Interference source location

Abstract

Determining a location region of an interference source affecting a cellular telecommunications network comprises receiving 202 an indication of a first cell that is affected by an interference source and determining 204 related cells most likely to be affected by the interference source. Correlation coefficients between uplink power data of the first cell and uplink power data of each of the related cells are determined 208 and the related cells are ranked 210 based on their respective determined correlation coefficients. Coverage areas are determined 212 for the first cell and each of the related cells and an overlap area is determined 214 comprising overlap between the coverage area of the first cell and the coverage area of the highest ranked related cell. The overlap area is iteratively reduced 216 by sequentially selecting the related cells and reducing the overlap area to include only a portion that overlaps with the coverage area of the selected cell until a criterion is met, when the reduced overlap area is determined 218 as the location region of the interference source.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods and apparatus for determining a location region of an interference source in a cellular telecommunications network. BACKGROUND

[0002] Demand for wireless data traffic has undergone a large increase in recent years and continues to increase. Accordingly, mobile networks are becoming increasingly complex in order to satisfy the continuous and increasing demand for connectivity, not only for human communications but also for machines, sensors, and other devices connected to the internet.

[0003] To provide wireless connectivity to support these data communications, mobile network operators assemble Radio Access Networks (RAN) of base stations such as eNodeBs providing cells of a radio communications system implementing various Radio Access Technologies (RATs), such as UMTS, LTE and 5G NR. These network providers installing these RATs rely on radio spectrum assets to provide uplink and downlink connectivity by, for example, transmitter and receiver devices encoding and decoding data onto transmissions of different radio frequency subcarriers using a suitable multiplexing method to access the radio channels, such as Orthogonal Frequency Division Multiple Access (OFDMA) or Wideband Code Division Multiple Access (WCDMA). The various RATs specify suitable communications protocols using these multiplexing methods by which base stations and multiple user communication devices in a geographic region can connect and exchange data communications.

[0004] To ensure a high availability of connectivity for users of their networks, operators seek to secure the reliable use of spectrum assets sufficient to support the demanded data traffic. For example, to satisfy the anticipated growth in traffic demand with the development of new applications, mobile network operators are deploying cells operating in the millimetre wave spectrum. This provides superior capacity to serve various applications and devices.

[0005] A challenge arises from serving such huge amount of devices as well as serving such various frequency bands with extended number of cells in the form of interference. Sources of interference in the radio spectrum assets can come, for example, from a fault in the mobile network equipment itself, or from a device, such as a user-installed relay, radio transceiver, a satellite receiver, or a military radio source, provided in the geographic region of the network transmitting signals in the radio spectrum that interfere with normal radio communications. Such interference sources will cause high impact on other users and base stations in their 1 ability to receive and correctly decode signals above the interference noise. This can affect both downlink (base station to user) and uplink (user to base station) channels. However, the effect of interference is more severe in uplink where mobile device power is limited, and the base station uses sensitive receivers in order to be able to decode the users’ signals. Typically, a relatively high received power in base station indicates the reception of undesired interfered signal. However, there are challenges for mobile network operators with identifying and locating the sources of interference within their network, with field engineers typically being deployed to search for them using field equipment such as a spectrum analyser. This can take a significant amount of time before a source of interference is identified, located, and addressed, during which data communication in the network is disrupted. [00061 It is in this context that the present disclosure has been devised. SUMMARY

[0007] According to an aspect of the present disclosure there is provided a computer-implemented method of determining a location region of an interference source affecting a cellular telecommunications network comprising a plurality of cells. The method may comprise: receiving an indication of a first cell of the cellular telecommunications network which is affected by an interference source; determining a plurality of related cells most likely to be affected by an interference source which is affecting the first cell; receiving, for the first cell and each of the related cells, uplink power data representative of a power of uplink signals received at a base station operating the respective cells; determining correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells; ranking the related cells based on their respective determined correlation coefficients; determining, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received at a base station operating the respective cell; determining an overlap area comprising a geographic area in which the coverage area of the first cell overlaps with the coverage area of the highest ranked related cell; iteratively reducing the overlap area by sequentially selecting, in order of the ranking of the related cells, a related cell and reducing the overlap area to include only a portion of the overlap area which overlaps with the coverage area of the selected cell, wherein the overlap area is iteratively reduced until a criterion is met; and determining the reduced overlap area when the criterion is met as the location region of the interference source.

[0008] In this way an efficient method is provided which uses data from multiple cells to narrow down a location region in which an interference source may be situated. Ranking the related cells according to their determined correlation coefficient and then iterating through the related cells in order of their ranking means that highly correlated cells are initially used to determine an overlap area which is then iteratively reduced to narrow down the overlap area. The overlap area may be efficiently reduced until it is small enough to allow for easy investigation in the field. For example, the overlap area may be reduced to a size roughly corresponding to a single building. An entirely automatic process may therefore be utilised to efficiently direct field investigations to a narrow search area (such as a single building). Furthermore, the method utilises data which is already collected as part of routine operation of the cellular communications network and thus no extra measurement and / or data collection may be needed in order to determine the location region.

[0009] The indication of a first cell which is affected by an interference source may be generated as part of routine monitoring of cells. The indication of a first cell which is affected by an interference source may be generated, for example, as a key performance indicator (KPI) indicating that the first cell may be affected by an interference source. The indication of a first cell which is affected by an interference source may, for example, be generated in dependence on detecting abnormal uplink signals in the first cell. For example, abnormally high power may be received at a base station in one or more frequency bands. Abnormally high power received in one or more frequency bands may, for example, comprise power which is much greater than power being received in other frequency bands over the same or similar time intervals.

[0010] The determining the plurality of related cells most likely to be affect by a same interference source which is affecting the first cell may comprise determining neighbouring cells and / or cells which are situated within a threshold distance of the first cell. The determining the plurality of related cells most likely to be affected by a same interference source which is affecting the first cell may comprise determining a geographic extent of antenna beams used in the first cell and in a plurality of other cells. For example, each cell may be operated by a base station using one or more antennas which have a spatial antenna beam representing a geographic region over which downlink signals are transmitted and / or a geographic region from which uplink signals are received. Determining the plurality of related cells may comprise determining cells having an antenna beam which intersects and / or overlaps with an antenna beam of the first cell.

[0011] The uplink power data may comprise received power in one or more frequency bands. The uplink power data may, for example, comprise received Power Spectral Density (PSD) of power received at a base station. The uplink power data may comprise measures such as Received Interference Power (RIP) and / or Received Signal Strength Indicator (RSSI). The uplink power data may be representative of power received in a plurality of time intervals. The plurality of time intervals may extend over a plurality of hours and / or a plurality of days. For example, the plurality of time intervals may extend over a period of six days or more. The received uplink power data comprises uplink power data corresponding to the first cell and uplink power data corresponding to each of the related cells. For example, the uplink power data may comprise first uplink power data representative of a power of uplink signals received at a base station operating the first cell, second uplink power data representative of a power of uplink signals received at a base station operating a first of the related cells, and third uplink power data representative of a power of uplink signals received at a base station operating a second of the related cells etc. The received power data for the first cell and each of the related cells are each representative of power received during a time period (which may extend over a plurality of time intervals for which received power is included in the received power data). The received power data for the first cell and each of the related cells may correspond to the same or at least overlapping time periods such that they include data representative of power received during a common time period.

