JP5511637B2 - Wireless communication system and antenna selection method - Google Patents

Description

The present invention relates to a radio communication system and an antenna selection method, and more particularly to a radio communication system using a distributed antenna and an antenna selection method when MIMO or the like is applied in a distributed antenna system applied to the radio communication system. .

A distributed antenna system is known as a technique for efficiently constructing an area in a wireless communication system. For example, as a background art in this technical field, there is JP 2010-68496 A (Patent Document 1). Patent Document 1 shows an example in which MIMO (Multiple Input Multiple Output) is applied in a distributed antenna system.
When MIMO is applied to a wireless communication system, the maximum number of antennas used for transmission and reception is predetermined by the system. For example, in the case of an LTE system (Release 8) standardized by 3GPP, the maximum number of downlink transmission antennas is four.
When applying MIMO in a distributed antenna system, since the maximum number of antennas that can be used in MIMO is determined, MIMO is performed using only some of the plurality of antennas constituting the distributed antenna system. Become. At that time, it is necessary to select an antenna to be used in MIMO from among a plurality of antennas constituting the distributed antenna system. As an antenna selection method in the distributed antenna system, for example, in Patent Document 1, an antenna having a large received power is selected, and in Japanese Patent Laid-Open No. 2007-53768 (Patent Document 2), an antenna is selected based on a relative value of distance attenuation. .
In general, one of the effects expected by applying MIMO is an improvement in throughput when the SNR (Signal To Noise Ratio) is high. As described in Non-Patent Document 1, in MIMO, by performing appropriate signal processing based on the state of the radio channel between the transmitting and receiving antennas (MIMO channel response matrix), a plurality of different information is transmitted in parallel, Improved throughput.
At this time, a higher throughput can be realized as the number of pieces of information that can be transmitted in parallel increases. Here, in order to realize higher throughput, it is necessary to transmit a plurality of pieces of more information in parallel. For this purpose, it is necessary that the radio channels between the transmitting and receiving antennas are independent. If the variation between the transmitting and receiving antennas does not change in the combination between the transmitting and receiving antennas, even if MIMO is applied, a plurality of different information cannot be transmitted in parallel. End up.

JP 2010-68496 A JP 2007-53768 A

Yoshio Karasawa, “MIMO Propagation Channel Modeling,” IEICE B, vol. J86-B, no. 9, pp. 1706-1720, 2003.

When applying MIMO in a distributed antenna system, it is necessary to select an antenna to be used in MIMO as described above. At that time, in the case of a distributed antenna system, since there are many antennas, it is considered that the realizable throughput varies greatly depending on the antenna selection method. Since the throughput can be increased as the SNR is higher and more different information can be transmitted in parallel when MIMO is applied, it is desirable to select such an antenna.
In the method described in Patent Document 1, an antenna having a large reception power is selected from the antennas of the distributed antenna system. Therefore, it can be expected that an antenna having a good SNR on average, that is, an antenna capable of realizing a high throughput can be expected. On the other hand, when MIMO is applied using the selected antenna, whether multiple pieces of information can be transmitted in parallel. It is unknown and is insufficient in terms of maximizing throughput in the antenna selection method in the distributed antenna system to which MIMO is applied.
In the method described in Patent Document 2, an antenna to be used for communication is selected from the relative value of distance attenuation, and it can be expected that this also has an average SNR, that is, an antenna that can realize high throughput. On the other hand, when MIMO is applied using a selected antenna, it is unclear whether multiple pieces of information can be transmitted in parallel, and the viewpoint of maximizing throughput as an antenna selection method in a distributed antenna system to which MIMO is applied Is not enough.
In view of the above points, an object of the present invention is to obtain a throughput improvement effect when MIMO is applied to a distributed antenna system. Another object of the present invention is to perform MIMO communication using a combination of antennas that maximize the throughput improvement effect of MIMO in a distributed antenna system.

  The present invention has been invented in view of these problems, and when selecting an antenna of a distributed antenna system, an antenna to which MIMO is applied is used instead of using only elements that affect SNR such as received power and distance attenuation. The channel response matrix and the eigenvalue are calculated for each of the combinations, and the orthogonality of the channel in the selected antenna combination is determined from the total square root of the calculated eigenvalues. High channel orthogonality means that more information can be transmitted in parallel when MIMO is applied. Therefore, according to the present invention, an antenna combination that can be expected to have the highest throughput can be selected.

