JP5128311B2 - Base station apparatus, terminal apparatus and radio communication system - Google Patents

Description

  The present invention relates to a base station apparatus and the like that communicate with a second terminal apparatus connected via a relay between the first terminal apparatus and the relay station apparatus.

  In order to solve the tightness of frequency resources accompanying the increase in data traffic in recent years, a new radio frequency is allocated for mobile communication, and a new mobile communication system that uses the allocated frequency band (for example, IMT-Advanced system) is underway.

  For such a new mobile communication system, a higher frequency band than the frequency band allocated to the previous system will be allocated, but higher frequency signals will be attenuated more greatly. , Coverage will be narrower than in previous systems.

  As a means for solving such a problem, there is a method in which a relay station device that relays communication between a base station device and a terminal device is provided in a cell. FIG. 17 shows a conventional wireless communication system. As illustrated in FIG. 17, the base station device 90 communicates with the terminal device 80, the terminal device 82, and the terminal device 84.

  Here, a relay station device 92 is interposed between the base station device 90 and the terminal device 80, and a relay station device 94 is interposed between the base station device 90 and the terminal device 84.

  Here, the relay station device can only amplify and transmit the received signal (Amplify-and-Forward: AF type), or can re-modulate and transmit if there is no error once (Decode- and-Forward (DF type) etc., and the terminal device (terminal device located near the cell edge) far away from the base station device communicates with the base station device via the relay station device, so that these terminal devices The cell coverage can be maintained in the same manner as in the conventional system without degrading the reception characteristics.

  As shown in FIG. 17, when such a relay station apparatus is provided in a cell, for example, from the viewpoint of effective use of resources, for example, downlink transmission from the base station apparatus 90 to the terminal apparatus 82, and the relay station apparatus 94 The downlink transmission from the terminal device 84 to the terminal device 84 may be performed using the same resource.

  In such a case, since the signal transmitted from the relay station device 94 to the terminal device 84 is received as an interference signal in the terminal device 82, the reception characteristics of the terminal device 82 are significantly deteriorated.

  As means for solving this problem, a method of performing beamforming at the time of transmission from the relay station device 94 to the terminal device 84 is disclosed. FIG. 18 shows an outline of the wireless communication system in this case.

As shown in FIG. 18, each of the base station device, the relay station device, and the terminal device has a plurality of transmission / reception antennas, the downlink from the base station device to the relay station device, the base station device to the terminal device, and the terminal device. In the uplink from the relay station apparatus to the relay station apparatus, transmission is performed in a normal MIMO (Multi-Input Multi-Output) multiplex mode without performing beamforming. In the downlink from the relay station apparatus to the terminal apparatus, a method of transmitting in a mode in which beam forming is performed (referred to as an eigenmode) is shown. In this way, for example, when transmitting from the relay station device 94 to the terminal device 84, by performing beamforming toward the terminal device 84, the interference received by the terminal device 82 from the relay station device 94 is significantly suppressed. (For example, refer to Patent Document 1).
JP 2007-67726 A

  However, when the transmission from the base station apparatus to the terminal apparatus and the transmission from the relay station apparatus to another terminal apparatus (both are downlink transmissions) using the same resource, There was a problem that a plurality of transmission / reception antennas were required.

  In addition, due to the relationship between the number of transmitting and receiving antennas, the degree of freedom of directivity control is insufficient, and depending on the positional relationship of the terminal device, interference may not be suppressed even if beam forming is used. Many antennas have become necessary.

  In view of the above-described problems, the present invention has an object that when a base station apparatus and a terminal apparatus communicate with each other, even if there is a relay station apparatus that communicates with another terminal apparatus, the base station can be efficiently It is to provide a base station device, a terminal device, and a wireless communication system in which the device and the terminal device can communicate.

In view of the problems described above, the purpose of the base station apparatus of the present invention is as follows.
In the base station device that communicates with the first terminal device and the second terminal device connected via the relay station device,
Interference signal generating means for generating an interference signal received by the first terminal device from the relay station device;
When transmitting a desired signal to the first terminal apparatus, and the desired signal transmission means for transmitting by subtracting the interference signal from the desired signal,
It is characterized by providing.

Further, in the base station apparatus of the present invention, the interference signal is a transmission signal of the second terminal device addressed, and generates based on the previously transmitted signal to the relay station device.

The base station apparatus of the present invention further comprises propagation path information receiving means for receiving propagation path information from the first terminal apparatus,
A transmission signal of the second terminal device addressed, the signal transmitted to the relay station device previously and generates the interference signal based on said channel information.

Further, in the base station apparatus of the present invention, the propagation path information, and the channel variation information and / or a base station apparatus and the first terminal device between the relay station apparatus and the first terminal device It is characterized in that it includes information on the propagation path fluctuations between the two.

Moreover, the base station apparatus of the present invention is
Further comprising reception quality acquisition means for acquiring information relating to reception quality in the first terminal device;
The desired signal transmitting means is means for transmitting the desired signal as it is to the first terminal device when the reception quality is higher than a threshold value.

Moreover, the base station apparatus of the present invention is
The relay station apparatus further comprises a confirmation signal receiving means for receiving a positive response as a confirmation signal for successful communication or a negative response as a confirmation signal for communication failure,
The desired signal transmitting means is means for transmitting the desired signal as it is to the first terminal device when the negative response is received.

Moreover, the base station apparatus of the present invention is
It further comprises signal level adjusting means for adjusting the signal level to be transmitted so that the transmission level of the desired signal falls within a certain range.

In the base station apparatus of the present invention, the signal level adjusting means is a modulo operation.

