A control device that selectively uses multiple antennas, a terminal device that communicates with the control device, a communication method, and a program.

Abstract

To efficiently establish a connection between a base station device and a terminal device in a system in which some of a large number of antennas is selected and used for communication between the base station device and the terminal device.SOLUTION: A control device that wirelessly communicates with a terminal device holds second identification information different from first identification information corresponding to the control device, and information of a random access preamble corresponding to the second identification information, and scrambles communication with the terminal device after receiving a random access preamble by using a scrambling sequence based on the second identification information at the time of receiving the random access preamble from the terminal device when the random access preamble corresponds to the second identification information.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a connection control technique in wireless communication. [Background technology]

[0002] A technology is being considered in which a large number of antennas are arranged at high density and some of the antennas are used to communicate with terminal devices. According to this technology, a cell is virtually formed for each terminal device by using a different antenna for each terminal device, and the terminal device is generally located at the center of the virtual cell (see Non-Patent Document 1). With this technology, the terminal device can obtain uniform communication quality regardless of its location. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] M. Karlsson et al., “Techniques for System Information Broadcast in Cell-Free Massive MIMO,” IEEE Transaction on Communication, January 2019. Summary of the Invention [Problem to be solved by the invention]

[0004] In a system in which antennas are densely arranged and at least one of them is selectively used as described above, there is no definition as to what procedure a terminal device should use to communicate with a base station device. Therefore, there is a demand for the establishment of a procedure for efficiently connecting a base station device and a terminal device. [Means for solving the problem]

[0005] The present invention provides a technology that enables efficient establishment of a connection between a base station device and a terminal device in a system in which a portion of a large number of antennas are selected and used for communication between the base station device and the terminal device.

[0006] A control device according to one aspect of the present invention comprises: , wirelessly A control device that communicates with a terminal device includes: a storage means for storing second identification information different from a first identification information corresponding to the control device and information on a random access preamble corresponding to the second identification information; and a control means for scrambling communication with the terminal device after reception of the random access preamble using a scrambling sequence based on the second identification information when the random access preamble corresponds to the second identification information upon receiving the random access preamble from the terminal device.

[0007] A terminal device according to another embodiment of the present invention has a communication means for transmitting a message including a random access preamble, including second identification information which is different from a first identification information corresponding to the control device and is stored in the control device in association with information of the random access preamble, and for transmitting the message including a random access preamble, the second identification information being used by a control device receiving the message to scramble communications with the terminal device, and for performing communications with the control device scrambled using the scrambling sequence identified by the second identification information after transmitting the message. Effect of the Invention

[0008] According to the present invention, in a system in which a portion of a large number of antennas are selected and used for communication between a base station device and a terminal device, it is possible to efficiently establish a connection between the base station device and a terminal device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device and a terminal device. [Diagram 3] FIG. 2 is a diagram illustrating an example of a functional configuration of a control device. [Figure 4] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. [Diagram 5] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. [Figure 6] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. [Figure 7] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] (System Configuration) Fig. 1 shows an example of the configuration of a wireless communication system according to this embodiment. As shown in Fig. 1, in the wireless communication system according to this embodiment, a large number of antennas are arranged in a planar manner with high density, and each of these antennas is connected to a control device 101 such as a base station device, for example, by using optical fibers or the like. The control device 101 connects to and communicates with a terminal device 102 via at least one antenna. Note that, in Fig. 1, only a small number of control devices 101 and terminal devices 102 are shown for the sake of simplicity of explanation, but there may naturally be more of these devices than are shown in Fig. 1.

[0012] In the following description, the antennas are assumed to be distributed and connected to the control device, but only the antennas may be densely arranged, or antenna units including RF processing functions such as RF (radio frequency) filters may be densely arranged. The control device 101 executes communication processing other than the processing performed on the antenna side. That is, baseband processing of received signals and subsequent signal processing in higher layers are performed by the control device 101. When constructing a system using a large number of antennas as shown in FIG. 1, it is assumed that multiple control devices 101 are connected to multiple antennas and transmit and receive signals, taking into account the computation load, etc. This system can be configured by applying a conventional Centralized Radio Access Network (C-RAN), and each antenna corresponds to a Transmission / Reception Point (TRP) of the C-RAN, and the control device 101 can correspond to a Baseband Unit (BBU) of the C-RAN.

