TECHNICAL FIELD

[001] Disclosed are embodiments related to methods and control systems for controlling drone base stations.

BACKGROUND

[002] There is a growing interest to evolve aerial communication for wireless networks.

One approach is to use drones to carry base stations. This approach enables a base station to be physically moved to serve users.

[003] The market for drone base stations is at an early stage. The major vendors for telecommunications are not pushing a portfolio related to drone base stations at this moment but some operators may use propriety solutions. However, in the long run, several aspects related to drone base stations will be standardized.

[004] 3GPP technologies (e.g., 5G and its successors) open opportunities to advance aerial communication including drone base stations.

[005] Today there is research ongoing where solutions are proposed for controlling drone base stations from the perspective of delivering services to users and ensuring

communication with users with high performance.

[006] Exemplary ways of controlling drone base stations are disclosed in European

Patent Publication No. 2938117A1. In this publication, the main idea is to adjust the position of a drone base station (DBS) with respect to its initial location to optimize radio link quality. The adjustment is based on radio link conditions between a user equipment (UE) and the DBS, and between the UE and the backhaul node serving the DBS.

SUMMARY

[007] This EP publication does not disclose, however, any concept of coverage areas or zones where the DBS should be configured to operate and serve UEs. The solution provided in the publication may lead to a situation where multiple DBSs are located close to each other due to lack of designated zones. This will not ensure good overall network performance. For example, even though certain UEs may be served optimally, overall performance of all UEs in the network may not be secured.

[008] Thus if drone base stations are configured to operate only based on optimizing performance of wireless networks in areas that need performance boost, the result could be sub- optimizations on total wireless network level where the drone base stations can end up in concentrations in certain places and are not able to cope with coverage holes in other areas outside the proximity of the drone base stations.

[009] It can also lead to that operators will have lack of control over the drone base stations. Accordingly, better control of the movements of drone base stations is needed to secure good overall wireless performance of the network.

[0010] According to the embodiments of this disclosure, a method for improving the overall network performance is provided. The method controls the movement of a drone base station to enable its operation in allowed operational areas. In the allowed operational areas, the drone base station (DBS) serves one or more UEs. The DBS may move only within the allowed operational areas.

[0011] The DBS may be configured to operate in a particular operational area by receiving information (e.g., a pre-defined area identifier, geographical coordinates, or an operational validity period) directly or indirectly from a network node (e.g., a fixed base station, a network node in a backhaul, or a core network). The network node may determine the particular operational area for the DBS based on one or more criteria. Examples of such criteria are traffic load situation in one or more areas, radio conditions of UE(s) with respect to a base station (BS) and/or the DBS, timing related information (e.g., round trip time between UE(s) and the BS and/or the DBS), or location of the UEs.

[0012] The method allows limited dynamicity in the movement of the DBS inside and along a set of operational areas. To support the operations of DBSs and base stations, in the method, the DBS’s communication and wireless network capabilities may be considered to optimize both drone operations and wireless performance of the DBS. The method may include determining wireless performance and supporting decisions for DBS flight paths into different operational areas. [0013] The method allows that operators can better control overall performance of the wireless network. The method also allows a possibility to combine both proximity of drone base station operations but a dynamicity in movement of the drone base stations.

[0014] Accordingly, in one aspect there is a method for controlling a set of drone base stations (DBSs) including a first DBS and a second DBS. In one embodiment, the method includes assigning a first set of operational areas to the first DBS. The first set of operational areas includes a first operational area and a second operational area. The method also includes determining whether a network condition within a particular operational area satisfies a criteria. The method further includes as a result of determining that the network condition within the particular operational area satisfies the criteria, selecting a DBS from a subset of DBSs, wherein each DBS included in the subset of DBSs is assigned a set of operational areas that includes the particular operational area. The method further includes based on a rule associated with the selected DBS, determining whether the rule permits the selected DBS to begin serving the particular operational area. The method further includes as a result of determining that the rule permits the selected DBS to begin serving the particular operational area, configuring the selected DBS to begin serving the particular operational area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0016] FIG. 1 illustrates a system according to some embodiments.

[0017] FIG. 2 illustrates exemplary operational areas of a DBS.

[0018] FIG. 3 is a flow chart illustrating a process according to some embodiments.

[0019] FIGS. 4A and 4B illustrate exemplary arrangements of sub-areas according to some embodiments.

[0020] FIG. 5 is a flow chart illustrating a process according to some embodiments.

[0021] FIG. 6 is a flow chart illustrating a process according to some embodiments.

[0022] FIG. 7 is a flow chart illustrating a process according to some embodiments.

