JP2006101211A - Communication terminal apparatus and closed loop type transmission diversity method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the deterioration of transmitting/receiving signals due to multipath fading or the like which may be generated in delay time from the transmission of a feedback information by a mobile station apparatus up to the interpretation of the feedback information by a base station apparatus and the adjustment of weighting of respective antennas and to improve combined gain between respective antennas. <P>SOLUTION: An inter-antenna phase difference prediction part 108 predicts a phase difference between respective antennas at time that feedback information is reflected to the base station apparatus by using inter-antenna phase differences acquired at the time of transmitting feedback information outputted from a multiplication part 107 and in the past. An FBI generation part 109 generates feedback information to the base station apparatus based on the prediction result of the inter-antenna phase difference prediction part 108. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication terminal apparatus and a closed-loop transmission diversity method in a mobile communication system that implements closed-loop transmission diversity.

  In a mobile communication system, in order to eliminate the influence of multipath fading, a closed loop transmission diversity in which a base station apparatus transmits from a plurality of antennas and a received communication terminal apparatus transmits feedback information to the base station apparatus is provided. It has been adopted (Patent Document 1, Non-Patent Document 1). Here, in order to facilitate understanding of the present invention, a conventional communication terminal apparatus will be schematically described with reference to FIGS.

  FIG. 3 is a block diagram showing a configuration example of a communication terminal apparatus that transmits feedback information by closed-loop transmission diversity implemented in a conventional mobile communication system. In addition, in FIG. 3, the structural example of the communication terminal device in a CDMA mobile communication system is shown. Further, a base station apparatus (not shown) performs diversity transmission using two antennas (antenna # 1 and antenna # 2).

  Communication terminal apparatus 300 shown in FIG. 3 includes antenna section 301 that receives a radio signal from a base station apparatus, radio section 302 that downconverts the radio signal received by antenna section 301 and outputs a baseband signal, Despreading unit 303 that despreads the baseband signal output from unit 302, phase estimation unit 304 that measures the phase rotation amount of the signal after primary demodulation by despreading for antenna # 1, and despreading for antenna # 2 A phase estimation unit 305 that measures the amount of phase rotation of the signal after the primary demodulation by A, a complex conjugate calculation unit 306 that calculates a complex conjugate of the phase estimation result for antenna # 1 serving as a reference in closed-loop transmission diversity, and a complex conjugate The output of the calculation unit 306 (antenna # 1 phase estimation result) and the phase estimation unit 305 output (antenna # 2 phase estimation result) And a multiplier 307 that calculates the phase difference between the antennas, and an FBI generator 308 that generates feedback information FBI to the base station apparatus based on the phase difference between the antennas obtained by the multiplier 307. Yes.

A base station apparatus (not shown) adjusts the weight of each antenna using the phase difference between the antennas included in the received feedback information FBI, and transmits the downlink data signal by subtracting the known phase difference between the antennas. Thereby, in a communication terminal device, the phase difference between antennas of a reception data signal becomes small, and the synthetic | combination gain between antennas can be improved. This is closed-loop transmission diversity.
JP 2001-44900 A 3GPP TS 25.214

However, in the closed loop transmission diversity in the conventional mobile communication system,
There is a delay of approximately 100 μs to several hundred μs before the feedback information generated by the phase difference between antennas measured in the communication terminal device is interpreted in the base station device and the weight adjustment of each antenna is performed. There is a problem that deterioration due to multipath fading or the like occurring during that time cannot be reduced.

  Specifically, a description will be given with reference to FIG. FIG. 4 is a diagram showing the operation of closed-loop transmission diversity in the communication terminal apparatus configured as shown in FIG. 3 over time. In FIG. 4, “communication terminal uplink channel transmission” in which the communication terminal apparatus transmits feedback information FBI, “base station uplink channel reception” in which the base station apparatus receives the feedback information FBI, and feedback information received by the base station apparatus. “Base station downlink channel transmission” in which FBI is reflected in transmission data and transmission and “communication terminal downlink channel reception” in which the communication terminal apparatus receives transmission data in which feedback information FBI is reflected from the base station apparatus are from time T1 to time T1. It is shown in association with time T5.

  In FIG. 4, an uplink channel propagation delay 400 and a downlink channel propagation delay 401 exist between the communication terminal apparatus and the base station apparatus. The communication terminal apparatus measures the phase difference between the antennas at times T1, T2, and T4, generates feedback information FBI, and transmits it to the base station apparatus. In the base station apparatus, it is received after the propagation delay 400 has elapsed since the time when the communication terminal apparatus transmitted the feedback information FBI. The base station apparatus weights each antenna based on the received feedback information FBI and transmits data to the communication terminal apparatus. The time when the communication terminal apparatus measures the inter-antenna phase difference and transmits the feedback information FBI. Reflection delay of feedback information FBI of about several hundred to several hundred μs between T2 and time T3 when each antenna is weighted based on feedback information FBI received by the base station apparatus and data is transmitted to the communication terminal apparatus 402 exists. In the base station apparatus, the same operation is performed at time T5.

