We consider a multi-antenna broadcast channel with more users K than transmit antennas operating in the low SNR regime. By applying low-power analysis tools, we derive sum-rate and energy efficiency bounds for dirty paper coding (DPC) and time-division multiple access (TDMA) with full channel state information at the transmitter (CSIT), as well as for random multiuser beamforming with partial CSIT. The optimality of multiuser transmission is established and large K asymptotic analysis is provided. Finally, we analytically show the efficiency of random beamforming and determine the optimal number of users to transmit to in the low SNR regime.
Low SNR analysis for MIMO broadcast channels with different types of CSIT
WSIT 2007, Winter School on Coding and Information Theory, March 12-16, 2007, La Colle sur Loup, France
La Colle sur Loup
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