JP5622621B2 - Communication apparatus and antenna selection method - Google Patents

Description

  The present invention relates to a communication apparatus that performs wireless communication using a plurality of antennas.

  In wireless communication, when a signal transmitted from a transmission apparatus is received by a reception apparatus, fading that significantly reduces reception power due to multipath occurs. When the received power decreases due to fading, a problem that the received signal cannot be demodulated correctly occurs. As a technique for solving such a problem, there is a diversity technique using a plurality of antennas. Diversity techniques include transmission diversity applied at the time of transmission and reception diversity applied at the time of reception. There are various techniques, and one of them is selection diversity for selecting an antenna that optimizes reception performance. Selection diversity is applicable to both transmission and reception.

  Patent Literature 1 discloses a transmission diversity technique. In this transmission diversity, an antenna used for transmission is stored as the latest communication history for each communication partner so that an optimum antenna can be selected at the time of transmission. The transmission antenna memorized at the next transmission is used. In addition, when an error occurs in the transmission signal and retransmission is performed, transmission is performed by switching to another antenna.

  On the other hand, Patent Literature 2 discloses a reception diversity technique, and in this reception diversity, in order to be able to select an optimal antenna at the time of reception, the antenna is switched in the middle of the preamble arranged in the radio frame, The average received power of the signal received by each antenna is measured, and an antenna with higher received power is selected.

JP-A-8-256162 Special table 2007-529160 gazette

  In the selection of the transmission antenna in the conventional transmission diversity described above, since the antenna that was successfully transmitted last time is selected at the time of transmission, there is a possibility that the reception quality is better if the transmission is performed by another antenna. Not necessarily selected. In the selection of the reception antenna in the conventional reception diversity, the antenna is selected according to the reception power at each antenna. However, the optimal antenna cannot always be selected with the reception power. In wireless communication, a transmission signal of another communication device may be mixed into the received signal as interference. In such a case, although the received power is high, the quality of the received signal may be deteriorated and reception may not be possible.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a communication apparatus and an antenna selection method that can improve communication quality by selecting an optimum antenna at the time of transmission and reception.

  In order to solve the above-described problems and achieve the object, the present invention provides a communication apparatus that transmits and receives a radio frame signal including a preamble section storing a known sequence and a data section storing data, and includes a plurality of antennas. And repeatedly performing the process of receiving the known sequence using any one of the plurality of antennas in the preamble section included in one radio frame, and calculating the SINR for each antenna, Use antenna selection means for selecting an antenna having the maximum SINR as an antenna to be used for reception of the data, and a source of a known sequence received when calculating the SINR of the antenna selected by the use antenna selection means Storage means for storing as an antenna for use in radio frame signal transmission to the communication device of Characterized in that it obtain.

  According to the present invention, when each antenna is used, the SINR for each is calculated, and the antenna to be used in the transmission / reception process is determined based on the calculated SINR comparison result. It becomes possible to select an antenna, and it is possible to obtain performance improvement due to diversity on each of the transmission side and the reception side, and there is an effect that communication quality is improved.

FIG. 1 is a diagram illustrating a configuration example of a communication apparatus according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the PR adding unit. FIG. 3 is a diagram illustrating a configuration example of the preamble generation unit. FIG. 4 is a diagram illustrating a configuration of radio frame data and an example of a preamble. FIG. 5 is a diagram illustrating an example of the basic sequence # 2. FIG. 6 is a diagram illustrating a configuration of radio frame data and an example of a preamble. FIG. 7 is a diagram illustrating a configuration example of the PR detection unit. FIG. 8 is a diagram illustrating a processing image of the correlation power and timing detection unit. FIG. 9 is a flowchart illustrating an example of the operation of the control unit that generates antenna selection information. FIG. 10 is a flowchart illustrating an example of the operation of the control unit that generates antenna selection information. FIG. 11 is a flowchart illustrating an example of the operation of the control unit that generates antenna selection information. FIG. 12 is a flowchart illustrating an example of the operation of the control unit that generates antenna selection information.

