Non-orthogonal multiple access semi-authorization-free multi-user transmission method for ensuring fair access

Abstract

The invention provides a non-orthogonal multiple access semi-authorization-free multi-user transmission method for ensuring fair access, and belongs to the field of semi-authorization-free wireless network transmission scheduling. And the base station BS determines the maximum user number K in each time slot according to the maximum interference power I tolerated by the authorized user and a preset receiving signal-to-noise ratio SNR. And then, the base station determines K unlicensed users (GFUs) which do not complete transmission by using a distributed competition method, and determines the unlicensed users which finally access the network in the time slot through a designed power matching scheme. The base station adopts a serial interference cancellation (SIC) decoding mode, and the SNR of each GFU is a preset level, so that the information of each GFU can be successfully decoded. And the successfully transmitted GFU is kept silent in the round and is not accessed any more. According to the method, the user access fairness is effectively guaranteed, and the average information age AAoI of the system is remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the field of semi-unlicensed wireless network transmission scheduling, and relates to a non-orthogonal multiple access semi-unlicensed multi-user transmission method for ensuring fair access. Background Art

[0002] With the large-scale application of Internet of Things technology, more and more devices need to send short packet data through wireless networks. These data packets are bursty, resulting in the access of devices being restricted by available spectrum resources in wireless networks using traditional orthogonal multiple access technologies, making it difficult to meet the needs of large-scale device access. To improve system capacity and achieve key performance indicators such as low-latency access, non-orthogonal multiple access technology superimposes the signals of multiple users in the time domain and frequency domain through differential channel state information and power allocation, distinguishes them in the power domain, and decodes and eliminates signals one by one through the successive interference cancellation (SIC) technology. However, in practical applications, due to hardware device limitations, the SIC technology process often retains part of the power of the decoded signal, affecting the performance of subsequent decoded users. At the same time, Internet of Things devices mainly transmit short packet data, and the traditional guaranteed-by-authorization transmission (GB) protocol designed for long packet data is inefficient in this scenario because it requires a long handshake process, resulting in signaling overhead equivalent to the short packet data volume and reducing spectrum efficiency.

[0003] Therefore, the unlicensed transmission (GF) protocol becomes a more suitable choice, eliminating the handshake process and reducing latency and additional overhead. However, due to the limited reserved unlicensed spectrum resources and the inability of the base station to effectively control user access, transmission conflicts are likely to occur, restricting system performance. To integrate the advantages of the guaranteed-by-authorization transmission (GB) protocol and the unlicensed transmission (GF) protocol, scholars have proposed a semi-unlicensed transmission protocol, where some users transmit data through the GB protocol and other users access the channels of authorized users through the GF protocol. By reasonably designing the access rules for unlicensed users, interference can be controlled while avoiding conflicts between users, thereby achieving fast access with low overhead. However, when faced with a large number of unlicensed users, users who can access the channel need to be carefully selected, and scheduling methods include random selection and greedy scheduling, etc., but there may be problems of unfair user scheduling.

[0004] In the prior art, for example, a method for multi-user transmission scheduling in a semi-persistent grant network to ensure non-orthogonal multiple access is disclosed in Chinese Patent Application No. 202410585369.7. The drawback of this patent is that all time slots select the grant-free transmission GF protocol users with the best channels from all M users to access the network. This will cause users closer to the base station (due to smaller path loss) to be more easily scheduled, while users at the cell edge are difficult to access and be scheduled due to large path loss. At the same time, this patent only considers the case of ideal successive interference cancellation SIC in non-orthogonal multiple access, which does not conform to the non-ideal characteristics of devices in actual application scenarios. Summary of the Invention

[0005] In view of the problems in the prior art, the present invention proposes a non-orthogonal multiple access semi-persistent grant multi-user transmission method to ensure fair access. In the present invention, one user uses the traditional grant-based transmission GB protocol for data transmission, called the grant-based user GBU, while several other users use the grant-free transmission GF protocol to access the channel of the grant-based user GBU, called the grant-free users GFU. In this network, there are two types of users: one is the grant-based user GBU that ensures access to the network through the traditional grant protocol, and the other is the grant-free user GFU that accesses the network through the grant-free protocol.

[0006] While improving the fairness of user access, the present invention effectively reduces the average age of information AAoI of the system, ensures that grant-free users GFU with poor channel conditions can also obtain fair access opportunities, and provides an important technical reference for the design of multi-user scheduling methods in semi-persistent grant networks.

