Wireless communication system, wireless communication method, wireless communication device, and wireless communication program

Abstract

To provide: a radio communication system that can secure fairness of a throughput between terminals of which the number of available channels is different; a radio communication method; a radio communication device, and a radio communication program.SOLUTION: A radio communications system of the present disclosure, comprises: a plurality of IoT terminals; and a transmission traffic control device. Each IoT terminal is configured to execute processing for transmitting a list of available channels. The transmission traffic control device is configured to execute: processing for grouping the terminals on the basis of the list of available channels; processing for calculating a transmission ratio to be achieved in each channel in each group of each IoT terminal by an objective function on the basis of a fairness policy; and processing for broadcasting the transmission ratio to the IoT terminals. In addition, each IoT terminal is configured to execute control of channel selection and a transmission traffic amount on the basis of the transmission ratio.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This disclosure relates to wireless communication systems, wireless communication methods, wireless communication devices, and wireless communication programs. [Background technology]

[0002] In recent years, IoT services, which involve communication with physical objects, have been developing rapidly. IoT devices can connect to the internet using wireless communication. Therefore, IoT devices are expected to be applied to a variety of services, such as remote monitoring and telemetering.

[0003] The CRDSA (Contention Resolution Diversity Slotted ALOHA) method is known as an access method in which IoT devices autonomously control themselves. However, with the CRDSA method, when the number of devices reaches a certain value, packet collisions increase, causing interference cancellation to fail. As a result, communication capacity drops sharply, which can disrupt IoT services.

[0004] Non-patent document 1 discloses a technique for controlling the channels used and the amount of traffic transmitted, as a method to improve the characteristics of the CRDSA method described above. In this technique, terminal groups are grouped based on the channels available to each terminal. Then, the transmission rate on each channel is calculated for each group, and traffic control is performed based on that transmission rate to improve the characteristics of the CRDSA method. [Prior art documents] [Patent Documents]

[0005] [Non-Patent Document 1] Kumazawa et al., "A Study on Transmission Control of the CRDSA Method to Prevent Performance Degradation Due to Channel Utilization Bias in Satellite IoT Systems," IEICE Society Conference, March 1, 2022, Vol. 2022, B-3-8 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the method described above aims to maximize the total throughput of the system. Therefore, groups with more available channels, i.e., groups with greater freedom to transmit, will have more opportunities to transmit traffic. In other words, the throughput between terminals will differ significantly depending on the number of available channels, which raises the issue of compromising the fairness of throughput between terminals.

[0007] The primary objective of this disclosure is to provide a wireless communication system that can maintain fairness in throughput between terminals with different numbers of available channels, in order to solve the aforementioned problems.

[0008] Furthermore, a second objective of this disclosure is to provide a wireless communication method that can maintain fairness in throughput between terminals with different numbers of available channels.

[0009] Furthermore, a third objective of this disclosure is to provide a wireless communication device that can maintain fairness in throughput between terminals with different numbers of available channels.

[0010] Furthermore, a fourth objective of this disclosure is to provide a wireless communication program that can maintain fairness in throughput between terminals with different numbers of available channels. [Means for solving the problem]

[0011] A first aspect of this disclosure is preferably a wireless communication system comprising a plurality of IoT terminals and a transmit traffic controller, wherein the IoT terminals are configured to perform a process of sending a list of available channels, the transmit traffic controller is configured to perform a process of grouping IoT terminals based on the list of available channels, a process of calculating the transmission rate to be achieved on each channel for each group of IoT terminals using an objective function based on a fairness policy, and a process of broadcasting the transmission rate to the IoT terminals, and the IoT terminals are configured to perform channel selection and control of the amount of transmit traffic based on the transmission rate.

