A method for controlling visibility regions in ELAA-based wireless networks and a wireless network therefor

Abstract

The present invention provides a method for minimizing interference problem occurs between VRs (2b) of a communication device (1) provided in a communication network. The method ensures signal transmission from a user device (4) to the communication device (1) over a smart surface (3) without providing a direct communication link between the user device (4) and the communication device (1). The method comprises the steps of calculating a tuning information that is necessary for the active elements of the smart surface (3) to reflect / retransmit communication signals received from the user devices (4) to the subarrays (2a) of ELAA (2) of the communication device (1); sending the calculated tuning information from the communication device (1) to the smart surface (3) for configuring the active elements of the smart surface (3) to receive communication signals from user devices (4) and send those signals as reflection signals to the communication device (1) in a manner eliminating interference of the different VRs (2b); starting the communication between user devices (4) and the communication device (1) over the smart surface (3).

Description

[0001] A METHOD FOR CONTROLLING VISIBILITY REGIONS IN ELAA-BASED WIRELESS NETWORKS AND A WIRELESS NETWORK THEREFOR

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for controlling visibility regions (VRs) and easily multiplexing user devices to deal with interference in an Extra Large Antenna Arrays (ELAA) based wireless networks and the wireless networks for performing the method.

[0004] BACKGROUND OF THE INVENTION

[0005] 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.

[0006] Since ELAAs have large aperture sizes, they can effectuate several new channel characteristics. Furthermore, thanks to transceiver architecture of ELAA used in the base stations, most of the user devices and scatterers are able to fall within the near-field region of the base station. 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 d_F=(2DA2) / A, where D is the array aperture size and A 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 byproduct 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.

[0007] 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.

[0008] 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 to user scheduling process.

[0009] 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 nonoverlapping VRs on the ELAA. While this approach can potentially reduce the randomaccess 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 (SlC)-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. Furthermore, apart from the interference problem, considering the extremely large sizes of ELAA, the computational complexity problem is inevitable.

[0010] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0011] BRIEF DESCRIPTION OF THE INVENTION

[0012] The present invention relates to a method for controlling visibility regions (VRs) in an Extra Large Antenna Arrays (ELAA) based communication networks and the communication networks for performing the method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0013] An object of the invention is to develop a method for controlling visibility regions (VRs) and easily multiplexing user devices to deal with interference problem in an Extra Large Antenna Arrays (ELAA) based communication networks and communication networks for performing the method.

[0014] Another object of the invention is to develop a method for controlling visibility regions (VRs) and multiplexing user devices in an Extra Large Antenna Arrays (ELAA) based communication networks by reducing computational complexity problem and communication networks for performing the method.

[0015] Yet another object of the invention is to develop a method minimising the need for complex, iterative interference cancellation procedures which suffer error propagation problems while eliminating the interference phenomenon and communication networks for performing the method.

[0016] The other object of the invention is to develop a method to facilitate an interference free VRs-based communication and communication networks for performing the method.

[0017] 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

[0018] §at least one communication device equipped with ELAA which has a plurality of array elements used for creating subarrays of ELAA; § at least one smart surface which is a smart / controllable entity that can be placed within the propagation environment of the communication device to help the communication process in one way or another, which is connected to the communication device with wired and / or wireless manner, which is controlled by the communication device, which has a plurality of active elements that are able to be configured by the communication device, which is in the near-field of the ELAA and can be in the far-field of the subarrays of the ELAA, preferably, dimension of which is in the order of the traditional mMIMO system and which has a line-of-sight with communication device; and

[0019] §at least one user device which is able to communicate with the smart surface, which is in the far-field of the smart surface such that all active elements are visible to the user device’s signal wherein the method ensures signal transmission from the user device to communication device over smart surface without providing a direct communication link between the user device and the communication device and comprises the steps of:

[0020] • calculating a tuning information that is necessary for the active elements of the smart surface to reflect / retransmit communication signals received from the user devices to the subarrays of ELAA of the communication device by ensuring that a subarray of the ELAA is assigned to only one user device, wherein the calculation is performed by a control unit of the communication device;

[0021] • sending the calculated tuning information from the communication device to the smart surface for configuring the active elements of the smart surface to receive communication signals from user devices and retransmit / reflect received communication signals as reflection signals towards communication device in a manner eliminating interference of the different VRs;

[0022] • following the configuration of the active elements, starting the communication between user devices and the communication device over the smart surface without providing a direct communication link between the user device and the communication device.

