A random access method for IRSA-NOMA based on terminal priority

Abstract

A terminal priority-based IRSA-NOMA random access method is designed to address the high collision rate of random access by heterogeneous terminals in large-scale machine-type communications (mMTC). Specifically, the IRSA-NOMA protocol is designed, combining irregularly repeated slotted ALOHA and power-domain non-orthogonal multiple access (POMA) based on terminal priority. Secondly, uplink diversity degree and power level selection schemes are designed for high- and low-priority terminals based on the proportion of high-priority terminals. Terminals then use the IRSA-NOMA protocol to perform uplink access transmissions. Finally, the base station receives uplink access signals from multiple terminals and uses sequential interference cancellation (SIC) to detect and eliminate access conflicts frame by frame. This method optimizes uplink transmission parameters based on terminal priority, reducing the probability of random access collisions for large-scale terminals and improving the overload capacity and throughput of the mMTC system.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to an IRSA-NOMA random access method based on terminal priority. Background Art

[0002] With the explosive growth of the mobile internet and IoT industries, the number of wireless devices is rapidly increasing, giving rise to massive machine-type communication (mMTC). As a supporting technology for the IoT and one of the three major 5G scenarios, mMTC is being widely adopted in healthcare, smart homes, smart cities, and other fields, supporting the connectivity and short packet communication of massive numbers of devices. However, due to the large number of mMTC devices and limited wireless spectrum, terminal access bottlenecks have become prominent. Reducing or eliminating access contention has become a key issue that needs to be addressed in mMTC.

[0003] As a derivative of contention resolution diversity slotted ALOHA, irregular repetition slotted ALOHA (IRSA) has rekindled widespread academic attention. IRSA resolves RA conflicts by randomly retransmitting multiple copies of a data packet in multiple time slots within a frame, leveraging time diversity and time-domain SIC technology. This promises unlicensed random access for large-scale terminals. Non-Orthogonal Multiple Access (NOMA) leverages power diversity to improve spectral efficiency, increasing random access throughput without expanding bandwidth. Therefore, integrating NOMA with IRSA is expected to significantly improve the unlicensed random access performance of mMTC terminals.

[0004] However, current research on combining NOMA and IRSA is immature, and most existing studies focus on random access scenarios involving homogeneous terminals. Access strategies for heterogeneous service terminals are relatively limited. mMTC, in fact, contains a large number of heterogeneous terminals, and different types of terminals have different access quality requirements. For example, emergency service terminals require a higher access success rate, while general data terminals can tolerate a slightly lower access success rate. Therefore, it is necessary to design new random access schemes for heterogeneous mMTC terminals, balancing the access requirements of different terminals while improving random access performance. Summary of the Invention

[0005] To address the above issues, a terminal priority-based IRSA-NOMA random access method is proposed. This method adjusts the number of transmitted copies based on the proportion of high-priority terminals and selects the available power level set for different terminal types. This improves the throughput under high system load conditions and solves the overload access problem of terminals of different priorities in the mMTC system. This method is suitable for scenarios where a large number of machine-type devices transmit sporadic small data packets in bursts. The main contents of this invention include:

[0006] mMTC terminals use a combination of irregularly repetitive slotted ALOHA (IRSA) and power-domain non-orthogonal multiple access (NOMA) technology to perform uplink unlicensed random access. Uplink transmission parameters are adjusted based on terminal priority optimization to reduce the probability of random access collisions for large-scale terminals and improve the overload capacity and system throughput of the mMTC system.

[0007] In order to achieve the above object, the present invention is achieved through the following technical solutions:

[0008] An IRSA-NOMA random access method based on terminal priority includes the following steps:

[0009] Step 1: Considering the mMTC uplink random access scenario, terminals are divided into high-priority and low-priority terminals according to their service types. A random access protocol based on terminal priority, combining irregularly repeated slotted ALOHA and power-domain non-orthogonal multiple access (IRSA-NOMA), is designed.

[0010] In the IRSA-NOMA protocol, the terminal's received replication distribution and target detection power level set are obtained. The terminal selects a time slot and uplink power level based on its own priority and the base station's broadcast message to transmit data to the base station. After receiving the data, the base station restores the power level signal on the time slot and returns an acknowledgment message.

