Patent ID: 12245218

DESCRIPTION OF EMBODIMENTS

Embodiments will be described in detail below with reference to the figures. The problems and embodiments described in this description are examples and do not limit the scope of rights of this application. More specifically, even when different expressions are used in the description, as long as the expressions are technically equivalent, the technology of the present application can be applied even to these different expressions, and the scope of rights is not limited thereby. Moreover, the embodiments can be combined as appropriate within a scope that does not contradict the processing content.

In addition, terms and technical contents described in specifications and contributions as standards related to communication such as the 3GPP may appropriately be used for the terms and technical contents described in the present description. Examples of such specifications include 3GPP TS38.211 V15.1.0 (2018-03).

The 3GPP specifications are updated as needed. Therefore, the latest specifications at the time of filing the present application may be used as the specifications described above. Further, the terms and technical contents described in the latest specifications may appropriately be used in the present description.

Hereinafter, examples of a terminal apparatus, a base station apparatus, and a communication system disclosed in the present application will be described in detail with reference to the drawings. The following embodiments do not limit the disclosed technique.

First Embodiment

<1. Configuration Example of Wireless Communication System>

FIG.1illustrates a configuration example of a communication system10according to a first embodiment.

The communication system10includes a plurality of terminal apparatuses (or communication devices, which may hereinafter be referred to as “terminals”)100-2and100-3. The communication system10may include a base station apparatus (which may hereinafter be referred to as a “base station”)200and a terminal100-1. In the latter case, the terminal100-1can receive information about a selection criterion, etc. from the base station200and use the received information to perform wireless communication with the other terminals100-2and100-3. As with the terminal100-1, the terminals100-2and100-3can receive information about a selection criterion within the coverage range of the base station200.

The terminals100-1to100-3are, for example, communication devices capable of wireless communication, such as wireless communication chipsets, feature phones, smartphones, personal computers, tablet terminals and game devices.

In addition, the terminals100-1to100-3can perform wireless communication via V2X communication, for example. As described above, V2X is a general term for V2V, V2P, V2I, or the like. Thus, for example, inFIG.1, in a case where the terminal100-2is provided on a vehicle100-v2, the terminal100-3, which is a communication peer, may be held by a pedestrian, rather than a vehicle, or provided on a road sign. However, the following description will be made assuming that the terminals100-1to100-3are provided on vehicles100-v1to100-v3, respectively. Further, the terminals100-1to100-3can perform wireless communication via V2X communication in mode 4, for example. As described above, mode 4 is, for example, a method in which the terminals100-1to100-3can autonomously select resources. In the case ofFIG.1, the terminal100-1can perform V2X communication in mode 4 when in a Radio Resource Control (RRC) idle (RRC_IDLE) state and in an RRC connected state within the coverage range of the base station200. In addition, as illustrated inFIG.1, the terminals100-2and100-3can perform V2X communication in mode 4 outside the coverage range of the base station200.

The RRC idle state is, for example, a standby state in which the terminal100-1is not RRC-connected to the network side including the base station200. The RRC connected state (RRC_CONNECTED) is, for example, a state in which the terminal100-2is connected to the network including the base station200so that data can be transmitted and received.

The number of terminals100-2and100-3included in the communication system10is not limited to two, but may be three or more.

Unless otherwise specified, the terminals100-1to100-3may be hereinafter referred to as the terminal100.

<2. Configuration Example of Terminal Apparatus>

FIG.2illustrates a configuration example of the terminal100.

To support cellular signals, the terminal100includes a data traffic processing unit101, a channel encoder102, an Inverse Fast Fourier transform (IFFT)103, a Cyclic Prefix (CP) addition unit104, a Radio Frequency (RF) transmitter105, and a transmission antenna106. In addition, to support cellular signals, the terminal100includes a reception antenna110, an RF receiver111, and a channel demodulator112.

The data traffic processing unit101generates data to be used in cellular communication, such as voice data and image data. The data traffic processing unit101outputs the generated data to the channel encoder102.

The channel encoder102performs error correction encoding processing (which may hereinafter be referred to as “encoding processing”) and modulation processing, etc. on the data to covert the data into a transmission signal. The channel encoder102outputs the converted transmission signal to the IFFT103.

The IFFT103performs an inverse fast Fourier transform on the transmission signal to covert the transmission signal in the frequency domain into a transmission signal in the time domain. The IFFT103outputs the transmission signal in the time domain to the CP addition unit104.

The CP addition unit104adds a cyclic prefix (CP) to the transmission signal in the time domain. The CP addition unit104outputs the transmission signal, to which the CP is added, to the RF transmitter105.

The RF transmitter105performs Digital-to-Analogue (D/A) conversion processing, frequency conversion processing, etc. on the transmission signal, to which the CP is added, to generate a cellular signal of a radio band. The RF transmitter105outputs the cellular signal to the transmission antenna106.

The transmission antenna106transmits the cellular signal to the base station200.

The reception antenna110receives the cellular signal transmitted from the base station200and outputs the received cellular signal to the RF receiver111.

