A spatio-temporal equalization method for indoor wireless LANs with beamforming criterion selection

Spatio-temporal equalization is a technique which utilizes both spatial and temporal information of the received signal to compensate for intersymbol interference due to multipath fading. Considering the application of a spatio-temporal equalizer to high speed wireless communications systems, such as wireless LANs, this paper proposes a new spatio-temporal equalization method using a cascade configuration of an adaptive array and a DFE (decision feedback equalizer), which can be realized with small number of weights, and hence, low computational complexity. However, it has to pay a price for the simplicity, namely, the error performance surface becomes a fourth-order function of the weights, and possibly has two minima. In order to avoid a wrong trap by a local minimum during the adaptation of the MMSE (minimum mean-squared error) based adaptation algorithm with any initial values, the proposed equalizer calculates the weights of the adaptive array and the DFE separately in two steps, and the adaptive array selects a path or paths to capture depending on channel conditions. Computer simulation results show that the proposed method can achieve good performance in various channel models, which are based on measurement reports, in low computational complexity.