JP2010130082A - Communication device and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology, capable of suppressing the interruption of communication with an external communication device and performing a loop-back test, in a communication device which performs communication by a TDD system. <P>SOLUTION: A transmission/reception part 19 transmits and receives signals to/from a terminal 2 by the TDD (time division duplexing) system, in which a transmission period and a reception period appear repeatedly. A digital signal generating/analyzing section 11 performs loop-back test for determining whether the loop-back test data output to the transmission/reception part 19 and loop-back test data fed back from the transmitting/receiving section 19 match. The digital signal generating/analyzing section 11 performs loop-back test, only during the transmission period or only during the reception period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a communication apparatus and a communication method for transmitting / receiving a signal to / from an external communication apparatus by a TDD (Time Division Duplexing) method in which a transmission period and a reception period repeatedly appear.

  In the communication device, a loopback test may be performed in order to perform self-diagnosis as to whether signal transmission / reception is performed correctly. In this loopback test, it is determined whether the test information output to the transmission / reception unit that transmits / receives a signal to / from the external communication device matches the test information fed back from the transmission / reception unit. Patent Document 1 discloses a loopback test in a communication apparatus that performs communication using the TDD method. Patent Document 2 describes a base station apparatus that includes two base stations and performs a loopback test so as not to stop communication.

JP-A-6-152561 Japanese Patent No. 2004-282500

  In the conventional TDD communication apparatus, the loopback test is performed after the communication line with the external communication apparatus is disconnected. As a result, the external communication device cannot completely transmit and receive signals to and from the communication device for a long period of time, and there is a problem that communication quality with the communication device deteriorates.

  The present invention has been made in view of the above-described problems, and in a communication apparatus that performs communication by the TDD method, it is possible to perform a loopback test while suppressing interruption of communication with an external communication apparatus. The purpose is to provide.

  In order to solve the above-described problem, a communication device according to the present invention outputs a signal to and from the transmission / reception unit by a TDD (Time Division Duplexing) method in which a transmission period and a reception period repeatedly appear and a signal transmitted to and received from the external communication device. And a control unit that performs a loopback test for determining whether at least a part of the test information returned from the transmission / reception unit matches, the control unit is only in the transmission period, or The loopback test is performed only during the reception period.

  Further, in one aspect of the communication apparatus according to the present invention, the control unit performs the loopback test using predetermined subcarriers included in a plurality of subcarriers only in the reception period, and the external communication apparatus Control information for controlling the external communication device to transmit signals using the plurality of subcarriers other than the predetermined subcarrier in the reception period in which the loopback test is performed, Before the test, the data is transmitted to the external communication device through the transmission / reception unit.

  Further, in one aspect of the communication apparatus according to the present invention, the control unit performs the loopback test in the plurality of reception periods, and the loop is performed during the plurality of reception periods in which the loopback test is performed. The predetermined subcarrier is changed for each reception period in which the loopback test is performed so that all the plurality of subcarriers are allocated to the predetermined subcarrier used in the back test.

  In one aspect of the communication apparatus according to the present invention, the communication apparatus is a base station in WiMAX (Worldwide Interoperability for Microwave Access).

  The communication method according to the present invention includes (a) a step of transmitting / receiving a signal to / from an external communication device via a transmission / reception unit by a TDD (Time Division Duplexing) method in which a transmission period and a reception period repeatedly appear; and (b) A step of performing a loopback test for determining whether the test information output to the transmission / reception unit matches at least a part of the test information fed back from the transmission / reception unit, and the step (b) includes the transmission period. Or only during the reception period.

  In the communication method according to the aspect of the invention, in the step (b), only in the reception period of the step (a), predetermined subcarriers included in a plurality of subcarriers are used, and the loopback is performed. A test is performed, and (c) the external communication device transmits a signal in the reception period in which the loopback test is performed using the plurality of subcarriers other than the predetermined subcarrier. Further includes a step of transmitting control information for controlling the external communication device through the transmission / reception unit before the loopback test.