The RF receiver111performs frequency conversion processing, Analogue-to-Digital (A/D) conversion processing, etc. on the cellular signal to convert the cellular signal of the radio band into a reception signal of the base band. The RF receiver111outputs the reception signal to the channel demodulator112.

The channel demodulator112performs demodulation processing, error correction decoding processing (which may hereinafter be referred to as “decoding processing”), etc. on the reception signal to reproduce (or extract) the data, the control information, or the like. When the channel demodulator112has reproduced the information about the resource pool and information about the selection criterion, the channel demodulator112stores the reproduced information about the resource pool and information about the selection criterion in a resource information memory113. Hereinafter, the information about the resource pool and the information about the selection criterion may collectively be referred to as the resource information.

In addition, to support a sidelink signal, the terminal100includes the resource information memory113, a sidelink scheduler (which may hereinafter be referred to as a “scheduler”)114, a signal (PSCCH: Physical Sidelink Control Channel) generator (which may hereinafter be referred to as a “control signal generator”)115including Sidelink Control Information (SCI). A signal including sidelink control information (SCI) may be referred to as sidelink control signal. Further, to support a sidelink signal, the terminal100includes a sidelink data generator (which may hereinafter be referred to as a “data generator”)116, an RF transmitter117, a transmission antenna118, a reception antenna120, and an RF receiver121. Further, to support a sidelink signal, the terminal100includes a sidelink control signal detector (which may hereinafter be referred to as a “control signal detector”)122, a sidelink data detector (which may hereinafter be referred to as a “data detector”)123, and an energy measuring device124.

The resource information memory113stores resource information (information about the resource pool and information about the selection criterion). The information about the resource pool includes information113-aabout the resource pool (k−1) and information113-babout the resource pool k.

The information113-aabout the resource pool (k−1) includes information indicating the resource range of the resource pool (k−1), namely, the range of the frequency resources and time resources to be used by the resource pool (k−1), for example. The information113-babout the resource pool k includes information indicating the resource range of the resource pool k, namely, the range of the frequency resources and the time resources to be used by the resource pool k, for example.

When the information113-aabout the resource pool (k−1) and the information113-babout the resource pool k are represented on two-dimensional coordinates in which the horizontal axis represents the time axis direction and the vertical axis represents the frequency axis direction, for example, a resource allocation example illustrated inFIG.5is obtained.FIG.5will be described in detail below.

Returning toFIG.2, the information about the selection criterion is, for example, information about usage ranking indicating that at least one of the resource pool k and the resource pool (k−1) is preferentially used per Quality of Service (QOS). Namely, the information about the selection criterion includes, for example, QoS and usage ranking. For example, the terminal100selects the resource pool k or the resource pool (k−1) in order of the usage ranking based on whether QoS matches the conditions.

For example,FIG.6illustrates an example of a selection criteria table113-cin which the information about the selection criteria is summarized in a table format.FIG.6will be described in detail below. The selection criteria table113-cis stored in the resource information memory113.

QoS is, for example, QoS requested when data is transmitted via sidelink communication. QoS is also parameters related to the data or information about sidelink communication. Details of the QoS will be described below.

Returning toFIG.2, the scheduler114performs scheduling related to sidelink communication. Specifically, the scheduler114selects the resource pool k or the resource pool (k−1) in accordance with the selection criterion set for each of the resource pool k and resource pool (k−1) and the information about sidelink communication. That is, for example, the scheduler114selects at least one resource pool that corresponds to the QoS output from the data generator116by using the selection criteria table113-c(for example,FIG.6). Next, the scheduler114performs carrier sense by using a sensing method set for each of the resource pool k and the resource pool (k−1) selected. Hereinafter, “sensing” and “carrier sense” may be used without distinction.

FIG.5illustrates an example of resource allocation of the resource pool k and the resource pool (k−1).

The resource pool k is, for example, a resource pool in which slot-level (or subframe) sensing is performed. When using the resource pool k, the scheduler114sets a past number ms (for example, 1000 ms) before the resource selection as the sensing window and sets the selection window in the range of 10 ms to 100 ms after the resource selection. The scheduler114then performs a resource exclusion step and a resource narrowing step on each resource in the selection window on a slot basis (or on a subframe basis) based on each resource in the sensing window. The resource exclusion step and the resource narrowing step are performed based on a reception energy measurement for the reception signal received using each resource, as described with reference toFIG.19, for example. Thus, the scheduler114performs the resource exclusion step and the resource narrowing step based on the reception energy of each resource output from the energy measuring device124. The scheduler114randomly selects any one of the candidate resources narrowed down in the selection window. The scheduler114also determines a Modulation and Coding Scheme (MCS), the number of repetitions, etc. The scheduler114outputs information about the selected resource, the MCS, the number of repetitions, etc. to the control signal generator115and the data generator116as control information.

Note that one subframe is composed of 14 symbols in 4G, and one slot is composed of 14 symbols in 5G. In the resource pool k, one resource unit is one subframe in 4G, and one resource unit is one slot in 5G. Hereinafter, one resource unit may be described as a slot.

