JP2017028627A - Wireless communication system, wireless base station device, and wireless communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless base station device that can reduce a communication error rate, and reduce power consumption.SOLUTION: A wireless base station device is a wireless base station device (101) that performs wireless communication with a plurality of wireless terminal devices (102a-102c). The wireless base station device includes: a reception unit (111) that performs reception and receives the residual quantity of batteries of the plurality of wireless terminal devices; and a transmission unit (115) that performs transmission and transmits a transmission power reduction instruction to a wireless terminal device in which the residual quantity of its battery is larger than a first threshold value if there is a wireless terminal device in which the residual quantity of its battery is equal to or less than the first threshold value, the total time of the transmission time and reception time of wireless waves is equal to or more than a second threshold value, and the ratio of a communication time between the wireless base station device and the plurality of wireless terminal devices to the total time of the transmission time and reception time of wireless waves is equal to or more than a third threshold value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radio communication system, a radio base station apparatus, and a radio communication method.

  A mobile communication system including a mobile communication network having a radio base station and a radio base station control station and a mobile communication terminal is known (see Patent Document 1). The mobile communication terminal has means for notifying the mobile communication network of battery remaining amount information. The mobile communication network has means for controlling the maximum transmission power of the mobile communication terminal according to the remaining battery level.

  Also, a wireless communication device that communicates with at least a master station of the first unit wireless communication network is known as a slave station of the first unit wireless communication network (see Patent Document 2). The wireless communication device forms a second unit wireless communication network with another slave station belonging to the first unit wireless communication network as a slave station and itself as a master station when lowering the wireless transmission power. Use the station as a relay station. Thereby, communication with the master station of the first unit wireless communication network is maintained.

  Also, a radio base station having a transmission / reception unit for transmitting / receiving a radio signal to / from the wireless terminal device, and a battery information acquisition unit for acquiring battery information relating to a battery state of the wireless terminal device via the transmission / reception unit An apparatus is known (see Patent Document 3).

  Further, communication having battery remaining amount detecting means for detecting the remaining amount of the battery and communication method selecting means for selecting a communication method having a different number of channels to be multiplexed based on the remaining amount detected by the remaining battery amount detecting means. A terminal device is known (see Patent Document 4). The transmission means transmits a transmission signal to the communication partner using the communication method selected by the communication method selection means when the communication partner permits transmission using the communication method selected by the communication method selection means. To do.

JP 2003-309516 A JP 2003-69580 A JP 2013-201501 A JP-A-2005-341176

  Patent Document 1 reduces power consumption by reducing the maximum transmission power when the remaining battery level is low. However, if the transmission power is reduced, a transmission error is likely to occur. When a transmission error occurs, it needs to be retransmitted, so that the power consumption may increase.

  An object of the present invention is to provide a radio communication system, a radio base station apparatus, and a radio communication method that can reduce a communication error rate and reduce power consumption.

  In one aspect, the wireless communication system is a wireless communication system having a wireless base station device and a plurality of wireless terminal devices that perform wireless communication with the wireless base station device, wherein the plurality of wireless terminal devices Each is a battery, a first reception unit that performs reception, and a first transmission unit that performs transmission, wherein the remaining amount of the battery is transmitted to the radio base station apparatus, and the first reception unit A first transmission unit that lowers transmission power when a transmission power reduction instruction is received from the radio base station device, and the radio base station device is a second reception unit that performs reception, A second receiving unit that receives the remaining amount of the battery from a plurality of wireless terminal devices, and a second transmitting unit that performs transmission, wherein the remaining amount of the battery is the first among the plurality of wireless terminal devices. There is a wireless terminal device that is below the threshold of The total time of the reception time and the reception time is equal to or greater than a second threshold, and the ratio of the communication time between the wireless base station device and the plurality of wireless terminal devices to the total time of the transmission time and reception time of the radio wave is a first value. A second transmission unit configured to transmit a transmission power reduction instruction to the wireless terminal device in which the remaining amount of the battery is greater than the first threshold.