[0012] Furthermore, a second aspect of this disclosure is preferably a wireless communication method comprising sending a list of available channels to an IoT terminal, grouping IoT terminals based on the list of available channels, calculating a transmission rate for each channel for each group of IoT terminals using an objective function based on a fairness policy, broadcasting the transmission rate to the IoT terminal, and the IoT terminal performing channel selection and control of the amount of transmitted traffic based on the transmission rate.

[0013] Furthermore, a third aspect of this disclosure is preferably a wireless communication device configured to perform the following: receiving a list of available channels sent by an IoT terminal; grouping IoT terminals based on the list of available channels; calculating the transmission rate on each channel for each group of IoT terminals using an objective function based on a fairness policy; and broadcasting the transmission rate to the IoT terminals.

[0014] Moreover, a fourth aspect of the present disclosure is a wireless communication program to be implemented in a wireless communication device, the program including: a process of receiving a list of available channels sent by an IoT terminal; a process of grouping IoT terminals based on the list of available channels; a process of calculating a transmission rate for each channel for each group of IoT terminals by an objective function based on a fairness policy; and a process of broadcasting the transmission rate to the IoT terminals. It is preferable that the wireless communication program is a program for causing a computer to execute these processes.

Effects of the Invention

[0015] According to the first to fourth aspects of the present disclosure, it is possible to maintain fairness in throughput among terminals having different numbers of available channels.

Brief Description of the Drawings

[0016] [Figure 1] A diagram showing a wireless communication system in a comparative example. [Figure 2] A diagram showing the CRDSA method. [Figure 3] A diagram showing interference in the CRDSA method. [Figure 4] A diagram showing the CRDSA method with FH introduced. [Figure 5] A diagram showing the configuration of a wireless communication system according to Embodiment 1 of the present disclosure. [Figure 6] A diagram showing the hardware configuration of a transmission traffic controller according to Embodiment 1 of the present disclosure. [Figure 7] A flowchart showing packet transmission processing of a wireless communication system according to Embodiment 1 of the present disclosure. [Figure 8] A diagram showing grouped IoT terminals according to Embodiment 1 of the present disclosure. [Figure 9] A flowchart showing the setting process of an objective function according to Embodiment 1 of the present disclosure. [Figure 10] A graph showing the calculation result of traffic transmission load with respect to degrees of freedom. [Figure 11]This is a graph showing the throughput characteristics according to Embodiment 1 of this disclosure. [Figure 12] This flowchart shows the process for setting the objective function according to Embodiment 2 of this disclosure. [Modes for carrying out the invention]

[0017] Embodiment 1 [Wireless communication system in comparative example] Prior to describing the wireless communication system according to Embodiment 1 of this disclosure, the wireless communication standards and wireless communication systems in comparative examples will be described. In recent years, IoT services that communicate with objects have been developing. IoT terminals can connect to the internet using wireless communication. Therefore, IoT terminals are expected to be applied to various services such as remote monitoring or telemetering.

[0018] Wireless communication standards include existing mobile communication systems such as Wi-Fi (IEEE 802.11ah) and LTE, as well as LPWA (Low Power Wide Area), which is characterized by low power consumption. LPWA standards that use unlicensed bands include Sigfox, LoRaWAN, and ELTRES. LPWA standards that use licensed bands include LTE-M and NB-IoT.

[0019] Meanwhile, 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 orbit at altitudes of several hundred kilometers to 2,000 kilometers. Ground-based wireless terminals can connect to these communication satellites to achieve high-speed communication. For example, Oneweb and SpaceX have launched numerous communication satellites and commenced communication services.

[0020] Furthermore, IoT services using low-Earth orbit satellites, which combine these communication satellites, are being considered. For example, a service that connects IoT terminals to low-Earth orbit satellites and then connects to the internet via those satellites. Such IoT services are promising as systems that can provide IoT services even in remote areas such as mountainous regions where ground networks are not developed, or in areas at sea or in the air where ground network signals cannot reach. For example, Globalstar provides satellite IoT services using low-Earth orbit satellites.

