Patent Description:
A radio access system and a wireless network (hereinafter, also called "Long Term Evolution (LTE)", "LTE-Advanced (LTE-A)", "LTE-Advanced Pro (LTE-A Pro)", "New Radio (NR)", "New Radio Access Technology (NRAT)", "Evolved Universal Terrestrial Radio Access (EUTRA)", or "Further EUTRA (FEUTRA)") for cellular mobile communication have been examined in the 3rd Generation Partnership Project (3GPP). Note that, in the following description, LTE includes LTE-A, LTE-A Pro, and EUTRA, and NR includes 5th generation mobile wireless communication (<NUM>), NRAT, and FEUTRA. In LTE and NR, a base station device (base station) is also called evolved NodeB (eNodeB), and a terminal device (a mobile station, a mobile station device, and a terminal) is also called User Equipment (UE). LTE and NR are cellular communication systems in which a plurality of areas covered by base station devices are arranged in a cell shape. A single base station device may manage a plurality of cells.

NR is Radio Access Technology (RAT), which is different from LTE, as a next-generation radio access system for LTE. NR is access technology that can support various use cases including Enhanced mobile broadband (eMBB), Massive machine type communications (mMTC), and Ultra reliable and low latency communications (URLLC). NR has been examined aiming at a technical framework that corresponds to use scenarios, requirements, and arrangement scenarios in those use cases.

As one of technologies examined in NR, there is transmission equalization technology. Typical equalization technology enables a reception terminal to perform reception equalization by adding a reference signal for channel estimation to a data signal and transmitting the data signal. On the other hand, transmission equalization is technology that eliminates the need for the reception equalization by performing transmission equalization processing for compensating for variations in amplitude and/or phase received from a communication channel in advance in transmission processing. Details of the technology for the transmission equalization are disclosed in, for example, the following Patent Literature <NUM>.

However, the technology proposed in the above Patent Literature <NUM> has been just developed, and it is hard to say that the technology sufficiently satisfies the improvement of transmission efficiency of the entire system required in NR.

Accordingly, the present disclosure proposes a mechanism capable of further improving transmission efficiency of an entire system.

According to the present disclosure, there is provided a communication device, a communication method, and a recording medium according to the appended claims.

Hereinafter, preferred examples will be described in detail with reference to the accompanying drawings. Note that, in the present specification and the drawings, redundant description of components having substantially the same functional configuration is omitted by assigning the same reference numerals.

Note that the description will be given in the following order.

Equalization is to multiply a signal whose amplitude and/or phase is changed by a communication channel, for example, by an inverse matrix of the channel and return the signal to an original signal. Hereinafter, reception equalization and transmission equalization will be described with reference to <FIG> and <FIG>.

<FIG> is a diagram for explaining the reception equalization. As illustrated in <FIG>, when a transmitter transmits a transmission signal s, and the transmission signal propagates through a communication channel H and is received by a receiver, the reception signal becomes Hs. In a case of the reception equalization in which the equalization is performed by the receiver, the receiver estimates an inverse matrix H-<NUM> of the communication channel H, multiplies the reception signal Hs by the inverse matrix H-<NUM>, and decodes the transmission signal s.

<FIG> is a diagram for explaining the transmission equalization. As illustrated in <FIG>, the transmitter transmits a transmission signal H-<NUM>s obtained by multiplying the signal s by the inverse matrix H-<NUM> of the communication channel H estimated in advance. When the transmission signal H-<NUM>s propagates through the communication channel H and is received by the receiver, the reception signal becomes s. As described above, the equalization is performed on the transmitter side in advance, so that it is possible to decode the signal s without performing the equalization on the receiver side.

A reference signal is used in the estimation of the communication channel performed in the equalization. The communication channel is estimated on the basis of a reception result of the reference signal, and the equalization is performed on the basis of the estimated communication channel.

Here, if the transmission equalization is performed, it is considered that it is unnecessary to transmit the reference signal from the transmitter to the receiver because the reception side does not need to perform the reception equalization. Further, if there is a small change in the channel after performing the channel estimation based on the reference signal on the reception side even though the transmission equalization is not performed, the reception equalization may be performed by diverting a past channel estimation result. Even in that case, it is considered that it is unnecessary to transmit the reference signal again and estimate the channel again. In addition, it is considered that there are cases where the transmission of the reference signal can be omitted.

Therefore, the present disclosure proposes a mechanism capable of switching transmission/non-transmission of the reference signal. As a result, the transmission of the reference signal is omitted when the reference signal is not always necessary to decode the transmission signal, so that transmission efficiency of an entire system can be improved.

<FIG> is a diagram illustrating an overall configuration of a communication system. As illustrated in <FIG>, a communication system <NUM> includes a base station <NUM>, a plurality of terminal devices <NUM>, a core network <NUM>, and a packet data network (PDN) <NUM>.

The base station <NUM> is a communication device that operates a cell <NUM> and provides wireless communication services to one or more terminal devices <NUM> located inside the cell <NUM>. The cell <NUM> is operated according to any wireless communication system such as LTE or NR. The base station <NUM> is connected to the core network <NUM>. The core network <NUM> is connected to the packet data network (PDN) <NUM> via a gateway device (not illustrated).

The core network <NUM> can include a mobility management entity (MME), a serving gateway (S-GW), a PDN gateway (P-GW), a policy and charging rule function (PCRF), and a home subscriber server (HSS). Alternatively, the core network <NUM> can include entities of NR having similar functions. The MME is a control node that handles signals of a control plane, and manages a movement state of the terminal device. The S-GW is a control node that handles signals of a user plane, and is a gateway device that switches a transfer path of user data. The P-GW is a control node that handles signals of the user plane, and is a gateway device that functions as a connection point between the core network <NUM> and the PDN <NUM>. The PCRF is a control node that controls policies such as Quality of Service (QoS) for bearers and billing. The HSS is a control node that handles subscriber data and controls services.

The terminal device <NUM> is a communication device that performs wireless communication on the basis of the control of the base station <NUM>. The terminal device <NUM> can perform wireless communication with the base station <NUM>. A communication link in a direction from the base station <NUM> to the terminal device <NUM> is also called a downlink, and the terminal device <NUM> receives a downlink signal from the base station <NUM>. A communication link in a direction from the terminal device <NUM> to the base station <NUM> is also called an uplink, and the terminal device <NUM> transmits an uplink signal to the base station <NUM>. Further, the terminal device <NUM> can perform wireless communication with another terminal device <NUM>. A communication link between the terminal devices <NUM> is also called a sidelink, and the terminal device <NUM> transmits and receives a sidelink signal to and from another terminal device <NUM>.

Here, each device included in the communication system <NUM> can function as a first communication device <NUM>, a second communication device <NUM>, or a communication control device <NUM>, which will be described in detail later with reference to <FIG>.

The first communication device <NUM> is a communication device that switches whether or not to transmit a reference signal and transmits the reference signal according to a switching result. Hereinafter, the reference signal transmitted by the first communication device <NUM> may also be called a first reference signal. The second communication device <NUM> is a communication device that receives the first reference signal transmitted from the first communication device <NUM>. However, the second communication device <NUM> can also transmit the reference signal. Hereinafter, the reference signal transmitted by the second communication device <NUM> may also be called a second reference signal. The second reference signal can be used to determine switching of transmission/non-transmission of the first reference signal. The communication control device <NUM> is a device that performs setting related to switching of transmission/non-transmission of the reference signal by the first communication device <NUM>.

In uplink communication and downlink communication, one of the base station <NUM> and the terminal device <NUM> functions as the first communication device <NUM>, and the other functions as the second communication device <NUM>. The device that functions as the communication control device <NUM> in the uplink communication and the downlink communication is typically the base station <NUM>. In addition, for example, any entity within the core network <NUM> may function as the communication control device <NUM>.

In sidelink communication, one of the terminal devices <NUM> that perform the sidelink communication functions as the first communication device <NUM>, and the other functions as the second communication device <NUM>. The device that functions as the communication control device <NUM> in the sidelink communication is typically the base station <NUM> or the terminal device <NUM>. In addition, for example, any entity within the core network <NUM> may function as the communication control device <NUM>.

Note that the device that functions as the first communication device <NUM> and the device that functions as the second communication device <NUM> can be appropriately switched. For example, at a first time, the base station <NUM> may function as the first communication device <NUM>, and the terminal device <NUM> may function as the second communication device <NUM>. Then, at a second time, the terminal device <NUM> may function as the first communication device <NUM>, and the base station <NUM> may function as the second communication device <NUM>.

<FIG> is a block diagram illustrating an example of a configuration of the first communication device <NUM>. Referring to <FIG>, the first communication device <NUM> includes an antenna unit <NUM>, a wireless communication unit <NUM>, a storage unit <NUM>, and a control unit <NUM>.

The antenna unit <NUM> radiates a signal output by the wireless communication unit <NUM> into a space as a radio wave. Further, the antenna unit <NUM> converts the radio wave in the space into a signal and outputs the signal to the wireless communication unit <NUM>.