  Therefore, when the time transition of the phase difference between the antennas is a propagation path environment as shown in FIG. 4, the base station apparatus is based on the feedback information at time T3 with respect to the measured value of the phase difference between antennas measured at time T2. Thus, an error 403 occurs in the phase difference between the antennas when weighting each antenna. As a result, the base station apparatus cannot subtract all the phase differences between the antennas, and the combined gain between the antennas in the communication terminal apparatus deteriorates.

  The present invention has been made in view of such points, and in a mobile communication system employing closed-loop transmission diversity, the feedback information is interpreted by the base station apparatus after the communication terminal apparatus transmits the feedback information. A communication terminal device and a closed-loop transmission diversity method capable of reducing degradation of transmission / reception signals due to multipath fading, etc. occurring during delay until the weighting of each antenna is adjusted, and improving the combined gain between the antennas The purpose is to provide.

  In order to solve this problem, a communication terminal apparatus according to the present invention is a means for obtaining a phase difference between a plurality of antennas of a base station apparatus from a wirelessly received signal in a mobile communication system using closed-loop transmission diversity. And means for predicting the inter-antenna phase difference at the time when the feedback information is reflected in the base station apparatus using the inter-antenna phase difference acquired at the time of feedback information transmission and in the past, based on the prediction result Means for generating feedback information to be transmitted to the base station apparatus.

  According to this configuration, a transmission / reception signal due to multipath fading or the like generated during a delay from when the communication terminal apparatus transmits feedback information until the feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. Can be reduced, and the combined gain between the antennas can be improved.

  In the communication terminal device according to the present invention, in the above invention, the predicting means uses a phase difference between the antennas acquired at the time of feedback information transmission and at least two points in the past, and uses the phase difference between the antennas. A straight line that minimizes the sum of the differences between the acquired antenna phase differences on a plane defined by the phase difference axis is selected, and the inter-antenna phase difference per unit time is selected on the straight line. By obtaining the amount of change, a configuration is adopted in which the phase difference between antennas at the time when feedback information is reflected in the base station apparatus is predicted.

  According to this configuration, it is possible to predict the phase difference between antennas at the time when the communication terminal apparatus transmits feedback information and the feedback information is interpreted by the base station apparatus and the weighting of each antenna is adjusted. .

  A closed-loop transmission diversity method according to the present invention includes a step of obtaining a phase difference between a plurality of antennas included in a base station apparatus from a wirelessly received signal, and a phase difference between antennas acquired at the time of feedback information transmission and in the past And a step of predicting a phase difference between antennas at a time when feedback information is reflected in the base station device, and a step of generating feedback information to be transmitted to the base station device based on the prediction result. I made it.

  According to this method, a transmission / reception signal due to multipath fading or the like that occurs during a delay from when the communication terminal apparatus transmits feedback information until the feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. Can be reduced, and the combined gain between the antennas can be improved.

  The closed-loop transmission diversity method according to the present invention is the above-described invention, wherein the step of predicting the phase difference between the antennas using the phase difference between the antennas acquired at the time of feedback information transmission and at least two points in the past. Selecting a straight line that reduces the difference between them, obtaining a change amount per unit time of the phase difference between the antennas on the straight line, and sending feedback information based on the obtained change amount when the feedback information is transmitted to the base station And a step of obtaining a phase difference between the antennas at a time reflected by the apparatus.

  According to this method, it is possible to predict the phase difference between antennas at the time when the communication terminal apparatus transmits feedback information and the feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. .

  According to the present invention, a transmission / reception signal due to multipath fading or the like generated during a delay from when the communication terminal apparatus transmits feedback information until the feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. Can be reduced, and the combined gain between the antennas can be improved.

  The essence of the present invention is that, in a mobile communication system using closed-loop transmission diversity, a communication terminal apparatus determines a phase difference between antennas at a time when feedback information is reflected in a base station apparatus, when feedback information is transmitted, and in the past. Is predicted using the phase difference between the antennas acquired in step 1, and feedback information is generated based on the predicted amount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a communication terminal apparatus that transmits feedback information by closed-loop transmission diversity implemented in a mobile communication system according to an embodiment of the present invention. FIG. 1 shows a configuration example of a communication terminal apparatus in a CDMA mobile communication system. In addition, a base station apparatus (not shown) uses two antennas.