In the resource pool (k−1), for example, sensing is performed on a symbol basis. While details will be described below, for example, the scheduler114performs sensing at the “0th” symbol as illustrated inFIG.9Aor performs sensing using three symbols from the “0th” to “2nd” symbols as illustrated inFIG.9D. In this case, the scheduler114determines whether the slot including the measured symbol can be used, based on the symbol-based reception energy measurement result output from the energy measuring device124. For example, when the reception energy measurement result is equal to or greater than a threshold, the scheduler114determines “busy” and defers the transmission by its own terminal. In contrast, when the reception energy measurement result is lower than the threshold, the scheduler114determines “idle” and determines that the slot can be used. When determining that the slot can be used, the scheduler114determines the slot as information about the resource. The scheduler114also determines the MCS, the number of repetitions, etc. The scheduler114outputs these items of information to the control signal generator115as control information.

The control signal generator115generates a control signal by performing encoding processing and modulation processing on the control information. The control signal generator115outputs the generated control signal to the RF transmitter117.

The data generator (or data generation unit)116generates data to be transmitted by the terminal100. In this step, the data generator116determines QoS based on the parameters of the generated data. Examples of such parameters include communication delay, communication reliability, and priority of the data.

For example, the data generator116may determine the delay and reliability based on a use case (or a scenario) in which the data is used. Examples of the use case include a case in which a vehicle equipped with the terminal100performs vehicle platooning, automatic driving (advanced driving), extended sensors, remote driving, or the like. Alternatively, the data generator116may determine the delay and reliability based on whether the vehicle equipped with the terminal100performs semi-automatic driving or fully automatic driving. In addition, the data generator116may determine the data priority based on the type of data, for example, whether or not the data is urgent data.

In this way, the data generator116determines the delay and reliability based on the use case or the like and determines the priority based on the type of data, for example. The data generator116uses the delay, the reliability, and all or part of the priority to determine QoS of the data. The data generator116outputs the determined QoS to the scheduler114. Further, the data generator116receives MCS from the scheduler114, performs encoding processing, modulation processing, etc. on the generated data in accordance with the MCS, and generates a transmission signal. The data generator116outputs the transmission signal to the RF transmitter117.

The RF transmitter117performs D/A conversion processing, frequency conversion processing, etc. on the control signal and the transmission signal to convert these signals into a sidelink signal of the radio band. The RF transmitter117transmits the sidelink signal to another terminal via the transmission antenna118. In this step, the RF transmitter117transmits the sidelink signal in accordance with the information about the resource included in the control signal. This enables the control signal to be transmitted by using the PSCCH and the data to be transmitted by using the PSSCH. The RF transmitter117is also a transmission unit that transmits the control signal and the data to another terminal, for example.

The transmission antenna118transmits a sidelink signal to another terminal.

The reception antenna120receives a sidelink signal transmitted from another terminal and outputs the received sidelink signal to the RF receiver121.

The RF receiver121performs frequency conversion processing, A/D conversion processing, etc. on the sidelink signal to convert the sidelink signal into a reception signal of the base band. The RF receiver121outputs the reception signal to the control signal detector122and the data detector123.

The control signal detector122extracts the reception signal received by using the PSCCH as a control signal, performs demodulation processing and decoding processing on the extracted control signal, and reproduces (or extracts) the control information. The control signal detector122outputs the reproduced control information to the data detector123.

The data detector123senses the reception signal received by using the PSSCH as a data signal based on the control information. The data detector123outputs the sensed data signal to the energy measuring device124. The data detector123may perform demodulation processing, decoding processing, etc. on the sensed data signal to reproduce the data and output the reproduced data to an application processing unit or the like.

The energy measuring device124measures the reception energy of the sensed data signal.

FIG.4illustrates a configuration example of the energy measuring device124. A reception signal yR(t) is converted into a digital signal by an Analogue-to-Digital Converter (ADC)1211of the RF receiver121and is converted from the signal in the time domain to a signal in the frequency domain by a Fast Fourier Transform (FFT)1231of the data detector123.

The energy measuring device124includes squaring coefficients1241and mean value1242. The squaring coefficients1241calculates, for example, a square of the reception signal yR(t) in the frequency domain to obtain reception energy of the reception signal yR(t). The mean value1242calculates an average value ER of the reception energy. The energy measuring device124outputs the average reception energy ER to the scheduler114as a reception energy measurement result. As described above, the scheduler114compares the reception energy measurement result with a threshold to determine “busy” or “idle”.

<3. Configuration Example of Base Station Apparatus>

FIG.3illustrates a configuration example of the base station200.

The base station200includes a radio unit210, a processor211, and an Interface (IF).

