Terminal device, base station device, control method, and storage medium for performing two-step random access procedure

Abstract

The terminal device sends a predetermined message to the base station device based on a two-step random access procedure. Upon receiving a signal sent by the base station device in response to the predetermined message, i.e., a signal that multiplexes control information of the upper layer for each of the terminal device and other terminal devices, the terminal device determines a first radio resource based on a control signal for sending the signal and at least one of the signals. The first radio resource is used to send a first response signal indicating whether the reception of the control information for the terminal device contained in the signal was successful. The first radio resource is different from a second radio resource used to send a second response signal indicating whether the transmission of control information for other terminal devices contained in the signal was successful. The first response signal is sent using the first radio resource.

Description

Technical Field

[0001] This invention relates to terminal devices, base station devices, control methods, and storage media; more specifically, it relates to techniques for improving the efficiency and reliability of message transmission in a two-step random access process. Background Technology

[0002] The 3rd Generation Partnership Project (3GPP) has established standards for wireless communication systems such as Long Term Evolution (LTE) and New Radio (NR) for 5G. LTE and NR define random access procedures for initial connections between terminal devices and base station devices. Furthermore, in 3GPP, to establish an initial connection in a shorter time than the previous four-step random access procedure, a two-step random access procedure was investigated (see Non-Patent Document 1). In this two-step random access procedure, firstly, the terminal device sends message A, which is equivalent to messages 1 and 3 in a four-step random access procedure and includes a random access preamble and predetermined information for initial access. Then, in response to message A, the base station device sends message B, which is equivalent to messages 2 and 4 in a four-step random access procedure. It should be noted that in message B, under normal connection establishment conditions, information from the MAC (Media Access Control) layer such as timing advance and RRC (Radio Resource Control) layer information such as RRC connection settings can be sent to the terminal device.

[0003] Existing technical documents

[0004] Non-patent literature

[0005] Non-patent literature 1: 3GPP, RP-182894 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Imagine a base station receiving message A from multiple terminal devices in parallel. In this scenario, it is required to send message B to each terminal device efficiently. Furthermore, as mentioned above, message B is used to notify the terminal devices of MAC layer information and RRC layer information; therefore, it is important to send the message to the terminal devices with high reliability.

[0008] means for solving problems

[0009] This invention provides a technique for reliably and efficiently notifying a terminal device of information sent by a base station device during a two-step random access process.

[0010] One aspect of the terminal device of the present invention is a terminal device having a communication unit, wherein the communication unit is controlled to send a predetermined message to a base station device based on a two-step random access procedure; and upon receiving a signal sent from the base station device in response to the predetermined message, namely, a signal multiplexed including upper-level control information for each of the terminal device and other terminal devices, determining a first radio resource based on a control signal for sending the signal and at least one of the signal, the first radio resource being used to send a first response signal indicating whether the reception of the control information for the terminal device contained in the signal was successful, the first radio resource being different from a second radio resource used to send a second response signal indicating whether the other terminal devices successfully received the control information for the other terminal devices contained in the signal, and using the first radio resource to send the first response signal.

[0011] One aspect of the base station apparatus of the present invention is a base station apparatus having a communication unit, wherein the communication unit is controlled to receive a predetermined message from a plurality of terminal devices based on a two-step random access procedure; in response to the predetermined message, send a signal multiplexed and including upper-level control information for each of the plurality of terminal devices to the plurality of terminal devices; for the signal, using a control signal for sending the signal and at least one of the signals, specify a radio resource that should be sent to indicate whether the reception of the control information was successful, i.e., a different radio resource for each of the plurality of terminal devices; and in each of the radio resources specified for the plurality of terminal devices, receive the response signal from each of the plurality of terminal devices.

[0012] Invention Effects

[0013] According to the present invention, in the two-step random access process, the information sent by the base station device can be transmitted to the terminal device with high reliability and high efficiency.

