JP2007274134A - Radio communication equipment and transmission power control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an abrupt increase in transmission power caused by transmission power control in response to a communication state by quickly tracking the transmission power to a change in the communication state when the communication state is abruptty deteriorated. <P>SOLUTION: A base station apparatus 10 for carrying out radio communication includes: a transmission power target value determining section 66 for determining a target value of the transmission power for radio transmission in the radio communication in response to the communication state of the radio communication; a transmission power target value correction section 67 for correcting the target value determined by the transmission power target value determining section 66 depending on a difference between the target value determined by the transmission power target value determining section 66 and the present transmission power of the radio transmission; and a transmission power control section 68 for controlling the transmission power of the radio transmission on the basis of the target value determined by the transmission power target value determining section 66 or the target value corrected by the transmission power target value correction section 67. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a transmission power control method, and more particularly to a technique for suppressing a rapid increase in transmission power due to transmission power control according to a communication state.

Some mobile communication systems perform transmission power control of radio waves in accordance with the communication state. Specific examples of transmission power control include open loop control and closed loop control. The open loop control is transmission power control according to the reception state in the transmission side communication device, and the closed loop control is transmission power control according to the reception state in the reception side communication device. In any case, when the communication state changes, the transmission power is made to follow the change in the communication state as quickly as possible (see Patent Document 1).
JP 2005-532739 A

  However, if this is done, the transmission power may increase rapidly. That is, when fading occurs, the communication state rapidly deteriorates, so that the transmission power rapidly increases following this.

  When the transmission power increases rapidly, the transmission power of communications other than the communication whose transmission power has increased rapidly may increase rapidly. For example, in a mobile communication system that multiplexes communication using CDMA (Code Division Multiple Access), a radio wave applied to a certain communication becomes an interference wave of a radio wave applied to another communication. When the transmission power increases, the SINR (Signal to Interference plus Noise Ratio) of other communications decreases. For this reason, when the transmission power of a radio wave of a certain communication suddenly increases, the SINR of another communication rapidly decreases, and as a result, the transmission power of another communication rapidly increases.

  In order to prevent this sudden increase, it is simply not possible to moderate the rate at which the transmission power follows the change in the communication state. That is, if the communication state deteriorates rapidly, communication may be disconnected unless the transmission power is made to follow the change in the communication state promptly.

  Accordingly, one of the problems of the present invention is to suppress a rapid increase in transmission power by transmission power control according to the communication state while quickly following the change of the communication state when the communication state deteriorates rapidly. It is an object of the present invention to provide a wireless communication apparatus and a transmission power control method that can be used.

  A wireless communication device according to the present invention for solving the above-described problems is a wireless communication device that performs wireless communication, and sets a target value of transmission power of wireless transmission in the wireless communication according to a communication state of the wireless communication. The transmission power target value determining means to be determined is determined by the transmission power target value determining means according to the difference between the target value determined by the transmission power target value determining means and the current transmission power of the radio transmission. Transmission power target value correcting means for correcting the target value, and the transmission power of the radio transmission based on the target value determined by the transmission power target value determining means or the target value corrected by the transmission power target value correcting means And a transmission power control means for controlling the wireless communication device.

  When the communication state is rapidly improved, the communication is not disconnected without promptly changing the transmission power to the change in the communication state.

  On the other hand, in fading, there is a case where the communication state moves rapidly and then deteriorates rapidly.In such a case, the transmission power suddenly increases and then increases rapidly. If there is not, the subsequent rapid increase can be suppressed.

  According to the wireless communication device, the target value when the transmission power is decreased can be made larger than the target value determined according to the communication state, and transmission when the communication state is rapidly improved. Since the power change can be made gradual, when the communication state deteriorates rapidly, the transmission power quickly follows the change of the communication state, and when the communication state rapidly improves and then deteriorates rapidly, A sudden increase in transmission power due to transmission power control according to the communication state can be suppressed.

  Further, in the wireless communication apparatus, the transmission power target value correcting unit may be configured such that the difference between the target value determined by the transmission power target value determining unit and the current transmission power of the wireless transmission is a negative value. The target value determined by the transmission power target value determining means may be corrected so as to approach the current transmission power.

  According to this, the target value when the transmission power is decreased can be made larger than the target value determined according to the communication state.

  A transmission power control method according to the present invention is a transmission power control method for controlling transmission power of radio transmission related to radio communication performed by a radio communication device, wherein the radio communication is performed according to a communication state of the radio communication. In accordance with the difference between the target value determined in the transmission power target value determination step and the current transmission power of the radio transmission, the transmission power target value determination step for determining the target value of the transmission power of the radio transmission in A transmission power target value correction step for correcting the target value determined in the transmission power target value determination step, a target value determined in the transmission power target value determination step, or a target corrected in the transmission power target value correction step And a transmission power control step of controlling the transmission power of the wireless transmission based on the value.

