Efficient retransmission scheduling method and system in a TDMA system

Abstract

The application discloses a kind of efficient retransmission scheduling method and system in TDMA system, it is related to wireless communication technical field.The method is led by network coordinator AP, and superframe is divided into main TDMA period and shared retransmission time slot period SRS.In main TDMA period, device STA must send NULL frame in the uplink time slot of allocation if there is no data transmission, so that AP can reliably detect uplink failure.AP detects transmission failure event in real time during TDMAP, and incrementally constructs retransmission scheduling table, immediately broadcasts SRS-MAP frame after main TDMA period ends, and performs conflict-free retransmission in SRS period.The application solves the contradiction between resource efficiency and retransmission delay in traditional TDMA system, and realizes the beneficial effects of high spectral efficiency, low retransmission delay, reliable failure detection and adaptive network change.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and specifically to an efficient retransmission scheduling method and system in a TDMA system. Background Technology

[0002] In industrial TDMA wireless systems, each device (STA) is typically allocated a dedicated transmission time slot to ensure deterministic communication. However, electromagnetic interference (EMI) and channel fading in industrial environments inevitably lead to data transmission failures and packet loss. How to handle retransmissions becomes a core challenge in TDMA system design.

[0003] In traditional technology, there are two main retransmission schemes: Time slot reservation scheme: as attached Figure 1 As shown, time for the "worst-case scenario" (e.g., the time for transmission plus three retransmissions) is reserved for each TDMA time slot. While this approach is reliable, it results in a catastrophic waste of spectrum resources in most scenarios where transmissions succeed on the first try, with 90% of the time slots potentially being wasted due to idle time.

[0004] Next superframe retransmission scheme: If the current transmission fails, it waits for the corresponding time slot of the next superframe before retransmitting. This introduces a delay of a complete superframe cycle (e.g., 10ms or 100ms), which is completely unacceptable for low-latency applications such as industrial control and motion synchronization.

[0005] Therefore, a pressing technical problem in this field is how to provide low-latency, fast retransmission opportunities for failure scenarios without reserving excessive redundant resources for "average cases" and thus causing waste. Existing technologies struggle to achieve a balance between "resource efficiency" and "retransmission latency." Summary of the Invention

[0006] The purpose of this invention is to address the difficulty in balancing resource efficiency and retransmission latency in existing TDMA retransmission mechanisms by providing an efficient retransmission scheduling method and system. This invention separates the "initial transmission" and "retransmission" in time and introduces a "shared retransmission slot period" (SRS) centrally scheduled by the AP (Access Point / Coordinator). This achieves a highly efficient (no redundancy) primary TDMA slot while providing an immediate, low-latency, and conflict-free retransmission opportunity for all failed transmissions (uplink and downlink).

[0007] To address the aforementioned technical problems, embodiments of the present invention provide the following technical solution: a retransmission scheduling method for wireless communication, applied to a TDMA system, wherein the method is executed by a network coordinator (AP), and includes the following steps: The superframe is divided into a main TDMA period for initial transmission and a shared retransmission slot period (SRS) for retransmission. During the main TDMA cycle, a dedicated time slot is allocated to each device for the first data transmission, and an instant confirmation mechanism is adopted. During the shared retransmission time slot period, retransmission of all failed data frames in the main TDMA period is processed centrally.

[0008] Preferably, during the main TDMA cycle, when no data is being transmitted in the allocated uplink time slot, the device sends a no-data frame; the network coordinator AP determines whether the uplink is successful by detecting whether a data frame or no data frame is received, and determines that the uplink transmission has failed if no frame is received.

[0009] Preferably, during the main TDMA cycle, the network coordinator (AP) detects all uplink and downlink transmission failure events in real time and incrementally builds a retransmission schedule table, wherein the incremental construction includes: An empty retransmission schedule table draft is initialized at the start of the main TDMA cycle; Whenever a transmission failure event is detected, the scheduler is immediately triggered to decide whether to add the failure event to the retransmission schedule table draft according to the arbitration algorithm, and to pre-allocate micro-slots within the shared retransmission time slot period (SRS).

[0010] Preferably, after the main TDMA cycle ends, the network coordinator AP immediately broadcasts the finalized retransmission scheduling table frame within a short inter-frame interval. This frame explicitly defines the offset, duration, and corresponding device identifier of each retransmission micro-slot within the shared retransmission slot period.

[0011] Preferably, when the number of detected failure events exceeds the number of retransmissions that the shared retransmission time slot period can accommodate, the network coordinator AP, when executing the arbitration algorithm, makes a decision based on device priority, historical retransmission count, or random number to prioritize scheduling the failure frames of high-priority devices.

[0012] Preferably, the network coordinator (AP) dynamically adjusts the total duration of the shared retransmission time slot period in subsequent beacon frames based on the statistical network transmission failure rate to adapt to changes in network quality.

