JP4740205B2 - Satellite communication system and base station apparatus - Google Patents

Description

  The present invention relates to a satellite communication system that includes a single base station apparatus and a plurality of user station apparatuses and uses a plurality of beams.

  Non-Patent Document 1 describes a multi-beam satellite communication system based on frequency division multiple access (FDMA).

  FIG. 6 is a system configuration diagram of a multi-beam satellite communication system. According to FIG. 6, the system includes a plurality of user station apparatuses 11 to 15, a relay station apparatus 2 that is a satellite, and a base station apparatus 3. In FIG. 6, the relay station apparatus 2 uses four beams 41 to 44, the user station apparatuses 11 and 12 are in the area of the beam 41, and the user station apparatus 13 is in the area of the beam 42, The user station apparatus 14 exists in the area of the beam 43, and the user station apparatus 15 and the base station apparatus 3 exist in the area of the beam 44.

  FIG. 7 is a diagram for explaining relay of a signal transmitted by each user station device to the base station device 3 by the relay station device 2. In FIG. 7A, reference numeral 51 denotes a signal transmitted by the user station device 11, and the signal 51 includes a training signal unique to the user station device 11. Similarly, reference numerals 52 to 55 are signals transmitted by the user station apparatuses 12 to 15, respectively, and the signals 52 to 55 include training signals specific to the user station apparatuses 12 to 15, respectively.

  Since the user station apparatuses 11 to 15 transmit the signals 51 to 55 at the same frequency f1, respectively, the receiving unit of the beam 41 of the relay station apparatus 2 receives the signal 61 including the components of the signals 51 to 55. become. Similarly, the receiving units of the beams 42 to 44 of the relay station device 2 receive the signals 62 to 64 including the components of the signals 51 to 55, respectively. The relay station device 2 frequency-multiplexes the received signals 61 to 64 after frequency conversion, and transmits a frequency multiplexed signal including the signals 61 to 64 shown in FIG. 7B to the base station device 2.

  FIG. 8 is a block diagram of the base station apparatus 3 according to the prior art. The frequency multiplexed signal including the signals 61 to 64 shown in FIG. 7B is branched into four, which is the same as the number of beams, and then the corresponding beam signal is extracted by the frequency conversion / filter unit corresponding to each beam. . That is, the signal 61 from the first frequency conversion / filter unit, the signal 62 from the second frequency conversion / filter unit, the signal 63 from the third frequency conversion / filter unit, and the signal 63 from the fourth frequency conversion / filter unit. Signals 64 are respectively output.

  The propagation path matrix estimation unit has a matched filter having a high correlation value with the training signal of each of the user station apparatuses 11 to 15 and determines a propagation path matrix component from the input signal. For example, the component estimation unit that receives the signal 61 in the channel matrix estimation unit estimates the channel matrix components h11, h12, h13, h14, and h15 from the correlation between the signal 61 and each training signal. The same applies to the other component estimation units, and the channel matrix estimation unit estimates a 4 × 5 channel matrix.

  Based on the propagation path matrix estimated in this way, the interference compensation unit converts the signals 61 to 64 into signals 51 to 55, and the demodulation unit performs the respective demodulation processes. Details of the interference compensation are described in Non-Patent Document 2.

Michael L. Moher, “Multiuser Decoding for Multibeam Systems”, IEEE Trans. on Vehicular Technology, Vol. No. 49 4 Ogane et al., “MIMO System Fundamentals and Elemental Technologies”, Design / Analysis Method Workshop Materials for Antennas and Propagation (29/30), Organizer: IEICE Technical Committee on Antennas and Propagation

  In the configuration described in Non-Patent Document 1, it is not considered how to determine the user station apparatus to which the same frequency is assigned. Since the interference compensation characteristic varies depending on the propagation environment with the user station apparatus, depending on the selection of the user station apparatus to which the same frequency is assigned, the line quality is deteriorated and the total system capacity is reduced.

  Therefore, an object of the present invention is to provide a multi-beam satellite communication system that performs frequency allocation in consideration of a propagation environment with a user station apparatus, and a base station apparatus that determines frequency allocation in the system.

