Hybrid retransmission method for industrial urllc on 5g network uplink

Abstract

The present application relates to industrial wireless network technology, in particular to a 5G network uplink hybrid retransmission method for industrial URLLC. The present application is applicable to an uplink transmission network model composed of a single base station and multiple user devices, a 5G subframe structure supporting reliable retransmission is constructed to ensure reliable transmission of 1ms period data; a hybrid retransmission strategy combining on-demand retransmission mechanism and cyclic retransmission mechanism is proposed, and the reliability of the two retransmission mechanisms in each round of retransmission process is analyzed and compared to select the retransmission mechanism with high reliability online. The hybrid retransmission method proposed in the present application can make up for the shortcomings of the traditional single retransmission mechanism, and by analyzing and comparing the reliability of the two retransmission mechanisms in each round of retransmission process, the retransmission mechanism with high reliability is selected online to improve the utilization rate of communication resources, improve the overall reliability of the transmission process, and meet the reliability requirements of URLLC.

Description

Technical Field

[0001] This invention relates to industrial wireless network technology, specifically a 5G network uplink hybrid retransmission method for industrial URLLC. Background Technology

[0002] Ultra-Reliable Low Latency Communications (URLLC), enhanced mobile broadband, and massive machine-type communications are three core services supported by 5G networks. Among them, URLLC plays a crucial role in applications such as autonomous driving, industrial automation, vehicle-to-everything (V2X) communication, and smart grids. Although 5G URLLC can ideally achieve network performance with a transmission latency of no more than 1ms and a reliability of no less than 99.999%, the actual factory radio frequency environment presents adverse factors such as high path loss, strong noise interference, and multipath effects, making wireless communication extremely unreliable. Implementing industrial URLLC remains a highly challenging task.

[0003] Current research on retransmission methods for URLLC mainly focuses on aperiodic data transmission. In typical industrial scenarios, sensing and control information has a fixed cycle and stringent requirements for data transmission reliability. Therefore, aperiodic data retransmission methods are not suitable for periodic data retransmission. Furthermore, periodic data uplink retransmission methods primarily employ a pre-allocated resource retransmission mode, which is inefficient and cannot meet the requirements of industrial URLLC. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a hybrid retransmission method for 5G uplink data in industrial URLLC. For a downlink transmission network model consisting of a single base station and multiple user devices, a 5G subframe structure supporting reliable retransmission is constructed to ensure reliable transmission of data within a 1ms period. A hybrid retransmission strategy combining on-demand retransmission and cyclic retransmission mechanisms is proposed. By analyzing and comparing the reliability of the two retransmission mechanisms in each round of retransmission, the retransmission mechanism with higher reliability is selected online, achieving highly reliable uplink data transmission on industrial 5G networks.

[0005] The present invention adopts the following technical solution:

[0006] A 5G network uplink hybrid retransmission method for industrial URLLC includes the following steps:

[0007] Based on the uplink transmission network model, a 5G subframe structure supporting reliable retransmission is constructed.

[0008] On the 5G subframe structure, a network working mechanism is constructed, and uplink data retransmission is performed based on the network working mechanism.

[0009] The uplink transmission network model consists of a single base station and N user equipments, wherein:

[0010] User equipment sends uplink data with a period of T to the base station. In 5G networks, time is composed of frames, with one frame divided into 10 subframes, and each subframe is divided into s=2... μ There are 14 OFDM symbols in each time slot. Two OFDM symbols form a mini-time slot. The number of mini-time slots in a subframe is s. mini =7×2 μ Set the data period to 1 subframe, μ is a given parameter, μ≥0;

[0011] The subcarrier spacing λ in a 5G network is determined by a given parameter μ, i.e., λ = 2. μ ×15kHz; 12 consecutive subcarriers are spaced apart to form a subcarrier, and its bandwidth is λ′=12λ;

[0012] A combination of a subcarrier and a mini-slot constitutes a resource block (RB). Let the packet size be b bits, the spectral efficiency be η bits / s / Hz, and the number of resource blocks occupied by each packet be... This represents rounding up. R resource blocks are grouped into one resource unit (RU). A channel with a total bandwidth of W is divided into M RUs, where... This represents rounding down. Within each control cycle, there are a total of Ms. mini Each data packet occupies one RU for transmission. Data that is not successfully received by the base station at the end of the transmission cycle will be discarded.

