Managing PCI conflicts

Abstract

The present disclosure relates in an aspect to a method of a serving radio base station (11) of performing handover of a wireless communication device (10) in a wireless communication system. The method comprises receiving (S102) a radio measurement report from the wireless communication device (10) comprising measurement data acquired by the wireless communication device (10) from at least one neighbouring radio base station (14) indicating that a handover to said at least one neighbouring radio base station (14) is to be performed, determining (S103) whether a physical cell identifier (PCI) of the radio measurement report identifying a cell of the neighbouring radio base station (14) for which the measurement data is acquired already has been assigned to a cell of another neighbouring radio base station (12) and defined in a neighbour list of the serving radio base station (11) and if so determining (S104) a current position of the wireless communication device (10). The method further comprises comparing (S105) the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells of neighbouring radio base stations (12, 14) having the same PCI as the identified cell of the radio measurement report by taking into account the current position of the wireless communication device (10) and if there is match between the measurement data and one of the preconfigured radio profiles for the current position of the wireless communication device, performing (S106a, S106b) a handover of the wireless communication device (10) to the cell of a neighbouring radio base station (12, 14) for which there is a radio profile match.

Description

MANAGING PCI CONFLICTSTECHNICAL FIELD

[0001] The present disclosure relates to a method of a serving radio base station of performing handover of a wireless communication device in a wireless communication system, and a serving radio base station performing the method.

[0002] The present disclosure further relates to a method of a device of creating radio profiles representing radio conditions of physical radio cells formed by radio base stations in a wireless communication system, and a device performing the method.

[0003] The disclosure further relates to computer programs and computer program products.BACKGROUND

[0004] To ensure seamless mobility and an uninterrupted user experience, an approach known as automated neighbour relations (ANR) is considered an integral part in wireless communication systems.

[0005] A radio cell formed by a radio base station (RBS) is identified by means of a Physical Cell ID (PCI). An RBS may form one or more radio cells and PCIs are allocated uniquely to each cell formed by an RBS.

[0006] However, PCIs can be re-used for cells of a neighbouring RBS. The currently available count of unique PCIs is limited e.g. to 1008 in fifth generation (5G) New Radio (NR) and 504 in fourth generation (4G) Long-Term Evolution (LTE), so depending on the total cells in a network, PCIs maybe re-used. For example, if total count of cells in a network for a given operating frequency is 2016 in 5G, then each PCI needs to be used twice in the network. As is understood, cells with the same PCI but different operating frequency will not interfere with each other.

[0007] An RBS serving a wireless communication device such as a smart phone will only perform a handover of the device to a neighbouring RBS if the PCI of a cell formed by the neighbouring RBS is included in a neighbour list of the serving RBS.

[0008] Thus, if another more newly deployed neighbouring RBS forms a cell which is assigned the same PCI (and operates at the same frequency) as a cell of thepreviously deployed neighbouring RBS, a conflict will occur and the ANR approach will have the serving RBS try to perform handover to the neighbouring RBS with which the PCI already is associated in the neighbour list, even in a scenario where the newly deployed neighbouring RBS using the same PCI is a better handover candidate.SUMMARY

[0009] One objective is to solve, or at least mitigate, the above mentioned problem and thus to provide an improved method of a serving radio base station of performing handover of a wireless communication device.

[0010] This objective is attained in a first aspect by a method of a serving radio base station of performing handover of a wireless communication device in a wireless communication system. The method comprises receiving a radio measurement report from the wireless communication device comprising measurement data acquired by the wireless communication device from at least one neighbouring radio base station indicating that a handover to said at least one neighbouring radio base station is to be performed, determining whether a physical cell identifier (PCI) of the radio measurement report identifying a cell of the neighbouring radio base station for which the measurement data is acquired already has been assigned to a cell of another neighbouring radio base station and defined in a neighbour list of the serving radio base station and if so, determining a current position of the wireless communication device. The method further comprises comparing the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells of neighbouring radio base stations having the same PCI as the identified cell of the radio measurement report by taking into account the current position of the wireless communication device and if there is match between the measurement data and one of the preconfigured radio profiles for the current position of the wireless communication device, performing a handover of the wireless communication device to the cell of a neighbouring radio base station for which there is a radio profile match.

[0011] This objective is attained in a second aspect by a serving radio base station configured to perform handover of a wireless communication device in a wireless communication system, the serving radio base station comprising a processing unit and a memory, said memoiy containing instructions executable by said processingunit, whereby the radio base station is operative to receive a radio measurement report from the wireless communication device comprising measurement data acquired by the wireless communication device from at least one neighbouring radio base station indicating that a handover to said at least one neighbouring radio base station is to be performed, determine whether a PCI of the radio measurement report identifying a cell of the neighbouring radio base station for which the measurement data is acquired already has been assigned to a cell of another neighbouring radio base station and defined in a neighbour list of the serving radio base station and if so, determine a current position of the wireless communication device. The radio base station is further operative to compare the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells of neighbouring radio base stations having the same PCI as the identified cell of the radio measurement report by taking into account the current position of the wireless communication device and if there is match between the measurement data and one of the preconfigured radio profiles for the current position of the wireless communication device, to perform a handover of the wireless communication device to the cell of a neighbouring radio base station for which there is a radio profile match.

[0012] This objective is attained in a third aspect by a method of a device of creating radio profiles representing radio conditions of physical radio cells formed by radio base stations in a wireless communication system. The method comprises creating a grid for a complete network coverage area including the radio base stations, wherein each grid cell is associated with a unique grid cell identifier, receiving signal strength values of wireless communication devices communicating with the radio base stations at different wireless communication device position, and a PCI of the physical radio cell for which the signal strength values are received, and identifying a grid cell identifier for each wireless communication device position. The method further comprises creating a distribution of signal strength values reported by the wireless communication devices for each grid cell identifier, creating a radio profile for each cell comprising the distribution of signal strength values for each grid cell identifier geographically covered by the physical radio cell, and storing the created radio profiles.

[0013] This objective is attained in a fourth aspect by a device configured to create radio profiles representing radio conditions of physical radio cells formed by radio base stations in a wireless communication system, the device comprising a processing unit and a memory, said memory containing instructions executable by said processing unit, whereby the device is operative to create a grid for a complete network coverage area including the radio base stations, wherein each grid cell is associated with a unique grid cell identifier, receive signal strength values of wireless communication devices communicating with the radio base stations at different wireless communication device position, and a PCI of the physical radio cell for which the signal strength values are received, and identify a grid cell identifier for each wireless communication device position. The device is further operative to create a distribution of signal strength values reported by the wireless communication devices for each grid cell identifier, create a radio profile for each cell comprising the distribution of signal strength values for each grid cell identifier geographically covered by the physical radio cell and to store the created radio profiles.

