The location of mobile communications equipment technical and legal aspects

Author:Maxim Dobrinoiu; Dorel Constantinescu
Pages:467-474

Maxim Dobrinoiu. Lecturer Ph.D., „Nicolae Titulescu” University, Bucharest. Author of www.e-crime.ro platform.

Dorel Constantinescu. Assistant, Ph.D. candidate, System Engineering and Computer Science Faculty, Politehnica University, Bucharest.

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Introduction

The developing of the Information Technology and the large scale use of modern means of electronic communications constitute an undisputable progress of the Knowledge Society and the creation of the new social relations based on these platforms necessitated in time also a change in the Law philosophy.

If the communication made by electronic means still poses nowadays an attraction for the legal experts and professionals, chiefly for the law enforcement agencies or the intelligence services, another product of science, the location, starts highlighting its benefits but also the legal challenges.

For the beginning we plan to present the process of locating the mobile communications equipment, as it must be regarded and understood more like as an Information Society service for the citizens.

Positioning techniques and technologies largely available these days have risen to a high level performance. The so called Location Based Services (LBS) are in fact information services functioning on technologies capable of providing the location of any user. Complex computer programs, called Geographic Information Systems (GIS), have been developed in order to process and execute an array of operations on spatial data and to further present them to the user in a respective format.

A call can be dialed on a landline phone, a simple mobile phone or a sophisticated and performing smartphone which embeds cutting-edge technologies. Comparing with the case of a call made from a landline phone, where the location information is fixed and can be stored and found in a database, in the case of a call made from a mobile phone the location information is notPage 468 a priori known (with the certainty needed for a good location) and for the positioning of the caller that information has to be created in real time, during the call.

Constructing the location information depends on the technological possibilities available. The developed countries are working now for the unification of all these technologies with the purpose to obtain the proper location information of a caller.

In the following instances we will approach the topic of the location of a caller in a mobile network, taking into consideration the present techniques and the future development perspectives.

The techniques used to determine the location in the mobile networks differ by accuracy, coverage level, updating frequency, cost of installation and maintenance.1

In a first evaluation, for the location there are the following techniques to be considered, such as: network-based techniques, terminal-based techniques and hybrid location techniques.

In the case of network-based techniques, the location of the mobile equipment is calculated by the Base Station Network which receives the radio signal of the caller mobile phone. These techniques benefit from the advantages of undertaking the location of any mobile terminal active in the network, implying a technological advantage only on the operator‘s side, with a general low cost, being easier to implement and with the burden of the location calculations left on the network.

Terminal-based location techniques request the embedding of a certain positioning technologies into the mobile equipment. The location is thus processed following the receipt of the signals sent by the neighbor positioning devices, such as the satellites. The most popular technology of this kind is Global Positioning System – GPS. The advantages of these technologies are the high precision in non-urban areas and a better control over own privacy (the user having the choice to broadcast or not GPS signals, whilst switching-off a mobile terminal means it is useless). By examining both the GSM/CDMA and terminal/GPS technology features one could notice that they are complementary in certain areas, and their simultaneously usage in so called hybrid location techniques could lead to very efficient positioning.

According to GSM Association, the location techniques could be split into three: primary, enhanced and advanced.2 The primary location techniques are based on the cell identification (Cell ID). This could be used alone or in conjunction with Timing Advance (TA) or Network Measurement Report (NMR) methods. The Enhanced Observed Time Difference (E-OTD) technique may be classified as an improved one, while the Assisted GPS (A-GPS) could be very well regarded as an advanced one.

During the positioning based on the Cell Identification, the location data is provided by the cell which has the Transmission-Reception Base Station connected to the monitored mobile terminal in a certain timeframe. This data is stored both in the network and in the mobile device and the location could be done by searching the Cell ID in a specific database, for example the operator coverage database, and extracting the geographical position of the cell. The localization could be much accurate by decomposing the terrestrial area into Voronoi cells.

If available, the Timing Advance (TA) information could be used as well. TA is a number from 0 to 63 which measure of the distance between the mobile terminal and the serving Base Station.

Although not bringing much enhancements in what regards the accuracy of the positioning (the resolution of such location being round 554m), using TA could determine whether the monitored mobile device is connected to the closest Base Station. TA parameter has the disadvantage of being sent by the mobile device only in active mode, whereas for the transmissionPage 469 in idle mode being necessary to have a modified terminal or to obtain a forced handover (technical procedure allowed by the most of the commercial devices by which the Base Station forces a connection between the mobile terminal and a neighbor station; the handover connection is refused but is only done with the purpose to measure various TAs).

Moreover, by refining these technologies the operator could obtain the Network Measurement Reports (NMR) – various level of the signals received from the Base Station the monitored mobile device is connected with, and also from other stations in vicinity (RXLEV). These levels are estimated in every cellular-type network by the mobile terminal and then sent to the Base Stations for the handover process. The...

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