A method for simultaneous communication in a wireless local area network that includes a first communication device and a plurality of second communication devices, the method comprising: forming an orthogonal frequency division multiple access, OFDMA, group that Includes two or more second communication devices of the plurality of second devices; allocating, at the first communication device, respective sub-channel blocks to the two or more second communication devices, including statically allocating a respective primary sub-channel block to each of the two or more second communication devices, wherein the respective statically allocated primary sub-channel blocks remain allocated to the second communication devices for transmission of at least two PHY data units, and dynamically allocating at least some of remaining sub-channel blocks, that are not allocated as primary sub-channel blocks to the two or more second communication devices, among the two or more second communication devices, wherein the at least some of the remaining sub-channel blocks are dynamically allocated for transmission of each of the at least two PHY data units; providing, from the first communication device to the two or more second communication devices, indications of the respective sub-channel blocks allocated to the two or more second communication devices; and performing, at the first communication device, one of i) transmitting a physical layer, PHY, data unit to the two or more second communication devices or ii) receiving a physical layer PHY, data unit from the two or more second communication devices, wherein the PHY data unit includes respective orthogonal frequency division multiplexing, OFDM, data units transmitted using respective sub-channel blocks allocated to the two or more second communication devices. forming an orthogonal frequency division multiple access, OFDMA, group that Includes two or more second communication devices of the plurality of second devices; allocating, at the first communication device, respective sub-channel blocks to the two or more second communication devices, including statically allocating a respective primary sub-channel block to each of the two or more second communication devices, wherein the respective statically allocated primary sub-channel blocks remain allocated to the second communication devices for transmission of at least two PHY data units, and dynamically allocating at least some of remaining sub-channel blocks, that are not allocated as primary sub-channel blocks to the two or more second communication devices, among the two or more second communication devices, wherein the at least some of the remaining sub-channel blocks are dynamically allocated for transmission of each of the at least two PHY data units; statically allocating a respective primary sub-channel block to each of the two or more second communication devices, wherein the respective statically allocated primary sub-channel blocks remain allocated to the second communication devices for transmission of at least two PHY data units, and dynamically allocating at least some of remaining sub-channel blocks, that are not allocated as primary sub-channel blocks to the two or more second communication devices, among the two or more second communication devices, wherein the at least some of the remaining sub-channel blocks are dynamically allocated for transmission of each of the at least two PHY data units; providing, from the first communication device to the two or more second communication devices, indications of the respective sub-channel blocks allocated to the two or more second communication devices; and performing, at the first communication device, one of i) transmitting a physical layer, PHY, data unit to the two or more second communication devices or ii) receiving a physical layer PHY, data unit from the two or more second communication devices, wherein the PHY data unit includes respective orthogonal frequency division multiplexing, OFDM, data units transmitted using respective sub-channel blocks allocated to the two or more second communication devices.