Random access channel (RACH) response (RAR) reception in an unlicensed radio frequency (RF) spectrum band

An apparatus for wireless communications, comprising:

• a first interface configured to obtain a random access preamble associated with a radio network temporary identifier (RNTI) in a physical random access channel (PRACH) occasion;
• a processing system to determine timing information corresponding to obtaining the random access preamble, wherein the timing information comprises a timing information indicator comprising a last portion of a system frame number (SFN) corresponding to one or more PRACH occasions comprising the PRACH occasion;
• and
• a second interface configured to output, in response to the random access preamble, a random access response (RAR) message for transmission within a RAR window, wherein the RAR message comprises the RNTI and the timing information indicator indicating the one or more PRACH occasions.

A method for wireless communications at a user equipment (UE), comprising:

• transmitting a random access preamble associated with a radio network temporary identifier (RNTI) in a first physical random access channel (PRACH) occasion;
• receiving, from a base station, a random access response (RAR) message within a RAR window, wherein the RAR message comprises the RNTI and a timing information indicator comprising a last portion of a system frame number (SFN) corresponding to one or more PRACH occasions;
• determining whether the one or more PRACH occasions comprise the first PRACH occasion based at least in part on the timing information indicator;
• and
• identifying whether the RAR message is in response to the random access preamble based at least in part on the determining.

A method for wireless communications, comprising:

• receiving, from a user equipment (UE), a random access preamble associated with a radio network temporary identifier (RNTI) in a physical random access channel (PRACH) occasion;
• determining timing information corresponding to receiving the random access preamble, wherein the timing information comprises a timing information indicator comprising a last portion of a system frame number (SFN) corresponding to one or more PRACH occasions comprising the PRACH occasion;
• and
• transmitting, to the UE and in response to the random access preamble, a random access response (RAR) message within a RAR window, wherein the RAR message comprises the RNTI and the timing information indicator indicating the one or more PRACH occasions.