JP5752996B2 - Base station apparatus, terminal apparatus, and communication system including the same - Google Patents

Description

  The present invention is composed of a plurality of cells having different zone radii, and when performing wireless communication in a range where zones overlap, a base station apparatus, terminal apparatus, and The present invention relates to a communication system provided.

  In a system composed of a plurality of cells having different zone radii, when communication is performed using the same frequency band, inter-cell interference occurring between cells having different zone radii becomes a serious problem. For example, in a system where a pico cell or femto cell with a small zone radius exists in a macro cell with a large zone radius and covering a wide range, for example, a macro base station (MeNB: Macro eNodeB) transmits to a terminal (macro terminal) The signal to be used becomes very large interference for a terminal (femto terminal) that receives a signal transmitted from a femto base station (HeNB: Home eNodeB). Therefore, the reception characteristics in the femto terminal are significantly deteriorated due to the influence of such interference.

  In response to this problem, there has been proposed a method of suppressing the interference that the macro base station gives to the femto terminal by stopping transmission in the macro cell when transmission in the femto cell is performed (see Non-Patent Document 1 below). . In Non-Patent Document 1, when a femto base station transmits a signal addressed to a femto terminal, the macro base station stops transmission of both a control signal and a data signal, thereby reducing interference given to the femto terminal. . By such a method, it is possible to prevent the reception characteristics from being deteriorated in the femto terminal.

3GPP TSG RAN WG1 # 61 R1-102678, May. 2010

  The proposed technique of Non-Patent Document 1 is to stop transmission in a macro cell when transmission in a femto cell is performed. When such a method is used, it is possible to avoid inter-cell interference and improve reception characteristics in the femto terminal, but resources that can be used in the macro cell are reduced, and the frequency of the macro cell and the entire system are reduced. The problem that utilization efficiency falls arises.

  In view of such a situation, the present invention can reduce interference given to a terminal device in an overlapping area when communication areas of base station apparatuses overlap, and can construct a system with excellent frequency utilization efficiency. A base station device, a terminal device, and a communication system including them are provided.

The present invention is a second base station apparatus that has a communication area that overlaps a communication area in a first base station apparatus that communicates with a first terminal apparatus, and that communicates with the second terminal apparatus,
Precoding selected from a plurality of predetermined precoding vectors as information for determining a precoding vector used by the first base station apparatus for communication with the first terminal apparatus Information about the vector is notified to the first base station apparatus.

  Here, the information on the selected precoding vector is information notified from the second terminal apparatus.

In addition, the present invention is a first base station apparatus that has a communication area that overlaps a communication area in a second base station apparatus that communicates with a second terminal apparatus and communicates with the first terminal apparatus. ,
Information on one or more precoding vectors selected from a plurality of precoding vectors determined in advance is acquired from the second base station apparatus, and based on the notified information on the precoding vector, A precoding vector used for communication with the first terminal device is determined.

  Here, the information on the precoding vector is information notified from the second terminal apparatus to the second base station apparatus.

  Furthermore, the information acquired from the second base station apparatus is also acquired from the first terminal apparatus from the second base station apparatus by acquiring information on one or more precoding vectors selected from a plurality of predetermined precoding vectors. And a precoding vector used for communication with the first terminal device is determined based on the information acquired from the first terminal device.

In addition, the present invention provides a second base station apparatus having a communication area overlapping with a communication area in the first base station apparatus that communicates with the first terminal apparatus counterpart, in the second communication area. A terminal device,
One or more precoding vectors are selected from a plurality of predetermined precoding vectors, and information about the selected precoding vector is transmitted from the first base station apparatus to the first terminal apparatus. The second base station apparatus is notified as information for determining a precoding vector used for communication.

  The present invention is a communication system comprising the second base station device, the first base station device, and the second terminal device.

  According to the present invention, when communication areas overlap, information from a terminal device that receives interference, that is, information on one or more precoding vectors selected in descending order of interference that the second terminal device receives. Thus, since the first base station apparatus that gives interference communicates using a precoding vector other than the notified precoding vector, the interference given to the second terminal apparatus can be reduced.

  Furthermore, the first base station apparatus performs communication based on information on one or more precoding vectors selected in the order in which the first terminal apparatus can receive the strongest from a plurality of predetermined precoding vectors. Therefore, there is no problem in communication with the first terminal device.

  Thus, by using the present invention, a cell having a large zone radius in a system in which a plurality of cells having a small zone radius (cells having a small covering area) are present in a cell having a large zone radius (a cell having a large covering area). However, interference with a cell having a small zone radius can be reduced. As a result, it is not necessary to use separate resources for cells having a large zone radius and cells having a small zone radius, and a system with excellent frequency utilization efficiency can be constructed.

It is explanatory drawing which shows the structural example of the radio | wireless communications system which has the macrocell and femtocell of 1st Embodiment. And u _n of formula (1) is a table showing the precoding vector obtained thereby. It is a block diagram which shows the apparatus structure of MeNB (macro base station) in 1st Embodiment. It is a block diagram which shows the apparatus structure of HeNB (femto base station) in 1st Embodiment. It is a block diagram which shows the apparatus structure of the terminal in 1st Embodiment. It is explanatory drawing which shows the structural example of the radio | wireless communications system with which the communication range of 2nd Embodiment overlaps.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
In the first embodiment of the present invention, first, a macro cell that covers a wide communication area and a plurality of femto cells that cover a narrow communication area exist in the macro cell, and a terminal is accommodated in each of the cells. 1 shows a configuration in which a femtocell selects several vectors from predetermined precoding vector candidates (codebook) and notifies a macrocell of information on the selected vectors. In this case, in the macro cell notified of several precoding vectors from the femto cell, the precoding vector used when performing transmission using the same resource as the femto cell is calculated based on the information. By adopting such a configuration, for example, the femtocell can notify the macrocell of a precoding vector convenient for itself, and can cause the macrocell to perform transmission using the precoding vector. Even when the femto cell performs transmission using the same resource, interference from the macro cell to the femto cell can be reduced.

  Here, precoding is a process of weighting each signal transmitted from each transmission antenna, and can be performed by multiplying a vector (or matrix) representing a weight (weight) by a transmission signal vector. Moreover, the base station apparatus in a macro cell is also called MeNB, and the base station apparatus in a femto cell is also called HeNB. Furthermore, although a macro cell and a femto cell are assumed here as an example, it is a combination of cells that are a plurality of cells having different zone radii and in which a desired signal in one cell interferes with another cell. Alternatively, a cell or zone including a light projecting base station (RRE: Remote Radio Equipments), a pico cell (PeNB), a hot spot, a relay station, or the like may be targeted.

