JP2006279197A - Diversity apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity apparatus capable of properly controlling transmission diversity without the need for feedback information exclusively for controlling the transmission diversity. <P>SOLUTION: The diversity apparatus calculates an average transmission power from a received signal and sets a threshold on the basis of the average transmission power value. The diversity apparatus determines the transmission power value on the basis of RPC bits for instructing a transmission output and compares the transmission power value with the threshold to select a transmission antenna. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

 The present invention relates to a diversity apparatus.

In a wireless communication system in which transmission and reception carrier frequencies are different as in an FDD (frequency division full duplex) communication method or the like, there is a possibility that transmission and reception radio wave propagation conditions may be different. Even if transmission diversity is controlled, the effect may not be obtained, and the communication quality is not stable. For this reason, conventionally, the receiving station generates dedicated feedback information for controlling the transmission diversity of the transmitting station based on the received signal from the transmitting station, and provides this dedicated feedback information to the transmitting station. The diversity technique is disclosed in Patent Document 1.
Japanese Patent Laid-Open No. 2002-359587

 However, the conventional technology described above requires communication resources (such as channels and usable areas in the transmission format) for transmitting feedback information dedicated to transmission diversity control from the receiving station to the transmitting station. However, in the existing wireless communication system, there may be a case where the communication resource cannot be newly allocated. For example, in one of the existing CDMA (Code Division Multiple Access) type mobile communication systems, means for generating feedback information must be added in the base station. Furthermore, unless the transmission format in the direction from the base station to the mobile station is revised, the dedicated feedback information cannot be transmitted from the base station to the mobile station, and therefore the transmission diversity of the mobile station cannot be appropriately controlled. Even if the transmission format is revised, there is a possibility that the data transmission efficiency is lowered by the amount of feedback information transmission.

 In addition, there is a problem that the load of processing for generating feedback information dedicated to transmission diversity control increases at the receiving station. Furthermore, the transmission diversity control function of the transmitting station must correspond to the dedicated feedback information, which may cause adverse effects such as a limited transmission diversity control method.

 The present invention has been made in view of such circumstances, and an object of the present invention is to provide a diversity apparatus that can appropriately control transmission diversity without requiring feedback information dedicated to transmission diversity control. It is in.

 In order to solve the above problem, the diversity apparatus according to claim 1 is a diversity apparatus including a plurality of antennas, and includes a control signal (for example, RPC bit {power control) indicating a transmission output of the diversity apparatus. Bit}), the transmission power determining means for determining the transmission power based on the control signal, the attenuation amount estimating means for estimating the attenuation amount of the radio propagation path based on the received signal, and the attenuation amount estimating means Threshold value setting means for estimating a power value (average transmission power value) required at the time of transmission based on the estimated attenuation amount of the radio propagation path, and setting a threshold value based on the estimated power value; and the transmission power A comparison means for comparing the transmission power (transmission power value) determined by the determination means with the threshold value, and based on a result of the comparison by the comparison means, It comprises a control means for controlling the transmit diversity Citi device, and is characterized in that.

 The diversity apparatus according to claim 2 is characterized in that the threshold value setting means is controlled so that the threshold value can be changed according to communication quality.

 The diversity apparatus according to claim 3 is characterized in that the control means controls transmission diversity of the diversity apparatus by switching an antenna to transmit.

 The diversity apparatus according to claim 4 is characterized in that transmission diversity of the diversity apparatus is controlled by weighting transmission signals supplied to the plurality of antennas.

 According to the present invention, since the power value of the transmission power determined based on the existing control information for transmission output instruction is used for transmission diversity control, feed pack information dedicated to transmission diversity control is not required. Furthermore, since transmission diversity is controlled based on the instruction content of transmission output, it is possible to appropriately control transmission diversity according to increase or decrease of transmission output.

 Hereinafter, embodiments of the present invention will be sequentially described with reference to the drawings. In this embodiment, a case where a mobile station of a CDMA mobile communication system includes the diversity apparatus according to the present invention will be described as an example. In this CDMA mobile communication system, the base station controls increase / decrease of the communication output of the mobile station according to the reception intensity from the axis-shifting station. The transmission output control is intended to suppress variations in the reception intensity from each mobile station in the base station due to the distance between the mobile station and the base station and fading. That is, the reception intensity from each mobile station increases as the mobile station is closer to the base station according to the distance between the mobile station and the base station under the condition that the transmission output of the mobile station is constant. Further, the magnitude of attenuation varies depending on fading. Therefore, it is difficult to receive from a mobile station with low reception power at the base station as it is. Therefore, conventionally, the base station controls the transmission output of the mobile station to balance the reception intensity from each mobile station.

