A method and mechanisim for spatial aliasing exploitation in 1 d and 2d extra-large antenna arrays (ELAA)-based communication networks

Abstract

The present invention relates to a method and mechanism for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks. The main aim of invention is to achieve at least one of the following: energy efficient system design with low latency and low computational complexity, enhance the multiplexing capabilities of the system design, effectively mitigate interference from the system design.

Description

[0001] A METHOD AND MECHANISIM FOR SPATIAL ALIASING EXPLOITATION IN 1 D AND 2D EXTRA-LARGE ANTENNA ARRAYS (ELAA)-BASED COMMUNICATION NETWORKS

[0002] TECHNICAL FIELD

[0003] The present invention relates to a method and mechanism for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks.

[0004] PRIOR ART

[0005] In the next generations of the wireless networks, due to high frequency bands as a potential candidate to meet the ever increasing traffic crunch for its large available spectrum as the case of millimeter wave (mmWave) and terahertz (THz), larger antenna arrays with drastically increased sizes (i.e., number of antenna elements) as compared to the current massive multiple-inputs multiple-outputs (mMIMO) systems are utilized to compensate for the unfavorable large propagation loss at these bands. Such larger arrays are expected to significantly improve the spectral efficiency as well as the spatial resolutions. These arrays are referred to 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] In Multiple Antennas systems, the antennas are spaced within specific distances between each other as usually When there is beamforming beam, one beam and other side lob are occurred. If the distances change between antenna elements to larger than then grating lobe in generally called spatial aliasing. Assuming one normal main beam in the system, if there is spacing between the antenna element, when starting to increase antenna element spacing, noticing the something similar mirror of main lobe goes to another direction which is calling grating lobe. As the distance increasing as the number of grating lobes would be increased. This grating lobe definition is a replica of antenna gain defined on different angles. This phenomenon is happening when spacing larger than A between antenna elements. This side lobe or grating lobe has their properties are having the same amplitude as main lobe beam but they are located in different directions as shown in figure 5. This situation is unintended. It means that they are going to create interfere with main lobes of other beams. Thus, they limit the MIMO system performance. Basically, the problem faced in MIMO systems. Increasing the spacing of antenna elements, it is possible to get a more decorrelated channel. If antenna element spacing increases, it is possible to get benefit more separation, better multiplexing, but grating lobe will reduce performance in another direction and this creates new interference.

[0007] When reviewing characteristic of grating lobe, increasing of spacing more than it causes to increases number of grating lobes clearly. Grating lobe locations are basically based on specific equations as

[0008] -The number of grating lobes depends on distance.

[0009] Another thing field of view. If antenna array only can see at a specific angle, it means more grating lobe for example angles between -80 to 80. When the angles decrease, occurs less grating lobe for example angles between -40 to 40.

[0010] The grating lobe starts appearing based on the dcritical = if d>dcritical, grating lobes start, dcritical>d no grating lobes.

[0011] From above information, the grating lobe depends on antenna spacing and total scanning range. The beam gain of grating lobes (and main lobe) depends on the number of activated antennas as related to spacing. mMIMO systems aim to serve many users on the same time-frequency resources while reducing the amount of fading due to the employment of a high number of antennas in reference document

[0001] . However, achieving orthogonality of user channels for achieving the promised spatial multiplexing gains is in a major system design concern. Users’ separability can be achieved by generating very narrow beams especially in distinguishing the closely located users in a line-of-sight (LoS) scenario. Although these narrow beams can be generated using a massive number of antenna elements, the system will suffer from signal processing and hardware complexity issues in reference document [2], Another way to generate narrow beams is by increasing the inter-element spacing d between the antenna elements in the array which increase the antenna array aperture while keeping the number of antenna elements constant. Increasing the inter-element spacing can also potentially reduce the power variation at the antenna array in reference document [3].

[0012] In a rich scattering environment and with inter-element spacing of d = A / 2 , if the channel is rich enough such that the received signal arrives from all directions, increasing the inter-element spacing does not further increase the degree of freedom in the channel. However, in high frequency bands such as in mmWave and THz bands, due to limited scatters, by increasing the aperture size with a fixed number of antenna elements, the minimum resolvability angular resolution of the array is improved and the signal paths originating in the transmit antennas become less and less correlated. In another word, employing inter-element spacing larger than A / 2 can enhance the angular resolution of an array with a fixed number of antenna elements and reduce the channel correlation.

