JP2016116123A - Base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station device for achieving Point-to-Multipoint type wireless full-duplex communication between a base station device and a plurality of radio stations by using a single frequency channel.SOLUTION: A base station device includes a transmission antenna group, a transmission signal processing part for generating a transmission analog signal of a radio frequency transmitted from the transmission antenna group, a reception antenna group, and a reception signal processing part for performing signal processing including at least frequency conversion to a reception analog signal of a radio frequency received by the reception antenna group. The transmission signal processing part and the reception signal processing part are housed in a different housing to exchange prescribed information by a wired connection, the transmission antenna group is arranged ahead of the reception antenna group only by a prescribed distance when seen in the direction of a radio station device from the reception antenna group, and the transmission antenna group is arranged outside a first Fresnel zone formed between each reception antenna element of the reception antenna group and an antenna element of the radio station device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a base station apparatus that performs space division multiplex transmission with a plurality of radio station apparatuses using the same frequency channel.

FIG. 16 shows an outline of a space division multiplex transmission system.
In FIG. 16, 1 is a base station apparatus, 2 is a radio station apparatus, 3 is a line-of-sight wave, 4 is a stable reflected wave, 5 to 6 are random multiple reflected waves, and 7 is a structure. The base station apparatus 1 includes a large number (for example, 100 or more) of antenna elements and is installed at a high place such as a rooftop of a building or a high steel tower. Similarly, the radio station apparatus 2 is installed at a high place such as on the roof of a building, on the roof of a house, on a telephone pole or a steel tower. Therefore, the base station apparatus 1 and the radio station apparatus 2 are generally in a line-of-sight environment. Between the base station 1 and the radio station 2, in addition to the path of the line-of-sight 3 and the stable reflected wave 4 reflected on the large stable structure 7, the mobile object such as a car or a person near the ground Multiple reflected waves 5 to 6 to be reflected are mixed. However, when a directional antenna is used, the reception levels of the multiple reflected waves 5 to 6 near the ground are lower than those of the line-of-sight wave 3 and the stable reflected wave 4.

FIG. 17 shows impulse responses in line-of-sight and non-line-of-sight environments.
In FIG. 17, the horizontal axis represents the delay time, and the vertical axis represents the reception level of each delayed wave. In the case of the non-line-of-sight environment shown in FIG. 17 (a), there is no direct wave component in the line-of-sight section, multiple reflected waves of various paths exist as components, and each amplitude and complex phase fluctuate violently randomly with time. To do.

  On the other hand, in the case of the line-of-sight environment shown in FIG. 17B, the stable paths such as the line-of-sight 3 and the stable reflected wave 4 shown in FIG. On the other hand, time-varying paths such as multiple reflected waves 5 to 6 have relatively low levels due to multiple reflections and attenuation due to path length. When such channel information is acquired and averaged a plurality of times, the stable path component is stable both in amplitude and complex phase every time, so that the change from the averaged channel information is small. On the other hand, since the time-varying path is synthesized and averaged randomly in the complex space, it converges near the origin of the complex space, and as a result, only the stable path component can be extracted effectively.

Based on the averaged channel information obtained in this way, the base station apparatus 1 calculates transmission / reception weights. The base station apparatus 1 performs directivity control for performing in-phase synthesis with a large number of antenna elements using the calculated transmission / reception weights. By using this transmission / reception weight, the base station 1 can increase the directivity gain to the radio station apparatus of the communication partner that is the target of directivity control in proportion to the square of the number N of antennas. In addition, since the directivity gain of interference to radio station apparatuses other than the target remains N times, a gap of N times is generated between the desired signal and the interference signal by simple calculation. As a result, the expected value of SIR (Signal to Interference Ratio) is ₁₀ Log ₁₀ (N) dB. This expected value is 20 dB when N is 100. In addition, when a radio station apparatus having a small correlation is selectively spatially multiplexed, further improvement in SIR characteristics is expected, and higher spatial multiplexing can be realized.

  Here, in directivity control using these many antennas, channel information is required to calculate the transmission / reception weight. When the base station apparatus includes a large number of antenna elements and the radio station side includes one or a small number of antenna elements, the uplink signal, for example, transmits a training signal for channel estimation for one symbol. MIMO channels between a large number of base station antennas that receive the base station antennas can be acquired in a lump, but for the downlink, it is fundamental to transmit training signals for channel estimation for the number of base station antennas. However, if the symmetry between the uplink and downlink channels is ensured, the downlink channel information can be estimated from the uplink channel information using a method called the implicit feedback method shown below, for example. It becomes possible.

(General implicit feedback method)
FIG. 18 shows an overview of the implicit feedback method.
In FIG. 18, 301-1 and 301-2 are antennas, 302-1 and 302-2 are changeover switches, 303-1 and 303-2 are high-power amplifiers (HPA), and 304-1 and 304-2 are low-noise amplifiers. (LNA). For convenience, the left side in the figure is the base station apparatus and the right side is the radio station apparatus. When transmitting and receiving signals, the base station apparatus and the radio station apparatus transmit via high power amplifiers 303-1 and 303-2 and receive via low noise amplifiers 304-1 and 304-2. The amount of change in the phase / amplitude of each amplifier is as follows: A _Tx1 exp (iθ _Tx1 ) in the high power amplifier 303-1, A _Tx2 exp (iθ _Tx2 ) in the high power amplifier 303-2, and A _Rx1 exp in the low noise amplifier 304-1. (iθ _Rx1 ), A _Rx2 exp (iθ _Rx2 ) in the low noise amplifier 304-2. If the channel coefficient between the antennas of the base station apparatus and the radio station apparatus is set to h, downlink channel information h _DL is expressed by the following equation (1).
h _DL = hA _Tx1 A _Rx2 exp i (θ _Tx1 + θ _Rx2 ) (1)
Similarly, uplink channel information h _UL is expressed by equation (2).
h _UL = hA _Tx2 A _Rx1 exp i (θ _Tx2 + θ _Rx1 )… (2)

Here, the calibration coefficient C _BS Equation (3) relates to an antenna of the base station apparatus, the calibration coefficient C _TE to antennas of the radio station apparatus is defined by equation (4).
C _BS = A _Tx1 exp (iθ _Tx1 ) / A _Rx1 exp (iθ _Rx1 ) (3)
C _TE = A _Rx2 exp (iθ _Rx2 ) / A _Tx2 exp (iθ _Tx2 ) (4)
The relationship of Equation (1) to Equation (4) to Equation (5) is established between the uplink and downlink channel information.
h _DL = C _BS · C _TE · h _UL (5)

Here, only one antenna is used for both transmission and reception. However, if the calibration coefficient for each antenna element of the base station apparatus and the calibration coefficient for each antenna element of the radio station apparatus are used, this also applies to the MIMO channel. Can be extended. For example, as channel information uplink channel information h _i from the j antenna radio station apparatus to the i antenna of the base station _{apparatus, j,} the j calibration coefficient of the antenna C _{TE, j} of the radio station, If the calibration coefficient of the i-th antenna of the base station apparatus is C _{BS, i} , the downlink channel matrix H _DL can be expressed by Equation (6).

It defines a calibration matrix C _TE leftmost matrix of the right side of the radio station apparatus specific formula (6), defines the right end of the matrix and the base station device-specific calibration matrix C _BS, a further channel matrix uplink Let _HUL denote. Here, the number of antenna elements of the base station apparatus is N, and the number of antenna elements of the radio station apparatus is M. At this time, Expression (6) can be expressed as Expression (7) as an extended matrix form of Expression (5).
H _DL = C _BS · H _UL ^T · C _TE (7)

Here, H _UL ^T represents a transposed matrix of the matrix H _UL . Thus, if the calibration matrices C _BS and C _TE of the base station apparatus and the radio station apparatus are known, the base station apparatus can estimate the downlink channel matrix from the uplink channel matrix. In particular, when the radio station apparatus is a single-element antenna (or when a virtual one beam is formed by a plurality of elements), the calibration coefficient C _TE of the radio station apparatus is simply a constant, and the transmission / reception weight Since it does not affect the formation, it is possible to ignore this coefficient and process. Actually, this calibration coefficient is obtained by preparing a one-element test station as a wireless station device at the time of factory shipment, and acquiring _HUL and _HDL channel information via the test station. _{CBS, j} · _CTE is obtained from the matrix relationship. Although C _TE is not meant just constant as described above, the constant is be multiplied to all the calibration coefficients, there is no problem substantially.

  When estimating an uplink channel, even if the radio station apparatus transmits one channel estimation signal to one antenna, the receiving side can simultaneously measure channel information on N antennas at the same time. Is possible. That is, even in a large-scale antenna system (Non-Patent Documents 1 to 4) or Massive MIMO system, channel feedback can be efficiently performed without being affected by an increase in the number of antenna elements of the base station apparatus.

FIG. 19 shows a channel estimation procedure using the implicit feedback method.
In FIG. 19, when the processing is started (S101), first, an uplink channel matrix H _UL ^(k) between the focused radio station apparatus and the base station apparatus is acquired (S102), and further, Expression (6) or Expression ( get the calibration matrix of the base station apparatus BS C _BS ^(k) and the radio station apparatus TE calibration matrix C _TE ^(k) according to 7) (S103), down in accordance with the equation (6) or (7) The link channel matrix H _DL ^(k) is calculated (S104), and the process is terminated (S105). In the above description, each channel matrix or calibration matrix generally has a different value for each frequency component, and the frequency component is explicitly described. In the present specification, generally, a broadband system is assumed, and each signal processing including calibration or implicit feedback is performed for each of a plurality of frequency components included in the broadband. In order to make the description of the components complicated, in the following description, unless otherwise specified, the description for each frequency component is omitted, and the same processing is performed with individual frequency components.

  The above is the outline of the implicit feedback method, but there are two requirements for the application of this method. The first requirement is that it is necessary to perform uplink channel estimation using the same combination as the physical combination of the base station transmission antenna and the radio station reception antenna used in the downlink channel to be obtained. The second requirement is that the frequency for transmitting the training signal for uplink channel estimation is the same as the frequency for transmitting the signal in the downlink. That is, using the frequency used in the downlink, the uplink channel estimation signal is transmitted from the same antenna as the radio station reception antenna, and the uplink channel estimation signal is received by the same antenna as the base station transmission antenna. There is a need. However, there is no problem when using Time Division Duplex (TDD) that divides time between uplink and downlink at the same frequency to realize uplink and downlink bidirectional communication. However, in the case of frequency division duplex (FDD) using different frequencies, the frequency may be different between the uplink and the downlink, and the antenna itself may be different depending on the system.

  As a conventional technique for avoiding such a problem, the following technique is disclosed in Patent Document 1. This Patent Document 1 is premised on use in combination with the above-described large-scale antenna system, and here, as a technique disclosed in Patent Document 2, it is fixed individually for each radio station apparatus as a communication partner. It is assumed that a circuit for constantly multiplying a transmission / reception signal by a reception weight and a transmission weight and a circuit for processing a transmission / reception baseband signal are provided. Details of the technology are shown below.

(Implicit feedback method in FDD system)
The number of radio station apparatuses that the base station apparatus is subject to spatial multiplexing transmission is N, and the number of antenna elements provided in the base station apparatus is K (in the case of FDD, the number of pairs of transmitting antenna elements and receiving antenna elements is (K set) will be described.

  FIG. 20 shows an example of downlink channel information estimation in the FDD system. FIG. 20A shows the flow of radio signals in the normal operation state, and FIG. 20B shows the flow of radio signals (training signals) at the time of channel information estimation.

  When the FDD scheme is used, as shown in FIG. 20A, the base station apparatus 500 and the terminal apparatus 700 use physically different antenna elements for transmission and reception. Furthermore, in uplink and downlink, base station apparatus 500 and radio station apparatus 700 communicate using different frequency channels.

  Specifically, during normal communication, as shown in FIG. 20A, in the uplink, the radio station apparatus 700 transmits a signal transmitted from the antenna element 701t at the frequency F1, and the base station apparatus 500 transmits the antenna elements 401r-1 to 401r. Receive at -K. In the downlink, the radio station apparatus 700 receives the signal transmitted from the antenna elements 401t-1 to 401t-K at the frequency F2 by the base station apparatus 500 by the antenna element 701r. That is, in the lower arrow (uplink) and the upper arrow (downlink) in FIG. 20A, the physical path of propagation is completely different due to the combination of antenna elements used, and the frequency itself is also different. For this reason, it is difficult to predict downlink channel information with high accuracy from the estimation result of uplink channel information.

