WO2024171386A1 - Terminal device, base station device, and wireless communication system - Google Patents

Abstract

A terminal device for executing a random access procedure, said terminal device comprising a transmission unit for transmitting, to a base station device, a request for allocation of wireless resources to be used for the random access procedure, a reception unit for receiving, from the base station device, an allocation response to the allocation request transmitted by the transmission unit, and a control unit for performing first control for changing the number of transmissions of the allocation request, and/or second control for changing transmission power of the allocation request, if no allocation response is received by the reception unit, wherein the transmission unit retransmits the allocation request to the base station device in accordance with the number of transmissions changed by the first control and/or the transmission power changed by the second control.

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 the 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-type random access procedure and a non-contention-type random access procedure (Non-Patent Document 21).

Specifically, for example, in a four-step contention-based random access procedure, the terminal device transmits a RACH preamble (hereinafter also referred to as PRACH (Physical Random Access CHannel)) to the base station device as message 1. The base station device then transmits a RACH response to the terminal device as message 2. After that, the terminal device transmits an RRC (Radio Resource Control) Connection Request as message 3. The base station device then transmits an RRC Connection setup as message 4. Note that message 4 is also referred to as contention resolution.

Furthermore, it is specified that the above-mentioned message 1 can be repeatedly transmitted. The technology related to the random access procedure is described in the following prior art documents.

3GPP TS 36.133 V17.7.0 3GPP TS 36.211 V17.2.0 3GPP TS 36.212 V17.1.0 3GPP TS 36.213 V17.3.0 3GPP TS 36.214 V17.0.0 3GPP TS 36.300 V17.2.0 3GPP TS 36.321 V17.2.0 3GPP TS 36.322 V17.0.0 3GPP TS 36.323 V17.1.0 3GPP TS 36.331 V17.2.0 3GPP TS 37.324 V17.0.0 3GPP TS 37.340 V17.2.0 3GPP TS 38.133 V17.7.0 3GPP TS 38.201 V17.0.0 3GPP TS 38.202 V17.2.0 3GPP TS 38.211 V17.3.0 3GPP TS 38.212 V17.3.0 3GPP TS 38.213 V17.3.0 3GPP TS 38.214 V17.3.0 3GPP TS 38.215 V17.2.0 3GPP TS 38.300 V17.2.0 3GPP TS 38.321 V17.2.0 3GPP TS 38.322 V17.1.0 3GPP TS 38.323 V17.2.0 3GPP TS 38.331 V17.2.0 3GPP TS 38.420 V17.2.0 3GPP TS 38.423 V17.2.0

Here, if the terminal device described above cannot receive message 2 from the base station device after transmitting message 1 to the base station device, it may retransmit message 1 to the base station device (PRACH retransmission).

However, for example, if message 1 is retransmitted under the same conditions as when it was transmitted, there is a high possibility that the terminal device will not be able to receive message 2 from the base station device. Therefore, there is a need for a method to improve the probability that message 1 transmitted from the terminal device will reach the base station device in the random access procedure (i.e., the success rate of the random access procedure).

Therefore, one disclosure provides a terminal device, a base station device, and a communication system that improve the success rate of the random access procedure.

A terminal device that executes a random access procedure, the terminal device having a transmitter that transmits an allocation request for radio resources used in the random access procedure to a base station device, a receiver that receives an allocation response from the base station device to the allocation request transmitted by the transmitter, and a control unit that performs at least one of a first control that changes the number of times the allocation request is transmitted and a second control that changes the transmission power of the allocation request when the receiver does not receive the allocation response, and the transmitter retransmits the allocation request to the base station device in accordance with at least one of the number of times the transmission is changed by the first control and the transmission power changed by the second control.

One disclosure can improve the success rate of the random access procedure.

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 illustrating an example of a sequence of a terminal retransmission control process in the first embodiment. FIG. 5 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the first embodiment. FIG. 6 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the first embodiment. FIG. 7 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the second embodiment. FIG. 8 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the second embodiment. FIG. 9 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the second embodiment. FIG. 10 is a diagram showing an example of a sequence of a terminal retransmission control process in the third embodiment. FIG. 11 is a diagram illustrating an example of a sequence of a terminal retransmission control process in the fourth embodiment. FIG. 12 is a diagram showing an example of the contents of a specification. FIG. 13 is a diagram showing an example of the contents of a specification. FIG. 14 is a diagram showing an example of the contents of a specification. FIG. 15 is a diagram showing an example of the contents of a specification. FIG. 16 is a diagram showing an example of the contents of a specification.