According to the first solution of the present invention,
A radio communication system that performs MIMO communication between a base station apparatus having a plurality of distributed antennas and a radio terminal having a plurality of terminal antennas, and an antenna selection method in the radio communication system ,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
The wireless terminal transmits each unique value information held in response to the previous SL amount distributed antenna combination candidate, and a combination candidate of information distributed antenna used for the calculation of the eigenvalues information and the unique value information to the base station apparatus And
The base station apparatus, depending on the size of each eigenvalue information notified from the wireless terminal, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
A base station apparatus notifies a radio terminal of selected antenna information including information on a combination of selected distributed antennas, whereby a radio communication system that performs communication between the base station apparatus and the radio terminal, and an antenna selection method Is provided.

According to the second solution of the present invention,
A radio communication system that performs MIMO communication between a base station apparatus having a plurality of distributed antennas and a radio terminal having a plurality of terminal antennas, and an antenna selection method in the radio communication system ,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
Wireless terminal holds in response to a combination candidate of the pre-Symbol partial dispersion antennas each unique value information,
The wireless terminal, depending on the size of each eigenvalue information, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
Radio terminal communicates between base station apparatus and radio terminal by notifying base station apparatus of selected antenna information including information of combination of selected distributed antennas, and antenna selection method Is provided.

According to the third solution of the present invention,
A radio communication system that performs MIMO communication between a base station apparatus having a plurality of distributed antennas and a radio terminal having a plurality of terminal antennas, and an antenna selection method in the radio communication system ,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The wireless terminal generates and transmits an uplink pilot signal that can individually identify the distributed antenna,
The base station apparatus based on the result of receiving the uplink pilot signal from the wireless terminal, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The base station apparatus, an eigenvalue information calculated on the combination candidates of each of said distributed antenna,
The base station apparatus holds in response to a combination candidate for each unique value information distributed prior Symbol fraction antenna,
The base station apparatus according to the magnitude of the eigenvalues information, by selecting a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna, the communication with the base station apparatus and the wireless terminal A wireless communication system to perform and an antenna selection method are provided.

When MIMO is applied to the distributed antenna system, an effect of improving throughput can be obtained. In the case of a distributed antenna system, the number of antennas that can be used for communication is greater than the number of antennas that can be used for MIMO. Therefore, by selecting a combination that provides the best throughput improvement effect by MIMO, the throughput improvement effect by MIMO can be improved Expect to be bigger.

It is an example of a block diagram of a distributed antenna system. It is an example of the block diagram of a radio | wireless terminal. It is an example of the block diagram of a base station apparatus. It is an example of explanatory drawing about the transmission-line expression of a MIMO channel. It is an example of explanatory drawing about the reception power from each RAU antenna. It is an example of explanatory drawing about the eigenvalue which has comparable magnitude | size. It is an example of explanatory drawing about the eigenvalue from which a magnitude | size differs. 3 is an operation sequence according to the first embodiment. 6 is an example of a configuration diagram of a wireless terminal in Embodiment 2. FIG. 6 is an example of a configuration diagram of a base station apparatus in Embodiment 2. FIG. 10 is an example of a configuration diagram of a third embodiment. FIG. 10 is an example of a configuration diagram of a radio terminal in Embodiment 3. FIG. FIG. 10 is an example of a configuration diagram of a base station apparatus in a third embodiment. It is an example of an explanatory view of a MIMO specific transmission mode. It is a sequence diagram of the second embodiment. It is a sequence diagram of the third embodiment.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1. Embodiment 1
FIG. 1 is an example of a configuration diagram of a distributed antenna system according to the present embodiment.
In the system of FIG. 1, a plurality of distributed RAUs (Remote Antenna Units) 101 that perform wireless communication with a wireless terminal 102 are routed via an antenna switch (antenna SW) 104 by a wired cable 103 such as an optical fiber or a coaxial cable. Are connected to a base station apparatus 105 that is a CU (Control Unit), and the base station apparatus 105 has a configuration connected to a high-speed backhaul line 107 via a high-speed backhaul line termination apparatus 106. . The antenna SW 104 is a device for connecting and switching a signal from the antenna of each RAU and the antenna port of the base station device 105. For example, when only two (e.g., # 1 and # 5) of six RAU antennas are used at a certain moment, two signals of the base station apparatus 105 are connected only to # 1 and # 5. To do. Although six RAUs are illustrated here, the number of RAUs is not limited to six.
FIG. 2 shows an example of a configuration diagram of the wireless terminal 102 in the present embodiment. The radio terminal 102 includes an eigenvalue calculation target antenna selection unit 206, an eigenvalue calculation unit 207, a channel estimation unit 208, a data demodulation unit 209 that demodulates downlink data, and a received power / SNR measurement unit 210.
FIG. 3 shows an example of a configuration diagram of base station apparatus 105 in the present embodiment.
Base station apparatus 105 includes pilot signal transmission section 301 that generates a pilot signal, antenna selection section 302 that selects an antenna to be used in MIMO based on eigenvalue information 202, and data transmission section 303 that transmits downlink data.
FIG. 8 shows an operation sequence of the present embodiment.
In step 801, the pilot signal transmission section 301 of the base station apparatus generates and transmits a downlink pilot signal that can individually identify the RAU antenna. As a method for individually identifying antennas, for example, at a specific time and a specific frequency, the number of antennas that transmit downlink pilot signals is limited to one, and the time and frequency are preliminarily determined by the base station apparatus and the radio terminal. There is a way to share. As a result, it is possible to uniquely identify from which antenna the downlink pilot signal received at a specific time and a specific frequency is transmitted from the radio terminal on the receiving side. Alternatively, the downlink pilot signal may be transmitted by including identification information for identifying the antenna, and the wireless terminal may identify it.

