Determining an estimated location of a source of interference

Abstract

Computer-implemented methods, computing apparatus and computer readable media are disclosed for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area. The method includes, for first and second base stations at different first and second locations, determining estimated respective first and second angles of arrival for the interference source at the first and second base station based on a determined difference between a received signal strength (RSS) of the interference source for first and second antennas of the each base station. The method further includes determining, based on the estimated first and second angles of arrival at the respective first and second locations, an estimated location of the interference source in the geographical area.

Description

[0001] DETERMINING AN ESTIMATED LOCATION OF A SOURCE OF INTERFERENCE TECHNICAL FIELD [1] The present application relates to determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area. In particular, the present application provides methods, apparatuses and computer program products for use in determining an estimated location. BACKGROUND [2] Demand on data traffic is increasing every day where mobile technology is playing major role on satisfying such demand. 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. [3] 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 GSM, 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. [4] 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. Thus cells will shortly support easily more than nine concurrent different frequency 115432419.JCJ.MEW bands. This provides superior capacity to serve various application and billions of devices, not only limited to handheld devices, but extends to almost every device. [5] A challenge arises from serving such huge amount of devices manufacturing by diverse suppliers 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 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. [6] It is in this context that the present disclosure has been devised. SUMMARY OF THE INVENTION [7] Viewed from one aspect, the present disclosure provides a computer-implemented method for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area, the method comprising receiving data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of a first base station at a first location in the geographical area, determining an estimated first angle of arrival for the interference source at the first base station at the first location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the first base station, receiving data representative of a received signal strength (RSS) of the interference source for differently directed first and second antennas of a 215432419.JCJ.MEW second base station at a second location in the geographical area, different from the first location, determining an estimated second angle of arrival for the interference source at the second base station at the second location based on a determined difference between the received signal strength (RSS) of the interference source for first and second cells of the second base station, and determining, based on the estimated first and second angles of arrival at the respective first and second locations, an estimated location of the interference source in the geographical area. [8] In this way, the angle of arrival of the signal from the interference source at a base station can be estimated based on the RSS of the received signal at two different antennas at the same base station. By determining the angle of arrival at two interfered base stations, the location of the inference source can be estimated. Thus the angle of arrival estimation of an interference source can be achieved using only the properties of a passive antenna. This can be achieved without having to use expensive active antenna arrays operating massive multiple- input multiple-output (MIMO) technologies to perform beamforming and determine the angle of arrival. Such massive MIMO and beamforming technologies are restricted to certain wavebands and radio access technologies, and, further, mobile network equipment providers of active antennas do not readily make available positioning data relating to received signals that would allow location detection. In contrast, the methods of determining an estimated location of a source of interference disclosed herein can be deployed without limitation to particular wavebands or technologies, using RSS data that is readily available from the mobile network equipment. [9] In embodiments, the method may further comprise receiving data representative of power spectral density, PSD, in carrier signals across different frequency bands received at the base stations for cells of the cellular radio communication system over time intervals, determining, for a cell having abnormal received signal levels in a frequency band indicative of interference in the received PSD data, a correlation coefficient with the PSD data in the same frequency band for neighbouring cells within a maximum distance, identifying groups of interfered cells for which interference may be present based on groups of cells having a correlation coefficient above a threshold, selecting, the first and second antennas of the first base station and the first and second antennas of the second base station from a group of interfered cells associated with two base stations having interference present in two cells thereof. In embodiments, the two base stations selected from the group of interfered cells may 315432419.JCJ.MEW be selected to be the base stations having cells with the highest RSS in the interfered frequency bands in the PSD data thereof. In this way, groups of interfered cells can be identified, and the base stations to be used to determine an estimated location of the interference source.

[0010] In embodiments, the RSS data for an antenna may be based on the received power in the PSD data for the frequency bands indicative of interference. In embodiments, the RSS data may be based on an average received power in the PSD data for the frequency bands indicative of interference, over an observation window, the observation window comprising PSD data captured at intervals over at least one day. In this way, the effects of the interference source on the received signal at the base stations can be clearly identified.

[0011] In embodiments, the method may further comprise selecting a third base station from the group of interfered cells, the third base station also having interference present in two cells thereof at a third location in the geographical area; receiving data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of the third base station serving the two cells having interference present; determining an estimated third angle of arrival for the interference source at the third base station at the third location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the third base station; and wherein the determining of the estimated location of the interference source in the geographical area is further based on the estimated third angle of arrival at the third locations. In this way, using third (and further) base stations to determine an estimated angle of arrival can increase the accuracy of the estimated location of the interference source.