[0013] However, the major drawback of increasing the inter-element spacing is the appearance of grating lobes (GL) (spatial aliasing or it called beamforming ambiguities). GLs are a replica of the antenna gain with the same amplitude as the main beam lobe but at other directions rather than the target one, as shown in Figure 1 . They can cause a high correlation among the channel vectors of the users with a large angular separation (i.e., the non-co-located users) in reference document [4], GL appearance in the system depends on the amount of inter-element spacing d compared to a reference spacing and the antenna array field-of-view (FOV) in reference document [5]. FOV is defined as the fraction observation of the space that is detectable at the array side. Such a large FOV allows repeatedly observing large fractions of the sky in an acceptable time. This will not only detect weaker objects but also detect rare types of variable objects and opens a new dimension in observing space in reference document [6]. Maximum allowable inter-element spacing dmaxis defined / given / calculated by the maximum possible angular separation between two nodes in the FOV of the antenna array. For a fix FOV, increasing d to a value larger than dmaxmight lead to zero-forcing singularity along the antenna array due to the GL effect. Therefore, an upper bound is defined in reference document [3] for the maximum inter-element spacing to guarantee that no grating lobes exist in the FOV of the antenna array as

[0014] 0.5 A < where ipmaxis the maximum FOV of the given antenna array.

[0015] GLs appear at the angles of

[0016] Where is the main lobe direction of the beam. Hence, the GL direction depends on inter-antenna spacing d , operating wavelength A , and the direction of the main lobe 0ML. With increased inter-elment spacing, for a fixed direction, the GLs position gets closer relative to the main lobe.

[0017] The beamwidth of the GLs can be calculated similar to the main lobe beam calculation where the beamwidth in general depends on operating wavelength A and total antenna array size (=Md with M is the number of antenna elmenets in the array in case of uniform linear antenna array) (i.e., beamwidth > for uniform linear array as given

[0018] Md in reference document [7]). If the inter-element spacing is fixed between all antenna elements, the gain of these GLs is as strong as the main lobe and depends on the number of activated antenna elements in the array. The invention is about exploiting some phenomena in mimo system which is called the spatial aliasing. In the invention, the method is trying to utilize beam out of multiple antenna systems. In this way, invention provides to get more benefit or better performance for the system.

[0019] Traditional antenna array designs have often been limited by fixed inter-element spacings, optimized for specific frequencies. However, as wireless communication systems increasingly operate on multiple frequency bands, this rigid approach hampers their versatility and efficiency.

[0020] Many beamforming techniques and antennas designs are utilized in the literature for GL mitigation, which is given reference documents [8,9,10,11 ,12,13]. For instance, reference document

[0011] investigated a unique property of circular microstrip patch antenna elements to address the GL issue in a scanning planar phased array antenna with a rectangular lattice and large element spacing in the order of one wavelength. The GL reduction technique in reference document

[0011] is based on the utilization of dual-mode antenna elements, as opposed to single-mode ones in conventional phased array antennas. More specifically, the self-scanning and nulling properties of the antenna elements are effectively utilized to nullify the grating lobes and provide better radiation-matched elements in scanning phased array antennas. Similarly, reference document

[0012] optimized the array excitation coefficients and utilized dual-mode elements with self-scanning and adaptive nulling properties to extremely reduce the GLs in linear scanning arrays.

[0021] Beamforming methodology for GL suppression is proposed in reference document

[0014] with the use of integrated dual-mode 16-element linear phased array antenna with 1 A interelemental spacing using the Anokiwave RFICs (AWMF-01 17). Overlapping subarray (OSA) phased array structure is utilized to push the grating lobes out of the FOV in given reference document

[0015] and reference document

[0016] which increase the scanning range of the system design by grouping antenna elements together and overlapping the subarrays, thus reducing the spacing between the adjacent subarrays. In the OSA structure, the antenna elements can be part of a few different sub-arrays. Using Chebychev configuration in reference document

[0017] , the GLs are suppressed due to the non-equidistant spacing of the antennas. However, Chebychev configuration is not uniform, resulting in a higher antenna density towards the ends of the array. Therefore, a sub-array configuration is implemented within the same work reference document

[0017] where antennas at the ends of the array are spaced with an inter-element spacing of 0.5A. There are no grating lobes are present between the broadside and end fire direction for the sub-array configuration which reduces the interuser correlation. However, this increases the sidelobe level near to the main lobe beam resulting in increasing the inter-user correlation for the closely spaced users.

[0022] In the literature, providing orthogonality between the GLs within one generated beam is provided by using different separation mechanisms such as the mechanism introduced in reference document

[0018] .

[0023] Traditional antenna array designs have often been limited by fixed inter-element spacings, optimized for specific frequencies. However, as wireless communication systems increasingly operate on multiple frequency bands, this rigid approach hampers their versatility and efficiency.

[0024] The current literature focuses on devising beamforming techniques and antenna designs to counteract the GL effect within the system. Nevertheless, none of these studies explore the possibility of harnessing the GL beams and exerting control over them to augment system performance. As a result, the lack of consideration for utilizing GL beams leads to substantial energy losses and high inter-user correlation, especially for non-co-located users. These issues present significant challenges and may impede the exploitation of the complete capabilities of antenna arrays in mmWave frequencies and future networks. To fully realize the potential of such antenna arrays, it becomes crucial to address these concerns and investigate novel methods that incorporate the utilization and management of GL beams to improve overall system efficiency and performance. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0025] BRIEF DESCRIPTION OF THE INVENTION

[0026] The present invention relates to a method and mechanism for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0027] The method occurs from large antenna spacing between elements to reduce the conventional beam sweeping approach. In this way, the grating lobes phenomena is utilized.

