A non-orthogonal multiple access semi-grant-free multi-user transmission method ensuring fair access

Abstract

This invention provides a non-orthogonal multiple access (NMO) semi-unlicensed multi-user transmission method to ensure fair access, belonging to the field of semi-unlicensed wireless network transmission scheduling. In each time slot, the base station (BS) determines the maximum number of users K based on the maximum tolerable interference power I of licensed users and a preset received signal-to-noise ratio (SNR). Subsequently, the base station uses a distributed contention method to identify K unlicensed user units (GFUs) that have not completed transmission, and determines the unlicensed users who will ultimately access the network in this time slot through a designed power matching scheme. The base station employs a serial interference cancellation (SIC) decoding method. Since the SNR of each GFU is a preset level, it ensures that the information of each GFU can be successfully decoded. Successfully transmitted GFUs will remain silent in this round and will not access the network again. This method effectively guarantees the fairness of user access and significantly reduces the average information age (AAoI) of the system.

Description

Technical Field

[0001] This 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 that ensures fair access. Background Technology

[0002] With the large-scale application of IoT technology, more and more devices need to send short data packets via wireless networks. These data packets are bursty, causing device access in wireless networks using traditional orthogonal multiple access (OMA) technology to be limited by available spectrum resources, 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 (NMO) technology uses differentiated channel state information and power allocation to superimpose signals from multiple users in the time and frequency domains, while distinguishing them in the power domain, and then decodes and cancels the signals one by one using serial interference cancellation (SIC) technology. However, in practical applications, due to hardware limitations, the SIC process often leaves some power of the decoded signal, affecting the performance of subsequent decoded users. At the same time, IoT devices mainly transmit short data packets. The traditional Guaranteed Grant (GB) protocol, designed for long data packets, is inefficient in this scenario because it requires a lengthy handshake process, resulting in signaling overhead comparable to the amount of short data packets, thus reducing spectrum efficiency.

[0003] Therefore, the unlicensed transmission (GF) protocol becomes a more suitable choice, eliminating the handshake process and reducing latency and overhead. However, due to the limited reserved unlicensed spectrum resources and the inability of base stations to effectively control user access, transmission conflicts are prone to occur, limiting system performance. To combine the advantages of the licensed transmission (GB) protocol and the unlicensed transmission (GF) protocol, researchers have proposed a semi-unlicensed transmission protocol. In this protocol, some users transmit data using the licensed transmission (GB) protocol, while other users access the channels of licensed users using the unlicensed transmission (GF) protocol. By rationally designing the access rules for unlicensed users, interference can be controlled while avoiding conflicts between users, thus achieving low-overhead and fast access. However, when dealing with a large number of unlicensed users, careful selection of users who can access the channel is required. Scheduling methods include random selection and greedy scheduling, but these may lead to unfair user scheduling.

[0004] In the prior art, for example, Chinese patent application No. 202410585369.7 discloses a method for scheduling multi-user transmission in a semi-unlicensed network to ensure non-orthogonal multiple access. The shortcoming of this patent is that all time slots in this patent select the unlicensed transmission GF protocol user access network from all M users with the best channel. This will make it easier for users close to the base station (due to lower path loss) to be scheduled, while users at the cell edge are difficult to access and be scheduled due to higher path loss. At the same time, this patent only considers the case of ideal serial 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] To address the problems in existing technologies, this invention proposes a non-orthogonal multiple access (NMO) semi-unlicensed multi-user transmission method that ensures fair access. In this invention, one user uses the traditional licensed transport (GB) protocol for data transmission, referred to as a licensed user (GBU), while several other users use the unlicensed transport (GF) protocol to access the channel of the licensed user (GBU), referred to as unlicensed users (GFUs). In this network, there are two types of users: one is the licensed user (GBU) ensuring access to the network via the traditional licensed protocol, and the other is the unlicensed user (GFU) accessing the network via the unlicensed protocol.

[0006] This invention improves the fairness of user access while effectively reducing the average information age (AAoI) of the system, ensuring that unlicensed users (GFUs) 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-unlicensed networks.

