- In this paper, the asymptotic performance of multiuser opportunistic cooperative system over frequency selective fading channels is investigated. Specifically, we consider a system comprising multiple sources, multiple relays with best relay selection, and a single destination. At the selected relay, a decode-and-forward (DF) relaying with a combining scheme is employed to enhance the bandwidth efficiency. Minimum mean squared error (MMSE) single carrier frequency domain equalization (SC-FDE) is assumed at the receivers (the relays and the destination). For this system, we invoke the matched filter bound (MFB) to derive the asymptotic outage probability with the aim of revealing the maximum diversity order that can be achieved by such systems. We use this bound to derive a limit on the code rate that the transmitters should use to be able to achieve the maximum diversity possible for a given number of sources using MMSE SC-FDE. We provide numerical examples that validate the analytical results. 2013 IEEE.