JP2009111790A - Radio communication device and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication device capable of accurately estimating reception quality even when propagation environments vary as time passes, and to provide a radio communication method. <P>SOLUTION: A radio base station 200 determines a weighting factor D in accordance with a trend of variation indicating the trend in which six pieces of reception quality information X in six frame periods vary as time passes, and calculates estimated reception quality information by giving the weighting factor D to the reception quality information X. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method for measuring reception quality of a wireless signal.

  In recent years, in wireless communication systems, for the purpose of speeding up wireless communication, the wireless communication device on the receiving side changes the modulation method of the encoded information according to the reception quality of the wireless signal received from the wireless communication device on the transmitting side. Adaptive modulation techniques have been introduced. In general, in a wireless communication system, transmission power control according to reception quality is performed. As the reception quality, SNR (Signal to Noise Ratio), CNR (Carrier to Noise Ratio), BER (Bit Error Rate), or the like can be used.

Conventionally, in the adaptive modulation technique, there has been proposed a method of controlling the reception quality measurement interval in accordance with the intensity of fluctuations in a predetermined time of the propagation environment (for example, Patent Document 1). According to this method, the reception quality can be accurately estimated even when the reception quality fluctuates drastically.
JP 2005-64947 A (paragraph [0019])

  However, if the reception quality measurement interval is shortened, the processing load on the reception-side wireless communication apparatus increases. For this reason, it is desired that the reception quality can be accurately estimated without increasing the processing load on the radio communication apparatus on the reception side.

  By the way, when the reception quality is expressed with the passage of time, it is observed that the reception quality fluctuates according to some trends. Such fluctuations in reception quality are caused by fluctuations in the radio signal propagation environment. Therefore, in order to accurately estimate the reception quality, it is important to grasp the fluctuation tendency of the propagation environment.

  Therefore, the present invention has been made in view of such a situation, and a wireless communication apparatus and a wireless communication method capable of accurately estimating reception quality even when the propagation environment fluctuates with time. The purpose is to provide.

  In order to solve the problems described above, the present invention has the following features. First, the first feature of the present invention relates to a radio communication apparatus (radio base station 200), and receives reception quality information (reception quality information X) indicating reception quality of a radio signal at a predetermined interval (one frame). In accordance with the quality information acquisition unit (reception quality information acquisition unit 231) and the fluctuation tendency indicating the tendency that the reception quality information fluctuates with time in the predetermined period, the reception quality in the predetermined period (six frame periods) A weighting factor determination unit (weighting factor determination unit 233) that determines a weighting factor (weighting factor D) to be assigned to each of the information (X11 to X16), and an estimated reception quality calculated by adding a weighting factor to the reception quality information The gist is to include a control unit (transmission control unit 240) that controls wireless communication based on the information.

  In this way, the wireless communication device gives the weighting coefficient to the reception quality information according to the variation tendency of the reception quality. In other words, the wireless communication device gives higher or lower importance to the reception quality information X in accordance with the variation tendency of the propagation environment. Therefore, the wireless communication apparatus can estimate the reception quality in accordance with the variation tendency of the propagation environment even when the propagation environment varies with time. Therefore, the wireless communication apparatus can estimate the reception quality with high accuracy. Furthermore, the wireless communication apparatus can appropriately perform adaptive modulation and power control by referring to such reception quality estimated with high accuracy.

  A second feature of the present invention relates to the first feature of the present invention, wherein the weighting factor determination unit indicates that the reception quality information has changed within a predetermined threshold (predetermined threshold α) with the passage of time. A first tendency (first tendency A), a second tendency (second tendency B) indicating that the reception quality information has changed in a direction in which the reception quality is improved over a predetermined threshold as time passes, The gist is to determine the variation tendency by the combination with the third tendency (third tendency C) indicating that the reception quality information has fallen below the predetermined threshold and has been lowered in the direction in which the reception quality decreases with time. To do.

  The third feature of the present invention is related to the second feature of the present invention, and the weighting factor determination unit makes the weighting factor uniform when the variation tendency is constituted only by the first tendency.

  A fourth feature of the present invention relates to the second feature of the present invention, and the weighting factor determination unit performs weighting when the variation tendency is constituted only by the second tendency or by the first tendency and the second tendency. The gist is to increase the coefficient over time.