  A configuration example of a system targeted in this embodiment is shown in FIG. As shown in FIG. 1, in the present embodiment, a system in which three femto cells (femto cells 1 to 3) exist in one macro cell will be described as an example. Here, MeNB10 (1st base station apparatus) which controls the whole macrocell shall have four transmission / reception antennas, and shall perform the data transmission to macroterminal 20 (1st terminal device). In addition, it is assumed that HeNBs 11 to 13 (second base station apparatuses) that control femto cells are installed in the macro cell controlled by the MeNB 10. These HeNBs 11 to 13 all have four transmission / reception antennas, the HeNB 11 to the femto terminal 21 (second terminal apparatus), the HeNB 12 to the femto terminal 22 (second terminal apparatus), and the HeNB 13 to the femto terminal. Data transmission is performed to 23 (second terminal apparatus). All terminals (macro terminal 20, femto terminals 21 to 23) each have two receiving antennas. However, the number of terminals accommodated in each cell, the number of femto cells, and the number of transmission / reception antennas of each device are not limited to this, and may be any number.

  In such a situation, when each cell performs downlink transmission using the same resource, as shown in FIG. 1, the terminals 21 to 23 in each femtocell will receive very large interference from the MeNB 10. . However, the magnitude of the interference received from the MeNB 10 greatly depends not only on the distance between the MeNB 10 and the femto terminal and the propagation path, but also on the precoding vector used in the MeNB 10.

  Therefore, in the present embodiment, among the predetermined precoding vector candidates (codebooks), the top several vectors that cause greater interference when used in the MeNB 10 are used as the femto terminals 21 to 21. 23 or HeNB11-13 will select and the information regarding the selected vector shall be notified to MeNB10. Then, in the MeNB 10 notified of such a vector, it is determined that transmission using the notified vector has a large influence (interference strength) on the femto cell, and transmission using other precoding vectors is performed. Do.

  Here, for example, a precoding vector (matrix) when four transmission antennas are provided is given by the following equation.

In Equation (1), u _n (n = 0, 1,..., 15) is a vector of 4 rows and 1 column shown in FIG. 2, and I is a unit matrix of 4 rows and 4 columns. Further, the rightmost column in FIG. 2 represents 16 precoding vectors that are actually used, and W _n ^{1} is the first column of W _n obtained by Equation (1) as the precoding vector. It means to use. Such a precoding vector is a part of a precoding vector employed in Release 8 of LTE (Long Term Evolution) which is a mobile communication standard standardized in 3GPP.

However, although only a vector for transmitting a data signal of one stream (or also called a layer) is shown here, a precoding vector used for transmitting a plurality of streams is also calculated based on Expression (1). can do. For example, when 2 streams are transmitted, any 2 columns of W _n obtained by Equation (1) are transmitted. When 3 streams are transmitted, any 3 columns of W _n are transmitted 4 streams. the matrix rearranged columns of W _n is the precoding is performed by multiplying the transmitted signal.

  In this embodiment, the precoding vector shown in Expression (1) and FIG. 2 is used as described above, but the present invention is not limited to this, and a configuration using other vectors may be used.

Here, the propagation path between the MeNB 10 and the macro terminal 20 is H _MM , the propagation path between the HeNB 11 and the femto terminal 21 is H _FF1 , and the propagation path between the HeNB 12 and the femto terminal 22 is H _FF2 , the HeNB 13 and the femto The propagation path between the terminals 23 is assumed to be _HFF3 . Further, a propagation path between the MeNB 10 and the femto terminal 21 is denoted as H _MF1 , a propagation path between the MeNB 10 and the femto terminal 22 is denoted as H _MF2 , and a propagation path between the MeNB 10 and the femto terminal 23 is denoted as H _MF3 .
Here, since each eNB in the present embodiment has four antennas and each terminal has two antennas, the above propagation paths are all in a matrix of 2 rows and 4 columns.

In such a system, the femto terminal in the present embodiment first receives a propagation path estimation signal (sometimes referred to as a reference signal or a pilot signal) transmitted from the MeNB 10, and receives the received known propagation path estimation signal. The propagation path between MeNB10 is estimated using a signal. By multiplying this estimated propagation path by a precoding vector, an equivalent propagation path when precoding is performed in the MeNB 10 can be calculated. For example, _H MF1 _W ^{0 {1}} obtained by multiplying the channel _{H MF1} estimated precoding vectors _W ^{0 {1}} at the femto terminal 21 is performed precoding with _W ^{0 {1}} in MeNB10 It can be said that the transmitted signal is an equivalent propagation path when the femto terminal 21 receives the signal. Therefore, by calculating H _MF1 W _n ^{1} for W _n ^{1} _where n = 0 to 15, an equivalent propagation path when each precoding vector is used can be obtained. Then, by calculating the size of the obtained equivalent propagation path, when each precoding vector is used in the MeNB 10, it is possible to estimate the influence of interference received by the femto terminal 21 from the MeNB 10. In the present embodiment, the size of the equivalent propagation path is evaluated by the square of the norm represented by Expression (2).

However, _HMFm has shown the propagation path between the femto terminal in MeNB10 and the femtocell m. Further, instead of equation (2) _may be described as ^{_{tr [(H MFm W n {}} 1}) (H MFm W n {1}) H]. This tr [A] is a trace operation for obtaining the sum of the diagonal components of the matrix A.

  Thus, in each femto terminal, it is possible to estimate the influence of interference received from the MeNB 10 by performing the calculation of Expression (2) for each precoding vector. It is an influence on the road. In general, femtocells that are often installed in homes are connected to a cellular network through the Internet, so that the delay that occurs when information is exchanged between HeNB and MeNB is relatively large. The selection of precoding vectors is often not valid.

  Therefore, in the present embodiment, in each femto terminal, the influence evaluation (Equation (2)) for each precoding vector is averaged over a long time, and each precoding vector is used based on the averaged result. Guess the magnitude of the effect on the self.

  At this time, equation (2) may be averaged for each precoding vector over a relatively long time (predetermined time), or the propagation path is estimated over a wide band, equation (2) is calculated, and these are averaged. May be used. However, here, the result obtained by averaging the values represented by the formula (2) is used. However, when the base station is connected to the MeNB by a dedicated line such as a pico cell, it is always necessary to average. Instead, the magnitude of the effect when each precoding vector is used may be estimated based only on the instantaneous propagation path. Also in the femtocell, when the propagation path is in a quasi-stationary state, it may be based only on the instantaneous propagation path.

  Thus, based on the value averaged for each precoding vector, each femto terminal 21 to 23 estimates the magnitude of the influence on itself, and determines the precoding vector estimated to have a large influence on itself. Select some.

  Here, for example, if the index n of the top three precoding vectors is selected from those having the greatest influence, this processing can also be expressed as in Expression (3).

