CN107360628B - Random access method, base station and terminal - Google Patents
Random access method, base station and terminal Download PDFInfo
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- CN107360628B CN107360628B CN201610305767.4A CN201610305767A CN107360628B CN 107360628 B CN107360628 B CN 107360628B CN 201610305767 A CN201610305767 A CN 201610305767A CN 107360628 B CN107360628 B CN 107360628B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0833—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure
- H04W74/0841—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure with collision treatment
- H04W74/085—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure with collision treatment collision avoidance
Abstract
The invention provides a random access method, a base station and a terminal, wherein the method comprises the following steps: acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent; generating access response information carrying an identifier according to the first lead code and the second lead code, and sending the access response information to the terminal; receiving uplink data sent by the terminal according to the identified access response information, wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier; and feeding back a competition resolving message to the terminal according to the uplink data. The scheme of the invention can avoid the blocking of the random access process and improve the probability of successful access of the terminal.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a method, a base station, and a terminal for random access.
Background
In the contention-based random access process of the existing terminal (UE), a base station (eNB) receives random access request messages Msg1 of a plurality of terminals, deduces an RA-RNTI (radio network temporary identifier for random access response) according to time-frequency resources of Msg1, and can solve a preamble selected by the terminal on the time-frequency resources to obtain the preamble, and the eNB can solve all preambles because the preambles are orthogonal.
The eNB may identify UEs that select different time-frequency resources and different preambles, and allocate C-RNTIs (radio network temporary identifiers), timing advance, etc. to the UEs in the random access request response message, but the eNB cannot distinguish the UEs that select the same preamble.
In the existing random access process, no matter whether the random access is competitive random access or non-competitive random access, when a plurality of UEs send the same lead code on the same time-frequency resource, an eNB can not sense the conflict and sends access response information to the UEs, and all the UEs which are matched with RA-RNTIs (radio network temporary identifications) and the lead codes corresponding to the access response information use the same uplink authorization to send the subsequent messages, so that the conflict is generated and the random access process is blocked.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a random access method, a base station and a terminal, which can avoid the occurrence of blocking in the random access process and improve the probability of successful access of the terminal.
To solve the foregoing technical problem, an embodiment of the present invention provides a method for random access, including:
acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent;
generating access response information carrying an identifier according to the first lead code and the second lead code, and sending the access response information to the terminal;
receiving uplink data sent by the terminal according to the identified access response information, wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier;
and feeding back a competition resolving message to the terminal according to the uplink data.
The step of acquiring a first preamble in a first random access request sent by a terminal and a second preamble in a second random access request sent after the first random access request is sent includes:
receiving a first random access request which is sent by a terminal through a first time-frequency resource and carries a first lead code, and acquiring the first lead code from the first random access request;
feeding back indication information to the terminal according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal to send the second random access request;
and receiving a second random access request which is sent by the terminal through the second time frequency resource and carries a second lead code, and obtaining the second lead code from the second random access request.
Wherein, the step of feeding back the indication information to the terminal according to the first random access request comprises:
and when the first time-frequency resource is a fixed time-frequency resource pre-configured by the base station or the first lead code is a lead code selected non-randomly, feeding back indication information to the terminal according to the first random access request.
Wherein the second time-frequency resource is different from the first time-frequency resource.
Wherein, according to the first lead code and the second lead code, generating access response information carrying an identifier, and sending the access response information to the terminal comprises the following steps:
combining the first lead code and the second lead code to obtain an identifier;
and generating access response information carrying the identifier according to the identifier, and sending the access response information to the terminal.
Wherein, according to the identifier, generating access response information carrying the identifier, and sending the access response information to the terminal comprises the following steps:
when the second lead code is different from the first lead code, a random access radio network temporary identifier TC-RNTI is reallocated for the terminal;
and generating access response information according to the identifier and the TC-RNTI, and sending the access response information to the terminal.
Wherein, the access response information also carries: and the terminal sends the time-frequency resources used when the uplink data is sent according to the access response information.
The step of receiving the uplink data sent by the terminal according to the identified access response information includes:
and the receiving terminal receives the uplink data sent by accessing the time-frequency resource used when the uplink data is sent and carried in the response information.
