Outer-Loop Power Control in a live UMTS network: Measurement, analysis and improvements

The Outer Loop Power Control (OLPC) in WCDMA systems allows to achieve a defined Quality of Service (QoS) for every link. This reduces resources and interference, hence, increases the system-wide throughput. In this paper we present uplink OLPC related large-scale measurements, performed on live Iub-interfaces. Evaluations of the actual implemented algorithm show that it converges slowly; the reason being that the QoS is estimated by CRC. As the uncoded Bit Error Ratio (BER) holds information about the QoS, this parameter can be used to increase convergence speed of the OLPC. We present a statistical model of the control path of the OLPC which takes the uncoded BER information into account. Additionally, we propose a new OLPC algorithm that shows fast convergence in simulations, resulting in a reduction of 0.2 dB to 1 dB of the mean required signal-to-interference ratio, depending on the user mobility.