In the present work, cooperative orthogonal relay networks are investigated, including the properties and performance of certain relay protocols. Furthermore, a framework is presented and analyzed in depth, based on the extended information combining/concatenation technique, to semi-analytically predict practical (possibly non-error free decoding) orthogonal relay networks. Compared to the usual Monte Carlo simulation, this framework provides reliably end-to-end mutual information of such a Network in a fraction of computational time.