The embodiment of the invention also provides a random access method, which comprises the following steps:
sending a first random access request carrying a first lead code and a second random access request carrying a second lead code after sending the first random access request to a base station;
receiving access response information which is fed back by the base station and carries an identifier, wherein the access response information is generated by the base station according to the first lead code and the second lead code;
identifying access response information of the terminal according to the identifier, and sending uplink data to the base station according to the access response information;
and receiving a competition resolving message fed back to the terminal by the base station according to the uplink data.
The step of sending a first random access request carrying a first lead code to a base station and a second random access request carrying a second lead code after sending the first random access request comprises the following steps:
sending a first random access request carrying a first lead code to a base station through a first time-frequency resource;
receiving indication information fed back to the terminal by the base station according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal for sending the second random access request;
and sending a second random access request carrying a second lead code to the base station through the second time-frequency resource according to the indication message.
Wherein, the step of identifying the access response information of the terminal according to the identifier comprises:
combining the first lead code and the second lead code to obtain a first identifier;
and according to the first identifier, identifying that the access response information with the first identifier is the access response information of the terminal from the received multiple access response information.
Wherein, the step of sending uplink data to the base station according to the access response information comprises:
and sending the uplink data to the base station according to the time-frequency resource adopted by the terminal to send the uplink data carried in the access response information.
An embodiment of the present invention further provides a base station, including:
the first receiving module is used for acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent;
the first feedback module is used for generating access response information carrying an identifier according to the first lead code and the second lead code and sending the access response information to the terminal;
a second receiving module, configured to receive uplink data sent by the terminal according to the identified access response information, where the access response information is the access response information of the terminal identified by the terminal according to the identifier;
and the second feedback module is used for feeding back a competition resolving message to the terminal according to the uplink data.
An embodiment of the present invention further provides a terminal, including:
a first sending module, configured to send a first random access request carrying a first preamble and a second random access request carrying a second preamble, which is sent after the first random access request is sent, to a base station;
a first receiving module, configured to receive access response information carrying an identifier and fed back by a base station, where the access response information is generated by the base station according to the first preamble and the second preamble;
a second sending module, configured to identify access response information of the terminal according to the identifier, and send uplink data to the base station according to the access response information;
and the second receiving module is used for receiving the competition resolving message fed back to the terminal by the base station according to the uplink data.
The technical scheme of the invention has the following beneficial effects:
in the scheme, a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request are obtained; generating access response information carrying an identifier according to the first lead code and the second lead code, and sending the access response information to the terminal; receiving uplink data sent by the terminal according to the identified access response information, wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier; and feeding back a competition resolving message to the terminal according to the uplink data. Therefore, the random access process can be prevented from being blocked, and the probability of successful access of the terminal is improved.
Drawings
Fig. 1 is a flowchart of a random access method according to an embodiment of the present invention;
fig. 2 is a flowchart illustrating a random access method according to an embodiment of the present invention;
fig. 3 is another flowchart of a random access method according to an embodiment of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The invention aims at the problems that in the prior art, when a plurality of UEs send the same lead code on the same time-frequency resource, an eNB can not sense conflict and sends access response information to the UEs, and all the UEs which are matched with RA-RNTIs (radio network temporary identifications) and the lead codes corresponding to the access response information use the same uplink authorization to send the subsequent messages, so that conflict is generated and the random access process is blocked. Therefore, the random access process can be prevented from being blocked, and the probability of successful access of the terminal is improved.
First embodiment
As shown in fig. 1, a first embodiment of the present invention provides a method for random access, including:
and step 14, feeding back a competition resolving message to the terminal according to the uplink data.
In the first embodiment, a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request are obtained; generating access response information carrying an identifier according to the first lead code and the second lead code, and sending the access response information to the terminal; receiving uplink data sent by the terminal according to the identified access response information, wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier; and feeding back a competition resolving message to the terminal according to the uplink data. Therefore, the random access process can be prevented from being blocked, and the probability of successful access of the terminal is improved.
