Determination of the coating status of a radome

Abstract

A method is disclosed for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. The method comprises acquiring measurements of attenuation in the radio link, detecting (based on the measurements) a damping event of the radome, deriving (based on the measurements) a metric value indicative of a current drying capacity of the radome following the damping event, and determining the coating status by comparing (based on the derived metric value) the current drying capacity of the radome with at least one reference drying capacity. For example, the at least one reference drying capacity may comprise an uncoated drying capacity and / or a newly coated drying capacity. The metric can, for example, comprise a drying period and / or a rate of attenuation decrease of the drying period. Corresponding computer program product, apparatus, radio communication node, network node, and server node are also disclosed.

Description

[0001] DETERMINATION OF THE COATING STATUS OF A RADOME

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to the field of radio communication. More particularly, it relates to determination of the coating status of a radome for an antenna arrangement at an end of a radio link.

[0004] BACKGROUND

[0005] In the context of radio communication, radio links between two (typically fixed) antenna sites are commonly employed. For example, such radio links may be employed to provide wireless backhaul for mobile communication systems. Generally, radio links can employ any suitable frequency spectrum (e.g., microwave, mm-wave, etc.).

[0006] To protect the antenna arrangements of a radio link from the elements of the surroundings (e.g., wind, rain, snow, etc.), a radome is commonly used for the antenna arrangement at an end of a radio link to cover at least part of the antenna arrangement.

[0007] During rainfall or wet snowfall, a water film is created on the radome that attenuates the radio signal (often referred to as the "wet antenna effect”). It is not uncommon that the water film causes an attenuation in the order of 3dB per antenna - in the order of up to 6dB for a radio link - in addition to any other attenuation (e.g., free-space path loss, gas attenuation, rain attenuation, etc.). In cold weather, the water film can freeze before the radome dries up and the frozen layer can create a starting point for build-up of snow and / or ice on the radome, which typically causes further attenuation of the radio signal. In some situations, the attenuation can be so high that the communication on the radio link is interrupted.

[0008] To mitigate problems caused by the water film, suitable coating may be applied for the outer surface of the radome to cause speedy rinse off of water from the radome. For example, some hydrophobic material may be used as coating; typically applied as a thin coating layer. Thus, radome coating typically enables reduction of the attenuation experienced by a radio link. For example, by causing speedy rinse off of water from the radome, the radome coating can reduce the attenuation experienced after rainfall, and prevent (or at least reduce) build-up of snow and / or ice.

[0009] Radome coating typically has a limited lifetime. For example, the coating material may be eroded by the elements of the surroundings (e.g., wind, rain, snow, etc.). Alternatively or additionally, the coating material may attract particles (e.g., due to air pollution) which alters its composition over time. Yet alternatively or additionally, the coating material may be gradually broken down due to ultra violet (UV) radiation. This causes deterioration of the performance of the radome coating (e.g., its hydrophobic effects).

[0010] Hence, the radome coating needs to be replenished at some point in time. However, the deterioration of the radome coating varies with the conditions experienced at the location of the radome (e.g., climate, weather, UV radiation, pollution, etc.). For example, a radome located in a region with high pollution and strong UV radiation typically needs more frequent replenishment than a radome located in a region with clean air and weak UV radiation. For some experienced conditions, replenishment of radome coating may be needed on a yearly basis, while radome coating may be fully functional during ten years without replenishment for other experienced conditions.

[0011] Thus, it is typically cumbersome to determine when to replenish the radome coating for a specific antenna arrangement. It is desirable to replenish radome coating before its performance deteriorates to an unacceptable level. However, it is also desirable to avoid excessive replenishment of radome coating (e.g., since it is costly). Thus, it would be beneficial to have an approach for determining the coating status of a radome, to enable effective scheduling of coating replenishment.

[0012] Therefore, there is a need for alternative approaches for determining the coating status of a radome.

[0013] SUMMARY

[0014] It should be emphasized that the term "comprises / comprising” (replaceable by “includes / includi ng”) when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0015] Generally, when an arrangement is referred to herein, it is to be understood as a physical product; e.g., an apparatus. The physical product may comprise one or more parts, such as controlling circuitry in the form of one or more controllers, one or more processors, or the like.

[0016] It is an object of some embodiments to solve or mitigate, alleviate, or eliminate at least some of the above or other disadvantages.

[0017] A first aspect is a method for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. The method comprises acquiring measurements of attenuation in the radio link, detecting (based on the measurements) a damping event of the radome, deriving (based on the measurements) a metric value indicative of a current drying capacity of the radome following the damping event, and determining the coating status by comparing (based on the derived metric value) the current drying capacity of the radome with at least one reference drying capacity.

[0018] In some embodiments the at least one reference drying capacity comprises an uncoated drying capacity and / or a newly coated drying capacity.

[0019] In some embodiments, detecting the damping event comprises mapping increase of attenuation in the measurements to an attenuation pattern which is typical for damping events, and / or correlating increase of attenuation in the measurements to information indicating wet weather conditions. In some embodiments, the increase in attenuation comprises attenuation that exceeds a threshold value associated with wet radome conditions.

[0020] In some embodiments, detecting the damping event comprises determining an estimated end time of the damping event.

[0021] In some embodiments, a drying period corresponds to a duration between the estimated end time of the damping event and a time when the attenuation falls below a threshold value associated with dry radome conditions. The metric may comprise one or more of a duration of the drying period, and a rate of attenuation decrease within the drying period.

[0022] In some embodiments, the rate of attenuation decrease is determined by fitting of a straight line to attenuation samples in a time window comprised in the drying period, and deriving the rate of attenuation decrease based on the slope of the fitted straight line.