  Embodiments of a communication apparatus and an antenna selection method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of a communication apparatus according to the present invention. The communication apparatus according to the present embodiment calculates a CRC (Cyclic Redundancy Check) of transmission data, adds a CRC generation unit 1 to the transmission data, and a modulation unit 2 generates a transmission modulation symbol from the transmission data to which the CRC is added. A PR adding unit 3 that generates a preamble and adds it to a transmission modulation symbol; and a radio unit 4 that converts a digital transmission signal into an RF signal transmitted from an antenna and converts an RF signal received by the antenna into a digital reception signal. A PR detector 5 for detecting a preamble from the received signal and measuring a SINR (Signal to Interference and Noise Ratio) of the received signal; a demodulator 6 for demodulating the received signal and outputting the received data; and received data CRC check unit 7 that performs the CRC check of the demodulator 6 and the demodulator 6 based on the PR detection information and SINR from the PR detection unit 5 A control unit 8 that controls the antenna switching unit 10, a storage unit 9 that stores information on the communication partner and antenna identification information (antenna number) having a high SINR at the time of reception, and one antenna that is connected to the radio unit 4. An antenna switching unit 10 for switching, and an antenna 11 and an antenna 12 for transmitting or receiving RF signals are provided. In the following description, antenna 11 may be antenna # 1, and antenna 12 may be antenna # 2.

  Next, the operation will be described. In the communication apparatus shown in FIG. 1, a transmission operation is performed in accordance with a transmission request from a higher-level control unit (not shown). When the transmission operation is not performed, the reception operation is performed. Hereinafter, it will be described in detail by dividing it into an operation at the time of transmission and an operation at the time of reception.

(Operation when sending)
In the communication apparatus according to the present embodiment, transmission data is input to the CRC generation unit 1. The CRC generator 1 calculates the CRC of the input transmission data and adds it to the transmission data. The CRC calculation method is a general process and will not be described in detail.

  The transmission data to which the CRC is added is input to the modulation unit 2. Modulation section 2 generates a modulation symbol from transmission data to which CRC is added. The modulation method may be a general method such as BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying), and detailed description thereof is omitted.

  The generated modulation symbol is input to the PR adding unit 3. The PR adding unit 3 adds a preamble to the modulation symbol.

  The configuration and operation of the PR adding unit 3 will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration example of the PR adding unit 3. As illustrated, the PR adding unit 3 includes a preamble generating unit 31 that generates a preamble added to data, and a combining unit 32 that combines the preamble and data. In the PR adding unit 3, the combining unit 32 combines the input modulation symbol (data) and the preamble generated by the preamble generating unit 31. At this time, the preamble is generally arranged before the data (modulation symbol), but the preamble may be arranged not only before the data but also in the middle of the data.

  The configuration and operation of the preamble generation unit 31 will be described with reference to FIG. 3 showing an exemplary configuration of the preamble generation unit 31. As illustrated in FIG. 3, the preamble generation unit 31 includes basic sequence generation units 311 and 312, an adder 313, and a conversion unit 314.

  The basic sequence generation unit 311 generates, for example, a PN code having a code length of 7 bits as the basic sequence # 1. The generation method of the PN code may be a general method and will not be described in detail. The basic sequence generation unit 312 generates, for example, an orthogonal code having a code length of 4 bits as the basic sequence # 2. An orthogonal code generation method may be a general method, and detailed description thereof is omitted. The basic sequence generation unit 312 outputs 1 bit of the basic sequence # 2 every time the basic sequence generation unit 311 outputs the basic sequence # 1 for the code length (7 bits). Adder 313 calculates the exclusive OR of basic sequence # 1 output from basic sequence generation section 311 and basic sequence # 2 output from basic sequence generation section 312. The output of the adder 313 is 0 or 1 data. The conversion unit 314 converts the data output from the adder 313 into transmission symbols. For example, 0 is converted to 1 and 1 is converted to -1. Note that the basic sequence # 1 and the basic sequence # 2 are sequences that are known among communication apparatuses that perform communication.