The wireless communication unit <NUM> transmits and receives a signal. For example, the wireless communication unit <NUM> transmits a signal to the second communication device <NUM> and receives a signal from the second communication device <NUM>.

The storage unit <NUM> temporarily or permanently stores programs and a variety of data for the operation of the first communication device <NUM>.

The control unit <NUM> controls the operation of the entire first communication device <NUM> and provides various functions of the first communication device <NUM>. The control unit <NUM> includes a notification unit <NUM> and a communication control unit <NUM>. The notification unit <NUM> has a function of notifying the communication control device <NUM> of information regarding switching of transmission/non-transmission of the reference signal of the first communication device <NUM>. The communication control unit <NUM> has a function of controlling communication processing by the first communication device <NUM>. In particular, the communication control unit <NUM> switches transmission/non-transmission of the reference signal according to the control by the communication control device <NUM>. Note that the control unit <NUM> can also include components other than these components. That is, the control unit <NUM> can also exhibit functions other than the functions of these components.

The first communication device <NUM> can further include a network communication unit for communicating with the communication control device <NUM>. For example, when the base station <NUM> functions as the first communication device <NUM> and the communication control device <NUM>, the network communication unit performs communication within the base station <NUM>. As another example, when the base station <NUM> functions as the communication control device <NUM> and the terminal device <NUM> functions as the first communication device <NUM>, a function as the network communication unit is realized by the wireless communication unit <NUM>.

<FIG> is a block diagram illustrating an example of a configuration of the second communication device <NUM>. Referring to <FIG>, the second communication device <NUM> includes an antenna unit <NUM>, a wireless communication unit <NUM>, a storage unit <NUM>, and a control unit <NUM>.

The wireless communication unit <NUM> transmits and receives a signal. For example, the wireless communication unit <NUM> transmits a signal to the first communication device <NUM> and receives a signal from the first communication device <NUM>.

The storage unit <NUM> temporarily or permanently stores programs and a variety of data for the operation of the second communication device <NUM>.

The control unit <NUM> controls the operation of the entire second communication device <NUM> and provides various functions of the second communication device <NUM>. The control unit <NUM> includes a communication control unit <NUM>. The communication control unit <NUM> has a function of controlling communication processing by the second communication device <NUM>. In particular, the communication control unit <NUM> performs reception processing according to switching of transmission/non-transmission of the reference signal by the first communication device <NUM>. Note that the control unit <NUM> can also include components other than these components. That is, the control unit <NUM> can also exhibit functions other than the functions of these components.

<FIG> is a block diagram illustrating an example of a configuration of the communication control device <NUM>. Referring to <FIG>, the communication control device <NUM> includes a communication unit <NUM>, a storage unit <NUM>, and a control unit <NUM>.

The communication unit <NUM> transmits and receives a signal. For example, the communication unit <NUM> transmits a signal to the first communication device <NUM> and receives a signal from the first communication device <NUM>.

The storage unit <NUM> temporarily or permanently stores programs and a variety of data for the operation of the communication control device <NUM>.

The control unit <NUM> controls an operation of the entire communication control device <NUM> and provides various functions of the communication control device <NUM>. The control unit <NUM> includes a notification unit <NUM>. The notification unit <NUM> has a function of notifying the first communication device <NUM> under control of a variety of information. In particular, the notification unit <NUM> notifies the first communication device <NUM> of setting information regarding switching of transmission/non-transmission of the reference signal. Note that the control unit <NUM> can also include components other than these components. That is, the control unit <NUM> can also exhibit functions other than the functions of these components.

The first communication device <NUM> (for example, the notification unit <NUM>) transmits capability information regarding switching whether or not to transmit the first reference signal using a scheduled resource scheduled to be used to transmit the reference signal to the communication control device <NUM>. The capability information includes at least information indicating whether or not the first communication device <NUM> can switch transmission/non-transmission of the first reference signal. Further, the capability information can include type information of a channel where the first communication device <NUM> can switch transmission/non-transmission of the first reference signal and identification information of the scheduled resource.

The scheduled resource is a resource secured in advance for transmitting the reference signal. For example, as the scheduled resource, a plurality of resource elements are secured in a unit resource including a predetermined frequency resource (for example, a resource block) and a predetermined time resource (for example, a slot or a subframe).

The first communication device <NUM> (for example, the communication control unit <NUM>) switches whether or not to transmit the first reference signal using the scheduled resource scheduled to be used to transmit the first reference signal. That is, the first communication device <NUM> switches between transmitting a signal including the first reference signal in the scheduled resource and transmitting a signal not including the first reference signal in the scheduled resource. The switching of transmission/non-transmission of the first reference signal may be performed for a plurality of scheduled resources (for example, for each unit resource). For example, the first communication device <NUM> may switch between transmitting the first reference signal in all scheduled resources included in the unit resource and not transmitting the first reference signal in at least a part of the scheduled resources included in the unit resource. When the first communication device <NUM> communicates with the plurality of second communication devices <NUM>, the switching may be performed for each of the second communication devices <NUM>.

The first communication device <NUM> measures the second reference signal transmitted from the second communication device <NUM>, estimates a communication channel between the first communication device <NUM> and the second communication device <NUM>, and acquires channel information. The first communication device <NUM> performs the reception equalization on the basis of the acquired channel information. Further, the first communication device <NUM> can perform the transmission equalization on the basis of the acquired channel information.

Typically, the first communication device <NUM> performs the transmission equalization in a case of not transmitting the first reference signal in the scheduled resource. For the transmission equalization, the channel information acquired on the basis of the second reference signal transmitted from the second communication device <NUM> is used. When the transmission equalization is performed, the second communication device <NUM> can decode the transmission signal without performing the reception equalization. The first communication device <NUM> may not perform the transmission equalization even in a case of not transmitting the first reference signal in the scheduled resource. In that case, in the second communication device <NUM>, the reception equalization is performed on the basis of the channel information obtained from the first reference signal previously transmitted from the first communication device <NUM>.

The first communication device <NUM> may perform zero power transmission in a scheduled resource in which the first reference signal is not transmitted. In this case, it is possible to suppress a power consumption amount. Further, the first communication device <NUM> may use the scheduled resource in which the first reference signal is not transmitted as another transmission channel. In this case, it is possible to improve frequency efficiency.

The second communication device <NUM> (for example, the communication control unit <NUM>) transmits the second reference signal using the scheduled resource scheduled to be used to transmit the reference signal. That is, the second communication device <NUM> transmits a signal including the second reference signal in the scheduled resource. As a result, the first communication device <NUM> can acquire channel information.

The second communication device <NUM> (for example, the communication control unit <NUM>) performs reception processing according to whether or not the first reference signal has been transmitted in the scheduled resource. For example, the second communication device <NUM> determines whether or not the first reference signal has been transmitted in the scheduled resource. When the first reference signal is transmitted in the scheduled resource, the second communication device <NUM> performs the reception equalization on the basis of the channel information obtained from the first reference signal. On the other hand, when it is determined that the first reference signal is not transmitted in the scheduled resource, the second communication device <NUM> determines whether or not the transmission equalization is completed. Then, when the transmission equalization is completed, the second communication device <NUM> simply treats the received signal as a decoded transmission signal. On the other hand, when the transmission equalization is not completed, the reception equalization is performed on the basis of the channel information obtained from the first reference signal transmitted previously.

When the reception equalization is performed, the second communication device <NUM> selects which first reference signal is used for the reception equalization. Typically, the second communication device <NUM> uses the first reference signal received more recently. This is because it is assumed that the channel change is smaller than others.

The second communication device <NUM> acquires information for reception processing from the first communication device <NUM> or the communication control device <NUM>. The information for the reception processing may be, for example, information indicating whether or not the first reference signal has been transmitted in the scheduled resource, and information indicating whether or not the transmission equalization is performed when the first reference signal is not transmitted in the scheduled resource. In addition, the information for the reception processing may be, for example, information for determining whether or not the first reference signal has been transmitted in the scheduled resource, and information for determining whether or not the transmission equalization is performed when the first reference signal is not transmitted in the scheduled resource. Specifically, the information for the reception processing may be setting information described later. The setting information can be notified directly from the communication control device <NUM> or indirectly via the first communication device <NUM>.

The transmission of the first reference signal using the scheduled resource is not performed in communication in a first direction, and the transmission of the second reference signal using the scheduled resource may be performed in communication in a second direction facing the first direction. The first direction and the second direction are a downlink and an uplink, an uplink and a downlink, or a sidelink and a sidelink, respectively. For example, the second reference signal may be transmitted on the downlink, and transmission/non-transmission of the first reference signal may be switched on the uplink. As another example, the second reference signal may be transmitted on the uplink, and the transmission/non-transmission of the first reference signal may be switched on the downlink. As another example, the second reference signal may be transmitted in the first direction of the sidelink, and the transmission/non-transmission of the first reference signal may be switched in the second direction of the sidelink. Note that scheduled resources of the downlink, the uplink, or the sidelink can be determined by a TDD configuration or a slot format indicator.

