Packet collision mitigation in side links

Abstract

Certain aspects of this disclosure provide techniques for collision mitigation in sidelinks. One method, performable by a user equipment (UE), includes: measuring a channel busy ratio (CBR); estimating the number of UEs using the channel; and estimating a congestion level based on the CBR and the estimated number of UEs. Another method, performable by a sidelink UE, includes: determining a semi-persistent scheduling (SPS) resource reservation including a first subframe; determining a second subframe for the generated packet transmission; determining to skip transmissions in the second subframe; listening to transmissions of another sidelink UE during the second subframe; and determining whether to reselect resources. Yet another method includes: listening to transmissions of another sidelink UE during the first subframe; detecting a conflict between the transmission and transmission resources scheduled for that sidelink UE based on the amount of frequency resource overlap; and determining to reselect resources.

Description

[0001] background

[0002] open field

[0003] Various aspects of this disclosure relate to wireless communications, and more specifically to techniques for mitigating packet collisions in side links, such as techniques for avoiding or reducing UE-UE collisions in cellular vehicle-to-everything (C-V2X) systems.

[0004] Related technical descriptions

[0005] Wireless communication systems are widely deployed to provide a variety of telecommunications services such as telephone, video, data, messaging, and broadcasting. These wireless communication systems can employ multiple access technologies that enable communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple access systems include 3GPP Long Term Evolution (LTE) systems, LTE-A Advanced systems, Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) systems, to name just a few.

[0006] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol enabling different wireless devices to communicate at the city, country, region, and even global levels. New radios (e.g., 5G NR) are examples of emerging telecommunications standards. NR is an enhancement set of the LTE mobile standard issued by 3GPP. NR is designed to better support mobile broadband Internet access by using OFDMA with a cyclic prefix (CP) on both the downlink (DL) and uplink (UL) to improve spectrum efficiency, reduce costs, improve service, utilize new spectrum, and better integrate with other open standards. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0007] However, with the continued growth in demand for mobile broadband access, there is a need for further improvements to NR and LTE technologies. Preferably, these improvements should be applicable to other multiple access technologies and telecommunications standards that employ these technologies.

[0008] Overview

[0009] The systems, methods, and apparatus of this disclosure each have several aspects, and their desired properties are not solely attributed to any single aspect. Without limiting the scope of this disclosure as set forth in the appended claims, some features will now be briefly discussed. Upon consideration of this discussion, and especially after reading the section entitled "Detailed Description," it will be understood how the features of this disclosure provide advantages including improved grouping conflict mitigation.

[0010] Some aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by user equipment (UE). This method generally includes measuring the channel busy ratio (CBR). This method generally includes estimating the number of UEs using the channel. This method generally includes estimating a congestion level based on the CBR and the estimated number of UEs.

[0011] Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a sidelink user equipment (UE). The method generally includes determining a semi-persistent scheduling (SPS) resource reservation comprising one or more first subframes in which the sidelink UE is scheduled to transmit. The method generally includes determining that the sidelink UE has generated packets to transmit in the first or more subframes. The method generally includes determining that transmissions in one or more of the second or more subframes should be skipped. The method generally includes listening for transmissions from another sidelink UE during the one or more of the second or more subframes. The method generally includes determining, based on the listening, whether to reselect resources.

[0012] Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a sidelink user equipment (UE). The method generally includes listening for transmissions from another sidelink UE during a first subframe. The method generally includes detecting, based on the listening, whether the transmission from the other sidelink UE conflicts with transmission resources scheduled for that sidelink UE. This detection is based on the amount of frequency resource overlap between the transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE. The method generally includes determining whether to reselect resources based on whether one or more conflicts are detected.

[0013] Although the subject matter described in this disclosure relates to both a first-sidelink UE and a second-sidelink UE, the methods and apparatus described herein can be applied to scenarios with any number of conflicting UEs.

[0014] Various aspects of this disclosure provide apparatus, devices, processors, and computer-readable media for performing the methods described herein.

[0015] Various aspects of this disclosure provide apparatus, devices, processors, and computer-readable media for performing techniques and methods that can complement the operations performed by the UE (e.g., by the BS) described herein.

[0016] To achieve the foregoing and related objectives, these one or more aspects include the features fully described below and specifically pointed out in the claims. Certain illustrative features of these one or more aspects are set forth in detail in the following description and drawings. However, these features merely indicate a few of the various ways in which the principles of these aspects may be employed. Brief description of the attached diagram

[0018] To gain a more detailed understanding of the manner in which the features described above are presented in this disclosure, reference can be made to various aspects of the above brief overview, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only certain typical aspects of this disclosure and should not be considered as limiting its scope, as other equivalent aspects are permissible in this description.

[0019] Figure 1 It is a block diagram that conceptually illustrates an example wireless communication network according to certain aspects of this disclosure.

[0020] Figure 2 It is a block diagram that conceptually illustrates the design of an example base station (BS) and user equipment (UE) according to certain aspects of this disclosure.

[0021] Figure 3 This is an example frame format for certain wireless communication systems, based on certain aspects of this disclosure.

[0022] Figure 4A and Figure 4B A schematic representation of an example vehicle-to-everything (V2X) system according to certain aspects of this disclosure is shown.

[0023] Figure 5 Example operations for silent, event-driven, one-time transfer (Tx) and resource reselection according to certain aspects of this disclosure are explained.

[0024] Figure 6 This is a flowchart illustrating example operations for wireless communication performed by a UE according to certain aspects of this disclosure.

[0025] Figure 7 This is a flowchart illustrating an example operation for wireless communication by a first sidelink UE according to certain aspects of this disclosure.

[0026] Figure 8 Example operations of silence in irregular semi-persistent scheduling (SPS) are explained according to certain aspects of this disclosure, taking into account actual packet transmission.

[0027] Figure 9 This is a flowchart illustrating an example operation for wireless communication by a first sidelink UE according to certain aspects of this disclosure.

[0028] Figure 10 Three scenarios for SPS conflict detection based on certain aspects of this disclosure are explained.

[0029] Figure 11 Example operations for smarter silent selection and event-driven one-off Tx in SPS conflicts are explained according to certain aspects of this disclosure.

[0030] Figure 12 The description of various aspects of this disclosure includes communication devices that may include various components configured to perform operations for the various techniques disclosed herein.

[0031] Figure 13 The description of various aspects of this disclosure includes communication devices that may include various components configured to perform operations for the various techniques disclosed herein.

[0032] Figure 14 The description of various aspects of this disclosure includes communication devices that may include various components configured to perform operations for the various techniques disclosed herein.

[0033] To facilitate understanding, the same reference numerals are used wherever possible to designate common elements shared by all figures. Elements disclosed in one aspect are conceived to be usefully applied in other aspects without specific citation.

[0034] Detailed description

[0035] This disclosure provides apparatus, methods, processing systems, and computer-readable media for mitigating packet collisions in sidelinks.

[0036] In some systems (such as certain vehicle-to-everything (C-V2X) systems), half-duplex (HD) operation can be used. Collisions can occur when devices use the same resources for transmission. Additionally, the resources may be semi-persistently scheduled (SPS) resources. Therefore, techniques to mitigate collisions are needed. In some cases, silent and one-time transmissions are used to monitor for collisions and determine whether to reselect resources.

[0037] This disclosure provides improved techniques for congestion estimation, smarter silent and conflict detection, and improved resource reselection.

[0038] The following description provides examples of packet collision mitigation in a sidelink communication system and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the elements discussed without departing from the scope of this disclosure. Various procedures or components may be appropriately omitted, substituted, or added to various examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Moreover, features described with reference to some examples may be combined in others. For example, any number of aspects set forth herein may be used to implement an apparatus or practice. Furthermore, the scope of this disclosure is intended to cover such apparatuses or methods practiced using additional structures, functionalities, or structures and functionalities that complement or supplement the various aspects of this disclosure set forth herein. It should be understood that any aspect of this disclosure disclosed herein may be implemented by one or more elements of the claims. The term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as superior to or overriding other aspects.

[0039] Generally, any number of wireless networks can be deployed in a given geographical area. Each wireless network can support a specific Radio Access Technology (RAT) and can operate on one or more frequencies. A RAT may also be referred to as a radio technology, air interface, etc. A frequency may also be referred to as a carrier, subcarrier, frequency channel, frequency modulation, subband, etc. Each frequency can support a single RAT in a given geographical area to avoid interference between wireless networks using different RATs.

[0040] The techniques described herein can be used in a variety of wireless networks and radio technologies. While the aspects may be described herein using terms commonly associated with 3G, 4G, and / or newer radio technologies (e.g., 5G NR), the aspects of this disclosure can be applied to communication systems based on other generations.

[0041] NR access supports a variety of wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80MHz or more), millimeter wave (mmW) targeting high carrier frequencies (e.g., 24GHz to 53GHz or above), massive machine-type communications (mMTC) targeting non-backward-compatible MTC technologies, and / or mission-critical services targeting ultra-reliable low latency communications (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTIs) to meet corresponding quality of service (QoS) requirements. Furthermore, these services can coexist in the same subframe. NR supports beamforming, and beam direction can be dynamically configured. Precoded MIMO transmission is also supported. MIMO configurations in DL can support up to 8 transmit antennas (with up to 8 streams in multilayer DL transmission) and up to 2 streams per UE. Multilayer transmission with up to 2 streams per UE is supported. Up to 8 serving cells can be used to support the aggregation of multiple cells.

