Patent Application
20210274474
The embodiments discussed herein are related to a communication device and a wireless communication system including a communication device.
Currently, many of network resources are occupied by traffic used by mobile terminals (including smartphones or feature phones). In addition, it is assumed that traffic used by mobile terminals will continue to expand in future.
Meanwhile, along with the expansion of IoT (Internet of things) services (for example, traffic systems, monitoring systems such as smart meters and devices), support for services with various requirement conditions is required. For this reason, in the communication standard of the Fifth Generation Mobile Communication (5G (NR: New Radio)), in addition to the standard technology of the Fourth Generation Mobile Communication (4G (LTE: Long Term Evolution)) (for example, see Non-Patent Documents 1 through 11), technologies for realizing higher data rates, larger capacities, lower delays are further required. Meanwhile, the Fifth Generation Communication Standard is considered in the working groups of 3GPP (for example, TSG-RAN WG1, TSG-RAN WG2 and so on) (for example, Non-Patent Documents 12 through 38).
In 5G, in order to support various services, support for use cases categorized as eMBB (Enhanced Mobile BroadBand), Massive MTC (Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communication) is assumed.
Meanwhile, in the working groups of 3GGP, D2D (Device to Device) communication is also discussed. D2D communication is also called sidelink communication in some cases. In addition, as an example of D2D communication, V2X is considered. V2X includes V2V, V2P, V2I. V2V represents communication between vehicles. V2P represents communication between a vehicle and a pedestrian. V2I represents communication between a vehicle and a road infrastructure such as a sign or the like. The rules regarding V2X are described in Non-Patent Documents 39 and 40.
In V2X of 4G, for example, the autonomous resource allocation method (mode 4) is used. In the autonomous resource allocation method, candidate resources are decided from Selection Window including a plurality of resources according to the average RSSI (Received Signal Strength Indicator), and a resource is randomly selected from the candidate resources. Then, the communication device transmits the traffic using the selected resource.
The autonomous resource allocation method (mode 4) used in V2X of 4G is optimized for periodic traffic. However, in 5G, in order to support various services, traffics with different cycles may exist in a mixed manner. In addition, in 5G, transmission of traffic that is not periodic may be required. For example, when an on-vehicle sensor detects a danger in automatic driving, transmission of emergency data with a small latency may be required. For this reason, when the autonomous resource allocation method of 4G is applied to V2X communication that supports various services, an inappropriate resource may be allocated to the transmission traffic. Then, as a result, interference with respect to the V2X signal may become large.
According to an aspect of the embodiments, a communication device includes a processor that divides a first section including a plurality of resources into a plurality of second sections; provides, for each of the second sections, a first evaluation value related to a channel usage rate; calculates, for each of selectable resources included in the first section, a second evaluation value according to the first evaluation value; and selects one or a plurality of resources to be allocated to transmission data from the selectable resources according to the second evaluation value.
The object and advantages of the disclosure will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the disclosure.
Hereinafter, embodiments of the present disclosure are described in detail with reference to the drawings. The objects and examples disclosed herein are an example and are not to limit the scope of claims in the present patent application. For example, even when expressions of description are different, if technically equivalent, the arts of the present patent application may be applied. In addition, the embodiments disclosed herein may be combined appropriately as long as there is no inconsistency.
For the terms and technical contents used herein, the terms and technical contents may be used that are described as the standards of 3GPP or the like related to communications in the specifications (for example, 3GPP TS 38.211 V15.2.0) or contributions.
The base station 10 controls cellular communication (uplink/downlink communications via the Uu interface) of the wireless communication device 20. That is, the base station 10 receives uplink signals (the control signal and the data signal) from the wireless communication device 20. In addition, the base station 10 transmits downlink signals (the control signal and the data signal) to the wireless communication device 20.
The wireless communication device 20 can communicate with another communication device via the base station 10. In addition, the wireless communication device 20 can also communicate with another wireless communication device without via the base station 10. That is, the wireless communication device 20 supports D2D (Device-to-Device) communication. D2D communication transmits a signal via the PC5 interface, for example. Meanwhile, D2D communication may also be called “sidelink communication”. In addition, the wireless communication device 20 may be called “UE (User Equipment)” or “VUE {Vehicle UE}”.
