Patent Publication Number: US-2022225238-A1

Title: Coordinating Control of Average EIRP of Multiple Radio Transmitters

Description:
TECHNICAL FIELD 
     Embodiments presented herein relate to methods, a coordinating controller, inner controllers, computer programs, and a computer program product for average power control of radio power sources. 
     BACKGROUND 
     When any radio equipment is to be deployed, regulatory radio frequency (RF) electromagnetic field (EMF) exposure requirements should be accounted for. These RF EMF exposure regulations may typically be based on the guidelines from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) but may take different forms in some countries and regions. The aim of RF EMF exposure regulations is to ensure that human exposure to RF energy is kept within prescribed limits, which typically have been set with wide safety margins. 
     Some newly developed base stations and other radio equipment are equipped with so-called advanced antenna systems (AAS). These antenna systems increase the capacity and/or coverage compared to traditionally used antenna system by addition of one or more antenna arrays. In turn, this enables the simultaneous transmission of parallel data streams between a base station on the network side and a terminal device at the user-side by means of so-called multiple-input-multiple-output (MIMO) transmission. 
     For base stations and other radio equipment having AAS systems with a large number of antenna elements in order to achieve a high directivity, there may be a large maximum beamforming gain. A consequence of a large beamforming gain is typically that the radiated power is concentrated in directional beams, meaning that the Equivalent Isotropic Radiated Power (EIRP) rating of the base station, i.e. the power radiated from an antenna with unity antenna gain in all directions, is increased as compared to the situation without AAS systems. 
     The RF EMF exposure limitations are typically expressed in terms of power density (in units of W/m 2 ) which in the far field is proportional to the EIRP. Consequently, the EIRP can be used to determine the power density in the far field. 
     The ICNIRP and other RF EMF exposure limitations are usually expressed in terms of average power densities over a specified averaging time interval T. This means that the momentary power density can be higher during a shorter time than T, however the time-averaged power density over any time period T must be below the specified limit. To maintain a certain RF EMF compliance boundary or exclusion zone, that is smaller than what is obtained using the maximum EIRP of the AAS, the time-averaged total transmit power needs to be controlled to be less than an average power threshold that is computed based on the RF exposure limitations and the selected exclusion zone. In cases where more than one power source share the same AAS or where several AASs are co-sited and aligned, the threshold may have to be computed in terms of the combined EIRP of the site. 
     Hence, there may be a need for efficient control of the average EIRP for base stations and other radio equipment. 
     SUMMARY 
     An object of embodiments herein is to provide efficient control of radio power sources of base stations and other radio equipment, so that RF EMF exclusion zones are maintained by the controlled time-averaged powers of the base stations and radio equipment. 
     This objective is generally solved by mechanisms performed by a coordinating controller for controlling the combined average EIRP of the power sources. 
     According to a first aspect there is presented a method for average EIRP control of at least two radio power sources. The method is performed by a coordinating controller of a site. The site comprises the at least two radio power sources. The method comprises obtaining, from a respective inner controller of each of the at least two radio power sources, power control feedback information. The method comprises determining, according to an inner control loop for each of the at least two radio power sources, coordinating control information from the power control feedback information. The method comprises performing individual average power control of each of the at least two radio power sources by providing, to each respective inner controller, the coordinating control information, whereby total average transmission power of each of the at least two radio power sources is selectively adjusted based on the inner control loop. 
     According to a second aspect there is presented a coordinating controller of a site for average EIRP control of at least two radio power sources. The site comprises the at least two radio power sources. The coordinating controller comprises processing circuitry. The processing circuitry is configured to cause the coordinating controller to obtain, from a respective inner controller of each of the at least two radio power sources, power control feedback information. The processing circuitry is configured to cause the coordinating controller to determine, according to an inner control loop for each of the at least two radio power sources, coordinating control information from the power control feedback information. The processing circuitry is configured to cause the coordinating controller to perform individual average power control of each of the at least two radio power sources by providing, to each respective inner controller, the coordinating control information, whereby total average transmission power of each of the at least two radio power sources is selectively adjusted based on the inner control loop. 
     According to a third aspect there is presented a coordinating controller of a site for average EIRP control of at least two radio power sources. The site comprises the at least two radio power sources. The coordinating controller comprises an obtain module configured to obtain, from a respective inner controller of each of the at least two radio power sources, power control feedback information. The coordinating controller comprises a determine module configured to determine, according to an inner control loop for each of the at least two radio power sources, coordinating control information from the power control feedback information. The coordinating controller comprises a control module configured to perform individual average power control of each of the at least two radio power sources by providing, to each respective inner controller, the coordinating control information, whereby total average transmission power of each of the at least two radio power sources is selectively adjusted based on the inner control loop. 
     According to a fourth aspect there is presented a computer program for average EIRP control of at least two radio power sources. The computer program comprises computer program code which, when run on processing circuitry of a coordinating controller, causes the coordinating controller to perform a method according to the first aspect. 
