Method and system for user equipment to parse a second message

Abstract

The present application relates to the technical field of mobile communication, and in particular to a method and system for user equipment to analyze a second message, comprising: step S1: obtaining a current access procedure of the user equipment, and generating an expected response according to the access procedure; step S2: obtaining an indication bit from the second message, judging whether the currently received message conforms to the expected response according to the indication bit, and outputting a judgment result. The beneficial effect is that, in view of the relatively lengthy process of analyzing the second message in the prior art, the present application adds an indication bit at the first bit of the second message sent by the base station, and adjusts the content of the indication bit according to the current access procedure of the user equipment, so that the user equipment can read the indication bit to quickly judge and locate the field in the second message, thereby improving the efficiency of analyzing the second message.

Description

Technical Field

[0001] This invention relates to the field of mobile communication technology, and more specifically to a method and system for parsing a second message by a user equipment. Background Technology

[0002] 5G NR (New Radio) is a global 5G standard based on a new air interface design using OFDM (Orthogonal Frequency Division Multiplexing). In this system, during initial network access and uplink synchronization, User Equipment (UE) can send requests to the base station (gNB) using random access to execute corresponding service scenarios, including Radio Resource Control (RRC) initial access, RRC connection reconstruction, and RRC uplink synchronization.

[0003] In the prior art, when a user equipment (UE) needs to interact with a base station via random access, the UE first sends a first message (Msg1, message1) to the base station via a random access preamble. This first message contains the UE's preamble, which indicates to the base station the system message it needs to request. After receiving the first message from the UE, the base station sends a second message (Msg2, message2) to the UE. Upon receiving the second message, the UE reads the random access response (MAC RACH Access Response, MacRAR) and random access preamble (Random Access Preamble IDdentifier, RAPID) fields in the second message and compares them with the preamble to determine whether the base station has received the first message and responded correctly. This determines whether to proceed with the subsequent process of sending a third message (Msg3, message3) and receiving a fourth message (Msg4, message4) to compete for access.

[0004] However, in actual implementation, the inventors discovered that in the prior art, according to the description in Section 6.1.5 of the 3GPP TS 38.321 protocol, a Media Access Control Protocol Data Unit (MAC PDU) can contain one or more data sub-units (MAC subPDUs), and possibly a padding field. Each data sub-unit can be: a subheader containing only the Backoff Indicator (BI); a subheader containing only the random access preamble, such as an acknowledgment response for a system message broadcast request; or a subheader containing the random access preamble and a random access response field. According to the above provisions, the subheader containing only the Backoff Indicator is placed first in the protocol data unit; the subheader containing only the random access preamble, the subheader containing the random access preamble, and the random access response field can be arbitrarily placed between the subheader containing only the Backoff Indicator and the padding field. This results in low processing efficiency when the user equipment parses the second message. If the random access preamble does not match the preamble index sent by the user equipment, it needs to determine whether the data sub-unit contains the random access response field based on the current network configuration. Summary of the Invention

[0005] In view of the above-mentioned problems in the prior art, a method for parsing a second message by a user equipment is provided; on the other hand, a system for parsing a second message by a user equipment using the method is also provided.

[0006] The specific technical solution is as follows:

[0007] A method for parsing a second message by a user equipment, applicable to a random access procedure between a user equipment and a base station; the second message includes an indication bit;

[0008] The method by which the user equipment parses the second message includes:

[0009] Step S1: Obtain the current access procedure of the user equipment and generate the expected response according to the access procedure;

[0010] Step S2: Obtain the indicator bit from the second message, determine whether the currently received message meets the expected response based on the indicator bit, and output the determination result.

[0011] On the other hand, when the access procedure is initiated by the user equipment through the random access procedure, the expected response is that the second message does not contain a random access response field, and the indicator bit is used to indicate the number of random access response fields;

[0012] Then step S2 includes:

[0013] Step A21: Determine whether the value of the indicator bit is zero;

[0014] If so, proceed to step A22;

[0015] If not, proceed to step A26.

[0016] Step A22: Read the type field of the sub-header following the indicator bit and determine whether the value of the type field is zero;

[0017] If so, proceed to step A23;

[0018] If not, proceed to step A24;

[0019] Step A23: Indicates that the sub-header contains a random access preamble, extract the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result;

[0020] Step A24: Read the extended field of the sub-header and determine whether the value of the extended field is zero;

[0021] If so, it indicates that the base station is not responding normally, and the judgment result is generated;

[0022] If not, proceed to step A25:

[0023] Step A25: Skip the backoff time indicator bit to obtain the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result;

[0024] Step A26: Read the extended field of the sub-header and determine whether the value of the extended field is zero;

[0025] If so, it indicates that the base station is not responding normally, and the judgment result is generated;

[0026] If not, proceed to step A27:

[0027] Step A27: Skip the random access response field according to the indicated bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the judgment result.