In step 802, the eigenvalue calculation target antenna selection unit 206 of the wireless terminal selects a set of antennas used for eigenvalue calculation. The eigenvalue calculation target antenna selection unit 206 generates a plurality of RAU antenna combinations equal to or less than the maximum number of RAU antennas that can be used in MIMO. As a method of generating a combination of RAU antennas, a method of generating all combinations of RAU antennas or a method targeting only a part of RAU antennas having large received power and SNR can be used.
For example, consider the case where there are six RAU antennas as shown in FIG. 1, and the maximum number of antennas that can be used in MIMO is two. As a method of generating a combination of RAU antennas that are candidates for MIMO, for example, the following two methods are conceivable.
The first method is a method of generating all the combinations of all six RAU antennas. In this case, a set of ₆ C ₂ = 15 antennas is generated, and an eigenvalue is calculated by the eigenvalue calculation unit 207 for each of the 15 antenna sets. Since this method generates all RAU antenna combinations, there is a demerit that the number of eigenvalue calculations is increased, but there is an advantage that antenna combinations with higher throughput can be used as candidates.
The second method is a method of selecting a part of the six RAU antennas and generating a set of the selected antennas. At this time, as a method of selecting a part of the RAU antennas, it is conceivable to use only information of the received power / SNR measurement unit 210 and target only a part of the RAU antennas having large received power and SNR.
FIG. 5 shows an example of an explanatory diagram regarding received power from each RAU antenna. As an example of the received power of the signal from each antenna, when the distribution is as shown in FIG. 5, the received power of # 3 and # 6 is smaller than a separately defined threshold and is high even when used for MIMO. Since it is not expected to obtain a throughput, it is preferable to generate a set of antennas by a combination of antennas # 1, # 2, # 4, and # 5. In this case, a set of ₄ C ₂ = 6 antennas is generated, and an eigenvalue is calculated by the eigenvalue calculation unit 207 for each of the 6 antenna sets. This method has a demerit that there is a possibility that a combination of antennas with higher throughput may be excluded because the combination of RAU antennas is limited compared to the first method. There is a merit that the number of times decreases.

