Switching between network based and relay based operation for mission critical voice call

Abstract

A device, serving cell and method of switching between modes of operation for the device in a cellular network comprises receiving a service via a connection with the serving cell. A condition indicative of deterioration in network service and an absence of a suitable neighbor cell are detected. In response, discovery of relay nodes is initiated. When a suitable relay node is discovered, a mechanism to switch to receiving the service via the suitable relay node is initiated. The service may be a mission critical push-to-talk over Long Term Evolution service. The relay node may be user equipment acting as a user equipment-to-network relay node. When the device is in an RCC_CONNECTED state, the mechanism to switch includes sending a relay mode preference indication to the serving cell, receiving a connection release message from the serving cell, releasing the serving cell connection, and establishing a sidelink connection with the relay.

Dependencies are inferred from the claim text.