base station apparatus of this invention WHEREIN: The said precoding part selects the estimation result of the said 1 or more propagation path state from the said propagation path estimation result memory | storage part in order newest.

  (5) In the base station apparatus of the present invention, the propagation path estimation unit further estimates the reception quality of the first radio frame, and the propagation path estimation result storage unit stores the propagation path state estimation result. The reception quality estimation result and the acquired terminal ID are stored in association with each other, and the precoding unit receives the reception related to the terminal device of one or more neighboring cells stored in the propagation path estimation result storage unit Based on a quality estimation result, one or more propagation path state estimation results are selected from the propagation path estimation result storage unit.

  (6) Moreover, in the base station apparatus of the present invention, the precoding unit is arranged in descending order of the reception quality estimation results related to terminal devices of one or more neighboring cells stored in the propagation path estimation result storage unit. One or more propagation path state estimation results are selected from the propagation path estimation result storage unit.

  (7) Moreover, in the base station apparatus of the present invention, the precoding unit includes a terminal device of one or more neighboring cells from the propagation path estimation result storage unit, with the number of degrees of freedom of antennas of the base station device as an upper limit. The estimation result of the propagation path state between is selected.

  (8) Moreover, in the base station apparatus of the present invention, the precoding unit is a terminal device of a corresponding neighboring cell based on one or more propagation path state estimation results selected from the propagation path estimation result storage unit. In this case, precoding is performed on transmission data addressed to the terminal device of the own cell so that nulls are suitable.

(9) Also, the base station apparatus of the present invention stores propagation path information based on the propagation path state between the own base station apparatus and the own cell terminal apparatus notified from the own cell terminal apparatus. Further comprising a path information storage unit, wherein the radio reception unit further receives a third radio frame that is a radio frame including the propagation path information notified from the terminal device of the own cell, and the precoding unit Between the channel information notified from one or more terminal devices of the own cell stored in the channel information storage unit and the one or more terminal devices of the neighboring cells selected from the channel estimation result storage unit Based on the estimation result of the propagation path state, precoding is performed on transmission data addressed to the terminal device of the one or more own cells.
(10) Further, in the base station apparatus of the present invention, the precoding unit excludes the degree of freedom of antenna necessary for transmitting transmission data addressed to the terminal apparatus of the one or more own cells. The number of surplus antenna degrees of freedom is set as the upper limit, and the propagation path state estimation result between the terminal apparatuses of one or more neighboring cells is selected from the propagation path estimation result storage unit.

  (11) Moreover, in the base station apparatus of the present invention, the precoding unit is configured to transmit the plurality of channel information based on channel information notified from terminal devices of a plurality of own cells stored in the channel information storage unit. Based on the estimation result of one or more propagation path states selected from the propagation path estimation result storage unit while suppressing inter-user interference when spatially multiplexing transmission data addressed to the terminal device of the own cell and transmitting simultaneously Then, precoding is performed on transmission data addressed to the terminal devices of the plurality of own cells so that nulls are directed to the terminal devices of the corresponding neighboring cells.

  (12) The wireless communication system of the present invention includes a base station device and a terminal device, and the base station device receives a radio frame transmitted from a terminal device in a neighboring cell, and receives a reception signal of the radio frame. Based on the above, the propagation path state between the terminal device of the neighboring cell and the own base station apparatus is estimated, and null is directed to the terminal device of the corresponding neighboring cell based on the estimation result of the propagation path state As described above, the transmission data addressed to the terminal device in the own cell is precoded and transmitted.

  (13) The wireless communication system of the present invention includes a base station device and a terminal device, and the base station device receives a radio frame transmitted from a terminal device in a neighboring cell, and receives a received signal of the radio frame. Based on the above, the propagation path state between the terminal device of the neighboring cell and the own base station device is estimated, and notified from the terminal device of the own cell, between the own base station device and the terminal device of the own cell. Receiving the propagation path information based on the propagation path state of the mobile station, and based on the propagation path information notified from the terminal apparatus of the one or more own cells and the estimation result of the propagation path state, the terminal of the one or more own cells 1 or more so that interference between users when transmitting transmission data addressed to a device and performing simultaneous transmission is suppressed and null is directed to a terminal device of a neighboring cell corresponding to the estimation result of the propagation path state Sending to the terminal device of its own cell And transmitting performing precoding against over data.

  (14) The radio communication method of the present invention is a radio communication method for performing communication between a base station apparatus and a terminal apparatus, wherein the base station apparatus transmits a radio frame transmitted by a terminal apparatus in a neighboring cell. Based on the reception step, on the basis of the received signal of the radio frame, estimating the propagation path state between the terminal device of the neighboring cell and the own base station apparatus, on the basis of the estimation result of the propagation path state, Precoding the transmission data addressed to the terminal device of the own cell, and transmitting the signal subjected to the precoding so that null is directed to the terminal device of the corresponding neighboring cell. It is characterized by that.

