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LTE for Public Safety by Jürgen Merkel, Curt Wong, Devaki Chandramouli, Rainer Liebhart

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4Proximity Services

4.1 Introduction to Proximity Services

4.1.1 Proximity Services Overview

Proximity Services, in short ProSe, provides mechanisms for devices to discover other devices in close proximity and to communicate with other devices directly, that is, without the data path being routed via the network infrastructure. This is illustrated with an example – Fireman John and Fireman Bob are located in the same building and they are trying to discover each other's presence and communicate when they are in proximity. In a traditional cellular network, if John and Bob want to communicate even when they are in proximity, their devices have to connect to the network first in order to transmit any kind of data through the mobile radio and core network infrastructure. With the introduction of ProSe, devices like the ones owned by John and Bob can discover each other and transmit user plane traffic directly between them in proximity. The “proximity range” depends certainly on the strength of the radio signal and other radio conditions such as interference. The actual range (e.g., 50 m, 200 m, or 1 km) varies depending on the power level used for transmitting the radio signal.

The ProSe function consists mainly of mechanisms on LTE radio level in order to enable direct discovery and communication between two or more devices. Functions and capabilities introduced by ProSe can be used by any application running on top of a ProSe-enabled device. Public Safety (PS) is one of the ...

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