[0013] The present invention also proposes a wireless network coordinator for a TDMA system, the coordinator including a processor and a memory, the memory storing a computer program, the processor executing the computer program to implement the method described above.

[0014] The present invention also proposes a wireless communication system, including a network coordinator and at least one device, characterized in that the system is configured to perform the method as described in any of the preceding claims.

[0015] Preferably, the device is configured to send a no-data frame if no data is being sent in its allocated uplink time slot, and to perform retransmission strictly in accordance with the schedule during the shared retransmission time slot period after receiving the retransmission schedule table frame.

[0016] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the method described in any of the preceding claims.

[0017] The beneficial effects of the above-mentioned technical solution of the present invention are as follows: 1. This invention moves retransmission out of the main TDMA cycle, allowing the main time slot to be designed very compactly with no time redundancy, greatly improving the network throughput in a "good" state. Failed frames do not need to wait for the next superframe, but immediately get a retransmission opportunity within the SRS cycle of the same superframe, reducing retransmission latency from the superframe level to the time slot level.

[0018] 2. The innovative "forced NULL frame" mechanism of this invention enables the AP to deterministically detect uplink failures, solving the detection ambiguity problem in traditional TDMA. The SRS period itself is also a "mini TDMA" centrally scheduled by the AP, ensuring that no secondary collisions occur between retransmissions and guaranteeing determinism. The AP's "incremental scheduling" and "intelligent arbitration" algorithms ensure that the most critical devices can obtain retransmission resources first; the "dynamically scalable" SRS period enables the system to automatically adapt to changes in network quality. Attached Figure Description

[0019] Figure 1 This is a comparison chart of the retransmission efficiency of the present invention and the existing TDMA technology.

[0020] Figure 2 This is a diagram showing the superframe structure and timing of the present invention.

[0021] Figure 3 This is the timing diagram for incremental scheduling on the AP side. Detailed Implementation

[0022] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0023] This invention proposes a retransmission scheduling method for wireless communication, as shown in the appendix. Figure 2 As shown, it is dominated by the network coordinator (AP). The superframe structure defined by the AP is divided into at least two consecutive periods in time: The main TDMA cycle (TDMAP) contains multiple compact time slots allocated to a specific STA for the first transmission. Each time slot uses an "instant acknowledgment" mechanism (e.g., transmit + SIFS + ACK).

[0024] Shared Repeat Slot Period (SRS): A dedicated time period used to centrally process all failed data frames from the previous TDMAP.

[0025] The core innovation of this invention lies in its inclusion of three components: "bidirectional failure detection," "incremental scheduling," and "centralized retransmission." 1. Two-way failure detection step (executed in TDMAP): AP-side detection: a) Downlink (DL) failure: The AP sends data to the STA, but does not receive an ACK from the STA within the time slot.

[0026] b) Uplink (UL) failure: The STA does not receive either its Data frame or its NULL Data frame within its allocated time slot (core innovation: the STA must send a NULL frame when there is no data).

[0027] STA side detection: a) Uplink (UL) failure: The STA sends a Data or NULL frame but does not receive an ACK from the AP within the time slot. The STA buffers the frame and waits for retransmission.

[0028] 2. Incremental scheduling phase (AP executes in real time in TDMAP): When TDMAP starts, the AP initializes an empty "retransmission schedule table" (SRS-MAP draft).

[0029] During TDMAP, whenever the AP detects a DL or UL failure, the AP's scheduler is immediately triggered.

[0030] The AP scheduler determines in real time whether to add the failed frame to the SRS-MAP draft and pre-allocate a micro-slot within the SRS based on an arbitration algorithm (e.g., based on device priority, historical retransmissions, or random numbers).

[0031] 3. Centralized retransmission process (executed in SRS): After the last time slot of the main TDMA cycle ends, the AP scheduler performs a final update on the SRS-MAP draft based on the results of the last time slot.

[0032] After one SIFS (Short Interframe Spacing), the AP immediately broadcasts this finalized SRS-MAP frame.

[0033] An SRS-MAP frame is a “mini TDMA scheduling table” that explicitly defines the [offset, duration, STA_ID] of each retransmission microslot within an SRS period.

[0034] After receiving the SRS-MAP, all STAs (including the AP itself) strictly follow the scheduling in the table and perform conflict-free retransmission (or receive retransmission) on the retransmission micro-slots allocated to them.

[0035] In addition, the AP can dynamically increase or decrease the total duration of the SRS cycle in the next superframe Beacon based on the statistical network failure rate to adapt to changes in network quality.

[0036] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0037] Example 1: Uplink Failure Detection Based on NULL Frames To address the industry-wide problem of APs being unable to distinguish between "STA has no data" and "STA transmission failed," this invention stipulates: During the main TDMA cycle (TDMAP), any STA, when it is its turn to send an uplink time slot, sends a Data frame if it has data to send.

[0038] If the STA has no data to send, it must send a NULL Data frame (a short frame containing only the MAC header).

[0039] Therefore, for the AP, receiving either a Data or NULL frame within its time slot indicates "uplink success".