[0014] Now, a wireless communication device will acquire a measure of radio conditions in a cell formed by a radio base station being a candidate for handover and send a report to a radio base station currently serving the wireless communication device, which report comprises the measure of the radio conditions in the form of e.g. reference signal received power (RSRP).

[0015] The PCI of the cell being a candidate for handover is further provided to the serving radio base station. However, if this particular PCI already has been defined in a neighbour list of the serving radio base station for a cell of another neighbouring radio base station, a conflict arises since the serving radio base station will assume that the reported PCI is the PCI of the cell already defined in the neighbour list. In the prior art approach, a handover will thus be performed to the already defined cell, even if that cell is an inferior handover candidate.

[0016] To resolve this issue, the serving radio base station will, by taking into account a current position of the wireless communication device, compare the RSRP of the received report with a preconfigured radio profile representing radio conditions of a wireless communication device communicating in the candidate cell with the neighbouring RBS at the current position and with a preconfigured radio profile representing radio conditions of a wireless communication devicecommunicating in the already defined cell with said another neighbouring radio base station.

[0017] As is understood, the radio profiles may be created and stored by a central device which also performs the comparison upon being provided with required data from the serving radio base station.

[0018] It the report RSRP matches the radio profile of the cell of the neighbouring being a candidate for handover (rather than the already defined cell having the same PCI), then the handover can successfully be initiated. Advantageously, this resolves the above issue and handover will be performed to the best candidate cell, even if the candidate cell has not been defined in the neighbour list.

[0019] In an embodiment, in case the cell for which there is a radio profile match is the cell of the neighbouring radio base station already defined in the neighbour list, the handover is performed to said already defined cell of the neighbouring radio base station.

[0020] In an embodiment, in case the cell for which there is a radio profile match is a cell of the neighbouring radio base station not defined in the neighbour list, the handover is performed to said non-defined cell of the neighbouring radio base station and the method further comprises incrementing, in case of successful handover, a counter for a combination of a cell of the serving radio base station from which the handover is performed, the cell of the neighbouring radio base station to which the handover is performed and the PCI of the cell to which the handover is performed, and initiating a timer, adding said combination, counter value and timer value as an entry in a table comprising corresponding combinations, counter values and timers of other handovers from the serving radio base station to cells with the identified PCI, determining if the counter value exceeds a set counter threshold value for one or more of the combinations in the table and if so determining a cell of a neighbouring radio base station having a highest counter value. The method further comprises setting a new PCI for the cell having the highest counter value and storing the new PCI for the cell having the highest counter value.

[0021] In an embodiment, the method further comprises updating the PCI for the cell having the highest counter value with the set new PCI and deleting all entries in the table containing the cell for which the PCI is updated.

[0022] In an embodiment, the method further comprises, upon determining that the counter value does not exceed the set counter threshold value for one or more of the combinations in the table, determining if the timer value for a combination exceeds a set timer threshold value and if so deleting the entry corresponding to said combination from the table.

[0023] In an embodiment, the radio profiles representing radio conditions of cells comprise distributions of signal strength values for communication being performed by radio base stations serving the cells with wireless communication devices at different wireless communication device positions in the cells.

[0024] In an embodiment, the signal strength being represented by one or more of reference signal received power (RSRP), reference signal received quality (RSRQ) and signal-to-noise and interference ratio (SINR).

[0025] In an embodiment, the comparing of the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells comprises comparing a signal strength value of the received radio measurement report with a mean value of the distribution of signal strength values for the current wireless communication device position for the radio profiles, wherein the radio profile having a smallest difference between the signal strength value of the received radio measurement report and said mean value is considered to be a match.

[0026] In an embodiment, the comparing further comprises dividing the difference between the signal strength value of the received radio measurement report and said mean value with standard deviation of the distribution, wherein the radio profile having a smallest quota after the division with the standard deviation is considered to be a match.

[0027] In an embodiment, the cells of neighbouring radio base stations having the same PCI as the identified cell which are selected for comparing is selected using a K- Nearest Neighbor (KNN) algorithm, where the selected N nearest neighbours are determined for the comparing.

[0028] In a fifth aspect, a computer program is provided comprising computerexecutable instructions for causing a radio base station to perform steps recited in the method of the first aspect when the computer-executable instructions are executed on a processing unit included in the radio base station.

[0029] In a sixth aspect, a computer program product is provided comprising a computer readable medium, the computer readable medium having the computer program according to the fifth aspect embodied thereon.

[0030] In a seventh aspect, a computer program is provided comprising computer-executable instructions for causing a device to perform steps recited in the method of the third aspect when the computer-executable instructions are executed on a processing unit included in the device.

[0031] In an eighth aspect, a computer program product is provided comprising a computer readable medium, the computer readable medium having the computer program according to the seventh aspect embodied thereon.

[0032] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0034] Figure 1 shows a prior art scenario illustrating general mobile management in a wireless communication system;

[0035] Figure 2 illustrates a scenario where the currently applied ANR approach fails to perform properly;

[0036] Figure 3 illustrates an embodiment proposed for resolving the issue illustrated in Figure 2;

[0037] Figure 4 shows a flowchart illustrating a method of an embodiment; and

[0038] Figures 5a and 5b illustrate creation of radio profiles for all cells in a network coverage area according to an embodiment;

[0039] Figure 6 illustrates network nodes being involved in the creation of the radio profile for each cell formed by an RBS in the network coverage area defined by the grid of Figure 5a, according to an embodiment;

[0040] Figure 7 illustrates a flowchart illustrating an embodiment applying the KNN algorithm in combination with computing a so-called Z-score for determining a best match;

[0041] Figure 8 illustrates the Z-score in an embodiment;

[0042] Figure 9 shows a flowchart illustrating a method of correcting PCIs according to an embodiment;

[0043] Figure 10 illustrates an embodiment where some of the data held at the central node may be stored as local copies at the serving RBS;

[0044] Figure 11 illustrates an RBS configured to perform handover of a wireless communication device in a wireless communication system according to an embodiment;

[0045] Figure 12 illustrates a central node configured to create radio profiles representing radio conditions of physical radio cells formed by radio base stations in a wireless communication system according to an embodiment; and

[0046] Figure 13 illustrates a network in which embodiments may be implemented.DETAILED DESCRIPTION

[0047] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0048] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0049] Figure 1 shows a prior art scenario illustrating general mobile management in a wireless communication system.

[0050] To ensure seamless mobility and an uninterrupted user experience, an approach known as automated neighbour relations (ANR) is considered an integral part in wireless communication systems. The wireless communication system will be discussed from a fifth generation (5G) New Radio (NR) perspective, but the embodiments discussed herein are applicable to other generations of wireless communication systems as well.

[0051] Now, assuming a wireless communication device, commonly referred to as a User Equipment (UE) 10, is served by radio base station (RBS) 11. The UE 10 may be embodied on the form of for instance a smart phone, tablet, laptop, connected vehicle, etc.

