WO2012136245A1

WO2012136245A1 - Considering privacy when using area-based minimization of drive-tests (mdt)

Info

Publication number: WO2012136245A1
Application number: PCT/EP2011/055210
Authority: WO
Inventors: Gyula Bodog; Silke Holtmanns; Ulrich Dropmann
Original assignee: Nokia Siemens Networks Oy
Priority date: 2011-04-04
Filing date: 2011-04-04
Publication date: 2012-10-11

Abstract

A method is disclosed, comprising maintaining (402), in a network apparatus, a threshold value regarding a minimum number of user terminals in a predefined area of a network. The apparatus determines (404) a value of a counter regarding a number of active user terminals currently located in said area, and compares (405) the threshold value and the value of the counter. If, based on the comparing, it is found out (406) that the value of the counter is below the threshold value, the method comprises defining (407), in the network apparatus, that the activation of a minimization of drive-tests function is not allowed in said area.

Description

CONSIDERING PRIVACY WHEN USING AREA-BASED MINIMIZATION OF DRIVE-TESTS (MDT)

FIELD OF THE INVENTION

The exemplary and non-limiting embodiments of this invention relate generally to wireless communications net- works, and more particularly to minimization of drive- tests.

BACKGROUND

The following description of background art may include insights, discoveries, understandings or disclo- sures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.

Minimization of drive-tests (MDT) refers to a functionality in which a wireless network operator has a possibility to collect MDT data via user terminals located in the operator's network. MDT data provides the network operator with valuable information on the network performance, thus reducing the need for separate drive-tests ter^¬ minals .

SUMMARY

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an ex^¬ tensive overview of the invention. It is not intended to identify key/critical elements of the invention or to de^¬ lineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Various aspects of the invention comprise a method, apparatus, and a computer-readable storage medium as defined in the independent claims. Further embodiments of the invention are disclosed in the dependent claims.

According to an aspect of the present invention, there is provided a method for maintaining a threshold value regarding a minimum number of user terminals in a predefined area of a network; determining a value of a counter regarding a number of active user terminals currently located in said area; comparing the threshold value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defin^¬ ing that the activation of a minimization of drive-tests function is not allowed in said area.

According to another aspect of the present inven- tion, there is provided an apparatus configured to main^¬ tain a threshold value regarding a minimum number of user terminals in a predefined area of a network; determine a value of a counter regarding a number of active user terminals currently located in said area; compare the thresh- old value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the apparatus is configured to define that the activation of a minimization of drive-tests function is not allowed in said area.

According to yet another aspect of the present in^¬ vention, there is provided a computer-readable storage me^¬ dium embodying a program of instructions executable by a processor to perform actions directed toward maintaining, in a network apparatus, a threshold value regarding a minimum number of user terminals in a predefined area of a network; determining, in the network apparatus, a value of a counter regarding a number of active user terminals currently located in said area; comparing, in the network ap^¬ paratus, the threshold value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defining, in the network apparatus, that the activation of a minimization of drive-tests function is not allowed in said area.

Although the various aspects, embodiments and fea- tures of the invention are recited independently, it should be appreciated that all combinations of the various aspects, embodiments and features of the invention are possible and within the scope of the present invention as claimed . BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of exemplary embodiments with reference to the attached drawings, in which

Figure 1 shows a simplified block diagram illus- trating an exemplary system architecture;

Figure 2 shows a simplified block diagram illus^¬ trating exemplary apparatuses;

Figure 3 shows a messaging diagram illustrating an exemplary messaging event according to an exemplary em- bodiment;

Figure 4 shows a schematic diagram of a flow chart according to an exemplary embodiment.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

In 3GPP Rel-10, a functionality is defined for substituting drive-tests at operators' networks to deter^¬ mine coverage holes or areas with weak coverage in their networks. This functionality is called minimization of drive-tests (MDT) . Within MDT, the aim is to utilize com^¬ mercial mobile terminals in the network to collect cover- age related information. But the usage of such a function^¬ ality raises privacy concerns with operators and regula^¬ tors.

According to the minimization of drive-tests (MDT) functionality, MDT data collection may be carried out on a user terminal having a certain IMSI or IMEI number (or some other device identifier) , for a specific area, or for a combination of these. In the case of area-based MDT data collection, the selection of the user terminal is carried out, for example, on the basis of certain user terminal capabilities (e.g. memory capacity, battery capacity, GPS module availability, logging support, and/or general MDT specific signalling support) .

As commercial UEs are used to collect coverage re^¬ lated measurement with time and location wise, this raises issues regarding privacy of the user's location. For exam^¬ ple, if MDT is started in a cell where there is only one subscriber at that time (e.g. in the middle of a desert, or in Camp David which is the summer resident of the president of the United States), the collected MDT data may be easily associated to a specific subscriber even if there are no subscriber identities in the collected data. Also during low activity times and/or due to moving pat^¬ terns the user may be identifiable, which conflicts with privacy regulations of the European Union.

