  A unified approach to energy-efficient power control, applicable to a large
family of receivers including the matched filter, the decorrelator, the
(linear) minimum-mean-square-error detector (MMSE), and the individually and
jointly optimal multiuser detectors, has recently been proposed for
code-division-multiple-access (CDMA) networks. This unified power control (UPC)
algorithm exploits the linear relationship that has been shown to exist between
the transmit power and the output signal-to-interference-plus-noise ratio (SIR)
in large systems. Based on this principle and by computing the multiuser
efficiency, the UPC algorithm updates the users' transmit powers in an
iterative way to achieve the desired target SIR. In this paper, the convergence
of the UPC algorithm is proved for the matched filter, the decorrelator, and
the MMSE detector. In addition, the performance of the algorithm in finite-size
systems is studied and compared with that of existing power control schemes.
The UPC algorithm is particularly suitable for systems with randomly generated
long spreading sequences (i.e., sequences whose period is longer than one
symbol duration).