  By reducing the transmission power of the wireless terminal device whose remaining battery level is greater than the first threshold, it is possible to reduce interference with the wireless terminal device whose remaining battery level is equal to or lower than the first threshold. As a result, the signal-to-interference noise ratio (SINR) in the wireless terminal device having a remaining battery level equal to or less than the first threshold value is increased, the communication error rate is reduced, the number of retransmissions due to errors is reduced, and the power consumption is reduced. be able to.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. FIG. 2 is a diagram illustrating another configuration example of the radio base station apparatus. FIG. 3 is a graph showing an example of the relationship between the signal-to-noise ratio (SNR) and the packet communication error rate (PER). FIG. 4 is a diagram illustrating an example of communication between the radio base station apparatus and the radio terminal apparatus. FIG. 5 is a flowchart showing a wireless communication method of the wireless communication system of FIG.

  FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. The wireless communication system includes a wireless base station device 101 and a plurality of wireless terminal devices 102a to 102c. The number of wireless terminal apparatuses 102a to 102c is not limited to three, and may be two or four or more. The radio base station apparatus 101 performs radio communication with a plurality of radio terminal apparatuses 102a to 102c.

  First, the plurality of wireless terminal apparatuses 102a to 102c will be described. Each of the plurality of wireless terminal devices 102 a to 102 c includes a battery 121, a battery remaining amount monitoring unit 122, a first transmission unit 123, a first reception unit 124, and a transmission power setting unit 125. The battery 121 is a secondary battery or a primary battery attached to, for example, a solar battery (solar battery). The first transmission unit 123 performs radio transmission to the radio base station apparatus 101. For example, the first transmission unit 123 transmits data detected by the sensor. The first receiving unit 124 performs radio reception with respect to the radio base station apparatus 101.

  The battery remaining amount monitoring unit 122 detects the remaining amount of the battery 121 and outputs the detected remaining amount of the battery 121 to the first transmitting unit 123. The first transmission unit 123 wirelessly transmits the remaining amount of the battery 121 detected by the remaining battery amount monitoring unit 122 to the wireless base station device 101.

  Next, the radio base station apparatus 101 will be described. The radio base station apparatus 101 includes a second receiving unit 111, a band occupation time monitoring unit 112, a remaining battery level monitoring unit 113, a transmission power control unit 114, and a second transmission unit 115. The second reception unit 111 performs wireless reception with respect to the plurality of wireless terminal devices 102a to 102c. The second transmission unit 115 performs wireless transmission to the plurality of wireless terminal apparatuses 102a to 102c.

  The second receiving unit 111 receives the remaining amount of the battery 121 of each of the plurality of wireless terminal devices 102a to 102c from each of the plurality of wireless terminal devices 102a to 102c. Then, the second reception unit 111 outputs the remaining amount of the battery 121 of each of the plurality of wireless terminal devices 102 a to 102 c to the remaining battery amount monitoring unit 113. The battery remaining amount monitoring unit 113 determines whether there is a wireless terminal device in which the remaining amount of the battery 121 is equal to or less than the first threshold among the plurality of wireless terminal devices 102a to 102c. When there is a wireless terminal device in which the remaining amount of the battery 121 is less than or equal to the first threshold, the remaining battery amount monitoring unit 113 sends the wireless terminal device in which the remaining amount of the battery 121 is less than or equal to the first threshold to the transmission power. Notify the control unit 114.

  The band occupation time monitoring unit 112 adds the reception time of the second reception unit 111 and the transmission time of the second transmission unit 115 for the plurality of wireless terminal devices 102a to 102c, and adds the wireless base station device 101 and the plurality of wireless terminals. A communication time Ts between the devices 102a to 102c is detected. The communication time Ts is a communication time within a certain time T0.

