Detection of an interference occurring in a cell of a mobile communication network

Abstract

It is disclosed a method for detecting an interference occurring in a cell of a mobile communication network. The method provides for receiving a performance parameter measured by the base station of the cell, which is indicative of the performance of the cell as a whole; and receiving couples of further performance parameters measured by the mobile user devices located within the cell, each couple comprising a performance parameter indicative of the power received by the mobile user device and a performance parameter indicative of a signal to noise ratio at a receiver of the same mobile user device. Based on the performance parameter measured by the base station, it is determined whether an interference is potentially occurring in the cell. In the affirmative, based on the couples of further performance parameters, it is determined whether the interference is actually occurring in the cell.

Description

[0001] DETECTION OF AN INTERFERENCE OCCURRING IN A CELL OF A MOBILE COMMUNICATION NETWORK

[0002] Technical field

[0003] The present invention relates to the field of radio communication networks. In particular, the present invention relates to a method for detecting an interference occurring in a cell of a mobile communication network.

[0004] Background art

[0005] As known, a mobile communication network is a wireless telecommunication network distributed over land areas called cells, each served by a fixed-location apparatus called base station. Each base station provides the respective cell with radio coverage which can be used for transmission of voice, data and various types of content.

[0006] Since their introduction, mobile communications networks have constantly evolved over time, giving rise to several generations of mobile networks based on different and increasingly performing technologies, namely GSM, UMTS, LTE and 5G NR (New Radio). Depending on the technology upon which the mobile communication network is based, the base station may take a different name, such as for example BTS in GSM, NodeB in UMTS, eNodeB in LTE or gNodeB in 5G NR.

[0007] The transmission of radio signals between base station and mobile user devices located in its cell is typically continuously affected by interferences. Interferences may be classified in two types, namely internal or external to the mobile communications network.

[0008] Internal interference is typically related to the traffic of the network itself and it may be due for example to problems of planning and optimization of the network, or to high traffic.

[0009] External interference is instead typically due to events external to the network, which in general are not predictable. Typical sources of external interference may be for example radio transmissions of communication devices of different operators (for example, radio links, TV transmissions, private radio transmissions), or microwave ovens or other home appliance emitting microwaves nearby a mobile user device. External interference may also be due to devices or systems which generate intentional interference, such as military devices.

[0010] Summary of the invention

[0011] Detecting interferences which may occur in the cell of a mobile communication network (and, when possible, reducing or eliminating them) is important to preserve proper operation of the cell.

[0012] The Applicant has indeed noticed that an interference (either internal or external) occurring in a cell of a mobile communication network produces on the receiver of the base station a reduction of the signal- to-noise ratio and, accordingly, of the receiver’s sensitivity. This ultimately results in a reduction of the effective coverage area of the cell and a degradation of the quality of data and voice services provided to the mobile user devices located in the cell.

[0013] In view of the above, the Applicant has realized that, in order to detect interferences that may occur in a cell, performance parameters shall be analysed which are indicative of the received power and of the quality of the radio connections implemented in the cell.

[0014] The base station of a cell typically provides a number of performance parameters of these types. The Applicant has however noticed that such performance parameters provided by the base station are not reciprocally correlated, meaning that in general they vary independently of each other, according to various factors (not only interference) which affect the operating condition of the cell. An interference detection technique exclusively based on such performance parameters may then result in a number of false positives. In order to discriminate a false positive from a performance degradation due to interference, further complex tests (also involving manual operations) shall be carried out by the operators, which require a lot of time and expertise.

[0015] In view of the above, the Applicant has tackled the problem of providing a method for detecting an interference occurring in a cell of a mobile communication network which overcomes the aforesaid drawbacks.

[0016] In particular, the Applicant has tackled the problem of providing a method for detecting an interference occurring in a cell of a mobile communication network which enables a fully automatic (and then fast) and accurate detection of interferences that may occur in the cell.

[0017] According to embodiments of the present invention, this problem is solved by a method for detecting an interference occurring in a cell of a mobile communication network which provides for: (i) receiving at least one first performance parameter measured by the base station and indicative of the performance of the cell as a whole, and receiving a plurality of couples of further performance parameters measured by a corresponding plurality of mobile user devices located within the cell, the couple of further performance parameters measured by each mobile user device comprising a second performance parameter indicative of the power received by the mobile user device and a third performance parameter indicative of a signal to noise ratio at the receiver of the mobile user device; (ii) based on the measured at least one first performance parameter, determining whether an interference is potentially occurring in the cell; and, in the affirmative: (iii) based on the plurality of couples of further performance parameters, determining whether the interference is actually occurring in the cell.

[0018] Advantageously, the method for detecting an interference according to embodiments of the present invention enables a fully automatic (and then fast) and accurate detection of interferences that may occur in the cell. According to embodiments of the present invention, indeed, a two- level analysis is performed to detect an interference.

[0019] The first-level analysis is conducted on the performance parameters) measured by the base station (e.g. indicative of the received power and / or of the quality of the radio connections implemented in the cell), which allows performing a first rough distinction between the case in which the cell is properly operating (and hence occurrence of an interference is excluded) and the case in which the cell is not properly operating, due to possible interference or other issues such as a hardware failure.

[0020] Only in the latter case, a second-level analysis is performed on the couples of performance parameters measured by mobile user devices located in the cell. Specifically, the Applicant has realized that the power received by a mobile user device located in a certain position of the cell and the signal to noise ratio at the receiver of the same mobile user device are reciprocally correlated, and their relationship depends on the interference conditions occurring in that position of the cell at the measurement time of the two performance parameters. Hence, by measuring both these performance parameters for each mobile user device located in the cell at a certain measurement time, an empirical function signal to noise ratio vs received power may be determined, which is basically a “picture” of the interference conditions on the cell at that measurement time. By comparing for example this function with a reference function determined for the same cell when it is properly operating (namely, when it is free from interference or other issues), it can therefore be determined whether an interference is actually occurring in the cell or not. In the affirmative, appropriate actions may be taken to reduce or eliminate the interference and restore proper operation of the cell.

[0021] Similarly to the first-level analysis, also the second-level analysis may be performed by one or more computers, and accordingly enables a fast and efficient detection of possible interferences without requiring complex manual tests by the operators. Besides, this enables performing the detection on several cells at the same time, thereby automatically monitoring in real time the interference conditions for example of a whole mobile communication network.

[0022] Moreover, the detection of possible interferences is accurate, in that it is based on the correlation of performance parameters (namely, received power and signal to noise ratio) measured by mobile user devices located in the cell, which strongly depends on the interference conditions to which each mobile user device is being subjected. The risk of false positives is therefore advantageously minimized.

[0023] According to a first aspect, the present invention provides a method for detecting an interference occurring in a cell of a mobile communication network, the method being performed by a data processing apparatus and comprising: a) receiving at least one first performance parameter measured by the base station of said cell, said at least one first performance parameter being indicative of the performance of the cell as a whole, and receiving a plurality of couples of further performance parameters measured by a corresponding plurality of mobile user devices located within the cell, the couple of further performance parameters measured by each mobile user devices comprising a second performance parameter indicative of the power received by the mobile user device and a third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device, b) based on the at least one first performance parameter, determining whether an interference is potentially occurring in the cell; and, in the affirmative: c) based on said plurality of couples of further performance parameters, determining whether the interference is actually occurring in the cell. According to an embodiment, the second performance parameter indicative of the power received by the mobile user device is an average power received by the mobile user device from a single reference signal transmitted by the base station (e.g. RSRP, namely Reference Signal Received Power), and the third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device is a power of the received radio signal divided by a sum of interference power and background noise power (e.g. SINR, namely Signal to Interference plus Noise Ratio).

[0024] Preferably, the couple of further performance parameters measured by each mobile user device is received by the base station in a respective message also comprising data indicative of the geographical position of the mobile user device at the measurement time.

[0025] Preferably, step c) comprises using the plurality of couples of further performance parameters for determining an empirical function of the signal to noise ratio at the receivers of the plurality of mobile user devices located within the cell as a function of the power received by the mobile user devices located within the cell, and determining whether the interference is actually occurring in the cell based on said empirical function.

[0026] Preferably, step c) comprises determining for the empirical function the value of the power received at which the signal to noise ratio falls below a predefined threshold, and determining whether the interference is actually occurring in the cell based on said value of the power received.

[0027] According to an embodiment, step c) comprises:

[0028] - comparing said value of the power received with a reference value of the power received, said reference value of the power received being determined as an average value for a cluster of reference cells when free of interference; and

[0029] - determining that the interference is actually occurring in the cell if said value of the power received is higher than said reference value.

[0030] According to an alternative embodiment, step c) comprises:

[0031] - comparing said value of the power received with previous values of the power received determined for said cell; and

[0032] - determining that the interference is actually occurring in the cell if said value of the power received differs from said previous values of the power received by more than a predefined amount.

[0033] Preferably, the at least one first performance parameter comprises at least one performance parameter indicative of a power received by the base station and at least one performance parameter indicative of a quality of radio connections implemented in the cell, and step b) comprises:

[0034] - based on the at least one performance parameter indicative of the power received by the base station, determining whether it is excluded that an interference is occurring in the cell; and, in the negative:

[0035] - based on at least one performance parameter indicative of the quality of the radio connections implemented in the cell, determining whether an interference is potentially occurring in the cell.

[0036] Preferably, the at least one performance parameter indicative of the power received by the base station comprises one or more of:

[0037] - a total level of noise within the frequency band used in the cell (e.g. RTWP, namely Received Total Wideband Power);

[0038] - a power present in a received radio signal (e.g. RSSI, namely Received Signal Strength Indicator) measured on a physical uplink shared channel (PUSCH) and / or on a physical uplink control channel (PUCCH); and

[0039] - a ratio between power of the received radio signal divided by a sum of interference power and background noise power (e.g. SINR, namely Signal to Interference plus Noise Ratio).

[0040] Preferably, the at least one performance parameter indicative of the quality of the radio connections implemented in the cell comprises one or more of:

[0041] - accessibility of a radio access channel of the cell;

[0042] - uplink throughput;

[0043] - modulation and coding scheme indicator;

[0044] - usage percentage of a MIMO system of the cell;

[0045] - number of packet retransmissions;

[0046] - latency;

[0047] - time a radio signal takes to reach the base station from a mobile user device (e.g. TA, namely Time Advance);

[0048] - channel quality indicator (CQI);

[0049] - voice call integrity (VCI).

[0050] According to an embodiment, step b) comprises:

[0051] - comparing the at least one first performance parameter with a predefined threshold, said predefined threshold being determined as an average value of said at least one first performance parameter for a cluster of reference cells when free of interference; and

[0052] - determining that an interference is potentially occurring in the cell if the at least one first performance parameter overcomes the predefined threshold.

[0053] According to an alternative embodiment, step b) comprises:

[0054] - comparing the at least one first performance parameter with previously received measurements of the at least one first performance parameter relating to the cell; and

[0055] - determining that an interference is potentially occurring in the cell if the at least one first performance parameter differs from said previously received measurements.

[0056] Preferably, step a) comprises receiving the at least one first performance parameter measured by the base station periodically with a first measurement period, and receiving the plurality of couples of further performance parameters measured by the corresponding plurality of mobile user devices located within the cell periodically with a second measurement period.

[0057] Preferably, the first measurement period is higher than 5 minutes; and / or the second measurement period is comprised between 1 second and 60 seconds.

[0058] According to a second aspect, the present invention provides a data processing apparatus cooperating with a mobile communication network, said data processing apparatus being configured to: a) receive at least one first performance parameter measured by the base station of said cell, said at least one first performance parameter being indicative of the performance of the cell as a whole, and receive a plurality of couples of further performance parameters measured by a corresponding plurality of mobile user devices located within the cell, the couple of further performance parameters measured by each mobile user devices comprising a second performance parameter indicative of the power received by the mobile user device and a third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device, b) based on the at least one first performance parameter, determine whether an interference is potentially occurring in the cell; and, in the affirmative: c) based on said plurality of couples of further performance parameters, determine whether the interference is actually occurring in the cell.

[0059] According to a third aspect, the present invention provides a computer program comprising instructions which, when the program is executed by a data processing apparatus, cause the data processing apparatus to carry out the steps of the method as set forth above.

[0060] Brief description of the drawings

[0061] The present invention will become clearer from the following detailed description, given by way of example and not of limitation, to be read with reference to the accompanying drawings, wherein:

[0062] - Figure 1 schematically shows a mobile communication network comprising a plurality of cells to which the method according to embodiments of the present invention may be applied;

[0063] - Figure 2 is a flow chart of the method according to embodiments of the present invention applied to a cell of the mobile communication network of Figure 1 ;

[0064] - Figure 3 is an exemplary graph of empirical functions SINR vs RSRP measured for a cell of a mobile communication network, in absence of interference and when an interference is occurring in the cell;

[0065] - Figures 4a, 4b and 4c are histograms of exemplary empirical functions SINR vs RSRP measured in three different cells of a mobile communication network which make use of three different frequency bands; and

[0066] - Figures 5a and 5b are flow charts that show in further detail some steps of the flow chart of Figure 2, according to an advantageous variant of the method of the invention.

[0067] Detailed description of preferred embodiments of the invention

[0068] Figure 1 schematically shows a portion of a mobile communication network 100 comprising a plurality of cells to which the method according to embodiments of the present invention may be applied.

[0069] The mobile communication network 100 may be any kind of mobile communication network, such as for example a GSM, UMTS, LTE or 5G NR mobile communication network.

[0070] For clarity, only three cells 10, 11 and 12 of the mobile communication network 100 are depicted in Figure 1. Each cell 10, 11 , 12 is provided with a respective base station 20, 21 , 22. Each base station 20, 21 , 22 provides radio coverage to the respective cell 10, 11 , 12, meaning that it is capable of exchanging radio signals with mobile user devices 30, 31 , 32 located within the respective cell 10, 11 , 12 for the purpose of providing voice and / or data services to such mobile user devices.

[0071] The number of the mobile user devices 30, 31 , 32 within each cell 10, 11 , 12 depends on the size of the cell, its location (urban area, rural area, etc.) and time of the day. Figure 1 is an “instant photography” of the cells 10, 11 , 12 taken at a certain time instant, at which each plurality of mobile user devices 30, 31 , 32 comprises 5 mobile user devices. The number of mobile user devices 30, 31 , 32 located in each cell 10, 11 , 12 may be of course higher (even much higher) than 5, or lower (even zero). Herein below, the reference numbers 30, 31 , 32 will be used both to indicate cumulatively the plurality of mobile user devices located in each cell, and to indicate a single mobile user device of the plurality.

[0072] Each mobile user device 30, 31 , 32 is preferably configured to measure (namely, to provide values of) a couple of performance parameters, comprising:

[0073] - a performance parameter PPrp indicative of the power received by the mobile user device; and

[0074] - a performance parameter PPsnr indicative of the signal to noise ratio at its receiver.

[0075] According to an advantageous embodiment, if the mobile communication network 100 is a LTE or 5G network, the performance parameter PPrp indicative of the power received by the mobile user device is RSRP (Reference Signal Received Power) which, as known, is the average power received by a mobile user device in a single reference signal transmitted by the base station. This is merely exemplary, since other performance parameters indicative of the power received by the mobile user device may be used.

[0076] Besides, according to an advantageous embodiment, if the mobile communication network 100 is a LTE or 5G network, the performance parameter PPsnr indicative of the signal to noise ratio is SINR (Signal to Interference + Noise Ratio) which, as known, is the power of the received radio signal divided by the sum of the interference power and the power of background noise. This is merely exemplary, since other performance parameters indicative of the signal to noise ratio may be used.

[0077] Preferably, each mobile user device 30, 31 , 32 is configured to periodically measure the couple of performance parameters PPrp, PPsnr. The measurement period of the couple of performance parameters PPrp, PPsnr by each mobile user device 30, 31 , 32 is preferably comprised between 1 second and 60 seconds, more preferably between 2 seconds and 20 seconds, for example 5 seconds. Start of the periodic measurement of the couple of performance parameters PPrp, PPsnr may be triggered by reception of a suitable command from the respective base station 20, 21 , 22. The periodic measurement of the couple of performance parameters PPrp, PPsnr may be performed according to the known MDT (Minimization of Drive Test) technique as defined by 3GPP TS 37.320 V18.3.0 (2024-09) “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Radio measurement collection for Minimization of Drive Tests (MDT); Overall description; Stage 2 (Release 18)”.

[0078] Preferably, each mobile user device 30, 31 , 32 is configured to transmit the couple of measured performance parameters PPrp, PPsnr to the respective base station 20, 21 , 22 in a message. The message also preferably comprises data indicative of the geographical position of the mobile user device 30, 31 , 32 at the measurement time. Such data for example may comprise GPS coordinates of the mobile user device 30, 31 , 32 as provided by its GPS receiver (not depicted in Figure 1 ). Further, the message preferably comprises a timestamp indicating the measurement time. As to the base stations 20, 21 , 22, they are preferably connected to a management server 4. The connection of each base station 20, 21 , 22 to the management server 4 (represented by solid lines in Figure 1 ) may be implemented as a radio connection, as a wired connection or as a combination of radio and wired connections.

[0079] The management server 4 is a data processing apparatus which may be implemented as a single computer or as a cluster of cooperating computers. The management server 4 may also be implemented in a distributed way, e.g. using a cloud computing technique. The management server 4 may be provided with a screen 4a for showing the results of its processing.

[0080] Each base station 20, 21 , 22 is preferably configured to measure at least one performance parameter PPcum indicative of the performance of the respective cell 10, 11 , 12 as a whole.

[0081] According to an advantageous embodiment, each base station 20, 21 , 22 is configured to measure the at least one performance parameter PPcum for each time resource and / or each frequency resource used in the respective cell 10, 11 , 12. For example, if the mobile communication network 100 is a LTE or 5G network, each base station 20, 21 , 22 is configured to measure the at least one performance parameter PPcum for each PRB (Physical Resource Block) used in the respective cell 10, 11 , 12, namely for each time-frequency resource of the physical layer used in the respective cell 20, 21 , 22.

[0082] Preferably, each base station 20, 21 , 22 is configured to periodically measure the at least one performance parameter PPcum. The measurement period of the at least one performance parameter PPcum by each base station 20, 21 , 22 is preferably higher than 5 minutes; for example, it may be equal to 15 minutes or an integer multiple of 15 minutes.

[0083] According to a preferred embodiment, the at least one performance parameter PPcum measured by each base station 20, 21 , 22 comprises:

[0084] - at least one performance parameter indicative of the power received by the base station 20, 21 , 22; and / or

[0085] - at least one performance parameter indicative of the quality of the radio connections implemented in the respective cell 10, 11 , 12.

[0086] For example, if the mobile communication network 100 is a LTE or 5G network, the at least one performance parameter indicative of the power received by the base station 20, 21 , 22 comprises one or more of:

[0087] - RTWP (Received Total Wideband Power) which, as known, is the total level of noise within the whole frequency band used in the cell 10, 11 , 12;

[0088] - RSSI (Received Signal Strength Indicator) which, as known, is the power present in a received radio signal. Preferably, the RSSI is measured on channel PUSCH (Physical Uplink Shared Channel) and / or on channel PUCCH (Physical Uplink-Control Channel); and

[0089] - SINR (Signal to Interference + Noise Ratio) which, as known, is the power of the received radio signal divided by the sum of the interference power and the power of background noise.

[0090] It may be appreciated that the value of each one of these performance parameters is affected by the presence of interferences which may occur in the cell.

[0091] For example, when a cell is properly operating (namely, it is free from interferences or other issues) the parameter RTWP has a value (e.g. -115 dBm) which depends on the operating conditions of the cell, including the occupancy of its time-frequency physical resources; an interference occurring in the cell typically produces an increase of the parameter RTWP, e.g. by 10 dB or more. Further, when a cell is properly operating (namely, it is free from interferences or other issues) the parameter SINR is higher than 0 dB; the higher its value, the higher the quality of transmission; an interference occurring in the cell typically produces a decrease of the parameter SINR; if the SINR becomes lower than 0, the quality of transmission is very poor and a risk also exists that the connection is lost.

[0092] If the mobile communication network 100 is a LTE or 5G network, the at least one performance parameter indicative of the quality of the radio connections implemented in the respective cell 10, 11 , 12 comprises one or more of:

[0093] - accessibility of RACH (Random Access Channel);

[0094] - TP UL (Uplink Throughput);

[0095] - MCS (Modulation and Coding Scheme) indicator;

[0096] - usage percentage of MIMO (Multiple-Input and Multiple-Output) system;

[0097] - number of packet retransmissions;

[0098] - latency;

[0099] - TA (Timing Advance) which, as known, is the time a radio signal takes to reach the base station from a mobile user device;

[0100] - CQI (Channel Quality Indicator) which, as known, is an index whose value ranges from 1 to 15, where a higher value indicates a better channel quality; and

[0101] - VCI (Voice Call Integrity).

[0102] It may be appreciated that the value of each one of these performance parameters is affected by the presence of interferences which may occur in the cell.

[0103] Interferences which may occur in the cell indeed decrease the value of the accessibility of RACH, TP UL, MCS indicator, usage percentage of MIMO systems, CQI and VCI. For example, with reference to the MCS indicator, in case of interference the base station typically changes its modulation scheme from a more efficient one (e.g. 256 QAM) to other modulations schemes (e.g. 16 QAM or even 4PSK) which are more robust but have a lower capacity; in addition or alternatively, the base station may also change its coding scheme from a more efficient one (less redundancy bits) to a more protected one (more redundancy bits). In any case, the MCS indicator of the base station will decrease. On the other hand, interferences which may occur in the cell 10, 11 , 12 typically increase both the number of packet retransmissions and the latency.

[0104] Each base station 20, 21 , 22 is configured to provide the measured at least one performance parameter PPcum to the management server 4. Each base station 20, 21 , 22 is also configured to forward the couples of performance parameters PPrpand PPsnr measured by the mobile user devices 30, 31 , 32 located in the respective cell 10, 11 , 12 to the management server 4.

[0105] In turn, the management server 4 is configured to receive the at least one performance parameter PPcum measured by each base station 20, 21 , 22 and the couples of performance parameters PPrp, PPsnr measured by the mobile user devices 30, 31 , 32 located in each cell 10, 11 , 12, and process them for detecting interferences which may occur in the cells 10, 11 , 12.

[0106] More specifically, with reference to the flow chart of Figure 2 and by referring to a single cell 10 for simplicity, the management server 4 preferably periodically receives (step 200) from the base station 20:

[0107] - the at least one performance parameter PPcum indicative of the performance of the cell 10 as a whole, as measured by the base station 20; and

[0108] - the couples of performance parameters PPrp(n), PPsm-(n) measured by the mobile user devices 30 located in the cell 10, “n” being a mobile user device integer index ranging from 1 to the number N of mobile user devices 30 located in the cell 10 at the measurement time.

[0109] The management server 4 then preferably processes the received at least one performance parameter PPcum (step 201 ) to determine whether an interference is potentially occurring in the cell 10 (step 202). Exemplary embodiments of the process of step 201 will be described in the following.

[0110] If, at step 202, the management server 4 determines that no interference is potentially occurring in the cell 10, it preferably reverts to step 200 and waits for the next at least one performance parameter PPcum and the next couples of performance parameters PPrp(n), PPsnr(n) from the base station 20.

[0111] Otherwise, if at step 202 the management server 4 determines that an interference is potentially occurring in the cell 10, it preferably processes the couples of performance parameters PPrp(n), PP snr (n) received at step 200 (step 203) to determine whether the interference is actually occurring in the cell 10 (step 204).

[0112] For this purpose, at steps 203-204 the management server 4 may use the received couples of performance parameters PPrp(n), PPsnr(n) (n = 1 , ... N) to determine an empirical function PPsnr = f(PPrP), which is basically a “picture” of the interference conditions of the cell 10 at that measurement time of the couples of performance parameters PPrp(n), PPsnr(n) (n = 1 , ... N) received at step 200.

[0113] By comparing for example this function PPsnr = f(PPrP) with a reference function PPsnr = fref(PPrp) determined for the same cell 10 when it is properly operating (namely, when it is free from interference or other issues), the management server 4 can therefore determine whether the cell 10 is actually currently subjected to interference or not.

[0114] Figure 3 shows an exemplary case of a cell of a 5G network.

[0115] At a first measurement time when no interference issues are present in the cell, each mobile user device located in the cell measures a respective couple of performance parameters RSRP(n), SINR(n), “n” being a mobile user device integer index ranging from 1 to the number N of mobile user devices located in the cell at the first measurement time. The N couples of performance parameters RSRP(n), SINR(n) measured by the N mobile user devices located in the cell at the first measurement time provide the empirical function SINR = fret(RSRP) depicted in Figure 3 as a dashed line. The empirical function fret is the reference function of the cell, in that it is determined while no interference issues are present the cell.

[0116] At a second measurement time when an interference issue is present the cell, each mobile user device located in the cell measures again the respective couple of performance parameters RSRP(n’), SINR(n’), “n”’ being a mobile user device integer index ranging from 1 to the number N’ of mobile user devices located in the cell at the second measurement time (it may be appreciated that N’ may be different from N, the number of mobile user devices in the cell being variable over time). The N’ couples of performance parameters RSRP(n’), SINR(n’) measured by the N’ mobile user devices located in the cell at the second measurement time provide the empirical function SINR = f(RSRP) depicted in Figure 3 as a dotted line.

[0117] By comparing the function f with the reference function fret, it is apparent that the relationship between the performance parameters RSRP and SINR depends on the interference conditions in the cell. Absent any interference, SINR decreases as RSRP decreases, but is still above 3 dB (namely, a value that typically provides an acceptable performance of the receiver of the mobile user device) at least for values of RSRP down to -120 dBm. When the interference issue occurs, instead, SINR decreases more sharply as RSRP decreases, and falls below 3 dB for a higher value of RSRP, namely about -100 dBm.

[0118] The management server 4 may accordingly determine whether an interference is actually occurring in the cell or not by determining the value of RSRP at which SINR falls below a predefined threshold SINRth, for example 3 dB.

[0119] If the value of RSRP at which SINR falls below the predefined threshold SINRth is higher than a reference value RSRPret (about -120 dB, in the example of Figure 3), then it can be concluded that an interference is actually occurring in the cell. The reference value RSRPref may be determined in different ways. For example, the reference value RSRP ref may be determined as an average of the values of RSRP at which SINR falls below a predefined threshold SINRth for a selected cluster of reference cells of the mobile communication network 100 when properly operating (namely, free from interferences or other issues). The cluster of reference cells may include one or more of cells 10, 11 , 12, possibly together with other cells close to cells 10, 11 , 12 and not depicted in Figure 1 .

[0120] Alternatively, the manager server 4 may compare the value of RSRP at which SINR falls below the predefined threshold SINRth determined based on the last received couples of performance parameters RSRP(n), SINR(n) with values of RSRP at which SINR falls below the predefined threshold SINRth determined based on previously received couples of performance parameters RSRP(n), SINR(n). The previously received couples of performance parameters RSRP(n), SINR(n) may be those received by the management server 4 from the mobile user devices in the cell during a predefined observation time window.

[0121] It may be appreciated that the relationship between the performance parameters RSRP and SINR depends on the frequency band used by the cell.

[0122] Figures 4a, 4b and 4c show exemplary values of RSRP and SINR measured for three different cells of an LTE network, which make use of three different frequency bands. The empirical function SINR = f(RSRP) correlating the two performance parameters for each cell considered is depicted in the form of a histogram. The three cells use respective frequency band at 1800 MHz (Figure 4a), 800 MHz (Figure 4b) and 2600 MHz (Figure 4c). The three frequency bands are exemplary, and the same analysis may be conducted on any frequency band used by the cells of a mobile communication network (e.g. 2100 MHz). It may be appreciated that the empirical function obtained for each cell depends on the used frequency band. In all the three cells indeed SINR decreases as RSRP decreases, but the value of RSRP at which SINR becomes lower than 0 (which indicates a severely degraded quality of the connection, with a risk that the connection is interrupted) is different in the three cells. Specifically, the cell using the frequency band at 800 MHz is apparently the one with worst performance, its value of RSRP at which SINR falls below 0 being higher than for the other two frequencies. The Applicant assumes that this is due to the fact that this frequency band is closer to the ones used by external sources (e.g. TV transmission).

[0123] The analysis of the received couples of performance parameters RSRP(n), SINR(n) may be conducted separately for each time-frequency resource used at the physical layer in the cell. Hence, if an analysis of interference on each PRB used in a cell has to be conducted, a reference function SINR = fref(RSRP) is preferably determined for each PRB, which is then compared with the function SINR = f(RSRP) obtained from the couples of performance parameters RSRP(n), SINR(n) periodically received in connection with that PRB, to determine whether that PRB is affected by an interference issue or not.

[0124] Returning the flow chart of Figure 2, if the management server 4 determines that an interference is actually occurring in the cell 10, the management server 4 may activate appropriate measures to reduce or eliminate the interference and restore proper operation of the cell 10 (step 205).

[0125] Otherwise, the management server 4 concludes that, in spite of the fact that the at least one performance parameter PPcum received at step 200 indicates that the cell 10 is apparently not properly operating (steps 201 -202), no interference is occurring. The management server 4 then reverts to step 200 and waits for the next at least one performance parameter PPcum and the next couples of performance parameters PPrp(n), PPsnr(n) from the base station 20.

[0126] The operation of the management server 4 as described above preferably continues until the interference detection mechanism on the cell 10 is stopped (step 206).

[0127] Advantageously, detection of interferences according to embodiments of the present invention enables a fully automatic (and then fast) and accurate detection of interferences that may occur in the cell.

[0128] As described above with reference to the flow chart of Figure 2, indeed, a two-level analysis is performed to detect an interference.

[0129] The first-level analysis (steps 201 -202) is conducted on the at least one performance parameter PPcum measured by the base station 20, which allows performing a first rough distinction between the case in which the cell 10 is properly operating (and accordingly occurring of an interference is excluded) and the case in which the cell 10 is not properly operating, due to possible interference or other issues such as a hardware failure.

[0130] Only in the latter case, a second-level analysis (steps 203-204) is performed on the couples of performance parameters PPrp(n), PPsnr(n) measured by the mobile user devices 30 located in the cell 10, to confirm whether an interference is actually occurring in the cell 10 or not.

[0131] Similarly to the first-level analysis, also the second-level analysis may be performed by one or more computers (namely, the management server 4), and accordingly enables a fast and efficient detection of possible interferences without requiring complex manual tests by the operators. Besides, this enables performing the detection not only on the cell 10, but also on the other cells of the mobile communication network 100 at the same time, thereby automatically monitoring in real time the interference conditions for example of the whole mobile communication network 100. Moreover, the detection of possible interferences carried out by the management server 4 according to the flow chart of Figure 2 is accurate, in that it is based on the correlation of couples of performance parameters PPrp(n), PPsnr(n) provided by mobile user devices 30 located in the cell 10, which strongly depends on the interference conditions to which each mobile user device 30 is being subjected. The risk of false positives is therefore advantageously minimized.

[0132] Steps 201 -202 of the flow chart of Figure 2 according to embodiments of the present invention will be now described in further detail.

[0133] As described above, at step 201 the management server 4 processes the at least one performance parameter Pcum measured by the base station 20 and received at step 200 to determine whether an interference is potentially occurring in the cell 10 (step 202).

[0134] In case of single performance parameter Pcum (for example, the parameter RTWP), the management server 4 may for example compare the received performance parameter PPcum with a predefined threshold, and conclude that an interference is potentially occurring in the cell 10 if the predefined threshold is overcome. The predefined threshold may be determined for example as an average of the measurements of the performance parameter Pcum performed by the base stations of a selected cluster of reference cells of the mobile communication network 100 when properly operating (namely, free from interferences or other issues). The cluster of reference cells may include one or more of cells 10, 11 , 12, possibly together with other cells close to cells 10, 11 , 12 and not depicted in Figure 1 .

[0135] Alternatively, the management server 4 may compare the last received performance parameter PPcum with previously received ones, and conclude that an interference is potentially occurring in the cell 10 if the last received performance parameter PPcum differs from the previously received ones by more than a predefined amount. The previously received performance parameters PPcum may be those received by the management server 4 from the base station 20 during a predefined observation time window.

[0136] According to advantageous embodiments of the invention, the management server 4 receives (step 200) and processes (step 201 ) a set of performance parameters measured by the base station 20 and indicative of the performance of the cell 10 as a whole (step 202).

[0137] Such set of performance parameters preferably comprise both at least one performance parameter indicative of the power received by the base station 20 itself, and at least one performance parameter indicative of the quality of the radio connections implemented in the cell 10.

[0138] According to this advantageous embodiment, steps 201 -202 of the flow chart in Figure 2 comprise two separate and cascaded checks: a first check is performed only on the at least one performance parameter indicative of the power received by the base station 20; if the first check does not allow excluding that an interference is occurring in the cell 10, then the management server 4 performs a second check on the at least one performance parameter indicative of the quality of the radio connections implemented in the cell 10. If also the outcome of this second check does not allow excluding that an interference is occurring in the cell 10, then the management server 4 performs steps 203-204 as described above.

[0139] Figures 5a-5b show an example of steps 201 -202 implemented according to this embodiment of the invention.

[0140] According to this example, the base station 20 periodically measures and provides to the management server 4 the following performance parameters indicative of the power received by the base station 20: RTWP (since a base station typically comprises 2 antennas, two separate parameters RTWP1 and RTWP2 may be received, one for each antenna of the base station 20), RSSI and SINR. Further, the base station 20 periodically measures and provides to the management server 4 the following performance parameters indicative of the quality of the radio connections implemented in the cell 10: accessibility of RACH, TP UL, usage percentage of MIMO system, MCS index, LAT (latency), PRT (number of packet retransmissions) and TA (Timing Advance).

[0141] For each one of the above performance parameters, the management server 4 is provided with a respective predefined threshold. As described above, each predefined threshold is preferably determined as an average of measurements of the corresponding performance parameter performed by the base stations of a selected cluster of reference cells of the mobile communication network 100 when they are properly operating (namely, free from interference or other issues such as hardware failures).

[0142] As shown in Figure 5a, as the management server 4 receives the above set of performance parameters at step 200, first of all it checks whether both the received performance parameters RTWP1 and RTWP2 are below a predefined threshold RTWPth (e.g. -115 dBm) (step 501 ).

[0143] In the affirmative, the management server 4 excludes that an interference is occurring in the cell 10 (step 502); hence, it preferably reverts to step 200 and waits for the next set of performance parameters measured by the base station 20. In the negative (namely, if at least one of RTWP1 and RTWP2 is above the predefined threshold RTWPth), the management server 4 performs further checks to determine whether the performance degradation indicated by the received parameters RTWP1 and RTWP2 is actually due to an interference or to a hardware failure.

[0144] For this purpose, the management server 4 preferably first of all checks whether the two received parameters RTWP1 and RTWP2 are substantially different from each other (step 503), meaning that their difference RTWP1 -RTWP2 has a modulus higher than few dBs. In the affirmative, the management server 4 checks whether a hardware failure has been reported for the base station 20 (step 504).

[0145] In the affirmative, the management server 4 concludes that the performance degradation of the cell 10 as indicated by the received parameters RTWP1 and RTWP2 is due to the hardware failure. The management server 4 then excludes that an interference is occurring in the cell 10; hence, it preferably reverts to step 200 and waits for the next set of performance parameters measured by the base station 20.

[0146] Otherwise, if the two received parameters RTWP1 and RTWP2 are not substantially different, or if their values are substantially different from each other but no hardware failure has been reported for the base station 20, the management server 4 preferably goes on with further checks.

[0147] Specifically, the management server 4 checks whether the received parameter RSSI is above a respective predefined threshold RSSIth (step 505).

[0148] In the negative, the management server 4 concludes that a not yet reported hardware failure may affect the base station 20 (step 506). The management server 4 then activates measures for checking hardware failures and reverts to step 200, waiting for the next set of performance parameters measured by the base station 20. If instead the received parameter RSSI is above the respective predefined threshold RSSIth, the management server 4 checks whether the received parameter SINR is below a respective predefined threshold SINRth (step 507).

[0149] In the negative, the management server 4 concludes that a not yet reported hardware failure may affect the base station 20 (step 506). The management server 4 then activates measures for checking hardware failures and reverts to step 200, waiting for the next set of performance parameters measured by the base station 20. If instead the received parameter SINR is below the respective predefined threshold SINRth, the management server 4 concludes that occurrence of an interference in the cell 10 cannot be excluded, and accordingly starts checking the received performance parameters indicative of the quality of the radio connections implemented in the cell 10.

[0150] It may be appreciated that, according to this example, by analysing the received parameters RTWP1 , RTWP2, RRSI and SINR, the management server 4 is advantageously capable not only of identifying performance degradations of the cell 10 - which as such may be due either to interferences or to hardware failures - but also to discriminate between interference issues and hardware failures. When the parameters RTWP1 and RTWP2 indicate a performance degradation but the parameters RSSI and SINR are fine, interference may indeed be excluded; hence, it shall be checked whether the performance degradation is due to a still unreported hardware failure. When instead the parameters RTWP1 , RTWP2, RSSI and SINR all indicate a performance degradation, then interference in the cell 10 cannot be excluded, and accordingly further checks in this respect are needed, as it will be described herein below.

[0151] Specifically, with reference to Figure 5b, the management server 4 first of all checks whether the received accessibility of RACH is below a respective predefined threshold RACHth (step 508).

[0152] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 checks whether the received parameter TP UL is below a respective predefined threshold TPth (step 510).

[0153] In the negative, the management server 4 concludes that, even if an interference were occurring in the cell 10, anyway it does not impair the quality of the service (step 511 ). The management server 4 then reverts to step 200 of the flow chart in Figure 2, and waits for the next set of performance parameters measured by the base station 20. Otherwise, the management server 4 checks whether the received usage percentage of the MIMO system is below a respective predefined threshold MIMOth (step 512).

[0154] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 checks whether the received MCS index is below a respective predefined threshold MCSth (step 513).

[0155] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 checks whether the received parameter LAT (latency) is above a respective predefined threshold LATth (step 514).

[0156] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 checks whether the received parameter PRT (number of packet retransmissions) is above the respective predefined threshold PRTth (step 515).

[0157] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 checks whether the received parameter TA (Timing Advance) is above a respective predefined threshold TAth (step 516).

[0158] In the affirmative, the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509). In the negative, the management server 4 concludes that, even if an interference were occurring in the cell 10, anyway it does not impair the quality of the service (step 511 ). The management server 4 then reverts to step 200 of the flow chart in Figure 2, and waits for the next set of performance parameters measured by the base station 20.

[0159] When the management server 4 concludes that an interference is potentially occurring in the cell 10 (step 509), the management server 4 then performs the analysis according to steps 203-204 of the flow chart in Figure 2, to confirm the actual occurrence of an interference in the cell 10.

[0160] The order according to which the various performance parameters - accessibility of RACH, TP UL, MIMO usage percentage, MCS index, LAT, PRT and TA - are checked (namely, the order of steps 508, 510, 512, 513, 514, 515 and 516) in the flow chart of Figure 5b is merely exemplary. In general, the management server 4 may consider these performance parameters according to a different order. In any case, however, the accessibility of RACH is preferably the first performance parameters to be checked (step 508), since it is the most indicative one as far as the potential occurrence of interference is concerned. Further, according to some embodiments, only a subset of the performance parameters shown in Figure 5b is considered by the management server 4, namely one or more of steps 508, 510, 512, 513, 514, 515 and 516 are omitted. In any case, however, the subset of considered performance parameters preferably comprises at least the accessibility of RACH.

[0161] As described above, in order to analyze the received performance parameters PPcum, PPrp(n) and PPsnr(n) the management server 4 may compare them (or data obtained therefrom) with predefined thresholds or reference values determined on a cluster of reference cells, or with previous measurements obtained for the same cell.

[0162] According to an alternative embodiment, steps 201 -202 and steps 203-204 of the flow chart of Figure 2 may be implemented using machine learning techniques.

[0163] According to this alternative embodiment, the management server 4 receives the at least one performance parameters PPcum and the couples of further performance parameters PPrp(n), PPsnr(n) and uses them to train a machine learning algorithm for building a model of the cell. Then, the model may be applied to the subsequently received at least one performance parameters PPcum and the couples of further performance parameters PPrp(n), PPsnr(n) to determine whether an interference is occurring in the cell.

[0164] For example, the machine learning algorithm may be a neural network or an ensemble learning method such as for example the known random forest method. This is a non-limiting example, since other types of machine learning algorithms may be used. The random forest method is however advantageous over other machine learning algorithms, in that it allows managing both classification tasks and regression tasks.

[0165] Preferably, the training of the machine learning algorithm is based on a training set of parameters PPcum and PPrp(n), PPsnr(n), which is formed by a first subset of parameters PPcum and PPrp(n), PPsnr(n) obtained by performing the measurement when the cell is normally operating (no interference and no failure), a second subset of parameters PPcum and PPrP(n), PPsnr(n) obtained by performing the measurement when an interference issue is occurring in the cell, and a third subset of parameters PPcum and PPrp(n), PPsnr(n) obtained by performing the measurement when a failure affects its base station. Such training set is used to train the machine learning algorithm and build a model of the cell that, when the model receives as input the parameters PPcum and PPrP(n), PPsnr(n) currently measured for the cell, is capable of providing as an output a classification of the operating condition of the cell (namely normal, interference or failure).

Claims

CLAIMS1 . A method for detecting an interference occurring in a cell (10) of a mobile communication network (100), said method being performed by a data processing apparatus (4) and comprising: a) receiving at least one first performance parameter measured by the base station (20) of said cell (10), said at least one first performance parameter being indicative of the performance of the cell (10) as a whole, and receiving a plurality of couples of further performance parameters measured by a corresponding plurality of mobile user devices (30) located within the cell (10), the couple of further performance parameters measured by each mobile user devices (30) comprising a second performance parameter indicative of the power received by the mobile user device (30) and a third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device (30), b) based on the at least one first performance parameter, determining whether an interference is potentially occurring in the cell (10); and, in the affirmative: c) based on said plurality of couples of further performance parameters, determining whether the interference is actually occurring in the cell (10).

2. The method according to claim 1 , wherein the second performance parameter indicative of the power received by the mobile user device (30) is an average power received by the mobile user device (30) in a single reference signal transmitted by the base station (20), and the third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device (30) is a power of the received radio signal divided by a sum of interference power and background noise power.

3. The method according to claim 1 or 2, wherein the couple of further performance parameters measured by each mobile user device (30) is received by the base station (20) in a respective message also comprising data indicative of the geographical position of the mobile user device (30) at the measurement time.

4. The method according to any of the preceding claims, wherein step c) comprises using the plurality of couples of further performance parameters for determining an empirical function of the signal to noise ratio at the receivers of the plurality of mobile user devices (30) located within the cell (10) as a function of the power received by the mobile user devices (30) located within the cell (10), and determining whether the interference is actually occurring in the cell (10) based on said empirical function.

5. The method according to claim 4, wherein step c) comprises determining for the empirical function the value of the power received at which the signal to noise ratio falls below a predefined threshold, and determining whether the interference is actually occurring in the cell (10) based on said value of the power received.

6. The method according to claim 5, wherein step c) comprises: comparing said value of the power received with a reference value of the power received, said reference value of the power received being determined as an average value for a cluster of reference cells when free of interference; and determining that the interference is actually occurring in the cell (10) if said value of the power received is higher than said reference value.

7. The method according to claim 5, wherein step c) comprises: comparing said value of the power received with previous values of the power received determined for said cell (10); and determining that the interference is actually occurring in thecell (10) if said value of the power received differs from said previous values of the power received by more than a predefined amount.

8. The method according to any of the preceding claims, wherein said at least one first performance parameter comprises at least one performance parameter indicative of a power received by the base station (20) and at least one performance parameter indicative of a quality of radio connections implemented in the cell (10), and wherein step b) comprises: based on the at least one performance parameter indicative of the power received by the base station (20), determining whether it is excluded that an interference is occurring in the cell (10); and, in the negative: based on at least one performance parameter indicative of the quality of the radio connections implemented in the cell (10), determining whether an interference is potentially occurring in the cell (10).

9. The method according to claim 8, wherein the at least one performance parameter indicative of the power received by the base station (20) comprises one or more of: a total level of noise within the frequency band used in the cell (10); a power present in a received radio signal measured on a physical uplink shared channel and / or on a physical uplink control channel; and a ratio between power of the received radio signal divided by a sum of interference power and background noise power.

10. The method according to claim 8 or 9, wherein the at least one performance parameter indicative of the quality of the radio connections implemented in the cell (10) comprises one or more of:accessibility of a radio access channel of the cell (10); uplink throughput; modulation and coding scheme indicator; usage percentage of a MIMO system of the cell (10); number of packet retransmissions; latency; time a radio signal takes to reach the base station (20) from a mobile user device (TA); channel quality indicator (CQI); voice call integrity (VCI).11 . The method according to any of the preceding claims, wherein step b) comprises: comparing the at least one first performance parameter with a predefined threshold, said predefined threshold being determined as an average value of said at least one first performance parameter for a cluster of reference cells when free of interference; and determining that an interference is potentially occurring in the cell (10) if the at least one first performance parameter overcomes the predefined threshold.

12. The method according to any of claims 1 to 10, wherein step b) comprises: comparing the at least one first performance parameter with previously received measurements of the at least one first performance parameter relating to the cell (10); and determining that an interference is potentially occurring in the cell (10) if the at least one first performance parameter differs from said previously received measurements.

13. The method according to any of the preceding claims, wherein step a) comprises receiving the at least one first performanceparameter measured by the base station (20) periodically with a first measurement period, and receiving the plurality of couples of further performance parameters measured by the corresponding plurality of mobile user devices (30) located within the cell (10) periodically with a second measurement period.

14. The method according to claim 13, wherein: the first measurement period is higher than 5 minutes; and / or the second measurement period is comprised between 1 second and 60 seconds.

15. A data processing apparatus (4) cooperating with a mobile communication network (100), said data processing apparatus (4) being configured to: a) receive at least one first performance parameter measured by the base station (20) of said cell (10), said at least one first performance parameter being indicative of the performance of the cell (10) as a whole, and receive a plurality of couples of further performance parameters measured by a corresponding plurality of mobile user devices (30) located within the cell (10), the couple of further performance parameters measured by each mobile user devices (30) comprising a second performance parameter indicative of the power received by the mobile user device (30) and a third performance parameter indicative of a signal to noise ratio at a receiver of the mobile user device (30), b) based on the at least one first performance parameter, determine whether an interference is potentially occurring in the cell (10); and, in the affirmative: c) based on said plurality of couples of further performance parameters, determine whether the interference is actually occurring in the cell (10).

6. A computer program comprising instructions which, when the program is executed by a data processing apparatus (4), cause the data processing apparatus (4) to carry out the steps of the method of any of claims 1 to 14.

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