WO2024165174A1

WO2024165174A1 - Identification of weather impact on wireless links

Info

Publication number: WO2024165174A1
Application number: PCT/EP2023/053387
Authority: WO
Inventors: Lars-Erik LINDBERG; Jan Sandberg
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-02-10
Filing date: 2023-02-10
Publication date: 2024-08-15
Anticipated expiration: 2025-08-10

Abstract

There is provided techniques for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link. A method is performed by a controller entity. The method comprises obtaining link attenuation values of the point-to-point microwave wireless link and link attenuation values of the point-to-point free-space optical link. The method comprises identifying, based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link and the link attenuation values of the point-to-point free-space optical link, that the operating conditions of the point-to-point microwave wireless link and/or the point-to-point free-space optical link is/are impacted by a weather condition.

Description

IDENTIFICATION OF WEATHER IMPACT ON WIRELESS LINKS

TECHNICAL FIELD

Embodiments presented herein relate to a method, a controller entity, a computer program, and a computer program product for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link.

BACKGROUND

In a microwave system, digital information is sent over point-to-point wireless microwave links between two nodes. These two nodes are typically spaced from a few hundred meters up to several kilometers. Each node comprises link equipment, such as an antenna, a radio for frequency up- and down-conversion, and a modem for digital signal processing, used for transmission and reception of microwave signals over the point-to-point wireless microwave links. Likewise, in free-space optical systems, digital information is sent over point-to-point free-space optical links between two nodes. These two nodes can typically also be spaced from a few hundred meters up to several kilometers. Each node comprises link equipment, such as an optical transceiver, a converter for frequency up- and down-conversion, and a modem for digital signal processing, used for transmission and reception of free-space optical signals over the point-to-point free-space optical links.

Point-to-point wireless microwave links as well as point-to-point free-space optical links are sometimes subjected to disturbances. Such disturbances affect the received signal power and quality. This might trigger alarms that are sent to the network operator. When a network operator suspects that the link equipment is not working properly, a common response is to make a site visit (i.e., to send maintenance personnel to inspect the link equipment). Such a site visit sometimes results in the link equipment, or at least part thereof, being shipped back to the manufacturer for maintenance, or even replacement.

It has been found during inspections that a significant fraction of the link equipment sent back to the manufacturer in fact does not suffer from impaired operation and no faults are found. This indicates that resources, such as time and money, might be saved if network operators are provided with more accurate feedback about their network equipment.

In turn, it might be challenging to separate different types of operating conditions which cause the same type of performance degradation.

Hence, there is still a need for improved identification of the operating conditions of point-to-point wireless microwave links and free-space optical links.

SUMMARY

An object of embodiments herein is to address the above issues. A particular object is to enable identification of what causes the operating conditions of point-to-point wireless microwave link and/or free-space optical links to be impacted, and especially if the operating conditions are impacted by weather.

According to a first aspect there is presented a controller entity for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link. The controller entity comprises processing circuitry. The processing circuitry is configured to cause the controller entity to obtain link attenuation values of the point-to-point microwave wireless link and link attenuation values of the point-to-point free-space optical link. The processing circuitry is configured to cause the controller entity to identify, based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link and the link attenuation values of the point-to-point free-space optical link, that the operating conditions of the point-to-point microwave wireless link and/or the point-to-point free-space optical link is/are impacted by a weather condition.

According to a second aspect there is presented a controller entity for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link. The controller entity comprises an obtain module configured to obtain link attenuation values of the point-to-point microwave wireless link and link attenuation values of the point-to-point free-space optical link. The controller entity comprises an identify module configured to identify (S106), based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link and the link attenuation values of the point-to-point free-space optical link, that the operating conditions of the point-to-point microwave wireless link and/or the point-to-point free-space optical link is/are impacted by a weather condition.

According to a third aspect there is presented a method for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link. The method is performed by a controller entity. The method comprises obtaining link attenuation values of the point-to-point microwave wireless link and link attenuation values of the point-to-point free-space optical link. The method comprises identifying, based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link and the link attenuation values of the point-to-point free-space optical link, that the operating conditions of the point-to-point microwave wireless link and/or the point-to-point free-space optical link is/are impacted by a weather condition.

