JP5753520B2 - Wireless communication system and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication system and a wireless communication method for simultaneously communicating with a plurality of communication partners using spatial multiplexing.

  In recent years, as a high-speed wireless access system using the 2.4 GHz band or the 5 GHz band, base station apparatuses (AP: Access point) based on the IEEE802.11g standard, the IEEE802.11a standard, and the like are widely spread. In systems based on these standards, an orthogonal frequency division multiplexing (OFDM) modulation method, which is a technology for stabilizing the characteristics in a multipath fading environment, is used, and a transmission rate of 54 Mbps is realized at the maximum. doing.

  However, the transmission rate described above is a transmission rate on the physical layer, and is not a data throughput effective for the user. Actually, since the transmission efficiency in the MAC (Medium Access Control) layer is about 50 to 70%, the throughput has an upper limit of about 30 Mbps.

  On the other hand, the communication speed of a wired LAN (Local Area Network) has been increasing with the spread of FTTH (Fiber to the home). Along with this, it is assumed that further increase in transmission speed will be demanded in the wireless LAN. Therefore, various spatial signal processing techniques such as MIMO (Multiple Input Multiple Output) and multi-user MIMO are being studied in order to increase the throughput of the radio section. As another method, the communication frequency band is expanded. In IEEE802.11a, a frequency band of 20 MHz is used for each channel. In IEEE802.11n, a frequency band of 40 MHz is used. Further, IEEE 802.11ac is considered up to 160 MHz when options are included. In this way, channel band expansion is progressing.

  As described above, the frequency band of the channel extends from IEEE802.11a to 11ac and is expanded eight times. However, no major expansion has been recognized for the entire frequency band that can be used for a wireless LAN. Thus, with the spread of wireless terminal stations, frequency resources are becoming insufficient. For example, an environment in which a plurality of base stations use the same frequency band is increasing. For this reason, depending on the channel selected by the base station, there is a problem that the throughput decreases due to the influence of packet signals from other base stations with which communication cells overlap each other, and the throughput efficiency of the entire system decreases. It was.

  Therefore, multiple base stations control the directivity of radio waves (transmit beamforming), and each base station performs its own communication simultaneously while suppressing interference to nearby communication cells, thereby allowing the transmission rate of the entire system Is being studied (see, for example, Non-Patent Document 1 and Non-Patent Document 2). In this technique, a plurality of base stations controls the directivity of radio waves using a plurality of antennas mounted on each base station, and changes the phase rotation amount of a signal transmitted from each antenna.

  FIG. 13 shows an example of conventional base station cooperative transmission. Base station 101 and base station 102 are wired to network 100, base station 101 communicates wirelessly with terminal stations 201-1 to 201-2 which are terminal stations under its own base station, and base station 102 Consider wireless communication with terminal stations 202-1 to 202-2 which are terminal stations under its own base station. When trying to perform wireless communication at the same time and frequency, the base station 101 uses a plurality of antennas, and directivity control is applied to the terminal stations 201-1 and 201-2 under its own base station (own cell). In addition to wireless communication, since radio signals interfere with terminal stations 202-1 and 202-2 which are terminal stations under other base stations (other cells), interference control is performed by null directivity control. Similarly, the base station 102 wirelessly communicates with the terminal station 202-1 and the terminal station 202-2 under its own base station (own cell) by directivity control using a plurality of antennas, and is also under the control of other base stations ( Since radio signals interfere with terminal stations 201-1 and 201-2, which are terminal stations of other cells, interference control is performed by null directivity control. As described above, the base station 101 and the base station 102 can simultaneously communicate with terminal stations under their own base station at the same time and at the same frequency.

A. Nosratinia, T. E. Hunter, and A. Hedayat, “Cooperative Communication in Wireless Networks,” IEEE Communication Magazine, Oct. 2004. Koichi Ishihara, Tomonori Murakami, Riichi Kudo, Yusuke Asai, Takeo Ichikawa, Tomoaki Kumagai, Hayato Mizoguchi, "Indoor experiment evaluation of real-time downlink MU-MIMO transmission equipment using inter-cell interference control in next-generation wireless LAN", IEICE Society Conference, B-5-98, September 2011

  However, in the coordinated transmission technology in which a plurality of base stations simultaneously transmit data to the terminal stations under their control at the same frequency, in order to perform directivity control by transmission beam forming, the transmission base station to the connection terminal station in its own cell In addition to channel state information (CSI), CSI with terminal stations in other cells that perform interference control is also required. There are two CSI feedback methods for obtaining CSI, a closed loop type and an open loop type. In the case of the closed-loop type, the amount of CSI feedback increases as the number of transmission / reception antennas and the number of terminal stations increase. Furthermore, in coordinated transmission, overhead due to CSI feedback between other cells becomes larger than in conventional multi-user MIMO transmission, and more accurate CSI estimation values are required. On the other hand, when the base station 101 and the terminal station 202-2 in FIG. 13 are distant from the base station that transmits the interference signal, as in the relationship between the base station 102-2 and the base station 102 and the terminal station 201-1 (communication cell). Because the reception sensitivity of radio signals from interfering base stations is reduced, there is no need to perform interference control for such terminal stations, and in addition, radio signals are received from interfering base stations. Since the sensitivity is small, an estimation error of CSI occurs. For this reason, when performing interference control for all terminal stations as in the prior art, throughput deteriorates due to overhead generated by terminal stations that are distant from the base station that transmits the interference signal and performing CSI feedback. In addition, the characteristics may be deteriorated due to a loss of diversity gain due to an estimation error of CSI and a loss of freedom of antenna.

  The present invention has been made to solve the above problems, and a wireless communication system and a wireless communication in which a plurality of transmitting station apparatuses such as base stations can perform wireless communication at the same frequency at the same time without degrading characteristics due to high system throughput. Provide a method.

  In order to solve the above-described problem, the present invention is a wireless communication system in which a plurality of transmitting station apparatuses perform simultaneous transmission of data to receiving station apparatuses under their own transmitting station apparatuses using the same frequency. The plurality of transmission station apparatuses include a transmission station side radio unit that transmits and receives radio signals, a control signal generation unit that generates a known signal and transmits the known signal, and the subordinate station under the own transmission station apparatus Among the receiving station devices under the receiving station device and the other transmitting station devices, the receiving station device from which the receiving sensitivity of the known signal transmitted by the transmitting station device is equal to or higher than a threshold value A transmission weight for performing interference control on the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity is equal to or higher than a threshold, using the channel information received by Calculate the sending Using the weight calculation unit and the transmission weight calculated by the transmission weight calculation unit, a data transmission signal to be transmitted to the reception station device under its own transmission station device is generated, and the generated data transmission signal is transmitted to the transmission station A transmission signal generating unit that simultaneously transmits with another transmitting station device from a station-side wireless unit, and the receiving station device to which any of the plurality of transmitting station devices is assigned receives and transmits a wireless signal A station-side radio unit, a reception sensitivity measuring unit that measures the reception sensitivity of the known signal received by the receiving station-side radio unit from the transmitting station device other than the assigned station, and the receiving station from the transmitting station device that is the assigned destination Estimating channel information with the transmitting station device to which it is assigned based on the known signal received by the side radio unit, and when the reception sensitivity measured by the reception sensitivity measurement unit is greater than or equal to the threshold value, In addition, a channel information estimation unit that estimates channel information with the transmission station device other than the assigned destination based on the known signal received from the transmission station device other than the assigned destination, and the channel information estimating unit estimates the channel information And a channel information transmitting unit that transmits the channel information from the receiving station side wireless unit.

  Further, the present invention is a wireless communication system in which a plurality of transmitting station apparatuses perform simultaneous transmission of data to receiving station apparatuses under their own transmitting station apparatuses using the same frequency, and the plurality of transmitting station apparatuses A transmission station side radio unit that transmits and receives radio signals, and a reception sensitivity measurement unit that measures reception sensitivity of the control signal received by the transmission station side radio unit from the reception station device under the other transmission station device, And generating a known signal to the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose receiving sensitivity measured by the receiving sensitivity measuring unit is equal to or higher than a threshold value. On the other hand, from the control signal generation unit to be transmitted from the transmitting station side radio unit, the receiving station device subordinate to the own transmitting station device, and the receiving station device subordinate to the other transmitting station device whose reception sensitivity is equal to or higher than a threshold value No transmission station Using the channel information received by the transmission unit, interference control is performed on the receiving station device subordinate to the own transmitting station device and the receiving station device subordinate to the other transmitting station device whose reception sensitivity is equal to or higher than a threshold value. A transmission weight calculation unit for calculating a transmission weight, and a data transmission signal to be transmitted to the reception station device under its transmission station device using the transmission weight calculated by the transmission weight calculation unit, A transmission signal generating unit that simultaneously transmits a data transmission signal from the transmitting station side wireless unit to another transmitting station device, and the receiving station device to which any of the plurality of transmitting station devices is assigned is a wireless Channel information between the receiving station side radio unit that transmits and receives signals and the destination station transmitting unit based on the known signal received by the receiving station side radio unit from the assigned transmitting station device is estimated. A channel information estimating unit that estimates channel information between the transmitting station device other than the assigned destination based on the known signal received by the receiving station side wireless unit from the transmitting station device other than the assigned destination; A wireless communication system comprising: a channel information transmitting unit that transmits the channel information estimated by the channel information estimating unit from the receiving station side wireless unit.

Further, the present invention is a radio communication system that performs simultaneous transmission of data to a plurality of transmission stations receiving station device of its own transmission station under each using the same frequency, the plurality of transmission stations instrumentation From a transmitting station side radio unit that transmits and receives radio signals, a control signal generation unit that generates a known signal and transmits it by the transmitting station side radio unit, and the receiving station device under the other transmitting station device A reception sensitivity measurement unit that measures reception sensitivity of channel information received by the transmission station side radio unit, channel information received by the transmission station side radio unit from the reception station device under its own transmission station device, and the other Of the channel information received by the transmitting station side radio unit from the receiving station device under the transmitting station device, the channel information whose reception sensitivity measured by the reception sensitivity measurement unit is equal to or greater than a threshold is used. A transmission weight calculation unit for calculating a transmission weight for performing interference control on the reception station device under the communication station device and the reception station device under the other transmission station device whose reception sensitivity is equal to or higher than a threshold; Using the transmission weight calculated by the transmission weight calculation unit, a data transmission signal to be transmitted to the receiving station device under its own transmitting station device is generated, and the generated data transmission signal is transmitted from the transmitting station side radio unit. A transmission signal generating unit that transmits simultaneously with the other transmitting station devices, and the receiving station device to which any of the plurality of transmitting station devices is assigned includes: a receiving station side radio unit that transmits and receives radio signals; , Estimating channel information between the transmitting station apparatus to which the receiving station side radio unit is assigned based on the known signal received from the transmitting station apparatus to which the receiving station is assigned, and from the transmitting station apparatus other than the assigning destination. Previous Based on the known signal received by the receiving station side radio unit, a channel information estimation unit that estimates channel information with the transmitting station device other than the destination, and the channel information estimated by the channel information estimation unit A wireless communication system comprising: a channel information transmitting unit that transmits from a receiving station side wireless unit.

