Two alternate physical layers (PHYs), TASK and RS-GFSK, are specified in this amendment in addition to the PHYs of IEEE Std 802.15.4-2015. The amendment also defines the medium access control (MAC) modifications needed to support the implementation of the TASK and RS-GFSK PHYs. These alternate PHYs enable low-cost, ultra-low power consumption, as well as extended battery life, in various frequency...