  A fifth feature of the present invention relates to the second feature of the present invention, and the weighting factor determination unit performs weighting when the variation tendency is constituted only by the third tendency or by the first tendency and the third tendency. The gist is to increase the coefficient over time.

  A sixth feature of the present invention relates to the second feature of the present invention, wherein the weighting factor determination unit has the first tendency and the fluctuation tendency after the first trend and the second trend, or after the second trend. In the case where the third tendency or the third tendency is continuous, the gist is to increase the weighting coefficient with the passage of time.

  A seventh feature of the present invention relates to the second feature of the present invention, wherein the weighting factor determination unit has a first tendency and a fluctuation tendency after the first trend and the third trend, or after the third trend. In the case where the second trend or the second trend is configured, the weighting factor after the last third trend is set larger than the weighting factor before the last third trend, and the last The gist is to increase the weighting coefficient after the three trends with the passage of time.

  An eighth feature of the present invention relates to the second feature of the present invention, and the weighting factor determination unit, when the variation tendency repeatedly includes the second tendency and the third tendency, the weight associated with the last third tendency. The gist is to make the coefficient larger than the weighting coefficient before the last third tendency and to increase the weighting coefficient after the last third tendency with the passage of time.

  A ninth feature of the present invention relates to a wireless communication method, the step (S101) of acquiring reception quality information indicating reception quality of a radio signal at a predetermined interval, and the reception quality information as time elapses within a predetermined period. A step (S104) of determining a weighting factor to be given to each reception quality information within a predetermined period in accordance with a fluctuation tendency indicating a tendency to vary, and an estimated reception calculated by adding a weighting factor to the reception quality information And a step (S106) of controlling wireless communication based on the quality information.

  According to the features of the present invention, it is possible to provide a wireless communication apparatus and a wireless communication method that can accurately estimate reception quality even when reception quality varies with time.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

(1) Schematic Configuration of Radio Communication System First, the schematic configuration of the radio communication system according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of a wireless communication system according to the present embodiment.

  As shown in FIG. 1, the radio communication system includes a radio communication terminal 100 and a radio base station 200. The radio communication terminal 100 performs radio communication with the radio base station 200 using the channel assigned by the radio base station 200.

  The radio communication terminal 100 and the radio base station 200 execute radio communication using a time division multiple access-time division duplex (TDMA-TDD) scheme, specifically, radio communication based on the iBurst (registered trademark) standard. can do.

  In the iBurst (registered trademark) standard, according to the reception quality indicated by SNR (Signal to Noise Ratio), CNR (Carrier to Noise Ratio), BER (Bit Error Rate), etc., for the purpose of increasing the communication rate. An adaptive modulation technique for selecting a modulation method of encoded information has been introduced. In the adaptive modulation technique, an appropriate modulation method is selected from a plurality of modulation methods such as BPSK (Binary Phase Shift Keying) and 24QAM (Quadrature Amplitude Modulation).

(2) Configuration of Radio Base Station Next, the configuration of the radio base station 200 will be described with reference to FIG. FIG. 2 is a functional block diagram showing the configuration of the radio base station 200. In the following, the configuration related to the present invention will be mainly described.

  As shown in FIG. 2, the radio base station 200 includes an antenna 210, a transmission / reception unit 220, a reception control unit 230, and a transmission control unit 240.

  The transmission / reception unit 220 transmits and receives wireless signals via the antenna 210. The transmission / reception unit 220 performs amplification, down-conversion, A / D conversion, and the like of the radio signal received from the radio communication terminal 100. In addition, the transmission / reception unit 220 performs up-conversion and D / A conversion of a radio signal received to the radio communication terminal 100.

  The reception control unit 230 calculates estimated reception quality information indicating the estimated reception quality according to a fluctuation tendency indicating a tendency that the reception quality information of the received radio signal varies with the passage of time. The detailed configuration of the reception control unit 230 will be described later.

  The transmission control unit 240 can perform modulation method selection, transmission power control, and the like by using the estimated reception quality information calculated by the reception control unit 230.

(3) Configuration of Reception Control Unit As shown in FIG. 2, the reception control unit 230 includes a reception quality information acquisition unit 231, a memory unit 232, a weighting factor determination unit 233, and an estimated reception quality information calculation unit 234.