  The band occupation time monitoring unit 112 adds the reception time of the second reception unit 111 and the transmission time of the second transmission unit 115 to all external devices, and calculates the total time Tc of the reception time and transmission time of radio waves. To detect. The total time Tc is the total time within the fixed time T0. The total time Tc is a time obtained by adding the communication time Ts and the reception time Tn of interference radio waves from external devices other than the radio base station device 101 and the radio terminal devices 102a to 102c. The interference radio wave from the external device does not comply with the communication protocol of the radio base station device 101. The first receiving unit 111 cannot decode the data in the interference wave from the outside, but can detect the reception time of the interference wave from the outside.

  When the reception time Tn of interference radio waves from the outside becomes longer, the radio base station apparatus 101 has a smaller signal-to-interference noise ratio (SINR), a larger communication error rate, an increased number of retransmissions, and an increase in power consumption. Resulting in.

  The band occupation time monitoring unit 112 outputs the communication time Ts between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c and the total time Tc of radio wave reception time and transmission time to the transmission power control unit 114. To do.

  The transmission power control unit 114 transmits a transmission power control instruction based on the determination result of whether or not there is a wireless terminal device whose remaining amount of the battery 121 is equal to or less than the first threshold, the communication time Ts, and the total time Tc. Is output to the second transmitter 115. Then, the second transmission unit 115 wirelessly transmits the transmission power control instruction to the wireless terminal devices 102a to 102c.

  Next, the plurality of wireless terminal devices 102a to 102c will be described. When the first reception unit 124 wirelessly receives a transmission power control instruction from the radio base station apparatus 101, the first reception unit 124 outputs the transmission power control instruction to the transmission power setting unit 125. The transmission power control instruction is a transmission power decrease instruction or a transmission power increase instruction. The transmission power setting unit 125 sets the transmission power of the first transmission unit 123 according to the transmission power control instruction received by the first reception unit 124. For example, when a transmission power reduction instruction is input from the first reception unit 124, the transmission power setting unit 125 decreases the transmission power of the first transmission unit 123 by a certain amount. In addition, when a transmission power increase instruction is input from the first reception unit 124, the transmission power setting unit 125 increases the transmission power of the first transmission unit 123 by a certain amount. The first transmission unit 123 performs transmission with the transmission power set by the transmission power setting unit 125.

  FIG. 2 is a diagram illustrating another configuration example of the radio base station apparatus 101. The radio base station apparatus 101 includes a bus 200, a central processing unit (CPU) 201, a random access memory (RAM) 202, a read only memory (ROM) 203, a storage device 204, a radio interface 205, and an antenna 206. And have. The radio base station apparatus 101 can realize the functions of the radio base station apparatus 101 of FIG. 1 by a CPU (computer) 201 executing a program in the RAM 202, the ROM 203, or the storage device 204.

  Also, each of the wireless terminal devices 102a to 102c may have the same configuration as the wireless base station device 101 of FIG. Each of the wireless terminal devices 102a to 102c can realize the functions of the wireless terminal devices 102a to 102c of FIG. 1 by executing a program in the RAM 202, ROM 203, or storage device 204 by a CPU (computer) 201.

  FIG. 3 is a graph showing an example of the relationship between the signal-to-noise ratio (SNR) and the packet communication error rate (PER). Hereinafter, the case of the wireless terminal device 102a will be described as an example, but the same applies to the wireless terminal devices 102b and 102c. In general, the wireless terminal apparatus 102a can reduce power consumption by reducing the transmission power of the first transmission unit 123. However, by reducing the transmission power of the first transmission unit 123, the power consumption of the wireless terminal device 102a may increase. The reason will be described below.