[0012] The determined correlation coefficients may each comprise a numerical value indicative of a similarity between the received uplink power data of the first cell and the received uplink power data of a respective related cell. The determined correlation coefficients may, for example, comprise values of the Pearson correlation coefficient. A determined correlation coefficient having a relatively high value may be indicative of relatively high similarity between the uplink power data of the first cell and the uplink power data of the respective related cell. A determined correlation coefficient having a relatively low value may be indicative of relatively low similarity between the uplink power data of the first cell and the uplink power data of the respective related cell. For example, a first correlation coefficient may be determined for a first related cell (and being a measure of correlation between uplink power date of the first cell and uplink power data of the first related cell) and a second correlation coefficient may be determined for a second related cell (and being a measure of correlation between uplink power data of the first cell and uplink power data of the second related cell). If the first correlation coefficient is greater than the second correlation coefficient then this may indicate that the uplink power data of the first related cell is more similar to the uplink power data of the first cell than the uplink power data of the second related cell. Conversely, if the first correlation coefficient is less than the second correlation coefficient then this may indicate that the uplink power data of the first related cell is less similar to the uplink power data of the first cell than the uplink power data of the second related cell. [00131 A correlation coefficient is determined for each of the related cells. That is, a separate correlation coefficient (e.g., a correlation coefficient) is determined for each related cell (the correlation coefficient being representative of the correlation between the uplink power data of the first cell and the uplink power data of the respective related cell).

[0014] Ranking the related cells may comprise ranking the related cells in order of their determined correlation coefficient. For example, a related cell having a highest correlation coefficient amongst the determined correlation coefficients may be ranked highest of the related cells. A related cell having a lowest correlation coefficient amongst the determined correlation coefficients may be ranked lowest of the related cells.

[0015] Determining, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received may comprise determining a geographic area in which terminal devices have been situated whilst attached to the respective cell. For example, historical data indicative of the location of terminal devices when attached to the cell may be used to determine a coverage area. The historical data may, for example, comprise timing advance data indicative of a timing advance used for terminal devices when attached to the respective cell. The timing advance data may be representative of distances from a base station operating the cell of terminal devices attached to the cell. The timing advance data may therefore be used to determine a maximum distance from the base station to which the coverage area should extend.

[0016] A coverage area may be based, for example, on a maximum distance from a base station operating a respective cell, a direction from the base station in which the cell extends and an angular extent of the cell.

[0017] Separate coverage areas are determined for each of the first cell and each of the related cells. For example, a first coverage area may be determined for the first cell, a second coverage area may be determined for a first cell of the related cells, a third coverage area may be determined for a second cell of the related cells, and a fourth coverage area may be determined for a third cell of the related cells, etc.

[0018] Determining an overlap area comprising a geographic area in which the coverage area of the first cell overlaps with the coverage of the highest ranked related cell may comprise determining the overlap area as a geographic area which is common to both the coverage area of the first cell and the coverage area of the highest ranked related cell. The highest ranked related cell may comprise the related cell having the largest correlation coefficient of the correlation coefficients determined for each of the related cells. The highest ranked related cell may comprise the related cell with uplink power data which is most similar to the uplink power data of the first cell.

[0019] Iteratively reducing the overlap area may comprise a plurality of iterations. Each iteration comprises selecting a related cell. The related cells are selected sequentially in order of the ranking of the related cells. For example, after the highest ranked related area is used to determine the overlap area, in a first iteration the second highest ranked related cell may be selected. In a second iteration the third highest ranked related cell may be selected. In a third iteration the fourth highest ranked related cell may be selected and so on.

[0020] Each iteration further comprises reducing the overlap area to include only a portion of the overlap area which overlaps with the coverage area of the selected cell. For example, in a first iteration the reduced overlap area may be determined as a geographic area in which the originally determined overlap area (the area of overlap between the coverage area of the first cell and the coverage area of the highest ranked related cell) overlaps with the coverage area of the selected cell (the second highest ranked related cell for the first iteration). In each subsequent iteration, the reduced overlap for that iteration may be determined as a geographic area in which the reduced overlap area from the previous iteration overlaps with the coverage area of the selected cell for that iteration. In this way the reduced overlap area is iteratively reduced based on overlap between the reduced coverage area from a previous iteration and a coverage area of the related cell selected for that iteration.

[0021] The overlap area is iteratively reduced until a criterion is met such as the overlap area being reduced to less than a threshold area and / or all of the related cells having been iterated through to reduce the overlap area. Once the criterion is met, the location region of the interference source is based on the reduced overlap area at the point at which the criterion is met. The criterion may comprise a plurality of criteria. The overlap area may be iteratively reduced until at least one of a plurality of criteria are met. For example, the overlap area my be iteratively reduced until the overlap area is reduced to less than a threshold area or all of the related cells have been iterated through to reduce the overlap area (whichever comes first).

[0022] The determining the plurality of related cells most likely to be affected by a same interference source as an interference source which is affecting the first cell may comprise: receiving physical cell data associated with the first cell and a plurality of candidate cells, the physical cell data associated with each cell comprising data related to the physical location of the respective cell; ranking the plurality of candidate cells based on the physical cell data in order of likelihood of being affected by a same interference source as an interference source affecting the first cell; and determining the plurality of related cells as a subset of the candidate cells based on the ranking of the candidate cells.

[0023] The uplink power data may comprise data representative of a power spectral density (PSD) in carrier signals across a plurality of different frequency bands and in a plurality of time intervals received at the base station operating the respective cell.

[0024] The determining correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells may comprise: generating an image representative of the uplink power data of the first cell; generating images representative of the uplink power data of each of the related cells; and performing image processing to determine a correlation coefficient between the image representative of the uplink power data of the first cell and each of the images representative of the uplink power data of each of the related cells.

[0025] Generating an image representative of the uplink power data of the first cell may comprise filtering the uplink power data of the first cell to only include uplink power data which exceeds a power threshold and generating the image based on the filtered uplink power data.

[0026] Generating an image representative of the uplink power data of each of the related cells may comprise filtering the uplink power data of each of the related cells to only include uplink power data which exceeds a power threshold and generating an image representative of the filtered uplink power data for each related cell.

[0027] Generating an image representative of the uplink power data of the first cell may comprise adding image padding to an image representative of the uplink power data of the first cell.

[0028] Generating an image representative of the uplink power data of each of the related cells may comprise adding image padding to an image representative of the uplink power data of each of the related cells.

[0029] The determining, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received at a base station operating the respective cell, may comprise: receiving, for the first cell and each of the related cells, a geographic location of a base station operating the respective cell; receiving, for the first cell and each of the related cells, timing advance data representative of a timing advance of terminals attached to the respective cell; determining, for the first cell and each of the related cells, and in dependence on the respective timing advance data, a maximum distance from the base station operating the respective cell; and determining the coverage area for the first cell and each of the related cells in dependence on the geographic location of the base station operating the respective cell and the determined maximum distance from the base station for the respective cell.

[0030] The method may further comprise: receiving, for the first cell and each of the related cells, an angular extent of the respective cell; and determining the coverage area for the first cell and each of the related cells in dependence on the geographic location of the base station operating the respective cell, the determined maximum distance from the base station for the respective cell and the angular extent of the respective cell.

[0031] Iteratively reducing the overlap area until a criterion is met may comprise iteratively reducing the overlap area until the reduced overlap area has an area which is less than a threshold area.

[0032] Iteratively reducing the overlap area until a criterion is met may comprise iteratively reducing the overlap area until all of the related cells have been selected and the overlap area has been reduced based on all of the related cells.

[0033] The method may further comprise outputting data representative of the determined location region of the interference source.

[0034] Outputting data representative of the determined location region of the interference source may comprise generating a visualisation of the determined location region of the interference source.