  According to the present invention, the communication apparatus performs the loopback test only in the transmission period appearing in the TDD communication or in the reception period appearing in the TDD communication. As a result, the communication device can perform TDD communication with the external communication device before and after the period during which the loopback test is performed. Therefore, the communication device can perform the loopback test in a state where interruption of communication with the external communication device is suppressed as much as possible. As a result, it is possible to suppress deterioration in communication quality of the external communication device.

  According to one embodiment of the present invention, in the reception period performed in the loopback test, the communication device transmits data superimposed on a plurality of subcarriers other than the predetermined subcarrier used in the loopback test. Can be received from. Therefore, the loopback test can be performed without reducing the throughput in transmission of the communication device and almost without reducing the throughput in transmission of the external communication device.

  According to one embodiment of the present invention, a loopback test can be performed on all subcarriers used in an external communication device. As a result, it is possible to confirm whether the transmission / reception unit correctly transmits / receives signals on all subcarriers.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a radio communication system according to Embodiment 1 of the present invention. The wireless communication system includes a base station 1 and a plurality of terminals 2. For the sake of simplicity, FIG. 1 shows one terminal among the plurality of terminals 2. A base station 1 that is a communication apparatus according to the present embodiment is a base station that conforms to mobile WiMAX defined in IEEE 802.16e. The base station 1 transmits / receives a radio signal to / from the terminal 2 that is an external communication device by the TDD scheme. Thereby, the base station 1 performs wireless communication with the terminal 2.

  FIG. 2 is a diagram showing the configuration of the base station 1 according to the first embodiment. As shown in FIG. 2, the base station 1 includes a digital unit 4, an RF unit 5, and an antenna 6. The digital unit 4 includes a digital signal generation / analysis unit 11, a modulation unit 12, and a demodulation unit 13. The RF unit 5 includes a DAC (Digital-to-Analog Converter) 14, a mixer 15, a transmission / reception switch unit 16, a mixer 17, and an ADC (Analog-to-Digital Converter) 18.

  The digital signal generation / analysis unit 11 of the digital unit 4 generates transmission data and outputs the transmission data to the modulation unit 12. For the digital signal generation / analysis unit 11, for example, a DSP (Digital Signal Processor) is used. The modulation unit 12 modulates the carrier based on the transmission data from the digital signal generation / analysis unit 11. The demodulator 13 demodulates the digital signal from the ADC 18 to obtain received data, and outputs the received data to the digital signal generator / analyzer 11. For example, an FPGA (Field Programmable Gate Array) is used for the modulation unit 12 and the demodulation unit 13.

  The DAC 14 of the RF unit 5 converts the digital signal on which the transmission data is superimposed in the modulation unit 12 into an analog signal. The mixer 15 converts the frequency of the analog signal from the DAC 14 into a frequency used for communication with the terminal 2. A space is provided between the terminals B and C of the transmission / reception switch unit 16, and the transmission / reception switch unit 16 selectively connects either the terminal B or C and the terminal A. When the transmission / reception switch unit 16 connects the terminal A and the terminal B, a signal from the mixer 15 is transmitted to the terminal 2 via the antenna 6. Thereby, the base station 1 transmits a signal to the terminal 2 (downlink).

  On the other hand, when the transmission / reception switch unit 16 connects the terminal A and the terminal C, the signal from the terminal 2 received by the antenna 6 is input to the mixer 17. The mixer 17 converts the frequency of the input signal into a frequency that can be processed by the digital signal generation / analysis unit 11. The ADC 18 of the RF unit 5 converts the analog signal from the mixer 17 into a digital signal. Thereby, the base station 1 receives the signal from the terminal 2 (uplink).

  The transmission / reception switch unit 16 alternately connects the terminal A and the terminal B and connects the terminal A and the terminal C under the control of the digital signal generation / analysis unit 11. FIG. 3 is a diagram illustrating a state in which the base station 1 transmits and receives signals to and from the terminal 2 by radio. The horizontal axis in the figure indicates time. The upper side of the line dividing the upper and lower sides in the figure shows the operation of the base station 1 transmitting a signal from the antenna 6 to the terminal 2, and the lower side of the line shows the base station 1 and the signal from the terminal 2 via the antenna 6. Indicates the operation to receive. As shown in the figure, the base station 1 transmits / receives a signal to / from the terminal 2 by a TDD scheme in which transmission of a signal to the terminal 2 and reception of a signal from the terminal 2 appear alternately.