It is also possible that a user consent is col^¬ lected from each and every subscriber, and MDT data is collected only from such UEs the subscriber /user of which has given his/her consent beforehand. This has been pro^¬ posed in 3GPP, but it limits the usability of MDT as if many subscribers are not willing to give their consent due to technical misunderstanding. Operators are not able to collect enough data in the network to really substitute the ordinary drive-test tasks and make the feature useful for them.

User consent handling is already discussed in

3GPP. For signalling-based MDT, it has already been agreed that user consent information is added as part of the sub^¬ scription data in a home subscriber server (HSS) .

When signalling-based MDT is started for a spe- cific IMSI or IMEI to improve the network service for an individual user, the user consent information is checked and the MDT activation continues only when the user consent is available. It should be noted that the signalling- based MDT focuses to improve the network for an individual user; hence, in that situation, it is clear that the user is identifiable.

For management-based MDT (which is targeting to improve the network service in a certain area) , one option is to provide a subscriber ID to the MDT record only when there is a user consent available, otherwise the MDT data is anonymous. Another option is to transfer the user consent information to the radio network, and when the radio network selects suitable UEs for MDT participation, the radio network also takes the user consent information into account. This has a strong impact on the network and also the user may not understand the difference between area MDT and signalling MDT.

According to an exemplary embodiment, data on an individual user cannot be identified with MDT management functionality, if a "sufficient amount" of measurement data is accumulated and personal information like the user identity is removed. Instead, the individual user data that may identify the user or his location, is then hidden by the crowd even if the node processing the MDT data has received further information from other nodes, and the user privacy may thus be protected. An exemplary embodi^¬ ment outlines a method how to protect the user privacy by ensuring that there is a sufficient amount of measurement data, and what is to be done when the user moves in/out of the location area, routing area, and/or tracking area.

In an exemplary embodiment, a counter is imple^¬ mented to eNB/RNC, which counter shows the number of users in a cell. The counter is updated when a user leaves the cell or joins the cell, i.e. joining and/or leaving the cell triggers a change to the counter. Alternatively, the counter may also be implemented with a status inspection, i.e. by checking the amount of active users in the area periodically, e.g. every 5 second or so. A threshold is defined, which threshold may be configured by OAM directly to eNB/RNC according to local privacy legislation and is set by a regulator. If the number of users in the cell ex- ceeds the threshold, eNB/RNC may activate MDT for the us^¬ ers in the cell. If the threshold is not reached (i.e. the number of users in the cell is below the threshold) , then no drive-test data is collected and MDT is not activated for the users in the cell.

In an exemplary embodiment, the collected MDT data may be anonymized to not include any temporary or perma^¬ nent subscriber IDs. The data may be stored in a union of data to avoid that by matching different sets of data one could trace a user.

In an exemplary embodiment, MDT data is collected from at least a certain number of users. Thus it is not possible to determine by the fact that as there is an ac^¬ tivity in the cell a certain user is available in that lo^¬ cation .

In an exemplary embodiment, a counter is imple^¬ mented in eNB/RNC. An attribute is defined in a UTRAN/E- UTRAN network resource model, which attribute defines the threshold. This attribute is configurable from the network management system.

Another option is that the threshold parameter is added as an additional parameter to the MDT activation pa^¬ rameters for the management-based MDT. In that case an ad^¬ ditional attribute may be needed in an act ivateTraceJob operation in a traceIRP functionality.

Thus, an exemplary embodiment relates to privacy handling in management-based MDT. In management-based MDT, to ensure the user privacy, a data collection big enough is required. An exemplary embodiment technically ensures that the MDT data is collected for a certain (at least a minimum) number of users to ensure user privacy. In an exemplary embodiment a counter in eNB/RNC configurable by network management allows to determine whether the minimum number of users is to participate the MDT session, i.e. whether the data to be collected from the terminals is sufficiently anonymous. An attribute re^¬ siding in eNB/RNC does not require a chain of interfaces, and it enables providing sufficient data anonymity. The counter may not only be used to count the number of active users in the area, but the counter may also be used to count the number of active users that have GPS (active) in the area.

Exemplary embodiments of the present invention will now be de-scribed more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal re- quirements. Although the specification may refer to "an" , "one", or "some" embodiment ( s ) in several locations, this does not necessarily mean that each such reference is to the same embodiment ( s ) , or that the feature only applies to a single embodiment. Single features of different em- bodiments may also be combined to provide other embodi^¬ ments. Like reference numerals refer to like elements throughout .

The present invention is applicable to any user terminal, server, corresponding component, and/or to any communication system or any combination of different communication systems that support a minimization of drive- tests (MDT) functionality. The communication system may be a fixed communication system or a wireless communication system or a communication system utilizing both fixed net- works and wireless networks. The protocols used, the specifications of communication systems, servers and user terminals, especially in wireless communication, develop rapidly. Such development may require extra changes to an embodiment. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment.

With reference to Figure 1, let us examine an ex^¬ ample of a radio system to which embodiments of the inven^¬ tion can be applied. In this example, the radio system is based on LTE network elements. However, the invention de- scribed in these examples is not limited to the LTE radio systems but can also be implemented in other radio sys^¬ tems, such as UMTS (universal mobile telecommunications system) , GSM, EDGE, WCDMA, bluetooth network, WLAN or other mobile or wireless network. In an embodiment, the presented solution may be applied between user equipment belonging to different but compatible systems such as LTE and UMTS.

