Operation in case of radio link failure

An apparatus comprising:

• at least one processor, and
• at least one memory including computer program code,
• wherein the at least one memory and the computer code are configured to, with the at least one processor, cause the apparatus to at least perform or control the following:
• create of a backup user context for a terminal device served currently by a relay base station, wherein the relay base station is a mobile relay base station, relaying a radio connection between the terminal device and fixed cellular network infrastructure comprising a fixed base station communicating with the relay base station, wherein the backup user context is prepared for use in case of an unexpected radio link failure, wherein an unexpected radio link failure is where a drop of the radio link is so sudden that the cellular network cannot prepare for the drop;
• apply the backup user context upon detection of a radio link failure in a primary user context being used in the communication and before the terminal device enters an idle state as a result of the radio link failure;
• and
• update the backup user context when the relay base station is handed over to another fixed base station of the fixed cellular network infrastructure.

A method, comprising:

• creating a backup user context for a terminal device served currently by a relay base station relaying a radio connection between the terminal device and fixed cellular network infrastructure comprising a fixed base station communicating with the relay base station, wherein the backup user context is prepared for use in case of an unexpected radio link failure, wherein an unexpected radio link failure is where a drop of the radio link is so sudden that the cellular network cannot prepare for the drop;
• applying the backup user context upon detection of a radio link failure in a primary user context being used in the communication and before the terminal device enters an idle state as a result of the radio link failure;
• configuring the terminal device to store communication parameters to be used when the backup user context is applied, wherein the stored communication parameters include carrier information of the fixed base station, an identifier of the terminal device in the backup user context, a transmission timing advance used by the relay base station in communication with the fixed base station and a scheduling request configuration;
• and
• accessing the fixed base station by using the stored communication parameters upon detection of the radio link failure.

An apparatus comprising:

• at least one processor, and
• at least one memory including computer program code,
• wherein the at least one memory and the computer code are configured to, with the at least one processor, cause the apparatus to at least perform or control the following:
• create of a backup user context for a terminal device served currently by a relay base station relaying a radio connection between the terminal device and fixed cellular network infrastructure comprising a fixed base station communicating with the relay base station, wherein the backup user context is prepared for use in case of an unexpected radio link failure, wherein an unexpected radio link failure is where a drop of the radio link is so sudden that the cellular network cannot prepare for the drop;
• apply the backup user context upon detection of a radio link failure in a primary user context being used in the communication and before the terminal device enters an idle state as a result of the radio link failure;
• configure the terminal device to store communication parameters to be used when the backup user context is applied, wherein the stored communication parameters include carrier information of the fixed base station, an identifier of the terminal device in the backup user context, a scheduling request configuration and/or transmission timing advance used by the relay base station in communication with the fixed base station;
• and
• access the fixed base station by using the stored communication parameters upon detection of the radio link failure.