A multiple access random access method based on multi-slot serial interference cancellation

Abstract

The present invention discloses a multiple access random access method based on multi-time slot serial interference elimination, comprising: a base station receives and caches a data symbol sequence of a current frame; uses a matched filter to perform user detection on all time slots and estimates channel parameters; determines the time slot type in the frame according to the detection result, and demodulates the corresponding symbol sequence according to the time slot type to obtain the bit code of the time slot; the time slot type is obtained based on whether the user exists and the number of users detected; performs linear block code decoding and error correction on all bit codes of a certain terminal to obtain the final data bit code, and outputs the data of the terminal to a data server or a base station for local processing. The present invention utilizes the error correction function of the linear block code to improve the effect of serial interference elimination, significantly improves the data detection success rate in the case of multiple users' uplink concurrent access conflicts; increases the number of user accesses, thereby increasing the throughput of the Internet of Things access network for massive terminals.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to a multiple access random access method based on multi-time slot serial interference elimination. Background Art

[0002] In wireless communication systems, multiple access is a technology that allows two or more users to share a physical channel and access the system at the same time. If the transmission signals from two or more users reach the base station receiver at the same time, and the signals are not orthogonal to each other, destructive interference will occur, causing the receiver to be unable to detect and decode the signals of all users. In order to avoid interference between different users, it is a common method to make the transmission signals of different users orthogonal to each other, including space division multiple access (SDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA) technologies, which distinguish user signals through different dimensions of space, frequency, time, and orthogonal codes to achieve orthogonal effects. These are all conflict-free multiple access technologies, and this conflict-free property is achieved through mutual coordination between all users participating in the communication.

[0003] In the uplink, random access is a type of uncoordinated multiple access, that is, two or more users send non-orthogonal signals simultaneously and independently. The direct problem caused by non-orthogonal signals is access conflict. The superposition of multiple user signals causes the receiving end (i.e., base station) to be unable to demodulate and decode. With the development of 5G\6G mobile communication systems, the Internet of Things, sensor networks, etc., the number of wireless terminals has increased dramatically. There are not enough resources (frequency, time slot, orthogonal codeword) to ensure the orthogonality of the terminal transmission signals. In addition, due to the large number of terminals, the long coordination establishment time, and the unpredictable terminal transmission data, it is impossible to coordinate with each other in practice. Therefore, the conflict caused by random access is an inevitable problem in the future development of wireless networks.

[0004] The slotted Aloha system is the prototype of random access. It is essentially a packet switching system. The time interval required to transmit a packet is called a time slot. The method in which users can only send signals at the time slot boundary is called slotted Aloha. The transmission arrangement consistent with the time slot boundary means that the packets can overlap completely. When multiple signals overlap in the same time slot, they will destroy each other, causing the data to fail to be received successfully. In order to resolve the conflict of the slotted Aloha system, Carrier Sense Multiple Access (CSMA) is a popular and mature solution. In CSMA, the user monitors the channel before sending. If the user monitors that the channel is idle, it sends. Otherwise, a collision is detected during the data transmission process, and it is resent after a random delay until the channel is idle and the transmission is successful. This solution is applied to the Ethernet (DIX Ethernet V2) standard and the IEEE 802.3 standard.

[0005] The latest academic research results have found that the effectiveness of random access can be significantly enhanced through iterative signal processing technology, making the network throughput using random access close to that of conflict-free multiple access. Interference cancellation stands out in this regard, making full use of conflicts rather than avoiding them. The basic idea is to calculate the multiple access interference of each user to other users at the receiving end, and then partially or completely eliminate the multiple access interference from the received signal. The decision used to estimate the multiple access interference can be a soft decision or a hard decision. The hard decision requires a reliable estimate of the signal amplitude. There are three main types of interference cancellation multi-user detection: serial interference cancellation, parallel interference cancellation, and decision feedback detection.