[0011] Step 2: Based on the proportion of high-priority terminals, an uplink transmission diversity degree selection scheme and a transmit power level selection scheme are designed for high- and low-priority terminals; the terminals use the IRSA-NOMA protocol to perform uplink access transmission;

[0012] In the uplink transmission diversity selection scheme, the transmission replication distribution function of high- and low-priority terminals is adjusted based on the proportion of high-priority terminals. For high- and low-priority terminals, a random number is generated before each frame and compared with the replication distribution, that is, the probability of high- and low-priority terminals sending r replicas. The corresponding number r of replicas is then sent.

[0013] In the transmit power level selection scheme, the target receive power of high-priority terminals at the base station is randomly and uniformly selected, while the target receive power of low-priority terminals at the base station is selected at the minimum power level. The corresponding transmit power sets are then calculated. The high- and low-priority terminals then generate r random numbers and compare them with their own transmit power sets. The corresponding transmit power is then selected to send data packet replicas, ultimately establishing a terminal uplink transmit signal model.

[0014] In step 3, the base station receives uplink transmission signals from multiple terminals according to the IRSA-NOMA protocol, uses sequential interference cancellation (SIC) technology to detect uplink signals frame by frame and eliminate access conflicts, analyzes the random access performance of the terminals, and feeds back confirmation messages to the terminals that have successfully accessed.

[0015] The beneficial results of the present invention are:

[0016] (1) The present invention adopts an irregularly repeated time slot ALOHA random access protocol based on power diversity. The receiving end uses SIC technology to detect multi-user uplink signals. The traditional IRSA protocol has not been considered for combination with NOMA technology. The solution adopted by the present invention reduces the probability of user collision.

[0017] (2) The present invention proposes to design uplink power level and diversity degree selection schemes for terminals of different levels based on the proportion of high-priority and low-priority terminals. The terminals use the IRSA-NOMA protocol to perform uplink access transmission, thereby improving the system throughput and the access probability of high-priority terminals when the system load is high and the proportion of high-priority terminals is large.

[0018] (3) The traditional IRSA-NOMA protocol does not jointly consider the impact of terminal type, replication distribution, and available power level set on system performance. The solution adopted by the present invention improves the system throughput. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a network model diagram in an embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of the transmission protocol in an embodiment of the present invention.

[0021] Figure 3 It is a flowchart of the implementation of the method in the embodiment of the present invention.

[0022] Figure 4 4 is a diagram showing the simulation results of the system throughput in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.

[0024] Set the system scenario:

[0025] In a single-cell mMTC system, M machine type terminals compete for access to the base station at the same time. Both the terminal and the base station are equipped with a single antenna; U m represents the mth terminal, m∈Γ, Γ={1,2,...,M} represents the terminal number set, M represents the total number of terminals; Γ H represents the set of high priority terminal labels, Γ L Represents a set of low-priority terminal labels, Γ L +Γ H =Γ. Each terminal sends r copies of its data packet in r randomly selected time slots, thus forming transmit time diversity. Each terminal sends at most R copies, that is, 1≤r≤R≤N. The transmit power of each copy of the same terminal can be different. Different terminals can occupy the same time slot to send copies through NOMA technology.

[0026] like Figure 1-3 As shown, the present invention is an IRSA-NOMA random access method based on terminal priority, which specifically includes the following steps:

[0027] Step 1: Design an uplink random access protocol (IRSA-NOMA) that combines irregularly repeated slotted ALOHA and power-domain non-orthogonal multiple access to support diversity transmission of large-scale mMTC terminals in both the time and power domains.

[0028] Step 1-1: The base station calculates the terminal uplink transmission replication (diversity) distribution according to the proportion of high priority terminals in the system α and in and They represent the probability that high-priority and low-priority terminals send r copies respectively; the base station broadcasts the above parameters to the terminals.

[0029] Step 1-2: The terminal listens to the base station broadcast, calculates the available power level set based on its own priority and the broadcast message, and determines the uplink transmission diversity degree according to the diversity degree selection criterion. r , randomly selected from N time slots in a frame r In each time slot, the terminal randomly selects an uplink power level from the available power level set to transmit a copy of the data packet to the base station; it is stipulated that each terminal can send a maximum of R copies, 1≤r≤R≤N.

[0030] In steps 1-3, the base station receives multiple uplink data frames from multiple terminals. It first uses power-domain SIC to recover the signals at each power level in each time slot. Then, it uses the signals from the previously detected terminals to perform time-domain SIC to eliminate access conflicts. Finally, the base station sends an access success confirmation message to the terminals whose data has been successfully detected.

