Patent Description:
To access a wireless network and send uplink data, UE needs to establish a connection to a cell by using a random access process and obtain uplink synchronization. In long term evolution (English: Long Term Evolution, LTE), the following six events trigger the random access process.

Random access processes are usually classified into a "contention-based" access process and a "non-contention-based" access process. For example, the "contention-based" access process is applicable to the first five events, and the "non-contention-based" access process is applicable to three events: the third, fourth, and sixth events.

The contention-based random access process includes the following four steps:.

When the UE sends the MSG <NUM>, usually, a spectrum shift is performed on a generated preamble, the preamble is converted into time domain data, and then the time domain data is directly configured on a subcarrier. A preamble obtained after the foregoing processing is sent through an antenna port of the UE.

As new services such as an Internet of things service are popularized, some services having a small data volume but relatively high delay requirement need to be served in time. In terms of an access delay, it is difficult to meet the delay requirement of the services in the contention-based random access process. <CIT> discloses uplink scrambling during random access. <CIT> discloses random access procedures for machine-type communications. <CIT> discloses a method for preventing misuse of a random access procedure in a mobile station.

To describe the technical solutions in the embodiments of this application more clearly, the following briefly describes the accompanying drawings required for describing the embodiments or the prior art. Apparently, the accompanying drawings in the following descriptions show some embodiments of this application, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

In an existing contention-based random access process, message interaction needs to be performed between UE and a base station at least four times, so that uplink synchronization can be obtained and a connection to a cell can be established. In such a random access manner, it is usually difficult to meet a requirement of a service having a small data volume but a very high delay requirement. Specifically, for some services, after a random access process including four steps is completed, service data further needs to be transmitted between the UE and a network side by using more time-frequency resources. For example, in an Internet of things service or an Internet of vehicles service, the UE needs to report measurement parameter values in aspects of a current location, an environment, and the like, so that the network side delivers a control instruction to the UE. In this way, the UE needs to wait a relatively long time before obtaining a service provided by the network side. When the UE obtains the service, a location of a vehicle in which the UE is located and an ambient environment may be different from a location of the vehicle in which the UE is located and an ambient environment that exist when the UE initiates the random access process.

To reduce an access delay, an embodiment of this application provides a random access method. UE adds both a preamble and service data to an MSG <NUM> in a random access process. In this way, a base station may obtain the service data from the received MSG <NUM>. Therefore, the base station does not need to wait for completion of the random access process before obtaining service data that is transmitted by the UE by using an extra time-frequency resource. The base station may provide a service to the UE based on the service data carried in the MSG <NUM>. Therefore, a service delay can be reduced based on a random access solution provided in this embodiment of this application.

A main implementation principle and specific implementations of the technical solutions of the embodiments of the present invention and corresponding advantageous effects that can be achieved by the technical solutions are described below in detail with reference to the accompanying drawings.

To transmit data to a network side, UE first needs to establish a connection to a cell. Downlink synchronization and uplink synchronization are involved in a process of establishing a connection to a cell. The UE obtains downlink synchronization with a cell and system information of the cell by using a cell search process. In addition to performing cell search during power-on, to support mobility, the UE continuously searches neighboring cells, obtains synchronization, and estimates signal received quality of the cell, so that the UE determines, in an RRC_CONNECTED state, whether to perform switching, or the UE determines, in an RRC_IDLE state, whether to perform cell reselection. After obtaining the downlink synchronization, the UE establishes, by using a random access process, uplink synchronization with the cell with which downlink synchronization is obtained.

<FIG> is a schematic diagram of a random access method according to an embodiment of this application. The random access method is applicable to a "contention-based" access process and a "non-contention-based" access process. Before step <NUM> in <FIG>, UE has obtained downlink synchronization with a cell by using a cell search process, that is, has obtained frequency and symbol synchronization with the cell, has obtained a start position of a downlink frame, and has determined a physical-layer cell identifier (English: Physical-layer Cell Identity, PCI) of the cell. However, the UE has not obtained uplink synchronization with the cell. In the random access method described in this application, the cell is a cell with which the UE has obtained downlink synchronization, but has not obtained uplink synchronization in the cell search process, that is, a cell used as a random access target.

Step <NUM>: The UE sends an MSG <NUM> to a base station to which the cell belongs. The MSG <NUM> includes both a preamble sequence and scrambled service data. Time-frequency resources respectively occupied by the preamble sequence and the scrambled service data conform to a predetermined resource mapping relationship.

