- User Datagram Protocol
- Universal Mobile Telecommunications Service
UMTS provides the European standard for 3G specified by ETSI. Whereas GSM uses TDMA , where each device has a fixed time slot allocation for the duration of a call, UMTS uses W-CDMA.
- Unstructured Supplementary Services Data
USSD is a means of transmitting data or instructions over GSM Networks. It operates by providing a connection across the GSM network over which data is sent. Text messages can be up to 182 characters in length.