[0028] The invention uses a new mechanism (switching mechanism) used in codebook design of massive MIMO systems. The mechanism for controlling and exploiting the grating lobes (GLs) is proposed for better system performance. In specific, the mechanism leverages and optimizes various aspects of the system performance, including computational complexity, latency, energy consumption, multiplexing capabilities, and interference cancellation.

[0029] The approach is not limited to only these two ways of ordering the inter-element spacing between the antenna elements (60). Any random ordering can be acceptable as well, given that the location and number of GLs should be calculated carefully in the design.

[0030] In addition to the low-latency beam sweeping approach, the proposed approach can be extended to different applications such as joint sensing and communication, user multiplexing enhancement, massive machine type communication networks.

[0031] The proposed approach can be extended to different antenna array types such as uniform planar array, uniform circular array, etc. Furthermore, in case that the antenna elements (60) in the XL array are capable of adaptively changing their location / position in the array, more inter-element spacing choices can be considered while designing / controlling / utilizing the GLs.

[0032] The aim of the invention is to provide energy efficient system design by both reducing the number of activating antennas and the overall sweeping time in 1 d and 2d extralarge antenna arrays (ELAA)-based communication networks.

[0033] The codebook is utilized in the invention. The codebook is designed to guarantee scanning the overall space with minimum transmitted beams based on an on grid approach to create the orthogonal beams. To design codebook, the total number of available antenna elements in the array is considered and possible antenna spacing is assumed (1 / 1,2 A ...X A).

[0034] A set of distance values and their corresponding angles need to be chosen to achieve energy efficient and time saving.

[0035] When grating lobe appears that in a different direction it means it will be interfered with for every user and it will limit system performance. As understand above, there are some solutions to reduce these problems by creating different algorithms, using different antenna array designs doing distances. However, the invention tries to exploit this phenomenon instead of removing this problem to enhance system performance.

[0036] If there is fix antenna array, spacing . This case called fixed design. In the invention 2

[0037] Hardware design is already fixed by between antenna spacing

[0038] 2

[0039] In the invention, another main goal is to create grating lobes with similar / equal beamwidth to the original one by dynamically selecting antenna spacing for fixed antenna array with M element. And then grating lobes are exploited in beam management procedure, in specific, beam sweeping, to reduce the sweeping time overhead.

[0040] Exploiting the grating lobes in the beam sweeping can also reduce the number of activated antennas and their corresponding phase shifters which provide energy- efficient system design. As is known, phase shifters are used to change the transmission phase angle of an input signal. Phase shifters are used for the same purpose in this invention.

[0041] Energy efficiency can be achieved by activating a smaller number of antenna elements while getting same beamwidth and also reducing the total sweeping time. So, it is possible to reduce the latency.

[0042] Generating grating lobe what is the design that is exactly needed;

[0043] • Since the same-time frequency resources are utilized in the beam and its grating lobes, the grating lobes cannot be distinguished. Therefore, a separation mechanism is needed.

[0044] • A method of embedding orthogonal sequences / signals within one beam can be used,

[0045] • This ensures the orthogonality of the grating lobes within one beam and the ability to separate between them without ambiguity.

[0046] In the invention, increasing the distance by activating antennas, grating lobes appear. Invention provides to adaptively control antenna distance by switching on / off some antennas. Antenna distance not physically fixed. This is what the invention wants to achieve is. Each antenna element needs to be connecting a specific amplifier phase shifter all of them connected one of each other reducing the number of activating elements in each other. In this way, consuming less power becomes possible.

[0047] Switching mechanisms are used on the antennas / antenna arrays. In this way, switching on / off antenna is possible. By changing spacing between activated elements to create grating lobes. Then by controlling phase shifters to let main lobes go to specific directional. Based on adjusting the main lobe, where the grating lobe appears. By doing that a codebook is designed, start generating different beams and directions, these directions where the grating lobe exists. Optimize depend on application.

[0048] In the first aspect, the embodiment of the present application provides a method, which can be executed by a network device, or by a component of the network device (such as a processor, a chip, or a chip system, etc.), or can be implemented by all or logical modules or software implementations of some network device functions or computer implemented device.

[0049] In the invention, the grating lobes phenomena are utilized due to large antenna spacing between the elements to reduce the conventional beam sweeping approach.

[0050] The main object of the invention is to provide energy efficient system design by both reducing the number of activating antennas and the overall sweeping time.

[0051] The invention proposes dynamically adjust the inter-element spacing to cater to different frequencies. Thereby maximizing system performance and coverage.

