A method for identifying visibility regions in ELAA-based wireless networks

Abstract

The present invention provides a method for identifying visibility regions (VRs (140)) on the ELAA (100) by detecting the information related with VRs (140). The method comprises the steps of omnidirectionally transmitting a pilot signal from the user device (120) to the communication device (200) for channel estimation; omnidirectionally receiving the pilot signal by the ELAA (100) of the communication device transmitted from the user device (120) (210); measuring, by the communication device, the received power across the array element (110) in ELAA (100) from the received signal (220) and obtaining power distribution of the measured powers that are above a predefined threshold power in power domain; estimating the channel frequency response by the communication device from the received pilot signal (230); transforming the estimated channel frequency response to the beamspace domain (240); extracting the VR-related information from the beamspace domain representation of the estimated and transformed channel (250); identifying the VRs (140) by using the information obtained from beamspace domain and from the power domain (260).

Description

[0001]DESCRIPTION A METHOD FOR IDENTIFYING VISIBILITY REGIONS IN ELAA-BASED WIRELESS NETWORKS FIELD OF THE INVENTION The present invention relates to a method for identifying visibility regions (VRs) in an Extra- Large Antenna Arrays (ELAA) based wireless networks to ensure reduction of transmission / reception processing complexity in ELAA systems and to perform multiplexing of user devices not only exploiting from non-overlapping VRs but also from overlapping VRs. BACKGROUND OF THE INVENTION Within the wireless networks, to improve the spectral efficiency as well as the spatial resolutions, use of larger antenna arrays with respect to the current massive multiple-inputs multiple-outputs (mMIMO) systems becomes widespread. Such larger arrays are referred in the literature with different names, such as extra-large antenna array (ELAA), extra-large MIMO (XL-MIMO), ultra-massive MIMO (UM-MIMO), extremely large aperture massive MIMO (xMaMIMO), etc. Since ELAAs have large aperture sizes, they can effectuate several new channel characteristics. Furthermore, thanks to transceiver architecture of ELAA used in the communication systems (such as base stations), most of the user devices and scatterers are able to fall within the near-field region of the communication systems. Accordingly, the near-field of an antenna array is defined as the region where the signal propagates in a distance smaller than the Fraunhofer distance (the Fraunhofer distance is defined as ^^=^^^^ , where D is the array aperture size and λ is the wavelength of the signal) of the array.In the near-field, a non-stationary channel is observed across the array, which is called as array non-stationarity and which is a by-product of two fundamental phenomena; spherical- wavefront (SW) propagation and the cluster visibility region (VR) across the array. In the near-field, electromagnetic waves propagate with SW instead of the traditional planar wavefront. Accordingly, the curvature of the SW induces an extra phase shift to each array element (as a function of the element’s index) across ELAA. It also induces different angles of arrival (AoAs) to each element which makes the received signal at each element experience different effective aperture areas and polarization mismatch losses. Additionally, in a complex propagation environment, different portions of the ELAA may be exposed to distinct sets of blockages and scatterers / clusters (i.e. different VRs) and thus experience different channel characteristics. Therefore, these two phenomena, i.e., SW and VR, cause significant variation of the channel parameters, in terms of received power, path gain, AoA, K-factor, small-scale fading, etc., across the array elements even in the poor scattering environment. In order to deal with the VR phenomenon, in the prior art, a subarray-based ELAA architecture is widely used. In an exemplary embodiment of the prior art, each user device, based on its location, is associated with a certain VR(s) on the ELAA. Thus, array elements of the ELAA falling within the VR of a given user device is used to serve that user device. In this way, multiple users are being simultaneously served through different subsets of the array elements of ELAA based on their VRs for multiple access and / or the initial random access. By using VRs the processing of the received signal is able to be simplified. Since the channel statistics vary significantly between the VRs, highly complex signal processing approach would be required to equalize and detect the desired information. Therefore, the subarray-based approach allows the VR-based received signal processing through the traditional techniques and combine them later. Second, the subarray-based approach inherently paves the way for the VR-based user / service multiplexing. In this case, each subarray can be scheduled to serve different user based on its visibility with respect to the user location. The signal on each subarray can be processed independently to detect the signal of the intended user. However, these state-of-the art VR-based multiple access approaches relies on the naturally occurring VRs, i.e., the