The radio unit210includes a transmission unit201and a reception unit202. The transmission unit201performs encoding processing, modulation processing, frequency conversion processing, etc. on resource information output from a scheduler203to convert the resource information into a cellular signal. The transmission unit201transmits the cellular signal to the terminal100. The reception unit202receives the cellular signal transmitted from the terminal100, performs frequency conversion processing, demodulation processing, decoding processing, etc. on the received cellular signal, and reproduces the information transmitted from the terminal100. The reception unit202outputs the reproduced information to the scheduler203.

The processor211includes the scheduler203. The scheduler203performs scheduling of the wireless communication for each terminal100within the coverage range of the base station200. In the first embodiment, the scheduler203generates resource information and transmits the generated resource information to the terminal100-1via the transmission unit201.

The processor211may be, for example, a Central Processing Unit (CPU), a Micro Processing Unit (MPU), a Digital Signal Processor (DSP), or a Field Programmable Gate Array (FPGA).

The IF212includes a backhaul communication unit204. The backhaul communication unit204transmits information output from the scheduler203to a server device connected via a wired network and other base stations and outputs information received from a server device and other base stations to the scheduler203.

<4. Resource Pool>

As described above, in the first embodiment, a plurality of resource pools k and k−1 are used as illustrated inFIG.5. As illustrates inFIG.6, the resource pool k or k−1 can be selected based on QoS of data.

FIG.6illustrates an example of the selection criteria table113-c.

As illustrated inFIG.6, in the first embodiment, QoS represents, for example, transmission delay (latency) and communication reliability.

In the example illustrated inFIG.6, “QoS0” represents QoS that requests a delay of 3 ms or less and reliability of 10−5. A delay of “3 ms” represents, for example, that an allowable transmission delay is 3 ms or less. Reliability of “10-5” represents, for example, a degree of reliability such that, when the amount of transmission packet data is “100,000”, the terminal on the reception side can receive “99,999” transmission packets.

“QoS1” represents QoS that requests a delay of 10 ms or less and reliability of104. That is, an allowable transmission delay is 10 ms or less, and a degree of reliability is such that, when the amount of transmission packet data is “10,000”, the terminal on the reception side can receive “9,999” transmission packets.

When QoS is “QoS0”, the terminal100can use the resource pool (k−1) with a higher usage ranking than the resource pool k in accordance with the selection criteria table113-c. This is because, for example, “QoS0” represents the strictest conditions (low delay and high reliability) in the QoS levels illustrated inFIG.6, and the use of the resource pool (k−1) in which symbol-level sensing is performed enables data transmission that satisfies such strict conditions. That is, the terminal100can perform communication with low delay and high reliability by using the resource pool (k−1).

When QoS is “QoS1”, the terminal100can use the resource pool k with a higher usage ranking than the resource pool (k−1) in accordance with the selection criteria. This is because, for example, “QoS1” is a QoS level that needs normal delay and reliability, and the use of the resource pool k in which slot-level sensing is performed is sufficient to satisfy such a level of QoS.

However, as illustrated inFIG.6, even when QoS is “QoS0”, the resource pool k can be used, and even when QoS is “QoS1”, the resource pool (k−1) can be used. For example, if only the resource pool (k−1) is used for all the cases of “QoS0”, While the resources of the resource pool (k−1) are used by many terminals100for data transmission, the resources of the resource pool k are hardly used. Such a situation may occur. Thus, for example, to prevent deterioration of resource utilization efficiency, another resource pool can be utilized.

In the examples illustrated inFIGS.5and6, only one resource pool (k−1) is illustrates as the resource pool in which symbol-level sensing is performed. In the first embodiment, symbol-level sensing may be performed in a plurality of resource pools (k−1), (k−2), and so on. In this case, any one of the resource pools (k−1), (k−2), . . . , in which symbol-level sensing is performed, may serve as “Priority1”. Alternatively, the resource pools (k−1), (k−2), . . . , in which symbol-level sensing is performed, may be allocated in accordance with the type of data (whether or not the data is emergency data) to be transmitted or the type of service. For example, in a case of “emergency data” with “QoS=0”, the resource pool (k−1) is selected, and in a case of “normal data” with “QoS=0” and for “remote operation”, the resource pool (k−2) is selected.

In addition,FIG.6illustrates the example with two types of QoS, which are “QoS0” and “QoS1”. For example, three or more types of QoS, such as “QoS3”, “QoS4”, . . . , may also be used. The QoS may be allocated in accordance with the magnitude of the delay and the degree of the reliability.

Further, the magnitude of the delay and the degree of the reliability of each QoS illustrated inFIG.6are also examples. For example, the delay may be 2 ms and the reliability may be 10-5 for “QoS0”.

<5. Usage Examples of Resource Pools and Specific Example of Symbol-Level Sensing>

FIGS.7to11illustrate usage examples of the resource pools. Specific examples of symbol-level sensing will be described by referring to these usage examples.

In these usage examples, the terminal100-1(UE #1) transmits “QoS0” data, and the terminal100-2(UE #2) transmits “QoS1” data. The delay and reliability of “QoS0” and “QoS1” are assumed to be the same as those illustrated inFIG.6. InFIGS.7,8,10, and11, the horizontal axis represents time, and the vertical axis represents frequency.

