5G network downlink high reliability retransmission method for industrial URLLC

Abstract

The present invention relates to industrial wireless network technology, specifically to a 5G network downlink high-reliability retransmission method for industrial URLLC. This method is applicable to a downlink transmission network composed of a single base station and multiple user devices. The present invention constructs a new frame structure for resource allocation, supports an on-demand retransmission strategy based on hybrid data coordinated scheduling and a dynamic switching strategy based on on-demand / cyclic retransmission reliability analysis; by jointly considering the data packets and retransmission packets in the downlink data queue, and allocating communication resources on demand for data that failed to be transmitted according to the data packet transmission results of each round and the available communication resources, the resource utilization rate is significantly improved, thereby improving the reliability of downlink data transmission; then, combined with the low communication overhead characteristics of the cyclic retransmission strategy, the most reliable retransmission strategy is selected online according to the data queue and the available communication resources, thereby further improving the reliability of downlink data transmission.

Description

Technical Field

[0001] The present invention relates to industrial wireless network technology, and specifically to a 5G network downlink high-reliability retransmission method for industrial URLLC. Background Art

[0002] URLLC is one of the three major 5G application scenarios, playing a critical role in applications such as autonomous driving, industrial automation, connected vehicles, and smart grids. Different industries have different standards for URLLC. In factory automation, industrial applications require transmission latency of no more than 10ms and reliability of at least 99.999% across hundreds of networks. Due to unfavorable factors such as high path loss, strong noise interference, and multipath effects in real-world factory RF environments, wireless communications are extremely unreliable. While 5G ideally achieves transmission latency of no more than 1ms and reliability of at least 99.999%, implementing industrial URLLC for 5G remains a significant challenge.

[0003] Current research on retransmission methods for URLLC implementations primarily focuses on uplink data transmission. Unlike uplink data retransmission, downlink data retransmission requires ACK / NACK to determine data reception status, making uplink retransmission methods unsuitable for downlink data retransmission. Furthermore, downlink transmission methods primarily utilize a retransmission mode with pre-allocated resources, resulting in low resource efficiency and failing to meet industrial URLLC requirements. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a 5G network downlink high-reliability retransmission method for industrial URLLC. For the downlink transmission network model composed of a single base station and multiple user devices, a new frame structure for resource allocation is constructed, which supports an on-demand retransmission strategy based on hybrid data coordinated scheduling and a dynamic switching strategy based on on-demand / cyclic retransmission reliability analysis; by jointly considering the data packets and retransmission packets in the downlink data queue, and allocating communication resources on demand for the data that failed to be transmitted according to the data packet transmission results of each round and the available communication resources, the reliability of downlink data transmission is improved; then, combined with the low communication overhead characteristics of the cyclic retransmission strategy, the most reliable retransmission strategy is selected online according to the data queue and available communication resources, further improving the reliability of downlink data transmission.

[0005] The present invention adopts the following technical solution: a 5G network downlink high-reliability retransmission method for industrial URLLC, comprising the following steps:

[0006] For a downlink transmission network model consisting of a single base station and multiple user devices, a frame structure oriented to resource allocation is constructed to support an on-demand retransmission strategy based on hybrid data coordinated scheduling and a dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis.

[0007] Implement an on-demand retransmission strategy based on hybrid data coordination scheduling: By jointly considering the data packets and retransmission packets in the downlink data queue, communication resources are allocated on demand to data with failed transmissions based on the packet transmission results of each round and available communication resources, thereby improving the reliability of downlink data transmission;

[0008] Then, a dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis is implemented: combining the communication overhead characteristics of the cyclic retransmission strategy, the most reliable retransmission strategy is selected online according to the data queue and available communication resources to further improve the reliability of downlink data transmission.

[0009] The downlink transmission network model consisting of a single base station and multiple user equipments is as follows:

[0010] A 5G network consists of a single base station and N0 user devices. The base station sends periodic downlink data to the user devices, with a period T that does not exceed the latency requirement. The base station centrally schedules the N0 downlink data packets.

