JP5043169B2 - Signal converter, radio signal transmission system, and radio signal reception system - Google Patents

Description

  The present invention relates to a radio signal transmission / reception system and a signal converter used in the system, and more particularly, to the system and signal converter using adaptive array technology as a main part.

Conventionally, in order to make a radio base station that does not support an adaptive array compatible with the adaptive array, it is necessary to replace the baseband unit. FIG. 3 shows the configuration of a radio base station that does not support the conventional adaptive array, and FIG. 4 shows the configuration of the radio base station that supports the conventional adaptive array.
In the case of the baseband unit 300 that performs omnidirectional communication as shown in FIG. 3, a MAC processing unit 301, a signal modulation unit 302, an inverse FFT (Inverse Fast Fourier Transfer) unit 303, a CP addition unit 304, A signal demodulating unit 305, an FFT (Fast Fourier Transfer) unit 306, and a CP (Cyclic Prefix) removing unit 307 are included. This is a functional unit that functions only when the signal modulation unit 302, the inverse FFT unit 303, and the CP addition unit 304 transmit signals, and only when the signal demodulation unit 305, the FFT unit 306, and the CP removal unit 307 receive signals. It is a functional part that functions. When the radio base station shown in FIG. 3 is adapted to an adaptive array, the baseband unit 300 needs to be replaced.

  FIG. 4 is a functional configuration diagram of an adaptive array-compatible radio base station that replaces the baseband unit 300 with the baseband unit 400 and includes as many radio units as the number of antennas. In the case of the baseband unit 400, the MAC processing unit 401, the signal modulation unit 402, the inverse FFT units 404 and 406, the CP addition units 405 and 407, the signal modulation unit 412, the FFT units 414 and 416, and the CP removal Parts 415 and 417.

As can be seen from a comparison between FIG. 3 and FIG. 4, in order to cope with an adaptive array, only the number of antennas requires FFT units, CP adding units, inverse FFT units, and CP removing units.
Patent Document 1 discloses a radio base station capable of switching between an adaptive array and omnidirectional communication.

JP 2008-48236 A

  By the way, the replacement of the baseband unit is not so much welcomed because of the installation cost. This is because functional units such as a MAC processing unit, a signal modulation unit, and a signal demodulation unit in the baseband unit need to use a relatively high performance CPU for performing signal processing. Creation is costly. It may be possible to extract a signal output from the signal modulation unit of the original baseband unit, but depending on the baseband unit, it may not be possible if it is a product of another company.

  Therefore, in the present invention, without replacing the baseband unit and without modifying the original baseband unit, a signal for making the radio base station that does not support the adaptive array correspond to the adaptive array. It is an object of the present invention to provide a converter and a transmission / reception system including such a signal converter.

  In order to solve the above problems, a signal converter according to the present invention is a signal converter connected to a plurality of wireless units, and a first interface unit that receives an input of one time axis signal used for wireless transmission; A first conversion unit that converts the time axis signal received by the first interface unit into a frequency axis signal that is a frequency component signal, and generates a plurality of different frequency axis signals by performing a weighting operation on the frequency axis signal Generating means, a second converting means for converting a plurality of frequency axis signals generated by the generating means into a plurality of time axis signals, and a plurality of time axis signals output from the second converting means. And a second interface unit for outputting to different wireless units.

  With the configuration as described above, the time base signal used for one radio transmission by the signal converter is converted back to the frequency axis signal and weighted to generate time base signals corresponding to the number of radio units. Is connected so that the output of the baseband unit is input, the radio base station can perform adaptive array transmission. In addition, in this case, since the baseband unit is not exchanged and the baseband unit does not need to be changed, the above-described problems can be solved drastically.

  The signal converter according to the present invention includes a second interface unit that receives input of a plurality of time axis signals, and a plurality of frequency axes that are a plurality of time axis signals received by the second interface unit as signals of frequency components. A first converting means for converting into a signal; a combining means for combining a plurality of converted frequency axis signals to generate one frequency axis signal; and one frequency axis signal generated by the combining means for one time. A second conversion means for converting into an axis signal and a first interface unit for outputting the one time axis signal are provided.

  With the above-described configuration, even when a plurality of radio units receive time axis signals, they can be combined into an array to generate one time axis signal and output it to the original baseband unit. Therefore, adaptive array reception can be performed by providing a signal converter on a line connecting the baseband unit and the wireless unit without exchanging the baseband unit.