The transmission of the reference signal using the scheduled resource in resources for a first use is not performed, and the transmission of the reference signal using the scheduled resource in resources for a second use different from the first use may be performed. The resources for the first use and the resources for the second use are resources for control and resources for data, or resources for data and resources for control, respectively. For example, the second reference signal may be transmitted in the resource for the control, and transmission/non-transmission of the first reference signal may be switched in the resource for the data. As another example, the second reference signal may be transmitted in the resource for the data, and transmission/non-transmission of the first reference signal may be switched in the resource for the control. As a specific example, the second communication device <NUM> transmits a data signal including the second reference signal using the resource for the data, and the first communication device <NUM> switches whether or not to include the first reference signal in a reception response (ACK/NACK) to the data signal. Examples of the resource for the control include a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), and a physical sidelink control channel (PSCCH). Examples of the resource for the data include a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), and a physical sidelink shared channel (PSSCH).

The reference signal is a demodulation reference signal (DM-RS), a phase-tracking reference signal (PT-RS), a sounding reference signal (SRS), or a channel state information reference signal (CSI-RS).

The communication control device <NUM> notifies the first communication device <NUM> of setting information for controlling whether or not to transmit the first reference signal using the scheduled resource in the first communication device <NUM>. The communication control device <NUM> generates the setting information by referring to the capability information of the first communication device <NUM>.

For notification of the setting information, for example, system information, RRC signaling, MAC control element (CE), or downlink control information (DCI) can be used.

The setting information may include an explicit switching instruction as to whether or not the first communication device <NUM> transmits the first reference signal using the scheduled resource. In that case, the first communication device <NUM> switches transmission/non-transmission of the first reference signal according to the explicit switching instruction in the setting information. The setting information regarding the explicit switching instruction will be described below.

The setting information can include information indicating whether or not to transmit the first reference signal using the scheduled resource. The first communication device <NUM> switches transmission/non-transmission of the first reference signal as instructed.

The setting information can include information indicating types of channels instructed not to be used to transmit the first reference signal. The first communication device <NUM> does not transmit the first reference signal using the scheduled resource in the instructed types of channels. For example, PDSCH, PDCCH, PUSCH, PUCCH, PSSCH, and PSCCH can be instructed not to be used to transmit the first reference signal.

The setting information can include identification information of the scheduled resource instructed not to be used to transmit the first reference signal. The first communication device <NUM> does not transmit the first reference signal in the instructed scheduled resource. For example, the identification information may be a subcarrier index, a symbol index, or a slot index.

The setting information may include an implied switching instruction as to whether or not the first communication device <NUM> transmits the first reference signal using the scheduled resource. In that case, the first communication device <NUM> switches transmission/non-transmission of the first reference signal on the basis of the implied instruction in the setting information. The setting information regarding the implied switching instruction will be described below.

The setting information can include information indicating a criterion for switching whether or not to transmit the first reference signal using the scheduled resource. The first communication device <NUM> performs condition determination on the basis of the notified setting information and switches transmission/non-transmission of the first reference signal according to a determination result. The information notified as the setting information and the details of the switching based on the condition determination will be described in detail in a next section.

The first communication device <NUM> switches whether or not to transmit the first reference signal using the scheduled resource, on the basis of the setting information including the implied switching instruction notified from the communication control device <NUM>.

In particular, the first communication device <NUM> (for example, the communication control unit <NUM>) switches whether or not to transmit the first reference signal using the scheduled resource, on the basis of the channel information acquired in advance. Here, the channel information is information indicating characteristics of the communication channel between the first communication device <NUM> and the second communication device <NUM>. For example, the first communication device <NUM> does not transmit the first reference signal when the channel information is acquired in advance and transmission equalization based on the channel information is possible, and transmits the first reference signal otherwise. As another example, the first communication device <NUM> does not transmit the first reference signal when the channel information is acquired in advance by the second communication device <NUM> and reception equalization based on the channel information is possible, and transmits the first reference signal otherwise. In any case, the second communication device <NUM> can obtain an equalized transmission signal.

An example of the switching criterion will be described below. Note that a plurality of switching criteria may be used in combination.

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of an elapsed time from receiving the second reference signal from the second communication device <NUM> to be a communication partner. Specifically, the first communication device <NUM> acquires channel information in advance on the basis of the second reference signal. Then, the first communication device <NUM> transmits a transmission equalization completed signal without including the first reference signal until the elapsed time exceeds a predetermined threshold value. In this case, the first communication device <NUM> may perform transmission equalization using the channel information acquired in advance. When an elapsed time from the channel estimation based on the second reference signal is short, it is assumed that there is a small change in the channel, so that it is possible to perform the transmission equalization by diverting the channel information acquired in advance. On the other hand, when the elapsed time exceeds the predetermined threshold value, the first communication device <NUM> transmits a signal including the first reference signal.

As an example, on the basis of an elapsed time until the reception response (ACK/NACK) of the signal including the second reference signal is transmitted, the first communication device <NUM> may switch whether or not to include the first reference signal in the reception response. Specifically, the first communication device <NUM> acquires channel information on the basis of the second reference signal. Then, the first communication device <NUM> performs transmission equalization of the reception response using the channel information acquired in advance until the elapsed time exceeds a predetermined threshold value, and transmits a transmission equalization completed reception response without including the first reference signal. On the other hand, when the elapsed time exceeds the predetermined threshold value, the first communication device <NUM> transmits the reception response including the first reference signal. The predetermined threshold value may be, for example, an N slot, an M symbol, or a reception response in the same slot as the received signal.

As the setting information, for example, a predetermined threshold value related to the elapsed time until the reception response can be notified.

An example of a flow of switching processing based on the reception response time will be described with reference to <FIG> and <FIG>.

<FIG> is a sequence diagram illustrating an example of a flow of switching processing of transmission/non-transmission of the first reference signal executed in the communication system <NUM>. In the present sequence, the base station <NUM> and the terminal device <NUM> are involved. In the present sequence, the base station <NUM> functions as the second communication device <NUM> and the communication control device <NUM>, and the terminal device <NUM> functions as the first communication device <NUM>.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S100). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S102). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including a predetermined threshold value related to an elapsed time until a reception response (step S104). Next, when a packet is generated in the base station <NUM> (step S106), the base station <NUM> notifies the terminal device <NUM> of DCI (step S108). Note that the above setting information may be included in the DCI and notified. Next, the base station <NUM> transmits a data signal including a reference signal A to the terminal device <NUM> (step S110). Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S112).

After that, the terminal device <NUM> determines whether or not to include a reference signal B in the reception response to the data signal (step S114). The determination is performed on the basis of whether or not an elapsed time from the reception of the data signal to the transmission of the reception response exceeds the predetermined threshold value notified in the setting information. When it is determined that the reference signal B is not included (step S114/NO), the terminal device <NUM> performs transmission equalization using the reference signal A (step S116), and transmits a transmission equalized reception response that does not include the reference signal B (step S118). On the other hand, when it is determined that the reference signal B is included (step S114/YES), the terminal device <NUM> transmits a reception response including the reference signal B (step S120). Then, the base station <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S122).

<FIG> is a sequence diagram illustrating an example of a flow of switching processing of transmission/non-transmission of the first reference signal executed in the communication system <NUM>. In the present sequence, the base station <NUM> and the terminal device <NUM> are involved. In the present sequence, the base station <NUM> functions as the first communication device <NUM> and the communication control device <NUM>, and the terminal device <NUM> functions as the second communication device <NUM>.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S130). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S132). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including a predetermined threshold value related to an elapsed time until a reception response (step S134). Next, when a packet is generated in the terminal device <NUM> (step S136), the terminal device <NUM> notifies the base station <NUM> of a scheduling request (SR) (step S138). Next, the base station <NUM> performs scheduling and notifies the terminal device <NUM> of DCI (step S140). Next, the terminal device <NUM> transmits a data signal including the reference signal A to the base station <NUM> (step S142). Next, the base station <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S144).

After that, the base station <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S146). The determination is performed on the basis of whether or not an elapsed time from the reception of the data signal to the transmission of the reception response exceeds the predetermined threshold value notified in the setting information. When it is determined that the reference signal B is not included (step S146/NO), the base station <NUM> performs transmission equalization using the reference signal A (step S148), and transmits a transmission equalized reception response that does not include the reference signal B (step S150). On the other hand, when it is determined that the reference signal B is included (step S146/YES), the base station <NUM> transmits a reception response including the reference signal B (step S152). Then, the terminal device <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S154).

Note that, in steps S150 and S152, DCI for retransmission may be transmitted instead of the reception response (ACK/NACK).

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of the number of symbols included in the slot. For example, when the number of symbols included in one slot is larger than a predetermined threshold value, the first communication device <NUM> transmits the first reference signal using the scheduled resource. On the other hand, when the number of symbols included in one slot is small, the first communication device <NUM> does not transmit the first reference signal using the scheduled resource. In this case, the first communication device <NUM> may perform transmission equalization using the channel information acquired in advance. When the number of symbols per slot is small, it is assumed that an elapsed time from the channel estimation based on the second reference signal to the transmission of the response is short. Therefore, since it is assumed that there is a small change in the channel, it is possible to perform the transmission equalization by diverting the channel information acquired in advance.