However, max ₃ represents an operation for selecting three in descending order, and E [A] represents an average of A. Also, here, the top three are selected from the influences, that is, the ones with large values in () of the expression (3). However, the number is not limited to this, and any number as long as the number is less than the number of precoding vectors. As good as

  Each femto terminal 21-23 performs a calculation as shown in this equation (3), and selects a precoding vector having a large influence when used in the MeNB 10. And the index (identification number shown in FIG. 2) of the selected precoding vector is each notified to HeNB11-13 which self connects. Thus, each HeNB11-13 which received the information regarding a precoding vector from a femto terminal notifies this information to MeNB10 via a wired network.

  Here, for example, the HeNB 11 has an index of {1, 3, 4} from the femto terminal 21, the HeNB 12 has an index of {3, 4, 6} from the femto terminal 22, and the HeNB 13 has an index of {7, 10, 11}, the HeNBs 11 to 13 notify all of the indexes to the MeNB 10, and therefore the MeNB 10 is notified of the indexes {1, 3, 4, 6, 7, 10, 11}. Will be.

  The index notified in this way gives large interference to all femto terminals (femto terminals 21 to 23) in the femto cells 1 to 3 when the MeNB 10 uses precoding vectors indicated by the indexes. It represents a precoding vector that can be considered. Therefore, if transmission to the macro terminal 20 is performed using the precoding vectors other than those in the MeNB 10, it is considered that the interference given to the femtocell cannot be completely suppressed, but can be greatly reduced.

  Therefore, the MeNB 10 selects any one of the precoding vectors indicated by the indexes other than those notified from the HeNBs 11 to 13, and performs precoding on the signal addressed to the macro terminal 20 using the selected precoding vector. Thus, each HeNB 11-13 transmits using the same resource as that used for transmission to each femto terminal 21-23. That is, here, one of the precoding vectors indicated by the indexes {0, 2, 5, 8, 9, 12, 13, 14, 15} is selected and precoding is performed.

  Thus, in the MeNB 10, it is necessary to select and use one of the precoding vectors other than those notified from each of the HeNBs 11 to 13, but information on the precoding vector that the macro terminal 20 desires to transmit is used. When notifying the MeNB 10, a precoding vector can be selected based on information notified from the macro terminal 20. This can be performed, for example, by selecting an index of a precoding vector that can receive the signal (desired signal) most strongly and notifying the MeNB 10 of the index using the formula (2) also in the macro terminal 20. . However, in this case, it is not necessary to select based on the result of averaging the signal strength for each precoding vector.

  Thus, when the index notified from the macro terminal 20 is 8, for example, precoding vectors ({0, 2, 5, 8, 9, 12, 13) other than those notified from each femtocell are used. , 14, 15}), it is considered that even if transmission is performed using this precoding vector, the influence on each femto cell is not so great. Therefore, the MeNB 10 can select a precoding vector having an index of 8, multiply the signal by this precoding vector, and transmit the signal to the macro terminal 20. On the other hand, when the index notified from the macro terminal 20 is 11, for example, among the precoding vectors ({1, 3, 4, 6, 7, 10, 11}) notified from each femtocell. Therefore, when transmission using this precoding vector is performed, it is considered that at least one femtocell is greatly affected. Therefore, in such a case, one of precoding vectors other than those notified from the femtocell may be randomly selected and used, or the notification from the macro terminal 20 may be used. A precoding vector that is closest (highly correlated) to the generated one may be selected.

  In this way, by selecting a vector used for precoding based on information notified from each HeNB and information notified from a macro terminal, it is possible to reduce interference given to the femtocell and to some extent receive characteristics even in the macrocell. Can be secured. Therefore, it is possible to perform transmission using the same resource in the macro cell and the femto cell, and it is possible to construct a system that is superior in frequency utilization efficiency compared to the case of using different resources.

  In addition, here, precoding is performed only in the MeNB 10, and the signal is transmitted. However, in each of the HeNBs 11 to 13, a signal is transmitted after precoding is performed on the signals addressed to the femto terminals 21 to 23. It is good. For this purpose, in the same way as the macro terminal 20 estimates the propagation path with the MeNB 10 and notifies the desired precoding vector, the propagation path between the femto terminals 21 to 23 also with the HeNBs 11 to 13. It is necessary to select the index of the precoding vector that can receive the signal (desired signal) most strongly using Equation (2), and notify the HeNBs 11 to 13 of the index. Accordingly, each femto terminal 21 to 23 in this case sends three precoding vectors not desired to be used in the MeNB 10 and one precoding vector desired to be used in the HeNBs 11 to 13 to which the femto terminals 21 to 23 are connected to the HeNBs 11 to 13, respectively. You will be notified.

  Here, apparatus configurations of the MeNB 10, the HeNBs 11 to 13, and the macro / femto terminals 20 and 21 to 23 that perform the above-described processes are shown. First, the device configuration of the MeNB 10 is shown in FIG. As shown in FIG. 3, the MeNB 10 in the present embodiment includes an upper layer 30, a modulation unit 31, a precoding unit 32, a signal multiplexing unit 33, a vector selection unit 34, a channel estimation signal generation unit 35, and a D / A. Units 36-1 to 36-4, radio units 37-1 to 4, 41, transmitting antenna units 38-1 to 38-4, receiving unit 39, A / D unit 40, and receiving antenna unit 42. However, this FIG. 3 has shown the apparatus structure of MeNB10 in case single carrier transmission is performed.

In the MeNB 10 shown in FIG. 3, as described above, a propagation path estimation signal for causing each terminal apparatus to estimate a propagation path (H _MM , H _MF1 , H _MF2 , H _MF3 ) is transmitted. This propagation path estimation signal is a known signal generated in the propagation path estimation signal generation unit 35, and since precoding is not performed on this signal, the propagation path estimation signal generation unit 35 to the signal multiplexing unit 33 Is input to the D / A sections 36-1 to 36-4. In the D / A units 36-1 to 36-4, digital / analog conversion is performed on the input signals, and the radio units 37-1 to 37-4 perform frequency conversion to frequencies that can be wirelessly transmitted. -1 to 4, respectively.

  Here, it is assumed that the propagation path estimation signal for estimating the propagation path with each terminal device is not multiplexed with the data signal. In addition, the propagation path estimation signals transmitted from the respective transmission antennas have different resources (timing) so that the propagation paths between the respective transmission antennas of the MeNB 10 and the reception antennas of the respective terminal apparatuses can be estimated. ). Furthermore, as described above, in the femto terminals 21 to 23, it is necessary to average the influence of the MeNB 10 on itself over a long period of time, and thus it is necessary to estimate the propagation path for that time. Therefore, MeNB10 shall transmit the above-mentioned propagation path estimation signal over a long time to some extent. This transmission may be periodic, irregular, or continuous.

