In a wireless local area network that includes high-throughput communication devices with multiple antennas and legacy communication devices with single antennas, training tones are transmitted over a plurality of spatial channels during a first portion of an orthogonal frequency division multiplexed packet-training preamble. When estimating a ratio of pilot power to traffic power, a problem caused by an unevenness of the power ratio is prevented. Apparatus of the disclosure may also comprise one or more atomizers operable to produce atomized droplets of impregnant. The optical system preferably further comprises a reflective aperture element positioned substantially adjacent to the output surface of each concentrator element. A liquid crystal display device includes at least one pixel including at least one color sub-pixel and at least one white sub-pixel, wherein liquid crystal molecules in the white sub-pixel are aligned to be driven in a different direction than liquid crystal molecules in the color sub-pixel.