In the setting of the two-user (M, N) multiple-input multiple-output (MIMO) broadcast channel (BC), recent work by Maddah-Ali and Tse, and Vaze and Varanasi have revealed the usefulness of delayed channel state information at the transmitter (perfect delayed CSIT). Our work studies the general case of communicating with imperfect delayed CSIT, and proceeds to present novel precoding schemes and degrees-of-freedom (DoF) bounds that are often tight, and to constructively reveal that even substantially imperfect delayed-CSIT, is in fact sufficient to achieve the optimal DoF performance previously associated to perfect delayed CSIT. Going one step further, we also constructively show that, this same optimal performance can in fact be achieved in the presence of additional imperfection of the global CSIR -- i.e., even with imperfect receiver estimates of the channel of the other receiver. Specifically, for feedback-quality exponent β describing the high-SNR asymptotic rate-of-decay of the mean square error of the delayed CSIT estimate, the derived DoF d(β) for a given exponent β Є [0,1], reveals that the optimal two-user MIMO-BC DoF region previously associated to perfect delayed CSIT, can in fact be achieved for any imperfect β ≥ N/min(M, 2N) + N. Interestingly, for all the cases studied here, the derived quality threshold β∗ ≜ arg min
MIMO BC with imperfect and delayed channel state information at the transmitter and receivers
SPAWC 2013, 14th IEEE International Workshop on Signal Processing Advances in Wireless Communications, 16-19 June 2013, Darmstadt, Germany
Type:
Conférence
City:
Darmstadt
Date:
2013-06-16
Department:
Systèmes de Communication
Eurecom Ref:
4040
Copyright:
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PERMALINK : https://www.eurecom.fr/publication/4040