Ofdma-based hard real-time and Anti-interference communication scheduling method

Abstract

The present invention relates to the technical field of wireless communications. Disclosed is an OFDMA-based hard real-time and anti-interference communication scheduling method, comprising: downlink data sending: a wireless access point fills a predetermined downlink time slot with the content of each RU in an OFDMA frame, the content of each RU being filled with data of different destination addresses in a send queue, and the wireless access point sends a downlink OFDMA frame; and uplink data sending: wireless field devices synchronously trigger OFDMA parallel uplink data sending in a pre-configured same time slot, or the wireless access point sends an uplink OFDMA data start trigger frame, to trigger scheduling of multiple field devices to immediately and synchronously start the OFDMA parallel uplink data sending. The present invention can not only effectively alleviate congestion caused by multiple users competing for limited bandwidth resources, but also reduce the number of unnecessary data retransmissions by more intelligently managing the use of frequency resources, finally achieving more efficient and reliable industrial-grade wireless communication services.

Description

A Hard Real-Time, Interference-Resistant Communication Scheduling Method Based on OFDMA Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a hard real-time, interference-resistant communication scheduling method based on OFDMA. Background Technology

[0002] Key industrial sectors such as manufacturing, power, energy, and transportation typically 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, there are still no reliable wireless communication technologies for some industrial applications that require high real-time performance and high reliability.

[0003] Wireless communication technologies with TDMA access mechanisms at the underlying level (such as WIA-FA) can guarantee relatively deterministic communication latency. However, in large-scale networks, multiple field terminal wireless devices needing to transmit uplink data simultaneously can cause congestion due to queuing for TDMA transmission time slots, resulting in lower-than-expected communication efficiency and wireless resource utilization. In addition, although the TDMA mechanism can ensure that wireless data transmission within the network is based on time-division scheduling and will not cause data packet loss due to air collisions, there is a large amount of random interference on the same frequency in actual industrial applications. It is necessary to increase retransmission time slots to ensure communication reliability, but this increases the data polling transmission cycle and reduces communication real-time performance.

[0004] In the ISM band, multiple wireless technologies coexist, and wireless communication systems are frequently subjected to co-channel interference, severely reducing the reliability and real-time performance of TDMA systems. Taking WiFi systems as an example of interference sources, the time it typically takes for WiFi systems to send data aggregation frames is 1–100 ms, meaning the duration of continuous co-channel interference in the air is 1–100 ms. However, industrial business applications typically involve small amounts of data and high concurrency, with TDMA scheduling time slots on the order of hundreds of microseconds (covering the time required to complete a short data transmission). When encountering continuous co-channel interference from protocols like WiFi, the interference will persist on the same frequency point from the initial transmission until after several retransmissions, causing multiple retransmissions to fail, as shown in Figure 1, thus compromising communication reliability.

[0005] To address the issues of long polling cycles and low data retransmission efficiency in interference environments caused by the TDMA mechanism, which is suitable for industrial applications, this invention proposes a hard real-time, interference-resistant communication scheduling method based on OFDMA to achieve a highly reliable 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 the number of unnecessary data retransmissions by more intelligently managing the use of frequency resources, and ultimately achieve a more efficient and reliable industrial-grade wireless communication service.

[0007] Therefore, the present invention provides the following technical solution:

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

[0009] Downlink data transmission: The radio access point fills the contents of each resource unit (RU) in the OFDMA frame in the predetermined downlink time slot. The contents of each RU are filled with data from different destination addresses in the transmission queue, and the downlink OFDMA frame is transmitted.

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

[0011] Furthermore, downlink data transmission also includes:

[0012] After receiving a downlink OFDMA frame, the wireless field device replies with an ACK. If the wireless access point does not receive the corresponding ACK, it indicates that the data sent in the corresponding RU failed, and the data will be retransmitted to other RUs in the retransmission time slot.

[0013] Furthermore, uplink data transmission also includes:

[0014] The wireless access point replies with an ACK frame. If the wireless field device does not receive an ACK, it will change the RU frequency point and retransmit.

