JP7768386B2 - Wireless communication system, wireless communication method, and wireless communication device - Google Patents

Description

The present disclosure relates to a wireless communication system, a wireless communication method, and a wireless communication device.

Wireless LAN base stations and terminals use CSMA/CA to access channels and transmit data.

The wireless LAN communication standard IEEE 802.11be is equipped with a multi-link function that allows multiple frequency bands to be used simultaneously. Using the multi-link function, multiple links using multiple frequency bands can be formed simultaneously between a base station and a terminal. This allows different data to be transmitted simultaneously over multiple frequency bands, improving throughput and delay characteristics.

When transmitting data, packets generated in the upper layer are first passed to the Upper MAC (Media Access Controller). The Upper MAC then passes the packet to the Lower MAC, which exists for each link. When the Lower MAC acquires the right to transmit a frame, the packet that has arrived at the front of the queue in the order it holds is passed to the PHY (Physical) layer, which is the physical layer, and then transmitted.

IEEE802.11 2020 IEEE Standard for Information Technology-Telecommunications and Information Exchange between SystemsLocal and Metropolitan Area Networks-Specific Requirements IEEE802.11be D2.0 Draft Standard for Information technology－ Telecommunications and information exchange between systems Local and metropolitan area networks－ Specific requirements

However, when performing high-volume communications, the Lower MAC of all links used by the multi-link function may already have multiple packets being transmitted. In this case, suppose a high-priority packet is generated, which is a transmission packet for an application that requires low latency. This high-priority packet cannot be immediately handed over to the PHY for transmission, regardless of which link is used. In other words, there is a problem of queuing delays.

The primary objective of this disclosure is to provide a wireless communication system that can reduce queuing delays for high-priority packets in order to solve the above-mentioned problems.

A second object of this disclosure is to provide a wireless communication method that can reduce queuing delays for high-priority packets.

A third object of this disclosure is to provide a wireless communication device that can reduce queuing delays for high-priority packets.

A first aspect of the present disclosure is a wireless communication system comprising a base station having a multi-link function and a terminal having a multi-link function, configured so that the base station and the terminal communicate via multiple links, wherein the base station comprises an Upper MAC that receives packets generated in a higher layer and a Lower MAC that exists for each link, and is preferably configured to perform a dummy packet transmission process that causes the Upper MAC to transmit a dummy packet to the Lower MAC, a process that replaces a high-priority packet with a dummy packet, and a process that causes the Lower MAC to transmit a packet to the terminal via the link.

A second aspect of the present disclosure is a wireless communication method performed by a wireless communication system including a base station having a multi-link function and a terminal having a multi-link function, and configured for the base station and terminal to communicate via multiple links, wherein the base station includes an Upper MAC that receives packets generated in a higher layer and a Lower MAC that exists for each link, and the wireless communication method preferably includes the steps of: transmitting dummy packets from the Upper MAC to the Lower MAC; replacing high-priority packets with dummy packets; and transmitting packets held by the Lower MAC to the terminal via the links.

A third aspect of the present disclosure is preferably a wireless communication device comprising an Upper MAC that receives packets generated in a higher layer and a Lower MAC that exists for each link, and having the following functions: a function for transmitting dummy packets from the Upper MAC to the Lower MAC; a function for replacing high-priority packets with dummy packets; and a function for transmitting packets held by the Lower MAC via the link.

The first, second and third aspects of the present disclosure enable the queuing delay of high priority packets to be reduced.

FIG. 10 is a diagram illustrating an example of the configuration of a wireless communication system without a multi-link function. FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system having a multi-link function. 10 is a flowchart showing a multi-link setup procedure. FIG. 10 is a diagram illustrating a packet categorization process. 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. 1 is a flowchart illustrating a packet processing method according to a first embodiment of the present disclosure. 1 is a flowchart illustrating a method for managing dummy packets according to the first embodiment of the present disclosure. FIG. 2 is a block diagram showing the device configuration of a base station according to the first embodiment of the present disclosure. 1 is a block diagram showing the device configuration of a terminal according to a first embodiment of the present disclosure. 10 is a table illustrating an example of data held by a dummy packet management unit according to the first embodiment of the present disclosure. FIG. 10 is a diagram illustrating a configuration example of a wireless communication system according to a second embodiment of the present disclosure. FIG. 10 is a diagram illustrating a configuration example of a wireless communication system according to a third embodiment of the present disclosure.