[0052] A radio cell formed by the first RBS 11 is identified by means of a Physical Cell ID (PCI) exemplified as Pi. An RBS may form one or more radio cells. In a common deployment, an RBS forms three cells operating with the same frequency.

[0053] As previously mentioned, the PCIs are allocated uniquely to each cell formed by an RBS. However, PCIs can be re-used for cells of a neighbouring RBS, thereby causing a conflict in case the cells operate at the same frequency.

[0054] Upon the UE 10 moving away from the serving RBS 11 towards neighbouring RBS 12, the UE 10 will consider a handover (HO) to the neighbouring RBS 12 (the cell of which is identified by P2) upon reaching a border of the cell formed by the serving RBS 11. Each 5G NR cell is assigned with a PCI for distinguishing cells at the physical layer.

[0055] In order to evaluate whether or not an HO is to be performed, the UE 10 will measure quality and / or strength of the neighbouring RBS 12 in step Sil.Typically, indicators such as e.g. synchronization signal reference signal received power (SS-RSRP), synchronization signal reference signal received quality (SS- RSRQ), synchronization signal signal-to-noise and interference ratio (SS-SINR) will be measured in S11 and sent to the serving RBS 10 in step S12 in a measurement report along with PCI P2. Such measurement report maybe part of the reporting of an event in 5G NR, e.g. any one of 5G NR events A1-A6.

[0056] The serving RBS 11 checks P2 received with the measurement report in S12 and concludes in this example that P2 is unknown. In other words, the serving RBS 11turns to its neighbour list (also referred to as neighbour relation table) and finds that P2 has not been previously recorded.

[0057] In response thereto, and given that the quality indicators are such that an HO indeed can be performed (for instance the SS-RSRP exceeding a threshold value), the serving RBS 11 requests UE 10 in S13 to undertake measurements to provide a new radio cell global identity (NCGI) measurement report for the unknown PCI P2 that was reported.

[0058] The UE 10 will in S14 create the NCGI measurement report by reading the master information block (MIB) and the first system information block (SIB1). SIB1 contains among other things the cell identity of the unknown PCI P2 along with the new radio tracking area code (nrTAC), which is mandatory for the serving RBS 11 to add the reported unknown cell formed by the neighbouring RBS 12 as a neighbour, and send the NCGI measurement report to the serving RBS 11 in S15.

[0059] After receiving the NCGI measurement report in S15, the serving RBS 11 adds the reported cell of the neighbouring RBS 12 as a neighbour relation. From the next received measurement report, the serving RBS 11 considers the neighbouring RBS 12 now being included in the list along with PCI P2 as a legitimate and permanent neighbour and thus successfully proceeds with the HO in S16.

[0060] Figure 2 illustrates a scenario where the currently applied ANR approach fails to perform properly.

[0061] Now, assuming that the currently serving RBS 11 has added first neighbouring RBS 12 (the cell of which is identified by P2) to its ANR neighbour list as discussed above. In this particular example, a second neighbouring RBS 13 the cell of which is identified by P4 has also been added to the ANR neighbour list.

[0062] Assuming that a third neighbouring RBS 14 is either (a) deployed with the same cell PCI as that assigned to the first neighbouring RBS 12 (i.e. P2), or (b) the PCI of the cell formed by the third neighbouring RBS 14 is changed from, say, P3 to P2.

[0063] In this example, the UE 10 acquires one or more of SS-RSRP, SS-RSRQ and SS-SINR of the second neighbouring RBS 13 and the third neighbouring RBS 14, respectively, in S11 as previously discussed and sends a measurement report of the measured quality indicators to the serving RBS 11 in S12. The signal strength of thethird neighbouring RBS 14 is assumed to be stronger than that of the second neighbouring RBS 13, making the third neighbouring RBS 14 a better HO candidate. As is understood, the measurement report may include measurements of a plurality of cells formed by the respective RBS.

[0064] The serving RBS 11 already has PCI P2 in its neighbour list however not being assigned to the third neighbouring RBS 14 but to the first neighbouring RBS 12. Since according to the neighbour list the RBS having a cell with PCI P2 is indicated in S11 to be a better HO candidate - i.e. the third neighbouring RBS 14 - than the second neighbouring RBS 13, the RBS having the cell identified by PCI P2 is selected for HO.

[0065] However, in the neighbour list, this is not the third neighbouring RBS 14, but the first neighbouring RBS 12. As a result, the serving RBS 11 sends an HO request to the first neighbouring RBS 12 in S16, but since the UE 10 is distant from the first neighbouring RBS 12, such HO will in contrast to the HO of Figure 1 likely fail due the low signal strength. Thus, the HO of the UE 10 that effectively should have been made to the third neighbouring RBS 14 (being the best candidate from a signal strength perspective) is instead performed to the first neighbouring RBS 12, since the cells of the two RBSs are assigned the same PCI, i.e. P2.

[0066] Currently in the ANR approach being implemented, this can only be resolved by flushing the neighbouring RBSs and the cells from the ANR list and then re-enter the neighbouring RBSs and the cells to the neighbour list, which is a tedious process further leading to network downtime. Also, in the scenario of Figure 2, the third neighbouring RBS 14 having the cell identified by PCI P2 will be added, but not the first neighbouring RBS whose cell also is identified by PCI P2.

[0067] Since the system is incapable of adding a potential neighbouring RBS forming a cell having the same PCI as an already existing neighbouring RBS (which potential neighbouring RBS possibly was added to the network at a later point in time), the only solution is to determine such anomalies manually and flush the neighbour list, but the problem still remains that only one of the third neighbouring RBS 14 and the first neighbouring RBS 12 and their cells will be added since the two RBSs each forms a cell having the same PCI.

[0068] Figure 3 illustrates an embodiment proposed for resolving this issue, assuming again that the serving RBS 11 already successfully has added the firstneighbouring RBS 12 and the second neighbouring RBS 13 to its ANR neighbour list along with their cells identified by P2 and P4, respectively, but that an attempt is made to deploy the third neighbouring RBS 14 forming a cell identified with PCI P2, i.e. the same PCI as the cell of the first neighbouring RBS 12, which was illustrated in Figure 2 as resulting in an unsuccessful HO attempt of the UE 10 to the first neighbouring RBS 12.

[0069] Reference will further be made to Figure 4 showing a flowchart illustrating a method of an embodiment.

[0070] In this embodiment, the UE 10 will in Slot acquire one or more of SS- RSRP, SS-RSRQ and SS-SINR of the second neighbouring RBS 13 and the third neighbouring RBS 14 previously discussed and send a measurement report of the measured quality indicators to the serving RBS 11 in S102. Again, the signal strength of the third neighbouring RBS 14 is assumed to be greater than that of the second neighbouring RBS 13, making the third neighbouring RBS 14 a better HO candidate. It is thus assumed that the measurement report indicates that an HO of the UE 10 to the third neighbouring RBS 14 should be performed.

