  UWB communication is a recent research area for indoor propagation channels.
Time Reversal (TR) communication in UWB has shown promising results for
improving the system performance. In multiuser environment, the system
performance is significantly degraded due to the interference among different
users. TR reduces the interference caused by multiusers due to its spatial
focusing property. The performance of a multiuser TR communication system is
further improved if the TR filter is modified. In this paper, multiuser TR in
UWB communication is investigated using simple TR filter and a modified TR
filter with circular shift operation. The concept of circular shift in TR is
analytically studied. Thereafter, the channel impulse responses (CIR) of a
typical indoor laboratory environment are measured. The measured CIRs are used
to analyze the received signal peak power and signal to interference ratio
(SIR) with and without performing the circular shift operation in a multiuser
environment.
