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

Abstract

The present disclosure relates to a wireless communication system, a wireless communication device, a wireless communication method, and a wireless communication program. The wireless communication system performs wireless communication using a plurality of links and comprises a schedule control unit and a data distribution unit. The schedule control unit is configured to execute a setting process for setting a schedule for a transmission opportunity including a priority period, and the data distribution unit is configured to execute a process for transmitting data received from an upper layer on the basis of the schedule. The schedule is set so that a priority period in at least two or more links has an overlap period. The overlap period is set to have a length equal to or greater than the maximum packet length assumed by the wireless communication system for a priority packet to be generated.

Description

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

[0001] The present disclosure relates to a wireless communication system, a wireless communication device, a wireless communication method, and a wireless communication program.

[0002] In wireless communication, a priority terminal may be designated as a specific terminal for the purpose of low latency and high-priority transmission. Hereinafter, packets from a priority terminal are referred to as priority packets, and a period during which transmission of priority packets is treated preferentially and exclusively is referred to as a priority period. In addition, MLO (Multi-Link Operation) performs wireless communication using links of multiple frequency bands simultaneously.

[0003] In MLO, a method is known in which priority periods are distributed among links to enable packet transmission by priority terminals at all times. For example, Non-Patent Documents 1 and 2 disclose a wireless communication method for controlling a contention free period (CFP), which is a priority period. In this wireless communication method, control is performed under the condition that the link to which the priority period is allocated is switched so that the priority period is secured on one of the links.

[0004] Saito, et al., "Ethernet Wireless LAN Communication Quality Control Method Using Priority Control," IEICE Transactions on Information and Communication Engineers, Vol. J84-B, No. 9, pp. 1598-1612, September 2001. Yagi, et al., "Proposal of HCCA Control Method to Achieve Fair Throughput Among Multiple Nearby Wireless LANs," IEICE Technical Report, Vol. 116, No. 485, February 23, 2017, pp. 49-54.

[0005] However, if the length of the priority packet is longer than the remaining time of the priority period at the time when the priority packet occurs, the transmission of the priority packet must wait until the next priority period. In other words, the above-mentioned wireless communication method has a problem in that if a priority packet occurs immediately before the priority period switching timing, there will be a period during which the priority packet cannot be transmitted.

[0006] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication system that can transmit priority packets of any length at any time.

[0007] A second object of the present disclosure is to provide a wireless communication device that can transmit a priority packet of any length at any time.

[0008] A third object of the present disclosure is to provide a wireless communication method that can transmit a priority packet of any length at any time.

[0009] A fourth object of the present disclosure is to provide a wireless communication program that can transmit a priority packet of any length at any time.

[0010] A first aspect of the present disclosure is a wireless communication system that performs wireless communication using multiple links, and is provided with a schedule control unit and a data allocation unit, wherein the schedule control unit is configured to perform a setting process for setting a schedule of transmission opportunities including a priority period, and the data allocation unit is configured to perform a process for transmitting data received from a higher layer based on the schedule, and the schedule is set so that the priority periods in at least two or more links have overlapping periods, and the overlapping periods are set so that the length of any occurring priority packets is equal to or greater than the maximum packet length assumed by the wireless communication system.

[0011] A second aspect of the present disclosure is a wireless communication device that performs wireless communication using multiple links, and is configured to perform a process of setting a schedule of transmission opportunities including a priority period, and a process of transmitting data received from a higher layer based on the schedule, wherein the schedule is set so that the priority periods in at least two or more links have overlapping periods, and the overlapping periods are set so that the length of any occurring priority packets is equal to or greater than the maximum packet length assumed by the wireless communication system.

[0012] A third aspect of the present disclosure is a wireless communication method for performing wireless communication using multiple links, comprising: setting a schedule of transmission opportunities including a priority period; and transmitting data received from a higher layer based on the schedule; wherein the schedule is set so that the priority periods in at least two or more links have an overlapping period, and the overlapping period is set so that the length of an occurring priority packet is equal to or greater than the maximum packet length assumed by the wireless communication system.

[0013] A fourth aspect of the present disclosure is a wireless communication program that performs wireless communication using multiple links and is executed by a wireless communication device having a processor and a memory, the wireless communication program being stored in the memory and computer-readable, and including a program that causes the processor to perform a process of setting a schedule of transmission opportunities including a priority period, and a process of transmitting data received from a higher layer based on the schedule, and preferably the wireless communication program is configured so that the priority periods in at least two or more links have overlapping periods, and the overlapping periods are set so that the length of any occurring priority packets is equal to or greater than the maximum packet length assumed by the wireless communication system.

[0014] According to the first to fourth aspects of the present disclosure, priority packets of any length can be transmitted at any time.

