Performance analysis of a truncated closed-loop power-control scheme for DS/CDMA cellular systems

Abstract

This paper analyzes the system performance of a truncated closed-loop power-control (TCPC) scheme for uplinks in direct-sequencelcode-division multiple-access cellular systems over frequency-selective fading channels. In this TCPC scheme, a mobile station (MS) suspends its transmission when the short-term fading is less than a preset cutoff threshold; otherwise, the MS transmits with power adapted to compensate for the short-term fading so that the received signal power level remains constant. Closed-form formulas are successfully derived for performance measures, such as system capacity, average system transmission rate, MS average transmission rate, MS power consumption, and MS suspension delay. Numerical results show that the analysis provides reasonable accuracy and that the TCPC scheme can substantially improve the system capacity, the average system transmission rate, and power saving over conventional closed-loop power-control schemes. Moreover, the TCPC scheme under realistic consideration of power-control error due to power-control step size, power-control period, power-control command loop delay, and MS velocity is further investigated. A closed-form formula is obtained to accurately approximate the system capacity of the realistic TCPC scheme.