The terminal device of the present invention
A terminal device connected to a communication system including a base station device and a relay station device,
  Propagation path information acquisition means for acquiring propagation path information between the relay station apparatus and the terminal apparatus and / or propagation path information between the base station apparatus and the terminal apparatus;
  Propagation path information transmitting means for transmitting at least one of the propagation path information to the base station apparatus when directly communicating with the base station apparatus;
Receiving means for receiving, from the base station apparatus, a signal obtained by subtracting an interference signal generated based on the signal transmitted from the relay station apparatus and the propagation path information from a desired signal;
  It is characterized by providing.

The terminal device according to the present invention is characterized in that when performing direct communication with the base station device, a modulo operation is performed on a signal received from the base station device.

The wireless communication system of the present invention includes:
A base station apparatus, a relay station apparatus that receives a signal transmitted from the base station apparatus and retransmits the signal to a terminal apparatus, a first terminal apparatus that directly receives a signal transmitted from the base station apparatus, and In a wireless communication system including a second terminal device that receives a signal transmitted from a base station device via the relay station device,
In the base station apparatus, a signal obtained by subtracting an interference signal that the relay station apparatus gives to the first terminal apparatus from a signal addressed to the first terminal apparatus is transmitted to the first terminal apparatus.

In the wireless communication system of the present invention, the interference signal to be subtracted from the signal addressed to the first terminal device in the base station device is based on at least a signal previously transmitted from the base station device to the relay station device. It is generated.

The radio communication system of the present invention is characterized in that the signal previously transmitted from the base station apparatus to the relay station apparatus is a signal addressed to the second terminal apparatus .

  In the radio communication system of the present invention, an amplitude of a signal transmitted to the first terminal device by subtracting an interference signal from the signal addressed to the first terminal device in the base station device is within a predetermined fixed range. It adjusts in the said base station apparatus so that it may fit in.

  According to the present invention, when the first terminal device generates an interference signal received from the relay station device in the base station device and transmits the desired signal to the first terminal device, the interference signal is subtracted from the desired signal. Send. By transmitting the desired signal from which the interference signal has been subtracted, the first communication terminal can receive only the desired signal.

  Also, the propagation path information includes information on propagation path fluctuation between the relay station apparatus and the first terminal apparatus and / or propagation path fluctuation information between the base station apparatus and the first terminal apparatus. It is included. Therefore, it is possible to reproduce an interference signal for subtraction based on the propagation path fluctuation information.

  Further, the signal level to be transmitted is adjusted so that the transmission level of the desired signal falls within a certain range. Therefore, it is possible to prevent the signal after the interference signal is subtracted from having a very large peak.

  Further, when the reception level is detected from the propagation path information and the reception level is larger than the threshold value, the desired signal is transmitted as it is to the first terminal device. Therefore, when the reception level of the terminal is good, the signal can be transmitted without performing the interference signal subtraction process.

  Further, when the base station apparatus receives a negative response indicating that the communication has failed from the relay station apparatus, the desired signal is transmitted as it is to the first terminal apparatus without subtracting the interference signal. That is, when a negative response is received from the relay station device, the signal is not transmitted from the relay station device to the second terminal device, so that the first terminal device is not affected by interference. It is possible to cope with a situation where it is not necessary to perform processing.

  Further, according to the wireless communication system of the present invention, the base station apparatus transmits, to the first terminal apparatus, a signal obtained by subtracting in advance the interference signal that the relay station apparatus gives to the first terminal apparatus from the signal of the first terminal addressed apparatus. Will be sent. Therefore, the first terminal apparatus can appropriately and efficiently receive the signal that should be received from the base station apparatus without being affected by the interference signal from the relay station apparatus.

  The best embodiment in a wireless communication system when the present invention is applied will be described with reference to the drawings.

  First, an outline of a wireless communication system to which the present invention is applied will be described using the drawings. FIG. 1 is a diagram for explaining the entire wireless communication system, and FIG. 2 is a diagram schematically showing frames to be communicated.

  As shown in FIG. 1, a base station device 10, a relay station device 20, and terminal devices 30 and 32 are arranged in the wireless communication system. When the desired signal A is transmitted from the base station device 10 to the terminal device 32, the desired signal A is first transmitted to the relay station device 20. The relay station device 20 transmits a desired signal A1 based on the received desired signal A to the terminal device 32.

  Further, the base station apparatus 10 transmits a desired signal B to the terminal apparatus 30. Here, the terminal device 30 receives the interference signal A2 together with receiving the desired signal B from the base station device 10. Therefore, when transmitting a signal to the terminal device 30, the base station device 10 subtracts the interference signal A2 in advance and transmits the signal.

  The signal status will be described with reference to FIG. First, the desired signal A is transmitted from the base station apparatus 10 in the first frame (F10). Subsequently, when the desired signal B is transmitted (F12), the desired signal A1 (F14) transmitted from the relay station apparatus 20 is determined as the interference signal A2, and the interference signal A2 is subtracted from the desired signal B and transmitted. . Here, the frame in which desired signal B is transmitted and the frame in which desired signal A1 (interference signal A2 for terminal device 30) is transmitted are transmitted in the same frame.

  2 shows a state in which transmission from the relay station apparatus 20 to the terminal apparatus 30 is performed in a frame immediately after the frame F10, transmission from the relay station apparatus 20 to the terminal apparatus 30 is If the number of frames after transmission from the base station device 10 to the relay station device 20 is determined in advance, it may not be the immediately following frame.