     The objective is generally further solved by mechanisms performed by an inner controller for controlling the average power a radio power source. 
     According to a fifth aspect there is presented a method for average power control of a radio power source. The method is performed by an inner controller of the radio power source. The method comprises providing power control feedback information of the radio power source to a coordinating controller of a site. The site comprises the radio power source and at least one further radio power source. The method comprises obtaining coordinating control information from a coordinating controller, the coordinating control information is determined according to a respective inner control loop for each of the radio power source and the at least one further radio power source from the power control feedback information. The method comprises performing average power control of the radio power source according to the coordinating control information whereby total average transmission power of the radio power source is selectively adjusted based on the inner control loop. 
     According to a sixth aspect there is presented an inner controller of a radio power source for average power control of the radio power source. The inner controller comprises processing circuitry. The processing circuitry is configured to cause the inner controller to provide power control feedback information of the radio power source to a coordinating controller of a site. The site comprises the radio power source and at least one further radio power source. The processing circuitry is configured to cause the inner controller to obtain coordinating control information from a coordinating controller, the coordinating control information is determined according to a respective inner control loop for each of the radio power source and the at least one further radio power source from the power control feedback information. The processing circuitry is configured to cause the inner controller to perform average power control of the radio power source according to the coordinating control information whereby total average transmission power of the radio power source is selectively adjusted based on the inner control loop. 
     According to a seventh aspect there is presented an inner controller of a radio power source for average power control of the radio power source. The inner controller comprises a provide module configured to provide power control feedback information of the radio power source to a coordinating controller of a site. The site comprises the radio power source and at least one further radio power source. The inner controller comprises an obtain module configured to obtain coordinating control information from a coordinating controller, the coordinating control information is determined according to a respective inner control loop for each of the radio power source and the at least one further radio power source from the power control feedback information. The inner controller comprises a control module configured to perform average power control of the radio power source according to the coordinating control information whereby total average transmission power of the radio power source is selectively adjusted based on the inner control loop. 
     According to an eight aspect there is presented a computer program for average power control of a radio power source, the computer program comprising computer program code which, when run on processing circuitry of an inner controller, causes the inner controller to perform a method according to the fifth aspect. 
     According to a ninth aspect there is presented a computer program product comprising a computer program according to at least one of the fourth aspect and the eight 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 methods, these coordinating controllers, these inner controllers, these computer programs, and this computer program product enable efficient average power and EIRP control of radio power sources. 
     Advantageously these methods, these coordinating controllers, these inner controllers, these computer programs, and this computer program product improves stability of the inner control loop. 
     Advantageously these methods, these coordinating controllers, these inner controllers, these computer programs, and this computer program product enable uniform behavior of the inner control loop for different radio power sources. 
     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: 
         FIGS. 1 and 2  are schematic diagrams illustrating communication networks according to embodiments; 
         FIGS. 3, 6, 7  are block diagrams of controllers according to embodiments; 
         FIGS. 4 and 5  are flowcharts of methods according to embodiments; 
         FIGS. 8 and 9  shows simulation results according to embodiments; 
         FIG. 10  is a signalling diagram of a method according to an embodiment; 
         FIG. 11  is a schematic diagram showing functional units of a coordinating controller according to an embodiment; 
         FIG. 12  is a schematic diagram showing functional modules of a coordinating controller according to an embodiment; 
         FIG. 13  is a schematic diagram showing functional units of an inner controller according to an embodiment; 
         FIG. 14  is a schematic diagram showing functional modules of an inner controller according to an embodiment; and 
         FIG. 15  shows one example of a computer program product comprising computer readable means 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 lo 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  and  FIG. 2  are schematic diagrams illustrating communications networks  100   a ,  100   b  where embodiments presented herein can be applied. The communications networks  100   a ,  100   b  could be a third generation (3G) telecommunications network, a fourth generation (4G) telecommunications network, or a fifth (5G) telecommunications network, or any combination thereof, and support any 3GPP telecommunications standard, where applicable. 
     The communications networks  100   a ,  100   b  comprise a coordinating controller  200  configured to control a radio power source  170   a,    170   b  of a site  140 ,  140   a,    140   b  that provides network access to at least one terminal device  160   a,    160   b  in a radio access network  110 , thus enabling the terminal device  160   a,    160   b  to communicate over a wireless link  150   a,    150   b.  The radio access network  110  is operatively connected to a core network  120 . The core network  120  is in turn operatively connected to a service network  130 , such as the Internet. The terminal device  160   a,    160   b  is thereby enabled to, via the site  140 ,  140   a,    140   b,  access services of, and exchange data with, the service network  130 . 
