JP2007195151A - Diversity apparatus and transmission diversity control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately control transmission diversity without requiring feedback information dedicated to transmission diversity control. <P>SOLUTION: A power control bit A instructing transmission output is received and on the basis of the power control bit A, transmission diversity is controlled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a diversity apparatus.

In wireless communication systems with different carrier frequencies for transmission and reception, such as FDD (Frequency Division Duplex) communication method, there is a possibility that the radio wave propagation status of transmission and reception 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, a receiving station generates dedicated feedback information for controlling transmission diversity of the transmitting station based on a received signal from the transmitting station, and provides the 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 arises a problem 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, and there is a possibility that adverse effects such as limiting the transmission diversity control method may occur.

  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-described problem, the diversity device according to claim 1, in the diversity device including a plurality of antennas, determines whether or not the antenna switching means for switching the antenna to be transmitted and is currently transmitting, In the case of non-transmission, assuming that the antenna switching means can be switched, switching control means for causing the antenna switching means to perform switching, and control information for instructing increase or decrease in the transmission output of the diversity device The switching control means, when the ratio of the control information that instructs to increase the transmission output of the diversity device is not large among the plurality of control information received by the receiving means. Causes the antenna switching means to wait for execution of switching until the first predetermined time has elapsed, and When the ratio of the control information for instructing the increase of the transmission output of the diversity apparatus is large, after the antenna switching means is switched, the switching is made to wait until the second predetermined time elapses. It is characterized by.

  In the diversity apparatus according to claim 2, as a result of determining whether or not the transmission is currently being transmitted, the switching control means has an adverse effect on communication quality even if transmission data is further lost during transmission. If the antenna switching means is switchable when it is determined that the communication quality is not adversely affected, the antenna switching means is made to perform switching. To do.

  The diversity apparatus according to claim 3 is characterized in that the antenna switching means comprises a switch.

  The diversity apparatus according to claim 4, wherein the antenna switching unit switches the antenna to be transmitted by weighting a transmission signal supplied to the plurality of antennas.

  The diversity apparatus according to claim 5, wherein the weighted transmission signal is a baseband signal.

  The diversity apparatus according to claim 6, wherein the weighted transmission signal is a radio output signal.

The transmission diversity control method according to claim 7 is a transmission diversity control method in a diversity apparatus having a plurality of antennas. In the transmission diversity control method, it is determined whether transmission is currently being performed. Assuming that it is possible, after switching the transmitting antenna, after switching the transmitting antenna, receiving a plurality of control information instructing increase or decrease of the transmission output of the diversity device, and the plurality of received control If the ratio of the control information instructing the increase of the transmission output of the diversity device is not large among the information, the step of waiting for the switching of the transmitting antenna until the first predetermined time elapses; Among the control information, the control information that instructs to increase the transmission output of the diversity device. When the proportion of large, after switching the antenna to the transmitting until a second predetermined time has passed is characterized by comprising a step of waiting the switching of antennas the transmission.
In the transmission diversity control method according to claim 8, as a result of determining whether or not transmission is currently being performed, in the case of transmission, whether or not the transmission quality is further adversely affected even if transmission data is impaired. If it is determined that the communication quality is not adversely affected, the method further includes a step of switching the antenna to be transmitted, assuming that the antenna to be transmitted can be switched.

  According to the present invention, since the existing control information for transmission output instruction is used for transmission diversity control, feedback 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 performs increase / decrease control of the transmission output of the mobile station according to the reception strength from the mobile station. The transmission output control is intended to suppress variations in 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 a power control bit to the mobile station to be controlled. The power control bit has a 1-bit configuration, and a bit value “0” is an instruction to increase transmission power of 0.5 dB or 1 dB, and a bit value “1” is an instruction to decrease transmission power of 0.5 dB or 1 dB. The mobile station increases or decreases its transmission power according to the instruction of the power control bit received from the base station. As a result, the transmission output of the mobile station changes.