It is the functional block diagram which showed the system configuration | structure of the wireless base station which concerns on embodiment. It is a figure which shows the usage pattern of the signal converter which concerns on embodiment. It is the functional block diagram which showed the function structure of the wireless base station which does not respond | correspond to the conventional adaptive array. It is the functional block diagram which showed the function structure of the wireless base station corresponding to the conventional adaptive array.

Hereinafter, a signal converter according to an embodiment of the present invention will be described with reference to the drawings.
<Embodiment>
<Configuration>
FIG. 1 is a configuration diagram showing a system configuration of a radio base station.
The radio base station includes a baseband unit (BBU (Base Band Unit)) 300, a signal converter 100, and radio units (RRU (Remote Radio Unit)) 420 and 421.

The baseband unit 300 and the wireless unit 420 are originally installed in a wireless base station that does not support the adaptive array, and further convert the signal to a configuration on a communication path connecting the baseband unit 300 and the wireless unit 420. It is a feature of the present invention that the device 100 is inserted.
<Baseband unit 300>
The baseband unit 300 includes a MAC processing unit 301, a signal modulation unit 302, an inverse FFT unit 303, a CP addition unit 304, a signal modulation unit 305, an FFT unit 306, and a signal demodulation unit 307. Is done.

The MAC processing unit 301 analyzes and analyzes the function of outputting data (actual data, etc.) constituting the signal to be transmitted to the signal modulation unit 302 and the demodulated signal input from the signal demodulation unit 305 It has a function of outputting a signal to an upper layer (not shown).
<Sender>
The signal modulation unit 302 has a function of modulating the signal input from the MAC processing unit 301 and outputting the frequency axis signal to the inverse FFT unit 303.

The inverse FFT unit 303 has a function of performing an inverse FFT on the frequency axis signal input from the signal modulation unit 302 to convert the frequency axis signal into a time axis signal and outputting the time axis signal to the CP adding unit 304.
The CP adding unit 304 has a function of adding a CP to the time axis signal input from the inverse FFT unit 303 and outputting it to the outside of the baseband unit 300. CP and Cyclic Prefix are used to make the receiving side recognize the beginning and end of the actual data of the time axis signal to be transmitted. CP addition is a copy of a predetermined number of bits of the last part of the time axis signal. Is added to the beginning of the time axis signal. The CP is sometimes called a guard interval.

<Receiving side>
The CP removal unit 307 has a function of removing the CP added to the time axis signal input from the outside of the baseband unit 300 and outputting the time axis signal from which the CP has been removed to the FFT unit 306.
The FFT unit 306 has a function of performing FFT on the time axis signal from which the CP has been removed input from the CP removing unit 307, converting it to a frequency axis signal, and outputting it to the signal demodulating unit 305.

The signal demodulation unit 305 has a function of demodulating the frequency axis signal input from the FFT unit 306 and outputting a demodulated signal obtained by the demodulation to the MAC processing unit 301.
<Signal converter 100>
The signal converter 100 includes a CP removal unit 101, an FFT unit 102, a weight calculation unit 103, an inverse FFT unit 104, a CP addition unit 105, an inverse FFT unit 106, a CP addition unit 107, and a CP addition unit. 111, an inverse FFT unit 112, an array processing unit 113, an FFT unit 114, a CP removal unit 115, an FFT unit 116, and a CP removal unit 117.

  In the signal converter 100, the time axis signal output from the baseband unit 300 is received by the first interface unit 118 and input to the CP removal unit 101. Further, the time axis signal to which the CP is added by the CP adding unit 111 is output from the first interface unit 118 to the baseband unit 300. The first interface unit 118 includes one port for transmitting or receiving a time-axis signal that has not been subjected to adaptive array processing.

  In the signal converter 100, the time axis signals output from the wireless units 420 and 421 are received by the second interface unit 119 and input to the CP removing units 115 and 117. Further, the time axis signal to which the CP is added by the CP adding units 105 and 107 is output from the first interface unit 118 to the wireless units 420 and 421, respectively. The second interface unit 119 includes two ports for transmitting or receiving time-axis signals that have been subjected to adaptive array processing.

  The first interface unit 118 and the second interface unit 119 are ports according to the standard of the communication path to which the baseband unit 300 and the wireless unit were originally connected. For example, when the baseband unit 300 and the wireless unit are connected by an optical fiber cable according to the standard of OBSAI (Open Basestation Standard Initiative), the first interface unit 118 and the second interface unit 119 also comply with the OBSAI standard. For example, when the baseband unit 300 and the wireless unit are connected by an optical fiber cable according to the CPRI (Common Public Radio Interface) standard, the first interface unit 118 and the second interface unit 119 are also connected to the CPRI. It becomes a port according to the standard.

