WO2025032768A1 - Terminal device, base station device, and wireless communication system - Google Patents

Abstract

A terminal device for executing a non-contention-type random access procedure, wherein the device includes: a reception unit for receiving, from a base station device, threshold information including a threshold related to the received electric power of a signal from the base station device, candidate information indicating a plurality of candidates for a preamble used for transmission of a PRACH in a random access procedure, and first transmission timing indicating the beginning of the transmission timing of the PRACH; a control unit for determining the number of transmission times of the PRACH in accordance with the received electric power and the threshold information, referring to the candidate information, selecting a preamble corresponding to the number of transmission times from the plurality of candidates of the candidate information, and determining a second transmission timing of each PRACH to be transmitted after the first transmission timing in accordance with the first transmission timing and the number of transmission times; and a transmission unit for transmitting the PRACH to the base station device at each of the first transmission timing and the second transmission timing by using the selected preamble.

Description

Terminal device, base station device, and wireless communication system

This disclosure relates to a terminal device, a base station device, and a wireless communication system.

In today's networks, traffic from mobile devices (smartphones and feature phones) accounts for the majority of network resources, and this trend is likely to continue. In addition to traffic used by mobile devices, IoT (Internet of Things) services (such as transportation systems, smart meters, and monitoring systems for devices, etc.) are also being developed. For this reason, such networks are being required to support services with diverse requirements.

In order to accommodate such diverse services, the 5th generation mobile communications (5G or NR (New Radio)) communication standards (e.g., non-patent documents 11 to 27) have been formulated to support many use cases classified as eMBB (Enhanced Mobile Broadband), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communications) in addition to the standard technologies of 4G (4th generation mobile communications) (e.g., non-patent documents 1 to 10).

The 3rd Generation Partnership Project (3GPP (registered trademark)), an international standardization project, is currently continuing to study and standardize extension technologies for the above communication standards.

Here, in a wireless communication system, a random access procedure (RACH: Random Access CHannel procedure) is performed to perform data communication between a terminal device and a base station device. The random access procedure includes, for example, a two-step random access procedure and a four-step random access procedure. In addition, the random access procedure includes, for example, a contention-based random access procedure (CBRA: Contention Based Random Access) and a non-contention-based random access procedure (CFRA: Contention Free Random Access) (Non-Patent Documents 6 and 21).

The 3GPP working group is currently considering the introduction of a technology called PRACH Multiple Transmission, which is a physical channel used in random access procedures (PRACH Multiple Transmission) (Non-Patent Document 28). This technology makes it possible to expand coverage by transmitting multiple PRACHs.

3GPP TS 36.133 V17.10.0 3GPP TS 36.211 V17.3.0 3GPP TS 36.212 V17.1.0 3GPP TS 36.213 V17.5.0 3GPP TS 36.214 V17.0.0 3GPP TS 36.300 V17.4.0 3GPP TS 36.321 V17.5.0 3GPP TS 36.322 V17.0.0 3GPP TS 36.323 V17.2.0 3GPP TS 36.331 V17.4.0 3GPP TS 37.324 V17.0.0 3GPP TS 37.340 V17.5.0 3GPP TS 38.133 V17.10.0 3GPP TS 38.201 V17.0.0 3GPP TS 38.202 V17.3.0 3GPP TS 38.211 V17.5.0 3GPP TS 38.212 V17.5.0 3GPP TS 38.213 V17.6.0 3GPP TS 38.214 V17.6.0 3GPP TS 38.215 V17.3.0 3GPP TS 38.300 V17.5.0 3GPP TS 38.321 V17.5.0 3GPP TS 38.322 V17.3.0 3GPP TS 38.323 V17.5.0 3GPP TS 38.331 V17.5.0 3GPP TS 38.420 V17.2.0 3GPP TS 38.423 V17.5.0 R1-2306069

Here, the continuous transmission of PRACH as described above is linked to the random access preamble (hereinafter also simply referred to as the preamble) used for transmitting PRACH. Therefore, when multiple transmissions of PRACH are performed in CBRA, the terminal device determines the number of multiple transmissions of PRACH (hereinafter also simply referred to as the number of multiple transmissions) by using the measurement results of RSRP (Reference Signal Received Power), and then selects a preamble according to the determined number of multiple transmissions.

However, when CFRA is performed, the selection of the preamble is performed by the base station device. Therefore, in this case, the base station device cannot determine the number of multiple transmissions using the RSRP measurement results in the terminal device, and cannot select the preamble.

Therefore, in a wireless communication system, for example, when CFRA is performed, multiple transmissions of PRACH cannot be performed.

Therefore, one disclosure provides a terminal device, a base station device, and a communication system that enable multiple PRACH transmissions when CFRA is performed.

