WO2012045333A1

WO2012045333A1 - Configuration handling in communications systems

Info

Publication number: WO2012045333A1
Application number: PCT/EP2010/064834
Authority: WO
Inventors: Gyula Bodog; Malgorzata Tomala
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-10-05
Filing date: 2010-10-05
Publication date: 2012-04-12

Abstract

A method (200) of notifying a mobile communications network (204) about a minimisation of drive test MDT configuration, the method comprising the steps of: a mobile terminal (202) making a transition (218) from an idle state to a state in which a connection is established with the network; the mobile terminal determining whether it has already been configured with a previous MDT configuration; and the mobile terminal, in establishing the connection, providing a configuration indication to the network to prevent inadvertent replacement of the previous MDT configuration with a new MDT configuration (222).

Description

CONFIGURATION HANDLING IN COMMUNICATIONS SYSTEMS

This invention relates to configuration handling in communi- cations systems. It is particularly, but not exclusively, re^¬ lated to configurations applied for measurement reporting in mobile communications systems. It may apply to a cellular mo^¬ bile communications system. An important aspect in network planning to provide a wireless communications system is in ensuring that a network provides the necessary coverage. This may be to provide even coverage or to provide uneven coverage, for example better coverage being provided in areas in which there is the heaviest wire- less communications traffic. Coverage in this sense usually refers to the signal strength experienced by a mobile termi^¬ nal in a cell. It may also refer to the reliability of inter- cell handover. Although there have been considerable improvements made in network planning over the past few years enabling a planned network to have the kind of coverage which is desired, the operation of a network implemented according to such a plan may not be exactly as intended. For this reason, mobile net- work operators employ a procedure referred to as drive test^¬ ing in which vehicles equipped with special testing equipment travel around the area covered by a mobile network and col^¬ lect measurement data at different geographical locations in the form of parameters such as signal strength. This means that a mobile network operator can identify problems such as coverage holes or places where handover tends to fail and change the configuration of the network to ameliorate these problems, for example by adding base stations, or changing beam orientation of existing base stations.

Carrying out drive testing to obtain measurement data is ex^¬ pensive and inconvenient both in terms of the cost of the necessary equipment and of employees' or contractors' time. Therefore, it is desired to minimise the amount of drive testing which is conducted. It has been proposed in 3GPP (3rd Generation Partnership Project) to use subscriber mobile terminals (also referred to as user equipment or UE) to provide measurement data related to quality of connection over an air interface between themselves and a radio access network (RAN) of a mobile network and to use this data in a network manage^¬ ment system of the network in order to reduce the need to carry out drive tests. Although this may not completely eliminate the need for drive testing, it is hoped that if the majority of coverage assessments can be carried out based on measurement data obtained by the RAN in communicating with subscriber mobile terminals, there is scope for considerable cost savings. The capability to provide the necessary meas^¬ urement data from subscriber mobile terminals to minimise the amount of drive testing required is referred to as minimisa- tion of drive test (MDT) functionality.

Accordingly, it will be understood that it is known to have automatic collection of measurements from mobile terminals to enable easier monitoring of network performance and conse- quently to replace expensive drive tests performed manually by network operators .

It has been proposed to use trace functionality present within a network to gather the measurement data required for MDT. Trace functionality is able to carry out traces of two basic trace types:

i) a cell trace in which trace data is collected in one cell or a pre-defined list of cells; and

ii) a subscriber trace in which trace data is collected for a particular mobile terminal irrespective of which cell it has moved to.

To use a cell trace to gather the measurement data required for MDT, a command to carry out trace activation is sent to a suitable entity in the RAN such as a functionality control^¬ ling radio resource management of base station-type network elements which determines the mobile terminals present in a cell and then activates selected mobile terminals to carry out MDT measurements and provide MDT measurement data to the entity which can then provide this data to higher hierarchical levels for processing to produce results relating to geo^¬ graphical determination of coverage. It will be understood that a cell trace is transformed into a number of individual activation commands, each of which is received, and accepted, by relevant mobile terminals.

There are two types of MDT which correspond to the two trace types. The first is area-based MDT for which cell trace is used to activate MDT functionality in mobile terminals and the second is subscriber-based MDT for which subscriber trace is used for activating the MDT. In the case of area-based MDT, an MDT measurement command (also referred to as an MDT request) is sent by a management entity present in an operations and maintenance (OAM) func^¬ tion to one or more base stations of a particular cell or set of cells, and a base station which receives the command then sends individual MDT measurement commands to one or more se^¬ lected mobile terminals in its cell.

