Radio resource location services (LCS) protocol (RRLP) applies to

GSM The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital cellular networks used by mobile devices such ...

and

UMTS The Universal Mobile Telecommunications System (UMTS) is a third generation mobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the In ...

Cellular Networks. It is used to exchange messages between a handset and an

SMLC Serving Mobile Location Center In GSM Networks, the SMLC is a network element that resides in the BSC A Bachelor of Science (BS, BSc, SB, or ScB; from the Latin ') is a bachelor's degree awarded for programs that generally last three to five yea ...

in order to provide geolocation information; e.g., in the case of emergency calls. The protocol was developed in order to fulfil the Wireless Enhanced 911 requirements in the United States. However, since the protocol does not require any authentication, and it can be used outside a voice call or SMS transfer, its use is not restricted to emergency calls and can be used by law enforcement to pinpoint the exact geolocation of the target's mobile phone. RRLP was first specified in 3GPP TS 04.31 - Location Services (LCS); Mobile Station (MS) - Serving Mobile Location Centre (SMLC); Radio Resource LCS Protocol (RRLP).

Harald Welte Harald Welte, also known as LaForge, is a German programmer. Welte is the founder of the free software project Osmocom and was formerly involved in the netfilter/iptables and Openmoko projects. He is a member of the Chaos Computer Club. Bi ...

proved at HAR2009Harald Welte on OpenBSC and HAR2009
/ref> that many high-end smart-phones submit their GPS location to the mobile operator when requested. This happened without any sort of authentication.

RRLP parameters

Positioning methods

RRLP supports two positioning methods: ;E-OTD: The

Enhanced Observed Time Difference Enhanced Observed Time Difference (E-OTD) is a standard for the location of mobile telephones. The location method works by multilateration. The standardisation was first carried out for GSM by the GSM standard committees (T1P1.5 and ETIS) in LCS ...

(E-OTD) is based on measurements inside the mobile phone, where the phone measures the observed time difference of arrival of bursts sent by nearby pairs of

base transceiver station A base transceiver station (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless Internet connectivity, ...

s. ;GPS: This method uses the

GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

(Global Positioning System) for achieving geolocation. To support this, the phone needs to have a built-in GPS receiver.

Method type

The method type indicates whether MS based or assisted location is to be performed. ;MS assisted: The MS (mobile phone) performs E-OTD or GPS measurements, and passes the raw measurement data to the network. The computation of the geolocation is then performed inside the carrier network, not on the phone itself. ;MS based: The MS (mobile phone) performs E-OTD or GPS measurements, and successively performs the complete computation of the geolocation inside the phone. The result of this computation is then sent back to the carrier network. In this mode, the network typically needs to send so-called assistance data to the phone.

References

Mobile telecommunications standards GSM standard