A method for beam tracking enhancement in v2x scenarios in multiple antenna arrays-based communication networks using spatial aliasing

Abstract

The present invention relates to a method for beam tracking enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing. The main objective of the invention is to provide a method of circumventing the impact of the cumulative beam tracking error in multiple antenna arrays-based communication network such as in V2X scenarios.

Description

[0001] DESCRIPTION

[0002] A METHOD FOR BEAM TRACKING ENHANCEMENT IN V2X SCENARIOS IN MULTIPLE ANTENNA ARRAYS-BASED COMMUNICATION NETWORKS USING SPATIAL ALIASING

[0003] TECHNICAL FIELD

[0004] The present invention relates to a method for beam tracking enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing.

[0005] PRIOR ART

[0006] Several works are proposed for beam tracking techniques for wireless communication networks. The first work in this direction is presented in references document [9], where an analog beamforming strategy is selected and an extended Kalman filter (EKF) based tracking algorithm for a sudden change detection method is proposed to track beam angles (i.e., angle of arrival (AoA) and angle of departure (AoD)) while assuming a constant channel coefficient in a mmWave system. This filter uses Jacobian matrices to transform the non-linear system into linear approximations around the current state. The results show that, while the EKF algorithm can perform even at low SNR and requires low pilot overhead, it causes system performance loss due to acquisition error. Furthermore, it has difficulties tracking a fast-varying channel environment since it requires pre-requisites for a full scan that causes long time measurement. To decrease the measurement time and provide a more suitable tracking algorithm, the authors in references document

[0010] proposed an alternative solution that requires only a single measurement with EKF estimation and a beam switching design. As an extension for the work in references document

[0010] , the authors in references document

[0011] proposed a joint minimum mean square error (MSE) beamforming with the help of EKF tracking strategy. Using the same filter, references document

[0012] proposes a beam tracking model for motion tracking (position, velocity, and channel coefficient) in mmWave vehicular communication system. The main difference of this model is shown in its state variables where approximate linear motion equations are derived from the beam angles to avoid the nonlinearity of using angles in the state variables which reduces the complexity in calculating the Jacobians matrix.

[0007] Note that the above-discussed techniques are limited to the scenarios where only a single beam is considered. In references document

[0013] , a Markov jump linear system (MJLS) and an optimal linear filter are designed to track the dynamics of the channel with two beams considering the correlation between them. This system iteratively tracks the AoA of the incoming beams only, considering the channel gain correlation between different paths. However, the computational complexity of this method increases exponentially with the number of target beams. An improved version of Kalman filter called unscented Kalman filter (UKF) is adopted in references document

[0014] and references document

[0015] for channel tracking in the angle space transmission. The UKF uses a deterministic sampling approach for its state distribution to get the true posterior mean and covariance of the transformed nonlinear system instead of approximated it as in the case of EKF. This reduces the error performance of the system and prevents the filter to diverge with a high nonlinear system. However, the UKF is applied to track the AoA only while the channel gain is obtained by a beam training method.

[0008] Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, referred to as vehicle-to-everything (V2X), is a wireless technology aimed at enabling data exchanges between a vehicle and its surroundings. V2X technology enables two key features in autonomous vehicles: cooperative sensing which increases the sensing range by means of the mutual exchange of sensed data, and cooperative manoeuvring which enables a group of autonomous vehicles to drive coordinately according to a common centralized or decentralized decision-making strategy. V2X communications can enhance the safety and efficiency of transportation systems. The V2X communications along with existing vehicle-sensing capabilities provide support for enhanced safety applications, passenger infotainment, and vehicle traffic optimization. In addition, V2X communications should support a variety of use cases like “do not pass” warning, forward collision warning, queue warning, parking discovery, optimal speed advisory, and curve speed warning in references document

[0001] . Millimeter wave (mmWave) communications have been envisioned for 5G V2X to provide high data rate connections between vehicles and nearby roadside infrastructures. However, mmWave faces several challenges. On the physical layer, mmWave is vulnerable to high attenuation. This shadowing effect limits mmWave to point-to-point line-of-sight connections up to a few hundred meters.