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 and a base station device 200.

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

The base station device 200 is a device that is wirelessly connected to the terminal device 100 and transmits and receives data, and is, for example, an eNodeB or gNodeB. The base station device 200 supports, for example, various communication generations (for example, 4G, 5G, or Beyond 5G, etc.). The base station device 200 may be configured as a single device, or may be configured as 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 performed, for example, so that the terminal device 100 can 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 a CPU (Central Processing Unit) 110, a storage 120, a memory 130, and a wireless communication circuit 150.

Storage 120 is an auxiliary storage device that stores programs and data, and is a flash memory, HDD (Hard Disk Drive), SSD (Solid State Drive), etc. Storage 120 stores a terminal communication program 121 and a terminal retransmission control program 122.

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

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

The CPU 110 is a processor that loads programs stored in the storage 120 into the memory 130 and executes them to build each component and realize each process.

The CPU 110 executes the terminal communication program 121 to construct a receiving section (hereinafter also referred to as a terminal receiving section) and a transmitting section (hereinafter also referred to as a terminal transmitting section) and to perform terminal communication processing. The terminal communication processing is processing for establishing a wireless connection with the base station device 200 and performing wireless communication.

The CPU 110 executes the terminal retransmission control program 122 to construct a terminal retransmission control unit (hereinafter also simply referred to as the control unit) and perform terminal retransmission control processing. The terminal retransmission control processing is a process of retransmitting message 1 to the base station device 200 when message 2 (hereinafter also referred to as the allocation response) cannot be received from the base station device 200 despite having sent message 1 (hereinafter also referred to as the allocation request) to the base station device 200.

(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 a CPU 210, a storage 220, a memory 230, and a wireless communication circuit 250.

Storage 220 is an auxiliary storage device that stores programs and data, and is a flash memory, HDD, SSD, etc. Storage 220 stores a base station communication program 221 and a base station retransmission control program 222.

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

The wireless communication circuit 250 is a device that performs wireless communication with the terminal device 100. The wireless communication circuit 250 has 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 loads programs stored in the storage 220 into the memory 230 and executes them to build each component and realize each process.

The CPU 210 executes the base station communication program 221 to construct a receiving section (hereinafter also referred to as a base station receiving section) and a transmitting section (hereinafter also referred to as a base station transmitting section) and perform base station communication processing. The base station communication processing is 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, RACH processing with the terminal device 100.

The CPU 210 executes the base station retransmission control program 222 to construct a base station retransmission control unit and perform base station retransmission control processing. The base station retransmission control processing is processing for transmitting retransmission control information (hereinafter also simply referred to as control information) including information on the method by which the terminal device 100 retransmits message 1 (hereinafter also referred to as retransmission method information) to the terminal device 100.

(Terminal retransmission control process)
Next, the terminal retransmission control process in the first embodiment will be described. Figures 4 to 6 are diagrams showing an example of a sequence of the terminal retransmission control process in the first embodiment. In the following, the arrow in the sequence indicates the number of times a message is transmitted, and the thickness of the arrow in the sequence indicates the transmission power (transmission power) of the message. In addition, in the following, the description will be given assuming that a four-step contention-type random access procedure is performed between the terminal device 100 and the base station device 200.

As shown in FIG. 4, the terminal device 100 measures the RSRP (Reference Signal Received Power) of one or more SSBs (Synchronization Signal Blocks) reported by the base station device 200 (S10). Then, the terminal device 100 selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs.

Then, the terminal device 100 transmits message 1 (PRACH) in, for example, a RACH Occasion linked to the index of the selected SSB (S11). Note that a PRACH Occasion is, for example, a PRACH transmission opportunity allocated within a PRACH slot. In other words, a PRACH Occasion corresponds to, for example, a resource in which a PRACH can be transmitted. In other words, a PRACH Occasion indicates, for example, an area in which a PRACH transmission is possible.