[0013] The terminal device 102 connects to one of the control devices 101 via an antenna present in the vicinity and communicates with it. When a connection with the terminal device 102 is established, the control device 101 communicates with the terminal device 102 using at least a part of the antennas connected to the control device 101 itself. At this time, two or more control devices 101 can establish connections with the terminal device 102 in parallel and communicate with them. As a result, one or more control devices 101 form a virtual area (sometimes called a user-centric area) centered on the terminal device 102, and can provide high-quality and highly stable communication services regardless of the location of the terminal device 102.

[0014] In contrast, no consideration has been given to processing at the start of a connection in a system using such a large number of antennas. In a conventional cellular radio communication system such as LTE (Long Term Evolution), cell-specific scrambling corresponding to cell identification information (cell ID) is applied to a reference signal sequence and user data. This randomizes interference between cells, improving communication quality. In addition, in a conventional cellular radio communication system, terminal-specific scrambling may be further applied to a reference signal sequence and user data. By using such terminal-specific scrambling, when cooperative communication is performed between different cells corresponding to different cell IDs, interference is randomized and simultaneous transmission in cooperative communication is possible. On the other hand, in a system such as that shown in FIG. 1, when the conventional method is applied, it is assumed that cell-specific scrambling is applied in a random access process (hereinafter sometimes referred to as "RACH" or "RACH process") for establishing a connection, and after the connection is established, terminal-specific scrambling is set for a terminal device as necessary, and thereafter communication is performed by applying the terminal-specific scrambling. However, since two or more control devices 101 correspond to different cell IDs, when the terminal device 102 executes the RACH process, only the antenna connected to the control device 101 to which the terminal device 102 attempts to connect by the RACH process is used. As a result, the communication quality of the terminal device 102 during the RACH process cannot be sufficiently improved by using a large number of antennas, and the probability of the RACH process failing may increase. In addition, after the terminal device 102 connects to a specific control device 101 after the RACH process, high-quality communication cannot be provided to the terminal device 102 until a scrambling sequence specific to the terminal device 102 is shared between two or more control devices 101 that communicate with the terminal device 102. In this embodiment, in view of such a situation, a technique is provided that improves the method by which the terminal device 102 performs an initial connection with one or more control devices 101.

[0015] In this embodiment, the first control device determines whether or not the random access preamble received from the terminal device 102 (for example, in message A of the 2-step RACH or as message 1 of the 4-step RACH) is based on the setting notified from the own device to the terminal device. Then, if the random access preamble is based on the setting of the own device, the first control device performs communication thereafter using a first scrambling sequence corresponding to the first cell ID of the own device. On the other hand, if the random access preamble is not based on the setting notified from the own device to the terminal device, the first control device does not use the first scrambling sequence corresponding to the first cell ID in the subsequent communication, but uses a second scrambling sequence corresponding to the second cell ID.

[0016] The second cell ID may be, for example, the cell ID of a second control device adjacent to the first control device. With this, the first control device can communicate with the terminal device 102 that has transmitted a random access preamble to the second control device by using a scrambling sequence corresponding to the cell ID of the second control device. With this, the first control device and the second control device can cooperate to execute processing after the transmission of a response message to the random access preamble, and the reliability of the RACH processing can be improved. In addition, since the scrambling sequence corresponding to the second cell ID is used even after the RACH processing, it is not necessary to set a scrambling sequence specific to the terminal device 102 again. Therefore, it is possible to provide a high-quality wireless communication service to the terminal device 102 immediately after the connection is established.