とすると、受信アンテナにおける受信信号ベクトルＹは、

で示される。ここで、Ａは、送受信アンテナの各素子間のチャネル応答であり、次のＮ行Ｍ列の行列で示される。

ここで、上添字Ｔは転置を表す。また、ａ_ｎｍは、送信アンテナ＃ｍから送信され、受信アンテナ＃ｎにて受信されるパスに対応するチャネル応答である。チャネル応答は、各アンテナから送信された既知のパイロット信号を受信することで生成する。
このチャネル応答行列Ａは特異値分解により以下のように表記できる。 In step 803, eigenvalues are calculated for the set of antennas selected in step 802. The eigenvalue calculation unit 207 of the wireless terminal calculates a MIMO channel response matrix and eigenvalue when the antenna selected by the eigenvalue calculation target antenna selection unit 206 is used. The eigenvalue calculation method is obtained, for example, by performing singular value decomposition on the channel response matrix as described in Non-Patent Document 1.
FIG. 4 shows an example of an explanatory diagram regarding the transmission path representation of the MIMO channel. For example, consider a transmission path opposite to the array antenna of M transmitting antennas 400 and N receiving antennas 401 as shown in FIG. The signal vector X to be transmitted

Then, the received signal vector Y at the receiving antenna is

Indicated by Here, A is the channel response between the elements of the transmission / reception antenna, and is indicated by the following matrix of N rows and M columns.

Here, the superscript T represents transposition. A _nm is a channel response corresponding to a path transmitted from the transmission antenna #m and received by the reception antenna #n. The channel response is generated by receiving a known pilot signal transmitted from each antenna.
This channel response matrix A can be expressed as follows by singular value decomposition.

である。また、上添字Ｈは複素共役転置、λ_ｉは相関行列ＡＡ^ＨあるいはＡ^ＨＡのｉ番目（値の大きい順にｉ＝１，２，・・・，Ｍ_０）の固有値であり、ｖ_ｉはＡ^ＨＡの固有値λ_ｉに属する固有ベクトル、ｕ_ｉはＡＡ^Ｈの固有値λ_ｉに属する固有ベクトルである。
例えば、Ｎ＝Ｍ＝２でチャネル応答行列Ａが、

となる場合を考える。この時、

であり、この固有値は、λ_１＝８,λ_２＝２であり、それぞれの固有値に対応する固有ベクトルは、

となる。

It is. The superscript H is a complex conjugate transposition, λ _i is the i-th eigenvalue (i = 1, 2,..., M _{0 in} descending order of value) of the correlation matrix AA ^H or A ^H A, and v _i is eigenvector belonging to the eigenvalue λ _i of a ^H a, _{u i} is the eigenvector belonging to the eigenvalue λ _i of AA ^H.
For example, N = M = 2 and the channel response matrix A is

Consider the case. At this time,

The eigenvalues are λ ₁ = 8, λ ₂ = 2 and the eigenvectors corresponding to the respective eigenvalues are

It becomes.

から固有値は、λ_１＝８,λ_２＝２であり、また、それぞれの固有値に対応する固有ベクトルは、

となる。したがって、Ａの特異値分解結果は、

であり、固有値はλ_１＝８,λ_２＝２となる。
ステップ８０３における計算の結果、固有値情報２０２は、例えば２×２ＭＩＭＯの場合には、２つの複素数λ_１とλ_２となる。例えば前述のチャネル応答行列Ａの場合は、固有値はλ_１＝８,λ_２＝２となる。この固有値情報２０２を固有値計算対象アンテナ選択部２０６で選択したアンテナの組合せに応じて保持し、例えば制御チャネルを介して、固有値計算に用いたアンテナの情報（例えば、各アンテナの識別情報を含む、アンテナの組合せ候補の情報）とともに基地局装置１０５へ送信する。 Similarly,

The eigenvalues are λ ₁ = 8, λ ₂ = 2 and the eigenvectors corresponding to the respective eigenvalues are

It becomes. Therefore, the singular value decomposition result of A is

The eigenvalues are λ ₁ = 8 and λ ₂ = 2.
As a result of the calculation in step 803, the eigenvalue information 202 becomes _two complex numbers λ ₁ and λ _{2 in} the case of 2 × 2 MIMO, for example. For example, in the case of the above-described channel response matrix A, the eigenvalues are λ ₁ = 8 and λ ₂ = 2. This eigenvalue information 202 is held according to the combination of antennas selected by the eigenvalue calculation target antenna selection unit 206, and information on the antenna used for eigenvalue calculation (for example, including identification information of each antenna, for example, via the control channel, And information on antenna combination candidates) to base station apparatus 105.

