JP6189764B2 - Communication apparatus and communication control method - Google Patents

Description

  The present invention relates to a communication device and a communication control method for controlling wireless communication.

  Conventionally, in the LTE (Long Term Evolution-Advanced) system, what controls transmission of an uplink signal is known even when Inter-band CA is performed in CA (Carrier Aggregation). (For example, refer to Patent Document 1).

  Specifically, a mobile station UE used in a mobile communication system configured to be able to perform carrier aggregation using a primary cell and a secondary cell selects a predetermined number of cells for each group including only secondary cells. In the selected cell, the radio link is monitored.

JP 2013-162327 A

  However, in the conventional communication apparatus, the radio link is monitored due to the deterioration of the signal quality, and no measures for improving the signal quality have been taken.

  Therefore, the present invention has been made to solve the conventional problems, and in a communication apparatus performing carrier aggregation, the transmission signal is transmitted under the influence of transmitting signals in different frequency bands within the communication apparatus. An object of the present invention is to provide a communication device and a communication control method that can appropriately correct a transmission signal when quality deteriorates.

  The communication device according to the present invention is a communication device that performs carrier aggregation in a first frequency band and a second frequency band, and a harmonic that affects the second frequency band from a transmission signal in the first frequency band. A component is calculated, and a harmonic correction unit that corrects the transmission signal of the second frequency band based on the harmonic component is provided.

  The communication device of the present invention is configured such that the harmonic correction unit performs the correction according to a difference between the transmission power of the first frequency band and the transmission power of the second frequency band.

  Moreover, the communication apparatus of this invention is comprised so that the said harmonic correction | amendment part may perform the said correction | amendment from the relationship between the said harmonic level and a threshold value.

  Further, the threshold value of the communication apparatus of the present invention is configured to be determined based on the MCS of the transmission signal in the first frequency band.

  The present invention provides a communication device and a communication control method capable of appropriately correcting a transmission signal when the quality of the transmission signal deteriorates due to the effect of transmitting signals of different frequency bands inside the communication device. It is.

It is a block diagram of the radio | wireless communications system which concerns on embodiment of this invention. It is a block diagram of the relay apparatus which concerns on embodiment of this invention. It is a block diagram of the radio | wireless terminal which concerns on embodiment of this invention. It is a figure showing a mode that the power of the transmission signal with a high transmission power level leaks to the transmission signal with a low transmission power level. It is a flowchart which shows operation | movement of the radio | wireless terminal which concerns on embodiment of this invention. . It is a flowchart which shows the transmission power monitoring operation | movement of the radio | wireless terminal which concerns on embodiment of this invention. It is a figure showing the relationship between MCS and the threshold value for correction determination. It is a flowchart which shows the leak occupation monitoring operation | movement of the radio | wireless terminal which concerns on embodiment of this invention. It is a flowchart which shows the signal correction processing operation | movement of the radio | wireless terminal which concerns on embodiment of this invention.

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

  FIG. 1 is a configuration diagram of a radio communication system according to an embodiment of the present invention. The radio communication system shown in FIG. 1 provides CA (Carrier Aggregation) by LTE (Long Term Evolution-Advanced) scheme.

  The radio communication system includes a base station 20a that performs radio communication in a frequency band A, a base station 20b that performs radio communication in a frequency band B, and a radio terminal 10 that communicates with the base station 20a and the base station 20b. In addition, when distinguishing each base station 20, it describes as base stations 20a and 20b, and when not distinguishing each, it describes as base station 20.

  In FIG. 1, the radio terminal 10 communicates with the base station 20a with an average transmission power A (PavgA), and communicates with the base station 20b with an average transmission power B (PavgB). In the wireless communication system, inter-band is performed in CA.

  FIG. 2 is a diagram showing each CA communication method.

  FIG. 2A shows an intra-band contiguous system, which has two continuous intraband signals in one frequency band.

  FIG. 2B shows an intra-band non-contiguous system, which has two discontinuous intraband signals in one frequency band.

