Two-step contention-based random access over radio resources in LAA

A recipient radio node for facilitating contention-based random access over one or more radio resources, the recipient radio node comprising:

• processing circuitry and a memory, the memory containing instructions executable by the processing circuitry whereby the recipient radio node is configured to:
• receive, from a contending radio node and on the one or more radio resources, a timing advance sequence and a contention-resolving identity of the contending radio node that have been transmitted using the same transmission advancement timing, wherein the timing advance sequence is susceptible to contention;
• responsive to said receiving and based on the received timing advance sequence, derive a timing advance for transmission from the contending radio node to the recipient radio node;
• and
• responsive to said deriving, transmit, via radio circuitry, from the recipient radio node to the contending radio node a response signal that indicates the derived timing advance as well as a contention-resolving identity that corresponds to the contention-resolving identity received from the contending radio node.

A method implemented by a contending radio node for attempting contention-based random access over one or more radio resources, the method comprising:

• obtaining a timing advance sequence based on which a timing advance for transmission from the contending radio node to a recipient radio node is derivable, wherein the timing advance sequence is susceptible to contention;
• obtaining a contention-resolving identity of the contending radio node;
• transmitting, using the same transmission advancement timing, the timing advance sequence and the contention-resolving identity to the recipient radio node on the one or more radio resources;
• responsive to said transmitting, receiving from the recipient radio node a response signal that indicates a contention-resolving identity as well as a timing advance derived from a timing advance sequence received by the recipient radio node;
• resolving the contention in favor of the contending radio node when the contention-resolving identity indicated by the response signal corresponds to the contention-resolving identity that the contending radio node transmitted;
• and
• responsive to resolving the contention in favor of the contending radio node, adjusting the transmission advancement timing that governs the timing advancement of transmissions from the contending radio node to the recipient radio node, according to the timing advance indicated by the response signal.

A method implemented by a recipient radio node for facilitating contention-based random access over one or more radio resources, the method comprising:

• receiving, from a contending radio node and on the one or more radio resources, a timing advance sequence and a contention-resolving identity of the contending radio node that have been transmitted using the same transmission advancement timing, wherein the timing advance sequence is susceptible to contention;
• responsive to said receiving and based on the received timing advance sequence, deriving a timing advance for transmission from the contending radio node to the recipient radio node;
• and
• responsive to said deriving, transmitting from the recipient radio node to the contending radio node a response signal that indicates the derived timing advance as well as a contention-resolving identity that corresponds to the contention-resolving identity received from the contending radio node.