Patent Description:
When any radio equipment is to be deployed, regulatory radio frequency (RF) exposure regulations should be accounted for. These exposure limitations are typically based on the guidelines from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) but may take different forms in some countries and regions. One aim of the RF exposure regulations is to secure that the human exposure to RF energy is kept within safe limits, which 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 transmitters in order to achieve a high directivity, when emissions are correlated between the transmitters then there could be a large "antenna gain" for the emissions. Therefore, in order to meet RF exposure limits, the power of the transmitters would need to be significantly reduced to compensate for the beamforming, or antenna gain, if the RF emissions are defined as Equivalent Isotropic Radiated Power (EIRP), i.e. the power radiated from an antenna with unity antenna gain in all directions. A consequence of increasing beamforming gain is that the radiated energy is concentrated in directional beams, in which the effective radiated power is increased as compared to the situation without AAS systems.

The RF exposure limits are typically expressed in terms of power density (in units of W/m<NUM>) 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. This implies that at a given distance from the antenna, and in the far field, the experienced EIRP and power density will be a factor of G higher in a beam generated by an AAS system with beam forming gain G than without such an AAS system.

The ICNIRP and other RF exposure limitations are commonly expressed as an average power density over a specified time interval T. This means that the momentary power can be significantly higher during shorter times than the value of T. However, the average power density must be below the specified limit. To maintain a certain RF exposure compliance distance, that is shorter than what is obtained using the maximum EIRP of the AAS, the time-averaged power needs to be reduced by a factor that can be easily determined. However, this is presently not the case. <CIT> discloses a method and apparatus for controlling EIRP, emitted from an array of antenna elements at an access point of a wireless communication network, the access point being configured to form one or more beams by applying a weight set for a beamforming weights matrix to one or more signal streams in a first mode of operation.

Hence, there is a need for efficient control of the average transmitted power for base stations and other radio equipment.

An object of embodiments herein is to provide efficient determination of power for base stations and other radio equipment.

This objective is generally solved by mechanisms performed by a control device for determining average total transmission power for an antenna array configured for beamformed transmission within an angular coverage region.

The proposed technology is set out in the appended set of claims.

Advantageously this method, these control devices, this computer program and this computer program product enable reduced processing and signalling for efficient determination of the average total transmission power applied to the antenna array.

<FIG> is a schematic diagram illustrating a communications network <NUM> where embodiments presented herein can be applied. The communications network <NUM> could be a third generation (<NUM>) telecommunications network, a fourth generation (<NUM>) telecommunications network, or a fifth (<NUM>) telecommunications network and support any 3GPP telecommunications standard, where applicable.

The communications network <NUM> comprises a control node <NUM> configured to control an antenna array <NUM> of a network node that provides network access to at least one terminal device <NUM> in a radio access network <NUM>, thus enabling the terminal device <NUM> to communicate over a wireless link <NUM>. The radio access network <NUM> is operatively connected to a core network <NUM>. The core network <NUM> is in turn operatively connected to a service network <NUM>, such as the Internet. The terminal device <NUM> is thereby enabled to, via the network node, access services of, and exchange data with, the service network <NUM>.

Examples of network nodes are radio access network nodes, radio base stations, base transceiver stations, Node Bs, evolved Node Bs, g Node Bs, access points, and access nodes, and backhaul nodes. Examples of terminal devices <NUM> 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.

The control node <NUM> might comprise, be collocated with, integrated with, or be in operational communications with, the antenna array <NUM> of the network node.

<FIG> schematically illustrates an idealized one-dimensional beamforming case. In case it is assumed that the terminal device <NUM> is located far away from the antenna array <NUM>, i.e. in the far-field, it follows that the difference in travel distance of radio waves from the antenna array <NUM> to the terminal device <NUM>, between adjacent antenna elements of the antenna array <NUM>, is: <MAT> where kλ is the antenna element separation. Here λ is the carrier wavelength, k is the separation factor which may be <NUM>-<NUM> in a typical correlated antenna element arrangement. This means that if a reference signal SBS is transmitted from the base station, it will be received at the terminal device <NUM> as the signal: <MAT>.