A terminal device that executes a non-contention type random access procedure, the terminal device having a receiver that receives from the base station device threshold information including a threshold related to the reception power of a signal from the base station device, candidate information indicating a plurality of candidates for a preamble used in transmitting a PRACH (Physical Random Access CHannel) in the random access procedure, and a first transmission timing indicating the beginning of the transmission timing of the PRACH, a controller that determines the number of transmissions of the PRACH according to the reception power and the threshold information, refers to the candidate information to select the preamble corresponding to the number of transmissions from the plurality of candidates, and determines the second transmission timing of each of the PRACHs that are transmitted after the first transmission timing according to the first transmission timing and the number of transmissions, and a transmitter that transmits the PRACH to the base station device at each of the first transmission timing and the second transmission timing by using the selected preamble.

One disclosure makes it possible to perform multiple PRACH transmissions when CFRA is performed.

FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 10. FIG. 2 is a diagram showing an example of the configuration of the terminal device 100. As shown in FIG. FIG. 3 is a diagram showing an example of the configuration of the base station device 200. As shown in FIG. FIG. 4 is a diagram showing an example of a sequence of a terminal transmission process and a base station transmission control process in the first embodiment. FIG. 5 is a diagram illustrating a specific example of the threshold information DT1. FIG. 6 is a diagram illustrating a specific example of the candidate information DT2. FIG. 7 is a diagram for explaining the terminal transmission process and the base station transmission control process in the first embodiment. FIG. 8 is a diagram illustrating an example of a sequence according to the second embodiment.

Below, an embodiment of the present disclosure will be described with reference to the drawings. However, such description should not be construed in a limiting sense, and does not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, different embodiments can be combined as appropriate.

[First embodiment]
(Regarding wireless communication system 10)
1 is a diagram showing an example of the configuration of a wireless communication system 10. The wireless communication system 10 includes, for example, a terminal device 100, a base station device 200a, and a base station device 200b. Hereinafter, the base station device 200a and the base station device 200b will be collectively referred to simply as the base station device 200.

The terminal device 100 is, for example, a communication device that wirelessly connects to the base station device 200 and transmits and receives data. Specifically, the terminal device 100 is, for example, a smartphone or a tablet terminal.

The base station device 200 is, for example, a device that wirelessly connects to the terminal device 100 and transmits and receives data. Specifically, the base station device 200 is, for example, an eNodeB or a gNodeB. The base station device 200 may be compatible with various communication generations (for example, 4G, 5G, or Beyond 5G, etc.). The base station device 200 may be, for example, a single device, or may be composed of multiple devices such as a CU (Central Unit) and a DU (Distributed Unit).

When the terminal device 100 communicates with the base station device 200, for example, the terminal device 100 performs a wireless connection procedure (for example, a random access procedure: RACH procedure). The random access procedure is, for example, a procedure performed by the terminal device 100 to synchronize with the base station device 200.

(Configuration example of terminal device 100)
2 is a diagram showing an example of the configuration of the terminal device 100. The terminal device 100 includes, for example, a CPU (Central Processing Unit) 110, a storage 120, a memory 130, and a wireless communication circuit 150.

Storage 120 is, for example, an auxiliary storage device that stores programs and data, such as a flash memory, a hard disk drive (HDD), or a solid state drive (SSD). Storage 120 stores, for example, a terminal communication program 121 and a terminal transmission program 122.

Memory 130 is, for example, an area into which programs stored in storage 120 are loaded. Note that memory 130 may also be used, for example, as an area in which programs store data.

The wireless communication circuit 150 is, for example, a circuit that performs wireless communication with the base station device 200. The wireless communication circuit 150 has, for example, an antenna 151. The antenna 151 includes, for example, a directional antenna that can control the direction of transmission and reception of radio waves.

The CPU 110 is a processor that builds each part and realizes each process, for example, by loading a program stored in the storage 120 into the memory 130 and executing it.

The CPU 110 executes the terminal communication program 121, for example, to construct a receiving section and a transmitting section, and to perform terminal communication processing. The terminal communication processing is, for example, processing to establish a wireless connection with the base station device 200 and perform wireless communication.

The CPU 110 executes the terminal transmission program 122, for example, to construct a terminal transmission unit (hereinafter also simply referred to as a control unit) and perform terminal transmission processing. The terminal transmission processing is, for example, processing to transmit multiple PRACHs to the base station device 200. Hereinafter, the PRACH is also referred to as message 1. Specifically, the terminal transmission processing is processing to transmit multiple PRACHs when, for example, a CFRA is performed. Note that a CFRA is performed, for example, in conjunction with a Handover, a PDCCH (Physical Downlink Control CHannel) order, or a Beam Failure Recovery.

(Configuration example of base station device 200)
3 is a diagram showing an example of the configuration of the base station device 200. The base station device 200 includes, for example, a CPU 210, a storage 220, a memory 230, and a wireless communication circuit 250.