In the case of subscriber-based MDT, a particular mobile ter^¬ minal is identified by an international mobile subscriber identity (IMSI) or by an international mobile equipment iden^¬ tity (IMEI) (or IMEI software version IMEI (SV) ) . The management entity sends the MDT measurement command, together with a subscriber identifier, to a core network entity such as a mobility management entity (MME) or any other suitable entity depending on the network configuration such as a home subscriber server (HSS) , a serving GPRS support node (SGSN) , or a mobile switching centre (MSC) server. The relevant mobility entity determines the location of the subscriber in the net^¬ work and this core network mobility entity sends the MDT measurement command to a base station of the cell in which the subscriber is located and the base station then applies a suitable MDT configuration to the subscriber' s mobile terminal . An MDT measurement command indicates the type of reporting to be used and also the type of MDT configuration to be applied to mobile terminals. Currently, in 3GPP, two MDT reporting approaches are being considered. One is Immediate MDT report- ing and another is Logged MDT reporting. In Immediate MDT reporting, a mobile terminal carries out specified measurements and provides periodic and event-based real-time MDT reports while there is a Radio Resource Control (RRC) connection available between it and the network. If there is no RRC con- nection, the mobile terminal stops measuring (and therefore stops reporting) only to resume when an RRC connection again becomes available. In Logged MDT reporting, a mobile terminal does not carry out MDT reporting while there is an RRC con^¬ nection available between it and the network, but when there no RRC connection available, it carries out specified meas^¬ urements and generates MDT logs. These can then be sent to the network when an RRC connection is established or reestablished. The mobile terminal does not carry out specified MDT measurements until the RRC connection is released.

To configure a mobile terminal for Logged MDT reporting, a suitable MDT configuration is applied to the mobile terminal when there is an RRC connection in place between it and a base station. In this so-called RRC-connected mode, the mo- bile terminal is actively using a channel for control plane signalling between itself and the network. MDT data collection is done by the mobile terminal when it is in idle mode. Idle mode refers to periods of time during which no dedicated resources, for example radio resources, are being used by the mobile terminal. In idle mode, the mobile terminal listens to channels which are concerned with obtaining network access, for example channels which provide parameters needed by the mobile terminal to identify the network and gain access to it and which broadcast paging and notification messages. During such time periods there is no RRC connection in place between the mobile terminal and the network.

A Logged MDT reporting configuration typically specifies pa^¬ rameters to be measured, frequencies of measuring and report- ing, a period over which reporting is to be carried out, and a trace reference. It is known from standardisation activities, that when the mobile terminal gets RRC-connected again from idle mode, it will send an MDT log availability indica^¬ tion to the network to indicate the availability of a stored MDT log if it has an MDT log relevant to the radio access technology (RAT) type of the RRC connection. The log avail^¬ ability indication is sent in RRC signalling from the mobile station to the base station in a suitable RRC related mes^¬ sage. The base station can then decide whether to retrieve the data, and if so, the base station uses a suitable RRC signalling message, for example an UEInformationRequest mes^¬ sage, to initiate the mobile terminal to upload the MDT log to the base station. As discussed in the foregoing, a management entity may re^¬ quest a cell trace operation for MDT purposes in respect of a certain area. In this case, a base station may have been re^¬ quested to set up area-based logged MDT and a corresponding configuration applied to a mobile terminal when it was in RRC-connected mode. Accordingly, the mobile terminal is con- figured to collect, and log, MDT data. In this case there is a cell trace session ongoing in the base station. It is then possible that the management entity may be directed to carry out a subscriber trace in respect of that mobile terminal. In this case, the management entity will send the relevant MDT request to a suitable mobility entity in the core network which will then provide the MDT request to a base station which is responsible for the cell in which the subscriber is recorded as being located. The mobile terminal of the sub- scriber will then be configured for subscriber-based MDT data collection. This may be in respect of logged MDT reporting or immediate MDT reporting.

In arranging the subscriber' s mobile terminal to be config- ured for subscriber-based MDT, the core network is unaware that an area-based MDT configuration had previously been ap^¬ plied to the mobile terminal because it was located in the relevant cell. This is because the area-based MDT request was carried out based on cell trace functionality in which cell trace session activation is applied to the concerned base station directly from the management entity. Therefore, there is nothing to stop the subscriber-based MDT request being sent to the RAN. Although the management entity may know that there is a cell trace active in respect of a particular cell, and will also know a subscriber-based MDT operation has been requested, the management entity does not know whether the subscriber' s mobile terminal for which the subscriber-based MDT operation is to be applied is located in the particular cell. As a consequence, any MDT log which has been generated in the mobile terminal as a result of the area-based logged MDT operation may be overwritten when a subscriber-based MDT is applied to the mobile terminal.

Although it is possible for the radio network to infer from an MDT log availability indication that the mobile terminal has been configured for MDT, this is not wholly reliable be^¬ cause it is possible that no MDT log has yet been collected or the mobile terminal is connected via a RAT type other than the one for which MDT measurement data has been logged. Look- ing for a moment at the latter of these, if the mobile termi^¬ nal has been MDT configured in respect of a third generation RAN, that is a UTRAN, MDT log availability is sent only to a radio network controller (RNC) , but not to an eNodeB (eNB) of an long term evolution (LTE) RAN, that is an e-UTRAN, and therefore an eNB is unable to become aware that the mobile terminal has been configured for MDT. As a result, the eNB may seek to configure the mobile terminal for MDT in respect of an e-UTRAN. As a consequence, any MDT log which has been generated in the mobile terminal as a result of the MDT meas- urements carried out in relation to the UTRAN may be over^¬ written if the eNB configures the mobile terminal for MDT in respect of an LTE RAN. The same problem may occur if a UTRAN, and particularly an RNC, configures the mobile terminal for MDT when there is already present in the mobile terminal an MDT configuration for an e-UTRAN.