A process in which the UE determines the preamble sequence is similar to that in an existing random access process, and includes obtaining, from a broadcast system information SIB <NUM> sent by the base station, a resource that can be used to transmit the preamble sequence, and configuring preamble sequence groups for contention-based random access and non-contention-based random access. The UE selects a preamble sequence from the preamble sequence groups based on an estimated size of an MSG <NUM>. Other details about determining the preamble sequence by the UE are not described herein.

After determining the preamble sequence, the UE configures, based on the predetermined resource mapping relationship, the time-frequency resources required for sending the determined preamble sequence and the service data. Then the UE sends, on the configured time-frequency resources, the preamble sequence and service data to the base station to which the cell belongs. The resource mapping relationship and sending the MSG <NUM> by the UE are described in further detail in the following embodiments.

In this application, the service data includes various types of control information or service information of an application. For example, in an Internet of things service or an Internet of vehicles service, service information of an application may be measurement parameter values in aspects of a current location of the UE, an environment, and the like.

To enable the base station to distinguish between service data from different users, before sending the service data, the UE may scramble the service data based on a scrambling code that is in a one-to-one correspondence with the preamble sequence of the UE.

Step <NUM>: The UE receives an MSG <NUM> sent by the base station, where the MSG <NUM> is a random access response. The random access response includes optional information, such as an RA-RNTI, an identifier of the random access preamble sequence, a time advance instruction determined based on an estimated delay between the base station and the UE, a temporary C-RNTI, and an uplink resource allocated to an MSG <NUM>. The UE may determine, based on the RA-RNTI and the identifier of the preamble sequence that are carried in the MSG <NUM>, whether the MSG <NUM> corresponding to the sent MSG <NUM> is successfully received, and perform subsequent processing.

If the foregoing steps are performed in the non-contention-based random access, the preamble sequence is specially used by the UE. Therefore, there is no conflict. In addition, the UE already has a unique identifier C-RNTI in an accessed cell. Therefore, the base station does not need to allocate a C-RNTI to the UE, and the access process is completed. Performing of subsequent steps needs to be continued only in the contention-based random access, to be specific, the UE sends the MSG <NUM> and receives an MSG <NUM> sent by the base station. The subsequent steps are basically similar to those in the existing random access process.

In the random access method provided in this embodiment of this application, when the UE sends the MSG <NUM>, the UE sends the preamble sequence and the service data to the base station on the configured time-frequency resources. In other words, the MSG <NUM> carries both the preamble and the service data. In this way, the base station may obtain the service data from the received MSG <NUM> in time, to provide a service for the UE. Therefore, the base station does not need to wait for completion of a random access process before obtaining service data that is transmitted by the UE by using an extra time-frequency resource, thereby reducing a service delay.

<FIG> is a schematic diagram of a random access method according to an embodiment of this application. Implementation details of the random access method are emphasized in <FIG> from a perspective of UE.

Step <NUM>: After obtaining downlink synchronization with a cell, the UE determines a preamble sequence of the UE in the cell. A process in which the UE determines the preamble sequence is similar to that in an existing random access process. Optionally, the preamble sequence is a Zadoff-Chu ZC sequence, an M sequence, a Golden sequence, or the like.

Step <NUM>: The UE obtains service data. The UE may obtain the service data from an application program installed on the UE.

There is no need to limit an order of performing step <NUM> and step <NUM>. After step <NUM> and step <NUM> are performed, the UE performs step <NUM>.

Step <NUM>: The UE determines a scrambling code used to scramble the service data.

Optionally, the scrambling code is in a one-to-one correspondence with the preamble sequence determined in step <NUM>. In this case, an RRC state of the UE is not limited. Alternatively, when the UE is in an RRC_CONNECTED state or an RRC_INACTIVE state, the scrambling code is in a one-to-one correspondence with an identifier of the UE; or the scrambling code is in a one-to-one correspondence with a combination of the preamble sequence determined in step <NUM> and an identifier of the UE. An RRC_INACTIVE state has the following features: A network side reserves context (context) information of the UE in an RRC_INACTIVE state. The base station and a core network reserve connection information of the UE in an RRC_INACTIVE state. The network side may learn a location of the UE in an RRC_INACTIVE state at an RNA layer. In other words, a network layer may learn a specific RNA in which the UE is located. In this embodiment, the identifier of the UE is a unique identifier of the UE in the base station, and includes a cell radio network temporary identifier (English: Cell Radio Network Temporary Identifier, C-RNTI), a temporary mobile subscriber identity (English: Temporary Mobile Subscriber Identity, TMSI), an international mobile subscriber identity (English: international mobile subscriber identity, IMSI), and the like.

Optionally, a manner of determining the scrambling code is learned in advance by the UE and the base station to which the cell belongs. After determining the preamble sequence, the UE may determine the corresponding scrambling code based on the preamble sequence and/or the identifier of the UE.