Storage 220 is, for example, an auxiliary storage device that stores programs and data, such as a flash memory, HDD, or SSD. Storage 220 stores, for example, a base station communication program 221 and a base station transmission control program 222.

Memory 230 is, for example, an area into which programs stored in storage 220 are loaded. Note that memory 230 may be used, for example, as an area in which programs store data.

The wireless communication circuit 250 is, for example, a device that performs wireless communication with the terminal device 100. The wireless communication circuit 250 has, for example, an antenna 251. The antenna 251 includes, for example, a directional antenna that can control the direction of transmission and reception of radio waves.

The CPU 210 is a processor that builds each part and realizes each process, for example, by loading a program stored in the storage 220 into the memory 230 and executing it.

The CPU 210 executes the base station communication program 221, for example, to construct a receiving section and a transmitting section, and to perform base station communication processing. The base station communication processing is, for example, processing for performing wireless communication with the terminal device 100. Specifically, in the base station communication processing, the base station device 200 establishes a wireless connection with the terminal device 100, transmits data to the terminal device 100, and receives data from the terminal device 100. Note that the base station communication processing includes, for example, processing associated with a random access procedure with the terminal device 100.

The CPU 210 executes the base station transmission control program 222, for example, to construct a base station transmission control unit (hereinafter also simply referred to as a control unit) and perform base station transmission control processing. The base station transmission control processing is, for example, processing to control multiple transmissions of PRACH from the terminal device 100 to the base station device 200. Specifically, the base station transmission control processing is, for example, processing to control multiple transmissions of PRACH when CFRA is performed.

[First embodiment]
Next, the terminal transmission process and the base station transmission control process in the first embodiment will be described. Fig. 4 is a diagram showing an example of the sequence of the terminal transmission process and the base station transmission control process in the first embodiment. Figs. 5 to 7 are diagrams explaining the terminal transmission process and the base station transmission control process in the first embodiment. Specifically, Fig. 4 is a diagram showing an example of the sequence of the terminal transmission process and the base station transmission control process when CFRA is performed in conjunction with Handover.

The terminal device 100 measures the RSRP of one or more SSBs (Synchronization Signal Blocks) reported by the base station device 200a, for example. The terminal device 100 then selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs reported by the base station device 200a. The terminal device 100 also measures the RSRP of one or more SSBs reported by the base station device 200b, for example. The terminal device 100 then selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs reported by the base station device 200b. The terminal device 100 may select, for example, multiple SSBs instead of selecting the SSB with the highest measured RSRP. Thereafter, the terminal device 100 transmits to the base station device 200a a measurement report including information (hereinafter also referred to as information about the measurement result) about the result (e.g., RSRP) measured using at least one of the CSI-RS (Channel State Information-Reference Signal) and the SSB transmitted from each of the base station device 200a and the base station device 200b (S11). Note that the terminal device 100 may include information indicating the SSB used to obtain the measurement result in the measurement report.

For example, when the base station device 200a receives a measurement report transmitted from the terminal device 100, the base station device 200a refers to information regarding the measurement results included in the received measurement and determines whether or not to perform a Handover from the base station device 200a to the base station device 200b (S12).

If it is determined that base station device 200a should perform a Handover to base station device 200b, base station device 200a transmits, for example, a HANDOVER REQUEST to base station device 200b (S13).

Specifically, the base station device 200a transmits a HANDOVER REQUEST to the base station device 200b, the HANDOVER REQUEST including information on the measurement result included in the measurement report received from the terminal device 100 (e.g., the RSRP for the base station device 200b).

Note that, although the following description will be given of a case where terminal device 100 measures RSRP for base station device 200a and base station device 200b, terminal device 100 may measure RSRP for three or more base station devices 200. Also, the following description will be given of a case where base station device 200a performs a Handover to base station device 200b, but base station device 200a may perform a Handover to a base station device 200 other than base station device 200.

Returning to FIG. 4, for example, when base station device 200b receives a HANDOVER REQUEST transmitted from base station device 200a, it determines whether or not to permit a Handover from base station device 200a (S14).

If it is determined that the Handover from base station device 200a is permitted, base station device 200b transmits, for example, a HANDOVER REQUEST ACKNOWLEDGE to base station device 200a (S15).

Specifically, base station device 200b transmits a HANDOVER REQUEST ACKNOWLEDGE to base station device 200a, the HANDOVER REQUEST ACKNOWLEDGE including information including a threshold value for RSRP (hereinafter also referred to as threshold information DT1) and information including multiple candidates for the preamble used in PRACH transmission (hereinafter also referred to as candidate information DT2). Threshold information DT1 is, for example, information generated in base station device 200b, which is information that associates one or more threshold values for RSRP with multiple transmission counts corresponding to ranges separated by each threshold. Candidate information DT2 is, for example, information generated in base station device 200b, which is information that associates multiple candidates for the preamble used in PRACH transmission with multiple transmission counts corresponding to each candidate.