[0023] In some embodiments, the method further comprises determining whether one or more attenuation samples has a deviation from the fitted straight line that exceeds a deviation threshold, and, if so, disqualifying the fitted straight line as basis for deriving the rate of attenuation decrease.

[0024] In some embodiments, determining the coating status comprises deriving a collective metric value for the current drying capacity of the radome from a plurality of metric values derived from different damping events, and comparing the collective metric value to corresponding metric value(s) for the at least one reference drying capacity.

[0025] In some embodiments, the method further comprises determining which end(s) of the radio link are exposed to the damping event based on one or more of measurements of attenuation in one or more other radio links in vicinity of the antenna arrangement, and information indicating wet weather conditions in vicinity of the antenna arrangement.

[0026] A second aspect is a computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit and configured to cause execution of the method according to the first aspect when the computer program is run by the data processing unit.

[0027] A third aspect is an apparatus for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. The apparatus comprises controlling circuitry configured to cause acquisition of measurements of attenuation in the radio link, detection (based on the measurements) of a damping event of the radome, derivation (based on the measurements) of a metric value indicative of a current drying capacity of the radome following the damping event, and determination of the coating status by comparing (based on the derived metric value) the current drying capacity of the radome with at least one reference drying capacity.

[0028] A fourth aspect is a radio communication node comprising the apparatus of the third aspect.

[0029] A fifth aspect is a network node comprising the apparatus of the third aspect. A sixth aspect is a server node comprising the apparatus of the third aspect.

[0030] In some embodiments, any of the above aspects may additionally have features identical with or corresponding to any of the various features as explained above for any of the other aspects.

[0031] An advantage of some embodiments is that the coating status of a radome may be determined. For example, it is desirable to replenish the coating before its performance deteriorates to an unacceptable level, while unnecessary replenishment of the coating may be relatively costly, so it is beneficial that the coating status of can be determined to enable efficient scheduling of coating replenishment. In some examples, coating replenishment for a radome may be preferably scheduled to coincide with other activities (e.g., inspection and / or maintenance) at the antenna site of the radome.

[0032] An advantage of some embodiments is that the coating status of a radome may be determined remotely. For example, an inspection (e.g., a manual inspection) of the antenna site to determine the status of the radome coating may be relatively costly, so is beneficial that the coating status can be determined without on-site inspection.

[0033] An advantage of some embodiments is that the coating status of a radome may be determined automatically.

[0034] An advantage of some embodiments is that the coating status of a radome may be determined repeatedly, such that the coating status is suitable updated over time.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

[0037] Figure 1 is a flowchart illustrating example method steps according to some embodiments;

[0038] Figure 2 is a flowchart illustrating example method steps according to some embodiments;

[0039] Figure 3 is a collection of plots illustrating an example situation according to some embodiments;

[0040] Figure 4 is a collection of plots illustrating example approaches according to some embodiments;

[0041] Figure 5 is a schematic diagram illustrating example approaches according to some embodiments;

[0042] Figure 6 is a schematic block diagram illustrating an example apparatus according to some embodiments;

[0043] Figure 7 is a schematic drawing illustrating an example radio link according to some embodiments; and

[0044] Figure 8 is a schematic drawing illustrating an example computer readable medium according to some embodiments.

[0045] DETAILED DESCRIPTION As already mentioned above, it should be emphasized that the term "comprises / comprising” (replaceable by “includes / including”) when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0046] Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0047] As explained above, it is typically cumbersome to determine the coating status of a radome, which may be desired - for example - to determine when to replenish the radome coating. Some embodiments address this by providing an approach for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. In various embodiments, the monitoring approach enables remote, automatic, and repeated determination of the coating status.

[0048] Generally, when replenishment of radome coating is referred to herein, it should be understood that this reference is intended to include replacing not only the coating, but replacing the radome itself with one that has fresh coating.

[0049] It should be understood that the determined coating status resulting from the approaches suggested herein may, alternatively or additionally, be utilized for other purposes than determining when to replenish the radome coating. For example, the determined coating status may be used to improve accuracy for an estimation of rainfall (or snowfall) intensity between two microwave nodes. By estimating the additional attenuation caused by the wet antenna effect based on knowledge of the coating status, the attenuation that depends in the rainfall (or snowfall intensity can be more accurately estimated.

[0050] Figure 1 illustrates an example (at least partly computer-implemented) method 100 according to some embodiments. The method 100 is suitable for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link.

[0051] Measurements of attenuation in the radio link are acquired, as illustrated by 110. For example, the measurements of attenuation may comprise a collection of attenuation samples, wherein each sample corresponds to the attenuation at a specific moment in time.

[0052] The measurements of attenuation may be acquired in any suitable way. For example, 110 may comprise performing the measurements of attenuation and / or receiving an indication of the measurements of attenuation (or any information derived therefrom).

[0053] In some examples, the measurements of attenuation are derived from measurements of received signal level (RSL); e.g., as a ratio between a transmitted signal level (power) and the measured received signal level (power). Alternatively or additionally, the measurements of attenuation are expressed as related to a baseline attenuation. For example, the baseline attenuation may correspond to the minimum attenuation of the radio link, and / or the attenuation of the radio link when normal or typical or optimal conditions are experienced, and / or the attenuation of the radio link when dry conditions are experienced.

[0054] Based on the measurements of attenuation, a radome damping event is detected as illustrated by 120. Generally, the damping event may include any event that causes the radome to experience damp / wet conditions. Examples include rainfall, snowfall, condensation, etc.

[0055] The damping event detection based on the measurements of attenuation may be achieved in any suitable way. In some embodiments, the detection may be performed using a suitable machine learning approach. For example, a neural network may be trained to recognize damping events based on typical measurements of attenuation collected during known damping events.

