Random access control in a communication system

Abstract

According to the present invention, a communication control device 3 is provided with: a random access channel specifying unit 311 for specifying a plurality of random access channels "PRACH#1" and "PRACH#2" through which random access information can be transmitted to base stations 111, 121, 131 from communication machines 2; a communication machine grouping unit 32 for grouping the communication machines 2 into a plurality of random access groups "UEGP#1" and "UEGP#2" associated with a plurality of different portions of the plurality of random access channels "PRACH#1" and "PRACH#2"; and a random access information transmission restriction unit 33 for restricting the communication machines 2 that have been grouped into the random access groups "UEGP#1" and "UEGP#2" from transmitting the random access information through a random access channel other than the random access channels "PRACH#1" and "PRACH#2" that have been associated with the plurality of random access groups "UEGP#1" and "UEGP#2".

Description

[Technical field]

[0001] The present disclosure relates to random access control in communication systems. [Background technology]

[0002] The number, types, and uses of wireless communication devices, such as smartphones and Internet of Things (IoT) devices, are constantly increasing, and wireless communication standards are continually being expanded and improved. For example, commercial services for the fifth generation mobile communication system, known as "5G," began in 2018, and standardization is still underway at the Third Generation Partnership Project (3GPP). In addition, efforts have begun to develop standards for the sixth generation mobile communication system, or "6G," as the next-generation wireless communication standard following 5G.

[0003] A random access (RA) procedure is defined for a mobile or portable communication device (hereinafter collectively referred to as a communication device), such as a smartphone or a mobile phone, to start communication with a mobile communication (hereinafter also referred to as a mobile communication) network after power-on. In the RA procedure disclosed in Patent Document 1, a predetermined time-frequency resource (hereinafter also referred to as a resource for simplicity) in a 10 ms uplink frame used for uplink communication or uplink communication from the communication device to a base station is reserved as a physical random access channel (PRACH: Physical Random Access Channel). A communication device attempting random access to a base station selects any one preamble from a maximum of 64 predetermined random access preambles (hereinafter also referred to as a preamble for simplicity) that the base station can accept, and transmits the selected preamble to the base station on the PRACH. If there is no other communication device that has transmitted the same preamble to the base station on the same PRACH, the base station that has received the preamble from the communication device through the PRACH transmits a random access response (hereinafter also referred to as a response for simplicity) to the communication device, and proceeds to a subsequent connection establishment step or the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2012-533211 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, if multiple communication devices transmit the same preamble on the same PRACH to the base station, none of the communication devices can proceed to the connection establishment step, etc., or only one communication device can proceed to the connection establishment step, etc. If a normal response is not transmitted from the base station and the communication device cannot proceed to the connection establishment step, etc., it must wait until the next PRACH according to the PRACH configuration index set in the network.

[0006] In 5G, which claims to support massive machine-type communications (mMTC), the number of communication devices, including IoT devices, that are simultaneously connected to one base station is increasing, and there is a possibility that "traffic jams" (hereinafter also referred to as PRACH congestion) will occur due to the above-mentioned RA procedure or communication devices waiting for PRACH. In addition, in addition to or instead of general base stations (hereinafter also referred to as terrestrial base stations) installed on the ground, consideration and introduction of non-terrestrial base stations such as communication satellites and unmanned aerial vehicles that fly in the atmosphere, such as outer space and the stratosphere, is underway, but as will be described later, there is a risk that PRACH congestion will become more serious in non-terrestrial base stations than in terrestrial base stations.

[0007] The present disclosure has been made in consideration of these circumstances, and has an object to provide a communication control device and the like that can improve the efficiency of random access control. [Means for solving the problem]

[0008] In order to solve the above problems, a communication control device according to one aspect of the present disclosure includes a random access channel identification unit that identifies multiple random access channels through which a communication device can transmit random access information to a base station, a communication device grouping unit that groups each communication device into multiple random access groups corresponding to different portions of the multiple random access channels, and a random access information transmission restriction unit that restricts the communication devices grouped into each random access group from transmitting random access information on channels other than the random access channels corresponding to each random access group.

[0009] In this embodiment, the random access information of the communication devices grouped into each random access group is restricted from being transmitted to the base station through the random access channel other than the random access channel corresponding to each random access group. That is, the number of communication devices that transmit random access information on each random access channel is restricted, so that the possibility of collision of the random access information of multiple communication devices on the same random access channel is reduced. Therefore, the random access procedure of each communication device can be made more efficient.

[0010] Another aspect of the present disclosure is a communication control method, comprising: identifying a plurality of random access channels through which a communication device can transmit random access information to a base station; grouping each communication device into a plurality of random access groups corresponding to different portions of the plurality of random access channels; and restricting the communication devices grouped into each random access group from transmitting the random access information on a random access channel other than the random access channel corresponding to each random access group.

[0011] Yet another aspect of the present disclosure is a storage medium that stores a communication control program that causes a computer to execute the following operations: identifying a plurality of random access channels through which a communication device can transmit random access information to a base station, grouping each communication device into a plurality of random access groups corresponding to different portions of the plurality of random access channels, and restricting the communication devices grouped into each random access group from transmitting the random access information through a random access channel other than the random access channel corresponding to each random access group.

[0012] Any combination of the above components, and conversion of the present disclosure into a method, device, system, recording medium, computer program, etc. are also valid aspects of the present disclosure. Effect of the Invention

[0013] According to the present disclosure, it is possible to improve the efficiency of random access control of a communication device. [Brief description of the drawings]

[0014] [Figure 1] 1 illustrates a schematic overview of a wireless communication system to which a communication control device is applied. [Diagram 2] FIG. 2 is a functional block diagram of a communication control device. [Diagram 3] A specific example will be given. [Figure 4] A specific example will be given. [Diagram 5] A specific example will be given. [Figure 6] 13 is a flowchart of random access control by the communication control device. [Figure 7] 1 illustrates a schematic diagram of the CBRA procedure between a communication device and a terrestrial base station. [Figure 8] 1 illustrates a schematic diagram of a CBRA procedure between a communication device and a non-terrestrial base station. [Figure 9] The results of trial calculations regarding PRACH congestion in NTN when this embodiment is not applied are shown. [Figure 10] The results of trial calculations regarding PRACH congestion in NTN when this embodiment is not applied are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The communication control device according to the present disclosure can be applied to a terrestrial network (TN) constructed by communication cells (hereinafter also referred to as terrestrial communication cells) provided to the ground by terrestrial base stations installed on the ground, a non-terrestrial network (NTN) constructed by communication cells (hereinafter also referred to as non-terrestrial communication cells) provided to the ground by flying non-terrestrial base stations, a network in which TN and NTN coexist, and other mobile communication networks. In this embodiment, in order to comprehensively explain TN and NTN, a network in which TN and NTN coexist is exemplified.

