  Beamforming is indispensable in the operation of 60-GHz millimeter-wave
directional multi-gigabit Wi-Fi. Simple power method and its extensions enable
the transmitting and receiving antenna arrays to form a beam for single spatial
stream. To further improve the spectral efficiency in future 60-GHz directional
Wi-Fi, alternating least square (ALS) algorithm can form multiple beams between
the transmitter and receiver for multi-input-multi-output (MIMO) operations.
For both shared and split MIMO architecture, the ALS beamforming algorithm can
be operated in both frequency-flat and frequency-selective channels. In the
split architecture, MIMO beamforming approximately maximizes the capacity of
the beam-formed MIMO channel.