[0007] To achieve the above object, the technical method adopted by the present invention is as follows:

[0008] A non-orthogonal multiple access semi-persistent grant multi-user transmission method to ensure fair access. The semi-persistent grant transmission network includes two types of users, the grant-based user GBU that accesses the network based on the traditional grant-based transmission GB protocol and the grant-free user GFU that accesses the network based on the grant-free transmission GF protocol. The number of time slots required for all grant-free users GFU to complete one data update is called a transmission round, and it includes the following steps:

[0009] S1: In each time slot, the base station BS determines the grant-based user GBU communicating in this time slot based on the traditional grant protocol. To ensure the performance of the grant-based user GBU, the signal of the grant-based user GBU is decoded first at the receiving end. Assuming that there are a total of M grant-free users GFU who wish to access the channel, before selecting the grant-free users GFU accessing the network in this time slot, the base station BS needs to determine the maximum number K of grant-free users GFU allowed to access the channel of the grant-based user GBU in this time slot according to the principle of non-ideal successive interference cancellation SIC;

[0010] S1.1: At the beginning of each time slot, the base station BS sends pilot signals to the authorized user GBU and all the unauthorized users GFU. All users obtain their respective channel state information by measuring the pilot signals. The authorized user GBU feeds back its target rate R 0 and the effective received SNR to the base station BS, where ρ B is the transmission SNR of the authorized user GBU, and h B are the channel coefficients of the authorized user GBU respectively. After receiving the target rate R 0 and the effective received SNR of the authorized user GBU, the base station BS can determine the maximum interference power I that the authorized user GBU can tolerate. The maximum interference power I is calculated based on the successful decoding of the signal of the authorized user GBU at the base station BS first;

[0011] S1.2: According to the non-ideal successive interference cancellation (SIC) decoding rule, the target rate R of the unauthorized user GFU, and the maximum interference power I that the authorized user GBU can tolerate, the base station BS sets a series of received SNR levels These received SNR levels will be assigned to the unauthorized users GFU accessing the channel of the authorized user GBU in this time slot;

[0012] S1.3: According to the received SNR levels set by the base station BS and the maximum interference power I that the authorized user GBU can tolerate, the base station BS can determine the maximum number of users K that the channel of the authorized user GBU allows to access in this time slot;

[0013] S2: After determining the maximum number of users K that the channel of the authorized user GBU allows to access in this time slot and the received SNR levels set by the authorized user GBU, the base station BS needs to determine the specific unauthorized users GFU that can access the channel of the authorized user GBU and allow them to transmit data;

[0014] S2.1: The base station BS uses a distributed competition method to select K unauthorized users GFU with the largest effective received SNR that have not completed data update;

[0015] S2.2: After the base station BS uses the distributed competition technique to select the maximum number of users K unauthorized users GFU, it performs power matching on U (n) and the preset received SNR levels in S1.2 , where U (n) represents the unauthorized user GFU with the n-th weakest received SNR among the selected maximum number of users K unauthorized users GFU;

[0016] S2.3: Receive the n-th weakest grant-free user GFUU in terms of SNR (n) Compare with the received SNR level set by the base station BS After power matching, check one by one from U(1) to U (the maximum number of users K) whether their maximum effective received SNR is greater than the corresponding matched received SNR level If the maximum effective received SNR of all grant-free users GFU is greater than the matched received SNR level Then the power matching is completed, go to S2.4; otherwise, remove the grant-free user GFU with the lowest received SNR from the selected grant-free users GFU, and go to S2.2;

[0017] S2.4: The base station BS broadcasts the finally selected grant-free users GFU and their matched power levels The size indicates that the base station BS allows these grant-free users GFU to utilize their matched received SNR levels to access the channel. The transmit SNR of these grant-free users GFU is is the received SNR level at the receiving end of the base station BS, h i is the channel coefficient of this grant-free user GFU;

[0018] S2.5: After determining the grant-free users GFU that can access the channel of the grant-bearing user GBU, within the remaining time of this time slot, the grant-free users GFU use the channel of the grant-bearing user GBU to send data to the base station BS together with the grant-bearing user GBU, while the grant-free users GFU that are not selected or not successfully matched remain silent until the next time slot and then try to access the channel of the grant-free users GFU again;

[0019] S3: At the beginning of the next time slot, the base station BS resends the pilot signal, and its scheduling process is still divided into two stages for scheduling as described in S1~S2. When all grant-free users GFU have completed one data update, this transmission round ends and a new transmission round starts, and all grant-free users GFU are re-labeled as grant-free users GFU that have not completed data update.