  Next, the preamble generated by the preamble generator 31 will be described with reference to FIG. FIG. 4 is a diagram illustrating a configuration of radio frame data generated by adding a preamble to a modulation symbol (data) and an example of the preamble. FIG. 4 shows an example in which a sequence obtained by repeating a basic sequence # 1 having a code length of 7 bits a plurality of times is used as a preamble. Specifically, the basic sequence # 1 is repeated eight times. Further, when the basic sequence # 1 is repeated, an exclusive OR is performed with 1 bit of the basic sequence # 2. By preparing a plurality of basic sequences # 2, a plurality of preambles can be generated. For the basic sequence # 2, for example, four orthogonal codes having a sequence length of 4 shown in FIG. 5 are used. The preambles # 1 to # 4 shown in FIG. 4 are exclusively ORed with the code numbers # 1 to # 4 of the basic sequence # 2 shown in FIG. The basic sequence # 1 shaded in FIG. 4 indicates that 0 and 1 are inverted by exclusive OR. In this example, since the basic sequence # 1 is repeated 8 times, the basic sequence # 2 is repeated twice.

  Note that when the basic sequence # 2 is repeated twice, the second 0 and 1 may be reversed. In this case, preambles # 1 to # 4 are as shown in FIG.

  In addition, although PN code is used for basic sequence # 1 and orthogonal code is used for basic sequence # 2, any code may be used as long as it has good autocorrelation characteristics and cross-correlation characteristics. It is not limited.

  Returning to the description using FIG. 1, the radio frame data generated by the PR adding unit 3 is input to the radio unit 4. The radio unit 4 performs D / A conversion, up-conversion, amplification, etc. on the input radio frame data, and converts it into a transmission RF signal. The process of the wireless unit 4 is a general process, and detailed description thereof is omitted.

  The transmission RF signal is input to the antenna switching unit 10. The antenna switching unit 10 outputs a transmission RF signal to the antenna 11 or the antenna 12. Which antenna is output is determined by the antenna indicated by the antenna selection information input from the control unit 8. A method for generating the antenna selection information will be described later.

(Operation when receiving)
In the communication apparatus according to the present embodiment, antenna 11 is used out of the two antennas when the reception operation starts. That is, the antenna switching unit 10 is controlled by the control unit 8 so as to connect the antenna 11 and the radio unit 4.

  The received RF signal received by the antenna 11 is input to the radio unit 4 via the antenna switching unit 10. The wireless unit 4 performs amplification, down-conversion, A / D conversion, and the like on the received reception RF signal to convert it into a complex (I, Q) reception baseband signal. The process of the wireless unit 4 is a general process, and detailed description thereof is omitted.

  The received baseband signal is input to the PR detector 5. The PR detection unit 5 performs radio frame timing detection, SINR measurement, and basic sequence # 2 determination from the received baseband signal.

  The configuration and operation of the PR detection unit 5 will be described with reference to FIG. FIG. 7 is a diagram illustrating a configuration example of the PR detection unit 5. As illustrated, the PR detection unit 5 includes a basic sequence generation unit 51 that generates the basic sequence # 1, a correlation calculation unit 52 that performs a correlation calculation between the received baseband signal and the basic sequence # 1, and a correlation calculation result. A power generation unit 53 that generates power, a timing detection unit 54 that detects peak timing of correlation power, a SINR measurement unit 55 that measures SINR from correlation power, a basic sequence generation unit 56 that generates basic sequence # 2, A basic sequence determination unit 57 that determines a sequence number (code number) of the basic sequence # 2.

