Two-step random access procedure in next generation wireless networks

Abstract

Some of the present implementations provide a method for a base station (BS) for performing a random access (RA) procedure. The method includes transmitting, to a UE, a system information block (SIB) including a two-step RA configuration with a reference signal received power (RSRP) threshold, the SIB further indicating whether switching an RA procedure from a two-step type to a four-step type by the UE is allowed; and transmitting, to the UE, a four-step RA configuration, wherein: the UE determines whether a detected RSRP exceeds the received RSRP threshold once the RA procedure is triggered, and performs the RA procedure using the two-step type after determining that the detected RSRP exceeds the received RSRP threshold.

What is claimed is: 
     
         1 . A method for a base station (BS) for performing a random access (RA) procedure, the method comprising:
 transmitting, to a user equipment (UE), a system information block (SIB) comprising a two-step RA configuration with a reference signal received power (RSRP) threshold, the SIB further indicating whether switching an RA procedure from a two-step type to a four-step type by the UE is allowed; and   transmitting, to the UE, a four-step RA configuration, wherein:   the UE determines whether a detected RSRP exceeds the received RSRP threshold once the RA procedure is triggered, and   performs the RA procedure using the two-step type after determining that the detected RSRP exceeds the received RSRP threshold.   
     
     
         2 . The method of  claim 1 , wherein performing the RA procedure using the two-step type comprises:
 setting a counter to one;   transmitting, to the BS, a first message in a first step of the RA procedure using the two-step type; and   iteratively performing the following steps while the RA procedure uses the two-step type and the RA procedure using the two-step type is not successful:
 adding one to the counter, 
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is less than a first threshold, transmitting another first message to the BS, and 
 in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is equal to the first threshold, switching the RA procedure from the two-step type to the four-step type. 
   
     
     
         3 . The method of  claim 2 , wherein the iteratively performing the following steps further comprises:
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is less than a second threshold, transmitting another first message to the BS, and   in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is equal to the second threshold, declaring, to an upper layer of the UE, a failure of the RA procedure.   
     
     
         4 . The method of  claim 2 , wherein performing the RA procedure using the two-step type further comprises:
 determining, after transmitting the first message to the BS, whether a second message from the BS in a second step of the RA procedure using the two-step type is received successfully, wherein:
 the first message comprises a preamble and a payload, and 
 the second message comprises at least one response including at least one of contention resolution information associated with the RA procedure using the two-step type and fallback information. 
   
     
     
         5 . The method of  claim 4 , wherein the second message comprises a media access control (MAC) subheader of a MAC sub-Protocol Data Unit (subPDU) having at least one field that indicates whether the at least one response contains the contention resolution information associated with the RA procedure using the two-step type for indicating a successful RA procedure using the two-step type or the fallback information for transmitting a third message to the BS. 
     
     
         6 . The method of  claim 4 , wherein determining whether the RA procedure using the two-step type is successful comprises:
 determining that the RA procedure using the two-step type is not successful when the second message is not received successfully before an RA response time threshold has expired.   
     
     
         7 . The method of  claim 4 , wherein the second message comprises a radio resource control (RRC) message that is a response message to an RRC procedure request indicated in the first message. 
     
     
         8 . A base station (BS), comprising:
 one or more non-transitory computer-readable media storing one or more instructions for performing a random access (RA) procedure; and   at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the one or more instructions to cause the BS to:
 transmit, to a user equipment (UE), a system information block (SIB) comprising a two-step RA configuration with a reference signal received power (RSRP) threshold, the SIB further indicating whether switching from a two-step type to a four-step type by the UE is allowed; and 
 transmit, to the UE, a four-step RA configuration, wherein: 
 the UE determines whether a detected RSRP exceeds the received RSRP threshold once the RA procedure is triggered, and 
 performs the RA procedure using the two-step type after determining that the detected RSRP exceeds the received RSRP threshold. 
   