[0040] If the AP receives nothing within that time slot (including ACK timeout), the AP can be 100% certain that the uplink of the STA has experienced a transmission failure (or a power outage), and will add it to the failure list in preparation for scheduling SRS for it.

[0041] Example 2: Incremental Scheduling and Arbitration Algorithm on the AP Side See attached document Figure 3 (Sequence diagram) The AP's "incremental scheduling" process is as follows: T=0 (TDMAP start): AP initializes an empty SRS-MAP_Draft.

[0042] T=T1(Slot1,STA1,UL): The AP did not receive the NULL frame from STA1, and the decision failed. The AP scheduler runs arbitration and adds {STA1,Slot1} to the SRS-MAP_Draft.

[0043] T=T2(Slot2,AP,DL): AP did not receive an ACK from STA2, so the decision failed. The AP scheduler runs arbitration and adds {AP→STA2,Slot2} to the SRS-MAP_Draft.

[0044] T=T3(Slot3,STA3,UL): The AP received the Data frame and the determination was successful. The scheduler took no action. ... T=Tn(SlotN, last time slot): This time slot ends, the AP completes the last update of SRS-MAP_Draft, and SRS-MAP is officially determined.

[0046] T=Tn+SIFS: The AP immediately broadcasts this SRS-MAP frame.

[0047] Arbitration algorithm implementation: When the AP detects a failure and attempts to add it to the SRS-MAP_Draft, if the SRS period is already full: The AP will prioritize "new losers" and "devices already in draft".

[0048] If the new loser has a higher priority, it will be "kicked out" of the lowest priority one in the draft.

[0049] Priorities can be based on: 1. Static configuration (e.g., security devices > sensors); 2. Dynamic factors (e.g., devices that have failed 3 times consecutively > devices that have failed for the first time); 3. Random numbers (lottery).

[0050] Example 3: Dynamically Scalable SRS Period AP continuously calculates the "failure rate" (e.g., number of failed time slots / total number of time slots) within a time window.

[0051] When the failure rate increases (e.g., due to network interference), the AP will increase the total duration of the SRS period in the Beacon of the next superframe (e.g., from 5ms to 10ms) to accommodate more retransmissions.

[0052] When the failure rate decreases (e.g., network quality improves), the AP will shorten the total duration of the SRS cycle in the Beacon, or even shorten it to 0, freeing up valuable air interface time for (e.g.) CSMA / CA cycles or shortening the total length of superframes.

[0053] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A retransmission scheduling method for wireless communication, applied to a TDMA system, characterized in that, The method is executed by the network coordinator (AP) and includes the following steps: The superframe is divided into a main TDMA period for initial transmission and a shared retransmission time slot period (SRS) for retransmission. During the main TDMA period, the device sends a no-data frame in the allocated uplink time slot when there is no data to send. The network coordinator (AP) determines the success of the uplink by detecting whether a data frame or no data frame is received. If no frame is received, the uplink transmission is considered to have failed. During the main TDMA cycle, the network coordinator (AP) detects all uplink and downlink transmission failure events in real time and incrementally builds a retransmission schedule table, wherein the incremental construction includes: An empty retransmission schedule table draft is initialized at the start of the main TDMA cycle; Whenever a transmission failure event is detected, the scheduler is immediately triggered to decide whether to add the failure event to the retransmission schedule table draft according to the arbitration algorithm, and to pre-allocate micro-slots within the shared retransmission time slot period (SRS). After the main TDMA cycle ends, the network coordinator AP immediately broadcasts the final retransmission scheduling table frame within a short inter-frame interval. This frame explicitly defines the offset, duration, and corresponding device identifier of each retransmission micro-slot within the shared retransmission slot period. The network coordinator (AP) dynamically adjusts the total duration of the shared retransmission time slot period in subsequent beacon frames based on the statistical network transmission failure rate. During the main TDMA cycle, a dedicated time slot is allocated to each device for the first data transmission, and an instant confirmation mechanism is adopted. During the shared retransmission time slot period, retransmission of all failed data frames in the main TDMA period is processed centrally.

2. The method according to claim 1, characterized in that, When the number of detected failure events exceeds the number of retransmissions that the shared retransmission time slot period can accommodate, the network coordinator AP makes a decision based on device priority, historical retransmission count, or random number when executing the arbitration algorithm.

3. A wireless network coordinator for a TDMA system, characterized in that, The coordinator includes a processor and a memory, the memory storing a computer program, and the processor executing the computer program to implement the method as described in any one of claims 1 or 2.

4. A wireless communication system, comprising a network coordinator and at least one device, characterized in that, The system is configured to perform the method as described in any one of claims 1 or 2.

5. The system according to claim 4, characterized in that, The device is configured to send a no-data frame if no data is being sent in its allocated uplink time slot, and to retransmit strictly in accordance with the schedule during the shared retransmission time slot period after receiving the retransmission schedule table frame.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 or 2.

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