According to a fourth aspect there is presented a computer program for identifying weather impact on operating conditions of a point-to-point microwave wireless link and/or a point-to-point free-space optical link. The computer program comprises computer code which, when rim on processing circuitry of a controller entity, causes the controller entity to perform actions. One action comprises the controller entity to obtain link attenuation values of the point-to-point microwave wireless link and link attenuation values of the point-to-point free-space optical link. One action comprises the controller entity to identify, based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link and the link attenuation values of the point-to-point free-space optical link, that the operating conditions of the point-to-point microwave wireless link and/or the point- to-point free-space optical link is/are impacted by a weather condition

According to a fifth aspect there is presented a computer program product comprising a computer program according to the fourth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

Advantageously, these aspects enable identification of what causes the operating conditions of point-to- point wireless microwave link and/or free-space optical links to be impacted, and especially if the operating conditions are impacted by weather.

Advantageously, these aspects can be used to provide network operators with information what is causing a disturbance on the point-to-point microwave wireless link and/or the point-to-point free-space optical link.

Advantageously, combined information from wireless microwave and optical links is used to separate malfunctioning wireless links from normal weather disturbances.

Advantageously, these aspects provide efficient identification of the operating conditions of the wireless micro wave and optical links.

Advantageously, these aspects enable the accuracy of the weather classification model for all operating conditions to be high.

Advantageously, these aspects enable the risk of misclassification to be reduced.

Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram illustrating a communications network according to embodiments;

Fig. 2 is a block diagram of a controller entity according to an embodiment

Fig. 3 is a flowchart of methods according to embodiments;

Fig. 4 schematically illustrates attenuation for a point-to-point microwave wireless link and a point-to- point free-space optical link as impacted by different weather conditions according to embodiments;

Fig. 5 schematically illustrates the use of representing atmospheric conditions by transfer function according to an embodiment;

Fig. 6 is a schematic block diagram of an adaptive equalizer according to an embodiment;

Fig. 7 is a schematic diagram illustrating different scenarios according to embodiments;

Fig. 8 is a flowchart of methods according to embodiments;

Fig. 9 is a schematic diagram showing functional units of a controller entity according to an embodiment;

Fig. 10 is a schematic diagram showing functional modules of a controller entity according to an embodiment; and

Fig. 11 shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

Fig. 1 is a schematic diagram illustrating a communications network 100 where embodiments presented herein can be applied. The communications network 100 comprises two nodes 140a, 140b configured to communicate with each other over a point-to-point microwave wireless link 150 and a point-to-point free- space optical link 160. In turn, each node 140a, 140b comprises, or is operatively connected to, a respective microwave transceiver 110a, 110b, and optical transceiver 120a, 120b for wireless transmission and reception of data in signals over the links 150, 160. Microwave transceivers 110a, 110b are configured for transmission and reception of microwave signals whereas optical transceivers 120a, 120b are configured for transmission and reception of free-space optical signals. Each node 140a, 140b (and microwave transceiver 110a, 110b and optical transceiver 120a, 120b) might be part of a respective site. Each microwave transceiver 110a, 110b and optical transceiver 120a, 120b is at each site mounted on a cell tower 130a, 130b. Although illustrated as separate cell towers, one, or both, of the cell towers 130a, 130b may, alternatively, be a monopole that is mounted to a building, or the like. Each node 140a, 140b is operatively connected to a controller entity 200. The controller entity 200 denotes, according to some aspects, an entity responsible for monitoring, or even controlling, the actual operation of the communications network 100. The controller entity 200 might thus be the entity responsible for taking action when the system’s performance is not up to par. It can for example be an entity with which personnel in a network operating center (NOC) might interact, an entity running a computer program which in some examples is capable of employing machine learning techniques, or similar. Further aspects of the controller entity 200 will be disclosed below.

As noted above, there is still a need for improved identification of the operating conditions of point-to- point wireless microwave links and free-space optical links.

In this respect, it can be advantageous to distinguish if it is a weather condition or any component of the sites (such as any of the microwave transceivers 110a, 110b, or the optical transceivers 120a, 120b) that is causing a performance degradation of the point-to-point microwave wireless link 150 and/or the point-to- point free-space optical link 160. If such a distinction is not made, there is a risk that a technician, or other type of maintenance personnel, is dispatched to perform maintenance at one of the sites in vain.

Some weather conditions, such as the presence of fog, cannot be accurately detected using existing techniques. Further this respect, it can therefore be advantageous to know what type of weather condition that is causing the performance degradation of the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160.