[0052] The other objects of the invention;

[0053] • Proposing a codebook in which it guarantees scanning the overall space with minimum generated beams at the BS side from the radio frequency (RF) frontend by utilizing the grating lobes of each main beam,

[0054] • For a fixed antenna array with M elements, different grating lobes can be generated with similar / equal beamwidth to the original one by dynamically selects the antenna spacing d,

[0055] • Grating lobes are exploited in beam management procedures, in specific, beam sweeping, to reduce sweeping time overhead,

[0056] • Exploiting the grating lobes in the beam sweeping can also reduce the number of activated antennas and their corresponding phase shifters which provide energy-efficient system design.

[0057] Energy efficiency can be achieved by active less antenna elements while getting the same beamwidth, and also reduced total sweeping time.

[0058] The method for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks proposed by the embodiment of the present application can be applied to the 5G, 5G beyond, 6G or similar networks. By carefully designing and implementing this mechanism, it aims to achieve several key objectives:

[0059] • Computational Complexity: The mechanism strives to reduce the computational burden on the system, making it more efficient and capable of handling complex tasks with lower processing requirements.

[0060] • Latency: Minimizing latency is crucial in time-sensitive applications, and the mechanism aims to decrease communication delays and response times, leading to improved real-time performance.

[0061] • Energy Consumption: By employing energy-efficient algorithms and strategies, the mechanism seeks to conserve power and extend the operational lifespan of battery-powered devices.

[0062] • Multiplexing Capabilities: The mechanism enhances the system's ability to transmit multiple signals simultaneously over the same / different channel within one transmitted beam serving a different location / direction simultaneously. This results in increasing the overall data throughput and spectral efficiency.

[0063] • Interference Cancellation: Effectively mitigating interference is essential in crowded wireless environments. The mechanism employs advanced interference cancellation techniques to improve signal quality and enhance overall system reliability.

[0064] One another aspect of the invention also provides GL utilization mechanism.

[0065] The benefits of utilizing the GLs in the system depend on the applied scenario. This approach can be applied to;

[0066] 1 ) Provide a better low-latency beam sweeping approach,

[0067] 2) Better sensing and communication approach,

[0068] 3)lncrease the number of served users within one generated beam to meet the requirement of massive machine type communication networks.

[0069] GL utilization mechanism offers a comprehensive approach to optimize and enhance various performance metrics in wireless communication systems, addressing challenges related to complexity, latency, energy efficiency, capacity, interference management, and beamforming management. Through its implementation, it can significantly improve the overall performance and user experience in wireless networks.

[0070] Several advantages or one can be achieved in the system based. For example, beam management is an essential part of beam-based systems in 5G networks. One critical part of the beam management process is beam sweeping. Beam sweeping refers to the process where the base station (BS) or the user covers a spatial area by sequentially using different analog beams when transmitting or receiving reference signals. In beam sweep processing, if the antenna array is massive, the conventional beam generated from the array has a very narrow beamwidth. Hence, more beams are needed to scan the whole environment for possible connection with a user which introduces unwanted latency to the system and thus degrades the system performance. Therefore, by utilizing the GLs, more areas can be scanned within one generated beam which reduces the system latency.

[0071] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks.

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The present disclosure, in accordance with one or more various examples, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict examples of the disclosure. These drawings are provided to facilitate the reader's understanding of the disclosure and should not be considered limiting the breadth, scope, or applicability of the disclosure. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.

[0074] Figure 1 : Illustration of the grating lobes (GLs)

[0075] Figure 2: Illustration of the system model Figure 3: The flow chart of the proposed approach for generating, controlling, and utilizing the GLs in XL-MIMO systems.

[0076] Figure 4: The time overhead versus the number of available antenna elements in the XL-MIMO system.

[0077] Figure 5: Location of grating lobes in different directions.

[0078] REFERENCE LIST

[0079] The reference numbers of the elements included in the figures are explained below.

[0080] 10 Multiple Accessing Precoding Technique

[0081] 20 RF Chain

[0082] 30 Switching apparatus

[0083] 40 Phase Shifter

[0084] 50 Controller

[0085] 60 Antenna Elements

[0086] 70 Main lobe beam

[0087] 80 Grating lobe beam

[0088] 90 Side lobe beam

[0089] DETAILED DESCRIPTION OF THE INVENTION

[0090] In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only to make the subject more understandable.

[0091] The present invention relates to a method and mechanism for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks.

[0092] In the invention, a method and mechanism is developed to control antennas by activating some of the antennas as on / off. In this way, appearance beam depends on the only active antenna. The invention proposes a new mechanism (switching mechanism) to use codebook design for wireless communication systems such as MIMO, massive MIMO. This mechanism comprises switching network and switching apparatus (30). The switching apparatus (30) for turning on and off the antenna elements (60) in the array in a way that the inter-element spacing changes and GLs are generated based on how many GLs are needed from the given main beam. A switching network for passing the signal to the antenna elements (60) that are needed for generating the beams with / without grating lobes,

[0093] The proposed method in the invention for spatial aliasing exploitation in 1 d and 2d extra-large antenna arrays (ELAA)-based communication networks which is shown in figure 3. The method depends on the computer implemented method. Furthermore, the method can be implemented by a processor of a network device for spatial aliasing exploitation in 1d and 2d extra-large antenna arrays (ELAA)-based communication networks.