[0009] Due to the short wavelength, mmWave propagation is confronted with the issues of high isotropic path loss and weak penetration. Fortunately, the small-size antennas for mmWave make it possible to obtain adequate gains by directional beamforming. Such directional transmission, albeit enhancing the link connectivity and reducing the interference effect, poses enormous challenges to the beam alignment process in references document [2],

[0010] Thus, in addition to detecting the presence of the base station and access requests from the users, the mmWave initial access procedure must provide a mechanism or method by which both the users and the base station can determine suitable beamforming directions on which subsequent directional communication can be carried out. With very large antenna arrays as in massive MIMO where the beam becomes very narrow, this angular search can significantly slow down the initial access, due to the potentially large beam search space. The added time for directional search in initial access can slow what is known as control plane latency, which is the delay a user experiences during the transition from idle mode to connected state.

[0011] This transition may occur much more often in mmWave than in current LTE deployments since mmWave links are acutely susceptible to blockage problem which causes frequent radio link connection failure. This, in turn, calls for the frequent implementation of the time-consuming initial access procedures to re-establish the radio link. This problem becomes more severe in the context of the V2X scenario due to the high-speed moving user equipment (UE) (i.e., vehicle) due to the frequent beam misalignment problem in additional to the link blockage problem. For connectivity, there is a need for accurate beam alignment and connection robustness against rapid channel changes in references document [3]. Moreover, new solutions for the timely switching of beams are needed in the case of high-mobility vehicles in references document [4], While being connected, the UE will encounter two types of mobility in mmWave, namely the cell level and beam level mobility as specified in 3GPP Rel. 16 in references document [5].

[0012] To support mobility for vehicular communication, 3GPP specifies that V2X technology is expected to support up to 250 km / h for high-speed vehicles (up to 500km / h for trains) and to support ideally 0 ms of mobility interruption time in references document [6]. Unlike an omni-directional transmission, mmWave beams offer a much narrower radiation footprint which causes beam switching events to occur more frequently for a fast-moving UE. Supporting rapid and seamless switching will be necessary to avoid constant connection interruption. Switching decision-making at the point of the drop event needs to be not only fast but also smart in selecting an adequate beam for switching, which depends on both sufficient link quality and data availability references document [7],

[0013] The high mobility in V2X communications necessitates more beam training samples to reliably track vehicle movement. However, this beam alignment significantly increases the beam training overhead. In order to resolve this trade-off problem, a vehicle tracking algorithm with low overhead is required to make V2X communication systems robust to fast-moving vehicle environments in references document [8].

[0014] The previous tracking techniques in the literature attempt to reduce the beam misalignment between the nodes due to nodes' movement or / and change in the environment, extending the connection duration between the nodes to control the beam alignment within an acceptable margin error. However, the beam misalignment does not only occur due to environment or / and node variation but also due to the inherent imperfection of the tracking algorithms. Hence, the error in aligning the beam accumulated during the tracking process ultimately becomes significant enough to disrupt the connection and trigger the initial access / beam training procedure again. None of the tracking techniques documented in the literature have demonstrated the capability to effectively mitigate this cumulative error stemming from the tracking process / algorithm itself. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0015] BRIEF DESCRIPTION OF THE INVENTION

[0016] The present invention relates to a method for beam tracking enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0017] The main objective of the invention is to provide a method of circumventing the impact of the cumulative beam tracking error in V2X scenarios in multiple antenna arrays- based communication networks and thus eliminate or minimize the frequency of beam training process (that could be triggered due to this error) within the coverage area of a given network node (Base station (BS), roadside unit (RSU) etc.)

[0018] In the first aspect, the embodiment of the present application provides a method for beam tracking enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing 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.

[0019] In this invention, a method to track and correct the amount of beam misalignment due to the accumulated tracking error which, as a result, eliminates the beam training / sweeping / switching process within the coverage area of a given roadside unit in V2X scenario.

[0020] Grating lobe (GL) concept can be exploited to generate multiple beams using a single RF chain. In specific, within one RF chain, the antenna elements are activated in a way that the inter-element spacing is larger than A / 2 and GLs are generated. The main lobe beam is used for communication connection with the user while the GLs beams are used as stationary beams on specific direction for enhancing the tracking process in the system while providing better capacity and lower cost comparing to activating multiple RF chains.