[0023] In addition, within the present invention a communication network configured for performing the above-mentioned method is provided. The communication network comprises § at least one communication device equipped with ELAA which has a plurality of array elements used for creating subarrays of ELAA;

[0024] §at least one smart surface which is a smart / controllable entity that can be placed within the propagation environment of the communication device, which is connected to the communication device with wired and / or wireless manner, which is controlled by the communication device, which has a plurality of active elements that are able to be configured by the communication device, which is in the near-field of the ELAA and can be in the far-field of the subarrays of the ELAA, preferably, dimension of which is in the order of the traditional mMIMO system and which has a line-of-sight with communication device;

[0025] §and at least one user device which is able to communicate with the smart surface, which is in the far-field of the smart surface such that all active elements are visible to the user device’s signal, wherein the ELAA comprises an adaptive switching mechanism which generates subarrays by grouping the array elements with respect to the size of the corresponding VR for an associated user device wherein the adaptive switching mechanism comprises switches that connect the array elements belonging to a given subarray to the same RF chain and / or RF combiner; and the communication device comprises at least one control unit for performing the steps of the above-mentioned method.

[0026] Thanks to the method and the communication network of the present invention, full control of the number and distribution of the VRs on ELAA is given to the network. Accordingly, possibility of occurrence of interference between VRs is able to be minimized and this makes the VR based scheduling / user multiplexing easier. Since the VR scheduling and control only depends on the relative location of the smart surface and ELAA, the changing of the user-link does not necessitate the recalculation of VRs. Therefore, a robust method even for mobile users is obtained.

[0027] DESCRIPTION OF THE DRAWINGS

[0028] Exemplary embodiment of the method developed according to the present invention is illustrated in the attached drawings, wherein:

[0029] 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 block illustration of an ELAA transceiver.

[0030] Figure 3 is a schematic representation for calculating angle of departure for each subarray.

[0031] Figure 4 is a schematic representation for optimizing beamwidth of each beam coming from smart surface to the related subarray of ELAA.

[0032] Figure 5 and Figure 6 are graphical views of the received signal power analysis over antenna array at the ELAA side for a single subarray.

[0033] Figure 7 is a graphical view of capacity versus subarray indices analysis in ELAA systems

[0034] Figure 8 is a schematic view of another embodiment of a communication network with which the method developed by the invention is suitable for use.

[0035] All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:

[0036] 1 Communication device

[0037] 1 a Control unit

[0038] 2 ELAA

[0039] 2a Subarray

[0040] 2b VR

[0041] 2c Array element

[0042] 3 Smart surface

[0043] 4 User device

[0044] 5 Adaptive switching mechanism

[0045] 6 RF combiner

[0046] 7 Rf chain

[0047] 8 Baseband processing

[0048] 9 Beam

[0049] 9 AoD of a signal from smart surface (3) to the ELAA (2) with respect to the centre of the whole array

[0050] 9UAoD of a reflection signal required to focus the uthuser device to the uthsubarray of the ELAA d2Dthe horizontal distance between the smart surface and the ELAA

[0051] N Number of array elements in ELAA

[0052] NuNumber of array elements in the uthsubarray of ELAA ncthe index of the centremost array element in ELAA ncuthe index of the centremost array element in the uthsubarray of ELAA duthe vertical distance between the centremost array element in ELAA and the centremost array element in the uthsubarray of ELAA fl3dB3dB beamwidth

[0053] A0UAngular span

[0054] DESCRIPTION OF THE INVENTION

[0055] Within the wireless networks, to improve the spectral efficiency as well as the spatial resolutions, extra-large antenna arrays (ELAAs) are expected to be used in the communication networks such as in the base stations. However, during communication with user devices, Visibility Regions (VRs) of the ELAAs can overlap with each other and can cause interference problems. In the prior art, this interference problem is dealt with by simply applying some interference cancellation applications. However, the existing studies in the literature establish the VR-aware communication in ELAA-based network by only considering the naturally / randomly occurring VRs. Nothing has been done to gain control over the occurrence and distributions of these VRs in favour of the considered communication scenario. Consequently, the interference and computational complexity issues have become critical and may hinder the realization of the full potential of ELAA. For that reason, the present invention provides a method for controlling visibility regions (VRs) and multiplexing user devices to deal with interference in an Extra Large Antenna Arrays (ELAA) based communication networks.