 Specifically, the base station transmits an RPC (Reverse Power Control) bit (power control bit) to the mobile station to be controlled. The RPC bit is a 1-bit signal for the base station to control the transmission power of the mobile station, and the bit value “0” means an instruction to increase the transmission power of 1 dB, for example, and the bit value “1” is For example, it means an instruction to reduce the transmission power by 1 dB. The mobile station increases or decreases its transmission power according to the instruction of the RPC bit received from the base station. As a result, the transmission output of the mobile station changes.

 The present invention focuses on the existing power control information (RPC) for the transmission output instruction described above, and is conceived to utilize the existing control information for transmission diversity control. Hereinafter, a configuration for using the above-described existing RPC bits for transmission diversity control will be mainly described.

 FIG. 1 is a block diagram showing a configuration of a mobile station according to the first embodiment of the present invention. FIG. 1 shows a configuration related to a radio transmission / reception function among the configurations of the mobile station, and other configurations are omitted. In FIG. 1, a mobile station is provided with two antennas 1-1 and 2, and antennas 1-1 and 2 are provided with antenna duplexers 2-1 and 2, respectively. The reception RF unit 3 is provided so as to correspond to each of the antenna duplexers 2-1 and 2, converts each RF signal received by the antennas 1-1 and 2 into a baseband signal, and converts the converted signal to Further, it is digitized and output to the adaptive array control unit (attenuation amount estimation means) 4. The adaptive array control unit 4 uses the reference signal and each received signal to perform adaptive signal processing using an adaptive algorithm based on MMSE (Minimum Mean Square Error) and the like by an adaptive array antenna. Receive. The adaptive array antenna output signal is output to a data receiving unit (not shown) to perform data reception processing.

 In the adaptive array control unit 4, the following processing is performed in parallel with the adaptive signal processing.

(1) An average received power from which fading has been removed is obtained by performing received signal synthesizing, time average of received power fluctuation or frequency distribution average (filtering), and rake combining (or a combination thereof).

(2) By using the power value of average received power (average received power value: Pr), even in an FDD system (Frequency Division Duplex) with a frequency difference between transmission and reception (for example, reception: 860 MHz, transmission: 915 MHz), Estimate the attenuation of the radio propagation path with little error. The attenuation value (g) is specifically obtained by subtracting the average received power value (Pr) obtained by the adaptive array control unit 4 from the transmission power value of the base station (base station transmission power value: Po). (See FIG. 7). The received power information including the attenuation amount information is output to a transmission power comparison / determination unit (threshold setting unit and comparison unit) 5 described later.

 The adaptive array antenna output from the adaptive array control unit 4 described above is also input to the RPC bit detection unit (transmission power determination means) 6. The RPC bit detector 6 detects the RPC bit from the adaptive array antenna output signal, determines the current transmission power of the mobile station instructed by the base station based on the RPC bit, and determines the value ( A transmission power value {Pt}) is calculated. The transmission power value (Pt) is calculated as a cumulative result of changes of 1 dB in RPC bits (bit values “0” and “1”) (a specific calculation method will be described with reference to FIG. 5). The transmission power value (Pt) is output to the transmission power comparison / determination unit 5 and the transmission diversity control unit (control unit) 7, respectively.

 The transmission power comparison / determination unit 5 receives the received power information from the adaptive array control unit 4 (in this case, the attenuation value {g}) and the power value required for reception at the base station (base station reception required power). Value: Pbr), that is, by adding the attenuation value (g) to the base station reception required power value (Pbr), the power value required by the mobile station during transmission (average transmission power value: Pu) is estimated and calculated (see FIG. 5), and a threshold (th) is calculated (set) based on the average transmission power value (Pu) (see FIG. 6: a specific threshold {th} calculation method) Will be described later). Then, the threshold value (th) is compared with the transmission power value (Pt) input from the RPC bit detection unit 6.

