Wireless communication method, wireless communication system, and wireless terminal

Abstract

To make it possible to reduce a decrease in communication capacity of an entire system even if the number of wireless terminals connected to one wireless communication device increases.SOLUTION: A wireless communication method in which a plurality of wireless terminals transmit packets in time slots randomly selected from a plurality of wireless channels includes: a calculation step of calculating at least one of a transmission traffic limit value and a usage weight for each of the plurality of wireless channels; a transmission step of transmitting data indicating a calculated result to each wireless terminal; a reception step in which each wireless terminal receives the transmitted data; and a control step of controlling at least one of selection of a wireless channel to be used and an amount of transmission traffic based on the data received by each wireless terminal.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method, a wireless communication system, and a wireless terminal. [Background technology]

[0002] In recent years, IoT services, which involve communication with physical objects, have been developing rapidly. IoT terminals (wireless terminals) can connect to the internet using wireless communication devices, and various services such as remote monitoring and telemetering are expected to be available.

[0003] Wireless communication standards include existing mobile communication systems such as Wi-Fi (IEEE 802.11ah) and LTE, as well as LPWA, which is characterized by its low power consumption. LPWA standards that use unlicensed bands include Sigfox, LoRaWAN, and ELTRES. Standards that use licensed bands include LTE-M and NB-IoT.

[0004] Furthermore, satellite communication services using low-Earth orbit satellites are attracting attention as wireless communication devices. In satellite communication services, multiple communication satellites are placed into orbits at altitudes of several hundred kilometers to 2,000 kilometers, and ground-based wireless terminals can connect to these communication satellites to perform high-speed communication.

[0005] For example, companies like Oneweb and SpaceX have launched numerous communications satellites and commenced communication services. Furthermore, IoT services using low Earth orbit satellites in combination with these are being explored.

[0006] For example, an IoT device connects to a low-Earth orbit satellite and connects to the internet via the satellite. IoT services using low-Earth orbit satellites are promising as a system for providing IoT services in remote areas such as mountainous regions where ground networks are not well-developed, as well as in areas at sea and in the air where ground network signals cannot reach. For example, Globalstar provides satellite IoT services using low-Earth orbit satellites.

[0007] IoT devices using low Earth orbit satellites transmit packets to the satellites using, for example, multiple radio channels. Furthermore, access methods such as TDMA and FDMA are used to enable multiple IoT devices to transmit packets using these radio channels.

[0008] When using TDMA or FDMA access methods, for example, a system-side control device manages and allocates resources such as time and frequency for transmitting packets to each IoT terminal. Another access method where IoT terminals autonomously manage the system is the Slotted ALOHA method. Furthermore, Non-Patent Document 1 discloses a method for controlling transmitted traffic as a way to improve the characteristics of the ALOHA system. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2000-299692 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] However, with methods to improve the characteristics of the ALOHA system as described above, the overall communication capacity of the system may decrease if the number of wireless terminals connected to the satellite increases.

[0011] The present invention aims to provide a wireless communication method, a wireless communication system, and a wireless terminal that can mitigate the reduction in the overall communication capacity of a system even when the number of wireless terminals connected to a single wireless communication device increases. [Means for solving the problem]

[0012] A wireless communication method according to one aspect of the present invention is a wireless communication method in which a plurality of wireless terminals transmit packets in time slots randomly selected from a plurality of wireless channels, and is characterized by including a calculation step of calculating at least one of a limit value for the amount of transmission traffic and a utilization weight for each of the plurality of wireless channels; a transmission step of transmitting data indicating the calculated results to each of the wireless terminals; a reception step of each of the wireless terminals receiving the transmitted data; and a control step of controlling at least one of the selection of the wireless channel to be used and the amount of transmission traffic based on the data received by each of the wireless terminals.

[0013] Furthermore, a wireless communication system according to one aspect of the present invention is a wireless communication system in which a plurality of wireless terminals transmit packets in time slots randomly selected from a plurality of wireless channels, comprising: a calculation unit that calculates at least one of a limit value for the amount of transmission traffic and a usage weight for each of the plurality of wireless channels; and a transmission unit that transmits data indicating the results calculated by the calculation unit to each of the wireless terminals, wherein each of the wireless terminals has a receiving unit that receives the data transmitted by the transmission unit, and a control unit that controls at least one of the selection of the wireless channel to be used and the amount of transmission traffic based on the data received by the receiving unit.

