Multiuser incremental decode-and-forward relaying under outdated channel estimates

An exact closed-form expression is derived for the outage probability of a recently proposed multiuser, incremental, decode-and-forward (DF) relaying scheme, when affected by outdated channel estimates. In this scheme, one source communicates with the best destination under the assistance of an incremental DF relay, with the direct- and relaying-link signals being merged via maximal-ratio combining. A simple asymptotic expression is also derived for the outage probability, revealing that the outdated channel estimates reduce the system diversity order to two, regardless of the amount of destinations available.