[0006] Successive Interference Cancellation (SIC) is to gradually reduce the interference of the largest user. The SIC detector makes data decisions for multiple users in the received signal one by one, and reconstructs it if one is determined. At the same time, it reduces the MAI (Multiple Access Interference) interference caused by the user's signal. The operation is performed in the order of signal power. The signal with higher power is operated first. Therefore, it can be seen that the signal with higher power benefits first. SIC has a significant improvement in performance compared with traditional detectors, and the hardware changes are not large, so it is easy to implement. However, each level of SIC requires a character delay, and reordering is required when the signal power changes. If the initial data decision is unreliable, it will have a greater performance impact on the lower level.

[0007] Parallel Interference Cancellation (PIC) simultaneously judges, regenerates and eliminates all multiple access interference at each stage. That is, PIC uses the information of the previous stage judgment to construct the interference signal of all users, then cancels the interference signal from the received signal, and finally judges at the same time. PIC has a small processing delay but a large amount of calculation; while SIC has a large processing delay but a small amount of calculation.

[0008] Decision feedback multi-user detection is mainly proposed for the case where the received signal power is inconsistent. It includes a pre-filter and a post-filter. First, the signal output by the matched filter is sorted and processed by the pre-filter; then it is compared with the feedback signal of the previous moment and sent to the decision device for decision. The information after the decision is fed back to the signal processing at the next moment. Summary of the invention

[0009] The technical problem to be solved by the embodiments of the present invention is to provide a multiple access random access method based on multi-slot serial interference cancellation to avoid non-coordinated multi-user random uplink access conflicts.

[0010] In order to solve the above technical problems, the present invention provides a multiple access random access method based on multi-slot serial interference cancellation, comprising:

[0011] Step S1, the base station receives and caches the data symbol sequence of the current frame;

[0012] Step S2, using a matched filter to perform user detection on all time slots and estimate channel parameters;

[0013] Step S3, judging the time slot type in the frame according to the detection result, and demodulating the corresponding symbol sequence according to the time slot type to obtain the bit code of the time slot; the time slot type is obtained based on whether the user is detected and the number of users;

[0014] Step S4, performing linear block code decoding and error correction on all bit codes of a terminal to obtain a final data bit code, and outputting the data of the terminal to a data server or a base station for local processing.

[0015] Furthermore, the time slot classification includes non-collision time slots, collision time slots and idle time slots.

[0016] Furthermore, the step S3 specifically includes:

[0017] Step S30, determine whether there is a conflict-free time slot. If so, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot; if not, select the time slot with the largest channel gain and the corresponding terminal among all the conflicting time slots, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot.

[0018] Furthermore, if all bit codes of a certain terminal are not obtained, the interference caused by the terminal is eliminated for the occupied time slot, and the process returns to step S3.

[0019] Furthermore, after step S4, the method further includes: discarding the cache of the current frame.

[0020] Further, if all time slots are idle time slots, the process ends successfully and the cache of the current frame is discarded, otherwise the process goes to step S30.

[0021] Further, in step S30, if the current k time slot is a non-conflicting time slot, the base station receives a signal:

[0022] y k =h i ·x i +n k

[0023] Among them, x i is the transmission symbol rate at terminal i, n k is the noise, h i is the channel gain of the uplink from terminal i to the base station; the signal to interference and noise ratio is expressed as:

[0024]

[0025] Among them, p x is the constant transmit power of the terminal, is the power spectral density of the noise.

[0026] Further, in step S30, if the current k time slot is a conflicting time slot, the base station receives a signal:

[0027]

[0028] Among them, k is the set of user sequences active in time slot k, x i The transmission symbol rate at terminal i, n k is the noise, h i is the channel gain of the uplink from terminal i to the base station. The specific terminal i selected by R6 satisfies |h i |2 ≥|h j | 2 , Then the signal to interference and noise ratio is expressed as:

[0029]

[0030] Furthermore, before step S1, a process of uplink sending of terminal data is also included, and the process is specifically as follows:

[0031] Encode the bit stream of IoT terminal data using linear block code and cache the encoded bit code;

[0032] The terminal sends with probability p frame Determine whether to use the current frame for data transmission. If it is determined to use the current frame for transmission, group the bit codes into data packets and randomly select the data packets to be sent in all time slots of the current frame. Otherwise, proceed to the next frame for determination.

[0033] The modulated bit code is a symbol sequence and sent, ending the sending of the current terminal data and waiting for new data to be sent.