(3.1) Reception Quality Information Acquisition Unit The reception quality information acquisition unit 231 acquires reception quality information X indicating reception quality of a radio signal received from the radio communication terminal 100 at predetermined intervals. As the predetermined interval for acquiring the reception quality information X, a communication period (one frame) repeated in TDMA-TDD wireless communication can be used.

  In order to acquire the reception quality information X, the reception quality information acquisition unit 231 measures SNR, CNR, BER and the like indicating the reception quality of the received radio signal. For example, the reception quality information acquisition unit 231 measures the SNR using the first known signal and the second known signal included in the received radio signal. The first known signal and the second known signal are arranged continuously on the time axis. First, the reception quality information acquisition unit 231 multiplies the propagation path estimation information calculated using the first known signal by the second known signal. Next, reception quality information acquisition section 231 calculates noise power based on the difference between the second known signal multiplied by propagation path estimation information and the second known signal not multiplied by propagation path estimation information. The reception quality information acquisition unit 231 acquires the SNR based on the calculated noise power and the power of the received radio signal. In the present embodiment, the reception quality information acquisition unit 231 will be described as acquiring the SNR as the reception quality information X.

  The reception quality information acquisition unit 231 transmits the acquired reception quality information X to the memory unit 232. The reception quality information acquisition unit 231 can sequentially transmit the reception quality information X to the memory unit 232 every time the reception quality information X is acquired.

(3.2) Memory Unit The memory unit 232 stores a predetermined number of reception quality information X. In the present embodiment, the memory unit 232 can store six pieces of reception quality information X. Therefore, the memory unit 232 discards the reception quality information X six frames before every time the reception quality information X transmitted from the reception quality information acquisition unit 231 is newly stored.

(3.3) Weighting Factor Determination Unit The weighting factor determination unit 233 acquires six pieces of reception quality information X stored in the memory unit 232. The weighting factor determination unit 233 determines a weighting factor D to be given to each of the reception quality information X according to the fluctuation tendency indicating the tendency of the six reception quality information X to change with time. The fluctuation tendency is configured by combining three kinds of trends A, B, and C.

(3.3.1) Trends A, B, C
The tendencies A, B, and C will be described with reference to FIG. FIG. 3 schematically shows how the reception quality information X varies from X1 to any one of X2 to X5 as time (one frame period) elapses. In this embodiment, since the reception quality information X is an SNR, in FIG. 3, a change in the reception quality information X in the positive direction indicates that the reception quality is improved. On the other hand, the fluctuation in the negative direction of the reception quality information X indicates that the reception quality is lowered.

  First, the first tendency A will be described. The first tendency A indicates that the reception quality information X has fluctuated within a predetermined threshold value α. Specifically, when the reception quality information X varies from X1 to X2, the reception quality information X varies within a predetermined threshold α in a direction in which the reception quality improves. Similarly, when the reception quality information X varies from X1 to X3, the reception quality information X varies within a predetermined threshold value α in a direction in which the reception quality decreases.

  Here, the predetermined threshold α is set to a range in which the reception quality can be determined to be stable (about the fluctuation width due to the noise of the reception quality). Therefore, the first tendency A indicates that the reception quality is maintained.

  Next, the second tendency B will be described. The second tendency B indicates that the reception quality information X has changed in a direction in which the reception quality is improved by exceeding a predetermined threshold value α. Specifically, when the reception quality information X varies from X1 to X4, the reception quality information X varies beyond a predetermined threshold value α in a direction in which the reception quality is improved. Therefore, the second tendency B indicates that the reception quality has improved.

  Next, the third tendency C will be described. The third tendency C indicates that the reception quality information X has fallen below the predetermined threshold value α and the reception quality has decreased. Specifically, when the reception quality information X varies from X1 to X5, the reception quality information X varies below a predetermined threshold value α in a direction in which the reception quality decreases. Therefore, the third tendency C indicates that the reception quality has deteriorated.

(3.3.2) Fluctuation Trend The weighting coefficient determination unit 233 determines a fluctuation tendency based on a combination of trends A, B, and C. Hereinafter, the fluctuation tendency will be described with specific examples in FIGS.

