Aligned configuration for random access channel-less handover/secondary cell group change
A process allows a UE to acquire a System Frame Number (SFN) before accessing a target base station/node during a RACH-less handover. The SFN may be provided to the UE in various ways. For example, the SFN may be provided as part of a handover command message (e.g., RRCReconfiguration) or a master information block (MIB). In this manner, the UE acquires the SFN before accessing the target base station/node, which allows the target base station/node and the UE to effect certain timings for the handover. For example, the target base station/node and the UE may set time bounds in which the handover must occur. As another example, different types of uplink grants may be set.
1. A method performed by a user equipment (UE) for performing Random Access Channel (RACH)-less handover or Secondary Cell Group (SCG) change, the method comprising:
receiving a message;
reading a System Frame Number (SNF) for a target cell from the message;
based on the SFN number, performing one or more of the following:
changing a transmit power;
determining a change in size of a pre-allocated uplink (UK) grant;
determining a change in periodicity of a pre-allocated UL grant; and
changing a modulation and coding scheme; and
accessing the target cell during a RACH-less handover or SCG change according to the SFN.
2. The method of claim 1 , further comprising determining a validity of a RACH-less configuration using the SFN.
3. The method of claim 1 , wherein the message is a handover command message generated by a base station controlling the target cell.
4. The method of claim 1 , wherein the message is a master information block acquired from the target cell.
5. A user equipment (UE) for performing Random Access Channel (RACH)-less handover or Secondary Cell Group (SCG) change, the UE comprising:
power supply circuitry configured to supply power to the UE; and
processing circuitry configured to perform any of the steps of claim 1 .
6. A user equipment (UE) for performing RACH-less handover or SCG change, the UE comprising:
an antenna configured to send and receive wireless signals;
radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry;
an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry;
an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry;
a battery connected to the processing circuitry and configured to supply power to the UE; and
the processing circuitry being configured to perform the steps of claim 1 .
7. A method performed by a base station for performing Random Access Channel (RACH)-less handover or Secondary Cell Group (SCG) change, the method comprising:
configuring a user equipment (UE) using a target cell System Frame Number (SFN) value prior to the UE performing RACH-less handover or SCG change to the target cell;
wherein based on the SFN value:
a transmit power is changed;
a change in size of a pre-allocated uplink (UL) grant is determined;
a change in periodicity of a pre-allocated UL grant is determined; or
a modulation and coding scheme is changed; and
detecting access by the UE according to the SFN value.
8. The method of claim 7 , wherein a validity of a RACH-less configuration is determined using the SFN.
9. The method of claim 7 , further comprising generating a message containing the SFN, the message is conveyed to the UE prior to the UE accessing the target cell.
10. The method of claim 9 , wherein the message is a handover command.
11. The method of claim 9 , wherein the message is a master information block transmitted in the target cell.
12. A base station for performing Random Access Channel (RACH)-less handover or Secondary Cell Group (SCG) change, the base station comprising:
power supply circuitry configured to supply power to the base station; and
processing circuitry configured to perform any of the steps of claim 7 .