WO2022067713A1

WO2022067713A1 - Random access method, communication system, communication device, and readable storage medium

Info

Publication number: WO2022067713A1
Application number: PCT/CN2020/119522
Authority: WO
Inventors: 張博裕
Original assignee: 深圳市万普拉斯科技有限公司
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2022-04-07
Also published as: CN116368929A

Abstract

Disclosed are a random access method, a communication system, a communication device, and a readable storage medium. The random access method comprises: a terminal sending a first message to a network device and receiving a second message returned by the network device; determining whether the second message simultaneously carries RAR and CR messages; if yes, using 2-step RACH; and if not, using 4-step RACH. The present invention standardizes an uplink synchronization processing mode when 2-step RACH is returned to 4-step RACH, facilitates flexibly switching random access modes of a terminal, and improves the communication efficiency.

Description

Random access method and communication system, communication device, and readable storage medium

technical field

The present invention relates to the field of communications, in particular to the field of random access (Random Access, RA) technologies, and in particular, to a random access method, a communications system, a communications device, and a readable storage medium.

Background technique

The 5th generation mobile network (or 5th generation wireless systems, 5G) is a new generation of cellular mobile communication technology, its main goals are high data rate, reduce delay, improve system capacity and large-scale device connection. Currently, the 5G system supports two types of competitive random access: 4-step Random Access Channel (4-step RACH) and 2-step Random Access Channel (2-step RACH).

4-step RACH belongs to the random access method of the Long Term Evolution (LTE) system. The random access process is shown in Figure 1, which is mainly divided into four steps:

The user terminal sends Msg1 to the network device: the user terminal (User Equipment, UE) selects preamble (preamble) and PRACH (Physical Random Access Channel, physical random access channel) resources, and uses the PRACH resource to send the preamble to the network device.

The network device sends Msg2 to the user terminal: the network device receives the preamble, calculates TA (Time Alignment, timing advance), and sends RAR (Random Access Response, random access response) to the user terminal, where the RAR contains TA information and messages for Msg3 The UL grant (uplink scheduling grant), and the temporary C-RNTI (Cell Radio Network Temporary Identity, cell wireless network temporary identity) allocated by the network device. The PDCCH (Physical Downlink Control Channel, physical downlink control channel) carrying Msg2 is scrambled with RA-RNTI (Random Access RNTI), and the RA-RNTI uniquely corresponds to the time-frequency resource for sending Msg1 within a 10ms window; Msg2 also carries a preamble ID , the user terminal determines that the Msg2 corresponds to the Msg1 through the RA-RNTI and the preamble ID.

The user terminal sends Msg3 to the network device: the user terminal sends uplink transmission on the UL grant specified by the aforementioned Msg2. For different random access reasons or transmission requirements, the data transmitted by the Msg3 uplink is different. For example, for the transmission requirements of the initial access, the Msg3 uplink transmits an RRC (Radio Resource Control, Radio Resource Control) connection establishment request.

The network device sends Msg4 to the user terminal: the Msg4 can be understood as a contention resolution (Contention Resolution, CR) message. The user terminal can judge whether the random access is successful this time according to the Msg4. For the transmission requirement of the initial access, after the contention is successfully resolved, the temporary C-RNTI is automatically converted into the C-RNTI, which is the unique identifier of the user terminal in the cell, that is, the permanent C-RNTI.

In order to shorten the random access delay, the 5G system supports 2-step RACH in addition to the 4-step RACH of the LTE system. The process flow of the 2-step RACH is shown in Figure 2.

The user terminal sends Msg A to the network device: the Msg A may include a preamble and data.

The network device sends Msg B to the user terminal: the Msg B may include RAR and CR.

The wireless cellular network based on the 5G system can provide wireless communication services for user terminals by deploying network equipment, such as base stations, thereby enabling network equipment and user terminals to perform data transmission. When a user terminal sends data to a network device, it needs to establish uplink synchronization with the network device. The current 5G system generally obtains uplink synchronization through 4-step RACH or 2-step RACH.