[0071] The serving RBS 11 will in S103 determine that PCI P2 received in the measurement report from the UE 10 in S102 already is defined in the neighbour list held by the serving RBS 11, having been associated with a cell of the first neighbouring RBS 12. In other words, the first neighbouring RBS 12 is defined in the neighbour list, while the third neighbouring RBS 14 is undefined. As is understood, if PCI P2 has not yet been added to the neighbour list, there is no conflict and the method proceeds in accordance with steps S13-S16 of Figure 1, by simply performing legacy ANR.

[0072] To determine the correct target neighbouring RBS for HO, the serving RBS 11 will utilize a radio profiles created for cells of neighbouring RBSs having the same PCI as that reported in S102, i.e. PCI P2, which profiles represent radio conditions of each cell. The creating of the radio profiles will be discussed in detail in the following with reference to Figures 5a, 5b and 6.

[0073] However, in brief, the radio profile for each cell will be created based on a great number of UEs served over the given coverage area and providing radio measurement reports for specified UE locations within the cells. The network willthus be able to create a radio profile for each cell based on radio measurement reports provided by the UEs at different positions within the cells. As is understood, due to the physical size of each so-called grid-cell to be discussed in more detail with reference to Figures 5a, 5b and 6, UE measurements are required at numerous different positions of the cell to create an adequate radio profile representative of the radio conditions for each cell.

[0074] In an embodiment, the created radio profile for a cell will be based on RSRP included in the radio measurement reports measured at different UE positions in the cell. Thus, from the created radio profile, a particular RSRP can be expected for a specific UE position in each cell.

[0075] Generally, a reported UE position indicates absolute position of the UE 10 in terms of latitude and longitude of the UE 10 or the relative position of the UE 10 in terms of distance from the serving RBS 11 and angle on a horizontal plane with respect to the azimuth of the serving RBS 11, which in its turn is converted to a position on horizontal plane, i.e. the latitude and longitude of the UE 10.

[0076] For reference, 3GPP TS 37.355 describes multiple methods for UE positioning in a 5G Network. Using one of these methods, UE position on the horizontal plane can be estimated by the RBS (referred to as gNodeB in 5G) and can be stored or used later for other purposes. In 4G LTE, mobile networks support observed time difference of arrival (OTDOA), uplink time difference of arrival (UL- TDOA) and positioning methods based on power measurements for UE positioning. In 5G, the list of supported methods has been extended to include round trip time (RTT) and angle-based positioning. The inclusion of new positioning methods and enhancements of existing positioning methods enables high accuracy positioning for several use cases in 5G. The actual performing of the UE positioning will not be discussed in further detail herein.

[0077] The method of this embodiment resolves the above-described issue by the serving RBS 11 validating to which of the neighbouring RBSs 12, 14 the reported PCI (i.e. PCI P2) actually belongs based on the radio profiles of neighbouring RBSs available to the serving RBS, with which radio profiles the serving RBS 11 is preconfigured. As will be discussed in more detail, the radio profiles are typically stored at a central network node to which the RBSs turn for accessing the radio profiles,

[0078] Hence, the serving RBS 11 determines in S104 a current position of the UE 10 before proceeding to comparing in S105 measured data of the radio measurement report received from the UE 10 for the third neighbouring RBS 14 with radio profile of cells of the neighbouring RBSs 12, 14 having cells with PCI P2 based on the current position of the UE 10.

[0079] In other words, upon determining whether a cell of a neighbouring RBS with the same PCI already is defined in the neighbour list in S103, the serving RBS 11 detects the position of the UE 10 in S104 and derives measurement data, e.g. the RSRP, from the radio measurement report for the detected UE position and tries to match the derived RSRP for the detected UE position to created radio profiles of neighbouring cells with PCI P2, with which radio profiles the RBS 11 is preconfigured (or the serving RBS 11 may turn to a central node storing the radio profiles) in S105.

[0080] If in S105, the serving RBS 11 would determine that the derived RSRP matches the radio profile of the already defined cell P2 of the first neighbouring RBS 12 for the current UE position, an HO of the UE 10 is initiated in Sio6a by the serving RBS 11 to the first neighbouring RBS 12.

[0081] In practice, the radio profile for a cell may consist of a plurality of distributions of RSRP values (one distribution for each of a number of UE positions in the cell). A match may be considered to occur for the RSRP distribution of the radio profile that best corresponds to the reported RSRP for the given UE position. For instance, the distribution for which a mean RSRP is closest to the reported RSRP may be considered a match, and HO would thus be undertaken to the cell for which the match occurs.

[0082] Now, assuming that the serving RBS 11 in this exemplifying embodiment finds in S105 that the RSRP at the reported UE position matches the RSRP at the same UE position of the radio profile created for the reported cell P2 formed by the third neighbouring RBS 14. The serving RBS 11 can thus conclude in S105 that PCI P2 reported by the UE 10 in step S102 likely did not originate from the first neighbouring RBS 12 (even if the neighbour list indeed indicates that P2 is assigned to the first neighbouring RBS 12).

[0083] As a result, in contrast to the unsuccessful HO illustrated in Figure 2, the serving RBS 11 sends an HO request to the third neighbouring RBS 14 in Sio6b,which likely is successful since the third neighbouring RBS 14 is the best candidate from a signal strength perspective. As will be discussed hereinbelow with reference to Figure 9, some configuration is preferred if HO is successfully effected to the undefined cell with PCI P2 of the third neighbouring RBS 14 as compared to if HO is effected to the already defined cell with PCI P2 of the first neighbouring RBS 12.

[0084] As will be discussed in more detail in the following, since one or more neighbour cells with PCI P2 may exist, it needs to be determined how many such neighbour cells and which specific neighbour cell’s radio profile(s) will be considered for evaluation. Several methods are envisaged, for instance a so-called K-Nearest Neighbor (KNN) algorithm, where the N nearest neighbours are determined to make the evaluation process more efficient and faster.

[0085] Figure 5a and 5b illustrate creation of radio profiles for all cells in a network coverage area according to an embodiment.

[0086] To create the radio profiles, the following is performed:1. Firstly, a grid is created for the complete network coverage area. The grid size is m x n. Size of each cell in the grid is [W meter x H meter]. This is referred to as a grid cell and should not be confused with a physical radio cell formed by an RBS (and identified by means of a PCI as has been described in detail hereinabove). A practical value for W and H maybe 50 meters. Cells in the grid are indexed based on a unique ID which is used to refer any cell within the grid. This ID is referred as Grid Cell ID. Each cell within the grid thus defines a unique geographical area of size W x H m2.2. For every measurement report received at a serving RBS from a UE in a radio cell formed by the serving RBS, the position of the UE is estimated, and based on the UE position a Grid Cell ID is identified for the received measurement report. A radio cell geographically covers a plurality of grid cells.3. RSRP values are reported by UEs from an estimated UE position based on which the Grid Cell ID is identified, wherein a distribution of RSRP values is created for the identified Grid Cell ID (and thus the estimated UE position).4- Steps 2 and 3 are repeated and eventually a radio profile is created for each physical radio cell formed by the RBSs in the network coverage area of Figure 5a. The radio profile for a radio cell will hence comprise a plurality of RSRP distributions, one for each grid cell geographically covered by the radio cell.

