Method for transmitting a response packet by a user equipment, computer program product, and user equipment

Abstract

The present invention relates to a method in D2D communication for a user equipment to transmit a response packet (BWP) in response to a received packet (FWP) received from another user equipment, the method comprising: the user equipment receiving a received packet (FWP) from another user equipment; the user equipment selecting radio resources to be used for transmitting the response packet (BWP), wherein the selected radio resources are selected from among the radio resources within a selection window such that the delay between the reception of the received packet and the last radio resource among the radio resources within the selection window depends on the duration associated with the received packet (FWP); and the user equipment transmitting the response packet to another user equipment using at least one resource among the selected radio resources.

Description

Technical Field

[0001] The present invention relates to device-to-device communication in a wireless communication system.

Background Art

[0002] More precisely, the present invention relates to applications that require round-trip transmission between two user devices, i.e., applications that require a user device to send a response packet in response to a request packet. Such response packets may be referred to as response packets or backward packets. Request packets may be referred to as received packets or forward packets. Such applications are, for example, positioning applications, trajectory monitoring applications, robotic motion applications, or more generally any control-related application that requires a timely response from another device.

[0003] Such applications, also called closed-loop applications, have their performance related to the time (RTT) required to perform round-trip transmission. The quality of service perceived by an application often serves as a basis for setting and / or changing system parameters, including the actually experienced RTT, and has a direct impact on various important performance indicators such as the convergence speed of control algorithms or the stability of the system. Therefore, by having a small, predictable, and stable RTT, the application can optimize its function.

[0004] Such RTT is an application metric not known by the radio access layer. Therefore, controlling for RTT is difficult because the transmission delay strongly depends on these radio access layers that have no information about the experienced RTT. For example, when the radio access layer encounters a bad radio condition, the transmission may fail and several retransmissions may be required. In that case, it is not possible to know with very high accuracy the moment when the reception of one packet is successful. In such a situation, the measured RTT, which can be a value close to the sum of the PDBs (packet delay budgets) of two UEs communicating with each other, is overly unstable and thus harmful to the performance of the application.

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0005] An object of the present invention is to improve the above situation.

MEANS FOR SOLVING THE PROBLEM

[0006] For the above object, in D2D communication, the present invention is to transmit a response packet (BWP) in response to a received packet (FWP) received by a user equipment from another user equipment, the user equipment receiving a received packet (FWP) from the other user equipment, the user equipment selecting radio resources to be used for transmitting the response packet (BWP), wherein the selected radio resources are selected from among the radio resources within a selection window such that the delay between the reception of the received packet and the last radio resource among the radio resources within the selection window depends on the duration associated with the received packet (FWP), the user equipment transmitting the response packet to the other user equipment using at least one resource among the selected radio resources, relates to transmitting, including.

[0007] When a user device (also called a response-side user device) receives a received packet (also called an FWP or a forward packet), the user device generates a response packet (also called a BWP or a backward packet). To transmit this BWP, a resource is selected. This selection of the radio resource is performed by applying supplementary constraints regarding the selection as compared with the selection of a conventional radio resource. In fact, in the selection of a conventional radio resource, a packet delay budget (PDB) that induces a time limit after which the radio resource is not selected is used. That is, all radio resources have a size corresponding to the PDB and are associated with the BWP and are selected within a selection window that starts, for example, at the time of generation of the packet BWP. This PDB is given by the application layer and does not depend on the duration related to the received packet (FWP), for example, the duration between the generation of the FWP by another user device and its transmission.

[0008] In contrast, in the present invention, the radio resources are selected within a selection window having a size that depends on the duration associated with the received packet (FWP). The selection window can start at the time of generation or after generation of the BWP, similar to the selection of conventional radio resources, or can start in a way different from the conventional method, for example, before the generation of the BWP. This constraint can make it possible to adapt the size of the selection window according to the duration associated with the FWP, and thus make it possible to adapt the size of the selection window so as to adjust the RTT (or ultimately another metric or equivalent metric) to the target RTT. Advantageously, the selection window is a reduced selection window or ends at least before the selection window defined in the selection of conventional radio resources. That is, at least the last radio resource within the selection window defined in the selection of conventional radio resources cannot be a candidate for selection according to the present invention. Thus, this provides radio resources for transmission and retransmission within a shorter time. By reducing the selection window or ending the selection window at least before the conventional selection window, that is, by reducing the delay between the reception (or final generation) of the FWP and the last possible radio resource that can be used by the user equipment to transmit the BWP, it becomes possible to reduce the RTT (that is, the delay starting from the generation of the FWP by another user equipment, also called the requesting user equipment, to the reception of the BWP by the other user equipment), and thus it becomes possible to stabilize the RTT or at least reduce its instability.

[0009] The selection window can be started even before the generation of the BWP, for example, based on a flag associated with the reception of the FWP, and in some cases, it can also be started before the decoding of the content of the FWP and / or before the generation of the content of the BWP. Advantageously, the selection window starts before the selection of conventional radio resources, and thus, it is an advanced selection window that includes radio resources that conventionally would not be included in the selection window. Therefore, this makes it possible to reduce the RTT (i.e., the delay from the generation of the FWP by another user equipment, also called the requesting user equipment, to the reception of the BWP by the said another user equipment), and thus, it is possible to stabilize the RTT or at least reduce its instability.

