A handover method based on location of user equipment

Abstract

Invention is a handover method for a system comprising multiple base stations and multiple user equipment characterized in that comprising steps of: monitoring, by the serving base station, location of at least a user equipment that the serving base station serves; determining by, the serving base station, whether the user equipment is located in a near field region of the serving base station wherein the near field region is an area having a distance that is less than a The Rayleigh distance of the XL-MIMO base station or a far field region of the serving base station wherein the far field region is an area having The Rayleigh distance of the XL-MIMO base station; if the user equipment is located in the far field region, requesting measurement reports from user equipment; determining whether a handover is required and executing handover steps if it is determined that a handover is required.

Description

[0001] DESCRIPTION

[0002] A HANDOVER METHOD BASED ON LOCATION OF USER EQUIPMENT

[0003] TECHNICAL FIELD

[0004] Invention relates to a handover method for a system comprising multiple base stations and multiple user equipment.

[0005] PRIOR ART

[0006] Timely handovers are of critical importance in cellular networks, as they ensure uninterrupted service and optimal user experience during mobility. A handover refers to the process of transferring an active connection from one base station to another as a user moves through the network without interruption. This procedure is essential to maintain connectivity, prevent call drops, and optimize resource utilization. To ensure successful handovers, users continuously send measurement reports to the serving base station. However, this process leads to significant signaling overhead and reduced spectral efficiency, as signaling resources are consumed without carrying user data. Additionally, the serving base station repeatedly transmits handover (HO) requests to potential target base stations in conditional handover (CHO), making the HO preparation phase a key challenge and a resource-intensive process in cellular networks. This challenge is particularly significant in networks that support high mobility and dense user environments, such as 5G and beyond.

[0007] Investigations are being carried out to identify and develop efficient handover (HO) implementation techniques that guarantee optimized performance, while ensuring scalability and practicality in real-world applications.

[0008] Conditional Handover (CHO) is a feature introduced in 3GPP Release 16. This functionality was standardized to enhance the reliability of handovers such as reducing the handover failures, a critical process in cellular networks that ensures seamless and robust mobility for users. In the handover preparation phase, the CHO creates multiple target cells and chooses the most appropriate cell. The User Equipment (UE) executes the handover only when the specified conditions are met. In [1] a Fast Conditional Handover (FCHO) is introduced as part of 3GPP proposals, optimizes the handover process by reusing previously prepared target cell configurations after each handover. This approach eliminates the need for reconfiguring and re-preparing target cells during subsequent handovers, significantly reducing the signaling overhead. As a result, FCHO enhances network efficiency and reduces mobility failures, which are particularly critical in dense and high-mobility environments such as urban areas and transportation networks [1].

[0009] Similarly, [2] proposes a conditional handover algorithm for 5G. This approach leverages artificial neural networks to analyze historical data and predict radio link failures (RLF) with high accuracy, enabling the network to make informed and timely handover decisions. The conditional handover of the user equipment (UE) is triggered when the UE is predicted to experience a radio link failure (RLF) in the near future, based on the neural network's prediction. By preemptively initiating the handover process, the network ensures seamless connectivity, reduces service disruptions, and improves user experience. This not only reduces the likelihood of service interruptions but also enhances the overall adaptability and intelligence of the network in complex scenarios.

[0010] With the recent paradigm shift toward extra-large array systems, envisioned for nextgeneration communication networks, new channel characteristics are emerging compared to classical MIMO systems. These include, but are not limited to, array non-stationarity and the spherical wavefront phenomenon under the umbrella of near-field communication. This paradigm shift necessitates the development of novel communication techniques tailored to XL-MIMO systems, leveraging their unique characteristics and benefits. In this context, the handover procedure for XL-MIMO systems remains a critical aspect in handover field in terms of utilizing the near field and far field, as the concept is still relatively new in cellular and communication systems. In a nutshell, XL-MIMO systems are designed with the premise that integrating a large number of antenna elements within the same form factor can significantly enhance diversity gain, multiplexing gain, and spectral efficiency.

[0011] 1. S. Bin Iqbal, A. Awada, U. Karabulut, I. Viering, P. Schulz and G. P. Fettweis, “On the Modeling and Analysis of Fast Conditional Handover for 5G-Advanced,” 2022 IEEE 33rd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2022.