 When the transmission power comparison / determination unit 5 determines that the transmission power value (Pt) is larger than the threshold (th) by a certain value or more as a result of the comparison, the currently used antenna (antenna 1-1 or antenna 1− Switching control to switch to an antenna that is not currently used because it is determined that the environment of the radio propagation path in 2) is likely to be bad for the average radio propagation path environment where the mobile station is located The signal is output to the transmission diversity controller 7.

 The transmission RF unit 8 converts the baseband transmission signal A into an RF signal (see FIG. 1), and further amplifies the power to output it as a radio output signal B to the transmission diversity control unit 7. Note that the power amplification level is increased or decreased according to an instruction based on the RPC bit as in the conventional case.

 In the transmission diversity control unit 7, the switching control signal from the transmission power comparison / determination unit 5 is input to the control unit 9, and the control unit 9 switches and controls the switch 10.

  Next, the result of performing the algorithm of the present invention is shown (FIG. 2: a chart showing the transmission power of each antenna and the antenna selection result by the algorithm of the present invention).

 As shown in FIG. 2, as a result of comparing the threshold value (th) with the current transmission power value (Pt) (TxAnt1, TxAnt2: the value of the transmission power of the antenna used in FIG. 2), the transmission power When the value (Pt) is larger than the threshold value (th), it is determined that the environment of the radio propagation path of the currently used antenna is worse than the environment of the average radio propagation path where the mobile station is placed. It will be. Therefore, in this case, the antenna currently used can be switched to another antenna.

 Since the mobile station of the present invention is controlled to switch antennas based on the result of such comparison (the cross mark in FIG. 2), the characteristics of the radio propagation path in transmission can be improved. As a result, average throughput can be improved.

  Since the radio propagation path varies depending on the movement status of the mobile station and the like, it is preferable to control the threshold (th) to vary in order to improve the characteristics of the radio propagation path. For example, when the antenna is frequently switched due to the movement of the mobile station or the like, a threshold value (in order to be able to switch the antenna when the higher transmission power value (Pt) is reached) th). A function is provided to count the number of times the transmission power value (Pt) exceeds the threshold, and when the transmission power value (Pt) continuously exceeds the threshold N times, the antenna is switched. May be. Furthermore, a hysteresis characteristic may be provided for antenna switching by the threshold value (th).

  Next, the threshold value changing operation described above will be described. FIG. 3 is a flowchart showing the threshold fluctuation operation, FIG. 4 is a subroutine showing the calculation processing of the average received power value (Pr) in FIG. 3, and FIG. 5 is a calculation of the transmission value (Pt) in FIG. FIG. 6 is a subroutine showing the threshold value (th) calculation process in FIG. 3, FIG. 7 is a subroutine showing the average transmission power value (Pu) calculation process in FIG. 6, and FIG. , A subroutine showing control processing of the parameter “α”. Note that (S1) to (S26) in the flowchart show step processing of each operation.

 First, “antenna 1-1” or “antenna 1-2” is set as the antenna that the mobile station first transmits (S1). In Step 1, a parameter “α” and a base station transmission power value (Po) for changing the threshold value (th) are appropriately set. Note that the parameter “α” is a value set based on factors such as fading at the time of reception, device operation error, and application error, and this value indicates the communication quality after the switching of the antennas 1-1 and 2. Accordingly, it is set so as to vary appropriately (the control of the parameter “α” will be described later).

 In step 2, the RPC bit is detected from the adaptive array antenna output signal, and the initial transmission power value (Pt) of the mobile station indicated by the base station is calculated based on the RPC bit.

 After Step 2, when the mobile station starts a call, the mobile station enters a loop indicating a wireless communication state (repeating a range surrounded by symbols of the same name), and further enters a time loop with the start of the call. The time loop is a process that is repeated for a predetermined time by a first timer provided in advance in the mobile station. In the time loop, transmission diversity control is not performed until the first timer expires. In addition, it is assumed that the first timer is initialized at the time of step 2.

  When the time loop is entered, conventional communication processing is performed (S3), and then a step of calculating an average received power value (Pr) from the power received by the mobile station is performed (S4). Specifically, as shown in FIG. 4, first, received waves received by the two antennas 1-1 and 2 are isotopically synthesized by the adaptive array control unit 4 (S5). Then, the power obtained by the isotope synthesis is averaged (time average or frequency distribution average {filtering}) of the received power variation (S6) by the time axis (or frequency axis), and rake synthesis or the like is performed, thereby fading. The average received power from which is removed is obtained, and thereby the average received power value (Pr) is calculated (S7).