  Further, the present invention is the above-described wireless communication system, wherein the transmission weight calculation unit uses the calculated transmission weight from the transmitting station device in the receiving station device subordinate to the other transmitting station device. When interference power is calculated, and there is the receiving station apparatus with the calculated interference power equal to or greater than a threshold, the transmission weight is recalculated using the channel information of the receiving station apparatus with the interference power equal to or greater than the threshold. It is characterized by.

Further, the present invention is a radio communication system described above, pre-Symbol transmitting station radio unit, following reception sensitivity threshold between the subject transmission station device and another of said receiving station device of said subordinate transmitting station The transmission power is controlled so that

  Further, the present invention is the above-described wireless communication system, wherein the reception sensitivity measurement unit includes, as the reception sensitivity, reception intensity, signal-to-noise power ratio, carrier-to-noise power ratio, signal-to-interference power ratio, signal-to-interference -Measuring at least one of the noise power ratios.

  Further, the present invention is a wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station devices using the same frequency, The plurality of transmitting station devices transmit a known signal, and the receiving station device to which any of the plurality of transmitting station devices is assigned is received from the transmitting station device other than the assigned destination. Receiving sensitivity measurement step for measuring the receiving sensitivity of the known signal, and estimating channel information between the transmitting station apparatus to which it is assigned based on the known signal received from the transmitting station apparatus to which it is assigned, and the reception If the reception sensitivity of the known signal measured in the sensitivity measurement step is greater than or equal to a threshold value, further, before the other than the assigned destination based on the known signal received from the transmitting station device other than the assigned destination A channel information estimating step for estimating channel information between the transmitting station device, a channel information transmitting step for transmitting the channel information estimated in the channel information estimating step, and the plurality of transmitting station devices comprising: The receiving station apparatus in which the reception sensitivity of the known signal transmitted by the own transmitting station apparatus among the receiving station apparatuses subordinate to the other transmitting station apparatus and the channel information received from the receiving station apparatus under control is equal to or greater than a threshold value Interference with the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity of the known signal is equal to or higher than a threshold using the channel information received from A transmission weight calculation step for calculating a transmission weight to be controlled, and a self-transmission using the transmission weight calculated in the transmission weight calculation step Generates data transmission signal to be transmitted to the receiving station apparatus under the station apparatus, a wireless communication method characterized by comprising: a data transmission step of transmitting simultaneously with the other of said transmitting station, the.

  Further, the present invention is a wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station devices using the same frequency, The plurality of transmitting station apparatuses measure a receiving sensitivity of a control signal received from the receiving station apparatus under the other transmitting station apparatus, the receiving station apparatus under its own transmitting station apparatus, and A known signal transmitting step of transmitting a known signal to the other receiving station devices under the transmitting station device whose receiving sensitivity measured in the receiving sensitivity measuring step is equal to or greater than a threshold; and a plurality of transmitting station devices The receiving station apparatus to which any one of the destinations is assigned estimates channel information with the destination transmitting station apparatus based on the known signal received from the destination transmitting station apparatus, and the destination station A channel information estimation step for estimating channel information with the transmission station device other than the destination based on the known signal received from the other transmission station device; and the channel information estimated in the channel information estimation step. The channel information transmission step for transmitting, and the plurality of transmitting station devices receive from the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity is equal to or higher than a threshold value. The transmission weight for performing interference control on the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity is equal to or higher than a threshold using the channel information A transmission weight calculation step to calculate, and the transmission weights calculated in the transmission weight calculation step using the transmission weights Generates data transmission signal to be transmitted to the signal station apparatus, a wireless communication method characterized by comprising: a data transmission step of transmitting simultaneously with the other of said transmitting station, the.

  Further, the present invention is a wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station devices using the same frequency, The plurality of transmitting station devices transmit a known signal, and the receiving station device to which any of the plurality of transmitting station devices is assigned is received from the transmitting station device to which it is assigned. Estimating channel information with the transmitting station device to which it is assigned based on a known signal, and with the transmitting station device other than the destination based on the known signal received from the transmitting station device other than the destination A channel information estimation step for estimating the channel information, a channel information transmission step for transmitting the channel information estimated in the channel information estimation step, and the plurality of transmission station apparatuses A reception sensitivity measurement step for measuring the reception sensitivity of the channel information received from the receiving station device under the other transmitting station device; channel information received from the receiving station device under the own transmitting station device; Using the channel information with the reception sensitivity measured in the reception sensitivity measurement step of the channel information received from the reception station device under the transmission station device being a threshold value or more, the subordinate under the transmission station device In a transmission weight calculating step for calculating a transmission weight for performing interference control with respect to a receiving station device and the other receiving station devices under the transmitting station device whose receiving sensitivity is equal to or higher than a threshold value, and in the transmitting weight calculating step Generate a data transmission signal to be transmitted to the receiving station device under its own transmitting station device using the calculated transmission weight, Is a wireless communication method characterized by having a data transmission step of transmitting station apparatus simultaneously transmits.

  According to the present invention, the transmitting station apparatus feeds back channel information to a receiving station apparatus whose receiving sensitivity is equal to or higher than a predetermined threshold among receiving station apparatuses under other transmitting station apparatuses that may cause interference. Is performed to perform interference control (null directivity control), and a transmission beamforming method that does not perform feedback of channel information and does not perform interference control is established for a receiving station apparatus that does not satisfy the threshold. As a result, overhead due to feedback of channel information is reduced, transmission characteristics are improved by suppressing CSI estimation errors and antenna diversity gain, and multiple transmitter stations can be simultaneously characterized by high system throughput at the same frequency. It is possible to perform wireless communication with a plurality of receiving station apparatuses without degrading.

It is a figure which shows the structural example of the radio | wireless communications system by 1st Embodiment of this invention. It is a schematic block diagram which shows the internal structure of the base station by the embodiment. It is a schematic block diagram which shows the internal structure of the terminal station by the embodiment. It is a figure which shows the frame sequence by the embodiment. It is a flowchart which shows the example of a process sequence of the necessity determination process of the CSI feedback in the terminal station by the embodiment. It is a schematic block diagram which shows the internal structure of the base station by 2nd Embodiment. It is a schematic block diagram which shows the internal structure of the terminal station by the embodiment. It is a figure which shows the frame sequence by the embodiment. It is a flowchart which shows the example of a process sequence of the necessity determination process of the CSI feedback in the base station by the embodiment. It is a flowchart which shows the example of a process sequence of the weight calculation process by the base station in the embodiment. It is a figure which shows the item of the computer simulation of 1st Embodiment. It is a figure which shows the result of the computer simulation of 1st Embodiment. It is a figure which shows an example of the conventional base station cooperation transmission.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram illustrating a configuration example of a radio communication system according to the first embodiment of the present invention.
As shown in the figure, the wireless communication system according to the first embodiment includes a plurality of base stations as transmission station apparatuses connected to a network 1000 by wire, and a plurality of reception station apparatuses that wirelessly communicate with the transmission station apparatus. And a terminal station. A plurality of base stations simultaneously transmit data to terminal stations under their own base station using the same frequency.

In the following description, in order to simplify the description, as shown in the figure, there are two base stations 1001 and 1002 as a plurality of base stations connected to the network 1000, and the base station 1001 is the own base station. A data signal is transmitted to terminal stations 2001-1 to 2001 -N ₁ (N ₁ ≧ 1, N ₁ is an integer) which is a terminal station in the subordinate (in its own cell). Consider transmitting a data signal to terminal stations 2002-1 to 2002-N ₂ (N ₂ ≧ 1, N ₂ is an integer) which are terminal stations in the own cell. Hereinafter, the terminal stations 2001-1 to 2001 -N ₁ assigned to the base station 1001 (under the base station 1001) are collectively referred to as the terminal station 2001, and the assigned destination is the base station 1002 (base station 1002 under the) are collectively terminal station _{2002-1~2002-N 2} to as terminal station 2002.

Among the terminal stations 2001 subordinate to the base station 1001, the terminal stations 2001-1 to 2001-M ₁ (1 ≦ M ₁ ≦ N ₁ , M ₁ is an integer) are among the communication cells of the adjacent (interfering) base station 1002. Or, it is arranged in an area where the reception sensitivity of the interference signal from the base station 1002 is equal to or higher than a threshold, and the terminal stations 2001- (M ₁ +1) to 2001-N ₁ are located outside the communication cell of the base station 1002 or It is arranged in an area where the reception sensitivity of the interference signal from the station 1002 is less than the threshold value. Also, among the terminal stations 2002 under the base station 1002, terminal stations 2002-1 to 2002-M ₂ (1 ≦ M ₂ ≦ N ₂ , M ₂ is an integer) are adjacent (interfering) communication cells of the base station 1001 that are adjacent (interfering). Or in an area where the reception sensitivity of the interference signal from the base station 1001 is equal to or higher than the threshold, and the terminal stations 2002- (M ₂ +1) to 2002-N ₂ are outside the communication cell of the base station 1001, or In the area where the reception sensitivity of the interference signal from the base station 1001 is less than the threshold value.

  For simplicity of explanation, the number of antenna elements in each of the base stations 1001 and 1002 is A (A ≧ 2, A is an integer), and the number of antenna elements in each of the terminal stations 2001 and 2002 is B (B ≧ 1, B Is an integer) book. However, this embodiment is applicable even when there are three or more base stations, and the number of antenna elements of the base station and the terminal station may be different.