First Embodiment
[Conventional wireless communication system]
Prior to describing the first embodiment, a conventional multi-link will be described. Fig. 1 shows an example of the configuration of a wireless communication system without a multi-link function. That is, a wireless communication system 500 transmits multiple types of packets using a single link.

The wireless communication system 500 includes a base station 2. The base station 2 transmits high-priority packets 4 generated in an upper layer to a MAC unit 12. The MAC unit 12 includes a queue 8. The queue 8 orders and stores received packets so that they can be transmitted in the order they were received. When a frame transmission right is acquired, the order of the packets stored in the queue 8 is checked and the packets are transmitted in order, starting with the packet at the front of the queue. Note that when the wireless communication system used is Wi-Fi (registered trademark), the base station corresponds to an access point.

Base station 2 does not have a multi-link function and therefore has only one queue 8. Therefore, even if a high-priority packet 4 is generated, if queue 8 already contains multiple packets 6, the high-priority packet 4 is ordered so that it becomes the last packet in the queue 8.

The MAC unit 12 transmits the packets to the PHY 10. More specifically, the packet that arrives at the front of the queue 8 is transmitted to the PHY 10. In other words, the high-priority packet 4 transmitted to the PHY 10 is transmitted to the terminal 16 after all packets 6 held in the queue 8 up to that point have been transmitted. Note that the base station 2 does not have a multi-link function and therefore only has one PHY 10.

As mentioned above, in a wireless communication system 500 that uses only one link, even if a high priority packet 4 occurs, no processing is performed to prioritize it.

Figure 2 shows an example configuration of a wireless communication system with a multi-link function. Here, we describe a wireless communication system 600 that forms three links by utilizing the multi-link function.

The wireless communication system 600 includes a base station 2. The base station 2 transmits a high-priority packet 4 generated in a higher layer to a MAC unit 12. The MAC unit 12 includes an Upper MAC 18 and Lower MACs 20a, 20b, and 20c, each of which exists for a different link.

The MAC unit 12 first receives the high-priority packet 4 at the Upper MAC 18. The Upper MAC 18 then assigns the high-priority packet 4 to one of the Lower MACs 20a, 20b, and 20c. More specifically, the high-priority packet 4 is ordered so that it becomes the last packet held in the queue of the assigned Lower MAC. This assignment is performed based on a predetermined process. Here, the process is assumed to assign the high-priority packet 4 to the queue with the shortest waiting time among the queues 8a, 8b, and 8c of the Lower MACs 20a, 20b, and 20c, respectively. Note that the waiting time in this case varies depending on the number or size of packets 6 in each queue.

The MAC unit 12 transmits the packets to the PHY unit 14. This PHY unit 14 includes PHYs 10a, 10b, and 10c. More specifically, the packets that arrive at the front of the queues 8a, 8b, and 8c are transmitted to PHYs 10a, 10b, and 10c, respectively. In other words, the high-priority packet 4 is transmitted to the terminal 16 after all packets 6 held in the assigned queue have been transmitted.

As mentioned above, high priority packets 4 are assigned to the queue with the shortest waiting time. Therefore, compared to a wireless communication system 500 that uses only one link, there is a higher chance that transmission to the PHY will occur with a shorter waiting time.

In this way, using the multi-link function to simultaneously transmit different data over multiple frequency bands can improve throughput and delay characteristics. However, there are cases where the Lower MACs of all links used with the multi-link function already have multiple packets being transmitted. In this case, the generated high-priority packet cannot be immediately passed to the PHY for transmission, regardless of which link is used. In other words, a problem arises in which queuing delays occur. The present disclosure solves this problem.