A general architecture of a communication system is illustrated in Figure 1. Figure 1 is a simplified sys- tern architecture only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the systems also comprise other functions and structures. It should be appreciated that the functions, structures, elements, and protocols used in or for wire^¬ less communication are irrelevant to the actual invention. Therefore, they need not be discussed in more detail here.

The exemplary radio system of Figure 1 comprises a network node 101. The network node 101 may include e.g. an operations, administrations and maintenance (OAM) node, or any other network element or a combination of network elements. The network node 101 is connected to a radio net- work node 102. The radio network node 102 may include e.g. a radio network controller (RNC) , base station, access point, enhanced node B (eNB) or any other radio network element or a combination of radio network elements. The network node 101 and the radio network node 102 are con^¬ nected to each other via a connection 103 or via one or more further network elements. In Figure 1, the radio net^¬ work node 102 that may also be called eNB/RNC (enhanced node B/radio network controller) of the radio system hosts the functions for radio resource management in a public land mobile network. Figure 1 shows one or more user equipment 104 located in the service area of the radio network node 102. The user equipment refers to a portable computing device, and it may also be referred to as a user terminal. Such computing devices include wireless mobile communication devices operating with or without a sub- scriber identification module (SIM) in hardware or in software, including, but not limited to, the following types of devices: mobile phone, smart-phone, personal digital assistant (PDA), handset, laptop computer. In the example situation of Figure 1, the user equipment 104 is capable of connecting to the radio network node 102 via a connection 105.

Figure 1 only illustrates a simplified example. In practice, the net-work may include more base stations and radio network controllers, and more cells may be formed by the base stations. The networks of two or more operators may overlap, the sizes and form of the cells may vary from what is depicted in Figure 1, etc. The communication sys^¬ tem may also be able to communicate with other networks, such as a public switched telephone network. The embodi- ments are not, however, restricted to the network given above as an example, but a person skilled in the art may apply the solution to other communication networks provided with the necessary properties. For example, the con^¬ nections between different network elements may be real- ized with internet protocol (IP) connections. Figure 2 illustrates examples of apparatuses ac^¬ cording to embodiments of the invention. Figure 2 shows a user equipment 104 located in the area of the radio net^¬ work node or eNB/RNC 102. The user equipment is configured to be in connection with the radio network node 102. The user equipment or UE 104 comprises a controller 201 opera^¬ tionally connected to a memory 202 and a transceiver 203. The controller 201 controls the operation of the user equipment 104. The memory 202 is configured to store soft- ware and data. The transceiver 203 is configured to set up and maintain a wireless connection to the radio network node 102. The transceiver is operationally connected to a set of antenna ports 204 connected to an antenna arrange^¬ ment 205. The antenna arrangement 205 may comprise a set of antennas. The number of antennas may be one to four, for example. The number of antennas is not limited to any particular number. The user equipment 104 may also comprise various other components, such as a user interface, camera, and media player. They are not displayed in the figure due to simplicity. The radio network node or eNB/RNC 102 comprises a controller 206 operationally con^¬ nected to a memory 207 and a transceiver 208. The control^¬ ler 206 controls the operation of the radio network node 102. The memory 207 is configured to store software and data. The transceiver 208 is configured to set up and maintain a wireless connection to the user equipment 104 within the service area of the radio network node 102. The transceiver 208 is operationally connected to an antenna arrangement 209. The antenna arrangement may comprise a set of antennas. The number of antennas may be two to four, for example. The number of antennas is not limited to any particular number. The radio network node may be operationally connected (directly or indirectly) to an^¬ other network element 101 of the communication system. The network element 101 may be an operations, administrations and maintenance (OAM) node, a home location register (HLR) , visitor location register (VLR) , MSC server (MSS), a mobile switching centre (MSC) , serving GPRS support node, MME (mobility management entity) , a base station controller (BSC), a gateway, or a server, for example. The network node 102 may be connected to more than one network element. The network node 102 may comprise an interface 210 configured to set up and maintain connections with the network elements. The network element or OAM 101 may com^¬ prise a controller 211 and a memory 212 configured to store software and data and an interface 213 configured to be in connection with the network node 102. The network element 101 may be operationally connected (directly or indirectly) to another network element of the communica^¬ tion system. The embodiments are not, however, restricted to the network given above as an example, but a person skilled in the art may apply the solution to other commu^¬ nication networks provided with the necessary properties. For example, the connections between different network elements may be realized with internet protocol (IP) con- nections.

The memory may include volatile and/or non^¬ volatile memory and typically stores content, data, or the like. For example, the memory may store computer program code such as software applications (for example for the detector unit and/or for the adjuster unit) or operating systems, information, data, content, or the like for the processor to perform steps associated with operation of the apparatus in accordance with embodiments. The memory may be, for example, random access memory (RAM) , a hard drive, or other fixed data memory or storage device. Fur^¬ ther, the memory, or part of it, may be removable memory detachably connected to the apparatus.