It will be understood that potential conflicts between al^¬ ready existing MDT configurations and newly applied MDT con^¬ figurations in mobile terminals is not correctly handled in management entities, and networks, according to the prior art. This is because the core network is in control of mobil^¬ ity management but the management entity does not exercise any such control, and does not have access to mobility- related information. Furthermore, when area-based MDT is re- quested, the core network is not actively involved.

According to a first aspect of the invention there is pro^¬ vided a method of notifying a network about a configuration, the method comprising the steps of:

a mobile terminal making a transition from an idle state to a state in which a connection is established with the network; the mobile terminal determining whether it has already been configured with a previous configuration; and

in the event that the mobile terminal has already been con- figured with a previous configuration, the mobile terminal, in establishing the connection, providing a configuration indication to the network to prevent inadvertent replacement of the previous configuration with a new configuration. The mobile station may determine whether it has previously been configured with a configuration prior to setting up the connection. Alternatively, it may do this during setting up the connection. The configuration may be one which has been applied to the mobile terminal for measuring and/or gathering data. It may have been applied for carrying out measurements and then re^¬ porting them. It may have been applied to cause the mobile terminal to gather and/or measure MDT measurements. The previous and/or the new configuration may have been applied to the mobile terminal by a network as a result of a management entity sending a request. The management entity may be an OAM function. The management entity may comprise a sub-system capable of generating and sending the request. The request may be received by a base station which then applies a configuration, corresponding to the request, to the mobile terminal . Preferably, the previous and/or the new configuration may be for the mobile terminal to carry out measure and/or gather data in a specified area. A corresponding configuration may have been applied to a number of mobile terminals. It may be a configuration applied specifically to that mobile terminal. In such a case, an associated request may be handled by a mo^¬ bility entity which determines the location of the mobile terminal and sends the request to that location.

Preferably, the previous and/or the new configuration may be for the mobile terminal to carry out measure and gather data. The previous and/or the new configuration may be for the mo^¬ bile terminal to measure and immediately report data, for ex^¬ ample by sending it to the network. Preferably, the configuration indication is provided to a base station in the network. The network may be able to use the configuration indication in a decision making process about whether the new configuration is to be applied to the mobile terminal. In its simplest form, the decision making is "yes, apply the pending new configuration" if the configura- tion indication indicates that the mobile terminal has not already been configured with a previous configuration, and "no, do not apply the new configuration" if the configuration availability indication indicates that the mobile terminal has already been configured with a previous configuration.

A method according to the invention may prevent inadvertent overwriting of a log of data which would otherwise result if a previous configuration is replaced by a new configuration.

Preferably, the configuration indication indicates that the configuration is for creating a log of data.

The connection may be a connection related to radio re- sources. It may be an RRC connection.

In addition to sending the configuration indication, the mobile terminal may send a log indication indicating that there is a log of data waiting in the mobile terminal to be re- trieved by the network.

Preferably, the mobile terminal is able to establish a con^¬ nection to a first network of a first type and a second net^¬ work of a second, different, type. The first and second net- works may cover a common area.

Preferably, if the mobile terminal has had applied to it the previous configuration, it has a flag set indicating this, generated as a result of a configuration relating to the first network or the second network having been applied. How- ever, it is not necessary for the flag to be associated with either network or either network type, and it may simply indicate "a configuration". If the mobile terminal has a con^¬ figuration relating to the first network, it will provide the configuration indication when it becomes connected to that network, and if the mobile terminal has a configuration re^¬ lating to the second network, it will provide the configura^¬ tion indication when it becomes connected to that network. Accordingly, if the mobile terminal has a configuration re- lating to the first network, when it becomes connected to the second network, the configuration indication may be sent even though the sending of this is triggered by the presence of a configuration in respect of the first network. In this way, the configuration indication is network-type agnostic.

The method may have a first part in which there is a set^¬ up/establishment procedure, a second part in which there is a request to apply a new configuration to one or more mobile terminals, and a third optional/conditional part in which there is a configuration command. The method may also have a network-based decision step. The method may also have a mo^¬ bile terminal-based step.

The mobile terminal may be configured with the previous con- figuration during a first period of time in which there is a connection between the mobile terminal and the network. During this period, the mobile terminal may send a message to the network indicating that no configuration has been set. In response to this, the network may decide to apply a new con- figuration to the mobile terminal. The first period of time may be followed by a second period of time during which the mobile terminal is idle. The mobile terminal may remain configured during this second period of time.