The embodiments disclosed herein therefore relate to techniques for identifying weather impact on operating conditions of a point-to-point microwave wireless link 150 and/or a point-to-point free-space optical link 160. In order to obtain such techniques there is provided a controller entity 200, a method performed by the controller entity 200, a computer program product comprising code, for example in the form of a computer program, that when run on a controller entity 200, causes the controller entity 200 to perform the method. Microwave wireless links 150 are much less atenuated by fog compared to free-space optical links 160. The infra-red spectrum (e.g., from 700 nm to 2200 nm) is commonly used for communication over free- space optical links, but any part of the optical spectrum can be used.

Combining atenuation information for a point-to-point microwave wireless link 150 and a point-to-point free-space optical link 160 allows for classification of the weather conditions snow, rain, and fog. This can be achieved because of the difference in atenuation behavior between microwave and optical transmissions for these weather conditions.

Fig. 2 provides a block diagram of a controller entity 200 according to an embodiment. The controller entity 200 comprises a free-space optical link data collector 240 for collecting time-series of link atenuation values of the point-to-point free-space optical link 160. The link atenuation values can be obtained from measurements on optical signals transmited over the point-to-point free-space optical link 160. The measurements might be received signal strength indicator (RSSI) measurements or pathloss measurements. The controller entity 200 comprises a microwave link data collector 250 for collecting time-series of link atenuation values of the point-to-point microwave wireless link 150. The link atenuation values can be obtained from measurements on microwave signals transmited over the point- to-point microwave wireless link 150. The measurements might be RSSI measurements or pathloss measurements. The link atenuation values might be collected for either one direction of the links or for both directions of the links. More details regarding this will be disclosed below. The controller entity 200 comprises an operating conditions identifier 260 configured to obtain the time-series of link atenuation values from the free-space optical link data collector 240 and the microwave link data collector 250 and to therefrom identify that the operating conditions of the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160 is/are impacted by a weather condition. Further details regarding this will be disclosed below with reference to Fig. 3.

Fig. 3 is a flowchart illustrating embodiments of methods for identifying weather impact on operating conditions of a point-to-point microwave wireless link 150 and/or a point-to-point free-space optical link 160. The methods are performed by the controller entity 200. The methods are advantageously provided as computer programs 1020.

SI 02: The controller entity 200 obtains link atenuation values of the point-to-point microwave wireless link 150 and link atenuation values of the point-to-point free-space optical link 160.

SI 06: The controller entity 200 identifies that the operating conditions of the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160 is/are impacted by a weather condition. The identifications based on the obtained link atenuation values and a relation between the link atenuation values of the point-to-point microwave wireless link 150 and the link atenuation values of the point-to-point free-space optical link 160. Advantageously, this method enables identification of what causes the operating conditions of point-to- point wireless microwave link and/or free-space optical links to be impacted, and especially if the operating conditions are impacted by weather.

Advantageously, this method can be used to provide network operators with information what is causing a disturbance on the point-to-point microwave wireless link and/or the point-to-point free-space optical link.

Advantageously, this method provides efficient identification of the operating conditions of the wireless micro wave and optical links.

Advantageously, this method enables the accuracy of the weather classification model for all operating conditions to be high.

Advantageously, this method enables the risk of misclassification to be reduced.

Embodiments relating to further details of identifying weather impact on operating conditions of a point- to-point microwave wireless link 150 and/or a point-to-point free-space optical link 160 as performed by the controller entity 200 will now be disclosed with continued reference to Fig. 3.

There may be different examples of weather conditions that can be identified. In some non-limiting examples, the weather condition is any of: haze, fog, rain, snow, or smog.

At least some embodiments are based on the fact that there is a difference in attenuation behaviour between microwave and optical transmissions for different weather conditions. In particular, in some embodiments, the relation is based on that the operating conditions of the point-to-point microwave wireless link 150 are impacted differently by different weather conditions than the operating conditions of the point-to-point free-space optical link 160.

Therefore, in some examples, to identify the weather condition, the difference in attenuation behavior between microwave (MW) and optical (FSO) transmissions for different weather conditions are used. An overview is provided in Table 1 and, in more detail in Fig. 4.