     Examples of sites  140 ,  140   a,    140   b  are radio base stations, radio access network nodes, base transceiver stations, Node Bs (NBs), evolved Node Bs (eNBs), gNBs, access points, and access nodes, and backhaul nodes. Examples of terminal devices  160   a ,  160   b  are wireless devices, mobile stations, mobile phones, handsets, wireless local loop phones, user equipment (UE), smartphones, laptop computers, tablet computers, network equipped sensors, network equipped vehicles, and so-called Internet of Things devices. 
     A coordinating controller  200  might comprise, be collocated with, integrated with, or be in operational communications with, the site  140 ,  140   a,    140   b.  The site  140 ,  140   a ,  140   b  might be configured for dual connectivity and/or carrier aggregation. 
     In general terms, according to dual connectivity (or more generally, multi connectivity) a terminal device  160   a,    160   b  might may simultaneously receive and transmit to at least two different sites, such as sites  140   a  and  140   b . The two sites are sometimes denoted as Master eNB (MeNB) and Secondary eNB (SeNB). According to an example of the split bearer architecture option of dual connectivity, in the downlink, data is split on the Packet Data Convergence Protocol (PDCP) layer in the MeNB. The site may route PDCP protocol data units (PDUs) dynamically via the radio link control (RLC) protocol at the MeNB directly to the terminal device  160   a ,  160   b,  or via a backhaul channel to the SeNB and then via the RLC protocol at the SeNB to the terminal device  160   a,    160   b.  The data flow from MeNB to SeNB via the backhaul channel is typically controlled by a flow control protocol in order to balance the SeNB buffer fill state. As the skilled person understands, the MeNB could use a first radio access technology (RAT) whilst the SeNB could use a second RAT. In other scenarios the MeNB and the SeNB both use the same RAT. 
     In general terms, according to carrier aggregation a terminal device  160   a,    160   b  might simultaneously receive and transmit on at least two different carriers while using a common PDCP, RLC and medium access control (MAC) layer for the carriers but a separate physical layer for each carrier. The site  140 ,  140   a,    140   b  selects the radio resources, modulation, coding and MIMO layers to use on each carrier and schedule MAC PDUs on the carriers based on this selection and on feedback from the terminal device  160   a,    160   b.  This is in general referred to as scheduling. The carriers are synchronized in time. This implies that a common controller of the site  140 ,  140   a ,  140   b  can coordinate and control the use of each carrier per transmission time interval (TTI). Each carrier is also associated with a cell as resource owner. 
     Dual connectivity and carrier aggregation can be combined. For example, when more than one RAT, such as LTE and NR, are combined at a site  140 ,  140   a,    140   b,  dual connectivity can be used such that one leg of the dual connectivity is used for LTE whilst another leg is used for NR. In such a situation carrier aggregation groups of terminal devices on one RAT might be used on each of the legs of the dual connectivity. 
     As mentioned above there is a need for efficient control of the average EIRP for base stations and other radio equipment, in particular when co-sited. 
     For example, assume a scenario where multiple carriers in single site  140 , or co-sited sites  140   a ,  140   b  possibly using different RATs, are transmitting over the same geographical region, like a cell. For simplicity, antenna array sharing is assumed. Assume for simplicity that each site  140 ,  140   a,    140   b  provides power to their antenna arrays independently. Assume further that each site has an inner controller  300  that implements functionality for single node average power control. The inner control loop of each radio power source  170   a,    170   b  might be supervised by the inner controller  300  in each radio power source  170   a,    170   b  whereas the average EIRP control of the radio power sources  170   a,    170   b  is collectively and individually controlled by the coordinating controller  200  by providing coordinating control information to the inner controllers  300 . 
     The embodiments disclosed herein in particular relate to mechanisms for average EIRP control of radio power sources  170   a,    170   b.  In order to obtain such mechanisms there is provided a coordinating controller  200 , a method performed by the coordinating controller  200 , a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the coordinating controller  200 , causes the coordinating controller  200  to perform the method. In order to obtain such mechanisms there is further provided an inner controller  300 , a method performed by the inner controller  300 , and a computer program product comprising code, for example in the form of a computer program, that when run on processing circuitry of the inner controller  300 , causes the inner controller  300  to perform the method. 
       FIG. 3  is a block diagram of the control node  200  where feedback control has been enabled by a feedback control loop, in this disclosure denoted a back-off power control loop. In  FIG. 3 ,  P tot     ref  denotes the setpoint for the averaged power (typically slightly less than the computed threshold value for the averaged power), 1/s denotes the actuator dynamics with lower and upper limits inactive,  y (t) denotes the scheduler limitation after lower and upper limitation (inactive in  FIG. 3 ), P max,source  denotes the maximal momentary total power of the power source, w(t) denotes a disturbance representing predicted power errors, 1/(sT+1) represents an autoregressive simplified model of the averaging,  P tot   (s) denotes the averaged total power, e(s) denotes a measurement disturbance, G denotes the antenna gain and EIRP (s) denotes the EIRP. All quantities are in  FIG. 3  expressed in the Laplace transform domain, which is allowed since the feedback control mechanism design is performed with constraints inactive. 
     In some aspects the controller block is given by: 
         u ( s )= CT (1 +T   D   s )(   P   tot     ref   −     P   tot   ( s )). 
     Here, u(s) is the control signal. A controller implementing this controller block is of proportional-derivative (PD) type. C denotes the proportional gain, and T D  the differentiation time. To implement the feedback control mechanism,  P tot     ref ,  P tot   (t) and  P tot   ·   (t) are needed. The first two quantities can be obtained by configuration and averaging of measured spectral density&#39;s by C, while the second quantity needs to be estimated. This can e.g. be achieved by autoregressive filtering of  P tot   (t) with the filter: 
     