Here, the terminal device 100 may transmit one PRACH in the first PRACH transmission. Also, the terminal device 100 may determine the number of PRACH transmissions based on the RSRP used in the SSB selection, and transmit the PRACH according to the number of PRACH transmissions. The number of PRACH transmissions may be, for example, one, two, four, or eight. Also, two or more PRACH transmissions may be referred to as multiple PRACH transmissions.

Specifically, the terminal device 100 determines the number of PRACH transmissions by, for example, comparing the RSRP measured in S10 with a threshold value (hereinafter also referred to as a reference threshold value) previously stored in the terminal device 100. The number of PRACH transmissions may be the number of PRACHs transmitted in one RACH procedure.

More specifically, the terminal device 100, for example, compares the RSRP measured in S10 with a reference threshold (hereinafter also referred to as the first reference threshold). If the terminal device 100 determines that the RSRP measured in S10 is equal to or greater than the first reference threshold, the terminal device 100, for example, determines the number of PRACH transmissions to be a first number (for example, one time). On the other hand, if the terminal device 100 determines that the RSRP measured in S10 is less than the first reference threshold, the terminal device 100 further compares the RSRP measured in S10 with another reference threshold (hereinafter also referred to as the second reference threshold) that is smaller than the first reference threshold. If the terminal device 100 determines that the RSRP measured in S10 is equal to or greater than the second reference threshold and less than the first reference threshold, the terminal device 100, for example, determines the number of PRACH transmissions to be a second number (for example, two times) that is greater than the first number. On the other hand, if it is determined that the RSRP measured in S10 is less than the second reference threshold, the terminal device 100 determines, for example, the number of times of PRACH transmission to be a third number (for example, four times) that is greater than the second number. After that, the terminal device 100 waits to receive an RAR (Random Access Response) transmitted from the base station device 200. The RAR may also be referred to as message 2.

If the RAR for the PRACH transmitted in S11 cannot be received from the base station device 200, the terminal device 100 determines the number of initial PRACH retransmissions according to the number of PRACH transmissions in S11 (S12). The number of PRACH retransmissions may be, for example, 1, 2, 4, or 8. The number of PRACH retransmissions may also be, for example, the number of PRACHs retransmitted in one RACH procedure. Below, a case where the number of initial PRACH retransmissions is determined to be 2 will be described.

Then, the terminal device 100 performs PRACH retransmission according to the determined number of PRACH retransmissions (S12). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 for the PRACH transmitted in S12 cannot be received from the base station device 200 and the number of PRACH retransmissions has not reached the maximum number, the terminal device 100 re-determines the number of PRACH retransmissions (S13). The maximum number of PRACH retransmissions is, for example, a number stored in advance in the terminal device 100, for example, four times. The maximum number of PRACH retransmissions may also be given by the base station device 200, for example. Message 1 may be PRACH. The number of retransmissions of message 1 may be the number of PRACH retransmissions. Furthermore, the retransmission of message 1 may be PRACH retransmission.

Specifically, for example, if the number of retransmissions immediately prior to message 1 was n, the terminal device 100 determines the number of retransmissions of message 1 the next time to be 2×n. Even more specifically, as shown in FIG. 4, for example, if the number of retransmissions of message 1 the first time (the number of retransmissions of message 1 in S12) is 2, the terminal device 100 determines the number of retransmissions of message 1 the second time to be 4.

In other words, when the terminal device 100 in the first embodiment determines the number of times to retransmit message 1 from the second time onward, it determines the number of times to retransmit message 1 without measuring RSRP again.

Then, the terminal device 100 retransmits message 1 according to the determined number of retransmissions (S13). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from the base station device 200 in response to message 1 sent in S13, and the number of retransmissions of message 1 has reached the maximum number, the terminal device 100 increases the transmission power (power ramping) (S14-1).

In other words, in this case, the terminal device 100 determines that the number of retransmissions of message 1 cannot be further changed (increased), and increases the transmission power of message 1 instead of redetermining the number of retransmissions of message 1.