[0016] 1 is a schematic diagram showing an overview of a wireless communication system 1 to which a communication control device according to the present embodiment is applied. The wireless communication system 1 includes a 5G wireless communication system 11 conforming to a fifth generation mobile communication system (5G) using NR (New Radio) or 5G NR (Fifth Generation New Radio) as a radio access technology (RAT) and 5GC (Fifth Generation Core) as a core network (CN), a 4G wireless communication system 12 conforming to a fourth generation mobile communication system (4G) using LTE (Long Term Evolution) or LTE-Advanced as a radio access technology and EPC (Evolved Packet Core) as a core network, and a satellite communication system 13 for satellite communication via a communication satellite 131. Although not shown, the wireless communication system 1 may include a wireless communication system of a generation earlier than 4G, a wireless communication system of a generation later than 5G (6G, etc.), or any wireless communication system not related to a generation such as Wi-Fi (registered trademark).

[0017] The 5G wireless communication system 11 includes communication devices 2A, 2B, 2C, and 2D (hereinafter collectively referred to as communication devices 2) such as smartphones that are installed on the ground and are also called UE (User Equipment), and a plurality of 5G base stations 111A, 111B, and 111C (hereinafter collectively referred to as 5G base stations 111) that can communicate by 5G NR. The base station 111 in 5G is also called gNodeB (gNB). The communication range or support range of each of the 5G base stations 111A, 111B, and 111C is called a cell, and is illustrated as 112A, 112B, and 112C (hereinafter collectively referred to as 5G cell 112).

[0018] The size of the 5G cell 112 of each 5G base station 111 is arbitrary, but typically has a radius of several meters to tens of kilometers. Although there is no established definition, a cell with a radius of several meters to tens of meters is called a femtocell, a cell with a radius of tens to tens of meters is called a picocell, a cell with a radius of tens to hundreds of meters is called a microcell, and a cell with a radius of more than several hundred meters is called a macrocell. 5G often uses high-frequency radio waves such as millimeter waves, and because of their high linearity, the radio waves are blocked by obstacles and the communication distance is shortened. For this reason, 5G tends to use smaller cells than 4G and earlier generations.

[0019] The communication device 2 can perform 5G communication if it is in at least one of the multiple 5G cells 112A, 112B, and 112C. In the illustrated example, the communication device 2B in the 5G cells 112A and 112B can communicate with both the 5G base stations 111A and 111B by 5G NR. Also, the communication device 2C in the 5G cell 112C can communicate with the 5G base station 111C by 5G NR. The communication devices 2A and 2D are outside all of the 5G cells 112A, 112B, and 112C, and therefore cannot communicate by 5G NR. The 5G communication by 5G NR between each communication device 2 and each 5G base station 111 is managed by the 5GC, which is a core network. For example, the 5GC performs data exchange with each 5G base station 111, data exchange with external networks such as EPC, satellite communication system 13, and the Internet, and mobility management of the communication device 2.

[0020] The 4G wireless communication system 12 includes a plurality of 4G base stations 121 (only one of which is shown in FIG. 1) that are installed on the ground and can communicate with the communication device 2 by LTE or LTE-Advanced. The base station 121 in 4G is also called an eNodeB (eNB). As with each 5G base station 111, the communication range or support range of each 4G base station 121 is also called a cell and is illustrated as 122.

[0021] If the communication device 2 is inside the 4G cell 122, it can perform 4G communication. In the illustrated example, the communication devices 2A and 2B inside the 4G cell 122 can communicate with the 4G base station 121 by LTE or LTE-Advanced. The communication devices 2C and 2D are outside the 4G cell 122 and therefore cannot communicate by LTE or LTE-Advanced. The 4G communication by LTE or LTE-Advanced between each communication device 2 and each 4G base station 121 is managed by the EPC, which is a core network. For example, the EPC performs data exchange with each 4G base station 121, data exchange with external networks such as 5GC, satellite communication system 13, and the Internet, and mobility management of the communication device 2.

[0022] Focusing on each of the communicators 2A, 2B, 2C, and 2D, in the illustrated example, the communicator 2A is in a state where 4G communication with the 4G base station 121 is possible, the communicator 2B is in a state where 5G communication with the 5G base stations 111A and 111B and 4G communication with the 4G base station 121 are possible, and the communicator 2C is in a state where 5G communication with the 5G base station 111C is possible. When there are multiple base stations (111A, 111B, 121) that can communicate like the communicator 2B, one base station that is determined to be optimal in terms of communication quality and the like is selected under the management of the 5GC and / or EPC, which are the core networks, and communicates with the communicator 2B. In addition, the communicator 2D is not in a state where it can communicate with any of the 5G base stations 111 and the 4G base station 121, so it communicates through the satellite communication system 13 described below.

[0023] The satellite communication system 13 is a wireless communication system that uses a communication satellite 131 as a low-orbit satellite flying in space at a low orbit at an altitude of about 500 km to 700 km above the earth's surface as a non-terrestrial base station. As with the 5G base station 111 and the 4G base station 121, the communication range or support range of the communication satellite 131 is also called a cell and is illustrated as 132. In this way, the communication satellite 131 as a non-terrestrial base station provides the satellite communication cell 132 as a non-terrestrial communication cell to the ground. If the terrestrial communication device 2 is inside the satellite communication cell 132, it can perform satellite communication. As with the 5G base station 111 in the 5G wireless communication system 11 and the 4G base station 121 in the 4G wireless communication system 12, the communication satellite 131 as a base station in the satellite communication system 13 can wirelessly communicate with the communication device 2 in the satellite communication cell 132 directly or indirectly via an aircraft or the like. The wireless access technology that the communication satellite 131 uses for wireless communication with the communication device 2 in the satellite communication cell 132 may be 5G NR, the same as the 5G base station 111, LTE or LTE-Advanced, the same as the 4G base station 121, or any other wireless access technology that can be used by the communication device 2. For this reason, the communication device 2 does not need to be provided with special functions or components for satellite communication.

[0024] The satellite communication system 13 includes a gateway 133 as a ground station installed on the ground and capable of communicating with a communication satellite 131. The gateway 133 includes a satellite antenna for communicating with the communication satellite 131, and is connected to a 5G base station 111 and a 4G base station 121 as terrestrial base stations constituting a terrestrial network via their respective wireless access technologies, 5G NR and LTE, or other wired or wireless access technologies or interfaces. In this way, the gateway 133 connects the NTN constituted by the communication satellite 131 and the TN constituted by the terrestrial base stations 111 and 121 so that they can communicate with each other. When the communication satellite 131 performs 5G communication with the communication device 2 in the satellite communication cell 132 by 5G NR, the 5GC connected via the gateway 133 and the 5G base station 111 (or a 5G radio access network) in the TN is used as a core network, and when the communication satellite 131 performs 4G communication with the communication device 2 in the satellite communication cell 132 by LTE or LTE-Advanced, the EPC connected via the gateway 133 and the 4G base station 121 (or a 4G radio access network) in the TN is used as a core network. In this way, appropriate cooperation is achieved between different wireless communication systems such as 5G communication, 4G communication, and satellite communication via the gateway 133.

