JP5111019B2 - Offset correction method and communication apparatus using the same - Google Patents

Description

  The present invention relates to a technique for correcting an offset in wireless communication, and more particularly to an offset correction method suitable for OFDMA (Orthogonal Frequency Division Multiple Access) and a communication apparatus using the same.

In mobile communication systems such as PHS (Personal Handyphone System), radio wave propagation delay time depends on the distance from the base station (CS: Cell Station) to the terminal (PS: Personal Station). In the signal from the terminal device received by the station device, a shift (hereinafter, timing offset) occurs with respect to the reference time in the base station device. The presence of such a timing offset leads to a decrease in signal transmission quality. Therefore, after establishing timing synchronization with the terminal device, the base station device allocates a communication channel TCH (Traffic Channel) for transmitting and receiving data to the terminal device. For this reason, the base station apparatus is assigned a specific control channel CCH (Control Channel), for example, a radio resource acquisition request SCCH (Signaling Control Channel) in which the terminal apparatus requests the base station apparatus to allocate radio resources. Based on the received message in the time slot, a timing offset with the terminal device is detected, and a message instructing correction of the timing offset is transmitted to the terminal device. (For example, Patent Document 1)
JP 2006-507753

  By the way, the amount of information that can be used to instruct the correction of the timing offset is defined in advance, and the amount of timing offset that the base station apparatus can instruct the terminal apparatus to perform correction is limited. On the other hand, the timing offset amount to be corrected can take various values according to the relative positional relationship between the base station apparatus and the terminal apparatus. For this reason, the base station apparatus may transmit a message instructing correction of timing offset in a plurality of times before establishing synchronization of timing with the terminal apparatus, and establishes synchronization in a short required time. It was difficult.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an offset correction method for shortening a required time until establishment of synchronization and a communication apparatus using the offset correction method.

  One embodiment of the present invention is a communication device. The communication device includes a detection unit that detects a deviation amount for a known signal included in a signal received from a communication target communication device, and the communication target communication device that instructs the correction of the deviation amount. In view of this, the gist includes a correction unit that corrects a transmission target signal and a transmission unit that transmits the transmission target signal to the communication target communication device.

  In addition, the communication device includes a calculation unit that calculates a statistic regarding the variation in the detected deviation amount, and a generation unit that generates a message that instructs the communication target communication device to correct the deviation amount. The transmission unit includes the message in the transmission target signal and transmits the message to the communication target communication device, and the correction unit preliminarily defines a threshold value related to the statistic. If the amount is greater than the threshold, it is desirable not to perform the correction.

  In addition, the detection unit generates a timing offset indicating a difference between a start timing of the first known signal defined by the communication apparatus and a start timing of the second known signal included in the received signal by the timing offset. (2) It is preferable that detection is performed based on a first phase rotation amount in a frequency domain added to a known signal, and the correction unit corrects the transmission target signal so as to superimpose the first phase rotation amount.

  In addition, the detection unit generates a frequency offset indicating a deviation between a frequency of the first known signal defined by the communication device and a frequency of the second known signal included in the received signal, according to the frequency offset. It is preferable to detect the second phase rotation amount in the time domain added to the signal, and the correction unit corrects the transmission target signal so as to superimpose the second phase rotation amount.

  Another aspect of the present invention is also a communication device. The communication device includes a detection unit that detects a deviation amount for a known signal included in a signal received from a communication device that is a communication target, a correction unit that corrects a transmission target signal so as to cancel the deviation amount, It is desirable to include a transmission unit that transmits a transmission target signal to the communication target communication device.

  The communication device further includes an extraction unit that extracts a message from the communication target communication device instructing correction of the deviation amount from the received signal, and the correction unit has the detected deviation amount. When the positive / negative direction to be corrected is different from the positive / negative direction to be corrected indicated by the extracted message, it is preferable to execute the correction based on an instruction of the message.

  According to the present invention, the communication device corrects the transmission target signal so as to superimpose the detected deviation amount of the known signal, and transmits the corrected transmission target signal to the communication target communication device. Since the offset correction is performed so as to cancel out the error, the communication device does not need to send the message for instructing the offset correction to the communication device to be communicated in multiple times, and the time required for establishing synchronization is shortened. it can.

(First embodiment)
The outline will be described before the present invention is specifically described. The embodiment of the present invention is a base station apparatus that connects a plurality of terminal apparatuses by the TDMA-TDD system, as in the second generation cordless telephone system. In the second generation cordless telephone system, as shown in FIG. 1, a TDMA frame (hereinafter referred to as a TDMA frame) is composed of four time slots for uplink communication (terminal device to base station device) and four time slots for downlink communication (base station device to terminal device). Frame), and the frames are continuously arranged.