[1] Stable type fluctuation tendency First, the tendency (stable type fluctuation tendency) that the reception quality information X fluctuates stably will be described with reference to FIG. FIG. 4A is a graph showing fluctuations in the reception quality information X over time. FIG. 4B is a table for explaining a method for determining a weighting factor.

  In FIG. 4A, new reception quality information X is plotted as time elapses from time t1 to t6. That is, X11 is reception quality information of a radio signal received five frame periods before X16, and X16 is reception quality information of a radio signal received one frame period before.

  As shown in FIG. 4A, the change from X11 to X12 is a change within a predetermined threshold value α. Therefore, as shown in FIG. 5B, the variation from X11 to X12 is shown as the first tendency A. Similarly, each of the four fluctuations from X12 to X16 is shown as four first trends A.

  The weighting factor determination unit 233 determines that the fluctuation tendency is a stable fluctuation tendency based on the five combinations of the first tendency A (AAAAA).

  In the case of such a stable fluctuation tendency, the weighting factor determination unit 233 sets the weighting factors D1 to D6 assigned to X11 to X16 to uniform values. That is, the weighting coefficient D has a relationship of D1 = D2 = D3 = D4 = D5 = D6 ≠ 0.

[2] Improvement-type Fluctuation Trend Next, the tendency of reception quality information X to fluctuate (improvement fluctuation tendency) will be described with reference to FIG. FIG. 5A is a graph showing fluctuations in the reception quality information X over time. FIG. 5B is a table for explaining a method for determining a weighting factor.

  As shown in FIG. 5A, the change from X21 to X22 is a change within a predetermined threshold value α. Therefore, as shown in FIG. 5B, the variation from X21 to X22 is shown as the first tendency A. Further, the change from X22 to X23 is a change in a direction in which the reception quality is improved by exceeding a predetermined threshold value α. Therefore, the variation from X22 to X23 is shown as the second tendency B as shown in FIG. Similarly, each of the three fluctuations from X23 to X26 is shown as three second trends B.

  The weighting factor determination unit 233 determines that the fluctuation tendency is an improved fluctuation tendency based on a combination of one first tendency A and four second trends B (ABBBB).

  In the case of such an improved fluctuation tendency, the weighting factor determination unit 233 increases the weighting factors D1 to D6 given to the respective X21 to X26 with the passage of time. Therefore, the weight coefficient D has a relationship of D1 <D2 <D3 <D4 <D5 <D6.

  In addition to the above, all the configurations configured by the first trend A and the second trend B correspond to the improved fluctuation trend.

[3] Decreasing-type fluctuation tendency Next, the tendency (decreasing-type fluctuation tendency) of the reception quality information X to fluctuate is described with reference to FIG. FIG. 6A is a graph showing fluctuations in the reception quality information X over time. FIG. 6B is a table for explaining a method for determining a weighting factor.

  As shown in FIG. 6A, the change from X31 to X32 is a change within a predetermined threshold value α. Therefore, as shown in FIG. 5B, the variation from X31 to X32 is shown as the first tendency A. Further, the fluctuation from X32 to X33 is a fluctuation in a direction in which the reception quality is lowered below a predetermined threshold value α. Therefore, the variation from X32 to X33 is shown as the third tendency C as shown in FIG. Similarly, the change from X33 to X34 is shown as a first trend A. Each of the two fluctuations from X34 to X36 is shown as two third trends C.

  Based on these combinations (ACACC), the weighting factor determination unit 233 determines that the variation tendency is a decreasing variation tendency.

  In the case of such a decreasing fluctuation tendency, the weighting factor determination unit 233 increases the weighting factors D1 to D6 given to the respective X31 to X36 with the passage of time. Therefore, the weight coefficient D has a relationship of D1 <D2 <D3 <D4 <D5 <D6.

  In addition to the above, the improved fluctuation tendency includes a configuration based on the third tendency C alone.

[4] Mountain-shaped fluctuation tendency Next, a tendency (mountain fluctuation tendency) that the reception quality information X fluctuates in a direction that improves and then decreases (a mountain-shaped fluctuation tendency) will be described with reference to FIG. FIG. 7A is a graph showing fluctuations in the reception quality information X over time. FIG. 7B is a table for explaining a method for determining a weighting factor.