[0010] The selection of radio resources is understood to be the selection of radio resources that a user equipment selects for potential use in packet transmission and ultimately for the retransmission of this packet. These radio resources are selected in the selection window. The selected radio resources may not be used by the user equipment, or at least not all of them are necessarily used. The selection of radio resources can be performed by pre-executing resource sensing. That is, the user equipment determines the reserved radio resources and unused radio resources in the portion of the resource grid corresponding to the selection window. Some resources may be required for packet transmission, and in that case, all the radio resources used for performing the transmission are among the selected radio resources. Especially when retransmission is not required, all the selected radio resources may not be used for packet transmission by the user equipment.

[0011] The packet delay budget, also called the packet delay budget of the packet, is first configured by the application involved in the generation of the response packet.

[0012] The generation of a response packet is understood to be the determination of the packet, payload data, and control data of the response packet. The response packet is determined based on a response, for example, an FWP that requests the geographical location of a user equipment. Therefore, the content of the BWP depends on the FWP.

[0013] Regarding an application that executes RTT communication, the BWP is a response to the FWP and contains the latest information. This response can be automatically generated using data of the user equipment, for example, data provided by the application layer or from any other layer. Automatically generating a packet means that when the user equipment receives the FWP, the data required to generate the response packet is on the user equipment, for example, without the need for the intervention of the user of the user equipment. The data required to generate the response packet represents, for example, the state of the user equipment at the time of receiving the FWP (or command packet), or a state predictable by the user equipment at the time of receiving the FWP, and it can be seen that it is transmitted in a timely manner without being overdue.

[0014] The last radio resource of the selection window is understood to be the radio resource that is the last in terms of time among the radio resources included in the selection window.

[0015] Receiving a received packet can include decrypting the received packet by a user equipment, and this decryption can be performed using, for example, the previously received packets when the received packet is a retransmission of the previously received packets. The reception of the FWP is considered to be the time corresponding to the first resource occupied by the FWP or by the control channel associated with the transmission of the FWP (for example, the slot index representing the start of the physical sidelink shared channel carrying the FWP, or the slot index representing the start of the physical sidelink control channel scheduling the FWP), and thus does not include the time related to the duration of the FWP nor the processing time related to the decryption of the FWP. The reception of the FWP can also be considered to be the time corresponding to the decryption of the control channel scheduling the FWP (or associated with the FWP).

[0016] The delay between the reception of a packet and a radio resource is understood to be the delay between one of the times defined above (for example, the time when the packet is transmitted, the time when the packet is received, the time when the packet is retransmitted, etc.) and the end of the time unit hosting the radio resource.

[0017] The duration related to the received packet (FWP) is understood to be any duration that depends on at least one of the generation time of the FWP, the transmission time of the FWP by another user equipment, the reception (or decryption) time of the FWP by the user equipment, the start of the procedure for selecting the resources of the FWP by another UE, the time when another UE first attempts to transmit the FWP, or the reception (or decryption) time of the control information associated with the FWP. That is, the duration that depends on one of these times changes when the dependent time is delayed or advanced.

[0018] For example, the duration related to the FWP is - the delay between the generation of the received packet (FWP) by another user equipment and the reception (or decryption) of the received packet by the user equipment; - The delay between the generation of the FWP by another user equipment and the transmission of the FWP by another user equipment; and / or - The delay between the start of the procedure for selecting the resources of the FWP by another UE and the transmission of the FWP by another user equipment, can be set as such.

[0019] The duration can be directly known by the user equipment, and thus the user equipment determines the duration. The duration may not be known to the user equipment. For example, the radio resources are determined as meeting the conditions regarding the values, and among the selected radio resources, the radio resources for transmitting the BWP can be directly indicated to the user equipment. Therefore, the user equipment selects radio resources based on the set of radio resources indicated to the user equipment.

[0020] When the user equipment requests the above value, the user equipment can obtain this value based on the data received from another user equipment. This data depends on the duration described above. This value can also be received by the user equipment from another user equipment.

[0021] According to one aspect of the present invention, the above value depends on the target RTT.

[0022] This enables the above value to be adapted to the target RTT, thereby enhancing the performance of the overall communication loop, that is, applications that require RTT for round-trip packet exchange. The target RTT can be known by the user equipment (e.g., by receiving the target RTT from the base station or by receiving the target RTT configured using the application). The target RTT may not be known by the user equipment but may be known by another user equipment.

[0023] For example, if the measured or at least experienced RTT is close to or exceeds the sum of the packet delay budget (PDB2), the packet delay budget of another user equipment (PDB1), and the processing time for generating a response packet starting from the reception of the received packet, the resource selection can be optimized by reducing the RTT to the target RTT. PDB2 is the packet delay budget implemented by the user equipment when the selection window does not depend on the duration associated with the received packet (FWP).

[0024] Therefore, it is advantageous to set the target RTT to be smaller than the sum of PDB1, PDB2, and the processing time for generating a response packet starting from the reception of the received packet.

[0025] According to one aspect of the present invention, a user equipment determines a selection window based on data received from another user equipment, and the data depends on the duration between the generation and transmission of a received packet (FWP) by the other user equipment.

[0026] Therefore, such data makes it possible to take into account the time that has already elapsed (or at least a good estimate of this time) since the generation of the received packet by another user equipment. For example, the time remaining for performing round-trip communication according to the target RTT can be indicated to the user equipment by this data, or the user equipment can calculate it based on this data.

[0027] That the data depends on the duration (TD E ) between the generation and transmission of a received packet by another user equipment is understood to mean that when this duration is changed, the data also changes accordingly.

