EIRP-Restricted Downlink Beamforming in WLAN OFDM Systems

Downlink beamforming for a wireless local area network (WLAN) orthogonal frequency-division multiplexing (OFDM) system is addressed, where an access point (AP) is equipped with multiple antennas and a terminal uses a single antenna. A joint optimization problem for the beamforming weights over all the sub-carriers subject to the equivalent isotropic radiated power (EIRP) constraint is formulated and two sub-optimal solutions are compared in terms of their performance and complexity in the typical IEEE 802.11 environment. It is shown that the proposed beamformer based on non-adjacent sub-carriers grouping demonstrates much better trade off between performance and complexity compared to the conventional simplification approach based on the highly correlated sub-carriers grouping