Evaluation and Modeling of Power Control Information in a 3G Cellular Mobile Network

In modern 3 Generation (3G) networks such as Universal Mobile Telecommunication System (UMTS) Wide-band Code Division Multiple Access (WCDMA) is used for communication radio links. Power control is a very important issue in WCDMA, it reduces interference and power consumption of the transmission and therefore it needs to be addressed in relation with throughput maximization. Due to this fact UMTS deploys a strict power control, composed by the Inner Loop Power Control (ILPC) and the Outer Loop Power Control (OLPC). Whereas the ILPC was hardly tried to optimize in the last couple of years, the OLPC did not receive a comparable amount of attention. It seems not to undergo any evolution and there finds only few literature about optimization issues. The OLPC is a controller which adjusts the received Signal to Interference Ratio (SIR) to a predefined Block Error Ratio (BLER) by means of feedback to the transmitter. In resent research the OLPC algorithm was identified to introduce regular error patterns into radio connections, what is a sign for possible room of improvement. This thesis aims to identify impairments of the OLPC algorithm and to find room for improvement by means of extensive measurements in a live UMTS network. The measurements were performed in the UMTS Terrestrial Radio Access Network (UTRAN), by the aid of a powerful tracing tool. Measurement results have shown the nature of the uplink OLPC algorithm in detail. The behavior was characterized with the aid of statistical models. Furthermore additional parameters have been investigated, whereas especially one revealed a strong correlation to the BLER, i.e. the uncoded Bit Error Ratio (BER). In consequence a new OLPC algorithm is proposed in this work, which exploits the additional information of the uncoded BER. In order to evaluate the possible gain simulations have been performed, which compare the old and new algorithm. The outcome is that the new algorithm is able to improve the power control mechanism. Under different conditions, i.e. constant and dynamic SIR demands, the gain was estimated between 0.2 dB and 1 dB difference in mean SIR, what can directly be interpreted as power savings of the same magnitude. The new algorithm is totally standard compliant and easy to implement in existing networks.