[0017] The first control device may acquire and hold information on the cell ID in advance from a control device with which an adjacent relationship is established. For example, when the first control device receives a random access preamble, if the random access preamble is not based on the setting notified from the first control device to the terminal device, the first control device may transmit the random access preamble to the second control device in the adjacent relationship to inquire about the cell ID and acquire the second cell ID. If the received random access preamble is based on the setting notified from the first control device to the terminal device, the second control device may notify the second cell ID of the first control device. The control device may hold information on the cell ID for each of one or more second control devices in advance, and may transmit a random access preamble to acquire only a response as to whether or not the random access preamble is based on the setting notified from the second control device to which the inquiry is directed. In this case, the control device that has received the inquiry may notify the control device that originated the inquiry of an ACK as a response if the received random access preamble is based on the setting notified from the control device itself to the terminal device, and may notify the control device that originated the inquiry of an NACK as a response in other cases. In addition to ACK / NACK, information of a small number of bits, such as one bit, indicating whether the random access preamble is based on the setting notified from the control device to which the inquiry is made to the terminal device may be transmitted and received. In addition, the first control device may store, for each of one or more second control devices, a cell ID and setting information such as a seed for generating a sequence of a random access preamble (information that can identify a random access preamble) in association with each other. In this case, the first control device, for example, identifies which control device the received random access preamble is associated with by performing correlation detection using a sequence based on a seed associated with the second control device in addition to a sequence based on a seed associated with the first control device.Then, when the first control device detects a random access preamble based on a seed associated with a device other than the first control device, it identifies a cell ID stored in association with the seed, and in subsequent communications, uses a scrambling sequence corresponding to the identified cell ID.

[0018] Also, the terminal device 102 may transmit a virtual cell ID in a PUSCH (physical uplink shared channel) transmitted in addition to a random access preamble in a message A of a two-step RACH. In this case, the first control device may use this virtual cell ID as the above-mentioned second cell ID regardless of whether the random access preamble is addressed to the first control device. According to this, the control device that has received the message A uses a scrambling sequence based on this virtual cell ID as a scrambling sequence specific to the terminal device from the transmission of the message B after the reception of the message A, and it becomes possible for a plurality of control devices to transmit signals in cooperation. Note that the information notified from the terminal device may be any information capable of identifying a scrambling sequence, and may not be a virtual cell ID.

[0019] As described above, in this embodiment, multiple control devices can use a common scrambling sequence in response to the transmission of a random access preamble in RACH processing, thereby improving the wireless quality during RACH processing and enabling a high-quality communication environment to be quickly provided to a terminal device after a connection is established.

[0020] (Device configuration) Next, the configuration of the control device that executes the above-mentioned processing will be described. The terminal device may have a similar configuration. FIG. 2 shows an example of the hardware configuration of the control device. In one example, the control device has a processor 201, a ROM 202, a RAM 203, a storage device 204, and a communication circuit 205. In the control device, a computer-readable program that realizes each function of the control device as described above, which is recorded in, for example, the ROM 202, the RAM 203, or the storage device 204, is executed by the processor 201. The processor 201 may 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).

[0021] The control device controls the communication circuit 205 by, for example, the processor 201 to communicate with a counterpart device (for example, a terminal device, another control device, a higher-level node, etc.). Note that, although a schematic diagram of the control device having one communication circuit 205 is shown in Fig. 2, this is not limiting. For example, the control device may have a communication device for communication with a terminal device and a communication device for communication with other control devices and higher-level nodes.

[0022] 3 shows an example of the functional configuration of the control device. The control device includes, for example, a communication control unit 301, a scrambling sequence setting unit 302, an information acquisition unit 303, and an information notification unit 304. The communication control unit 301 controls communication with a terminal device. For example, the communication control unit 301 receives a random access preamble from the terminal device, and in response thereto, transmits a random access response (for example, in message B in a 2-step RACH or as message 2 in a 4-step RACH), thereby establishing a connection with the terminal device.