[0056] For example, an increase of attenuation in the measurements may be mapped (or otherwise compared) to an attenuation pattern which is typical for damping events, and detection of a damping event may be responsive to suitable correlation between the increase of attenuation in the measurements and the attenuation pattern which is typical for damping events. Such suitable correlation could include that the shape of the increase of attenuation in the measurements is similar to a shape of the attenuation pattern which is typical for damping events. The attenuation pattern which is typical for a damping event may, for example, indicate how the attenuation typically varies with time during a damping event. There may be a single attenuation pattern which is typical for damping events in general, or there may be two or more attenuation patterns which is each typical for a respective type of damping event (e.g., rainfall, snowfall, etc.).

[0057] Alternatively or additionally, an increase of attenuation in the measurements may be correlated to information (e.g., radar measurements, weather data received from a remote source, etc.) indicating wet weather conditions, and detection of a damping event may be responsive to suitable correlation between the increase of attenuation in the measurements and wet weather conditions. Such suitable correlation could include that the increase of attenuation in the measurements occurs within (or is sufficiently close to) a duration of time for which wet weather conditions are indicated by the information.

[0058] Generally, an increase in attenuation may be defined as attenuation that exceeds a (first) threshold value. Thus, according to some embodiments, damping event detection may be considered only when the attenuation exceeds the (first) threshold value. For example, the (first) threshold value may be a value associated with (e.g., typically exceeded / occurring for) wet radome conditions. Alternatively or additionally, the (first) threshold value may be a value related to (e.g., exceeding by a certain amount) the baseline attenuation.

[0059] Thus, damping events that do not exceed the (first) threshold value may be discarded from consideration in the determination of coating status according to some embodiments. This may be beneficial since the derived metric may be less indicative of the actual drying capacity when the radome is not thoroughly wet before the drying begins. Generally, any suitable condition may be applied for determining which events should be considered in the determination of coating status and which should be discarded. For example, it could be required that the attenuation exceeds the (first) threshold value for a minimum number of consecutive samples, or for a minimum duration.

[0060] Typically, detection of a damping event may include determination of a time reference for the damping event. For example, detecting the damping event may comprise determining an estimated end time of the damping event as time reference. The estimated end time typically corresponds to a time when the radome is no longer exposed to dampening conditions (e.g., when a rainfall has ended, when a snowfall has ended, etc.) but is still damp. Generally, the time reference for the damping event may be determined in any suitable way.

[0061] For example, the estimated end time may correspond to a time when the measurements of attenuation for a detected damping event fall below a (second) threshold value (which may be the same as, or lower than, the (first) threshold value associated with wet radome conditions). Alternatively or additionally, the estimated end time may correspond to a time when the measurements of attenuation for a detected damping event fall below the second threshold value for a minimum duration of time, where the estimated end time may correspond to the start of the minimum duration, the end of the minimum duration, or any time there between.

[0062] Alternatively or additionally, the estimated end time may correspond to a time when the measurements of attenuation for a detected damping event decrease (close to) monotonically (e.g., for a minimum duration of time), where the estimated end time may correspond to the start of the minimum duration, the end of the minimum duration, or any time there between.

[0063] According to some examples, the following algorithm may be applied to detect separate damping events within a collection of attenuation measurements (e.g., within attenuation measurements that have been identified - for example using machine learning - as having a behavior which is typical to a damping situation - rainfall, snowfall, etc.). The baseline attenuation is represented by aBLand the (first) threshold value associated with wet radome conditions is represented by aBL+ aA.

[0064] Algorithm 1

[0065] Let ANbe a sequence with N samples akof attenuation measurements, acquired at sampling times tk, wherein k = 0,1, ... , N - 1 and k is initialized to 0. Let Tabe a set of sample indexes that correspond to attenuation peaks (due to damping), wherein Tais initialized as an empty set { }.

[0066] 1) Take the attenuation sample akacquired at sampling times tkif k < N. Otherwise go to step 6.

[0067] 2) Go to step 3 if ak> aBL+ aA. Otherwise, set k = k + 1 and return to step 1 .

[0068] 3) Create Akas the samples acquired at sampling times within the time window [tfc- T / 2, ... , tk+ T / 2], where T is long enough to cause Akto comprise at least two samples.

[0069] 4) Add the index of tkto Taif akis the maximum attenuation in Ak(a damping peak is identified, which may be regarded as a separate damping event). Otherwise, set k = k + 1 and return to step 1 . 5) Set k = tk+ T / 2 ] and return to step 1.

[0070] 6) END.

[0071] Based on the measurements of attenuation, a metric value is also derived, as illustrated by 140. The metric value is indicative of a current drying capacity of the radome following the detected damping event.

[0072] Generally, the metric value indicative of a current drying capacity of the radome may be derived in any suitable way. For example, the metric may be associated with a duration of a drying period, corresponding to a time required for the attenuation to fall below some threshold value after the cause of damping is removed (e.g., rainfall has stopped). Alternatively or additionally, the metric may be associated with a rate of decrease for the attenuation during a drying period. Both of these example metrics are indicators of the hydrophobic properties of the coated radome.

[0073] Generally, the drying period may be defined in any suitable way. In some embodiments, the drying period corresponds to a duration between the estimated end time (or another suitable reference time) of the damping event and a time when the attenuation falls below a (third) threshold value associated with dry radome conditions (which is typically lower than the (first) threshold value associated with wet radome conditions, and lower than the (second) threshold value). Additional condition(s) for a drying period could include that the attenuation should be monotonically decreasing (or almost so) during the entire drying period, or that the attenuation should not increase during the drying period beyond a (fourth) threshold value (which is typically lower than - or equal to - the (first) threshold value associated with wet radome conditions, lower than - or equal to - the (second) threshold value, and higher than the (third) threshold value associated with dry radome conditions).