In this case, the base station device 200b, for example, refers to information on the measurement result included in the HANDOVER REQUEST received from the base station device 200a, and identifies an RO (Rach Occasion) linked to the index of the SSB corresponding to the SSB used by the terminal device 100 for the measurement according to the information on the measurement result. The RO is, for example, a PRACH transmission opportunity. In other words, the RO corresponds to, for example, a resource capable of transmitting the PRACH. Then, the base station device 200b includes, for example, the identified RO in the HANDOVER REQUEST ACKNOWLEDGE. Specific examples of the threshold information DT1 and the candidate information DT2 will be described below.

(Specific example of threshold information DT1)
First, a specific example of the threshold information DT1 will be described. Fig. 5 is a diagram for explaining a specific example of the threshold information DT1. In the following examples, "-" indicates that no information is set.

In the first line of the threshold information DT1 shown in FIG. 5, for example, "a" is set as the "threshold" and "1 (times)" is set as the "number of multiple transmissions." In addition, in the second line of the threshold information DT1 shown in FIG. 5, for example, "b" is set as the "threshold" and "2 (times)" is set as the "number of multiple transmissions." In addition, in the third line of the threshold information DT1 shown in FIG. 5, for example, "c" is set as the "threshold" and "4 (times)" is set as the "number of multiple transmissions." In addition, in the fourth line of the threshold information DT1 shown in FIG. 5, for example, "-" is set as the "threshold" and "8 (times)" is set as the "number of multiple transmissions."

In other words, the threshold information DT1 shown in FIG. 5 indicates that, for example, the number of multiple transmissions corresponding to when RSRP is a or greater is 1 (times), the number of multiple transmissions corresponding to when RSRP is b or greater but less than a is 2 (times), the number of multiple transmissions corresponding to when RSRP is c or greater but less than b is 4 (times), and the number of multiple transmissions corresponding to when RSRP is less than c is 8 (times).

(Specific example of candidate information DT2)
Next, a specific example of the candidate information DT2 will be described with reference to FIG.

In the first line of the candidate information DT2 shown in FIG. 6, for example, "Preamble #A" is set as the "preamble" and "1 (times)" is set as the "number of multiple transmissions". In the second line of the candidate information DT2 shown in FIG. 6, for example, "Preamble #B" is set as the "preamble" and "2 (times)" is set as the "number of multiple transmissions". In the third line of the candidate information DT2 shown in FIG. 6, for example, "Preamble #C" is set as the "preamble" and "4 (times)" is set as the "number of multiple transmissions". In the fourth line of the candidate information DT2 shown in FIG. 6, for example, "Preamble #D" is set as the "preamble" and "8 (times)" is set as the "number of multiple transmissions".

In other words, the candidate information DT2 shown in FIG. 6 indicates that, for example, the preamble corresponding to the number of multiple transmissions being 1 is Preamble #A, the preamble corresponding to the number of multiple transmissions being 2 is Preamble #B, the preamble corresponding to the number of multiple transmissions being 4 is Preamble #C, and the preamble corresponding to the number of multiple transmissions being 8 is Preamble #D.

Returning to FIG. 4, for example, when the base station device 200a receives a HANDOVER REQUEST ACKNOWLEDGE transmitted from the base station device 200b, the base station device 200a transmits an RRC Reconfiguration to the terminal device 100 (S16).

Specifically, the base station device 200a transmits to the terminal device 100 an RRC Reconfiguration in which the RO (the RO included in the HANDOVER REQUEST ACKNOWLEDGE) is specified in the ra-ssb-occasionMakingIndex or ssb-SharedRO-MaskIndex in the RACH-ConfigDecatet.

In this case, the base station device 200a also includes, for example, the threshold information DT1 and candidate information DT2 contained in the HANDOVER REQUEST ACKNOWLEDGE transmitted from the base station device 200b in the RRC Reconfiguration.

For example, when the terminal device 100 receives an RRC Reconfiguration transmitted from the base station device 200a, the terminal device 100 transmits a PRACH to the base station device 200b (S17).

Specifically, the terminal device 100 transmits PRACH in multiple ROs including the RO indicated by the ra-ssb-occasionMakingindex or ssb-SharedRO-MaskIndex in the RRC Reconfiguration received from the base station device 200a. The process of S17 is described in detail below.

(Details of the process of S17)
The terminal device 100, for example, refers to threshold information DT1 included in the RRC Reconfiguration transmitted from the base station device 200a, and identifies the number of multiple transmissions corresponding to the RSRP measured in the terminal device 100.