As the setting information, for example, the number of symbols included in the slot can be notified. As another example, as the setting information, a predetermined threshold value related to the number of symbols included in the slot can be notified.

An example of a flow of switching processing based on the number of symbols included in the slot will be described with reference to <FIG> and <FIG>.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S160). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S162). Next, the base station <NUM> notifies the terminal device <NUM> of the setting information including the number of symbols included in the slot (step S164). Next, when a packet is generated in the base station <NUM> (step S166), the base station <NUM> notifies the terminal device <NUM> of DCI (step S168). Note that the above setting information may be included in the DCI and notified. Next, the base station <NUM> transmits a data signal including the reference signal A to the terminal device <NUM> (step S170). Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S172).

After that, the terminal device <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S174). The determination is performed on the basis of whether or not the number of symbols included in the slot notified in the setting information exceeds a predetermined threshold value. When it is determined that the reference signal B is not included (step S174/NO), the terminal device <NUM> performs transmission equalization using the reference signal A (step S176), and transmits a transmission equalized reception response that does not include the reference signal B (step S178). On the other hand, when it is determined that the reference signal B is included (step S174/YES), the terminal device <NUM> transmits a reception response including the reference signal B (step S180). Then, the base station <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S182).

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S190). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S192). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including the number of symbols included in the slot (step S194). Next, when a packet is generated in the terminal device <NUM> (step S196), the terminal device <NUM> notifies the base station <NUM> of a scheduling request (SR) (step S198). Next, the base station <NUM> performs scheduling and notifies the terminal device <NUM> of DCI (step S200). Next, the terminal device <NUM> transmits a data signal including the reference signal A to the base station <NUM> (step S202). Next, the base station <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S204).

After that, the base station <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S206). The determination is performed on the basis of whether or not the number of symbols included in the slot notified in the setting information exceeds a predetermined threshold value. When it is determined that the reference signal B is not included (step S206/NO), the base station <NUM> performs transmission equalization using the reference signal A (step S208), and transmits a transmission equalized reception response that does not include the reference signal B (step S210). On the other hand, when it is determined that the reference signal B is included (step S206/YES), the base station <NUM> transmits a reception response including the reference signal B (step S212). Then, the terminal device <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S214).

Note that, in steps S210 and S212, DCI for retransmission may be transmitted instead of the reception response (ACK/NACK).

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of whether or not a predetermined timer has expired or whether or not a time is within a predetermined time interval. Specifically, the first communication device <NUM> does not transmit the first reference signal using the scheduled resource until the predetermined timer expires or when the time is within the predetermined time interval. On the other hand, when the predetermined timer expires or the time exceeds the predetermined time interval, the first communication device <NUM> transmits the first reference signal using the scheduled resource. When the elapsed time from the transmission of the first reference signal is short, it is assumed that there is a small change in the channel, so that it is possible to perform reception equalization and transmission equalization by diverting the first reference signal transmitted once.

Start timing of the timer or the time interval is arbitrary. As an example, the start timing may be timing at which the first reference signal has been transmitted using the scheduled resource. Specifically, the first communication device <NUM> does not transmit the first reference signal using the scheduled resource, until a predetermined time elapses after transmitting the first reference signal using the scheduled resource. Then, after the predetermined time has elapsed, the first communication device <NUM> transmits the first reference signal again using the scheduled resource. As another example, the start timing of the timer or the time interval may be timing at which the first reference signal has been received by the second communication device <NUM>, or may be a boundary of slots.

As the setting information, for example, the length of the timer or the time interval, the start timing, and the like can be notified.

An example of a flow of switching processing based on the timer or the time interval will be described with reference to <FIG>.

<FIG> are sequence diagrams illustrating an example of a flow of switching processing of transmission/non-transmission of the first reference signal executed in the communication system <NUM>. In the present sequence, the base station <NUM> and the terminal device <NUM> are involved. In the present sequence, the base station <NUM> functions as the communication control device <NUM>. Further, the base station <NUM> and the terminal device <NUM> function as the first communication device <NUM> and the second communication device <NUM>, respectively.

Specifically, when one of the base station <NUM> and the terminal device <NUM> transmits the first reference signal, both the base station <NUM> and the terminal device <NUM> do not transmit the first reference signal using the scheduled resource, until the timer expires or a time exceeds the predetermined time interval. Then, after the timer expires or when the time exceeds the predetermined time interval, one of the base station <NUM> and the terminal device <NUM> transmits the first reference signal.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S300). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S302). Next, the base station <NUM> notifies the terminal device <NUM> of the setting information including the setting of the timer or the time interval (step S304). Next, when a packet is generated in the base station <NUM> (step S306), the base station <NUM> notifies the terminal device <NUM> of DCI (step S308). Note that the above setting information may be included in the DCI and notified. Next, the base station <NUM> transmits a data signal including the reference signal A to the terminal device <NUM> (step S310). Next, the terminal device <NUM> starts the timer (step S312). Timing at which the timer starts may be timing at which the data signal including the reference signal A has been received, or any other timing. Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S314).

Next, the terminal device <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S316). The determination is performed on the basis of whether or not the timer has expired. At the present timing, since the timer has not expired yet, it is determined that the reference signal B is not included. Therefore, the terminal device <NUM> performs transmission equalization using the reference signal A (step S318), and transmits a transmission equalized reception response that does not include the reference signal B (step S320).

Then, as illustrated in <FIG>, when a packet is generated in the base station <NUM> (step S322), the base station <NUM> determines whether or not to include a reference signal C in the data signal (step S324). The determination is performed on the basis of whether or not the timer has expired. At the present timing, since the timer has not expired yet, it is determined that the reference signal C is not included. Next, the base station <NUM> notifies the terminal device <NUM> of DCI (step S326). Note that the DCI may include setting information for updating timer or time interval information. Next, the base station <NUM> transmits a data signal not including the reference signal C to the terminal device <NUM> (step S328). Next, the terminal device <NUM> performs reception equalization using the reference signal A received in step S310 and decodes the data signal (step S330).

Next, the terminal device <NUM> determines whether or not to include a reference signal D in the reception response to the data signal (step S332). The determination is performed on the basis of whether or not the timer has expired. At the present timing, since the timer has not expired yet, it is determined that the reference signal D is not included. Therefore, the terminal device <NUM> performs transmission equalization using the reference signal A (step S334), and transmits a transmission equalized reception response that does not include the reference signal D (step S336).

After that, as illustrated in <FIG>, the base station <NUM> detects the expiration of the timer and restarts the timer (step S338). Then, when a packet is generated in the base station <NUM> (step S340), the base station <NUM> determines whether or not to include a reference signal E in the data signal (step S342). The determination is performed on the basis of whether or not the timer has expired. At the present timing, since the timer has expired once, it is determined that the reference signal E is included. Next, the base station <NUM> notifies the terminal device <NUM> of DCI (step S344). Note that the DCI may include setting information for updating timer or time interval information. Next, the base station <NUM> transmits a data signal including the reference signal E to the terminal device <NUM> (step S346). Next, the terminal device <NUM> performs reception equalization using the reference signal E and decodes the data signal (step S348).

Next, the terminal device <NUM> determines whether or not to include a reference signal F in the reception response to the data signal (step S350). The determination is performed on the basis of whether or not the timer has expired. At the present timing, since the timer has not expired yet, it is determined that the reference signal F is not included. Therefore, the terminal device <NUM> performs transmission equalization using the reference signal E (step S352), and transmits a transmission equalized reception response that does not include the reference signal F (step S354).

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of the number of repeated transmissions. When the number of repeated transmissions is less than a predetermined threshold value, the first communication device <NUM> does not transmit the first reference signal using the scheduled resource. For example, when the number of repeated transmissions is less than N, the first communication device <NUM> transmits the first reference signal using the scheduled resource only for the first time, and does not transmit the first reference signal using the first resource for the second and subsequent times. On the other hand, when the number of repeated transmissions is equal to or more than the predetermined threshold value, the first communication device <NUM> transmits the first reference signal using the scheduled resource for the first time. Then, the first communication device <NUM> transmits the first reference signal using the scheduled resource periodically, and does not transmit the first reference signal using the scheduled resource at other timings. For example, when the number of repeated transmissions is equal to or more than N, the first communication device <NUM> transmits the first reference signal using the scheduled resource for the first time, and transmits the first reference signal using the first resource every predetermined number of times (for example, every N times) for the second and subsequent times. When the number of repeated transmissions after transmitting the first reference signal is small, the elapsed time from the transmission of the first reference signal is short, and it is assumed that there is a small change in the channel. Therefore, it is possible to perform reception equalization by diverting the first reference signal transmitted once.

Here, the periodic transmission indicates, for example, that the first reference signal is transmitted every time the transmission is repeated twice. When the total number of repeated transmissions is <NUM> or more, the first reference signal is included in the first transmission, the first reference signal is not included in the second transmission, the first reference signal is included in the third transmission, and the first reference signal is not included in the fourth transmission. Of course, the total number of repeated transmissions and the transmission interval are not limited to the above examples.