The techniques described herein may be implemented by various means so that an apparatus implementing one or more functions of a corresponding mobile entity described with an embodiment comprises not only prior art means, but also means for implementing the one or more functions of a corresponding apparatus described with an embodiment and it may comprise separate means for each separate function, or means may be configured to perform two or more func- tions. For example, these techniques may be implemented in hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or combina^¬ tions thereof. For a firm-ware or software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in any suitable, proces^¬ sor/computer-readable data storage medium(s) or memory unit(s) or article (s) of manufacture and executed by one or more processors/computers. The data storage medium or the memory unit may be implemented within the proces^¬ sor/computer or external to the processor/computer, in which case it can be communicatively coupled to the proc^¬ essor/computer via various means as is known in the art.

User equipment may refer to any user communication device. A term "user equipment" as used herein may refer to any device having a communication capability, such as a wireless mobile terminal, a PDA, tablet, a smart phone, a personal computer (PC) , a laptop computer, a desktop com^¬ puter, etc. For example, the wireless communication termi- nal may be an UMTS or GSM/EDGE smart mobile terminal hav^¬ ing wireless modem. Thus, the application capabilities of the device according to various embodiments of the inven^¬ tion may include native applications available in the ter^¬ minal, or subsequently installed applications by the user or operator or other entity. The operations, administra^¬ tions and maintenance node may be implemented in any net^¬ work element, such as a server.

The signalling chart of Figure 3 illustrates the required signalling. In the example of Figure 3, an appa- ratus 102 which may comprise e.g. an enhanced node-B/radio network controller (eNB/RNC) , receives, in step 302, a threshold value transmitted 301 from a network node 101 such as an operations, administrations and maintenance (OAM) node. The received threshold value may be stored 302 in a memory by the apparatus 102. In message 303 the appa- ratus receives 304 signalling from one or more active user terminals 104 located in the area of the apparatus 102. Based on the received signalling, the apparatus 102 is able to determine 304 the number of active user terminals in a predefined area of the network (the predefined area may comprise e.g. a cell, a location area, a routing area and/or a tracking area) . The signalling 303 may comprise e.g. location update signalling and/or some other call setup/session setup signalling between the user terminals 104 and the apparatus 102. The terminal may send the MDT measurements on its own initiative or the terminal may be triggered by the network to send the MDT measurements. Based on the number of the active user terminals in the predefined area, the apparatus is configured determine a value of a counter (which counter value is updated 304 by the apparatus 102 when a user terminal enters and/or leaves the area) . The counter may also be implemented by using a sampling method, i.e. the apparatus may be confi^¬ gured to check the number of active UEs or connections pe^¬ riodically (in predetermined time intervals, e.g. every 5 second) . A threshold value is set by the operator and de^¬ fined by local legislation/regulator. In step 304, the apparatus is configured to compare the threshold value and the value of the counter. If, based on the comparing, it is found out that the value of the counter is below the threshold value, the apparatus is configured to define 304 that activation of a minimization of drive-tests function is not allowed in the area in question (i.e. the number of user terminals located in the area is too low, which jeop^¬ ardizes the anonymity/privacy of the user terminals; thus, minimization of drive-tests function is not allowed at that time in said area e.g. due to legislative privacy re- quirements) . If, based on the comparing, it is found out that the value of the counter exceeds the threshold value or equals to the threshold value, the apparatus may define 304 that the activation of a minimization of drive-tests function is allowed in said area. When/if the threshold value is updated by OAM, the apparatus is configured to store the updated threshold value and perform the compar^¬ ing and defining steps by using the updated threshold value. When the UE counter value is updated by eNB/RNC, the apparatus 102 is configured to store the updated counter value and perform the comparing and defining steps by using the updated counter value and the latest thresh^¬ old value. The apparatus is thus able to decline drive- tests whenever the number of the active user terminals in the area is lower than the threshold value defined for that area. "Active" user terminals herein may refer to user terminals that have an on-going call and/or session, or that are in a standby/idle mode.

Figure 4 is a flow chart illustrating a non- limiting embodiment of the invention. In step 401, the ap^¬ paratus 102 receives the threshold value from the network element 101. In step 402, the apparatus 102 may store the threshold value in a memory. In step 403, the apparatus 102 receive signalling from one or more active user termi- nals 104 located in the area of the apparatus 102. In step 404, the apparatus 102 determines, based on the received signalling, the number of active user terminals 104 in the predefined area. In step 405, the apparatus 102 deter^¬ mines, based on the number of the user terminals 104 in the predefined area, the value of the UE counter. The counter may not only be used to count the number of active users in the area, but the counter may also be used to count the number of active users that have GPS (active) in the area. In step 406, the apparatus 102 compares the threshold value and the value of the counter. If, based on the comparing, it is found out that the value of the counter is below the threshold value, the apparatus 102 is configured to define, in step 407, that the activation of the minimization of drive-tests function is not allowed in the area. If, based on the comparing, it is found out that the value of the counter exceeds the threshold value or equals to the threshold value, the apparatus 102 defines, in step 408, that the activation of the minimization of drive-tests function is allowed in the area. When/if the threshold value is updated by OAM, the apparatus 102 re- ceives, in step 409, the updated threshold value, and re- performs the steps 402 to 407/408 by using the updated threshold value. When/if a user terminal 104 enters and/or leaves the area, the apparatus 102 receives, in step 410, corresponding signalling, and re-performs the steps 404 to 407/408 by using the updated counter value.