The wireless communication device 20 is implemented in a vehicle, as described above. Therefore, the wireless communication device 20 is able to perform V2X communication, in this example. V2X includes V2V, V2P, V2I. V2V represents communication between vehicles. V2P represents communication between a vehicle and a pedestrian. V2I represents communication between a vehicle and a road infrastructure such as a sign or the like. Meanwhile, in this example, the allocation of a resource for sidelink communication is autonomously performed by each of the wireless communication device 20.
The UE3 configures a sensing window just before the time n and configures a selection window immediately after time n+T (T≤4). The length of the sensing window is, while it is not particularly limited, 1000 m seconds for example. In addition, in this example, the length of the selection window is the time corresponding to seven subframes. Then, the UE3 selects the resource to be allocated to V2X traffic autonomously by the following procedures.
In step 1, the UE3 excludes resources used by another UE. The resources to be excluded are decided according to RSRP (Reference Signal Received Power) of control information and data transmitted from other UEs. For example, in the example illustrated in
In step 2, the UE3 calculates average RSSI (Received Signal Strength Indicator) with respect to each resource included in the set A. Here, the UE measures RSSI of each frequency channel constantly or regularly and records the measured value in a memory. Therefore, the UE3 is able to calculate average RSSI for each frequency channel from a plurality of RSSI values obtained in the past (for example, a plurality of RSSI values obtained in the sensing window).
For example, in the example illustrated in
Here, when a signal is transmitted using a resource with a large average RSSI, the quality of the signal may become low. Therefore, the UE3 selects resources with a small average RSSI as candidates for transmitting V2X traffic. At this time, the UE3 ranks the respective resources included in the set A according to their average RSSI. Then, the UE3 selects 20 percent (or 20 percent or more) of the resources in the ascending order from the resource with the lowest average RSSI. After this, the resources selected from the set A are moved to a set B.
In step 3, the UE3 randomly selects (or reserve) one resource from the plurality of resources included in the set B. Then, the UE3 transmits V2X traffic using the selected resource. At the time of the transmission using the selected resource, a time/frequency resource for transmitting data in the next period is reserved.
As described above, the wireless communication device autonomously selects a resource for transmitting V2X traffic. Here, the wireless communication device uses a resource with which a good radio wave environment is expected, according to the reservation mechanism of resources and the average RSSI of each resource regardless of the distribution of the resources occupied or reserved in the time domain. Therefore, in D2D communication, autonomous resource allocation is realized with which a good communication quality is obtained. Meanwhile, autonomous resource allocation in LTE-V2X is described in 3GPP TS 36.213 V15.2.0 14.1.1.6, for example.
However, in the 5G communication system, in order to support various services, traffics with different transmission cycles may exist in a mixed manner. In addition, in 5G, transmission of traffic that is not periodic may be required. For example, when an on-vehicle sensor detects a danger in automatic driving, transmission of emergency data with a small latency may be required. For this reason, when occupied or reserved resources are distributed unevenly in the time domain, reliability of the communication may deteriorate.
For example, in the example illustrated in
Specifically, there are eight resources that are not reserved in the selection window. That is, there are eight resources that are included in the set A. In this instance, for example, there are two cases.
In the first case, the wireless communication device selects resources with a small average RSSI from the eight resources included in the set A. Here, the resources selected from the set A according to the average RSSI are included in the set B. Then, the wireless communication device allocates a resource that is randomly selected from the resources included in the set B to the transmission traffic.
In this case, there are small amount of resources that are not reserved (that is, selectable resources) in the selection window, and therefore, the possibility increases that a plurality of wireless communication devices selects the same resource. As a result, reliability of communication may deteriorate.
In the second case, the wireless communication device relaxes the removal condition of resources regarding RSRP or the selection condition of resources regarding RSSI to increase the number of selectable resources and increases the number of resources included in the set A or in the set B. Here, the possibility that resources with bad quality remain in the set A or in the set B increases. In other words, the wireless communication device may have no choice but to select a resource with bad quality. As a result, reliability of communication may deteriorate.
