Achieving Full Sum DoF in the SISO Interference Channel With Feedback Delay

Yohan Lejosne (1, 2) , Dirk Slock (2) , Yi Yuan-Wu (1)

1 Orange Labs [Issy les Moulineaux]
2 Eurecom [Sophia Antipolis]

Channel state information at the transmitter (CSIT) is of utmost importance to manage interference in multi-user wireless networks, in which transmission rates at a high signal-to-noise ratio are characterized by (sum) degrees of freedom (DoF). Ingenious techniques have been proposed to deal with delayed CSIT, notably a scheme by Maddah-Ali and Tse, providing significant DoF with outdated CSIT. However, with most techniques, any delay in the CSIT feedback still results in a DoF loss. A notable exception is the work by Lee and Heath, allowing one to preserve the optimal DoF in the underdetermined MISO BC and IC, but for feedback delays Tfb decreasing with the number of users K, up to a fraction 1/K of the channel coherence time Tc. In this work, an ergodic interference alignment scheme that preserves the K/2 sum DoF of the K-user IC is proposed for Tfb ≤ Tc/2. It is also proven that Tfb = Tc/2 is the longest for which the optimal K/2 DoF can still be obtained for all K.

Keywords: SISO IC; delayed CSIT; interference alignment

Domains: Networking and Internet Architecture [cs.NI]

Yohan Lejosne, Dirk Slock, Yi Yuan-Wu. Achieving Full Sum DoF in the SISO Interference Channel With Feedback Delay. IEEE Communications Letters, 2014, 18 (7), pp.1202 - 1205. ⟨hal-01070432⟩