[0028] Such data is the duration (TD E) It can be the same. In that case, it is advantageous for the user equipment to know the target RTT (e.g., from the application layer or by previous transmissions via, for example, a base station, another user equipment or even a third user equipment). Thus, the user equipment, for example, TD E and, finally, the processing time PT for generating the response packet (BWP) starting from the reception of the FWP UE By subtracting from the target RTT, the size of the selection window can be easily determined. Subtracting the processing time can be advantageous when PT UE is large. On the other hand, when PT UE is small or negligible compared to the PDB, or when PT UE is considered in the target RTT, such PT UE may not be considered on the user equipment side.

[0029] Such data can be the remaining duration (TD R ), that is, the duration corresponding to subtracting the duration (TD E ) from the target RTT. In that case, the user equipment does not need to know the target RTT. On the other hand, in that case, it is another user equipment that knows the target RTT (e.g., from the application layer or the base station). The user equipment can easily determine the size of the selection window based on TD R by, for example, setting the size of the selection window equal to TD R . The user equipment can also calculate the duration by subtracting the processing time PT R from TD UE to obtain a more sufficient duration with respect to the target RTT.

[0030] TD R depends on the target RTT.

[0031] According to one aspect of the present invention, a packet delay budget (PDB) is required by a user equipment for selecting radio resources, and the packet delay budget depends on the duration between the generation and transmission of received packets (FWP) by another user equipment.

[0032] In that case, the user equipment does not use the packet delay budget (initial packet delay budget) first received from the upper layer (or that would have been received if the present invention had not been implemented) for selecting radio resources, but uses a new PDB (PDB2'). This new PDB (PDB2') can be a reduced PDB compared to the initial PDB. Therefore, in order to obtain a selection window that depends on the duration, the selection window is determined based on this new PDB (PDB2') that also depends on the duration. This imposes additional constraints on the selection compared to the conventional radio resource selection.

[0033] Thereby, the selection of radio resources can be performed as usual by using the new PDB (PDB2'), so the need to adapt the user equipment to process the radio resource selection according to the present invention is reduced.

[0034] According to one aspect of the present invention, a user equipment adapts an initial selection window according to data received from another user equipment to obtain a selection window.

[0035] Normally, for selecting radio resources, the PDB is used to determine a selection window starting from the generation of the packet to be transmitted. The size of such a window is defined by the PDB. For example, the size of this window is equal to the PDB. Instead of the selection window being defined by the PDB, the selection window is defined by the duration (for example, the size of this window is equal to or similar to the duration). The UE can also change the selection window pre-defined by the PDB2 or directly define the selection window based on the duration.

[0036] According to one aspect of the present invention, the present invention further includes a user equipment receiving a preferred set of radio resources that are preferentially used over the selection of radio resources, and the user equipment determines a selection window based on the last radio resource of the preferred set of radio resources.

[0037] Therefore, the user equipment determines a selection window based on the last radio resource of the preferred set of radio resources. For example, the last radio resource of the preferred set corresponds to the last radio resource of the selection window.

[0038] Since the delay between the last radio resource of the preferred set of radio resources and the reception of the BWP of the response packet is determined according to the duration, selecting a radio resource that is before the last radio resource of the preferred set of radio resources or is simultaneous with this last radio resource ensures that the selection window depends on the duration.

[0039] Advantageously, the selected radio resource is selected from among the radio resources of the preferred set. Therefore, the UE performs radio selection based on the set of radio resources indicating the radio resources preferentially used. This indicates the radio resources that can be used for performing radio selection and makes it possible to take into account interference with other user equipment on the other user equipment side.

[0040] This set of radio resources is received by the user equipment and can be transmitted, for example, by another user equipment. The set of radio resources is indicated to the user equipment by data. This data can explicitly indicate the radio resources of the set of radio resources, or can also give the user equipment information that enables the user equipment to extract the set of radio resources (for example, the set can be predefined and known to both the user equipment and another user equipment, and each set can be recalled by a specific index).

[0041] The wireless resources to be preferentially used are understood to be the wireless resources that are selected by the user equipment if possible. Even if other wireless resources are available or not used for wireless selection, these wireless resources are not selected when there are sufficient wireless resources to be preferentially used.

[0042] According to one aspect of the present invention, when a preferred set of wireless resources is not available to the user equipment, the selected wireless resource is selected from among the other wireless resources in the selection window.

[0043] That the wireless resources are not available means that the user equipment cannot transmit data on these resources (e.g., due to half-duplex constraints), or that the above resources are occupied / reserved by other users, or are blocked by other users, or, in another way, appear to be declared unavailable as a result of the detection procedure executed by the user equipment.

[0044] According to one aspect of the present invention, the user equipment determines the selection window based on the information contained in the control data of the received packet (FWP).

[0045] Such information contained in the control data can be, for example, a specific flag / trigger (e.g., indicating that it is necessary to transmit future response packets after detection of the content of the FWP), or an indication of retransmission resources, or any other information associated with the FWP.

[0046] Therefore, based on the resources for retransmission indicated by another user equipment, the user equipment can select radio resources. This makes it possible to select radio resources without requiring supplementary information. In fact, another user equipment that transmits an FWP to receive a BWP before the end of the target RTT can transmit the FWP and any other retransmissions of the FWP to leave sufficient time for the user equipment to generate and transmit the BWP. More specifically, another user equipment can determine the retransmission radio resources indicated in the control data of the FWP according to the duration associated with the FWP. Therefore, the user equipment can determine a selection window that depends on the duration associated with the FWP based on the retransmission radio resources.

[0047] For example, the last radio resource among the radio resources within the selection window may correspond to one of the retransmission radio resources indicated by the information.

