Systems and methods of phase-tracking reference signal transmission for OFDM

An apparatus for communicating a phase-tracking reference signal (PT-RS) for orthogonal frequency division multiplexing (OFDM) in a wireless communication system, the apparatus comprising:

• a processor;
• and
• a memory storing instructions that, when executed by the processor, configure the apparatus to:
• determine one or more PT-RS groups of adjacent subcarriers in a resource allocation for a physical uplink shared channel (PUSCH), wherein to determine the one or more PT-RS groups of adjacent subcarriers in the resource allocation is in response to a determination that a modulation and code scheme (MCS) indicated by downlink control information (DCI) is above an MCS threshold;
• modulate PT-RS subcarriers within the one or more PT-RS groups of adjacent subcarriers with a predetermined PT-RS modulation sequence, wherein the predetermined PT-RS modulation sequence is based on a Zadoff-Chu sequence;
• cyclically extend the Zadoff-Chu sequence to zero-power guard subcarriers, wherein the predetermined PT-RS modulation sequence comprises:
• s
• ⁡
• (
• n
• )
• =
• x
• q
• (
• {
• n
• +
• N
• 0
• }
• ⁢
• mod
• ⁢
• N
• ZC
• )
• ,
• x
• q
• =
• e
• -
• j
• ⁢
• π
• ⁢
• qm
• ⁡
• (
• m
• +
• 1
• )
• N
• ZC
• ,
• n
• =
• 0
• ,
• 1
• ,
• …
• ,
• N
• -
• 1
• ,
• where q is a root of the Zadoff-Chu sequence, Nzc is a length of the Zadoff-Chu sequence, N is a number of non-zero subcarriers in a PT-RS group, m is an integer between zero and Nzc, and N0 determines a length of a cyclic extension;
• encode data to be transmitted by the PUSCH in data subcarriers within the resource allocation for the PUSCH;
• and
• encode phase-tracking reference signals within the one or more PT-RS groups of adjacent subcarriers.