Methods and systems for mobility management in non-terrestrial networks

A method performed by a first communication node, the method comprising:

• during a first time period, communicating with a first non-terrestrial communication node utilizing a first communication link, wherein the first non-terrestrial communication node provides a first geographic cell in which a user equipment device (UE) is present during the first time period;
• during a second time period, communicating with a second communication node utilizing a second communication link during the second time period, the method further comprising, during the second time period:
• establishing a third communication link between the second communication node and a second non-terrestrial communication node, wherein the UE has moved within a second geographic cell provided by the second non-terrestrial communication node,
• receiving downlink data from a core network,
• performing service data adaptation protocol (SDAP) processing and packet data convergence protocol (PDCP) processing on the downlink data to provide processed downlink data, and
• transmitting the processed downlink data to the second communication node, wherein the second communication node is configured to forward the processed downlink data to the non-terrestrial communication node without further SDAP and PDCP processing by performing only data relaying between the first communication node and the non-terrestrial communication node;
• and
• determining to maintain the first communication node as an anchor node for communications between a core network and the UE during both the first and second time periods, wherein security keys associated with the UE remain unchanged during both the first and second time periods.