Communication control method and user device

Abstract

A communication control method according to one aspect of the present invention is used in a cellular communication system. The communication control method comprises a step for transmitting, by a network node to a user device, a parameter for use in a random access procedure. The parameter is exclusive for the user device that is located at an altitude equal to or greater than a prescribed threshold value.

Description

Communication Control Method

[0001] The present disclosure relates to a communication control method in a mobile communication system.

[0002] The specifications of the Third Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter), a standardization project for mobile communication systems, define an aerial UE (e.g., Non-Patent Document 1 and Non-Patent Document 2). For example, an aerial UE can report its altitude and location information including vertical and horizontal speeds. Through these specifications, 3GPP appropriately supports communication with an aerial UE flying in the sky.

[0003] 3GPP TS 36.300 V17.1.0 (2022-6)3GPP TS 36.331 V17.1.0 (2022-6)

[0004] A communication control method according to one aspect is a communication control method in a mobile communication system, the communication control method comprising a step of transmitting, by a network node (or a network device), parameters used in a random access procedure to a user device, the parameters being dedicated to a user device located at an altitude equal to or higher than a predetermined threshold.

[0005] FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a UE (user equipment) according to the first embodiment. FIG. 3 is a diagram illustrating an example of the configuration of a gNB (base station) according to the first embodiment. FIG. 4 is a diagram illustrating an example of the configuration of a protocol stack related to a user plane according to the first embodiment. FIG. 5 is a diagram illustrating an example of the configuration of a protocol stack related to a control plane according to the first embodiment. FIG. 6 is a diagram illustrating an example of a cell configuration according to the first embodiment. FIG. 7 is a diagram illustrating an example of an operation according to the first embodiment.

[0006] The present disclosure aims to avoid interference in random access procedures.

[0007] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0008] [First embodiment]

[0009] (Configuration of mobile communication system) Fig. 1 is a diagram showing the configuration of a mobile communication system according to the first embodiment. The mobile communication system 1 conforms to the 5th Generation System (5GS) of the 3GPP standard. Although the following description will be given using 5GS as an example, the mobile communication system may also be at least partially applied to an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially applied to a 6th Generation (6G) system.

[0010] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Furthermore, the 5GC 20 may be simply referred to as the core network (CN) 20.

[0011] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0012] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0013] In addition, the gNB 200 can also be connected to the EPC (Evolved Packet Core), which is the LTE core network. An LTE base station (eNB: evolved Node B) can also be connected to the 5GC 20. The LTE base station and the gNB 200 can also be connected via an inter-base station interface.

[0014] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0015] 2 is a diagram illustrating an example of the configuration of a UE 100 (user equipment) according to the first embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0016] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0017] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0018] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 130 may perform each process or operation in the UE 100 in each of the embodiments described below.

[0019] 3 is a diagram showing the configuration of a gNB 200 (base station) according to the first embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN 20.

[0020] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0021] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0022] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer described below. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 230 may perform each process or operation in the gNB 200 in each of the embodiments described below.

[0023] The backhaul communication unit 240 is connected to adjacent base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected by an F1 interface, which is a fronthaul interface.

[0024] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0025] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0026] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC parity bit scrambled by the RNTI added.

[0027] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE 100.

[0028] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0030] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0031] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0032] The protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) instead of the SDAP layer shown in FIG.

[0033] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0034] The NAS, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS of the UE 100 and the NAS of the AMF 300. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, the layer below the NAS is called an Access Stratum (AS).

[0035] (UAV) Here, an unmanned aerial vehicle (UAV: Unmanned Aerial Vehicle or Uncrewed Aerial Vehicle; hereinafter, "unmanned aerial vehicle" may be referred to as "UAV") according to the first embodiment will be described.

[0036] A UAV generally refers to an unmanned aerial vehicle such as a drone. However, in the first embodiment, a UE located at an altitude equal to or greater than a predetermined threshold (or exceeding the predetermined threshold) is referred to as a UAV. A UAV may be a UE capable of wireless communication with a gNB 200 while flying unmanned in the sky, like an unmanned aerial vehicle. Alternatively, a UAV may be provided on an unmanned aerial vehicle. Alternatively, a UAV may be provided on a manned aerial vehicle. For example, when an airplane is flying at an altitude equal to or greater than a predetermined threshold, a UE owned by a user on board the airplane may also be a UAV. A UAV may be a UAV UE. Alternatively, a UAV may be an aerial UE (aerial UE). A UAV may be used to distinguish it from a UE used on the ground. However, when there is no particular distinction between the UE and the UAV, a UAV may be included in the UE as an example of a UE. In this case, a UAV and a UE may be collectively referred to as a UE. The configuration example of UE 100 shown in Figure 2 may represent a configuration example of a UAV.

[0037] In 3GPP, the following specifications are provided as functions to support an aerial UE:

[0038] First, the flying UE can report its altitude. For example, the flying UE can report its altitude when its altitude is above or below a threshold. At this time, the flying UE can also report its location information. The location information can include the horizontal and vertical speed of the flying UE.

[0039] Second, the LTE system network (E-UTRAN) can request the flying UE to report flight route information. The flight route information represents waypoints (passing point information or point information) on the route of the flying UE. The flight route information may include multiple waypoints. The waypoints are represented as three-dimensional position information. The flying UE may report time information (timestamp) for each waypoint by including it in the flight route information.

[0040] Third, whether or not a flying UE is supported (or whether or not it is permitted to function as a flying UE) is included in the subscription information for each user. A Home Subscriber Server (HSS) in an LTE system stores subscriber information for each user. Whether or not a flying UE is supported is included in the subscription information. The subscription information is transmitted from the HSS to an eNB, which is a base station in the LTE system, under the control of a Mobility Management Entity (MME). The eNB can determine whether or not the UE is permitted to function as a flying UE.

[0041] Fourth, the event H1 and the event H2 can be used as trigger conditions for a measurement report. The event H1 represents an event condition when the altitude of the flying UE exceeds a threshold. Meanwhile, the event H2 represents an event condition when the altitude of the flying UE falls below the threshold. These event conditions are determined to be satisfied using a hysteresis value, an offset value, and a threshold value in addition to the altitude.

[0042] The 3GPP specifications are based on the assumption that flying UEs (i.e., UAVs) will be used in the LTE system.

[0043] Meanwhile, 3GPP has begun discussions on introducing UAVs into NR (New Radio). Regarding UAVs, 3GPP has agreed to use the above-mentioned events H1 and H2, to report the altitude, position, and speed of the UAV, and to report the flight path plan.

[0044] (Terrestrial Cells and Aerial Cells) For example, assume that terrestrial cells and aerial cells coexist within a network. Fig. 6 is a diagram showing an example of a cell configuration in such a case.

[0045] As shown in Figure 6, the mobile communication system 1 includes a ground cell and an air cell. In the example shown in Figure 6, a ground cell is formed by gNB200-T1 and gNB200-T2, and an air cell is formed by gNB200-U. In Figure 6, in the ground cell, UE100-1 to 100-4 perform wireless communication with gNB200-T1 and 200-T2, and in the air cell, UAV150-1 and 150-2 perform wireless communication with gNB200-U.

[0046] Here, in order for the UEs 100-1 to 100-4 to perform appropriate wireless communication in the ground cell and for the UAVs 150-1 and 150-2 to perform appropriate wireless communication in the air cell, the following two scenarios are assumed.

[0047] In the first scenario, a dedicated frequency is assigned to the air cell, and different frequencies are used for the ground cell and the air cell. In the first scenario, for example, wireless communication by UAVs 150-1 and 150-2 and wireless communication by UEs 100-1 to 100-4 are performed using different frequencies, so that interference between the two wireless communications can be avoided.

[0048] On the other hand, the second scenario is a scenario in which the same frequency (or the same frequency range) is used in the terrestrial cell and the aerial cell. In the second scenario, since the terrestrial cell and the aerial cell share the same frequency, there is no need to increase frequency resources. Therefore, in the second scenario, frequency resources can be used more effectively.

[0049] (Communication Control Method According to the First Embodiment) Wireless communication by UAV 150 suffers from a problem specific to UAVs: the effect of interference is greater than when a ground-based UE 100 performs wireless communication. For example, as shown in FIG. 6 , consider a case in which UAVs 150-1 and 150-2 (hereinafter, when UAV 150-1 and UAV 150-2 are not distinguished from each other, they may be referred to as UAV 150) located in the sky perform uplink communication. In such a case, the wireless signal transmitted from UAV 150 may reach not only the serving cell and its neighboring cells but also a wider area. If ground-based UE 100 uses the same frequency as UAV 150, the signal from UAV 150 may interfere with the signal from ground-based UE 100. Future discussions in 3GPP are expected to include various interference avoidance measures for UAVs 150 in an RRC-connected state.

[0050] On the other hand, even if UAV 150 performs a random access procedure, if a UE on the ground simultaneously performs a random access procedure using the same frequency, interference may occur, as in the case described above.

[0051] However, there is currently no workaround for the interference caused by the UAV 150 performing the random access procedure.

[0052] Therefore, the first embodiment aims to avoid interference in the random access procedure.

[0053] Therefore, in the first embodiment, an example will be described in which parameters used in the random access procedure (hereinafter, sometimes referred to as "RACH" parameters) are parameters dedicated to the UAV 150. Specifically, a base station (e.g., gNB 200) transmits parameters used in the random access procedure to a user device (e.g., UE 100 or UAV 150). Here, the parameters are dedicated to a user device (e.g., UAV 150) located at an altitude equal to or higher than a predetermined threshold.

[0054] As described above, in the first embodiment, the gNB 200 can set RACH parameters dedicated to the UAV 150 for the UAV 150. Therefore, when the UAV 150 executes the random access procedure, it is possible to appropriately set, for example, the transmission power of the random access preamble and the number of retransmissions of the random access preamble. Such settings make it possible to avoid interference with the UE 100 that occurs when the UAV 150 executes the random access procedure.

[0055] (Examples of Parameters Used in Random Access Procedure) Here, examples of parameters used in the random access procedure will be described.

[0056] The random access procedure is performed when a UE 100 in an RRC idle state performs initial access to a network, when a UE in an RRC inactive state performs an RRC connection resumption procedure, or when the UE 100 performs an RRC connection re-establishment procedure. The random access procedure allows the UE 100 to establish uplink synchronization with the gNB 200 (or cell).

[0057] First, parameters used in the random access procedure include parameters used when transmitting a PRACH preamble. The PRACH preamble is a signal that is first transmitted by the UE 100 in the random access procedure. The parameters are used by performing the following transmission control on the PRACH preamble.

[0058] That is, the UE 100 first sets values ​​to predetermined variables (such as a preamble transmission counter, a preamble power ramping counter, and a preamble power ramping step). Of the predetermined variables, the preamble transmission counter is set using a maximum number of PRACH transmissions parameter (preambleTransMax). The maximum number of PRACH transmissions parameter represents the maximum number of PRACH preamble transmissions. Also, of the predetermined variables, the preamble power ramping step is set using a transmission power ramping step parameter (powerRampingStep). The transmission power ramping step parameter is a parameter that is incremented each time a PRACH preamble is retransmitted.

[0059] Next, the UE 100 sets the preamble reception target power (PREAMBLE_RECEIVED_TARGET_POWER) of the PRACH preamble using the predetermined variable and a preamble reception target power parameter (preambleReceivedTargetPower), etc. Since the preamble reception target power is the target reception power on the gNB 200 side, the UE 100 calculates the transmission power of the PRACH preamble by calculating the path loss for the gNB 200. The UE 100 transmits the PRACH preamble at the calculated transmission power.

[0060] As such, parameters used when transmitting a PRACH preamble include, for example, a PRACH transmission maximum number of times parameter (preambleTransMax), a transmission power ramping step parameter (powerRampingStep), and a preamble reception target power parameter (preambleReceivedTargetPower).

[0061] Second, parameters used in the random access procedure include parameters used when retransmitting a PRACH preamble. The parameters used for transmitting the PRACH preamble described above are also used when retransmitting the PRACH preamble. Furthermore, a backoff time parameter (backoff time) is a parameter used when retransmitting a PRACH preamble. The backoff time represents, for example, the time until the PRACH preamble is retransmitted. The backoff time parameter is set as follows. That is, when the UE 100 receives a random access response (RAR) (Msg2) including a MAC sub PDU with a backoff instruction after transmitting the PRACH preamble, the UE 100 sets a preamble backoff variable (PREAMBLE_BACKOFF). The UE 100 multiplies the value included in the BI field of the MAC sub PDU by a scaling factor (SCALING_FACTOR_BI) to obtain a preamble backoff variable. The backoff time parameter is set using a random number between "0" and the preamble backoff variable.

[0062] In this way, parameters used when retransmitting a PRACH preamble include, for example, a PRACH transmission maximum number of times parameter (preambleTransMax), a transmission power ramping step parameter (powerRampingStep), a preamble reception target power parameter (preambleReceivedTargetPower), and a backoff time parameter (backoff time).

[0063] Third, parameters used in the random access procedure include parameters used when the UE 100 receives a random access response (Msg2). For example, a parameter used when receiving a random access response is an RAR reception window parameter (ra-ResponseWindow). The RAR reception window parameter is, for example, a parameter representing a time window for monitoring a random access response. If the UE 100 fails to receive a random access response within the time window indicated by the RAR reception window parameter, the UE 100 retransmits the PRACH preamble until a backoff time has elapsed. On the other hand, if the UE 100 receives a random access response within the time window indicated by the RAR reception window parameter, the UE 100 stops the RAR reception window parameter.

[0064] In addition, the PRACH transmission maximum number parameter (preambleTransMax), the transmission power ramping step parameter (powerRampingStep), the preamble reception target power parameter (preambleReceivedTargetPower), and the RAR reception window parameter (ra-ResponseWindow) are included in the information element (RACH-ConfigGeneric). RACH-ConfigGeneric is an information element included in the system information (SIB1) broadcast from the gNB 200. RACH-ConfigGeneric is used to identify parameters used in the random access procedure.

[0065] (Example of Operation According to First Embodiment) Next, an example of operation according to the first embodiment will be described.

[0066] FIG. 7 is a diagram illustrating an example of operation according to the first embodiment.

[0067] As shown in Figure 7, in step S10, gNB200 transmits RACH parameters dedicated to UAV150.

[0068] First, the RACH parameters dedicated to UAV150 are linked to information representing the sky. The information representing the sky may be a predetermined threshold for identifying the sky. The predetermined threshold is a threshold for identifying whether UE100 is in the sky or on the ground, for example, an altitude threshold. When there is one predetermined threshold, two layers, "sky" and "ground," can be configured depending on whether the UE100 is higher or lower than the threshold. The number of predetermined thresholds may be two or more. For example, when there are two thresholds, three layers, "high altitude," "low altitude," and "ground," can be configured. Alternatively, the information representing the sky may be information representing a state (e.g., "sky") indicating that UE100 is located "in the sky." This link indicates that the RACH parameters are used by UE100 (i.e., UAV150) located in the sky.

[0069] Second, the RACH parameter dedicated to the UAV 150 may be at least one parameter included in the above-mentioned information element (RACH-ConfigGeneric). Specifically, it may be any of the following:

[0070] (A1) PRACH Transmission Maximum Count Parameter (preambleTransMax)

[0071] (A2) Transmission power ramping step parameter (powerRampingStep)

[0072] (A3) Preamble Received Target Power Parameter (preambleReceivedTargetPower)

[0073] (A4) RAR reception window parameter (ra-ResponseWindow) For example, by setting the preamble reception target power parameter (preambleReceivedTargetPower) dedicated to UAV150 to a value lower than the preamble reception target power parameter of the terrestrial UE100, gNB200 can make the transmission power of the PRACH preamble transmitted from UAV150 lower than the transmission power of the PRACH preamble transmitted from the terrestrial UE100. This also makes it possible to avoid interference when the random access procedure is executed in UAV150. By setting other parameters to values ​​lower (or smaller) than the parameters for the terrestrial UE100, for example, it is possible to avoid interference when the random access procedure is executed in UAV150.

[0074] Furthermore, the RACH parameter dedicated to UAV 150 may be a backoff time parameter (backoff time). Alternatively, the RACH parameter dedicated to UAV 150 may be a parameter representing an upper limit of the backoff time. As described above, the backoff time itself is a random number ranging from "0" to the preamble backoff variable (PREAMBLE_BACKOFF). However, by setting an upper limit on the random number, it is possible to prevent the backoff time from being set longer than necessary. This prevents, for example, the backoff time when the PRACH preamble is retransmitted from UAV 150 from being set longer than necessary, thereby preventing the PRACH preamble from being retransmitted from UAV 150 for an unnecessarily long time, and making it possible to avoid interference when the random access procedure is executed in UAV 150. Alternatively, the RACH parameter dedicated to UAV 150 may be a parameter representing a maximum value of the backoff time. The maximum backoff time indicates that the backoff time is not set using a random number, but is set to a specified maximum value. Alternatively, the RACH parameter dedicated to the UAV 150 may be a parameter indicating a lower limit value (e.g., "0") of the backoff time. This lower limit value allows the backoff time set using a random number to always be "0." This allows, for example, the gNB 200 to control the UAV 150 so that it must wait a certain time before retransmitting the PRACH preamble, thereby making it possible to avoid interference with the random access procedure of the terrestrial UE 100.

[0075] In this way, the parameter values ​​included in the RACH parameters dedicated to the UAV 150 are parameter values ​​that are different from the parameter values ​​for the ground UE 100. This allows the RACH parameters to be dedicated to the UAV 150.

[0076] Note that the above (A1) to (A4) and the backoff time parameter may be transmitted by broadcast using system information (SIB).

[0077] In step S11, UE 100 executes a random access procedure using RACH parameters dedicated to UAV 150 at an altitude equal to or higher than a predetermined threshold. The altitude of UE 100 may be measured by an altitude sensor provided in UE 100. The altitude of UE 100 may be measured by a distance sensor (such as radar or lidar) provided in UE 100. The altitude may be expressed in terms of height above sea level. The altitude may be expressed in terms of altitude above sea level. The altitude may be expressed in terms of height from the ground.

[0078] Note that gNB200 may transmit some of the RACH parameters dedicated to UAV150 described above. In this case, UE100 may apply some of the RACH parameters dedicated to UAV150 and apply terrestrial (or conventional) RACH parameters to other RACH parameters that have not been transmitted, to perform the random access procedure.

[0079] [Other Embodiments] The above-described operational flows are not limited to being implemented independently, but can be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0080] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0081] Also, the term "network node" primarily refers to a base station, but may also refer to a device in the core network or part of a base station (CU, DU, or RU).

[0082] A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100 or the gNB 200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0083] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0084] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made within the scope of the gist. Furthermore, it is also possible to combine all or part of each embodiment, each operation, each process, and each step within the scope of consistent combinations.

[0085] This application claims priority from Japanese Patent Application No. 2022-161585 (filed October 6, 2022), the entire contents of which are incorporated herein by reference.

[0086] (Supplementary Note) (Supplementary Note 1) A communication control method in a mobile communication system, comprising: a step in which a network node transmits parameters used in a random access procedure to a user equipment, the parameters being parameters dedicated to a user equipment located at an altitude equal to or higher than a predetermined threshold.

[0087] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the parameter is a parameter used by the user equipment when transmitting a PRACH preamble.

[0088] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, wherein the parameter is a parameter used by the user equipment when retransmitting a PRACH preamble.

[0089] (Supplementary Note 4) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the parameter is a parameter used by the user equipment when receiving a random access response.

[0090] 1: Mobile communication system 20: 5GC 100: UE 110: Receiving unit 130: Control unit 150: UAV 200: gNB 210: Wireless communication unit 230: Control unit

Claims

1. A communication control method in a mobile communication system, comprising: a user equipment receiving from a network node parameters for use in a random access procedure; The parameter is a parameter dedicated to a user device located at an altitude equal to or higher than a predetermined threshold. Communications control method.

2. The parameters are parameters used when the user equipment transmits a PRACH preamble. The communication control method according to claim 1.

3. The parameter is a parameter used when the user equipment retransmits a PRACH preamble. The communication control method according to claim 1.

4. The parameter is a parameter used by the user equipment when receiving a random access response. The communication control method according to claim 1.

5. The parameter is a parameter representing a time window for monitoring a random access response.

5. The communication control method according to claim 4.

6. A user device in a mobile communication system, comprising: a receiving unit for receiving parameters for use in a random access procedure from a network node, The parameter is a parameter dedicated to a user device located at an altitude equal to or higher than a predetermined threshold. User equipment.