Second embodiment
As shown in fig. 2, a second embodiment of the present invention provides a method for random access, including:
step 21, receiving a first random access request (Msg1) carrying a first preamble (1) sent by a terminal through a first time-frequency resource, and obtaining the first preamble from the first random access request;
step 22, feeding back indication information (Msg2) to the terminal according to the first random access request, wherein the indication information carries an indication message (retransmission indication bit) indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal to send the second random access request;
in the step, when the first time-frequency resource is a time-frequency resource pre-configured and fixed by the base station or the first lead code is a lead code selected non-randomly, the indication information is fed back to the terminal according to the first random access request; if the first time-frequency resource adopted when the terminal sends the Msg1 selects the time-frequency resource which is pre-configured and fixed by the base station, the success requirement of the terminal for random access is higher, therefore, the terminal can be indicated to send the lead code again, and the conflict with other terminals is avoided to the maximum extent; similarly, if the terminal selects a fixed preamble, which indicates that the success requirement of the terminal for random access is high, the terminal may be instructed to retransmit the preamble, and if the retransmitted second preamble is different from the last transmitted first preamble, collision with other terminals may be avoided to the maximum extent; certainly, the triggering condition for sending the indication information may also be that the terminal fails to access after passing through the random access process for several times, and considers that the terminal conflicts with other terminals when the sending power for sending the preamble is increased or is greater than a threshold, and in order to improve the probability of successful access of the terminal, the terminal may be instructed to send the preamble again so as to avoid the conflict with other terminals to the maximum extent; in this embodiment of the present invention, the triggering condition for instructing the terminal to resend the preamble may be any condition as long as the triggering condition satisfies the condition that the terminal fails to access and conflicts with other terminals;
step 23, receiving a second random access request (Msg1bis) carrying a second preamble (preamble2) sent by the terminal through the second time-frequency resource, and obtaining the second preamble from the second random access request;
in this embodiment, the second time-frequency resource is different from the first time-frequency resource, and the terminal transmits the preamble twice by using different time-frequency resources, so as to reduce the possibility of collision to the greatest extent;
step 24, generating access response information (Msg2bis) carrying an identifier according to the first preamble (preamble1) and the second preamble (preamble2), and sending the access response information to the terminal;
in this step, the method may specifically include: combining the first lead code and the second lead code to obtain an identifier; generating access response information carrying the identifier according to the identifier, and sending the access response information to the terminal; for example, if the first preamble is 01 and the second preamble is 02, the identifier may be 0102, and the access response information sent to the terminal carries 0102, so that after the terminal receives the access response information, the terminal can search the access response information belonging to the terminal from the received multiple access response information according to the 0102 combined by the terminal;
further, when the second preamble is different from the first preamble, a random access radio network temporary identifier (TC-RNTI) is reallocated for the terminal; and generating access response information according to the identifier and the TC-RNTI, and sending the access response information to the terminal. That is, if the preamble selected again by the terminal is different from the preamble selected again for the first time, the possibility of collision with other terminals is greatly reduced, and the TC-RNTI newly allocated to the terminal is also included in the access response information; in the random access process, when a lead code is selected by a terminal, a TC-RNTI matched with the lead code is distributed for identifying the terminal; wherein the second preamble is preferably selected from other preambles in the same group as the first preamble; the possibility of terminal collision can also be reduced if the second preamble transmitted by a terminal is the same as the first preamble, while the second preamble transmitted again by other terminals that collide with the terminal is different from the first preamble last time.
Further, the access response information also carries: the terminal sends time-frequency resources used when the uplink data (Msg3) are sent according to the access response information;
step 25, receiving uplink data (Msg3) sent by the terminal according to the identified access response information (Msg2bis), wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier;
the step may specifically be that the receiving terminal receives the uplink data sent by accessing the time-frequency resource used when sending the uplink data carried in the response information.
And step 26, feeding back a competition resolving message (Msg4) to the terminal according to the uplink data (Msg 3).
In the embodiment, a retransmission indication bit is added in the Msg2 to indicate the terminal to retransmit a preamble, and when the terminal receives multiple pieces of access response information according to the two preambles, the identifier of the access response information belonging to the terminal can be identified from the multiple pieces of access response information, and the identifier is carried in the response information and transmitted to the terminal, so that the terminal continues to transmit uplink data on respective time-frequency resources, and thus the uplink data transmitted by the multiple terminals do not collide, and the random access process is blocked, thereby improving the probability of successful access of the terminal.
The following describes a specific implementation process of the above method with reference to a specific application scenario flow:
step 1, a terminal sends Msg1 to a base station, the Msg1 carries a lead code 1, the lead code 1 is randomly selected by the terminal, and in an LTE system, the random access lead code is used for identifying the terminal initiating a random access request and is used as a basis for uplink transmission delay measurement of an eNB. The Preamble is identified by a unique identifier Preamble ID. The terminal may obtain the configuration of the preamble through a broadcasted System Information (SI), including an available random access resource, the preamble, a TTI (transmission time interval) window, a power ramping stepsize, a maximum number of transmissions of the preamble, an initial transmit power of the preamble, and a maximum transmit power.
