Secondary physical random access channel (PRACH) configuration for contention based random access in new radio systems
A device of a New Radio (NR) evolved Node B (gNodeB), a method and a machine readable medium to implement the method. The method includes: processing a first signal sent by a NR evolved NodeB (gNodeB) regarding a primary physical random access channel (PRACH) configuration to be used to encode for transmission a first communication to the gNodeB; processing a second signal sent by the gNodeB regarding a secondary PRACH configuration different from the primary PRACH configuration and to be used to encode for transmission a second communication to the gNodeB; determining the primary PRACH configuration from the first signal and the secondary PRACH from the second signal; and switching from the primary PRACH configuration to the secondary PRACH configuration and encode for transmission the second communication to the gNodeB based on the secondary PRACH configuration.
1. A user equipment (UE), comprising:
a Radio Frequency (RF) interface, and
a baseband processor configured to:
receive information from a base station indicating a first physical random access channel (PRACH) configuration and a second PRACH configuration different from the first PRACH configuration;
transmit, via the RF interface, a first communication based on the first PRACH configuration; and
in response to satisfaction of a triggering condition or explicit signaling from the base station, switch from the first PRACH configuration to the second PRACH configuration; and
transmit, via the RF interface, a second communication based on the second PRACH configuration.
2. The UE of claim 1 , wherein the base station is an integrated access and backhaul (IAB) parent node, and wherein the UE is one of a NR UE or an IAB child node.
3. The UE of claim 1 , wherein the information is received from the base station in one of a radio resource control (RRC) signal, a system information (SI) signal, or a group-common physical downlink control channel (GC-PDCCH) signal.
4. The UE of claim 1 , wherein the first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations.
5. The UE of claim 1 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station using the first PRACH configuration.
6. The UE of claim 1 , wherein the explicit signaling is part of one of:
a system information (SI) radio resource control (RRC) message from the base station;
a group-common physical downlink control channel (PDCCH) including a downlink control information (DCI) format 2_4;
a user equipment-specific (UE-specific) RRC message including a downlink downlink control channel message (DL-DCCH-message);
a medium access control control channel (MAC CE); or
a UE-specific DCI format.
7. The UE of claim 6 , wherein:
the explicit signaling is part of the SI RRC message, the SI RRC message includes an cell-specific indication of a selection as between the first PRACH configuration and the second PRACH configuration;
the explicit signaling is part of the DCI format 2_4, the DCI format 2_4 includes an indication of a selection as between the first PRACH configuration and the second PRACH configuration that is for one user equipment (UE), or for a group of UEs from one or multiple serving cells;
the explicit signaling is part of the DL-DCCH-message, the DL-DCCH message includes a RRC information element (IE) to indicate a cell-specific selection as between the first PRACH configuration and the second PRACH configuration;
the explicit signaling is part of the MAC CE, the MAC CE includes a 1-bit field to indicate a selection as between the first PRACH configuration and the second PRACH configuration; or
the explicit signaling is part of the UE-specific DCI format, the UE-specific DCI format includes a selection as between the first PRACH configuration and the second PRACH configuration for multiple serving cells.
8. The UE of claim 7 , wherein the explicit signaling is part of the DCI format 2_4, and the baseband processor is configured to decode a cyclic redundancy check (CRC) based on a secondary random access (SRA) radio network temporary identifier (RNTI) (SRA-RNTI).
9. The UE of claim 1 , wherein the information includes information regarding a triggering condition to trigger a switch between the first PRACH configuration and the second PRACH configuration, and the baseband processor is configured to switch based on the triggering condition.
10. The UE of claim 1 , wherein the baseband processor is configured to use the second PRACH configuration to encode uplink (UL) slots within a semi-static downlink/uplink (DL/UL) period to avoid interference from remote cells.
11. A method, comprising:
receiving information from a base station indicating a first physical random access channel (PRACH) configuration and;
a second PRACH configuration different from the first PRACH configuration;
transmitting a first communication based on the first PRACH configuration;
in response to satisfaction of a triggering condition or explicit signaling from the base station switching from the first PRACH configuration to the second PRACH configuration; and
transmitting a second communication based on the second PRACH configuration.
12. The method of claim 11 , wherein first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations.
13. The method of claim 12 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station have taken place using the first PRACH configuration.
14. The method of claim 12 , wherein the explicit signaling is part of one of:
a system information (SI) radio resource control (RRC) message from the base station;
a group-common physical downlink control channel (PDCCH) including a downlink control information (DCI) format 2_4;
a user equipment-specific (UE-specific) RRC message including a downlink downlink control channel message (DL-DCCH-message);
a medium access control control channel (MAC CE); or
a UE-specific DCI format.
15. The method of claim 14 , wherein:
where the explicit signaling is part of the SI RRC message, the SI RRC message includes an cell-specific indication of a selection as between the first PRACH configuration and the second PRACH configuration;
where the explicit signaling is part of the DCI format 2_4, the DCI format 2_4 includes an indication of a selection as between the first PRACH configuration and the second PRACH configuration that is for one user equipment (UE), or for a group of UEs from one or multiple serving cells;
where the explicit signaling is part of the DL-DCCH-message, the DL-DCCH message includes a RRC information element (IE) to indicate a cell-specific selection as between the first PRACH configuration and the second PRACH configuration;
where the explicit signaling is part of the MAC CE, the MAC CE includes a 1-bit field to indicate a selection as between the first PRACH configuration and the second PRACH configuration; or
where the explicit signaling is part of the UE-specific DCI format, the UE-specific DCI format includes a selection as between the first PRACH configuration and the second PRACH configuration for multiple serving cells.
16. The method of claim 15 , further including, where the explicit signaling is part of the DCI format 2_4, decoding a cyclic redundancy check (CRC) based on a secondary random access (SRA) radio network temporary identifier (RNTI) (SRA-RNTI).
17. The method of claim 16 , further including determining the SRA-RNTI from higher layer signaling by the base station.
18. A baseband processor configured to perform operations, the operations comprising
receiving information from a base station indicating a first physical random access channel (PRACH) configuration and;
a second PRACH configuration different from the first PRACH configuration;
instructing a transceiver to transmit a first communication based on the first PRACH configuration;
in response to satisfaction of a triggering condition or explicit signaling from the base station switching from the first PRACH configuration to the second PRACH configuration; and
instructing the transceiver to transmit a second communication based on the second PRACH configuration.
19. The baseband processor of claim 18 , wherein the base station is an integrated access and backhaul (IAB) parent node, and wherein the baseband processor is associated with one of a NR User Equipment (UE) or an IAB child node.
20. The baseband processor of claim 18 , wherein the triggering condition includes a predetermined number of failed transmission attempts of the first communication to the base station using the first PRACH configuration.
21. The baseband processor of claim 18 , wherein the first PRACH configuration and the second PRACH configuration are both contention-based PRACH configurations.