     
     
         9 . The BS of  claim 8 , wherein performing the RA procedure using the two-step type comprises:
 setting a counter to one;   transmitting, to the BS, a first message in a first step of the RA procedure using the two-step type; and   iteratively performing the following steps while the RA procedure uses the two-step type and the RA procedure using the two-step type is not successful:
 adding one to the counter, 
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is less than a first threshold, transmitting another first message to the BS, and 
 in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is equal to the first threshold, switching the RA procedure from the two-step type to the four-step type. 
   
     
     
         10 . The BS of  claim 9 , wherein the iteratively performing the following steps further comprises:
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is less than a second threshold, transmitting another first message to the BS, and   in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is equal to the second threshold, declaring, to an upper layer of the UE, a failure of the RA procedure.   
     
     
         11 . The BS of  claim 9 , wherein performing the RA procedure using the two-step type further comprises:
 determining, after transmitting the first message to the BS, whether a second message from the BS in a second step of the RA procedure using the two-step type is received successfully, wherein:
 the first message comprises a preamble and a payload, and 
 the second message comprises at least one response including at least one of contention resolution information associated with the RA procedure using the two-step type and fallback information. 
   
     
     
         12 . The BS of  claim 11 , wherein the second message comprises a media access control (MAC) subheader of a MAC sub-Protocol Data Unit (subPDU) having at least one field that indicates whether the at least one response contains the contention resolution information associated with the RA procedure using the two-step type for indicating a successful RA procedure using the two-step type or the fallback information for transmitting a third message to the BS. 
     
     
         13 . The BS of  claim 11 , wherein determining whether the RA procedure using the two-step type is successful comprises:
 determining that the RA procedure using the two-step type is not successful when the second message is not received successfully before an RA response time threshold has expired.   
     
     
         14 . The BS of  claim 11 , wherein the second message comprises a radio resource control (RRC) message that is a response message to an RRC procedure request indicated in the first mes sage. 
     
     
         15 . A method for a user equipment (UE) for performing a random access (RA) procedure, the method comprising:
 receiving, from a base station (BS), a system information block (SIB) comprising a two-step RA configuration with a reference signal received power (RSRP) threshold, the SIB further indicating whether switching from a two-step type to a four-step type is allowed;   receiving, from the BS, a four-step RA configuration;   determining whether a detected RSRP exceeds the RSRP threshold once the RA procedure is triggered; and   performing the RA procedure using the two-step type after determining that the detected RSRP exceeds the received RSRP threshold.   
     
     
         16 . The method of  claim 15 , wherein performing the RA procedure using the two-step type comprises:
 setting a counter to one;   transmitting, to the BS, a first message in a first step of the RA procedure using the two-step type; and   iteratively performing the following steps while the RA procedure uses the two-step type and the RA procedure using the two-step type is not successful:
 adding one to the counter, 
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is less than a first threshold, transmitting another first message to the BS, and 
 in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is allowed and the counter is equal to the first threshold, switching the RA procedure from the two-step type to the four-step type. 
   
     
     
         17 . The method of  claim 16 , wherein the iteratively performing the following steps further comprises:
 when the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is less than a second threshold, transmitting another first message to the BS, and   in a case that the SIB indicates that switching the RA procedure from the two-step type to the four-step type is not allowed and the counter is equal to the second threshold, declaring, to an upper layer of the UE, a failure of the RA procedure.   
     
     
         18 . The method of  claim 16 , wherein performing the RA procedure using the two-step type further comprises:
 determining, after transmitting the first message to the BS, whether a second message from the BS in a second step of the RA procedure using the two-step type is received successfully, wherein:
 the first message comprises a preamble and a payload, and 
 the second message comprises at least one response including at least one of contention resolution information associated with the RA procedure using the two-step type and fallback information. 
   
     
     
         19 . The method of  claim 18 , wherein the second message comprises a media access control (MAC) subheader of a MAC sub-Protocol Data Unit (subPDU) having at least one field that indicates whether the at least one response contains the contention resolution information associated with the RA procedure using the two-step type for indicating a successful RA procedure using the two-step type or the fallback information for transmitting a third message to the BS. 
     
     
         20 . The method of  claim 18 , wherein determining whether the RA procedure using the two-step type is successful comprises:
 determining that the RA procedure using the two-step type is not successful when the second message is not received successfully before an RA response time threshold has expired.