[0031] Step 2: Based on the proportion of high- and low-priority terminals, design uplink power level and diversity degree selection schemes for terminals of different levels; the terminals use the IRSA-NOMA protocol to perform uplink access transmission.

[0032] Step 2-1-1, designing a diversity transmission replication degree distribution function;

[0033] Let the transmission replication degree distributions of high priority terminals and low priority terminals be and in and They represent the probability of high-priority terminals and low-priority terminals sending r copies; their degree distribution functions are defined as and Where x represents the function variable, and α represents the proportion of high priority terminals. When α = 1, all terminals are high priority terminals. At this time, the terminals are distributed according to the degree distribution function. Select the number of copies to send; as the value of α decreases, the copy degree distribution functions of high- and low-priority terminals are adjusted to be as shown in formula (1) and formula (2), respectively, where That is the power exponent term x in formula (1) r The coefficient of That is the power exponent term x in formula (2) r The coefficient of .

[0034]

[0035]

[0036] in, It represents the probability that each terminal chooses to transmit r copies when α=1, that is, when all terminals are high-priority terminals.

[0037] Step 2-1-2: Design the selection criteria for the number of replicas for diversity transmission;

[0038] Based on the replica distribution and Design the following diversity degree selection criteria:

[0039] If U m For high priority terminals, it generates a [0,1] uniformly distributed random number before each frame starts. like U m Send 1 copy; if U m Send 2 copies, and so on, if U m Send r copies.

[0040] If U m For low priority terminals, it generates a [0,1] uniformly distributed random number before each frame starts. like U m Send 1 copy; if U m Send 2 copies, and so on, if U m Send r copies.

[0041] Step 2-2-1: Determine the terminal uplink transmit power level set.

[0042] Let the base station target detection power level set be P = {P1, P2, ..., P k ,...,P K}, where P k represents the kth target detection power level, 1≤k≤K, and P1<P2<...<P k <...<P K In order to reduce the interference of low-priority terminal data packet transmission on high-priority terminal data packet decoding under high load conditions and to ensure the quality of random access of high-priority terminals, it is stipulated that the target receiving power of high-priority terminals at the base station is randomly and uniformly selected from the set P, and the target receiving power of low-priority terminals at the base station can only be selected from the minimum power level P. K .

[0043] That is to say, if U m It is a high priority terminal, U m The received power of the data packet copy at the base station is P m,k =P k , k∈{1,2,...,K}; if terminal U m It is a low priority terminal, U m The target receiving power of the data packet copy at the base station is P m,k =P k , k=K.

[0044] Therefore, terminal U m Transmit power It can be calculated as:

[0045]

[0046] Among them, h m For terminal U m Uplink channel attenuation coefficient to the base station, known by default.

[0047] In summary, if terminal U m For high priority terminals, their transmit power level set for:

[0048]

[0049] If the terminal U m For low priority terminals, their transmit power level set for:

[0050]

[0051] Step 2-2-2: Design the terminal uplink transmit power level selection strategy.

[0052] If the terminal U m is a high priority terminal that sends a copy of each data packet with probability η k Select a transmit power level set The kth power level in Power level selection probability η k Obey the uniform distribution of [0,1] and satisfy

[0053] If the terminal U m For low priority terminals, they select a set of transmit power levels when sending each packet copy Power level in

[0054] The terminal uplink transmit power level selection strategy is specifically designed as follows:

[0055] Terminal U m Before executing access transmission, first confirm the diversity degree r according to step 2-1-2, and then generate r [0,1] uniformly distributed random numbers i represents the serial number of the copy of the data packet to be sent, i=1,2,...,r; if U m Select Collection The first power level in Send a copy of the i-th data packet; if When U m Select Collection The second power level in Send a copy of the i-th data packet; and so on, if Select Collection The Kth power level in

[0056] Step 2-2-3: Establish a terminal uplink signal transmission model.

[0057] Terminal U m The transmitted signal on the nth time slot of a frame Expressed as:

[0058]

[0059] Among them, D m Indicates terminal U m The data vector sent in the current frame, is a double indicator function, indicating terminal U m Is the kth power level used to transmit the data packet in time slot n of the current frame? If so, otherwise, And there is

[0060] Step 3: The base station receives uplink transmission signals from multiple terminal users, uses sequential interference cancellation (SIC) technology to detect uplink signals frame by frame and eliminate access conflicts, and feeds back confirmation messages to the terminals that have successfully accessed.

