  Performance improvement has been among the foci of all previous amendments of
IEEE 802.11 protocol. In addition, the draft high efficiency (HE) amendment
IEEE 802.11ax, proposed by TGax, aims at increasing network performance. One of
the main obstacles to improving spectral and power efficiency is the presence
of hidden terminals which degrade throughput, in particular in uplink
transmission. IEEE 802.11ax does provide mechanisms such as trigger based
uplink transmission that mitigate this degradation to some extent, but are
incapable of eliminating it, esp. at high arrival rates. To combat the hidden
terminal problem, we propose to increase the carrier sensing threshold (CSTH)
of STAs during association with an HE access point. Our results confirm that
the proposed mechanism can lead to significant reduction of collision
probability in uplink transmission.