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

  FIG. 1 is a diagram showing a system configuration of a mobile communication system 1 according to the present embodiment. As shown in the figure, the mobile communication system 1 includes a base station device 10, a mobile station device 20, and a network 30.

  Each of the base station device 10 and the mobile station device 20 is a computer including a CPU and a memory. The CPU is a processing unit for executing a program stored in the memory, and performs processing for controlling each part of each device and realizes functions described later. The memory stores programs and data for carrying out the present embodiment. It also operates as a work memory for the CPU.

  The base station device 10 functions as a wireless communication device. Further, the mobile station device 20 is connected to the network 30 and relays communication performed by the mobile station device 20 with the network 30.

  The mobile station device 20 functions as a movable wireless communication device. The mobile station device 20 performs wireless communication with the base station device 10 to wirelessly transmit / receive communication data to / from each other. The communication state (in particular, SINR) of this wireless communication changes as the mobile station device 20 moves.

  The network 30 is constituted by an exchange network constituted by exchanges, an IP network constituted by routers, or the like.

  FIG. 2 is a diagram illustrating functional blocks of the base station apparatus 10. As shown in the figure, the base station device 10 functionally includes an RF transceiver 50, a signal synthesizer 51, a reception weight calculator 52, a demodulator 53, a decoder 54, an encoder 55, a modulator 56, Signal distribution unit 57, uplink communication state acquisition unit 60, transmission power target value determination unit 61, transmission power target value correction unit 62, transmission power control unit 63, downlink communication state acquisition unit 65, transmission power target value determination unit 66, transmission A power target value correction unit 67 and a transmission power control unit 68 are included.

  The RF transmitting / receiving unit 50 includes an adaptive array antenna. The radio signal transmitted by the mobile station apparatus 20 is received by each antenna constituting the adaptive array antenna and output to the signal combining unit 51.

  The signal synthesizer 51 synthesizes signals received by the respective antennas to obtain a synthesized signal. At this time, the reception weight calculator 52 calculates the reception weight based on the reception power and the phase difference of the signal received by each antenna.

  The demodulator 53 demodulates the synthesized signal obtained by the signal synthesizer 51 and outputs the demodulated signal to the decoder 54. At this time, the uplink communication state acquisition unit 60 acquires the reception state of the composite signal (uplink reception state, here it is assumed to be SINR).

  The decoding unit 54 decodes the demodulated combined signal and outputs the received communication data (received data) to a communication processing unit (not shown). When the mobile station device 20 receives a radio signal transmitted by the base station device 10, the mobile station device 20 acquires the reception state (downlink reception state, here, SINR) in the mobile station device 20. It is transmitted to the base station apparatus 10 as a part of communication data. The downlink communication state acquisition unit 60 acquires the downlink reception state thus included in the communication data by the mobile station device 20 from the reception data.

  The encoding unit 55 receives communication data (transmission data) to be transmitted from a communication processing unit (not shown), obtains a communication signal by encoding, and outputs the communication signal to the modulation unit 56.

  The modulation unit 56 modulates the communication signal input from the encoding unit 55 and outputs it to the signal distribution unit 57 as a modulation signal.

  The signal distribution unit 57 determines the transmission weight based on the reception weight calculated by the reception weight calculation unit 52. Then, a transmission power ratio and a phase difference between the antennas are obtained based on the determined transmission weight. The signal distribution unit 57 distributes the modulation signal input from the modulation unit 56 to each antenna, amplifies the modulation signal distributed to each antenna according to the obtained transmission power ratio, and distributes the modulation signal to each antenna according to the obtained phase difference. The modulated signal is delayed and output to the RF transceiver 50.

  The RF transmission / reception unit 50 wirelessly transmits the modulated signal distributed to each antenna constituting the adaptive array antenna from each antenna.

  The transmission power control unit 63 controls the transmission power of radio transmission performed by the mobile station apparatus 20 according to the uplink reception state acquired by the uplink communication state acquisition unit 60. Further, the transmission power control unit 68 controls the transmission power of radio transmission performed by the base station apparatus 10 according to the downlink reception state acquired by the downlink communication state acquisition unit 65. Hereinafter, each will be described in detail.

  First, functions related to transmission power control of the transmission power control unit 63 will be described. First, the transmission power target value determining unit 61 determines a target value for the transmission power of radio transmission performed by the mobile station apparatus 20 according to the uplink communication state. Specifically, the optimum transmission power corresponding to the uplink communication state is determined, and the optimum transmission power is set as the target value.

  The transmission power target value correction unit 62 determines the transmission power target value determination unit 61 according to the difference between the target value determined by the transmission power target value determination unit 61 and the current transmission power of radio transmission performed by the mobile station apparatus 20. The target value determined by is corrected. For this processing, the transmission power target value correction unit 62 stores the previous corrected target value, and uses the corrected target value as the current transmission power of radio transmission performed by the mobile station apparatus 20.