VRs observed at ELAA as a function of the random environmental scatterers and user device locations with respect to those scatterers and the ELAA. In practical scenarios, these VRs are not completely separable from each other since they are generally fully or partially overlapping and this leads to interference problem and also complicates the subarray allocation / assignment process. In order to deal with the interference problem, two main approaches are proposed. The first one is “turning off” the array (antenna) elements of ELAA that experience strong overlapping between the VRs. In an exemplary embodiment, the pilot collision (i.e., interference) is avoided during the random-access procedures in the ELAA based networks by proposing a VR-aware strongest user collision resolution (SUCRe) protocol. The protocol schedules the same pilot to more than one user device as long as the user devices have non- overlapping VRs on the ELAA. While this approach can potentially reduce the random- access latency, it is an opportunistic based approach since the network has no control over the occurrence of the non-overlapping VRs. The second one employs interference cancellation mechanisms to deal with the interference between the VRs. For example, in this approach, the successive interference cancellation (SIC)-based signal detection among the subarrays is employed. However, since SIC does not allow a simultaneous processing of the subarrays, long processing delays as well as error propagation problems are inevitable in this approach. Apart from the interference problem, the computational complexity problem is also reveals while considering the extremely large sizes of ELAA. Accordingly, some studies focusing on the computational complexity aspect of the ELAA system are provided in the prior art. In these studies, mainly VR-based multi-user detection techniques are also, mainly to tackle the computational complexity problem. An exemplary study of the prior art proposes the randomized Kaczmarz algorithm (rKA)-based multi-user detection in different VRs (subarrays) that has been shown to reduce the computational complexity problem at the expense of some performance loss. In another study, a distributed receiver design based on the variational message passing approach where local processing units are introduced to facilitate parallel processing of the subarrays signals which then share their output with the central processing unit, is disclosed. VRs are being considered as extra resources for user multiplexing in ELAA-based networks. Based on user device’s location and distribution of scatterers in the propagation, each user device can have different number of VRs and the VRs may be of different sizes, partially or fully overlapping with each other or with the VRs of other user devices. Therefore, effective utilization of the VRs for user multiplexing requires full information about VRs of each user device. Availability of such information will not only minimize the interference problem but also pave a way for better VR-aware scheduling technique that may improve fairness among the user devices in accessing the network. However, the techniques that facilitate acquisition of VRs characteristics are still limited. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result. BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a method for identifying visibility regions (VRs) in an Extra Large Antenna Arrays (ELAA) based communication networks to eliminate the above- mentioned disadvantages and bring new advantages to the relevant technical field. An object of the invention is to develop a method for identifying visibility regions (VRs) of the user devices to deal with interference problem in an Extra Large Antenna Array (ELAA) based communication networks. Another object of the invention is to develop a method for controlling visibility regions (VRs) in an Extra Large Antenna Array (ELAA) based communication networks to ensure reduction of transmission / reception processing complexity in ELAA systems. Yet another object of the invention is to develop a method for controlling visibility regions (VRs) in an Extra-Large Antenna Array (ELAA) based communication networks to perform multiplexing of user devices not only exploiting from non-overlapping VRs but also from overlapping VRs. To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method which is suitable for being used with a communication network comprising § at least one communication device equipped with at least one ELAA which has a plurality of array elements used for creating subarrays of ELAA; § at least one user device which is able to communicate with the ELAA by transmitting signals to ELAA such that the transmitted signals are received from a group of array elements that is defining the visibility region (VR) of that user device, wherein the user device is able to communicate with ELAA directly and / or over at least one scatterer / cluster of scatterers, wherein the method ensures identifying visibility regions (VRs) on the ELAA by detecting the information related with VRs and comprises the steps of: · omnidirectionally transmitting a pilot signal from the user device to the communication device for channel estimation; · omnidirectionally receiving the pilot signal by the ELAA of the communication device transmitted from the user device; · measuring, by