[0015] If the wireless access point does not reply with an ACK frame, it will reassemble the RU order of the data of each wireless field device and resend the uplink OFDMA frame after reassembling the RU. This process will continue for multiple retransmissions.

[0016] Furthermore, the bandwidth of the wireless access point and the wireless field device is divided according to the data transmission requirements of each device, and each sub-bandwidth of the divided device contains several RUs.

[0017] Furthermore, the data transmitting device is capable of transmitting a single data set simultaneously on two or more RUs.

[0018] Furthermore, when allocating RUs, the transceiver can transmit the same frame of data on either consecutive or discontinuous RUs.

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

[0020] Retransmitted data is assigned to unattended RUs for data transmission.

[0021] The retransmission data allocation RU adopts frequency hopping, and the interval is far away from the RU used in 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, the system comprising a real-time wireless communication system for industrial applications based on a TDMA transmission scheduling mechanism, wherein each device in the wireless communication system achieves strict time synchronization based on a timestamp, and data transmission is based on microsecond-level time slot scheduling, and the devices in the wireless communication system utilize the aforementioned hard real-time, anti-interference communication scheduling method based on OFDMA for data communication.

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

[0025] Advantages and positive effects of this invention: This invention designs a parallel data transmission scheme for multiple devices using OFDMA technology under the TDMA access mechanism, saving TDMA communication time slot resources, shortening the TDMA superframe polling cycle, and significantly improving communication real-time performance. When subjected to co-channel interference, in the traditional TDMA access mechanism, multiple retransmissions occur on the same frequency point, and the retransmission interval is short, falling within the duration of the co-channel interference, leading to a high probability of consecutive retransmission failures. This invention utilizes the characteristic of RUs (Retrievers) in OFDMA operating at different frequencies, randomly switching data from different source / destination addresses to different RUs for transmission during retransmission using a random algorithm, greatly increasing the retransmission success rate and achieving anti-interference functionality. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. It is easy to understand that the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

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

[0030] Figure 4 is a flowchart of the retransmission scheduling method for multiple RUs in an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[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 across multiple devices, greatly increasing communication transmission efficiency, and is suitable for small data and high real-time transmission scenarios such as industrial data acquisition and control.

[0034] This invention provides a hard real-time, interference-resistant communication scheduling method based on OFDMA. This method is designed for industrial control and data acquisition scenarios, where the transmitted data types are small, high-concurrency, and frequent. This method is applicable to WIA-FA industrial wireless network systems and other real-time wireless communication systems used in manufacturing, power, energy, transportation, and other industrial sectors. This wireless communication system is based on a TDMA transmission scheduling mechanism, where each device in the communication system achieves strict time synchronization based on timestamps, and data transmission is based on microsecond-level time slot scheduling. The method includes:

[0035] Downlink data transmission: The wireless access point fills the content of each resource unit (RU) in the OFDMA frame in a 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 forcibly transmitted. As shown in Figure 2, after receiving the downlink OFDMA frame, the wireless field device replies with an ACK. If the wireless access point does not receive the corresponding ACK, it indicates that the data transmission in the corresponding RU failed. In the retransmission time slot, the data is retransmitted in another RU (switched frequency) based on a random algorithm, and so on.

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

[0037] For data packet loss retransmission scheduling, there are two schemes: with ACK frames and without ACK frames.

[0038] ① The wireless access point replies with an ACK frame. Wireless field devices that do not receive an ACK change the RU frequency point and retransmit based on pre-configured random rules. As shown in Figure 4, the RU for the first transmission, the first retransmission, and the second retransmission can be randomly selected from multiple RUs. For example, if RU1 is used to transmit STA1 data Frame1 and no ACK is received, RU3 is randomly selected for the first retransmission. If no ACK is received, RU7 is randomly selected for the second retransmission.

[0039] Specifically, the RU frequency point can be changed according to the following principles:

[0040] (1) Retransmission data is assigned to the RU that has not been tried for data transmission.

[0041] (2) The retransmission data allocation RU adopts frequency hopping and the interval is far away from the RU used in the last transmission.