[0020] Preferably, the maximum interference power I described in S1.1 should satisfy:

[0021]

[0022] where represents the SNR size required to successfully decode the signal of the grant-bearing user GBU, R 0 is the target rate of the grant-bearing user GBU. Here, through the transmit SNR ρ of the grant-bearing user GBU B and the channel coefficient h of the grant-bearing user GBU BSetting the maximum interference power I ensures the stable operation of the entire system.

[0023] Preferably, the receiving SNR level set by the base station BS in S1.2 The calculation method is as follows:

[0024]

[0025] Where R is the target rate of all grant-free users GFU. Assuming that all grant-free users GFU are of the same type and have the same target rate R, c is the residual power coefficient of the non-ideal successive interference cancellation SIC technology. Based on the non-ideal successive interference cancellation SIC decoding rule, cρ B |h B | 2 represents the partial power remaining in the decoding of the SNR transmitted by the grant-based user GBU, represents the partial power remaining in the signal decoded before the nth signal decoding, represents the SNR required for decoding the last grant-free user GFU, represents the SNR required for decoding the signal of the i-th grant-free user GFU from the bottom. n represents the serial number of each target receiving SNR level According to the principle of successive interference cancellation SIC in the non-orthogonal multiple access network, the SNR of the signal decoded first needs to be greater than the SNR of the signal decoded later, that is Here, this calculation method considers the residual power coefficient c of the non-ideal successive interference cancellation SIC to design the receiving SNR level such that the receiving SNR level is more in line with the non-ideal characteristics of the devices in the actual application scenario.

[0026] Preferably, the maximum number of users K of the grant-free users GFU allowed to access in S1.3 satisfies the following conditions:

[0027] Where M is the total number of grant-free users GFU to communicate, and μ is the number of grant-free users GFU that have completed data update before this transmission round. Therefore, the maximum number of users K allowed to access needs to be less than M - μ, It means that the sum of the receiving SNRs of all grant-free users GFU accessing the channel needs to be less than the maximum interference power I of the grant-based user GBU. Through formula (2) and formula (3), the maximum number of users K of the grant-free users GFU that can access in this time slot can be calculated. In particular, when That is, the receiving SNR level of the transmitted signal that needs to be set for serving a single grant-free user GFU When the maximum interference power I of the authorized user GBU is exceeded, no unauthorized user GFU can access the channel. At this time, the maximum number of users K = 0. Here, the maximum number of users K needs to be less than M - μ, that is, considering that users who have completed transmission will not access again, which improves the fairness of the system. At the same time, the sum of the received SNR of all unauthorized users GFU accessing the channel needs to be less than the maximum interference power I of the authorized user GBU, ensuring that the authorized user GBU channel can still maintain sufficient interference tolerance ability after multiple unauthorized users GFU are connected, so as to avoid signal decoding failure.

[0028] Preferably, the distributed competition method described in S2.1 means that each unauthorized user GFU hoping to access the channel needs to set a backoff time at the beginning of each time slot. Here, it is assumed that the backoff time of the i-th unauthorized user GFU is τ i , and the base station broadcasts a competition time window τ max . If the backoff time τ i of the i-th unauthorized user GFU is less than a competition time window τ max broadcast by the base station, then the i-th unauthorized user GFU will send a beacon to the base station BS at the backoff time τ i of the i-th unauthorized user GFU, and set the backoff time τ i of the i-th unauthorized user GFU as a decreasing function of the maximum effective received SNR of the unauthorized user GFU. The unauthorized user GFU that has completed data update will not participate in the distributed competition and will always remain silent. By applying the distributed competition technology, the base station BS can obtain the relative magnitude of the maximum received SNR of the unauthorized user GFU, and at the same time, through the backoff time τ i of the i-th unauthorized user GFU, the maximum received SNR values of these users can be inversely deduced. Only the users whose inversely deduced maximum received SNR values are greater than the required to decode the last unauthorized user GFU will participate in the power matching, otherwise they will be discarded by the base station BS. Here, the setting of the backoff time makes the access opportunity of each user more fair. Users with good channel quality can access as early as possible, ensuring their network experience, while users with poor channel quality will not affect their access opportunities due to excessive competition. The backoff mechanism enables them to access the network in a later time slot, thus avoiding the situation where users with poor signals cannot access. This design avoids concentrating all competition pressures in one time slot, effectively avoiding excessive competition for network resources, and thus improving the fairness of the overall system.