[0087] Figure 5b illustrates an RSRP distribution for a single Grid Cell ID. As mentioned, the radio profile for a physical radio cell formed by an RBS is based on multiple grid cells geographically covered by the radio cell, having as a result that the radio profile of the physical radio cell will comprise a number of RSRP distributions, one for each grid cell.

[0088] The grid may be formed by using a so-called S2 Geometry approach where any estimated UE positons is converted to an S2 Cell Grid ID and the associated RSRP distribution is determined. The S2 Geometiy approach removes the requirement of any search algorithm and a Grid Cell ID can be directly identified based on the estimated UE position. With S2 Geometiy, the latency of the evaluation process is reduced significantly.

[0089] Figure 6 illustrates network nodes being involved in the creation of the radio profile for each cell formed by an RBS in the network coverage area defined by the grid of Figure 5a according to an embodiment.

[0090] Initially in S200, a central node creates the grid of Figure 5a.

[0091] A UE 10 (in practice many UEs) sends in S201 a measurement report to a serving RBS 11, which estimates the position of the UE 10 and sends in S202 the reported RSRP of the cell - i.e. physical radio cell - formed by the RBS 11 for serving the UE 10 to the central node 15, which all RBSs of the network coverage area has access to, along with the UE position and the PCI of the cell for which the reporting is undertaken.

[0092] The central node 15 has access to the grid structure of Figure 5a and identifies Grid Cell ID based on the current UE position in S203. The central node 15 creates in S204 the radio profile for the cell(s) formed the by the serving RBS 11 by gathering numerous RSRP values for different UE locations (and thus grid cells), and will eventually form an RSRP distribution for the identified Grid Cell ID such as that illustrated with reference to Figure 5b. The radio profile for each physical radio cellformed by each RBS in the network coverage area of Figure 5a is created by including all RSRP distributions associated with the grid cells geographically covered by the radio cell. The central node 15 will typically store the radio profiles S205, and any RBS wishing to evaluate one or more radio profiles will turn to the central node 15 for the evaluation, even if it may be envisaged that the radio profiles are sent to the respective RBS.

[0093] As has been discussed, each cell in the network is assigned a PCI, and each radio profile is associated with the PCI of the cell for which the radio proifle is created. If due to changes in the network the PCI of a cell is changed, such change must be reflected by the radio profile being updated to be associated with the changed PCI.

[0094] Thus, with reference to the flowchart of Figure 4 and Figure 6 illustrating the central node 15. In a scenario where the radio profiles of all cells formed by the RBSs in the network coverage area are stored at the central node, steps S102-S104 are performed by the serving RBS 11, while the comparing and matching of S105 is performed by the central node 15. This requires the serving RBS 11 to send the RSRP and the PCI reported by the UE 10, as well as the determined current position of the UE 10, to the central node 15 which performs the comparing and matching of S105 based on the data received by the serving RBS 11. The central node 15 will thereafter provide the serving RBS 11 with the result of the matching, whereupon the serving RBS 11 performs the HO of Sio6a or Sio6b based on the result of the matching.

[0095] In an embodiment, as previosuly mentioned, since one or more neighbour cells with the same PCI may exist, it may be determined how many such neighbour cells exist and which specific neighbour cell’s radio profile(s) will be considered for evaluation in S105, i.e. to which selected radio profiles the reported RSRP should be compared for finding a match.

[0096] One approach is to utilize the K-Nearest Neighbor (KNN) algorithm, where the N nearest neighbours are determined to make the evaluation process more efficient and faster.

[0097] Thus, the central node 15 (or the serving RBS 11 itself depending on implementation) determines for example K = 3 nearest neighbouring cells to a serving cell of the serving RBS 11. In 5G NR, a New Radio Cell Identifier (NCI) isdefined which comprises a gNB Identity and a Cell Identity (the RBS being called gNB in 5G NR). The gNB identity uniquely identifies the serving RBS 11. Further, the RBS 11 may form multiple cells which within the RBS are uniquely identified by the Cell Identity (CI). As is understood, such identifiers typically need to be provided to the central node 15 for identification purposes and the central node 15 further has access to site location information for determining position of any neighbouring RBSs.

[0098] Figure 7 illustrates a flowchart illustrating an embodiment applying the KNN algorithm in combination with computing a so-called Z-score for determining a best match. However, it should be noted that the KNN algorithm is applicable for selecting neighbouring RBSs for which to perform a matching operation in accordance with step S105 of Figure 4.

[0099] Steps S102 and S103 are identical to those already described with reference to Figure 4, and will not be discussed further. However, before or after the UE position is determined in S104, the central node 15 or the serving RBS 11 determines in 8104a the K = 3 nearest neighbouring cells to a serving cell of the serving RBS 11 for which a radio profile comparison is to be undertaken subsequently in S105. It is assumed in the following the steps from 8104a and on is undertaken by the central node 15.

[0100] Thereafter, to perform the matching in S105, a metric referred to as Z- score is computed for the K = 3 nearest neighbouring cells to a serving cell of the serving RBS 11.

[0101] Reference is further made to Figure 8 illustrating the Z-score in an embodiment. Shown in Figure 8 is the RSRP distribution for each neighbouring radio cell -nk (where K = 3) at the reported UE position from which the central node 15 derives the corresponding Grid Cell Id

[0102] As previously has been described, using the reported RSRP (of step S102) and the UE position estimated in S104, the central node determines an appropriate Grid Cell ID and accordingly a radio profile for each of the three neighbouring cells.

[0103] The Z-score is then computed in 8104b as :[Reported RSRP] — [Mean RSRP] Z — score = -[Standard Deviation of RSRP]

[0104] Thus, the reported RSRP is the RSRP reported in S102, while the mean and standard deviation of the RSRP is the mean and standard deviation of the RSRP distribution of the radio profile for each of the three neighbouring cells.

[0105] In this embodiment, the neighbouring cell being considered to be the best match in S105 is the cell having a lowest Z-score as computed in 8104b.

[0106] As previously discussed with reference to Figure 4, in case the matching cell is a cell of the already defined first neighbouring RBS 12, an HO of the UE 10 is effected in Sio6a by the serving RBS 11 to the matching cell of the first neighbouring RBS 12.

[0107] However, as previously discussed with reference to Figure 4, in case the matching cell e.g. is a cell of the undefined third neighbouring RBS 14, an HO of the UE 10 is effected in Sio6b by the serving RBS 11 to the matching cell of the third neighbouring RBS 14.

[0108] As mentioned in case of HO to an undefined neighbouring RBS, some configuration is preferably performed as will be discussed in the following.

