Wikipedia
GMLC
The Gateway Mobile Location Centre contains functionality required to support LBS ( Location-based Service). In one PLMN ( Public Land Mobile Network), there may be more than one GMLC. The GMLC is the first node an external LBS client accesses in a GSM, UMTS or LTE network. The GMLC may request routing information from the HLR ( Home Location register) or HSS ( Home Subscriber Server). After performing registration authorization, it sends positioning requests to either the VMSC (Visited Mobile Switching Centre), SGSN (Serving GPRS Support Node) or MSC (Mobile Switching Centre) Server and receives final location estimates from the corresponding entity.