Fig. 2

System configuration for multiple relay network. It shows the case of multiple relay nodes. Suppose that we have M relay nodes \(\mathbb {R}_{1},\mathbb {R}_{2},\ldots,\mathbb {R}_{M}\). Let the channels from \(\mathbb {T}_{i}\) to \(\mathbb {R}_{m}\) be denoted as \(\mathbf {f}_{i}^{(m)}\) and the channels from \(\mathbb {R}_{m}\) to \(\mathbb {T}_{i}\) be denoted as \(\mathbf {g}_{i}^{(m)}\)