[0042] Figure 1 An example wireless communication network 100 in which various aspects of this disclosure can be implemented is described. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network). Figure 1 As shown, the wireless communication network 100 can communicate with the core network 132. The core network 132 can communicate with one or more base stations (BS) 110 and / or user equipment (UE) 120 in the wireless communication network 100 via one or more interfaces.

[0043] Depending on certain aspects, BS 110 and UE 120 can be configured for packet collision mitigation in sidelinks. In some examples, UE 120 can be configured for C-V2X communication. For example... Figure 1 As shown, UE 120a includes a V2X manager 112, which can be configured for conflict mitigation according to various aspects of this disclosure.

[0044] like Figure 1 As explained herein, the wireless communication network 100 may include several BSs 110a-z (each individually referred to herein as BS 110, or collectively as BS 110) and other network entities. BS 110 may provide communication coverage for a specific geographic area (sometimes referred to as a “cell”), which may be stationary or mobile depending on the location of the mobile BS 110. In some examples, BS 110 may interconnect with each other and / or interconnect to one or more other BSs or network nodes (not shown) in the wireless communication network 100 using any suitable transport network through various types of backhaul interfaces (e.g., direct physical connection, wireless connection, virtual network, etc.). Figure 1 In the example shown, BS 110a, 110b, and 110c can be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x can be a pico BS for pico cell 102x. BS 110y and 110z can be femto BSs for femto cells 102y and 102z, respectively. A BS can support one or more cells.

[0045] BS 110 communicates with UEs 120a-y (each individually referred to herein as UE 120, or collectively as UE 120) in the wireless communication network 100. UEs 120 (e.g., 120x, 120y, etc.) may be distributed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. The wireless communication network 100 may also include relay stations (e.g., relay station 110r) (also referred to as relays, etc.) that receive transmissions of data and / or other information from upstream stations (e.g., BS 110a or UE 120r) and transmit such transmissions of data and / or other information to downstream stations (e.g., UE 120 or BS 110), or that relay transmissions between the UEs 120 to facilitate communication between the devices.

[0046] Network controller 130 can communicate with a group of BSs 110 and provide coordination and control over these BSs 110 (e.g., via backhaul). In various aspects, network controller 130 can communicate with core network 132 (e.g., 5G core network (5GC)) which provides various network functions such as access and mobility management, session management, user plane functions, policy control functions, authentication server functions, unified data management, application functions, network openness functions, network repository functions, network slice selection functions, etc.

[0047] Figure 2 The BS 110a and UE 120a (e.g., which can be used to implement various aspects of this disclosure) are explained. Figure 1 Example components of a wireless communication network 100.

[0048] At BS 110a, the transmit processor 220 can receive data from the data source 212 and control information from the controller / processor 240. This control information can be used for the Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Hybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel (PDCCH), Group Shared PDCCH (GC PDCCH), etc. This data can be used for the Physical Downlink Shared Channel (PDSCH), etc. The Media Access Control (MAC)-Control Element (MAC-CE) is a MAC layer communication structure that can be used for exchanging control commands between wireless nodes. The MAC-CE can be carried in shared channels, such as the Physical Downlink Shared Channel (PDSCH), Physical Uplink Shared Channel (PUSCH), or Physical Sidelink Shared Channel (PSSCH).

[0049] Processor 220 can process (e.g., encode and symbol mapping) data and control information to obtain data symbols and control symbols, respectively. Transmit processor 220 can also generate reference symbols (such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), PBCH demodulation reference signal (DMRS), and channel state information reference signal (CSI-RS)). Transmit (TX) multiple-input multiple-output (MIMO) processor 230 can perform spatial processing (e.g., precoding) on ​​data symbols, control symbols, and / or reference symbols where applicable, and can provide the output symbol stream to modulators (MODs) 232a-232t. Each modulator 232 can process its respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator can further process (e.g., convert to analog, amplify, filter, and up-convert) the output sample stream to obtain a downlink signal. The downlink signal from modulators 232a-232t can be transmitted via antennas 234a-234t, respectively.

[0050] At UE 120a, antennas 252a-252r can receive downlink signals from BS 110a and can provide the received signals to demodulators (DEMODs) 254a-254r in the transceiver, respectively. Each demodulator 254 can condition (e.g., filter, amplify, down-convert, and digitize) its respective received signal to obtain an input sample. Each demodulator can further process the input sample (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 256 can obtain the received symbols from all demodulators 254a-254r, perform MIMO detection on these received symbols where applicable, and provide detected symbols. Receiver processor 258 can process (e.g., demodulate, deinterleave, and decode) these detected symbols, provide the decoded data to UE 120a to data sink 260, and provide the decoded control information to controller / processor 280.

[0051] On the uplink, at UE 120a, transmit processor 264 can receive and process data from data source 262 (e.g., for the Physical Uplink Shared Channel (PUSCH)) and control information from controller / processor 280 (e.g., for the Physical Uplink Control Channel (PUCCH)). Transmit processor 264 can also generate reference symbols for reference signals (e.g., probe reference signals (SRS)). Symbols from transmit processor 264 can be pre-encoded by TX MIMO processor 266 where applicable, further processed by modulators 254a-254r in the transceiver (e.g., for SC-FDM, etc.), and transmitted to BS 110a. At BS 110a, uplink signals from UE 120a can be received by antenna 234, processed by demodulator 232, detected by MIMO detector 236 where applicable, and further processed by receive processor 238 to obtain decoded data and control information transmitted by UE 120a. The receiver processor 238 can provide decoded data to the data trap 239 and decoded control information to the controller / processor 240.

[0052] Memory 242 and 282 can store data and program code for use by BS 110a and UE 120a, respectively. Scheduler 244 can schedule UE for data transmission on downlink and / or uplink.

[0053] Antenna 252, processors 266, 258, 264 and / or controller / processor 280 of UE 120a, and / or antenna 234, processors 220, 230, 238 and / or controller / processor 240 of BS 110a can be used to perform the various techniques and methods described herein. For example, such as Figure 2As shown, according to the aspects described herein, the controller / processor 280 of UE 120a has a V2X manager 281 that can be configured for conflict mitigation. Although shown at the controller / processor, other components of UE 120a and BS 110a may also be used to perform the operations described herein.

[0054] NR can utilize Orthogonal Frequency Division Multiplexing (OFDM) with a cyclic prefix (CP) on both the uplink and downlink. NR supports half-duplex operation using Time Division Duplex (TDD). OFDM and Single-Carrier Frequency Division Multiplexing (SC-FDM) divide the system bandwidth into multiple orthogonal subcarriers, which are often referred to as frequency modulation, frequency slots, etc. Each subcarrier can be modulated with data. Modulation symbols can be transmitted in the frequency domain using OFDM and in the time domain using SC-FDM. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The minimum resource allocation (so-called resource block (RB)) can be 12 consecutive subcarriers. The system bandwidth can also be divided into subbands. For example, a subband can cover multiple RBs. NR supports a base-subcarrier spacing (SCS) of 15 kHz and can define other SCSs relative to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.).

[0055] Figure 3 This is a diagram illustrating an example of frame format 300 for NR. The transmission timeline for each of the downlink and uplink can be divided into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be divided into 10 subframes with indices 0 to 9, each subframe being 1 ms long. Each subframe may contain a variable number of time slots (e.g., 1, 2, 4, 8, 16, ... time slots), depending on the SCS. Each time slot may include a variable number of symbol periods (e.g., 7, 12, or 14 symbols), depending on the SCS. An index may be assigned to the symbol periods in each time slot. A mini-time slot (which may be referred to as a sub-time slot structure) refers to a transmission time interval with a duration less than a time slot (e.g., 2, 3, or 4 symbols). Each symbol in a time slot may indicate the link direction for data transmission (e.g., DL, UL, or flexible), and the link direction for each subframe can be dynamically switched. The link direction may be based on the time slot format. Each time slot may include DL / UL data and DL / UL control information.

[0056] In NR, synchronization signal blocks (SSBs) are transmitted. In some respects, each SSB can be transmitted in a burst, where each SSB in the burst corresponds to a different beam direction for use in UE-side beam management (e.g., including beam selection and / or beam refinement). An SSB includes a PSS, an SSS, and a two-symbol PBCH. SSBs can be transmitted at fixed time slot locations (such as...). Figure 3 The symbols 0-3 shown are transmitted. PSS and SSS can be used by the UE for cell search and acquisition. PSS provides half-frame timing, and SS provides CP length and frame timing. PSS and SSS provide cell identity. PBCH carries basic system information such as downlink system bandwidth, timing information within the radio frame, SS burst set periodicity, system frame number, etc. SSB can be organized into SS bursts to support beam sweeping. Further system information (such as Residual Minimum System Information (RMSI), System Information Block (SIB), Other System Information (OSI)) can be transmitted in certain subframes on the Physical Downlink Shared Channel (PDSCH). SSB can be transmitted up to 64 times, for example, up to 64 different beam directions for millimeter waves. Multiple transmissions of SSB are called SS burst sets. SSBs in an SS burst set can be transmitted in the same frequency region, while SSBs in different SS burst sets can be transmitted in different frequency regions.

[0057] In some examples, communication between UE 120 and BS 110 is referred to as an access link. The access link can be provided via the Uu interface. Communication between devices can be referred to as a side link.

