1,709 research outputs found
Cooperative Precoding with Limited Feedback for MIMO Interference Channels
Multi-antenna precoding effectively mitigates the interference in wireless
networks. However, the resultant performance gains can be significantly
compromised in practice if the precoder design fails to account for the
inaccuracy in the channel state information (CSI) feedback. This paper
addresses this issue by considering finite-rate CSI feedback from receivers to
their interfering transmitters in the two-user multiple-input-multiple-output
(MIMO) interference channel, called cooperative feedback, and proposing a
systematic method for designing transceivers comprising linear precoders and
equalizers. Specifically, each precoder/equalizer is decomposed into inner and
outer components for nulling the cross-link interference and achieving array
gain, respectively. The inner precoders/equalizers are further optimized to
suppress the residual interference resulting from finite-rate cooperative
feedback. Further- more, the residual interference is regulated by additional
scalar cooperative feedback signals that are designed to control transmission
power using different criteria including fixed interference margin and maximum
sum throughput. Finally, the required number of cooperative precoder feedback
bits is derived for limiting the throughput loss due to precoder quantization.Comment: 23 pages; 5 figures; this work was presented in part at Asilomar 2011
and will appear in IEEE Trans. on Wireless Com
Optimality of binary power-control in a single cell via majorization
This paper considers the optimum single cell power-control maximizing the
aggregate (uplink) communication rate of the cell when there are peak power
constraints at mobile users, and a low-complexity data decoder (without
successive decoding) at the base station. It is shown, via the theory of
majorization, that the optimum power allocation is binary, which means links
are either "on" or "off". By exploiting further structure of the optimum binary
power allocation, a simple polynomial-time algorithm for finding the optimum
transmission power allocation is proposed, together with a reduced complexity
near-optimal heuristic algorithm. Sufficient conditions under which
channel-state aware time-division-multiple-access (TDMA) maximizes the
aggregate communication rate are established. Finally, a numerical study is
performed to compare and contrast the performance achieved by the optimum
binary power-control policy with other sub-optimum policies and the throughput
capacity achievable via successive decoding. It is observed that two dominant
modes of communication arise, wideband or TDMA, and that successive decoding
achieves better sum-rates only under near-perfect interference cancellation
efficiency.Comment: 24 pages, 11 figure
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