[0025] Satellite communication by the communication satellite 131 is mainly used to cover areas where no or few terrestrial base stations such as the 5G base station 111 and the 4G base station 121 are installed. In the illustrated example, the communication device 2D located outside the communication cells of all terrestrial base stations communicates with the communication satellite 131. On the other hand, the communication devices 2A, 2B, and 2C that can communicate well with any of the terrestrial base stations are also able to communicate with the communication satellite 131 because they are located within the satellite communication cell 132. However, by communicating with the terrestrial base station instead of the communication satellite 131 as a satellite base station in principle, the limited communication resources (including power) of the communication satellite 131 are saved for the communication device 2D and the like. The communication satellite 131 improves the quality of communication with the communication device 2D by directing communication radio waves to the communication device 2D within the satellite communication cell 132 by beamforming.

[0026] The size of the satellite communication cell 132 of the communication satellite 131 as a satellite base station can be set arbitrarily according to the number of beams emitted by the communication satellite 131. For example, a maximum of 2,800 beams can be combined to form a satellite communication cell 132 with a diameter of about 24 km. As shown in the figure, the satellite communication cell 132 is typically larger than a terrestrial communication cell such as the 5G cell 112 or the 4G cell 122, and may include one or more 5G cells 112 and / or 4G cells 122 therein. Note that, although the communication satellite 131 flying in a low orbit space at an altitude of about 500 km to 700 km above the earth's surface has been exemplified above as a flying non-terrestrial base station, a communication satellite flying in a high orbit space such as a geostationary orbit or an unmanned or manned aircraft flying in the atmosphere such as the stratosphere at a lower altitude (for example, about 20 km above the earth's surface) may be used as a non-terrestrial base station in addition to or instead of the communication satellite 131.

[0027] As described above, the wireless communication system 1 according to this embodiment includes terrestrial networks (TN) 11, 12 capable of communicating with the communication devices 2 in terrestrial communication cells 112, 122 provided on the ground by terrestrial base stations 111, 121 installed on the ground, and a non-terrestrial network (NTN) 13 capable of communicating with the communication devices 2 in a non-terrestrial communication cell 132 provided on the ground by a flying non-terrestrial base station 131. The communication control device according to this embodiment controls the TN and the NTN.

[0028] FIG. 2 is a functional block diagram of the communication control device 3 according to this embodiment. The communication control device 3 includes a system information acquisition unit 31, a communication device grouping unit 32, and a random access information transmission restriction unit 33. These functional blocks are realized by the cooperation of hardware resources such as a central processing unit of a computer, a memory, an input device, an output device, and peripheral devices connected to the computer, and software executed using them. Regardless of the type of computer or the installation location, each of the above-mentioned functional blocks may be realized by the hardware resources of a single computer, or may be realized by combining hardware resources distributed among multiple computers. For example, some or all of the functional blocks of the communication control device 3 may be realized in a distributed or centralized manner by computers and processors provided in the communication device 2, the terrestrial base stations 111 and 121, the non-terrestrial base station 131, and the core network CN. Particularly in this embodiment, most of the functional blocks of the communication control device 3 are realized by the communication device 2, and the remaining functional blocks are mainly realized by the terrestrial base stations 111 and 121, and the non-terrestrial base station 131.

[0029] The communication device 2 equipped with the system information acquisition unit 31 acquires system information from the downlink frame DL transmitted from the base stations 111, 121, and 131. FIG. 2 illustrates a schematic example of the concept of the downlink frame DL adopted in 5G and the like. In the following, specific configurations and numerical values ​​of the downlink frame DL and the uplink frame UL are illustrated in accordance with an operation example in 5G, but the present disclosure is also applicable to downlink frames DL and uplink frames UL adopting different configurations and numerical values. In FIG. 2, the horizontal direction of the downlink frame DL and the uplink frame UL typically represents the time direction, and the vertical direction of the downlink frame DL and the uplink frame UL typically represents the frequency direction. The downlink frame DL can be sequentially transmitted by the base stations 111, 121, and 131 on the right side of FIG. 2 to the communication device 2 on the left side of FIG. 2. The uplink frame UL can be sequentially transmitted by the communication device 2 on the left side of FIG. 2 to the base stations 111, 121, and 131 on the right side of FIG. 2.

[0030] Each downlink frame DL with a length of 10 ms is composed of 10 subframes with a length of 1 ms each. In 5G, one subframe contains one slot (when the subcarrier spacing is 15 kHz), two slots (when the subcarrier spacing is 30 kHz), four slots (when the subcarrier spacing is 60 kHz), eight slots (when the subcarrier spacing is 120 kHz), or 16 slots (when the subcarrier spacing is 240 kHz) depending on the subcarrier spacing set in the network. Each slot contains 14 OFDM symbols regardless of the subcarrier spacing. In the following, a case where the subcarrier spacing is 15 kHz, that is, a case where one slot is included in one subframe, will be described as an example. Therefore, in the following description, a subframe and a slot are synonymous.

[0031] In a half frame (5 ms) that is half of each downlink frame DL composed of five subframes, a plurality of SS / PBCH (Synchronization Signal / Physical Broadcast Channel) blocks are transmitted from the base stations 111, 121, 131 to the communication devices 2 in the communication cells 112, 122, 132 using a predetermined time-frequency resource in the predetermined subframe in a predetermined half frame (4 subframe period=20 ms period in the example of FIG. 2). The plurality of SS / PBCH blocks transmitted in each half frame correspond to a plurality of different beams that the base stations 111, 121, 131 can transmit. For example, in the example of FIG. 2, the first to fourth SS / PBCH blocks included in each half frame are transmitted by the first to fourth beams emitted by the base stations 111, 121, 131, respectively.

[0032] The SS / PBCH block is a block for the communication device 2 that receives it to establish frame synchronization and acquire system information required for establishing a connection with the base stations 111, 121, and 131 by random access, which will be described later. Specifically, the SS / PBCH block includes a primary synchronization signal (PSS: Primary SS) and a secondary synchronization signal (SSS: Secondary SS) as synchronization signals (SS: Synchronization Signals) for frame synchronization. In addition, a master information block (MIB) including basic system information such as a system frame number (SFN: System Frame Number) is transmitted on a physical broadcast channel (PBCH) in the SS / PBCH block.