Meanwhile, a problem caused by uneven distribution of reserved resources may be solved by making the selection window long. However, when the selection window becomes long, latency becomes high. Therefore, it is not preferable to make the selection window long for a service that requires a low latency (for example, URLLC).
In addition, the wireless communication device usually does not reserve a resource for the next transmission in a case of transmitting traffic that is not periodic. That is, the wireless communication device may perform one-shot transmission. Then, in a case in which one-shot transmission is performed, the average RSSI calculated with respect to each resource in the selection window may not represent the influence of interference with a good accuracy.
For example, it is assumed that, in
As described above, in a case in which periodic transmission and one-shot transmission exist in a mixed manner, the average RSSI calculated with respect to each resource in a selection window may not represent the influence of interference with a good accuracy.
The controller 11 controls cellular communication provided by the base station 10. In addition, the controller 11 may decide a parameter for D2D communication (that is, sidelink communication) performed by the wireless communication device 20. Meanwhile, in this example, the controller 11 is realized by a processor. However, a part of the functions of the controller 11 may be realized by a hardware circuit.
The storage unit 12 stores a software program executed by the processor. In addition, the storage unit 12 stores data and information required for controlling the operations of the base station 10. Meanwhile, the storage unit 12 is realized by a semiconductor memory, for example. The network interface 13 provides an interface for connecting to the core network. That is, the base station 10 is able to connect to another base station 10 or the network management system that controls the base station 10 via the network interface 13.
The wireless transmitter 14 transmits the wireless signal of cellular communication, according to the instruction given by the controller 11. That is, the wireless transmitter 14 transmits the downlink signal to the wireless communication device 20 in the cell. The wireless receiver 15 receives the wireless signal of cellular communication, according to the instruction given by the controller 11. That is, the wireless receiver 15 receives the uplink signal transmitted from the wireless communication device 20 in the cell. Meanwhile, cellular communication is provided using the 2.4 GHz band and/or the 4 GHz band, for example.
The controller 21 controls cellular communication and D2D communication provided by the wireless communication device 20. Meanwhile, in this example, the controller 21 is realized by a processor. In this case, the controller 21 provides the functions to control cellular communication and D2D communication by executing a software program stored in the storage unit 22. However, a part of the functions of the controller 21 may be realized by a hardware circuit.
The storage unit 22 stores a software program executed by the processor. In addition, the storage unit 22 stores data and information required for controlling the operations of the wireless communication device 20. Meanwhile, the storage unit 22 is realized by a semiconductor memory, for example.
The wireless transmitter 23 transmits the wireless signal of cellular communication, according to the instruction given by the controller 21. That is, the wireless transmitter 23 transmits the uplink signal to the base station 10. The wireless receiver 24 receives the wireless signal of cellular communication, according to the instruction given by the controller 21. That is, the wireless receiver 24 receives the downlink signal transmitted from the base station 10.
The wireless transmitter 25 transmits the wireless signal of D2D communication, according to an instruction given by the controller 21. That is, the wireless transmitter 25 transmits the D2D signal to another wireless communication device, using a resource selected autonomously in the wireless communication device 20. The wireless receiver 26 receives the wireless signal of D2D communication, according to an instruction given by the controller 21. That is, the wireless receiver 26 receives the D2D signal transmitted from another wireless communication device. Meanwhile, in this example, the D2D signal includes V2X data and V2X control information.
In the example illustrated in
The resource information memory 31 stores resource allocation control information related to the allocation of resources for sidelink communication. The resource allocation control information includes section information (it may also be paraphrased as window information), a resource selection criterion, and so on. Meanwhile, the resource allocation control information is given by the user of the wireless communication device 20 or the network administrator, for example. Alternatively, the resource allocation control information may be given from the base station 10.
The sidelink data generator 32 generates a sidelink data signal from data generated by the application of the wireless communication device 20. For example, in a case in which the wireless communication device 20 is implemented on the vehicle and the application is an automatic driving program, data that represent sensor information is generated. Then, the sidelink data generator 32 outputs a sidelink data according to a transmission instruction given from the scheduler 33.