In the first embodiment, first, the base station 1001 wirelessly transmits a known signal frame (hereinafter referred to as “sounding frame”) for CSI (Channel state information) estimation to a terminal station group. . Each of the terminal stations 2001-1 to 2001 -N ₁ , 2002-1 to 2002 -M ₂ estimates the CSI between the base station 1001 and the terminal station using the received sounding frame. However, for the terminal stations 2002- (M ₂ +1) to 2002-N _{2 in} which the sounding frame from the base station 1001 cannot be received or the reception sensitivity of the sounding frame is less than the threshold value P _Th , CSI is not estimated.

Subsequently, the base station 1002 wirelessly transmits a sounding frame, which is a known signal frame for CSI estimation, to the terminal station group. Each of the terminal stations 2001-1 to 2001-M ₁ and 2002-1 to 2002-N ₂ estimates the CSI between the base station 1002 and the terminal station using the received sounding frame. However, for the terminal stations 2001- (M ₁ +1) to 2001-N _{1 in} which the sounding frame from the base station 1002 cannot be received or the reception sensitivity of the sounding frame is less than the threshold value P _Th , CSI is not estimated.

Thereafter, each of the terminal stations 2001-1 to 2002 -N ₁ and 2002-1 to 2002 -N ₂ feeds back the estimated CSI to the base station 1001 and the base station 1002. However, the terminal stations 2002- (M ₂ +1) to 2002-N ₂ that have not estimated the CSI with the base station 1001 are not fed back to the base station 1001, and the CSI with the base station 1002 is estimated. not be fed back to the base station 1002 for never been terminal station _{2001- (M 1 +1) ~2001-} N 1. Finally, each base station 1001 and base station 1002 is based on the feedback CSI, and the reception sensitivity of the sounding frame transmitted from the terminal station under its own base station and its own base station is more than a threshold. A transmission weight for performing interference control with a receiving station apparatus under the base station is calculated, and base station cooperative transmission is performed using the calculated transmission weight.

[Mathematical Expression of First Embodiment]
Hereinafter, as an example, the base station 1001 communicates with a terminal station 2001-n ₁ (1 ≦ n ₁ ≦ N ₁ , where n ₁ is an integer) that is _one of the terminal stations 2001-1 to 2001-N ₁ , base station 1002 is a terminal station _2002-n 2 is either a terminal station _{2002-1~2002-n 2 (1 ≦ n} 2 ≦ n 2, n 2 is an integer) given that communicate respect. Further, as an example of the transmission weight, a description will be given using the zero forcing transmission weight shown in Reference Document 1 below. With the zero forcing transmission weight, the transmission weight is determined so that an interference signal does not arrive.

(Reference 1) Riichi Kudo, Tomonori Murakami, Takeo Ichikawa, Yasushi Takatori, Hayato Mizoguchi, Masahiro Morikura, “Allocation of Spatial Resources in Overlapping Communication Cells 1-Characteristic Analysis Using Office Propagation Measurement Channels”, Shin Academic Report, AP2010-33, pp.7-12, June 2010

First, the received signal vector y _{n1 of} the terminal station 2001-n ₁ and the received signal vector y _n2 of the terminal station 2002-n ₂ can be expressed as the following equations (1) and (2), respectively.

_{However, H D, 1, n1} is the channel matrix of B × A from the base station 1001 to the terminal station _{2001-n 1, H D,} 2, n2 is, B from the base station 1002 to the terminal station _{2002-n 2} channel matrix _{× a, H I, 1,} n2 is the interference channel matrix B × a from the base station 1001 to the terminal station _{2002-n 2, H I,} 2, n1 is the terminal station from the base station 1002 2001- Represents a B × A interference channel matrix for n ₁ . W _{1, n} represents an A × B transmission weight matrix in the base station 1001, and W _{2, n} represents an A × B transmission weight matrix in the base station 1002. x _{1, n} is a transmission symbol vector from the base station 1001 to the terminal station 2001-n (1 ≦ n ≦ N ₁ , n is an integer), and x _{2, n} is from the base station 1002 to the terminal station 2002-n (1 ≦ n ≦ N ₂ , where n is an integer). n _n1 represents a noise vector in the terminal station 2001-n ₁ , and n _n2 represents a noise vector in the terminal station 2002-n ₂ .

In the following, calculation of transmission weight matrix W _{1, n} for terminal station 2001-n ₁ and transmission weight matrix W _{2, n} for terminal station 2002-n ₂ will be described. When performing OFDM (Orthogonal Frequency Division Multiplexing) transmission in a wireless LAN system or the like, this operation is performed for each subcarrier.

Base station 1001, between the terminal station 2001, and the terminal station 2002 causes interference other than the terminal station _{2001-n 1} of the communication target, i.e., the terminal station in the own cell other than the terminal station _{2001-n 1} 2001-1 ˜2001- (n ₁ −1), 2001- (n ₁ +1) ˜2001-N ₁ , and terminal stations 2002-1 to 2002-M ₂ having a reception sensitivity equal to or higher than the threshold value P _Th among the terminal stations in other cells. A singular value decomposition (SVD) is performed on the combined matrix obtained by combining the estimated values of the CSI matrix of B (N ₁ −1 + N) × A between

However, right shoulder ^T represents transposition, and right shoulder ^H represents Hermitian transposition. ^~ H _{D, 1, n} is the channel matrix _{H D} of B × A from the base station 1001 to the terminal station 2001-n (1 ≦ n ≦ N 1, n is an _{integer), 1,} estimate of ^_n, ~ H _{I, 1, n} are estimated values of the B × A interference channel matrix H _{I, 1, n} from the base station 1001 to the terminal station 2002-n (1 ≦ n ≦ M ₂ , where n is an integer). The coupling matrix _{^{[~ H T D, 1,1 ···}} ~ H T D, 1, n1-1 ~ H T D, 1, n1 + 1 ··· ~ H T D, 1, N1 ~ H T I, When _{^{1,1 ··· ~ H T I, 1}} , M2] T = ~ H 1, n1, U I, 1, n1 ^is left singular vectors of _{~ H 1, n1, Σ I} , 1, n1 is , diagonal ^matrix, _{V (s) I,} the singular values _{1, n1} ^is, ~ _{H 1, n1} matrix contains the corresponding vectors eigenvalues of right singular vectors _{^{of, V (n) I, 1}} , n1 Is a matrix including a vector corresponding to a zero matrix among right singular vectors of ^~ H1 _{, n1} . At this time, V ⁽ⁿ⁾ _{I, 1, n1} is a vector that does not correspond to a singular value. Therefore, when transmission is performed using this vector V ⁽ⁿ⁾ _{I, 1, n1} , Terminal stations 2002-1 to 2001- (n ₁ -1), 2001- (n ₁ +1) to 2001-N ₁ , and terminal stations 2002 having a reception sensitivity equal to or higher than a threshold value P _Th among other terminal stations in other cells. so that interference does not occur in 1 to _{2,002-M 2.} Therefore, since it is only necessary to determine the transmission weight in this non-interference space, the channel matrix of the terminal station 2001 of the own cell may be projected onto the non-interference space. SVD is performed on the channel matrix in the non-interference space as shown in the following equation (4).

Here, U _{N, 1, n1} is the left singular vector of the matrix ^to _{HD, 1, n1} V ⁽ⁿ⁾ _{I, 1, n1} , and ΣN _{, 1, n1} is a diagonal matrix of singular values. ^~ V ^(s) _{N, 1, n1} is a matrix containing a vector corresponding to an eigenvalue among right singular vectors of ^~ _{HD , 1, n1V} ⁽ⁿ⁾ _{I, 1, n1} , ^~ V ⁽ⁿ⁾ _{n, 1, n1} ^{is _{~ H D, 1, n1 V}} (n) I, 1, n1 matrix that contains the vector corresponding to the zero matrix of right singular vectors of. The right singular matrix V ^(s) _{N, 1, n1 corresponding} to the singular value at this time is changed from the base station 1001 to the terminal stations 2001-1 to 2001- (n ₁ -1), 2001- (n ₁ +1) in the own cell. ˜2001-N ₁ and the transmission capacity to the terminal station 2001-n ₁ without interfering with the terminal stations 2002-1 to 2002-M ₂ having a reception sensitivity equal to or higher than the threshold value P _Th among the terminal stations in other cells. Corresponds to the transmission weight to be maximized. Therefore, the transmission weight W _n1 in the zero forcing transmission is expressed by the following equation (5).

Similarly, the base station 1002 is between the terminal station 2001 and the terminal station 2002 that cause interference other than the terminal station 2002-n ₂ to be communicated, that is, the terminal station in its own cell other than the terminal station 2002-n _2. Among terminal stations in 2002-1 to 2002- (n ₂ -1), 2002 (n ₂ +1) to 2002-N ₂ , and terminal stations in other cells, the terminal stations 2001-1 to 2001 having a reception sensitivity equal to or higher than the threshold value P _Th. The SVD for the combined matrix obtained by combining the estimated values of the CSI matrix of B (N ₂ −1 + N) × A between −M ₁ is performed as in the following Expression (6).

^However, ~ _{H D, 2, n} is the estimate of the channel matrix _{H D, 2, n} of B × A from the base station 1002 to the terminal station 2002-n (1 ≦ n ≦ N 2, n is an integer), ^~ H _{I, 2, n} is from base station 1002 terminal station 2001-n (1 ≦ n ≦ M 1, n is an integer) is the estimate of the interference channel matrix _{H I, 2, n} of B × a to . The coupling matrix _{^{[~ H T D, 2,1 ···}} ~ H T D, 2, n2-1 ~ H T D, 2, n2 + 1 ··· ~ H T D, 2, N2 ~ H T I, When _{^{2,1 ··· ~ H T I, 2}} , M1] T = ~ H 2, n2, U I, 2, n1 ^is left singular vectors of _{~ H 2, n2, Σ I} , 2, n2 is diagonal matrix of singular _{^{values, V (s) I, 2}} , n2 ^is, ~ _{H 2, n2} matrix contains the corresponding vectors eigenvalues of right singular vectors _{^{of, V (n) I, 2}} , n2 Is a matrix including a vector corresponding to a zero matrix among right singular vectors of ^~ H2 _{, n2} . At this time, since V ⁽ⁿ⁾ _{I, 2, n2} is a vector that does not correspond to a singular value, if transmission is performed using this vector V ⁽ⁿ⁾ _{I, 2, n2} , the base station 1002 transmits the signal within its own cell. Terminal stations 2002-1 to 2002- (n ₂ -1), 2002 (n ₂ +1) to 2002-N ₂ , and terminal stations 2001 having a reception sensitivity equal to or higher than a threshold value P _Th among other terminal stations in other cells. No interference occurs between ₁ and 2001-M1. Therefore, since it is only necessary to determine the transmission weight in this non-interference space, the channel matrix of the terminal station 2002 of the own communication cell may be projected onto the non-interference space. SVD is performed on the channel matrix in the non-interference space as shown in the following equation (7).

