A method and system for conditional handover

Abstract

The invention relates to a method and a system for enabling a user equipment (UE) (10) exchanging data with a source base station (20) connected to a radio access network (RAN) to perform a conditional handover to connect to at least one of the destination base stations connected to the radio access network.

Description

[0001] A METHOD AND SYSTEM FOR CONDITIONAL HANDOVER

[0002] TECHNICAL FIELD

[0003] The invention relates to a method and a system for enabling a user equipment (UE) exchanging data with a source base station connected to a radio access network (RAN) to perform a conditional handover to connect to at least one of the destination base stations connected to the radio access network.

[0004] PRIOR ART

[0005] Handover is the process of a mobile device switching from one base station to another. Handover enables users to communicate continuously and without interruption while on the move. Handover is implemented in cellular networks by different methods. One of them; hard handover, where the device disconnects the connection with the current base station and establishes a connection with the new base station. This method is commonly used in 2G (GSM) networks and although it is simple to implement, it carries the risk of connection interruption. Another method is soft handover, where the device establishes a connection with more than one base station at the same time and switches to the base station with the strongest signal. This method is widely used in 3G (UMTS) networks and provides less risk of connection interruption. However, it is more complex and costly.

[0006] Conditional handover is an advanced method that allows the classical handover process to occur under certain conditions. This method is more widely used in 5G networks. In this method, network operators define certain conditions for handover to occur, such as signal strength dropping below a certain threshold or connection quality being poor. The mobile device constantly monitors these conditions and switches from the current base station to a new base station when the conditions are met. Since the conditions are predetermined with conditional handover, the handover process is faster and more efficient. This reduces the risk of connection interruptions and optimizes the overall performance of the network. It provides significant advantages, especially in high-speed data transfer and real-time applications (video streaming, online games, etc.).

[0007] Conditional handover has many advantages. Firstly, it helps users to have a smoother experience by ensuring that the connection of the mobile device continues without interruption. Additionally, it ensures more efficient use of network resources and balances the network load. This mechanism provides higher quality service by improving performance metrics such as signal quality and data rate. It is especially important to ensure connection continuity for users moving at high speeds (for example, in trains or vehicles) and to improve performance in dense network environments. Conditional handover is an important technology that increases the performance of mobile networks and improves the user experience.

[0008] Handover (HO) procedure refers to the transition of a mobile device (User Equipment - UE) from one base station to another in communication systems. This process is performed to ensure that the UE receives uninterrupted service on the move and to optimise the quality of the connection. The handover process starts with the UE measuring the signal strength and quality of the surrounding base stations and reporting the results to the current base station. The serving base station or the control center of the network evaluates these reports and makes the handover decision, and after the necessary preparations are made, the UE connects to the new base station and continues data transfer. For the UE, handover means uninterrupted service, high connection quality and reliable connection even on the move. It also ensures efficient use of network resources and balances the load on the network.

[0009] In the current state of the art, terrestrial cellular networks are designed primarily with terrestrial users in mind and the transmitting and receiving multiple antenna systems at the base stations are usually inclined downwards. Thus, terrestrial users can receive a stronger signal. This design decision causes users at a higher altitude, such as unmanned aerial vehicle (UAV) users, to receive service from the side lobes of the antenna beams instead of the main lobes. Additionally, as the UEs reach higher altitudes, they are more likely to receive direct line-of-sight (LoS) signals from terrestrial base stations. This may cause them to receive signals from very distant base stations. Receiving service from side lobes and the possibility of high LoS cause high-altitude users to encounter more inconsistent signal levels and therefore to handover more frequently.

[0010] UAV users may particularly move at high speed in urban areas with dense deployments and therefore they receive signals from more cells per unit time, which increases the number of base stations they visit. In addition, signal exposure increases at higher altitudes, resulting in more handover. Even a successful handover may cause a short interruption in data transmission. Because data transmission stops while the UE synchronizes with the target cell. Since these interruptions cause delay, it is important to avoid frequent handovers, especially for URLLC applications that require high reliability and low delay. There are two types of data in UAV communication: command-control data and application data. Command-control data includes ultrareliable low latency communications (URLLC) data, while application data includes video streaming and other sensor data. Therefore, in UAV communication, there must be a balance between the handover mechanism, signal level / quality, and the number of handovers.

[0011] Application WO2023208321 discloses a device and method for determining the coverage limits of a satellite cell and optimising the handover of the terminal. The device comprises one or more processors and memory. When the instructions stored on the mentioned memory are executed by the processors, they perform steps such as determining the coverage limits, controlling the position of the terminal and initiating the handover process. This method provides an uninterrupted and secure handover process in satellite communication systems, increasing service continuity and improving the overall connection quality. The mentioned system does not provide a method for unmanned aerial vehicles to perform handover without interruption.

[0012] 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 The present invention relates to a method to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0014] An object of the invention is to provide a dynamic and real-time method and system for seamless and secure handover of a user equipment (UE) from a source base station to at least one destination base station connected to a radio access network.

[0015] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method for realising a conditional handover enabling a user equipment (10) exchanging data with a source base station (20) connected to a radio access network, to connect to at least one of the target base stations (30) connected to the radio access network. Accordingly, comprising step of, measuring the signal parameters between the user equipment (10) and the source base station (20) and at least one target base station (30), transmitting to the source base station (20) the measured signal parameters, transmitting to the source base station (20) the route information of the user equipment (10), detecting at least one candidate target base station (30) connected to the radio access network, which can perform handover with the user equipment (10), through the source base station (20), according to signal parameters, route information and the network characteristic information which is available at the radio access network, transmitting the handover conditions regarding at least one candidate target base station (30) to user equipment by the source base station (20) for the user equipment to perform a handover with at least one of the detected target base stations, monitoring the conditions regarding target base stations contained in the handover conditions received from the source base station (20) by the user equipment, selecting at least one of the target base stations which is monitored by the user equipment, transmitting a handover signal to the selected target base station by the user equipment, exchanging data by establishing a handover connection between the user equipment (10) and the selected candidate target base station (30).

[0016] A possible embodiment of the invention is characterized comprises the signal parameters are at least one of RSRP, RSRQ, SINR, RSSI. A possible embodiment of the invention is characterized comprises the route information comprises at least one of location, velocity, orientation, flight path, altitude of the user equipment.

[0017] A possible embodiment of the invention is characterized comprises the network characteristic information comprises at least one of measurements map that is created with measurements taken from different points of the radio access network, antenna gain map that contains the calculation of predicted signal conditions based on large scale signal propagation.

[0018] A possible embodiment of the invention is characterized comprises the handover conditions comprise at least one of signal strength thresholds, proximity thresholds, timing information.

[0019] A possible embodiment of the invention is characterized comprises the system is configured to realize the method of claim 1 -5.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a drawing illustrating schematic view of the system

[0022] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0023] 10 User equipment

[0024] 20 Source base station

[0025] 30 Candidate target base station

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] 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. The invention relates to a method and a system for enabling a user equipment (UE) (10) exchanging data with a source base station (20) connected to a radio access network (RAN) to perform a conditional handover to connect to at least one of the destination base stations connected to the radio access network. The system comprises a user equipment (10), a source base station (20) that enables data exchange with the user equipment (10) and target base stations (30) that can be connected by handover of the user equipment (10). The handover described herein comprises procedures for enabling a user equipment (10) to connect from one base station to another base station. In a possible embodiment of the invention, it is preferred to use constantly moving devices such as unmanned aerial vehicles as user equipment (10). The mentioned method enables the user equipment (10) to be aware of suitable target base station (30), which would not be visible to the user equipment (10) with the methods in the state-of-the-art, enabling efficient handover from source base station to at least one of the target base stations (30). The method supports dynamic adaptation to real-time network conditions and user mobility. Additionally, the method provides optimal connection and resource management.

[0028] As shown in Figure 1 , the user equipment (10) enables the measurement of signal parameters between the source base station (20) and the user equipment (10) at predetermined time intervals. In a possible embodiment of the invention, the signal parameters may be at least one of Reference Signal Reception Power (RSRP), Reference Signal Reception Quality (RSRQ), Signal-to-Noise Plus Noise Ratio (SINR) and Received Signal Strength Indicator (RSSI). These parameters enable the user equipment (10) to determine the current quality of the connection and the necessity to switch to the target base stations (30). Each parameter is expressed with a specific measurement value. These values must be at certain reference values for the handover process to be triggered. These signal parameters may vary depending on the location and movement status of the user equipment (10). The user equipment (10) provides the transmission of the measured signal parameters to the source base station (20). The user equipment (10) also provides the transmission of route information to the source base station (20). The route information described herein may include information such as UE’s location, velocity, orientation, flight path, and altitude of the user equipment (10). This information is not limited to the information described herein. Route information is used to predict the future location of user equipment (10) and make optimal handover decisions. Especially for high-speed moving user equipment (10), this information ensures accurate timing of the handover process. By transmitting the measured signal parameters and route information to the source base station (20), the source base station (20) can accurately estimate the movement and location of the user equipment (10).

[0029] As shown in Figure 1 , the source base station (20) enables the detection of at least one target base station connected to the radio access network network that can perform handover with the user equipment (10) according to the measured signal parameters, route information and network characteristic information received from the radio access network. In a possible embodiment of the invention, the network characteristic information comprises at least one of measurements map that is created with measurements taken from different points of the radio access network, antenna gain map that contains the calculation of predicted signal conditions based on large scale signal propagation. This information is not limited to the information described herein. This network characteristic information is used to determine the overall performance of the network and to determine to which base stations the user equipment (10) can be better connected. Measurement maps provide an indication of network coverage and signal strengths, while antenna gain maps provide an indication of the broadcast capacity and coverage of base stations.

[0030] In order for the user equipment (10) to perform handover with at least one of the detected target base stations, the source base station (20) is provided to transmit the handover conditions regarding at least one candidate target base station (30) to the user equipment. In a possible embodiment of the invention, the handover conditions may include signal strength thresholds, proximity thresholds and timing information. This information is not limited to the information described herein. These conditions enable the user equipment (10) to perform handover in an optimal way. These conditions determine when and how the handover process will take place. For example, the handover process is initiated when the signal strength falls below a certain threshold value or when a certain movement pattern is detected in a certain time period. The user equipment (10) is enabled to monitor the target base stations (30) containing the handover conditions received from the source base station (20). The user equipment (10) enables selection of at least one of the monitored target base stations (30). Various factors such as signal quality, capacity of the target base station (30) and the current condition of the user equipment (10) are taken into consideration when making this selection. The user equipment (10) ensures the transmission of a handover signal containing the handover conditions of the user equipment (10) to the selected target base station (30). Data exchange is ensured by establishing a handover connection between the user equipment (10) and the selected target base station (30). Thus, the necessary handover connection protocols between the user equipment (10) and the target base station (30) are completed and data transmission is started. In this case, the handover process can be carried out quickly and without interruption. This allows data flow to be uninterrupted.

[0031] This conditional handover method can be applied in various radio access networks, including 5G NR and future wireless communication systems. This method improves the handover process by dynamically adapting to real-time network conditions and user mobility, ensuring uninterrupted connectivity and optimal resource utilization. By improving the user experience, especially in dense urban environments where signal conditions can change rapidly, service continuity and connection reliability are increased.

[0032] In order to achieve all the objects stated above and arising from the above detailed description, the present invention relates to a method for realising a conditional handover enabling a user equipment (10) exchanging data with a source base station (20) connected to a radio access network, to connect to at least one of the target base stations (30) connected to the radio access network. This method is characterized by including the following steps; measuring the signal parameters between the user equipment (10) and the source base station (20) and at least one target base station (30), transmitting to the source base station (20) the measured signal parameters, transmitting to the source base station (20) the route information of the user equipment (10), detecting at least one candidate target base station (30) connected to the radio access network, which can perform handover with the user equipment (10), through the source base station (20), according to signal parameters, route information and the network characteristic information which is available at the radio access network, transmitting the handover conditions regarding at least one candidate target base station (30) to user equipment (10) by the source base station (20) for the user equipment (10) to perform a handover with at least one of the detected target base stations (30), monitoring the conditions regarding target base stations contained in the handover conditions received from the source base station (20) by the user equipment (10), selecting at least one of the target base stations (30) which is monitored by the user equipment (10), transmitting a handover signal to the selected target base station by the user equipment (10), exchanging data by establishing a handover connection between the user equipment (10) and the selected candidate target base station (30).

[0033] A possible embodiment of the invention is that this method includes the signal parameters are at least one of RSRP, RSRQ, SINR, RSSI.

[0034] A possible embodiment of the invention is that this method includes the route information comprises at least one of location, velocity, orientation, flight path, altitude of the user equipment (10).

[0035] A possible embodiment of the invention is that this method the network characteristic information comprises at least one of measurements map that is created with measurements taken from different points of the radio access network, antenna gain map that contains the calculation of predicted signal conditions based on large scale signal propagation.

[0036] A possible embodiment of the invention is that this method the handover conditions comprise at least one of signal strength thresholds, proximity thresholds, timing information. 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.

Claims

CLAIMS1. A method for realising a conditional handover enabling a user equipment (10) exchanging data with a source base station (20) connected to a radio access network, to connect to at least one of the target base stations (30) connected to the radio access network, characterized in that comprising step of;- measuring the signal parameters between the user equipment (10) and the source base station (20) and at least one target base station (30),- transmitting to the source base station (20) the measured signal parameters,- transmitting to the source base station (20) the route information of the user equipment (10),- detecting at least one candidate target base station (30) connected to the radio access network, which can perform handover with the user equipment (10), through the source base station (20), according to signal parameters, route information and the network characteristic information which is available at the radio access network,- transmitting the handover conditions regarding at least one candidate target base station (30) to user equipment (10) by the source base station (20) for the user equipment (10) to perform a handover with at least one of the detected target base stations (30),- monitoring the conditions regarding target base stations (30) contained in the handover conditions received from the source base station (20) by the user equipment (10),- selecting at least one of the target base stations (30) which is monitored by the user equipment (10),- transmitting a handover signal to the selected target base station (30) by the user equipment (10),- exchanging data by establishing a handover connection between the user equipment (10) and the selected candidate target base station (30).

2. The method according to claim 1 , characterized in that the signal parameters are at least one of RSRP, RSRQ, SINR, RSSI.

3. The method according to claim 1 , characterized in that the route information comprises at least one of location, velocity, orientation, flight path, altitude of the user equipment (10).

4. The method according to claim 1 , characterized in that the network characteristic information comprises at least one of measurements map that is created with measurements taken from different points of the radio access network, antenna gain map that contains the calculation of predicted signal conditions based on large scale signal propagation.

5. The method according to claim 1 , characterized in that the handover conditions comprise at least one of signal strength thresholds, proximity thresholds, timing information.

6. A system comprising of a user equipment (10), a source base station (20) that enables data exchange with the user equipment (10) and target base stations (30) that can be connected by handover of the user equipment (10) wherein the system is configured to realize the method of claim 1 -5.

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