the communication device, the received power across the array element in ELAA from the received signal and obtaining power distribution of the measured powers that are above a predefined threshold power in power domain; · estimating the channel frequency response by the communication device from the received pilot signal; · transforming the estimated channel frequency response to the beamspace domain; · extracting the VR-related information from the beamspace domain representation of the estimated and transformed channel frequency response; · identifying the VRs by using the information obtained from beamspace domain and from the power domain. Thanks to the method of the present invention, identification of VRs on the ELAA is able to be performed by reducing the process complexity and by ensuring more precise identification. DESCRIPTION OF THE DRAWINGS Exemplary embodiment of the method developed according to the present invention is illustrated in the attached drawings, wherein: Figure 1 is a schematic view of an embodiment communication network with which the method developed by the invention is suitable for use. Figure 2 is a flow diagram of the method developed by the invention. Figure 3 is an exemplary channel representation in the beamspace domain All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows: 100 ELAA 110 Array element 120 User device 130 Scatterer 140 VR 150 VR Birth point 160 VR Death point 200 omnidirectionally transmitting a pilot signal from the user device to the communication device 210 omnidirectionally receiving the pilot signal by the ELAA of the communication device transmitted from the user device 220 measuring the received power across the array element in ELAA from the received signal 230 estimating the channel frequency response by the communication device from the received pilot signal 240 transforming the estimated channel frequency response to the beamspace domain 250 extracting the VR related information from the beamspace representation of the estimated and transformed channel frequency response 260 identifying the VRs by using the information obtained from beamspace domain and from the power domain 300 Channel gain axis 310 Angle of Arrival (AoA) axis 320 Angle of Departure (AoD) axis 330 Peak / Beam 340 Width 350 Angle of maximum gain 360 Angle of 3dB gain 370 Maximum gain 3803dB gain DESCRIPTION OF THE INVENTION Within the wireless networks, extra-large antenna arrays (ELAAs) are used in the communication networks such as in the base stations. In the communication networks having ELAA system, different user devices may see different parts / portions of the array and / or user devices at different locations may see different scatterers (or clusters), and clusters at different locations may see different array parts. The part of array seen by a user device and / or a scatter / cluster of scatterers is termed as visibility region (VR). In the communication networks having ELAA system, VR-based design is used to reduce Transmission / Reception processing complexity in ELAA systems, since VRs facilitate dimension-reduced channels for easy baseband processing (Subarray-based processing). Furthermore, in these networks non-overlapping VRs can serve as extra spatial resources for user multiplexing without inter-user interference and overlapping VRs can also be exploited for user multiplexing with some interference cancellation mechanisms to improve the spectral efficiency. Accordingly, in order to exploit from VRs, they should first be identified such that the number and sizes of the VRs associated with each user device should be identified. However, the existing works that exploit VRs phenomenon assume the full knowledge of the VR distribution for each user. For that reason, the present invention provides a method for identifying visibility regions (VRs) in an Extra-Large Antenna Arrays (ELAA) based communication networks. The method developed by the invention is suitable for use with a communication network, an exemplary embodiment of which is given in figure 1, comprising at least one communication device (the communication device can be defined as an access point such as a base station) equipped with at least one ELAA (100) which has a plurality of array elements (110) (preferably in the form of uniform linear arrays) used for creating subarrays of ELAA (100); at least one user device (120) (such as smartphone, tablet, laptop computer etc.) which is able to communicate with the ELAA (100) by transmitting signals through ELAA (100) such that the transmitted signals are received from a group of array elements (110) that is defining the visibility region (VR (140)) of that user device (120), wherein the user device (120) is able to communicate with ELAA (100) directly and / or over at least one scatterer (130) (the scatterer (130) is an entity [the entity can be a device (for instance smart-scatterer like reconfigurable intelligent surface(RIS) / Smart repeaters / etc,) receiving signal from the user device (120) and transmitting the signal to the ELAA (100) and / or it can be an ordinary object such as building / people / car / tree etc.] within the propagation environment [for instance in the network] that interact with the signal transmitted from the user device (120) by scattering / reflecting / diffracting / transmitting etc. it to ensure communication