  Specifically, the transmission power target value correction unit 62 is a case where the difference between the target value determined by the transmission power target value determination unit 61 and the current transmission power of radio transmission performed by the mobile station device 20 is a negative value. Then, the target value determined by the transmission power target value determination unit 61 is corrected so as to approach the current transmission power of the radio transmission performed by the mobile station apparatus 20. Thereby, when the transmission power of the radio transmission performed by the mobile station apparatus 20 is to be reduced, the reduction width is reduced.

  More specifically, correction may be performed in accordance with the transmission power for the past predetermined number of control times and the target value determined by the transmission power target value determination unit 61 as in the following equation (1). In Expression (1), the transmission power target value correction unit 62 sets the average value of the transmission power and the target value for the past K control times as the transmission power for the Nth control.

  In addition, the transmission power target value correction unit 62 determines the maximum value of the reduction amount in advance, and corrects the reduction amount to be the determined reduction amount when the reduction amount exceeds the determined reduction amount. Also good.

  Based on the target value determined by the transmission power target value determination unit 61 or the target value corrected by the transmission power target value correction unit 62, the transmission power control unit 63 determines the transmission power of radio transmission performed by the mobile station apparatus 20. Control. Specifically, when the difference between the target value determined by the transmission power target value determination unit 61 and the current transmission power of radio transmission performed by the mobile station apparatus 20 is a positive value, the transmission power target value determination unit 61 The transmission power of the radio transmission performed by the mobile station device 20 is controlled based on the target value determined by the mobile station device 20, and the target value determined by the transmission power target value determination unit 61 and the current wireless transmission performed by the mobile station device 20 are controlled. When the difference from the transmission power is a negative value, the transmission power of radio transmission performed by the mobile station device 20 is controlled based on the target value corrected by the transmission power target value correction unit 62.

  A specific transmission power control method will be described. The transmission power control unit 63 includes the transmission power (corrected target value) of the mobile station device 20 in a part of communication data transmitted to the mobile station device 20. The mobile station apparatus 20 acquires the transmission power included in the communication data in this way, and starts transmission with the transmission power.

  Next, functions related to transmission power control of the transmission power control unit 68 will be described. First, the transmission power target value determination unit 66 determines a target value of transmission power for radio transmission performed by the base station apparatus 10 according to the downlink communication state. Specifically, the optimum transmission power corresponding to the downlink communication state is determined, and the optimum transmission power is set as the target value.

  The transmission power target value correction unit 67 determines the transmission power target value determination unit according to the difference between the target value determined by the transmission power target value determination unit 66 and the current transmission power of the radio transmission performed by the base station apparatus 10. The target value determined by 66 is corrected. For this processing, the transmission power target value correction unit 67 stores the previous corrected target value, and uses the corrected target value as the current transmission power of the wireless transmission performed by the base station apparatus 10. .

  Specifically, the transmission power target value correction unit 67 has a negative value between the target value determined by the transmission power target value determination unit 66 and the current transmission power of radio transmission performed by the base station apparatus 10. In this case, the target value determined by the transmission power target value determination unit 66 is corrected so as to approach the current transmission power of the radio transmission performed by the base station apparatus 10. Thereby, when the transmission power of the radio transmission performed by the base station apparatus 10 is to be reduced, the reduction amount is reduced.

  More specifically, correction may be performed in accordance with the transmission power for the past predetermined number of control times and the target value determined by the transmission power target value determination unit 66 as in the following equation (2). In Expression (2), the transmission power target value correction unit 67 uses the average value of the transmission power and the target value for the past control K times as the control N-th transmission power.

  Further, the transmission power target value correction unit 67 determines the maximum value of the reduction amount in advance, and corrects the reduction amount to be the determined reduction amount when the reduction amount exceeds the determined reduction amount. Also good.

  Based on the target value determined by the transmission power target value determination unit 66 or the target value corrected by the transmission power target value correction unit 67, the transmission power control unit 68 performs transmission power of radio transmission performed by the base station apparatus 10 To control. Specifically, when the difference between the target value determined by the transmission power target value determination unit 66 and the current transmission power of radio transmission performed by the base station apparatus 10 is a positive value, the transmission power target value determination unit Based on the target value determined by 61, the transmission power of radio transmission performed by the base station apparatus 10 is controlled, and the target value determined by the transmission power target value determination unit 66 and the radio transmission performed by the base station apparatus 10 When the difference from the current transmission power is a negative value, the transmission power of the radio transmission performed by the base station apparatus 10 is controlled based on the target value corrected by the transmission power target value correction unit 67. In addition, the transmission power control unit 68 controls the transmission power of radio transmission performed by the base station apparatus 10 by amplifying the modulation signal by an amount corresponding to the corrected target value in the modulation unit 56.