[0014] Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. It should be noted that, in the drawings, the same or identical structures are labeled with the same reference numerals. Attached Figure Description

[0015] The accompanying drawings, which are included in and form a part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0016] Figure 1 This is a diagram illustrating an example of the configuration of a wireless communication system.

[0017] Figure 2 This is a diagram illustrating an example of the hardware configuration of a base station device and a terminal device.

[0018] Figure 3 This is a diagram illustrating an example of the functional configuration of a terminal device.

[0019] Figure 4 This is a diagram illustrating an example of the functional structure of a base station device.

[0020] Figure 5 This is a diagram illustrating an example of the process flow performed by the system.

[0021] Figure 6 This is a diagram illustrating an example of the process flow performed by the system. Detailed Implementation

[0022] The embodiments will now be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention as defined in the claims. Multiple features are described in the embodiments, but not all of these features are limited to those essential to the invention; furthermore, multiple features can be arbitrarily combined. Furthermore, in the accompanying drawings, the same or identical structures are labeled with the same reference numerals, and repeated descriptions are omitted.

[0023] (System Architecture)

[0024] Figure 1 This illustrates a structural example of the wireless communication system according to this embodiment. In one example, this system is a 5G cellular communication system. However, it is not limited to this; the system could be a successor to 5G or a non-cellular wireless communication system. This system is configured to include a base station device 101, a terminal device 102, and a terminal device 103. It should be noted that... Figure 1 For the sake of simplicity, only one base station device and two terminal devices are shown in the diagram, but the number of these devices is not limited, and there may be more base station devices and terminal devices.

[0025] In this embodiment, terminal devices 102 and 103 attempt to establish a connection with base station device 101 by executing a two-step random access procedure (hereinafter referred to as "two-step RACH"). As described above, in the two-step RACH, the terminal device sends message A, which includes a preamble and predetermined information for initial access, to the base station device. Then, in response to message A, base station device 101 sends RRC layer information, such as timing advance MAC layer information and RRC connection settings, to the terminal device that sent message A via message B.

[0026] Base station device 101 sometimes receives message A from multiple terminal devices in parallel. In this case, efficient transmission of message B is important. Therefore, in this embodiment, base station device 101 multiplexes the MAC layer information and RRC layer information for each of the multiple terminal devices before transmission. Furthermore, since this information is control information, it should be transmitted to the terminal devices in a highly reliable manner. In this embodiment, given that the transmitted information is upper-layer information such as the RRC layer, Hybrid Automatic Repeat Request (HARQ) is used to ensure reliability. By properly functioning these mechanisms, efficient and highly reliable transmission of message B to the terminal devices can be achieved.

[0027] Message B is transmitted via the Physical Downlink Shared Channel (PDSCH). In this case, where information intended for multiple terminal devices is multiplexed and transmitted, this information can be transmitted via a single PDSCH. Furthermore, when transmitting a PDSCH, base station device 101 can specify radio resources via a Physical Downlink Control Channel (PDCCH).

[0028] When using HARQ to send message B, a response signal (ACK or NACK) needs to be sent to indicate whether the terminal device can normally receive message B. However, it is conceivable that the terminal device cannot determine the radio resources used to send this response signal. Alternatively, for example, the radio resources for sending the response signal could be determined based on the radio resources used to send the PDCCH, but if multiple terminal devices use a single PDCCH, the result of multiple terminal devices using the same radio resources will be that the response signals will collide.

[0029] In this embodiment, considering the situation, a method is applied to enable HARQ to function appropriately when message B is multiplexed by appropriately sending a response signal. In this embodiment, as such a method, when a base station receives message A in parallel from multiple terminal devices, it sends a signal (message B) that multiplexes information for the respective MAC layer and RRC layer (i.e., upper-layer information). At this time, in the first example, the base station sends a downlink control signal (e.g., containing scheduling information) for sending this signal via a separate PDCCH. Then, via each PDCCH, radio resources (time / frequency resources) for sending the HARQ response signal (HARQ-ACK) for the upper-layer information are notified to each terminal device. It should be noted that in these two or more PDCCHs, a physical packet (PDSCH) is designated as the subsequent downlink signal. Then, in this physical packet, the upper-layer information for each terminal device is multiplexed and transmitted. The terminal device extracts and receives information destined for itself from the physical packet, and sends a response signal to the base station device indicating whether the reception was successful using the radio resources specified in the PDCCH sent to the terminal device. It should be noted that the response signal is transmitted, for example, via the Physical Uplink Control Channel (PUCCH). It should also be noted that, in one example, the PDCCHs for two or more terminal devices are scrambled using different sequences.