[0074] The metric value indicative of a current drying capacity of the radome may comprise the duration of the drying period. Alternatively or additionally, the metric value indicative of a current drying capacity of the radome may comprise a rate of attenuation decrease within the drying period.

[0075] The rate of attenuation decrease within the drying period may, for example, be determined as the slope of a straight line that approximates the measurements of attenuation within the drying period. For example, the straight line may be determined as a straight line passing through the attenuation value at the start of the drying period and through the attenuation value at the end of the drying period. Alternatively, the straight line may be determined by fitting of a straight line to the attenuation samples of the drying period using any suitable fitting approach (e.g., least square fitting, minimum mean square fitting, etc.).

[0076] In some examples, the rate of attenuation decrease within the drying period is determined by fitting of a straight line to attenuation samples of the drying period as above, but using only attenuation samples in a time window comprised in the drying period (the time window being shorter than the drying period). Then, the rate of attenuation decrease is derived based on the slope of the fitted straight line. Several (overlapping or non-overlapping) time windows may be applied, a respective slope of the fitted line for each of the time windows may be determined, and the rate of attenuation decrease may be derived as an average value of the slopes.

[0077] According to some embodiments, one or more fitted straight lines may be disqualified as basis for deriving the decrease rate of attenuation (e.g., if the fitting is not acceptably tight). For example, it may be determined whether one or more attenuation samples has a deviation from the fitted straight line(s) that exceeds a deviation threshold, and, if so, the fitted straight line(s) may be disqualified as basis for deriving the rate of attenuation decrease (e.g., discarding only the fitted straight line for which the deviation threshold was exceeded, or discarding the entire drying period).

[0078] According to some examples, the following algorithm may be applied to find an estimated end time of a damping event and derive the corresponding metric value as a rate of attenuation decrease. The baseline attenuation is represented by aBL, the (second) threshold value is represented by aBL+ altand the (third) threshold value associated with dry radome conditions is represented by aBL+ a2.

[0079] Algorithm 2

[0080] Let ANbe a sequence with N samples akof attenuation measurements, acquired at sampling times tk, wherein k = 0,1, ... , N - 1. Let Tabe a set of M sample indexes that correspond to attenuation peaks, wherein each attenuation peak may be regarded as a separate damping event. For example, the attenuation peaks may be as identified by "Algorithm 1”.

[0081] For each attenuation peak indicated in Ta

[0082] 1) Set k to the sample index of the considered attenuation peak, and increment k until ak< aBL+ a or k equals the index of the next attenuation peak indicated in Ta, whichever occurs first.

[0083] 2) Discard the considered attenuation peak and return to step 1 for consideration of the next attenuation peak if k equals the index of the next attenuation peak indicated in Ta.

[0084] 3) To estimate the attenuation slope (rate of attenuation decrease) for the K samples of ANthat were acquired between time instants and T2(corresponding to attenuations aBL+ a and aBL+ a2, respectively), consider one or more sub-windows of [T1;... , T2], where each sub-window has a duration TA< T2- I . For each sub-window (each ranging between time instants TA 1and TA 2): a. Fit a straight line (e.g., using least square fitting) to the samples in the sub-window. b. Optionally, if there is at least one sample that deviates more than a deviation threshold from the straight line approximation at the time instant of the sample, discard the sub-window and return to step 3a for consideration of the next sub-window (or discard the attenuation peak from consideration altogether). c. Determine the slope of the straight line for the considered sub-window as where aA 1and aA 2represent the attenuation samples at time instants TA 1and TA 2, respectively. d. Return to step 3a for consideration of the next sub-window, until all sub-windows have been considered.

[0085] 4) Estimate the rate of attenuation decrease for the considered attenuation peak as an average over subwindows of the determined slopes.

[0086] This approach typically results in one metric value per attenuation peak which has not been discarded. The subwindows may be over-lapping or non-overlapping. For example, a first sub-window may have TA 1= Tltthe next sub-window may start one sample after the start of the first sub-window, and so on until the last sub-window which has TA 2= T2. More generally, a first sub-window may have T& 1> Tltthe next sub-window may start tAafter the start of the first sub-window, and so on until the last sub-window which has TA 2< T2.

[0087] Generally, the method 100 (or parts thereof) may be performed for a plurality of damping events with an associated drying period (e.g., for each detected damping event with an associated drying period), and the resulting metric value(s) may be incorporated with statistics regarding the drying capacity.

[0088] The statistics may be implemented in any suitable form. For example, the statistics may comprise a database of metric values for historic damping events (e.g., for a specific number of most recent damping events and / or for damping events within a window of time of a specific duration that ends at the current moment in time). Alternatively, or additionally, the statistics may comprise one or more collective metric value(s) which is based on metric values for historic damping events (e.g., for a specific number of most recent damping events and / or for damping events within a window of time of a specific duration that ends at the current moment in time), such as, for example, a mean value of the respective metrics of the considered damping events, a median value of the respective metrics of the considered damping events, a filtered version of the respective metrics of the considered damping events, a probability distribution (e.g., Gaussian) estimated based on the respective metrics of the considered damping events, etc.

[0089] Based on the derived metric value, the coating status is determined, as illustrated by 150. The coating status is determined by comparing the current drying capacity of the radome with at least one reference drying capacity.

[0090] The reference drying capacity may be any suitable drying capacity that can be used as a reference to determine the coating status. For example, an uncoated drying capacity and / or a newly coated drying capacity may be used as reference drying capacity. Alternatively or additionally, an aging profile associated with the coating may indicate one or more typical drying capacity(-ies) along with their respective typical point of occurrence in relation to the start and end of the coating lifetime, and such a typical drying capacity may be used as reference drying capacity. In some examples, the derived metric value for current drying capacity is compared directly to a corresponding metric value(s) for the reference drying capacity(-ies). Thus, the current drying capacity may be represented directly by the metric value derived in 140.