  Further, as shown in FIG. 2, the base station apparatus also applies OFDMA and allocates a plurality of terminal apparatuses to one time slot. FIG. 2 shows the arrangement of time slots on the time axis in the direction of the horizontal axis, and the arrangement of subchannels on the frequency axis in the direction of the vertical axis. That is, the multiplexing on the horizontal axis corresponds to TDMA, and the multiplexing on the vertical axis corresponds to OFDMA. FIG. 2 includes the first time slot (shown as T1 in the figure) to the fourth time slot (shown as T4 in the figure) in one frame. FIG. 2 includes the first subchannel (indicated as SC1 in the figure) to the 16th subchannel (indicated as SC16 in the figure) in each time slot. In FIG. 2, the terminal apparatus A is in the second subchannel of the first time slot, the terminal apparatus B is in the second subchannel to the fourth subchannel of the second time slot, and the terminal apparatus is in the 16th subchannel of the third time slot. C and terminal equipment D are assigned to the 13th to 15th subchannels of the fourth time slot, respectively. In FIG. 2, the first subchannel is reserved as a control channel CCH dedicated subchannel. In the figure, the first base station apparatus uses the control channel CCH assigned to the first subchannel of the first time slot. Yes.

  Here, the control channel CCH includes a broadcast channel BCCH indicating the start of system information, an incoming call information channel PCH, and a channel assignment control channel SCCH. Further, the channel assignment control channel SCCH includes a radio resource acquisition request SCCH in which a terminal device requests radio resource assignment, and a radio resource assignment SCCH in which a base station device responds. The base station apparatus intermittently transmits and receives these channels at predetermined time intervals (for example, 20 frame intervals) in the subchannel of the time slot to which the control channel CCH is allocated, that is, the subchannel block, and between the terminal apparatuses. Send and receive control information.

  FIG. 3 is a conceptual diagram showing a configuration of a subchannel block specified by a time slot and a subchannel in FIG. The horizontal direction in FIG. 3 is the time axis, and the vertical direction is the frequency axis. The numbers “1” to “29” indicate subcarrier numbers. In this way, the subchannel is composed of OFDM multicarrier signals. In the figure, “TS” corresponds to a training symbol, and includes known signals such as a symbol “STS” for synchronization detection and a symbol “LTS” for estimation of channel characteristics. “GS” corresponds to a guard symbol, and no effective signal is arranged here. “PS” corresponds to a pilot symbol, and is configured by a known signal. “SS” corresponds to a signal symbol, and a control signal is arranged. “DS” corresponds to a data symbol and is data to be transmitted. “GT” corresponds to a guard time, and no effective signal is arranged.

  The base station device performs communication with the terminal device by assigning a subchannel block that can be used as the communication channel TCH to the terminal device. Here, there is a timing offset due to the relative positional relationship from the base station apparatus and the like with the terminal apparatus. Therefore, when a base station apparatus receives a message from a terminal apparatus in a subchannel block to which a specific control channel CCH (for example, a radio resource acquisition request SCCH) is assigned, the base station apparatus uses a training symbol of the subchannel block. The timing offset with the terminal device is detected. Then, after instructing the terminal device to perform the correction and establishing synchronization with the terminal device, the communication channel TCH is assigned. Here, if the timing offset correction instruction is performed using a message from the upper network layer, for example, the MAC layer, only a predetermined timing offset amount can be expressed. The message needs to be transmitted separately, and the time required to establish synchronization becomes longer.

  Therefore, in the base station apparatus according to the embodiment of the present invention, a timing offset is detected for a known signal included in a signal received from the terminal apparatus, and this timing offset is superimposed on the transmission target signal and transmitted to the terminal apparatus. . As a result, the terminal device can realize the timing offset correction by detecting the timing offset of the known signal included in the signal transmitted from the base station device, and canceling this timing offset. The required time can be shortened.

  FIG. 4 is a conceptual diagram showing a configuration of the mobile communication system 10 according to the embodiment of the present invention. The mobile communication system includes a base station device 1 and a terminal device 2. In FIG. 4, three terminals, ie, the first terminal apparatus 2a, the second terminal apparatus 2b, and the third terminal apparatus 2c, which are collectively referred to as the terminal apparatus 2, are illustrated, but there are two or less or four or more terminal apparatuses. May be.

  The base station apparatus 1 connects the terminal apparatus 2 to one end via a wireless network, and connects a wired network (not shown) to the other end. The terminal device 2 is connected to the base station device 1 via a wireless network. The base station device 1 executes communication with the plurality of terminal devices 2 by assigning the communication channel TCH to the plurality of terminal devices 2. Specifically, the terminal apparatus 2 transmits a radio resource acquisition message in the subchannel block to which the radio resource acquisition request SCCH is allocated, and the base station apparatus 1 transmits to the terminal apparatus 2 according to the received acquisition message. Assign communication channel TCH.

  FIG. 5 is a conceptual diagram showing a configuration of a communication apparatus that executes communication processing in the base station apparatus 1 of FIG. In FIG. 5, an antenna 100 transmits and receives radio frequency signals.