Here ω is the angular carrier frequency, hi is the complex channel from the i:th antenna element, t is the time index, and fc is the carrier frequency. In the above equation θ and hi are unknown. In case of a feedback solution, the UE therefore needs to search for all complex channel coefficients hi and the unknown angle θ. For this reason, the standard defines a codebook of beams in different directions given by steering vector coefficients like <MAT> where m indicates a directional codebook entry. The terminal device <NUM> then tests each codebook and estimates the channel coefficients. The information rate achieved for each codebook entry m is computed and the best one defines the direction and channel coefficients. This is possible since the pilot signal transmitted from the network node of the antenna array <NUM> is a known signal at the receiver. The result is encoded and reported back to the network node. This provides the base station with a best direction (codebook entry) and information that allows it to build up a channel matrix H. This matrix represents the channel from each of the transmit antenna elements to each of the receive antenna elements. Typically, each element of H is represented by a complex number.

The fed back information is denoted CSI, for Channel State Information, and consists of CQI (Channel Quality Indication), a quantity directly related to the received signal to noise ratio, the PMI (Pre-code Matrix Index) which is the codebook entry, and the RI (Rank Indication) which expresses the richness of the channel which essentially tells how many parallel MIMO channels that can be sustained between the transmitter and receiver at the specific frequency.

The channel matrix H can then be used for beamforming computations, or the direction represented by the reported codebook entry can be used directly.

To exploit reciprocity, the channel coefficients can be directly estimated by the network node from uplink transmission of known pilot signals (for example so called sounding reference signals, SRSs) from the terminal device <NUM>. These signals are available in both the <NUM> and <NUM> standards. The estimated channel can then be used to compute the combining weight matrix with a selected principle, and then used for downlink transmission. This works since the uplink and downlink channels are the same (to within a transpose) when reciprocity is valid.

As mentioned above there is a need for efficient determination of power for base stations and other radio equipment.

One drawback of current mechanisms for limiting the AAS time-averaged radiated power for RF EMF exposure regulation compliance is the current lack of a dynamic and at the same time smooth limitation of scheduled resources in the scheduler, where the limitation is dependent on multiple averaged output power measurements.

Another drawback of current mechanisms for limiting the AAS time-averaged radiated power for RF EMF exposure regulation compliance is the current lack of a feedback control mechanism that controls the actuator mechanism with a control signal computed from the multiple averaged powers and a reference value, where the multiple averaged power is dependent on beamforming gains computed from either precoder matrix indices of so-called codebook based beamforming, where the beamforming gains is precomputed and stored, or where the averaged power is dependent on beamforming gains computed from beamforming weights generated by the solutions to a reciprocity based optimization problem.

The embodiments disclosed herein therefore relate to mechanisms for determining average total transmission power for an antenna array <NUM> configured for beamformed transmission within an angular coverage region. In order to obtain such mechanisms there is provided a control device <NUM>, a method performed by the control device <NUM>, a computer program product comprising code, for example in the form of a computer program, that when run on a control device <NUM>, causes the control device <NUM> to perform the method.

<FIG> is a flowchart illustrating embodiments of methods for determining average total transmission power for an antenna array <NUM> configured for beamformed transmission within an angular coverage region. The methods are performed by the control device <NUM>. The methods are advantageously provided as computer programs <NUM>.

S102: The control node <NUM> determines bin-wise values of beamforming gain for a set of non-overlapping bins collectively covering the angular coverage region of the antenna array <NUM>.

In this respect, each bin might thus correspond to a angle interval, where each bin is (approximately) defined by the following selection of ranges in azimuth angle (θ) and elevation angle (φ): Ωi,j = [θi, θi+<NUM>] × [φj, φj+<NUM>], i = <NUM>,. , N - <NUM>, and j = <NUM>,. , M - <NUM>, where N represents the number of bins in azimuth direction and M represents the number of bins in elevation direction.

S104: The control node <NUM> obtains values of total transmission power of the beamformed transmission. The values are obtained over time such that one value is obtained at time index t.

S106: The control node <NUM> determines bin-wise values of average transmission power from the bin-wise values of beamforming gain and the values of total transmission power.

S108: The control node <NUM> combines the bin-wise values of average transmission power into one value of average total transmission power for the antenna array <NUM>.

This yields an efficient way to assess the time-averaged radiated power in a certain direction, valid for codebook based beamforming as well as for reciprocity assisted transmission. Below it will be disclosed how this can be integrated into a feedback control system, that is designed to control the RF emissions.

Embodiments relating to further details of determining average total transmission power for an antenna array <NUM> configured for beamformed transmission within an angular coverage region as performed by the control device <NUM> will now be disclosed.