[0023] FIG. 8 is a flow chart illustrating a process according to some embodiments. [0024] FIG. 9 is a block diagram illustrating an apparatus according to some embodiments.

DETAILED DESCRIPTION

[0025] In an aerial communication system according to some embodiments of this disclosure, stationary base stations may interact with drone base stations. The stationary base stations may be responsible for basic coverage of operational areas. The introduction of the drone base stations can complement the existing stationary base stations with an opportunity to handle variations in load and secure performance.

[0026] Beam optimizations may be performed for the beams that operate within the operational areas.

[0027] The term“base station” (BS) used in this disclosure refers to a stationary BS whose geographical location does not change over time. The BS may also be called as stationary, fixed, or immovable BS. Unless stated otherwise, the BS mentioned in this disclosure refers to stationary BS. The BS may be any type of a network node which communicates over an air interface with a UE and/or with another network node.

[0028] The term“drone base station” (DBS) used in this disclosure refers to a BS whose geographical location may change over time or that at least has the capability to change its geographical location. For example, the DBS has necessary circuitry and aerodynamic capability for enabling it to physically fly or move in the air or in a 3-dimensional space in any direction. The DBS may, however, also remain stationary for certain time-period. The movement of the DBS may be controlled by another node or autonomously (e.g., based on pre-configured information such as of an occurrence of an event such as planned race). The DBS may also be called as non- stationary BS, mobile BS, or movable BS. Unless stated otherwise, the DBS mentioned in this disclosure refers to non- stationary BS. The DBS may be any type of a network node which communicates over an air interface with a UE and/or with another network node (e.g., a BS).

[0029] Examples of“network node” mentioned in this disclosure are NodeB, MeNodeB,

SeNodeB, gNodeB, sgNodeB, a network node belonging to MCG or SCG, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, backhaul node, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. MSC, MME, etc.), O&M, OSS, SON, positioning node (e.g. E-SMLC), MDT, and test equipment, etc.

[0030] In this disclosure, the term“user equipment” (UE) refers to any type of communication device capable of communicating with a BS and/or with another UE via an air interface. The UE may also be an aerial vehicle, which can be any type of flying object equipped with a UE. Examples of UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, tablet computer, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, ProSe UE, V2V UE, V2X UE, MTC UE, eMTC UE, FeMTC UE, UE Cat 0, UE Cat Ml, narrowband Internet of Things (NB-IoT) UE, UE Cat NB 1, etc.

[0031] FIG. 1 shows a communication system 100 according to some embodiments of this disclosure. System 100 may comprise a DBS 102, a DBS 122, and a BS 104. BS 104 may serve UEs 106 in a cell 108. Similarly, another BS may serve UEs in a cell 128. The number of DBS, BS, and/or UEs shown in FIG. 1 is provided just for illustration purpose and does not limit the embodiments of this disclosure in any way. Each of DBS 102 and DBS 104 is configured to serve UEs 106 in any of a number of operational areas (preferably two). The term“operational area” may interchangeably called as drone coverage areas / zones, geographical areas/zones, operational zones, serving areas/zones, or target areas/zones. For simplicity, the term

“operational area” is used in this disclosure.

[0032] The number of operational areas in which DBS 102 or DBS 122 is configured to serve UEs may be any number that is greater than or equal to 1. For example, DBS 102 or DBS 122 may be configured to serve two operational areas A1 and A2. Each operational area may be defined by certain topology (e.g., straight path, circular shape, rectangular shape, and irregular shape), which can be 1 -dimensional, 2-dimensional, or 3-dimensional in space. Each operational area may be defined by a set of geographical coordinates. BS 104 and DBS 102 or DBS 122 may communicate directly, through BS-DBS interface, or via another network node (e.g., a higher network node controlling DBS operation). [0033] The operational areas where DBS 102 or DBS 122 can operate may be fully located within the geographical boundaries of cell 108 and/or cell 128 served by base stations, partially located within the geographical boundaries of cell 108 and/or cell 128, or fully outside the geographical boundaries of cell 108 and/or cell 128.

[0034] In some embodiments of this disclosure, multicarrier operation involving at least one DBS may be utilized. The term“multicarrier” refers to carrier aggregation, multi connectivity, or combination thereof. Multi-connectivity operation involves two or more cell groups.

[0035] In carrier aggregation (CA), a UE may be configured with a primary CC (or a cell or a serving cell) which is referred to as the Primary Cell or PCell. The PCell is particularly important because, for example, control signaling is signalled on this cell. The UE may also perform monitoring of the radio quality on the PCell. A CA capable terminal can be configured with additional carriers (or cells or serving cells) which are referred to as Secondary Cells (SCells). For example, the UE can be served with a PCell via a BS and with one or more SCells via DBS(s).

