Random access process in new radio
Systems, apparatuses, and methods are described for wireless communications. Random access procedures may include various types of procedures, such as four-step or two-step random access procedures.
1. A method comprising:
transmitting, by a wireless device and as part of a two-step random access procedure, a preamble and one or more transport blocks;
receiving, by the wireless device, a media access control (MAC) packet data unit comprising:
a MAC subheader; and
a random access response (RAR);
determining, based on a field in the MAC subheader, a type of the received RAR from a plurality of types of RARs comprising:
a first type of RAR that is indicative of random access procedure success and that has a first size; and
a second type of RAR that is indicative of falling back from the two-step random access procedure and that has a second size different from the first size; and
transmitting, based on the received RAR being the second type of RAR indicative of falling back from the two-step random access procedure, the one or more transport blocks.
2. The method of claim 1 , wherein the second type of RAR is indicative of falling back from the two-step random access procedure to a four-step random access procedure, and wherein the transmitting the one or more transport blocks based on the received RAR being the second type of RAR comprises transmitting the one or more transport blocks as part of the four-step random access procedure.
3. The method of claim 1 , wherein the transmitting the one or more transport blocks based on the received RAR being the second type of RAR comprises transmitting the one or more transport blocks as a third step of a four-step random access procedure.
4. The method of claim 1 , wherein the received RAR comprises a timing advance command, and wherein the transmitting the one or more transport blocks based on the received RAR being the second type of RAR comprises transmitting the one or more transport blocks using a timing advance that is based on the timing advance command.
5. The method of claim 1 , wherein the MAC subheader comprises a random access preamble identifier (RAPID) associated with the preamble.
6. The method of claim 1 , wherein the field is a single bit.
7. The method of claim 1 , further comprising:
determining, based on the field, a size of the received RAR as being the second size; and
decoding, based on the second size, the received RAR.
8. The method of claim 1 , further comprising:
transmitting contention resolution information associated with the transmitting the one or more transport blocks based on the received RAR being the second type of RAR; and
receiving a contention resolution message that is based on the contention resolution information.
9. A method comprising:
transmitting, by a wireless device and as part of a two-step random access procedure, a preamble and a first one or more transport blocks;
receiving, by the wireless device, a media access control (MAC) packet data unit comprising:
a MAC subheader; and
a random access response (RAR);
determining, based on a field in the MAC subheader, a type of the received RAR from a plurality of types of RARs comprising:
a first type of RAR that is indicative of random access procedure success and that has a first size; and
a second type of RAR that is indicative of falling back from the two-step random access procedure and that has a second size different from the first size; and
transmitting, based on the received RAR being the first type of RAR indicative of random access procedure success, a second one or more transport blocks.
10. The method of claim 9 , further comprising:
receiving, after the receiving the MAC packet data unit, an uplink grant,
wherein the transmitting the second one or more transport blocks comprises transmitting, based on the uplink grant, the second one or more transport blocks.
11. The method of claim 9 , wherein the received RAR comprises a timing advance command, and wherein the transmitting the second one or more transport blocks comprises transmitting the second one or more transport blocks using a timing advance that is based on the timing advance command.
12. The method of claim 9 , wherein the second type of RAR is indicative of falling back from the two-step random access procedure to a four-step random access procedure.
13. The method of claim 9 , wherein the field is a single bit.
14. The method of claim 9 , further comprising:
determining, based on the field, a size of the received RAR as being the first size; and
decoding, based on the first size, the RAR.
15. A wireless device comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, configure the wireless device to:
transmit, as part of a two-step random access procedure, a preamble and one or more transport blocks;
receive a media access control (MAC) packet data unit comprising:
a MAC subheader; and
a random access response (RAR);
determine, based on a field in the MAC subheader, a type of the received RAR from a plurality of types of RARs comprising:
a first type of RAR that is indicative of random access procedure success and that has a first size; and
a second type of RAR that is indicative of falling back from the two-step random access procedure and that has a second size different from the first size; and
transmit, based on the received RAR being the second type of RAR indicative of falling back from the two-step random access procedure, the one or more transport blocks.
16. The wireless device of claim 15 , wherein the second type of RAR is indicative of falling back from the two-step random access procedure to a four-step random access procedure, and wherein the instructions, when executed by the one or more processors, configure the wireless device to transmit the one or more transport blocks based on the received RAR being the second type of RAR by transmitting the one or more transport blocks as part of the four-step random access procedure.
17. The wireless device of claim 15 , wherein the instructions, when executed by the one or more processors, configure the wireless device to transmit the one or more transport blocks based on the received RAR being the second type of RAR by transmitting the one or more transport blocks as a third step of a four-step random access procedure.
18. The wireless device of claim 15 , wherein the received RAR comprises a timing advance command, and wherein the instructions, when executed by the one or more processors, configure the wireless device to transmit the one or more transport blocks based on the received RAR being the second type of RAR by transmitting the one or more transport blocks using a timing advance that is based on the timing advance command.
19. The wireless device of claim 15 , wherein the MAC subheader comprises a random access preamble identifier (RAPID) associated with the preamble.
20. The wireless device of claim 15 , wherein the field is a single bit.
21. The wireless device of claim 15 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
determine, based on the field, a size of the received RAR as being the second size; and
decode, based on the second size, the received RAR.
22. The wireless device of claim 15 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
transmit contention resolution information associated with the transmitting the one or more transport blocks based on the received RAR being the second type of RAR; and
receive a contention resolution message that is based on the contention resolution information.
23. A wireless device comprising:
one or more processors; and
memory storing instructions that, when executed by the one or more processors, configure the wireless device to:
transmit, as part of a two-step random access procedure, a preamble and a first one or more transport blocks;
receive a media access control (MAC) packet data unit comprising:
a MAC subheader; and
a random access response (RAR);
determine, based on a field in the MAC subheader, a type of the received RAR from a plurality of types of RARs comprising:
a first type of RAR that is indicative of random access procedure success and that has a first size; and
a second type of RAR that is indicative of falling back from the two-step random access procedure and that has a second size different from the first size; and
transmit, based on the received RAR being the first type of RAR indicative of random access procedure success, a second one or more transport blocks.
24. The wireless device of claim 23 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
receive, after the receiving the MAC packet data unit, an uplink grant; and
transmit the second one or more transport blocks by transmitting, based on the uplink grant, the second one or more transport blocks.
25. The wireless device of claim 23 , wherein the received RAR comprises a timing advance command, and wherein the instructions, when executed by the one or more processors, configure the wireless device to transmit the second one or more transport blocks by transmitting the second one or more transport blocks using a timing advance that is based on the timing advance command.
26. The wireless device of claim 23 , wherein the second type of RAR is indicative of falling back from the two-step random access procedure to a four-step random access procedure.
27. The wireless device of claim 23 , wherein the field is a single bit.
28. The wireless device of claim 23 , wherein the instructions, when executed by the one or more processors, configure the wireless device to:
determine, based on the field, a size of the received RAR as being the first size; and
decode, based on the first size, the RAR.