Here, U _{N, 2, n2} is the left singular vector of the matrix ^to _{HD, 2, n2} V ⁽ⁿ⁾ _{I, 2, n2} , _{and ΣN , 2, n2} is a diagonal matrix of singular values. ^~ V ^(s) _{N, 2, n2} is a matrix containing a vector corresponding to an eigenvalue among right singular vectors of ^~ _{HD , 2, n2V} ⁽ⁿ⁾ _{I, 2, n2} , ^~ V ⁽ⁿ⁾ _{n, 2, n2} ^is the ^{_{~ H D, 2, n2 V}} (n) I, 2, n2 corresponding vector to zero matrix of right singular vectors of were included matrix. The right singular matrix V ^(s) _{N, 2, n2} for the singular values at this time is determined from the base station 1002 as terminal stations 2002-1 to 2002- (n ₂ -1), 2002- (n ₂ +1) in its own cell. _{~2002-n 2,} and the transmission capacity to the terminal station _{2002-n 2} without causing interference reception sensitivity threshold _{P Th} or more terminal stations _{2001-1~2001-M 1} of the terminal station in another cell Corresponds to the transmission weight to be maximized. Therefore, the transmission weight W _n2 in the zero forcing transmission is represented by the following formula (8).

When the transmission weights W _n1 and W _n2 are used, the expressions (1) and (2) can be expressed as the following expressions (9) and (10).

Here, terminal stations 2002- (M ₂ +1) to 2002-N ₂ that did not perform CSI estimation and CSI feedback with base station 1001, and terminals that did not perform CSI estimation and CSI feedback with base station 1002 As for the stations 2001- (M ₁ +1) to 2001-N ₁ , interference control (null directivity control) is not performed as shown in the equations (9) and (10). Therefore, although an interference component term exists, as described above, the base station 1001 and the terminal stations 2002- (M ₂ +1) to 2002-N ₂ , and the base station 1002 and the terminal stations 2001- (M ₁ +1) to 2001. The radio signal hardly reaches (or at all) due to the propagation loss between −N ₁ and the amount of interference is small (or 0), and a reception signal with no actual interference can be obtained. Further, CSI feedback is performed between the base station 1001 and the terminal stations 2002- (M ₂ +1) to 2002-N ₂ and between the base station 1002 and the terminal stations 2001- (M ₁ +1) to 2001-N _1. Therefore, overhead can be reduced.

[Base station configuration in the first embodiment]
FIG. 2 is a schematic block diagram showing the internal configuration of the base station 1001 in the first embodiment. Note that since the same configuration of the base station 1002 in the first embodiment can be used, only the base station 1001 will be described here. As shown in the figure, the base station 1001 includes a control signal generation unit 3001, a transmission signal generation unit 3002, radio units 3003-1 to 3003-A, antenna elements 3004-1 to 3004-A, and received signals. A demodulator 3005 and a transmission weight calculator 3006 are provided.

  The control signal generation unit 3001 generates a sounding frame and a control signal for performing wireless communication, and outputs the control signal to the transmission signal generation unit 3002. The transmission signal generation unit 3002 receives a signal from the network 1000 or the control signal generation unit 3001, generates a transmission signal in the baseband, and outputs the transmission signal to the radio units 3003-1 to 3003-A. Here, as a transmission signal generation method, for example, a method as shown in Reference Document 2 below can be used.

(Reference 2) "IEEE Standard for Information technology- Telecommunications and information exchange between systems Local and metropolitan area networks-Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications," IEEE Std 802.11TM -2012, March 2012.

  The radio unit 3003-i (i = 1 to A) converts the baseband signal for each antenna element output from the transmission signal generation unit 3002 into a radio signal and transmits the radio signal from the antenna element 3004-i. Radio section 3003-i (i = 1 to A) converts a radio signal received by antenna element 3004-i into a baseband signal and outputs the baseband signal to reception signal demodulation section 3005.

  Received signal demodulation section 3005 demodulates the baseband signal input from radio sections 3003-1 to 3003-A and outputs a data signal. Further, the CSI transmitted from the terminal station 2001 and the terminal station 2002 is demodulated and output to the transmission weight calculation unit 3006. Transmission weight calculation section 3006 calculates a transmission weight using CSI input from reception signal demodulation section 3005 and outputs the result to transmission signal generation section 3002. The transmission signal generation unit 3002 performs transmission beam forming using the weight calculated by the transmission weight calculation unit 3006 when performing coordinated transmission.

[Terminal Station Configuration in the First Embodiment]
FIG. 3 is a schematic block diagram showing the internal configuration of the terminal station 2001 in the first embodiment. Since the same configuration can be used for the terminal station 2002 in this embodiment, only the terminal station 2001 will be described here. As shown in the figure, the terminal station 2001 includes antenna elements 4001-1 to 4001-B, radio units 4002-1 to 4002-B, a transmission signal generation unit 4003, a control signal generation unit 4004, and a reception signal. A demodulation unit 4005, a reception sensitivity measurement unit 4006, and a CSI estimation unit 4007 are provided.

  The antenna elements 4001-1 to 4001-B, the radio units 4002-1 to 4002-B, the control signal generation unit 4004, and the reception signal demodulation unit 4005 are the antenna elements 3004-1 to 3004-A and radio units shown in FIG. 3003-1 to 3003-A, the control signal generation unit 3001, and the reception signal demodulation unit 3005 have the same functions.

  The reception sensitivity measurement unit 4006 measures the reception sensitivity of a signal transmitted from the base station 1001 or the base station 1002 and received by the terminal station from the reception signals output from the radio units 4002-1 to 4002-B. . In the present embodiment, the reception sensitivity measurement unit 4006 measures a received signal strength (RSSI) value as the reception sensitivity. As a measurement method of the RSSI value, it can be measured using a beacon as in a conventional wireless LAN, or can be measured using a known signal such as a sounding frame. As reception sensitivity, instead of RSSI value, reception CNR (Carrier-to-noise power ratio) and reception SNR (Signal-to-noise power ratio) are measured. May be. Further, the received SIR (Signal-to-interference power) is calculated from the ratio of the power measured using the known signal transmitted from the own cell base station and the power measured using the known signal transmitted from the neighboring cell base station. ratio: signal-to-interference power ratio) or received SINR (Signal-to-interference plus noise power ratio) may be measured. Further, any combination of these RSSI, reception CNR, reception SNR, reception SIR, and reception SINR may be used. Reception sensitivity measurement section 4006 outputs the measured RSSI value to CSI estimation section 4007.

The CSI estimating unit 4007 receives from the received signal demodulating unit 4005 the input of the sounding frame transmitted from the base station 1001 and received by the terminal station. CSI estimation section 4007 estimates the CSI between base station 1001 and the terminal station using the input sounding frame, and outputs the estimated CSI to transmission signal generation section 4003. Thereby, the transmission signal generation section 4003 generates a CSI frame that notifies the estimated CSI and feeds back to the base station 1001. The CSI estimation unit 4007 uses the sounding frame transmitted from the base station 1002 and received at the terminal station when the RSSI value input from the reception sensitivity measurement unit 4006 is equal to or greater than a preset threshold value P _Th. Then, the CSI between the base station 1002 and the terminal station is estimated and output to the transmission signal generation section 4003. As a result, the transmission signal generation unit 4003 generates a CSI frame that notifies the estimated CSI and feeds back to the base station 1002. On the other hand, when the RSSI value is smaller than the threshold value P _Th , the CSI estimating unit 4007 does not estimate the CSI between the base station 1002 and the own terminal station.
Transmission signal generation section 4003 receives the signal from control signal generation section 4004 and CSI from CSI estimation section 4007 as input, generates a transmission signal in baseband, and outputs the transmission signals to radio sections 4002-1 to 4002-B.

  In the case of the terminal station 2002, the base station 1001 in the description of the internal configuration of the terminal station 2001 in FIG. 3 described above is the base station 1002, and the base station 1002 is the base station 1001.

[Communication Procedure in First Embodiment]
FIG. 4 is a diagram showing an example of a frame sequence in the first embodiment of the present invention. Hereinafter, the communication procedure in this embodiment will be described with reference to FIG.

First, the control signal generation unit 3001 of the base station 1001 generates a sounding frame, and the transmission signal generation unit 3002 converts the generated sounding frame into a baseband signal. Radio units 3003-1 to 3003-A convert the sounding frame of the baseband signal generated by transmission signal generation unit 3002 into a radio signal, and antenna elements 3004-1 to 3004-A perform the sounding frame at time t1. 501 is transmitted to the terminal stations 2001-1 to 2001 -N ₁ and the terminal stations 2002-1 to 2002 -N ₂ .

  The terminal station 2001 and the terminal station 2002 that have received the sounding frame 501 receive the sounding frame 501 by the antenna elements 4001-1 to 4001-B, and the radio units 4002-1 to 4002-B have the antenna elements 4001-1 to 4001-B. The sounding frame 501 received by 4001-B is converted into a baseband signal and output to the received signal demodulation section 4005. The radio units 4002-1 to 4002-B of the terminal station 2002 that has received the sounding frame 501 further output the sounding frame 501 converted into the baseband signal to the reception sensitivity measuring unit 4006.

The terminal station 2001 that has received the sounding frame 501 and the received signal demodulation section 4005 of the terminal station 2002 demodulate the sounding frame 501 of the baseband signal and output the result to the CSI estimation section 4007. Also, the reception sensitivity measurement unit 4006 of the terminal station 2002 that has received the sounding frame 501 outputs the RSSI value measured based on the sounding frame 501 of the baseband signal to the CSI estimation unit 4007. The CSI estimator 4007 of the terminal stations 2002-1 to 2002 -M ₂ that has determined that the RSSI measured by the terminal stations 2001-1 to 2001 -N ₁ and the reception sensitivity measuring unit 4006 is equal to or greater than the threshold value P _Th . The CSI with the base station 1001 is estimated using the sounding frame 501 input from the received signal demodulator 4005. Note that the terminal stations 2002- (M ₂ +1) to 2002-N ₂ do not estimate CSI because the CSI estimation unit 4007 determines that the RSSI is less than the threshold value P _Th .