The specific random access method that the user terminal should adopt to achieve uplink synchronization will affect the delay improvement and communication efficiency to a large extent. Corresponding technical solutions are urgently needed in the current industry.

technical problem

The prior art does not specify how to handle uplink synchronization when 2-step RACH falls back to 4-step RACH.

technical solutions

The present invention provides a random access method, comprising:

The terminal sends the first message to the network device;

The terminal receives the second message replied by the network device;

The terminal determines whether the second message carries both a random access response and a contention resolution message;

When the second message carries both the random access response and the contention resolution message, the terminal adopts a two-step random access to perform a random access procedure; and

When the second message only carries the random access response and the contention resolution determination fails, the terminal adopts a four-step random access to perform a random access procedure.

The present invention provides another random access method, including:

The network device receives the first message sent by the terminal;

The network device replies to the terminal with a second message, which is used by the terminal to determine whether the second message carries both a random access response and a contention resolution message;

When the second message carries the random access response and the contention resolution message at the same time, the network device adopts a two-step random access to perform a random access procedure; and

When the second message only carries the random access response and the contention resolution determination fails, the network device adopts a four-step random access to perform a random access procedure.

The present invention provides a communication system, including a terminal and a network device, where the terminal is used to perform the steps of the above-mentioned random access method, and the network device is used to perform the steps of the above-mentioned another random access method.

The present invention provides a communication device comprising a memory and a processor, the memory stores a program, and the program is configured to be executed by the processor to perform one or more steps of any of the above random access methods.

The present invention provides a computer-readable storage medium storing a program for being executed by a processor to perform one or more steps of any of the above random access methods.

beneficial effect

The invention regulates the processing mode of uplink synchronization when the 2-step RACH falls back to the 4-step RACH, which is beneficial to improve the communication efficiency.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. , for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

Fig. 1 is the schematic flow chart of 4-step RACH;

Fig. 2 is the schematic flow chart of 2-step RACH;

3 is a schematic structural diagram of a wireless communication system according to an embodiment of the present invention;

4 is a schematic flowchart of a random access method according to an embodiment of the present invention;

5 is a schematic flowchart of a random access method according to another embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a communication device according to an embodiment of the present invention.

Detailed ways

The technical solutions of the following embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some but not all of the embodiments. Based on the following embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention. In the case of no conflict, the following embodiments and their technical features can be combined with each other.

An embodiment of the present invention provides a random access method, which can be applied to the wireless communication system shown in FIG. 3 . The wireless communication system is, for example: the fifth generation (5th Generation, 5G) system or the new radio (New Radio, NR), the global system for mobile communications (Global System for mobile communications, GSM) system, long term evolution (long term evolution, LTE) ) system, LTE Frequency Division Duplex (FDD) system, LTE Time Division Duplex (TDD) system, Code Division Multiple Access (CDMA) system, Wideband Code Division Multiple Access ( wideband code division multiple access (WCDMA) system, general packet radio service (GPRS) system, universal mobile telecommunication system (UMTS), worldwide interoperability for microwave access (WiMAX) ) system, etc. Of course, the wireless communication system is not limited to this. A wireless communication system will be referred to herein below as a communication system or system for the convenience of the description.

The wireless communication system includes a network device 31 and a terminal 32 for accessing a wireless network 33, such as a radio access network (Radio Access Network, RAN) or a core network (Core Network, CN).

The network device 31 can be any kind of electronic device with wireless transceiver function. The network device 31 includes but is not limited to: a base station (base station, BS), an evolved Node B (evolved Node B, eNB), a radio network controller (radio network controller, RNC), a Node B (Node B, NB), Base station controller (BSC), base transceiver station (base transceiver station, BTS), home base station (such as home evolved Node B or home Node B, HNB), baseband unit (baseband unit, BBU); wireless fidelity Access point (AP), wireless relay node, wireless backhaul node, transmission point (TP), or transmission and reception point (TRP) in the (wireless fidelity, WIFI) system etc.; it can also be TRP or TP in the 5G system, one or a group of antenna panels of the base station in the 5G system; or it can be a network node that constitutes a TRP or TP, such as a BBU or a distributed unit (DU), etc. . The wireless network 33 provides network services for the terminal 32 through the network device 31. Different operators may provide different network services for the terminal 32, and it can also be understood that different operators correspond to different operator networks.