Optionally, the manner of determining the scrambling code is configured on the base station and the UE by default.

Optionally, the manner of determining the scrambling code is notified by the base station to the UE by using a scrambling code mapping indication. For example, the base station uses three scrambling code mapping indications to respectively indicate the three correspondences and specific mapping modes.

The scrambling code mapping indications and the specific mapping modes are described below with reference to specific examples.

The mapping mode of a preamble sequence and a scrambling code includes, but is not limited to, any one of the following (<NUM>) to (<NUM>).

A second scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and an identifier of the UE. For example, the second scrambling code mapping indication is 2X, <NUM> is used to indicate that the scrambling code is in a one-to-one correspondence with the identifier of the UE, and X is used to indicate the mapping mode of a preamble sequence and an identifier of the UE.

The mapping mode of a preamble sequence and an identifier of the UE includes: If the UE is in an RRC_CONNECTED state or an RRC_ACTIVE state, the scrambling code is a ZC sequence in a one-to-one correspondence with the identifier of the UE in a predetermined codebook. The second scrambling code mapping indication may be <NUM>.

A third scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE. For example, the third scrambling code mapping indication is 3X, <NUM> is used to indicate that the scrambling code is in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE, and X is used to indicate the mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE.

The mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE includes: The scrambling code is a ZC sequence in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE in a predetermined codebook. The third scrambling code mapping indication may be <NUM>.

If the scrambling code is in a one-to-one correspondence with the preamble sequence, the UE receives the first scrambling code mapping indication sent by the base station. The UE determines the scrambling code in a one-to-one correspondence with the preamble sequence based on the mapping mode indicated by the first scrambling code mapping indication and the preamble sequence.

If the scrambling code is in a one-to-one correspondence with the identifier of the UE, the UE receives the second scrambling code mapping indication sent by the base station. The UE determines the scrambling code in a one-to-one correspondence with the identifier of the UE based on the mapping mode indicated by the second scrambling code mapping indication and the identifier of the UE.

If the scrambling code is in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE, the UE receives the third scrambling code mapping indication sent by the base station to which the cell belongs. The UE determines the scrambling code in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE based on the mapping mode indicated by the third scrambling code mapping indication and the combination of the preamble sequence and the identifier of the UE.

Optionally, the base station notifies the UE of one of the three scrambling code mapping indications in any one of the following manners, and notification manners include, but are not limited to, the following manners:.

Step <NUM>: The UE scrambles the service data based on the scrambling code, to obtain scrambled service data.

Scrambling (Scrambling) is encrypting, by using a scrambling code, a signal carrying service data. Data transmission security can be improved through scrambling.

Step <NUM>: The UE configures, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by the preamble sequence and the scrambled service data.

The predetermined resource mapping relationship is learned in advance by the UE and the base station to which the cell belongs. The UE determines, based on a resource that can be used to transmit the preamble sequence and that is indicated in an SIB <NUM>, the time-frequency resource used to subsequently transmit the preamble sequence, and then determines, based on the time-frequency resource used by the preamble sequence and the predetermined resource mapping relationship, the time-frequency resource correspondingly occupied by the scrambled service data.

Optionally, the predetermined resource mapping relationship is configured on the base station and the UE by default.

Optionally, the predetermined resource mapping relationship is notified by the base station to the UE. For example, the base station uses a resource mapping indicator to indicate the predetermined resource mapping relationship. The base station sends the resource mapping indicator to the UE, and the UE receives the resource mapping indicator sent by the base station. The UE configures, based on the resource mapping relationship indicated by the resource mapping indicator, the time-frequency resources respectively occupied by the preamble sequence and the scrambled service data.

The base station notifies the UE of the resource mapping indicator in any one of the following manners, and notification manners include, but are not limited to, the following manners:.

Optionally, the predetermined resource mapping relationship includes a time domain resource mapping relationship and a frequency domain resource mapping relationship.

The time domain resource mapping relationship includes any one of the following (<NUM>) to (<NUM>). The preamble sequence and the scrambled service data use symbols in a same radio subframe, as described in (<NUM>) to (<NUM>). Alternatively, the preamble sequence and the scrambled service data may use symbols in different radio subframes, as described in (<NUM>) to (<NUM>). Such a manner is more applicable to a scenario in which there is a relatively large service data volume. In this embodiment of this application, symbols occupied by the preamble sequence and the scrambled service data are orthogonal frequency division multiplexing (English: Orthogonal Frequency Division Multiplexing, OFDM) symbols in a radio subframe except a cycle prefix (English: Cycle Prefix, CP). Whether the CP is added to the radio subframe and a length of the CP may be set based on an application requirement. Whether a GT (Guard Time) is added to the radio subframe and a length of the GT may be set based on an application requirement.

