No abstract

Power control is considered as an important technique to mitigate the near-farfading effect and thus improve the system performance. In this paper, we present an adaptive decentralized power control algorithm. Power control in the uplink direction is been considered The proposed algorithm is a first order algorithm and utilizes bit error rate (BER) as a decision criterion for power update. Pilot bits in the uplink frame are used to measure the BER. We incorporate a nonlinear exponential term in the power update function to improve the speed of convergence of the algorithm which is also demonstrated through simulation results. Changing the adaptation parameter also changes the speed of convergence. The algorithm is examined in a time varying Rayleigh fading environment with frequency selective channel. We also demonstrate that the proposed algorithm achieves gain in the average required signal-to-noise ratio (SNR) value compared to other algorithms. The users are assumed to be mobile during the simulation period The proposed algorithm also performs well at higher mobile speed.

Taking into consideration the dominance of the multiple access interference (MAI) in spread spectrum based CDMA systems, power control plays a vital role in reducing the system interference and helps in increasing the capacity of the system while maintaining the quality of the received signal. Closed loop power control is mainly used to mitigate the nearfar effect in the uplink direction. In this paper, we propose a bit error rate (BER)-based first order distributed power control algorithm. Being distributed, the proposed algorithm has the flexibility of using the benefits of fast closed loop power control and thus can be used to update the transmit power of a single user at a time. Signal-to-interference ratio (SIR) based algorithms are in extensive use. But considering that the SIR is time variant, the BER would be a better quality of service (QoS) parameter because it can be easily measured using already known pilot bits. We analyze the convergence performance of the proposed algorithm and show that its convergence is always guaranteed. We demonstrate that a considerable improvement in the convergence speed along with the required average signal-tonoise ratio (SNR) is achieved as compared with other BER-based algorithms under comparison. We also show that the proposed algorithm performs well at different mobile speeds.Index Terms-Bit error rate, power control, uplink channel, WCDMA.