[0013] The 5G subframe structure consists of two parts: the initial transmission period and the retransmission period, wherein:

[0014] The initial transmission period is when each user equipment sends a data packet to the base station by occupying one RU, with a length of [missing information].

[0015] The retransmission period is the time when the base station sends NACK and the user equipment retransmits data packets to the base station. The base station occupies a mini time slot to send NACK to the user equipment, which contains information such as the duration of the subframe, the scheduling list, the modulation and coding scheme, and the scheduling list for the next round of transmission.

[0016] The network operating mechanism includes: reliability analysis of on-demand retransmission and cyclic retransmission mechanisms, and an online selection mechanism based on the reliability analysis of on-demand retransmission and cyclic retransmission mechanisms, specifically:

[0017] At the start of each retransmission round, the transmission reliability R of the on-demand retransmission mechanism is calculated. ODR (Lω N ω Furthermore, the reliability of the cyclic retransmission mechanism (R) is assessed. CRDR (L ω N ω The reliability R of "retransmit on demand, one round of retransmission, and then retransmit in a loop" HR (L ω N ω The comparison is performed to select a retransmission mechanism with higher reliability; where N ω L represents the number of user devices that need to retransmit during the ω-th retransmission round. ω This represents the remaining number of mini-time slots.

[0018] The on-demand retransmission mechanism allows the base station to send a NACK at the beginning of each round of retransmission. If the NACK received by the user equipment contains scheduling information that requires it to retransmit, it means that the user equipment failed to transmit information in the previous round of retransmission. The user equipment that failed to transmit will occupy the RU reserved in the NACK for retransmission.

[0019] The cyclic retransmission mechanism does not require NACK and uses all communication resources for retransmission by user equipment. After the user equipment receives the scheduling table sent by the base station, it uses the pre-allocated RU to transmit data packets. Regardless of whether the data packets are successfully transmitted, each user equipment will occupy the remaining pre-allocated resources in the subframe to continue transmitting data packets until the subframe ends.

[0020] The transmission reliability of the cyclic retransmission mechanism is R CRDR (L ω N ω The analysis includes three cases, where R ′ CRDR (L ω N ω For each case, the reliability of the cyclic retransmission mechanism from the start of the ωth retransmission round to the end of the subframe is:

[0021] Scenario 1: The number of user devices requiring retransmission is 0, i.e., N. ω =0, then

[0022] R ′ CRDR (L ω N ω ) = 1;

[0023] Scenario 2: The number of user devices requiring retransmission is less than or equal to the number of resource units in a mini-slot, i.e., N. ω ≤M, then

[0024]

[0025] Where P is the uplink packet error rate and Q is the downlink packet error rate;

[0026] Scenario 3: The number of user devices requiring retransmission is greater than the number of resource units in a mini-slot, i.e., N. ω If M > ω, then from the start of the ωth retransmission round to the end of the subframe, the minimum number of retransmissions for each data packet is ω.

[0027]

[0028] The number of data packets retransmitted q+1 times in a loop is

[0029]

[0030] Then, the reliability of the ω-th cyclic retransmission is

[0031]

[0032] Considering factors 1, 2, and 3, the overall reliability of the cyclic retransmission process is:

[0033]

[0034] The on-demand retransmission mechanism has a transmission reliability R ODR (L ω N ω The analysis includes two cases, where R ′ ODR (L ω N ω For each case, the reliability of the on-demand retransmission mechanism from the start of the ωth retransmission round to the end of the subframe is:

[0035] Case 1: The remaining mini-slots in the subframe are only enough to complete the ωth round of on-demand retransmission, i.e. but

[0036] R ′ ODR (L ω N ω )=1-(Q(1Q)P);

[0037] Scenario 2: The remaining number of mini-slots in the subframe is insufficient to complete the ωth round of on-demand retransmission, i.e. The subframe will end during the on-demand retransmission process. User equipment with retransmission opportunities will use all remaining resource units for retransmission. At this time, the ωth round of retransmission is equivalent to one round of retransmission.