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

[0008] A non-orthogonal multiple access (NMO) semi-unlicensed multi-user transmission method to ensure fair access is proposed. The semi-unlicensed transmission network includes two types of users: licensed users (GBUs) accessing the network based on the traditional licensed transmission (GB) protocol, and unlicensed users (GFUs) accessing the network based on the unlicensed transmission (GF) protocol. The number of time slots required for all unlicensed GFUs to complete one data update is defined as one transmission round. The method includes the following steps:

[0009] S1: In each time slot, the base station BS determines the licensed user GBU for communication in that time slot based on the traditional licensing protocol. To ensure the performance of the licensed user GBU, the signal of the licensed user GBU is first decoded at the receiving end. Assuming there are M unlicensed user GFUs that want to access the channel, before selecting the unlicensed user GFUs to access the network in that time slot, the base station BS needs to determine the maximum number of unlicensed user GFUs K that the licensed user GBUs are allowed to access the channel in that time slot based on the principle of non-ideal serial interference cancellation (SIC).

[0010] S1.1: At the beginning of each time slot, the base station (BS) sends pilot signals to licensed users (GBUs) and all unlicensed users (GFUs). All users obtain their respective channel state information by measuring the pilot signals. Licensed users (GBUs) set their target rate (R0) and effective reception... Feedback is sent to the base station (BS), where ρ B For authorized user GBU's transmitted SNR, h B These are the channel coefficients of the licensed user GBU. After receiving the target rate R0 and effective received SNR of the licensed user GBU, the base station BS can determine the maximum tolerable interference power I of the licensed user GBU. The maximum interference power I is calculated based on the successful decoding of the licensed user GBU's signal at the base station BS.

[0011] S1.2: Based on the non-ideal serial interference cancellation SIC decoding rules, the target rate R of the unlicensed user GFU, and the maximum tolerable interference power I of the licensed user GBU, the base station BS sets a series of receive SNR levels. These receive SNR levels Unlicensed user GFUs will be allocated to access the licensed user GBU channel in this time slot;

[0012] S1.3: Received SNR level set according to the base station (BS) configuration. Given the maximum tolerable interference power I of the licensed user GBU, the base station BS can determine the maximum number of users K that the licensed user GBU is allowed to access the channel in that time slot;

[0013] S2: Determine the maximum number of users K allowed to access the channel for the licensed user GBU in this time slot, and the receive SNR level set by the licensed user GBU. Afterwards, the base station (BS) needs to identify the specific unlicensed user (GFU) users who can access the authorized user (GBU) channel and allow them to transmit data;

[0014] S2.1: The base station (BS) uses a distributed contention method to select the K unlicensed users (GFUs) with the largest valid received SNR that have not yet completed data updates;

[0015] S2.2: After the base station (BS) selects the maximum number of unlicensed users (GFUs) using distributed contention technology, it will then assign U... (n) The received SNR level preset in S1.2 Perform power matching, where U (n) This indicates that the GFU with the weakest SNR among the maximum number of K unlicensed user GFUs is selected.

[0016] S2.3: Receive the nth weakest unlicensed user GFUU with SNR (n)Received SNR level set by base station (BS) After power matching, check each of U(1) to U(maximum number of users K) to see if its maximum effective received SNR is greater than the corresponding matched received SNR level. If the maximum effective received SNR of all unlicensed user GFUs is greater than the matched received SNR level If power matching is complete, proceed to S2.4; otherwise, remove the unlicensed user GFU with the lowest received SNR from the selected unlicensed user GFUs and proceed to S2.2.

[0017] S2.4: The base station (BS) broadcasts the final selected unlicensed user GFU and its matching power level. The size indicates that the base station (BS) allows these unlicensed user GFUs to utilize their matched receive SNR rating. Access channel, the transmit SNR of these unlicensed user GFUs is h represents the received SNR level of the base station (BS) receiver. i For the unlicensed user's GFU channel coefficients;

[0018] S2.5: After determining that an unlicensed user GFU can access the authorized user GBU channel, during the remaining time of the time slot, the unlicensed user GFU uses the authorized user GBU channel and sends data to the base station BS together with the authorized user GBU. The unlicensed user GFU that is not selected or fails to match remains silent until the next time slot and then tries to access the unlicensed user GFU channel.

[0019] S3: At the start of the next time slot, the base station BS retransmits the pilot signal. Its scheduling process is still divided into two stages as described in S1 to S2. When all unlicensed user GFUs have completed a data update, the transmission round ends and a new transmission round begins. All unlicensed user GFUs are remarked as unlicensed user GFUs that have not completed the data update.