  The present invention focuses on the existing control information (power control bit) for the transmission output instruction described above and conceives that the existing control information is used for transmission diversity control. Hereinafter, a configuration for using the above-described existing power control 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, the mobile station has two antennas 1-1 and 2. The antenna duplexer 2 shares the antennas 1-1 and 2 for transmission and reception. The reception RF unit 3 converts each RF signal received by the antennas 1-1 and 2 into a baseband signal, further digitizes it, and outputs it to the adaptive array antenna processing unit 4. The adaptive array antenna processing 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), etc. Receive by. The adaptive array antenna output signal is output to the data receiving unit, and data reception processing is performed.

  The adaptive array antenna output signal is also input to the power control bit detector 5. The power control bit detector 5 detects a power control bit from the adaptive array antenna output signal. The detected power control bit A is input to the transmission diversity control unit 7.

  The transmission RF unit 6 converts the baseband transmission signal into an RF signal, further amplifies the power, and outputs the radio output signal B to the transmission diversity control unit 7. Then, the power amplification level is increased or decreased according to the instruction of the power control bit A as in the conventional case.

  The transmission diversity control unit 7 controls the transmission diversity based on the transmission power instruction content by the power control bit A. The transmission diversity control unit 7 selects an antenna to be transmitted by the transmission diversity control, and outputs a radio output signal B to the selected antenna. Therefore, when transmitting using the antenna 1-1, the radio | wireless output signal B is output from the transmission diversity control part 7 as the radio | wireless output signal C1. On the other hand, when transmitting using the antenna 1-2, the radio | wireless output signal B is output from the transmission diversity control part 7 as the radio | wireless output signal C2.

  FIG. 2 is a block diagram showing a configuration of the transmission diversity control unit 7 shown in FIG. In FIG. 2, the control unit 11 performs transmission diversity control processing using the power control bit A. The transmission diversity control unit 7 selects an antenna to be transmitted by the transmission diversity control process, and switches and controls the switch 12 according to the selection result.

  Moreover, the control part 11 can acquire the information which shows a transmission state. For example, it is possible to know whether it is currently waiting for transmission, transmitting, or in any state. Further, it is possible to know the presence and type of untransmitted transmission data. Then, the control unit 11 determines whether or not the switch 12 can be switched based on the current transmission state. For example, it is determined that switching is possible when waiting for transmission, when there is no untransmitted transmission data, and when communication quality is not adversely affected even if untransmitted transmission data is lost.

Next, an operation related to transmission diversity control will be described.
FIG. 3 is a flowchart showing the flow of an embodiment of the transmission diversity control process performed by the control unit 11 shown in FIG.
In FIG. 3, first, the control unit 11 determines whether or not the switch 12 can be switched based on the current transmission state (step S101). If the result of this determination is that switching is possible, the switch 12 is switched (step S102). Thereby, the antenna which has not been transmitted until now becomes the transmission antenna.

  Next, the control unit 11 calculates the sum of the power control bits A input after the switch 12 is switched (step S103). As described above, the power control bit A has a 1-bit configuration, and the bit value “0” is an instruction to increase transmission power and the bit value “1” is an instruction to decrease transmission power. The sum of the control bits A becomes smaller as the number of transmission power increase instructions increases. That is, the sum of the power control bits A indicates the ratio of the transmission power increase instruction by the transmission antenna after switching. The smaller the sum is, the larger the ratio of the transmission power increase instruction from the base station is. It can be determined that the effect of switching is small.

  Further, the number of power control bits A for calculating the sum in step S103 may be several (for example, 2 to 4). The reason for this is to reduce the number of power control bits A for calculating the sum as much as possible in order to improve the followability to changes in the radio wave propagation environment and to eliminate the effects of changes in the transmission power itself. This is because it is desirable.