Then, the base station 1002 performs the same processing as when the base station 1001 transmits the sounding frame 501, a sounding frame 502 at a timing of time t2 the terminal station _{2001-1~2001-N 1} and the terminal station 2002- and transmits it to the _{1~2002-N 2.} Terminal station 2001 has received the sounding frame _502, and the terminal station 2002 performs the same processing as when receiving the sounding frame 501. As a result, the terminal stations 2002-1 to 2002-N ₂ and the terminal stations 2001-1 to 2001-M _{1 that} have determined that the RSSI is equal to or greater than the threshold value P _Th use the sounding frame 502 to communicate with the base station 1002. The CSI between is estimated. On the other hand, since the terminal stations 2001- (M ₁ +1) to 2001-N ₁ are determined that the RSSI is less than the threshold value P _Th , the CSI is not estimated.

The CSI estimation unit 4007 of the terminal stations 2001-1 to 2001 -N ₁ outputs the estimated CSI to the transmission signal generation unit 4003. The transmission signal generator 4003 of the terminal stations 2001-1 to 2001 -N ₁ generates a CSI frame of a baseband signal in which the estimated CSI is set, and the radio units 4002-1 to 4002 -B are transmission signal generators 4003. Converts the CSI frame of the baseband signal generated by the method into a radio signal. The antenna elements 4001-1 to 4001-B of the terminal station 2001-i (i = 1 to N ₁ ) transmit the CSI frame 503-1-i at the timing of time t3.

In this way, the CSI estimated by terminal stations 2001-1 to 2001 -N ₁ is transmitted to base station 1001 and base station 1002 as CSI frames 503-1-1 to 503-1 -N ₁ at the timing of time t 3. Provide feedback. Here, the terminal stations 2001-1 to 2001 -M ₁ use the CSI frames 503-1-1 to 503-1 as the estimated CSI values between the base station 1001 and the own terminal station and between the base station 1002 and the own terminal station, respectively. It is set to -M ₁ to feedback. On the other hand, each of the terminal stations 2001- (M ₁ +1) to 2001-N ₁ uses only the CSI estimated value between the base station 1001 and the terminal station CSI frame 503- (M ₁ +1) -1 to 503-1. Set to N ₁ and feed back. Therefore, the CSI frames 503-1-(M ₁ +1) to 503-1-N ₁ of the terminal stations 2001- (M ₁ +1) to 2001-N ₁ are the CSI frames of the terminal stations 2001-1 to 2001-M ₁ . _{503-1-1~503-1-M} shorter than _1, the overhead due to CSI feedback is reduced.

Base station 1001 and base station 1002, receives a CSI frame _{503-1-1~503-1-N 1} by the antenna element 3004-1~3004-A, the radio unit 3003-1~3003-B includes an antenna the CSI frame _{503-1-1~503-1-N 1} of elements 3004-1~3004-B received into a baseband signal, and outputs to the reception signal demodulation unit 3005. Receiving signal demodulating unit of the base station 1001 and base station 1002, 3005 demodulates the CSI frame _{503-1-1~503-1-N 1} of the baseband signal at each terminal station _{2001-1~2001-N 1} When the estimated CSI is acquired, it is output to transmission weight calculation section 3006. Note that the base station 1002 may not be able to receive the CSI frames 503-1- (M ₁ +1) to 503-1-N ₁ .

The terminal station 2002-j (j = 1 to N ₂ ) performs the same processing as when the terminal station 2001-i (i = 1 to N ₁ ) transmits the CSI frame 503-1-i. Is transmitted as a CSI frame 503-2-j at the timing of time t4. Thereby, the CSI estimated by the terminal stations 2002-1 to 2002-N ₂ is fed back to the base station 1001 and the base station 1002 as CSI frames 503-2-1 to 503-2-N ₂ at the timing of time t4. The Here, the terminal station _{2002-1~2002-M 2} CSI frame, respectively, the base station 1001 and the own terminal station and between base station 1002 estimates the CSI between the own terminal station 503-2-1～503-2 It is set to -M ₂ is fed back. On the other hand, each of the terminal stations 2002- (M ₂ +1) to 2002-N ₂ uses the CSI frame 503-2- (M ₂ +1) to 503-2- only as an estimate of the CSI between the base station 1002 and its own terminal station. Set to N ₂ and feed back. Therefore, the CSI frames 503-2- (M ₂ +1) to 503-2-N ₂ of the terminal stations 2002- (M ₂ +1) to 2002-N ₂ are the CSI frames of the terminal stations 2001-1 to 2001-M ₂ . shorter than _{503-2-1~503-2-M 2,} overhead CSI feedback is reduced.

Base station 1001 and base station 1002, performs the same processing as when receiving the CSI frame _{503-1-1~503-1-N 1,} was estimated in each terminal station _{2002-1~2002-N 2} to get the CSI from CSI frame _{503-2-1~503-2-M 2.} Note that the base station 1001 may not be able to receive the CSI frames 503-2- (M ₂ +1) to 503-2-N ₂ .

The transmission weight calculation unit 3006 of the base station 1001 uses the CSI estimation values fed back from the terminal stations 2001-1 to 2001 -N ₁ and the terminal stations 2002-1 to 2002 -M ₂ to use the data transmission destination terminal station When the left side coupling matrix of equation (3) is obtained according to 2001, the transmission weight for cooperative transmission is calculated by the above equations (3) to (5), and is output to the transmission signal generator 3002.
Also, the transmission weight calculation section 3006 of the base station 1002 uses the CSI estimation values fed back from the terminal stations 2001-1 to 2001 -M ₁ and the terminal stations 2002-1 to 2002 -N ₂ to determine the data transmission destination. When the left-side coupling matrix of Equation (6) is obtained according to terminal station 2002, the transmission weight for cooperative transmission is calculated by Equations (6) to (8) above, and output to transmission signal generator 3002 .

  The base station 1001 and the transmission signal generation unit 3002 of the base station 1002 perform transmission beam forming on the transmission data input from the network 1000 using the transmission weight input from the transmission weight calculation unit 3006 to obtain a data transmission signal. Generate. A data transmission signal subjected to transmission beamforming in the transmission signal generation unit 3002 is transmitted from the base station 1001 to the base station through the radio units 3003-1 to 3003-A and the antenna elements 3004-1 and 3004-A. The frame 504-1 is transmitted from the base station 1002 as a base station cooperation transmission frame 504-2.

In the above description, the CSI frame is fed back from each of the terminal stations 2001 and 2002 after the base station 1001 and the base station 1002 transmit the sounding frame. However, the frame sequence is not necessarily required. For example, after transmitting the sounding frame 501 from the base station 1001, the terminal station _{2001-1~2001-N 1} and the terminal station _{2002-1~2002-M 2} is a base station 1001 that is estimated using the sounding frame 501 first feedback CSI frame CSI estimation value between the own terminal station, subsequently, after transmitting the sounding frame 502 from the base station 1002, the terminal station _{2002-1~2002-N 2} and the terminal station 2001-1～ The CSI estimated value between the base station 1002 and the terminal station estimated by the 2001-M ₁ using the sounding frame 502 can also be fed back using the CSI frame.

[Signal processing procedure example]
FIG. 5 shows a flowchart of a processing procedure example for determining whether or not to feed back CSI between the base station 1002 and the terminal station in the terminal station 2001. The same process is performed when the terminal station 2002 determines whether or not to feed back CSI between the base station 1001 and the own terminal station.

Radio units 4002-1 to 4002-B of terminal station 2001 convert known signals such as beacons and sounding frames transmitted by antenna elements 4001-1 to 4001-B from base station 1002 into baseband signals, and receive signals. The data is output to the demodulation unit 4005 and the reception sensitivity measurement unit 4006. The reception sensitivity measurement unit 4006 measures the RSSI value of the signal from the base station 1002 using the known baseband signal output from the radio units 4002-1 to 4002-B (step S401). Here, as described above, SNR or CNR may be measured instead of the RSSI value. Next, the CSI estimation unit 4007 determines whether or not the RSSI value measured by the reception sensitivity measurement unit 4006 is greater than or equal to a threshold value P _Th (step S402).

When it is determined that the measured RSSI value is equal to or greater than the threshold value P _Th (step S402: YES), the CSI estimation unit 4007 uses the sounding frame transmitted from the base station 1002 to establish a connection between the base station 1002 and the terminal station. Is estimated (step S403). The transmission signal generation unit 4003 outputs the CSI estimation result by the CSI estimation unit 4007 to the transmission signal generation unit 4003 via the radio units 4002-1 to 4002-A and the antenna elements 4001-1 to 4001-B. The signal generation unit 4003 generates a CSI frame in which CSI is set between the base station 1002 and the terminal station, and feeds back to the base station 1002 (step S404).

On the other hand, if the CSI estimating unit 4007 determines that the measured RSSI value is smaller than the threshold value P _Th (step S402: NO), the process of steps S403 to S404 is not performed and the process ends.

[Second Embodiment]
A second embodiment of the present invention will be described. In the present embodiment, the description will focus on the differences from the first embodiment, and the description of the same parts as in the first embodiment will be omitted.

The configuration of the radio communication system according to the second embodiment is that the base station 1001 and base station 1002 of the radio communication system according to the first embodiment shown in FIG. Terminal stations 2101-1 to 2101-N ₁ and terminal stations 2102-1 to 2102-N ₂ are respectively replaced by terminal stations 2101-1 to 2101-N ₁ and terminal stations 2102- it is replaced with a _{1~2102-N 2.} Hereinafter, described as the terminal station 2101 are collectively terminal station _{2101-1~2101-N 1,} are collectively terminal station _{2102-1~2102-N 2} to as terminal station 2102.

In the second embodiment, first, the base station 1101, and the base station 1102, a beacon signal and a control signal transmitted from each terminal station _{2101-1~2101-N 1} and the terminal station _{2102-1~2102-N 2} Etc., and measure the RSSI value. Subsequently, each of the base stations 1101 and 1102 determines that the terminal stations 2101-1 to 2101-N ₁ and the terminal stations 2102-1 to 2102-N ₂ have the RSSI values based on the measured RSSI values. It is divided into a terminal station group having a threshold value P _Th or higher and a terminal station group having a threshold value P _Th smaller than that.

