A random access mechanism selection method for 5G cellular networks

Abstract

The present invention proposes a random access mechanism selection method for 5G cellular networks, which relates to the technical field of wireless communications. The present invention is based on a four-step random access process initiated by devices in 5G cellular networks in CBRA and PBRA. On the premise of determining the number of devices in the 5G cellular network, the data arrival rate of each device, and the length of data messages, the method determines whether the data message length and the data arrival rate of each device meet the transmission constraints according to different service traffic characteristics of the 5G cellular network, and then selects a suitable random access mechanism considering the average signaling overhead, thereby realizing the connection between the device and the base station and optimizing the overall performance of the 5G cellular network.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and more specifically, to a random access mechanism selection method for a 5G cellular network. Background Art

[0002] With the rapid development of information technology, wireless communication has been integrated into people's daily life and industrial production. As the network with the widest coverage, cellular communication (a mobile communication hardware architecture, named after the hexagonal signal coverage of each communication base station that constitutes the network coverage, making the entire network look like a honeycomb, such as the current 4G network and 5G network) has become the infrastructure for social operations to support various applications with wireless communication needs.

[0003] In the prior art, 4G networks and cellular networks of previous eras use a connection-based random access mechanism (CBRA), that is, each device must perform a random access process to establish a connection with a base station before transmitting data, and then transmit data through the uplink and downlink time and frequency resources allocated by the base station. In traditional mobile phone communication scenarios, the number of devices is relatively small, and each device transmits a large amount of data, but the signaling overhead generated during the connection establishment process is negligible.

[0004] However, in the current emerging IoT communication scenarios, IoT devices are often huge in number, and each device only transmits small data packets infrequently. Therefore, if the CBRA mechanism is still used, the network will transmit a small amount of data packets at the expense of huge signaling overhead. To solve this problem, the current 5G network has introduced a packet-based random access mechanism (PBRA, Packet-Based Random Access), that is, the IoT device can transmit a small data packet in the third step of random access without establishing a subsequent connection with the base station.

[0005] like Figure 1 As shown in the figure, MTD represents a device in a cellular network. In the PBRA scheme, the device initiates a four-step random access process. In the first step, the device randomly selects one from M (1≤M≤64) orthogonal preambles and sends it to the base station; in the second step, the base station replies with a random access response message according to each preamble it receives; the device transmits a data message in the third step; and the base station replies with a confirmation reply message in the fourth step. Therefore, if the data message is successfully transmitted in the third step, its signaling overhead is 3 signalings; if the random access fails, its signaling overhead is 4 signalings.

[0006] like Figure 2As shown in the figure, MTD represents the device in the cellular network. In the CBRA scheme, the device also initiates a four-step random access process. The difference is that the device sends a connection establishment request in the third step. After the connection is established in the fifth step, the device can start transmitting data to the base station. Therefore, if the device successfully establishes a connection with the base station, its signaling overhead is 5 signalings; if it fails in the random access process, its signaling overhead is 4. Therefore, compared with the CBRA mechanism, the PBRA mechanism can significantly reduce the signaling overhead in scenarios where small data packets are not frequently transmitted.

[0007] The two random access mechanisms coexisting in 5G networks are suitable for communication services with different traffic characteristics. If the random access mechanism is not selected properly, the 5G network performance and service quality will be adversely affected. Therefore, how to select the random access mechanism according to the data traffic characteristics of the service is crucial to optimizing the communication performance and communication services of the 5G network. Summary of the invention

[0008] In order to solve the problem of selecting a random access mechanism in a 5G cellular network, the present invention proposes a random access mechanism selection method for a 5G cellular network, which selects a random access mechanism according to different data traffic characteristics of the service, so as to optimize the overall performance of the 5G network and support the development of 5G communication services.

[0009] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0010] A random access mechanism selection method for a 5G cellular network is used for selecting a random access mechanism for a device in a 5G cellular network to establish a connection with a base station. The random access mechanism to be selected includes a connection-based random access mechanism CBRA and a message-based random access mechanism PBRA. In both CBRA and PBRA, the device initiates a four-step random access process. The method includes:

[0011] S1. Obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel to 1 / e;

[0012] S2. Based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel 1 / e, determine whether the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA;

[0013] S3. Calculate the average signaling overhead S of PBRAPBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, and execute step S4; otherwise, select the connection-based random access mechanism CBRA, and execute step S4;

[0014] S4. The base station informs the device of the selected random access mechanism by broadcasting.

