Hard real-time and anti-interference communication scheduling method based on orthogonal frequency division multiple access (OFDMA)

Abstract

The invention discloses a hard real-time and anti-interference communication scheduling method based on OFDMA (Orthogonal Frequency Division Multiple Access), which relates to the technical field of wireless communication, and comprises the following steps: downlink data transmission: a wireless access point fills the content of each RU (Resource Unit) in an OFDMA frame in a preset downlink time slot, the content of each RU is filled by data of different destination addresses in a transmission queue, and the downlink OFDMA frame is transmitted; and uplink data sending: the wireless field device synchronously triggers OFDMA parallel uplink data sending in the same pre-configured time slot, or the wireless access point sends an uplink OFDMA data start trigger frame, and triggers and dispatches a plurality of field devices to immediately and synchronously start OFDMA parallel uplink data sending. According to the method, the congestion condition caused by the fact that multiple users compete for limited bandwidth resources can be effectively relieved, the number of unnecessary data retransmission times can be reduced by more intelligently managing frequency resource use, and finally more efficient and reliable industrial-grade wireless communication service is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of wireless communications, and in particular to an OFDMA-based hard real-time and anti-interference communication scheduling method. Background Art

[0002] Key industrial sectors such as manufacturing, electricity, energy, and transportation usually use high-speed wireless communication technologies such as WIA-FA (Wireless Network for Industrial Automation–Factory Automation), WiFi (Wireless Fidelity), and 5G (5th Generation Mobile Communication Technology) for wireless data transmission. However, some scenarios require high real-time and high-reliability industrial application scenarios without reliable wireless communication technologies.

[0003] Wireless communication technologies with TDMA access mechanisms at the bottom layer (such as WIA-FA, etc.) can guarantee relatively certain communication delays. However, in large-scale networks, multiple field terminal wireless devices need to transmit uplink data at the same time, which will cause a large number of congestion waiting in line for TDMA transmission time slots, and the communication efficiency and wireless resource utilization rate will be lower than expected. In addition, although the TDMA mechanism can ensure that the wireless data transmission within this network is based on time division scheduling and will not cause data packet loss due to air collisions, there are a lot of random interferences at the same frequency in actual industrial application scenarios. It is necessary to ensure communication reliability by increasing the retransmission time slot, but this will increase the data polling transmission cycle and reduce the real-time performance of communication.

[0004] In the ISM frequency band, multiple wireless technologies coexist, and wireless communication systems are subject to frequent co-channel interference, which seriously reduces the reliability and real-time performance of the TDMA system. Taking the WiFi system as an example of an interference source, the time it takes for the WiFi system to send data aggregation frames is usually 1 to 100 ms, that is, the continuous co-existence interference time in the air is 1 to 100 ms. The data mode of industrial business applications is small data and high concurrency, and the TDMA scheduling time slot length is hundreds of microseconds (covering the time to complete a short data transmission). When encountering continuous co-channel interference from protocols such as WiFi, the TDMA protocol will always have interference at the same frequency from the beginning of the transmission to the end of several retransmissions, resulting in multiple retransmissions still failing, such as Figure 1 As shown, communication reliability cannot be guaranteed.

[0005] In view of the long polling cycle of TDMA mechanism wireless technology suitable for industrial application scenarios and the low efficiency of data retransmission in interference environment, the present invention proposes a hard real-time and interference-resistant communication scheduling method based on OFDMA to realize a high-reliability retransmission scheduling scheme under the TDMA mechanism. Summary of the invention

[0006] In view of this, the present invention provides a hard real-time, anti-interference communication scheduling method based on OFDMA, which can not only effectively alleviate the congestion caused by multiple users competing for limited bandwidth resources, but also reduce unnecessary data retransmission times by more intelligently managing the use of frequency resources, ultimately achieving more efficient and reliable industrial-grade wireless communication services.

[0007] To this end, the present invention provides the following technical solutions:

[0008] On the one hand, the present invention discloses a hard real-time, anti-interference communication scheduling method based on OFDMA, the method comprising:

[0009] Downlink data transmission: The wireless access point fills the content of each RU in the OFDMA frame in the predetermined downlink time slot. The content of each RU is filled with data of different destination addresses in the transmission queue, and the downlink OFDMA frame is sent;

[0010] Uplink data transmission: The wireless field devices synchronously trigger OFDMA parallel uplink data transmission in the same pre-configured time slot, or the wireless access point sends an uplink OFDMA data start trigger frame, triggering and scheduling multiple field devices to immediately and synchronously start OFDMA parallel uplink data transmission.

[0011] Furthermore, the downlink data transmission also includes:

[0012] The wireless field device replies with ACK after receiving the downlink OFDMA frame. When the wireless access point does not receive the corresponding ACK, it indicates that the data sent in the corresponding RU has failed, and the data is resent in other RUs in the retransmission time slot.

[0013] Furthermore, uplink data transmission also includes:

[0014] The wireless access point replies with an ACK frame, and the wireless field devices that do not receive the ACK change the RU frequency point and resend;

[0015] The wireless access point does not reply to the ACK frame, reassembles the RU sequence of the data of each wireless field device, and resends the uplink OFDMA frame after the reassembled RU, and the same applies to multiple retransmissions.