[0048] For example, the last radio resource among the radio resources within the selection window is before one of the indicated retransmission radio resources, and the delay between the last radio resource among the radio resources within the selection window and one of the indicated retransmission radio resources is equal to the estimated delay of the propagation of the response packet between the user equipment and another user equipment.

[0049] According to one aspect of the present invention, the user equipment starts executing the selection of radio resources before finishing generating the response packet (BWP).

[0050] The user equipment starts selecting radio resources without waiting for the complete decoding of the FWD or the completion of the generation of the BWP. Therefore, the selection window used for selection can start at a time (TBR) before the generation of the BWP. The time (TBR) at which the UE starts the selection can be, for example, the time when the UE receives the FWP, the time when the UE decodes the control data of the FWP, the time when the UE finishes decoding the FWP, or the time when the UE starts generating the BWP.

[0051] As a result, the UE can respond to the FWP more quickly, thus making it possible to reduce the measured RTT. This is particularly advantageous when the target RTT is short or when the duration associated with the FWP is long, and thus there is only a short delay left to respond while complying with the target RTT.

[0052] A second aspect of the present invention relates to a computer program product including the code instructions that, when executed by a processor, execute the method described above.

[0053] A third aspect of the present invention is a user equipment, at least a transmission unit configured to receive and transmit packets with another user equipment in D2D communication, a processor, a non-transitory computer-readable medium including stored instructions, and comprising, the instructions, when executed by the processor, read a received packet (FWP) transmitted by another user equipment and received by the transmission unit, select radio resources for transmitting a response packet (BWP) in response to the received packet, wherein the selected radio resources are selected from among the radio resources within a selection window such that the delay between the reception of the received packet and the last radio resource within the selection window of radio resources depends on the duration associated with the received packet (FWP). Instructing a transmission unit to transmit a response packet to another user equipment using at least one resource among the selected radio resources, relates to a user equipment, which configures the user equipment to perform the above.

[0054] A fourth aspect of the present invention is a requesting user equipment, comprising at least a transmission unit configured to receive and transmit packets with a responding user equipment in D2D communication, a processor, a non-transitory computer-readable medium including stored instructions, wherein the instructions, when executed by the processor, cause the requesting user equipment to transmit a first packet requesting a response to the responding user equipment, and to transmit data to the responding user equipment, the data being dependent on a duration between generation and transmission of the first packet by the requesting user equipment, and / or the following, namely, a preferred set of radio resources preferentially used over a selection of radio resources, where the selected radio resources are selected by the responding user equipment to transmit a second packet to the requesting user equipment in response to the first packet, and a delay between generation of the first packet and a last radio resource of the preferred set of radio resources depends on a target round-trip time (RTT), the preferred set of radio resources, or radio resources used for retransmission of the first packet, where a delay between generation of the first packet and the radio resources used for retransmission of the first packet depends on a target round-trip time (RTT), and to receive the second packet with a delay from generation of the first packet, the delay being dependent on the data transmitted to the responding user equipment, relates to a requesting user equipment, which configures the requesting user equipment to perform the above. ​​

Brief Description of the Drawings

[0055]

Figure 1

Figure 2.1

Figure 2.2

Figure 3.1

Figure 3.2

Modes for Carrying Out the Invention

[0056] The present invention is shown by way of example and not limitation in the figures of the accompanying drawings. In the accompanying drawings, like reference numerals refer to like elements.

[0057] Referring to FIG. 1, two user equipment in D2D communication, namely, a requesting user equipment 1 (UE1) that sends a wireless signal and a responding user equipment 2 (UE2) that receives this wireless signal, are shown. The requesting user equipment 1 and / or the responding user equipment 2 can be within the coverage of the base station 3. This D2D communication can be, for example, OFDM-based transmission. The requesting user equipment 1 and the responding user equipment 2 are mobile devices. That is, these user equipment are engaged in D2D communication, for example, vehicle-to-everything (V2X) communication in the context of standard specifications such as LTE or NR. More generally, the requesting user equipment 1 and / or the responding user equipment 2 can be any type of mobile user equipment, such as a vehicle communication system, a personal communication device (e.g., a user equipment), etc. The D2D communication is carried out in the context of a forward packet (FWP) that requests specific data from UE2, and the requested data is transmitted to UE1 by UE2 in a backward packet (BWP). This specific exchange between UE1 and UE2 is called a round-trip transmission.

[0058] The requesting user equipment 1 includes one communication module (COM) 1.1, one processing module (PROC) 1.2, and a memory unit (MEMO) 1.3. MEMO 1.3 includes a non-volatile unit that retrieves a computer program and a volatile unit that retrieves parameters that can be implemented for round-trip transmission. For example, the volatile unit can retrieve PDB (PDB1), target RTT, measured RTT, an estimated value of the propagation delay between UE1 and UE2, request packet content, TD E TD R , a preferred set of radio resources, retransmission resources for a specific packet, etc.

[0059] PROC1.2 is configured to generate a forward packet (FWP) and to configure COM1.1 to transmit this forward packet to the response-side user equipment 2. PROC1.2 is E also configured to perform the calculation of TD R , the determination of a preferred set of radio resources, or the determination of retransmission resources for a specific packet. PROC1.2 is configured to decode the BWP and to obtain the information requested by the FWP.

[0060] COM1.1 is configured to send the FWP and to finally retransmit the packet. COM1.1 is also configured to receive the BWP.