[0056] 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 (1 ) (such as base station) equipped with ELAA (2) which has a plurality of array elements (2c) used for creating subarrays (2a) of ELAA (2); at least one smart surface (3) which is a smart / controllable entity that can be placed within the propagation environment of the communication device (1 ) to help the communication process in one way or another (for instance, but not limited to, a reconfigurable intelligent surface (RIS), smart relays / repeaters, network-controlled repeaters (NCR) etc.), which is connected to the communication device (1 ) with wired and / or wireless manner, which is controlled by the communication device (1 ), which has a plurality of active elements, such as antennas and / or reflective elements, that are able to be configured by the communication device (1 ), which is in the near-field of the ELAA (2) and can be in the far-field of the subarrays (2a) of the ELAA (2), dimension of which is in the order of the traditional mMIMO (massive multiple-input multiple-output) system and which has a line-of-sight with communication device (1 ) (the smart surface (3) side has active elements equal to or larger than the maximum number of array elements (2c) needs to be activated for a given subarray (2a)); and at least one user device (4) (such as smartphone, tablet, laptop computer etc.) which is able to communicate with the smart surface (3), which is in the far-field of the smart surface (3) such that all active elements are visible to the user device’s (4) signal. The method of the present invention, which ensures signal transmission from the user device (4) to communication device (1 ) over smart surface (3) without providing a direct communication link between the user device (4) and the communication device (1 ), comprises the steps of: calculating a tuning information that is necessary for the active elements of the smart surface (3) to reflect / retransmit communication signals received from the user devices (4) to the subarrays (2a) of ELAA (2) of the communication device (1 ) by ensuring that a subarray (2a) of the ELAA (2) is assigned to only one user device (4) for an uplink transmission time interval, wherein the calculation is performed by a control unit (1 a) of the communication device (1 ); sending the calculated tuning information from the communication device (1 ) to the smart surface (3) for configuring the active elements of the smart surface (3) to receive communication signals from user devices (4) and retransmit / reflect received communication signals as reflection signals towards communication device (1 ) in a manner eliminating interference of the different VRs (2b); following the configuration of the active elements, starting the communication between user devices (4) and the communication device (1 ) over the smart surface (3) without providing a direct communication link between the user device (4) and the communication device (1 ).

