An improved hot wire gas flow sensor is disclosed having a housing with a passageway in series with a passageway through which the gas flow is measured. The second image at least includes a first portion entirely formed from a plurality of mirrored or unmirrored, rotated or unrotated, and non-overlapping instances of the first image arranged in the shape of a complete rectangle. A wireless channel is selected as an uplink channel for uplink transmission of the data to the relay node, and an alternate wireless channel is selected as a downlink channel for downlink transmission of the data from the relay node.