The base station apparatus according to the present invention is a base station apparatus that receives transmission signals from a plurality of user station apparatuses via a relay station apparatus that uses a plurality of beams, and is included in the transmission signals of the user station apparatus. Based on a training signal unique to the user station apparatus, a column component corresponding to each user station apparatus of the propagation path matrix is estimated corresponding to each beam that is a row component of the propagation path matrix, and the same frequency is assigned. a plurality of user stations is a candidate, select one or more user stations, the propagation channel matrix for the set of the user station apparatus selected, to seek based on the column components of the user station apparatus selected, 1 means for performing a plurality of combinations of selecting more than three user stations, each channel matrix obtained, the propagation channel matrix, the product matrix is a product of the Hermitian transpose matrix, the total power of absolute eigenvalues The user who calculates the absolute value of the value or determinant, selects one product matrix from the product matrices whose absolute value is greater than the predetermined value, and corresponds to the column component of the channel matrix from which the selected product matrix is based The station apparatus has means for assigning the same frequency.

According to another embodiment of the base station apparatus of the present invention,
Preferably, the means for assigning the same frequency selects a product matrix in which the maximum number of user station apparatuses included in the same beam is the smallest among product matrices having absolute values greater than a predetermined value.

Further, according to another embodiment of the base station apparatus of the present invention,
A base station device that receives transmission signals from a plurality of user station devices via a relay station device that uses a plurality of beams, based on a training signal unique to the user station device included in the transmission signals of the user station device , A means for estimating a column component corresponding to each user station apparatus of the propagation path matrix corresponding to each beam that is a row component of the propagation path matrix, and a plurality of user station apparatuses that are allocation candidates of the same frequency, select one or more user stations, the propagation channel matrix for the set of the user station apparatus selected, to seek based on the column components of the user station apparatus selected, a plurality of selecting one or more user stations means for performing combination of, for each channel matrix obtained, the propagation channel matrix, the product matrix is a product of the Hermitian transpose matrix, the total power of the absolute values of the eigenvalues, or the absolute value of the determinant Calculate A means for selecting the product matrix having the maximum absolute value and allocating the same frequency to the user station apparatus corresponding to the column component of the propagation path matrix that is the source of the selected product matrix. .

Furthermore, according to another embodiment of the base station apparatus of the present invention,
It is also preferable that the number of user station apparatuses to be selected from user station apparatuses that are candidates for assignment of the same frequency is fixed.

According to the satellite communication system of the present invention,
The base station apparatus includes a relay station apparatus having a plurality of beams, and a plurality of user station apparatuses.

  The channel capacity can be increased by selecting the user station apparatus to which the base station apparatus assigns the same frequency based on the propagation path matrix. Therefore, the channel quality after interference compensation can be greatly improved in the base station apparatus. As a result, for example, the communication speed per user station apparatus can be increased even with the same transmission power.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings. As shown in FIG. 6, the multi-beam satellite communication system includes one base station apparatus, one satellite, that is, a relay station apparatus, and a plurality of user station apparatuses. In the following description, it is assumed that the number of beams used by the relay station apparatus is b, the number of user station apparatuses to which the same frequency is assigned is a, and the number of user station apparatuses that desire communication is u greater than a.

  The user station apparatus holds a training signal unique to the user station apparatus and transmits it by including it in the transmission signal, and the relay station apparatus receives the signal from each user station apparatus received by the antenna corresponding to each beam. For example, as shown in FIG. 7, the frequency is converted and frequency-multiplexed, and transmitted to the base station apparatus as a frequency-multiplexed signal including the same number of signals as the number of beams.

  FIG. 1 is a block diagram of a base station apparatus according to the present invention. According to FIG. 1, the base station apparatus includes a branching unit 31, a frequency converting / filtering unit 32, an interference compensating unit 33, a demodulating unit 34, a propagation path matrix estimating unit 35, and a frequency allocation determining unit 36. Yes.