[0109] Figure 9 shows a flowchart illustrating a method of correcting PCIs according to an embodiment. Since the cell of the third neighbouring RBS 14 to which an HO was performed in Sio6b was not defined in the neighbour list of the serving RBS 11, it is determined in S107 whether the HO is successful based on information received form the third neighbouring RBS 14, and if so a counter HO_Count is incremented by 1 for the combination of the UE 10 being handed over from a source cell of the serving RBS 11 to a target cell of the third RBS 14 having PCI P2, i.e.[Source Cell, Target Cell, Target PCI]. This information is then sent stored at the central node 15.

[0110] As previously discussed, PCI P2 of the cell of the third neighbouring RBS 14 to which the HO is made cannot be defined in the neighbour list of the serving RBS 11 since PCI P2 already is defined in the neighbour list for a cell of the first neighbouring RBS 12.[oom] For the HO combination [Source Cell, Target Cell, Target PCI], a timer T is further set in Sio / indicating elapsed time from the HO being performed for the first time for this combination.

[0112] Table 1 below illustrates HOs being performed from a cell (i.e. source cell denoted Ni) of the serving RBS 11 to any of the cells (i.e. target cells N2, N3, N4) of the first neighbouring RBS 12, the second neighbouring RBS 13 and the third neighbouring RBS 14.Table 1. HOs from source cell Ni to target cells N2-N4.

[0113] Thus, for each HO being performed by the serving RBS 11, the specific HO combination is added to Table 1 with updated HO_Count in S108. Table 1 will thus continuously be updated with new entries. As is understood, the table will only be updated for handovers made to cells of neighbouring RBSs which have not been defined in the neighbour list.

[0114] Correspondingly, the combinations entered in Table 1 are continuously evaluated as will be described in the following.

[0115] Thus, in S109, it is determined if any combination in Table 1 has a HO_Count which exceeds a set handover threshold value HO_Tresh. HO_Tresh may be set by an operator of the network to any appropriate value.

[0116] If so, it is determined in S110 which target cell has a highest handover threshold value HO_Tresh and for such target cell a new PCI is set in Sin. This newPCI may be temporarily stored in S112 in a PCI change database since it is not possible to instantly update PCIs without avoiding network downtime.

[0117] As is understood, PCI planning is a well-known process in this technical field and will not be described herein.

[0118] However, with the example embodiment hereinabove where the UE 10 is handed over to a cell of the third neighbouring RBS 14, a new PCI may appropriately be set to PCI P3 (since none of the neighbouring RBSs forms any cells to which PCI P3 already is assigned) in S111.

[0119] Thus, once the PCI is updated from P2 to P3 in S113 (and thus can be added to the neighbour list of the serving RBS 11 as previously described), all entries in Table 1 containing target cell N3 is deleted in S114 and evaluation of Table 1 proceeds.

[0120] Again with reference to S109, if HO_Count does not exceed the handover threshold HO_Tresh, it is determined in S115 for the evaluated combination in Table 1 whether or not elapsed time T exceeds a set timer threshold value T_Tresh, which also may be set by an operator of the network to any appropriate value.

[0121] If not, the process proceeds with further evaluations of the entries in Table 1 without any action being taken. If the timer threshold has been exceeded, the combination is deleted from Table 1 in S116 before the evaluation of Table 1 is proceed with.

[0122] Advantageously, in contrast to the prior art where identification of PCI conflicts is purely manual, time consuming and reactive, which leads to a longer time to identify and address the PCI conflicts (through manual deletion of all defined neighbour relations), the proposed embodiment of Figure 9 provides a method to automatically identify and rectify such PCI conflicts conditions, thereby ensuring better network performance without manual intervention.

[0123] Figure 10 illustrates an embodiment where some of the data held at the central node 15 may be stored as local copies at the serving RBS 11 for facilitating handover.

[0124] As previously discussed, determination of appropriate target cell is required and triggering of handover to that cell in real time will thereafter be performed, it is thus important to reduce the latency of the overall evaluation process.To achieve this, local copies of the following two data sets are stored in the serving RBS 11 and updated periodically.1. Site location data - using a common topology service (CTS), a copy of the site location data is pushed to every RBS for local storage and access. As mentioned, the site location data may comprise latitude, longitude and azimuth of cells. A common topology service provides this information to the network nodes based on the predefined conditions or triggers. Whenever there is any addition or change in the site location data, the central node 15 pushes the delta changes to the RBS 11. This information is used to determine the K-nearest neighbours at the RBS 11. In other words, the central node 15 will not send the complete site location data altogether, but only the accumulated changes (i.e. delta).2. Radio profiles - the central node 15 stores the radio profiles (comprising the RSRP distribution of each radio cell for each Grid Cell ID), see S205 of Figure 6. However, to evaluate the Z-score, the RBS 11 only needs the mean and standard deviation of the RSRP distribution for each neighbour cell, as illustrated in Figure 8 (i.e. for the K-nearest neighbours). To make this information locally accessible to an RBS, the central node 15 provides the RBS 11 with the mean value and standard deviation of the RSRP distribution and pushes the delta changes to the RBS 11 whenever there is any change in RSRP distribution of any cell or Grid Cell ID.

[0125] Figure 11 illustrates a device 11, such as an RBS, configured to perform handover of a wireless communication device in a wireless communication system according to an embodiment, where steps of the method performed by the RBS 11 in practice are performed by a processing unit 111 embodied in the form of one or more microprocessors arranged to execute a computer program 112 downloaded to a storage medium 113 associated with the microprocessor, such as a Random Access Memory (RAM), a Flash memory or a hard disk drive. The processing unit 111 is arranged to cause the RBS 11 to cariy out the method according to embodiments when the appropriate computer program 112 comprising computer-executable instructions is downloaded to the storage medium 113 and executed by the processing unit 111. The storage medium 113 may also be a computer program product comprising the computer program 112. Alternatively, the computer program 112 maybe transferred to the storage medium 113 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 112 may be downloaded to the storage medium 113 over a network. The processing unit 111 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc. The RBS 11 further comprises a communication interface 114 (wired and / or wireless) over which the RBS 11 is configured to transmit and receive data.

[0126] Figure 12 illustrates a device 15, such as a central node, configured to create radio profiles representing radio conditions of physical radio cells formed by radio base stations in a wireless communication system according to an embodiment, where steps of the method performed by the central node 15 in practice are performed by a processing unit 211 embodied in the form of one or more microprocessors arranged to execute a computer program 212 downloaded to a storage medium 213 associated with the microprocessor, such as a RAM, a Flash memory or a hard disk drive. The processing unit 211 is arranged to cause the central node 15 to carry out the method according to embodiments when the appropriate computer program 212 comprising computer-executable instructions is downloaded to the storage medium 213 and executed by the processing unit 111. The storage medium 213 may also be a computer program product comprising the computer program 212. Alternatively, the computer program 212 may be transferred to the storage medium 213 by means of a suitable computer program product, such as a DVD or a memory stick. As a further alternative, the computer program 212 maybe downloaded to the storage medium 213 over a network. The processing unit 211 may alternatively be embodied in the form of a DSP, an ASIC, an FPGA, a CPLD, etc. The central node 15 further comprises a communication interface 214 (wired and / or wireless) over which the central node 15 is configured to transmit and receive data.

