  In this paper we present an experimental study on the performance of spatial
Interference Alignment (IA) in indoor wireless local area network scenarios
that use Orthogonal Frequency Division Multiplexing (OFDM) according to the
physical-layer specifications of the IEEE 802.11a standard. Experiments have
been carried out using a wireless network testbed capable of implementing a
3-user MIMO interference channel. We have implemented IA decoding schemes that
can be designed according to distinct criteria (e.g. zero-forcing or MaxSINR).
The measurement methodology has been validated considering practical issues
like the number of OFDM training symbols used for channel estimation or
feedback time. In case of asynchronous users, a time-domain IA decoding filter
is also compared to its frequency-domain counterpart. We also evaluated the
performance of IA from bit error rate measurement-based results in comparison
to different time-division multiple access transmission schemes. The comparison
includes single- and multiple-antenna systems transmitting over the dominant
mode of the MIMO channel. Our results indicate that spatial IA is suitable for
practical indoor scenarios in which wireless channels often exhibit relatively
large coherence times.