The scheduler 33 allocates, when a sidelink data signal is generated by the sidelink data generator 32, a resource to the sidelink data signal. At this time, the scheduler 33 executes the resource allocation referring to the resource allocation control information stored in the resource information memory 31 and sidelink control information received from another wireless communication device. In addition, as needed, the scheduler 33 refers to the value measured by the energy detector 39.
The sidelink control signal generator 34 generates a sidelink control signal that represents the resource allocation decided by the scheduler 33. Therefore, the sidelink control signal includes resource allocation information that represent the resource allocated to sidelink data. In addition, when sidelink data is transmitted periodically, the sidelink control signal may also include information that represents the reservation of the resource that is to be used for next data transmission.
The RF transmitter 35 transmits the sidelink data signal generated by the sidelink data generator 32 and the sidelink control signal generated by the sidelink control signal generator 34 via an antenna. The RF receiver 36 receives a wireless signal transmitted from another wireless communication device.
The sidelink control signal detector 37 detects a sidelink control signal from a received signal and obtains sidelink control information transmitted from another wireless communication device. The sidelink control information includes resource allocation information that represents the resource allocated to sidelink data, and information related to the reservation of a resource.
The sidelink data detector 38 detects a sidelink data signal from a received signal according to the sidelink control information that the sidelink control signal detector 37 has obtained. Then, the sidelink data detector 38 reproduces data from the detected sidelink data signal. The data is passed to the application.
The energy detector 39 measures the energy of a received signal. Here, the energy detector 39 measures the RSSI of a received signal. However, the energy detector 39 may also measure another indicator. For example, the energy detector 39 may measure the RSRP of a received signal. In addition, the energy detector 39 measures the energy of the received signal for each resource. For example, the energy detector 39 measures, for each frequency, and for each subframe (that is, the data channel or the control channel), the energy of the received signal. Alternatively, the energy detector 39 may regularly measure the energy of the received signal in each frequency channel.
The scheduler 33 is realized by the controller 21 illustrated in
The division unit 41 generates a plurality of second sections by dividing the selection window including a plurality of resources, in the time domain. In this example, the second section is called a “subwindow.” At this time, the division unit 41 divides the selection window according to the section information stored in the resource information memory 31. Meanwhile, the section information includes information representing the size of the subwindow.
The selection window is divided into subwindows SW1 through SW5 that have the same size with each other, as illustrated in
The calculator 42 determines whether each resource in the selection window is reserved by another wireless communication device, according to the sidelink control information that the wireless communication device 20 received from other wireless communication devices. Meanwhile, each wireless communication device reserves, when periodically transmitting sidelink data, a resource for transmitting next sidelink data. The reservation of the resource is reported to each wireless communication device by the sidelink control information.
Then, the calculator 42 calculates the channel usage rate for each subwindow. The channel usage rate CUR(i) of a subwindow SWi is calculated by the expression (2).
NT represents the total number of resources included in the subwindow SWi. Nr represents the number of resources reserved by another wireless communication device in the resources included in the subwindow SWi.
For example, in the subwindow SW1, in the twelve resources, two resources are reserved by another wireless communication device. Therefore, the channel usage rate CUR(1) of the subwindow SW1 is “⅙ (17 percent).” Meanwhile, in the subwindow SW2, in the twelve resources, four resources are reserved by another wireless communication device. Therefore, the channel usage rate CUR(2) of the subwindow SW2 is “⅓ (33 percent).” Note that the resources that are not reserved by another communication device are included in the set A.
In addition, the channel usage rate may also be calculated as a parameter that indicates the congestion level of the channel, for example. For example, in the same manner as in the method for averaging RSSI, the average of a plurality of CBR (Channel Busy Ratio) measurement values obtained in the sensing window is calculated. Meanwhile, the channel usage rate may also be the largest value in the plurality of CBR measurement values.
The calculator 42 calculates the average reception energy for each resource included in the set A. That is, the calculator 42 calculates the average reception energy for each resource that is not reserved by another wireless communication device. In this example, it is assumed that, as the average reception energy, the average of a plurality of RSSI measurement values (that is, the average RSSI) is calculated.