  Radio section 101 performs frequency conversion on the baseband signal from transmission / reception section 102 as a transmission operation, derives a radio frequency multicarrier signal, and transmits it via antenna 100. In addition, as a reception operation, the radio frequency multicarrier signal received by the antenna 100 is frequency-converted to derive a baseband signal and output it to the transmission / reception unit 102. Note that the baseband signal is formed of an in-phase component (In-phase) and a quadrature component (Quadrature-phase), but only one signal line is shown in FIG. 5 to simplify the description. The wireless unit 101 includes an AGC (Auto Gain Control) and an A / D (Analog / Digital) conversion unit.

  The transmission / reception unit 102 allocates the frequency domain signal transmitted from the modulation / demodulation unit 103 to a predetermined subchannel according to an instruction from the control unit 105 as a transmission operation. Here, the subchannel includes a plurality of subcarriers. That is, the transmission / reception unit 102 assigns a frequency domain signal to a plurality of subcarriers for each subchannel, thereby forming a frequency domain multicarrier signal. The transmission / reception unit 102 converts this into a time domain signal and outputs it to the radio unit 101. Note that IFFT (Inversed Fast Fourier Transform) is used for the conversion from the frequency domain signal to the time domain signal. The transmission / reception unit 102 also adds a guard interval.

  The transmission / reception unit 102 converts the time-domain signal transmitted from the radio unit 101 as a reception operation into a multi-carrier signal in the frequency domain. The transmission / reception unit 102 separates this into frequency domain signals for each subcarrier, and outputs them to the demodulation unit 105. Note that FFT (Fast Fourier Transform) is used for conversion from a time-domain signal to a frequency-domain multicarrier signal. The transmission / reception unit 102 also deletes the guard interval and sets the FFT window position.

  The modulation / demodulation unit 103 modulates the input from the IF unit 104 as a transmission operation and outputs the result to the transmission / reception unit 102. As a modulation method, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 32QAM, 64QAM, 256QAM, or the like is used. Further, the modem unit 103 adds control information received from the control unit 105 to the input from the IF unit 104, and forms a PDU (Protocol Data Unit) of each network layer in order from the upper network layer, The signal finally stored in the data symbols of the subchannel block is configured.

  The modulation / demodulation unit 103 demodulates the input from the transmission / reception unit 102 as a reception operation and outputs the result to the IF unit. Further, the modem unit 103 extracts control information of each network layer in order from the lower network layer in response to the input from the transmission / reception unit 102 and outputs the control information to the control unit 105.

  The IF unit 104 is connected to a network (not shown), inputs data from the network as a transmission operation, and outputs the data to the modem unit 103. The IF unit 104 outputs the signal demodulated by the modem unit 103 as a reception operation to a network (not shown).

  The control unit 105 performs control of the timing of the base station apparatus 1 as a whole. The control unit 105 also controls the transmission / reception unit 102 to execute offset notification control. Specifically, when a radio resource acquisition message is received from the terminal device 2 in the subchannel block to which the radio resource acquisition request SCCH is allocated, the control unit 105 controls the transmission / reception unit 102 to control the base station device 1 and the terminal. A timing offset with respect to the device 2 is detected. Then, the detected timing offset is superimposed on the control channel CCH storing the response message, that is, the signal of the subchannel block to which the radio resource allocation SCCH is allocated, and transmitted to the terminal device 2.

  FIG. 6 is a conceptual diagram of functional blocks that execute offset notification processing in the transmission / reception unit 102 of FIG. In FIG. 6, the FFT unit 200 sets the FFT window position and executes an FFT operation, and the IFFT unit 201 executes an IFFT operation.

  Here, the relationship between the timing offset included in the received signal and the amount of phase rotation generated in the frequency domain signal (hereinafter referred to as a symbol) when this signal is subjected to an FFT operation will be described.

  The signal just received

とし、この信号を正しいタイミングでFFT演算を行って算出したシンボルを

The symbol calculated by performing FFT calculation on this signal at the correct timing

とする。

And

  Since the received signal contained a timing offset, the FFT window position was moved backward.

だけ移動したとすると、この信号をFFT演算して算出したシンボルは、離散的フーリエ変換の推移定理により、

The symbol calculated by FFT calculation of this signal is calculated by the discrete Fourier transform transition theorem.

となる。すなわち、このときのシンボルには、正しいタイミングでFFT演算を行って算出したシンボルに対して、

It becomes. In other words, for the symbol at this time, the symbol calculated by performing the FFT operation at the correct timing,

で示される位相回転量が生じている。

The amount of phase rotation indicated by

  The phase rotation amount detection unit 202 detects the amount of phase rotation generated in the symbol due to the timing offset using the training symbol shown in FIG. Specifically, a training symbol is extracted from the input from the FFT unit 200, and a complex conjugate operation and an arc tangent operation are performed on the extracted training symbol to calculate a phase rotation amount between the training symbols. To do. At this time, the calculated phase rotation amount may be averaged, or the phase rotation amount of training symbols spaced apart may be calculated. This is because the influence of propagation environment and calculation error can be suppressed.