Then, the terminal device 100 retransmits message 1 with the increased transmission power (S14-1). In this case, as shown in FIG. 4, the terminal device 100 resets the number of retransmissions of message 1 to the number when n is 1 (i.e., 2 times), and then retransmits message 1 with the increased transmission power. Thereafter, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from base station device 200 in response to message 1 transmitted in S14-1, and the number of retransmissions of message 1 has not reached the maximum number, terminal device 100 re-determines the number of retransmissions of message 1 (S15), as in the case of S13, as shown in FIG. 5. The sum of the transmission power of one or more PRACHs transmitted in S15 may be the same as the sum of the transmission power of one or more PRACHs transmitted in S14-1.

Then, the terminal device 100 retransmits message 1 according to the determined number of retransmissions (S15). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from the base station device 200 in response to message 1 transmitted in S15, the number of retransmissions of message 1 has reached the maximum number, and the number of increases in the transmission power of message 1 has not reached the maximum number, the terminal device 100 further increases the transmission power (S16). The maximum number of increases in the transmission power of message 1 may be, for example, two. In this case, the terminal device 100 may determine whether the transmission power of message 1 has reached the maximum transmission power, instead of determining whether the number of increases in the transmission power of message 1 has reached the maximum number. The maximum transmission power may be 26 dBm. The maximum transmission power may be a value that differs depending on the power class. Also, 0 dBm may be 1 mW (milliwatt).

Then, the terminal device 100 retransmits message 1 with the further increased transmission power (S16). Note that in this case, as shown in FIG. 5, the terminal device 100 resets the number of retransmissions of message 1 to the number when n is 1 (i.e., 2 times), as in the case of S14-1, and then retransmits message 1 with the further increased transmission power.

　After that, if the terminal device 100 is unable to receive message 2 from the base station device 200 in response to message 1 sent in S15, the terminal device 100 re-determines the number of times to retransmit message 1, as in the case of S13, etc., and retransmits message 1 the number of times corresponding to the re-determined number of times.

In this way, when the terminal device 100 in this embodiment is unable to receive message 2 from the base station device 200 and retransmits message 1 to the base station device 200, it increases the number of retransmissions of message 1 in priority over increasing the transmission power of message 1. Then, when the terminal device 100 is unable to receive message 2 from the base station device 200, even after increasing the number of retransmissions of message 1, it returns the number of retransmissions to the number used when message 1 was first retransmitted, and then increases the transmission power of message 1.

As a result, the terminal device 100 in this embodiment can, for example, improve the success rate of the random access procedure (the rate at which message 1 transmitted from the terminal device 100 reaches the base station device 200) while suppressing the occurrence of interference between terminal devices.

Note that when the number of retransmissions of message 1 reaches the maximum number, as shown in FIG. 6, the terminal device 100 may, for example, retransmit message 1 without resetting the number of transmissions of message 1 to the number when n is 1 (S14-2). In other words, in this case, the terminal device 100 may retransmit message 1 while maintaining the number of retransmissions of message 1.

[Second embodiment]
Next, a terminal retransmission control process according to the second embodiment will be described. Figures 7 to 9 are diagrams showing an example of a sequence of the terminal retransmission control process according to the second embodiment.

As shown in FIG. 7, the terminal device 100 measures the RSRP of one or more SSBs notified by the base station device 200 (S20). Then, the terminal device 100 selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs.

Then, the terminal device 100 transmits, for example, message 1 in a RACH Occasion linked to the index of the selected SSB (S21).

Then, the terminal device 100 waits to receive, for example, message 2 transmitted from the base station device 200.

If message 2 in response to message 1 sent in S21 cannot be received from the base station device 200, the terminal device 100 increases the transmission power of message 1 without changing the number of retransmissions of message 1 (S22).

In other words, unlike the terminal retransmission control process in the first embodiment, the terminal device 100 in the second embodiment prioritizes increasing the transmission power of message 1 over redetermining the number of retransmissions of message 1.

Then, the terminal device 100 retransmits message 1 with the increased transmission power (S22). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from the base station device 200 in response to message 1 sent in S22, and the transmission power of message 1 has not reached the maximum transmission power, the terminal device 100 further increases the transmission power of message 1 (S23).