  Therefore, in order to acquire channel information in a wireless communication system using the FDD scheme, as shown in FIG. 20B, when the channel information is estimated, the wireless station device 700 uses an antenna element 701r used as a receiving antenna during normal operation. Send training signals. Base station apparatus 500 receives the training signal transmitted from radio station apparatus 700 using antenna elements 401t-1 to 401t-K used as transmission antennas during normal operation, and based on the received training signal, Get channel information. That is, it is configured to be able to estimate uplink channel information indicated by the upper arrow in FIG. The base station apparatus 500 multiplies this uplink channel information by a calibration coefficient based on the uplink channel information obtained by using the training signal received at the frequency F2, thereby obtaining the downlink channel information. Channel information is estimated (FIG. 19).

  As described above, when communication is performed using the FDD scheme, the antenna element used for transmission and the antenna element used for reception in the base station apparatus and the radio station apparatus are different. The transmission path and the downlink transmission path from the base station apparatus to the radio station apparatus are different and the implicit feedback method is not established.

  Therefore, a training signal is transmitted from the radio station apparatus to the base station apparatus at the downlink frequency using the reception antenna element of the radio station apparatus and the transmission antenna element of the base station apparatus that are used in the downlink during normal operation. This problem can be solved by estimating uplink channel information from the combination and frequency of antennas used in the downlink, and estimating downlink channel information from the obtained uplink channel information.

FIG. 21 shows the configuration of base station apparatus 500 in the prior art.
In FIG. 21, base station apparatus 500 performs space division multiplex transmission at the same time on the same frequency as a plurality of radio station apparatuses using the FDD scheme. Further, the base station apparatus 500 includes K uplink antenna elements 401r-1 to 401r-K, K downlink antenna elements 401t-1 to 401t-K, and K radio signal processes. Circuits 510-1 to 510 -K, N transmission / reception signal processing units 430-1 to 430 -N, transmission / reception weight calculation unit 502, communication control circuit 503, and interface unit 404 are provided. Hereinafter, the whole or any one of the antenna elements 401r-1 to 401-K is referred to as the antenna element 401r. Similarly, the whole antenna element 401t-1 to 401t-K or any one of them is referred to as an antenna element 401t. Further, the wireless signal processing circuit 510 is referred to when the whole or any one of the wireless signal processing circuits 510-1 to 510 -K is shown.

  The antenna element 401r-i (i = 1, 2,..., K) and the antenna element 401t-i are paired. Further, the antenna element 401r-i and the antenna element 401t-i are connected to the wireless signal processing circuit 510-i in a one-to-one correspondence.

  The communication control circuit 503 controls the wireless signal processing circuits 510-1 to 510-K and the transmission / reception signal processing units 430-1 to 430-N.

  The radio signal processing circuit 510 converts a received signal received via the connected antenna element 401r from a radio frequency to an analog baseband, and further converts the signal into a digital signal by A / D conversion to transmit / receive signal processing unit Output to 430-1 to 430-N. The radio signal processing circuit 510 converts the digital signal of each frequency component input from each of the transmission / reception signal processing units 430-1 to 430-N into an analog baseband signal by D / A conversion, and further, an analog signal in the radio frequency band The frequency is converted into a frequency and transmitted through the antenna element 401t. The radio signal processing circuit 510 is connected to the communication control circuit 503, and various control information is input from the communication control circuit 503. For example, information on frame timing and transmission and reception symbol timing is also input from the communication control circuit 503 to the radio signal processing circuit 510, and signal processing such as FFT and IFFT is performed in accordance with the symbol timing.

  The transmission / reception weight calculation unit 502 receives an uplink training signal transmitted from the radio station apparatus using the uplink frequency and received by the antenna element 401r from the radio signal processing circuit 510. Entered. The transmission / reception weight calculation unit 502 calculates a reception weight based on the input uplink training signal, and stores the calculated reception weight.

  The transmission / reception weight calculation unit 502 receives an uplink training signal transmitted from the radio station apparatus using the downlink frequency and received by the antenna element 401 t from the radio signal processing circuit 510. The transmission / reception weight calculation unit 502 calculates a transmission weight based on the training signal transmitted using the input downlink frequency, and stores the calculated transmission weight. The transmission / reception weight calculation unit 502 calculates a transmission weight after performing a calibration process when calculating channel information from a training signal transmitted using a downlink frequency.

  The transmission / reception weight calculation unit 502 calculates a reception weight from long-term average channel information corresponding to the training signal received by the antenna element 401r. Also, long-term average channel information corresponding to the training signal received by the antenna element 401t is acquired, and downlink channel information is acquired by multiplying the calibration coefficient.

FIG. 22 shows a configuration example of the radio signal processing circuit 510 of the base station device 500.
In FIG. 22, a radio signal processing circuit 510 includes a low noise amplifier (LNA) 412, a mixer 414, a filter 415, an A / D converter 416, an FFT circuit 417, an addition synthesis circuit 421, an IFFT / GI addition circuit 422, and a D / A. A converter 423, a mixer 425, a filter 426, a high power amplifier (HPA) 427, and switches (SW) 521, 531 and 541 are provided.

  The local oscillator 413 and the local oscillator 424 are provided outside the wireless signal processing circuit 510. The local oscillator 413 supplies an uplink local oscillation signal (frequency: F1) to each radio signal processing circuit 510 included in the base station device 500. The local oscillator 424 supplies a downlink local oscillation signal (frequency: F2) to each radio signal processing circuit 510 provided in the base station device 500. That is, one local oscillator 413 and one local oscillator 424 are provided in the base station apparatus 500 and supply local oscillation signals to each radio signal processing circuit 510. As a result, each wireless signal processing circuit 510 is supplied with the synchronized local oscillation signal for uplink and the synchronized local oscillation signal for downlink.

  The switches 521 and 531 connect the antenna element 401t and the low-noise amplifier 412 when acquiring channel information before performing communication with the radio station apparatus or when acquiring new channel information to update the channel information. Connecting. As a result, the training signal received by the downlink antenna element 401 t is output to the low noise amplifier 412. In other cases, the switch 521 connects the antenna element 401t and the high power amplifier 427 so that the signal amplified by the high power amplifier 427 is transmitted from the antenna element 401t. Similarly, the switch 531 includes the low noise amplifier 412. And the antenna element 401r are connected, the signal received by the antenna element 401r is amplified by the low noise amplifier 412, and this is output to the mixer 414. Note that the switches 521 and 531 are controlled by the communication control circuit 503.

  In the wireless signal processing circuit 510, when the digital baseband signal to be transmitted is input from each of the transmission / reception signal processing units 430-1 to 430-N, the summing circuit 421 generates a digital baseband signal for each frequency component. Additive synthesis. The signal obtained by the addition synthesis is converted from the signal on the frequency axis to the signal on the time axis by the IFFT / GI adding circuit 422, and a guard interval is added. At this time, processing such as waveform shaping between symbols is performed as necessary. The signal to which the guard interval is given is converted into an analog signal by the D / A converter 423, multiplied by the local oscillation signal (frequency: F 2) input from the local oscillator 424 by the mixer 425, and the baseband band Frequency conversion is performed from the signal to a signal in a radio frequency band. Further, the signal in the radio frequency band is removed from the band by the filter 426, amplified by the high power amplifier 427, and transmitted from the antenna element 401 t via the switch 521.

  When a normal signal other than the training signal is received from the radio station apparatus, the reception signal received by the antenna element 401r is input to the low noise amplifier 412, and the low noise amplifier 412 amplifies the weak reception signal. The amplified reception signal is multiplied by a local oscillation signal (frequency: F1) input from the local oscillator 413 by the mixer 414 to be converted from a radio frequency band to a baseband signal, and an out-of-band signal is converted. It is removed by the filter 415 and converted to a digital baseband signal by the A / D converter 416. The guard interval is further removed from the digital baseband signal, and the FFT circuit 417 converts the signal on the time axis to the signal on the frequency axis, and outputs the signals to the transmission / reception signal processing units 430-1 to 430-N. The

  On the other hand, at the time of channel information estimation different from the normal operation state, the radio signal processing circuit 510 receives a training signal via the antenna element 401t in order to obtain a reception signal for estimating downlink channel information. At this time, the antenna element 401t and the low noise amplifier 412 are connected via the switch 521 and the switch 531 according to an instruction from the communication control circuit 503. The switch 541 connects the local oscillator 424 to the mixer 414.

  The training signal received by the antenna element 401t is amplified by the low noise amplifier 412, and multiplied by a local oscillation signal (frequency: F2) input from the local oscillator 424 via the switch 541 by the mixer 414, thereby wirelessly Conversion from frequency band to baseband signal. From this baseband signal, an out-of-band signal is removed by a filter 415 and converted into a digital baseband signal by an A / D converter 416. The digital baseband signal is input to the FFT circuit 417, and the FFT circuit 417 converts the signal on the time axis into a signal on the frequency axis. The signal on the frequency axis is output to the transmission / reception weight calculation unit 502.

  A feature of the radio signal processing circuit 510 is that a local oscillation signal (frequency: F2) output from the local oscillator 424 for downlink is used when acquiring channel information that is a basis for estimating downlink channel information. Is a point.

  Switching of connections by the switches 521, 531, and 541 is performed based on the control of the communication control circuit 503. The communication control circuit 503 switches the switches 521, 531, and 541 in the above-described manner, and receives from the low noise amplifier 412 to the FFT circuit 417 in the downlink channel information acquisition process and the uplink reception process. The system can be shared.

FIG. 23 shows a configuration example of the radio station apparatus 700.
23, the radio station device 700 includes antenna elements 701t and 701r, a communication control device 710, a MAC layer processing circuit 720, a transmission signal processing circuit 730, a reception signal processing circuit 740, an interface circuit 750, and a radio signal processing circuit 760. . The radio station device 700 inputs and outputs data via an interface circuit 750 with an external device or network not shown here.

  When data is input to the interface circuit 750, the MAC layer processing circuit 720 performs necessary MAC layer processing, and between the base station apparatus 500 and the radio station apparatus 700 for a normal signal flowing on the network here. Convert to the format of the signal sent and received by. This signal is input from the MAC layer processing circuit 720 to the transmission signal processing circuit 730 in accordance with an instruction from the communication control circuit 710. The transmission signal processing circuit 730 performs a predetermined physical layer process on the input signal. The radio signal processing circuit 760 converts the digital baseband signal into a radio frequency band analog signal by a predetermined process on the signal subjected to the physical layer process, and transmits the signal via the antenna element 701t.

  A signal received by the antenna element 701r is converted from an analog signal in a radio frequency band to a digital baseband signal by a predetermined process in a radio signal processing circuit 760. The received signal processing circuit 740 performs predetermined physical layer processing on the digital baseband signal. The MAC layer processing circuit 720 converts a signal subjected to physical layer processing from a format of a signal transmitted / received on a wireless line to a format of a signal transmitted on a normal network, and externally via an interface circuit 750. Output data. For example, basic control of a series of transmission / reception operations such as various timing control is performed by the communication control circuit 710 instructing.

FIG. 24 shows a configuration example of a radio signal processing circuit 760 in the radio station device 700.
24, a radio signal processing circuit 760 includes a low noise amplifier (LNA) 712, a local oscillator 713, a mixer 714, a filter 715, an A / D converter 716, an FFT circuit 717, an IFFT / GI adding circuit 722, and a D / A conversion. 723, a local oscillator 724, a mixer 725, filters 726 and 736, a high power amplifier (HPA) 727, and switches (SW) 711, 741, 742, 744 and 745.

  Since the frequencies used for the uplink and the downlink are different, the local oscillation signals used for frequency conversion are different. Therefore, the radio station device 700 includes a local oscillator 724 that generates a local oscillation signal used for frequency conversion in the uplink and a local oscillator 713 that generates a local oscillation signal used for frequency conversion in the downlink.

  During normal operation in which data communication is performed between the base station apparatus 500 and the radio station apparatus 700, a reception signal received by the antenna element 701r is input to the low noise amplifier 712 via the switch 711. The low noise amplifier 712 to the FFT circuit 717 converts the received signal into a digital baseband signal of each frequency component and outputs it to the received signal processing circuit 740. Note that a local oscillation signal (frequency: F2) generated by the local oscillator 713 is used for frequency conversion from the radio frequency band to the baseband.