between the ELAA (100) and the user device (120)) and wherein the user device (120) is preferably equipped with an array of antenna elements preferably in the form of a uniform linear array. The method of the present invention, an exemplary flow chart of which is given in figure 2, which ensures identifying visibility regions (VRs (140)) on the ELAA (100) by detecting the details of VRs (140) (such as number of VRs (140), sizes of VRs (140), and scatterer (130) / cluster of scatterers (130) associated with each of them), comprises the steps of: · omnidirectionally transmitting a pilot signal (the pilot signal can be any signal that is used for channel estimation, which is known by both the user device and the communication device) from the user device (120) to the communication device (200) for channel estimation; · omnidirectionally receiving the pilot signal by the ELAA (100) of the communication device transmitted from the user device (120) (210); · measuring, by the communication device, the received power across the array element (110) in ELAA (100) from the received signal (220) and obtaining power distribution of the measured powers that are above a predefined threshold power in power domain; · estimating the channel frequency response by the communication device (for example by a processor provided in the communication device) from the received pilot signal (230); · transforming the estimated channel frequency response to the beamspace domain (240) (an exemplary embodiment is given in figure 3); · extracting the VR-related information from the beamspace domain representation of the estimated and transformed channel frequency response (250); · identifying the VRs (140) by using the information obtained from beamspace domain and from the power domain (260) such that the VR-related information provided by the beamspace domain are maximum possible number of VRs (140) in the beamspace domain, angular information of those VRs (140) and sizes of those VRs (140), and the VR-related information provided by the power domain are number of VRs (140) in the power domain, sizes of those VRs (140) and birth and death indices of each of those VRs (140). In the method of the present invention, VRs (140) on the ELAA (100) is able to be determined by combining two distinct VR-related information obtained from power domain and beamspace domain. By starting the method, a pilot signal which is a signal that is used for channel estimation and which is known by both the user device (120) and the communication device is sent from the user device (120) to the ELAA (100) omnidirectionally and received by the ELAA (100) omnidirectionally. Sending the pilot signal omnidirectionally makes sure that the effect of all significant scatterer (130) in the propagation environment (i.e. in the communication network) that are visible to the user device (120) is captured. Furthermore, the omnidirectional reception of the pilot signal by the ELAA (100) ensures that all multipath from all possible directions that may cause distinct or overlapping VRs (140) are capture by the array. So, anything that can interact with the signal can be seen on the receiver side. After reception of the pilot signal, communication device measures the power, compares the power with a predefined threshold power related with the received pilot signal, and obtains a power distribution of the measured powers that are above the predefined threshold power in power domain. Then, the communication device estimates the channel frequency response (channel frequency response estimation can be done by any suitable technique provided in the prior art) by using the received pilot signal and transforms the estimated channel frequency response to the beamspace domain (channel frequency response transformation into the beamspace domain can be done by any suitable technique provided in the prior art). The predefined threshold power is the design parameter that can be determined during network design process. Accordingly, it could be above the noise threshold of the system or any other adjustment can be done to make sure to improve the accuracy of the detection. Both power domain and beamspace domain give information about the VRs (140) on the ELAA (100). By combining these information, VRs (140) are able to be identified. Thanks to the method of the present invention, by using beamspace channel representation, the complexity of beams weeping, which is a known literature method used for VR (140) identification, is able to be reduced and / or avoided because beamspace conversion process is done at the communication device side, not at the user device (120) side. Furthermore, by combining beamspace domain and power domain, more information about the VRs (140) is able to be extracted. In a preferable embodiment of the present invention, the received power measurement step further comprises the steps of: determining the adjacent array elements (110) whose power is above the predefined threshold power and defining those as a VR (140) of a user device (120) on the ELAA (100); determining the non-adjacent groups of array elements (110) whose power is above the predefined threshold power and defining those as non-overlapping VRs (140) of the said user device (120); determining the size of each VR (140) by detecting the number of determined adjacent array elements (110) in