[0015] In the present technical scheme, compared with the connection-based random access mechanism CBRA, in the scenario of infrequent transmission of small data packets, the message-based random access mechanism PBRA can significantly reduce the signaling overhead. Therefore, based on the four-step random access process initiated by the devices in the 5G cellular network in CBRA and PBRA, on the premise of determining the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data packet length L, according to the different service traffic characteristics of the 5G cellular network, it is determined whether the data packet length L and the data arrival rate λ of each device meet the transmission constraints, and then considering the average signaling overhead, a suitable random access mechanism is selected to achieve the connection between the device and the base station, thereby optimizing the overall network performance.

[0016] Preferably, the four-step random access process initiated by the device in the message-based random access mechanism PBRA includes:

[0017] Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station;

[0018] Step 2: The base station replies with a random access response message according to the received orthogonal preamble code;

[0019] Step 3: The device transmits data message;

[0020] Step 4: The base station replies with confirmation and reply message.

[0021] Preferably, the four-step random access process initiated by the device in the connection-based random access mechanism CBRA includes:

[0022] Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station;

[0023] Step 2: The base station replies with a random access response message according to the received orthogonal preamble code;

[0024] Step 3: The device establishes a connection request via RRC;

[0025] Step 4: The base station replies with an RRC connection configuration information message;

[0026] When the RRC connection between the device and the base station is established, the device transmits data to the base station.

[0027] Preferably, the number n of devices in the 5G cellular network described in step S1 is obtained by the base station recording the registered devices through the MAC addresses of the devices.

[0028] Preferably, each device can report its data arrival rate λ and data message length L to the base station through an RRC connection establishment request message.

[0029] Preferably, the transmission constraint conditions described in step S2 include:

[0030] S21. Determine whether the data packet length L satisfies: L<β, if so, execute step S22; otherwise, select the connection-based random access mechanism CBRA;

[0031] S22. Determine whether the data arrival rate λ satisfies: nλ<1 / e. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA.

[0032] Here, due to the limitation of time domain and frequency domain resources, the length of the data message that can be transmitted in the third step of the random access process is also limited. Only when the length of the data message is less than the maximum data message length β that can be transmitted in the third step of the random access process, can the message-based random access mechanism PBRA be selected. Otherwise, the connection-based random access mechanism CBRA should be selected, that is, when L<β, execute step S22, otherwise, select the connection-based random access mechanism CBRA.

[0033] Preferably, the transmission constraint conditions described in step S2 include:

[0034] like Then execute step S3, otherwise, select the connection-based random access mechanism CBRA.

[0035] Preferably, in step S3, the signaling overhead S of PBRA PBRA The calculation expression is:

[0036]

[0037] in, It represents the throughput of the message-based random access mechanism PBRA, F1 represents the number of data packets that fail to be transmitted per unit time in PBRA, satisfy:

[0038]

[0039] F1 meets:

[0040]

[0041] in, represents the total data arrival rate in the 5G cellular network, and Throughput of 5G cellular network in PBRA, a message-based random access mechanism Equal to the total data arrival rate represents the Lambert W function.

[0042] Preferably, in step S3, the average signaling overhead S of CBRA PBRA The calculation expression is:

[0043]

[0044] in, represents the throughput of the connection-based random access mechanism CBRA, F2 represents the number of data packets that fail to be transmitted per unit time in CBRA, satisfy:

[0045]

[0046] Where n represents the number of devices. represents the total data arrival rate in the 5G cellular network; D represents the data transmission rate, that is, the number of data packets transmitted in each time slot; q represents the probability of a device initiating a random access request when it has data to transmit, and p represents the probability of successful transmission when the device initiates an access request;

[0047] F2 meets:

[0048] F2=nρq(1-p L )

[0049] Among them, ρ represents the probability that each node queue is not empty, and the expression satisfied is:

[0050]