[0014] Furthermore, a wireless terminal according to one aspect of the present invention is a wireless terminal that transmits packets in a time slot randomly selected from a plurality of wireless channels, and is characterized by having a receiving unit that receives data indicating the result of calculating at least one of the limit value of the amount of transmission traffic and the usage weight for each of the plurality of wireless channels, and a control unit that controls at least one of the selection of the wireless channel to be used and the amount of transmission traffic based on the data received by the receiving unit. [Effects of the Invention]

[0015] According to the present invention, even if the number of wireless terminals connected to a single wireless communication device increases, the reduction in the overall communication capacity of the system can be mitigated.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a first configuration example of a wireless communication system. [Figure 2] It is a diagram conceptually showing communication by Slotted ALOHA. [Figure 3] It is a diagram showing the throughput characteristics of a wireless terminal. [Figure 4] It is a diagram showing a second configuration example of a wireless communication system. [Figure 5] It is a functional block diagram exemplifying the functions of a wireless terminal. [Figure 6] It is a functional block diagram exemplifying the functions of a satellite. [Figure 7] It is a functional block diagram exemplifying the functions of a control device. [Figure 8] It is a flowchart showing a first operation example of a wireless communication system. [Figure 9] It is a diagram exemplifying the arrangement of a plurality of wireless terminals in a wireless communication system. [Figure 10] It is a diagram exemplifying the available channels of each wireless terminal. [Figure 11] It is a diagram exemplifying the selection rate for selecting a wireless channel. [Figure 12] It is a flowchart showing a second operation example of a wireless communication system. [Figure 13] It is a graph showing the throughput characteristics by simulation for a wireless communication system. [Figure 14] It is a diagram showing the simulation parameters in the simulation shown in FIG. 13.

Modes for Carrying Out the Invention

[0017] The configuration of the wireless communication system will be described below using diagrams. Figure 1 shows a first example configuration of the wireless communication system. As shown in Figure 1, the first example configuration of the wireless communication system (wireless communication system 1) includes, for example, two wireless terminals 2-1 to 2-n, a satellite 3, a ground base station 10, and a server 12, with the ground base station 10 and the server 12 connected via a network 100. When one of the multiple configurations, such as wireless terminals 2-1 to 2-n, is not specified, it is simply abbreviated as wireless terminal 2, etc.

[0018] Wireless terminal 2 is a satellite IoT terminal located on the ground that communicates wirelessly with satellite 3 and transmits packets containing IoT data to the satellite. These packets are then transmitted to server 12 via satellite 3 and ground base station 10.

[0019] Server 12 is an IoT application server that performs data processing, analysis, and data cleansing necessary for various IoT services.

[0020] Each wireless terminal 2 transmits packets to satellite 3 using one of several wireless channels. In addition to centralized access control in which server 12 allocates resources such as time and frequency for each wireless terminal 2 to transmit packets, there is also the Slotted ALOHA method, which is an access method in which the wireless terminals 2 autonomously control their access.

[0021] Figure 2 is a conceptual diagram illustrating communication using Slotted ALOHA. Multiple radio channels are separated by multiple time slots. Radio terminal 2 randomly selects a slot and transmits packets through the selected slot.

[0022] In the example shown in Figure 2, wireless terminal 2-1 selects the ch2 slot between t0 and t1, wireless terminal 2-2 selects the ch1 slot between t1 and t2, and wireless terminal 2-3 selects the ch3 slot between t2 and t3, and transmits packets. Thus, the Slotted ALOHA method does not require control by the server 12, making it suitable for wireless communication systems 1 such as IoT services where a large number of wireless terminals 2 are connected and the transmission traffic per wireless terminal is low.

[0023] However, in IoT services using low-Earth orbit satellites, a large number of wireless terminals 2 connect to the satellite because the area covered by satellite 3 on the Earth's surface is vast. When the number of wireless terminals 2 increases, interference between multiple wireless terminals 2 can cause communication problems, which can reduce the communication capacity of the wireless communication system 1.

[0024] In the Slotted ALOHA method, communication capacity increases as the number of connected wireless terminals 2 increases, but once the number of wireless terminals 2 reaches a predetermined number, the communication capacity may drop sharply. This is because the probability of multiple wireless terminals 2 selecting the same slot and transmitting packets increases, making it impossible to receive packets due to interference. A decrease in the overall communication capacity of the wireless communication system 1 will disrupt IoT services.