The terminal 32 may also be referred to as user equipment or user terminal, mobile station (Mobile Station, MS), mobile terminal (Mobile Terminal, MT), etc., and is a device that provides audio, video and/or data connectivity to users, for example, The terminal 32 may be a handheld device, a vehicle-mounted device, or the like with a wireless connection function. At present, some specific examples of the terminal 32 may be: a smart phone (Mobile Phone), a pocket computer (Pocket Personal Computer, PPC), a handheld computer, a personal digital assistant (Personal Digital Assistant, PDA), a notebook computer, a tablet computer, a wearable computer equipment, or in-vehicle equipment.

The process in which the terminal 32 sends data to the network device 31 is called uplink data transmission, and the process in which the network device 31 sends data to the terminal 32 is called downlink data transmission. Before performing uplink data transmission, uplink synchronization needs to be established between the terminal 32 and the network device 31 . Usually, the terminal 32 establishes uplink synchronization with the network device 31 through a random access procedure (Random Access Procedure).

Specifically, when the terminal 32 has new uplink data to transmit, and has lost or has not established uplink synchronization with the network device 31, it generally needs to first obtain the uplink synchronization through the competition-based 4-step RACH process shown in FIG. 1, and then Then perform uplink data transmission. In order to further reduce the delay and signaling overhead, the industry proposes to use the 2-step RACH process shown in Figure 2 to obtain uplink synchronization. For different random access modes, how the terminal 32 chooses, for example, how to determine that it should fall back from 2-step RACH to 4-step RACH at certain moments, there is no corresponding solution in the prior art.

Therefore, the present invention provides a random access method, which regulates the processing method of uplink synchronization when 2-step RACH falls back to 4-step RACH, so as to improve communication efficiency.

FIG. 4 is a schematic flowchart of a random access method according to an embodiment of the present invention. Referring to FIG. 4 , the random access method in this embodiment may include the following steps S11 to S15.

S11: The terminal sends a first message to the network device.

The first message may be the Msg A message corresponding to the 2-step RACH, which at least simultaneously carries a random access preamble and a data part, wherein the data part includes but is not limited to one or a combination of the following contents: terminal identification, Buffer Status Report (BSR) and real business data. Here, it can be considered that the terminal attempts to obtain uplink synchronization with the network device in a 2-step RACH manner at the current moment. In order to more appropriately describe the way in which the 2-step RACH rolls back to the 4-step RACH, the first message is Msg A as an example below.

The preamble and the data part may be frequency division multiplexing (Frequency Division Multiplexing, FDM), or may be time division multiplexing (Time Division Multiplexing, TDM).

Of course, the first message may also be the Msg 1 message corresponding to the 4-step RACH, which at least carries a preamble but does not carry a data part, and the data part is referred to above. In this regard, it can be considered that the terminal attempts to obtain uplink synchronization with the network device using the 4-step RACH method.

S12: The network device replies the second message to the terminal.

The second message is determined by the network device according to the reception condition of the first message by the network side (or the network device). The reception of the first message can be divided into: both the preamble and the data part in the first message are successfully received; the preamble in the first message is not successfully received, but the data part is successfully received; Neither the preamble nor the data portion was successfully received.

The second message is determined by the network device according to the reception of the first message, and the terminal determines whether the 2-step RACH fails according to the reply of the network device (that is, the second message). specifically:

If both the preamble and the data part in the first message are successfully received by the network device, it is determined that the current 2-step RACH has not failed, and the second message replied by the network device can be regarded as the Msg B message corresponding to the 2-step RACH, It carries at least both RAR and CR messages.

If the preamble in the first message is not successfully received, but the data part is successfully received, the network device determines that the 2-step RACH fails. At this time, the terminal will continue to try the 2-step RACH and execute it when the 2-step RACH succeeds. The corresponding uplink synchronization mode, or, until the maximum number of preamble transmissions configured by the network device for the terminal is reached, and then fall back to 4-step RACH; or directly fall back to 4-step RACH.