[0011] The communication resources of 5G networks are divided into time and frequency domains. In the time domain, the control period is divided into multiple basic time units (TTIs). In the frequency domain, the total bandwidth is divided into multiple subchannels. The combination of each TTI and subchannel is called a resource block (RB). Let the spectrum efficiency be η, the subcarrier spacing be ω, the TTI size be τ, the data packet size be b bits, and the bandwidth of a resource block be ω. b ,ω b =12; the number of resource blocks R required to transmit a data packet in each TTI num for R num A resource block is recorded as a resource unit RU;

[0012] A control cycle is divided into L0 TTIs, where A channel with a total bandwidth of W is divided into K RUs, where In each control cycle, a total of L0K RUs are available to transmit data packets.

[0013] Assuming the packet error rate of the downlink is p, the data packets that are not successfully received by the user equipment at the end of the control period will be discarded by the base station.

[0014] The frame structure for resource allocation is as follows:

[0015] The length of the frame structure is L0 basic time units TTI, which consists of two parts: on-demand retransmission and cyclic retransmission based on hybrid data coordinated scheduling;

[0016] The on-demand retransmission part based on hybrid data coordinated scheduling is used by the base station to send data packets to each user equipment;

[0017] The cyclic retransmission part is used by the base station to cyclically send data packets to each user equipment.

[0018] The on-demand retransmission strategy based on hybrid data coordinated scheduling specifically involves jointly scheduling data packets and retransmission packets in the downlink transmission data queue, and allocating communication resources on demand for data that failed to be transmitted based on the packet transmission results of each round and available communication resources, including the following steps:

[0019] The base station uses a round-robin scheduling method to allocate resource units RU for downlink data packets; X(i) represents the number of data packets that the base station needs to transmit in the i-th transmission round, and R(i) is defined as: = X(i) mod K; if R(i) = 0, there is no RU vacancy problem; otherwise, there is an RU vacancy in the last TTI of the data segment, and the base station uses the last R(i) data packets in the queue and the data packets that failed to be transmitted in the i-th transmission round as the data packets X(i+1) that need to be transmitted in the next round; the base station repeats the scheduling process of the i-th transmission round until the end of the control period.

[0020] The dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis specifically analyzes the reliability of the two retransmission strategies and selects the most reliable retransmission strategy online, including the following steps:

[0021] In the rth transmission round, the indicator parameter is introduced It is used to indicate the number of transmission rounds that the base station must wait when switching from the on-demand retransmission strategy based on hybrid data coordination scheduling to the cyclic retransmission strategy;

[0022] when When , the base station continues to use the on-demand retransmission strategy based on hybrid data coordinated scheduling for data transmission;

[0023] when When , the base station uses a cyclic retransmission strategy until the end of the period.

[0024] The base station uses a cyclic retransmission strategy until the end of the period and finds the optimal switching time through reliability modeling, that is, The following steps are involved:

[0025] 6.1 Process Analysis of On-Demand Retransmission Strategy

[0026] Let the number of TTIs that need to be reserved for data segments and ACK segments in round i be β i ,but

[0027]

[0028] Among them, N 1,i Indicates the number of data packets that the base station needs to transmit to the user equipment in the i-th round, and the number of data packets N transmitted by the base station to the user equipment in the i-th round 2,i =β i K; K represents the number of resource units RU;

[0029] The number of data packets N that the base station needs to transmit to the user equipment in the (i+1)th round 1,i+1 for

[0030] N 1,i+1 =N 1,i -N 2,i (1-p) 2

[0031] p is the packet error rate of the downlink;

[0032] 6.2 Process Analysis of Cyclic Retransmission Strategy

[0033] In the current control cycle, the base station Before the round of data transmission, the on-demand retransmission strategy based on hybrid data coordinated scheduling is switched to a cyclic retransmission strategy:

[0034] when When All data packets are transmitted; the number of TTIs remaining in the control cycle is recorded as The number of transmissions for each packet is also Right now

[0035]

[0036] when When , each data packet is transmitted at least

[0037]

[0038] If there are any remaining TTIs in the current control cycle, the expected number of successful data packets that the base station can increase by using the remaining TTIs is C:

[0039]

[0040] 6.3 Reliability Model

[0041] make Represents the reliability of dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis;

[0042] when hour, The expression is as follows

[0043]

[0044] when hour, The expression is as follows

[0045]

[0046] In summary, for

[0047]

[0048] The parameters The specific solution process is as follows:

[0049] make Indicates the number of TTIs actually allocated by the base station for the data segment and ACK segment in the rth round of transmission; Indicates the number of ACKs actually successfully received by the base station in the rth round of transmission; Indicates the number of TTIs actually available to the base station before the start of the rth round of transmission; Indicates the number of data packets that the base station actually needs to transmit in the rth round;

[0050] According to the actual transmission results and Model, obtained by one-dimensional exhaustive search In the rth round of transmission, The solution process is as follows:

[0051] First, according to and renew and

[0052]

[0053]

[0054] Then, let and L0 is the number of basic time units TTI in the length of the frame structure, N i is the number of downlink data packets; and calculates the maximum number of consecutive rounds that the base station can use the on-demand retransmission strategy based on hybrid data coordinated scheduling from the current transmission round to the end of the current cycle, that is,

[0055]

[0056] Finally, get the current transmission round Right now

[0057]

[0058] The present invention has the following beneficial effects and advantages:

[0059] 1. The present invention proposes for the first time an on-demand retransmission strategy based on hybrid data coordinated scheduling. This strategy jointly schedules data packets and retransmission packets in the downlink transmission data queue, and allocates communication resources on demand to data that fails to be transmitted based on the results of each round of data packet transmission and available communication resources, significantly improving the utilization of communication resources.

[0060] 2. This paper combines the low communication overhead of the cyclic retransmission strategy with a dynamic switching strategy based on on-demand / cyclic retransmission reliability analysis. This strategy enables the network to select the most reliable retransmission strategy online based on the data queue and available communication resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is the downlink transmission network model;

[0062] Figure 2 Schematic diagram of the frame structure;

[0063] Figure 3 Schematic diagram of on-demand retransmission strategy based on mixed data coordinated scheduling;

[0064] Figure 4 Flowchart for finding the optimal switching timing for the cyclic retransmission strategy. DETAILED DESCRIPTION

[0065] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0066] The present invention mainly includes three parts: downlink transmission network model, frame structure design and network working mechanism design.

[0067] 1 Downlink Transmission Network Model

[0068] like Figure 1 As shown in the figure, the present invention considers a 5G network consisting of a single base station and N0 user devices. For factory automation applications, the base station sends periodic downlink data to the user devices, with a period T that does not exceed the latency requirements of industrial URLLC. To ensure reliable transmission of downlink data, the base station uses the OFDMA mechanism to centrally schedule N0 downlink data packets.

[0069] The communication resources of the 5G network are divided into time and frequency domains. In the time domain, the control period is divided into multiple basic time units (TTIs). In the frequency domain, the total bandwidth is divided into multiple subchannels. The combination of each TTI and subchannel is called a resource block (RB). Let the spectrum efficiency be η, the subcarrier spacing be ω, the TTI size be τ, the data packet size be b bits, and the bandwidth of a resource block be ω. b (ω b =12). The number of resource blocks R required to transmit a data packet in each TTI num for R num Resource blocks are recorded as a resource unit (RU). Therefore, a control period can be divided into L0 TTIs, where A channel with a total bandwidth of W can be divided into K RUs, where In each control cycle, a total of L0K RUs are available to transmit data packets.

[0070] Assume that the packet error rate of the downlink (base station → user equipment) is p. At the end of the control period, the data packets that are not successfully received by the user equipment will be discarded by the base station.

[0071] 2-frame structure design

[0072] like Figure 2 As shown, the frame structure is as follows:

[0073] The length of the frame structure is L0 TTIs, and it consists of two parts: on-demand retransmission and cyclic retransmission based on hybrid data coordinated scheduling.

[0074] On-demand retransmission part based on hybrid data coordinated scheduling: used by the base station to send data packets to each user equipment.

[0075] Cyclic retransmission part: used by the base station to cyclically send data packets to each user equipment.

[0076] 3. Network working mechanism design

[0077] This section mainly introduces the on-demand retransmission strategy based on hybrid data coordinated scheduling, the dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis, the reliability modeling and parameters of the two retransmission strategies. The solution process.

[0078] The on-demand retransmission strategy based on hybrid data coordinated scheduling is as follows:

[0079] like Figure 3 As shown in Figure 3, this strategy jointly schedules data packets and retransmission packets in the downlink transmission data queue, and allocates communication resources on demand for data that fails to be transmitted based on the packet transmission results of each round and the available communication resources.