Minimization of drive tests (MDT) is one of the most promising technologies to substantially reduce the operational costs in context of increased self- organization of networks and to improve the general and individual connectivity service offered to the user. An exemplary embodiment enables protecting the privacy of the user location against direct extraction and against at^¬ tempts to determine the user's location by combining in^¬ formation. A distinction between signalling and management MDT may be made. A better understanding of the management MDT functionality and its relation to the potential loca^¬ tion privacy of the user. The collected data may be criti^¬ cally reviewed and the collection of data for the network management purpose may be minimized.

The minimization of drive-tests (MDT) functional^¬ ities include different trace types signalling trace and management trace: signalling MDT is mainly used to im- prove/troubleshoot services of one specific sub^¬ scriber/user based on radio measurements; management or area MDT is based on radio measurements to improve the ra^¬ dio network performance for a specific area. They may be deployed together or independently of each other, i.e. an operator may deploy management MDT without deploying sig^¬ nalling MDT and the other way around. The usage may also depend on the use cases within an operator. For example, after a customer complaint, operator may use signalling MDT, while for optimizing the network or checking the network coverage after new capacity expansion/cell installa^¬ tion, the operator may use management MDT.

In data in management based MDT, the collected data sets are differentiated for two modes: device con^¬ nected mode also called immediate MDT, and logged MDT mode (i.e. when the terminal is in an idle mode) . The following information is collected for management based MDT. In logged MDT the following data is collected:

- RSRP (reference signal received power) /RSRQ

(reference signal received quality) in E-UTRA,

- CPICH RSCP (common pilot channel - received sig^¬ nal code power) & Ec/NO in UTRA) ,

- Ec/No is the received signal code power (RSCP) divided by the received signal strength indicator (RSSI),

- GPS data if available or cell-ID,

- timestamp (to identify the source of the network "weakness", e.g. storm, festival, etc.).

Regarding the cell-ID, when UE goes to an idle mode, eNB deletes any context, but the logging ability re^¬ sides purely in UE . Thus information which is available in UE may be stored in its memory as logged data for MDT pur^¬ poses. UE reads broadcasted system information and searches for a suitable cell even if UE is in the idle mode. If a suitable cell is found UE "camps on" this cell. Therefore, UE knows the cell-ID (even though UE does not have dedicated connection to the cell) .

Regarding the GPS information, MDT does not require a specific action from the network to get detailed location information (more detailed than the cell-ID) . The intention of MDT is to provide the best data to the opera- tor to support the operator in improving the network service i.e. potentially GPS. But there needs to be an active GPS modem (not only present, but also activated) . Then UE may get geographical coordinates based on user plane posi- tioning flow (a positioning server and client reside on the application layer and communicate over a packet data connection) but without radio access network assistance. This is possible if UE does not have an active dedicated connection to the network. The MDT data gathered and ob- tained in the idle mode is not immediately communicated to eNB . If UE connects to eNB at the same point, UE indicates that it has logged some MDT data that eNB may decide to retrieve .

In connected mode the following data is collected: - In E-UTRAN:

o RSRP/RSRQ by the UE in E-UTRAN,

o power headroom measured by UE,

o uplink signal strength/SINR (signal to interference plus noise ratio) measured by eNB,

o GPS data if available or cell-ID,

o timestamp.

- In UTRAN:

o CPICH RSCP and CPICH Ec/no measurement by UE, o uplink signal strength/SINR measurement by node- B,

o P-CCPCH RSCP and timeslot ISCP (interference signal code power,

o P-CCPCH RSCP and timeslot ISCP (interference signal code power) for UTRA 1.28 TDD,

o GPS data if available or cell-ID,

o timestamp.

The data flow may be as follows. The UE measure^¬ ments are transferred to eNB/RNC. Then eNB/RNC forwards them to a management entity that is called TCE . TCE pairs the measurements with subscriber identities based (re^¬ ceived from MME) on a trace reference (TR) and a trace re- cording session reference (TRSR) embedded in each report sent to TCE by the network entities. These references are used at TCE to correlate the collected data that belongs to the same MDT session for a specific area.

If several different areas are checked it is pos^¬ sible that several MDT session is started. The collected data is differentiated based on trace reference. The trace recording session reference is allocated for each connec^¬ tion separately, that is used to correlate the data that belongs to one MDT session.