[0033] The communication device 2 (system information acquisition unit 31) that establishes frame synchronization by SS and acquires basic system information from the MIB acquires a system information block of type 1 (SIB1: System Information Block Type 1) from a physical downlink shared channel (PDSCH: Physical Downlink Shared Channel) designated by the MIB. The MIB and SIB1 configure Minimum System Information (MSI: Minimum System Information) in 5G, and include all information necessary for establishing a connection between the communication device 2 and the base stations 111, 121, and 131 by random access, which will be described later. Note that the number of groups n (n is a natural number of 2 or more), which will be described later and is used for establishing a connection in this embodiment, is not included in the MSI in the current 5G, but can be operated as part of the MSI by additionally storing it in the SIB1, for example.

[0034] The system information acquisition unit 31 includes a random access channel identification unit 311. The random access channel identification unit 311 identifies a plurality of random access channels through which the communication device 2 can transmit random access information to the base stations 111, 121, and 131. Specifically, the communication device 2 functioning as the random access channel identification unit 311 refers to the received MSI (particularly SIB1) and identifies a time-frequency domain of a physical random access channel (PRACH: Physical Random Access Channel) reserved for transmitting a random access preamble as random access information in each uplink frame UL that can be transmitted to the base stations 111, 121, and 131.

[0035] Like each of the above-mentioned downlink frames DL, each uplink frame UL has a length of 10 ms and is composed of 10 subframes, each of which has a length of 1 ms. Each uplink frame UL is assigned a consecutive (cyclic) system frame number from "0" to "1023" that can be recognized by the communication device 2 through the MIB received by the system information acquisition unit 31. In FIG. 2, an uplink frame "SFN#1" with a system frame number "1" and an uplink frame "SFN#2" with a system frame number "2" are illustrated as schematic examples.

[0036] In 5G, a part or all of the frequency resources of one or more slots (each slot is composed of 14 OFDM symbols) in one uplink frame UL can be reserved as a PRACH. In the example of Fig. 2, when the slot length is 1 ms, which is the same as the subframe length (when the subcarrier interval is 15 kHz), a part of the frequency resources of the third slot of the first uplink frame "SFN#1" is reserved as the first physical random access channel "PRACH#1", and a part of the frequency resources of the second slot of the second uplink frame "SFN#2" is reserved as the second physical random access channel "PRACH#2".

[0037] The communication device 2 functioning as the random access channel identification unit 311 refers to the received SIB1, etc., and identifies the time-frequency domains of the physical random access channels "PRACH#1" and "PRACH#2" in a series of uplink frames "SFN#1" and "SFN#2". Note that multiple PRACHs may be reserved in one uplink frame UL. In the following, a case will be described in which the communication control device 3 performs random access control on N physical random access channels (RO: RACH Occasion) "PRACH#1", "PRACH#2", "PRACH#N" (typically M≦N) included in M ​​(e.g., 1024) uplink frames "SFN#1", "SFN#2", "SFN#M" having different system frame numbers. In the range shown in FIG. 2, M=N=2.

[0038] The communication device grouping unit 32 groups each communication device 2 into a plurality of random access groups "UEGP#1" and "UEGP#2" corresponding to different portions of the plurality of physical random access channels "PRACH#1" and "PRACH#2" identified by the random access channel identification unit 311. In the example of Fig. 2, the first random access group "UEGP#1" of the communication device 2 corresponds to the first physical random access channel "PRACH#1", and the second random access group "UEGP#2" of the communication device 2 corresponds to the second physical random access channel "PRACH#2". In the following, the number of random access groups of the communication device 2 is represented as n.

[0039] In the range shown in FIG. 2, the number of groups n, the number of physical random access channels N, and the number of uplink frames M are all 2 (M = N = n = 2). Note that the association between the n random access groups of the communication device 2 and the N physical random access channels does not have to be one-to-one as shown in FIG. 2. For example, when n < N, a plurality of physical random access channels are associated with at least one random access group. When n > N, a plurality of random access groups are associated with at least one physical random access channel.

[0040] The communication device grouping unit 32 groups each communication device 2 into n random access groups according to the remainder obtained by dividing the communication device identification information of each communication device 2 by the number of groups n included in the SIB1 etc. received by the system information acquisition unit 31 from the base stations 111, 121, 131. Examples of the communication device identification information of the communication device 2 include user identification numbers such as IMSI (International Mobile Subscriber Identity) assigned to the user of the communication device 2. Since the remainder obtained by dividing IMSI etc. by the number of groups n (hereinafter also referred to as "IMSI mod n" etc. using congruence) has n values from 0 to n - 1, a large number of communication devices 2 can be efficiently grouped into n random access groups. When the communication device grouping unit 32 is provided in each communication device 2, it groups itself into a random access group according to the remainder obtained by dividing its own communication device identification information by the number of groups n.

[0041] As the communication device identification information of the communication device 2, identification information unique to the communication device 2, such as the telephone number, IP address, or IMEI (International Mobile Equipment Identity) of the communication device 2, may be used. Also, since it is sufficient to group a large number of communication devices 2 into n random access groups, communication device identification information or other information that may be the same for a plurality of communication devices 2 may be used. For example, a random number or an arbitrary constant previously assigned to each communication device 2, or a random number or an arbitrary constant generated by each communication device 2 when performing processing of the communication device grouping unit 32, may be divided by the number of groups n to calculate the remainder.

[0042] The random access information transmission restriction unit 33 restricts the communication devices 2 grouped into each of the n random access groups from transmitting random access preambles on channels other than the physical random access channel associated with each random access group. In the example of FIG. 2, the communication devices 2 grouped into the first random access group "UEGP#1" are restricted from transmitting random access preambles on channels other than the first physical random access channel "PRACH#1" associated with the first random access group "UEGP#1". That is, the communication devices 2 can transmit random access preambles only on the first physical random access channel "PRACH#1" and cannot transmit random access preambles on the second physical random access channel "PRACH#2".

[0043] Similarly, the communication devices 2 grouped into the second random access group "UEGP#2" are restricted from transmitting random access preambles on channels other than the second physical random access channel "PRACH#2" associated with the second random access group "UEGP#2". That is, the communication devices 2 can transmit random access preambles only on the second physical random access channel "PRACH#2" and cannot transmit random access preambles on the first physical random access channel "PRACH#1". In this way, the number of communication devices 2 that can transmit random access preambles on each of the physical random access channels "PRACH#1" and "PRACH#2" is restricted, so that the possibility of contention or collision of random access preambles of multiple communication devices 2 on the same physical random access channel "PRACH#1" and "PRACH#2" is reduced. Therefore, the random access procedure of each communication device 2 can be made more efficient.

