JP2007180875A - Radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a reception timing and a frequency of a composite signal. <P>SOLUTION: The base station apparatus 10 provided with a plurality of antennas 11 includes: a composite signal acquisition section 18 for composing signals received by the antennas 11 to acquire the composite signal; a timing offset detection section 19 and a frequency offset detection section 20 which acquire at least either of a reception timing offset and a frequency offset of the composite signal; and a reception timing correction section 21 and a frequency correction section 22 for correcting the composite signal on the basis of one or a plurality of offsets acquired by the detection sections 19, 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus, and more particularly to a technique for correcting frequency and reception timing.

  When wireless communication is performed while the transmission-side wireless communication device and the reception-side wireless communication device are synchronized, the wireless signal reception timing at the reception-side wireless communication device may be deviated from the scheduled timing. Further, when at least one of the wireless communication apparatuses moves, a frequency shift (frequency offset) due to the Doppler effect may occur.

When these deviations occur, the reception quality deteriorates. Therefore, for example, in Patent Document 1, a reception timing offset and a frequency offset are detected from a received signal, and the received signal is corrected based on these.
JP 2003-60542 A

  In Patent Document 1, a reception timing offset and a frequency offset are detected for each antenna from a radio signal received by each antenna constituting the adaptive array antenna, and are corrected for each antenna.

  However, since this correction is not always perfect, a reception timing offset and a frequency offset may remain even after the radio signals received by a plurality of antennas such as an adaptive array antenna are combined.

  Accordingly, it is an object of the present invention to provide a wireless communication apparatus that can correct the reception timing and frequency of a composite signal.

  A wireless communication apparatus according to the present invention for solving the above-described problem is a wireless communication apparatus including a plurality of antennas, and combines a signal received by each antenna to acquire a combined signal. And a combined signal offset acquiring unit that acquires at least one of the reception timing offset and the frequency offset of the combined signal, and the combined signal is corrected based on one or more offsets acquired by the combined signal offset acquiring unit, respectively. And a correction means.

  According to this, it becomes possible to correct the reception timing and frequency of the composite signal.

  In the wireless communication apparatus, for each signal received by each antenna, a reception signal offset acquisition unit that acquires at least one of a reception timing offset and a frequency offset, and each of the signals acquired by the reception signal offset acquisition unit Correction means for correcting each signal based on one or more offsets for each signal received by the antenna may be further included.

  According to this, it is possible to further correct the reception timing and frequency of the combined signal after correcting each antenna.

  Furthermore, in this wireless communication apparatus, a transmission signal acquisition unit that acquires a transmission signal, a transmission signal correction unit that corrects the transmission signal based on one or more offsets acquired by the combined signal offset acquisition unit, One or a plurality of distribution output means for distributing and outputting the transmission signal corrected by the transmission signal correction means to each antenna, and each of the signals received by each antenna acquired by the reception signal offset acquisition means And a post-distribution transmission signal offset means for offsetting the transmission signals distributed and output to the antennas based on the respective offsets.

  When transmission and reception are performed at approximately the same time, it can be considered that there is almost no difference in the position and movement of the wireless communication device of the communication partner between transmission and reception. In this case, if the same offset as the offset of the received signal is added to the transmission signal, a signal having no offset is received in the wireless communication apparatus of the communication partner.

  In this regard, the wireless communication apparatus obtains an offset in two stages of the combined signal and the received signal of each antenna. Further, the offset in the combined signal stage is determined for each antenna with respect to the transmission signal of all antennas. Since the offset at the reception signal stage is added to the transmission signal at each antenna, the same offset as that of the reception signal is added to the transmission signal.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a system configuration and functional blocks of a base station apparatus 10 according to the present embodiment. The base station device 10 is a computer that has a CPU, a memory, a clock, and a wireless communication function and functions as a wireless communication device, and is used in a mobile communication system. The memory stores a program and data necessary for executing the program. The CPU operates in accordance with a program stored in the memory, and reads and writes the data as necessary. The clock is synchronized with the network.

  The base station apparatus 10 performs radio communication with a plurality of mobile station apparatuses (not shown) by performing multiplexing by space division multiplexing and time division multiplexing. Furthermore, the base station apparatus 10 multiplexes uplink communication and downlink communication on the same frequency by time division duplex.