[0016] Furthermore, the working bandwidth of the wireless access point and the wireless field device is divided according to the data transmission requirement of each device, and each device sub-bandwidth after division includes a number of RUs.

[0017] Furthermore, the device sending data can send one piece of data simultaneously on two or more RUs.

[0018] Furthermore, when the transceiver device allocates RUs, the same frame of data can be transmitted on continuous RUs or discontinuous RUs.

[0019] Furthermore, the retransmission data RU allocation includes:

[0020] The retransmission data is allocated to the RU that was not attempted for data transmission.

[0021] The RUs for retransmitted data are allocated using frequency hopping, with the interval being farther from the RU used for the last transmission.

[0022] Furthermore, after multiple retransmissions, the sending device occupies multiple RUs or all RUs to transmit the same data.

[0023] On the other hand, the present invention also provides a real-time wireless communication system, which includes a real-time wireless communication system for industrial industries based on a TDMA transmission scheduling mechanism. In the wireless communication system, each device in the communication system implements strict time synchronization based on a timestamp, and data transmission is based on microsecond time slot scheduling. The devices in the wireless communication system use the above-mentioned OFDMA-based hard real-time, anti-interference communication scheduling method to communicate data.

[0024] Furthermore, the real-time wireless communication system includes a WIA-FA industrial wireless network system.

[0025] Advantages and positive effects of the present invention: The present invention designs a parallel transmission scheme for multi-device data using OFDMA technology under the TDMA access mechanism, saving TDMA communication time slot resources, shortening the TDMA superframe polling cycle, and greatly improving the real-time performance of communication; when subject to co-frequency interference, multiple retransmissions under the traditional TDMA access mechanism are all at one frequency point, and the retransmission interval is short, which is included in the duration of the co-frequency interference, resulting in a high probability of continuous retransmission failure. The present invention utilizes the characteristics of RU at different frequencies in OFDMA, and randomly switches data with different source addresses / destination addresses to different RUs for transmission through a random algorithm during retransmission, greatly increasing the retransmission success rate and realizing the anti-interference function. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1 A schematic diagram of a typical scenario in which a TDMA mechanism wireless network is subject to co-channel interference in the prior art;

[0028] Figure 2 This is a flowchart of downlink OFDMA data anti-interference retransmission scheduling in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of RU division in an embodiment of the present invention;

[0030] Figure 4 This is a flow chart of a retransmission scheduling method for occupying multiple RUs in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] OFDMA (Orthogonal Frequency Division Multiple Access) technology allows multiple users to communicate using different subcarrier sets at the same time, thereby improving spectrum utilization and system capacity. OFDMA technology is suitable for synchronous transmission of small data under multiple devices, greatly increasing communication transmission efficiency, and is suitable for small data and high real-time transmission scenarios such as industrial collection and control.

[0034] In an embodiment of the present invention, a hard real-time, anti-interference communication scheduling method based on OFDMA is provided. The method is oriented to industrial control and acquisition scenarios, and the data types transmitted are small data, high concurrency, and frequent transmission. The method is applied to WIA-FA industrial wireless network systems and other real-time wireless communication systems that can be used in manufacturing, electricity, energy, transportation and other industrial industries. The wireless communication system is based on the TDMA transmission scheduling mechanism. Each device in the communication system implements strict time synchronization based on timestamps, and data transmission is based on microsecond time slot scheduling. The method includes:

[0035] Downlink data transmission: The wireless access point fills the content of each RU in the OFDMA frame in the predetermined downlink time slot. The content of each RU is filled with data from different destination addresses in the transmission queue, and then the downlink OFDMA frame is forced to be sent. Figure 2 As shown, the wireless field device replies with ACK after receiving the downlink OFDMA frame. When the wireless access point does not receive the corresponding ACK, it indicates that the data sent in the corresponding RU has failed. The data is resent in other RUs (switching frequency points) based on a random algorithm in the retransmission time slot, and so on.

[0036] Uplink data transmission: The wireless field devices (STA) in the network should strictly perform synchronous triggering of OFDMA parallel uplink data transmission within the same pre-configured time slot, or send an uplink OFDMA data start trigger frame through a wireless access point (AP) to trigger and schedule multiple field devices to immediately and synchronously start OFDMA parallel uplink data transmission.

[0037] There are two schemes for data packet loss retransmission scheduling: with ACK frame and without ACK frame:

[0038] ① The wireless access point replies with an ACK frame, and the wireless field devices that have not received the ACK change the RU frequency based on the pre-configured random rules and resend; Figure 4 As shown, the RUs for the first transmission, the first retransmission and the second retransmission can be randomly selected from multiple RUs. For example, RU1 is used to transmit STA1 data Frame1. If Ack is not received, RU3 is randomly selected for the first retransmission. If Ack is not received, RU7 is randomly selected for the second retransmission.

[0039] Specifically, you can change the RU frequency according to the following principles:

[0040] (1) Retransmission data is allocated to the RU that was not attempted for data transmission.