[0094] The proposed approach has the potential to dynamically adjust the inter-element spacing to cater to different frequencies. Thereby maximizing system performance and coverage. This is done by designing the inter-element spacing for the given antenna array based on the highest operating frequency. Then, the switching mechanism controls the switching network to adjust the effective inter-element spacing between the active antenna elements (60) according to the given operating frequency for beamforming and controlling the main lobes and GLs of the beam.

[0095] The scenario can also be extended to the case of non-uniform inter-element spacing in order to increase the number of GLs within one beam with more possible directions. The non-uniform spacing can be utilized either in localized, interleaved, or both ways. In the localized non-uniform inter-element spacing, the antenna elements (60) in the XL array are grouped, and in each group, a specific inter-element spacing is set. For example, for 64 antenna elements (60) activated in the XL array, two groups can be considered, 32 antenna elements (60) in each. The inter-element spacing in the first group is set to d = 1.5A while the second group to d = 2.5 A. This results in 6 GLs within one generated beam. Changing between group one and two results in the same generated beam with the same GLs numbers and locations. Hence, there is no meaning of how to order the inter-element spacing between the groups.

[0096] In the interleaved non-uniform inter-element spacing, the first inter-element spacing is set between the first two antenna elements (60), the second inter-element spacing is set between the next two antenna elements (60), and so on. For the same example above, for 64 active antenna elements (60) in the XL array, assuming two inter-element spacings in the array, d = i .5A and d = 2.5 , the number of GLs generated from each beam is 12. However, the GLs gain in the non-uniform spacing is lower than the main lobe beam (70) leading to the need of having a power control mechanism in addition to the interference cancelation mechanism.

[0097] In a scenario with on-grid codebook is generated as an optimum codebook as a predefined codebook. This can be extended to off-grid codebook where the beam angles in the codebook are refined to match with the continuous channel angles referring to specific users / target locations. Then, the orthogonality and beam separation are guaranteed at the baseband precoding stage. Hence, the digital domain precoding processing contains two stages: interference cancelation between the main lobes’ beams (70), and interference cancelation between the GLs of the same beam.

[0098] Implementation procedures of the proposed method in invention are given below.

[0099] Based on the number of antenna elements (60) M at the array side in BS and its operating frequency, the BS creates a pre-defined codebook contains2dMorthogonal

[0100] A beams with angle spacing of The pre-defined codebook contains all possible beams M that orthogonally scans the overall space which can be available for users serving and sensing in communication and / or sensing networks regarding to the hardware limitations. The inter-element spacing is adaptively changed in order to generate GLs using switching network and mechanism. For each inter-element spacing, a beam codebook is generated. The final selected codebook is based on the generated codebook at each inter-element spacing and some specific system requirements such as low-latency and low computational overhead. The process is set for a once and a separation mechanism is then applied to ensure the GLs within one beam.

[0101] The overall system procedures can be summarized as follow:

[0102] 1 . A pre-defined codebook is introduced as a target optimum codebook which is based on the original design of the antenna array with half-wavelength interelement spacing and M activated antenna elements (60). The codebook represents the possible beams for transmission that can scan the entire space orthogonally. Let’s assume that the XL-array can scan between to directions, the beam angles in the codebook start from and spaced with step size between the generated beams to ensure the orthogonality between the beams. Defining these angles and put them in a set as 0ML=

[0103] 2. Defining a possible set of inter-element spacings that the antenna array can provide such that d = A, 1.5A, 2A, 2.5A, ..., xA. For each inter-element spacing, given the angle set 0ML, calculating the number of GLs and its corresponding location

[0104] 3. A selection criterion is needed based on the system / users requirement which can reduce the time overhead and energy consumption. The selection mechanism selects the GL that satisfies two conditions: 1 ) It is within the visible scanning range of the XL-array, 2) its location matches with one of the angles sets in the pre-defined codebook (a specific threshold can be put to measure the difference between the main lobe beam (70) angle in the pre-defined codebook and the GL beam angle. If the absolute difference is less than the threshold, the GL beam is selected).

[0105] 4. After selecting the optimum GLs with their corresponding inter-element spacing, in order to generate the corresponding beam, the number of active antenna elements (60) is set as M' = Given that the total power in the system is fixed, the power is distributed uniformally over the activated antenna elements (60) in order to keep the overall beam gain equal to the original beam gain in the predefined codebook. 5. Since the analog domain of the design is set, a mechanism to provide orthogonality between the GLs within one generated beam is needed. This can be done using different separation mechanisms such as the mechanism introduced in the prior art document. Hence, the GL beam angle is distinguishable from its corresponding main lobe beam (70) at the receiver side.

