Patent Publication Number: US-2023156558-A1

Title: Method and apparatus for mobility handling in wireless communication system

Description:
BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure relates to a mobility handling in wireless communications. 
     Related Art 
     3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement. 
     Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future. 
     The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible. 
     Due to a mobility of a user equipment (UE) in a wireless communication system, there may be a situation where serving cell quality may degrade and/or neighbor cell quality may become better. In this situation, the UE may perform a mobility. The mobility may comprise two kinds of mobility: legacy mobility and conditional mobility. According to legacy mobility, the UE may perform a mobility upon receiving a legacy mobility command. In contrast, according to conditional mobility, upon receiving a conditional mobility command, the UE may evaluate mobility condition(s), and perform a mobility when/if the mobility condition(s) are satisfied. 
     SUMMARY OF THE DISCLOSURE 
     Technical Problem 
     An aspect of the present disclosure is to provide method and apparatus for mobility handling in a wireless communication system. 
     Another aspect of the present disclosure is to provide method and apparatus for handling a legacy mobility and a conditional mobility in a wireless communication system. 
     Another aspect of the present disclosure is to provide method and apparatus for handling mobility when receiving a legacy mobility command and a conditional mobility command together in a wireless communication system. 
     Another aspect of the present disclosure is to provide method and apparatus for handling an evaluation of a mobility condition related to a conditional mobility in a wireless communication system. 
     Technical Solution 
     According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: receiving, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiating a legacy mobility procedure upon receiving the legacy mobility command; and stopping an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to an embodiment of the present disclosure, a wireless device in a wireless communication system comprises: a transceiver; a memory; and at least one processor operatively coupled to the transceiver and the memory, and configured to: control the transceiver to receive, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiate a legacy mobility procedure upon receiving the legacy mobility command; and stop an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to an embodiment of the present disclosure, a method performed by a base station (BS) in a wireless communication system comprises: transmitting, to a wireless device, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command, wherein a legacy mobility procedure is initiated upon the wireless device receiving the legacy mobility command, and wherein an evaluation of the mobility condition is stopped during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to an embodiment of the present disclosure, a base station (BS) in a wireless communication system comprises: a transceiver; a memory; and at least one processor operatively coupled to the transceiver and the memory, and configured to: control the transceiver to transmit, to a wireless device, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command, wherein a legacy mobility procedure is initiated upon the wireless device receiving the legacy mobility command, and wherein an evaluation of the mobility condition is stopped during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to an embodiment of the present disclosure, a processor for a wireless device in a wireless communication system is configured to control the wireless device to perform operations comprising: receiving, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiating a legacy mobility procedure upon receiving the legacy mobility command; and stopping an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to an embodiment of the present disclosure, a computer-readable medium having recorded thereon a program for performing each step of a method on a computer is provided. The method comprises: receiving, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiating a legacy mobility procedure upon receiving the legacy mobility command; and stopping an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     Advantageous Effect 
     The present disclosure can have various advantageous effects. 
     For example, various embodiments of the present disclosure may provide solutions to prevent ambiguous handling from the RRC configuration handling including the legacy HO command and the CHO configuration together. The UE may not override mobility unnecessarily due to CHO triggering during the legacy handover. 
     Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows examples of 5G usage scenarios to which the technical features of the present disclosure can be applied. 
         FIG.  2    shows an example of a wireless communication system to which the technical features of the present disclosure can be applied. 
         FIG.  3    shows an example of a wireless communication system to which the technical features of the present disclosure can be applied. 
         FIG.  4    shows another example of a wireless communication system to which the technical features of the present disclosure can be applied. 
         FIG.  5    shows a block diagram of a user plane protocol stack to which the technical features of the present disclosure can be applied. 
         FIG.  6    shows a block diagram of a control plane protocol stack to which the technical features of the present disclosure can be applied. 
         FIG.  7    illustrates a frame structure in a 3GPP based wireless communication system. 
         FIG.  8    illustrates a data flow example in the 3GPP NR system. 
         FIG.  9    shows an example of a legacy handover procedure to which technical features of the present disclosure can be applied. 
         FIG.  10    shows an example of a conditional mobility procedure to which technical features of the present disclosure can be applied. 
         FIG.  11    shows an example of a method for handling a conditional mobility during a legacy mobility according to an embodiment of the present disclosure. 
         FIG.  12    shows an example of a signal flow for handling a conditional mobility during a legacy mobility according to an embodiment of the present disclosure. 
         FIG.  13    shows an example of a case in which a legacy HO successes and UE stops monitoring candidate cells for CHO during a legacy HO. 
         FIG.  14    shows an example of a case in which a legacy HO fails and UE stops monitoring candidate cells for CHO according to an embodiment of the present disclosure. 
         FIG.  15    shows an example of a case in which a legacy HO successes and UE refrains from executing CHO towards any candidate cell according to an embodiment of the present disclosure. 
         FIG.  16    shows an example of a case in which a legacy HO fails and UE stop executing CHO towards any candidate cells according to an embodiment of the present disclosure. 
         FIG.  17    shows a UE to implement an embodiment of the present disclosure. 
         FIG.  18    shows another example of a wireless communication system to which the technical features of the present disclosure can be applied. 
         FIG.  19    shows an example of an AI device to which the technical features of the present disclosure can be applied. 
         FIG.  20    shows an example of an AI system to which the technical features of the present disclosure can be applied. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The technical features described below may be used by a communication standard by the 3rd generation partnership project (3GPP) standardization organization, a communication standard by the institute of electrical and electronics engineers (IEEE), etc. For example, the communication standards by the 3GPP standardization organization include long-term evolution (LTE) and/or evolution of LTE systems. The evolution of LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G new radio (NR). The communication standard by the IEEE standardization organization includes a wireless local area network (WLAN) system such as IEEE 802.11a/b/g/n/ac/ax. The above system uses various multiple access technologies such as orthogonal frequency division multiple access (OFDMA) and/or single carrier frequency division multiple access (SC-FDMA) for downlink (DL) and/or uplink (UL). For example, only OFDMA may be used for DL and only SC-FDMA may be used for UL. Alternatively, OFDMA and SC-FDMA may be used for DL and/or UL. 
     Here, the radio communication technologies implemented in the wireless devices in the present disclosure may include narrowband internet-of-things (NB-IoT) technology for low-power communication as well as LTE, NR and 6G. For example, NB-IoT technology may be an example of low power wide area network (LPWAN) technology, may be implemented in specifications such as LTE Cat NB1 and/or LTE Cat NB2, and may not be limited to the above-mentioned names Additionally and/or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may communicate based on LTE-M technology. For example, LTE-M technology may be an example of LPWAN technology and be called by various names such as enhanced machine type communication (eMTC). For example, LTE-M technology may be implemented in at least one of the various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTE Machine Type Communication, and/or 7) LTE M, and may not be limited to the above-mentioned names Additionally and/or alternatively, the radio communication technologies implemented in the wireless devices in the present disclosure may include at least one of ZigBee, Bluetooth, and/or LPWAN which take into account low-power communication, and may not be limited to the above-mentioned names. For example, ZigBee technology may generate personal area networks (PANs) associated with small/low-power digital communication based on various specifications such as IEEE 802.15.4 and may be called various names. 
     In the present disclosure, “A or B” may mean “only A”, “only B”, or “both A and B”. In other words, “A or B” in the present disclosure may be interpreted as “A and/or B”. For example, “A, B or C” in the present disclosure may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”. 
     In the present disclosure, slash (/) or comma (,) may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B or C”. 
     In the present disclosure, “at least one of A and B” may mean “only A”, “only B” or “both A and B”. In addition, the expression “at least one of A or B” or “at least one of A and/or B” in the present disclosure may be interpreted as same as “at least one of A and B”. 
     In addition, in the present disclosure, “at least one of A, B and C” may mean “only A”, “only B”, “only C”, or “any combination of A, B and C”. In addition, “at least one of A, B or C” or “at least one of A, B and/or C” may mean “at least one of A, B and C”. 
     Also, parentheses used in the present disclosure may mean “for example”. In detail, when it is shown as “control information (PDCCH)”, “PDCCH” may be proposed as an example of “control information”. In other words, “control information” in the present disclosure is not limited to “PDCCH”, and “PDDCH” may be proposed as an example of “control information”. In addition, even when shown as “control information (i.e., PDCCH)”, “PDCCH” may be proposed as an example of “control information”. 
     Technical features that are separately described in one drawing in the present disclosure may be implemented separately or simultaneously. 
     The terms used throughout the disclosure can be defined as the followings: 
     ‘Mobility’ refers to a procedure for i) changing a PCell of a UE (i.e., handover or PCell change), ii) changing a PSCell of a UE (i.e., SN change or PSCell change), and/or iii) adding a PSCell for a UE (i.e., SN addition or PSCell addition). Therefore, the mobility may comprise at least one of a handover, an SN change or an SN addition. In other words, the mobility may comprise at least one of PCell change, PSCell change or PSCell addition. Throughout the disclosure, performing a mobility to a target cell may refer to applying a mobility command of the target cell or applying a target cell configuration for the target cell in the mobility command of the target cell. The target cell configuration for the target cell may comprise RRC reconfiguration parameters associated with the mobility to the target cell. Further, RRC reconfiguration and RRC connection reconfiguration may be used interchangeably. 
     ‘SN mobility’ refers to a procedure for i) changing a PSCell of a UE (i.e., SN change or PSCell change), and/or ii) adding a PSCell for a UE (i.e., SN addition or PSCell addition). Therefore, the SN mobility may comprise at least one of an SN change or an SN addition. In other words, the SN mobility may comprise at least one of PSCell change or PSCell addition. Throughout the disclosure, performing an SN mobility to a target cell may refer to applying an SN mobility command of the target cell or applying a target cell configuration for the target cell in the SN mobility command of the target cell. The target cell configuration for the target cell may comprise RRC reconfiguration parameters associated with the SN mobility to the target cell. The SN mobility may be a kind of a mobility. The SN mobility command may comprise a SN change command for performing SN change, or SN addition command for performing SN addition. 
     ‘Mobility condition for a target cell’ refers to a triggering condition for a mobility to the target cell. That is, the mobility condition for a target cell refers to a condition that should be satisfied for triggering a mobility to the target cell. Mobility condition may comprise at least one of event A3 condition (i.e., mobility condition for event A3) or event A5 condition (i.e., mobility condition for event A5). The event A3 condition may comprise at least one of an offset value, or a time-to-trigger (TTT). The event A5 condition may comprise at least one of a serving cell threshold, a target cell threshold, or a TTT. The mobility condition for an event may be satisfied if/when an entering condition (or, also referred to as entry condition) for the event is satisfied for at least the TTT. For example, the entering condition for event A3 may be satisfied if a signal quality for a target cell is better than that for a serving cell more than or equal to the offset value. For another example, an entering condition for event A5 may be satisfied if a signal quality for a target cell is better than the target cell threshold and a signal quality for a serving cell is lower than the serving cell threshold. The mobility condition may also be referred to as an execution condition/conditional execution condition/conditional mobility execution condition (e.g., CHO execution condition). 