  Further, the signal A, the signal A1, and the signal A2 indicate that the transmitted data (signals) are the same, but the received channel fluctuations are different. In such subtraction, the signal transmitted from the relay station device 20 to the terminal device 32 is a signal transmitted from the base station device 10 to the relay station device 20 in the previous frame, and the base station device 10 is transmitted from the relay station device 20. This is made possible by knowing in advance what kind of signal to transmit.

  By transmitting a signal in which the interference signal is subtracted in advance, the terminal device 30 receives the signal of (desired signal B−interference signal A2) + interference signal A2, and obtains only the desired signal B. be able to.

  Therefore, in a system including the relay station device 20 in a cell, even when transmission between a base station device and a terminal device and between a relay station device and a terminal device is performed using the same resource, the wireless communication system to which the present invention is applied is applied. According to this, it is possible to suppress interference that the relay station apparatus gives to the terminal apparatus that receives a signal from the base station apparatus. At this time, one transmitting / receiving antenna provided in each station is sufficient.

[First Embodiment]
First, the first embodiment will be described. The configuration of each device in the first embodiment will be described with reference to the drawings.

  FIG. 3 is a diagram for explaining a functional configuration of the base station apparatus 10. The base station apparatus 10 includes a coding unit 102, a modulation unit 104, a pilot signal insertion unit 106, an interference subtraction unit 108, a D / A conversion unit 110, a radio unit 112, a transmission antenna unit 114, and a buffer unit. 116, a propagation path multiplication unit 118, a reception unit 120, an A / D conversion unit 122, a radio unit 124, and a reception antenna unit 126.

  First, the encoding unit 102 performs error correction encoding on the input transmission data, and the modulation unit 104 modulates the encoded data. Then, a pilot signal insertion unit 106 adds a known pilot signal for propagation path estimation to the modulated signal.

  The signal to which the pilot signal is added is input to the interference subtraction unit 108, where the interference signal is subtracted. At this time, in the present embodiment, if the signal modulated by modulation section 104 (the signal to be transmitted) is directly transmitted to the terminal device (for example, addressed to terminal device 30), interference subtraction is performed. However, if the modulation signal is addressed to the relay station device (for example, addressed to the terminal device 32 via the relay station device 20), no interference subtraction is performed.

  The interference signal subtracted by the interference subtracting unit 108 is obtained by using the downlink propagation path information between the relay station apparatus 20 and the terminal apparatus 30 (the terminal apparatus that is the destination of the signal to be transmitted) as the base station apparatus 10-. This is a signal obtained by multiplying the value divided by the propagation path information between the terminal apparatuses 30 and the modulated signal addressed to the relay station apparatus 20 transmitted in the previous frame by the propagation path multiplication unit 118.

  However, the propagation path information here is not only the fluctuation due to fading but also considering distance attenuation and shadowing. In the interference subtraction unit 108, the signal transmitted from the relay station apparatus 20 to the terminal apparatus 32 is transmitted. However, the signal when observed by the terminal device 30 is subtracted.

  The fluctuation of power due to distance attenuation and shadowing can usually be obtained from a measured value of RSSI (Received Signal Strength Indicator), and the RSSI and information indicating propagation path fluctuation due to fading are separately notified to the base station apparatus. It is good also as a structure.

For example, the propagation path information between the base station apparatus 10 and the terminal apparatus 30 is H ₁ , the signal addressed to the terminal apparatus 30 from the base station apparatus 10 is S ₁ , and the propagation path information between the relay station apparatus 20 and the terminal apparatus 30 is When H ₂ and the signal addressed to the terminal device 32 from the relay station device 20 is S ₂ , the output of the interference subtracting unit 108 is expressed by Equation (1). However, here, it is assumed that the transmission power of the base station apparatus 10 and the transmission power of the relay station apparatus 20 are the same, and their transmission powers are different (normally, the relay station apparatus has a lower transmission than the base station apparatus). In the case of using power), the second term of the following expression is multiplied by a coefficient related to the transmission power difference.

  Here, in the present embodiment, interference subtraction is performed on the pilot signal in the same manner as the modulation signal, but this also applies to the relay station apparatus 20 the same pilot signal as in the base station apparatus 10. In the case where different pilot signals are transmitted between the base station apparatus 10 and the relay station apparatus 20, interference subtraction is not performed on the pilot signal.

  In order to perform such subtraction, it is necessary to store the modulation signal transmitted to the relay station apparatus 20 transmitted in the previous frame, but this is performed in the buffer unit 116. In the buffer unit 116, when the output of the modulation unit 104 is a signal addressed to the relay station device 20, it is stored. On the other hand, when the output of the modulation unit 104 is a signal directly transmitted to the terminal device (addressed to the terminal device 30), the signal is discarded without being stored.

  Further, in the base station apparatus 10 according to the present embodiment, all the scheduling information in the cell such as to which terminal apparatus is to be transmitted next from the relay station apparatus 20 is grasped and subtracted by the interference subtraction unit 108. It is assumed that the interference signal can be appropriately selected. The pilot signal does not need to be stored in the buffer unit 116 when the same signal is always added, but is stored in the buffer unit 116 in the same manner as the modulation signal otherwise.

  The propagation path information is notified from the terminal device (terminal device 30), received by the receiving antenna unit 126, converted to a frequency that can be A / D converted by the radio unit 124, and then A / D converted. The signal is converted into a digital signal by the unit 122 and reproduced by the receiving unit 120.

  After such subtraction of the interference signal is performed, the transmission signal (modulated signal-interference signal) is converted into an analog signal in the D / A converter 110 and converted into a frequency that can be transmitted in the radio unit 112. It is transmitted from the transmission antenna unit 114.