[0012] 2. Z. H. Huang, Y. S. Chen, and M. J. Tsai, "Efficient Conditional Handover Algorithm in 5G with Blockages using Recurrent Neural Network," in 2023 IEEE 20th Consumer Communications & Networking Conference (CCNC), 2023, pp. 686-687. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] The present invention relates to a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0015] An object of the invention is to reduce premature handover requests.

[0016] Another object of the invention is to reduce signaling overhead.

[0017] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a handover method for a system comprising multiple base stations and multiple user equipment. Accordingly, it is characterized in that comprising steps of:

[0018] - monitoring, by the serving base station, location of at least a user equipment that the serving base station serves;

[0019] - determining by, the serving base station, whether the user equipment is located in a near field region of the serving base station wherein the near field region is an area having a distance that is less than a Rayleigh distance to the base station or a far field region of the serving base station wherein the far field region is an area having a distance more than a Rayleigh distance to the base station;

[0020] - if the user equipment is located in the far field region, requesting measurement reports from user equipment;

[0021] - determining whether a handover is required and executing handover steps if it is determined that a handover is required. Thus, by identifying when a user is still in the near-field region, the invention helps prevent unnecessary handover triggers, thereby reducing signaling load, conserving resources, and improving system efficiency. Handover Measurement reports are only required when the user enters the far-field region of the serving base station and the near- field region of the target base station. This selective reporting reduces excessive signaling load, prevents resource waste, and improves spectral efficiency.

[0022] A possible embodiment of the invention is characterized in that the monitoring is performed with the steps of: - identifying a visibility region associated with the serving base station, the visibility region defining a set of antenna elements of the XL-MIMO array visible to a user. These antenna elements receive a significant portion of the signal power transmitted by the user equipment;

[0023] - determining the location of the user equipment based on the detection of the user equipment within the visibility region; and

[0024] - updating the location of the user equipment upon a transition of the user equipment from one region to another region based on the change in the size of its visibility region on the serving XL-MIMO base station.

[0025] Another possible embodiment of the invention is characterized in that adjusting, by the serving base station active antennas based on user equipment location. Thus, resources are used more efficiently.

[0026] Another possible embodiment of the invention characterized in that the monitoring is performed with the steps of:

[0027] - determining the wavefront type of signals received from the user equipment;

[0028] - determining whether the user equipment in near field region or far field region based on determined wavefront type.

[0029] Another possible embodiment of the invention is characterized in that determining, by the serving base station, the user equipment is in far field region of the serving base station if the determined wavefront type is planar and in the near field region of the serving base station if the determined wavefront type is spherical. By utilizing the array's spatial non-stationarity, characterized by spherical wavefronts and visibility regions, the invention eliminates the need for measurement reports in the near-field region. This significantly reduces signaling load during the handover preparation phase.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a drawing illustrating top schematic view of the system.

[0032] Figure 2 is a drawing illustrating flow chart of the method.

[0033] DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

[0034] Referring to figure 1 , invention relates to a method realized by a system comprising a multiple of extra-large antenna multiple input multiple output (XL-MIMO) base stations (100) that serve to user equipment (200). Base stations (100) which is serving a user equipment (200) is defined as the serving base station (101 ) and a neighboring base station (100) which is a candidate for handover is defined as a target base station (102).

[0035] An XL-MIMO base station (100) is a communication node equipped with an extensive array of antennas, a signal processing unit configured to manage massive multi-user data streams, transceivers for transmitting and receiving signals, and a centralized control unit to coordinate beamforming, channel estimation, and resource allocation for enhanced network capacity and coverage. User equipment (200) refers to a communication device operated by an end-user, comprising a transceiver for sending and receiving signals, a processing unit for handling communication protocols and data, an antenna system for establishing connectivity with base stations, (100) and a power unit for enabling mobility, wherein the user equipment (200) may include devices such as smartphones, tablets, laptops, loT devices, or any wireless terminal capable of interacting with the network.

[0036] The method utilizes locations of the user equipment (200) in order to avoid unnecessary measurement reporting in the areas where a handover possibility is reduced compared to areas such as edge of a coverage area.

[0037] The method comprises following steps:

[0038] Serving base station (100) (101 ) tracks, location of at least a user equipment (200) that the serving base station (101 ) serves. Serving base station (101 ) determines whether the user equipment (200) is located in a near field region (310) or a far field region (320) of the serving base station (101 ). The near field region (310) is an area having a distance that is less than a Rayleigh distance to the base station (100) and a far field region (320) of the serving base station (101 ) wherein the far field region (320) is an area having a distance more than a Rayleigh distance to the base station. (100) For instance, area closer than an X distance may be defined as near field region (310) and an area further than the distance X may be defined as far field region (320). Exemplary regions depicted in figure 1.

[0039] If the user equipment (200) is located in the far field region (320), serving base station (101 ) requests measurement reports from user equipment (200). Then the serving base station (101 ) evaluates the handover conditions and triggers handover if its required based on evaluation. Thus, the method enables avoiding unnecessary handover requests and measurement reports in the near-field region due to high quality signal in near field region. if the user equipment (200) is located in the near field region (310), measurement reports are excluded from the user equipment (200) while it remains in the near-field region (310) to reduce the signaling overhead.

[0040] The Rayleigh distance, also known as the Fraunhofer distance, is a critical concept in wireless propagation used to distinguish between the near-field and far-field regions of an antenna. It is defined as the distance from the antenna at which the phase difference across the aperture of the antenna becomes significant, leading to the beginning of far-field behavior. The Rayleigh distance can be expressed by the following Equation: where D is the maximum dimension of the antenna.

[0041] In a possible embodiment, serving base station (101 ) may monitor user equipment (200) status with uplink monitoring.

[0042] In another possible embodiment serving base station (101 ) may track user equipment (200) based on visibility regions.

[0043] In another possible embodiment, target base station (102) determines based on visibility region that the user equipment (200) is associated with the target base station (102). Based on visibility region, angle of arrival of the signal and location of the user equipment (200) may be estimated. Base station (100) adjusts active antennas based on user equipment’s (200) location. Determining position based on visibility region is well known in the art, thus it is not disclosed with further details herein.

[0044] In another possible embodiment, location of user equipment (200) may be determined based on wavefront type. If the wavefront type is determined to be is planar, the user equipment (200) is determined to be in the far field region (320). If the wavefront type is spherical, the user equipment (200) is determined to be in near field region (310). Determination of wavefront type is well known in the art, thus it is not disclosed with further details herein. The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

[0045] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0046] 100 Base station 101 Serving base station

[0047] 102 Target base station

[0048] 200 User equipment

[0049] 310 Near field region 320 Far field region

Claims

CLAIMS1 . A handover method for a system comprising multiple extra large antenna multiple input multiple output (XL-MIMO) base stations (100) and multiple user equipment (200) characterized in that comprising steps of:- monitoring, by the serving base station (101 ), location of at least a user equipment (200) that the serving base station (101 ) serves;- determining by, the serving base station (101 ), whether the user equipment (200) is located in a near field region (310) of the serving base station (101 ) wherein the near field region (310) is an area having a distance that is less than a Rayleigh distance to the base station (100) or a far field region (320) of the serving base station (101 ) wherein the far field region (320) is an area having a distance more than a Rayleigh predetermined distance to the base station; (100)- if the user equipment (200) is located in the far field region (320), requesting measurement reports from user equipment (200);- determining whether a handover is required and executing handover steps if it is determined that a handover is required.

2. The method according to claim 1 , characterized in that the monitoring is performed with the steps of:- identifying a visibility region associated with the serving base station (101 ), the visibility region defining a set of XL-MIMO array elements where the user equipment (200) is detectable by the serving base station;- determining (101 ) the location of the user equipment (200) based on the detection of the user equipment (200) within the visibility region; and- updating the location of the user equipment (200) upon a transition of the user equipment (200) from one region to another region based on the change in the size of its visibility region on the serving XL-MIMO base station.

3. The (100) method according to claim 2, characterized in that adjusting, by the serving base station (101 ) active antennas based on user equipment (200) location.

4. The method according to one of the preceding claims, characterized in that the monitoring is performed with the steps of:- determining the wavefront type of signals received from the user equipment (200);- determining whether the user equipment (200) is in near field region (310) or far field region (320) based on determined wavefront type.

5. The method according to claim 4, characterized in that determining, by the serving base station (101 ), the user equipment (200) is in far field region (320) of the serving base station(101 ) if the determined wavefront type is planar and in the near field region (310) of the serving base station (101 ) if the determined wavefront type is spherical.

6. The method according to claim 1 , characterized in that comprising the step of if it is determined that the user equipment (200) is located in the near field region (310), measurement reports are excluded from the user equipment (200) while it remains in the nearfield region (310) to reduce the signaling overhead.

7. A system comprising multiple extra large antenna multiple input multiple output (XL-MIMO) base stations and multiple user equipment (200) for controlling handover characterized in that the system is configured to perform the method of one of the claims 1-6.