[0042] If the 20MHz bandwidth is divided into 5 RU resources, namely: RU1, RU2, RU3, RU4, and RU5; device 1 sends data in RU1 and fails;

[0043] The first retransmission of data from device 1, attempting to send it via RU5, failed.

[0044] Device 1 attempted to retransmit data a second time, selecting RU3 for transmission; however, this attempt failed.

[0045] Device 1 retransmitted data for the third time, selecting RU2 for transmission; and it was successful.

[0046] ② The wireless access point does not reply with an ACK frame. Based on the pre-configured random rules, it reassembles the RU order of the data of each field device (switching frequency points) and retransmits the uplink OFDMA frame after reassembling the RUs to avoid the influence of co-channel interference. The retransmission situation is the same.

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

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

[0049] The 160MHz bandwidth is evenly divided into 20MHz segments; each 20MHz segment contains 2 RUs; wireless devices can be configured to use one or more RUs for data transmission.

[0050] The transmitting and receiving devices transmit data on pre-designated RUs; to ensure data transmission reliability and improve anti-interference capabilities, the sending device may transmit a single data set simultaneously on two or more RUs.

[0051] When allocating RUs, the transceiver can transmit the same frame of data on consecutive RUs or non-consecutive RUs (a method known as puncturing).

[0052] The retransmission data RU allocation 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] The above embodiments designed a parallel data transmission scheme for multiple devices using OFDMA technology under the TDMA access mechanism, saving TDMA communication time slot resources, shortening the TDMA superframe polling cycle, and significantly improving communication real-time performance. When subjected to co-channel interference, in the traditional TDMA access mechanism, multiple retransmissions occur on the same frequency point, and the retransmission interval is short, falling within the duration of the co-channel interference, leading to a high probability of consecutive retransmission failures. This method utilizes the characteristic of RUs (Retrievers) in OFDMA operating at different frequencies, randomly switching data from different source / destination addresses to different RUs for transmission during retransmission using a random algorithm, greatly increasing the retransmission success rate and achieving anti-interference functionality.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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, interference-resistant communication scheduling method based on OFDMA, characterized in that, The method includes: Downlink data transmission: The radio access point fills the contents of each resource unit (RU) in the OFDMA frame in the predetermined downlink time slot. The contents of each RU are filled with data from different destination addresses in the transmission queue, and the downlink OFDMA frame is transmitted. Uplink data transmission: Wireless field devices synchronously trigger OFDMA parallel uplink data transmission within the same pre-configured time slot, or the wireless access point sends an uplink OFDMA data start trigger frame to trigger and schedule 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: After receiving a downlink OFDMA frame, the wireless field device replies with an ACK. If the wireless access point does not receive the corresponding ACK, it indicates that the data sent in the corresponding RU failed, and the data will be retransmitted to 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. If the wireless field device does not receive an ACK, it will change the RU frequency point and retransmit. If the wireless access point does not reply with an ACK frame, it will reassemble the RU order of the data of each wireless field device and resend the uplink OFDMA frame after reassembling the RU. This process will continue for multiple retransmissions.

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

5. The OFDMA-based hard real-time, anti-interference communication scheduling method according to claim 1, characterized in that, The data transmitting device can transmit a single data set simultaneously on two or more RUs.

6. The OFDMA-based hard real-time, interference-resistant communication scheduling method according to claim 1, characterized in that, When allocating RUs (Receiving Units), the transceiver can transmit the same frame of data on either consecutive or discontinuous RUs.

7. The OFDMA-based hard real-time, interference-resistant communication scheduling method according to claim 1, characterized in that, The RU allocation for retransmitted data includes: Retransmitted data is assigned to unattended RUs for data transmission. The retransmission data allocation RU adopts frequency hopping, and the interval is far away from the RU used in the last transmission.

8. The OFDMA-based hard real-time, interference-resistant communication scheduling method according to claim 1, characterized in that, After multiple retransmissions, the sending device may occupy 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 applications based on a TDMA transmission scheduling mechanism. Each device in the wireless communication system achieves 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 use a hard real-time, anti-interference communication scheduling method based on OFDMA as described in any one of claims 1 to 8 for data communication.

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

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