[0035] According to an aspect of the present disclosure there is provided a computing apparatus for determining a location region of an interference source affecting a cellular telecommunications network comprising a plurality of cells, the computing apparatus comprising: one or more processors; and memory comprising instructions which when executed by one or more of the processors cause the computing apparatus to be operable to: receive an indication of a first cell of the cellular telecommunications network which is affected by an interference source; determine a plurality of related cells most likely to be affected by an interference source which is affecting the first cell; receive, for the first cell and each of the related cells, uplink power data representative of a power of uplink signals received at a base station operating the respective cells; determine correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells; rank the related cells based on their respective determined correlation coefficients; determine, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received at a base station operating the respective cell; determine an overlap area comprising a geographic area in which the coverage area of the first cell overlaps with the coverage area of the highest ranked related cell; iteratively reduce the overlap area by sequentially selecting, in order of the ranking of the related cells, a related cell and reducing the overlap area to include only a portion of the overlap area which overlaps with the coverage area of the selected cell, wherein the overlap area is iteratively reduced until a criterion is met; and determine the reduced overlap area when the criterion is met as the location region of the interference source.

[0036] According to an aspect of the present disclosure there is provided a computer readable medium carrying instructions which when executed by one or more processors of a computing apparatus, cause the computing apparatus to be operable to carry out a method according to an aspect disclosed herein.

[0037] It will be appreciated from the foregoing disclosure and the following detailed description of the examples that certain features and implementations described as being optional in relation to any given aspect of the disclosure set out above should be understood by the reader as being disclosed also in combination with the other aspects of the present disclosure, where applicable. Similarly, it will be appreciated that any attendant advantages described in relation to any given aspect of the disclosure set out above should be understood by the reader as being disclosed as advantages of the other aspects of the present disclosure, where applicable. That is, the description of optional features and advantages in relation to a specific aspect of the disclosure above is not limiting, and it should be understood that the disclosures of these optional features and advantages are intended to relate to all aspects of the disclosure in combination, where such combination is applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Certain examples of the present disclosure will now be described, with reference to the accompanying drawings, in which: - FIG. I is a schematic illustration of an example cellular telecommunications network; - FIG. 2 is a flowchart of a method according to examples disclosed herein; - FIG. 3 is a representation of received uplink power for a first cell and a second cell which are affected by a common source of interference; - FIG. 4 is a representation of received uplink power for a cell before and after filtering and padding; - FIG. 5 is a flowchart of a method of iteratively reducing an overlap area as disclosed herein; - FIG. 6A is a schematic illustration of a portion of a cellular telecommunications network illustrating a part of a method described herein; - FIG. 6B is a schematic illustration of a portion of a cellular telecommunications network illustrating a further part of a method described herein; - FIG. 6C is a schematic illustration of a portion of a cellular telecommunications network illustrating a further part of a method described herein; - FIG. 6D is a schematic illustration of a portion of a cellular telecommunications network illustrating a further part of a method described herein; - FIG. 6E is a schematic illustration of a portion of a cellular telecommunications network illustrating a further part of a method described herein; - FIG. 6F is a schematic illustration of a portion of a cellular telecommunications network illustrating a further part of a method described herein; - FIG. 7 is an example visualisation of a location region determined according to a method disclosed herein; - FIG. 8 is a further example visualisation of location regions determined according to a method disclosed herein; and - FIG. 9 is a schematic illustration of an electronic device which may be used to implement all or part of a method disclosed herein. DETAILED DESCRIPTION

[0039] Hereinafter, examples of the disclosure are described with reference to the accompanying drawings. However, it should be appreciated that the disclosure is not limited to the described examples, and all changes and / or equivalents or replacements thereto also belong to the scope of the disclosure. The same or similar reference denotations may be used to refer to the same or similar elements throughout the specification and the drawings.

[0040] As used herein, the terms “have,” “may have,” “include,” or “may include” a feature (e.g., a number, function, operation, or a component such as a part) indicate the existence of the feature and do not exclude the existence of other features. Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0041] As used herein, the terms “A or B,” “at least one of A and / or B,” or “one or more of A and / or B” may include all possible combinations of A and B. For example, “A or B,” “at least one of A and B,” “at least one of A or B” may indicate all of (1) including at least one A, (2) including at least one B, or (3) including at least one A and at least one B.

[0042] As used herein, the terms “first” and “second” may modify various components regardless of importance and do not limit the components. These terms are only used to distinguish one component from another. For example, reference to a first component and a second component may indicate different components from each other regardless of the order or importance of the components.

[0043] It will be understood that when an element (e.g., a first element) is referred to as being (physically, operatively or communicatively) “coupled with / to,” or “connected with / to” another element (e.g., a second element), it can be coupled or connected with / to the other element directly or via a third element. In contrast, it will be understood that when an element (e.g., a first element) is referred to as being “directly coupled with / to” or “directly connected with / to” another element (e.g., a second element), no other element (e.g., a third element) intervenes between the element and the other element.

[0044] The terms as used herein are provided merely to describe some embodiments thereof, but not to limit the scope of other embodiments of the disclosure. It is to be understood that the singular forms “a,” “'an,” and “the” include plural references unless the context clearly dictates otherwise. All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the disclosure belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0045] FIG. 1 is a schematic illustration of an example cellular telecommunications network 102 comprising a first base station 104a, a second base station 104b, a third base station 104c, a fourth base station 104d, and a fifth base station 104e coupled to a computing apparatus implementing an interference location estimator 106. The coupling between the interference location estimator 106 and the cellular telecommunications network 102 is a network connection so that data, including uplink power data representative of uplink power received at base stations 104a - 104e of the cellular telecommunications network 102 can be provided to the interference location estimator 106. The interference location estimator 106 may form part of a Radio Access Network (RAN), a core network or may be realised as a separate computing apparatus (e.g., a server) in network communication (e.g., over the internet) with the base stations 104a - 104e. The interference location estimator 106 may be realised as one or more computing apparatus (such as a general purpose computing apparatus).

[0046] The base stations 104a - 104e together provide a patchwork of coverage across the geographic area 110 through which terminal devices can be seamlessly served with wireless connections. Each base station 104a - 104c operates at least one cell corresponding to a geographic area served by the base station 104a - 104e and in which radio coverage is provided to terminal devices situated within the geographic area. A base station 104a - 104e may operate a single cell or may operate a plurality of different cells from the same base station site. For example, a base station 104a - 104c may comprise directional antennas (which may include multi-element antenna arrays) and may operate multiple cells which correspond with different angular segments relative to the base station 104a - 104e. Additionally or alternatively a base station may operate multiple cells using different frequency bands and / or radio access technologies (RATs).

[0047] A base station 104a - 104e may take any suitable form and may, for example, comprise a radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), evolved Node B (eNB or eNodeB), Node B, next generation eNodeB (ng-eNodeB), gNodeB (gNB), multi-standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), and suchlike. Each base station may support voice and data communication by one or more Radio Access Technologies (RATs), such as UMTS, LTE, 5G NR and 6G.

[0048] Whilst the cellular telecommunications network 102 is depicted in FIG. 1 as comprising five base stations 104a - 104e, it will be appreciated that a cellular telecommunications networks 102 may comprise any number of base stations and may for example comprise many more than five base stations.

[0049] In the example illustrated in FIG. 1, an interference source 108 is also located in the geographic area 110 in which the cellular telecommunications network 102 provides cellular coverage to terminals. An interference source 108 may be any source of radiation in frequency bands that can be allocated as radio resources by the base stations 104a - 104e. Examples of typical interference sources 108 may include (but are not limited to) faulty network hardware (e.g., a faulty base station or faulty repeater) and / or an unlicensed device such as a repeater, jammer, relay, radio transceiver, satellite receiver and / or military radio source.