If neither the preamble nor the data part in the first message is successfully received by the network device, it is determined that the current 2-step RACH fails. Similarly, the terminal will continue to try the 2-step RACH, and execute the corresponding 2-step RACH when the 2-step RACH succeeds. The processing method of uplink synchronization, or, until the maximum number of preamble transmissions configured by the network device for the terminal is reached, it will not fall back to 4-step RACH; or, the network device instructs the terminal to directly fall back to 4-step RACH.

When it is determined that the 2-step RACH fails, for the case where the terminal falls back to the 4-step RACH, the second message replied by the network device can be regarded as the Msg 2 message corresponding to the 4-step RACH, and the Msg 2 message carries at least RAR, It does not carry a CR message.

S13: The terminal determines whether the second message carries both the random access response and the contention resolution message.

The terminal judges whether the 2-step RACH fails according to the reply of the network device. In the case of failure and success, the information content carried by the second message is different. For details, refer to the above.

S14: When the second message carries both a random access response and a contention resolution message, the terminal adopts a two-step random access to perform a random access procedure.

S15: When the second message only carries a random access response and the contention resolution determination fails, the terminal adopts a four-step random access to perform a random access procedure.

In this embodiment, the RAR contains at least the TA information and the UL grant for the data part, as well as the temporary C-RNTI allocated by the network device, and the CR message is used to indicate that a terminal with a certain ID is in wireless access (Random Access, RA) wins the competition. Based on this, the second message carries both RAR and CR messages, which means that the network device allows the terminal to use 2-step RACH.

In step S14, the second message replied by the network device can be regarded as the Msg B of the 2-step RACH, which carries at least the RAR and CR messages at the same time, the terminal determines that the current 2-step RACH has not failed, and the terminal continues to use the 2-step RACH and The network device acquires uplink synchronization. The terminal using 2-step RACH to perform random access procedure includes: the terminal sends Msg A carrying the preamble and data part to the network device, and the network device replies to the terminal Msg B carrying at least both RAR and CR messages.

In step S15, the second message replied by the network device can be regarded as the Msg 2 message of the 4-step RACH, which does not carry the CR message, or carries the CR message but the CR message indicates that the contention conflict resolution failed, indicating that the current 2-step If the RACH fails, the terminal should fall back from the 2-step RACH to the 4-step RACH, and obtain uplink synchronization with the network device according to the RAR message. The terminal adopts the 4-step RACH to perform the random access procedure, including: the terminal sends the Msg 1 carrying at least the preamble to the network device, the network device replies the Msg 2 that carries at least the RAR, and then the terminal sends to the network device Msg 3 that carries at least the data part, The network device replies with Msg 4 carrying at least the CR message.

In other embodiments, when the 2-step RACH fails, the terminal may continue to try the 2-step RACH, and execute the corresponding uplink synchronization method when the 2-step RACH succeeds, or until the maximum preamble configured by the network device for the terminal is reached The number of transmissions will fall back to 4-step RACH; or the terminal will fall back to 4-step RACH directly.

Based on the foregoing, in the Msg B message corresponding to the 2-step RACH, the network device must send the RAR and CR messages to the terminal at the same time point or integrated in the same subframe, otherwise the terminal will fall back to 4-step step RACH achieves uplink synchronization with network equipment. That is to say, the embodiment of the present invention regulates the uplink synchronization processing mode that should be adopted when the 2-step RACH falls back to the 4-step RACH, so as to facilitate flexible switching of the random access that the terminal access network device should adopt. way to improve communication efficiency.

According to common sense in the field of random access, the CR message will carry the identification of the winning terminal in the wireless access competition. If the identifications match, the terminal determines that the wireless access competition has been won, otherwise the competition has failed. On the other hand, if the second message replied by the network device does not carry a CR message, it means that the random access mode currently adopted by the terminal fails. At this time, even if the second message carries RAR, the terminal cannot use the current The random access method obtains uplink synchronization with network equipment. Based on this, in the aforementioned step S13, within the receiving window of the second message, the terminal may first determine whether the CR message is decoded, and then determine whether the second message carries the RAR.