[0061] Step 3-1-1: The uplink signal received by the base station in a certain frame time slot n Modeled as:

[0062]

[0063] in, represents the power level p in time slot n k Carried received signal; h m Indicates terminal U m Uplink channel attenuation coefficient to the base station.

[0064] Step 3-1-2, the base station uses power domain SIC from the signal detecting signals at various power levels;

[0065] For the received signal on time slot n Detect the power levels P1, P2, ..., P in descending order. k ,...,P K Signal Y carried on n,1 ,Y n,2 ,...,Y n,k ,...,Y n,K ; Power level signal Y on time slot n n,k The condition for successful detection is that its preceding k-1 power levels P1, P2, ..., P k-1 and the current power level Pk The signal-to-interference-noise ratio of the carried signal is higher than the detection threshold γ th ,Right now

[0066]

[0067] Among them, γ n,i represents the power level P of the i-th time slot n i Signal-to-interference-and-noise ratio of the carried signal; Indicates terminal U m whether to use collections at time slot n The kth power level in the equation is, if otherwise, Indicates the power level P in time slot n k The number of packets carried, the total number of packets on time slot n can be expressed as

[0068] Step 3-1-3: The base station uses time domain SIC to detect the power level signal Y in multiple time slots. n,k Joint interference cancellation is performed to further recover the data packets of the conflicting users.

[0069] Once a data packet from a terminal is successfully detected through power-domain SIC, the replica pointer contained in the packet is used to locate the time slot positions of other copies of the packet, eliminate the interference of the packet copy on the signal in the time slot, and continue to restore the uplink signals of other terminals until no new signals can be detected.

[0070] Step 3-2-1: Analyze the random access success rate of the terminal.

[0071] Step 3-2-1-1, calculate the power level signal Y on time slot n n,k The detection probability

[0072] Power level signal Y on time slot n n,k The probability of successful detection Calculated as:

[0073]

[0074] Step 3-2-1-2, calculate the power level P of the terminal in time slot n k The probability of successful detection of the transmitted data packet p m,n,k .

[0075] Let the received signal on time slot n be For L n The superposition signal of the terminal data packet replicas, 1≤L n ≤M, including L n,H The data packet copy of the high priority terminal and Ln,L The data packet copy of the low priority terminal, L n =L n,H +L n,L .

[0076] Let terminal U m At power level P in time slot n k A copy of the packet is sent if and only if U m Exclusive power level P k Therefore, the packet L is carried on time slot n. n Terminal data package copies and L n,H Under the condition that the data packet of the high priority terminal is copied, the terminal U m At power level P k Probability of successful detection of a transmitted packet copy Calculated as

[0077]

[0078] For the number of copies L n Traverse and sum to get terminal U m At power level P k The probability p of successful detection of a transmitted packet copy m,n,k for

[0079]

[0080] Among them, Pr(L n ,L n,H ) indicates that time slot n carries L n Terminal data package copies and L n,H The probability of a high priority packet copy is calculated as

[0081]

[0082] in, represents the probability that a high-priority terminal transmits a data packet in each time slot; It represents the probability that a low priority terminal transmits a data packet in each time slot.

[0083] Step 3-2-1-3, calculate the terminal U in time slot n m The probability of successful detection of a packet copy

[0084] For power level P k Traverse and sum to get terminal U m The probability of successful detection of a replica transmitted at time slot n is for:

[0085]

[0086] Terminal U m The probability of failure to detect a replica transmitted in time slot n is Calculated as:

[0087]

[0088] One replica of the terminal is decoded at the base station, and the interference caused by the terminal is eliminated from the remaining time slots, and the received signal Y on all N time slots is n Repeat detection and deletion of interfering copies until all terminal copies are detected.

[0089] Step 3-2-1-4, calculate terminal U m The access success probability p m .

[0090] Terminal U m The access success probability p m Calculated as:

[0091]

[0092] in, and are the access failure probabilities of high-priority terminals and low-priority terminals, respectively.

[0093] Step 3-2-2: Calculate the uplink system throughput T.

[0094] The system throughput T is defined as the number of terminals successfully processed in each frame time slot, that is, the number of terminals in the time slot and the probability of successful terminal access p. m The system throughput T is calculated as:

[0095]

[0096] The effects of the present invention are further verified through the following simulations.