[0025] Assuming that the distribution of the number of packets k per slot follows a Poisson distribution, and G is the normalized traffic volume per slot, the probability that there are k packets in each slot is given by equation (1) below.

[0026]

number

[0027] Furthermore, the percentage of channels used in each slot (channel utilization rate) is shown in equation (2) below.

[0028]

number

[0029] Furthermore, the throughput is as shown in equation (3) below.

[0030]

number

[0031] Figure 3 shows the throughput characteristics of wireless terminal 2. The throughput of wireless terminal 2 is maximum when G=1, and decreases due to packet collisions when G is greater than 1.

[0032] To improve the characteristics of the ALOHA system, one method is to adjust the amount of transmitted traffic by independently setting time periods when packets can be transmitted and time periods when they cannot for each wireless terminal 2.

[0033] However, this method does not take into account the adjustment of the transmission traffic volume based on the characteristics of Slotted ALOHA, and therefore cannot optimize the transmission traffic volume. Furthermore, if the wireless communication system 1 is an IoT system that can utilize multiple channels, the wireless terminal 2 cannot select the optimal channel, and thus the overall communication capacity of the system cannot be maximized.

[0034] Figure 4 shows a second example configuration of a wireless communication system. As shown in Figure 4, the second example configuration of the wireless communication system (wireless communication system 1a) includes, for example, n wireless terminals 2a-1 to 2a-n, a satellite 3a, a ground base station 10, a server 12, and a control device 4, with the ground base station 10 and the server 12 connected via a network 100. Wireless communication system 1a is a wireless communication system in which multiple wireless terminals 2a transmit packets using time slots randomly selected from multiple wireless channels.

[0035] Wireless terminal 2a performs measurements and sensing as an IoT service, and transmits the obtained IoT information as packets to satellite 3a via wireless communication. Wireless terminal 2a also transmits available channel information as packets to satellite 3a.

[0036] Satellite 3a relays packets transmitted from wireless terminal 2a to ground base station 10. Satellite 3a also broadcasts the usage weight and transmission traffic limits for each wireless channel, as notified by the control device 4, to each wireless terminal 2a. Details regarding the usage weight and transmission traffic limits will be described later.

[0037] The ground base station 10 receives packets transmitted via satellite 3a and transmits them to the control device 4 and server 12. For example, the ground base station 10 transmits packets containing available channel information to the control device 4.

[0038] Server 12 performs data processing such as data manipulation, analysis, and data cleansing using the data transmitted from each wireless terminal 2a.

[0039] The control device 4 calculates the usage weight and transmission traffic limit for each wireless channel based on the available channel information transmitted from each wireless terminal 2a.

[0040] The wireless communication system 1a periodically calculates the usage weight and transmission traffic limit for each wireless channel. Based on the usage weight and transmission traffic limit, the wireless terminal 2a selects the channel to transmit packets and determines the amount of transmission traffic, and then performs the packet transmission process.

[0041] Next, specific configuration examples of each device constituting the wireless communication system 1a will be explained using Figures 5 to 7.

[0042] Figure 5 is a functional block diagram illustrating the functions of the wireless terminal 2a. As shown in Figure 5, the wireless terminal 2a has a receiving unit 20, a control unit 22, and a transmitting unit 24.

[0043] The receiving unit 20 receives data transmitted by satellite 3 and outputs it to the control unit 22.

[0044] The control unit 22 includes a channel information acquisition unit 220, a channel selection unit 222, a list creation unit 224, and a traffic control unit 226, and controls each part that constitutes the wireless terminal 2a.

[0045] The channel information acquisition unit 220 acquires information indicating available radio channels based on the data received by the receiving unit 20. The channel selection unit 222 selects available radio channels and the radio channel to be used based on the data received by the receiving unit 20. The list creation unit 224 lists the radio channels selected by the channel selection unit 222. The traffic control unit 226 controls at least one of the selection of the radio channel to be used and the amount of transmitted traffic based on the data received by the receiving unit 20.

[0046] The transmitting unit 24 transmits the data output by the control unit 22 to the satellite 3.

[0047] Figure 6 is a functional block diagram illustrating the functions of satellite 3a. As shown in Figure 6, satellite 3a has a receiving unit 30, a measuring unit 32, an amplification unit 34, and a transmitting unit 36.

[0048] The receiving unit 30 receives data transmitted by the wireless terminal 2a or the ground base station 10 and outputs it to the measuring unit 32 and the amplification unit 34.