[0061] The response-side user equipment 2 includes one communication module (COM) 2.1, one processing module (PROC) 2.2, and a memory unit (MEMO) 2.3. MEMO2.3 includes a non-volatile unit for retrieving computer programs and a volatile unit for retrieving parameters that can be implemented for round-trip transmission. For example, the volatile unit can retrieve PDB (PDB2), target RTT, duration, an estimated value of the propagation delay between UE1 and UE2, requested packet content (FWP content), response packet content, TD E , TD R , a preferred set of radio resources, retransmission resources for a specific packet, a new PDB2 (PDB2’), TBR, processing time of another user equipment, etc.

[0062] PROC2.2 configures COM2.1 to receive and decode the FWP from UE1. PROC2.2 is configured to generate a backward packet (BWP) in response to the FWP and to configure COM2.1 to transmit this backward packet to UE1. PROC2.2 is configured to determine the duration (e.g., TD E , TD R) and / or PDB2’ as well. PROC2.2 is also configured to select wireless resources from among a preferred set of wireless resources or based on the retransmission wireless resources indicated for FWP. PROC2.2 is configured to determine a selection window SW based on the duration associated with FWP. PROC2.2 is configured to decode the BWP and obtain the information requested by the FWP.

[0063] COM2.1 is configured to send the FWP and finally retransmit the packet. COM2.1 is also configured to receive the BWP.

[0064] Figure 1 also shows a base station 3 (BS). UE1 and / or UE2 can communicate with BS3 and thus can receive data from BS3 via their respective communication modules (COM1.1 and COM2.1). For example, UE1 and / or UE2 can receive the target RTT if the target RTT has not yet been configured at UE1 and / or UE2.

[0065] The example in Figure 1 shows only two user equipments. However, the present invention is not limited to such one-to-one D2D communication and also includes cases where two or more user equipments are intended to receive the FWP and respond to the FWP.

[0066] Referring to Figure 2.1, the transmission of the FWP and the transmission of the BWP according to the present invention are shown. Referring to Figure 2.2, the steps of performing such transmission of the FWP and the transmission of the BWP according to the present invention are shown.

[0067] In step S11, one of the UEs determines the target RTT. For example, the target RTT can be sent to this UE by BS3, or an application that requires data from UE2 (which can be installed on both UEs) can be configured to determine the target RTT. For example, when the RTT measured at UE1 changes significantly, UE1 can determine the target RTT by, for example, setting the target RTT to the average RTT, which can be repeated using the target RTT implemented for several transmissions. The application can also be directly configured using the target RTT. In the first case (Case 1), the target RTT is known at least by UE1, and in the second case (Case 2), the target RTT is known at least by UE2.

[0068] In Case 1, UE1 extracts the target RTT. This target RTT is obtained from at least one of the methods described in S11.

[0069] In Case 2, UE2 extracts the target RTT. This target RTT is obtained from at least one of the methods described in S11.

[0070] In step S12, UE1 generates an FWP based on the type of information required by UE1. The FWP may require, for example, specific information from UE2, such as the speed of UE2 or its geographical location.

[0071] In step S13, UE1 selects radio resources for transmitting the FWP. This step can be performed according to standards, such as M. H. C. Garcia et al.'s "A Tutorial on 5G NR V2X Communications" (IEEE Communications Surveys & Tutorials, vol. 23, no. 3, pp. 1972 - 2026).

[0072] For example, UE1 retrieves PDB1 assigned to UE1. UE1 determines a selection window SW1 that starts at the time of FWD generation. The size of SW1 is equal to PDB1.

[0073] UE1 performs radio resource sensing according to SW1 and obtains a map of unused radio resources in the resource grid.

[0074] UE1 then randomly selects radio resources from those unused radio resources within window SW1. These selected radio resources are candidates that may be used for the transmission of FWP and, if necessary, the retransmission of FWP. In step S14, UE1 determines one of the durations TD E or TD R . TD R is determined in case 1, and TD E is determined in case 2. TD E or TD R is related to FWP and is thus an example of the duration related to FWP.

[0075] In case 2, TD E is calculated by UE1. TD E is the duration between the generation of FWP and the time of the radio resources used to transmit FWP to UE2. In the case of retransmission, other durations (TD’ E , TD’’ E ,...) can be calculated for each retransmission.

[0076] In case 1, UE1 calculates TD E , and then calculates TD E based on TD R . Actually, TD R is the duration corresponding to the target RTT from which TD E is subtracted (target RTT - TD E ). In the case of retransmission, other durations (TD’ R , TD’’ Rcan be calculated for each retransmission (...).

[0077] In step S15, UE1 transmits the FWP to UE2 using some of the radio resources selected in step S13. TD E or TD R is added to or included in the FWP, for example, in the control data of the FWP.

[0078] In step S16, UE2 receives and processes the FWP. That is, UE2 decodes the FWP, reads the content of the FWP to obtain the required data, and / or interrogates the application layer to obtain the required data. For example, an application layer or another upper layer, or a protocol specific to the implementation that exchanges data with a positioning unit or a measurement unit, determines or extracts the geographical location of UE2 and transmits this to the layer that generates the BWP. In addition, UE2 reads the duration TD E or TD R .

[0079] In step S17, UE2 generates the BWP. That is, UE2 generates a BWP in which data corresponding to the data required by the FWP is inserted into the BWP. In step S18, UE2 determines the value V.

[0080] In case 1, this value may be equal to TD R or may be considered equal to TD from which the time processing required to execute step S16 has been subtracted. This time processing can be made relatively similar for each user equipment, in which case the target RTT can take this time processing into account. That is, the target RTT can be reduced. On the other hand, if the target RTT does not take this time processing into account, UE2 calculates the time processing and subtracts this time processing from TD R R ​It can be subtracted from. The duration of the propagation of the BWP between UE2 and UE1 can also be considered, but this duration is short compared to other durations to be considered. Therefore, for simplicity, the duration of the propagation of the BWP between UE2 and UE1 can be regarded as negligible.