[0044] The random access information transmission restriction unit 33 restricts the transmission of random access preambles on channels other than the physical random access channel included in the uplink frame UL, where the remainder (hereinafter, also referred to as "SFN mod n" using the congruence formula) obtained by dividing the system frame number included in the MIB etc. received by the system information acquisition unit 31 from the base stations 111, 121, 131 by the number of groups n is equal to the remainder (IMSI mod n) obtained by dividing the IMSI as the communication device identification information of the communication device 2 by the number of groups n.

[0045] In the example of Fig. 2, the communication device 2 grouped into the first random access group "UEGP#1" because it has an IMSI with IMSI mod n=1 is restricted from transmitting a random access preamble on any channel other than the first physical random access channel "PRACH#1" included in the first uplink frame "SFN#1" of the system frame number "1" with SFN mod n=1. In this manner, the first random access group "UEGP#1" satisfying IMSI mod n=SFN mod n=1 and the first uplink frame "SFN#1" are associated with each other, and the communication device 2 belonging to the first random access group "UEGP#1" can transmit a random access preamble only on the first physical random access channel "PRACH#1" in the corresponding first uplink frame "SFN#1", but cannot transmit a random access preamble on the second physical random access channel "PRACH#2" in the second uplink frame "SFN#2" that does not satisfy IMSI mod n=SFN mod n.

[0046] Similarly, the communication device 2 grouped into the second random access group "UEGP#2" because it has an IMSI with IMSI mod n=2 is restricted from transmitting a random access preamble in any channel other than the second physical random access channel "PRACH#2" included in the second uplink frame "SFN#2" of the system frame number "2" with SFN mod n=2. In this manner, the second random access group "UEGP#2" satisfying IMSI mod n=SFN mod n=2 and the second uplink frame "SFN#2" are associated with each other, and the communication device 2 belonging to the second random access group "UEGP#2" can transmit a random access preamble only in the second physical random access channel "PRACH#2" in the corresponding second uplink frame "SFN#2", but cannot transmit a random access preamble in the first physical random access channel "PRACH#1" in the first uplink frame "SFN#1" that does not satisfy IMSI mod n=SFN mod n.

[0047] As described above, the communication device grouping unit 32 and the random access information transmission restriction unit 33 in the communication control device 3, in which most of the functions are realized by the communication device 2, perform grouping of itself (the communication device 2) and association with the uplink frame UL including the available physical random access channel at once by solving a single equation "IMSI mod n=SFN mod n" based on the system frame number (SFN) and the number of groups (n) included in the MSI such as MIB and SIB1 received by the system information acquisition unit 31 through the downlink frame DL from the base station 111, 121, 131 and the communication device identification information (IMSI) of the communication device 2 itself. In this way, the communication device grouping unit 32 and the random access information transmission restriction unit 33 shown as different functional blocks in Fig. 2 can be realized as a single functional block that solves a single equation "IMSI mod n=SFN mod n".

[0048] The equation "IMSI mod n=SFN mod n" is a calculation that associates n random access groups of the communication devices 2, which are formed according to the value (0, 1, ..., n-1) of "IMSI mod n" on the left side, with n frame groups, in which M (e.g., 1024) uplink frames UL with different system frame numbers are grouped according to the value (0, 1, ..., n-1) of "SFN mod n" on the right side. That is, the communication device grouping unit 32 groups each communication device 2 into n random access groups corresponding to the n frame groups. Then, the random access information transmission restriction unit 33 restricts the communication devices 2 grouped into each of the n random access groups from transmitting random access preambles on channels other than the physical random access channel included in the uplink frame UL belonging to the frame group associated with each random access group.

[0049] In the above example, n random access groups of the communication device 2 are associated with n frame groups of the uplink frame UL by the equation "IMSI mod n=SFN mod n", but when identification information of N physical random access channels such as "PRACH#1" and "PRACH#2" illustrated in Fig. 2 (hereinafter also referred to as random access channel identification information, PRACH identification information, etc.) is set and the system information acquisition unit 31 can acquire it through MSI such as MIB or SIB1, n random access groups of the communication device 2 may be associated with n random access channel groups of the physical random access channel by the equation "IMSI mod n=PRACH mod n" (here "PRACH" represents PRACH identification information). In this case, the random access groups are not indirectly associated with the random access channel groups via the frame groups as in the above example, but are directly associated with the random access channel groups.

[0050] 3 to 5 show a specific embodiment. As shown in FIG. 3, in this embodiment, five communication devices "UE1" to "UE5" having five consecutive IMSIs "1013016041741" to "1013016041745" are assigned or mapped to physical random access channels in three uplink frames having system frame numbers "768" to "770". The number of groups n in this embodiment is "3" as also shown in FIG. 4. FIG. 4 illustrates the process of solving the above-mentioned equation "IMSI mod n=SFN mod n". Based on the communication device identification information (IMSI), system frame number (SFN), and number of groups (n) of each communication device 2, "IMSI mod n" and "SFN mod n" are calculated, and it is determined whether the two match (TRUE) or not (FALSE). Only combinations of the inter-communication device identity (IMSI) and the system frame number (SFN) for which the determination result is “TRUE” are permitted for random access by the inter-communication device 2 .

[0051] As shown diagrammatically in FIG. 5, the communication devices “UE2” and “UE5” having “IMSI mod n” of “0” and grouped into the 0th random access group “UEGP#0” are associated with an uplink frame having system frame number “768” having “SFN mod n” of “0”, and can transmit a random access preamble to the 0th physical random access channel “PRACH Window#0” included in the uplink frame (they cannot transmit a random access preamble to the other physical random access channels “PRACH Window#1” and “PRACH Window#2”). Similarly, the communication device "UE3" whose "IMSI mod n" is "1" and which is grouped into the first random access group "UEGP#1" is associated with an uplink frame of system frame number "769" whose "SFN mod n" is "1", and can transmit a random access preamble to the first physical random access channel "PRACH Window#1" included in the uplink frame (it cannot transmit a random access preamble to the other physical random access channels "PRACH Window#0" and "PRACH Window#2"). In addition, the communication devices "UE1" and "UE4" whose "IMSI mod n" is "2" and which are grouped into the second random access group "UEGP#2" are associated with an uplink frame of system frame number "770" whose "SFN mod n" is "2", and can transmit a random access preamble to the second physical random access channel "PRACH Window#2" included in the uplink frame (they cannot transmit a random access preamble to the other physical random access channels "PRACH Window#0" and "PRACH Window#1").