[0030] In the second example, base station device 101 transmits downlink control signals for transmitting the response signal via a shared PDCCH, but in the subsequent PDSCH, it transmits information specifying different radio resources for each terminal to transmit the response signal. For example, the base station device can include the information specifying the radio resources for transmitting the response signal of each terminal device along with the aforementioned multiplexed upper-layer information in a single PDSCH. Upon receiving the PDSCH, each terminal device extracts and receives the information destined for it, determining the radio resources to be used in transmitting the response signal. Then, each terminal device uses the determined radio resources to transmit a response signal to the base station device indicating whether the reception was successful. Alternatively, for example, the radio resources for transmitting the response signal of a terminal device can be specified via the PDCCH, and this can be done by including a value representing the difference between the radio resources used for transmitting the response signal of the terminal device and those used for transmitting the response signal of other terminal devices in the PDSCH. For example, the frequency resources used for transmitting the response signal of the first terminal device can be specified as "f" via the PDCCH, and "Δf" can be specified via the PDSCH as information associated with the frequency resources used for transmitting the response signal of the second terminal device. In this scenario, the first terminal device can transmit a response signal in frequency resource "f", and the second terminal device can transmit a response signal in frequency resource "f+Δf". Similarly, for time resources, the time resource for transmitting a terminal device's response signal can be specified via PDCCH, and the difference between this time resource and the time resources for transmitting response signals of other terminal devices can be specified via PDSCH. It should be noted that the defined reference radio resource can be specified via PDCCH, and the difference between the radio resource for transmitting response signals of each terminal device and the reference radio resource can be specified separately via PDSCH.

[0031] It should be noted that when transmitting information specifying radio resources for transmitting a response signal via PDSCH, this information can be included in the MAC subheader of the PDSCH and transmitted. Alternatively, when transmitting information specifying radio resources for transmitting a response signal via PDSCH, the radio resources corresponding to the multiplexing order of each terminal device in the PDSCH can be determined as the radio resources for transmitting the response signal for that terminal device. That is, the multiplexing order of the terminal devices can also implicitly indicate the radio resources that the terminal device should use in transmitting the response signal. In this case, the relationship between the multiplexing order and the radio resources to be used in transmitting the response signal is shared in advance between the base station device and the terminal device. In one example, the base station device broadcasts information specifying this relationship in a broadcast signal, and the terminal device can determine this relationship by receiving the broadcast signal. Then, when the terminal device receives the PDSCH, it determines the multiplexing order of its own device, determines the radio resources to be used according to this order, and transmits the response signal to the base station device using the determined radio resources. It should be noted that the information of the radio resources represented by this relationship can be, for example, the difference between the radio resources determined based on the radio resources used in the transmission of PDCCH. That is, a radio resource can also be determined from the radio resources used in the transmission of PDCCH, and based on the determined radio resource, the radio resources that the terminal device should use in the transmission of the response signal can be determined according to the multiplexing order.

[0032] In this way, upper-layer control information for each of the multiple terminal devices is multiplexed and transmitted to those terminal devices via a single Physical Packet Scheduling (PDSCH). The radio resources for sending a response signal indicating whether the control information was successfully received are specified differently for each terminal device. Thus, in the two-step RACH, control information can be transmitted efficiently through multiplexing, and HARQ can be used to improve reliability.