[0021] Through this method that makes it possible to; exploited the GL concept to generate multiple beams using a single RF chain.

[0022] Main advantages of the invention;

[0023] • Eliminate / minimize the frequency of the beam training / sweeping / switching process within the coverage area of a given network node (Base station (BS), roadside unit (RSU) etc.),

[0024] • Performs beam training only when the vehicle enters the coverage area of the network node (Base station (BS), roadside unit (RSU) etc.),

[0025] • Minimizing the cumulative tracking error without resorting to the beam training process,

[0026] • Minimizing the latency (incurred to the frequent beam / training / sweeping / switching process), which is very critical for V2X usecase.

[0027] The method proposed by the embodiment of the present application can be applied to the 5G, 5G beyond and 6G or similar networks (and any other V2X networks that employ massive MIMO antenna systems).

[0028] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method for beam tracking enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] Figure 1 : Illustration of the conventional beam training and tracking model

[0032] Figure 2: Illustration of the system model

[0033] Figure 3: The flow chart of the proposed approach.

[0034] Figure 4: The MSE of AoA for each time instance at SNR = 30 dB for the proposed approach compared to the approach in references document

[0020] .

[0035] REFERENCE LIST

[0036] The reference numbers of the elements included in the figures are explained below.

[0037] 1 Beam tracking

[0038] 2 Realignment

[0039] 3 Beam tracking Process

[0040] 4 Misalignment

[0041] 5 Initial accessing process

[0042] 6 Beam training

[0043] 7 Perfect initial conditions

[0044] 8 Vehicle

[0045] 9 Direction of Motion

[0046] 10 Communication Beam

[0047] 11 Stationary Tracking Beam

[0048] 12 Time lapse

[0049] 13 RF Chain

[0050] 14 RF Chain for GL based stationary tracking beams

[0051] 15 RF Chain for communication beams

[0052] 16 Antenna array at the RSU

[0053] 17 Switching network DETAILED DESCRIPTION OF THE INVENTION

[0054] 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.

[0055] The present invention relates to a method for beam tracking (1 ) enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing which is shown in figure 3.

[0056] The proposed method which is for beam tracking (1 ) enhancement in V2X scenarios in multiple antenna arrays-based communication networks using spatial aliasing, is dependent on the computer implemented method.

[0057] The method can be implemented by a processor of network device / devices for integrated sensing and communication beamforming. The implementation procedure of the proposed approach is summarized in a flowchart in Figure 3.

[0058] A computer implemented method for beam tracking (1 ) enhancement in V2X scenarios in multiple antenna arrays-based communication networks comprising o At least one network node with multiple antenna element and radio frequency (RF) chains, o At least one user (example: vehicle) is equipped with an antenna element (antenna element can be single antenna or antenna array) (the users which are distributed uniformly in the environment and having a single antenna element or multiple antenna array), o At least one switching network (17) is connected between one radio frequency (RF) chain and the antenna array characterized in that the method comprises the steps of:

[0059] • Performing beam training (6) and initial accessing process (5) to start the connection and find an optimum beam direction <p that provides maximum channel gain or maximum received signal strength (RSS) between a network node (Base station (BS), roadside unit (RSU)) and a target user using conventional initial accessing process (5), • Based on the optimum beam direction from the previous step, generating a communication beam (10) to the user using one of the RF chains (13) and all antenna elements in the array,

[0060] • Deciding on the number of grating lobe (GL)-based stationary tracking beams based on how frequently the beam switching process has been being triggered within the coverage area of the network node (Base station (BS), roadside unit (RSU) etc.),

[0061] • Selecting the directions <pGL’s of the GL-based stationary tracking beams based on the angles at which the beam switching process has been being frequently triggered within the coverage area of the network node (Base station (BS), roadside unit (RSU) etc..)

[0062] • Generating grating lobe-based receiving beams toward the directionsGLobtained from the previous steps using a different RF Chain (apart from the one that used to generate the communication beam in the previous step) that is connected to the switching network (17) for GL based stationary tracking beams (14) in order to track the effect of the accumulated beam tracking error (4), where the switching network (17) is controlling the antenna elements in the antenna array to generate the GLs by turning on and off the antenna elements in away that the inter-element spacing between the active antenna elements are larger than A / 2.

[0063] • Receiving the user’s communication signal from both the communication beam (10) and the GL-based stationary tracking beam (1 1 ) at the base station (BS),

[0064] • Measuring the received signal strength (RSS) pcat the communication beam (10) and the received signal strength (RSS) pGLat the GL-based stationary tracking beam (11 ) and comparing them with each other: o if pc> pGL, continuing with the beam tracking process using the user’s signal received on the communication beam (10) by applying any of the traditional beam tracking algorithms available in the literature to predict the direction for the next transmission or reception of the user’s signal:

[0065] § updating the current direction of the communication beam (10) to = ±thrif the difference between the predicted communication beam (10) direction and the current communication beam (10) is larger than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated , and then continuing to receive new user’s signal for communication and next beam tracking iteration,

[0066] § continuing to receive user’s signal for communication and next beam tracking iteration if the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) is less than a pre-specified threshold o if pc< pGL, continuing with the beam tracking process using the user’s signal received on the communication beam (10) by applying any of the traditional beam tracking algorithms available in the literature to predict the direction 0 for the next transmission / reception of the user’s signal:

[0067] § updating the current direction of the communication beam (10) to 0 = <pGL± rjthrif the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) 0 is larger than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated 0, and then continuing to receive new user’s signal for communication and next beam tracking iteration,

[0068] § updating the current direction 0 of the communication beam (10) to 0 = 0GLif the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) 0 is less than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated 0, and then continuing to receive new user’s signal for communication and next beam tracking iteration,

[0069] • Repeating of the process until it is determined that the user equipment is beyond the coverage area of the network node (Base station (BS), roadside unit (RSU) etc.) or if the communication connection is not reliable anymore due to blockage, shadowing, deep fading, or finishing the connection. network node is base station (BS) or roadside unit (RSU) with antenna array with interarray element spacing of half-wavelength and multiple radio frequency (RF) chains whereby at least one RF chain is connected to the array elements through a switching network (17).

[0070] Optimum beam is the beam that provides maximum channel gain or maximum received strength among all trained beams.

[0071] Base station (BS) or roadside unit (RSU) is comprising be with multiple antenna array, radio frequency (RF) chains, and one switching network (17) connecting to one of the RF chains.

[0072] At least multiple antenna elements are located in a one uniform linear array with interelement spacing of half-wavelength.

[0073] User equipment where it can be equipped with single antenna or multiple antenna elements (i.e., antenna array).

[0074] The proposed enhanced beam tracking (1 ) approach has the following procedures:

[0075] 1 . Beam training (6) and initial accessing process (5) is performed to start the connection between network node (Base station (BS), roadside unit (RSU) etc.) and a target user using conventional initial accessing process (5). In this process, the channel between the user and the BS is estimated and channel parameters such as angle and path gain are extracted. Furthermore, the user ID is extracted.

[0076] 2. Based on the optimum selected beam from the previous step, a communication beam (10) is generated in the direction of the given user using one RF chain (13) where all antenna elements in the antenna array are activated to generate a narrow beam aligned towards the target user.

[0077] 3. Based on long-term observation of the environment, the places that trigger the beams to have frequent switching are defined <psw. Then, the directions of the GL-based stationary tracking beam are decided based on these frequent beams switching where < >GL< (f>sw. 4. For a better control on the locations of the stationary beams, RF Chain for GL based stationary tracking beams (14) is activated to generate a grating lobebased receiving beams in order to track the effect of the accumulated beam tracking (1 ) error. In order to generate these beams, the beamforming and switching network (17) that is connected to a specific RF Chain for GL based stationary tracking beams (14) activates a specific number of antenna elements in the array where the activated elements have an inter-element spacing larger than A / 2 (the possible choices are multiple of A / 2 due to fix design of the antenna array) so that the generated beam has multiple replicas of the main lobe called grating lobes pointing in specific directions. The directions of these grating lobes can be given asm>

[0078] 0,± l ,± 2,± 3, ...where pML= <pML, 0MLis the main lobe direction of the beam.

[0079] 5. During the communication connection, the BS receives the user’s signal from both beams, the communication beam (10) and GL-based stationary tracking beam. Note that the received signal from both communication and GL-based stationary tracking beams contains pilots and data symbols.

[0080] 6. In order to correct the accumulated beam alignment error, the received signal strength (RSS) is measured at both beams (i.e., the communication beam pc(10) and the GL-based stationary tracking beam (pGL) and compared with each other: a. If pc> pGL, it means that the user has better alignment with the communication beam (10) compared to the GL-based stationary tracking beam. Therefore, at the communication beam (10), a beam tracking (1 ) algorithm is applied such as the methods in reference document

[0017] and reference document

[0018] where the beam direction is tracked and updated based on a specified misalignment (4) threshold that can be tolerated by the system. To this end, the received pilot signals from step 5 are fed to the tracking algorithm for processing. For the specified threshold -qthr, if the difference between the beam direction and its tracked one is larger than the threshold -qthr, then the beam is updated based on = ± rjthr. If the difference is less than the threshold -qthr, the beams continue to receive new measurements (go to step 5). b. If pc< pGL, it means that the user has better alignment with the GL-based stationary tracking beam compared to the communication beam (10). In this case, the communication beam performs beam tracking (1 ) to find the tracked beam angle < >. such as the methods in reference documents

[0017] and reference document

[0018] where the beam direction is tracked and updated based on a specified misalignment (4) threshold that can be tolerated by the system. T o this end, the received pilot signals from step 5 are fed to the tracking algorithm for processing. i.lf the difference between the beam direction and its updated one < > is larger than the threshold -qthr, then the beam is updated based on =GL± -qthr. ii.lf the difference between the beam direction and its updated one is less than the threshold -qthr, the beam is updated based on 0 = 0GL.

[0081] 7. The process is repeated until the user goes beyond the coverage area of the BS / RSU or if the communication connection is not reliable anymore due to certain blockage, shadowing, deep fading, or finishing the connection.

[0082] In this invention, a method to track and correct the amount of beam misalignment (4) due to the accumulated tracking error which, as a result, eliminates the beam training (6) / sweeping / switching process within the coverage area of a given roadside unit in V2X scenario.

[0083] In particular, exploiting of the grating lobes (GL) (also known as spatial aliasing or beamforming ambiguities), which appear by increasing the inter-element spacing d larger than A / 2, where A represents the wavelength, to enhance the tracking process in the system. GLs are a replica of the antenna gain with the same amplitude as the main beam lobe but at other directions rather than the targeted one.

[0084] 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). 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 [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 for the maximum inter-element spacing to guarantee that no grating lobes exist in the FOV of the antenna array as

[0085] 0.5 A < where ipmaxis the maximum FOV of the given antenna array.

[0086] GLs appear at the angles of

[0087] Where , <PnML - TT-sin UMLML is the main lobe direction of the beam. Hence, the GL direction depends on inter-antenna spacing d , operating wavelength 2 , and the direction of the main lobe 0ML. With increased inter-element spacing, for a fixed direction, the GLs position gets closer relative to the main lobe.

[0088] In this invention, the grating lobe-based beam is responsible for sensing the user’s signal during the connection to adjust and correct the accumulated tracking error in the communication beam (10). At the RF front-end, a switching network (17) and mechanism / method is needed which is built between the RF Chain for GL based stationary tracking beams (14) and the phase shifter network. The switching network (17) is responsible for passing the signal to the antenna elements that are needed for generating the beams with / without GLs. The role of the switching network (17) is to turn on on / off some of the array elements based on the input configuration during grating lobe generation.

[0089] In the considered scenario, a method to track and correct the amount of beam misalignment (4) due to the accumulated tracking error is proposed in the V2X scenario. Here, assuming a network node (Base station (BS), roadside unit (RSU) etc.) with multiple antenna array and NRFradio frequency (RF) chains. The antenna elements located in a uniform linear array with inter-element spacing of half- wavelength d = 2 / 2 and M antenna elements. The users in the system are distributed uniformly in the environment. The users can have a single antenna element or multiple antenna array. The system model is illustrated in Figure 2.

[0090] The basic idea here is to launch fix beams on specific directions before the place where the beam switching occurs frequently based on the long-term learning of the environment. These beams refer to as stationary tracking beams (STBs) (1 1 ). During the user connection with a communication beam (10), the BS tracks the user using both the communication beam (10) and the stationary tracking beams (11 ). If the detected received signal strength (RSS) at the communication beam (10) is less than the one detected from the stationary beam, the communication beam (10) updates its direction to the direction of the stationary tracking beam (1 1 ). This means that the misalignment (4) in the communication beam (10) is large enough which may cause significant degradation in the connection performance and hence drop the beam connection.

[0091] The stationary tracking beams (1 1 ) can be generated by using multiple RF chains. However, this causes cost and resources overhead which reduces the users and system capacity. Hence, in this invention, the GL concept can be exploited to generate multiple beams using a single RF Chain for GL based stationary tracking beams (14). In specific, within one RF Chain for GL based stationary tracking beams (14), the antenna elements are activated in a way that the inter-element spacing is larger than 2 / 2 and GLs are generated. The main lobe beam is used for communication connection with the user while the GLs beams are used as stationary beams on specific direction for enhancing the tracking process in the system while providing better capacity and lower cost comparing to activating multiple RF chains.

[0092] In the above discussion, the scenario considered one user. However, the scenario can be extended to multiple users’ transmission and tracking. One RF chain (13) is activated for each user connection while only one RF chain for GL based stationary tracking beams (14) is used to activate the GL-based stationary tracking beam. The GL-based stationary tracking beam can be used to receive signals from all active users given that the users’ pilot signals are orthogonal to each other. In this case, the users’ signals can be separable at the BS / RSU side to detect the RSS for each user using only the GL-based stationary tracking beam.

[0093] In the above scenario, the sensing mechanism / method can be added to the system. This can be done by assuming that the user has the capability to continuously send a triggering signal in an omnidirectional way based on the wake-up signal concept introduced in reference document

[0019] .

[0094] In specific, the user sends an omnidirectional triggering signal which is a basic unmodulated signal that contains user ID and orthogonal to other users’ triggering signals. The BS receives the triggering signal using the GL-based stationary tracking beam. From that, the BS detects the location and the speed of the user which can enhance the alignment of the communication beam (10) between the BS and user. The speed can be detected by considering the time difference between the receiving signal from the grating lobes giving that the distances and locations of the grating lobes are fixed and known at the network node (Base station (BS), roadside unit (RSU) etc.) side. The user location can be detected by considering detecting the received signal power over time giving that the initial location of the user is known.

[0095] Considering a single-user MIMO system with one network node (Base station (BS) or roadside unit (RSU)) equipped with M antenna elements and one moving user with N antenna elements.

[0096] The system operates at fc= 60 GHz frequency. The user has 16 antenna elements (N = 16) placed in uniform linear array with half-wavelength spacing (d = Al 2) while the BS design is set as follows:

[0097] 1 . It is equipped with M = 64 antenna elements placed in uniform linear array with half-wavelength spacing (d = Al 2).

[0098] 2. The antenna array can scan the area from to It is equipped with a switching network (17) at its analog part where the switching controls the number of active antenna elements.

[0099] 3. It has NRFRF chains (13) for communication with users and at least one RF chain (14) for generating a beam with grating lobes (GL). For the GL-based RF chain, the switching network (17) activates antenna elements with inter-element spacing of d = * 2.5 to generate 4 GL beams located 5° before the frequent beam switching occurs in the environment within the scanning area. Assuming that the possible orthogonal beams can be generated in the system in general is given in the range to with step of with M = 64. Hence, the possible orthogonal beams with their GLs locations are given in Table 1 . 2.5. I 8i s

[0100] For a specific case, assume that the user is connected to the BS with a communication RF chain with initial angles 0AoD= 0AoA= 45° after estimating the channel between them. One of the GL beams can be activated at around 47° direction. The communication RF chain applies the proposed enhanced tracking algorithm discussed through the invention where the EKF is used as a tracking algorithm for the beam tracking process (3) as presented in

[0020] . The tracking algorithm parameters are set as in reference document

[0020] for far comparison. The performance of the proposed method is evaluated in terms of mean square error (MSE). The MSE is defined as follow:

[0101] MSE = E[<pest- ]

[0102] Whereestis the estimated beam angle (i.e., AoA or AoD) and E[. ] Is the expected value. The threshold Tthris set to 4 * io-3-

[0103] The results are compared with the method proposed in the given reference document

[0020] . The MSE performance is illustrated in Figure 4. It is noticed from the figure that the proposed approach stays below the given threshold during the tracking period.

[0104] References

[0105]

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[0113]

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Claims

CLAIMS1. A computer implemented method for beam tracking (1 ) enhancement in V2X scenarios in multiple antenna arrays-based communication networks comprising o At least one network node with multiple antenna elements and radio frequency (RF) chains, o At least one user is equipped with an antenna element, o At least one switching network (17) is connected between one radio frequency (RF) chain and the antenna array characterized in that the method comprises the steps of:• Performing beam training (6) and initial accessing process (5) to start the connection and find an optimum beam direction <p that provides maximum channel gain or maximum received signal strength (RSS) between network node and a target user using conventional initial accessing process (5),• Based on the optimum beam direction from the previous step, generating a communication beam (10) to the user using one of the RF chains (13) and all antenna elements in the array,• Deciding on the number of grating lobe (GL)-based stationary tracking beams based on how frequently the beam switching process has been being triggered within the coverage area of the network node,• Selecting the directions <pGL’s of the GL-based stationary tracking beams based on the angles at which the beam switching process has been being frequently triggered within the coverage area of the network node,• Generating grating lobe-based receiving beams toward the directionsGLobtained from the previous steps using a different RF Chain that is connected to the switching network (17) for GL based stationary tracking beams (14) in order to track the effect of the accumulated beam tracking error (4), where the switching network (17) is controlling the antenna elements in the antenna array to generate the GLs by turning on and off the antenna elements in away that the inter-element spacing between the active antenna elements are larger than A / 2,• Receiving the user’s communication signal from both the communication beam (10) and the GL-based stationary tracking beam (1 1 ) at the network node,• Measuring the received signal strength (RSS) pcat the communication beam (10) and the received signal strength (RSS) pGLat the GL-based stationary tracking beam (11 ) and comparing them with each other: o if pc> pGL, continuing with the beam tracking process using the user’s signal received on the communication beam (10) by applying any of the traditional beam tracking algorithms available in the literature to predict the direction 0 for the next transmission or reception of the user’s signal: § updating the current direction of the communication beam (10) to 0 = 0 ±thrif the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) is larger than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated , and then continuing to receive new user’s signal for communication and next beam tracking iteration,§ continuing to receive user’s signal for communication and next beam tracking iteration if the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) is less than a pre-specified thresholdo if pc< pGL, continuing with the beam tracking process using the user’s signal received on the communication beam (10) by applying any of the traditional beam tracking algorithms to predict the direction 0 for the next transmission / reception of the user’s signal:§ updating the current direction of the communication beam (10) to 0 = <pGL± rjthrif the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) 0 is larger than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated 0, and then continuing to receive new user’s signal for communication and next beam tracking iteration,§ updating the current direction of the communication beam (10) to 0 = <pGLif the difference between the predicted communication beam (10) direction 0 and the current communication beam (10) 0 is less than a pre-specified threshold -qthr, regenerating the communication beam (10) based on the updated 0, and then continuing to receive new user’s signal for communication and next beam tracking iteration,• Repeating of the process until it is determined that the user equipment is beyond the coverage area of the network node or if the communication connection is not reliable anymore due to blockage, shadowing, deep fading, or finishing the connection.

2. The method of according to claim 1 , wherein said network node is base station (BS) or roadside unit (RSU) with antenna array with inter-array element spacing of half-wavelength and multiple radio frequency (RF) chains whereby at least one RF chain is connected to the array elements through a switching network (17).

3. The method of according to claim 1 , wherein said multiple antenna elements are located in a one uniform linear array with inter-element spacing of halfwavelength.

4. The method of according to claim 1 , wherein said user equipment is single antenna or multiple antenna element.

5. The method of according to claim 1 , wherein said base station (BS) or roadside unit (RSU) is comprising with multiple antenna array, radio frequency (RF) chains, and one switching network (17) connecting to one of the RF chains.

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