aspect of the invention a header format includes a legacy preamble having at least one legacy long training field and an extended portion having at least n additional long training fields on each of the n transmit antennas wherein one or more of the at least n additional long training fields are comprised of only one orthogonal frequency division multiplexing symbol the extended portion optionally comprises one or more repeated ofdm symbols for frequency offset estimation in one implementation the extended portion comprises a first high throughput long training field comprised of two repeated ofdm symbols and n u2212 1 high throughput long training fields comprised of only one ofdm symbol in another variation the extended portion comprises n high throughput long training fields comprised of only one ofdm symbol application_number US 201113012964 A description the present invention provides preamble formats and techniques for preamble training for mimo system the training phase of a mimo transmission will contain two phases the first training phase is a legacy training phase particularly suited for example to wlan ofdm legacy systems and the second phase is particularly suited to a multiple antenna system such as a mimo system to overcome the problems in the prior systems the automatic gain control agc of a receiver will perform one training sequence during the first training phase and the.