  Impulse-Radio (IR) is a wideband modulation technique that can support
multiple users by employing random Time-Hopping (TH) combined with repeated
transmissions. The latter is aimed at alleviating the impact of collisions.
This work employs a graphical model for describing the multiuser system which,
in turn, facilitates the inclusion of general coding schemes. Based on factor
graph representation of the system, several iterative multiuser detectors are
presented. These detectors are applicable for any binary linear coding scheme.
The performance of the proposed multiuser detectors is evaluated via
simulations revealing large gains with low complexity.