[0023] The scrambling sequence setting unit 302 sets the scrambling sequence to be used. For example, when the random access preamble is not based on the setting notified to the terminal device by the own device, the scrambling sequence setting unit 302 sets the communication control unit 301 to use a scrambling sequence based on a second cell ID different from the first cell ID of the own device. The second cell ID may be, for example, a cell ID of another control device in an adjacent relationship. Note that, when a virtual cell ID is included in the PUSCH in the message A from the terminal device, the scrambling sequence setting unit 302 sets the communication control unit 301 to use a scrambling sequence based on the virtual cell ID. Note that, when such a virtual cell ID is notified, the scrambling sequence setting unit 302 may set the communication control unit 301 to use a scrambling sequence based on the virtual cell ID, regardless of whether the random access preamble is based on the setting notified to the terminal device by the own device. On the other hand, when a virtual cell ID has not been notified and the random access preamble is not based on the setting notified to the terminal device by the own device, the scrambling sequence setting unit 302 can set the communication control unit 301 to use a scrambling sequence based on the cell ID of the own device.

[0024] The information acquisition unit 303 acquires the second cell ID described above. For example, the information acquisition unit 303 transmits an inquiry including a random access preamble to another control device in an adjacent relationship. Then, by receiving a response to the inquiry, the information acquisition unit 303 specifies whether the received random access preamble is based on the setting notified to the terminal device by the other control device. Then, when the received random access preamble is based on the setting notified to the terminal device by the other control device, the information acquisition unit 303 sets the cell ID of the other control device as the second cell ID. Note that the information acquisition unit 303 may acquire information indicating only whether the received random access preamble is based on the setting notified to the terminal device by the other control device from the other control device, or may acquire the cell ID of the other control device itself. When a similar inquiry is made from another control device, the information notification unit 304 notifies the other control device that originated the inquiry of information on whether the random access preamble included in the inquiry is based on the setting notified to the terminal device by the own device and the cell ID. In addition, the information acquisition unit 303 may, for example, store the seeds of random access preambles in association with cell IDs, identify which seed the received random access preamble corresponds to, and identify the cell ID associated with the identified seed as the second cell ID.

[0025] 4 shows an example of a functional configuration of a terminal device that transmits a message A of a two-step RACH including a virtual cell ID. The terminal device has, for example, a communication processing unit 401 and a cell ID notifying unit 402. The communication processing unit 401 establishes a connection with a control device and performs wireless communication. The cell ID notifying unit 402 transmits message A including a virtual cell ID in a PUSCH portion to a nearby control device. Note that the virtual cell ID is an example, and any information capable of identifying a scrambling sequence specific to the terminal device may be notified to the control device.

[0026] (Processing flow) Next, some examples of the flow of processes executed in the wireless communication system according to the present embodiment will be described. Note that the above-mentioned detailed content will not be repeated here, and only the outline of the flow of the processes will be described.

[0027] FIG. 5 shows a first example of the process flow. First, each control device transmits broadcast information including parameters to be used for transmitting a random access preamble to its own device (S501, S502). The parameters include, for example, seed information for generating a sequence of the random access preamble, and information on the time-frequency resource to which the random access preamble should be transmitted. Then, the terminal device transmits a random access preamble (for example, in message A of a 2-step RACH or as message 1 of a 4-step RACH) to the control device A based on the broadcast information A received from the control device A (S503). By receiving the random access preamble based on the broadcast information A from its own device, the control device A then scrambles communication with the terminal using a scrambling sequence based on the cell ID (cell ID-A) of its own device (S506). On the other hand, since the control device B has received a random access preamble based on the broadcast information A different from the broadcast information B from its own device, it attempts to acquire a cell ID, for example, by making an inquiry including a random access preamble to other control information in an adjacent relationship (S504). Then, the control device B acquires a cell ID (cell ID-A) from the control device A, which is the transmission source of the broadcast information A used when generating the random access preamble (S505). Note that the control device B can make a similar inquiry to other control devices, but since the random access preamble is not based on the broadcast information of its own device, the other control device does not notify the cell ID (not shown). Then, the control device B scrambles the communication with the terminal thereafter using a scrambling sequence based on the cell ID (cell ID-A) acquired in S505 (S506). In this method, by making an inquiry about the cell ID each time, it becomes possible to flexibly respond to changes in the adjacent relationship between the control devices.

