How does UMTS paging work?
First, get the latest 3GPP specifications 25-211, 25-304 and 25-331 Note: PI = Paging Indicator (value calculated by higher layers) Pq = Paging Indicator (indicator set by physical layer) 25-304 Chapter 8 shows how Paging Occasion and PI is calculated: Paging Occasion = {(IMSI div K) mod (DRX cycle length div PBP)} * PBP + n * DRX cycle length + Frame Offset Where n = 0,1,2… as long as SFN is below its maximum value. PI = DRX Index mod Np Where DRX Index = IMSI div 8192 ‘In FDD mode, Np = (18,36,72,144) is the number of Page Indicators per frame, and is given in IE “Number of PI per frame”, part of system information in FDD mode.’ 25-211 (FDD) Chapter 5.3.3.10 shows how Pq is calculated for channel mapping, the structure of paging indicator channel and the mapping of paging indicators Pq to PICH bits. 25-331 is also worth reading.