A first communication device generates and transmits to a second communication device: first and second information elements that respectively indicate capabilities regarding physical layer protocol data units (PPDUs) conforming to a first communication protocol and a second communication protocol. The first communication device generates and transmits a MAC data unit that includes a number corresponding to a maximum number spatial streams supported by the first communication device. The number in the MAC data unit, and one or more of i) the first information element, ii) the second information element, and iii) other information in the MAC data unit, indicate first and second maximum numbers of spatial streams supported by the first communication device with respect to PPDUs conforming to the first communication protocol, and PPDUs conforming to the second communication protocol, respectively.