  Next, within this time loop, a transmission power value (Pt) is calculated (S8). That is, the RPC bit detection unit 6 detects the RPC bit from the adaptive array antenna output signal (S9), and whether this RPC bit means an instruction to increase the transmission power of 1 dB (in this embodiment, “0 ") Or whether it means an instruction to decrease the transmission power of 1 dB (" 1 "in the present embodiment) (S10). As a result of the determination, if the RPC bit is “0”, the transmission power value (Pt) is controlled to increase by 1 dB (S11). If the RPC bit is “1”, the transmission power is 1 dB. Control is made to decrease (S12).

  After exiting the time loop, a threshold value (th) is calculated (S13). As described above, the threshold (th) is calculated based on the average transmission power value (Pu). Specifically, as shown in FIG. 6, after calculating the average transmission power value (Pu) (S14). Thus, calculation is performed by adding the parameter “α” (S15). As shown in FIG. 7, the average transmission power value (Pu) is calculated by subtracting the average reception power value (Pr) from the base station transmission power value (Po) to calculate the attenuation value (g). (S16) and a step (S17) of adding the attenuation value (g) to the base station reception required power value (Pbr).

 Next, the transmission power comparison / determination unit 5 compares the transmission power value (Pt) with the threshold value (th) (S18). As a result of the comparison, if the transmission power value (Pt) is equal to or less than the threshold value (th), it is determined that the communication quality is good, and as a result, the currently used antenna is not switched (S19). On the other hand, when the transmission power value (Pt) is larger than the threshold value (th) and gradually increases (S20), it is determined that the communication quality is deteriorated or deteriorates. In this case, a control signal is output to the control unit 9 of the transmission diversity control unit 7, and the transmission diversity control unit 7 performs antenna switching based on this control signal (S21).

 By the way, when the communication quality (the state of the radio propagation path) of the two antennas 1-1 and 2 is poor, antenna switching is performed with a high frequency, and the transmission state is not stable. Therefore, the controller 9 may be provided with a second timer for performing control so that the antenna is not switched for a predetermined time after the antenna is switched in advance. In this case, the second timer is started immediately after the antenna is switched (S22).

  Note that the control unit 9 may be configured to be able to appropriately change the activation time of the second timer according to the communication quality, and based on the result of antenna switching, the current threshold value It may be possible to configure a means for determining whether or not is appropriate and changing the threshold value as a result of the determination.

 Next, step 23 in FIG. 3, that is, the “α control” subroutine shown in FIG. 8 will be described. The control of the parameter “α” is performed, for example, by grasping the communication quality from the RPC bits detected by the RPC bit detection unit 6 (S24), and as a result of switching the antennas 1-1 and 2, for example, in the mobile station When there is an instruction from the base station to reduce the transmission power (instruction based on the RPC bit), that is, when the communication quality is improved after switching the antennas 1-1 and 2, the radio propagation is further improved. In anticipation of improvement in the characteristics of the road, control is performed to lower the value of the parameter “α” (S25). On the other hand, when the communication quality is deteriorated, control is performed to increase the value of the parameter “α” (S26). In addition, in a state where the communication quality is improved by switching, it is considered that there are relatively many attenuation factors (fading) that deteriorate the conditions of the transmitting antenna, in addition to the attenuation based on the distance of the radio propagation path. Therefore, the probability of antenna switching is increased by lowering the value of the parameter “α”.

 In this way, by controlling the parameter “α”, it is possible to absorb the calculation error of the attenuation value (g) that occurs because the antenna adaptive control at the time of reception does not sufficiently remove fading.

 As described above, in the mobile station according to the present embodiment, transmission power is determined based on the RPC bit for transmission output instruction from the base station, and further, transmission diversity control is performed based on the value of this transmission power. Therefore, the feed pack information dedicated to transmission diversity control is not required as in the prior art. Furthermore, since transmission diversity is controlled based on the transmission output instruction content by the RPC bit, transmission diversity can be appropriately controlled according to increase or decrease of transmission output. Furthermore, since only one transmission RF unit 8 is required, on / off control of the operation of the transmission RF unit is not required.