  On the other hand, at the time of signal transmission, a signal to be transmitted to the base station apparatus 500 is input from the transmission signal processing circuit 730 to the IFFT / GI assignment circuit 722. The IFFT / GI adding circuit 722 to the high power amplifier 727 converts a signal to be transmitted into a signal of a radio frequency band and transmits it from the antenna element 701t. Note that the local oscillation signal (frequency: F1) generated by the local oscillator 724 is used for frequency conversion from the baseband to the radio frequency band.

  On the other hand, when the base station apparatus acquires channel information that is used to estimate downlink channel information different from that during normal operation, the D / A converter 723 includes the base station apparatus 500. A digital baseband signal corresponding to a training signal used when acquiring uplink channel information is input from the IFFT / GI adding circuit 722. The D / A converter 723 converts the input digital baseband signal into an analog signal and outputs it to the mixer 725. The mixer 725 multiplies the signal input from the D / A converter 723 by a local oscillation signal (frequency: F 2) generated by the local oscillator 713, and converts the frequency into a radio frequency band signal. Output to the filter 736. The filter 736 removes a signal outside the band of the channel to be transmitted from the signal input from the mixer 725, and outputs the signal to the high power amplifier 727 via the switch 742. The high power amplifier 727 amplifies the signal input from the filter 736 and transmits the amplified signal via the switch 741 and the switch 711 via the antenna element 701r.

  During normal operation (except when the base station apparatus 500 acquires channel information on which downlink and uplink channel information is estimated), the switch 711 connects the antenna element 701r and the low noise amplifier 712. Then, the reception signal received by the antenna element 701r is output to the low noise amplifier 712. The switch 741 connects the high power amplifier 727 and the antenna element 701t, and transmits the signal output from the high power amplifier 727 from the antenna element 701t. On the other hand, when the base station apparatus 500 that is different from the normal operation acquires channel information on which downlink channel information is estimated, the switches 741 and 711 include the high power amplifier 727 and the antenna element 701r. The signal is transmitted from the antenna element 701r.

  The IFFT / GI adding circuit 722 converts an input signal into a signal on a time axis, except when the base station apparatus 500 acquires downlink channel information, and further adds a guard interval to perform D / A conversion. Output to the device 723. When the base station device 500 acquires downlink channel information, the IFFT / GI assignment circuit 722 receives a training signal for channel estimation, converts the training signal into a signal on a time axis that does not include a guard interval. The data is output to the D / A converter 723.

  The operation of the output destinations of the switches 711 and 741, the switches 745 and 742, and the switch 744 is switched according to the instruction of the communication control circuit 710. Unlike the normal operation mode, the communication control circuit 710 may set the timing at which the base station apparatus 500 acquires downlink channel information by any method. For example, you may perform based on the control signal received from the base station apparatus 500. When the radio station apparatus 700 receives this control signal from the base station apparatus 500, a training signal for channel estimation is input to the IFFT / GI adding circuit 722 at a timing instructed by the control signal, and the IFFT / GI adding circuit 722 is input. The training signal is converted into a signal on the time axis, and the signal on the time axis is converted into an analog signal by the D / A converter 723, and the mixer 725, the switch 745, the filter 736, the switch 742, and the high power amplifier are converted. 727, a switch 741 and a switch 711, and transmitted from the antenna element 701r.

  When the base station apparatus 500 acquires channel information that is a basis for estimating downlink channel information, a local oscillation signal (frequency: F2) generated by the local oscillator 713 is used for up-conversion. It should be noted that means other than transmitting a control signal indicating that base station apparatus 500 acquires channel information that is the basis for estimating downlink channel information from base station apparatus 500 to radio station apparatus 700 are used. Thus, the switches 711, 741, 744, and 745 and the IFFT / GI provision circuit 722 of the wireless station device 700 may be controlled. For example, if the base station device 500 and the wireless station device 700 are before the start of service before communication, when the wireless station device 700 is installed, an installation operator gives a trigger to start channel estimation manually. Also good. Further, control for acquiring downlink channel information may be performed between the base station apparatus 500 and the radio station apparatus 700 using a line different from a radio line performing normal data communication.

  As described above, in the base station apparatus in Patent Literature 1, base station concentration is performed by regularly performing transmission / reception processing using transmission weights and reception weights calculated based on an estimated value obtained by averaging channel information. Spatial multiplexed transmission with each radio station apparatus can be performed without performing radio resource allocation management for each radio station apparatus under control. Furthermore, since each base station device has a processing unit that performs reception processing and transmission processing for each wireless station device to be communicated, communication with each wireless station device can be performed independently and in parallel. . As a result, it is not necessary to grasp the bandwidth required by each wireless station device using control information for bandwidth request, etc., avoiding overhead due to transmission / reception of unnecessary control signals and impairing efficiency of the MAC layer. In addition, spatial multiplexing transmission can be performed with a plurality of radio station apparatuses.

  In addition, each wireless station device and base station device perform individual point-to-point communication in parallel, but manage the upper limit of the number of spatial multiplexing so that it does not lead to characteristic degradation. Communication can be realized efficiently.

(About wireless full-duplex communication)
When communicating in both the uplink and downlink directions between the base station apparatus and the radio station apparatus, in general, the TDD that separates the uplink and the downlink by time division on the time axis and the frequency channels having different frequency axes. There is a separate FDD. Each advantage is that, for example, in the case of TDD, it is possible to dynamically change the allocation of uplink and downlink time ratios according to traffic, and adaptive operation according to the situation is possible. However, on the other hand, even when an urgent signal is to be transmitted (control signal including highly real-time application data, retransmission request signal, etc.), downlink transmission cannot be performed in the uplink time zone. As an example, when retransmission control is performed, transmission of an ACK signal or the like for data transmitted on the downlink is at the next uplink time zone at the earliest, and retransmission is performed even if the need for retransmission is recognized there. It can only be done at the next downlink time zone at the earliest.

  As described above, even in the technique disclosed in Patent Document 1 premised on use in combination with the above-described large-scale antenna system, at least uplink and downlink are used when TDD is used for access control. The delay time due to the frame configuration constituted by is inevitable. That is, TDD corresponds to half-duplex communication, while FDD or the like corresponds to full-duplex communication. In general, FDD is generally used to perform full-duplex communication wirelessly. However, full-duplex communication using the same frequency channel is also possible with the following configuration, for example.

FIG. 25 shows an outline of full-duplex communication using the same frequency channel in radio.
In FIG. 25, the base station apparatus 101 includes transmission antennas 103-1 and 104-1 and a reception antenna 105-1. The radio station apparatus 102 includes transmission antennas 103-2 and 104-2 and a reception antenna 105-2. In the base station apparatus 101, the distance between the receiving antenna 105-1 and the transmitting antenna 103-1 is set to the wavelength λ of the signal to be used, and the distance between the receiving antenna 105-1 and the transmitting antenna 104-1 is 1.5 of the wavelength λ. It is set to double. Similarly, in radio station apparatus 102, the distance between reception antenna 105-2 and transmission antenna 103-2 is set to wavelength λ, and the distance between reception antenna 105-2 and transmission antenna 104-2 is 1.5 times wavelength λ. Is set.

  The important point here is that the two transmitting antennas are set with a shift of ½ wavelength with respect to the receiving antenna. For example, when the base station apparatus 101 transmits exactly the same signal from the two transmission antennas 103-1 and 104-1, the signal received by its own reception antenna 105-1 has a path length of exactly 1 / Since they are shifted by two wavelengths, they are input in opposite phases. Therefore, the signals transmitted from the transmitting antennas 103-1 and 104-1 cancel each other out on the analog signal even though the distance to the receiving antenna 105-1 is very short. The same applies to the radio station apparatus 102. On the other hand, when the signal is received by the receiving antenna of the other station, the path length difference between the two transmitting antennas is random, and various reflected waves are synthesized in a multipath environment. The signal is not weakened as a signal of the total transmission power for this antenna. Therefore, a signal transmitted from the base station apparatus 101 on the same frequency channel can be normally received while the radio station apparatus 102 transmits a signal. Similarly, the signal transmitted from the radio station apparatus 102 can be normally received while the base station apparatus 101 transmits the signal. This situation does not have to be a special relationship between the base station apparatus 101 and the radio station apparatus 102, and can be realized even in point-to-multipoint type communication in which the radio station apparatus 102 is plural. is there.

  In such a full-duplex communication by radio, three approaches are considered in order to suppress leakage of a transmission signal to the reception side. As described above, an approach for reducing interference accompanying loopback of a transmission signal at an analog signal level to the local station reception side is applied as described above. This is a tradeoff between the assumed system and the following two approaches, but generally analog interference reduction is often incomplete.

  In the second approach, for example, as shown in Non-Patent Document 5, a transmitting antenna and a receiving antenna with high directivity gain are arranged side by side, and a signal from the transmitting antenna leaks directly to the receiving antenna side in terms of radio wave propagation. This approach is to reduce For example, if only point-to-point communication is assumed, if the directivity gain is extremely increased and two stations face each other with a narrow beam width in the form of a pencil beam, the influence of the reflected wave from the reflector on the way In addition, it is possible to reduce the leakage of the transmission signal to the reception side to some extent. However, assuming point-to-multipoint communication, the base station can communicate with multiple wireless stations located within a certain spatial extent. As a result, an interference signal accompanying reflection remains.

  The third approach corresponds to an approach in which interference signals that cannot be eliminated are removed by digital signal processing. Similar to the multi-user MIMO and large-scale antenna system described above, in addition to spatial multiplexing of a plurality of signal sequences in the uplink, if the downlink signal is also considered as a kind of spatial multiplexing, the signal leaks to the receiving antenna. The suppression of the squeezed signal is also based on the idea that it can be canceled by digital signal processing. However, these only require the premise that the interference signal that cannot be eliminated in the final digital signal processing is weak.

JP 2014-68174 A JP 2014-68173 A

Atsushi Ota, Kaoru Kurosaki, Kazuki Maruta, Takuto Arai, Masataka Iizuka, “B-5-175 Proposal of Large-scale Antenna Wireless Entrance System”, Proceedings of the IEICE General Conference 2013 (Communication_1), 2013 March 5, p. 585 Takuto Arai, Atsushi Ota, Atsushi Kurosaki, Kazuki Maruta, Masataka Iizuka, “B-5-176 Calculation Method of Transmit / Receive Weights in Large Antenna Radio Entrance System”, IEICE General Conference Proceedings 2013 (Communication_1) March 5, 2013, p. 586 Kazuteru Maruta, Atsushi Ota, Atsushi Kurosaki, Takuto Arai, Masataka Iizuka, “B-5-177 Inter-User Interference Suppression Method in Large Antenna Wireless Entrance System”, IEICE General Conference Proceedings 2013 (Communication_1) ), March 5, 2013, p. 587 Satoshi Kurosaki, Atsushi Ota, Kazuki Maruta, Takuto Arai, Masataka Iizuka, "B-5-178 Low Correlation Scheduling Method in Large Antenna Radio Entrance System", IEICE General Conference Proceedings 2013 (Communication_1) March 5, 2013, p. 588 Karimori, Jiro Hirokawa, Makoto Ando, "B-1-99 Development of a double-layered four-corner-fed waveguide slot array antenna for 40GHz band direction multi-duplex communication system", IEICE General Conference Proceedings 2014 (Communication_1), March 4, 2014, p. 99

  When constructing a system such as the large-scale antenna system described in Non-Patent Documents 1 to 4, it is generally important how efficiently channel information is fed back, and the use of the implicit feedback technology is very important. Promising. In this implicit feedback technique, the spatial channel symmetry, that is, the channel information between the antenna end of the base station apparatus and the antenna end of the radio station apparatus is symmetric between the uplink and the downlink, and the antenna end and the base By correcting the frequency-dependent complex phase rotation and amplitude increase / decrease caused by various circuits such as amplifiers and filters with the band transmission / reception signal processing circuit, the uplink channel information can be obtained. It is possible to acquire downlink channel information. This spatial channel symmetry is established only when the combination of transmitting and receiving antennas to be used and the frequency of the signals to be used coincide with each other. Therefore, when applying implicit feedback, it is fundamental to use TDD communication.