  The phase correction unit 203 performs phase correction on the input from the FFT unit 200 so as to cancel out the phase rotation amount detected by the phase rotation amount detection unit 202. Specifically, the arc tangent operation is performed on the symbol, the declination component when the symbol is expressed in polar coordinates is calculated, and the phase rotation amount detected by the phase rotation amount detection unit 202 is calculated from the declination component. Subtract.

  The offset correction unit 204 performs phase correction so that the phase rotation amount detected by the phase rotation amount detection unit 202 is superimposed on the input from the modem unit 103. Specifically, an arctangent operation is performed on the symbol, a declination component when the symbol is expressed in polar coordinates is calculated, and the phase rotation detected by the phase rotation amount detection unit 202 with respect to this declination component Add the amount.

  The offset notification control described so far corresponds to a function in the base station apparatus 1. On the other hand, in order to execute the correction of the timing offset, not only the base station device 1 but also the terminal device 2 needs to execute a predetermined operation. That is, the terminal apparatus 2 detects the amount of phase rotation superimposed on the transmission signal by the base station apparatus 1 and corrects the timing offset generated with the base station apparatus 1 based on the amount of phase rotation. Here, the operation is described as the operation of the terminal device 2, but this function may be included in the base station device 1.

  Note that the configuration of the communication device included in the terminal device 2 is the same type as that of the communication device shown in FIG. 5, and therefore only the differences will be described in the following description with reference to FIG.

  IF section 104 is connected to a voice decoding section (not shown) and the like, receives data from the voice coding section as a transmission operation, and outputs this to modulation / demodulation section 103. In addition, IF section 104 outputs the signal demodulated by modem 103 as a reception operation to a voice decoding section (not shown).

  The control unit 105 controls the timing of the entire terminal device 2 and the like. The control unit 105 also controls the transmission / reception unit 102 to execute offset correction control. Specifically, when receiving the radio resource assignment message from the base station apparatus 1 in the control channel CCH, that is, the subchannel block to which the radio resource assignment SCCH is assigned, the control unit 105 controls the transmission / reception unit 102 to The timing offset detected by the station device 1 is extracted. Then, the timing offset is corrected so as to cancel the extracted timing offset, and timing synchronization is established with the base station apparatus 1.

  Since the configuration of the functional block that executes the offset correction processing in the transmission / reception unit 102 is also the same type as the functional block shown in FIG. 6, only the differences will be described in the following description with reference to FIG.

  The offset correction unit 203 performs phase correction on the input from the modem unit 103 so as to cancel out the phase rotation amount detected by the phase rotation amount detection unit 201. Specifically, an arctangent operation is performed on the symbol, a declination component when the symbol is expressed in polar coordinates is calculated, and the phase rotation detected by the phase rotation amount detection unit 201 with respect to this declination component Subtract amount to correct timing offset.

  When transmitting a radio resource acquisition message to the base station apparatus 1, the control unit 105 performs control so that the offset correction unit 203 does not perform phase correction. If the offset correction unit 203 is operated before the timing offset generated between the base station apparatus 1 and the terminal apparatus 2 is notified, the timing offset detection accuracy in the base station apparatus 1 may deteriorate. It is for preventing.

  As described above, the base station apparatus 1 notifies the timing offset generated between the base station apparatus 2 and the signal transmitted to the terminal apparatus 2 in a superimposed manner. That is, the base station apparatus 1 issues a timing offset correction instruction at the PHY layer level. Then, the terminal device 2 corrects the timing offset based on the correction instruction at the PHY layer level, and establishes timing synchronization with the base station device 1. In this way, it is not necessary to issue a timing offset correction instruction at the MAC layer level where the amount of information that can be transmitted is limited, and rapid synchronization can be established.

  The operation of the mobile communication system 10 having the above configuration will be described. FIG. 7 is a sequence diagram showing a timing offset correction procedure based on a PHY layer level correction instruction.

  The terminal apparatus 2 transmits a radio resource acquisition message to the base station apparatus 1 in the subchannel block to which the radio resource acquisition request SCCH is allocated (S100). When the base station apparatus 1 receives the radio resource acquisition message in the subchannel block to which the radio resource acquisition request SCCH is allocated, the base station apparatus 1 calculates the phase rotation amount using the training symbol of the subchannel block, and The timing offset generated in step S101 is detected (S101). This amount of phase rotation is superimposed on the transmission signal of the allocation message corresponding to the acquisition message, and the timing offset control value is added to the transmission signal at the PHY layer level (S102). Then, the base station apparatus 1 transmits this allocation message in the subchannel block to which the radio resource allocation SCCH is allocated (S103). When the terminal device 2 receives the assignment message, the terminal device 2 calculates the amount of phase rotation using the training symbol of the subchannel block, and extracts the control value of the timing offset. The terminal device 2 executes timing offset correction with the control value (S104), and establishes timing synchronization in the communication channel TCH with the base station device 1 (S105).