The frequency domain resource mapping relationship includes either of the following (<NUM>) and (<NUM>).

The resource mapping relationship may be determined by combining any one of the time domain resource mapping relationships and any one of the frequency domain resource mapping relationships. For example, a resource mapping relationship determined by combining the first time domain resource mapping relationship and the first frequency domain resource mapping relationship is that the preamble sequence and the scrambled service data use symbols in the same radio subframe in the same subcarrier, the preamble sequence occupies the first P OFDM symbols in the radio subframe, and the scrambled service data occupies the (P+<NUM>)th to (P+Q)th OFDM symbols in the first radio subframe. Other combinations are not listed one by one.

Step <NUM>: The UE sends, on the configured time-frequency resources, the preamble sequence and the scrambled service data to the base station to which the cell belongs.

Step <NUM>: The UE receives a random access response sent by the base station based on the preamble sequence.

It should be noted herein that the base station may notify the UE of the scrambling code mapping indication and the resource mapping indicator in a same manner, or may notify the UE of the scrambling code mapping indication and the resource mapping indicator in different manners. For example, the base station may notify the UE of the scrambling code mapping indication and the resource mapping indicator by using different time-frequency resources on the physical broadcast channel. Alternatively, the base station may notify the UE of the scrambling code mapping indication by using the physical broadcast channel, and may notify the UE of the resource mapping indicator by using the SI.

Optionally, to increase efficiency of coding the service data and improve decoding accuracy of the base station, the service data may be further coded based on a predetermined coding scheme before the service data is scrambled based on the scrambling code. Then coded service data is scrambled. The coding further helps distinguish between different types of service data. A flowchart of such a random access method is shown in <FIG>. Steps <NUM> to <NUM> and step <NUM> are similar to the corresponding steps in <FIG>. For implementation steps, refer to the descriptions in the corresponding steps in <FIG>. Details are not repeated herein again.

Step <NUM>: After obtaining downlink synchronization with a cell, UE determines a preamble sequence of the UE in the cell.

Step <NUM>: The UE obtains service data.

After obtaining the service data, the UE performs step <NUM>.

Step <NUM>: The UE codes the service data based on a predetermined coding scheme, to obtain coded service data.

Optionally, the predetermined coding scheme is learned in advance by the UE and a base station to which the cell belongs.

Optionally, the predetermined coding scheme is configured on a base station and the UE by default.

Optionally, the predetermined coding scheme is notified by a base station to the UE by using a coding scheme indicator, and the coding scheme indicator is used to indicate the predetermined coding scheme. The coding scheme includes, but is not limited to, a Turbo code or a polar code. For example, a first coding scheme indicator indicates the Turbo code, a second coding scheme indicator indicates the polar code, and a third coding scheme indicator indicates a low-density parity-check code (English: Low Density Parity Check Code, LDPC).

It should be noted that there is no need to limit an order of performing step <NUM> and step <NUM>. After step <NUM> and step <NUM> are performed, step <NUM> is performed.

Step <NUM>: The UE scrambles the coded service data in step <NUM> based on the scrambling code determined in step <NUM>, to obtain scrambled service data.

Step <NUM>: The UE configures, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by the preamble sequence and the scrambled service data obtained in step <NUM>.

It should be noted herein that the base station may notify the UE of a scrambling code mapping indication, a resource mapping indicator, and the coding scheme indicator in a same manner, or may notify the UE of a scrambling code mapping indication, a resource mapping indicator, and the coding scheme indicator in different manners. Alternatively, the base station may notify the UE of a scrambling code mapping indication, a resource mapping indicator, and the coding scheme indicator by using different time-frequency resources in SI, for example, notify the UE of a scrambling code mapping indication, a resource mapping indicator, and the coding scheme indicator by using different symbols in an SIB <NUM>. Alternatively, the base station may notify the UE of a scrambling code mapping indication and a resource mapping indicator by using a physical broadcast channel, and may notify the UE of the coding scheme indicator by using SI.

Optionally, for some services that require the base station to provide corresponding response data based on service data sent by the UE, such as an Internet of things service or an Internet of vehicles service, the base station needs to deliver response data including a control instruction to the UE based on service data that includes measurement parameter values in aspects of a current location, an environment, and the like and that is reported by the UE. This application provides two manners in which the base station delivers the response data to the UE. In this application, the two response manners are respectively described in detail with reference to <FIG>.