[0127] The devices 11, 15 may be composed of multiple physically separate components (e.g., a NodeB component and a radio network controller (RNC) component, or a base transceiver station (BTS) component and a base station controller (BSC) component, etc.), which may each have their own respective components. In certain scenarios in which the devices 11, 15 comprise multiple separate components (e.g., BTS and BSC components), one or more of the separatecomponents maybe shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate device. In some embodiments, the devices 11, 15 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components maybe duplicated (e.g., separate memory for different RATs) and some components maybe reused (e.g., a same antenna may be shared by different RATs). The devices 11, 15 may also include multiple sets of the various illustrated components for different wireless technologies integrated into devices 11, 15, for example Global System for Mobile Communications (GSM), Wideband Code Division Multiple Access (WCDMA), Long Term Evolution (LTE), New Radio (NR), WiFi, Zigbee, Z-wave, Long Range Wide Area Network (LoRaWAN), Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies maybe integrated into the same or different chip or set of chips and other components within devices 11, 15.

[0128] Figure 13 illustrates a network in the form of an Open RAN 101 (O-RAN), in which embodiments may be implemented. For example, the method of performing handover of a wireless communication device may be implemented in an O-eNB 300.

[0129] With reference to the O-RAN 101, the role of a Non-Real Time RAN intelligent controller (RIC) 200 is among other things, such as providing a service management and orchestration framework, to serve one or more radio base stations 300 (i.e. RAN sites) referred to as O-eNB via 01 interface and to provide high-level control signals to Near- Real Time RICs 400 via Al interface; such signals include but not limited to policy-based guidance, machine-learning (ML) model management, and enrichment of data. The role of Near- Real Time RICs 400 is to perform low-level control signals to O-RAN compatible network elements including the one or more O- eNBs 300, O-CU-CP 500, O-CU-UP 600 and 0-DU 700 via E2 interface. Further included is an 0-RU 800 connected to the 0-DU 700 via a control, user and synchronization (CUS) plane as well as via a management (M) plane, and an O-Cloud 900, i.e. a cloud platform.

[0130] With reference to embodiments described hereinabove, the CTS and a module for creating radio profiles may reside e.g. in the Near-Real Time RIC 400, for instance in an application referred to as an rApp. The evaluation of radio profiles, i.e. the comparing of reported RSRPs with preconfigured radio profiles and any PCIcorrection, maybe performed in the Non-Real Time RIC 200. The actual performing of the handovers based on the evaluation of radio profiles may be performed in the O- CU-CP 500.

[0131] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

[0132] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

CLAIMS1. A method of a serving radio base station (11) of performing handover of a wireless communication device (to) in a wireless communication system, comprising: receiving (S102) a radio measurement report from the wireless communication device (10) comprising measurement data acquired by the wireless communication device (10) from at least one neighbouring radio base station (14) indicating that a handover to said at least one neighbouring radio base station (14) is to be performed; determining (S103) whether a physical cell identifier, PCI, of the radio measurement report identifying a cell of the neighbouring radio base station (14) for which the measurement data is acquired already has been assigned to a cell of another neighbouring radio base station (12) and defined in a neighbour list of the serving radio base station (11); and if so: determining (S104) a current position of the wireless communication device (10); comparing (S105) the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells of neighbouring radio base stations (12, 14) having the same PCI as the identified cell of the radio measurement report by taking into account the current position of the wireless communication device (10); and if there is match between the measurement data and one of the preconfigured radio profiles for the current position of the wireless communication device (10): performing (Sio6a, Sio6b) a handover of the wireless communication device (10) to the cell of a neighbouring radio base station (12, 14) for which there is a radio profile match.

2. The method of claim 1, wherein in case the cell for which there is a radio profile match is the cell of the neighbouring radio base station (12) already defined in the neighbour list, the handover is performed (Sio6a) to said already defined cell of the neighbouring radio base station (12).

3. The method of claim 1, wherein in case the cell for which there is a radio profile match is a cell of the neighbouring radio base station (14) not defined in the neighbour list, the handover is performed (Sio6b) to said non-defined cell of theneighbouring radio base station (14), the method further comprises: incrementing (S107), in case of successful handover, a counter for a combination of a cell of the serving radio base station (11) from which the handover is performed, the cell of the neighbouring radio base station (14) to which the handover is performed and the PCI of the cell to which the handover is performed, and initiating a timer; adding (S108) said combination, counter value and timer value as an entry in a table comprising corresponding combinations, counter values and timers of other handovers from the serving radio base station (11) to cells with the identified PCI; determining (S109) if the counter value exceeds a set counter threshold value for one or more of the combinations in the table; and if so determining (S110) a cell of a neighbouring radio base station (12, 14) having a highest counter value; setting (S111) a new PCI for the cell having the highest counter value; and storing (S112) the new PCI for the cell having the highest counter value.

4. The method of claim 3, further comprising: updating (S113) the PCI for the cell having the highest counter value with the set new PCI; and deleting (S114) all entries in the table containing the cell for which the PCI is updated.

5. The method of claims 3 or 4, further comprising, upon determining (S109) that the counter value does not exceed the set counter threshold value for one or more of the combinations in the table: determining (S 115) if the timer value for a combination exceeds a set timer threshold value, and if so deleting (S116) the entry corresponding to said combination from the table.

6. The method of any one of the preceding claims, wherein the radio profiles representing radio conditions of cells comprise distributions of signal strength values for communication being performed by radio base stations serving the cells withwireless communication devices at different wireless communication device positions in the cells.

7. The method of claim 6, the signal strength being represented by one or more of reference signal received power, RSRP, reference signal received quality, RSRQ, and signal-to-noise and interference ratio, SINR.

8. The method of claims 6 or 7, wherein the comparing (S105) of the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells comprises: comparing a signal strength value of the received radio measurement report with a mean value of the distribution of signal strength values for the current wireless communication device position for the radio profiles, wherein the radio profile having a smallest difference between the signal strength value of the received radio measurement report and said mean value is considered to be a match.

9. The method of claim 8, wherein the comparing further comprises: dividing (8104b) the difference between the signal strength value of the received radio measurement report and said mean value with standard deviation of the distribution, wherein the radio profile having a smallest quota after the division with the standard deviation is considered to be a match.

10. The method of any one of the preceding claims, wherein the cells of neighbouring radio base stations (12, 14) having the same PCI as the identified cell which are selected for comparing (S105) is selected (8104a) using a K-Nearest Neighbor, KNN, algorithm, where the selected N nearest neighbours are determined for the comparing (S105).