       
         
           
             
               
                 
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     where α is a filter parameter. 
     In order to further emphasize the back-off control performance it could be advisable to only allow differential control action that reduces the scheduler threshold γ(t), meaning that only negative contributions from the second term of the feedback mechanism should be allowed. This means that in the time domain, the following restriction to the derivative  P tot   ·   (t) might be applied: 
         u ( t )= CT (   P   tot     ref   −     P   tot   ( t ))−CTT D max (0,   P   tot   ·   ( t )).
 
     It might occur that the feedback control mechanism is not fast enough to prevent a small overshoot of the threshold value. To prevent this from occurring, a hard back-off might be superimposed over the herein disclosed feedback control mechanism. In some aspects this hard back-off operates by setting the scheduler threshold γ(t) to its minimum value γ low  whenever the following holds: 
           P   tot   ( t )&gt;margin·EIRP threshold  
 
     where margin is a value slightly below 1 and where EIRP threshold  is the maximum averaged EIRP threshold determined to meet a regulatory RF EMF exposure requirement. Further aspects of the scheduler threshold γ(t) will be disclosed below. 
     In some aspects there is one control signal u i (s), i=1, . . . , n, for each of then radio power sources and hence the index i can be appended to any relevant quantities, such as  P tot,i     ref ,  P tot,i   (t) and  P tot,i   (t), etc. 
     Reference is now made to  FIG. 4  illustrating a method for EIRP control of at least two radio power sources  170   a,    170   b  as performed by the coordinating controller  200  of a site  140 ,  140   a,    140   b,  the site  140 ,  140   a,    140  comprising the at least two radio power sources  170   a,    170   b  according to an embodiment. 
     The control of the at least two radio power sources  170   a,    170   b  as performed by the coordinating controller  200  is based on information from the at least two radio power sources  170   a,    170   b  as provided by the inner controllers  300 . Hence the coordinating controller  200  is configured to perform step S 102 : 
     S 102 : The coordinating controller  200  obtains, from a respective inner controller  300  of each of the at least two radio power sources  170   a,    170   b,  power control feedback information. 
     Examples of power control feedback information will be disclosed below. 
     The control of the at least two radio power sources  170   a,    170   b  is then determined according to an inner control loop. Particularly, the coordinating controller  200  is configured to perform step S 104 : 
     S 104 : The coordinating controller  200  determines, according to an inner control loop for each of the at least two radio power sources  170   a,    170   b,  coordinating control information from the power control feedback information. 
     Examples of coordinating control information and of how the coordinating control information can be determined will be disclosed below. 
     Individual average power control of each of the at least two radio power sources  170   a ,  170   b  is then performed. Particularly, the coordinating controller  200  is configured to perform step S 106 : 
     S 106 : The coordinating controller  200  performs individual average power control of each of the at least two radio power sources  170   a,    170   b  by providing, to each respective inner controller  300 , the coordinating control information, whereby total average transmission power  P tot,i   (s) of each of the at least two radio power sources  170   a,    170   b  is selectively adjusted based on the inner control loop. 
     Embodiments relating to further details of average EIRP control of at least two radio power sources  170   a,    170   b  as performed by the coordinating controller  200  will now be disclosed. 
     There could be different ways in which the coordinating controller  200  determines the coordinating control information from the power control feedback information. According to an embodiment the coordinating control information is determined using a dynamic input-output relation. In one example the dynamic input-output relation at a given time t is given by: 
     
       
         