  In FIG. 3, a transmission period 21 in which the base station 1 transmits data to the terminal 2 and a reception period 24 in which the base station 1 receives data from the terminal 2 are shown. The transmission / reception unit 19 including the modulation unit 12, demodulation unit 13, DAC 14, mixer 15, transmission / reception switch unit 16, mixer 17, and ADC 18 transmits the signal to the terminal 2 by the TDD method in which the transmission period 21 and the reception period 24 appear repeatedly. Send and receive.

  Here, in WiMAX, a header including a preamble, a DL-MAP message, and a UL-MAP message must be transmitted from the base station 1 to the terminal 2. In WiMAX, one frame includes a downlink subframe transmitted from the base station 1 to the terminal 2 and an uplink subframe transmitted from the terminal 2 to the base station 1. The DL-MAP message is information indicating the position and size of the burst area in the downlink subframe, that is, radio resource allocation information in the downlink subframe. The UL-MAP message is information indicating the position and size of the burst area in the uplink subframe, that is, radio resource allocation information in the uplink subframe.

  The base station 1 transmits a header to the terminal 2 in the header transmission period 22 of the transmission period 21, and transmits data other than the header to the terminal 2 in the data transmission period 23 of the transmission period 21. In the present embodiment, the transmission power of the header transmitted by the transmission / reception unit 19 in the header transmission period 22 is set to the same value as the transmission power of the data transmitted by the transmission / reception unit 19 in the data transmission period 23. As shown in the figure, when the base station 1 switches from transmission to reception, a TTG (Transmit Transition Gap) 25 that is a guard time is provided, and when the base station 1 switches from reception to transmission, the guard time is set. A certain RTG (Receive Transition Gap) 26 is provided.

  The base station 1 according to the present embodiment performs a loopback test of the transmission / reception unit 19 in order to perform self-diagnosis as to whether the transmission / reception unit 19 correctly transmits and receives signals. The loopback test according to the present embodiment will be described below.

  First, in FIG. 2, the digital signal generation / analysis unit 11 connects the terminal A and the terminal C in the transmission / reception switch unit 16 of the transmission / reception unit 19. Then, the digital signal generation / analysis unit 11 generates pseudo data (hereinafter also referred to as loopback test data) that is information for loopback testing, and outputs the pseudo data to the modulation unit 12. The modulation unit 12 modulates the carrier based on the loopback test data. In the modulation unit 12, a signal on which loopback test data is superimposed (hereinafter also referred to as a loopback test signal) is output to the DAC 14. The loopback test signal output to the DAC 14 is output to the terminal B via the mixer 15.

  Then, since the terminal B of the transmission / reception switch unit 16 is not connected to either the terminal A or the terminal C, the loopback test signal output to the terminal B is input from the terminal B to the terminal C through the space. The loopback test signal input to the terminal C is input to the demodulation unit 13 via the mixer 17 and the ADC 18. The demodulator 13 demodulates the loopback test signal to obtain loopback test data, and outputs the loopback test data to the digital signal generator / analyzer 11.

  Whether the digital signal generation / analysis unit 11, which is a control unit according to the present embodiment, matches the loopback test data that is the test information output to the transmission / reception unit 19 and the loopback test data fed back from the transmission / reception unit 19. Determine. When the digital signal generation / analysis unit 11 determines that the data match, the base station 1 determines that the transmission / reception unit 19 is in a normal state. On the other hand, when the digital signal generation / analysis unit 11 determines that the data do not match, the base station 1 determines that there is some abnormality in the transmission / reception unit 19. In determining that the data do not match, it may be determined by confirming that the returned loopback test data matches the entire loopback test data that has been output, or output. The determination may be made by confirming that a part of the loopback test and a part corresponding to the part of the returned loopback test data match. Further, if all of the output loopback test data does not match the returned loopback test data, it may be determined that there is an abnormality, and the output loopback test data and the returned loopback test data The degree of abnormality may be evaluated according to the probability of matching in whole or in part, and it may be determined that there is an abnormality when there is no matching over a predetermined probability.