the defined VR (140); and determining the VR birth point (150) and the VR death point (160) of each VR (140), wherein the VR birth point (150) is a point on the array where the VR (140) starts to appear on the array and VR death point (160) is a point where the VR (140) ends. Thanks to the embodiment, the number of non-overlapping VRs (140), the size of these VRs (140), the VR birth point (150) and the VR death point (160) of those VRs (140) are able to be determined from the power domain. For instance, by measuring the power, if it is determined that there are 10 number of adjacent array elements (110) whose power is above the predefined threshold power, then the part of the ELAA (100) having that 10 adjacent array elements (110) is defined as a VR (140) of a user device (120) whose pilot signal is received by that part and accordingly the size of the VR (140) would be 10. The most upper array element (110) of that 10 adjacent array element (100) would be the VR birth point (150) and the most lower array element (100) of that 10 adjacent array element (110) would be the VR death point (160). By determining the VR birth point (150) and the VR death point (160), the location of the VR (140) on the ELAA (100) is able to be detected. If there is another group of adjacent array elements (110) with a number of 6 for instance and whose power is above the predefined threshold power, then these 6 elements group is also defined as another VR (140) of the same user device (120). This can be determined such that while there is a different group of array elements (110) between these 10- numbered group and 6-numbered group, whose power is below the predefined threshold power. So, as can be seen from figure 1, a user device (120) can have more than one visibility region (VR (140)) based on how the power of the pilot signal related with that user device (120) is distributed over the ELAA (100). Accordingly, it can be said that, for determining VRs (140) of different user devices (120), different predefined threshold power values can be used. In detail, for different pilot signals of the different user devices (120), the communication device comprises different predefined threshold power values, provided in a memory for instance. Additionally same predefined threshold can also be used to determine VRs (140) of different user devices (120) depending on the type of services that user devices (120) are performing. For instance, different services may have different sensitivity to interference or noise, so they would require different threshold level however, same services may require same threshold level. Accordingly, threshold values are determined according to the design parameters. By the embodiment, the presence of multiple VRs (140) is able to be identified only if these VRs (140) are non-overlapping. In another preferred embodiment of the present invention, the extracting the VR-related information from the beamspace domain representation (an exemplary embodiment is given in figure 3) step further comprises the steps of: determining the number of peaks (330) (beams / paths / principle components) observed in the beamspace domain (the beam space domain comprises a channel gain axis (300), an Angle of Arrival (AoA) axis (310) and an Angle of Departure (AoD) axis (320)) and defining this as a maximum number of VRs (140) that the user device (120) can have with respect to its current location; obtaining angular locations of the scatterer (130) with respect to the communication device (i.e. ELAA (100)) and to the user device (120) in the network by determining the angular coordinates, on the angle of arrival (AoA) axis (310) (related to the user device side) and the angle of departure (AoD) axis (320) (related to the communication device side), of each of the peaks (330); obtaining the size of a VR (140) associated with a peak (330) in the beamspace domain by calculating the width (340) of that peak (330). Thanks to this embodiment, the maximum possible number of VRs (140) (this is the maximum possible number since overlapping / non-overlapping distinguishment cannot be done and since the total number of VRs (140) cannot exceed the number of beams / paths / principle components that cause them), locations of scatterer (130) and sizes of the VRs (140) are able to be obtained. In detail, the number of peaks (330) (beams / paths / principle components) observed in the beamspace domain gives the maximum possible number of VRs (140), i.e. ^^^^^^, that the user device (120) can have with respect to its current location. The angular coordinates (^^^^, ^^^^) on the angle of arrival (AoA) axis (310) and angle of departure (AoD) axis (320), respectively, of each of the peaks (330) gives the angular locations of the environmental scatterer (130) with respect to the communication device and the user device (120). These scatterer (130) are the potential causes of different VRs (140) on ELAA (100). Therefore, this knowledge about their locations with respect to the communication device and the user device (120) is very crucial for controlling the inter-VRs (140) interference for the same user device (120) or between different user devices (120), exploiting VRs (140) as radio resources, etc. In addition to these, the width (340) of a given peak (330) in the beamspace domain gives the size of the VR (140) on the ELAA (100) associated