  According to such an embodiment of the present invention, the following operational effects can be enjoyed.

  The phase rotation amount detection unit 202 detects the phase rotation amount caused by the timing offset using the training symbol of the subchannel block that has received the radio resource acquisition message, and the offset correction unit 204 assigns an allocation message corresponding to the acquisition message. The amount of phase rotation is superimposed on the transmitted signal. For this reason, even when the detected timing offset amount is large, there is no need to issue a correction instruction to the terminal device 2 in multiple steps, and it is necessary to establish timing synchronization with the terminal device 2. Time can be shortened.

(Second Embodiment)
A second embodiment of the present invention will be described. Similar to the first embodiment, the second embodiment also relates to an offset correction method. Here, between the terminal device and the base station device, in addition to the timing offset, the terminal device and the base station device perform processing with independent local oscillators. There is also a frequency offset. When such a frequency offset occurs, interference may occur between subcarriers, and transmission characteristics may deteriorate. Here, when a frequency offset is generated, a phase rotation amount in the time domain is generated in the signal received by the base station apparatus.

  Therefore, the base station apparatus according to the second embodiment detects a frequency offset of a known signal included in the signal received from the terminal apparatus, superimposes this frequency offset on the transmission target signal, and transmits the signal to the terminal apparatus. As a result, if the terminal device detects the frequency offset of the known signal included in the signal transmitted from the base station device and performs control so as to cancel this frequency offset, frequency offset correction can be realized. The time required for establishment can be shortened.

  Since the configuration of the base station apparatus 1 in the second embodiment is the same type as that of the base station apparatus 1 in the first embodiment, only the differences will be described in the following description.

  The control unit 105 controls the transmission / reception unit 102 to execute offset notification control. Specifically, when a radio resource acquisition message is received from the terminal device 2 in the subchannel block to which the radio resource acquisition request SCCH is allocated, the control unit 105 controls the transmission / reception unit 102 to control the base station device 1 and the terminal. A frequency offset between the apparatus 2 is detected. Then, the detected frequency offset is superimposed on the control channel CCH storing the response message, that is, the signal of the subchannel block to which the radio resource allocation SCCH is allocated, and transmitted to the terminal device 2.

  FIG. 8 is a conceptual diagram of functional blocks that execute offset notification processing in the transmission / reception unit 102 of FIG. 6 is compared with the functional block of FIG. 8, in FIG. 8, the phase rotation amount detection unit 202 and the phase correction unit 203 are arranged in the preceding stage of the FFT unit 200, and the offset correction unit is placed in the subsequent stage of the IFFT unit 201. The configuration in which 204 is arranged is different.

  The phase rotation amount detection unit 202 detects the phase rotation amount generated in the known signal due to the frequency offset, using the known signal in the time domain corresponding to the training symbol shown in FIG.

  The phase correction unit 203 performs phase correction on the input from the radio unit 100 so as to cancel out the phase rotation amount detected by the phase rotation amount detection unit 202.

  The offset correction unit 204 performs phase correction so that the phase rotation amount detected by the phase rotation amount detection unit 202 is superimposed on the input from the IFFT unit 201.

  In addition, in order to detect the amount of phase rotation in the time domain, the same configuration as in FIG. 6 can be used, and a symbol can be the processing target. In this case, the phase rotation amount detection unit 202 detects the phase rotation amount in the time domain using the pilot symbol shown in FIG.

  The terminal device 2 in the second embodiment detects the phase rotation amount superimposed on the transmission signal by the base station device 1, and corrects the frequency offset generated between the base station device 1 and the base station device 1 based on the phase rotation amount. Execute.

  The operation of the mobile communication system 10 having the above configuration will be described with reference to the sequence diagram of FIG.

  The terminal apparatus 2 transmits a radio resource acquisition message to the base station apparatus 1 in the subchannel block to which the radio resource acquisition request SCCH is allocated (S100). When the base station apparatus 1 receives the radio resource acquisition message in the subchannel block to which the radio resource acquisition request SCCH is assigned, the base station apparatus 1 calculates the phase rotation amount using a time domain known signal corresponding to the training symbol of the subchannel block. Then, the frequency offset generated between the terminal device 2 is detected (S101). This phase rotation amount is superimposed on the transmission signal of the allocation message corresponding to the acquisition message, and the control value of the frequency offset is added to the transmission signal at the PHY layer level (S102). Then, the base station apparatus 1 transmits this allocation message in the subchannel block to which the radio resource allocation SCCH is allocated (S103). When the terminal device 2 receives the allocation message, the terminal device 2 calculates the amount of phase rotation using a known signal in the time domain corresponding to the training symbol of the subchannel block, and the control value of the timing offset instructed by the base station device 1 To extract. The terminal device 2 executes timing offset correction with the control value (S104), and establishes timing synchronization in the communication channel TCH with the base station device 1 (S105).