  The base station apparatus receives the frequency multiplexed signal transmitted from the relay station apparatus, the branching unit 31 branches the received signal into b signals equal to the number of beams, and the frequency conversion / filter unit 32 is frequency multiplexed. Each of b signals is taken out. The propagation path matrix estimation unit 35 has a matched filter having a high correlation value with the training signal of each user station apparatus, and estimates a propagation path matrix from b signals and each matched filter. Here, when all the user station apparatuses # 1 to #u that desire communication use the same frequency f, each component of the propagation path matrix of b rows u columns is expressed as follows:

とすると、ｈ１１、ｈ２１、ｈ３１、・・・、ｈｂ１の各成分は、ユーザ局装置＃１がユーザ局装置＃１固有のトレーニング信号を含む周波数ｆの信号を送信することで基地局装置の伝搬路行列推定部３５は求めることできる。以下、ユーザ局装置＃ｋ、ｋは１以上ｕ以下の整数、が固有のトレーニング信号を含む信号を周波数ｆにて送信することにより基地局装置が推定できる伝搬路行列成分ｈ１ｋ、ｈ２ｋ、ｈ３ｋ、・・・、ｈｂｋ、をユーザ局装置＃ｋに対応する伝播路行列の列成分と呼ぶ。

Then, each component of h11, h21, h31,..., Hb1 is propagated by the base station apparatus by the user station apparatus # 1 transmitting a signal of frequency f including a training signal specific to the user station apparatus # 1. The path matrix estimation unit 35 can obtain the value. Hereinafter, propagation path matrix components h1k, h2k, h3k, which can be estimated by the base station apparatus by transmitting a signal including a training signal inherent in user station apparatus #k, k, which is an integer between 1 and u, at a frequency f. .., Hbk are called column components of the propagation path matrix corresponding to the user station apparatus #k.

  FIG. 2 is a flowchart of frequency allocation in the base station apparatus according to the present invention. The propagation path matrix estimation unit 35 first transmits a control signal at a frequency f to each of the user station apparatuses that desire communication, and based on a training signal specific to the user station apparatus included in the control signal. Then, the column component of the propagation path matrix corresponding to the user station apparatus is obtained (S21 and S22). Although transmission of the control signal is preferably performed for each user station apparatus, the control signal may be transmitted to a plurality of user station apparatuses at the same time.

Subsequently, the frequency allocation determination unit 36 obtains a propagation path matrix for the selected combination of user station devices for each of the combinations that select a from the user station devices that desire communication. Specifically, the b-row a-column propagation path matrix Fi, i = 1, 2,..., _U C, with the column component of the propagation path matrix corresponding to the user station apparatus included in the set as the column component. _a is obtained (S23). The frequency allocation determining unit 36 obtains Gi = Fi ^H × Fi for each channel matrix Fi, and c eigenvalues existing when the rank value of the matrix Gi is c, λi1, λi2,. , The absolute value of the sum of λic,
Vi = | λi1 × λi2 ×... × λic | (1)
Is obtained (S24). Note that Fi ^H is a Hermitian transposition of Fi. Finally, the frequency allocation determination unit 36 allocates the same frequency to the user station apparatus corresponding to the column component of the channel matrix Fi that maximizes Vi (S25).

  As described in Non-Patent Document 2, the larger the maximum value of Vi, the larger the channel capacity of the channel matrix, and therefore the user station apparatus corresponding to the column component of the channel matrix Fi having the maximum Vi. By assigning the same frequency, the transmission path capacity is increased.

Also,
det (Fi ^H × Fi) = λi1 × λi2 ×... × λic
Applying the equivalent transformation shown in Equation (1),
Vi = | det (Fi ^H × Fi) | (2)
It becomes. Therefore, the flowchart of FIG. 2 can be changed as shown in FIG. That is, in S34 of FIG. 3, the frequency allocation determining unit 36 obtains the absolute value of the determinant of each matrix Gi = Fi ^H × Fi, and the user station corresponding to the column component of the channel matrix Fi having the maximum value. The same frequency is assigned to the device (S35). Note that the processing from S31 to S33 is the same as the processing from S21 to S23 in FIG.

FIG. 4 is a flow chart of frequency allocation in the base station apparatus according to another embodiment of the present invention, and FIG. 5 is a modification thereof. In the present embodiment, instead of the maximum value of the absolute value of the determinant of Vi or Fi ^H × Fi, the absolute value of the determinant of Vi or Fi ^H × Fi is determined to a predetermined threshold value is greater than the channel matrix Fi ( S44, S54), one propagation path matrix Fi is selected from the obtained propagation path matrix Fi, and the same frequency is assigned to the user station apparatus corresponding to the column component of the selected propagation path matrix Fi (S45, S55). As a criterion for selecting one from the propagation path matrix Fi larger than the threshold value, for example, the one having the smallest maximum number of user station apparatuses existing in the same beam is selected.