<FIG> is a flowchart of a random access method according to an embodiment of this application. After generating corresponding response data based on service data in an MSG <NUM>, a base station sends the response data to UE by using an MSG <NUM>. The method includes the following steps:.

Step <NUM>: The UE sends the MSG <NUM> to the base station to which a cell belongs. The MSG <NUM> includes both a preamble sequence and scrambled service data. This step is similar to step <NUM> in <FIG>. For a specific process in which the UE generates the MSG <NUM>, refer to <FIG>, <FIG>, <FIG>, and the descriptions about <FIG>, <FIG>, and <FIG>.

Step <NUM>': The UE receives the MSG <NUM> sent by the base station, where the MSG <NUM> is a random access response. The random access response further includes the response data, and the response data is generated by the base station based on the service data. The base station may send the response data in a plurality of manners by using the MSG <NUM>. For example, the base station adds the response data to a padding field; or redefines field content of an existing random access response, and adds the response data to some existing fields in the random access response, such as a UL-Grant field and a temporary C-RNTI field.

For a service that has a relatively small service data volume, or a service for which a procedure in which the base station generates response data based on service data is relatively simple and consumes a relatively short time, the base station may send the response data to the UE by using the MSG <NUM>. On one hand, this makes little impact on an existing random access process, and does not greatly prolong a time for completing the random access process. On the other hand, the UE may obtain the service after receiving the MSG <NUM>, thereby greatly reducing a service delay, and improving service timeliness.

<FIG> is a flowchart of another random access method according to this application. After a random access process is completed, the UE receives response data sent by a base station. The method includes the following steps:.

Step <NUM>: The UE sends an MSG <NUM> to the base station to which a cell belongs. The MSG <NUM> includes both a preamble sequence and scrambled service data. This step is similar to step <NUM> in <FIG>. For a specific process in which the UE generates the MSG <NUM>, refer to <FIG>, <FIG>, <FIG>, and the descriptions about <FIG>, <FIG>, and <FIG>.

Step <NUM>: The UE receives an MSG <NUM> sent by the base station, where the MSG <NUM> is a random access response. This step is similar to step <NUM> in <FIG>.

Step <NUM>: The UE receives the response data sent by the base station after the random access process is completed.

For a service that has a relatively small service data volume, or a service for which a procedure in which the base station generates response data based on service data is relatively complex and consumes a relatively long time, the base station may send the response data to the UE by using a downlink channel after the random access process is completed. Optionally, the downlink channel is a physical downlink shared channel (English: Physical Downlink Shared Channel, PDSCH), a physical downlink control channel (English: Physical Downlink Control Channel, PDCCH), or the like.

In an existing random access solution, the UE needs to send service data to the base station after random access is completed, and then waits to receive response data sent by the base station. In the random access solution provided in this embodiment, the UE already sends the service data to the base station by using the MSG <NUM>. Therefore, the UE does not need to send the service data after random access is completed. After the random access process is completed, the UE may directly receive the response data. Compared with the existing random access solution, the random access method provided in this embodiment can reduce a time used by the UE to obtain a service, thereby improving timeliness of the service.

<FIG> is a schematic diagram of a random access method according to this application. Implementation details of the random access method are emphasized in <FIG> from a perspective of a base station.

Step <NUM>: The base station determines, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by a preamble sequence and service data that are in a cell covered by the base station.

A quantity of preamble sequences that can be used by each cell is limited. For example, in an LTE network, each cell has <NUM> preamble sequences that can be used. The preamble sequence is sent on a physical random access channel (English: Physical Random Access Channel, PRACH). The base station notifies, by using broadcast system information SIB <NUM>, all UEs of specific time-frequency resources on which sending preamble sequences is allowed.

The base station may determine, based on the predetermined resource mapping relationship and a time-frequency resource occupied by each preamble sequence, a time-frequency resource occupied by the corresponding service data.

Optionally, the predetermined resource mapping relationship is learned by the base station and the UE in advance before the UE sends the preamble sequence and the service data.

Optionally, the predetermined resource mapping relationship is notified by the base station to the UE. For example, the base station uses a resource mapping indicator to indicate the predetermined resource mapping relationship. The base station sends the resource mapping indicator to the UE, and the UE receives the resource mapping indicator sent by the base station. The UE configures, based on the resource mapping relationship indicated by the resource mapping indicator, the time-frequency resources respectively occupied by the preamble sequence and the scrambled service data. For details about the resource mapping relationship, refer to the descriptions in the foregoing embodiment.

Step <NUM>: The base station receives, on the determined time-frequency resources, the preamble sequence and the service data that are sent by the UE, where the UE has obtained downlink synchronization with the cell, but has not obtained uplink synchronization with the cell.