Table 1: Attenuation comparison for different weather conditions

It here noted that in Table 1 the attenuation of the point-to-point microwave wireless link 150 on the one hand and the attenuation of the point-to-point free-space optical link 160 on the other hand not necessarily are at the same scale. That is, the absolute value of the “medium” attenuation of the point-to-point microwave wireless link 150 is not equal to the absolute value of the “medium” attenuation of the point- to-point free-space optical link 160, etc.

In any case, as can be seen from Table 1, there are significant differences in how wireless microwave and optical links are affected by different weather conditions. In fact, each pair of link attenuation values (i.e., with one value for the point-to-point microwave wireless link 150 and one value for the point-to-point free-space optical link 160) uniquely corresponds to one weather condition. From Table 1 follows, for example, that if the attenuation for the point-to-point free-space optical link is very high at the same time as the attenuation for the point-to-point microwave wireless link is very low, then it can be concluded that the weather condition is fog, etc. Therefore, in some embodiments, according to the relation, each pair of one link attenuation value of the point-to-point microwave wireless link 150 and one link attenuation value of the point-to-point free-space optical link 160 uniquely corresponds to one weather condition in a set of possible weather conditions.

In Fig. 4(a) is shown the attenuation [dB/km] as a function of rain [mm/h] for a point-to-point free-space optical link. As a comparison, the attenuation [dB/km] as a function of rain [mm/h] for a point-to-point microwave wireless link is shown in Fig. 4(b). Further, in Fig. 4(c) is shown the attenuation [dB/km] as a function of snow as water [mm/h] for a point-to-point free-space optical link. As a comparison, the attenuation [dB/km] as a function of snow as water [mm/h] for a point-to-point microwave wireless link is shown in Fig. 4(d). Finally, in Fig. 4(e) is shown the attenuation [dB/km] as a function of visibility [km] for a point-to-point free-space optical link subjected to fog/haze.

One example of how microwave frequencies and all the way up to the optical spectrum is affected by different weather conditions as illustrated in Figure 1 in “Visibility in degraded visual environments (DVE)” by John N. Sanders-Reed, Stephen J. Fenley, Proc. SPIE 10642, Degraded Environments: Sensing, Processing, and Display 2018, 106420S (2 May 2018); doi: 10.1117/12.2305008. In some aspects, the identifying in action SI 06 is based on a linear regression model. Therefore, in some embodiments, the relation is implemented as a regression model. This regression model could be based on known behavior. One example of such a known behavior is given by Table 1.

In general terms, the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160, by means of the weather condition, is/are subjected to atmospheric conditions. These atmospheric conditions can be represented by transfer functions. In particular, in some embodiments, the atmospheric conditions are represented by a first transfer function for the point-to-point free-space optical link 160 and a second transfer function for the point-to-point microwave wireless link 150. An illustration of this is provided in Fig. 5. In particular, in Fig. 5, the atmospheric conditions are represented by transfer function HAtm,o_Pto for a point-to-point free-space optical link extending from optical transmitters 510a, 510b to optical receivers 520a, 520b and by transfer function Hm .w for a point-to-point microwave wireless link extending from microwave transmitters 513a, 530b to optical receivers 540a, 540b.

HAtm,opto is a function of hop length [km], wavelength [nm], precipitation [mm_water/hour], visibility [km], relative humidity [%], and wind [m/s]. Hence, in some non-limiting examples, the first transfer function depends on hop length of the point-to-point free-space optical link 160, operating wavelength of the point-to-point free-space optical link 160, precipitation as measured for the point-to-point free-space optical link 160, visibility with respect to the point-to-point free-space optical link 160, relative humidity experienced by the point-to-point free-space optical link 160, wind and/or air turbulence experienced by the point-to-point free-space optical link 160.

H Atm is a function of hop length [km], frequency [GHz], and precipitation [mm_water/hour] . Hence, in some non-limiting examples, the second transfer function depends on hop length of the point-to-point microwave wireless link 150, operating frequency of the point-to-point microwave wireless link 150, precipitation as measured for the point-to-point microwave wireless link 150.

Several models exist that can approximate these two transfer functions. One example is provided in “Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications” by Isaac I. Kim; Bruce McArthur; Eric J. Korevaar, in Proc. SPIE 4214, Optical Wireless Communications III, (6 February 2001); doi: 10.1117/12.417512.

