protocol we design in the next section, the cooperative scheme will be more efficient when it is $$\begin{aligned}
\label{ineq:3}
&&\frac{L}{\widetilde{R}_{COOP}}+T_{OVHD,COOP}<\frac{L}{\widetilde{R}_{DIR}}.\end{aligned}$$ The aforementioned condition can also be interpreted as follows: The COOP transmission mode is more efficient when the time duration of the cooperative transmission is shorter from the direct transmission based on the estimated rate, plus the associated protocol overhead ($T_{OVHD}$) that is incurred by the cooperative protocol. Similar conditions are used by other cooperative protocols [@coopmac]. This condition can also determine the optimal packet length $L^*$ for which direct or cooperative transmission is optimal.

Now we present the estimated sum-rate of the ANC-OL transmission from the present relay and for the unicast transmissions depicted in Fig. \[fig:topology-mac-cc2\], i.e. $N_1 \rightarrow N_2$ and $N_4 \rightarrow N_5$. This sum-rate expression for two interfering transmissions incorporates the overheard information that is used for decoding the respective signals/packets at each receiver. This will be equal to [@argyriou:twc-ancol]: $$\begin{aligned}
\widetilde{R}_{ANCOL}&=& W \cdot\log_2 \Big (1+\frac{P\gamma_1}{\sigma^2}+\frac{P\gamma_8}{\sigma^2}+\frac{P\gamma_2\gamma_4g^2}{\sigma^2(1+\gamma_4g^2)}\nonumber\\
&+&\frac{P\gamma_4\gamma_7g^2}{\sigma^2(1+\gamma_4g^2)}+\frac{P^2\gamma_1\gamma_4\gamma_7g^2}{\sigma^4(1+\gamma_4g^2)}\\
& +&\frac{P^2\gamma_2\gamma_4\gamma_8g^2}{\sigma^4(1+\gamma_4g^2)}\nonumber-\frac{P^2\gamma_4 Re(h_1h_2^*h_7h_8^{*})g^2}{\sigma^4(1+\gamma_4g^2)} \Big ).  \label{ria}\end{aligned}$$ The above formula is not a pre-requisite for the operation of the proposed rate estimation algorithm and of course the entire protocol. Similar transmission modes like ANC-OL could be utilized in conjunction with 