[0058] In some examples, two or more subordinate entities (e.g., UE 120) may use sidelink signaling to communicate with each other. Real-world applications of such sidelink communication may include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communication, Internet of Things (IoE) communication, IoT communication, mission-critical mesh networks, and / or various other suitable applications. Generally, sidelink signaling can refer to a signal that is relayed from one subordinate entity (e.g., UE 120a) to another subordinate entity (e.g., another UE 120) without relaying the communication through a scheduling entity (e.g., UE 120 or BS 110), even if the scheduling entity may be used for scheduling and / or control purposes. In some examples, sidelink signaling may use licensed spectrum for transmission (unlike wireless LANs, which typically use unlicensed spectrum). An example of sidelink communication is PC5, for example, as used in V2V, LTE, and / or NR.

[0059] Various sidelink channels can be used for sidelink communication, including the Physical Sidelink Discovery Channel (PSDCH), Physical Sidelink Control Channel (PSCCH), Physical Sidelink Shared Channel (PSSCH), and Physical Sidelink Feedback Channel (PSFCH). The PSDCH carries discovery expressions that enable neighboring devices to discover each other. The PSCCH carries control signaling (such as sidelink resource configuration and other parameters for data transmission), while the PSSCH carries data transmission. The PSFCH carries feedback, such as CSI related to sidelink channel quality.

[0060] Figure 4A and Figure 4B A schematic representation of an example V2X system according to some aspects of this disclosure is shown. For example, Figure 4A and Figure 4B The vehicles shown can communicate via a sidelink channel and can perform sidelink CSI reporting as described herein.

[0061] Figure 4A and Figure 4B The V2X system provided in China offers two complementary transmission modes. Figure 4A The first transmission mode, illustrated by example, involves direct communication between participants that are adjacent to each other in a local area (e.g., also known as sidelink communication). Figure 4B The second transmission mode illustrated by way of example involves network communication over a network, which may be implemented via a Uu interface (e.g., a wireless communication interface between a radio access network (RAN) and a UE).

[0062] Reference Figure 4A The V2X system 400 (e.g., including vehicle-to-vehicle (V2V) communication) is illustrated using two vehicles 402 and 404. A first transmission mode allows direct communication between different participants in a given geographic location. As illustrated, the vehicles may have a wireless communication link 406 (V2P) with an individual (e.g., via a UE) through a PC5 interface. Communication between vehicles 402 and 404 may also occur via PC5 interface 408. Communication (V2I) from vehicle 402 to other highway components (e.g., highway component 410, such as traffic signals or signs) may occur similarly via PC5 interface 412. For Figure 4AEach communication element in the V2X system can communicate bidirectionally, thus each element can be both a sender and receiver of information. The V2X system 400 can be a self-managing system implemented without the assistance of network entities. Self-managing systems enable improved spectrum efficiency, reduced costs, and increased reliability because no network service interruption occurs during handover operations for mobile vehicles. V2X systems can be configured to operate in licensed or unlicensed spectrum, allowing any vehicle equipped with the system to access shared frequencies and share information. This coordinated / shared spectrum operation allows for safe and reliable operation.

[0063] Figure 4B A V2X system 450 is illustrated for communication between vehicles 452 and 454 via network entity 456. These network communications can occur via discrete nodes (such as BSs (e.g., BS 110a)) that send and receive information to and from vehicles 452 and 454 (e.g., relaying information between vehicles 452 and 454). Network communications via vehicle-to-network (V2N) links 458 and 410 can be used for long-range communication between vehicles, such as to inform of a traffic accident at a distance along a road or highway. Other types of communication can be sent to vehicles by wireless nodes, such as traffic flow conditions, road hazard warnings, environmental / weather reports, and service station availability, etc. Such data can be obtained from cloud-based shared services.

[0064] Roadside Units (RSUs) can be utilized. RSUs can be used for V2I communication. In some examples, RSUs can act as forwarding nodes to extend UE coverage. In some examples, RSUs can be located alongside BSs or can be independent. RSUs can be classified in different ways. For example, RSUs can be classified as UE-type RSUs and micro-node B-type RSUs. Micro-NB-type RSUs have similar functionality to macro eNBs / gNBs. Micro-NB-type RSUs can utilize the Uu interface. UE-type RSUs can be used to meet stringent Quality of Service (QoS) requirements by minimizing collisions and improving reliability. UE-type RSUs can use centralized resource allocation mechanisms to allow for efficient resource utilization. Critical information (e.g., traffic conditions, weather conditions, congestion statistics, sensor data, etc.) can be broadcast to UEs in the coverage area. Relays can rebroadcast critical information received from some UEs. UE-type RSUs can be reliable synchronization sources.

[0065] This disclosure relates to various aspects of sidelink communication, such as cellular vehicle-to-everything (C-V2X) communication. C-V2X is a unified connectivity platform designed to provide low-latency vehicle-to-vehicle (V2V) communication, vehicle-to-road infrastructure (V2I) communication, and vehicle-to-pedestrian (V2P) communication to vehicles. C-V2X networks can operate without cellular infrastructure support. Vehicles can autonomously select their radio resources using the SPS algorithm specified by the 3GPP (3rd Generation Partnership Project).

[0066] In some examples, the 3GPP SPS algorithm involves the UE performing channel sensing and resource selection. UE sensing is based on SPS packets to consider resource exclusion and to select from resource candidates ranked according to energy measurements taken during channel sensing.

[0067] In C-V2X sidelink mode 4 communication, a message collision avoidance algorithm based on listener-based SPS is implemented to address undesirable radio channel congestion. SPS reserves periodic transmit (Tx) resources (i.e., subframes or RBs) but maintains Tx resources probabilistically. Therefore, the current standard mechanism generates a large number of packet collisions, which may hinder the high-reliability communication that might be expected for future C-V2X applications.

[0068] Additionally, sidelink devices can be configured for half-duplex (HD) operation. In HD mode, a device cannot perform both Tx and receive (Rx) operations simultaneously. Therefore, a device cannot use the same Tx resources (e.g., within the same subframe) to receive from other UEs, even if they are transmitting using different subchannels. HD operation can limit the ability to effectively support a large number of vehicles.

[0069] Networks that implement both HD and SPS, such as C-V2X networks, can generate some packet collisions. For example, collisions can occur every few minutes to every few hours (10). -4 ~10 -5 Conflicts can even occur between two separate UEs. These conflicts can last from hundreds of milliseconds to several seconds.

[0070] In some situations, silent, event-driven one-time Tx operations and resource reselection can be performed for certain SPS reserved Tx resources to help avoid or reduce conflicts, such as Figure 5 As shown. For example, as Figure 5 As shown, UE1 and UE2 may have SPS resource reservations. UEs may reselect SPS resources randomly or semi-randomly based on listening.

[0071] As used herein, silence can refer to dropping or suppressing transmissions. If each UE reselects to the same subframe, they may be unable to hear (e.g., or detect) transmissions from other UEs (e.g., due to HD operation). UEs can perform silence to detect transmissions from other UEs. Figure 5 As shown, UE 2 silences one of its SPS-scheduled transmissions in subframe 502 to listen for transmissions from UE 1. The silenced UE 2 can detect collisions and further decode UE 1's packet transmissions via its Rx on the silenced SPS Tx subframe.

[0072] After silencing, UE 2 may, for example, perform a one-time transmission in the next subframe 504 to transmit the transmission from the silenced subframe. For example, an event-driven one-time transmission could be a transmission that does not use SPS resources, but rather a one-time transmission following the silence.

[0073] When UE2 detects a transmission from UE1, UE2 can determine that there is a conflict in the SPS reservation and perform a reselection of its SPS resources, such as... Figure 5 As shown in the diagram. Therefore, the conflict with UE 1 can be avoided.

[0074] By silencing the packet, the maximum inter-packet gap (IPG) is reduced; however, this may increase the block error rate (BLER). BLER can be improved by transmitting in one go. However, further improvements are expected. Additionally, if the collision is a resource block (RB) level collision or a subframe level collision without RB overlap, other UEs can still decode the transmission of the colliding UE.

[0075] Accordingly, there is a need for technologies and devices to reduce packet collisions in sidelinks (such as for reducing or avoiding SPS collisions in C-V2X systems).

[0076] Example packet collision mitigation in side links

[0077] Various aspects of this disclosure provide enhancements for packet collision mitigation in sidelinks. For example, various aspects of this disclosure provide improved techniques for congestion estimation, smarter silencing and collision detection, and improved resource reselection.

[0078] Although the subject matter described in this disclosure relates to both first-sidelink user equipment (UE) and second-sidelink UE, the methods and apparatus described herein can be applied to scenarios with any number of conflicting or potentially conflicting devices.

[0079] Figure 6 , 7Figures 600, 700, and 900 are flowcharts illustrating example operations 600, 700, and 900 for wireless communication according to certain aspects of this disclosure. Operations 600, 700, and 900 may be performed, for example, by a user equipment (UE) (e.g., UE120a in wireless communication network 100). Operations 600, 700, and 900 may be implemented in one or more processors (e.g., ...). Figure 2 The software components executed and running on the controller / processor 280. Furthermore, the signal transmission and reception performed by the UE in operations 600, 700, and 900 may be, for example, performed by one or more antennas (e.g., Figure 2 This can be achieved via antenna 252. In some respects, signal transmission and / or reception by the UE can be achieved by obtaining and / or outputting signals via a bus interface of one or more processors (e.g., controller / processor 280).

[0080] Example congestion level estimation:

[0081] In some respects, techniques are provided for improving congestion level estimation by taking into account the number of UEs plus the channel busy ratio (CBR).

[0082] Figure 6 This is a flowchart illustrating example operation 600 for congestion level estimation that can be performed by a sidelink UE.

[0083] Operation 600 can be initiated at 602 by measuring the Channel Busy Ratio (CBR).

