Patent ID: 8718185

Claim:
A method comprising: in a base station: forming two or more blocks of output symbols for orthogonal frequency division multiplexing (OFDM) transmissions over a multiple-input multiple-output (MIMO) channel, wherein the forming comprises (i) identifying different positions within the two or more blocks of output symbols based at least on (a) one or more block index values, (b) one or more subcarrier index values, (c) a cyclic prefix parameter selected to compensate for intersymbol interference (ISI) associated with the MIMO channel, and (d) a hopping code that is based, at least in part, on the cyclic prefix parameter, and (ii) inserting, based at least on the hopping code, training symbols and null subcarriers within two or more blocks of information-bearing symbols, the hopping code directing at least a portion of the null subcarriers to be inserted at the different positions within the two or more blocks of output symbols; and transmitting, via two or more antennas, transmission signals in accordance with the two or more blocks of output symbols, wherein the two or more blocks of output symbols include a first block of output symbols and a second block of output symbols, and wherein inserting the training symbols and null subcarriers comprises: inserting a first null subcarrier at a first subcarrier position within the first block of output symbols; and inserting a second null subcarrier at a second subcarrier position within the second block of output symbols, wherein the first subcarrier position is different from the second subcarrier position.