A communication device receives a physical layer (PHY) protocol data unit (PPDU). The PPDU includes i) a PHY preamble and ii) PHY data portion that includes one or more PHY midambles, and the PHY preamble includes i) an indication of a length of the PPDU, and ii) an indication of a periodicity of PHY midambles in the PHY data portion. The communication device calculates a number of PHY midambles in the PPDU using i) the indication of the length of the PPDU, and ii) the indication of the periodicity of PHY midambles. The communication device calculates a reception time for the PPDU using the calculated number of PHY midambles, and processes the PPDU using the calculated reception time.