As the setting information, for example, a predetermined threshold value related to the number of repeated transmissions can be notified. Further, as the setting information, for example, an interval of the number of repeated transmissions in which the first reference signal should be transmitted (for example, every two times in the above example) can be notified. Note that the predetermined threshold value related to the number of repeated transmissions and the interval of the number of repeated transmissions in which the first reference signal should be transmitted may be the same value. For example, when the number of repeated transmissions is N or more, the first reference signal may be transmitted every N times.

An example of a flow of switching processing based on the number of repeated transmissions will be described with reference to <FIG> and <FIG>.

<FIG> and <FIG> are sequence diagrams illustrating an example of a flow of switching processing of transmission/non-transmission of the first reference signal executed in the communication system <NUM>. In the present sequence, the base station <NUM> and the terminal device <NUM> are involved. In the present sequence, the base station <NUM> functions as the communication control device <NUM>. Further, the base station <NUM> and the terminal device <NUM> function as the first communication device <NUM> and the second communication device <NUM>, respectively. In the present sequence, for example, it is assumed that the first reference signal is transmitted every time the number of repeated transmissions N = <NUM> after the first transmission.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S400). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S402). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including the setting related to the number of repeated transmissions N (step S404). Next, when a packet is generated in the base station <NUM> (step S406), the base station <NUM> notifies the terminal device <NUM> of DCI (step S408). Note that the above setting information may be included in the DCI and notified. Next, the base station <NUM> transmits a data signal including the reference signal A to the terminal device <NUM> as the first transmission of the data signal (first repeated transmission) (step S410). Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S412).

Next, the base station <NUM> determines whether or not to include the reference signal B in the second repeated transmission (step S414). The determination is performed on the basis of a relation between the number of repeated transmissions N notified in the setting information and the current number of repeated transmissions. Here, since the transmission is the second repeated transmission and is the first repeated transmission after the first transmission, it is determined that the reference signal B is not included. Next, the base station <NUM> notifies the terminal device <NUM> of DCI (step S416). Next, the base station <NUM> transmits a data signal not including the reference signal B to the terminal device <NUM> as the second repeated transmission of the data signal (step S418). Next, the terminal device <NUM> performs transmission equalization using the reference signal A received in step S410 (step S420).

After that, as illustrated in <FIG>, the base station <NUM> determines whether or not to include the reference signal C in the third repeated transmission (step S422). Here, since the transmission is the third repeated transmission and is the second repeated transmission after the first transmission, it is determined that the reference signal C is included. Next, the base station <NUM> notifies the terminal device <NUM> of DCI (step S424). Next, the base station <NUM> transmits a data signal including the reference signal C to the terminal device <NUM> as the third repeated transmission of the data signal (step S426). Next, the terminal device <NUM> performs transmission equalization using the reference signal C (step S428).

Next, the terminal device <NUM> determines whether or not to include the reference signal D in the reception response to the data signal (step S430). The determination is performed on the basis of whether or not an elapsed time from the reception of the data signal to the transmission of the reception response exceeds a predetermined threshold value. Here, it is assumed that it is determined that the reference signal D is not included. Therefore, the terminal device <NUM> performs transmission equalization using the reference signal C (step S432), and transmits a transmission equalized reception response that does not include the reference signal D (step S434).

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of a duplex system. Here, the duplex system is a duplex system in communication between the first communication device <NUM> and the second communication device <NUM>.

As an example, when the duplex system is time division duplex, the first communication device <NUM> does not transmit the reference signal in the scheduled resource. This is because, in a case of the time division duplex, a frequency used for bidirectional communication is the same, so that channel information related to the bidirectional communication is the same or similar, and transmission equalization based on the channel information obtained by the second reference signal becomes possible. On the other hand, when the duplex system is frequency division duplex, the first communication device <NUM> transmits the reference signal in the scheduled resource. This is because, in a case of the frequency division duplex, a frequency used for bidirectional communication is different, so that channel information related to the bidirectional communication is different, and transmission equalization based on the channel information obtained by the second reference signal becomes difficult.

As another example, the first communication device <NUM> may not transmit a reference signal in the scheduled resource regardless of whether the duplex system is the time division duplex or the frequency division duplex.

As the setting information, for example, information indicating the duplex system can be notified.

An example of switching processing based on the duplex system will be described with reference to <FIG> and <FIG>.

As illustrated in <FIG>, first, the first communication device <NUM> notifies the terminal device <NUM> of setting information including the information indicating the duplex system (step S500). Next, the terminal device <NUM> transmits capability information to the base station <NUM> (step S502). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S504). Next, when a packet is generated in the base station <NUM> (step S506), the base station <NUM> notifies the terminal device <NUM> of DCI (step S508). Next, the base station <NUM> transmits a data signal including the reference signal A to the terminal device <NUM> (step S510). Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S512).

After that, the terminal device <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S514). The determination is performed on the basis of the duplex system notified in the setting information. When it is determined that the reference signal B is not included (step S514/NO), the terminal device <NUM> performs transmission equalization using the reference signal A (step S516), and transmits a transmission equalized reception response that does not include the reference signal B (step S518). On the other hand, when it is determined that the reference signal B is included (step S514/YES), the terminal device <NUM> transmits a reception response including the reference signal B (step S520). Then, the base station <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S522).

As illustrated in <FIG>, first, the first communication device <NUM> notifies the terminal device <NUM> of setting information including the information indicating the duplex system (step S530). Next, the terminal device <NUM> transmits capability information to the base station <NUM> (step S532). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S534). Next, when a packet is generated in the terminal device <NUM> (step S536), the terminal device <NUM> notifies the base station <NUM> of a scheduling request (SR) (step S538). Next, the base station <NUM> performs scheduling and notifies the terminal device <NUM> of DCI (step S540). Next, the terminal device <NUM> transmits a data signal including the reference signal A to the base station <NUM> (step S542). Next, the base station <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S544). After that, the base station <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S546). The determination is performed on the basis of the duplex system notified in the setting information. When it is determined that the reference signal B is not included (step S546/NO), the base station <NUM> performs transmission equalization using the reference signal A (step S548), and transmits a transmission equalized reception response that does not include the reference signal B (step S550). On the other hand, when it is determined that the reference signal B is included (step S546/YES), the base station <NUM> transmits a reception response including the reference signal B (step S552). Then, the terminal device <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S554).

Note that, in steps S550 and S552, DCI for retransmission may be transmitted instead of the reception response (ACK/NACK).

The first communication device <NUM> may switch whether or not to transmit the first reference signal using the scheduled resource, on the basis of whether or not a beam correspondence is held. Here, the beam correspondence relates to a relation between a transmission beam and a reception beam of the first communication device <NUM> suitable for communication with the second communication device <NUM>. When the beam correspondence is held, it means that at least one of a case where the transmission beam can be determined on the basis of the reception beam and a case where the reception beam can be determined on the basis of the transmission beam is realized. When the beam correspondence is not held, it means that both the above cases are not realized.

As an example, when the beam correspondence is held, the first communication device <NUM> does not transmit the first reference signal using the scheduled resource. This is because, in the case where the beam correspondence is held, it is assumed that channel information related to bidirectional communication is the same or similar, and transmission equalization based on the channel information obtained by the second reference signal becomes possible. On the other hand, when the beam correspondence is not held, the first communication device <NUM> transmits the first reference signal using the scheduled resource.

As the setting information, for example, information regarding the beam correspondence can be notified. Examples of the information regarding the beam correspondence include position information of the second communication device <NUM>, information indicating the mobility of the second communication device <NUM>, and information indicating that the first communication device <NUM> or the second communication device <NUM> currently holds the beam correspondence.

An example of switching processing based on the beam correspondence will be described with reference to <FIG> and <FIG>.

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step <NUM>). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S602). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including the information regarding the beam correspondence (step S604). Next, when a packet is generated in the base station <NUM> (step S606), the base station <NUM> notifies the terminal device <NUM> of DCI (step S608). Note that the above setting information may be included in the DCI and notified. Next, the base station <NUM> transmits a data signal including the reference signal A to the terminal device <NUM> (step S610). Next, the terminal device <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S612).

After that, the terminal device <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S614). The determination is performed on the basis of whether or not the beam correspondence is held. When it is determined that the reference signal B is not included (step S614/NO), the terminal device <NUM> performs transmission equalization using the reference signal A (step S616), and transmits a transmission equalized reception response that does not include the reference signal B (step S618). On the other hand, when it is determined that the reference signal B is included (step S614/YES), the terminal device <NUM> transmits a reception response including the reference signal B (step S620). Then, the base station <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S622).

As illustrated in <FIG>, first, the terminal device <NUM> transmits capability information to the base station <NUM> (step S630). Next, the base station <NUM> and the terminal device <NUM> execute an initial access procedure (step S632). Next, the base station <NUM> notifies the terminal device <NUM> of setting information including the information regarding the beam correspondence, or the terminal device <NUM> notifies the base station device <NUM> of information indicating that the beam correspondence is currently held (step S634). Next, when a packet is generated in the terminal device <NUM> (step S636), the terminal device <NUM> notifies the base station <NUM> of a scheduling request (SR) (step S638). Next, the base station <NUM> performs scheduling and notifies the terminal device <NUM> of DCI (step S640). Next, the terminal device <NUM> transmits a data signal including the reference signal A to the base station <NUM> (step S642). Next, the base station <NUM> performs reception equalization using the reference signal A and decodes the data signal (step S644).