  1 includes an antenna unit 101 that receives a radio signal from a base station device, a radio unit 102 that down-converts a radio signal received by the antenna unit 101 and outputs a baseband signal, Despreading section 103 that despreads the baseband signal output from section 102, phase estimation section 104 that measures the phase rotation amount of the signal after primary demodulation by despreading for antenna # 1, and despreading for antenna # 2 , A phase estimation unit 105 that measures the phase rotation amount of the signal after the primary demodulation, a complex conjugate calculation unit 106 that calculates a complex conjugate of the phase estimation result for antenna # 1 that is a reference in closed-loop transmission diversity, and a complex conjugate The output of the calculation unit 106 (the phase estimation result of the antenna # 1) and the output of the phase estimation unit 105 (the phase estimation result of the antenna # 2) The multiplication unit 107 that calculates the phase difference between the antennas and the multiplication unit 107 calculates the phase difference between the antennas at the time when the transmitted feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. The inter-antenna phase difference prediction unit 108 that predicts based on the obtained inter-antenna phase difference, and the FBI generation unit 109 that generates feedback information to the base station device based on the prediction result of the inter-antenna phase difference prediction unit 108 It has.

Next, the operation of the communication terminal apparatus configured as described above will be described. First, the operation of each part will be described with reference to FIG. The outputs of the phase estimation units 104 and 105 that have passed through the radio unit 102 and the despreading unit 103 can be expressed by the following equations (1) and (2).
C1 (n) = | C1 (n) | × exp {jθ (n)} (1)
C2 (n) = | C2 (n) | × exp {jθ (n) + jΦ (n)} (2)

  In equations (1) and (2), C1 (n) and C2 (n) indicate phase estimation values (complex numbers) for the respective antennas at time n. Θ (n) represents the amount of phase rotation of the signal for antenna # 1 at time n. Φ (n) indicates the phase difference between the signal of antenna # 1 and the signal of antenna # 2.

The next complex conjugate calculation unit 106 calculates the complex conjugate of the phase estimation value for antenna # 1 according to equation (3).
conj [C1 (n)] = | C1 (n) | × exp {−jθ (n)} (3)

In the next multiplication unit 107, calculation of Expression (4) by multiplying Expression (2) and Expression (3) is performed, and the inter-antenna phase difference is obtained.
conj [C1 (n)] × C2 (n) =
| C1 (n) || C2 (n) | × exp {jΦ (n)} (4)

In the next inter-antenna phase difference prediction unit 108, based on the inter-antenna phase difference obtained by the multiplication unit 107, the antenna at the time when the transmitted feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. The phase difference between the two is predicted (formula (5)).
est [C1 (n)] × C2 (n) =
| C1 ′ (n) || C2 ′ (n) | × exp {jΦ ′ (n)} (5)

  Then, the FBI generation unit 109 generates FBI (feedback information) using the predicted amount of inter-antenna phase difference shown in Expression (5), and transmits it to the base station apparatus.

  Next, the operation of the inter-antenna phase difference prediction unit 108 will be described with reference to FIG. 2 is a diagram showing the operation of closed-loop transmission diversity in the communication terminal apparatus having the configuration shown in FIG. In FIG. 2, “communication terminal uplink channel transmission” in which the communication terminal apparatus transmits feedback information FBI, “base station uplink channel reception” in which the base station apparatus receives the feedback information FBI, and feedback information received by the base station apparatus. “Base station downlink channel transmission” in which FBI is reflected in transmission data and transmission and “communication terminal downlink channel reception” in which the communication terminal apparatus receives transmission data in which feedback information FBI is reflected from the base station apparatus are from time T1 to time T1. It is shown in association with time T5.

  In FIG. 2, an uplink channel propagation delay 200 and a downlink channel propagation delay 201 exist between the communication terminal device and the base station device. The communication terminal apparatus measures the phase difference between the antennas at times T1, T2, and T4, generates feedback information FBI, and transmits it to the base station apparatus. In the base station apparatus, it is received after the propagation delay 200 has elapsed since the time when the communication terminal apparatus transmitted the feedback information FBI. The base station apparatus weights each antenna based on the received feedback information FBI and transmits data to the communication terminal apparatus. The time when the communication terminal apparatus measures the inter-antenna phase difference and transmits the feedback information FBI. Reflection delay of feedback information FBI of about several hundred to several hundred μs between T2 and time T3 when each antenna is weighted based on feedback information FBI received by the base station apparatus and data is transmitted to the communication terminal apparatus 202 exists. In the base station apparatus, the same operation is performed at time T5.

  Therefore, in this embodiment, the base station apparatus predicts the phase difference between the antennas at times T3 and T5 at which each antenna is weighted based on the feedback information FBI received as described above, for example, as follows. I have to.