[0038] R ′ ODR (L ω N ω ) = R′ CRDR (L ω N ω )

[0039]

[0040] Combining situations 1 and 2, the overall reliability of the on-demand retransmission process is:

[0041]

[0042] The reliability R of the "on-demand retransmission in one round followed by loop retransmission" is... HR (L ω N ω The analysis includes two cases:

[0043] Case 1: The remaining mini-slots in the subframe are only enough for the ωth round of on-demand retransmission, i.e. but

[0044] R HR (L ω N ω ) = R ODR (L ω N ω );

[0045] Case 2: The remaining number of mini-slots in the subframe supports the (ω+1)th round of cyclic retransmission, i.e. At this point, the remaining number of mini time slots is

[0046]

[0047] Let β = Q + (1Q)P, then the probability p of packet loss after one round of retransmission on demand and then another round of retransmission is... ω for

[0048]

[0049] at this time

[0050] R HR (L ω N ω )=1-p ω

[0051] Right now

[0052]

[0053] The online selection mechanism is as follows:

[0054] If R CRDR (L ω N ω )≥R HR(L ω N ω ), at the start of the ωth retransmission round, a cyclic retransmission mechanism is used until the end of the subframe; if R CRDR (L ω N ω ) < R HR (L ω N ω In the ω-th retransmission round, an on-demand retransmission mechanism is used, and at the start of the next retransmission round, R is retransmitted. CRDR (L ω+1 N ω+1 ) and R HR (L ω+1 N ω+1 Compare them until the ωth digit. * The conditions are met when the round-robin retransmission begins. Switch from on-demand retransmission to cyclic retransmission until the end of the subframe.

[0055] The present invention has the following beneficial effects and advantages:

[0056] 1. This invention constructs a 5G subframe structure supporting reliable retransmission to ensure reliable transmission of data in 1ms cycles, and proposes a hybrid retransmission strategy combining on-demand retransmission and cyclic retransmission mechanisms. On-demand retransmission reserves resources based on the packet loss situation of the previous round, which can avoid resource waste caused by repeated transmission. However, when the number of retransmitting user equipment is small, sending NACK will consume too many resources, resulting in a lot of mini-slot overhead. Cyclic retransmission allocates all resources cyclically to user equipment that failed to send data packets, saving the mini-slot overhead of sending NACK, but will cause resource waste due to repeated transmission.

[0057] 2. The hybrid retransmission method proposed in this invention can overcome the shortcomings of traditional single retransmission mechanisms. By analyzing and comparing the reliability of the two retransmission mechanisms in each round of retransmission, the retransmission mechanism with higher reliability is selected online to improve the utilization rate of communication resources, enhance the overall reliability of the transmission process, and meet the reliability requirements of URLLC. Attached Figure Description

[0058] Figure 1 A schematic diagram of a 5G frame (μ=0);

[0059] Figure 2 This is a schematic diagram of the subframe structure;

[0060] Figure 3 This is a schematic diagram of the subframe retransmission period. Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings.

[0062] For an uplink transmission network model consisting of a single base station and multiple user devices, this invention constructs a 5G subframe structure that supports reliable retransmission to ensure reliable transmission of 1ms periodic data. It proposes a hybrid retransmission strategy that combines on-demand retransmission mechanism and cyclic retransmission mechanism, and selects the retransmission mechanism with higher reliability online by analyzing and comparing the reliability of the two retransmission mechanisms in each round of retransmission.

[0063] This invention mainly comprises three parts: uplink transmission network model, subframe structure design, and network working mechanism design.