  When the transmission power of the first transmission unit 123 is lowered, the power of the transmission signal is lowered, so that the signal-to-noise ratio (SNR) of the wireless terminal device 102a is reduced. For example, when the transmission power of the first transmission unit 123 is 20 mW, the signal-to-noise ratio (SNR) is A1, the communication error rate (PER) is 0.5, and the number of retransmissions due to an error is one. . On the other hand, when the transmission power of the first transmission unit 123 is 1 mW, the signal-to-noise ratio (SNR) is A2, the communication error rate (PER) is 0.9, and the number of retransmissions due to an error is 9 times. It is. The difference between the signal-to-noise ratio (SNR) A1 and A2 is 1 dB. When the transmission power of the first transmission unit 123 is reduced from 20 mW to 1 mW, the reception power of the second reception unit 111 is reduced by 13 dB. Therefore, even if the transmission power is reduced, the power consumption increases due to an increase in the number of retransmissions.

  In the above, an example of the signal-to-noise ratio (SNR) is shown, but the same applies to the case of the signal-to-interference noise ratio (SINR). A signal-to-interference noise ratio (SINR) of communication between the wireless terminal device 102a and the wireless base station device 101 will be described. When the remaining amount of the battery 121 of the wireless terminal device 102a is equal to or smaller than the first threshold, the transmission power control unit 114 performs the following first to third transmission powers in order to reduce the power consumption of the wireless terminal device 102a. Take control.

  First, the first transmission power control will be described. When the total time Tc of the radio wave reception time and transmission time is less than the second threshold T, the communication traffic is not congested, so the interference is small, the signal-to-interference noise ratio (SINR) is large, and the communication error The rate (PER) is small and the number of retransmissions is small. In that case, the transmission power control unit 114 lowers the transmission power of the first transmission unit 123 of the wireless terminal device 102a. Thereby, the power consumption of the radio | wireless terminal apparatus 102a can be reduced.

  Next, the second transmission power control will be described. Between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c, the total time Tc of the radio wave transmission time and reception time is equal to or greater than the second threshold T, and the radio wave transmission time and reception time total time Tc. A case where the ratio Ts / Tc of the communication time Ts is larger than the third threshold value Sh will be described. In this case, communication traffic between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c is congested, and the radio terminal apparatus 102a has large interference from the radio terminal apparatuses 102b and 102c, and the signal-to-interference noise ratio. (SINR) is small, communication error rate (PER) is large, and the number of retransmissions is large. In that case, the transmission power control unit 114 reduces the transmission power of the wireless terminal apparatuses 102b and 102c. As a result, the radio terminal apparatus 102a has less interference from the radio terminal apparatuses 102b and 102c, the signal-to-interference noise ratio (SINR) is increased, the communication error rate (PER) is decreased, and the number of retransmissions is decreased. As a result, the power consumption of the wireless terminal device 102a can be reduced.

  Next, the third transmission power control will be described. Between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c, the total time Tc of the radio wave transmission time and reception time is equal to or greater than the second threshold T, and the radio wave transmission time and reception time total time Tc. A case where the ratio Ts / Tc of the communication time Ts is equal to or less than the third threshold Sh will be described. In this case, the radio terminal apparatus 102a has a large interference from external apparatuses other than the radio base station apparatus 101 and the radio terminal apparatuses 102a to 102c, a small signal-to-interference noise ratio (SINR), and a large communication error rate (PER). The number of retransmissions increases. In that case, the transmission power control unit 114 increases the transmission power of the wireless terminal device 102a. As a result, the wireless terminal device 102a increases the power of the transmission signal of the wireless terminal device 102a, increases the signal-to-interference noise ratio (SINR), decreases the communication error rate (PER), and decreases the number of retransmissions. As a result, the power consumption of the wireless terminal device 102a can be reduced.

  FIG. 4 is a diagram illustrating a communication example between the radio base station apparatus 101 and the radio terminal apparatuses 102a to 102c. An example of a carrier sense multiple access / collision avoidance (CSMA / CA) is shown as a wireless communication method.

  The frame period FR has a data frame length Td, a short inter-frame space SIFS (Short Inter Frame Space), and an ACK frame length Ta. Between a plurality of frame periods FR, there is a distributed inter frame space (DIFS) and a back-off Tb.

