A method for communications within a wireless communications system, comprising: configuring a wireless device to operate within the wireless communications system, wherein the wireless communications system is partially defined through a first layer, wherein first layer transmissions have a first subframe type and a first round trip time, RTT, between a first layer transmission and acknowledgement of receipt of the first layer transmission; and operating the wireless device at a second layer multiplexed with the first layer, wherein second layer transmissions have a second subframe type and a second RTT between a second layer transmission and acknowledgement of receipt of the second layer transmission, wherein the second RTT is less than the first RTT; wherein the first subframe type comprises orthogonal frequency division multiplexed, OFDM, symbols or single carrier frequency division multiplexed, SC-FDM, symbols of a first duration and a first tone spacing for subcarriers and the second subframe type comprises OFDM symbols or SC-FDM symbols of a second duration that is shorter than the first duration and a second tone spacing for subcarriers that is higher than the first tone spacing; wherein the wireless communication system comprises at least one user equipment, UE, and at least one base station, and wherein the wireless device is either the at least one UE or the at least one base station, and further wherein the wireless device operating at the first layer acknowledges receipt of a first layer transmission in a subframe following the subframe in which the first layer transmission was received, and wherein the wireless device operating at the second layer acknowledges receipt of a second layer transmission in a same subframe as the subframe in which the second layer transmission was received. configuring a wireless device to operate within the wireless communications system, wherein the wireless communications system is partially defined through a first layer, wherein first layer transmissions have a first subframe type and a first round trip time, RTT, between a first layer transmission and acknowledgement of receipt of the first layer transmission; and operating the wireless device at a second layer multiplexed with the first layer, wherein second layer transmissions have a second subframe type and a second RTT between a second layer transmission and acknowledgement of receipt of the second layer transmission, wherein the second RTT is less than the first RTT; wherein the first subframe type comprises orthogonal frequency division multiplexed, OFDM, symbols or single carrier frequency division multiplexed, SC-FDM, symbols of a first duration and a first tone spacing for subcarriers and the second subframe type comprises OFDM symbols or SC-FDM symbols of a second duration that is shorter than the first duration and a second tone spacing for subcarriers that is higher than the first tone spacing; wherein the wireless communication system comprises at least one user equipment, UE, and at least one base station, and wherein the wireless device is either the at least one UE or the at least one base station, and further wherein the wireless device operating at the first layer acknowledges receipt of a first layer transmission in a subframe following the subframe in which the first layer transmission was received, and wherein the wireless device operating at the second layer acknowledges receipt of a second layer transmission in a same subframe as the subframe in which the second layer transmission was received. <EOS>