  In IEEE 802.11 based wireless networks adding more access points does not
always guarantee an increase of network capacity. In some cases, additional
access points may contribute to degrade the aggregated network throughput as
more interference is introduced.
  This paper characterizes the power interference in CSMA/CA based networks
consisting of nodes using directional antenna. The severity of the interference
is quantized via an improved form of the Attacking Case metric as the original
form of this metric was developed for nodes using omnidirectional antenna.
  The proposed metric is attractive because it considers nodes using
directional or omnidirectional antenna, and it enables the quantization of
interference in wireless networks using multiple transmission power schemes.
The improved Attacking Case metric is useful to study the aggregated throughput
of IEEE 802.11 based networks; reducing Attacking Case probably results in an
increase of aggregated throughput. This reduction can be implemented using
strategies such as directional antenna, transmit power control, or both.