[0034] Furthermore, the sending probability p frame It is determined according to the priority of the terminal service data. The higher the priority, the higher the sending probability. Or it is set according to whether the current data transmission is the first transmission or retransmission. The sending probability of retransmission is greater than or equal to the sending probability of the first transmission.

[0035] The implementation of the present invention has the following beneficial effects: the present invention utilizes the error correction function of the linear block code to improve the effect of serial interference elimination, and significantly improves the data detection success rate in the case of multi-user uplink concurrent access conflicts. The use of random transmission of multiple time slots can increase the number of user accesses, thereby increasing the throughput of the Internet of Things access network with a large number of terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 Schematic diagram of timing and frame composition.

[0038] Figure 2 Schematic diagram of the bit stream composition of a single time slot.

[0039] Figure 3 The figure is a schematic diagram of the data transmission process of the Internet of Things terminal in an embodiment of the present invention.

[0040] Figure 4 The figure is a schematic diagram of random uplink access of n terminals in an embodiment of the present invention.

[0041] Figure 5 The present invention is a flowchart of a multiple access random access method based on multi-slot serial interference cancellation according to an embodiment of the present invention.

[0042] Figure 6 The present invention is a schematic diagram of a specific process of a multiple access random access method based on multi-slot serial interference cancellation according to an embodiment of the present invention.

[0043] Figure 7 The figure is a schematic diagram of the data transmission process of the terminal and the decoding process of the base station in the embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following descriptions of the embodiments refer to the accompanying drawings to illustrate specific embodiments in which the present invention may be implemented.

[0045] The present invention is applied to the scenario where multiple IoT terminals randomly send data to a wireless base station via an uplink. In order to facilitate the description of the technical solution, N IoT data terminals are deployed within the coverage of a single wireless base station, each terminal has a data packet to send, and all terminals share the same physical channel (the same wireless signal frequency). The transmission power of all terminals is the same and fixed.

[0046] A frame is the smallest unit for uplink transmission of terminal data. One frame in the physical channel is divided into K time slots, and the time length of each time slot is the same. The terminal can randomly select several time slots in the frame to send data. The frames and time slots of all terminals are time synchronized, that is, the length of all data packets is equal to the length of the time slot, and all data packets are sent at the start time of a certain time slot, which is consistent with the time slot-based Aloha system. All data packets have the same number of bits. When the data that the terminal needs to send is larger than the length of a single data packet, it is divided into multiple data packets and sent. If the length of the last data packet is less than the length of the time slot, it can be padded with zeros at the end. Figure 1 Shown is the time slot composition of 2 frames.

[0047] The terminals adopt a random access mode, that is, each terminal does not know whether other terminals send data packets and the selected time slots, and each terminal sends its own data packet independently. There is no mutual cooperation between the data transmissions of different terminals.

[0048] The time lengths of the time slots and frames vary according to different TDMA system settings. For example, in a DMR system, the length of a time slot is 30 ms and the length of a frame is 360 ms, that is, there are 12 time slots in one frame.

[0049] In the time slot where data is sent, different terminals use different synchronization sequences to embed them (such as Figure 2 As shown, the synchronization sequence is at the initial position of the time slot, or the synchronization sequence can be placed in the middle of the time slot). On the base station side, the matching filter of the corresponding synchronization sequence is used to determine which terminal the data comes from, and the channel estimation of the user's uplink is performed through the matching filter. Following the synchronization sequence is the control signaling, which can be used to determine the position of the time slot in the entire data stream (data packets are not sent sequentially, but randomly), and to determine whether the terminal service bits contained in the time slot are check codes. Following the control signaling is the terminal service bit, which can be the original data or the check code of the linear block code.

[0050] like Figure 3 As shown, the specific steps of sending terminal data uplink are as follows:

[0051] T1: IoT terminal data (bit stream) is to be uploaded to the base station, the sending process starts, and then goes to T2;

[0052] T2: Encode the bit stream with linear block code, cache the encoded bit code (including the linear block code check code), and transfer to T3;

[0053] T3: The terminal sends with probability p frame Determine whether to use the current frame for data transmission. If it is determined to use the current frame for transmission, go to T4. Otherwise, proceed to determine the next frame.