Specifically, the information in the second row of the threshold information DT1 described in FIG. 5 indicates that the number of multiple transmissions corresponding to the range in which the RSRP is equal to or greater than b and less than a is 2 (times). Therefore, for example, when the RSRP measured in the terminal device 100 is equal to or greater than b and less than a, the terminal device 100 specifies 2 (times) as the number of multiple transmissions.

The terminal device 100 also identifies an RO group that includes an RO that was included in the RRC Reconfiguration transmitted from the base station device 200a. The RO group is a group of ROs used in multiple transmissions of the PRACH and associated with the same SSB.

Specifically, in the example of each RO shown in FIG. 7, for example, the RO group including RO4, RO16, RO28, and RO40 is the RO group associated with SSB4. Therefore, for example, if the RO included in the RRC Reconfiguration transmitted from the base station device 200a is RO4, the terminal device 100 identifies the RO group corresponding to SSB4 as the RO group to be used in multiple transmissions of the PRACH.

Then, the terminal device 100 selects, for example, from the ROs corresponding to the identified RO group, a number of ROs corresponding to the number of multiple transmissions, starting from the top, and transmits the PRACH in each of the selected ROs.

Specifically, in the example of each RO shown in FIG. 7, for example, if the RO included in the RRC Reconfiguration transmitted from the base station device 200a is RO4 and the number of multiple transmissions is 2, the terminal device 100 transmits the PRACH in both RO4 and RO16.

Returning to FIG. 4, for example, when the base station device 200b receives a PRACH transmitted from the terminal device 100, the base station device 200b transmits an RAR (Random Access Response) corresponding to the received PRACH to the base station device 200a (S18). Hereinafter, the RAR is also referred to as message 2.

For example, when the terminal device 100 receives an RAR transmitted from the base station device 200b, it transmits an RRC Reconfiguration Complete to the base station device 200b (S19).

In this way, the base station device 200b in this embodiment transmits to the terminal device 100, for example, threshold information DT1 including a threshold related to the received power of the signal from the base station device 200b (hereinafter also referred to as the first received power), candidate information DT2 indicating multiple candidates for the preamble to be used for transmitting the PRACH, and an RO indicating the start of the transmission timing of the PRACH (hereinafter also referred to as the first RO or the first transmission timing).

Then, the terminal device 100 in this embodiment determines the number of times of multiple transmissions of the PRACH (hereinafter also referred to as the first multiple transmissions) according to, for example, the first reception power and the threshold information DT1, selects a preamble (hereinafter also referred to as the first preamble) corresponding to the first multiple transmissions from among multiple candidates by referring to the candidate information DT2, and determines each RO (hereinafter also referred to as the second RO or the second transmission timing) of the PRACH to be transmitted after the first RO according to the first RO and the first multiple transmissions. After that, the terminal device 100 in this embodiment transmits the PRACH to the base station device 200b in each of the first RO and the second RO, for example, by using the selected first preamble.

In other words, the base station device 200b assigns to the terminal device 100, for example, a preamble to be used for transmitting the PRACH corresponding to each number of times that the terminal device 100 may calculate as the number of multiple transmissions. Specifically, if the number of times that the terminal device 100 may calculate as the number of multiple transmissions is 2, 4, and 8, the base station device 200b assigns to the terminal device 100, for example, a preamble corresponding to 2 times, a preamble corresponding to 4 times, and a preamble corresponding to 8 times. Then, the base station device 200a generates candidate information DT2 that associates the multiple preambles assigned to the terminal device 100 with the number of multiple transmissions corresponding to each preamble, and transmits it to the terminal device 100. In addition, the base station device 200b transmits, for example, threshold information DT1 used by the terminal device 100 to identify the number of multiple transmissions to the terminal device 100.

Then, the terminal device 100 identifies the first multiple transmission counts from, for example, the threshold information DT1 transmitted from the base station device 200b and the first reception power at the terminal device 100. Then, the terminal device 100 selects a first preamble corresponding to the first multiple transmission counts from among the multiple preamble candidates indicated in the candidate information DT2 received from the base station device 200b. Also, the terminal device 100 identifies, for example, one or more second ROs from the first RO specified by the base station device 200b. Then, the terminal device 100 repeatedly transmits the PRACH for the first multiple transmission counts in each of the first RO and the one or more second ROs.

As a result, the terminal device 100 in this embodiment is able to identify the number of times that the PRACH is transmitted multiple times and the RO that transmits each of the PRACHs corresponding to the number of times of transmission, even when, for example, CFRA is performed. Therefore, the wireless communication system 10 in this embodiment is able to perform multiple transmissions of the PRACH from the terminal device 100 to the base station device 200b, even when, for example, CFRA is performed.

When CFRA is performed in conjunction with a PDCCH order or Beam Failure Recovery, the base station device 200a transmits the RO transmitted from the base station device 200b to the terminal device 100 by, for example, a Random Access Preamble Assignment (hereinafter also referred to as message 0). In this case, the base station device 200a also reports, for example, threshold information DT1 and candidate information DT2 by SIB1 (System Information Block Type 1).