[0015] Fig. 1 is a diagram showing an example of scheduling transmission opportunities according to a comparative example; Fig. 2 is a diagram showing an example of scheduling transmission opportunities according to embodiment 1 of the present disclosure; Fig. 3 is a block diagram showing an example of the configuration of a wireless communication system according to embodiment 1 of the present disclosure; Fig. 4 is a block diagram showing an example of the configuration of an MLD unit according to embodiment 1 of the present disclosure; Fig. 5 is a block diagram showing a hardware configuration of an MLD unit according to embodiment 1 of the present disclosure; Fig. 6 is a diagram showing an example of modification in scheduling transmission opportunities according to embodiment 1 of the present disclosure.

[0016] 1 is a diagram showing an example of scheduling transmission opportunities according to a comparative example, in which scheduling of transmission opportunities is shown in MLO using three links.

[0017] A priority period 20a is set for Link 1. The priority period is a period during which communications from a specific terminal are treated preferentially and exclusively, such as a CFP. The priority period can be set by determining, for example, the start timing and length of the period. Similarly, a priority period 20b is set for Link 2, and a priority period 20c is set for Link 3.

[0018] Although the CFP is a priority period in the Hybrid Coordination Function (HCF) introduced in the IEEE 802.11e communication standard, the priority period set in the present disclosure is not limited to this. For example, the CFP may be the Point Coordination Function (PCF) used in the IEEE 802.11 communication standard. Alternatively, the CFP may be the Restricted Target Wake Time (rTWT) introduced in the IEEE 802.11be communication standard.

[0019] In the comparative example, control is performed based only on the condition that the link to which the priority period is allocated is switched so that the priority period is secured for one of the links. As a result, the priority periods 20a, 20b, and 20c are switched in sequence, and no overlapping periods exist.

[0020] Assume that priority packet 4 occurs just before the priority period 20a ends. If priority packet 4 is processed on Link 1, the end of priority packet 4 will extend beyond the priority period 20a. Therefore, priority packet 4 cannot be processed until priority period 20b begins.

[0021] That is, the wireless communication method of the comparative example has a problem in that there is a period from the occurrence of priority packet 4 until the start of priority period 20b during which priority packets cannot be transmitted. Alternatively, the wireless communication method of the comparative example has a problem in that it cannot handle priority packets that occur non-periodically or suddenly. The present disclosure solves this problem.

[0022] 2 is a diagram illustrating an example of scheduling transmission opportunities according to the first embodiment of the present disclosure. Here, the scheduling of transmission opportunities is shown in MLO using three links. Note that the number of links may be any number equal to or greater than two.

[0023] Priority periods 2a and 2d are set for Link 1. Similarly, priority period 2b is set for Link 2, and priority period 2c is set for Link 3. Priority periods 2a and 2b overlap in overlapping period 6a. Similarly, priority periods 2b and 2c overlap in overlapping period 6b, and priority periods 2c and 2d overlap in overlapping period 6c.

[0024] In this embodiment, the priority periods in at least two or more links are set to have an overlapping period, and this overlapping period is set to be equal to or longer than the maximum packet length assumed by the wireless communication system for the priority packets that occur.

[0025] Now, let's assume that priority packet 4 occurs just before the end of priority period 2a. If priority packet 4 were processed on Link 1, the end of priority packet 4 would extend beyond priority period 2a. However, in this embodiment, priority period 2b is used, so priority packet 4 can be processed immediately after its occurrence. In other words, there is no period during which priority packets cannot be transmitted, so priority packets of any length can be transmitted at any time.

[0026] 3 is a block diagram showing a configuration example of a wireless communication system according to the first embodiment of the present disclosure. The wireless communication system 100 includes an access point 30 and a terminal 40. The wireless communication system 100 is a wireless communication system in which the access point 30 and the terminal 40 implement MLO using three links.

[0027] The access point 30 includes an MLD unit 32. The MLD unit 32 is configured to control wireless communications in the access point 30, which is an MLD (Multi-Link Device). Examples of wireless communications control include setting a priority period and transmitting and receiving packets based on the set priority period. The detailed configuration of the MLD unit 32 will be described later.

[0028] The MLD unit 32 controls wireless communication by controlling the transceivers 34a, 34b, and 34c. The transceiver 34a uses, for example, a 2.4 GHz frequency band. The transceiver 34b uses, for example, a 5 GHz frequency band. The transceiver 34c uses, for example, a 6 GHz frequency band.

[0029] Although the access point 30 shown here uses the 2.4 GHz, 5 GHz, and 6 GHz frequency bands, it is acceptable for the configuration to be such that each transmitter / receiver uses a different channel. Also, it is acceptable for the access point 30 to be configured to use two or more links.

[0030] The terminal 40 includes an MLD unit 42. The MLD unit 42 is configured to control wireless communication in the terminal 40, which is an MLD (Multi-Link Device). Examples of wireless communication control include setting a priority period and transmitting and receiving packets based on the set priority period. The detailed configuration of the MLD unit 42 is the same as the configuration of the MLD unit 32, which will be described later.