A logging area may be configured, which may be taken into account before investigating privacy risks. When configuring a logging area, UE logs measurements as long as it is within the configured logging area. The scope of the logging area may include one of: 1) a list of 32 global cell identities; if this list is configured, UE only logs measurements when camping in any of these cells, 2) a list of 8 TAs or 8 LAs or 8 RAs . If this list is con^¬ figured, UE only logs measurements when camping in any cell belonging to the preconfigured TA/LA/RAs. If no area scope is configured, the configuration is valid in the en^¬ tire MDT PLMN of UE, i.e. UE logs measurements throughout MDT PLMN. There is necessarily no need to introduce a measurement identity for logged MDT. An additional meas- urement object parameter such as a cell specific offset is not necessary for logged MDT. As can be seen, this is not bound to a specific and configurable GPS area, which would allow fine-tuned and may end up in making it so small that an individual user may be traced. Hence, this risk is not there.

When considering potential user privacy risks, a concern is the GPS coordinate of the user. It should be noted, that there is no user identity collected. So there is no possibility to identify an individual user directly. The combination with time, may allow some deduction, i.e. an unknown person is living here, but there is no individ- ual user identifier for this person to link the user to other measurements (e.g. if you have a trajectory, and are able to associate one point on the trajectory with a known user, e.g. his home, then you know the movements of the user) . Another issue is the tracking of a user using the point on a trajectory. Again, it is anonymous tracking, since the individual measurements have no identifier, the tracking of a user is made impossible. Another risk may stem from the unlikely situation that there is only a sin- gle user (or very few users) in a tracking area. Then the data may allow tracking, but as soon as the data set be^¬ comes larger, this will become increasingly hard and later on impossible. For practical purposes, the threshold may be seen in relation to the size of the area (if you have quite fine-grained location data and time, then, assuming a certain user speed, you may have a software trying to map out trajectories; the degree of privacy protection may depend on the effort an attacker is willing to spend; these aspects may be taken into account here when deter- mining a threshold value (as with the number of users that have to be present in an area) so that privacy may be con^¬ sidered guaranteed for practical purposes) . A solution to hide individual data in a larger crowd of k may be re^¬ ferred to as k-anonymity or optimal k-anonymization . In area based MDT, trace reference cannot be associated to any subscriber as that identifies the trace session, which is for one or a set of cells.

MDT management may be deployed in an area where just few users are present. One approach is to add a blan- ket user consent information element for the management MDT as it is today. This user consent element distin^¬ guishes between "signalling based MDT" and "management based MDT" to the MDT privacy solution (i.e. duplicating the signalling based MDT approach) . The reason may be that there are different data elements handled and the level privacy impact of signalling MDT is larger than for man- agement based MDT . Also, the unlikely case of a single user in an MDT measurement area might raise the concern. Then the "management based MDT consent" information ele^¬ ment may be set to "yes" in certain areas for all sub- scribers. Equally users may be willing to consent for man^¬ agement based MDT while not for signalling based MDT. On the other hand, this brings the practical issue of how to obtain educated user consent. How to explain to the user the differences and avoiding that users by default say no and make it impossible for the network operator to improve their services. Another issue is that that this may re^¬ quire contacting legacy users manually i.e. sending them a message or a letter to individually request their agree^¬ ment. It may be that users either do not agree or do not answer at all, i.e. the operator may not be able to obtain a critical mass of data to improve the network, but still has the costs for contacting the users. Another approach is to remove not needed data, remove user identifiers from the network protocols, prevent collection of identifiers that allows data combination in addition then combining data sets to a larger set making the identification of an individual device impossible. In addition, one may want to hide any sort of location information in a larger set of location information. For this the counter that is already available in eNB may be re-used. A function in eNB may be used to measure the number of active users for layer 2 measurements. This function may also be utilized here to prevent potential user tracking for the unlikely case, that there is only one or very few users in a certain measurement area. In other words, this function allows one to set a threshold value and the management MDT function is only activated, when the threshold is reached. By stripping off sensitive data on one hand, and hiding the location information (without any user identifier) in the crowd by reusing existing functionality the users privacy may be protected without requiring explicit user consent, since there is no personable identifiable information any longer. This allows operator to take management MDT into use based on their existing subscriber base and to reduce OPEX using management MDT.

In an exemplary embodiment, a more fine grained approach is used (than asking for a "white-card" user consent), including minimizing data collection, making an individual user no-recognizable in the crowd, improving the service for the user, preventing that an operator has to contact his legacy users, preventing investments to be made without being able to improve the network, keeping this feature in Release 10. Based on the information above, following changes to the existing work. There is no need to introduce a measurement identity for logged MDT. To prevent any sort of potential mappings, this may be mandated. There is no sending of IMSI or IMEI or other user identifier to MME, i.e. no possibility to identify individual, no sending of IMSI or IMEI or other user identifier to MME, i.e. no possibility to identify individual subscriber. It is technically not needed. Re-use the counter in the eNB/RNC which shows the number of users in a cell, also for routing area and location area. Manage^¬ ment MDT measurements are only collected, when a prede^¬ fined minimum threshold value is reached to avoid the unlikely case that only few users are in the management area. Also, small data sets do not provide a good database to improve the network. Combine the measured data into a cell data set to prevent individual extraction. Allow a local legislator to define an acceptable threshold value according to local legislation. Do not collect data in the MME for roaming users. With those changes it is possible to protect the user privacy for management MDT, because the technical possibilities to track an individual user are removed. If those critical elements are removed, then no user consent needs to be required. On the other hand, this change allows operators to use management MDT without explicit user consent and collect a sufficient amount of data that is needed to improve their network services for the user.