In step 804, an antenna selection unit 302 of the base station apparatus performs the selection based on the eigenvalue information 202 notified from the terminal. Multiple selection methods are possible. Examples are given below.
In the first selection method, for example, in the case of 2 × 2 MIMO, the eigenvalue information 202 is a maximum of two complex numbers λ ₁ and λ ₂ , but the sum of the sizes of √λ ₁ and √λ ₂ is the largest. The RAU antenna is selected. At this time, it can be limited to RAU antennas in which λ ₁ and λ ₂ are equal to or larger than a certain value. As described in Non-Patent Document 1, since the square root √λ of each eigenvalue is a value proportional to the amplitude gain during MIMO transmission, the sum of √λ is the amplitude when transmission is performed using all eigenmodes. Proportional to the sum of gains. Therefore, a higher transmission rate can be realized when the sum of √λ is large. Similarly, for example, in the case of 4 × 4 MIMO, an antenna combination that maximizes the sum of the square roots of the eigenvalues may be selected.
FIG. 6 shows an example of an explanatory diagram for eigenvalues having similar magnitudes. FIG. 7 shows an example of an explanatory diagram for eigenvalues having different sizes.

となる。一般にＭＩＭＯによる高い伝送速度を実現する場合にはＳＮＲは高いため、ＳＮＲが十分高い場合を想定すると、

となる。この式から、ＭＩＭＯによって高い伝送速度を実現するには、各固有モードのＳＮＲによらず、固有値λ_iの２を底とする対数の和が最も大きくなるＲＡＵのアンテナの組合せを選択するのがよいことが分かる。 In the second selection method, for example, in the case of 2 × 2 MIMO, the eigenvalue information 202 is two complex numbers λ ₁ and λ ₂ at the maximum, but the magnitudes of the eigenvalues √λ ₁ and √λ ₂ as shown in FIG. The RAU antenna with the smallest difference is selected. At this time, it is more preferable to limit the antenna to RAU antennas in which λ ₁ and λ ₂ are equal to or greater than the threshold value. When the difference between the magnitudes of λ ₁ and λ ₂ is large as shown in FIG. 7 or when one eigenvalue is less than or equal to the threshold value, the antenna combination is not selected. According to Non-Patent Document 1, since the eigenvalue λ is a value proportional to the power gain at the time of MIMO transmission, a high transmission rate can be realized when λ is comparable and large. For example, in the case of 4 × 4 MIMO, the eigenvalue information 202 is a maximum of four complex numbers λ ₁ , λ ₂ , λ ₃ , and λ ₄ . At this time, for the eigenvalue having a magnitude equal to or larger than the threshold value, an antenna combination that minimizes eigenvalue dispersion may be selected.
The third selection method is to select an RAU antenna that maximizes the sum of logarithms with the eigenvalue λ being 2 as the base. According to Non-Patent Document 1, channel capacity C at the time of MIMO transmission using a specific mode, if the SNR of the gamma _i in eigenmode i,

It becomes. In general, when realizing a high transmission rate by MIMO, since the SNR is high, assuming that the SNR is sufficiently high,

It becomes. From this equation, in order to achieve a high transmission rate by MIMO, it is necessary to select a combination of RAU antennas that has the largest sum of logarithms with eigenvalues λ _i as bases, regardless of the SNR of each eigenmode. I know it ’s good.

Although three selection methods are illustrated here, the present invention and the present embodiment can be applied to other antenna selection methods as long as the antenna selection method can achieve a high transmission rate by MIMO based on eigenvalues. Applicable.

The antenna selection unit 203 of the base station apparatus transmits a combination of antenna information of the selected RAU (for example, antenna combination information including identification information of each antenna selected from the antenna combination candidates) to the radio terminal 102. Notice. For example, when # 1 and # 5 among the six antennas # 1 to # 6 are used as a result of antenna selection, the numbers (# 1, # 5) are notified.