[0091] Alternatively, a collective metric value for the current drying capacity may be derived from a plurality of metric values derived from different damping events (e.g., based on the statistics regarding the drying capacity), and the collective metric value may be compared to corresponding metric value(s) for the reference drying capacity(-ies). Thus, the current drying capacity may be represented by the metric value derived in 140 in combination with previously derived metric values.

[0092] For example, the collective metric value may be based on a specific number of most recent damping events, or on the damping events within a window of time of a specific duration that ends at the current moment in time. Alternatively, or additionally, the collective metric may be a mean or median value of the respective metrics of the considered damping events, or a filtered version of the respective metrics of the considered damping events, or a probability distribution (e.g., Gaussian) estimated based on the respective metrics of the considered damping events, etc.

[0093] The determination of the coating status based on the comparison of the current drying capacity with the reference drying capacity(ies) may comprise determining a probable time to replenishing based on a difference between the current drying capacity and the reference drying capacity(ies).

[0094] For example, when the reference drying capacities include an uncoated drying capacity and a newly coated drying capacity, their respective metric values m (e.g., duration of drying period and / or rate of attenuation decrease within drying period) may be plotted as values as a function of time, where a first time value (e.g., "0”) corresponds to "newly coated” with metric value mnewand a second time value (e.g., "1”) corresponds to "uncoated” with metric value mun. Depending on the definition of the metric mnew> mun Orm^ < mun. A straight line (or any other suitable function) may be determined that passes the function values. Then, the comparison of the current drying capacity with the reference drying capacities may comprise finding the time value between the first and second time values for which the function value corresponds to the (collective) metric value for current drying capacity, and determining the coating status as corresponding to the found time value (e.g., time value "0.7” corresponding to coating status 30%) and / or as corresponding to a relation of the (collective) metric value for current drying capacity to the respective metric values for "newly coated” and "uncoated” (e.g., coating status equaling a ratio of the difference between the (collective) metric value for current and the metric value for "uncoated” to the difference between the metric values for "newly coated” and "uncoated”).

[0095] Generally, the coating status may be represented in any suitable way (e.g., as a remaining drying capacity, as an estimated time to next replenishment, etc.). For example, the remaining drying capacity may be determined as a (mun~mcurr / (.mun ~mnewl where mnewrepresents the newly coated drying capacity (e.g., in the form of a metric value), munrepresents the uncoated coated drying capacity (e.g., in the form of a metric value), and mcurr represents the current drying capacity (e.g., in the form of a derived or collective metric value). Alternatively or additionally, the estimated time to next replenishment may be determined as Tnew(mun— mcurr) / (mcurr— mnew), where Tnewrepresents the time which has passed since a most recent replenishment and mcurr#= mnew.

[0096] The determined coating status may be used in any suitable way. For example, the determined coating status may be provided to a controller configured for replenishment planning. Alternatively or additionally, a replenishment request may be issued (e.g., in the form of a control signal configured to cause rendering of the request via a user interface) when the determined coating status fulfills some suitable condition (e.g., remaining drying capacity falling below a capacity threshold, estimated time to next replenishment falling below a time threshold, etc.).

[0097] It could be noted that it is typically not possible to determine - based only on the measurements of attenuation in the radio link - if a detected damping event is experienced at a first end of the radio link, at a second end of the radio link, or at both ends of the radio link.

[0098] In some embodiments, this inconvenience may be handled by assuming that the determined coating status applies for both ends of the radio link. Alternatively or additionally, if it is possible to identify two different clusters of derived metric values for different damping events, it can be assumed that each cluster is associated with damping events at a respective end of the radio link. Then, the cluster that indicates the poorer drying capacity can be used to determine a (worst case) coating status to apply for both ends of the radio link.

[0099] In some embodiments, it is determined which end(s) of the radio link are exposed to the damping event under consideration, as illustrated by optional 130.

[0100] For example, the determination of 130 may be based on measurements of attenuation in one or more other radio links in a (geographical) vicinity of one - but not the other - end of the radio link (e.g., another radio link that shares one antenna site with the radio link under consideration). If a damping event is detected in the attenuation measurements for the other radio link(s), it may be assumed that the damping event under consideration is experienced (at least) at the end of the radio link under consideration which is closest to the other radio link(s).

[0101] Alternatively or additionally, the determination of 130 may be based on information indicating wet weather conditions in vicinity of one - but not the other - end of the radio link. Examples of such information includes weather data, radar measurements, etc.

[0102] Figure 2 illustrates an example (at least partly computer-implemented) method 200 according to some embodiments. The method 200 is suitable for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. The method 200 may be seen as an exemplification of the method 100 of Figure 1 .

[0103] Measurements of attenuation in the radio link are acquired in the form of sample(s) of received signal level, as illustrated by 210 (compare with 110 of Figure 1). Based on the measurements of attenuation, it is determined whether the sample(s) of received signal level indicate a radome damping event, as illustrated by 220 (compare with 120 of Figure 1). When it is determined that the sample(s) of received signal level indicate a radome damping event, a damping event is considered as detected (Y- path out of 220) and the method 200 proceeds to 240. Otherwise (N-path out of 220) the method 200 returns to 210 where new samples(s) are acquired.

[0104] When a damping event is considered as detected, a corresponding metric value is derived in the form of an estimated time (duration of a drying period) and / or slope (rate of decrease for the attenuation during a drying period), as illustrated by 240 (compare with 140 of Figure 1).

[0105] The derived metric value can be used to update statistics regarding the drying capacity, as illustrated by optional 245.

[0106] Based on the derived metric value and / or the statistics, the coating status is determined, as illustrated by 250 (compare with 150 of Figure 1).