Since once the terminal decodes the CR message replied by the network device (carried in the second message) and judges that the random access is successful, it means that the network device allows the terminal to use the current random access mode. In the case where the network device has already obtained the uplink synchronization, the terminal can stop searching and decoding the RAR without decoding the RAR carried in the second message this time.

When the CR message is not decoded and it is determined that the contention resolution fails, the terminal rolls back from the 2-step RACH to the 4-step RACH, and when the 4-step RACH is subsequently adopted, the embodiment of the present invention may consider that it is still possible with the communication process. Switch back to 2-step RACH to shorten the access delay.

The signal used for communication between the terminal and the network device is delayed in space. For example, the terminal moves away from the network device during a call, and the signal sent from the network device will arrive at the terminal "later and later". , at the same time, the terminal's signal will also arrive at the network device "more and later", and the delay will cause the network device to receive the terminal's signal in this time slot and the network device to receive the next signal from other terminals. The slots overlap each other, causing intersymbol interference. In order to solve this problem, the network device carries TA in the RAR and sends it to the terminal during the random access process, and the terminal uses the TA to realize the time alignment of uplink transmission, so as to eliminate the different transmission delays between the terminals.

The TA is carried in the RAR and sent to the terminal. Therefore, when the 2-step RACH is rolled back to the 4-step RACH, the TA timer is still kept running, which can ensure that the time alignment of the uplink transmission is realized in the 4-step RACH to eliminate the transmission delay.

FIG. 5 is a schematic flowchart of a random access method according to another embodiment of the present invention. Referring to FIG. 5, the random access method in this embodiment may include the following steps S21-S27.

S21: The terminal sends the first message to the network device.

S22: The network device replies the second message to the terminal.

S23: The terminal determines whether the second message carries both RAR and CR messages.

When the second message carries both RAR and CR messages, step S24 is performed. When the second message only carries the RAR message and the contention resolution determination fails, step S27 is performed.

S24: The terminal determines whether the TA timer is running.

If the TA timer is running, step S25 is executed. If the TA timer is not running, step S27 is executed.

S25: The terminal determines whether the TA timer has timed out.

If the TA timer times out, step S27 is executed. If the TA timer has not timed out, step S26 is executed.

S26: The terminal adopts two-step random access.

S27: The terminal falls back to four-step random access.

For the current situation of adopting 2-step RACH, on the basis of the foregoing description, once the TA timer is detected not running in this embodiment, it means that the 2-step RACH fails, and it should fall back to the 4-step RACH. Similarly, once it is detected that the TA timer expires, it means that the terminal is out of synchronization in the uplink, and it is also determined that the 2-step RACH cannot continue to be executed, and it should fall back to the 4-step RACH.

On the basis of the description of the foregoing embodiment, but different from it, in this embodiment, for the case of using 2-step RACH, it is also necessary to determine whether to continue to execute 2-step RACH according to the operation and timeout of the TA timer, thereby It can ensure the time alignment of upstream transmission to eliminate transmission delay.

Of course, other embodiments may only judge whether the TA timer is running, or only judge whether the TA timer has expired, and select the corresponding random access mode according to the judgment result.

Please continue to refer to FIG. 4 and FIG. 5. In these two embodiments, the terminal determines the random access mode to be adopted by parsing the message carried in the second message. In short, the terminal needs to make the determination. The process can determine the random access method that should be used. In other embodiments of the present invention, the foregoing judgment process may also be performed by the network device, and then the terminal adopts a corresponding uplink synchronization manner according to the judgment result.

Specifically, the second message may further include indication information, where the indication information is used to indicate the random access mode of the terminal. After receiving the second message, the terminal obtains the indication information by decoding, so as to directly determine the random access mode allowed by the network device.

Further, the terminal may also detect whether the random access mode specified by the indication information is the same as the random access mode obtained according to the foregoing judgment. If they are the same, the random access mode is implemented; if they are different, the random access mode obtained by one of them may be implemented. Generally speaking, as the decision maker of the random access mode, the network device issues the most accurate instruction information, so the terminal may preferably try to establish uplink synchronization with the network device using the random access mode specified by the instruction information.