           
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     where ƒ and g are vector-valued functions, where a represent a value of the power control feedback information, where b represents a value of the coordinating control information, and where x is an internal state of the coordinating controller  200 . 
     There could be different parameters to which the average EIRP control pertains. In some aspects the inner controller  300  is responsible for setting transmission power for at least one of: a carrier, a node, a cell, a base station, or a RAT. That is, according to an embodiment the individual average power control of each of the at least two radio power sources  170   a,    170   b  pertains to transmission power for an individual carrier, node, cell, base station, or radio access technology of each radio power source  170   a,    170   b.    
     Further aspects of the power control feedback information and the coordinating control information will now be disclosed. 
     According to an embodiment, the coordinating control information specifies a respective reference value for time average transmission power for each of the at least two radio power sources  170   a,    170   b.    
     According to a first example the power control feedback information is given as a value of momentary transmission power P tot,i (s) of each of the at least two radio power sources  170   a,    170   b.    
     According to a second example the power control feedback information is given as a value of the total average transmission power  P tot,i   (s) of each of the at least two radio power sources  170   a,    170   b.    
     According to a third example the power control feedback information is given as a time fraction value, denoted an activity factor, representing how long the inner controller  300  of each of the at least two radio power sources  170   a,    170   b  is active within a given time frame. The activity factor might thus represent the fraction of the time each inner controller  300  is activated. 
     There could be different protocol layers on which the power control feedback information is obtained. There could also be different protocol layers on which the coordinating control information is provided. According to a first embodiment the power control feedback information is obtained at the MAC protocol layer and the coordinating control information is provided at the MAC protocol layer. According to a second embodiment, the power control feedback information is obtained at the physical (PHY) protocol layer and the coordinating control information is provided at the PHY protocol layer. 
     In some aspects the control signals u i (s) are computed by the coordinating controller  200  directly, thereby affecting the dynamic actuator thresholds γ i (s) directly. That is, according to an embodiment, the coordinating control information is given as a direct control signal u i (s) for each of the at least two radio power sources  170   a,    170   b.  The power control feedback information needed by the coordinating controller  200  would be either the momentary powers P tot,i (s) or the corresponding averages  P tot,i   (s), depending on whether the averaging block is located in the coordinating controller  200  or in the respective inner controllers  300 . 
     In some aspects the coordinating controller  200  rather computes time varying reference values to the respective inner controllers  300 , i.e. the signals  P tot,i     ref (s), i=1, . . . , n, are computed by the coordinating controller  200 . That is, according to an embodiment, the coordinating control information is given as a reference value  P tot,i     ref (S) of time-varying transmission power for each of the at least two radio power sources  170   a,    170   b.  The power control feedback information needed by the coordinating controller  200  would still be either the momentary powers P tot,i (s) or the corresponding averages  P tot,i   (s), depending on whether the averaging block is located in the coordinating controller  200  or in the respective inner controllers  300 . Alternatively, the power control feedback information might be the activity factor of each inner controllers  300 , for example measured as the fraction of the time each inner controllers  300  is activated. Still another possibility is to use the amount of momentary or averaged incoming traffic at each site  140 ,  140   a,    140   b.    
     In some aspects certain carriers in one or more of the sites  140 ,  140   a,  moa are dedicated or prioritized, to carry out tasks that are more important than tasks handled by other carriers. Non-limiting examples include, but are not limited to, random access and other key functionalities for enabling a terminal device  160   a,    160   b  to maintain an operational connection to the network. Prioritization might also occur between co-sited sites  140   a ,  140   b  using different RATs. It might for example be the case that it is desired to promote terminal devices using NR over terminal devices using LTE, or vice versa. Hence, according to an embodiment, the power control feedback information obtained from at least one of the inner controllers  300  comprises priority information p(i), and the coordinating control information is determined based on the priority information p(i). 
     In further detail, assume that each radio power source  170   a,    170   b  (defined by a site  140 ,  140   a,    140   b  or a carrier) are given a priority order, defined by the set {p(i)} i=1   n , where p(i) is the priority of radio power source i, for i=1, . . . , n. 
     Each radio power source  170   a,    170   b  is associated with parameters and thresholds like e.g. P max,source,i , P max,regulatory,i ,  P tot,i     ref , δ 1,i , δ 2,i , and margin i , for i=1, . . . , n. These parameters and thresholds are all given initial values, as are all other quantities of the inner control loop. The above notation is as follows: P max,source,i  denotes the maximum power of radio power source i, P max,regulatory,i  denotes that maximum threshold set for radio power source i when defining the exclusion zone,  P tot,i     ref  denotes the reference value of backoff power control loop i. Further, δ 1,i  and δ 2,i  are parameters that define when back off control is turned on/off for radio power source i, and margin i  is the additional fractional margin for radio power source i. 
     According to an embodiment, the priority information p(i) indicates that the radio power source  170   a,    170   b  for which the priority information p(i) is obtained is to have as high part of the total available EIRP as possible. In some aspects, at regular first time instants, it is then checked whether the average power controller is active with a measured average power for a radio power source  170   a,    170   b  that has prioritization level higher than a prioritization threshold, where the check is carried out in priority order. In particular, according to an embodiment the coordinating controller  200  is configured to perform (optional) step S 104   a  as part of S 104 : 
     S 104   a : The coordinating controller  200  checks, at first regular time instances, whether the average power control prevents the radio power source  170   a,    170   b  for which the priority information p(i) is obtained from using as high EIRP budget as possible. 
     In case a checked radio power source  170   a,    170   b  has its prioritization level above the threshold, the EIRP budget of that radio power source  170   a,    170   b  is increased, while the EIRP budget of any radio power sources  170   a,    170   b  with lower priority levels is correspondingly reduced. In case there is no radio power source  170   a,    170   b  with lower priority, or if the EIRP budget cannot be lowered for the lower priority nodes, no action is taken. That is, according to an embodiment the coordinating controller  200  is configured to perform (optional) steps S 104   b,  S 104   c  as part of S 104 : 
     S 104   b : The coordinating controller  200  checks whether the EIRP budget of any of the remaining radio power sources  170   a,    170   b  with lower priority can be reduced. 
     S 104   c : The coordinating controller  200  increases the EIRP budget of the radio power source  170   a,    170   b  for which the priority information p(i) is obtained and correspondingly reducing the EIRP budget of said any of the remaining radio power sources  170   a,    170   b.    
     At specific second time instances, the EIRP budget of each radio power source  170   a ,  170   b  is reduced/increased, toward the initial value setting. That is, according to an embodiment the coordinating controller  200  is configured to perform (optional) steps S 104   d,  S 104   e  as part of S 104 : 
     S 104   d : The coordinating controller  200  checks, at second regular time instances, whether any of the at least two radio power sources  170   a,    170   b  have, according to the coordinating control information, an EIRP budget that is different from a default EIRP budget. 
     S 104   e : The coordinating controller  200  adjusts the EIRP budget of said any of the at least two radio power sources  170   a,    170   b  towards the default EIRP budget. 
     This creates a counterforce that acts to restore the EIRP budget setting to the initial one, in case re-distribution is no longer needed. 
     As disclosed above, in some aspects the control is of proportional-derivative (PD) type. That is, according to an embodiment the inner control loop is of PD type. As also disclosed above, in some aspects the control is of derivative (D) type. That is, according to an embodiment the inner control loop is of D type. Thus, in some aspects only differential control is allowed. 
     In some aspects the average transmission power applied to each site  140 ,  140   a,    140   b  is limited. Particularly, in some aspects the average transmission power applied to each site  140 ,  140   a,    140   b  is limited by the scheduler threshold γ(t). In more detail, in order to get a smooth behavior of the limiting scheduler threshold to limit the average transmission power, it might be rate controlled. That means that the control signal commands adjustments to the limiter, making it increase or decrease, typically in small steps. The dynamics of the actuator mechanism might therefore be determined to be: 
       {dot over (γ)}( t )= u ( t ),
 