As illustrated inFIG.7, the terminal100-2generates “QoS1” data and performs resource selection at the timing of the second slot from the beginning (S10). In this case, since QoS of the data is “QoS1”, the terminal100-2selects the resource pool k in accordance with the selection criteria table113-c. The terminal100-2then sets a selection window in the resource pool k and performs the resource exclusion step and the resource narrowing step within the range of the selection window.

Next, as illustrated inFIG.8, the terminal100-1generates “QoS0” data and performs resource selection at the timing of the fourth slot from the beginning (S11). In this case, since QoS of the data is “QoS0”, the terminal100-1selects the resource pool (k−1) in accordance with the selection criteria table113-c.

The terminal100-1performs symbol-level sensing in the resource pool (k−1) at the time of the fifth slot (S12).

FIG.9Aillustrates an example of symbol-level sensing performed by the terminal100-1. InFIG.9A, an example of a PSSCH of the resource pool (k−1) is illustrated. A PSSCH is allocated to a different frequency band of the same slot.

FIG.9Aillustrates an example in which the leading “0” symbol is used for sensing. For example, the terminal100-1performs carrier sense on the leading “0” symbol before data transmission. When the reception energy of a signal transmitted from another terminal is equal to or greater than the threshold, the terminal100-1determines that the resource in the resource pool (k−1) that has been sensed is “busy”. In this case, the terminal100-1postpones (defers) its own data transmission.

In the example inFIG.9A, since the reception energy is lower than the threshold, the terminal100-1determines “idle” and starts the transmission from the “1” symbol. The example illustrated inFIG.9Aincludes a symbol in which Automatic Gain Control (AGC) is performed and a symbol used for transmitting a Demodulation Reference Signal (DMRS), and blank symbols other than the above are used for data transmission. Namely, in the example inFIG.9A, the terminal100-1uses the “3” symbol, the “4” symbol, the “6” symbol, and the like to transmit the “QoS0” data.

FIGS.9C and9Dillustrate examples in which the terminal100-2performs sensing on the same frequency band (the resource pool (k−1)) at the same timing as the terminal100-1. In this case, the terminal100-2performs carrier sense by using the first three symbols, namely, from the “0” to “2” symbols. The terminal100-2also performs symbol-level sensing when using the resource pool (k−1). However, in the examples inFIGS.9C and9D, the terminal100-2performs sensing by using three symbols.

As illustrated inFIGS.9A and9D, while the number of symbols used by the terminal100-1for sensing is “1”, the number of symbols used by the terminal100-2for sensing is “3”. As described above, the number of symbols used for sensing varies even for the same resource pool (k−1). This is because QoS of the data transmitted by the terminal100-1and QoS of the data transmitted by the terminal100-2are different. That is, since the terminal100-1transmits the “QoS0” data, low delay and high reliability are needed. Thus, the terminal100-1performs sensing by using the first one symbol. In contrast, since the terminal100-2transmits the “QoS1” data, normal delay and normal reliability are needed. Thus, the terminal100-2uses more symbols than in the case of transmission of the “QoS0” data to perform sensing. That is, in the example ofFIG.9D, the terminal100-2uses three symbols to perform sensing.

Therefore, for example, the higher the QoS level is, the smaller the number of symbols used for sensing may be, and the lower the QoS level is, the larger the number of symbols used for sensing may be. The number of symbols (or the number of resources used for sensing on a symbol basis) differs depending on the QoS level.

In other words, for example, when QoS is equal to or greater than a first threshold, the number of symbols used for sensing is equal to or less than a second threshold, and when QoS is lower than the first threshold, the number of symbols used for sensing is more than the second threshold.

For example, when transmitting “QoS” data, the terminal100-1may set no sensing symbol. Further, when transmitting “QoS1” data, the terminal100-2may set two symbols (two symbols, which are the “0” symbol and the “1” symbol) as sensing symbols. Any number of symbols may be set to be used for sensing as long as the number of symbols is smaller for “QoS0” than for “QoS1”.

In the example inFIG.9C, as a result of carrier sense performed by the terminal100-2for the sensing period from the “0” symbol to the “2” symbol, the reception energy of the signal transmitted from the terminal100-1has been sensed to be equal to or greater than the threshold. Thus, the terminal100-2determines “busy” and defers its own transmission for one slot. The terminal100-2then performs carrier sense on the same frequency band (the frequency band of the resource pool (k−1)) in the (n+1)th slot next and obtains the result that the reception energy of the signal transmitted from another terminal100-1is lower than the threshold. Thus, the terminal100-2transmits the “QoS1” data by using the “3rd” symbol from the (n+1)th slot onward.

In the example illustrated inFIG.8, first, the terminal100-2performs sensing (S10), and subsequently, the terminal100-1performs sensing (S11). As a result of performing carrier sense on the resource pool (k−1), the terminal100-1obtains the result “idle”. Thus, the terminal100-1transmits “QoS0” data by using the resource in the resource pool (k−1) (S12). Hereinafter, this example will be described.