After that, the base station <NUM> determines whether or not to include the reference signal B in the reception response to the data signal (step S646). The determination is performed on the basis of whether or not the beam correspondence is held. When it is determined that the reference signal B is not included (step S646/NO), the base station <NUM> performs transmission equalization using the reference signal A (step S648), and transmits a transmission equalized reception response that does not include the reference signal B (step S650). On the other hand, when it is determined that the reference signal B is included (step S646/YES), the base station <NUM> transmits a reception response including the reference signal B (step S652). Then, the terminal device <NUM> performs reception equalization using the reference signal B and decodes the reception response (step S654).

Note that, in steps S650 and S652, DCI for retransmission may be transmitted instead of the reception response (ACK/NACK).

The technology according to the present disclosure can be applied to various products. For example, the communication control device <NUM> may be realized as any type of server such as a tower server, a rack server, or a blade server. Further, the communication control device <NUM> may be a control module mounted on the server (for example, an integrated circuit module formed of one die, or a card or blade inserted into a slot of the blade server).

Further, for example, each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may be realized as any type of evolved Node B (eNB) such as a macro eNB or a small eNB. The small eNB may be an eNB that covers a cell smaller than a macro cell, such as a pico eNB, a micro eNB, or a home (femto) eNB. Instead, each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may be realized as another type of base station such as a Node B or a base transceiver station (BTS). Each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may include a main body (also called a base station device) that controls wireless communication and one or more remote radio heads (RRHs) that are disposed at a location different from a location of the main body. Further, various types of terminals, which will be described later, may operate as the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> by temporarily or semi-permanently executing a base station function.

Further, for example, each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may be realized as a smartphone, a tablet personal computer (PC), a notebook PC, a portable game terminal, a mobile terminal such as a portable/dongle type mobile router or a digital camera, or an in-vehicle terminal such as a car navigation device. Further, each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may be realized as a terminal (also called a machine type communication (MTC) terminal) that performs machine to machine (M2M) communication. Further, each of the first communication device <NUM>, the second communication device <NUM>, and the communication control device <NUM> may be a wireless communication module (for example, an integrated circuit module formed of one die) mounted on the terminal.

<FIG> is a block diagram illustrating an example of a schematic configuration of a server <NUM> to which the technology according to the present disclosure can be applied. The server <NUM> includes a processor <NUM>, a memory <NUM>, a storage <NUM>, a network interface <NUM>, and a bus <NUM>.

The processor <NUM> may be, for example, a central processing unit (CPU) or a digital signal processor (DSP), and controls various functions of the server <NUM>. The memory <NUM> includes a random access memory (RAM) and a read only memory (ROM), and stores programs and data executed by the processor <NUM>. The storage <NUM> can include a storage medium such as a semiconductor memory or a hard disk.

The network interface <NUM> is a wired communication interface for connecting the server <NUM> to a wired communication network <NUM>. The wired communication network <NUM> may be a core network such as an evolved packet core (EPC) or a packet data network (PDN) such as the Internet.

The bus <NUM> connects the processor <NUM>, the memory <NUM>, the storage <NUM>, and the network interface <NUM> to each other. The bus <NUM> may include two or more buses (for example, a high-speed bus and a low-speed bus) having different speeds.

In the server <NUM> illustrated in <FIG>, one or more components (for example, the notification unit <NUM>) included in the control unit <NUM> described with reference to <FIG> may be mounted in the processor <NUM>. As an example, a program for causing the processor to function as one or more of the above components (in other words, a program for causing the processor to execute the operations of one or more of the above components) may be installed on the server <NUM>, and the processor <NUM> may execute the program. As another example, the server <NUM> may be equipped with a module including the processor <NUM> and the memory <NUM>, and one or more of the above components may be mounted in the module. In this case, the module may store a program for causing the processor to function as one or more of the above components in the memory <NUM> and may execute the program by the processor <NUM>. As described above, the server <NUM> or the module may be provided as a device including one or more of the above components, and the program for causing the processor to function as one or more of the above components may be provided. Further, a readable recording medium on which the above program has been recorded may be provided.

Further, in the server <NUM> illustrated in <FIG>, for example, the communication unit <NUM> described with reference to <FIG> may be mounted in the network interface <NUM>. Further, the storage unit <NUM> may be mounted in the memory <NUM> and/or the storage <NUM>.

<FIG> is a block diagram illustrating a first example of a schematic configuration of an eNB to which the technology according to the present disclosure can be applied. An eNB <NUM> has one or more antennas <NUM> and a base station device <NUM>. Each antenna <NUM> and the base station device <NUM> can be connected to each other via an RF cable.

Each of the antennas <NUM> has one or more antenna elements (for example, a plurality of antenna elements forming a MIMO antenna) and is used for transmission and reception of radio signals by the base station device <NUM>. The eNB <NUM> has a plurality of antennas <NUM> as illustrated in <FIG>, and the plurality of antennas <NUM> may correspond to a plurality of frequency bands used by the eNB <NUM>, for example. Although <FIG> illustrates an example in which the eNB <NUM> has the plurality of antennas <NUM>, the eNB <NUM> may have a single antenna <NUM>.

The base station device <NUM> includes a controller <NUM>, a memory <NUM>, a network interface <NUM>, and a wireless communication interface <NUM>.

The controller <NUM> may be, for example, a CPU or a DSP and operates various functions of upper layers of the base station device <NUM>. For example, the controller <NUM> generates a data packet from data in a signal processed by the wireless communication interface <NUM> and transfers the generated packet via the network interface <NUM>. The controller <NUM> may generate a bundled packet by bundling data from a plurality of baseband processors and transfer the generated bundled packet. Further, the controller <NUM> may have a logical function that executes control such as radio resource control, radio bearer control, mobility management, admission control, or scheduling. Further, the control may be executed in cooperation with a peripheral eNB or core network node. The memory <NUM> includes a RAM and a ROM, and stores a program executed by the controller <NUM> and a variety of control data (for example, a terminal list, transmitted power data, and scheduling data).

The network interface <NUM> is a communication interface for connecting the base station device <NUM> to a core network <NUM>. The controller <NUM> may communicate with the core network node or other eNB via the network interface <NUM>. In that case, the eNB <NUM> and the core network node or other eNB may be connected to each other by a logical interface (for example, an S1 interface or an X2 interface). The network interface <NUM> may be a wired communication interface or a wireless communication interface for a wireless backhaul. When the network interface <NUM> is a wireless communication interface, the network interface <NUM> may use a higher frequency band than a frequency band used by the wireless communication interface <NUM> for wireless communication.

The wireless communication interface <NUM> supports a cellular communication system such as Long Term Evolution (LTE) or LTE-Advanced, and provides wireless connection to a terminal located in the cell of the eNB <NUM> via the antenna <NUM>. The wireless communication interface <NUM> can typically include a baseband (BB) processor <NUM> and an RF circuit <NUM>. The BB processor <NUM> may perform, for example, encoding/decoding, modulation/demodulation, and multiplexing/demultiplexing, and executes various signal processing of each layer (for example, L1, Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP)). The BB processor <NUM> may have some or all of the above-mentioned logical functions instead of the controller <NUM>. The BB processor <NUM> may be a module including a memory for storing a communication control program, a processor for executing the program, and related circuits, and the functions of the BB processor <NUM> may be changed by updating the above program. Further, the module may be a card or a blade inserted into a slot of the base station device <NUM>, or may be a chip mounted on the card or the blade. On the other hand, the RF circuit <NUM> may include a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna <NUM>.

The wireless communication interface <NUM> includes a plurality of BB processors <NUM> as illustrated in <FIG>, and the plurality of BB processors <NUM> may correspond to a plurality of frequency bands used by the eNB <NUM>, for example. Further, the wireless communication interface <NUM> includes a plurality of RF circuits <NUM> as illustrated in <FIG>, and the plurality of RF circuits <NUM> may correspond to, for example, a plurality of antenna elements. Although <FIG> illustrates an example in which the wireless communication interface <NUM> includes the plurality of BB processors <NUM> and the plurality of RF circuits <NUM>, the wireless communication interface <NUM> may include a single BB processor <NUM> or a single RF circuit <NUM>.

In the eNB <NUM> illustrated in <FIG>, one or more components (the notification unit <NUM> and the communication control unit <NUM> or the communication control unit <NUM>, and/or the notification unit <NUM>) included in the control unit <NUM> described with reference to <FIG> or the control unit <NUM> described with reference to <FIG>, and the control unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM>. Alternatively, at least some of these components may be mounted in the controller <NUM>. As an example, the eNB <NUM> may be equipped with a module including a part (for example, the BB processor <NUM>) or all of the wireless communication interface <NUM> and/or the controller <NUM>, and one or more of the above components may be mounted in the module. In this case, the module may store a program for causing the processor to function as one or more of the above components (in other words, a program for causing the processor to execute the operations of one or more of the above components), and may execute the program. As another example, the program for causing the processor to function as one or more of the above components may be installed in the eNB <NUM>, and the wireless communication interface <NUM> (for example, the BB processor <NUM>) and/or the controller <NUM> may execute the program. As described above, the eNB <NUM>, the base station device <NUM>, or the module may be provided as a device including one or more of the above components, and the program for causing the processor to function as one or more of the above components may be provided. Further, a readable recording medium on which the above program has been recorded may be provided.