  A part of the radio wave radiated from the terminal B to the space is radiated from the antenna 6 to the outside of the base station 1 as a leakage signal. This leakage signal is a jamming radio wave for the terminal 2. In order to prevent the terminal 2 from receiving this leaked signal, the output level of the mixer 15 is determined so that the power of the leaked signal is sufficiently weak.

  FIG. 4 is a diagram illustrating the operation of the base station 1 before and after the loopback test. The digital signal generation / analysis unit 11 according to the present embodiment performs a loopback test only in the transmission period 21. As shown in the figure, in this embodiment, the loopback test is performed during the entire data transmission period 23 of one transmission period 21 between a certain reception period 24 and the next reception period 24. To do. Hereinafter, a period during which the loopback test is performed may be referred to as a test period 27. In FIG. 4, in order to show that the power of the leakage signal in the test period 27 is weaker than the power of the signal in the normal transmission period 21, the upper rectangle indicating the header and the leakage signal are divided on the upper side in the upper and lower parts of the figure. A step is provided between the upper quadrangle and the upper quadrangle.

  According to the base station 1 according to the present embodiment as described above, the loopback test is performed only in the transmission period 21. Thereby, the base station 1 can perform TDD communication with the terminal 2 in the reception period 24 before and after the test period 27 without disconnecting the communication line with the terminal 2. Therefore, the base station 1 can perform a loopback test in a state where interruption of communication with the terminal 2 is suppressed as much as possible. As a result, deterioration of the communication quality of the terminal 2 can be suppressed.

  In the present embodiment, the test period 27 is described as being the entire period of the data transmission period 23 of one transmission period 21. However, the test period 27 is not limited to this, and may be an arbitrary period within one transmission period 21 or may extend over a plurality of transmission periods 21.

<Embodiment 2>
In the wireless communication system according to the first embodiment, the digital signal generation / analysis unit 11 performed a loopback test only in the data transmission period 23. Therefore, as illustrated in FIG. 4, the base station 1 according to Embodiment 1 transmits a header with normal power in the header transmission period 22, but substantially transmits a signal in the test period 27 immediately thereafter. Stop. Therefore, the terminal 2 does not receive a signal immediately after receiving the header.

  If the terminal 2 is performing open loop power control and does not receive a signal immediately after receiving the header, the AGC (Automatic Gain Control) circuit of the terminal 2 converts the weak power of the noise signal to a normal value. Amplification is performed with an amplification factor having a larger value, and control is performed to amplify to a power level usable for the terminal 2. This amplification factor having a large value is maintained until the transmission period 21 immediately after the test period 27. In this state, when the terminal 2 receives a signal from the base station 1 in the transmission period 21 immediately after the test period 27, the signal has normal power in the transmission period 21, so the AGC of the terminal 2 is Then, control is performed to return the amplification factor to the original normal value. Here, if this control is not in time for the timing at which the terminal 2 should receive a signal after the test period 27, there is a problem that the terminal 2 cannot receive a signal from the base station 1.

  In the radio communication system according to Embodiment 1, the base station 1 performs an operation of receiving a signal from the terminal 2 in the reception period 24 immediately after the test period 27. Therefore, the base station 1 needs to perform a loopback test determination process and a signal reception process from the terminal 2 in a short time, and an expensive high-performance arithmetic processing unit must be provided in the base station 1. The problem arises. Hereinafter, the radio communication system according to the present embodiment capable of solving these problems will be described focusing on differences from the radio communication system according to the first embodiment. The configuration of base station 1 according to Embodiment 2 is the same as the configuration of base station 1 according to Embodiment 1.

  FIG. 5 is a diagram illustrating operations of the base station 1 according to the present embodiment before and after the loopback test. As shown in the figure, unlike the digital signal generation / analysis unit 11 according to the first embodiment, the digital signal generation / analysis unit 11 according to the present embodiment performs a loopback test only in the reception period 24. As shown in the figure, in this embodiment, it is assumed that the loopback test is performed during the entire period of one reception period 24 between a certain transmission period 21 and the next transmission period 21.