[0028] On the other hand, when the expected response is that the second message contains a random access response field, the indicator bit is used to indicate the number of the random access response fields;

[0029] Step S2 includes:

[0030] Step B21: Determine whether the value of the indicator bit is zero;

[0031] If so, it indicates that the base station is not responding normally, and the judgment result is generated;

[0032] If not, proceed to step B22;

[0033] Step B22: Skip the random access response field according to the indicated bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the judgment result.

[0034] On the other hand, when the expected response is that the second message contains a random response preamble, the indicator bit is used to indicate the number of the random response preamble;

[0035] Then step S2 includes:

[0036] Step C21: Determine whether the value of the indicator bit is zero;

[0037] If so, it indicates that the base station is not responding normally, and the judgment result is generated;

[0038] If not, proceed to step C22;

[0039] Step C22: Sequentially obtain the random access preamble and compare the random access preamble with the preamble index initiated by the user equipment to obtain the judgment result.

[0040] On the other hand, the second message includes, in sequence: the indicator bit, the rollback time indicator bit, and at least one protocol data unit;

[0041] The protocol data unit includes the random access response field and / or the random access preamble.

[0042] A system for parsing a second message by a user equipment, comprising implementing the aforementioned method for parsing a second message by a user equipment, including:

[0043] The expected response generation module obtains the current access process of the user equipment and generates an expected response according to the access process.

[0044] The discrimination module is connected to the expected response generation module. The discrimination module obtains an indication bit from the second message, determines whether the currently received message conforms to the expected response based on the indication bit, and outputs the judgment result.

[0045] On the other hand, the discrimination module includes a first discrimination module, which is used to generate the discrimination result when the expected response is that the second message does not contain a random access response field;

[0046] The indicator bit is used to indicate the number of the random access response fields;

[0047] The first discrimination module includes:

[0048] The first indicator bit determination module generates a first determination result based on the value of the indicator bit;

[0049] A type field reading module, which reads the type field of the sub-header following the indicator bit based on the first judgment result to generate a second judgment result;

[0050] An extended field reading module, wherein the extended field reads the extended field of the sub-header based on the second judgment result to generate a third judgment result;

[0051] A preamble comparison module, which generates a preamble comparison result based on the second judgment result and the third judgment result;

[0052] The first output module generates and outputs the judgment result based on the third judgment result and the preamble comparison result.

[0053] On the other hand, the discrimination module includes a second discrimination module, which is used to generate the discrimination result when the expected response is that the second message contains a random access response field;

[0054] The indicator bit is used to indicate the number of the random access response fields;

[0055] The second discrimination module includes:

[0056] The second indicator bit discrimination module generates a first judgment result based on the value of the indicator bit;

[0057] The first preamble lookup module finds the random access preamble by skipping the random access response field according to the first judgment result and the indication bit, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the first preamble lookup result.

[0058] The second output module generates and outputs the judgment result based on the first judgment result and the first preamble lookup result.

[0059] On the other hand, the discrimination module includes a third discrimination module, which is used to generate the discrimination result when the expected response is that the second message contains a random response preamble;

[0060] The indicator bit is used to indicate the number of the random response preamble;

[0061] The third discrimination module includes:

[0062] The third indicator bit discrimination module generates a second judgment result based on the value of the indicator bit;

[0063] The first preamble lookup module finds the random access preamble by skipping the random access response field according to the first judgment result and the indication bit, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the second preamble lookup result.

[0064] The third output module generates and outputs the judgment result based on the first judgment result and the first preamble lookup result.

[0065] The above technical solution has the following advantages or beneficial effects:

[0066] To address the issue of the relatively lengthy process of parsing the second message in existing technologies, this solution adds an indicator bit to the first position of the second message sent by the base station and adjusts the content of the indicator bit according to the current access procedure of the user equipment. This allows the user equipment to quickly determine and locate fields in the second message by reading the indicator bit, thereby improving the efficiency of parsing the second message. Attached Figure Description

[0067] Embodiments of the invention will be described more fully with reference to the accompanying drawings. However, the drawings are for illustration and explanation only and do not constitute a limitation on the scope of the invention.