with it (i.e. the number of the array elements (110) within the VR (140)). This is due to the fact that beamwidth is inversely proportional to the aperture size of the array used to generate it. For example, if a 3dB beamwidth Ω^^^for a given peak (330) is considered, the size, i.e. ^^^^, of the VR (140)associated with it can be given by the below equation (1) where ^ and ^ are the system operational carrier wavelength and inter-array element spacing in ELAA (100) respectively. The 3dB beamwidth Ω^^^of a given peak (330) can befound by the below equation (2) where ^^^^(angle of maximum gain (350)) and ^^^^^^^(angle of 3dB gain (360)) are angles associated with the directions of the directions with maximum gain (370), i.e. ^^^^, and the 3dB gain (380), ^^^^, 3dB below the ^^^^of the peak (330) on the angle of arrival axis (310). ^^^^can be calculated for all peaks (330) observed in the beamspace domain by using the above discussed approach or any other approach available in the literature. The VR-related information provided by the beamspace domain comprises maximum possible number of VRs (140) ^^^^^^; angular information related with angle of arrival and angle of departure ^,^ = [^^ ^^^^(1),^^^^(1)^, ^^^^^(2),^^^^(2)^, … , ^^^^^(^^^^^ ),^^^^(^^^^^^ )^]; andsizes of each VR (140) ^^ = [^^ (1),^^ ( ) ^ ^^^ ^^ ^^ 2 , … ,^^^ (^^^^^ )].Accordingly, the VR-related information provided by the power domain comprises maximum possible number of VRs (140) ^^^^^^; sizes of each birth and death indices (VR birth point (150) and VR death point (160) of each VR With respect to these, in another embodiment of the present invention, the step of identifying the VRs (140) by using the information obtained from beamspace domain and from the power domain comprises the steps of a) if the maximum possible number of VRs (140) obtained from power domain and beamspace domain is equal to each other and if the sizes of each VR (140) obtained from beamspace domain are distinguishable from each other (i.e. ∈ {1,2, … ,^^^^^^ } and ^ ≠ ^), determining all detected VRs(140) as non-overlapping and matching directly the power domain parameters and the beamspace domain parameters of the VRs (140) to each other to establish final VR (140) parameters such that ·Number of VRs (140) ^^^ ^ ^^^ = ^^^^^ = ^^^^^ ,· ^^^ VR (140) size ^^^(^) = ^^^^ (^) ≈ ^^^^ (^),∀^ ∈ {1,2, … ,^^^^^},· VR birth and VR death indices of an ^^^ VR (140) is given by^^^(^),∀^ ∈ {1,2, … ,^^^^^},· Angular locations of the scatter device / cluster associated with an ^^^VR (140) is given by ^^^^^(^),^^^^(^)^,∀^ ∈ {1,2, … ,^^^^^}; b) if the maximum possible number of VRs (140) obtained from power domain and beamspace domain is equal to each other, if the sizes of some number of VRs (140) obtained from beamspace domain are distinguishable from each other (i.e.^^^^ (^) ≠ ^^^^ (^),∀(^, ^) ∈ {1,2, … ,^^^^^^ } and ^ ≠ ^) and if the sizes of some “K”number VRs (140) (such as the rest of the VRs (140)) are equal to each other (i.e.^^^^ (^) = ^^^^ (^), for some (^, ^) ∈ {1,2, … ,^^^^^^ } and ^ ≠ ^), determining alldetected VRs (140) as non-overlapping, matching directly the power domain parameters and the beamspace domain parameters of the VRs (140) to each other to establish final VR (140) parameters for the number of VRs (140) sizes of which are distinguishable from each other, as given above step “a” and implementing the following sub-steps to establish final VR (140) parameters for the “K” number of VRs (140) sizes of which are equal · exploiting the angular information ^, requesting from the user device (120) to sequentially transmit ^ − 1 beams in the directions ^^^^(^),∀^ ∈ {1,2, … ,^ − 1} associated with the formation of VRs (140) with thesame sizes, · receiving by the communication device each of the transmitted beam and identifying the VR birth point (150) and the VR death point (160) to find the indices ^^^(^),^^(^)^ of the ^^^VR (140) associated with angular information · once the angular information and the VR birth and VR death indices are resolved for the VRs (140) with the same sizes, establishing the final VR (140) parameters as provided in the step “a”; c) if the maximum possible number of VRs (140) obtained from power domain is smaller than the maximum possible number of VRs (140) obtained from beamspace domain (i.e. ^^^^^^ < ^^^^^^ ), determining that some of the VRs(140) are fully or partially overlapping and implementing the following sub-steps to establish final VR (140) parameters · exploiting the angular information ^, requesting from the user device (120) to sequentially transmit beams in the directions ∀^ ∈{1,2, … ,^^^^^^ },· receiving by the communication device each of the transmitted beam and determining the adjacent array elements (110) whose power is above the predefined threshold power and defining those as a VR (140) of a user device (120) on the ELAA (100), determining the size of each VR (140) by detecting the number of determined adjacent array elements (110) in the defined VR (140), and determining the VR birth point (150) and VR death point (160) of each VR (140), · once the power domain information related to the overlapping VRs (140) are resolved, establishing the final VR (140) parameters as provided in the step “a”. The step “a” represents the base case where all VRs (140) are non-overlapping. Accordingly, direct matching of the power