  The data frame length Td is the length of the data frame. The data frame includes communication data. The ACK frame length Ta is the length of the ACK frame. The ACK frame is a frame indicating that the data frame has been correctly received. The short inter-frame space SIFS is a time from when a data frame is received to when an ACK frame is transmitted. The distributed inter-frame space DIFS is the time until it is determined that the communication usage state has shifted to the unused state. The back-off Tb is a random time for waiting for frame transmission in order to avoid a collision between frames of the plurality of wireless terminal apparatuses 102a to 102c, and is different for each wireless terminal apparatus 102a to 102c.

  First, a case where the radio base station apparatus 101 transmits a data frame to the radio terminal apparatus 102a will be described. In this case, when the radio terminal apparatus 102a correctly receives the data frame, the radio terminal apparatus 102a transmits an ACK frame to the radio base station apparatus 101. Then, the radio base station apparatus 101 receives an ACK frame. In this case, in radio base station apparatus 101, the transmission time of second transmission section 115 is data frame length Td, and the reception time of second reception section 111 is ACK frame length Ta. The band occupation time monitoring unit 112 detects the time obtained by adding the data frame length Td and the ACK frame length Ta as the communication time Ts between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c.

  Next, a case where the radio terminal apparatus 102a transmits a data frame to the radio base station apparatus 101 will be described. In that case, when the radio base station apparatus 101 correctly receives the data frame, the radio base station apparatus 101 transmits an ACK frame to the radio terminal apparatus 102a. Then, the wireless terminal device 102a receives the ACK frame. In this case, in the radio base station apparatus 101, the reception time of the second reception unit 111 is the data frame length Td, and the transmission time of the second transmission unit 115 is the ACK frame length Ta. The band occupation time monitoring unit 112 detects the time obtained by adding the data frame length Td and the ACK frame length Ta as the communication time Ts between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c.

  FIG. 5 is a flowchart showing a wireless communication method of the wireless communication system of FIG. Each of the wireless terminal devices 102a to 102c performs steps S501 to S509. The radio base station apparatus 101 performs the processes of steps S510 to S520.

  First, in step S501, in each of the wireless terminal devices 102a to 102c, the remaining battery level monitoring unit 122 waits until the remaining battery level detection time is reached in order to detect the remaining battery level at regular time intervals. When the remaining battery charge detection time is reached, the process proceeds to step S502. In step S <b> 502, the battery remaining amount monitoring unit 122 detects the remaining amount of the battery 121 in each of the wireless terminal devices 102 a to 102 c. Next, in step S503, in each of the wireless terminal devices 102a to 102c, the first transmission unit 123 transmits the remaining amount of the battery 121 detected by the remaining battery amount monitoring unit 122 to the wireless base station device 101. Then, it progresses to step S504 and S510.

  In step S <b> 510, in the radio base station apparatus 101, the battery remaining amount monitoring unit 113 waits until the second receiving unit 111 receives the remaining amount of the battery 121. When the second receiving unit 111 receives the remaining amount of the battery 121, the process proceeds to step S511. In step S511, in the radio base station apparatus 101, the remaining battery level monitoring unit 113 determines the remaining battery level of each of the radio terminal apparatuses 102a to 102c based on the remaining battery level 121 received by the first receiving unit 111. Update quantity. Next, in step S512, in the radio base station apparatus 101, the remaining battery level monitoring unit 113 is a radio terminal apparatus in which the remaining capacity of the battery 121 is equal to or less than the first threshold value among the plurality of radio terminal apparatuses 102a to 102c. It is determined whether or not there is. If there is, the process proceeds to step S513, and if not, the process returns to step S510.

  In step S513, in the radio base station apparatus 101, the bandwidth occupation time monitoring unit 112 performs a total time Tc of radio wave reception time and transmission time, and communication time between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c. Ts is detected, and the times Tc and Ts are output to the transmission power control unit 114. Next, in step S514, in the radio base station apparatus 101, the transmission power control unit 114 determines whether the total time Tc of radio wave reception time and transmission time is less than the second threshold T. When the total time Tc is less than the second threshold T, the process proceeds to step S515, and when the total time Tc is equal to or greater than the second threshold T, the process proceeds to step S518.