In a practical application scenario, the indication information may be carried in physical layer control information or a medium access control (medium access control, MAC) control unit. Wherein, the physical layer control information or the MAC layer can be understood as non-higher layer signaling. Non-higher layer signaling is relative to higher layer signaling. The high-level signaling may refer to signaling sent by the high-level protocol layer, and the high-level protocol layer is at least one protocol layer above the MAC layer. The high-layer signaling may refer to broadcast messages or terminal-specific radio resource control (radio resource control, RRC), etc. In order to reduce the possible transmission delay caused by the high-layer signaling, this embodiment carries the indication information in the non-high-layer signaling. Alternatively, it can also be understood that the network device indicates the random access mode of the terminal through non-higher layer signaling (eg, DCI or MAC control unit). Wherein, the non-higher layer signaling may be a MAC control unit or physical layer control information, such as downlink control information (DCI) or side-link control information (SCI).

Specifically, the indication information is carried in physical layer control information or one or more reserved bits in the MAC control element. For example, the network device may add a field on the basis of the PDCCH instruction, and use the added field to indicate the random access mode of the terminal. The lengths of the DCI after adding the field and the DCI before the adding may be the same or different. When the network device sends the DCI to the terminal, the network device indicates the random access mode of the terminal through one or more reserved bits in the DCI.

FIG. 6 is a schematic structural diagram of a communication device according to an embodiment of the present invention. Referring to FIG. 6 , the communication apparatus 60 can be used as both a terminal and a network device. The communication device 60 includes a processor 61 and a memory 62, and the processor 61 and the memory 62 can be connected through a communication bus 63 for data or signal transmission.

The processor 61 is the control center of the communication device 60, uses various interfaces and lines to connect various parts of the entire communication device 60, executes communication by running or loading programs stored in the memory 62, and calling the data stored in the memory 62. Various functions of the device 60 and processing data to monitor the communication device 60 as a whole.

The communication device 60 loads the instructions corresponding to the processes of one or more programs into the memory 62 according to the aforementioned steps, and the processor 61 executes the programs stored in the memory 62, thereby realizing any one of the aforementioned The random access method of the embodiment.

For the communication transmission mode between the terminal and the network device, the specific content of the steps executed by the processor 61 to invoke the program may refer to the foregoing embodiments, which will not be repeated here.

It should be understood that in actual application scenarios, according to the device type to which the communication device 60 belongs, the execution bodies of the above steps may not be the processor 61 and the memory 62, but are implemented by other modules and units respectively.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by instructions, or by instructions that control relevant hardware, and the instructions can be stored in a readable storage medium and can be accessed by The processor loads and executes. To this end, the embodiments of the present invention provide a readable storage medium, in which a plurality of instructions are stored, and the instructions can be loaded by a processor to execute any one of the random access methods provided by the embodiments of the present invention. or multiple steps.

The readable storage medium may include a read only memory (ROM, Read Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and the like.

Since the instructions stored in the readable storage medium can execute the steps in any random access method provided by the embodiments of the present invention, any random access method provided by the embodiments of the present invention can be implemented For the beneficial effects that can be achieved, refer to the foregoing embodiments for details, which will not be repeated here.

While the invention has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art upon a reading and understanding of the specification and drawings. The present invention includes all such modifications and variations and is supported by the foregoing embodiments. Particularly with regard to the various functions performed by the above-described components, the terms used to describe the above-described components are intended to be any component that performs the specified function of the described component (eg, which is functionally equivalent), even if indicated otherwise, even in Not structurally equivalent to the disclosed structures that perform the functions in the exemplary implementations shown herein.

That is, the above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the contents of the description and the drawings, such as the combination of technical features between the embodiments, or the direct or indirect application in Other related technical fields are all within the scope of patent protection of the present invention.

In addition, in the description of the foregoing embodiments, the terms "first" and "second" are only for convenience of description, and cannot be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more technical features. "Plurality" means two or more, unless expressly specifically limited otherwise.

Further, although the steps in the flow charts of the above embodiments are displayed in sequence according to the arrows, they are not necessarily executed in sequence according to the sequence of the arrows. Unless explicitly stated herein, the steps are performed in no strict order and may be performed in other orders. Moreover, at least a part of the steps in the figure may include multiple sub-steps or multiple stages, and may not necessarily be executed and completed at the same time, but may be executed at different times, and the execution sequence is not necessarily sequential, but may be performed with other steps or At least a portion of the sub-steps or phases of the other steps are performed in turn or alternately.

