Two crucial properties of a wireless communication channel are (i) interference between signals of simultaneously transmitting users and (ii) uncontrollable and unknown to the users rapid variations of the channel quality. These properties make it difficult to find the optimal strategy for reliable communication over wireless channels. This work presents a novel way of using relays to clean-up interference in large wireless networks. Further, it investigates under which conditions the performance degradation due to the lack of information about the channel quality is the most severe. Finally, it is shown how to use multiple antennas at the receiver to improve the performance of a wireless system operating under these challenging conditions.