Step <NUM>: The base station determines a scrambling code, where the scrambling code is in a one-to-one correspondence with the received preamble sequence, or the scrambling code is in a one-to-one correspondence with an identifier of the UE, or the scrambling code is in a one-to-one correspondence with a combination of the received preamble sequence and an identifier of the UE.

Optionally, the scrambling code is in a one-to-one correspondence with the preamble sequence sent by the UE. In this case, an RRC state of the UE is not limited. Alternatively, when the UE is in an RRC_CONNECTED state or an RRC_INACTIVE state, the scrambling code is in a one-to-one correspondence with the identifier of the UE. Alternatively, the scrambling code is in a one-to-one correspondence with the combination of the preamble sequence sent by the UE and the identifier of the UE. Optionally, a manner of determining the scrambling code is learned in advance by the UE and the base station to which the cell belongs. The base station determines a corresponding scrambling code based on the preamble sequence and/or the identifier of the UE in an RRC_CONNECTED state or an RRC_INACTIVE state in a known manner of determining the scrambling code. Optionally, the manner of determining the scrambling code is configured on the base station and the UE by default. Optionally, the manner of determining the scrambling code is notified by the base station to the UE by using a scrambling code mapping indication.

For the manner of determining the scrambling code and details about each of the three correspondences, refer to the descriptions in the foregoing embodiment.

Step <NUM>: The base station descrambles the received service data based on the scrambling code, to obtain descrambled service data.

Descrambling (Descrambling) is reverse processing of scrambling, that is, decrypting, by using a scrambling code, a signal carrying service data. After obtaining the descrambled service data, the base station may provide a corresponding service for a user based on the service data.

Step <NUM>: The base station sends a random access response to the UE based on the preamble sequence.

In the random access method provided in this embodiment of this application, when the base station receives an MSG <NUM>, the base station receives, on the time-frequency resources having a mapping relationship, the preamble sequence and the service data that are sent by the UE. In other words, the MSG <NUM> carries both the preamble and the service data. Therefore, the base station does not need to provide a service for the UE after waiting for completion of a random access process, thereby reducing a service delay.

Optionally, before the base station receives the preamble sequence and the service data from the UE in step <NUM>, the method shown in <FIG> further includes: sending, by the base station, a resource mapping indicator to the UE, where the resource mapping indicator is used to indicate the predetermined resource mapping relationship.

Optionally, before the base station receives the preamble sequence and the service data from the UE in step <NUM>, the method shown in <FIG> further includes: sending, by the base station, a scrambling code mapping indication to the UE. Specifically, a first scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a scrambling code, a second scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and an identifier of the UE, and a third scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE.

For a manner in which the base station sends the resource mapping indicator or the scrambling code mapping indication to the UE, refer to the descriptions in the foregoing embodiment.

Optionally, for some services that require the base station to provide corresponding response data based on service data sent by the UE, this application provides two manners in which the base station delivers the response data to the UE. Optionally, the base station may add the response data to the random access response and send the random access response to the UE, or may send the response data to the UE after the random access process is completed. For specific sending manners, refer to the descriptions in the foregoing embodiment. The two manners of sending the response data may be selected based on a data volume of the service data and a processing time and a processing difficulty of the service data.

Optionally, to improve data transmission reliability, before the scrambling, the UE may code the service data. Correspondingly, after performing the descrambling, the base station further needs to perform corresponding decoding. As shown in <FIG>, the random access method further includes the following step:.

Step <NUM>: The base station decodes the descrambled service data based on a decoding scheme corresponding to a predetermined coding scheme.

Optionally, the predetermined coding scheme is learned in advance by the UE and the base station to which the cell belongs.

Optionally, the predetermined coding scheme is configured on the base station and the UE by default.

Optionally, the predetermined coding scheme is notified by the base station to the UE by using a coding scheme indicator, and the coding scheme indicator is used to indicate the predetermined coding scheme. Before the base station receives the preamble sequence and the service data that are sent by the UE, the method further includes: sending, by the base station, a coding scheme indicator to the UE, where the coding scheme indicator is used to indicate the predetermined coding scheme. For a manner in which the base station sends the coding scheme indicator, refer to the descriptions in the foregoing embodiment.

It should be noted that when the UE codes the service data, the base station needs to decode the descrambled service data, and then generates the response data based on the decoded service data after obtaining the decoded service data.

