JP5653838B2 - Radio base station apparatus and transmission power control method - Google Patents

Description

The present invention relates to a radio base station apparatus and a transmission power control method for performing transmission power control according to success or failure of transmission and quality of a communication environment.

  In a wireless communication system, when a receiver normally receives a packet signal transmitted by a transmitter, an ACK (Acknowledgement) signal is returned, and when the transmitter receives this ACK signal, the previous transmission succeeded. There is a control method for determining that the next packet signal is transmitted.

  Here, when the communication environment is good, the packet signal transmitted by the transmitter is normally received by the receiver, and the ACK signal reaches the transmitter. However, when the communication environment is bad, the ACK signal does not reach and retransmission processing, etc. Is done. In the prior art, the transmitter achieves an improvement in throughput by increasing or decreasing the transmission rate according to whether or not an ACK signal reflecting such a communication environment is received (Non-patent Document 1).

FIG. 10 shows an example of a conventional wireless communication system.
In FIG. 10, a STA (station: wireless terminal) that communicates with the AP is arranged in a cell formed according to the transmission power of the AP (access point: wireless base station). By receiving the ACK signal from the STA, the AP determines that the communication environment is good and increases the transmission rate. When the ACK signal does not reach the AP, the communication environment is judged to be bad and the transmission speed is reduced. For example, Non-Patent Document 1 proposes a control in which the transmission rate is increased by one step when an ACK signal is continuously received a plurality of times, and then immediately returned to the original transmission rate if no ACK signal is received. ing. Note that, since the transmission power of the AP at this time is constant, the cell radius does not change regardless of the change in the transmission rate.

FIG. 11 shows a configuration example of a conventional wireless communication apparatus.
In FIG. 11, the wireless communication apparatus includes an antenna 91, a demodulation circuit 92, an ACK measurement circuit 93, a transmission rate setting circuit 94, and a modulation circuit 95. Here, only the main part of the wireless communication device is shown, and an amplifier circuit, a frequency conversion circuit, and the like are omitted.

  The received signal received by the antenna 91 is demodulated by the demodulation circuit 92. Here, since an ACK signal for the transmission signal is assumed, an ACK signal extracted from the reception signal is output to the ACK measurement circuit 93. The ACK measurement circuit 93 counts the ACK signal with respect to the transmission signal and notifies the transmission speed setting circuit 94. The transmission rate setting circuit 94 outputs a control signal for increasing the transmission rate to the modulation circuit 95 when the number of received ACK signals exceeds a specified number. On the other hand, when no ACK signal is received or when the number of non-received ACK signals exceeds a specified number, a control signal for reducing the transmission rate is output. The modulation circuit 95 sets the transmission rate according to the control signal input from the transmission rate setting circuit 94, and modulates the transmission data by a modulation method in which the number of bits per symbol is different, for example, QPSK or QAM according to the transmission rate. Then, the data is transmitted from the antenna 91.

  As described above, in the conventional wireless communication apparatus, the transmission rate is controlled according to reception / non-reception of the ACK signal with respect to the transmission signal.

Inoue et al., "Examination of rate adaptation function in IEEE802.11," Communications Society 2002 Society Conference, B-5-192, September 2002

  By the way, in an environment where cells formed by a plurality of APs are adjacent to each other as in the conventional wireless communication system shown in FIG. 10, interference occurs with each other and communication quality deteriorates. In particular, when there is an AP that transmits at a high output, the interference that the AP gives to other APs and STAs increases.

  In the prior art, the transmission speed is made variable according to the reception / non-reception of the ACK signal reflecting the communication environment, but the transmission power is constant. Therefore, the size of the communication cell is also constant, the situation of communication quality deterioration due to interference does not change, and the throughput also decreases due to a decrease in transmission speed. In addition, when appropriate segregation is not performed with respect to frequency resources, there is a problem that a large amount of retransmission occurs due to a collision and a large amount of power is consumed.

  In addition, since the transmission power of the AP is constant and the size of the communication cell is also constant, it is difficult to place many APs, and the number of STAs accommodated is limited.

It is an object of the present invention to provide a radio base station apparatus and a transmission power control method that can reduce interference by transmission power control according to the quality of a communication environment and achieve both reduction in power consumption and improvement in communication quality. Objective.

A first aspect of the present invention is a wireless base station apparatus in which cells formed by a plurality of wireless base station apparatuses are adjacent to each other and communicates with wireless terminals belonging to the respective cells, modulation means for outputting a transmission signal transmitted from an antenna, and demodulation means for demodulating a received signal received in the antenna, the communication environment determining means for determining the quality of the communication environment between the wireless terminal in accordance with the reception / non-reception of the ACK signal to the transmission signal demodulated by the demodulating means If, enter the quality information of the communication environment from a communication environment determination means, to reduce the range of cells by reducing the transmission power of the transmission signal when the communication environment is good, the transmission signal when the communication environment is bad and a transmission power control means for expanding the range of cells by increasing the transmission power of.

The radio base station apparatus according to the first aspect of the present invention comprises reception level detection means for detecting the reception level of the received signal and outputting it to the transmission power control means, and the transmission power control means is adapted to communicate with the communication environment when the reception level exceeds a threshold value. When the reception level is equal to or lower than the threshold, the communication environment is determined to be bad and the transmission power of the transmission signal is controlled.