  In step S515, in the radio base station apparatus 101, the transmission power control unit 114 sets the packet reception error rate (PER) from the radio terminal apparatus in which the remaining amount of the battery 121 determined in step S512 is equal to or less than the first threshold value. get. Next, in step S516, in the radio base station apparatus 101, the transmission power control unit 114 determines whether or not the packet reception error rate (PER) acquired in step S515 is less than the fourth threshold PERr. If it is less than the fourth threshold PERr, the process proceeds to step S517, and if it is greater than or equal to the fourth threshold PERr, the process returns to step S510.

  In step S517, in the radio base station apparatus 101, the second transmission unit 115 is a radio terminal in which the remaining amount of the battery 121 determined in step S512 is less than or equal to the first threshold value under the control of the transmission power control unit 114. A transmission power reduction instruction is transmitted to the apparatus. This process is the first transmission power control. Thereafter, the process returns to step S510. Further, the process proceeds to step S504 of the wireless terminal apparatuses 102a to 102c.

  In step S518, in the radio base station apparatus 101, the transmission power control unit 114 sets the communication time Ts between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c with respect to the total time Tc of radio wave transmission time and reception time. It is determined whether the ratio Ts / Tc is greater than the third threshold value Sh. When the ratio Ts / Tc is larger than the third threshold Sh, the process proceeds to step S519, and when the ratio Ts / Tc is equal to or smaller than the third threshold Sh, the process proceeds to step S520.

  In step S519, in the radio base station apparatus 101, the second transmitter 115 is a radio terminal in which the remaining amount of the battery 121 determined in step S512 is less than or equal to the first threshold under the control of the transmission power controller 114. A transmission power reduction instruction is transmitted to wireless terminal devices other than the device (wireless terminal device in which the remaining amount of the battery 121 is greater than the first threshold value). For example, when it is determined that only the remaining amount of the battery 121 of the wireless terminal device 102a is equal to or less than the first threshold value, the remaining amount of the battery 121 of the wireless terminal devices 102b and 102c is larger than the first threshold value. In this case, the second transmission unit 115 transmits a transmission power reduction instruction to the wireless terminal devices 102b and 102c in which the remaining amount of the battery 121 is greater than the first threshold. This process is the second transmission power control. Thereafter, the process returns to step S510. Further, the process proceeds to step S504 of the wireless terminal apparatuses 102a to 102c.

  In step S520, in the radio base station apparatus 101, the second transmission unit 115 is a radio terminal in which the remaining amount of the battery 121 determined in step S512 is less than or equal to the first threshold value under the control of the transmission power control unit 114. A transmission power increase instruction is transmitted to the apparatus. This process is the third transmission power control. Thereafter, the process returns to step S510. Further, the process proceeds to step S504 of the wireless terminal apparatuses 102a to 102c.

  In step S504, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 determines whether or not the first reception unit 124 has received a transmission power control instruction (transmission power reduction instruction or transmission power increase instruction). judge. If received, the process proceeds to step S505. If not received, the process returns to step S501.

  In step S505, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 controls the transmission power of the first transmission unit 123 according to the transmission power control instruction received by the first reception unit 124. . For example, the transmission power setting unit 125 decreases the transmission power of the first transmission unit 123 by a certain value when the first reception unit 124 receives a transmission power reduction instruction. In addition, when the first reception unit 124 receives a transmission power increase instruction, the transmission power setting unit 125 increases the transmission power of the first transmission unit 123 by a certain value.

  Next, in step S506, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 determines whether or not the transmission power has been reduced in step S505. If it has been lowered, the process proceeds to step S507, and if it has not been lowered, the process returns to step S501.