The average RSSI is calculated using the expression (1), for example, as explained with reference to
In the expression (3), the value of x depends on whether or not one-shot transmission was performed at the measurement timing. For example, when one-shot transmission was performed, a value smaller than 1 is used as the weight x. In this case, the value of x may be decided in advance. Meanwhile, the value of x may be determined according to the instruction from the base station. On the other hand, when one-shot transmission was not performed, the weight x is 1. In this case, the expression (3) becomes the same as the expression (1).
Next, the calculator 42 calculates a ranking index RI for each resource included in the set A. That is, the calculator 42 calculates the ranking index RI for each resource that is not reserved by another wireless communication device. The ranking index RI is an example of an evaluation value that represents the selection criterion for the resources (that is, the criterion for moving a resource from the set A to the set B). In this example, the ranking index RI is calculated by the expression (4).
RIxy=RSSIxy·max{f(CUR(i))}
f(CUR(i))=α(i)·CUR(i) (4)
RIxy represents the ranking index for a resource Rxy. As illustrated in
An example of the calculation of the ranking index RI is presented. Here, the ranking indexes (RI32, RI35) for the two resources R32, R35 presented in
CUR(1)=⅙ (17 percent)
CUR(2)=⅓ (33 percent)
CUR(3)=⅓ (33 percent)
CUR(4)=½ (50 percent)
CUR(5)=¼ (25 percent)
Here, it is assumed that the average RSSI of the resources RI32, RI35 are the same as that of each other, and that is referred to as “E”. The coefficient α(i) is “1” for both.
The resource R32 is included in both of the subwindows SW1 and SW2. Here, the largest value of the channel usage rates of the subwindow S1 and S2 is “CUR(2)=⅓.” Therefore, the ranking index RI32 of the resource R32 is E/3.
coding (variable-length coding) and outputs a coded video.
The resource R35 is included in the subwindows SW3 through SW5. Here, the largest value of the channel usage rates of the subwindows SW3 through SW5 is “CUR(4)=½.” Therefore, the ranking index RI35 of the resource R35 is E/2.
The calculation method for the ranking index RI is not limited to the expression (4). For example, the calculator 42 may calculate the ranking index RI according to the sum of the average RSSI and the channel usage rate CUR. In this case, the weight may be multiplied with either one or both of the average RSSI and the channel usage rate CUR.
However, when the calculation is made according to any method, it is preferable that the lower the channel usage rate CUR, the smaller the value of the ranking index RI, and the lower the average RSSI, the smaller the value of the ranking index RI. The expression (4) satisfies this policy.
The calculator 42 calculates the ranking index RI for each resource (hereinafter, a selectable resource) that is not reserved by another wireless communication device, as described above. Then, the calculator 42 arranges the selectable resources in the ascending order of the ranking index. That is, ranking is performed with respect to the selectable resources according to the ranking index.
The selector 43 selects a resource to be allocated to transmission data from the selectable resources whose rank according to the ranking index RI is higher than a prescribed threshold. For example, the selector 43 extracts, from all the selectable resources, β percent of the selectable resources of whose value of ranking index RI is small. In the example illustrated in
Meanwhile, the value of β may be decided according to the size of the selection window and/or the size of each subwindow. In addition, the value of β may also be decided according to the channel usage rate of the selection window. Alternatively, β may be a fixed value decided in advance.
The selector 43 randomly selects one resource from the extracted selectable resources. In addition, the selector 43 allocates the selected resource for the transmission data. Then, the wireless communication device 20 transmits V2X data using the resources allocated by the selector 43.