The radio base station apparatus according to the first aspect of the invention comprises interference level detection means for identifying that the received signal is a signal from another system, detecting the interference level from the other system and outputting it to the transmission power control means, The transmission power control means is configured to control the transmission power of the transmission signal as a good communication environment when the interference level is equal to or lower than the threshold and as a bad communication environment when the interference level exceeds the threshold.

In the radio base station apparatus of the first invention, when the received signal is a signal from another system, the interference level detecting means for detecting the interference level from the other system, and when the interference level exceeds a threshold, Transmission control means for adjusting the transmission timing of the other system and that of the own system to perform segregation.

In the radio base station apparatus of the first invention, when the received signal is a signal from another system, the interference level detecting means for detecting the interference level from the other system, and when the interference level exceeds a threshold, Frequency conversion means for converting at least one of the carrier frequency of the transmission signal or the carrier frequency of the reception signal and setting the carrier frequency of the other system to be different from that of the own system.

In the radio base station apparatus according to the first aspect of the present invention, when the communication environment is bad even if the communication environment determination means inputs the quality information of the communication environment and the transmission power control means increases the transmission power, Transmission control means for adjusting the transmission timing of the system to perform segregation is provided.

In the radio base station apparatus according to the first aspect of the present invention, if the communication environment is bad even if the communication environment determination unit inputs the quality information of the communication environment and the transmission power control unit increases the transmission power, Frequency conversion means is provided for converting at least one of the frequency and the carrier frequency of the received signal and setting the other system and the own system so that the carrier frequency differs.

In the radio base station apparatus of the first invention, the transmission power control means performs transmission power control according to the quality information of the communication environment when the transmission speed of the transmission signal is the same as the transmission speed of the previous transmission signal, In this configuration, the transmission power control according to the quality information of the communication environment is not performed when the transmission rate of the transmission signal is not the same as the transmission rate of the previous transmission signal.

According to a second aspect of the present invention, there is provided a transmission power control method for a radio base station apparatus in which cells formed by a plurality of radio base station apparatuses are adjacent to each other and communicate with radio terminals belonging to the respective cells. Is transmitted from the antenna, the received signal received by the antenna is demodulated by the demodulating means , and the communication environment determining means determines whether the received signal is received or not received with respect to the transmission signal demodulated by the demodulating means. Determining the quality of the communication environment, inputting the quality information of the communication environment from the communication environment determination means to the transmission power control means, and reducing the transmission power of the transmission signal and reducing the cell range when the communication environment is good When the communication environment is poor, transmission power control is performed to increase the transmission power of the transmission signal and expand the cell range .

  The transmission power control means performs transmission power control according to the quality information of the communication environment when the transmission speed of the transmission signal is the same as the transmission speed of the previous transmission signal, and the transmission speed of the transmission signal is When the signal transmission speed is not the same, the transmission power control according to the quality information of the communication environment may not be performed.

The radio base station apparatus of the present invention can reduce interference with neighboring radio communication apparatuses by autonomously performing transmission power control according to the quality of the communication environment. In particular, by reducing the transmission power when it is determined that the communication environment is good, it is possible to achieve both reduction in power consumption and improvement in communication quality. Furthermore, the probability that communication quality improves and transmission succeeds further increases, and frequency resources can be used effectively.

  In addition, by applying to a wireless communication system composed of many APs and STAs, the cell radius is reduced by reducing the transmission power of the APs, so that many APs can be installed and the number of STAs (users) accommodated is reduced. Can be improved. Further, it is possible to distinguish between a large number of APs or new APs.

It is a figure explaining the transmission power control principle by this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 1 of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus which combined transmission rate control and transmission power control. It is a flowchart which shows the transmission power control procedure combined with transmission rate control. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 2 of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 3 of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 4 of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 5 of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus of Example 6 of this invention. It is a figure which shows an example of the conventional radio | wireless communications system. It is a figure which shows the structural example of the conventional radio | wireless communication apparatus.

  FIG. 1 shows the principle of transmission power control according to the present invention. Here, in the conventional wireless communication system (for example, wireless LAN) in FIG. 10 in which cells formed by a plurality of APs are adjacent and STAs exist in each cell, AP transmission power control will be described as an example. The present invention can also be applied to STA transmission power control or AP and STA transmission power control. Further, a general wireless communication system, for example, a mobile phone system such as HSPA (High Speed Packet Access) or LTE (Long Term Evolution) standard, or a WiMAX (Worldwide interoperability for microwave access) system defined by the IEEE 802.16 standard group. It can also be applied to transmission power control of a wireless communication device in a short-range wireless system such as Bluetooth.

  In FIG. 1, an STA that communicates with the AP is arranged in a cell having a radius corresponding to the transmission power of the AP. The STA transmits an ACK signal when the transmission signal of the AP can be normally received. When an AP receives an ACK signal for a transmission signal (transmission success) and satisfies a condition for reducing transmission power (for example, receiving an ACK signal continuously several times), the AP determines that the communication environment is good and increases the transmission power. Reduce. This reduces the cell radius. Further, when the AP does not receive the ACK signal for the transmission signal (transmission failure) and satisfies the condition for increasing the transmission power (for example, the ACK signal is not continuously received a plurality of times), the AP determines that the communication environment is bad. To increase the transmission power. This increases the cell radius.