[0033] It should be noted that when a base station receives message A from one terminal device, it can also wait for message A to be received from other terminal devices within a predetermined time. That is, when receiving message A from one terminal device, it can choose not to immediately send message B, but instead wait for message A from other terminal devices, thereby increasing the probability of multiplexing and sending upper-level control information destined for multiple terminal devices.

[0034] Furthermore, when the base station device multiplexes message A from multiple terminal devices and transmits upper-level control information for each of those terminal devices, and receives a response signal indicating signal reception failure from at least one of the multiple terminal devices, it retransmits the transmitted signal. At this time, it retransmits not only the information for the terminal devices that failed to receive the signal, but also the information for the terminal devices that successfully received the signal. Thus, by retransmitting signals related to the same information, a gain based on the synthesized received signal can be obtained in the terminal device receiving the signal. It should be noted that it is also possible to retransmit only the information for the terminal devices that failed to receive the signal. For example, after signals destined for multiple terminal devices are multiplexed and transmitted, if only a few terminal devices fail to receive the signal, the reduction in frequency utilization efficiency caused by transmitting signals destined for multiple terminal devices for those few terminal devices can be suppressed.

[0035] (Device Structure)

[0036] Next, the structure of the terminal device and the base station device that perform the above-described processing will be explained. Figure 2 This section illustrates an example of the hardware structure of a terminal device and a base station device. In one example, the terminal device and base station device include a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. In the terminal device, for example, the processor 201 executes a computer-readable program, recorded in any one of the ROM 202, RAM 203, and storage device 204, that implements the functions of the terminal device as described above. Similarly, in the base station device, the processor 201 executes, for example, a program, recorded in any one of the ROM 202, RAM 203, and storage device 204, that implements the functions of the base station device as described above. It should be noted that the processor 201 can also be replaced by one or more processors such as an ASIC (Application-Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a DSP (Digital Signal Processor).

[0037] The terminal device and base station device, for example, control the communication circuit 205 through the processor 201 to conduct communication with the target device (e.g., the base station device for the terminal device, the terminal device or a network node for the base station device). It should be noted that in Figure 2 The diagram shows a schematic of a terminal device and a base station device having a communication circuit 205, but is not limited thereto. For example, the terminal device may include a communication device for communicating with the base station device and a communication device for communication such as a wireless LAN. Additionally, the base station device may, for example, have a communication device for communicating with the terminal device and a communication device for communicating with network nodes.

[0038] Figure 3Example of the functional structure of a terminal device. Figure 3 The functions shown are implemented, for example, by the processor 201 of the terminal device executing programs stored in ROM 202, RAM 203, and storage device 204. It should be noted that the terminal device may also have hardware corresponding to at least any of the functions described later. Figure 3 The functional parts of the terminal device that are particularly relevant to this embodiment are selectively shown. Of course, the terminal device has the functions of a general terminal device.

[0039] As part of its functions, the terminal device may be configured to include, for example, a communication control unit 301, a message sending unit 302, a message receiving unit 303, a resource determination unit 304, and a response signal sending unit 305.

[0040] The communication control unit 301 controls the communication (e.g., wireless communication conforming to 5G communication standards) performed between the terminal device and the base station device. For example, the communication control unit 301 acquires information sent from the base station device, performs a two-step RACH based on this information, and performs control for establishing a connection with the base station device to conduct communication. The message sending unit 302 generates message A, which involves the two-step RACH, and sends it to the base station device via the communication control unit 301. The message receiving unit 303 receives message B, sent from the base station device in response to the transmission of message A, via the communication control unit 301. Here, message B is assumed to be a message contained in a PDSCH scheduled by a PDCCH sent from the base station device, but sometimes it also refers to a combination of PDCCH and PDSCH. It should be noted that this message can be received as a physical packet multiplexed from information from the upper-level layer (especially the RRC layer) for the terminal device itself and information from the upper-level layer for other terminal devices. Therefore, when the message receiving unit 303 receives a packet multiplexed with information destined for multiple terminal devices, it extracts the information destined for its own device from it. The resource determination unit 304 determines, based on information contained in at least one of the PDCCH and PDSCH, the radio resources (frequency / time resources) for transmitting a response signal indicating whether the reception of a message from the upper layer was successful. The response signal transmission unit 305 transmits the response signal in the radio resources determined by the resource determination unit 304 via the communication control unit 301.