[0068] Figure 1 This is a schematic diagram illustrating a method for a user equipment to parse a second message in an embodiment of the present invention;

[0069] Figure 2A This is a schematic diagram of the second message in an embodiment of the present invention;

[0070] Figure 2B This is a schematic diagram of the second message in another embodiment of the present invention;

[0071] Figure 3 This is a schematic diagram of sub-step S2 in an embodiment of the present invention;

[0072] Figure 4This is a schematic diagram of sub-step S2 in another embodiment of the present invention;

[0073] Figure 5 This is a schematic diagram of sub-step S2 in another embodiment of the present invention;

[0074] Figure 6 This is a schematic diagram of a system for parsing a second message by a user equipment in an embodiment of the present invention;

[0075] Figure 7 This is a schematic diagram of the first discrimination module in an embodiment of the present invention;

[0076] Figure 8 This is a schematic diagram of the second discrimination module in an embodiment of the present invention;

[0077] Figure 9 This is a schematic diagram of the third discrimination module in an embodiment of the present invention. Detailed Implementation

[0078] The technical solutions of the 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0080] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0081] This invention includes:

[0082] A method for parsing a second message by a user equipment, applicable to a random access procedure between a user equipment and a base station; the second message includes an indication bit;

[0083] The methods by which user equipment parses the second message include:

[0084] Step S1: Obtain the current access procedure of the user equipment and generate the expected response according to the access procedure;

[0085] Step S2: Obtain the indicator bit from the second message, determine whether the currently received message meets the expected response based on the indicator bit, and output the determination result.

[0086] Specifically, addressing the issue of the relatively lengthy parsing process of the second message in existing technologies, this embodiment adds an indicator bit to the first part of the second message sent by the base station. This indicator bit can be used to indicate the number of different types of fields, including the number of random access response fields or random access preambles contained in the current protocol data unit, thereby constructing a new second message. When the user equipment receives the second message, it can determine whether the sent second message meets the expected response through the indicator bit, thus simplifying the parsing process, reducing the steps of reading each media access data subunit and obtaining the next data subunit in existing technologies, and improving the parsing efficiency.

[0087] In one embodiment, such as Figure 2A and Figure 2B As shown, the second message includes, in sequence: an indicator bit, a rollback time indicator bit, and at least one data sub-unit;

[0088] The data sub-unit includes a random access response field and / or a random access preamble, and data sub-units of the same type are arranged sequentially.

[0089] Specifically, addressing the issue of the relatively lengthy parsing process for the second message in existing technologies, this embodiment adjusts the order of data sub-units in the second message. Data sub-units of the same type, such as those containing only a random access preamble or those containing both a random access response field and a random access preamble, are arranged sequentially. This allows for the subsequent parsing process to read the value of the indicator bit as needed and skip corresponding data sub-units to directly read specific data sub-units, thereby improving parsing efficiency.

[0090] In one embodiment, when the access procedure is a random access procedure initiated by the user equipment, the expected response is that the second message does not contain a random access response field, such as... Figure 3 As shown, the indicator bit is used to indicate the number of random access response fields;

[0091] Then step S2 includes:

[0092] Step A21: Determine if the value of the indicator bit is zero;

[0093] If so, proceed to step A22;

[0094] If not, proceed to step A26.

[0095] Step A22: Read the type field of the sub-header following the indicator bit and determine whether the value of the type field is zero;

[0096] If so, proceed to step A23;

[0097] If not, proceed to step A24;

[0098] Step A23: This indicates that the subheading contains a random access preamble. Extract the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result.

[0099] Step A24: Read the extended field of the subheader and determine whether the value of the extended field is zero;

[0100] If so, it indicates that the base station has not responded normally, and a judgment result is generated;

[0101] If not, proceed to step A25:

[0102] Step A25: Skip the backoff time indicator bit to obtain the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result;

[0103] Step A26: Read the extended field of the subheader and determine whether the value of the extended field is zero;

[0104] If so, it indicates that the base station has not responded normally, and a judgment result is generated;

[0105] If not, proceed to step A27:

[0106] Step A27: Skip the random access response field according to the indicator bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in turn to obtain the judgment result.

