First and second communication devices and methods

First communication device configured to transmit data to a second communication device, the first communication device comprising circuitry configured to:

• generate a second number of mutually orthogonal sequences;
• generate a third number of one or more spatial streams, each spatial stream carrying payload data;
• generate a fourth number of transmission training sequences, each comprising, in addition to a distinct orthogonal sequence of said mutually orthogonal sequences, one or more zeros and/or a subset of said distinct orthogonal sequence;
• generate a training field by mapping the transmission training sequences into a first number of training symbols, each training symbol spanning a plurality of tones;
• and
• arrange the training field before and/or between the payload of the spatial streams to enable channel estimation by the second communication device,
• wherein the first number of training symbols equals the length of the transmission training sequences,
• wherein the first number of training symbols is set to be larger than the third number of spatial streams and/or the second number of orthogonal sequences is set to be larger than the third number of spatial streams, and
• wherein the fourth number of transmission training sequences is set to be larger than or equal to the third number of spatial streams.