[0051] p L It represents the steady-state probability of successful transmission when the device initiates an access request, and the expression it satisfies is:

[0052]

[0053] The present application also proposes a random access mechanism selection system for a 5G cellular network, the system comprising:

[0054] The data acquisition setting module is used to obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time of the cellular network random access channel to 1 / e;

[0055] A judgment module, based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number 1 / e of data packets successfully transmitted per unit time of the cellular network random access channel, judges whether the data message length L and the data arrival rate λ of each device meet the transmission constraint condition;

[0056] The calculation and analysis module calculates the average signaling overhead S of PBRA when the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, otherwise, select the connection-based random access mechanism CBRA;

[0057] The broadcast module informs the device of the selected random access mechanism in a broadcast manner.

[0058] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0059] The present invention proposes a random access mechanism selection method for 5G cellular networks, which is based on a four-step random access process initiated by devices in 5G cellular networks in CBRA and PBRA. On the premise of determining the number of devices in the 5G cellular network, the data arrival rate of each device, and the length of data packets, the method determines whether the data packet length and the data arrival rate of each device meet the transmission constraints according to different service traffic characteristics of the 5G cellular network, and then selects a suitable random access mechanism considering the average signaling overhead to achieve connection between the device and the base station, thereby optimizing the overall network performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A flow chart showing a message-based random access mechanism PBRA proposed in the background technology of the present invention;

[0061] Figure 2 A flow chart showing a connection-based random access mechanism CBRA proposed in the background technology of the present invention;

[0062] Figure 3 A schematic diagram showing a flow chart of a random access mechanism selection method for a 5G cellular network proposed in Embodiment 1 of the present invention;

[0063] Figure 4 A structural diagram showing the random access mechanism selection system for 5G cellular networks proposed in Example 3 of the present invention. DETAILED DESCRIPTION

[0064] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0065] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual size;

[0066] It is understandable to those skilled in the art that descriptions of certain well-known contents in the drawings may be omitted.

[0067] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0068] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent;

[0069] Example 1

[0070] Consider two random access mechanisms coexisting in the 5G network: a connection-based random access mechanism CBRA and a message-based random access mechanism PBRA, which are suitable for communication services with different traffic characteristics. If the random access mechanism is not selected properly, the 5G network performance and service quality will be adversely affected. Therefore, this embodiment proposes a random access mechanism selection method for a 5G cellular network, which is used for selecting a random access mechanism for a device in a 5G cellular network to establish a connection with a base station. The random access mechanism to be selected includes a connection-based random access mechanism CBRA and a message-based random access mechanism PBRA, wherein the basic processes of PBRA and CBRA are as follows: Figure 1 and Figure 2 As shown, in both CBRA and PBRA, the device initiates a four-step random access process, see Figure 1 , MTD represents a device in a cellular network. The four-step random access process initiated by a device in the message-based random access mechanism PBRA includes:

[0071] Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station;

[0072] Step 2: The base station replies with a random access response message according to the received orthogonal preamble code;

[0073] Step 3: The device transmits data message;

[0074] Step 4: The base station replies with confirmation and reply message.

[0075] See also Figure 2 The four-step random access process initiated by the device in the connection-based random access mechanism CBRA includes:

[0076] Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station;

[0077] Step 2: The base station replies with a random access response message according to the received orthogonal preamble code;

[0078] Step 3: The device establishes a connection request via RRC;

[0079] Step 4: The base station replies with an RRC connection configuration information message;

[0080] When the RRC connection between the device and the base station is established, the device transmits data to the base station.

[0081] Based on this, this embodiment proposes a random access mechanism selection method for 5G cellular networks, see Figure 3 The method comprises the following steps:

[0082] S1. Obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel to 1 / e;

[0083] Among them, the number of devices n in the 5G cellular network is obtained by the base station recording the registered devices through the MAC address of the device. Each device can report its data arrival rate λ and data message length L to the base station through the RRC connection establishment request message.

[0084] S2. Based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel 1 / e, determine whether the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA;

[0085] In this embodiment, the transmission constraints include:

[0086] S21. Determine whether the data packet length L satisfies: L<β, if so, execute step S22; otherwise, select the connection-based random access mechanism CBRA;

[0087] S22. Determine whether the data arrival rate λ satisfies: nλ<1 / e. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA.