[0052] FIG. 6 is a flowchart of random access control by the communication control device 3. In the explanation of the flowchart, "S" means a step or a process. In S1, the system information acquisition unit 31 acquires system information from the downlink frame DL transmitted from the base station 111, 121, 131. In S2, the communication device grouping unit 32 and the random access information transmission restriction unit 33 solve the equation "IMSI mod n=SFN mod n" based on the system frame number (SFN) and the number of groups (n) included in the system information such as MIB and SIB1 acquired in S1 and the communication device identification information (IMSI) of the communication device 2, thereby associating the communication device 2 with the uplink frame. A communication device 2 for which "IMSI mod n=SFN mod n" does not hold for the current uplink frame (No in S2) proceeds to S3, waits until an uplink frame with a system frame number for which "IMSI mod n=SFN mod n" holds, and returns to S1. If the communication device 2 satisfies "IMSI mod n=SFN mod n" for the current uplink frame (Yes in S2), the process proceeds to S4, where the random access channel identification unit 311 identifies a random access channel (RO: RACH Occasion) in the uplink frame. In S5, the communication device 2 transmits a random access preamble to the base station 111, 121, or 131 on the random access channel identified in S4.

[0053] FIG. 7 shows a schematic diagram of a contention-based random access (CBRA) procedure between the communication device 2 and the terrestrial base stations 111 and 121. The CBRA procedure is composed of four messages exchanged between the communication device 2 (UE) and the terrestrial base stations 111 and 121 (gNB / eNB). The first message (Msg1) is a random access request (RA Request) that the communication device 2 transmits to the terrestrial base stations 111 and 121. The communication device 2 that attempts random access to the terrestrial base stations 111 and 121 for establishing a connection selects any one preamble from a maximum of 64 mutually orthogonal predetermined random access preambles (hereinafter also simply referred to as preambles) that the terrestrial base stations 111 and 121 can accept, and transmits the selected preamble in a first message to the terrestrial base stations 111 and 121 on a physical random access channel.

[0054] The second message (Msg2) is a random access response (RA Response) that the terrestrial base stations 111 and 121 transmit to the communication device 2. When the terrestrial base stations 111 and 121 receive a preamble from the communication device 2 through the physical random access channel and there is no other communication device 2 that has transmitted the same preamble to the terrestrial base station 111 and 121 on the same physical random access channel (no collision of preambles), they transmit a random access response (hereinafter also simply referred to as a response) to the communication device 2 and proceed to a connection establishment step using the subsequent third and fourth messages.

[0055] On the other hand, when a plurality of communication devices 2 transmit the same preamble to the terrestrial base station 111, 121 on the same physical random access channel, the terrestrial base station 111, 121 takes measures such as transmitting a response to only one communication device 2, transmitting a response permitting a transition to a connection establishment step to only one communication device 2 and transmitting a response instructing a waiting time until the next random access to the other communication devices 2, or not transmitting a response to any communication device 2. A communication device 2 that does not receive a normal response from the terrestrial base station 111, 121 must wait until the next or subsequent physical random access channel. In the example of FIG. 2, the interval between adjacent physical random access channels in terms of time is about the frame length (10 ms) of the uplink frame UL, which is the delay time of each communication device 2 associated with waiting for at least one PRACH.

[0056] In 5G, which claims to support massive machine-type communications (mMTC), the number of communication devices 2, including IoT devices, simultaneously connected to one terrestrial base station 111, 121 is increasing, and there is a possibility that "traffic jam" (hereinafter also referred to as PRACH congestion) will occur due to the communication devices 2 waiting for PRACH as described above. That is, one physical random access channel can only accept a maximum of 64 mutually different (orthogonal) preambles, and each communication device 2 randomly selects one preamble, so that it is not possible to know in advance the preambles transmitted by other communication devices 2. For this reason, if the number of communication devices 2 attempting random access simultaneously increases, preamble collisions will occur frequently, in which multiple communication devices 2 select the same preamble, causing serious PRACH congestion.

[0057] According to the present embodiment described with reference to FIG. 2, for the communication devices 2 grouped into each random access group "UEGP#1" and "UEGP#2", transmission of preambles to the base stations 111, 121, and 131 is restricted on physical random access channels other than "PRACH#1" and "PRACH#2" corresponding to each random access group "UEGP#1" and "UEGP#2". That is, since the number of communication devices 2 that can transmit preambles (first messages) on each physical random access channel "PRACH#1" and "PRACH#2" is effectively restricted (or since many communication devices 2 are effectively distributed to multiple physical random access channels "PRACH#1" and "PRACH#2"), the possibility of contention or collision of preambles of multiple communication devices 2 on the same physical random access channel "PRACH#1" and "PRACH#2" is reduced. Therefore, the random access procedure of each communication device 2 can be made more efficient.

[0058] The communication device 2 that has received a normal response (second message) from the terrestrial base station 111, 121 transmits a third message (Msg3) to the terrestrial base station 111, 121 in accordance with the timing information and scheduling permission (which specify resources in the uplink frame UL or a Physical Uplink Shared Channel (PUSCH) that can be used to transmit the third message) contained in the second message. The third message contains communication device identification information of the communication device 2, etc. The terrestrial base station 111, 121 that has received the third message identifies or authenticates the communication device 2 based on the communication device identification information, etc., while appropriately cooperating with the core network CN, and transmits a completion notification to the communication device 2 as a fourth message (Msg4). After the above series of four messages have been successfully exchanged, a connection between the communication device 2 and the terrestrial base station 111, 121 is established.

[0059] Fig. 8 shows a schematic diagram of the CBRA procedure between the communication device 2 and the communication satellite 131 as a non-terrestrial base station. As in Fig. 7 relating to the terrestrial base stations 111 and 121, the CBRA procedure is composed of four messages exchanged between the communication device 2 (UE) and the communication satellite 131 (Satellite). Since the distance between the communication device 2 and the communication satellite 131 is large, the communication of each message involves a propagation delay that cannot be ignored (typically greater than 20 ms). Therefore, the communication device 2 that transmits the first message and the third message to the communication satellite 131 calculates the distance or the propagation delay between itself and the communication satellite 131 based on its own positioning information by a GNSS (Global Navigation Satellite System) or the like and the orbit information of the communication satellite 131. Then, the communication device 2 transmits each message at an early timing taking into consideration the propagation delay so that each message arrives in a timely manner in the physical random access channel window (a time frame of the length (1 ms) of each physical random access channel in Figure 2) for receiving the first message (random access request including a preamble) prepared on the communication satellite 131 side, or in the message window for receiving the third message.