  The processing of the base station device 10 described above will be described again in more detail with reference to the processing flow.

  FIG. 3 is a diagram showing a processing flow of the base station apparatus 10. Here, downlink transmission power control when mobile station apparatus 20 performs packet communication will be described as an example. As shown in FIG. 3, the base station apparatus 10 first determines whether or not the wireless communication is based on VoIP (Voice over IP) (S1).

  If it is not based on VoIP, the base station apparatus 10 moves the process to S5. If it is based on VoIP, the base station apparatus 10 performs header compression (for example, ROHC (RObust Header Compression)) of a packet (S2). Also, link adaptation (modulation method changing process according to the reception state) is turned off to prevent link adaptation (S3).

  In the case of using VoIP, the base station apparatus 10 further increases the downlink transmission power control width by 7 dB (S4). The transmission power control unit 68 uses the optimum transmission power according to the downlink communication state as the target value as described above, but actually there is a limitation on the range of change of the transmission power, and the radio transmission performed by the base station apparatus 10 Only a predetermined transmission power control width can be changed from the current transmission power. For this reason, when the transmission power control width is changed, the transmission power control unit 68 determines the transmission power full of the transmission power control width as a target value. In S4, the base station apparatus 10 increases the transmission power control width. This is because VoIP does not perform link adaptation, so it is necessary to cope with a change in communication state only by changing transmission power.

  The base station apparatus 10 acquires reception state information (SINR) from the mobile station apparatus 20 (S5). Then, the transmission power target value determination unit 66 determines a target value (S6). This is called conventional transmission power determination processing). Then, it is determined whether or not the target value is lower than a predetermined value from the current transmission power of radio transmission performed by the base station apparatus 10 (S7). The target value is corrected by the value correction unit 67 (S8). This is called transmission power smoothing processing). Then, the base station apparatus 10 performs transmission power control based on the target value after correction when corrected, or the target value determined in S6 when not corrected (S9).

  As described above, according to the base station apparatus 10, the target value when the transmission power is decreased can be made larger than the target value determined according to the communication state, and the communication state is rapidly increased. The transmission power change when the communication status is improved can be moderated. Therefore, if the communication status deteriorates rapidly, the transmission power is quickly followed by the change in the communication status, and then suddenly improved after the communication status is improved rapidly. When it gets worse, it is possible to suppress a sudden increase in transmission power due to transmission power control according to the communication state. Further, the target value when the transmission power is decreased can be made larger than the target value determined according to the communication state.

  The present invention is not applicable only to mobile communication systems, and can be widely applied to transmission power control in wireless communication apparatuses.

It is a figure which shows the system configuration | structure of the mobile communication system concerning this Embodiment. It is a figure which shows the functional block of the base station apparatus concerning this Embodiment. It is a figure which shows the processing flow of the base station apparatus concerning this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mobile communication system, 10 Base station apparatus, 20 Mobile station apparatus, 30 Network, 50 RF transmission / reception part, 51 Signal synthetic | combination part, 52 Reception weight calculating part, 53 Demodulation part, 54 Decoding part, 55 Encoding part, 56 Modulation unit, 57 signal distribution unit, 60 uplink communication state acquisition unit, 61, 66 transmission power target value determination unit, 62, 67 transmission power target value correction unit, 63, 68 transmission power control unit, 65 downlink communication state acquisition unit.

Claims (3)

A wireless communication device that performs wireless communication,
Transmission power target value determining means for determining a target value of transmission power of wireless transmission in the wireless communication according to the communication state of the wireless communication;
Transmission power target value correction for correcting the target value determined by the transmission power target value determination means according to the difference between the target value determined by the transmission power target value determination means and the current transmission power of the radio transmission Means,
Transmission power control means for controlling the transmission power of the radio transmission based on the target value determined by the transmission power target value determination means or the target value corrected by the transmission power target value correction means;
A wireless communication apparatus comprising: The wireless communication device according to claim 1,
When the difference between the target value determined by the transmission power target value determination means and the current transmission power of the radio transmission is a negative value, the transmission power target value correction means Correcting the determined target value so as to approach the current transmission power;
A wireless communication apparatus. A transmission power control method for controlling transmission power of wireless transmission related to wireless communication performed by a wireless communication device,
A transmission power target value determining step for determining a target value of transmission power of wireless transmission in the wireless communication according to a communication state of the wireless communication;
Transmission power target value correction for correcting the target value determined in the transmission power target value determination step according to the difference between the target value determined in the transmission power target value determination step and the current transmission power of the radio transmission Steps,
A transmission power control step for controlling the transmission power of the radio transmission based on the target value determined in the transmission power target value determination step or the target value corrected in the transmission power target value correction step;
Including a transmission power control method.

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