Method and apparatus for intercell cross-trp seamless mobility

A user equipment (UE), comprising:

• at least one processor;
• and
• a non-transitory computer readable storage medium storing programming, the programming including instructions that, when executed by the at least one processor, cause the UE to perform operations including:
• measuring a timing offset between a UE-tracked source transmission and reception point (TRP) reference signal (RS) timing and a target TRP RS timing to obtain a latest measured timing difference between RSs from the source TRP and from a target TRP;
• transmitting, to the target TRP, an uplink signal following the UE-tracked source TRP RS timing;
• receiving a current target TA from the source TRP or the target TRP of a current serving cell, the current target TA measured by the current serving cell of the source TRP and the target TRP on the uplink signal aligning with the UE-tracked source TRP RS timing for UL transmission to the target TRP;
• determining a target TRP TA of the target TRP based on the latest measured timing difference and the current target TA;
• and
• performing random-access channel (RACH)-less mobility access to the target TRP based on the target TRP TA and a UE-tracked target TRP RS timing for the UL transmission to the target TRP.

A user equipment (UE), comprising:

• at least one processor;
• and
• a non-transitory computer readable storage medium storing programming, the programming including instructions that, when executed by the at least one processor, cause the UE to perform operations including:
• receiving and maintaining, from a serving source cell, a mobility pre-configuration message, the mobility pre-configuration message indicating layer 1 (L1) measurement configuration information of the serving source cell, first L1 measurement configuration information of a first candidate cell, and second L1 measurement configuration information of a second candidate cell, the second candidate cell being a subsequent cell of the first candidate cell on a predicted trajectory of the UE;
• receiving, from the serving source cell, a first lower layer target access command to switch to the first candidate cell as a target cell;
• switching to the first candidate cell such that the first candidate cell becomes a current serving cell of the UE;
• performing first L1 measurement based on the first L1 measurement configuration information;
• reporting, to the current serving cell, first L1 measurement results based on the first L1 measurement configuration information of the current serving cell;
• receiving, from the current serving cell, a second lower layer target access command to switch to the second candidate cell;
• performing cell switch access to the second candidate cell as a new serving cell of the UE;
• performing, by the UE in the new serving cell, second L1 measurement only based on the second L1 measurement configuration information;
• and
• reporting, to the new serving cell, second L1 measurement results based on the second L1 measurement configuration information.

A method, comprising:

• determining, by a centralized unit (CU), mobility candidate cell(s) and associated transmission and reception point (TRP) (s) based on a measurement report and additional information including a predicted trajectory of a user equipment (UE);
• sending, by the CU to a candidate cell with a subset of the associated TRP(s), a mobility pre-configuration request;
• receiving, by the CU from the candidate cell, a mobility pre-configuration response indicating target cell timing advance (TA) assistance information;
• sending, by the CU to a source cell, a second mobility pre-configuration request requesting;
• and
• receiving, by the CU from the source cell, a second mobility pre-configuration response indicating source assistance information;
• sending, by the CU to the source cell, a final target TA assistance information;
• and
• transmitting, by the source cell to the UE, a radio resource control (RRC) message for random-access channel (RACH)-less access, the RRC message indicating the target TA assistance information.