As illustrates inFIG.10, next, the terminal100-2repeats the resource exclusion step n (n is an integer of 2 or more) times in the selection window of the resource pool k, and after n times of repetitions, remaining candidate resources are less than 20% of all the resources within the range of the selection window. Thus, the terminal100-2switches the resource pool from the resource pool k to the resource pool (k−1) and performs symbol-level sensing in the resource pool (k−1) (S13).

The terminal100-2senses “idle”, as a result of the carrier sense, and thus transmits “QoS1” data by using the resource in the resource pool (k−1) (S14).

Next, as illustrated inFIG.11, the terminal100-2selects the resource pool k in accordance with the selection criteria table113-cto transmits “QoS1” data as the next data. The terminal100-2then performs the resource exclusion step in the selection window of the resource pool k, selects one resource from the remaining candidate resources, and transmits the “QoS1” data (S15).

6. Operation Examples

Next, operation examples will be described. Firstly, an example of a sequence performed by the base station200and the terminals100will be described, and secondly, an example of an operation of the terminal100will be described.

<6.1 Example of Sequence Performed by Base Station Apparatus and Terminal Apparatuses>

FIG.12illustrates an example of a sequence performed by the base station200and the terminals100-1and100-2. It is assumed that the terminals100-1and100-2are within the coverage range of the base station200and in an RRC-connected state with the base station200.

The base station200transmits resource information to the terminals100-1and100-2(S20, S21). For example, the scheduler203or the transmission unit201may transmit the resource information to the terminals100-1and100-2using the RRC protocol. For example, the scheduler203or the transmission unit201may be a transmission unit that transmits the resource information.

Next, the terminals100-1and100-2store the received resource information in the resource information memory113(S22, S23). For example, the resource information is received by the RF receiver111of each of the terminals100-1and100-2, reproduced by the channel demodulator112, and stored in the resource information memory113by the channel demodulator112. The RF receiver111is also a reception unit that receives the resource information, for example. As illustrated inFIG.2, information about the resource pool (k−1)113-a, information about the resource pool k113-b, and the selection criteria table113-care stored in the resource information memory113.

Returning toFIG.12, next, the terminals100-1and100-2transmit and receive data via V2X communication (S24) while being in the coverage range of the base station200and being in an RRC idle state or while being outside the coverage range of the base station200.

By performing the operation example described above, for example, the base station200can determine (or designate) the selection criterion and the resource pool, and the terminal100can perform V2X communication by using the selection criterion and resource pool determined by the base station200.

Next, an example of an operation up to data transmission via V2X communication (S24) after the terminals100-1and100-2store the resource pool information, etc. in the resource information memory113(S22) will be described.

<6.2 Operation Example of Terminal Apparatus>

FIG.13is a flowchart illustrating an operation example of the terminal100-1. Hereinafter, the terminal100-1may be referred to as the terminal100.

The terminal100starts processing (S30) and generates data (S31). For example, the data generator116generates the data.

Next, the terminal100determines whether QoS=0 (S32). For example, the terminal100performs the following processing. That is, the data generator116determines QoS of the data based on the delay, the reliability, and all or part of the priority of the generated data and outputs the QoS to the scheduler114. The scheduler114determines whether the QoS received from the data generator116is “0”.

When the QoS=0 (Yes in S32), the terminal100selects a resource pool (S33). For example, when the QoS=0, the scheduler114selects a resource pool in accordance with the selection criteria of the selection criteria table113-c. In the example inFIG.6, when the QoS=0, the scheduler114selects the resource pool (k−1), which has the highest usage ranking.

However, when certain conditions are satisfied, the scheduler114may select the resource pool k, which has the second highest usage ranking. An example of the certain conditions includes a case where many remaining or narrowed resources with good quality are within the range of the selection window of the resource pool k (for example, the remaining resources are X % or more, the energy measured for the narrowed resources is smaller than a threshold, etc.). In such a case, for example, the scheduler114is likely to select a resource within the range of 1 to 3 ms from the time of resource selection in the selection window. This is because, if the scheduler114selects a resource within the range of 1 to 3 ms, it is possible to satisfy the delay and reliability needed when QoS=0.

When the terminal100selects the resource pool (k−1) (Yes, in S34), the terminal100sets a symbol to be sensed based on the QoS (S35). For example, when the QoS=0, the scheduler114may set the sensing symbol to the “0” symbol or may set no sensing symbol. Since information about a symbol to be set as the sensing symbol in accordance with the QoS is stored, for example, in the resource information memory113, the scheduler114may read the information and set the sensing symbol. For example, such setting information may be transmitted from the base station200and stored in the resource information memory113, as with the resource information.

Next, the terminal100determines whether no transmission from another terminal is sensed as a result of the sensing (S36). For example, the scheduler114makes this determination by obtaining, from the energy measuring device124, an average reception energy ER of a reception signal yR(t) received using the sensing symbol of the resource pool (k−1) and determining whether the average reception energy ER is smaller than a threshold.