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

[0021]

[0022] in, This represents the SNR required to successfully decode the authorized user GBU signal, where R0 is the target rate of the authorized user GBU. Here, it is determined by the transmitted SNRρ of the authorized user GBU. B Channel coefficient h with licensed user GBU B Setting the maximum interference power I ensures the stable operation of the entire system.

[0023] Preferably, the received 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 unlicensed user GFUs, assuming all unlicensed user GFUs are of the same type and have the same target rate R, and c is the residual power coefficient of the non-ideal serial interference cancellation (SIC) technique. Based on the SIC decoding rules, cρ B |h B | 2 This indicates the residual power of the SNR sent by the authorized user GBU during decoding. This represents the residual power of the signal decoded before the nth signal is decoded. This indicates the SNR required to decode the last unlicensed user's GFU. This represents the SNR required to decode the i-th unlicensed user GFU signal from the end, where n represents the SNR level of each target reception. According to the principle of Sequence Interference Cancellation (SIC) in non-orthogonal multiple access networks, the SNR of the first decoded signal must be greater than the SNR of the second decoded signal, i.e. Here, the calculation method considers the residual power factor c of the non-ideal serial interference cancellation SiC to design the receive SNR level. This makes the received SNR level It better reflects the non-ideal characteristics of devices in real-world application scenarios.

[0026] Preferably, the maximum number K of unauthorized user GFUs allowed to access as described in S1.3 satisfies the following condition:

[0027] Where M is the total number of unlicensed user GFUs waiting to communicate, and μ is the number of unlicensed user GFUs that have completed data updates before this time slot in this transmission round. Therefore, the maximum number of users allowed to access, K, must be less than M-μ. This means that the sum of the received SNRs of all unlicensed user GFUs accessing the channel must be less than the maximum interference power I of licensed user GFUs. The maximum number of unlicensed user GFUs that can access the channel in this time slot can be calculated using formulas (2) and (3). Specifically, when... That is, the received SNR level of the transmitted signal that needs to be set for a single unlicensed GFU user. When the interference power I of an unlicensed user GFU is greater than that of a licensed user GFU, no unlicensed user GFU can access the channel. In this case, the maximum number of users K = 0. Here, the maximum number of users K must be less than M-μ, which takes into account that users who have completed transmission will not access the channel again, thus improving the fairness of the system. At the same time, the sum of the received SNR of all unlicensed user GFUs accessing the channel must be less than the maximum interference power I of the licensed user GFU. This ensures that the licensed user GFU channel can still maintain sufficient interference tolerance after multiple unlicensed user GFUs are accessed, so as to avoid signal decoding failure.

[0028] Preferably, the distributed contention method described in S2.1 refers to the requirement that each unlicensed user GFU wishing 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 then broadcasts a contention time window τ max If the backoff time τ of the i-th unauthorized user's GFU is... i If the value is less than that of the base station, a contention time window τ is broadcast. max Then the i-th unauthorized user GFU will be at the backoff time τ of the i-th unauthorized user GFU. i Then, a beacon is sent to the base station (BS) to set the backoff time τ for the i-th unlicensed user's GFU. i Let τ be a decreasing function of the maximum effective received SNR of the unlicensed user GFU. Unlicensed user GFUs that have completed data updates will not participate in distributed contention and will remain silent. By applying distributed contention technology, the base station (BS) can obtain the relative magnitude of the maximum received SNR of the unlicensed user GFU, and can also determine the backoff time τ of the i-th unlicensed user GFU. i By reverse engineering, the maximum received SNR value for these users is determined. Only when the reverse-engineered maximum received SNR value is greater than the value required to decode the last unlicensed user's GFU is the maximum SNR value that can be obtained. Only users with good channel quality participate in power matching; otherwise, they are discarded by the base station (BS). Here, the backoff time setting makes the access opportunity for each user more equitable. Users with good channel quality can access the network as early as possible, ensuring their network experience, while users with poor channel quality will not have their access opportunity affected by excessive competition. The backoff mechanism allows them to access the network in a later time slot, thus avoiding the situation where users with poor signal cannot access the network. This design avoids concentrating all competitive pressure in a single time slot, effectively avoiding excessive competition for network resources, thereby improving the fairness of the overall system.