     where {dot over (γ)}(t) is the derivative of the scheduler threshold γ(t) and where u(t) is the control signal above expressed in the time domain. The scheduler threshold just expresses a fractional limitation not to use more than a fraction, as given by γ(t), of the total resources. 
     lo In some aspects the scheduler threshold γ(t) is set to its minimum value when the value of average transmission power is larger than a threshold value. In more detail, the maximum value of γ(t) is 1 since it is to express a fraction of the maximum amount of scheduler resources. There might also be a need to limit its lower value in order to avoid that the dynamic feedback control mechanism reduces it to an unphysical value below 0. The following scheduler threshold limitation might therefore be applied: 
       γ low ≤γ( t )≤1.
 
     In some aspects a supervision mechanism is employed for enabling and disabling the proposed controlling of average transmission power of each site  140 ,  140   a,    140   b.  That is, in some aspects performing the individual average power control is selectively enabled and disabled. Further, the scheduler threshold γ(t) might be set to its maximum value when performing the individual average power control is enabled. 
     There could be different ways to determine when to enable and disable the control. In some aspects a comparison to threshold values is made in order to determine when to enable and disable the control. In particular, in some aspects, performing the individual average power control is enabled when the value of the average transmission power is larger than a fractional first threshold value δ 1 , and performing the individual average power control is disabled when the value of the average transmission power is smaller than a second fractional power threshold value δ 2 , where δ 2 ≤δ 1 . In more detail, one scope of the proposed control is to control the averaged transmission power to be below the threshold determined to meet a regulatory requirement. When this is not needed, the proposed control could be disabled, leaving at least one of the sites  140 ,  140   a,    140   b  to operate without any scheduler limitation. Therefore, according to an example: 1) Enable the control when  P tot   (t)&gt;δ 1 P max,source , and set γ(t)=1, and 2) Disable the control when  P tot   (t)&lt;δ 2 P max,source . In some aspects the values fulfil: δ 2 P max,source ≤ P tot     ref ≤δ 1 P max,source , where P max,source  denotes the maximum transmission power per source. 
     The total transmission power of an antenna array can be measured in the radio, just before the antenna. In one example this is achieved by means of by couplers that measure the radio signal amplitude at each signal path to an antenna element. These amplitudes can then be combined into a total transmission power of the radio, with the antenna gain removed. 
     Based on such measurements, the averaged transmission power can be constructed by integration as: 
     
       
         
           
             