[0057] Thanks to the method of the present invention, a mechanism for controlling the VRs (2b) on the ELAA (2) is proposed. Especially, in the wireless communication network, with which the method of the present invention is performed, the communication device (1 ) is a device which is able to communicate (for instance capable to receive signals and broadcast signals) with the smart surface (3) and preferably with the user device (4) and, which can have the functions of a Node B, a gNB, an access point, a radio head, a transmission / reception point, a 5G Node B. More preferably the communication device (1 ) is a base station. The smart surface (3) acts as relay or intelligent / controllable scatterer of the electromagnetic signals to control the VRs (2b) on ELAA (2). In other words, with respect to the VRs (2b) of ELAA (2), the active elements of the smart surface (3) are configured such that the active element that has received a communication signal from a user device (4) transmits this signal to a VR (2b) that is assigned to that user device (4) as a reflection signal. Therefore, the smart surface (3) is used to scatterer / retransmit signal of each user device (4) in an optimized manner such that their resultant VRs (2b) on ELAA (2) are not overlapping. This is motivated by the fact that the occurrence and distribution of VRs (2b) on ELAA (2) depends on how the received communication signal is reflected by the environmental scatterers in terms of direction and angular span. For the random ordinary scatterers, the direction and angular span of their reflected / scattered signal depends on the size of the scatterer as well as the relative location of the scatterers and the user device (4) that originally transmitted the communication signal. Since all these factors are totally random under such uncontrolled environment, the formed VRs (2b) are also random. However, with controllable scatterers like smart surface (3), the communication signal can be scattered toward any direction independent of how it arrived (to the scatter) from the user device (4). Therefore, by properly controlling directions and angular spans of the different user devices’ (4) communication signals by using smart surface (3), it is possible to effectuate non-overlapping VRs (2b) related to different user devices (4) on the ELAA (2) as demonstrated by figure 1. In addition, since smart surface (3) operates in the near-field with respect to ELAA (2), but it can be in the far-field of the subarrays (2a) of ELAA (2), the traditional far-field based signal processing techniques are valid at subarray level. Furthermore, since the user devices (4) are in the far-field of the smart surface (3) all active elements such as antenna / reflective elements are visible to the user devices’ (4) communication signal. Accordingly, the network is flexible in partitioning / scheduling / optimizing the smart surface (3) elements to different user devices’ (4) signals. More specifically, the user devices (4) can be separated in the angle resources that are available between the smart surface (3) and the user devices (4). Hence, each user device (4) is able to be served with one angle and with one subarray (2a) accordingly. For the case of multiple user devices that are very close to each other and cannot be separated in the angle domain between the device and the smart surface, these user devices can be served with at least one subarray and these signals can be separated at the digital domain in the communication device by using different frequency or code resources instead of angle resources. However, in the case that user devices (4) are in the near-field of the smart surface (3), VRs (2b) with respect to different user devices (4) will also exist on smart surface (3). Thus, the optimization / portioning / scheduling of the smart surface (3) elements will need to take this VRs (2b) and the other near-field effects into account. In short, thanks to the method of the present invention, controllable VRs (2b) are able to be created on the ELAA (2) via the reconfigurable smart surface (3) and accordingly, interference-free VR- based communication with the communication device (1 ) is able to be ensured. In a preferred embodiment of the present invention, the step of calculating a tuning information comprises deciding the number of VRs (2b) and generating the subarrays (2a) each of which is associated with a corresponding VR (2b) and at least one of which is allocated to serve one user device (4). The number of VRs (2b) to be generated is determined based on the number of user devices (4) to be served during that uplink transmission time interval (TTI). Note that, it is also possible to assign more than one VR (2b) to one user device (4) for the sake of enhancing diversity or achieving any other performance requirements for that user device (4). In such a case, the total number of VRs (2b) should be calculated accordingly. Furthermore, the size of each VR (2b) (which corresponds to the size of its corresponding subarray (2a), in terms of number of array elements (2c) in that subarray (2a)) can be fixed based on the ELAA’s (2) size and total number of user devices (4) (for instance, the array elements (2c) can be clustered into groups with respect to the number of user devices (4) waiting for service from ELAA (2) in an uplink transmission time interval such that the ELAA (2) will have subarrays (2a) and corresponding VRs (2b) will be formed with at least in the number of the user devices waiting for service from ELAA (2) in that uplink transmission time interval). In this case, different number of VRs (2b) / subarrays (2a) (adjacent to each other or separated) can be assigned to different user devices (4) based on their requirements. In another preferred embodiment, the size of each VR (2b) can be determined based on the user device (4) requirement, i.e., user device centric (such as data rate, latency, reliability, quality of service, and scalability). For instance, in case of high data rate, the size of the subarray (2a) should be large enough to fulfill this requirement, while in case of scalable system design, the subarray (2a) should be small enough so that more subarrays (2a) are exist in the design to serve large number of user devices (4). However, how much the subarray (2a) should be narrow depends on the available user devices (4) waiting to be served without significant reduction in system performance. But it can also be beneficial to decide the VR (2b) sizes jointly for all user devices (4) such that fairness and the total system capacity are also enhanced. Afterwards, subarrays (2a) are generated by grouping the array elements (2c) (in other words antenna elements) through an adaptive switching mechanism with respect to the size of the corresponding VR (2b) for an associated user device (4). The switches connect the array elements (2c) that belong to a given subarray (2a) to the same RF (radio frequency) chain (7) and / or RF combiner (6), as shown in Figure 2. An adaptive switching mechanism (5) is preferred in order to allow dynamic generation of the subarrays (2a). Note that, the subarrays (2a) and accordingly VRs (2b) targeted for the same user device (4) can be connected to the same RF chain (7) and RF combiner (6). The number and sizes of the subarrays (2a) and accordingly the VRs (2b) depend on the number, distribution and requirements of the user devices (4) to be served. User devices (4) scheduled on the same subarray (2a) need to be scheduled on the frequency and time resources (traditionally). The time and frequency resources are reused across the VRs (2b).