[0084] At 604, the UE estimates the number of UEs using the channel. Estimating the number of UEs using the channel may include counting the number of packets received in a time window and estimating the number of UEs using the channel based on that number of packets. Estimating the number of UEs using the channel may also include counting the number of source addresses in the packets received in a time window and estimating the number of UEs using the channel based on that number of source addresses.

[0085] In 606, the UE estimates the congestion level based on the CBR and the estimated number of UEs.

[0086] The operation at 600 may further include: at 608, using the estimated channel congestion level to determine the periodicity of transmissions in the skipped subframe to listen for transmissions from the UE on the other side link.

[0087] Silence (e.g., as Figure 5 As shown in the diagram, C-V2X performance can depend on the congestion level. Accordingly, the congestion level can be controlled. Figure 5The protocol described herein includes UE silencing, event-driven one-time Tx, and the frequency of reselection. In some systems, only CBR is used for congestion level estimation; however, CBR measurement may be less relevant to C-V2X performance. In an illustrative example, a test scenario with 50 UEs may have a CBR of less than 10%, while a test scenario with only 8 UEs may have a CBR of more than 10%. Although a higher CBR is expected for a larger number of UEs, the CBR value for 10 UEs is lower than that for the test scenario with only 8 UEs. Therefore, improved techniques for congestion level estimation in C-V2X are desired.

[0088] Accordingly, aspects of this disclosure estimate the C-V2X congestion level at the modem by considering the estimated number of UEs plus the CBR. To estimate the number of UEs using the channel, the UE may count the number of packets and / or Packet Resource Blocks (RBs) received by the UE within a time window (e.g., a 1-second time window). In some examples, the UE estimates the number of UEs using the channel by counting the number of source addresses (e.g., Layer 2 source addresses) received by the UE within a time window (e.g., a 1-second time window). The UE can then estimate the congestion level by considering the number of UEs using the channel plus the CBR. The CBR can be determined through channel sensing.

[0089] The estimated congestion level can then be used to determine silence, one-time Tx, and reselection. For example, the frequency (or periodicity) at which the UE performs a silence process can be determined at least in part based on the estimated congestion level.

[0090] Example of smart silence for irregular SPS Tx:

[0091] Depending on certain aspects, intelligent silence can be used. For example, intelligent silence can take into account irregular SPS transmissions.

[0092] Figure 7 This is a flowchart illustrating an example operation 700 for intelligent silence in an irregular SPS Tx that can be performed by a sidelink UE.

[0093] Operation 700 can be initiated at 702 by determining, through the sidelink UE, the SPS resource reservation including the first one or more subframes in which the sidelink UE is scheduled to transmit.

[0094] At 704, the sidelink UE determines that it has a second or more subframes in the first or more subframes in which it has generated packets to transmit. In some examples, determining that the sidelink UE has a second or more subframes in which it has generated packets to transmit includes: randomly selecting a first candidate subframe to skip transmission, and if there are no generated packets to transmit in the first candidate subframe, waiting until the sidelink UE actually transmits in several subframes, and determining the second or more subframes based on the subframes in which the sidelink UE actually transmits. In some examples, determining that the UE has a second or more subframes in which it has generated packets to transmit includes: randomly selecting a first candidate subframe to skip transmission, and if there are no generated packets to transmit in the first candidate subframe, waiting until the next subframe in which the sidelink UE actually transmits, and determining the next subframe as one of the second or more subframes.

[0095] In 706, the sidelink UE determines to skip transmissions in one or more of the second or more subframes.

[0096] In 708, the sidelink UE listens for transmissions from the other sidelink UE during one or more of the second or more subframes. After listening in one or more of the second or more subframes, the sidelink UE may send the skipped transmissions in subsequent subframes.

[0097] In 710, the first sidelink UE uses this listening to determine whether to reselect resources.

[0098] In the operation of 700, the side-link UE can be a vehicle UE.

[0099] SPS resources can be periodically reserved. In an illustrative example, an SPS Tx is reserved every 100 milliseconds (ms). However, actual SPS Tx packets may be irregular. For example, although the reservation is every 100 ms, the UE may actually generate an SPS Tx (e.g., a packet) every 100 ms to 600 ms. Irregular SPS Tx from the application may be due to distributed congestion control, decentralized congestion control (DCC), jitter, etc., used in the Intelligent Transport System (ITS). If silence does not consider actual SPS Tx, SPS collision detection may not align with actual SPS Tx. In this case, even if the UE detects a transmission from another UE in a silent subframe, there may actually be no collision because the UE does not actually transmit in that subframe.

[0100] Accordingly, aspects of the present invention provide smarter silent decision-making by enabling the UE to skip transmissions / silence transmissions by taking into account the actual packet Tx / counting the actual packet Tx (e.g., instead of scheduling transmissions only via SPS).

[0101] In some examples, the UE considers actual SPS transmission. For instance, the UE randomly selects a silent subframe. In some examples, the UE performs random silence after SPS resource selection (reselection). Figure 8 As shown, the UE has actual SPS packet transmissions at subframes 1 and 3 (7 subframes after subframe 1). The UE randomly selects a subframe, such as subframe 802 (e.g., subframe 4), between actual SPS transmissions (e.g., within subframes [2,6]).

[0102] In some examples, a randomly selected subframe (e.g., subframe 802) has no actual SPS Tx. After a random selection, if no actual SPS Tx exists for that random selection, silence can be applied to the next actual SPS Tx packet.

[0103] exist Figure 8 In the example, the UE can perform random silence at subframe 802. If there is no actual transmission, the UE can, for example, randomly select from subframes [5, 15]. For example, in Figure 8 In the example, the UE selects subframe 11 for its next random silence.

[0104] Once the UE is silent in a subframe with an actual generated packet Tx, the UE can perform collision detection, one-time transmission, and decide whether to perform resource reselection.

[0105] Example SPS collision detection:

[0106] SPS collision detection / reselection can be improved in several ways. For example, collisions can be detected (e.g., resource reselection can be determined) based on the amount of RB-level overlap in the transmission resources by the UE. Collision detection / reselection can be based on the priority associated with the transmission. Collision detection / reselection can be based on the transmission range and / or signal strength difference. Collision detection / reselection can be based on flow tracking.

[0107] Figure 9 This is a flowchart illustrating example operation 900 for SPS collision detection that can be performed by a sidelink UE.

[0108] Operation 900 can begin at 902 by the sidelink UE listening for transmissions from another sidelink UE during the first subframe. In some examples, the first subframe includes a subframe in which the sidelink UE transmits or a subframe in which the sidelink UE skips transmissions based on jitter or silence. In some examples, where the first subframe is a subframe in which the sidelink UE skips transmissions based on silence, after listening in one or more of the second or more subframes, the sidelink UE transmits the skipped transmissions in subsequent subframes.

[0109] In 904, the sidelink UE detects whether a transmission from the other sidelink UE conflicts with transmission resources scheduled for that sidelink UE based on the monitoring. This detection is based on the amount of frequency resource overlap between the transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE. In some examples, detection includes detecting a conflict when the transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE appear in the subframe. The transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE are on non-overlapping frequency resources. In some examples, detection includes detecting a conflict when the transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE are on at least partially overlapping frequency resources. In some examples, detection includes detecting a conflict when the frequency resources used for one of the transmission from the other sidelink UE and the transmission resources scheduled for that sidelink UE completely overlap with the other's frequency resources.

[0110] In some examples, detecting whether a transmission from the other side link UE conflicts with transmission resources scheduled for that side link UE is based on listening, further based on periodicity associated with the transmission from the other side link UE and the transmission resources scheduled for that side link UE. Detection may include detecting a conflict when the difference between the periodicities is greater than a threshold.

[0111] In 906, the sidelink UE determines whether to reselect resources based on whether one or more collisions are detected. Determining to reselect resources based on whether one or more collisions are detected may include: determining to reselect resources when at least a single collision is detected in the case of a non-Hybrid Automatic Repeat Request (HARQ) transmission, when the channel congestion level is below a threshold, or both; and determining to reselect resources when multiple collisions are detected in the case of a HARQ transmission, when the channel congestion level is above a threshold, or both. In some examples, determining to reselect resources is based on the distance between the other sidelink UE and the first sidelink UE, the signal strength of the transmission from the other sidelink UE, the congestion level, or a combination thereof.

[0112] In the operation of 900, the side-link UE can be a vehicle UE.

[0113] The operation at 900 may further include: determining the periodicity of skipping transmissions in a subframe to listen for transmissions from the UE on the other side link based on the semi-persistent scheduling (SPS) stream priority associated with the scheduled transmission, detecting collisions, reselecting resources, or a combination thereof.

[0114] The operation at 900 may further include: reselecting the resource for the scheduled transmission, detecting that one or more expected SPS streams are not detected after the reselection, and triggering a skip transmission and listening in another subframe based on the detection that one or more expected SPS streams are not detected.

[0115] Depending on certain aspects, various overlapping / collision situations may exist between transmissions (e.g., detected during silent / listen subframes). Figure 10 Three scenarios for SPS collision detection in three different subframes 1002a, 1002b and 1002c according to certain aspects of this disclosure are explained.

[0116] In some examples, collisions are detected for any time-domain overlap, regardless of any frequency-domain collisions that occur. Thus, collisions can be detected as transmissions occur within a subframe, even if these transmissions use different frequency resources, as shown in subframe 1002a. In half-duplex (HD) operation, UEs that collide in subframes may not be able to receive each other (e.g., UE 1 cannot hear or detect UE 2 at subframe 1002a and UE 2 cannot hear or detect UE 1 at subframe 1002a), but other UEs can receive the colliding UEs.

