that this decision can only be made by the relay since it is the only node in the network configuration that can obtain all the necessary information for doing so as we described in Section \[sec:channel-estimation\].

In the general case of cooperative systems, the transmitter may select to use cooperative transmission when a desired rate is not met with a direct transmission. However, without loosing generality we assume that with the proposed protocol the optimal mode is always selected whether it is ANC-OL, COOP, or Direct. Now consider that the channel bandwidth is $W$, the transmitter power $P$, additive white Gaussian noise (AWGN) with zero mean and variance $\sigma^2$, and $\gamma_i=|h_i|^2$. If we assume Rayleigh block fading channels where the attenuation is considered constant throughout the transmission of a single frame then the SNR between two nodes in our system is given by $SNR=\frac{P\gamma}{\sigma^2}$. The estimated rate of the Direct transmission mode is then: $$\label{ineq:1}
\widetilde{R}_{DIR}=W\cdot log_2(1+\frac{P\tilde{\gamma}_1}{\sigma^2}).$$ On the other hand, the estimated rate of the cooperative transmission COOP that occurs in two orthogonal time slots for the example in Fig. \[fig:topology-mac-cc2\] will be [@laneman04]: $$\begin{aligned}
\label{ineq:2}
\widetilde{R}_{COOP}&=&\frac{W}{2} \cdot min\big\{log_2(1+\frac{P\tilde{\gamma}_2}{\sigma^2}),\\
&&log_2(1+\frac{P\tilde{\gamma}_1}{\sigma^2}\frac{P\tilde{\gamma}_2\tilde{\gamma}_4g^2}{\sigma^2(1+\tilde{\gamma}_4g^2)})\big\}. \nonumber\end{aligned}$$ If we consider the overhead of the complete 