Thus, according to an exemplary embodiment, there is provided a method comprising performing, in a network apparatus, the method steps of maintaining a threshold value regarding a minimum number of user terminals in a predefined area of a network; determining a value of a counter regarding a number of active user terminals cur- rently located in said area; comparing the threshold value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defin^¬ ing that the activation of a minimization of drive-tests function is not allowed in said area.

According to another exemplary embodiment, there is provided a method, wherein if, based on the comparing, it is found out that the value of the counter exceeds the threshold value or equals to the threshold value, the method comprises defining, in the network apparatus, that activation of a minimization of drive-tests function is allowed in said area.

According to yet another exemplary embodiment, there is provided a method, wherein if the value of the counter exceeds or equals to the threshold value, the method comprises defining that collecting drive-test data on the user terminals is allowed in said area.

According to yet another exemplary embodiment, there is provided a method, wherein if the value of the counter is below the threshold the method comprises defin^¬ ing that collecting drive-test data on the user terminals is not allowed in said area.

According to yet another exemplary embodiment, there is provided a method comprising updating the thresh- old value in response to recognising a predefined event in the network apparatus . According to yet another exemplary embodiment, the predefined event comprises receiving an update message from an operations, administrations and maintenance node, the message including information on an updated threshold value.

According to yet another exemplary embodiment, there is provided a method comprising refraining from performing drive-tests on the user terminals in said area when the number of user terminals in said area is too low.

According to yet another exemplary embodiment, there is provided a method comprising updating the value of the counter when the number of user terminals in said area changes.

According to yet another exemplary embodiment, there is provided a method comprising updating the value of the counter when a user terminal leaves and/or enters said area.

According to yet another exemplary embodiment, said area comprises a network cell, a location area, a routing area and/or a tracking area.

According to a yet another exemplary embodiment, there is provided an apparatus configured to maintain a threshold value regarding a minimum number of user terminals in a predefined area of a network; determine a value of a counter regarding a number of active user terminals currently located in said area; compare the threshold value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the apparatus is configured to define that the activation of a minimization of drive-tests function is not allowed in said area.

According to a yet another exemplary embodiment, there is provided an apparatus, wherein if, based on the comparing, it is found out that the value of the counter exceeds the threshold value or equals to the threshold value, the apparatus is configured to define that activa- tion of a minimization of drive-tests function is allowed in said area.

According to a yet another exemplary embodiment, there is provided an apparatus, wherein if the value of the counter exceeds or equals to the threshold value the apparatus is configured to define that collecting drive- test data on the user terminals is allowed in said area.

According to a yet another exemplary embodiment, there is provided an apparatus, wherein if the value of the counter is below the threshold the apparatus is con^¬ figured to define that collecting drive-test data on the user terminals is not allowed in said area.

According to a yet another exemplary embodiment, there is provided an apparatus configured to update the threshold value in response to recognising a predefined event in the apparatus .

According to a yet another exemplary embodiment, there is provided an apparatus configured to refrain from performing drive-tests on the user terminals in said area when the number of user terminals in said area is too low.

According to a yet another exemplary embodiment, there is provided an apparatus configured to update the value of the counter when the number of user terminals in said area changes.

According to a yet another exemplary embodiment, there is provided an apparatus configured to update the value of the counter when a user terminal leaves and/or enters said area.

According to a yet another exemplary embodiment, there is provided an apparatus configured to update the value of the counter periodically.

According to a yet another exemplary embodiment, there is provided a computer-readable storage medium embo^¬ dying a program of instructions executable by a processor to perform actions directed toward maintaining, in a net^¬ work apparatus, a threshold value regarding a minimum num- ber of user terminals in a predefined area of a network; determining, in the network apparatus, a value of a counter regarding a number of active user terminals currently located in said area; comparing, in the network ap- paratus, the threshold value and the value of the counter; wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defining, in the network apparatus, that the activation of a minimization of drive-tests function is not allowed in said area.

The steps/points, signalling messages and related functions de-scribed above in Figures 1 to 4 are in no ab^¬ solute chronological order, and some of the steps/points may be performed simultaneously or in an order differing from the given one. Other functions can also be executed between the steps/points or within the steps/points and other signalling messages sent between the illustrated messages. Some of the steps/points or part of the steps/points can also be left out or replaced by a corre- sponding step/point or part of the step/point. The appara^¬ tus operations illustrate a procedure that may be imple^¬ mented in one or more physical or logical entities. The signalling messages are only exemplary and may even comprise several separate messages for transmitting the same information. In addition, the messages may also contain other information.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

List of abbreviations

3GPP third generation partnership project Rel-10 release 10

MDT minimization of drive-tests UE user equipment

HSS home subscriber server

IMSI international mobile subscriber identity

IMEI international mobile equipment identity

ID identifier

eNB enhanced node-B

RNC radio network controller

OAM operations, administrations and mainte- nance

UTRAN UMTS terrestrial radio access network E-UTRAN enhanced UMTS terrestrial radio access network