[0117] In some examples, collision detection is performed on transmissions using partially overlapping frequency domain resources within the same subframe. Since control information can be located at the beginning of a data transmission, partial overlap between transmissions causes the control portions of one transmission to overlap. Specifically, in (RB... Tx-start +LRB TX )>RB Rx-start And RB Tx-Start <(RB) Rx-start +LRB Rx A time conflict occurs. As used in this article, RB start `RB` is the index of the starting RB of the packet, and `LRB` is the number of RBs in the packet. As shown in subframe 1002b, UE 3 and UE 4 transmit with partial RB-level collision in the same subframe. In this case, other UEs may or may not receive the transmission from the colliding UE (e.g., UE 3 and UE 4 collide). For example, because the control portion of UE 3's transmission overlaps, other UEs may not be able to receive the transmission from UE 3.

[0118] In some examples, collisions are detected for transmissions using fully overlapping frequency domain resources within the same subframe. Since control information can be located at the beginning of a data-bearing transmission, the complete overlap between transmissions causes the control portions of the two transmissions to overlap. The collision detected in subframe 1002c involves the initial RB collision where both time-domain and frequency-domain collisions occur. Specifically, in the RB... Tx-start =RB Rx-start A timing conflict occurs. As shown in subframe 1002c, the transmissions of UE 5 and UE 6 in the same subframe involve RB conflicts and initial RB conflicts. In this situation, for example, because the control portions of the transmissions from both conflicting UEs (e.g., UE 5 and UE 6 are conflicting) overlap, other UEs may be unable to receive transmissions from either of the conflicting UEs.

[0119] Therefore, collision detection / determination of resource reselection can be based not only on the detection of transmissions in a subframe, but also on the amount of frequency (e.g., RB level) overlap of the transmissions.

[0120] According to certain aspects of this disclosure, conflict detection / determination to perform resource reselection may be further based on other conditions. For example, conflict detection / determination to perform resource reselection may be based on whether the transmission uses Hybrid Automatic Repeat Request (HARQ) and / or on congestion levels. For example, because the probability of successfully decoding a transmission is greater in the presence of HARQ transmissions, the conditions for resource reselection can be more stringent, while in the absence of HARQ transmissions, the conditions for resource reselection can be relaxed, thus making it more likely that the UE will reselect resources to ensure that the transmission is received.

[0121] Automatic Repeat Request (ARQ) is a method for enhancing communication performance by retransmitting data that has been received incorrectly. HARQ may include a combination of ARQ and / or forward error correction (FEC) techniques that retain failed decoding attempts for future joint decoding. In C-V2X HARQ, the UE can blindly transmit HARQ retransmissions without any ACK / NACK messages from the receiver.

[0122] In some examples, when a transmission is a subframe-level collision (e.g., a time-domain collision rather than a frequency-domain collision, as explained at subframe 1002a), the UE can reselect resources based on whether the transmission is a HARQ transmission. For example, for a non-HARQ transmission, the UE can detect a collision / determine to reselect resources when the transmission resources are in the same subframe. For a HARQ transmission, the UE can detect a collision / determine to reselect resources when the transmissions are in the same subframe and further based on whether there is one or multiple colliding transmissions in that subframe. For example, for a HARQ transmission, the UE can detect a collision / determine to reselect resources based on a single collision or two collisions, further based on a congestion level threshold (e.g., a CBR threshold). The UE can use single collision detection when the congestion level is at or below the threshold, and double collision detection when the congestion level is above the threshold.

[0123] According to certain aspects of this disclosure, in cases where the conflict is a conflict between two starting RBs (e.g., complete overlap, as explained at subframe 1002b), resource reselection can be determined based on whether the scheduled transmission is a HARQ transmission. For non-HARQ transmissions, the UE may detect a conflict / determine to reselect resources when there is a conflict with a starting RB of another transmission (complete overlap) or only when there are multiple conflicts with starting RBs of other transmissions. For example, for HARQ transmissions, the UE may detect a conflict / determine to reselect resources when there is a conflict with a single RB of another transmission (complete overlap) and the congestion level is at or below a threshold, while the UE may detect a conflict / determine to reselect resources only when there are multiple conflicts with starting RBs when the congestion level is above a threshold.

[0124] According to certain aspects of this disclosure, in cases where a conflict involves any RB-level conflict (e.g., partial overlap, as explained at subframe 1002b), resource reselection can be determined based on whether the scheduled transmission is a HARQ transmission. For non-HARQ transmissions, the UE can detect a conflict / determine to reselect resources when a single RB-level conflict (e.g., any partial overlap) exists with another transmission. For HARQ transmissions, the UE can detect a conflict / determine to reselect resources when a single RB-level conflict condition exists or only when multiple RB-level conflicts with other transmissions exist. For example, the UE can detect a conflict / determine to reselect resources when any RB-level conflict with a transmission exists if the congestion level is at or below a threshold, while the UE can detect a conflict / determine to reselect resources only when multiple RB-level conflicts with other transmissions exist if the congestion level is above a threshold.

[0125] In some examples, subframe collision conditions, initial RB collision conditions, and RB-level collision conditions can be used together. For instance, when the congestion level is at or below a threshold, a subframe collision condition (e.g., no frequency overlap) can be used for SPS collision detection / resource reselection. When the congestion level is above a threshold, an initial RB collision (full frequency overlap) or an RB-level collision (partial overlap) can be used for SPS collision detection / resource reselection.

[0126] According to certain aspects of this disclosure, the listening and collision detection techniques applied above can be implemented in subframes other than silent subframes. For example, SPS Tx-Tx collision detection and resource reselection can be enabled for any Rx subframe. For example, the UE can listen (e.g., detect, decode) transmissions from other UEs in subframes in which the UE skips transmissions due to jitter, in subframes in which the UE skips transmissions based on silence, or in any other Rx subframe.

[0127] According to certain aspects of this disclosure, collision detection / resource reselection may be further based on the periodicity associated with the transmissions involved in the collision. In some examples, SPS periods of 20, 50, 100, 200…1000 ms (or other periods) may be used for SPS transmissions. The periodicity associated with SPS transmissions may be indicated in the control channel of the transmission. In some examples, when one transmission has a large SPS Tx period and the other has a small SPS period (e.g., when the difference between the two periods is greater than or exceeds a threshold), the UE is more likely to trigger reselection compared to transmissions with similar periods. In some examples, when either of the SPS periods of these transmissions in a subframe is large, the UE is more likely to trigger reselection compared to none of the SPS periods being large.

[0128] According to certain aspects of this disclosure, silencing / skipping, event-driven one-time Tx, collision detection, and resource reselection can be further based on priorities associated with transmissions in the subframe (e.g., based on SPS stream priorities). Priority-based SPS collision mitigation can control the level of protection provided in collision detection based on the associated priorities. The 3GPP specification identifies eight different scheduling priorities (1–8), which are assigned to each data stream in an SPS. The priority stream associated with each SPS can be indicated in the control channel of that transmission.

[0129] When considering flow priority, higher SPS flows associated with scheduled transmissions can be given more protection. In some examples, more frequent silencing / skipping and event-driven Txes and / or more frequent reselections (e.g., more relaxed collision detection / resource reselection conditions) can be used for higher priority flows compared to lower priority flows. For example, a high-priority SPS flow may trigger a single-start RB or single-subframe collision condition, while a low-priority SPS flow may trigger a multi-start RB or multi-subframe collision condition. In another example, flow priority can be considered in addition to congestion level. In some examples, reselection can be triggered only for SPS flows with a priority below a threshold when the congestion level is above a threshold.

[0130] According to certain aspects of this disclosure, collision detection / resource reselection may be further based on the distance between UEs (e.g., range), transmitted signal strength, and / or congestion level. In some examples, at high congestion levels (e.g., when the congestion level is above a threshold), collision avoidance or resource reselection may be biased towards nearby UEs (e.g., within a distance of or below a threshold and / or with signal strength above a threshold). For example, resource reselection may be biased by making resource reselection more likely when the congestion level is above a threshold and the distance is at or below a threshold or the signal strength is above a threshold (e.g., when a collision is detected / the condition for determining that a resource should be reselected is relaxed). The distance between a first-sidelink UE and a second-sidelink UE may be detected based on a security message that may include location information, while signal strength may be received / measured by a modem. The modem may, for example, determine the received signal strength indicator (RSSI) or reference signal received power (RSRP). In some embodiments, when the congestion level is high and an SPS collision is detected, resource reselection will be triggered when the RSRP or RSSI is greater than a threshold.

[0131] Figure 11 This disclosure describes a smarter silent selection and event-driven one-time transfer (Tx) for SPS collisions, according to certain aspects. According to some aspects, silent selection, one-time transfer, and reselection can be triggered based on tracking of received SPS streams. In some examples, the number of SPS streams received during a first window can be tracked by the UE and then compared by the same UE with the number of SPS streams received during a second window after reselection. If the UE detects that some SPS streams have disappeared (e.g., several SPS streams previously received in the first window were not received in the second window), silent selection and an event-driven one-time Tx can be triggered. Figure 11As shown in the illustrative example, the UE detects the number of SPS streams during a 200ms window 1102. After resource reselection 1104, the UE detects the number of SPS streams that have disappeared within a 500ms window 1106. When the UE detects the number of SPS streams that have disappeared within the 500ms window, it can trigger a silent or event-driven Tx.