[0107] The determined coating status may be used to update a coating status log (e.g., a log for a plurality of radomes; such as, for example, all radomes in a service area of an operator), as illustrated by optional 260.

[0108] As illustrated by optional 270, the determined coating status and / or the coating status log may be used (e.g., by a controller configured for replenishment planning) to determine whether there is a replenishment need for one or more radome(s) (e.g., by determining whether the corresponding coating status fulfills some suitable condition). If so (Y- path out of 270) the method 200 proceeds to optional 280. Otherwise (N-path out of 270) the method 200 returns to 210 where new samples(s) are acquired.

[0109] As illustrated by optional 280, a replenishment request may be issued (e.g., in the form of a job ticket specifying service and maintenance - including radome coating replenishment - in relation to one or more radio link end site(s)). Then, the method 200 may return to 210 where new samples(s) are acquired.

[0110] Some further exemplification of the approaches disclosed herein will now be provided with reference to Figures 3-5.

[0111] Figure 3 illustrates example measurements 300 of attenuation (vertical axis; ranging from 20 dB to 90 dB) over time (horizontal axis; covering 24 hours).

[0112] In the upper plot of Figure 3, there is an increase in attenuation at time 310, which may be detected as the start of a damping event (e.g., rainfall) as explained herein, and the time 320 may be identified as an estimated end time of the damping event. Associated periods where the attenuation approaches a baseline attenuation are indicated by 330 for the damping event at time 310 as well as for a following damping event.

[0113] In the lower plot of Figure 3, a drying period 331 is illustrated for the damping event at time 310, wherein the drying period 331 corresponds to a duration between the estimated end time 320 of the damping event and a time when the attenuation 300 falls below a threshold value associated with dry radome conditions. Also illustrated is a drying period 332 for the following damping event. The lower plot also illustrates a straight line 333 which approximates the decrease rate for the attenuation 300 during the drying period 331 , as well as a straight line 334 which approximates the decrease rate for the attenuation 300 during the drying period 332. As already mentioned, either or both of the duration of the drying period and the rate of attenuation decrease may be used as a metric for indicating current drying capacity.

[0114] Figure 4 illustrates example measurements 400 of attenuation (vertical axis; ranging from 45 dB to 90 dB in the upper plot and from 48 dB to 53 dB in the lower plot) over time (horizontal axis; covering 12 hours in the upper plot and 0.6 hours in the lower plot). The measurements 400 of attenuation are shown in relation to a baseline attenuation 412 (dotted line) at approximately 48 dB.

[0115] In the upper plot of Figure 4, there is also shown a (first) threshold value 411 associated with wet radome conditions. In this example, the (first) threshold value 411 exceeds the baseline attenuation 412 by 10 dB, as illustrated by 410. According to some embodiments, damping events that do not exceed the threshold value 411 may be discarded from consideration in the determination of coating status. This may be beneficial since the derived metric may be less indicative of the actual drying capacity when the radome is not thoroughly wet before the drying begins. For example, the previously described "Algorithm 1” may be used to identify the peak that exceeds the (first) threshold value 411 as a damping event.

[0116] A portion 420 of the measurements 400 of attenuation (which includes a drying period of a damping event) are illustrated in more detail in the lower plot of Figure 4. Also shown in the lower plot of Figure 4 is (second) threshold value 415 and a (third) threshold value 416 associated with dry radome conditions. In this example, the (second) threshold value 415 exceeds the baseline attenuation 412 by 3 dB, as illustrated by 417, and the (third) threshold value 416 exceeds the baseline attenuation 412 by 0.5 dB, as illustrated by 418.

[0117] The time 413 when the measurements 400 of attenuation fall below the (second) threshold value 415 may be seen as an estimated end time of the damping event and / or as a start of the drying period. The time 414 when the measurements 400 of attenuation fall below the (third) threshold value 416 may be seen as an end of the drying period. The (second) threshold value 415 is lower than the (first) threshold value 411 , and the (third) threshold value 416 is slightly higher than the baseline attenuation 412.

[0118] Also shown in the lower plot are a number of straight lines 430 fitted to the samples in a plurality of respective subwindows for the drying period between times 413 and 414, to determine the rate of attenuation decrease (e.g., according to the previously described "Algorithm 2” with nine sub-windows of TA= 10 minutes and tA= 1 minute, resulting in an average slope of -8.9 dB per hour to form the metric as the rate of attenuation decrease).

[0119] Figure 5 schematically illustrates an example probability distribution 500 of metric values (e.g., duration of drying period or rate of attenuation decrease within the drying period; represented on the horizontal axis), wherein the probability distribution 500 represents the current drying capacity of a radome. Also shown are a corresponding distribution 510 for a newly coated radome and a corresponding distribution 520 for an uncoated radome. The width of the distributions may vary depending on, for example, geographic location, climate zone, time of year, etc. Over time - as the coating deteriorates - the distribution 500 will move further away from the distribution 510 and closer to the distribution 520 as illustrated by 530. The coating status of the radome may be determined by the position of the distribution 500 relative the distributions 510 and 520.

[0120] Generally, the coating status may be represented in any suitable way as exemplified herein. For example, the position of the distribution 500 relative the distributions 510 and 520 may be expressed as a remaining drying capacity that corresponds to the distance between peaks of 500 and 520 over the distance between peaks of 510 and 520. Thus, in the example of Figure 5 the remaining drying capacity may be considered to be approximately 40% of the newly coated drying capacity, if linear decline is assumed.

[0121] Figure 6 schematically illustrates an example apparatus 600 for monitoring a coating status of a radome for an antenna arrangement at an end of a radio link. The apparatus 600 comprises a controller (CNTR; e.g., controlling circuitry, or a control module) 620.

