Always-on bearer for small data transfers in LTE systems

摘要

When a UE in an LTE system enters the RRC_IDLE state, only the S5/S8 EPS bearer context is retained, and the S1-U, S1-AP and radio bearers are released. These bearers have to be re-established on per UE basis when the UE returns to RRC_CONNECTED state. A number of UE applications may send small data frequently, which causes the UE to toggle between IDLE and CONNECTED states. This leads to a great deal of signaling overhead as the radio bearer and the S1-U bearer must be frequently re-established as the UE transitions between IDLE to CONNECTED states. Described herein are methods and systems that provide an always-on S1-U bearer to reduce this signaling overhead.

主权项

1. An evolved Node B (eNB) for operating in an LTE (Long Term Evolution) network, comprising:
processing circuitry; a radio interface for communicating with user equipment (UEs); an S1-MME network interface for communicating with a mobile management entity (MME); an S1-U network interface for communicating with a serving gateway (S-GW); an X2 network interface for communicating with another eNB; wherein the processing circuitry is to, when a request for an always-on S1-U bearer is received from a UE, instruct the MME to provide the UE with an S1-U bearer that persists as the UE moves between RRC_CONNECTED and RRC_IDLE states and preserve the UE context information during an S1 Release procedure or when the UE otherwise goes into an RRC_IDLE or ECM-IDLE state; and, after receiving an NAS (non-access stratum) Service Request message from a UE with an always-on S1-U bearer along with an S-GW IP address, S-GW TEID assigned to the always-on S1-U bearer, last eNB IP address, and last eNB ECGI (E-UTRAN Cell Global Identifier), and if the UE's eNB has changed and a low mobility indication has been received from the UE, the processing circuitry is further to: send an enhanced UE Context Release message to the UE's last eNB that informs the last eNB to release resources associated with the always-on S1-U bearer; re-establish security context with the UE.