[0049] The measurement unit 32 measures the channel utilization rate of multiple wireless channels and outputs the measurement results to the receiving unit 30.

[0050] The amplification unit 34 amplifies the data output by the receiving unit 30 and outputs it to the transmitting unit 36.

[0051] The transmitting unit 36 ​​transmits the data amplified by the amplification unit 34 to the wireless terminal 2a or the ground base station 10.

[0052] Figure 7 is a functional block diagram illustrating the functions of the control device 4. As shown in Figure 7, the control device 4 includes a receiving unit 40, a control processing unit 42, and a transmitting unit 44.

[0053] The receiving unit 40 receives data received by the ground base station 10 from satellite 3a via the network 100.

[0054] The control processing unit 42 includes a throughput measurement unit 420, a channel utilization rate measurement unit 421, a traffic volume estimation unit 422, a list creation unit 423, and a calculation unit 5, and controls each of the units that make up the control device 4.

[0055] The throughput measurement unit 420 measures the throughput of each of the multiple wireless channels. The channel utilization rate measurement unit 421 measures the utilization rate of each of the multiple wireless channels. The traffic volume estimation unit 422 estimates the traffic volume of each of the multiple wireless channels based on at least one of the throughput measured by the throughput measurement unit 420 and the utilization rate measured by the channel utilization rate measurement unit 421. The list creation unit 423 lists, for example, the available wireless channels and the wireless channels to be used.

[0056] The calculation unit 5 includes a usage weight calculation unit 50 and a limit value calculation unit 52.

[0057] The utilization weight calculation unit 50 calculates the utilization weight for each of the multiple wireless channels based on at least one of the information acquired by the channel information acquisition unit 220 of the wireless terminal 2a and the traffic volume estimated by the traffic volume estimation unit 422. Details of the utilization weight will be described later.

[0058] The limit value calculation unit 52 calculates a limit value for the amount of transmitted traffic for each of the multiple wireless channels based on at least one of the information acquired by the channel information acquisition unit 220 of the wireless terminal 2a and the traffic amount estimated by the traffic amount estimation unit 422. Details of the limit value for the amount of transmitted traffic will be described later.

[0059] The transmitting unit 44 transmits data processed by the control processing unit 42, such as data showing the results calculated by the calculation unit 5, to the satellite 3a via the network 100 and the ground base station 10.

[0060] Next, a first example of operation of the wireless communication system 1a will be described. Figure 8 is a flowchart of the first example of operation of the wireless communication system 1a. As shown in Figure 8, in step 100 (S100), for example, each wireless terminal 2a sends a list of channels available for data transmission (a list of wireless channels) to the control device 4 via satellite 3a.

[0061] In step 102 (S102), the control device 4 calculates the utilization weight of each channel (radio channel) based on the channel list received from each satellite 3a.

[0062] In step 104 (S104), the control device 4 calculates the limit value for the amount of transmitted traffic for each channel.

[0063] In step 106 (S106), the control device 4 notifies each wireless terminal 2 of the calculated usage weight and the limit value of the transmission traffic amount.

[0064] In step 108 (S108), each wireless terminal 2 performs wireless communication by selecting the channel to be used and controlling the transmission traffic.

[0065] A specific example of the operation of the wireless communication system 1a will be described. Figure 9 is a diagram illustrating the arrangement of multiple wireless terminals 2a in the wireless communication system 1a. Here, it is assumed that there are four wireless channels for IoT services. In addition, to prevent interference with IoT services that use the terrestrial network, wireless terminals 2a will disable channels used by other wireless terminals 2a connected to the terrestrial network.

[0066] Furthermore, let's assume that eight wireless terminals 2a are deployed to two service areas, A and B. Service area A houses two wireless terminals 2a, and service area B also houses two wireless terminals 2a.

[0067] Furthermore, channels 2, 3, and 4 are used in service area A, while channels 1, 3, and 4 are used in service area B. The available channels for each wireless terminal 2a at this time are shown in Figure 10.

[0068] Each wireless terminal 2a periodically transmits information indicating available wireless channels to the control unit 4 via satellite 3a. The control unit 4 collects the information on available channels transmitted from each wireless terminal 2a and classifies them into groups.

[0069] For example, a wireless terminal 2a that can only use channel 1 is designated as Group 1, a wireless terminal 2a that can only use channel 2 is designated as Group 2, and a wireless terminal 2a that can use all channels (channels 1, 2, 3, and 4) is designated as Group 3.