[0041] (2) The RUs for retransmitted data are allocated using frequency hopping, with the interval being as far away from the RU used for the last transmission.

[0042] For example, if the 20MHz bandwidth is divided into five RU resources, namely: RU1, RU2, RU3, RU4, and RU5; the data of device 1 is sent in RU1 and fails;

[0043] Device 1 retransmits data for the first time, and selects RU5 to send it; and fails;

[0044] Device 1 retransmits data for the second time, choosing to send it on RU3; and fails;

[0045] Device 1 retransmits data for the third time, choosing to send it on RU2; and it succeeds.

[0046] ② The wireless access point does not reply to the ACK frame, but reassembles the RU order of the data of each field device based on the pre-configured random rules (switching the frequency), and resends the uplink OFDMA frame after the reassembled RU to avoid the influence of co-channel interference. The same applies to multiple retransmissions.

[0047] Therefore, under the TDMA mechanism, a large amount of cyclic time slot communication resources reserved for uplink data transmission of each field device can be saved.

[0048] The wireless device described in this method can operate in bandwidths of 20MHz, 40MHz, 80MHz, 160MHz, 320MHz and above. Figure 3 As shown, an example using 160MHz bandwidth is as follows:

[0049] The 160MHz bandwidth is evenly divided into 20MHz sections. Each 20MHz bandwidth contains 2 RUs. A wireless device can be configured to use one RU or multiple RUs for data transmission.

[0050] The sending and receiving devices transmit data on pre-specified RUs. To improve the reliability of data transmission and anti-interference capability, the data sender can send a piece of data simultaneously on two or more RUs.

[0051] When the transceiver device allocates RUs, the same frame of data may be transmitted on consecutive RUs or discontinuous RUs (which may be referred to as a puncturing method).

[0052] The RU allocation of retransmitted data can be implemented according to a certain algorithm to ensure reliable data transmission as much as possible.

[0053] After multiple retransmissions, a device can occupy multiple RUs or all RUs to transmit the same data.

[0054] In the above embodiment, a scheme for parallel transmission of multi-device data using OFDMA technology under the TDMA access mechanism is designed, which saves TDMA communication time slot resources, shortens the TDMA superframe polling cycle, and greatly improves the real-time performance of communication; when subject to co-frequency interference, multiple retransmissions under the traditional TDMA access mechanism are all at one frequency point, and the retransmission interval is short, which is included in the duration of the co-frequency interference, resulting in a high probability of continuous failure of continuous retransmissions. This method utilizes the characteristics of RUs at different frequencies in OFDMA, and randomly switches data with different source addresses / destination addresses to different RUs for transmission through a random algorithm during retransmission, which greatly increases the retransmission success rate and realizes the anti-interference function.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hard real-time, anti-interference communication scheduling method based on OFDMA, characterized in that: The method comprises: Downlink data transmission: The wireless access point fills the content of each RU in the OFDMA frame in the predetermined downlink time slot. The content of each RU is filled with data of different destination addresses in the transmission queue, and the downlink OFDMA frame is sent; Uplink data transmission: The wireless field devices synchronously trigger OFDMA parallel uplink data transmission in the same pre-configured time slot, or the wireless access point sends an uplink OFDMA data start trigger frame, triggering and scheduling multiple field devices to immediately and synchronously start OFDMA parallel uplink data transmission.

2. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: Downlink data transmission also includes: The wireless field device replies with ACK after receiving the downlink OFDMA frame. When the wireless access point does not receive the corresponding ACK, it indicates that the data sent in the corresponding RU has failed, and the data is resent in other RUs in the retransmission time slot.

3. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: Uplink data transmission also includes: The wireless access point replies with an ACK frame, and the wireless field devices that do not receive the ACK change the RU frequency point and resend; The wireless access point does not reply to the ACK frame, reassembles the RU sequence of the data of each wireless field device, and resends the uplink OFDMA frame after the reassembled RU, and the same applies to multiple retransmissions.

4. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: The working bandwidth of the wireless access point and the wireless field device is divided according to the data transmission requirement of each device, and each divided device sub-bandwidth includes a number of RUs.

5. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: The device that sends data can send one piece of data simultaneously on two or more RUs.

6. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: When the transceiver device allocates RUs, the same frame of data can be transmitted on consecutive RUs or discontinuous RUs.

7. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: Retransmission data RU allocation includes: The retransmission data is allocated to the RU that was not attempted for data transmission. The RUs for retransmitted data are allocated using frequency hopping, with the interval being farther from the RU used for the last transmission.

8. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that: After multiple retransmissions, the sending device occupies multiple RUs or all RUs to transmit the same data.

9. A real-time wireless communication system, characterized in that: The system includes a real-time wireless communication system for industrial industries based on a TDMA transmission scheduling mechanism. In the wireless communication system, each device in the communication system implements strict time synchronization based on a timestamp, and data transmission is based on microsecond-level time slot scheduling. The devices in the wireless communication system perform data communication using a hard real-time, anti-interference communication scheduling method based on OFDMA as described in any one of claims 1 to 8.

10. A real-time wireless communication system according to claim 8, characterized in that: The real-time wireless communication system includes a WIA-FA industrial wireless network system.

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