Communication management
The Communication Management layer (CM) is responsible for Call Control (CC), supplementary service management, and short message service management. Each of these may be considered as a separate sublayer within the CM layer. Call control attempts to follow the ISDN procedures specified in Q.931, although routing to a roaming mobile subscriber is obviously unique to GSM. Other functions of the CC sublayer include call establishment, selection of the type of service (including alternating between services during a call), and call release.
The document John writes about is explained by Brian Holmes. "The black text of section 5.3, entitled 'Communication management,' speaks of call control, and references ITU's Q-series document Q.931. The document is entitled, 'ITU-T RECOMMENDATION Q.931: ISDN USER-NETWORK INTERFACE LAYER 3 SPECIFICATION FOR BASIC CALL CONTROL.' These are ITU specifications and not freely available, and thus there is no satisfactory link to them.
Brian continues, "To help your readers, the 3GPP 'numbering scheme' page is a good place to start when looking for a specific 3GPP document. These are for 3G and GSM specifications. That start page can be found at http://www.3gpp.org/specs/numbering.htm (external link). It contains links to 'series index' pages (e.g. the 09.31 document is listed on the 09 series index page) that contain document titles. The series index pages link to 'specification detail' pages that list every version of a specific document that has been produced."
Thanks, Brian, for the helpful comments. These specs are really helpful only to those studying cellular radio for a career or those working in the field.
Brian Holmes' company is Holmespun Solutions, LLC. The site is here: http://www.holmespun.biz (external link)