In the above example, the case where the base station device 200a and the base station device 200b are different base station devices 200 has been described, but this is not limited to the case. Specifically, the base station device 200a and the base station device 200b may be, for example, the same base station device 200, and CFRA may be performed in conjunction with inter-cell handover in multiple cells corresponding to the base station device 200.

[Second embodiment]
Next, the terminal transmission process and the base station transmission control process in the second embodiment will be described. Fig. 8 is a diagram showing an example of a sequence in the second embodiment. Specifically, Fig. 8 is a diagram showing an example of a sequence of the terminal transmission process and the base station transmission control process in the case where CFRA is performed along with Handover. Note that, as in the case described in Fig. 4, the case where Handover is performed from the base station device 200a to the base station device 200b will be described below.

As in the case described in FIG. 4, the terminal device 100 transmits to the base station device 200a a measurement report including information (information about the measurement result) about the result of measurement using at least one of the CSI-RS and the SSB transmitted from each of the base station device 200a and the base station device 200b (S21). Note that the terminal device 100 may include, for example, information indicating the SSB used to obtain the measurement result in the measurement report.

Similar to the case described in FIG. 4, when the base station device 200a receives a measurement report transmitted from the terminal device 100, the base station device 200a refers to information on the measurement results included in the received measurement and determines whether or not to perform a Handover from the base station device 200a to the base station device 200b (S22).

If it is determined that base station device 200a should perform a Handover to base station device 200b, base station device 200a transmits, for example, a HANDOVER REQUEST to base station device 200b, as described in FIG. 4 (S23).

Similar to the case described in FIG. 4, when base station device 200b receives a HANDOVER REQUEST transmitted from base station device 200a, it determines whether or not to permit the Handover from base station device 200a (S24).

If it is determined that the Handover from base station device 200a is permitted, base station device 200b transmits, for example, a HANDOVER REQUEST ACKNOWLEDGE to base station device 200a (S25).

Specifically, unlike the case described in FIG. 4, base station device 200b identifies the number of multiple PRACH transmissions from terminal device 100 to base station device 200b, for example, from the RSRP included in base station device 200a (RSRP for base station device 200b) and threshold information DT1. Then, base station device 200b transmits a HANDOVER REQUEST ACKNOWLEDGE including the identified number of multiple transmissions to base station device 200a, for example.

In other words, in the wireless communication system 10 in the example shown in FIG. 8, unlike the case described in FIG. 4, for example, the number of times the PRACH is transmitted from the terminal device 100 to the base station device 200b is determined by the base station device 200b. Therefore, in the wireless communication system 10 in the example shown in FIG. 8, unlike the case described in FIG. 4, for example, threshold information DT1 and candidate information DT2 are not transmitted from the terminal device 100 to the base station device 200b.

In this case, the base station device 200b, for example, refers to information regarding the measurement result included in the HANDOVER REQUEST received from the base station device 200a, and identifies the RO linked to the SSB index corresponding to the SSB used by the terminal device 100 for the measurement according to the information regarding the measurement result. Then, the base station device 200b, for example, includes the identified RO in the HANDOVER REQUEST ACKNOWLEDGE.

For example, when the base station device 200a receives a HANDOVER REQUEST ACKNOWLEDGE transmitted from the base station device 200b, the base station device 200a transmits an RRC Reconfiguration to the terminal device 100 (S26).

Specifically, the base station device 200a transmits to the terminal device 100 an RRC Reconfiguration in which the RO (the RO included in the HANDOVER REQUEST ACKNOWLEDGE) is specified in the ra-ssb-occasionMakingIndex or ssb-SharedRO-MaskIndex in the RACH-ConfigDecatet, as in the case described in FIG. 4.

Furthermore, unlike the case described in FIG. 4, the base station device 200a includes, for example, the number of multiple transmissions included in the HANDOVER REQUEST ACKNOWLEDGE transmitted from the base station device 200b in the RRC Reconfiguration.

For example, when the terminal device 100 receives an RRC Reconfiguration transmitted from the base station device 200a, the terminal device 100 transmits a PRACH to the base station device 200b (S27).

Specifically, the terminal device 100 transmits PRACH in multiple ROs including the RO indicated by the ra-ssb-occasionMakingindex or ssb-SharedRO-MaskIndex in the RRC Reconfiguration received from the base station device 200a, for example.

More specifically, unlike the case described in FIG. 4, the terminal device 100 identifies, for example, the number of multiple transmissions included in the RRC Reconfiguration transmitted from the base station device 200a. The terminal device 100 also identifies, for example, an RO group including an RO included in the RRC Reconfiguration transmitted from the base station device 200a. The terminal device 100 then selects, for example, from the RO group corresponding to the identified RO group, a number of ROs corresponding to the number of multiple transmissions, starting from the top, and transmits the RO to the base station device 200a for each of the selected ROs.