[0080] Specific process: The base station uses a round-robin scheduling method to allocate RUs for downlink data packets. Let X(i) represent the number of data packets that the base station needs to transmit in the i-th transmission round, and define R(i): = X(i) mod K. If R(i) = 0, there is no RU idle problem; otherwise, there must be an RU idle in the last TTI of the data segment. To this end, the base station uses the last R(i) data packets in the queue and the data packets that failed to be transmitted in the i-th transmission round as the data packets X(i+1) to be transmitted in the next round. The base station repeats the scheduling process for the i-th transmission round until the end of the control period.

[0081] The dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis is as follows:

[0082] The dynamic switching strategy analyzes the reliability of the two retransmission strategies and selects the most reliable retransmission strategy online.

[0083] Specific process: In the rth transmission round, the indicator parameter is introduced Indicates the number of transmission rounds the base station must wait for when switching from an on-demand retransmission strategy based on hybrid data coordination scheduling to a cyclic retransmission strategy. when When , the base station continues to use the on-demand retransmission strategy based on hybrid data coordinated scheduling for data transmission; when When , the base station uses the cyclic retransmission strategy until the end of the period. This process requires finding the optimal switching time through reliability modeling, that is, satisfying

[0084] Reliability modeling is as follows:

[0085] Step 1: Process Analysis of On-demand Retransmission Strategy

[0086] Let the number of TTIs that need to be reserved for data segments and ACK segments in round i be β i ,but

[0087]

[0088] where N 1,i Indicates the number of data packets that the base station needs to transmit to the user equipment in the i-th round, and the number of data packets N transmitted by the base station to the user equipment in the i-th round 2,i for

[0089] N 2,i =β i K.

[0090] The number of data packets N that the base station needs to transmit to the user equipment in the (i+1)th round 1,i+1 for

[0091] N1,i+1 =N 1,i -N 2,i (1-p) 2 .

[0092] Step 2: Process analysis of cyclic retransmission strategy

[0093] In the current control cycle, it is assumed that the base station Before the round of data transmission, the on-demand retransmission strategy based on hybrid data coordinated scheduling is switched to a cyclic retransmission strategy. The value of and Two situations are discussed.

[0094] when When All data packets are transmitted. The number of TTIs remaining in the control cycle is recorded as Therefore, the number of transmissions for each data packet is also Right now

[0095]

[0096] when When , each data packet is transmitted at least

[0097]

[0098] If there are any remaining TTIs in the current control cycle, the expected number of successful data packets that the base station can increase by using the remaining TTIs is C:

[0099]

[0100] Step 3: Build a reliability model

[0101] make Indicates the reliability of the dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis.

[0102] when hour, The expression is as follows

[0103]

[0104] when hour, The expression is as follows

[0105]

[0106] In summary, for

[0107]

[0108] parameter The specific solution process is as follows (such as Figure 4 ):

[0109] make represents the number of TTIs actually allocated by the base station for the data segment and ACK segment in the rth round of transmission; let represents the number of ACKs actually successfully received by the base station in the rth round of transmission; let represents the number of TTIs actually available to the base station before the start of the rth round of transmission; Indicates the number of data packets that the base station actually needs to transmit in the rth round.

[0110] According to the actual transmission results and Model, which can be obtained through one-dimensional exhaustive search In the rth round of transmission, The detailed solution process is as follows:

[0111] First, according to and renew and

[0112]

[0113]

[0114] Then, let and And calculate the maximum number of consecutive rounds that the base station can use the on-demand retransmission strategy based on hybrid data coordination scheduling from the current transmission round to the end of the current period, that is,

[0115]

