2013/11/26 by Borzoo Rassouli, Rassouli, Borzoo, Chenxi Hao +3 · 2 citations
Computer Science · Engineering · Mathematics · #Advanced MIMO Systems Optimization #Cooperative Communication and Network Coding #Wireless Communication Security Techniques #cs.IT #math.IT
paper · pdf · doi:10.48550/arxiv.1311.6647
24 pages, submitted to IEEE Trans. on Information Theory
arxiv created 2013/11/26 · arxiv updated 2013/11/27
We consider a K-user multiple-input single-output (MISO) broadcast channel (BC) where the channel state information (CSI) of user i(i=1,2,…,K) may be either perfect (P), delayed (D) or not known (N) at the transmitter with probabilities λPi, λDi and λNi, respectively. In this channel, according to the three possible CSIT for each user, joint CSIT of the K users could have at most 3K realizations. Although the results by Tandon et al. show that the Degrees of Freedom (DoF) region for the two user MISO BC with symmetric marginal probabilities (i.e., λQi=λQ ∀ i∈ \1,2,…,K\, Q∈ \P,D,N\) depends only on the marginal probabilities, we show that this interesting result does not hold in general when the number of users is more than two. In other words, the DoF region is a function of the CSIT pattern, or equivalently, all the joint probabilities. In this paper, given the marginal probabilities of CSIT, we derive an outer bound for the DoF region of the K-user MISO BC. Subsequently, the achievability of these outer bounds are considered in certain scenarios. Finally, we show the dependence of the DoF region on the joint probabilities.