[0064] 1. Uplink transmission network model

[0065] like Figure 1 As shown, this invention considers a 5G network consisting of a single base station and N user equipments. The user equipments send uplink data to the base station with a period of T. The 5G network time is composed of frames, each 10ms long. Each frame is divided into 10 subframes, each 1ms long. The number of time slots in each subframe is determined by a parameter μ (μ≥0), and each subframe is divided into s=2... μ There are 3 time slots, each with a length of t. s =1 / 2 μ ms; Each time slot contains 14 OFDM symbols. Let two OFDM symbols form a mini-time slot. The number of mini-time slots in a subframe is S. mini =7×2 μ The length of each mini-slot is τ = t s / 7ms; Considering the latency of 5G URLLC, the data period is set to 1 subframe, i.e., T = 1ms;

[0066] The subcarrier spacing λ in a 5G network is determined by a given parameter μ, i.e., λ = 2. μ ×15kHz; 12 consecutive subcarriers spaced together constitute a subcarrier, with a bandwidth of λ′=12λ; a combination of a subcarrier and a mini-slot is called a resource block RB; let the data packet size be b bits, and the spectral efficiency be ηbit / s / Hz; the number of resource blocks occupied by each data packet is... in This represents rounding up, where R resource blocks are denoted as one resource unit (RU); a channel with a total bandwidth of W is divided into M RUs, where... This represents rounding down; within each control cycle, there are a total of Ms mini Each data packet occupies one RU for transmission, and data that is not successfully received by the base station at the end of the transmission cycle will be discarded.

[0067] 2. Subframe Structure Design

[0068] like Figure 2 As shown, the subframe structure is as follows:

[0069] The length of a subframe is 1ms, and it consists of two parts: the initial transmission period and the retransmission period.

[0070] Initial transmission period: Each user equipment sends a data packet to the base station by occupying one RU, with a length of [length missing].

[0071] Retransmission period: The base station sends NACK and the user equipment retransmits data packets to the base station; the base station occupies a mini time slot to send NACK to the user equipment, which contains information such as the duration of the subframe, the scheduling list, the modulation and coding scheme, and the scheduling list for the next round of transmission.

[0072] 3. Network Working Mechanism Design

[0073] This section mainly introduces the reliability analysis of on-demand retransmission mechanism and cyclic retransmission mechanism, as well as the online selection mechanism based on the reliability analysis of on-demand retransmission mechanism and cyclic retransmission mechanism.

[0074] like Figure 3 As shown, at the beginning of each retransmission round, the transmission reliability R of the on-demand retransmission mechanism is calculated. ODR (L ω N ω Furthermore, the reliability of the cyclic retransmission mechanism (R) is assessed. CRDR (L ω N ω The reliability R of "retransmit on demand, one round of retransmission, and then retransmit in a loop" HR (L ω N ω The comparison is performed to select a retransmission mechanism with higher reliability; where N ω L represents the number of user devices that need to retransmit during the ω-th retransmission round. ω This represents the remaining number of mini-time slots.

[0075] Reliability analysis of the cyclic retransmission mechanism:

[0076] Cyclic retransmission mechanism transmission reliability R CRdR (L ω N ω The calculation of R′ includes three cases, where R′ CRDR (L μ N ω For each case, the reliability of the cyclic retransmission mechanism from the start of the ωth retransmission round to the end of the subframe is:

[0077] Case 1.1: The number of user devices requiring retransmission is 0, i.e., N. ω =0, then

[0078] R ′ CRDR (L ω N ω ) = 1

[0079] Case 1.2: The number of user devices requiring retransmission is less than or equal to the number of resource units in a mini-slot, i.e., N. ω ≤M, then

[0080]

[0081] Where P is the uplink packet error rate and Q is the downlink packet error rate.

[0082] Case 1.3: The number of user devices requiring retransmission is greater than the number of resource units in a mini-slot, i.e., N. ω If M > ω, then from the start of the ωth retransmission round to the end of the subframe, the minimum number of retransmissions for each data packet is ω.

[0083]

[0084] The number of data packets retransmitted q+1 times in a loop is

[0085]

[0086] The reliability of the ωth round of retransmission is

[0087]

[0088] Therefore, the overall reliability of the cyclic retransmission process is obtained as follows:

[0089]

[0090] Reliability analysis of on-demand retransmission mechanism:

[0091] On-demand retransmission mechanism ensures transmission reliability. ODR (L ω N ω The calculation of R includes two cases, where R ′ ODR (L ω N ω For each case, the reliability of the on-demand retransmission mechanism from the start of the ωth retransmission round to the end of the subframe is:

[0092] Case 2.1: The remaining mini-slots in the subframe are only enough to complete the ωth round of on-demand retransmission, i.e. but

[0093] R ′ ODR (L ω N ω)=1-(Q+(1)P)

[0094] Case 2.2: The remaining number of mini-slots in the subframe is insufficient to complete the ωth round of on-demand retransmission, i.e. The subframe will end during the on-demand retransmission process, and user equipment with retransmission opportunities will occupy all remaining resource units for retransmission. At this point, the ω-th retransmission round is equivalent to one cyclic retransmission.