Accuracy of the identifying in action S106 might be improved by, over time, collecting data and labelling the collected data with observed weather conditions. The collected and thus labelled data could then be used to train a model with any type of machine learning method. That is, the input to the machine learning method are sets of attenuation values (one set of values for the point-to-point microwave wireless link 150 and one set of values for the point-to-point free-space optical link 160) with correct weather conditions, and possible also equalization coefficients, as disclosed below. Accuracy of the identifying in action SI 06 might further be improved by considering environmental, or weather condition indicating, data. In particular, in some embodiments, the relation further is dependent on environmental data for the point-to-point microwave wireless link 150 and/or the point-to-point free- space optical link 160 in terms of any, or any combination of: temperature, relative humidity, air particle concentration, wind. In this respect, temperature can be used to further distinguish between snow condition on the one hand and rain condition on the other hand, etc. The environmental, or weather condition indicating, data can be collected from different available sources, or be measured directly by sensors located at the cell towers 130a, 130b.

Accuracy of the identifying in action SI 06 might further be improved by considering equalizer taps as input to the identifying. This is since, in general terms, reflections scattering from transmitted optical signals will appear differently at the optical receiver of the point-to-point free-space optical link 160 if caused by fog, rain or snow. Therefore, in some embodiments, the relation is dependent on equalizer tap values of the point-to-point free-space optical link 160. Intermediate reference is here made to Fig. 6 in which is shown a block diagram of an adaptive equalizer 600, which by means of a receiver (RX) block 610, receives a measured signal to be analyzed. The top row with boxes 620 labelled Z^A-1 can be thought of as a tapped delay line. Each box marked Z^A-1 is a delay element, with the amount of time delay per box equal to the reciprocal of the symbol rate in a T-spaced equalizer. A delay element is often called a tap, but a tap also can be considered the combination of a delay element, the point where some of the signal is tapped off, and a multiplier. The boxes 630 labelled b-4, b-3, ... , b+3, b+4 are multipliers with equalization coefficients that set the gain for each tap. The algorithm adjusts the equalization coefficients that set the gain for each multiplier. The boxes 640 labelled E are summing or combining circuits. One tap is called the main tap. The main tap has a gain of 1 and passes the input signal at its original amplitude. Other taps represent either the past or future relative to the main tap and vary the amplitudes of the respective signals passing through them as required. Scatter will be compensated for with the signal sample that has be sampled earlier than the current sample, i.e., the taps representing the past, i.e. b+1, ... , b+4 are used. These equalization coefficients should have comparatively large values. Smog will give attenuation and almost no scatter, implying that that the equalization coefficients b+1, ... , b+4 are less used, and hence should have comparatively small values. The sizes of snowflakes and raindrops also effect the number of taps used. The model used for the evaluation takes this into account. The update logic block 650 is configured to determine the equalization coefficients according to some design goal. One design goal is to optimize the performance of the optical receiver of the point-to-point free-space optical link 160. The performance is checked in a receiver (RX) filter output block 660. Once the equalization coefficients have been determined, the equalization coefficients are observed and compared to different sets of tabulated equalization coefficients. Here, each tabulated set of equalization coefficients corresponds to a certain weather condition. Thereby, by comparing the determined equalization coefficients with different sets of tabulated equalization coefficients it can be determined which weather condition that the determined equalization coefficients correspond to. As disclosed above, the link attenuation values might be collected for either one direction of the links or for both directions of the links. Accuracy of the identifying in action SI 06 might further be improved by considering link attenuation values for both directions of the links. Therefore, in some embodiments, each of the point-to-point microwave wireless link 150 and of the point-to-point free-space optical link 160 has two directions, and the link attenuation values are obtained for both directions the of the point-to-point microwave wireless link 150 and of the point-to-point free-space optical link 160. However, it will still be possible to do perform the identifying in action SI 06 based on data collected from only one direction of each link. In the case that only one direction is used it does not matter in what direction. The limitation introduced is less available data, and by that less accuracy in the identifying in action SI 06.

In some aspects, the obtained link attenuation values are utilized to classify the weather condition for a geographical area over which the point-to-point microwave wireless link 150 and the point-to-point free- space optical link 160 extend. In this respect, the point-to-point microwave wireless link 150 and the point-to-point free-space optical link 160 can be considered to extend over a geographical area 710, 720, 730. In particular, in some embodiments, the controller entity 200 is configured to perform (optional) action S104.