  As shown in FIG. 7A, the change from X41 to X42 is a change in a direction in which the reception quality exceeds a predetermined threshold value α. Therefore, as shown in FIG. 5B, the variation from X41 to X42 is shown as the second tendency B. In addition, two fluctuations from X42 to X44 are shown as two third trends C. Two fluctuations from X44 to X46 are shown as two first trends A.

  Based on these combinations (BCCAA), the weighting factor determination unit 233 determines that the variation tendency is a mountain-shaped variation tendency.

  In the case of such a mountain-shaped fluctuation tendency, the weighting factor determination unit 233 increases the weighting factors D1 to D6 given to the respective X41 to X46 with the passage of time. Therefore, the weight coefficient D has a relationship of D1 <D2 <D3 <D4 <D5 <D6.

  In addition to the above, as the mountain-shaped fluctuation trend, a configuration in which the first trend A and the third trend C or the third trend C is connected after the first trend A and the second trend B is applicable.

[5] Valley-Type Fluctuation Trend Next, a tendency (valley-type fluctuation tendency) of changing in a direction in which the reception quality information X changes and then improving in the direction of reduction will be described with reference to FIG. FIG. 8A is a graph showing fluctuations in the reception quality information X over time. FIG. 8B is a table for explaining a method for determining a weighting factor.

  As shown in FIG. 8A, the two fluctuations from X51 to X53 are fluctuations in a direction in which the reception quality is lowered below a predetermined threshold value α. Therefore, as shown in FIG. 4B, the two fluctuations from X51 to X53 are shown as the third tendency C twice. The variation from X53 to X54 is shown as the second trend B. The variation from X54 to X55 is shown as the first trend A. The variation from X55 to X56 is shown as the second trend B.

  Based on these combinations (CCBAB), the weighting factor determination unit 233 determines that the fluctuation tendency is a valley-type fluctuation tendency.

  In the case of such valley-shaped fluctuation tendency, the weighting factor determination unit 233 sets the weighting factors D3 to D6 related to the last third tendency C to be higher than the weighting factors D1 and D2 related to the last third tendency C. Enlarge. Further, the weighting factor determination unit 233 increases the weighting factors D3 to D6 related to the last third tendency C with the passage of time.

  On the other hand, the weighting factors D1 and D2 may be uniform or may increase with the passage of time. However, the weighting factors D1 and D2 are preferably much smaller than the weighting factor D3, and may each be 0.

  Accordingly, the weighting factors D1 to D6 have a relationship of D1 ≦ D2 << D3 <D4 <D5 <D6 as shown in FIG. 8B.

  In addition to the above, the valley-type fluctuation tendency corresponds to a configuration in which only the first tendency A and the second tendency B or the second tendency B is connected after the first tendency A and the third tendency C.

[6] Random / Lower Type Fluctuation Trend Next, a tendency to repeat the fluctuation in the direction in which the reception quality information X decreases and the fluctuation in the direction of improvement (the irregular / lower type fluctuation tendency) will be described with reference to FIG. FIG. 9A is a graph showing fluctuations in the reception quality information X over time. FIG. 9B is a table for explaining a method for determining a weighting factor.

  As shown in FIG. 9A, the reception quality information X varies from X61 to X66 in a direction in which the reception quality is improved beyond a predetermined threshold α, and the reception quality is reduced below the predetermined threshold α. Repeat to change the direction. Therefore, as shown in FIG. 5B, each variation from X61 to X66 is shown as a repetition of the second tendency B and the third tendency C.

  Based on these combinations (BCBCB), the weighting factor determination unit 233 determines that the fluctuation tendency is a turbulent and lower type fluctuation tendency.

  In the case of such a fluctuation-type fluctuation tendency, the weighting factor determination unit 233 sets the weighting factors D5 and D6 related to the last third tendency C to be higher than the weighting factors D1 to D4 related to the last third tendency C. Enlarge. Further, the weighting factor determination unit 233 increases the weighting factors D5 and D6 related to the last third tendency C with the passage of time.

  On the other hand, the weighting factors D1 to D4 may be uniform or may be increased as time passes. However, the weighting factors D1 to D4 are preferably extremely smaller than the weighting factor D5, and may be 0 respectively.

  Therefore, the weighting factors D1 to D6 have a relationship of D1 ≦ D2 ≦ D3 ≦ D4 << D5 <D6 as shown in FIG. 9B.