[0021] Figure 1 shows a wireless communication system in a comparative example. A satellite IoT terminal 2 located on the ground transmits packets containing IoT data to satellite 4 via service link 3. The packets are transmitted to a ground base station 6 via feeder link 5, and further transmitted to an IoT application server 10 via network 9. The IoT application server 10 performs data processing such as data processing, analysis, or data cleansing necessary for various IoT services.

[0022] These satellite IoT terminals 2 transmit packets to the satellite using a wireless channel. In this process, access methods such as TDMA (Time Division Multiple Access) or FDMA (Frequency Division Multiple Access) are used to allow multiple terminals to transmit data using the wireless channel.

[0023] In TDMA or FDMA access methods, a system-side control unit manages the process and allocates resources such as time or frequency to each IoT terminal for sending packets. Another access method where IoT terminals autonomously manage the process is the CRDSA method, an evolution of the Slotted ALOHA method. In this method, IoT terminals duplicate the packets they send and transmit the duplicated packets in different time slots.

[0024] Figure 2 shows the CRDSA method. Here, we show an example where IoT terminal #1 transmits packets using channel 1, with time slot 12. First, IoT terminal #1 transmits packet 14 in time slots t2 to t3. IoT terminal #1 then duplicates packet 14 and transmits the duplicated packet 16 in time slots t4 to t5.

[0025] Figure 3 shows interference in the CRDSA method. Here, we show an example where the transmission timing from one IoT terminal overlaps with the transmission timing from another IoT terminal. In this case, the transmitted packets collide and interfere with each other, preventing the packets from being received correctly. Even in this case, if the subsequent duplicate packets are received correctly, the receiving end can use those packets to perform interference cancellation processing, potentially allowing all packets to be received correctly.

[0026] Figure 3 shows an example where IoT terminals #1, #2, and #3 transmit packets using the CRDSA method with eight time slots. IoT terminal #1 transmits packet 14 and duplicate packet 16 in different time slots. IoT terminal #2 transmits packet 18 and duplicate packet 20 in different time slots. IoT terminal #3 transmits packet 22 and duplicate packet 24 in different time slots.

[0027] In this case, packet 18 and duplicate packet 20 sent by IoT terminal #2 collide with packet 14 and duplicate packet 24, respectively, and therefore neither is received correctly. In other words, the information from IoT terminal #2 is not transmitted correctly. However, duplicate packets 16 and 22 are received correctly in other time slots. In other words, the information from IoT terminals #1 and #3 is transmitted correctly.

[0028] Therefore, by performing interference cancellation processing using duplicate packet 16 or packet 22, it becomes possible to correctly receive the packets transmitted by IoT terminal #2. For example, the information of duplicate packet 16 is subtracted from the information received in the time slots t2 to t3. Since duplicate packet 16 is a duplicate of packet 14, this process makes it possible to recognize the correct contents of packet 18. In other words, the CRDSA method can improve the accuracy of information transmission by using multiple packet transmissions and interference cancellation processing in combination.

[0029] Figure 4 shows a CRDSA scheme with FH (Frequency Hopping) implemented. When multiple channels are available, FH can be introduced as an extension of the CRDSA scheme. This is a method of transmitting packets on any different channels and time slots. Figure 4 shows an example where IoT terminal #1 generates and transmits two duplicate packets. Here, packet 14, duplicate packet 16, and duplicate packet 26 each use different channels and different time slots. By using multiple channels in this way, the possibility of packet collisions between terminals is reduced, thus improving throughput characteristics.

[0030] There is also the IRSA (Irregular-Repetition Slotted ALOHA) method, which probabilistically selects the number of packet copies in the CRDSA method. Table 1 shows an example of the distribution of the number of copies in the IRSA method. In the example in Table 1, when the maximum number of copies is 4, the control is performed to set the number of packet copies to 2 with a probability of 0.5102 and to set the number of packet copies to 4 with a probability of 0.4898.