Claims

A random access method, wherein the random access method includes:

The terminal sends the first message to the network device;

The terminal receives the second message replied by the network device;

The terminal determines whether the second message carries both a random access response and a contention resolution message;

When the second message carries both the random access response and the contention resolution message, the terminal adopts a two-step random access to perform a random access procedure; and

When the second message only carries the random access response and the contention resolution determination fails, the terminal adopts a four-step random access to perform a random access procedure.
The random access method according to claim 1, wherein determining, by the terminal, whether the second message carries both a random access response and a contention resolution message, comprises:

Within the receiving window of the second message, the terminal first determines whether a contention resolution message is decoded, and then determines whether the second message carries a random access response.
The random access method according to claim 1, wherein after the terminal decodes the contention resolution message, the random access method further comprises:

The terminal stops searching for and decoding the random access response.
The random access method according to claim 1, wherein when the terminal fails to decode the contention resolution message, the random access method comprises:

The terminal falls back to four-step random access, and keeps the timing advance timer running.
The random access method according to claim 1, wherein before the terminal adopts two-step random access to perform a random access procedure, the random access method comprises:

Determine whether the timing advance timer is running;

If the timing advance timer is running, the terminal adopts two-step random access;

If the timing advance timer is not running, the terminal falls back to four-step random access.
The random access method according to claim 5, wherein the terminal adopts two-step random access to perform a random access procedure, and the random access method comprises:

The terminal determines whether the timing advance timer has timed out;

If the timing advance timer expires, the terminal falls back to four-step random access;

If the timing advance timer does not expire, the terminal continues to use two-step random access.
The random access method according to claim 1, wherein the terminal adopts two-step random access to perform a random access procedure, comprising:

The terminal sends the Msg A carrying the preamble and the data part to the network device.
The random access method according to claim 1, wherein the terminal adopts four-step random access to perform a random access procedure, comprising:

The terminal sends the Msg 1 carrying the preamble without the data part to the network device.
The random access method according to claim 1, wherein the first message is Msg A that carries both a preamble and a data part, or a Msg 1 that carries a preamble but no data part.
The random access method according to claim 1, wherein the second message further includes indication information, wherein the indication information is used to indicate a random access mode of the terminal.
The random access method according to claim 10, wherein the indication information is carried in physical layer control information or a medium access control (MAC) control element.
The random access method according to claim 10, wherein the indication information is carried in the physical layer control information or one or more reserved bits in the MAC control element.
A random access method, wherein the random access method includes:

The network device receives the first message sent by the terminal;

The network device replies to the terminal with a second message, for the terminal to determine whether the second message carries both a random access response and a contention resolution message;

When the second message carries the random access response and the contention resolution message at the same time, the network device adopts a two-step random access to perform a random access procedure; and

When the second message only carries the random access response and the contention resolution determination fails, the network device adopts a four-step random access to perform a random access procedure.
The random access method according to claim 13, wherein the second message further includes indication information, wherein the indication information is used to indicate a random access mode of the terminal.
The random access method according to claim 14, wherein the indication information is carried in physical layer control information or a medium access control (MAC) control element.
The random access method according to claim 14, wherein the indication information is carried in the physical layer control information or one or more reserved bits in the MAC control element.
A communication system, characterized in that the communication system includes a terminal and a network device, the terminal is configured to execute the steps of the random access method according to any one of claims 1 to 12, and the network device is configured to execute the right The steps of the random access method described in any one of requirements 13 to 16 are required.
A communication device, characterized in that the communication device comprises a memory and a processor, the memory stores a program, and the program is used to be executed by the processor to execute any one of claims 1-12 or 13-16 One or more steps in the random access method described in item 1.
A computer-readable storage medium, characterized in that a program is stored in the computer-readable storage medium, and the program is configured to be executed by a processor to execute any one of claims 1 to 12 or 13 to 16 above. one or more steps in the random access method described above.