  In addition, as for the fluctuation trend type, the second tendency B and the third tendency C are not limited to the case where the second tendency B and the third tendency C are alternately repeated continuously, and all configurations in which one of the second tendency or the third tendency is included are all applicable. To do.

(3.4) Estimated Reception Quality Information Calculation Unit Next, the configuration of the estimated reception quality information calculation unit 234 will be described with reference to FIG. FIG. 10 is a functional block diagram showing the configuration of the estimated reception quality information calculation unit 234. FIG. 10 illustrates the case where the reception quality has a stable fluctuation tendency (see FIG. 4).

  As shown in the figure, the estimated reception quality information calculation unit 234 includes a multiplication unit 234a and an averaging processing unit 234b.

  The multiplication unit 234 a acquires the reception quality information X from the memory unit 232 and acquires the weight coefficient D from the weight coefficient determination unit 233. The multiplier 234a multiplies the reception quality information X by the weighting coefficient D. Specifically, the multiplication unit 234a multiplies X11 to X16 and weighting factors D1 to D6 corresponding to X11 to X16, respectively, by using six multiplication circuits. The multiplier 234a transmits the multiplication value output from the multiplier circuit to the averaging processor 234b.

  The averaging processing unit 234b calculates estimated reception quality information by calculating an average value of the multiplication values output from the multiplication circuit of the multiplication unit 234a.

  As described above, by adding the weighting coefficient D to the reception quality information X, the estimated reception quality information calculation unit 234 calculates the estimated reception quality information. The estimated reception quality information calculation unit 234 transmits the calculated estimated reception quality information to the transmission control unit 240.

(4) Operation of Radio Base Station Next, the operation of the radio base station 200 will be described with reference to FIG. FIG. 11 is a flowchart showing the operation of the radio base station 200.

  In step S101, the reception quality information acquisition unit 231 acquires reception quality information X indicating the reception quality of the radio signal received from the radio communication terminal 100 at predetermined intervals.

  In step S102, the memory unit 232 stores a predetermined number of reception quality information X while updating them as needed.

  In step S103, the weighting factor determination unit 233 determines a variation tendency indicating a tendency that the reception quality information X within a predetermined time varies with the passage of time. The weighting factor determination unit 233 can determine the fluctuation tendency of the stable type, the improvement type, the reduction type, the mountain type, the valley type, and the ups and downs type as representative fluctuation trends.

  In step S104, the weighting factor determination unit 233 determines the weighting factor D to be given to the reception quality information X within a predetermined time according to the fluctuation tendency.

  In step S <b> 105, the estimated reception quality information calculation unit 234 calculates the estimated reception quality information by adding a weight coefficient D to the reception quality information X. Specifically, the reception quality information X multiplied by the weight coefficient D is averaged. The calculated estimated reception quality information is an estimated value of reception quality.

  In step S106, the transmission control unit 240 performs wireless communication control (modulation method selection, transmission power control, etc.) by using the calculated estimated reception quality information.

  The radio base station 200 repeats steps S101 to S106.

(5) Operation and Effect The radio base station 200 according to the present embodiment determines the weighting coefficient D according to the fluctuation tendency indicating that the six reception quality information X within the six frame period tend to fluctuate with time. Then, the estimated reception quality information is calculated by adding the weighting coefficient D to the reception quality information X.

  As described above, the radio base station 200 assigns the weighting coefficient D to the reception quality information X according to the variation tendency of the reception quality. In other words, the radio base station 200 assigns high or low importance to each of the six reception quality information X in accordance with the variation tendency of the propagation environment.

  Therefore, the radio base station 200 can estimate the reception quality according to the variation tendency of the propagation environment even when the propagation environment varies with time. Therefore, the radio base station 200 can estimate the reception quality with high accuracy. Furthermore, the radio base station 200 can appropriately perform adaptive modulation and power control by referring to such reception quality estimated with high accuracy.

  Further, in the present embodiment, the radio base station 200 changes the first tendency A indicating that the reception quality information X has fluctuated within a predetermined threshold value α and the direction in which the reception quality is improved beyond the predetermined threshold value α. The variation tendency is determined based on the combination of the second tendency B indicating that the reception has been performed and the third tendency C indicating that the reception quality has decreased in a direction that is lower than the predetermined threshold value α.

