Degrees of coordination in cognitive networks

The paradigm shift from coordinated to uncoordinated wireless networks comes along with the need of new concepts for the frequency usage since interference will be an ubiquitous phenomenon. In this work, we analyze unknown varying interference in wireless networks with the help of the concept of arbitrarily varying channels. This concept shows that the unknown interference has a dramatic impact on the communication. In the case of high interference, it can happen that no communication is possible, not even at very low rates, if traditional interference coordination with pre-specified encoders and decoders is applied. We introduce more sophisticated coordination schemes as the transmitter-receiver or the correlated side information coordination. Here, an access to a common randomness is advantageously used to coordinate the choice of the encoders and decoders. This enables successfully a communication even in such situations where the traditional approach fails.