[0029] Preferably, the base station BS described in S2.1 uses the distributed competition technology to determine that the maximum received SNR in a certain time slot is greater than the The maximum number of users is K grant-free users (GFUs). When there are more than K users whose maximum received SNR is greater than that required for decoding the last grant-free user (GFU), the base station (BS) will select the maximum number K of users with the maximum effective received SNR. Therefore, the number k of grant-free users (GFUs) that can access each time slot satisfies k ≤ the maximum number K. Subsequently, the BS needs to perform power matching for the SNR levels of the k grant-free users (GFUs) that can access each time slot and the SNR levels of the maximum number K of received SNRs. Only the grant-free users (GFUs) that successfully match can finally access the channel. At the same time, these grant-free users (GFUs) that access the channel will be regarded as grant-free users (GFUs) that have completed data update and will remain silent in the remaining time slots of this transmission round. Here, this method preferentially selects users with the maximum received SNR to ensure that users with better signal conditions can access the network first to maximize system performance, while avoiding some users continuously accessing in multiple time slots, thus over-occupying system resources.

[0030] Preferably, in S2.3, check one by one from U(1) to U(the maximum number K) whether their maximum effective received SNR is greater than the corresponding matched received SNR level that is, whether it satisfies where is the maximum received SNR of the grant-free user (GFU), and h (n) is the channel coefficient of this grant-free user (GFU). Here, by calculating the maximum effective received SNR of the grant-free user (GFU), it is determined whether this grant-free user (GFU) meets the condition for accessing in this time slot, which is determined by the parameters of the grant-free user (GFU) itself, ensuring the fairness of system operation.

[0031] Preferably, in S2.5, the grant-free user (GFU) uses the channel of the grant-based user (GBU) to send data to the base station (BS) together with the grant-based user (GBU). After receiving the signals sent by the grant-based user (GBU) and multiple grant-free users (GFUs), the BS uses the non-ideal successive interference cancellation (SIC) decoding rule for decoding. Since the SNR of each grant-free user (GFU) received at the BS is the pre-designed received SNR level therefore, it can be ensured that each grant-free user (GFU) accessing the channel can be successfully decoded during the decoding process. Here, decoding according to the SIC decoding rule avoids the situation where the grant-free user (GFU) accessing the channel does not have a matched received SNR level to ensure the stability of system operation.

[0032] Preferably, the scheduling process in S3 is still divided into two stages for scheduling as described in S1 - S2. Among them, S1 - S1.3 is for the base station BS to determine the maximum number of users K that the authorized users GBU in this time slot are allowed to access the channel, and S2 - S2.4 is for the base station BS to determine the specific unauthorized users GFU to access and transmit data. Here, through the scheduling of two stages, it is ensured that all unauthorized users GFU can access in one time slot, ensuring the fairness of the system.

[0033] The beneficial effects of the present invention are as follows:

[0034] A non - orthogonal multiple access semi - grant - free multi - user transmission method for ensuring fair access provided by the present invention, on the one hand, sets a series of received SNR levels for the non - ideal successive interference cancellation (SIC) technology to be assigned to the accessed grant - free users GFU to determine the decoding order and ensure that all accessed grant - free users GFU can successfully decode. On the other hand, it restricts each grant - free user GFU to transmit data only once in each transmission round, enabling users with poor channel conditions to have the opportunity to communicate. At the same time, it also uses distributed competition technology and multi - user scheduling algorithms to allow the selected grant - free users GFU to match a more reasonable received SNR level Thus, it is possible to ensure fairness in access while reducing the system's average age of information (AAoI), providing an important technical reference for the design of user scheduling methods in semi - grant - free networks. Brief Description of the Drawings

[0035] Figure 1 A schematic diagram of a non - orthogonal multiple access semi - grant - free multi - user transmission network for ensuring fairness; among them, 1 is the aerial base station, 2 is the authorized user, and 3 is the grant - free user.