The second period of time may be followed by a third period of time in which there is a connection between the mobile terminal and the network. During this third period of time, the mobile terminal may send a message to the network indi^¬ cating that a previous configuration has been set. In response to this, the network may decide not to apply a new configuration to the mobile terminal. In one embodiment of the invention replacement of the previ^¬ ous configuration by the new configuration may only be prohibited if the previous configuration relates to one in which a collection of data such as a data log is generated. How^¬ ever, the network may be able to arrange for replacement of a previous configuration relating to one in which a collection of data is generated by the new configuration if a new configuration request has associated with it a sufficiently level of priority. In such an arrangement in which replace^¬ ment is permitted because of a priority request, the network may delay applying the new configuration until after the collection of data has been transferred to the network.

Preferably, the invention applies in the case of preventing a configuration relating to one in which a collection of data is generated being unintentionally overwritten by another configuration .

Inadvertent or unintentionally does not necessarily mean that overwriting is prevented in all cases. It may mean that over^¬ writing may be permitted if it is determined, for example in a network, that this may be permitted.

The network may be a mobile communications network. It may comprise a core network and a radio access network. It may be a cellular mobile communications network. It may be an LTE network. It may be a third generation network.

According to a second aspect of the invention there is pro- vided a network element, the network element being capable of:

handling a transition of a mobile terminal from an idle state to a state in which a connection is established with a net^¬ work;

receiving a configuration indication from the mobile terminal indicating whether the mobile terminal has already been con^¬ figured with a previous configuration; and

using the configuration indication in order not to request inadvertent replacement of the previous configuration with a new configuration.

Preferably, the network element is a base station. The net^¬ work element may be a functionality controlling radio re^¬ source management of base station-type network elements. According to a third aspect of the invention there is pro^¬ vided a mobile terminal, the mobile terminal being capable of:

making a transition from an idle state to a state in which a connection is established with the network;

determining whether it has already been configured with a previous configuration; and

in the event that it has already been configured with a pre^¬ vious configuration, in establishing the connection, provid- ing a configuration indication to the network to prevent inadvertent replacement of the previous configuration with a new configuration.

According to a fourth aspect of the invention there is pro- vided a communication network comprising a network element and a plurality of mobile terminals, the network element be^¬ ing capable of:

handling a transition of a mobile terminal from an idle state to a state in which a connection is established with a net- work;

using the configuration indication in order not to request inadvertent replacement of the previous configuration with a new configuration,

and the mobile terminal being capable of:

making a transition from an idle state to a state in which the connection is established with the network; determining whether it has already been configured with a previous configuration; and

According to a fifth aspect of the invention there is pro- vided a computer program product comprising software code that when executed on a computing system performs a method of notifying a network about a configuration, the method comprising the steps of:

in the event that the mobile terminal has already been con^¬ figured with a previous configuration, the mobile terminal, in establishing the connection, providing a configuration indication to the network to prevent inadvertent replacement of the previous configuration with a new configuration.

According to a sixth aspect of the invention there is pro- vided a method of handling a notification concerning a configuration, the method comprising the steps of:

a network element handling a transition of a mobile terminal from an idle state to a state in which a connection is estab^¬ lished with a network; the network element receiving a configuration indication from the mobile terminal indicating whether the mobile terminal has already been configured with a previous configuration; and

the network element using the configuration indication in order not to request inadvertent replacement of the previous configuration with a new configuration.

According to a seventh aspect of the invention there is pro- vided a computer program product comprising software code that when executed on a computing system performs a method of handling a notification concerning a configuration, the method comprising the steps of:

a network element handling a transition of a mobile terminal from an idle state to a state in which a connection is estab^¬ lished with a network;

the network element receiving a configuration indication from the mobile terminal indicating whether the mobile terminal has already been configured with a previous configuration; and

the network element using the configuration indication in order not to request inadvertent replacement of the previous configuration with a new configuration. Preferably, the computer program product has executable code portions which are capable of carrying out the steps of the method . Preferably, the computer program product is stored on a com^¬ puter-readable medium. It may be stored in a non-transient way . Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which :

Figure 1 shows a system according to the invention; and

Figure 2 shows a message sequence diagram according to the invention.

The invention will now be described in more detail in rela^¬ tion to Figure 1. Figure 1 shows an LTE mobile communications network 100 comprising a RAN 102 and a core network 104. The RAN has a number of base stations 106, 108, and 110 which provide radio access to mobile terminals 112, 114, and 116 present in cells 106', 108', and 110', and the core network 104 has functionality to provide for call switching/routing and call control, service provision, authentication and charging, and interconnection enabling access to other networks. In this embodiment, the base stations are eNBs .

In addition, an operations, administration, and maintenance (OAM) function 118 is linked to the core network 104 and is capable of configuring and provisioning network nodes of the RAN 102 and the core network 104. It also carries out various related tasks such as collecting network statistics, alarm monitoring and logging of events. The resulting statistics, alarms, and logs are used by a network operator to monitor the health and performance of the network 100. Although in this embodiment, the OAM function 118 is shown as being sepa^¬ rate from the core network 104, in other embodiments of the invention, the OAM function 118 may be present in the core network 104. In either case, both the core network 104 and the OAM function 118 are present within the domain of the network operator and both are under its control.

