Method for sending response packets by 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] This invention relates to device-to-device communication in wireless communication systems. [Background technology]

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

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

[0004] Such RTT is an application metric not known to the radio access layer. Therefore, controlling RTT is difficult because the transmission delay strongly depends on these radio access layers that have no information on 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 is thus harmful to the performance of the application. Summary of the Invention Problems to be Solved by the Invention

[0005] An object of the present invention is to improve the above situation. Means for Solving the Problems

[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, relating to transmitting, including.

[0007] When a user device (also referred to as the response-side user device) receives a received packet (also referred to as FWP or forward packet), the user device generates a response packet (also referred to as BWP or backward packet). To transmit this BWP, resources are selected. This selection of radio resources is performed by applying additional constraints regarding the selection as compared to the selection of conventional radio resources. In fact, in the selection of conventional radio resources, a packet delay budget (PDB) that induces a time limit after which the radio resources are no longer 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 associated with 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, radio resources are selected within a selection window having a size dependent on the duration associated with the received packet (FWP). The selection window can be started at or after the generation of a BWP, as in conventional radio resource selection, or it can be started in a different way, for example, before the generation of a BWP. This constraint makes 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 to adjust the RTT (or by extension another metric or equivalent metric) to a target RTT. Advantageously, the selection window is either a reduced selection window or ends before at least the selection window defined in conventional radio resource selection. That is, at least the last radio resource within the selection window defined in conventional radio resource selection cannot be a candidate for selection according to the present invention. Thus, radio resources for transmission and retransmission are provided within a shorter time. By shrinking the selection window, or by 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 (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 said other user equipment), and thus it becomes possible to stabilize the RTT or at least reduce its instability.

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

[0010] Wireless resource selection is understood as the selection of wireless resources that a user device may potentially use to send and ultimately retransmit packets. These wireless resources are selected in a selection window. Selected wireless resources may not be used by the user device, and not all of them may be used. Wireless resource selection can be performed by performing resource discovery in advance. That is, the user device determines the reserved and unused wireless resources in the portion of the resource grid corresponding to the selection window. Some resources may be required to send a packet, in which case all the wireless resources used to perform the transmission are among the selected wireless resources. Notably, if retransmission is not required, not all of the selected wireless resources may be used by the user device to send packets.

[0011] The packet delay budget, also known as the packet delay budget for a packet, is initially configured by the application involved in generating 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 the response, for example, the FWP requesting the geographical location of the user's equipment. Therefore, the content of the BWP depends on the FWP.

[0013] For applications performing RTT communication, the BWP is a response to the FWP and contains the latest information. This response can be automatically generated using data from the user device, for example, data provided by the application layer or any other layer. Automatic packet generation is understood to mean that when the user device receives the FWP, the data necessary to generate the response packet is present on the user device, and does not require, for example, user intervention on the user device. The data required to generate the response packet is understood to represent, for example, the state of the user device at the time of receiving the FWP (or command packet), or a state that can be predicted by the user device at the time of receiving the FWP, and is transmitted in a timely manner without delay.

[0014] The last wireless resource in the selection window is understood to be the last wireless resource in time among the wireless resources included in the selection window.

[0015] Receiving an incoming packet may include decoding the incoming packet by the user equipment, and this decoding may be performed, for example, using previously received packets if the incoming packet is a retransmission of a previously received packet. Receiving an FWP can be considered the time corresponding to the first resource occupied by the FWP or the control channel associated with the transmission of the FWP (e.g., a slot index representing the start of the physical sidelink shared channel carrying the FWP, or a slot index representing the start of the physical sidelink control channel scheduling the FWP), and therefore does not include time related to the duration of the FWP or processing time related to the decoding of the FWP. Receiving an FWP can also be considered the time corresponding to the decoding of the control channel scheduling (or associated with) the FWP.

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

[0017] The duration associated with a received packet (FWP) is understood to be any duration that depends on at least one of the following: the time the FWP was generated, the time the FWP was transmitted by another user device, the time the user device received (or decoded) the FWP, the start of the resource selection procedure for the FWP by another UE, the time the other UE first attempted to transmit the FWP, or the time the control information associated with the FWP was received (or decoded). In other words, 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 FWP is - The delay between the generation of a received packet (FWP) by another user device and the reception (or decoding) of the received packet by the user device; - Delay between the generation of an FWP by another user device and the transmission of an FWP by another user device; and / or - Delay between the initiation of the FWP resource selection procedure by another UE and the transmission of the FWP by another user device. It can be done this way.

[0019] The duration can be directly known by the user device, and therefore the user device determines the duration. The duration may also be unknown to the user device; for example, a radio resource may be determined as satisfying a value condition, and from the selected radio resources, the radio resource for BWP transmission may be directly indicated to the user device. Therefore, the user device makes a selection of radio resources based on the set of radio resources indicated to the user device.

[0020] When a user device determines the above value, it can do so based on data received from another user device. This data depends on the duration described above. This value can also be received by one user device from another user device.

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

[0022] This makes it possible to adapt the above value to a target RTT that improves the performance of the entire communication loop, i.e., applications that require RTT for round-trip packet exchange. The target RTT can be known by user equipment (for example, by receiving the target RTT from a base station or by receiving the target RTT configured using the application). The target RTT may not be known by user equipment but may be known by another user's equipment.

[0023] For example, resource selection can be optimized by reducing the RTT to a target RTT 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 (PDB1) of another user device, and the processing time to generate a response packet starting from the reception of an incoming packet. PDB2 is the packet delay budget implemented by the user device when the selection window does not depend on the duration associated with the incoming packet (FWP).

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

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

[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 device. For example, the time remaining to perform round-trip communication according to the target RTT can be shown to the user device by this data, or the user device can calculate it based on this data.

[0027] Data is the duration between the generation and transmission of a received packet by another user device (TD E To depend on something means that if this duration changes, the data will also change accordingly.

[0028] Such data is transmitted to the user's device as described above, including the duration (TD) EIt 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 at 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 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 determined by the user device to select a wireless resource, and the packet delay budget depends on the duration between the generation and transmission of a received packet (FWP) by another user device.

[0032] In this case, the user device does not use the packet delay budget (initial packet delay budget) initially received from the upper layer (or would have been received if the invention had not been implemented) to select a wireless resource, but instead uses a new PDB (PDB2'). This new PDB (PDB2') may be a reduced PDB compared to the initial PDB. Therefore, to obtain a duration-dependent selection window, the selection window is determined based on this new PDB (PDB2'), which is also duration-dependent. This imposes supplemental constraints on the selection compared to conventional wireless resource selection.

[0033] This allows wireless resource selection to be performed as usual by using a new PDB (PDB2'), thus reducing the need to adapt user equipment to handle wireless resource selection according to the present invention.

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

[0035] Typically, to select wireless resources, a PDB is used to determine a selection window that starts from the generation of the packets 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 can be defined by the duration (for example, the size of this window is equal to or similar to the duration). The UE can either modify a selection window predefined by PDB2 or define a selection window directly based on the duration.

[0036] According to one aspect of the present invention, the present invention further includes the user device receiving a preferred set of wireless resources to be used in preference for the selection of wireless resources, and the user device determining a selection window based on the last wireless resource in the preferred set of wireless resources.

[0037] Therefore, the user device determines the selection window based on the last wireless resource in the preferred set of wireless resources. For example, the last wireless resource in the preferred set corresponds to the last wireless resource in the selection window.

[0038] Since the delay between the reception of the BWP of the response packet for the last radio resource in the preferred set of radio resources is determined according to the duration, selecting a radio resource that is either earlier than or at the same time as the last radio resource in the preferred set of radio resources ensures that the selection window is duration-dependent.

[0039] Advantageously, the selected wireless resources are chosen from a preferred set of wireless resources. Therefore, the UE makes wireless selections based on a set of wireless resources that indicate which wireless resources are preferred for use. This allows for the identification of wireless resources that can be used to make wireless selections and enables consideration of interference with other user devices on the other user device side.

[0040] This set of wireless resources can be received by a user device and transmitted, for example, by another user device. The set of wireless resources is indicated to the user device by data. This data may explicitly indicate the wireless resources of the set of wireless resources, or it may provide the user device with information that allows it to retrieve the set of wireless resources (for example, the sets may be predefined and known to both the user device and other user devices, and each set may be recalled by a specific index).

[0041] The preferred wireless resource is understood to be the wireless resource selected by the user's device, if possible. Even if other wireless resources are available or not being used for wireless selection, these wireless resources will not be selected if sufficient preferred wireless resources exist.

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

[0043] Unavailability of wireless resources is understood to mean that the user's equipment is unable to transmit data over these resources (for example, due to half-duplex constraints), or that such resources are occupied / reserved by another user, or are being interfered with by another user, or otherwise appear to be declared unavailable as a result of detection procedures performed by the user's equipment.

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

[0045] Such information included in the control data may be, for example, specific flags / triggers (e.g., indicating that it is necessary to send subsequent response packets after the content of the FWP has been detected), or the display of retransmission resources, or any other information associated with the FWP.

[0046] Therefore, based on the retransmission resources indicated by another user device, the user device can select radio resources. This makes it possible to select radio resources without requiring supplemental information. In fact, another user device 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 the user device with sufficient time to generate and transmit the BWP. More specifically, the other user device can determine the retransmission radio resources indicated in the FWP control data according to the duration associated with the FWP. Therefore, the user device 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 in the selection window may correspond to one of the retransmit radio resources indicated by the information.

[0048] For example, the last radio resource in the selection window precedes one of the indicated retransmit radio resources, and the delay between the last radio resource in the selection window and one of the indicated retransmit radio resources is equal to the estimated delay of response packet propagation between one user device and another user device.

[0049] According to one aspect of the present invention, the user device starts the process of selecting a wireless resource before terminating the generation of a response packet (BWP).

[0050] The user device begins selecting a radio resource without waiting for the FWD to be fully decoded or for the BWP generation to be completed. Therefore, the selection window used to make the selection can begin at a time before the BWP is generated (TBR). The time when the UE begins selection (TBR) 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 decodes the FWP, or the time when the UE begins generating the BWP.

[0051] This allows the UE to respond to the FWP more quickly, thus reducing the measured RTT. This is particularly advantageous when the target RTT is short, or when the duration associated with the FWP is long, leaving only a short delay to respond while adhering to the target RTT.

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

[0053] A third aspect of the present invention is a user device, At a minimum, a transmission unit configured to receive and transmit packets with another user device in D2D communication, Processor and A non-temporary computer-readable medium containing stored instructions, Equipped with, When the instruction is executed by the processor, Reading received packets (FWP) transmitted by another user device and received by the transmission unit, The process involves selecting a radio resource to be used to transmit a response packet (BWP) in response to an received packet, wherein the selected radio resource is chosen from among the radio resources in the selection window such that the delay between the reception of the received packet and the last radio resource in the selection window depends on the duration associated with the received packet (FWP). Instructing the transmission unit to send a response packet to another user device using at least one of the selected wireless resources, This relates to a user device configured to perform the following actions.

[0054] A fourth aspect of the present invention is a requesting user device, At a minimum, a transmission unit configured to receive and transmit packets with the responding user equipment in D2D communication, Processor and A non-temporary computer-readable medium containing stored instructions, Equipped with, When the instruction is executed by the processor, Sending a first packet requesting a response to the responding user device, The process involves transmitting data to the responding user device, and the data is: The duration between the generation and transmission of the first packet by the requesting user equipment, and / or The following, namely, A preferred set of radio resources to be used in preference for the selection of radio resources, wherein the selected radio resources are selected by the responding user equipment to transmit a second packet in response to a first packet, and the delay between the generation of the first packet and the last radio resource in the preferred set of radio resources depends on the target round trip time (RTT), or A radio resource used to retransmit a first packet, wherein the delay between the generation of the first packet and the radio resource used to retransmit the first packet depends on the target round-trip time (RTT). It corresponds to, Receiving the second packet with a delay from the generation of the first packet, which depends on the data sent to the responding user device, This relates to a requesting user device configured to perform the following actions. [Brief explanation of the drawing]

[0055] [Figure 1] This figure shows two user devices in device-to-device communication according to the present invention. [Figure 2.1] This diagram illustrates the transmission of FWP and BWP according to the first embodiment. [Figure 2.2] This is a flowchart illustrating the steps for transmitting the FWP and BWP according to the first embodiment. [Figure 3.1] This diagram illustrates the transmission of FWP and BWP according to the second embodiment. [Figure 3.2] This is a flowchart illustrating the steps for transmitting the FWP and BWP according to the second embodiment. [Modes for carrying out the invention]

[0056] The present invention is not limited to but is illustrated in the accompanying drawings as an example. In the accompanying drawings, similar reference numerals refer to similar elements.

[0057] Referring to Figure 1, two user devices in D2D communication are shown: a requesting user device 1 (UE1) that transmits a radio signal and a responding user device 2 (UE2) that receives this radio signal. Requesting user device 1 and / or responding user device 2 can be located within the coverage of base station 3. This D2D communication can be, for example, OFDM-based transmission. Requesting user device 1 and responding user device 2 are mobile devices. That is, these user devices engage in D2D communication, for example, vehicle-to-everything (V2X) communication in the context of standard LTE or NR. More generally, requesting user device 1 and / or responding user device 2 can be any type of mobile user device, for example, a vehicle communication system, personal communication equipment (e.g., user equipment), etc. D2D communication is performed in the context of a forward packet (FWP) requesting specific data from UE2, and the requested data is then sent back 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 device 1 comprises one communication module (COM) 1.1, one processing module (PROC) 1.2, and a memory unit (MEMO) 1.3. MEMO 1.3 comprises a non-volatile unit for retrieving a computer program and a volatile unit for retrieving parameters that can be implemented for round-trip transmission. For example, the volatile unit may include PDB (PDB1), target RTT, measured RTT, estimated propagation delay between UE1 and UE2, request packet content, and TD. E , TD R This allows you to extract a preferred set of wireless resources, retransmission resources for specific packets, and so on.

[0059] PROC1.2 is configured to generate forward packets (FWPs) and to configure COM1.1 to send these forward packets to the responding user device 2. PROC1.2 is configured to TD E , TD R PROC1.2 is also configured to perform calculations, determine a preferred set of radio resources, or determine retransmission resources for a particular packet. PROC1.2 is configured to decode the BWP and obtain the information requested by the FWP.

[0060] COM1.1 is configured to send out FWPs and ultimately retransmit packets. COM1.1 is also configured to receive BWPs.

[0061] The responding user device 2 comprises one communication module (COM) 2.1, one processing module (PROC) 2.2, and a memory unit (MEMO) 2.3. MEMO 2.3 comprises a non-volatile unit for extracting a computer program and a volatile unit for extracting parameters that can be implemented for round-trip transmission, for example, the volatile unit may include PDB (PDB2), target RTT, duration, estimated propagation delay between UE1 and UE2, request packet content (FWP content), response packet content, and TD. E , TD R This allows you to extract a preferred set of wireless resources, retransmission resources for specific packets, a new PDB2 (PDB2'), TBR, processing time for another user device, and so on.

[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 send this backward packet to UE1. PROC2.2 is configured to set the duration (e.g., TD) E , TD RPROC2.2 is also configured to calculate ) and / or PDB2'. PROC2.2 is also configured to select radio resources from a preferred set of radio resources or based on the retransmit radio resources indicated for the FWP. PROC2.2 is configured to determine the selection window SW based on the duration associated with the FWP. PROC2.2 is configured to decode the BWP and obtain the information requested by the FWP.

[0063] COM2.1 is configured to send out FWPs and ultimately retransmit packets. COM2.1 is also configured to receive BWPs.

[0064] Figure 1 also shows base station 3 (BS). UE1 and / or UE2 can communicate with BS3 and therefore can receive data from BS3 via their own 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 in UE1 and / or UE2.

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

[0066] Referring to Figure 2.1, the transmission of the FWP and BWP according to the present invention is shown. Referring to Figure 2.2, the steps for performing such transmission of the FWP and 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 may be transmitted to this UE by BS3, or an application (which can be installed on both UEs) that requires data from UE2 may be configured to determine the target RTT. For example, when the RTT measured in UE1 changes significantly, UE1 may determine the target RTT by setting the target RTT to the average RTT, which can be repeated using the target RTT performed for several transmissions. The application may also be configured directly using the target RTT. In the first case (Case 1), the target RTT is known by at least UE1, and in the second case (Case 2), the target RTT is known by at least UE2.

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

[0069] In Case 2, UE2 retrieves 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 requested by UE1. The FWP may require specific information from UE2, such as the speed or geographical location of UE2.

[0071] In step S13, UE1 selects a radio resource to transmit the FWP. This step can be performed according to a standard, such as "A Tutorial on 5G NR V2X Communications" by MHC Garcia et al. (IEEE Communications Surveys & Tutorials, vol. 23, no. 3, pp. 1972-2026).

[0072] For example, UE1 retrieves the PDB1 assigned to it. UE1 determines the selection window SW1 to start with when generating the FWD. The size of SW1 is equal to the size of PDB1.

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

[0074] UE1 then randomly selects a radio resource from among the unused radio resources in window SW1. These selected radio resources are candidates that may be used for transmitting the FWP and, if necessary, for retransmitting the FWP. In step S14, UE1 sets the duration TD E or TD R Decide one of the two. TD R This was determined in Case 1, TD E This will be determined in Case 2. TD E or TD R This is related to FWP, and therefore is an example of duration related to FWP.

[0075] In Case 2, TD E However, this is calculated by UE1. TD E This is the duration between the generation of the FWP and the time of the radio resource used to transmit the FWP to the UE2. In the case of retransmission, there is another duration (TD'). E ,TD'' E The calculation can be performed for each retransmission.

[0076] In Case 1, UE1 is TD E Calculate, and then TD E Based on TD R Calculate the actual TD. R TD E The duration corresponding to the target RTT (Target RTT - TD) is subtracted. E ) is the case. In the case of retransmission, other durations (TD') apply. R ,TD'' RThe calculation can be performed for each retransmission.

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

[0078] In step S16, UE2 receives and processes the FWP. That is, UE2 decodes the FWP, reads the contents of the FWP to determine the required data, and / or interrogates the application layer to obtain the required data. For example, an embodiment-specific protocol for exchanging data with the application layer or another higher layer, or a positioning unit or measurement unit, determines or retrieves the geographic location of UE2 and transmits it to the layer that generates the BWP. In addition, UE2 also processes the duration TD. E or TD R Read it.

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

[0080] In Case 1, this value is TD R It may also be equal to the TD minus the processing time required to perform step S16. R It can also be considered equivalent to this. This time processing can be relatively similar for each user device, 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 uses this time processing as TD. RIt can be subtracted from this. The duration of BWP propagation between UE2 and UE1 can also be considered, but this duration is short compared to the other durations considered. Therefore, for simplicity, the duration of BWP propagation between UE2 and UE1 is considered negligible.

[0081] In Case 2, UE2 knows the target RTT, and UE2 knows the TD. E The above value can be calculated by subtracting from the target RTT. Similar to Case 1, TD E In addition to subtracting the time required to perform step S16, the duration of BWP propagation between UE2 and UE1 can also be subtracted. However, as in case 1, the time required can also be considered directly through the target RTT, and the duration of BWP propagation between UE2 and UE1 can be considered negligible.

[0082] When FWP retransmission is performed, the value V is the duration (TD') of the last FWP sent with the decrypted FWP. R ,TD'' R , TD' E ,TD'' E It is calculated based on...

[0083] In step S19, UE2 selects a wireless resource to send the BWP to UE1.

[0084] UE2 can determine a new PDB2 (e.g., a reduced PDB2, also called PDB2') in place of the PDB2 assigned to UE2 in the conventional wireless resource selection. PDB2' is chosen to be equal to or similar to the above value. In fact, PDB2' may not be equal to the value V, as PDB2' can be a multiple of the duration of the wireless resource, whereas the value V may not correspond to such a multiple. In that case, PDB2' can be a multiple of the minimum (or maximum) duration of the wireless resource that is greater than (or less than) the value V.

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

[0086] The selection window can be determined directly. That is, UE2 can retrieve the PDB2 to be assigned to UE2, similar to the selection of conventional wireless resources. On the other hand, the selection window SW2 may not be determined based on PDB2 or PDB2', but may be calculated directly based on the value V. In that case, PDB2' is not calculated. In that case, the size of SW2 can be a value equal to or similar to the above value (for the same reasons as determining RPDB2).

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

[0088] The selection window SW2 may be started before the BWP is generated (more specifically, before the BWP generation is complete). For example, when UE2 receives the FWP or decodes part or all of the FWP, the selection of radio resources can be started immediately 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 a wireless resource from among those unused wireless resources in window SW2. These selected wireless resources are candidates that may be used for transmitting the BWP and, if necessary, for retransmitting the BWP.

[0090] In step S110, UE2 transmits a 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 in preparation for future transmissions (UE1 either reduces the target RTT (Case 1) or transmits the reduced target RTT to UE2 via control data, and ultimately via BS3 (Case 2)). Thus, the target RTT can be maintained when the measured RTT is stabilized.

[0091] In step S111, UE1 processes the BWP. That is, UE1 decodes the BWP and reads the data requested by the FWP. This data is sent 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. If the measured RTT changes, the moment of positioning becomes inaccurate, and the application's performance deteriorates.

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

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

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

[0095] In step S33, UE1 selects a radio resource to transmit the FWP. This step can be performed in the same way as in step S13.

[0096] For example, UE1 retrieves the PDB1 assigned to it. UE1 determines the selection window SW1 to start with when generating the FWD. The size of SW1 is equal to the size of PDB1.

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

[0098] UE1 then randomly selects a wireless resource from among the unused wireless resources in window SW1. These selected wireless resources are candidates that may be used for transmitting the FWP and, if necessary, for retransmitting the FWP.

[0099] Subsequently, UE1 performs radio resource allocation for the transmission of the FWP, and thus UE1 determines which radio resources from these randomly selected radio resources will be used for retransmitting the FWP. UE1 determines that the duration between the radio resources used to initially transmit the FWP and the radio resources used for at least the first retransmission of the FWP, and ultimately the second retransmission, is less than the value V. UE1 can determine the value V as the target RTT-PDB1, and finally, UE1 can also take into account the propagation delay between UE1 and UE2 and the processing time in UE2. Therefore, when UE2 receives the FWP before retransmission, UE2 can make a selection of radio resources for the BWP according to the radio resources indicated in the FWP's control data for retransmission, for example, selecting the radio resources prior to the radio resources indicated for retransmission (or, ultimately the second retransmission, if the duration between the radio resources used to initially transmit the FWP and the radio resources used for the second retransmission of the FWP is set to be less than the value V).

[0100] In step S34, UE1 selects a radio resource to transmit the FWP. This step can be performed in the same way as in step S13.

[0101] For example, UE1 retrieves the PDB1 assigned to it. UE1 determines the selection window SW1 to start with when generating the FWD. The size of SW1 is equal to the size of PDB1.

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

[0103] UE1 then randomly selects a wireless resource from among the unused wireless resources in window SW1. These selected wireless resources are candidates that may be used for transmitting the FWP and, if necessary, for retransmitting the FWP.

[0104] UE1 allocates wireless resources for FWP transmission.

[0105] In step S35, UE1 determines a preferred set of radio resources to be used preferentially by UE2 for transmitting the BWP.

[0106] For this reason, UE1, as with step 14, TD R And finally, UE1 can also take into account the propagation delay between UE1 and UE2, and therefore this delay is TD R It can be subtracted from. However, for the sake of brevity, such propagation delays are considered negligible, and TD R Only this is considered. UE1 uses all radio resources of the preferred set from the radio resources allocated for FWP transmission. R The wireless resources can be determined from a preferred set of wireless resources that are designed to have a latency of less than 1 / 2.

[0107] Steps S34 and S35 are performed 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. If steps S34 and S35 are performed, a preferred set is added to the FWP. If step S33 is performed, the radio resources used for retransmitting the FWP are indicated in the FWP's control data.

[0109] In step S37, UE2 receives and processes the FWP. That is, UE2 decodes the FWP, reads its contents, determines the necessary data, interrogates the application layer to obtain the necessary data, or obtains the necessary data from an external module or another communication layer. For example, the application layer determines or retrieves the geographic location of UE2 and transmits this geographic location to the layer that generates the BWP.

[0110] If steps S34 and S35 are performed, the UE2 identifies a preferred set of wireless resources.

[0111] If step S33 is performed, UE2 identifies the radio resource indicated for retransmitting 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 a wireless resource to send the BWP to UE1.

[0114] When steps S34 and S35 are performed, UE2 selects a wireless resource based on the wireless resources shown in the preferred set of wireless resources.

[0115] For example, UE2 determines the selection window SW2 to start when generating the BWP. The last resource in SW2 is either before or at the same time as the last wireless resource in the preferred set of wireless resources.

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

[0117] UE2 then randomly selects radio resources from the detected unused radio resources. These selected radio resources are candidates that may be used for transmitting BWP and, if necessary, for retransmitting BWP. The preferred set of radio resources are selected from the radio resources allocated for transmitting FWP. R Since the delay is less than TD and BWP generation occurs after FWP reception, the radio resources used by UE2 to transmit the BWP can be considered as the duration associated with the FWP from the time of BWP generation. R It is delayed by less than [amount missing].

[0118] If step S33 is performed, UE2 selects a radio resource according to the radio resources indicated in the control data of the FWP with respect to the radio resources to be used to retransmit the FWP.

[0119] For example, UE2 determines a selection window SW2 that starts when the BWP is generated and ends by the time the radio resources indicated for retransmission are available (the retransmission is either the first or second retransmission, depending on the duration between these radio resources and the radio resources used to initially transmit the FWP).

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

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

[0122] The duration between the radio resource designated for retransmission and the radio resource used to initially transmit the FWP is selected by UE1 such that it is less than the value V determined in step S33, and since the selected radio resource is either earlier than or simultaneous with the radio resource designated for retransmission, the radio resource used by UE2 to transmit the BWP is delayed by less than the target RTT-PDB1 from the transmission of the FWP.

[0123] In either case, the selection window SW2 may be started before the BWP is generated (more specifically, before the BWP generation is complete). For example, when UE2 receives the FWP or decodes part or all of the FWP, the selection of radio resources can be started immediately without waiting for the BWP to be generated. Thus, 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. Value V or TD used in the embodiments of Figures 3.1 and 3.2 R As a result, the duration between FWP generation and BWP reception by UE1 can be kept below 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. This data is sent to the application layer. For example, an application that performs relative positioning of UE2 with respect to UE1 requires the reception of these positionings, which have a certain periodicity. If the measured RTT changes, the moment of positioning becomes inaccurate, and the application's performance deteriorates.

Claims

1. A method in D2D communication in which a user device sends a response packet <<BWP>> in response to a received packet <<FWP>> received from another user device, The aforementioned user device receives the received packet <<FWP>> from the other user device, The user device selects a radio resource to be used to transmit the response packet <<BWP>>, wherein the selected radio resource is selected from among the radio resources in the selection window such that the delay between the reception of the received packet <<FWP>> and the last radio resource in the selection window depends on a target round-trip time <<RTT>>. The user device transmits the response packet to the other user device using at least one of the selected wireless resources, Methods that include...

2. The method according to claim 1, wherein the user device determines the selection window based on data received from the other user device, and the data depends on the duration between the generation and transmission of the received packet <<FWP>> by the other user device.

3. The method according to claim 2, wherein a packet delay budget <<PDB>> is determined by the user device to select the wireless resource, and the packet delay budget <<PDB>> depends on the duration between the generation and transmission of the received packet <<FWP>> by the other user device.

4. The method according to claim 2, wherein the user device adapts the initial selection window according to the data received from the other user device to obtain the selection window.

5. The user device further includes receiving a preferred set of wireless resources to be used in preference to the selection of the wireless resources, The method according to claim 1, wherein the user device determines the selection window based on the last wireless resource in the preferred set of wireless resources.

6. The method according to claim 5, wherein if the wireless resources of the preferred set of wireless resources are not available to the user device, the selected wireless resource is selected from other wireless resources in the selection window.

7. The method according to claim 1, wherein the user device determines the selection window based on information contained in the control data of the received packet <<FWP>>.

8. The method according to claim 7, wherein the last radio resource among the radio resources in the selection window corresponds to one of the retransmitted radio resources indicated by the information.

9. The method according to claim 7, wherein the last radio resource among the radio resources in the selection window precedes one of the retransmit radio resources indicated by the information, and the delay between the last radio resource among the radio resources in the selection window and one of the indicated retransmit radio resources is equal to the estimated delay of the propagation of the response packet between the user device and the other user device.

10. The method according to any one of claims 1 to 9, wherein the user device starts the selection of the wireless resource before finishing the generation of the response packet <<BWP>>.

11. A computer program product that, when executed by a processor, includes instructions that perform the method according to any one of claims 1 to 9.

12. User equipment, At a minimum, a transmission unit configured to receive and transmit packets with another user device in D2D communication, Processor and A non-temporary computer-readable medium containing stored instructions, Equipped with, When the aforementioned instruction is executed by the processor, Reading the received packet <<FWP>> transmitted by the aforementioned other user device and received by the transmission unit, The process involves selecting a radio resource to be used to transmit a response packet <<BWP>> in response to the received packet, wherein the selected radio resource is selected from among the radio resources in the selection window such that the delay between the reception of the received packet and the last radio resource in the selection window depends on a target round-trip time <<RTT>>. Commanding the transmission unit to transmit the response packet to the other user device using at least one of the selected wireless resources, A user device configured to perform the following actions.

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