[0036] In dual connectivity (DC), which is a special case of multi-connectivity with two nodes, a UE may be served with a Master Cell Group (MCG) and a Secondary Cell Group (SCG). Cell Group (CG) is a group of serving cells associated with either a master network node (MN) or a secondary network node (SN). Examples of MN and SN are BS and DBS. The MCG and SCG may be defined as follows:

[0037] Master Cell Group (MCG) is a group of serving cells associated with the MN, comprising the PCell and optionally one or more SCells.

[0038] Secondary Cell Group (SCG) is a group of serving cells associated with the SN comprising pSCell (Primary SCell) and optionally one or more SCells.

[0039] In both CA and DC, the UE can handle the reception of signals from any two serving base stations involved in the CA or DC provided that the maximum receive timing difference (MRTD) between the signals from these two serving base stations received at the UE is within certain MRTD threshold (e.g., up to magnitude of 30 ps). In CA and DC, the UE can also handle the transmission of signals in two serving cells belonging to different timing advanced groups (TAGs) involved in the CA or DC provided that the maximum transmission timing difference (MTTD) between the signals transmitted by the UE in these two serving cells is within certain MTTD threshold (e.g., 32.51 ps).

[0040] The MRTD threshold and MTTD threshold may depend on the numerology of the signals such as subcarrier spacings (e.g., whether subcarrier spacings of signals in serving cells are 15 kHz, 30 kHz, 60 kHz, 120 kHz, or any combination thereof). The MRTD and MTTD may also be referred as maximum operational time difference (MOTD) between the signals of different serving cells in CA or DC.

[0041] In some embodiments of this disclosure, performance of a wireless system in an operational area of the DBS (e.g., current traffic volume/capacity limit or other key parameters) may be measured and how to utilize DBSs may be determined based on the performance of the wireless system in the operational area.

[0042] According to some embodiments of this disclosure, a DBS may have a total operation area defined by a set of operational areas as shown in FIG. 2.

[0043] As shown in FIG. 2, DBS 102 may be configured to serve UEs in one of three operational areas including Al, A2, and A3. But the number of operational areas (e.g., Al, A2,

..., An) in which DBS 102 may be configured to serve UEs may be any number (i.e., n can be any positive integer). Each of operational areas Al, A2, and A3 may be further divided into sub- areas.

[0044] For example, operational area Al may comprise sub-areas A11, A12, ..., Aim and operational area A2 may comprise sub-areas A21, A22, ..., A2m. The number of sub-areas may be any number (i.e., m can be any positive integer). Each sub-area may be associated with a sub-area identifier or other information such as geographical coordinates and/or topology.

[0045] DBS 102 may be configured by a network node to operate in certain operational area or to move between different operational areas. DBS 102 may further be configured by a network node to operate in certain sub-area within an operational area or to move between different sub-areas belonging to the same operational area or different operational areas. The sub-areas may be used for DBS operation if the network node can determine more precise locations of UEs in different sub-areas within the same operational area and/or if there is large concentration of UEs in sub-areas within the operational area.

[0046] The network node configuring DBS 102 may be a BS (i.e., a fixed BS) and/or another node (e.g., Access Mobility Function (AMF). Configuring DBS 102 by the network node requires exchange of messages between DBS 102 and the network node. At least the network node maintains information about potential operational areas associated with each DBS.

[0047] The potential operational areas where DBS 102 can operate may change over time and therefore the list of the potential operational areas may be updated over time. DBS 102 may be pre-configured with information about two or more potential operational areas (e.g., Al, A2, and A3) where DBS 102 can be configured to operate. The pre-configuration may be based on pre-defined information and/or information about the potential operational areas received by DBS 102 from a network node.

[0048] According to some embodiments of this disclosure, the network node that preconfigures DBS 102 with information about all potential operational areas where DBS 102 can operate may also configure DBS 102 with the information about the actual operational area where DBS 102 is required to serve the UEs.

[0049] According to other embodiments of this disclosure, a first network node (NW1) preconfigures DBS 102 with information about all potential operational areas where DBS 102 can operate and a second network node (NW2) configures DBS 102 with the information about the actual operational area where DBS 102 is required to serve UEs. The NW1 and NW2 are different network nodes. For example, NW1 may be a part of the backhaul or core network while NW2 can be a BS. The second network node may configure DBS 102 with the information about the operational area into which DBS 102 is requested to move and serve the UEs.