  FIG. 2C shows an inter-band system, and has respective signals in different frequency bands.

  FIG. 3 is a configuration diagram of the radio terminal according to the embodiment of the present invention.

  The wireless terminal 10 includes a baseband unit 11, IFFT 12, harmonic correction unit 13, DAC 14, mixer 15, PA 16, DUPLEXER 17, DIPLEXER 18, and antenna 19. Although the wireless terminal 10 includes a receiving unit, the receiving unit is not the gist of the present invention, and thus the description thereof is omitted.

  The baseband unit 11a processes communication data corresponding to the frequency band A. The baseband unit 11b processes communication data corresponding to the frequency band B.

  The IFFT 12a performs inverse Fourier transform on communication data corresponding to the frequency band A. The IFFT 12b performs inverse Fourier transform on communication data corresponding to the frequency band B.

  The harmonic correction unit 13 corrects the harmonics of the baseband signal output by the IFFT 12.

  Note that the baseband unit 11, the IFFT 12, and the harmonic correction unit 13 constitute a digital unit.

  The DAC 14a performs analog conversion of a baseband signal corresponding to the frequency band A. The DAC 14b performs analog conversion of a baseband signal corresponding to the frequency band B.

  The mixer 15a outputs a desired radio signal corresponding to the frequency band A. The mixer 15b outputs a desired radio signal corresponding to the frequency band B.

  The PA 16a amplifies a radio signal corresponding to the frequency band A. The PA 16a amplifies a radio signal corresponding to the frequency band B.

  The DUPLEXER 17a switches between transmission and reception of radio signals corresponding to the frequency band A. The DUPLEXER 17b switches between transmission and reception of radio signals corresponding to the frequency band B.

  The DIPLEXER 18 exists for coupling the DUPLEXER 17a and the DUPLEXER 17b, and transmits and receives radio signals to and from the antenna 19. At this time, the radio signal may leak to the other DUPLEXER 17 via the DIPLEXER 18 (in FIG. 3, the signal leaks from the DUPLEXER 17a to the DUPLEXER 17b).

  For example, when the wireless terminal 10 is communicating with the base station 20 a and the base station 20 b by CA, the base station 20 receives an instruction for transmission power control (Power Control). At this time, the level difference between the transmission power level of the base station 20a and the transmission power level of the base station 20b may increase depending on the communication status. When the level difference increases, the radio terminal 10 leaks transmission power harmonics (2nd Harmonics, 3rd harmonics) from the DUPLEXER 17 having the higher transmission power level to the DUPLEXER 17 having the lower transmission power level via the DIPLEXER 18. There is.

  As a result, leakage power is superimposed on a low output transmission signal, SNR: signal noise rate (or EVM: error vector amplitude) is deteriorated, and communication quality is deteriorated.

  FIG. 4 is a diagram illustrating a state in which the power of a transmission signal having a high transmission power level leaks to a transmission signal having a low transmission power level. In the frequency band A, the frequency is fA and the frequency width is ΔfA. In the frequency band B, the frequency is fB, and the frequency width is ΔfB.

  In FIG. 4A, the wireless terminal 10 transmits the average transmission power A (PavgA) corresponding to the base station 20a and the frequency band A. At this time, harmonics are generated, that is, leakage power (PhmA) is generated in a frequency band double the frequency band A.

  FIG. 4B illustrates a state in which the base station 20a and the transmitting wireless terminal 10 simultaneously transmit the base station 20b and the frequency band B with the average transmission power B (PavgB). .

  As a result, a state in which the leakage power and the transmission signal transmitted to the base station 20b are superimposed is shown in FIG. The average transmission power A is larger than the average transmission power B.

FIG. 5 is a flowchart showing the operation of the radio terminal according to the embodiment of the present invention.
The operation of the wireless terminal according to the embodiment of the present invention is composed of three operations: a transmission power monitoring operation (S1), a leakage occupation monitoring operation (S2), and a signal correction processing operation (S3). These operations will be described as operations of the digital unit (harmonic correction unit 13) of the wireless terminal according to the embodiment of the present invention.