If no transmission from another terminal is sensed (Yes in S36), the terminal100transmits the data by using a resource in the resource pool (k−1), which has been sensed (S37). For example, the terminal100performs the following processing.

That is, when the average reception energy ER is smaller than the threshold, the scheduler114determines that the resource in the resource pool (k−1) is in an “idle” state. The scheduler114then outputs the resource allocation information illustrated inFIG.9Ato the control signal generator115. The control signal generator115generates a control signal including the resource allocation information and outputs the resource allocation information to the RF transmitter117. The RF transmitter117transmits the control signal by using the PSCCH of the resource pool (k−1) and the data by using the PSSCH of the resource pool (k−1) to another terminal (for example, the terminal100-2).

Returning toFIG.13, after transmitting the data (S37), the terminal100ends the series of processes (S38).

In contrast, if transmission from another terminal is sensed as a result of the sensing (No in S36), the terminal100defers its own transmission (S40). For example, the terminal100performs the following processing.

That is, when the average reception energy ER is equal to or greater than the threshold, the scheduler114determines that the resource pool (k−1) is in a “busy” state. Consequently, the scheduler114outputs no resource allocation information to the control signal generator115and controls the data generator116to defer the data output to the RF transmitter117for a period of one slot.

The terminal100then repeats the processing of S35onward in the next slot.

If the resource pool (k−1) is not selected (No in S34), the terminal100sets “1” to n (S41). For example, n represents the number of repetitions of the resource exclusion step.

“If the resource pool (k−1) is not selected” indicates, for example, “if the resource pool k is selected”. Sensing on a slot basis is performed in the resource pool k.

Next, the terminal100sets the selection window and the sensing window in the resource pool k and performs the resource exclusion step and the resource narrowing step (S42).

Next, the terminal100determines whether the candidate resources remain 20% or more of all the resources in the selection window as a result of the resource exclusion step, (S43). If the candidate resources remain 20% or more (Yes in S43), the terminal100randomly selects one resource from the candidate resources (S44). Next, the terminal100transmits the data by using the selected resource (S37). The terminal100then ends the series of processes (S38).

If the candidate resources remain less than 20% as a result of the resource exclusion step (No in S43), the terminal100determines whether the number of repetitions n is smaller than a limit count NQoS(S45).

When the candidate resources are less than 20% as a result of the resource exclusion step, the terminal100increases the threshold for the reception energy (or relaxes the conditions) and repeats the resource exclusion step. Here, a limit is given to the number of repetitions n, and the terminal100determines whether the number of repetitions n has reached the limit count NQoS. For example, the scheduler114counts the number of repetitions n of the resource exclusion step and determines whether the number of repetitions n counted is less than the limit count NQoS.

When the number of repetitions n is less than the limit count NQoS(Yes in S45), the terminal100increments the number of repetitions n (S46), increases the threshold for the reception energy, and performs the resource exclusion step again (S42). For example, when the number of repetitions n is less than the limit count NQoS, the scheduler114increments the number of repetitions n, increases the threshold for the reception energy, and performs the resource exclusion step again.

The terminal100repeats the resource exclusion step (a loop of S42, S43, S45, and S46), and when the number of repetitions n reaches the limit count NQoS(No in S45), the terminal100switches the resource pool from the resource pool k to the resource pool (k−1) and preforms the processing of S35onward. This process corresponds to, for example, the process of S13inFIG.10. For example, when the number of repetitions n counted reaches the limit count NQoS, the scheduler114switches the resource pool from the resource pool k to the resource pool (k−1) and performs symbol-level sensing in the resource pool (k−1).

The terminal100switches the resource pool from the resource pool k to the resource pool (k−1) since, when the number of repetitions n reaches the limit count NQoS, even if the resource exclusion step is further performed, the candidate resources are highly unlikely to be 20% or more. In a case where many terminals use the resource pool k, although the terminal100has selected the resource pool k first, the terminal100uses the resource pool (k−1) instead. Subsequently, the terminal100performs the processing of S35onward.

If the QoS is not zero (No in S32), the terminal100selects the resource pool k in accordance with the selection criteria table113-c. The terminal100then perform the processing of S41onward. In this case, too, when the candidate resources are less than 20% (No in S43) and when the number of repetitions n of the resource exclusion step reaches the limit count NQoS(No in S45), the terminal100switches to the resource pool (k−1) and performs the resource selection (S35to S38).

FIG.14is a flowchart illustrating another operation example of the terminal100.

InFIG.14, the terminal100performs the resource exclusion step in the resource pool k (S42), selects the resource in the resource pool k when the available resources are a % or more in the selection window (Yes in S50), selects a resource in the resource pool k (S44), and transmits the data by using the selected resource (S37).

Here, “a” is, for example, a numerical value that varies in accordance with the QoS of the data. For example, when the QoS=1, a=20, and when the QoS=2, a=10.