[0097] Experimental scenario:

[0098] There is one base station in a cell, one frame has 30 time slots, the proportion of high-priority terminals is 0.7, the number of power levels that high-priority terminals can choose is 3, and the number of power levels that low-priority terminals can choose is 1. Citing the optimal degree distribution when the number of power levels K = 3 in the work of Xinye Shao et al. in NOMA-Based Irregular Repetition Slotted ALOHA for Satellite Networks, the degree distribution function of the terminal when α = 1 is set to φ H(x,1)=0.7439x 2 +0.0906x 3 +0.0156x 4 +0.1499x 8 , the signal-to-noise ratio threshold is 3dB.

[0099] Experimental content and results:

[0100] Figure 4 The following are simulation results. The horizontal axis represents the number of terminals per time slot per frame, i.e., the system load, and the vertical axis represents the system throughput. IRSA is a traditional irregularly repeated time slot ALOHA scheme. IRSA-NOMA is a traditional irregularly repeated time slot ALOHA scheme based on power diversity. In this scheme, each terminal sends replicas following the same degree distribution, and each terminal selects a power level with equal probability. These schemes all experience degraded system performance under high load. However, the solution of the present invention clearly demonstrates that, even under heavy system loads, it still maintains better system throughput than the other two schemes.

[0101] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed in the present invention should be included in the protection scope recorded in the claims.

Claims

1. An IRSA-NOMA random access method based on terminal priority, characterized by: The method comprises the following steps: Step 1: Considering the uplink random access scenario for massive machine-type communications (mMTC), terminals are divided into high-priority and low-priority terminals based on their service types. A random access protocol based on terminal priority, combining irregularly repeated slotted ALOHA and power-domain non-orthogonal multiple access (i.e., IRSA-NOMA), is designed. In the IRSA-NOMA protocol, the terminal's received replication distribution and target detection power level set are obtained. The terminal selects a time slot and uplink power level based on its own priority and the base station's broadcast message to transmit data to the base station. After receiving the data, the base station restores the power level signal on the time slot and returns an acknowledgment message. Step 2: Based on the proportion of high-priority terminals, an uplink transmission diversity degree selection scheme and a transmit power level selection scheme are designed for high- and low-priority terminals; the terminals use the IRSA-NOMA protocol to perform uplink access transmission; In the uplink transmission diversity selection scheme, the transmission replication distribution function of high- and low-priority terminals is adjusted based on the proportion of high-priority terminals. For high- and low-priority terminals, a random number is generated before each frame and compared with the replication distribution, that is, the probability of high- and low-priority terminals sending r replicas. The corresponding number r of replicas is then sent. In the transmit power level selection scheme, the target receive power of high-priority terminals at the base station is randomly and uniformly selected, while the target receive power of low-priority terminals at the base station is selected at the minimum power level. The corresponding transmit power sets are then calculated. The high- and low-priority terminals then generate r random numbers and compare them with their own transmit power sets. The corresponding transmit power is then selected to send data packet replicas, ultimately establishing a terminal uplink transmit signal model. In step 3, the base station receives uplink transmission signals from multiple terminals according to the IRSA-NOMA protocol, uses sequential interference cancellation (SIC) technology to detect uplink signals frame by frame and eliminate access conflicts, analyzes the random access performance of the terminals, and feeds back confirmation messages to the terminals that have successfully accessed.

2. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The mMTC uplink random access scenario described in step 1 is described as follows: In a single cellular cell served by a single antenna base station, there are M massive machine type communication (mMTC) terminals performing uplink random access. Let U m represents the mth mMTC terminal, m∈Γ, Γ={1,2,...,M} represents the mMTC terminal number set, and M represents the total number of mMTC terminals; Γ H represents the high-priority mMTC terminal number set, Γ L Indicates the low-priority mMTC terminal number set, Γ L +Γ H =Γ.

3. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The IRSA-NOMA protocol based on terminal priority described in step 1 specifically includes the following steps: Step 1-1: The base station calculates the terminal uplink transmission diversity, i.e., the replication distribution, based on the proportion of high-priority terminals in the system. and in and Respectively represent the probability of high and low priority terminals sending r copies; the base station broadcasts the above parameters to the terminal; Step 1-2: The terminal listens to the base station broadcast, calculates the available power level set based on its own priority and the broadcast message, determines the uplink transmission diversity degree r according to the diversity degree selection criterion, randomly selects r time slots from the N time slots in a frame for diversity transmission, and in each time slot, randomly selects an uplink power level from the available power level set and transmits a copy of the data packet to the base station; It is stipulated that each terminal sends at most R copies, 1≤r≤R≤N; In steps 1-3, the base station receives multiple uplink data frames from multiple terminals. It first uses power-domain SIC to recover the signals at each power level in each time slot. Then, it uses the signals from the previously detected terminals to perform time-domain SIC to eliminate access conflicts. Finally, the base station sends an access success confirmation message to the terminals whose data has been successfully detected.

4. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The uplink transmission diversity degree selection scheme described in step 2 is as follows: Step 2-1-1, designing a diversity transmission replication degree distribution function; Let the transmission replication degree distributions of high priority terminals and low priority terminals be and in and They represent the probability of high-priority terminals and low-priority terminals sending r copies; their degree distribution functions are defined as and Where x represents the function variable, α represents the proportion of high priority terminals; when α = 1, all terminals are high priority terminals, and the terminals are distributed according to the degree distribution function. Select the number of copies to send; as the value of α decreases, the copy degree distribution functions of high-priority and low-priority terminals are adjusted to be as shown in formula (1) and formula (2), respectively, where That is the power exponent term x in formula (1) r The coefficient of That is the power exponent term x in formula (2) r The coefficient of in, represents the probability that each terminal chooses to transmit r copies when α = 1, that is, when all terminals are high-priority terminals; Step 2-1-2: Design the selection criteria for the number of replicas for diversity transmission; Based on the replica distribution and Design the following diversity degree selection criteria: If U m For high priority terminals, it generates a [0,1] uniformly distributed random number before each frame starts. like U m Send 1 copy; if U m Send 2 copies, and so on, if U m Send r copies; If U m For low priority terminals, it generates a [0,1] uniformly distributed random number before each frame starts. like U m Send 1 copy; if U m Send 2 copies, and so on, if U m Send r copies.

5. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The transmit power level selection scheme described in step 2 is as follows: Step 2-2-1, determining a terminal uplink transmit power level set; Let the base station target detection power level set be P = {P1, P2, ..., P k ,...,P K }, where P k represents the kth target detection power level, 1≤k≤K, and P1<P2<...<P k <...<P K In order to reduce the interference of low-priority terminal data packet transmission on high-priority terminal data packet decoding under high load conditions and to ensure the quality of random access of high-priority terminals, it is stipulated that the target receiving power of high-priority terminals at the base station is randomly and uniformly selected from the set P, and the target receiving power of low-priority terminals at the base station is only selected from the minimum power level P. K ; That is, if U m It is a high priority terminal, U m The received power of the data packet copy at the base station is P m,k =P k , k∈{1,2,...,K}; if terminal U m It is a low priority terminal, U m The target receiving power of the data packet copy at the base station is P m,k =P k , k = K; Therefore, terminal U m Transmit power Calculated as: Among them, h m For terminal U m Uplink channel attenuation coefficient to the base station; In summary, if terminal U m For high priority terminals, their transmit power level set for: If the terminal U m For low priority terminals, their transmit power level set for: Step 2-2-2, design the terminal uplink transmit power level selection strategy; If the terminal U m is a high priority terminal that sends a copy of each data packet with probability η k Select a transmit power level set The kth power level in Power level selection probability η k Obey the uniform distribution of [0,1] and satisfy If the terminal U m For low priority terminals, they select a set of transmit power levels when sending each packet copy Power level in The terminal uplink transmit power level selection strategy is specifically designed as follows: Terminal U m Before executing access transmission, first confirm the diversity degree r according to step 2-1-2, and then generate r [0,1] uniformly distributed random numbers i represents the serial number of the copy of the data packet to be sent, i=1,2,...,r; if U m Select Collection The first power level in Send a copy of the i-th data packet; if When U m Select Collection The second power level in Send a copy of the i-th data packet; and so on, if U m Select Collection The Kth power level in Step 2-2-3, establish a terminal uplink signal transmission model; Terminal U m The transmitted signal on the nth time slot of a frame Expressed as: Among them, D m Indicates terminal U m The data vector sent in the current frame, is a double indicator function, indicating terminal U m Is the kth power level used to transmit the data packet in time slot n of the current frame? If so, otherwise, And there is 6. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The base station in step 3 uses sequential interference cancellation technology to detect uplink signals frame by frame and eliminate access conflicts. The details are as follows: Step 3-1-1: The uplink signal received by the base station in a certain frame time slot n Modeled as: in, represents the power level P in time slot n k Carried received signal; h m Indicates terminal U m Uplink channel attenuation coefficient to the base station; Step 3-1-2, the base station uses power domain SIC from the signal detecting signals at various power levels; For the received signal on time slot n Detect the power levels P1, P2, ..., P in descending order. k ,...,P K Signal Y carried on n,1 ,Y n,2 ,...,Y n,k ,...,Y n,K ; Power level signal Y on time slot n n,k The condition for successful detection is that its preceding k-1 power levels P1, P2, ..., P k-1 and the current power level P k The signal-to-interference-noise ratio of the carried signal is higher than the detection threshold γ th ,Right now Among them, γ n,i represents the power level P of the i-th time slot n i Signal-to-interference-and-noise ratio of the carried signal; Indicates terminal U m whether to use collections at time slot n The kth power level in the equation is, if otherwise, Indicates the power level P in time slot n k The number of packets carried, the total number of packets on time slot n is expressed as Step 3-1-3: The base station uses time domain SIC to detect the power level signal Y in multiple time slots. n,k Perform joint interference cancellation to further recover data packets of conflicting users; Once a data packet from a terminal is successfully detected through power-domain SIC, the replica pointer contained in the packet is used to locate the time slot positions of other copies of the packet, eliminate the interference of the packet copy on the signal in the time slot, and continue to restore the uplink signals of other terminals until no new signals can be detected.

