Method and apparatuses for determining cellular parameter re-use relations

Abstract

According to an example aspect of the present invention, there is provided an apparatus configured to process a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value, determine, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and consider, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

Description

METHOD AND APPARATUSES FOR DETERMINING CELLULAR PARAMETER RE-USE RELATIONSFIELD

[0001] The present disclosure relates to managing a cellular communication network.BACKGROUND

[0002] Cellular communication systems comprise plural cells, which are controlled by base stations. A user equipment, UE, attaches itself to a cell to access services of the cellular communication system.

[0003] Deploying cellular communication systems includes establishing, usually, plural base stations, in some cases hundreds or even thousands of base stations, each base station being capable of controlling one or more cells of the cellular communication system.SUMMARY

[0004] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims.

[0005] According to a first aspect of the present disclosure, there is provided a method comprising processing a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value, determining, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and considering, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

[0006] According to a second aspect of the present disclosure, there is provided an apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to process a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value, determine, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and consider, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

[0007] According to a third aspect of the present disclosure, there is provided an apparatus comprising means for processing a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value, determining, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and considering, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

[0008] According to a fourth aspect of the present disclosure, there is provided a non- transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least process a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value, determine, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and consider, in the determining of the cellular parameter reuse relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGURE 1 illustrates example system in accordance with at least some embodiments of the present invention;

[0010] FIGURE 2A illustrates an example coverage map of a cellular network;

[0011] FIGURE 2B illustrates an example coverage map of a cellular network;

[0012] FIGURE 2C illustrates an example coverage map of a cellular network;

[0013] FIGURE 2D illustrates an example coverage map of a cellular network;

[0014] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0015] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention, and

[0016] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention.EMBODIMENTS

[0017] Disclosed herein are methods to configure cells of a cellular communication system, taking into account terrain features such as ground elevation in determining how to re-use finite resources of the system, such as frequencies. In particular, a polygonal representation of cells and ground elevation values may be used to determine pairs of cells which may share the same parameters, such as frequency or cell identity. Likewise, neighbour relations may be determined, at least initially, based at least in part on the ground elevation information. More effective re-use of cellular parameters, such as frequencies, provides the benefit of increased throughput using the limited resources available. Likewise more realistic neighbour cell lists enhance handover processes in the network. The ground elevation may be assumed to be constant within a coverage area of a single cell. A ground elevation value may be an elevation of ground on which a base station is installed, or it may be an elevation or height of an antenna of such a base station, for example a height of a midpoint of a transmit antenna. When the antenna option is used, the elevation or height of the antenna may be a sum of the elevation of the ground on which a base station is installed and a height of an antenna construction.

[0018] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. This system includes a base stations 130, 135 in communication with UEs, such as UE 110. A radio link connects base station 130 with UE 110, The radio link may be bidirectional, comprising an uplink, UL, to convey information from UE 110 toward base station 130 and a downlink, DL, to convey information from the base station 130 toward UE 110.

[0019] Base station 130 is further coupled communicatively with core network node 140, which may comprise, for example, a mobility management entity, MME, or access and mobility management function, AMF. The core network node 140 may be coupled with further core network nodes, and with a network 150, which may comprise the Internet or a corporate network, for example. The system may communicate with further networks via network 150. Examples of the further core network nodes, which are not illustrated in FIGURE 1 for the sake of clarity, include gateways and subscriber information repositories.

[0020] Base station 130 has, in the example of FIGURE 1, plural cells, or beams, 130A, 130B, of which UE 110 is in the situation illustrated in FIGURE 1 attached with cell or beam 130A, and base station 135 has, in the example of FIGURE 1, plural cells or beams 135A, 135B. In FIGURE 1, cells or beams 130A and 130B are at a first elevation, E=l, and cells or beams 135 A and 135B are at a second elevation, E=2. The number of cells or beams may be in excess of what is illustrated in FIGURE 1. It is also possible that a base station has a single cell or beam. A mobility event may comprise a switch from one beam to another beam of the same cell, or a switch from one cell to another cell. To support mobility procedures, UEs, including UE 110, are configured to conduct mobility measurements to measure signal strengths of adjacent beams and / or cells, and report results of these measurements to the network, which may then take a decision concerning a mobility event, such as a beam change or a cell switch.

[0021] Such mobility measurements at the UE side may be layer-3 measurements, and the corresponding reports may be layer-3, or L3, reports. Likewise a handover command from the network to a UE may be a layer-3 message. A cell switch or beam change directed using a layer-3 command involves a reset of layers lower than layer-3, which causes some delays. Layer 3 is in technology standardized by the 3rdgeneration partnership project, 3GPP, the radio resource control, RRC, layer. Of the lower layers layer- 1, or LI, is in 3GPP technology the physical layer, and layer-2, or L2, comprises the medium access control,MAC layer, radio link control, RLC, layer and packet data convergence protocol, PDCP, layer. Of note is that the elevations, which may be elevations relative to sea level, for example, affect the results of mobility measurements. In detail, if a neighbouring cell is on a similar elevation than a cell where a UE is attached, a signal from the neighbouring cell may be received well in the UE. On the other hand if there is a significant difference in elevation, say 50 metres or 70 metres, this will reduce the strength at which the signal from the neighbouring cell is received in the UE, for two reasons, namely the distance to a base station controlling the neighbouring cell is greater, and there may be physical obstacles, such as terrain, impeding the propagation of signals from the neighbouring cell to the UE.

[0022] If mobility measurements, also known as radio resource management, RRM, measurements, indicate that a signal strength of a cell or beam the UE is currently attached with is declining and a signal strength of another cell or beam is increasing, then a switch to another cell or beam may be commanded by the network based on mobility measurement reports the UE has delivered to the network.

[0023] Cells of the system are configured with cellular parameters. In particular, a frequency band allocated to the system may be subdivided to frequencies used by individual cells. To avoid interference between neighbouring cells, the cell frequencies may be configured so that no two adjacent cells use the same frequency, to avoid interference from the neighbouring cell. Further, the frequencies may be so configured, that even two-hop neighbours do not use the same frequency. By two-hop neighbour it is meant a cell which is a neighbour of a neighbour cell, thus it is not adjacent but nonetheless nearby. Depending on the radio-access technology used, other cellular parameters may be so allocated in addition to, or alternatively to, the frequency. For example, spreading codes, scrambling codes and random access resources may be allocated in a similar manner, as may be cell identities. The pool of cell identities may be kept limited, such that the cell identity may be communicated using a relatively small number of bits. However, the cell identity cannot be the same value in cells that are close to each other, to avoid confusion. The cellular parameter may comprises one of the following: a cell frequency, a random access preamble, a random access preamble set or a cell identity. Alternatively or in addition, any other re-usable parameter which requires re-use may be so applied.

[0024] On the other hand, in case cellular parameters may be re-used to a greater extent, that is, in cells closer to each other, more communication capacity may be obtainedfrom the same parameter resources. For example, if frequencies may be re-used by more base stations, there is effectively more frequency resources usable on a local level, where the UEs operate. Thus cellular parameter re-use is both necessary and useful. Increasing reuse is beneficial to the network, but on the other hand increased re-use may lead to the kind of problems mentioned above, such as interference and / or cell identity confusion. A re-use relation between two sites or cells may define whether these sites or cells share a same cellular parameter.

[0025] When accessing existing neighbours, planning new neighbours of a cell based on geo location or allocating best possible cellular parameters, various items of information may be taken into account: azimuth angles, distances between base station sites, etc. Herein by azimuth angle it is meant a direction from an antenna which ranges from zero to 359 degrees, such that, for example, zero is North and 90 degrees is East. This enables prioritizing neighbouring cells, creating neighbour relations and allocating parameters from other cells with the least overlapping coverage and a lower interference level. One factor which is useful to take into account in calculations is ground elevation information. Planning neighbour relationships with elevation information allows to take into account topography of the environment and terrain features, such as hills which may function as signal attenuators. For example, two cells may use a same cellular parameter if there is a hill between their base station sites, even if without the hill interference would prevent using the same parameter in these two cells. Network coverage maps with elevation information may require cumbersome software to be used. Further, for self-organizing networks, SON, network calculations with ground elevation information may require software which is too time consuming, as elevation is a continually changing variable as a function of distance. Methods disclosed herein use information that is usually available for SON networks, such as, ground elevation of a site where a base station site is situated, and determine a tiled coverage map to perform neighbour relationship planning and cellular parameter re-use configuration based on such information.

[0026] FIGURE 2A illustrates an example coverage map of a cellular network. Cells of the network are represented in perspective and as hexagonal, although in general cells may have more complex shapes, as will be discussed in more detail herein below. In FIGURE 2A, several cells are provided with respective ground elevation values, which indicate an elevation value of the cell’s coverage area with reference to a reference elevation, such as sea level, for example. This the ground elevation values may be used to compareelevations of the cells to each other. The ground elevation value of a cell may be the ground elevation value of a site of a base station which controls the cell. The ground elevation is assumed to be constant within a coverage area of a single cell.

[0027] Cell 201 has a ground elevation value of 27.0, cell 202 has a ground elevation value of 28.0, cell 203 has a ground elevation value of 17.0, cell 204 has a ground elevation value of 15.0 and cell 105 has a ground elevation value of 16.0. Cell 202 is a two-hop neighbour of cell 201, and cells 204 and 205 are two-hop neighbours of cell 203.

[0028] Cells 201 and 202 have higher elevation than the other cells, while cells 203, 204 and 205 have roughly average elevation. Signals from cells 201 and 202 may carry far in the landscape, wherefore cellular parameters they use may be restricted in their re-use to farther-away cells than in case all the cells had the same elevation. This may be referred to as restricting re-use of parameters used in these cells, since a stricter re-use rule is used which results in re-use of these parameters farther away than in case all the cells had the same elevation.

[0029] Turning then to cell 203, which has a ground elevation value of 17.0, there is a cell between cell 203 and cell 201 which is significantly lower. Signals from this cell are not likely to propagate far, and its cellular parameters may be re-used closer than in the case where all cells had the same elevation. Thus re-use of these parameters may be promoted, since this has the effect that their re-use takes place closer. The cell between cell 203 and cell 201 may be referred to as a cell surrounded by cells of higher elevation. The ground elevation is assumed to be constant within a coverage area of a single cell. The elevation assigned to the cell may be the elevation of the base station site which hosts the base station which controls the cell. This simplifies calculations considerably compared to using an elevation map which has plural elevation values in each cell, or at least in some cells.

[0030] As to the relationship of cell 203 with cells 204 and 205, we note that in terms of parameter re-use these relationships are clearly different. In particular, cell 202, which has higher elevation than either cell 203 or 204, is between cells 203 and 204, wherefore it forms a natural barrier to signal propagation, and re-use of cellular parameters of cell 203 may be promoted in cell 204. In other words, considering of the ground elevation values of cells may be done by determining a straight line between a centre of a first cell 203 and a centre of a respective second cell 204 and determining whether the straight line intersects a coverage area of a third cell 202 associated with a higher ground elevation value than boththe first 203 and the respective second cell 204, and responsive to the straight line intersecting the coverage area of such a third cell 202, re-use of the cellular parameter may be promoted between the first 203 and the respective second cell 204.

[0031] On the other hand, no higher-elevation cell is between cell 203 and cell 205. Thus interference from cell 203 may reach cell 205 fairly easily, and there is no cause to promote re-use of cellular parameters of cell 203 in cell 205. Further, since the only cell between cells 203 and 205 is of lower elevation than either cell 203 or 205, signal propagation between cells 203 and 205 may in fact be stronger than implied by distance alone, and re-use of cellular parameters between these cells may be restricted relative to the case where all cells have the same ground elevation. In other words, re-use of a cellular parameter may be restricted responsive to determining that a straight line between a centre of a first cell 203 and a centre of a respective second cell 205 intersects a coverage area of a third cell associated with a lower ground elevation value than both the first 203 and the respective second cell 205.

[0032] FIGURE 2B illustrates an example coverage map of a cellular network. The figure is similar to FIGURE 2A. In FIGURE 2B, cell 206 and cell 208 have lower ground elevation values than cell 207, which is in between cells 206 and 208. Thus, as outlined above, a straight line connecting the centres of cells 206 and 208 intersects a coverage area of cell 207 which has a higher ground elevation than either of cells 206 and 208. Re-use of cellular parameters between cells 206 and 208 may thus be considered, even if it would not be considered in case cell 207 didn’t have a higher elevation.

[0033] In addition to cellular parameter allocation, also initial neighbour lists may be generated based on coverage maps such as those in FIGURES 2 A and 2B. In detail, an adjacent site with significantly higher elevation may be excluded from being a neighbour. Further, a cell with higher elevation than adjacent sites may have an extended neighbour list, since signals may propagate quite far from such a cell. Yet further, a two-hop neighbour cell may be excluded from a neighbour list of a cell if a further cell, with higher elevation, is in between the two-hop neighbour cell and the cell whose neighbour list is being compiled. On the other hand, a two-hop neighbour cell may be included in a neighbour list of a cell if a further cell, with lower elevation, is in between the two-hop neighbour cell and the cell whose neighbour list is being compiled. Neighbour lists may be modified further based on SON principles, using measurement reports, to discover actual neighbouring cells, but initiallists may be generated using coverage maps with elevation values, as in FIGURES 2A and 2B. Expressed in other words, a neighbour list of a cell having lower elevation than at least one or two adjacent cells may be less extensive than in case all cells had the same elevation. Further, a neighbour list of a cell having higher elevation than at least one or two adjacent cells may be more extensive than in case all cells had the same elevation.

[0034] FIGURE 2C illustrates an example coverage map of a cellular network. While the cells in the coverage maps of FIGURES 2 A and 2B are hexagonal in shape, the cells may more generally have a polygonal shape, further such that not all the cells need have the same polygon as their basic shape. In the map of FIGURE 2A, cell 209 has a hexagonal shape, cell 210 has a triangular shape, cell 211 has a heptagonal shape and cell 212 has a pentagonal shape.

[0035] As in the earlier figures, each cell coverage area may be associated with a single ground elevation value, and determinations to promote and restrict cellular parameter re-use and / or devise initial neighbour lists may be determined based on at least the ground elevation values of the cells.

[0036] FIGURE 2D illustrates an example coverage map of a cellular network. Cells 209, 210 and 211 of FIGURE 2C are present, in a slightly modified configuration. Elevations of these cells are, respectively, 12, 22 and 13, wherefore cell 210 has a significantly higher elevation than either cell 209 or cell 211. As in the other examples, the ground elevation is assumed to be constant inside a cell, that is, each cell has one and only one ground elevation value. The cell coverage areas are polygonal.

[0037] A straight line 220 connects a centre of cell 209 with a centre of cell 211. In this example, this line intersects the coverage area of cell 210, which has higher elevation than either cell 209 or cell 211, thus the base station sites of cells 209 and 211 are occluded from each other by the intervening cell 210, and re-use of cellular parameters may be promoted between cells 209 and 211. On the other hand, a neighbour relationship between cells 209 and 211 may be left out of initial neighbour cell lists of cells 209 and 211, for the same reason.

[0038] A map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, may be generated using one of plural possible algorithms. Alternatively or additionally, a coverage footprintin the form of polygons from, for example, a radio network planning tool, may be used in generating such a map. Using different polygons enables the generation of a varied and accurate map which may take into account a diverse range of different cell shapes. For example, the map may be a Voronoi diagram. Herein, a Voronoi diagram refers to a partition of a plane into regions or sub-planes in the neighbourhood of a given set of objects. The objects may be the base station sites in the context of the present disclosure. A Voronoi diagram may refer to representation of a set of points that divide the plane such that each point is assigned an individual Voronoi cell. The Delaunay triangulation diagram is the straight-line dual of the Voronoi Diagram. Beneficially, the triangulation diagram is used in construction of a discrete model or representation of the plurality of the base stations and the one or more directional antennas that may be used to define and delineate proximal regions around individual point sites via implementation of polygonal boundaries to generate the Voronoi triangulation diagram for enabling management of the cellular network via the method.

[0039] In use, SON principles may be used to adjust cell borders from the initial polygon map, such as the Voronoi diagram, for example. Thus the map of coverage areas may be used as an initial set of cell coverage areas, which the network may automatically adjust to real-life signal propagation characteristics of the terrain where the cellular network is installed.

[0040] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 300, which may comprise, for example, a network configuration node. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. When processor 310 comprises more than one processor, device 300 may be a distributed device wherein processing of tasks takes place in more than one physical unit. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex- A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. A processing core or processor may be, or may comprise, at least one qubit. Processor 310 may comprise at least one Qualcomm Snapdragon and / or Intel Atom processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise atleast one field-programmable gate array, FPGA. Processor 310, optionally together with memory and computer instructions, may be means for performing method steps in device 300, such as processing, determining and considering. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0041] Device 300 may comprise memory 320. Memory 320 may comprise randomaccess memory and / or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may be a computer readable medium. Memory 320 may comprise solid- state, magnetic, optical and / or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and / or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part external to device 300 but accessible to device 300. Memory 320 may be transitory or non-transitory. The term “non-transitory”, as used herein, is a limitation of the medium itself (that is, tangible, not a signal) as opposed to a limitation on data storage persistency (for example, RAM vs. ROM).

[0042] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and / or receiver 340 may be configured to operate in accordance with suitable communication standard, such as a core network inter-node communication protocol in case device 300 is in a core network of a cellular communication system.

[0043] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker or a microphone. A user may be able to operate device 300 via UI 360, for example configure mapping, neighbour cell listing or cellular parameter sharing procedures.

[0044] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver. Device 300 may comprise further devices not illustrated in FIGURE 3.

[0045] Processor 310, memory 320, transmitter 330, receiver 340 and / or UI 360 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0046] FIGURE 4 illustrates a method to determine whether to promote or restrict cellular parameter re-use between cells. In phase 410, a cell is chosen from the map of coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape. Processing advances to phase 420, where an adjacent, that is, 1- hop neighbour, cell is chosen for the cell selected in phase 410. Processing advances to phase 430, where a cell is chosen which is adjacent to the cell chosen in phase 420 and also a 2- hop neighbour of the cell chosen in phase 410. Processing advances to phase 440, where it is determined, if a cell with higher elevation than either of the cells chosen in phases 410 and 430 is in between, that is, whether a straight line connecting centres of the chosen cells intersects a coverage area of a cell with higher elevation than either of the chosen cells. If this is the case, then cellular parameter re-use is promoted between the chosen cells. On the other hand, if there is a cell in between the chosen cells with a lower elevation than either of the chosen cells, then cellular parameter re-use is restricted between the chosen cells.

[0047] Processing advances from phase 440 to phase 450, where it is determined whether all 2-hop neighbours of the cell chosen in phase 410 which are adjacent to the cell chosen in phase 420 have been considered. If this is not the case, then processing advances back to phase 430. On the other hand if this is the case, then processing advances to phase 460, where it is determined, if all cells adjacent to the one selected in phase 410 have been considered. If this is not the case, then processing advances back to phase 420, where a new cell adjacent to the one selected in phase 410 is chosen. If this is the case, processing advances from phase 460 to phase 470, where it is determined whether all the cells have been chosen in phase 410. If this is not the case, then processing returns from phase 470 to phase 410. If all cells have been treated, then processing advances from phase 470 to phase 480, where processing ends.

[0048] While discussed herein as ground elevation value, in some embodiments the ground elevation value used is the elevation at which an antenna assembly used by the base station controlling the cell in question is used as the ground elevation value. The methods disclosed herein may be used in planning small cells, in particular, small cells may be preferentially placed behind elevated ground, to benefit from the signal attenuation caused by elevated ground between the new small cell and an existing cell, to enable re-use of cellular parameters of the existing cell in the new small cell.

[0049] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in device 110, an auxiliary device or a personal computer, for example, or in a control device configured to control the functioning thereof, when installed therein.

[0050] Phase 510 comprises processing a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value. Phase 520 comprises determining, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell. Finally, phase 530 comprises considering, in the determining of the cellular parameter reuse relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

[0051] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but areextended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0052] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0053] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0054] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0055] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited,except as by the claims set forth below.

[0056] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

[0057] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.INDUSTRIAL APPLICABILITY

[0058] At least some embodiments of the present invention find industrial application in cellular communications.ACRONYMS LIST SON self-organizing networkUE user equipmentREFERENCE SIGNS LIST

Claims

CLAIMS:

1. A computer implemented method comprising:- processing a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value;- determining, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and- considering, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

2. The method according to claim 1, comprising performing the considering of the ground elevation values by determining a straight line between a centre of a first cell and a centre of respective second cell and determining whether the straight line intersects a coverage area of a third cell associated with a higher ground elevation value than both the first and the respective second cell, and responsive to the straight line intersecting the coverage area of the third cell, promoting re-use of the cellular parameter between the first and the respective second cell.

3. The method according to claim 1, wherein the cellular parameter comprises one of the following: a cell frequency, a random access preamble, a random access preamble set or a cell identity.

4. The method according to any of claims 1 - 3, wherein each one of the second cells is a one-hop, two-hop or three-hop neighbour of a respective first cell with which the cellular parameter re-use relations are determined.

5. The method according to claim 4, wherein each one of the second cells is a one-hop or two-hop neighbour of the respective first cell with which the cellular parameter re-use relations are determined.

6. The method according to any of claims 1 - 5, wherein each one of the polygonal coverage areas is a hexagon.

7. The method according to any of claims 1 - 5, wherein the polygonal coverage areas are not all of a same polygonal shape.

8. The method according to any of claims 1 - 7, wherein the map is a Voronoi diagram.

9. The method according to claim 8, further comprising determining the Voronoi diagram using, at least in part, measurement data obtained from the plural cells of the cellular communication system.

10. The method according to claim 9, wherein the measurement data is minimization of drive tests measurement data.

11. The method according to any of claims 1 - 10, wherein each ground elevation value is an elevation of a ground level on which a base station serving the respective coverage area is installed, or each ground elevation value is an elevation or height of an antenna of the base station serving the respective coverage area.

12. The method according to any of claims 1 - 11, wherein each ground elevation value comprises a sum of the elevation of the ground on which a base station is installed and a height of an antenna construction.

13. An apparatus comprising at least one processing core and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus at least to:- process a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value;- determine, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, andconsider, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

14. An apparatus according to claim 13, configured to perform the considering of the ground elevation values by determining a straight line between a centre of a first cell and a centre of a respective second cell and determining whether the straight line intersects a coverage area of a third cell associated with a higher ground elevation value than both the first and the respective second cell, and responsive to the straight line intersecting the coverage area of the third cell, promoting re-use of the cellular parameter between the first and the respective second cell.

15. An apparatus comprising means for:- processing a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value;- determining, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, and- considering, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

16. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least:- process a map which comprises coverage areas of plural cells of a cellular communication system, wherein each coverage area is in polygonal shape, and each coverage area is associated with a ground elevation value;- determine, based at least in part on the map, cellular parameter re-use relations between at least one first cell from among the plural cells and one or more second cell, andconsider, in the determining of the cellular parameter re-use relations, the ground elevation values associated with the coverage areas of the at least one first cell and the respective one or more second cell.

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