[0132] Figure 12 The description may include operations that are configured to perform the techniques disclosed herein (such as, Figure 6 The communication device 1200 comprises various components (e.g., corresponding to device plus functional components) of the operation described herein. The communication device 1200 includes a processing system 1202 coupled to a transceiver 1208 (e.g., a transmitter and / or receiver). The transceiver 1208 is configured to transmit and receive signals (such as the various signals described herein) for the communication device 1200 via an antenna 1210. The processing system 1202 may be configured to perform processing functions for the communication device 1200, including processing signals received and / or to be transmitted by the communication device 1200.

[0133] Processing system 1202 includes processor 1204 coupled to computer-readable medium / memory 1212 via bus 1206. In some aspects, computer-readable medium / memory 1212 is configured to store data that, when executed by processor 1204, causes processor 1204 to perform... Figure 6 The computer-readable medium / memory 1212 stores instructions (e.g., computer-executable code) for the operations described herein or for performing other operations of the various techniques discussed herein for enhancing C-V2X UE and UE packet collision mitigation. In some aspects, according to various aspects of this disclosure, the computer-readable medium / memory 1212 stores: code 1214 for measuring the channel busy ratio (CBR); code 1216 for estimating the number of UEs using the channel; code 1218 for estimating the congestion level based on the CBR and the estimated number of UEs; and / or code 1220 for using the estimated channel congestion level to determine the periodicity for skipping transmissions in subframes to listen for transmissions from UEs on the other side of the link. In some aspects, the processor 1204 has a circuit system configured to implement the code stored in the computer-readable medium / memory 1212. According to various aspects of this disclosure, processor 1204 includes: circuitry 1222 for measuring channel busy ratio (CBR); circuitry 1224 for estimating the number of UEs using the channel; circuitry 1226 for estimating a congestion level based on the CBR and the estimated number of UEs; and / or circuitry 1228 for using the estimated channel congestion level to determine periodicity for skipping transmissions in a subframe to listen for transmissions from UEs on the other side of the link.

[0134] Figure 13 The explanation may include operations that can be configured to perform the techniques disclosed herein (such as...). Figure 7 The communication device 1300 comprises various components (e.g., corresponding to device plus functional components) of the operation described herein. The communication device 1300 includes a processing system 1302 coupled to a transceiver 1308 (e.g., a transmitter and / or receiver). The transceiver 1308 is configured to transmit and receive signals (such as the various signals described herein) for the communication device 1300 via an antenna 1310. The processing system 1302 may be configured to perform processing functions for the communication device 1300, including processing signals received and / or to be transmitted by the communication device 1300.

[0135] Processing system 1302 includes processor 1304 coupled to computer-readable medium / memory 1312 via bus 1306. In some aspects, computer-readable medium / memory 1312 is configured to store data that, when executed by processor 1304, causes processor 1304 to perform... Figure 7 The computer-readable medium / memory 1312 stores instructions (e.g., computer-executable code) for the operations described herein or for performing other operations of the various techniques discussed herein for enhancing C-V2X UE and UE packet collision mitigation. In some aspects, according to aspects of this disclosure, the computer-readable medium / memory 1312 stores: code 1314 for determining a semi-persistent scheduling (SPS) resource reservation including a first one or more subframes in which the sidelink UE is scheduled to transmit; code 1316 for determining a second one or more subframes in which the sidelink UE has generated packets to transmit; code 1318 for determining to skip transmissions in one or more of the second one or more subframes; code 1320 for listening to transmissions from another sidelink UE during the second one or more subframes; and / or code 1322 for determining, based on the listening, whether to reselect resources. In some aspects, the processor 1304 has a circuitry configured to implement the code stored in the computer-readable medium / memory 1312. According to various aspects of this disclosure, processor 1304 includes: circuitry 1324 for determining a semi-persistent scheduling (SPS) resource reservation including a first one or more subframes in which the UE is scheduled to transmit; circuitry 1326 for determining a second one or more subframes in which the UE has generated packets to transmit; circuitry 1328 for determining to skip transmissions in one or more of the second one or more subframes; circuitry 1330 for listening to transmissions from a UE on another link during the one or more of the second one or more subframes; and / or circuitry 1332 for determining, based on the listening, whether to reselect resources.

[0136] Figure 14 The explanation may include operations that can be configured to perform the techniques disclosed herein (such as...). Figure 9 The communication device 1400 comprises various components (e.g., corresponding to device plus functional components) of the operation described herein. The communication device 1400 includes a processing system 1402 coupled to a transceiver 1408 (e.g., a transmitter and / or receiver). The transceiver 1408 is configured to transmit and receive signals (such as the various signals described herein) for the communication device 1400 via an antenna 1410. The processing system 1402 may be configured to perform processing functions for the communication device 1400, including processing signals received and / or to be transmitted by the communication device 1400.

[0137] Processing system 1402 includes processor 1404 coupled to computer-readable medium / memory 1412 via bus 1406. In some aspects, computer-readable medium / memory 1412 is configured to store data that, when executed by processor 1404, causes processor 1404 to perform... Figure 9 The instructions (e.g., computer-executable code) for performing the operations described herein or other operations for executing the various techniques discussed herein for enhancing C-V2X UE and UE packet collision mitigation. In some aspects, according to aspects of this disclosure, the computer-readable medium / memory 1412 stores: code 1414 for listening to transmissions from a UE on the other side link during a first subframe; code 1416 for detecting, based on the listening, whether a transmission from the other side link UE conflicts with transmission resources scheduled for that side link UE, wherein the detection is based on the amount of frequency resource overlap between the transmission from the other side link UE and the transmission resources scheduled for that side link UE; and / or code 1418 for determining whether to reselect resources based on whether one or more conflicts are detected. In some aspects, the processor 1404 has a circuit system configured to implement the code stored in the computer-readable medium / memory 1412. According to various aspects of this disclosure, processor 1404 includes: circuitry 1424 for listening to transmissions from a UE on another side link during a first subframe; circuitry 1426 for detecting, based on the listening, whether the transmission from the UE on the other side link conflicts with transmission resources scheduled for the UE on that side link, wherein the detection is based on the amount of frequency resource overlap between the transmission from the UE on the other side link and the transmission resources scheduled for the UE on that side link; and / or circuitry 1428 for determining, based on whether one or more conflicts are detected, to reselect resources.

[0138] The techniques described in this document can be used in various wireless communication technologies, such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-A Advanced (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. CDMA networks can implement radio technologies such as Universal Terrestrial Radio Access (UTRA) and cdma2000. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers the IS-2000, IS-95, and IS-856 standards. TDMA networks can implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as NR (e.g., 5G RA), evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDMA. UTRA and E-UTRA are parts of the Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are UMTS versions using E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization called the 3rd Generation Partnership Project (3GPP). cdma2000 and UMB are described in documents from an organization called the 3rd Generation Partnership Project 2 (3GPP2). NR is an emerging wireless communication technology under development.

[0139] In 3GPP, the term "cell" can refer to the coverage area of ​​a B-node (NB) and / or the NB subsystem serving that coverage area, depending on the context in which the term is used. In NR systems, the terms "cell" and BS, next-generation B-node (gNB or g B-node), access point (AP), distributed cell (DU), carrier, or transmit / receive point (TRP) can be used interchangeably. A BS can provide communication coverage for macrocells, picocells, femtocells, and / or other types of cells. A macrocell can cover a relatively large geographic area (e.g., a radius of several kilometers) and allows unrestricted access by UEs with a service subscription. A picocell can cover a relatively small geographic area and allows unrestricted access by UEs with a service subscription. A femtocell can cover a relatively small geographic area (e.g., a residential area) and allows restricted access by UEs associated with that femtocell (e.g., UEs in a closed subscriber group (CSG), UEs of users in a residential area, etc.). A BS used for a macrocell can be referred to as a macro BS. A BS used for picocells can be called a picoBS. A BS used for femtocells can be called a femtoBS or a home BS.

[0140] A UE can also be referred to as a mobile station, terminal, access terminal, subscriber unit, station, customer premises equipment (CPE), cellular phone, smartphone, personal digital assistant (PDA), wireless modem, wireless communication device, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, tablet computer, camera, gaming device, netbook, smartbook, ultrabook, appliance, medical device or medical equipment, biometric sensor / device, wearable device (such as smartwatch, smart clothing, smart glasses, smart wristband, smart jewelry (e.g., smart ring, smart bracelet, etc.)), entertainment device (e.g., music device, video device, satellite radio, etc.), vehicle component or sensor, smart meter / sensor, industrial manufacturing equipment, GPS device, or any other suitable device configured to communicate via wireless or wired media. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which can communicate with a BS, another device (e.g., a remote device), or another entity. Wireless nodes can provide connectivity to or to a network (e.g., a wide area network such as the Internet) or a cellular network, for example, via wired or wireless communication links. Some UEs can be considered Internet of Things (IoT) devices, which can be narrowband IoT (NB-IoT) devices.

[0141] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, the subordinate entity utilizes the resources allocated by the scheduling entity. A base station is not the only entity that can be used as a scheduling entity. In some examples, a UE may act as a scheduling entity and can schedule resources for one or more subordinate entities (e.g., one or more other UEs), and other UEs may utilize the resources scheduled by that UE for wireless communication. In some examples, a UE may act as a scheduling entity in a peer-to-peer (P2P) network and / or in a mesh network. In the mesh network example, UEs may communicate directly with each other in addition to communicating with a scheduling entity.

[0142] The methods disclosed herein include one or more steps or actions for implementing the method. These method steps and / or actions may be interchanged without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0143] As used herein, the phrase “at least one of” refers to any combination of these items, including a single member. As an example, “at least one of a, b, or c” is intended to cover: a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical elements (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c).

