  Multiple-input multiple-output (MIMO) techniques allow for multiplexing
and/or diversity gain, and will be widely deployed in future wireless systems.
In this paper, we propose a MIMO-assisted channel-based authentication scheme,
exploiting current channel estimation mechanisms in MIMO systems to detect
spoofing attacks with very low overhead. In this scheme, the use of multiple
antennas provides extra dimensions of channel estimation data, and thus leads
to a "security gain" over single-input single-output (SISO) systems. We
investigate the security gain of MIMO systems in several system configurations
via simulations for a specific real indoor environment using ray-tracing
software. We also discuss the effect of increasing the number of transmit and
receive antennas on the security gain and contrast that to the
diversity/multiplexing gain.
