Institute of Electrical & Electronic Engineers
Interference alignment is a powerful technique that can be used to achieve optimal Degrees of Freedom (DoF) for a variety of wireless networks. With the help of the Channel State Information (CSI) at the Transmitters (CSIT), the transmitters can steer the signals in such a way that the interfering signals occupy the fewest signal space dimensions at each receiver. Not surprisingly, a key assumption for the interference alignment schemes is that the transmitters and the receivers both have accurate instant global CSI, which the authors term as full CSI. In a practical system, however, obtaining full CSIT is difficult. Consequently, references have studied the DoF of various channel models with the assumption that no CSIT is available, and loss of DoF is observed for many scenarios.