<FIG> is a schematic structural diagram of UE according to an embodiment of this application. The UE may complete the functions of the UE in the procedures shown in <FIG>, <FIG>, <FIG>, and <FIG>. For ease of description, <FIG> shows only main components of the UE. As shown in <FIG>, the UE includes a processor <NUM>, a memory, a control circuit, an antenna, and an input/output apparatus. The processor is mainly configured to: process a communications protocol and communication data, control the entire user equipment, execute a software program, and process data of the software program, for example, configured to support the UE in performing some of the described actions in the procedures shown in <FIG>, <FIG>, and <FIG>. The memory is mainly configured to store the software program and the data. The control circuit is mainly configured to perform conversion between a baseband signal and a radio frequency signal and process the radio frequency signal. The control circuit and the antenna are referred to as a transceiver <NUM> that is mainly configured to receive and send a radio frequency signal in a form of an electromagnetic wave, for example, send an MSG <NUM> to a base station, and receive an MSG <NUM> sent by the base station.

After the user equipment is powered on, the processor <NUM> may read the software program in the memory, interpret and execute an instruction in the software program, and process the data of the software program.

The processor <NUM> is configured to: after the UE obtains downlink synchronization with a cell, determine a preamble sequence of the UE in the cell, where the UE has not obtained uplink synchronization with the cell; obtain service data; determine a scrambling code, where the scrambling code is in a one-to-one correspondence with the preamble sequence, or the scrambling code is in a one-to-one correspondence with an identifier of the UE, or the scrambling code is in a one-to-one correspondence with a combination of the preamble sequence and an identifier of the UE; and scramble the service data based on the scrambling code, to obtain scrambled service data; and configure, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by the preamble sequence and the scrambled service data.

The transceiver <NUM> is configured to: send, on the time-frequency resources configured by the processor <NUM>, the preamble sequence and the scrambled service data to the base station to which the cell belongs; and receive a random access response sent by the base station based on the preamble sequence.

When the UE provided in this embodiment of this application sends an MSG <NUM>, the UE sends the preamble sequence and the service data to the base station on the configured time-frequency resources. In other words, the MSG <NUM> carries both the preamble and the service data. In this way, the base station may obtain the service data from the received MSG <NUM> in time, to provide a service for the UE. Therefore, the base station does not need to wait for completion of a random access process before obtaining service data that is transmitted by the UE by using an extra time-frequency resource, thereby reducing a service delay.

The scrambling code is in a one-to-one correspondence with the preamble sequence, and the transceiver <NUM> is further configured to receive a first scrambling code mapping indication sent by the base station, where the first scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a scrambling code. The processor <NUM> is further configured to determine the scrambling code in a one-to-one correspondence with the preamble sequence based on the mapping mode and the preamble sequence.

Optionally, the scrambling code is in a one-to-one correspondence with the identifier of the UE, and the transceiver <NUM> is further configured to receive a second scrambling code mapping indication sent by the base station, where the second scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and an identifier of the UE; and the processor <NUM> is further configured to determine the scrambling code in a one-to-one correspondence with the identifier of the UE based on the mapping mode and the identifier of the UE.

Optionally, the scrambling code is in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE, and the transceiver <NUM> is further configured to receive a third scrambling code mapping indication sent by the base station to which the cell belongs, where the third scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE; and the processor <NUM> is further configured to determine the scrambling code in a one-to-one correspondence with the combination of the preamble sequence and the identifier of the UE based on the mapping mode and the combination of the preamble sequence and the identifier of the UE.

The transceiver <NUM> is further configured to receive a resource mapping indicator sent by the base station, where the resource mapping indicator is used to indicate the predetermined resource mapping relationship; and the processor <NUM> is further configured to configure, based on the resource mapping relationship indicated by the resource mapping indicator, the time-frequency resources respectively occupied by the preamble sequence and the scrambled service data.

Optionally, the transceiver <NUM> is further configured to receive a coding scheme indicator sent by the base station, where the coding scheme indicator is used to indicate a predetermined coding scheme.

For manners of sending the scrambling code mapping indications, the resource mapping indicator, and the coding scheme indicator, and more implementation details, refer to the descriptions in the foregoing method embodiment.

<FIG> is a schematic structural diagram of a base station according to an embodiment of this application. The base station device may be used as the base station in <FIG>, <FIG>, <FIG>, and <FIG>. As shown in <FIG>, the base station device includes one or more transceivers <NUM> and one or more baseband units (English: baseband unit, BBU for short) <NUM>. The transceiver <NUM> may be referred to as a remote radio unit (English: remote radio unit, RRU for short), a transceiver unit, a transceiver machine, a transceiver circuit, or the like. The transceiver <NUM> may include at least one antenna <NUM> and a radio frequency unit <NUM>.