               
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     Here P tot (t) is the total measured power in the radio at time t and T is the averaging time specified in the regulation. 
     Another example is to replace the measured transmission power by a predicted transmission power using information available in the scheduler or elsewhere in baseband. Such a quantity could be obtained e.g. by summing up the momentary scheduled transmission power as estimated by the fraction of physical resource blocks (PRBs) used at each time instant, over the time T. 
     Reference is now made to  FIG. 5  illustrating a method for average power control of a radio power source  170   a,    170   b  as performed by the inner controller  300  of the radio power source  170   a,    170   b  according to an embodiment. 
     As disclosed above, the control of the radio power source  170   a,    170   b  as performed by the coordinating controller  200  is based on information from the radio power source  170   a,    170   b  as provided by the inner controllers  300 . Hence the inner controller  300  is configured to perform step S 202 : 
     S 202 : The inner controller  300  provides power control feedback information of the radio power source  170   a,    170   b  to a coordinating controller  200  of a site  140 ,  140   a ,  140   b , the site  140 ,  140   a,    140   b  comprising the radio power source  170   a,    170   b  and at least one further radio power source  170   a,    170   b.    
     As further disclosed above, control of the radio power source  170   a,    170   b  is by the coordinating controller  300  determined according to an inner control loop and coordinating control information thereof is provided to the inner controllers  300 . Hence the inner controller  300  is configured to perform step S 204 : 
     S 204 : The inner controller  300  obtains coordinating control information from a coordinating controller  200 , the coordinating control information being determined according to a respective inner control loop for each of the radio power source  170   a ,  170   b  and the at least one further radio power source  170   a,    170   b  from the power control feedback information. 
     Average power control of the radio power source  170   a,    170   b  is then performed. In particular, the inner controller  300  is configured to perform step S 206 : 
     S 206 : The inner controller  300  performs average power control of the radio power source  170   a,    170   b  according to the coordinating control information whereby total average transmission power  P tot,i   (s) of the radio power source  170   a,    170   b  is selectively adjusted based on the inner control loop. 
     The skilled person would understand how to modify and adapt the embodiments, examples and average power control of a radio power source  170   a,    170   b  as performed by the coordinating controller  200  to apply also for the inner controller  300 . Detailed description thereof is therefore omitted. 
     As disclosed above, there may be different ways to obtain the values of total transmission power P tot (t). 
     In some aspect the values of total transmission power P tot (t) are measured.  FIG. 6  illustrates an architecture of the site  140 ,  140   a,    140   b  where a measured averaged total power feedback from the antenna system of the site  140 ,  140   a,    140   b  is used. According to  FIG. 6 , the site  140 ,  140   a,    140   b  comprises a back-off power controller, a dynamic threshold scheduler actuator, a total average transmission power estimator, radio equipment and an antenna system (such as an AAS), where the radio equipment and the antenna system are separated from the remaining components over an interface, such as the C2 interface or similar. The back-off power controller, the dynamic threshold scheduler actuator, and the total average transmission power estimator are either part of the coordinating controller  200  or of each inner controller  300 . Particularly, in some examples the values of total transmission power are measured at input to the antenna system of the site  140 ,  140   a,    140   b.  In this respect, the total output power of an antenna system, over all antenna elements of the antenna system, can be measured in the radio equipment, just before the antenna elements of the antenna system. In some examples this can be done by couplers that measure the radio signal amplitude at each signal path to an antenna element. These amplitudes can then be combined into a total output power of the radio equipment, with the antenna gain removed. This quantity is denoted P tot (t). 
     In other aspects the values of total transmission power P tot (t) are predicted.  FIG. 7  illustrates an architecture of the site  140 ,  140   a,    140   b  where a predicted averaged total power is used. According to  FIG. 7 , the site  140 ,  140   a,    140   b  comprises a back-off power controller, a dynamic threshold scheduler actuator, a total average transmission power estimator, a total transmission power computer, and radio equipment, where the radio equipment is separated from the remaining components over an interface, such as the C2 interface or similar. The back-off power controller, the dynamic threshold scheduler actuator, the total average transmission power estimator, and the total transmission power computer are either part of the coordinating controller  200  or of each inner controller  300 . For example, the values of total transmission power P tot (t) can be predicted using information available in the scheduler or elsewhere in baseband. Such a quantity could be obtained, e.g. by summing up the momentary scheduled power as estimated by the fraction of resources used at each time instant t, over the time T. 
     Depending on the implementation, different blocks of the control mechanism (as enclosed by the dotted rectangles in  FIGS. 6 and 7 ) of the site  140 ,  140   a,    140   b  may be implemented by the coordinating controller  200  and each inner controller  300 . This could, for example, depend on whether the power control feedback information is given as P tot,i (t), as  P tot,i   (t), or as an activity factor, and whether the coordinating control information is given as u i (t) or as  P tot,i     ref (t). It does not matter whether any of these quantities are given in the Laplace domain or in the time domain. 
     Simulation results of the herein disclosed control of the average power of a radio power source  170   a,    170   b  will now be presented with reference to  FIGS. 8 and 9 . In those figures, the EIRP normalized with the maximum antenna gain, denoted G max , is plotted. In order to illustrate the performance, a reference simulation was performed for the case with an averaging window of 6 minutes using a sampling period of 0.5 seconds. The following typical values were used in the simulations: P max,source =200 W, P max,regulatory =50 W,  P tot     ref =0.215· P   max,site =43 W. 
       FIG. 8  illustrates the uncontrolled momentary power (dotted) and the dynamic threshold (solid). 
       FIG. 9  illustrates the computed average power limit (solid), the reference power for the back-off controller (dashed-dotted), the uncontrolled average power (dotted), and the controlled average power (solid). 
       FIG. 10  is a signalling diagram of a method for average EIRP control of two radio power sources  170   a,    170   b  based on at least some of the herein disclosed embodiments. The method is performed by a coordinating controller  200  of a site  140 ,  140   a,    140   b,  where the site  140 ,  140   a,    140   b  comprises the two radio power sources  170   a,    170   b.  The skilled person would understand how the method could be generalized to more than two radio power sources  170   a,    170   b.    
     S 301   a,  S 301   b : The inner controller  300  of each radio power source  170   a,    170   b  provides power control feedback information of its radio power source  170   a,    170   b  to the coordinating controller  200 . 
     S 302 : The coordinating controller  200  determines, according to an inner control loop for each of the at least two radio power sources  170   a,    170   b,  coordinating control information from the power control feedback information. 
     S 303   a,  S 303   b : The coordinating controller  200  performs individual average power control of each of the radio power sources  170   a,    170   b  by providing, to each respective inner controller  300 , the coordinating control information. 
     S 304   a,  S 304   b : The inner controller  300  of each radio power source  170   a,    170   b  performs average power control of its radio power source  170   a,    170   b  according to the coordinating control information whereby total average transmission power  P tot,i   (s) of the radio power source  170   a,    170   b  is selectively adjusted based on the inner control loop. 