Further, in the eNB <NUM> illustrated in <FIG>, the wireless communication unit <NUM> described with reference to <FIG> or the wireless communication unit <NUM> described with reference to <FIG>, and the communication unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM> (for example, the RF circuit <NUM>). Further, the antenna unit <NUM> or the antenna unit <NUM> may be mounted on the antenna <NUM>. Further, the storage unit <NUM> or the storage unit <NUM> and the storage unit <NUM> may be mounted in the memory <NUM>.

<FIG> is a block diagram illustrating a second example of a schematic configuration of an eNB to which the technology according to the present disclosure can be applied. An eNB <NUM> has one or more antennas <NUM>, a base station device <NUM>, and an RRH <NUM>. Each antenna <NUM> and the RRH <NUM> can be connected to each other via an RF cable. Further, the base station device <NUM> and the RRH <NUM> can be connected to each other by a high-speed line such as an optical fiber cable.

Each of the antennas <NUM> has one or more antenna elements (for example, a plurality of antenna elements forming a MIMO antenna) and is used for transmission and reception of radio signals by the RRH <NUM>. The eNB <NUM> has a plurality of antennas <NUM> as illustrated in <FIG>, and the plurality of antennas <NUM> may correspond to a plurality of frequency bands used by the eNB <NUM>, for example. Although <FIG> illustrates an example in which the eNB <NUM> has the plurality of antennas <NUM>, the eNB <NUM> may have a single antenna <NUM>.

The base station device <NUM> includes a controller <NUM>, a memory <NUM>, a network interface <NUM>, a wireless communication interface <NUM>, and a connection interface <NUM>. The controller <NUM>, the memory <NUM>, and the network interface <NUM> are similar to the controller <NUM>, the memory <NUM>, and the network interface <NUM> described with reference to <FIG>.

The wireless communication interface <NUM> supports a cellular communication system such as LTE or LTE-Advanced, and provides wireless connection to terminals located in a sector corresponding to the RRH <NUM> via the RRH <NUM> and the antenna <NUM>. The wireless communication interface <NUM> can typically include a BB processor <NUM> and the like. The BB processor <NUM> is similar to the BB processor <NUM> described with reference to <FIG>, except that it is connected to an RF circuit <NUM> of the RRH <NUM> via the connection interface <NUM>. The wireless communication interface <NUM> includes a plurality of BB processors <NUM> as illustrated in <FIG>, and the plurality of BB processors <NUM> may correspond to a plurality of frequency bands used by the eNB <NUM>, for example. Although <FIG> illustrates an example in which the wireless communication interface <NUM> includes the plurality of BB processors <NUM>, the wireless communication interface <NUM> may include a single BB processor <NUM>.

The connection interface <NUM> is an interface for connecting the base station device <NUM> (wireless communication interface <NUM>) to the RRH <NUM>. The connection interface <NUM> may be a communication module for communication on the high-speed line that connects the base station device <NUM> (wireless communication interface <NUM>) and the RRH <NUM>.

The RRH <NUM> further includes a connection interface <NUM> and a wireless communication interface <NUM>.

The connection interface <NUM> is an interface for connecting the RRH <NUM> (wireless communication interface <NUM>) to the base station device <NUM>. The connection interface <NUM> may be a communication module for communication on the high-speed line.

The wireless communication interface <NUM> transmits and receives radio signals via the antenna <NUM>. The wireless communication interface <NUM> can typically include an RF circuit <NUM> and the like. The RF circuit <NUM> may include a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna <NUM>. The wireless communication interface <NUM> includes a plurality of RF circuits <NUM> as illustrated in <FIG>, and the plurality of RF circuits <NUM> may correspond to, for example, a plurality of antenna elements. Although <FIG> illustrates an example in which the wireless communication interface <NUM> includes the plurality of RF circuits <NUM>, the wireless communication interface <NUM> may include a single RF circuit <NUM>.

In the eNB <NUM> illustrated in <FIG>, one or more components (the notification unit <NUM> and the communication control unit <NUM> or the communication control unit <NUM>, and/or the notification unit <NUM>) included in the control unit <NUM> described with reference to <FIG> or the control unit <NUM> described with reference to <FIG>, and the control unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM> and/or the wireless communication interface <NUM>. Alternatively, at least some of these components may be mounted in the controller <NUM>. As an example, the eNB <NUM> may be equipped with a module including a part (for example, the BB processor <NUM>) or all of the wireless communication interface <NUM> and/or the controller <NUM>, and one or more of the above components may be mounted in the module. In this case, the module may store a program for causing the processor to function as one or more of the above components (in other words, a program for causing the processor to execute the operations of one or more of the above components), and may execute the program. As another example, the program for causing the processor to function as one or more of the above components may be installed in the eNB <NUM>, and the wireless communication interface <NUM> (for example, the BB processor <NUM>) and/or the controller <NUM> may execute the program. As described above, the eNB <NUM>, the base station device <NUM>, or the module may be provided as a device including one or more of the above components, and the program for causing the processor to function as one or more of the above components may be provided. Further, a readable recording medium on which the above program has been recorded may be provided.

Further, in the eNB <NUM> illustrated in <FIG>, for example, the wireless communication unit <NUM> described with reference to <FIG> or the wireless communication unit <NUM> described with reference to <FIG>, and the communication unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM> (for example, the RF circuit <NUM>). Further, the antenna unit <NUM> or the antenna unit <NUM> may be mounted on the antenna <NUM>. Further, the storage unit <NUM> or the storage unit <NUM> and the storage unit <NUM> may be mounted in the memory <NUM>.

<FIG> is a block diagram illustrating an example of a schematic configuration of a smartphone <NUM> to which the technology according to the present disclosure can be applied. The smartphone <NUM> includes a processor <NUM>, a memory <NUM>, a storage <NUM>, an external connection interface <NUM>, a camera <NUM>, a sensor <NUM>, a microphone <NUM>, an input device <NUM>, a display device <NUM>, a speaker <NUM>, a wireless communication interface <NUM>, one or more antenna switches <NUM>, one or more antennas <NUM>, a bus <NUM>, a battery <NUM>, and an auxiliary controller <NUM>.

The processor <NUM> may be, for example, a CPU or a System on Chip (SoC), and controls functions of an application layer and other layers of the smartphone <NUM>. The memory <NUM> includes a RAM and a ROM and stores programs and data executed by the processor <NUM>. The storage <NUM> can include a storage medium such as a semiconductor memory or a hard disk. The external connection interface <NUM> is an interface for connecting an external device such as a memory card or a universal serial bus (USB) device to the smartphone <NUM>.

The camera <NUM> has an imaging element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and generates an imaging image. The sensor <NUM> can include, for example, a group of sensors such as a positioning sensor, a gyro sensor, a geomagnetic sensor, and an acceleration sensor. The microphone <NUM> converts a voice input to the smartphone <NUM> into a voice signal. The input device <NUM> includes, for example, a touch sensor that detects a touch on a screen of the display device <NUM>, a keypad, a keyboard, a button, or a switch, and receives an operation or information input from a user. The display device <NUM> has a screen such as a liquid crystal display (LCD) or an organic light emitting diode (OLED) display, and displays an output image of the smartphone <NUM>. The speaker <NUM> converts the voice signal output from the smartphone <NUM> into a voice.

The wireless communication interface <NUM> supports a cellular communication system such as LTE or LTE-Advanced and performs wireless communication. The wireless communication interface <NUM> can typically include a BB processor <NUM> and an RF circuit <NUM>. The BB processor <NUM> may perform, for example, encoding/decoding, modulation/demodulation, and multiplexing/demultiplexing, and executes various signal processing for wireless communication. On the other hand, the RF circuit <NUM> may include a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna <NUM>. The wireless communication interface <NUM> may be a one-chip module in which the BB processor <NUM> and the RF circuit <NUM> are integrated. The wireless communication interface <NUM> may include a plurality of BB processors <NUM> and a plurality of RF circuits <NUM> as illustrated in <FIG>. Although <FIG> illustrates an example in which the wireless communication interface <NUM> includes the plurality of BB processors <NUM> and the plurality of RF circuits <NUM>, the wireless communication interface <NUM> may include a single BB processor <NUM> or a single RF circuit <NUM>.

Further, the wireless communication interface <NUM> may support other types of wireless communication systems such as a short-range wireless communication system, a near-field wireless communication system, or a wireless local area network (LAN) system, in addition to the cellular communication system. In that case, the wireless communication interface <NUM> may include the BB processor <NUM> and the RF circuit <NUM> for each wireless communication system.