[0088] Here, due to the limitation of time domain and frequency domain resources, the length of the data message that can be transmitted in the third step of the random access process is also limited. Only when the length of the data message is less than the maximum data message length β that can be transmitted in the third step of the random access process, can the message-based random access mechanism PBRA be selected. Otherwise, the connection-based random access mechanism CBRA should be selected, that is, when L<β, execute step S22, otherwise, select the connection-based random access mechanism CBRA.

[0089] S3. Calculate the average signaling overhead S of PBRA PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, and execute step S4; otherwise, select the connection-based random access mechanism CBRA, and execute step S4;

[0090] In step S3, the signaling overhead of PBRA S PBRA The calculation expression is:

[0091]

[0092] in, It represents the throughput of the message-based random access mechanism PBRA, F1 represents the number of data packets that fail to be transmitted per unit time in PBRA, satisfy:

[0093]

[0094] F1 meets:

[0095]

[0096] in, represents the total data arrival rate in the 5G cellular network, and Throughput of 5G cellular network in PBRA, a message-based random access mechanism Equal to the total data arrival rate represents the Lambert W function.

[0097] The average signaling overhead of CBRA is S PBRA The calculation expression is:

[0098]

[0099] in, represents the throughput of the connection-based random access mechanism CBRA, F2 represents the number of data packets that fail to be transmitted per unit time in CBRA, satisfy:

[0100]

[0101] Where n represents the number of devices. represents the total data arrival rate in the 5G cellular network; D represents the data transmission rate, that is, the number of data packets transmitted in each time slot; q represents the probability of a device initiating a random access request when it has data to transmit, and p represents the probability of successful transmission when the device initiates an access request;

[0102] F2 meets:

[0103] F2=nρq(1-p L )

[0104] Among them, ρ represents the probability that each node queue is not empty, and the expression satisfied is:

[0105]

[0106] p L It represents the steady-state probability of successful transmission when the device initiates an access request, and the expression it satisfies is:

[0107]

[0108] Finally, execute step S4:

[0109] S4. The base station informs the device of the selected random access mechanism by broadcasting.

[0110] In general, the implementation process of this embodiment is as follows:

[0111] On the premise of determining the number of devices n, the data arrival rate λ of each device, and the data message length L in the 5G cellular network, the different service traffic characteristics of the 5G cellular network are used to determine whether the data message length L and the data arrival rate λ of each device meet the transmission constraints. Then, considering the average signaling overhead, a suitable random access mechanism is selected to achieve connection between the device and the base station, thereby optimizing the overall network performance.

[0112] Example 2

[0113] This embodiment is basically similar to the random access mechanism selection method for the 5G cellular network proposed in Embodiment 1, and includes the following steps:

[0114] S1. Obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel to 1 / e;

[0115] Among them, the number n of devices in the 5G cellular network is obtained by the base station through the registered devices recorded by the MAC address of the device. Each device can report its data arrival rate λ and data message length L to the base station through the RRC connection establishment request message.

[0116] S2. Based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel 1 / e, determine whether the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA;

[0117] In this embodiment, the transmission constraint conditions described in step S2 include:

[0118] like Then execute step S3, otherwise, select the connection-based random access mechanism CBRA. That is, comprehensively judge whether the data message length L and the data arrival rate λ of each device meet the transmission constraint condition.

[0119] S3. Calculate the average signaling overhead S of PBRA PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, and execute step S4; otherwise, select the connection-based random access mechanism CBRA, and execute step S4;

[0120] In step S3, the signaling overhead of PBRA S PBRA The calculation expression is:

[0121]

[0122] in, It represents the throughput of the message-based random access mechanism PBRA, F1 represents the number of data packets that fail to be transmitted per unit time in PBRA, satisfy:

[0123]

[0124] F1 meets:

[0125]

[0126] in, represents the total data arrival rate in the 5G cellular network, and Throughput of 5G cellular network in PBRA, a message-based random access mechanism Equal to the total data arrival rate represents the Lambert W function.