[0107] Specifically, when the expected response is that the second message contains a random access response field, in this embodiment, since the indicator bits have been pre-configured to correspond to the number of random access response fields, it is possible to determine whether a random access response field is included by reading the indicator bits. If not, starting from the indicator bit, the extension field and type field of the subsequent sub-header can be read to determine whether the following indicator bit is a backoff time indicator bit or a random access preamble. If it is a random access preamble, the process of matching the random access preamble in each subsequent data sub-unit with the preamble index sent in the random access request initiated by the user equipment is performed one by one to determine whether the base station has responded normally. If it is a backoff time indicator bit, it can be skipped, and the next data sub-unit can be read to obtain the random access preamble. If neither is true, it indicates that an error has occurred in the transmission process of the second message. The above method achieves a simpler parsing process for the second message, thereby improving parsing efficiency.

[0108] In one embodiment, when the expected response is a second message containing a random access response field, the indicator bit is used to indicate the number of random access response fields;

[0109] like Figure 4 As shown, step S2 includes:

[0110] Step B21: Determine if the value of the indicator bit is zero;

[0111] If so, it indicates that the base station has not responded normally, and a judgment result is generated;

[0112] If not, proceed to step B22;

[0113] Step B22: Skip the random access response field according to the indicator bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in turn to obtain the judgment result.

[0114] Specifically, addressing the relatively cumbersome process of parsing the second message in existing technologies, in this embodiment, when the expected response is that the second message contains a random access response field, the base station can be directly judged to determine whether it is responding normally by checking if the value of the indicator bit is zero. If it is, the random access response field is skipped according to the value of the indicator bit, and the random access preamble is read directly. This allows for the matching of the random access preamble in each subsequent data sub-unit with the preamble index sent in the random access request initiated by the user equipment, thereby determining whether the base station is responding normally and improving the parsing efficiency.

[0115] In one embodiment, when the expected response is a second message containing a random response preamble, the indicator bit is used to indicate the number of random response preambles;

[0116] Then as Figure 5 As shown, step S2 includes:

[0117] Step C21: Determine if the value of the indicator bit is zero;

[0118] If so, it indicates that the base station has not responded normally, and a judgment result is generated;

[0119] If not, proceed to step C22;

[0120] Step C22: Sequentially obtain the random access preamble and compare it with the preamble index initiated by the user equipment to obtain the judgment result.

[0121] Specifically, addressing the relatively cumbersome process of parsing the second message in existing technologies, this embodiment addresses the issue that when the expected response is a second message containing a random response preamble, the data sub-units in the second message are pre-arranged as follows: indicator bits, backoff time indicator bits, sub-units containing only a random access preamble, and sub-units containing both a random access preamble and a random access response field. Therefore, the indicator bits can be used to determine whether the base station has responded normally. Subsequently, the backoff time indicator bits are skipped to read the random access preamble and compare it with the preamble index. During this process, the indicator bits indicate the number of data sub-units available for comparison by the user equipment. When the number of extracted random access preambles reaches the number of indicator bits, it indicates that all data sub-units containing only a random access preamble in the second message have been read, followed by data sub-units containing both a random access preamble and a random access response field. If no matching random access preamble is found, the response is considered to have failed, and the judgment result can be directly output without traversing the second message, thereby reducing the time required to parse the second message.

[0122] A system for parsing a second message by a user equipment, used to implement the aforementioned method for parsing a second message by a user equipment, such as... Figure 6 As shown, it includes:

[0123] Expected response generation module 1: Expected response generation module 1 obtains the current access process of the user equipment and generates an expected response according to the access process;

[0124] The discrimination module 2 is connected to the expected response generation module 1. The discrimination module 2 obtains the indicator bit from the second message, judges whether the currently received message meets the expected response based on the indicator bit, and outputs the judgment result.

[0125] Specifically, addressing the issue of the relatively lengthy parsing process of the second message in existing technologies, this embodiment adds an indicator bit to the first part of the second message sent by the base station. This indicator bit can be used to indicate the number of different fields, including the number of random access response fields or random access preambles contained in the current protocol data unit, thereby constructing a new second message. When the user equipment receives the second message, the expected response generation module 1 can generate an expected response based on the access process, and the discrimination module 2 can determine whether the sent second message conforms to the expected response through the indicator bit. This simplifies the parsing process, reduces the steps of reading each media access data subunit and obtaining the next data subunit in existing technologies, and improves the parsing efficiency.