  As shown in FIG. 1, the base station apparatus 10 includes a plurality of antennas 11, and for each antenna 11, a duplexer 12, a timing offset detection unit 13, a frequency offset detection unit 14, a reception timing correction unit 15, and a frequency correction unit 16. The frequency offset unit 33 and the transmission timing offset unit 34 are included. In addition to these, the synthesized signal acquisition unit 18, the timing offset detection unit 19, the frequency offset detection unit 20, the reception timing correction unit 21, the frequency correction unit 22, the weighting factor calculation unit 25, the frequency offset unit 30, the transmission timing offset The unit 31, the signal distribution unit 32, the reference signal storage unit 40, and the communication processing unit 41 are further included.

  Note that the subscripts (a and b) of the reference numerals in FIG. 1 indicate the antenna system, where the subscript “a” corresponds to the antenna 11a, and the subscript “b” corresponds to the antenna 11b. Shows things. Here, an example in which there are two antennas 11 is described, but the base station apparatus 10 may include more antennas 11.

  The antenna 11a and the antenna 11b constitute an adaptive array antenna and receive a radio signal (uplink radio signal) transmitted from the same transmission source (here, a mobile station apparatus). In addition, a radio signal having the same content (downlink radio signal) is transmitted to the radio section.

  FIG. 2 is a diagram showing a format of a radio signal transmitted and received in this way. The radio signal is a burst signal having a predetermined length obtained by modulating a bit string having an arbitrary length. As shown in FIG. 2, this radio signal includes reference signals, which are signals having predetermined contents, at two locations (reference signal 2-1 and reference signal 2-2). Here, the reference signal 2-1 and the reference signal 2-2 have the same contents. Since the wireless signal is transmitted and received sequentially from the head, the reference signal 2-2 is received (transmitted) after the reference signal 2-1 is received (transmitted). The reference signal storage unit 40 holds this reference signal.

  The duplexer 12 connects the antenna 11 and the reception timing correction unit 15 corresponding to the antenna 11 in a time zone in which uplink communication is performed, and the antenna 11 and the antenna in a time zone in which downlink communication is performed. 11 is connected to the transmission timing offset unit 34 corresponding to 11.

  Hereinafter, processing of the received signal will be described first.

  As described above, the clock of the base station apparatus 10 is network-synchronized, and the reference signal storage unit 40 holds the reference signal generated based on this clock. Each timing offset detection unit 13 compares this reference signal with the reference signal 2-1 included in the reception signal received by the corresponding antenna 11, thereby obtaining a reception timing offset (reception timing offset) of the reception signal. ) Is detected.

  Further, the reference signal held by the reference signal storage unit 40 is a signal having a frequency (reference frequency) used for communication. Each frequency offset detector 14 detects the frequency difference (frequency offset) between the frequency of the reference signal and the frequency of the reference signal 2-1 portion of the received signal received by the corresponding antenna 11 for each antenna 11. .

  Each reception timing correction unit 15 corrects the reception timing of the reception signal output from the duplexer 12 based on the reception timing offset detected by the corresponding timing offset detection unit 13. Specifically, the received signal is delayed according to the reception timing offset. This delay amount has an upper limit, and the upper limit of the reception timing offset that can be corrected by the reception timing correction unit 15 is determined according to this upper limit. Further, since the correction is performed based only on the reference signal 2-1, if the reception timing offset differs between the first half and the second half of the signal due to high-speed fading or the like, it cannot be corrected accurately. .

  The frequency correction unit 16 corrects the frequency of the reception signal output from the reception timing correction unit 15 based on the frequency offset detected by the corresponding frequency offset detection unit 14. Specifically, the received signal is delayed according to the frequency offset. This delay amount also has an upper limit, and the upper limit of the frequency offset that can be corrected by the frequency correction unit 22 is determined according to this upper limit. Further, since the correction is performed based only on the reference signal 2-1, if the frequency offset is different between the first half and the second half of the signal due to high-speed fading or the like, it cannot be corrected accurately.

  The combined signal acquisition unit 18 acquires a combined signal by combining the reception signals of the antennas 11 corrected by the reception timing correction units 15 and the frequency correction units 22 in this way.

  The timing offset detection unit 19 compares the reference signal held by the reference signal storage unit 40 with the reference signal 2-1 and the reference signal 2-2 included in the combined signal, thereby offsetting the reception timing of the combined signal. (Reception timing offset) is detected. Specifically, the reception timing offset detected by comparing the reference signal held in the reference signal storage unit 40 with the reference signal 2-1 included in the synthesized signal, and the reference signal storage unit 40 The average of the received timing offset detected by comparing the reference signal included in the synthesized signal with the reference signal 2-2 included in the synthesized signal is defined as the received timing offset of the synthesized signal.