[0058] In order to create non-overlapping VRs (2b) on the generated subarrays (2a), angle of departure (AoDs) of the reflection signals coming from the smart surface (3) to each subarray (2a) must be calculated. Also, the angular span of the signal reflected / scattered by the smart surface (3) toward a given subarray (2a) must be optimized. This is tantamount to controlling the beamwidth of a u-th beam (9) from smart surface (3) to the u-th subarray (2a) such that the beam (9) energy does not spread to the adjacent subarrays (2a). In other words, when a subarray (2a) is assigned to a user device (4), reflection signals beam of the communication signals of that user device (4) should be directed to that subarray (2a) without overflowing the limit edges of the subarray (2a) through the neighbour subarrays (2a) of that subarray (2a). So, calculation of AoD of reflection signals of that user device (4) ensure directing the reflected signals to the assigned subarray (2a) and optimization of angular span ensures the beamwidth of the beam (9) of that reflected signals stay within the limits of that subarray (2a). To accomplish these requirements, the step of calculating a tuning information further comprises calculation of AoDs of reflection signals which are the reflection of the communication signals reached from user devices (4) to the smart surface

[0059] (3) and which come from the smart surface (3) to each subarray (2a) and optimizing the beamwidth of the beam (9) of the reflection signals from smart surface (3) to the subarrays (2a) to ensure minimal interference between VRs (2b). Accordingly, a schematic representation of the calculation of the AoDs of the reflection signals for each subarray (2a) is given in figure 3. In figure 3, an AoD of a signal coming from smart surface (3) to the ELAA (2) with respect to the centre of the whole array is represented by 9. 9 can be determined through the conventional channel measurement procedures. Since the locations of both smart surface (3) and communication device (1 ) are fixed and well known, 9 is able to be known beforehand through some straightforward geometry-based calculations. In figure 3, an AoD of a reflection signal required to focus the uthuser device

[0060] (4) to the uthsubarray (2a) of the ELAA (2) is represented by 9U. 9Uis a data that is required to configure the active elements of the smart surface (3) to ensure reflection of the signals of the communication signals, coming from the user devices (4) and reaching to the smart surface (3), to the correct subarrays (2a) and to the correct VRs (2b) accordingly. 9Uis calculated by the equation-1 given below: 6U= tan Stance) where d2Dis the horizontal distance between the smart surface (3) and the ELAA (2) (an example for the calculation of the said horizontal distance can be found in the 3GPP document titled as “Study on channel model for frequencies from 0.5 to 100 GHz,” 3rd Generation Partnership Project (3GPP), Technical Specification (TS)38.901 , Dec. 2019, version 16.1 .0) and duis calculated by the equation-2 given below: where ncis the index of the centremost array element (2c) in ELAA (2). That is, if ELAA (2) is a uniform linear array with N array elements (2c), nc« N / 2. ncuis the index (with respect to the whole ELAA (2)) of the centremost array element (2c) of the u-th subarray (2a). d = A / 2 is the inter-elements separation distance with A being the wavelength (the communication signal received from the user device (4), and the reflected signal from smart surface (3) to the communication device (1 ) should operate in the same wavelength). In addition, if the active elements of the smart surface (3) are reflective elements (in other words, if the smart surface (3) is a RIS for instance), phases of the reflective elements should be optimized based on the user devices (4) communication signals’ angle of arrival (AoA) and the above calculated desired 9U. If the active elements of the smart surface are antenna elements (in other words if the smart surface (3) is a smart relay and NCR), their steering vector should be determined by the calculated 9U. Furthermore, a schematic representation of the optimization of the beamwidth of the beam (9) from smart surface (3) to the subarrays (2a) is given in figure 4. Same as figure 3, in figure 4, an AoD of a reflection signal required to focus the uthuser device (4) to the uthsubarray (2a) of the ELAA (2) is represented by 9U. Accordingly, to optimize the beamwidth of the beam (9) coming from smart surface (3) to the subarrays (2a) to ensure minimal interference between VRs (2b), the 3dB beamwidth fl3dBis approximated to the physical size of the targeted subarray (2a). For approximation, first angular span A0Uis calculated by using the Sine rule with the below equation-3: where y = d2D / cos 0Uand Nuis the number of array (antenna) elements (2c) in the u-th subarray (2a). Then equation-3 is simplified by using the trigonometric identities by the equation-4 given below to get angular span A0U: wherein Nuis the spatial guard interval (in terms of number of array elements (2c)) introduced at the edges of the subarray (2a) to ensure that the energy of the beam (9) is well contained within the subarray (2a). After that 3dB beamwidth fl3dBis approximated with the equation-5 given below:

[0061] The calculated fl3dBis then used to determine the minimum number of elements, Ns, that should be activated on the smart surface (3) for u-th subarray (2a) to minimize interference on the adjacent subarrays (2a). If smart surface (3) serves the subarray (2a) by using a uniform linear array, can be found by using equation-6 given below:

[0062] Similarly, uniform planar / circular arrays on the smart surface (3), relevant equations available in the literature to find N^s. An exemplary application of the above-mentioned calculations is given below.

