Log-convexity of minimal feasible total power in CDMA channels

Power control is an important mechanism for interference management in CDMA channels. When developing power control strategies, CDMA system designers need to ensure that each user meets its signal-to-interference ratio (SIR) requirement. The minimal total power at which each user meets its SIR requirement is called the minimal feasible total power (MFTP). This paper shows that MFTP is a log-convex function on the set of feasible inverse SIR requirements. This implies that the set of feasible inverse SIR requirements is a convex set.