[0070] Here, gx is the amount of generated traffic for each group x, and C is the vector of the channels available in each group. x Let Cx = (c x1 , c x2 , c x3 , c x4 ) is defined as follows.

[0071] c xj In group x, this is set to 1 if jch is available, and 0 if it is unavailable. The amount of traffic generated in each group is equal to the number of wireless terminals 2a. In this case, g corresponds to groups 1, 2, and 3. x and C x It will be as follows:

[0072] g1=2, g2=2, g3=4 C1=(1,0,0,0), C2=(0,1,0,0), C3=(1,1,1,1)

[0073] Next, the control device 4 calculates the utilization weight of each radio channel. Define W = (w1, w2, w3, w4) as the utilization weight matrix. Here, w j represents the utilization weight of jch.

[0074] The utilization weight calculation unit 50 calculates the utilization weight matrix W so as to satisfy the following formula (4).

[0075]

Equation

[0076] m is the number of groups, N is the total number of terminals, and C is the number of channels. Here, assume m = 3, N = 8, and C = 4. Also, T represents transpose.

[0077] According to the above formula (4), the weight W is calculated as follows. W = (0.001, 0.001, 1, 1)

[0078] However, w1 and w2 are set to 0.001, which are numerical values approaching 0 infinitely.

[0079] Also, for the wireless terminal 2a, the limit value calculation unit 52 calculates the limit value of the transmission traffic volume. Let G be the transmission traffic volume of each radio channel after using the utilization weight. When using the utilization weight, the transmission traffic volume of each channel is equalized and calculated as in the following formula (5).

[0080]

Equation

[0081] Also, define the limit value Tr of the transmission traffic volume of the radio channel as in the following formula (6).

[0082]

Equation

[0083] Here, the average number of wireless terminals 2a connected to each wireless channel is 2, The limit value Tr is calculated to be 1 / 2.

[0084] The control device 4 calculates the utilization weight matrix and transmission traffic limit values ​​for each wireless channel, and then notifies the wireless terminal 2a of the calculation results. That is, the control device 4 broadcasts W and Tr to each wireless terminal 2a.

[0085] After receiving information on the utilization weight matrix and the limit value of the transmit traffic amount for each wireless channel, the wireless terminal 2a performs wireless channel selection and transmit traffic control. The selectivity of each wireless channel is calculated by the following equation (7).

[0086]

number

[0087] The denominator of equation (7) above is calculated as shown in equations (8) to (10) below.

[0088]

number

[0089]

number

[0090]

number

[0091] The selectivity rates for each wireless channel within each group are shown in Figure 11. Wireless terminals 2a-1 and 2a-2, belonging to Group 1, select channel 1 and perform transmission processing with the transmission traffic amount limited to 1 / 2. In this case, wireless terminals 2a-1 and 2a-2 control the transmission traffic amount by reducing the transmission opportunity by 1 / 2.

[0092] For example, wireless terminal 2a generates random numbers of 0 and 1 when transmitting data, stopping transmission if a 0 is generated and continuing transmission if a 1 is generated. Similarly, wireless terminals 2a-7 and 2a-8, belonging to group 2, select channel 2 to limit the amount of transmission traffic to half and perform the transmission process.

[0093] Groups 3, specifically 2a-3 to 2a-6, select a radio channel based on its usage weight and limit the transmission traffic to half before processing the transmission.

[0094] In this way, the wireless communication system 1a can distribute the traffic volume among multiple wireless channels and adjust the traffic volume to perform transmission control so that the throughput of each wireless channel is maximized.

[0095] Next, a second example of operation of the wireless communication system 1a will be described. In the second example of operation of the wireless communication system 1a, the control device 4 will not use information on available wireless channels from each wireless terminal 2a.

[0096] Figure 12 is a flowchart showing a second example of operation of the wireless communication system 1a. As shown in Figure 12, in step 200 (S200), for example, satellite 3a measures the channel utilization rate of each wireless channel and transmits the measurement results to the control device 4.

[0097] In step 202 (S202), the control device 4 calculates the utilization weight of each channel (radio channel) based on the channel utilization rate received from each satellite 3a.

[0098] In step 204 (S204), the control device 4 calculates the limit value for the amount of transmitted traffic for each channel.