  However, for example, it is possible to obtain advantages such as simplifying access control by using the technology such as Patent Document 1 described above. However, in TDD, the transmission time in the uplink or the downlink is limited and arbitrary. It is not possible to send at the time. On the other hand, when the wireless full-duplex communication technology using the same frequency channel is used in the uplink / downlink including the technology described in FDD, Non-Patent Document 5, etc., in both the uplink and the downlink, any Transmission and reception at the timing becomes possible. Here, for example, if the technique disclosed in Patent Document 1 described above is used, a large-scale antenna system to which implicit feedback is applied at least in FDD can be constructed. However, the number of antenna elements in the base station apparatus is enormous. This causes problems.

  In a large-scale antenna system, high-order spatial multiplexing is performed simultaneously with a plurality of radio station apparatuses. In general, the total transmission power from the base station apparatus and the transmission power from one radio station apparatus at that time are generally Becomes asymmetric. A large-scale antenna system has an enormous number of transmission / reception systems, and a high power amplifier (HPA) is installed in each transmission system. In order to transmit from a single HPA with high power, the linearity of the amplifier is required, but when transmitting using a large number of HPAs, the number of antenna elements (that is, the number of HPAs) is simple even if the individual HPAs are inexpensive. It is possible to increase the total transmission power by increasing. For example, when the base station apparatus includes 100 antennas, it is possible to easily realize transmission with a total transmission power that is 100 times the transmission power per element. Of course, there is no necessity of transmitting all of the antenna elements from the HPA with the maximum transmission power. However, when focusing on the transmission of one signal sequence, for example, 20 stations are simultaneously allocated for the transmission power required for the line design. In the case of multiplexing, at least 20 times the transmission power is required for transmission of 20 signal sequences. For this reason, the total transmission power transmitted from a large number of antenna elements of the transmission system provided in the base station apparatus increases, and the signal leakage level from the transmission antenna side to the reception antenna side in wireless full-duplex communication is correspondingly increased. Double.

  Of the above three approaches in wireless full-duplex communication, the last digital interference signal suppression is an efficient way to eliminate the loopback signal from the transmitting antenna to the receiving antenna. The level of the loopback interference signal to the low-noise amplifier (LNA) on the receiving side and the reception level of the desired signal from the radio station that is the communication partner are within a predetermined range, and both signals are at least in the dynamic range. Must be within. However, in the case of point-to-multipoint type communication, it is impossible to make the base station device and the radio station device face each other with an excessively narrow beam width, and there are a plurality of spatially spread points. When accommodating radio stations scattered in the area, leakage of transmission signals to the reception antenna side due to reflection cannot be ignored.

  This problem becomes prominent in wireless full-duplex communication using the same frequency channel in the uplink and downlink, but this problem cannot be ignored even in actual FDD. Usually, the signal received by the receiving antenna is weak, and the signal is first amplified by the LNA. At this time, for example, if the channels of the frequencies F1 and F2 are used in the uplink and downlink, when the signal is received in F1, the leakage of the signal transmitted in F2 from the transmission antenna (least recently) The reflected wave may not be ignored. At this time, if the signal level of F2 leakage is too high, the LNA may be saturated and a desired F1 signal may not be received. Of course, this problem can be avoided if a band-pass filter is inserted between the antenna and the LNA. However, in general, if the filter is passed in a weak signal state, the loss and deterioration cannot be ignored, and as much as possible. After performing signal amplification with the LNA, it is preferable to remove out-of-band frequencies using a filter.

  In addition, since the antenna to be used is tuned to the frequency to be used to some extent, if the frequency channel is different, the signal reception gain decreases, and this can be expected to show a filter effect, but FDD. When two frequency channels used in the above are close to each other, it is not realistic to expect the antenna to have a frequency characteristic that is agile enough to separate the channels. Industrially, there is also a demand for reducing the manufacturing cost by unifying the antenna specifications for transmission and reception using antennas that can be used in close proximity to both F1 and F2, and as a result, transmission when FDD is used. Looping back a signal to a receiving antenna can be problematic as with wireless full-duplex communication when using the same frequency channel.

  As described above, in a radio system having a large-scale antenna system or a super-multi-element antenna using Massive MIMO, the total transmission power by a huge number of antenna elements in FDD or wireless full-duplex communication when using the same frequency channel is used. Problems associated with the increase in power consumption will be an issue. There is a demand for a base station apparatus configuration that can reduce leakage due to loopback of a transmission signal to a receiving antenna by a method different from narrowing the directivity of individual antenna elements.

  The present invention reduces the interference signal that the transmission signal from the transmission antenna side of the base station apparatus leaks to the reception antenna side when realizing wireless full-duplex communication using the same frequency channel. An object of the present invention is to provide a base station apparatus that can suppress interference by digital signal processing using information.

  The present invention includes a base station that includes a plurality of transmitting antenna elements and a plurality of receiving antenna elements having predetermined directivity with respect to a plurality of radio station apparatuses, and performs spatial multiplexing transmission with a plurality of radio station apparatuses on the same frequency channel In the apparatus, a transmission antenna group configured by arranging a plurality of transmission antenna elements on a plane, a transmission signal processing unit that generates a transmission analog signal of a radio frequency transmitted from the transmission antenna group, and a plurality of reception antenna elements And a reception signal processing unit configured to perform signal processing including at least frequency conversion on a radio frequency reception analog signal received by the reception antenna group. Unit and reception signal processing unit are housed in different housings and exchange predetermined information by wired connection, from the reception antenna group to the wireless station Is formed between each receiving antenna element of the receiving antenna group and the antenna element of the radio station apparatus. The transmission antenna group is arranged outside the first Fresnel zone.

  In the base station apparatus of the present invention, the radio station apparatus transmits a training signal transmitted by the radio station apparatus with a receiving antenna element, and acquires uplink first channel information based on the received signal. Means for receiving a training signal at a transmitting antenna element, acquiring uplink second channel information based on the received signal, and acquiring downlink channel information from the second channel information; Means for transmitting a training signal in order from each element, means for receiving the training signal transmitted from the transmitting antenna element by the receiving antenna element, obtaining channel information of the loop-back link based on the received signal, and data Based on the loopback link channel information acquired in advance and the signal transmitted in data communication during communication A means for estimating a replica of the interference signal received by the receiving antenna element after looping back from the transmitting antenna element, and generating a signal obtained by subtracting the estimated interference signal replica from the received signal received by the receiving antenna element. Received signal processing means for estimating a signal transmitted by the radio station apparatus using the uplink first channel information based on the base station apparatus to the radio station apparatus direction The same frequency channel is used for the downlink to the base station and the uplink from the radio station apparatus toward the base station apparatus, and bidirectional communication is performed at the same time.

  According to the present invention, a transmission signal from the transmission antenna side of the base station apparatus reduces interference signals that leak into the reception antenna side, so that a large number of antenna elements can be used between the base station apparatus and a plurality of radio stations. Point-to-multipoint wireless full-duplex communication can be realized using a single frequency channel. This makes it possible to effectively use frequency resources.

It is a figure which shows the basic structural example of the base station apparatus of this invention. It is a figure which shows the basic structural example of the base station apparatus of this invention. 3 is a diagram illustrating a positional relationship between a transmission antenna group 11 and a reception antenna group 21. FIG. 3 is a diagram illustrating a configuration example of a transmission signal processing unit 13 in Embodiment 1. FIG. 6 is a diagram illustrating a configuration example of a transmission RF circuit 81 of a transmission signal processing unit 13 in Embodiment 1. FIG. 3 is a diagram illustrating a configuration example of a reception signal processing unit 23 in Embodiment 1. FIG. 3 is a diagram illustrating a configuration example of a reception RF circuit 91 of a reception signal processing unit 23 in Embodiment 1. FIG. It is a figure which shows the structural example of the radio signal processing circuit 760b of the radio station apparatus corresponding to the base station apparatus of this invention. It is a figure which shows the example of estimation of each channel information in Example 1. FIG. It is a figure which shows the structural example of Example 2 and Example 3 of the base station apparatus of this invention. It is a figure which shows the structural example of the transmission signal process part 35a in Example 2, and the reception signal process part 36a. It is a figure which shows the structural example of the expansion control part 34a in Example 2. FIG. It is a figure which shows the structural example of the transmission signal process part 35b in Example 3. FIG. It is a figure which shows the structural example of the received signal process part 36b in Example 3. FIG. It is a figure which shows the structural example of the expansion control part 34b in Example 3. FIG. It is a figure which shows the outline | summary of a space division multiplex transmission system. It is a figure which shows the impulse response in a line-of-sight environment and a non-line-of-sight environment. It is a figure which shows the outline | summary of an implicit feedback method. It is a flowchart which shows the channel estimation procedure using an implicit feedback method. It is a figure which shows the channel information estimation example of the downlink in a FDD system. It is a figure which shows the structural example of the base station apparatus 500 in a prior art. It is a figure which shows the structural example of the radio signal processing circuit 510 of the base station apparatus 500. FIG. It is a figure which shows the structural example of the radio station apparatus 700. FIG. It is a figure which shows the structural example of the radio signal processing circuit 760 in the radio station apparatus 700. FIG. It is a figure which shows the outline | summary of the full-duplex communication using the same frequency channel in radio | wireless.

(Basic principle of the present invention)
When performing wireless full-duplex communication, there are three approaches as described above. In the analog interference signal suppression method using an omnidirectional antenna as shown in FIG. If the phase of the radio signal is slightly shifted in the cable or connector up to the element, the signal received by the receiving antenna will not be completely out of phase but will remain as a residual interference. Advanced quality control of cables is necessary. On the other hand, in the method of reducing radio wave propagation interference signals using the ultra-high directivity antenna as shown in Non-Patent Document 5, in order to avoid the inflow of interference signals from the transmission system to the reception system due to extra reflected waves. In addition, the radiation direction of radio waves is limited to a very narrow range. However, assuming point-to-multipoint type communication that accommodates multiple radio stations simultaneously, it is necessary to widen the radiation direction of radio waves to some extent, and it is difficult to reduce interference signals that leak from the transmission system to the reception system Become.

  Here, in the large-scale antenna systems described in Non-Patent Documents 1 to 4 and the like, it is assumed that radio station apparatuses distributed in all directions of 360 degrees are accommodated. It can also be used when concentrating. For example, when installing access radio base stations on the walls of buildings on both sides of a straight road, there are cases where it is difficult to draw a new optical line up to that point. The entrance line to the wireless base station is made wireless. In that case, the entrance base station has a two-dimensional directional antenna (for example, a planar patch antenna) on the plane, and the area covered is limited to an area sufficiently smaller than 360 degrees. An antenna system will be realized. A radio station (relay station) function that communicates with the entrance base station side is implemented on the access radio base station side, and this radio station is also equipped with one or more directional antennas, with directivity on the entrance base station side. Will be directed. Since this radio station is limited to only the entrance base station, it is possible to use an ultra-high directivity antenna. In this case, an interference signal from the transmission system to the reception system due to extra reflected waves It becomes easy to avoid the inflow. Further, when the entrance base station simultaneously performs spatial multiplexing with 10 radio stations simultaneously and communicates in parallel, the total transmission power for the 10 destination stations is a radio station that transmits only to one station. This means that the inflow of interference signals directly from the transmission system to the reception system becomes 10 times as an expected value. In this way, when using wireless full-duplex communication in a large-scale antenna system of the point-to-multipoint type, the condition at the entrance base station is stricter than that of the point-to-point type. Forced to operate.

  Therefore, in the present invention, the transmission antenna element group of the transmission system and the reception antenna group of the reception system are physically separated from each other. Usually, in a cellular system such as a mobile phone, the carrier company desires a lower frequency band allocation in order to ensure the communication quality of the last one-hop access system. Therefore, microwave bands with low frequencies are assigned to access systems. Considering frequency allocation to entrance systems that require a wide band in particular, high frequency bands such as quasi-millimeter waves or millimeter waves are used in entrance systems. Must be used. The higher the frequency, the more loss occurs in the transmission of the signal through the coaxial cable, etc., and when the transmission system and the reception system are separated from each other, the radio frequency band signal is expensive and low loss coaxial between them. The configuration for transmission by cable is not efficient when considering signal loss and economy. In particular, in a large-scale antenna system having a large number of transmitting / receiving antenna elements, it is necessary to input individual radio signals to each antenna element. Therefore, a huge number of expensive low-loss coaxial cables are routed over a long distance, which is also a physical restriction in that the thickness and bending resistance are low due to the requirement for low loss.

