have the option of falling back to standalone or autonomous GPS. Related technologies Many mobile phones combine A-GPS and other location services, including Wi-Fi positioning system and cell-site multilateration and sometimes a hybrid positioning system. High-Sensitivity GPS is an allied technology that addresses some of these issues in a way that does not require additional infrastructure. However, unlike some forms of A-GPS, high-sensitivity GPS cannot provide a fix instantaneously when the GPS receiver has been off for some time. Standards A-GPS protocols are part of Positioning Protocol defined by two different standardization bodies, 3GPP and Open Mobile Alliance (OMA). Control Plane Protocol Defined by the 3GPP for various generations of mobile phone systems. These protocols are defined for circuit switched networks. The following positioning protocols have been defined. RRLP – 3GPP defined RRLP (Radio Resource Location Protocol) to support positioning protocol on GSM networks. TIA 801 – CDMA2000 family defined this protocol for CDMA 2000 networks. RRC position protocol – 3GPP defined this protocol as part of the RRC standard for UMTS network. LPP – 3GPP defined LPP or LTE positioning protocol for LTE networks. User Plane Protocol Defined by the OMA to support positioning protocols in packet switched networks. Three generations of Secure User Plane Location (SUPL) protocol have been defined, from version 1.0 to 3.0. SUPL The SUPL (Secure User Plane Location) protocol, unlike its control-plane equivalents restricted to mobile networks, runs on the Internet's TCP/IP infrastructure. As a result, its application goes beyond the original intended use of mobile devices and may be used by general-purpose computers. SUPL 3.0 legitimizes such use by adding allowance for WLAN and broadband connections. Actions defined by SUPL 3.0 include a wide range of services such as geofencing and billing. The A-GNSS functions are defined in the SUPL Positioning Functional Group. It includes: SUPL Assistance Delivery Function (SADF), which provides the basic information sent to the device in both A-GNSS modes. SUPL Reference Retrieval Function (SRRF), which tells the server to prepare the information mentioned above by receiving from the satellites. SUPL Position Calculation Function (SPCF), which lets the client or the server ask for the client's location. The server-generated location may result from MSA or from mobile cell. If a MSB (SET based) mode is used, the client reports its location to the server instead. The specifics of communication is defined in the ULP (Userplane Location Protocol) substandard of SUPL