  For example, the transmission from the AP to the STA at the cell edge is successful and the communication environment is judged to be good and the transmission power is reduced, but if the STA is out of the cell due to the cell radius reduction and the transmission fails, A situation where communication is resumed by increasing the transmission power can be considered.

  As described above, in the wireless communication apparatus and the transmission power control method of the present invention, it is possible to reduce the transmission power of the AP by receiving the ACK signal (successful transmission), and to reduce the interference to adjacent cells by reducing the cell radius. it can. On the other hand, the AP of the neighboring cell also performs similar transmission power control, thereby reducing interference from the neighboring cell. As a result, interference decreases with each other even though the transmission power is reduced in each cell, thereby further increasing the probability that communication quality is improved and transmission is successful and frequency resources can be used effectively. Furthermore, by reducing the transmission power of the AP when transmission is successful, it is possible to reduce unnecessary power of the AP and save power.

  In addition, since the cell radius is reduced by reducing the transmission power of the AP, a large number of APs can be installed, and the accommodation number of STAs (users) can be improved. Further, it is possible to distinguish between a large number of APs or new APs.

  In addition, the transmission power control in the present invention does not require cooperation between APs that exchange information between APs, for example, and can be handled by autonomous distributed control that is completely independent for each AP. Thereby, since signal transmission accompanying information exchange between APs is refrained, interference generation factors are reduced, and frequency resources can be improved.

  In the present invention, the quality of the communication environment is determined from the reception status of the ACK signal, and the reduction or increase of the transmission power is controlled. However, the quality of the communication environment is not limited to the ACK signal, and a NACK signal may be used. Also, transmission power control may be performed by determining whether the communication environment is good or bad according to the error rate of the received signal and the reception level (for example, RSSI in a wireless LAN). For example, if the error rate of the received signal is equal to or lower than a threshold value or the reception level is equal to or higher than a threshold value determined by the transmission rate (modulation method), it can be determined that the communication environment is good. Moreover, you may judge the quality of communication environment by these combination. In addition, by using information other than the information elements defined in the control channel, newly defining received packet information in the field of the conventional data part, and determining the quality of the communication environment by measuring and receiving the received packet information Is also possible.

  FIG. 2 shows a configuration example of the wireless communication apparatus according to the first embodiment of the present invention. In the first embodiment, a configuration example is shown in which the quality of the communication environment is determined from the ACK signal, the NACK signal, the error rate of the received signal, and the like, and transmission power control is performed according to the quality of the communication environment.

  In FIG. 2, the wireless communication apparatus includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, and a transmission power control circuit 15. Here, only the main part of the wireless communication device is shown, and an amplifier circuit, a frequency conversion circuit, and the like are omitted.

  The received signal received by the antenna 11 is demodulated by the demodulation circuit 12. The communication environment determination circuit 13 determines the quality of the communication environment with the reception side of the transmission signal according to the demodulated signal of the demodulation circuit 12 and notifies the transmission power control circuit 15 of the quality. The modulation circuit 14 is set to a predetermined transmission rate, for example, modulates transmission data by a modulation scheme with different number of bits per symbol such as QPSK or QAM according to the transmission rate, and outputs the modulated transmission data to the transmission power control circuit 15. The transmission power control circuit 15 receives information on the quality of the communication environment from the communication environment determination circuit 13 and reduces the transmission power when the communication environment is good (such as when ACK is received), and the communication environment is bad. When (such as when ACK is not received), the transmission power is increased and transmitted from the antenna 11.

  Here, the fact that the ACK signal is received (successful transmission) even though the transmission power is reduced indicates that communication can be continued while suppressing interference with neighboring cells. Moreover, when AP which comprises a neighboring cell reduces transmission power by the same control, the interference wave from the said cell will reduce. As a result, although the transmission power is reduced in each cell, the interference decreases with each other, thereby increasing the probability of successful transmission and enabling effective use of frequency resources.

  Furthermore, the transmission power control according to the quality of the communication environment of the present invention is combined with the conventional technology that realizes the throughput improvement by the transmission rate control according to the quality of the communication environment, and it is possible to suppress high-accuracy cell design and interference. It is possible to realize a system that realizes division and provides high throughput. However, if the transmission speed and transmission power are changed at the same time, for example, if the transmission speed is lowered and the transmission power is increased due to a poor communication environment, even if transmission is successful in the transmission, the transmission is successful. Since it is not known whether it is due to a change in speed or a change in transmission power, even if it is applied as it is, transmission power control, that is, control of the amount of interference cannot be performed accurately. Further, when the transmission speed is increased due to a good communication environment and the transmission power is reduced, an operation that conflicts with the required quality of the signal is performed.

  Therefore, the transmission power control circuit 15 changes the transmission power only when the previous transmission rate (modulation method) set in the modulation circuit 14 is also used in the current transmission. That is, when the transmission speed is the same as the previous time, transmission power control is performed according to the quality of the communication environment determined by the communication environment determination circuit 13. Through these procedures, it is possible to reduce the amount of interference by reducing the transmission power after confirming that transmission is successful at a certain transmission rate (modulation method), and when the subsequent transmission fails, return the transmission power and improve the communication quality. Therefore, it is possible to control both the transmission speed and the transmission power with high accuracy. Hereinafter, a specific apparatus configuration and processing procedure will be described.

