03.133GPPDiscontinuous Reception (DRX) in the GSM systemTS
At the BSS page requests are received. It is implicit (single cell BSSs) or explicit (multi cell BSSs) within the page requests from the MSC to which cell the page request is destined (Technical Specifications GSM 08.08 and GSM 08.02 refers).
The BSS analyses the IMSI in order to derive the page group of the MS involved. The air interface page request is then constructed and transmitted in the appropriate TDMA burst. If the page request includes a TMSI and IMSI then the IMSI is used to derive the page population and the TMSI is inserted into the actual page request message. The scheduling of the page requests is therefore completely controlled by the BSS.
The relationship between paging group and TDMA burst, and IMSI and paging group is given in Technical Specification GSM 05.02.
The exact scheduling mechanism used at the BSS is not defined in the present document.
However the BSS may set the "page mode" bits as described in Technical Specification GSM 04.08. This can be used to optimise paging load and reduce missed page requests during system reconfiguration.