TY - GEN

T1 - Degrees of freedom (DoF) of locally connected interference channels with cooperating multiple-antenna transmitters

AU - Gamal, Aly El

AU - Annapureddy, V. Sreekanth

AU - Veeravalli, Venugopal V.

PY - 2012

Y1 - 2012

N2 - We consider locally connected K-user MISO interference channels where each transmitter has N antennas and is connected to the receiver with the same index as well as [L/2] successively preceding receivers and [L/2] following receivers. We assume that each receiver is interested in one message, which can be available at a maximum of M transmitters. Under these assumptions, we study the available degrees of freedom as well as the optimal way to assign messages to transmitters. For the case where each message is assigned to the transmitter with the same index, we know from [1] that [KN/N+1] DoF is achievable for the considered locally connected channel using interference alignment as the number of symbol extensions goes to infinity. In this work, we show that a simple linear strategy employing zero forcing transmit beams achieves min {2MN/M(N+1)+L, 1} per user degrees of freedom. In particular, the N/N+1 per user DoF is achievable by coding over only one channel realization, for any value of M ≥ L/N+1. Moreover, we show that the proposed scheme is optimal among a class of linear strategies where each receiver is either inactive or enjoys interference-free communication. Finally, we generalize the upper bound proved for Wyner's asymmetric channel model (L = 1) in [2], and show that message assignments satisfying a local cooperation constraint are optimal for a general setting of the parameters.

AB - We consider locally connected K-user MISO interference channels where each transmitter has N antennas and is connected to the receiver with the same index as well as [L/2] successively preceding receivers and [L/2] following receivers. We assume that each receiver is interested in one message, which can be available at a maximum of M transmitters. Under these assumptions, we study the available degrees of freedom as well as the optimal way to assign messages to transmitters. For the case where each message is assigned to the transmitter with the same index, we know from [1] that [KN/N+1] DoF is achievable for the considered locally connected channel using interference alignment as the number of symbol extensions goes to infinity. In this work, we show that a simple linear strategy employing zero forcing transmit beams achieves min {2MN/M(N+1)+L, 1} per user degrees of freedom. In particular, the N/N+1 per user DoF is achievable by coding over only one channel realization, for any value of M ≥ L/N+1. Moreover, we show that the proposed scheme is optimal among a class of linear strategies where each receiver is either inactive or enjoys interference-free communication. Finally, we generalize the upper bound proved for Wyner's asymmetric channel model (L = 1) in [2], and show that message assignments satisfying a local cooperation constraint are optimal for a general setting of the parameters.

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U2 - 10.1109/ISIT.2012.6283522

DO - 10.1109/ISIT.2012.6283522

M3 - Conference contribution

AN - SCOPUS:84867514323

SN - 9781467325790

T3 - IEEE International Symposium on Information Theory - Proceedings

SP - 1538

EP - 1542

BT - 2012 IEEE International Symposium on Information Theory Proceedings, ISIT 2012

T2 - 2012 IEEE International Symposium on Information Theory, ISIT 2012

Y2 - 1 July 2012 through 6 July 2012

ER -