  In the present invention, the baseband signal processing to D / A conversion and A / D conversion, radio frequency conversion of up-conversion and down-conversion, so-called RF section such as signal amplification and out-of-band signal removal filter, etc. The transmission system to which the transmission antenna group is added and the reception system to which the many reception antenna groups are added are configured to be physically separated (at least in different cases), and signals exchanged between the cases are digital signals. To do. Although this digital signal can be transmitted through an optical fiber or a coaxial cable, a large cable loss such as a high-frequency signal does not occur. Furthermore, since an individual cable (optical fiber or coaxial cable) corresponding to each antenna element is not required, it is inexpensive, economical, and has few physical restrictions.

  In addition, the transmission system and the reception system are separated from each other and installed physically, so that it is necessary to transmit information that must be exchanged between the transmission system and the reception system over the cable. Basically, the additional information generated here is only some limited control information. For example, when performing retransmission control, a retransmission request signal must be generated based on information received by the reception system and transmitted from the transmission system. However, unlike wireless entrance lines where 1 Gbit / s or 10 Gbit / s (or higher) is required, for example, the amount of control information such as ACK and NACK is less than several orders of magnitude. Even if is used, it is possible to easily transmit information to a distance of 10 meters without being aware of signal loss.

  As will be described later, in order to cancel an interference signal in which a signal transmitted from the transmission antenna group 11 of the base station apparatus loops back to the reception antenna group 21, information on the transmission signal is transmitted to generate a replica for that purpose. Although it is necessary to notify the reception signal processing unit 23 from the signal processing unit 13, when an optical fiber is used, an increase in the amount of information due to the notification can be easily handled.

FIG. 1 shows a basic configuration example of a base station apparatus of the present invention.
In FIG. 1, 11 is a transmission antenna group, 12 is each antenna element of the transmission antenna group, 13 is a transmission signal processing unit, 14 is an arrow indicating the maximum directivity gain direction of each element of the transmission antenna group, and 15 is a transmission-side analog. Signal transmission signal line, 16 is a transmission side digital signal transmission signal line, 21 is a reception antenna group, 22 is each antenna element of the reception antenna group, 23 is a reception signal processing unit, and 24 is the maximum directivity of each element of the reception antenna group An arrow indicating a gain direction, 25 is a reception side analog signal transmission signal line, 26 is a reception side digital signal transmission signal line, 30 is a control unit, and 31 is a network side optical line. When the transmission antenna group 11 and the transmission signal processing unit 13 are housed in one housing and the reception antenna group 21 and the reception signal processing unit 23 are housed in one housing, the transmission-side analog signal transmission signal line 15 The line corresponding to the reception-side analog signal transmission signal line 25 can be realized by using a waveguide or the like in addition to a coaxial cable having a certain degree of installation freedom. Further, the control unit 30, the transmission signal processing unit 13, and the reception signal processing unit 23 are also housed in individual housings as shown in FIG. 2 (a), in addition to FIG. 2 (b) and FIG. 2 (c). ), The control unit 30 and the transmission signal processing unit 13, or the control unit 30 and the reception signal processing unit 23 may be housed in one casing.

  The important point is that the transmission antenna group 11 and the transmission signal processing unit 13 are arranged in a short distance or in the same housing in order to suppress the transmission loss of the transmission-side analog signal transmission signal line 15, and similarly receive the reception antenna group 21 and reception. The signal processing unit 23 is also disposed at a short distance or in the same housing in order to suppress the passage loss of the reception-side analog signal transmission signal line 25, while the transmission antenna group 11 and the reception antenna group 21 are physically separated. Therefore, as a result, the transmission signal processing unit 13 and the reception signal processing unit 23 are physically separated into separate cases. This makes it impossible for the transmission signal processing unit 13 and the reception signal processing unit 23 to share components such as a local oscillator, and exchanges high-frequency signals (or large-capacity information) with each other. It has become difficult. Therefore, each is basically operated independently, and only a small amount of control information represented by a retransmission request signal can be exchanged.

  Incidentally, when the transmission signal processing unit 13, the reception signal processing unit 23, and the control unit 30 exchange various signals with each other, the interface unit that controls the terminal function of the signal is generally included. To do. However, if each part is independent as shown in FIG. 2 (a), the signal is terminated at the interface part. However, as shown in FIG. 2 (b) and FIG. When the transmission signal processing unit 13 or the reception signal processing unit 23 is in the same housing, the interface unit between them may be omitted. However, FIG. 2 does not consider such a slight difference and considers only a basic functional part and gives the same number.

  As shown in FIGS. 1 and 3, the positional relationship between the transmitting antenna group 11 and the receiving antenna group 21 of the base station apparatus is such that the receiving antenna group 21 and the antenna element 18 of the radio station apparatus that is a communication partner of the base station apparatus are The transmitting antenna group 11 is arranged at a position x (m) ahead of the receiving antenna group 21 in the connecting straight line direction, and further transmitted to the range of the first Fresnel zone formed between the receiving antenna group 21 and the antenna element 18. The transmitting antenna group 11 is set to a position shifted by at least the Fresnel radius y (m) so that the antenna group 11 does not enter.

Here, the Fresnel radius y is defined as a distance from the receiving antenna group 21 to the antenna element 18 with respect to a position where a perpendicular line is dropped from the transmitting antenna group 11 to a straight line connecting the receiving antenna group 21 and the antenna element 18. When the distance is z and the signal wavelength is λ, the following equation is defined.
y = [(λ · x · z) / (x + z)] ^1/2 (8)

  FIG. 3B shows the positional relationship between the transmitting antenna group 11 and the receiving antenna group 21 when the receiving antenna group 21 is viewed from the antenna element 18 of the radio station apparatus of the communication counterpart. Strictly speaking, it is sufficient that the shortest distance between the housing of the transmitting antenna group 11 and the antenna element 22 of the receiving antenna group 21 is larger than the Fresnel radius y. However, x is preferably 3 m or more (in order to further improve the stability, 10 m or more).

  As an example, when x is 10 m, z is 300 m, the frequency is 60 GHz, and the wavelength is 0.005 m, the Fresnel radius y is 0.220 m. In other words, when the antenna elements 18 of a plurality of radio station apparatuses as communication partners are in a range of about 300 m, if the transmitting antenna group 11 is arranged about 10 m ahead of the receiving antenna group 21 and is displaced about 22 cm, It can be avoided that the transmitting antenna group 11 becomes an obstacle in the first Fresnel zone for the receiving antenna group 21. In the case of point-to-multipoint type communication, this relationship is satisfied with all of the plurality of radio station apparatuses.

  Here, when the transmission antenna group 11 and the reception antenna group 21 are arranged side by side, for example, it is assumed that a signal reflected at a location of about 1 m near the transmission antenna group 11 is incident on the reception antenna group 21. Since the path length in this case is a round trip, it is about 2 m. On the other hand, in the arrangement where x is 10 m in FIG. 1, the path length is 12 m. Since the path length is 6 times, the signal can be relatively reduced by about 15.6 dB if it is assumed to be attenuated by the free space square law. Furthermore, if the polarization of each antenna element 12 of the transmission antenna group 11 and the polarization of each antenna element 22 of the reception antenna group 21 are set differently, the polarization plane rotates due to reflection, so that leakage between the polarizations is completely achieved. Cannot be cut, but a certain degree of signal separation is possible. Here, if a degree of separation of about 10 dB can be secured, signal suppression of about 25 dB can be achieved. For example, when a 256-element antenna is mounted on a transmission / reception antenna group, there is a possibility that the total transmission power is 256 times that of a single-element antenna, which corresponds to an increase of 24.1 dB, and the above-described 25 dB signal suppression. It is equivalent to being able to cancel with.

  Considering the dynamic range in LNA, for example, the difference in reception level between a signal reflected by a path length of 12 m as described above (assuming that power is lost by 3 dB at the time of reflection) and a radio station apparatus signal 300 m away is Even if free space is assumed, it is about 40 dB. This is the worst value, and the actual reflection point is likely to be further away. The desired signal is dominated by the line-of-sight wave, so there is almost no need for a margin for fading, and the dynamic range of the LNA is 50 to 50. With 60 dB, it is possible to realize wireless transmission while avoiding saturation of LNA due to reflected waves.

Although the basic configuration of the base station apparatus of the present invention has been described above, more detailed examples will be described below.
Example 1
First, an application example to wireless full-duplex communication in which the uplink and downlink frequency channels are the same will be described with reference to the drawings. The base station apparatus of the present invention basically has the apparatus configuration shown in FIG. 2, and the transmission signal processing unit 13 and the reception signal processing unit 23 are physically different.

FIG. 4 illustrates a configuration example of the transmission signal processing unit 13 in the first embodiment.
4, 11 is a transmission antenna group, 12-1 to 12-K are antenna elements of the transmission antenna group, 13 is a transmission signal processing unit, 68 is a local oscillator, 69 is a transmission weight calculation / storage circuit, 81-1 ˜81-K are transmission RF circuits # 1 to #K, 82-1 to 82-K are addition circuits # 1 to #K, and 83-1 to 83-N are transmission weight multiplication circuits # 1 to #N, 84−. Reference numerals 1 to 84-N denote transmission signal processing circuits # 1 to #N, reference numerals 85-1 to 85-N denote transmission MAC layer processing circuits # 1 to #N, and 86 denotes an interface unit.

  When a transmission signal is input to the transmission signal processing unit 13 from the control unit 30 shown in FIGS. 1 and 2 via the transmission-side digital signal transmission signal line 16, the interface unit 86 terminates the optical or electrical digital signal, Retrieve the transmission data. The processing here may be either a packet-based signal such as an Ethernet (registered trademark) frame or a signal assembled in a predetermined frame, and a digital signal based on a general wired signal transmission mechanism. Correspond with processing. A transmission MAC layer processing circuit corresponding to the destination radio station apparatus based on the destination information, referring to the header area of the data acquired here, various control information, and the like, and selecting data to be transferred via the radio line Information is input to 85-i (i is 1 to N). The signal subjected to the MAC layer signal processing in the transmission MAC layer processing circuit 85-i is input to the subsequent transmission signal processing circuit 84-i, where the physical layer signal processing is performed. Here, various schemes such as OFDM and SC-FDE can be applied. In order to perform transmission weight multiplication on the frequency axis, a signal for each frequency component is generated by the transmission signal processing circuit 84-i. To do. As an example, if an OFDM modulation method is used, error correction encoding processing and interleaving processing are performed as necessary, bit string information to be transmitted is associated with each subcarrier, and modulation processing is performed for each subcarrier. The generated signal is generated for each symbol and input to the subsequent transmission weight multiplication circuit 83-i. If there is no signal to be transmitted, the signal of each frequency component of each symbol is input as zero.

  The transmission weight multiplying circuit 83-i multiplies the signal from the transmission signal processing circuit 84-i in the previous stage by a different transmission weight for each antenna element, and adds this to the adding circuits 82-1 to 82-K corresponding to the transmission weight. input. For example, the transmission weight multiplication circuit 83-i adds the signal obtained by multiplying the transmission weight corresponding to the antenna element 12-1 to the addition circuit 82-1, and the signal obtained by multiplying the transmission weight corresponding to the antenna element 12-2 to the addition circuit. A signal obtained by multiplying 82-2 by the transmission weight corresponding to the antenna element 12-K is output to the adder circuit 82-K. Note that the above multiplication is performed individually for each frequency component.

  The adder circuits 82-1 to 82-K individually add the signals input from the preceding transmission weight multiplying circuits 83-1 to 83-N for each frequency component. For example, the adder circuit 82-1 adds the signals input from the transmission weight multiplication circuits 83-1 to 83 -N for each frequency component, aggregates the N system signals into one system, and transmits the RF circuit 81- Enter 1 The transmission RF circuits 81-1 to 81-K convert the digital signals of the respective frequency components input from the adder circuits 82-1 to 82-K into analog signals of radio frequencies used for radio transmission and output them. Usually, a digital signal is converted into an analog baseband signal, and further frequency conversion is performed from a baseband signal to a radio frequency signal. In the frequency conversion to the radio frequency, a signal input from the local oscillator 68 is used. Details of this processing will be described again with reference to FIG. Radio frequency analog signals output from the transmission RF circuits 81-1 to 81-K are respectively output to the corresponding antenna elements 12-1 to 12-K of the transmission antenna group 11, and transmitted as radio signals.