[0029] Preferably, in S2.1, the base station BS uses distributed contention technology to determine that the maximum received SNR in a certain time slot is greater than the value required to decode the last unlicensed user GFU. The maximum number of unlicensed user GFUs is K. When there are more than K users, the maximum received SNR is greater than the signal required to decode the last unlicensed user GFU. At that time, the base station (BS) will select the maximum number of users K with the highest effective received SNR. Therefore, the number of unlicensed user GFUs k that can be accessed in each time slot is less than or equal to the maximum number of users K. Subsequently, the base station (BS) needs to determine the SNR level of the number of unlicensed user GFUs k that can be accessed in each time slot and the maximum number of users K received SNR levels. Power matching is performed, and only unlicensed user GFUs that are 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 updates and will remain silent for the remaining time slots of this transmission round. Here, the method prioritizes the user with the highest received SNR to ensure that users with better signal conditions can access the network first, so as to maximize system performance and avoid some users accessing the network continuously in multiple time slots, thereby excessively consuming system resources.

[0030] Preferably, in S2.3, the maximum effective received SNR of each of U(1) to U(maximum number of users K) is checked one by one to see if it is greater than the corresponding matching received SNR level. That is, whether it satisfies in For unlicensed users, the maximum received SNR of GFU is h (n) Here, the channel coefficient of the unlicensed user GFU is determined by calculating the maximum effective received SNR of the unlicensed user GFU to determine whether the unlicensed user GFU has the conditions for access in this time slot. This is determined by the parameters of the unlicensed user GFU itself, which ensures the fairness of system operation.

[0031] Preferably, in S2.5, the unlicensed user GFU uses the channel of the licensed user GBU and transmits data to the base station BS together with the licensed user GBU. After receiving the signals transmitted by the licensed user GBU and multiple unlicensed user GFUs, the base station BS uses the non-ideal serial interference cancellation (SIC) decoding rule for decoding. Since the SNR of each unlicensed user GFU received by the base station BS is a pre-designed receive SNR level, Therefore, during the decoding process, it can be guaranteed that each unlicensed user GFU on the access channel can be successfully decoded. Here, decoding is performed according to the SIC decoding rules to avoid the unlicensed user GFU on the access channel not having a matching receive SNR level. This ensures the stability of the system operation.

[0032] Preferably, the scheduling process described in S3 is still divided into two stages as described in S1 to S2. In S1 to S1.3, the base station BS determines the maximum number of licensed user GFUs allowed to access the channel in the time slot, K. In S2 to S2.4, the base station BS determines the specific unlicensed user GFUs to access and transmits data. Here, through the two-stage scheduling, it is ensured that all unlicensed user GFUs can access the system in a time slot, thus ensuring the fairness of the system.

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

[0034] This invention provides a non-orthogonal multiple access semi-unlicensed multi-user transmission method to ensure fair access. On one hand, it sets a series of receive SNR levels for non-ideal serial interference cancellation (SIC) technology. This is used to allocate unlicensed user GFUs for access, determining the decoding order and ensuring that all accessing unlicensed user GFUs can successfully decode. On the other hand, it limits each unlicensed user GFU to transmitting data only once per transmission round, allowing users with poor channel conditions to have a chance to communicate. It also utilizes distributed contention techniques and multi-user scheduling algorithms to ensure that the selected unlicensed user GFUs are matched with a more reasonable receive SNR level. This can reduce the system's AAoI while ensuring access fairness, providing an important technical reference for the design of user scheduling methods in semi-unlicensed networks. Attached Figure Description

[0035] Figure 1 A schematic diagram of a non-orthogonal multiple access semi-unlicensed multi-user transmission network that ensures fairness; wherein, 1 is an airborne base station, 2 is an authorized user, and 3 is an unlicensed user.

[0036] Figure 2 A schematic diagram of a non-orthogonal multiple access semi-unlicensed multi-user transmission method to ensure fair access;

[0037] Figure 3 In this invention, the AAoI of the unlicensed user GFU changes with the maximum transmit power Pmax of the unlicensed user GFU;

[0038] Figure 4 In this invention, the AAoI of the unlicensed user GFU changes with the number M of the unlicensed user GFUs;

[0039] Figure 5 In this invention, the AAoI of the unlicensed user GFU changes with the transmission rate R of the unlicensed user GFU;

[0040] Figure 6 In this invention, the AAoI of the unlicensed user GFU changes with the distribution range of the unlicensed user GFU. Detailed Implementation

[0041] This invention proposes a non-orthogonal multiple access semi-unlicensed multi-user transmission method to ensure fair access, and its application scenarios are described below. Figure 1 The specific scheduling method is illustrated in the diagram below. Figure 2 In this method, a series of receive SNR levels γ are preset to ensure that the non-ideal serial interference cancellation (SIC) technique is designed. n (K) Furthermore, a multi-user power matching algorithm is implemented to ensure successful decoding, effectively improving the AAoI of unlicensed user GFUs and providing important technical reference for the design of user scheduling methods in semi-unlicensed networks. To better understand the above methods, detailed experimental results will be explained below with reference to the accompanying figures and specific implementation examples.