  The basic sequence generation unit 51 generates the above-described basic sequence # 1 by the same processing as the above-described basic sequence generation unit 311. Correlation calculation section 52 performs a convolution calculation of the received baseband signal and basic sequence # 1, and outputs a complex (I, Q) correlation value. The power generation unit 53 calculates the power of the correlation value and outputs the calculated correlation power. The timing detection unit 54 compares the correlation power with a predetermined threshold value Pth, and outputs a detection timing to the control unit 8 when a peak of the correlation power is detected in a state where the correlation power is equal to or greater than the threshold value Pth. The threshold value Pth is given from an upper control unit (not shown).

  FIG. 8 shows a processing image of the correlation power and timing detection unit. In the graph of FIG. 8, the horizontal axis is time, the vertical axis is correlation power, and the peak timing of correlation power (timing indicated by an arrow) that is equal to or greater than the threshold value Pth indicated by a thin dotted line is the detection timing. Although details of the operation will be described later, the antenna switching unit 10 switches the antenna to be used from the antenna # 1 to the antenna # 2 during the preamble reception operation in accordance with an instruction from the control unit 8. In the example shown in FIG. 8, the switching timing is a time point (a timing corresponding to the middle of the preamble) at which the basic sequence # 1 is repeated four times.

  The SINR measurement unit 55 calculates SINR with the correlation power at the timing indicated by the detection timing input from the timing detection unit 54 as signal power (S) and the correlation power at other timings as interference + noise power (I + N). To the control unit 8. This operation will be described with reference to FIG. 8. Assume that the correlation power at the detection timing indicated by the arrow is signal power (S), and the correlation power at other timings is interference + noise power (I + N). The signal power (S) and interference + noise power (I + N) may be averaged over a plurality of timings. However, power at different timings of the antennas is not averaged.

  The basic sequence generation unit 56 generates the above-described basic sequence # 2 (each basic sequence # 2 with code numbers # 1 to # 4 shown in FIG. 5) by the same processing as the basic sequence generation unit 312 described above. Output all series. The basic sequence determination unit 57 calculates the correlation power between the complex correlation value input from the correlation calculation unit 52 and all the basic sequences # 2 at the timing detected by the timing detection unit 54, and the basic power with the largest correlation power is obtained. The sequence number (code number) of sequence # 2 is output to control unit 8.

  Returning to the description using FIG. 1, the received baseband signal output from the wireless unit 4 is also input to the demodulating unit 6. The demodulator 6 performs demodulation processing based on timing information from the controller 8 and outputs demodulated bits. The demodulation process is a general process, and detailed description thereof is omitted.

  The demodulated bits are input to the CRC check unit 7. The CRC check unit 7 performs a CRC check on the demodulated bits, and determines whether the CRC matches (OK) or does not match (NG). The CRC check is a general process and will not be described in detail. After the CRC check, the CRC check unit 7 outputs the received bit from which the CRC has been removed and the CRC determination result.

  The control unit 8 instructs the demodulation unit 6 to start demodulation based on the detection timing output from the PR detection unit 5. Further, the antenna selection information is output to the antenna switching unit 10 based on the SINR output from the PR detection unit 5 and the detection timing. A method for generating the antenna selection information will be described later.

  The storage unit 9 stores the sequence number of the basic sequence # 2 corresponding to the communication partner number (identification information) and the antenna number used in the communication in association with each other. The antenna number may be stored at the time of transmission and at the time of reception.

  A method for generating the antenna selection information will be described with reference to FIGS. 9 to 12 are flowcharts illustrating an example of the operation of the control unit 8 that generates antenna selection information, and FIG. 9 is a main flowchart of the operation of generating antenna selection information. FIG. 10 is a transmission process flowchart. FIG. 11 is a reception process flowchart. FIG. 12 is a flow when the transmission timer expires.

  When starting the operation of generating the antenna selection information, the control unit 8 determines the presence / absence of a transmission request from a host control unit (not shown) as shown in FIG. 9 (step S11). If there is a transmission request (step S11: Yes), transmission processing is performed (step S12). This transmission processing is performed according to the flowchart shown in FIG. On the other hand, when there is no transmission request (step S11: No), a reception process is performed (step S13). This reception process is performed according to the flowchart shown in FIG.