  In step S507, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 acquires the packet transmission error rate (PER) from the wireless terminal device itself to the wireless base station device 101.

  Next, in step S508, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 determines whether or not the packet transmission error rate (PER) acquired in step S507 is equal to or less than the fourth threshold PERt. To do. If it is less than or equal to the fourth threshold PERt, the process returns to step S501. If it is greater than the fourth threshold PERt, the process proceeds to step S509.

  In step S509, in each of the wireless terminal devices 102a to 102c, the transmission power setting unit 125 returns the transmission power of the first transmission unit 123 to the value before the control in step S505. That is, the transmission power setting unit 125 returns the value before control by increasing the transmission power of the first transmission unit 123 by a certain value. As a result, the lower limit value of the transmission power of the first transmission unit 123 can be set so that the packet transmission error rate (PER) does not become larger than the fourth threshold value PERt, the number of retransmissions due to errors can be reduced, and the power consumption Can be reduced. Thereafter, the process returns to step S501.

Next, an example of the second threshold value T in step S514 will be described. The total time Tc of the radio wave transmission time and reception time is the total time within a certain time T0. The fixed time T0 is, for example, a beacon interval time or a data regular transmission interval time. The second threshold T is set by the following equation in FIG. Here, Tb0 is an average time of the back-off Tb. Further, 0 <α ≦ 1. The data frame length Td is the minimum value within the specification.
T = T0 × α × (Td + Ta) / {(Td + Ta) + (DIFS + Tb0 + SIFS)}

Next, an example of step S518 will be described. A communication time Ts between the radio base station apparatus 101 and the plurality of radio terminal apparatuses 102a to 102c is a communication time within a predetermined time T0. The third threshold value Sh0 is set by the following equation in FIG.
Sh0 = [T0 × α × (Td + Ta) / {(Td + Ta) + (DIFS + Tb0 + SIFS)}] − (Tc−Ts)

  In step S518, the transmission power control unit 114 determines whether or not the communication time Ts is greater than the third threshold value Sh0. If it is greater than the third threshold value Sh0, the process proceeds to step S519, and if it is less than or equal to the third threshold value Sh0, the process proceeds to step S520.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

101 radio base station apparatus 102a to 102c radio terminal apparatus 111 second receiving unit 112 band occupation time monitoring unit 113 remaining battery level monitoring unit 114 transmission power control unit 115 second transmission unit 121 battery 122 remaining battery level monitoring unit 123 1 transmission unit 124 first reception unit 125 transmission power setting unit

Claims (8)