[0095] R ′ ODR (L ω N ω ) = R ′ CRDR (L ω N ω )

[0096] This leads to the overall reliability of the on-demand retransmission process.

[0097]

[0098] Reliability analysis of "on-demand retransmission followed by a round of retransmission":

[0099] The reliability of "retransmit on demand, one round of retransmission followed by a loop retransmission" is R. HR (L ω N ω The calculation includes two cases.

[0100] Case 3.1: The remaining number of mini-slots in the subframe is only enough for the ωth round of on-demand retransmission, i.e. but

[0101] R HR (L ω N ω ) = R ODR (L ω N ω )

[0102] Case 3.2: The remaining number of mini-slots in the subframe supports the (ω+1)th round of cyclic retransmission, i.e. At this point, the remaining number of mini time slots is

[0103]

[0104] Let β = Q + (1)P, then the probability of packet loss after one round of retransmission on demand and then another round of retransmission is:

[0105]

[0106] at this time

[0107] R HR (L ω Nω )=1-p ω

[0108] Right now

[0109]

[0110] The online selection mechanism based on reliability analysis of on-demand retransmission and cyclic retransmission mechanisms is as follows:

[0111] If R CRDR (L ω N ω )≥R HR (L ω N ω ), at the start of the ωth retransmission round, a cyclic retransmission mechanism is used until the end of the subframe; if R CRDR (L ω N ω ) < R HR (L ω N ω In the ω-th retransmission round, an on-demand retransmission mechanism is used, and at the start of the next retransmission round, R is retransmitted. CRDR (L ω+1 N ω+1 ) and R GR (L ω+1 N ω+1 ) for comparison. Until the ωth * The conditions are met when the round-robin retransmission begins. Switch from on-demand retransmission to cyclic retransmission until the end of the subframe.

Claims

1. A method for hybrid retransmission on uplink of 5G network for industrial URLLC, characterized in that, The method comprises the following steps: Based on the uplink transmission network model, a 5G subframe structure supporting reliable retransmission is constructed; On the 5G subframe structure, a network working mechanism is constructed, and uplink data retransmission is carried out based on the network working mechanism; The network working mechanism comprises reliability analysis of on-demand retransmission mechanism and cyclic retransmission mechanism and online selection mechanism based on reliability analysis of on-demand retransmission mechanism and cyclic retransmission mechanism, specifically: At the start of each retransmission round, the transmission reliability of the on-demand retransmission mechanism is calculated. Furthermore, it addresses the reliability of the cyclic retransmission mechanism. Reliability of "retransmit on demand, one round, then retransmit in a loop" The comparisons are made to select the retransmission mechanism with higher reliability; among which In the first The number of user devices that need to retransmit during round-robin retransmission. This represents the remaining number of mini-slots; Cyclic retransmission mechanism transmission reliability The analysis includes three cases, where The cyclic retransmission mechanism reliability for each case starts from the first Cyclic retransmission mechanism reliability from the start of the first retransmission to the end of the subframe: Case 1: the number of user equipments requiring retransmission is 0, i.e. then ； Case 2: the number of user equipments requiring retransmission is less than or equal to the number of resource units in one mini-slot, i.e. then ； wherein Pul is the packet error rate for the uplink, Pdl is the packet error rate for the downlink; Case 3: the number of user equipments requiring retransmission is greater than the number of resource units in one mini-slot, i.e. , then the number of retransmission times of each data packet from the start of the nth round of retransmission to the end of the subframe is at least ； Cyclic retransmission The number of data packets of the next ； Then, the first The round robin retransmission reliability is ； Comprehensive cases 1, 2 and 3, the overall reliability of the cyclic retransmission process is 。 2. The method of claim 1, wherein the method further comprises: The uplink transmission network model is composed of a single base station and a user equipment, wherein: The user equipment sends uplink data with a period of to the base station, the time of the 5G network is composed of frames, one frame is divided into 10 subframes, each subframe is divided into slots, each slot contains 14 OFDM symbols, let two OFDM symbols be a mini-slot, the number of mini-slots in a subframe is , set the data period to 1 subframe, for a given parameter, ; Subcarrier spacing of a 5G network Decided by given parameters Decided, i.e. kHz; 12 subcarrier spacings in succession form a subcarrier with a bandwidth of ; A combination of one subcarrier and one mini-slot is a resource block (RB), and the data packet size is bits, the spectrum efficiency is bits / s / Hz, and the number of resource blocks occupied by each data packet is , represents rounding up, and resource blocks are recorded as one resource unit (RU), and a channel with a total bandwidth of is divided into RUs, wherein , represents rounding down, and there are RUs in each control period, and each data packet occupies one RU for transmission, and the data that is not successfully received by the base station at the end of the transmission period will be discarded.