[0031] [Table 1]

[0032] In IoT services using low Earth orbit satellites, each satellite covers a vast area on the Earth's surface. As a result, a large number of terminals connect to a single satellite. When the number of connected terminals increases, interference between terminals can cause communication problems, leading to a decrease in the communication capacity of the communication system.

[0033] Furthermore, each terminal must avoid interfering with the terrestrial network when transmitting packets to the satellite. For this reason, different terminals have different available channels.

[0034] Similar to the long-used Slotted ALOHA method, the CRDSA method incorporating FH (hereinafter referred to as the "CRDSA+FH method") also sees an increase in communication capacity as the number of connected terminals increases. However, once the number of terminals reaches a certain value, the communication capacity drops sharply. This is because the probability of multiple terminals selecting the same slot and sending packets increases, leading to an increase in packet collisions. When a certain number of packet collisions occur, interference cancellation processing stops working, and the communication capacity drops sharply. This decrease in communication capacity disrupts IoT services.

[0035] Non-patent document 1 discloses a technique for controlling the channels used and the amount of traffic transmitted, as a method to improve the characteristics of the CRDSA method described above. In this technique, terminal groups are grouped based on the channels available to each terminal. Then, the transmission rate on each channel is calculated for each group, and traffic control is performed based on that transmission rate to improve the characteristics of the CRDSA method.

[0036] However, the method described above aims to maximize the total throughput of the system. Therefore, groups with more available channels, i.e., groups with greater transmission freedom, have more opportunities to transmit traffic. As a result, throughput between terminals differs greatly depending on the number of available channels, which raises the issue of undermining fairness among terminals. This disclosure solves this problem.

[0037] [Wireless communication system according to Embodiment 1 of this disclosure] Figure 5 shows the configuration of a wireless communication system according to Embodiment 1 of the present disclosure. The wireless communication system 100 differs from the wireless communication system 500 in the comparative example in that it includes a transmit traffic controller 8.

[0038] Satellite IoT terminal 2 converts information such as a list of available channels and the amount of traffic to be transmitted into packets and transmits them to satellite 4 via service link 3.

[0039] Satellite 4 relays information packets transmitted from satellite IoT terminal 2 to ground base station 6 via feeder link 5. Ground base station 6 transmits the relayed information packets to transmission traffic controller 8 via network 9.

[0040] The transmit traffic controller 8 groups the satellite IoT terminals 2 based on the transmitted information and calculates the transmission rate to be achieved for each channel for each group. It then notifies the satellite 4 of the transmission rate to be achieved for each channel via the ground base station 6.

[0041] The transmission rate to be achieved in each channel is calculated based on an objective function set by the wireless communication system 100. This objective function is set periodically based on the policy. The flow for calculating the transmission rate is shown in Figure 7, and the flow for setting the objective function based on the policy is shown in Figure 9, both of which will be described later.

[0042] Satellite 4 broadcasts information about the transmission rate to be achieved on each channel to all satellite IoT terminals 2. Based on this information, satellite IoT terminals 2 select the channel to send packets, determine the amount of transmission traffic, and then perform the packet transmission process.

[0043] Furthermore, the satellite IoT terminal 2 performs observations and sensing as an IoT service and obtains IoT information. It then converts the obtained IoT information into packets and transmits them to satellite 4 via service link 3. Satellite 4 relays the transmitted information packets to ground base station 6 via feeder link 5.

[0044] The ground base station 6 transmits the relayed information packets to the IoT application server 10 via the network 9. The IoT application server 10 performs processing such as data processing, analysis, and data cleansing based on the transmitted IoT information.

[0045] In this example, the terminal equipped with the wireless communication system 100 is shown as a satellite IoT terminal 2. However, if the wireless communication system 100 performs wireless communication by a method other than relaying via satellite 4, this terminal may also be an IoT terminal.