and beamspace domain parameters of the VRs (140) can be done to establish final VR (140) parameters. The step “b” represents the case where all VRs (140) are non-overlapping but some of them (i.e. “K” number of them) have the same size. The VRs (140) whose sizes are distinguishable from each other are treated as in step “a”. On the other hand, for the “K” number of VRs (140), which are with the same sizes, it is difficult to correctly match the angular information ^^^^^(^),^^^^(^)^ and the VRbirth and VR death indices ^^^(^),^^(^)^,∀^ ∈ {1,2, … ,^} obtained in beamspace domainbecause it is not known which one is related to which one. Accordingly, the user device (120) is requested to transmit a beam through particular directions, Θ, that have been detected in the beamspace domain associated with the formation of the VRs (140) with the same sizes. The communication device receives that beam and thus it is known that this particular beam is related to this particular angle, because the user device (120) has been told by the communication device to transmit this particular beam at this particular angle. Since the beams are transmitted sequentially, so for each one of them, where the visibility region occurs is detected one by one on the ELAA (100). Therefore, it is able to detected for a particular angle related to which part of the ELAA (100). This process performed for all “K” number of VRs (140), one by one and therefore all VRs (140) are able to be resolved. The step “c” represents the case where that some of the VRs (140) are fully or partially overlapping (the areas that could not be resolved in the power domain) which makes it impossible to identify / distinguish them through power measurement. To resolve the information of the overlapping the angle information obtained from the beamspace domain are exploited, and then same as step “b”, user device (120) is requested to sequentially transmit beams in those directions in which the potentially overlapping VRs (140) are detected. The beams are received by the communication device one-by-one and then necessary measurements according to power domain are performed one-by-one. Therefore, when it is transmitted one by one, it is easy to get the size of each individual visibility region among those which are overlapping. Thanks to the method of the present invention, identification of VRs (140) on the ELAA (100) is able to be performed by reducing the process complexity and by ensuring more precise identification.

Claims

CLAIMS 1. A method which is suitable for being used with a communication network comprising § at least one communication device equipped with at least one ELAA (100) which has a plurality of array elements (110); § at least one user device (120) which is able to communicate with the ELAA (100) by transmitting signals through ELAA (100) such that the transmitted signals are received from a group of array elements (110) that is defining the visibility region (VR (140)) of that user device (120), wherein the user device (120) is able to communicate with ELAA (100) directly and / or over at least one scatterer (130), characterized in that the method ensures identifying visibility regions (VRs (140)) on the ELAA (100) by detecting the information related with VRs (140) and comprises the steps of: · omnidirectionally transmitting a pilot signal from the user device (120) to the communication device (200) for channel estimation; · omnidirectionally receiving the pilot signal by the ELAA (100) of the communication device transmitted from the user device (120) (210); · measuring, by the communication device, the received power across the array element (110) in ELAA (100) from the received signal (220) and obtaining power distribution of the measured powers that are above a predefined threshold power in power domain; · estimating the channel frequency response by the communication device from the received pilot signal (230); · transforming the estimated channel frequency response to the beamspace domain (240); · extracting the VR-related information from the beamspace domain representation of the estimated and transformed channel (250); · identifying the VRs (140) by using the information obtained from beamspace domain and from the power domain (260).

2. The method according to claim 1 wherein; the information related with VR (140) comprises at least one of number of VRs (140), sizes of VRs (140), and scatterer (130) / cluster of scatterers (130) associated with each of them.

3. The method according to any one of the preceding claims wherein; the power measurement step further comprises the steps of: · determining the adjacent array elements (110) whose power is above the predefined threshold power and defining those as a VR (140) of a user device (120) on the ELAA (100); · determining the non-adjacent groups of array elements (110) whose power is above the predefined threshold power and defining those as non-overlapping VRs (140) of the said user device (120); · determining the size of each VR (140) by detecting the number of determined adjacent array elements (140) in the defined VR (140); and · determining the VR birth point (150) and the VR death point (160) of each VR (140), wherein the VR birth point (150) is a point on the array where the VR (140) starts to appear on the array and VR death point (160) is a point where the VR (140) ends.