[0054] T4: Group the bit codes into data packets, randomly select the data packets to be sent in all time slots of the current frame, and go to T6;

[0055] T5: If the previously sent data packet cannot be correctly detected (decoded) on the base station side, the base station sends a feedback signal to the corresponding terminal. After receiving the signaling, the terminal determines the bit code that needs to be retransmitted and goes to T4;

[0056] T6: Modulate the bit code into a symbol sequence and send it, ending the current terminal data transmission and waiting for new data to be sent.

[0057] Terminal sending probability p frame It can be determined based on the priority of the terminal business data, with higher priority data having a higher sending probability; it can also be set based on whether the current data transmission is the first transmission or a retransmission, and generally the sending probability of the retransmission is set to be greater than or equal to the first transmission.

[0058] The base station processes received data in frames. After receiving a complete frame, it starts processing the data in the time slots within the frame, detecting and decoding the data uploaded by multiple users. The base station knows the synchronization sequences used by different users and the codewords of the linear block codes used.

[0059] like Figure 2 As shown, different terminals use different synchronization sequences, so the base station can design a matched filter corresponding to each synchronization sequence to detect whether the synchronization sequence exists. If it exists, the channel gain |h| is calculated. 2 For example, if n terminals send data simultaneously in a time slot, the uplink channel gain of each terminal can be calculated as |h1| 2 ,|h2| 2 ,…,|h n | 2 ,like Figure 4 shown.

[0060] Based on whether the presence of users is detected and the number of users, the time slots in the frame are classified, including:

[0061] Non-collision time slot: only one terminal is detected in this time slot;

[0062] Conflict time slot: more than one terminal is detected in this time slot;

[0063] Idle time slot: No terminal is detected in this time slot.

[0064] Please refer to Figure 5 As shown, an embodiment of the present invention provides a multiple access random access method based on multi-slot serial interference cancellation, including:

[0065] Step S1, the base station receives and caches the data symbol sequence of the current frame;

[0066] Step S2, using a matched filter to perform user detection on all time slots and estimate channel parameters;

[0067] Step S3, judging the time slot type in the frame according to the detection result, and demodulating the corresponding symbol sequence according to the time slot type to obtain the bit code of the time slot; the time slot type is obtained based on whether the user is detected and the number of users;

[0068] Step S4, performing linear block code decoding and error correction on all bit codes of a terminal to obtain a final data bit code, and outputting the data of the terminal to a data server or a base station for local processing.

[0069] The step S3 specifically includes:

[0070] Step S30, determine whether there is a conflict-free time slot. If so, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot; if not, select the time slot with the largest channel gain and the corresponding terminal among all the conflicting time slots, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot.

[0071] Specifically, please combine Figure 6 As shown, the specific process of a multiple access random access method based on multi-slot serial interference cancellation provided by this embodiment is as follows:

[0072] Step R1, the base station receives the data symbol sequence of the current frame and buffers it; when the complete frame is received, it goes to step R2;

[0073] Step R2, use a matched filter to perform user detection on all time slots and estimate channel parameters, and then go to step R3;

[0074] Step R3, update the time slot classification, as mentioned above, all time slots are classified into non-conflict time slots, conflict time slots and idle time slots, and go to step R4;

[0075] Step R4, if all time slots are idle time slots, go to step R14, otherwise go to step R5;

[0076] Step R5, determine whether there is a conflict-free time slot, if yes, go to step R7, otherwise go to step R6;

[0077] Step R6, among all conflicting time slots, select the time slot with the largest channel gain (obtained from step R2) and the corresponding terminal, and go to step R7;

[0078] Step R7, using the channel estimation parameters obtained in step R2, demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot, and then go to step R8;

[0079] Step R8: if all bit codes (including data bit codes and check codes) of a terminal have been obtained, go to step R9; otherwise, go to step R11;

[0080] Step R9, decode the linear block code and correct the error to obtain the final data bit code of the user. If the decoding is successful, go to step R10, otherwise go to step R12 if the decoding fails;

[0081] Step R10: the data of the terminal has been successfully obtained, and the data is output to the data server or the base station for local processing; go to step R11;

[0082] Step R11, eliminating interference caused by the terminal for the occupied time slot. The terminal no longer occupies the time slot, and the process goes to step R3;

[0083] Step R12, the base station requires all undecoded terminals to retransmit, and then goes to step R13;

[0084] Step R13, the process ends in failure and the cache of the current frame is discarded;

[0085] Step R14 ends successfully and discards the cache of the current frame.