  According to the base station 1 according to the present embodiment as described above, the loopback test is performed only in the reception period 24. Thereby, the base station 1 can perform TDD communication with the terminal 2 in the transmission period 21 before and after the test period 27 without disconnecting the communication line with the terminal 2. Therefore, the base station 1 can perform a loopback test in a state where interruption of communication with the terminal 2 is suppressed as much as possible. As a result, deterioration of the communication quality of the terminal 2 can be suppressed.

  Moreover, according to the base station 1 which concerns on this Embodiment, unlike Embodiment 1, the terminal 2 receives data immediately after receiving a header. That is, since the terminal 2 does not receive a signal immediately after receiving the header, it is possible to prevent a malfunction from occurring in the AGC operation of the terminal 2. As a result, the terminal 2 can correctly receive the signal from the base station 1 even after the test period 27. Further, according to the base station 1 according to the present embodiment, the transmission period 21 is sandwiched between the reception period 24 and the test period 27. For this reason, the base station 1 does not have to perform the signal reception processing from the terminal 2 and the loopback test determination processing in a short time, so that an expensive high-performance arithmetic processing device is not provided in the base station 1. However, these processes can be performed.

<Embodiment 3>
In the wireless communication system according to the first embodiment, since the loopback test is performed in the transmission period 21, the base station 1 cannot transmit the data originally intended to be transmitted during that period. As a result, the radio communication system according to Embodiment 1 has a problem that the throughput of the base station 1 is reduced. On the other hand, in the radio communication system according to the second embodiment, since a loopback test is performed in the reception period 24, there is a problem that the base station 1 cannot receive data originally intended to be received during that period. Hereinafter, the radio communication system according to the present embodiment capable of solving these problems will be described focusing on differences from the radio communication system according to the second embodiment. The configuration of base station 1 according to Embodiment 3 is the same as the configuration of base station 1 according to Embodiment 1.

  As in the second embodiment, in this embodiment, the test period 27 is the entire period of one reception period 24. FIG. 6 is a diagram illustrating signals input to the mixer 17 of the base station 1 according to the present embodiment during the test period 27 in which the loopback test is performed. The horizontal direction in the figure indicates time, and the vertical direction indicates subchannels. Here, the WiMAX subchannel includes a plurality of specific subcarriers.

  In the present embodiment, the digital signal generation / analysis unit 11 performs modulation so as to superimpose loopback test data on a predetermined subcarrier 32 included in a fixed number of subcarriers 31 defined by WiMAX. The unit 12 is controlled. Thereby, the digital signal generation / analysis unit 11 according to the present embodiment performs a loopback test using the predetermined subcarriers 32 included in the plurality of subcarriers 31 in the test period 27. As a result, the predetermined subcarrier 32 on which the loopback test data is superimposed is input to the mixer 17 of the base station 1 as a loopback test signal.

  On the other hand, the base station 1 controls the terminal 2 so that the terminal 2 superimposes and transmits data on a plurality of subcarriers 31 other than the predetermined subcarrier 32 in the test period 27. As a result, a plurality of subcarriers 31 other than the predetermined subcarrier 32 on which data from the terminal 2 is superimposed are input to the mixer 17 of the base station 1. The base station 1 transmits the UL-MAP message for controlling the terminal 2 in this way to the terminal 2 through the transmission / reception unit 19 before the loopback test. In the present embodiment, the header having the UL-MAP message is transmitted in the header transmission period 22 immediately before the test period 27.

  The base station 1 according to the present embodiment as described above has the data superimposed on the plurality of subcarriers 31 other than the predetermined subcarrier 32 used in the loopback test in the test period 27 performed in the loopback test. Can be received from the terminal 2. Therefore, the loopback test can be performed without reducing the throughput in the transmission of the base station 1 and hardly reducing the throughput in the transmission of the terminal 2.

  In the embodiment, it has been described that the test period 27 is the entire period of one reception period 24. However, the test period 27 is not limited to this, and may be an arbitrary period within one reception period 24. Further, the transmission period 27 may extend over a plurality of reception periods 24. Hereinafter, a case where the digital signal generation / analysis unit 11 performs a loopback test in a plurality of reception periods 24 will be described. In the following description, it is assumed that the plurality of reception periods 24 in which the loopback test is performed, that is, the plurality of test periods 27 are configured by four reception periods 24. The four test periods 27 may be provided apart from each other across one or more transmission periods 21.