[0050] The presence of the interference source 108 can generate significant interference in one or more frequency bands in which the base stations 104a - 104e are configured by the RATs they implement to communicate by means of one or more antennas located at each base station. For example, an interference source 108 may transmit signals in frequency bands that can be allocated as radio resources by the base stations 104a - 104c. This raises the noise floor, causing significant errors in the detection of the symbols encoded on the relatively weak modulated signals transmitted by terminal devices allocated radio resources in the frequency bands suffering from interference. This interference and noise leads to high error rates in the uplink channel, limiting cellular connectivity for terminal devices near the interference source 108 and bandwidth overall. An interference source 108 can thus disrupt the spectrum assets used by a cellular telecommunications network 102 to serve wireless connections to terminal devices (which may be refereed to as user equipment), which thus limits the capacity of the cellular telecommunications network 102 to serve terminal devices reliably.

[0051] When an interference source 108 begins to disrupt the spectrum assets and thus coverage in a geographic area 110, the mobile network operator providing the cellular telecommunications network 102 needs to identify and locate the interference source 108 and take action to remove it. To achieve this, the mobile network operator typically deploys a drive test on the network, deploying field engineers to search for the interference source 108 using field equipment such as a spectrum analyser. This can take a significant amount of time before a source of interference is identified, located, and addressed, during which data communication in the network is disrupted. An interference source 108 may be situated in a fixed location for a relatively long period of time, may be mounted to a moveable platform (e.g., a vehicle) and / or may itself be portable, which may further complicate the process of locating an interference source 108 in the field.

[0052] As will be described below, the interference location estimator 106 and the methods described herein can drastically speed up the process of locating the interference source 108 by determining a location region in which the interference source 108 is situated. The location region for the interference source 108 in the geographic area 110 may be determined using an automatic process using received uplink signals at one or more of the base stations 104a -104e.

[0053] FIG. 2 is a flowchart illustrating a method of determining a location region of an interference source 108 affecting a cellular telecommunications network 102. All or part of the method 200 of FIG. 2 may be implemented by one or more computing apparatus. For example, all or part of the method 200 may be implemented by an interference location estimator 106.

[0054] At step 202, of the method 200 of FIG. 2, an indication of a first cell affected by an interference source 108 is received. The first cell may be any cell of a cellular telecommunications network 102 and may, for example, be operated by any base station 104a - base station 104e. The indication that the first cell is affected by an interference source 108 may be based on measurements of received uplink power at a base station operating the first cell. For example, the indication may be based on detecting abnormal received uplink power in one or more frequency bands at a base station operating the first cell. Abnormal received uplink power, may, for example, comprise received uplink power exceeding a threshold. The threshold may be equal to or greater than a maximum received power which would be expected during normal operation of terminal devices in the network and thus received power exceeding the threshold may be indicative of another source of radiation in the one or more frequency bands such as an interference source 108.

[0055] The indication that the first cell is affected by an interference source 108 may be generated as part of routine monitoring for interference. For example, a base station 104a -104c or other network entity may routinely monitor received uplink power and detect any abnormalities which may be indicative of an interference source 108. A detected abnormality may then be reported (e.g., to the interference location estimator 106) as in indication that a first cell is affected by an interference source 108. The indication may, for example, be generated as a key performance indicator (KPI).

[0056] The indication received at step 202 identifies a first cell which is affected by an interference source 108 but may not provide sufficient information in itself to sufficiently narrow down the location of the interference source 108.

[0057] At step 204 a plurality of related cells are determined which are most likely to be affected by an interference source which is affecting the first cell (for which the indication was received at step 202). The plurality of related cells may be determined in dependence on physical cell data representative of the physical location and / or orientation of one or more cells. For example, physical cell data may be received for the first cell and a plurality of candidate cells. The candidate cells may then be ranked based on their physical cell data in order of their likelihood of being affected by an interference source which affects the first cell. For example, a highest ranked candidate cell may represent a cell most likely (of the candidate cells) to be affected by an interference source which affects the first cell. A lowest ranked candidate cell may represent a cell which is least likely (of the candidate cells) to be affected by an interference source which affects the first cell. The plurality of related cells may be determined as a subset of the candidate cells based on the ranking of the candidate cells. For example, the highest ranked candidate cells may be selected as the related cells. The highest ranked candidate cells may comprise a given number of highest ranked candidate cells. For example, the 30 highest ranked candidate cells may be selected as the related cells. Of course, a different number of cells to select as the related cells may be used. For example, the 20 highest ranked candidate cells may be selected as the related cells, the 40 highest ranked candidate cells may be selected as the related cells (or any other suitable number of candidate cells).

[0058] Physical cell data may include an indication of the geographic location of a cell. For example, physical cell data may include an indication of the geographic location of a base station operating the cell. The physical cell data may include an indication of a coverage area in which network coverage is provided by the cell. The physical cell data may include an indication of, for example, an orientation of one or more antenna used to provide the cell. The physical cell data may include an indication of, for example, an angular extent and / or a maximum beam coverage distance of one or more antenna used to provide the cell.

[0059] In some examples, a simulation may be performed to determine the likely coverage of the first cell and one or more candidate cells. In some examples, a simulation may be performed to determine the likely extent and position of antenna beams used to provide the first cell and one or more candidate cells. An extent and position of an antenna beam may be referred to as an antenna beam area. Such simulations may be based on physical cell data corresponding to the first cell and the one or more candidate cells. Simulation results may be used to determine the related cells and / or to rank candidate cells for selecting the related cells.

[0060] In some examples, selection of related cells and / or ranking of candidate cells may be based on one or more factors indicative of a relationship between the first cell and each respective candidate cell. For example, selection of related cells and / or ranking of candidate cells may be based on a distance between the first cell and each respective candidate cell. Candidate cells with a relatively smaller distance from the first cell may be highly ranked and / or selected as a related cell. Selection of related cells and / or ranking of candidate cells may be based on an overlap of a coverage area of the first cell and a coverage area of a respective candidate cell. Candidate cells with a coverage area which overlaps with a coverage area of the first cell may be highly ranked and / or selected as a related cell. Selection of related cells and / or ranking of candidate cells may be based on an overlap of an antenna beam area of the first cell and an antenna beam area of a respective candidate cell. Candidate cells with an antenna beam area which overlaps with an antenna beam area of the first cell may be highly ranked and / or selected as a related cell. Selection of related cells and / or ranking of candidate cells may be based on a base station operating a respective candidate cell being situated within a coverage area and / or an antenna beam area of the first cell. Candidate cells with a base station situated within a coverage area and / or an antenna beam of the first cell may be highly ranked and / or selected as a related cell. Selection of related cells and / or ranking of candidate cells may be based on a base station operating the first cell being situated within a coverage area and / or an antenna beam area of a respective candidate cell. Candidate cells with a coverage area and / or antenna beam in which a base station of the first cell is situated may be highly ranked and / or selected as a related cell. Selection of related cells and / or ranking of candidate cells may be based on a coverage area and / or an antenna beam of a respective candidate cell facing a base station, coverage area and / or an antenna beam area of the first cell. Candidate cells with a coverage area and / or an antenna beam facing a base station, coverage area and / or an antenna beam area of the first cell may be highly ranked and / or selected as a related cell.

[0061] The determination of related cells at step 204 may comprise a first selection of potential cells which may have collected uplink power data which is affected by the interference source 108 and can therefore be used in order to determine a potential location of the interference source 108.