S104: The controller entity 200 classify the weather condition for the geographical area 710, 720, 730 based on the obtained link attenuation values and the relation between the link attenuation values of the point-to-point microwave wireless link 150 and the link attenuation values of the point-to-point free-space optical link 160.

A map can then be created for the geographical area 710, 720, 730 that show where in the geographical area 710, 720, 730 it is raining, snowing, foggy, or smog, etc.

The accuracy of the classification in action SI 04 might depend on how the point-to-point microwave wireless link 150 and the point-to-point free-space optical link 160 are geographically related to each other. Intermediate reference is here made to Fig. 7 which shows different scenarios 700a, 700b, and 700c of how one point-to-point microwave wireless link 150 and one point-to-point free-space optical link 160 are geographically related to each other, so as to extend over different geographical areas 710, 720, 730. Scenario 700a is an example of where the end-points of the point-to-point microwave wireless link 150 and the point-to-point free-space optical link 160 are collocated. That is, microwave transceiver 110a is collocated with optical transceiver 120a and microwave transceiver 110b is collocated with optical transceiver 120b. Scenario 700b is an example of where the point-to-point microwave wireless link 150 and the point-to-point free-space optical link 160 cross each other. Scenario 700c is an example of where the end-points of the point-to-point microwave wireless link 150 and the point-to-point free-space optical link 160 are not collocated and where the point-to-point microwave wireless link 150 and the point-to- point free-space optical link 160 do not cross each other. According to these examples, the classification in action S104 might be highest for scenario 700a and lowest for scenario 700b or scenario 700c, for example depending on the distance between the end-points. In some examples an action is performed in response to the controller entity 200 having identified that the operating conditions of the point-to point microwave wireless link 150 and/or the point-to-point free- space optical link 160 is/are impacted by the weather condition, as in action SI 06. In particular, in some embodiments, the controller entity 200 is configured to perform (optional) action SI 08.

SI 08: The controller entity 200 perform an action in response to having identified that that the operating conditions of the point-to point microwave wireless link 150 and/or the point-to-point free-space optical link 160 is/are impacted by the weather condition.

In some non-limiting examples, the action pertains to issuing a notification that the operating conditions are impacted by the weather condition.

In this way, maintenance personnel can be notified that the point-to point microwave wireless link 150 and/or the point-to-point free-space optical link 160 is/are affected by weather, so that personnel is not sent out in vain with a goal to repair a link that otherwise might be considered as damaged or faulty.

Reference is next made to the flowchart of Fig. 8 in which is disclosed a method for identifying weather impact on operating conditions of a point-to-point microwave wireless link 150 and/or a point-to-point free-space optical link 160 based on at least some of the above disclosed embodiments, aspects, and examples. The method is performed by the controller entity 200.

S201: The controller entity 200 obtains microwave and optical link data in terms of link attenuation values of the point-to-point microwave wireless link 150 and link attenuation values of the point-to-point free-space optical link 16O.The controller entity 200 might further obtain the equalization coefficients determined by the update logic block 650 (if such coefficients are available)

S202: The controller entity 200 identifies whether the operating conditions of the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160 are affected by a weather condition or not, for example by comparing the equalization coefficients to sets of tabulated equalization coefficients as disclosed above. S203 is entered if yes. Otherwise, execution of the method is terminated.

S203 : The controller entity 200 issues a notification that the operating conditions are impacted by a weather condition.

S204: The controller entity 200 identifies the type of weather condition (e.g., haze, fog, rain, snow, or smog) that is causing the operating conditions to be affected.

S204-1: Optionally, complement data (such as environmental data for the point-to-point microwave wireless link 150 and/or the point-to-point free-space optical link 160 is obtained to support the identification of the type of weather condition. S204-2: The controller entity 200, based on the microwave and optical link data, the equalization coefficients, and the complement data, calculates the probability for each weather conditions listed in Table 1.

S204-3 : The controller entity 200 selects the weather condition for which of the probability as calculated in S204-2 is the highest.

Fig. 9 schematically illustrates, in terms of a number of functional units, the components of a controller entity 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 1010 (as in Fig. 11), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

Particularly, the processing circuitry 210 is configured to cause the controller entity 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the controller entity 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed. The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The controller entity 200 may further comprise a communications (comm.) interface 220 at least configured for communications with other entities, functions, nodes, and devices, as in Fig. 1. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 210 controls the general operation of the controller entity 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the controller entity 200 are omitted in order not to obscure the concepts presented herein.