  When terminating at the interface unit 86, the header area of the acquired data, various control information, and the like are referred to. The circuit 85 generates a wireless packet containing control information as necessary, and outputs it to the transmission signal processing circuit 84 in the same way as normal data, and performs the subsequent processing.

  In addition, the transmission RF circuits 81-1 to 81-K have a function of acquiring downlink channel information for each radio station and frequency component as a communication partner using an implicit feedback method. The link channel information is output to the transmission weight calculation / storage circuit 69. The transmission weight calculation / storage circuit 69 collects channel information of each frequency component from all the transmission RF circuits 81-1 to 81-K, and finally calculates and stores a transmission weight used for spatial multiplexing for each frequency component. To do. The transmission weight multiplication circuits 83-1 to 83 -N obtain transmission weight information for each frequency component addressed to the corresponding radio station from the transmission weight calculation / storage circuit 69, and perform transmission weight multiplication based on this information. Here, the transmission weight is fixed to some extent in a large-scale antenna system, but it is also possible to adopt a configuration in which the transmission weight is sequentially updated.

  Further, the signals multiplied by the transmission weights in the transmission weight multiplication circuits 83-1 to 83-N are added and synthesized as signals for the transmission RF circuits 81-1 to 81-K by the addition circuits 82-1 to 82-K. The transmission signal is input to the transmission RF circuits 81-1 to 81-K and is also transferred from the interface unit 86 to the reception signal processing unit 23 via the control unit 30. This transmission signal is used for generating a replica for canceling an interference signal in which a signal transmitted from the transmission antenna group 11 of the base station apparatus loops back to the reception antenna group 21 as described later.

FIG. 5 shows a configuration example of the transmission RF circuit 81 of the transmission signal processing unit 13 in the first embodiment.
In FIG. 5, 52 is a switch, 53 is a low noise amplifier, 54 is a mixer, 55 is a filter, 56 is an A / D converter, 57 is an FFT circuit, 58 is a channel estimation circuit, 61 is an IFFT / GI adding circuit, and 62 is Reference numeral 63 denotes a D / A converter, 64 a mixer, 65 a filter, 66 a high power amplifier, 67 a switch, 68 a local oscillator, and 69 a transmission weight calculation / storage circuit. Since the transmission RF circuit 81 exists for each antenna element 12, the individual circuits should be explained by adding an explanatory note “connected to the i-th antenna element... In the description, the description is omitted for simplification of description, and the description is made without assigning a subscript child number to the number. Further, as described above, the present invention can be applied to techniques such as OFDM and SC-FDE. However, since the present invention is a general general-purpose similar technique, the case of OFDM will be described as an example here.

  Here, in the transmission signal processing unit 13 shown in FIG. 4, in order to realize the implicit feedback in performing full-duplex wireless communication using the same frequency channel in the uplink and downlink, the transmission RF circuit 81 Includes a low noise amplifier 53, a mixer 54, a filter 55, an A / D converter 56, an FFT circuit 57, an IFFT / GI adding circuit 61, a memory 62, a D / A converter 63, and a mixer 64. A transmission system including a filter 65 and a high power amplifier 66 is provided. These transmission system and reception system are branched via the switch 52, and the reception system is used when channel information is fed back, and the transmission system is used during normal operation.

  Note that the local oscillator 68 is shared by all the transmission RF circuits 81 as shown in FIG. 4, thereby eliminating the uncertainty of the phase of each transmission RF circuit 81 and highly accurate transmission directivity control. Is possible.

  First, the transmission system will be described. The digital signal for each frequency component input from the adder circuit 82 of the transmission signal processing unit 13 in FIG. 4 is converted into a signal on the time axis by the IFFT / GI adding circuit 61, and a guard interval is added. The sampling signal on the time axis to which the guard interval is given is input to the D / A converter 63, where it is converted from a digital sampling signal to an analog baseband signal. This analog baseband signal is input to the mixer 64, where it is multiplied by the signal input from the local oscillator 68 via the switch 67, and up-converted to a signal in the radio frequency band. Further, the out-of-band frequency component is removed by the filter 65, the signal is amplified by the high power amplifier 66, and output to the transmitting antenna element 12 via the switch 52. Here, the switch 67 at the time of normal operation is switched so that the signal is conducted in the direction of “local oscillator 68 → switch 67 → mixer 64”, and the signal from the local oscillator 68 is output to the mixer 64. Similarly, the switch 52 during normal operation is switched so that signal conduction in the direction of “high power amplifier 66 → switch 52 → transmission antenna element 12” is performed, and the signal from the high power amplifier 66 is transmitted to the transmission antenna element 12. Output

  On the other hand, when channel information is fed back to and from the radio station apparatus, a signal received by the transmission antenna element 12 is input to the low noise amplifier 53 via the switch 52, where signal amplification is performed. The amplified received signal is input to the mixer 54, where it is multiplied by the signal input from the local oscillator 68 via the switch 67, and down-converted from a radio frequency band signal to a baseband signal. Further, the out-of-band frequency component is removed by the filter 55, converted to a digital sampling signal by the A / D converter 56, and the time axis signal is separated into signals of each frequency component by the FFT circuit 57. When a continuous signal that does not include a guard interval is used as a training signal when channel information is fed back, a time-axis signal with a period of the number of FFT points at an arbitrary symbol timing synchronized by each transmission RF circuit 81 Is separated into signals of each frequency component by the FFT circuit 57. On the other hand, when a normal OFDM training signal including a guard interval is used when feedback of channel information is performed, symbol timing detection such as OFDM is required for performing FFT, but any timing detection is possible. It is possible to use a technique, and it is assumed that the function is mounted in the FFT circuit 57 as necessary, and the description is omitted here. Actually, the channel information feedback performed in Non-Patent Documents 1 to 4 has a configuration capable of processing without detecting symbol timing. After the signal is converted to the signal on the frequency axis in this way, the channel estimation circuit 58 performs uplink channel estimation, and based on this uplink channel information, the above-described calibration processing is performed to obtain the downlink channel information. The data is converted and output to the transmission weight calculation / recording circuit 69. The transmission weight calculation / recording circuit 69 collects and stores these channel information, and calculates the transmission weight after obtaining all the channel information necessary for spatial multiplexing. The calculated transmission weight is stored in the transmission weight calculation / storage circuit 69 and output to the transmission weight multiplication circuit 83 as necessary.

  In general, when performing wireless full-duplex communication using the same frequency channel, a signal transmitted from the transmitting antenna group 11 is looped back to the receiving antenna group 21, and is converted into an uplink received signal from the radio station apparatus. On the other hand, since it becomes an interference signal, the reception signal processing circuit 23 needs to cancel the signal. In order to cancel the interference signal, it is necessary to acquire channel information to be looped back for all combinations of the antenna elements 12 on the transmission side and the antenna elements 22 on the reception side. Need to send. The transmission RF circuit 81 of the transmission signal processing unit 13 is provided with a memory 62 for storing a training signal sampling pattern for this purpose, and a signal input from the transmission signal processing circuit 84 as necessary for loopback channel estimation. Instead, the sampling pattern read from the memory 62 is output to the D / A converter 63 via the IFFT / GI adding circuit 61. The signal processing after the D / A converter 63 is the same as the signal processing during general data communication. When acquiring loopback channel information, the plurality of transmission RF circuits 81 transmit signals one by one in order, and training signals including the same frequency component are transmitted simultaneously from different transmission antenna elements 12 at the same time. Never happen. Also, in the case of loopback channel estimation as well as channel estimation in the uplink, it is possible to use a training signal that does not include a guard interval similar to the feedback of channel information performed in Non-Patent Documents 1 to 4. In this case, the IFFT / GI adding circuit 61 may be configured to perform only IFFT processing without providing guard intervals.

FIG. 6 illustrates a configuration example of the reception signal processing unit 23 in the first embodiment.
In FIG. 6, 21 is a reception antenna group, 22-1 to 22-K are antenna elements of the reception antenna group, 23 is a reception signal processing unit, 79 is a local oscillator, 80 is a reception weight calculation / storage circuit, and 87 is an interference. Signal replica generation circuits, 91-1 to 91-K are reception RF circuits # 1 to #K, 92-1 to 92-K are replication circuits # 1 to #K, and 93-1 to 93-N are reception weight multiplication circuits. # 1 to #N, 94-1 to 94-N are reception signal processing circuits # 1 to #N, 95-1 to N are reception MAC layer processing circuits # 1 to #N, and 96 is an interface unit.

  First, in the case of normal data communication, signals received by the antenna elements 21-1 to 21-K of the reception antenna group 21 are input to the corresponding reception RF circuits. The reception RF circuits 91-1 to 91-K amplify the signals received by the corresponding antenna elements 21-1 to 21-K, and convert the radio frequency analog signals to digital baseband signals of the respective frequency components. To do. Details of the processing here will be described again with reference to FIG. The digital baseband signals are input to the corresponding duplicating circuits 92-1 to 92-K, where they are duplicated into signals having the same contents and input to the receiving weight multiplying circuits 93-1 to 93-N. In the reception weight multiplication circuits 93-1 to 93-N, a reception weight is input from the reception weight calculation / storage circuit 80, and an interference signal replica is also input from the interference signal replica generation circuit 87.

  In the interference signal replica generation circuit 87, the transmission signals output from the addition circuits 82-1 to 82-K of the transmission signal processing unit 13 shown in FIG. 4 are transmitted to the interface unit 86 and the control unit 30 of the transmission signal processing unit 13. The interference signal for inputting the loop back link channel information from the reception RF circuits 91-1 to 91-K and canceling the looped back interference signal. A replica is generated and output to reception weight multiplication circuits 93-1 to 93-N.

  In the reception weight multiplication circuits 93-1 to 93-N, the vector-like interference signal replica output from the interference signal replica generation circuit 87 is subtracted from the vector-like signals from the respective duplication circuits 92-1 to 92-K. The signal obtained by the vector subtraction is vector-multiplied by a vector-like reception weight for each frequency component. The processing here is basically performed regardless of whether or not a signal is actually received from the corresponding radio station apparatus. The vector multiplication result is input to the corresponding reception signal processing circuits 94-1 to 94-N, where reception signal processing is performed. The received signal processing here is general signal processing when a series of signals input from the reception weight multiplication circuits 93-1 to 93-N are recognized as signals of a predetermined level, and conversely, predetermined signals are processed. If it is not determined that the signal is at the level, no processing is performed assuming that no signal has been received. In general signal processing, for example, in the case of OFDM, channel estimation is performed using a training signal attached to the head of a series of received signals, and each frequency component of each OFDM symbol is calculated based on the channel estimation result. The signal is divided, and signal detection processing is performed based on the result. In general wireless communication, error correction encoding and interleaving processing are performed on the transmission side. However, in the embodiment of the present invention, when similar error correction processing is performed, signal detection is subjected to soft decision processing. Then, after deinterleaving, error correction is performed based on likelihood information and the like, and transmission data is reproduced.

  The reproduced data is input to the corresponding reception MAC layer processing circuits 95-1 to 95 -N, and the presence or absence of a code error is determined by an error detection code. Is transferred to the control unit 30 via the receiving-side digital signal transmission signal line 26. In the reception MAC layer processing circuits 95-1 to 95 -N, for example, when a retransmission control function is implemented, the continuity of the sequence numbers given to the reproduced transmission data is confirmed, Control information for requesting retransmission of unreceived data corresponding to the sequence number is generated, and this control information is also transferred from the interface unit 96 to the control unit 30. The control information transferred to the control unit 30 is determined by the control unit 30 based on some identification information such as header information added to the information, and transferred to the transmission signal processing unit 13 as necessary. When retransmission control is performed, the reception MAC layer processing circuits 95-1 to 95 -N receive data before being output from the reception MAC layer processing circuits 95-1 to 95 -N to the interface unit 96. The order of data output is adjusted so that the sequence number is output with reference to the sequence number.