  FIG. 3 shows a configuration example of a wireless communication apparatus that combines transmission rate control and transmission power control. Here, an example applied to the wireless communication apparatus of the first embodiment shown in FIG. 2 is shown, but also in each of the embodiments shown below, a combination of transmission rate control and transmission power control is possible.

  In FIG. 3, a transmission speed setting circuit 10 receives information on the quality of the communication environment from the communication environment determination circuit 13, increases the transmission speed when the communication environment is good, and transmits the transmission speed when the communication environment is bad. Control to reduce the. Further, the transmission power control circuit 15 receives the information on the quality of the communication environment from the communication environment determination circuit 13, reduces the transmission power when the communication environment is good, and increases the transmission power when the communication environment is bad. Control. Furthermore, in order not to compete between transmission rate control and transmission power control, for example, when the transmission rate setting circuit 10 changes the transmission rate, the transmission power control circuit 15 is notified not to perform transmission power control.

FIG. 4 shows a transmission power control procedure combined with transmission rate control.
In FIG. 4, the transmission rate setting circuit 10 determines whether or not the condition for increasing the transmission rate is satisfied according to the communication environment quality information output from the communication environment determination circuit 13 (S11). Here, the conditions for increasing the transmission rate include the number of times the ACK signal is received exceeding the threshold, the error rate of the received signal in a certain period is lower than the threshold, and the RSSI exceeds a threshold determined for each transmission rate. When the condition for increasing the transmission rate is satisfied (S11: Yes), the transmission rate is increased by one step or a plurality of steps depending on the communication environment (S12). If the transmission speed increase condition is not satisfied (S11: No), it is determined whether the transmission speed reduction condition is satisfied (S13). The conditions for reducing the transmission rate include the number of times the ACK signal has not been received exceeds a threshold, the error rate in a certain period exceeds the threshold, and the RSSI falls below a threshold determined for each transmission rate. If the condition for reducing the transmission rate is satisfied (S13: Yes), the transmission rate is reduced by one step or a plurality of steps depending on the communication environment (S14). If the transmission rate increase condition is not satisfied (S11: No), and if the transmission rate reduction condition is not satisfied (S13, No), the current transmission rate is maintained. For example, the current transmission rate is maintained until the number of ACK signal receptions exceeds a threshold value or until the number of ACK signal non-receptions exceeds a threshold value.

  Next, when control for increasing or decreasing the transmission rate is performed by the above processing, the processing ends without performing transmission power control. At this time, a condition for changing the transmission power, for example, a condition (parameter) such as a threshold of the number of times of reception of the ACK signal for reducing the transmission power may be reset (S19). In this case, by resetting the condition, it is possible to restart the transmission power change determination using the change in the transmission rate as a trigger. In addition, the transmission power may be returned to the initial value.

  On the other hand, if the transmission speed increase condition is not satisfied (S11: No), the transmission speed reduction condition is not satisfied (S13, No), and the current transmission speed is maintained, the communication environment determination circuit 13 outputs It is determined whether or not the condition for transmission power reduction is satisfied according to the quality information of the communication environment to be performed (S15). Here, the conditions for reducing the transmission power include the number of times of receiving the ACK signal exceeds the threshold, the error rate of the received signal in a certain period is lower than the threshold, and the RSSI exceeds the threshold determined for each transmission rate. If the condition for reducing the transmission power is satisfied (S15: Yes), the transmission power is reduced by one stage or a plurality of stages depending on the communication environment (S16), and the process is terminated. If the transmission power reduction condition is not satisfied (S15: No), it is determined whether the transmission power increase condition is satisfied (S17). The conditions for increasing the transmission power include the number of times the ACK signal has not been received exceeds a threshold, the error rate in a certain period exceeds the threshold, and the RSSI falls below a threshold determined for each transmission rate. If the condition for increasing transmission power is satisfied (S17: Yes), the transmission power is increased by one stage or a plurality of stages depending on the communication environment (S18), and the process is terminated. If the transmission power reduction condition is not satisfied (S15: No), and further the transmission power increase condition is not satisfied (S17: No), the current transmission power is maintained and the process is terminated.

  As described above, the transmission speed control and the transmission power control are controlled so as not to compete with each other according to the communication environment quality information output from the communication environment determination circuit 13. Also, by setting the transmission / reception thresholds to be different from each other, for example, when transmission success / failure continues for a predetermined number of times while sequentially adjusting transmission power for transmission success / failure. Control such as increasing / decreasing the transmission speed becomes possible. That is, when the next transmission in which the transmission success is continued for a predetermined number of times and the transmission rate is increased fails, control is performed to increase the transmission power. Also, when transmission fails due to a reduction in transmission power, control is performed to switch to a separately defined low transmission rate.

  As a modulation method applied in the present invention, a single carrier modulation method such as QPSK, 16QAM, or 64QAM can naturally be applied, but subsequent OFDM modulation using IFFT or spreading code is used for secondary modulation. Applying Spread Spectrum modulation is also possible. Furthermore, like DFE-Spread OFDM and single carrier modulation-frequency domain equalization-based methods, signal processing is performed after single carrier modulation, transmission is performed with GI or CP added, and frequency equalization processing is performed on the receiving side. The present invention can also be applied to a transmission method that performs.