The OAM function 118 is provided with an MDT management en^¬ tity 120. This entity 120 controls MDT operation within the network 100, for example receiving instructions to arrange for MDT measurements to be gathered in respect of a particu^¬ lar subscriber or a specific geographic area of the network 100 and then sending out a necessary MDT request so that a base station or base stations can activate MDT measuring by a particular mobile terminal or by mobile terminals present in a particular location or locations (if relevant) . The MDT management entity 120 in the OAM function 118 cooperates with MDT units 122 in the base stations which receive MDT-related commands and take appropriate action. For example, an MDT unit 122 in a particular base station receives a command that MDT measurements are to be carried out in a particular cell, and as a result, it applies individual MDT configurations to suitable mobile terminals located in the cell which cause the mobile terminals to start making MDT measurements and to pro- vide MDT reports to the base station. The base station sends the MDT measurements in the form they are received or col^¬ lates or otherwise processes them, and then sends them to the OAM function 118 where they are processed and used to gener^¬ ate output data suitable for use in managing the network 100. It should be understood that Figure 1 is highly schematic and so is very simplified. In reality, there may be RANs of dif^¬ ferent RAT types extending over a common area with mobile terminals being able to connect to both. For example, there may be both a third generation 3G RAT type and an LTE RAT type. Each RAT type is able to send MDT requests so that mo^¬ bile terminals carry out MDT measurements in respect of that particular RAT type. Since MDT-related interactions between the mobile terminals and a RAN occur when there is an RRC connection, a network of a particular RAT type carries out MDT-related operations in ignorance of MDT-related operations being carried out in a network of another RAT type. There^¬ fore, in the prior art, it is possible in certain circum^¬ stances for an MDT request in respect of one RAT type to cause overwriting of an existing MDT configuration in a mobile terminal of another RAT type.

As discussed in the foregoing, a base station may have re^¬ ceived a request to apply an MDT configuration to a mobile terminal. This may be a subscriber-based MDT request which is specific to a particular mobile terminal (according to its IMSI or IMEI), or an area-based MDT request for which the base station will choose available mobile terminals which meet relevant criteria.

The base station is able to apply an MDT configuration when the mobile terminal becomes RRC-connected to the base sta^¬ tion. As discussed in the foregoing, the core network does not play any part in arranging area-based MDT activation be- yond routing the necessary messages. But the core network does play a part in arranging subscriber-based MDT activation because the core network has to locate the relevant mobile terminal and route the necessary messages to it. According to the invention, if the mobile terminal has been configured for MDT, it has a flag set indicating "MDT configuration already present" which has been generated as a re^¬ sult of a UTRAN MDT configuration or an e-UTRAN MDT configuration having been applied. However, the flag does not have to be specific in that it may be associated with either.

When the mobile terminal carries out an RRC set-up procedure with a base station to make an RRC connection to a base sta^¬ tion, the flag triggers the sending of a configuration avail- ability indication to the base station. This may be an indi^¬ cation capable of indicating to the base station that the mo^¬ bile station has already been configured to carry out MDT- related measurements or that the mobile station has not been configured to carry out MDT-related measurements. The con- figuration availability indication can be considered to be an indication that the configuration may be of the type to cause the collection and creation of a data log.

The base station receives the configuration availability in- dication and is then able to use it in a decision-making process about whether the MDT configuration is to be applied to the mobile terminal. In its simplest form, the decision making is "yes, apply the MDT configuration" if the configu^¬ ration availability indication indicates that the mobile ter- minal has not already been configured to carry out MDT- related measurements, and "no, do not apply the MDT configu^¬ ration" if the configuration availability indication indicates that the mobile terminal has already been configured to carry out MDT-related measurements.

Therefore, whenever a mobile terminal becomes connected to the base station in a way in which it makes itself available to be MDT configured, the sending and use of the configura^¬ tion availability indication is able to control whether or not a pending, or newly received (that is, received during the period of time during which the mobile terminal is RRC- connected to the base station) , MDT configuration is to be applied to the mobile terminal. In this way, the loss of MDT logged data can be avoided.