[0081] In Case 2, UE2 knows the target RTT, and UE2 can calculate the above value by subtracting TD E from the target RTT. Similar to Case 1, in addition to subtracting TD E the time processing required to execute Step S16 and / or the duration of the propagation of the BWP between UE2 and UE1 can also be subtracted. However, similar to Case 1, the time processing can also be directly considered through the target RTT, and the duration of the propagation of the BWP between UE2 and UE1 can also be regarded as negligible.

[0082] When the retransmission of the FWP is executed, the value V is calculated based on the duration (TD’ R TD’’, R TD’, E TD’’, E ...) transmitted together with the last decoded FWP.

[0083] In Step S19, UE2 selects radio resources to transmit the BWP to UE1.

[0084] UE2 can obtain a new PDB2 (for example, a reduced PDB2 also called PDB2’) instead of the PDB2 assigned to UE2 in the conventional radio resource selection. PDB2’ is selected as a value equal to or similar to the above value. In fact, PDB2’ can be a multiple of the duration of the radio resource, while the value V may not correspond to such a multiple, so PDB2’ is not equal. In that case, PDB2’ can be set as a multiple of the minimum (or maximum) duration of the radio resource that is greater (or smaller) than the value V.

[0085] UE2 then determines a selection window SW2 that starts when generating the BWP. The size of SW2 is equal to PDB2'.

[0086] The selection window can be determined directly. That is, UE2 can extract PDB2 assigned to UE2 in the same way as the selection of conventional radio resources. On the other hand, the selection window SW2 may not be determined based on PDB2 or PDB2', and may be directly calculated based on the value V. In that case, PDB2' is not calculated. In that case, the size of SW2 can be set to a value equal to or similar to the above value (for the same reason as the determination of RPDB2).

[0087] Regardless of how SW2 is determined, UE2 performs radio resource sensing and obtains a map of unused radio resources in the resource grid according to SW2.

[0088] The selection window SW2 may start before the generation of the BWP (more specifically, before the completion of the generation of the BWP). For example, when UE2 receives the FWP or when UE2 decodes part or all of the FWP, it can immediately start selecting radio resources without waiting for the BWP to be generated. Therefore, the radio resources are already selected when the BWP is generated.

[0089] UE2 then randomly selects radio resources from among those unused radio resources in window SW2. These selected radio resources are candidates that may be used for the transmission of the BWP and, if necessary, the retransmission of the BWP.

[0090] In step S110, UE2 transmits the BWP to UE1 using some of the radio resources selected in step S19. The duration between the generation of the FWP and the reception of the BWP by UE1 corresponds to the duration of the RTT, i.e., the measured RTT. If the measured RTT is less than the target RTT, the target RTT can be reduced for future transmissions (UE1 can reduce the target RTT (case 1), or transmit the reduced target RTT to UE2 via control data, ultimately via BS3 (case 2)). Therefore, when the measured RTT is stabilized, the target RTT can be maintained.

[0091] In step S111, UE1 processes the BWP. That is, UE1 decodes the BWP and reads the data requested by the FWP. These data are transmitted to the application layer. For example, an application that performs relative positioning of UE2 with respect to UE1 requires the reception of these positionings at a certain periodicity. When the measured RTT changes, the moments regarding the positioning become inaccurate and the performance of the application degrades.

[0092] Referring to FIG. 3.1, the transmission of the FWP and the transmission of the BWP according to the present invention are shown. Referring to FIG. 3.2, the steps of performing the transmission of the FWP and the transmission of the BWP according to the present invention are shown.

[0093] In step S31, UE1 determines the target RTT. For example, the target RTT can be transmitted to UE1 by BS3, or an application that requires data from UE2 can be configured to determine the target RTT. For example, when the RTT measured at UE1 changes significantly, UE1 can determine the target RTT by, for example, setting the target RTT to the average RTT, which can be repeated when the target RTT is implemented for several transmissions. The application can also be directly configured using the target RTT.

[0094] In step S32, UE1 generates an FWP based on the type of information requested by UE1. The FWP may require, for example, specific information from UE2, such as the speed or geographical location of UE2.

[0095] In step S33, UE1 selects radio resources for transmitting the FWP. This step can be executed in the same manner as step S13.

[0096] For example, UE1 retrieves PDB1 allocated to UE1. UE1 determines a selection window SW1 that starts at the time of FWD generation. The size of SW1 is equal to PDB1.

[0097] UE1 performs radio resource detection and obtains a map of unused radio resources in the resource grid according to SW1.

[0098] UE1 then randomly selects radio resources from those unused radio resources within window SW1. These selected radio resources are candidates that may be used for transmitting the FWP and, if necessary, retransmitting the FWP.

[0099] After that, UE1 performs radio resource allocation for the transmission of the FWP. Therefore, UE1 determines the radio resources to be used for the retransmission of the FWP from among these randomly selected radio resources. UE1 determines the duration between the radio resources used for initially transmitting the FWP and the radio resources used for at least the first retransmission of the FWP, and ultimately the second retransmission, to be less than the value V. UE1 can obtain the value V as the target RTT-PDB1, and ultimately, UE1 can also take into account the propagation delay between UE1 and UE2 and the processing time at UE2. Therefore, when UE2 receives the FWP before retransmitting the FWP, UE2 can select the radio resources of the BWP according to the radio resources indicated in the control data of the FWP for retransmission. For example, when the duration between the radio resources used for retransmission (or, if set such that the duration between the radio resources used for initially transmitting the FWP and the radio resources used for the second retransmission of the FWP is less than the value V, ultimately the second retransmission) is less than the value V, UE2 selects the radio resources before the radio resources indicated for retransmission.

