Interference Alignment Via Cooperation In Wireless Communication Networks

Interference is identified as a major bottleneck in realizing a ubiquitous and high-speed wireless world. There has been considerable interest in understanding the best ways to manage interference in wireless networks. Hence, the optimal way of managing interference to maximize users’ rate, is of great importance. In this thesis, cooperation between users is exploited in different ways to manage their interference in different channels.For the K-user interference channel (IC) with partial transmitter cooperation between subsets of M users, we prove that the outer bound of the degrees of freedom (DoF) of this channel, which is KM/(M+1), is achievable for the case when K=M+L(L=1,2,3,...,K-2) Moreover, we studied the IA (Interference Alignment) schemes under practical constraints, and proposed algorithms that attempt to maximize the sum-rate of the system’s users. Some fairness conditions between the different users in the network are also taken into consideration.For cellular channels with limited allowable cooperation between base-stations via limited capacity backhaul, we find how the base-stations’power and backhaul bits could be optimally allocated in order to maximize the data rate of the users. We also investigate how this scheme can guarantee the fairness constraints between users.For the cognitive radio based cellular channel, with relay cooperation. We studied the uplink case, and designed a multi-user distributed Space-Frequency code that can be used by the cooperating relays in order to manage the interference between secondary network users and achieve the maximum possible diversity gain.Our results show that efficient exploitation of cooperation can play a significant role in managing interference, and increasing the data rate in different channel setups.