In a case in which there are two RAT types extending over a common area, in respect of each RAN a mobile terminal will provide the configuration availability indication when it be^¬ comes RRC-connected if it has been configured to carry out MDT measurements. Therefore, if the mobile terminal is con^¬ figured to carry out MDT measurements in a UTRAN network, it will provide the configuration availability indication when it becomes RRC-connected to the UTRAN. Likewise, if the mo^¬ bile terminal is configured to carry out MDT measurements in an e-UTRAN network, it will provide the configuration availability indication when it becomes RRC-connected to the e- UTRAN. According to the invention, if a mobile terminal is already MDT configured for a first RAT type, when it becomes RRC-connected to a RAN of a second, different, RAT type, the RRC connection set-up complete message sent to the RAN of a second, different, RAT type includes the configuration avail^¬ ability indication even though the corresponding flag in the mobile terminal has been set as a result of there being an MDT configuration in respect of the first RAT type. In this way, information (configuration availability indication) related to one RAT type is used in the base station interacting with another RAT type. This is possible because the configu^¬ ration availability information is RAT agnostic. Figure 2 shows a sequence 200 of messages exchanged between a mobile terminal (indicated as UE) 202 and a RAN 204, and an OAM function 206 and the RAN 204 according to the invention. In the embodiment of Figure 2, the RAN is a UTRAN 204, al^¬ though it will be understood that the invention also applies to message exchange between a mobile terminal and other kinds of RAN, for example an e-UTRAN. The message exchange has two sections with each section based on an RRC connection set-up. The first section has three parts, a first part 208 having a modified RRC set-up/establishment procedure, a second part 210 having a MDT request to apply a new configuration to one or more mobile terminals, and a third part 212 having a MDT configuration command. In addition, there are two steps which do not involve message exchange, a first RAN-based decision 214, and a second mobile terminal-based step 216. The second section has two parts, a first part 218 having a modified RRC set-up/establishment procedure and a second part 220 having a MDT request to apply a new configuration to one or more mo^¬ bile terminals. In addition, there is a RAN-based decision step 222 which does not involve message exchange. Although Figure 2 shows a UTRAN 204 (and can also apply to an e-UTRAN) , the network element which receives and sends mes^¬ sages and carries out steps 214 and 222 is a base station and may be an RNC (or an eNB) .

Initially, the mobile terminal 202 is idle. It has not been configured with an MDT configuration. An event then occurs, for example an RRC Connection Request message is sent from the mobile terminal 202 due to a mobile-originating call, to cause the mobile terminal 202 to set up an RRC connection 208 with the UTRAN 204 and so it makes an idle mode-RRC-connected transition. The modified RRC set-up/establishment procedure 208 comprises three messages: an RRC connection request mes^¬ sage sent by the mobile terminal 202; an RRC connection set- up message sent by the UTRAN 204; and an RRC connection set^¬ up complete message sent by the mobile terminal 202. The first two messages are the same as those used in known RRC connection procedures. The third message is a modified ver^¬ sion of the known RRC connection set-up complete message since it has been modified to be able to include the configu^¬ ration availability indication. In this case, because the mo^¬ bile terminal 202 has not been configured with an MDT con^¬ figuration, the configuration availability indication is set to "no configuration set". It may be possible in the case that no configuration has been set for no configuration availability indication to be included in the RRC connection set-up complete message in which case this message could be the same as the corresponding message in the prior art. Al^¬ ternatively, the RRC connection set-up complete message may be modified so that it contains an extra field to show ex- plicitly whether the state of the mobile terminal is "con^¬ figuration set" or "no configuration set". Since in this implementation, the configuration availability indication simply indicates a "set" or a "not set" state, it may take the form of a single bit having a 1 or 0 value.

Following this, the mobile terminal 202 is RRC-connected with the UTRAN 204 and the UTRAN sets a flag to indicate that, in respect of that RRC connection, the associated mobile termi- nal 202 has not been configured with an MDT configuration.

The OAM function 206 then sends an MDT request 210 to the UTRAN 204. This can be either for area-based MDT or for subscriber-based MDT. In the latter case, the MDT request to ap- ply a new configuration 210 will not go directly to the UTRAN 204 but will have been routed via a mobility entity as dis^¬ cussed in the foregoing.

The UTRAN 204 receives the MDT request 210, and makes the RAN-based decision 214 to decide whether to apply the new configuration. In this case, the UTRAN 204 refers to the flag indicating that, in respect of that RRC connection, the asso^¬ ciated mobile terminal has not previously been configured with an MDT configuration, and so decides that the MDT re- quest can be acceded to and the UTRAN 204 sends the MDT con^¬ figuration command 212 to the mobile terminal 202. The mobile terminal 202 then carries out the mobile terminal-based step 216 and the MDT configuration is applied to the mobile termi^¬ nal 202. At some later point, the mobile terminal 202 becomes idle again. As a result, the RRC connection is dismantled and the UTRAN does not keep any MDT context information indicating that there has been an MDT configuration applied to the mo- bile terminal. However, the mobile terminal 202 remains con^¬ figured with the MDT configuration.

An event then occurs, for example network paging of the mo^¬ bile terminal 202 to inform it about an incoming call, to cause the mobile terminal 202 to set up an RRC connection 218 with the UTRAN 204 and so it makes an idle mode-RRC-connected transition. The modified RRC set-up/establishment procedure 218 comprises the same messages as the modified RRC set^¬ up/establishment procedure 208 although the third message (RRC connection set-up complete) contains different informa^¬ tion. In this case, because the mobile terminal 202 has been configured with an MDT configuration, the configuration availability indication in the RRC connection set-up complete message is set to "configuration set".

Following this, the mobile terminal 202 is RRC-connected with the UTRAN 204 again and the UTRAN sets a flag to indicate that, in respect of that RRC connection, the associated mo^¬ bile terminal has been configured with an MDT configuration.