[0144] As used herein, the term "determine" encompasses a wide variety of actions. For example, "determine" can include calculation, computation, processing, derivation, research, searching (e.g., looking in a table, database, or other data structure), ascertaining, and the like. Furthermore, "determine" can include receiving (e.g., receiving information), accessing (e.g., accessing data in memory), and the like. Moreover, "determine" can include parsing, selecting, choosing, building, and the like.

[0145] The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will readily be understood by those skilled in the art, and the universal principles defined herein may be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but are to be granted the full scope consistent with the language of the claims, wherein references to the singular form of an element are not intended to mean “one and only one” (unless specifically stated otherwise) but “one or more.” Unless specifically stated otherwise, the term “some / a” refers to one or more. All structural and functional equivalents of the aspects described throughout this disclosure that are now or hereafter known to a person skilled in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended to be donated to the public, whether or not such disclosure is expressly stated in the claims. No element of a claim should be interpreted in accordance with the provisions of 35 U.S.SC §112(f) unless the element is expressly stated using the phrase “means for…” or, in the case of a method claim, the element is stated using the phrase “steps for…”.

[0146] The various operations of the methods described above can be performed by any suitable means capable of performing the corresponding functions. These means may include various hardware and / or software components and / or modules, including but not limited to circuits, application-specific integrated circuits (ASICs), or processors. Generally, where the operations illustrated in the figures are present, these operations may have corresponding paired means with similar numbers plus functional components.

[0147] The various illustrative logic blocks, modules, and circuits described in this disclosure can be implemented or executed using a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but in alternatives, the processor may be any commercially available processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

[0148] If implemented in hardware, an example hardware configuration could include a processing system in a wireless node. The processing system can be implemented using a bus architecture. Depending on the specific application and overall design constraints of the processing system, the bus can include any number of interconnect buses and bridges. The bus can link together various circuits, including a processor, machine-readable media, and a bus interface. The bus interface can be used to connect network adapters, etc., to the processing system via the bus. The network adapter can be used to implement signal processing functions at the PHY layer. In the user terminal (see...), Figure 1 In such cases, the user interface (e.g., keypad, display, mouse, joystick, etc.) can also be connected to the bus. The bus can also link various other circuits (such as timing sources, peripherals, voltage regulators, power management circuits, etc.), which are well known in the art and will therefore not be described further. The processor can be implemented using one or more general-purpose and / or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuit systems capable of executing software. Depending on the specific application and the overall design constraints imposed on the system, those skilled in the art will recognize how best to implement the functionality described for the processing system.

[0149] If implemented in software, the functions can be stored or transmitted as one or more instructions or codes on a computer-readable medium. Software should be broadly interpreted to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media includes both computer storage media and communication media, encompassing any medium that facilitates the transfer of a computer program from one location to another. The processor may be responsible for managing the bus and general processing, including executing software modules stored on the machine-readable storage medium. The computer-readable storage medium may be coupled to the processor so that the processor can read and write information to / from the storage medium. Alternatively, the storage medium may be integrated into the processor. As an example, the machine-readable medium may include a transmission line, a data-modulated carrier wave, and / or a separate computer-readable storage medium containing instructions stored thereon, all accessible to the processor via a bus interface. Alternatively or additionally, the machine-readable medium or any portion thereof may be integrated into the processor, such as caches and / or general-purpose register files. As an example, examples of machine-readable storage media may include RAM (random access memory), flash memory, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), registers, disks, optical disks, hard drives, or any other suitable storage media, or any combination thereof. Machine-readable media may be implemented in computer program products.

[0150] Software modules may comprise a single instruction or a number of instructions, and may be distributed across several different code segments, across different programs, and across multiple storage media. Computer-readable media may include several software modules. These software modules include instructions that, when executed by an instrument (such as a processor), enable the processing system to perform various functions. These software modules may include transfer modules and receive modules. Each software module may reside in a single storage device or be distributed across multiple storage devices. As an example, when a trigger event occurs, a software module may be loaded from a hard drive into RAM. During the execution of a software module, the processor may load some instructions into a cache to improve access speed. One or more cache lines may subsequently be loaded into a general-purpose register file for processor execution. In the context of the functionality of a software module described below, it will be understood that such functionality is implemented by the processor when the processor executes the instructions from that software module.

[0151] Similarly, any connection is also legitimately referred to as computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology (such as infrared (IR), radio, and microwave), then that coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology (such as infrared, radio, and microwave) is included in the definition of medium. As used herein, disks and discs include compact discs (CDs), laser discs, optical discs, digital multi-purpose discs (DVDs), floppy disks, and... Disks, where disks often magnetically reproduce data, and discs optically reproduce data using lasers. Therefore, in some aspects, computer-readable media may include non-transient computer-readable media (e.g., tangible media). Additionally, in other aspects, computer-readable media may include transient computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0152] Therefore, certain aspects may include computer program products for performing the operations described herein. For example, such computer program products may include computer-readable media on which instructions are stored (and / or encoded) that can be executed by one or more processors to perform the operations described herein, such as those for performing the operations described herein and in... Figure 6 , Figure 7 and / or Figure 9 The instructions for the operation explained in the text.

[0153] Furthermore, it should be understood that modules and / or other suitable means for performing the methods and techniques described herein may be downloaded and / or otherwise obtained by the user terminal and / or base station where applicable. For example, such devices can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage device (e.g., RAM, ROM, physical storage media such as CDs or floppy disks, etc.) so that the device can obtain the various methods once the storage device is coupled to or provided to the user terminal and / or base station. Furthermore, any other suitable techniques appropriate for providing the methods and techniques described herein to the device may be utilized.

[0154] It will be understood that the claims are not limited to the precise configurations and components described above. Various modifications, substitutions, and variations may be made to the layout, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A method for wireless communication by a first user equipment (UE), comprising: Determine the semi-persistent scheduling (SPS) resource reservation, including the first set of subframes in which the first UE is scheduled to transmit sidelink transmissions; Determine whether to skip the transmission of a subset of subframes in the first group of subframes; During at least one subframe in the subset of subframes, listen for transmissions from the second UE; Based on the aforementioned monitoring: Measure the channel busy ratio (CBR) of the channel. Estimate the number of UEs using the channel; as well as The congestion level of the channel is estimated based on the number of CBRs and UEs. as well as SPS resource reselection is triggered based on the congestion level.

2. The method of claim 1, wherein estimating the number of UEs using the channel comprises: Count the number of packets received within the time window; as well as The number of UEs using the channel is estimated based on the number of packets.

3. The method of claim 1, wherein estimating the number of UEs using the channel comprises: Count the number of source addresses in packets received within the time window; as well as The number of UEs using the channel is estimated based on the number of source addresses.

4. The method according to any one of claims 1-3, further comprising: The periodicity of transmissions in a subset of subframes in the set of reselection subframes to listen for transmissions from the sidelink UE is determined, wherein the determination is based on the congestion level.

5. The method of claim 1, further comprising: In response to determining that the first UE has no packets to transmit in the at least one subframe; Skip the transmission in the next subframe in which the first UE has packets to transmit in the first group of subframes; as well as Listen for transmissions from the second UE during the next subframe.

6. The method of claim 1, wherein the first UE comprises a vehicle UE.

7. The method of claim 1, further comprising: The skipped transmission is transmitted in a subframe that is different from the first set of subframes after the at least one subframe.

8. The method of any one of claims 5-7, further comprising determining the subset of subframes to be skipped during transmission, wherein the determination includes: Randomly select at least one subframe to skip transmission; as well as Based on the fact that the first UE has no packets to transmit in the at least one subframe and the first UE has packets to transmit in the subframes following the at least one subframe, one or more other subframes to skip transmission are determined.

9. The method of claim 1, further comprising: The detection of a conflict between a transmission from the second UE and an SPS resource scheduled for the first UE in at least one subframe is based on the monitoring, wherein the detection of the conflict is based on the amount of frequency resource overlap between the transmission from the second UE and the SPS resource reservation scheduled for the first UE in at least one subframe, and the triggering of the SPS resource reselection is further based on the amount of the detected conflict.

10. The method of claim 9, wherein detecting a collision comprises: In response to the detection that a transmission from the second UE and an SPS resource scheduled for the first UE appear in the same subframe, a conflict is detected between the transmission from the second UE and the SPS resource scheduled for the first UE.

11. The method of claim 10, wherein the transmissions from the second UE and the SPS resources scheduled for the first UE are reserved on the non-overlapping frequency resources of the same subframe.

12. The method of any one of claims 10-11, wherein detecting a collision comprises: In response to the detection of a conflict between a transmission from the second UE and an SPS resource scheduled for the first UE on frequency resources that at least partially overlap in the same subframe, the system detects a conflict between a transmission from the second UE and an SPS resource scheduled for the first UE.

13. The method of any one of claims 9-11, wherein detecting a collision comprises: In response to the detection that the frequency resources of one of the transmissions from the second UE and the SPS resource reservations scheduled for the first UE completely overlap with the frequency resources of the other, a conflict is detected between the transmissions from the second UE and the SPS resources scheduled for the first UE.

14. The method of claim 1, wherein triggering the SPS resource reselection comprises: In response to determining that at least a single collision is detected in a non-Hybrid Automatic Repeat Request (HARQ) SPS transmission, triggering the SPS resource reselection when the congestion level is below a threshold, or both; and In response to the detection of multiple collisions when the scheduled SPS transport is a HARQ transport, the SPS resource reselection is triggered when the congestion level is equal to or higher than the threshold, or both.