In the following the following notation and definitions will be helpful. The steering vector with index i,j is denoted αi,j and is representative of the direction in azimuth and elevation for the bin with index i,j. The beamforming weights multi-user group ng are denoted w<NUM>,ng, w<NUM>,ng,. , wnw,ng, ,. , wNw-<NUM>,ng, where the number of beamforming weights for multi-user group ng is denoted Nw,ng. These beamforming weights can be generated in any way, e.g. by codebook based beamforming or by the solution of a reciprocity assisted transmission optimization problem. The number of multi-user groups is denoted Ng. These quantities are valid for a certain point in time, e.g. a transmission time index (TTI).

There may be different ways to obtain the values of total transmission power Ptot(t).

In some aspect the values of total transmission power Ptot(t) are measured. Particularly, according to an embodiment the values of total transmission power are measured at input to the antenna array <NUM>. In this respect, the total output power of an antenna array <NUM>, over all antenna elements of the antenna array <NUM>, can be measured in the radio equipment, just before the antenna elements. 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 Ptot(t).

In other aspects the values of total transmission power Ptot(t) are predicted. For example, the values of total transmission power Ptot(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.

There may be different ways to obtain the bin-wise values of beamforming gain.

In some aspects the bin-wise values of beamforming gain are based on the steering vectors and the beamforming weights. Particularly, according to an embodiment each of the bins is associated with a respective bin-wise steering vector representing a direction of the beamformed transmission and a respective bin-wise beamforming weight of its steering vector. The bin-wise values of beamforming gain are then proportional the squared norm of the bin-wise steering vector and the bin-wise beamforming weight. In some examples the bin-wise values of beamforming gain are then proportional to the squared norm of the bin-wise steering vector and the bin-wise beamforming weight.

In some aspects the bin-wise values of beamforming gain are based on the fraction <MAT> of transmission resources η used by multi-user group ng. In some examples each transmission resource is defined by a physical resource block (PRB).

According to an embodiment a respective fraction of transmission resources is transmitted per time unit during the beamformed transmission. All fractions of transmission resources collectively form a total amount of resources, and the bin-wise values of beamforming gain are proportional to the fraction of transmitted transmission resources.

Let Gaini,j(t) denote the bin-wise value of the beamforming gain for the bin with indices i,j at time index t and let Ptot(t) denote the value of total transmission power at time index t.

Then, according to an embodiment, when the beamformed transmission is to Ng multi-user groups ng, the bin-wise value of the beamforming gain Gaini,j(t) for the bin with indices i,j is determined as: <MAT> where vi,j,nw,ng(t) represents a combination of steering vector αi,j(t) and beamforming weight wnw,ng(t) for beam nw of multi-user group ng at time index t, and where <MAT> is the fraction of transmission resources used by multi-user group ng at time index t.

In some aspects the beamforming gains, as denoted G<NUM>,ng, G<NUM>,ng,. , Gnw,ng, ,. , GNw-<NUM>ng, are available. In other words, there are Nw,ng possible beamforming gains available. This is a typical situation when codebook based beamforming is used, e.g., to operate a grid of beams beamforming at the antenna array <NUM>. However, it may be applied for reciprocity assisted transmission beamforming as well. In such cases, vi,j,nw,ng(t) can be determined according to: <MAT> where Gnw,ng(t) represents a power ratio between a user beam and a common beam used during the beamformed transmission. That is, <MAT> is expressing the power ratio between a user beam and the common (control channel) beam. Both codebook based beamformed transmission and reciprocity assisted transmission based beamformed transmission can have the power ratio calculated, but it is mostly used for codebook based beamformed transmission.

In some aspects the beamforming gains are not available. This is a typical situation when reciprocity assisted transmission is applied, however it may be applied for codebook-based beamforming as well. In such cases, vi,j,nw,ng(t) can be determined according to: <MAT>.

It is evident that an estimate of the total average power in direction i,j is composed of the main lobe transmission to users in direction i,j, and the sidelobe transmissions for users in all other directions. Fortunately, all these effects are captured by the summation employed to compute Gaini,j,casex(t), where x ∈ {<NUM>, <NUM>}. This means that the equivalent radio power contributing in direction i,j becomes: <MAT>.

In this equation 〈Ptot〉i,j(t) is the average power quantity for direction i,j, and Ptot(t) is obtained as disclosed above. This means that all quantities are transformed back to relate to the maximum radiated power in one single direction. When a single user exploits all resources and applies the maximum gain of the antenna array, the above equation collapses to the average of Ptot(t), as desired. It is here noted that the above expression can be discretized and hence that the integral in the above equation can be substituted by a summation. When implemented with computer control, discretization can be done e.g. with the Euler approximation or with the so called Tustin approximation. These techniques are as such well known in the art.

