A downlink switched-beam OFDM pilot scheme based on subcarrier-multiplexing

In this paper, we explore the use of the OFDM symbol structure to both select the beam and estimate the channel on the downlink of an OFDM switched-beam system, The channel estimation and beam selection use special OFDM pilot symbols which consist in beam-specific pilot samples frequency multiplexed on the available downlink subcarriers. At the reception, beam channels seen on each subcarrier are estimated, then the best serving beam is selected. For equalization purposes, an interpolation is used between channel estimates for the selected beam, to obtain the missing beam channel estimates on the subcarriers that were allocated to other beams on the pilot symbol. In contrast to previous works, which assumed an uplink/downlink channel symmetry to select the serving beam from uplink measurements, our proposition considers the use of the MISO downlink channel measurements obtained at the mobile. It is the mobile that identifies the best-serving beam and requests that beam.