Fig. 10 schematically illustrates, in terms of a number of functional modules, the components of a controller entity 200 according to an embodiment. The controller entity 200 of Fig. 10 comprises a number of functional modules; an obtain module 210a configured to perform action S102, and an identify module 210c configured to perform action S106. The controller entity 200 of Fig. 10 may further comprise a number of optional functional modules, such as any of a classify module 210b configured to perform action S104, and an action module 210d configured to perform action S108. In general terms, each functional module 210a:210d may in one embodiment be implemented only in hardware and in another embodiment with the help of software, i.e., the latter embodiment having computer program instructions stored on the storage medium 230 which when run on the processing circuitry makes the controller entity 200 perform the corresponding steps mentioned above in conjunction with Fig 9. It should also be mentioned that even though the modules correspond to parts of a computer program, they do not need to be separate modules therein, but the way in which they are implemented in software is dependent on the programming language used. Preferably, one or more or all functional modules 210a:210d may be implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and/or the storage medium 230. The processing circuitry 210 may thus be configured to from the storage medium 230 fetch instructions as provided by a functional module 210a:210d and to execute these instructions, thereby performing any steps as disclosed herein.

The controller entity 200 may be provided as a standalone device or as a part of at least one further device. For example, the controller entity 200 may be provided in a node of an access network or in a node of a core network. Alternatively, functionality of the controller entity 200 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the access network or the core network) or may be spread between at least two such network parts. In general terms, the controller entity 200 could be implemented in one of the nodes 140a, 140b (for example as part of the digital signal processing in a modems) or in some external device having access to data from the links. A first portion of the instructions performed by the controller entity 200 may be executed in a first device, and a second portion of the of the instructions performed by the controller entity 200 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the controller entity 200 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a controller entity 200 residing in a cloud computational environment. Therefore, although a single processing circuitry 210 is illustrated in Fig. 9 the processing circuitry 210 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 210a:210d of Fig. 10 and the computer program 1020 of Fig. 11.

Some (antenna) access network architectures define network nodes (or gNBs) comprising multiple component parts or nodes: a central unit (CU), one or more distributed units (DUs), and one or more antenna units (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and the RUs, with one or more lower layers of the stack implemented in the RUs, and one or more higher layers of the stack implemented in the CU and/or DUs. The CU is coupled to the DUs via a fronthaul higher layer split (HLS) network; the CU/DUs are connected to the RUs via a fronthaul lower-layer split (LLS) network. The DU may be combined with the CU in some embodiments, where a combined DU/CU may be referred to as a CU or simply a baseband unit. A communication link for communication of user data messages or packets between the RU and the baseband unit, CU, or DU is referred to as a fronthaul network or interface. Messages or packets may be transmitted from the network node 200 in the downlink (i.e., from the CU to the RU) or received by the network node 200 in the uplink (i.e., from the RU to the CU).

Fig. 11 shows one example of a computer program product 1010 comprising computer readable storage medium 1030. On this computer readable storage medium 1030, a computer program 1020 can be stored, which computer program 1020 can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 1020 and/or computer program product 1010 may thus provide means for performing any steps as herein disclosed.

In the example of Fig. 11, the computer program product 1010 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1010 could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 1020 is here schematically shown as a track on the depicted optical disk, the computer program 1020 can be stored in any way which is suitable for the computer program product 1010.

The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

1. A controller entity (200) for identifying weather impact on operating conditions of a point-to-point microwave wireless link (150) and/or a point-to-point free-space optical link (160), the controller entity (200) comprising processing circuitry (210), the processing circuitry being configured to cause the controller entity (200) to: obtain link attenuation values of the point-to-point microwave wireless link (150) and link attenuation values of the point-to-point free-space optical link (160); and identify, based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link (150) and the link attenuation values of the point-to- point free-space optical link (160), that the operating conditions of the point-to-point microwave wireless link (150) and/or the point-to-point free-space optical link (160) is/are impacted by a weather condition.

2. The controller entity (200) according to claim 1, wherein the relation is based on the operating conditions of the point-to-point microwave wireless link (150) being impacted differently by different weather conditions than the operating conditions of the point-to-point free-space optical link (160).

