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On the capacity of MIMO broadcast channels with partial side information

Sharif, Masoud and Hassibi, Babak (2005) On the capacity of MIMO broadcast channels with partial side information. IEEE Transactions on Information Theory, 51 (2). pp. 506-522. ISSN 0018-9448. http://resolver.caltech.edu/CaltechAUTHORS:SHAieeetit05

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Abstract

In multiple-antenna broadcast channels, unlike point-to-point multiple-antenna channels, the multiuser capacity depends heavily on whether the transmitter knows the channel coefficients to each user. For instance, in a Gaussian broadcast channel with M transmit antennas and n single-antenna users, the sum rate capacity scales like Mloglogn for large n if perfect channel state information (CSI) is available at the transmitter, yet only logarithmically with M if it is not. In systems with large n, obtaining full CSI from all users may not be feasible. Since lack of CSI does not lead to multiuser gains, it is therefore of interest to investigate transmission schemes that employ only partial CSI. We propose a scheme that constructs M random beams and that transmits information to the users with the highest signal-to-noise-plus-interference ratios (SINRs), which can be made available to the transmitter with very little feedback. For fixed M and n increasing, the throughput of our scheme scales as MloglognN, where N is the number of receive antennas of each user. This is precisely the same scaling obtained with perfect CSI using dirty paper coding. We furthermore show that a linear increase in throughput with M can be obtained provided that M does not not grow faster than logn. We also study the fairness of our scheduling in a heterogeneous network and show that, when M is large enough, the system becomes interference dominated and the probability of transmitting to any user converges to 1/n, irrespective of its path loss. In fact, using M=αlogn transmit antennas emerges as a desirable operating point, both in terms of providing linear scaling of the throughput with M as well as in guaranteeing fairness.


Item Type:Article
Additional Information:© Copyright 2005 IEEE. Reprinted with permission. Manuscript received June 25,2003; revised August 31, 2004. [Posted online: 2005-01-24] This work was supported in part by the National Science Foundation under Grant CCR-0133818, by the Office of Naval Research under Grant N00014-02-1-0578, and by the Lee Center for Advanced Networking at the California Institute of Technology.
Subject Keywords:Broadcast channel, channel state information (CSI), multiuser diversity, wireless communications
Record Number:CaltechAUTHORS:SHAieeetit05
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SHAieeetit05
Alternative URL:http://dx.doi.org/10.1109/TIT.2004.840897
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6795
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:21 Dec 2006
Last Modified:26 Dec 2012 09:25

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