  Based on the propagation path estimation signal transmitted in this way, each of the terminal devices 21 to 23 performs propagation path estimation, and selects the precoding vector described above. Then, the macro terminal 20 notifies the MeNB 10 and the femto terminals 21 to 23 notify the HeNBs 11 to 13 of the index of the selected precoding vector. The HeNBs 11 to 13 that have received the index from the femto terminals 21 to 23 notify the MeNB 10 of the index through the wired network. The signal indicating the index notified from the macro terminal 20 is received by the reception antenna unit 42 of the MeNB 10, and after being frequency-converted by the radio unit 41 from a radio frequency to a frequency that can be analog / digital converted, the A / D unit 40 The analog / digital conversion is performed. The signal converted into the digital signal in the A / D unit 40 is input to the reception unit 39, subjected to processing such as demodulation, reproduced as an index of the precoding vector, and then input to the vector selection unit 34. . In addition, the MeNB 10 also receives the index of the precoding vector from the HeNBs 11 to 13, but this information is input to the upper layer 30 via the wired network. Then, it is input from the upper layer 30 to the vector selection unit 34.

  In the vector selection unit 34 to which these indexes are input, information on some precoding vectors that are not desired to be used in the MeNB 10 selected by all the femto terminals 21 to 23 and the use in the MeNB 10 that is selected by the macro terminal 20 The precoding vector that is actually used for transmission is selected based on the information related to the precoding vector desired to be transmitted. As described above, this selection is basically made from those other than those selected by the femto terminals 21 to 23. In particular, when there is a precoding vector notified from the macro terminal 20 among those other than those selected by the femto terminals 21 to 23, the precoding vector is selected. On the other hand, when there is no precoding vector notified from the macro terminal 20 other than the one selected by the femto terminals 21 to 23, the precoding vector is randomly selected from those other than the one selected by the femto terminals 21 to 23. May be selected. The precoding vector selected in this way is input to the precoding unit 32.

  After the selection of the precoding vector in the vector selection unit 34, the MeNB 10 transmits a data signal addressed to the macro terminal 20 in the same resource as the HeNBs 11 to 13. This signal is a signal obtained by modulating the information signal input from the upper layer 30 to the modulation unit 31 by the modulation unit 31 and is precoded by the precoding unit 32 after modulation. This precoding is performed by multiplying the signal by the precoding vector selected by the vector selection unit 34. The precoding unit 32 also receives a channel estimation signal from the channel estimation signal generation unit 35. This propagation path estimation signal is a propagation path estimation signal used for demodulation in the macro terminal 20, and is subjected to the same precoding as the data signal.

  The pre-coded data signal and propagation path estimation signal are input to the signal multiplexing unit 33, and a transmission frame is configured. However, the propagation path estimation signals for demodulation are transmitted orthogonally so that they do not interfere with each other, like the propagation path estimation signals described above. The frame configured in the signal multiplexing unit 33 is digital / analog converted in the D / A units 36-1 to 36-4, frequency-converted to frequencies that can be wirelessly transmitted in the radio units 37-1 to 3-4, and then transmitted to the transmitting antenna unit. It is transmitted from 38-1 to the macro terminal 20.

  By adopting such a configuration of the MeNB 10, the femto cell while ensuring the reception characteristics in the macro terminal 20 to some extent based on the precoding vector selected by the femto terminals 21 to 23 and the precoding vector selected by the macro terminal 20 is achieved. It is possible to select a precoding vector that can reduce interference with the signal and to perform transmission using the precoding vector. As described above, since interference with the femtocell can be reduced, it is not necessary to perform transmission using resources different from those of the femtocell, and it is possible to reduce a decrease in frequency utilization efficiency.

  Next, the apparatus configuration of the HeNB in the present embodiment is shown in FIG. However, it is assumed that all the three HeNBs (HeNBs 11 to 13) illustrated in FIG. 1 have the same configuration. As illustrated in FIG. 4, the HeNBs 11 to 13 in the present embodiment include an upper layer 50, a modulation unit 51, a precoding unit 52, a signal multiplexing unit 53, a channel estimation signal generation unit 54, and a D / A unit 55−. 1 to 4, radio units 56-1 to 4 and 60, transmission antenna units 57-1 to 4, a reception unit 58, an A / D unit 59, and a reception antenna unit 61. However, like the MeNB 10 illustrated in FIG. 3, the device configurations of the HeNBs 11 to 13 when single carrier transmission is performed are illustrated.

As can be seen from FIGS. 3 and 4, since the HeNBs 11 to 13 have almost the same configuration as the MeNB 10 described above, the description will focus on differences from the MeNB 10.
First, the receiving antenna unit 61 to the receiving unit 58 have a function of receiving information on precoding vectors notified from the femto terminals 21 to 23. In the present embodiment, the precoding vectors notified from the femto terminals 21 to 23 are some precoding vectors not desired to be used in the MeNB 10 and precoding vectors desired to be used in the HeNBs 11 to 13. Of the information, the former is input to the upper layer 50 and the latter is input to the precoding unit 52. In the upper layer 50 to which information on some precoding vectors not desired to be used in the MeNB 10 is input, a process of notifying the input information to the MeNB 10 via the wired network is performed. Further, the precoding vector desired to be used in the HeNBs 11 to 13 is used for multiplication with the signals addressed to the femto terminals 21 to 23 in the precoding unit 52. Then, the precoded signal is multiplexed with the propagation path estimation signal and transmitted to the femto terminals 21-23.

  By setting it as such a structure, the information regarding the precoding vector which the femto terminals 21-23 selected can be notified to MeNB10, and the precoding vector which has little influence on femto terminals 21-23 is used for MeNB10. Is possible.

  FIG. 5 shows the device configuration of the terminal in this embodiment. However, the macro terminal 20 and the three femto terminals (femto terminals 21 to 23) shown in FIG. As shown in FIG. 5, the terminals in the present embodiment include reception antenna units 70-1 and 70-2, radio units 71-1 and 82, A / D units 72-1 and 72, signal separation unit 73, and reception. A weight multiplication unit 74, a demodulation unit 75, an upper layer 76, a propagation path estimation unit 77, a reception weight calculation unit 78, a vector selection unit 79, a transmission unit 80, a D / A unit 81, a radio unit 82, and a transmission antenna unit 83 Is done. However, the device configuration of the terminal when single carrier transmission is performed is shown here.

  In the terminal shown in FIG. 5, first, signals transmitted from MeNB 10 and HeNBs 11 to 13 are received by reception antenna units 70-1 and 70-2, and received signals are analog / digital from radio frequencies in radio units 71-1 to 71-2. After frequency conversion to a convertible frequency, analog / digital conversion is performed in the A / D units 72-1 and 72-2. The signals converted into digital signals in the A / D units 71-1 and 7-2 are input to the signal separation unit 73. When the propagation path estimation signal and the data signal are multiplexed, they are separated and the propagation path is separated. The estimation signal is input to the propagation path estimation unit 77, and the data signal is input to the reception weight multiplication unit 74. In addition, when a signal for channel estimation for selecting a precoding vector is received, this signal is input from the signal separation unit 73 to the channel estimation unit 77.

