# Dual optimization methods for multiuser orthogonal frequency division multiplex systems

### Venue

Proceedings of IEEE Globecom, IEEE (2004), pp. 225-229

### Publication Year

2004

### Authors

Wei Yu, Raymond Lui, Raphael Cendrillon

### BibTeX

## Abstract

The design and optimization of orthogonal frequency division multiplex (OFDM)
systems typically take the following form. The design objective is to maximize the
total data rate which is the sum of individual rates in each frequency tone. The
design constraints are usually linear constraints imposed across all tones. The
paper shows that, regardless of whether the objective and the constraints are
convex, the duality gap for this class of problems is always zero in the limit as
the number of frequency tones goes to infinity. As the dual problem typically
decouples into many smaller per-tone problems, solving the dual problem is much
more efficient. This observation leads to an efficient method to find the global
optimum of non-convex optimization problems for the OFDM system. Multiuser optimal
power allocation, optimal frequency planning and optimal low-complexity crosstalk
cancellation for vectored DSL are used to illustrate this point.