[0028] The control device may store information on the random access preamble (for example, the sequence of the random access preamble itself or a seed for generating the sequence) associated with the cell ID in the device itself, and identify the cell ID based on the received random access preamble. An example of the process flow in this case is shown in FIG. 6. In FIG. 6, the control device B executes a process of identifying the cell ID corresponding to the received random access preamble from the information stored in the device itself (S601), instead of S504 and S505 in FIG. 5. This method makes it unnecessary to make an inquiry, and therefore the processing time can be shortened.

[0029] Alternatively, the terminal device may transmit a message A of the two-step RACH including a virtual cell ID to be used for generating a scrambling sequence, and the control device may perform communication using a scrambling sequence based on the virtual cell ID. An example of the flow of this process is shown in FIG. 7. In FIG. 7, the terminal device transmits a message A including a random access preamble based on the broadcast information A from the control device A and a PUSCH including a cell ID-C as a virtual cell ID (S701). Then, the control device A detects the random access preamble based on the parameters transmitted by the control device in the broadcast information A, and acquires the cell ID-C from the subsequent PUSCH. Also, the control device B acquires information similar to that notified by the broadcast information A, for example, by acquiring seed information for generating a preamble sequence of a random access preamble used in another control device that is adjacent to the control device B in advance, as shown in FIG. 6. Then, the control device B detects the random access preamble in the same manner as the control device A, and acquires the cell ID-C from the subsequent PUSCH. Thereafter, the control device A and the control device B perform subsequent communication using the scrambling sequence based on the notified cell ID-C (S702).

[0030] According to the above-mentioned process examples, a plurality of control devices can use a common scrambling sequence in response to the transmission of the random access preamble of the RACH process, which improves the wireless quality during the RACH process and quickly provides a high-quality communication environment to the terminal device after the connection is established.

[0031] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

Claims

1. A control device that wirelessly communicates with a terminal device, A storage means for storing second identification information different from the first identification information corresponding to the control device and information on a random access preamble corresponding to the second identification information; A control means for scrambling communication with the terminal device after reception of the random access preamble using a scrambling sequence based on the second identification information when the random access preamble corresponds to the second identification information when the random access preamble is received from the terminal device; A control device comprising:

2. A terminal device, A terminal device characterized in that the terminal device has a communication means for transmitting a message including a random access preamble, the second identification information being different from a first identification information corresponding to the control device and being stored in the control device in association with information of the random access preamble, the second identification information being used by a control device that receives the message to scramble communications with the terminal device, and after transmitting the message, performing communications with the control device that are scrambled using the scrambling sequence identified by the second identification information.

3. A communication method performed by a control device that wirelessly communicates with a terminal device, comprising: Holding second identification information different from first identification information corresponding to the control device and information of a random access preamble corresponding to the second identification information; When receiving a random access preamble from the terminal device, if the random access preamble corresponds to the second identification information, scrambling communication with the terminal device after receiving the random access preamble using a scrambling sequence based on the second identification information; A communication method comprising:

4. A communication method performed by a terminal device, comprising: A communication method comprising: transmitting a message including a random access preamble, the message including the random access preamble including second identification information, the second identification information being different from first identification information corresponding to the control device and being stored in the control device in association with information of the random access preamble, for identifying a scrambling sequence to be used by a control device that has received the message to scramble communications with the terminal device; and, after transmitting the message, performing communications with the control device scrambled using the scrambling sequence identified by the second identification information.

5. A computer provided in a control device that wirelessly communicates with a terminal device, storing second identification information different from the first identification information corresponding to the control device and information of a random access preamble corresponding to the second identification information; When receiving a random access preamble from the terminal device, if the random access preamble corresponds to the second identification information, scrambling communication with the terminal device after reception of the random access preamble using a scrambling sequence based on the second identification information. Program for.

6. A program for causing a computer provided in a terminal device to transmit a message including a random access preamble, including second identification information which is different from first identification information corresponding to the control device and is stored in the control device in association with information of the random access preamble, and for causing a communication between the control device and the message-containing ...

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