[0086] The process is described in further detail below.

[0087] In step R7, if the current k time slot is a non-conflicting time slot (i.e., directly transferred from R5 to R7), the base station receives the signal

[0088] y k =h i ·x i +n k

[0089] Among them, x i is the transmission symbol rate at terminal i, n k is the noise, h i is the channel gain of the uplink from terminal i to the base station. The signal-to-interference-noise ratio is expressed as

[0090]

[0091] where p x is the constant transmit power of the terminal, is the power spectral density of the noise.

[0092] In step R7, if the current k time slot is a conflicting time slot (i.e., switching from R6 to R7), the base station receives the signal

[0093]

[0094] Among them, k is the set of user sequences active in time slot k, x i The transmission symbol rate at terminal i, n k is the noise, h i is the channel gain of the uplink from terminal i to the base station. The specific terminal i selected by R6 satisfies |h i | 2 ≥|h j | 2 , Then the signal-to-interference-noise ratio is expressed as

[0095]

[0096] It can be seen that SNR1≥SNR2, that is, compared with the non-collision time slot, the collision time slot will cause the demodulated bit stream to have a higher bit error rate due to the interference of other users.

[0097] R9 is the decoding of linear block codes. There are many types of decoding algorithms. Generally speaking, they have error correction functions. If there are too many erroneous bits, error correction cannot be completed and the decoding can be declared failed. Choosing different decoding algorithms has different computational complexity and different decoding effects.

[0098] R11 is for interference elimination. If it is transferred directly from R8 to R11, the interference caused by the user in the current time slot will be directly eliminated, which is convenient for demodulation by other users. If it is transferred from R10 to R11, the linear block code has an error correction function for the original data (changing the data bits), so it is necessary to update the interference calculation before the error correction and apply the new interference elimination to make the demodulation of other users more accurate.

[0099] When a terminal fails to decode, the base station notifies all terminals that have not decoded (including the current failed decoding) to retransmit through the feedback channel. There is no need to notify the terminal of successful decoding, which reduces the signaling overhead of the feedback channel.

[0100] The following example illustrates the data transmission process of the terminal and the decoding process of the base station.

[0101] Assume that there are N = 4 service terminals under the base station, there are K = 8 time slots in each frame, terminals 1 and 2 use (4,2) linear block code, terminals 3 and 4 use (3,2) linear block code, and each terminal randomly selects to send the coded bit stream (modulated) in 8 time slots. Assume that the channel gain size is: |h1| 2 >|h2| 2 >|h3| 2 >|h4| 2 .

[0102] Then based on Figure 7 As shown, the order of base station decoding is:

[0103] (1) Terminal 1 Time Slot 2, Terminal 1 Time Slot 6: Both are non-collision time slots.

[0104] (2) Terminal 1 time slot 5, terminal 1 time slot 8: both are conflicting time slots. Linear block code decoding is performed on the codeword of terminal 1. If the decoding fails, the decoding is terminated and all terminals are notified to retransmit.

[0105] (3) Terminal 3 time slot 8: The interference from terminal 1 has been eliminated and this time slot is a non-collision time slot.

[0106] (4) Terminal 2 time slot 1: conflicting time slot.

[0107] (5) Terminal 4 time slot 1: The interference of terminal 2 has been eliminated and this time slot is a non-conflicting time slot.

[0108] (6) Terminal 2 time slot 3: conflicting time slot.

[0109] (7) Terminal 4 time slot 3: The interference of terminal 2 has been eliminated and this time slot is a non-conflicting time slot.

[0110] (8) Terminal 2 Time Slot 5, Terminal 2 Time Slot 7: Both are conflicting time slots. Linear block code decoding is performed on the codeword of terminal 2. If the decoding fails, the process is terminated and terminals 2, 3, and 4 are notified to retransmit.