  In the transmission process shown in step S12, as shown in FIG. 10, the control unit 8 first obtains the antenna number at the time of previous communication from the storage unit 9, and further receives the antenna at the time of previous communication. The presence or absence of a number is confirmed (steps S21 and S22). As a result of the confirmation, if there is an antenna number (step S22: Yes), antenna selection information for instructing to use the antenna number acquired from the storage unit 9 is generated and output to the antenna switching unit 10 (step S23). On the other hand, when there is no antenna number (step S22: No), the antenna selection information which instruct | indicates to use antenna number # 1 (initial value) is produced | generated, and it outputs to the antenna switch part 10 (step S24). After step S23 or step S24 is executed, transmission processing is next performed (step S25). The process of step S25 is a process of the entire apparatus including components other than the control unit 8, but the control unit 8 does nothing specifically. When the transmission process in step S25 ends, the control unit 8 stores the antenna number used for transmission (antenna number indicated by the antenna selection information) in the storage unit 9 (step S26). Next, the control part 8 determines whether this transmission is ACK transmission (step S27). Whether or not to transmit ACK is determined by checking information input from a higher-level control unit (not shown). In the case of ACK transmission (step S27: Yes), the transmission process is terminated. On the other hand, when it is not ACK transmission (step S27: No), a transmission timer is started (step S28) and a transmission process is complete | finished.

  In the reception process shown in step S13, the control unit 8 first generates antenna selection information instructing to use antenna number # 1 (initial value) as shown in FIG. (Step S31). Next, preamble detection determination is performed from the output of the PR detection unit 5 (step S32). If no detection is detected, preamble detection determination is repeated (step S32: No). On the other hand, when there is a detection (step S32: Yes), antenna selection information instructing to use antenna number # 2 is generated, and output to the antenna switching unit 10 at the antenna switching timing to switch the receiving antenna (step) S33). This antenna switching timing is as shown in FIG. 8, and is a break of the basic sequence # 1 corresponding to the middle of the preamble. When the reception of the preamble using the antenna # 2 is completed, the control unit 8 then uses the SINR # 1 that is the SINR of the signal received from the antenna # 1 output from the PR detection unit 5 and the antenna # 2. SINR # 2, which is the SINR of the received signal, is compared (step # 34). When SINR1 # 1 ≧ SINR # 2 (step S34: Yes), it is determined to select antenna # 1, and antenna selection information instructing to use antenna number # 1 is generated and output to antenna switching unit 10 (Step S35). On the other hand, when SINR # 1 <SINR # 2 (step S34: No), antenna selection information instructing to use antenna number # 2 is generated and output to the antenna switching unit 10 (step S36). When step S35 or step S36 is executed, the control unit 8 next activates the demodulation unit 6 based on the timing detected by the PR detection unit 5 to perform data reception processing (step S37). Next, it is determined whether the CRC is OK or NG (step S38). If OK (step S38: Yes), the antenna number with the high SINR used for data reception (selected according to the comparison result in step S34 above) The antenna number is stored in the storage unit 9 (step S39), and the process is terminated. On the other hand, when the CRC is NG (step S38: No), the process returns to step S31 and the reception process is continued. Note that this reception process ends when the CRC is OK, and also ends when the control from the upper control unit (not shown) and the transmission timer expires.

  When the reception process is terminated when the transmission timer expires, as shown in FIG. 12, the control unit 8 first acquires the transmission antenna number from the storage unit 9 (step S41), and adds 1 to this acquired number. In addition, the antenna number is changed. When the value added by 1 becomes larger than the number of antennas, the antenna number is set to the minimum value. And the antenna selection information which instruct | indicates to use the antenna corresponding to the antenna number after a change is produced | generated, and it outputs to the antenna switch part 10 (step S42). Next, a transmission process is performed (step S43). The process of step S43 is the same process as step S25 of FIG. 10 described above. When the transmission process in step S43 ends, the control unit 8 stores the transmission antenna number in the storage unit 9 (step S44), starts a transmission timer (step S45), and ends the process.