[0042] Example 1

[0043] Please see Figure 1 A non-orthogonal multiple access (NMO) semi-unlicensed multi-user transmission method to ensure fair access is proposed. First, an IoT network with UAV-assisted communication is considered, where the UAV acts as the base station (BS). On the ground, there is one licensed user (GBU) and M = 8 unlicensed user (GFU) waiting to access the network. The target transmission rate for both types of users is R = R0 = 1 bit / s / Hz. Regarding the channel, the combined effects of large-scale fading and small-scale fading are considered. In the case of large-scale fading, the flight altitude of the base station (BS) is set to H = 200m, and the users are randomly distributed in a circular area with a radius of 200m, with a path loss coefficient of α = 3.8. For small-scale fading, a NaKagami-m distribution is considered, with channel parameters set to m = 2 and Ω = 1.

[0044] Please see Figure 2 At the start of each time slot, each user first estimates its own channel state information using pilot signals transmitted by the base station (BS). Licensed users (GBUs) then send their target rate and effective received signal-to-noise ratio (SNR) to the BS. The BS calculates the maximum number of unlicensed user gigabytes (GFUs) that can be allowed to access the channel in that time slot, using the GFUs' target rate and effective SNR. Simultaneously, employing distributed contention technology, the BS calculates the maximum SNR of each unlicensed user GFU based on the beacon transmission time of those GFUs that have not completed data transmission in this round. Furthermore, the BS determines the unlicensed user GFUs that will ultimately access the channel and their corresponding BS SNR levels by executing a power matching algorithm. Will receive SNR level The system also broadcasts the unlicensed user GFU number for the accessible channel, and each unlicensed user GFU is assigned a corresponding receive SNR level. Calculate the transmit power. Unlicensed user GFUs that have not accessed the channel and those that have already communicated in this round remain silent. Assume the maximum transmit power Pmax of the unlicensed user GFU varies between -5dBm and 15dBm, while the transmit power of the licensed user GBU is ten times Pmax. At the receiving end, the base station BS uses SIC technology to decode the information transmitted by all users, with the licensed user GBU signal decoded first to match the received SNR level. The higher the level of the unlicensed user's GFU signal, the earlier it is decoded.

[0045] Please see Figure 3 First, the impact of the maximum transmit power of the unlicensed user GFU on its AAoI (Average Access Interchange) was analyzed. As the transmit power of the unlicensed user GFU increases, its AAoI decreases. Furthermore, compared to the greedy scheduling method that schedules the unlicensed user GFU with the best channel state information in each time slot, the proposed fairness-assured scheduling method effectively improves the AAoI of the unlicensed user GFU, thereby enhancing the overall communication performance of the system. The results also show that the theoretical analysis and simulation results are in excellent agreement.

[0046] For further information, please refer to [link / reference]. Figure 4 ,exist Figure 4 The study investigated the impact of the total number of unlicensed user GFUs on the AAoI of unlicensed user GFUs, with the transmit power set to P. max =0dBm. It can be seen that as the total number of unlicensed user GFUs increases, the AAoI of the unlicensed user GFUs also increases. This is because, under the premise of constant transmit power, the number of unlicensed user GFUs that a licensed user GBU can support per time slot is a relatively stable value. However, the increase in the total number of unlicensed user GFUs means that a transmission round requires more time slots to complete one data transmission for all unlicensed user GFUs, thus leading to an increase in the AAoI of the unlicensed user GFUs. Next, please refer to... Figure 5 ,exist Figure 5 The impact of the transmission rate and AAoI of the unlicensed user GFU was 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 leads to a higher AAoI across different receiver SNR levels. The number of unlicensed user GFUs that an authorized user GFU can allow to access, as well as the number of receive SNR levels that can be matched, needs to be increased accordingly. The number of unlicensed user GFUs has decreased, leading to an increase in the AAoI of unlicensed user GFUs.