[0111] (9) Terminal 3 time slot 7: The interference from terminal 2 has been eliminated and this time slot is a non-conflicting time slot.

[0112] (10) Terminal 3, time slot 5: Linear block code decoding is performed on the codeword of terminal 3. If the decoding fails, the process is terminated and terminals 3 and 4 are notified to retransmit.

[0113] (11) Time slot 5 of terminal 4: The interference from terminal 3 has been eliminated, and this time slot is a non-collision time slot. Linear block code decoding is performed on the codeword of terminal 4. If the decoding fails, the decoding is terminated. If the decoding succeeds, the decoding output results of the four terminals are successfully completed.

[0114] It can be seen from the above description that compared with the prior art, the beneficial effects of the present invention are: the present invention utilizes the error correction function of the linear block code to improve the effect of serial interference elimination, and significantly improves the data detection success rate in the case of multi-user uplink concurrent access conflicts. The use of random transmission of multiple time slots can increase the number of user accesses, thereby increasing the throughput of the Internet of Things access network with massive terminals.

[0115] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A multiple access random access method based on multi-slot serial interference cancellation, characterized in that: include: Step S1, the base station receives and caches the data symbol sequence of the current frame; Step S2, using a matched filter to perform user detection on all time slots and estimate channel parameters; Step S3, judging the time slot type in the frame according to the detection result, and demodulating the corresponding symbol sequence according to the time slot type to obtain the bit code of the time slot; the time slot type is obtained based on whether the user is detected and the number of users; the time slot classification includes conflict-free time slot, conflict time slot and idle time slot; Step S4, performing linear block code decoding and error correction on all bit codes of a terminal to obtain a final data bit code, and outputting the data of the terminal to a data server or a base station for local processing; The step S3 specifically includes: Step S30, determine whether there is a conflict-free time slot. If so, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot; if not, select the time slot with the largest channel gain and the corresponding terminal among all the conflicting time slots, use the channel estimation parameters obtained in step S2 to demodulate the symbol sequence of the conflict-free time slot to obtain the bit code of the time slot.

2. The method according to claim 1, characterized in that If all the bit codes of a certain terminal are not obtained, the interference caused by the terminal is eliminated for the occupied time slot, and the process returns to step S3.

3. The method according to claim 1, characterized in that After step S4, the method further includes discarding the cache of the current frame.

4. The method according to claim 1, characterized in that If all time slots are idle time slots, the process ends successfully and the cache of the current frame is discarded, otherwise the process goes to step S30.

5. The method according to claim 1, characterized in that In step S30, if the current k time slot is a non-conflicting time slot, the base station receives the signal: y k =h i ·x i +n k Among them, x i is the transmission symbol rate at terminal i, n k is the noise, h i is the channel gain of the uplink from terminal i to the base station; the signal to interference and noise ratio is expressed as: Among them, p x is the constant transmit power of the terminal, is the power spectral density of the noise.

6. The method according to claim 1, characterized in that In step S30, if the current k time slot is a conflicting time slot, the base station receives the signal: Among them, k is the set of user sequences active in time slot k, x i is the transmission symbol rate of terminal i, nk is the noise, h i is the channel gain of the uplink from terminal i to the base station. The specific terminal i selected in step S30 satisfies Then the signal to interference and noise ratio is expressed as: Among them, p x is the constant transmit power of the terminal, is the power spectral density of the noise.

7. The method according to any one of claims 1 to 6, characterized in that: Before step S1, a process of uplink transmission of terminal data is also included, and the process is specifically as follows: Encode the bit stream of IoT terminal data using linear block code and cache the encoded bit code; The terminal sends with probability p frame Determine whether to use the current frame for data transmission. If it is determined to use the current frame for transmission, group the bit codes into data packets and randomly select the data packets to be sent in all time slots of the current frame. Otherwise, proceed to the next frame for determination. The modulated bit code is a symbol sequence and sent, ending the sending of the current terminal data and waiting for new data to be sent.

8. The method according to claim 7, characterized in that Sending probability p frame It is determined according to the priority of the terminal service data. The higher the priority, the higher the sending probability. Or it is set according to whether the current data transmission is the first transmission or retransmission. The sending probability of retransmission is greater than or equal to the sending probability of the first transmission.

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