  In the present embodiment, the case where the number of antennas is two has been described, but the number of antennas may be more than two. The embodiment in which there are more than two antennas can be easily expanded from this embodiment by those skilled in the art. For example, in the reception process (see FIG. 11), after detecting the preamble, each antenna is switched in the preamble section to calculate the SINR when each antenna is used, and the antenna having the maximum SINR may be selected and used.

  As described above, in the communication apparatus according to the present embodiment, the SINR is calculated for each of the antennas used, and the antenna to be used in the transmission / reception process is determined based on the calculated SINR comparison result. It was decided to. As a result, it is possible to select an optimal antenna at the time of transmission and at the time of reception, and it is possible to obtain performance improvement due to diversity on each of the transmission side and the reception side, thereby improving communication quality.

  As described above, the communication device according to the present invention is useful for a wireless communication system, and is particularly suitable for a communication device to which selection diversity using a plurality of antennas selectively is applied.

DESCRIPTION OF SYMBOLS 1 CRC production | generation part 2 Modulation part 3 PR addition part 4 Radio | wireless part 5 PR detection part 6 Demodulation part 7 CRC check part 8 Control part 9 Storage part 10 Antenna switching part 11, 12 Antenna 31 Preamble generation part 32 Combining part 51,56, 311 and 312 Basic sequence generation unit 52 Correlation calculation unit 53 Power generation unit 54 Timing detection unit 55 SINR measurement unit 57 Basic sequence determination unit 313 Adder 314 Conversion unit

Claims (4)

A communication apparatus for transmitting and receiving a radio frame signal including a preamble section for storing a known sequence and a data section for storing data,
Multiple antennas,
The process of receiving the known sequence using any one of the plurality of antennas is repeatedly performed in a preamble section included in one radio frame to calculate the SINR for each antenna, and the SINR Use antenna selection means for selecting an antenna having a maximum value as an antenna to be used for receiving the data;
Storage means for storing the antenna selected by the use antenna selection means as an antenna to be used for radio frame signal transmission to a communication device of a transmission source of a known sequence received when calculating the SINR;
Equipped with a,
Examples known sequence, the communication device characterized that you use the sequence obtained by logical operation using the first code and the second code auto-correlation and cross-correlation properties are good. The use antenna selection means includes:
An antenna switching unit for switching an antenna used for transmission / reception of a radio frame signal;
A preamble detector that detects the preamble interval using the known sequence and calculates SINR in the preamble interval;
The antenna switching unit is controlled based on the detection result of the preamble section by the preamble detecting unit, and the known sequence is received using each of the plurality of antennas, and the data is received based on the SINR. A control unit that determines an antenna to be used at the time, and instructs the antenna switching unit to use the determined antenna;
The communication apparatus according to claim 1, further comprising: Communication device according to claim 1 or 2, characterized by using an exclusive OR of said first code to repeated sequence and said second code as the known sequence. An antenna selection method that is performed in a communication apparatus that includes a plurality of antennas and that transmits and receives a radio frame signal including a preamble section for storing a known sequence and a data section for storing data,
A SINR calculating step of repeatedly performing the process of receiving the known sequence using any one of the plurality of antennas in a preamble section of one radio frame, and calculating an SINR for each antenna;
A use antenna selection step of selecting an antenna having the maximum SINR as an antenna to be used for reception of the data;
Storing the selected antenna as an antenna to be used in radio frame signal transmission to a communication device of a transmission source of a known sequence received in the SINR calculation step;
Only including,
An antenna selection method characterized by using a sequence obtained by a logical operation using a first code and a second code having good autocorrelation characteristics and cross-correlation characteristics as the known series .

Images