  Here, an application example of transmission power control in a wireless communication apparatus combining transmission rate control and transmission power control will be described.

  When a plurality of STAs belong, for example, when a lower limit or an upper limit transmission rate in a basic-rate-set (a combination of available transmission rates) of a plurality of STAs obtained from a beacon packet is selected, Transmission power control may be performed according to the quality of the communication environment, and when an intermediate transmission rate is selected, control may be performed to prioritize the transmission rate control according to the quality of the communication environment.

  Also, when the communication environment is determined to be poor due to transmission failure (no ACK received) at the lower limit transmission rate, the transmission rate is not further lowered, so the transmission power is increased to improve the communication quality. On the other hand, when the communication environment is judged to be good due to successful transmission (ACK reception) at the lower limit transmission rate, it is possible to select control to reduce transmission power and control to increase transmission rate. By reducing transmission power without increasing it, priority can be given to reducing interference with other radio systems. Alternatively, the throughput can be improved by increasing the transmission speed without reducing the transmission power.

  In addition, when the communication environment is determined to be good due to successful transmission (ACK reception) at the upper limit transmission rate, control is performed to reduce transmission power because the transmission rate cannot be further increased. On the other hand, when it is determined that the communication environment is bad due to transmission failure at the upper limit transmission rate (no ACK received), control for increasing transmission power and control for reducing transmission rate can be selected. By reducing the transmission rate without increasing the power, it is possible to avoid an unnecessarily large transmission power and reduce interference with other communication systems.

  Further, when a plurality of STAs belong, transmission power control may be uniformly performed for all STAs, or transmission power control may be performed individually for each STA. When performing transmission power control uniformly for all STAs, a reference STA is determined based on the transmission frequency (the number of transmission packets) with the STA, and transmission power control with the reference STA is performed with other STAs. This also applies to communication. In this case, since it is not necessary to perform control for each STA, the control can be simplified. However, since the communication environment with the reference STA is good and the transmission power is reduced, it is assumed that the communication environment with some STAs deteriorates. The transmission power may be increased as a trigger. That is, the transmission power may be reduced when the communication environment with the reference STA is good, and the transmission power may be increased when the communication environment becomes defective in any of the STAs.

  Further, the present invention is not only based on layer 2 information for determining the quality of the communication environment, but also for layer 1 (information described in the PLCP header of IEEE802.11 wireless LAN, RSSI, control information exchange in the physical layer) Etc.) may be performed based on other layer information.

  In addition, when a wireless communication system to which transmission power control of the present invention is applied and another wireless communication system coexist at the same frequency, the present invention is applied by detecting that the received power from the other wireless communication system is large. It is also possible to control to increase the transmission power of the wireless communication system. Specifically, this will be described as Example 3. According to this configuration, it is possible to ensure fairness between cells from the cell radial plane.

FIG. 5 shows a configuration example of a wireless communication apparatus according to the second embodiment of the present invention.
In the second embodiment, in addition to the transmission power control according to the quality of the communication environment obtained from the presence / absence of reception of the ACK signal of the first embodiment and the error rate of the received signal, the reception level (for example, RSSI in a wireless LAN) is used. The structural example which performs transmission power control is shown. Note that the transmission power control according to only the reception level may be performed.

  In FIG. 5, the wireless communication apparatus includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, and a reception level detection circuit 16. Here, only the main part of the wireless communication device is shown, and an amplifier circuit, a frequency conversion circuit, and the like are omitted.

  The received signal received by the antenna 11 is demodulated by the demodulation circuit 12. The communication environment determination circuit 13 determines the quality of the communication environment with the reception side of the transmission signal according to the demodulated signal of the demodulation circuit 12 and notifies the transmission power control circuit 15 of the quality. The reception level detection circuit 16 detects the reception level and notifies the transmission power control circuit 15 of the reception level. The modulation circuit 14 is set to a predetermined transmission rate, for example, modulates transmission data by a modulation scheme with different number of bits per symbol such as QPSK or QAM according to the transmission rate, and outputs the modulated transmission data to the transmission power control circuit 15.

  The transmission power control circuit 15 inputs the quality information of the communication environment from the communication environment determination circuit 13, inputs the reception level detected by the reception level detection circuit 16, and receives the ACK when the communication environment is good (and receives ACK, and When the reception level exceeds the threshold specified by the transmission rate (modulation method), the transmission power is reduced. When the communication environment is bad (ACK is not received or the reception level is the transmission rate (modulation method)) For example, when it falls below a prescribed threshold value, the transmission power is increased and transmitted from the antenna 11.

  The condition for determining the quality of the communication environment may be any one of the presence / absence of reception of the ACK signal, the comparison result between the error rate of the received signal and the threshold, and the comparison result between the reception level and the threshold. A combination of criteria may be used. The combination means of two or more judgment criteria can be realized by AND, OR, etc. of each judgment criteria.

FIG. 6 shows a configuration example of a wireless communication apparatus according to the third embodiment of the present invention.
In the second embodiment, the reception level in the own system is detected and used to judge whether the communication environment is good or bad by comparing with a threshold defined by the transmission rate (modulation method). The third embodiment shows a configuration example in which an interference level from another system is detected and transmission power control is performed according to the interference level.