The OAM function 206 then sends an MDT request 220 to the UTRAN 204. This can be either for area-based MDT or for subscriber-based MDT. In the latter case, the MDT request 220 will not go directly to the UTRAN 204 but will have been routed via a mobility entity as discussed in the foregoing. It should be noted that the OAM function which sent the "first MDT request" does not have to be the same OAM function as that which sent the "second MDT request". The OAM function which sent the "first MDT request" may be an OAM function controlling OAM aspects of a first network type such as a third generation network and the OAM function which sent the "second MDT request" may be an OAM function controlling OAM aspects of a second network type such as an LTE network.

The UTRAN 204 receives the MDT request 210, and makes the RAN-based decision 222 to decide whether to apply the new configuration. In this case, the UTRAN 204 refers to the flag indicating that, in respect of that RRC connection, the asso^¬ ciated mobile terminal has previously been configured with an MDT configuration and so decides that the MDT request cannot be acceded to and so the UTRAN 204 does not send an MDT con^¬ figuration command to the mobile terminal 202. As a result, the mobile terminal 202 does not apply a new MDT configura^¬ tion to itself, and therefore, any MDT logged measurements which have been collected are not overwritten.

The decision-making in the RAN (and particularly the relevant base station in the RAN) may be as simple as that described in the foregoing in which a previously applied MDT configura- tion cannot be overwritten or might be more sophisticated. For example, since it is recognised in the invention that it is advantageous to avoid overwriting an MDT log, then such overwriting may only be prohibited by the RAN (and particu^¬ larly the relevant base station in the RAN) , that is in the decision 222 (Decision: new configuration to be applied? - no) if a previously applied MDT configuration relates to Logged MDT, irrespective of whether this is subscriber-based Logged MDT or area-based Logged MDT. The RAN may permit over^¬ writing when a previously applied MDT configuration relates to Immediate MDT.

In a variant of the invention, even if the configuration availability indication of a mobile terminal indicates that the mobile terminal has already been configured to carry out MDT-related measurements, the base station is permitted to apply a new MDT configuration to the mobile terminal if a new MDT configuration request has associated with it a suffi^¬ ciently level of priority. For example, in the case of rela^¬ tively serious network problems in a particular area, the OAM function might need to quickly collect as many measurements as possible relating to network performance in order that re^¬ medial action can be taken as soon as reasonably practicable. Accordingly, a new area-based MDT request generated in re^¬ sponse to these problems by the management entity, that is the MDT management entity 120, might be sufficiently impor^¬ tant to justify the overwriting of any MDT configurations which are currently being used in the area, irrespective of whether this is subscriber-based Logged MDT or area-based Logged MDT. In a case where overwriting is permitted because of a priority request, the base station may delay applying the new MDT configuration immediately, and may instruct the mobile terminal to transfer any MDT log or any MDT measure^¬ ments to the base station and only when this has been done, apply the new, priority, MDT configuration to the mobile ter- minal . In another variant of the invention, the configuration availability indication may be sent in a message involved in RRC re-establishment, that is the connection procedure used, for example, in case of radio link failure (RLF) rather than in the case of "pure" RRC establishment. It may be sent in an RRC Reestablishment Complete message which completes the re- establishment procedure and confirms that is successful. This message corresponds to the RRC connection set-up complete message. Sending the configuration availability indication in a message involved in RRC re-establishment serves to remind the network, and particularly the relevant base station, that the mobile terminal has an MDT configuration. The mobile terminals and the base stations are specifically configured to operate according to the invention. A mobile terminal is configured to use the application of an MDT con^¬ figuration to set a flag indicate its state as to whether an MDT configuration has already been applied to it, and also to include a corresponding configuration availability indication in a message sent during establishment of an RRC connection, and a base station is configured to receive the configuration availability indication and take appropriate measures with respect to applying an MDT configuration.

The invention may be applied to prevent a Logged MDT configu^¬ ration in a mobile terminal being unintentionally overwritten by another MDT configuration, whether this is another Logged MDT configuration or an Immediate MDT configuration. In a particular embodiment of the invention, the mobile terminal may be capable of being configured with both a Logged MDT configuration and an Immediate MDT configuration. In this case, the invention may apply to prevent overwriting in the following situations:

In this embodiment, it is not necessary for the invention to prevent overwriting in situations in which the mobile termi^¬ nal 202 has been configured with a Logged MDT configuration, whether this is area-based or subscriber-based, and the OAM function 206 requests that a base station applies an Immedi^¬ ate MDT configuration, whether this is are-based a or subscriber-based, to the mobile terminal 202

The configuration availability indication may be independent of the log availability indication since it is used for a different purpose. Therefore, they may be sent to the base station in different messages, or different parts of the same message. In one embodiment of the invention, the mobile ter^¬ minal omits the sending of the configuration availability in- dication if the mobile is going to send the log availability indication when the mobile terminal becomes RRC-connected again from idle mode. This may save on messaging/data trans^¬ mission. In this case, the base station is able to use the log availability indication in decision-making about whether to apply a pending or a newly received MDT configuration to the mobile terminal. In another embodiment of the invention, there is a common field useable both for the log availability indication and the configuration availability indication. The mobile terminal puts an indication indicating the availabil^¬ ity of a log of data into this field which such a log is available or puts an indication indicating that an MDT configuration has been applied to the mobile terminal if this is the case and there is no MDT log available. Of course, if there is no MDT log, and no MDT configuration has been ap^¬ plied to the mobile terminal, this field may contain a "null" entry.