  By adopting such a base station apparatus configuration, the relay station apparatus 20 uses another resource for the base station apparatus 10 using the same resource as the signal that the base station apparatus 10 is going to transmit directly to the terminal apparatus (addressed to the terminal apparatus 30). It can be transmitted to (terminal device 32). Further, by generating a signal obtained by subtracting in advance the signal that causes interference for the terminal device (terminal device 30) that communicates directly with the base station device 10 in the base station device 10, a desired signal is transmitted to the terminal device (terminal device 30). Can be sent.

On the terminal device (terminal device 30) side that directly communicates with the base station device 10, a signal obtained by adding interference to a signal obtained by subtracting interference in advance is received as shown in Equation (2). Only the desired signal can be received. However, as described above, when the transmission power of the base station apparatus 10 and the transmission power of the relay station apparatus 20 are different, it is necessary to multiply the term representing the interference signal by a coefficient related to the transmission power difference.

  Next, the functional configuration of the relay station apparatus 20 will be described with reference to FIG. As illustrated in FIG. 4, the relay station device 20 includes a reception antenna unit 202, a radio unit 204, an A / D conversion unit 206, a propagation path estimation unit 208, a propagation path compensation unit 210, and a demodulation unit 212. , Decoding section 214, error detection section (CRC section) 216, encoding section 218, modulation section 220, pilot signal insertion section 222, A / D conversion section 224, radio section 226, and transmitting antenna section 228. Part.

  When receiving a signal from the base station device (for example, a signal addressed to the terminal device 32 from the base station device 10 via the relay station device 20), the relay station device 20 receives the signal received by the receiving antenna unit 202. The radio unit 204 performs conversion to a frequency that can be A / D converted. The converted signal is converted into a digital signal by the A / D conversion unit 206.

  Next, the pilot signal added for propagation path estimation is sent to the propagation path estimation unit 208 to perform propagation path estimation. Then, propagation path compensation of the modulated signal is performed in the propagation path compensation unit 210 using the estimated propagation path fluctuation, and demodulation and error correction decoding are performed in the demodulation unit 212 and the decoding unit 214, respectively, and then the error detection unit In 216, a check (CRC: Cyclic Redundancy Check) is performed to determine whether there is an error in the decoding result.

  As a result of checking by the error detection unit 216, when it is determined that there is no error in the decoding result, it is modulated again in the blocks subsequent to the coding unit 218 and transmitted to the terminal device (terminal device 32). However, in the present embodiment, the pilot signal added by pilot signal insertion section 222 is the same as that added by pilot signal insertion section 106 of base station apparatus 10.

  On the other hand, if it is determined that there is an error in the decoding result as a result of the check in the error detection unit 216, remodulation is not performed and signal transmission is not performed in this embodiment. Thus, when a decoding error occurs in the relay station device 20, the base station device 10 in the present embodiment transmits a signal without performing the interference subtraction process described above.

  Next, the functional configuration of the terminal device 30 in the present embodiment will be described with reference to FIG. As illustrated in FIG. 5, the terminal device 30 includes a reception antenna unit 302, a radio unit 304, an A / D conversion unit 306, a channel estimation unit 308, a channel compensation unit 310, a demodulation unit 312, The decoding unit 314, the transmission unit 316, the D / A conversion unit 318, the radio unit 320, and the transmission antenna unit 322 are configured.

  In the reception system (receiving antenna unit 302 to decoding unit 314) of the terminal device 30, the same processing as that of the reception system of the relay station device 20 shown in FIG. 4 is performed, and the transmitted data is reproduced. Further, since it is necessary to notify the base station apparatus 10 of the propagation path information estimated by the propagation path estimation unit 308, after being input to the transmission unit 316 and subjected to processing such as modulation, the D / A conversion unit 318 and The data is transmitted from the transmission antenna unit 322 via the wireless unit 320.

  In this embodiment, such notification of propagation path information is performed in a terminal device that directly receives a signal transmitted from the base station device 10, such as the terminal device 30, and is transmitted from the base station device 10 to the terminal device 30. Notifying the base station apparatus 10 of the propagation path fluctuation in the case of transmission and the propagation path fluctuation when the signal transmitted by the relay station apparatus 20 is observed in the terminal apparatus 30 (the destination of the signal is another terminal apparatus). It becomes.

  By configuring the base station device, the relay station device, and the terminal device as described above, it is possible to transmit a signal obtained by subtracting in advance the interference that the relay station device gives to the terminal device (terminal device 30) by the base station device. Thus, the interference given to the terminal device can be suppressed.

  In the present embodiment, there is one relay station apparatus that gives interference to the terminal apparatus, but the present invention can also be applied to a case where there are a plurality of relay station apparatuses serving as interference sources. For example, FIG. 6 is an example of a wireless communication system in which the relay station device 20 and the relay station device 22 are arranged.

  The desired signal A transmitted from the base station device 10 to the terminal device 32 is transmitted via the relay station device 20. At this time, the terminal device 30 receives the interference signal A2 from the relay station device 20. The desired signal B transmitted from the base station device 10 to the terminal device 34 is transmitted via the relay station device 22. At this time, the terminal device 30 receives the interference signal B <b> 2 from the relay station device 22.

  Therefore, the base station apparatus 10 sends a signal (desired signal C-interference signal A2-interference signal B2) obtained by subtracting the interference signal A2 and the interference signal B2 from the desired signal C to be transmitted to the terminal apparatus 30 to the terminal apparatus 30. Will be sent.

  Also, in a system using multicarrier transmission, there is a situation in which the influence of interference differs greatly for each subcarrier. However, when targeting such a system, only a subcarrier to which interference exceeding a certain threshold is applied is preliminarily determined in advance. It is good also as a structure which subtracts interference with an apparatus.