[0046] [Hardware configuration of the transmit traffic controller according to Embodiment 1] Figure 6 shows the hardware configuration of a transmit traffic controller according to Embodiment 1 of the present disclosure. The transmit traffic controller 8 includes a CPU 118. The CPU 118 is connected to a bus line 120. Memory devices such as a ROM 122, RAM 124, and storage 126 are connected to the bus line 120. The memory devices store a wireless communication program executed by the CPU 118. The transmit traffic controller 8 can realize functions specific to this embodiment by having the CPU 118 execute its wireless communication program.

[0047] A communication interface 128 is also connected to the bus line 120. The transmit traffic controller 8 communicates with the network via the communication interface 128. An operation unit 130 and a display unit 132 are further connected to the bus line 120. The operation unit 130 and the display unit 132 function as a user interface for operating the transmit traffic controller 8.

[0048] As described above, the transmit traffic controller 8 can realize functions specific to this embodiment by having the CPU 118 execute a wireless communication program. In other words, the transmit traffic controller 8 can also be realized by a computer and the program. Furthermore, the program can be recorded on a recording medium or provided via a network.

[0049] [Processing performed by the wireless communication system according to Embodiment 1 of this disclosure] Figure 7 is a flowchart showing the packet transmission process of a wireless communication system according to Embodiment 1 of this disclosure. This shows the process that is periodically performed by the wireless communication system 100 in order to calculate the transmission rate to be achieved in each channel.

[0050] First, in step 100, the satellite IoT terminal 2 sends a list of available channels. As mentioned above, this information is transmitted to the transmit traffic controller 8 via satellite 4 and ground base station 6.

[0051] Next, in step 102, the transmit traffic controller 8 sets the objective function based on the policy. That is, the transmit traffic controller 8 performs the process of confirming the policy and setting the objective function based on the confirmed policy. Details of setting the objective function will be described later in Figure 9. Prior to setting this objective function, the transmit traffic controller 8 groups the satellite IoT terminals 2 of the wireless communication system 100. This grouping is performed based on the list of available channels sent in step 100.

[0052] Next, in step 104, the transmit traffic controller 8 calculates the transmission rate to be achieved for each channel. The transmit traffic controller 8 calculates the transmission rate to be achieved for each channel for each pre-set group based on the objective function.

[0053] Next, in step 106, the transmit traffic controller 8 broadcasts the necessary information to the satellite IoT terminal 2. The necessary information includes the group of satellite IoT terminal 2 and the transmission rate to be achieved on each channel calculated for each group. As mentioned above, this information is broadcast to the satellite IoT terminal 2 via the ground base station 6 and the satellite 4.

[0054] Finally, in step 108, the satellite IoT terminal 2 performs channel selection and control of the transmit traffic amount. That is, it performs packet transmission processing based on the transmission rate to be achieved on each announced channel.

[0055] The setting of the objective function will now be explained. Figure 8 shows a grouped IoT terminal according to Embodiment 1 of this disclosure. Here, an example is shown in which 10 satellite IoT terminals 2, each capable of using up to 10 channels, are divided into 6 groups. The CRDSA+FH method is used as the communication method.

[0056] Here, satellite IoT terminal 2 will not use the channels used by surrounding ground IoT terminals. Therefore, the channels available to satellite IoT terminal 2 will differ depending on the location of satellite IoT terminal 2 and the presence of surrounding ground IoT terminals.

[0057] The transmit traffic controller 8 divides the satellite IoT terminals 2 into six groups based on the information of available channels received from the satellite IoT terminals 2. Here, terminals that have the same available channels are grouped together. For example, group 28-1 is a group of terminals that can only use channel 1. Similarly, groups 28-2, 28-3, 28-4, and 28-5 are groups of terminals that can only use channels 2, 3, 4, and 5. Group 28-6 is a group of terminals that can use all channels from 1 to 10. In this embodiment, it is assumed that the total generated traffic of groups 28-1 to 28-5 is equal to the generated traffic of group 28-6.