3. The controller entity (200) according to any preceding claim, wherein, according to the relation, each pair of one link attenuation value of the point-to-point microwave wireless link (150) and one link attenuation value of the point-to-point free-space optical link (160) uniquely corresponds to one weather condition in a set of possible weather conditions.

4. The controller entity (200) according to any preceding claim, wherein the relation is implemented as a regression model.

5. The controller entity (200) according to any preceding claim, wherein the relation is dependent on equalizer tap values of the point-to-point free-space optical link (160).

6. The controller entity (200) according to any preceding claim, wherein the relation is dependent on environmental data for the point-to-point microwave wireless link (150) and/or the point-to-point free- space optical link (160) in terms of any, or any combination of: temperature, relative humidity, air particle concentration, wind.

7. The controller entity (200) according to any preceding claim, wherein the point-to-point microwave wireless link (150) and/or the point-to-point free-space optical link (160), by means of the weather condition, is/are subjected to atmospheric conditions, and wherein the atmospheric conditions are represented by a first transfer function for the point-to-point free-space optical link (160) and a second transfer function for the point-to-point microwave wireless link (150).

8. The controller entity (200) according to claim 7, wherein the first transfer function depends on hop length of the point-to-point free-space optical link (160), operating wavelength of the point-to-point free- space optical link (160), precipitation as measured for the point-to-point free-space optical link (160), visibility with respect to the point-to-point free-space optical link (160), relative humidity experienced by the point-to-point free-space optical link (160), wind and/or air turbulence experienced by the point-to- point free-space optical link (160).

9. The controller entity (200) according to claim 7 or 8, wherein the second transfer function depends on hop length of the point-to-point microwave wireless link (150), operating frequency of the point-to- point microwave wireless link (150), precipitation as measured for the point-to-point microwave wireless link (150).

10. The controller entity (200) according to any preceding claim, wherein each of the point-to-point microwave wireless link (150) and of the point-to-point free-space optical link (160) has two directions, and wherein the link attenuation values are obtained for both directions the of the point-to-point microwave wireless link (150) and of the point-to-point free-space optical link (160).

11. The controller entity (200) according to any preceding claim, wherein the point-to-point microwave wireless link (150) and the point-to-point free-space optical link (160) extend over a geographical area (710, 720, 730), the processing circuitry further being configured to cause the controller entity (200) to: classify the weather condition for the geographical area (710, 720, 730) based on the obtained link attenuation values and the relation between the link attenuation values of the point-to-point microwave wireless link (150) and the link attenuation values of the point-to-point free-space optical link (160).

12. The controller entity (200) according to any preceding claim, wherein the weather condition is any of: haze, fog, rain, snow, smog.

13. The controller entity (200) according to any preceding claim, the processing circuitry further being configured to cause the controller entity (200) to: perform an action in response to having identified that that the operating conditions of the point-to- point microwave wireless link (150) and/or the point-to-point free-space optical link (160) is/are impacted by the weather condition.

14. A method for identifying weather impact on operating conditions of a point-to-point microwave wireless link (150) and/or a point-to-point free-space optical link (160), the method being performed by a controller entity (200), the method comprising: obtaining (SI 02) link attenuation values of the point-to-point microwave wireless link (150) and link attenuation values of the point-to-point free-space optical link (160); and identifying (SI 06), based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link (150) and the link attenuation values of the point-to-point free-space optical link (160), that the operating conditions of the point-to-point microwave wireless link (150) and/or the point-to-point free-space optical link (160) is/are impacted by a weather condition.

15. A computer program (1020) for identifying weather impact on operating conditions of a point-to- point microwave wireless link (150) and/or a point-to-point free-space optical link (160), the computer program comprising computer code which, when run on processing circuitry (210) of a controller entity (200), causes the controller entity (200) to: obtain (SI 02) link attenuation values of the point-to-point microwave wireless link (150) and link attenuation values of the point-to-point free-space optical link (160); and identify (SI 06), based on the obtained link attenuation values and a relation between the link attenuation values of the point-to-point microwave wireless link (150) and the link attenuation values of the point-to-point free-space optical link (160), that the operating conditions of the point-to-point microwave wireless link (150) and/or the point-to-point free-space optical link (160) is/are impacted by a weather condition.

16. A computer program product (1010) comprising a computer program (1020) according to claim 15, and a computer readable storage medium (1030) on which the computer program is stored.