Then, the terminal device 100 retransmits message 1 with a further increased transmission power (S23). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 in response to message 1 sent in S23 cannot be received from base station device 200 and the transmission power of message 1 has reached the maximum transmission power, terminal device 100 determines the number of times to resend message 1 for the first time according to the RSRP measured in S20, as in the case of S12 (S24-1).

Then, the terminal device 100 retransmits message 1 according to the determined number of retransmissions (S24-1). In this case, the terminal device 100, for example, recalculates the transmission power of message 1, and retransmits message 1 the determined number of times with the recalculated transmission power. Thereafter, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 in response to message 1 sent in S24-1 cannot be received from the base station device 200, the terminal device 100 increases the transmission power of message 1, as in S22 (S25).

Then, the terminal device 100 retransmits message 1 with the increased transmission power (S25). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 in response to message 1 sent in S25 cannot be received from the base station device 200 and the transmission power of message 1 has not reached the maximum transmission power, the terminal device 100 further increases the transmission power of message 1 (S26), as in the case of S23, as shown in FIG. 8.

Then, the terminal device 100 retransmits message 1 with a further increased transmission power (S26). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from the base station device 200 in response to message 1 sent in S26, the transmission power of message 1 has reached the maximum transmission power, and the number of retransmissions of message 1 has not reached the maximum number, the terminal device 100 re-determines the number of retransmissions of message 1, as in S13 (S27).

Then, the terminal device 100 retransmits message 1 according to the re-determined number of transmissions (S27). In this case, the terminal device 100, for example, recalculates the transmission power of message 1, and retransmits message 1 with the recalculated transmission power corresponding to the re-determined number of transmissions. Thereafter, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 in response to message 1 sent in S27 cannot be received from the base station device 200 and the transmission power of message 1 has not reached the maximum transmission power, the terminal device 100 increases the transmission power of message 1 (S28).

Then, the terminal device 100 retransmits message 1 with increased transmission power (S28).

　After that, if the terminal device 100 is unable to receive message 2 from the base station device 200 in response to message 1 sent in S28, the terminal device 100 further increases the transmission power of message 1 and resends message 1, as in the case of S26, etc.

In this way, when the terminal device 100 in this embodiment is unable to receive message 2 from the base station device 200 and retransmits message 1 to the base station device 200, it prioritizes increasing the transmission power of message 1 over increasing the number of retransmissions of message 1. Then, when the terminal device 100 is unable to receive message 2 from the base station device 200 even after increasing the transmission power of message 1, it returns the transmission power to the level it was at the time of the initial retransmission of message 1 and then increases the number of retransmissions of message 1.

As a result, the terminal device 100 in this embodiment can, for example, improve the success rate of the random access procedure while suppressing the use of radio resources.

Note that when the transmission power of message 1 reaches the maximum transmission power, the terminal device 100 may, for example, resend message 1 without recalculating the transmission power of message 1 (S24-2), as shown in FIG. 9. In other words, in this case, the terminal device 100 may resend message 1 while maintaining the transmission power of message 1.

[Third embodiment]
Next, a terminal retransmission control process according to the third embodiment will be described below. Fig. 10 is a diagram showing an example of a sequence of the terminal retransmission control process according to the third embodiment.

As shown in FIG. 10, the terminal device 100 measures the RSRP of one or more SSBs notified by the base station device 200 (S30). Then, the terminal device 100 selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs.

Then, the terminal device 100 transmits message 1 in the RACH Occasion linked to the index of the selected SSB (S31). After that, the terminal device 100 waits to receive message 2 transmitted from the base station device 200.

If the terminal device 100 is unable to receive message 2 from the base station device 200 in response to message 1 sent in S31, the terminal device 100 increases the transmission power of message 1 and, as in the case of S12, determines the number of times to resend the initial message 1 according to the RSRP measured in S30 (S32).

In other words, unlike the terminal retransmission control process in the first embodiment and the terminal retransmission control process in the second embodiment, the terminal device 100 in the third embodiment simultaneously re-determines the number of retransmissions of message 1 and increases the transmission power of message 1.