  (15) A radio communication method of the present invention is a radio communication method for performing communication between a base station apparatus and a terminal apparatus, wherein the base station apparatus transmits a radio frame transmitted by a terminal apparatus in a neighboring cell. A step of receiving, a step of estimating a propagation path state between the terminal device of the neighboring cell and the own base station device based on a received signal of the radio frame, and a self-report notified from the terminal device of the own cell. A step of receiving propagation path information based on a propagation path state between a base station apparatus and a terminal apparatus of the own cell; the propagation path information notified from one or more terminal apparatuses of the own cell; and the propagation path state Based on the estimation result, the neighboring cells corresponding to the estimation result of the propagation path state are suppressed, and the inter-user interference when the transmission data addressed to the terminal device of the one or more own cells is spatially multiplexed and transmitted simultaneously For terminal equipment As directed null, and having a step of performing precoding on transmission data addressed to the terminal device the one or more of the own cell, and sending a signal subjected to the precoding.

  (16) Moreover, the integrated circuit of the present invention is an integrated circuit that causes the base station device to perform a plurality of functions by being mounted on the base station device, and that is configured to transmit a radio frame transmitted from a terminal device in a peripheral cell. Based on the reception function, the function of estimating the propagation path state between the terminal device of the neighboring cell and the own base station apparatus based on the received signal of the radio frame, and the estimation result of the propagation path state, A series of a function of performing precoding on transmission data addressed to a terminal device of its own cell and a function of transmitting the signal subjected to the precoding so that null is directed to the terminal device of the corresponding neighboring cell The base station apparatus is allowed to exhibit the above function.

  (17) An integrated circuit according to the present invention is an integrated circuit that is mounted on a base station device to cause the base station device to perform a plurality of functions, and that is configured to transmit a radio frame transmitted by a terminal device in a peripheral cell. A function of receiving, a function of estimating a propagation path state between the terminal device of the neighboring cell and the own base station device based on a received signal of the radio frame, and a self-report notified from the terminal device of the own cell. A function of receiving propagation path information based on a propagation path state between a base station apparatus and the terminal apparatus of the own cell, the propagation path information notified from one or more terminal apparatuses of the own cell, and the propagation path state Based on the estimation result, the neighboring cells corresponding to the estimation result of the propagation path state are suppressed, and the inter-user interference when the transmission data addressed to the terminal device of the one or more own cells is spatially multiplexed and transmitted simultaneously For other terminal devices The base station has a series of functions of a function of performing precoding on transmission data addressed to the terminal device of the one or more own cells and a function of transmitting the signal subjected to the precoding. The apparatus is characterized by being exhibited.

  The present invention is suitable for use in base station apparatuses, wireless communication systems, wireless communication methods, and integrated circuits.

100, 100-1, 100-2 Base station apparatus 201 Error correction coding section 202 Modulation section 203 Reference signal multiplexing section 204 Precoding section 205 IFFT section 206 GI insertion section 207 Radio transmission section 208 Antenna section 209 Radio reception section 210 GI Removal unit 211 FFT unit 212 Reference signal separation unit 213 Channel estimation unit 214 Equalization unit 215 Demodulation unit 216 Error correction decoding unit 217 Upper layer 218 Channel information storage unit 219 Channel estimation result storage unit 220 Terminal ID acquisition unit 300 , 300-1 to 300-6 Terminal device 301 Antenna unit 302 Radio reception unit 303 GI removal unit 304 FFT unit 305 Reference signal separation unit 306 Channel estimation unit 307 Equalization unit 308 Demodulation unit 309 Error correction decoding unit 310 Error correction Encoding unit 311 Modulating unit 312 Reference signal multiplexing unit 313 IFF Part 314 GI inserting section 315 radio transmission unit 316 upper layer

Claims (9)