[0012] In embodiments, determining an estimated angle of arrival for the interference source at a base station may be further based on equation modelling the antenna gain for the first and second antennas of the base station at different receive angles. In embodiments, the equation for modelling the antenna gain radiation pattern G(θ) for a given angle of arrival θ relative to the angle of the maximum antenna gain G0 may be: ^^^^ = ^^− 12 , wherein ψ is the half power beam width. Using a reference antenna equation that accurately models the radiation pattern of the received signal for the or each antenna allows the angle of arrival to be accurately estimated. Different reference antenna equations are possible that model different antennas, without limitation to the examples disclosed herein. Using a reference antenna 415432419.JCJ.MEW equation that models a practical antenna leads to an accurate and simple method of estimation of angle of arrival.

[0013] In embodiments, determining an estimated angle of arrival for the interference source at a base station may further comprise determining, from the modelled antenna gain patterns for the first and second antennas of the base station arranged at the angles of orientation of the first and second antennae, the angle of arrival at the base station that gives a difference in the modelled antenna gain for the first and second antennas corresponding to the a determined difference between the received signal strength (RSS) of the interference source for first and second antennas.

[0014] In embodiments, the estimated angle of arrival θ for the interference source at a base station may be determined as: wherein Go1and Go2are the peak antenna gain for the first and second antennas, respectively, and wherein ϕ1and ϕ2are the angles of orientation of the first and second antennas, respectively, where the peak gain of the main lobe is expected, and c is the differential RSS of the interfered signal measured at both antennas.

[0015] In embodiments, the estimated location (x, y) of the interference source in the geographical area may be determined as: wherein θ1 and θ2 are the estimated angles of arrival at the first and second base stations, respectively, and (x1, y1) and (x2, y2) are the locations of the first and second base stations, respectively.

[0016] In embodiments, the signal data from the first and second antennas of the first base station and the first and second antennas of the second base station used to determine their angle of arrival may be received signal strength data from their use as passive antennas. 515432419.JCJ.MEW

[0017] In embodiments, the method may further comprise performing a drive test in the estimated location using field equipment to localise the source of interference.

[0018] Viewed from another aspect, the present disclosure provides computing apparatus for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area, the 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 data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of a first base station at a first location in the geographical area; determine an estimated first angle of arrival for the interference source at the first base station at the first location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the first base station; receive data representative of a received signal strength (RSS) of the interference source for differently directed first and second antennas of a second base station at a second location in the geographical area, different from the first location; determine an estimated second angle of arrival for the interference source at the second base station at the second location based on a determined difference between the received signal strength (RSS) of the interference source for first and second cells of the second base station; and determine, based on the estimated first and second angles of arrival at the respective first and second locations, an estimated location of the interference source in the geographical area.

[0019] In embodiments, viewed from another aspect, the present disclosure provides 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 methods disclosed herein.

[0020] 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 615432419.JCJ.MEW 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 SEVERAL VIEWS OF THE DRAWINGS

[0021] Certain embodiments of the disclosure will now be described by way of example only, with reference to the accompanying figures, in which:

[0022] FIG. 1 shows an example cellular radio communication system providing coverage in a geographical area and computing apparatus implementing an interference location estimator in accordance with aspects of the disclosure;

[0023] FIG. 2 shows an example base station having three directional antennas arranged as sectors to provide cellular coverage in the form of wireless radio connections to user equipment, showing how radio interference from an interference source can be incident on the radiation pattern of the main lobes of different antennas;

[0024] FIG. 3 shows in more detail an example computing apparatus implementing an interference location estimator for determining an estimated location of a source of interference in accordance with aspects of the disclosure;

[0025] FIG. 4 shows an example method for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area in accordance with aspects of the disclosure;

[0026] FIG. 5 shows an example reference antenna equation modelling a practical antenna against the radiation pattern of the main lobe of the practical antenna;

[0027] FIG. 6 shows an example of the estimated angles of arrival of the interference signal at two base stations determined by the interference location estimator, and the estimated location of the interference source where they intersect;

[0028] FIG. 7 shows an example method for determining groups of interfered cells and for identifying two base stations in a group of interfered cells for use in the method described in relation to FIG. 4 in accordance with aspects of the disclosure;

[0029] FIG. 8 shows an example geographical area in which a cellular radio communication system provides coverage in the form of wireless connections, and in which two identified groups of interfered cells are indicated; 715432419.JCJ.MEW

[0030] FIG. 9 shows a detailed view of one of the groups of interfered cells shown in FIG. 8, including three base stations affected by an interference source;

[0031] FIG. 10A shows the spectrograms of PSD of signals received over eight days for five directional antennas serving five cells in a first base station affected by an interference source of the group of interfered cells shown in FIG. 9;

[0032] FIG. 10B shows the spectrograms of PSD of signals received over eight days for four directional antennas serving five cells in a second base station affected by an interference source of the group of interfered cells shown in FIG. 9;

[0033] FIG. 10C shows the spectrograms of PSD of signals received over eight days for four directional antennas serving four cells in a third base station affected by an interference source of the group of interfered cells shown in FIG. 9;

[0034] FIG. 11 shows the estimated angles of arrival of the interference signal at first and second base stations shown in FIG. 9, as determined by the interference location estimator, and the estimated location of the interference source. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the disclosure are described with reference to the accompanying drawings. However, it should be appreciated that the disclosure is not limited to the embodiments, 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.