[0063] Exemplary application: Considering a network with ELAA (2) and smart surface (3) controlled by the ELAA (2) located 20m away from the center of the ELAA (2) array 20) with a line-of-sight path only between them. It is assumed that the ELAA (2) and smart surface (3) are equipped with a uniform linear array with N=500 array elements (2c) at the ELAA (2) side. The smart surface (3) side has antenna elements (active elements) equal to or larger than the maximum number of array elements (2c) needs to be activated for a given subarray (2a). In this scenario, there are 5 user devices (4) with similar requirements with one VR (2b) for each user. The ELAA (2) is divided into 5 subarrays (2a) with Ns= 100 array elements (2c) for each subarray (2a). The AoD from the smart surface (3) to the ELAA (2) is assumed to be = ^ . The system is operated at fc= 28GHz frequency. First, the AoD 9Urequired for each subarray (2a) is calculated using equation-1 and equation-2 with nc=

[0064] = 250. Then, the number of activated active elements at the smart surface (3) side is calculated by using equation-4, equation-5 and equation-6, assuming that the guard interval ANUis fixed for all subarrays (2a) and equal to 20 (ANU= 20 Vu). The above procedures are done for each subarray (2a). The received signal power at the ELAA (2) side for a single subarray (2a) and the interference it causes to the adjacent subarrays (2a) is shown in Figure 5. The effect of the guard on the interference level is also presented in the figure.

[0065] The resultant received power at the ELAA (2) side from all subarrays (2a) is shown in Figure 6 with and without guard between all subarrays (2a), where the signal power varies from one subarray (2a) to another due to different in the subarray (2a) angle which leads to slightly different in channel characteristics over each subarray (2a). This difference is also reflected on the capacity analysis as shown in Figure 7. The capacity for a specific subarray (2a) is also determined by considering the interference from other subarrays (2a) as follows where Puis the received signal power at u-th subarray (2a) that is sent toward the subarray (2a) u, Ptis the received signal power at u-th subarray (2a) that is sent toward the subarray (2a) i, and a2is the noise power. T o show the effect of the interference from other subarrays (2a) to the given one, the noise power is assumed to be small enough to be ignored during the simulation. Therefore, the capacity analysis for each subarray (2a) is shown in Figure 7.

[0066] In another exemplary embodiment, the user devices (4) can be close to each other such that their user device (4) - smart surface (3) channel links are highly correlated and making it difficult to have independent precoder on the smart surface (3) (as smart surface (3) reflect / scatter / retransmit them to the communication device (1 )). In such a case the same VR (2b) should be used by multiple user devices (4). Accordingly, these user devices (4) may be scheduled on the same VR (2b) to simplify the processing and apply other multiple accessing techniques on them, such as orthogonal frequency domain multiple access (OFDMA), frequency domain multiplexing (FDMA), time division multiple access (TDMA), code domain multiple access (CDMA), etc. By using these multiple access techniques, the user devices (4) signals are able to be separated from each other and accordingly a subarray is able to be assigned to serve more than one user.

[0067] In another exemplary embodiment, the communication device (1 ) equipped with ELAA (2) can communicate with multiple smart surfaces (3) located in different locations, as shown in figure 8. In that case, since use of centre of the ELAA (2) as the reference point (as mentioned above) can create overlapping VRs (2b) for all smart surfaces (3) around the centre of the ELAA (2). In order to eliminate interference, for each smart surface (3), a different reference point is assigned on the ELAA (2). The reference point from which the AoD from smart surface (3) to the ELAA (2) is calculated corresponds to the centre of the subarray (2a) (or VR (2b)) allocated for the given smart surface (3). Accordingly, the AoDs and beamwidth pertained to each smart surface (3) can be calculated by following similar procedures described above.

