A method for generating multi-user, MU, physical layer, PHY, data unit for transmission via a composite communication channel that comprises a plurality of individual communication channels that collectively span a bandwidth of the composite communication channel, wherein each individual communication channel includes a plurality of basic resource allocation, RA, units that collectively span a bandwidth of the individual communication channel, wherein each individual communication channel includes 9 basic RA units, and each basic RA unit includes 26 orthogonal frequency division multiplexing, OFDM, tones, the method comprising: generating, at a communication device, a PHY preamble that includes formatting information regarding the MU PHY data unit, the generating including: generating an RA indication field of the PHY preamble to be transmitted within a first individual communication channel among the plurality of individual communication channels, wherein the RA indication field is generated to indicate a plurality of groupings of basic RA units, wherein at least one of the plurality of groupings of basic RA units includes basic RA units of one or more other individual communication channels, generating a plurality of basic RA configuration subfields to be transmitted within the first communication channel, wherein each RA configuration subfield corresponds to a respective one of the groupings of basic RA units, wherein each RA configuration subfield corresponds to a respective set of one or more client stations, individually encoding the RA indication field as a first encoded block, and jointly encoding pairs of RA configuration subfields as respective second encoded blocks; generating, at the communication device, a data portion of the MU PHY data unit according to the formatting information in the PHY preamble, generating, at the communication device, the MU PHY data unit to include the PHY preamble and the data portion, and transmitting the generated MU PHY data unit to the one or more client stations. generating, at a communication device, a PHY preamble that includes formatting information regarding the MU PHY data unit, the generating including: generating an RA indication field of the PHY preamble to be transmitted within a first individual communication channel among the plurality of individual communication channels, wherein the RA indication field is generated to indicate a plurality of groupings of basic RA units, wherein at least one of the plurality of groupings of basic RA units includes basic RA units of one or more other individual communication channels, generating a plurality of basic RA configuration subfields to be transmitted within the first communication channel, wherein each RA configuration subfield corresponds to a respective one of the groupings of basic RA units, wherein each RA configuration subfield corresponds to a respective set of one or more client stations, individually encoding the RA indication field as a first encoded block, and jointly encoding pairs of RA configuration subfields as respective second encoded blocks; generating an RA indication field of the PHY preamble to be transmitted within a first individual communication channel among the plurality of individual communication channels, wherein the RA indication field is generated to indicate a plurality of groupings of basic RA units, wherein at least one of the plurality of groupings of basic RA units includes basic RA units of one or more other individual communication channels, generating a plurality of basic RA configuration subfields to be transmitted within the first communication channel, wherein each RA configuration subfield corresponds to a respective one of the groupings of basic RA units, wherein each RA configuration subfield corresponds to a respective set of one or more client stations, individually encoding the RA indication field as a first encoded block, and jointly encoding pairs of RA configuration subfields as respective second encoded blocks; generating, at the communication device, a data portion of the MU PHY data unit according to the formatting information in the PHY preamble, generating, at the communication device, the MU PHY data unit to include the PHY preamble and the data portion, and transmitting the generated MU PHY data unit to the one or more client stations.