A radio base station device;
A wireless communication system having a plurality of wireless terminal devices that perform wireless communication with the wireless base station device,
Each of the plurality of wireless terminal devices is
Battery,
A first receiving unit for receiving;
A first transmission unit that performs transmission, wherein the remaining amount of the battery is transmitted to the radio base station device, and the first reception unit receives a transmission power reduction instruction from the radio base station device; A first transmission unit for reducing transmission power,
The wireless base station device
A second receiving unit that performs reception, the second receiving unit receiving the remaining amount of the battery from the plurality of wireless terminal devices;
A second transmission unit that performs transmission, wherein among the plurality of wireless terminal devices, there is a wireless terminal device in which a remaining amount of the battery is equal to or less than a first threshold value, and a total of radio wave transmission time and reception time When the time is greater than or equal to a second threshold and the ratio of the communication time between the radio base station apparatus and the plurality of radio terminal apparatuses with respect to the total time of the radio wave transmission time and reception time is greater than a third threshold Comprises a second transmission unit that transmits a transmission power reduction instruction to the wireless terminal device in which the remaining amount of the battery is greater than the first threshold value.   The second transmission unit includes a wireless terminal device having a remaining battery level equal to or less than the first threshold value among the plurality of wireless terminal devices, and a total time of the transmission time and the reception time of the radio wave. 2. The wireless communication according to claim 1, wherein a transmission power reduction instruction is transmitted to a wireless terminal device whose remaining battery capacity is equal to or less than the first threshold when the battery is smaller than the second threshold. system. The second transmission unit includes a wireless terminal device having a remaining battery level equal to or less than the first threshold value among the plurality of wireless terminal devices, and a total time of the transmission time and the reception time of the radio wave. When the ratio of the communication time between the radio base station apparatus and the plurality of radio terminal apparatuses with respect to the total time of the transmission time and the reception time of the radio wave is equal to or greater than the second threshold and equal to or less than the third threshold Transmits a transmission power increase instruction to the wireless terminal device whose remaining battery capacity is equal to or less than the first threshold,
2. The radio communication system according to claim 1, wherein the first transmission unit increases transmission power when the first reception unit receives the transmission power increase instruction from the radio base station apparatus. 3. The second transmitter is
There is a wireless terminal device in which the remaining amount of the battery is equal to or less than the first threshold value among the plurality of wireless terminal devices, and the total time of the transmission time and the reception time of the radio wave is smaller than the second threshold value Transmits a transmission power lowering instruction to the wireless terminal device in which the remaining amount of the battery is equal to or less than the first threshold,
Among the plurality of wireless terminal devices, there is a wireless terminal device in which the remaining amount of the battery is equal to or less than the first threshold value, and a total time of the transmission time and reception time of the radio wave is equal to or greater than the second threshold value. And the ratio of the communication time between the radio base station apparatus and the plurality of radio terminal apparatuses to the total time of the radio wave transmission time and reception time is equal to or less than the third threshold value, the remaining battery level Transmits a transmission power increase instruction to the wireless terminal device having a value equal to or less than the first threshold,
2. The radio communication system according to claim 1, wherein the first transmission unit increases transmission power when the first reception unit receives the transmission power increase instruction from the radio base station apparatus. 3.   The second transmission unit includes a wireless terminal device having a remaining battery level equal to or less than the first threshold value among the plurality of wireless terminal devices, and a total time of the transmission time and the reception time of the radio wave. When the reception error rate from the wireless terminal device that is smaller than the second threshold and the remaining amount of the battery is equal to or less than the first threshold is less than the fourth threshold, the remaining amount of the battery is The wireless communication system according to claim 2 or 4, wherein a transmission power reduction instruction is transmitted to a wireless terminal device that is equal to or less than a first threshold value.   The wireless communication system according to claim 1, wherein the first transmission unit increases transmission power when a transmission error rate is equal to or higher than a fourth threshold value. A wireless base station device that performs wireless communication with a plurality of wireless terminal devices,
A receiving unit for receiving, the receiving unit for receiving the remaining battery capacity of the plurality of wireless terminal devices; and
A transmitting unit that performs transmission, wherein among the plurality of wireless terminal devices, there is a wireless terminal device in which a remaining amount of the battery is equal to or less than a first threshold, and a total time of radio wave transmission time and reception time is When the ratio of the communication time between the radio base station apparatus and the plurality of radio terminal apparatuses with respect to the total time of the radio wave transmission time and reception time is greater than a third threshold, A radio base station apparatus, comprising: a transmission unit that transmits a transmission power reduction instruction to a radio terminal apparatus having a remaining battery level greater than the first threshold value. A wireless communication method of a wireless base station device that performs wireless communication with a plurality of wireless terminal devices,
The reception unit receives the remaining battery power of the plurality of wireless terminal devices,
There is a wireless terminal device in which the remaining amount of the battery is less than or equal to a first threshold value among the plurality of wireless terminal devices, and the total time of radio wave transmission time and reception time is greater than or equal to a second threshold value by the transmission unit And if the ratio of the communication time between the radio base station apparatus and the plurality of radio terminal apparatuses to the total time of the radio wave transmission time and reception time is greater than a third threshold, the remaining battery level is A wireless communication method, comprising: transmitting a transmission power reduction instruction to a wireless terminal device greater than the first threshold.

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