[0068] The communication network of the present invention comprises at least one communication device (1 ) (such as base station) equipped with ELAA (2) which has a plurality of array elements (2c) used for creating subarrays (2a) of ELAA (2); at least one smart surface (3) which is a smart / controllable entity that can be placed within the propagation environment of the communication device (1 ) to help the communication process in one way or another (for instance a reconfigurable intelligent surface (RIS), smart relays / repeaters, network- controlled repeaters (NCR) etc.), which is connected to the communication device (1 ) with wired and / or wireless manner, which is controlled by the communication device (1 ), which has a plurality of active elements, such as antennas and / or reflective elements, that are able to be configured by the communication device (1 ), which is in the near-field of the ELAA (2) and can be in the far-field of the subarrays (2a) of the ELAA (2), dimension of which is in the order of the traditional mMIMO (massive multiple-inputs multiple-outputs) system and which has a line-of sight with communication device (1 ) (the smart surface (3) side has active elements equal to or larger than the maximum number of array elements (2c) needs to be activated for a given subarray (2a)); and at least one user device (4) (such as smartphone, tablet, laptop computer etc.) which is able to communicate with the smart surface (3), which is in the far-field of the smart surface (3) such that all active elements are visible to the user device’s (4) signal. The ELAA (2) comprises an adaptive switching mechanism which generates subarrays (2a) by grouping the array elements (2c) (in other words antenna elements) with respect to the size of the corresponding VR (2b) for an associated user device (4) wherein the adaptive switching mechanism (5) comprises switches that connect the array elements (2c) belonging to a given subarray (2a) to the same RF (radio frequency) chain (7) and / or RF combiner (6). Furthermore, the communication device (1 ) comprises at least one control unit (1 a) for performing the steps of the above-mentioned method of the present invention.

[0069] Thanks to the method and the communication network of the present invention, full control of the number and distribution of the VRs (2b) on ELAA (2) is given to the network. Accordingly, possibility of occurrence of interference between VRs (2b) is able to be minimized and this makes the VR (2b) based scheduling / user multiplexing easier. Since the VR (2b) scheduling and control only depends on the relative location of the smart surface (3) and ELAA (2), the changing of the user-link does not necessitate the recalculation of VRs (2b). Therefore, a robust method even for mobile users is obtained.

Claims

CLAIMS1. A method which is suitable for being used with a communication network comprising§at least one communication device (1 ) equipped with ELAA (2) which has a plurality of array elements (2c) used for creating subarrays (2a) of ELAA (2);§at least one smart surface (3) which is a smart / controllable entity that can be placed within the propagation environment of the communication device (1 ) to help the communication process, which is connected to the communication device (1 ), which is controlled by the communication device (1 ), which has a plurality of active elements that are able to be configured by the communication device (1 ), which is in the near-field of the ELAA (2) and can be in the far-field of the subarrays (2a) of the ELAA (2), which has a line-of- sight with communication device (1 ); and§at least one user device (4) which is able to communicate with the smart surface (3), which is in the far-field of the smart surface (3) such that all active elements are visible to the user device’s (4) signal characterized in that the method allows signal transmission from the user device (4) to communication device (1 ) over smart surface (3) without providing a direct communication link between the user device (4) and the communication device (1 ) and comprises the steps of:• calculating a tuning information for the active elements of the smart surface(3) to reflect / retransmit communication signals received from the user devices(4) to the subarrays (2a) of ELAA (2) of the communication device (1 ) by ensuring that a subarray (2a) of the ELAA (2) is assigned to only one user device (4), wherein the calculation is performed by a control unit (1 a) of the communication device (1 );• sending the calculated tuning information from the communication device (1 ) to the smart surface (3) for configuring the active elements of the smart surface (3) to receive communication signals from user devices (4) and retransmit / reflect received communication signals as reflection signals toward the communication device (1 ) in a manner eliminating interference of the different VRs (2b);• following the configuration of the active elements, starting the communication between user devices (4) and the communication device (1 ) over the smart surface (3) without providing a direct communication link between the user device (4) and the communication device (1 ).

2. The method according to claim 1 wherein; the step of calculating a tuning information comprises deciding the number of VRs (2b) and generating the subarrays (2a) each of which is associated with a corresponding VR (2b) and at least one of which is allocated to serve at least one user device (4).

3. The method according to claim 2 wherein; the number of VRs (2b) to be generated is determined based on the number of user devices (4) to be served during that uplink transmission time interval (TTI).

4. The method according to claim 2 or claim 3 wherein; the size of each VR (2b) is fixed based on the ELAA’s (2) size and total number of user devices (4).

5. The method according to claim 2 or claim 3 wherein; the size of each VR (2b) is determined based on the numbers, distributions and requirements of user devices (4).

