Linear multiuser receivers: effective interference, effectivebandwidth and user capacity
Tse, D.N.C.; Hanly, S.V.
Information Theory, IEEE Transactions on
Volume 45, Issue 2, Mar 1999 Page(s):641 - 657
Digital Object Identifier 10.1109/18.749008
Summary:Multiuser receivers improve the performance of spread-spectrum and
antenna-array systems by exploiting the structure of the multiaccess
interference when demodulating the signal of a user. Much of the
previous work on the performance analysis of multiuser receivers has
focused on their ability to reject worst case interference. Their
performance in a power-controlled network and the resulting user
capacity are less well-understood. We show that in a large system with
each user using random spreading sequences, the limiting interference
effects under several linear multiuser receivers can be decoupled, such
that each interferer can be ascribed a level of effective interference
that it provides to the user to be demodulated. Applying these results
to the uplink of a single power-controlled cell, we derive an effective
bandwidth characterization of the user capacity: the
signal-to-interference requirements of all the users can be met if and
only if the sum of the effective bandwidths of the users is less than
the total number of degrees of freedom in the system. The effective
bandwidth of a user depends only on its own SIR requirement, and simple
expressions are derived for three linear receivers: the conventional
matched filter, the decorrelator, and the MMSE receiver. The effective
bandwidths under the three receivers serve as a basis for performance
comparison
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