Latency reduction in LTE systems
Systems, methods, and instrumentalities are disclosed for a wireless transmit/receive unit (WTRU) autonomously synchronizing. For example, a WTRU may be configured to receive a downlink timing synchronization. The WTRU may be configured to determine a synchronization signal. The WTRU may be configured to determine a synchronization mode. The synchronization mode may be RRC CONNECTED mode. The synchronization mode may be RRC IDLE mode. The WTRU may communicate data to the network while in an unsynchronized state in an RRC IDLE and/or an RRC CONNECTED mode. The communication of data while unsynchronized may reduce latency relative to one or more of a random access channel (RACH) procedure, a resource radio control (RRC) connection establishment procedure, or a data packet scheduling, for example.
1. A method performed by a wireless transmit/receive unit (WTRU), the method comprising:
determining that uplink data is available for transmission to a base station;
sending a transmission to the base station before receiving synchronization information from the base station, wherein the transmission comprises a preamble and at least a portion of the uplink data; and
receiving a message from the base station in response to the transmission, wherein the message indicates the synchronization information.
2. The method of claim 1 , wherein the synchronization information indicates a timing advance command (TAC) and wherein the method further comprises receiving data in accordance with a timing reference indicated by the TAC.
3. The method of claim 1 , wherein the uplink data comprises a radio resource control (RRC) re-establishment request.
4. The method of claim 1 , wherein the method further comprises determining a random access procedure based on a signal measurement and a threshold, and wherein the transmission is based on the determined random access procedure.
5. The method of claim 1 , wherein the method further comprises receiving a radio resource control (RRC) message, wherein the RRC message indicates configuration information for a random access procedure.
6. The method of claim 5 , wherein the configuration information indicates a reception window, and wherein the message is received during a duration of time indicated by the reception window.
7. The method of claim 1 , wherein the method further comprises determining configuration information to be used for the transmission, wherein the configuration information indicates at least one of a subcarrier spacing, a transmission time interval (TTI) length, or a waveform for the transmission.
8. The WTRU of claim 7 , wherein the processor is configured to determine that the uplink data is available for transmission to the base station by determining an arrival of uplink data or downlink data when the WTRU is in a radio resource control (RRC) connected state.
9. The method of claim 1 , wherein determining that the uplink data is available for transmission to the base station, comprises determining an arrival of uplink data or downlink data when the WTRU is in a radio resource control (RRC) connected state.
10. A wireless transmit/receive unit (WTRU), the WTRU comprising:
a processor, wherein the processor is configured to:
determine that uplink data is available for transmission to a base station;
send a transmission to the base station before receiving synchronization information from the base station, wherein the transmission comprises a preamble and at least a portion of the uplink data; and
receive a message from the base station in response to the transmission, wherein the message indicates the synchronization information.
11. The WTRU of claim 10 , wherein the synchronization information indicates a timing advance command (TAC), and wherein the processor is further configured to receive data in accordance with a timing reference indicated by the TAC.
12. The WTRU of claim 10 , wherein the uplink data comprises a radio resource control (RRC) re-establishment request.
13. The WTRU of claim 10 , wherein the processor is further configured to determine a random access procedure based on a signal measurement and a threshold, and wherein the transmission is based on the determined random access procedure.
14. The WTRU of claim 10 , wherein the processor is further configured to receive a radio access control (RRC) message, wherein the RRC message indicates configuration information for a random access procedure.
15. The WTRU of claim 14 , wherein the configuration information indicates a reception window, and wherein the message is received during a duration of time indicated by the reception window.
16. The WTRU of claim 10 , wherein the processor is further configured to determine a configuration information to be used for the transmission, wherein the configuration information indicates at least one of a subcarrier spacing, a transmission time interval (TTI) length, or a waveform for the transmission.
17. A wireless transmit/receive unit (WTRU), the WTRU comprising:
a processor, wherein the processor is configured to:
determine that uplink data is available for transmission to a base station;
send a transmission to the base station before receiving synchronization information from the base station, wherein the transmission comprises a preamble and at least a portion of the uplink data; and
receive a message from the base station in response to the transmission during a duration of time indicated by a reception window, wherein the message indicates the synchronization information.
18. The WTRU of claim 17 , wherein the synchronization information indicates a timing advance command (TAC), and wherein the processor is further configured to receive data in accordance with a timing reference indicated by the TAC.
19. The WTRU of claim 17 , wherein the uplink data comprises a radio resource control (RRC) re-establishment request.
20. The WTRU of claim 17 , wherein the processor is further configured to determine a random access procedure based on a signal measurement and a threshold, and wherein the transmission is based on the determined random access procedure.
21. The WTRU of claim 17 , wherein the processor is further configured to receive a radio access control (RRC) message, wherein the RRC message indicates a configuration for a random access procedure.
22. The WTRU of claim 17 , wherein the processor is further configured to determine a configuration information to be used for the transmission, wherein the configuration information indicates at least one of a subcarrier spacing, a transmission time interval (TTI) length, or a waveform for the transmission.
23. The WTRU of claim 17 , wherein the processor is configured to determine that the uplink data is available for transmission to the base station by determining an arrival of uplink data or downlink data when the WTRU is in a radio resource control (RRC) connected state.
24. A method performed by a network node, the method comprising:
receiving a transmission from a wireless transmit/receive unit (WTRU) before sending synchronization information to the WTRU, wherein the transmission comprises a preamble and at least a portion of uplink data;
determining synchronization information associated with the WTRU; and
sending a message to the WTRU in response to the transmission, wherein the message indicates the synchronization information.
25. The method of claim 24 , wherein the synchronization information indicates a timing advance command (TAC) and wherein the method further comprises sending data in accordance with a timing reference indicated by the TAC.
26. The method of claim 24 , wherein the uplink data comprises a radio resource control (RRC) re-establishment request.
27. The method of claim 24 , wherein transmission further comprises an indication of a random access procedure.
28. The method of claim 24 , wherein the method further comprises sending a radio resource control (RRC) message, wherein the RRC message indicates confirmation information for a random access procedure.
29. The method of claim 27 , wherein the configuration information indicates a reception window, and wherein the message is sent during a duration of time indicated by the reception window.
30. The method of claim 24 , wherein the method further comprises sending configuration information to the WTRU, wherein the configuration information indicates at least one of a subcarrier spacing, a transmission time interval (TTI) length, or a waveform for the transmission.
31. A network node, the network node comprising:
a processor, wherein the processor is configured to:
receive a transmission from a wireless transmit/receive unit (WTRU) before sending synchronization information to the WTRU, wherein the transmission comprises a preamble and at least a portion of uplink data;
determine synchronization information associated with the WTRU; and
send a message to the WTRU in response to the transmission, wherein the message indicates the synchronization information.
32. The network node of claim 31 , wherein the synchronization information indicates a timing advance command (TAC) and wherein the processor is further configured to send data in accordance with a timing reference indicated by the TAC.
33. The network node of claim 31 , wherein the uplink data comprises a radio resource control (RRC) re-establishment request.
34. The network node of claim 31 , wherein transmission further comprises an indication of a random access procedure.
35. The network node of claim 31 , wherein the processor is further configured to send a radio resource control (RRC) message, wherein the RRC message indicates confirmation information for a random access procedure.
36. The network node of claim 35 , wherein the configuration information indicates a reception window, and wherein the message is sent during a duration of time indicated by the reception window.
37. The network node of claim 31 , wherein the method further comprises sending configuration information to the WTRU, wherein the configuration information indicates at least one of a subcarrier spacing, a transmission time interval (TTI) length, or a waveform for the transmission.