  In FIG. 6, the wireless communication apparatus includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, and an interference level detection circuit 17. Here, only the main part of the wireless communication device is shown, and an amplifier circuit, a frequency conversion circuit, and the like are omitted.

  The received signal received by the antenna 11 is demodulated by the demodulation circuit 12. The communication environment determination circuit 13 determines the quality of the communication environment with the reception side of the transmission signal according to the demodulated signal of the demodulation circuit 12 and notifies the transmission power control circuit 15 of the quality. The interference level detection circuit 17 can apply the received signal level and RSSI value of the interference signal when the interference signal is known in advance, and if the interference signal and the desired signal cannot be distinguished, the received signal 2 detects an interference level from another system identified by an SSID (network identifier) included in the ID and an identifier indicating another transmitting station, and notifies the transmission power control circuit 15 of the interference level. The modulation circuit 14 is set to a predetermined transmission rate, for example, modulates transmission data by a modulation scheme with different number of bits per symbol such as QPSK or QAM according to the transmission rate, and outputs the modulated transmission data to the transmission power control circuit 15.

  The transmission power control circuit 15 receives the ACK and receives the interference when the communication environment is good according to the quality of the communication environment determined by the communication environment determination circuit 13 and the interference level detected by the interference level detection circuit 17. The transmission power is reduced when the level is lower than the threshold), and the transmission power is increased when the communication environment is bad (such as when ACK is not received or the interference level exceeds the threshold), and transmitted from the antenna 11. To do. The transmission power control based on the combination of the interference level output from the interference level detection circuit 17 and the communication environment information output from the communication environment determination circuit 13 is realized by appropriately combining AND and OR of these determination criteria. can do.

  In addition, the identification of whether or not the signal is a received signal of another system is, for example, an authentication ID (AID) for identifying each terminal defined in the IEEE802.11e standard or later, or a terminal that has been discussed in IEEE802.11 TGac It can be performed using a technique such as Group ID of an identifier for grouping intervals.

  The interference level detection circuit 17 can also realize low power consumption by using the AID and Group ID in the preamble signal part of the physical layer signal and the header part of the physical layer signal for identification. is there. Further, the interference level detection circuit 17 is identified from information related to the base station of the other system / own system, the physical layer signal of the preamble signal of the other system / own system, or the signal demodulated to the MAC layer. But you can.

  Also, the transmission power control circuit 15 increases the transmission power due to transmission failure when interference of another system is detected. If the next transmission is successful, the interference level of the other system detected at that time is detected. Is set as the lower limit of the transmission power for. After that, when the interference level is detected, even when control is performed to reduce transmission power in response to successful transmission, the lower limit value is prevented. That is, when interference waves from other systems occur without being detected by carrier sense in other systems due to a reduction in transmission power, by setting the lower limit value of transmission power, the other systems can detect by carrier sense. Since transmission power can be ensured, communication quality can be ensured.

  In this embodiment, it is possible to realize transmission power control according to interference source attributes, installation positions, and the like by utilizing identifiers for determining other systems, such as SSID, base station ID, and base station position information. . Moreover, each adjacent system operates autonomously and reduces transmission power, so that the transmission power of the own system can be reduced as much as possible. Accordingly, segregation can be performed while reducing power consumption, and effective use of frequency resources and the number of users accommodated in each system can be improved.

FIG. 7 shows a configuration example of a wireless communication apparatus according to the fourth embodiment of the present invention.
In the first to third embodiments, for example, in the wireless communication system illustrated in FIG. 1, the cell radius is increased or decreased by transmission power control, and a plurality of cells can be divided. The fourth embodiment is applied in a wireless communication system in which each cell is operated at the same frequency, when there are cells that are so close that it is difficult to separate spatially by transmission power control alone. That is, in this embodiment, even when it is difficult to sort cells by transmission power control, power saving is achieved by controlling the transmission power to the minimum necessary.

  In FIG. 7, the wireless communication apparatus includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, an interference level detection circuit 17, and a transmission control circuit 18. Here, only the main part of the wireless communication device is shown, and an amplifier circuit, a frequency conversion circuit, and the like are omitted.

  The received signal received by the antenna 11 is demodulated by the demodulation circuit 12. The communication environment determination circuit 13 determines the quality of the communication environment with the reception side of the transmission signal according to the demodulated signal of the demodulation circuit 12 and notifies the transmission power control circuit 15 of the quality. The interference level detection circuit 17 can apply the received signal level and RSSI value of the interference signal when the interference signal is known in advance, and if the interference signal and the desired signal cannot be distinguished, the received signal The interference level from the other system identified by the SSID (network identifier) and the identifier indicating the other transmitting station included in the transmission is detected and notified to the transmission power control circuit 15 and the transmission control circuit 18. The modulation circuit 14 is set to a predetermined transmission rate, for example, modulates transmission data by a modulation scheme with different number of bits per symbol such as QPSK or QAM according to the transmission rate, and outputs the modulated transmission data to the transmission power control circuit 15.

  The transmission power control circuit 15 receives the ACK and receives the interference when the communication environment is good according to the quality of the communication environment determined by the communication environment determination circuit 13 and the interference level detected by the interference level detection circuit 17. The transmission power is reduced when the level is lower than the threshold), and the transmission power is increased when the communication environment is bad (such as when ACK is not received or the interference level exceeds the threshold), and transmitted from the antenna 11. To do.