  According to such an embodiment of the present invention, the following operational effects can be enjoyed.

  The phase rotation amount detection unit 202 detects a phase rotation amount caused by the frequency offset using a known signal in the time domain corresponding to the training symbol of the subchannel block that has received the radio resource acquisition message, and the offset correction unit 204 The phase rotation amount is superimposed on the transmission signal of the assignment message corresponding to the acquisition message. For this reason, even when the detected frequency offset amount is large, there is no need to issue a correction instruction to the terminal device 2 in a plurality of times, and until the frequency synchronization with the terminal device 2 is established. Time required can be shortened.

(Third embodiment)
A third embodiment of the present invention will be described. The third embodiment also relates to an offset correction method as in the first or second embodiment. Here, the offset such as the timing offset detected by the base station device includes an offset depending on the terminal device and an offset depending on the propagation environment such as multipath. When the ratio of the offset depending on the propagation environment increases, the transmission signal at the PHY layer level is easily affected by this, and the reliability when notifying the offset depending on the terminal apparatus may be reduced. On the other hand, since the MAC layer level transmission signal (hereinafter appropriately referred to as a message) is not easily affected, it is possible to accurately notify the offset depending on the terminal device.

  Here, since the offset depending on the propagation environment has a larger variation rate than the offset depending on the terminal device, the offset is detected by referring to a statistic (for example, variance) regarding the offset variation detected by the base station device. The contribution ratio to the offset can be estimated to some extent.

  Therefore, in the base station apparatus according to the third embodiment, an offset is detected for a known signal included in a signal received from a terminal apparatus, and the variance is calculated from these offsets. If the variance is larger than the threshold, the offset detected using the transmission signal at the MAC layer level is notified to the terminal device. On the other hand, if the variance is smaller than the threshold value, the terminal device is notified of the offset detected using the transmission signal at the PHY layer level. As a result, it is possible to switch between the offset correction instruction at the MAC layer level that can improve reliability and the offset correction instruction at the PHY layer level that can reduce the required time according to the influence of the propagation environment. Establishing efficient synchronization.

  Since the configuration of the base station apparatus 1 in the third embodiment is the same type as that of the base station apparatus 1 in the first or second embodiment, only the differences will be described in the following description.

  FIG. 9 is a flowchart showing a procedure for switching the offset correction instruction in the base station apparatus 1.

  When a radio resource acquisition message is received from the terminal device 2 in the subchannel block to which the radio resource acquisition request SCCH is allocated, the control unit 105 controls the transmission / reception unit 102 to establish a connection between the base station device 1 and the terminal device 2. Is detected, and an offset control value for instructing the terminal device 2 to perform offset correction is calculated. (S200). Then, the variance is calculated from the detected phase rotation amount (S201). Then, this variance is compared with a threshold related to the variance (S202). If the variance is smaller than the threshold (N in S202), the control channel CCH storing the response message, that is, the radio resource allocation SCCH is assigned. The detected phase rotation amount is superimposed on the subchannel block signal, that is, an offset control value is added to the transmission signal at the PHY layer level and transmitted to the terminal apparatus 2 (S204).

  On the other hand, if the variance is greater than the threshold (Y in S202), the calculated offset control value is stored in the response message, and the response message is stored in the data symbol of the subchannel block to which the radio resource allocation SCCH is allocated. In other words, the offset control value is stored in the transmission signal at the MAC layer level and transmitted to the terminal device 2 (S203).

  FIG. 10 is a conceptual diagram of a message format transmitted / received in the MAC layer when radio resources are allocated. FIG. 10A shows a radio resource acquisition message format. In the figure, “message identifier” identifies the type of message, and “service flow identifier” identifies the service flow assigned to the terminal device 2.

  FIG. 10B shows a radio resource allocation message format. In the figure, “message identifier” identifies the type of message, “service flow identifier” identifies the service flow assigned to the terminal device 2, and “slot number” and “subchannel number” are assigned to the terminal device 2. Specifies the assigned subchannel block. “Offset control” stores a control value of the offset. Further, when the offset control value is stored in the “offset control”, the control unit 105 includes identification information for identifying the fact in the “offset control”.

  The terminal device 2 refers to this identification information included in the “offset control” of the received assignment message, so that the base station device 1 adds the offset control value to the transmission signal at the PHY layer level, or at the MAC layer level. It is determined whether an offset control value is stored in the transmission signal, and an offset correction process corresponding to that is executed.

  The operation of the mobile communication system 10 having the above configuration will be described. FIG. 11 is a sequence diagram showing the synchronization establishment procedure when the offset correction instruction is switched.