[0041] Figure 4 Example of the functional structure of a base station device. Figure 4 The functions shown are implemented, for example, by the processor 201 of the base station device executing programs stored in ROM 202, RAM 203, and storage device 204. It should be noted that the base station device may have hardware corresponding to at least any of the functions described later. Figure 4The functions of the base station device that are particularly relevant to this embodiment are selectively represented. Of course, the base station device has the functions of a general base station device.

[0042] The base station device, as its function, is configured to include, for example, a communication control unit 401, a message receiving unit 402, a resource designation unit 403, a message sending unit 404, and a response signal receiving unit 405.

[0043] The communication control unit 401 controls the communication (e.g., wireless communication conforming to 5G communication standards) performed between the base station device and the terminal device. For example, the communication control unit 301 performs control for establishing a connection with the terminal device and performing communication based on the two-step RACH initiated by the terminal device.

[0044] The message receiving unit 402 receives message A, representing the two-step RACH process, from the terminal device via the communication control unit 401. It should be noted that, even when receiving message A from one terminal device, the message receiving unit 402 can wait for messages A from other terminal devices for a predetermined time. That is, the base station device waits to receive messages A from multiple terminal devices for a predetermined time, thereby multiplexing and transmitting upper-level information intended for multiple terminal devices as much as possible. This increases the probability of efficiently executing the two-step RACH process.

[0045] When message B is sent to message A containing information from the upper-level layer such as the RRC layer, the resource designation unit 403 designates radio resources for the terminal device to send a response signal indicating whether the signal can be received normally. For example, when message A is received in parallel from multiple terminal devices and the upper-level information such as the RRC layer is multiplexed for these terminal devices, the resource designation unit 403 designates radio resources differently for each terminal device to send its response signal. It should be noted that when the resource designation unit 403 sends upper-level information to message A from a single terminal device, it may not need to designate special radio resources.

[0046] The resource designation unit 403 designates different radio resources for each of the multiple terminal devices, for example, by using a separate PDCCH for each. Then, each PDCCH designates shared radio resources used in the transmission of PDSCH containing upper-layer information from the base station device, and designates different radio resources for transmitting response signals. It should be noted that the designation of radio resources can be implicitly performed through the radio resources used in the PDCCH, explicitly performed through the information transmitted in the PDCCH, or through a combination thereof. Thus, multiple terminal devices can receive PDCCHs that are individually transmitted to their own devices, and receive PDSCHs that are shared among these terminal devices and multiplexed with information for these terminal devices, transmitting response signals using the radio resources individually designated by each PDCCH.

[0047] Alternatively, the resource designation unit 403 may use a shared PDCCH for multiple terminal devices, designating the radio resources used in the shared PDSCH, and specifying the radio resources for transmitting response signals for each terminal device in the multiplexed information in the PDSCH. In this case, each terminal device that sent message A receives the shared PDCCH and determines the radio resources for transmitting the PDSCH based on the PDCCH. Then, the terminal device can extract the information destined for itself from the multiplexed information in the PDSCH and determine the radio resources for transmitting response signals based on this information. It should be noted that the radio resources for transmitting response signals can be explicitly designated by including information determining the radio resources to be used by each terminal device in the multiplexed information, such as MAC subframes. Alternatively, the radio resources for transmitting response signals can be implicitly designated by establishing an association between the multiplexing order of the multiplexing of the multiple terminal devices and the radio resources in advance, thereby specifying them through the multiplexing order. In this case, the terminal device determines the radio resources for transmitting response signals based on which multiplexed information destined for itself is multiplexed in the multiplexed information.