[0047] Example 2

[0048] This invention provides a method for enabling real-time communication and ensuring fairness among a large number of unlicensed user GFUs with significantly different channel states. Since each unlicensed user GFU communicates once in a transmission round, the method can also be used to schedule several unlicensed user GFUs with significantly different distances to the base station (BS) to ensure overall information freshness.

[0049] Specifically, in a drone-assisted IoT network, the drone acts as the base station (BS). On the ground, there is one authorized user (GBU) and M=4 unauthorized user (GFU) waiting to access the network to transmit data. The transmission rate for both types of users is R=R0=1 bit / s / Hz. Regarding the channel, the combined effects of large-scale and small-scale fading are considered. For large-scale fading, the BS is set to fly at an altitude of H=200m, and the four users are randomly distributed in circular areas (0-150m), ring areas (150-200m), ring areas (200-250m), and ring areas (250-300m), with a path loss coefficient of α=3.8. For small-scale fading, a Nakagami-m distribution is considered, with channel parameters set to m=2 and Ω=1.

[0050] At the start of each time slot, each user first needs to estimate its own channel state information via pilot signals transmitted by the base station (BS). Licensed users (GBUs) then need to send their target rate and effective received signal-to-noise ratio (SNR) to the BS. The BS calculates the maximum number of unlicensed user gigabytes (GFUs) that can be allowed to access the channel in that time slot, based on the GFUs' target rate and effective SNR. Simultaneously, employing distributed contention technology, the BS can calculate the maximum SNR of each unlicensed user GFU based on the beacon transmission time of those GFUs that have not completed data transmission in this round. Furthermore, the BS determines the unlicensed user GFUs that will ultimately access the channel and their corresponding SNR levels by executing a power matching algorithm. The base station (BS) will assign the accessibility code to the unlicensed user's GFU and its received SNR rating. In addition to broadcasting, each unlicensed user GFU can calculate its transmit power based on the matched receive SNR level. Unlicensed user GFUs that have not accessed the channel or have already communicated in this round remain silent. Assume that the maximum transmit power Pmax of the unlicensed user GFU varies between -5dBm and 15dBm, while the transmit power of the licensed user GBU is ten times Pmax. At the receiving end, the base station BS uses non-ideal SIC technology to decode the information transmitted by all users, with the licensed user GBU signal decoded first to match the receive SNR level. The higher the level of the unlicensed user's GFU signal, the earlier it is decoded.

[0051] Please see Figure 6 , Figure 6 The study investigated the AAoI of users at different distances. It can be seen that in the greedy scheduling method that schedules the unlicensed user GFU with the best channel state information in each time slot, the user's AAoI will increase rapidly with the increase of the distance from the user to the base station BS. However, the proposed method can ensure that the AAoI does not change much with the increase of the distribution distance. This is because the proposed method can avoid users with better channel state information from repeatedly accessing the channel in one transmission round, which can ensure fairness and thus ensure that the AAoI does not change much with the distribution radius.