It will be understood that in the foregoing, references to "base stations" may refer to those network elements providing wireless connectivity, such as eNBs, or to the functional- ities controlling radio resource management of base station- type network elements, such as RNCs, or the relevant part of eNBs, as the context requires.

Therefore, the invention is able to solve the problem that although a base station control functionality might have con^¬ figured mobile terminals in a cell for Logged MDT, and in particular for area-based Logged MDT, such an MDT-configured mobile station going into an idle state dismantles its RRC connection so that, when the mobile terminal establishes a new RRC connection at a later time, the base station control functionality is unable to associate this new RRC connection with the mobile terminal which it configured for Logged MDT.

Although in the foregoing example, the invention is imple- mented in an LTE system and the network elements are eNBs, the invention may be applied to other systems, including in a third generation system. In this case, the base station is an RNC . It will be understood that although the invention has been described in the context of MDT configurations, it can be applied to any type of configuration, whether this relates to a configuration to carry out measurements or a configura^¬ tion to log any kind of information. Furthermore, it is not limited to applications within a mobile communications net^¬ work and may apply to fixed networks.

In addition, although the embodiments described include send^¬ ing a configuration availability indication in an RRC connection set-up complete message, the indication does not have to be sent in this message but may be sent in any message in- volved in RRC set-up. Furthermore, in another implementation of the invention, a configuration availability indication may be sent in a message unrelated to any RRC set-up procedure and may be sent in any message involved in a different kind of connection establishment or re-establishment procedure.

While preferred embodiments of the invention have been shown and described, it will be understood that such embodiments are described by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the scope of the present inven- tion. Accordingly, it is intended that the following claims cover all such variations or equivalents as fall within the spirit and the scope of the invention.

Claims

1. A method of handling a notification concerning a configuration, the method comprising the steps of:

2. A method of notifying a network about a configuration, the method comprising the steps of:

in the event that the mobile terminal has already been con^¬ figured with a previous configuration, the mobile terminal, in establishing the connection, providing a configuration in- dication to the network to prevent inadvertent replacement of the previous configuration with a new configuration.

3. A method according to claim 1 or claim 2 in which the previous configuration and the new configuration are applied as a result of a management entity sending a request.

4. A method according to claim 3 in which the request is received by a base station which then decides whether to ap^¬ ply a configuration, corresponding to the request, to the mo- bile terminal.

5. A method according to any preceding claim in which the network is able to use the configuration indication in a decision making process about whether the new configuration is to be applied to the mobile terminal.

6. A method according to any preceding claim in which the mobile terminal is able to establish a connection to a first network of a first type and a second network of a second, different, type covering a common area.

7. A method according to claim 6 in which the mobile terminal has a configuration relating to the first network and when the mobile terminal becomes connected to the second net- work, the configuration indication is sent even though the sending of this is triggered by the presence of a configura^¬ tion in respect of the first network.

8. A method according to any preceding claim in which the network is able to arrange for replacement of a previous con^¬ figuration relating to one in which a collection of data is generated by the new configuration if a new configuration request has associated with it a sufficiently level of prior^¬ ity.

9. A method according to any preceding claim in which the configuration has been applied to the mobile terminal for gathering data.

10. A method according to any preceding claim in which the network uses the configuration indication to prevent inadvertent overwriting of a log of data which would otherwise re^¬ sult if the previous configuration is replaced by the new configuration .

11. A method according to any preceding claim in which the configuration applied is to cause the mobile terminal to gather MDT measurements.

12. A network element, the network element being capable of: handling a transition of a mobile terminal from an idle state to a state in which a connection is established with a net^¬ work;

13. A mobile terminal, the mobile terminal being capable of: making a transition from an idle state to a state in which a connection is established with the network;

determining whether it has already been configured with a previous configuration; and in the event that it has already been configured with a pre^¬ vious configuration, in establishing the connection, providing a configuration indication to the network to prevent inadvertent replacement of the previous configuration with a new configuration.

14. A communication network comprising a network element and a plurality of mobile terminals, the network element being capable of:

receiving a configuration indication from the mobile terminal indicating whether the mobile terminal has already been con- figured with a previous configuration; and

and the mobile terminal being capable of:

making a transition from an idle state to a state in which the connection is established with the network;

in the event that it has already been configured with a pre- vious configuration, in establishing the connection, providing a configuration indication to the network to prevent inadvertent replacement of the previous configuration with a new configuration.

15. A computer program product comprising software code that when executed on a computing system performs a method of han^¬ dling a notification concerning a configuration, the method comprising the steps of: