WO2015195010A1

WO2015195010A1 - Method and device for detecting a neighbor cell relation in a cellular communication network

Info

Publication number: WO2015195010A1
Application number: PCT/SE2014/050755
Authority: WO
Inventors: Sofia BRISMAR; Lena MELIN
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2014-06-18
Filing date: 2014-06-18
Publication date: 2015-12-23

Abstract

There is provided a method performed by a network node for detecting a neighbor cell relation between cells in a cellular communication network. The method comprises the step of triggering (S1) a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell. The method also comprises the step of receiving (S2) information enabling a determination of the identity of the second cell selected by the UE. The method also comprises the step of identifying (S3), based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor cell relation between the first cell and the second cell. In this way, an efficient way of detecting a neighbor cell relation is provided. There is also disclosed a corresponding network node, apparatus, computer program and a computer program carrier.

Description

METHOD AND DEVICE FOR DETECTING A NEIGHBOR CELL RELATION IN A CELLULAR COMMUNICATION NETWORK

TECHNICAL FIELD

The proposed technology generally relates to a method for detecting a neighbor cell relation between different radio access technologies, and a corresponding network node, apparatus, computer program and a computer program carrier.

BACKGROUND

Later generations of cellular communication networks are renowned for their complexity. A large amount of wireless devices and User Equipment's should be able to communicate with each other and with relevant network nodes as seamless as possible. The complexity related to the management of such networks has created an urge to design network solutions where the demands on management are softened. As an example, the evolvement of Self-Organized Networks, SONs, have become an important feature to achieve such a simplification of network management. The development of SONs is, beside the potentially overarching aim to reduce the complexity, also important when considering the need for heterogeneous networks and for optimizing, e.g. Wideband Code Division Multiple Access, WCDMA, Radio Access Network, RAN, for the next wave of mass-market operators.

An important feature in modern and future cellular communication networks, in general, and the development of SONs, in particular, is related to the management of neighbor cell relations. The management of neighbor cell relations can be seen as an important cornerstone in order to achieve efficient Self Organized Networks, SON. Moreover, if such neighbor cell relations can be automatically generated this would, aside from lowering installation and operation costs for operators, also improve the Key Performance Indicator, KPI, retainability. The technology behind automatically generated neighbor cell relations is generally referred to as Automatic Neighbor Relations, ANR and such neighbor cell relations are often maintained in one or more databases; for example in a neighbor cell list or, equivalently, a neighbor cell table. It would be highly desirable if a network node had an at least satisfactory knowledge about the neighbor cell relations between the cells within the network since this would make a lot of the operations that are managed by, or under the control of, the network node more robust. Some standardized network solutions, for example, even require information about neighbor cell relations to function properly. A possible example of an operation that would benefit from information about neighbor cell relations is the handover of a User Equipment between different cells. A knowledge about neighbor cell relations would, for example, reduce the amount of dropped calls during handover. It would also facilitate the management of the network, for example by making manually performed additions of neighbor relations more or less redundant. Since a cellular communication network in general is gradually evolving over time, new neighbor cells will frequently be added to the cellular communication network and new interference patterns among the cells will emerge. In order for the network node to maintain relevant information about neighbor cell relations, measures are needed that will enable a network node to update its knowledge about neighbor cell relations^{^}between cells^hrough the means of detecting missing neighbor cell relations.

A problem is that manual configuration of neighbor cell relations takes a lot of time for operators. In light of this, the design of efficient mechanisms that are able to detect missing neighbor cell relations has become increasingly important and several different measures have been proposed.

In one of the known methods, the User Equipment, UE reports detected cells to the Radio Network Controller, RNC. The RNC may order the UE to measure and report missing cells, i.e. cells that are not already defined in a neighbor cell list. The order is sent to the UE in a MEASUREMENT CONTROL message together with other measurement control information such as event/reporting criteria, neighbor cell list, measurement quantities, measurement command. The UE will apply the same measurement control information on all cells, i.e. both detected set cells and cells listed in a neighbor cell list. If a detected set cell triggers a measurement event the UE will send a MEASUREMENT REPORT message to the RNC. The RNC will evaluate the MEASUREMENT REPORT message to find out if the reported cell is already defined as a neighbor or not. If not, it can be added as a new neighbor relation. UE has to be in compressed mode in order to measure and report detected set cells. Compressed mode consumes additional downlink, DL, power and reduces uplink, UL, coverage as well as UL/DL data throughput. ANR logging has been proposed as an optional feature to detect missing neighbor relations in Ref [1]. When the feature is activated the User Equipment, UE, will measure and record detected set cells in Idle mode, UTRAN Registration Area Paging Channel, URA_PCH, state and Cell Paging Channel, CELL_PCH, state. The report can be retrieved by the Radio Network Controller, RNC, when the UE becomes active, i.e. when the UE is in Cell Dedicated Channel, CELL_DCH, and Cell Forward Access Channel, CELL_FACH, state. Each report contains up to four missing relations detected by the UE. The UE may log and report Intra-frequency, IAF, Inter-frequency, IEF, Long Term Evolution, LTE and Global Systems for Mobile communications, GSM, relations.

WO 2014/011091 relates to a technique for updating neighbor cell relations in a cellular communication network. A User Equipment, UE, switches from being served in a source cell by a source base station to being served in a target cell by a target base station. The UE sends an identifier of the source cell and a request for a mobility report to the target base station. The target base station sends a mobility report to the source base station. The mobility reporting that a successful switch has taken place between the source cell and the target cell enables updating of the neighbor cell relations based on the mobility report. SUMMARY

The proposed technology aims to provide mechanisms that at least partially overcome some of the drawbacks within the art and ensures an efficient detection of a neighbor cell relation between cells in a cellular communication network.

It is an object to provide efficient detection of a neighbor cell relation in cellular communications.

It is a specific object to provide a method, performed by a network node, for detecting a neighbor cell relation.

It is another specific object to provide a network node configured to detect a neighbor cell relation.

It is also a specific object to provide an apparatus configured to detect a neighbor cell relation. Yet another a specific object is to provide a computer program comprising instructions, which when executed by at least one processor, cause the at least one processor to detect a neighbor cell relation.

Still another specific object is to provide a carrier comprising such a computer program.

This and other objects are met by embodiments of the proposed technology.

According to a first aspect, there is provided a method performed by a network node for detecting a neighbor cell relation between cells in a cellular communication network. The method comprises the steps of: • triggering a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell;

• receiving information enabling a determination of the identity of the second cell selected by the UE;

• identifying, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor cell relation between the first cell and the second cell.

In this way it is provided an efficient way of detecting a neighbor cell relation.

According to a second aspect, there is provided a network node configured to detect a neighbor cell relation between cells within a cellular communication network,

• wherein the network node is configured to trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell; and

• wherein the network node is configured to receive information enabling a determination of the identity of the second cell selected by the UE; and

• wherein the network node is configured to identify, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

According to a third aspect, there is provided a computer program comprising instructions, which when executed by at least one processor, cause the processor(s) to:

• trigger a User Equipment, UE, served in a first cell in a cellular communication network, to perform a cell selection process causing the UE to select a second cell;

• read information enabling a determination of the identity of the second cell selected by the UE; • identify, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

According to a fourth aspect, there is provided a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

According to a fifth aspect, there is provided a network node for detecting a neighbor cell relation between cells in a cellular communication network, wherein the network node comprises:

• an initiating module for triggering a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell;

• a reading module for reading information enabling a determination of the identity of the second cell selected by the UE; and

•an identification module for identifying, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

According to a sixth aspect there is provided a an apparatus configured to detect a neighbor cell relation between cells within a cellular communication network, wherein the apparatus comprises a processor and a memory, the memory comprising instruction executable by the processor, whereby the processor is operative to:

• trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell; and

• read information enabling a determination of the identity of the second cell selected by the UE; and • identify, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

Other advantages will be appreciated when reading the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating an example of a cellular communication network.

FIG. 2 is a schematic flow diagram illustrating an example of a method, performed by a network node, for detecting a neighbor cell relation in a cellular communication network according to an embodiment. FIG.3 is a schematic flow diagram illustrating an example of a method, performed by a network node, for detecting a neighbor cell relation in a cellular communication network and creating an instance of a neighbor cell relation according to an embodiment. FIG.4 is a schematic block diagram illustrating an example of a network node according to an embodiment.

FIG. 5 is a schematic block diagram illustrating an example an example of an apparatus/network node that is configured to detect a neighbor cell relation in a cellular communication network, as well as a computer program and corresponding computer program product according to an embodiment. FIG. 6 is a schematic block diagram illustrating a network node configured to detect a neighbor cell relation in a cellular communication network.

FIG. 7 is a schematic signaling diagram illustrating an example of signaling for detection of a neighbor cell.

FIG. 8 is a schematic signaling diagram illustrating an example of signaling for detection of a neighbor cell relation between cells controlled by a common Radio Network Controller.

FIG. 9 is a schematic signaling diagram illustrating an example of signaling for detection of a neighbor cell relation between cells under the control of different Radio Network Controllers, RNCs FIG. 10 is a schematic signaling diagram illustrating an example of signaling for detection of a neighbor cell relation during a RRC Connection Release with redirect to another frequency.

FIG. 1 is a schematic diagram illustrating an example of how to create an instance of a neighbor cell relation according to an embodiment.

DETAILED DESCRIPTION Throughout the drawings, the same reference designations are used for similar or corresponding elements.

For a better understanding of the proposed technology, it may be useful to begin with a brief overview of a cellular communication network with reference to the particular example of FIG. 1.

In this example, the overall cellular communication network comprises a base station 20. Base station 20, has a number of cells, of which at least one serves one or more User Equipments, UEs, such as UE 10. For simplicity only three cells, a first cell, a second cell and a further cell defined as neighbour cell to these are shown in in the figure. In the cellular communication network, the base station 20 may be connected to a network node 100. By way of example, the network node 100 may be responsible for controlling the base station. The network node 100 may also be responsible for detecting and/or managing neighbor cell relations, as will be explained below. It should be noted that cells within a cellular communication network may belong to the same base station but that it is also possible that they belong to different base stations.

FIG.2 is a schematic flow diagram illustrating an example of a method performed by a network node for detecting a neighbor cell relation between cells in a cellular communication network. The method basically comprises the steps of:

•triggering S1 a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell;

•receiving S2 information enabling a determination of the identity of the second cell selected by the UE;

•identifying S3, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor cell relation between the first cell and the second cell.

The proposed method provides an efficient way of detecting a neighbor cell relation between cells within a cellular communication network. The proposed technology does not require any UE impact. The technology does not require the UE to perform measurements in active mode, and compressed mode is not needed. The proposed technology further provides a time efficient way for detecting neighbor cell relations between cells within a cellular communication network that avoids time consuming post-processing of statistics. A schematic signaling diagram showing the signaling for finding a neighbor cell relation is disclosed in FIG.7. In an exemplary embodiment, the neighbor relation may be identified by checking whether the second cell is defined as a neighbor cell of the first cell and, if the second cell is not defined as a neighbor cell of the first cell, identifying the second cell as a neighbor cell of the first cell. This may for example be effectuated by checking existing neighbor cell relations in a neighbor cell list or equivalent representation of the neighbor cell relations.

In an optional embodiment, the network node may also create an instance of the identified neighbor cell relation between the first cell and the second cell, as indicated by the optional step S4 in FIG. 3. As will be exemplified later on, although the actual neighbor cell relation may be detected by the network node, an instance of the neighbor cell relation may be created and/or managed in another network component such as an Operations Support System or similar network management system in another part of the network. By way of example, the instance of the neighbor cell relation may be created as an entry representing the neighbor cell relation in a neighbor cell list, as will be explained in more detail later on.

In an optional embodiment the network node may update a neighbor cell list by entering the neighbor cell relation instance into the neighbor cell list. As will be exemplified below with reference to FIG. 11 , although the actual neighbor cell relation may be detected by the network node, an instance of the neighbor cell relation may be created and/or managed in another network component such as an Operations Support System or similar network management system in another part of the network. By way of example, the instance of the neighbor cell relation may be created as an instance representing the neighbor cell relation in a neighbor cell list, as will be explained in more detail below.

FIG. 11 is a schematic diagram illustrating an example of how to create an instance of a neighbor cell relation according to an embodiment. As an example, the neighbor cell relation can be manifested and created as an instance of a neighbor cell list. FIG. 11 shows an example of neighbor cell lists for a number of cells A to Z. For each cell, such as Cell A, there is a list of neighbor cells. In this example, the neighbor cell list for Cell A indicates that Cell A has neighbor relations with Cell I, Cell J, and Cell K. When a new neighbor cell relation is detected for Cell A, an instance of the new cell such as Cell B is created in the neighbor cell list of Cell A, as indicated in the example of FIG. 11.

In another exemplary embodiment, the network node may trigger the cell selection process by ordering the UE to change Radio Resource Control, RRC, mode or Radio Resource Control, RRC, state.

The above mentioned RRC is a protocol that belongs to the Universal Mobile Telecommunications System, UMTS, Wideband Code Division Multiple Access, WCDMA, protocol stack and normally handles the control plane signaling between UEs and the radio access network.

As a particular example, the network node may order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH, state or from a RRC connected mode to a RRC Idle mode.

In one possible embodiment may the network node order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH state and provides the UE with information relating to the target frequency to be used by the UE when in the CELL_FACH state. It might for example provide the UE with information that it should change the frequency to a different frequency than the frequency currently used. By way of example, the network node may trigger the UE to perform the cell selection process during UE inactivity to avoid disturbing the end-users. For example, the network node could, in an optional embodiment, trigger the UE to perform the cell selection process based on performed downlink throughput measurements. In other words, the network node keeps track of downlink throughput and selects a particular instance in time when to initiate the cell selection procedure. The network node may in a possible alternative embodiment trigger the UE to perform a cell selection process by initiating a Radio Resource Control, RRC, connection release procedure. According to a particular example, the network node may order the UE to release its radio connections by sending a Radio Resource Control, RRC, connection release message including redirection information to the UE.

Ultimately, the network node receives information, also referred to as cell identity information, representing the identity of the second cell selected by the UE. By way of example, this information may originate from an appropriate node for example a Base Station, BS. In other words, according to an exemplary embodiment the information enabling the determination of the identity of the second cell may be obtained from a base station serving the UE in the second cell.

In an alternative embodiment the network node could instead receive information, also referred to as cell identity information, representing the identity of the second cell selected by the UE, from the RNC serving the base station in the cell selected by the UE.

In a particular embodiment of the method, the network node may trigger the UE to perform the cell selection process without indicating any target cell. In this way the UE itself will select an appropriate cell. It should though be understood that the selection of cell(s) may be limited to cells operating in a certain frequency interval, or other suitable constraint, but it is not desirable to restrict the redirection to a single target cell.

In a possible exemplary embodiment the network node elects, from a number of cells serving the UE, the first cell to act as a basis relative to which a neighbor relation should be identified. With reference to the example of FIG. 1 , this means that the UE 10 may actually be served by a number of cells of the base station 20 40. The network node 100 may elect one of the cells, e.g. the cell denoted the first cell in FIG. 1 relative to which new neighbor cell relations should be detected or identified.

The network node may, in an optional embodiment, send a paging message to the UE in order reveal the identity of the selected second cell based on the response to the paging message. This might be performed in order for the UE to reveal the identity of the second cell as soon as possible and not wait until it becomes necessary to transmit uplink/downlink, UL/DL, data. This could also ensure that the neighbor relation is securely detected since it avoids the possibility that the UE have moved over cell borders in the time between the cell selection and the time when data for UL/DL traffic arrives.

In an optional embodiment of the proposed method, the network node could provide the UE with information relating to the target frequency when triggering the UE to perform a cell selection process.

According to a particular embodiment the network node could be a Radio Network Controller, RNC.

To provide a better understanding of the proposed technology a few non-limiting examples will now be described with reference to FIGs 8- 0.

Example 1 : Detection of a neighbour cell relation between cells controlled by a common Radio Network Controller.

FIG. 8 is a schematic signalling diagram illustrating an example of the signalling for detection of a neighbor cell relation. The diagram illustrates the signalling between two Radio Base Stations, RBSs, a RBS-Cell A serving a Cell A and RBS-Cell B serving Cell B, a Serving Radio Network Controller, SRNC and a User Equipment. By way of example, initially the UE is served in a first cell, Cell A by RBS-Cell A under the control of SRNC. A possible initial configuration could be that the UE is in an initial state CELL_DCH and a Packed Switched Radio Bearer, PS RB, is established between the UE and the serving RNC, SRNC. 1: At a particular moment the SRNC decides to trigger a down-switch of the UE from the initial CELL_DCH state to a CELL_FACH. This could for example be triggered by inactivity of the UE or by means of downlink, DL, throughput measurements or by reception of a SIGNALLING CONNECTION RELEASE INDICATION message sent by the UE.

The serving RNC, SRNC might further decides whether the connection should be switched down to CELL_FACH on the same frequency, or to another frequency covering the same geographical area. A decision to switch the UE to another frequency might be based on inter-frequency load sharing criteria, i.e. the UE is redirected to another WCDMA carrier that could provide better user experience. Existing load sharing triggers might be used but it might also be possible to introduce additional specific triggers in order to speed up detection of new Inter- frequency, IEF, relations. Some example of such specific triggers are listed below:

- Trigger redirect to another frequency for a fraction of all CELL_DCH to CELL_FACH transitions where the load sharing criteria are not fulfilled. The

RNC could ensure that the triggered redirections are spread among the users, i.e. to avoid that the same user is repeatedly redirected back and forth.

- Triggering redirections at down-switch can be done at low load, and during a predefined time period, to ensure that traffic is not negatively impacted.

- Using triggering redirections at down-switch when additional carriers are deployed in the same area thus making it likely to find new inter frequency, IEF, relations.

2: The SRNC orders the UE to change state to CELL_FACH by sending a RRC RB RECONFIGURATION message on the downlink.

The message might optionally contain the information element "Frequency Info" that informs the UE about the target frequency to use in CELL_FACH state. 3: The UE changes the RRC state to CELL_FACH and performs a cell selection for example according to Ref [3]. A suitable second cell, which is referred to as Cell B, might be selected based on the frequency signaled to the UE in IE "Frequency info" in the RB RECONFIGURATION message. The UE could, in this step, select any suitable cell obeying the constraints set by the signaled frequency which means that the UE may find a missing neighbor Cell B in this step.

4: The UE sends a message, such as a RRC CELL UPDATE message, to the Radio Base Station, RBS, serving Cell B, RBS-Cell B indicating a cell reselection. The message is forwarded to the SRNC controlling Cell B.

5: The RNC checks if the second cell, Cell B, is defined as a neighbor to the first cell, Cell A. If the neighbor relation does not exist, a new IEF relation is defined from Cell A to Cell B.

6-7: The Cell Update procedure is completed. And the missing neighbor relation is detected.

Example 2: Detection of a neighbor cell relation between cells under the control of different Radio Network Controllers, RNCs.

In a second non-limiting example reference is made to FIG.9. Here a first cell, referred to as Cell A is under the control of a serving RNC, SRNC. A second cell, referred to as Cell B, is controlled by the Drift RNC. The two RNCs might communicate over an lur communication interface. The initial configuration of the UE is in this example are the same as in the above example, that is, the UE is in an initial state CELL_DCH.

In this example the steps 1-4 are the same as in Example 1. It is however possible that, for the exemplary triggers that might be used in step 4, the RNC only orders a redirection to another frequency if the best cell in the active set is still in the SRNC. 5: The DRNC might evaluate the RNC id signaled as part of, for example, the UTRAN-Radio Network Temporary Identifier, U-RNTI, in a CELL UPDATE message and determine that the UE is connected to another SRNC. The CELL UPDATE message is here forwarded to the SRNC in Radio Network Subsystem Application Part, RNSAP, UL SIGNALLING TRANSFER INDICATION together with the RNC id of the DRNC and the Cell identity of the target cell (i.e. the second cell or Cell B). See Ref [4] for details.

6: SRNC checks if the target cell, the second cell, Cell B, is defined as a cell controlled by another RNC that could be defined as a neighbor to cells to the own RNC and whether a relation already exists between the first and second cell, Cell A and Cell B, respectively

7: SRNC respond to the DRNC for example through a RNSAP UL SIGNALLING TRANSFER RESPONSE that could contain an RRC CONNECTION RELEASE message to be sent to the UE.

8: The DRNC forwards a message, such as a RRC CONNECTION RELEASE message to the UE with cause Directed Signaling Connection Re-establishment. This will trigger a re-establishment of the connection in the new cell. The UE goes in to idle mode.

Finally it is possible for the SRNC to identify the second cell, or Cell B, as a mirrored or external cell. Further information, such as for example SC, UARFCN and cell capabilities could be retrieved from the DRNC by conventional methods, using for example the procedure Information Exchange Initiation as disclosed in Ref [4] or proprietary RNSAP signaling. Instead of using RNSAP signaling the SRNC might also request OSS-RC to configure the external cell.

Once the cell is defined as such a mirrored or external cell in the SRNC it is possible to configure the neighbor relation between the first cell, Cell A, and the second cell, the mirrored/external cell B. Example 3: Detection of a neighbor cell relation during RRC Connection release with redirection to another frequency

In the third example reference is made to the signaling diagram of FIG.10. In this particular example the initial configuration is such that the UE is in connected state in a first cell, Cell A, controlled by a RNC. The UE is connected to a WCDMA. The UE is furthermore in one of the CELL_DCH, CELL_FACH or URA_PCH, states. There is also a Radio Base Station, RBS 1 Cell A, serving the UE in the first cell. 1 : The RNC decides when to trigger the RRC connection release procedure and to what UTRA Absolute Radio Frequency Number, UARFCN, to redirect the UE. The RNC could maintain information relating to the identity of the UE, the Cell identity of Cell A and the UARFCN command sent to the UE in one or more databases, for example a list. The command UARFCN is used to identify a frequency in a UMTS frequency band.

Step 1 can be initiated in situations where the RNC assumes that the UE is in a place where a neighbor cell relation is missing. Such assumptions can for example be inferred from received messages that displays bad signal quality but good signal strength.

2: The RNC sends a message, such as a RRC Connection Release message with redirect information to other UARFCN. This commands forces the UE to release its radio connections and camp on the other WCDMA frequency, indicated as UARFCN in the IE Redirection Info. See Ref [2] for details.

3: After having received the message the UE goes to idle mode and performs a cell selection process to select a new suitable cell, a second cell or cell B, see Ref [3] for details. This cell might be a cell included or not included in a neighbor cell list. 4: When there is uplink, UL, or downlink, DL, data for this UE. The UE sends a RRC Connection Request message to cell B. At RRC establishment in cell B the RNC checks if the UE is redirected from another cell. If that is the case a neighbor cell relation is created in cell A if it does not already exist.

An optional feature for the network node, in this case the RNC, might be to issue a page or a paging message for the released UE to reduce the time it takes until the new RRC establishment.

The proposed technology will now be described with reference to FIG. 1 , FIG. 4, FIG. 5 and FIG.6.

The proposed technology also provides a network node 100; 200 configured to detect a neighbor cell relation between cells within a cellular communication network,

•wherein the network node 100; 200 is configured to trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell; and •wherein the network node 100; 200 is configured to receive information enabling a determination of the identity of the second cell selected by the UE; and

©wherein the network node 100; 200 is configured to identify, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

All the advantages associated with the earlier described proposed method are equally valid for the proposed network node and will not be described again.

In a possible embodiment of a network node 100; 200 is the network node configured to identify the neighbor relation by checking whether the second cell is defined as a neighbor cell of the first cell and, if the second cell is not defined as a neighbor cell of the first cell, identify the second cell as a neighbor cell of the first cell. By way of example, the network node 100; 200 could be configured to create an instance of the identified neighbor cell relation between the first cell and the second cell.

The network node 100; 200 may in an optional embodiment be configured to update a neighbor cell list by entering the neighbor cell relation instance into the neighbor cell list.

In an exemplary embodiment is the network node 00; 200 configured to trigger the cell selection process by ordering the UE to change Radio Resource Control, RRC, mode or Radio Resource Control, RRC, state.

In another possible embodiment is the network node 100; 200 configured to order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH, state or from a RRC connected mode to a RRC Idle mode.

In still another exemplary embodiment is the network node 100; 200 configured to order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH and configured to provide the UE with information relating to the target frequency to be used by the UE when in the CELL_FACH state.

In an example of the proposed network node 100; 200 is the network node configured to trigger the UE to perform a cell selection process by initiating a Radio Resource Control, RRC, connection procedure.

In a particular embodiment is the network node 100; 200 configured to send a Radio Resource Control, RRC, connection release message including redirection information to the UE ordering the UE to release its radio connections.

In an optional exemplary embodiment of a network node 100; 200 is the network node configured to trigger the UE to perform the cell selection process during UE inactivity. In yet another possible embodiment of the proposed network node is the network node 100; 200 configured to trigger the UE to perform the cell selection process 5 based on performed downlink throughput measurements.

According to a particular example is the network node 100; 200 configured to obtain the information enabling the determination of the identity of the second cell from a base station serving the UE in the second cell.

10

In an optional embodiment is the network node 100; 200 configured to trigger the UE to perform the cell selection process without indicating any target cell.

In a particular example of an embodiment is the network node 100; 200 configured 15 to elect, from a number of cells serving the UE, a first cell to act as a basis relative to which a neighbor relation should be identified.

By way of example, the network node 100; 200 could be configured to provide the UE with information relating to the target frequency when triggering the cell selection 20 process.

A particular example of a network node is schematically illustrated in Fig. 4, here the network node 100 comprises a processor 120 and a memory 30, the memory 130 comprising instructions executable by the processor 120, whereby the processor 25 20 is operative to detect the neighbor cell relation.

The network node 00 may also include communication circuitry for communication with one or more other nodes, including transmitting and/or receiving information. In a particular embodiment the network comprises communication circuitry 110 30 configured to receive information enabling a determination of the identity of the second cell selected by the UE. This is also schematically shown in FIG.4. In all of the described embodiments could the network node 100; 200 be a Radio Network Controller, RNC.

As used herein, the non-limiting terms "User Equipment" and "wireless device" may refer to a mobile phone, a cellular phone, a Personal Digital Assistant, PDA, equipped with radio communication capabilities, a smart phone, a laptop or Personal Computer, PC, equipped with an internal or external mobile broadband modem, a tablet PC with radio communication capabilities, a target device, a device to device UE, a machine type UE or UE capable of machine to machine communication, iPAD, customer premises equipment, CPE, laptop embedded equipment, LEE, laptop mounted equipment, LME, USB dongle, a portable electronic radio communication device, a sensor device equipped with radio communication capabilities or the like. In particular, the term "UE" and the term "wireless device" should be interpreted as non-limiting terms comprising any type of wireless device communicating with a radio network node in a cellular or mobile communication system or any device equipped with radio circuitry for wireless communication according to any relevant standard for communication within a cellular or mobile communication system. As used herein, the non-limiting term "network node" may refer to base stations, network control nodes such as network controllers, radio network controllers, base station controllers, and the like. In particular, the term "base station" may encompass different types of radio base stations including standardized base stations such as Node Bs, or evolved Node Bs, eNBs, and also macro/micro/pico radio base stations, home base stations, also known as femto base stations, relay nodes, repeaters, radio access points, base transceiver stations, BTSs, and even radio control nodes controlling one or more Remote Radio Units, RRUs, or the like.

The network node may also include radio circuitry for communication with one or more other nodes, including transmitting and/or receiving information. It will be appreciated that the methods and devices described herein can be combined and re-arranged in a variety of ways.

For example, embodiments may be implemented in hardware, or in software for execution by suitable processing circuitry, or a combination thereof.

The steps, functions, procedures, modules and/or blocks described herein may be implemented in hardware using any conventional technology, such as discrete circuit or integrated circuit technology, including both general-purpose electronic circuitry and application-specific circuitry.

Particular examples include one or more suitably configured digital signal processors and other known electronic circuits, e.g. discrete logic gates interconnected to perform a specialized function, or Application Specific Integrated Circuits (ASICs).

Alternatively, at least some of the steps, functions, procedures, modules and/or blocks described herein may be implemented in software such as a computer program for execution by suitable processing circuitry such as one or more processors or processing units.

Examples of processing circuitry includes, but is not limited to, one or more microprocessors, one or more Digital Signal Processors (DSPs), one or more Central Processing Units (CPUs), video acceleration hardware, and/or any suitable programmable logic circuitry such as one or more Field Programmable Gate Arrays (FPGAs), or one or more Programmable Logic Controllers (PLCs).

It should also be understood that it may be possible to re-use the general processing capabilities of any conventional device or unit in which the proposed technology is implemented. It may also be possible to re-use existing software, e.g. by reprogramming of the existing software or by adding new software components.

The proposed technology also provides an apparatus configured to detect a neighbor cell relation between cells within a cellular communication network, wherein the apparatus comprises a processor and a memory, the memory comprising instruction executable by the processor, whereby the processor is operative to:

•trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell; and

•read information enabling a determination of the identity of the second cell selected by the UE; and

•identify, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

FIG. 4 is a schematic block diagram illustrating an example of an apparatus comprising a processor and an associated memory.

In this particular example, at least some of the steps, functions, procedures, modules and/or blocks described herein are implemented in a computer program, which is loaded into the memory for execution by processing circuitry including one or more processors. The processor(s) and memory are interconnected to each other to enable normal software execution. An optional input/output device may also be interconnected to the processor(s) and/or the memory to enable input and/or output of relevant data such as input parameter(s) and/or resulting output parameter(s). Such an embodiment is schematically illustrated in the block diagram of FIG.5. The term 'processor' should be interpreted in a general sense as any system or device capable of executing program code or computer program instructions to perform a particular processing, determining or computing task.

The processing circuitry including one or more processors is thus configured to perform, when executing the computer program, well-defined processing tasks such as those described herein. The processing circuitry does not have to be dedicated to only execute the above- described steps, functions, procedure and/or blocks, but may also execute other tasks. The proposed technology also provides a computer program 35; 145 comprising instructions, which when executed by at least one processor, cause the processor(s) to:

•trigger a User Equipment, UE, served in a first cell in a cellular communication network, to perform a cell selection process causing the UE to select a second cell;

•read information enabling a determination of the identity of the second cell selected by the UE;

The proposed technology also provides a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium 130; 255.

By way of example, the software or computer program may be realized as a computer program product 30; 255, which is normally carried or stored on a computer-readable medium. The computer-readable medium may include one or more removable or non- removable memory devices including, but not limited to a Read-Only Memory (ROM), a Random Access Memory (RAM), a Compact Disc (CD), a Digital Versatile Disc (DVD), a Blueray disc, a Universal Serial Bus (USB) memory, a Hard Disk Drive (HDD) storage device, a flash memory, a magnetic tape, or any other conventional memory device. The computer program may thus be loaded into the operating memory of a computer or equivalent processing device for execution by the processing circuitry thereof. The proposed technology also provides a network node 200 for detecting a neighbor cell relation between cells in a cellular communication network, wherein the network node comprises: »an initiating module 225 for triggering a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing the UE to select a second cell;

•a reading module 235 for reading information enabling a determination of the identity of the second cell selected by the UE; and

»an identification module 245 for identifying, based on the determined identity of the second cell and information representing the identity of the first cell, a neighbor relation between the first cell and the second cell.

This network node is schematically illustrated by the block diagram of FIG.6.

The flow diagram or diagrams presented herein may therefore be regarded as a computer flow diagram or diagrams, when performed by one or more processors. A corresponding network node may be defined as a group of function modules, where each step performed by the processor corresponds to a function module. In this case, the function modules are implemented as a computer program running on the processor. Hence, the network node may alternatively be defined as a group of function modules, where the function modules are implemented as a computer program running on at least one processor. The computer program residing in memory may thus be organized as appropriate function modules configured to perform, when executed by the processor, at least part of the steps and/or tasks described herein. An example of such function modules is illustrated in FIG. 6. Alternatively it is possibly to realize the modules in figure 6 predominantly by hardware modules, or alternatively by hardware. The extent of software versus hardware is purely implementation selection. The embodiments described above are merely given as examples, and it should be understood that the proposed technology is not limited thereto. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the present scope as defined by the appended claims. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible.

REFERENCES

[1 ] 3GPP TS 25.484, VERSION 10.2.0.

[2] 3GPP TS 25.331 , VERSION 10.15.0, SECTION 8.2.2.3 & 8.5.2

[3] 3GPP TS 25.304, VERSION 10.7.0, SECTION 5.2.3.1

[4] 3GPP TS 25.423, VERSION 10.10.0, SECTIONS 9.1.24.1 & 9.2.1.71 & 8.5.2

Claims

A method performed by a network node for detecting a neighbor cell relation between cells in a cellular communication network, wherein the method comprises the steps of:

triggering (S1) a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing said UE to select a second cell;

receiving (S2) information enabling a determination of the identity of the second cell selected by said UE;

identifying (S3), based on the determined identity of said second cell and information representing the identity of said first cell, a neighbor cell relation between said first cell and said second cell.

The method according to claim 1 , wherein the neighbor relation is identified by checking whether said second cell is defined as a neighbor cell of said first cell and, if said second cell is not defined as a neighbor cell of said first cell, identifying said second cell as a neighbor cell of said first cell.

The method according to claim 1 or 2, wherein the network node creates (S4) an instance of the identified neighbor cell relation between said first cell and said second cell.

The method according to any of the claims 1 - 3, wherein the network node triggers said cell selection process by ordering the UE to change Radio Resource Control, RRC, mode or Radio Resource Control, RRC, state.

The method according to claim 4, wherein the network node orders the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH, state or from a RRC connected mode to a RRC Idle mode.

6. The method according to claim 5, wherein the network node orders the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH state and provides the UE with information relating to the target frequency to be used by the UE when in the CELL_FACH state.

7. The method according to any of the claims 1-6, wherein the network node trigger the UE to perform said cell selection process during UE inactivity.

8. The method according to any of the claims 1-3, wherein said network node triggers said UE to perform a cell selection process by initiating a Radio Resource Control, RRC, Release procedure.

9. The method according to claim 8, wherein said network node orders the UE to release its radio connections by sending a Radio Resource Control, RRC, connection release message including redirection information to said UE.

10. The method according to any of the claims 1-9, wherein the information enabling the determination of the identity of the second cell is obtained from a base station serving the UE in the second cell.

11. The method according to any of the claims 1-10, wherein the network node trigger the UE to perform the cell selection process without indicating any target cell.

12. The method according to any of the claims 1-11 , wherein said network node elects, from a number of cells serving said UE, the first cell to act as a basis relative to which a neighbor relation should be identified.

13. The method according to any of the claims 1-12, wherein the network node provides the UE with information relating to the target frequency when triggering said UE to perform a cell selection process.

14. The method according to any of the claims 1-13, wherein the network node sends a paging message to the UE in order to reveal the identity of the selected second cell based on a response to the paging message.

15. The method according to any of the claims 1-14, wherein the network node is a Radio Network Controller, RNC.

16. A network node (100) configured to detect a neighbor cell relation between cells within a cellular communication network, - wherein the network node (100) is configured to trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing said UE to select a second cell; and

wherein the network node (100) is configured to receive information enabling a determination of the identity of the second cell selected by said

UE; and

wherein the network node (100) is configured to identify, based on the determined identity of said second cell and information representing the identity of said first cell, a neighbor relation between said first cell and said second cell.

17. The network node according to claim 16, wherein the network node is configured to identify the neighbor relation by checking whether said second cell is defined as a neighbor cell of said first cell and, if said second cell is not defined as a neighbor cell of said first cell, identify said second cell as a neighbor cell of said first cell.

18. The network node according to claim 17, wherein the network node is configured to create an instance of identified neighbor cell relation between said first cell and said second cell.

19. The network node according to any of the claims 16-18, wherein the network node is configured to trigger said cell selection process by ordering the UE to change Radio Resource Control, RRC, mode or Radio Resource Control, RRC, state.

20. The network node according to claim 19, wherein the network node is configured to order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH, state or from a RRC connected mode to a RRC Idle mode.

21. The network node according to claim 20, wherein the network node is configured to order the UE to change from a CELL Dedicated Channel, CELL_DCH, state to a Cell Forward Access Channel, CELL_FACH and configured to provide the UE with information relating to the target frequency to be used by the UE when in the CELL_FACH state.

22. The Network node according to any of the claims 16-18, wherein said network node is configured to trigger said UE to perform a cell selection process by initiating a Radio Resource Control, RRC, connection release procedure.

23. The network node according to claim 22, wherein said network node is configured to send a Radio Resource Control, RRC, connection release message including redirection information to said UE ordering the UE to release its radio connections.

24. The network node according to any of the claims 16-23, wherein the network node is configured to trigger the UE to perform said cell selection process during UE inactivity.

25. The network node according to any of the claims 16-24, wherein the network node is configured to trigger the UE to perform said cell selection process based on performed downlink throughput measurements.

26. The network node according to any of the claims 16-25, wherein the network node is configured to obtain the information enabling the determination of the identity of the second cell from a base station serving the UE in the second cell.

27. The network node according to any of the claims 16-26, wherein the network node is configured to trigger the UE to perform the cell selection process without indicating any target cell.

28. The network node according to any of the claims 16-27, wherein the network node is configured to elect, from a number of cells serving said UE, a first cell to act as a basis relative to which a neighbor relation should be identified.

29. The network node according to any of the claims 16-28 wherein the network node is configured to send a paging message to the UE in order to reveal the identity of the selected second cell based on a response to the paging message

30. The network node according to any of the claims 16-29, wherein the network node comprises a processor (120) and a memory ( 30), said memory (130) comprising instructions executable by the processor (120), whereby the processor (120) is operative to detect said neighbor cell relation.

31. The network node according to claim 30, wherein the network node comprises communication circuitry (110) configured to receive information enabling a determination of the identity of the second cell selected by said UE.

32. The network node according to any of the claims 16-31 , wherein the network node is a Radio Network Controller, RNC.

33. A computer program comprising instructions, which when executed by at least one processor, cause the processor(s) to: - trigger a User Equipment, UE, served in a first cell in a cellular communication network, to perform a cell selection process causing said

UE to select a second cell;

read information enabling a determination of the identity of the second cell selected by said UE;

- identify, based on the determined identity of said second cell and information representing the identity of said first cell, a neighbor relation between said first cell and said second cell.

34. A carrier comprising the computer program of claim 33, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

35. A network node for detecting a neighbor cell relation between cells in a cellular communication network, wherein said network node comprises: an initiating module (125) for triggering a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing said UE to select a second cell;

- a reading module (135) for reading information enabling a determination of the identity of the second cell selected by said UE; and an identification module (145) for identifying, based on the determined identity of said second cell and information representing the identity of said first cell, a neighbor relation between said first cell and said second cell.

36. An apparatus configured to detect a neighbor cell relation between cells within a cellular communication network, wherein the apparatus comprises a processor and a memory, the memory comprising instruction executable by the processor, whereby the processor is operative to:

- trigger a User Equipment, UE, served in a first cell under the control of the network node, to perform a cell selection process causing said UE to select a second cell; and

read information enabling a determination of the identity of the second cell selected by said UE; and