OFDM Blind Signal Detection Based on the Sphere Decoder

The detection ordering for the sphere decoder (SD) and its application in the blind signal detection of the time- varying orthogonal frequency division multiplexing (OFDM) systems are considered. For any matrix H and any permutation matrix P, the equation HP = QR always holds where P represents the detection ordering. In order to find an appropriate P to reduce the SD search complexity, we propose a novel detection ordering mechanism based on the principle of maximizing the minimal row entry (MMRE). Its corresponding QR factorization method is also presented. Different from other ordering mechanisms, the MMRE mechanism prevents the SD search from going deep on the incorrect subtrees by introducing an error-amplifying strategy. The simulations prove the effectiveness of the MMRE.