  On the other hand, when channel information is fed back at a timing when data communication is not performed, the reception RF circuits 91-1 to 91-N perform channel estimation by uplink channel estimation with each radio station apparatus. Information is acquired and this channel information is output to the reception weight calculation / storage circuit 80. The reception weight calculation / storage circuit 80 stores this channel information for each radio station and each frequency component. The reception weight calculation / storage circuit 80 once aggregates channel information for each radio station, calculates reception weights when performing spatial multiplexing based on these channel information, and stores the reception weights. In the reception weight multiplication circuits 93-1 to 93-N, the reception weight is obtained from the reception weight calculation / storage circuit 80, and the reception weight is regularly multiplied.

  Further, in the process of performing feedback of channel information, in addition to the feedback process of acquiring channel information between the antenna elements of the radio station apparatus and the base station apparatus, from each antenna element 12 of the transmission antenna group 11 of the base station apparatus, Channel information that loops back to each antenna element 22 of the receiving antenna group 21 of the base station apparatus is also acquired. This is because the training signal for acquiring the loopback channel information output from the transmission RF circuit of the transmission signal processing unit 13 is transmitted from the transmission antenna group 11, and the received RF signal is received by the reception antenna group 12. The channel estimation results performed by the circuits 91-1 to 91-N are input to the interference signal replica generation circuit 87, and the interference signal replica generation circuit 87 stores the loopback channel information. This loopback channel information includes signal components transmitted from the transmission antenna group 11 side from signals received by mixing the signals transmitted from the transmission antenna group 11 side of the base station apparatus with the transmission signals of the radio station apparatus. Is used to generate an interference signal replica for canceling.

  Also, the reception weight and loopback matrix may be updated sequentially. For example, when the reception weight is gradually updated using a forgetting factor or the like, the channel information is updated using the forgetting factor or the like, and updated in the reception weight calculation / storage circuit 80 based on the updated channel information. The reception weight is updated based on the channel information.

FIG. 7 illustrates a configuration example of the reception RF circuit 91 of the reception signal processing unit 23 in the first embodiment.
In FIG. 7, 71 is a low noise amplifier, 72 is a mixer, 73 is a filter, 74 is an A / D converter, 75 is an FFT circuit, 77 is a channel estimation circuit, 79 is a local oscillator, and 80 is a reception weight storage circuit.

  First, signal processing in the case of normal data communication will be described. The signal received by the receiving antenna element 22 is input to the low noise amplifier 71 where signal amplification is performed. The amplified received signal is input to the mixer 72, where it is multiplied by the signal input from the local oscillator 79, and down-converted from a radio frequency band signal to a baseband signal. Further, an out-of-band frequency component is removed by the filter 73, converted into a digital sampling signal by the A / D converter 74, and a guard interval is obtained from the sampling signal for one symbol by the FFT circuit 75 using the time axis signal. By removing and then performing FFT, it is separated into signals of each frequency component. In order to perform FFT, symbol timing detection such as OFDM is required, but any method can be used for timing detection, and the function is implemented in the FFT circuit 75 as necessary. The description is omitted here. The signal separated into frequency components by the FFT circuit 75 is output and input to the duplicating circuit 92 in the received signal processing unit 23.

  On the other hand, the channel information feedback process is slightly different. In channel information feedback, when a signal for channel estimation is transmitted from the radio station apparatus or when a signal for channel estimation is transmitted from the transmission signal processing unit 13 of the base station apparatus, the FFT circuit 75 The signal converted to the on-axis signal is subjected to channel estimation by the channel estimation circuit 77, the estimated uplink channel information is output to the reception weight calculation / storage circuit 80, and the loopback channel information is generated as an interference signal replica. It is output to the circuit 87. The above is the content of the signal processing of the reception RF circuit 91.

  Here, the local oscillator 79 is shared by all the reception RF circuits 91 of the reception signal processing unit 23 shown in FIG. 6, thereby eliminating the uncertainty of the phase of each reception RF circuit 91 and receiving directivity. Sex control is possible.

  By the way, since the antenna of the radio station apparatus requires a smaller number of elements than that of the base station apparatus, it is not necessarily required that the transmission system and the reception system are physically separated as shown in FIG. In general, it is preferable that the radio station apparatus is housed in a small casing, and therefore an example of an integrated configuration will be described below.

  FIG. 8 shows a configuration example of a radio signal processing circuit of a radio station apparatus corresponding to the base station apparatus of the present invention. With regard to the radio station apparatus, the radio signal processing circuit 760 in FIGS. 23 and 24 in the prior art can be replaced with the radio signal processing circuit 760b so as to correspond to the base station apparatus of the present invention.

  In FIG. 8, the wireless signal processing circuit 760b omits the local oscillator 713, the switch 745, the filter 736, the switch 742, and the switch 744 in the wireless signal processing circuit 760 in FIG. 24, and converts the signal from the local oscillator 724 into a mixer 714 and a mixer. This is a configuration to multiply by 725. The switching of the switch 711 and the switch 741 is as follows. When transmitting a signal in a normal communication state, the switch 741 outputs a signal from the high power amplifier 272 to the antenna element 701t. Conversely, when receiving a signal, the switch 741 receives a signal received by the antenna element 701r as a low noise amplifier 712. Output to. On the other hand, when the channel information is fed back, the switch 741 and the switch 711 are switched so that the signal from the high power amplifier 272 is transmitted from the antenna element 701r.

  About the above operation | movement, the channel information of the downlink by an implicit feedback will be estimated by the structure of FIG. 9 contrasted with FIG. The difference between FIG. 20 and FIG. 9 is as follows. The base station apparatus includes a control unit 30, a transmission signal processing unit 13, a reception signal processing unit 23, a transmission antenna group 11, and a reception antenna group 21. In order to achieve wireless full-duplex communication using the same frequency channel, a signal from the transmission antenna group 11 of the base station apparatus of FIG. 9 (a) to the antenna element 701r of the wireless station apparatus, and a wireless station of FIG. 9 (b) In the case of the wireless full-duplex communication using the same frequency channel in FIG. 9, the signal from the antenna element 701r of the apparatus to the transmission antenna group 11 of the base station apparatus is the frequency F2 corresponding to the FDD in FIG. In addition, the frequency F1 is used similarly to the signal in the opposite direction. For this reason, as shown in FIG. 8, the filter 736 corresponding to the frequency channel F2 in the radio signal processing circuit 760 of FIG. 24 becomes unnecessary, and as a result, the switch 745 and the switch 742 for switching between the filter 726 and the filter 736 are provided. It is unnecessary. Similarly, the input to the mixer 725 does not need to be switched between the local oscillator 713 and the local oscillator 724, and the switch 744 is unnecessary.

  9 (a) and 9 (b) is the most important difference from FIG. 20 in that the signals transmitted from the transmission antenna group 11 of the base station apparatus use the same frequency channel in the uplink and downlink. Therefore, it is necessary to estimate the channel similarly for the channel that loops back to the receiving antenna group 21. In FIG. 20 (b), in order to perform downlink channel estimation using the implicit feedback method, a channel estimation training signal is transmitted at frequency F2 from 701r, which is originally a receiving antenna of the radio station device 700. The base station apparatus 500 receives signals at transmission antennas 401t-1 to 401t-K, which are originally transmission antennas, and performs uplink channel estimation. On the other hand, in the case where wireless full-duplex communication using the same frequency channel is applied in the present invention, a radio station apparatus 700 transmits a channel estimation training signal at a frequency F1 from the original receiving antenna 701r, and the base station In addition to performing signal reception by the transmission antenna group 11 that is the transmission antenna of the apparatus and performing uplink channel estimation, a transmission signal for channel estimation is transmitted from the transmission antenna group 11, and this is received as the reception antenna group. 21, loopback channel information for all combinations of the antenna elements of the transmission antenna group 11 and the reception antenna group 21 is acquired. When acquiring this channel information, the sampling pattern of the training signal stored in the memory 62 is read out one by one from the transmission RF circuits 81-1 to 81-K in the transmission signal processing unit 13, and the signal is transmitted. I do. The transmission timing of the signal from the transmission signal processing unit 13 and the reception timing of the training signal in the reception signal processing unit 23 are assumed to be synchronized via the control unit 30, and the reception signal processing unit 23 performs all reception. The RF circuit 91 simultaneously performs signal reception and channel estimation to obtain a loopback MIMO channel matrix.

(Signal processing for eliminating looped-back interference signals)
The above is the description of the first embodiment of the present invention. Note that details of signal processing for removing the interference signal component transmitted from the transmission antenna group 11 of the base station apparatus whose details are omitted in the above description and looped back to the reception antenna group 21 will be described below.

First, a signal output from the transmission RF circuit 81-i of the transmission signal processing unit 13 of the base station apparatus is transmitted from the antenna element 12-i of the transmission antenna group 11 and received by the antenna element 22-j of the reception antenna group 21. Assuming that the channel information when being input to the reception RF circuit 91-j is b _{j, i} , the loopback channel matrix H _LB is defined as follows.

同様に、アップリンクでの受信ウエイトＷ_Rxを以下のように定義する。

Here, the transmission weight matrix W _Tx for the base station apparatus and the n-th radio station apparatus is defined as follows.

Similarly, the uplink reception weight W _Rx is defined as follows.

  The transmission weight matrix and the reception weight matrix may be calculated by any method. For example, any of the conventional techniques such as block diagonalization method, ZF (Zero Forcing) method, and MMSE (Minimum Mean Square Error) method used in multi-user MIMO may be used. Similarly to the large-scale antenna system described in Non-Patent Document 1 or the like, a weight for in-phase synthesis or a weight for maximum ratio synthesis may be used.

Next, s _n is a signal transmitted from the base station apparatus to the n-th radio station apparatus, and transmission signal vectors s _{1 to} s _N having transmission signals addressed to all radio station apparatuses as vectors are multiplied by transmission weights. Thus, the signal vectors t _{1 to} t _N actually transmitted from the transmitting antenna elements 22-1 to 22-K are expressed by the following equations.

In this way, when the transmission signal vector is s, the signal t _i transmitted from the i transmission antennas of the base station apparatus is obtained, when the transmission signal vector t is transmitted, in these signals somewhere The interference signal vector δr received by the receiving antenna of the base station apparatus in the form of reflection or diffraction and looping back is given by the following equation.

That is, a signal r _j received by the j-th antenna of the base station apparatus in a form in which a signal transmitted from the n-th radio station apparatus and an interference signal transmitted from the base station apparatus and looped back are mixed. In this case, if the interference signal δr _j included in the received signal is canceled, it is possible to extract a signal transmitted from each radio station apparatus purely from the received signal of the jth receiving antenna of the base station apparatus. If the signal is multiplied by the reception weight, the signal can be converted into a signal in which the interference component is suppressed.

Here, denoted for convenience the signal "^" is inscribed on the r _j "^ r _j", which is a signal interference components are suppressed, so to speak by the signal processing in the SISO transmission from MIMO transmission The received signal processing circuit 94-i may perform general received signal processing on the converted signal, and r ^ _j generated by such a procedure. For example, it performs channel estimation for each frequency component based on the training signal and the like of the head area of a received radio packet, performs predetermined signal detection processing such as dividing the channel estimation result in ^ r _j. Further, the accompanying signal processing such as error correction processing is also performed in the received signal processing circuit 94-j. In Non-Patent Document 3 and the like, signal processing for further suppressing the crosstalk component of the signal from each wireless station remaining in this signal processing is proposed because in-phase synthesis processing without null control is adopted. It is of course possible to perform such additional signal processing.

(Example 2, Example 3)
FIG. 10 shows a configuration example of Embodiment 2 and Embodiment 3 of the base station apparatus of the present invention. The configuration example shown here corresponds to the basic configuration of the base station apparatus of the present invention shown in FIG.

  In the base station apparatus of the present invention, the transmission RF circuit 81 and the transmission antenna group 11 of the transmission signal processing unit 13 to which the radio frequency signal is transmitted, and the reception RF circuit 91 and the reception antenna group 21 of the reception signal processing unit 23 are transmitted. Must be close to each other. On the other hand, the transmission signal processing unit 13 and the reception signal processing unit 23 are also physically separated corresponding to the transmission antenna group 11 and the reception antenna group 21 that are physically separated, but each of them handles a baseband signal. Can be separated and collected on the control unit 30 side. However, between the transmission weight multiplication circuit 83 and the addition circuit 82 in the transmission signal processing unit 13 and between the reception weight multiplication circuit 93 and the duplication circuit 92 in the reception signal processing unit 23, the number of wirings depends on the number of antenna elements. Since it becomes enormous, separation between them is not preferable.