Figure 3 is a flowchart showing the multi-link setup procedure. The dummy packet management units 64 and 74, described below, perform the processing shown in Figure 3 to set up wireless communication via specific links. This allows the wireless communication system to establish multi-link communication.

Figure 4 shows the packet categorization process. The wireless communication system transmits multiple types of packets. This shows the process of identifying these multiple types of packets by traffic in the STA unit, which will be described later.

Packets with a MAC header added at a higher layer are input to one of queues 22, 24, 26, and 28. The destination queue is determined by the TID (Traffic Indicator) included in the MAC header. For example, when WME (Wireless Multimedia Extensions) assigns priorities, queue 22 can be identified as the VO category for voice, queue 24 as the VI category for video, queue 26 as the BE category for best effort, and queue 28 as the BK category for background.

Packets input to each queue are input to CSMA/CA units 32, 34, 36, 38, and 40. Each CSMA/CA unit accesses the channel using unique access parameters and performs CSMA/CA. Examples of unique access parameters include Cwmax, Cwmin, AIFS, and TXOPlimit. When each CSMA/CA unit obtains the right to transmit, it obtains a MAC frame from each queue and outputs it to the internal collision resolution unit 42.

Note that CSMA/CA units 32, 34, 36, and 38 process data that arrives at the front of queues 22, 24, 26, and 28. CSMA/CA unit 40 processes low-latency data.

When multiple CSMA/CA units simultaneously acquire the transmission right, the internal conflict resolution unit 42 selects and outputs the one with the highest priority.

[Wireless communication system of the present disclosure]
5 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. The wireless communication system according to the first embodiment differs from conventional systems in that a dummy packet is periodically transmitted to one of the links used by the multi-link function. Here, a wireless communication system 100 that forms three links by utilizing the multi-link function will be described.

Wireless communication system 100 transmits packets in the same procedure as wireless communication system 600. However, in addition to packets generated in higher layers, wireless communication system 100 periodically transmits dummy packets 44. Dummy packets 44 form a queue, just like packets 6 and high-priority packets 4. When they reach the top of the queue, they begin counting down the CW (Contention Window) value.

If a high priority packet 4 occurs while the CW value is counting down, the high priority packet 4 is replaced with a dummy packet 44. This process can be performed immediately after the high priority packet 4 occurs, or when the CW value reaches a specific value.

If no high-priority packets are generated during the CW value countdown, the transmission process of the dummy packet 44 is treated as completed. First, when the CW value reaches 0 or a specific value, the transmission process of the dummy packet 44 is canceled.

After canceling the transmission process for dummy packet 44, the packet following dummy packet 44 is moved to the head of the queue. Then, the CW value of that packet is not counted down, and the process moves directly to frame transmission processing. In other words, the packet that is now at the head of the queue where dummy packet 44 was located performs frame transmission processing in place of dummy packet 44.

After canceling the transmission process of dummy packet 44, the packet that was performing the CW value countdown at the head of a different link may be moved to the link where dummy packet 44 was present, and the frame transmission process may be performed.

Alternatively, the process may simply be to cancel the transmission of dummy packet 44. That is, after canceling the transmission of dummy packet 44, the packet following dummy packet 44 is moved to the head of the queue as usual. Then, the countdown of the CW value of that packet may begin, and the frame transmission process may continue as usual.

Packet Processing Method of the Present Disclosure
6 is a flowchart showing a packet processing method according to the first embodiment of the present disclosure. First, in step 100, the Upper MAC 18 receives a packet from an upper layer.

Next, in step 102, it is confirmed whether the received packet has a high priority. The priority determination is performed by the MLD unit 59 of the base station, which will be described later. This determination may be made using the TID. For example, a method can be considered in which packets assigned a pre-specified TID, or a TID indicating a higher priority than that TID, are determined to be "high priority packets." If the priority is high, proceed to step 104. If the priority is not high, proceed to step 108.

In step 104, all links used in the wireless communication system are checked to see if dummy packets exist. In the case of wireless communication system 100, all links including Lower MAC 20a, 20b, and 20c are checked to see if dummy packets exist. If dummy packets exist, proceed to step 106. If dummy packets do not exist, proceed to step 108.

In step 106, the dummy packet and the high priority packet are swapped. For example, a process is performed in which the tag indicating the order of packets held in the queue of the Lower MAC 20a is swapped between the dummy packet 44 and the high priority packet 4. Alternatively, a process is performed in which the bit information of the high priority packet 4 is transcribed onto the bit information of the dummy packet 44. This process may be performed immediately after the high priority packet 4 is generated, or when the CW value reaches a specific value.

In step 108, normal queuing is performed, i.e., packets held by each Lower MAC are transmitted in order, regardless of their type.

As described above, in embodiment 1, dummy packets are periodically sent to one of the links used by the multi-link function. If a high-priority packet is generated later, the high-priority packet is replaced with a dummy packet. This allows the queuing delay of a high-priority packet to be reduced, regardless of when it is generated.

The size of the dummy packet may be specified as a predetermined size in advance. For example, the maximum configurable size may be specified. Alternatively, the size may be determined by referring to the size of the high-priority packet received by the Upper MAC immediately before. If the sizes of the dummy packet and the high-priority packet do not match, padding or other processing may be performed during replacement or aggregation processing.

[Dummy Packet Management Method of the Present Disclosure]
An example of a method for managing dummy packets is shown in FIG. 7. FIG. 7 is a flowchart showing the method for managing dummy packets according to the first embodiment of the present disclosure. Here, an example is shown in which a base station 2 that forms links using a multi-link function transmits dummy packets 44 to three links in order. Note that the three links including Lower MACs 20a, 20b, and 20c are assumed to have been assigned numbers 1, 2, and 3 in advance.

First, in step 110, the Upper MAC 18 generates a dummy packet 44 and transmits it to link 1. When the dummy packet 44 reaches the front of the queue for link 1, the CW value starts to count down. After a certain period of time has elapsed, the CW value for link 1 becomes 0, as in step 112.

Next, in step 114, the Upper MAC 18 generates a dummy packet 44 and transmits it to link 2. When the dummy packet 44 reaches the front of the queue for link 2, the CW value starts to count down. After a certain period of time has elapsed, the CW value for link 2 becomes 0, as in step 116.

Next, in step 118, Upper MAC 18 generates a dummy packet 44 and transmits it to link 3. When the dummy packet 44 reaches the front of the queue for link 3, the CW value starts to count down. After a certain period of time has passed, the CW value for link 3 becomes 0, as in step 120. After this, the process returns to step 110 and repeats the same process.

In addition, the timing for generating the dummy packet 44 shown in steps 112, 116 and 120 may be when the CW value becomes a specific value other than 0.

The link through which the dummy packet 44 is sent may also be selected based on pre-measured statistics. More specifically, a selection method may be considered based on the PER (Packet Error Rate) value or average CW value calculated from pre-measured statistics. For example, by sending the dummy packet 44 to the link with the lowest PER value, the high-priority packet 4 is more likely to be sent to the link with the lowest PER value. In other words, the queuing delay of the high-priority packet 4 is more likely to be shortened.

By following the above procedure, the queue size occupied by dummy packets can be distributed by appropriately changing the link that sends the dummy packets. Furthermore, since the latency of each link changes over time, determining the destination based on this information improves the probability that high-priority packets will be assigned to links with shorter latency.

[Configuration of devices included in the wireless communication system of the present disclosure]
8 is a block diagram showing the device configuration of a base station according to the first embodiment of the present disclosure. First, data transmission from the base station 2 to other terminals will be described.

Base station 2 is equipped with an LLC unit 58. The LLC unit 58 is a sublayer that performs logical link control. The LLC unit 58 outputs input packets to the MLD unit 59.