  Returning to FIG. 1, the interference compensator 33 transmits the transmission signal of each user station apparatus based on the signal corresponding to each beam output from the frequency converter / filter 32 and the channel matrix from the channel matrix estimator 35. The demodulator 34 demodulates the transmission signal of each user station apparatus.

  As described above, the channel capacity can be increased by selecting the user station apparatus to which the base station apparatus assigns the same frequency based on the propagation path matrix. Therefore, the channel quality after interference compensation can be greatly improved in the base station apparatus. As a result, for example, the communication speed per user station apparatus can be increased even with the same transmission power.

In the above-described embodiment, the number of user station apparatuses to which the same frequency is allocated is a fixed value a, and a combination _u C _a propagation path matrices for selecting a from the number u of user station apparatuses that desire communication. However, a may be variable. For example, if the user station that wishes to communicate is 10 stations, the number of users stations assign the same frequency, and four stations or 5 station, one transmission from the channel matrix of ₁₀ C ₄ + ₁₀ C ₅ For example, a route matrix may be selected.

It is a block diagram of the base station apparatus by this invention. It is a flowchart of the frequency allocation in the base station apparatus by this invention. It is a flowchart which shows the change aspect of the frequency allocation of FIG. It is a flowchart of the frequency allocation in the base station apparatus in other embodiment of this invention. It is a flowchart which shows the change aspect of the frequency allocation of FIG. 1 is a system configuration diagram of a multi-beam satellite communication system. It is a figure explaining the relay by a relay apparatus. It is a block diagram of the base station apparatus by a prior art.

Explanation of symbols

11 to 15 User station device 2 Relay station device 3 Base station device 31 Branch unit 32 Frequency conversion / filter unit 33 Interference compensation unit 34 Demodulation unit 35 Channel matrix estimation unit 36 Frequency allocation determination unit 41 to 44 Beams 51 to 55, 61 ~ 64 signals

Claims (5)

A base station device that receives transmission signals from a plurality of user station devices via a relay station device that uses a plurality of beams,
Based on the training signal specific to the user station device included in the transmission signal of the user station device, the column component corresponding to each user station device of the channel matrix corresponds to each beam that is the row component of the channel matrix. Means to estimate;
A plurality of user stations is assigned candidates of the same frequency, and select one or more user stations, the propagation channel matrix for the set of the user station apparatus selected, determined on the basis of the column components of the user station apparatus selected Means for performing a plurality of combinations for selecting one or more user station devices;
For each channel matrix obtained, the propagation channel matrix, the product matrix is a product of the Hermitian transpose matrix, the total power of the absolute values of the eigenvalues, or calculates the absolute value of the determinant, the absolute value of the predetermined Selecting one product matrix from a product matrix larger than the value, and allocating the same frequency to the user station apparatus corresponding to the column component of the propagation path matrix that is the source of the selected product matrix;
A base station apparatus. The means for assigning the same frequency is:
Selecting a product matrix in which the maximum number of user station apparatuses included in the same beam is the smallest among product matrices having an absolute value greater than a predetermined value;
The base station apparatus according to claim 1. A base station device that receives transmission signals from a plurality of user station devices via a relay station device that uses a plurality of beams,
Based on the training signal specific to the user station device included in the transmission signal of the user station device, the column component corresponding to each user station device of the channel matrix corresponds to each beam that is the row component of the channel matrix. Means to estimate;
A plurality of user stations is assigned candidates of the same frequency, and select one or more user stations, the propagation channel matrix for the set of the user station apparatus selected, determined on the basis of the column components of the user station apparatus selected Means for performing a plurality of combinations for selecting one or more user station devices;
Maximum for each channel matrix obtained, the propagation channel matrix, the product matrix is a product of the Hermitian transpose matrix, the total power of the absolute values of the eigenvalues, or the absolute value of the determinant is calculated, the absolute value Means for assigning the same frequency to the user station apparatus corresponding to the column component of the propagation path matrix that is the source of the selected product matrix;
A base station apparatus.   The base station apparatus according to any one of claims 1 to 3, wherein the number of user station apparatuses selected from user station apparatuses that are candidates for the same frequency is fixed.   A satellite communication system including the base station apparatus according to any one of claims 1 to 4, a relay station apparatus having a plurality of beams, and a plurality of user station apparatuses.

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