For example, when the base station device 200b receives a PRACH transmitted from the terminal device 100, it transmits an RAR corresponding to the received PRACH to the base station device 200a (S28).

For example, when the terminal device 100 receives an RAR transmitted from the base station device 200b, it transmits an RRC Reconfiguration Complete to the base station device 200b (S29).

In this way, the terminal device 100 in this embodiment transmits, for example, the reception power of a signal from the base station device 200b (hereinafter also referred to as the second reception power) to the base station device 200b.

Then, the base station device 200b in this embodiment calculates the number of times of multiple transmission of the PRACH (hereinafter also referred to as the second number of times of multiple transmission) according to, for example, the second reception power and threshold information including a threshold related to the second reception power. Furthermore, the base station device 200b in this embodiment transmits, for example, the second number of times of multiple transmission and a transmission timing indicating the beginning of the transmission timing of the PRACH (hereinafter also referred to as the third RO or the third transmission timing) to the terminal device 100.

Then, the terminal device 100 in this embodiment determines the respective ROs of the PRACH to be transmitted after the third RO (hereinafter also referred to as the fourth RO or the fourth transmission timing) in accordance with, for example, the second multiple transmission number and the third transmission timing. Then, the terminal device 100 in this embodiment transmits the PRACH to the base station device 200b in each of the third RO and the fourth RO, for example.

In other words, unlike the case described in FIG. 4, the base station device 200b calculates the second multiple number of transmissions by using, for example, the second received power received from the terminal device 100. Then, the base station device 200b transmits, for example, the calculated second multiple number of transmissions to the terminal device 100.

Then, the terminal device 100 identifies, for example, one or more fourth ROs from the third RO specified by the base station device 200b. Then, the terminal device 100 repeatedly transmits, for example, the third multiple number of PRACH transmissions in each of the third RO and the one or more fourth ROs.

As a result, the terminal device 100 in this embodiment, as in the case described in FIG. 4, is able to identify the number of times that the PRACH is transmitted multiple times and the RO that transmits each of the PRACHs corresponding to the number of times of transmission, even when, for example, CFRA is performed. Therefore, the wireless communication system 10 in this embodiment is able to perform multiple transmissions of the PRACH from the terminal device 100 to the base station device 200b, even when, for example, CFRA is performed.

When CFRA is performed in conjunction with a PDCCH order, the base station device 200a may notify the terminal device 100 of the number of multiple transmissions, for example, by using the reserved bits-2 bit of DCI format1_0.

The base station device 200a may also notify the terminal device 100 of the number of multiple transmissions, for example, by using reserved bits of the PRACH Mask Index.

Furthermore, the base station device 200a may notify the terminal device 100 of the multiple transmission count, for example, by using a preamble index associated with the multiple transmission count. That is, each preamble corresponds to each multiple transmission count. Therefore, the base station device 200a can notify the terminal device 100 of the multiple transmission count, for example, by notifying the preamble index.

In the above example, the case where the number of multiple transmissions is determined by using RSRP has been described, but this is not limited to the above. Specifically, the base station device 200b may determine the number of multiple transmissions by using, for example, SINR (Signal to Interference Noise Ratio).

In the above example, the case where the number of multiple transmissions is determined by using threshold information DT1 has been described, but this is not limited to the above. Specifically, base station device 200b may determine the number of multiple transmissions by using information such as Power Class information or the number of terminal devices under base station device 200b.

In the above example, the case where the base station device 200a and the base station device 200b are different base station devices 200 has been described, but this is not limited to the case. Specifically, the base station device 200a and the base station device 200b may be, for example, the same base station device 200, and CFRA may be performed in conjunction with inter-cell handover in multiple cells corresponding to the base station device 200.

10: Wireless communication system 100: Terminal device 110: CPU
120: Storage 121: Terminal communication program 122: Terminal transmission program 130: Memory 150: Wireless communication circuit 151: Antenna 200: Base station device 210: CPU
220: Storage 221: Base station communication program 222: Base station transmission control program 230: Memory 250: Wireless communication circuit 251: Antenna

Claims (10)