[0052] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A non-orthogonal multiple access (NMO) semi-unlicensed multi-user transmission method to ensure fair access, wherein the semi-unlicensed transmission network includes two types of users: licensed users (GBUs) accessing the network based on the traditional licensed transmission (GB) protocol and unlicensed users (GFUs) accessing the network based on the unlicensed transmission (GF) protocol. The number of time slots required for all unlicensed users (GFUs) to complete one data update is called a transmission round. The method is characterized in that... Includes the following steps: S1: In each time slot, the base station BS determines the licensed user GBU for communication in that time slot based on the traditional licensing protocol. To ensure the performance of the licensed user GBU, the signal of the licensed user GBU is first decoded at the receiving end. There are a total of M unlicensed user GFUs that want to access the channel. Before selecting the unlicensed user GFUs to access the network in that time slot, the base station BS needs to determine the maximum number of unlicensed user GFUs K that the licensed user GBUs are allowed to access the channel in that time slot based on the principle of non-ideal serial interference cancellation (SIC). S1.1: At the beginning of each time slot, the base station (BS) sends pilot signals to licensed users (GBUs) and all unlicensed users (GFUs). All users obtain their respective channel state information by measuring the pilot signals. Licensed users (GBUs) set their target rates. and effective received SNR Feedback is sent to the base station (BS), among which For authorized user GBU to send SNR, These are the channel coefficients of the licensed user GBU and the target rate received by the base station BS from the licensed user GBU. After obtaining a valid SNR, the maximum interference power I that the licensed user GBU can tolerate can be determined. The maximum interference power I is calculated based on the successful decoding of the licensed user GBU's signal at the base station BS. S1.2: Based on the non-ideal serial interference cancellation SIC decoding rules, the target rate R of the unlicensed user GFU, and the maximum tolerable interference power I of the licensed user GBU, the base station BS sets a series of receive SNR levels. These received SNR levels Unlicensed user GFUs will be allocated access to the licensed user GBU channel in this time slot; the receive SNR level set by the base station BS. The calculation method is as follows: （2） Where R is the target rate of all unlicensed user GFUs, all unlicensed user GFUs are of the same type of user and have the same target rate R, and c is the residual power coefficient of the non-ideal serial interference cancellation (SIC) technique. Based on the SIC decoding rules, c This indicates the residual power of the SNR sent by the authorized user GBU during decoding. This represents the residual power of the signal decoded before the nth signal is decoded. This indicates the SNR required to decode the last unlicensed user's GFU. This represents the SNR required to decode the i-th unlicensed user GFU signal from the end, where n represents the SNR level of each target reception. According to the principle of Sequence Interference Cancellation (SIC) in non-orthogonal multiple access networks, the SNR of the first decoded signal must be greater than the SNR of the second decoded signal, i.e. ; S1.3: Received SNR level set according to the base station (BS) configuration. Given the maximum tolerable interference power I of the licensed user GBU, the base station BS can determine the maximum number of users K that the licensed user GBU is allowed to access the channel in that time slot; S2: Determine the maximum number of users K allowed to access the channel for the licensed user GBU in this time slot, and the receive SNR level set by the licensed user GBU. Afterwards, the base station (BS) needs to identify the specific unlicensed user (GFU) users who can access the authorized user (GBU) channel and allow them to transmit data; S2.1: The base station (BS) uses a distributed contention method to select the K unlicensed users (GFUs) with the largest valid received SNR that have not yet completed data updates; S2.2: After the base station (BS) selects the maximum number of unlicensed users (GFUs) using distributed contention technology, it will... The received SNR level preset in S1.2 Power matching is performed, where, This indicates that the GFU with the weakest SNR among the maximum number of K unlicensed user GFUs is selected. S2.3: Receive the nth weakest unlicensed user GFU with SNR Received SNR level set by base station (BS) After power matching, check each of U(1) to U(maximum number of users K) to see if its maximum effective received SNR is greater than the corresponding matched received SNR level. If the maximum effective received SNR of all unlicensed user GFUs is greater than the matched received SNR level If the power matching is successful, proceed to S2.4; otherwise, remove the unlicensed user GFU with the lowest received SNR from the selected unlicensed user GFUs and proceed to S2.

2. S2.4: The base station (BS) broadcasts the final selected unlicensed user GFU and its matching power level. The size indicates that the base station (BS) allows these unlicensed user GFUs to utilize their matched receive SNR rating. Access channel, the transmit SNR of these unlicensed user GFUs is , The received SNR level of the base station (BS) receiver. For the unlicensed user's GFU channel coefficients; S2.5: After determining that an unlicensed user GFU can access the authorized user GBU channel, during the remaining time of the time slot, the unlicensed user GFU uses the authorized user GBU channel and sends data to the base station BS together with the authorized user GBU. The unlicensed user GFU that is not selected or fails to match remains silent until the next time slot and then tries to access the unlicensed user GFU channel. S3: At the start of the next time slot, the base station BS retransmits the pilot signal. Its scheduling process is still divided into two stages as described in S1~S2. When all unlicensed user GFUs have completed a data update, the transmission round ends and a new transmission round begins. All unlicensed user GFUs are remarked as unlicensed user GFUs that have not completed the data update.

2. The non-orthogonal multiple access semi-unlicensed 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 satisfy: （1） in, This indicates the SNR required to successfully decode the authorized user's GBU signal. The target rate for authorized users' GBUs.