The propagation path estimation unit 77 estimates a propagation path using a known propagation path estimation signal. Here, as described above, since the channel estimation signal used for selecting the precoding vector is not precoded, by performing channel estimation based on this, MeNB10 and HeNB11- 13 (H _MM , H _FFm , H _MFm, etc.) can be estimated. The propagation path estimated in this way is input to the vector selection unit 79 and used for selection of the precoding vector. As described above, this selection can be performed by the equations (2) and (3). Information relating to the precoding vector selected by the vector selection unit 79 is input to the transmission unit 80, modulated and converted into a transmittable format, and then digital / analog converted by the D / A unit 81, and wirelessly transmitted. After being frequency-converted to a frequency that can be wirelessly transmitted by the unit 82, it is transmitted from the transmission antenna unit 83 to the MeNB 10 and the HeNBs 11 to 13.

The propagation path estimation unit 77 also performs propagation path estimation based on a propagation path estimation signal precoded using the same precoding vector as the data signal. Such a propagation path estimation signal is a signal multiplexed with a data signal, and is used to estimate an equivalent propagation path required when demodulating the data signal. The equivalent propagation path for data signal demodulation estimated in this manner is input to the reception weight calculation unit 78 and used for calculation of the reception weight. This reception weight is a weight for combining the signals respectively received by the two reception antennas into one reception signal, and any weight can be used as long as it is a weight for that purpose. In this embodiment, it is assumed that a weight for performing maximum ratio combining is used. This weight is expressed as (HW ′) ^H , where HW ′ is the estimated equivalent propagation path. However, here, the propagation path between the transmission device (MeNB 10 or HeNB 11 to 13) and the terminals 20 and 21 to 23 is H, and the precoding vector used in the transmission device is W ′.

  The reception weight calculated in this way is input to the reception weight multiplication unit 74 and is multiplied by the data signal input from the signal separation unit 73. By this multiplication, it is possible to combine the signals respectively received by the two receiving antennas into one received signal. Then, the combined received signal is demodulated by the demodulating unit 75, and data transmitted from the transmission device (MeNB 10 or HeNB 21 to 23) is reproduced and input to the upper layer 76.

  By adopting the device configurations of the terminals 20 and 21 to 23 as described above, a desired or undesired precoding vector can be selected based on the propagation path between the MeNB 10 and the HeNBs 11 to 13, and Data signals transmitted from the MeNB 10 and the HeNBs 11 to 13 can be received and demodulated. In particular, when this terminal is connected to the HeNBs 11 to 13, it is possible to notify the MeNB 10 of a precoding vector that has little influence on the terminal, and it is possible to cause the MeNB 10 to perform transmission with reduced interference on the femto cell. It becomes. Therefore, it is possible to perform transmission using the same resource in the macro cell and the femto cell, and it is possible to construct a system that is superior in frequency utilization efficiency compared to the case of using different resources.

  In the above embodiment, a system that performs single carrier transmission has been described as an example. However, the present invention is not limited to this, and can be applied to a system that performs multicarrier transmission. When applied to a system that performs multi-carrier transmission, it may be configured to select a precoding vector according to the propagation path for each subcarrier, or several subcarriers may be collected and an average propagation path in the unit. May be calculated and a precoding vector corresponding thereto may be selected. In the multicarrier transmission system, the propagation path estimation signal transmitted from each antenna can be arranged in different subcarriers.

In addition, the femto terminals 21 to 23 described above select several precoding vectors that are not desired to be used in the MeNB 10 and perform processing for notifying the HeNBs 11 to 13 of information related thereto, The precoding vector is selected on the assumption that one stream is transmitted. This is because the precoding vector is selected from W _n ^{1} which is the first column of W _n (n = 0 to 15) in the equations (2) and (3).

Here, since the MeNB 10 does not always transmit only one stream, the femto terminals 21 to 23 may select an undesired precoding vector on the assumption that the MeNB 10 transmits a plurality of streams. Good. For example, an evaluation of the precoding vector using Equation (2) or the formula (3) _may be performed on a plurality of vectors such as ^{W n {12}} and _W ^{n {134}.} However, W _n ^{12} indicates that the first and second columns of W _n are pre-coding vectors for two streams, and W _n ^{134} is the first, third, fourth columns of W _n. Represents a precoding vector for three streams. As described above, a precoding vector may be selected on the premise of transmission of a plurality of streams.

Conversely, when a plurality of streams are transmitted in the MeNB 10, the femto terminals 21 to 23 may select and notify only one undesired precoding vector. This, even if the transmission of the plurality of streams is performed in the MeNB, 1 (1 column of W _n) precoding vector used in the stream th is always used, is because it is considered to be the most representative vector .

  Further, in this way, the configuration may be such that how many streams of precoding vectors are selected as undesired precoding vectors and notified are changed according to an instruction from MeNB 10. For example, when the MeNB 10 instructs to notify the precoding vectors for two streams, the femto terminals 21 to 23 select and notify several pairs of vectors for two streams, and the MeNB 10 When instructing to notify the precoding vector for the stream, the femto terminals 21 to 23 select and notify several sets of vectors for one stream. Such an instruction from the MeNB 10 is first sent from the MeNB 10 to the HeNBs 11 to 13 via the wired network, and then sent to the femto terminals 21 to 23 via the HeNBs 11 to 13.

  Further, in the present embodiment, the femto terminals 21 to 23 select several precoding vectors that are not desired to be used in the MeNB 10, but this selection process may be performed in the HeNBs 11 to 13. This is because interference from the MeNB 10 is originally received by the femto terminals 21 to 23. Therefore, as described above, it is desirable to estimate the influence of the femto terminals 21 to 23 and select an undesired precoding vector. However, the femto cell is a cell having a very small cell radius, and the positions of the femto terminals 21 to 23 and the positions of the HeNBs 11 to 13 viewed from the MeNB 10 are considered to be substantially the same. In such a case, there is a high possibility that the same precoding vector is selected by the femto terminals 21 to 23 and the HeNBs 11 to 13, and the HeNBs 11 to 13 instead of the femto terminals 21 to 23 do not want to use the MeNB 10. This is based on the idea that such a precoding vector may be selected. As described above, when the precoding vector is selected in the HeNBs 11 to 13, the apparatus configuration illustrated in FIG. 4 is changed to include a plurality of reception functions as in FIG. 5, and propagation path estimation is performed in the reception unit 58. It is necessary to provide a section and a vector selection section. Then, the precoding vector selected by the vector selection unit in the reception unit 58 is input to the upper layer 50 and notified from the upper layer 50 to the MeNB 10 via the wired network. By making such a change, the HeNBs 11 to 13 can select and notify the MeNB 10 of several precoding vectors that are not desired to be used in the MeNB 10 as femtocells.