In step 805, MIMO transmission is performed between the base station apparatus and the wireless terminal. The channel estimation unit 208 of the radio terminal generates a CQI (Channel Quality Indicator) and a U ^H matrix necessary for data transmission by MIMO from the selected antenna information 203 and the pilot signal 201 notified from the base station apparatus 105, and the base station Notify the device 105.
The data transmission unit 303 of the base station apparatus transmits data 205 using the selected antenna information 203 and the CQI / ^UH matrix 204.
FIG. 14 shows an example of eigenmode transmission using singular value decomposition. Here, a case where M ₀ different data streams are transmitted is illustrated. In the eigenmode transmission, the transmission data stream is transmitted after being converted by a matrix U ^H ≡ [u ₁ u ₂ ... U _M0 ] obtained as a result of singular value decomposition. The demodulator of the wireless terminal can restore the original data stream by multiplying the received signal by the matrix V≡ [v ₁ v ₂ ... V _M0 ] obtained as a result of the singular value decomposition.
Data transmission unit 303 of the base station apparatus using an antenna that is specified by the selected antenna information 203 at the time of downlink data transmission, determines the modulation and demodulation method from the CQI notified from the wireless terminal, and using the U ^H matrix The data is transmitted in the MIMO specific transmission mode shown in FIG. Here, the MIMO specific transmission mode using the U ^H matrix has been described as an example, but the present invention and the present embodiment are similarly implemented even if PMI (Precoded Matrix Indicator) is used instead of the U ^H matrix. Is possible.
It should be noted that in order to follow fluctuations in the radio wave environment accompanying the movement of the terminal, it is desirable that the operations from step 802 to step 804 should be repeated as time passes, rather than being performed only once. Thereby, the antenna used in MIMO can be changed following the movement of the terminal and the change of the radio wave environment.

According to Embodiment 1 described above, in the distributed antenna system, it is possible to select a combination of RAU antennas that achieve high throughput when MIMO is applied.

2. Embodiment 2

The present embodiment is an embodiment in the case where the antenna selection performed in the base station apparatus in the first embodiment is performed by a wireless terminal. The configuration diagram of the distributed antenna system is the same as that of Embodiment 1, but the configurations of radio terminal 102 and base station apparatus 105 are different.
FIG. 9 shows an example of a configuration diagram of a radio terminal in this embodiment, and FIG. 10 shows an example of a configuration diagram of a base station apparatus. Of the constituent parts in FIGS. 9 and 10, the description of the parts having the same functions as the constituents denoted by the same reference numerals as those already described in FIGS. 2 and 3 is omitted.
FIG. 15 shows a sequence diagram of the second embodiment. Note that among the steps in FIG. 15, the steps with the same signs as in FIG. 8 indicate the same processing.
In the wireless terminal 901 of FIG. 9, an antenna selection unit 902 is newly added as compared with the wireless terminal 102 of FIG. 2 of the first embodiment. The antenna selection unit 902 has the same function as the antenna selection unit 302 in Embodiment 1, and in this embodiment, the wireless terminal has an antenna selection unit. Therefore, the information notified to the base station apparatus 1001 is not the eigenvalue information but the selected antenna information, and the amount of information notified to the base station apparatus can be reduced as compared with the first embodiment. Channel estimation section 903 performs channel estimation using the selected antenna information of antenna selection section 902.
In base station apparatus 1001 of FIG. 10, data transmission section 303 transmits downlink data based on selected antenna information 904 and CQI / ^UH matrix 204 notified from the terminal.
According to the second embodiment described above, it is possible to select a combination of RAU antennas that achieve high throughput when MIMO is applied in a distributed antenna system. Compared to Embodiment 1, it is not necessary to transmit eigenvalue information 202 from radio terminal 901 to base station apparatus 1001, and therefore information transmitted from radio terminal 901 to base station apparatus 1001 that is necessary for antenna selection. The amount can be reduced.

3. Embodiment 3

This embodiment is an embodiment when MIMO is applied in the uplink direction in a distributed antenna system. FIG. 11 is an example of a configuration diagram of the present embodiment, but the terminal is performing uplink MIMO and the configurations of the radio terminal 1101 and the base station apparatus 1102 are different from those in FIG. Of the constituent parts shown in FIGS. 12 and 13 shown below, parts having the same names as constituent parts of the first or second embodiment have the same functions.
FIG. 16 shows a sequence diagram of the third embodiment. In addition, each step of the same code | symbol as FIG. 8 among each step of FIG. 16 shows the same process.