The MLD unit 59 is a link management unit and includes a data processing unit 60. The data processing unit 60 processes data and outputs the results to the base station measurement unit 62 and the dummy packet management unit 64. The base station measurement unit 62 records the link number through which the dummy packet was sent and measures the PER of each link, etc.

The dummy packet management unit 64 selects the link to transmit the dummy packet. This link selection is made based on the information about each link obtained by the base station measurement unit 62. The dummy packet management unit 64 then transmits the dummy packet to the STA unit corresponding to the selected link.

The dummy packet management unit 64 also switches between high priority packets and dummy packets. Furthermore, the dummy packet management unit 64 performs the multi-link setup described in Figure 3.

STA units 66a, 66b, and 66c are transmitter/receivers that receive packets input from the dummy packet management unit 64. They then transmit the MAC frames contained in the packets as wireless frames to other terminals. Data transmission and reception with other terminals is performed via antennas.

Next, we will explain data transmission from other terminals to base station 2. STA units 66a, 66b, and 66c output wireless frames received from other terminals to dummy packet management unit 64.

The dummy packet management unit 64 processes the header and other data from the MAC frame contained in the input wireless frame, and outputs the resulting data to the data processing unit 60. The data processing unit 60 outputs this data to the LLC unit 58.

Figure 9 is a block diagram showing the device configuration of a terminal according to embodiment 1 of the present disclosure. First, data transmission from terminal 16 to other terminals will be described.

The terminal 16 is equipped with an LLC unit 68. The LLC unit 68 outputs the input packets to the MLD unit 69.

The MLD unit 69 includes a data processing unit 70. The data processing unit 70 processes packets and outputs the results to the terminal measurement unit 72 and the dummy packet management unit 74. The terminal measurement unit 72 measures the PER, etc. of each link as necessary. These measurement results are notified to the base station measurement unit 62 possessed by the base station within the wireless communication system. The terminal measurement unit 72 may have the same functions as the base station measurement unit 62. The dummy packet management unit 74 has the same functions as the dummy packet management unit 64.

The STA units 76a, 76b, and 76c receive packets input from the dummy packet management unit 74. They then transmit the MAC frames contained in the packets as wireless frames to other terminals. Data transmission and reception with other terminals is performed via antennas.

Next, we will explain data transmission from other terminals to terminal 16. STA units 76a, 76b, and 76c output wireless frames received from other terminals to the dummy packet management unit 74.

The dummy packet management unit 74 processes the header and other data from the MAC frame contained in the input wireless frame, and outputs the resulting data to the data processing unit 70. The data processing unit 70 outputs this data to the LLC unit 68.

Note that terminal 16 may be configured without a dummy packet management unit 74. In this case, terminal 16 does not generate dummy packets. Terminal 16 notifies the base station only of information such as PER measured on the terminal side.

Figure 10 is a table showing example data held by a dummy packet management unit according to embodiment 1 of the present disclosure. The dummy packet management unit holds various data for each link in order to manage dummy packets. As an example, a data set for a base station equipped with three STA units is shown here.

In this example, STA1, 2, and 3 all support the multilink function. However, only STA1 and 2 are used for multilink transmission. And only STA1 is used as the destination for dummy packets. STA1 currently has a dummy packet, and its CW value is 6. Packets are distributed based on this data.

The PER value is also stored here. It can be seen that the PER values indicated by the three STAs are different. It is also possible to set the destination link for dummy packets based on this PER value.

Embodiment 2
11 is a diagram illustrating a configuration example of a wireless communication system according to a second embodiment of the present disclosure. The wireless communication system according to the second embodiment differs from the first embodiment in that a plurality of terminals are targets of wireless communication with one base station.

The wireless communication system 200 includes a base station 2. The base station 2 communicates wirelessly with terminals 16a, 16b, and 16c. This configuration enables queuing delays to be reduced when high-priority packets are generated, even in wireless communication covering a wide area, such as when multiple terminals are involved.

The link for transmitting dummy packets and the transmission rate of dummy packets may be determined by referring to the PER of all terminals 16, or to the PER of a specific terminal 16. An example of a method for selecting a specific terminal 16 to focus on is to select the terminal with the highest high-priority frame transmission rate.

In addition, the selection of the link for transmitting dummy packets may be set independently by the base station 2 and the terminal 16. Alternatively, the selection may be set to synchronize or not synchronize between the base station 2 and a specific terminal 16.

Note that it is not necessary to send dummy packets to all links used by the multi-link function. For example, if there is a link where many legacy base stations exist, it is possible to prevent dummy packets from being sent to that link.

Embodiment 3
12 is a diagram illustrating a configuration example of a wireless communication system according to a third embodiment of the present disclosure. The wireless communication system according to the third embodiment differs from the first embodiment in that a controller that aggregates a plurality of base stations is installed.

The wireless communication system 300 includes a controller 46. The controller 46 is connected to base stations 2a and 2b. Base station 2a performs wireless communication with terminal 16a. Base station 2b performs wireless communication with terminal 16b. This configuration enables queuing delays to be reduced when high-priority packets are generated, even in wireless communication covering a wide area, such as when multiple base stations are involved.

The method for selecting the link through which the dummy packets are sent may be specified independently within each base station and terminal. Alternatively, the controller 46 may specify the link through which the dummy packets are sent for the connected base stations 2a and 2b.

In the above case, the controller 46 may specify the link for transmitting dummy packets based on the degree of congestion or PER of the channel used by the terminal 16. For example, the link may be specified so that there is no imbalance in the ratio of dummy packets between channels.

2, 2a, 2b Base station 4 High priority packet 6 Packet 16, 16a, 16b Terminal 44 Dummy packet 46 Controller 100, 200, 300, 500, 600 Wireless communication system

Claims (8)

A wireless communication system comprising a base station having a multi-link function and a terminal having a multi-link function, the base station and the terminal being configured to communicate with each other via a plurality of links,
The base station
an Upper MAC that receives packets generated in an upper layer;
a Lower MAC present for each of the links;
a dummy packet transmission process for transmitting a dummy packet from the upper MAC to the lower MAC;
a process of replacing the dummy packet with a high-priority packet having a high priority;
and a process of causing the terminal to transmit the packet held by the Lower MAC via the link. The dummy packet transmission process
The wireless communication system according to claim 1 , further configured to execute a process of determining the size of the dummy packet by referring to the size of the high-priority packet received immediately before by the Upper MAC. The dummy packet transmission process
a process of transmitting the dummy packets to different links at regular intervals;
and transmitting the dummy packet to a link selected based on pre-measured statistics. the terminal includes a plurality of terminals;
The wireless communication system according to claim 1 , wherein the base station performs wireless communication with the plurality of terminals. the base station includes a plurality of base stations;
a controller for controlling the plurality of base stations;
The wireless communication system according to claim 1 , wherein the controller specifies a destination of the dummy packet. The terminal
an Upper MAC that receives packets generated in an upper layer;
a Lower MAC present for each of the links;
A process of transmitting a dummy packet from the Upper MAC to the Lower MAC;
a process of replacing the dummy packet with a high-priority packet having a high priority;
The wireless communication system according to claim 1 , further configured to execute a process of causing the terminal to transmit the packet held by the Lower MAC via the link. A wireless communication method performed by a wireless communication system comprising a base station having a multi-link function and a terminal having a multi-link function, the base station and the terminal being configured to communicate via a plurality of links,
The base station:
an Upper MAC that receives packets generated in an upper layer;
a Lower MAC present for each of the links;
transmitting a dummy packet from the Upper MAC to the Lower MAC;
replacing the dummy packet with a high-priority packet;
causing the terminal to transmit the packet held by the Lower MAC via the link. an Upper MAC that receives packets generated in an upper layer;
A Lower MAC exists for each link;
a function of transmitting a dummy packet from the Upper MAC to the Lower MAC;
a function of replacing the dummy packet with a high-priority packet having a high priority;
a function of transmitting packets held by the Lower MAC via the link.