Thereafter, the base station 1101, the sounding frames for CSI estimation, RSSI value is wirelessly transmitted to the threshold _{P Th} or more terminal stations _{2101-1~2101-N 1} and addressed to the terminal station _{2102-1~2102-M 2} . Note that the base station 1101 and the base station 1102 may set all of the terminal stations under their own base station as transmission objects of the sounding frame without measuring the RSSI value. The terminal stations 2101-1 to 2101-N ₁ and the terminal stations 2102-1 to 2102-M ₂ estimate the CSI between the base station 1101 and the terminal station using the received sounding frame. Subsequently, the base station 1102, the radio transmission of the sounding frame for CSI estimation, RSSI value is the threshold value _{P Th} or more terminal stations _{2102-1~2102-N 2} and addressed to the terminal station _{2101-1~2101-M 1} To do. The terminal stations 2102-1 to 2102-N ₂ and the terminal stations 2101-1 to 2101-M ₁ estimate the CSI between the base station 1102 and the terminal station using the received sounding frame.

Thereafter, the terminal station 2101 and the terminal station 2102 feed back the estimated CSI to the base station 1101 and the base station 1102. However, terminal stations 2102- (M ₂ +1) to 2102-N ₂ that have not performed CSI estimation with the base station 1101 do not perform CSI feedback to the base station 1101, and estimate CSI with the base station 1102. For the terminal stations 2101- (M ₁ +1) to 2101-N ₁ that have not been performed, CSI feedback to the base station 1102 is not performed. Finally, each base station 1101 and base station 1102 determines, based on the fed back CSI, terminal stations under its own base station and terminal stations under other base stations whose RSSI value is greater than or equal to the threshold value P _Th . A transmission weight for performing interference control is calculated in the same manner as in the first embodiment, and base station cooperative transmission is performed using the calculated transmission weight.

[Base Station Configuration in Second Embodiment]
FIG. 6 is a schematic block diagram showing the internal configuration of the base station 1101 in the second embodiment. In addition, since the same configuration can be used for the base station 1102 in this embodiment, only the base station 1101 will be described here.

As shown in the figure, the base station 1101 is different from the base station 1001 of the first embodiment shown in FIG. 2 in that the control signal generator 3001a and the transmission weight calculator 3006 are replaced with the control signal generator 3001 and the transmission weight calculator 3001. The point is that a weight calculation unit 3006a is provided, and that a reception sensitivity measurement unit 3101 is newly provided. Reception sensitivity measurement unit 3101, a reception signal output from the radio unit 3003-1~3003-A, is transmitted from the terminal station _{2101-1~2101-N 1} and the terminal station _{2102-1~2102-N 2,} the own The RSSI value of the signal received at the base station is measured. As a measurement method of the RSSI value, it can be measured using a beacon or a control signal as in a conventional wireless LAN. Further, instead of the RSSI value, a received CNR, received SNR, received SINR, or received SIR may be measured, or any combination thereof may be used.

Reception sensitivity measurement section 3101 outputs the measured RSSI value to control signal generation section 3001a and transmission weight calculation section 3006a. The control signal generation unit 3001a sets a terminal station group having a measured RSSI value equal to or greater than the threshold value P _{Th as} a target of CSI estimation, and generates a sounding frame for the target terminal station group. Transmission weight calculating unit 3006a generates a transmission weight by using the CSI RSSI value measured by the reception sensitivity measurement unit 3101 is fed back from the threshold _{P Th} or more terminal stations group.

[Terminal Station Configuration in Second Embodiment]
FIG. 7 is a schematic block diagram showing the internal configuration of the terminal station 2101 in the second embodiment. Since the same configuration can be used for the terminal station 2102 in this embodiment, only the terminal station 2101 will be described here.

As shown in the figure, the terminal station 2101 is different from the terminal station 2001 of the first embodiment shown in FIG. 3 in that it does not include a reception sensitivity measurement unit 4006, and a CSI estimation unit is used instead of the CSI estimation unit 4007. It is a point provided with 4007a.
The CSI estimation unit 4007a receives the input of the sounding frame transmitted from the base station 1101 and received at the terminal station from the received signal demodulation unit 4005. CSI estimation section 4007a estimates the CSI between base station 1101 and the terminal station using the input sounding frame, and outputs the estimated CSI to transmission signal generation section 4003. Also, CSI estimating section 4007a estimates the CSI between base station 1102 and the own terminal station using the sounding frame transmitted from base station 1102 and received at the own terminal station, and transmits to transmission signal generating section 4003. Output.

[Communication Procedure in Second Embodiment]
FIG. 8 is a diagram showing an example of a frame sequence in the second embodiment of the present invention. The difference from the first embodiment is that a control signal such as a beacon is transmitted from each terminal station 2101 and terminal station 2102 to the base station 1101 and base station 1102 at the timing of time t0.

First, the control signal generator 4004 of each terminal station 2101 and the terminal station 2102 generates a control signal such as a beacon, and the antenna element 4001 through the transmission signal generator 4003 and the radio units 4002-1 to 4002-B. 1 to 4001-B. At this time, the terminal stations 2101-1 to 2101-N ₁ and the terminal stations 2102-1 to 2102-N ₂ sequentially transmit control signals such as beacons between time t0 and t1. The base station 1101 and the base station 1102 estimate the RSSI value using a control signal such as a beacon received from each terminal station 2101 and the terminal station 2102.

Thereafter, the base station 1101 sets a terminal station group having an estimated RSSI value equal to or greater than the threshold value P _Th as the CSI estimation target, and at the time t1, the terminal stations 2101-1 to 2101-N ₁ to be estimated and the terminals transmitting a sounding frame 501 addressed to the station _{2102-1~2102-M 2.} Similarly, the base station 1102 sets a terminal station group having an estimated RSSI value equal to or greater than the threshold value P _Th as the CSI estimation target, and at the time t2, the terminal stations 2101-1 to 2101-M ₁ to be estimated and transmitting a sounding frame 502 to the terminal station _{2102-1~2102-N 2.}

When the base station 1101 and the base station 1102 transmit the sounding frame 501 and the sounding frame 502, respectively, the estimated RSSI value is greater than or equal to the threshold value P _Th at the head of the sounding frame 501 and the sounding frame 502, that is, CSI is estimated. Information of terminal stations 2101 and 2102 that need to be fed back may be set. Further, the base station 1101 and the base station 1102 transmit a control signal or the like in advance before transmitting the sounding frame, and the estimated RSSI value is equal to or greater than the threshold value P _Th , that is, the terminal station that needs to estimate and feed back the CSI. Information may be transmitted to the terminal stations 2101 and 2102.

The terminal stations 2101-1 to 2101-N ₁ perform the same processing as in FIG. 4, and the CSI estimated by the terminal station is set as CSI frames 503-1-1 to 503-1-N ₁ at the timing of time t3. Feedback is made to the base station 1101 and the base station 1102. The terminal station _{2102-1~2102-N 2} performs the same processing as FIG. 4, the CSI estimated by the own terminal station, CSI frame 503-2-1~503-2-N at a timing of time t4 ₂ is fed back to the base station 1101 and the base station 1102.
However, the terminal station 2101 and the terminal station 2102 do not calculate the RSSI value, and the CSI estimation unit 4007a calculates the CSI with the base station that has notified that the terminal station needs to estimate and feed back the CSI. presume.

[Signal processing procedure example]
FIG. 9 shows a flowchart of a processing procedure example for determining whether or not the base station 1101 requests the terminal station 2102 for CSI feedback. The same processing is performed when the base station 1102 determines whether to request CSI feedback from the terminal station 2101.

The base station 1101 receives a control signal such as a beacon transmitted from the terminal station 2102-n ₂ (1 ≦ n ₂ ≦ N ₂ , where n ₂ is an integer) by the antenna elements 3004-1 to 3004-A. Radio units 3003-1 to 3003-B convert the control signals received by antenna elements 3004-1 to 3004-B into baseband signals and output the received signals to received signal demodulation unit 3005. Received signal demodulation section 3005 of base station 1101 demodulates the control signal of the baseband signal and outputs it to reception sensitivity measurement section 3101. The reception sensitivity measurement unit 3101 measures the RSSI value of the signal from the terminal station 2102-n using the control signal input from the reception signal demodulation unit 3005 (step S601). Here, as described above, SNR, CNR, SIR, SINR, and the like may be measured instead of the RSSI value.

Next, the reception sensitivity measurement unit 3101 determines whether the measured RSSI value is greater than or equal to the threshold value P _Th (step S602). If the reception sensitivity measurement unit 3101, the measured RSSI values it is determined that the threshold value _{P Th} is smaller than (Step S602: NO), the base station 1101 to the terminal station _{2102-n 2,} estimation and its CSI No value feedback is requested (step S603).

On the other hand, the reception sensitivity measurement unit 3101, the measured RSSI value when it is determined that greater than or equal to the threshold value _{P Th} (step S602: YES), the terminal station _{2102-n 2,} feedback estimation and its value of CSI A request is made (step S604). Specifically, receiver sensitivity measurement unit 3101 notifies the information of the terminal station _{2102-n 2} is RSSI value measured threshold _{P Th} than the control signal generating unit 3001a. Control signal generating unit 3001a generates a sounding frame including the head information for identifying the terminal station _{2102-n 2.} The sounding frame generated in the control signal generation unit 3001a is transmitted as a radio signal from the antenna elements 3004-1 to 3004-A via the transmission signal generation unit 3002 and the radio units 3003-1 to 3003-A.
Alternatively, the control signal generation unit 3001a generates a control signal that instructs the terminal station 2102-n ₂ whose measured RSSI value is equal to or greater than the threshold value P _Th to estimate and feed back the CSI, and the transmission signal generation unit 3002 The antenna elements 3004-1 to 3004-A transmit by radio signals via the radio units 3003-1 to 3003-A. After transmitting the control signal, the base station 1101 further transmits a sounding frame.

When receiving the CSI estimation value feedback from the terminal station 2102-n ₂ that requested the CSI estimation and the feedback of the CSI, the base station 1101 determines to use the fed back CSI for the calculation of the transmission weight ( Step S605). Specifically, receiving the CSI frame antenna elements 3004-1~3004-A has been transmitted from the terminal station _{2102-n 2,} the radio unit 3003-1~3003-B includes an antenna element 3004-1～3004- The CSI frame received by B is converted into a baseband signal and output to the received signal demodulation section 3005. Received signal demodulation section 3005 demodulates the CSI frame of the baseband signal, acquires the CSI estimated by each terminal station 2102, and outputs it to transmission weight calculation section 3006 a. Transmission weight calculating unit 3006a obtains an estimate of the terminal stations _{2101-1~2101-N 1,} and fed back from the terminal station _{2102-1~2102-M 2} CSI, transmission weights of the first embodiment Similar to the calculation unit 3006, a transmission weight for cooperative transmission is calculated and output to the transmission signal generation unit 3002.