  Also, in general, the HeNBs 11 to 13 operate only when there is a terminal to be connected (active mode), and enter the sleep mode at other times, and do not transmit signals, thereby causing interference to the surroundings. Reduced. As described above, since it is preferable to evaluate the influence of the interference received from the MeNB 10 over a certain period of time, when selecting the precoding vector in the HeNB 11-13, the HeNB 11-13 is in the sleep mode. During a certain period, the propagation path may be estimated, the expression (2) may be calculated and averaged. Then, when a femto terminal that wants to connect to HeNBs 11 to 13 appears, the sleep mode is canceled and the active mode is shifted. At this time, some precoding vectors that are not desired to be used in MeNB 10 are selected. And you may make it notify MeNB10. By performing such processing even during the sleep mode, it becomes possible to select a precoding vector that needs to be selected over a long period of time as soon as the femto terminal appears, and the macro cell and the femto cell. In this case, transmission using the same resource can be efficiently realized. Furthermore, after moving from the sleep mode to the active mode, the HeNBs 11 to 13 may update the information related to the precoding vector periodically or irregularly and notify the MeNB 10.

  On the other hand, when the HeNBs 11 to 13 move from the active mode to the sleep mode, the information on the precoding vector notified from the HeNBs 11 to 13 before that is used in the MeNB 10 when actually transmitted. Since there is no need to select a precoding vector, information that resets the information may be notified from the HeNB 11 to the MeNB 10. At this time, the information notified from the HeNBs 11 to 13 to the MeNB 10 may be, for example, information of an arbitrary number of bits indicating a shift from the active mode to the sleep mode, or information indicating that the use of all precoding vectors is permitted. Good. Further, an index different from the precoding vector candidates prepared in advance, for example, an index of 16 not prepared in FIG. 2 prepared in advance may be notified. Thus, in MeNB10 which received the information which resets the precoding vector notified from HeNB11-13, it judges that the transmission is not performed in the HeNB11-13, and the precoding notified from the other HeNB11-13 Based on the vector information, a precoding vector to be actually used for transmission is selected. When all the HeNBs 11 to 13 are in the sleep mode, the precoding vector is selected based only on the notification information from the macro terminal 20.

  Further, in the present embodiment, for the three femtocells, the precoding vector used in the MeNB 10 is selected based on the information on the precoding vectors respectively notified from the HeNBs 11 to 13 configuring the femtocells. However, in an actual system, more femtocells may be formed. Thus, when a very large number of femto cells are formed in a macro cell, many of the precoding vectors notified from each femto cell do not overlap, and all of the 16 candidates shown in FIG. It may be an unfavorable precoding vector for any femtocell. In such a case, by calculating the average value of Equation (2) for each femtocell and comparing the values, some femtocells that are expected to receive large interference from the macrocell are extracted. Based on the information on the precoding vector notified from the femtocell, a precoding vector that is actually used for transmission may be selected. However, in this case, in each femtocell, a precoding vector is selected on the basis of a value obtained by averaging Equation (2) over a relatively long time, and the selected precoding vector is selected together with information on some selected precoding vectors. Further, regarding the average value of the expression (2) regarding some precoding vectors, a value obtained by further taking a set average is notified to the MeNB.

  Also, instead of averaging equation (2) for each femtocell, the value averaged for each precoding vector is notified from each femtocell to MeNB10, and the precoding vector that minimizes the sum is used in MeNB10. It may be a thing. In this case, in each femtocell, a precoding vector is selected based on a value obtained by averaging Equation (2) over a relatively long time, and information on the selected precoding vector is associated with the selected precoding vector. The average value of Formula (2) is notified to MeNB10, respectively. Then, the MeNB 10 adds the value of Equation (2) related to each precoding vector notified from each femtocell for each precoding vector, and selects a precoding vector that minimizes the sum.

  Apart from these, among the precoding vectors notified from each femtocell, the precoding vector notified redundantly from a plurality of femtocells is considered to be a vector that affects more femtocells. Therefore, such a vector is not used, that is, a precoding vector notified from a smaller number of femtocells may be actually used. In this case, it is possible to prevent the use of a precoding vector that affects more femtocells without notifying additional information other than information related to the precoding vector selected in the femtocell.

  Furthermore, when there are a large number of femtocells and there is no precoding vector that is convenient for all femtocells, transmission in the macrocell may be stopped. Such control makes it possible to completely suppress interference from the macro cell to the femto cell. Only when it is determined that any precoding vector can be used in the MeNB 10 (when there is an undesired precoding vector for any femtocell), transmission in the macro cell is performed. You can also. That is, in this case, it is determined whether transmission in the macro cell is permitted based on information notified from the femto cell.

  In addition, until now, in all femtocell terminals 21 to 23 or HeNBs 11 to 13, some precoding vectors that are not desired to be used in the MeNB 10 are selected and notified to the MeNB 10. It is good also as a structure which notifies such information only from the femtocell with which the influence received from MeNB10 is different. In this case, in the terminals 21 to 23 or the HeNBs 11 to 13 of each femtocell, the influence of interference is evaluated by calculating the average value of the formula (2) and the like and receiving interference exceeding a predetermined threshold. Only in the femtocell evaluated as follows, some precoding vectors not desired to be used in the MeNB 10 are selected and notified to the MeNB 10.

  Moreover, you may make it switch on / off of evaluation of such an influence according to the instruction | indication from MeNB. For example, when the number of HeNBs in the active mode is small, information on the precoding vector is notified from all the HeNBs in the active mode, and conversely, the mode is in the active mode. When the number of HeNBs is large, it is realized by notifying only the information related to the precoding vector from the HeNB in the femtocell that is greatly affected by the MeNB among the HeNBs in the active mode. Can do. In this case, MeNB needs to notify each HeNB of the information which instruct | indicates the said switching according to the number of HeNBs which are in active mode.

  In the above embodiment, the precoding vector selected by the femto terminals 21 to 23 or the HeNBs 11 to 13 is a precoding vector that is not desired to be used in the MeNB 10, but is different from the precoding vector that is desired to be used in the MeNB 10. A vector may be selected. In this case, Equation (3) is not max but min, and the MeNB 10 selects one of the precoding vectors notified from the femtocell and uses it for transmission. Moreover, you may make it switch whether Formula (3) is set to max or min according to the instruction | indication from MeNB10. This is because when the number of femtocells existing in a macro cell is very small, such as 1 in Equation (3), min is used, and by selecting a precoding vector that is convenient for the femtocell to be used in the MeNB 10, It becomes possible to more effectively suppress the interference to that one femtocell, and conversely, when there are a large number of femtocells in the macro cell, Equation (3) is set to max and the use in the MeNB 10 This is because by selecting a precoding vector that is inconvenient for the femtocell, it is possible to perform transmission that is less likely to cause interference to more femtocells. Therefore, more efficient transmission can be performed by switching the precoding vector selection criterion according to the number of active femtocells and the like.