  Next, in step S104, the sum of the power control bits A is compared with a predetermined threshold value, and it is determined whether or not the sum is equal to or less than the predetermined threshold value. This threshold value is a boundary value for determining whether or not the transmission diversity effect has been obtained by switching the transmitting antenna. For example, when the ratio of the transmission power increase instruction from the base station is large, it is determined that the transmission diversity effect has not been obtained. In this embodiment, since the bit value “0” of the power control bit A is an instruction to increase transmission power and the bit value “1” is an instruction to decrease transmission power, when the number of sums to be calculated is 2, Is a value greater than 0 and less than 1, for example 0.5, 0.5 or 1.5 when the number is 3, and 1.5 when the number is 4. Thereby, when the sum of the power control bits A is equal to or smaller than the threshold value, it is determined that the transmission diversity effect due to the antenna switching is not obtained, and when the threshold value is exceeded, it is determined that the effect is obtained. The sum may be calculated by simply calculating the ratio of “0” and “1” or by using another method (such as a ratio within a unit time).

  Next, if the result of determination in step S104 is that the threshold has been exceeded, the effect of antenna switching has been obtained, so the current transmission antenna is maintained as it is, and the timer 1 is started and waits for a certain period of time until time-out ( Steps S105 and S106). Then, after timeout, the process returns to step S101.

  On the other hand, if the result of determination in step S104 is equal to or less than the threshold value, the effect of antenna switching was not obtained, so switch 12 is switched back and the antenna before switching is set as the transmission antenna (step S107). Next, the timer 2 is started and waits for a certain period until time-out, and after time-out, the process returns to step S101 (steps S108 and S109).

  In the embodiment of FIG. 3 described above, an antenna that is not transmitting is tried as a transmitting antenna at a fixed period, and the ratio of the transmission power increase instruction from the base station is verified. If it is determined that the transmission diversity effect due to the antenna switching is obtained because the ratio of the transmission power increase instruction is small, the current transmission antenna is maintained as it is. On the other hand, when there is a large ratio of instructions for increasing transmission power, when it is determined that the transmission diversity effect due to antenna switching cannot be obtained, the antenna is switched back to the antenna before switching. As a result, transmission diversity control is performed so that the ratio of the transmission power increase instruction from the base station is reduced. This means that transmission diversity is appropriately controlled so that the reception strength of the base station becomes better. As a result, an excellent effect that communication quality can be improved is obtained.

  Note that the timeout times of the timers 1 and 2 are set based on the change speed of the radio wave propagation environment. Accordingly, it is possible to verify the ratio of the instruction to increase the transmission power in accordance with the change speed of the radio wave propagation environment and to switch to an appropriate antenna, so that the followability to the change of the radio wave propagation environment is improved.

FIG. 4 is a flowchart showing the flow of another embodiment of the transmission diversity control process performed by the control unit 11 shown in FIG.
In FIG. 4, first, the control unit 11 calculates the sum of the input power control bits A, compares this sum with a predetermined threshold value, and determines whether or not the sum is equal to or less than the threshold value (Step S11). S201, S202). This threshold value is a boundary value for determining the good transmission effect of the currently transmitting antenna. In this example, as in the above-described embodiment of FIG. 3, it is determined that the transmission effect is not good when the sum of the power control bits A is equal to or less than the threshold value, and the transmission effect is determined good when the sum exceeds the threshold value.

  As a result of the determination in step S202, if the effect is obtained by the current transmission antenna (NO in step S202), the timer 1 is started and waits for a certain period of time until timeout, and returns to step S201 after the timeout ( Steps S203 and S204).

  On the other hand, as a result of the determination in step S202, if the effect is not obtained with the current transmission antenna (YES in step S202), it is determined whether or not the antenna can be switched (step S205). If switching is possible, the switch 12 is switched, and an antenna that has not been transmitted so far is set as a transmission antenna. Next, the timer 2 is started and waits for a certain period of time until time-out, and after time-out, the process returns to step S201 (steps S206, S207, S208).

  In the embodiment of FIG. 4 described above, the ratio of the transmission power increase instruction from the base station by the current transmission antenna is verified at a fixed period. When it is determined that the transmission effect by the current transmission antenna is good because the ratio of the transmission power increase instruction is small, the current transmission antenna is maintained as it is. On the other hand, when it is determined that the transmission effect by the current transmission antenna is not good because the ratio of the instruction to increase the transmission power is large, the antenna to be transmitted is switched. As a result, transmission diversity control is performed so that the ratio of the transmission power increase instruction from the base station is reduced, and therefore transmission diversity control is performed so that the reception strength of the base station is in a better state. Done properly.