[0058] The objective function setting process performed for the satellite IoT terminals 2 grouped in Figure 8 will now be explained. Figure 9 is a flowchart showing the objective function setting process according to Embodiment 1 of this disclosure. This setting process is performed by the transmit traffic controller 8.

[0059] First, in step 110, determine the policy of the wireless communication system. If the policy is fairness, proceed to step 112. If the policy is total throughput, proceed to step 114. If the policy is priority transmission, proceed to step 116.

[0060] In step 112, the objective function for when the policy is fairness is set, and the setting process is completed. Here, the first objective function is Equation 1, which maximizes the fairness value, and the second objective function is Equation 2, which maximizes the total throughput value. In addition, the first constraint is Equation 3, which relates to the traffic transmission load, and the second constraint is Equation 4, which relates to the bias in the transmission rate.

[0061]

number

[0062]

number

[0063]

number

[0064]

number

[0065] Each formula will be explained in detail. Here, the transmission rate to be achieved in channel j of each group 28-i is p ij gi is defined as. The transmission traffic controller 8 sets Equation 1 as the first objective function. That is, p is calculated such that the numerical value of fairness is maximized. ij is calculated.

[0066] Note that the equation aiming for maximization in Equation 1 is an equation for quantifying fairness, and the "Jain's fairness index", which is known as an index indicating fairness such as access control, is used. However, other equations may be used as long as they are indices indicating fairness.

[0067] When there are multiple p that satisfy Equation 1, that is, p that maximizes the numerical value of fairness ij exists, Equation 2 is set as the second objective function, and p that maximizes the throughput is calculated from among the p that maximizes the numerical value of fairness. ij ij is calculated.

[0068] When calculating p described above ij two constraint conditions are set. The first constraint condition is Equation 3. Here, the right side of Equation 3 is the traffic transmission load at which no performance degradation occurs in the channel j. f j c is. f j c is shown by Equation 5.

[0069]

Number

[0070] Note that f i g is defined as the degree of freedom in group 28 - i, that is, the number of available slots. After calculating the degree of freedom f based on Equation 5, the right side of Equation 3 can be derived by using Equation 6 described later. j c

[0071] The second constraint condition is Equation 4. d min ​​This represents the minimum value of the transmission rate bias that does not affect the degrees of freedom. The transmission rate bias is defined as the ratio of the minimum transmission rate to the maximum transmission rate for each channel in each group.

[0072] d min The throughput characteristics when d is changed are shown in the graph described later in Figure 11. Therefore, in this embodiment, d min Set it to =0.02.

[0073] Table 2 shows the transmission rate calculated based on the above process. Here, the calculation results are shown for the CRDSA method when the total traffic load G of the wireless communication system 100 is 1 and 2. In this case, for example, group 28-6 transmits almost all of the traffic on channels 6 to 10.

[0074] [Table 2]

[0075] By controlling traffic transmission using the transmission rate to be achieved for each channel for each group, calculated using the method described above, the amount of transmission traffic from satellite IoT terminal 2 becomes nearly equal, thus maintaining fairness in throughput.

[0076] In step 114, the objective function is set when the policy is total throughput, and the setting process is completed. Here, the first objective function is equation 2, which maximizes the total throughput value. The first constraint is equation 3, which relates to the traffic transmission load, and the second constraint is equation 4, which relates to the bias in the transmission rate.

[0077] By controlling traffic transmission using the transmission rate to be achieved for each channel in each group, calculated using the method described above, the total throughput can be maximized.

[0078] In step 116, set the transmission rate for the group with the highest transmission priority, and then proceed to step 118.

[0079] This section explains the necessity of pre-setting the transmission rate for groups with high transmission priority. The wireless communication system according to Embodiment 1 of this disclosure may accommodate various IoT services. IoT services have required QoS (Quality of Service). For example, an IoT service that monitors the occurrence of disasters requires a certain throughput as QoS. In this case, since the IoT service in question has a higher transmission priority compared to other IoT services, it becomes necessary to pre-set the transmission rate.