11. A computer program (112) comprising computer-executable instructions for causing a radio base station (11) to perform steps recited in any one of claims 1-10 when the computer-executable instructions are executed on a processing unit (111) included in the radio base station (11).

12. A computer program product comprising a computer readable medium (113), the computer readable medium having the computer program (112) according to claim 11 embodied thereon.

13. A method of a device (15) of creating radio profiles representing radio conditions of physical radio cells formed by radio base stations (11, 12, 13, 14) in a wireless communication system; creating (S200) a grid for a complete network coverage area including the radio base stations (12, 14), wherein each grid cell is associated with a unique grid cell identifier; receiving (S202) signal strength values of wireless communication devices (10) communicating with the radio base stations (11, 12, 13, 14) at different wireless communication device position, and a physical cell identifier, PCI, of the physical radio cell for which the signal strength values are received; identifying (S203) a grid cell identifier for each wireless communication device position; creating (S204) a distribution of signal strength values reported by the wireless communication devices for each grid cell identifier; creating (S204) a radio profile for each cell comprising the distribution of signal strength values for each grid cell identifier geographically covered by the physical radio cell; and storing (S205) the created radio profiles.

14. A computer program (212) comprising computer-executable instructions for causing a device (15) to perform steps recited in claim 13 when the computerexecutable instructions are executed on a processing unit (211) included in device (15)-15. A computer program product comprising a computer readable medium (213), the computer readable medium having the computer program (212) according to claim 14 embodied thereon.

16. A serving radio base station (n) configured to perform handover of a wireless communication device (10) in a wireless communication system, the serving radio base station (n) comprising a processing unit (ill) and a memory (113), said memory containing instructions (112) executable by said processing unit (111), whereby the radio base station (10) is operative to: receive (S102) a radio measurement report from the wireless communication device (10) comprising measurement data acquired by the wireless communication device (10) from at least one neighbouring radio base station (14) indicating that a handover to said at least one neighbouring radio base station (14) is to be performed; determine (S103) whether a physical cell identifier, PCI, of the radio measurement report identifying a cell of the neighbouring radio base station (14) for which the measurement data is acquired already has been assigned to a cell of another neighbouring radio base station (12) and defined in a neighbour list of the serving radio base station (11); and if so: determine (S104) a current position of the wireless communication device (10); compare (S105) the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells of neighbouring radio base stations (12, 14) having the same PCI as the identified cell of the radio measurement report by taking into account the current position of the wireless communication device (10); and if there is match between the measurement data and one of the preconfigured radio profiles for the current position of the wireless communication device (10): perform (Sio6a, Sio6b) a handover of the wireless communication device (10) to the cell of a neighbouring radio base station (12, 14) for which there is a radio profile match.

17. The serving radio base station (11) of claim 16, wherein in case the cell for which there is a radio profile match is the cell of the neighbouring radio base station (12) already defined in the neighbour list, the handover is performed (Sio6a) to said already defined cell of the neighbouring radio base station (12).

18. The serving radio base station (11) of claim 16, wherein in case the cell for which there is a radio profile match is a cell of the neighbouring radio base station (14) notdefined in the neighbour list, the handover is performed (Sio6b) to said non-defined cell of the neighbouring radio base station (14), the method further comprises: incrementing (S107), in case of successful handover, a counter for a combination of a cell of the serving radio base station (11) from which the handover is performed, the cell of the neighbouring radio base station (14) to which the handover is performed and the PCI of the cell to which the handover is performed, and initiating a timer; adding (S108) said combination, counter value and timer value as an entry in a table comprising corresponding combinations, counter values and timers of other handovers from the serving radio base station (11) to cells with the identified PCI; determining (S109) if the counter value exceeds a set counter threshold value for one or more of the combinations in the table; and if so determining (S110) a cell of a neighbouring radio base station (12, 14) having a highest counter value; setting (S111) a new PCI for the cell having the highest counter value; and storing (S112) the new PCI for the cell having the highest counter value.

19. The serving radio base station (11) of claim 18, further being operative to: update (S113) the PCI for the cell having the highest counter value with the set new PCI; and delete all entries in the table containing the cell for which the PCI is updated.

20. The serving radio base station (11) of claims 18 or 19, further being operative to, upon determining (S109) that the counter value does not exceed the set counter threshold value for one or more of the combinations in the table: determine (S115) if the timer value for a combination exceeds a set timer threshold value, and if so delete (S116) the entry corresponding to said combination from the table.

21. The serving radio base station (11) of any one of claims 16-20, wherein the radio profiles representing radio conditions of cells comprise distributions of signal strength values for communication being performed by radio base stations servingthe cells with wireless communication devices at different wireless communication device positions in the cells.

22. The serving radio base station (11) of claim 21, the signal strength being represented by one or more of reference signal received power, RSRP, reference signal received quality, RSRQ, and signal-to-noise and interference ratio, SINR.

23. The serving radio base station (11) of claims 21 or 22, further being operative to, when comparing (S105) the measurement data of the received radio measurement report with preconfigured radio profiles representing radio conditions of cells: compare a signal strength value of the received radio measurement report with a mean value of the distribution of signal strength values for the current wireless communication device position for the radio profiles, wherein the radio profile having a smallest difference between the signal strength value of the received radio measurement report and said mean value is considered to be a match.

24. The serving radio base station (11) of claim 23, further being operative to, when performing the comparing of the signal strength value: divide (8104b) the difference between the signal strength value of the received radio measurement report and said mean value with standard deviation of the distribution, wherein the radio profile having a smallest quota after the division with the standard deviation is considered to be a match.

25. The serving radio base station (11) of any one of claims 16-24, wherein the cells of neighbouring radio base stations (12, 14) having the same PCI as the identified cell which are selected for comparing (S105) is selected (8104a) using a K-Nearest Neighbor, KNN, algorithm, where the selected N nearest neighbours are determined for the comparing (S105).

26. A device (15) configured to create radio profiles representing radio conditions of physical radio cells formed by radio base stations (11, 12, 13, 14) in a wireless communication system, the device (15) comprising a processing unit (211) and a memory (213), said memory containing instructions (212) executable by saidprocessing unit (211), whereby the device (15) is operative to: create (S200) a grid for a complete network coverage area including the radio base stations (12, 14), wherein each grid cell is associated with a unique grid cell identifier; receive (S202) signal strength values of wireless communication devices (10) communicating with the radio base stations (11, 12, 13, 14) at different wireless communication device position, and a physical cell identifier, PCI, of the physical radio cell for which the signal strength values are received; identify (S203) a grid cell identifier for each wireless communication device position; create (S204) a distribution of signal strength values reported by the wireless communication devices for each grid cell identifier; create (S204) a radio profile for each cell comprising the distribution of signal strength values for each grid cell identifier geographically covered by the physical radio cell; and store (S205) the created radio profiles.

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