Step 2, after receiving the Msg1, the base station feeds back an Msg2 to the terminal, in the embodiment of the invention, a 1-bit 'retransmission indication bit' is added in the Msg2 to indicate whether the UE needs to initiate a second random access request, wherein 1 represents initiation, and 0 represents no initiation;
if the 'retransmission indication bit' is '1', the UE specifies the time-frequency resource location of random access in the Msg2, and sends the reselected preamble (i.e., Msg1bis) again, where the code is sent to facilitate the eNB to distinguish UEs in the Msg1 that select the same random access time-frequency resource and the same preamble code, so as to reduce the blocking probability.
Step 3, the eNB receives the Msg1bis transmitted by the terminal for the second time, and can judge the TC-RNTI allocated to the UE for the first time and the lead code transmitted by the UE for the first time according to the time-frequency resource position of the lead code uploaded for the second time; for the base station, if in step 1, multiple terminals use the same time-frequency resource and transmit the same preamble, then when the terminal retransmits the preamble once again, the base station also receives multiple preambles transmitted for the second time, for example, when the terminal 1, the terminal 2, and the terminal 3, and the terminal 4 transmit the preambles for the first time, the preambles transmitted to the base station are all 01, and when the 4 terminals transmit the preambles for the second time, the preambles transmitted to the base station sequentially: 02, 03, 04, 05; then, in order to distinguish the 4 terminals, it is necessary to generate an identifier by combining the preambles of two times, for example, the identifier of the terminal 1 is 0102, that is, there is a correspondence between 02 and 01, so that the preamble 01 uploaded by the terminal 1 for the first time can be determined according to the preamble 02 uploaded by the terminal 1 for the second time; similarly, for terminal 2, the identifier of terminal 2 is 0103, and preamble 01 uploaded by terminal 2 for the first time can be determined from 03.
the base station sends Msg2bis for each terminal, and feeds back Msg1 to the terminal on the first time-frequency resource, that is, Msg2bis is addressed by RA-RNTI (corresponding to the first time-frequency resource).
Step 5, the UE addresses and finds Msg2bis of a plurality of UEs in a PDCCH (physical downlink control channel) according to RA-RNTI corresponding to a first time-frequency resource for sending the lead codes for the first time, and finds messages corresponding to the UE through combined IDs of the lead codes for two times; for example, the terminal 1 combines the preambles 0102 twice, and finds the Msg2bis containing the 0102 identifier among the multiple Msg2bis received, so that the Msg2bis is the own access response message, and only sends Msg3 for the own access response message, and no longer sends uplink data for other Msg2bis, thereby avoiding collision and reducing the blocking probability.
And step 6, the UE sends the Msg3 aiming at the access response message of the UE.
And step 7, the base station sends the Msg4 aiming at the access response message of the terminal.
In the above process, after a Medium Access Control (MAC) layer of the UE receives a random Access command, first selecting a random Access resource, including the following three steps:
firstly, selecting a preamble group, wherein two preamble groups are arranged in an LTE system, and UE selects the preamble group according to the size of data needing to be sent currently;
secondly, randomly selecting a preamble code in the selected preamble group;
thirdly, randomly selecting the time frequency resource for sending the lead code, wherein the time frequency resource corresponds to the only RA-RNTI.
After the random access resource is selected, the UE calculates the sending power of the lead code according to the initial sending power and the sending times of the lead code, and sends the selected lead code on the selected time-frequency resource.
Up to this point, the UE will transmit the selected random access preamble at the determined transmission power and set the transmission counter of the random access preamble to 0.
If no other UE selects the same preamble sequence in the same random access opportunity, the base station at the network side can correctly detect the access sequence of the terminal and obtain the transmission delay of the UE, but if other UE selects the same preamble sequence and selects the same preamble code, the method of the invention can well solve the conflict between the terminals selecting the same preamble code.
In the above procedure, the eNB receives Msg1 of many UEs, deduces RA-RNTI from the Msg1 time-frequency resource, and can solve the preamble on the resource to obtain the preamble ID (since the preambles are orthogonal, the eNB can solve all preambles).
The eNB can identify the UEs which select different time-frequency resources and different lead codes, and allocates C-RNTI and time lead to the UEs in the Msg 2;
for the UE that selects the same preamble, the terminal is instructed to select the preamble again once by Msg2 and send the preamble once, and an identifier that allows the terminal to recognize Msg2bis belonging to the terminal is obtained from the preambles twice.