[0048] It should be noted that when radio resources for transmitting response signals are specified in the PDSCH, and reference radio resources are specified in the PDCCH, the PDSCH can specify information on the difference between the reference radio resources and the radio resources for transmitting response signals of each terminal device. That is, the resource specification unit 403 specifies radio resources for transmitting response signals that differ for each terminal device through at least one of the PDCCH and PDSCH.

[0049] In response to receiving message A from a terminal device, message sending unit 404 sends message B via communication control unit 401. Message B may contain, for example, upper-layer information such as MAC layer or RRC layer, and may contain this information for multiple terminal devices in a multiplexed form. Message sending unit 404 sends message B in a form corresponding to the radio resource allocation method of resource allocation unit 403. For example, if resource allocation unit 403 determines that a different PDCCH is used for each terminal device, message sending unit 404 sends message B (PDSCH) that does not contain information on radio resources for transmitting response signals for each terminal device in the message transmitted within the PDSCH. On the other hand, if resource allocation unit 403 determines that a shared PDCCH is used for each terminal device, message sending unit 404 sends message B in a form that contains information on radio resources for transmitting response signals for each terminal device (information on directly allocated radio resources, and information on the difference between allocated and referenced radio resources). It should be noted that when specifying the radio resources for transmitting response signals of each terminal device according to the multiplexing order, the message sending unit 404 does not need to include explicit information in the message for specifying the radio resources for transmitting response signals of each terminal device.

[0050] The response signal receiving unit 405 receives response signals from each terminal device within the radio resources designated by the resource designation unit 403, indicating whether the reception of information (message B) sent from the base station device was successful. When the response signal receiving unit 405 receives response signals indicating successful signal reception from all multiple terminal devices, the connection between the base station device and each terminal device is established, and each terminal device transitions to a connected state. Conversely, when the response signal receiving unit 405 receives a response signal indicating signal reception failure from any of the multiple terminal devices, the message sending unit 404 retransmits a signal that reuses the information for the multiple terminal devices, similar to the previously transmitted signal. It should be noted that this retransmitted signal can be the same as the previously transmitted signal, or it can be a signal containing the same information in a different form, such as a signal containing different redundant versions of the information. Thus, the terminal device that failed to receive the signal combines the retransmitted signal with the previously received signal and attempts demodulation again. By combining the signals transmitted multiple times in this way, a combining gain can be obtained, increasing the probability of the terminal device successfully receiving the signal. Furthermore, if the response signal receiving unit 405 receives a response signal indicating a signal reception failure from any of the multiple terminal devices, the message sending unit 404 may also send a signal containing information specific to the terminal device that failed to receive the signal. In this case, the synthesis gain cannot be obtained in the terminal device, but signal retransmission can be performed efficiently, for example, when the number of terminal devices that failed to receive the signal is small.

[0051] (Processing flow)

[0052] Next, the processing flow according to this embodiment will be outlined. Figure 5 This example illustrates the scenario where different PDCCHs are used for each terminal device. Figure 6 This illustrates an example where the radio resources for transmitting a response signal can be determined via PDSCH. It should be noted that... Figure 5 as well as Figure 6 In the middle, it is explained that in Figure 1 In that state, the processing occurs when two terminal devices 102 and 103 send message A (S501, S502) to the base station device 101. However, the number of terminal devices is not limited to two. The same processing can be performed even if three or more terminal devices send message A in parallel.

[0053] exist Figure 5 In this scenario, if base station device 101 receives message A from two terminal devices 102 and 103, it correspondingly sends message B. Base station device 101 specifies radio resources for transmitting a data signal (PDSCH) containing the message via a control signal (PDCCH), and transmits the data signal through the specified radio resources. At this time, in... Figure 5 In the example, PDCCHs are sent to each terminal device using different radio resources (S503, S504). Furthermore, these two PDCCHs specify a shared radio resource for PDSCH transmission. Therefore, terminal devices 102 and 103 use the same radio resource to receive the PDSCH (S505). Through this PDSCH, a multiplexed message B containing RRC messages for each terminal device is sent. Terminal devices 102 and 103 extract and obtain information destined for themselves from the multiplexed information. Then, terminal devices 102 and 103 use the uplink control signal (PUCCH) to send a signal (HARQ-ACK) to the base station device 101 indicating whether the information acquisition was successful (S506, S507). At this time, the radio resource used by each terminal device to send the HARQ-ACK is determined based on the radio resource used when sending the PDCCH to each terminal device and the information contained in each PDCCH.