[0100] In step S34, UE1 selects radio resources for transmitting the FWP. This step can be executed in the same manner as step S13.

[0101] For example, UE1 extracts PDB1 assigned to UE1. UE1 determines the selection window SW1 that starts at the time of generating the FWD. The size of SW1 is equal to PDB1.

[0102] UE1 performs radio resource sensing and obtains a map of unused radio resources in the resource grid according to SW1.

[0103] UE1 then randomly selects radio resources from among those unused radio resources in the window SW1. These selected radio resources are candidates that may be used for the transmission of the FWP and, if necessary, the retransmission of the FWP.

[0104] UE1 allocates radio resources for transmitting the FWP.

[0105] In step S35, UE1 determines a preferred set of radio resources that are preferentially used by UE2 for BWP transmission.

[0106] For this purpose, UE1 obtains TD in the same way as in step 14, and finally, UE1 can also take into account the propagation delay between UE1 and UE2, and thus can subtract this delay from TD. However, for simplicity, such a propagation delay is considered negligible and only TD is considered. UE1 can determine radio resources from a preferred set of radio resources such that all radio resources in the preferred set are delayed by less than TD from the radio resources allocated for transmitting the FWP. R and finally, UE1 can also take into account the propagation delay between UE1 and UE2, and thus can subtract this delay from TD. However, for simplicity, such a propagation delay is considered negligible and only TD is considered. UE1 can determine radio resources from a preferred set of radio resources such that all radio resources in the preferred set are delayed by less than TD from the radio resources allocated for transmitting the FWP. R from TD. However, for simplicity, such a propagation delay is considered negligible and only TD is considered. UE1 can determine radio resources from a preferred set of radio resources such that all radio resources in the preferred set are delayed by less than TD from the radio resources allocated for transmitting the FWP. R from TD. However, for simplicity, such a propagation delay is considered negligible and only TD is considered. UE1 can determine radio resources from a preferred set of radio resources such that all radio resources in the preferred set are delayed by less than TD from the radio resources allocated for transmitting the FWP. R from TD. However, for simplicity, such a propagation delay is considered negligible and only TD is considered. UE1 can determine radio resources from a preferred set of radio resources such that all radio resources in the preferred set are delayed by less than TD from the radio resources allocated for transmitting the FWP.

[0107] Steps S34 and S35 are implemented as alternative steps to step S33.

[0108] In step S36, UE1 transmits the FWP to UE2 using some of the radio resources selected in step S33 or S34. When steps S34 and S35 are executed, the preferred set is added to the FWP. When step S33 is executed, the radio resources used for retransmitting the FWP are indicated in the control data of the FWP.

[0109] In step S37, UE2 receives and processes the FWP. That is, UE2 decodes the FWP, reads the content of the FWP, requests the required data, interrogates the application layer to obtain the required data, or obtains the required data from an external module or another communication layer. For example, the application layer requests or extracts the geographical location of UE2 and transmits this geographical location to the layer that generates the BWP.

[0110] When steps S34 and S35 are executed, UE2 identifies a preferred set of radio resources.

[0111] When step S33 is executed, UE2 identifies the radio resources indicated for retransmission of the FWP.

[0112] In step S38, UE2 generates a BWP. That is, UE2 generates a BWP into which data corresponding to the data required by the FWP is inserted.

[0113] In step S39, UE2 selects radio resources to transmit the BWP to UE1.

[0114] When steps S34 and S35 are executed, UE2 selects radio resources based on the radio resources indicated in the preferred set of radio resources.

[0115] For example, UE2 determines a selection window SW2 that starts when generating the BWP. The last resource of SW2 is before or simultaneous with the last resource of the preferred set of radio resources.

[0116] UE2 then performs radio resource sensing to obtain a map of unused radio resources from among the radio resources of the preferred set of radio resources within SW2. If there are no unused radio resources available within SW2 among the radio resources of the preferred set of radio resources, UE2 performs radio resource sensing to obtain a map of unused radio resources in the resource grid within SW2.

[0117] UE2 then randomly selects radio resources from among the detected unused radio resources. These selected radio resources are candidates that may be used for BWP transmission and, if necessary, BWP retransmission. The preferred set of radio resources is TD from the radio resources allocated for FWP transmission R Less than and delayed, and since BWP generation is performed after FWP reception, the radio resources used by UE2 to transmit BWP can be considered as the duration related to FWP from BWP generation TD R Less than and delayed.

[0118] When step S33 is executed, UE2 selects radio resources according to the radio resources indicated in the control data of FWP regarding the radio resources used for retransmitting FWP.

[0119] For example, UE2 determines a selection window SW2 that starts at the time of BWP generation and ends at the radio resources indicated for retransmission (retransmission is the first retransmission or the second retransmission according to the duration between these radio resources and the radio resources used to initially transmit FWP).

[0120] UE2 then performs radio resource detection and obtains a map of unused radio resources in the resource grid within SW2.

[0121] UE2 then randomly selects radio resources from among these unused radio resources within window SW2. These selected radio resources are candidates that may be used for BWP transmission and, if necessary, BWP retransmission.