15. The method of claim 1, wherein the at least one subframe comprises: The first UE skips the transmitted subframes based on jitter or silence.

16. The method of claim 1, wherein triggering the SPS resource selection is further based on one of the transmissions having a large SPS Tx period and the other transmission having a small SPS period.

17. The method of claim 16, wherein triggering the SPS resource reselection includes triggering the SPS resource reselection when the difference between the periods is greater than or exceeds a threshold.

18. The method of claim 1, further comprising determining a subset of subframes to skip transmission, wherein at least one of the following: Determining the subset of subframes to be skipped includes determining the periodicity of the transmissions to be skipped based on the SPS stream priority associated with the scheduled SPS resource reservation; The SPS resource reselection is further triggered based on the SPS stream priority; or Its combination.

19. The method of claim 1, wherein triggering the SPS resource reselection is further based on the distance between the second UE and the first UE, the signal strength transmitted from the second UE, or a combination thereof.

20. The method of claim 1, further comprising: Perform the SPS resource reselection; It was detected that one or more expected SPS flows were not detected during the time window following the reselection, wherein the expected SPS flows included SPS flows detected by the first UE prior to the reselection; and Based on the detection that one or more expected SPS streams are not detected, a skip transmission is triggered and listening is performed in another subframe.

21. A first device for wireless communication, the first device comprising: Memory that stores executable code for a computer; as well as At least one processor is configured to execute the computer-executable code individually or collectively to cause the device to perform the following operations: Determine the semi-persistent scheduling (SPS) resource reservation, which includes the first set of subframes in which the first device is scheduled to transmit side-link transmissions; Determine whether to skip the transmission of a subset of subframes in the first group of subframes; During at least one subframe in the subset of subframes, listen for transmissions from the second device; Based on the aforementioned monitoring: Measure the channel busy ratio (CBR) of the channel. Estimate the number of devices using the channel; as well as The congestion level of the channel is estimated based on the CBR and the number of devices. as well as SPS resource reselection is triggered based on the congestion level.

22. The first apparatus of claim 21, wherein estimating the number of UEs using the channel comprises: Count the number of packets received within the time window; as well as The number of UEs using the channel is estimated based on the number of packets.

23. The first apparatus of claim 21, wherein estimating the number of UEs using the channel comprises: The number of source addresses in the packets received in the at least one subframe is counted; as well as The number of UEs using the channel is estimated based on the number of source addresses.

24. The first apparatus of any one of claims 21-23, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operations: The periodicity of transmissions in a subset of subframes in the set of reselection subframes to listen for transmissions from the sidelink UE is determined, wherein the determination is based on the congestion level.

25. The first device as claimed in claim 21: The computer-executable code is further executed individually or collectively by the at least one processor to cause the first device to perform the following operations: In response to determining that the first device has no packets to transmit in the at least one subframe: Skip the transmission in the next subframe in which the first device has packets to transmit in the first group of subframes; and During the next subframe, listen for transmissions from the second device.

26. The first device of claim 25, wherein the first device includes a vehicle UE.

27. The first apparatus of claim 21, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operations: The skipped transmission is transmitted in a subframe that is different from the first set of subframes after the at least one subframe.

28. The first apparatus of any one of claims 25-26, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operation: determining the subset of subframes to be skipped from transmission, wherein the determination includes: Randomly select at least one subframe to skip transmission; as well as Based on the fact that the first device has no packets to transmit in the at least one subframe and that the first device has packets to transmit in a subframe that is different from the first set of subframes, it determines one or more other subframes to skip transmission.

29. The first apparatus of claim 21, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operations: Based on the monitoring, a conflict is detected between a transmission from the second device and an SPS resource scheduled for the first device in at least one subframe, wherein the detection of the conflict is based on the amount of frequency resource overlap between a transmission from the second device and a reserved SPS resource for the first device in at least one subframe, wherein triggering the SPS resource reselection is further based on the amount of the detected conflict.

30. The first apparatus as claimed in claim 21, wherein: The computer-executable code is further executed individually or collectively by the at least one processor to cause the first device to perform the following operations: Based on the monitoring, a conflict is detected between a transmission from the second device and an SPS resource scheduled for the first device in at least one subframe, wherein the detection of the conflict is based on the amount of frequency resource overlap between a transmission from the second device and a reserved SPS resource for the first device in at least one subframe, wherein triggering the SPS resource reselection is further based on the amount of the detected conflict.

31. The first apparatus of claim 30, wherein the transmissions from the second apparatus and the SPS resources scheduled for the first apparatus are reserved on non-overlapping frequency resources of the same subframe.

32. The first device as claimed in any one of claims 30-31, wherein detecting a collision comprises: In response to the detection that a transmission from the second device and an SPS resource scheduled for the first device at least partially overlap in the same subframe, a conflict is detected between the transmission from the second device and the SPS resource scheduled for the first device.

33. The first apparatus as claimed in any one of claims 30-31, wherein detecting a collision comprises: In response to the detection that the frequency resources of one of the transmissions from the second device and the SPS resource reservations scheduled for the first device completely overlap with the frequency resources of the other, a conflict is detected between the transmissions from the second device and the SPS resources scheduled for the first device.

34. The first apparatus of claim 21, wherein triggering the SPS resource reselection comprises: In response to determining that at least a single collision is detected in a non-Hybrid Automatic Repeat Request (HARQ) SPS transmission, triggering the SPS resource reselection when the congestion level is below a threshold, or both; and In response to the detection of multiple collisions when the scheduled SPS transport is a HARQ transport, the SPS resource reselection is triggered when the congestion level is equal to or higher than the threshold, or both.

35. The first apparatus of claim 21, wherein the at least one subframe comprises: The first device skips the transmitted subframes based on jitter or silence.

36. The first apparatus of claim 21, wherein triggering the SPS resource selection is further based on one of the transmissions having a large SPS Tx period and the other transmission having a small SPS period.

37. The first apparatus of claim 36, wherein triggering the SPS resource reselection includes triggering the SPS resource reselection when the difference between the periods is greater than or exceeds a threshold.

38. The first apparatus of claim 21, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operation: determining a subset of subframes to be skipped from transmission, wherein at least one of the following: Determining the subset of subframes to be skipped includes determining the periodicity of the transmissions to be skipped based on the SPS stream priority associated with the scheduled SPS resource reservation; The SPS resource reselection is further triggered based on the SPS stream priority; or Its combination.

39. The first apparatus of claim 21, wherein triggering the SPS resource reselection is further based on the distance of the second apparatus from the first apparatus, the signal strength transmitted from the second apparatus, or a combination thereof.

40. The first apparatus of claim 21, wherein the computer-executable code is further executed individually or collectively by the at least one processor to cause the first apparatus to perform the following operations: Perform the SPS resource reselection; It was detected that one or more expected SPS flows were not detected during a time window following the reselection, wherein the expected SPS flows included SPS flows detected by the first device prior to the reselection; and Based on the detection that one or more expected SPS streams are not detected, a skip transmission is triggered and listening is performed in another subframe.

41. A first device for wireless communication, comprising: Means for determining a semi-persistent scheduling (SPS) resource reservation including a first set of subframes in which the first device is scheduled to transmit side link transmissions; A means for determining which subset of subframes in the first set of subframes should be skipped during transmission; A means for listening to transmissions from a second means during at least one subframe in the subset of said subframes; Based on the aforementioned monitoring: A device used to measure the channel busy ratio (CBR) of a channel; A means for estimating the number of devices using the channel; as well as A means for estimating the congestion level of the channel based on the CBR and the number of devices; as well as A means for triggering SPS resource reselection based on the congestion level.

42. The first device as claimed in claim 41, further comprising: In response to determining that the first device has no packets to transmit in the at least one subframe; Means for skipping transmissions in the next subframe in which the first device has packets to transmit in the first group of subframes; as well as A means for listening to transmissions from the second device during the next subframe.

43. The first device as claimed in claim 41, further comprising: A means for detecting, based on the monitoring, a conflict between a transmission from the second device and an SPS resource scheduled for the first device in at least one subframe, wherein the detection of the conflict is based on the amount of frequency resource overlap between a transmission from the second device and an SPS resource reservation scheduled for the first device in at least one subframe, wherein triggering the SPS resource reselection is further based on the amount of the detected conflict.

44. A computer-readable medium having computer-executable code stored thereon for wireless communication, comprising: Code used to determine the semi-persistent scheduling (SPS) resource reservation, including the first set of subframes in which the first device is scheduled to transmit side link transmissions; Code used to determine which subset of subframes in the first set of subframes should be skipped during transmission; Code for listening to transmissions from the second device during at least one subframe in the subset of said subframes; Based on the aforementioned monitoring: The code used to measure the channel busy ratio (CBR) of a channel; Code used to estimate the number of sidelink devices using the channel; as well as Code for estimating the congestion level of the channel based on the number of CBRs and sidelink devices; as well as Code used to trigger SPS resource reselection based on the congestion level.

45. The computer-readable medium of claim 44, further comprising: In response to determining that the first device has no packets to transmit in the at least one subframe; Code for skipping transmission in the next subframe in which the first device has a packet to transmit; as well as Code used to listen for transmissions from the second device during the next subframe.

46. ​​The computer-readable medium of claim 44, further comprising: Code for detecting, based on the monitoring, a conflict between a transmission from the second device and an SPS resource scheduled for the first device in at least one subframe, wherein the detection of the conflict is based on the amount of frequency resource overlap between a transmission from the second device and an SPS resource reservation scheduled for the first device in at least one subframe, wherein triggering the SPS resource reselection is further based on the amount of the detected conflict.

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