Next, an example of procedures for allocating a resource for transmission data is presented. In this example, it is assumed that a first section (for example, a selection window) illustrated in
RI11=41×max{17}=41×17=697
RI12=41×max{17,33}=41×33=1353
RI13=41×max{17,33,33}=41×33=1353
RI15=41×max{33,50,25}=41×50=2050
RI16=41×max{50,25}=41×50=2050
RI17=41×max{25}=41×25=1025
RI21=40×max{17}=40×17=680
RI23=40×max{17,33,33}=40×33=1320
RI25=40×max{33,50,25}=40×50=2000
RI27=40×max{25}=40×25=1000
RI31=39×max{17}=39×17=663
RI32=39×max{17,33}=39×33=1287
RI33=39×max{17,33,33}=39×33=1287
RI34=39×max{33,33,50}=39×50=1950
RI35=39×max{33,50,25}=39×50=1950
RI37=39×max{25}=39×25=975
RI42=50×max{17,33}=50×33=1650
RI43=50×max{17,33,33}=50×33=1650
RI46=50×max{50,25}=50×50=2500
RI47=50×max{25}=50×25=1250
The 20 resources included in the set A are arranged in the ascending order of the ranking index RI. Then, from the resources included in the set A, β percent of the resources that have a small ranking index RI are extracted. Here, assuming β=20, four resources are extracted. Specifically, resources RI31, RI21, RI11, RI37 are extracted. Then, the extracted four resources are moved to the set B.
After this, the selector 43 randomly selects one resource from the four resources included in the set B. In addition, the selector 43 allocates this selected resource for the transmission data. Then, the wireless communication device 20 transmits sidelink data using the resources allocated by the selector 43. At this time, the wireless communication device 20 generates resource allocation information that represents the selected resource and transmits a sidelink control signal including the resource allocation information.
As described above, in the communication device 20, resources included in a subwindow in which, many resources that are not reserved (that is, selectable resources) remain are selected with high priority. Therefore, the possibility that a resource in a bad radio-wave environment (that is, the average RSSI is high) is selected becomes low, and the communication quality may improve. Meanwhile, in the example illustrated in
The energy detector 39 regularly measures the reception energy for each of the plurality of frequency channels for sidelink communication. In this example, it is assumed that the energy detector 39 regularly measures the RSSI of each frequency channel. The measurement result of the energy detector 39 is recorded in the resource information memory 31 or in another memory.
In S1, the scheduler 33 configures a first section (may be referred to as a selection window below) that includes a plurality of resources, according to the generation of transmission data. The size of the selection window follows the section information stored in the resource information memory 31.
In S2, the scheduler 33 excludes resources that are reserved by another wireless communication device from the resources included in the selection window. That is, the scheduler 33 creates the set A. The set A includes the resources in the selection window that are not reserved by another wireless communication device. Meanwhile, the scheduler 33 is able to detect a resource that is reserved by another wireless communication device by obtaining sidelink control information transmitted from another wireless communication device.
In S3, the scheduler 33 calculates the average reception energy (in this example, the average RSSI) of each resource included in the set A. At this time, the scheduler 33 may calculate the average RSSI using the expression (1) or the expression (3).
In S4, the division unit 41 divides the selection window into a plurality of second sections (may be referred to as subwindows below). The size and the position in the time domain of each subwindow follows the section information stored in the resource information memory 31. Meanwhile, the sizes of the plurality of subwindows do not have to be the same with each other. In addition, the plurality of subwindows may be arranged so as to overlap with each other or may be arranged not to overlap with each other.
In S5, the calculator 42 calculates a first evaluation value for each subwindow. The first evaluation value is calculated as the channel usage rate using the expression (2), for example. Meanwhile, as described above, the scheduler 33 recognizes a resource in the selection windows that is reserved by another wireless communication device, by obtaining sidelink control information transmitted from another wireless communication device.
In S6, the calculator 42 calculates a second evaluation value with respect to each resource included in the set A. The second calculation value is the ranking index RI, for example. The ranking index RI is calculated using the expression (4), for example. In this case, the ranking index RI depends on the average RSSI and the channel usage rate. Specifically, the lower the average RSSI of the frequency of a given resource (hereinafter, the “target resource”) is lower, the smaller the value of the ranking index. In addition, the lower the channel usage of the subwindow including the target resource, the smaller the value of the ranking index RI. Then, the calculator 42 arranges the respective resources included in the set A in the ascending order of the ranking index RI.