  In the above description, the base station 1101 and the base station 1102 measure the RSSI value with a control signal such as a beacon in advance and determine whether to feed back CSI from the terminal station 2101 and the terminal station 2102. The sounding frame may be transmitted in the same manner as in the first embodiment without being determined at the stage of transmitting the sounding frame. The terminal station 2101 and the CSI estimation unit 4007a of the terminal station 2102 estimate the CSI with the base station 1101 and the CSI with the base station 1102, and output to the transmission signal generation unit 4003 to output the terminal station 2101, The CSI frame is fed back to the terminal station 2102. The transmission weight calculation unit 3006a of the base station 1101 and the base station 1102 performs threshold value determination of the RSSI value measured by the reception sensitivity measurement unit 3101 based on the fed back CSI frame, and the CSI frame whose RSSI value is equal to or greater than the threshold value The CSI obtained by the received signal demodulator 3005 is used to calculate the transmission weight. As a result, the base station 1101 and the transmission weight calculation unit 3006a of the base station 1102 perform interference control on the terminal stations subordinate to the base station and the terminal stations subordinate to the other base station whose reception sensitivity is equal to or higher than the threshold. The transmission weight is calculated in the same manner as in the first embodiment. In this case, the beacon signal is unnecessary, and the RSSI value is measured by the CSI frame.

  Further, in the above embodiment, the base station 1101 and the base station 1102 have determined whether to feed back CSI from the terminal station 2101 and the terminal station 2102 based on the RSSI value. When transmission is performed using the calculated transmission weight, the range of the communication cell changes, that is, the degree of radio wave interference changes. Therefore, the base station 1101 and the base station 1102 may determine again whether or not the power is equal to or lower than the threshold based on the calculated transmission weight.

For example, the signal power that causes interference from the base station 1102 in the terminal station 2101-n ₁ (1 ≦ n ₁ ≦ N ₁ , n ₁ is an integer) is expressed by the terminal station 2102-n ₂ (1 ≦ n ₂ ≦ N ₁ , where n ₂ is an integer), the signal power that causes interference from the base station 1101 is calculated by the following equation (12).

The transmission weight calculation unit 3006a compares the interference power Q _{1, n1} obtained from Expression (11) (or the interference power Q _{2, n2} obtained from Expression (12)) with the threshold P ′ _Th . If it is smaller than the threshold, the transmission weight may be left as it is. On the other hand, if the interference power Q _{1, n1} (or interference power Q _{2, n2} ) is equal to or greater than the threshold, the terminal station 2101-n ₁ (or terminal station 2102-n ₂ ) uses the base station 1102 (or The interference power from the base station 1101) is large. Therefore, transmission weight calculating unit 3006a of the base station 1101, and the base station 1102, the fed-back between the terminal station _{2101-n 1} and the base station 1102 (or between the terminal station _{2102-n 2} and the base station 1101) In addition to CSI, the transmission weight is calculated again. Here, the threshold value P ′ _Th may be the same value as the threshold value P _Th used in the RSSI value determination, or may be a different value.

  FIG. 10 shows an example of a flowchart for calculating the transmission weight of the base station 1101 when it is determined again whether the transmission weight is equal to or less than the threshold power. Hereinafter, the base station 1101 will be described, but the same applies to the base station 1102.

First, the transmission weight calculating unit 3006a of the base station 1101, from the terminal station _{2102-1~2102-N 2} of another cell, the reception sensitivity measurement unit 3101 RSSI value output from the threshold _{P Th} is less than the terminal station 2102 Is searched (step S701). If there is not (step S701: NO), the transmission weight calculation section 3006a ends the process, and if there is (step S701: YES), the interference power from the terminal station 2102 of another cell whose RSSI value is smaller than the threshold value. Is calculated using equation (11) (step S702).

Here, the transmission weight calculation unit 3006a determines whether there is a terminal station 2102 of another cell in which the calculated interference power is equal to or greater than the threshold P ′ _Th among the terminal stations 2102 whose RSSI value is smaller than the threshold P _Th. Search is performed (step S703). If it does not exist (step S703: NO), the transmission weight calculation unit 3006a ends the process. On the other hand, when there is a terminal station 2102 of another cell in which the interference power is equal to or higher than the threshold P ′ _Th (step S703: YES), the transmission weight calculation unit 3006a selects the terminal station 2102 as a terminal whose RSSI value is equal to or higher than the threshold P _Th. The transmission weight is recalculated by further adding the estimated value of CSI with the base station 1101 that is regarded as a station and fed back from the terminal station 2102 (step S704). The transmission weight calculation unit 3006a further classifies the terminal station 2102 of another cell that has been recalculated by adding the estimated CSI value, assuming that the RSSI value is equal to or greater than the threshold value P _Th (step S705). ), The process returns to step S701 again.

  By performing the above operation, even when the shape of the communication cell is changed by using the transmission weight, the interference power can be set to be equal to or less than the threshold value.

Further, the size of the communication cell can be arbitrarily changed by performing transmission power control in the base station. Therefore, in the radio units 3003-1 to 3003-A of the base stations 1101 and 1102, transmission power control is performed so that the RSSI value between the base station and the terminal station of another cell is equal to or less than the threshold value P " _Th. The above-described processing may be performed.

In the above description, the common threshold value P _Th , P ′ _Th , or P ″ _Th is used in all the cells. However, the threshold value is not necessarily the same, and the threshold value may be different for each cell.

  In the above description, the method of controlling interference using singular value decomposition is shown as an example. However, the transmission weight is not necessarily set as described above. For example, the transmission weight may be derived by QR decomposition or the like. Alternatively, a transmission weight that does not cause interference may be generated using another method.

  In the above description, each base station is connected to the network. However, it is not necessarily connected to the network, and each base station independently generates data, and each subordinate terminal The present invention can also be applied to a wireless communication system that transmits a signal to a group.

[Effect of this embodiment]
FIG. 11 shows specifications when a computer simulation is performed on the wireless communication system of the first embodiment described above. The antenna elements of the base station and terminal station were A = 8 and B = 1, respectively, and the number of terminal stations per base station was N ₁ = N ₂ = 4. The transmission signal format was a parameter based on the IEEE802.11ac draft (reference document 3). In the figure, AP represents a base station and STA represents a terminal station.

(Reference 3) IEEE802.11ac Draft D3.0, July 2012.

FIG. 12 shows transmission capacity (Achievable bit rate) obtained as a result of computer simulation of the wireless communication system of the first embodiment described above in the overlap cell environment using the specifications of FIG. (A) shows the result when there is no channel estimation error, (B) shows the result when there is a channel estimation error, and the threshold value P _Th is set to −75 dBm. In the figure, for comparison, (a) when two base stations perform communication without collision in time division, and (b) when inter-cell interference control is performed for terminal stations of all adjacent cells (reference). The transmission capacity of document 1) is also shown. In (A), from the computer simulation results shown in (c), the median of the cumulative probability distribution (CDF) is 1.64 times that of (a) and 1.07 times that of (b). It can be seen that This is because, for terminal stations where interference power is not a problem, null directivity control is not used, and space resources are effectively used for the diversity gain of the own cell. Further, as shown in (B), when there is a channel estimation error equivalent to the thermal noise level, the difference in transmission capacity from (b) widens 1.14 times. This is because a terminal station with low interference power does not perform channel estimation and does not perform null directivity control, thereby reducing the effect of interference leakage due to channel estimation errors.

  As described above, the base station performs CSI for terminal stations whose reception sensitivity is equal to or higher than a predetermined threshold among terminal stations in neighboring cells (subordinate to other base stations) that may cause interference. Performs feedback control to perform interference control (null directivity control), and establishes a transmission beamforming method that does not perform CSI feedback and does not perform interference control (null directivity control) for terminal stations that do not satisfy the threshold. . As a result, overhead can be reduced by CSI feedback. Also, by performing beam forming that increases SNR for terminal stations in its own cell rather than performing null beam forming (interference control) for terminal stations with low interference power, it is possible to improve antenna diversity gain. Transmission characteristics are improved, and a plurality of base stations can wirelessly communicate with a plurality of terminal stations without degrading characteristics due to high system throughput at the same time and the same frequency.

[Additional notes]
Note that the functional units of the base stations 1001, 1002, 1101, 1102, and the terminal stations 2001, 2002, 2101, and 2102 in the above-described embodiments may be realized by dedicated hardware (for example, wired logic). Even if a program for realizing each functional unit is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed, the function is realized. Good. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

100 Network 101, 102 Base station 201-1, 201-2, 202-1, 202-2 Terminal station 1000 Network 1001, 1002, 1101, 1102 Base station (transmitting station apparatus)
2001, 2001-1 to 2001-N ₁ , 2002, 2002-1 to 2002-N ₂ , 2101, 2101-1 to 2101-N ₁ , 2102, 2102-1 to 2102-N ₂ terminal stations (receiving station apparatus)
3001, 3001a Control signal generation unit 3002 Transmission signal generation unit 3003-1 to 3003-A Radio unit (transmission station side radio unit)
3004-1 to 3004-B Antenna element (radio section on transmitting station side)
3005 Reception signal demodulation unit 3006, 3006a Transmission weight calculation unit 3101 Reception sensitivity measurement unit 4001-1 to 4001-B Antenna element (reception station side radio unit)
4002-1 to 4002-B wireless unit (receiving station side wireless unit)
4003 Transmission signal generator (channel information transmitter)
4004 Control signal generation unit 4005 Reception signal demodulation unit 4006 Reception sensitivity measurement unit 4007, 4007a CSI estimation unit (channel information estimation unit)

Claims (9)

