Timing advance validation for transmission in preconfigured uplink resources in NB-IoT
Various examples and schemes pertaining to timing advance validation for transmission in preconfigured uplink resources in narrowband Internet of Things (NB-IoT) are described. When in a first mode, an apparatus (e.g., a user equipment) receives a plurality of different values for a time alignment timer (TAT) from a network before entering a second mode from the first mode. When in the second mode, the apparatus selects one of the plurality of values to apply to the TAT and also starts the TAT to count. When there is data for uplink transmission while the apparatus is still in the second mode, the apparatus performs an early data transmission in an event that a timing advance (TA) value is valid and that the apparatus is in the same serving cell as it was before entering the second mode.
1. A method, comprising:
receiving, by a processor of an apparatus in a first mode, a configuration of a plurality of different values for a time alignment timer (TAT) from a network before entering a second mode from the first mode; and
when the apparatus is in the second mode, performing, by the processor, operations comprising:
selecting one of the plurality of values to apply to the TAT;
starting the TAT to count; and
responsive to the TAT having not expired, performing an early data transmission (EDT) to the network by skipping a Message 1 and a Message 2 in an EDT random access procedure to directly transmit data in a Message 3 to the network node.
2. The method of claim 1 , wherein the performing of the EDT comprises:
determining, by the processor, a validity of a timing advance (TA) value in a TA command received from the network before entering the second mode; and
performing, by the processor, the EDT to the network using preconfigured uplink (UL) resources responsive to the TA value being determined as valid.
3. The method of claim 2 , wherein the performing of the EDT to the network further comprises:
determining whether the apparatus is in a same serving cell as that when the apparatus was in the first mode; and
performing the EDT to the network responsive to the TA value being determined as valid and the apparatus being determined to be in the same serving cell.
4. The method of claim 2 , wherein the determining of the validity of the TA value comprises:
determining the TA value to be valid in an event that the TAT has not expired; and
determining the TA value to be invalid in an event that the TAT has expired.
5. The method of claim 4 , further comprising:
determining, by the processor, that there is data for UL transmission; and
initiating, by the processor, a random access channel (RACH) preamble transmission for UL timing alignment responsive to the TAT having expired.
6. The method of claim 1 , wherein the performing of the EDT comprises:
determining, by the processor, whether the apparatus is in a same serving cell as that when the apparatus was in the first mode; and
performing, by the processor, the EDT to the network using preconfigured uplink (UL) resources responsive to the apparatus being determined to be in the same serving cell.
7. The method of claim 6 , wherein the performing of the EDT to the network further comprises:
determining a validity of a timing advance (TA) value in a TA command received from the network before entering the second mode; and
performing the EDT to the network responsive to the TA value being determined as valid and the apparatus being determined to be in the same serving cell.
8. The method of claim 7 , wherein the determining of the validity of the TA value comprises:
determining the TA value to be valid in an event that the TAT has not expired; and
determining the TA value to be invalid in an event that the TAT has expired.
9. The method of claim 8 , further comprising:
determining, by the processor, that there is data for UL transmission; and
initiating, by the processor, a random access channel (RACH) preamble transmission for UL timing alignment responsive to the TAT having expired.
10. The method of claim 1 , wherein the first mode comprises a radio resource control (RRC) connected mode, and wherein the second mode comprises an RRC idle mode or an RRC suspend mode.
11. An apparatus, comprising:
a communication device configured to wirelessly communicate with a network; and
a processor coupled to the communication device and configured to perform operations comprising:
receiving, via the communication device when the apparatus is in a first mode, a configuration of a plurality of different values for a time alignment timer (TAT) from the network before entering a second mode from the first mode; and
when the apparatus is in the second mode, performing operations comprising:
selecting one of the plurality of values to apply to the TAT;
starting the TAT to count; and
responsive to the TAT having not expired, performing, via the communication device, an early data transmission (EDT) to the network by skipping a Message 1 and a Message 2 in an EDT random access procedure to directly transmit data in a Message 3 to the network node.
12. The apparatus of claim 11 , wherein, in performing the EDT, the processor is configured to perform operations comprising:
determining a validity of a timing advance (TA) value in a TA command received from the network before entering the second mode; and
performing, via the communication device, the EDT to the network using preconfigured uplink (UL) resources responsive to the TA value being determined as valid.
13. The apparatus of claim 12 , wherein, in performing the EDT to the network, the processor is further configured to perform operations comprising:
determining whether the apparatus is in a same serving cell as that when the apparatus was in the first mode; and
performing the EDT to the network responsive to the TA value being determined as valid and the apparatus being determined to be in the same serving cell.
14. The apparatus of claim 12 , wherein, in determining the validity of the TA value, the processor is configured to perform operations comprising:
determining the TA value to be valid in an event that the TAT has not expired; and
determining the TA value to be invalid in an event that the TAT has expired.
15. The apparatus of claim 14 , wherein the processor is further configured to perform operations comprising:
determining that there is data for UL transmission; and
initiating, via the communication device, a random access channel (RACH) preamble transmission for UL timing alignment responsive to the TAT having expired.
16. The apparatus of claim 11 , wherein, in performing the EDT, the processor is configured to perform operations comprising:
determining whether the apparatus is in a same serving cell as that when the apparatus was in the first mode; and
performing, via the communication device, the EDT to the network using preconfigured uplink (UL) resources responsive to the apparatus being determined to be in the same serving cell.
17. The apparatus of claim 16 , wherein, in performing the EDT to the network, the processor is further configured to perform operations comprising:
determining a validity of a timing advance (TA) value in a TA command received from the network before entering the second mode; and
performing the EDT to the network responsive to the TA value being determined as valid and the apparatus being determined to be in the same serving cell.
18. The apparatus of claim 17 , wherein, in determining the validity of the TA value, the processor is configured to perform operations comprising:
determining the TA value to be valid in an event that the TAT has not expired; and
determining the TA value to be invalid in an event that the TAT has expired.
19. The apparatus of claim 18 , wherein the processor is further configured to perform operations comprising:
determining that there is data for UL transmission; and
initiating, via the communication device, a random access channel (RACH) preamble transmission for UL timing alignment responsive to the TAT having expired.
20. The apparatus of claim 11 , wherein the first mode comprises a radio resource control (RRC) connected mode, and wherein the second mode comprises an RRC idle mode or an RRC suspend mode.