[0036] Figure 2 A schematic diagram of a non - orthogonal multiple access semi - grant - free multi - user transmission method for ensuring fair access;

[0037] Figure 3 The average age of information (AAoI) of the grant - free user GFU in the present invention varies with the maximum transmit power Pmax of the grant - free user GFU;

[0038] Figure 4 The average age of information (AAoI) of the grant - free user GFU in the present invention varies with the number M of grant - free users GFU;

[0039] Figure 5 The average age of information (AAoI) of the grant - free user GFU in the present invention varies with the transmission rate R of the grant - free user GFU;

[0040] Figure 6 The average age of information (AAoI) of the grant - free user GFU in the present invention varies with the distribution range of the grant - free user GFU. Detailed implementation manners

[0041] In the present invention, a non-orthogonal multiple access semi-persistent multi-user transmission method for ensuring fair access is proposed. The application scenario is shown in Figure 1 , and the schematic diagram of the specific scheduling method is shown in Figure 2 . In this method, by designing to ensure a non-ideal successive interference cancellation (SIC) technology to preset a series of received SNR levels γ n (K) and a multi-user power matching algorithm to ensure successful decoding, the average age of information (AAoI) of the grant-free users (GFUs) is effectively improved, providing an important technical reference for the design of the user scheduling method in the semi-persistent network. To better understand the above method, the following will combine the accompanying drawings of this specification with specific implementation examples to illustrate the detailed experimental results.

[0042] Example 1

[0043] Please refer to Figure 1 , a non-orthogonal multiple access semi-persistent multi-user transmission method for ensuring fair access. First, consider an Internet of Things network assisted by a drone, where the drone serves as the base station (BS). There is one grant-based user (GBU) and M = 8 grant-free users (GFUs) on the ground waiting to access the network. The target transmission rate of both types of users is R = R0 = 1 bit / s / Hz. Regarding the channel, the combined influence of large-scale fading and small-scale fading is considered. In large-scale fading, the flight altitude of the base station BS is set to H = 200 m, and the users are randomly distributed in a circular area with a radius of 200 m, and the path loss coefficient is α = 3.8. For small-scale fading, the Nakagami-m distribution is considered, and the channel parameter is set to m = 2, Ω = 1.

[0044] Please refer to Figure 2 , at the beginning of each time slot, each user first estimates its own channel state information through the pilot signal sent by the base station BS, and the grant-based user GBU sends its target rate and effective received SNR to the base station BS. The base station BS calculates the maximum number of grant-free users GFU that the grant-based user GBU can allow to access, i.e., the maximum number of users K, based on the target rate and effective received SNR of the grant-based user GBU. At the same time, by using a distributed contention technology, the base station BS can calculate the maximum received SNR of each grant-free user GFU according to the time when each grant-free user GFU that has not completed data transmission in this transmission round sends a beacon. Further, the base station BS can determine the grant-free users GFU that finally access the channel and their corresponding base station BS received SNR levels and the received SNR levels Broadcast the unlicensed user GFU numbers that can access the channel. At the same time, each unlicensed user GFU calculates its transmission power according to the matched received SNR level The unlicensed user GFUs that are not accessing the channel and the unlicensed user GFUs that have communicated in this round remain silent. Assume that the maximum transmission power Pmax of the unlicensed user GFU varies between -5 dBm and 15 dBm, and the transmission power of the licensed user GBU is ten times that of Pmax. At the receiving end, the base station BS uses SIC technology to decode the information sent by all users. Among them, the signal of the licensed user GBU is decoded first, and the unlicensed user GFU with a higher matched received SNR level has its signal decoded earlier.

[0045] Please refer to Figure 3 , first, the impact of the maximum transmission power of the unlicensed user GFU on the AAoI of the unlicensed user GFU is analyzed. As the transmission power of the unlicensed user GFU increases, the AAoI of the unlicensed user GFU decreases. At the same time, compared with the greedy scheduling method that schedules the unlicensed user GFU with the best channel state information in each time slot, the proposed fairness - ensuring scheduling method can effectively improve the AAoI of the unlicensed user GFU to enhance the overall communication performance of the system. At the same time, the results of this figure also show that the results of the theoretical analysis are in good agreement with the results of the simulation experiment.

[0046] Furthermore, please refer to Figure 4 , in Figure 4 , the impact of the total number of unlicensed user GFUs on the AAoI of the unlicensed user GFU is studied. The transmission power is set to P max = 0 dbm. It can be seen that as the total number of unlicensed user GFUs increases, the AAoI of the unlicensed user GFU also increases. This is because, on the premise of constant transmission power, the number of unlicensed user GFUs that the licensed user GBU can support in each time slot is a relatively stable value. And the increase in the total number of unlicensed user GFUs makes it take more time slots to complete one - time data transmission of all unlicensed user GFUs in one transmission round, thus resulting in an increase in the AAoI of the unlicensed user GFU. Next, please refer to Figure 5 , in Figure 5 , the impact of the transmission rate of the unlicensed user GFU on the AAoI of the unlicensed user GFU is simulated. It can be seen that as the transmission rate of the unlicensed user GFU increases, the AAoI of the unlicensed user GFU also increases. This is because the increase in the transmission rate of the unlicensed user GFU requires a corresponding increase in each received SNR level , which makes the total number of unlicensed user GFUs that the licensed user GBU can allow to access and the received SNR levels that can be matched The number of grant-free users GFU has decreased, resulting in an increase in the AAoI of grant-free users GFU.