[0054] It should be noted that, here, we assume that terminal device 102 fails to receive information (S506). In this case, base station device 101 retransmits the information to terminal device 102. At this time, in order to obtain the synthesis gain in the terminal device, a signal containing the amount of information indicating that the information was successfully received by terminal device 103 is transmitted, similar to the signal transmitted in S505 (S508, S509). This prevents an unnecessary increase in the number of retransmissions and prevents a decrease in efficiency. It should be noted that, as described above, it is also possible to retransmit only the information of terminal device 102. If the information is successfully received through the retransmission in S509, terminal device 102 returns ACK (S510) and establishes a connection with base station device 101.

[0055] exist Figure 6 In this process, base station device 101 transmits a shared PDCCH to two terminal devices 102 and terminal device 103 (S601). In this case, since there is only one PDCCH, if each terminal device determines the radio resources used for its response signal based on this PDCCH, the same radio resources will be determined, leading to conflicting response signals. On the other hand, in... Figure 6 In the example, in the PDSCH (S602), the information used by each multiplexed terminal device includes information for differentiating the radio resources used to transmit the response signal. This information can be explicitly represented, for example, by the multiplexed MAC sub-header, or implicitly represented, for example, by the multiplexing order. Then, each terminal device uses the radio resources represented by the PDSCH to transmit HARQ-ACK (S603, S604). At this time, each terminal device can further determine the radio resources used to transmit the response signal based on the radio resources used in the transmission of the PDCCH and the information contained in the PDCCH. For example, the frequency resources obtained by adding the differential value represented by the PDSCH to the reference frequency resources determined by the PDCCH can be determined as the radio resources used to transmit the response signal.

[0056] In this way, the two-step RACH is made more efficient by multiplexing the transmission of information from higher layers such as RRC messages in message B, and more reliable by using HARQ.

[0057] This invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, claims have been added to disclose the scope of the invention.

[0058] This application claims priority based on Japanese Patent Application No. 2019-174156, filed on September 25, 2019, the entire contents of which are incorporated herein by reference.

Claims

1. A terminal device, the terminal device having a communication unit, wherein, The communication unit is controlled to be such that... Based on a two-step random access process, a predetermined message is sent to the base station device; as well as Upon receiving a signal transmitted from the base station device in response to the predetermined message, namely a signal containing a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH), the PDCCH and PDSCH multiplexedly contain upper-layer control information for each of the terminal devices and other terminal devices. The first radio resource is determined based on information specifying a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource specified by the PDSCH of the one signal. The first radio resource is used to transmit a first response signal indicating whether the reception of control information for the terminal device contained in the one signal was successful. The first radio resource is different from a second radio resource used to transmit a second response signal indicating whether the reception of control information for the other terminal device contained in the one signal was successful. The first wireless resource is used to send the first response signal.

2. The terminal device according to claim 1, wherein, The difference between the first radio resource and the predetermined reference radio resource is provided by a MAC (Media Access Control) subheader in the PDSCH of the signal for transmitting control information for the terminal device.

3. A base station apparatus, the base station apparatus having a communication unit, wherein, The communication unit is controlled to be such that... Based on a two-step random access process, predetermined messages are received from multiple terminal devices. In response to the predetermined message, a signal containing a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) is sent to the plurality of terminal devices. The physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) are multiplexed and contain upper-layer control information for each of the plurality of terminal devices. For the one signal, using information that specifies a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource by the PDSCH of the one signal, the first radio resource that should be sent as a response signal indicating whether the reception of the control information was successful is specified, i.e., a different first radio resource for each of the plurality of terminal devices. as well as In each of the first wireless resources designated for the plurality of terminal devices, the response signal is received from each of the plurality of terminal devices.

