Attenuators enable inversely proportional transmission power and carrier sense threshold setting in WLANs

Inserting attenuators between transceivers and antennas is proposed to improve spatial channel reuse in carrier sense multiple access with collision avoidance based WLANs. Using attenuators enables the access points or stations to decrease the powers of transmission signals and received signals, which equivalently results in the increase of the carrier sense threshold. Thus, the attenuation value control enables inversely proportional setting of transmission power and carrier sense threshold, which is known to provide a novel solution for the unfairness problem caused by variable transmission power or variable carrier sense threshold. We first derive a simple and useful sufficient condition such that the aggregate spectral efficiency is higher when attenuators are used than they are not by using some approximations. Through a numerical evaluation as well as a testbed for using attenuators, the sufficient condition is shown to be valid despite the approximations and throughput improvement is verified. The result from the testbed also discloses a new unfairness problem due to an individual difference in transmission power or carrier sense threshold.