[0047] Embodiment 2

[0048] The present invention provides a method for enabling instant communication among a large number of grant-free users GFU with significantly different channel states and ensuring fairness. Since each grant-free user GFU needs to communicate once in a transmission round, the method can also be used to schedule a number of grant-free users GFU with significantly different distances to the base station BS to ensure the overall freshness of information.

[0049] Specifically, in a drone-assisted Internet of Things network, where the drone serves as the base station BS, there is one authorized user GBU and M = 4 grant-free users GFU on the ground waiting to access the network to transmit data. The transmission rate of both types of users is R = R0 = 1 bit / s / Hz. In terms of the channel, the combined effects of large-scale fading and small-scale fading are considered. In large-scale fading, the flight altitude of the base station BS is set to H = 200m, and the four users are randomly distributed in a circular area of 0 - 150m, an annular area of 150 - 200m, an annular area of 200 - 250m, and an annular area of 250 - 300m. The path loss coefficient is α = 3.8. For small-scale fading, the Nakagami-m distribution is considered, and the channel parameters are set to m = 2 and Ω = 1.

[0050] At the beginning of each time slot, each user needs to first estimate its own channel state information through the pilot signal sent by the base station BS. And the authorized user GBU needs to send its target rate and effective received SNR to the base station BS. The base station BS calculates the maximum number of grant-free users GFU, the maximum number of users K, that the authorized user GBU can allow to access in this time slot based on the target rate and effective received SNR of the authorized user GBU. Meanwhile, using a distributed competition technique, the base station BS can calculate the maximum received SNR of each grant-free user GFU based on the time when each grant-free user GFU that has not completed data transmission in this transmission round sends a beacon. Further, the base station BS can determine the grant-free users GFU that finally access the channel and their corresponding received SNR levels by executing a power matching algorithm. The base station BS will send the numbers of the grant-free users GFU that can be accessed and their received SNR levels And perform broadcasting. At the same time, each license-free user GFU can calculate its transmission power according to the matched received SNR level, and the license-free users GFU that have not accessed the channel and have communicated in this round remain silent. Assume that the maximum transmission power Pmax of the license-free user GFU varies between -5 dBm and 15 dBm, and the transmission power of the licensed user GBU is ten times that of Pmax. At the receiving end, the base station BS uses non-ideal SIC technology to decode the information sent by all users. Among them, the signal of the licensed user GBU is decoded first, and the signal of the license-free user GFU with a higher matched received SNR level is decoded earlier. The higher the matched received SNR level of the license-free user GFU, the earlier its signal is decoded.

[0051] Please refer to Figure 6 , Figure 6 for the respective AAoIs of these users with different distances. It can be seen that in the greedy scheduling method of scheduling the license-free user GFU with the best channel state information in each time slot, the AAoI of the user will increase rapidly as the distance from the user to the base station BS increases. However, the method can ensure that the AAoI does not change too much as the distribution distance increases. This is because the method can avoid the users with better channel state information from repeatedly accessing the channel multiple times within a transmission round, which can ensure fairness and thus ensure that the AAoI does not change much with the distribution radius.