[0036] 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.

[0037] 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 815432419.JCJ.MEW 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] FIG. 1 shows an example cellular radio communication system 100 comprising a first base station 102a, a second base station 102b, a third base station 102c, a fourth base station 102d, a fifth base station 102e coupled to a computing apparatus implementing an interference location estimator 104 in accordance with aspects of the disclosure. The coupling between the interference location estimator 104 and the cellular radio communication system 100 is a network connection so that data, including received signal strength (RSS) data corresponding to an interference signals received at base stations 102a-102e of the cellular radio communication system 100 can be provided to the interference location estimator 104. 915432419.JCJ.MEW

[0042] An interference source 106 is also located in the geographical area 108 in which the cellular radio communication system 100 provides cellular coverage to user equipment by providing them with wireless radio connections that can support wireless voice and data communications.

[0043] The presence of the interference source 106 can generate significant interference in one or more wavebands in which the base stations are configured by the radio access technologies they implement to communicate by means of one or more antennas located at each base station. The interference signal can thus disrupt the spectrum assets used by a cellular radio communication system 100 to serve wireless connections to user equipment, which thus limits the capacity of the cellular radio communication system 100 to serve end users reliably.

[0044] The base stations 102a-102e together provide a patchwork of coverage across the geographical area 108 through which user equipment can be seamlessly served with wireless connections.

[0045] When an interference source 106 begins to disrupt the spectrum assets and thus coverage in a geographical area 108, the mobile network operator providing the cellular radio communication system 100 needs to identify and locate the interference source 106 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 106 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.

[0046] As will be described below, the interference location estimator 104 can drastically speed up the process of locating interference source 106 by determining an estimated location of the interference source 106 in the geographical area 108 using received signal strength data from the base stations 102a-102e.

[0047] Turning now to FIG. 2, shows in more detail an example of base station 102a showing three directional antennas 202a, 202b, and 202c arranged as sectors to provide cellular coverage in the geographical area 108. The arrangement and number of antennas shown is not limiting, and, as can be seen from the examples below, base stations can include a different number of antennas arranged at azimuthally non-uniform angles to provide desired coverage in the geographical area dependent on geography, topology and demand. For example, a base station at the edge of a residential area may include five different antennas with three directed 1015432419.JCJ.MEW towards the main settlement where the majority of user demand will be, and two antennas directed away from the main settlement and into the rural surroundings where the user demand is lower.

[0048] The three antennas 202a-202c in the base station 102a shown in FIG. 2 are indicated schematically by radiation patterns of their antenna lobes 204a-204c. That is, the first antenna 202a may have a radiation pattern as shown for first antenna lobe 204a, the second antenna 202b may have a radiation pattern as shown for second antenna lobe 204b, and the third antenna 202c may have a radiation pattern as shown for third antenna lobe 204c. The radiation patterns of the antenna lobes indicate a nominal polar plot of the field strength of main lobe of the antennas as it reduces at azimuthal angles away from the direction of the peak of the main beam axis. The receiving pattern of the received signal strength corresponds to the radiation pattern for the antenna. That is, a signal of a given power received at the aziumuthal peak of the main beam of an antenna will be detected by the antenna at a high received signal strength, whereas the same signal with the given power detected at azimuthal angles away from the peak of the main lobe will be detected with a received signal strength proportionally reduced based on the radiation pattern at that angle of arrival.

[0049] Where there are plural directional antennas orientated at different azimuthal angles at the same base station, they will receive a signal from the same signal source at the same power, but the received signal strength for the same received signal will be different for each antenna based on the radiation pattern of that antenna.

[0050] For example, the interference source 106 transmits a signal in a given waveband that propagates to the base station 102a and arrives at that location with a given signal power. As can be seen, the interference signal overlaps the azimuthal polar plots of the radiation patterns of the first antenna lobe 204a and the third antenna lobe 204c. However, the interference signal is located in the geographical area 108 relative to the base station such that, for the angle of arrival of the interference signal, the radiation pattern of the first antenna lobe 204a is greater than for the third antenna lobe 204c. This means that, all else being equal, the received signal strength of the interference signal will be greater at the first antenna 202a than at the third antenna 202c.

[0051] It has been realised that, as will be described below, this principle can be used to estimate the angle of arrival of an interference signal at a base station, using the received signal strength (RSS) data of two antennas at the base station. By using the estimated angle of arrival 1115432419.JCJ.MEW of the interference signal at two base stations affected by the same interference source, the present disclosure allows the determination of an estimated location of the interference source simply using RSS data from passive directional antennas only. This can facilitate the fast identification, location and removal of interference sources, minimising the time needed for drive tests in the field.