  The frequency offset detection unit 14 is a frequency difference between the frequency of the reference signal (reference frequency) held by the reference signal storage unit 40 and the frequency of the reference signal 2-1 part and the reference signal 2-2 part of the synthesized signal. (Frequency offset) is detected. Specifically, a frequency offset detected by the reference frequency and the frequency of the reference signal 2-1 portion of the combined signal, and a frequency offset detected by the reference frequency and the frequency of the reference signal 2-2 portion of the combined signal, Is the frequency offset of the combined signal.

  The reception timing correction unit 21 corrects the composite signal output from the composite signal acquisition unit 18 based on the reception timing offset detected by the timing offset detection unit 19. Specifically, the composite signal is delayed according to the reception timing offset. This delay amount has an upper limit, and the upper limit of the reception timing offset that can be corrected by the reception timing correction unit 21 is determined in accordance with this upper limit, similarly to the reception timing correction unit 15. However, unlike the reception timing correction unit 15, correction is performed based on the reference signal 2-1 and the reference signal 2-2, and therefore, the timing offset differs between the first half and the second half of the signal due to high-speed fading or the like. Even in such a case, the correction can be made relatively accurately.

  The frequency correction unit 22 corrects the frequency of the combined signal output from the reception timing correction unit 21 based on the frequency offset detected by the frequency offset detection unit 20. Specifically, the synthesized signal is delayed according to the frequency offset. This delay amount also has an upper limit, and the upper limit of the frequency offset that can be corrected by the frequency correction unit 22 is determined according to the upper limit in the same manner as the frequency correction unit 16. However, unlike the frequency correction unit 16, correction is performed based on the reference signal 2-1 and the reference signal 2-2, so that the frequency offset differs between the first half and the second half of the signal due to high-speed fading or the like. Even in such a case, correction can be made relatively accurately.

  The combined signal that has been subjected to the timing offset correction and the frequency offset correction in two stages in this manner is input to the communication processing unit 41, and the communication processing unit 41 performs communication processing according to the combined signal.

  Next, transmission signal processing will be described.

  The communication processing unit 41 acquires a transmission signal and inputs it to the frequency offset unit 30.

  The frequency offset unit 30 offsets the frequency of the transmission signal input from the communication processing unit 41 based on the frequency offset detected by the frequency offset detection unit 20. Specifically, the transmission signal is delayed according to the frequency offset.

  The transmission timing offset unit 31 offsets the transmission timing of the transmission signal output from the frequency offset unit 30 based on the reception timing offset detected by the timing offset detection unit 19. Specifically, the transmission signal is delayed according to the reception timing offset.

  The signal distribution unit 32 distributes and outputs the transmission signals thus corrected by the frequency offset unit 30 and the transmission timing offset unit 31 to a plurality of frequency offset units 33 provided corresponding to each antenna 11.

  Each frequency offset unit 33 offsets the frequency of the transmission signal output from the signal distribution unit 32 based on the frequency offset detected by the corresponding frequency offset detection unit 14. Specifically, the transmission signal is delayed according to the frequency offset.

  Here, the weighting factor calculation unit 25 relatively offsets the timing of the reference signal held in the reference signal storage unit 40 based on the reception timing offset for each antenna 11 detected by each timing offset detection unit 13. Based on the plurality of reference signals thus obtained, the weighting coefficient of each antenna 11 related to the adaptive array is calculated by, for example, the least square error method. The weighting coefficient calculated in this way indicates a relative difference between the antennas 11 of the reception timing offset.

  Each transmission timing offset unit 34 offsets the transmission timing of the transmission signal input from the corresponding frequency offset unit 33 based on the weighting factor calculated by the weighting factor calculation unit 25. Specifically, the reception timing offset is obtained by multiplying the weighting factor of each antenna 11 calculated by the weighting factor calculation unit 25 by the transmission signal input from the frequency offset unit 33 provided corresponding to each antenna 11. The transmission signal is delayed according to

  A plurality of transmission signals having transmission timing offsets and frequency offsets in two stages are transmitted from each antenna 11 to the radio section.

  The process described above will be described again in detail with reference to the flowchart of the process.

  FIG. 3 is a processing flowchart showing processing of the base station apparatus 10.

