Space time interference alignment scheme for the MIMO BC and IC with delayed CSIT and finite coherence time

Lejosne, Yohan; Slock, Dirk T M; Yuan-Wu, Yi
ICASSP 2013, 38th IEEE International Conference on Acoustics, Speech, and Signal Processing, May 26-31, 2013, Vancouver, Canada

Most techniques designed for the the multi-input multipleoutput (MIMO) Broadcast Channel (BC) andMIMO Interference Channel (IC) require accurate current and instantaneous
channel state information at the transmitter (CSIT). This is not a realistic assumption because of feedback delay. A novel approach by Lee and Heath, space-time interference alignment (STIA), proves that in the underdetermined (overloaded) multi-input single-output (MISO) BC with Nt transmit antennas and K = Nt + 1 users Nt (sum) Degrees of Freedom (DoF) are achievable if the feedback delay is not too big, thus disproving the conjecture that any delay in the feedback necessarily causes a DoF loss. However the feedback delay needs to remain less or equal to Tc/Nt+1 , where Tc is the coherence time. We consider the MIMO BC and show that the use of multi-antenna receivers allows to achieve full (sum) DoF with bigger feedback delay, up to Tc/Nt/Nr  +1. We also extend this result to the MIMO IC.

Systèmes de Communication
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