UMTS universal mobile telecommunications sys- tern

GPS global positioning system

LTE long term evolution

GSM global system for mobile communications

EDGE enhanced data rates for GSM evolution

WCDMA wideband code division multiple access

WLAN wireless local area network

TA tracing area

LA location area

RA routing area

Claims

1. A method for a communications system, the method comprising

maintaining (302, 402), in a network apparatus (102), a threshold value regarding a minimum number of user terminals (104) in a predefined area of a network;

determining (304, 404), in the network apparatus (102), a value of a counter regarding a number of active user terminals (104) currently located in said area;

comparing (304, 405), in the network apparatus

(102), the threshold value and the value of the counter;

wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defining (304, 407), in the network apparatus (102), that the activation of a minimization of drive-tests function is not allowed in said area .

2. A method as claimed in claim 1, characterized in that if, based on the comparing (304, 405), it is found out (406) that the value of the counter exceeds the threshold value or equals to the threshold value, the method comprises defining (304, 408), in the network appa^¬ ratus (102), that activation of a minimization of drive- tests function is allowed in said area.

3. A method as claimed in claim 1 or 2, characterized in that if the value of the counter exceeds or equals to the threshold value, the method comprises defin^¬ ing (304, 408) that collecting drive-test data on the user terminals (104) is allowed in said area.

4. A method as claimed in claim 1, 2 or 3, characterized in that if the value of the counter is below the threshold the method comprises defining (304, 407) that collecting drive-test data on the user terminals (104) is not allowed in said area.

5. A method as claimed in any one of the preceding claims, characterized in that it comprises updating (302, 402) the threshold value in response to recognising a predefined event in the network apparatus (102) .

6. A method as claimed in claim 5, character- ized in that the predefined event comprises receiving

(302, 409) an update message from an operations, admini^¬ strations and maintenance node (101), the message includ^¬ ing information on an updated threshold value.

7. A method as claimed in any one of the preceding claims, characterized in that the method comprises refraining (407) from performing drive-tests on the user terminals in said area when the number of user terminals (104) in said area is too low.

8. A method as claimed in any one of the preceding claims, characterized in that the method comprises updating (304, 404) the value of the counter when the number of user terminals (104) in said area changes.

9. A method as claimed in any one of the preceding claims, characterized in that the method comprises updating (304, 404) the value of the counter when a user terminal (104) leaves and/or enters said area.

10. A method as claimed in any one of the preced^¬ ing claims, characterized in that said area com^¬ prises a network cell, a location area, a routing area and/or a tracking area.

11. An apparatus for a communications system, wherein the apparatus (102) is configured to

maintain a threshold value regarding a minimum number of user terminals (104) in a predefined area of a network;

determine a value of a counter regarding a number of active user terminals (104) currently located in said area;

compare the threshold value and the value of the counter;

wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the apparatus (102) is configured to define that the activation of a minimization of drive-tests function is not allowed in said area.

12. An apparatus as claimed in claim 11, characterized in that if, based on the comparing, it is found out that the value of the counter exceeds the threshold value or equals to the threshold value, the ap^¬ paratus (102) is configured to define that activation of a minimization of drive-tests function is allowed in said area .

13. An apparatus as claimed in claim 11 or 12, characterized in that if the value of the counter exceeds or equals to the threshold value the apparatus (102) is configured to define that collecting drive-test data on the user terminals (104) is allowed in said area.

14. An apparatus as claimed in claim 11, 12 or 13, characterized in that if the value of the counter is below the threshold the apparatus (102) is configured to define that collecting drive-test data on the user termi^¬ nals (104) is not allowed in said area.

15. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that the apparatus (102) is configured to update the threshold value in re- sponse to recognising a predefined event in the apparatus (102) .

16. An apparatus as claimed in claim 15, characterized in that the predefined event comprises re^¬ ceiving an update message from an operations, administra- tions and maintenance node (101), the message including information on an updated threshold value.

17. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that the apparatus (102) is configured to refrain from performing drive-tests on the user terminals (104) in said area when the number of user terminals (104) in said area is too low.

18. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that the apparatus (102) is configured to update the value of the counter when the number of user terminals (104) in said area changes.

19. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that the apparatus (102) is configured to update the value of the counter when a user terminal leaves and/or enters said area.

20. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that it is config^¬ ured to update the value of the counter periodically.

21. An apparatus as claimed in any one of the pre^¬ ceding claims, characterized in that said area com- prises a network cell, a location area, a routing area and/or a tracking area.

22. A computer-readable storage medium embodying a program of instructions executable by a processor to per^¬ form actions directed toward

maintaining, in a network apparatus (102), a threshold value regarding a minimum number of user terminals (104) in a predefined area of a network;

determining, in the network apparatus (102), a value of a counter regarding a number of active user ter- minals (104) currently located in said area;

comparing, in the network apparatus, the threshold value and the value of the counter;

wherein if, based on the comparing, it is found out that the value of the counter is below the threshold value, the method comprises defining, in the network appa^¬ ratus (102), that the activation of a minimization of drive-tests function is not allowed in said area.