[0122] The duration between the radio resources indicated for retransmission and the radio resources used to first transmit the FWP is selected by UE1 to be less than the value V obtained in step S33, and the selected radio resources are before or simultaneous with the radio resources indicated for retransmission. Therefore, the radio resources used by UE2 to transmit the BWP are delayed by less than the target RTT-PDB1 from the transmission of the FWP.

[0123] In any case, the selection window SW2 may start before the generation of the BWP (more specifically, before the completion of the generation of the BWP). For example, when UE2 receives the FWP or when UE2 decodes part or all of the FWP, the selection of radio resources can be immediately started without waiting for the BWP to be generated. Therefore, the radio resources are already selected when the BWP is generated.

[0124] In step S310, UE2 transmits the BWP to UE1 using some of the radio resources selected in step S39. Due to the value V or TD used in the embodiments of FIGS. 3.1 and 3.2 R the duration between the generation of the FWP and the reception of the BWP by UE1 can be maintained to be less than the target RTT.

[0125] In step S311, UE1 processes the BWP. That is, UE1 decodes the BWP and reads the data requested by the FWP. These data are transmitted to the application layer. For example, an application that performs relative positioning of UE2 with respect to UE1 requires the reception of these positionings with a certain periodicity. When the measured RTT changes, the moments related to the positioning become inaccurate and the performance of the application deteriorates.

Claims

1. In D2D communication, a method for a user equipment to transmit a response packet (BWP) in response to a received packet (FWP) received from another user equipment, comprising: the user equipment receiving the received packet (FWP) from the other user equipment; the user equipment selecting radio resources to be used for transmitting the response packet (BWP), wherein the selected radio resources are selected from among the radio resources within a selection window such that a delay between the reception of the received packet (FWP) and a last radio resource among the radio resources within the selection window depends on a duration associated with the received packet (FWP); the user equipment transmitting the response packet to the other user equipment using at least one resource among the selected radio resources; A method comprising the above.

2. The method according to claim 1, wherein the delay between the reception of the received packet (FWP) and the last radio resource among the radio resources within the selection window depends on a target round-trip time (RTT).

3. The method according to claim 1 or 2, wherein the user equipment determines the selection window based on data received from the other user equipment, and the data depends on a duration between generation and transmission of the received packet (FWP) by the other user equipment.

4. The method according to claim 3, wherein a packet delay budget (PDB) is determined by the user equipment for selecting the radio resources, and the packet delay budget depends on the duration between generation and transmission of the received packet (FWP) by the other user equipment.

5. The method according to claim 3, wherein the user equipment adapts an initial selection window according to the data received from the other user equipment to obtain the selection window.

6. The method further comprising the user equipment receiving a preferred set of radio resources to be preferentially used for the selection of the radio resources, The method according to claim 1 or 2, wherein the user equipment determines the selection window based on a last radio resource of the preferred set of radio resources.

7. The method according to claim 6, wherein when the wireless resources of the preferred set of wireless resources are not available to the user equipment, the selected wireless resources are selected from among other wireless resources of the selection window.

8. The method according to claim 1 or 2, wherein the user equipment determines the selection window based on information included in the control data of the received packet (FWP).

9. The method according to claim 8, wherein the last wireless resource among the wireless resources within the selection window corresponds to one of the retransmission wireless resources indicated by the information.

10. The method according to claim 8, wherein the last wireless resource among the wireless resources within the selection window is before one of the indicated retransmission wireless resources, and the delay between the last wireless resource among the wireless resources within the selection window and the one of the indicated retransmission wireless resources is equal to the estimated delay of the propagation of the response packet between the user equipment and the other user equipment.

11. The method according to any one of claims 1 to 10, wherein the user equipment starts execution of the selection of the wireless resources before finishing generation of the response packet (BWP).

12. A computer program product comprising instructions which, when executed by a processor, execute the method according to any one of claims 1 to 11.

13. A user equipment, comprising at least a transmission unit configured to receive and transmit packets with another user equipment in D2D communication, a processor, a non-transitory computer-readable medium including stored instructions, wherein the instructions, when executed by the processor, read a received packet (FWP) transmitted by the other user equipment and received by the transmission unit, and perform a selection of wireless resources to be used for transmitting a response packet (BWP) in response to the received packet, wherein the selected wireless resources are selected from among the wireless resources within the selection window such that the delay between the reception of the received packet and the last wireless resource among the wireless resources within the selection window depends on the duration associated with the received packet (FWP). ​ Instructing the transmission unit to transmit the response packet to the other user equipment by using at least one resource among the selected radio resources; A user equipment configured to perform the above. **Claim 14** A requesting user equipment, Comprising at least a transmission unit configured to receive and transmit packets with a responding user equipment in D2D communication, A processor, A non-transitory computer-readable medium including stored instructions, And comprising, When the instructions are executed by the processor, Transmitting a first packet requesting a response to the responding user equipment; Transmitting data to the responding user equipment, where the data Depends on the duration between the generation and the transmission of the first packet by the requesting user equipment, and / or The following, that is, A preferred set of radio resources preferentially used in the selection of radio resources, where the selected radio resources are selected by the responding user equipment to transmit a second packet to the requesting user equipment in response to the first packet, and the delay between the generation of the first packet and the last radio resource of the preferred set of radio resources depends on the target round-trip time (RTT), a preferred set of radio resources, or The radio resources used for retransmission of the first packet, where the delay between the generation of the first packet and the radio resources used for retransmission of the first packet depends on the target round-trip time (RTT), radio resources, Corresponding thereto; Receiving the second packet with a delay from the generation of the first packet depending on the data transmitted to the responding user equipment; A requesting user equipment configured to perform the above.

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