In this paper, a Decode-and-Forward cooperative diversity scheme for performance enhancement is extended to the context of impulse radio ultra-wideband. Due to multiple accesses, the interference distribution is not Gaussian. We propose a symmetric α-stable model compatible with the impulsive nature due to its heavy tailed distribution. Taking advantage of the stability property, we develop the α-stable interference modelling application in the cooperative transmission and analytical average bit error probability expressions are derived. It is shown that, based on the consideration of the interference term, the relay selection strategy is changed and an efficient interference aware criteria is investigated.