4. The base station apparatus according to claim 3, wherein, The communication unit uses information contained in the MAC (Media Access Control) subheader in the PDSCH of the signal for transmitting control information for each of the plurality of terminal devices to specify the difference between each of the first radio resources for each of the plurality of terminal devices and the predetermined reference radio resource.

5. The base station apparatus according to claim 3, wherein, If the communication unit receives the predetermined message from only one terminal device, it will not send the signal during a predetermined time period, but will wait for the predetermined message from other terminal devices.

6. The base station apparatus according to claim 3, wherein, When the communication unit receives a response signal from one of the plurality of terminal devices indicating a failure to receive the control information, it retransmits the signal containing the PDCCH and the PDSCH to that terminal device. The PDCCH and the PDSCH are multiplexed and contain upper-level control information for each of the plurality of terminal devices.

7. A control method, wherein the control method is executed by a terminal device, wherein, The control method includes: Based on a two-step random access procedure, a predetermined message is sent to the base station device; and Upon receiving a signal transmitted from the base station device in response to the predetermined message, namely a signal containing a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH), the PDCCH and PDSCH multiplexedly contain upper-layer control information for each of the terminal devices and other terminal devices. The first radio resource is determined based on information specifying a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource specified by the PDSCH of the one signal. The first radio resource is used to transmit a first response signal indicating whether the reception of control information for the terminal device contained in the one signal was successful. The first radio resource is different from a second radio resource used to transmit a second response signal indicating whether the reception of control information for the other terminal device contained in the one signal was successful. The first wireless resource is used to send the first response signal.

8. A control method, wherein the control method is executed by a base station device, wherein, The control method includes: Based on a two-step random access process, predetermined messages are received from multiple terminal devices. In response to the predetermined message, a signal containing a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) is sent to the plurality of terminal devices. The physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) are multiplexed and contain upper-layer control information for each of the plurality of terminal devices. For the one signal, using information that specifies a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource by the PDSCH of the one signal, the first radio resource that should be sent as a response signal indicating whether the reception of the control information was successful is specified, i.e., a different first radio resource for each of the plurality of terminal devices. as well as In each of the first radio resources designated for the plurality of terminal devices, the response signal is received from each of the plurality of terminal devices.

9. A storage medium storing a program, wherein, This program enables the computer on the terminal device to perform the following functions: Based on a two-step random access procedure, a predetermined message is sent to the base station device; and Upon receiving a signal transmitted from the base station device in response to the predetermined message, namely a signal containing a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH), the PDCCH and PDSCH multiplexedly contain upper-layer control information for each of the terminal devices and other terminal devices. The first radio resource is determined based on information specifying a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource specified by the PDSCH of the one signal. The first radio resource is used to transmit a first response signal indicating whether the reception of control information for the terminal device contained in the one signal was successful. The first radio resource is different from a second radio resource used to transmit a second response signal indicating whether the reception of control information for the other terminal device contained in the one signal was successful. The first wireless resource is used to send the first response signal.

10. A storage medium storing a program, wherein, This program enables the computer in the base station device to perform the following functions: Based on a two-step random access process, predetermined messages are received from multiple terminal devices. In response to the predetermined message, a signal containing a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) is sent to the plurality of terminal devices. The physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) are multiplexed and contain upper-layer control information for each of the plurality of terminal devices. For the one signal, using information that specifies a predetermined reference radio resource by the PDCCH of the one signal and the difference between the first radio resource and the predetermined reference radio resource by the PDSCH of the one signal, the first radio resource that should be sent as a response signal indicating whether the reception of the control information was successful is specified, i.e., a different first radio resource for each of the plurality of terminal devices. as well as In each of the first radio resources designated for the plurality of terminal devices, the response signal is received from each of the plurality of terminal devices.

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