  FIG. 6 is a flowchart showing a transmission power monitoring operation of the wireless terminal according to the embodiment of the present invention.

  In the carrier aggregation, the digital unit performs correction processing on the baseband signal so as to cancel out the harmonic distortion component under the condition that EVM degradation occurs so that the transmission power difference between the two frequency bands becomes large. . Note that this processing is not always performed to reduce power consumption of the wireless terminal. This is performed only when the transmission power difference at the time of carrier aggregation is large.

In step S11, the transmission power difference in each frequency band is monitored. The transmission power difference can be expressed by the following formula 1.
(Expression 1) Transmission power difference ΔPavg = (PavgA-PavgB)

  In step S12, when the transmission power difference is equal to or greater than a certain value, a PAPR (Peak to Average Power Ratio) in a signal having a larger transmission power is estimated. For example, if PavgA is larger, the PAPR of the signal in frequency band A is estimated, and if PavgB is larger, the PAPR of the signal in frequency band B is estimated.

  In step S13, a harmonic level ΔPhm when a leakage harmonic is generated is estimated from a harmonic generation polynomial or the like. As the harmonic level ΔPhm, for example, if PavgA is larger, Phm_A of the signal in frequency band A is estimated, and if PavgB is larger, Phm_B of the signal in frequency band B is estimated.

A general nth-order generator polynomial is as shown in Equation 2 below. In Equation 2, x is an input signal (a transmission signal generated in the baseband), and y is an output signal including a harmonic term.
(Formula 2) y (n) = a0 + a1 * x (n) + a2 * | x (n) | ^ 2 + a3 * | x (n) | ^ 3 +

  Since harmonics depend on the radio characteristics of each device, the order of the generator polynomial to be used and the coefficient for each order are determined in advance according to the radio characteristics. The second order coefficient is a2, and the third order coefficient is a3. For example, when the second harmonic influences, the second order term: a2 * | x (n) | ^ 2 may be set as the harmonic level. If the second and third harmonics are affected, the second order term: a2 * | x (n) | ^ 2 and the third order term: a3 * | x (n) | ^ 3 may be used as the harmonic level. .

  In step S14, a correction determination threshold value Pth is determined. Here, an example will be described in which the threshold value Pth is determined by MCS (Modulation and Coding Scheme) defined in LTE, that is, the modulation scheme (QPSK, 16QAM, 64QAM) and the error correction coding rate (Coding Rate). To do.

  FIG. 7 is a diagram illustrating the relationship between MCS and the threshold value for correction determination. Since the required SNR required for communication on the demodulator side differs depending on the MCS, the threshold for applying this processing differs depending on the MCS, and is calculated from the relationship between the required SNR and EVM. Using the relationship of FIG. 7, the threshold value Pth is determined according to the MCS currently used for the signal having the larger transmission power.

In step S15, it is determined whether or not the PAPR, harmonic level ΔPhm, and threshold value Pth obtained in the above-described steps satisfy the following (Equation 3).
(Formula 3) Pth <ΔPhm + PAPR

  If the condition of step S15 is satisfied, the process proceeds to the next step. If not satisfied, the process is periodically repeated from S11.

  FIG. 8 is a flowchart showing the leakage occupation monitoring operation of the wireless terminal according to the embodiment of the present invention.

  In step S21, a harmonic band of leakage in a signal having a higher transmission power level (for example, average transmission power Pavg) is calculated. For example, in LTE, the harmonic band generated from the reference block band is calculated. For example, if the transmission frequency fx is fA if the transmission power level of the frequency band A is high and fB if the transmission power level of the frequency band B is high, the transmission band is fx ± Δf / 2 (Δf is the bandwidth) In the case of the second harmonic, the harmonic band is 2fx ± Δf. In general, the n-th harmonic is n * (fx ± Δf / 2).