<Sender>
The CP removal unit 101 removes the CP added to the time axis signal input from the baseband unit 300 via the first interface unit 118, and outputs the time axis signal from which the CP has been removed to the FFT unit 102. Has the function of
The FFT unit 102 has a function of performing FFT on the time axis signal from which the CP has been removed from the CP removing unit 101 and converting it to a frequency axis signal to output to the weight calculating unit 103.

  The weight calculation unit 103 has a function of multiplying the weight signals calculated by the array processing unit 113 to perform a weighting calculation and outputting frequency axis signals for the number of antennas. Note that the weighting calculation is performed conventionally, and details thereof are omitted here. The weight calculation unit 103 outputs the frequency axis signal for the radio unit 420 to the inverse FFT unit 104 and the frequency axis signal for the radio unit 421 to the inverse FFT unit 106.

The inverse FFT unit 104 has a function of performing an inverse FFT on the frequency axis signal input from the weight calculation unit 103 to convert it to a time axis signal and outputting it to the CP adding unit 105.
The CP adding unit 105 has a function of adding a CP to the time axis signal input from the inverse FFT unit 104 and outputting the CP to the wireless unit 420 via the second interface unit 119.
The inverse FFT unit 106 has a function of performing an inverse FFT on the frequency axis signal input from the weight calculation unit 103 to convert it to a time axis signal and outputting the time axis signal to the CP adding unit 107.

The CP adding unit 107 has a function of adding a CP to the time axis signal input from the inverse FFT unit 104 and outputting it to the wireless unit 421 via the second interface unit 119.
<Receiving side>
The CP removing unit 117 removes the CP added to the time axis signal input from the wireless unit 421 via the second interface unit 119, and outputs the time axis signal from which the CP has been removed to the FFT unit 116. Have

The FFT unit 116 has a function of performing FFT on the time axis signal from which the CP has been removed input from the CP removing unit 117, converting it to a frequency axis signal, and outputting it to the array processing unit 113.
The CP removing unit 115 removes the CP added to the time axis signal input from the wireless unit 420 via the second interface unit 119, and outputs the time axis signal from which the CP is removed to the FFT unit 114. Have

The FFT unit 114 has a function of multiplying the time axis signal from which the CP has been removed from the CP removing unit 115 by FFT, converting it to a frequency axis signal, and outputting it to the array processing unit 113.
The array processing unit 113 has a function of performing array synthesis processing on a plurality of frequency axis signals input from the FFT unit 114 and the FFT unit 116, returning to a normal signal, and outputting one frequency axis signal to the inverse FFT unit 112. Have. The array processing unit 113 also has a function of notifying the weight calculation unit 103 of a weight signal to be multiplied at the time of output. Note that the array synthesis processing has been performed conventionally, and therefore details thereof are omitted here.

The inverse FFT unit 112 has a function of performing an inverse FFT on the frequency axis signal input from the array processing unit 113 to convert the frequency axis signal into a time axis signal and outputting the time axis signal to the CP adding unit 111.
The CP adding unit 111 has a function of adding a CP to the time axis signal input from the inverse FFT unit 112 and outputting the CP to the baseband unit 300 via the first interface unit 118.
<Wireless unit 420>
The wireless unit 420 has a function of analog-converting the time axis signal to which the CP is added by the CP adding unit 105 input from the signal converter 100 and wirelessly transmitting the signal via the antenna 430. The wireless unit 420 also has a function of digitally converting a time axis signal wirelessly received via the antenna 430 and outputting the digital signal to the signal converter 100.
<Wireless unit 421>
The wireless unit 421 has a function of analog-converting the time axis signal to which the CP is added by the CP adding unit 107 input from the signal converter 100 and wirelessly transmitting the signal via the antenna 431. The wireless unit 421 also has a function of digitally converting a time axis signal wirelessly received via the antenna 431 and outputting the digital signal to the signal converter 100.

In addition, about the radio | wireless unit and an antenna, in addition to what was provided in the original base station, it is necessary to add only the required number.
<Usage pattern>
FIG. 2 shows an actual usage pattern of the radio base station described above, that is, an example of arrangement of each unit.

  The antennas 430 and 431 are installed on the roof of a building, for example, and the radio units 420 and 421 are also arranged in association therewith. Two optical fiber cables are extended from the wireless unit 420 to the signal converter 100 in the operator room 200 together with transmission and reception. Two optical fiber cables are extended from the wireless unit 421 to the signal converter 100 in the operator room 200 together with transmission and reception. The signal converter 100 is connected to the baseband unit 300 with two optical fiber cables.

The operator room 200 may be in a building where the wireless units 420 and 421 are arranged.
As described above, in a radio base station that does not support the conventional adaptive array, a signal converter is inserted between the baseband unit and the optical fiber cable connecting the radio unit, and the required number The wireless base station can be adapted to the adaptive array simply by preparing the antenna and the wireless unit.

In the baseband unit, the cost is the MAC processing unit, the signal modulation unit, and the signal demodulation unit, and these functional units are the CP removal unit 101, the FFT unit 102, the CP addition unit 111, and the inverse FFT unit 112. It costs more than preparing each functional unit.
Accordingly, since the signal converter is not provided with a MAC processing unit, a signal demodulating unit, or a signal modulating unit, even when a radio base station that does not support the adaptive array is made to support the adaptive array, the baseband It is possible to provide a radio base station corresponding to an adaptive array at a lower cost than replacing a unit.
<Supplement>
In the above embodiment, the method of implementing the present invention has been described, but it is needless to say that the embodiment of the present invention is not limited to this. Hereinafter, various modified examples included in the concept of the present invention other than the above embodiment will be described.
(1) In the above embodiment, the case of two antennas (antennas 430 and 431) has been described. However, the number of antennas is not limited to two, and may be plural, for example, four. . In this case, the signal converter needs to include inverse FFT units, CP addition units, FFT units, and CP removal units as many as the number of antennas, and the weight calculation unit and the array processing unit match the number of antennas. It is necessary to perform weighting operation and array composition operation.
(2) In the above embodiment, the radio base station is described as having one antenna at a stage that does not support the adaptive array, and the baseband unit 300 has a configuration of one input and one output. It was.

However, when the wireless base station is a WiMAX base station, the WiMAX base station is capable of MIMO, and thus has a configuration of two antennas. In this case, the baseband unit has two inputs and two inputs. The output configuration will be taken.
Therefore, in such a case, the first interface unit 118 has a port configuration of two inputs and two outputs in accordance with the number of inputs and outputs of the baseband unit.
(3) The time axis signal in the above embodiment may be any signal as long as it includes information on the time axis, and may be a modulation signal including time axis information.

  The signal converter according to the present invention is useful as a device that can make a radio base station that does not support the adaptive array compatible with the adaptive array without exchanging the baseband unit.

100 Signal converter 101, 115, 117, 307 CP removal unit 102, 114, 116, 306 FFT unit 103 Weight calculation unit 104, 106, 112, 303 Inverse FFT unit 105, 107, 111, 304 CP addition unit 113 Array calculation Part 118 first interface part 119 second interface part 300 baseband unit (BBU)
301 MAC processor 302 Signal modulator 305 Signal demodulator 420, 421 Radio unit (RRU)
430, 431 antenna

Claims (2)

Used in a radio apparatus including a signal processing unit that generates a signal to be transmitted to a communication terminal, and a first radio unit that transmits a signal generated by the signal processing unit via a first antenna. A signal converter inserted in a signal path between a radio unit and the signal processing unit,
A second antenna;
A second radio unit for transmitting a signal via the second antenna;
An input unit for receiving an input of the signal generated by the signal processing unit;
A first signal converter that converts a signal input to the input unit into a frequency axis signal;
A generating unit that performs a weighting operation on the frequency axis signal obtained by conversion in the first signal converting unit and generates a plurality of different frequency axis signals;
A second signal converter that converts each of the plurality of frequency axis signals generated by the generator into a time axis signal;
An output unit that outputs a part of the time axis signal among the plurality of time axis signals obtained by the conversion by the second signal conversion unit to the first radio unit;
The second radio unit transmits time axis signals other than those output to the first radio unit among a plurality of time axis signals obtained by the conversion by the second signal conversion unit. Signal converter. The wireless device includes: a first wireless unit that receives a signal via a first antenna; and a signal processing unit that performs a predetermined process on a signal received by the first wireless unit. 1 is a signal converter inserted in a signal path between a radio unit and the signal processing unit ,
A second antenna;
A second radio unit for receiving a signal via the second antenna;
An input unit that receives input of the first signal received by the first radio unit and the second signal received by the second radio unit ;
A first signal converter that converts the first signal and the second signal input to the input unit into a frequency axis signal;
A signal synthesizer for synthesizing a plurality of frequency axis signals obtained by conversion by the first signal converter ;
A second signal conversion unit that converts a frequency axis signal obtained by synthesis in the signal synthesis unit into a time axis signal;
An output unit for outputting a time axis signal obtained by conversion by the second signal conversion unit to the signal processing unit ;
A signal converter comprising:

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