[0031] The MLD unit 42 controls wireless communication by controlling the transceivers 44a, 44b, and 44c. The transceiver 44a uses, for example, a 2.4 GHz frequency band. The transceiver 44b uses, for example, a 5 GHz frequency band. The transceiver 44c uses, for example, a 6 GHz frequency band.

[0032] Although the terminal 40 shown here uses frequency bands of 2.4 GHz, 5 GHz, and 6 GHz, it is sufficient that each transmitting / receiving unit uses a different channel. Furthermore, the terminal 40 is sufficient that it uses two or more links.

[0033] 4 is a block diagram showing an example configuration of an MLD unit according to the first embodiment of the present disclosure. The MLD unit 32 includes a schedule control unit 36. The schedule control unit 36 ​​sets a schedule of transmission opportunities including a priority period.

[0034] The schedule is set so that the priority periods of at least two or more links have an overlapping period, and the overlapping period is set so that the length of an occurring priority packet is equal to or greater than the maximum packet length assumed by the wireless communication system.

[0035] The schedule control unit 36 ​​notifies the set schedule to the data allocation unit 38, which will be described later. When the schedule is changed, the schedule change is notified to the surrounding terminals using the transmission / reception units 34a, 34b, and 34c.

[0036] The MLD unit 32 also includes a data distribution unit 38. The data distribution unit 38 distributes data received from the upper layer. This distribution is performed by transmitting the data received from the upper layer via the transmission / reception unit 34a, 34b, or 34c based on a schedule notified by the schedule control unit 36.

[0037] 5 is a block diagram showing a hardware configuration of an MLD unit according to the first embodiment of the present disclosure. Fig. 5 shows a configuration in which the functions of the wireless communication device according to the first embodiment of the present disclosure are realized by software.

[0038] The MLD unit 32 includes a processor 35 and a memory 37 instead of the schedule control unit 36 ​​and the data distribution unit 38 in Fig. 4. The memory 37 stores a wireless communication program executed by the processor 35. The MLD unit 32 can realize functions specific to this embodiment by the processor 35 executing the wireless communication program.

[0039] That is, the functions of the MLD unit 32 can be realized by a computer and the program. The program can also be recorded on a recording medium or provided via a network.

[0040] 6 is a diagram illustrating an example of modification in scheduling of transmission opportunities according to the first embodiment of the present disclosure. Here, an example of modification in scheduling of transmission opportunities in MLO using three links is shown. The modification here includes changing the length and start timing of the priority period. Note that in the modification examples shown below, modification information is notified to surrounding terminals before modifying the priority period.

[0041] Link 1 is set with priority periods 2e and 2g. Here, Link 1 is a congested link used by many non-priority terminals and packets. Therefore, in Link 1, in order to make the contention period 8a longer than the initial setting, priority periods 2e and 2g are modified to be shorter than the initial setting. Here, a contention period is a period during which non-priority terminals can also communicate, such as a contention period (CP). Specifically, the length of each priority period is shortened so that priority periods 2e and 2g are shorter than the initial setting.

[0042] A priority period 2f is set for Link 2. Link 2 is a congested link used by many priority terminals. Therefore, the priority period 2f for Link 2 is modified to be longer than the initial setting.

[0043] As described above, the priority period may be modified based on the initial setting in accordance with the number of priority terminals or the amount of packets in the link. For example, if the number of priority terminals and the amount of packets in the link are equal to or greater than a threshold, the priority period may be modified to be shorter than the initial setting. This threshold may be set in advance or may be set as needed depending on the wireless communication situation. This can improve the availability of non-priority terminals and fairness between priority terminals and non-priority terminals.

[0044] A priority period of 2h is set for Link 3. Link 3 is a link used by few terminals. Therefore, Link 3 is set to a priority period for a period in which it is no longer possible to set a priority period as a result of the corrections made to Link 1 and Link 2.

[0045] As described above, a priority period may be set for a link with a low level of congestion so as to cover a period for which a priority period cannot be set as a result of a modification to another link. For example, if a link for which a priority period cannot be set arises as a result of a modification to another link, a priority period may be set for a link with a congestion level equal to or less than a threshold so as to cover this priority period. Alternatively, in a similar case, a priority period may be set for the link with the lowest level of congestion so as to cover this priority period. This threshold may be set in advance or may be set as needed depending on the wireless communication situation.

[0046] This results in a link with a high degree of freedom in setting priority periods, which improves the degree of freedom in setting schedules for transmission opportunities in other links.

[0047] In addition to the above, three modified examples of setting the priority period will be described. First, a link whose packet error rate is below a threshold may be set with the same priority period as that set for other links. First, the packet error rate is detected for all links used in the wireless communication system. Then, a link whose packet error rate is below a threshold is set with the same priority period as that set for other links. This threshold may be set in advance, or may be set as needed depending on the wireless communication situation.