[0062] At step 206 uplink power data is received for the first cell and each of the related cells determined at step 204. The uplink power data is representative of a power of uplink signals received at a base station operating the respective cells. For example, the uplink power data may comprise first uplink power data representative of a power of uplink signals received at a base station operating the first cell, second uplink power data representative of a power of uplink signals received at a base station operating a first of the related cells, third uplink power data representative of a power of uplink signals received at a base station operating a second of the related cells and so on for each of the related cells.

[0063] The power of uplink signals received at a base station may comprise (or at least may be based upon) measurements of radio signal power received in one or more frequency bands. The uplink power data may, for example, comprise received Power Spectral Density (PSD) of power received at a base station. The uplink power data may comprise measures such as Received Interference Power (RIP) and / or Received Signal Strength Indicator (RSSI). In some examples raw received uplink power data may be generated by post-processing data provided by the base stations. In some examples, one or more cells may operate with a plurality of antennas (e.g., using a multi-element antenna array). In such examples, the received uplink power data may be provided as received uplink power split per receiving beam and compute angle of arrival.

[0064] The uplink power data (e.g., PSD) may be representative of power received in a plurality of time intervals. The plurality of time intervals may extend over a plurality of hours and / or a plurality of days. For example, the plurality of time intervals may extend over a period of six days or more. In an example, the uplink power data may be provided by the base stations as an average power for each frequency band (such as a resource block) taken periodically for a given time period (e.g. every hour),

[0065] The uplink power data (e.g., a PSD) may be aggregated for a number days, and it may be generated as a snapshot or as an average of raw uplink power over a plurality of time intervals. The time intervals may, for example, be every 15 minutes, every hour, or any other suitable interval to characterise the development in the received uplink power over time. In some examples, sources of interference may be introduced and persist, or be intermittent, over a matter of days or hours, and require observation over a timeframe of at least a few hours or a few days to allow their detection, correlation and location.

[0066] The uplink power data corresponding to the first cell and each of the related cells may correspond to the same or at least overlapping time periods such that they include data representative of power received during a common time period. For example, the uplink power data corresponding to the first cell and each of the related cells may correspond to the same hours and / or days. In some examples, the uplink power data corresponding to the first cell and each of the related cells may correspond to the last N number of days from a current time. For example, the uplink power data corresponding to the first cell and each of the related cells may correspond to the last six or more days.

[0067] FIG. 3 is a representation of received uplink power for a first cell and a second cell which are affected by a common source of interference. FIG. 3 includes a includes a first spectrogram 302 and a second spectrogram 304. In each spectrogram 302, 304, different frequency bands are represented by different positions on the vertical axis and different time intervals are represented by different positions on the horizontal axis. The shading provided for each frequency band and time interval is representative of received uplink power in that frequency band and over that time interval. The first spectrogram 302 and the second spectrogram 304 represent approximately the same frequency bands and time intervals.

[0068] The first spectrogram 302 is representative of received uplink power detected at a base station operating a first cell. The first cell may correspond with a first cell for which an indication of being affected by an interference source is being received. For example, the first spectrogram 302 indicates abnormally high received uplink power in at least some of the illustrated frequency bands and for at least some of the illustrated time period.

[0069] The second spectrogram 304 is representative of received uplink power detected at a base station operating a second cell. The second cell may be a neighbouring cell to the first cell, or at least a cell which is affected by an interference source which affects the first cell. The second cell might therefore be selected as a related cell in step 204. As can be seen through a comparison of the first spectrogram 302 and the second spectrogram 304, the second spectrogram 304 includes similar power signatures in at least some of the illustrated frequency bands and for at least some of the illustrated time period as those seen in the first spectrogram 302. In particular, power signatures which may be indicative of an interference source 108 (e.g., abnormally high received power) appear in corresponding time intervals and frequency bands in both the first spectrogram 302 and the second spectrogram 304. This may indicate that the first cell and the second cell are affected by a common interference source 108.

[0070] In step 208 correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells are determined. That is, for each of the related cells a correlation coefficient is determined which comprises a measure of a correlation between the uplink power data of the first cell and the uplink power data of the respective related cell.

[0071] The determined correlation coefficients may each comprise a numerical value indicative of a similarity between the received uplink power data of the first cell and the received uplink power data of a respective related cell. The determined correlation coefficients may, for example, comprise values of the Pearson correlation coefficient. A determined correlation coefficient having a relatively high value may be indicative of relatively high similarity between the uplink power data of the first cell and the uplink power data of the respective related cell. A determined correlation coefficient having a relatively low value may be indicative of relatively low similarity between the uplink power data of the first cell and the uplink power data of the respective related cell.

[0072] The correlation coefficients may be determined, for example, based on matrices representing the uplink power data of the first cell and each of the related cells. For example, values indicative of power received in a plurality of frequency bands and during a plurality of time intervals may be placed in a two-dimensional matrix, where the position in the matrix represents the frequency band and time interval to which the power corresponds. Corresponding matrix representations may be formulated for the uplink power data of the first cell and each of the related cells. Correlation coefficients (e.g., Pearson correlation coefficients) may then be determined for the matrix representing the first cell and matrices representing each of the related cells.

[0073] Additionally or alternatively, correlation coefficients may be determined by generating an image representative of the uplink power data of the first cell and generating corresponding images representative of the uplink power data of each of the related cells. Generated images may, for example, comprise generating spectrograms such as the spectrograms shown in FIG. 3 and described above. Image processing may then be performed to determine correlation coefficients between the image representative of the uplink power data of the first cell and each of the images representative of the uplink power data of the related cells. For example, a correlation coefficient may be determined between the first spectrogram 302 and the second spectrogram 304.

[0074] In some examples, uplink power data may undergo pre-processing before determination of the correlation coefficients. For example, the uplink power data may be filtered to only include uplink power data which exceeds a threshold power. The threshold power may be approximately -100 decibel-milliwatts (dBm) and / or approximately -95 dBm.

[0075] As was explained above, an interference source 108 may show up in uplink power data in the form of abnormally high received power in one or more frequency bands and / or time intervals. It might therefore be reasonable to assume that an interference source 108 will result in received power which is greater than a threshold power in the uplink power data. By filtering the uplink power data using a threshold power, the uplink power data can be filtered to only include uplink power for time intervals and frequency bands whose uplink power indicates that they may be affected by an interference source 108. Correlation coefficients may then be computed more efficiently based on filtered uplink power data (when compared to computing correlation coefficients based on unfiltered uplink power data). Additionally or alternatively, filtering the uplink power data may mean that the correlation coefficients are more representative of a correlation between interference source 108 power signatures in the respective uplink power data, since other contributions to the data (which may naturally vary from cell to cell, e.g., due to different levels of data traffic and congestion in each cell) are filtered out. [00761 In at least some examples, uplink power data for the first cell may be filtered using a first threshold power and uplink power data for the related cells may be filtered using a second (different) threshold power. Since the first cell is a cell for which an interference indication has been received, it may be reasonable to assume that the first cell is relatively close to the interference source 108 and / or that the first cell is relatively strongly affected by the interference source 108. It might therefore be reasonable to assume that the interference source 108 will cause higher received uplink power in the first cell than at least some of the related cells. For this reason, a higher first threshold power may be used to filter the uplink power data for the first cell than the second threshold power used to filter the uplink power data for the second cell. That is, the first threshold power may be greater than the second threshold power. In at least one illustrative example, the first threshold power may be -95 dBm and the second threshold power may be -100 dBm. However, other values for the threshold powers may be used.