Even in a case where the resource pool k is used, when the QoS is the strictest (for example, the QoS=1) and when the candidate resources are less than 20%, the resource pool (k−1) is immediately used without repeatedly performing the resource exclusion step. In this way, data transmission that satisfies such a strict QoS can be performed. In contrast, when the QoS has milder conditions (for example, QoS=2) than the strictest QoS, the resource pool is not switched to the resource pool (k−1) when the candidate resources are less than 10%. Instead, the resource pool k is used. In this way, for example, data transmission that corresponds to such a mild QoS can be performed.

Next, another example according to the first embodiment will be described.

FIG.15illustrates another example of the selection criteria table113-c.

The selection criteria table113-cinFIG.15illustrates a case where the resource pool k and the resource pool (k−1) have the same usage ranking for “QoS0”. For example, the scheduler114may select the resource pool k or the resource pool (k−1) when the QoS is “QoS0”. While the terminal100may select the resource pool k, when the terminal100selects the resource pool (k−1), symbol-level sensing is performed. Thus, compared with the case where the resource pool k is always selected, since the terminal100may select the resource pool (k−1), the communication delay can be reduced, and the communication reliability can be improved.

In addition, according to the first embodiment, the resource information is transmitted from the base station200and received by the terminal100, and the terminal100performs V2X communication by using the received resource information. For example, the resource information may be stored in the resource information memory113at the time of factory shipment. In this case, the terminal100can perform V2X communication with another terminal by using the resource information stored in the resource information memory113without receiving the resource information from the base station200.

As described above, the selection criterion may be determined by the terminal100or by the base station200as described above in <6.1 Example of Sequence Performed by Base Station Apparatus and Terminal Apparatuses>, for example. In addition, even when the selection criterion is determined by the terminal100, the selection criterion determined (or designated) by the base station200may be used by performing the above <6.1 Example of Sequence Performed by Base Station Apparatus and Terminal Apparatuses>, for example.

As described above, according to the first embodiment, the terminal100can select any one of the resource pool (k−1), in which symbol-level sensing is performed, and the resource pool k, in which slot-level sensing is performed, based on the QoS and the selection criterion of the data to be transmitted. Since the sensing is performed on a symbol basis in the resource pool (k−1), for example, when the resource pool (k−1) is selected, a communication delay requirement of 3 ms can be achieved. Thus, the terminal100according to the first embodiment can reduce the communication delay.

In addition, when the terminals100use only one of the resource pools, this resource pool will be used by many terminals100. This may lead to deterioration of the communication reliability. However, according to the first embodiment, the terminal100can use any one of the resource pools. This allows the resource pools to be allocated to the individual terminals. For example, while one terminal uses the resource pool k, another terminal uses the resource pool (k−1). Thus, according to the first embodiment, compared with the case where only one of the resource pools is used, the probability that only one resource pool is used can be reduced. Therefore, according to the first embodiment, the communication reliability can be improved.

Further, when only one of the resource pools is used, as described above, the resource utilization efficiency may decrease. However, according to the first embodiment, since the terminal100can use any one of the resource pools, more resources are available, compared with the case where only one of the resource pools is used. Consequently, the resource utilization efficiency can also be improved.

OTHER EMBODIMENTS

FIG.16illustrates an example of a hardware configuration of the terminal100.

The terminal100includes a Read Only (ROM)130, a Random Access Memory (RAM)131, a processor132, a memory133, a radio unit134, and an antenna140.

The processor132reads a program stored in the ROM130, loads the program onto the RAM131, and executes the loaded program to realize the functions of the data traffic processing unit101, the channel encoder102, the IFFT103, and the CP addition unit104. In addition, the processor132executes the program to realize the functions of the channel demodulator112, the scheduler114, the control signal generator115, the data generator116, the control signal detector122, the data detector123, and the energy measuring device124. The processor132corresponds to, for example, the data traffic processing unit101, the channel encoder102, the IFFT103, the CP addition unit104, the channel demodulator112, and the scheduler114in the first embodiment. In addition, the processor132corresponds to, for example, the control signal generator115, the data generator116, the control signal detector122, the data detector123and the energy measuring device124in the first embodiment. Further, the memory133corresponds to, for example, the resource information memory113in the first embodiment.

In addition, the radio unit134corresponds to, for example, the RF transmitters105and117and the RF receivers111and121in the first embodiment. Further, the antenna140corresponds to, for example, the transmission antennas106and118and the reception antennas110and120in the first embodiment.

Communication delay can be reduced, and communication reliability can be improved.

All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.

REFERENCE SIGNS LIST

10: communication system100(100-1to100-3): terminal apparatus (terminal)100-v1to100-v3: vehicle105,117: RF transmitter106,118: transmission antenna110,120: reception antenna111,121: RF receiver112: channel demodulator113: resource information memory113-a: information about the resource pool (k−1)113-b: information about the resource pool k113-c: selection criteria table114: sidelink scheduler (scheduler)115: sidelink control signal generator (control signal generator)116: sidelink data generator (data generator)122: sidelink control signal detector (control signal detector)123: sidelink data detector (data detector)124: energy measuring device132: processor200: base station apparatus (base station)203: scheduler211: processor