[0099] In step 206 (S206), the control device 4 notifies each wireless terminal 2 of the calculated usage weight and transmission traffic limit values.

[0100] In step 208 (S208), each wireless terminal 2 performs wireless communication by selecting the channel to be used and controlling the transmission traffic. The wireless communication system 1a then periodically repeats the process from S200 to S208.

[0101] Here, we assume that multiple wireless terminals 2a are deployed as in Figure 9, and that there are four wireless channels. The available wireless channels for each wireless terminal 2a are also the same as in Figure 10. Furthermore, to prevent interference with IoT services connected to the terrestrial network, each wireless terminal 2a will be disabled from using channels already utilized by other wireless terminals 2a connected to the terrestrial network.

[0102] The control device 4 periodically measures the channel utilization rate of each radio channel. The control device 4 measures the channel utilization rate of channel j u measured by satellite 3a. j Therefore, based on equation (11) below, the amount of transmitted traffic G for each radio channel j is calculated. j We estimate this.

[0103]

number

[0104] Next, the control device 4 determines the utilization weight w in channel j. j The control device 4 calculates the weights sequentially in accordance with the timing of the channel utilization rate measurement. For example, the control device 4 calculates the utilization weight at time k in channel j based on the following equation (12).

[0105]

number

[0106] Next, the control device 4 calculates the limit value for the amount of transmitted traffic. The control device 4 also updates the limit value for the amount of transmitted traffic sequentially, similar to the utilization weight for each radio channel. First, the control device 4 calculates an estimated value of the normalized traffic using the following equation (13).

[0107]

number

[0108] Here, C is the number of channels. The control device 4 calculates the limit value Tr for the amount of transmitted traffic for each radio channel based on the estimated normalized traffic value using the following equation (14).

[0109]

number

[0110] The control device 4 calculates the usage weight and transmission traffic limit for each radio channel, and then notifies satellite 3a of the calculated information. Satellite 3a broadcasts the notified information to each radio terminal 2a.

[0111] The wireless terminal 2a selects a wireless channel and limits transmission traffic based on the information it receives.

[0112] The wireless communication system 1a then updates the usage weight and transmission traffic limit values ​​for each wireless channel by repeating the above-described process, thereby optimizing the usage weight and transmission traffic limit values ​​for each wireless channel.

[0113] Next, a third example of operation of the wireless communication system 1a will be described. In the second example of operation of the wireless communication system 1a, the traffic amount G of each wireless channel j is described. jAlthough this was estimated from the measured channel utilization rate, in the third operating example of the wireless communication system 1a, the amount of traffic is estimated by combining the wireless channel utilization rate and the throughput value. The control device 4 sets the measured throughput value of channel j to Th j Therefore, the traffic amount Gj for each wireless channel j is calculated based on the following equation (15).

[0114]

number

[0115] Subsequently, the control device 4 calculates the channel weight and transmission traffic limit for each wireless channel, similar to the second operation example.

[0116] In this way, the wireless communication system 1a controls at least one of the following: the selection of the wireless channel to be used and the amount of transmitted traffic. Therefore, even if the number of wireless terminals connected to a single satellite 3a increases, the reduction in the overall communication capacity of the system can be mitigated.

[0117] In other words, the wireless communication system 1a can perform channel selection and transmit traffic control based on the characteristics of Slotted ALOHA, thereby mitigating the impact of reduced communication capacity caused by an excessive number of connected wireless terminals 2a, and achieving maximum system capacity.

[0118] Figure 13 is a graph showing the throughput characteristics of the wireless communication system 1a based on simulation. G is the amount of generated traffic per slot (normalized). Here, half of the wireless terminals 2a are available for use with half of the wireless channels. Figure 14 shows the simulation parameters in the simulation shown in Figure 13.

[0119] As shown in Figure 13, throughput is improved when channel utilization weight calculation and control are performed compared to when there is no calculation and control of channel utilization weight. Furthermore, by limiting transmit traffic, transmission is suppressed even when the amount of transmit traffic increases, and throughput is kept at its maximum. Note that when the wireless communication system 1a controls the amount of transmit traffic, the amount of traffic transmitted by the wireless terminal 2a is the amount of generated (latent transmit) traffic, and not all traffic is necessarily transmitted due to the transmission limit.

[0120] Furthermore, the functions of the wireless terminal 2a, satellite 3a, and control device 4 may be partially or entirely comprised of hardware such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array), or they may be comprised of programs executed by a processor such as a CPU.