[0080] Here, let's assume that satellite IoT terminal 2, belonging to group 28-3, is performing an IoT service to monitor the occurrence of a disaster. In this case, group 28-3 has a higher transmission priority compared to other groups. Therefore, in step 116, the transmission rate of group 28-3 is set based on the throughput required to monitor the occurrence of a disaster. For example, the relevant transmission rate is set to P 33 We determine that it is = 0.8.

[0081] In step 118, the objective function is set for groups other than the group for which the transmission rate was set in step 116, and the setting process is terminated. Here, the first objective function is equation 2, which maximizes the total throughput. The first constraint is equation 3, which relates to the traffic transmission load, and the second constraint is equation 4, which relates to the bias in the transmission rate. That is, P 33 Enter =0.8 into equation 2, which is the first objective function, and calculate the other transmission rates based on the first and second constraints.

[0082] By controlling traffic transmission using the transmission rate to be achieved for each channel in each group, calculated using the method described above, it is possible to maximize total throughput while ensuring the throughput required for services with high transmission priority.

[0083] In step 118, the objective function was set to maximize total throughput for the transmission rate that groups other than those with high transmission priority should achieve. However, the objective function may also be set to maximize the fairness value. In this case, the first objective function in step 118 should be set to Equation 1. This ensures the throughput required for services with high transmission priority while maximizing fairness for terminals handling services with lower transmission priority.

[0084] Furthermore, in step 118, an example was shown where the objective function is set to maximize total throughput for the transmission rate that groups other than the high-transmission-priority group should achieve. However, it is also possible to start again from the selection of a policy. For example, the policy confirmed in step 110 could be set as the first policy, and if the first policy is priority transmission, a second policy could be set to calculate the transmission rate that groups other than the high-transmission-priority group should achieve.

[0085] In this embodiment, the satellite IoT terminal 2 is assumed not to use channels used by surrounding ground IoT terminals, but this is not limited to this. For example, the channels available to each satellite IoT terminal 2 may differ depending on the channels supported by the satellite IoT terminal 2 or channel usage restrictions imposed by radio wave laws in each country. In any case, this embodiment provides the effect of maintaining fairness in throughput.

[0086] Figure 10 is a graph showing the calculation results of traffic transmission load against degrees of freedom. The plot in Figure 10 shows data on maximum throughput against the number of slots. By approximating this data, Equation 6 is derived. Therefore, based on Equation 5, the degrees of freedom f j c By calculating and then using equation 6, we can derive the right-hand side of equation 3.

[0087]

number

[0088] Figure 11 is a graph showing the throughput characteristics according to Embodiment 1 of this disclosure. In Figure 11, d min This shows the throughput characteristics when d is changed. As can be seen from this graph, min If it is 0.02, there is almost no degradation in throughput characteristics. Therefore, as mentioned above, in this embodiment, d min It is set to =0.02.

[0089] Embodiment 2 Figure 12 is a flowchart showing the objective function setting process according to Embodiment 2 of this disclosure. This setting process is performed by the transmit traffic controller 8. The wireless communication system and packet transmission process according to this embodiment are the same as those in Embodiment 1. The objective function setting process according to this embodiment differs from Embodiment 1, which aimed to maximize the fairness value, in that it maximizes the total throughput within a range that can ensure the fairness value of throughput is above a threshold.

[0090] First, in step 110, the policy of the wireless communication system is determined. If the policy is fairness, proceed to step 120. If the policy is total throughput, proceed to step 114. If the policy is priority transmission, proceed to step 116. Steps 114, 116, and 118 are the same as in Embodiment 1, so their explanation is omitted.