The eNB feeds back an Msg2(RAR) message on the PDCCH resource indicated by the RA-RNTI, wherein the message may contain response information of a plurality of random access preambles, so that the RAR is actually a multicast message, and the UE which selects the same time-frequency resource to send the preamble can receive the message.
Therefore, after receiving Msg2bis, the UE also needs to detect whether the message contains a matching preamble.
If the Msg2bis message received by the UE does not have a preamble matched with the Msg1, the UE performs backoff according to the backoff indication value in the Msg2bis message, and reselects the preamble sequence when the preamble is sent again, and sets the transmission power of the preamble as the sum of the initial power and the product of the power boosting step size and the transmission frequency.
And if the Msg2bis message received by the UE contains the lead code matched with the UE, the UE considers that the Msg2bis is successfully received.
By analyzing the Msg2bis message, the UE can obtain TA (tracking area location area update) information for uplink synchronization;
and acquiring uplink time-frequency resources allocated by the eNB for sending subsequent uplink data, and extracting a Temporary Cell identifier (TC-RNTI).
For the scene of UE initial access in an IDLE state, the TC-RNTI is changed into the C-RNTI after RRC connection is established;
for the RLF (connected state) scenario, the TC-RNTI is used as the C-RNTI of the UE after connection reestablishment.
For the switching scene, the UE uses the original C-RNTI, namely the newly allocated TC-RNTI is not used;
for a scenario with loss of uplink synchronization, the UE has a connection with the eNB.
Therefore, by using the original C-RNTI, in the latter two scenarios, the TC-RNTI allocated by the eNB for the UE in the Msg2bis message is discarded after the connection establishment is completed.
And if the UE does not receive the Msg2bis in the TTI time window, the UE considers that the Msg2bis is failed to receive, reselects the lead code and the time-frequency resource sent by the lead code, increases the power boosting step length defined by the system on the basis of the last time of the sending power, and sends the lead code from the first step of random access again.
And sending random access Msg3, wherein the Msg3 is UE which successfully receives the Msg2bis message, and after finishing uplink synchronization, uplink data are sent in uplink authorized time-frequency resources designated by the Msg2bis message.
For the initial access scenario, the UE sends a connection establishment request message of an RRC (radio link control) layer on the uplink grant time-frequency resource.
For the RLF scene, the UE sends a connection reestablishment request message of an RRC layer on the uplink authorized time-frequency resource, wherein the message contains the original C-RNTI of the UE.
For the HO (handover) scenario, the UE sends a connection reconfiguration complete message of the RRC layer on the uplink grant time-frequency resource, which is used to confirm the handover completion to the eNB of the target cell.
For the scene of losing uplink synchronization, the UE sends uplink data and a C-RNTI Control unit (CE) on the uplink authorized time-frequency resource, and the CE is used for informing the eNB that the UE uses the original C-RNTI and is not applicable to the TC-RNTI allocated to the UE by the eNB in the time-frequency resource.
In the first step of random access, when the eNB receives the lead code of the UE, the eNB does not know the scene of the UE initiating the random access process and can not judge whether the UE needs a new C-RNTI or not, so that the eNB can only allocate TC-RNTI to each UE initiating the random access process in Msg2bis, but the UEs already in the RRC connection state do not need the C-RNTIs and still use the original C-RNTI.
Therefore, after receiving the Msg3, the eNB must maintain the mapping relationship between the TC-RNTI allocated to the UE in Msg2bis and the original C-RNTI of the UE.
The specific implementation method comprises the following steps: after receiving the Msg3, the eNB can determine whether the UE uses the new C-RNTI by checking whether the Msg3 contains the C-RNTI CE:
if the Msg3 sent by the UE contains the C-RNTI CE, the fact that the UE does not use the C-RNTI distributed in the random access process Msg2bis but uses the C-RNTI indicated by the C-RNTI CE is stated, otherwise, the UE uses the C-RNTI distributed in the Msg2 bis.