When only one total average power is to be controlled, the directional average powers 〈Ptot〉i,j(t) needs to be combined. One way to achieve this is to take: <MAT>.

Hence, according to an embodiment the control node <NUM> is configured to perform (optional) step S108a as part of step S108:
S108a: The control node <NUM> determines the maximum value of all the bin-wise values of average transmission power when combining the bin-wise values of average transmission power into one value of average total transmission power for the antenna array <NUM>.

Since the estimates of the directional angular powers are all likely to be lower than an averaged power valid for the whole cell, it is likely that also the combined total power will be less than an averaged power directly averaged over the whole cell. A gain can therefore be expected to that case. A less conservative, but also less stringent combination would be to use.

Another way to achieve this is to take: <MAT>.

Hence, according to an embodiment the control node <NUM> is configured to perform (optional) step S108b as part of step S108:
S108b: The control node <NUM> determines an average value of all the bin-wise values of average transmission power when combining the bin-wise values of average transmission power into one value of average total transmission power for the antenna array <NUM>.

Yet another way to achieve this is to take: <MAT>.

Hence, according to an embodiment the control node <NUM> is configured to perform (optional) step S108c as part of step S108:
S108c: The control node <NUM> determines a median value of all the bin-wise values of average transmission power when combining the bin-wise values of average transmission power into one value of average total transmission power for the antenna array <NUM>.

Still further combinations are possible.

In some aspects the average output power applied to the antenna array <NUM> is limited. Particularly, according to an embodiment the average output power applied to the antenna array <NUM> is limited by a resource factor value γ(t). In more detail, in order to get a smooth behavior of the limiting resource threshold applied in the scheduler to limit the averaged output 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: <MAT> where γ(t) is the resource threshold and where u(t) is the control signal further discussed below. The resource threshold is decoupled from the scheduler algorithms themselves, and just expresses a fractional limitation of the scheduler not to use more than a fraction γ(t) of its total resources. The scheduler may then limit the number of transmission resources it uses, or limit any other quantity that correlates well with the momentary output power.

In some aspects the resource factor value γ(t) is set to its minimum value when the value of average total transmission power is larger than a power threshold value. In more detail, the maximum value of γ(t) is <NUM> 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 <NUM>. The following scheduler threshold limitation might therefore be applied: <MAT>.

In the claimed invention cell-wide control of average output power of the antenna array <NUM> is performed based on the average total transmission power. Hence, according to an embodiment the control node <NUM> is configured to perform step S110:
S110: The control node <NUM> performs cell-wide control of average output power of the antenna array <NUM> based on the above determined one value of the average total transmission power.

In some aspects only one feedback control loop is used for this control, which reduces the complexity of the solution in the scheduler, at the same time as gains as compared to a cell-wide assessment of the averaged power are obtained. Hence, according to a non-claimed embodiment the control node <NUM> is configured to perform (optional) step S112:
S112: The control node <NUM> performs cell-wide back-off power feedback control based on the bin-wise values of average transmission power.

In some aspects a setpoint is used for the averaged power. Particularly, according to an embodiment, performing the control in step S110 comprises to compare the value of average total transmission power to a setpoint value 〈Ptot〉ref of the average total transmission power.

There could be different types of controllers used in step S110.

In some aspects the controller is of proportional-derivative (PD) type. That is, according to an embodiment the control in step S110 (and S112) is of PD type.

In some aspects the controller is of derivative (D) type. That is, according to an embodiment the control in step S110 (and S112) is of D type. Thus, in some aspects only differential control is allowed.

In some aspects a supervision mechanism is employed for enabling and disabling the proposed actuator and feedback control mechanisms. That is, according to an embodiment the control in step S110 (and S112) is selectively enabled and disabled. Further, the resource factor value γ(t) might be set to its maximum value when performing the 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, according to an embodiment, performing the control (as in step S110) is enabled when the determined one value of the average total transmission power is larger than a fractional first power threshold value δ<NUM>, and performing the control is disabled when the determined one value of the average total transmission power is smaller than a second fractional power threshold value δ<NUM>, where δ<NUM> ≤ δ<NUM>. In more detail, one scope of the thus proposed actuator and feedback control mechanisms is to control the averaged output power, to be below the regulatory requirement. When this is not needed, these mechanisms could be disabled, leaving the radio equipment to operate with out any scheduler limitation. Therefore, according to an example: <NUM>) Enable the actuator and feedback control mechanisms when 〈Ptot〉(t) > δ<NUM>Pmax,site , and set γ(t) = <NUM>, and <NUM>) Disable the actuator and feedback control mechanisms when 〈Ptot〉(t) < δ<NUM>Pmax,site. In some aspects the values fulfil: δ<NUM>Pmax,site ≤ 〈Ptot〉ref ≤ δ<NUM>Pmax,site, where Pmax,site denotes the maximum transmission power of the site comprising the site.