The transceiver <NUM> is mainly configured to: receive and send a radio frequency signal and perform conversion between the radio frequency signal and a baseband signal. The processor <NUM> is mainly configured to perform baseband processing, control the base station, and the like. The transceiver <NUM> and the baseband unit <NUM> may be physically disposed together, or may be physically separated. In other words, the base station is a distributive base station.

The baseband unit <NUM> is mainly used to complete a baseband processing function, such as channel coding, multiplexing, modulation, or spectrum spreading.

In an example, the baseband unit <NUM> may include one or more boards, and the plurality of boards may jointly support a radio access network (for example, an LTE network) of a single access standard, or may respectively support radio access networks of different access standards. The baseband unit <NUM> includes a processor <NUM>. The processor <NUM> may be configured to control the base station shown in <FIG> to perform the procedure performed by the base station in each of the foregoing embodiments. Optionally, the baseband unit <NUM> may further include a memory <NUM>, configured to store a necessary instruction and necessary data.

The processor <NUM> is configured to determine, based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by a preamble sequence and service data that are in a cell covered by the base station.

The transceiver <NUM> is configured to receive, on the determined time-frequency resources, the preamble sequence and the service data that are sent by UE, where the UE has obtained downlink synchronization with the cell, but has not obtained uplink synchronization with the cell.

The processor <NUM> is further configured to: determine a scrambling code, where the scrambling code is in a one-to-one correspondence with the received preamble sequence, or the scrambling code is in a one-to-one correspondence with an identifier of the UE, or the scrambling code is in a one-to-one correspondence with a combination of the received preamble sequence and an identifier of the UE; and descramble, based on the scrambling code, the service data sent by the UE, to obtain descrambled service data.

The transceiver <NUM> is further configured to send a random access response to the UE based on the preamble sequence.

When the base station provided in this embodiment of this application receives an MSG <NUM>, the base station receives, on the time-frequency resources having a mapping relationship, the preamble sequence and the service data that are sent by the UE. In other words, the MSG <NUM> carries both the preamble and the service data. Therefore, the base station does not need to provide a service for the UE after waiting for completion of a random access process, thereby reducing a service delay.

Optionally, the transceiver <NUM> is further configured to send a resource mapping indicator to the UE, where the resource mapping indicator is used to indicate the predetermined resource mapping relationship.

Optionally, the transceiver <NUM> is further configured to: before receiving the preamble sequence and the service data that are sent by the UE, send a first scrambling code mapping indication to the UE, where the first scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a scrambling code.

Optionally, the transceiver <NUM> is further configured to: before receiving the preamble sequence and the service data that are sent by the UE, send a second scrambling code mapping indication to the UE, where the second scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and an identifier of the UE.

Optionally, the transceiver <NUM> is further configured to: before receiving the preamble sequence and the service data that are sent by the UE, send a third scrambling code mapping indication to the UE, where the third scrambling code mapping indication is used to indicate a mapping mode of a preamble sequence and a combination of the preamble sequence and an identifier of the UE.

Optionally, to improve transmission reliability of the service data, the UE further codes to-be-sent data before scrambling the to-be-sent service data. Correspondingly, the base station also needs to decode the received service data after descrambling the received service data. In this case, the processor <NUM> is further configured to: after obtaining the descrambled service data, decode the descrambled service data based on a decoding scheme corresponding to a predetermined coding scheme. The transceiver <NUM> is further configured to: before receiving the preamble sequence and the service data that are sent by the UE, send a coding scheme indicator to the UE, where the coding scheme indicator is used to indicate the predetermined coding scheme.

An embodiment of this application further provides a random access system of UE. The random access system includes a base station and the UE. For a structure of the base station, refer to the descriptions in <FIG>. For a structure of the UE, refer to the descriptions in <FIG>. For a process of interaction between the base station and the UE, refer to the descriptions in the foregoing method embodiment.

Claim 1:
A random access method, comprising:
after obtaining downlink synchronization with a cell, determining (<NUM>), by a user equipment, UE, a preamble sequence of the UE in the cell, wherein the UE has not obtained uplink synchronization with the cell;
obtaining (<NUM>), by the UE, service data;
determining (<NUM>), by the UE, a scrambling code, wherein the scrambling code is in a one-to-one correspondence with the preamble sequence;
scrambling (<NUM>), by the UE, the service data based on the scrambling code, to obtain scrambled service data;
determining (<NUM>), by the UE based on a predetermined resource mapping relationship, time-frequency resources respectively occupied by the preamble sequence and the scrambled service data;
sending (<NUM>, <NUM>), by the UE on the determined time-frequency resources, the preamble sequence and the scrambled service data to a base station to which the cell belongs; and
receiving (<NUM>, <NUM>), by the UE, a random access response from the base station.