FIG. 12 shows an example of a configuration diagram of the wireless terminal 1101. The wireless terminal has a pilot signal transmission unit 1204 and a data transmission unit 1205. Pilot transmission section 1204 generates and transmits uplink pilot signal 1201 that can individually identify the antenna of the terminal. The data transmission unit 1205 transmits the uplink data 1203 using the CQI / ^UH matrix 1202 notified from the base station.
FIG. 13 shows an example of a configuration diagram of the base station apparatus 1102. Base station apparatus 1102 includes received power / SNR measurement section 1301, eigenvalue calculation target antenna selection section 1302, eigenvalue calculation section 1303, antenna selection section 1304, channel estimation section 1305, and data demodulation section 1306.
The eigenvalue calculation target antenna selection unit 1302 generates a plurality of sets of RAU antennas that are equal to or less than the maximum number of RAU antennas that can be used in MIMO. As a method for generating a set of RAU antennas, the same idea as in the first embodiment can be applied. The eigenvalue calculation unit 1303 calculates a channel response matrix and an eigenvalue when the antenna selected by the eigenvalue calculation target antenna selection unit 1302 is used. The eigenvalue calculation method is the same as that of the first embodiment except that the uplink and downlink are different. The antenna selection unit 1304 and the channel estimation unit 1305 are the same as the antenna selection unit 302 and the channel estimation unit 208 of the first embodiment except that the uplink and downlink are different, and notify the terminal of the CQI / ^UH matrix 1202. The data demodulation unit 1306 demodulates the uplink data 1203 from the wireless terminal 1101 based on information from the channel estimation unit.
According to the third embodiment described above, a combination of RAU antennas that achieve high throughput can be selected even when uplink MIMO is applied in a distributed antenna system.

In addition to MIMO, the present invention can be applied to SIMO, SISO, and the like, and can be applied to various wireless communication systems in which a plurality of antennas are distributed.

101 RAU (Remote Antenna Unit)
102 Wireless terminal 103 Wired line 104 Antenna SW (Switch)
105 CU (Control Unit): base station apparatus 106 high-speed backhaul line termination apparatus 107 high-speed backhaul line 201 pilot signal 202 eigenvalue information 203 selection antenna information 204 CQI · U ^H matrix 205 data 206 eigenvalue calculation target antenna selection section 207 eigenvalue calculation Unit 208 channel estimation unit 209 data demodulation unit 210 reception power / SNR measurement unit 301 pilot signal transmission unit 302 antenna selection unit 303 data transmission unit 400 transmission antenna 401 reception antenna 901 wireless terminal 902 in the second embodiment antenna in the second embodiment Selection unit 903 Channel estimation unit 904 in Embodiment 2 Selected antenna information 1001 in Embodiment 2 Base station apparatus 1101 in Embodiment 2 Wireless terminal in Embodiment 3 102 uplink pilot signal transmission unit 1205 embodiment in the third uplink data 1204 carried in CQI · ^{U H} matrix 1203 Embodiment 3 in the upstream pilot signal 1202 Embodiment 3 according to the third base station apparatus 1201 implemented in the third embodiment Uplink data transmission section 1301 in Embodiment 3 Received power / SNR measurement section 1302 in Embodiment 3 Eigenvalue calculation target antenna selection section 1303 in Embodiment 3 Eigenvalue calculation section 1304 in Embodiment 3 Antenna selection section in Embodiment 3 1305 Channel estimation unit 1306 in Embodiment 3 Data demodulation unit in Embodiment 3

Claims (10)

