  We propose a blind interference alignment (BIA) through staggered antenna
switching scheme with no ideal channel assumption. Contrary to the ideal
assumption that channels remain constant during BIA symbol extension period,
when the coherence time of the channel is relatively short, channel
coefficients may change during a given symbol extension period. To perform BIA
perfectly with realistic channel assumption, we propose a grouping based
supersymbol structure for $K$-user interference channels which can adjust a
supersymbol length to given coherence time. It is proved that the supersymbol
length could be reduced significantly by an appropriate grouping. Furthermore,
it is also shown that the grouping based supersymbol achieves higher degrees of
freedom than the conventional method with given coherence time.