Msg 4: collision resolution in random access cannot completely avoid collision in the Msg2bis reception and the Msg3 transmission. This is because there may still be a situation that the preambles selected for the second time are the same after a plurality of UEs retransmit the preambles, that is, there still exists a situation that the same preambles are transmitted on the same time-frequency resource of the plurality of UEs, the eNB cannot sense the collision and transmits Msg2bis to these UEs, and all UEs matching the RA-RNTI and the preamble of the Msg2bis use the same uplink grant to transmit Msg3, thereby generating the collision. At this time, the above method of the present invention may be adopted to instruct the terminal to retransmit a new preamble again, which is different from the previously selected preambles, so that the possibility of collision of the terminals may be further reduced.
The contention-based random access procedure is described below with reference to a specific application scenario:
1) after triggering random access, the UE firstly selects a random access time-frequency resource and a lead code, and then sends a random access request message Msg1 at a corresponding time-frequency resource position;
2) the UE receives random response information Msg2 sent by a base station in a PDCCH in a specified time window, the UE uses RA-RNTI addressing corresponding to Msg1 time-frequency resources one by one to find a corresponding control information position on the PDCCH, finds corresponding Msg2 information (information such as time lead, Msg3 uplink time-frequency resource sending position, TC-RNTI and 1bit 'retransmission indicating bit' (only 1bit 'retransmission indicating bit' is added relative to the existing protocol) according to a lead code of the UE, if the 'retransmission indicating bit' is 1, the information is turned to 3), and if not, the information is 5); the 'retransmission indication bit' is introduced as follows:
the base station may determine the setting of the retransmission indication bit according to the random access blocking condition and the received power of the Msg1, and if the received power of the Msg1 message is larger or the radio channel condition is worse, the retransmission indication bit needs to be set to '1' to reduce the Msg3 blocking, otherwise, the retransmission indication bit is '0'. The 'retransmission indication bit' is used to indicate whether the preamble needs to be transmitted a second time.
If the UE receives the 'retransmission indication bit' of '1' in the Msg2, it represents that retransmission is required. The UE restarts the TTI time window timer. And if the UE does not receive the random access response in the TTI time window, the UE considers that the random reception fails, the UE reselects the lead code and the time-frequency resource sent by the lead code, increases the power boosting step length defined by the system on the basis of the last time, and retransmits the lead code from the first step of the random access, wherein the message is Msg1 bis.
If the UE receives the 'retransmission indication bit' of '0' in Msg2, it indicates that Msg1b is not required to be retransmitted, and Msg3 is directly transmitted.
3) In Msg1bis, the UE reselects another preamble in the same preamble group and transmits the selected preamble at the resource location indicated by Msg 2.
4) After receiving the Msg1bis, the base station obtains a plurality of lead codes in the same time-frequency resource, respectively allocates new TC-RNTIs for a plurality of UEs corresponding to the codes, and judges the TC-RNTIs of the UEs according to the time-frequency position;
and then sending a Msg2bis message on the PDCCH, wherein the message is addressed through RA-RNTI, the cascade combination of the lead codes selected for the first time and the second time is used as an identifier, and the message corresponding to the identifier comprises a new TC-RNTI and a PUSCH time-frequency position allocated for the Msg 3. The UE receives random response information Msg2bis transmitted by the base station on the PDCCH within a predetermined time window.
Concatenated group of preambles selected for the first and second times: if the preamble of the first time is 03 and the preamble of the second time is 05, the preamble of the Msg2bis is 0305;
if the random access blocking probability in the network is still large, repeating the step 2)3) for many times until the network blocking probability is reduced;
if the UE does not receive the random access response within the TTI time window, the UE considers that the random reception fails.
5) The UE demodulates the PUSCH position indicated by the Msg2bis message and sends the Msg3 first scheduling information, namely uplink data
6) The base station sends a contention resolution message Msg 4.
In the above embodiments of the present invention, the probability of random access failure can be reduced as long as the UE selects different preambles in Msg1 and Msg1 bis.
Third embodiment
As shown in fig. 3, a third embodiment of the present invention provides a method for random access, including:
and step 34, receiving a contention resolution message fed back to the terminal by the base station according to the uplink data.
In the third embodiment, a first random access request carrying a first lead code and a second random access request carrying a second lead code and sent after the first random access request is sent are sent to a base station; wherein the first preamble is different from the second preamble; receiving access response information which is fed back by the base station and carries an identifier, wherein the access response information is generated by the base station according to the first lead code and the second lead code; identifying access response information of the terminal according to the identifier, and sending uplink data to the base station according to the access response information; and receiving a competition resolving message fed back to the terminal by the base station according to the uplink data. Therefore, the terminal can identify the access response information of the terminal, only transmits uplink data aiming at the access response information of the terminal, and does not need to transmit the uplink data aiming at the received access response information of other terminals, thereby greatly reducing the conflict among the terminals and reducing the blockage.