  Although FIG. 4 shows an example of a DF type relay station apparatus, the present invention can also be applied to a system including an AF type relay station apparatus that amplifies and retransmits a received signal. However, since the AF type relay station apparatus normally only amplifies the received signal and does not perform propagation path compensation or the like, when subtracting the interference signal in the base station apparatus, the base station apparatus-relay station apparatus It is also necessary to take into account the propagation path fluctuations.

For example, the propagation path information between the base station apparatus 10 and the terminal apparatus 30 shown in FIG. 1 is H ₁ , the signal addressed to the terminal apparatus 30 from the base station apparatus 10 is S ₁ , and the signal between the relay station apparatus 20 and the terminal apparatus 30 is The propagation path information is H ₂ , the signal addressed from the relay station apparatus 20 to the terminal apparatus 32 is S ₂ , the propagation path information between the base station apparatus 10 and the relay station apparatus 20 is H ₃ , and the amplification factor in the relay station apparatus 20 is α In this case, the output of the interference subtracting unit 108 in FIG.

However, it is assumed that the propagation path information H ₃ and the amplification factor α are notified from the relay station device 20 to the base station device 10. Since a signal with noise added is transmitted from the AF type relay station device, compared with the case where a correctly demodulated and remodulated signal is transmitted as in the DF type relay station device, the relay station device Although the added noise greatly affects the reception characteristics of the terminal device, it is possible to suppress interference that the relay station device gives to the terminal device by transmitting a signal that has been subjected to such subtraction processing in advance.

  In both DF type and AF type relay station apparatuses, there is one that retransmits a signal converted into a format different from a received signal. For example, a signal is generated and retransmitted using a puncture pattern different from the received signal, and a signal is retransmitted by assigning subcarriers and subchannels different from the received signal.

  The present invention can also be applied to such a relay station device if the base station device knows in advance what kind of conversion is performed in the relay station device. When the puncture pattern is changed in the relay station device, the puncture pattern used in the relay station device is grasped by the base station device, and the same pattern as that used in the relay station device is used, so that the relay The base station apparatus can generate the same signal as the interference signal that the station apparatus gives to the terminal apparatus, and this interference signal can be subtracted in advance in the base station apparatus.

  Also, even when subcarriers are rearranged in the relay station device, the same signal as the interference signal that the relay station device gives to the terminal device is generated by performing the same rearrangement in the base station device. It can be generated in the base station apparatus. However, if the rearrangement of subcarriers is performed according to the propagation path fluctuation between the relay station apparatus and the terminal apparatus (relay station apparatus 20-terminal apparatus 32), the base station apparatus performs the propagation path fluctuation. It is necessary to know.

  As described above, even in a system using a relay station apparatus of a type that performs conversion of a received signal, the same conversion as that of the relay station apparatus is performed in the base station apparatus to generate an interference signal that is subtracted in advance. Can be expected. Here, only an example of changing the puncture pattern, subcarrier, and subchannel to be used has been described, but any conversion can be applied as long as the conversion can be grasped in advance by the base station apparatus.

  In the present embodiment, only the subtraction of the interference signal given to the terminal device 30 by the relay station device 20 has been described. Separately, interference (intersymbol interference) occurs due to the influence of the delayed wave in the propagation path. In some cases, the received signal power may drop due to propagation path fluctuations. In the present embodiment, since the base station apparatus 10 grasps in advance the propagation path fluctuation when transmitting from the base station apparatus 10 to the terminal apparatus 30, such characteristic degradation due to the influence of the propagation path is compensated in advance. be able to.

For example, in equation (1), when not only S ₂ but also S ₁ is divided by H ₁ and transmitted, the terminal device may receive S ₁ instead of H ₁ S ₁ as in equation (2). it can. Therefore, a case where the received power fluctuations of an H ₁ will depressed significantly, it is possible to improve reception characteristics by performing the processing (transmission equalization) in accordance with the propagation path also signal to be originally transmitted.

[Second Embodiment]
Next, the second embodiment will be described. In the first embodiment, an example is shown in which the base station device 10 transmits a signal obtained by subtracting in advance the interference that the relay station device 20 gives to the terminal device 30. However, the signal after interference subtraction is very simple by simply subtracting the interference. May have a large peak. Therefore, in the present embodiment, an example in which a method for suppressing the peak of a transmission signal is applied to a base station apparatus is shown.

The transmission signal peak suppression method of interest in this embodiment is a method called THP (Tomlinson-Harashima Precoding), which can be realized by performing a modulo operation on the signal after the interference signal subtraction. The output M (x) of this modulo calculation is expressed by Equation (4).

  However, x represents the input to the modulo operation, that is, the signal after the interference signal is subtracted from the signal to be originally transmitted, and [y] represents the maximum integer (floor function) not exceeding y. Further, k is a constant determined only by the modulation scheme of the signal originally desired to be transmitted. When the modulation scheme of the signal originally intended to be transmitted is, for example, QPSK, k is 2√2.

  Here, when x is a complex signal, the modulo operation may be performed separately for the real part and the imaginary part. FIG. 7 shows input / output characteristics of the modulo calculation. As shown in FIG. 7, the output M (x) of the modulo operation is suppressed within a certain range regardless of the value of the input x. Therefore, the peak of the transmission signal can be suppressed by using the modulo operation.

  In a receiver (terminal device) that receives a signal subjected to such processing on the transmission side, it is necessary to estimate a signal that should be received originally (a signal that the transmission side originally wants to transmit) from the received signal. This can be done by using arithmetic.