[0116] Finally, get the current transmission round Right now

Claims

1. A 5G network downlink high-reliability retransmission method for industrial URLLC is characterized by: The following steps are involved: For a downlink transmission network model consisting of a single base station and multiple user devices, a frame structure oriented to resource allocation is constructed to support an on-demand retransmission strategy based on hybrid data coordinated scheduling and a dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis. Implement an on-demand retransmission strategy based on hybrid data coordination scheduling: By jointly considering the data packets and retransmission packets in the downlink data queue, communication resources are allocated on demand to data with failed transmissions based on the packet transmission results of each round and available communication resources, thereby improving the reliability of downlink data transmission; Then, a dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis is implemented. Taking into account the communication overhead characteristics of the cyclic retransmission strategy, the most reliable retransmission strategy is selected online based on the data queue and available communication resources to further improve the reliability of downlink data transmission. The dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis specifically analyzes the reliability of the two retransmission strategies and selects the most reliable retransmission strategy online, including the following steps: In the rth transmission round, the indicator parameter is introduced It is used to indicate the number of transmission rounds that the base station must wait when switching from the on-demand retransmission strategy based on hybrid data coordination scheduling to the cyclic retransmission strategy; when When , the base station continues to use the on-demand retransmission strategy based on hybrid data coordinated scheduling for data transmission; when When , the base station uses a cyclic retransmission strategy until the end of the period; The base station uses a cyclic retransmission strategy until the end of the period and finds the optimal switching time through reliability modeling, that is, The following steps are involved: 1) Process Analysis of On-demand Retransmission Strategy Let the number of TTIs that need to be reserved for data segments and ACK segments in round i be β i ,but Among them, N 1,i Indicates the number of data packets that the base station needs to transmit to the user equipment in the i-th round, and the number of data packets N transmitted by the base station to the user equipment in the i-th round 1,i =β i K; K represents the number of resource units RU; The number of data packets N that the base station needs to transmit to the user equipment in the (i+1)th round 1,i+1 N 1,i+1 =N 1,i -N 1,i (1-p) 2 p is the packet error rate of the downlink; 2) Process Analysis of Cyclic Retransmission Strategy In the current control cycle, the base station Before the round of data transmission, the on-demand retransmission strategy based on hybrid data coordinated scheduling is switched to a cyclic retransmission strategy: when When All data packets are transmitted; the number of TTIs remaining in the control cycle is recorded as L0 is the number of basic time units TTI in the length of the frame structure; the number of transmission times of each data packet is also Right now when When , each data packet is transmitted at least If there are any remaining TTIs in the current control cycle, the expected number of successful data packets that the base station can increase by using the remaining TTIs is C: 3) Reliability model make Represents the reliability of dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis; when hour, The expression is as follows when hour, The expression is as follows In summary, for 2. The 5G network downlink high-reliability retransmission method for industrial URLLC according to claim 1 is characterized in that The downlink transmission network model consisting of a single base station and multiple user equipments is as follows: A 5G network consists of a single base station and N0 user devices. The base station sends periodic downlink data to the user devices, with a period T that does not exceed the latency requirement. The base station centrally schedules the N0 downlink data packets. The communication resources of 5G networks are divided into time and frequency domains. In the time domain, the control cycle is divided into multiple basic time units (TTIs). In the frequency domain, the total bandwidth is divided into multiple subchannels; each combination of TTI and subchannel is called a resource block (RB); let the spectral efficiency be η, the subcarrier spacing be ω, the TTI size be τ, the packet size be b bits, and the bandwidth of a resource block be ω b ,ω b =12ω; the number of resource blocks R required to transmit a data packet in each TTI num for R num A resource block is recorded as a resource unit RU; A control cycle is divided into L0 TTIs, where A channel with a total bandwidth of W is divided into K RUs, where In each control cycle, a total of L0K RUs are available to transmit data packets; Assuming the packet error rate of the downlink is p, the data packets that are not successfully received by the user equipment at the end of the control period will be discarded by the base station.

3. The 5G network downlink high-reliability retransmission method for industrial URLLC according to claim 1 is characterized in that The frame structure for resource allocation is as follows: The length of the frame structure is L0 basic time units TTI, which consists of two parts: on-demand retransmission and cyclic retransmission based on hybrid data coordinated scheduling; The on-demand retransmission part based on hybrid data coordinated scheduling is used by the base station to send data packets to each user equipment; The cyclic retransmission part is used by the base station to cyclically send data packets to each user equipment.

4. The 5G network downlink high-reliability retransmission method for industrial URLLC according to claim 1 is characterized in that The on-demand retransmission strategy based on hybrid data coordinated scheduling specifically involves jointly scheduling data packets and retransmission packets in the downlink transmission data queue, and allocating communication resources on demand for data that failed to be transmitted based on the packet transmission results of each round and available communication resources, including the following steps: The base station uses a round-robin scheduling method to allocate resource units RU for downlink data packets; X(i) represents the number of data packets that the base station needs to transmit in the i-th transmission round, K represents the number of resource units RU, and R(i) is defined as: = X(i) mod K; if R(i) = 0, there is no RU vacancy problem; otherwise, there is a RU vacancy in the last TTI of the data segment, and the base station uses the last R(i) data packets in the queue and the data packets that failed to be transmitted in the i-th transmission round as the data packets X(i+1) that need to be transmitted in the next round; the base station repeats the scheduling process of the i-th transmission round until the end of the control period.