     ‘SN mobility condition for a target cell’ refers to a triggering condition for an SN mobility (i.e., SN addition or SN change) to the target cell. That is, the SN mobility condition for a target cell refers to a condition that should be satisfied for triggering an SN mobility to the target cell. SN mobility condition for a target cell may be classified as: 
     i) SN addition condition for a target cell, which refers to a triggering condition for an SN addition of the target cell; or 
     ii) SN change condition for a target cell, which refers to a triggering condition for an SN change to the target cell. 
     SN mobility condition may comprise at least one of an event, time-to-trigger (TTT), offset value, or threshold value(s). The SN mobility condition for an event may be satisfied if an entering condition for the event is satisfied for at least the TTT. 
     For example, SN addition condition may be related to event A4 or event B1. The entering condition for event A4 or B1 may be satisfied if a signal quality for a target cell is better than a threshold. 
     For example, SN change condition may be related to event A3 or event A5. The entering condition for event A3 may be satisfied if a signal quality for a target cell is better than that for a source PScell more than or equal to the offset value. For another example, the entering condition for event A5 may be satisfied if a signal quality for a target cell is better than a first threshold and a signal quality for a source PScell is lower than a second threshold. 
     ‘Conditional mobility’ refers to a mobility that is performed to a target cell which satisfies a triggering condition among a plurality of candidate target cells. Throughout the disclosure, performing a conditional mobility to a target cell may refer to applying a conditional mobility command of a target cell which satisfies a mobility condition for the target cell among a plurality of candidate target cells or applying a target cell configuration for the target cell in the conditional mobility command of the target cell which satisfies a mobility condition for the target cell among the plurality of candidate target cells. The target cell configuration for the target cell may comprise RRC reconfiguration parameters associated with the conditional mobility to the target cell. 
     Throughout the disclosure, the terms ‘radio access network (RAN) node’, ‘base station’, ‘eNB’, ‘gNB’ and ‘cell’ may be used interchangeably. Further, a UE may be a kind of a wireless device, and throughout the disclosure, the terms ‘UE’ and ‘wireless device’ may be used interchangeably. 
     Throughout the disclosure, the terms ‘cell quality’, ‘signal strength’, ‘signal quality’, ‘channel state’, ‘channel quality’, ‘ channel state/reference signal received power (RSRP)’ and ‘ reference signal received quality (RSRQ)’ may be used interchangeably. 
     Further, in the disclosure, T304 timer is defined. UE may start the T304 timer upon reception of RRCReconfiguration message including reconfigurationWithSync (i.e., legacy mobility command) or upon a conditional reconfiguration execution/conditional mobility execution (i.e., when applying stored RRCReconfiguration message including reconfigurationWithSync/stored conditional mobility command/stored target cell configuration in the conditional mobility command. 
     The UE may stop the T304 timer upon successful completion of random access on the corresponding SpCell (i.e., upon successful completion of mobility). For T304 of SCH, the UE may stop the T304 timer upon SCG release. 
     At the expiry of the T304 timer (e.g., mobility failure): 
     For T304 of MCG, in case of a mobility from NR or intra-NR mobility, the UE may initiate the RRC re-establishment procedure; and 
     For T304 of SCG, the UE may inform network among the reconfiguration with failure by initiating the SCG failure information procedure. 
     The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals/messages/fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings. 
       FIG.  1    shows examples of 5G usage scenarios to which the technical features of the present disclosure can be applied. 
     The 5G usage scenarios shown in  FIG.  1    are only exemplary, and the technical features of the present disclosure can be applied to other 5G usage scenarios which are not shown in  FIG.  1   . 
     Referring to  FIG.  1   , the three main requirements areas of 5G include (1) enhanced mobile broadband (eMBB) domain, (2) massive machine type communication (mMTC) area, and (3) ultra-reliable and low latency communications (URLLC) area. Some use cases may require multiple areas for optimization and, other use cases may only focus on only one key performance indicator (KPI). 5G is to support these various use cases in a flexible and reliable way. 
     eMBB focuses on across-the-board enhancements to the data rate, latency, user density, capacity and coverage of mobile broadband access. The eMBB aims ˜10 Gbps of throughput. eMBB far surpasses basic mobile Internet access and covers rich interactive work and media and entertainment applications in cloud and/or augmented reality. Data is one of the key drivers of 5G and may not be able to see dedicated voice services for the first time in the 5G era. In 5G, the voice is expected to be processed as an application simply using the data connection provided by the communication system. The main reason for the increased volume of traffic is an increase in the size of the content and an increase in the number of applications requiring high data rates. Streaming services (audio and video), interactive video and mobile Internet connectivity will become more common as more devices connect to the Internet. Many of these applications require always-on connectivity to push real-time information and notifications to the user. Cloud storage and applications are growing rapidly in mobile communication platforms, which can be applied to both work and entertainment. Cloud storage is a special use case that drives growth of uplink data rate. 5G is also used for remote tasks on the cloud and requires much lower end-to-end delay to maintain a good user experience when the tactile interface is used. In entertainment, for example, cloud games and video streaming are another key factor that increases the demand for mobile broadband capabilities. Entertainment is essential in smartphones and tablets anywhere, including high mobility environments such as trains, cars and airplanes. Another use case is augmented reality and information retrieval for entertainment. Here, augmented reality requires very low latency and instantaneous data amount. 
     mMTC is designed to enable communication between devices that are low-cost, massive in number and battery-driven, intended to support applications such as smart metering, logistics, and field and body sensors. mMTC aims ˜10 years on battery and/or ˜1 million devices/km2. mMTC allows seamless integration of embedded sensors in all areas and is one of the most widely used 5G applications. Potentially by 2020, internet-of-things (IoT) devices are expected to reach 20.4 billion. Industrial IoT is one of the areas where 5G plays a key role in enabling smart cities, asset tracking, smart utilities, agriculture and security infrastructures. 
     URLLC will make it possible for devices and machines to communicate with ultra-reliability, very low latency and high availability, making it ideal for vehicular communication, industrial control, factory automation, remote surgery, smart grids and public safety applications. URLLC aims ˜1 ms of latency. URLLC includes new services that will change the industry through links with ultra-reliability/low latency, such as remote control of key infrastructure and self-driving vehicles. The level of reliability and latency is essential for smart grid control, industrial automation, robotics, drones control and coordination. 
     Next, a plurality of use cases included in the triangle of  FIG.  1    will be described in more detail. 
     5G can complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS) as a means of delivering streams rated from hundreds of megabits per second to gigabits per second. This high speed can be required to deliver TVs with resolutions of 4K or more (6K, 8K and above) as well as virtual reality (VR) and augmented reality (AR). VR and AR applications include mostly immersive sporting events. Certain applications may require special network settings. For example, in the case of a VR game, a game company may need to integrate a core server with an edge network server of a network operator to minimize delay. 
     Automotive is expected to become an important new driver for 5G, with many use cases for mobile communications to vehicles. For example, entertainment for passengers demands high capacity and high mobile broadband at the same time. This is because future users will continue to expect high-quality connections regardless of their location and speed. Another use case in the automotive sector is an augmented reality dashboard. The driver can identify an object in the dark on top of what is being viewed through the front window through the augmented reality dashboard. The augmented reality dashboard displays information that will inform the driver about the object&#39;s distance and movement. In the future, the wireless module enables communication between vehicles, information exchange between the vehicle and the supporting infrastructure, and information exchange between the vehicle and other connected devices (e.g. devices accompanied by a pedestrian). The safety system allows the driver to guide the alternative course of action so that he can drive more safely, thereby reducing the risk of accidents. The next step will be a remotely controlled vehicle or self-driving vehicle. This requires a very reliable and very fast communication between different self-driving vehicles and between vehicles and infrastructure. In the future, a self-driving vehicle will perform all driving activities, and the driver will focus only on traffic that the vehicle itself cannot identify. The technical requirements of self-driving vehicles require ultra-low latency and high-speed reliability to increase traffic safety to a level not achievable by humans. 
     Smart cities and smart homes, which are referred to as smart societies, will be embedded in high density wireless sensor networks. The distributed network of intelligent sensors will identify conditions for cost and energy-efficient maintenance of a city or house. A similar setting can be performed for each home. Temperature sensors, windows and heating controllers, burglar alarms and appliances are all wirelessly connected. Many of these sensors typically require low data rate, low power and low cost. However, for example, real-time high-definition (HD) video may be required for certain types of devices for monitoring. 
     The consumption and distribution of energy, including heat or gas, is highly dispersed, requiring automated control of distributed sensor networks. The smart grid interconnects these sensors using digital information and communication technologies to collect and act on information. This information can include supplier and consumer behavior, allowing the smart grid to improve the distribution of fuel, such as electricity, in terms of efficiency, reliability, economy, production sustainability, and automated methods. The smart grid can be viewed as another sensor network with low latency. 
     The health sector has many applications that can benefit from mobile communications. Communication systems can support telemedicine to provide clinical care in remote locations. This can help to reduce barriers to distance and improve access to health services that are not continuously available in distant rural areas. It is also used to save lives in critical care and emergency situations. Mobile communication based wireless sensor networks can provide remote monitoring and sensors for parameters such as heart rate and blood pressure. 
     Wireless and mobile communications are becoming increasingly important in industrial applications. Wiring costs are high for installation and maintenance. Thus, the possibility of replacing a cable with a wireless link that can be reconfigured is an attractive opportunity in many industries. However, achieving this requires that wireless connections operate with similar delay, reliability, and capacity as cables and that their management is simplified. Low latency and very low error probabilities are new requirements that need to be connected to 5G. 
     Logistics and freight tracking are important use cases of mobile communications that enable tracking of inventory and packages anywhere using location based information systems. Use cases of logistics and freight tracking typically require low data rates, but require a large range and reliable location information. 
     NR supports multiple numerology (or, subcarrier spacing (SCS)) to support various 5G services. For example, when the SCS is 15 kHz, wide area in traditional cellular bands may be supported. When the SCS is 30 kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth may be supported. When the SCS is 60 kHz or higher, a bandwidth greater than 24.25 GHz may be supported to overcome phase noise. 
     The NR frequency band may be defined as two types of frequency range, i.e., FR1 and FR2. The numerical value of the frequency range may be changed. For example, the frequency ranges of the two types (FR1 and FR2) may be as shown in Table 1 below. For ease of explanation, in the frequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”, FR2 may mean “above 6 GHz range,” and may be referred to as millimeter wave (mmW). 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Frequency 
                 Corresponding 
                   