  Specifically, when the received signal to which interference is added is y, the above M (y) may be calculated, and M (y) is an estimated value of the signal that should be received. This means that an adjustment value for suppressing the peak is added on the transmission side, and the adjustment value added on the transmission side is restored using the same calculation on the reception side.

  FIG. 8 shows the configuration of the base station apparatus in the present embodiment that transmits a signal in which a peak is suppressed using such a modulo operation. However, in FIG. 8, blocks having the same functions as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 8, the base station apparatus 15 in the present embodiment basically includes the base station apparatus 10 shown in the first embodiment with a modulo operation unit 150 that performs the modulo operation described above, and an interference subtraction unit. The configuration is added to the subsequent stage of 108 (preceding stage of the pilot signal insertion unit 106).

  However, in the present embodiment, the pilot signal is not subjected to interference subtraction or modulo calculation, and in order to distinguish the pilot signal transmitted from the base station apparatus and the relay station apparatus, Different pilot signals are transmitted from the relay station devices. As described above, by providing the base station device 15 with the modulo arithmetic unit 150, even when a signal obtained by subtracting in advance the interference that the relay station device 20 gives to the terminal device is transmitted, a signal with a suppressed peak is generated and transmitted. It becomes possible.

  Next, the structure of the terminal device 35 in this embodiment is shown in FIG. However, in FIG. 9, blocks having the same functions as those in FIG. As illustrated in FIG. 9, the terminal device 35 according to the present embodiment includes a modulo operation unit 350 that performs a modulo operation in the terminal device 30 illustrated in the first embodiment and a subsequent stage of the propagation path compensation unit 310 (an upstream stage of the demodulation unit 312). ).

  By performing the modulo operation in the modulo operation unit 350, the adjustment value added in the modulo operation unit 150 of the base station apparatus 15 shown in FIG. 8 can be restored to obtain the modulation signal that should be originally received.

  Further, the relay station device 20 in the present embodiment can be realized with the same configuration as the relay station device 20 of FIG. 4 shown in the first embodiment. Furthermore, as described in the first embodiment, the present embodiment can be applied not only to the DF type relay station apparatus but also to the AF type relay station apparatus.

  As described above, according to this embodiment, when the base station apparatus transmits a signal obtained by subtracting in advance the interference that the relay station apparatus gives to the terminal apparatus, a very large peak does not occur in the signal after interference subtraction. In this way, the terminal apparatus can reproduce a signal that should be received (which should be transmitted to the transmitting side) from the transmitted signal.

  In 2nd Embodiment, the structure which subtracts the interference signal from the relay station apparatus observed in the terminal device which is directly communicating with the base station apparatus, and performs modulo calculation in order to suppress the peak of the signal after interference subtraction However, the interference signal from the relay station apparatus may be estimated and subtracted to be smaller than that actually observed. FIG. 10 shows the configuration of the base station apparatus in such a case.

  As shown in FIG. 10, the base station apparatus in the case of subtracting interference estimated smaller than that actually observed in the terminal apparatus has a configuration in which a coefficient multiplication unit 500 is added to the configuration in FIG. Coefficient multiplication section 500 multiplies the interference signal by a coefficient greater than 0 and less than or equal to 1. For example, this coefficient may be set to a value according to the received SNR. When the received SNR is different for each subcarrier in multicarrier transmission, a different coefficient may be calculated and multiplied for each subcarrier. Good. However, when this coefficient is set to 1, the base station apparatuses in FIG. 10 and FIG. 8 are exactly the same.

  In the modulo calculation, the energy of the desired signal is used to subtract the interference, and the characteristics may be slightly deteriorated. However, by subtracting the interference multiplied by such a coefficient, the terminal device actually performs the subtraction. Although a signal slightly different from the observed interference signal is subtracted, the extra energy of the desired signal is not used, so that good characteristics can be obtained.

  FIG. 11 shows the configuration of a terminal apparatus that receives a signal transmitted from the base station apparatus shown in FIG. As shown in FIG. 11, the terminal device that receives the signal transmitted from the base station apparatus of FIG. 10 has a configuration in which a coefficient multiplication unit 700 is added to the configuration of FIG. After the base station is multiplied by the same coefficient as that multiplied by the interference signal, the modulo operation is performed. With such a configuration, a signal transmitted from the base station apparatus shown in FIG. 10 can be received with good characteristics.

[Third Embodiment]
Subsequently, the third embodiment will be described. In the first embodiment and the second embodiment described above, the method in which the base station apparatus transmits a signal obtained by subtracting in advance the interference that the relay station apparatus gives to the terminal apparatus has been described, but depending on the position of the terminal apparatus Thus, this process may be switched.

  As shown in FIG. 12, when the terminal device 30 that directly communicates with the base station device 10 is located relatively close to the relay station device, the influence of the interference signal A2 from the relay station device 20 is strong. A method of transmitting a signal obtained by subtracting interference in advance in the apparatus is very effective.

  However, as shown in FIG. 13, when the terminal device 30 is located in the vicinity of the base station device 10, the influence of the interference signal A2 arriving from the relay station device 20 is weakened. Even if not, the characteristics will not deteriorate much.

  Therefore, FIG. 14 shows a control flow of the base station apparatus 10 when the operation is switched according to the position of the terminal apparatus 30. The base station apparatus 10 first receives propagation path information from the terminal apparatus 30 (step S10). Then, an average reception SIR is calculated based on the received propagation path information (step S12). However, the received SIR here represents the ratio of the signal power transmitted from the base station apparatus 10 to the terminal apparatus 30 and the interference power that the relay station apparatus 20 gives to the terminal apparatus 30, and will be described in the first embodiment. It may be calculated from the RSSI (that is, it is not necessary to consider even the fading fluctuation).