[0091] In step 120, the objective function for when the policy is fairness is set, and the setting process is completed. Here, the first objective function is Equation 7, which ensures that the fairness value is above the threshold, and the second objective function is Equation 2, which maximizes the total throughput value. In addition, the first constraint is Equation 3, which relates to the traffic transmission load, and the second constraint is Equation 4, which relates to the bias in the transmission rate.

[0092]

number

[0093] T is the fairness threshold, for example, set to T=0.9. In this case, the transmit traffic controller 8 sets equation 7 as the first objective function and maximizes p. ij Calculate.

[0094] Maximize the value of equation 7. ij If multiple objective functions exist, set the throughput objective function shown in Equation 2 as the second objective function, and maximize fairness p ij From among them, p maximizes throughput ij Calculate p ij When calculating, first and second constraints are set.

[0095] By controlling traffic transmission using the transmission rate to be achieved for each channel for each group, calculated using the method described above, the total throughput can be maximized while ensuring that the throughput fairness value is above the threshold. [Explanation of Symbols]

[0096] 2 Satellite IoT terminal 8. Transmit Traffic Controller 28-1 Group 28-2 Group 28-3 Group Group 28-4 Group 28-5 Group 28-6 28-i Group 100 Wireless Communication Systems 500 Wireless Communication Systems

Claims

1. Equipped with multiple IoT terminals and a transmission traffic controller, The IoT terminal is configured to perform the process of sending a list of available channels. The aforementioned transmission traffic controller, The process of grouping the IoT terminals based on the list of available channels, A process to calculate the transmission rate to be achieved in each channel for each group of IoT terminals, based on an objective function that is based on a fairness policy, The process of broadcasting the aforementioned transmission rate to the IoT terminal and It is configured to implement, The IoT terminal is configured to perform channel selection and control of the amount of transmitted traffic based on the transmission rate. Wireless communication system.

2. The objective function has a formula that quantifies fairness, and the transmission rate is calculated so as to maximize the fairness value obtained from the formula. The wireless communication system according to claim 1.

3. The objective function has a formula that quantifies fairness, and the transmission rate is calculated such that the fairness value obtained from the formula exceeds a threshold. The wireless communication system according to claim 1.

4. If multiple transmission rates with equal fairness values ​​are obtained, the transmission rate that maximizes total throughput is selected. The wireless communication system according to claim 2 or 3.

5. The aforementioned transmission traffic controller, The process of checking the policy, A setting process to set the objective function based on the aforementioned policy. It is configured to further implement, If the aforementioned policy is priority transmission, The aforementioned setting process, The process of setting the transmission rate to be achieved on each channel available in the group with high transmission priority, The process of setting an objective function based on the fairness policy for groups other than the group with high transmission priority. including The wireless communication system according to claim 1.

6. Send a list of available channels on IoT devices, The IoT terminals are grouped based on the list of available channels, Based on an objective function that follows a fairness policy, the transmission rate to be achieved in each channel for each group of IoT terminals is calculated, Broadcasting the aforementioned transmission rate to the IoT terminal, The IoT terminal performs channel selection and control of the amount of transmitted traffic based on the transmission rate. A wireless communication method that includes the following features.

7. The process of receiving a list of available channels sent by an IoT device, The process of grouping the IoT terminals based on the list of available channels, A process to calculate the transmission rate to be achieved in each channel for each group of IoT terminals, based on an objective function that is based on a fairness policy, The process of broadcasting the aforementioned transmission rate to the IoT terminal and A wireless communication device configured to perform the following actions.

8. A wireless communication program to be implemented by a wireless communication device, The process of receiving a list of available channels sent by an IoT device, The process of grouping the IoT terminals based on the list of available channels, A process to calculate the transmission rate to be achieved in each channel for each group of IoT terminals, based on an objective function that is based on a fairness policy, The process of broadcasting the aforementioned transmission rate to the IoT terminal and A wireless communication program that includes a program to cause a computer to perform a certain action.

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