Further, in the foregoing embodiment, step 31 includes:
311, sending a first random access request carrying a first lead code to a base station through a first time-frequency resource;
step 312, receiving indication information fed back to the terminal by the base station according to the first random access request, where the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal to send the second random access request;
step 313, according to the indication message, sending a second random access request carrying a second preamble to the base station through the second time-frequency resource.
Wherein, in step 33, identifying the access response information of the terminal according to the identifier includes:
combining the first lead code and the second lead code to obtain a first identifier;
and according to the first identifier, identifying that the access response information with the first identifier is the access response information of the terminal from the received multiple access response information.
Further, the step of sending uplink data to the base station according to the access response information includes:
and sending the uplink data to the base station according to the time-frequency resource adopted by the terminal to send the uplink data carried in the access response information.
The terminal of the embodiment can identify the access response information of the terminal, only transmits uplink data after the access response information of the terminal is transmitted, and does not need to transmit the uplink data to the received access response information of other terminals, so that the conflict among the terminals is greatly reduced, and the blocking is reduced.
Fourth embodiment
A fourth embodiment of the present invention further provides a base station, including:
the first receiving module is used for acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent;
the first feedback module is used for generating access response information carrying an identifier according to the first lead code and the second lead code and sending the access response information to the terminal;
a second receiving module, configured to receive uplink data sent by the terminal according to the identified access response information, where the access response information is the access response information of the terminal identified by the terminal according to the identifier;
and the second feedback module is used for feeding back a competition resolving message to the terminal according to the uplink data.
The base station corresponds to the methods of the first and second embodiments one to one, and can achieve the same technical effects as the first and second embodiments.
Fifth embodiment
A fifth embodiment of the present invention provides a terminal, including:
a first sending module, configured to send a first random access request carrying a first preamble and a second random access request carrying a second preamble, which is sent after the first random access request is sent, to a base station;
a first receiving module, configured to receive access response information carrying an identifier and fed back by a base station, where the access response information is generated by the base station according to the first preamble and the second preamble;
a second sending module, configured to identify access response information of the terminal according to the identifier, and send uplink data to the base station according to the access response information;
and the second receiving module is used for receiving the competition resolving message fed back to the terminal by the base station according to the uplink data.
The terminal is further configured to implement the functions that can be implemented by the method described in the third embodiment, and can achieve the same technical effects as those achieved by the third embodiment.
While the principles of the invention have been described in connection with specific embodiments thereof, it should be noted that it will be understood by those skilled in the art that all or any of the steps or elements of the method and apparatus of the invention may be implemented in any computing device (including processors, storage media, etc.) or network of computing devices, in hardware, firmware, software, or any combination thereof, which will be within the skill of those in the art after reading the description of the invention and applying their basic programming skills.
Thus, the objects of the invention may also be achieved by running a program or a set of programs on any computing device. The computing device may be a general purpose device as is well known. The object of the invention is thus also achieved solely by providing a program product comprising program code for implementing the method or the apparatus. That is, such a program product also constitutes the present invention, and a storage medium storing such a program product also constitutes the present invention. It is to be understood that the storage medium may be any known storage medium or any storage medium developed in the future. It is further noted that in the apparatus and method of the present invention, it is apparent that each component or step can be decomposed and/or recombined. These decompositions and/or recombinations are to be regarded as equivalents of the present invention. Also, the steps of executing the series of processes described above may naturally be executed chronologically in the order described, but need not necessarily be executed chronologically. Some steps may be performed in parallel or independently of each other.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method of random access, comprising:
the method for acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent comprises the following steps: receiving a first random access request which is sent by a terminal through a first time-frequency resource and carries a first lead code, and acquiring the first lead code from the first random access request; feeding back indication information to the terminal according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal to send the second random access request; receiving a second random access request carrying a second lead code and sent by the terminal through the second time frequency resource, and obtaining the second lead code from the second random access request;
generating access response information carrying an identifier according to the first preamble and the second preamble, and sending the access response information to the terminal, wherein the access response information comprises: combining the first lead code and the second lead code to obtain an identifier; generating access response information carrying the identifier according to the identifier, and sending the access response information to the terminal;
receiving uplink data sent by the terminal according to the identified access response information, wherein the access response information is the access response information of the terminal identified by the terminal according to the identifier;
and feeding back a competition resolving message to the terminal according to the uplink data.