In S7, the selector 43 extracts, from the resources included in the set A, the β% of the resources that have a small value of the ranking index RI. The extracted resources are included in the set B. That is, the scheduler 33 creates the set B.
In S8, the selector 43 randomly selects a resource to be allocated to the transmission data from the resources included in the set B. After this, the wireless communication device 20 transmits the transmission data using the resource selected in S8. Meanwhile, the order for executing the steps in this flowchart may be changed arbitrarily as long as there is no inconsistency. For example, the first section may be divided to generate a plurality of second sections before executing S2 or S3.
In S11, the calculator 42 arranges the resources included in the set A in the ascending order of the channel usage rate of the corresponding subwindow. Meanwhile, the subwindow corresponding to a given resource represents the subwindow that includes this resource. For example, in the example illustrated in
In S12, the selector 43 extracts, from the resources included in the set A, β% of the resources for which the channel usage rate of the corresponding subwindow is low. Here, the extracted resources are included in the set B. That is, the scheduler 33 creates the set B.
The process in S8 is substantially the same in
As described above, in the example illustrated in
In S21, the scheduler 33 calculates the average reception energy of each resource included in the set B. In this example, the average RSSI of each resource included in the set B is calculated. The average RSSI is calculated using the expression (1) or the expression (3) for example.
In S22, the calculator 42 arranges the resources included in the set B according to the ascending order of the average RSSI. In S23, the selector 43 extracts b % of the resources that have a small RSSI. The extracted resources are included in a set C. That is, the scheduler 33 creates a set C.
The process in S8 is mostly the same in
Meanwhile, the resource selection criterion stored in the resource information memory 31 may include information to select one of the methods illustrated in
In Option 2, PSCCH and PSSCH are placed in the same time domain. Therefore, in a case in which Option 2 is used, the wireless communication device is not able to recognize a resource occupied by another wireless communication device immediately. Therefore, in a case in which Option 2 is used, the wireless communication device is able to remove only a resource reserved for periodic transmission.
In Options 1A and 1B, PSCCH and PSSCH are placed in different time domains. Specifically, PSCCH is placed before PSSCH. That is, the scheduling allocation information of a data signal is transmitted before the data signal. Therefore, in a case in which Options 1A or 1B is used, the wireless communication device is able to recognize a resource occupied by another wireless communication device immediately. In a similar manner, in Option 3, a resource occupied by another wireless communication device may be recognized. Therefore, in a case in which Options 1A, 1B or 3 is used, the wireless communication device is able to remove a resource occupied not only for periodic transmission but also for one-shot transmission.
The UE1 performs periodic transmission. For example, the UE1 transmits sidelink data using a resource Ra. At this time, the UE1 reserves the resource for the next data transmission using PSCCH of the resource Ra. Here, a resource R6 is reserved.
A UE2 transmits sidelink data using a plurality of successive subframes. In the example illustrated in
The UE3 recognizes that the resource R6 is occupied by the UE1 by decoding PSCCH and that the resource R1 is occupied by the UE2. That is, the UE3 determines that the resources R1 and R6 cannot be allocated for its own transmission data. Then, the UE3 creates the set A by excluding the resources R1 and R6 from the resources R1 through R8 included in the selection window. As a result, the set A includes the resources R2-R5, R7 and R8. Meanwhile, each resource included in the set A is used as a selectable resource (or a candidate resource) that has the possibility to be allocated for transmission data.
Thus, when creating the set A, the wireless communication device excludes not only a resource that is reserved by another wireless communication device but also a resource that is actually occupied by another wireless communication device. Therefore, the selectable resource may represent a resource that is not reserved or occupied by another wireless communication device, in the resources included in the selection window (that is, the first section). In addition, the channel usage rate (that is, the first evaluation value) may represent the proportion of resources that are reserved or occupied by another wireless communication device, in the resources included in the selection window.
Then, according to one of the methods illustrated in
All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the disclosure 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 disclosure. Although one or more embodiments of the present disclosures 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 disclosure.
This application is a continuation application of International Application PCT/JP2018/043271 filed on Nov. 22, 2018 and designated the U.S., the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2018/043271 | Nov 2018 | US |
| Child | 17325367 | US |