[0048] This increases the number of periods during which priority periods are set for multiple links, thereby increasing redundancy in the transmission of priority packets, thereby reducing delays and deterioration in reliability due to retransmission or loss of priority packets.

[0049] Second, the priority period may be transitioned so that the priority period can be set to the link with the least airtime occupancy time or ratio at that time. First, the airtime occupancy time or airtime occupancy ratio of non-priority terminals is monitored for all links used in the wireless communication system. Next, the link with the least airtime occupancy time or airtime occupancy ratio is selected. Next, the priority period set for another link is transitioned to the selected link. Furthermore, information about the transition destination link is notified to the data transmission destination.

[0050] This allows the priority period to be dynamically and timely modified, thereby improving the flexibility in scheduling transmission opportunities for all links used in a wireless communication system.

[0051] Third, the priority period may be lengthened so that the maximum time difference between the links is added to the overlap time. For example, if the links used in a wireless communication system do not share a common clock, the clocks on the links may be out of sync. In this case, the priority periods of the links may not overlap as expected.

[0052] Therefore, the priority period may be lengthened so that the maximum time lag between each link is added to the overlap time taken into account when setting the priority period. The time lag is determined, for example, by the clock frequency offset. The allowable range of the clock frequency offset is determined, for example, by the oscillator accuracy.

[0053] This allows a priority packet of any length to be transmitted at any time, even if the links used in a wireless communication system do not share a common clock.

[0054] An example of a case where a common clock is not used is when multiple links across multiple access points are controlled. In this case, a network controller is required to send and receive information to and from the multiple access points and control the corresponding links.

[0055] 2a, 2b, 2c, 2d, 2e, 2f, 2g, 2h: priority period 4: priority packet 6a, 6b, 6c: overlapping period 20a, 20b, 20c: priority period 35: processor 36: schedule control unit 37: memory 38: data distribution unit 100: wireless communication system

Claims

1. A wireless communication system that performs wireless communication using multiple links, comprising a schedule control unit and a data allocation unit, wherein the schedule control unit is configured to perform a setting process to set a schedule of transmission opportunities including a priority period, and the data allocation unit is configured to perform a process to transmit data received from a higher layer based on the schedule, wherein the schedule is set so that the priority periods in at least two or more links have an overlapping period, and the overlapping period is set so that the length of an occurring priority packet is equal to or longer than the maximum packet length assumed by the wireless communication system.

2. The wireless communication system according to claim 1, wherein said setting process further includes a correction process for correcting said priority period to be shorter than an initial setting when the number of priority terminals and the amount of packets of the link in question are equal to or greater than a threshold value.

3. The wireless communication system according to claim 2, wherein the setting process further includes a process of setting a priority period to a link whose congestion level is equal to or lower than a threshold so as to cover a link for which a priority period cannot be set as a result of the correction process.

4. The wireless communication system according to claim 1, wherein said setting process further includes a process of setting, for a link having a packet error rate equal to or lower than a threshold, a priority period that is the same as the priority period set for another link.

5. A wireless communication system as described in claim 1, wherein the setting process further includes a process of monitoring the airtime occupancy time or airtime occupancy ratio of non-priority terminals for the multiple links, a process of selecting a link having the smallest airtime occupancy time or airtime occupancy ratio, a process of transferring the priority period set for other links to the selected link, and a process of notifying a data destination of information on the link to which the data is to be sent.

6. A wireless communication device that performs wireless communication using multiple links, the wireless communication device being configured to perform the following processes: setting a schedule of transmission opportunities including a priority period; and transmitting data received from a higher layer based on the schedule, the schedule being set so that the priority periods in at least two or more links have an overlapping period, and the overlapping period being set so that the length of an occurring priority packet is equal to or longer than the maximum packet length assumed by the wireless communication system.

7. A wireless communication method for performing wireless communication using a plurality of links, comprising: setting a schedule of transmission opportunities including a priority period; and transmitting data received from a higher layer based on said schedule, wherein said schedule is set so that the priority periods in at least two or more links have an overlapping period, and said overlapping period is set so that an occurring priority packet has a length equal to or greater than a maximum packet length assumed by the wireless communication system.

8. A wireless communication program for performing wireless communication using multiple links and to be executed by a wireless communication device having a processor and a memory, the program being stored in the memory and computer-readable, and including a program for causing the processor to perform the following processes: setting a schedule of transmission opportunities including a priority period; and transmitting data received from a higher layer based on the schedule, wherein the schedule is set so that the priority periods in at least two or more links have an overlapping period, and the overlapping period is set so that the length of an occurring priority packet is equal to or longer than the maximum packet length assumed by the wireless communication system.

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