A terminal device that performs a non-contention type random access procedure,
a receiving unit that receives, from the base station device, threshold information including a threshold related to a reception power of a signal from the base station device, candidate information indicating a plurality of candidates for a preamble used in transmitting a PRACH (Physical Random Access CHannel) in the random access procedure, and a first transmission timing indicating a beginning of a transmission timing of the PRACH;
a control unit that determines a number of times of transmission of the PRACH according to the received power and the threshold information, selects the preamble corresponding to the number of times of transmission from the plurality of candidates by referring to the candidate information, and determines a second transmission timing of each of the PRACHs to be transmitted after the first transmission timing according to the first transmission timing and the number of times of transmission;
A transmitter that transmits the PRACH to the base station device at each of the first transmission timing and the second transmission timing by using the selected preamble.
A terminal device comprising: In claim 1,
The threshold information, the candidate information, and the first transmission timing are included in RRC Reconfiguration,
The receiving unit receives the RRC Reconfiguration transmitted from the base station device.
A terminal device comprising: In claim 2,
The threshold information and the candidate information are included in SIB1 (System Information Block Type 1),
The first transmission timing is included in a message 0 in the random access procedure,
The receiving unit receives the SIB1 and the message 0 transmitted from the base station device.
A terminal device comprising: In claim 1,
Each of the first transmission timing and the second transmission timing is a RACH Occasion.
A terminal device comprising: In claim 1,
the candidate information is information in which each of the plurality of candidates is associated with the number of transmissions corresponding to each of the plurality of candidates,
The control unit selects, as the preamble, a candidate corresponding to the number of transmissions from among the plurality of candidates.
A terminal device comprising: A terminal device that performs a non-contention type random access procedure,
a transmitting unit that transmits to the base station device a reception power of a signal from the base station device;
a receiving unit that receives a number of times of transmitting the PRACH in the random access procedure calculated according to the reception power and threshold information including a threshold value related to the reception power, and a third transmission timing indicating a beginning of a transmission timing of the PRACH;
a control unit that determines a fourth transmission timing of each of the PRACHs that is transmitted after the third transmission timing, in accordance with the number of transmissions and the third transmission timing;
The transmission unit includes a transmission unit configured to transmit the PRACH to the base station device at each of the third transmission timing and the fourth transmission timing.
A terminal device comprising: A base station device that performs a non-contention type random access procedure,
a transmitting unit that transmits to a terminal device threshold information including a threshold related to a received power of a signal from a base station device, candidate information indicating a plurality of candidates for a preamble used in transmitting a PRACH in the random access procedure, and a first transmission timing indicating a beginning of a transmission timing of the PRACH, thereby causing the terminal device to perform a process of determining a number of transmissions of the PRACH according to the received power and the threshold information, selecting the preamble corresponding to the number of transmissions from the plurality of candidates by referring to the candidate information, and determining a second transmission timing of each of the PRACHs transmitted after the first transmission timing according to the first transmission timing and the number of transmissions;
A receiving unit that receives, from the terminal device, each of the PRACHs transmitted using the selected preamble and transmitted at each of the first transmission timing and the second transmission timing.
A base station device comprising: A base station device that performs a non-contention type random access procedure,
A receiving unit that receives a signal from the base station device based on a received power in the terminal device;
A control unit that calculates the number of times a PRACH is transmitted in the random access procedure according to the received power and threshold information including a threshold related to the received power;
a transmitting unit that transmits the number of transmissions and a third transmission timing indicating a beginning of the transmission timing of the PRACH to the terminal device, and causes the terminal device to determine a fourth transmission timing of each of the PRACHs transmitted after the third transmission timing in accordance with the number of transmissions and the third transmission timing;
The receiving unit receives, from the terminal device, each of the PRACHs that is transmitted at the third transmission timing and the fourth transmission timing and that corresponds to the number of transmissions.
A base station device comprising: A wireless communication system having a terminal device and a base station device, the wireless communication system performing a non-contention type random access procedure between the terminal device and the base station device,
The base station device transmits, to the terminal device, threshold information including a threshold related to a received power of a signal from the base station device, candidate information indicating a plurality of candidates for a preamble used for transmitting a PRACH in the random access procedure, and a first transmission timing indicating a beginning of a transmission timing of the PRACH;
The terminal device determines the number of times of transmission of the PRACH according to the received power and the threshold information, selects the preamble corresponding to the number of times of transmission from the plurality of candidates by referring to the candidate information, and determines second transmission timings of the PRACHs to be transmitted after the first transmission timing according to the first transmission timing and the number of times of transmission;
The terminal device transmits the PRACH to the base station device at each of the first transmission timing and the second transmission timing by using the selected preamble.
1. A wireless communication system comprising: A wireless communication system having a terminal device and a base station device, the wireless communication system performing a non-contention type random access procedure between the terminal device and the base station device,
The terminal device transmits to the base station device a reception power of a signal from the base station device;
The base station device calculates a number of times of transmitting the PRACH in the random access procedure according to the received power and threshold information including a threshold related to the received power;
the base station device transmits the number of transmissions and a third transmission timing indicating a beginning of a transmission timing of the PRACH to the terminal device;
The terminal device determines a fourth transmission timing of each of the PRACHs to be transmitted after the third transmission timing, according to the number of transmissions and the third transmission timing;
The terminal device transmits the PRACH to the base station device at each of the third transmission timing and the fourth transmission timing.
1. A wireless communication system comprising:

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