<FIG> is a block diagram of the control node <NUM> where feedback control has been enabled by the supervision mechanism. In <FIG>, 〈Ptot〉ref denotes the setpoint for the averaged power (typically slightly less than the threshold value), <NUM>/s denotes the actuator dynamics with lower and upper limits inactive, γ(t) denotes the scheduler limitation after lower and upper limitation (inactive in <FIG>), Pmax,site denotes the maximal total power of the antenna array <NUM>, w(s) denotes a disturbance representing predicted power errors, <NUM>/(sT + <NUM>) represents an autoregressive simplified model of the averaging, 〈Ptot〉(s) denotes the averaged total power, G denotes the antenna gain and EIRP(s) denotes the EIRP. All quantities are in <FIG> 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: <MAT>.

A control node <NUM> implementing this controller block is of PD type. C denotes the proportional gain, and TD the differentiation time. The poles of the closed loop system of <FIG> are given by the following second order equation: <MAT>.

These poles govern the closed loop dynamics of the feedback control mechanism, the actuator mechanism, and the averaged power. In order to determine the proportional gain and the differentiation time, a closed loop polynomial with desired poles in -α<NUM> and -α<NUM> is specified as: <MAT>.

An identification of coefficients and solution of the resulting system of equations reveal that the proportional gain and differentiation time shall be selected as: <MAT> and: <MAT>.

One reason for this choice is that a system with two negative real poles can be expected to be well damped, which is a result of a significant differentiation action. This might be advantageous when differentiation action is needed for fast back-off close to the determined threshold.

To implement the feedback control mechanism, 〈Ptot〉ref, 〈Ptot〉(t) and <MAT> are needed. The first two quantities can be obtained as described above, while the second quantity might be estimated. This can e.g. be achieved by autoregressive filtering of 〈Ptot〉(t) with the filter given by: <MAT>.

In order to further emphasize the back-off control performance only negative differential control action might be allowed. This could reduce 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 <MAT> is applied: <MAT>.

Sometimes it may happen that the feedback control mechanism is not fast enough to prevent a small overshoot of the determined power threshold. To prevent that from happening a hard back-off is superimposed over the disclosed feedback control mechanism. This hard back-off operates by setting the scheduler threshold to its minimum value γlow whenever: <MAT> where margin is a value slightly below <NUM> and where Pmax is the determined maximum average power threshold.

As stated above, an advantage with the present invention is that it is able to operate both with predicted and measured average power signals. This is illustrated with <FIG> and <FIG>. <FIG> is a block diagram of an architecture of the control node <NUM> where measured averaged total power feedback from the AAS system of the radio is used. <FIG> is a block diagram of an architecture of the control node <NUM> where predicted averaged total power is used.

In <FIG> and <FIG> some functional blocks are indexed with indices i,j, each indicating one of azimuth or elevation of the direction in question. As can be seen, there is in <FIG> and <FIG> an averaging block (as in <FIG>) where an additional quantity, denoted Ki,j, represents the reduction of the average power as compared to the case when a cell wide average power measurement is made. Thus the value of Ki,j is nonnegative and typically less than <NUM>. The per beam direction average powers 〈Ptot〉i,j(s), are then combined , e.g. by taking the maximum value over all indices i,j. In <FIG> the momentary measured power in the radio is the input to the average per beam direction power block. <FIG> illustrates an alterative where a predicted power in base band provides the input.

The remaining parts of <FIG> and <FIG> are common. When activated, the resulting average total average power 〈Ptot〉(s) is sent to the controller block, where in one example PD control is applied to the control error formed by 〈Ptot〉(s) and the reference value 〈Ptot〉(s)ref, thereby generating the control signal u(s). The control signal affects the dynamic threshold in the scheduler, represented by the integration <NUM>/s. To secure that the relative dynamic threshold stays between γlow and <NUM>, the limiting block transforms γ(t) to the final relative dynamic threshold γ(t). The scheduler then performs data traffic scheduling, accounting for γ(t), thereby producing the data transmission which closes the loop.

