Determining timing advance validity in idle mode

A method performed by a wireless device for determining a validity of a timing advance configuration of the wireless device for an idle mode transmission, the method comprising:

• obtaining, while the wireless device is operating in a connected mode, a timing advance value for the wireless device;
• performing, while the wireless device is in the connected mode, a measurement on a serving cell of the wireless device;
• performing, while the wireless device is in the connected mode, measurements on one or more neighbor cells of the wireless device;
• transitioning from the connected mode to an idle mode;
• performing another measurement on the serving cell of the wireless device while the wireless device is in the idle mode;
• performing, while the wireless device is in the idle mode, measurements on the one or more neighbor cells of the wireless device;
• and
• determining whether the timing advance configuration is valid for an idle mode transmission based on:
• the measurement on the serving cell made while the wireless device is in the connected mode, the measurements on the one or more neighbor cells while the wireless device is in the connected mode, the other measurement on the serving cell made while the wireless device is in the idle mode, and the measurements on the one or more neighbor cells while the wireless device is in the idle mode.

A User Equipment (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;
• the processing circuitry being configured to perform operations comprising:
• obtaining a timing advance value for the UE while the UE is operating in a connected mode;
• transitioning from the connected mode to an idle mode;
• performing a measurement on a serving cell of the UE while the UE is in the idle mode;
• determining, while in the idle mode, whether a timing advance configuration is valid for an idle mode transmission based on the measurement;
• and
• performing the idle mode transmission using the timing advance value if the timing advance configuration is determined to be valid;
• 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;
• and a battery connected to the processing circuitry and configured to supply power to the UE.

A method performed by a wireless device for determining a validity of a timing advance configuration of the wireless device for an idle mode transmission, the method comprising:

• performing a measurement on a serving cell of the wireless device while the wireless device is in the idle mode;
• determining whether the timing advance configuration is valid for an idle mode transmission based on the measurement;
• and
• performing the idle mode transmission using a timing advance value if the timing advance configuration is determined to be valid.