In a wireless communication system that performs MIMO communication between a base station device having a plurality of distributed antennas and a wireless terminal having a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
The wireless terminal transmits each unique value information held in response to the previous SL amount distributed antenna combination candidate, and a combination candidate of information distributed antenna used for the calculation of the eigenvalues information and the unique value information to the base station apparatus And
The base station apparatus, depending on the size of each eigenvalue information notified from the wireless terminal, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
A radio communication system in which a base station apparatus communicates between a base station apparatus and a radio terminal by notifying a radio terminal of selected antenna information including information on a combination of selected distributed antennas. The radio terminal generates MIMO transmission information necessary for data transmission by MIMO from the selected antenna information and the pilot signal notified from the base station apparatus, and notifies the MIMO transmission information to the base station apparatus,
The radio communication system according to claim 1, wherein the base station apparatus transmits data using the selected antenna information and the MIMO transmission information. In a wireless communication system that performs MIMO communication between a base station device having a plurality of distributed antennas and a wireless terminal having a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
Wireless terminal holds in response to a combination candidate of the pre-Symbol partial dispersion antennas each unique value information,
The wireless terminal, depending on the size of each eigenvalue information, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
A radio communication system in which a radio terminal communicates between a base station apparatus and a radio terminal by notifying the base station apparatus of selected antenna information including information on a combination of selected distributed antennas. In a wireless communication system that performs MIMO communication between a base station device having a plurality of distributed antennas and a wireless terminal having a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The wireless terminal generates and transmits an uplink pilot signal that can individually identify the distributed antenna,
The base station apparatus based on the result of receiving the uplink pilot signal from the wireless terminal, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The base station apparatus, an eigenvalue information calculated on the combination candidates of each of said distributed antenna,
The base station apparatus holds in response to a combination candidate for each unique value information distributed prior Symbol fraction antenna,
The base station apparatus according to the magnitude of the eigenvalues information, by selecting a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna, the communication with the base station apparatus and the wireless terminal A wireless communication system to perform. The base station device generates MIMO transmission information necessary for data transmission by MIMO from the selected antenna information and the uplink pilot signal notified from the wireless terminal, and notifies the MIMO transmission information to the wireless terminal,
The wireless communication system according to claim 4, wherein the wireless terminal transmits data using the selected antenna information and the MIMO transmission information. An antenna selection method in a wireless communication system that performs MIMO communication between a base station apparatus including a plurality of distributed antennas arranged in a distributed manner and a wireless terminal including a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
The wireless terminal transmits each unique value information held in response to the previous SL amount distributed antenna combination candidate, and a combination candidate of information distributed antenna used for the calculation of the eigenvalues information and the unique value information to the base station apparatus And
The base station apparatus, depending on the size of each eigenvalue information notified from the wireless terminal, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
An antenna selection method in which a base station apparatus communicates between a base station apparatus and a wireless terminal by notifying a wireless terminal of selected antenna information including information on a combination of selected distributed antennas. An antenna selection method in a wireless communication system that performs MIMO communication between a base station apparatus including a plurality of distributed antennas arranged in a distributed manner and a wireless terminal including a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The base station apparatus generates and transmits a downlink pilot signal that can individually identify the distributed antenna,
Based on the result of the wireless terminal receives a downlink pilot signal from the base station apparatus, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The wireless terminal, the eigenvalues information calculated on the combination candidates of each of said distributed antenna,
Wireless terminal holds in response to a combination candidate of the pre-Symbol partial dispersion antennas each unique value information,
The wireless terminal, depending on the size of each eigenvalue information, selects a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna,
An antenna selection method in which a radio terminal communicates between a base station apparatus and a radio terminal by notifying the base station apparatus of selected antenna information including information on a combination of selected distributed antennas. An antenna selection method in a wireless communication system that performs MIMO communication between a base station apparatus including a plurality of distributed antennas arranged in a distributed manner and a wireless terminal including a plurality of terminal antennas,
When the number of distributed antennas is N and the maximum number of antennas usable in the MIMO is M, when selecting M antennas to be used in MIMO from the N distributed antennas,
The wireless terminal generates and transmits an uplink pilot signal that can individually identify the distributed antenna,
The base station apparatus based on the result of receiving the uplink pilot signal from the wireless terminal, by the select part of a distributed antenna of the N number of distributed antenna, the M from the dispersion antenna part the selected MIMO seeking a combination candidate of distributed antennas used,
The base station apparatus, an eigenvalue information calculated on the combination candidates of each of said distributed antenna,
The base station apparatus holds in response to a combination candidate for each unique value information distributed prior Symbol fraction antenna,
The base station apparatus according to the magnitude of the eigenvalues information, by selecting a combination of distributed antennas used in MIMO from the combinations candidates of the distributed antenna, the communication with the base station apparatus and the wireless terminal Antenna selection method to be performed.   When obtaining the combination candidate,
  5. The wireless communication system according to claim 1, wherein a plurality of distributed antennas having received power and / or SNR larger than a predetermined threshold are selected as the partial distributed antennas. When asking you to the combination candidate,
As a distributed antenna of the part, the antenna selection method according to any one of claims 6 to 8 receives power and / or SNR is characterized by selecting a distributed antenna of advance greater than determined threshold Ifuku number .

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