[0122] For example, the apparatus 600 may be configured to perform (or cause performance of) the method 100 of Figure 1 and / or the method 200 of Figure 2. Alternatively or additionally, the apparatus 600 may be comprised (or comprisable) in a node 610 configured to monitor (or cause monitoring of) the coating status of one or more radome(s). Examples of nodes 610 include a radio communication node (e.g., co-located with the antenna arrangement at an end of the radio link) such as a base station or similar, a network node (e.g., a central control node for a communication network in which the radio link provides service), and a server node (e.g., providing distributed and / or cloud-based processing).

[0123] The controller 620 is configured to cause acquisition of measurements of attenuation in the radio link (compare with 110 of Figure 1 and 210 of Figure 2). To this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), an acquirer (ACQ; e.g., acquiring circuitry, or an acquisition module) 621. The acquirer 621 may be configured to acquire the measurements of attenuation in the radio link.

[0124] For example, the measurements of attenuation may be acquired by performing attenuation measurements (e.g., when the apparatus 600 is comprised in a radio communication node co-located with the antenna arrangement at an end of the radio link). Alternatively or additionally, the measurements of attenuation may be acquired by reception of the measurements of attenuation via an interface (IF) 630 (e.g., when the apparatus 600 is comprised in a network node or a server node).

[0125] The controller 620 is also configured to cause detection of a damping event of a monitored radome (compare with 120 of Figure 1 and 220 of Figure 2). To this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), a detector (DEC; e.g., detecting circuitry, or a detection module) 622. The detector 622 may be configured to detect a damping event of a monitored radome.

[0126] The controller 620 is also configured to cause derivation of a metric value indicative of a current drying capacity of the radome following the damping event (compare with 140 of Figure 1 and 240 of Figure 2). To this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), a deriver (DER; e.g., deriving circuitry, or a derivation module) 623. The deriver 623 may be configured to derive the metric value indicative of a current drying capacity of the radome following the damping event. Also to this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), a statistics storage (STAT; e.g., storing circuitry, or a storage module) 640, where statistics regarding the drying capacity is maintained based on the derived metric value(s).

[0127] The controller 620 is also configured to cause determination of the coating status by comparing the current drying capacity of the radome with at least one reference drying capacity (compare with 150 of Figure 1 and 250 of Figure 2). To this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), a determiner (DEM; e.g., determining circuitry, or a determination module) 624. The determiner 624 may be configured to determine the coating status by comparing the current drying capacity of the radome with at least one reference drying capacity. Also to this end, the controller 620 may comprise, or be otherwise associated with (e.g., connected, or connectable, to), a reference drying capacity storage (REF; e.g., storing circuitry, or a storage module) 650, where information pertaining to the one or more reference drying capacity is maintained.

[0128] Figure 7 is a schematically illustrates an example radio link 710 according to some embodiments. At each end of the radio link 710, there is an antenna arrangement for providing the radio link 710, and the antenna arrangements are covered by respective radomes 711 , 712. In relation to the example of Figure 7, a coating status may be monitored for one or both of the radomes 711 , 712 as described and exemplified herein.

[0129] To this end, a monitoring node may be configured to monitor, or cause monitoring of, the coating status for one or both of the radomes 711 , 712. For example, the monitoring node may comprise the apparatus 600 of Figure 6. Alternatively or additionally, a monitoring node may be configured to execute, or cause execution of, one or more steps of the method 100 of Figure 1 and / or one or more steps of the method 200 of Figure 2.

[0130] Examples of monitoring nodes suitable for such approaches include radio communication node (RON; e.g., co-located with the antenna arrangement at an end of the radio link 710) 730, a network node (NWN; e.g., a central control node for a communication network in which the radio link 710 provides service) 740, and a server node (SERV; e.g., providing distributed and / or cloud-based processing) 750.

[0131] The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. The embodiments may be performed by general purpose circuitry. Examples of general purpose circuitry include digital signal processors (DSP), central processing units (CPU), co-processor units, field programmable gate arrays (FPGA) and other programmable hardware. Alternatively or additionally, the embodiments may be performed by specialized circuitry, such as application specific integrated circuits (ASIC). The general purpose circuitry and / or the specialized circuitry may, for example, be associated with or comprised in an apparatus (e.g., a device), such as a radio communication node, a network node, or a server node. Embodiments may appear within an electronic apparatus (such as a radio communication node, a network node, or a server node) comprising arrangements, circuitry, and / or logic according to any of the embodiments described herein. Alternatively or additionally, an electronic apparatus (such as a radio communication node, a network node, or a server node) may be configured to perform methods according to any of the embodiments described herein.

[0132] According to some embodiments, a computer program product comprises a non -transitory computer readable medium such as, for example, a universal serial bus (USB) memory, a plug-in card, an embedded drive, or a read only memory (ROM). Figure 8 illustrates an example computer readable medium in the form of a compact disc (CD) ROM 800. The computer readable medium has stored thereon a computer program comprising program instructions. The computer program is loadable into a data processor (PROC; e.g., a data processing unit) 820, which may, for example, be comprised in an apparatus (such as a radio communication node, a network node, or a server node) 810. When loaded into the data processor, the computer program may be stored in a memory (MEM) 830 associated with, or comprised in, the data processor. According to some embodiments, the computer program may, when loaded into, and run by, the data processor, cause execution of method steps according to, for example, any of the methods illustrated in Figures 1-2, or otherwise described herein.

[0133] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used.

[0134] Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims.

[0135] For example, the method embodiments described herein discloses example methods through steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence. Thus, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step.

[0136] In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means intended as limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. Furthermore, functional blocks described herein as being implemented as two or more units may be merged into fewer (e.g. a single) unit.

[0137] Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever suitable. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa.

