  Time Reversal (TR) has been proposed as a competitive precoding strategy for
low-complexity devices, relying on ultra-wideband waveforms. This transmit
processing paradigm can address the need for low power and low complexity
receivers, which is particularly important for the Internet of Things, since it
shifts most of the communications signal processing complexity to the
transmitter side. Due to its spatio-temporal focusing property, TR has also
been used to design multiple access schemes for multi-user communications
scenarios. However, in wideband time-division multiple access schemes, the
signals received by users suffer from significant levels of inter-symbol
interference as well as interference from uncoordinated users, which often
require additional processing at the receiver side. This paper proposes an
iterative TR scheme that aims to reduce the level of interference in wideband
multi-user settings, while keeping the processing complexity only at the
transmitter side. The performance of the proposed TR-based protocol is
evaluated using analytical derivations. In addition, its superiority over the
conventional Time Reversal Division Multiple Access (TRDMA) scheme is
demonstrated through simulations as well as experimental measurements at $2.5$
GHz carrier frequency with variable bandwidth values.