[0126] In one embodiment, the discrimination module includes a first discrimination module, which is used to generate a discrimination result when the expected response is that the second message does not contain a random access response field;

[0127] The indicator bit is used to indicate the number of fields in the random access response;

[0128] like Figure 7 As shown, the first discrimination module includes:

[0129] The first indicator bit judgment module A21 generates a first judgment result based on the value of the indicator bit;

[0130] The type field reading module A22 reads the type field of the sub-header following the indicator bit based on the first judgment result to generate a second judgment result;

[0131] The extended field reading module A23 reads the extended fields of the sub-header based on the second judgment result and generates a third judgment result.

[0132] Preamble comparison module A24 generates a preamble comparison result based on the second judgment result and the third judgment result;

[0133] The first output module A25 generates and outputs a judgment result based on the third judgment result and the comparison result of the preamble.

[0134] Specifically, when the expected response is that the second message contains a random access response field, in this embodiment, since the indicator bits have been pre-configured to correspond to the number of random access response fields, it is possible to determine whether a random access response field is included by reading the indicator bits. If not, starting from the indicator bit, the extension field and type field of the subsequent sub-header can be read to determine whether the following indicator bit is a backoff time indicator bit or a random access preamble. If it is a random access preamble, the process of matching the random access preamble in each subsequent data sub-unit with the preamble index sent in the random access request initiated by the user equipment is performed one by one to determine whether the base station has responded normally. If it is a backoff time indicator bit, it can be skipped, and the next data sub-unit can be read to obtain the random access preamble. If neither is true, it indicates that an error has occurred in the transmission process of the second message. The above method achieves a simpler parsing process for the second message, thereby improving parsing efficiency.

[0135] In one embodiment, the discrimination module includes a second discrimination module, which is used to generate a discrimination result when the expected response is a second message containing a random access response field;

[0136] The indicator bit is used to indicate the number of fields in the random access response;

[0137] like Figure 8 As shown, the second discrimination module includes:

[0138] The second indicator bit discrimination module B21 generates a first judgment result based on the value of the indicator bit.

[0139] The first preamble lookup module B22 finds the random access preamble by skipping the random access response field according to the first judgment result and the indication bit, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the first preamble lookup result.

[0140] The second output module B23 generates and outputs a judgment result based on the first judgment result and the first preamble lookup result.

[0141] Specifically, addressing the relatively cumbersome process of parsing the second message in existing technologies, in this embodiment, when the expected response is that the second message contains a random access response field, the base station can be directly judged to determine whether it is responding normally by checking if the value of the indicator bit is zero. If it is, the random access response field is skipped according to the value of the indicator bit, and the random access preamble is read directly. This allows for the matching of the random access preamble in each subsequent data sub-unit with the preamble index sent in the random access request initiated by the user equipment, thereby determining whether the base station is responding normally and improving the parsing efficiency.

[0142] In one embodiment, the discrimination module includes a third discrimination module, which is used to generate a judgment result when the expected response is that the second message contains a random response preamble;

[0143] The indicator bit is used to indicate the number of random response preambles;

[0144] like Figure 9 As shown, the third discrimination module includes:

[0145] The third indicator bit discrimination module C21 generates a second judgment result based on the value of the indicator bit.

[0146] The first preamble lookup module C22 finds the random access preamble by skipping the random access response field according to the first judgment result and the indication bit, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the second preamble lookup result.

[0147] The third output module C23 generates and outputs a judgment result based on the first judgment result and the first preamble lookup result.

[0148] Specifically, addressing the relatively cumbersome process of parsing the second message in existing technologies, this embodiment addresses the issue that when the expected response is a second message containing a random response preamble, the data sub-units in the second message are pre-arranged as follows: indicator bits, backoff time indicator bits, sub-units containing only a random access preamble, and sub-units containing both a random access preamble and a random access response field. Therefore, the indicator bits can be used to determine whether the base station has responded normally. Subsequently, the backoff time indicator bits are skipped to read the random access preamble and compare it with the preamble index. During this process, the indicator bits indicate the number of data sub-units available for comparison by the user equipment. When the number of extracted random access preambles reaches the number of indicator bits, it indicates that all data sub-units containing only a random access preamble in the second message have been read, followed by data sub-units containing both a random access preamble and a random access response field. If no matching random access preamble is found, the response is considered to have failed, and the judgment result can be directly output without traversing the second message, thereby reducing the time required to parse the second message.