[0138] Hence, it should be understood that the details of the described embodiments are merely examples brought forward for illustrative purposes, and that all variations that fall within the scope of the claims are intended to be embraced therein.

Claims

CLAIMS1. A method (100, 200) for monitoring a coating status of a radome (711 , 712) for an antenna arrangement at an end of a radio link (710), the method comprising: acquiring (110, 210) measurements (300, 400) of attenuation in the radio link; detecting (120, 220), based on the measurements, a damping event (310) of the radome; deriving (140, 240), based on the measurements, a metric value indicative of a current drying capacity of the radome following the damping event; and determining (150, 250) the coating status by comparing, based on the derived metric value, the current drying capacity of the radome with at least one reference drying capacity.

2. The method of claim 1 , wherein the at least one reference drying capacity comprises an uncoated drying capacity(520) and / or a newly coated drying capacity (510).

3. The method of any of claims 1 through 2, wherein detecting the damping event comprises one or more of: mapping increase of attenuation in the measurements to an attenuation pattern which is typical for damping events; and correlating increase of attenuation in the measurements to information indicating wet weather conditions.

4. The method of claim 3, wherein the increase in attenuation comprises attenuation that exceeds a threshold value(411) associated with wet radome conditions.

5. The method of any of claims 1 through 4, wherein detecting the damping event comprises determining an estimated end time (320) of the damping event.

6. The method of claim 5, wherein a drying period corresponds to a duration between the estimated end time of the damping event and a time when the attenuation falls below a threshold value associated with dry radome conditions, and wherein the metric comprises one or more of: a duration (331 , 332) of the drying period, and a rate (333, 334) of attenuation decrease within the drying period.

7. The method of claim 6, wherein the rate of attenuation decrease is determined by fitting of a straight line to attenuation samples in a time window comprised in the drying period, and deriving the rate of attenuation decrease based on the slope of the fitted straight line.

8. The method of claim 7, further comprising determining whether one or more attenuation samples has a deviation from the fitted straight line that exceeds a deviation threshold, and, if so, disqualifying the fitted straight line as basis for deriving the rate of attenuation decrease.

9. The method of any of claims 1 through 8, wherein determining the coating status comprises: deriving a collective metric value for the current drying capacity of the radome from a plurality of metric values derived from different damping events; and comparing the collective metric value to corresponding metric value(s) for the at least one reference drying capacity.

10. The method of any of claims 1 through 9, further comprising determining (130) which end(s) of the radio link are exposed to the damping event based on one or more of: measurements of attenuation in one or more other radio links in vicinity of the antenna arrangement; and information indicating wet weather conditions in vicinity of the antenna arrangement.

11. A computer program product comprising a non-transitory computer readable medium (800), having thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to any of claims 1 through 10 when the computer program is run by the data processing unit.

12. An apparatus (600) for monitoring a coating status of a radome (711 , 712) for an antenna arrangement at an end of a radio link (710), the apparatus comprising controlling circuitry (620) configured to cause: acquisition of measurements (300, 400) of attenuation in the radio link; detection, based on the measurements, of a damping event (310) of the radome; derivation, based on the measurements, of a metric value indicative of a current drying capacity of the radome following the damping event; and determination of the coating status by comparing, based on the derived metric value, the current drying capacity of the radome with at least one reference drying capacity.

13. The apparatus of claim 12, wherein the at least one reference drying capacity comprises an uncoated drying capacity (520) and / or a newly coated drying capacity (510).

14. The apparatus of any of claims 12 through 13, wherein the controlling circuitry is configured to cause the detection of the damping event by causing one or more of: mapping of increase of attenuation in the measurements to an attenuation pattern which is typical for damping events; and correlation of increase of attenuation in the measurements to information indicating wet weather conditions.

15. The apparatus of claim 14, wherein the increase in attenuation comprises attenuation that exceeds a threshold value (411) associated with wet radome conditions.

16. The apparatus of any of claims 12 through 15, wherein detection of the damping event comprises determination of an estimated end time (320) of the damping event.

17. The apparatus of claim 16, wherein a drying period corresponds to a duration between the estimated end time of the damping event and a time when the attenuation falls below a threshold value associated with dry radome conditions, and wherein the metric comprises one or more of: a duration (331 , 332) of the drying period, and a rate (333, 334) of attenuation decrease within the drying period.

18. The apparatus of claim 17, wherein the controlling circuitry is configured to cause determination of the rate of attenuation decrease by fitting of a straight line to attenuation samples in a time window comprised in the drying period, and deriving the rate of attenuation decrease based on the slope of the fitted straight line.

19. The apparatus of claim 18, wherein the controlling circuitry is further configured to cause determination of whether one or more attenuation samples has a deviation from the fitted straight line that exceeds a deviation threshold, and, if so, disqualification of the fitted straight line as basis for deriving the rate of attenuation decrease.

20. The apparatus of any of claims 12 through 19, wherein the controlling circuitry is configured to cause determination of the coating status by causing: derivation of a collective metric value for the current drying capacity of the radome from a plurality of metric values derived from different damping events; and comparison of the collective metric value to corresponding metric value(s) for the at least one reference drying capacity.

21. The apparatus of any of claims 12 through 20, wherein the controlling circuitry is further configured to cause determination of which end(s) of the radio link are exposed to the damping event based on one or more of: measurements of attenuation in one or more other radio links in vicinity of the antenna arrangement; and information indicating wet weather conditions in vicinity of the antenna arrangement.

22. A radio communication node (610, 730) comprising the apparatus (600) of any of claims 12 through 21.

23. A network node (610, 740) comprising the apparatus (600) of any of claims 12 through 21.

24. A server node (610, 750) comprising the apparatus (600) of any of claims 12 through 21.

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