  In this way, the radio base station 200 can grasp in detail and accurately the fluctuation of the reception quality information X for each frame. In addition, since the fluctuation of the reception quality information X for each frame is classified based on the predetermined threshold value α, it is possible to suppress the slight fluctuation of the reception quality from being regarded as the fluctuation of the propagation environment.

  In addition, the radio base station 200 according to the present embodiment sets the weighting coefficient D to a uniform value when there is a stable fluctuation tendency. That is, when the reception quality is stable, the radio base station 200 makes no difference in the importance of the six reception quality information X. As a result, the six pieces of reception quality information X are equally averaged, so that the reception quality can be estimated with high accuracy.

  In addition, the radio base station 200 according to the present embodiment increases the weighting coefficient D with the passage of time in the case of an improved fluctuation tendency. Here, when the reception quality is uniformly improved, the reception quality information X is closer to the reception quality as the reception quality information X is newer. Therefore, in the case of an improved fluctuation tendency, the new reception quality information X can be estimated with high accuracy by increasing the importance.

  Also, the radio base station 200 according to the present embodiment increases the weighting coefficient D with the passage of time in the case of a decreasing fluctuation tendency. Here, when the reception quality uniformly decreases, the newer the reception quality information X is, the closer the reception quality is. Therefore, in the case of a decreasing fluctuation tendency, the reception quality can be accurately estimated by increasing the importance of new reception quality information X.

  In addition, the radio base station 200 according to the present embodiment increases the weighting coefficient D with the passage of time when there is a mountain-shaped fluctuation tendency. Therefore, the reception quality can be accurately estimated by increasing the importance of new reception quality information X.

  In addition, in the case of valley-shaped fluctuation tendency, the radio base station 200 according to the present embodiment makes the weighting factor D related to the last third tendency C larger than the weighting factor D related to the last third tendency C. At the same time, the weighting coefficient D after the last third tendency C is increased with the passage of time. Here, when the propagation environment fluctuates, there may be a sudden drop in received quality due to fading. In addition, the reception quality tends to gradually improve after dropping sharply. Therefore, in the case of the valley-shaped fluctuation tendency, there is a high possibility that the reception quality before the last third tendency C is greatly different from the reception quality. Thus, by particularly increasing the importance of the weighting coefficient D after the last third tendency C, it is possible to accurately estimate the reception quality.

  Also, the radio base station 200 according to the present embodiment has a weighting factor D that is greater than the last third trend C and is greater than the weighting factor D that is before the last third trend C in the case of a turbulent and lower fluctuation trend. At the same time, the weighting coefficient D after the last third tendency C is increased with the passage of time. As described above, when the propagation environment fluctuates violently, a sudden drop in reception quality occurs due to fading. Therefore, there is a high possibility that the reception quality before the last third tendency C is greatly different from the reception quality. Thus, by particularly increasing the importance of the weighting coefficient D after the last third tendency C, it is possible to accurately estimate the reception quality.

(6) Other Embodiments As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it is understood that the description and drawings constituting a part of this disclosure limit the present invention. Should not. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

  For example, in the above embodiment, the wireless communication system based on the iBurst (registered trademark) standard has been described as an example. However, the above embodiment can be applied not only to the iBurst (registered trademark) standard but also to a system based on PHS (Personal Handyphone system) or the IEEE 802.16 communication standard (WiMAX).

  In the above embodiment, the reception quality information X is acquired at every communication interval (one frame) of the TDMA-TDD system. However, the interval at which the reception quality information X is acquired depends on the processing load on the radio base station 200 and the like. It can be set as appropriate in consideration.

  In the above embodiment, the configuration of the radio base station 200 has been described. However, the above embodiment can also be applied to the radio communication terminal 100.