A radio reception unit that receives a first radio frame transmitted from a first terminal device belonging to a neighboring cell to a base station device of the neighboring cell ;
Based on the received signal of the first radio frame, reception of the first and the propagation path state, the base station apparatus of the first radio frame between said first terminal apparatus and the base station apparatus Quality A channel estimation unit for estimating
A propagation path estimation result storage unit for storing the estimation result of the first propagation path state and the estimation result of the reception quality;
Select the estimation result of the first channel state regarding a high one or more of the first terminal device of the reception quality estimation result from the channel estimation result storage unit, the first propagation path state in which the selected A precoding unit that performs precoding on transmission data addressed to a second terminal device belonging to the own cell so that nulls are directed to the corresponding first terminal device based on the estimation result;
A base station apparatus comprising: a wireless transmission unit that transmits transmission data subjected to the precoding. The precoding unit selects one or more first propagation path state estimation results from the propagation path estimation result storage unit with the number of antenna degrees of freedom of the base station apparatus as an upper limit. Item 8. The base station apparatus according to Item 1. A propagation path information storage unit for storing propagation path information based on a second propagation path state between the base station apparatus and the second terminal apparatus notified from the second terminal apparatus;
The wireless reception unit further receives a third wireless frame that is a wireless frame including the propagation path information notified from the second terminal device;
The precoding unit includes the channel information notified from the one or more second terminal devices stored in the channel information storage unit and the one or more first channels selected from the channel estimation result storage unit. 2. Precoding is performed on transmission data addressed to the one or more second terminal apparatuses based on an estimation result of the first propagation path state with one terminal apparatus. Or the base station apparatus of Claim 2 . The precoding unit uses, as an upper limit, the number of surplus antenna degrees of freedom of the base station apparatus excluding antenna degrees of freedom necessary for transmitting transmission data addressed to the one or more second terminal apparatuses. The base station apparatus according to claim 3 , wherein an estimation result of the first propagation path state between one or more first terminal apparatuses is selected from a propagation path estimation result storage unit . The precoding unit spatially multiplexes transmission data addressed to the plurality of second terminal apparatuses based on the propagation path information notified from the plurality of second terminal apparatuses stored in the propagation path information storage unit. And inter-user interference when simultaneously transmitting, and based on one or more first propagation path state estimation results selected from the propagation path estimation result storage unit, the corresponding first The base station apparatus according to claim 3 or 4 , wherein precoding is performed on transmission data addressed to the plurality of second terminal apparatuses so that nulls are directed toward the terminal apparatus. A wireless communication system comprising a base station device and a terminal device,
The base station device
A first terminal device belonging to a neighboring cell receives a first radio frame transmitted to a base station device of the neighboring cell;
Based on the received signal of the first radio frame, the first propagation path state between the first terminal device and the own base station device, and the reception quality of the first radio frame at the own base station device Estimate
In order from the highest reception quality estimation result, select the first propagation path state estimation result for one or more corresponding first terminal apparatuses, and select the first propagation path state estimation result for each of the selected first propagation path state estimation results. A radio communication system, wherein transmission data addressed to a second terminal device belonging to the own cell is precoded and transmitted so that null is directed to the corresponding first terminal device . A wireless communication system comprising a base station device and a terminal device,
The base station device
A first terminal device belonging to a neighboring cell receives a first radio frame transmitted to a base station device of the neighboring cell ;
Based on the received signal of the first radio frame, reception of the first and the propagation path state, the base station apparatus of the first radio frame between said first terminal apparatus and the base station apparatus Quality Estimate
Receiving the propagation path information based on the second propagation path state between the own base station apparatus and the second terminal apparatus notified from the second terminal apparatus belonging to the own cell;
The one or more corresponding first or more first selected in descending order of the estimation result of the reception quality in the base station apparatus of the first radio frame and the propagation path information notified from the one or more second terminal apparatuses Based on the estimation result of the first propagation path state relating to the terminal device, suppressing interference between users when the transmission data addressed to the one or more second terminal devices is spatially multiplexed and simultaneously transmitted, and Precoding is performed on transmission data addressed to the one or more second terminal apparatuses so that nulls are directed to the first terminal apparatuses corresponding to estimation results of the one or more first propagation path states. A wireless communication system characterized by performing transmission. By being mounted on a base station device, an integrated circuit that allows the base station device to perform a plurality of functions,
A function of receiving a first radio frame transmitted from a first terminal device belonging to a neighboring cell to a base station device of the neighboring cell;
Based on the received signal of the first radio frame, the first propagation path state between the first terminal device and the own base station device, and the reception quality of the first radio frame at the own base station device A function for estimating
Selecting the corresponding one or more first propagation path state estimation results in descending order of the reception quality estimation results;
Based on the selected one or more first propagation path state estimation results, the transmission data addressed to the second terminal device belonging to the own cell is transmitted so that the null is directed to the corresponding first terminal device. The ability to pre-code for
A function of transmitting the precoded signal and a series of functions of the base station device
An integrated circuit characterized by being exhibited in a device . By being mounted on a base station device, an integrated circuit that allows the base station device to perform a plurality of functions,
A function of receiving a first radio frame transmitted from a first terminal device belonging to a neighboring cell to a base station device of the neighboring cell ;
Based on the received signal of the first radio frame, reception of the first and the propagation path state, the base station apparatus of the first radio frame between said first terminal apparatus and the base station apparatus Quality A function for estimating
A function of receiving propagation path information based on a propagation path state between the own base station apparatus and the second terminal apparatus belonging to the own cell, notified from the second terminal apparatus belonging to the own cell;
A function of selecting one or more corresponding first propagation path state estimation results in descending order of the reception quality estimation results;
Transmission to the one or more second terminal apparatuses based on the propagation path information notified from the one or more second terminal apparatuses and the estimated result of the selected one or more first propagation path states Suppresses inter-user interference when data is spatially multiplexed and transmitted simultaneously, and nulls are directed toward the first terminal device corresponding to the selected one or more first propagation path state estimation results. A function of performing precoding on transmission data addressed to the one or more second terminal devices;
An integrated circuit characterized by causing the base station apparatus to exhibit a series of functions including a function of transmitting the precoded signal.

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