  That is, using the phase difference measurement values between three antennas, one for the current time and two in the past, a straight line that minimizes the sum of the differences between the antennas is selected, and a unit time on this straight line is selected. The amount of change in hit is obtained, and the phase difference between the antennas at the time when the base station apparatus weights each antenna on the extension of this straight line is predicted.

  In the example shown in FIG. 2, the inter-antenna phase difference 203 before FBI reflection, which is the inter-antenna phase difference measured at the current time T3, and the inter-antenna phase difference 204 measured at the past times T2 and T1. , 205 is used to select the straight line 206 that minimizes the difference between the phase differences between the antennas, and the unit on the straight line 206 at the inter-antenna phase difference prediction point 207 at the current time T3 when the feedback information FBI is transmitted. The amount of change per time is obtained, and the inter-antenna phase difference at time T5 when the base station apparatus weights each antenna is predicted on the extension of the straight line 206.

  As described above, according to the present embodiment, the communication terminal apparatus determines the inter-antenna phase difference at the time when the feedback information is reflected in the base station apparatus, based on the mutual antenna phase obtained at the time of feedback information transmission and in the past. Since the feedback information can be generated based on the prediction amount and the communication terminal apparatus transmits the feedback information, the feedback information is interpreted by the base station apparatus and weighted for each antenna. It is possible to reduce deterioration of transmitted / received signals due to multipath fading or the like that occurs during a delay until the adjustment of the signal, and to improve the combined gain between the antennas.

  In addition, although the prediction method by a straight line was demonstrated as a prediction method, you may use another prediction method.

  The present invention relates to a communication terminal apparatus in a mobile communication system using closed-loop transmission diversity, and after the communication terminal apparatus transmits feedback information, the feedback information is interpreted by the base station apparatus and the weight of each antenna is adjusted. It is suitable for reducing deterioration of transmitted / received signals due to multipath fading or the like occurring between delays up to and improving combined gain between antennas.

The block diagram which shows the structure of the communication terminal device which transmits the feedback information by the closed-loop transmission diversity implemented in the mobile communication system which concerns on one embodiment of this invention The figure which showed operation | movement of the closed-loop transmission diversity in the communication terminal device of the structure shown in FIG. 1 by time transition A block diagram showing a configuration example of a communication terminal device that transmits feedback information by closed-loop transmission diversity implemented in a conventional mobile communication system The figure which showed the operation | movement of the closed-loop transmission diversity in the communication terminal device of the structure shown in FIG. 3 by time transition

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Communication terminal device 101 Antenna part 102 Radio | wireless part 103 Despreading part 104 Phase estimation part 105 Phase estimation part 106 Complex conjugate calculating part 107 Multiplication part 108 Inter-antenna phase difference prediction part 109 FBI production | generation part

Claims (4)

  In a mobile communication system using closed-loop transmission diversity, a communication terminal apparatus obtains a phase difference between a plurality of antennas of a base station apparatus from a wirelessly received signal, and is acquired at the time of feedback information transmission and in the past. A means for predicting the inter-antenna phase difference at the time when the feedback information is reflected in the base station apparatus using the inter-antenna phase difference, and generating feedback information to be transmitted to the base station apparatus based on the prediction result And a communication terminal device.   The means for predicting is obtained on a plane defined by a time axis and an axis of phase difference between antennas by using phase differences between antennas obtained at the time of feedback information transmission and at least two points in the past. By selecting the straight line that minimizes the sum of the differences between the respective antennas that have been interpolated and obtaining the amount of change per unit time of the inter-antenna phase difference on the straight line, the feedback information is sent to the base station apparatus. The communication terminal apparatus according to claim 1, wherein a phase difference between the antennas at a time reflected is predicted.   A step of obtaining a phase difference between a plurality of antennas possessed by a base station apparatus from a wirelessly received signal, and feedback information is transmitted at the base station apparatus using the phase difference between antennas acquired at the time of feedback information transmission and in the past A closed-loop transmission diversity method, comprising: a step of predicting a phase difference between antennas at a reflected time; and a step of generating feedback information to be transmitted to a base station apparatus based on the prediction result.   The predicting step includes a step of selecting a straight line in which a difference between the phase differences between the antennas is reduced by using the phase difference between the antennas acquired at the time of feedback information transmission and at least two points in the past, and on the straight line A step of obtaining a change amount per unit time of an inter-antenna phase difference in step, and obtaining a phase difference between antennas at a time when feedback information is reflected in the base station apparatus when feedback information is transmitted based on the obtained change amount A closed-loop transmission diversity method according to claim 3, further comprising: a step.

Images