5. The 5G network downlink high-reliability retransmission method for industrial URLLC according to claim 1 is characterized in that The parameters The specific solution process is as follows: make Indicates the number of TTIs actually allocated by the base station for the data segment and ACK segment in the rth round of transmission; Indicates the number of ACKs actually successfully received by the base station in the rth round of transmission; Indicates the number of TTIs actually allocated by the base station for the data segment and ACK segment in the r-1th round of transmission; Indicates the number of ACKs actually successfully received by the base station in the r-1th round of transmission; Indicates the number of TTIs actually available to the base station before the start of the rth round of transmission; Indicates the number of data packets that the base station actually needs to transmit in the rth round; According to the actual transmission results and Model, obtained by one-dimensional exhaustive search In the rth round of transmission, The solution process is as follows: First, according to and renew and Then, let and L0 is the number of basic time units TTI in the length of the frame structure, and N0 is the number of downlink data packets; And calculate the maximum consecutive rounds of the base station using the on-demand retransmission strategy based on hybrid data coordinated scheduling from the current transmission round to the end of the current cycle, that is, Finally, get the current transmission round Right now 6. The 5G network downlink high-reliability retransmission system for industrial URLLC is characterized by: include: The frame structure construction module is used to construct a frame structure for resource allocation in a downlink transmission network model consisting of a single base station and multiple user devices, to support an on-demand retransmission strategy based on hybrid data coordinated scheduling and a dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis; An on-demand retransmission strategy execution module based on hybrid data coordinated scheduling is used to jointly consider the data packets and retransmission packets in the downlink data queue, and allocate communication resources on demand to data that failed to be transmitted based on the data packet transmission results of each round and the available communication resources, thereby improving the reliability of downlink data transmission; A dynamic switching strategy execution module based on on-demand and cyclic retransmission reliability analysis is used to combine the communication overhead characteristics of the cyclic retransmission strategy and select the most reliable retransmission strategy online based on the data queue and available communication resources to further improve the reliability of downlink data transmission; The dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis is specifically configured to perform online selection of the most reliable retransmission strategy by analyzing the reliability of the two retransmission strategies: In the rth transmission round, the indicator parameter is introduced It is used to indicate the number of transmission rounds that the base station must wait when switching from the on-demand retransmission strategy based on hybrid data coordination scheduling to the cyclic retransmission strategy; when When , the base station continues to use the on-demand retransmission strategy based on hybrid data coordinated scheduling for data transmission; when When , the base station uses a cyclic retransmission strategy until the end of the period; The base station uses a cyclic retransmission strategy until the end of the period and finds the optimal switching time through reliability modeling, that is, Configured to execute: 1) Process Analysis of On-demand Retransmission Strategy Let the number of TTIs that need to be reserved for data segments and ACK segments in round i be β i ,but Among them, N 1,i Indicates the number of data packets that the base station needs to transmit to the user equipment in the i-th round, and the number of data packets N transmitted by the base station to the user equipment in the i-th round 1,i =β i K; K represents the number of resource units RU; The number of data packets N that the base station needs to transmit to the user equipment in the (i+1)th round 1,i+1 N 1,i+1 =N 1,i -N 1,i (1-p) 2 p is the packet error rate of the downlink; 2) Process Analysis of Cyclic Retransmission Strategy In the current control cycle, the base station Before the round of data transmission, the on-demand retransmission strategy based on hybrid data coordinated scheduling is switched to a cyclic retransmission strategy: when When All data packets are transmitted; the number of TTIs remaining in the control cycle is recorded as L0 is the number of basic time units TTI in the length of the frame structure; the number of transmission times of each data packet is also Right now when When , each data packet is transmitted at least If there are any remaining TTIs in the current control cycle, the expected number of successful data packets that the base station can increase by using the remaining TTIs is C: 3) Reliability model make Represents the reliability of the dynamic switching strategy based on on-demand and cyclic retransmission reliability analysis; when hour, The expression is as follows when hour, The expression is as follows In summary, for

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