Automatic threshold control for improved paging detection performance in wireless systems

Wireless systems, such as UMTS, use a paging indication channel (PICH) to signal whether a mobile is being paged. The threshold for PICH detection must he set to balance the tradeoff between missed calls (due to missed page) and lowered battery life (due to false alarms). Threshold selection is one of many factors that affect those metrics and, often, the sensitivity of those metrics to the PICH detection performance is highly dependent on the operating SNR. The paper provides a methodology for automatically setting the PICH detection threshold by taking such an SNR dependent sensitivity of the performance metrics into account in order to achieve the right tradeoff across all SNRs. Furthermore, we correctly account for imperfect channel estimation in the threshold setting. For each SNR value, we determine which metric (the metrics are false alarm probability and missed PICH probability) is the binding constraint and determine what its value should be. Using an analytic approach that correctly accounts for channel estimation error, we then determine the appropriate threshold to use at that SNR. Simulation results are presented for a UMTS system and show that substantial improvements in battery life can be obtained while also improving missed call rate compared to maximum likelihood (ML) detection. Significant gains over a Neyman-Pearson (NP) based approach are also obtained.