[0106] A computer implemented method for spatial aliasing exploitation in 1d and 2d extralarge antenna arrays (ELAA)-based communication networks wherein the method comprises,

[0107] • Implementing codebook design which is comprising switching mechanism to make the distance adaptively between antenna element and controlling the switching network to adjust the effective inter-element spacing between the active antenna elements (60) according to the given operating frequency for beamforming and controlling the main lobes and grating lobes of the beam by switching on / off antennas,

[0108] • Creating a pre-defined codebook based on the original antenna array design to maintain the orthogonality between the generated beams using an on-grid approach,

[0109] • Defining a possible set of inter-element spacings that the antenna array can provide as more than L

[0110] 2

[0111] • For each inter-element spacing, to create grating lobe by calculating the number of grating lobes (GLs) each orthogonal beam and its corresponding location, (grating lobe as

[0112] • Selecting the optimum inter-element spacing with its GLs on the GL which is within the visible scanning range of the XL-array, and matching GL location which matches with one of the angles sets in the pre-defined codebook,

[0113] • For each inter-element spacing, setting the number of active antennas as

[0114] 2x

[0115] (The power is distributed uniformly over the activated antenna elements (60) in order to keep the overall beam gain equal to the original beam gain in the predefined codebook.), • Applying an analog precoder to control both the switching and phase shifter (40) networks by based on the selected optimized codebook to create orthogonal grating lobes,

[0116] • Applying of an orthogonal beams-based algorithm to the design to ensure the orthogonality of the grating lobes by utilizing the resources of time, frequency, or / and code domains.

[0117] In this invention, the mechanism for controlling and exploiting the GLs is proposed for better system performance. In specific, the mechanism leverages and optimizes various aspects of the system performance, including computational complexity, latency, energy consumption, multiplexing capabilities, and interference cancellation.

[0118] Here, assuming a base station (BS) with an XL-MIMO antenna located in a uniform linear array with inter-element spacing of half-wavelength and M antenna elements (60). The users in the system are distributed close to each other (co-located users) or far from each other (non co-located users).

[0119] A switching mechanism for codebook design which is scanning the overall space with minimum generated beams at the base station (BS) side from the radio frequency (RF) front-end by utilizing the grating lobes of each main beam in MIMO systems configured to ;

[0120] • At least one digital precoder,

[0121] • At least one radio frequency chain for allowing passband communication signals to be processed in the baseband and which is connected with the switch mechanism,

[0122] • An antenna elements (60) which are capable of adaptively changing their location / position in the array, more inter-element spacing choices can be considered while designing / controlling / utilizing the grating lobe,

[0123] • A phase shifter (40) which is connected to each antenna element (60) to let main lobes go to specific directional by changing the phase angel of the radio frequency signal, characterized in that the switching mechanism comprising;

[0124] • A switching apparatus for turning on and off the antenna elements (60) in the array in a way that the inter-element spacing changes and GLs are generated based on how many GLs are needed from the given main beam,

[0125] • A switching network which is responsible for passing the signal to the antenna elements (60) that are needed for generating the beams with / without grating lobes and comprising a switching mechanism,

[0126] • A controller (50) for switching to adaptively make the distance antenna elements (60).

[0127] For simplicity, the expected transmitted beams codebook is generated using an on- grid approach where the number of beams that can be generated orthogonally in the design to scan the space is defined as2dMwith a spacing of 2L.

[0128] A M

[0129] In the considered scenario, a codebook is proposed in which it guarantees scanning the overall space with minimum generated beams at the BS side from the radio frequency (RF) front-end by utilizing the grating lobes of each main beam. At the RF front-end, a switching network and mechanism is needed which is built between the RF chain (20) and the phase shifter (40) network. The switching network is responsible for passing the signal to the antenna elements (60) that are needed for generating the beams with / without GLs. The switching network is controlled by a mechanism that turns on and off the antenna elements (60) in the array in a way that the inter-element spacing changes and GLs are generated based on how many GLs are needed from the given main beam.

[0130] To design the codebook, several points need to be noticed:

[0131] • The possible inter-element spacing that is available from the design is a multiple of the half-wavelength (d = A, 1.5A, 2A, 2.52., ..., xX). Hence, the number and locations of GLs are strict to these inter-elements spacing.

[0132] • A pre-defined codebook is considered as an optimum codebook for the design where the proposed one should be as close as possible to the optimum one. This pre-defined codebook is generated based on an on-grid approach with — . orthogonal beams. Since the GLs of a single beam shared the same data resources, a separation mechanism is needed to ensure the orthogonality between the GLS within the same beam. The design of the system is illustrated in Figure 2.

[0133] In this invention, a mechanism for controlling and exploiting the GLs is proposed for better system performance. In specific, the mechanism leverages and optimizes various aspects of the system performance, including computational complexity, latency, energy consumption, multiplexing capabilities, and interference cancellation.

[0134] Here, assuming a base station (BS) with an XL-MIMO antenna located in a uniform linear array with inter-element spacing of half-wavelength and M antenna elements (60). The users in the system are distributed close to each other (co -located users) or far from each other (non co-located users). For simplicity, the expected transmitted beams codebook is generated using an on-grid approach where the number of beams that can be generated orthogonally in the design to scan the space is defined as2dMwith a spacing of .

[0135] A M

[0136] In the considered scenario, a codebook is proposed in which it guarantees scanning the overall space with minimum generated beams at the BS side from the radio frequency (RF) front-end by utilizing the grating lobes of each main beam. At the RF front-end, a switching network and mechanism is needed which is built between the RF chain (20) and the phase shifter (40) network. The switching network is responsible on passing the signal to the antenna elements (60) that are needed for generating the beams with / without GLs. The switching network is controlled by a mechanism that turns on and off the antenna elements (60) in the array in a way that the inter-element spacing changes and GLs are generated based on how many GLs are needed from the given main beam.

[0137] Table 1 : The pre-defined analog beam codebook

[0138] Table 2: GL matching indices with the original beam indices.

[0139]

[0140] An example of the use case of our invention is given below. The invention is not limited to the example given below, the proposed method can be implemented and applied to different system conditions and applications.

[0141] Example:

[0142] Considering a beam-based XL-MIMO system where the beam management is an essential part of the network design. The system operates at fc= 60 GHz frequency. With a BS contains M = 256 antenna elements (60) located in a uniform linear array with half-wavelength inter-element spacing ( d = 2 / 2 ) and K single-antenna users distributed uniformly in a specific area where the BS beams can cover, the focus will be on designing better low-latency beam sweeping approach. As a first step, the BS builds a pre-defined analog beam codebook. Assuming that the XL array can scan the area from to Z, there will be 86 beams orthogonal in the pre-defined analog beam 3 3 codebook with £2 step between two adjacent beams. The pre-defined codebook is given M in Table 1. After that, a possible set of inter-element spacing is defined as d = 2, 1.52, 22, 2.52, 32,3.52,42,4.52, 52, 5.52, 62 where the number of active antenna elements (60) is determine using M' = Ml (2%), as

[0143] M' = 128, 85, 64, 51 ,42, 36, 32,28,25,23,21 respectively.

[0144] Within one inter-element spacing, for each orthogonal beam in the pre-defined codebook, the locations of the GLs are determined using ’

[0145] 9GL,m,i = sin-

[0146] Then, a comparison between the location of the GLs and the main lobes beams (70) in the pre-defined codebook is done. The comparison is done as follow: Where eML jis the angle of the main lobe of beam (70) j in the pre-defined codebook, GL angle of beam j, and Tthis a certain threshold. For simplicity, here in this simulation, since the beamwidth of the original beams is heamwidth =0 892which Md is equal to 0.4011° in the system here, the threshold value is set to o.O5°- The GL that satisfies the comparison is set in Table 2. The table shows the beam index of the matched GL with the main beam index in the pred-defined beam codebook.

[0147] The subsequent procedure involves the implementation of a selection mechanism based on a specific cost function, with the primary objective of minimizing the sweeping time overhead.

[0148] The steps for the selection mechanism are as follows:

[0149] 1. Sorting GLs Indices: The beam indices that have GLs align with the pre-defined beams listed in Table 2 are sorted based on the number of GLs matching. The sorting is done in descending order, starting from the largest number of matching GLs with the pre-defined beams and proceeding to the lowest, irrespective of the inter-element spacing.

[0150] 2. Initiating Selection Process: The selection process begins with the beam that exhibits the largest number of GLs matching degree with the pre-defined codebook, along with its corresponding inter-element spacing.

[0151] 3. Handling Multiple Choices: For a given jthpre-defined beam, if there are multiple choices available in Table 2, an additional condition is applied. Among these similar selections, the one displaying the least variation concerning the pre-defined beam is selected. This selection process is mathematically represented as: i* = arg min 10ML j- 0GL m i\ where i* denotes the chosen index for the GL matching the fhpre-defined beam, eML- represents the main lobe angle of the jthpre-defined beam, and 0GL m iis the angle of themthGL associated with the ithchoice in Table 2. 4. Handling Unmatched Pre-Defined Beams: In situations where no generated GL matches a specific pre-defined beam, the traditional half-wavelength inter-element spacing is utilized to generate that particular beam.

[0152] In order to evaluate the performance of the proposed approach in the invention, the time of sweeping the beams is evaluated in Figure 4 for the proposed beam sweeping approach compared to the conventional bean sweeping approach. In the conventional beam sweeping approach, the design sweeps over all pre-defined beams in the codebook. The time of beam sweeping, or time overhead as given in Figure 4 is defined as the number of beams that need to be generated and swept to scan a specific area in the XL-MIMO system which directly reflect the system latency performance. A considerable enhancement in the system latency using the proposed approach is noticed in Figure 4 significantly when the number of available antenna elements (60) increases in the array.

[0153] During the selection process, the extra GLs that are not matching with the pre-defined beams can cause interference since their gains are in order with the main lobe beam (70) which degrades the system performance while enhancing the latency.

[0154] Based on consideration of the foregoing technical solution, possible embodiments of the invention are as follows;

[0155] • The method wherein said inter-element spacing is larger than A / 2 for enhancing the angular resolution of an array with a fixed number of antenna elements (60) and reducing the channel correlation.

[0156] • The mechanism wherein said switching network and switching apparatus which is built between the radio frequency chain (20) and the phase shifter (40) network at the radio frequency front-end,

[0157] • The mechanism wherein said the antenna elements (60) are uniform linear array, uniform planar array, uniform circular array, uniform hexagonal array, and so on.

[0158] The mechanism wherein said the antenna elements are extra-large antenna array (ELAA), extra-large MIMO (XL-MIMO), ultra-massive MIMO (UM-MIMO) or extremely large aperture massive MIMO (xMaMIMO). References

[0159]

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[0166] [8] Elsallal, M.W.A. and West, J.B., Rockwell Collins Inc, 2006. Multi-band wide-angle scan phased array antenna with novel grating lobe suppression. U.S. Patent 7,034,753.

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[0014] Laffey, C., Chieh, J.C.S., Sharma, S.K. and Farkouh, R., 2022. 1 A Spaced Dual Radiating Modes Based Phased Array Antenna Using Silicon RFICs With Grating Lobe Cancellation. IEEE Transactions on Antennas and Propagation, 70(12), pp.12328- 12333.

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Claims

CLAIMS1. A computer implemented method for spatial aliasing exploitation in 1 d and 2d extra-large antenna arrays (ELAA)-based communication networks wherein the method comprises,• Implementing codebook design which is comprising switching mechanism to make the distance adaptively between antenna element and controlling the switching network to adjust the effective inter-element spacing between the active antenna elements (60) according to the given operating frequency for beamforming and controlling the main lobes and grating lobes of the beam by switching on / off antennas,• Creating a pre-defined codebook based on the original antenna array design to maintain the orthogonality between the generated beams using on-grid approach,• Defining a possible set of inter-element spacings that the antenna array can provide as more than• For each inter-element spacing, to create grating lobe by calculating the number of grating lobes (GLs) each orthogonal beam and its corresponding location,• Selecting the optimum inter-element spacing with its GLs on the GL which is within the visible scanning range of the XL-array, and matching GL location which matches with one of the angles sets in the pre-defined codebook,• For each inter-element spacing, setting the number of active antenna as for distributed of the power uniformly over the activated antenna 2x elements (60) in order to keep the overall beam gain equal to the original beam gain in the pre-defined codebook,• Applying an analog precoder to control both the switching and phase shifter (40) networks by based on the selected optimized codebook to create orthogonal grating lobes,• Applying of an orthogonal beams-based algorithm to the design to ensure the orthogonality of the grating lobes by utilizing the resources of time, frequency, or / and code domains.

2. The method of according to claim 1 , wherein said inter-element spacing is larger than 2 / 2 for enhancing the angular resolution of an array with a fixed number of antenna elements (60) and reducing the channel correlation.

3. A switching mechanism for codebook design which is scanning the overall space with minimum generated beams at the base station (BS) side from the radio frequency (RF) front-end by utilizing the grating lobes of each main beam in MIMO systems configured to• At least one digital precoder,• At least one a radio frequency chain for allowing passband communication signals to be processed in baseband and which is connected with switch mechanism,• An antenna elements (60) more inter-element spacing choices can be considered while designing / controlling / utilizing the grating lobe,• A phase shifter (40) which is connected each antenna element (60) to let main lobes go to specific directional by changing phase angel of radiofrequency signal, characterized in that the switching mechanism comprising;• A switching apparatus (30) for turning on and off the antenna elements (60) in the array in a way that the inter-element spacing changes and grating lobes (GLs) are generated based on how many GLs are needed from the given main beam,• A switching network which is responsible for passing the signal to the antenna elements (60) that are needed for generating the beams with / without grating lobes and comprising switching mechanism,• A controller (50) for switching to adaptively make the distance antenna elements (60).

4. The switching mechanism of according to claim 3, wherein said switching network and switching apparatus (30) which is built between the radio frequency chain (20) and the phase shifter (40) network at the radio frequency front-end.

5. The switching mechanism of according to claim 3, wherein said the antenna elements (60) are uniform linear array, uniform planar array, uniform circular array, uniform hexagonal array.

6. The switching mechanism of according to claim 3, wherein said the antenna elements (60) are extra-large antenna array (ELAA), extra-large MIMO (XL- MIMO), ultra-massive MIMO (UM-MIMO) or extremely large aperture massive MIMO (xMaMIMO).

7. The mechanism of according to claim 5, wherein said the switching mechanism is used on the antennas or antenna arrays.

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