  As described above, according to the first embodiment, transmission diversity can be appropriately controlled using the existing power control bit received from the base station. Therefore, feedback information dedicated to transmission diversity control is unnecessary, and the base station does not need to generate feedback information dedicated to transmission diversity control. Thereby, the problem that the processing load increases due to the generation of the dedicated feedback information is solved. Further, the problem that the data transmission efficiency is reduced by the amount of transmission of the dedicated feedback information is also solved.

  Furthermore, since the mobile station does not need to support feedback information dedicated to transmission diversity control, the transmission diversity control method adopted by the mobile station terminal device is arbitrary. As a result, the degree of freedom in designing the mobile station is increased, so that an effect of improving the performance of the terminal device and reducing costs can be expected.

  In addition, since the ratio of instructions to increase the transmission power by the power control bit from the base station is verified at regular intervals, it is possible to indirectly detect that the radio wave propagation environment has changed, and to follow the change in the radio wave propagation environment. Thus, transmission diversity can be controlled.

Next, a second embodiment of the present invention will be described.
FIG. 5 is a block diagram showing a configuration of a mobile station according to the second embodiment of the present invention. In FIG. 5, 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. 5, the transmitting antenna is not switched using a switch, but is switched by weighting the transmission signals individually supplied to the antennas 1-1 and 1-2. The weighting is performed on the baseband signal.

  Specifically, two transmission RF units 6 that generate radio output signals for the antennas 1-1 and 2 are provided. Further, the transmission diversity control unit 7 a is provided with a weighting unit 21 corresponding to each of the transmission RF units 6. Then, the control unit 11a supplies the weighting factors W1 and W2 for the antennas 1-1 and 2 to each weighting unit 21. The weighting unit 21 weights the baseband transmission signal using the weighting coefficient supplied from the control unit 11a. Thus, the radio output signal converted into the RF signal is supplied to the antenna 1-1 after the baseband transmission signal is weighted by the weighting coefficient W1. The antenna 1-2 is supplied with a radio output signal converted into an RF signal after the baseband transmission signal is weighted by the weighting factor W2.

  Further, the control unit 11a performs the same process as the transmission diversity control process of FIG. 3 or FIG. However, instead of switching the switch 12, the weighting factors W1 and W2 are controlled. The weight coefficient control method will be described below.

  First, as an initial value of the weighting factors W1 and W2, one value is set to 0 and the other value is set to 1. As a result, the antenna with the weight coefficient value of 1 becomes the transmission antenna. Then, when changing the antenna to transmit, while maintaining the condition that the sum of W1 and W2 is 1, the weighting factor of 1 is gradually changed to 0 and the weighting factor of 0 is set. Gradually change to 1. Thus, the antenna to transmit is switched by reversing the value of two weighting factors W1 and W2.

  In addition, the control unit 11a stops the operation of the transmission RF unit 6 whose weight coefficient is 0. For example, power supply to the transmission RF unit 6 is stopped. When the antenna switching operation is performed, both the transmission RF units 6 are operated, and when the switching is completed by reversing 0/1 of the values of the two weighting factors W1 and W2, the one with the weighting factor of 0 is set. The operation of the transmission RF unit 6 is stopped.

  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, transmission signals can be easily weighted in the baseband region. In addition, noise caused by switching with a mechanical switch can be eliminated.

Next, a third embodiment of the present invention will be described.
FIG. 6 is a block diagram showing a configuration of a mobile station according to the third embodiment of the present invention. In FIG. 6, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
In the mobile station shown in FIG. 6, as in the second embodiment of FIG. 5 described above, the transmission antenna is switched by weighting the transmission signals individually supplied to the antennas 1-1 and 1-2. . However, the weighting is performed on the radio output signal.