 Next, a second embodiment of the present invention will be described. FIG. 9 is a block diagram showing a configuration of a mobile station according to the second embodiment of the present invention. In FIG. 9, parts corresponding to those in FIG. 1 are given the same reference numerals, and explanation thereof is omitted.

 In the mobile station shown in FIG. 9, the antenna to be transmitted is not switched using a switch, but is switched by weighting the radio output signals B supplied individually to the antennas 1-1 and 1-2.

 Specifically, the transmission diversity controller 7A is provided with a weighting unit 11 corresponding to each of the antennas 1-1 and 2. Then, the control unit 9A performs diversity control processing similar to that of the first embodiment, and supplies weighting factors W1 and W2 for the antennas 1-1 and 2 to each weighting unit 11. The weighting unit 11 weights the wireless output signal B output from the transmission RF unit 8 using the weighting coefficient supplied from the control unit 9A. The control unit 9A sets the weighting factor based on the switching control signal from the transmission power comparison / determination unit 5. Thereby, the unselected output signal B is supplied to the antenna 1-1 after being weighted by the weighting factor W1. The antenna 1-2 is supplied with the wireless output signal B after being weighted by the weighting factor W2.

 According to the second embodiment described above, the same effects as those of the first embodiment described above can be obtained. Furthermore, transmission antennas can be switched smoothly by weighting control. In addition, noise caused by switching with a mechanical switch can be eliminated.

 As mentioned above, although each embodiment of the present invention has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention. . For example, in each of the embodiments described above, two antennas are used, but the present invention can be similarly applied to the case where three or more antennas are used. Further, the present invention may be similarly applied to a radio apparatus that does not constitute an adaptive array antenna for reception, and may be similarly applied to a radio apparatus for a base station. Further, any wireless communication system that transmits control information for instructing transmission output to a transmission station can be applied to various wireless communication systems.

 In each of the above-described embodiments, the baseband transmission signal A is converted into an RF signal by the transmission RF unit 8, further power amplified, and the radio output signal B is output to the transmission diversity control units 7 and 7A. For example, the baseband transmission signal is output to the transmission diversity control units 7 and 7A, and the signals output from the transmission diversity control units 7 and 7A are output to the transmission RF unit 8, respectively. May be.

It is a block diagram which shows the structure of the mobile station which concerns on the 1st Embodiment of this invention. It is the graph which showed the transmission power of each antenna, and the antenna selection result by the algorithm of this invention. It is the flowchart which showed the fluctuation | variation operation | movement of a threshold value. 4 is a subroutine showing an average received power value calculation process in FIG. 3. It is the subroutine which showed the calculation process of the transmission value in FIG. 4 is a subroutine showing threshold value calculation processing in FIG. 3. 7 is a subroutine showing an average transmission power value calculation process in FIG. 6. It is a subroutine showing the control processing of the parameter “α”. It is a block diagram which shows the structure of the mobile station which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

1: Antenna,
4: Adaptive array control unit (attenuation amount estimation means),
5: Transmission power comparison determination unit (threshold setting means and comparison means),
6: RPC bit detection unit (transmission power determination means),
7, 7A: Transmission diversity control unit (control means).

Claims (4)

A diversity device with a plurality of antennas,
A transmission power determining means for receiving a control signal instructing a transmission output of the diversity apparatus and determining a transmission power based on the control signal;
Attenuation amount estimation means for estimating the attenuation amount of the radio propagation path based on the received signal;
Threshold value setting means for estimating a power value required at the time of transmission based on the attenuation amount of the radio wave path estimated by the attenuation amount estimation means, and setting a threshold value based on the estimated power value;
A comparison means for comparing the transmission power determined by the transmission power determination means with the threshold;
And a control unit that controls transmission diversity of the diversity apparatus based on a result of the comparison performed by the comparison unit. The diversity apparatus according to claim 1, wherein the threshold setting unit is controlled so that the threshold can be changed according to communication quality. The diversity apparatus according to claim 1, wherein the control unit controls transmission diversity of the diversity apparatus by switching an antenna to transmit. The said control means controls the transmission diversity of the said diversity apparatus by weighting with respect to the transmission signal supplied to these antennas, The claim of Claim 1 or Claim 2 characterized by the above-mentioned. The diversity apparatus as described.

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