  The terminal apparatus 2 transmits a radio resource acquisition message to the base station apparatus 1 in the subchannel block to which the radio resource acquisition request SCCH is allocated (S300). When the base station apparatus 1 receives the radio resource acquisition message in the subchannel block to which the radio resource acquisition request SCCH is allocated, the base station apparatus 1 calculates the phase rotation amount using the training symbol of the subchannel block, and The offset generated in step S301 is detected (S301). Then, the variance of the phase rotation amount is calculated, and it is determined whether this phase rotation amount is notified by the PHY layer or the MAC layer (S302). When notifying in the PHY layer, this phase rotation amount is superimposed on the transmission signal of the allocation message corresponding to the acquisition message, and when notifying in the MAC layer, the offset corresponding to the phase rotation amount in the “offset control” of the allocation message. The control value is stored (S303). The terminal device 2 refers to the identification information included in the “offset control” of the received allocation message, executes offset correction indicated by the identification information (S304), and communicates with the base station device 1 through the communication channel. Timing synchronization in TCH is established (S305).

  According to such an embodiment of the present invention, the following operational effects can be enjoyed.

  The phase rotation amount detection unit 202 detects the phase rotation amount using the training symbol of the subchannel block that has received the radio resource acquisition message, and the control unit 105 calculates the dispersion of the phase rotation amount. Then, the control unit 105 compares this variance with a threshold value. If the variance is smaller than the threshold value, the control unit 105 controls the offset correction unit 204 to superimpose the phase rotation amount on the transmission signal of the allocation message corresponding to the acquired message. To do. On the other hand, if it is larger than the threshold value, the modem unit 103 is controlled and stored in the allocation message. For this reason, the offset correction instruction can be switched according to the propagation environment, and efficient synchronization with the terminal device 2 can be established.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. Similar to the third embodiment, the present invention relates to an offset correction method. Here, depending on the propagation environment, it is better to select the offset control value notified by the appropriate notification method in the terminal device that is the notification destination, rather than switching the notification method in the base station device that is the notification source of the offset control value. May be preferred.

  Therefore, the base station apparatus in the fourth embodiment detects an offset for a known signal included in the signal received from the terminal apparatus. Then, the offset detected using the transmission signals at the PHY layer level and the MAC layer level is notified to the terminal device. On the other hand, the terminal apparatus delays the timing if the offset control value notified by the PHY layer level transmission signal and the offset control value notified by the MAC layer level transmission signal should be corrected (if timing offset, Whether the oscillation frequency is increased or decreased if it is a frequency offset). When the positive and negative directions to be corrected are different, the offset correction is executed based on the instruction of the offset control value notified at the MAC layer level with higher reliability. Thereby, offset correction based on an appropriate correction instruction can be executed in accordance with the influence of the propagation environment, so that establishment of accurate synchronization can be realized.

  Since the configuration of the terminal device 2 in the third embodiment is the same type as the terminal device 2 in the third embodiment, only the differences will be described in the following description.

  FIG. 12 is a flowchart illustrating a procedure for selecting an offset correction instruction in the terminal device 2.

  When a radio resource allocation message is received from the base station apparatus 1 in the subchannel block to which the radio resource allocation SCCH is allocated, the control unit 105 controls the transmission / reception unit 102 to connect the base station apparatus 1 and the terminal apparatus 2. Is detected, and the offset control value notified by the PHY layer level transmission signal is extracted (S400). Next, the control unit 105 controls the modem unit 103 to extract the offset control value notified by the MAC layer level transmission signal from the “offset control” of the assignment message (S401). The control unit 105 compares the signs of the two offset control values and checks whether the positive and negative directions to be corrected are different (S402). When the directions to be corrected are different (S403), the terminal apparatus 2 executes offset correction based on the offset control value notified by the MAC layer level transmission signal (S403). On the other hand, when the positive and negative directions to be corrected are the same (S404), the terminal apparatus 2 executes offset correction based on the offset control value notified by the transmission signal at the PHY layer level (S404).

  The operation of the mobile communication system 10 having the above configuration will be described. FIG. 13 is a sequence diagram showing a synchronization establishment procedure when an offset correction instruction is selected.

  The terminal apparatus 2 transmits a radio resource acquisition message to the base station apparatus 1 in the subchannel block to which the radio resource acquisition request SCCH is allocated (S500). When the base station apparatus 1 receives the radio resource acquisition message in the subchannel block to which the radio resource acquisition request SCCH is allocated, the base station apparatus 1 calculates the phase rotation amount using the training symbol of the subchannel block, and The offset generated in step S501 is detected (S501). Then, an offset control value corresponding to the phase rotation amount is added to the transmission signal at the PHY layer level and the MAC layer level, and notified to the terminal device 2 (S503). The terminal device 2 extracts the offset control values added to the transmission signals at the PHY layer level and the MAC layer level, and checks whether the positive and negative directions to be corrected indicated by these offset control values are different. If the positive and negative directions to be corrected are different, offset control is executed based on the offset control value notified by the MAC layer level transmission signal (504), and the communication channel with the base station apparatus 1 is executed. Timing synchronization in TCH is established (S505).

  According to such an embodiment of the present invention, the following operational effects can be enjoyed.