[0060] Also, on the communication satellite 131 side, in order to reliably receive the third message from the communication device 2, the length of the message window for receiving the third message (the length of the PUSCH set for the third message communication) is set to be larger than that of the terrestrial base stations 111 and 121. In this way, the CBRA procedure for the communication satellite 131 requires a longer time due to propagation delay than the CBRA procedure for the terrestrial base stations 111 and 121, and consumes more resources for reliable message communication. For this reason, in the NTN formed by the communication satellite 131, PRACH congestion is more likely to occur and become more serious than in the TN in FIG. 7. For this reason, as in the present embodiment described with reference to FIG. 2, it is extremely important to effectively limit the number of communication devices 2 that can transmit preambles (first messages) on each of the physical random access channels "PRACH#1" and "PRACH#2" to reduce the possibility of contention or collision of preambles of multiple communication devices 2 on the same physical random access channel "PRACH#1" and "PRACH#2".

[0061] PRACH congestion in NTN may occur, for example, when a large number of NB-IoT devices (communication devices 2) that receive signals intermittently according to a DRX (Discontinuous Reception) cycle transition or start up all at once from a standby state to a signal reception state. That is, a large number of NB-IoT devices that start up all at once may transmit duplicate preambles to the same physical random access channel all at once. In addition, PRACH congestion in NTN may also be caused by the discontinuity of non-terrestrial communication cells provided to the ground by non-terrestrial base stations such as the communication satellite 131. For example, when a second communication satellite flies so as to follow a first communication satellite, and there is a gap between the first satellite communication cell of the first communication satellite and the second satellite communication cell of the second communication satellite, a large number of communication devices that are disconnected from the first satellite communication cell due to the flight of the first communication satellite may attempt random access all at once to the second communication satellite that flies later.

[0062] Although a four-step CBRA procedure consisting of four messages is shown in FIG. 7 and FIG. 8, this embodiment can also be applied to a two-step CBRA procedure consisting of two messages. In the two-step CBRA procedure, information corresponding to the third message in the four-step CBRA procedure is included in the first message, and information corresponding to the fourth message in the four-step CBRA procedure is included in the second message. In an NTN in which communication of each message involves a large propagation delay, the propagation delay can be minimized by the two-step CBRA procedure in which the number of messages is minimized. On the other hand, in the two-step CBRA procedure, when preambles of multiple communication devices 2 collide, resources used to transmit information equivalent to the third message may be wasted. However, according to this embodiment, the possibility of collision of preambles can be reduced, so that the propagation delay can be minimized while efficiently using resources.

[0063] 9 and 10 show the results of calculations on PRACH congestion in NTN when the present embodiment described with reference to FIG. 2 and the like is not applied. Specifically, calculation results are shown for a communication satellite 131 flying in a geosynchronous equatorial orbit (GEO: Geosynchronous Equatorial Orbit) at an altitude of about 36,000 km above the earth's surface and a communication satellite 131 flying in a low earth orbit (LEO: Low Earth Orbit) at an altitude of 2,000 km or less above the earth's surface, the communication range (Coverage) of each communication satellite 131, the number of random access attempts per second (RACH per second per UE) by each communication device 2, and the density of communication devices 2 that each communication satellite 131 can support (Supported UE density). This calculation was performed using one typical set of parameters, specifically, a collision rate of "0.01", a preamble number of "56", a preamble format of "0", a PRACH configuration index of "27", a frequency multiplexing number of "8", and the like.

[0064] As shown in FIG. 9, the wider the communication range is, such as with GEO satellites, and the higher the frequency of random access of each communication device 2, the lower the density of communication devices 2 that each communication satellite 131 can support. 2 The supportable communication density of less than 10 UE / km is highlighted in bold and framed in bold. Figure 10 shows the calculation results when the condition stipulated in "3GPP TR 38.821 Section 7.2.1.1.1.2" is further added to Figure 9 (the interval between adjacent ROs (RACH Occasions) is greater than twice the maximum delay within the satellite communication cell). Compared to Figure 9, the supportable communication density drops significantly (below "0 UE / km", which means that not even one communication device 2 can be supported). 2 ").

[0065] As described above, in the NTN constituted by the communication satellite 131, PRACH congestion is likely to occur and become more serious. For this reason, as in the present embodiment described with reference to Fig. 2, it is extremely important to effectively limit the number of communication devices 2 that can transmit preambles (first messages) on each physical random access channel "PRACH#1" and "PRACH#2" (corresponding to lowering "RACH per second per UE" in Figs. 9 and 10) to reduce the possibility of contention or collision of preambles of multiple communication devices 2 on the same physical random access channel "PRACH#1" and "PRACH#2".

[0066] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present disclosure.

[0067] The functional configuration of each device described in the embodiment can be realized by hardware resources, software resources, or by the cooperation of hardware resources and software resources. A processor, ROM, RAM, and other LSIs can be used as hardware resources. An operating system, an application, and other programs can be used as software resources.

[0068] The present disclosure may be expressed as follows:

[0069] Item 1: a random access channel identifying unit that identifies a plurality of random access channels through which the communication device can transmit random access information to the base station; a communication device grouping unit configured to group each communication device into a plurality of random access groups corresponding to different portions of the plurality of random access channels; a random access information transmission restriction unit that restricts transmission of random access information by communication devices grouped in each random access group through a random access channel other than the random access channel associated with each random access group; A communication control device comprising: Item 2: A plurality of frames capable of transmitting information from the communication device to the base station are grouped into n frame groups (n is a natural number equal to or greater than 2); the communication device grouping unit groups the communication devices into n random access groups corresponding to the n frame groups; the random access information transmission restriction unit restricts the communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than that included in a frame belonging to a frame group associated with each of the random access groups; Item 1. A communication control device according to item 1. Item 3: the communication device grouping unit groups each of the communication devices into n random access groups according to a remainder obtained by dividing communication device identification information of each of the communication devices by n; The random access information transmission restriction unit restricts the communication devices grouped into each random access group from transmitting random access information on a random access channel other than that included in a frame whose remainder when a frame number is divided by n is equal to the remainder when the communication device identification information is divided by n. 3. The communication control device according to item 2. Item 4: 4. The communication control device according to item 3, wherein the communication device identification information is a user identification number given to a user of the communication device. Item 5: The communication device grouping unit is provided in each communication device, and groups each communication device into a random access group according to a remainder obtained by dividing its own communication device identification information by n; The random access information transmission restriction unit is provided in each communication device, and restricts transmission of the random access information on a random access channel other than that included in a frame in which a remainder obtained by dividing a frame number calculated based on a frame number and a group number n received from a base station by n is equal to a remainder obtained by dividing the communication device identification information of the communication device by n. 5. The communication control device according to item 3 or 4. Item 6: 6. The communication control device according to any one of items 1 to 5, wherein the random access channel identifying unit, the communication device grouping unit, and the random access information transmission restriction unit are provided in each communication device. Item 7: The communication control device according to any one of items 1 to 6, wherein the base station is an airborne non-terrestrial base station. Item 8: 8. The communication control device according to item 7, wherein the non-terrestrial base station is a communication satellite flying in outer space. Item 9: The plurality of random access channels are grouped into n random access channel groups (n is a natural number equal to or greater than 2); the communication device grouping unit groups the communication devices into n random access groups corresponding to the n random access channel groups; the random access information transmission restriction unit restricts the communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than the random access channel group corresponding to each of the random access groups; 9. A communication control device according to any one of items 1 to 8. Item 10: the communication device grouping unit groups each of the communication devices into n random access groups according to a remainder obtained by dividing communication device identification information of each of the communication devices by n; the random access information transmission restriction unit restricts, for the communication devices grouped into each of the random access groups, transmission of the random access information on a random access channel other than a random access channel whose remainder when the random access channel identification information is divided by n is equal to the remainder when the communication device identification information is divided by n. Item 10. The communication control device according to item 9. Item 11: identifying a plurality of random access channels over which the communication device can transmit random access information to the base station; grouping each communication unit into a plurality of random access groups corresponding to different portions of the plurality of random access channels; restricting communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than the random access channel associated with each of the random access groups; A communication control method comprising: Item 12: identifying a plurality of random access channels over which the communication device can transmit random access information to the base station; grouping each communication unit into a plurality of random access groups corresponding to different portions of the plurality of random access channels; restricting communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than that associated with each of the random access groups; A storage medium that stores a communication control program that causes a computer to execute the above.