  In step S22, fy ± Δfy / 2 is calculated for the counterpart transmission band with the lower transmission power level. (Fy is fB if the transmission power level of frequency band A is high, and fA if the transmission power level of frequency band B is high).

In step S23, it is determined whether or not the harmonic band is superimposed on the counterpart transmission band. For example, when the harmonic band and the counterpart transmission band obtained above are used, it is determined whether or not there is one that satisfies the following conditional expressions (Expression 4) and (Expression 5).
(Expression 4) fy−Δfy / 2 <2fx + Δf <fy + Δfy / 2
(Expression 5) fy−Δfy / 2 <2fx−Δf <fy + Δfy / 2

  If the conditional expression of step S23 is satisfied, the process proceeds to the next step. If not satisfied, the process may be stopped or periodically monitored for power saving.

  FIG. 9 is a flowchart showing a signal correction processing operation of the wireless terminal according to the embodiment of the present invention.

  In step S <b> 31, the harmonic correction unit 13 calculates a harmonic component generated on the other party having the lower transmission power level. The harmonic component is calculated from, for example, a predetermined harmonic generation polynomial. The generator polynomial is as described above.

  In step S32, the harmonic correction unit 13 generates a correction signal that cancels the calculated harmonic component.

  In step S33, the harmonic correction unit 13 corrects the generated correction signal by adding it to the counterpart baseband signal. For example, when the second harmonic influences, the second order term: a2 * | x (n) | ^ 2 is added to the counterpart baseband signal so as to cancel out.

  As described above, the wireless terminal (communication device) according to the embodiment of the present invention performs carrier aggregation (based on the LTE-Advanced standard) for transmitting signals in different frequency bands within the communication device, and performs the first In order to calculate the harmonic component that affects the second frequency band from the transmission signal in the frequency band (with higher transmission power), and to correct the transmission signal in the second frequency band based on the harmonic component When the quality of the transmission signal of the wireless terminal deteriorates, the transmission signal can be corrected appropriately.

  In addition, the radio terminal according to the embodiment of the present invention performs correction when necessary by performing correction according to the difference between the transmission power of the first frequency band and the transmission power of the second frequency band. The power consumption of the wireless terminal can be reduced.

  Also, the radio terminal according to the embodiment of the present invention can correct the transmission signal appropriately by performing correction based on the relationship between the harmonic level and the threshold value.

  In addition, since the threshold value of the wireless terminal according to the embodiment of the present invention is determined based on the MCS of the transmission signal in the first frequency band, the reduction of power consumption required for the wireless terminal performing high data rate communication is considered. However, it can be performed at an appropriate timing for correcting the waveform quality.

10 Wireless terminal 11 Baseband part 12 IFFT
13 Harmonic correction part 14 DAC
15 Mixer 16 PA
17 DUPLEXER
18 DIPLEXER
19 antenna 20 base station

Claims (4)

In a communication device that performs carrier aggregation in the first frequency band and the second frequency band,
A harmonic that calculates a harmonic component that affects the second frequency band from the transmission signal in the first frequency band, and corrects the transmission signal in the second frequency band based on the harmonic component. With a correction unit ,
The said harmonic correction | amendment part is a communication apparatus which performs the said correction | amendment according to the difference of the transmission power of the said 1st frequency band, and the transmission power of the said 2nd frequency band . The harmonic correction unit, from the relationship between the level and the threshold of the harmonic, the communication apparatus according to claim 1 for pre SL correction.   The communication apparatus according to claim 2, wherein the threshold is determined based on MCS of a transmission signal in the first frequency band. In a communication control method for a communication apparatus that performs carrier aggregation in a first frequency band and a second frequency band,
Calculating a harmonic component that affects the second frequency band from the transmission signal of the first frequency band;
Correcting the transmission signal of the second frequency band based on the harmonic component according to the difference between the transmission power of the first frequency band and the transmission power of the second frequency band ;
A communication control method comprising: