Patent Description:
Wireless communication may be implemented with a cellular radio network comprising transmission sites that offer communication services via multiple cells corresponding to certain geographical coverage areas. Because of free propagation of radio signals, coverage areas of cells may overlap and therefore signals from different transmission sites may cause interference. Document <CIT> relates to systems and methods for overshooting cell device detection. The system ranks neighbor relationships between first, second, and third cell devices in a cellular network, based on handover statistics directly received from the cellular network. The system thereafter identifies one of the second cell device or the third cell device as an outlier neighbor cell device based on a ranking of the neighbor relationships and identifies, as a function of an azimuth direction and a distance between respective cell devices of a group of screened cell devices, an overshooting cell device that propagates a transmitted radio frequency signal causing interference to a cell device included in the group of screened cell devices. Document <CIT> discloses method and a device for processing an overshoot coverage. Document <CIT> discloses a method of implementing a discontinuous reception pattern at user equipment operating to receive an independent stream of data traffic from at least two cells in a multi flow wireless communication network. Document <CIT> discloses a device and method for selecting cell in wireless communication system. Document <CIT> relates to priority control of radio resource allocation in a base station connected to a plurality of core networks having different quality-of-service (QoS) requirements. Document <CIT> discloses a method and base station for dynamic adjustment of a carrier resource. Document <CIT> discloses a communication method, where a first base station sets, for a user device, a wireless local area network (WLAN) mobility set, which is a set of one or more WLAN identifiers. The first base station determines handover of the user device to a second base station. Document <CIT> discloses a method of controlling handover of a user equipment in a first base station connected with the user equipment (UE) in a mobile communication system.

The scope of protection is defined in the independent claims. Further features are defined in the dependent claims.

The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to understand the example embodiments. In the drawings:.

The invention made is disclosed in the embodiments relating to <FIG>. Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

<FIG> illustrates an example of a wireless communication network. Communication network <NUM> may comprise one or more devices, which may be also referred to as client nodes, user nodes, or user equipment (UE). An example of a device is UE <NUM>, which may communicate with one or more access nodes of a radio access network (RAN) <NUM>. Signals transmitted by an access node to UE <NUM> may be referred to as downlink signals. Signals transmitted by UE <NUM> to an access node may be referred to as uplink signals. An access node may be also referred to as an access point or a base station. Communication network <NUM> may be configured for example in accordance with the <NUM>th or <NUM>th generation (<NUM>, <NUM>) digital cellular communication networks, as defined by the <NUM>rd Generation Partnership Project (3GPP). In one example, communication network <NUM> may operate according to 3GPP (<NUM>) LTE (Long-Term Evolution) or 3GPP <NUM> NR (New Radio). Communication network <NUM> may hence comprise a cellular radio network. It is however appreciated that example embodiments presented herein are not limited to these example networks and may be applied in any present or future wireless communication networks, or combinations thereof, for example other type of cellular networks, short-range wireless networks, multicast networks, broadcast networks, or the like. Access nodes <NUM>, <NUM>, <NUM> of RAN <NUM> may for example comprise <NUM>th generation access nodes (gNB) or <NUM>th generation access nodes (eNodeB).

An access node may provide communication services within one or more cells, illustrated with dotted circles, which may correspond to geographical area(s) covered by signals transmitted by the access node. Dominance area of a cell may comprise is a physical (geographical) area in which certain cell has the strongest signal level among different cells. Handover between cells may be performed when UE <NUM> is at or near the border of the dominance area. Coverage areas of cells may overlap to some extent, for example to facilitate smooth handover for a mobile UE. Serving cell of a UE may be changed when another cell has the strongest signal level. Even though some overlapping may be useful for handover purposes, it may be generally desired to minimize the signal level outside the dominance area. Excessive overlapping between cells may cause unnecessary interference and hence degrade performance of the network, for example in terms of achievable data rate.

A cell may be determined to be overshooting if its signal level remains high also outside its dominance area. Overshooting may occur for example due to wrong antenna tilting. It may be desired to effectively detect overshooting cells such that corresponding counteraction(s) (e.g. antenna downtilting) may be performed. In the example of <FIG>, coverage area of cell <NUM>, served by access node <NUM>, extends near access node <NUM>, thereby causing interference deep within the coverage area of cell <NUM>. Cell <NUM> may be considered to be overshooting, because its coverage area extends unnecessarily far. Example embodiments of the present disclosure enable overshooter detection based on monitoring data traffic within multiple cells, when restricting amount of data traffic in one of the cells. The network topology may be temporarily "broken", for example by intentionally turning off one cell, and information from the surrounding network, such as for example timing advance values or received signal strength values, may be utilized for detecting overshooting cells.

Communication network <NUM> may further comprise a core network <NUM>, which may comprise various network functions (NF) for establishing, configuring, and controlling data communication sessions of users, for example UE <NUM>. The data communication sessions may carry data traffic, for example application data associated with one or more applications running on UE <NUM>. Communication network <NUM> may further comprise a network controller <NUM>, which may be responsible of configuring various operations of RAN <NUM> and/or core network <NUM>. Even though illustrated as a separate entity, network controller <NUM> may be also embodied as part of core network <NUM>. Even though some operations have been described as being performed by network controller <NUM>, it is understood that similar functions may be performed alternatively by other network device(s) or network function(s) of communication network <NUM>. One task of network controller <NUM> may be to detect overshooting cells, such as cell <NUM>, within RAN <NUM>. Network controller <NUM> may be also configured to remotely control antenna tilts of access node, for example to downtilt antenna(s) of overshooting cells.

<FIG> illustrates an example embodiment of an apparatus <NUM> configured to perform one or more example embodiments. Apparatus <NUM> may be for example used to implement network controller <NUM>. Apparatus <NUM> may comprise at least one processor <NUM>. The at least one processor <NUM> may comprise, for example, one or more of various processing devices or processor circuitry, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

Apparatus <NUM> may further comprise at least one memory <NUM>. The at least one memory <NUM> may be configured to store, for example, computer program code or the like, for example operating system software and application software. The at least one memory <NUM> may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination thereof. For example, the at least one memory <NUM> may be embodied as magnetic storage devices (such as hard disk drives, floppy disks, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

Apparatus <NUM> may further comprise a communication interface <NUM> configured to enable apparatus <NUM> to transmit and/or receive information to/from other devices, functions, or entities. In one example, apparatus <NUM> may use communication interface <NUM> to transmit or receive information over a service based interface (SBI) message bus of core network <NUM>, for example to core network <NUM> and/or RAN <NUM> about detected overshooting cells, to output indication(s) of the detected overshooting cells to a human user or an automated service ticket system, or to provide network configuration instructions (e.g. for remote antenna tilting) to RAN <NUM> to prevent or reduce overshooting in one or more cells. Apparatus <NUM> may further comprise a user interface, for example for configuring apparatus <NUM> or for providing user output by the apparatus, such as for example visual and/or audible signal(s), for example by speaker(s), display(s), light(s), or the like.

When apparatus <NUM> is configured to implement some functionality, some component and/or components of apparatus <NUM>, such as for example the at least one processor <NUM> and/or the at least one memory <NUM>, may be configured to implement this functionality. Furthermore, when the at least one processor <NUM> is configured to implement some functionality, this functionality may be implemented using program code <NUM> comprised, for example, in the at least one memory <NUM>.

The functionality described herein may be performed, at least in part, by one or more computer program product components such as for example software components. According to an embodiment, the apparatus comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. A computer program or a computer program product may therefore comprise instructions for causing, when executed, apparatus <NUM> to perform the method(s) described herein. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), application-specific Integrated Circuits (ASICs), application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

Apparatus <NUM> comprises means for performing at least one method described herein. In one example, the means comprises the at least one processor <NUM>, the at least one memory <NUM> including program code <NUM> configured to, when executed by the at least one processor, cause the apparatus <NUM> to perform the method.

Apparatus <NUM> may comprise a computing device such as for example an access point, a base station, a server, a network device, a network function device, or the like. Although apparatus <NUM> is illustrated as a single device it is appreciated that, wherever applicable, functions of apparatus <NUM> may be distributed to a plurality of devices, for example to implement example embodiments as a cloud computing service.

<FIG> illustrates an example of two access nodes, each communicating data traffic with two cells within same sector. Access node <NUM>, which may be also referred to as a first access node, may comprise cells <NUM>-<NUM> and <NUM>-<NUM>, which are illustrated in terms of their dominance areas. These cells may be also referred to as first and second cells, respectively. Cells <NUM>-<NUM> and <NUM>-<NUM> may belong to same sector (Sector B). Cells <NUM>-<NUM> and <NUM>-<NUM> may be therefore located substantially at the same direction from access node <NUM>. A sector may comprise a certain angular range from an access node, for example <NUM>°. An access node may comprise a plurality of sectors, for example three sectors as illustrated in <FIG>. Cells <NUM>-<NUM> and <NUM>-<NUM> may be associated with different frequency bands, for example to substantially prevent interference between signals of cells <NUM>-<NUM> and <NUM>-<NUM>. As an example, cell <NUM>-<NUM> may be configured to communicate data traffic at a first frequency band (e.g., <NUM> band). Cell <NUM>-<NUM> may be configured to communicate data traffic at a second frequency band (e.g., <NUM> band). The first frequency band may be higher than the second frequency band. Cell <NUM>-<NUM> may therefore comprise a high band cell and cell <NUM>-<NUM> may comprise a low band cell. It is however noted that substantially interference less communication at cells of the same sector, for example cells <NUM>-<NUM> and <NUM>-<NUM>, may be implemented with any suitable method, such as for example code division multiplexing (CDMA) between the cells, for example by assigning different code spaces for the cells.

Access node <NUM>, which may be also referred to as a second access node, may comprise cells <NUM>-<NUM> and <NUM>-<NUM>. Cell <NUM>-<NUM> is illustrated in terms of its dominance area <NUM>-1A and coverage area <NUM>-1B. Cell <NUM>-<NUM> is illustrated in terms of its dominance area. Cells <NUM>-<NUM> and <NUM>-<NUM> may belong to same sector (Sector A). Cells <NUM>-<NUM> and <NUM>-<NUM> may be therefore located substantially at the same direction from access node <NUM>. Cells <NUM>-<NUM> and <NUM>-<NUM> may be associated with different frequency bands, for example similar to cells <NUM>-<NUM> and <NUM>-<NUM> of access node <NUM>. Cell <NUM>-<NUM> may be configured to communicate data traffic at the first frequency band (e.g., <NUM> band). Cell <NUM>-<NUM> may be configured to communicate data traffic at the second frequency band (e.g., <NUM> band). Cell <NUM>-<NUM> may therefore comprise a high band cell and cell <NUM>-<NUM> may comprise a low band cell. Cell <NUM>-<NUM> or cell <NUM>-<NUM> may be referred to as a third cell.

In the example of <FIG>, communication of data traffic may be ongoing normally at cell <NUM>-<NUM>, for example the amount of data traffic may not be restricted at this time (e.g., during daytime). UE <NUM> may be served by cell <NUM>-<NUM> in this situation. For example, data traffic of UE <NUM> may be communicated via cell <NUM>-<NUM>. However, coverage area <NUM>-1B of cell <NUM>-<NUM> extends deep within dominance areas of cells <NUM>-<NUM> and <NUM>-<NUM>, thereby causing interference to UE <NUM>. Cell <NUM>-<NUM> may be therefore considered to be overshooting.

<FIG> illustrates an example of two, where communication of data traffic is restricted in one cell. In order to determine whether cell <NUM>-<NUM>, or in general any cell of access node <NUM> or other access node(s), is overshooting, the amount of data traffic via cell <NUM>-<NUM> may be restricted, for example by locking cell <NUM>-<NUM> such that no data traffic is communicated via cell <NUM>-<NUM>. For example, radio transceiver(s) or other equipment associated with cell <NUM>-<NUM> may be partially powered down or switched off completely. This not only enables overshooter detection, but it also reduces power consumption. In the example of <FIG>, communication via cell <NUM>-<NUM> has been terminated and therefore cell <NUM>-<NUM> is not illustrated. If cell <NUM>-<NUM> is overshooting and therefore it has a high signal level, UE <NUM> may perform handover to cell <NUM>-<NUM> or <NUM>-<NUM> rather than cell <NUM>-<NUM>. Furthermore, a priority of cell <NUM>-<NUM> or cell <NUM>-<NUM> may be higher than a priority of cell <NUM>-<NUM>. Therefore, when the amount of data traffic communicated via cell <NUM>-<NUM> is restricted, UE <NUM> may have preference to perform handover from cell <NUM>-<NUM> to cell <NUM>-<NUM> or cell <NUM>-<NUM>, rather than cell <NUM>-<NUM> of the same access node or sector. Performing overshooter detection by restricting data traffic at a cell of an access node may be therefore more effective when cells of other access node(s) are prioritized over cells of the same access node. For example, the influence on the data traffic moving to the other cells may be stronger and therefore easier to detect.

Restricting the amount of data traffic communicated via cell <NUM> may be performed for an expected period of low data traffic, e.g., when the amount of data traffic in communication network <NUM> is expected to be low, for example relative to the amount of data traffic during other periods of time. For example, the amount of data traffic may be restricted during night time, for example between <NUM> a. and <NUM> a. The amount of data traffic or (at least partial) powering down of access node <NUM> may be controlled by network controller <NUM>. Alternatively, network controller <NUM> may monitor the amount of data traffic at cells (e.g., cells <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and/or <NUM>-<NUM>) of communication network <NUM> and restrict the amount of data traffic, for example in response to determining that a total amount of data traffic of the cells is below a threshold. Restricting the amount of data traffic in one cell during a period of low data traffic of communication network <NUM> enables overshooter detection to be performed without causing degradation in quality-of-service.

<FIG> illustrates an example of average timing advance distance and average received signal strength before and after downtilting an overshooting cell. Timing advance may be used in communication network <NUM> to synchronize transmission and reception between a UE and an access node such that the propagation time of the signal over a particular distance between the UE and the access node is compensated. Timing advance values may therefore correlate with distances of UEs from the access node and the same applies also to received signal strength due to propagation loss. In this example the received signal strength is represented by reference signal received power (RSRP). Network controller <NUM> may for example calculate hourly levels for key performance indicators (KPI), such as for example received signal strength (at the access node) and the timing advance (TA), which may be translated to a TA distance. The hourly KPI levels may be used for monitoring performance of communication network <NUM>.

In the example of <FIG>, which illustrates the TA and RSRP levels for cell <NUM>-<NUM>, the amount of data traffic communicated via cell <NUM>-<NUM> is restricted during night time. This results in increase of the average timing advance distance at cell <NUM>-<NUM> during the restriction. This may happen because UEs located at dominance area of cell <NUM>-<NUM> move to cell <NUM>-<NUM>, which is overshooting. The RSRP of cell <NUM>-<NUM> decreases during the restriction, because access node <NUM> receives the signals over a longer average distance. It is therefore possible to determine, based on the timing advance values or the received signal strength values, that data traffic has moved from cell <NUM>-<NUM> to cell <NUM>-<NUM> and that cell <NUM>-<NUM> is overshooting, as will be further described below with reference to <FIG>. For example, network controller <NUM> may calculate an average TA distance for power saving hours (e.g. <NUM> a. ), and non-power saving hours (<NUM> a. Based on the difference of the TA distance between these two time periods, network controller <NUM> may determine whether cell <NUM>-<NUM>, or in general a third cell, is overshooting.

In response to detecting cell <NUM>-<NUM> to be overshooting, the antenna of cell <NUM>-<NUM> may be downtilted, as will be further described with reference to <FIG>. This causes coverage area of cell <NUM>-<NUM> to be reduced such that it no longer extends to, or at least not as deep within, the dominance area of cell <NUM>-<NUM>. Network controller <NUM> may determine to downtilt antenna of cell <NUM>-<NUM> for example if the ratio between the average TA distance at night time (data traffic restricted) and the average TA distance at daytime (data traffic not restricted) is over a threshold. This may be implemented for example based on the following pseudocode, where n is the threshold:
<IMG>.

The threshold (n) for the ratio between the average TA distance when the amount of data traffic restricted and the average TA distance when the amount of data traffic is not restricted may be for example equal to or less than <NUM> (n ≤ <NUM>).

Alternatively, or additionally, network controller <NUM> may cause downtilting, in response to determining that difference between the average RSRP values between night time and daytime is above a threshold, for example m dB. This may be implemented for example based on the following pseudocode, where m is the threshold:
<IMG>.

The threshold (m) for the difference between the average RSRP when the amount of data traffic restricted and the average RSRP when the amount of data traffic is not restricted may be for example <NUM>-<NUM> dB. Night time is herein used to represent a period of time when data traffic at cell <NUM>-<NUM> is restricted. Day time is used to represent a period of time when data traffic at cell <NUM>-<NUM> is not restricted. The above implementations may be generalized to any suitable time periods associated with low and high amounts of data traffic. The above criteria for TA distance and/or received signal strength may be also monitored periodically, for example daily, and the decision on the downtilting, or determination whether the cell is overshooting, may be made based on the number of observation periods where the threshold(s) are exceeded. For example, if the ratio average_distance_night/average_distance_day exceeds the threshold n on M days during an observation period of N days, network controller <NUM> may determine to cause the downtilt. In one example, M = <NUM> and N = <NUM>.

It can be observed from <FIG> that the variance between daytime and night time for the TA or RSRP values is reduced after the downtilt. Based on this, network controller <NUM> may determine that overshooting was successfully reduced with the downtilt.

<FIG> illustrates an example of a flow chart for overshooter detection. Operations of flow chart <NUM> may be performed for example by network controller <NUM> and/or core network <NUM>.

At operation <NUM>, data traffic may be communicated via cell <NUM>-<NUM>. Data traffic may be communicated to/from UEs, for example UE <NUM>, located within coverage area of cell <NUM>-<NUM>, but primarily within its dominance area.

At operation <NUM>, network controller <NUM> may restrict the amount of data traffic communicated via cell <NUM>-<NUM>, as discussed above. Restricting the amount of data traffic communicated via cell <NUM>-<NUM> may for example comprise terminating communication of the data traffic via cell <NUM>-<NUM>. It is however possible that transmission of signalling data or reference signals continues after termination of the data traffic or that some amount of data traffic is still communicated during the restriction.

At operation <NUM>, network controller <NUM> may determine, after the restriction of the amount of data traffic at operation <NUM>, whether data traffic has moved from cell <NUM>-<NUM> to cell <NUM>-<NUM>, or in general to a third cell of another access node. Cell <NUM>-<NUM> is used herein as an example of a third cell. As described above, network controller <NUM> may determine that data traffic has moved to cell <NUM>-<NUM> based on detecting an increase in TA values (e.g., their average) in cell <NUM>-<NUM> and/or a decrease in received signal strength values (e.g., their average) in cell <NUM>-l. In general, any suitable statistical measure (e.g., average, median, or a percentile) of the TA values or received signal strength values may be used. Therefore, determining that after the restriction of the amount of data traffic at cell <NUM>-<NUM> at least part of the data traffic is communicated via cell <NUM>-l (and not cell <NUM>-<NUM> of the same sector) may be in response to detecting a statistical increase of TA values of cell <NUM>-l and/or a statistical decrease of received signal strength values of cell <NUM>-l.

At operation <NUM>, network controller <NUM> may determine that cell <NUM>-l is overshooting. This may be in response to determining at operation <NUM> that, after restricting the amount of data traffic communicated via cell <NUM>-<NUM>, at least part of that data traffic is communicated via cell <NUM>-l (and not via cell <NUM>-<NUM>). In response to detecting cell <NUM>-l to be overshooting, network controller <NUM> may output an indication of cell <NUM>-l being overshooting. The indication may comprise a visual and/or audible alert signal, or an automated service ticket, which may be configured to be presented to a human user for taking care of the overshooting. Network controller <NUM> may transmit an indication of the overshooting of cell <NUM>-l to another device or cause performance of a counteraction. For example, network controller <NUM> may initiate operations of flow chart <NUM> to downtilt antenna(s) of cell <NUM>-l, or in general any overshooting cell. By efficient overshooter detection and enablement of repairing actions, either automatically or manually by a service man, overall network performance may be improved, since unnecessary interference between cells may be effectively avoided.

It is noted that after restricting the amount of data traffic at cell <NUM>-<NUM>, network controller <NUM> may monitor the TA values and/or received signal strength values in more than one cells, for example neighbouring cells of cell <NUM>-<NUM>. The third cell may therefore comprise any of the monitored cells. Network controller <NUM> may also determine that there are more than one overshooting cell in the neighbourhood of cell <NUM>-<NUM>. In that case, there may be more than one third cell.

At operation <NUM>, network controller <NUM> may determine that no overshooting has been detected in the neighbourhood of cell <NUM>-<NUM>, in response to determining at operation <NUM> that, after restricting the amount of data traffic communicated via cell <NUM>-<NUM>, the data traffic of cell <NUM>-<NUM> has not moved to cell <NUM>-l, for example based on determining the statistics of the timing advance values and/or received signal strength of cell <NUM>-l to maintain substantially constant.

At operation <NUM>, network controller <NUM> may select another access node, in order to determine whether cells in the neighbourhood of the other access node are overshooting. Alternatively, network controller <NUM> may determine to end overshooter detection, for example if overshooter detection has been already performed for all relevant access nodes.

Overshooter detection may be performed for all access nodes of communication network <NUM> or a subset of the access nodes. This may include restricting the amount of data traffic in one cell at a time and monitoring the timing advance and/or received signal strength values of the neighbouring cells of the restricted cell. It is however noted that the amount of data traffic may be restricted in more than one cell in parallel, for example when the respective access nodes are located sufficiently far from each other.

Access nodes may be selected or prioritized for overshooter detection, for example in order to improve efficiency of overshooter detection. If a subset of access nodes is selected or prioritized for overshooter detection, the selection or prioritization may be based on at least one of the following:.

<FIG> illustrates an example of a flow chart for controlling antenna tilt of an overshooting cell. Network controller <NUM> may initiate performance of flow chart <NUM>, for example in response to detecting an overshooting cell (third cell) at operation <NUM>. Cell <NUM>-<NUM> is again used as an example of such as cell.

At operation <NUM>, network controller <NUM> may cause downtilting of cell <NUM>-l. Downtilting of cell <NUM>-l may comprise downtilting of at least one antenna of cell <NUM>-l, e.g., an antenna through which data traffic is communicated at cell <NUM>-l. Downtilting may comprise directing the radiation pattern of the antenna downwards. This restricts the coverage area of signals communicated via the antenna. Network controller <NUM> may cause the downtilting by remotely controlling the antenna tilt of cell <NUM>-l, or, by outputting an automated service ticket that triggers a service man to downtilt the antenna. Downtilting may be performed for one or more overshooting cells of communication network <NUM>, for example one cell at a time such that performance of the network is monitored separately after each downtilt.

At operation <NUM>, network controller <NUM> may monitor performance indicator(s) of communication network <NUM>, for example performance indicators of cell <NUM>-l and/or its neighbouring cell(s), such as for example cell <NUM>-<NUM> or <NUM>-<NUM>. Monitoring the performance indicators may be used for checking that quality of service remains at least on the same level in cell <NUM>-l and cell(s) affected by its downtilting. Network controller <NUM> may monitor any suitable performance indicators, for example key performance indicators (KPI). The performance indicators may include one or more of the following: a channel quality indicator (CQI), spectral efficiency, a change in amount of data traffic, or a number of dropped calls of cell <NUM>-<NUM> and/or other cell(s) of communication network <NUM>.

<FIG> illustrates an example of average CQI before and after downtilting an overshooting cell. CQI may indicate the most spectrally efficient modulation and coding scheme (MCS) applicable for achieving a certain error rate for given channel conditions. A low CQI may indicate poor radio performance while a higher CQI may indicate better radio performance. CQI may comprise an integer number (index), for example between <NUM> and <NUM>. CQI may increase with increasing spectral efficiency of the associated MCS. UE <NUM> may be configured to estimate the CQI, for example based on reference signals received from an access node, and to report the CQI to the access node and/or core network <NUM>. In the example of <FIG>, the average CQI of the downtilted cell <NUM>-<NUM> and its most dominant neighbouring cell in terms of coverage overlap (cell <NUM>-<NUM>) are plotted. It is observed that the quality in terms of average CQI of the downtilted cell <NUM>-<NUM> is improved and that the quality is substantially maintained at the neighbouring cell <NUM>-<NUM>.

<FIG> illustrates an example of spectral efficiency before and after downtilting an overshooting cell. Spectral efficiency is another performance indicator that can be used for monitoring performance of communication network <NUM>. Spectral efficiency indicates the data rate of the data traffic, normalized by the bandwidth used for communicating the data traffic (bit/s/Hz). Spectral efficiency provides a measure of how efficiently the bandwidth is utilized in physical layer data transmission. It is observed that spectral efficiency of cell <NUM>-<NUM>, which was previously suffering from the interference caused by overshooting of cell <NUM>-<NUM>, is improved. Also the spectral efficiency of the downtilted cell <NUM>-<NUM> is improved.

<FIG> illustrate examples of average data volume at uplink and downlink before and after downtilting an overshooting cell. The data volume (in gigabytes, GB) is plotted in terms of average packet data convergence protocol (PDCP) service data unit (SDU) volume. There is no major data traffic shift observed and the uplink data traffic of cell <NUM>-<NUM>, affected by downtilting of cell <NUM>-<NUM>, is varying a lot. Downtilting may potentially reduce the coverage area or service area of the downtilted cell and therefore the volume (amount) of the data traffic may be reduced in the downtilted cell. However, if this happens (which may not always be the case), surrounding cells may take over and carry this data traffic, at least with the same quality. If downtilting reduces the volume of data traffic in both the downtilted cell and the surrounding cell(s), downtilting may be determined to have caused a coverage hole in the network. However, in many cases there may not be any significant traffic shift and only the quality is improved due to reduced interference. Therefore, if the total volume of data traffic does not change (e.g., reduce) significantly (e.g., more than a threshold volume of data traffic) in the downtilted cell and its neighboring cell(s), it may be determined that downtilting did not cause a degradation in performance of the network. If the total volume of data traffic changes (e.g., reduces) significantly in the downtilted cell and its neighboring cell(s), it may be determined that downtilting caused degradation in performance of the network. Antenna(s) of the downtilted cell may be then uptilted (rollback) to avoid the performance degradation.

<FIG> illustrates examples of a dropped call ratios before and after downtilting an overshooting cell for all dropped calls and for a dropped calls associated with a quality-of-service class indicator equal to one (QCI1). It is observed that the downtilting does not cause any no major changes occur in the number of dropped calls.

Referring back to <FIG>, at operation <NUM> network controller <NUM> may determine whether performance of communication network <NUM> was degraded by the downtilting of the overshooting cell (cf. operation <NUM>). For example, if the average CQI of the downtilted cell or other cell(s) decreases, or decreases at least by a predefined amount (e.g. by one), network controller <NUM> may determine that performance of communication network <NUM> was degraded by the downtilting. Also, if the spectral efficiency of the downtilted cell or other cell(s) decreases, or decreases at least by a predefined amount(e.g. by <NUM> bits/s/Hz), network controller <NUM> may determine that performance of communication network <NUM> was degraded by the downtilting. Similarly, if network controller <NUM> detects a major data traffic shift between cells or an increase in the number of dropped calls, it many determine that performance of communication network <NUM> was degraded by the downtilt. In response to determining that downtilting of the antenna(s) of the overshooting cell caused a degradation in the performance of communication network <NUM>, network controller <NUM> may move to execution of operation <NUM>, for example to take back the downtilt of operation <NUM>.

If network controller <NUM> does not detect a performance degradation, or detects an improvement in the performance, it may end the procedure and determine to keep the downtilt caused at operation <NUM>. For example, based on the performance indicators of <FIG>, network controller <NUM> may determine to end the procedure because the performance indicators do not indicate a performance degradation.

At operation <NUM>, network controller <NUM> may cause uptilting of antenna(s) of the overshooting cell. For example, network controller <NUM> may cause the antenna(s) to be uptilted such that the downtilt of operation <NUM> is reversed. This enables to restore the state of communication network <NUM> as it was before the downtilt. Alternatively, network controller <NUM> may cause the uptilt to be performed progressively, for example such that the antenna(s) are uptilted in step(s) that are smaller than the downtilt. In response to completion of an uptilting step, network controller <NUM> may determine whether the performance of communication network <NUM> is still on a lower level compared to the performance before the downtilt. If yes, network controller <NUM> may cause another uptilting step. If not, network controller <NUM> may end the process and determine to keep the current antenna tilt. This enables optimization of the antenna tilt of the overshooting cell.

<FIG> illustrates an example of a computer-implemented method for detecting overshooting cells in a radio network.

At <NUM>, the method may comprise communicating data traffic via a first cell of a first access node of a communication network, wherein a sector of the first access node comprises the first cell and a second cell of the first access node.

At <NUM>, the method may comprise restricting amount of data traffic communicated via the first cell.

At <NUM>, the method may comprise determining that a third cell of a second access node is overshooting, in response to determining, after restricting the amount of data traffic communicated via the first cell, that at least part of the data traffic is communicated via the third cell and not via the second cell.

Further features of the method directly result for example from the functionalities of network controller <NUM> or in general apparatus <NUM>, as described throughout the specification and in the appended claims, and are therefore not repeated here. Different variations of the method may be also applied, as described in connection with the various example embodiments.

An apparatus, such as for example a network device configured to implement one or more network functions or entities, may be configured to perform or cause performance of any aspect of the method(s) described herein. Further, a computer program or a computer program product may comprise instructions for causing, when executed, an apparatus to perform any aspect of the method(s) described herein. Further, an apparatus may comprise means for performing any aspect of the method(s) described herein. According to an example embodiment, the means comprises at least one processor, and memory including program code, the at least one processor, and program code configured to, when executed by the at least one processor, cause performance of any aspect of the method(s). In general, computer program instructions may be executed on means providing generic processing functions. Such means may be embedded for example in a computer, a server, or the like. The method(s) may be thus computer-implemented, for example based algorithm(s) executable by the generic processing functions, an example of which is the at least one processor <NUM>.

The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

Claim 1:
A computer-implemented method, comprising:
communicating data traffic via a first cell (<NUM>-<NUM>) of a first access node (<NUM>) of a communication network (<NUM>), wherein a sector of the first access node (<NUM>) comprises the first cell (<NUM>-<NUM>) and a second cell (<NUM>-<NUM>) of the first access node (<NUM>), characterized by:
restricting amount of data traffic communicated via the first cell (<NUM>-<NUM>); and
determining that a third cell (<NUM>-<NUM>) of a second access node (<NUM>) is overshooting, in response to determining, after restricting the amount of data traffic communicated via the first cell (<NUM>-<NUM>), that at least part of the data traffic is communicated via the third cell (<NUM>-<NUM>) and not via the second cell (<NUM>-<NUM>).