The 802.16e PHY allows sub-channelization both on the uplink as well as the downlink. Sub-channeling concentrates the transmit power into fewer OFDM carriers; this is what increases the system gain that can either be used to extend the reach of the system, overcome the building penetration losses and/ or reduce the power consumption of the CPE. Sub-channels formed using distributed sub-carriers provide more frequency diversity, which is particularly useful for mobile applications.