[0121] For example, the wireless terminal 2a, satellite 3a, and control device 4 can be implemented using a computer and a program, and the program can be recorded on a storage medium or provided over a network.

[0122] While embodiments of the present invention have been described above with reference to the drawings, it is clear that the above-described embodiments are merely illustrative examples of the present invention, and the present invention is not limited to the above-described embodiments. Therefore, additions, omissions, substitutions, and other modifications of components may be made without departing from the technical concept and scope of the present invention. [Explanation of symbols]

[0123] 1,1a... Wireless communication system, 2,2a... Wireless terminal, 3,3a... Satellite, 4... Control device, 5... Calculation unit, 10... Ground base station, 12... Server, 20... Receiving unit, 22... Control unit, 24... Transmitting unit, 30... Receiving unit, 32... Measurement unit, 34... Amplification unit, 36... Transmitting unit, 40... Receiving unit, 42... Control processing unit, 44... Transmitting unit, 50... Usage weight calculation unit, 52... Limit value calculation unit, 220... Channel information acquisition unit, 222... Channel selection unit, 224... List creation unit, 226... Traffic control unit, 420... Throughput measurement unit, 421... Channel utilization rate measurement unit, 422... Traffic amount estimation unit, 423... List creation unit

Claims

1. A wireless communication method in which a plurality of wireless terminals transmit packets in time slots randomly selected from a plurality of wireless channels, comprising: a calculation step of calculating at least one of a limit value of a transmission traffic amount and a utilization weight for each of a plurality of wireless channels; a transmitting step of transmitting data indicating the calculated results to each of the wireless terminals; a receiving step in which each of the wireless terminals receives the transmitted data; a control step of controlling at least one of selection of a wireless channel to be used and a transmission traffic amount based on data received by each of the wireless terminals; A wireless communication method comprising:

2. a channel information acquisition step of acquiring information indicating available wireless channels for each of the wireless terminals; In the calculation step, Calculating at least one of a limit value of the amount of transmission traffic and a utilization weight for each of the plurality of wireless channels based on the information acquired in the channel information acquisition step.

2. The wireless communication method according to claim 1, wherein:

3. The method further includes a traffic volume estimation step of estimating a traffic volume of each of the plurality of wireless channels, In the calculation step, Calculating at least one of a limit value of the transmission traffic volume and a utilization weight for each of the plurality of wireless channels based on the traffic volume estimated in the traffic volume estimation step.

3. The wireless communication method according to claim 1 or 2, wherein:

4. further comprising a channel utilization rate measurement step of measuring utilization rates of each of the plurality of wireless channels; In the traffic volume estimation step, Estimating the traffic volume of each of the plurality of wireless channels based on the utilization rate estimated in the channel utilization rate measurement step.

4. The wireless communication method according to claim 3, wherein:

5. further comprising a throughput measurement step of measuring the throughput of each of the plurality of wireless channels; In the traffic volume estimation step, estimating the traffic volume of each of the plurality of wireless channels based on the throughput measured in the throughput measurement step; 5. The wireless communication method according to claim 4, wherein:

6. In a wireless communication system in which a plurality of wireless terminals transmit packets in time slots randomly selected from a plurality of wireless channels, a calculation unit that calculates at least one of a limit value of a transmission traffic amount and a utilization weight for each of a plurality of wireless channels; a transmitting unit that transmits data indicating the result calculated by the calculating unit to each of the wireless terminals; Equipped with Each of the wireless terminals a receiving unit that receives the data transmitted by the transmitting unit; a control unit that controls at least one of selection of a wireless channel to be used and an amount of transmission traffic based on the data received by the receiving unit; A wireless communication system comprising:

7. Each of the wireless terminals a channel information acquisition unit that acquires information indicating available wireless channels; The calculation unit Calculating at least one of a limit value of the amount of transmission traffic and a utilization weight for each of the plurality of wireless channels based on the information acquired by the channel information acquisition unit.

7. The wireless communication system according to claim 6, wherein:

8. In a wireless terminal that transmits a packet in a time slot randomly selected from a plurality of wireless channels, a receiving unit that receives data indicating a result of calculating at least one of a limit value of a transmission traffic amount and a utilization weight for each of a plurality of wireless channels; a control unit that controls at least one of selection of a wireless channel to be used and an amount of transmission traffic based on the data received by the receiving unit; A wireless terminal comprising:

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