  First, in the reception process, the base station apparatus 10 receives a radio signal by each antenna (S1). Next, the base station apparatus 10 substitutes 1 for the variable X (S2). Then, in the Xth antenna 11 (hereinafter referred to as antenna X) among the plurality of antennas 11, the reception timing offset of the reception signal is acquired (S3), and the frequency offset of the reception signal is acquired (S4). . Based on the acquired plurality of offsets, reception timing correction (S5) and frequency correction (S6) are performed. The base station apparatus 10 repeats the above-described processing of S3 to S6 while incrementing X by 1 (S7) until X exceeds the number of antennas (S8). That is, the base station apparatus 10 performs the processes from S3 to S6 for all antennas.

  When the processes of S3 to S6 are completed for all antennas, the base station apparatus 10 calculates a weighting factor indicating a relative difference in the reception timing offset based on the reception timing of each antenna 11 (S9). Further, the base station apparatus 10 synthesizes the reception signals of the respective antennas 11 and acquires a synthesized signal (S10).

  When the combined signal is acquired, the base station apparatus 10 acquires the reception timing offset of the combined signal (S11) and also acquires the frequency offset of the combined signal (S12). Then, based on the acquired plurality of offsets, reception timing correction (S13) and frequency correction (S14) are performed.

  Next, in the transmission process, when the base station apparatus 10 acquires a transmission signal (S20), the base station apparatus 10 performs frequency correction of the transmission signal based on the frequency offset acquired in S12 (S21). Further, the transmission timing of the transmission signal is corrected based on the reception timing offset acquired in S11 (S22). Then, the transmission signal is distributed to each antenna 11 (S23). Next, the base station apparatus 10 substitutes 1 for the variable X (S24). Then, in the antenna X, transmission timing correction is performed based on the weighting factor acquired in S9 (S25). Further, frequency correction is performed based on the frequency offset of the antenna X acquired in S4 (S26). The base station apparatus 10 repeats the above processes of S25 and S26 while incrementing X by 1 (S27) until X exceeds the number of antennas (S28). That is, the base station apparatus 10 performs the processes of S25 and S26 for all antennas. Then, a transmission signal is transmitted from each antenna (S29).

  As described above, the base station apparatus 10 can correct the reception timing and frequency of the combined signal. Further, after correcting these for each antenna, it is possible to further correct the reception timing and frequency of the combined signal.

  Also, the offset detected at the combined signal stage is added to the transmission signal at all antennas, and the offset detected at the reception signal stage at each antenna is added to the transmission signal at each antenna. Is added to the transmission signal.

It is a figure which shows the system configuration | structure and functional block of the base station apparatus which concern on embodiment of this invention. It is a figure which shows the format of the radio signal which concerns on embodiment of this invention. It is a processing flowchart which shows the process of the base station apparatus which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Base station apparatus, 11 Antenna, 12 Duplexer, 13 Timing offset detection part, 14 Frequency offset detection part, 15 Reception timing correction part, 16 Frequency correction part, 18 Synthetic signal acquisition part, 19 Timing offset detection part, 20 Frequency offset detection Unit, 21 reception timing correction unit, 22 frequency correction unit, 25 weight coefficient calculation unit, 30 frequency offset unit, 31 transmission timing offset unit, 32 signal distribution unit, 33 frequency offset unit, 34 transmission timing offset unit, 40 reference signal storage Part, 41 Communication processing part.

Claims (3)

A wireless communication device having a plurality of antennas,
A synthesized signal obtaining means for synthesizing signals received by the antennas and obtaining a synthesized signal;
Combined signal offset acquisition means for acquiring at least one of reception timing offset or frequency offset of the combined signal;
Correction means for correcting the composite signal based on one or more offsets acquired by the composite signal offset acquisition means;
A wireless communication apparatus comprising: The wireless communication device according to claim 1,
For each signal received by each antenna, received signal offset acquisition means for acquiring at least one of reception timing offset or frequency offset;
Correction means for correcting each of the signals based on one or more offsets for each of the signals received by each of the antennas acquired by the received signal offset acquisition means;
A wireless communication apparatus, further comprising: The wireless communication device according to claim 2,
A transmission signal acquisition means for acquiring a transmission signal;
Transmission signal correction means for correcting the transmission signal based on one or more offsets acquired by the combined signal offset acquisition means;
Distribution output means for distributing and outputting the transmission signal corrected by the transmission signal correction means to each antenna;
Post-distributed transmission signal offset means for offsetting the transmission signals distributed and output to the respective antennas based on one or more offsets for each of the signals received by the respective antennas acquired by the received signal offset acquiring means. When,
The wireless communication device further comprising:

Images