Then, the terminal device 100 retransmits message 1 the determined number of times with the increased transmission power (S32). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from base station device 200 in response to message 1 sent in S31, if the number of retransmissions of message 1 has not reached the maximum number, and if the transmission power of message 1 has not reached the maximum transmission power, terminal device 100 further increases the transmission power of message 1 and re-determines the number of retransmissions of message 1, as in S13 (S33).

Then, the terminal device 100 retransmits message 1 the number of times determined again with the increased transmission power (S33).

In this way, when the terminal device 100 in this embodiment is unable to receive message 2 from the base station device 200 and retransmits message 1 to the base station device 200, it increases the number of retransmissions of message 1 and also increases the transmission power of message 1.

As a result, the terminal device 100 in this embodiment can, for example, further improve the success rate of the random access procedure.

[Fourth embodiment]
Next, a terminal retransmission control process according to the fourth embodiment will be described below. Fig. 11 is a diagram showing an example of a sequence of the terminal retransmission control process according to the fourth embodiment.

As shown in FIG. 11, the terminal device 100 measures the RSRP of one or more SSBs notified by the base station device 200 (S40-1). Then, the terminal device 100 selects, for example, the SSB with the highest measured RSRP from among the one or more SSBs.

Then, the terminal device 100 transmits message 1 in the RACH Occasion linked to the index of the selected SSB (S41). After that, the terminal device 100 waits to receive message 2 transmitted from the base station device 200.

If the terminal device 100 is unable to receive message 2 from the base station device 200 in response to message 1 sent in S31, the terminal device 100 remeasures the RSRP of one or more SSBs notified by the base station device 200 (S40-2).

Then, the terminal device 100 increases the transmission power of message 1 and determines the number of times to retransmit the first message 1 in the RACH Occasion linked to the index of the SSB with the highest RSRP measured in S40-2 among one or more SSBs reported by the base station device 200 (S42).

Furthermore, the terminal device 100 retransmits message 1 the determined number of times with the increased transmission power (S42). After that, the terminal device 100 waits to receive message 2 from the base station device 200.

If message 2 cannot be received from base station device 200 in response to message 1 sent in S31, if the number of retransmissions of message 1 has not reached the maximum number, and if the transmission power of message 1 has not reached the maximum transmission power, terminal device 100 remeasures the RSRP of one or more SSBs reported by base station device 200 (S40-3).

Then, the terminal device 100 further increases the transmission power of message 1 and re-determines the number of retransmissions of message 1 in the RACH Occasion linked to the index of the SSB with the highest RSRP measured in S40-3 among the one or more SSBs reported by the base station device 200 (S43).

Furthermore, the terminal device 100 retransmits message 1 the number of times determined again with the increased transmission power (S43).

In this way, when the terminal device 100 in this embodiment is unable to receive message 2 from the base station device 200 and retransmits message 1 to the base station device 200, it remeasures the RSRP and determines the number of times to retransmit message 1.

As a result, the terminal device 100 in this embodiment can determine the number of times to retransmit message 1 based on, for example, the reception quality of the terminal device 100.

[Fifth embodiment]
Next, the terminal retransmission control process in the fifth embodiment will be described.

In the base station retransmission control process, the base station device 200 transmits to the terminal device 100 control information including retransmission method information for when the terminal device 100 performs retransmission, for example. The control information is, for example, SIB (System Information Block) 1 notified from the base station device 200. The retransmission method information is, for example, information specifying one of the method for performing terminal retransmission control processing in the first embodiment, the method for performing terminal retransmission control processing in the second embodiment, the method for performing terminal retransmission control processing in the third embodiment, and the method for performing terminal retransmission control processing in the fourth embodiment.

Specifically, in this case, SIB1 includes, for example, an information element (IE) called "prach-retransmissionType."

Then, the terminal device 100 performs terminal retransmission control processing, for example, using a method corresponding to the retransmission method information included in the control information transmitted from the base station device 200 (i.e., the method specified by the base station device 200).

As a result, the base station device 200 in this embodiment can control the method used when the terminal device 100 retransmits message 1, for example. The terminal device 100 in this embodiment can then perform terminal retransmission control according to the method specified by the base station device 200, for example.