[0127] The average signaling overhead of CBRA is S PBRA The calculation expression is:

[0128]

[0129] in, represents the throughput of the connection-based random access mechanism CBRA, F2 represents the number of data packets that fail to be transmitted per unit time in CBRA, satisfy:

[0130]

[0131] Where n represents the number of devices. It represents the total data arrival rate in the 5G cellular network; D represents the data transmission rate, that is, the number of data packets transmitted in each time slot; when the device has data to transmit, it requests access mechanism, q represents the probability of initiating a random access request when the device has data to transmit, and p represents the probability of successful transmission when the device initiates an access request;

[0132] F2 meets:

[0133] F2=nρq(1-p L )

[0134] Among them, ρ represents the probability that each node queue is not empty, and the expression satisfied is:

[0135]

[0136] p L It represents the steady-state probability of successful transmission when the device initiates an access request, and the expression it satisfies is:

[0137]

[0138] Finally, execute step S4:

[0139] S4. The base station informs the device of the selected random access mechanism by broadcasting.

[0140] Example 3

[0141] like Figure 4 As shown, this embodiment proposes a random access mechanism selection system for 5G cellular networks, see Figure 4 , the system comprising:

[0142] The data acquisition setting module 101 is used to obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time of the cellular network random access channel to 1 / e;

[0143] The judgment module 102 judges whether the data packet length L and the data arrival rate λ of each device meet the transmission constraint condition based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number 1 / e of data packets successfully transmitted per unit time of the cellular network random access channel;

[0144] The transmission conditions are:

[0145] S21. Determine whether the data packet length L satisfies: L<β, if so, execute step S22; otherwise, select the connection-based random access mechanism CBRA;

[0146] S22. Determine whether the data arrival rate λ satisfies: nλ<1 / e. If so, enter the calculation and analysis module 103 for calculation and analysis; otherwise, select the connection-based random access mechanism CBRA.

[0147] or:

[0148] like Then the calculation and analysis module 103 is entered for calculation and analysis. Otherwise, the connection-based random access mechanism CBRA is selected, that is, different transmission conditions can be encapsulated in the judgment module 102 according to actual needs.

[0149] The calculation and analysis module 103 calculates the average signaling overhead S of the PBRA when the data message length L and the data arrival rate λ of each device meet the transmission constraint condition. PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, otherwise, select the connection-based random access mechanism CBRA;

[0150] The broadcast module 104 informs the device of the selected random access mechanism in a broadcast manner.

[0151] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A random access mechanism selection method for a 5G cellular network, for selecting a random access mechanism for a device in a 5G cellular network to establish a connection with a base station, wherein the random access mechanism to be selected includes a connection-based random access mechanism CBRA and a message-based random access mechanism PBRA. In both CBRA and PBRA, the device initiates a four-step random access process, characterized in that: The method comprises: S1. Obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, and the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel to 1 / e; S2. Based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number of data packets successfully transmitted per unit time in the cellular network random access channel 1 / e, determine whether the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA; S3. Calculate the average signaling overhead S of PBRA PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, and execute step S4; otherwise, select the connection-based random access mechanism CBRA, and execute step S4; In step S3, the signaling overhead of PBRA S PBRA The calculation expression is: in, It represents the throughput of the message-based random access mechanism PBRA, F1 represents the number of data packets that fail to be transmitted per unit time in PBRA, satisfy: F1 meets: in, represents the total data arrival rate in the 5G cellular network, and Throughput of 5G cellular network in PBRA, a message-based random access mechanism Equal to the total data arrival rate represents the Lambert W function; In step S3, the average signaling overhead of CBRA S PBRA The calculation expression is: in, represents the throughput of the connection-based random access mechanism CBRA, F2 represents the number of data packets that fail to be transmitted per unit time in CBRA, satisfy: Where n represents the number of devices. represents the total data arrival rate in the 5G cellular network; D represents the data transmission rate, that is, the number of data packets transmitted in each time slot; q represents the probability of a device initiating a random access request when it has data to transmit, and p represents the probability of successful transmission when the device initiates an access request; F2 meets: F2=nρq(1-p L ) Among them, ρ represents the probability that each node queue is not empty, and the expression satisfied is: p L It represents the steady-state probability of successful transmission when the device initiates an access request, and the expression it satisfies is: S4. The base station informs the device of the selected random access mechanism by broadcasting.