     S 305   a,  S 305   b : The inner controller  300  implements the average power control in the scheduler of its radio power source  170   a,    170   b.    
     When the herein disclosed control is implemented in a computer, discretization can be used e.g. with the Euler approximation or with the so called Tustin approximation. Such discretization techniques are as such well known in the art. 
       FIG. 11  schematically illustrates, in terms of a number of functional units, the components of a coordinating controller  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  1510   a  (as in  FIG. 15 ), 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 coordinating controller  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 coordinating controller  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 coordinating controller  200  may further comprise a communications interface  220  for communications with other entities, functions, nodes, and devices, such as the inner controllers  300 . 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 coordinating controller  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 lo coordinating controller  200  are omitted in order not to obscure the concepts presented herein. 
       FIG. 12  schematically illustrates, in terms of a number of functional modules, the components of a coordinating controller  200  according to an embodiment. The coordinating controller  200  of  FIG. 12  comprises a number of functional modules; an obtain module  210   a  configured to perform step S 102 , a determine module  210   b  configured to perform step S 104 , and a control module  210   h  configured to perform step S 106 . The coordinating controller  200  of  FIG. 12  may further comprise a number of optional functional modules, such as any of a check module  210 C configured to perform step S 104   a,  a check module  210   d  configured to perform step S 104   b,  a increase/reduce module  210   e  configured to perform step S 104   c,  a check module  210   f  configured to perform step S 104   d,  and a adjust module  210   g  configured to perform step S 104   e.    
     In general terms, each functional module  210   a - 210   h  may be implemented in hardware or in software. Preferably, one or more or all functional modules  210   a - 210   h  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 arranged to from the storage medium  230  fetch instructions as provided by a functional module  210   a - 210   h  and to execute these instructions, thereby performing any steps of the coordinating controller  200  as disclosed herein. 
       FIG. 13  schematically illustrates, in terms of a number of functional units, the components of an inner controller  300  according to an embodiment. Processing circuitry  310  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  1510   b  (as in  FIG. 15 ), e.g. in the form of a storage medium  330 . The processing circuitry  310  may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA). 
     Particularly, the processing circuitry  310  is configured to cause the inner controller  300  to perform a set of operations, or steps, as disclosed above. For example, the storage medium  330  may store the set of operations, and the processing circuitry  310  may be configured to retrieve the set of operations from the storage medium  330  to cause the inner controller  300  to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus the processing circuitry  310  is thereby arranged to execute methods as herein disclosed. 
     The storage medium  330  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 inner controller  300  may further comprise a communications interface  320  for communications with other entities, functions, nodes, and devices, such as the coordinating controller  200 . As such the communications interface  320  may comprise one or more transmitters and receivers, comprising analogue and digital components. 
     The processing circuitry  310  controls the general operation of the inner controller  300  e.g. by sending data and control signals to the communications interface  320  and the storage medium  330 , by receiving data and reports from the communications interface  320 , and by retrieving data and instructions from the storage medium  330 . 
     Other components, as well as the related functionality, of the inner controller  300  are omitted in order not to obscure the concepts presented herein. 
       FIG. 14  schematically illustrates, in terms of a number of functional modules, the components of an inner controller  300  according to an embodiment. The inner controller  300  of  FIG. 14  comprises a number of functional modules; a provide module  310   a  configured to perform step S 202 , an obtain module  310   b  configured to perform step S 204 , and a control module  310   c  configured to perform step S 206 . The inner controller  300  of  FIG. 14  may further comprise a number of optional functional modules, such symbolized by module  310   d.  In general terms, each functional module  310   a - 310   d  may be implemented in hardware or in software. Preferably, one or more or all functional modules  310   a - 310   d  may be implemented by the processing circuitry  310 , possibly in cooperation with the communications interface  320  and/or the storage medium  330 . The processing circuitry  310  may thus be arranged to from the storage medium  330  fetch instructions as provided by a functional module  310   a - 310   d  and to execute these instructions, thereby performing any steps of the inner controller  300  as disclosed herein. 
     Each of the coordinating controller  200  and inner controller  300  may be provided as a standalone device or as a part of a respective at least one further device. For example, the coordinating controller  200  and the inner controller  300  may be provided in a node of the radio access network or in a node of the core network. Alternatively, functionality of the coordinating controller  200  and the inner controller  300  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 radio access network or the core network) or may be spread between at least two such network parts. In general terms, the functionality of the coordinating controller  200  may be implemented in one of the sites  140 ,  140   a,    104   b  or even in the core network whereas the functionality of the inner controller  300  may be implemented in each of the sites  140 ,  10   a,    10   b.    
     Thus, a first portion of the instructions performed by the coordinating controller  200  and the inner controller  300  may be executed in a respective first device, and a second portion of the instructions performed by the coordinating controller  200  and the inner controller  300  may be executed in a respective second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the coordinating controller  200  and the inner controller  300  may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a coordinating controller  200  and/or inner controller  300  residing in a cloud computational environment. Therefore, although a single processing circuitry  210 ,  310  is illustrated in  FIGS. 11 and 13  the processing circuitry  210 ,  310  may be distributed among a plurality of devices, or nodes. The same applies to the functional modules  210   a - 210   h,    310   a - 310   d  of  FIGS. 12 and 14  and the computer programs  1520   a,    1520   b  of  FIG. 15 . 
       FIG. 15  shows one example of a computer program product  1510   a,    1510   b  comprising computer readable means  1530 . On this computer readable means  1530 , a computer program  1520   a  can be stored, which computer program  1520   a  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  1520   a  and/or computer program product  1510   a  may thus provide means for performing any steps of the coordinating controller  200  as herein disclosed. On this computer readable means  1530 , a computer program  1520   b  can be stored, which computer program  1520   b  can cause the processing circuitry  310  and thereto operatively coupled entities and devices, such as the communications interface  320  and the storage medium  330 , to execute methods according to embodiments described herein. The computer program  1520   b  and/or computer program product  1510   b  may thus provide means for performing any steps of the inner controller  300  as herein disclosed. 
     In the example of  FIG. 15 , the computer program product  1510   a,    1510   b  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  1510   a,    1510   b  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  1520   a,    1520   b  is here schematically shown as a track on the depicted optical disk, the computer program  1520   a,    1520   b  can be stored in any way which is suitable for the computer program product  1510   a,    1510   b.    
     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.