The base station device 200 may notify the terminal device 100 of the retransmission method information by a method other than the transmission of SIB1. Specifically, the base station device 200 may notify the terminal device 100 of the retransmission method information by including the retransmission method information in other broadcast information.

Sixth embodiment
Next, the terminal retransmission control process in the sixth embodiment will be described.

In the terminal retransmission control process, the terminal device 100 performs, for example, a two-step contention-based random access procedure with the base station device 200.

Specifically, for example, if the terminal device 100 is unable to receive message B from the base station device 200 in response to message A that it sent to the base station device 200, it resends message A to the base station device 200.

In this case, the terminal device 100 may retransmit, for example, the contents corresponding to message 1 contained in message A to the base station device 200.

[Seventh embodiment]
Next, the terminal retransmission control process in the seventh embodiment will be described.

When the terminal device 100 retransmits data with high urgency such as URLLC to the base station device 200, the terminal device 100 does not follow a predetermined method or a method specified by the base station device 200 by control information (i.e., any of the method of performing terminal retransmission control processing in the first embodiment, the method of performing terminal retransmission control processing in the second embodiment, the method of performing terminal retransmission control processing in the third embodiment, and the method of performing terminal retransmission control processing in the fourth embodiment), but instead maximizes at least one of the number of transmissions of message 1 and the transmission power and retransmits the data. Data with high urgency such as URLLC is an example of first data. Data with lower urgency than data with high urgency such as URLLC (e.g. data such as eMMB) is an example of second data. The first data can be described as data with higher priority than the second data. In other words, the second data can be described as data with lower priority than the first data.

[Reflection in specifications]
Next, examples of the first to fifth embodiments reflected in the 3GPP specifications are shown. Figures 12 to 16 are diagrams showing examples of the contents of the specifications. The specifications are, for example, TS38.321. In the following figures, additional specifications are indicated by underlining. Also, the specification names, chapter numbers, item numbers, names, values, insertion positions, and the like in the additional specifications shown in the figures are merely examples and are not limited to these.

FIG. 12 is a diagram showing an example of a description of the terminal retransmission control process in the first embodiment. Specifically, in the example shown in FIG. 12, it is described that, for example, when retransmitting message 1 to the base station device 200, increasing the number of retransmissions of message 1 is given priority over increasing the transmission power of message 1.

FIG. 13 is a diagram showing an example of a description of the terminal retransmission control process in the second embodiment. Specifically, in the example shown in FIG. 13, it is described that, for example, when retransmitting message 1 to the base station device 200, increasing the number of retransmissions of message 1 is given priority over increasing the transmission power of message 1.

FIG. 14 is a diagram showing an example of a description of the terminal retransmission control process in the third embodiment. Specifically, in the example shown in FIG. 14, for example, when retransmitting message 1 to the base station device 200, it is described that the number of retransmissions of message 1 is increased and the transmission power of message 1 is increased at the same time.

FIG. 15 is a diagram showing an example of a description of the terminal retransmission control process in the fourth embodiment. Specifically, in the example shown in FIG. 15, for example, when retransmitting message 1 to the base station device 200, the number of retransmissions of message 1 is determined based on the reception quality of the terminal device 100.

Furthermore, FIG. 16 is a diagram showing an example of a description of the terminal retransmission control process in the fifth embodiment. Specifically, the example shown in FIG. 16 shows that the terminal device 100 retransmits message 1 using a method specified by the base station device 200.

10: Wireless communication system 100: Terminal device 110: CPU
120: Storage 121: Terminal communication program 122: Terminal retransmission control 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 retransmission control program 230: Memory 250: Wireless communication circuit 251: Antenna

Claims (13)

