On Imperfect CSI for the Downlink of a Two-Tier Network

Salam Akoum (1, 2) , Marios Kountouris (3) , Robert W. Heath Jr (2)

1 Chaire Radio Flexible - Chaire Radio Flexible Alcatel-Lucent/Supélec
2 ECE - Department of Electrical and Computer Engineering - University of Texas
3 E3S - Supélec Sciences des Systèmes

In this paper, we consider a hierarchical two-tier cellular network where a macrocell is overlaid with a tier of randomly distributed femtocells. We evaluate the combined effect of uncoordinated cross-tier interference, feedback delay, and quantization errors on the achievable rate of transmit beamforming with imperfect channel state information (CSI). We model the femtocell spatial distribution as a Poisson point process (PPP) and the temporal correlation of the channel according to a Gauss-Markov model. Using stochastic geometry tools, we derive the probability of outage at the macrocell users as a function of the temporal correlation, the femtocell density, and the feedback rate. We compute the maximum average achievable rate on the downlink of the macrocell network using a properly designed rate backoff scheme. We show that transmit beamforming with imperfect CSI is a viable option for the downlink of a two-tier cellular network, and that rate backoff recovers the loss in rate due to packet outage.

Domains: Computer Science [cs]; Information Theory [cs.IT]; Mathematics [math]; Information Theory [math.IT]

Salam Akoum, Marios Kountouris, Robert W. Heath Jr. On Imperfect CSI for the Downlink of a Two-Tier Network. 2011 IEEE International Symposium on Information Theory Proceedings, Jul 2011, Saint-Petersbourg, Russia. 5 p., ⟨10.1109/ISIT.2011.6034189⟩. ⟨hal-00647372⟩