Methods and apparatuses for facilitating D2D bearer switching

A method of performing path switching, for a communication path between a first user equipment (UE) and a second UE, from a device to device (D2D) path to network path, the method comprising:

• receiving, at the first UE, a first message from an access network;
• stopping, at the first UE, data transmission to the second UE through the D2D path, in response to the first message;
• determining a last data block sent from the first UE to the second UE based on contents of a transmission buffer at the first UE;
• sending, from the first UE, switch point information to the access network, the switch point information identifying the last data block;
• establishing, at the first UE, a connection with the access network over an uplink path between the first UE and the access network;
• and
• sending data from the first UE to the second UE over the network path, the network path including the uplink path to the access network.

A method of facilitating path switching, for a communication path between a first user equipment (UE) and a second UE, from a network path to a device to device (D2D) path, the method comprising:

• receiving, at an access network, a stream of uplink data blocks sent from the first UE to the second UE on an uplink path between the first UE and the access network;
• storing, in a buffer at the access network, data blocks from the stream of uplink data blocks;
• sending, from the access network, a stream of downlink data blocks on a downlink path between the access network and the second UE, the stream of downlink data blocks being blocks sent from the first UE to the second UE;
• determining, at the access network, whether the stream of uplink blocks is synchronized with the stream of downlink blocks based on an oldest data block stored in the buffer which has not yet been received at the second UE and a data block from the stream of downlink data blocks;
• and
• based on the determination, sending a D2D preparation message from the access network to the first UE, the D2D preparation message identifying an initial data block for the first UE to send over the D2D path.

A method of performing path switching, for a communication path between a first user equipment (UE) and a second UE, from a network path to a device to device (D2D) path, the method comprising:

• sending, from the first UE, a stream of uplink data blocks to the second UE through an uplink path from the first UE to an access network;
• receiving, at the first UE, a first message from the access network;
• storing, in a buffer at the first UE, copies of blocks from the stream of uplink data which have been acknowledged by the access network as being received, in response to the first message;
• receiving, at the first UE, a synchronization buffer status message from the access network;
• synchronizing the buffer at the first UE with a UL or DL synchronization buffer at the access network by removing data blocks from the buffer at the first UE based on the synchronization buffer status message;
• receiving, at the first UE, a D2D preparation message from the access network, the D2D preparation message identifying a first data block;
• selecting, as an initial data block to send to the second UE over the D2D path, the first data block identified by the D2D preparation message;
• and
• sending a stream of D2D data blocks to the second UE over the D2D path, the stream of D2D data blocks beginning with the identified first block.

A network element comprising:

• a processor;
• a memory device storing instructions that, when executed by the processor cause the processor to control operations for facilitating path switching, for a communication path between a first user equipment (UE) and a second UE, from a device to device (D2D) path to network path, the operations including,
• receiving, at the network element, switch point information from the first UE, the switch point information identifying a last data block that has been sent from the first UE to the second UE over the D2D path;
• establishing, at the network element, a connection with the first UE over an uplink path between the first UE and the network element;
• establishing, at the network element, a connection with the second UE over a downlink path between the network element and the second UE;
• setting, at the network element, a data block sequencing numbering to be the same for the uplink path and the downlink path based on the switch point information;
• and
• forwarding, at the network element, data from the first UE to the second UE via the network path, the network path including the uplink path and the downlink path.

A mobile device comprising:

• a processor;
• a memory device storing instructions that, when executed by the processor cause the processor to control operations for performing path switching, for a communication path between the mobile device and a user equipment (UE), from a device to device (D2D) path to network path, the operations including,
• receiving, at the mobile device, a first message from an access network;
• stopping, at the mobile device, data transmission to the UE through the D2D path, in response to the first message;
• determining a last data block sent from the mobile device to the UE based on contents of a transmission buffer at the mobile device;
• sending, from the mobile device, switch point information to the access network, the switch point information identifying the last data block;
• establishing, at the mobile device, a connection with the access network over an uplink path between the mobile device and the access network, and
• sending data from the mobile device to the UE over the network path, the network path including the uplink path to the access network.

A network element comprising:

• a processor;
• a memory device storing instructions that, when executed by the processor cause the processor to control operations for facilitating path switching, for a communication path between a first user equipment (UE) and a second UE, from a network path to a device to device (D2D) path, the operations including,
• receiving, at the network element, a stream of uplink data blocks sent from the first UE to the second UE on an uplink path between the first UE and the network element;
• storing, in a buffer at the network element, data blocks from the stream of uplink data blocks;
• sending, from the network element, a stream of downlink data blocks on a downlink path between the network element and the second UE, the stream of downlink data blocks being blocks sent from the first UE to the second UE;
• determining, at the network element, whether the stream of uplink blocks is synchronized with the stream of downlink blocks based on an oldest data block stored in the buffer which has not yet been received at the second UE and a data block from the stream of downlink data blocks;
• and
• based on the determination, sending a D2D preparation message from the network element to the first UE, the D2D preparation message identifying an initial data block for the first UE to send over the D2D path.

A mobile device comprising:

• a processor;
• a memory device storing instructions that, when executed by the processor cause the processor to control operations for performing path switching, for a communication path between the mobile device and a user equipment (UE), from a network path to a device to device (D2D) path, the operations including,
• through an uplink path from the mobile device to an access network;
• receiving, at the mobile device, a first message from the access network;
• storing, in a buffer at the mobile device, copies of blocks from the stream of uplink data which have been acknowledged by the access network as being received, in response to the first message;
• receiving, at the mobile device, a synchronization buffer status message from the access network;
• synchronizing the buffer at the mobile device with a UL or DL synchronization buffer at the access network by removing old data blocks from the buffer at the mobile device based on the synchronization buffer status message;
• receiving, at the mobile device, a D2D preparation message from the access network, the D2D preparation message identifying a first data block;
• selecting, as an initial data block to send to the UE over the D2D path, the first data block identified by the D2D preparation message;
• and
• sending a stream of D2D data blocks to the UE over the D2D path, the stream of D2D data blocks beginning with the identified first block.