A method to provide signals towards AIOT devices

Abstract

The present invention provides a method which is suitable for being used within a communication network comprising at least one main communication device (1) which has at least one antenna array (1a), and at least one AIoT device (2) which is capable of communicating with the main communication device (1) and / or at least one user device (3) which is capable of communicating with the main communication device (1) and the AIoT device (3). The method is configured to provide signals towards AIoT devices (2) for ensuring data communication, energy harvesting and identification by using grating lobes (5) generated from the main communication device (1) towards AIoT devices (2) at different angles. Thanks to the method of the present invention provide signals towards AIoT devices (2) for ensuring data communication, energy harvesting and identification, digital signal processing at the main communication device (1) is reduced.

Description

[0001] A METHOD TO PROVIDE SIGNALS TOWARDS AIOT DEVICES

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method to provide signals towards AloT (Ambient power- enabled Internet of Things) devices for ensuring data communication, energy harvesting and identification.

[0004] BACKGROUND OF THE INVENTION

[0005] Most of the existing wireless communication devices are powered by batteries that need to be replaced or recharged manually. By the developing technology, new loT (Internet of Things) technologies supporting battery-less devices with no energy storage capability or devices with energy storage that do not need to be replaced or recharged manually are provided in the state of the art. The devices called as Ambient power-enabled Internet of Things (AloT) devices are an loT device, being either battery-less or with limited energy storage capability (i.e., using a capacitor) and the energy is provided through the harvesting of radio waves, light, motion, heat, or any other power source that could be seen suitable. The AloT devices can be categorized into passive, semi-passive, and active devices based on the energy storage capabilities according to the standards. The passive device has no energy storage capacity while semi-passive and active devices have storage capacities, where the storage capacity of semi-passive devices are less than the active devices. Besides, the active devices can transmit active radio signal while the passive and semipassive devices only perform the passive communication such as backscatter communication and do not have the capability of generating an active radio signal.

[0006] Regarding the supported functions and uses cases, according to 3GPP standards, there are four main functionalities of the AloT devices including inventory, sensors, positioning, and command which can be applied to the use cases within indoor, outdoor, and indoor / outdoor. Considering the use cases and functionalities of the AloT devices, there are three major requirements for practical implementation of this technology; energy harvesting to power up these devices, identification for knowing the presence of these devices in the environment, and backscatter communication for the transfer of data. For the AloT devices, back-scattered data transmission by incorporation of beamforming techniques is used in data communication Although this provides several advantages, beamforming may constrain the availability of signals for ambient backscatter communication. In scenarios where AloT devices require flexibility in using signals generated by the RF transmission node (such as base stations) to facilitate data backscatter, this constraint becomes evident. This leads to the challenge of signal unavailability at the backscatter devices, necessitating dedicated signal transmission solely to support the backscatter communication. Inventory is one of the critical functions of the AloT devices which requires the identification of these devices in the environment to track the available things. Usually, the items and / or people that needs to be identified maybe connected to the low power AloT device or tag which has a stored information of a unique serial number, sequence and / or code like radio frequency identification device (RFID). To identify AloT device, a reader (such as base station) transmits a radio frequency (RF) carrier signal which is modulated by AloT with the stored information using backscatter modulation. As reader receives the backscattered signal from AloT, it extracts the serial number / code from the received signal and then matches that with codes / serial numbers of all AloT devices available. Within a specific region, the backscatter devices can be available anywhere in the environment. In the case, the reader uses directional communication with beamforming then it requires to search the coverage area to identify all the AloT devices in the area. The search can be done either by sweeping a single narrow beam in all the directions or by transmitting multiple beams simultaneously in different directions. The first approach creates the time overhead in the system for sweeping according to the beamwidth while the second approach requires to use more RF chains leading to the costly and complex system design.

[0007] Energy harvesting is another main feature of AloT which differentiates it from the rest of the loT technologies. To perform basic functionalities, the AloT devices need to power up through the energy harvesting which can be done from RF signals available in the environment. However, the energy harvested from the ambient RF signal may not be sufficient to support the AloT device’s functions. Additionally, the base station in the conventional communication systems normally use the beamforming to support its users, it is possible that the AloT devices may not receive RF signal at all for energy harvesting. This problem can be solved by enabling the cooperative communication through symbiotic radio, where the ambient RF source have the knowledge of the AloT devices and transmit the RF signals in their direction to support the energy harvesting. Although signal availability is achieved in this way, it adds the additional cost to the system. Furthermore, energy harvesting in backscatter-based beamforming networks is a multifaceted challenge that can benefit significantly from the precise control and optimization capabilities offered by beamforming techniques. It involves efficient RF energy capture, directional energy transmission towards AloT devices, dynamic energy allocation, and adaptation to environmental variability. By addressing these aspects, beamforming contributes to the sustainability and reliability of AloT devices within these networks.

[0008] Similar to the energy harvesting, AloT might face the same problem of signal unavailability in performing the backscatter communication for data transmission when the directional communication / beamforming is applied at the base station / RF source because both the passive and semi-passive devices can not generate the signal and rely on the received signal from the base station.

[0009] Therefore, all the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0010] BRIEF DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a method to provide signals towards AloT (Ambient power- enabled Internet of Things) devices for ensuring data communication, energy harvesting and identification by eliminating the above-mentioned disadvantages and bringing new advantages to the relevant technical field.

[0012] An object of the invention is to develop a method to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification.

[0013] Another object of the invention is to develop a method to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification efficiently.

[0014] Yet another object of the invention is to develop a method to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification which is cost-effective.

[0015] The other object of the invention is to develop a method to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification which is reliable. Another object of the invention is to develop a method to provide signals towards AloT devices for ensuring simultaneous identification of AloT device and user device.

[0016] Yet other object of the invention is to develop a method to provide signals towards AloT devices for ensuring simultaneous backscatter communication and user device communication.

[0017] The other object of the invention is to develop a method to provide signals towards AloT devices for ensuring energy harvesting during the connection.

[0018] 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 within a communication network comprising

[0019] • at least one main communication device which has at least one antenna array, which is able to provide service by broadcasting directional signal beams, defining a coverage area by creating a main lobe, through the devices within the coverage area, and which has beamforming function and

[0020] • at least one AloT device which is capable of communicating with the main communication device and / or which has backscattering function,

[0021] • at least one user device which is capable of communicating with the main communication device and the AloT device,

[0022] The method is configured to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification and comprises the steps of; o generating at least one grating lobe by increasing the inter-element spacing of the antenna array such that it is greater than the half of the operating wavelength of the antenna and the direction of the grating lobe is different from the main lobe wherein the value of the inter-element spacing is further larger than a maximum value of inter-element spacing given with the equation below

[0023] 0.5 A < where dmaxis maximum value of inter-element spacing, A represents the operating wavelength and ifjmaxis the maximum field-of-view of the antenna array, and wherein the direction angle of the grating lobe is given with the equation below +2, ± 3, ... where <pML= 27T7sin 0ML, dis value of inter-element spacing, and eMLis the z main lobe direction of the beam, and o performing identification process of the AloT device, energy harvesting process by the AloT device and / or backscatter communication process of the AloT device.

[0024] Thanks to the method of the present invention provide signals towards AloT devices for ensuring data communication, energy harvesting and identification, digital signal processing at the main communication device is reduced compared to the conventional beamforming approach. This has significant impact of reducing the processing overhead of scanning the environment if the number of AloT devices are huge in the networks. Accordingly, a method with low power consumption is ensured.

[0025] DESCRIPTION OF THE DRAWINGS

[0026] Exemplary embodiment of the method developed according to the present invention is illustrated in the attached drawings, wherein:

[0027] Figure 1 -3 are exemplary application embodiments of the method of the present invention.

[0028] Figure 4 is a comparison graphic of the method of the present invention with the conventional application.

[0029] All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:

[0030] 1 Main communication device

[0031] 1 a Antenna array

[0032] 2 AloT device

[0033] 3 User device

[0034] 4 Main lobe

[0035] 5 Grating lobe DESCRIPTION OF THE INVENTION

[0036] By the developing technology, use of loT (Internet of Things) devices getting larger and larger since they ease the daily works. For operation, these devices need power. The power is generally supplied from internal power supplies (such as batteries) of the devices and these internal power supplies should be recharged and replaced in time. The need of recharge and replace can be sometimes time consuming for the users. Accordingly, Ambient power-enabled loT (AloT) devices are developed. AloT devices meet the energy requirement by harvesting signals from the environment. Accordingly, these AloT devices should be in the coverage area of a signal beam to harvest signals. Furthermore, for performing operations, these AloT devices need to be identified by the other communication devices. For identification directional signal beams are used and due to this the Alot device should be in the coverage area of the signal beam. In addition to these, for data communication, AloT devices uses backscattering communication and for this also, the Alot device should be in the coverage area of the signal beam. To ensure the Alot device is in the coverage area of a signal beam, several technologies are used. However, these technologies are inefficient, sometimes can be insufficient, can need huge power and also can be costly. In order to eliminate these, with the present invention, a method to provide signals towards AloT devices for ensuring data communication, energy harvesting and identification is developed.

[0037] The method of the present invention, exemplary embodiments of which are given in figures 1 -3, is configured for being used by a communication network comprising

[0038] • at least one main communication device (1 ) (such as base stations) which has at least one antenna array (1 a), which is able to provide service by broadcasting directional signal beams, defining a coverage area by creating a main lobe (4), through the devices (such as user devices (3) [mobile phones, laptops etc.], loT devices, Ambient power-enabled loT (AloT) devices (2) etc.) within the coverage area, and which has beamforming function (preferably provided by using a massive MIMO (Multiple Input Multiple Output) system within the main communication device (1 )) and

[0039] • at least one AloT device (2) which is capable of communicating with the main communication device (1 ) and / or which has backscattering function

[0040] • at least one user device (3) which is capable of communicating with the main communication device (1 ) and the AloT device (2). The method is configured to provide signals towards AloT devices (2) for ensuring data communication, energy harvesting and identification and comprises the steps of

[0041] • generating at least one grating lobe (5) by increasing the inter-element spacing of the antenna array (1 a) such that it is greater than the half of the operating wavelength of the antenna and the direction of the grating lobe (5) is different from the main lobe (4) wherein the value of the inter-element spacing is further larger than a maximum value of inter-element spacing given with the equation below

[0042] 0.5 A < where dmaxis maximum value of inter-element spacing, A represents the operating wavelength and ifjmaxis the maximum field-of-view (FOV) of the antenna array (1 a), and wherein the direction angle of the grating lobe (5) is given with the equation below where <pML= 2it^sin 0ML, d is value of inter-element spacing, and 0MLis the main z lobe (4) direction of the beam, and

[0043] • performing identification process of the AloT device (2) as shown in figure 1 , energy harvesting process by the AloT device (2) as shown in figure 2 and / or backscatter communication process of the AloT device (2) as shown in figure 3.

[0044] By the method of the present invention, a method for supporting the AloT devices’ functionalities with enhanced beamforming is disclosed. Specifically, the present invention proposes a method for providing the carrier signal of the main communication device (1 ) to AloT devices (2) by exploiting the grating lobes (5) for identification, energy harvesting, and communication of the AloT devices (2). The method of the present invention can also be applied to a network where the AloT devices (2) can be connected to any smart surfaces such as Reconfigurable Intelligent Surfaces (RIS) to impose the AloT devices (2) capabilities in the network. In specific, the method leverages and improves various aspects of the symbiotic radio system performance, including computational complexity, energy consumption, multiplexing capabilities, and interference cancellation. In particular, the grating lobes (5) (spatial aliasing or it called beamforming ambiguities) generated by increasing the inter-element spacing, which is represented by “d”, of the antenna array (1 a) larger than A / 2, where “A” represents the wavelength, to provide the signals to AloT devices (2) for identification, energy harvesting and / or backscatter communication. Grating lobes (5) are a replica of the antenna gain with the same amplitude as the main lobe (4) but in other directions rather than the target one. Grating lobes (5) appearance in the communication network depends on the amount of inter-element spacing compared to a reference spacing and the antenna array (1 a) FOV (Field-Of-View). 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. Maximum allowable inter-element spacing (which is represented by dmax) is defined / given / calculated by the maximum possible angular separation between two nodes in the FOV of the antenna array (1 a). For a fix FOV, increasing inter-element spacing to a value larger than dmax might lead to zero-forcing singularity along the antenna array (1 a) due to the grating lobe (5) effect. Therefore, an upper bound is defined in for the maximum inter-element spacing to guarantee that no grating lobes (5) exist in the FOV of the antenna array (1 a) and given as the equation below:

[0045] 0.5 A < ( 1 ) where dmaxis maximum value of inter-element spacing, A represents the operating wavelength and ifjmaxis the maximum FOV of the antenna array (1 a). Accordingly, to obtain grating lobes (5) inter-element spacing of the antenna array (1 a) should be larger than the maximum inter-element spacing. With respect to this, the grating lobes (5) appear at the angles of where <pML= Anisin 0ML, d is value of inter-element spacing, and eMLis the main lobe (4) direction of the beam. With increased inter-element spacing, for a fixed direction, the grating lobes (5) position gets closer relative to the main lobe (4). Thanks to the method of the present invention, digital signal processing at the main communication device (1 ) (such as base station) is able to be reduced compared to the conventional beamforming approach. Furthermore, this has significant impact of reducing the processing overhead of scanning the environment if the number of backscatters is huge in the networks. In addition, the method of the present invention ensures low power consumption and cost reduction with respect to the conventional techniques.

[0046] In a preferable embodiment, example of which is given in figure 1 , of the present invention, for performing identification process of AloT device (2), the method further comprises the steps of

[0047] • beam sweeping by the main communication device (1 ) through the main lobe (4) and grating lobes (5) wherein the grating lobes (5) are generated using a code book at the predefined angles;

[0048] • receiving the signal by the AloT device (2), coming from the main communication device (1 ) via main lobe (4) and / or grating lobe (5) and being waked up of the AloT device (2) (the main communication device (1 ) can trigger a single or multiple AloT devices (2) through a command sequentially or randomly);

[0049] • backscattering / reflecting the received signal with an orthogonal code known to the main communication device (1 ) by the AloT device (2);

[0050] • receiving the backscattered / reflected signals by the main communication device (1 ) while beam sweeping and computing a correlation between the received backscattered / reflected signal and each possible code (pseudo random code) to identify the AloT devices (2) located at the angles of the transmitted main lobe (4) and grating lobes (5);

[0051] • preferably checking whether all AloT devices (2) have been identified or not, if yes ending the identification process, if no checking whether all the angles of the main lobe (4) and the grating lobes (5) have been swept or not, if yes ending the identification process, if no starting performing the steps from the beginning by generating the grating lobes (5).

[0052] The basic idea of the embodiment is that the switching network at the analogue side of the main communication device (1 ) activate and deactivate some of the antenna elements in the antenna array (1 a). Therefore, the activated antennas are with a specific inter-element spacing to create two or more grating lobe (5) beams based on the network requirement. A codebook is a predefined set of beamforming vectors from which the transmitter / receiver selects to transmit / receive the signal from a specific predefined direction. Each beamforming vector in the codebook corresponds to a specific direction or spatial mode chosen from finite angle sets according to the limited hardware resolution. The network (i.e. main communication device (1 )) dynamically chooses the most appropriate beamforming vector based on channel conditions, interference, or other relevant factors. In this embodiment, the initial accessing stage of the network where main communication device (1 ) (such as the reader / base station) transmits beams in all directions (within the FOV of the antenna array (1 a)) in a burst at regular defined intervals is focused on. At the beginning, the user devices (3) and the AloT devices (2) are in idle mode and ready for receiving the burst (the signal beam coming from the main communication device (1 )). The main communication device (1 ) has the capability of identifying the AloT devices (2) by using orthogonal codes. Accordingly, there are North number of orthogonal codes to serve the AloT devices (2) in the network. In other words, the number of orthogonal codes (Nort ) is equal or greater than the number of AloT devices (2) (NAIOT) (North s NAIOT). In addition, the main communication device (1 ) has accessibility to grating lobe-based codebooks (which can be designed with the knowledge of prior art such as “L. Afeef, A. Kihero, and H. Arslan, “Spatial aliasing exploitation in 1 D and 2D extra-large antenna arrays (ELAA)-based communication networks,” August 2023, ULAK patent.”) and accordingly a grating lobe-based codebook which is suitable for the environment conditions and network requirements (for instance latency can be a network requirement and if the main network requirement is the latency, the codebook should be generated with several grating lobes (5) within one beam in the predefined target (i.e. AloT device (2)) / user device (3) directions or if the main network requirement is sensing over communication, the grating lobes (5) need to be transmitted in the directions where the targets possibly exist while there is no need to generate grating lobes (5) in other directions or similarly, if the channel is highly sparse, few numbers of grating lobes (5) related to the number of channel paths from a single or few beams can be sufficient to cover the related environment) is selected (the grating lobe-based codebooks can be stored in a memory provided in the main communication device (1 ) or provided in an external device to which the main communication device (1 ) is able to connect). In each beam in the codebook that has grating lobes (5), each grating lobe (5) beam is modulated with specific grating lobe-based analogue beamformer according to the knowledge of prior art (such as provided in the article of “Dual-function radar-communications using QAM- based sidelobe modulation”, Digital Signal Processing, Ahmed, A., Zhang, Y.D. and Gu, Y., 2018., 82, pp.166-174). Therefore, when the grating lobe (5) beam is transmitted or received, the grating lobe (5) beam is able to be separable from the main lobe (4) beam to be distinguishable at both transmitter and receiver. Hence, “K” number of grating lobes (5) will have “K” number of grating lobe-based analogue beamformer extra over the main lobe (4) analogue beamformer that is performed to create a pre-defined main lobe (4) beam with its grating lobes (5). After selecting the optimum grating lobe-based codebook, the main communication device (1 ) starts transmitting the pre-defined beams (such as main lobe (4) beam and grating lobe (5) beam) with a transmitted signal. The transmitted signal may be a tone signal or any data modulated single carrier or multicarrier such as orthogonal frequency-division multiplexing (OFDM) signal to serve as the excitation signal and powering source of the AloT device (2). The AloT device (2) receives the transmitted signal and multiply it with an orthogonal code then send it back to the main communication device (1 ) over the same channel. In conventional AloT devices (2), the design of multiple-tag identification is extremely important in dense loT systems. Due to the limited capability of the backscatter device / tag (these are different kind of AloT devices (2) (there is no ADC [Analogue-Digital Converter] on the tag so that the strength of signal is unknown), it is infeasible to carry out carrier sense at the tag side, which leads to a completely different situation compared to the conventional multi-user device identification. Typically, in AloT devices (2), several methods can be applied to avoid collisions among tags. The code division multiple access (CDMA) based multiple access is one of them in which each tag has a local “pseudo-noise” (PN) code to spread its information. The PN code is referred to as “pseudo-random” since the code is predictable and repetitive, although it appears to be random noise. At the tag, each bit of the information is multiplied by the PN code, which is independent of the information, to produce a coded sequence being backscattered. Owing to the orthogonality properties among PN codes, the interference from the sequence with a different PN code is minimized. Therefore, multiple AloT device (2) identification is achieved by using different PN codes at different tags. In addition to encoding, the backscatter tag may perform the following operations, including framing, power selection, up sampling and frequency shifting processes. The user device (3) receives the transmitted signal, measures the beam strength, and decode and extract the beam ID from it. The user device (3) searches for the best beam (i.e. the beam for which the received power is maximum (and above predefined threshold)) periodically using the predefined threshold criteria (the predefined threshold is based on the system / network design itself, for example, the threshold can be noise level. In the 3GPP standard, this threshold is not defined with a specific value because it depends on the maximum transmit power, received signal power, channel conditions, transmitter / receiver capabilities.) defined by the main communication device (1 ) and identifies the beam that has the highest reference signal received power. The user device (3) informs the main communication device (1 ) with the best identified beam after the main communication device (1 ) finish the sweeping over all beams in the codebook. While the beams (main lobe (4) and the grating lobes (5)) are sweeping, the main communication device (1 ) is capable to receive the AloT device (2) signal due to the full-duplex mode. Assuming one codebook beam with K number of grating lobes (5) in all generated beams wherein there are K1 number of grating lobes (5) in the first beam, the main communication device (1 ) performs the following process on the received AloT device (2) signal: a) first, the main communication device (1 ) applies grating lobe-based analogue beamformer simultaneously to find the exact grating lobe (5) that the AloT device (2) exists which detect the locations of the AioT devices (2) for a beam (such as the first beam) having a number of (such as K1 number of) grating lobes (5), wherein the number of grating lobe-based analogue beamformer is equal to the number of grating lobes (5) in the beam; b) second, the main communication device (1 ) tests the North number of orthogonal codes to the received signal to detect / identify the AloT device (2) with its associated code. In these K1 number of grating lobes (5), the main communication device (1 ) can detect L1 number of AloT devices (2) simultaneously where L1 < K1. To identify the AloT device (2) from incoming backscattered signal at main communication device (1 ), it is necessary to determine which PN sequence is included in the signal. The main communication device (1 ) utilizes the orthogonality feature among PN sequences for AloT device (2) identification. Specifically, main communication device (1 ) uses each of the PN sequences to cross-correlate with the backscattered signal. If the correlation value of a PN sequence is larger than a predetermined threshold, the AloT device (2) with this PN sequence is determined to be in the frame with high probability. The main communication device (1 ) may perform some additional functions, for instance, if the AloT device (2) shifts the frequency of the signal, the main communication device (1 ) listens to the channel with the central frequency which is the shifted frequency. If the data frame is detected, the main communication device (1 ) takes the samples with a sampling frequency. The receiving process may also include frame synchronization and acknowledgement.

[0053] The steps a and b are repeated for each beam in the codebook, however, the number of tested orthogonal codes is North-L1 for the second beam, North-L1 -L2 for the third beam, and so on giving that {L1 ,L2,...,Li } are the number of detected AloT devices (2) within the given beam in the codebook assuming that 0<Li<Ki. Note that while the AloT devices (2) send signals during the full-duplex part, the AloT device (2) signal does not interfere with the main communication device (1 ) signal that is sent to the user device (3) due to the assumption that the AloT device (2) and the user device (3) are far enough from each other, and the signal comes from the AloT device (2) faces double attenuation due to the round trip path. Furthermore, the detection of the AloT devices (2) is done within the beam sweeping time since the full-duplex mode is adopted. Hence, the AloT devices (2) are detected and identified at the main communication device (1 ) side before the user device (3) feedbacks its selected beam for communication. Each AloT device (2) may have a specific unique ID for the case of inventory to identify a particular product or people in the environment.

[0054] In a preferable embodiment, example of which is given in figure 2, of the present invention, for performing energy harvesting process of AloT device (2), the method further comprises the steps of

[0055] • identifying the AloT devices (2) within the network by the main communication device (1 ), preferably performing the above-mentioned steps;

[0056] • directing the main lobe (4) and grating lobes (5) towards the AloT devices (2) for power transfer, according to the direction information (such as angle information) obtained by the identification process of the AloT devices (2) by the main communication device (1 );

[0057] • acknowledging (hand shaking), by the AloT device (2), the main communication device upon receiving the energy from the main lobe (4) and / or grating lobes (5) beams;

[0058] • sending acknowledgment, by the AloT device (2), to the main communication device (1 ), upon completing the energy harvesting;

[0059] • continuing the steps when energy harvesting is still required by the AloT device (2). By this embodiment the energy harvesting process is focused. In the network the main communication device (1 ) transmits beams to the identified AloT devices (2) in the network for energy harvesting purposes. In the exemplary application of this embodiment, the main communication device (1 ) detects and identifies the number of AloT devices (2) and user devices (3) in the network, their locations, and their requirement (i.e., how much energy the AloT device (2) is needed during one beam transmission etc.) (an exemplary approach is given in the article of "A multiantenna RFID reader with blind adaptive beamforming", Chen, Shaoyuan, et aL, IEEE Internet of Things Journal 3.6 (2016): 986-996.). Preferably the identification process steps mentioned above is used for detecting and identifying the AloT devices (2). After detection and identification, the total number of beams with their locations that is needed to serve the given number of AloT devices (2) and user devices (3) to fulfil their requirement are measured by the main communication device (1 ). The detection and identification process takes place at the main communication device (1 ) during the beam sweeping phase. Specifically, the main communication device (1 ) transmits reference signals to both the user devices (3) and AloT devices (2). In response, the user devices (3) provide feedback on the best beam information to the main communication device (1 ), while the AloT devices (2) backscatter the reference signals using orthogonal codes. By analysing the received information from the user devices (3) and the orthogonal codes from the AloT devices (2), the main communication device (1 ) determines the most suitable beam for the user devices (3), as well as the beams best suited for serving the AloT device (2) in terms of energy harvesting and communication. Assume that the number of AloT devices (2) and user devices (3) in the network is equal Naii, the total number of required beams Nbshould be equal or larger than Naii (Nb>Naii) due to different requirements of the AloT devices (2) in the network. For example, one AloT device (2) may need three times more energy harvesting than another AloT device (2) which simply it needs three beams to serve comparing to the another AloT device (2) that needs only one beam. Based on the total required beams and their locations, a beam codebook is designed by the main communication device (1 ). The designing step further comprises a) defining all possible beams with grating lobes (5) that can exist in the codebook, based on the number of antenna elements in the antenna array (1 a) of the main communication device (1 ), at different directions in orthogonal way (in this step the possible beams that can exist in the codebook are defined such that these beams should have grating lobes (5) that are orthogonal to each other and to the other beams. In this way, the codebook is designed and the beams in the codebook are defined); b) from the defined beams, selecting the beams that serve all AloT devices (2) and user devices (3) in the network with minimum processing overhead using different selection methods to generate a specific beam codebook wherein the selection can be done in iterative way or using intelligent mechanism such as machine learning or deep learning approaches; c) generating the selected beams that are defined in the codebook by using one RF chain by generating one beam by one beam or using multiple RF chains to generate several beams simultaneously.

[0060] Within one generated beam, the transmitted signal can be either a modulated signal or unmodulated carrier signal. If the generated beam serves a user device (3) while at least one AloT device (2) is harvesting energy, the transmitted signal would be a modulated signal carrying a data to that specific user device (3). If the generated beam only used for energy harvesting by AloT devices (2), the transmitted signal would be unmodulated carrier signal. This ensures maximum energy harvesting by the Alot devices (2) due to the constant envelop property of the unmodulated carrier signal. The AloT devices (2) receive the signal and harvest the energy. When the energy harvesting is completed, the AloT devices (2) send an acknowledgment to the main communication device (1 ). Preferably the total number of beams in the proposed codebook is less than the total number of AloT devices (2) and user devices (3) in the network which reduces the system complexity and latency.

[0061] In a preferable embodiment, example of which is given in figure 3, of the present invention, for performing backscatter communication process of AloT device (2), the method further comprises the steps of

[0062] • identifying the AloT devices (2) within the network by the main communication device (1 ), preferably performing the above-mentioned steps;

[0063] • directing, by the main communication device (1 ), the main lobe (4) and / or grating lobes (5) towards the identified AloT devices (2) for triggering the AloT devices (2) and for providing carrier signals to the AloT devices (2);

[0064] • modulating, by the Alot devices (2), the carrier signals with their data by using backscatter modulation and backscattering the modulated signal;

[0065] • receiving, by the main communication device (1 ) and / or user device (3), the backscattered signal and detecting the data of AloT devices (2) sent by the the backscattered signal;

[0066] • continuing the steps when backscattering communication is required.

[0067] By this embodiment, backscatter communication process is focused. In the network, the main communication device (1 ) transmits beams to the AloT devices (2) in the network for communicating purposes. In the exemplary application of this embodiment, the main communication device (1 ) detects and identifies the number of AloT devices (2) and user devices (3) in the network, their locations, and their requirement (i.e., how much energy the AloT device (2) is needed during one beam transmission etc.) (an exemplary approach is given in the article of "A multiantenna RFID reader with blind adaptive beamforming", Chen, Shaoyuan, et aL, IEEE Internet of Things Journal 3.6 (2016): 986-996.). Preferably the identification process steps mentioned above is used for detecting and identifying the AloT devices (2). It is assumed that the AloT devices (2) have enough energy harvested from the received signal or through any other way to perform their basic functions for backscatter communication. After detection and identification, a beam codebook that contains the beams of serving the AloT devices (2) and user devices (3) in the network is designed by the main communication device (1 ), based on their locations and requirements. This can be done by using the steps discussed in the energy harvesting embodiment of the method of the present invention. Then, the main communication device (1 ) starts transmitting the predefined beams (beams that are defined in the codebook) with a transmitted signal which can be represented by “x”. The transmitted signal may be a tone signal or data modulated single carrier or orthogonal frequency-division multiplexing (OFDM) signal to serve as the excitation signal and powering source of the backscatter system. Same signal can be sent to both user device (3) and AloT devices (2) or they can be served with different signals which can be represented by Xi and Xj. A same signal can be sent to different directions (AloT devices (2) and user device (3) directions) using a beam from the proposed codebook that has multiple grating lobes (5) pointed to the desired locations with a single RF chain which reduces the signal processing overhead and power consumption. When the AloT device (2) receives the transmitted signal (x or Xj), it modulates the signal using different type of modulation techniques such as on-off keying. The modulated signal is then transmitted back to the main communication device over same channel. When the user device (3) receives the signal (x or Xj), it detects the data out of the signal for user device (3) communication. In case the user device (3) receives a modulated signal from the AloT device (2), it interferes with the desired signal and hence reduce the network performance for communication. The main communication device (1 ) is capable to receive the signal coming from the AloT device (2) due to the full-duplex mode used. Assuming that the transmitted signal is generated from one codebook beam with K1 number of grating lobes (5), the method further comprises the steps, which are performed by the main communication device (1 ) on the received AloT device (2) signal, of; a) testing the North number of orthogonal codes by the main communication device (1 ) for the received signal to detect / identify the grating lobe (5) associated with a specific AloT device (2) wherein for the K1 number of grating lobes (5) L1 number of AloT devices (2) data is able to be received simultaneously where L1 < K1. b) for each detectable AloT device (2), extracting and demodulating the received signal by the main communication device (1 ) to perform communication connection with the AloT devices (2).

[0068] There are two main cases for the backscatter communication which are related to the presence of a user device (3), according to which the grating lobe (5) codebook is optimized. In the case where there is a user device (3), the main communication device (1 ) serves the user device (3) with the main lobe (4) and serves the AloT devices (2) with the grating lobes (5) while in the second case the main communication device serves the AloT devices (2) with both the main lobe (4) and grating lobes (5). Furthermore, the AloT devices (2) may also communicate with the main communication device (1 ) or user device (3).

[0069] For the above-given embodiments, a monostatic multiantenna backscatter-communication network (MBCN) is considered such that the network comprises a full-duplex main communication device (1 ) supporting a first number of AloT devices (2) (NAIOT) and a second number of user devices (3) (Nu). The main communication device (1 ) comprises a plurality of antenna elements located in uniform linear array with inter-element spacing of d = A / 2 while both user devices (3) and AloT devices (2) have single antenna element. The analog design part of the main communication device (1 ) comprises a switching network to control the number and location of the active antennas, and a phase shifter network where one phase shifter is connected to single antenna for a single RF chain. Due to the full-duplex feature, the main communication device (1 ) comprise (RF interference cancellation) at each antenna element to separate the transmit and receive signals. There are deterministic channels with strong dominant light-of-sight (LoS) signal paths between the main communication device (1 ) and the AloT devices (2) and user devices (3). The reflection coefficient in the AloT devices (2) is assumed to be between [0,1] and they reflect the maximum received power. The AloT devices (2) have enough energy harvesting from the received signal or through any other way to perform their basic functions.

[0070] A simulation example for the method of the present invention is given as follows. 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 main communication device (1 ) contains M = 256 antenna elements located in a uniform linear array with half-wavelength inter-element spacing (d = A / 2) and K number of single-antenna user devices (3) and L number of AloT devices (2) distributed uniformly in a specific area where the main communication device (1 ) beams can cover, the focus will be designing the orthogonal grating lobes (5) beams to identify the AloT devices (2) in the environment by transmitting less number of beams compared to the prior art applications. As a first step, the main communication device (1 ) builds a pre-defined analogue beam codebook. Assuming that the XL array can scan the area from to there will be 86 beams

[0071] 271 orthogonal in the pre-defined analogue beam codebook with — step between two adjacent beams. After that, a possible set of inter-element spacing is defined as d = A, 1.5 A, 2A, 2.5 A, 3A,3.5A,4A,4.5A,5A, 5.5 A, 6A where the number of active antenna elements is determined using M' = Ml (2%), as M' = 128, 85,64,51 ,42,36,32,28,25,23,21 respectively. Within one inter-element spacing, for each orthogonal beam in the pre-defined codebook, the locations of the grating lobes (5) are determined using below-given equation Then, a comparison between the location of the grating lobes (5) and the main lobes (4) beams in the pre-defined codebook is done. The comparison is done as follow:

[0072] Where 0MLJis the angle of the main lobe (4) of beam j in the pre-defined codebook, 6GL m iis the mthgrating lobe (5) angle of beam i, and rjthis a certain threshold. For simplicity, here in this simulation, since the beamwidth of the orig

[0073] 3inal beams is beamwidth = Md which is equal to 0.4011° in the system here, the threshold value is set to 0.05°. The grating lobe (5) that satisfies the comparison are generated from 50 beams. A line of sight (LoS) channel is considered between the main communication device (1 ) and AloT devices (2). Which is defined as ht= ata 9i), 1 = 1,2, ••• ,L, where hLdenotes the channel gain of the Z-th AloT device (2), is the complex channel gain and a(0£) represents the steering vector in the direction of the Z-th AloT device (2) et, which is uniformly distributed between - to Upon receiving a signal through main lobe (4) beam and / or grating lobe (5), a AloT device (2) modulates an orthogonal pseudo random sequence e.g., Gold codes of length 600 chips (Liu, Yanyan, Pinyi Ren, and Qinghe Du. "Symbiotic communication: Concurrent transmission for multi-users based on backscatter communication." 2020 International Conference on Wireless Communications and Signal Processing (WCSP). IEEE, 2020) using on-off keying. Upon receiving the backscattered signals consisting of the pseudo random sequence form AloT devices (2) over the grating lobes (5) and / or main lobe (4) beam. A correlation with all the sequences is performed at the main communication device (1 ) to identify the AloT devices (2). The detect / identif ied ones are removed from the sequence code book. In the next transmission, only the remaining sequences are correlated to find other AloT devices (2).

[0074] In order to evaluate the performance of the method, number of beams versus the AloT devices (2) is evaluated in Figure 4 for the proposed AloT device (2) detection / identification approach compared to the conventional beam approach. In the conventional detection / identification approach the number of beams required to detect / identify AloT device (2) is at least equal to the number of AloT devices (2). Figure 4 shows the number of beams for detecting / identifying the AloT devices (2), where for a smaller number of AloT devices (2) almost same number of beams are needed and the gains are not significant. However, as the number of AloT devices (2) increase the proposed scheme requires the transmission of a smaller number of beams. For instance, to detect 40 AloT devices (2) the conventional beam sweeping method requires to transmit 40 beams while the method of the present invention needs only 35 beams. This validates that the method of the present invention can provide the significant enhancement. As the identification of AloT devices (2) is necessary for other operations such as energy harvesting and backscatter communication, based on the results shown in Figure 4 for detection / identification, it is able to be said that the method of the present invention will also achieve gains in those two operations. If the number of AloT devices (2) are small, then the method of the present invention approaches to the conventional one.

[0075] Thanks to the method of the present invention provide signals towards AloT devices (2) for ensuring data communication, energy harvesting and identification, digital signal processing at the main communication device (1 ) is reduced compared to the conventional beamforming approach. This has significant impact of reducing the processing overhead of scanning the environment if the number of AloT devices (2) are huge in the networks. Accordingly, a method with low power consumption is ensured.

Claims

CLAIMS1. A method which is suitable for being used within a communication network comprising• at least one main communication device (1 ) which has at least one antenna array (1 a), which is able to provide service by broadcasting directional signal beams, defining a coverage area by creating a main lobe (4), through the devices within the coverage area, and which has beamforming function and• at least one AloT device (2) which is capable of communicating with the main communication device (1 ) and / or which has backscattering function,• at least one user device (3) which is capable of communicating with the main communication device (1 ) and the AloT device (3), and which is configured to provide signals towards AloT devices (2) for ensuring data communication, energy harvesting and identification characterised in that the method comprises the steps of; o generating at least one grating lobe (5) by increasing the inter-element spacing of the antenna array (1 a) such that it is greater than the half of the operating wavelength of the antenna and the direction of the grating lobe (5) is different from the main lobe (4) wherein the value of the inter-element spacing is further larger than a maximum value of inter-element spacing given with the equation below0.5 A <where dmaxis maximum value of inter-element spacing, A represents the operating wavelength and ifjmaxis the maximum field-of-view of the antenna array (1 a), and wherein the direction angle of the grating lobe (5) is given with the equation below + 2, ± 3, ...where <pML= Anisin eML, d is value of inter-element spacing, and eMLis the z main lobe (4) direction of the beam, and o performing identification process of the AloT device (2), energy harvesting process by the AloT device (2) and / or backscatter communication process of the AloT device (2).

2. The method according to claim 1 wherein; for performing identification process of AloT device (2), the method further comprises the steps of o beam sweeping by the main communication device (1 ) through the main lobe (4) and grating lobes (5) wherein the grating lobes (5) are generated using a code book at the predefined angles; o receiving the signal by the AloT device (2), coming from the main communication device (1 ) via main lobe (4) and / or grating lobe (5) and being waked up of the AloT device (2); o backscattering / reflecting the received signal with an orthogonal code known to the main communication device (1 ) by the AloT device (2); o receiving the backscattered / reflected signals by the main communication device (1 ) while beam sweeping and computing a correlation between the received backscattered / reflected signal and each possible code to identify the AloT devices (2) located at the angles of the transmitted main lobe (4) and grating lobes (5); o completing the identification of the AloT devices (2).

3. The method according to claim 2 wherein; the method further comprises checking whether all AloT devices (2) have been identified or not, if yes ending the identification process, if no checking whether all the angles of the main lobe (4) and the grating lobes (5) have been swept or not, if yes ending the identification process, if no starting performing the steps from the beginning by generating the grating lobes (5).

4. The method according to claim 2 or claim 3 wherein; the main communication device (1 ) performs the following process on the received AloT device (2) signal: o first, the main communication device (1 ) applies grating lobe-based analogue beamformer simultaneously to find the exact grating lobe (5) that the AloT device (2) exists which detect the locations of the AloT devices (2), and o second, the main communication device (1 ) tests the orthogonal codes to the received signal to detect / identify the AloT device (2) with its associated code.

5. The method according to claim 4 wherein; to identify the AloT device (2) from incoming backscattered signal at main communication device (1 ) by the main communication device (1 ), determining which pseudo-noise (PN) sequence is included in the signal by applying the orthogonality feature among PN sequences such that the main communication device (1 ) uses each of the PN sequences tocross-correlate with the backscattered signal and if the correlation value of a PN sequence is larger than a predetermined threshold, the AloT device (2) with this PN sequence is identified.

6. The method according to any one of the preceding claims wherein; for performing energy harvesting process of AloT device (2), the method further comprises the steps of o identifying the AloT devices (2) within the network by the main communication device (1 ); o directing the main lobe (4) and grating lobes (5) towards the AloT devices (2) for power transfer, according to the direction information obtained by the identification process of the AloT devices (2) by the main communication device(1 ); o acknowledging, by the AloT device (2), the main communication device upon receiving the energy from the main lobe (4) and / or grating lobes (5) beams; o sending acknowledgment, by the AloT device (2), to the main communication device (1 ), upon completing the energy harvesting; o continuing the steps when energy harvesting is still required by the AloT device(2).

7. The method according to claim 6 wherein; the identification is done according to the claims 2-5.

8. The method according to claim 6 or claim 7 wherein; the after detection and identification, the method further comprises the step of measuring the total number of beams with their locations that is required to serve the given number of AloT devices (2) and user devices (3) to fulfil their requirement by the main communication device (1)-9. The method according to claim 8 wherein; based on the total number of required beams and their locations, designing a beam codebook by the main communication device (1 ) following the below-given steps o defining all possible beams with grating lobes (5) that can exist in the codebook, based on the number of antenna elements in the antenna array (1 a) of the main communication device (1 ), at different directions in orthogonal way;o from the defined beams, selecting the beams that serve all AloT devices (2) and user devices (3) in the network with minimum processing overhead to generate a specific beam codebook; o generating the selected beams in the proposed beam codebook are using one RF chain by generating one beam by one beam or using multiple RF chains to generate several beams simultaneously.

10. The method according to any one of the preceding claims wherein; for performing backscatter communication process of AloT device (2), the method further comprises the steps of o identifying the AloT devices (2) within the network by the main communication device (1 ); o directing, by the main communication device (1 ), the main lobe (4) and / or grating lobes (5) towards the identified AloT devices (2) for triggering the AloT devices (2) and for providing carrier signals to the AloT devices (2); o modulating, by the AloT devices (2), the carrier signals with their data by using backscatter modulation and backscattering the modulated signal; o receiving, by the main communication device (1 ) and / or user device (3), the backscattered signal and detecting the data of AloT devices (2) sent by the backscattered signal; o continuing the steps when backscattering communication is required.

11. The method according to claim 10 wherein; the identification is done according to the claims 2-5.

12. The method according to claim 10 or claim 11 wherein; after detection and identification, the method further comprises the step of designing a beam codebook that contains the beams of serving the AloT devices (2) and user devices (3) in the network by the main communication device (1 ), based on their locations and requirements.

13. The method according to claim 12 wherein; designing the beam codebook is performed by following the below-given steps o generating all possible beams with grating lobes (5), based on the number of antenna elements in the antenna array (1 a) of the main communication device (1 ), at different directions in orthogonal way;o from the generated beams, selecting the beams that serve all AloT devices (2) and user devices (3) in the network with minimum processing overhead to generate a specific beam codebook; o generating the beams in the proposed beam codebook are using one RF chain by generating one beam by one beam or using multiple RF chains to generate several beams simultaneously.

14. The method according to claims 10-13 wherein; after receipt of the backscattered signal, testing the orthogonal codes by the main communication device (1 ) to detect / identify the grating lobe (5) associated with a specific AloT device (2) and for each detectable AloT device (2), extracting and demodulating the received signal by the main communication device (1 ) to perform communication connection with the AloT devices (2).

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