Each of the antenna switches <NUM> switches the connection destination of the antenna <NUM> between a plurality of circuits included in the wireless communication interface <NUM> (for example, circuits for different wireless communication systems).

Each of the antennas <NUM> has one or more antenna elements (for example, a plurality of antenna elements forming a MIMO antenna) and is used for transmission and reception of radio signals by the wireless communication interface <NUM>. The smartphone <NUM> may have a plurality of antennas <NUM> as illustrated in <FIG>. Although <FIG> illustrates an example in which the smartphone <NUM> has the plurality of antennas <NUM>, the smartphone <NUM> may have a single antenna <NUM>.

Further, the smartphone <NUM> may include the antenna <NUM> for each wireless communication system. In that case, the antenna switch <NUM> may be omitted from the configuration of the smartphone <NUM>.

The bus <NUM> connects the processor <NUM>, the memory <NUM>, the storage <NUM>, the external connection interface <NUM>, the camera <NUM>, the sensor <NUM>, the microphone <NUM>, the input device <NUM>, the display device <NUM>, the speaker <NUM>, the wireless communication interface <NUM>, and the auxiliary controller <NUM> to each other. The battery <NUM> supplies power to each block of the smartphone <NUM> illustrated in <FIG> via a feed line partially illustrated by a broken line in the drawing. The auxiliary controller <NUM> operates minimum necessary functions of the smartphone <NUM>, for example, in a sleep mode.

In the smartphone <NUM> illustrated in <FIG>, one or more components (the notification unit <NUM> and the communication control unit <NUM> or the communication control unit <NUM>, and/or the notification unit <NUM>) included in the control unit <NUM> described with reference to <FIG> or the control unit <NUM> described with reference to <FIG>, and the control unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM>. Alternatively, at least some of these components may be mounted in the processor <NUM> or the auxiliary controller <NUM>. As an example, the smartphone <NUM> may be equipped with a module including a part (for example, the BB processor <NUM>) or all of the wireless communication interface <NUM>, the processor <NUM>, and/or the auxiliary controller <NUM>, and one or more of the above components may be mounted in the module. In this case, the module may store a program for causing the processor to function as one or more of the above components (in other words, a program for causing the processor to execute the operations of one or more of the above components), and may execute the program. As another example, the program for causing the processor to function as one or more of the above components may be installed in the smartphone <NUM>, and the wireless communication interface <NUM> (for example, the BB processor <NUM>), the processor <NUM>, and/or the auxiliary controller <NUM> may execute the program. As described above, the smartphone <NUM> or the module may be provided as a device including one or more of the above components, and the program for causing the processor to function as one or more of the above components may be provided. Further, a readable recording medium on which the above program has been recorded may be provided.

Further, in the smartphone <NUM> illustrated in <FIG>, for example, the wireless communication unit <NUM> described with reference to <FIG> or the wireless communication unit <NUM> described with reference to <FIG>, and the communication unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM> (for example, the RF circuit <NUM>). Further, the antenna unit <NUM> or the antenna unit <NUM> may be mounted on the antenna <NUM>. Further, the storage unit <NUM> or the storage unit <NUM> and the storage unit <NUM> may be mounted in the memory <NUM>.

<FIG> is a block diagram illustrating an example of a schematic configuration of a car navigation device <NUM> to which the technology according to the present disclosure can be applied. The car navigation device <NUM> includes a processor <NUM>, a memory <NUM>, a global positioning system (GPS) module <NUM>, a sensor <NUM>, a data interface <NUM>, a content player <NUM>, a storage medium interface <NUM>, an input device <NUM>, a display device <NUM>, a speaker <NUM>, a wireless communication interface <NUM>, one or more antenna switches <NUM>, one or more antennas <NUM>, and a battery <NUM>.

The processor <NUM> may be, for example, a CPU or SoC, and controls a navigation function and other functions of the car navigation device <NUM>. The memory <NUM> includes a RAM and a ROM and stores programs and data executed by the processor <NUM>.

The GPS module <NUM> uses GPS signals received from GPS satellites to measure a position (for example, the latitude, the longitude, and the altitude) of the car navigation device <NUM>. The sensor <NUM> can include, for example, a group of sensors such as a gyro sensor, a geomagnetic sensor, and a barometric pressure sensor. The data interface <NUM> is connected to an in-vehicle network <NUM> via a terminal (not illustrated), and acquires data generated on the vehicle side such as vehicle speed data.

The content player <NUM> plays contents stored in a storage medium (for example, a CD or a DVD) inserted into the storage medium interface <NUM>. The input device <NUM> includes, for example, a touch sensor that detects a touch on the screen of the display device <NUM>, a button, or a switch, and receives an operation or information input from the user. The display device <NUM> has a screen such as an LCD or OLED display and displays an image of a navigation function or contents to be played. The speaker <NUM> outputs a voice of the navigation function or the contents to be played.

Further, the wireless communication interface <NUM> may support other types of wireless communication systems such as a short-range wireless communication system, a near-field wireless communication system, or a wireless LAN system, in addition to the cellular communication system. In that case, the wireless communication interface <NUM> may include the BB processor <NUM> and the RF circuit <NUM> for each wireless communication system.

Each of the antennas <NUM> has one or more antenna elements (for example, a plurality of antenna elements forming a MIMO antenna) and is used for transmission and reception of radio signals by the wireless communication interface <NUM>. The car navigation device <NUM> may have a plurality of antennas <NUM> as illustrated in <FIG>. Although <FIG> illustrates an example in which the car navigation device <NUM> has the plurality of antennas <NUM>, the car navigation device <NUM> may have a single antenna <NUM>.

Further, the car navigation device <NUM> may include the antenna <NUM> for each wireless communication system. In that case, the antenna switch <NUM> may be omitted from the configuration of the car navigation device <NUM>.

The battery <NUM> supplies power to each block of the car navigation device <NUM> illustrated in <FIG> via a feed line partially illustrated by a broken line in the drawing. Further, the battery <NUM> stores power supplied from the vehicle side.

In the car navigation device <NUM> illustrated in <FIG>, one or more components (the notification unit <NUM> and the communication control unit <NUM> or the communication control unit <NUM>, and/or the notification unit <NUM>) included in the control unit <NUM> described with reference to <FIG> or the control unit <NUM> described with reference to <FIG>, and the control unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM>. Alternatively, at least some of these components may be mounted in the processor <NUM>. As an example, the car navigation device <NUM> may be equipped with a module including a part (for example, the BB processor <NUM>) or all of the wireless communication interface <NUM> and/or the processor <NUM>, and one or more of the above components may be mounted in the module. In this case, the module may store a program for causing the processor to function as one or more of the above components (in other words, a program for causing the processor to execute the operations of one or more of the above components), and may execute the program. As another example, the program for causing the processor to function as one or more of the above components may be installed in the car navigation device <NUM>, and the wireless communication interface <NUM> (for example, the BB processor <NUM>) and/or the processor <NUM> may execute the program. As described above, the car navigation device <NUM> or the module may be provided as a device including one or more of the above components, and the program for causing the processor to function as one or more of the above components may be provided. Further, a readable recording medium on which the above program has been recorded may be provided.

Further, in the car navigation device <NUM> illustrated in <FIG>, for example, the wireless communication unit <NUM> described with reference to <FIG> or the wireless communication unit <NUM> described with reference to <FIG> and the communication unit <NUM> described with reference to <FIG> may be mounted in the wireless communication interface <NUM> (for example, the RF circuit <NUM>). Further, the antenna unit <NUM> or the antenna unit <NUM> may be mounted on the antenna <NUM>. Further, the storage unit <NUM> or the storage unit <NUM> and the storage unit <NUM> may be mounted in the memory <NUM>.

Further, the technology according to the present disclosure may be realized as an in-vehicle system (or a vehicle) <NUM> including one or more blocks of the car navigation device <NUM> described above, the in-vehicle network <NUM>, and a vehicle-side module <NUM>. The vehicle-side module <NUM> generates vehicle-side data such as a vehicle speed, an engine speed, or failure information, and outputs the generated data to the in-vehicle network <NUM>.

As described above, the first communication device <NUM> switches whether or not to transmit the first reference signal using the scheduled resource scheduled to be used to transmit the first reference signal. As an example, the first communication device <NUM> does not transmit the first reference signal when transmission equalization or reception equalization based on the channel information acquired in advance is possible, and transmits the first reference signal otherwise. As a result, the transmission of the reference signal, which is not always necessary for decoding the transmission signal, is omitted, so that transmission efficiency of the entire system can be further improved.

Claim 1:
A communication device (<NUM>), comprising:
a control unit (<NUM>) configured to switch between transmission and non-transmission of a first reference signal using a scheduled resource scheduled to be used to transmit a reference signal, based on channel information acquired in advance,
wherein the control unit (<NUM>) is configured to switch between transmission and non-transmission of the first reference signal using the scheduled resource, based on an elapsed time from receiving a second reference signal from a communication partner,
characterized in that the control unit (<NUM>) is further configured to switch between inclusion and non-inclusion of the first reference signal in a reception response of a signal including the second reference signal, based on an elapsed time until the reception response is transmitted.