## ``Performance Limits and Optimal Resource Allocation for Coded Multiuser
Communication Systems''

### Author: Dennis L. Goeckel, University of Michigan August 1996

### Date: June 26, 1996

### Advisor: Wayne Stark

In this thesis, a class of concatenated-coded multicarrier code-division
multiple-access (CDMA) systems is presented as a framework for the unified
optimization of coherent binary multi-user communication systems operating
in a frequency-selective Rayleigh fading environment. It is demonstrated
under the assumptions of perfect channel estimation and interleaving that
the framework is general enough to include systems which model the performance
of both resource-sharing allocation schemes such as direct-sequence CDMA
(DS-CDMA) and exclusive resource allocation schemes such as frequency-hopped
CDMA (FH-CDMA) with orthogonal hopping patterns.

It is possible to optimize over the coded multicarrier framework for various
objectives under a given set of system assumptions. This optimization is
performed over both the number of users in the system and the amount of
diversity allocated to the inner code of each user. The first objective
considered is the multi-user throughput, defined as the total number of
bits communicated across the channel by the aggregate of users when they
are employing optimal hard-decision decoded outer codes. Tight bounds are
obtained on the normalized multi-user throughput, and the systems which
achieve these bounds are presented. The second objective is obtained by
optimizing the multi-user throughput under the assumption that there is
a fixed number of users in the system. This problem translates into the
allocation of diversity slots so as to minimize the probability of error
of the inner code for each user. It is observed that the optimal systems
allocate either the smallest reasonable number of slots or the largest number
of slots possible to the inner code of each user. The conditions under which
each solution is preferable are considered. The optimizations are then reperformed
when systems in the class employ a simple multi-user receiver where the
inner codes of all of the users are decoding jointly, and the effects of
a cellular environment supporting voice activity are considered.

The author can be contacted at:

*Prof. Dennis Goeckel *

*Dept. of Electrical and Computer Engineering *

*Univ. of Massachusetts Box 35110 *

*Amherst, MA 01003-5110*

*Tel: (413) 545-3514 *

*FAX: (413) 545-4611 *

*e-mail: goeckel@ecs.umass.edu *