  In the second embodiment, in the transmission signal processing unit 13 of the first embodiment shown in FIG. 4, a transmission MAC layer processing circuit 85, a transmission signal processing circuit 84, a transmission weight multiplication circuit 83, an addition circuit 82, and a transmission that handle digital baseband signals. The weight calculation / storage circuit 69 is moved to the control unit 30 side, and only the remaining transmission RF circuit 81 and local oscillator 68 are used as the transmission signal processing unit 35a. Further, in the reception signal processing unit 23 of the first embodiment shown in FIG. 6, a reception MAC layer processing circuit 95, a reception signal processing circuit 94, a reception weight multiplication circuit 93, a duplication circuit 92, a reception weight calculation / processing for handling digital baseband signals. The storage circuit 80 and the interference signal replica generation circuit 87 are moved to the control unit 30 side, and only the remaining reception RF circuit 91 and local oscillator 79 are used as the reception signal processing unit 36a. On the other hand, the extended control unit 34 a includes the moved units and the control unit 30.

FIG. 11 illustrates a configuration example of the transmission signal processing unit 35a and the reception signal processing unit 36a in the second embodiment.
11A, the transmission signal processing unit 35a includes transmission RF circuits 81-1 to 81-K, a local oscillator 68, and an interface unit 97. In FIG. 11 (b), the reception signal processing unit 36 a includes reception RF circuits 91-1 to 91-K, a local oscillator 79, and an interface unit 98.

FIG. 12 illustrates a configuration example of the extension control unit 34a in the second embodiment.
In FIG. 12, the extension control unit 34a includes transmission MAC layer processing circuits 85-1 to 85-N, transmission signal processing circuits 84-1 to 84-N, transmission weight multiplication circuits 83-1 to 83-N, and an addition circuit 82. -1 to 82-K, transmission weight calculation / storage circuit 69, reception MAC layer processing circuits 95-1 to 95-N, reception signal processing circuits 94-1 to 94-N, reception weight multiplication circuits 93-1 to 93- N, duplication circuits 92-1 to 92-K, a reception weight calculation / storage circuit 80, an interference signal replica generation circuit 87, an interface unit 99a, and a control unit 30.

  The interface unit 99a of the expansion control unit 34a and the interface unit 97 of the transmission signal processing unit 35a are connected, and the transmission signal processing unit is added from the adders 82-1 to 82-K of the expansion control unit 34a via the interface units 99a and 97. The transmission signals are aggregated and transferred to the transmission RF circuits 81-1 to 81-K of 35a. Also, downlink channel information is aggregated from the transmission RF circuits 81-1 to 81-K of the transmission signal processing unit 35a to the transmission weight calculation / storage circuit 69 of the expansion control unit 34a via the interface units 97 and 99a. Forwarded.

  The interface unit 99a of the expansion control unit 34a and the interface unit 98 of the reception signal processing unit 36a are connected, and the expansion control is performed from the reception RF circuits 91-1 to 91-K of the reception signal processing unit 36a via the interface units 98 and 99a. The received signals are aggregated and transferred to the replica circuits 92-1 to 92-K of the unit 34a. Also, uplink channel information is aggregated from the reception RF circuits 91-1 to 91-K of the reception signal processing unit 36a to the reception weight calculation / storage circuit 80 of the expansion control unit 34a via the interface units 98 and 99a. Further, the loopback channel information is aggregated and transferred from the reception RF circuits 91-1 to 91-K of the reception signal processing unit 36a to the interference signal replica generation circuit 87 of the expansion control unit 34a. In addition, a transmission signal for canceling the loopback interference signal is transferred from the adders 82-1 to 82-K to the interference signal replica generation circuit 87 via the interface unit 99a.

  The control unit 30 of the expansion control unit 34a in FIG. 12 is basically equivalent to the control unit 30 in FIG. For example, in FIG. 2 (a), the control unit 30, the transmission signal processing unit 13 and the reception signal processing unit 23 are mutually provided with an interface unit for terminating signals exchanged with each other. As shown in the figure, such an interface unit can be omitted when it is put together in the extended control unit 34a, and is functionally the same except for the presence or absence of the interface unit.

In the third embodiment, in the transmission signal processing unit 13 of the first embodiment shown in FIG. 4, as shown in FIG. 13, only the transmission MAC layer processing circuit 85 is moved to the control unit 30 side to be a transmission signal processing unit 35b. . In the received signal processing unit 23 of the first embodiment shown in FIG. 6, as shown in FIG. 14, only the received MAC layer processing circuit 95 is moved to the control unit 30 side to be a received signal processing unit 35b.
As shown in FIG. 15, the extension control unit 34b includes a transmission MAC layer processing circuit 85, a reception MAC layer processing circuit 95, an interface unit 99b, and a control unit 30.

Example 4
In the first to third embodiments described above, the case where the same frequency channel is used in the uplink and the downlink has been described, but the base station apparatus of the present invention is also used in the FDD using different frequency channels in the uplink and the downlink. A configuration in which the transmitting antenna group 11 and the receiving antenna group 21 are physically separated from each other as described above is effective. In particular, the configuration of the present invention is effective when there is a possibility that the low-noise amplifier is saturated when a strong reflected wave is looped back from the transmission side to the reception side.

  In this case, the frequency of the local oscillator 68 of the transmission signal processing unit 13 shown in FIG. 4 and the frequency of the local oscillator 79 of the reception signal processing unit 23 shown in FIG. 6 are different, but the other configurations are the same. Further, the radio station apparatus can cope with the configuration shown in FIG.

(Supplementary items for each example)
Hereinafter, supplementary items according to each embodiment will be described.
In the above description, for the sake of simplicity, k (for example, the k-th subcarrier) representing a frequency component is omitted, and further explanations regarding individual frequency components are also omitted, but the system assumed by the present invention is It is a wideband system, and all signal processing in channel information, transmission / reception weights, transmission signals, reception signals, etc. should be individually defined and processed for each frequency component on the frequency axis. Within each signal processing circuit, for example, signal processing up to the previous stage of IFFT processing on the transmission side (bit string interleaving processing, signal point mapping, signal modulation processing, transmission weight multiplication, etc.) is all performed for each frequency component. Similarly, FFT processing Kono signal processing (reception weight multiplication, signal detection processing, signal demapping, deinterleaving processing, etc.) on the receiving side is also performed for each frequency component. In terms of circuit configuration, individual circuits may be provided for each frequency component, and since the same processing is performed, processing is sequentially performed serially for each frequency component, and the circuit is shared by frequency components. It is also possible to do. Further, in the middle, a plurality of circuits may be prepared, frequency components may be appropriately divided, and parallel processing may be serially performed by the plurality of circuits. These are common to all embodiments.

  Moreover, in the radio station apparatus corresponding to the base station apparatus of the present invention, the configuration including one element for each of the transmission antenna and the reception antenna has been described. In this case, for example, when forming a transmission weight from the base station side, signal separation between antenna elements of a signal addressed to a certain radio station is unnecessary, and a transmission weight generation method such as a block diagonalization method is used. If signal separation between different wireless stations is possible, signal separation within the same wireless station can be dealt with by signal processing on the wireless station side.

  In addition, various processes for normal data communication and channel information feedback (including acquisition of loopback channel information from the transmitting antenna group to the receiving antenna group) are basically performed independently. Judgment for performing these processes, instructions for starting the processes, and overall control are under the control of the control section, giving instructions to the transmission signal processing section and the reception signal processing section as necessary, and starting the processing. Also performs timing management. In the above description, not all signal lines for instruction are explicitly shown. However, necessary signal lines including timing, clock, etc. are present in individual circuits from each interface unit. And

  Furthermore, although feedback of channel information is performed at a timing (for example, before the start of service operation) different from normal data communication in the large-scale antenna systems described in Non-Patent Documents 1 to 4, If the radio station transmits a training signal for channel estimation without spatial multiplexing in accordance with the instructions described in the control information exchanged between the station apparatuses, the transmission signal processing unit and the reception signal processing unit are used using the training signal. It is also possible to acquire channel information at. At this time, in order to acquire downlink channel information, the radio station side transmits a training signal from the normal reception antenna side, not the normal transmission antenna, but the channel information feedback as well. .

DESCRIPTION OF SYMBOLS 11 Transmission antenna group 12 Each antenna element of a transmission antenna group 13 Transmission signal processing part 14 Arrow which shows the maximum directivity gain direction of each element of a transmission antenna group 15 Transmission side analog signal transmission signal line 16 Transmission side digital signal transmission signal line 18 Antenna element of radio station apparatus 21 Reception antenna group 22 Each antenna element of reception antenna group 23 Received signal processing section 24 Arrow indicating maximum directivity gain direction of each element of reception antenna group 25 Reception side analog signal transmission signal line 26 Reception side Digital signal transmission signal line 30 Control unit 31 Network side optical line 34 Extension control unit 35 Transmission signal processing unit 36 Reception signal processing unit 52 Switch 53 Low noise amplifier 54 Mixer 55 Filter 56 A / D converter 57 FFT circuit 58 Channel estimation circuit 61 IFFT / GI assignment circuit 62 Memo 63 D / A converter 64 Mixer 65 Filter 66 High power amplifier 67 Switch 68 Local oscillator 69 Transmission weight calculation / storage circuit 70 Reception RF circuit 71 Low noise amplifier 72 Mixer 73 Filter 74 A / D converter 75 FFT circuit 77 Channel estimation circuit 79 Local Oscillator 80 Reception Weight Calculation / Storage Circuit 81 Transmission RF Circuit 82 Addition Circuit 83 Transmission Weight Multiplication Circuit 84 Transmission Signal Processing Circuit 85 Transmission MAC Layer Processing Circuit 86 Interface Unit 87 Interference Signal Replica Generation Circuit 91 Reception RF Circuit 92 Replication Circuit 93 Reception weight multiplication circuit 94 Reception signal processing circuit 95 Reception MAC layer processing circuit 96 Interface unit 97 Interface unit 98 Interface unit

Claims (2)

In a base station apparatus comprising a plurality of transmitting antenna elements and a plurality of receiving antenna elements for a plurality of radio station apparatuses, and performing spatial multiplexing transmission with a plurality of radio station apparatuses on the same frequency channel,
A transmission antenna group configured by arranging the plurality of transmission antenna elements on a plane; and
A transmission signal processing unit for generating a radio frequency transmission analog signal transmitted from the transmission antenna group;
A receiving antenna group configured by arranging the plurality of receiving antenna elements on a plane;
A reception signal processing unit that performs signal processing including at least frequency conversion on a radio frequency reception analog signal received by the reception antenna group, and
The transmission signal processing unit and the reception signal processing unit are housed in different casings, and are configured to exchange predetermined information by wired connection,
When the direction of the radio station apparatus is viewed from the reception antenna group, the transmission antenna group is arranged in front of the reception antenna group by a predetermined distance, and each reception antenna element of the reception antenna group and the radio A base station apparatus, wherein the transmitting antenna group is arranged outside a first Fresnel zone formed between the antenna elements of the station apparatus. The base station apparatus according to claim 1,
Means for receiving a training signal transmitted by the radio station apparatus by the receiving antenna element, and acquiring uplink first channel information based on the received signal;
A training signal transmitted from the radio station apparatus is received by the transmitting antenna element, uplink second channel information is acquired based on the received signal, and downlink channel information is acquired from the second channel information. Means to
Means for transmitting a training signal in turn from each element of the transmitting antenna element;
Means for receiving the training signal transmitted from the transmitting antenna element by the receiving antenna element, and acquiring channel information of a loopback link based on the received signal;
During data communication, based on the channel information of the loop back link acquired in advance and a signal transmitted in data communication, a replica of an interference signal that is looped back from the transmitting antenna element and received by the receiving antenna element is estimated. Means to
A signal generated by subtracting the estimated replica of the interference signal from the received signal received by the receiving antenna element, and the signal transmitted by the radio station apparatus using the uplink first channel information based on this signal Received signal processing means for estimating
The same frequency channel is used for the downlink from the base station device toward the radio station device and the uplink from the radio station device toward the base station device, and at the same time with the radio station device. A base station device characterized in that it communicates in both directions.

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