  Next, the average reception SIR calculated in this way is compared with a predetermined threshold value (step S14). If the average reception SIR is higher than the threshold value, it is determined that the influence of interference is small, and signal transmission is performed without performing interference subtraction (step S14; Yes → step S18).

  On the other hand, when the average reception SIR is lower than the threshold value, it is determined that the interference greatly affects, and interference subtraction is performed as shown in the first embodiment or the second embodiment (Step S14; No → Step S16). ), A transmission signal is transmitted to the terminal device (step S18).

  However, here, description of processing such as signal transmission to the relay station device 20, notification of propagation path information, modulation, and modulo calculation is omitted. Further, the interference to be subtracted in step S16 is a signal transmitted from the relay station apparatus 20 to another terminal apparatus using the same resource as the signal transmitted in S18. By performing the control as shown in FIG. 14, it is possible to appropriately transmit a signal obtained by subtracting the interference to a terminal apparatus that is greatly affected by the interference.

  In addition, in an ordinary DF type relay station apparatus, if there is an error in the demodulation result, the signal is not re-modulated and transmitted. Therefore, if there is no error in the relay station apparatus, the interference according to the present invention It is important for the base station apparatus to transmit a signal that has been subtracted. In this case, subtraction of interference as shown in the first embodiment or the second embodiment may be performed only when the propagation path condition between the base station apparatus 10 and the relay station apparatus 20 is good.

  FIG. 15 shows a control flow of the base station apparatus 10 in this case. First, propagation path information is received from the relay station apparatus 20 (step S30). Then, it is determined whether or not the received SNR exceeds a threshold value (step S32).

  Here, when the reception SNR exceeds the threshold value, it is determined that the influence of the interference signal is large, and interference subtraction processing is executed (step S32; Yes → step S34). Then, a signal is transmitted to the terminal device.

On the other hand, when the reception SNR is less than or equal to the threshold value, it is determined that the influence of the interference signal is small, and the signal is transmitted to the terminal device as it is (step S32; No → step S36).
Send the signal without doing.

  By performing such control, when the reception situation in the relay station device 20 is good and no error occurs in the demodulation result in the DF type relay station device, the interference affecting the terminal device 30 is subtracted. The base station apparatus 10 can transmit the transmitted signal. In addition, when this control is applied to a multi-channel system in which a terminal device accesses a plurality of subchannels, the determination in S30 may be performed for each subchannel, and adaptive switching may be performed for each subchannel. Good.

  Further, in addition to the control shown in FIG. 15, a response signal indicating whether transmission is successful, such as ACK (ACKnowledgement) or NACK (Negative ACKnowledgement), is returned from the DF type relay station apparatus to the base station apparatus. Alternatively, control according to the response signal may be performed. FIG. 16 shows a control flow in the base station apparatus 10 in such a case.

  First, the base station apparatus 10 receives a response signal to the signal transmitted from the relay station apparatus 20 in the previous frame (step S50). When this response signal is an ACK indicating that the transmission is successful, the same signal as that transmitted from the base station apparatus 10 to the relay station apparatus 20 is transmitted from the relay station apparatus 20 to the terminal apparatus 30 in the subsequent frames. Will be shown. Therefore, in step S54, the corresponding interference component is subtracted from the signal addressed to the terminal device that receives interference by the transmission, and the signal is transmitted (step S52; Yes → Step S54 → Step S56).

  On the other hand, if the response signal is not ACK (NACK), transmission from the relay station device 20 to the terminal device 30 is not performed, and thus the signal is transmitted without subtraction of the interference component (step S52; No-> Step S56).

  However, here, it is assumed that the base station apparatus 10 knows how many frames after the ACK is returned to the base station apparatus 10 before the relay station apparatus 20 performs transmission to the terminal apparatus 30. It is possible to subtract in advance in the base station device 10 as interference between a signal transmitted directly from the terminal device 30 to the terminal device 30 and a signal transmitted from the relay station device 20 to another terminal device using the same resource.

  In addition, when this control is applied to a multi-channel system in which a terminal device accesses a plurality of subchannels, a signal is received in step S50 for each subchannel, and adaptive switching is performed for each subchannel. May be. By performing such control, it becomes possible to correctly determine which signal is received without error in the relay station apparatus and transmitted from the relay station apparatus to the terminal apparatus, and interference in the base station apparatus The subtraction process can be accurately performed without waste.

  In the above embodiment, as shown in FIG. 2, the signal transmitted when the signal transmitted from the base station apparatus 10 to the relay station apparatus 20 is transmitted from the relay station apparatus 20 to the terminal apparatus 30 within the following several frames. An example of handling as interference is shown.

  In addition to such a case, when the relay station device 20 once transmits to the terminal device 32 but an error occurs in the terminal device 32, the relay station device 20 performs retransmission to the terminal device 32. A signal to be retransmitted from the device 20 to the terminal device 32 can be treated as interference and subtracted in advance in the base station device 10. In order to cope with such retransmission, it is necessary for the base station apparatus to know the timing of retransmission from the relay station apparatus to the terminal apparatus, and the propagation path information notified from the terminal apparatus does not vary greatly. Is possible.