[0149] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for a user equipment to parse a second message, characterized in that, Applicable to random access procedures between user equipment and base stations; The second message includes an indication bit; The method by which the user equipment parses the second message includes: Step S1: Obtain the current access procedure of the user equipment and generate the expected response according to the access procedure; Step S2: Obtain the indicator bit from the second message, determine whether the currently received message conforms to the expected response based on the indicator bit, and output the determination result; when the access procedure is initiated by the user equipment to initiate the random access procedure, the expected response is that the second message does not contain a random access response field, and the indicator bit is used to indicate the number of random access response fields; Then step S2 includes: Step A21: Determine whether the value of the indicator bit is zero; If so, proceed to step A22; If not, proceed to step A26. Step A22: Read the type field of the sub-header following the indicator bit and determine whether the value of the type field is zero; If so, proceed to step A23; If not, proceed to step A24; Step A23: Indicates that the sub-header contains a random access preamble, extract the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result; Step A24: Read the extended field of the sub-header and determine whether the value of the extended field is zero; If so, it indicates that the base station is not responding normally, and the judgment result is generated; If not, proceed to step A25: Step A25: Skip the backoff time indicator bit to obtain the random access preamble and compare it sequentially with the preamble index initiated by the user equipment to obtain the judgment result; Step A26: Read the extended field of the sub-header and determine whether the value of the extended field is zero; If so, it indicates that the base station is not responding normally, and the judgment result is generated; If not, proceed to step A27: Step A27: Skip the random access response field according to the indicated bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the judgment result; When the expected response is that the second message contains a random access response field, the indicator bit is used to indicate the number of the random access response fields; Step S2 includes: Step B21: Determine whether the value of the indicator bit is zero; If so, it indicates that the base station is not responding normally, and the judgment result is generated; If not, proceed to step B22; Step B22: Skip the random access response field according to the indicated bit to find the random access preamble, and compare the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the judgment result; When the expected response is that the second message contains a random response preamble, the indicator bit is used to indicate the number of the random response preamble; Then step S2 includes: Step C21: Determine whether the value of the indicator bit is zero; If so, it indicates that the base station is not responding normally, and the judgment result is generated; If not, proceed to step C22; Step C22: Sequentially obtain the random access preamble and compare the random access preamble with the preamble index initiated by the user equipment to obtain the judgment result.

2. The method for parsing a second message by a user equipment according to claim 1, characterized in that, The second message includes, in sequence: the indicator bit, the rollback time indicator bit, and at least one protocol data unit; The protocol data unit includes the random access response field and / or the random access preamble.

3. A system for parsing a second message by a user equipment, characterized in that, include: The expected response generation module obtains the current access process of the user equipment and generates an expected response according to the access process. The discrimination module is connected to the expected response generation module. The discrimination module obtains an indication bit from the second message, determines whether the currently received message conforms to the expected response based on the indication bit, and outputs the judgment result. The discrimination module includes a first discrimination module, which is used to generate the discrimination result when the expected response is that the second message does not contain a random access response field; The indicator bit is used to indicate the number of the random access response fields; The first discrimination module includes: The first indicator bit determination module generates a first determination result based on the value of the indicator bit; A type field reading module, which reads the type field of the sub-header following the indicator bit based on the first judgment result to generate a second judgment result; An extended field reading module reads the extended fields of the sub-header based on the second judgment result to generate a third judgment result; A preamble comparison module, which generates a preamble comparison result based on the second judgment result and the third judgment result; The first output module generates and outputs the judgment result based on the third judgment result and the preamble comparison result. The discrimination module includes a second discrimination module, which is used to generate the discrimination result when the expected response is that the second message contains a random access response field; The indicator bit is used to indicate the number of the random access response fields; The second discrimination module includes: The second indicator bit discrimination module generates a first judgment result based on the value of the indicator bit; The first preamble lookup module skips the random access response field according to the first judgment result and the indicator bit to find the random access preamble, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the first preamble lookup result. The second output module generates and outputs the judgment result based on the first judgment result and the first preamble lookup result. The discrimination module includes a third discrimination module, which is used to generate the discrimination result when the expected response is that the second message contains a random response preamble; The indicator bit is used to indicate the number of the random response preamble; The third discrimination module includes: The third indicator bit discrimination module generates a second judgment result based on the value of the indicator bit; The first preamble lookup module skips the random access response field according to the second judgment result and the indicator bit to find the random access preamble, and compares the random access preamble with the preamble index initiated by the user equipment in sequence to obtain the second preamble lookup result. The third output module generates and outputs the judgment result based on the second judgment result and the second preamble lookup result.

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