  In the present embodiment, MeNB 10 is notified of information related to the precoding vector selected in femto terminals 21 to 23, and MeNB 10 selects a precoding vector that is actually used based on the information. MeNB10 can also select a precoding vector based on the information notified from the macro terminal 20 instead of the information notified from the femto terminals 21-23. This is because the femto cell is located in the macro cell, so that it is considered that the terminal always connects to the macro cell before entering the zone of the femto cell. As described above, the macro terminal 20 notifies the MeNB 10 of a desired precoding vector and receives a precoded signal in the MeNB 10, but the macro terminal 20 enters the zone of the femto cell, and the HeNB 11 When connection with ˜13 is started, the desired precoding vector that has been notified to the macro cell before entering the femto cell is changed to the position of the undesired precoding vector. Therefore, after the terminal moves to the femto cell, the information on the precoding vector notified to the MeNB 10 immediately before the terminal handovers from the macro cell to the femto cell is connected to the MeNB 10 as a precoding vector that is not desired to be used in the MeNB 10. This can be taken into account when selecting a precoding vector addressed to another terminal. Since it is desirable to average the influence of interference on the femtocell over a long period of time, an appropriate selection of precoding vectors cannot be made immediately after handover from the macrocell to the femtocell, but as described above Such a problem can be avoided by considering the immediately preceding precoding vector.

(Second Embodiment)
In the first embodiment according to the present invention, the MeNB 10 acquires information on the precoding vector selected in the femto terminals 21 to 23 or the HeNBs 11 to 13, and based on the information, any of the precoding vector candidates is obtained. However, it is not necessary to select a precoding vector from predetermined candidates, and the MeNB 10 may newly calculate and use a precoding vector. However, also in this case, the calculation is performed as follows based on information on the precoding vector selected in the femto terminals 21 to 23 or the HeNBs 11 to 13.

  First, in the present embodiment as well, as in the first embodiment, the influence of interference given to each femtocell by each precoding vector is estimated based on Expression (2). And the value of Formula (2) becomes large, that is, one precoding vector that is considered to give the largest interference to the femto cell is selected and notified to the MeNB 10. Such selection of precoding may be performed in the femto terminals 21 to 23 or may be performed in the HeNBs 11 to 13. When the precoding vector is selected in the femto terminals 21 to 23, information on the selected precoding vector is first notified to the HeNBs 11 to 13, and the MeNB 10 is notified from the HeNBs 11 to 13 through the wired network. In addition, regarding the selection / notification of the precoding vector, in the first embodiment, a plurality of precoding vectors are selected from predetermined candidates and notified thereof. The difference is that only one precoding vector is selected and notified.

Also in the present embodiment, as shown in FIG. 1, if there are three femtocells in a macro cell, one precoding vector is notified from each of the three femtocells. Three precoding vectors are notified from the cell. Here, for example, it is assumed that the predetermined precoding vector shown in FIG. 2 is used, W _n1 ^{1} from femtocell 1 and W _n2 ^{1} from femtocell 2 to femtocell 3. _Are notified of W _n3 ^{1} , respectively. That is, it means that W _nm ^{1} is notified from the femtocell m. Similarly to the first embodiment, the macro terminal 20 also selects a precoding vector and notifies the MeNB 10 of the selected precoding vector, and the selected and notified precoding vector is W _nM ^{1} . However, the macro terminal 20 selects and notifies a precoding vector desired to be used in the MeNB 10.

Thus, in this embodiment, a total of four precoding vectors are notified to MeNB 10, but MeNB 10 calculates new precoding vectors based on these precoding vectors. This calculation is performed based on SLNR (Signal to Leakage and Noise power Ratio) standards. Here, the SLNR standard is to calculate a precoding vector that maximizes the power ratio of the desired signal to the receiving device that is the destination of the signal and the interference and noise leaking to other receiving devices other than the destination. It is a standard to do. Based on this criterion, if the precoding vector calculated in the MeNB 10 is W _M , W _M is calculated as follows.

Here, evec (A) represents the eigenvector corresponding to the maximum eigenvalue of the matrix A, and σ _M ² represents the reciprocal (or noise power) of SNR (Signal to Noise power Ratio) in the macro terminal.

Such a precoding vector W _M is newly calculated in the MeNB and used for precoding performed at the time of transmission to the macro terminal 20, so that the reception quality to the macro terminal 20 is ensured to some extent, and three femtocells It is also possible to reduce the interference given to. Here, the number of femtocells is three, but the present invention is also applicable when there are more femtocells. Further, when overlapping precoding vectors are notified from a plurality of femtocells, when adding the covariance matrix of the precoding vectors in Equation (4), the overlaps need not be included in the calculation.

  As described above, the MeNB 10 that newly calculates the precoding vector based on the information about the precoding vector notified from the femtocell and the macro terminal 20 can be realized with substantially the same configuration as FIG. However, it is necessary to calculate the precoding vector by performing the calculation shown in Expression (4) in the vector selection unit 34. Moreover, HeNB11-13 and the terminal 20, 21-23 are realizable by the structure shown in FIG. 4, FIG. 5, respectively.

  In the above embodiment, information on the precoding vectors selected by the femto terminals 21 to 23 and the HeNBs 11 to 13 is collected in the MeNB 10, and the precoding vector actually used in the MeNB 10 is selected based on the information. However, when there is a centralized control station that controls a plurality of MeNBs, the centralized control station may select a precoding vector used in the MeNB. Here, since the centralized control station is connected to the MeNB via a wired network such as an optical fiber, information exchange is performed via the wired network.

  In addition, here, the case where the femto cell exists mainly in the macro cell has been described. For example, even when the femto cell exists in the pico cell, the same resource is allocated to the pico cell and the femto cell by the same control. Even when it is used, it is possible to suppress interference that the pico cell gives to the femto cell. In this case, it can be realized by selecting a precoding vector not desired to be used in the PeNB at the femto terminal or the HeNB and notifying the PeNB. Further, the femto terminal or the HeNB may notify the precoding vector only to either the MeNB or PeNB, but may notify the both of the precoding vectors not desired to be used.