In <FIG> and <FIG> there is a block denoted on-off logic. The on-off logic is configured to make sure that the control loop is disabled when not needed and enabled when needed. In one example this is implemented using two relative thresholds, δ<NUM> and δ<NUM>, that <NUM>) enables the actuator and feedback control mechanisms when 〈Ptot〉(t) > δ<NUM>Pmax,site , and sets γ(t) = <NUM>, and <NUM>) disables the actuator and feedback control mechanisms when 〈Ptot〉(t) < δ<NUM>Pmax,site. In some aspects the values fulfil: δ<NUM>Pmax,site ≤ 〈Ptot〉ref ≤ δ<NUM>Pmax,site, where Pmax,site denotes the maximum transmission power of the site.

<FIG> schematically illustrates, in terms of a number of functional units, the components of a control device <NUM> according to an embodiment. Processing circuitry <NUM> 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 <NUM> (as in <FIG>), e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

Particularly, the processing circuitry <NUM> is configured to cause the control device <NUM> to perform a set of operations, or steps, as disclosed above. For example, the storage medium <NUM> may store the set of operations, and the processing circuitry <NUM> may be configured to retrieve the set of operations from the storage medium <NUM> to cause the control device <NUM> to perform the set of operations.

Thus the processing circuitry <NUM> is thereby arranged to execute methods as herein disclosed. The control device <NUM> may further comprise a communications interface <NUM> at least configured for communications with other entities, nodes, functions, and devices. As such the communications interface <NUM> may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry <NUM> controls the general operation of the control device <NUM> e.g. by sending data and control signals to the communications interface <NUM> and the storage medium <NUM>, by receiving data and reports from the communications interface <NUM>, and by retrieving data and instructions from the storage medium <NUM>. Other components, as well as the related functionality, of the control device <NUM> are omitted in order not to obscure the concepts presented herein.

<FIG> schematically illustrates, in terms of a number of functional modules, the components of a control device <NUM> according to an embodiment. The control device <NUM> of <FIG> comprises a number of functional modules; a determine module 210a configured to perform step S102, an obtain module 210b configured to perform step S104, a determine module 210c configured to perform step S106, and a combine module 210d configured to perform step S108. The control device <NUM> of <FIG> may further comprise a number of optional functional modules, such as any of a determine module 210e configured to perform step S108a, a determine module 210f configured to perform step S108b, a determine module <NUM> configured to perform step S108c, a control module <NUM> configured to perform step S110, and a control module 210i configured to perform step S112.

In general terms, each functional module 210a-210i 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 <NUM> which when run on the processing circuitry makes the control device <NUM> perform the corresponding steps mentioned above in conjunction with <FIG>. 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-210i may be implemented by the processing circuitry <NUM>, possibly in cooperation with the communications interface <NUM> and/or the storage medium <NUM>. The processing circuitry <NUM> may thus be configured to from the storage medium <NUM> fetch instructions as provided by a functional module 210a-210i and to execute these instructions, thereby performing any steps as disclosed herein.

The control device <NUM> may be provided as a standalone device or as a part of at least one further device. For example, the control device <NUM> may be provided in a node of the radio access network or in a node of the core network. Alternatively, functionality of the control device <NUM> 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, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. In this respect, at least part of the control device <NUM> may reside in the radio access network, such as in the radio access network node, for cases when embodiments as disclosed herein are performed in real time.

Thus, a first portion of the instructions performed by the control device <NUM> may be executed in a first device, and a second portion of the of the instructions performed by the control device <NUM> 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 control device <NUM> may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a control device <NUM> residing in a cloud computational environment. Therefore, although a single processing circuitry <NUM> is illustrated in <FIG> the processing circuitry <NUM> may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 210a-210i of <FIG> and the computer program <NUM> of <FIG> (see below).

Claim 1:
A method for determining average total transmission power for an antenna array (<NUM>) configured for beamformed transmission within an angular coverage region, the method being performed by a control device (<NUM>), the method comprising:
determining (S102) bin-wise values of beamforming gain for a set of non-overlapping bins collectively covering the angular coverage region of the antenna array (<NUM>), wherein each bin-wise value corresponds to an angle interval;
obtaining (S104) values of total transmission power of the beamformed transmission;
determining (S106) bin-wise values of average transmission power over a time period T, by multiplication of the bin-wise values of beamforming gain and the values of total transmission power, divided by a maximum beamforming gain;
combining (S108) the bin-wise values of average transmission power into one value of average total transmission power for the antenna array (<NUM>), and
performing (S110) cell-wide control of average output power of the antenna array (<NUM>) based on said one value of the average total transmission power.