US Patent 7698616 MIMO Hybrid-ARQ using basis hopping

A Hybrid Automatic Retransmission Request (H-ARQ) technique is provided for Multi-Input Multi-Output (MIMO) systems. The technique changes the basis (V) upon retransmission, which helps reduce the error probability upon retransmission. This basis hopping technique provides for improved performance gain without significant increase in design complexity. In one embodiment, communication device (100) includes a receiver section (114) for receiving an acknowledgment (ACK) or a non-acknowledgment (NACK) signal in response to information transmitted by the transmitter section of the communication device. If a NACK is received, a new basis is selected from a set of basis stored in a basis set unit (110). The new basis that is selected is then used by a linear transformation unit (106) in the retransmission of the information.