  The control unit 105 controls the transmission / reception unit 102, detects the amount of phase rotation using the training symbol of the subchannel block that has received the radio resource allocation message, and sets the offset control value notified by the transmission signal at the PHY layer level. Extract. Also, the control unit 105 controls the modem unit 103 to extract an offset control value notified by a MAC layer level transmission signal from the assignment message. Then, the positive and negative directions indicated by the two offset control values are confirmed, and if they are different, offset correction is executed based on the offset control value notified by the MAC layer level transmission signal. For this reason, it is possible to select an appropriate offset correction instruction according to the propagation environment, and it is possible to realize accurate synchronization with the terminal device 1.

  Although the best mode for carrying out the present invention has been described above, the present invention is not limited to the configuration of this embodiment, and the scope of application of the present invention defined in the claims. As long as the functions of the configuration of the above-described embodiment can be achieved, various modifications are possible.

  For example, in the embodiment of the present invention, the phase correction is performed by calculating a declination component in polar coordinates using arctangent calculation, but an FIR (Finite Impulse Response) filter including a predetermined multiplier and adder is used. You may implement | achieve using etc.

  Further, in the embodiment of the present invention, the terminal apparatus differs in the positive and negative directions to be corrected between the offset control value notified by the PHY layer level transmission signal and the offset control value notified by the MAC layer level transmission signal. The offset correction was performed based on the instruction of the offset control value notified at the MAC layer level, but the difference between the offset control values notified by the PHY layer level and MAC level transmission signals is fed back to the base station apparatus. May be. While transmission signals at the PHY layer level are easily affected by the propagation environment, transmission signals at the MAC layer level are not easily affected, so by observing these differences, the base station device estimates the propagation environment. This is because it can be used as one of the indexes of radio resource allocation.

Conceptual diagram showing the TDMA frame structure Conceptual diagram showing time-multiplexed time slots by OFDMA Conceptual diagram showing the configuration of the subchannel block The conceptual diagram which shows the structure of the communication system which concerns on embodiment of this invention The conceptual diagram which shows the structure of the base station apparatus which concerns on embodiment of this invention Conceptual diagram of functional block for executing offset notification processing Sequence diagram showing the timing offset correction procedure based on PHY layer level correction instructions Conceptual diagram of a functional block that executes offset notification processing of different configurations The flowchart which shows the switching procedure of the offset correction instruction | indication in a base station apparatus Conceptual diagram of message format sent and received in the MAC layer Sequence diagram showing the procedure for establishing synchronization when switching the offset correction instruction The flowchart which shows the selection procedure of the offset correction instruction | indication in a terminal device Sequence diagram showing the procedure for establishing synchronization when selecting an offset correction instruction

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Radio | wireless part 102 Transmission / reception part 103 Modulation / demodulation part 104 IF part 105 Control part 200 FFT part 201 IFFT part 202 Phase rotation amount detection part 203 Phase correction part 204 Offset correction part

Claims (4)

A detection unit for detecting a deviation amount of a known signal included in a signal received from a communication device to be communicated;
A correction unit that corrects the transmission target signal of the local station in consideration of the deviation amount in order to cause the communication target communication device to correct the deviation amount;
A transmission unit that transmits the transmission target signal to the communication target communication device;
A calculation unit for calculating a statistic regarding the variation of the detected deviation amount;
A generating unit that generates a message for instructing correction of the shift amount to the communication target communication device ;
When the statistic is greater than a threshold related to the statistic defined in advance, the transmission unit includes the message in the transmission target signal and transmits the message to the communication target communication device,
The communication device , wherein the correction unit corrects the transmission target signal when the statistic is smaller than the threshold value . The detection unit uses a timing offset indicating a difference between a start timing of the first known signal defined by the communication device and a start timing of the second known signal included in the received signal as a second known by the timing offset. Detected by the first phase rotation amount in the frequency domain added to the signal,
Wherein the correction unit, the first so as to overlap the phase rotation amount, the communication apparatus according to claim 1, characterized in that for correcting the signal of the transmission object. The detection unit converts a frequency offset indicating a difference between a frequency of the first known signal defined by the communication device and a frequency of the second known signal included in the received signal into the second known signal by the frequency offset. Detected by the second phase rotation amount added in the time domain,
Wherein the correction unit, the second to overlap the phase rotation amount, the communication apparatus according to claim 1, characterized in that for correcting the signal of the transmission object. A detection unit for detecting a deviation amount of a known signal included in a signal received from a communication device to be communicated;
A correction unit that corrects a signal to be transmitted so as to cancel out the deviation amount;
A transmission unit that transmits the transmission target signal to the communication target communication device;
An extraction unit that extracts a message from the communication target communication device that instructs correction of the deviation amount from the received signal;
The correction unit performs the correction based on an instruction of the message when a positive / negative direction to be corrected indicated by the detected deviation amount is different from a positive / negative direction to be corrected indicated by the extracted message. A communication device characterized by the above.

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