  Here, if the interference level from another system exceeds the threshold and if transmission is not successful even though the transmission power is increased, it is determined that cell segregation by transmission power control is difficult. Then, the transmission control circuit 18 is operated. When the interference level from another system exceeds a threshold value, the transmission control circuit 18 performs a process for separating the time from the other system. For example, a radio channel is virtually reserved using a NAV (Network Allocation vector) signal, or an empty channel is secured by an RTS (Request to Send) / CTS (Clear to Send) signal, and transmission timings secured respectively are set. Notify the modulation circuit 14. The modulation circuit 14 outputs a transmission signal to the transmission power control circuit 15 at the transmission timing notified from the transmission control circuit 18. The transmission power control circuit 15 performs transmission power control according to the quality of the communication environment determined by the communication environment determination circuit 13.

FIG. 8 shows a configuration example of a wireless communication apparatus according to the fifth embodiment of the present invention.
In the wireless communication system in which each cell is operated at the same frequency, the fourth embodiment performs transmission at a transmission timing secured by NAV or the like when there is a cell that is close enough to make spatial separation difficult by transmission power control alone. It was the structure which performs electric power control. The fifth embodiment is applied in a wireless communication system in which each cell can be operated at different frequencies when there are cells that are so close that it is difficult to make a spatial separation only by transmission power control at the same frequency.

  In FIG. 8, the wireless communication apparatus includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, an interference level detection circuit 17, and frequency conversion circuits 19-1 and 19-2. Is done.

  The received signal received by the antenna 11 is input to the demodulation circuit 12 via the frequency conversion circuit 19-1 and demodulated. The communication environment determination circuit 13 determines the quality of the communication environment with the reception side of the transmission signal according to the demodulated signal of the demodulation circuit 12 and notifies the transmission power control circuit 15 of the quality. The interference level detection circuit 17 can apply the received signal level and RSSI value of the interference signal when the interference signal is known in advance, and if the interference signal and the desired signal cannot be distinguished, the received signal The interference level from the other system identified by the SSID (network identifier) and the identifier indicating the other transmitting station included in is detected and notified to the transmission power control circuit 15 and the frequency conversion circuits 19-1 and 19-2. The modulation circuit 14 is set to a predetermined transmission speed, for example, modulates transmission data by a modulation method with different number of bits per symbol such as QPSK and QAM according to the transmission speed, and passes through the frequency conversion circuit 19-2. Output to the transmission power control circuit 15. Here, the frequency conversion circuit 19-2 does not operate.

  The transmission power control circuit 15 receives the ACK and receives the interference when the communication environment is good according to the quality of the communication environment determined by the communication environment determination circuit 13 and the interference level detected by the interference level detection circuit 17. The transmission power is reduced when the level is lower than the threshold), and the transmission power is increased when the communication environment is bad (such as when ACK is not received or the interference level exceeds the threshold), and transmitted from the antenna 11. To do.

  Here, when the interference level from other systems exceeds the threshold value, and transmission is not successful even though the transmission power is increased, it is difficult to separate cells at the same frequency by transmission power control. In this case, the frequency conversion circuits 19-1 and 19-2 are operated. The frequency conversion circuits 19-1 and 19-2 perform processing for changing the carrier frequency on both the transmission side and the reception side, or on the other hand, when the interference level from another system exceeds a threshold value. The transmission power control circuit 15 performs transmission power control according to the quality of the communication environment determined by the communication environment determination circuit 13.

  Note that the frequency conversion in the frequency conversion circuits 19-1 and 19-2 can be uniquely changed to another frequency in this system, but is not changed uniquely, but for each specific station and for each packet. Alternatively, it may be adaptively or periodically changed according to the idle frequency.

  In addition, in the case of a modulation scheme that performs transmission using IFFT such as OFDM or DFE-Spread OFDM, it is of course possible to flexibly change the frequency to an empty band in each subcarrier, and to reduce interference more flexibly. A multi-user accommodation system can be constructed.

  When changing the frequency, only the communication partner may be instructed to change the frequency (only supported by the frequency conversion circuit 19-1 on the reception side), or the frequency changes individually on the transmission side and the reception side. You may do.

  It can also be implemented in combination with the DFS function defined in the wireless LAN standard IEEE802.11h. If there is an interference source, frequency conversion can be performed together with the communication partner so as to avoid it. Is possible.

FIG. 9 shows a configuration example of a wireless communication apparatus according to the sixth embodiment of the present invention.
In Embodiments 4 and 5, according to the interference level from other systems detected by the interference level detection circuit 17 in the wireless communication system in which the cells are so close that it is difficult to separate spatially by transmission power control alone. Thus, the transmission power control is performed without dividing each cell by transmission timing control or frequency conversion. In the sixth embodiment, the presence or interference level of another system is estimated based on the quality information of the communication environment determined by the communication environment determination circuit 13 without using the interference level detection circuit 17, and the transmission level control or frequency conversion is used to estimate each system. It is characterized in that transmission power control is performed without trying to sort cells.

  The wireless communication apparatus in FIG. 9 (1) corresponds to the fourth embodiment in FIG. 7 and includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, and a transmission control circuit 18. Consists of. Based on the quality information of the communication environment determined by the communication environment determination circuit 13, the presence or interference level of another system is estimated and notified to the transmission control circuit 18. The function of the transmission control circuit 18 is as described in the fourth embodiment.