3. The method of claim 1, wherein the method further comprises: The 5G subframe structure is composed of a first transmission period and a retransmission period, wherein: The first transmission period is that each user equipment sends a data packet to the base station by occupying one RU, and the length is ; The retransmission period is that the base station sends NACK and the user equipment retransmits the data packet to the base station; the base station occupies a mini-slot to send NACK to the user equipment, which contains the duration of the subframe, the scheduling list, the modulation and coding scheme and the scheduling list of the next round of transmission.

4. The method of claim 1, wherein the method further comprises: The on-demand retransmission mechanism allows the base station to send NACK at the beginning of each round of retransmission; if the user equipment receives NACK containing scheduling information that needs to be retransmitted, it means that the user equipment failed to transmit information in the last round of retransmission, and the user equipment that failed to transmit will occupy the reserved RU in NACK for retransmission.

5. The industrial URLLC oriented 5G network uplink hybrid retransmission method of claim 1, wherein, The cyclic retransmission mechanism does not require NACK, and all communication resources are used for retransmission of user equipment; after the user equipment receives the scheduling table sent by the base station, the pre-allocated RU is used to transmit the data packet, and whether the data packet is successfully transmitted, each user equipment will occupy the remaining pre-allocated resources in the subframe to continue transmitting the data packet until the end of the subframe.

6. The industrial URLLC oriented 5G network uplink hybrid retransmission method of claim 1, wherein, The on-demand retransmission mechanism ensures transmission reliability. The analysis includes two cases, among which For each case from the first Reliability of the on-demand retransmission mechanism from the start of round-robin retransmission to the end of the subframe: Case 1: The number of mini-slots left in the subframe is just enough to complete the 1st retransmission on demand, i.e. then ； Case 2: The number of mini-slots left in the subframe is not enough to complete the 1st round of retransmission on demand, i.e. , the subframe will end in the process of retransmission on demand, the user equipment with retransmission opportunity will occupy all the remaining resource units for retransmission, at this time, the 1st round of retransmission is equivalent to a cycle of retransmission, then ； ； Comprehensive cases 1 and 2, the overall reliability of the on-demand retransmission process is 。 7. The industrial URLLC oriented 5G network uplink hybrid retransmission method of claim 1, wherein, The reliability of the "one round of retransmission on demand - retransmission recycling" The analysis includes two cases: Case 1: The number of mini-slots left in the subframe is just enough to perform the first retransmission on demand, i.e. then ； Case 2: The number of mini-slots remaining in the subframe supports performing the first round-robin retransmission, i.e. The number of mini-slots remaining is ； Let the probability of retransmitting a packet after one round of on-demand retransmission and then recycling the packet be ； At this time ； That is 。 8. The industrial URLLC oriented 5G network uplink hybrid retransmission method of claim 1, wherein, The online selection mechanism, specifically: like In the At the start of round-robin retransmission, a circular retransmission mechanism is used until the end of the subframe; if In the The round-robin retransmission process employs an on-demand retransmission mechanism, and retransmission is performed again at the start of the next round of retransmission. Compare, up to the first The conditions are met when the round-robin retransmission begins. Switch the on-demand retransmission mechanism to the cyclic retransmission mechanism until the end of the subframe.

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