[0070] This application claims priority based on Japanese patent application No. 2021-177197, filed on October 29, 2021, the entire contents of which are incorporated by reference. [Industrial Applicability]

[0071] The present disclosure relates to random access control in communication systems. [Explanation of symbols]

[0072] 1 wireless communication system, 2 communication device, 3 communication control device, 11 5G wireless communication system, 12 4G wireless communication system, 13 satellite communication system, 31 system information acquisition unit, 32 communication device grouping unit, 33 random access information transmission restriction unit, 111 5G base station, 112 5G cell, 121 4G base station, 122 4G cell, 131 communication satellite, 132 satellite communication cell, 133 gateway, 311 random access channel identification unit.

Claims

1. a random access channel identifying unit that identifies a plurality of random access channels through which the communication device can transmit random access information to the base station; a communication device grouping unit configured to group each communication device into a plurality of random access groups corresponding to different portions of the plurality of random access channels; a random access information transmission restriction unit that restricts transmission of random access information by communication devices grouped in each of the random access groups through a random access channel other than the random access channel associated with each of the random access groups; Equipped with A plurality of frames in which the communication device can transmit information to the base station are grouped into n frame groups (n is a natural number equal to or greater than 2); the communication device grouping unit groups the communication devices into n random access groups corresponding to the n frame groups; The random access information transmission restriction unit is a communication control device that restricts the transmission of random access information for communication devices grouped into each random access group, other than through a random access channel included in a frame belonging to a frame group corresponding to each random access group.

2. the communication device grouping unit groups each of the communication devices into n random access groups according to a remainder obtained by dividing communication device identification information of each of the communication devices by n; the random access information transmission restriction unit restricts, for the communication devices grouped into each random access group, transmission of the random access information on a random access channel other than that included in a frame whose remainder when a frame number is divided by n is equal to the remainder when the communication device identification information is divided by n. The communication control device according to claim 1 .

3. The communication control device according to claim 2 , wherein the communication device identification information is a user identification number given to a user of the communication device.

4. The communication device grouping unit is provided in each communication device, and groups each communication device into a random access group according to a remainder obtained by dividing its own communication device identification information by n; the random access information transmission restriction unit is provided in each communication device, and restricts transmission of the random access information on a random access channel other than that included in a frame in which a remainder obtained by dividing a frame number calculated based on a frame number and a group number n received from a base station by n is equal to a remainder obtained by dividing the communication device identification information of the communication device by n; The communication control device according to claim 2.

5. The communication control device according to claim 1 , wherein the random access channel specifying unit, the communication device grouping unit, and the random access information transmission restriction unit are provided in each communication device.

6. The communication control device according to claim 1 , wherein the base station is an airborne non-terrestrial base station.

7. The communication control device according to claim 6 , wherein the non-terrestrial base station is a communication satellite flying in outer space.

8. The plurality of random access channels are grouped into n random access channel groups (n is a natural number equal to or greater than 2); The communication device grouping unit groups each communication device into n random access groups corresponding to the n random access channel groups; the random access information transmission restriction unit restricts the communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than the random access channel group corresponding to each of the random access groups; The communication control device according to claim 1 .

9. A random access channel identification unit that identifies a plurality of random access channels through which a communication device can transmit random access information to a base station; a communication device grouping unit configured to group each communication device into a plurality of random access groups corresponding to different portions of the plurality of random access channels; a random access information transmission restriction unit that restricts transmission of random access information by communication devices grouped in each of the random access groups through a random access channel other than the random access channel associated with each of the random access groups; Equipped with the communication device grouping unit groups each of the communication devices into n random access groups according to a remainder obtained by dividing communication device identification information of each of the communication devices by n; The random access information transmission restriction unit is a communication control device that restricts the transmission of random access information for communication devices grouped into each random access group on a random access channel other than a random access channel whose remainder when a random access channel identification information is divided by n is equal to the remainder when the communication device identification information is divided by n.

10. identifying a plurality of random access channels over which the communication device can transmit random access information to the base station; grouping each communication unit into a plurality of random access groups corresponding to different portions of the plurality of random access channels; restricting communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than that associated with each of the random access groups; Equipped with A plurality of frames in which the communication device can transmit information to the base station are grouped into n frame groups (n is a natural number equal to or greater than 2); The grouping includes grouping each communication device into n random access groups corresponding to the n frame groups; Restricting the transmission of the random access information is a communication control method that restricts the transmission of random access information for communication devices grouped in each random access group, other than through a random access channel included in a frame belonging to a frame group corresponding to each random access group.

11. identifying a plurality of random access channels over which the communication device can transmit random access information to the base station; grouping each communication unit into a plurality of random access groups corresponding to different portions of the plurality of random access channels; restricting communication devices grouped in each of the random access groups from transmitting random access information through a random access channel other than that associated with each of the random access groups; Run the following on your computer: A plurality of frames in which the communication device can transmit information to the base station are grouped into n frame groups (n is a natural number equal to or greater than 2); The grouping includes grouping each communication device into n random access groups corresponding to the n frame groups; The storage medium storing a communication control program for restricting the transmission of the random access information for communication devices grouped into each random access group, on channels other than the random access channel included in a frame belonging to a frame group corresponding to each random access group.

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