2. The method of random access according to claim 1, wherein the step of feeding back indication information to the terminal according to the first random access request comprises:
and when the first time-frequency resource is a fixed time-frequency resource pre-configured by the base station or the first lead code is a lead code selected non-randomly, feeding back indication information to the terminal according to the first random access request.
3. The method of random access according to claim 1, wherein the second time-frequency resource is different from the first time-frequency resource.
4. The method of claim 1, wherein the step of generating an access response message carrying an identifier according to the identifier and sending the access response message to the terminal comprises:
when the second lead code is different from the first lead code, a random access radio network temporary identifier TC-RNTI is reallocated for the terminal;
and generating access response information according to the identifier and the TC-RNTI, and sending the access response information to the terminal.
5. The method of random access according to claim 4, wherein the access response message further carries: and the terminal sends the time-frequency resources used when the uplink data is sent according to the access response information.
6. The method of claim 5, wherein the step of receiving uplink data transmitted by the terminal according to the identified access response information comprises:
and the receiving terminal receives the uplink data sent by accessing the time-frequency resource used when the uplink data is sent and carried in the response information.
7. A method of random access, comprising:
sending a first random access request carrying a first lead code to a base station and sending a second random access request carrying a second lead code after sending the first random access request, wherein the method comprises the following steps: sending a first random access request carrying a first lead code to a base station through a first time-frequency resource; receiving indication information fed back to the terminal by the base station according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal for sending the second random access request; according to the indication message, sending a second random access request carrying a second lead code to the base station through the second time-frequency resource;
receiving access response information which is fed back by the base station and carries an identifier, wherein the access response information is generated by the base station according to the first lead code and the second lead code;
identifying the access response information of the terminal according to the identifier comprises the following steps: combining the first lead code and the second lead code to obtain a first identifier; according to the first identifier, identifying the access response information with the first identifier as the access response information of the terminal from the received multiple access response information; sending uplink data to the base station according to the access response information;
and receiving a competition resolving message fed back to the terminal by the base station according to the uplink data.
8. The method of claim 7, wherein the step of sending uplink data to the base station according to the access response information comprises:
and sending the uplink data to the base station according to the time-frequency resource adopted by the terminal to send the uplink data carried in the access response information.
9. A base station, comprising:
the first receiving module is used for acquiring a first lead code in a first random access request sent by a terminal and a second lead code in a second random access request sent after the first random access request is sent, wherein the first random access request carrying the first lead code is sent by the receiving terminal through a first time-frequency resource, and the first lead code is acquired from the first random access request; feeding back indication information to the terminal according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal to send the second random access request; receiving a second random access request carrying a second lead code and sent by the terminal through the second time frequency resource, and obtaining the second lead code from the second random access request;
the first feedback module is used for generating access response information carrying an identifier according to the first lead code and the second lead code and sending the access response information to the terminal, wherein the first lead code and the second lead code are combined to obtain the identifier; generating access response information carrying the identifier according to the identifier, and sending the access response information to the terminal;
a second receiving module, configured to receive uplink data sent by the terminal according to the identified access response information, where the access response information is the access response information of the terminal identified by the terminal according to the identifier;
and the second feedback module is used for feeding back a competition resolving message to the terminal according to the uplink data.
10. A terminal, comprising:
the first sending module is used for sending a first random access request carrying a first lead code and a second random access request carrying a second lead code after the first random access request is sent to the base station, wherein the first random access request carrying the first lead code is sent to the base station through a first time-frequency resource; receiving indication information fed back to the terminal by the base station according to the first random access request, wherein the indication information carries an indication message indicating that the terminal initiates a second random access request, and a second time-frequency resource used by the terminal for sending the second random access request; according to the indication message, sending a second random access request carrying a second lead code to the base station through the second time-frequency resource;
a first receiving module, configured to receive access response information carrying an identifier and fed back by a base station, where the access response information is generated by the base station according to the first preamble and the second preamble;
a second sending module, configured to identify access response information of the terminal according to the identifier, and send uplink data to the base station according to the access response information, where the first preamble and the second preamble are combined to obtain the first identifier; according to the first identifier, identifying the access response information with the first identifier as the access response information of the terminal from the received multiple access response information;
and the second receiving module is used for receiving the competition resolving message fed back to the terminal by the base station according to the uplink data.
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