4. The method according to any one of the preceding claims wherein; the extracting the VR-related information from the beamspace domain representation step further comprises the steps of: · determining the number of peaks (330) observed in the beamspace domain and defining this as a maximum number of VRs (140) that the user device (120) can have with respect to its current location; · obtaining angular locations of the scatter devices (130) with respect to the communication device and to the user device (120) in the network by determining the angular coordinates, on the angle of arrival (AoA) axis (310) and the angle of departure (AoD) axis (320), of each of the peaks (330); · obtaining the size of a VR (140) associated with a peak (330) in the beamspace domain by calculating the width (340) of that peak (330).

5. The method according to any one of the preceding claims wherein; the VR-related information provided by the beamspace domain comprises · maximum possible number of VRs (140) ^^^^^^; ·angular information related with angle of arrival and angle of departure ^,and ·sizes of each6. The method according to any one of the preceding claims wherein; the VR-related information provided by the power domain comprises · maximum possible number of VRs (140) ^^^^^^; ·sizes of each VR (140) ^^^^ =; and· VR birth and VR death indices of each VR ^^^,7. The method according to claim 6 wherein; the step of identifying the VRs (140) by using the information obtained from beamspace domain and from the power domain comprises the steps of a) if the maximum possible number of VRs (140) obtained from power domain and beamspace domain is equal to each other and if the sizes of each VR (140) obtained from beamspace domain are distinguishable from each other (i.e.∈ {1,2, … ,^^^^^^ } and ^ ≠ ^), determining all detected(140) as non-overlapping and matching directly the power domain parameters and the beamspace domain parameters of the VRs (140) to each other to establish final VR (140) parameters such that ·Number of VRs (140) ^^^ = ^ ^^^ ^^^^^ = ^^^^^ ,· ^^^ VR (140) size ^^^(^) = ^^^^ (^) ≈ ^^^^ (^),∀^ ∈ {1,2, … ,^^^^^},· VR birth and VR death indices of an ^^^ VR (140) is given by^^^(^),∀^ ∈ {1,2, … ,^^^^^},· Angular locations of the scatter device / cluster associated with an ^^^VR (140) is givenb) if the maximum possible number of VRs (140) obtained from power domain and beamspace domain is equal to each other, if the sizes of some number of VRs (140) obtained from beamspace domain are distinguishable from each other (i.e.the sizes of somenumber VRs (140) (such as the rest of the VRs (140)) are equal to each other (i.e.^^ (^) = ^^^^ (^), for somedeterminingdetected VRs (140) as non-overlapping, matching directly the power domain parameters and the beamspace domain parameters of the VRs (140) to each other to establish final VR (140) parameters for the number of VRs (140) sizes of which are distinguishable from each other, as given above step “a” and implementing thefollowing sub-steps to establish final VR (140) parameters for the “K” number of VRs (140) sizes of which are equal · exploiting the angular information ^, requesting from the user device (120) to sequentially transmit ^ − 1 beams in the directions ^^^^(^),∀^ ∈ {1,2, … ,^ − 1} associated with the formation of VRs (140) with thesame sizes, · receiving by the communication device each of the transmitted beam and identifying the VR birth point (150) and the VR death point (160) to find the indices^^^(^),^^(^)^of the ^^^VR (140) associated with angular information· once the angular information and the VR birth and VR death indices are resolved for the VRs (140) with the same sizes, establishing the final VR (140) parameters as provided in the step “a”; c) if the maximum possible number of VRs (140) obtained from power domain is smaller than the maximum possible number of VRs (140) obtained from beamspace domain (i.e. ^^^^^^ < ^^^^^^ ), determining that some of the VRs(140) are fully or partially overlapping and implementing the following sub-steps to establish final VR (140) parameters · exploiting the angular information ^, requesting from the user device (120) to sequentially transmit beams in the directions ^^^^(^), ∀^ ∈{1,2, … ,^^^^^^ },· receiving by the communication device each of the transmitted beam and determining the adjacent array elements (110) whose power is above the predefined threshold power and defining those as a VR (140) of a user device (120) on the ELAA (100), determining the size of each VR (140) by detecting the number of determined adjacent array elements (110) in the defined VR (140), and determining the VR birth point (150) and VR death point (160) of each VR (140), · once the power domain information related to the overlapping VRs (140) are resolved, establishing the final VR (140) parameters as provided in the step “a”.

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