  The wireless communication apparatus of FIG. 9 (2) corresponds to the fifth embodiment of FIG. 8, and includes an antenna 11, a demodulation circuit 12, a communication environment determination circuit 13, a modulation circuit 14, a transmission power control circuit 15, and a frequency conversion circuit 19. -1, 19-2. Based on the quality information of the communication environment determined by the communication environment determination circuit 13, the presence or interference level of another system is estimated and notified to the frequency conversion circuits 19-1 and 19-2. The functions of the frequency conversion circuits 19-1 and 19-2 are as described in the fifth embodiment.

DESCRIPTION OF SYMBOLS 10 Transmission speed setting circuit 11 Antenna 12 Demodulation circuit 13 Communication environment determination circuit 14 Modulation circuit 15 Transmission power control circuit 16 Reception level detection circuit 17 Interference level detection circuit 18 Transmission control circuit 19 Frequency conversion circuit

Claims (10)

In a radio base station apparatus that is adjacent to cells formed by a plurality of radio base station apparatuses and communicates with radio terminals belonging to each cell,
Modulation means for outputting a transmission signal transmitted from an antenna;
Demodulation means for demodulating the received signal received by the antenna;
A communication environment determining means for determining the quality of the communication environment between the wireless terminal in response to the reception / non-reception of the ACK signal for the demodulated the transmission signal by the demodulating means,
The communication environment determination means inputs the quality information of the communication environment, and when the communication environment is good, the transmission power of the transmission signal is reduced to reduce the cell range, and the communication environment is bad. the transmission signal radio base station apparatus characterized by comprising a transmission power control means for expanding the range of the cell by increasing the transmission power of the case. The radio base station apparatus according to claim 1,
Receiving level detecting means for detecting the receiving level of the received signal and outputting to the transmission power control means,
The transmission power control means is configured to control the transmission power of the transmission signal as a good communication environment when the reception level exceeds a threshold value and as a bad communication environment when the reception level is equal to or less than the threshold value. A radio base station apparatus . The radio base station apparatus according to claim 1,
An interference level detection unit that identifies that the received signal is a signal from another system, detects an interference level from the other system, and outputs the interference level to the transmission power control unit;
The transmission power control means is configured to control the transmission power of the transmission signal as a good communication environment when the interference level is equal to or lower than a threshold value and as a bad communication environment when the interference level exceeds a threshold value. A radio base station apparatus . The radio base station apparatus according to claim 1,
An interference level detecting means for identifying that the received signal is a signal from another system and detecting an interference level from the other system;
A radio base station apparatus comprising: a transmission control unit that adjusts a transmission timing of the other system and that of the own system when the interference level exceeds a threshold. The radio base station apparatus according to claim 1,
An interference level detecting means for identifying that the received signal is a signal from another system and detecting an interference level from the other system;
A frequency conversion unit configured to convert at least one of the carrier frequency of the transmission signal or the carrier frequency of the reception signal when the interference level exceeds a threshold and set the carrier frequency of the own system different from that of the other system; A radio base station apparatus comprising the radio base station apparatus . The radio base station apparatus according to claim 1,
When the communication environment determination means inputs the quality information of the communication environment, and the transmission power is increased by the transmission power control means, but the communication environment is bad, the transmission timing of the other system and the own system is adjusted. the radio base station apparatus comprising the transmission control means for performing to segregation. The radio base station apparatus according to claim 1,
When the communication environment determination means inputs the quality information of the communication environment and the transmission power control means increases the transmission power and the communication environment is bad, the transmission signal carrier frequency or the received signal A radio base station apparatus comprising frequency conversion means for converting at least one of carrier frequencies and setting the carrier frequency of the own system different from that of the other system. The radio base station apparatus according to claim 1,
The transmission power control means performs transmission power control according to the quality information of the communication environment when the transmission speed of the transmission signal is the same as the transmission speed of the previous transmission signal, and the transmission speed of the transmission signal is A radio base station apparatus , wherein transmission power control according to the quality information of the communication environment is not performed when the transmission speed of the transmission signal is not the same. In a radio base station apparatus transmission power control method in which cells formed by a plurality of radio base station apparatuses are adjacent and communicate with radio terminals belonging to each cell,
Transmit the transmission signal output from the modulation means from the antenna,
Demodulate the received signal received by the antenna by the demodulating means,
In accordance with the reception / non-reception of an ACK signal for the transmission signal demodulated by the demodulating means, to determine the quality of the communication environment between the wireless terminal in a communication environment determination means,
The communication environment determination means inputs the quality information of the communication environment to the transmission power control means, and when the communication environment is good, the transmission power of the transmission signal is reduced to reduce the cell range, and the communication A transmission power control method for a radio base station apparatus , wherein transmission power control is performed to increase the transmission power of the transmission signal and expand the range of the cell when the environment is bad. In the transmission power control method of the radio base station apparatus according to claim 9,
The transmission power control means performs transmission power control according to the quality information of the communication environment when the transmission speed of the transmission signal is the same as the transmission speed of the previous transmission signal, and the transmission speed of the transmission signal is A transmission power control method for a radio base station apparatus , wherein transmission power control according to the quality information of the communication environment is not performed when the transmission speed of the transmission signal is not the same.

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