[0050] The information may comprise one or more of the followings: an area identifier, geographical coordinates characterizing or defining an area, topology or morphology of the area (e.g., whether the area is rectangular or circular), sojourn time (Ts) of the DBS in the area (e.g., duration over which the DBS should stay in the indicated area), and area validity time (Ta) over which the indicated area is valid. The parameters Ts and Ta may further be associated with one or more additional timing related information (e.g., starting reference time Tr and ending time Te). For example, according to some embodiments of this disclosure, the DBS may be indicated to stay in the area over Ta starting from Tr. Tr may be global clock (e.g., GNSS reference time or certain frame number (e.g., SFN and hyper SFN of the DBS)).

[0051] The operational areas where DBS 102 can operate may be associated with the same priority level, different priority levels, or a combination thereof. These different DBS area configuration mechanisms give rise to non-hierarchical or hierarchical approach for DBS 102 to serve UEs in different operational areas, as described below.

[0052] Non-hierarchical area configuration mechanism for DBS operation

[0053] In the non-hierarchical area configuration mechanism, all operational areas where

DBS 102 can operate are associated with the same priority level. The operational areas are called herein non-hierarchical operational areas. In this mechanism, a DBS may be configured to operate in any of the non-hierarchical operational areas based on one or more criteria. The network node (e.g., a BS) which configures the DBS with potential operational areas for operation may use one or more of these criteria when selecting the actual operational area or the actual sub-area to be served by the DBS.

[0054] Sub-areas within the same operational area may have the same priority level or different priority levels. In the latter case, the sub-areas may be determined using the hierarchical or semi-hierarchical area configuration mechanisms.

[0055] Non-limiting examples of the criteria are radio conditions, load/traffic situations in different areas, and locations of UEs. The assessment of the criteria may require the network node to obtain information internally (e.g., the BS performing measurements) and/or to obtain information from other nodes (e.g., the BS receiving measurement information from other BS or from UEs). These examples of the criteria are provided below.

[0056] System load

[0057] Examples of load related parameter indicating system load are number of UEs in an area, relative number of UEs in an area compared to a total number of UEs served by a BS, and used or unused resources in the BS. Examples of the resources are radio resources and hardware resources. Examples of the radio resources are physical channels (e.g., resource blocks in UL and/or DL) and transmit power of the BS. Examples of the hardware resources are memory and processors.

[0058] A DBS may be configured to operate based on one or more of load related parameters. In some embodiments, if the number of UEs in an area is above threshold (Gl), then the DBS can be configured to serve the UEs in that area. In case there are multiple areas that satisfy this criterion, then the DBS can be configured to serve UEs in the area that has largest number of UEs.

[0059] In some embodiments, if the ratio of the number of UEs in an area to the total number of UEs in a cell served by a BS (i.e., fixed BS) is above certain threshold (G2), then the DBS can be configured to serve UEs in that area. In other embodiments, if the percentage of currently used resources (e.g., unavailable resources) with respect to total resources in the BS (i.e., the fixed BS) is above certain threshold (G3), then the DBS can be configured to serve UEs in certain area. This will enable the BS to relieve some of the resources.

[0060] Radio conditions

[0061] Examples of radio conditions are signal level at the UE and/or at the BS, and total receive interference at the UE and/or at the BS. Examples of the signal level are signal strength, path loss, and signal quality. The BS may obtain measurement results from one or more UEs and/or may perform uplink measurements on signals received from one or more UEs to assess the radio condition in the cell served by the BS.

[0062] In some embodiments, if the signal level at the UE for at least HI number of UEs in certain area is below a threshold, then the DBS may be configured to move and serve the UEs in that area. This will reduce the interference in the cell since the BS (i.e., the fixed BS) does not have to serve those UEs which are in the identified area. In other embodiments, the DBS may serve the UEs in the indicated area with lower transmit power compared to that used by the BS. In such embodiments, the UE can transmit signals at lower transmit power as compared to the case where the UE is served by the BS in the cell.

[0063] Timing related information [0064] Examples of timing related information are round trip time (RTT) between a UE and a radio node, one way propagation delay between the UE and the radio node, timing advance for the UE estimated by the radio node, MRTD, and MTTD. The RTT and/or the one way propagation delay may be measured by the UE or by the radio node. Examples of the radio node are BS and DBS.

[0065] According to some embodiments of this disclosure, if the TA estimated by the BS for at least K1 number of UEs located in certain area within the cell exceeds certain threshold, then the BS may configure the DBS to serve that area. But if the TA estimated by the DBS for at least K2 number of UEs located in its serving area exceeds certain threshold, then a network node may reconfigure the DBS not to serve UEs in its serving area. Instead the network node may decide to serve those UEs via the BS or identify and configure another DBS with larger coverage to serve those UEs. This mechanism will allow both the BS and the DBS to serve only UEs whose signals can easily be received at the BS well within the cyclic prefix of the symbols.

[0066] The MRTD or MTTD experienced by the UE in CA or DC served by different

BSs may exceed their respective MRTD or MTTD thresholds. This may occur if the BSs are separated by large distance(s) and a UE comes closer to one of the BSs. Accordingly, in some embodiments of this disclosure, a network node may retain CA or DC operation as follows. The network node may configure a DBS to move to the area where the UE is located and to serve the UE with at least one of the serving cells involved in the CA or DC. The other serving cell(s) of the UE can be operated by the BS or by another DBS.

[0067] Positioning information

[0068] A network node managing DBS area configuration may determine locations of one or more UEs and, based on their locations, may decide whether to configure a DBS to serve some of the UE in certain areas or not. In some embodiments, if the number of UEs in an area exceeds certain threshold (LI 1), then a network node may configure the DBS to serve some of these UEs in that area. But if the number of UEs in an area served by the DBS falls below certain threshold (L12), then the network node may reconfigure the DBS to stop serving at least some of these UEs in that area. [0069] In some embodiments, if the ratio of the number of UEs in an area to the total number of the UEs in a cell served by the BS exceeds certain threshold (L21), then the network node may configure the DBS to serve some of these UEs in that area. But if the ratio of the number of UEs in an area to the total number of the UEs in a cell served by the BS falls below certain threshold (L22), then the network node may reconfigure the DBS to stop serving some of these UEs in that area. Instead the network node may decide to serve those UEs not being served by the DBS anymore using a BS or identify and configure another DBS to serve those UEs.

[0070] In some embodiments, the network node may configure the DBS to move and serve UEs in an area of which the distance with respect to the BS location is more than certain threshold (L31).

[0071] Hierarchical or semi-hierarchical area configuration mechanisms for DBS operation

[0072] In mechanisms according to some embodiments of this disclosure, at least two or more operational areas where a DBS can operate are associated with different levels of priority. These mechanisms are called herein hierarchical or semi-hierarchical area configuration mechanisms. Each of the at least two or more operational areas may include sub-areas and the sub-areas within the same operational area may have the same priority level or different priority levels. The hierarchical or semi-hierarchical configuration mechanisms are explained below with three examples. Even though the number of operational areas associated with the DBS in the examples below is two or three, the number of the associated operational areas may be any number.

[0073] In the first example, a hierarchical area configuration mechanism provides at least two different operational areas (A1 and A2) for DBS operation and the two different operational areas are associated with different priority levels. For example, one of the operational areas (e.g., Al) may be designated as a primary operational area (i.e., default area) and the other operational area (e.g. A2) may be designated as a secondary operational area.

[0074] In the second example, a hierarchical area mechanism provides three possible operational areas (Al, A2, and A3) and each one of the three possible operational areas is associated with a different priority level. For example, Al, A2, and A3 may be designated as a primary operational area, a secondary operational area, and a tertiary operational area, respectively.

[0075] In the third example, a semi-hierarchical area mechanism provides three possible operational areas (Al, A2, and A3). But in the third example, at least two operational areas among the three possible operational areas have the same priority level. For example, one operational area of the three possible operational areas (e.g., Al) may have a higher priority level compared to the other two operational areas (e.g., A2 and A3) and may be designated as a primary operational area. The remaining two operational areas (e.g., A2 and A3) may have the same priority level and each of the remaining two operational areas may be designated as a secondary operational area.

[0076] In the hierarchical or semi-hierarchical area configuration mechanisms, the DBS is configured to operate in operational areas to ensure that the communication of UEs in the operational area having the highest priority level is always secured. The DBS may be moved from an operational area having a higher priority level to an operational area having a lower priority level (e.g., from the primary operational area to the secondary operational area or from the secondary operational area to the tertiary operational area) provided that the communication of the UEs in the operational area having the higher priority level can be retained or at least the impact of moving the DBS from the operational area having the higher priority level to another operational area is minimal (e.g., when at least certain target performance can be maintained in the operational area). In these mechanisms, the DBS may be configured to operate in an operational area having a particular priority level but one or more criteria may further be considered for the operation of the DBS.

[0077] Examples of the criteria are provided in the preceding paragraphs of this disclosure, which describe the non-hierarchical area configuration mechanism. For example, the criteria may be radio conditions, load/traffic situations in different areas, or locations of UEs.

[0078] According to some embodiments of this disclosure, in order determine whether a

DBS should be moved to a primary operational area having a higher priority level or to a secondary operational area having a lower priority level, a network node may first determine radio conditions, traffic loads, and/or a number of UEs in the primary operational area. If the number of the UEs in the primary operational area is above certain threshold, then the DBS may be configured to first serve the UEs in the primary operational area.

[0079] On the other hand, if the DBS is not required to operate in the primary operational area (e.g., if the number of the UEs in the primary operational area is below the threshold), then the DBS may be moved between operational areas of equal lower priority (e.g., like the areas in the semi-hierarchical area arrangement) based on one or more of the criteria described above.

[0080] For example, a DBS may be moved from a higher priority operational area (e.g.,

Al) to a lower priority operational area (e.g., A2) provided that at least Xl% of UEs in A1 and/or X2 number of UEs in Al can be served by another node (e.g., by a fixed BS or by another DBS) even after the DBS moves from the higher priority operational area to the lower priority operational area. Otherwise the DBS is required to stay and serve the UEs in Al. Examples of XI are 80 and 90.

[0081] On the other hand, if the number of UEs served by the DBS in the lower priority operational area (e.g., A2) falls below certain threshold (e.g., 3 or 5), then the DBS may be moved back to the higher priority operational area. For example, when there is not enough UEs in the lower priority operational area (e.g. when the number of UEs is less than Y 1), the DBS may be moved to the higher priority operational area regardless of the number of UEs in the higher priority operational area. This ensures that the DBS is available to serve UEs in the higher priority operational area whenever they intend to start the communication.

[0082] In another example when there is not enough UEs in the lower priority

operational area, the DBS may be moved to the higher priority operational area only when there is at least Z1 number of UEs in the higher priority operational area. This second mechanism ensures that the DBS can serve UEs in the lower priority operational area as long as possible. Examples of Z1 are 1, 3, and 5.

[0083] According to some embodiments of this disclosure, operational areas allowed for a DBS may be prioritized so that the DBS will first secure wireless communication in a primary operational area (i.e., the operational area having a higher priority level as compared to other operational areas). In case the primary operational area is under-utilized from a wireless performance point of view, the DBS may be allowed to serve any of the secondary operational area through 11 ^th prioritized operational area according to the priority levels of the operational areas. The method of defining a list of allowed operational areas for a DBS to serve may combine proximity of operations as well as allowing limited dynamicity in movement inside and along a set of operational areas for the DBS.

[0084] The implementation of a prioritized list of operational areas for flight paths of a

DBS means that the DBS must interact with the wireless communication system to optimize the wireless communication and to secure optimal flight paths for the operational areas of the DBS.

[0085] FIG. 3 shows a process 300 for configuring a DBS to operate within operational areas according to some embodiments. Even though FIG. 3 shows a plurality of steps arranged in a particular sequence, the steps may be performed in any order.

[0086] Process 300 may begin with step s302. In step s302, a list of operational areas for the DBS is defined and stored in a wireless system. The list may be stored in a network node such as a fixed BS or a node in a core network. In 5G, the list of operational areas may be stored in the Unified Data Management (UDM) and may be retrieved by the Access and Mobility Function(s) (AMF).

[0087] The operational areas included in the list may be prioritized. Also, in some embodiments, one or more of the prioritized operational areas may be divided into sub-areas. Thus, in optional step s304, sub-areas of the operational areas may be defined and stored in the wireless system. The sub-areas may be defined in various ways. FIGS. 4A and 4B illustrate examples of sub-areas formed an operational area. As shown in FIG. 4A, in some embodiments, portions of a sub-area may be outside the operational area.

[0088] In step s306, wireless performance levels (e.g., load levels and/or other key parameters) of the operational areas (including the primary operational area, the secondary operational area, ..., and n ^lh operational area) defined for the DBS are determined. Determining the wireless performance levels of the operational areas may involve a process 500.

[0089] Process 500 may begin with step s502. In step s502, measurement objects supporting the decision to move the DBS are defined. The measurement objects may be any one or combination of the followings: thresholds for load levels in sub-areas of an operational area, thresholds for performance in different sub-areas of an operational area, thresholds for path loss and other characteristics in sub-areas of an operational area, and thresholds for key parameters for a specific spot or a sub-level in an operational area.

[0090] In step s504, user equipments (UEs) or a base station (BS) executes

measurements (e.g., obtaining radio condition information).

[0091] In step s506, load levels or other key parameters in the operational areas defined for the DBS are predicted.

[0092] Referring back to process 300, based on the wireless performance levels of the operational areas determined in step s306, a fixed base station within an operational area is defined as a master base station in step s308 and the DBS is defined as a serving base station in step s310.

[0093] In step s312, a decision on DBS movement within an operational area is made.

The procedure for making the decision may vary between realizations. Factors that can influence in making the decision are: choice of autonomous decision making, logical placement of decisions - DBS, a wireless network, or combinations of them, and choice of supporting system for decision making.

[0094] The decision may involve a process 600 shown in FIG. 6. Even though process

600 includes a plurality of steps arranged in a particular sequence, the steps may be performed in any order.

[0095] Process 600 may begin with step s602. In step s602, a decision system for making a decision on DBS movement within an operational area is defined.

[0096] In step s604, criteria(s) supporting the decision is defined.

[0097] In step s606, whether the master base station (i.e., the fixed base station) or the

DBS has the role of making the decision is determined. If the master base station has the role, process 600 may proceed to step s608. On the other hand, if the DBS has the role, process 600 may proceed to step s610.

[0098] In step s608, in case the master base station (i.e., the fixed base station) has a central role in the decision making and a communication in a certain part of the operational area needs to be improved, the master base station makes the decision to move the DBS. Then, the master base station instructs the secondary base station (i.e., the DBS) to move to the part of the operational area. Policy rules and policy engines may be added to support the decision making.

[0099] In some embodiments, if a separate drone flight control entity is provided, the wireless network may inform the drone flight control entity about the decision and get an acknowledgement from the drone flight control entity that the flight decision has been

implemented.

[00100] In step s610, in case the DBS has the role of making the decision as to whether to move the DBS, the DBS may communicate with the master base station about the decision and get acceptance/acknowledgement for the decision from the master base station. The decision can be supported by policy rules and policy engines.

[00101] In some embodiments, if a separate drone flight control entity is provided, the wireless network may inform the drone flight control entity about the decision and get an acknowledgement from the drone flight control entity that the flight decision has been

implemented.

[00102] Referring back to process 300, in step s314, wireless performance levels (e.g., load levels and/or other key parameters) of the operational areas (including the primary operational area, the secondary operational area, ... , and n ^lh operational area) defined for the DBS are determined. This step is similar to step s306 and thus detailed explanation regarding step s314 is omitted. In step s314, wireless performance levels of sub-areas within one or more operational areas may also be determined.

[00103] In step s316, a decision on DBS movement between the operational areas is made. The decision may involve a process 700 shown in FIG. 7. Even though process 700 includes a plurality of steps arranged in a particular sequence, the steps may be performed in any order.

[00104] Process 700 may begin with step s702. In step s702, a decision system for making the decision on DBS movement between the operational areas is defined.

[00105] In step s704, criteria(s) supporting the decision is defined.

[00106] In step s706, a network associated with the DBS decides if the DBS should move out from the current operational area (i.e., the operational area in which the DBS is currently located - for example, the primary operational area) and serve another operational area. In some embodiments, policy rules and policy engines may be added to support the decision making.

[00107] In 5G, AMF may get the information about wireless performance levels of different operational areas and analyze the wireless performance levels to determine whether the DBS should move in or out of the current operational area. If the list of the operational areas for the DBS includes operational areas of another AMF (i.e., a serving AMF), the primary AMF may be configured as a master AMF and the master AMF may instruct the serving AMF about any potential action.

[00108] In step s708, if it has been decided to move the DBS from the current operational area to another operational area, the wireless network associated with the DBS may

communicate to the DBS about the decision and instruct the DBS to move to said another operational area. According to some embodiments, after the DBS has been moved to said another operational area, a master base station may be changed.

[00109] Also, in some embodiments, if a separate drone flight control entity is provided, the wireless network may inform the drone flight control entity about the decision and get an acknowledgement from the drone flight control entity that the flight decision has been implemented.

[00110] Referring back to process 300, after performing step s316, at least some of the steps of process 300 may be repeated. For example, the list of the operational areas for the DBS may be updated or any new decision as to flight directions of the DBS may be made.

[00111] FIG. 8 is a flow chart illustrating a process 800 according to some embodiments. Process 800 may begin in step s802.

[00112] Step s802 comprises assigning a first set of operational areas to the first DBS. The first set of operational areas may include a first operational area and a second operational area.

[00113] Step s804 comprises determining whether a network condition within a particular operational area satisfies a criteria.

[00114] Step s806 comprises as a result of determining that the network condition within the particular operational area satisfies the criteria, selecting a DBS from a subset of DBSs. Each DBS included in the subset of DBSs may be assigned a set of operational areas that includes the particular operational area.

[00115] Step s808 comprises based on a rule associated with the selected DBS, determining whether the rule permits the selected DBS to begin serving the particular operational area.

[00116] Step s810 comprises as a result of determining that the rule permits the selected DBS to begin serving the particular operational area, configuring the selected DBS to begin serving the particular operational area. Configuring the selected DBS to begin serving the particular operational area may comprise or consist of causing the selected DBS to move from its current operational area to the particular operational area.

[00117] In some embodiments, process 800 further includes assigning a second set of operational areas to the second DBS. The second set of operational areas may include a third operational area, and the size of the first operational area and/or the second operational area and the size of the third operational area may be different.

[00118] In some embodiments, process 800 further includes assigning a second set of operational areas to the second DBS. The number of operational areas included in the first set of operational areas and the number of operational areas included in the second set of operational areas may be different.

[00119] In some embodiments, the particular operational area includes a plurality of sub- areas. Determining whether the network condition within the particular operational area satisfies the criteria may include determining whether a network condition within a particular sub-area of the particular operational area satisfies a criteria. In some embodiments, configuring the selected DBS to begin serving the particular operational area includes configuring the selected DBS to begin serving the particular sub-area of the particular operational area.

[00120] In some embodiments, process 800 further includes obtaining information regarding one or more operational areas and updating the first set of operational areas assigned to the first DBS based on the obtained information. [00121] In some embodiments, assigning the first set of operational areas to the first DBS is performed by a first network node and configuring the selected DBS to begin serving the particular operational area is performed by a second network node. Each of the first network node and the second network node may be one of a fixed base station, a network node in a core network, and a network node in a backhaul network. The first network node and the second network node may be the same network node or different network nodes.

[00122] In some embodiments, the first operational area is assigned a first priority level and the second operational area is assigned a second priority level. The first priority level may be higher than the second priority level.

[00123] In some embodiments, the first DBS is associated with a first rule that permits the first DBS to move from the first operational area into the second operational area when a first network condition is satisfied, and the first DBS is associated with a second rule that requires the first DBS to move from the second operational area into the first operational when a second network condition is satisfied.

[00124] In some embodiments, the selected DBS is currently serving an operational area. Determining whether the rule permits the selected DBS to begin serving the particular operational area may comprise obtaining information concerning the operational area that the selected DBS is currently serving and then using the obtained information to determine whether the rule permits the selected DBS to begin serving the particular operational area.

[00125] In some embodiments, determining whether the network condition within the particular operational area satisfies the criteria comprises determining any one or combination of:

(1) the number of active user equipments (UEs) operating within the particular operational area,

(2) an amount of used or unused resources of a base station (BS) serving the particular operational area, (3) a signal level at a UE or at the BS, (4) a round trip time (RTT) between a UE and a radio node, (5) one way propagation delay between a UE and a radio node, (6) a timing advance for a UE, (7) a maximum receiving time difference (MRTD) between signals received at a UE, and (8) a maximum transmission timing difference (MTTD) between signals transmitted by a UE. [00126] FIG. 9 is a block diagram of an apparatus 900, according to some embodiments, for implementing DBS 102, BS 104, UE 106, or any other network node involved in controlling DBS 102. As shown in FIG. 9, apparatus 900 may comprise: processing circuitry (PC) 902, which may include one or more processors (P) 955 (e.g., a general purpose microprocessor and/or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (i.e., apparatus 900 may be a distributed computing apparatus); a network interface 948 comprising a transmitter (Tx) 945 and a receiver (Rx) 947 for enabling apparatus 900 to transmit data to and receive data from other nodes connected to a network 110 (e.g., an Internet Protocol (IP) network) to which network interface 948 is connected; and a local storage unit (a.k.a.,“data storage system”) 908, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In embodiments where PC 902 includes a programmable processor, a computer program product (CPP) 941 may be provided. CPP 941 includes a computer readable medium (CRM) 942 storing a computer program (CP) 943 comprising computer readable instructions (CRI) 944. CRM 942 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 944 of computer program 943 is configured such that when executed by PC 902, the CRI causes apparatus 900 to perform steps described herein (e.g., steps described herein with reference to the flow charts and message flow diagrams described herein). In other embodiments, apparatus 900 may be configured to perform steps described herein without the need for code. That is, for example, PC 902 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and/or software.

[00127] While various embodiments of the present disclosure are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present disclosure should not be limited by any of the above- described exemplary embodiments. Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. Any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[00128] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel. That is, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step.