7. The IRSA-NOMA random access method based on terminal priority according to claim 1, characterized in that: The random access performance of the terminal in step 3 includes two indicators: the terminal random access success rate and the uplink system throughput. The analysis method is described in detail as follows: Step 3-2-1, analyzing the random access success rate of the terminal; Step 3-2-1-1, calculate the power level signal Y on time slot n n,k The detection probability Power level signal Y on time slot n n,k The probability of successful detection Calculated as: Step 3-2-1-2, calculate the power level P of the terminal in time slot n k The probability of successful detection of the transmitted data packet p m,n,k ; Let the received signal on time slot n be For L n The superposition signal of the terminal data packet replicas, 1≤L n ≤M, including L n,H The data packet copy of the high priority terminal and L n,L The data packet copy of the low priority terminal, L n =L n,H +L n,L ; Let terminal U m At power level P in time slot n k A copy of the packet is sent if and only if U m Exclusive power level P k Its data packet copy can be successfully detected; therefore, it carries L on time slot n. n Terminal data package copies and L n,H Under the condition that the data packet of the high priority terminal is copied, the terminal U m At power level P k Probability of successful detection of a transmitted packet copy Calculated as Among them 1 [...] It means that the value of the formula is 1 when the content in the brackets is achieved, and the value of the formula is 0 when the content in the brackets is not achieved. For the number of copies L n Traverse and sum to get terminal U m At power level P k The probability p of successful detection of a transmitted packet copy m,n,k for Among them, Pr(L n ,L n,H ) indicates that time slot n carries L n Terminal data package copies and L n,H The probability of a high priority packet copy is calculated as in, represents the probability that a high-priority terminal transmits a data packet in each time slot; represents the probability that a low-priority terminal transmits a data packet in each time slot; Step 3-2-1-3, calculate the terminal U in time slot n m The probability of successful detection of a packet copy For power level P k Traverse and sum to get terminal U m The probability of successful detection of a replica transmitted at time slot n is for: Terminal U m The probability of failure to detect a replica transmitted in time slot n is Calculated as: One replica of the terminal is decoded at the base station, and the interference caused by the terminal is eliminated from the remaining time slots, and the received signal on all N time slots is Repeat detection and deletion of interfering copies until all terminal copies are detected; Step 3-2-1-4, calculate terminal U m The access success probability p m ; Terminal U m The access success probability p m Calculated as: in, and are the access failure probabilities of high-priority terminals and low-priority terminals, respectively; Step 3-2-2, calculate the uplink system throughput T; The system throughput T is defined as the number of terminals successfully processed in each frame time slot, that is, the number of terminals in the time slot and the probability of successful terminal access p. m The system throughput T is calculated as:

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