3. The non-orthogonal multiple access semi-unlicensed multi-user transmission method for ensuring fair access according to claim 1, characterized in that, The maximum number K of unauthorized user GFUs allowed to access as described in S1.3 satisfies the following condition: （3） Where M represents the total number of unlicensed user GFUs to be communicated. The maximum number of unlicensed user GFUs (Guest Fuses) that have completed data updates before this time slot in this transmission round must be less than the number of users K allowed to access. , This means that the sum of the received SNR of all unlicensed user GFUs accessing the channel must be less than the maximum interference power I of licensed user GFUs. The maximum number of unlicensed user GFUs that can access the channel in this time slot can be calculated using formulas (2) and (3). That is, the received SNR level of the transmitted signal that needs to be set for a single unlicensed GFU user. When the interference power I is greater than that of the licensed user GBU, no unlicensed user GFU can access the channel, and the maximum number of users K=0.

4. The non-orthogonal multiple access semi-unlicensed multi-user transmission method for ensuring fair access according to claim 1, characterized in that, The distributed contention method described in S2.1 refers to the requirement that each unlicensed user GFU wishing to access the channel needs to set a backoff time at the beginning of each time slot. Here, the backoff time for the i-th unlicensed user GFU is... The base station then broadcasts a contention time window. If the backoff time of the i-th unauthorized user GFU If the contention time window is smaller than that of the base station, it will broadcast a contention time window. Then the i-th unauthorized user GFU will be at the backoff time of the i-th unauthorized user GFU. Then, a beacon is sent to the base station (BS) to set the backoff time for the i-th unlicensed user's GFU. Let be a decreasing function of the maximum effective received SNR of the unlicensed user GFU. Unlicensed user GFUs that have completed data updates will not participate in distributed contention and will remain silent. By applying distributed contention technology, the base station (BS) can obtain the relative magnitude of the maximum received SNR of the unlicensed user GFU, and can also determine the backoff time of the i-th unlicensed user GFU. The maximum received SNR value for these users can be deduced by reverse engineering. Only when the deduced maximum received SNR value is greater than the SNR required to decode the last unlicensed user's GFU can the maximum received SNR be determined. Only users who meet the requirements will participate in power matching; otherwise, they will be discarded by the base station (BS).

5. A method for ensuring fair access in a non-orthogonal multiple access semi-unlicensed multi-user transmission according to claim 1, characterized in that, The base station (BS) described in S2.1 uses distributed contention technology to determine that the maximum received SNR in a certain time slot is greater than the SNR required to decode the last unlicensed user's GFU. The maximum number of unlicensed user GFUs is K. When there are more than K users, the maximum received SNR is greater than the SNR required to decode the last unlicensed user GFU. At that time, the base station (BS) will select the maximum number of users K with the highest effective received SNR. Therefore, the number of unlicensed user GFUs k that can be accessed in each time slot is less than or equal to the maximum number of users K. Subsequently, the base station (BS) needs to determine the SNR level of the number of unlicensed user GFUs k that can be accessed in each time slot and the maximum number of users K received SNR levels. Power matching is performed, and only unlicensed user GFUs that are 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 updates and will remain silent for the remaining time slots of this transmission round.

6. A method for ensuring fair access in a non-orthogonal multiple access semi-unlicensed multi-user transmission according to claim 1, characterized in that, As described in S2.3, each of U(1) to U(maximum number of users K) is checked one by one to see if its maximum effective received SNR is greater than the corresponding matched received SNR level. That is, whether it satisfies ,in For unlicensed users, the maximum received SNR of GFU is... This is the channel coefficient for the unlicensed user's GFU.

7. A method for ensuring fair access in a non-orthogonal multiple access semi-unlicensed multi-user transmission according to claim 1, characterized in that, The unlicensed user GFU described in S2.5 uses the channel of the licensed user GBU to send data to the base station BS together with the licensed user GBU. After receiving the signals sent by the licensed user GBU and multiple unlicensed user GFUs, the base station BS uses the non-ideal serial interference cancellation (SIC) decoding rule for decoding. Since the SNR of each unlicensed user GFU received by the base station BS is a pre-designed receive SNR level. Therefore, during the decoding process, it can be guaranteed that each unlicensed user GFU on the access channel can successfully decode.

8. A method for ensuring fair access in a non-orthogonal multiple access semi-unlicensed multi-user transmission according to claim 1, characterized in that, The scheduling process described in S3 is still divided into two stages as described in S1~S2. In S1~S1.3, the base station BS determines the maximum number of users K allowed to access the channel of the licensed user GBU in the time slot. In S2~S2.4, the base station BS determines the specific unlicensed user GFU to access and transmits data.

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