$\mathcal{S}$) in the network apart from the intended transmitter $i$ and the thermal noise, and is given by $$\begin{aligned}
\label{interference}
I_{k}=\sum_{j\neq i, j \in \mathcal{S}}{g_{jk}P_{j} + n_{k}}.\end{aligned}$$ Therefore, the Signal-to-Interference-and-Noise Ratio (SINR) at the receiver $k$ is given by $$\begin{aligned}
\label{SINR1}
\Gamma_{k}=\frac{g_{ik}P_{i}}{\sum_{j\neq i, j \in \mathcal{S}}{g_{jk}P_{j} + n_{k}}}\ .\end{aligned}$$ The Quality of Service (QoS) is measured in terms of SINR. Hence, independently of nodal distribution and traffic pattern, a transmission from transmitter to its corresponding receiver is successful (error-free) if the SINR of the receiver is greater or equal to the *capture ratio* $\gamma_0$. Therefore, we require that $$\begin{aligned}
\label{SINR_geq}
\frac{g_{ik}P_{i}}{\sum_{j\neq i, j \in \mathcal{S}}{g_{jk}P_{j} + n_{k}}} \geq \gamma_0.\end{aligned}$$ The value of $\gamma_0$ depends on the modulation and coding characteristics of the radio. Due to battery limitations, we assume that each transmitting node $i$ (source and relays) has a maximum power $P_{i}^{\max}$.

Relay selection policies {#policies}
========================

In this Section, we briefly review the main buffer-based relay selection policies used in the literature.

$\max-\min$ relay selection
---------------------------

The $\max-\min$ relay selection policy [@BLE], [@KAR] is considered as the optimal selection scheme for conventional DF relay setups without buffers and is used as our baseline relay selection strategy. The selected relay 