               
               
                   
                 Range 
                 frequency 
                 Subcarrier 
               
               
                   
                 designation 
                 range 
                 Spacing 
               
               
                   
                   
               
             
            
               
                   
                 FR1 
                  450 MHz-6000 MHz 
                 15, 30, 60 kHz 
               
               
                   
                 FR2 
                 24250 MHz-52600 MHz 
                 60, 120, 240 kHz  
               
               
                   
                   
               
            
           
         
       
     
     As mentioned above, the numerical value of the frequency range of the NR system may be changed. For example, FR1 may include a frequency band of 410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more included in FR1 may include an unlicensed band. Unlicensed bands may be used for a variety of purposes, for example for communication for vehicles (e.g., autonomous driving). 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Frequency 
                 Corresponding 
                   
               
               
                   
                 Range 
                 frequency 
                 Subcarrier 
               
               
                   
                 designation 
                 range 
                 Spacing 
               
               
                   
                   
               
             
            
               
                   
                 FR1 
                  410 MHz-7125 MHz 
                 15, 30, 60 kHz 
               
               
                   
                 FR2 
                 24250 MHz-52600 MHz 
                 60, 120, 240 kHz  
               
               
                   
                   
               
            
           
         
       
     
       FIG.  2    shows an example of a wireless communication system to which the technical features of the present disclosure can be applied. Referring to  FIG.  2   , the wireless communication system may include a first device  210  and a second device  220 . 
     The first device  210  includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, an unmanned aerial vehicle (UAV), an artificial intelligence (AI) module, a robot, an AR device, a VR device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution. 
     The second device  220  includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, a UAV, an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution. 
     For example, the UE may include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a slate personal computer (PC), a tablet PC, an ultrabook, a wearable device (e.g. a smartwatch, a smart glass, a head mounted display (HMD)). For example, the HMD may be a display device worn on the head. For example, the HMD may be used to implement AR, VR and/or MR. 
     For example, the drone may be a flying object that is flying by a radio control signal without a person boarding it. For example, the VR device may include a device that implements an object or background in the virtual world. For example, the AR device may include a device that implements connection of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the MR device may include a device that implements fusion of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the hologram device may include a device that implements a 360-degree stereoscopic image by recording and playing stereoscopic information by utilizing a phenomenon of interference of light generated by the two laser lights meeting with each other, called holography. For example, the public safety device may include a video relay device or a video device that can be worn by the user&#39;s body. For example, the MTC device and the IoT device may be a device that do not require direct human intervention or manipulation. For example, the MTC device and the IoT device may include a smart meter, a vending machine, a thermometer, a smart bulb, a door lock and/or various sensors. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, handling, or preventing a disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, or correcting an injury or disorder. For example, the medical device may be a device used for the purpose of inspecting, replacing or modifying a structure or function. For example, the medical device may be a device used for the purpose of controlling pregnancy. For example, the medical device may include a treatment device, a surgical device, an (in vitro) diagnostic device, a hearing aid and/or a procedural device, etc. For example, a security device may be a device installed to prevent the risk that may occur and to maintain safety. For example, the security device may include a camera, a closed-circuit TV (CCTV), a recorder, or a black box. For example, the fin-tech device may be a device capable of providing financial services such as mobile payment. For example, the fin-tech device may include a payment device or a point of sales (POS). For example, the climate/environmental device may include a device for monitoring or predicting the climate/environment. 
     The first device  210  may include at least one or more processors, such as a processor  211 , at least one memory, such as a memory  212 , and at least one transceiver, such as a transceiver  213 . The processor  211  may perform the functions, procedures, and/or methods of the first device described throughout the disclosure. The processor  211  may perform one or more protocols. For example, the processor  211  may perform one or more layers of the air interface protocol. The memory  212  is connected to the processor  211  and may store various types of information and/or instructions. The transceiver  213  is connected to the processor  211  and may be controlled by the processor  211  to transmit and receive wireless signals. 
     The second device  220  may include at least one or more processors, such as a processor  221 , at least one memory, such as a memory  222 , and at least one transceiver, such as a transceiver  223 . The processor  221  may perform the functions, procedures, and/or methods of the second device  220  described throughout the disclosure. The processor  221  may perform one or more protocols. For example, the processor  221  may perform one or more layers of the air interface protocol. The memory  222  is connected to the processor  221  and may store various types of information and/or instructions. The transceiver  223  is connected to the processor  221  and may be controlled by the processor  221  to transmit and receive wireless signals. 
     The memory  212 ,  222  may be connected internally or externally to the processor  211 ,  212 , or may be connected to other processors via a variety of technologies such as wired or wireless connections. 
     The first device  210  and/or the second device  220  may have more than one antenna. For example, antenna  214  and/or antenna  224  may be configured to transmit and receive wireless signals. 
       FIG.  3    shows an example of a wireless communication system to which the technical features of the present disclosure can be applied. 
     Specifically,  FIG.  3    shows a system architecture based on an evolved-UMTS terrestrial radio access network (E-UTRAN). The aforementioned LTE is a part of an evolved-UTMS (e-UMTS) using the E-UTRAN. 
     Referring to  FIG.  3   , the wireless communication system includes one or more user equipment (UE)  310 , an E-UTRAN and an evolved packet core (EPC). The UE  310  refers to a communication equipment carried by a user. The UE  310  may be fixed or mobile. The UE  310  may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc. 
     The E-UTRAN consists of one or more evolved NodeB (eNB)  320 . The eNB  320  provides the E-UTRA user plane and control plane protocol terminations towards the UE  10 . The eNB  320  is generally a fixed station that communicates with the UE  310 . The eNB  320  hosts the functions, such as inter-cell radio resource management (RRM), radio bearer (RB) control, connection mobility control, radio admission control, measurement configuration/provision, dynamic resource allocation (scheduler), etc. The eNB  320  may be referred to as another terminology, such as a base station (BS), a base transceiver system (BTS), an access point (AP), etc. 
     A downlink (DL) denotes communication from the eNB  320  to the UE  310 . An uplink (UL) denotes communication from the UE  310  to the eNB  320 . A sidelink (SL) denotes communication between the UEs  310 . In the DL, a transmitter may be a part of the eNB  320 , and a receiver may be a part of the UE  310 . In the UL, the transmitter may be a part of the UE  310 , and the receiver may be a part of the eNB  320 . In the SL, the transmitter and receiver may be a part of the UE  310 . 
     The EPC includes a mobility management entity (MME), a serving gateway (S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts the functions, such as non-access stratum (NAS) security, idle state mobility handling, evolved packet system (EPS) bearer control, etc. The S-GW hosts the functions, such as mobility anchoring, etc. The S-GW is a gateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW  330  will be referred to herein simply as a “gateway,” but it is understood that this entity includes both the MME and S-GW. The P-GW hosts the functions, such as UE Internet protocol (IP) address allocation, packet filtering, etc. The P-GW is a gateway having a PDN as an endpoint. The P-GW is connected to an external network. 
     The UE  310  is connected to the eNB  320  by means of the Uu interface. The UEs  310  are interconnected with each other by means of the PC5 interface. The eNBs  320  are interconnected with each other by means of the X2 interface. The eNBs  320  are also connected by means of the S1 interface to the EPC, more specifically to the MME by means of the S1-MME interface and to the S-GW by means of the S1-U interface. The S1 interface supports a many-to-many relation between MMEs/S-GWs and eNBs. 
       FIG.  4    shows another example of a wireless communication system to which the technical features of the present disclosure can be applied. 
     Specifically,  FIG.  4    shows a system architecture based on a 5G NR. The entity used in the 5G NR (hereinafter, simply referred to as “NR”) may absorb some or all of the functions of the entities introduced in  FIG.  3    (e.g. eNB, MME, S-GW). The entity used in the NR may be identified by the name “NG” for distinction from the LTE/LTE-A. 
     Referring to  FIG.  4   , the wireless communication system includes one or more UE  410 , a next-generation RAN (NG-RAN) and a 5th generation core network (5GC). The NG-RAN consists of at least one NG-RAN node. The NG-RAN node is an entity corresponding to the eNB  320  shown in  FIG.  3   . The NG-RAN node consists of at least one gNB  421  and/or at least one ng-eNB  422 . The gNB  421  provides NR user plane and control plane protocol terminations towards the UE  410 . The ng-eNB  422  provides E-UTRA user plane and control plane protocol terminations towards the UE  410 . 
     The 5GC includes an access and mobility management function (AMF), a user plane function (UPF) and a session management function (SMF). The AMF hosts the functions, such as NAS security, idle state mobility handling, etc. The AMF is an entity including the functions of the conventional MME. The UPF hosts the functions, such as mobility anchoring, protocol data unit (PDU) handling. The UPF an entity including the functions of the conventional S-GW. The SMF hosts the functions, such as UE IP address allocation, PDU session control. 
     The gNBs  421  and ng-eNBs  422  are interconnected with each other by means of the Xn interface. The gNBs  421  and ng-eNBs  422  are also connected by means of the NG interfaces to the 5GC, more specifically to the AMF by means of the NG-C interface and to the UPF by means of the NG-U interface. 
     A protocol structure between network entities described above is described. On the system of  FIG.  3    and/or  FIG.  4   , layers of a radio interface protocol between the UE and the network (e.g. NG-RAN and/or E-UTRAN) may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. 
       FIG.  5    shows a block diagram of a user plane protocol stack to which the technical features of the present disclosure can be applied.  FIG.  6    shows a block diagram of a control plane protocol stack to which the technical features of the present disclosure can be applied. 
     The user/control plane protocol stacks shown in  FIG.  5    and  FIG.  6    are used in NR. However, user/control plane protocol stacks shown in  FIG.  5    and  FIG.  6    may be used in LTE/LTE-A without loss of generality, by replacing gNB/AMF with eNB/MME. 
     Referring to  FIG.  5    and  FIG.  6   , a physical (PHY) layer belonging to L1. The PHY layer offers information transfer services to media access control (MAC) sublayer and higher layers. The PHY layer offers to the MAC sublayer transport channels. Data between the MAC sublayer and the PHY layer is transferred via the transport channels. Between different PHY layers, i.e., between a PHY layer of a transmission side and a PHY layer of a reception side, data is transferred via the physical channels. 
     The MAC sublayer belongs to L2. The main services and functions of the MAC sublayer include mapping between logical channels and transport channels, multiplexing/de-multiplexing of MAC service data units (SDUs) belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), priority handling between UEs by means of dynamic scheduling, priority handling between logical channels of one UE by means of logical channel prioritization (LCP), etc. The MAC sublayer offers to the radio link control (RLC) sublayer logical channels. 
     The RLC sublayer belong to L2. The RLC sublayer supports three transmission modes, i.e. transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM), in order to guarantee various quality of services (QoS) required by radio bearers. The main services and functions of the RLC sublayer depend on the transmission mode. For example, the RLC sublayer provides transfer of upper layer PDUs for all three modes, but provides error correction through ARQ for AM only. In LTE/LTE-A, the RLC sublayer provides concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer) and re-segmentation of RLC data PDUs (only for AM data transfer). In NR, the RLC sublayer provides segmentation (only for AM and UM) and re-segmentation (only for AM) of RLC SDUs and reassembly of SDU (only for AM and UM). That is, the NR does not support concatenation of RLC SDUs. The RLC sublayer offers to the packet data convergence protocol (PDCP) sublayer RLC channels. 
     The PDCP sublayer belong to L2. The main services and functions of the PDCP sublayer for the user plane include header compression and decompression, transfer of user data, duplicate detection, PDCP PDU routing, retransmission of PDCP SDUs, ciphering and deciphering, etc. The main services and functions of the PDCP sublayer for the control plane include ciphering and integrity protection, transfer of control plane data, etc. 
     The service data adaptation protocol (SDAP) sublayer belong to L2. The SDAP sublayer is only defined in the user plane. The SDAP sublayer is only defined for NR. The main services and functions of SDAP include, mapping between a QoS flow and a data radio bearer (DRB), and marking QoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to 5GC QoS flows. 
     A radio resource control (RRC) layer belongs to L3. The RRC layer is only defined in the control plane. The RRC layer controls radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS. The main services and functions of the RRC layer include broadcast of system information related to A5 and NAS, paging, establishment, maintenance and release of an RRC connection between the UE and the network, security functions including key management, establishment, configuration, maintenance and release of radio bearers, mobility functions, QoS management functions, UE measurement reporting and control of the reporting, NAS message transfer to/from NAS from/to UE. 
     In other words, the RRC layer controls logical channels, transport channels, and physical channels in relation to the configuration, reconfiguration, and release of radio bearers. A radio bearer refers to a logical path provided by L1 (PHY layer) and L2 (MAC/RLC/PDCP/SDAP sublayer) for data transmission between a UE and a network. Setting the radio bearer means defining the characteristics of the radio protocol layer and the channel for providing a specific service, and setting each specific parameter and operation method. 
     Radio bearer may be divided into signaling RB (SRB) and data RB (DRB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane. 
     An RRC state indicates whether an RRC layer of the UE is logically connected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in the RRC connected state (RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE). In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced. RRC_INACTIVE may be used for various purposes. For example, the massive machine type communications (MMTC) UEs can be efficiently managed in RRC_INACTIVE. When a specific condition is satisfied, transition is made from one of the above three states to the other. 
     A predetermined operation may be performed according to the RRC state. In RRC_IDLE, public land mobile network (PLMN) selection, broadcast of system information (SI), cell re-selection mobility, core network (CN) paging and discontinuous reception (DRX) configured by NAS may be performed. The UE shall have been allocated an identifier (ID) which uniquely identifies the UE in a tracking area. No RRC context stored in the BS. 
     In RRC_CONNECTED, the UE has an RRC connection with the network (i.e. E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is also established for UE. The UE A5 context is stored in the network and the UE. The RAN knows the cell which the UE belongs to. The network can transmit and/or receive data to/from UE. Network controlled mobility including measurement is also performed. 
     Most of operations performed in RRC_IDLE may be performed in RRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging is performed in RRC_INACTIVE. In other words, in RRC_IDLE, paging for mobile terminated (MT) data is initiated by core network and paging area is managed by core network. In RRC_INACTIVE, paging is initiated by NG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN. Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRX for RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, in RRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established for UE, and the UE A5 context is stored in NG-RAN and the UE. NG-RAN knows the RNA which the UE belongs to. 
     NAS layer is located at the top of the RRC layer. The NAS control protocol performs the functions, such as authentication, mobility management, security control. 
     The physical channels may be modulated according to OFDM processing and utilizes time and frequency as radio resources. The physical channels consist of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in time domain and a plurality of subcarriers in frequency domain. One subframe consists of a plurality of OFDM symbols in the time domain. A resource block is a resource allocation unit, and consists of a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific OFDM symbols (e.g. first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), i.e. L1/L2 control channel A transmission time interval (TTI) is a basic unit of time used by a scheduler for resource allocation. The TTI may be defined in units of one or a plurality of slots, or may be defined in units of mini-slots. 
     The transport channels are classified according to how and with what characteristics data are transferred over the radio interface. DL transport channels include a broadcast channel (BCH) used for transmitting system information, a downlink shared channel (DL-SCH) used for transmitting user traffic or control signals, and a paging channel (PCH) used for paging a UE. UL transport channels include an uplink shared channel (UL-SCH) for transmitting user traffic or control signals and a random access channel (RACH) normally used for initial access to a cell. 
     Different kinds of data transfer services are offered by MAC sublayer. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels. 
     Control channels are used for the transfer of control plane information only. The control channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH) and a dedicated control channel (DCCH). The BCCH is a DL channel for broadcasting system control information. The PCCH is DL channel that transfers paging information, system information change notifications. The CCCH is a channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network. The DCCH is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used by UEs having an RRC connection. 
     Traffic channels are used for the transfer of user plane information only. The traffic channels include a dedicated traffic channel (DTCH). The DTCH is a point-to-point channel, dedicated to one UE, for the transfer of user information. The DTCH can exist in both UL and DL. 
     Regarding mapping between the logical channels and transport channels, in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH can be mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped to DL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped to UL-SCH, DCCH can be mapped to UL-SCH, and DTCH can be mapped to UL-SCH. 
       FIG.  7    illustrates a frame structure in a 3GPP based wireless communication system. 
     The frame structure illustrated in  FIG.  7    is purely exemplary and the number of subframes, the number of slots, and/or the number of symbols in a frame may be variously changed. In the 3GPP based wireless communication system, an OFDM numerology (e.g., subcarrier spacing (SCS), transmission time interval (TTI) duration) may be differently configured between a plurality of cells aggregated for one UE. For example, if a UE is configured with different SCSs for cells aggregated for the cell, an (absolute time) duration of a time resource (e.g. a subframe, a slot, or a TTI) including the same number of symbols may be different among the aggregated cells. Herein, symbols may include OFDM symbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbols). 
     Referring to  FIG.  7   , downlink and uplink transmissions are organized into frames. Each frame has Tf=10 ms duration. Each frame is divided into two half-frames, where each of the half-frames has 5 ms duration. Each half-frame consists of 5 subframes, where the duration Tsf per subframe is 1 ms. Each subframe is divided into slots and the number of slots in a subframe depends on a subcarrier spacing. Each slot includes 14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP, each slot includes 14 OFDM symbols and, in an extended CP, each slot includes 12 OFDM symbols. The numerology is based on exponentially scalable subcarrier spacing Δf=2 u*15 kHz. The following table shows the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per for the normal CP, according to the subcarrier spacing Δf=2 u*15 kHz. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 u 
                 Nslotsymb 
                 Nframe, uslot 
                 Nsubframe, uslot 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0 
                 14 
                 10 
                 1 
               
               
                   
                 1 
                 14 
                 20 
                 2 
               
               
                   
                 2 
                 14 
                 40 
                 4 
               
               
                   
                 3 
                 14 
                 80 
                 8 
               
               
                   
                 4 
                 14 
                 160 
                 16 
               
               
                   
                   
               
            
           
         
       
     
     The following table shows the number of OFDM symbols per slot, the number of slots per frame, and the number of slots per for the extended CP, according to the subcarrier spacing Δf=2 u*15 kHz. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 u 
                 Nslotsymb 
                 Nframe, uslot 
                 Nsubframe, uslot 
               
               
                   
                   
               
             
            
               
                   
                 2 
                 12 
                 40 
                 4 
               
               
                   
                   
               
            
           
         
       
     
     A slot includes plural symbols (e.g., 14 or 12 symbols) in the time domain. For each numerology (e.g. subcarrier spacing) and carrier, a resource grid of Nsize,ugrid,x*NRBsc subcarriers and Nsubframe,usymb OFDM symbols is defined, starting at common resource block (CRB) Nstart,ugrid indicated by higher-layer signaling (e.g. radio resource control (RRC) signaling), where Nsize,ugrid,x is the number of resource blocks (RBs) in the resource grid and the subscript x is DL for downlink and UL for uplink. NRBsc is the number of subcarriers per RB. In the 3GPP based wireless communication system, NRBsc is 12 generally. There is one resource grid for a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL). The carrier bandwidth Nsize,ugrid for subcarrier spacing configuration u is given by the higher-layer parameter (e.g. RRC parameter). Each element in the resource grid for the antenna port p and the subcarrier spacing configuration u is referred to as a resource element (RE) and one complex symbol may be mapped to each RE. Each RE in the resource grid is uniquely identified by an index k in the frequency domain and an index 1 representing a symbol location relative to a reference point in the time domain. In the 3GPP based wireless communication system, an RB is defined by 12 consecutive subcarriers in the frequency domain. In the 3GPP NR system, RBs are classified into CRBs and physical resource blocks (PRBs). CRBs are numbered from 0 and upwards in the frequency domain for subcarrier spacing configuration u. The center of subcarrier 0 of CRB 0 for subcarrier spacing configuration u coincides with ‘point A’ which serves as a common reference point for resource block grids. In the 3GPP NR system, PRBs are defined within a bandwidth part (BWP) and numbered from 0 to NsizeBWP,i−1, where i is the number of the bandwidth part. The relation between the physical resource block nPRB in the bandwidth part i and the common resource block nCRB is as follows: nPRB=nCRB+NsizeBWP,i, where NsizeBWP,i is the common resource block where bandwidth part starts relative to CRB 0. The BWP includes a plurality of consecutive RBs. A carrier may include a maximum of N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on a given component carrier. Only one BWP among BWPs configured to the UE can active at a time. The active BWP defines the UE&#39;s operating bandwidth within the cell&#39;s operating bandwidth. 
     In the present disclosure, the term “cell” may refer to a geographic area to which one or more nodes provide a communication system, or refer to radio resources. A “cell” of a geographic area may be understood as coverage within which a node can provide service using a carrier and a “cell” as radio resources (e.g. time-frequency resources) is associated with bandwidth (BW) which is a frequency range configured by the carrier. The “cell” associated with the radio resources is defined by a combination of downlink resources and uplink resources, for example, a combination of a downlink (DL) component carrier (CC) and a uplink (UL) CC. The cell may be configured by downlink resources only, or may be configured by downlink resources and uplink resources. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, the coverage of the node may be associated with coverage of the “cell” of radio resources used by the node. Accordingly, the term “cell” may be used to represent service coverage of the node sometimes, radio resources at other times, or a range that signals using the radio resources can reach with valid strength at other times. 
     In carrier aggregation (CA), two or more CCs are aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA is supported for both contiguous and non-contiguous CCs. When CA is configured the UE only has one radio resource control (RRC) connection with the network. At RRC connection establishment/re-establishment/handover, one serving cell provides the non-access stratum (NAS) mobility information, and at RRC connection re-establishment/handover, one serving cell provides the security input. This cell is referred to as the Primary Cell (PCell). The PCell is a cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure. Depending on UE capabilities, Secondary Cells (SCells) can be configured to form together with the PCell a set of serving cells. An SCell is a cell providing additional radio resources on top of Special Cell. The configured set of serving cells for a UE therefore always consists of one PCell and one or more SCells. For dual connectivity operation, the term Special Cell (SpCell) refers to the PCell of the master cell group (MCG) or the PSCell of the secondary cell group (SCG). An SpCell supports PUCCH transmission and contention-based random access, and is always activated. The MCG is a group of serving cells associated with a master node, comprising of the SpCell (PCell) and optionally one or more SCells. The SCG is the subset of serving cells associated with a secondary node, comprising of the PSCell and zero or more SCells, for a UE configured with dual connectivity (DC). For a UE in RRC_CONNECTED not configured with CA/DC there is only one serving cell comprising of the PCell. For a UE in RRC_CONNECTED configured with CA/DC the term “serving cells” is used to denote the set of cells comprising of the SpCell(s) and all SCells. In DC, two MAC entities are configured in a UE: one for the MCG and one for the SCG. 
       FIG.  8    illustrates a data flow example in the 3GPP NR system. 
     In  FIG.  8   , “RB” denotes a radio bearer, and “H” denotes a header. Radio bearers are categorized into two groups: data radio bearers (DRB) for user plane data and signalling radio bearers (SRB) for control plane data. The MAC PDU is transmitted/received using radio resources through the PHY layer to/from an external device. The MAC PDU arrives to the PHY layer in the form of a transport block. 
     In the PHY layer, the uplink transport channels UL-SCH and RACH are mapped to their physical channels PUSCH and PRACH, respectively, and the downlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH, PBCH and PDSCH, respectively. In the PHY layer, uplink control information (UCI) is mapped to PUCCH, and downlink control information (DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted by a UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCH is transmitted by a BS via a PDSCH based on a DL assignment. 
     Data unit(s) (e.g. PDCP SDU, PDCP PDU, RLC SDU, RLC PDU, RLC SDU, MAC SDU, MAC CE, MAC PDU) in the present disclosure is(are) transmitted/received on a physical channel (e.g. PDSCH, PUSCH) based on resource allocation (e.g. UL grant, DL assignment). In the present disclosure, uplink resource allocation is also referred to as uplink grant, and downlink resource allocation is also referred to as downlink assignment. The resource allocation includes time domain resource allocation and frequency domain resource allocation. In the present disclosure, an uplink grant is either received by the UE dynamically on PDCCH, in a Random Access Response, or configured to the UE semi-persistently by RRC. In the present disclosure, downlink assignment is either received by the UE dynamically on the PDCCH, or configured to the UE semi-persistently by RRC signalling from the BS. 
       FIG.  9    shows an example of a legacy handover procedure to which technical features of the present disclosure can be applied.  FIG.  9    illustrates steps for the handover procedure exemplary, but the illustrated steps can also be applied to a legacy mobility procedure (e.g., SN addition procedure and/or SN change procedure). 
     Referring to  FIG.  9   , in step S 901 , the source RAN node may transmit measurement control message to the UE. The source RAN node may configure the UE measurement procedures according to the roaming and access restriction information and, for example, the available multiple frequency band information through the measurement control message. Measurement control information provided by the source RAN node through the measurement control message may assist the function controlling the UE&#39;s connection mobility. For example, the measurement control message may comprise measurement configuration and/or report configuration. 
     In step S 903 , the UE may transmit a measurement report message to the source RAN node. The measurement report message may comprise a result of measurement on neighbor cell(s) around the UE which can be detected by the UE. The UE may generate the measurement report message according to a measurement configuration and/or measurement control information in the measurement control message received in step S 901 . 
     In step S 905 , the source RAN node may make a handover (HO) decision based on the measurement report. For example, the source RAN node may make a HO decision and determine a target RAN node for HO among neighbor cells around the UE based on a result of measurement (e.g., cell quality, signal quality, signal strength, reference signal received power (RSRP), reference signal received quality (RSRP), channel state, channel quality, signal to interference plus noise ratio (SINR)) on the neighbor cells. 
     In step S 907 , the source RAN node may transmit a HO request message to the target RAN node which is determined in step S 905 . That is, the source RAN node may perform handover preparation with the target RAN node. The HO request message may comprise necessary information to prepare the handover at the target RAN node. 
     In step S 909 , the target RAN node may perform an admission control based on information included in the HO request message. The target RAN node may configure and reserve the required resources (e.g., C-RNTI and/or RACH preamble). The AS-configuration to be used in the target RAN node can either be specified independently (i.e. an “establishment”) or as a delta compared to the AS-configuration used in the source RAN node (i.e. a “reconfiguration”). 
     In step S 911 , the target RAN node may transmit a HO request acknowledge (ACK) message to the source RAN node. The HO request ACK message may comprise information on resources reserved and prepared for a handover. For example, the HO request ACK message may comprise a transparent container to be sent to the UE as an RRC message to perform the handover. The container may include a new C-RNTI, target gNB security algorithm identifiers for the selected security algorithms, a dedicated RACH preamble, and/or possibly some other parameters i.e. access parameters, SIBs. If RACH-less handover is configured, the container may include timing adjustment indication and optionally a preallocated uplink grant. The HO request ACK message may also include RNL/TNL information for forwarding tunnels, if necessary. As soon as the source RAN node receives the HO request ACK message, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated. 
     In step S 913 , the source RAN node may transmit a handover command which may be a RRC message, to the UE. The target RAN node may generate the RRC message to perform the handover, (i.e., RRCConnectionReconfiguration message including mobilityControlInformation and/or RRCReconfiguration message including ReconfigurationWithSync), to be sent by the source RAN node towards the UE. The source RAN node may perform the necessary integrity protection and ciphering of the message. The UE may receive the RRCConnectionReconfiguration message with necessary parameters (i.e. new C-RNTI, target eNB security algorithm identifiers, and optionally dedicated RACH preamble, target eNB SIBs, etc.) and is commanded by the source eNB to perform the handover. If RACH-less handover is configured, the RRCConnectionReconfiguration may include timing adjustment indication and optionally preallocated uplink grant for accessing the target RAN node. If preallocated uplink grant is not included, the UE should monitor PDCCH of the target RAN node to receive an uplink grant. The UE may not need to delay the handover execution for delivering the HARQ/ARQ responses to source RAN node. If Make-Before-Break HO is configured, the connection to the source RAN node may be maintained after the reception of RRCConnectionReconfiguration message with mobilityControlInformation before the UE executes initial uplink transmission to the target RAN node. 
     In step S 915 , the UE may switch to a new cell i.e., the target RAN node. The UE may detach from the old cell i.e., the source RAN node and synchronize to a new cell i.e., the target RAN node. For example, the UE may perform a random access to the target RAN node. The UE may transmit a random access preamble to the target RAN node, and receive a random access response comprising an uplink grant from the target RAN node. If RACH-less handover is configured, the step S 915  may be omitted, and the uplink grant may be provided in step S 913 . The uplink grant may be used for the UE to transmit a handover complete message to the target RAN node. 
     In step S 917 , the UE may transmit a handover complete message (i.e., RRCConnectionReconfigurationComplete message) to the target RAN node. When the UE has successfully accessed the target RAN node or received uplink grant when RACH-less HO is configured, the UE may send the RRCConnectionReconfigurationComplete message comprising a C-RNTI to confirm the handover, along with an uplink Buffer Status Report, whenever possible, to the target RAN node to indicate that the handover procedure is completed for the UE. The target RAN node may verify the C-RNTI sent in the RRCConnectionReconfigurationComplete message. The target RAN node can now begin sending data to the UE. 
     According to  FIG.  9   , in the legacy mobility procedure, network (e.g., source RAN node) may determine a target cell for a mobility based on a measurement report received from the UE, and transmit a mobility command to the UE for the UE to perform a mobility to the determined target cell. Upon receiving the mobility command, the UE may initiate the legacy mobility procedure towards the target cell. That is, the legacy mobility may also be referred to as normal mobility and/or network-controlled (or, network-based) mobility, and the mobility command for the legacy mobility may also be referred to as legacy mobility command. 
       FIG.  10    shows an example of a conditional mobility procedure to which technical features of the present disclosure can be applied. The steps illustrated in  FIG.  10    can also be applied to a conditional handover procedure, conditional SN addition procedure and/or conditional SN change procedure. 
     Referring to  FIG.  10   , in step S 1001 , the source cell may transmit measurement control message to the UE. The source cell may configure the UE measurement procedures according to the roaming and access restriction information and, for example, the available multiple frequency band information through the measurement control message. Measurement control information provided by the source cell through the measurement control message may assist the function controlling the UE&#39;s connection mobility. For example, the measurement control message may comprise measurement configuration and/or report configuration. 
     In step S 1003 , the UE may transmit a measurement report message to the source cell. The measurement report message may comprise a result of measurement on neighbor cell(s) around the UE which can be detected by the UE. The UE may generate the measurement report message according to a measurement configuration and/or measurement control information in the measurement control message received in step S 1001 . 
     In step S 1005 , the source cell may make a mobility decision based on the measurement report. For example, the source cell may make a mobility decision and determine candidate target cells (e.g., target cell 1 and target cell 2) for mobility among neighbor cells around the UE based on a result of measurement (e.g., signal quality, reference signal received power (RSRP), reference signal received quality (RSRP)) on the neighbor cells. 
     In step S 1007 , the source cell may transmit mobility request messages to the target cell 1 and the target cell 2 which are determined in step S 1005 . That is, the source cell may perform mobility preparation with the target cell 1 and the target cell 2. The mobility request message may comprise necessary information to prepare the mobility at the target side (e.g., target cell 1 and target cell 2). 
     In step S 1009 , each of the target cell 1 and the target cell 2 may perform an admission control based on information included in the mobility request message. The target cell may configure and reserve the required resources (e.g., C-RNTI and/or RACH preamble). The AS-configuration to be used in the target cell can either be specified independently (i.e. an “establishment”) or as a delta compared to the AS-configuration used in the source cell (i.e. a “reconfiguration”). 
     In step S 1011 , the target cell and the target cell 2 may transmit a mobility request acknowledge (ACK) message to the source cell. The mobility request ACK message may comprise information on resources reserved and prepared for a mobility. For example, the mobility request ACK message may comprise a transparent container to be sent to the UE as an RRC message to perform the mobility. The container may include a new C-RNTI, target gNB security algorithm identifiers for the selected security algorithms, a dedicated RACH preamble, and/or possibly some other parameters i.e. access parameters, SIBs. If RACH-less mobility is configured, the container may include timing adjustment indication and optionally a preallocated uplink grant. The mobility request ACK message may also include RNL/TNL information for forwarding tunnels, if necessary. As soon as the source cell receives the mobility request ACK message, or as soon as the transmission of the conditional mobility command is initiated in the downlink, data forwarding may be initiated. 
     In step S 1013 , the source cell may transmit a conditional reconfiguration to the UE. The conditional reconfiguration may be also referred to as (or, may comprise) conditional handover (CHO) configuration and/or a conditional mobility command (e.g., CHO command). The conditional reconfiguration may comprise a conditional reconfiguration for each of the candidate target cells (e.g., target cell 1, target cell 2). For example, the conditional reconfiguration may comprise a conditional reconfiguration for the target cell 1, and a conditional reconfiguration for the target cell 2. The conditional reconfiguration for the target cell 1 may comprise a mobility condition for the target cell 1, and a target cell configuration for the target cell 1. The target cell configuration for the target cell 1 may comprise RRC reconfiguration parameters associated with a mobility to the target cell 1, including information on resources reserved for the mobility to the target cell 1. Similarly, the conditional reconfiguration for the target cell 2 may comprise a mobility condition for the target cell 2, and a target cell configuration for the target cell 2. The target cell configuration for the target cell 2 may comprise RRC reconfiguration parameters associated with a mobility to the target cell 2, including information on resources reserved for the mobility to the target cell 2. 
     The mobility condition may inform at least one measurement ID. For example, the mobility condition may inform at most 2 measurement IDs. If a mobility condition of a target cell informs a measurement ID which is related to a measurement object A and a report configuration B, evaluating the mobility condition may comprise determining whether a measurement result on the measurement object A satisfies a report condition in the report configuration B. If the measurement result on the measurement object A satisfies the report condition in the report configuration B according to the evaluation of the mobility condition, the UE may determine that the mobility condition of the target cell is satisfied (or, the target cell/measurement result for the target cell satisfies the mobility condition of the target cell), and perform a mobility to the target cell. 
     In step S 1015 , the UE may perform an evaluation of the mobility condition for the candidate target cells (e.g., target cell 1, target cell 2) and select a target cell for a mobility among the candidate target cells. For example, the UE may perform measurements on the candidate target cells, and determine whether a candidate target cell satisfies a mobility condition for the candidate target cell among the candidate target cells based on a result of the measurements on the candidate target cells. If the UE identifies that the target cell 1 satisfies a mobility condition for the target cell 1, the UE may select the target cell 1 as a target cell for the mobility. 
     In step S 1017 , the UE may perform a random access to the selected target cell (e.g., target cell 1). For example, the UE may transmit a random access preamble to the target cell 1, and receive a random access response comprising an uplink grant from the target cell 1. If RACH-less mobility is configured, the step S 1017  may be omitted, and the uplink grant may be provided in step S 1013 . 
     In step S 1019 , the UE may transmit a mobility complete message to the target cell 1. When the UE has successfully accessed the target cell 1 (or, received uplink grant when RACH-less mobility is configured), the UE may transmit a mobility complete message comprising a C-RNTI to confirm the mobility, along with uplink buffer status report, whenever possible, to the target cell 1 to indicate that the mobility procedure is completed for the UE. The target cell 1 may verify the C-RNTI transmitted in the mobility complete message. 
     In step S 1021 , the target cell 1 may transmit a sequence number (SN) status request message to the source cell. The target cell 1 may request the source cell to inform the target cell 1 of a SN of a packet the target cell 1 has to transmit after the mobility, via the SN status request message. 
     In step S 1023 , the source cell may transmit a conditional mobility cancellation message to the target cell 2 which is not selected as a target cell for a mobility among the candidate target cells. After receiving the conditional mobility cancellation message, the target cell 2 may release resources that are reserved in case of a mobility. 
     In step S 1025 , the target cell 2 may transmit a conditional mobility cancellation confirmation message to the source cell, as a response for the conditional mobility cancellation message. The conditional mobility cancellation confirmation message may inform that the target cell 2 has released resources reserved in case of a mobility. 
     In step S 1027 , the source cell may transmit a SN status transfer message to the target cell 1, as a response for the SN status request message. The SN status transfer message may inform the target cell 1 of a SN of a packet the target cell 1 has to transmit after the mobility. 
     In step S 1029 , the source cell may perform a data forwarding to the target cell 1. For example, the source cell may forward data received from a core network to the target cell 1 so that the target cell 1 can now transmit the data to the UE. 
     According to  FIG.  10   , in the conditional mobility procedure, the UE may receive a plurality of mobility commands from a network in advance, and determine a target cell for a mobility based on a mobility condition included in the mobility command received in advance. After determining the target cell, the UE may initiate the conditional mobility procedure towards the target cell based on a mobility command related to the target cell. That is, the conditional mobility may also be referred to as a UE autonomous mobility, and a mobility command for the conditional mobility may also be referred to as conditional mobility command. 
     Conditional mobility is a kind of conditional reconfiguration. Hereinafter, Conditional reconfiguration is described. 
     The network may configure the UE with conditional reconfiguration (i.e., conditional handover and/or conditional PSCell addition/change) including per candidate target cell an RRCConnectionReconfiguration (i.e., conditional mobility command) to only be applied upon the fulfilment of an associated execution condition (i.e., mobility condition). 
     For conditional reconfiguration, the UE shall: 
     1&gt; if the received conditionalReconfiguration includes the condReconfigurationToRemoveList: 
     2&gt; perform the conditional reconfiguration removal procedure; 
     1&gt; if the received conditionalReconfiguration includes the condReconfigurationToAddModList: 
     2&gt; perform the conditional reconfiguration addition/modification procedure. 
     I. Conditional Reconfiguration Addition/Modification 
     The UE shall: 
     1&gt; for each condReconfigurationId (i.e., index related to a mobility command) included in the received condReconfigurationToAddModList: 
     2&gt; if an entry with the matching condReconfigurationId exists in the condReconfigurationList within the VarConditionalReconfiguration (i.e., list of {index, mobility condition, mobility command} for each target cell stored in the UE): 
     3&gt; replace the entry with the values received for this condReconfigurationId; 
     2&gt; else: 
     3&gt; add a new entry for this condReconfigurationId within the VarConditionalReconfiguration; 
     3&gt; store the associated RRCConnectionReconfiguration (i.e., mobility command and/or mobility condition) in VarConditionalReconfiguration; 
     2&gt; monitor the triggering conditions (i.e., mobility conditions) associated to the measurement identities of that condReconfigurationId; 
     II. Conditional Reconfiguration Removal 
     The UE shall: 
     1&gt; for each condReconfigurationId included in the received condReconfigurationToRemoveList that is part of the current UE configuration in VarConditionalReconfiguration: 
     2&gt; stop the monitoring of triggering conditions linked by the measurement identities; 
     2&gt; remove the entry with the matching condReconfigurationId from the condReconfigurationList within the VarConditionalReconfiguration; 
     The UE does not consider the conditional reconfiguration message as erroneous if the condReconfigurationToRemoveList includes any condReconfigurationId value that is not part of the current UE configuration. 
     III. Conditional Reconfiguration Execution 
     For the measId for which the triggering condition for conditional reconfiguration was fulfilled, the UE shall: 
     1&gt; for each condReconfigurationId within the VarConditionalReconfiguration that has that measId associated to its stored RRCConnectionReconfiguration (i.e., mobility command) 
     2&gt; if all triggering conditions are fulfilled for that condReconfigurationId: 
     3&gt; consider the target cell candidate within the stored RRCConnectionReconfiguration, associated to that condReconfigurationId, as a triggered cell; 
     1&gt; if the more than one triggered cell exists: 
     2&gt; select one of the triggered cells as the selected cell for conditional reconfiguration; 
     1&gt; for the selected cell of conditional reconfiguration: 
     2&gt; if the stored RRCConnectionReconfiguration associated to the selected cell includes mobilityControlInfo (conditional handover): 
     3&gt; apply the stored RRCConnectionReconfiguration associated to that condReconfigurationId and perform a handover to the selected cell; 
     2&gt; else if the stored RRCConnectionReconfiguration includes nr-Config (conditional PSCell addition/change): 
     3&gt; apply the stored RRCConnectionReconfiguration associated to that condReconfigurationId and perform the SN change/addition procedure for the selected cell; 
     If multiple cells are triggered in conditional PSCell addition/change execution, the UE may consider beams and beam quality to select one of the triggered cells for execution. 
     The structure of the conditional reconfiguration message or the information element (IE) ConditionalReconfiguration may be as the following Table 5. The IE ConditionalReconfiguration may be used to add, modify or release the configuration of a conditional handover, a conditional PSCell addition/change per target candidate cell. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
             
            
               
                 --   ASN1STARTConditionalReconfiguration-r16   ::=   SEQUENCE 
               
               
                 {condReconfigurationToAddModList-r16   CondReconfigurationToAddModList-r16 
               
               
                 OPTIONAL,    --  Need  ONcondReconfigurationToRemoveList-r16 
               
               
                 CondReconfigurationToRemoveList-r16  OPTIONAL,    --  Need 
               
               
                 ON...}CondReconfigurationToRemoveList-r16 ::= SEQUENCE (SIZE (1..maxCondConfig- 
               
               
                 r16)) OF CondReconfigurationId-r16-- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     In Table 5, condReconfigurationToAddModList may refer to list of conditional reconfigurations (i.e. conditional handover or conditional PSCell change/addition) to add and/or modify. Also, condReconfigurationToRemoveList may refer to list of conditional reconfigurations (i.e. conditional handover or conditional PSCell change/addition) to remove. CondReconfigurationId may refer to an index related to a mobility command. The contents of the IE CondReconfigurationId may be as the following Table 6. The IE ConditionalReconfigurationId may be used to identify a conditional reconfiguration. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
             
            
               
                 -- ASN1STARTCondReconfigurationId-r16 ::=  INTEGER (1.. maxCondConfig-r16) -- 
               
               
                 ASN1STOP 
               
               
                   
               
            
           
         
       
     
     In Table 6, maxCondConfig may refer to the maximum number of conditional reconfigurations (i.e., CondReconfigurationAddMods). The structure of IE CondReconfigurationToAddModList may be as the following Table 7. The IE CondReconfigurationToAddModList may concern a list of conditional reconfigurations (i.e. conditional handover, conditional PSCell addition/change) to add or modify, with for each entry the measId (associated to the triggering condition configuration) and the associated RRCConnectionReconfiguration. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
             
            
               
                 -- ASN1STARTCondReconfigurationToAddModList-r16 ::= SEQUENCE (SIZE (1.. 
               
               
                 maxCondConfig-r16)) OF CondReconfigurationAddMod-r16CondReconfigurationAddMod- 
               
               
                 r16   ::=   SEQUENCE   {condReconfigurationId-r16CondReconfigurationId- 
               
               
                 r16,triggerCondition-r16SEQUENCE   (SIZE   (1..2))   OF 
               
               
                 MeasId,condReconfigurationToApply-r16OCTET   STRING   (CONTAINING 
               
               
                 RRCConnectionReconfiguration),...}-- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     In Table 7, CondReconfigurationAddMod may refer to a conditional reconfiguration for a target cell. CondReconfigurationId may refer to an index of the CondReconfigurationAddMod, which may be related to a mobility command of the target cell. 
     The triggerCondition may refer to a mobility condition for the target cell. The RRCConnectionReconfiguration contained in the condReconfigurationToApply may refer to a mobility command of the target cell. As described above, the conditional reconfiguration may also be referred to as CHO configuration. The structure of the CHO configuration or IE CHOConfiguration may be as the following Table 8: 
     
       
         
           
               
             
               
                 TABLE 8 
               
               
                   
               
             
            
               
                 CHOConfiguration ::=      SEQUENCE { choToReleaseList- 
               
               
                 r16CHOToReleaseList-r16OPTIONAL,--    Need    NchoToAddModList- 
               
               
                 r16CHOToAddModList-r16OPTIONAL-- Need NchoConditionListSEQUENCE (SIZE 
               
               
                 (1..maxFFS)) OF CHOCondition-r16     OPTIONAL}CHOToReleaseList- 
               
               
                 r16 ::=SEQUENCE (SIZE (1..maxCHO)) OF CHOToRelease-r16CHOToRelease- 
               
               
                 r16  ::=SEQUENCE  {choId-r16INTEGER  (1..maxCHO)}CHOToAddModList- 
               
               
                 r16 ::=SEQUENCE (SIZE (1..maxCHO)) OF CHOToAddMod-r16CHOToAddMod- 
               
               
                 r16 ::=SEQUENCE {choId-r16INTEGER (1..maxCHO),conditionId-r16ReportConfigId 
               
               
                 OPTIONAL,-- Need MchoCellConfiguration-r16OCTET STRING (CONTAINING FFS for 
               
               
                 CHOCellConfiguration-r16)OPTIONAL,-- Need M} 
               
               
                   
               
            
           
         
       
     
     In Table 8, CHOToReleaseList may correspond to condReconfigurationToRemoveList. CHOToAddModList may correspond to CondReconfigurationToAddModList. CHOCondition may correspond to triggerCondition. The maxCHO may correspond to maxCondConfig. That is, the maxCHO may refer to the maximum number of CHO configurations (i.e., CHOToAddMods). The choId may correspond to condReconfigurationId. CHOToAddMod may correspond to CondReconfigurationToAddMod, which may refer to a CHO configuration for a target cell. The choId may refer to an index of the CondReconfigurationToAddMod, which may be related to a mobility command of the target cell. The conditionId may refer to an index of the CHOCondition (i.e., mobility condition for the target cell), which may be related to a choConditionConfig. The CHOCellConfiguration contained in the choCellConfiguration may refer to a mobility command of the target cell. The choCellConfiguration may correspond to condReconfigurationToApply. The structure of IE CHOCondition may be as the following Table 9: 
     
       
         
           
               
             
               
                 TABLE 9 
               
               
                   
               
             
            
               
                 -- ASN1START-- TAG-CHOTRIGGERCONDITION-STARTCHOCondition-r16-IEs ::= 
               
            
           
           
               
               
            
               
                 SEQUENCE 
                 {conditionId-r16 
               
               
                 ReportConfigIdchoConditionConfigCHOConditionConfig-r16OPTIONAL-- 
                      Cond 
               
               
                 NewID}CHOConditionConfig-r16-IE ::= 
                   SEQUENCE 
               
            
           
           
               
               
               
            
               
                 {  eventId 
                 CHOICE { 
                     eventA3 
               
            
           
           
               
               
               
            
               
                 SEQUENCE 
                 { 
                    a3-Offset 
               
            
           
           
               
               
            
               
                 MeasTriggerQuantityOffset, 
                    hysteresis 
               
               
                 Hysteresis, 
                  timeToTrigger 
               
            
           
           
               
               
               
            
               
                 TimeToTrigger, 
                  }, 
                     eventA5 
               
            
           
           
               
               
               
            
               
                 SEQUENCE 
                 { 
                  a5-Threshold1 
               
            
           
           
               
               
            
               
                 MeasTriggerQuantity, 
                  a5-Threshold2 
               
               
                 MeasTriggerQuantity, 
                    hysteresis 
               
               
                 Hysteresis, 
                  timeToTrigger 
               
            
           
           
               
               
               
               
            
               
                 TimeToTrigger, 
                 },  ... 
                  }, 
                     rsType 
               
            
           
           
               
               
            
               
                 NR-RS-Type, 
                 ...}-- TAG-CHOTRIGGERCONDITION-STOP-- ASN1STOP 
               
               
                   
               
            
           
         
       
     
     Network may include both legacy handover (immediate HO) triggering configuration (i.e., legacy mobility command) and the CHO configuration (i.e., conditional mobility command) in a single RRC message such that UE can attempt to access a CHO candidate cells when the immediate HO attempt fails. By allowing the UE to try another mobility attempt towards a cell in the CHO candidate cells, the rate of handover failure may be dramatically decreased. However, if the UE receives the legacy HO command and the CHO configuration together in a single message, some ambiguous problems can occur. That is, while UE is performing the immediate HO, the CHO triggering condition may be fulfilled immediately and CHO can be executed as a consequence. This situation may happen because UE may already have the measurement results of the CHO candidate cells upon receiving the RRC message. Initiating CHO during the immediate HO procedure may result in the failure of the immediate HO, and the CHO cell selected by the UE may be different from the cell indicated by the immediate HO command, leading to the unpredicted UE behaviour from network perspective. This problematic situation can be illustrated by the following exemplary procedure: 
     1) The UE receives RRC Reconfiguration message including the legacy HO command (i.e. RRCReconfiguration message including ReconfiguraitonWithSync) and CHO configuration; 
     2) The UE performs a mobility according to the legacy HO command firstly (i.e., start T304 timer); 
     3) While performing the legacy HO (i.e., T304 is running), the UE configures or reconfigures the CHO configuration (e.g., adding or modifying candidate cells for CHO); 
     4) While performing the legacy HO (i.e., T304 timer is running), the UE monitors the candidate cells for checking the CHO triggering condition; and 
     5) While performing the legacy HO (i.e., T304 timer is running), the UE executes CHO towards a candidate cell if the triggering condition is immediately met. The overriding problem happens. 
     In the present disclosure, the UE may evaluate an additional condition to decide whether to execute CHO or whether to evaluate CHO triggering condition. The additional condition may be used to check whether the UE is already performing handover to a target cell. More specifically, upon receiving an RRC message, the UE may check whether the legacy HO command and the CHO configuration (i.e., conditional HO command) exist together in the same RRC message. If the RRC message includes both the legacy HO command (immediate HO) and CHO configuration, then the UE may not initiate a mobility triggered by the CHO configuration. To prevent the CHO mobility from occurring during the immediate HO, the UE may pend/suspend/stop evaluating the CHO execution condition(s) or triggering mobility towards any candidate cell indicated by the CHO configuration until the legacy HO procedure ends. 
       FIG.  11    shows an example of a method for handling a conditional mobility during a legacy mobility according to an embodiment of the present disclosure. Steps illustrated in  FIG.  11    may be performed by a wireless device and/or a UE. 
     Referring to  FIG.  11   , in step S 1101 , the wireless device may receive, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command. For example, the legacy mobility command may be received together with the conditional mobility command in a single RRC message. 
     In step S 1103 , the wireless device may initiate a legacy mobility procedure upon receiving the legacy mobility command. The wireless device may start a T304 timer upon receiving the legacy mobility command. 
     In step S 1105 , the wireless device may stop an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. The wireless device may stop the evaluation of the mobility condition while the T304 timer is running. 
     According to various embodiments, the wireless device may perform the evaluation of the mobility condition upon receiving the conditional mobility command. 
     According to various embodiments, the evaluation of the mobility condition may be performed based on that the legacy mobility procedure has not been initiated. 
     According to various embodiments, the stopping of the evaluation of the mobility condition during the legacy mobility procedure may comprise suspending the evaluation of the mobility condition after having started to perform the evaluation of the mobility condition. 
     According to various embodiments, the legacy mobility command may be received after the conditional mobility command is received. 
     According to various embodiments, the stopping of the evaluation of the mobility condition during the legacy mobility procedure may comprise skipping the evaluation of the mobility condition based on that the evaluation of the mobility condition has not been performed. 
     According to various embodiments, the stopping of the evaluation of the mobility condition while the T304 timer is running may comprise suspending the evaluation of the mobility condition after having started to perform the evaluation of the mobility condition, or skipping the evaluation of the mobility condition based on that the evaluation of the mobility condition has not been performed. 
     According to various embodiments, the wireless device may access to a target cell related to the legacy mobility command after receiving the conditional mobility command. 
     According to various embodiments, the wireless device may detect a failure of a legacy mobility related to the legacy mobility procedure. The wireless device may perform a cell selection to select a new cell after detecting the failure of the legacy mobility. The wireless device may, based on that the selected new cell is related to the conditional mobility command, perform a mobility to the selected new cell based on the conditional mobility command. 
     According to various embodiments, the wireless device may identify that the mobility condition is satisfied for the target cell based on the evaluation of the mobility condition. The wireless device may stop an execution of a mobility towards the target cell for which the mobility condition is satisfied during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to various embodiments, the stopping of the execution of the mobility may comprise suspending the execution of the mobility after having started to perform the execution of the mobility, or skipping the evaluation of the mobility based on that the execution of the mobility has not been performed. 
     According to various embodiments, the wireless device may receive a single message comprising a legacy mobility command for a first cell and a conditional mobility command for a second cell. The conditional mobility command for the second cell may comprise at least one of a triggering condition to trigger a conditional mobility towards the second cell or a target cell configuration for the second cell. The wireless device may perform a mobility towards the first cell using the legacy mobility command for the first cell. The wireless device may stop evaluating the triggering condition to trigger the conditional mobility towards the second cell while performing the mobility towards the first cell, and/or stop executing the conditional mobility towards the second cell while performing the mobility towards the first cell. 
       FIG.  12    shows an example of a signal flow for handling a conditional mobility during a legacy mobility according to an embodiment of the present disclosure. The signal flow illustrated in  FIG.  12    may be associated with a base station (BS) and a wireless device/UE. 
     Referring to  FIG.  12   , in step S 1201 , the BS may transmit, to the wireless device, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command. For example, the legacy mobility command may be received together with the conditional mobility command in a single RRC message. 
     In step S 1203 , the wireless device may initiate a legacy mobility procedure upon receiving the legacy mobility command. The wireless device may start a T304 timer upon receiving the legacy mobility command. 
     In step S 1205 , the wireless device may stop an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. The wireless device may stop the evaluation of the mobility condition while the T304 timer is running. 
     The BS in  FIG.  12    may be an example of a second device  220  in  FIG.  2   , and therefore, steps of the BS as illustrated in  FIG.  12    may be implemented by the second device  220 . For example, the processor  221  may be configured to control the transceiver  223  to transmit, to the wireless device, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command. The wireless device may initiate a legacy mobility procedure upon receiving the legacy mobility command. The wireless device may stop an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
       FIG.  13    shows an example of a case in which a legacy HO successes and UE stops monitoring candidate cells for CHO during a legacy HO. Steps illustrated in  FIG.  13    may be performed by a UE and/or a wireless device. 
     Referring to  FIG.  13   , in step S 1301 , the UE may receive a RRC reconfiguration message including a legacy handover (HO) command (i.e., reconfigurationWithSync) and CHO configuration (i.e., conditional mobility command) The CHO configuration may comprise a CHO triggering condition. 
     In step S 1303 , the UE may perform a mobility (i.e., legacy HO) according to the legacy HO command, and start T304 timer. That is, upon receiving the legacy HO command, the UE may initiate the legacy HO procedure and start T304 timer. 
     In step S 1305 , the UE may process the CHO configuration to add/modify or release CHO candidate cells, according to the received CHO configuration. 
     In step S 1307 , the UE may stop monitoring the candidate cells for checking the CHO triggering condition, while performing the legacy HO (i.e., while T304 timer is running) That is, the UE may stop evaluating the CHO triggering condition related to the candidate cells during the legacy HO procedure after the legacy HO procedure is initiated. 
     In step S 1309 , the UE may complete the legacy HO with successfully synchronizing towards the target cell related to the legacy HO command After/upon completing the legacy HO, the UE may stop the T304 timer. 
       FIG.  14    shows an example of a case in which a legacy HO fails and UE stops monitoring candidate cells for CHO according to an embodiment of the present disclosure. Steps illustrated in  FIG.  14    may be performed by a wireless device and/or a UE. 
     Referring to  FIG.  14   , in step S 1401 , the UE may receive a RRC reconfiguration message including a legacy handover (HO) command (i.e., reconfigurationWithSync) and CHO configuration (i.e., conditional mobility command) The CHO configuration may comprise a CHO triggering condition. 
     In step S 1403 , the UE may perform a mobility (i.e., legacy HO) according to the legacy HO command, and start T304 timer. That is, upon receiving the legacy HO command, the UE may initiate the legacy HO procedure and start T304 timer. 
     In step S 1405 , the UE may process the CHO configuration to add/modify or release CHO candidate cells, according to the received CHO configuration. 
     In step S 1407 , the UE may stop monitoring the candidate cells for checking the CHO triggering condition, while performing the legacy HO (i.e., while T304 timer is running) That is, the UE may stop evaluating the CHO triggering condition related to the candidate cells during the legacy HO procedure after the legacy HO procedure is initiated. 
     In step S 1409 , the UE may fail the legacy HO. For example, at the expiry of the T304 timer, the UE may detect/determine that the legacy HO has failed. 
     In step S 1411 , the UE may declare a handover failure (HOF) and perform a cell selection and/or RRC re-establishment procedure. 
     In step S 1413 , after cell selection, if the newly selected cell is in the candidate cell list stored in the UE as part of CHO configuration (i.e., if the newly selected cell is related to a conditional mobility command among a list of conditional mobility commands that had been received and are stored in the UE), the UE may perform a mobility to the selected cell according to the CHO configuration comprising a target cell configuration for the selected cell (i.e., perform a mobility to the selected cell by applying a target cell configuration for the selected cell included in the conditional mobility command related to the selected cell). 
       FIG.  15    shows an example of a case in which a legacy HO successes and UE refrains from executing CHO towards any candidate cell according to an embodiment of the present disclosure. Steps illustrated in  FIG.  15    may be performed by a UE and/or a wireless device. 
     Referring to  FIG.  15   , in step S 1501 , the UE may receive a RRC reconfiguration message including a legacy handover (HO) command (i.e., reconfigurationWithSync) and CHO configuration (i.e., conditional mobility command) The CHO configuration may comprise a CHO triggering condition. 
     In step S 1503 , the UE may perform a mobility (i.e., legacy HO) according to the legacy HO command, and start T304 timer. That is, upon receiving the legacy HO command, the UE may initiate the legacy HO procedure and start T304 timer. 
     In step S 1505 , the UE may process the CHO configuration to add/modify or release CHO candidate cells, according to the received CHO configuration. 
     In step S 1507 , the UE may monitor the candidate cells for checking the CHO triggering condition while performing the legacy HO (i.e., while the T304 timer is running). That is, the UE may perform an evaluation of the CHO triggering condition for the candidate cells while performing the legacy HO. 
     In step S 1509 , the UE may stop executing CHO towards any CHO candidate cell regardless of whether the CHO candidate cell fulfils the corresponding CHO triggering condition (i.e., Cho triggering condition for the CHO candidate cell), while performing the legacy HO (i.e., while the T304 timer is running). 
     In step S 1511 , the UE may complete the legacy HO with successfully synchronizing towards the target cell of the legacy HO command. After completing the legacy HO, the UE may stop the T304 timer. 
       FIG.  16    shows an example of a case in which a legacy HO fails and UE stop executing CHO towards any candidate cells according to an embodiment of the present disclosure. Steps illustrated in  FIG.  16    may be performed by a UE and/or a wireless device. 
     Referring to  FIG.  16   , in step S 1601 , the UE may receive a RRC reconfiguration message including a legacy handover (HO) command (i.e., reconfigurationWithSync) and CHO configuration (i.e., conditional mobility command) The CHO configuration may comprise a CHO triggering condition. 
     In step S 1603 , the UE may perform a mobility (i.e., legacy HO) according to the legacy HO command, and start T304 timer. That is, upon receiving the legacy HO command, the UE may initiate the legacy HO procedure and start T304 timer. 
     In step S 1605 , the UE may process the CHO configuration to add/modify or release CHO candidate cells, according to the received CHO configuration. 
     In step S 1607 , the UE may monitor the candidate cells for checking the CHO triggering condition while performing the legacy HO (i.e., while the T304 timer is running). That is, the UE may perform an evaluation of the CHO triggering condition for the candidate cells while performing the legacy HO. 
     In step S 1609 , the UE may stop executing CHO towards any CHO candidate cell regardless of whether the CHO candidate cell fulfils the corresponding CHO triggering condition (i.e., Cho triggering condition for the CHO candidate cell), while performing the legacy HO (i.e., while the T304 timer is running). 
     In step S 1611 , the UE may detect a failure of the legacy HO. For example, at the expiry of the T304 timer, the UE may detect/determine that the legacy HO has failed. 
     In step S 1613 , the UE may declare a handover failure (HOF) and perform a cell selection and/or RRC re-establishment procedure. 
     In step S 1615 , after cell selection, if the newly selected cell is in the candidate cell list stored in the UE as part of CHO configuration (i.e., if the newly selected cell is related to a conditional mobility command among a list of conditional mobility commands that had been received and are stored in the UE), the UE may perform a mobility to the selected cell according to the CHO configuration comprising a target cell configuration for the selected cell (i.e., perform a mobility to the selected cell by applying a target cell configuration for the selected cell included in the conditional mobility command related to the selected cell). 
     According to various embodiments, for each CHO-Configld (i.e., ID of a conditional mobility command) in a cho-ConfigToAddModList (i.e., list of conditional mobility commands) in a CHO configuration (CHO-Config) addition/modification, the UE shall: 
     1&gt; if an entry with the matching CHO-ConfigId exists in the cho-ConfigToAddModList within the VarCHO-Config (i.e., list of conditional mobility commands stored in the UE): 
     2&gt; replace the entry with the value received for this CHO-ConfigId; 
     1&gt; else: 
     2&gt; add a new entry for this CHO-ConfigId within the VarCHO-Config; 
     1&gt; if T304 is not running (i.e., reconfigurationWithSync is not configured in a message in which the cho-ConfigToAddModList is included and/or a legacy HO command is not configured in the same message): 
     2&gt; perform a conditional handover monitoring (i.e., perform an evaluation of a mobility command in the conditional mobility command). 
     According to various embodiments, in a conditional handover monitoring, the UE shall: 
     1&gt; for each CHO-ConfigId within the VarCHO-Config: 
     2&gt; consider the cell which has a physical cell identity matching the value indicated in the ServingCellConfigCommon in the received cho-RRCReconfig to be applicable cell; 
     2&gt; if the entry condition(s) applicable for all events associated with the CHO-ConfigId, i.e., the event(s) corresponding with the cho-eventId(s) of the corresponding cho-TriggerConfig within VarCHO-Config, are fulfilled for the applicable cells for all measurements after layer  3  filtering taken during the corresponding timeToTrigger defined for this event within the VarCHO-Config (i.e., if an entering condition of a mobility condition is satisfied for the applicable cells for time-to-trigger): 
     3&gt; consider the applicable cell as a triggered cell; 
     3&gt; if T304 is not running (i.e., reconfigurationWithSync is not configured in a message in which the cho-ConfigToAddModList is included and/or a legacy HO command is not configured in the same message): 
     4&gt; initiate the conditional handover execution. 
     According to various embodiments, a conditional handover (CHO) may be defined as a handover that is executed by the UE when one or more handover execution conditions are met. The UE may start evaluating the execution condition(s) upon receiving the CHO configuration (i.e., conditional reconfiguration/conditional handover command), and stop evaluating the execution condition(s) once handover is executed (legacy handover or conditional handover execution). 
       FIG.  17    shows a UE to implement an embodiment of the present disclosure. The present disclosure described above for UE side may be applied to this embodiment. The UE in  FIG.  17    may be an example of first device  217  as illustrated in  FIG.  2   . 
     A UE includes a processor  1710  (i.e., processor  211 ), a power management module  1711 , a battery  1712 , a display  1713 , a keypad  1714 , a subscriber identification module (SIM) card  1715 , a memory  1720  (i.e., memory  212 ), a transceiver  1730  (i.e., transceiver  213 ), one or more antennas  1731 , a speaker  1740 , and a microphone  1741 . 
     The processor  1710  may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor  1710 . The processor  1710  may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The processor  1710  may be an application processor (AP). The processor  1710  may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor  1710  may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor. 
     The processor  1710  may be configured to, or configured to control the transceiver  1730  to implement steps performed by the UE and/or the wireless device throughout the disclosure. 
     The power management module  1711  manages power for the processor  1710  and/or the transceiver  1730 . The battery  1712  supplies power to the power management module  1711 . The display  1713  outputs results processed by the processor  1710 . The keypad  1714  receives inputs to be used by the processor  1710 . The keypad  1714  may be shown on the display  1713 . The SIM card  1715  is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers). It is also possible to store contact information on many SIM cards. 
     The memory  1720  is operatively coupled with the processor  1710  and stores a variety of information to operate the processor  1710 . The memory  1720  may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in the memory  1720  and executed by the processor  1710 . The memory  1720  can be implemented within the processor  1710  or external to the processor  1710  in which case those can be communicatively coupled to the processor  1710  via various means as is known in the art. 
     The transceiver  1730  is operatively coupled with the processor  1710 , and transmits and/or receives a radio signal. The transceiver  1730  includes a transmitter and a receiver. The transceiver  1730  may include baseband circuitry to process radio frequency signals. The transceiver  1730  controls the one or more antennas  1731  to transmit and/or receive a radio signal. 
     The speaker  1740  outputs sound-related results processed by the processor  1710 . The microphone  1741  receives sound-related inputs to be used by the processor  1710 . 
     According to various embodiments, the processor  1710  may be configured to, or configured to control the transceiver  1730  to implement steps performed by the UE and/or the wireless device throughout the disclosure. For example, the processor  1710  may configured to control the transceiver  1730  to receive, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command. The processor  1710  may be configured to initiate a legacy mobility procedure upon receiving the legacy mobility command. The processor  1710  may be configured to stop an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to various embodiment, the processor  1710  may be configured to start a T304 timer upon receiving the legacy mobility command. The processor  1710  may be configured to stop the evaluation of the mobility condition while the T304 timer is running. The stopping of the evaluation of the mobility condition while the T304 timer is running may comprise suspending the evaluation of the mobility condition after having started to perform the evaluation of the mobility condition, or skipping the evaluation of the mobility condition based on that the evaluation of the mobility condition has not been performed. 
     According to various embodiments, the processor  1710  may be configured to perform the evaluation of the mobility condition upon receiving the conditional mobility command. 
     According to various embodiments, the evaluation of the mobility condition may be performed based on that the legacy mobility procedure has not been initiated. 
     According to various embodiments, the stopping of the evaluation of the mobility condition during the legacy mobility procedure may comprise suspending the evaluation of the mobility condition after having started to perform the evaluation of the mobility condition. 
     According to various embodiments, the legacy mobility command may be received after the conditional mobility command is received. 
     According to various embodiments, the stopping of the evaluation of the mobility condition during the legacy mobility procedure may comprise skipping the evaluation of the mobility condition based on that the evaluation of the mobility condition has not been performed. 
     According to various embodiments, the processor  1710  may be configured to access to a target cell related to the legacy mobility command after receiving the conditional mobility command. 
     According to various embodiments, the processor  1710  may be configured to detect a failure of a legacy mobility related to the legacy mobility procedure. The processor  1710  may be configured to may perform a cell selection to select a new cell after detecting the failure of the legacy mobility. The processor  1710  may be configured to, based on that the selected new cell is related to the conditional mobility command, perform a mobility to the selected new cell based on the conditional mobility command. 
     According to various embodiments, the processor  1710  may be configured to identify that the mobility condition is satisfied for the target cell based on the evaluation of the mobility condition. The processor  1710  may be configured to stop an execution of a mobility towards the target cell for which the mobility condition is satisfied during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to various embodiments, the stopping of the execution of the mobility may comprise suspending the execution of the mobility after having started to perform the execution of the mobility, or skipping the evaluation of the mobility based on that the execution of the mobility has not been performed. 
       FIG.  18    shows another example of a wireless communication system to which the technical features of the present disclosure can be applied. 
     Referring to  FIG.  18   , the wireless communication system may include a first device  1810  (i.e., first device  210 ) and a second device  1820  (i.e., second device  220 ). 
     The first device  1810  may include at least one transceiver, such as a transceiver  1811 , and at least one processing chip, such as a processing chip  1812 . The processing chip  1812  may include at least one processor, such a processor  1813 , and at least one memory, such as a memory  1814 . The memory may be operably connectable to the processor  1813 . The memory  1814  may store various types of information and/or instructions. The memory  1814  may store a software code  1815  which implements instructions that, when executed by the processor  1813 , perform operations of the first device  910  described throughout the disclosure. For example, the software code  1815  may implement instructions that, when executed by the processor  1813 , perform the functions, procedures, and/or methods of the first device  1810  described throughout the disclosure. For example, the software code  1815  may control the processor  1813  to perform one or more protocols. For example, the software code  1815  may control the processor  1813  to perform one or more layers of the radio interface protocol. 
     The second device  1820  may include at least one transceiver, such as a transceiver  1821 , and at least one processing chip, such as a processing chip  1822 . The processing chip  1822  may include at least one processor, such a processor  1823 , and at least one memory, such as a memory  1824 . The memory may be operably connectable to the processor  1823 . The memory  1824  may store various types of information and/or instructions. The memory  1824  may store a software code  1825  which implements instructions that, when executed by the processor  1823 , perform operations of the second device  1820  described throughout the disclosure. For example, the software code  1825  may implement instructions that, when executed by the processor  1823 , perform the functions, procedures, and/or methods of the second device  1820  described throughout the disclosure. For example, the software code  1825  may control the processor  1823  to perform one or more protocols. For example, the software code  1825  may control the processor  1823  to perform one or more layers of the radio interface protocol. 
     According to various embodiments, the first device  1810  as illustrated in  FIG.  18    may comprise a wireless device. The wireless device may comprise a transceiver  1811 , a processing chip  1812 . The processing chip  1812  may comprise a processor  1813 , and a memory  1814 . The memory  1814  may be operably connectable to the processor  1813 . The memory  1814  may store various types of information and/or instructions. The memory  1814  may store a software code  1815  which implements instructions that, when executed by the processor  1813 , perform operations comprising: receiving, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiating a legacy mobility procedure upon receiving the legacy mobility command; and stopping an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     According to various embodiments, a computer-readable medium having recorded thereon a program for performing each step of a method on a computer is provided. The method comprises: receiving, from a network, a conditional mobility command for a target cell including a mobility condition, and a legacy mobility command; initiating a legacy mobility procedure upon receiving the legacy mobility command; and stopping an evaluation of the mobility condition during the legacy mobility procedure after the legacy mobility procedure is initiated. 
     The present disclosure may be applied to various future technologies, such as AI, robots, autonomous-driving/self-driving vehicles, and/or extended reality (XR). 
     &lt;AI&gt; 
     AI refers to artificial intelligence and/or the field of studying methodology for making it. Machine learning is a field of studying methodologies that define and solve various problems dealt with in AI. Machine learning may be defined as an algorithm that enhances the performance of a task through a steady experience with any task. 
     An artificial neural network (ANN) is a model used in machine learning. It can mean a whole model of problem-solving ability, consisting of artificial neurons (nodes) that form a network of synapses. An ANN can be defined by a connection pattern between neurons in different layers, a learning process for updating model parameters, and/or an activation function for generating an output value. An ANN may include an input layer, an output layer, and optionally one or more hidden layers. Each layer may contain one or more neurons, and an ANN may include a synapse that links neurons to neurons. In an ANN, each neuron can output a summation of the activation function for input signals, weights, and deflections input through the synapse. Model parameters are parameters determined through learning, including deflection of neurons and/or weights of synaptic connections. The hyper-parameter means a parameter to be set in the machine learning algorithm before learning, and includes a learning rate, a repetition number, a mini batch size, an initialization function, etc. The objective of the ANN learning can be seen as determining the model parameters that minimize the loss function. The loss function can be used as an index to determine optimal model parameters in learning process of ANN. 
     Machine learning can be divided into supervised learning, unsupervised learning, and reinforcement learning, depending on the learning method. Supervised learning is a method of learning ANN with labels given to learning data. Labels are the answers (or result values) that ANN must infer when learning data is input to ANN. Unsupervised learning can mean a method of learning ANN without labels given to learning data. Reinforcement learning can mean a learning method in which an agent defined in an environment learns to select a behavior and/or sequence of actions that maximizes cumulative compensation in each state. 
     Machine learning, which is implemented as a deep neural network (DNN) that includes multiple hidden layers among ANN, is also called deep learning. Deep learning is part of machine learning. In the following, machine learning is used to mean deep learning. 
       FIG.  19    shows an example of an AI device to which the technical features of the present disclosure can be applied. 
     The AI device  1900  may be implemented as a stationary device or a mobile device, such as a TV, a projector, a mobile phone, a smartphone, a desktop computer, a notebook, a digital broadcasting terminal, a PDA, a PMP, a navigation device, a tablet PC, a wearable device, a set-top box (STB), a digital multimedia broadcasting (DMB) receiver, a radio, a washing machine, a refrigerator, a digital signage, a robot, a vehicle, etc. 
     Referring to  FIG.  19   , the AI device  1900  may include a communication part  1910 , an input part  1920 , a learning processor  1930 , a sensing part  1940 , an output part  1950 , a memory  1960 , and a processor  1970 . 
     The communication part  1910  can transmit and/or receive data to and/or from external devices such as the AI devices and the AI server using wire and/or wireless communication technology. For example, the communication part  1910  can transmit and/or receive sensor information, a user input, a learning model, and a control signal with external devices. The communication technology used by the communication part  1910  may include a global system for mobile communication (GSM), a code division multiple access (CDMA), an LTE/LTE-A, a 5G, a WLAN, a Wi-Fi, Bluetooth™, radio frequency identification (RFID), infrared data association (IrDA), ZigBee, and/or near field communication (NFC). 
     The input part  1920  can acquire various kinds of data. The input part  1920  may include a camera for inputting a video signal, a microphone for receiving an audio signal, and a user input part for receiving information from a user. A camera and/or a microphone may be treated as a sensor, and a signal obtained from a camera and/or a microphone may be referred to as sensing data and/or sensor information. The input part  1920  can acquire input data to be used when acquiring an output using learning data and a learning model for model learning. The input part  1920  may obtain raw input data, in which case the processor  1970  or the learning processor  1930  may extract input features by preprocessing the input data. 
     The learning processor  1930  may learn a model composed of an ANN using learning data. The learned ANN can be referred to as a learning model. The learning model can be used to infer result values for new input data rather than learning data, and the inferred values can be used as a basis for determining which actions to perform. The learning processor  1930  may perform AI processing together with the learning processor of the AI server. The learning processor  1930  may include a memory integrated and/or implemented in the AI device  1900 . Alternatively, the learning processor  1930  may be implemented using the memory  1960 , an external memory directly coupled to the AI device  1900 , and/or a memory maintained in an external device. 
     The sensing part  1940  may acquire at least one of internal information of the AI device  1900 , environment information of the AI device  1900 , and/or the user information using various sensors. The sensors included in the sensing part  1940  may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyro sensor, an inertial sensor, an RGB sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, an optical sensor, a microphone, a light detection and ranging (LIDAR), and/or a radar. 
     The output part  1950  may generate an output related to visual, auditory, tactile, etc. The output part  1950  may include a display unit for outputting visual information, a speaker for outputting auditory information, and/or a haptic module for outputting tactile information. 
     The memory  1960  may store data that supports various functions of the AI device  1900 . For example, the memory  1960  may store input data acquired by the input part  1920 , learning data, a learning model, a learning history, etc. 
     The processor  1970  may determine at least one executable operation of the AI device  1900  based on information determined and/or generated using a data analysis algorithm and/or a machine learning algorithm. The processor  1970  may then control the components of the AI device  1900  to perform the determined operation. The processor  1970  may request, retrieve, receive, and/or utilize data in the learning processor  1930  and/or the memory  1960 , and may control the components of the AI device  1900  to execute the predicted operation and/or the operation determined to be desirable among the at least one executable operation. The processor  1970  may generate a control signal for controlling the external device, and may transmit the generated control signal to the external device, when the external device needs to be linked to perform the determined operation. The processor  1970  may obtain the intention information for the user input and determine the user&#39;s requirements based on the obtained intention information. The processor  1970  may use at least one of a speech-to-text (STT) engine for converting speech input into a text string and/or a natural language processing (NLP) engine for acquiring intention information of a natural language, to obtain the intention information corresponding to the user input. At least one of the STT engine and/or the NLP engine may be configured as an ANN, at least a part of which is learned according to a machine learning algorithm. At least one of the STT engine and/or the NLP engine may be learned by the learning processor  1930  and/or learned by the learning processor of the AI server, and/or learned by their distributed processing. The processor  1970  may collect history information including the operation contents of the AI device  1900  and/or the user&#39;s feedback on the operation, etc. The processor  1970  may store the collected history information in the memory  1960  and/or the learning processor  1930 , and/or transmit to an external device such as the AI server. The collected history information can be used to update the learning model. The processor  1970  may control at least some of the components of AI device  1900  to drive an application program stored in memory  1960 . Furthermore, the processor  1970  may operate two or more of the components included in the AI device  1900  in combination with each other for driving the application program. 
       FIG.  20    shows an example of an AI system to which the technical features of the present disclosure can be applied. 
     Referring to  FIG.  20   , in the AI system, at least one of an AI server  2020 , a robot  2010   a , an autonomous vehicle  2010   b , an XR device  2010   c , a smartphone  2010   d  and/or a home appliance  2010   e  is connected to a cloud network  2000 . The robot  2010   a , the autonomous vehicle  2010   b , the XR device  2010   c , the smartphone  2010   d , and/or the home appliance  2010   e  to which the AI technology is applied may be referred to as AI devices  2010   a  to  2010   e.    
     The cloud network  2000  may refer to a network that forms part of a cloud computing infrastructure and/or resides in a cloud computing infrastructure. The cloud network  2000  may be configured using a 3G network, a 4G or LTE network, and/or a 5G network. That is, each of the devices  2010   a  to  2010   e  and  2020  consisting the AI system may be connected to each other through the cloud network  2000 . In particular, each of the devices  2010   a  to  2010   e  and  2020  may communicate with each other through a base station, but may directly communicate with each other without using a base station. 
     The AI server  2020  may include a server for performing AI processing and a server for performing operations on big data. The AI server  2020  is connected to at least one or more of AI devices constituting the AI system, i.e. the robot  2010   a , the autonomous vehicle  2010   b , the XR device  2010   c , the smartphone  2010   d  and/or the home appliance  2010   e  through the cloud network  2000 , and may assist at least some AI processing of the connected AI devices  2010   a  to  2010   e . The AI server  2020  can learn the ANN according to the machine learning algorithm on behalf of the AI devices  2010   a  to  2010   e , and can directly store the learning models and/or transmit them to the AI devices  2010   a  to  2010   e . The AI server  2020  may receive the input data from the AI devices  2010   a  to  2010   e , infer the result value with respect to the received input data using the learning model, generate a response and/or a control command based on the inferred result value, and transmit the generated data to the AI devices  2010   a  to  2010   e . Alternatively, the AI devices  2010   a  to  2010   e  may directly infer a result value for the input data using a learning model, and generate a response and/or a control command based on the inferred result value. 
     Various embodiments of the AI devices  2010   a  to  2010   e  to which the technical features of the present disclosure can be applied will be described. The AI devices  2010   a  to  2010   e  shown in  FIG.  20    can be seen as specific embodiments of the AI device  1900  shown in  FIG.  19   . 
     The present disclosure can have various advantageous effects. 
     For example, various embodiments of the present disclosure may provide solutions to prevent ambiguous handling from the RRC configuration handling including the legacy HO command and the CHO configuration together. The UE may not override mobility unnecessarily due to CHO triggering during the legacy handover. 
     Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure. 
     In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope of the present disclosure. 
     Claims in the present description can be combined in a various way. For instance, technical features in method claims of the present description can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. Other implementations are within the scope of the following claims.