  FIG. 7 is a diagram illustrating signals input to the mixer 17 of the base station 1 according to the present embodiment during the four test periods 27 in which the loopback test is performed. FIGS. 7A to 7D show signals input to the mixer 17 for each test period 27 in the same manner as in FIG. As shown in the figure, the digital signal generator / analyzer 11 performs the test so that all the subcarriers 31 are allocated to the predetermined subcarriers 32 used in the loopback test during the four test periods 27. The predetermined subcarrier 32 is changed every period 27.

  Such a base station 1 can perform a loopback test on all subcarriers 31 defined by WiMAX. As a result, it is possible to confirm whether the transmission / reception unit 19 is correctly transmitting / receiving signals on all the subcarriers 31.

  In the present embodiment, the header having the above control information is transmitted in the header transmission period 22 immediately before the test period 27. However, the present invention is not limited to this, and the above-described UL-MAP message may be transmitted in any period as long as it is the header transmission period 22 before the test period 27. In the first to third embodiments, the case where the loopback test is performed in the base station 1 has been described. However, the present invention is not limited to this, and the terminal 2 may perform a loopback test in the same manner as the base station 1.

1 is a diagram showing a configuration of a radio communication system according to Embodiment 1. FIG. 3 is a block diagram showing a configuration of a base station according to Embodiment 1. FIG. 6 is a diagram illustrating an operation of the base station according to Embodiment 1. FIG. 6 is a diagram illustrating an operation of the base station according to Embodiment 1. FIG. FIG. 10 is a diagram illustrating an operation of a base station according to the second embodiment. It is a figure which shows the signal input into the mixer of the base station which concerns on Embodiment 3. FIG. It is a figure which shows the signal input into the mixer of the base station which concerns on Embodiment 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station 2 Terminal 11 Digital signal generation and analysis part 19 Transmission / reception part 21 Transmission period 24 Reception period 31 Subcarrier 32 Subcarrier

Claims (6)

A TDD (Time Division Duplexing) method in which a transmission period and a reception period repeatedly appear, and a transmission / reception unit that transmits and receives a signal to and from an external communication device;
A control unit that performs a loopback test to determine whether the test information output to the transmission / reception unit matches at least a part of the test information fed back from the transmission / reception unit;
With
The communication device, wherein the control unit performs the loopback test only in the transmission period or only in the reception period. The communication device according to claim 1,
The controller is
Only during the reception period, the loopback test is performed using predetermined subcarriers included in a plurality of subcarriers,
Control information for controlling the external communication device so that the external communication device transmits a signal using the plurality of subcarriers other than the predetermined subcarrier in the reception period in which the loopback test is performed. A communication device that transmits to the external communication device through the transceiver before the loopback test. The communication device according to claim 2,
The controller is
Performing the loopback test in a plurality of the reception periods;
The loopback test is performed so that all the plurality of subcarriers are allocated to the predetermined subcarrier used in the loopback test during the plurality of reception periods in which the loopback test is performed. A communication apparatus that changes the predetermined subcarrier for each reception period. A communication device according to any one of claims 1 to 3,
The communication device is a communication device that is a base station for WiMAX (Worldwide Interoperability for Microwave Access). (A) A step of transmitting / receiving a signal to / from an external communication device via a transmission / reception unit by a TDD (Time Division Duplexing) method in which a transmission period and a reception period repeatedly appear;
(B) performing a loopback test for determining whether the test information output to the transmission / reception unit and at least a part of the test information fed back from the transmission / reception unit match;
With
The communication method, wherein the step (b) is performed only in the transmission period or only in the reception period. The communication method according to claim 5, wherein
In the step (b), only in the reception period, the loopback test is performed using predetermined subcarriers included in a plurality of subcarriers,
(C) For controlling the external communication device such that the external communication device transmits a signal in the reception period in which the loopback test is performed using the plurality of subcarriers other than the predetermined subcarrier. Transmitting control information to the external communication device through the transceiver before the loopback test,
A communication method further comprising:

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