On the Devroye–Mitran–Tarokh and Rini–Tuninetti–Devroye Achievable Rate Regions for the Cognitive Interference Channels

This letter includes two important comments on two well-cited papers in the field of the cognitive interference channel (CIC). First, it is shown that the Devroye-Mitran-Tarokh (DMT) achievable rate region for the discrete memoryless CIC can be enlarged by utilizing an important overlooked dependence between secondary auxiliary random variables. Then, it is shown that, with this new change, the strict inclusion of DMT region in an inner bound of the Rini-Tuninetti-Devroye (RTD) achievable region (proved by Rini et al.) is no longer true between the enlarged (indeed amended) version of DMT region and RTD region. Thus, it is still not clear whether the RTD region is strictly the largest to date known region.