A wireless communication system in which a plurality of transmitting station apparatuses perform simultaneous transmission of data to receiving station apparatuses under their own transmitting station apparatuses using the same frequency,
The plurality of transmitting station devices are:
A transmitting station side radio unit for transmitting and receiving radio signals;
A control signal generating unit that generates a known signal and transmits the known signal by the transmitting station side radio unit;
The receiving station apparatus under which the receiving sensitivity of the known signal transmitted by the transmitting station apparatus among the receiving station apparatuses under the transmitting station apparatus and the receiving station apparatus under the other transmitting station apparatus is equal to or greater than a threshold value. From the channel information received by the transmitting station side radio unit, the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity is equal to or higher than a threshold A transmission weight calculating unit for calculating a transmission weight for performing interference control,
Using the transmission weight calculated by the transmission weight calculation unit, a data transmission signal to be transmitted to the receiving station device under its own transmitting station device is generated, and the generated data transmission signal is transmitted from the transmitting station side radio unit. A transmission signal generation unit that transmits simultaneously with the other transmission station device,
The receiving station device to which any one of the plurality of transmitting station devices is assigned,
A receiving station side radio unit for transmitting and receiving radio signals;
A receiving sensitivity measuring unit that measures the receiving sensitivity of the known signal received by the receiving station side radio unit from the transmitting station device other than the assigned station; and
Based on the known signal received by the receiving station side radio unit from the transmitting station device to which it is assigned, estimates channel information with the transmitting station device to which it is assigned, and is measured by the reception sensitivity measuring unit A channel information estimation unit that estimates channel information between the transmission station device other than the assigned destination based on the known signal received from the transmitting station device other than the assigned destination when the reception sensitivity is equal to or higher than the threshold value; When,
A channel information transmission unit that causes the channel information estimation unit to transmit the channel information estimated from the receiving station side radio unit;
A wireless communication system. A wireless communication system in which a plurality of transmitting station apparatuses perform simultaneous transmission of data to receiving station apparatuses under their own transmitting station apparatuses using the same frequency,
The plurality of transmitting station devices are:
A transmitting station side radio unit for transmitting and receiving radio signals;
A receiving sensitivity measuring unit for measuring the receiving sensitivity of the control signal received by the transmitting station side radio unit from the receiving station device under the other transmitting station device;
For generating the known signal, the receiving station device under its own transmitting station device, and the receiving station device under the other transmitting station device whose receiving sensitivity measured by the receiving sensitivity measuring unit is equal to or greater than a threshold value Control signal generation unit to be transmitted from the transmission station side radio unit,
Using the channel information received by the transmitting station side radio unit from the receiving station device subordinate to the transmitting station device and the receiving station device subordinate to the other transmitting station device whose reception sensitivity is equal to or higher than a threshold, A transmission weight calculation unit for calculating a transmission weight for performing interference control on the reception station device under the station device and the reception station device under the transmission station device whose reception sensitivity is equal to or higher than a threshold;
Using the transmission weight calculated by the transmission weight calculation unit, a data transmission signal to be transmitted to the receiving station device under its own transmitting station device is generated, and the generated data transmission signal is transmitted from the transmitting station side radio unit. A transmission signal generation unit that transmits simultaneously with the other transmission station device,
The receiving station device to which any one of the plurality of transmitting station devices is assigned,
A receiving station side radio unit for transmitting and receiving radio signals;
Based on the known signal received by the receiving station side radio unit from the transmitting station device to which it is assigned, estimates channel information with the transmitting station device to which it is assigned, and from the transmitting station device other than the assigned destination, A channel information estimation unit that estimates channel information with the transmitting station device other than the assigned destination based on the known signal received by the receiving station-side radio unit;
A channel information transmission unit that transmits the channel information estimated by the channel information estimation unit from the receiving station side radio unit;
A wireless communication system. A wireless communication system in which a plurality of transmitting station apparatuses perform simultaneous transmission of data to receiving station apparatuses under their own transmitting station apparatuses using the same frequency,
Wherein the plurality of transmission stations equipment is
A transmitting station side radio unit for transmitting and receiving radio signals;
A control signal generating unit that generates a known signal and transmits the known signal by the transmitting station side radio unit;
A receiving sensitivity measuring unit for measuring the receiving sensitivity of channel information received by the transmitting station side radio unit from the receiving station device under the other transmitting station device;
Channel information received by the transmitting station side radio unit from the receiving station device subordinate to the own transmitting station device, and channel information received by the transmitting station side radio unit from the receiving station device subordinate to the other transmitting station device Of these, the channel information whose reception sensitivity measured by the reception sensitivity measurement unit is equal to or greater than a threshold is used to transmit the reception station device under its own transmission station device and the other transmissions whose reception sensitivity is equal to or greater than the threshold. A transmission weight calculating unit for calculating a transmission weight for performing interference control with the receiving station device under the station device;
Using the transmission weight calculated by the transmission weight calculation unit, a data transmission signal to be transmitted to the receiving station device under its own transmitting station device is generated, and the generated data transmission signal is transmitted from the transmitting station side radio unit. A transmission signal generation unit that transmits simultaneously with the other transmission station device,
The receiving station device to which any one of the plurality of transmitting station devices is assigned,
A receiving station side radio unit for transmitting and receiving radio signals;
Based on the known signal received by the receiving station side radio unit from the transmitting station device to which it is assigned, estimates channel information with the transmitting station device to which it is assigned, and from the transmitting station device other than the assigned destination, A channel information estimation unit that estimates channel information with the transmitting station device other than the assigned destination based on the known signal received by the receiving station-side radio unit;
A channel information transmission unit that transmits the channel information estimated by the channel information estimation unit from the receiving station side radio unit;
A wireless communication system. The transmission weight calculation unit calculates interference power from the own transmission station device in the reception station device under the transmission station device using the calculated transmission weight, and the calculated interference power is equal to or greater than a threshold value. When the receiving station device exists, the transmission power is recalculated using the channel information of the receiving station device having the interference power equal to or higher than a threshold value.
The wireless communication system according to claim 3. The transmitting station side radio unit controls transmission power so that a receiving sensitivity between the transmitting station device and the receiving station device under the control of the transmitting station device is equal to or less than a threshold;
The wireless communication system according to claim 2, wherein the wireless communication system is a wireless communication system. The reception sensitivity measurement unit measures at least one of reception intensity, signal-to-noise power ratio, carrier-to-noise power ratio, signal-to-interference power ratio, and signal-to-interference / noise power ratio as the reception sensitivity.
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. A wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station device using the same frequency,
A plurality of transmitting station devices, a known signal transmission step of transmitting a known signal;
The receiving station device to which any of the plurality of transmitting station devices is assigned,
A reception sensitivity measurement step of measuring the reception sensitivity of the known signal received from the transmitting station device other than the assigned station;
Based on the known signal received from the assigned transmission station apparatus, channel information between the assigned transmission station apparatus is estimated, and the reception sensitivity of the known signal measured in the reception sensitivity measurement step is a threshold value. If it is the above, further, a channel information estimation step for estimating channel information between the transmitting station device other than the assigned destination based on the known signal received from the transmitting station device other than the assigned destination;
A channel information transmission step for transmitting the channel information estimated in the channel information estimation step;
The plurality of transmitting station devices are
The channel information received from the receiving station device under its own transmitting station device and the reception sensitivity of the known signal transmitted by the own transmitting station device among the receiving station devices under the other transmitting station devices were greater than or equal to a threshold value Using the channel information received from the receiving station device, the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity of the known signal is equal to or higher than a threshold value, A transmission weight calculating step for calculating a transmission weight for performing interference control on
A data transmission step of generating a data transmission signal to be transmitted to the receiving station device under its own transmission station device using the transmission weight calculated in the transmission weight calculating step, and simultaneously transmitting with the other transmitting station device; ,
A wireless communication method comprising: A wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station device using the same frequency,
The plurality of transmitting station devices are
A reception sensitivity measurement step of measuring the reception sensitivity of the control signal received from the receiving station device under the other transmitting station device;
A known signal is transmitted to the receiving station device under its own transmitting station device and the other receiving station devices under the transmitting station device whose receiving sensitivity measured in the receiving sensitivity measuring step is equal to or higher than a threshold value. A known signal transmission step;
The receiving station device to which any of the plurality of transmitting station devices is assigned,
Based on the known signal received from the transmitting station device to which the terminal is assigned, channel information with the transmitting station device to which the terminal is assigned is estimated, and based on the known signal received from the transmitting station device other than the destination. A channel information estimation step for estimating channel information with the transmitting station device other than the assigned destination;
A channel information transmission step for transmitting the channel information estimated in the channel information estimation step;
The plurality of transmitting station devices are
Using the channel information received from the receiving station device subordinate to the transmitting station device and the receiving station device subordinate to the other transmitting station device whose reception sensitivity is equal to or higher than the threshold, the receiving station subordinate to the transmitting station device A transmission weight calculating step of calculating a transmission weight for performing interference control on the apparatus and the other receiving station apparatus under the transmitting station apparatus whose reception sensitivity is equal to or higher than a threshold;
A data transmission step of generating a data transmission signal to be transmitted to the receiving station device under its own transmission station device using the transmission weight calculated in the transmission weight calculating step, and simultaneously transmitting with the other transmitting station device; ,
A wireless communication method comprising: A wireless communication method executed by a wireless communication system in which a plurality of transmitting station devices perform simultaneous transmission of data to receiving station devices under their own transmitting station device using the same frequency,
A plurality of transmitting station devices, a known signal transmission step of transmitting a known signal;
The receiving station device to which any of the plurality of transmitting station devices is assigned,
Based on the known signal received from the transmitting station device to which the terminal is assigned, channel information with the transmitting station device to which the terminal is assigned is estimated, and based on the known signal received from the transmitting station device other than the destination. A channel information estimation step for estimating channel information with the transmitting station device other than the assigned destination;
A channel information transmission step for transmitting the channel information estimated in the channel information estimation step;
The plurality of transmitting station devices are
A receiving sensitivity measuring step for measuring the receiving sensitivity of the channel information received from the receiving station device under the other transmitting station device;
Of the channel information received from the receiving station device subordinate to the own transmitting station device and the channel information received from the receiving station device subordinate to the other transmitting station device, the reception sensitivity measured in the reception sensitivity measuring step is a threshold value. Using the channel information that has been described above, interference control is performed on the receiving station device under its own transmitting station device and the receiving station device under the other transmitting station device whose reception sensitivity is equal to or higher than a threshold value. A transmission weight calculating step for calculating a transmission weight for performing
A data transmission step of generating a data transmission signal to be transmitted to the receiving station device under its own transmission station device using the transmission weight calculated in the transmission weight calculating step, and simultaneously transmitting with the other transmitting station device; ,
A wireless communication method comprising:

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