A terminal device that performs a random access procedure,
a transmission unit that transmits a request for allocation of radio resources to be used in the random access procedure to a base station device;
a receiving unit that receives from the base station device an allocation response to the allocation request transmitted by the transmitting unit;
a control unit that performs at least one of a first control for changing the number of times the allocation request is transmitted and a second control for changing a transmission power of the allocation request when the receiving unit does not receive the allocation response,
the transmitter retransmits the allocation request to the base station device in accordance with at least one of the number of transmissions changed by the first control and the transmission power changed by the second control.
A terminal device comprising: In claim 1,
The control unit increases the number of transmissions in the first control until the receiving unit receives the allocation response or until the number of transmissions of the allocation request reaches a first threshold value;
The transmission unit retransmits the allocation request to the base station device every time the control unit increases the number of transmissions in the first control.
A terminal device comprising: In claim 2,
When the receiving unit does not receive the allocation response and the number of times the allocation request is transmitted reaches the first threshold, the control unit increases the transmission power in the second control until the receiving unit receives the allocation response or until the number of times the transmission power of the allocation request is increased reaches a second threshold;
the transmission unit retransmits the allocation request to the base station device every time the control unit increases the transmission power in the second control.
A terminal device comprising: In claim 1,
The control unit increases the transmission power in the second control until the receiving unit receives the allocation response or until the number of increases in the transmission power of the allocation request reaches a second threshold value;
the transmission unit retransmits the allocation request to the base station device every time the control unit increases the transmission power in the second control.
A terminal device comprising: In claim 4,
When the receiving unit does not receive the allocation response and the number of increases in transmission power of the allocation request reaches the second threshold, the control unit increases the number of transmissions in the first control until the receiving unit receives the allocation response or until the number of transmissions of the allocation request reaches a first threshold;
The transmission unit retransmits the allocation request to the base station device every time the control unit increases the number of transmissions in the first control.
A terminal device comprising: In claim 1,
The control unit performs the first control and the second control when the receiving unit does not receive the allocation response.
A terminal device comprising: In claim 1,
The control unit is
If the receiver does not receive the allocation response, it measures a reception strength of a signal transmitted from the base station device;
In the first control, the number of times of transmitting the allocation request is determined according to the measured reception strength.
A terminal device comprising: In claim 1,
The receiving unit receives control information broadcast from the base station device,
The control unit performs at least one of the first control and the second control in accordance with information included in the control information.
A terminal device comprising: In claim 8,
The control information is SIB1 (System Information Block Type 1).
A terminal device comprising: In claim 1,
When the transmission unit transmits information including the allocation request as a part thereof to the base station device and the reception unit does not receive information including the allocation response as a part thereof, the transmission unit retransmits the allocation request to the base station device.
A terminal device comprising: In claim 1,
The control unit is
When the transmission unit transmits the allocation request for second data having a lower priority than the first data to the base station device, and the reception unit does not receive the allocation response for the second data, performing at least one of the first control and the second control;
when the transmitter transmits the allocation request for the first data to the base station device and the receiver does not receive the allocation response for the first data, performing at least one of a third control of changing the number of transmissions of the allocation request to a maximum and a fourth control of changing a transmission power of the allocation request to a maximum;
The transmission unit is
when retransmitting the allocation response for the second data to the base station device, retransmitting the allocation request to the base station device in accordance with at least one of the number of transmissions changed by the first control and the transmission power changed by the second control;
When retransmitting the allocation response for the first data to the base station device, retransmitting the allocation request to the base station device in accordance with at least one of the number of transmissions changed by the third control and the transmission power changed by the fourth control.
A terminal device comprising: A base station device that performs a random access procedure,
a base station receiving unit that receives, from a terminal device, a request for allocation of radio resources to be used in the random access procedure;
a base station transmitter that transmits an allocation response corresponding to the allocation request received by the base station receiver to the terminal device,
the base station transmitter transmits control information to the terminal device before the base station receiver receives the allocation request from the terminal device, thereby causing the terminal device to perform at least one of a first control for changing a number of transmissions of the allocation request and a second control for changing a transmission power of the allocation request;
A base station device comprising: A wireless communication system having a terminal device and a base station device, the wireless communication system performing a random access procedure between the terminal device and the base station device,
the terminal device transmits, to a base station device, a request for allocation of radio resources to be used in the random access procedure;
the base station device receives the allocation request, and transmits an allocation response to the received allocation request to the terminal device;
The terminal device
When the allocation response is not received from the base station device, at least one of a first control for changing the number of times the allocation request is transmitted and a second control for changing a transmission power of the allocation request is performed;
retransmitting the allocation request to the base station device in accordance with at least one of the number of transmissions changed by the first control and the transmission power changed by the second control.
1. A wireless communication system comprising:

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