6. The method according to any one of the preceding claims wherein; the step of calculating a tuning information further comprises calculation of AoDs of reflection signals which are the reflection of the communication signals reached from user devices (4) to the smart surface (3) and which come from the smart surface (3) to each subarray (2a) and optimizing the beamwidth of the beam (9) of the reflection signals from smart surface (3) to the subarrays (2a) to ensure minimal interference between VRs (2b).

7. The method according to claim 6 wherein; an AoD of a reflection signal required to focus the uthuser device (4) to the uthsubarray (2a) of the ELAA (2) which is represented by 9Uis calculated with the equation-1 given below6U= tan-1(tan(where 0 is an AoD of a signal coming from smart surface (3) to the ELAA (2) with respect to the centre of the whole array and is able to be determined through the conventional channel measurement procedures, d2Dis the horizontal distance between the smart surface (3) and the ELAA (2) and duis calculated by the equation-2 given below:where ncis the index of the centremost array element (2c) in ELAA (2), ncuis the index of the centremost array element (2c) of the u-th subarray (2a) and d = A / 2 is the interelements separation distance with A being the wavelength.

8. The method according to claim 6 wherein; the optimization of the beamwidth of the beam (9) coming from smart surface (3) to the subarrays (2a), the 3dB beamwidth fl3dBis approximated to the physical size of the targeted subarray (2a) by first calculating the angular span which is represented by A0Uby using the Sine rule with the below equation- 3;where y = d2D / cos 0Uand Nuis the number of array elements (2c) in the u-th subarray (2a) and then the equation-3 is simplified by using the trigonometric identities by the equation-4 given below to get angular span A0U;wherein A / Vuis the spatial guard interval introduced at the edges of the subarray (2a) to ensure that the energy of the beam (9) is well contained / confined within the subarray (2a) and after that 3dB beamwidth fl3dBis approximated with the equation-5 given below:

9. The method according to claim 8 wherein; the minimum number of elements, N^ , that should be activated on the smart surface (3) for u-th subarray (2a) to minimize interference on the adjacent subarrays (2a) is determined by using equation-6 given below:Q3dB= ( 1.3 x l) / (d x Ns) = 2.6 / Ns(6)where the smart surface (3) is a uniform linear array.

10. The method according to any one of the claims 7-9 wherein; the reference point from which the AoD from smart surface (3) to the ELAA (2) 9 is calculated corresponds to the centre of the subarray (2a) allocated for the given smart surface (3) for the case that the communication device (1 ) equipped with ELAA (2) communicates with multiple smart surfaces (3) located in different locations.

11. A communication network configured for performing a method according to any one of the preceding claims and comprising at least one communication device (1 ) equipped with ELAA (2) which has a plurality of array elements (2c) used for creating subarrays (2a) of ELAA (2); at least one smart surface (3) which is a smart / controllable entity that can be placed within the propagation environment of the communication device (1 ), which is connected to the communication device (1 ) with wired and / or wireless manner, which is controlled by the communication device (1 ), which has a plurality of active elements that are able to be configured by the communication device (1 ), which is in the near-field of the ELAA (2) and can be in the far-field of the subarrays (2a) of the ELAA (2), which has a line-of-sight with communication device (1 ); and at least one user device (4) which is able to communicate with the smart surface (3), which is in the far-field of the smart surface (3) such that all active elements are visible to the user device’s (4) signal characterized in that the ELAA (2) comprises an adaptive switching mechanism (5) which generates subarrays (2a) by grouping the array elements (2c) with respect to the size of the corresponding VR (2b) for an associated user device (4) wherein the adaptive switching mechanism (5) comprises switches that connect the array elements (2c) belonging to a given subarray (2a) to the same RF chain (7) and / or RF combiner (6); and in that the communication device (1 ) comprises at least one control unit (1 a) for performing the steps of the method according to any one of the preceding claims.

12. The communication network according to claim 11 ; wherein the communication device (1 ) is a base station.

13. The communication network according to claim 1 1 ; wherein the smart surface (3) is a reconfigurable intelligent surface, smart relays / repeaters and / or network-controlled repeaters.

14. The communication network according to claim 11 ; wherein the active elements of the smart surface (3) are antennas and / or reflective elements.

15. The communication network according to claim 11 ; wherein the smart surface (3) has a number of active elements equal to or larger than the maximum number of array elements (2c) that needs to be activated for a given subarray (2a).

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