The figure for demonstrating the outline of the radio | wireless communications system in this embodiment. The figure which showed typically the communication frame in this embodiment. The figure for demonstrating the function structure of the base station apparatus in 1st Embodiment. The figure for demonstrating the function structure of the relay station apparatus in 1st Embodiment. The figure for demonstrating the function structure of the terminal device in 1st Embodiment. The figure for demonstrating the example of application of the radio | wireless communications system in 1st Embodiment. The figure for demonstrating the principle in 2nd Embodiment. The figure for demonstrating the function structure of the base station apparatus in 2nd Embodiment. The figure for demonstrating the function structure of the terminal device in 2nd Embodiment. The figure for demonstrating the function structure of the base station apparatus in 2nd Embodiment. The figure for demonstrating the function structure of the terminal device in 2nd Embodiment. The figure for demonstrating the radio | wireless communications system in 3rd Embodiment. The figure for demonstrating the radio | wireless communications system in 3rd Embodiment. The figure of the operation | movement flow for demonstrating the flow of the process in 3rd Embodiment. The figure of the operation | movement flow for demonstrating the flow of the process in 3rd Embodiment. The figure of the operation | movement flow for demonstrating the flow of the process in 3rd Embodiment. The figure for demonstrating the conventional radio | wireless communications system. The figure for demonstrating the conventional radio | wireless communications system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Base station apparatus 102 Encoding part 104 Modulation part 106 Pilot signal insertion part 108 Interference subtraction part 110 D / A conversion part 112 Radio | wireless part 114 Transmission antenna part 116 Buffer part 118 Propagation path multiplication part 120 Reception part 122 A / D conversion part 124 Radio unit 126 Transmission antenna unit 20 Relay station device 202 Reception antenna unit 204 Radio unit 206 A / D conversion unit 208 Channel estimation unit 210 Channel compensation unit 212 Demodulation unit 214 Decoding unit 216 Error detection unit (CRC unit)
218 Coding section 220 Modulation section 222 Pilot signal insertion section 224 A / D conversion section 226 Radio section 228 Transmission antenna section 30, 32 Terminal device 302 Reception antenna section 304 Radio section 306 A / D conversion section 308 Propagation path estimation section 310 Propagation path Compensator 312 Demodulator 314 Decoder 316 Transmitter 318 D / A converter 320 Radio unit 322 Transmit antenna unit

Claims (14)

In the base station device that communicates with the first terminal device and the second terminal device connected via the relay station device,
Interference signal generating means for generating an interference signal received by the first terminal device from the relay station device;
When transmitting a desired signal to the first terminal apparatus, and the desired signal transmission means for transmitting by subtracting the interference signal from the desired signal,
A base station apparatus comprising: The interference signal is a transmission signal of the second terminal device addressed, the base station apparatus according to claim 1, characterized in that to produce on the basis of the transmitted signal to the relay station device previously. Further comprising: propagation path information receiving means for receiving propagation path information from the first terminal device;
A transmission signal of the second terminal device addressed, the signal transmitted to the relay station apparatus previously described in claim 2, characterized in that to generate the interference signal based on said channel information Base station device. Wherein the channel information includes the information of the propagation path fluctuation between the information of the propagation path fluctuation and / or a base station apparatus and the first terminal device between the relay station apparatus and the first terminal device The base station apparatus according to claim 3 , wherein: Further comprising reception quality acquisition means for acquiring information relating to reception quality in the first terminal device;
The said desired signal transmission means is a means to transmit the said desired signal as it is to the said 1st terminal device, when the said reception quality is higher than a threshold value, The said any one of Claim 1 to 4 characterized by the above-mentioned. Base station equipment. The relay station apparatus further comprises a confirmation signal receiving means for receiving a positive response as a confirmation signal for successful communication or a negative response as a confirmation signal for communication failure,
The desired signal transmitting means, when receiving the negative response, according to any one of claims 1 to 5, characterized in that the means for transmitting the desired signal as it is to the first terminal device Base station equipment. Wherein the transmission level of the desired signal to fall within a certain range, the base station apparatus according to any one of claims 1 6, characterized by further comprising a signal level adjusting means for adjusting the signal level to be transmitted . The base station apparatus according to claim 7, wherein the signal level adjusting unit is a modulo operation. A terminal device connected to a communication system including a base station device and a relay station device,
Propagation path information acquisition means for acquiring propagation path information between the relay station apparatus and the terminal apparatus and / or propagation path information between the base station apparatus and the terminal apparatus;
Propagation path information transmitting means for transmitting at least one of the propagation path information to the base station apparatus when directly communicating with the base station apparatus;
Receiving means for receiving, from the base station apparatus, a signal obtained by subtracting an interference signal generated based on the signal transmitted from the relay station apparatus and the propagation path information from a desired signal;
A terminal device comprising: The terminal apparatus according to claim 9, wherein when performing direct communication with the base station apparatus, a modulo operation is performed on a signal received from the base station apparatus. And the base station apparatus, a relay station apparatus that retransmits towards the received terminal device signals transmitted from the base station apparatus, a first terminal apparatus that receives a signal transmitted from the base station apparatus directly, said a second terminal apparatus that receives signals transmitted from the base station apparatus via the relay station apparatus in a wireless communication system including,
The base station apparatus transmits to the first terminal apparatus a signal obtained by subtracting an interference signal that the relay station apparatus gives to the first terminal apparatus from a signal addressed to the first terminal apparatus. Communications system. The interference signal to be subtracted from the signal addressed to the first terminal device in the base station device is generated based on at least a signal previously transmitted from the base station device to the relay station device. 11. The wireless communication system according to 11 . The radio communication system according to claim 12 , wherein the signal previously transmitted from the base station device to the relay station device is a signal addressed to the second terminal device. In the base station apparatus, the base station apparatus adjusts the amplitude of the signal transmitted to the first terminal apparatus by subtracting the interference signal from the signal addressed to the first terminal apparatus so that the amplitude is within a predetermined range. The wireless communication system according to claim 11 , wherein the wireless communication system is a wireless communication system.

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