[0052] The above embodiments only represent the implementation manners of the present invention, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those skilled in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A non-orthogonal multiple access semi-unlicensed multi-user transmission method for ensuring fair access, wherein the semi-unlicensed transmission network includes two types of users, namely, licensed users GBU accessing the network based on the traditional licensed transmission GB protocol and unlicensed users GFU accessing the network based on the unlicensed transmission GF protocol, and the number of time slots required for all unlicensed users GFU to complete a data update is called a transmission round, characterized in that: The following steps are involved: S1: In each time slot, the base station BS determines the authorized user GBU for communication in the time slot based on the traditional authorization protocol. To ensure the performance of the authorized user GBU, the signal of the authorized user GBU is first decoded at the receiving end. Assuming that there are M unauthorized users GFU who want to access the channel, before selecting the unauthorized user GFU to access the network in the time slot, the base station BS needs to determine the maximum number of unauthorized users GFU K allowed to access the channel of the authorized user GBU in the time slot based on the non-ideal serial interference elimination SIC principle; S1.1: At the beginning of each time slot, the base station BS sends a pilot signal to the authorized user GBU and all unauthorized users GFU. All users obtain their own channel state information by measuring the pilot signal. The authorized user GBU sets its target rate R0 and effective received SNRρ B |h B | 2 Feedback to the base station BS, where ρ B is the sending SNR of the authorized user GBU, h B are the channel coefficients of the authorized user GBU respectively. After receiving the target rate R0 and the effective receiving SNR of the authorized user GBU, the base station BS can determine the maximum interference power I that the authorized user GBU can tolerate. The maximum interference power I is calculated based on the signal of the authorized user GBU being successfully decoded at the base station BS. S1.2: The base station BS sets a series of receiving SNR levels according to the non-ideal serial interference cancellation SIC decoding rules, the target rate R of the unlicensed user GFU, and the maximum interference power I that the licensed user GBU can tolerate. These receive SNR levels The unlicensed user GFU that will be assigned to the licensed user GBU channel in this time slot; S1.3: According to the receiving SNR level set by the base station BS With the maximum interference power I that the authorized user GBU can tolerate, the base station BS can determine the maximum number of users K that are allowed to access the channel of the authorized user GBU in this time slot; S2: Determine the maximum number of users K allowed to access the channel of the authorized user GBU in this time slot and the receiving SNR level set by the authorized user GBU After that, the base station BS needs to determine the specific unlicensed users GFU users that can access the licensed user GBU channel and allow them to transmit data; S2.1: The base station BS uses a distributed contention method to select K unlicensed users GFU with the largest effective receiving SNR that have not completed data updates; S2.2: The base station BS uses the distributed contention technology to select the maximum number of users K license-free users GFU and then (n) The received SNR level preset in S1.2 Power matching is performed, where U (n) Indicates selecting the unlicensed user GFU with the nth weakest receiving SNR among the unlicensed user GFUs with the maximum number of users K; S2.3: Receive the nth weakest SNR unlicensed user GFUU (n) The receiving SNR level set by the base station BS After power matching, check whether the maximum effective receiving SNR of each of U(1) to U(maximum number of users K) is greater than the corresponding matching receiving SNR level. If the maximum effective receiving SNR of all unlicensed user GFUs is greater than the matched receiving SNR level If the power matching is completed, go to S2.4, otherwise, remove the unlicensed user GFU with the lowest received SNR from the selected unlicensed user GFUs, and go to S2.2; S2.4: The base station BS broadcasts the finally selected unlicensed user GFU and its matching power level The size of indicates that the base station BS allows these unlicensed users GFU to use their matching receiving SNR level Access channel, the transmit SNR of these unlicensed user GFUs is is the receiving SNR level of the base station BS, h i is the channel coefficient of the unlicensed user GFU; S2.5: After determining the unlicensed user GFU that can access the authorized user GBU channel, the unlicensed user GFU uses the authorized user GBU channel to send data to the base station BS together with the authorized user GBU during the remaining time of the time slot, while the unlicensed user GFU that is not selected or matched successfully remains silent until the next time slot and then tries to access the unlicensed user GFU channel; S3: At the beginning of the next time slot, the base station BS resends the pilot signal, and its scheduling process is still divided into two stages as described in S1 to S2. When all unlicensed users GFU have completed a data update, the transmission round ends and a new transmission round begins. All unlicensed users GFU are re-marked as unlicensed users GFU that have not completed data update.

2. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: The maximum interference power I mentioned in S1.1 should meet the following requirements: in, It indicates the SNR required to successfully decode the authorized user GBU signal, and R0 is the target rate of the authorized user GBU.

3. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: The receiving SNR level set by the base station BS in S1.2 The calculation method is: Where R is the target rate of all unlicensed users GFU. It is assumed that all unlicensed users GFU are of the same type and have the same target rate R. c is the residual power coefficient of the non-ideal serial interference cancellation SIC technology. Based on the non-ideal serial interference cancellation SIC decoding rule, cρ B |h B | 2 Indicates the remaining power of the authorized user GBU when sending SNR during decoding. represents the residual power of the signal decoded before the nth signal is decoded, Indicates the SNR required to decode the last unlicensed user GFU. represents the SNR required to decode the GFU signal of the penultimate unlicensed user, and n represents the SNR level of each target receiver. According to the principle of serial interference cancellation (SIC) in non-orthogonal multiple access networks, the SNR of the first decoded signal must be greater than the SNR of the later decoded signal, that is, 4. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: The maximum number of users K of the unauthorized user GFU allowed to access as described in S1.3 satisfies the following conditions: Where M is the total number of unlicensed users GFU to communicate, and μ is the number of unlicensed users GFU that have completed data update before this time slot in this transmission round. Therefore, the maximum number of users K allowed to access must be less than M-μ. The sum of the received SNRs of all unlicensed users GFU accessing the channel must be less than the maximum interference power I of the licensed user GBU. The maximum number of users K that can access the unlicensed user GFU in this time slot can be calculated by formula (2) and formula (3). In particular, when That is, the receiving SNR level of the sending signal that needs to be set by the GFU user serving a single unlicensed user When it is greater than the maximum interference power I of the authorized user GBU, no unauthorized user GFU can access the channel. At this time, the maximum number of users K=0.

5. The method for ensuring fair access to non-orthogonal multiple access semi-grant-free multi-user transmission according to claim 1, characterized in that: The distributed contention method described in S2.1 means that each unlicensed user GFU that wants to access the channel needs to set a backoff time at the beginning of each time slot. Here, it is assumed that the backoff time of the i-th unlicensed user GFU is τ i , the base station broadcasts a contention time window τ max , if the backoff time τ of the i-th unauthorized user GFU i If it is smaller than the base station, it will broadcast a contention time window τ max , then the i-th unauthorized user GFU will be within the backoff time τ of the i-th unauthorized user GFU i Then send a beacon to the base station BS and set the backoff time τ of the i-th unauthorized user GFU i is a decreasing function of the maximum effective receiving SNR of the unlicensed user GFU, and the unlicensed user GFU that has completed data update will not participate in the distributed competition and will remain silent. By applying the distributed competition technology, the base station BS can obtain the relative size of the maximum receiving SNR of the unlicensed user GFU and can also use the backoff time τ of the i-th unlicensed user GFU i The maximum received SNR value of these users is deduced inversely, and only the deduced maximum received SNR value is greater than the value required to decode the last unlicensed user GFU Only users with certain power can participate in power matching, otherwise they will be discarded by the base station BS.

6. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: The base station BS described in S2.1 uses the distributed contention technique to determine that the maximum received SNR in a certain time slot is greater than the required decoding time for the last unlicensed user GFU. The maximum number of users K is the unlicensed user GFU. When the maximum received SNR of users with more than the maximum number of users K is greater than the required decoding of the last unlicensed user GFU When , the base station BS will select the maximum number of users K with the largest effective receiving SNR, so the number of unlicensed users GFU that can access each time slot k ≤ the maximum number of users K. Then the base station BS needs to calculate the SNR level of the number of unlicensed users GFU k that can access each time slot and the maximum number of users K receiving SNR level Power matching is performed, and only the unlicensed user GFU that has successfully matched can finally access the channel. At the same time, these unlicensed user GFUs that access the channel will be regarded as unlicensed user GFUs that have completed data update and will remain silent in the remaining time slots of this transmission round.

7. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: As described in S2.3, from U(1) to U(maximum number of users K), check whether their maximum effective received SNR is greater than the corresponding matched received SNR level. Whether it satisfies in The maximum receiving SNR of the unlicensed user GFU, h (n) is the channel coefficient of the unlicensed user GFU.

8. The method for ensuring fair access to non-orthogonal multiple access semi-grant-free multi-user transmission according to claim 1, characterized in that: The unlicensed user GFU described in S2.5 uses the channel of the authorized user GBU to send data to the base station BS together with the authorized user GBU. After receiving the signals sent by the authorized user GBU and multiple unlicensed user GFUs, the base station BS uses the non-ideal serial interference elimination SIC decoding rule for decoding. Since the SNR of each unlicensed user GFU received at the base station BS is a pre-designed receiving SNR level Therefore, during the decoding process, it can be ensured that each unlicensed user GFU accessing the channel can be successfully decoded.

9. A non-orthogonal multiple access semi-grant-free multi-user transmission method for ensuring fair access according to claim 1, characterized in that: The scheduling process described in S3 is still divided into two stages as described in S1~S2, where S1~S1.3 is for the base station BS to determine the maximum number of users K allowed to access the channel of the authorized user GBU in the time slot, and S2~S2.4 is for the base station BS to determine the specific unauthorized user GFU to access and transmit data.

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