  In the above embodiment, the reception quality information acquisition unit 231 may collectively transmit a plurality of reception quality information X acquired within a predetermined period (for example, 6 frame periods) to the memory unit 232. In this case, the memory unit 232 discards all the stored reception quality information X and stores the six newly received reception quality information X.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. It is a functional block diagram which shows the structure of the wireless base station 200 which concerns on embodiment of this invention. It is a figure which shows typically a mode that the reception quality information X which concerns on embodiment of this invention fluctuates with progress of time. It is a figure for demonstrating the tendency (stable type | mold fluctuation tendency) that the reception quality information X fluctuates stably. It is a figure for demonstrating the tendency (improvement type fluctuation tendency) which the reception quality information X fluctuates in the improvement direction. It is a figure for demonstrating the tendency (decreasing type fluctuation tendency) to which the reception quality information X changes in the direction which falls. It is a figure for demonstrating the tendency (mountain fluctuation tendency) which fluctuates in the direction which falls after the reception quality information X fluctuates in the improvement direction. It is a figure for demonstrating the tendency (valley-shaped fluctuation tendency) which changes to the direction which improves after changing to the direction where the reception quality information X falls. It is a figure for demonstrating the tendency (fluctuation type fluctuation tendency) which repeats the fluctuation | variation to the direction to which the reception quality information X falls, and the fluctuation | variation to the improvement direction. It is a functional block diagram which shows the structure of the estimation reception quality information calculation part 234 which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the radio base station 200 which concerns on embodiment of this invention.

Explanation of symbols

α ... threshold A ... first tendency B ... second tendency C ... third tendency D ... weighting coefficient X ... reception quality information 100 ... radio communication terminal 200 ... radio base station 210 ... antenna 220 ... transmission / reception unit 230 ... reception control unit 231 ... reception quality information acquisition unit 232 ... memory unit 233 ... weighting coefficient determination unit 234 ... estimated reception quality information calculation unit 234a ... multiplication unit 234b ... averaging processing unit 240 ... transmission control unit

Claims (9)

A reception quality information acquisition unit for acquiring reception quality information indicating the reception quality of the radio signal at predetermined intervals;
A weighting factor determination unit that determines a weighting factor to be given to each of the reception quality information in the predetermined period according to a fluctuation tendency indicating a tendency that the reception quality information fluctuates with time in the predetermined period;
A wireless communication device comprising: a control unit that controls wireless communication based on estimated reception quality information calculated by adding the weighting coefficient to the reception quality information. The weighting factor determination unit
A first trend indicating that the reception quality information has fluctuated within a predetermined threshold over time;
A second tendency indicating that the reception quality information has changed in a direction in which the reception quality is improved by exceeding the predetermined threshold over time;
The fluctuation tendency is determined by a combination with a third tendency indicating that the reception quality information has fluctuated in a direction in which the reception quality is lowered with the passage of time below the predetermined threshold. The wireless communication device according to 1. The weighting factor determination unit
The wireless communication apparatus according to claim 2, wherein the weighting factor is made uniform when the fluctuation tendency is constituted only by the first tendency. The weighting factor determination unit
The weighting factor is increased as time elapses when the fluctuation tendency is constituted only by the second tendency or by the first tendency and the second tendency. The wireless communication device described. The weighting factor determination unit
The weighting factor is increased as time elapses when the fluctuation tendency is constituted only by the third tendency or by the first tendency and the third tendency. The wireless communication device described. The weighting factor determination unit
When the fluctuation tendency is constituted by the first tendency and the third tendency or the third tendency after the first tendency and the second tendency, or after the second tendency. The wireless communication apparatus according to claim 2, wherein the weighting factor is increased as time elapses. The weighting factor determination unit
When the fluctuation tendency is constituted by the first tendency and the second tendency, or the second tendency after the first tendency and the third tendency, or after the third tendency. ,
Making the weighting factor after the last third trend greater than the weighting factor before the last third trend,
The wireless communication apparatus according to claim 2, wherein the weighting factor after the last third tendency is increased as time elapses. The weighting factor determination unit
When the fluctuation trend repeatedly includes the second trend and the third trend,
Making the weighting factor after the last third trend greater than the weighting factor before the last third trend,
The wireless communication apparatus according to claim 2, wherein the weighting factor after the last third tendency is increased as time elapses. Obtaining reception quality information indicating reception quality of the radio signal at predetermined intervals;
Determining a weighting factor to be given to each of the reception quality information within the predetermined period according to a variation tendency indicating a tendency of the reception quality information to vary over time within the predetermined period;
A wireless communication method comprising: controlling wireless communication based on estimated reception quality information calculated by adding the weighting coefficient to the reception quality information.

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