[0077] In at least some examples, padding may be added to uplink power data before determination of the correlation coefficients. Adding padding to uplink power data may comprise adding data (e.g., null data) to a periphery of the uplink power data. For example, in the context of a matrix representation of the uplink power data, additional columns and / or rows may be added to the beginning and / or the end of the columns and / or rows. The additional columns and / or rows my be populated with the same value (e.g., zero). In the context of image representations, additional regions of the image may be added around the periphery of the image. Such additional regions may be formed of the same shade or colour.

[0078] Adding padding to the uplink power data before determination of the correlation coefficients may reduce sensitivity of the determined correlation coefficients to specific frequency bands and / or time intervals. For example, different cells may not use exactly the same frequency bands and / or data may not be recorded in exactly the same time intervals. Additionally or alternatively, radio signals generated by a given interference source 108 may not appear in exactly the same frequency bands and / or time intervals in each cell. Consequently, received power signatures indicative of the same interference source 108 may not appear in exactly the same place in the uplink power data for each cell. Padding may therefore be used to reduce the sensitivity of the determination of correlation coefficients to precise locations within the uplink power data.

[0079] FIG. 4 is a representation of received uplink power for a cell before and after filtering and padding. FIG. 4 includes a first spectrogram 402 and a second spectrogram 404. The representation used to form the spectrograms 402, 404 of FIG. 4 are the same as the representation used to form the spectrograms 302, 304 of FIG. 3. For example, different 20 frequency bands are represented by different positions on the vertical axis and different time intervals are represented by different positions on the horizontal axis.

[0080] The first spectrogram 402 is a spectrogram representation of uplink power data before any filtering or padding. The second spectrogram 404 is a spectrogram representation of the same uplink power data after applying filtering and image padding as described above.

[0081] Returning again to the method 200 of FIG. 2, at step 210 the related cells are ranked based on their determined correlation coefficients. The related cells are ranked in order of their associated correlation coefficient. The related cells may be ranked so that the related cells with higher associated correlation coefficients are ranked higher. For example, the related cell with the highest correlation coefficient may be ranked highest (first) of the related cells, the related cell with the second highest correlation coefficient may be ranked second highest of the related cells, the related cell with the third highest correlation coefficient may be ranked third highest of the related cells, and so on until the related cells with the lowest correlation coefficient may be ranked lowest of the related cells.

[0082] As was explained above, the determined correlation coefficients for each related cell is a measure of the similarity between the uplink power data of the first cell and the uplink power data of each related cell. The ranking of the related cells based on their determined correlation coefficients therefore serves to rank the related cell in order of the similarity of their uplink power data to the uplink power data for the first cell. Since, the uplink power data for the first cell includes power signatures indicative of an interference source 108, related cells with a higher correlation coefficient (and thus ranked more highly) may be considered to be more likely to include corresponding power signatures indicative of the same interference source 108. Higher ranked related cells may therefore be more likely to also be affected by the same interference source 108 as the first cell. Higher ranked related cells may therefore be more useful for narrowing down the location of the interference source 108 since they are also affected by the same interference source 108.

[0083] At step 212 of the method 200 of FIG. 2, a coverage area is determined for the first cell and each of the related cells. The coverage area for each cell is determined to be representative of a geographic area from which uplink signals are received at a base station operating the respective cell. That is, the coverage area determined for the first cell is representative of a geographic area from which uplink signals are received at a base station operating the first cell and the same for each of the related cells. In at least some examples, determining, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received may comprise determining a geographic area in which terminal devices have been situated whilst attached to the respective cell. For example, historical data indicative of the location of terminal devices when attached to the cell may be used to determine a coverage area. The coverage area for each cell may be determined, at least in part, through simulation of each cell (e.g., using corresponding or the same simulations to those described above with reference to determining the related cells).

[0084] A coverage area for a given cell may be representative of a geographical area which, if an interference source 108 were to be situated in that geographic area, then it would affect the uplink signals received in that cell.

[0085] A coverage area may be determined for each cell based on physical cell data for that cell. As was explained above, physical cell data may include data such as an indication of a geographic location of a base station operating a cell, an indication of an orientation of one or more antenna used to provide a cell and / or an indication of an angular extent and / or a maximum beam coverage distance of one or more antenna used to provide a cell.

[0086] In at least some examples, the method 200 may comprise receiving timing advance data for the first cell and each of the related cells. The timing advance data may be representative of a timing advance of terminals attached to the respective cell. A timing advance is a measure commonly used in cellular telecommunications networks to ensure synchronisation between a base station and a terminal device and is typically indicative of a length of time which it takes for a signal transmitted from a terminal device to reach a base station to which it is attached. Signal transmission time is dependent, at least in part, on a distance between a terminal device and a base station. A timing advance of a given terminal is therefore indicative of a distance between the terminal and the base station. Timing advance data can therefore be used to determine a maximum distance from a base station to which a coverage area should extend for a cell operated by the base station.

[0087] A maximum distance from a base station to which a coverage area should extend may be determined according to a maximum or a given percentile of timing advances used by terminals attached to the base station over a historical time period. For example, timing advance data may be received for a cell which is representative of timing advances used by terminals attached to that cell over a time period which at least approximately corresponds to the time period to which the received uplink power data corresponds (e.g., the last several days). A maximum or given percentile of the timing advances may be used to determine a maximum distance. For example, a timing advance which represents a 99th percentile (other percentiles may be used) of all of the timing advances used by terminals attached to the cell over a given time period may be used to determine a maximum distance. The maximum distance may then be determined as a distance from the base station to which the 99th percentile timing advance corresponds.

[0088] In at least some examples, a coverage area for a cell may be determined based at least on the geographic location of a base station operating that cell and a maximum distance determined for that cell (e.g., based on timing advance data for the cell). For example, the coverage area may be determined as an area which extends from the geographic location of the base station and for the determined maximum distance.

[0089] In some examples, an angular extent of the cell may also be used to determine the coverage area. An angular extent may comprise a range of angles relative to the base station over which a coverage area extends. For example, an angular extent may be determined from an orientation and angular range of one or more antennas (or antenna beams) used to provide coverage to the cell. The angular extent of the cell may be used to determine an angular segment extending from a base station and for the maximum distance.

[0090] A determined coverage area may comprise a two-dimensional geographic region. For simplicity a determined coverage area may comprise a polygon. Alternatively, curved edges may be used to construct at least part of a determined coverage area.

[0091] FIG. 6A is a schematic illustration of a portion of a cellular telecommunications network 602 in which four base stations 604a, 604b, 604c and 604d are shown. A coverage area is determined for each base station 604a -604c and is illustrated in FIG. 6A by dotted lines extending from each base station 604a -604c (the dotted lines illustrating the outer extent of each coverage area). In particular, a first coverage area 606a is determined and shown representing a cell operated by a first base station 604a. A second coverage area 606b is determined and shown representing a cell operated by a second base station 604b. A third coverage area 606c is determined and shown representing a cell operated by a third base station 604c and a fourth coverage area 606d is determined and shown representing a cell operated by a fourth base station 604d.

[0092] At step 214 of the method 200 of FIG. 2 an overlap area is determined. The overlap area determined at step 214 comprises a geographic area in which the coverage area of the first cell overlaps with the coverage area of the highest ranked related cell. As was explained above, the coverage area of each cell corresponds with a region in which an interference source 108 in that region will affect uplink power data for that cell. Furthermore, the highest ranked related cell has uplink power data having a relatively high correlation with the uplink power data of the first cell (which has been indicated as being affected by an interference source 108). It is therefore likely that a common interference source 108 is affecting both the first cell and the highest ranked related cell and that the common interference source 108 is situated within the coverage area of the first cell and the coverage area of the highest ranked related cell. It may therefore be assumed that the the interference source 108 is situated within the overlap area which represents a geographic region which is common to the coverage area of the first cell and the coverage area of the highest ranked related cell.

[0093] An illustrative example, of the determination of an overlap area will be described below with reference to FIG. 6A to FIG. 6F. Each of FIG. 6B to FIG. 6F are schematic illustrations of the same portion of a cellular telecommunications network 602 as is depicted in FIG. 6A and as was described above. For the purposes of the illustrative example, which will be explained with reference to FIG. 6A to FIG. 6F, the first cell for which an indication of interference is received (as described above with reference to step 202) is taken to be a cell operated by the first base station 604a having a first coverage area 606a. A plurality of related cells (as determined in step 204 described above) are taken to be cells operated by the second base station 604b, the third base station 604c and the fourth base station 604d having second 606b, third 606c and fourth 606d coverage areas respectively. A highest ranked related cell (a related cell having the highest correlation coefficient of the related cells) is taken to be the cell operated by the second base station 604b and having the second coverage area 606b. As is shown in FIG. 6B the first coverage area 606a and the second coverage area 606b overlap in an overlap area 608. In the depicted example, the overlap area 608 marked in FIG. 6B is taken to be the overlap area 608 determined in step 214.

[0094] Returning again, to the method 200 of FIG. 2, at step 216 the overlap area 608 is iteratively reduced by sequentially selecting a related cell and reducing the overlap area 608 to include only a portion of the overlap area 608 which overlaps with the coverage area of the selected cell. The related cells are sequentially selected in order of their ranking and the overlap area is iteratively reduced until a criterion is met.

[0095] Iteratively reducing the overlap area 608 according to step 216 is illustrated in more detail in the flowchart of FIG. 5 in which step 502, step 504 and step 506 of the flowchart of FIG. 5 together form an iterative process corresponding to step 216 of the flowchart of FIG. 2. The flowchart of FIG. 5 begins with step 214, which is the same as step 214 described above with reference to FIG. 2. The method then proceeds to step 502 in which a next highest ranked related cell is selected. In a first iteration of the iterative process formed by step 502, step 504 and step 506, the next highest ranked related cell will be the second highest ranked related cell (next highest ranked after the highest ranked related cell used to determine the overlap area 608 in step 214). In the example illustrated in FIG. 6A to FIG. 6F the second highest ranked related cell is taken to be a cell operated by the third base station 604c and having the third coverage area 606c.

[0096] At step 504 the overlap area is reduced to include only a portion of the previously determined overlap area which overlaps with the coverage area of the selected cell. The previously determined overlap area is the overlap area determined in the last iteration or in the case of the first iteration, the overlap area determined in step 214. In the example illustrated in FIG. 6A to FIG. 6F, in a first iteration an overlap between the overlap area 608 determined in step 214 (and as described above with reference to Fig. 6B) and the third coverage area 606c (corresponding to the second highest ranked related cell) is determined as shown in FIG. 6C. The overlap area 608 is then reduced to include only a portion of the previously determined overlap area which overlaps with the third coverage area 606c. The reduced overlap area 608 after this step is shown in FIG. 6D.

[0097] At step 506 it is determined whether a criterion for terminating the iterative process is met. In some examples, at step 506 is may be determined whether at least one of a plurality of criteria is met. In some examples, a criterion may comprise whether the overlap area has been reduced to being less than a threshold area. The threshold area may comprise an area which represents a reasonable area for a field engineer to investigate to locate an interference source 108. For example, the threshold area may roughly correspond to an area of approximately one building so that the location of an interference source 108 is narrowed down to about a single building to be investigated by a field engineer. In some examples, the threshold area may be about 1000 metres squared (m2).

[0098] Additionally or alternatively, a criterion may comprise whether all of the related cells have been iterated through to reduce the overlap area. In some examples, the iterative process may proceed until either the overlap area has been reduced to being less than a threshold area or all of the related cells have been iterated through to reduce the overlap area (whichever is met first).

[0099] If a criterion has not yet been met at step 506 then the method returns to step 502 for another iteration and the next highest ranked related cell is selected. For example, in a second iteration the third highest ranked related cell is selected. In the example illustrated in FIG. 6A to FIG. 6F the third highest ranked related cell is taken to be a cell operated by the fourth base station 604d and having the fourth coverage area 606d.

[0100] The method then proceeds again to step 504 and the overlap area is again reduced to include only a portion of the previously determined overlap area which overlaps with the coverage area of the selected cell. The previously determined overlap area corresponds with the overlap area determined in the last iteration. In the example illustrated in FIG. 6A to FIG. 6F, in a second iteration an overlap between the overlap area 608 determined and shown in FIG. 6D and the fourth coverage area 606d (corresponding to the third highest ranked related cell) is determined as shown in FIG. 6E. The overlap area 608 is then reduced to include only a portion of the previously determined overlap area which overlaps with the fourth coverage area 606d. The reduced overlap area 608 after this step is shown in FIG. 6F.

[0101] After a further reduction in the overlap area, the method again proceeds to step 506 at which it is determined whether a criterion is met. If a criterion is not met then the method again returns to step 502 for another iteration to further reduce the overlap area. If a criterion is met (e.g., the overlap area is reduced to less than a threshold area and / or all related cells have been iterated through) then the method proceeds to step 218 which is shown in both FIG. 2 and in FIG. 5. At step 218 the reduced overlap area (the overlap area 608 as determined in the last iteration) is determined as a location region of the interference source 108. The overlap area 608 as reduced through the iterative reduction process thus corresponds with a narrowed down region in which the interference source 108 is likely to be situated.

[0102] A location region of an interference source 108 (as determined by a method 200 according to FIG. 2) may be output to aid investigation in the field in order to take action to remove the interference source 108. For example, the interference location estimator 106 may output data representative of the determined location region of the interference source 108. The data may, for example, be electronically transmitted to another device and / or displayed on an electronic device for inspection by a field engineer. In some examples, a visualisation of a determined location region of an interference source 108 may be determined and transmitted to another device and / or output through an electronic display.

[0103] FIG. 7 is an example visualisation 702 of a location region 704 which may be output. In the visualisation 702 of FIG. 7 a determined location region 704 is overlaid onto a map to illustrate the position and extent of the determined location region 704. The determined location region 704 which is shown in FIG. 7 is the result of finding the overlap of three coverage areas corresponding to three cells. In some examples, more than three cells may be considered to further reduce an overlap area and further narrow down a location region 704.

[0104] FIG. 8 is a further example visualisation 802 of a location region 804. In the example, of FIG. 8 a plurality of location regions 804 are overlaid onto a satellite image of a map in order to illustrate the position and extent of the location regions 804. The plurality of location regions 804 shown in FIG. 8 were determined as a result of a plurality of different instances of performing a method 200 of determining a location region of an interference source. For example, a method 200 the plurality of location regions 804 may be determined for a plurality of different interference sources and / or for a plurality of different times (e.g., in a case where an interference source moves over time).

[0105] Various methods have been described herein in which some of the method steps may be implemented on any suitable electronic device (such as a computing device) and / or combination of electronic devices (e.g. computing devices). FIG. 9 is a schematic illustration of an example electronic device 902 which may be used to implement all or part of any method described herein. For example, an electronic device 902 of the type shown in FIG. 9 and as described below may be used to implement all or part of an interference location estimator 106, a UE, a terminal device and / or a RAN node (e.g., a base station) as described herein. An electronic device 902 of the type shown in FIG. 9 and as described below may be used to implement all or part of method of determining a location region of an interference source as described herein.

[0106] The electronic device 902 may include at least one processing unit 904, memory 908 and an input / output interface 906 (I / O). The processing unit 904 may include any suitable processor and / or combination of processors. For example, the processing unit 904 may include one or more of a Central Processing Unit (CPU) and a Graphical Processing Unit (GPU). The memory 908 may include volatile memory and / or non-volatile / persistent memory. The memory 908 may, for example, be used to store data such as an operating system, instructions to be executed by the processing unit (e.g. in the form of software to be executed by the processing unit), configuration information related to the electronic device 902, session information and / or configuration or registration information associated with any other device, node or module in a network. In some examples, the memory 908 may be used to store instructions for executing any of the methods disclosed herein.

[0107] At least the processing unit 904 is connected to the input / output interface 906. The input / output interface 906 may facilitate communication with one or more other devices. For example, the input / output interface 906 may be operable to transmit and / or receive communications to / from other devices in a network. The input / output interface 906 may, for example, comprise one or more antennas to facilitate wireless communication with one or more other devices. Additionally, or alternatively, the input / output interface 906 may comprise a wired interface for establishing a wired connection with one or more other devices.

[0108] Optionally, the electronic device 902 may further include a display (not shown). The display may comprise any suitable electronic display such as a touch sensitive display. The display may be connected to at least to the processing unit 904. The processing unit 904 may generate display signals which are sent to the display in order to cause the display information.

[0109] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. In particular, any dependent claims may be combined with any of the independent claims and any of the other dependent claims.

[0110] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

Claims

1. A computer-implemented method of determining a location region of an interference source affecting a cellular telecommunications network comprising a plurality of cells, the method comprising:receiving an indication of a first cell of the cellular telecommunications network which is affected by an interference source;determining a plurality of related cells most likely to be affected by an interference source which is affecting the first cell;receiving, for the first cell and each of the related cells, uplink power data representative of a power of uplink signals received at a base station operating the respective cells;determining correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells;ranking the related cells based on their respective determined correlation coefficients;determining, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received at a base station operating the respective cell;determining an overlap area comprising a geographic area in which the coverage area of the first cell overlaps with the coverage area of the highest ranked related cell;iteratively reducing the overlap area by sequentially selecting, in order of the ranking of the related cells, a related cell and reducing the overlap area to include only a portion of the overlap area which overlaps with the coverage area of the selected cell, wherein the overlap area is iteratively reduced until a criterion is met; anddetermining the reduced overlap area when the criterion is met as the location region of the interference source.

2. The computer-implemented method of claim 1, wherein determining the plurality of related cells most likely to be affected by a same interference source as an interference source which is affecting the first cell comprises:receiving physical cell data associated with the first cell and a plurality of candidate cells, the physical cell data associated with each cell comprising data related to the physical location of the respective cell;ranking the plurality of candidate cells based on the physical cell data in order of likelihood of being affected by a same interference source as an interference source affecting the first cell; anddetermining the plurality of related cells as a subset of the candidate cells based on the ranking of the candidate cells.

3. The computer-implemented method of claim 1 or 2, wherein the uplink power data comprises data representative of a power spectral density, PSD, in carrier signals across a plurality of different frequency bands and in a plurality of time intervals received at the base station operating the respective cell.

4. The computer-implemented method of any one of claims 1 to 3, wherein the determining correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells comprises:generating an image representative of the uplink power data of the first cell;generating images representative of the uplink power data of each of the related cells; andperforming image processing to determine a correlation coefficient between the image representative of the uplink power data of the first cell and each of the images representative of the uplink power data of each of the related cells.

5. The computer-implemented method of claim 4, wherein generating an image representative of the uplink power data of the first cell comprises filtering the uplink power data of the first cell to only include uplink power data which exceeds a power threshold and generating the image based on the filtered uplink power data; and / orwherein generating an image representative of the uplink power data of each of the related cells comprises filtering the uplink power data of each of the related cells to only include uplink power data which exceeds a power threshold and generating an image representative of the filtered uplink power data for each related cell.

6. The computer-implemented method of claim 4 or 5, wherein generating an image representative of the uplink power data of the first cell comprises adding image padding to an image representative of the uplink power data of the first cell; and / orwherein generating an image representative of the uplink power data of each of the related cells comprises adding image padding to an image representative of the uplink power data of each of the related cells.

7. The computer-implemented method of any one of claims 1 to 6, wherein the determining, for the first cell and each of the related cells, a coverage area representative of a geographicarea from which uplink signals are received at a base station operating the respective cell, comprises:receiving, for the first cell and each of the related cells, a geographic location of a base station operating the respective cell;receiving, for the first cell and each of the related cells, timing advance data representative of a timing advance of terminals attached to the respective cell;determining, for the first cell and each of the related cells, and in dependence on the respective timing advance data, a maximum distance from the base station operating the respective cell; anddetermining the coverage area for the first cell and each of the related cells in dependence on the geographic location of the base station operating the respective cell and the determined maximum distance from the base station for the respective cell.

8. The computer-implemented method of claim 7, further comprising:receiving, for the first cell and each of the related cells, an angular extent of the respective cell; anddetermining the coverage area for the first cell and each of the related cells in dependence on the geographic location of the base station operating the respective cell, the determined maximum distance from the base station for the respective cell and the angular extent of the respective cell.

9. The computer-implemented method of any one of claims 1 to 8, wherein iteratively reducing the overlap area until a criterion is met comprises iteratively reducing the overlap area until the reduced overlap area has an area which is less than a threshold area.

10. The computer-implemented method of any one of claims 1 to 9, wherein iteratively reducing the overlap area until a criterion is met comprises iteratively reducing the overlap area until all of the related cells have been selected and the overlap area has been reduced based on all of the related cells.

11. The computer-implemented method of any one of claims 1 to 10, further comprising outputting data representative of the determined location region of the interference source.

12. The computer-implemented method of claim 11, wherein the outputting data representative of the determined location region of the interference source comprises generating a visualisation of the determined location region of the interference source.

13. Computing apparatus for determining a location region of an interference source affecting a cellular telecommunications network comprising a plurality of cells, the computing apparatus comprising:one or more processors; andmemory comprising instructions which when executed by one or more of the processors cause the computing apparatus to be operable to:receive an indication of a first cell of the cellular telecommunications networkwhich is affected by an interference source;determine a plurality of related cells most likely to be affected by an interference source which is affecting the first cell;receive, for the first cell and each of the related cells, uplink power data representative of a power of uplink signals received at a base station operating the respective cells;determine correlation coefficients between the uplink power data of the first cell and the uplink power data of each of the plurality of related cells;rank the related cells based on their respective determined correlation coefficients;determine, for the first cell and each of the related cells, a coverage area representative of a geographic area from which uplink signals are received at a base station operating the respective cell;determine an overlap area comprising a geographic area in which the coverage area of the first cell overlaps with the coverage area of the highest ranked related cell;iteratively reduce the overlap area by sequentially selecting, in order of the ranking of the related cells, a related cell and reducing the overlap area to include only a portion of the overlap area which overlaps with the coverage area of the selected cell, wherein the overlap area is iteratively reduced until a criterion is met; anddetermine the reduced overlap area when the criterion is met as the location region of the interference source.

14. A computer readable medium carrying instructions which when executed by one or more processors of a computing apparatus, cause the computing apparatus to be operable to carry out the method of any one of claims 1 to 12.

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