DoF Region of the Decentralized MIMO Broadcast Channelx2014How many informed antennas do we need?
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We study the impact of imperfect sharing of the Channel State Information (CSI) available at the transmitters on the capacity of the Network MIMO setting. In particular, we consider the setting in which a set of M transmit antennas jointly serve two multi-antenna users, where only a subset of k transmit antennas are endowed with perfect CSI whereas the other M-k transmit antennas have only access to finite precision CSI. By analyzing this configuration we aim to answer the question of how much an extra informed antenna can help. We characterize the Degrees-of-Freedom (DoF) region of the (M,N_1,N_2,k) Broadcast Channel (BC) and we show that only k = max(N_1,N_2) antennas with perfect CSI are needed to achieve the DoF of the conventional BC with perfect CSIT.
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