[0052] Thus, to determine estimated locations of interference sources in the geographical area 108, the computing apparatus implementing the interference location estimator 104 collects RSS data from the base station 102a-102e providing the cellular radio communication system 100.

[0053] In this regard, FIG. 3 shows an example computing apparatus implementing an interference location estimator 104 for determining an estimated location of a source of interference in accordance with aspects of the disclosure.

[0054] The interference location estimator 104 comprises a memory 302, one or more processors 304 and an input / output module 308. A bus system (not shown) may be provided which supports communication between at the least one processor 304, memory 302 and input / output module 308. The computing apparatus may be a general purpose computing apparatus.

[0055] The processor 304 executes instructions that can be loaded into memory 302. The processor 304 can include any suitable number(s) and type(s) of processors or other devices in any suitable arrangement. Example types of processor 304 include microprocessors, microcontrollers, digital signal processors, field programmable gate arrays and application specific integrated circuits.

[0056] The memory 302 may be provided by any structure(s) capable of storing and facilitating retrieval of information (such as data, program code, and / or other suitable information on a temporary or permanent basis). The memory 302 can represent a random access memory or any other suitable volatile or non-volatile storage device(s). The memory 302 may also contain one or more components or devices supporting longer-term storage of data, such as a read only memory, hard drive, flash memory, or optical disc, which may store software code for loading into the memory 302 at runtime. In use, the processor 304 and memory 302 provide a runtime environment 306 in which instructions or code loaded into the memory 302 can be executed by the processor to generate instances of software modules in the runtime environment 306. 1215432419.JCJ.MEW

[0057] The interference location estimator 104 also comprises input / output module 308 providing a communications interface for receiving data from at least the base station 102a- 102e providing radio access network of the cellular radio communication system 100.

[0058] The memory 302 comprises instructions which, when executed by the one or more processors 304, cause the one or more processors 304 to instantiate an RSS data receiver 310, an angle of arrival estimator 312 and a location estimator 314. In examples, the memory 302 may also comprise instructions which, when executed by the one or more processors 304, cause the one or more processors 304 to instantiate and configure an interference detector 316 (shown in dotted outlines to indicate that this feature is in examples not provided). Together, the RSS data receiver 310, an angle of arrival estimator 312 and a location estimator 314 may carry out the method 400 shown in FIG. 4 for determining an estimated location of a source of interference.

[0059] FIG. 4 shows an example method for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area in accordance with aspects of the disclosure.

[0060] In explaining the operation of the method 400, reference will also be made to FIG. 2, FIG. 5 and FIG. 6.

[0061] As described above, FIG. 2 shows an example base station 102a having three directional antennas arranged as sectors to provide cellular coverage in geographical area 108. FIG. 5 shows an example reference antenna equation modelling a practical antenna against the radiation pattern of the main lobe of the practical antenna. In this case, the practical antenna is the first antenna lobe 204a of the first antenna 202a of the base station 102a. FIG. 6 shows an example of the estimated angles of arrival of the interference signal at a first base station 102a and a second base station 102a at a respective first location (x1, y1) and a respective second location (x2, y2), as determined by the interference location estimator 104, and the estimated location of the interference source 106 where they intersect.

[0062] In step 402, method 400 receives, at RSS data receiver 310, data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of a first base station at a first location in the geographical area.

[0063] Received Signal Strength (RSS) data from a base station refers to the measurement of the power level of the radio signal received by the base station from a specific source or device. It indicates the strength or intensity of the signal as it reaches the base station's receiver. 1315432419.JCJ.MEW

[0064] Thus, in embodiments, as will be described below, the RSS data for an antenna may be based on the received power in the power spectral density (PSD) data for the frequency bands indicative of interference. In embodiments, the RSS data may be based on an average received power in the PSD data for the frequency bands indicative of interference, over an observation window. The observation window may comprise PSD data captured at intervals over at least one day. In the examples shown in FIG. 10A, FIG. 10B and FIG. 10C, the PSD data is collected over eight days. The average PSD for the frequency bands corresponding to the interfered physical resource blocks of the spectrum asses is used to generate the RSS data for the interference signal at each antenna.

[0065] In this respect, in the example shown in FIG. 2, the RSS data for the interference source 106 for the first and second antennas is the data representative of the received signal strength at the frequency of the interference signal as reported by the first antenna 202a and the third antenna 202c. Bearing in mind the first antenna 202a and the third antenna 202c are located at the same base station, the signal power of the interference signal at the base station 102a will be the same for both antennas. However, the received signal strength for the interference source 106 for each of the first antenna 202a and the third antenna 202c will be different, and will depend on the angle of arrival of the interference signal relative beam axis of the radiation pattern as indicated by the first antenna lobe 204a and the third antenna lobe 204c.

[0066] Once the RSS data for the interference signal is received for the first and second antennas at the RSS data receiver 310, this data is passed to the angle of arrival estimator 312 for analysis. It should be noted that the RSS data receiver 310 may process the received data to extract the appropriate RSS data for the relevant antenna to be used in the angle of arrival estimator 312. For example the PSD data may be received, which encompasses the relevant RSS data, and the RSS data receiver 310 may extract the relevant data.

[0067] In the example described below, with reference to FIG. 7, the RSS data receiver 310 may pass to the angle of arrival estimator 312: • RSS data for first and second antennas suffering the interference signal for a first base station 102a at a first location (x1, y1); and • RSS data for first and second antennas suffering the interference signal for a second base station 102a at a second location (x2, y2).

[0068] In step 404, angle of arrival estimator 312 determines, for a first base station 102a, shown in relation to FIG. 7, an estimated angle of arrival as a first angle of arrival estimator 1415432419.JCJ.MEW output 602a for the interference source at the first base station 102a at a first location (x1, y1). This is based on a determined difference between the received signal strength (RSS) of the interference source for first antenna 202a and the second antenna 202b of the first base station 102a.

[0069] In embodiments, determining an estimated angle of arrival for the interference source at a base station may be further based on equation modelling the antenna gain for the first and second antennas of the base station at different receive angles. An example modelled radiation pattern giving a polar plot of the antenna gain for an antenna lobe for the directional first antenna 202a and second antenna 202b antenna is shown in FIG. 5. In embodiments, the equation for modelling the antenna gain radiation pattern G(θ) for a given angle of arrival θ relative to the angle of the maximum antenna gain G0may be: wherein ψ is the half power beam width.

[0070] As can be seen in FIG. 5, the reference antenna equation shown above provides an antenna gain pattern closely the matching the radiation pattern of the practical antenna it is modelling.

[0071] Here it is assumed that the different antennas of the base stations can be modelled by the same reference antenna equation, albeit with different parameters, but this is no intended to be limiting. Different antennas may be best described using different reference antenna equation models. Using any reference antenna equation that accurately models the radiation pattern of the received signal for the or each antenna allows the angle of arrival to be accurately estimated. Different reference antenna equations are possible that model different antennas, without limitation to the examples disclosed herein. Using a reference antenna equation that models a practical antenna leads to an accurate and simple method of estimation of angle of arrival.

[0072] The angle of arrival estimator 312 may determine an estimated angle of arrival θ for the interference source 106 at a base station 102a by determining, from the modelled antenna gain patterns for the first and second antennas of the base station 102a arranged at the angles of orientation of the first and second antennae, the angle of arrival at the base station that gives a difference in the modelled antenna gain for the first and second antennas corresponding to the 1515432419.JCJ.MEW determined difference between the received signal strength (RSS) of the interference source for first and second antennas. That is, knowing the reference antenna equations for the affected antennas, orientated appropriately based on the beam axis of each directional antenna, an angle of arrival can be found in which the difference between the antenna gain models for the two antennas corresponds to the difference in the received signal strength for the interference signal in the RSS data for the two antennas.

[0073] That is, it is assumed that the difference in the received signal strength of the interference signal at the first and second interference-affected antennas at the same base station is affected primarily by the differential antenna gain, due to the directional antennas being pointed at differential azimuthal beam axes, with the differential antenna gain being given by the difference in their reference antenna equations.

[0074] For two different antennas having the same reference antenna equation as given above, the differential RSS of the interfered signal measured at both antennas, c, is given by the following equation: wherein is the estimated angle of arrival θ for the interference source at a base station, Go1 and Go2 are the peak antenna gain for the first and second antennas, respectively, ϕ1 and ϕ2 are the angles of orientation of the first and second antennas, respectively, where the peak gain of the main lobe is expected, and ψ is the half power beam width of the antennas, typically same antenna models are installed in the same base stations. Here, n is the measurement noise following a Gaussian distribution N(0, σ2). However, where the RSS data is collected by averaging the interference signal over large periods of time, the impact of the measurement noise can be reduced, and can be effectively discounted from the angle angles of arrival estimation calculation.

[0075] Following this, the angle of arrival estimator 312 may determine the estimated angle of arrival θ for the interference source at a base station as: 1615432419.JCJ.MEW where c is the measured differential RSS of the interfered signal measured at both antennas.

[0076] The equation above for determining the estimated angle of arrival θ may be different where the reference antenna equation used to describe the antennas is different. Nevertheless, regardless of the antenna equation used to model the reference antenna, the calculation of the estimated angle of arrival θ is always that which a difference in the modelled antenna gain for the first and second antennas corresponding to the determined difference between the received signal strength (RSS) of the interference source for first and second antennas.

[0077] In this way, in step 404, the angle of arrival estimator 312 determines an estimated first angle of arrival θ1 of the interference signal at the first base station 206a from the RSS data for the two interference-affected antennas of the first base station 206a.

[0078] Then in step 406, method 400 receives, at the RSS data receiver 310, data representative of a received signal strength (RSS) of the interference source for differently directed first and second antennas of a second base station at a second location in the geographical area, different from the first location. In the example shown in FIG. 6, the second base station may be base station 102b. Further, in step 408, the angle of arrival estimator 312 determines, for the second base station 102b, an estimated second angle of arrival θ2 for the interference source at the second base station 102b at the second location (x2, y2). This is based on a determined difference between the received signal strength (RSS) of the interference source for first and second interference-affected antennas of the second base station 102b.

[0079] Thus, step 406 and step 408 correspond respectively to step 402 and step 404, but the data is processed for a first and second interference-affected antennas of a different, second base station. In this way, by carrying our step 402, step 404, step 406, and step 408, the angle of arrival estimator 312 generates: • an estimated first angle of arrival θ1 for the interference source 106 at the first base station 206a at the first location (x1, y1); and • an estimated second angle of arrival θ2 for the interference source 106 at the second base station 102b at the second location (x2, y2).

[0080] The angle of arrival estimator 312 then passes the determined first angle of arrival θ1as a first angle of arrival estimator output 602a and the determined second angle of arrival θ2as a second angle of arrival estimator output 602b to the location estimator 314 to determine an estimated location of the interference source 106. 1715432419.JCJ.MEW

[0081] In step 410, the location estimator 314 determines, based on the estimated first angle of arrival θ1 and the estimated second angle of arrival θ2 of the interference signal at the respective first location (x1, y1) and the second location (x2, y2), an estimated location of the interference source 106 in the geographical area 108. The estimated location (x, y) of the interference source in the geographical area may be determined as: wherein θ1and θ2are the estimated angles of arrival at the first and second base stations, respectively, and (x1, y1) and (x2, y2) are the locations of the first and second base stations, respectively. The locations may be grid positions relative to some origin, or coordinates.

[0082] To further increase accuracy, angles of arrival can be determined for the interference signal at a third base station or even further base stations. By having more than two estimated angles of arrival, further information about the estimated location of the interference source can be revealed. However, in the above way, two base stations only are needed, such that the location of an interference source can be estimated based on the RSS data of the interference signal as received at first and second interference-affected antennas at each of a first and a second base station.

[0083] The interference location estimator 104 may operate by the RSS data for the first and second base stations affected being passed directly to the RSS data receiver 310 and to the angle of arrival estimator 312. However, to determine which first and second base stations should be used to identify and locate interference sources affecting coverage in the cellular radio communication system 100, the interference location estimator 104 may implement an interference detector 316 to process received PSD data for all or a large number of the base stations in the geographical area 108. The interference detector 316 may detect base stations making up group of interfered cells affected by an interference signal from the same interference source. From this, the interference detector 316 may determine the two most interfered base stations or antennas at the base stations for use in the method 400 of determining an estimated location of the interference source 106. 1815432419.JCJ.MEW

[0084] In this respect, FIG. 7 shows an example method 700 for determining groups of interfered cells and for identifying two base stations in a group of interfered cells for use in the method 400 described in relation to FIG. 4 in accordance with aspects of the disclosure.

[0085] Reference will also be made to the examples shown in FIG. 8, FIG. 9, FIG. 10A, FIG. 10B, FIG. 10C and FIG. 11.

[0086] In step 702 , interference detector 316 receives data representative of power spectral density, PSD, in carrier signals across different frequency bands received at the base stations for cells of the cellular radio communication system over time intervals. The base stations may be spread out in the cellular radio communication system 100 across the geographical area 108, as shown in FIG. 8.

[0087] Examples of the PSD data are shown in FIG. 10A, FIG. 10B and FIG. 10C as spectrograms of interference received signal strength (shown by shading intensity) over time (horizontal axis) for different physical resource blocks (PRBs) of radio resources at different frequencies (vertical axis). These cells correspond to antenna signals, and they are grouped by the base station at which they are located.

[0088] In step 704, interference detector 316 determines, for a cell having abnormal received signal levels in a frequency band indicative of interference in the received PSD data, a correlation coefficient with the PSD data in the same frequency band for neighbouring cells within a maximum distance. That is, where interference is identified in the form of abnormal RSS data at a given frequency, the interference detector 316 compares the RSS data in the same frequencies for antennas of neighbouring cells.

[0089] Where there is correlation, i.e. the correlation coefficients for a group of cells is above a given threshold, the interference detector 316 may assign the cells or base stations to a group of interfered cells. Thus, in step 706, interference detector 316 identifies groups of interfered cells for which interference is present based on groups of cells having a correlation coefficient above a threshold.

[0090] As can be seen in FIG. 8, the interference detector 316 has identified a first group of interfered cells 802a and a second group of interfered cells 802b in the geographical area 108. A detail of the first group of interfered cells 802a is shown in FIG. 9. This includes a first interference-affected base station 102a (identified as J3807), a second interference-affected base station 102b (identified as J0621), and a third interference-affected base station 102c (identified as J3715). 1915432419.JCJ.MEW

[0091] The spectrograms of the PSD signals of the four antennas of the first interference- affected base station 102a (identified as J3807) are shown in FIG. 10A (numbered J3807_01, J3807_02, J3807_03 and J3807_04).

[0092] The spectrograms of the PSD signals of the five antennas of the second interference- affected base station 102b (identified as J0621) are shown in FIG. 10B (numbered J0621_01, J0621_02, J0621_03, J0621_04 and J0621_05).

[0093] The spectrograms of the PSD signals of the four antennas of the third interference- affected base station 102c (identified as J3715) are shown in FIG. 10C (numbered J3715_01, J3715_02, J3715_03 and J3715_04).

[0094] To locate the interference source affecting the first group of interfered cells 802a, in step 708, interference detector 316 selects the first and second antennas of the first base station 102a. That is, the antenna J3807_01 (shown in the plot of power spectral density 1002a), and the antenna J3807_02 (shown in the plot of power spectral density 1002b). The interference detector 316 also selects the first and fifth antennas of the second base station 102b. That is, the antenna J0621_01 (shown in the plot of power spectral density 1004a), and the antenna J0621_05 (shown in the plot of power spectral density 1004b). The interference detector 316 may select these base stations and antennas based on them representing them suffering the most interference in the group of interfered cells 802a. Further base stations in the group of interfered cells 802a may also be used.

[0095] In this way, in step 708, the interference detector 316 selects two antennas of two base stations having interference present in two cells thereof for use in determining an estimated location of the interference source. In embodiments, the two base stations selected from the group of interfered cells may be selected to be the base stations having cells with the highest RSS in the interfered frequency bands in the PSD data thereof. In this way, groups of interfered cells can be identified, and the base stations to be used to determine an estimated location of the interference source.

[0096] Referring now to FIG. 11, which shows the result of the operation of the interference location estimator 104 on the RSS data for the first base station 102a and the second base station 102b in the group of interfered cells 802a. The interference detector 316 passes to the RSS data receiver 310 the received signal strength data for frequencies affected by the interference signal as detected in the PSD data for the antennas J3807_01 and J3807_02 for the first base station 102a, and for the antennas J0621_01 and J0621_05 for the second base station 2015432419.JCJ.MEW 102b. The angle of arrival estimator 312 then determines, from the RSS data for the first base station 102a an estimated first angle of arrival shown as angle of arrival estimator output 602a. The angle of arrival estimator 312 then determines, from the RSS data for the second base station 102b an estimated second angle of arrival shown as angle of arrival estimator output 602b.

[0097] From the determined first angle of arrival θ1and the determined second angle of arrival θ2, the location estimator 314 determines the estimated location of the interference source affecting the first group of interfered cells 802a as estimated location 1102. This lies at the intersection of the determined first angle of arrival θ1 and the determined second angle of arrival θ2projected from the locations of the first base station 102a and the second base station 102b, respectively.

[0098] The location of the interference source 106 was validated as being at the estimated location 1102 in the example shown by a targeted drive test by a field engineer. Without the estimated location 1102 produced by the interference location estimator 104, multiple drive tests by field engineers would be needed to identify and locate the interference source 106.

[0099] In this way, the angle of arrival of the signal from the interference source at a base station can be estimated based on the RSS of the received signal at two different antennas at the same base station. By determining the angle of arrival at two interfered base stations, the location of the inference source can be estimated. Thus, the angle of arrival estimation of an interference source can be achieved using only the properties of a passive antenna. This can be achieved without having to use expensive active antenna arrays operating massive multiple- input multiple-output (MIMO) technologies to perform beamforming and determine the angle of arrival. Such massive MIMO and beamforming technologies are restricted to certain wavebands and radio access technologies, and, further, mobile network equipment providers of active antennas do not readily make available positioning data relating to received signals that would allow location detection. In contrast, the methods of determining an estimated location of a source of interference disclosed herein can be deployed without limitation to particular wavebands or technologies, using RSS data that is readily available from the mobile network equipment.

[0100] 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 2115432419.JCJ.MEW 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.

[0101] 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. 2215432419.JCJ.MEW

Claims

CLAIMS 1. A computer-implemented method for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area, the method comprising: receiving data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of a first base station at a first location in the geographical area; determining an estimated first angle of arrival for the interference source at the first base station at the first location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the first base station; receiving data representative of a received signal strength (RSS) of the interference source for differently directed first and second antennas of a second base station at a second location in the geographical area, different from the first location; determining an estimated second angle of arrival for the interference source at the second base station at the second location based on a determined difference between the received signal strength (RSS) of the interference source for first and second cells of the second base station; and determining, based on the estimated first and second angles of arrival at the respective first and second locations, an estimated location of the interference source in the geographical area.

2. The method of claim 1, further comprising receiving data representative of power spectral density, PSD, in carrier signals across different frequency bands received at the base stations for cells of the cellular radio communication system over time intervals; determining, for a cell having abnormal received signal levels in a frequency band indicative of interference in the received PSD data, a correlation coefficient with the PSD data in the same frequency band for neighbouring cells within a maximum distance; identifying groups of interfered cells for which interference is present based on groups of cells having a correlation coefficient above a threshold; 2315432419.JCJ.MEWselecting, the first and second antennas of the first base station and the first and second antennas of the second base station from a group of interfered cells associated with two base stations having interference present in two cells thereof.

3. The method of claim 2, wherein the two base stations selected from the group of interfered cells are selected to be the base stations having cells with the highest RSS in the interfered frequency bands in the PSD data thereof.

4. The method of claim 2 or 3, wherein the RSS data for an antenna is based on the received power in the PSD data for the frequency bands indicative of interference.

5. The method of claim 4, wherein the RSS data is based on an average received power in the PSD data for the frequency bands indicative of interference, over an observation window, the observation window comprising PSD data captured at intervals over at least one day.

6. The method of any one of claims 2 to 5, further comprising selecting a third base station from the group of interfered cells, the third base station also having interference present in two cells thereof at a third location in the geographical area; receiving data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of the third base station serving the two cells having interference present; determining an estimated third angle of arrival for the interference source at the third base station at the third location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the third base station; and wherein the determining of the estimated location of the interference source in the geographical area is further based on the estimated third angle of arrival at the third locations.

7. The method of any one of claims 1 to 6, wherein determining an estimated angle of arrival for the interference source at a base station is further based on equation modelling the antenna gain for the first and second antennas of the base station at different receive angles.

8. The method of claim 7, wherein the equation for modelling the antenna gain radiation pattern G(θ) for a given angle of arrival θ relative to the angle of the maximum antenna gain G0 is: ^ ^^^^ = ^^− 12 2415432419.JCJ.MEWwherein ψ is the half power beam width.

9. The method of claim 7 or 8, wherein determining an estimated angle of arrival for the interference source at a base station further comprising determining, from the modelled antenna gain patterns for the first and second antennas of the base station arranged at the angles of orientation of the first and second antennae, the angle of arrival at the base station that gives a difference in the modelled antenna gain for the first and second antennas corresponding to the a determined difference between the received signal strength (RSS) of the interference source for first and second antennas.

10. The method of claim 9, wherein the estimated angle of arrival θ for the interference source at a base station is determined as:wherein Go1and Go2are the peak antenna gain for the first and second antennas, respectively, and wherein ϕ1and ϕ2are the angles of orientation of the first and second antennas, respectively, where the peak gain of the main lobe is expected, and c is the differential RSS of the interfered signal measured at both antennas.

11. The method of any one of claims 1 to 9, wherein the estimated location (x, y) of the interference source in the geographical area is determined as:wherein θ1 and θ2 are the estimated angles of arrival at the first and second base stations, respectively, and (x1, y1) and (x2, y2) are the locations of the first and second base stations, respectively.

12. The method of any one of claims 1 to 11, wherein the signal data from the first and second antennas of the first base station and the first and second antennas of the second base station used to determine their angle of arrival is received signal strength data from their use as passive antennas. 2515432419.JCJ.MEW13. The method of any one of claims 1 to 12, further comprising performing a drive test in the estimated location using field equipment to localise the source of interference.

14. Computing apparatus for determining an estimated location of a source of interference affecting a plurality of base stations of a cellular radio communication system providing coverage in a geographical area, the 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 data representative of a received signal strength (RSS) of an interference source for differently directed first and second antennas of a first base station at a first location in the geographical area; determine an estimated first angle of arrival for the interference source at the first base station at the first location based on a determined difference between the received signal strength (RSS) of the interference source for first and second antennas of the first base station; receive data representative of a received signal strength (RSS) of the interference source for differently directed first and second antennas of a second base station at a second location in the geographical area, different from the first location; determine an estimated second angle of arrival for the interference source at the second base station at the second location based on a determined difference between the received signal strength (RSS) of the interference source for first and second cells of the second base station; and determine, based on the estimated first and second angles of arrival at the respective first and second locations, an estimated location of the interference source in the geographical area.

15. 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 13. 2615432419.JCJ.MEW

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