  Specifically, the transmission diversity control unit 7 b is provided with a weighting unit 22 corresponding to each of the antennas 1-1 and 2. Then, the control unit 11b performs diversity control processing similar to that of the second embodiment described above, and supplies the weighting factors W1 and W2 for the antennas 1-1 and 2 to the weighting units 22, respectively. The weighting unit 22 weights the wireless output signal output from the transmission RF unit 6 using the weighting coefficient supplied from the control unit 11b. Thereby, the wireless output signal 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 after being weighted by the weighting factor W2.

  According to the third 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. Further, since only one transmission RF unit 6 is required, on / off control of the operation of the transmission RF unit 6 becomes unnecessary. In addition, noise caused by switching with a mechanical switch can be eliminated.

The embodiment of the present invention has been described in detail with reference to the drawings. However, 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 the above-described embodiment, 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 can be similarly applied to a radio apparatus that does not constitute an adaptive array antenna for reception. The present invention may also be applied to a base station radio device.

  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.

It is a block diagram which shows the structure of the mobile station which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the transmission diversity control part 7 shown in FIG. It is a flowchart which shows the flow of one Example of the transmission diversity control process which the control part 11 shown in FIG. 2 performs. It is a flowchart which shows the flow of the other Example of the transmission diversity control process which the control part 11 shown in FIG. 2 performs. It is a block diagram which shows the structure of the mobile station which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the mobile station which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

1-1, 2 ... Antenna, 5 ... Power control bit detection unit, 7, 7a, 7b ... Transmission diversity control unit, 11, 11a, 11b ... Control unit, 12 ... Switch, 21, 22 ... Weighting unit, A ... Power Control bit.

Claims (8)

In a diversity device with multiple antennas,
An antenna switching means for switching an antenna to transmit;
It is currently determined whether or not transmission is in progress, and if it has not been transmitted, the antenna switching unit can be switched, and a switching control unit that causes the antenna switching unit to perform switching,
Receiving means for receiving control information for instructing an increase or decrease in transmission power of the diversity device,
When the ratio of control information instructing an increase in the transmission output of the diversity apparatus is not large among the plurality of control information received by the receiving means, the switching control means until the first predetermined time elapses. The antenna switching unit is made to wait for switching, and when there is a large proportion of control information instructing an increase in the transmission output of the diversity device, the antenna switching unit is made to perform switching. After that, the execution of switching is made to wait until the second predetermined time elapses.
Diversity device characterized by that. As a result of determining whether or not the transmission is currently being transmitted, the switching control means further determines whether or not the transmission quality is adversely affected even if the transmission data is lost. If it is determined that the antenna switching unit can be switched, the antenna switching unit is switched.
The diversity apparatus according to claim 1.   The diversity apparatus according to claim 1, wherein the antenna switching unit includes a switch.   The diversity apparatus according to claim 1, wherein the antenna switching unit switches the antenna to be transmitted by weighting a transmission signal supplied to the plurality of antennas.   The diversity apparatus according to claim 4, wherein the transmission signal to be weighted is a baseband signal.   The diversity apparatus according to claim 4, wherein the weighted transmission signal is a radio output signal. In a transmission diversity control method in a diversity apparatus having a plurality of antennas,
It is determined whether or not transmission is currently being performed, and if not transmitted, assuming that the antenna to be transmitted can be switched, switching the antenna to be transmitted;
Receiving a plurality of control information instructing to increase or decrease the transmission output of the diversity device after switching the transmitting antenna;
A step of waiting for switching of the transmitting antenna until a first predetermined time elapses when a ratio of control information instructing an increase in transmission output of the diversity device is not large among the plurality of received control information; ,
When the ratio of the control information instructing to increase the transmission output of the diversity device is large among the plurality of received control information, the transmission is performed until the second predetermined time elapses after the antenna to be transmitted is switched. Waiting for antenna switching; and
A transmission diversity control method comprising:   As a result of determining whether or not transmission is currently being performed, if transmission is being performed, it is further determined whether or not the transmission quality is adversely affected, and whether communication quality is adversely affected. The transmission diversity control method according to claim 7, further comprising a step of switching the antenna to be transmitted on the assumption that the antenna to be transmitted can be switched when it is determined.

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