  Furthermore, the present invention is applicable to a wireless communication system or the like having overlapping communication ranges as shown in FIG. In FIG. 6, taking a wireless local area network (LAN) as an example, the terminal 100 moves to an AP (Access Point) 103 (second base station apparatus), and the AP 104 (second base station apparatus) moves to a terminal 101 (second base station apparatus). This represents a situation where the AP 105 (first base station apparatus) is transmitting a signal to the terminal 102 (first terminal apparatus). Here, it is assumed that interference comes from the AP 105 to the AP 103 and the terminal 101. In such a case, as in the above embodiment, the AP 103 and the terminal 101 select a precoding vector that is not desired to be used in the AP 105, and notify the AP 105 of the selected precoding vector. It is possible to reduce interference as shown. Such a configuration is effective not only in a wireless LAN system but also in a system in which a large number of transmission / reception devices are mixed in a relatively narrow area. For example, the present invention can also be applied to various appliances in the home that are connected to each other via a wireless network.

  In the above-described embodiment, the configuration and the like illustrated in the accompanying drawings are not limited to these, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In addition, a program for realizing the functions described in the present embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to execute processing of each unit. May be performed. The “computer system” here includes an OS and hardware such as peripheral devices.

  Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.

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

20 Macro Terminals 21 to 23 Femto Terminal 30 Upper Layer 31 Modulation Unit 32 Precoding Unit 33 Signal Multiplexing Unit 34 Vector Selection Unit 35 Channel Estimation Signal Generation Unit 36 D / A Unit 37 Radio Unit 38 Transmission Antenna Unit 39 Reception Unit 40 A / D unit 41 Radio unit 42 Reception antenna unit 50 Upper layer 51 Modulation unit 52 Precoding unit 53 Signal multiplexing unit 54 Channel estimation signal generation unit 55 D / A unit 56 Radio unit 57 Transmission antenna unit 58 Reception unit 59 A / D unit 61 Reception antenna unit 70 Reception antenna unit 71 Radio unit 72 A / D unit 73 Signal separation unit 74 Reception weight multiplication unit 75 Demodulation unit 76 Upper layer 77 Channel estimation unit 78 Reception weight calculation unit 79 Vector selection unit 80 Transmission Part 81 D / A part 82 Radio part 83 Transmitting antenna part

Claims (19)

A first base station apparatus that controls communication within the first communication range, and a second range that is smaller than the first communication range and that overlaps at least partially with the first communication range. A communication system including a second base station device that controls communication within a communication range of the terminal device and a terminal device that communicates with the second base station device,
Based on the control information notified from the first base station device to the terminal device via the second base station device,
The terminal device selects a precoding vector from a plurality of precoding vectors determined in advance, and notifies the second base station device of information indicating the selected precoding vector from the terminal device,
The second base station apparatus notifies the first base station apparatus of information indicating the precoding vector notified from the terminal apparatus. 2. The control information notified from the first base station apparatus to the terminal apparatus via the second base station apparatus is information related to the number of precoding vectors to be notified. The communication system according to 1. The communication system according to claim 2, wherein the number of precoding vectors to be notified includes zero. 4. The communication according to claim 2, wherein when the second base station apparatus is in a sleep mode, the notification of information indicating the precoding vector to the first base station apparatus is stopped. system. When the second base station device enters the sleep mode, the second base station device notifies the first base station device of information for resetting information indicating the precoding vector that was previously notified. The communication system according to any one of claims 2 to 4, wherein: When the second base station device is in a sleep mode,
In the second base station apparatus, estimate a propagation path with the first base station apparatus,
Averaging the estimated propagation path in time,
The communication according to any one of claims 2 to 5, wherein when the mode is changed from the sleep mode to another mode, the information about the averaged propagation path is notified to the first base station apparatus. System . The second base station apparatus is an indoor base station connected to the Internet via a wired network, and notifies the first base station apparatus of information indicating the precoding vector via the Internet. The communication system according to any one of claims 1 to 6. Based on the information indicating the precoding vector notified from the second base station apparatus, a precoding vector different from the predetermined plurality of precoding vectors, wherein the first base station apparatus The communication system according to claim 1, wherein a precoding vector to be actually used is calculated. A first base station apparatus that controls communication within the first communication range, and a second range that is smaller than the first communication range and that overlaps at least partially with the first communication range. A terminal device in a communication system comprising: a second base station device that controls communication within a communication range of; and a terminal device that communicates with the second base station device,
Receiving control information notified from the first base station device via the second base station device;
Based on the received control information, a precoding vector is selected from a plurality of predetermined precoding vectors, and information indicating the selected precoding vector is notified to the second base station apparatus. A terminal device characterized by the above. The control information notified from the first base station device via the second base station device is information on the number of precoding vectors to be notified,
The terminal apparatus according to claim 9, wherein the number of the precoding vectors notified by the control information is selected. A first base station apparatus that controls communication within the first communication range, and a second range that is smaller than the first communication range and that overlaps at least partially with the first communication range. The first base station apparatus in a communication system comprising a second base station apparatus that controls communication within the communication range of the terminal and a terminal apparatus that communicates with the second base station apparatus,
Via the second base station device, to notify the terminal device control information regarding the number of precoding vectors selected from among a plurality of precoding vectors,
  A first base station apparatus, wherein information indicating a precoding vector selected by the terminal apparatus based on the control information is received from the second base station apparatus. The first base station apparatus according to claim 11, wherein the number of precoding vectors includes zero. 12. The information for resetting information indicating a precoding vector notified before is received from the second base station apparatus when the second base station apparatus is in a sleep mode. Or the 1st base station apparatus of 12. Based on the information indicating the precoding vector notified from the second base station apparatus, a precoding vector that is different from the predetermined plurality of precoding vectors and is actually used is determined. It calculates, The 1st base station apparatus as described in any one of Claim 11 to 13 characterized by the above-mentioned. A first base station apparatus that controls communication within the first communication range, and a second range that is smaller than the first communication range and that overlaps at least partially with the first communication range. The second base station apparatus in a communication system comprising a second base station apparatus that controls communication within the communication range of the terminal apparatus and a terminal apparatus that communicates with the second base station apparatus,
Receiving control information related to the number of precoding vectors selected from among a plurality of precoding vectors, notified from the first base station apparatus;
Notifying the terminal device of the control information;
Receiving information indicating a precoding vector selected in the terminal device based on the control information;
The second base station apparatus, wherein information indicating the received precoding vector is notified to the first base station apparatus. The second base station apparatus according to claim 15, wherein the number of precoding vectors includes zero. The base station apparatus according to claim 15 or 16, wherein the first base station apparatus is notified of information for resetting information indicating a precoding vector that has been previously notified when the terminal is in a sleep mode. Second base station apparatus. If you are in sleep mode,
Estimating a propagation path with the first base station device;
Averaging the estimated propagation path in time,
The information on the averaged propagation path is notified to the first base station apparatus when moving from the sleep mode to another mode, according to any one of claims 15 to 17, 2 base station devices. 16. The second base station according to claim 15, wherein the base station is an indoor base station connected to the Internet via a wired network, and notifies the first base station apparatus of information indicating the precoding vector via the Internet. Base station equipment.

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