2. The random access mechanism selection method for 5G cellular network according to claim 1, characterized in that: The four-step random access process initiated by the device in the message-based random access mechanism PBRA includes: Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station; Step 2: The base station replies with a random access response message according to the received orthogonal preamble code; Step 3: The device transmits data message; Step 4: The base station replies with confirmation and reply message.

3. The random access mechanism selection method for 5G cellular network according to claim 1, characterized in that: The four-step random access process initiated by the device in the connection-based random access mechanism CBRA includes: Step 1: The device randomly selects one from the M orthogonal preamble codes of the preamble sequence and sends it to the base station; Step 2: The base station replies with a random access response message according to the received orthogonal preamble code; Step 3: The device establishes a request through RRC connection; Step 4: The base station replies with an RRC connection configuration information message; When the RRC connection between the device and the base station is established, the device transmits data to the base station.

4. The random access mechanism selection method for 5G cellular network according to claim 1, characterized in that: The number n of devices in the 5G cellular network described in step S1 is obtained by the base station recording the registered devices through the MAC addresses of the devices.

5. The random access mechanism selection method for 5G cellular network according to claim 4, characterized in that: Each device can report its data arrival rate λ and data message length L to the base station through an RRC connection establishment request message.

6. The random access mechanism selection method for 5G cellular network according to claim 5, characterized in that: The transmission constraints described in step S2 include: S21. Determine whether the data packet length L satisfies: L<β, if so, execute step S22; otherwise, select the connection-based random access mechanism CBRA; S22. Determine whether the data arrival rate λ satisfies: nλ<1 / e. If so, execute step S3; otherwise, select the connection-based random access mechanism CBRA.

7. The random access mechanism selection method for 5G cellular network according to claim 5, characterized in that: The transmission constraints described in step S2 include: like Then execute step S3, otherwise, select the connection-based random access mechanism CBRA.

8. A random access mechanism selection system for 5G cellular networks, characterized in that: The system comprises: The data acquisition setting module is used to obtain the number of devices n in the 5G cellular network, the data arrival rate λ of each device, the data message length L, and set the maximum length of the data packet that can be carried in the third step of the four-step random access process to β and the maximum number of data packets successfully transmitted per unit time of the cellular network random access channel to 1 / e; A judgment module, based on the maximum length β of the data packet that can be carried in the third step of the four-step random access process and the maximum number 1 / e of data packets successfully transmitted per unit time of the cellular network random access channel, judges whether the data message length L and the data arrival rate λ of each device meet the transmission constraint condition; The calculation and analysis module calculates the average signaling overhead S of PBRA when the data message length L and the data arrival rate λ of each device meet the transmission constraint conditions. PBRA And the average signaling overhead S of CBRA CBRA , if S PBRA <S CBRA , select the message-based random access mechanism PBRA, otherwise, select the connection-based random access mechanism CBRA; PBRA signaling overhead S PBRA The calculation expression is: in, It represents the throughput of the message-based random access mechanism PBRA, F1 represents the number of data packets that fail to be transmitted per unit time in PBRA, satisfy: F1 meets: in, represents the total data arrival rate in the 5G cellular network, and Throughput of 5G cellular network in PBRA, a message-based random access mechanism Equal to the total data arrival rate represents the Lambert W function; The average signaling overhead of CBRA is S PBRA The calculation expression is: in, represents the throughput of the connection-based random access mechanism CBRA, F2 represents the number of data packets that fail to be transmitted per unit time in CBRA, satisfy: Where n represents the number of devices. represents the total data arrival rate in the 5G cellular network; D represents the data transmission rate, that is, the number of data packets transmitted in each time slot; q represents the probability of a device initiating a random access request when it has data to transmit, and p represents the probability of successful transmission when the device initiates an access request; F2 meets: F2=nρq(1-p L ) Among them, ρ represents the probability that each node queue is not empty, and the expression satisfied is: p L It represents the steady-state probability of successful transmission when the device initiates an access request, and the expression it satisfies is: The broadcast module informs the device of the selected random access mechanism in a broadcast manner.

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